Method and control apparatus for manufacturing the optical system of a lithography apparatus

Abstract

The present invention relates to a method for manufacturing an optical system (100) of a lithographic apparatus (1), the optical system (100) comprising an optical component (102) having an optically effective surface (106) and a substrate (104). In the method, a) for the substrates (104', 204a, 204b, 204c) of one or more optical components (102, 202a, 202b, 202c), the zero-crossing temperature (ZCT', ZCT a 、ZCT b 、ZCT c ) of the coefficient of thermal expansion (ρ') of the substrate (104', 204a, 204b, 204c) as a function of the location (r) of the substrate (104', 204a, 204b, 204c), and the normalized distribution functions (g, h a 、h b 、h c ) are each provided (step S2); b) for each of the provided distribution functions (g, h a 、h b 、h c ) and a plurality of mutually different predetermined average zero-crossing temperatures (M j ), the imaging error (F i ) of the optical system (102) is calculated by computer implementation respectively (step S3); c) among the plurality of average zero-crossing temperatures (M j ), at least one selected average zero-crossing temperature (M i ) for the substrate (104) of the optical component (102) to be manufactured is specified as the one for which the calculated imaging error (F aw ) is less than a predetermined threshold value (SW) (step S4).

Description

[Technical Field]

[0001] The present invention relates to a method and control device for manufacturing the optical system of a lithography apparatus.

[0002] The entire contents of the priority application, German Patent Application No. 10 2023 205 439.6, are incorporated by reference. [Background technology]

[0003] Microlithography is used, for example, in the manufacturing of microstructured components such as integrated circuits. The microlithography process is performed using a lithography apparatus equipped with an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, which is coated with a photosensitive layer (photoresist) and placed on the image plane of the projection system, thereby transferring the mask structure to the photosensitive coating of the substrate.

[0004] Due to the desire for further miniaturization of structures in integrated circuit manufacturing, EUV lithography equipment that uses light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm, is currently under development. Since most materials absorb light of this wavelength, such EUV lithography equipment needs to use reflective optical units, i.e., mirrors, instead of refractive optical units, i.e., lens elements, that have been used until now.

[0005] The problem that arises in this process is that the mirror heats up as a result of absorbing the radiation emitted by the EUV light source. This can lead to thermal deformation of the mirror. Furthermore, the optical coating of the mirror may also deteriorate as a result of the temperature rise. Both thermal deformation of the mirror and damage to its optical coating can adversely affect the imaging characteristics of the mirror.

[0006] The imaging quality of the projection system in an EUV lithography apparatus largely depends on the quality of the mirror material. To reduce imaging errors caused by mirror heating, materials with a very low coefficient of thermal expansion are used for the mirror substrate. In particular, at the so-called zero-crossing temperature of the mirror material's coefficient of thermal expansion, the deformation of the mirror material in response to temperature is minimal and / or zero. The average zero-crossing temperature of the mirror material and the variation in zero-crossing temperature within the mirror substrate volume directly affect the imaging errors caused by mirror heating. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Against this backdrop, the object of the present invention is to provide an improved method and an improved apparatus for manufacturing the optical system of a lithography apparatus. [Means for solving the problem]

[0008] Therefore, a method for manufacturing the optical system of a lithography apparatus is proposed. The optical system comprises optical components having an optically effective surface and a substrate. Furthermore, this method, a) For one or more optical component substrates, the step of providing a normalized distribution function of the zero-crossing temperature of the thermal expansion coefficient of the substrate as a function of the substrate location, b) A step of calculating the imaging error of the optical system for each provided distribution function and a plurality of mutually different predetermined mean zero-crossing temperatures using a computer implementation, c) A step of identifying at least one selected mean zero-crossing temperature for the substrate of the optical component to be manufactured, such that the calculated imaging error among multiple mean zero-crossing temperatures is less than a predetermined threshold. Includes.

[0009] The average zero-crossing temperature of the thermal expansion coefficient of the substrate material for optical components can be set during the manufacturing of the substrate. Typically, the average zero-crossing temperature of the substrate material is set according to the expected operating temperature of the substrate.

[0010] The substrate material for optical components typically has heterogeneity, which leads to a non-uniform distribution of zero-crossing temperatures across the substrate volume. This is true even for high-performance substrate materials. This non-uniform distribution of zero-crossing temperatures affects the imaging performance of the optical component, and therefore the optical system containing it.

[0011] The applicant has found that, for a given (e.g., normalized) distribution of zero-crossing temperatures across the substrate volume of an optical component, the imaging error of the optical system depends on the mean zero-crossing temperature of the substrate. Furthermore, the mean zero-crossing temperature of the substrate can be adapted even after the substrate is manufactured (and therefore even if the zero-crossing temperature profile is calculated during manufacturing), for example, by heat treatment.

[0012] The method proposed herein makes it possible to identify a suitable and / or optimal mean zero-crossing temperature for an optical component substrate with respect to imaging quality for one or more predetermined normalized distributions of zero-crossing temperatures over the substrate volume.

[0013] The zero-crossing temperature distribution function of the thermal expansion coefficient of each substrate as a function of the substrate's location is, for example, the three-dimensional distribution function of the zero-crossing temperature across a three-dimensional substrate body.

[0014] The normalized distribution function of the zero-crossing temperature for each substrate is, for example, the distribution function of the zero-crossing temperature normalized based on the value of the distribution function (e.g., the mean value).

[0015] In a downstream step, the substrate of the optical component to be manufactured can subsequently be processed such that its mean zero-crossing temperature corresponds to (i.e., is the same as) the preferred and / or optimal mean zero-crossing temperature identified by this method. Having the substrate thus possess a preferred and / or optimal mean zero-crossing temperature reduces or avoids thermal deformation and associated degradation of imaging quality caused by heat input to the mirror (e.g., irradiation with EUV light).

[0016] The coefficient of thermal expansion indicates the change in the geometric shape and dimensions of a material in the event of a temperature change. For example, the coefficient of thermal expansion is the linear thermal expansion coefficient, which shows the change in material length as a function of temperature change. The coefficient of thermal expansion itself is temperature-dependent, i.e., a temperature-dependent function.

[0017] The coefficient of thermal expansion exhibits zero temperature dependence at its zero-crossing temperature (ZCT), meaning that in the vicinity of this temperature, thermal expansion of the mirror substrate material is negligible or nonexistent even with temperature changes.

[0018] The substrate material for the optical component being manufactured is particularly low in thermal expansion. For example, the thermal expansion coefficient is within the range of ±20 ppb / K (parts pervilions / Kelvin), ±15 ppb / K, ±10 ppb / K, and / or ±15 ppb / K at the desired operating temperature. However, the thermal expansion coefficient can also be within a different range. With such ultra-low thermal expansion materials (e.g., substrate materials sold by Corning, Inc. under the name "ULE," meaning "ultra-low expansion"), changes in geometric shape and dimensions due to temperature changes are minimal.

[0019] Examples of substrate materials for manufactured optical components include glass materials composed of TiO2-SiO2, where an ultra-low coefficient of thermal expansion can be achieved by varying the concentration of TiO2. Yet another example is a Li2O-Al2O3-SiO2 glass ceramic with a crystalline phase (sold by Schott under the name "Zerodur"), where an ultra-low coefficient of thermal expansion is achieved by nanocrystals uniformly dispersed in the residual glass phase.

[0020] For example, steps a) and / or c) are also performed by a computer implementation. For example, steps a), b), and / or c) are performed by a control device, such as the control devices of one or more computers.

[0021] In step a), one or more normalized distribution functions of the zero-crossing temperatures are provided, for example, by a control unit and also transmitted, for example, to a first calculation unit of the control unit.

[0022] In particular, in step a), a normalized distribution function of zero-crossing temperature as a function of location is provided for each of one or more optical components.

[0023] In the case of multiple normalized distribution functions, the multiple normalized distribution functions differ from one another in the form and magnitude of the variation in zero-crossing temperature as a function of location. In particular, each of the multiple distribution functions is different from all the others. As a result of normalization, the multiple distribution functions have the same mean zero-crossing temperature (e.g., the mean zero-crossing temperature of zero).

[0024] In step b), the imaging error of the optical system is calculated for each combination of one or more provided normalized distribution functions and a set of predetermined mean zero-crossing temperatures. For example, if two different normalized distribution functions and three different mean zero-crossing temperature values ​​are provided, there are six possible combinations. Therefore, based on these six different combinations, six different error values ​​for the imaging error of the optical system are calculated.

[0025] Therefore, in step b), multiple error values ​​F of the imaging process of the optical system are associated with the normalized distribution function or group of normalized distribution functions and multiple mean zero-crossing temperature values. i This is calculated.

[0026] In step c), the calculated error value F i This is then compared to a predetermined threshold. In particular, the error value F, which is less than the average zero-crossing temperature threshold, is compared. i The mean zero-crossing temperature associated with this is identified as one or more selected mean zero-crossing temperatures.

[0027] In step c), if two or more selected mean zero-crossing temperatures are identified at which the calculated imaging error is less than a predetermined threshold, the substrate of the optical component to be manufactured may be set to each of the identified selected mean zero-crossing temperatures. For example, the substrate may be heat-treated to set its mean zero-crossing temperature based on each of the identified selected mean zero-crossing temperatures.

[0028] If, in step c), a selected mean zero-crossing temperature is not identified at which the calculated imaging error falls below a predetermined threshold, the substrate (for example, the substrates of some representative examples of optical components described below) is not suitable for manufacturing optical components.

[0029] For example, if the calculated imaging errors include the focusing error of the imaging process (i.e., the actual focus deviation of the optical system from the target focus), the thresholds are, for example, 15 nm or less, 10 nm or less, and / or 5 nm or less.

[0030] For example, if the calculated imaging errors include the overlay error of the imaging process (i.e., the deviation of the actual position of the object imaged onto the image plane of the optical system from the target position), the thresholds are, for example, 3 nm or less, 1 nm or less, and / or 0.5 nm or less.

[0031] For example, if each calculated imaging error includes the spherical wavefront error of the imaging process (i.e., the deviation of the actual wavefront of the beam guided through the optical system from the ideal spherical wave), the thresholds are, for example, 200 pm or less, 100 pm or less, and / or 50 pm or less (RMS deviation).

[0032] According to one embodiment, in step c), the optimal average zero-crossing temperature of the substrate of the optical component to be manufactured is identified as the temperature at which the calculated imaging error is minimized among a plurality of average zero-crossing temperatures.

[0033] As a result, the average zero-crossing temperature of the substrate of the optical component to be manufactured can be determined even more favorably.

[0034] For example, a plurality of selected average zero-crossing temperatures can be first identified. Thereafter, among the plurality of selected average zero-crossing temperatures, the one with the smallest calculated imaging error can be identified as the optimal average zero-crossing temperature.

[0035] In this case, in step c), for example, a plurality of error values F of the imaging process of the optical system calculated in step b) i The minimum value of is the final error F E Is calculated as. F E = min(F i ) (where i = 1 to n)

[0036] In the above formula, n represents the number of possible combinations of the provided normalized distribution function(s) of zero-crossing temperature and a predetermined average zero-crossing temperature. Therefore, n is a natural number greater than 1. Further, i represents an index from 1 to n. Further, F i Is the imaging error calculated by simulation for the i-th combination among the possible combinations of the provided distribution function(s) and the average zero-crossing temperature. F E Is the minimum value of the n imaging errors F calculated by simulation i Indicates.

[0037] The average zero-crossing temperature related to this minimum value F E Is identified as the optimal average zero-crossing temperature of the substrate of the optical component to be manufactured.

[0038] Therefore, in the above example where two mutually different normalized distribution functions and three mutually different average zero-crossing temperature values are provided, six possible combinations are obtained, and n = 6. Therefore, the six different values F of the imaging error F of the optical system i Of iThis is calculated based on six different combinations, and the minimum value is determined as the final error. F E =min(F1, F2, F3, F4, F5, F6) (where n=6)

[0039] In yet another embodiment, in step a), a plurality of normalized distribution functions of zero-crossing temperatures are provided for corresponding substrates of a plurality of representative examples of optical components.

[0040] Therefore, if the distribution function of the zero-crossing temperature of the substrate of the optical component to be manufactured is unknown, the preferred and / or optimal mean zero-crossing temperature of the substrate of the optical component to be manufactured can be determined based on several representative distribution functions of the zero-crossing temperature.

[0041] Several representative examples of optical components are, for example, several physically realized optical components, each comprising a substrate having a corresponding distribution function of zero-crossing temperature.

[0042] In yet another embodiment, in step a), a normalized distribution function of zero-crossing temperatures is provided for the substrate of the optical component to be manufactured.

[0043] By providing a zero-crossing temperature distribution function for the substrate of the optical component being manufactured, the preferred and / or optimal mean zero-crossing temperature for this substrate can be determined with even greater precision.

[0044] If this substrate is subsequently post-processed in a downstream step, and its mean zero-crossing temperature corresponds to at least one selected and / or optimal mean zero-crossing temperature identified by this method, the imaging error of the optical system as a result of heat input to the optical component under manufacture can be further reduced.

[0045] In yet another embodiment, the multiple representative examples are physically realized optical components, and multiple distribution functions of the zero-crossing temperatures of the corresponding substrates of the multiple representative examples are measured.

[0046] This allows the measurement results of the zero-crossing temperature distribution function measurements for multiple representative examples to be applied in place of the unknown zero-crossing temperature distribution function of the component being manufactured.

[0047] In yet another embodiment, the substrate for the optical component to be manufactured is physically prepared, and the zero-crossing temperature distribution function of the substrate for the optical component to be manufactured is measured.

[0048] For example, the substrate for the optical component to be manufactured is manufactured before step a). For example, the substrate for the optical component to be manufactured is manufactured using the zero-crossing temperature distribution function and the initial mean zero-crossing temperature. Furthermore, in step c), at least one selection (i.e., preferred) and / or optimal mean zero-crossing temperature of the substrate is identified. Furthermore, it is also possible to calculate the offset as, for example, the difference between the initial mean zero-crossing temperature and at least one selection and / or optimal mean zero-crossing temperature.

[0049] According to yet another embodiment, this method A step of heat-treating the substrate of the optical component to be manufactured to set the mean zero-crossing temperature of the substrate, based on at least one identified selected mean zero-crossing temperature and / or identified optimal mean zero-crossing temperature. Includes.

[0050] Therefore, the substrate of the optical component to be manufactured can be post-processed so that its mean zero-crossing temperature corresponds to (is the same as) at least one selected and / or optimal mean zero-crossing temperature identified by this method. In particular, the substrate can be post-processed so that its initial mean zero-crossing temperature, set during the manufacturing of the substrate, is corrected by a calculated offset.

[0051] For example, heat treatment includes so-called annealing of the substrate.

[0052] In yet another embodiment, the step of calculating the imaging error of the optical system for each provided distribution function and a plurality of mutually different predetermined mean zero-crossing temperatures is as follows: The steps include calculating multiple distinct individual errors with respect to different error types of optical systems, The steps include: calculating the imaging error of the optical system based on multiple calculated individual errors; Includes.

[0053] For example, multiple relative individual errors are calculated for each of the different error types of the optical system. Furthermore, for example, each imaging error of the optical system is calculated as the maximum, mean, median, and / or quantile of the multiple calculated relative individual errors.

[0054] For example, in step c), at least one selected mean zero-crossing temperature can also be identified as the mean zero-crossing temperature among a plurality of mean zero-crossing temperatures in which each of the plurality of calculated individual errors is less than a predetermined individual threshold corresponding to the corresponding error type.

[0055] In particular, multiple mutually distinct individual errors have error values ​​for different types of individual errors.

[0056] By considering the individual errors of different types in the imaging process of the optical system, the final error of the imaging process can be calculated more accurately for each distribution function and offset.

[0057] Furthermore, in some cases, for each provided distribution function and considered mean zero-crossing temperature, the maximum, mean, median, and / or quantile values ​​of multiple calculated individual errors are calculated, and the final error of the optical system's imaging process is then taken as this maximum, mean, median, and / or quantile value. This allows for a more appropriate consideration of large error contributions. For example, the maximum value of multiple calculated individual errors is calculated based on the following formula: F i =bloom(f k (However, i=1 to n, k=1 to m)

[0058] In the above formula, F for the case i=1 to n i These are the n errors F calculated by simulation in step b) for n possible combinations of the provided distribution function (one or more) and the mean zero-crossing temperature. i This represents the case of f for k=1 to m. k This represents m individual errors for a specific distribution function and a specific mean zero-crossing temperature. In this case, k is an index from 1 to m, where m is a natural number greater than 1, and f represents mutually distinct individual errors. k It represents the number.

[0059] In yet another embodiment, the multiple calculated individual errors are weighted according to predetermined weights.

[0060] As a result, individual errors can be weighted according to the planned use of the optical component being manufactured and the optical system equipped with that component. This allows the error contribution to performance parameters that are particularly important for the specific application of the optical component / optical system to be kept as small as desired.

[0061] For example, the maximum value of multiple weighted individual errors is calculated based on the following formula: F i =bloom(f k / W k (However, i=1 to n, k=1 to m)

[0062] In the above formula, W k This is m individual errors f k Represents the m weights applied to the weighting. Weight W k This is a positive real number greater than 0.

[0063] In yet another embodiment, multiple distinct individual errors are calculated with respect to different error types and different setting parameters for the illumination of the optical component being manufactured in the optical system.

[0064] As a result, when calculating individual errors using computer implementation, different setting parameters for the planned illumination of the optical component being manufactured are taken into consideration. Therefore, different types of individual errors can be calculated for each simulated illumination scenario of the optical component being manufactured.

[0065] For example, different setting parameters for the planned illumination of an optical component being manufactured include the radiant intensity of the working light (e.g., EUV light) emitted to the optical component.

[0066] For example, different illumination setting parameters may also include the pattern in which the operating light is radiated onto the optical component (e.g., X-dipole, Y-dipole, ring, DRAM profile, stripe pattern, etc.). In other words, illumination setting parameters may include a heat flux distribution with fast poles resulting from the operating light radiated onto the optical component being manufactured in a specific pattern.

[0067] For example, different illumination setting parameters may also include the structure of the mask (e.g., lithography mask) that is imaged onto the wafer at the image plane of the optical system using the optical component being manufactured.

[0068] For example, F i It can be calculated as follows: F i =bloom(f k / W l (where i=1 to n, k=1 to m, l=1 to q)

[0069] In the above formula, W l f is the individual error k This represents the weight applied to the weighting. Weight W ll is a positive real number greater than 0. Furthermore, l is an index from 1 to q, where q is a multiple weight W. l It represents the number.

[0070] According to yet another embodiment, multiple calculated individual errors relating to mutually different error types are: The deviation of the optical system's actual focal point from the target focal point, The deviation of the actual position of an object imaged onto the image plane of an optical system from the target position of the imaged object. Image displacement of the image formed on the image plane of the optical system using an optical system, and / or The deviation of the actual wavefront from the target wavefront that is imaged at the image plane of the optical system. Includes.

[0071] Individual errors are calculated, for example, based on simulations of the imaging process using the optical system being manufactured, particularly through computer implementation.

[0072] For example, image displacement is the displacement of the image relative to its target position. For example, image displacement is the displacement of the image in a direction parallel to the image plane of the optical system.

[0073] The image formed on the image plane of an optical system is, for example, the image formed on a wafer in a lithography apparatus.

[0074] The actual wavefront is, in particular, the wavefront of the beam guided through the optical system. For example, the actual wavefront is the wavefront of the beam at the location of the image plane.

[0075] For example, the target wavefront is a spherical wave. The deviation of the actual wavefront from the target wavefront is, for example, the deviation from an ideal spherical wave.

[0076] In yet another embodiment, the deviation of the actual wavefront from the target wavefront includes the inclination of the wavefront, the displacement of the wavefront, the astigmatism of the wavefront, the coma aberration of the wavefront, the higher-order (n-th order) aberration of the wavefront, and / or the spherical aberration of the wavefront.

[0077] For example, the inclination of a wavefront is its tilt with respect to an axis (e.g., the x-axis and / or y-axis) that is parallel to the image plane of the optical system.

[0078] For example, the displacement of a wavefront is a displacement parallel to the image plane of the optical system (e.g., in the x-direction and / or y-direction).

[0079] Higher-order (n-th order) aberrations include, for example, wavefront trefoil aberration, quadrafoil aberration, pentafoil aberration, and hexafoil aberration.

[0080] In yet another embodiment, the deviation of the actual wavefront from the target wavefront is quantified in the form of a Zernike polynomial.

[0081] Using Zernike polynomials, it is possible to mathematically express the deviation of the actual wavefront from the ideal wavefront by summing the polynomials. Zernike polynomials are expressed using polar coordinates in a normalized unit circle. Mathematically, each Zernike polynomial in a circular region is characterized by polar coordinates having a power series in the radial direction ρ and a series expansion similar to a Fourier series in the direction of the angle θ. General form Z n,±m In this equation, n represents the degree of the radial polynomial, and m corresponds to the frequency of the angle θ per revolution. The polynomials for n being even and m=0 are rotationally symmetric, while all others depend on the angle.

[0082] For example, Zernike polynomial Z 1,±1 This describes the slope (+1 in the x direction, -1 in the y direction), and Zernike polynomial Z 2,0 This describes the defocus (spherical error), and the Zernike polynomial Z 2,±2 This describes astigmatism and Zernike polynomial Z 3,±1 This describes coma aberration, and Zernike polynomial Z 3,±3 This describes the Trefoil aberration and the Zernike polynomial Z 4,0 This describes spherical aberration, and Zernike polynomial Z 4,±2 This describes fourth-order astigmatism.

[0083] In yet another embodiment, the optical component is a mirror, and the substrate is a mirror substrate.

[0084] In this case, the optically effective surface is specifically the reflective surface.

[0085] In yet another embodiment, the optical system is the projection system of a lithography apparatus.

[0086] However, the optical system can also be the illumination system of a lithography apparatus (projection exposure apparatus). The lithography apparatus could be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and refers to the wavelength of the operating light from 0.1 nm to 30 nm. The projection exposure apparatus could also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and refers to the wavelength of the operating light from 30 nm to 250 nm.

[0087] In yet another embodiment, a computer program product is proposed that, when a program is executed by at least one computer, includes instructions causing at least one computer to perform the above-described method (for example, one or more embodiments of the above-described method).

[0088] For example, computer program products, such as computer program means, may be provided or supplied as storage media such as memory cards, USB sticks, CD-ROMs, DVDs, or as files downloadable from a server on a network. This can be done, for example, by transferring a suitable file containing a computer program product or computer program means over a wireless communication network.

[0089] In yet another embodiment, a control device for manufacturing the optical system of a lithography apparatus is proposed. The optical system comprises an optical component having an optically effective surface and a substrate. Furthermore, the control device, A providing unit that provides, for one or more optical component substrates, a normalized distribution function of the zero-crossing temperature of the thermal expansion coefficient of the substrate as a function of the substrate location, A first calculation unit calculates the imaging error of the optical system for each provided distribution function and multiple mutually distinct predetermined mean zero-crossing temperatures using computer implementation. A second calculation unit identifies a selected mean zero-crossing temperature for the substrate of the optical component to be manufactured, which is determined by selecting from multiple mean zero-crossing temperatures such that the calculated imaging error is below a predetermined threshold. It is equipped with.

[0090] The singular form or "one" in this context should not necessarily be understood as strictly limited to a single element. Instead, there could be multiple elements, such as two, three, or more. Any other numbers used here should not be understood as strictly limited to the number of elements listed. Rather, unless otherwise specified, the numerical values ​​can be increased or decreased.

[0091] The embodiments and features described in this method can be applied mutatis mutandis to the proposed control device, for example, to the extent that it can be implemented by computer, and vice versa.

[0092] Further possible embodiments of the present invention include combinations of features or embodiments described below with respect to the above-described or exemplary embodiments that are not explicitly mentioned. Those skilled in the art will also add individual aspects as improvements or supplements to each basic form of the present invention.

[0093] Further advantageous configurations and aspects of the present invention are the subject of the dependent claims and the exemplary embodiments of the present invention described below. The present invention will be described in more detail below based on preferred embodiments with reference to the accompanying drawings. [Brief explanation of the drawing]

[0094] [Figure 1] A schematic meridian cross-section of a projection exposure apparatus for EUV projection lithography according to one embodiment is shown. [Figure 2] Figure 1 shows the optical system of a projection exposure apparatus according to one embodiment, equipped with optical components. [Figure 3] A flowchart of a method for manufacturing an optical system according to one embodiment is shown. [Figure 4] Figure 2 shows the substrate of the optical component according to one embodiment. [Figure 5] The zero-crossing temperature distribution function of the substrate in Figure 4 according to one embodiment is shown. [Figure 6] Three representative examples of optical components according to one embodiment are shown. [Figure 7] The zero-crossing temperature distribution function of the substrate of the optical component shown in Figure 6 according to one embodiment is shown. [Figure 8] This section describes the individual errors in the imaging process of the optical system shown in Figure 2, calculated by computer implementation according to one embodiment. [Figure 9] This section describes yet another individual error in the imaging process of the optical system shown in Figure 2, calculated by computer implementation according to one embodiment. [Figure 10] The illumination settings for the optical component shown in Figure 2 according to one embodiment will be described. [Figure 11] This section describes the weighting used when calculating the imaging error of the optical system shown in Figure 2 according to one embodiment, using a computer implementation. [Figure 11A] Figure 2 shows the imaging error of the optical system compared to the threshold. [Figure 12] A control device is shown that performs the method of Figure 3 according to one embodiment. [Modes for carrying out the invention]

[0095] Unless otherwise specified, identical or functionally identical elements are given the same reference numeral in the figures. Furthermore, it should be noted that the figures are not necessarily drawn to a fixed scale.

[0096] Figure 1 shows one embodiment of a projection exposure apparatus 1 (lithography apparatus), particularly an EUV lithography apparatus. One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to a light source or radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 on the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0097] A reticle 7 positioned in the object field of view 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive 9.

[0098] Figure 1 shows a Cartesian coordinate system with x, y, and z directions for illustrative purposes. The x direction extends perpendicular to the plane of the figure. The y direction extends horizontally, and the z direction extends vertically. In Figure 1, the scanning direction extends along the y direction. The z direction extends perpendicular to the object plane 6.

[0099] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to form an image of the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object surface 6. Alternatively, angles other than 0° are possible between the object surface 6 and the image plane 12.

[0100] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the image field 11 region of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, particularly in the y-direction, by a wafer displacement drive 15. Firstly, the displacement of the reticle 7 by the reticle displacement drive 9 and secondly, the displacement of the wafer 13 by the wafer displacement drive 15 can be synchronized with each other.

[0101] Light source 3 is an EUV radiation source. Light source 3 specifically emits EUV radiation 16, which will be referred to below as the radiation used, illumination radiation, or illumination light. The radiation used 16 has wavelengths in the range of 5 nm to 30 nm. Light source 3 may be a plasma source, such as an LPP (Laser-Generated Plasma) source or a DPP (Gas Discharge Plasma) source. It may also be a synchrotron-based radiation source. Light source 3 may be an FEL (Free Electron Laser).

[0102] Illumination radiation 16 emitted from light source 3 is focused by collector 17. Collector 17 may be a collector having one or more elliptical and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of collector 17 at an oblique angle (GI), i.e., at an incident angle greater than 45°, or at a normal angle (NI), i.e., at an incident angle less than 45°. Collector 17 may be structured and / or coated to first optimize reflectivity for the radiation used, and second to suppress external light.

[0103] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 may represent the separation between the radiation source module, which includes the light source 3 and the collector 17, and the illumination optical unit 4.

[0104] The illumination optical unit 4 includes a deflection mirror 19 and a first facet mirror 20 positioned downstream of it in the beam path. The deflection mirror 19 may be a planar deflection mirror or a mirror having a beam influence effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 may be embodied as a spectral filter that separates the wavelength of light used by the illumination radiation 16 from external light of wavelengths deviating from it. When the first facet mirror 20 is positioned on the plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as a field of view, it is also referred to as a field of view facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which may also be referred to as field of view facets. Only some of these first facets 21 are shown as examples in Figure 1.

[0105] The first facet 21 can be embodied as a macroscopic facet, particularly as a rectangular facet, or as a facet having an arc-shaped or partial-circular edge contour. The first facet 21 can be embodied as a planar facet, or as a facet that is curved in a convex or concave manner.

[0106] For example, as is known from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of multiple individual mirrors, particularly multiple micromirrors. The first facet mirror 20 can be embodied in particular as a micro-electromechanical system (MEMS system). For further details, please refer to German Patent Application Publication No. 10 2008 009 600.

[0107] The illumination radiation 16 travels horizontally, i.e., in the y-direction y, between the collector 17 and the deflection mirror 19.

[0108] In the beam path of the illumination optical unit 4, a second facet mirror 22 is positioned downstream of the first facet mirror 20. When the second facet mirror 22 is positioned on the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be positioned away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from U.S. Patent Application Publication No. 2006 / 0132747, European Patent No. 1614008, and U.S. Patent No. 6,573,978.

[0109] The second facet mirror 22 includes multiple second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0110] Similarly, the second facet 23 may be a macroscopic facet having, for example, a circular, rectangular, or hexagonal boundary, or a facet composed of micromirrors. In this regard, see German Patent Application Publication No. 10 2008 009 600.

[0111] The second facet 23 may have a planar reflective surface or a curved reflective surface that is convex or concave.

[0112] Therefore, the illumination optical unit 4 forms a dual-facet system. This basic principle is also called a fly-eye condenser (fly-eye integrator).

[0113] It may be advantageous not to position the second facet mirror 22 precisely on a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, as described in German Patent Application Publication No. 10 2017 220 586, the second facet mirror 22 may be positioned at an angle to the pupil plane of the projection optical unit 10.

[0114] The individual first facets 21 are imaged into the object field of view 5 using the second facet mirror 22. The second facet mirror 22 is the last beam shaping mirror or, in fact, the final mirror for the illumination radiation 16 in the beam path upstream of the object field of view 5.

[0115] In yet another embodiment of the illumination optical unit 4 (not shown), a transfer optical unit, which contributes particularly to the imaging of the first facet 21 onto the object field of view 5, may be positioned in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit may have strictly one mirror, or two or more mirrors positioned one behind the other in the beam path of the illumination optical unit 4. The transfer optical unit may, in particular, include one or two mirrors for perpendicular incidence (NI mirrors) and / or one or two mirrors for oblique incidence (GI mirrors).

[0116] In the embodiment shown in Figure 1, the illumination optical unit 4 has exactly three mirrors downstream of the collector 17, specifically a deflection mirror 19, a first facet mirror 20, and a second facet mirror 22.

[0117] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 can be omitted, so the illumination optical unit 4 may have exactly two mirrors downstream of the collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0118] The imaging of the first facet 21 onto the object surface 6 by the second facet 23, or by using the second facet 23 and the transfer optics unit, is in most cases only an approximate image.

[0119] The projection optical unit 10 includes a plurality of mirrors Mi, which are numbered sequentially according to their arrangement in the beam path of the projection exposure apparatus 1.

[0120] In the example shown in Figure 1, the projection optical unit 10 includes six mirrors M1 to M6. It can also be replaced with four, eight, ten, twelve, or different numbers of mirrors Mi. The projection optical unit 10 is a double-shielded optical unit. The second-to-last mirror M5 and the last mirror M6 each have apertures through which illumination radiation 16 passes. The projection optical unit 10 has an image-side numerical aperture greater than 0.5 and may be greater than 0.6, for example, 0.7 or 0.75.

[0121] The reflective surface of mirror Mi can be realized as a free-form surface without a rotational symmetry axis. Alternatively, the reflective surface of mirror Mi can be designed as an aspherical surface with exactly one rotational symmetry axis of the reflective surface shape. Similar to the mirrors of illumination optical unit 4, mirror Mi can have a highly reflective coating for illumination radiation 16. These coatings can be designed in particular as multilayer coatings having alternating layers of molybdenum and silicon.

[0122] The projection optical unit 10 has a large object-image offset in the y-direction y between the y-coordinate of the center of the object field of view 5 and the y-coordinate of the center of the image field of view 11. This object-image offset in the y-direction y may be approximately the same magnitude as the z-distance between the object plane 6 and the image plane 12.

[0123] The projection optics unit 10 can be embodied in a particularly anamorphic manner. In particular, it has different imaging scales βx and βy in the x-direction and y-direction. The two imaging scales βx and βy of the projection optics unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign for the imaging scale β means imaging with image inversion.

[0124] As a result, the projection optical unit 10 is reduced in size in the x-direction, i.e., perpendicular to the scanning direction, at a ratio of 4:1.

[0125] The projection optical unit 10 reduces its size in the y-direction, i.e., in the scanning direction, at a ratio of 8:1.

[0126] Other imaging scales are also possible. Imaging scales with the same sign and absolute value in the x-direction x and y-direction y, for example, an absolute value of 0.125 or 0.25, are also possible.

[0127] The number of intermediate image planes in the x-direction x and y-direction y in the beam path between the object field of view 5 and the image field of view 11 may be the same or may differ depending on the design of the projection optical unit 10. An example of a projection optical unit with a different number of such intermediate images in the x-direction x and y-direction y is known from U.S. Patent Application Publication No. 2018 / 0074303.

[0128] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel that illuminates the object field of view 5. In particular, this allows for illumination according to Köhler's principle. The distant field of view is decomposed into multiple object fields of view 5 using the first facets 21. The first facets 21 generate multiple intermediate-focus images in the second facets 23 assigned to each of them.

[0129] The assigned second facet 23 causes the first facet 21 to be imaged onto the reticle 7 as an overlapping image for the purpose of illuminating the object field of view 5. The illumination of the object field of view 5 is particularly uniform. Preferably, the uniformity error is less than 2%. Field of view uniformity can be achieved by superimposing different illumination channels.

[0130] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facet 23. By selecting the illumination channel to guide light, particularly a subset of the second facet 23, the intensity distribution in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

[0131] Similarly desirable pupil uniformity in a defined illuminated area of ​​the illumination pupil of the illumination optical unit 4 can be achieved by redistributing the illumination channels.

[0132] Further aspects and details of the illumination of the object field of view 5, particularly the entrance pupil of the projection optical unit 10, will be described below.

[0133] The projection optics unit 10 may have a concentric entrance pupil, which can be made accessible or inaccessible.

[0134] The entrance pupil of the projection optical unit 10 cannot always be accurately illuminated using the second facet mirror 22. When the projection optical unit 10 forms a telecentric image on the wafer 13 with the center of the second facet mirror 22, the aperture rays often do not intersect at a single point. However, it is possible to find a plane where the distance between pairs of aperture rays is minimized. This plane represents the entrance pupil or a real-space plane conjugate to it. In particular, this plane exhibits a finite curvature.

[0135] In the projection optics unit 10, the position of the entrance pupil may differ between the tangential beam path and the sagittal beam path. In this case, an imaging element, particularly an optical component of the transfer optics unit, should be placed between the second facet mirror 22 and the reticle 7. This optical element can be used to account for the difference in the relative positions of the tangential and sagittal entrance pupils.

[0136] In the arrangement of the components of the illumination optical unit 4 shown in Figure 1, the second facet mirror 22 is positioned on a plane conjugate to the entrance pupil of the projection optical unit 10. The first facet mirror 20 is positioned at an angle with respect to the object surface 6. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the second facet mirror 22.

[0137] Figure 2 shows an optical system 100 (for example, a part of the optical system 100) equipped with an optical component 102 according to one embodiment. The optical component 102 includes a substrate 104 and an optically effective surface 106. For example, the optical component 102 is a mirror having a mirror substrate 104 and a reflective surface 106.

[0138] For example, the optical system 100 is the projection optical unit 10 (Figure 1) of the EUV lithography apparatus 1. However, the optical system 100 could also be, for example, the illumination optical unit 4 of the lithography apparatus 1.

[0139] For example, optical component 102 is one of the mirrors M1 to M6 of projection optical unit 10 (Figure 1). For example, optical component 102 could also be one of the mirrors 19, 20, or 22 of illumination optical unit 4 (Figure 1).

[0140] Although not shown in the illustration, the optical component 102 may also be a mirror or lens element of a DUV lithography apparatus.

[0141] The optical component 102 may be heated by irradiation with and absorption of the working light 16 (e.g., EUV light 16 from the lithography apparatus 1, Figure 1). This can lead to thermal deformation of the optical component 102. As a result of this thermal deformation, imaging errors may occur in the optical component 102 or the optical system 100 equipped with the optical component 102.

[0142] To reduce thermal deformation and the resulting imaging errors, a high-quality substrate material 108 is used for the substrate 104. In particular, the material 108 of the substrate 104 has a very small coefficient of thermal expansion ρ. Specifically, the material 108 has a zero-crossing temperature ZCT of the coefficient of thermal expansion ρ at which the thermal deformation of the mirror material in response to temperature rise is minimized and / or becomes zero.

[0143] Due to the non-uniformity of the material 108 of the substrate 104, the zero-crossing temperature ZCT of the substrate 104 does not have a uniform distribution across the substrate body 110 of the substrate 104, but rather has a variation ΔZCT as a function of location r in the substrate body 110. Location r in the substrate body 110 is, for example, a location in three-dimensional space spanned by directions x', y', and z'. The average zero-crossing temperature M of the mirror material 108 and the variation ΔZCT of the zero-crossing temperature ZCT as a function of location r directly affect the imaging error of the optical component 102.

[0144] It should be noted that the x', y', and z' or x'y'z' coordinate systems in Figures 2, 4, and 6 may coincide with or be misaligned with the x, y, and z or xyz coordinate systems in Figures 1, 8, and 9. In particular, the x', y', and z' or x'y'z' coordinate systems in Figures 2, 4, and 6 coincide with the x, y, and z or xyz coordinate systems in Figures 1, 8, and 9 only when the optical axis of the optical component 102 is positioned perpendicular to the image plane of the optical system 100 (for example, with respect to the image plane 19 in Figure 1 or the image plane 302 in Figure 8). For example, if the optical component 102 is one of the mirrors M3, M5, or M6 in Figure 1, then the x', y', and z' directions or x'y'z' coordinate system in Figures 2, 4, and 6 coincide with the x, y, and z directions or xyz coordinate system in Figures 1, 8, and 9.

[0145] A method for manufacturing the optical system 100 of the lithography apparatus 1 will be described below with reference to Figures 2 to 11. The optical system 100 comprises an optical component 102 having an optically effective surface 106 and a substrate 104 (Figure 2).

[0146] In the first step S1 of the method, the substrate 104' is manufactured (Figure 4). The manufactured substrate 104' contains material 108' which has a distribution function g(r) of zero-crossing temperature ZCT' as a function of location r of the substrate body 110' due to the manufacturing process. Furthermore, the distribution function g(r) has a mean zero-crossing temperature M'. Hereafter, we consider the distribution function g(r) to be a normalized distribution function g(r) that is normalized based on the actual (i.e., unnormalized) value of the distribution function (e.g., mean zero-crossing temperature M').

[0147] The manufacturing of the substrate 104' in step S1 can be performed before steps S2-S4. However, in other examples, step S1 can also be performed after one, more, or all of steps S2-S4.

[0148] The second step S2 of the method is to determine the zero-crossing temperature of the thermal expansion coefficient of the substrate (e.g., ZCT' in Figure 4 or ZCT' in Figure 7) as a function of the location r of the substrate for one or more optical components (e.g., 102 in Figure 2 or 202a, 202b, 202c in Figure 6) for the substrate (e.g., 104' in Figure 4 or 204a, 204b, 204c in Figure 6). a ZCT b ZCT c The normalized distribution function of (for example, g(r) in Figure 4 or h in Figure 7) a (r), h b (r), h c (r)) includes providing each of these.

[0149] In the first variant of step S2, step S21 provides a normalized distribution function g(r) of the zero-crossing temperature ZCT' for the substrate 104' (Figure 4) of the optical component 102 (Figure 2) to be manufactured. Figure 5 shows an exemplary normalized distribution function g(r) of the normalized zero-crossing temperature ΔZCT of the substrate 104' as a function of the z position of the substrate 104'.

[0150] For example, step S1 is performed before step S21. Subsequently, in step S21, the distribution function g(r) of the zero-crossing temperature ZCT' of the manufactured substrate 104' can be measured, and thus the distribution function g(r) can be provided.

[0151] If the distribution function g(r) of the zero-crossing temperature ZCT' of the substrate 104' (Figure 4) of the optical component 102 (Figure 2) to be manufactured is not provided and / or cannot be calculated, the second modified form S22 of step S2 of the method can be performed instead of the first modified form S21.

[0152] In the second variant of step S2, in step S22 of the method, several representative examples 202a, 202b, and 202c of optical components are provided (Figure 6). Representative examples 202a, 202b, and 202c of optical components each have substrates 204a, 204b, and 204c and optically effective surfaces 206a, 206b, and 206c, respectively.

[0153] Furthermore, in step S22, for each substrate 204a, 204b, 204b of multiple representative examples 202a, 202b, 202c of the optical component, the corresponding zero-crossing temperature (ZCT) is set. a ZCT b ZCT c The normalized distribution function h a (r), h b (r), h c (r) is provided. Figure 7 shows, as an example, an exemplary normalized distribution function h of the normalized zero-crossing temperature ΔZCT for the corresponding substrates 204a, 204b, and 204c. a (r), h b (r), h c (r) is shown as a function of the z position of the corresponding substrates 204a, 204b, and 204c.

[0154] Multiple representative examples of optical components 202a, 202b, 202c and their zero-crossing temperatures (ZCT) a ZCT b ZCT c The normalized distribution function h a (r), h b (r), h c (r) can be provided digitally, for example, in step S22.

[0155] Alternatively, several representative examples of optical components 202a, 202b, and 202c may be physically realized (and therefore physically provided) optical components. In this case, in step S22, the zero-crossing temperature (ZCT) of the corresponding substrates 204a, 204b, and 204c is set. a ZCT b ZCT c The normalized distribution function h a (r), h b (r), h c (r) can be measured and normalized.

[0156] In the third step S3 of the method, the provided normalized distribution functions are g(r) in Figure 5 and h in Figure 7. a (r), h b(r), h c (r) and a plurality of mutually different predetermined average zero-crossing temperatures M j In contrast, the error F of the imaging process of optical system 100 i This is calculated by computer implementation. In this case, j is an index from 1 to p, where p is the different average zero-crossing temperature M being tested. j F is a number and is a natural number greater than 1. Furthermore, i represents an index from 1 to n, where n is a natural number greater than 1 and indicates the number of possible combinations of the given distribution function (one or more) and mean zero-crossing temperature. Thus, F i This refers to the provided distribution function (one or more) (e.g., g(r) in Figure 5 or h in Figure 7). a (r), h b (r), h c (r) and mean zero-crossing temperature M j This is the error calculated by simulation for the i-th combination out of n possible combinations.

[0157] If the first modification form S21 is performed in step S2, in step S3, one provided normalized distribution function g(r) (Figure 5) of the substrate 104' and multiple mutually different mean zero-crossing temperatures M j In contrast, the error F of the imaging process of optical system 100 i This is calculated by computer implementation. As a simple example, as shown in Figure 5, four different average zero-crossing temperatures M are 25.0°C, 25.5°C, 26.5°C, and 27.5°C. j The mean zero-crossing temperatures M, which are different from each other, are thoroughly tested. That is, in the example in Figure 5, the mean zero-crossing temperatures M are different from each other. j There are four such values. Furthermore, there is a single distribution function g(r) and four different mean zero-crossing temperatures M. j Combining these, we get four possible combinations. Therefore, i=4, and there are four different imaging errors F. i This is calculated.

[0158] However, in other examples, the average zero-crossing temperature M j You can also apply different numbers of values ​​and other values ​​to this.

[0159] When the second deformation mode S22 is executed in step S2, in step S3, for a plurality of provided normalized distribution functions h a (r), h b (r), h c (r) and a plurality of mutually different mean zero-crossing temperatures M j of the imaging process of the optical system 100, an error F i is calculated. Merely as an example, as shown in FIG. 7, even in this deformation mode, four different mean zero-crossing temperatures M j of 25.0 °C, 25.5 °C, 26.5 °C, and 27.5 °C are fully tested. That is, even in the example of FIG. 7, the number of mutually different mean zero-crossing temperatures M j is four. Further, for example, when combining three distribution functions h a (r), h b (r), h c (r) and four different mean zero-crossing temperatures M j , 12 possible combinations can be obtained. Therefore, i = 12, and 12 different imaging errors F i are calculated.

[0160] In some cases, in the first deformation mode of step S3, each error F i can be calculated based on a plurality of mutually different individual errors f k . In particular, a plurality of individual errors f k related to mutually different error types of the imaging process of the optical system 100 can be applied to the calculation of each error F i . For example, the mutually different individual errors f k are considered as relative error values. In this first deformation mode of step S4, the error F i of the imaging process of the optical system 100 can be calculated, for example, as the maximum value of a plurality of calculated individual errors f k , for example, based on the following formula. F i = max(f k ) (where i = 1~n, k = 1~m)

[0161] In this case, f k This is a specific distribution function g(r) or h a (r), h b (r), h c (r) and a specific mean zero-crossing temperature M j This represents the (e.g., relative) individual error with respect to . In this case, k is an index from 1 to m, where m is a natural number greater than 1, and the individual errors f are mutually distinct. k It represents the number.

[0162] In another example, in step S4, the error F of the imaging process of the optical system 100 i This is a combination of multiple calculated (e.g., relative) individual errors f k It can also be calculated as the mean, median, and / or quantile.

[0163] Multiple mutually distinct individual errors f k As explained in Figure 8, for example, the target focus F Soll The actual focal length of the optical system from 100 F Ist This can be due to a shift (defocus, spherical aberration, Zernike polynomial ZP of Z²). Figure 8 shows radiation 300 (e.g., the operating light 16 in Figure 1) incident on the image plane 302 of the optical system 100 (Figure 2). Target focus F Soll This is located specifically on the image plane 302. Actual focal point F Ist The target focus F Soll The image is blurred because it is out of focus. Target focus F Soll The actual focal point F Ist The deviation is the individual error f k This is an example of representing the first (k=1) individual error f1.

[0164] Furthermore, Figure 8 shows the threshold SW (Figure 11A) and / or the error range ΔF as an example of an individual threshold. fokus This indicates, for example, range F Soll ±ΔF fokus The actual focus located within is an imaging error F less than the threshold SW. i However, the actual focal point F shown in Figure 8 Ist The tolerance range is F Soll ±ΔF fokusSince it is not located within the context, the relevant mean zero-crossing temperature M i This is the selected mean zero-crossing temperature M aw The following conditions are not met. Error range ΔF corresponding to the threshold SW and / or individual threshold of that focal point. fokus Examples of these values ​​include, for example, 15 nm or less, 10 nm or less, and / or 5 nm or less.

[0165] For example, multiple mutually different individual errors f k This could also be the displacement of the wavefront (for example, 304 in Figure 8) relative to the target wavefront 306. Therefore, the actual position P of the object 402 as imaged in the image 400 of the image plane 302 (Figure 8) of the optical system 100 is... Ist As explained in Figure 9, the target position P of the imaged object 404 is Soll It deviates from the target position P. Soll Actual position P Ist The discrepancy (overlay error) is the individual error f k Another example of this is the second (k=2) individual error f2.

[0166] Individual errors f for mutually different error types k In addition to, or instead of, multiple mutually different individual errors f k This is the individual error f for mutually different setting parameters of illumination of the optical component 102 of the optical system 100. k But it's possible.

[0167] For example, different setting parameters for the planned illumination of the optical component 102 to be manufactured include the radiant intensity of the working light (e.g., EUV light 16, Figure 1) emitted to the optical component 102.

[0168] For example, different setting parameters for illumination may also include the pattern 500 or heat flux distribution 500 in which the operating light 16 is radiated onto the optical component 102. As an example, Figure 10 illustrates two heat flux poles 502, 504 (dipole pattern) of the heat flux distribution 500 on the optical effective surface 506 of an optical component (e.g., optical component 102 in Figure 2).

[0169] In some cases, in the second variant of step S3, multiple calculated individual errors f k It can be weighted according to a predetermined weight W1.

[0170] As a result, individual errors can be weighted according to the planned use of the optical component 102 being manufactured and the optical system 100 equipped with this component 102.

[0171] In this second form of step S3, for example, based on the following equation, for example F i f is a multiple weighted individual error k It is calculated as the maximum value. F i =bloom(f k / W l (where i=1 to n, k=1 to m, l=1 to q)

[0172] In the above formula, W l f is the individual error k This represents the weight applied to the weighting. Weight W l l is a positive real number greater than 0. Furthermore, l is an index from 1 to q, where q is a multiple weight W. l It represents the number.

[0173] In another example, the error F of the imaging process of optical system 100 i This is a set of multiple weighted individual errors f k It can also be calculated as the mean, median, and / or quantile.

[0174] Figure 11 shows the weight W l This is shown as an example. As an example, the weight W1 = 0.5 is shown in the figure, and the term W l Since it is in the denominator of the above equation, this corresponds to a high weighting. As yet another example, the weight W2 = 1.5 is shown, which corresponds to a low weighting.

[0175] If p different setting parameters are considered for the illumination of the optical component 102 with the working light 16, then q is the product of p and m (i.e., q = p·m). If no different setting parameters are considered for the illumination of the optical component 102 with the working light 16 (i.e., only a single setting applies, so p = 1), then q is equal to m.

[0176] For example, two mutually different individual errors f k Considering (i.e., m=2) and only a single setting parameter for the illumination of the optical component 102 with the working light 16 (i.e., p=1 and q=m), the error F i It is calculated as follows: F i =bloom(f k / W l (where i=1 to n, k=1 to 2, l=1 to 2) F i =max(f1 / W1, f2 / W2) (where i=1 to n)

[0177] For example, two mutually different individual errors f k In an embodiment where, in addition to (i.e., m=2), two mutually different setting parameters for the illumination of the optical component 102 with the working light 16 are also considered (i.e., p=2 and q=2m), the error F i It is calculated as follows: F i =bloom(f kd / W l (However, i=1 to n, k=1 to 2, d=1 to 2, l=1 to 4) F i =bloom(f 11 / W1, f 12 / W2, f 21 / W3, f 22 / W4) (where i=~n)

[0178] In this case, f kd This represents the k-th individual error in the d-th lighting setting. In other words, f 11 represents the first individual error f1 in the first lighting setting, and f 12represents the first individual error f1 in the second lighting setting, and f 21 This represents the second individual error f2 in the first lighting setting, and f 22 This represents the second individual error f2 in the second lighting setting.

[0179] The fourth step S4 of the method is the calculated error F i The average zero-crossing temperature M is the temperature at which the temperature falls below a predetermined threshold SW. j As such, at least one selected mean zero-crossing temperature M for the substrate 104 of the optical component 102 (Figure 2) to be manufactured. aw This includes identifying the specifics.

[0180] Figure 11A shows the imaging error F of the optical system 102 in Figure 2, which is less than a predetermined threshold SW. i This is shown as an example. Therefore, in this example, in step S4, the imaging error F i The mean zero-crossing temperature M related to this j This is at least one selected mean zero-crossing temperature M aw It is identified as such.

[0181] In step S4, the image formation error F is calculated. i Since none of them are below the predetermined threshold SW, the selected mean zero-crossing temperature M aw If this is not determined, for example, it may be determined that the substrate 104 is not suitable for manufacturing the optical component 102. In this case, step S5 is not performed.

[0182] In some cases, instead of, or in addition to, the optimal mean zero-crossing temperature M of the substrate 104 of the optical component 102 being manufactured is used. opt The minimum imaging error F i It can also be determined based on the following: In other words, in step S4, the optimal mean zero-crossing temperature M of the substrate 104 of the optical component 102 (Figure 2) to be manufactured. opt The calculated error F i The average zero-crossing temperature M is the temperature at which the value is minimized. j It can also be identified as such.

[0183] In this case, in step S4, for example, multiple error values ​​F of the imaging process of the optical system 102, which were calculated by computer implementation in step S3, are used. i The minimum value F E However, the final error F follows the following formula E It is calculated as follows. F E =com(F i (However, i = 1 to n)

[0184] In the above formula, n is the zero-crossing temperature (for example, g(r) in Figure 4 or h in Figure 7). a (r), h b (r), h c (r)) represents the number of possible combinations of the provided normalized partition function (one or more) and the given mean zero-crossing temperature tested in step S3. Furthermore, F E These are n errors F calculated by simulation. i This shows the minimum value.

[0185] This minimum value F E The mean zero-crossing temperature M related to this j (For example, M j (=M2=25.5℃) Next, the optimal mean zero-crossing temperature M of the substrate 104 of the optical component 102 (Figure 2) to be manufactured is determined. opt It is identified as such.

[0186] In any fifth step S5 of the method, the substrate 104' (Figure 4) of the optical component 102 (Figure 2) to be manufactured has at least one selected and / or optimal mean zero-crossing temperature M identified in step S4. aw M opt The substrate 104' is heated to set the average zero-crossing temperature M' based on the following. For example, the substrate 104' is annealed with appropriate parameter settings. In particular, in step S5, the substrate 104' is heated to set the average zero-crossing temperature M' that was initially set during the manufacture of the substrate 104' to at least one selected and / or optimal average zero-crossing temperature M'. aw M optThe offset between the two points is corrected through post-processing.

[0187] At the end of step S5, the substrate 104 (Figure 2) manufactured in step S1 and post-processed in step S5 has at least one selected and / or optimal mean zero-crossing temperature M aw M opt (Figure 2)

[0188] Figure 12 shows a control device 600 for manufacturing the optical system 100 (Figure 2) of the lithography apparatus 1 (Figure 1). The optical system 100 comprises an optical component 102 having an optically effective surface 106 and a substrate 104 (Figure 2).

[0189] Furthermore, the control device 600 includes a supply unit 602. The supply unit 602 provides the zero-crossing temperature ZCT', ZCT' of the thermal expansion coefficient ρ of the substrates 104', 204a, 204b, 204c as a function of the location r of the substrates 104', 204a, 204b, 204c for one or more optical components 102, 204a, 204b, 204c. a ZCT b ZCT c The normalized distribution function g(r), h a (r), h b (r), h c It performs the function of providing (r).

[0190] Furthermore, the control device 600 includes a first calculation unit 604. The first calculation unit 604 calculates each of the provided normalized distribution functions g(r), h a (r), h b (r), h c (r) and a plurality of mutually different predetermined average zero-crossing temperatures M j For each of these, the error F of the imaging process of the optical system 102 i It is configured to be calculated by a computer implementation.

[0191] Furthermore, the second calculation unit 606 calculates the error F iis less than a predetermined threshold SW or the average zero-crossing temperature M reaches the minimum value j As the at least one selected average zero-crossing temperature M for the substrates 104’, 204a, 204b, 204c of the optical component 102 to be manufactured aw and / or the optimum average zero-crossing temperature M opt is provided for identification.

[0192] The present invention has been described based on exemplary embodiments, but can be modified in various forms.

Explanation of Reference Signs

[0193] 1 Projection exposure apparatus 2 Illumination system 3 Radiation source 4 Illumination optical unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle holder 9 Reticle displacement drive 10 Projection optical unit 11 Image field of view 12 Image plane 13 Wafer 14 Wafer holder 15 Wafer displacement drive 16 Illumination radiation 17 Collector 18 Intermediate focal plane 19 Deflection mirror 20 First facet mirror 21 First facet 22 Second facet mirror 23 Second facet 100 Optical system 102 Optical component 104, 104’ Substrate 106 Optically effective surface 108, 108’ Material 110, 110’ Body 202a, 202b, 202c Optical component 204a, 204b, 204c Substrate 206a, 206b, 206c Optical effective surface 300 radiation 302 Image plane 304 Actual wavefront 306 Target wavefront 400 statues 402 Object 404 Object 500 Heat flux distribution 502 Heat flux pole 504 Heat flux pole 506 Optically Effective Surface 600 Control Unit 602 Supply Units 604 calculation units 606 calculation units ΔF i Error range ΔF Fokus Error range Δx displacement ΔZCT temperature difference f k error f1, f2 error F error F i error F Ist Actual focus F Soll target focus g function h a h b h c function M' temperature M aw temperature M j temperature M opt temperature M1~M4 temperature M1~M6 Mirror P Ist Actual location P Soll target position ρ, ρ' Thermal expansion coefficient S1-S5 Method Steps S21, S22 Method Steps SW threshold W l Weight Weights W1 and W2 x, y, and z directions x’, y’, and z’ directions Temperatures ZCT and ZCT’ ZCT a , ZCT b , ZCT c Temperature ZP Zernike polynomial

Claims

1. A method for manufacturing an optical system (100) of a lithography apparatus (1), wherein the optical system (100) comprises an optical component (102) having an optically effective surface (106) and a substrate (104), a) For one or more optical components (102, 202a, 202b, 202c) and their substrates (104', 204a, 204b, 204c), the zero-crossing temperature (ZCT', ZCT) of the thermal expansion coefficient (ρ') of the substrate (104', 204a, 204b, 204c) as a function of the location (r) of the substrate (104', 204a, 204b, 204c) ａ ZCT ｂ ZCT ｃ The normalized distribution function of (g, h) ａ , h ｂ , h ｃ Step (S2) provides each of the following: b) For each of the provided distribution functions (g, h ａ , h ｂ , h ｃ ) and a plurality of mutually different predetermined mean zero-crossing temperatures (M ｊ ), respectively calculating the imaging error (F ｉ ) of the optical system (102) by computer implementation (step S3); c) The plurality of average zero-crossing temperatures (M ｊ ) of the above-calculated imaging error (F ｉ Assuming that the temperature is below a predetermined threshold (SW), at least one selected mean zero-crossing temperature (M) of the optical component (102) to be manufactured relative to the substrate (104) is set. ａｗ Step (S4) to identify ) and Methods that include...

2. In the method according to claim 1, in step c), the optimal mean zero-crossing temperature (M) of the substrate (104) of the optical component (102) to be manufactured. ｏｐｔ ) is the plurality of average zero-crossing temperatures (M ｊ ) of the above-calculated imaging error (F ｉ A method that is identified as minimizing ).

3. In the method according to claim 1 or 2, in step a), the zero-crossing temperature (ZCT ａ ZCT ｂ ZCT ｃ Multiple normalized distribution functions (h ａ , h ｂ , h ｃ A method is provided for corresponding substrates (204a, 204b, 204c) of several representative examples (202a, 202b, 202c) of optical components.

4. A method according to claim 1 or 2, wherein in step a), the normalized distribution function (g) of the zero-crossing temperature (ZCT') is provided for the substrate (104') of the optical component (102) to be manufactured.

5. In the method of claim 3, the plurality of representative examples (202a, 202b, 202c) are physically realized optical components, and the zero-crossing temperature (ZCT) of the corresponding substrate (204a, 204b, 204c) of the plurality of representative examples (202a, 202b, 202c) ａ ZCT ｂ ZCT ｃ The plurality of distribution functions (h ａ , h ｂ , h ｃ ) is the method by which it is measured.

6. A method according to claim 4, wherein the substrate (104') of the optical component (102) to be manufactured is physically prepared, and the distribution function (g) of the zero-crossing temperature (ZCT') of the substrate (104') of the optical component (102) to be manufactured is measured.

7. In the method according to any one of claims 1 to 6, The at least one specified selected mean zero-crossing temperature (M ａｗ ) and / or the identified optimal mean zero-crossing temperature (M ｏｐｔ Step (S5) to set the average zero-crossing temperature (M') of the substrate (104') of the optical component (102) to be manufactured by heat treatment based on the above. Methods that include...

8. In the method according to any one of claims 1 to 7, each provided distribution function (g, h ａ , h ｂ , h ｃ ) and the plurality of mutually different predetermined average zero-crossing temperatures (M ｊ Regarding the optical system (100), the imaging error (F ｉ The steps to calculate each of these are: Regarding the mutually different error types of the optical system (100), a plurality of mutually different individual errors (f ｋ The steps to calculate ) and The above-mentioned multiple calculated individual errors (f ｋ Based on this, the imaging error (F) of the optical system (100) ｉ The steps to calculate ) Methods that include...

9. In the method of claim 8, the plurality of calculated individual errors (f ｋ ) is a predetermined weight (W ｌ A method that is weighted according to the following criteria.

10. In the method according to claim 8 or 9, the plurality of mutually different individual errors (f ｋ A method which is calculated with respect to the mutually different error types and the mutually different setting parameters (500) for the illumination of the optical component (102) that is the subject of manufacture of the optical system (100).

11. The method according to any one of claims 8 to 10, wherein the plurality of calculated individual errors (f) relating to the mutually different error types ｋ )teeth, The actual focal point (F) of the optical system (100) Ｉｓｔ ) Target focus (F Ｓｏｌｌ ) deviation, The actual position (P) of the object (402) that is imaged on the image plane (302) of the optical system (100) using the optical system (100) Ｉｓｔ The target position (P) of the imaged object (404) Ｓｏｌｌ ) deviation, The image displacement of the image (400) formed on the image plane (302) of the optical system (100) using the optical system (100), and / or The deviation of the actual wavefront (304) from the target wavefront (306) that forms an image (400) on the image plane (302) of the optical system (100). Methods that include...

12. The method according to claim 11, wherein the deviation of the actual wavefront (304) from the target wavefront (306) includes the inclination of the wavefront (304), the displacement of the wavefront (304), the astigmatism of the wavefront (304), the coma aberration of the wavefront (304), the higher-order (n-th order) aberration of the wavefront (304), and / or the spherical aberration of the wavefront (304).

13. A method according to claim 11 or 12, wherein the deviation of the actual wavefront (304) from the target wavefront (306) is quantified in the form of a Zernike polynomial (ZP).

14. A method according to any one of claims 1 to 13, wherein the optical component (102) is a mirror and the substrate (104) is a mirror substrate.

15. A method according to any one of claims 1 to 14, wherein the optical system (100) is the projection system (10) of the lithography apparatus (1).

16. A control device (600) for manufacturing the optical system (100) of a lithography apparatus (1), wherein the optical system (100) comprises an optical component (102) having an optically effective surface (106) and a substrate (104), in the control device (600), For one or more optical components (102, 202a, 202b, 202c) and their substrates (104', 204a, 204b, 204c), the zero-crossing temperature (ZCT', ZCT) of the thermal expansion coefficient (ρ') of the substrate (104', 204a, 204b, 204c) is expressed as a function of the location (r) of the substrate (104', 204a, 204b, 204c). ａ ZCT ｂ ZCT ｃ The normalized distribution function of (g, h) ａ , h ｂ , h ｃ A supply unit (602) that provides each of the following: Each provided distribution function (g, h) ａ , h ｂ , h ｃ ) and a plurality of mutually different predetermined average zero-crossing temperatures (M ｊ Regarding the optical system (102), the imaging error (F ｉ A first calculation unit (604) calculates each of these using computer implementation, The plurality of average zero-crossing temperatures (M ｊ ) of the above-calculated imaging error (F ｉ The selected mean zero-crossing temperature (M) of the optical component (102) to be manufactured relative to the substrate (104) is assumed to be less than a predetermined threshold (SW). ａｗ The second calculation unit (606) identifies ) and A control device equipped with the following features.

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