 METHOD OF MEASURING THE DEALIGNMENT BETWEEN A FIRST AND A SECOND GRATING AREA
专利摘要:
This method of measuring the misalignment between a first and a second etching zone comprises: the embodiment (112) of a plasmonic antenna comprising a first and a second distinct element which each delimits, on one respective side, a hollow, all the elements of the plasmonic antenna located on a first side of a separation plane being entirely made inside the first zone and all the elements of the plasmonic antenna located on the second side of the separation plane being entirely realized within the second zone, - after the realization of the plasmonic antenna, the method comprises: • the measurement (114) of the absorption rate of the plasmonic antenna, and • the determination (128, 130) of the amplitude of misalignment between the first and second zones from the measured absorption rate and a predicted value for this absorption rate in the absence of misalignment. 公开号:FR3062516A1 申请号:FR1750759 申请日:2017-01-30 公开日:2018-08-03 发明作者:Guido Rademaker；Salim Boutami；Jonathan Pradelles 申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA； IPC主号:
专利说明:
@ Holder (s): COMMISSION FOR ATOMIC ENERGY AND ALTERNATIVE ENERGIES Public establishment. ® Agent (s): INNOVATION COMPETENCE GROUP. ® METHOD FOR MEASURING THE MISALIGNMENT BETWEEN A FIRST AND A SECOND ENGRAVING AREA. FR 3,062,516 - A1 (57) A method for measuring the misalignment between a first and a second etching zone comprises: - The realization (112) of a plasmonic antenna comprising a first and a second distinct elements which each delimit, on a respective side, a hollow, all the elements of the plasmonic antenna located on a first side of a plane of separation being entirely produced inside the first zone and all the elements of the plasmonic antenna situated on the second side of the separation plane being entirely produced inside the second zone, - after the plasmonic antenna has been produced, the method includes: measuring (114) the absorption rate of the plasmonic antenna, and determining (128,130) the amplitude of the misalignment between the first and second zones from the measured absorption rate and a predicted value for this absorption rate in the absence of misalignment. ÏÏÔ] ÏÏ2] ΓΪ161 pray to me 1122] ΓΪ28] ra □ 32] 114 126 METHOD FOR MEASURING THE MISALIGNMENT BETWEEN A FIRST AND A SECOND ENGRAVING AREA [001] The invention relates to a method for measuring the misalignment between a first and a second engraving area. It also relates to an information recording medium, a measuring device and a plan of a test pattern for the implementation of this method of measuring the misalignment. An etching zone is an area of a substrate inside which an element or part of an element is engraved. This substrate is known by the English term "wafer". The first and second etching zones are such that there may be an accidental misalignment between these two etching zones, that is to say an unwanted offset from one etching zone relative to the other. An offset is "unwanted" or "accidental" when this offset does not exist in the plane coding the dimensions, the arrangement and the location of the elements to be etched on the substrate whereas it exists once these elements have actually been made on the substrate. This offset is caused by faults or errors in the settings of the machines used to produce these elements on the substrate. Among the various machines used to produce these elements on the substrate, it is often the lithography machine which is the source of the largest shifts. A lithography machine is for example a lithography machine by electron beams. An electron beam lithography machine is often used to draw patterns in a layer of resin deposited on the face of the substrate. The resin layer is sensitive to beam electrons. Then, for example, regions of the resin which have not been irradiated by the electron beam are eliminated and a mask is thus obtained which obscures certain regions of the face of the substrate and leaves other regions directly exposed. outside. Then by applying an etching agent through this mask, the regions not obscured by the mask are eliminated while the regions obscured by this mask are protected and are therefore not engraved. Such a mask therefore makes it possible to engrave the patterns drawn in the face of the substrate. With a single beam electron beam lithography machine, without moving the substrate relative to the source of this electron beam, it is possible to draw a pattern in only a small etching area. For this, the electron beam is moved by deflection while keeping the source of this beam stationary relative to the substrate. This small area is called "field" in the case of an electron beam lithography machine. The surface of this field is often less than or equal to 1 cm 2 or 1 mm 2 . It is therefore much smaller than the surface of the face of the substrate to be etched. Therefore, to draw on the entire face of the substrate, it is necessary to move, relative to each other, the substrate and the source of the electron beam. In this case, the substrate and the source occupy, relative to each other, over time different relative positions. Each relative position of the substrate with respect to the source of the electron beam corresponds to a respective field. The different fields used to draw on the entire face of the substrate are generally aligned in contiguous or slightly overlapping lines and columns. However, due to inaccuracies in the positioning of the substrate relative to the electron beam, it may happen that two contiguous fields are not perfectly aligned with respect to each other. There is then a misalignment between these two fields. Such misalignment is also known by the English term "stitching" or "field stitching". Such misalignment can cause an abrupt rupture or an undesired distortion of a pattern straddling these two fields. It is therefore desirable to measure this misalignment, that is to say to measure the amplitude, to correct it and limit the amplitude. For this, known methods for measuring the misalignment include: the supply of a plan containing instructions coding in particular the dimensions, the arrangement and the location of a test pattern to be produced, on a substrate, straddling the first and second zones, - the realization of the target on the substrate by executing the instructions contained in the plan provided and using a lithography machine, then - the determination of the amplitude of the misalignment from the observation of the test pattern carried out on the substrate. For example, the following article describes the production on the substrate of a test pattern in the form of a Verniers scale and the measurement of the misalignment using a scanning electron microscope: Tine Greibe et Al: “ Quality control of JEOL JBX-9500FSZ e-beam lithography System in a multi-user laboratory ”, Microelectronic Engineering 155 (2016) 25-28. Such a method of measuring misalignment is slow and complicated because it is necessary to use a scanning electron microscope. The same problem exists with multi-beam machines for lithography by electron beams. These multi-beam machines, unlike a single-beam machine, make it possible to simultaneously irradiate, each with its own electron beam, several fields adjacent to each other. These adjacent fields are aligned next to each other. However, as in the case of a single-beam machine, there may be a misalignment between these different adjacent fields irradiated simultaneously. In the case of multibeam machines, at least one of the dimensions of the fields is generally much smaller than the dimensions of the fields of a single-beam machine. For example, this smaller dimension may be less than 10 µm or 2 µm. In the latter case, there is an additional problem, namely that the known patterns are too large to be produced within a single field of a multi-beam machine. When different structured layers are superimposed one above the other, there may also be a misalignment between these different layers. A structured layer is a layer that has been etched to create one or more elements. In this case, each structured layer corresponds to a respective etching zone and this misalignment is sometimes designated by the English expression "overlay accuracy". It is measured similarly to what has just been described in the particular case of the misalignment between two fields of a lithography machine by electron beams. It will be noted that the misalignment between two layers can exist whatever the technology used by the lithography machine to draw the patterns to be engraved. For example, the problem of misalignment between two structured layers is also encountered when a photolithography machine has been used to draw the elements to be engraved. Thus, there are many situations where the misalignment between two etching zones must be measured. The invention aims to provide a method of measuring the misalignment between two etching areas which is simple and rapid. Its subject is therefore such a process in which: - the target coded by the instructions contained in the plan comprises at least one plasmonic antenna capable, after having been produced on the substrate, of producing a resonance of the surface plasmons located inside a hollow when it is exposed to incident polarized radiation of wavelength A m so that the plasmonic antenna absorbs at least part of the incident radiation polarized at this wavelength A m , the absorption rate of this plasmonic antenna at the length of wave A m varying as a function of a dimension of the hollow, this plasmonic antenna comprising for this purpose first and second separate elements which each delimit, on a respective side, the hollow so that the dimension of the hollow is fixed by l spacing between these first and second elements, these first and second elements each being located entirely, respectively, of a first and a second side respectively of a separation plane, - during the creation of the target, all the elements of the plasmonic antenna located on the first side of the separation plane are entirely produced inside the first zone and all the elements of the plasmonic antenna located on the second side of the separation plan are entirely carried out inside the second zone, - after the plasmonic antenna has been produced, the method includes: • the measurement of the absorption rate of the plasmonic antenna carried out at the wavelength A m by exposing this plasmonic antenna to incident polarized radiation of wavelength A m and of known intensity, emitted by a source of radiation, and by measuring the intensity of the radiation reflected by the plasmonic antenna or transmitted through the plasmonic antenna at this same wavelength A m using a radiation intensity sensor, and • the determining the amplitude of the misalignment between the first and second zones from the measured absorption rate and a predicted value for this absorption rate in the absence of misalignment between the first and second zones. In the claimed process, if there is a misalignment between the first and the second etching zones, then this modifies the dimensions of the hollow of the plasmonic antenna and therefore the absorption rate of this plasmonic antenna. Thus, from the measured absorption rate of the plasmonic antenna and a predicted value for this absorption rate in the absence of misalignment, it is possible to determine the amplitude of the misalignment between these two etching zones. The absorption rate of the plasmon antenna can easily and quickly be measured using a source of polarized radiation and an intensity sensor of the reflected radiation. Consequently, the claimed method makes it possible to quickly and simply measure the misalignment between two etching zones without having to use complex and slow equipment for this, such as a scanning electron microscope. In addition, the dimensions of a plasmonic antenna can be less than 10 pm or 5 pm. Thus, the claimed method can be implemented to measure a misalignment between much smaller etching areas than is possible with conventional test patterns. Finally, in the case where the zones are fields of an electron beam lithography machine, in order to produce the plasmonic antenna, it is not necessary for these fields to overlap. Conversely, in order to carry out the conventional patterns, it is often necessary to provide for such an overlap between the two adjacent fields. The embodiments of this measurement method may include one or more of the following characteristics: the instructions contained in the plan provided code a plasmonic antenna in which: - The first and second elements are aligned on a first alignment axis so that the absorption rate of the plasmonic antenna produced reaches a first maximum when it is exposed to a first incident wavelength radiation At m and in the direction of polarization parallel to this first alignment axis, and - The plasmonic antenna comprises third and fourth distinct elements which limit, each on a respective side, the same hollow or another hollow, these third and fourth elements being entirely located inside, respectively, of the first and second sides and these third and fourth elements being aligned on a second alignment axis which intersects the first alignment axis at a point of intersection, so that the absorption rate of the plasmonic antenna reaches a second maximum when it is exposed to a second incident radiation of wavelength A m and of direction of polarization parallel to this second alignment axis, - the measurement of the absorption rate includes: a first measurement of an absorption rate Tml of the plasmonic antenna when it is exposed to the first incident radiation, and a second measurement of an absorption rate Tm2 of the plasmonic antenna when it is exposed to the second incident radiation, the determination of the amplitude of the misalignment comprises the determination of the amplitude of the misalignment between the first and second zones, in a direction parallel to a line of separation, this line of separation being formed by the intersection of the plane of separation and of the plane of the substrate, as a function of the difference between the ratio Tml / Tm2 and a ratio Tpl / Tp2, where Tpi and Tp2 are the predicted values of the absorption rate, in the absence of misalignment, for, respectively, the first and the second measurement; in the plane provided, the orthogonal projection in the plane of the substrate of the pair formed by the third and fourth elements is deduced from the orthogonal projection in this same plane of the pair formed by the first and second elements, by: - a rotation whose center is located on the separation line, combined with a translation parallel to this separation line, the amplitude of this translation being greater than or equal to zero; the point of intersection is located on the dividing line; the absorption rate measurement includes: a third measurement of an absorption rate Am3 of the plasmonic antenna carried out when it is exposed to a third incident radiation of wavelength A m and of direction of polarization parallel to the bisector of a first angular sector delimited by the first and second alignment axes, a fourth measurement of an absorption rate Am4 of the plasmonic antenna carried out when it is exposed to a fourth incident radiation of wavelength A m and of direction of polarization parallel to the bisector of a second angular sector delimited by the first and second alignment axes, this second angular sector having a common side with the first angular sector, and the determination of the amplitude of the misalignment comprises the determination of the amplitude of the misalignment between the first and second zones in a direction perpendicular to the separation line as a function of the difference between the ratio Tm3 / Tm4 and a ratio Tp3 / Tp4, where Tp3 and Tp4 are the predicted absorption rate values, in the absence of misalignment, for the third and fourth measurements, respectively; in the plan provided: - the orthogonal projections in the plane of the substrate of the first and fourth elements are the symmetrics of the orthogonal projections, in the same plane, of the second and third elements with respect to an axis perpendicular to the line of separation, and the orthogonal projections of the first and third elements in the plane of the substrate are the symmetrics of the orthogonal projections of the second and fourth elements with respect to the separation line, and - the orthogonal projection in the plane of the substrate of the first alignment axis intersects the line of separation with an angle of 45 °; in the plane provided, each element has a point whose apex is located on a respective side of the recess, each pair of elements whose apexes are opposite and located on respective opposite sides of said recess, thus forming a antenna known as "bowtie"; the elements are made of an electrically conductive material and directly deposited on a layer of dielectric material; the elements are made of dielectric material and directly deposited on a layer of electrically conductive material or correspond to cavities dug in a layer of dielectric material directly deposited on a layer of electrically conductive material; the wavelength A m is less than 2000 nm or 700 nm; the first and second zones are: - respectively, a first and a second field, located in the same plane parallel to the plane of the substrate, of an electron beam lithography machine, or - respectively, a first and a second structured layers superimposed one above the other. The invention also relates to an information recording medium comprising instructions for the implementation of the claimed method, when these instructions are executed by a microprocessor. The invention also relates to an apparatus for measuring the misalignment between a first and a second etching zone for the implementation of the claimed method, this apparatus comprising: a source capable of emitting incident polarized radiation of known intensity at a wavelength A m on a plasmonic antenna produced on a substrate, a radiation intensity sensor able to measure the intensity of the radiation reflected by the plasmonic antenna or transmitted through the plasmonic antenna at the wavelength A m , and - a microprocessor programmed to determine an absorption rate from the known intensity of the incident radiation and the measured intensity of the reflected or transmitted radiation, in which the microprocessor is programmed to determine the amplitude of the misalignment between the first and second zones from the measured absorption rate and a predicted value of this absorption rate in the absence of misalignment between the first and second zones. The invention also relates to a plan of a test pattern for the implementation of the claimed method, this plan containing instructions specific to an electron beam lithography machine which comprises at least a first and a second separate fields, said instructions coding in particular the dimensions, arrangement and location in the first and second fields of at least one plasmonic antenna to be produced on a substrate, this plasmonic antenna being suitable, after having been produced on the substrate, to produce a resonance of the surface plasmons located inside a trough when it is exposed to incident polarized radiation of wavelength A m so that the plasmonic antenna absorbs at least part of the incident polarized radiation at this wavelength A m , the absorption rate of this plasmonic antenna at the wavelength A m varying as a function of a dimension of the hollow, this plasmonic antenna comprising for this purpose first and second distinct elements which each delimit, on a respective side, the recess so that the dimension of the recess is fixed by the spacing between these first and second elements, these first and second elements being located each entirely, respectively, of a respective first and second side of a separation plane, in which the dimensions, arrangement and coded location of the plasmonic antenna are such that, all the elements of this Plasmon antenna located on the first side of the separation plane are entirely inside the first field and all the elements of the plasmon antenna located on the second side of the separation plane are entirely inside the second field. The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and made with reference to the drawings in which: - Figure 1 is a schematic illustration of an apparatus for measuring the misalignment between two etching areas; - Figure 2 is a schematic and partial illustration, in vertical section, of a portion of a substrate used to measure a misalignment between two etching zones; - Figure 3 is a schematic illustration of an electron beam lithography machine; - Figure 4 is a schematic illustration, partial, and in top view of a test pattern used to measure a misalignment between two etching zones; - Figure 5 is a more detailed illustration of a plasmonic antenna of the target of Figure 4; - Figure 6 is a schematic illustration of a test pattern actually produced on a substrate from a plane coding the test pattern of Figure 5; - Figures 7 to 10 are schematic illustrations in top view of different misalignments that may be encountered when producing the test pattern of Figure 4 on a substrate; - Figure 11 is a flowchart of a method for measuring the misalignment between two etching zones using the test pattern of Figure 4 and the apparatus of Figure 1; - Figures 12 to 14 are partial diagrammatic illustrations and in vertical section of other possible embodiments of the test pattern of Figure 4; FIGS. 15 to 20 are diagrammatic illustrations, seen from above, of various other possible embodiments for a plasmonic antenna of the target of FIG. 4. In these figures, the same references are used to designate the same elements. In the remainder of this description, the characteristics and functions well known to those skilled in the art are not described in detail. Figure 1 shows an apparatus 2 for measuring a misalignment between two etching zones. Thereafter, the description is made in the particular case where these etching zones correspond to adjacent fields of a multibeam machine 40 (Figure 3) of lithography by electron beams. The device 2 comprises a source 4 of radiation capable of emitting a beam 6 polarized at a wavelength A m towards a substrate 8 on the upper face 10 of which a test pattern 12 has been produced (FIG. 2 ). For example, the beam 6 is a collimated beam so as to irradiate only a selected portion of the test pattern 12. The beam 6 is an electromagnetic wave. Here, to increase the resolution of the device 2, the wavelength A m is less than 2000 nm or 700 nm and, generally, greater than 390 nm. Preferably, the wavelength A m is between 390 nm and 700 nm, that is to say comprised in the visible spectrum. In this case, the intensity of the beam 6 can be expressed in candela. In the case where the wavelength A m is outside the visible spectrum, the intensity corresponds to the radiated power, that is to say to the energy flux. The source 4 includes a rotating polarizer 14 which makes it possible to vary the direction of polarization of the beam 6 in response to a command. The apparatus 2 also includes: a sensor 16 capable of measuring the intensity of the radiation reflected 18 by a portion of the test pattern 12, an actuator 20 able to move the substrate 8 relative to the incident beam 6 so as to select the portion of the test pattern 12 exposed to the beam 6, and a processing unit 22 capable of determining the amplitude of the misalignment between two etching zones as a function of the measurements of the sensor 16 and of the intensity of the beam 6. For example, the sensor 16 has for this purpose one or more photodetectors. The unit 22 is connected: - to the sensor 16 to receive the intensity measurements, and - at source 4 and at actuator 20 to control them. For example, the unit 22 comprises a programmable microprocessor 24 and a memory 26. The memory 26 includes in particular the instructions and the data necessary for the execution of the method of FIG. 11. In this example, the memory 26 comprises also one or more conversion tables which make it possible to convert deviations E x and E y into amplitudes expressed in meters or in a sub-unit of the meter. Figure 2 shows a portion of the substrate 8 in vertical section. In this description, the figures are oriented relative to an orthogonal coordinate system XYZ in which Z is the vertical direction and X and Y are two horizontal orthogonal directions. The upper face 10 of the substrate 8 is formed by a layer 30 of dielectric material on which are directly deposited elements 32 of electrically conductive material. The association of this layer 30 with the elements 32 forms the test pattern 12. Here, by conductive material, we mean a material whose electrical conductivity at 20 ° C is greater than 10 5 S / m and, preferably, greater than 10 6 S / m. Typically, it is a metal such as gold or silver. By dielectric material is meant here a material whose electrical conductivity at 20 ° C is less than 10 -2 S / m or 10 -4 S / m. Here, the elements 32 are made of gold and the layer 30 is a layer of silica. 3 shows a multi-beam machine 40 of electron beam lithography used to draw in a resin layer sensitive to the electron beam the patterns of the test pattern 12 which define the dimensions, arrangement and l location of the various elements 32 of this target. For example, this resin layer is deposited on a metal layer itself directly deposited on the layer 30 of dielectric material. This machine 40 has several fields contiguous to each other and which extend parallel to the direction Y. The machine 40 also has a memory 42 containing a plane 44. The plane 44 includes instructions which define the dimensions, the arrangement and the location on the substrate 8 of the various elements 32 of the test pattern 12. Thus, when these instructions are executed by the machine 40, the latter draws, in the resin layer, patterns which make it possible to obtain a mask. This mask is then used to etch the metal layer and thus produce the elements 32 of the test pattern 12. Figure 4 shows in more detail the arrangement and location of the test pattern 12 as coded in the plane 44. In this figure, the wavy lines to the right and left indicate that only part of the test pattern 12 is represented. The test pattern 12 has several rows 50 to 54 parallel to the direction Y. These rows 50 to 54 are identical to each other and only the row 50 is described in more detail. Row 50 comprises several plasmonic antennas 60 to 64 each arranged on either side of the same vertical plane of separation. This vertical plane of separation intersects the horizontal plane of the substrate at the level of a line 66 of separation parallel to the direction Y. The plane of the substrate is the plane in which the substrate 8 mainly extends. Line 66 is located on the border between two adjacent fields 68 and 70 of the machine 40. Thus, part of the elements of each antenna 60 to 64 is located inside the field 68 and the other part of these elements is located inside the field 70. The antennas 60 to 64 are here identical to each other and only the antenna 60 is described in more detail. FIG. 5 represents the antenna 60 as coded by the instructions contained in the plan 44. The antenna 60 comprises two pairs 80 and 82 of elements 32. Here, the pairs 80 and 82 are located in the same horizontal plane. The pair 82 is deduced from the pair 80 by a rotation of angle β around a vertical axis passing through a point O located on the line 66. Here, the angle β is equal to 90 °. Therefore, only the pair 80 is now described in more detail. To distinguish the two elements 32 of the pair 80, in this figure and the following, they bear, respectively, the reference numerals 32a and 32b. Similarly, in this figure and the following, the two elements 32 of the pair 82 bear, respectively, the numerical references 32c and 32d. The elements 32a and 32b are located, respectively, to the right and to the left of the line 66. They are aligned on an oblique axis 84 which intersects the line 66 at the point O with an angle a. In this embodiment, the axis 84 is also an axis of symmetry for the elements 32a and 32b. The angle a is strictly greater than 0 ° and sufficiently large so that the element 32a is entirely situated on the right side of the line 66 and does not touch this line 66. The angle a is also strictly less than 90 ° so that element 32a does not touch element 32c. Typically, the angle a is between 25 ° and 65 ° or between 35 ° and 55 °. Here, the angle a is equal to 45 ° to ± 5 ° or ± 2 °. The elements 32c and 32d are in turn aligned on an axis 86. The angle between the axes 84 and 86 is equal to the angle β. In this embodiment, the element 32b is in addition the symmetrical of the element 32a with respect to a horizontal axis perpendicular to the axis 84 and passing through the point O. Here, this axis of symmetry is coincident with the axis 86. Consequently, subsequently, only the element 32a is described in more detail. The element 32a has a tip 90 directed towards the point O and separated from this point O by a distance g / 2. There therefore exists a distance g which separates the point 90 from the point facing the element 32b. Because of this distance g, there is a recess 92 between these two points. The same distance g exists between the points facing the elements 32c and 32d. This distance g therefore fixes the dimensions of the recess 92 between the elements 32a, 32b and between the elements 32c, 32d. In FIG. 5, only the horizontal dimension g x and the vertical dimension g Y of the recess 92 have been shown. These dimensions g x , g Y are deduced from the distance g using the following relationships: g x = g.cos (a) and g Y = g.sin (a), where the symbol «. "Indicates the multiplication operation. In this example, the horizontal section of the element 32a is a solid triangle and the point 90 is one of the vertices of this triangle. Under these conditions, the pairs 80 and 82 each form, respectively, a first and a second plasmonic antenna known under the English term of antenna "bowtie". For example, the triangle is an equilateral triangle. It is recalled here that a “bowtie” antenna produces a resonance of the surface plasmons located inside the hollow 92 when it is exposed to incident radiation polarized in a direction parallel to the plane of the substrate 8. In addition , typically, the pulsation ω of the incident radiation must be less than the pulsation ω ρ of the electrically conductive material of the antenna defined by the following relation: ω ρ = (Ne 2 / (e 0 .m *)) 0 ' 5 , or : - N is the concentration of free charge carriers in the electrically conductive material, - e is the charge of an electron, - ε 0 is the permittivity of the vacuum, and - m * is the effective mass of free electrons in the electrically conductive material. For a resonance of the surface plasmons to appear, it is also generally necessary for the real part of the relative permittivity of the electrically conductive material to be negative. Subsequently, we note A m a> the wavelength of the incident radiation at which the amplitude of the resonance of the surface plasmons is maximum. The value of this wavelength A max depends on the dimensions of the element 32a. Those skilled in the art know how to build and size a "bowtie" antenna so that resonance of the surface plasmons occurs at a desired wavelength A m . Here, the antenna 60 is dimensioned so that the wavelengths A max and A m are equal to ± 10% or ± 5%. For example, the dimensioning of element 32a can be determined by digital simulation FDTD (“Finite Differente Time Domain”). Indeed, the principle and the operating laws of the pair 80 are known and have already been simulated. On this subject, the reader can refer for example to the following studies: - Sylvain Vedraine, Renjie Hou, Peter R. Norton, and François Lagugné-Labarthet, “On the absorption and electromagnetic field spectral shifts in plasmonic nanotriangle arrays”, Opt. Exp. 22, 13308 (2014). - K. Schraml, M. Spiegl, M. Kammerlocher, G. Bracher, J. Bartl, T. Campbell, JJ Finley, and M. Kaniber, “Optical properties and interparticle coupling of plasmonic bowtie nanoantennas on a semiconducting substrate”, PRB 90, 035435 (2014). Here, the angle of incidence of the beam 6 at the wavelength A m is strictly less than 90 °. In addition, it is chosen so that the majority of the beam 6 is reflected by the antenna 60. Because of the phenomenon of resonance of the surface plasmons, part of the intensity of the beam 6 is absorbed by the antenna 60. The absorption rate of a plasmonic antenna can be measured from the reflection rate and / or the radiation transmission rate 6. The reflection rate is equal to the ratio l r / l · and the transmission rate is equal to the h / h ratio, where: - I r is the intensity of the radiation reflected by the plasmonic antenna, - h is the intensity of the radiation transmitted through the plasmonic antenna, and -1, is the intensity of the incident beam 6. Thereafter, in this embodiment, the absorption rate of the plasmonic antenna is measured by the reflection rate of the antenna 60. The absorption rate varies as a function of the dimensions g x and g Y of the trough 92. Conversely, the value of the wavelength A ma x is practically independent of these dimensions g x and g Y. FIG. 6 schematically represents a plasmonic antenna 100 produced on the substrate 8 by implementing the instructions coding the antenna 60 and contained in the plane 44. The antenna 100 is shown in the particular case where there is there is no misalignment between the fields 68 and 70. In FIG. 6, the elements of the antenna 100 corresponding to the elements of the antenna 60 have the same numerical references. As illustrated in this figure, in practice, with current lithography techniques, it is not possible to produce perfect tips, such as those represented in FIG. 5. On the contrary, when the antenna 60 is produced on the substrate 8 , the points, like the point 90, are replaced by rounding as illustrated in FIG. 6. These deformations introduced by the various stages of production of the antenna 60 can cause a modification of the value of the wavelength Amax. However, numerical simulations carried out have shown that the wavelength A m remains close enough to the wavelength Amax for the antenna 100 produced nevertheless to produce a resonance of the surface plasmons inside the trough 92 when exposed to radiation of wavelength A m . Thus, despite differences between the theoretical shape of the antenna 60 coded in the plane and the shape actually obtained, the method of measuring the misalignment described below works. Consequently, in the remainder of this description, as in the following figures, the differences between the dimensions of the antennas 60 and 100 are ignored to simplify the explanations. In particular, in the following figures, the elements 32a to 32d of the antenna 100 are shown as being identical to the elements 32a to 32d of the antenna 60. Figures 7 to 10 show the antenna 100 when the misalignment between the fields 68 and 70 is not zero. More precisely, we denote by Δχ and Δγ the amplitude of the misalignment between the fields 68 and 70 parallel, respectively, to the directions X and Y. By convention, the amplitudes Δχ and Δγ have a positive value if the misalignment corresponds to a displacement of the elements 32a, 32c with respect to the elements 32b and 32d in the direction of the directions, respectively, X and Y. Conversely, the amplitudes Δχ and Δγ have a negative value in the presence of a displacement of direction opposite to the direction of the directions X and Y. Figures 7 and 8 show the consequences of a misalignment when the amplitude Δχ is zero and the amplitude Δγ is positive (Figure 7) or negative (Figure 8). Figures 9 and 10 show the consequences of a misalignment when the amplitude Δγ is zero and the amplitude Δχ is positive (Figure 9) or negative (Figure 10). As illustrated in these Figures 7 to 10, a non-zero misalignment between the fields 68 and 70 results in a modification of the dimensions of the trough 92, and therefore in a modification of the absorption rate at the wavelength A m . On the other hand, a non-zero misalignment does not or practically not modify the value of the wavelength Amæ <because the dimensions of the elements 32a to 32d are not modified. Consequently, the absorption rate of the antenna 100 varies essentially as a function of the misalignment between the fields 68 and 70. Therefore, the amplitude of the misalignment can be determined from: a predicted value of the absorption rate of the antenna 100 in the absence of misalignment, that is to say for a misalignment of zero amplitude, and - the absorption rate actually measured for the antenna 100. In this particular embodiment, it is sought to measure the amplitude Δγ and, at the same time, the amplitude Δχ. In addition, in this embodiment, we also want to know the direction of movement of the elements 32a, 32c relative to the elements 32b and 32d. For this, it has been observed that when the amplitude Δγ of the misalignment is positive, the size of the recess 92 between the elements 32a and 32b increases while the size of the recess 92 between the elements 32c and 32d decreases. Under these conditions, when the amplitude Δγ increases, the absorption rate of the pair 80 decreases while, at the same time, the absorption rate of the pair 82 increases. The opposite behavior is observed when the amplitude Δγ is negative. To exploit this property, a relation A Y is defined by the following relation A y - T + 45 / T-45, where: T + 45 is the absorption rate of the antenna 100 measured using incident radiation at the wavelength A m and the direction of polarization of which is parallel to the axis 86, and - T_45 is the absorption rate of the antenna 100 measured using incident radiation at the wavelength A m and the direction of polarization of which is parallel to the axis 84. In addition, this ratio A Y has the advantage of being very little dependent on the amplitude of the misalignment Δχ. Indeed, a non-zero amplitude Δχ modifies the absorption rates T. 45 and T + 45 substantially in the same way so that the ratio A Y varies little in response to a modification of the amplitude Δχ. Finally, when the amplitude Ay is zero, the dimensions of the trough 92 between the elements 32a, 32b and between the elements 32c, 32d are identical so that the absorption rates T. 45 and T + 45 are equal. Thus, the predicted value A YP of the ratio A Y is easy to predict since it is equal to 1. Consequently, the difference E Y = 1-A Y varies mainly as a function of the amplitude Ay and much less as a function of the amplitude Δχ. This difference E Y is therefore mainly representative of the amplitude of the misalignment between the fields 68 and 70 in the only direction Y. If necessary, this difference E Y can be converted into a value of the amplitude Ay expressed in nanometers using a conversion table. For example, this conversion table is constructed by calculating, by numerical simulation or by experimental measurements, the value of the difference E Y for different known values of the amplitude Ay. Here, to simplify, as a first approximation, it is considered that the difference E Y is equal, to within a multiplicative constant, to the amplitude Ay. In other words, the conversion table here boils down to the following relation Ay = AE Y where A is a known multiplicative constant, determined during an initial calibration of the process. The rates T + 45 and T. 45 of the antenna 100 can be measured by exposing this antenna 100 to radiation polarized in the directions parallel, respectively, to axes 86 and 84. Indeed, polarized radiation parallel to the axis 84 almost only excites the pair of elements 32a, 32b, and hardly excites the pair of elements 32c, 32d which are aligned on an axis orthogonal to the axis 84. Consequently, the resonance of the plasmons surface area inside the recess 92 is mainly due to the elements 32a and 32b. Consequently, the absorption rate measured with such polarized radiation corresponds to the absorption rate T. 45 . Similarly, by exposing the antenna 100 to polarized radiation parallel to the direction 86, it is possible to measure the rate T + 45 . When the amplitude Δχ is greater than 0 (Figure 9) then the elements 32 closest to each other are the elements 32a and 32c and the elements 32b, 32d. In this case, by successively exposing the antenna 100 to radiation whose directions of polarization are parallel to the directions, respectively, Y and X, it can be observed that the absorption rate is greater with the radiation polarized in the direction Y than with the radiation polarized in the direction X. Indeed, the distance which separates the element 32a from the elements 32d and 32b is larger than that which separates this element 32a from the element 32c. Conversely, when the amplitude Δχ is less than 0 (Figure 10), it is the absorption rate measured with the radiation polarized in the Y direction which is lower than the absorption rate measured with the radiation polarized in the X direction. In fact, in the latter case, the element 32a is closer to the element 32d than to the elements 32b and 32c. To exploit this property, a ratio A x is defined as follows: A x = Tgo / To, where: T 90 is the absorption rate of the antenna 100 measured using incident radiation at the wavelength A m and whose polarization direction is parallel to the X direction, and - To is the absorption rate of the antenna 100 measured using incident radiation at the wavelength A m and the direction of polarization of which is parallel to the direction Y. This ratio A x varies as a function of the amplitude Δχ of the misalignment in the direction X. In addition, it has been observed, by numerical simulation, that the ratio A x is practically independent of the amplitude Ay. In the absence of misalignment, that is to say for amplitudes Δχ and Δγ zero, the element 32a is at the same distance from the elements 32c and 32d. Thus, in the absence of misalignment, the absorption rates T 90 and T o are equal and the predicted value A XP of the ratio A x is therefore equal to 1. Consequently, the difference E x = 1 - A x essentially varies as a function of the amplitude Δχ and practically not as a function of the amplitude Δγ. This difference E x is therefore representative of the amplitude of the misalignment in the only direction X. As for the transmission rates T. 45 and T +45 , the absorption rates T 90 and To can be measured by exposing the antenna 100 to radiation whose directions of polarization are parallel to the directions, respectively, Y and X. FIG. 11 represents a method of measuring the misalignment between the fields 68 and 70 using the apparatus 2 and the test pattern 12. During a step 110, initially, the plane 44 of the test pattern 12 is designed and then supplied to the machine 40. Typically, it is saved in the memory 42. Then, during a step 112, the test pattern 12 is produced on the substrate 8 using the machine 40 for this. Typically, during this step, the machine 40 exposes a layer of resin, directly deposited on a metal layer, to the electron beams of this machine 40. During this step, the electron beams draw the test pattern 12 in this layer of resin sensitive to electron beams. Then, the portions of this unexposed resin layer are removed to form an etching mask. The metallic layer is then etched through this mask to form, in this metallic layer, the elements 32 of the test pattern 12. The test pattern 12 and in particular the antenna 100 are thus obtained. During this step 112, the elements 32a, 32c are produced inside the field 70, while the elements 32b, 32d are produced inside the field 68. Thus, if there is a misalignment between these fields 68 and 70, this necessarily results in an offset of the elements 32a, 32c, with respect to the elements 32b and 32d, and therefore by a modification of the dimensions g x and g Y of the hollow 92. Once the test pattern 12 has been produced on the substrate 8, during a step 114, the absorption rates T + 45, T-45, T90 and To are measured using the device 2. During in this step, the beam 6 is, for example, directed on a single plasmonic antenna or on a restricted group of plasmonic antennas in the test pattern 12. For example, the restricted group contains only several plasmonic antennas straddling the same border between two contiguous fields. Such a small group can contain from two to ten plasmonic antennas. Here, the rest of this description is given in the particular case where the beam 6 is directed on the single antenna 100. However, everything that is described in this particular case also applies to the case of the other plasmonic antennas of the test pattern 12 and in the case of a small group of plasmonic antennas. To direct the beam 6 to the antenna 100, the actuator 20 is controlled by the unit 22 to move the substrate 8 relative to the beam 6. Once the beam 6 is directed onto the antenna 100, the unit 22 proceeds to an operation 116 for measuring the absorption rate T. 45 . For this, the unit 22 controls the polarizer 14 to select a direction of polarization parallel to the axis 84. Next, the unit 22 controls the source 4 to expose the antenna 100 to the beam 6 thus polarized. The intensity h of the beam 6 is known. In parallel, the sensor 16 measures the intensity l r of the radiation reflected by the antenna 100 and transmits this measurement to the unit 22 which acquires it. In response, unit 22 calculates the absorption rate T-45. Step 14 also includes operations 118, 120 and 122 identical to operation 116 except that during these operations, the unit 22 controls the polarizer 14 to have polarization directions parallel to, respectively, the axis 86, in direction Y then in direction X. Thus, at the end of operations 116, 118, 120 and 122, unit 22 measured the absorption rates T-45, T45, Tgo and To. Step 114 is repeated for each plasmonic antenna of the test chart 12 or for each restricted group of plasmonic antennas of the test chart 12. Furthermore, in this particular example, step 114 is repeated for different lengths of wave A m i, where the index i is an identifier of the wavelength used to carry out the measurements of the absorption rates T45, T-45, Tgo and To. Typically, this step 114 is repeated for at least two and preferably at least five or ten wavelengths Am, different. For example, these wavelengths Am, are uniformly distributed over an interval centered around the predicted value for the wavelength A ma x. Once the desired absorption rates have been measured, during a step 126, the unit 22 determines different production errors introduced by the machine 40. More precisely, during an operation 128, the unit 22 determines the amplitude Ay of the misalignment in the direction Y. For this, the unit 22 calculates the difference E Y then converts, using the conversion table, this difference in an amplitude Ay expressed in nanometers. In addition, the sign of this difference E Y gives the direction of movement, parallel to the direction Y, of the elements 32a, 32c relative to the elements 32b, 32d. During an operation 130, the unit 22 determines the amplitude Δχ of the misalignment in the direction X. The operation 130 is identical to the operation 128 except that the difference E x is used at the place of the gap E Y. Thus, at the end of these operations 128 and 130, the unit 22 determined the amplitude and the direction of the misalignment parallel to the directions X and Y of the fields 68 and 70. In addition to the misalignment between the fields 68, 70, there may also be errors which modify the dimensions of the elements 32. Typically, a dimensioning error is caused by a focusing error of the electron beam in the layer of resin. For example, if the focal point of the electron beam is located below the resin layer, then the dimensions of the elements 32a to 32d are enlarged. Such a dimensioning error can be expressed in the form of a scale factor expressed as a percentage with respect to the dimensions coded in the plane 44. Here, to quantify the dimensioning error, during an operation 132, the unit 22 estimates the value of the wavelength Amax. For this, the unit 22 uses the absorption rates calculated at the different wavelengths Ami. In fact, when the amplitude of the resonance of the surface plasmons is maximum, this also corresponds to a maximum of the absorption rate. To estimate this value of the wavelength Amax, the unit 22 can use only the absorption rates measured with a single one or, on the contrary, with several directions of polarization. Then, still during this operation 132, the unit 22 calculates a difference E D between the estimated value of the wavelength Amax and a predicted value for this wavelength Amax in the absence of misalignment. In fact, a modification of the dimensions of the trough 92 hardly changes the value of the wavelength A ma x. The predicted value of the wavelength Amax is for example predicted by digital simulation or measured experimentally in the absence of misalignment. Then, the difference E D thus calculated is converted into a percentage or an amplitude expressed in nanometers using a conversion table. Steps 128, 130 and 132 can be repeated for other plasmonic antennas located on the same line 66 of separation. In this case, typically, the amplitudes Δχ and Ay are equal to an average of the amplitudes Δχ and Ay obtained from each plasmonic antenna located on line 66. It has been observed that the ratios A x and A Y vary by practically 10% for an amplitude Δχ or Ay of a few nanometers. Thus, by applying the method described here, it is possible to measure a misalignment with a resolution of less than 1 nm or 2 nm. Figure 12 shows another embodiment of the test pattern 12 in which the antenna 100 is replaced by a plasmonic antenna 140. The antenna 140 is identical to the antenna 100 except that the elements 32b and 32d are arranged inside a layer 142 of dielectric material directly deposited on layer 10. The elements 32a and 32c are deposited inside a layer 144 of dielectric material directly deposited on layer 142. In FIG. 12, only elements 32a and 32b have been shown. In this embodiment, the layers 142 and 144 correspond to two distinct etching zones since they are etched one after the other using, for example, the same lithography machine. More specifically, the lithography machine is used a first time to build the etching mask of the layer 142 and then a second time to build the etching mask of the layer 144. In this embodiment, the lithography machine can be the machine 40 or another lithography machine, such as a photolithography machine. Similar to what has been described in the case of the misalignment between the fields 68, 70, there may be a misalignment in the X direction and / or in the Y direction between the layers 142 and 144. This misalignment can be measured in the X and Y directions by using the plasmonic antenna 140 in place of the antenna 100 and, for example, by implementing the same method as that described with reference to FIG. 11. In Figure 12 and in Figures 13 and 14, a vertical plane 146 of separation has been shown. This plan 146 corresponds to the separation plan previously described. In particular, all that has been described in the case of line 66 applies to the orthogonal projections of the elements 32 in the plane of the substrate. In fact, the orthogonal projection of the plane 146 in the plane of the substrate forms the line of separations between the orthogonal projections of the elements 32. FIG. 13 represents a plasmonic antenna 150 capable of replacing the antenna 100 to measure the misalignment in the X and Y directions between the fields 68 and 70. The antenna 150 is identical to the antenna 100 except that: the elements 32a to 32d are replaced, respectively, by elements 152a to 152d, and the layer 10 is replaced by a layer 152 of electrically conductive material. In Figure 13, only the elements 152a and 152b have been shown. In this embodiment, the elements 152a to 152d are identical, respectively to the elements 32a to 32d except that they are made of dielectric material. Typically, the elements 152a to 152d are made of a resin sensitive to the electron beam. Thus, this embodiment avoids a step of etching a layer of electrically conductive material to produce a plasmonic antenna. However, due to its construction, the variation in the absorption rate of the antenna 150 as a function of the dimensions g x and g Y is slower than in the case of the antenna 100 so that the resolution of the measurement method is weaker with antenna 150. 14 shows a plasmonic antenna 160 capable of replacing the antenna 150. The antenna 160 is identical to the antenna 150 except that the elements 152a to 152d are replaced, respectively, by elements 162a to 162d. In FIG. 14, only the elements 162a and 162b are shown. The shape of the elements 162a to 162d is identical to that of the elements 152a to 152d except that these elements 162a to 162d are cavities produced in a layer 164 of dielectric material directly deposited on the layer 154. This embodiment has the same advantages and disadvantages than that of Figure 13. Many other embodiments of a plasmonic antenna comprising at least two distinct elements and capable of being used for the implementation of the method of FIG. 11 are possible. For example, the elements 32a to 32d can be replaced by elements of different shape such as those shown in FIGS. 15 to 17. 15 shows a plasmonic antenna 180 identical to the antenna 60 except that the elements 32a to 32d are replaced, respectively, by elements 182a to 182d. In this embodiment, each element 182a to 182d is formed by the juxtaposition of a triangle and a rectangle or a square. One side of the rectangle forms one side of the triangle. Such an embodiment of a plasmonic antenna 180 is for example described in more detail in the following article: P. Biagoni and Al: "Cross Resonant Optical Antenna", Physical Review Letter, n ° 102, 256801, 26/6 / 2009. FIG. 16 represents a plasmonic antenna 190 identical to the antenna 60 except that the elements 32a to 32d are replaced, respectively, by elements 192a to 192d. The elements 192a to 192d are identical to the elements 32a to 32d except that it is a rectangle or square and no longer a triangle. FIG. 17 represents a plasmonic antenna 200 comprising two concentric elements 202 and 204. Such a plasmonic antenna is described in more detail in the following article: Alexei Smolyaninov and Al: "Broadband metacoaxial nanoantenna for metasurface and sensing applications", Optics Express 22786, Vol. 22, N ° 19, 09/22/2014. This embodiment is particularly suitable for the case where the etching zones between which a misalignment has to be measured are different layers like the layers 142 and 144 of FIG. 12. In this case, for example, the element 202 is produced at the inside of the layer 142 and element 204 is produced inside the layer 144. In this particular embodiment, the plane of separation between the elements 202 and 204 is horizontal and parallel to the plane of the substrate. Other embodiments of a plasmonic antenna can also be obtained by arranging the elements 32a to 32d differently with respect to each other. By way of illustration, FIGS. 18 to 20 represent three different plasmonic antennas each capable of being used in place of the antenna 60. FIG. 18 represents a plasmonic antenna 210 identical to the antenna 60 except that the axes 84 and 86 intersect at a point OO distant from the line 66. Figure 19 shows a plasmonic antenna 220 identical to the antenna 60 except that the elements 32a and 32c are replaced by a single element 32e of identical shape to element 32a. The element 32e is aligned on an axis 222 perpendicular to the line 66 and passing through the point O. FIG. 20 represents a plasmonic antenna 230 identical to the antenna 210 except that the axis 84 is replaced by an axis 232 perpendicular to the line 66. The method for measuring a misalignment with plasmonic antennas such as those represented in FIGS. 15 to 20 is deduced from the explanations given in the case of the method of FIG. 11. Variants of the test pattern 12: The number of plasmonic antennas contained in the test pattern 12 may be different. In a simplified case, the test pattern 12 comprises a single plasmonic antenna or a single plasmonic antenna per separation boundary between two etching zones. The test pattern 12 may include several plasmonic antennas different from each other. For example, these different plasmonic antennas differ from each other by their dimensions. Variants of the plasmonic antenna: Other metals can be used as an electrically conductive material to produce the plasmonic antenna such as, for example, copper, aluminum or cobalt. Metallic alloys can also be used, for example AuK. Metal nitrides can also be used such as for example TiN, ZrN, HfN and their tertiary forms such as TiZrN, ..., etc. The electrically conductive material used to make the plasmonic antennas is not necessarily a metal. For example, it may be a transparent conductive oxide such as indium-tin (ITO) or GZO (“Gallium Doped Zinc Oxide”) or AZO (“Aluminum Dopez Zinc Oxide”). , etc. The conductive material can also be a highly doped semiconductor material or even a two-dimensional material such as graphene or MoF 2 ("Molybdenum disulfide"). The angle β can be different from 90 °. For example, the angle β is between 60 ° and 85 °. The substrate 8 can be made of metal. In this case, the layer 10 is made of silica and its thickness is for example equal to A m / 2 or A m / 4. Variants of the method of measuring the misalignment: In certain special cases, for technical reasons, the amplitude Δχ or the amplitude Ay is systematically equal to 0. In these cases, only the difference E x or the difference E Y is measured. In addition, in the case where the misalignment can only exist in one direction, the plasmonic antenna can also be simplified. For example, if only the amplitude Δχ can take a value different from 0, then the elements 32c and 32d are omitted and the elements 32a and 32b are aligned on an axis perpendicular to the line 66. If on the contrary, the amplitude Δχ is systematically equal to 0, then the pair 80 or the pair 82 can be omitted. When the substrate 8 and the layer 10 are transparent to incident polarized radiation, it is possible to measure the absorption rate from the transmission rate of the incident radiation through the plasmon antenna instead, or in addition , using the reflection rate. To measure the transmission rate of the plasmonic antenna, the sensor 16 must be placed on the side of the substrate 8 opposite the side directly exposed to the beam 6. Alternatively, the beam 6 illuminates the entire surface of the substrate 8 or a region of the substrate 8 containing plasmonic antennas straddling different lines of separation. The measurement of the misalignment takes place as previously described. However, in this case, the measured misalignment is an average of the misalignments existing between the different fields illuminated by the beam 6. In a simplified embodiment, the direction of misalignment is not determined. If it is not necessary to determine the amplitude of the misalignment in two precise orthogonal directions and one simply wishes to obtain a quantity representative of the amplitude of the misalignment without it being necessary to know in which direction occurs misalignment, so the absorption rates measured T 45 , T. 45 , T 90 and T o can be combined differently. In particular, it is not necessary to calculate the ratios A x and A Y previously described. For example, it is possible to determine the amplitude in absolute value of the misalignment, from the relation (T 45 2 + T.45 2 ) 0 ' 5 or (T90 2 + To 2 ) 0 ' 5 . In the latter two cases, the method can be simplified by omitting either the measurements of the absorption rates T 90 and T o , or by omitting the measurement of the absorption rates T ^ and T. 45 . The conversion of the difference E x and / or E y into a nanometer can be omitted. For example, such a conversion is unnecessary for comparing measurements with each other. If necessary, it is possible to correct the measurement of the amplitude Ay using the amplitude Δχ measured. Indeed, the simulations carried out show that the measurement of the amplitude Δχ is more uncorrelated with the amplitude Ay than the reverse. Alternatively, the measurement of a sizing error is omitted. In this case, it is not necessary to repeat step 114 for different wavelengths Ami and operation 132 is omitted. Conversely, the measurement of a dimensioning error can be implemented independently of the measurement of the misalignment. In this case, the method of Figure 11 is simplified. In particular, steps 116, 118 or 120, 122 can be omitted and steps 128 and 130 are omitted. In the case where only a dimensioning error is measured, the antenna 60 does not have to straddle a separation border between two different etching zones. For example, the antenna 60 can in this case be located in the middle of a field. Main advantages of the embodiments described: The difference E there varies mainly as a function of the amplitude of the misalignment in a direction parallel to the line 66. Consequently, this difference makes it possible to measure the amplitude Ay of the misalignment in only one precise direction and that is a matter of fact. or the amplitude Δχ. [00112] Lorsgue the plasmonigue antenna coded in the plane 44 comprises elements 32c and 32d which are deduced, by rotation, from the elements 32a and 32b, the predicted value A YP of the ratio A therein is simple to calculate and to predict. Measuring absorption rates for incident radiation whose directions of polarization are parallel, respectively, to directions X and Y makes it possible to additionally measure the amplitude Δχ. [00114] When orthogonal projection, in the plane of the substrate, of the plasmonigue antenna coded by the plane 44 is symmetrical with respect to line 66 and with respect to a horizontal axis perpendicular to this line 66 and if in addition the axis 84 intersects line 66 with an inclination of 45 °, then the determination of the amplitude of the misalignment is simplified because the predicted values A YP and A XP of the ratios A y and A x are simple to predict. The fact that the elements 32a to 32d are triangles makes it possible to obtain a plasmonigue antenna for laguelle the wavelength A ma x hardly varies depending on the dimensions of the trough 92. Thus, when measuring the absorption rate, it is not necessary to vary the wavelength A m of the incident radiation as a function of the estimated amplitude of the misalignment. In addition, these triangle-shaped elements form bowtie antennas. With such antennas, it is possible to achieve a resolution of one nanometer for measuring the misalignment. Indeed, a modification of nanometer guelgues leads to a significant modification of the absorption rate. In this text, a significant change in the absorption rate is an increase or decrease in the absorption rate greater than or equal to Ο, ΟΙ.Αρ and, preferably, greater than or equal to 0.05.Ap or Ο, Ι .Αρ in response to a variation of one nanometer of the dimension g x or g y compared to the same dimension 5 coded in the plane 44, where Ap is the predicted value of the absorption rate in the absence of misalignment. The use of elements 32 made of conductive material makes it possible to obtain significant variations in the absorption rate and therefore very good resolution. When the elements 32 are made of dielectric material or are cavities hollowed out of a dielectric material, the measurement method is simpler to implement because the steps of etching a layer of conductive material are omitted. Measure the absorption rate at a length A m less than 2000 nm or 700 nm achieves a resolution less than or equal to 2 nm or 1 nm.
权利要求:
Claims (14) [1" id="c-fr-0001] 1. A method of measuring the misalignment between a first and a second etching zone, this method comprising: the supply (110) of a plan containing instructions coding in particular the dimensions, the arrangement and the location of a test pattern to be produced, on a substrate, straddling the first and second zones, - the realization (112) of the target on the substrate by executing the instructions contained in the plan provided and using a lithography machine, then the determination (128, 130) of the amplitude of the misalignment from the observation of the test pattern carried out on the substrate, characterized in that: - the target coded by the instructions contained in the plan comprises at least one plasmonic antenna capable, after having been produced on the substrate, of producing a resonance of the surface plasmons located inside a hollow when it is exposed to incident polarized radiation of wavelength A m so that the plasmonic antenna absorbs at least part of the incident radiation polarized at this wavelength A m , the absorption rate of this plasmonic antenna at the length of wave A m varying as a function of a dimension of the hollow, this plasmonic antenna comprising for this purpose first and second separate elements which each delimit, on a respective side, the hollow so that the dimension of the hollow is fixed by l spacing between these first and second elements, these first and second elements each being located entirely, respectively, of a first and a second side respectively of a separation plane, - during the creation (112) of the target, all the elements of the plasmonic antenna located on the first side of the separation plane are entirely made inside the first zone and all the elements of the plasmonic antenna located on the second side of the separation plane are entirely made inside the second zone, - after the plasmonic antenna has been produced, the method includes: • the measurement (114) of the absorption rate of the plasmonic antenna carried out at the wavelength A m by exposing this plasmonic antenna to incident polarized radiation of wavelength A m and of known intensity, emitted by a radiation source, and by measuring the intensity of the radiation reflected by the plasmonic antenna or transmitted through the plasmonic antenna at this same wavelength A m using a radiation intensity sensor, and • determining (128, 130) the amplitude of the misalignment between the first and second zones from the measured absorption rate and from a predicted value for this absorption rate in the absence of misalignment between the first and second zones. [2" id="c-fr-0002] 2. Method according to claim 1, in which the instructions contained in the plan supplied encode a plasmonic antenna in which: - The first and second elements are aligned on a first alignment axis so that the absorption rate of the plasmonic antenna produced reaches a first maximum when it is exposed to a first incident wavelength radiation At m and in the direction of polarization parallel to this first alignment axis, and - The plasmonic antenna comprises third and fourth distinct elements which limit, each on a respective side, the same hollow or another hollow, these third and fourth elements being entirely located inside, respectively, of the first and second sides and these third and fourth elements being aligned on a second alignment axis which intersects the first alignment axis at a point of intersection, so that the absorption rate of the plasmonic antenna reaches a second maximum when it is exposed to a second incident radiation of wavelength A m and of direction of polarization parallel to this second alignment axis, - the measurement of the absorption rate includes: • a first measurement (116) of an absorption rate Tml of the plasmonic antenna when it is exposed to the first incident radiation, and • a second measurement (118) of an absorption rate Tm2 of the antenna plasmonic when exposed to the second incident radiation, - determining the amplitude of the misalignment includes determining (128) the amplitude of the misalignment between the first and second zones, in a direction parallel to a dividing line, this dividing line being formed by the intersection of the plane of separation and of the plane of the substrate, as a function of the difference between the ratio Tml / Tm2 and a ratio Tpl / Tp2, where Tpi and Tp2 are the predicted values of the absorption rate, in the absence of misalignment, for, respectively, the first and second bars. [3" id="c-fr-0003] 3. Method according to claim 2, in which, in the plane supplied, the orthogonal projection in the plane of the substrate of the pair formed by the third and fourth elements is deduced from the orthogonal projection in this same plane of the pair formed by the first and second elements, by: - a rotation whose center is located on the separation line, combined with - A translation parallel to this separation line, the amplitude of this translation being greater than or equal to zero. [4" id="c-fr-0004] 4. The method of claim 3, wherein the point of intersection is located on the line of separation. [5" id="c-fr-0005] 5. The method of claim 4, wherein - the measurement of the absorption rate includes: • a third measurement (120) of an absorption rate Am3 of the plasmonic antenna carried out when it is exposed to a third incident radiation of wavelength A m and of direction of polarization parallel to the bisector of a first angular sector delimited by the first and second alignment axes, • a fourth measurement (122) of an absorption rate Am4 of the plasmonic antenna carried out when it is exposed to a fourth incident radiation of wavelength A m and in the direction of polarization parallel to the bisector of a second angular sector delimited by the first and second alignment axes, this second angular sector having a side common with the first angular sector, and the determination of the amplitude of the misalignment comprises the determination (130) of the amplitude of the misalignment between the first and second zones in a direction perpendicular to the separation line as a function of the difference between the ratio Tm3 / Tm4 and a Tp3 / Tp4 ratio, where Tp3 and Tp4 are the predicted absorption rate values, in the absence of misalignment, for the third and fourth measurements, respectively. [6" id="c-fr-0006] 6. Method according to claim 5, in which, in the plane provided: - the orthogonal projections in the plane of the substrate of the first and fourth elements are the symmetrics of the orthogonal projections, in the same plane, of the second and third elements with respect to an axis perpendicular to the line of separation, and the orthogonal projections of the first and third elements in the plane of the substrate are the symmetrics of the orthogonal projections of the second and fourth elements with respect to the separation line, and - the orthogonal projection in the plane of the substrate of the first alignment axis intersects the separation line with an angle of 45 °. [7" id="c-fr-0007] 7. Method according to any one of the preceding claims, in which, in the plane provided, each element comprises a point whose apex is situated on a respective side of the hollow, each pair of elements whose apexes are opposite and located on respective opposite sides of said hollow, thereby forming an antenna known as a "bowtie". [8" id="c-fr-0008] 8. Method according to any one of the preceding claims, in which the elements are made of an electrically conductive material and directly deposited on a layer of dielectric material. [9" id="c-fr-0009] 9. Method according to any one of claims 1 to 7, wherein the elements are made of dielectric material and directly deposited on a layer of electrically conductive material or correspond to cavities dug in a layer of dielectric material directly deposited on a layer of electrically conductive material. [10" id="c-fr-0010] 10. Method according to any one of the preceding claims, in which the wavelength A m is less than 2000 nm or 700 nm. [11" id="c-fr-0011] 11. Method according to any one of the preceding claims, in which the first and second zones are: - respectively, a first and a second field, located in the same plane parallel to the plane of the substrate, of an electron beam lithography machine, or - respectively, a first and a second structured layers superimposed one above the other. [12" id="c-fr-0012] 12. Information recording medium (26), characterized in that it includes instructions for implementing a measurement method according to any one of the preceding claims, when these instructions are executed by a microprocessor (24). [13" id="c-fr-0013] 13. Apparatus for measuring the misalignment between a first and a second etching zone for the implementation of a measurement method according to any one of the preceding claims, this apparatus comprising: a source (4) capable of emitting incident polarized radiation of known intensity at a wavelength A m on a plasmonic antenna produced on a substrate, a radiation intensity sensor (16) capable of measuring the intensity of the radiation reflected by the plasmonic antenna or transmitted through the plasmonic antenna at the wavelength A m , and - a microprocessor (24) programmed to determine an absorption rate from the known intensity of the incident radiation and the measured intensity of the reflected or transmitted radiation, characterized in that the microprocessor (24) is programmed to determine l amplitude of the misalignment between the first and second zones from the measured absorption rate and from a predicted value of this absorption rate in the absence of misalignment between the first and second zones. [14" id="c-fr-0014] 14. Plan (44) of a test pattern for the implementation of a measurement method according to any one of claims 1 to 11, this plan containing instructions specific to an electron beam lithography machine which comprises at least first and second distinct fields, said instructions coding in particular the dimensions, arrangement and location in the first and second fields of at least one plasmonic antenna to be produced on a substrate, this plasmonic antenna being suitable, after having been carried out on the substrate, to produce a resonance of the surface plasmons located inside a hollow when it is exposed to incident polarized radiation of wavelength A m so that the plasmonic antenna absorbs at least part of the incident radiation polarized at this wavelength A m , the absorption rate of this plasmonic antenna at the wavelength A m varying according to a dimension of the hollow, this a Plasmonic antenna comprising for this purpose first and second distinct elements which each delimit, on a respective side, the hollow so that the dimension of the hollow is fixed by the spacing between these first and second elements, these first and second elements being each located entirely, respectively, on a respective first and second side of a separation plane, characterized in that the dimensions, arrangement and coded location of the plasmonic antenna are such that, all the elements of this plasmonic antenna situated on the first side of the separation plane are entirely inside the first field and all the elements of the plasmonic antenna situated on the second side of the separation plane are entirely inside the second field.
类似技术:
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同族专利:
公开号 | 公开日 US20180233456A1|2018-08-16| EP3355118B1|2019-10-23| EP3355118A1|2018-08-01| FR3062516B1|2019-04-12| US10211162B2|2019-02-19|
引用文献:
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申请号 | 申请日 | 专利标题 FR1750759A|FR3062516B1|2017-01-30|2017-01-30|METHOD OF MEASURING THE DEALIGNMENT BETWEEN A FIRST AND A SECOND GRATING AREA| FR1750759|2017-01-30|FR1750759A| FR3062516B1|2017-01-30|2017-01-30|METHOD OF MEASURING THE DEALIGNMENT BETWEEN A FIRST AND A SECOND GRATING AREA| US15/879,577| US10211162B2|2017-01-30|2018-01-25|Method for determining misalignment between a first and a second etching zones| EP18153558.4A| EP3355118B1|2017-01-30|2018-01-26|Method for measuring the misalignment between first and second etching areas| 相关专利
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