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    公开号:NL2013657A
    申请号:NL2013657
    申请日:2014-10-21
    公开日:2015-05-27
    发明作者:Hako Botma
    申请人:Asml Netherlands Bv；
    IPC主号:
    专利说明:

    APPARATUS, LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD
    FIELD
    [0001] The present invention relates to an apparatus, a lithographic apparatus and a device manufacturing method. In particular, the present invention relates to an apparatus for measuring radiation in a lithographic apparatus.
    BACKGROUND
    [0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
    [0003] In order to reduce the size of the features of the circuit pattern, it is necessary to reduce the wavelength of the imaging radiation. To this end, lithographic apparatus using EUV radiation, e.g. having a wavelength in the range of from about 5 nm to 20 nm, are under development. EUV radiation is strongly absorbed by almost all materials, therefore the optical systems and mask must be reflective and the apparatus kept under a low pressure or vacuum.
    SUMMARY
    [0004] EUV radiation can be generated by forming a plasma of a suitable material, such that re-combination of free electrons with positive ions in the plasma results in emission of radiation of the desired wavelength. A plasma can be generated by laser irradiation of fuel or electrical discharge. A collector, e.g. in the form of a parabolic mirror, is used to collect the desired radiation and direct it to an intermediate focus in the entrance to an illumination system.
    [0005] It is desirable that the illumination of the patterning device, otherwise referred to as the irradiation of the patterning device, is controlled and consistent. In particular, the intensity of incident radiation should be uniform across at least the length of an illumination field and the angle of incidence of the radiation should be as desired. The patterning device has a slit through which radiation is directed. The illumination field is sometimes referred to as the slit. In an embodiment, the illumination field is defined by movable blades. The illumination of the patterning device is conventionally described in terms of the intensity distribution of the radiation in a pupil plane (often referred to simply as the pupil) of the illumination system.
    [0006] The distribution of the radiation in the pupil depends on the position of the plasma and the position and orientation of the collector, among other things.
    [0007] To assist in controlling illumination of the patterning device, a known sensing system measures the positions of the plasma and the collector during operation of the lithographic apparatus. Mirrors placed in the illumination system reflect radiation towards a receiving part of the sensor. The mirrors used are small and placed at the edge of the field facet module device. The mirrors are used to reflect different parts of the received radiation to position sensitive devices. In the known sensor, three mirrors are used to produce images of the plasma at the intermediate focus (IF) on three position sensitive devices. Three other mirrors are used to produce images of collector “pinholes” on three further position sensitive devices. If six mirrors are used, each reflecting light to a specific position sensitive device, this allows twelve degrees of freedom to be measured which can be used to determine the relevant degrees of freedom of the plasma and collector. From this, information related to the plasma and the collector can be derived. This information is available for each individual light pulse from the source.
    [0008] Measurements made in known sensors are not robust against collector contamination. The mirrors are limited in size and only sample the radiation at the field facet module device at relatively small positions. Additionally, the positioning of the “pinholes” in the collector can be inaccurate and the “pinholes” in the collector are expensive to make. The “pinholes” are small, bright, i.e. reflective, islands in dark, i.e. non-reflective, regions of the collector so that the radiation reflected to the position sensitive devices includes a small bright spot. Contamination of the collector can alter the apparent position of the “pinhole”.
    [0009] It is desirable to provide an improved sensor for measuring the illumination of the patterning means.
    [0010] According to an aspect of the invention there is provided an apparatus comprising an illumination system arranged to direct radiation from a radiation source to an illumination field on a surface; and a sensing module, the sensing module comprising: a reflector arranged to reflect radiation, the reflector being located adjacent to the illumination field; and a sensing device configured to receive an image of a pupil of the illumination system, reflected from the reflector.
    [0011 ] According to an aspect of the invention there is provided a lithographic apparatus.
    [0012] According to an aspect of the invention, there is provided a device manufacturing method using a lithographic apparatus comprising the steps of: exciting a fuel to form a plasma; collecting radiation omitted by the plasma and directing it into a beam; directing the beam onto an illumination field on a patterning device using an illumination system; directing the beam patterned by the patterning device onto a substrate; reflecting radiation received on a reflector adjacent to an illumination field; and receiving the reflected radiation at a sensing device , wherein the radiation received is an image of a pupil of the illumination system.
    BRIEF DESCRIPTION OF THE DRAWINGS
    [0013] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: [0014] - Figure 1 depicts a lithographic apparatus used in an embodiment of the invention; [0015] - Figure 2 is a more detailed view of the apparatus of Figure 1; [0016] - Figure 3 is a more detailed view of the source collector apparatus of the apparatus of Figures 1 and 2; [0017] - Figure 4 depicts a side view of the lithographic apparatus with a sensing module for use in an embodiment of the present invention; [0018] - - Figure 5 a depicts an example of an image of a pupil of the illumination system in which the pupil is aligned; [0019] - Figure 5b depicts an example of an image of a pupil of the illumination system in which the pupil is not aligned due to a shift of the source in the x-direction; [0020] - Figure 5c depicts an example of an image of a pupil of the illumination system in which the pupil is not aligned due to a shift of the source in the z-direction; [0021 ] - Figure 6 depicts the variation of the pupil adjacent to and at the illumination field in an embodiment of the present invention.
    DETAILED DESCRIPTION
    [0022] Figure 1 schematically depicts an EUV lithographic apparatus 4100 including a source collector apparatus SO. The apparatus comprises: - an illumination system (illuminator) EIL configured to condition a radiation beam EB (e.g. EUV radiation); - a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask or a reticle) MA and connected to a first positioner PM configured to accurately position the patterning device; - a substrate table (e.g. a wafer table) WT constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate; and - a projection system (e.g. a reflective projection system) PS configured to project a pattern imparted to the radiation beam EB by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.
    [0023] The support structure MT holds the patterning device. The support structure MT holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure MT may be a frame or a table, for example, which may be fixed or movable as required. The support stmcture MT may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device”.
    [0024] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.
    [0025] Examples of patterning devices include masks and programmable mirror arrays. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.
    [0026] The lithographic apparatus may be of a type having two or more substrate support structures, such as substrate stages or substrate tables, and/or two or more support structures for patterning devices. In an apparatus with multiple substrate stages, all the substrate stages can be equivalent and interchangeable. In an embodiment, at least one of the multiple substrate stages is particularly adapted for exposure steps and at least one of the multiple substrate stages is particularly adapted for measurement or preparatory steps. In an embodiment of the invention one or more of the multiple substrate stages is replaced by a measurement stage. A measurement stage includes at least a part of one or more sensor systems such as a sensor detector and/or target of the sensor system but does not support a substrate. The measurement stage is position able in the projection beam in place of a substrate stage or a support structure for a patterning device. In such apparatus the additional stages may be used in parallel, or preparatory steps may be carried out on one or more stages while one or more other stages are being used for exposure.
    [0027] In an EUV lithographic apparatus, it is desirable to use a vacuum or low pressure environment since gases can absorb too much radiation. A vacuum environment can therefore be provided to the whole beam path with the aid of a vacuum wall and one or more vacuum pumps.
    [0028] Referring to Figure 1, the EUV illuminator EIL receives an extreme ultraviolet radiation beam from the source collector apparatus SO. Methods to produce EUV radiation include, but are not necessarily limited to, converting a material into a plasma state that has at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV range. In one such method, often termed laser produced plasma ("LPP") the plasma can be produced by irradiating a fuel, such as a droplet, stream or cluster of material having the desired line-emitting element, with a laser beam. The source collector apparatus SO may be part of an EUV radiation system including a laser, not shown in Figure 1, to provide the laser beam exciting the fuel. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector, disposed in the source collector apparatus. The laser and the source collector apparatus may be separate entities, for example when a C02 laser is used to provide the laser beam for fuel excitation.
    [0029] In such cases, the laser is not considered to form part of the lithographic apparatus and the radiation beam is passed from the laser to the source collector apparatus with the aid of a beam delivery system comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the source collector apparatus, for example when the source is a discharge-produced plasma EUV generator, often termed as a DPP source.
    [0030] The EUV illuminator EIL may comprise an adjuster to adjust the angular intensity distribution of the radiation beam EB. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the EUV illuminator EIL may comprise various other components, such as facetted field and pupil mirror devices. The EUV illuminator EIL may be used to condition the radiation beam EB, to have a desired uniformity and intensity distribution in its cross section.
    [0031] The radiation beam EB is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. After being reflected from the patterning device (e.g. mask) MA, the radiation beam EB passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor PS2 (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam EB. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam EB. Patterning device (e.g. mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2. A sensing module (not shown) can be used comprising a reflector located on or adjacent to the patterning device MA. A sensing device of the sensing module is located to receive radiation reflected from the reflector, for example, in the illuminator EIL.
    [0032] The depicted apparatus could be used in at least one of the following modes: [0033] 1. In step mode, the support structure MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.
    [0034] 2. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.
    [0035] 3. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source (e.g. a source collector apparatus) is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.
    [0036] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.
    [0037] A control system (not shown) controls the overall operations of the lithographic apparatus and in particular performs an optimization process described further below. The control system can be embodied as a suitably-programmed general purpose computer comprising a central processing unit and volatile and non-volatile storage.
    [0038] Figure 2 shows the EUV apparatus 4100 in more detail, including the source collector apparatus SO, the EUV illumination system EIL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 4220 of the source collector apparatus SO. An EUV radiation emitting plasma 4210 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor or Sn vapor in which the plasma 4210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The plasma 4210 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, f 0 Pa of' Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.
    [0039] The radiation emitted by the plasma 4210 is passed from a source chamber 421 f into a collector chamber 4212 via an optional gas barrier and/or contaminant trap 4230 (in some cases also referred to as contaminant barrier or foil trap) which is positioned in or behind an opening in source chamber 4211. The contaminant trap 4230 may include a channel structure. Contamination trap 4230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 4230 further indicated herein at least includes a channel structure, as known in the art.
    [0040] The collector chamber 4212 may include a radiation collector CO which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 4251 and a downstream radiation collector side 4252. Radiation that traverses collector CO can be reflected by a grating spectral filter 4240 to be focused in a virtual source point IF. The virtual source point IF is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that the intermediate focus IF is located at or near an opening 4221 in the enclosing structure 4220. The virtual source point IF is an image of the radiation emitting plasma 4210.
    [0041 ] Subsequently the radiation traverses the illumination system EIL, which may include a facetted field mirror device 422 and a facetted pupil mirror device 424 arranged to provide a desired angular distribution of the radiation beam 421, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 421 at the patterning device MA, held by the support structure MT, a patterned beam 426 is formed and the patterned beam 426 is imaged by the projection system PS via reflective elements 428, 430 onto a substrate W held by the substrate stage or substrate table WT.
    [0042] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 4240 may optionally be present, depending upon the type of lithographic apparatus. There may be more mirrors present than those shown in the Figures, for example there may be from 1 to 6 additional reflective elements present in the projection system PS than shown in Figure 2.
    [0043] Collector optic CO, as illustrated in Figure 2, is depicted as a nested collector with grazing incidence reflectors 4253, 4254 and 4255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 4253, 4254 and 4255 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.
    [0044] Alternatively, the source collector apparatus SO may be part of an LPP radiation system as shown in Figure 3. A laser LA is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), creating the highly ionized plasma 4210 with electron temperatures of several 10’s of eV. The energetic radiation generated during de-excitation and recombination of these ions is emitted from the plasma, collected by a near normal incidence collector optic CO and focused onto the opening 4221 in the enclosing structure 4220, also known as the source chamber.
    [0045] A sensing module is used to determine how the radiation is reaching the substrate. Known sensors use small mirrors that reflect only a small percentage of the pupil. Therefore, information in relation to the whole pupil is not detected. Given that the system is very sensitive, it would be beneficial to provide a sensor which can detect a larger proportion of the radiation to provide more information about the radiation which reaches the patterning device.
    [0046] The present invention provides a sensing module for a lithographic apparatus which uses an image of the pupil to determine information relating to the radiation source. This information is available for each individual light pulse from the source. By using components of the pupil, i.e. bright spots, which represent the individual beams of radiation which make up the pupil, the effect of local collector contamination on the sensor is reduced. Ideally, the full pupil is used to minimize the impact of local collector contamination· Furthermore, because pupil information is used rather than the reflection of “pinholes” in the collector, it is not necessary to make markings (i.e. “pinholes”) on the collector.
    Additionally, information can be determined from the bright spots without having to calculate an average of the detected radiation.
    [0047] As described, EUV radiation can be generated by forming a plasma which results in emission of radiation of the desired wavelength. A collector, e.g. in the form of a parabolic mirror, is used to collect the desired radiation and direct it to an intermediate focus IF in the entrance to an illumination system.
    [0048] It is desirable that the illumination of the patterning device MA is controlled and consistent. In particular, the intensity of incident radiation should be uniform across at least the length of the illumination field and the angle of incidence of the radiation should be as desired. The distribution of the radiation in the pupil depends on the position of the plasma 4210 and the position and orientation of the collector CO. Information relating to the source collector apparatus SO, can be detected and used to optimize the illumination.
    [0049] A known sensing system measures the positions of the plasma and the collector during operation of the lithographic apparatus. Mirrors placed in the field facet module device in the illumination system reflect radiation towards a receiving part of the sensor. The mirrors used are small and placed at the edge of the field facet module device. The mirrors are used to reflect different parts of the received radiation to position sensitive devices. The position sensitive devices measure the radiation and determine the relevant degrees of freedom of the plasma and collector. From this, information related to the plasma and the collector can be derived.
    [0050] Measurements made in known sensors are not robust against collector contamination. The mirrors are limited in size and only sample the radiation at the field facet module device at relatively small areas. Additionally, the positioning of the pinholes in the collector can be inaccurate and the “pinholes” in the collector are expensive to make. The “pinholes” are markings made on the collector which can be used to determine alignment of the collector. The markings alter the radiation that is reflected such that the location of the “pinholes” can be detected throughout the lithographic apparatus. The “pinholes” are detected as dark areas with central bright spots.
    [0051] It is desirable to provide an improved sensor for measuring the illumination of the patterning means. The present invention can use the whole pupil to determine information related to the source collector apparatus SO. Therefore, local collector contamination does not affect the detected radiation as much as in known sensors. In known sensors, local contamination may affect the radiation which is later detected. Only small areas are measured which means that any local contamination would have a greater impact on the measurements made from the detected information than in the present invention in which at least a part of the pupil is measured.
    [0052] It is desirable to monitor in real time the position of the plasma and the collector so that the illumination of the patterning means is consistent and as desired. To achieve this, the sensing module is provided with a reflector positioned adjacent to the illumination field at the patterning stage.
    [0053] In the embodiment shown in Figure 4, the radiation is directed from the intermediate focus IF to a facetted field mirror device 422 to a facetted pupil mirror device 424. The radiation is further directed to an angled mirror 460 which alters the direction of the radiation onto the patterning device MA. A support structure can be provided to support the patterning device. Any number of other elements may be included to direct the radiation from the source to the patterning device MA. For example, additional reflective elements may be used. An illumination field is formed in which the intensity of the pupil is approximately at a given maximum across the illumination field, as shown in Figure 6. The illumination field is patterned by the patterning device MA and the image is projected onto substrate W. At the edge of the illumination field, the intensity of the light decreases, as shown in Figure 6. A reflector 480 can be placed adjacent to the illumination field to reflect radiation to a sensing device 470.
    [0054] A sensing module of the present invention can be used to detect the radiation received by the patterning device, as shown in Figure 4. Radiation is reflected from a reflector 480 adjacent to the illumination field on the patterning device MA. The radiation is reflected by the reflector 480 to a sensing device 470. The sensing device 470 can be placed in different locations. Figure 4 shows an embodiment of the present invention in which the receiving portion of the sensing module, i.e. the sensing device 470, is located in the illumination system EIL. The further away the sensing device 270 is from the reflector 480, the larger the sensing device 470 has to be in order to be capable of receiving radiation which could represent the entire pupil. An optimal level would be for the sensing device 470 to be in line with the facetted pupil mirror device 424. Ideally, the sensing device needs to be far away enough that the beams of light produce pinpoints on the sensing device. However, without being too far such that the sensing device 470 needs to be large to be able to detect information relating to the whole pupil. More defined pinpoints of light can be achieved by altering the resolution of the sensing device 470.
    [0055] Radiation outside of the illumination field is used for the sensing module such that the radiation being directed onto the wafer W is not affected and therefore, the efficiency of the apparatus is not reduced.
    [0056] It is possible to measure the full pupil at both the patterning device MA and the wafer W level. The reflector 480 of the present invention is placed at the patterning device MA level. The illumination field does not move, therefore, it is possible to place a stationary reflector 480 at this level which can effectively reflect radiation to the position sensor 470. It is preferable to have the reflector 480 as close as possible to the illumination field without affecting the radiation used to expose the wafer W.
    [0057] The reflected radiation is received by the sensing device which processes the image of the pupil received. An example of an image of the pupil of the illumination system can be seen in Figure 5. The sensing module comprises a processor to process the image received by the sensing device. The processor can be used to determine properties of the image of the pupil as received and/or the “fingerprints”, as they are described below.
    [0058] The properties of the individual bright spots that form the pupil as seen in Figure 5 a are influenced by the alignment of the source relative to the illuminator. The properties of the bright spots of the pupil can be the position of each spot in the pupil (i.e. the X and Y coordinates of each spot) and/or it can be the intensity of the spot. The latter is especially relevant when the source emits a beam which has a radial intensity gradient. Since the sensing module records both position and intensity, both effects can be measured.
    [0059] The change of properties of all spots in the pupil due to a single condition change of the source provides a unique “fingerprint”. For example, a position shift of the source (perpendicular to its optical axis, i.e. in the x-direction) leads to a shift of all of the pupil spots in the direction of the shift. This can thus be seen as a shift of the pupil as shown in Figure 5b.Therefore, when a shift of the pupil is observed, this fingerprint is the result of a source position error. Another example is a shift of the source along its optical axis, i.e. in the z-direction: the corresponding pupil changes such that the size of the fingerprint changes as shown in Figure 5c. Additionally, the overall “fingerprint” itself can be analyzed by breaking it down into a sum of unique “fingerprints”. In this way information related to the source collector apparatus SO can be determined e.g. the variation in the plasma and/or the collector, and furthermore, the apparatus can be adjusted accordingly.
    [0060] The source collector apparatus SO can be controlled until the received pupil matches a target pupil. Actuators at the collector could be used to control the orientation (i.e. tilt) of the collector CO in order to shift the received pupil. The position of the collector CO could be controlled in the optical axis to vary the relative position of the plasma 4210 and collector CO to vary the size of the received pupil. It is also possible to control the position of the plasma 4210 in the optical axis to vary the relative position of the plasma 4210 and collector CO. A compensating change could also be made elsewhere instead of, or in addition to a change at the radiation source, in order to as achieve the desired effect.
    [0061] The information received can also be analyzed to get information of the different facets at each stage. Each bright spot detected can be traced back to the source collector apparatus SO.
    [0062] It comprises a plurality of different beams of radiation i.e. bright spots. If the reflector is flat this will avoid altering the angle of any of the different beams of the pupil. The pinpoints of radiation received by the position device could be adjusted by altering the angled mirror, 460. If the mirror is slightly curved, it is likely that these spots appear as small lines. However, more defined spots would be achieved by using a flatter mirror.
    [0063] The sensing device could be placed in the illumination system EIL such that the reflector 480 reflects the radiation at almost any angle. The only limitation on the angle of reflection is that the radiation must be reflected to the sensing device 470 in some way. It is possible that elements e.g. mirrors, could be used to direct the radiation from the reflector 480 to the sensing device 470.
    [0064] If multiple sensing modules are provided, this could improve the accuracy of the information received. Furthermore, multiple reflectors 480 could be used with one sensing module such that a larger proportion of the pupil is received by a single sensing device 470.
    [0065] The sensing module can comprise a scintillator plate, optionally covered with a thin metal layer to prevent the detection of DUV and/or visible light. The sensing module can also comprise an image sensing device to measure the scintillated light, such as a CCD or CMOS sensor. In particular, the scintillator plate and/or the image sensing device may be part of the sensing device 470 of the sensing module. The image received by the image sensing device 470 can be converted into an electronic signal.
    [0066] In a pre-existing lithographic apparatus, an energy sensor is provided at the edge of the illumination field to determine the intensity of the radiation received. The sensing module of the present invention can additionally be used as an energy sensor by integrating the signal received by the sensing device 470. The sensing device 470 can be calibrated to improve the accuracy of the measurements made.
    [0067] The information determined and the “fingerprints” obtained can be used to determine information related to the source collector apparatus SO, as described. This information as measured could also be used to assess the efficiency and/or check the radiation that is being directed through the apparatus. Furthermore, the pupil could be altered deliberately during exposure such that the variation of the pupil could be measured to provide feedback on the system.
    [0068] Figure 6 shows a cross-section of the illumination field intensity and the corresponding filling of the pupil at several field points. As can be seen, in the left ramp the intensity and the pupil filling start at 0% intensity and thus a 0% filled pupil. Going to the right the intensity increases since radiation with maximum angle towards the left arrives there. The pupil starts filling up at the left side. By moving up the ramp, radiation having progressively smaller angles towards the left arrive until at the 50% point half of the pupil is filled. Moving further up the ramp even radiation which travels to the right will arrive thus the pupil fills up further until it is completely filled, i.e. when the 100% area is reached. A part of the 100% area, labelled “slit width”, is used for the illumination field and this area is exposed to the substrate. The margin area in the 100% field is used to make sure that the “slit width” can be fully placed in the 100% area despite potential errors, for example errors which could be caused by manufacturing tolerances. On the right hand side, the pupil filling decreases in a similar fashion from 100% to 0%. The ramps on either side of the illumination field, in which the intensity is less than 100% can be used to measure the intensity of the radiation. The reflector 480 can be placed adjacent to the illumination field, i.e. in the margin or in the ramp, such that information relating to the pupil can be detected by the sensing device 470without affecting the illumination field used to pattern the substrate W.
    [0069] The sensing module can be used with different types of lithographic apparatus 4100. For example, the sensing module could be used with EUV apparatus or the sensing module could be used with immersion apparatus. If the sensing module was used with an immersion apparatus, a different type of pupil would be detected. An immersion apparatus does not have different facets. Therefore, a continuous field pupil would be formed by the radiation rather than being formed of a plurality of beams of light, therefore, the pinpoints of light could no longer be detected. However, the continuous field pupil could be detected and any variation of the movement of the entire pupil could still be measured. From this measurement, variation in the radiation source could be determined.
    [0070] As will be appreciated, any of the above described features can be used with any other feature and it is not only those combinations explicitly described which are covered in this application.
    [0071 ] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications in manufacturing components with microscale, or even nanoscale features, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc.. In the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.
    [0072] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions, below atmospheric pressure conditions or ambient (non-vacuum) conditions.
    [0073] While specific embodiments of the invention have been described above, it will be appreciated that the invention, at least in the form of a method of operation of an apparatus as herein described, may be practiced otherwise than as described. For example, the embodiments of the invention, at least in the form of a method of operation of an apparatus, may take the form of one or more computer programs containing one or more sequences of machine-readable instructions describing a method of operating an apparatus as discussed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Further, the machine readable instruction may be embodied in two or more computer programs. The two or more computer programs may be stored on one or more different memories and/or data storage media.
    [0074] Any controllers described herein may each or in combination be operable when the one or more computer programs are read by one or more computer processors located within at least one component of the lithographic apparatus. The controllers may each or in combination have any suitable configuration for receiving, processing and sending signals. One or more processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors for executing the computer programs that include machine-readable instructions for the methods of operating an apparatus as described above. The controllers may include data storage media for storing such computer programs, and/or hardware to receive such media. So the controller(s) may operate according to the machine readable instmctions of one or more computer programs.
    [0075] An embodiment of the invention may be applied to substrates with a width (e.g., diameter) of 300 mm or 450 mm or any other size.
    [0076] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the clauses set out below. Other aspects of the invention are set out as in the following numbered clauses: 1. An apparatus comprising: an illumination system arranged to direct radiation from a radiation source to an illumination field on a surface ; and a sensing module, the sensing module comprising: a reflector arranged to reflect radiation, the reflector being located adjacent to the illumination field; and a sensing device configured to receive an image of a pupil of the illumination system, reflected from the reflector. 2. The apparatus of clause 1, wherein the illumination system has a reflector which has a plurality of facets so that the pupil comprises a plurality of bright spots, and the sensing device detects the position of at least one of the plurality of bright spots. 3. The apparatus of clause 1 or 2, wherein the sensing device is configured to receive all of the plurality of bright spots which comprise the pupil. 4. The apparatus of any one of the preceding clauses, wherein the sensing module further includes a processor for processing the image to determine information representative of a component of the radiation source. 5. The apparatus of clause 4, wherein the component of the radiation source is a plasma and/or a collector. 6. The apparatus of any one of the preceding clauses, wherein the sensing device converts the image of the pupil of the illumination system into an electronic signal. 7. The apparatus of any one of the preceding clauses, wherein the sensing device comprises an image sensing device and a scintillation layer. 8. The apparatus of clause 7, wherein the image sensing device is a CCD or CMOS device. 9. The apparatus of any one of the preceding clauses, wherein the sensing device is located relative to the reflector such that all of the plurality of bright spots are received by the sensing device. 10. The apparatus of any one of the preceding clauses, wherein the sensing device has a resolution and is placed at a distance from the reflector such that the bright spots can be separately resolved. 11. The apparatus of any one of the preceding clauses, further configured to adjust the position and/or tilt of the collector and/or the position of the plasma. 12. The apparatus of any one of the preceding clauses, wherein the sensing module is further configured to determine the radiation intensity from the received radiation. 13. The apparatus of any one of the preceding clauses, further comprising at least one additional sensing module, 14. A lithographic apparatus which is an apparatus according to any one of the preceding clauses, wherein the surface is a patterning device. 15. The apparatus of clause 14, wherein the patterning device has a slit through which radiation is directed, and the reflector is located adjacent to the slit. 16. A device manufacturing method using a lithographic apparatus comprising the steps of: exciting a fuel to form a plasma; collecting radiation omitted by the plasma and directing it into a beam; directing the beam onto an illumination field on a patterning device using an illumination system; directing the beam patterned by the patterning device onto a substrate; reflecting radiation received on a reflector adjacent to an illumination field; and receiving the reflected radiation at a sensing device , wherein the radiation received is an image of a pupil of the illumination system. 17. A device manufacturing method according to clause 16, wherein the illumination system has a reflector which has a plurality of facets so that the pupil comprises a plurality of bright spots, and the sensing device detects the position of at least one of the plurality of bright spots. 18. A device manufacturing method according to one of clauses 16 or 17, further comprising a step of processing the image to determine information representative of at least one component of the radiation source alignment with respect to the illuminator. 19. A device manufacturing method according to clause 18, wherein the component of the radiation source is the plasma and/or a collector. 20. A device manufacturing method according to any one of clauses 16 to 19, further comprising the step of converting the image of the pupil of the illumination system into an electric signal. 21. A device manufacturing method according to any one of clauses 16 to 20, further comprising a step of determining the intensity of the radiation at the substrate from the received radiation at the sensing device. 22. A device manufacturing method according to any one of clauses 16 to 21, further comprising a step of adjusting the position and/or tilt of the collector and/or the position of the plasma.
    权利要求:
    Claims (1)
    [1]
    A lithography device comprising: an illumination device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.
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    同族专利:
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    WO2015074816A1|2015-05-28|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2004031854A2|2002-09-30|2004-04-15|Carl Zeiss Smt Ag|Illumination system for a wavelength = 193 nm, comprising sensors for determining the illumination|
    US20090015814A1|2007-07-11|2009-01-15|Carl Zeiss Smt Ag|Detector for registering a light intensity,and illumination system equipped with the detector|
    DE102012211846A1|2012-07-06|2013-08-01|Carl Zeiss Smt Gmbh|Method for measuring angle-resolved intensity distribution in reticle plane of projection exposure system for microlithography with illumination system, involves arranging optical module in beam path of projection exposure system|
    法律状态:
    2015-08-12| WDAP| Patent application withdrawn|Effective date: 20150617 |
    优先权:
    申请号 | 申请日 | 专利标题
    EP13194287|2013-11-25|
    EP13194287|2013-11-25|
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