Processing method for optical system, projection optical system, exposure device, and method of manufacturing article

Abstract

To provide a processing method for processing an optical system having an optical element having an optical thin film simply deposited on an optical surface so as to suppress an increase in wave front aberration of the optical system used for an exposure device.SOLUTION: A processing method for processing an optical system used for an exposure device includes: a first arrangement step of arranging a first optical element provided in the optical system in a film deposition device; a first film deposition step of depositing an optical thin film having a predetermined film thickness distribution on a first optical surface of the first optical element in the film deposition device; a second arrangement step of arranging a second optical element provided in the optical system in the film deposition device; and a second film deposition step of depositing an optical thin film having a predetermined film thickness distribution on a second optical surface of the second optical element in the film deposition device. A first relative position of the center of the first optical surface to a reference position of the film deposition device in the first arrangement step is different from a second relative position of the center of the second optical surface to a reference position in the second arrangement step.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for processing an optical system, a projection optical system, an exposure apparatus, and a method for manufacturing an article. [Background technology]

[0002] 2. Description of the Related Art Conventionally, exposure apparatuses have been known that are provided with optical elements having optical thin films formed on their optical surfaces in order to increase the illuminance of exposure light by improving the transmittance and reflectance. On the other hand, if the optical thin film formed on the optical surface of the optical element has a non-uniform film thickness distribution, there is a risk that wavefront aberration will increase in an exposure apparatus that includes the optical element.

[0003] Patent Document 1 discloses a technique for depositing optical thin films on an optical surface of an optical element by depositing each film on the optical surface while changing the relative rotation angle position between a substrate and a film thickness distribution control plate, in order to reduce non-uniformity in the film thickness distribution of the optical thin film deposited on the optical surface of the optical element. In Patent Document 1, an optical element on which an optical thin film is formed by this technique is provided in an exposure apparatus, thereby suppressing an increase in wavefront aberration in the exposure apparatus. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-26396 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the relative rotation angle position between the substrate and the film thickness distribution control plate is changed each time each film of the optical thin film is deposited on the optical surface of the optical element, complicating the process of depositing the entire optical thin film. Therefore, an object of the present invention is to provide a processing method for an optical system used in an exposure apparatus, the optical system having an optical element having an optical thin film simply formed on its optical surface so as to suppress an increase in wavefront aberration of the optical system. [Means for solving the problem]

[0006] The processing method for processing an optical system used in the exposure apparatus of the present invention includes a first positioning step of positioning a first optical element to be provided in the optical system in a film forming apparatus, a first film forming step of forming an optical thin film having a predetermined film thickness distribution on a first optical surface of the first optical element in the film forming apparatus, a second positioning step of positioning a second optical element to be provided in the optical system in the film forming apparatus, and a second film forming step of forming an optical thin film having a predetermined film thickness distribution on a second optical surface of the second optical element in the film forming apparatus, characterized in that a first relative position of the center of the first optical surface with respect to a reference position of the film forming apparatus in the first positioning step and a second relative position of the center of the second optical surface with respect to the reference position in the second positioning step are different from each other. Effect of the Invention

[0007] According to the present invention, it is possible to provide a processing method for processing an optical system used in an exposure apparatus, the optical system having an optical element having an optical thin film simply formed on its optical surface so as to suppress an increase in wavefront aberration of the optical system. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic cross-sectional view of a film forming apparatus used in the present embodiment. [Diagram 2] 4 is a flowchart showing a process for forming an optical thin film on an optical surface in the present embodiment. [Diagram 3] A projection diagram of an optical surface in an XY cross section and the position dependency in the X direction of the thickness of an optical thin film formed on the optical surface. [Figure 4] 4 is a flowchart showing a process of forming an optical thin film on each of two optical surfaces in the present embodiment. [Diagram 5]FIG. 2 is a schematic cross-sectional view of a film forming apparatus used in the present embodiment. [Figure 6] A projection diagram of an optical surface in an XY cross section and the position dependency in the X direction of the thickness of an optical thin film formed on the optical surface. [Figure 7] FIG. 1 is a schematic cross-sectional view of an exposure apparatus that includes a projection optical system that is processed in this embodiment. [Figure 8] The position dependency in the X direction of the thickness of an optical thin film deposited in a deposition apparatus and an optical thin film deposited on a specified optical surface. [Figure 9] The position dependence in the X direction of the thickness of an optical thin film deposited on a given optical surface in a deposition system. [Figure 10] 13 is a diagram showing the calculation results of the wavefront aberration shape of an optical thin film formed on a predetermined optical surface. [Figure 11] 13 is a diagram showing the calculation results of the wavefront aberration shape of an optical thin film formed on a predetermined optical surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a method for processing (manufacturing) an optical system according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below may be drawn at a scale different from the actual scale in order to facilitate understanding of the present embodiment. In the following description, the direction in which the stage 111 and the optical element 106 face each other is defined as the Z direction (second direction), and the direction in which the multiple material sources 101 to 105 are arranged on the stage 111 is defined as the X direction (first direction). Then, the direction perpendicular to each of the Z direction and the X direction, in which the relative position between the optical element 106 and the stage 111 is changed when sputtered particles are deposited on the optical surface 10 of the optical element 106, is defined as the Y direction (third direction).

[0010] Conventionally, devices such as semiconductor devices and flat panel displays (FPDs) are manufactured through manufacturing processes that include a photolithography process. Specifically, photolithography uses an exposure apparatus that projects an image of a pattern drawn on an original such as a mask or reticle by a projection optical system including optical elements such as lenses and mirrors onto a substrate such as a glass plate or wafer coated with resist (photosensitive agent), thereby transferring the pattern onto the substrate.

[0011] In the projection optical system used in such an exposure apparatus, an optical element having an optical thin film formed on its optical surface is used in order to increase the intensity of the exposure light by improving the transmittance and reflectance. Specifically, the optical thin film includes a dielectric multilayer film in which a plurality of materials having mutually different refractive indices are laminated and which transmits or reflects light having a specific wavelength by interference action.

[0012] Generally, optical thin films are formed on the optical surfaces of optical elements by sputtering or vapor deposition. On the other hand, if the optical thin film formed on the optical surface of the optical element has a non-uniform film thickness distribution depending on the performance of the film forming apparatus that performs the film formation, there is a risk that wavefront aberration, particularly astigmatism and spherical aberration, will increase in a projection optical system that includes the optical element.

[0013] Known techniques for reducing wavefront aberration in a projection optical system include, for example, calculating the wavefront error that occurs through an optical element, and forming a correction film having a predetermined film thickness distribution on the optical surface of the optical element in order to reduce the calculated wavefront error. Furthermore, in this technique, a mask is used for depositing the optical thin film only on a predetermined portion of the optical surface, and additional processing such as ion beam processing or polishing is performed on the optical thin film deposited on the optical surface. However, this technique of performing such additional processing reduces throughput, and it is difficult to use this technique for optical systems in which it is difficult to perform the additional processing.

[0014] Furthermore, as a technique for suppressing an increase in wavefront aberration in a projection optical system by reducing the non-uniformity of the film thickness distribution in an optical thin film formed on the optical surface of an optical element, a technique for reducing the film thickness distribution in the circumferential direction of a multilayer film that forms the optical thin film is known. Specifically, in this technique, each film is formed while changing the relative rotation angle position between the substrate and the film thickness distribution control plate, thereby reducing the film thickness distribution in the circumferential direction of the optical thin film.

[0015] However, in this technique, the relative rotation angle position between the substrate and the film thickness distribution control plate is changed each time each film of the multilayer film is deposited, which complicates deposition of the entire multilayer film and reduces throughput. Therefore, the present embodiment aims to provide a method for processing an optical system having an optical surface on which an optical thin film is formed so as to suppress an increase in wavefront aberration of the optical system, such as a projection optical system, while being simple and suppressing a decrease in throughput.

[0016] FIG. 1 shows a schematic cross-sectional view of a film forming apparatus 100 used in the method for processing an optical system according to this embodiment. Specifically, the film forming apparatus 100 is a sputtering film forming apparatus for forming an optical thin film over a wide area on an optical surface 10 of a predetermined optical element 106 included in a projection optical system used in an exposure apparatus.

[0017] As shown in FIG. 1, a film forming apparatus 100 includes material sources 101 , 102 , 103 , 104 , and 105 , a chamber 107 , an exhaust port 108 , an intake port 109 , a holder 110 , a stage 111 , and a power supply unit 112 .

[0018] Specifically, in the film forming apparatus 100, a plurality of material sources 101 to 105 are mounted on a stage 111 so as to be spaced apart from each other in the X direction. Each of the multiple material sources 101 to 105 has, for example, a rectangular shape in the XY plane (second plane). However, the present invention is not limited to this, and each of the material sources 101 to 105 may have a shape that is elongated in the Y direction.

[0019] Moreover, the optical element 106 held by the holding portion 110 is disposed so that the optical surface 10 on which the optical thin film is to be formed faces the multiple material sources 101 to 105 . In addition, the holding unit 110 has a heating mechanism for applying heat to the optical element 106 .

[0020] In addition, an exhaust port 108 and an intake port 109 are formed in the chamber 107, and the internal space of the chamber 107 is connected to a vacuum pump (not shown) via the exhaust port 108, and is connected to a gas supply source (not shown) via the intake port 109. In addition, a power supply unit 112 is connected to each of the holding unit 110 and the stage 111, and the power supply unit 112 applies a voltage to each of the holding unit 110 and the stage 111 so that a potential difference is created between the optical element 106 and the multiple material sources 101 to 105.

[0021] FIG. 2 is a flow chart showing a process of depositing an optical thin film on the optical surface 10 of a predetermined optical element 106 included in the projection optical system using the deposition apparatus 100 in the method for processing an optical system according to this embodiment. When the process starts, first, the optical element 106 is carried into the chamber 107 (step S101).

[0022] Next, in order to remove impurities from the internal space of chamber 107, chamber 107 is evacuated by operating a vacuum pump (not shown) connected to exhaust port 108 to evacuate the gas in the internal space of chamber 107 (step S102). Next, a predetermined gas is supplied to the internal space of the chamber 107 by operating a gas supply source (not shown) connected to the intake port 109, and then a voltage is applied by the power supply device 112 to cause the sputtering phenomenon (step S103).

[0023] The gas supplied in step S103 includes an inert gas whose reaction with sputtered particles generated by the sputtering phenomenon is sufficiently suppressed. Furthermore, when an optical thin film made of a compound is formed on the optical surface 10 of the optical element 106, an active gas that reacts with the sputtered particles is also supplied in step S103. Specifically, oxygen gas is supplied in step S103 when an optical thin film made of an oxide is formed on the optical surface 10 of the optical element 106. Also, fluorine gas is supplied in step S103 when an optical thin film made of a fluoride is formed on the optical surface 10 of the optical element 106.

[0024] Next, while changing the relative position between the stage 111 and the optical element 106 in the Y direction, sputtered particles generated by the sputtering phenomenon from the multiple material sources 101 to 105 are deposited on the optical surface 10 of the optical element 106 (step S104). In this way, by adhering (depositing, evaporating) sputtered particles onto the optical surface 10 while changing the relative position between the stage 111 and the optical element 106 in the Y direction, the film thickness distribution in the Y direction of the optical thin film formed on the optical surface 10 of the optical element 106 can be made uniform.

[0025] In order to change the relative position between the stage 111 and the optical element 106 in the Y direction, at least one of the stage 111 and the optical element 106 may be scanned in the Y direction. This configuration of scanning at least one of the stage 111 and the optical element 106 without rotating the optical element 106 is advantageous when the optical element 106 is large or has a rotationally asymmetric optical surface such as a trapezoidal shape.

[0026] Next, the holding unit 110 anneals the optical element 106 by heating it, promoting the generation of compounds on the optical surface 10 of the optical element 106 and homogenizing the composition of the compounds that are generated (step S105). It should be noted that step S105 may be performed in parallel with step S104 described above.

[0027] Next, it is determined whether the number of layers formed on the optical surface 10 of the optical element 106 has reached a predetermined number (step S106). If the number of layers deposited on the optical surface 10 of the optical element 106 has not reached the predetermined number (No in step S106), the material sources 101 to 105 are changed (step S107), and the process continues by returning to step S102. On the other hand, if the number of layers formed on the optical surface 10 of the optical element 106 has reached the predetermined number (Yes in step S106), the process ends.

[0028] The thickness (film thickness) t of a film formed on the optical surface 10 of the optical element 106 by sputtered particles generated from a specific single material source among the multiple material sources 101 to 105 in the film forming apparatus 100 can be expressed by the following equation (1).

[0029]

number

[0030] In equation (1), k is a constant, α is the emission angle of the sputtered particle from a given single material source, β is the incidence angle of the sputtered particle with respect to optical surface 10, and r is the travel distance of the sputtered particle from the given single material source to optical surface 10. That is, the thickness t of the film formed on the optical surface 10 depends on the emission angle, the incidence angle, and the travel distance of the sputtered particles.

[0031] As shown in equation (1), the thickness t of the optical thin film deposited on the optical surface 10 is at its maximum when r is at its minimum. That is, the optical thin film formed on the optical surface 10 by a single material source has a film thickness distribution in which the thickness t decreases as the distance from the single material source increases.

[0032] FIG. 3(a) shows a projection view of the optical surface 10 of the optical element 106 in the XY cross section. FIG. 3(b) shows the position dependency in the X direction of the thickness t of the optical thin film formed on the optical surface 10 of the optical element 106.

[0033] As described above, in the film forming apparatus 100, the multiple material sources 101 to 105 are arranged spaced apart from one another at equal intervals in the X direction. Here, the positions of the multiple material sources 101, 102, 103, 104, and 105 in the X direction are represented as X101, X102, X103, X104, and X105, respectively. In the following description, the center position of the material source 103 in the film forming apparatus 100 is defined as the reference position of the film forming apparatus 100 .

[0034] Furthermore, when the film is formed on the optical surface 10 of the optical element 106 in the film forming apparatus 100, the optical element 106 is disposed so that the position in the X direction of the center of the optical surface 10 of the optical element 106 is X103. In this case, multiple material sources 101-105 would face the optical surface 10 as shown in FIG.

[0035] When a film is deposited on the optical surface 10 of the optical element 106 in this arrangement, the thickness t of the film formed on the optical surface 10 has a maximum value tmax (maximum value) at X102, X103 and X104, respectively, according to equation (1), as shown in FIG. 3(b). On the other hand, the thickness t of the film has a minimum value tmin (local minimum value) at the midpoint (X102+X103) / 2 in the X direction between material source 102 and material source 103, and at the midpoint (X103+X104) / 2 in the X direction between material source 103 and material source 104.

[0036] Also consider a region 15 where the film thickness t is tmin or more and tmin+(tmax-tmin) / 4 or less, and a region 14 where the film thickness t is tmin+(tmax-tmin) / 4 or more and tmin+(tmax-tmin) / 2 or less. Also consider a region 13 where the film thickness t is tmin+(tmax-tmin) / 2 or more and tmin+3×(tmax-tmin) / 4 or less, and a region 12 where the film thickness t is tmin+3×(tmax-tmin) / 4 or more and tmax or less. In this case, in FIG. 3(a), the regions 12, 13, 14 and 15 are shown as a black region, a gray region, a hatched region and a white region, respectively, and it can be seen that the regions 12, 13, 14 and 15 are arranged periodically in the X direction.

[0037] Next, a specific process for depositing optical thin films on the optical surfaces 10 and 20 of a predetermined optical element 106 included in a projection optical system using the deposition apparatus 100 in the optical system processing method according to this embodiment will be described. FIG. 4 is a flow chart showing a process of depositing optical thin films on the optical surfaces 10 and 20 of a predetermined optical element 106 included in a projection optical system using the deposition apparatus 100 in the method for processing an optical system according to this embodiment.

[0038] When the process starts, first, the optical element 106 (first optical element) is placed according to the flowchart shown in FIG. 2, and an optical thin film is formed on the optical surface 10 (first optical surface) (step S201, first placement step, first film formation step). Next, the peak interval L is obtained from the position dependency in the X direction of the thickness t of the film in the optical thin film formed on the optical surface 10 (step S202, measurement step).

[0039] Specifically, in step S202, for example, as shown in FIG. 3(b), the two closest positions among the positions where the thickness t of the film has the minimum value tmin are measured. Then, the peak interval L can be obtained from the difference between the two measured positions.

[0040] However, the present invention is not limited to this, and the peak interval L may be obtained from the two closest positions among the positions where the film thickness t has the maximum value tmax. That is, the peak interval L can be obtained from the distance between adjacent positions in the X direction among multiple positions where the film thickness t has a maximum value, or the distance between adjacent positions in the X direction among multiple positions where the film thickness t has a minimum value.

[0041] In addition, the peak interval L is determined by forming an optical thin film on the optical surface 10, and then forming the optical thin film on a monitor glass having a size equivalent to the film formation area of ​​the optical element 106 under the same conditions. Then, the peak interval L may be obtained from the position dependency in the X direction of the thickness t of the formed optical thin film. Furthermore, in the case where the multiple material sources 101 to 105 are arranged at equal intervals in the X direction as in the film forming apparatus 100, the interval between adjacent material sources may be used as the peak interval L.

[0042] Next, the optical surface 20 (second optical surface) of the optical element 106 (second optical element) is placed facing the multiple material sources 101 to 105, and the optical element 106 is shifted in the X direction by +L / 2, i.e., half the peak spacing L (step S203, second placement step). That is, the relative position (first relative position) of the center of the optical surface 10 with respect to the reference position of the film formation apparatus 100 in step S201 and the relative position (second relative position) of the center of the optical surface 20 with respect to the reference position in step S203 are different from each other.

[0043] FIG. 5 is a schematic cross-sectional view of the film forming apparatus 100 in step S203. In the example shown in FIG. 5, the optical element 106 is shifted and disposed so that the position in the X direction of the center of the optical surface 20 of the optical element 106 is X103+L / 2. In step S203, the holder 110 that holds the optical element 106 may be moved by −L / 2 in the X direction so that the optical element 106 is shifted by −L / 2 in the X direction.

[0044] Then, an optical thin film is formed on the optical surface 20 according to the flow chart shown in FIG. 2 (step S204, second film forming step), and the process ends. FIG. 6( a ) shows a projection view of the optical surface 20 of the optical element 106 in the XY cross section. FIG. 6(b) shows the position dependency in the X direction of the thickness t of the film formed on the optical surface 20 of the optical element 106.

[0045] As shown in FIG. 6(a), like the optical surface 10, on the optical surface 20, regions 12, 13, 14, and 15 are arranged periodically in the X direction. On the other hand, the positions on the optical surface 20 where the film thickness t has the maximum value tmax and the minimum value tmin are different from those on the optical surface 10 .

[0046] Specifically, the thickness t of the optical thin film formed on the optical surface 20 has a maximum value tmax at X102+L / 2, i.e., (X102+X103) / 2, and at X103+L / 2, i.e., (X103+X104) / 2. Furthermore, the thickness t of the optical thin film formed on the optical surface 20 has a minimum value tmin at each of X102, X103, and X104.

[0047] FIG. 7 shows a schematic cross-sectional view of an exposure apparatus 300 equipped with a projection optical system 304 that has been processed by the method for processing an optical system according to this embodiment. The exposure apparatus 300 includes an illumination optical system 301 , a projection optical system 304 , and a substrate stage 307 .

[0048] In the exposure apparatus 300 , exposure light emitted from an illumination optical system 301 is irradiated onto a mask 303 that is arranged so that a surface on which a pattern is formed is positioned on an object plane 302 of a projection optical system 304 . The exposure light that has passed through the mask 303 is guided by a projection optical system 304 to a substrate 306 that is held by a substrate stage 307 so that the substrate surface is positioned on an image plane 305 of the projection optical system 304 . As a result, an image of the pattern drawn on the mask 303 is projected onto the surface of the substrate 306 by the projection optical system 304, and the pattern is transferred onto the substrate surface.

[0049] Furthermore, the projection optical system 304 provided in the exposure apparatus 300 includes a first lens 1 and a second lens 5 for correcting aberration, a trapezoidal mirror 2, a concave mirror 3, and a convex mirror 4. The trapezoidal mirror 2 has optical surfaces 50 and 60 which are inclined by -45° and +45°, respectively, with respect to the XY plane. In addition, the first lens 1 has optical surfaces 30 and 40 , and the second lens 5 has optical surfaces 70 and 80 .

[0050] As shown in FIG. 7, the projection optical system 304 is double-telecentric, i.e., the direction of propagation of the chief ray of the exposure light when it enters the projection optical system 304 from the object plane 302 side and the chief ray when it exits the projection optical system 304 from the image plane 305 side are both parallel to the Z direction. In addition, in the projection optical system 304, a convex mirror 4 is disposed at the pupil position, and the object plane 302 and the image plane 305 are disposed at positions symmetrical to each other with respect to the pupil. The optical surfaces 50 and 60 are arranged at positions optically conjugate to each other, the optical surfaces 30 and 80 are arranged at positions optically conjugate to each other, and the optical surfaces 40 and 70 are arranged at positions optically conjugate to each other.

[0051] In the projection optical system 304 provided in the exposure apparatus 300, optical thin films are formed on the two optical surfaces 30 and 40 of the first lens 1 according to the process shown in the flowchart of FIG. Specifically, after an optical thin film is formed on the optical surface 30 of the first lens 1 according to the process shown in the flowchart of FIG. The optical thin films formed on the optical surfaces 30 and 40 of the first lens 1 are multi-layer films having a laminated structure of 12 layers as shown in Table 1 below.

[0052] [Table 1]

[0053] In addition, Table 1 shows the product of the refractive index n and the thickness d of each layer at a wavelength of 400 nanometers.

[0054] FIG. 8(a) shows the position dependency in the X direction of the thickness t of an optical thin film formed by the film forming apparatus 100. As shown in FIG. In FIG. 8, the thickness t of the optical thin film is normalized with a predetermined thickness as a design value set to 1, and the position of the center of the material source 103 in the X direction is set to 0.

[0055] As shown in FIG. 1, in a film forming apparatus 100, a plurality of material sources 101 to 105 are arranged in the X direction. At this time, the optical thin film formed by the film forming apparatus 100 has a film thickness distribution as expressed by the following formula (2) in accordance with formula (1).

[0056]

number

[0057] In formula (2), t is the thickness of the optical thin film deposited by the multiple material sources 101 to 105, t n indicates the thickness of an optical thin film formed by a specific material source among the multiple material sources 101 to 105. In addition, in formula (2), k is a constant, h is the distance in the Z direction between the optical thin film and a given material source, and X n denotes the position in the X direction of the center of a given material source.

[0058] Here, the distance between the centers of adjacent material sources among the plurality of material sources 101 to 105 is 800 mm, and the distance h is 605 mm. In this case, the optical thin film formed by the film forming apparatus 100 has a film thickness distribution as shown in FIG. 8(a).

[0059] When such a film-forming apparatus 100 is used to form an optical thin film on an optical surface 30 having a length of 1200 mm (±600 mm) in the X direction, the formed optical thin film has a film thickness distribution as shown in FIG. 8(b). As shown in FIG. 8(b), the thickness t of the optical thin film formed on the optical surface 30 has a maximum value at the position X of 0 mm and has a minimum value at the positions X of ±400 mm, and the peak interval L in the film thickness distribution is 800 mm.

[0060] FIG. 9 shows the position dependency in the X direction of the thickness t of the optical thin film deposited on the optical surface 40 by the deposition apparatus 100. As shown in FIG. When forming an optical thin film on the optical surface 40 according to the process shown in the flowchart of FIG. 4, the holding part 110 that holds the first lens 1 is shifted in the X direction by −L / 2=−400 mm. Therefore, the thickness of the optical thin film formed on the optical surface 40 has a maximum value at the position of X=±400 mm as shown in FIG. 9, and a minimum value at the position of X=0 mm.

[0061] FIG. 10 shows the calculation results of the wavefront aberration shape of the optical thin film formed on the optical surface 30. In FIG. FIG. 11 shows the calculation results of the wavefront aberration shape of the optical thin film formed on the optical surface 40. In FIG.

[0062] The calculation results shown in each of FIGS. 10 and 11 can be obtained by using, for example, an optical simulator. 10 and 11 show the calculation results when the wavelength λ is 400 nanometers.

[0063] 10 and 11 also show calculation results at positions of -400 mm, -300 mm, -200 mm, -100 mm, and 0 mm in the X direction. 10 and 11 also show the calculation results at positions 100 mm, 200 mm, 300 mm, and 400 mm away in the X direction.

[0064] In the exposure apparatus 300, the maximum difference between the beam diameters of the exposure light passing through the same positions on the XY plane of the optical surfaces 30 and 40 of the first lens 1 provided in the projection optical system 304 is 0.4 mm. Specifically, the beam diameter of the exposure light at a given position on optical surface 30 where the maximum difference is 0.4 mm is 42.0 mm, and the beam diameter of the exposure light at the given position on optical surface 40 is 41.6 mm.

[0065] In the optical surfaces 30 and 40 in which the difference between the beam diameters of the exposure light passing through the same position in the XY plane is small, wavefront aberration shapes that are symmetrical to each other are formed, as shown in Figures 10 and 11. In other words, by forming the optical thin films on the optical surfaces 30 and 40 as described above, the wavefront aberration shapes are formed on the optical surfaces 30 and 40 such that they cancel each other out. In other words, the signs of the wavefront aberration at a first position on the optical surface 30 and a second position on the optical surface 40 that are the same relative position to the optical axis of the projection optical system 304 in the XY plane are different from each other.

[0066] Table 2 shows the worst RMS (root mean square) values ​​for the wavefront aberration of the optical surfaces 30 and 40 when the holding portion 110 that holds the first lens 1 is not shifted by L / 2 in the X direction and an optical thin film is formed on the optical surface 40. Table 2 also shows the RMS worst values ​​for the wavefront aberrations of the optical surfaces 30 and 40 when an optical thin film is formed on the optical surface 40 while performing the shift.

[0067] [Table 2]

[0068] In obtaining the RMS worst value referred to here, first, the sum of the value of wavefront aberration at a specified position within the area through which the exposure light passes, which is shown as a perfect circle on optical surface 30 as shown in Figures 10 and 11, and the value of wavefront aberration at the same specified position on optical surface 40 is calculated. Next, the root mean square value of the acquired sum within the region through which the exposure light passes is calculated. Then, the maximum value of the root mean square values ​​obtained at each position from -400 mm to 400 mm is obtained as the RMS worst value.

[0069] In other words, if the shift is not performed, optical thin films having the film thickness distribution as shown in FIG. 8(b) are formed on the optical surfaces 30 and 40, respectively, and the wavefront aberrations generated on each surface are not offset by each other, resulting in a large RMS worst value. On the other hand, by performing this shift, optical thin films having the film thickness distributions shown in FIGS. 8(b) and 9 are formed on the optical surfaces 30 and 40, respectively, so that the wavefront aberrations occurring on each cancel each other out. Therefore, the worst RMS value when the shift is performed is reduced to 10% or less of the worst RMS value when the shift is not performed.

[0070] As described above, in the optical system processing method according to this embodiment, when optical thin films are formed on two optical surfaces provided in the projection optical system, the positions of the centers of the optical surfaces in the X direction are made to differ from each other by L / 2. This makes it possible to fabricate a projection optical system that includes two optical surfaces in which the wavefront aberrations occurring at the two optical surfaces are offset by each other.

[0071] In the above description, when the optical thin film is formed on each of the two optical surfaces provided in the projection optical system, the positions of the centers of the optical surfaces in the X direction are made to differ from each other by L / 2, but the present invention is not limited to this. That is, when forming optical thin films on the two optical surfaces, the effects of this embodiment can be achieved as long as the positions of the centers of the optical surfaces in the X direction are different from each other. Furthermore, when forming an optical thin film on each of the two optical surfaces, if the positions of the centers of the optical surfaces in a plane (first plane) parallel to the X direction and Z direction are different from each other, the effect of this embodiment can be achieved.

[0072] The above also describes a process for depositing an optical thin film on two optical surfaces 30 and 40 of a single first lens 1, i.e., one optical surface and the other optical surface of a specified optical element, in accordance with the flowchart shown in FIG. In other words, the above describes the process of forming an optical thin film on a given optical surface and the optical surface closest to the given optical surface in accordance with the flowchart shown in FIG. However, the present invention is not limited to this, and the processing may be performed on two optical surfaces where the difference between the beam diameters of the exposure light passing through the same position on the XY plane is sufficiently small.

[0073] For example, in the projection optical system 304 provided in the exposure apparatus 300, for two optical surfaces 50 and 60 of a trapezoidal mirror 2 that are optically conjugate to each other, the maximum difference between the beam diameters of the exposure light passing through the same position in the XY plane is 0.1 millimeters. Therefore, even if the process of forming optical thin films on the optical surfaces 50 and 60 of the trapezoidal mirror 2 is performed according to the flowchart shown in FIG. 4, the wavefront aberrations occurring on the optical surfaces 50 and 60 can cancel each other out.

[0074] Specifically, in the method for processing an optical system according to this embodiment, it is preferable to perform a process of forming an optical thin film on each of two optical surfaces in which the ratio of the maximum difference between the beam diameters of the exposure light passing through the same position in the XY plane is 1% or less. In other words, consider a first position on one optical surface and a second position on the other optical surface that have the same relative position with respect to the optical axis of the projection optical system 304 in the XY plane. In this case, for the two optical surfaces, the ratio of the maximum difference between the first beam diameter and the second beam diameter to one of the first beam diameter and the second beam diameter of the exposure light when passing through the first position and the second position, respectively, may be 1 percent or less.

[0075] When the optical thin film is formed on the optical surfaces 30 and 40 of the first lens 1, the optical thin film serves as an anti-reflection film for preventing reflection of the exposure light by the optical surfaces 30 and 40 (first transmitting surface and second transmitting surface) of the first lens 1, which serve as transmissive optical elements through which the exposure light passes. In addition, when an optical thin film is formed on the optical surfaces 50 and 60 of the trapezoidal mirror 2, the optical thin film serves as a reflective film for improving the reflection of the exposure light by the optical surfaces 50 and 60 (first reflective surface and second reflective surface) of the trapezoidal mirror 2, which serve as reflective optical elements that reflect the exposure light.

[0076] Furthermore, if necessary, after a first optical thin film is formed on a predetermined optical surface of a predetermined optical element, the predetermined optical element may be shifted a predetermined distance in the X direction, and a second optical thin film may be formed on the first optical thin film. The method for processing an optical system according to this embodiment can also be carried out using a film deposition apparatus capable of simultaneously depositing optical thin films on each of the first optical surface and the second optical surface of a given optical element.

[0077] Although the above describes the processing (manufacturing) of the projection optical system 304 used in the exposure apparatus 300, the present invention is not limited to this. That is, the above-described method for processing an optical system according to this embodiment can also be used for processing an optical system other than the projection optical system 304 , such as the illumination optical system 301 used in the exposure apparatus 300 .

[0078] [Production method] The method for manufacturing an article according to this embodiment includes a step of exposing a substrate, such as a wafer or a glass substrate, coated with a photosensitive agent, using an exposure apparatus 300 equipped with a projection optical system 304 processed by the method for processing an optical system according to this embodiment. The articles in question include semiconductor integrated circuit (IC) elements, liquid crystal display elements, and microelectromechanical systems (MEMS), etc.

[0079] The method for manufacturing an article according to this embodiment also includes a step of developing the exposed substrate (photosensitive agent) and other known steps of processing the developed substrate. The other well-known processes include etching, photoresist peeling, dicing, bonding, packaging, and the like.

[0080] According to the method for manufacturing an article according to this embodiment, it is possible to manufacture an article of higher quality than before. Although the preferred embodiments have been described above, the present invention is not limited to these embodiments and various modifications and changes are possible within the scope of the gist thereof.

[0081] The disclosure of this embodiment includes the following configurations and methods. (Method 1) A processing method for processing an optical system used in an exposure apparatus, comprising: a first arrangement step of arranging a first optical element to be provided in the optical system in a film formation apparatus; a first film formation step of forming an optical thin film having a predetermined film thickness distribution on a first optical surface of the first optical element in the film formation apparatus; a second arrangement step of arranging a second optical element to be provided in the optical system in the film formation apparatus; and a second film formation step of forming an optical thin film having a predetermined film thickness distribution on a second optical surface of the second optical element in the film formation apparatus, wherein a first relative position of the center of the first optical surface with respect to a reference position of the film formation apparatus in the first arrangement step and a second relative position of the center of the second optical surface with respect to the reference position in the second arrangement step are different from each other. (Method 2) A processing method according to Method 1, wherein the film formation apparatus has a plurality of material sources arranged at a distance from each other in the first direction. (Method 3) A processing method according to Method 2, characterized in that the first positioning step includes a step of positioning a first optical element so that the multiple material sources and the first optical surface face each other in a second direction perpendicular to the first direction, and the second positioning step includes a step of positioning a second optical element so that the multiple material sources and the second optical surface face each other in the second direction. (Method 4) A processing method according to Method 3, characterized in that the first relative position and the second relative position are different from each other within a first plane parallel to the first direction and the second direction. (Method 5) A processing method according to Method 3 or 4, characterized in that the first film formation step includes a step of scanning the first optical surface in a third direction perpendicular to the first direction and the second direction, and the second film formation step includes a step of scanning the second optical surface in the third direction. (Method 6) A processing method described in any one of Methods 2 to 5, characterized in that in the film formation apparatus, the multiple material sources are arranged so that the intervals between adjacent material sources are identical to each other, and when the interval is L, the first relative position and the second relative position differ by L / 2 in the first direction. (Method 7) A processing method according to any one of Methods 1 to 6, characterized in that in the predetermined film thickness distribution, the film thickness changes periodically in the first direction. (Method 8) The processing method described in Method 7, characterized in that the second arrangement step includes a measurement step of measuring at least one of the distance between adjacent positions in a first direction among a plurality of positions where the film thickness takes a maximum value in the optical thin film formed on the first optical surface by the first film formation step and the distance between adjacent positions in the first direction among a plurality of positions where the film thickness takes a minimum value, and a step of arranging the second optical element such that the first relative position and the second relative position differ from each other by half the distance measured in the measurement step in the first direction. (Method 9) A processing method described in any one of Methods 1 to 8, characterized in that the first optical surface of the first optical element is one optical surface of a predetermined optical element, and the second optical surface of the second optical element is the other optical surface of the predetermined optical element. (Method 10) The processing method according to any one of Methods 1 to 9, wherein the optical thin film is a multilayer film. (Method 11) A processing method described in any one of Methods 1 to 10, characterized in that the first film formation step includes a step of adhering sputtered particles onto a first optical surface, and the second film formation step includes a step of adhering sputtered particles onto a second optical surface. (Configuration 1) A projection optical system processed by the processing method described in any one of Methods 1 to 11. (Configuration 2) An exposure apparatus that projects an image of a pattern of an original onto a substrate and exposes the substrate, characterized in that it includes the projection optical system described in configuration 1 that projects an image onto the substrate surface of the substrate by guiding exposure light that has passed through the original to the substrate. (Configuration 3) An exposure apparatus as described in Configuration 2, characterized in that a ratio of a maximum value of a difference between a first beam diameter and a second beam diameter of the exposure light when passing through a first position on a first optical surface and a second position on a second optical surface, which have the same relative positions with respect to the optical axis within a second plane perpendicular to the optical axis of the projection optical system, to one of the first beam diameter and the second beam diameter is 1 percent or less. (Configuration 4) An exposure apparatus according to configuration 3, wherein the first optical surface and the second optical surface are disposed at positions optically conjugate with each other. (Configuration 5) An exposure apparatus described in any one of Configurations 2 to 4, characterized in that the first film formation process includes a process of forming an anti-reflection coating having a predetermined film thickness distribution on one transmitting surface of a transmitting optical element through which the exposure light passes, and the second film formation process includes a process of forming an anti-reflection coating having a predetermined film thickness distribution on the other transmitting surface of the transmitting optical element. (Configuration 6) An exposure apparatus described in any one of configurations 2 to 4, characterized in that the first film formation process includes a process of forming a reflective film having a predetermined film thickness distribution on a first reflective surface of a reflective optical element that reflects exposure light, and the second film formation process includes a process of forming a reflective film having a predetermined film thickness distribution on a second reflective surface of the reflective optical element. (Configuration 7) An exposure apparatus described in any one of configurations 2 to 6, characterized in that the signs of wavefront aberration at a first position on a first optical surface and a second position on a second optical surface, which have the same relative positions with respect to the optical axis in a second plane perpendicular to the optical axis of the projection optical system, are different from each other. (Method 12) A method for manufacturing an article, comprising the steps of exposing a substrate by the exposure apparatus according to any one of Structures 2 to 7, and developing the exposed substrate. [Explanation of symbols]

[0082] 10 Optical surface (first optical surface) 20 Optical Surface (Second Optical Surface) 100 Film deposition equipment 106 Optical element (first optical element, second optical element) 300 Exposure device 304 Projection optical system (optical system)

Claims

1. A processing method for processing an optical system used in an exposure apparatus, comprising the steps of: a first arrangement step of arranging a first optical element to be provided in the optical system in a film forming apparatus; a first film formation step of forming an optical thin film having a predetermined film thickness distribution on a first optical surface of the first optical element in the film formation apparatus; a second arrangement step of arranging a second optical element provided in the optical system in the film forming apparatus; a second film formation step of forming the optical thin film having the predetermined film thickness distribution on the second optical surface of the second optical element in the film formation device; Including, a first relative position of the center of the first optical surface with respect to a reference position of the film forming apparatus in the first positioning step, and a second relative position of the center of the second optical surface with respect to the reference position in the second positioning step, the first relative position of the center of the first optical surface with respect to the reference position of the film forming apparatus in the second positioning step being different from each other.

2. 2. The method according to claim 1, wherein the deposition apparatus has a plurality of material sources arranged at a distance from each other in a first direction.

3. the first arrangement step includes the step of arranging the first optical element such that the plurality of material sources and the first optical surface face each other in a second direction perpendicular to the first direction; The processing method according to claim 2 , wherein the second positioning step includes a step of positioning the second optical element so that the multiple material sources and the second optical surface face each other in the second direction.

4. 4. The processing method according to claim 3, wherein the first relative position and the second relative position are different from each other in a first plane parallel to the first direction and the second direction.

5. the first film forming step includes a step of scanning the first optical surface in a third direction perpendicular to the first direction and the second direction; 4. The processing method according to claim 3, wherein the second film forming step includes a step of scanning the second optical surface in the third direction.

6. In the film forming apparatus, the plurality of material sources are arranged such that the intervals between adjacent material sources are uniform; 3. The processing method according to claim 2, wherein when the distance is L, the first relative position and the second relative position differ by L / 2 in the first direction.

7. 2. The processing method according to claim 1, wherein the predetermined film thickness distribution has a film thickness that changes periodically in a first direction.

8. The second arrangement step includes: a measuring step of measuring at least one of a distance between adjacent positions in the first direction among a plurality of positions where the film thickness has a local maximum value, and a distance between adjacent positions in the first direction among a plurality of positions where the film thickness has a local minimum value, in the optical thin film formed on the first optical surface by the first film forming step; positioning the second optical element such that the first relative position and the second relative position differ from each other in the first direction by half the distance measured by the measuring step; The method according to claim 7, further comprising:

9. the first optical surface of the first optical element is one optical surface of a predetermined optical element, 2. The method according to claim 1, wherein the second optical surface of the second optical element is the other optical surface of the predetermined optical element.

10. 2. The processing method according to claim 1, wherein the optical thin film is a multi-layer film.

11. the first film forming step includes a step of depositing sputtered particles on the first optical surface, 2. The processing method according to claim 1, wherein the second film forming step includes a step of depositing the sputtered particles onto the second optical surface.

12. A projection optical system processed by the processing method according to any one of claims 1 to 11.

13. An exposure apparatus that projects an image of a pattern of an original onto a substrate and exposes the substrate, comprising:

13. An exposure apparatus comprising: the projection optical system according to claim 12, which projects the image onto a substrate surface of the substrate by guiding exposure light that has passed through the original to the substrate.

14. 14. The exposure apparatus according to claim 13, wherein a ratio of a maximum value of a difference between a first beam diameter and a second beam diameter of the exposure light when passing through a first position on the first optical surface and a second position on the second optical surface, the first position and the second position being the same relative position with respect to the optical axis in a second plane perpendicular to the optical axis of the projection optical system, is 1 percent or less.

15. 15. The exposure apparatus according to claim 14, wherein the first optical surface and the second optical surface are disposed at positions optically conjugate with each other.

16. the first film formation step includes a step of forming an antireflection film having the predetermined film thickness distribution on one transmission surface of a transmission optical element through which the exposure light passes, 14. The exposure apparatus according to claim 13, wherein the second film forming step includes a step of forming the anti-reflection film having the predetermined film thickness distribution on the other transmission surface of the transmission optical element.

17. the first film formation step includes a step of forming a reflective film having the predetermined film thickness distribution on a first reflecting surface of a reflective optical element that reflects the exposure light, 14. The exposure apparatus according to claim 13, wherein the second film forming step includes a step of forming the reflective film having the predetermined film thickness distribution on a second reflective surface of the reflective optical element.

18. The exposure apparatus of claim 13, wherein the signs of wavefront aberration at a first position on the first optical surface and a second position on the second optical surface, which have the same relative positions with respect to the optical axis in a second plane perpendicular to the optical axis of the projection optical system, are different from each other.

19. exposing a substrate by the exposure apparatus according to claim 13; developing the exposed substrate; A method for producing an article, comprising:

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