Optical film thickness controlling method, optical film thickness controlling apparatus, dielectric

专利摘要:
In order to provide a method for controlling the film thickness of a dielectric multilayer film such as an optical thin film with high precision, an optical film thickness control device and a dielectric multilayer film production device capable of controlling the film thickness based on the method, and the control device or the manufacture A dielectric multilayer film fabricated using the device is presented. The optical film thickness control apparatus detects each of the film forming apparatus 15 having the rotatable substrate 23 and the sputtering target 28 and a plurality of monochromatic rays applied along the radius of the rotatable substrate at predetermined intervals. Photoelectric diodes 16 and movable shutters 29 that move along the radial direction of the rotatable substrate 23 to block film formation in the substrate 23 are formed between the substrate 23 and the target 28. An A / D converter 17 is provided. When the second regression function of the reverse transmittance is calculated by the wrist square method from each monochromatic light absorbed by the photodiode 16 and the A / D converter 17, and the last surface film layer reaches a predetermined optical film thickness. The CPU 18 and the motor driver 19, which indicate the movement of the movable shutter based on each prediction value of the film growth time, move the movable shutter 29 to block the film formation in the film formation region where a predetermined optical film thickness has been reached. Move it.
公开号:KR20030077439A
申请号:KR10-2003-0018487
申请日:2003-03-25
公开日:2003-10-01
发明作者:다까하시하루오；한자와고이찌；마쯔모또다까후미
申请人:가부시키가이샤 아루박；
IPC主号:

专利说明:

OPTICAL FILM THICKNESS CONTROLLING METHOD, OPTICAL FILM THICKNESS CONTROLLING APPARATUS, DIELECTRIC MULTILAYER FILM MANUFACTURING APPARATUS AND DIEL MULTILAYER FILM MANUFACTURED USING THE SAME CONTROLLING APPARATUS OR MANUFACTURING APPARATUS}
[46] The present invention relates to a method for controlling the thickness of an optical thin film, particularly when forming a film based on optical technology, a film thickness control device for carrying out the method, and mainly used as an optical thin film, An apparatus for manufacturing a dielectric multilayer film whose thickness can be controlled with accuracy. Optical thin films are used in various kinds of optical components or devices such as wave guides, diffraction gratings, light emitters, indicators, optical memories and solar cells. In particular, the optical thin film used in the wheat wavelength division multiplexing device in the field of communication technology, including optical communication, tends to be manufactured in multiple layers. Therefore, in the multilayer structure of the optical thin film, it is important to control the film thickness of each layer with high accuracy.
[47] Measuring the thickness of a thin film during the growth of the thin film is important for controlling the stacking speed and the film thickness. In an optical thin film, an optical film thickness (refractive index x physical film thickness) for determining optical properties such as reflectance and transmittance is more useful than physical film thickness. Therefore, the optical film thickness is monitored by measuring the optical properties of the thin film during the growth of the thin film according to the so-called optical film thickness control method for measuring the optical properties of the thin film. Optical film thickness control methods include monochromatic photometry, dichroic photometry, and multicolor photometry. The simplest of these methods is monochrome photometry.
[48] In the monochromatic photometric method, the peaks (which correspond to the valleys, respectively, the maximum and the minimum) appear when the optical film thickness of the formed thin film becomes an integer multiple of λ / 4 (λ: wavelength of incident monochromatic light). The optical film thickness of the film to be formed if the optical film thickness of the substrate-side adjacent layer to be laminated on the coating surface is not an integer multiple of λ / 4, or if the admittance of the system including the adjacent layer is not expressed by a mathematical mistake. This peak does not always appear when is the integer multiple of lambda / 4 after the beginning of growth. In this case, however, once the peak appears, the peak appears periodically during the growth cycle of the optical film thickness corresponding to an integer multiple of λ / 4.
[49] However, in the monochromatic photometric method, the conventional method including the peak control using the appearing peak is in principle inevitable to a certain extent that the accuracy of the control is unavoidable, because the reason for the increase in the optical film thickness is that This is because the intensity hardly changes in the vicinity of the peak.
[50] The accuracy can be improved with interference filters for wavelengths slightly different from the desired wavelengths used to terminate film formation, at points other than near the peak, where the intensity of light changes significantly. With this approach, it is possible to measure the intensity of light (back transmittance), an optical property, to select an optical phase angle region that gives high control accuracy of optical film thickness growth, thereby determining the end point of film formation ( See, for example, Patent Document 1).
[51] On the other hand, for example, Patent Document 2 uses a conventional monochromatic photometric method using a desired wavelength. According to this approach, the group of data obtained immediately before the measured light intensity (transmittance) peaks as an integer multiple of / 4 of the optical film thickness is returned is returned to the quadratic function by the least squares method. To determine the end of film formation, one can predict when peaks can occur in the regression function. Most preferably, the timing is the predicted viewpoint itself, but considering specific conditions, the timing may be determined by referring to the prediction point as a basis of the viewpoint.
[52] Patent Document 1: Japanese Patent Application Laid-open No. S58-140605 (pages 2-3, Fig. 1)
[53] Patent Document 2: Japanese Patent Application Laid-Open No. S63-28862 (p. 2-6, FIGS. 1 and 2)
[54] As mentioned above, there is an increasing demand in the communication field to form optical thin films with more layers. In particular, the wavelength division multiplexer device (eg, band pass filter) has more than 100 layers. The multilayer structure is formed of alternating layers of high and low refractive index layers each having an optical film thickness corresponding to an odd multiple of λ / 4 (for a bandpass filter, optical equivalent to an even multiple of λ / 4). The cavity layer may be formed of a high refractive index layer or a low refractive index layer having a film thickness between the alternating layers). In this case, the conventional method of controlling the film thickness of each thin film of the multilayer structure by replacing the associated monitor substrate is not practical because the required process is complicated.
[55] Thus, a multilayer structure including alternating layers similar to a product thin film can be laminated to a monitor substrate to monitor this multilayer structure. In this case, however, as many layers are stacked, the reflectance of the multi-layer structure to be established becomes large, that is, the transmittance gradually decreases, and the reliability of the measured value is lowered. Therefore, if the above-described function regression is carried out, the measured transmission value does not coincide with the function curve in the vicinity of the peak of the quadratic regression function, and thus its correlation is lowered. Therefore, it becomes difficult to control the film thickness with high accuracy. In addition, in terms of accuracy, it is also questionable whether all the constituent thin films of the multilayer structure to be monitored on the monitor substrate can be an accurate reproduction of the product thin film layer.
[56] Therefore, for a multilayer optical thin film, the film thickness is controlled by a direct monitoring method, in which case many alternating layers themselves stacked on the product substrate are monitored. 1 shows an example of a film thickness control apparatus for a direct monitoring method. As shown in FIG. 1A, the electron gun 2 and the ion gun 3 are arranged side by side opposite to the rotating substrate 4 in the vacuum chamber 1, and the light emitter 5 is disposed outside the chamber 1. 4, located opposite to the light emitted from the light emitter 5 along the axis of rotation 4a of the rotary substrate 4, the light guide window 6 and the upper light guide window 7 Is incident on the photoreceptor 8 located outside the chamber 1. In the film thickness control according to this apparatus, the product substrate 4 is rotated by the drive motor 9, so that one monochromatic light flux from the light emitter 5 is lowered along the axis of rotation 4a. Pass (6). In this state, the shutter 2a is opened, and a laminated film is formed on the product substrate 4 with the electron gun 2. At this time, the photoreceptor 8 detects a change in the intensity of the light which is odd to the interference through the lower light guide window 6 and the upper light guide window 7. And the thickness of the laminated film formed is controlled based on the change of the intensity of light. That is, the end point of film formation is determined according to the film thickness control method described, for example, in Patent Documents 1 or 2. Then, the film formation using the electron gun 2 is interrupted by the shutter 2a to end the growth of the film thickness. In this way, a dielectric multilayer film having satisfactory spectral characteristics is formed in the vicinity of the product substrate.
[57] However, even in this case, as the number of layers increases, the reflectance of the growing multi-layer structure increases, i.e., the transmittance gradually decreases and the reliability of the measurement decreases, which brings about the same disadvantages as the monitor substrate. This effect is particularly severe in low pass filters made up of multiple alternating layers of high refractive index films of λ / 4 and low refractive index films of λ / 4. In addition, as the number of layers increases, the curve showing the change in transmitted light intensity that changes with increasing film thickness does not coincide with the second order regression function even in peaks and valleys, and it is difficult to control the film thickness with high accuracy. You lose. 2 shows a mismatch with this quadratic regression function. When the intensity of transmitted light decreases (ie, the high refractive index layer (H) above the low refractive index layer (L) is the most superficial layer), and when the intensity of the transmitted light increases (ie, above the high refractive index layer (H) When the high refractive index layer (H) is the outermost surface layer), the peaks and valleys predicted by the quadratic function regression are remarkably different, and as a result, the dispersion error is also large. Therefore, when the intensity of transmitted light decreases, the prediction end point for film formation is too early, and when the intensity of transmitted light increases, the prediction end point for film formation is too late.
[58] In view of such a problem, an object of the present invention is to provide a method capable of controlling the film thickness of a dielectric multilayer film such as an optical thin film with high accuracy, an optical film thickness control device capable of controlling the film thickness based on such a method, and To provide a dielectric multilayer and a dielectric multilayer film using such a control device and a manufacturing method.
[1] 1A is a schematic cross-sectional view of a conventional dielectric multilayer film fabrication apparatus intended for a direct monitoring method.
[2] FIG. 1B is a conceptual diagram illustrating an optical region on a substrate used in the manufacturing apparatus shown in FIG. 1A. FIG.
[3] 2 is a graph showing deviation from a second order regression function according to a conventional optical film thickness control method.
[4] 3 schematically shows an optical film thickness control apparatus according to the present invention;
[5] FIG. 4 is an optical signal measurement graph showing the mutual transmission values for eight optical channels detected by a photodiode when a monolayer film made of Ta ₂ O ₅ is formed using the optical film thickness controller shown in FIG.
[6] FIG. 5 is a graph showing the correlation between each optical signal of FIG. 4 and the expected time when a peak becomes an optical signal, and is returned to a cubic function. FIG.
[7] 6A is a schematic cross-sectional view of a dielectric multilayer film production apparatus according to the present invention.
[8] 6B is a plan view showing the positions of the substrate and the monitoring point of the apparatus shown in FIG. 6A;
[9] 6C is a plan view of the manufacturing apparatus shown in FIG. 6A.
[10] 7A is a schematic cross-sectional view of a dielectric multilayer film production apparatus according to the present invention.
[11] 7B is a plan view showing a substrate and a split shutter in the manufacturing apparatus shown in FIG. 7A.
[12] 7C is a plan view of the manufacturing apparatus shown in FIG. 7A.
[13] 8 is a graph comparing the accuracy between the second order regression function of the transmittance of the multilayer film composed of the Ta ₂ O ₅ film (H) and the SiO ₂ film (L) in Example 2 and the second order regression function of the mutual transmittance of the multilayer film. .
[14] 9 is a graph comparing the accuracy based on the regression range between the second regression function of the transmittance of the monolayer film composed of the Ta ₂ O ₅ membrane prepared in Example 3 and the second regression function of the mutual transmittance of the monolayer film.
[15] 10 is a graph showing the spectra for the bandpass filter prepared in Example 4. FIG.
[16] FIG. 11 is a conceptual diagram showing an optical region on a substrate provided in Example 5. FIG.
[17] 12 is a graph illustrating the operation of the movable shutter of Example 5. FIG.
[18] FIG. 13 is a graph showing the spectral transmittance of the intermediate band pass filter provided in Example 5. FIG.
[19] 14 is a graph showing the spectral transmittance of the narrow band pass filter provided in Example 6. FIG.
[20] 15 is a graph showing the spectral reflectivity of the antireflective film provided in Example 7. FIG.
[21] FIG. 16 is a conceptual diagram showing an optical region on a substrate provided in Example 8. FIG.
[22] 17 is a graph showing the spectral transmittance of the intermediate band pass filter provided in Example 8. FIG.
[23] 18 is a graph showing the spectral transmittance of the narrow band pass filter provided in Example 9. FIG.
[24] 19 is a graph showing the spectral reflectivity of the antireflective film provided in Example 10;
[25] Explanation of symbols on the main parts of the drawings
[26] 1, 61, 91: vacuum chamber 2: electron gun
[27] 2a: shutter 4, 23, 64, 94: rotating substrate
[28] 12 variable laser light source 13 optical coupler
[29] 14 fiber collimator 15 sputtering film forming apparatus
[30] 16: photodiode 17, 70, 100: 8-channel A / D converter
[31] 18: CPU (controller) 19: motor driver (controller)
[32] 20, 21: optical fiber
[33] 28, 62, 92: sputtering target (film forming source)
[34] 29, 81: movable shutter
[35] 63, 93: ion gun unit (reaction source)
[36] 65, 95: light emitter 66, 96: upper light guide window
[37] 67, 97: lower light guide window 68, 98: optical receiver (photometric means)
[38] 69, 99: 8-channel preamplifier 71, 101: digital signal processor (DSP)
[39] 72, 102: computer 74, 104: Ta target
[40] 75, 105: Si target 76, 106: sputtering gas pipe
[41] 77, 107: fixed openings 78, 108: reaction gas pipe
[42] 79, 109: ECR ion total 82 ~ 89: watch point
[43] 111a, 111b: variable openings (film accumulation rate control member)
[44] 112 to 114: Separate shutter (film thickness correction means)
[45] 116a to 116h: watch point
[59] In order to achieve the above object, according to the present invention, during the formation period of a single layer or a multilayer optical thin film, incident monochromatic light (wavelength: λ) is transmitted through a single layer or a multilayer structure to measure the transmittance of the optical thin film, and the reverse transmittance is Calculate by the inverse.
[60] Here, from the boundary conditions of the structure (i.e., the tangential components of B or C of the electric or magnetic fields are each continuous), the admittance (C / B) of the system is represented using the characteristic matrix of the single layer film using the following Equation 1. .
[61]
[62] In the above formula, N is the refractive index of the single layer film, θ represents the phase difference between different interferences in the single layer film, and Y represents the admittance of the substrate system.
[63] The transmittance | permeability T of a monolayer membrane is represented by following formula 2, and * represents a complex conjugate.
[64] T = 4Y / (B + C) (B + C) ^*
[65] Therefore, equation 3 is derived from equations 1 and 2.
[66] T = 4Y / [(1 + Y) ² + {(Y / N + N) ^2- (1 + Y) ² } sin ² θ]
[67] Here, it is assumed that the refractive index of air or vacuum is one.
[68] In the present invention, the optical phase angle θ is represented by the following equation 4 including the optical film thickness Nd of the most recent growth surface layer film laminated with the wavelength λ of monochromatic light (N is the refractive index of the thin film). D represents the physical thickness of the thin film).
[69] θ = 2πNd / λ
[70] And, with the least-square method, the film growth time (t) of the surface layer film in relation to the increase of the optical film thickness and the back transmittance (1 / T) of two variables, i.e., before the measurement data group reaches the maximum or minimum 2 Regression to the difference function, so a quadratic regression function such as
[71] 1 / T = A _O + B ₀ (tt _p ) ²
[72] (Where A ₀ and B ₀ are constant and t _p represents the film growth time when the maximum or minimum is reached.)
[73] For higher correlations of the regression function, sampling at or after the point where the optical film thickness of the surface layer film approaching the maximum or minimum of the function curve reaches the last 25 to 10% of the film thickness equal to λ / 4 for the maximum or minimum It is preferable to perform a function regression on the measured measurement data group (λ: wavelength of monochromatic light).
[74] Equation 3 may be modified to the following equation 6.
[75] 1 / T = (1 + Y) ² / 4Y + {(Y / N + N) ^2- (1 + Y) ² } sin ² θ / 4Y
[76] Both the top layer film at the time when the top layer film growth starts gwayul (T ₀₎ and, respectively, the following equation two gwayul of the top layer when the its optical film thickness reaches λ / 4 (T ₉₀₎ is 7, It is indicated by (8).
[77] T ₀ = 4Y / (1 + Y) ²
[78] T ₉₀ = 4Y / (Y / N + N) ²
[79] If the admittance (Y) is a real number, the following equation 9 is derived from these equations.
[80] (1 / T ₀ -1 / T) / (1 / T ₀ -1 / T ₉₀ ) = sin ² θ
[81] Thus, the back transmittance can be expressed as a function of optical phase angle only.
[82] According to the interference theory described above, the back transmittance has a periodic distribution at every interval of the optical film thickness corresponding to one quarter of the monochromatic light wavelength. Near the maximum and minimum of the reverse transmission, the function of the reverse transmission induced by the development of Equation 9 can be approached as a quadratic function (θ is a variable and sin ² θ is also included in the function). Therefore, as the predicted value of the film growth time when the optical film thickness at the maximum or minimum is reached, the film growth time at the maximum or minimum can be used in the quadratic regression function. When the film formation of the surface layer film is finished at the predicted time, the optical film thickness can be controlled to correspond to 1/4 of the monochromatic light wavelength.
[83] This optical film thickness control method is simple because the optical characteristics of the entire multilayer structure identical to the thin film products can be measured at once and peak control is performed accordingly. In addition, since peak control is performed based on quadratic regression with high correlation, the film thickness can be controlled with high accuracy.
[84] In this case, the optical film thickness of the surface layer film can be calculated as a function of the optical transmittance obtained by the development of Equation 9 above. Therefore, the optical film thickness can be controlled to a desired value by predicting the growth time of the surface layer film when reaching the target value of the optical film thickness at the lamination rate of the outermost surface layer film (which can be defined as time differential and time difference). That is, the optical film thickness to be controlled is not limited to 1/4 of the monochromatic light wavelength, and any optical film thickness can be predicted.
[85] In addition, since the transmittance associated with the formation of the optical thin film is measured on the product substrate, a field measurement of the product thin film, that is, a direct monitoring method of the optical film thickness of the outermost surface layer film can be performed. Therefore, the optical film thickness control method is further improved in its handling and accuracy.
[86] In order to implement the optical film thickness control method, a film forming apparatus having a rotating substrate, a film forming apparatus and a film material source facing each other, and a plurality of monochromatic light beams applied to the rotating substrate at prescribed intervals along the radius of the rotating substrate An optical film thickness control device is provided that includes a photoelectric conversion device for detecting a light emitting device, and a movable shutter capable of moving in a radial direction of a rotating substrate to stop film formation on the substrate is disposed between the substrate and the film material source. The optical film thickness control device is configured to cause the movable shutter to move in response to the controller-indicated movement of the shutter based on each predicted value of the film growth time predicted by the monochromatic light detected by the photoelectric conversion device. Therefore, the film growth time of the surface layer film when the intended optical film thickness is reached can be predicted by the above-described optical film thickness control method. In the surface layer film, the film forming process is terminated in the region where the film has grown to the desired optical film thickness, and the termination of this film forming process is performed continuously. In this way, a uniform film thickness can be obtained by controlling the film thickness with high accuracy.
[87] In the current optical communication field, the low pass filter used in the multiplexer / demultiplexer for a DWDM system includes various kinds of central wavelengths (eg, 4, 8, 16, etc.) determined by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). 128, a group of band pass filters is required. Therefore, it is necessary to make a large amount of filters for various kinds of wavelengths.
[88] However, in the multiplexer film production apparatus shown in FIG. 1, the monitoring monochromatic light flux passes only along the rotational center axis. Therefore, the direct monitoring method is effective only in the central area indicated by reference numeral "10" in FIG. 1B. Due to fluctuations in the evaporation distribution, differences in relative distances between the product substrate and the evaporation source, uneven temperatures on the surface of the product substrate, and so on, the optical thin film product provided from within the substrate region indicated by reference numeral "11" rather than the center of the substrate has a wavelength. There are variations in characteristics, etc., and it does not give satisfactory characteristics for the monitoring wavelength used in the direct monitoring method.
[89] Therefore, the position of the monitoring monochromatic flux applied while passing through the substrate moves from the rotational center axis to a point on the circumferential portion of the concentric circle in the rotational substrate area, and the region formed in the annular band shape along the circumference is directly Can be used as an effective area. In this case, however, only a small improvement in the effective area can be expected. In the area where the monitoring monochromatic flux for the direct monitoring method passes through the substrate, even when the film thickness of the layer formed immediately before the outermost surface layer is controlled with low accuracy, the end point of film formation of the next outermost surface layer can be precisely controlled at the peak and valleys. If yes, the error is naturally corrected and the error is reduced. Therefore, in order to obtain a high quality optical thin film product, since the monitoring area can have a significant advantage, it is important that the area is enlarged.
[90] Therefore, the vacuum chamber of the dielectric multilayer film production apparatus according to the present invention has a film material source and a reaction source, each arranged side by side facing the rotating substrate. The present dielectric multilayer film production apparatus includes: a film stacking speed control member having an opening for giving a gradient along the radius of the circle of the rotating substrate to the film stacking speed of the dielectric multilayer film formed on the rotating substrate; A film thickness correction member provided between the rotating substrate and the film material source together with the film stacking speed control material and correcting the film thickness of the dielectric multilayer film formed on the rotating substrate; Light intensity measuring means for measuring the intensity of the monitored monochromatic light passing through the plurality of monitoring points along the radius of the rotating substrate; Arranging monitoring monochromatic light fluxes of two or more wavelengths in ascending or descending order of the wavelength of the monochromatic light flux associated with the position of the monitoring point along the radius to allow the optical flux to pass through each monitoring point, and also measured by said light intensity measuring means And a control system capable of moving the film thickness compensating member according to the change of the intensity of the light.
[91] In the device, the monochromatic light fluxes are arranged in ascending or descending order of wavelength with respect to the position of the surveillance point along the radius, and the surveillance monochromatic fluxes of different wavelengths pass through each surveillance point.
[92] Here, as the monitoring points are arranged from the outer circumference of the rotating substrate along the radius to the inner circumference, the values of nd / λ and λ which become the monitoring wavelengths of the monitoring monochromatic light flux passing through the monitoring point on the substrate are arranged in ascending order. In this state in which the monitoring monochromatic light fluxes are arranged, the film stacking speed caused by the opening of the film stacking speed control member when the light intensity is detected by the light intensity measuring means in accordance with the increase in the film thickness of the outermost layer of the dielectric multilayer film. The gradient of decreases from the outer circumference to the inner circumference along the radius of the rotating substrate source, and peaks are formed faster at one monitoring point of the outer peripheral portion of the rotating substrate source, which is also given a shorter monitoring wavelength. Therefore, by correspondingly moving the film thickness correction member from the outer peripheral portion of the rotating substrate to the inner peripheral portion, it is possible to correct the increase in the film thickness of the dielectric multilayer film. That is, the film thickness of the outermost layer of the dielectric multilayer film can be controlled with high accuracy. In addition, since monochromatic light of one or more wavelengths is used as the monitoring light flux, a dielectric multilayer film can be produced by controlling the film thickness by using a direct monitoring method for various monitoring wavelengths.
[93] The movement direction of the film thickness correction member need not be limited only to the direction from the outer peripheral portion to the inner peripheral portion of the rotating substrate source. The values of nd / λ, λ, which are the monitoring wavelengths of the monitoring monochromatic light flux passing through the monitoring point on the rotating substrate, are from long wavelength to short wavelength as lambda points are arranged from the outer circumference of the substrate to the inner circumference along the radius. That is, arranged in descending order. In this case, when the light intensity is detected by the light intensity measuring means in accordance with the film thickness of the most superficial layer of the dielectric multilayer film, the gradient of the film stacking speed caused by the opening of the film stacking speed control member causes the radius of the rotating substrate source to be reduced. As a result, the peak is formed faster at one monitoring point of the inner circumference of the rotating substrate source, which increases from the outer circumference to the inner circumference and is also given a shorter monitoring wavelength. Accordingly, by correspondingly moving the film thickness correction member from the inner circumference to the outer circumference of the rotating substrate, the nonuniformity of the film thickness of the dielectric multilayer film can be corrected.
[94] A shutter movable in the radial direction of the rotating substrate is used as the film thickness correction member, and the film formation on the rotating substrate is interrupted by the movement of the movable shutter in the ascending or descending order described above along the radius.
[95] Therefore, film formation can be stopped under the same conditions in order to obtain an annular band-like dielectric multilayer film for each monochromatic light of a different wavelength passing through the monitoring point. Therefore, various high quality dielectric multilayer films obtained from the annular band-shaped monitoring region can be produced on a large scale.
[96] In addition, if the monitoring monochromatic light flux including one or more wavelengths passes through each of the plurality of monitoring points during the formation of the dielectric multilayer film on the rotating substrate, and the reverse transmittance is defined as the inverse of the transmittance, the control system of the dielectric multilayer film manufacturing apparatus is light. The change in light intensity measured by the intensity measuring means is first measured as a change in transmittance.
[97] Based on the interference theory described above, the reverse transmittance is periodically distributed at intervals of the optical film thickness corresponding to 1/4 of the monochromatic light wavelength, and inversely obtained by the development of Equation 9 above the maximum and minimum of the reverse transmittance. The function of transmittance can be approached as a quadratic function (the function depends on the variable θ in the sin ² θ term). Therefore, as the prediction time for the most superficial layer film to reach the optical film thickness at the maximum or minimum, the film growth time at the maximum or minimum in the quadratic regression function can be used. Film formation in the surface layer film ends at the prediction time. In this process, since peak control is performed based on quadratic regression with high correlation, the accuracy of control for reaching the optical film thickness corresponding to 1/4 of the monochromatic light wavelength is further improved.
[98] In this case, the optical film thickness of the surface layer film can be calculated based on the inverse transmittance function obtained by the development of Equation 9 above. Therefore, the time differential or time difference can be calculated as the film stacking speed of the outermost surface layer film, and the time taken for the outermost film to reach the defined optical film thickness can be predicted based on the film stacking speed. Therefore, the desired optical film thickness can be predicted and controlled. In other words, the optical film thickness to be controlled is not limited to the thickness corresponding to 1/4 of the monochromatic light wavelength, and any optical film thickness can be controlled.
[99] Further, in place of the above-described manufacturing apparatus, another dielectric multilayer film manufacturing apparatus according to the present invention includes a vacuum chamber for manufacturing having a film material source and a reaction source arranged side by side facing the rotating substrate. In addition, the manufacturing apparatus includes a film stacking speed control member having an opening for controlling the film stacking speed of the dielectric multilayer film formed on the rotating substrate; A film thickness correction member having an opening for correcting the film thickness of the dielectric multilayer film formed on the rotating substrate, the film thickness correction member being disposed between the rotating substrate and the film material source together with the film stacking speed control material; Light intensity measuring means for measuring the intensity of the monitored monochromatic light passing through the plurality of monitoring points along the radius of the rotating substrate; And a control system for partially and independently activating the opening of the film thickness compensating member in response to a change in light intensity measured by the light intensity measuring means when each of the monitoring monochromatic light fluxes of one or more wavelengths passes through the monitoring point. Include.
[100] With this apparatus, the light intensity depending on the increase in the film thickness of the most superficial layer of the dielectric multilayer film formed on the substrate is measured by the light intensity measuring means, and the opening of the film thickness correction member is opened and closed in accordance with the light intensity. As a result, the increase in the film thickness of the dielectric multilayer film can be corrected. That is, the film thickness of the outermost layer film of the dielectric multilayer film can be controlled with high accuracy. In this process, since monochromatic light of one or more wavelengths is used as the monitoring light flux, a dielectric multilayer film can be produced by controlling the film thickness by using a direct monitoring method for various monitoring wavelengths.
[101] A split shutter is used as a control system for partially and independently opening and closing the opening of the film thickness compensating member, which is an arcuate region formed along the circumference of the concentric circle drawn by the trajectory of each monitoring point when the rotating substrate rotates. Will be opened and closed independently.
[102] Thus, film formation can be stopped under the same conditions to obtain the same quality dielectric multilayer film of the same arc shape for all monochromatic light fluxes of different wavelengths passing through the monitoring point. Therefore, it is possible to produce a large amount of various high quality dielectric multilayer films obtained from the arcuate surveillance region.
[103] In addition, if the monitoring monochromatic light flux including one or more wavelengths passes through each of the plurality of monitoring points during the formation of the dielectric multilayer film on the rotating substrate, and the reverse transmittance is defined as the inverse of the transmittance, the control system of the dielectric multilayer film manufacturing apparatus is light. The change in the intensity of light measured by the intensity measuring means is first measured as the change in transmittance.
[104] Based on the interference theory described above, the reverse transmittance is periodically distributed at intervals of the optical film thickness corresponding to 1/4 of the monochromatic light wavelength, and inversely obtained by the development of Equation 9 above the maximum and minimum of the reverse transmittance. The function of transmittance can be approached as a quadratic function (the function depends on the variable θ in the sin ² θ term). Therefore, as the prediction time for the most superficial layer film to reach the optical film thickness at the maximum or minimum, the film growth time at the maximum or minimum in the quadratic regression function can be used. Film formation in the surface layer film ends at the prediction time. In this process, since peak control is performed based on quadratic regression with high correlation, the accuracy of control for reaching the optical film thickness corresponding to 1/4 of the monochromatic light wavelength is further improved.
[105] In this case, the optical film thickness of the surface layer film can be calculated based on the inverse transmittance function obtained by the development of Equation 9 above. Therefore, the film thickness can be controlled to the desired optical film thickness by detecting the prescribed optical film thickness at which the outermost surface layer film reaches. In other words, the optical film thickness to be controlled is not limited to the thickness corresponding to 1/4 of the monochromatic light wavelength, and any optical film thickness can be controlled.
[106] In the above two dielectric multilayer film fabrication apparatuses, sputtering targets of two or more different materials provided to select any target are used as the film forming material source. Therefore, a desired target material can be selected as a material for each constituent layer in the dielectric multilayer film, whereby the multilayer film production is easily improved.
[107] Using Ta and Si metals as different materials for sputtering targets, tantalum compound films such as Ta ₂ O ₅ films (which are common high refractive index layers in optical thin film products including BPF), and SiO ₂ films (in optical thin film products) Silicon compound films), such as conventional low refractive index layers).
[108] When the reaction source releases the reactive neutral spinning gas, an increase in the substrate temperature is suppressed if the compound film is formed in the surface layer film. As a result, the deterioration of the accuracy of the control of the optical film thickness does not occur.
[109] In addition, the dielectric multilayer film produced using the optical film thickness control apparatus or the dielectric multilayer film production apparatus described above has an optical film thickness that is precisely controlled, and thus can be suitably used for an optical thin film.
[110] Fig. 3 schematically shows an optical film thickness control apparatus for executing the optical film thickness control method according to the present invention. The optical film thickness controller is made of a tunable laser light source 12, an 8-branch optical coupler 13, an 8-throw fiber collimator 14, a sputtering film forming apparatus 15, InGaAs An eight-throw photodiode 16, an eight-channel A / D converter 17, a CPU 18 for data processing and a linear motor driver 19.
[111] The tunable laser light source 12 is connected to the optical coupler 13 via a single mode optical fiber cable 20, and the optical coupler 13 is connected to the fiber collimator 14 via a single mode optical fiber cable 21. do. The light from the laser light source 12 is separated into eight light beams by the optical coupler 13. Then, the eight light beams are made parallel to each other by the fiber collimator 14, and then to the photodiode 16 through the transparent window 22 and the rotating substrate 23 of the sputtering film forming apparatus 15. To pass. The CPU 18 for data processing and the linear motor driver 19 are connected to each other via an output / input interface 31 such as RS232C.
[112] The sputtering film forming apparatus 15 has an exhaust port 25 coupled to a vacuum pump (not shown in the figure). In this sputtering film forming apparatus, the rotatable substrate 23 supported by the rotating shaft 27 driven by the rotation driving mechanism 26 and the target 28 mounted on the sputtering cathode (not shown in the drawing) are mutually It is arranged to avoid. A movable shutter 29 movable radially of the substrate 23 is provided between the rotary substrate 23 and the target 28. The movable shutter 29 sandwiched between the substrate 23 and the target 28 can stop the film formation on the substrate 23. The movement of the movable shutter 29 is controlled externally by the linear motor 30 in accordance with the instruction from the linear motor driver 19.
[113] In performing the film thickness control according to the present invention by using the film thickness control device, the vacuum pump (not shown in the drawing) coupled to the exhaust port 25 is first operated so that the sputtering film forming apparatus 15 can be operated. do. Thereafter, the tunable laser light source 12 is operated to irradiate the above-mentioned eight parallel light beams on the rotatable substrate 23. In this state, sputtering film formation by the apparatus 15 is started. Here, this time point is defined as the starting point of the film formation time of the thin film.
[114] Each light beam of the eight parallel light beams passing through the substrate 23 is converted into a voltage signal by the photodiode 16. The voltage signal is converted into a digital hand signal by the A / D converter 17. The digital hand signal is input to the CPU 18 for data processing, where the signal is returned to a quadratic function having a range equivalent to 70 to 90% of the film formation time based on equation (5).
[115] 4 shows a cross transmission curve for eight optical signals detected by the photodiode 16. As can be seen in FIG. 4, parallel light beams applied to the substrate 23 are assigned based on the respective sensing positions by the photodiode 16, ie, the position from outside to inside in the radial direction of the substrate 23. Given a continuous number (1 to 8), the eight parallel light beams peak in order after about 120 seconds from the point where 80% of the film is formed. Here, the time point at which the cross transmission curve peaks is regarded as the time point at which the formed thin film has a desired optical film thickness.
[116] FIG. 5 is a graph showing the relationship between the sensing point and the expected peak time of parallel light beams 1 to 8 if the time is zero point when the light beam 1 of FIG. 4 first peaks. The solid line of this graph is derived from the regression on the cubic function of the correlation between parallel light beams 1 to 8 (sense position numbers) and their respective expected peak times (peak positions). This regression function is represented as follows:
[117] y =-0.0227x ³ + 0.4204x ² + 1.8345x-2.1685
[118] The derivative of Equation 10 gives the following Equation 11.
[119] y = 0.681x ² + 0.8408x + 1.8345
[120] Equation (11) is used as a function of the speed of the motor driver. Based on this function, the movable shutter 29 shown in FIG. 3 is moved inward in the radial direction of the substrate 23 to gradually stop film formation on the film forming region of the substrate 23.
[121] The optical film thickness of the thin film on the substrate 23 can be reliably controlled so that the film thickness is uniform.
[122] 6A shows a schematic cross-sectional view of a dielectric multilayer film production apparatus according to a first aspect of the present invention. Referring to Fig. 6, in the vacuum chamber 61, the sputtering target unit 62, which is a film forming source, and the ion gun unit 63, which is a reaction source, are arranged side by side to face the rotatable substrate 64. The light emitter 65 is disposed outside the chamber 61 on the rotatable substrate 64. Eight parallel monochromatic light fluxes from the eight-channel light emitter 65 pass through the upper photoguide window 66, the rotatable substrate 64, and the lower photoguide window 67 outside the chamber 61. Received by an 8-channel optical receiver 68 located at.
[123] The eight monochromatic light fluxes received by the optical receiver 68 are transmitted to the computer 72 and the 8-channel preamplifier 69, 8-channel A / D converter via the electrical signal lines shown by dashed lines in the figure. 70 and a digital signal processor (DSP) 71. The computer 72 calculates the time to reach the desired film thickness and controls the film thickness by indicating that the film formation is terminated based on the calculated estimated time, wherein the estimated time calculated is regarded as the end time point during the film formation. do.
[124] The sputtering target unit 62 has a Ta target 74 and a Si target 75, which can be reversed to the vertical position by the rotation mechanism 73. The targets 74 and 75 are provided with protective covers 74a and 75a, respectively, and the sputtering gas pipe 76 penetrates into a space surrounded by the respective protective covers 74a and 75a. One target of the targets 74 and 75 positioned on the other target faces the rotatable substrate 64 through the fixed opening 77, which is a film deposition rate control member. The ion gun unit 63 is composed of an ECR ion gun 79 through which the reaction gas pipe 78 passes.
[125] The rotatable substrate 64 is rotated by the drive motor 80, and a movable shutter 81, which is a film thickness correction member, is provided between the rotatable substrate 64 and the sputtering target unit 62.
[126] The arrangement between the rotatable substrate 64 and the sputtering target unit 62 will be described in detail. As shown in Fig. 6B, on the substrate 64 there are passing points (monitoring points; 82 to 89) of eight monitoring monochromatic light fluxes along the radius of the substrate 64. Here, the monitoring light flux passing through the monitoring point is arranged such that its wavelength becomes longer from the monitoring point 82 to the monitoring point 89.
[127] 6C is a plan view of an apparatus 61 including this substrate 64. In this figure, the sputtering targets 74 and 75 (not shown in the figure) are disposed on the floor, the flat plate 77a with the fixed opening 77 formed therein is disposed on the sputtering target, and the movable shutter 81 is the flat plate. It is disposed above 77a, and the rotatable substrate 64 is disposed above the movable shutter 81. The fixed opening 77 described above is intended to control the film deposition rate of the film formed in the monitoring region of the substrate 64. In this embodiment, the fixed opening 77 is fanned along the arc of the circle of the rotating substrate such that the film deposition rate at the outer edge of the circle of the rotating substrate is faster than the speed at the inner edge of the circle of the substrate. Is formed. By operation of a feed screw (not shown) driven by a drive motor 81a located outside the apparatus, the movable shutter 81 having an arc-shaped tip edge is passed through the monitoring monochromatic light flux. 89, in a straight line along the radius of the circle of the rotating substrate. This operation can stop the film formation in which the movable shutter 81 is executed through the fixed opening 77. The linear motion of the movable shutter 81 is controlled outside of the device according to the instructions from the computer 72 coupled with the optical receiver 68.
[128] When the dielectric multilayer film production apparatus shown in Fig. 6A performs film thickness control, a predetermined pressure state is established in the chamber 61 by the operation of a vacuum pump (not shown in the figure). Thereafter, the manufacturing substrate 64 is rotated by the drive motor 80. Thereafter, the eight monitoring monochromatic light fluxes from the light emitter 65 pass through the optical receiver 68 through the upper light guide window 66, the rotatable substrate 64 and the lower light guide window 67. Here, the eight surveillance monochromatic light beams consist of four sets of two channels of monochromatic light beams, each of which has different surveillance wavelengths and each set of two channels has the same wavelength. The movable shutter 81 is held outside the fixed opening 77 such that the rotatable substrate 64 and the Ta target 74 or the Si target 75 face without interfering with each other. Argon gas is introduced into the vicinity of the target 74 or 75 through the sputtering gas pipe 76, and the predetermined cathode power is supplied to start sputtering film formation. In this process, a mixed gas containing oxygen gas and argon gas is introduced into the ECR ion gun 79 to cause Ta or Si deposited on the substrate 64 by causing the ECR ion gun 79 to release neutral radical oxygen. Oxidation of the made metal species occurs.
[129] An alternating multilayer film consisting of a Ta ₂ O ₅ film having a high refractive index and a SiO ₂ film having a low refractive index is formed on the manufacturing substrate 64 by selectively adopting one of the Ta target 74 and the Si target 75. do. As described above, it is essential to control the optical film thickness of each component layer of the alternating multilayer film with high precision.
[130] Therefore, the time point at which sputtering film formation by the target 74 or 75 is made is defined as the starting point of the film formation time required to increase the film thickness. The eight supervised monochromatic light beams, which are parallel light fluxes of the four supervisory wavelengths described above, each assigned to two light fluxes, are received by the optical receiver 68 after passing through the rotatable substrate 64. Each monochromatic light beam is then converted into a voltage signal by an eight-channel preamplifier 69. The voltage signal is converted into a digital male signal by an 8-channel A / D converter 70. The digital hand signal is input to the DSP 71, where the signal is returned to the quadratic function, and its translation is a time period exceeding 80% of the film formation time based on equation (5).
[131] When referring to the expected time obtained as the time point at which film formation is terminated for the surveillance region for each surveillance wavelength when the desired film thickness is reached, the computer 72 instructs the movable shutter 81 to move. The tip part covers the watch point in the watch area where the film type is terminated. In this way, film formation in the surveillance region is stopped.
[132] According to the present invention, due to the fan-shaped fixed opening 77 which controls the arrangement of the film deposition rate and the monitoring wavelength, the monitoring point on the outer edge of the circle of the rotating substrate peaks earlier. Therefore, the movable shutter 81 whose speed is controlled by the instruction of the computer 72 moves in one direction from the outer edge of the circle of the rotating substrate to the inner edge.
[133] If the film formation is terminated in this way in the surveillance region for all the surveillance wavelengths, the target 75 or 74 of the target unit 62 which was idling in the lower position is lifted to the upper position to form the next surface layer film. Thereafter, the next film formation is performed in the same manner as described above. By repeating the peak control process, lamination is completed independently in each monitoring area.
[134] On the other hand, the optical film thickness that changes over time can be calculated from the initial transmittance, the transmittance obtained when the next peak is achieved, and the transmittance during film formation. In addition, the film deposition rate can be obtained from the differential between the optical film thicknesses or the difference between the optical film thicknesses calculated at regular intervals.
[135] In other words, a modification of equation 9 derived from equation 6 gives the following equation 12.
[136] θ = sin ⁻¹ [√ {(1-T _0-1 / T _θ ) / (1 / T _0-1 / T ₉₀ )}]. (12)
[137] For example, if the monitoring wavelength is 1550 nm and the desired optical film thickness at which film formation is terminated is 580 nm, the phase difference at which film formation is terminated is expressed as follows: θ = 2π ^* (optical film thickness) / (monitoring wavelength) ) = 134.7 degrees. If the calculated speed (optical film unit) is 1.2 nm / second (= 0.2787 degrees / second) and the current optical film thickness is 500 nm (= 116.13 degrees), the remaining time X (seconds) to the end point is given by It is represented by 13.
[138] 134.7 = 116.13 + 0.2787 * X
[139] Thus, the time X is measured as 66.63 seconds. In other words, in addition to peak control, any optical film thickness calculation can provide a termination time point during film formation.
[140] When referring to the expected time obtained as the time point at which film formation is terminated for the surveillance region for each surveillance wavelength when the desired film thickness is reached, the computer 72 instructs the movable shutter 81 to move. The tip part covers the watch point in the watch area where the film type is terminated. In this way, film formation in the surveillance region is stopped.
[141] If the film formation is terminated in this way in the surveillance region for all the surveillance wavelengths, the target 75 or 74 of the target unit 62 which was idling in the lower position is lifted to the upper position to form the next surface layer film. Thereafter, the next film formation is performed in the same manner as described above. By repeating the peak control process, lamination is completed independently in each monitoring area.
[142] 7A is a schematic cross-sectional view of a dielectric multilayer film production apparatus according to a second aspect of the present invention. Referring to FIG. 7, in the vacuum chamber 91, the sputtering target unit 92, which is a film forming source, and the ion gun unit 93, which is a reaction source, are arranged side by side to face the rotatable substrate 94. As shown in FIG. The light emitter 95 is disposed outside the chamber 91 on the rotatable substrate 94. Eight parallel monochromatic light fluxes from the eight-channel light emitter 95 pass through the upper photoguide window 96, the rotatable substrate 94, and the lower photoguide window 97 outside the chamber 91. Received by an 8-channel optical receiver 98 located at.
[143] The eight monochromatic light fluxes received by the optical receiver 98 are transmitted to the computer 102 and to the 8-channel preamplifier 99, 8-channel A / D converter via the electrical signal lines shown in dashed lines in the figures. 100 and a digital signal processor (DSP) 101. The computer 102 calculates the time to reach the desired film thickness and controls the film thickness by indicating that the film formation is terminated based on the calculated estimated time, wherein the estimated time calculated is regarded as the end time point during the film formation. do.
[144] The sputtering target unit 92 has a Ta target 104 and a Si target 105, which can be reversed to the vertical position by the rotation mechanism 103. The targets 104 and 105 are provided with protective covers 104a and 105a, respectively, and the sputtering gas pipe 106 penetrates into a space surrounded by the respective protective covers 104a and 105a. One of the targets 104, 105 located on the other target faces the rotatable substrate 94 through the fixed opening 107. The ion gun unit 93 is composed of an ECR ion gun 109 through which the reaction gas pipe 108 passes.
[145] The rotatable substrate 94 is rotated by the drive motor 110, and the variable apertures 111a and 111b, which are film deposition rate control members, and the split shutters 112 to 115, which are film thickness correction members, are rotatable substrate 94. And the sputtering target unit 92 are provided.
[146] The arrangement between the rotatable substrate 94 and the sputtering target unit 92 will be described in detail. As shown in FIG. 7B, the split shutters 112, 113, 114, and 115 provided in the vicinity of the substrate 94 are independently operated by each of the drive shafts 112a, 113a, 114a, and 115a, and on the substrate 94. It is shaped to open or close an arc-shaped opening region formed along the circumference of the concentric circle caused by the trace of each passing point (monitoring point; 116a to 116h) of the eight monitoring monochromatic light fluxes.
[147] 7C is a top view of an apparatus 91 that includes this substrate 94 and split shutters 112-115. In this figure, the sputtering targets 104 and 105 (not shown in the figure) are disposed on the bottom, the flat plate 107a in which the fixed openings 107 are formed is disposed on the sputtering target, and the variable openings 111a and 111b are It is disposed on the flat plate, the split shutters 112 to 115 are disposed on the flat plate, and the rotatable substrate 94 is disposed on the split shutter. The fixed opening 107 described above controls the deposition material distribution to provide a wide range of optical properties. This opening may be a variable opening. The variable openings 111a and 111b allow the film deposition rate to be reduced in order to control the film thickness with high precision when the film formation is almost finished. The variable apertures replace the sputtering targets 104 and 105 because reducing the film deposition rate by adjusting the output of the sputtering target does not provide a direct effect, but takes time and lowers productivity. In other words, the film formation is initially performed at a high film deposition rate, and when the film formation is almost finished, the film thickness is precisely controlled by reducing the opening of the variable openings 111a and 111b to reduce the film deposition rate. Split shutters 112, 113, 114, and 115 are independently pulled or pushed out by drive shafts 112a, 113a, 114a, and 115a, respectively, to pass through each pass of the monitoring monochromatic light flux on substrate 94 (drawings). Not shown in Fig. 116a to 116h, the film formation is stopped in the opening area by opening or closing the arc-shaped opening area formed along the circumference of the concentric circle. The opening degree of the variable openings 111a and 111b and the opening / closing of the split shutter are controlled outside of the apparatus according to the instructions from the computer 102 coupled with the optical receiver 98.
[148] When the dielectric multilayer film production apparatus shown in Fig. 7A performs film thickness control, a predetermined pressure state is established in the chamber 91 by the operation of a vacuum pump (not shown in the figure). Thereafter, the manufacturing substrate 94 is rotated by the drive motor 110. Thereafter, the eight monitoring monochromatic light fluxes from the light emitter 95 pass through the light receiver 98 through the upper light guide window 96, the rotatable substrate 94 and the lower light guide window 97. Here, the eight surveillance monochromatic light beams consist of four sets of two channels of monochromatic light beams, each of which has different surveillance wavelengths and each set of two channels has the same wavelength. Predetermined openings of the variable openings 111a and 111b are maintained, and the split shutters 112 to 115 are such that the rotatable substrate 94 and the Ta target 104 or the Si target 105 face each other without disturbing each other. Fully open. Argon gas is introduced into the vicinity of the target 104 or 105 through the sputtering gas pipe 106, and the predetermined cathode power is supplied to start sputtering film formation. In this process, a mixed gas containing oxygen gas and argon gas is introduced from the reactive gas pipe 108 into the ECR ion gun 109 so that the ECR ion gun 109 releases neutral radical oxygen, thereby allowing the substrate 94 to be discharged. Oxidation of the metal species consisting of Ta or Si deposited on the substrate) takes place.
[149] An alternating multilayer film consisting of a Ta ₂ O ₅ film having a high refractive index and a SiO ₂ film having a low refractive index is formed on the manufacturing substrate 94 by selectively adopting one of the Ta target 104 and the Si target 105. do. As described above, it is essential to control the optical film thickness of each component layer of the alternating multilayer film with high precision.
[150] Therefore, the time point at which sputtering film formation by the target 104 or 105 takes place is defined as the starting point of the film formation time required to increase the film thickness. The eight supervised monochromatic light beams, which are parallel light fluxes of the four supervisory wavelengths described above, each assigned to two light fluxes, are received by the optical receiver 98 after passing through the rotatable substrate 94. Each monochromatic light beam is then converted into a voltage signal by an eight-channel preamplifier 99. The voltage signal is converted into a digital male signal by the 8-channel A / D converter 100. The digital hand signal is input to the DSP 101, where the signal is returned to the quadratic function, and its translation is the film forming time starting from the time point when the variable aperture is operated based on equation (5).
[151] When referring to the film formation time corresponding to the maximum or minimum of the secondary regression function as the estimated time when the desired film thickness is reached, the computer 102 instructs the split shutters 112 to 115 to be closed, thereby forming an arc shape. Stop film formation in the surveillance zone.
[152] If the film formation is terminated in this manner in the surveillance region for all the surveillance wavelengths, the target 105 or 104 of the target unit 92 which was idling in the lower position is lifted to the upper position to form the next surface layer film. Thereafter, the next film formation is performed in the same manner as described above. By repeating this process, lamination is completed independently in each monitoring area.
[153] EXAMPLE
[154] In Examples 1 to 4, the precision of the control of the optical film thickness of the optical thin film obtained by using the optical film thickness control device implementing the control method according to the invention shown in FIG. 3 will be discussed.
[155] Example 1
[156] In the film thickness control apparatus shown in FIG. 3, one unbranched incident light beam (wavelength lambda: 1552 nm) was emitted onto the substrate, and the movement of the movable shutter 29 was terminated. In this state, a single layer film of Ta ₂ O ₅ was formed by sputtering on the substrate 23. When the Ta ₂ O ₅ film was a high refractive index layer and the state in which the optical film thickness of the Ta ₂ O ₅ film was λ / 4 was indicated by the letter “H”, the H single layer film and the HH single layer film were formed on a glass substrate. In this configuration, the film growth time was expected when the measured transmittance reached the bottom (minimum value in the secondary regression function) when forming the H monolayer film, and when the HH monolayer film was formed, the measured transmittance was peaked (2 The film growth time is expected when the maximum value in the next regression function is reached.
[157] Here, the above mentioned bottoms and peaks are related to the change in the measured transmittance. Particular attention should be paid to the fact that the bottom and peaks should be treated upside down if the mutual transmission is calculated based on the transmission. In order to avoid any confusion, consistent consideration should be given to the bottom and peaks in this embodiment related to the transmittance. This fact is still valid in the following examples.
[158] The deposition rate of Ta ₂ O ₅ is 0.17 nm / sec, and the time when the optical film thickness of the Ta ₂ O ₅ film reaches 80% of λ / 4 with respect to the actual peak or bottom is about 2 seconds from the time formed. If the measured data group obtained in the period of is used, the data group was input to the CPU 18 for data processing and returned to the quadratic function of the mutual transmittance based on equation (5).
[159] Then, the measured value of the film growth time at the peak or the bottom measured after the peak or the bottom was investigated by comparing with the expected value of the film growth time at the peak or the bottom derived from the second regression function. The plotting of the mean value obtained by ten investigations from the above mentioned measurements is regarded as the mean error, and the mean error and the standard deviation are shown in Table 1 below.
[160] In this example, this regression curve was performed with a group of measured data obtained up to 2 seconds before the actual peak or bottom. However, it was confirmed that the measured data group obtained up to 30 seconds before the actual peak or bottom gave the same result.
[161] Comparative Example 1
[162] The film growth time of the H monolayer film at the bottom and the film growth time of the HH monolayer film at the peak were expected in the same manner as in Example 1 except that the regression function was a quadratic function of the transmittance. The mean error and standard deviation obtained in this example are shown in Table 1 below.
[163] RegressionH: Regression at the bottomHH: Regression at Peak Example 1Square transmittanceMean error standard deviation2.4nm3.5nm2.6nm0.1nm Comparative Example 1Square transmittanceMean Error Standard Deviation1.8nm3.1nm4.2nm2.5nm
[164] As can be seen from Table 1, Comparative Example 1 provided a more accurate value than in Example 1 only when the film formation time of the H monolayer film at the bottom was expected. However, in all other cases, Example 1, where the regression function is a function of mutual transmission, provided much higher accuracy than in Comparative Example 1.
[165] Example 2
[166] Various multilayer films were formed on the glass substrate BK7 using the same optical film thickness control device as in Example 1 shown in FIG. 3 except that the sputtering device was replaced with the reactive type sputtering device. Each of the multilayer films consisted of alternating layers of a Ta ₂ O ₅ film, which is a high refractive index layer (H), and a SiO ₂ film, which is a low refractive index layer (L). Was expected. The multilayer film used was as follows. Letters (P) and (B) described after the alternating layer indicate the time when the estimated time reaches the peak and the time when the estimated time reaches the bottom, respectively.
[167] H (B), HH (P), HL (P), HLL (B), HLH (B), HLHH (P), HLHL (P), HLHLL (B), HLHLH (B), HLHLHH (P), HLHLHL (P), HLHLHLL (P), HLHLHLH (B), HLHLHLHH (P)
[168] In this embodiment, the period from the time at which the deposition rate of Ta ₂ O ₅ is 0.17 nm / sec and the optical film thickness of the Ta ₂ O ₅ film reaches 85% of λ / 4 to advance about 2 seconds is formed. It is assumed that the measured data group obtained in is used for the actual peak or bottom. This data group was input to the CPU 18 for data processing and returned to the quadratic function of the mutual transmittance based on the equation (5).
[169] &Quot; Example 2 " shown in Fig. 8 shows a correlation between the repetition error (average error in Fig. 8) of the layer arrangement of the multilayer film plotted on the horizontal axis and the multilayer arrangement plotted on the vertical axis.
[170] Comparative Example 2
[171] The film growth time of each multilayer film at the peak or bottom was expected in the same manner as in Example 2 except that the regression function was a quadratic function of transmittance. The data used were obtained by ten tests. "Comparative Example 2" shown in FIG. 8 shows the correlation between the layer arrangement of the multilayer film plotted on the horizontal axis and the regression error of the layer arrangement of the multilayer film plotted on the vertical axis.
[172] The comparison between Example 2 and Comparative Example 2 shows the following facts. In Comparative Example 2, in other words, if the regression function is a quadratic function of the transmittance, the plotting from the measured value of the film growth time at the peak or the bottom (the value lying on the line of the mean error of 0 seconds) results in fewer layers. It is small for a multilayer film composed of However, for a multilayer film composed of a larger number of layers, the error in the expected value of the film growth time at the peak that follows the increase in transmittance tends to be large.
[173] In Example 2, in other words, if the regression function is a quadratic function of mutual transmittance, high precision is stably maintained for each multilayer film.
[174] Example 3
[175] Instead of the various multilayer films of Example 2, a single layer film composed of Ta ₂ O ₅ films was formed using the reactive type sputtering apparatus of Example 2, and the film growth time when reaching the peak or bottom was measured in the optical film thickness control method. Was expected.
[176] In this example, the measured data group obtained at and after the time point formed by the optical film thickness of the Ta ₂ O ₅ film reaching a predetermined percentage range (70 to 90%) of λ / 4 was used. This data group was input to the CPU 18 for data processing and returned to the quadratic function of the mutual transmittance based on Equation 5, and this quadratic regression function was used to predict.
[177] In Fig. 9, a regression error is shown on the left vertical axis, and a regression starting point (a specific length of 70% to 90% of λ / 4) is shown on the horizontal axis, and is designated as "Example 3-1E" in Fig. 9. The graph shows the characteristic caused when the prediction at the bottom was performed, and the graph named "Example 3-2E" shows the characteristic caused when the prediction at the peak was performed.
[178] 9 is a composite graph in which standard deviation is written on the right vertical axis. In this figure, the standard deviation in the prediction time in "Example 3-1E" is named "Example 3-1σ", and the standard deviation in the prediction time in "Example 3-2E" is "Example 3-2σ". Is named.
[179] Comparative Example 3
[180] The film growth time was predicted in the same manner as in Example 3 except that a second regression transmittance function was used at the time of regression. In Fig. 9, the graph named "Comparative Example 3-1E" shows the characteristic when the prediction is performed at the bottom, and the graph named "Comparative Example 3-2E" shows the characteristic when the prediction is performed at the peak. .
[181] In Fig. 9, the standard deviation in the prediction time in Comparative Example 3-1E is named "Comparative Example 3-1σ", and the standard deviation in the prediction time in Comparative Example 3-2E is "Comparative Example 3-2σ". Is named.
[182] Comparing Example 3 with Comparative Example 3, in both cases, when the regression start point approaches the peak or bottom (the regression start point approaches 100%), the accuracy is improved even though the standard deviation is larger and the variance increases. It can be seen that higher. In particular, sufficient accuracy is not provided in the prediction at the peak of Comparative Example 3 (Comparative Example 3-2E).
[183] When a second regression curve of reverse transmission was used in Example 3, it was proved that the regression is preferably initiated at one point in the range of 70% to 90% of λ / 4.
[184] Example 4
[185] A bandpass filter (BPF) was prepared in accordance with the film thickness control method performed by the optical film thickness control apparatus shown in FIG. The bandpass filter was a 7-cavity bandpass filter with alternating 155 layers of Ta ₂ O ₅ (H) film and SiO ₂ (L). The bandpass filter is arranged as follows.
[186] Air | ARC | HLHLHLHL2HLHLHLHLHL
[187] HLHLHLHL0.39H0.2065L (A) 0.39H (B) L2HL0.39H0.2065L (A) 0.39H (B) LHL
[188] HLHLHL
[189] HLHLHLHLHL2HLHLHLHLHLHL
[190] HLHLHLHLHL2HLHLHLHLHLHL
[191] HLHLHLHLHL2HLHLHLHLHLHL
[192] HLHLHLHL0.39H0.2065L (A) 0.39H (B) L2HL0.39H0.2065L (A) 0.39H (B) LHL
[193] HLHLHL
[194] HLHLHLHL2HLHLHLHLH ｜ Glass
[195] In this arrangement, the index "B" imparted to the Ta ₂ O ₅ film is not dependent on the quadratic function regression by peak or bottom control, but on the temporal derivative of the optical film thickness obtained by conversion of the reverse transmission. The film formation was terminated by predicting the film formation end point based on the accumulation rate by any film thickness control method.
[196] In this arrangement, the index "A" imparted to the SiO ₂ film indicates a preset sputtering rate, and the film thickness of this film was controlled based on the accumulation time.
[197] The film thickness of the band pass filter thus obtained was controlled under the condition that a monitoring wavelength of 1552 nm was used, a glass disk having a diameter of 300 mm and an antireflective coating (ARC) on its rear surface was used, and the transmitted light measurement The sensors (the sensors in the photodiode 16 in FIG. 3) are arranged in eight places at regular intervals of 10 mm from a position 10 mm away from the outer periphery of the disk.
[198] The band pass filter has the spectrum shown in Fig. 10, and it has been confirmed that this band pass filter is a dielectric film having satisfactory characteristics over the entire monitoring interval.
[199] Now, in Examples 5 to 7, the accuracy of the optical film thickness control of the optical thin film product provided by the dielectric multilayer film production apparatus performing the control method according to the invention shown in FIG. 6 will be described.
[200] Example 5
[201] An intermediate band pass filter was prepared by the dielectric multilayer film production apparatus shown in Fig. 6, which was an accumulation of alternating layers of a Ta ₂ O ₅ film, a high refractive index layer, and a SiO ₂ film, a low refractive index layer. And the optical film thickness of all the constituent layers is an integer multiple of λ / 4 (λ: supervisory wavelength). The monitoring wavelengths used were 1552.52 nm, 1554.12 nm, 1555.72 nm, and 1557.32 nm. The optical thin films were arranged as follows.
[202] Glass Product Substrate with Anti-Reflective Coating (BK7) ｜ (HL) ³ L (HL) ⁶ L (HL) ⁶ L (HL) ³ L ｜ Air
[203] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and 1.5 for the product substrate BK7.
[204] Referring to FIG. 6B, the monitoring point 82 associated with the monitoring monochromatic light channel 1 was set at a position 5 mm inward from the outer periphery of the product substrate 64 having a diameter of 300 mm. The monitoring points 83 to 89 associated with the channels 2 to 8 were respectively set at positions having a constant distance of 10 mm from the monitoring point 82 in the direction toward the center of the rotating substrate source.
[205] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 65 in FIG. 6, channels 1 and 2 were assigned to the monochromatic light flux having a monitoring wavelength of 1552.52 nm, with channels 3 and 4 being Assigned to a monochromatic light flux with a supervisory wavelength of 1554.12 nm, channels 5 and 6 assigned to a monochromatic light flux with a supervisory wavelength of 1555.72 nm, and channels 7 and 8 to monochromatic light fluxes with a supervisory wavelength of 1557.32 nm. It became. The transmittance was calculated by the digital signal processor 71 with respect to the light flux received by the photoreceptor 68. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[206] 11 shows the characteristic distribution in the product substrate 64 obtained by repeatedly performing the above-described process. As shown in Fig. 11, each annular band region 90 to 93 having a width of about 10 mm has uniform optical characteristics.
[207] Fig. 12 shows a graph showing the motion of the movable shutter 81 in response to the indication of the end of film formation, where the indication is obtained by peak control in the third layer, which is a low refractive index layer. As can be seen from the graph, the movable shutter 81 is controlled to move at a variable speed in one direction from the outer circumferential portion of the rotating substrate circle to the inner circumferential portion.
[208] FIG. 13 shows spectral transmittance characteristics for the surveillance region in the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[209] Example 6
[210] An intermediate band pass filter was completed by the dielectric multilayer film fabrication apparatus shown in FIG. 6, which accumulated accumulation of alternating layers of a Ta ₂ O ₅ film as a high refractive index layer and a SiO ₂ film as a low refractive index layer. Sieves, and the optical film thicknesses of all the constituent layers are integer multiples of lambda / 4 (λ: supervisory wavelength). Monitoring wavelengths of 1552.52 nm, 1553.32 nm, 1554.12 nm, and 1554.92 nm were used. The optical thin films were arranged as follows.
[211] Of glass substrate having an antireflective coating ^{(BK7) | (HL) 8} L (HL) 16 L (HL) 16 L (HL) 8 | Air
[212] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and to 1.5 for the product substrate BK7.
[213] Referring to FIG. 6B, the monitoring point 82 associated with the monitoring monochromatic light channel 1 was set at a position 5 mm inward from the outer periphery of the product substrate having a diameter of 300 mm. The monitoring points 83 to 89 associated with the channels 2 to 8 were set at positions having a constant distance of 10 mm from the monitoring point 82 in the direction toward the center of the rotating substrate source.
[214] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 65 in FIG. 6, channels 1 and 2 were assigned to the monochromatic light flux having a monitoring wavelength of 1552.52 nm, with channels 3 and 4 being Assigned to monochromatic light fluxes with 1553.32 nm supervisory wavelength, channels 5 and 6 assigned to monochromatic light fluxes with 1554.12 nm supervisory wavelength and channels 7 and 8 to monochromatic light fluxes with 1554.92 nm supervisory wavelength It became. The transmittance was calculated by the digital signal processor 71 with respect to the light flux received by the photoreceptor 68. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[215] 14 shows the spectral transmittance characteristics for the surveillance region on the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[216] Example 7
[217] An anti-reflection film was prepared by the dielectric multilayer film production apparatus shown in Fig. 6, which had an accumulation of alternating layers of a Ta ₂ O ₅ film, which is a high refractive index layer, and a SiO ₂ film, which was a low refractive index layer. The optical film thicknesses of the first and second layers were not integer multiples of [lambda] / 4 ([lambda]: monitoring wavelength), and the film formation termination point of the final surface film (second film) was predicted by the peak control. Monitoring wavelengths of 1550 nm, 1555 nm, 1560 nm, and 1565 nm were used. The optical thin films were arranged as follows.
[218] Glassware substrate with antireflective coating (BK7) ｜ 0.35H, 1.288L ｜ Air
[219] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and to 1.5 for the product substrate BK7.
[220] Referring to FIG. 6B, the monitoring point 82 associated with the monitoring monochromatic light channel 1 has been set at a position 5 mm inward from the outer periphery of the product substrate 64 having a diameter of 300 mm. The monitoring points 83 to 89 associated with the channels 2 to 8 were respectively set at positions having a constant distance of 10 mm from the monitoring point 82 in the direction toward the center of the rotating substrate source.
[221] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 65 in FIG. 6, channels 1 and 2 are assigned to the monochromatic light flux having a monitoring wavelength of 1550 nm, and channels 3 and 4 Assigned to a monochromatic light flux with a surveillance wavelength of 1555 nm, channels 5 and 6 assigned to a monochromatic optical flux with a surveillance wavelength of 1560 nm, and channels 7 and 8 to a monochromatic optical flux with a surveillance wavelength of 1565 nm. It became. The transmittance was calculated by the digital signal processor 71 with respect to the light flux received by the photoreceptor 68. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[222] 15 shows the spectral transmittance characteristics for the surveillance region in the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[223] In Examples 8 to 10 to be described later, the accuracy of the control of the optical film thickness of the optical thin film product provided by the dielectric multilayer film production apparatus performing the control method according to the invention shown in FIG. 7 will be described.
[224] Example 8
[225] An intermediate band pass filter was prepared by the dielectric multilayer film production apparatus shown in Fig. 6, which was an accumulation of alternating layers of a Ta ₂ O ₅ film, a high refractive index layer, and a SiO ₂ film, a low refractive index layer. And the optical film thickness of all the constituent layers is an integer multiple of λ / 4 (λ: supervisory wavelength). The monitoring wavelengths used were 1552.52 nm, 1554.12 nm, 1555.72 nm, and 1557.32 nm. The optical thin films were arranged as follows.
[226] Glass Product Substrate with Anti-Reflective Coating (BK7) ｜ (HL) ³ L (HL) ⁶ L (HL) ⁶ L (HL) ³ L ｜ Air
[227] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and 1.5 for the product substrate BK7.
[228] Referring to FIG. 7B, the monitoring point 116a associated with the monitoring monochromatic light channel 1 was set at a position 5 mm inward from the outer periphery of the product substrate 94 having a diameter of 300 mm. The monitoring points 116b to 116h associated with the channels 2 to 8 were respectively set at positions having a constant distance of 10 mm from the monitoring point 82 in the direction toward the center of the rotating substrate source.
[229] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 95 in FIG. 7, channels 1 and 2 were assigned to the monochromatic light flux having a monitoring wavelength of 1552.52 nm, with channels 3 and 4 being Assigned to a monochromatic light flux with a supervisory wavelength of 1554.12 nm, channels 5 and 6 assigned to a monochromatic light flux with a supervisory wavelength of 1555.72 nm, and channels 7 and 8 to monochromatic light fluxes with a supervisory wavelength of 1557.32 nm. It became. The transmittance was calculated by the digital signal processor 101 with respect to the light flux received by the photoreceptor 98. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[230] FIG. 16 shows the characteristic distribution in the product substrate 94 obtained by repeatedly performing the above-described process. As shown in Fig. 16, each annular band region 117 to 120 having a width of about 10 mm has uniform optical characteristics.
[231] 17 shows the spectral transmittance characteristics for the surveillance region in the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[232] Example 9
[233] An intermediate band pass filter was provided by the dielectric multilayer film fabrication apparatus shown in Fig. 7, which was formed by accumulating an accumulation of alternating layers of a Ta ₂ O ₅ film as a high refractive index layer and a SiO ₂ film as a low refractive index layer. And the optical film thickness of all the component layers is an integer multiple of (lambda) / 4 ((lambda): monitoring wavelength). Monitoring wavelengths of 1552.52 nm, 1553.32 nm, 1554.12 nm, and 1554.92 nm were used. The optical thin films were arranged as follows.
[234] Of glass substrate having an antireflective coating ^{(BK7) | (HL) 8} L (HL) 16 L (HL) 16 L (HL) 8 | Air
[235] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and to 1.5 for the product substrate BK7.
[236] Referring to FIG. 7B, the monitoring point 116a associated with monitoring monochrome light channel 1 was set at a position 5 mm inward from the outer periphery of the product substrate having a diameter of 300 mm. The monitoring points 116b to 116h associated with the channels 2 to 8 were set at positions having a constant distance of 10 mm from the monitoring point 116a in the direction toward the center of the rotating substrate source, respectively.
[237] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 95 in FIG. 7, channels 1 and 2 were assigned to the monochromatic light flux having a monitoring wavelength of 1552.52 nm, with channels 3 and 4 being Assigned to monochromatic light fluxes with 1553.32 nm supervisory wavelength, channels 5 and 6 assigned to monochromatic light fluxes with 1554.12 nm supervisory wavelength and channels 7 and 8 to monochromatic light fluxes with 1554.92 nm supervisory wavelength It became. The transmittance was calculated by the digital signal processor 101 with respect to the light flux received by the photoreceptor 98. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[238] 18 shows the spectral transmittance characteristics for the surveillance region on the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[239] Example 10
[240] An anti-reflection film was prepared by the dielectric multilayer film production apparatus shown in FIG. 7, which has an accumulation of alternating layers of a Ta ₂ O ₅ film, which is a high refractive index layer, and a SiO ₂ film, which is a low refractive index layer. The optical film thicknesses of the first and second layers were not integer multiples of [lambda] / 4 ([lambda]: supervisory wavelength), and the film formation termination point of the final surface film (second film) was predicted by peak control. Monitoring wavelengths of 1550 nm, 1555 nm, 1560 nm, and 1565 nm were used. The optical thin films were arranged as follows.
[241] Glassware substrate with antireflective coating (BK7) ｜ 0.35H, 1.288L ｜ Air
[242] The design value of the refractive index was set to 1.444 for the low refractive index layer, 2.08 for the high refractive index layer and to 1.5 for the product substrate BK7.
[243] Referring to FIG. 7B, the monitoring point 116a associated with the monitoring monochromatic light channel 1 was set at a position 5 mm inward from the outer periphery of the product substrate 94 having a diameter of 300 mm. The monitoring points 116b to 116h associated with the channels 2 to 8 were respectively set at positions having a constant distance of 10 mm from the monitoring point 116a in the direction toward the center of the rotating substrate source.
[244] Of the eight monochromatic light fluxes emitted from the adjustable laser light source corresponding to the light emitter 95 in FIG. 7, channels 1 and 2 are assigned to the monochromatic light flux having a monitoring wavelength of 1550 nm, and channels 3 and 4 Assigned to a monochromatic light flux with a surveillance wavelength of 1555 nm, channels 5 and 6 assigned to a monochromatic optical flux with a surveillance wavelength of 1560 nm, and channels 7 and 8 to a monochromatic optical flux with a surveillance wavelength of 1565 nm. It became. The transmittance was calculated by the digital signal processor 101 with respect to the light flux received by the photoreceptor 98. Using the calculated transmittance, a quadratic function regression near the peak of the transmittance curve was performed, whereby the prediction time when the peak was reached was calculated. Prediction time was considered as the end of membrane formation.
[245] 19 shows the spectral transmittance characteristics for the surveillance region in the substrate associated with channels 1-8. It can be seen that satisfactory optical products are provided that serve as intermediate band pass filters.
[246] As is apparent from the foregoing, according to the optical film thickness control method according to the present invention, in the case where the last surface film to be formed is to be changed, there is no necessity for the monitoring substrate to be replaced, and to improve the accuracy of the measurement (prior art) An additional arrangement of phase differences (as in) is unnecessary, because peak or floor control is performed. Thus, the process is simplified. In addition, since the reverse transmission is used, the peak or bottom prediction is performed while the secondary regression has a satisfactory correlation, so that the film thickness can be controlled with high accuracy.
[247] Moreover, since the in-situ measurement, ie direct monitoring, of the product thin film can be performed, there is no need to consider the reproducibility of the monitored film.
[248] In the film thickness control apparatus according to the present invention, a plurality of parallel rays are used for monitoring the film thickness. Therefore, the distribution of the film thickness of the last surface layer film can be sensed with high accuracy, thus ensuring high uniformity of the film thickness.
[249] According to the apparatus for producing a dielectric multilayer film according to the present invention, a quadratic function regression is performed near a peak of reverse transmittance or transmittance, and a film growth time corresponding to the highest or lowest value of the resulting regression function reaches the required film thickness. It is used as the prediction time. Therefore, the increase in the optical film thickness can be controlled with high precision. Moreover, a direct monitoring method including various monitoring wavelengths can provide an enlarged monitoring region for perforating a dielectric thin film having satisfactory characteristics. Thus, high quality optical thin film products, which are devices for dense wavelength division multiplexing systems such as narrow bandpass filters, can be produced in large quantities.
[250] In addition, the dielectric multilayer film including the band pass filter manufactured by the above-described optical film thickness control device or dielectric multilayer film production device has satisfactory optical properties and thus high performance.

权利要求:
Claims (16)
[1" claim-type="Currently amended] A method of controlling the optical film thickness during the film formation period of a single layer or multilayer constituting optical thin film made of one or more dielectrics,
Incident monochromatic light is transmitted through the monolayer or multilayer configuration to measure the transmittance of the optical thin film and calculate the inverse of the transmittance as the reverse transmittance,
The measured data group of the two variables is returned to the quadratic function by the list square method, before this measured data group reaches its highest or lowest value,
The two variables are the film formation time and the reverse transmission rate of the last surface layer film accumulated as the film thickness of the last surface layer film increases,
The film growth time at the highest and lowest points of the second regression function is used as an estimate of the film growth time when the optical film thickness is achieved at the highest or lowest point of the reverse transmission, and the highest and lowest of the reverse transmission are interference. An optical film thickness control method, characterized in that it is periodically distributed at each interval of the optical film thickness corresponding to 1/4 of the monochromatic light wavelength based on the theory.
[2" claim-type="Currently amended] The monochromatic light wavelength according to claim 1, wherein the time derivative or time difference of the optical film thickness calculated from the periodically distributed reverse transmittance as the film thickness of the last surface layer film grows is calculated as the film accumulation rate of the last surface layer film. Calculated at each interval of optical film thickness equal to 1/4 of
The film growth time is estimated based on the film accumulation rate when the last surface layer film reaches the target value of the optical film thickness.
[3" claim-type="Currently amended] The optical film thickness control according to claim 1 or 2, wherein during the growth of the optical thin film, the transmittance is measured on the product substrate, and the optical film thickness of the last surface layer film is measured by a direct monitoring method. Way.
[4" claim-type="Currently amended] An optical film thickness control device for predicting the film growth time of the last surface layer film when the desired optical film thickness is reached by the method according to any one of claims 1 to 3,
A film forming apparatus having a rotatable substrate and a film forming source facing each other;
An optoelectronic conversion device for sensing a plurality of monochromatic rays applied to the rotatable substrate at predetermined intervals along a radius of the rotatable substrate,
A radially movable movable shutter of the rotatable substrate is provided between the substrate and the film forming source to block film formation on the substrate,
And the shutter moves in response to a controller indicating the movement of the shutter based on each prediction value of the film growth time predicted by the monochromatic light sensed by the photoelectric converter.
[5" claim-type="Currently amended] An apparatus for producing a dielectric multilayer film, comprising a vacuum chamber having a film forming source and a reaction source, wherein each source is arranged side by side to face a rotatable substrate,
A film accumulation rate control member having an opening along the rotatable substrate source, the opening having a gradient for the film accumulation rate of the dielectric multilayer film formed on the rotatable substrate;
A film thickness correction member for correcting a film thickness of a multilayer film of a dielectric formed on said rotatable substrate;
Photometric means for measuring the intensity of supervised monochromatic light passing through a plurality of surveillance points along a radius of the rotatable substrate;
A control system for arranging monitoring monochromatic light fluxes of one or more wavelengths in order of rising or falling wavelengths of the monochromatic light flux associated with the position of the monitoring point along the radius, so that the light flux passes through each of the monitoring points,
The film accumulation rate control member and the film thickness correction member are provided between the rotatable substrate and the film material source,
And said control system makes it possible to move said film thickness correction means in response to a change in light intensity measured by said light intensity measuring means.
[6" claim-type="Currently amended] 6. The film thickness correction member according to claim 5, wherein the film thickness correction member has a movable shutter that is movable in the radial direction of the rotatable substrate, wherein film formation on the rotatable substrate is performed along the radius by the movement of the movable shutter. Dielectric multilayer film manufacturing apparatus characterized in that the blocking in the rising or falling order.
[7" claim-type="Currently amended] The method of claim 5 or 6, wherein the control system of the dielectric multilayer film production apparatus measures the fluctuation of the light intensity measured by the light intensity measuring means,
During the formation of the dielectric multilayer film on the rotatable substrate, the respective transmission monochromatic fluxes having one or more wavelengths pass through each of the plurality of monitoring points, wherein the variation in the transmittance is calculated inversely as the inverse of the transmittance,
The control system returns the data group of the measured two variables to a quadratic function before the measured data group reaches its highest or lowest value by the List Square method, wherein the two variables are accumulated in the film of the last surface layer film. The film growth time and the reverse transmission required for the increase in thickness,
The control system uses the film growth time coincident at the highest or lowest point in the second regression function as an optical film thickness arrival prediction time of the last surface layer film at the highest or lowest value at the reverse transmission,
And the highest and lowest values of the reverse transmittance are periodically distributed at intervals of an optical film thickness corresponding to one fourth of the monochromatic light wavelength based on interference theory.
[8" claim-type="Currently amended] 8. The method according to any one of claims 5 to 7, wherein as the film thickness of the last surface layer film grows, it is calculated from the inverse transmittance periodically distributed at intervals of the optical film thickness corresponding to 1/4 of the monochromatic light wavelength. The time derivative or time difference of the optical film thickness is calculated as the film accumulation rate of the last surface layer film,
And a film growth time required for the final surface layer film to reach a predetermined optical film thickness is predicted based on the calculated film accumulation rate.
[9" claim-type="Currently amended] An apparatus for manufacturing a dielectric multilayer film, comprising a vacuum chamber having a film forming source and a reaction source, wherein each source is arranged to face a rotatable substrate, the apparatus comprising:
A film accumulation rate control member having an opening for controlling the film accumulation rate of the dielectric multilayer film formed on the rotatable substrate;
A film thickness correction member having an opening for correcting the film thickness of the multilayer film of a dielectric formed on said rotatable substrate;
Photometric means for measuring the intensity of supervised monochromatic light passing through a plurality of surveillance points along a radius of the rotatable substrate;
And a control system for activating the opening of the film thickness compensating member in response to the fluctuation of the brightness measured by the photometric means when each of the monitoring monochrome light flux of at least one wavelength passes through the monitoring point,
And said film accumulation rate control member and said film thickness correction member are provided between said rotatable substrate and said film material supply source.
[10" claim-type="Currently amended] 10. The split opening according to claim 9, wherein the movable opening of the film thickness correction member independently opens and closes an arc-shaped opening region formed along a circumference of a concentric circle drawn by the trajectory of each monitoring point while the rotatable substrate rotates. Dielectric multilayer film manufacturing apparatus characterized by including a shutter.
[11" claim-type="Currently amended] The control system of the dielectric multilayer film manufacturing apparatus according to claim 9 or 10, wherein the control system of the dielectric multilayer film manufacturing apparatus measures the fluctuation of the light intensity measured by the light intensity measuring means,
During the period of formation of the dielectric multilayer film on the rotatable substrate, each of the monitoring monochromatic light fluxes having one or more wavelengths passes through each of the plurality of monitoring points, the variation of the transmittance being computationally defining the inverse of the transmission as the reverse transmission,
The control system returns the data group of the measured two variables to a quadratic function before the measured data group reaches its highest or lowest value by the List Square method, wherein the two variables are accumulated in the film of the last surface layer film. The film growth time and the reverse transmission required for the increase in thickness,
The control system uses the film growth time coincident at the highest or lowest point in the second regression function as an optical film thickness arrival prediction time of the last surface layer film at the highest or lowest value at the reverse transmission,
And the highest and lowest values of the reverse transmittance are periodically distributed at intervals of an optical film thickness corresponding to one fourth of the monochromatic light wavelength based on interference theory.
[12" claim-type="Currently amended] The optical film thickness as set forth in claim 9 or 10, wherein the film thickness of the last surface layer film is calculated from the inverse transmittance periodically distributed at intervals of an optical film thickness corresponding to a quarter of the monochromatic light wavelength as the film thickness of the last surface layer film grows. And the film growth is controlled by detecting whether the last surface layer film has reached a predetermined optical film thickness based on the dielectric multilayer film production apparatus.
[13" claim-type="Currently amended] 13. The method of any one of claims 5-12, wherein the film-forming source has a sputtering target composed of two or more different materials, wherein the sputtering target is provided in a manner in which any of the targets can be selected. An apparatus for producing a dielectric multilayer film.
[14" claim-type="Currently amended] The apparatus of claim 13, wherein different materials of the sputtering target are Ta metal and Si metal.
[15" claim-type="Currently amended] The apparatus according to any one of claims 5 to 14, wherein the reaction source emits reactive neutral radical gas.
[16" claim-type="Currently amended] A dielectric multilayer film prepared by using the optical film thickness control device according to claim 4 or by using the dielectric multilayer film production apparatus according to any one of claims 5 to 15.

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同族专利:

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公开号 | 公开日

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KR100972769B1|2010-07-28|

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US20040008435A1|2004-01-15|

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TW200305710A|2003-11-01|

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CN1478920A|2004-03-03|

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TWI255906B|2006-06-01|

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CN100398694C|2008-07-02|

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US7927472B2|2011-04-19|

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US7247345B2|2007-07-24|

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US20080011229A1|2008-01-17|

引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
2002-03-25|Priority to JP2002083260A

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2002-03-25|Priority to JPJP-P-2002-00083260

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2002-10-31|Priority to JP2002317998A

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2002-10-31|Priority to JPJP-P-2002-00317998

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2002-10-31|Priority to JP2002317999A

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2002-10-31|Priority to JPJP-P-2002-00317999

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2003-03-25|Application filed by 가부시키가이샤 아루박

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2003-10-01|Publication of KR20030077439A

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2010-07-28|Application granted

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2010-07-28|Publication of KR100972769B1

优先权:

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申请号 | 申请日 | 专利标题

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JP2002083260A|JP4034979B2|2002-03-25|2002-03-25|Optical film thickness control method, optical film thickness control apparatus, and dielectric thin film produced using the optical film thickness control method|

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JPJP-P-2002-00083260|2002-03-25|

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JP2002317999A|JP4327440B2|2002-10-31|2002-10-31|Dielectric multilayer film manufacturing equipment|

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JPJP-P-2002-00317999|2002-10-31|

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JP2002317998A|JP4327439B2|2002-10-31|2002-10-31|Dielectric multilayer film manufacturing equipment|

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JPJP-P-2002-00317998|2002-10-31|