JP2014034497A - Method for manufacturing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid, on an occasion for manufacturing a photomask used for an exposure apparatus, predicaments affecting imaging performances of the exposure apparatus.SOLUTION: During a work for creating a substrate-for-photomask 9, the current shape of the substrate-for-photomask 9 is measured by computing the shape of a convex plane of a specified curvature constituting the upper plane 9b thereof or of a concave plane of a specified curvature constituting the lower plane 9c thereof. Next, the distribution of weights W mounted respectively on multiple load mounting regions A of the substrate-for-photomask 9 is determined based on the difference of the shape of the convex plane of the upper plane 9b or the concave plane of the lower plane 9c and the current shape. Subsequently, the substrate-for-photomask 9 is mounted on the upper side of the grinding plane of grinding means, and a work of creating the upper plane 9b or lower plane 9c of the substrate-for-photomask 9 is performed by relatively mobilizing the grinding plane against the substrate-for-photomask 9 in a state where weights W are being mounted on the regions A in compliance with the predetermined distribution of weights W. In a case where the substrate-for-photomask 9 thus processed is configured virtually horizontally in a state where the peripheral edge 9a thereof is being supported, the vicinity of the middle portion 9d thereof sags due to dead weight and embodies a flat surface.

Description

  The present invention relates to a method for manufacturing an optical element applied when manufacturing an optical element such as a photomask used in an exposure apparatus.

  Conventionally, when manufacturing this type of photomask, both sides of the photomask substrate are processed to be flat (flat) (see, for example, Patent Document 1). When this photomask is used in an exposure apparatus, the peripheral portion of the photomask is supported and arranged horizontally.

JP 2003-292346 A

  However, in such a photomask, when it is horizontally arranged in the exposure apparatus, there is a tendency that the vicinity of the center part hangs down due to its own weight and both surfaces become curved. For example, in a photomask made of quartz glass having a rectangular plate shape with a length of 1220 mm, a width of 1400 mm, and a thickness of 13 mm, there is a calculation example in which the most drooping center portion is bent by about 60 μm. Then, when the photomask arranged in the exposure apparatus bends, there is a problem in that it affects the imaging performance of the exposure apparatus.

  In view of such circumstances, the present invention has a situation in which the imaging performance of an exposure apparatus is affected by making both sides of the photomask flat when the photomask is horizontally arranged in the exposure apparatus. It is an object of the present invention to provide a method for manufacturing an optical element that can avoid the above-described problem.

  The first method for manufacturing an optical element according to the present invention creates both surfaces (9b, 9c) of an optical element substrate (9) to be used by being arranged substantially horizontally with the peripheral edge (9a) being supported. A method of manufacturing an optical element (1) to be processed and molded, wherein the optical element substrate has its center surface (9d) hanging down by its own weight when the peripheral edge portion is supported, and the both surfaces are flat. In such a manner that the one surface (9b) becomes a predetermined convex surface and the other surface (9c) becomes a predetermined concave surface before the peripheral edge is supported by the creation process. The forming process is molded, the target shape calculating step for calculating the shape of the predetermined convex surface or the predetermined concave surface of the optical element substrate, and the shape measuring step for measuring the current shape of the optical element substrate; , The optical calculated in the target shape calculating step Based on the difference between the shape of the predetermined convex surface or the predetermined concave surface of the child substrate and the current shape of the optical element substrate measured in the shape measurement step, a plurality of loading regions ( A load distribution determining step for determining the distribution of the load (W) acting on A), and placing the optical element substrate on the polishing surface (7a) of the polishing means (8). By moving the polishing surface relative to the optical element substrate in a state where a load is applied to the load region according to the determined load distribution, the one surface or the other surface of the optical element substrate is moved. And a substrate generating process for generating a surface of the optical element.

  Here, in order to explain the present invention in an easy-to-understand manner, the description has been made in association with the reference numerals of the drawings representing the embodiments. However, it goes without saying that the present invention is not limited to the embodiments.

  According to the present invention, when the optical element substrate is a photomask substrate, since both sides of the photomask are flat when the photomask is horizontally arranged in the exposure apparatus, the image of the exposure apparatus is formed. It is possible to avoid a situation that affects performance.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the photomask which concerns on Embodiment 1 of this invention, Comprising: (a) is a perspective view of a photomask, (b) is an enlarged side view of the state in which the photomask was set up vertically, (c) is It is an enlarged side view of the state where the photomask is horizontally arranged in the exposure apparatus. 3 is a flowchart showing a procedure of a photomask manufacturing method according to the first embodiment. It is a figure which shows the substrate for photomasks which concerns on the same Embodiment 1, Comprising: (a) is a top view of the substrate for photomasks, (b) is a front view which shows the loading state of the substrate for photomasks. It is a figure which shows the method of the primary creation process of the photomask substrate which concerns on the same Embodiment 1, Comprising: (a) is a top view of a single-side polish apparatus, (b) is a front view of a single-side polish apparatus. FIG. 6 is a diagram illustrating a part of a software display screen for determining weight distribution in the photomask manufacturing method according to the first embodiment. In the manufacturing method of the photomask which concerns on Example 1, it is a schematic diagram which shows transition of the shape of the lower surface of the board | substrate for photomasks, Comprising: (a) is a figure before a process, (b) is an example after a primary creation process. (C) is a figure which shows an example after final polishing, (d) is a figure which shows another example after final polishing. In the manufacturing method of the photomask which concerns on Example 1, it is a schematic diagram which shows transition of the shape of the upper surface of the board | substrate for photomasks, Comprising: (a) is a figure before a process, (b) is an example after a primary creation process. (C) is a figure which shows an example after final polishing, (d) is a figure which shows another example after final polishing. In the manufacturing method of the photomask which concerns on Example 1, it is a line graph which shows transition of the flatness of the lower surface and upper surface of a photomask substrate.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

  1 to 4 are diagrams according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the optical element according to the first embodiment is a photomask 1 made of rectangular plate-shaped quartz glass having a predetermined size (for example, length 1220 mm, width 1400 mm, thickness 13 mm), As shown in FIG. 1C, the exposure apparatus 2 is used by being arranged substantially horizontally with the peripheral edge 1a supported.

  Then, as shown in FIG. 1B, the photomask 1 has a predetermined upper surface 1b because its own weight does not act in the thickness direction (that is, the horizontal direction) of the photomask 1 when it is set up vertically. The lower surface 1c is shaped to be a concave surface having a predetermined curvature. However, as shown in FIG. 1C, when the peripheral portion 1a is supported by the exposure apparatus 2 and is arranged horizontally, its own weight acts in the thickness direction of the photomask 1 (that is, the vertical direction). As indicated by a solid line in 1 (c), the upper surface 1b and the lower surface 1c are both flat. Therefore, in the photomask 1, unlike the conventional photomask 1 in which the upper surface 1 b and the lower surface 1 c are curved due to their own weight when placed horizontally on the exposure apparatus 2, the imaging performance of the exposure apparatus 2 is affected. It can be avoided.

  When manufacturing such a photomask 1, when the photomask 1 is horizontally disposed with its peripheral edge 1 a supported, the vicinity of the center portion 1 d of the photomask 1 hangs down due to the weight of the photomask 1. In order to form both surfaces (upper surface 1b and lower surface 1c) as a flat surface, the lower surface 1c is previously formed as a concave surface with a predetermined curvature and the upper surface 1b is formed with a convex surface with a predetermined curvature.

  For this purpose, first, as shown in FIG. 3, a photomask substrate 9 having a predetermined size is prepared, and the upper surface 9b of the photomask substrate 9 is divided into six equal parts in the vertical and horizontal directions and divided into a grid. Thus, 36 loading areas A (A1, A2, A3) are formed on the photomask substrate 9. Then, in anticipation of deflection due to its own weight when the photomask 1 is disposed horizontally, the peripheral portion is created by the creation process of the photomask substrate 9 described below according to the procedure (steps S1 to S13) of the flowchart shown in FIG. In a state before 9a is supported, the lower surface 9c is formed into a concave surface with a predetermined curvature, and the upper surface 9b is formed into a convex surface with a predetermined curvature.

  That is, in the creation process of the photomask substrate 9, first, a concave surface having a predetermined curvature is formed on the lower surface 9c of the photomask substrate 9 (steps S1 to S6).

  Therefore, first, in the lower surface target shape calculation step, the target shape of the lower surface 9c of the photomask substrate 9 is calculated on the condition of the substrate characteristics relating to the specifications of the exposure apparatus and the deflection amount (step S1).

  Next, the process proceeds to the first bottom surface shape measuring step, and the current state (that is, photo) of the bottom surface 9c of the photomask substrate 9 is measured by a flatness measuring device (not shown) with the photomask substrate 9 standing vertically. The shape of the lower surface 9c of the mask substrate 9 is measured (step S2).

  Thereafter, the process proceeds to a lower surface load distribution determining step, and a predetermined size to be placed on each loading area A of the photomask substrate 9 based on the difference between the target shape of the lower surface 9c of the photomask substrate 9 and the current shape. The distribution of weights (weights) W made of brass having a rectangular plate shape with a weight (for example, 135 mm in length, 155 mm in width, 20 mm in thickness, 3.5 kg in weight) is determined (step S3).

  Here, since the concave surface is formed on the lower surface 9 c of the photomask substrate 9, the peripheral portion 9 a of the photomask substrate 9 is increased in order to increase the processing amount in the vicinity of the central portion 9 d than in the vicinity of the peripheral portion 9 a of the photomask substrate 9. The distribution of the weights W is determined so that more weights W are placed near the center portion 9d than in the vicinity and a large load is applied. For example, as shown in FIG. 3, among the 36 loading areas A, 20 loading areas A1 corresponding to the vicinity of the peripheral edge 9a of the photomask substrate 9 (portions lightly displayed in FIG. 3A). Two weights W are respectively mounted, and four weights W are respectively mounted on four loading areas A2 (parts darkly shown in FIG. 3A) corresponding to the vicinity of the center portion 9d of the photomask substrate 9; The distribution of the weights W is determined so that the three weights W are placed on the remaining twelve loading areas A3 (portions indicated by intermediate darkness in FIG. 3A).

  Next, the process proceeds to a lower surface creation process, and as shown in FIG. 4, primary creation is performed on the lower surface 9c of the photomask substrate 9 using a predetermined single-side polishing apparatus 8 (step S4).

  That is, this single-side polishing apparatus 8 has a machine body 5 as shown in FIG. 4, and a disk-shaped lower surface plate 7 is rotatable on the machine body 5 in the direction of arrow M around a predetermined axis CT1. Is attached. On the upper side of the lower surface plate 7, a disk-shaped carrier 6 having a diameter smaller than that of the lower surface plate 7 is mounted so as to be rotatable in the direction of arrow N around the axis center CT 2 that is eccentric from the axis center CT 1 of the lower surface plate 7. ing. A rectangular guide hole 6 a for guiding the photomask substrate 9 is formed through the center of the carrier 6. The arrow M direction and the arrow N direction are the same direction (counterclockwise as viewed from above the single-side polishing apparatus 8), as shown in FIG.

  Then, when primary generation processing is performed on the lower surface 9c of the photomask substrate 9 using the single-side polishing apparatus 8, by installing the photomask substrate 9 in the guide hole 6a of the carrier 6, After the photomask substrate 9 is placed above the polishing surface 7a of the lower surface plate 7, the distribution of the weight W determined in step S3 (that is, the central portion 9d compared to the vicinity of the peripheral portion 9a of the photomask substrate 9). The weight W is placed on the loading area A of the photomask substrate 9 according to a distribution in which many weights W are placed in the vicinity. In this state, while supplying an abrasive (not shown) between the polishing surface 7a of the lower surface plate 7 and the lower surface 9c of the photomask substrate 9, the lower surface plate 7 is moved in the direction of arrow M about the axis CT1. While rotating at a predetermined rotation speed, the carrier 6 is rotated together with the photomask substrate 9 in the direction of arrow N around the axis CT2 at substantially the same rotation speed. Then, the polishing surface 7a of the lower surface plate 7 is in relation to the lower surface 9c of the photomask substrate 9 with the abrasive interposed between the polishing surface 7a of the lower surface plate 7 and the lower surface 9c of the photomask substrate 9. The relative movement is performed, and the lower surface 9c of the photomask substrate 9 is subjected to primary generation processing evenly by the abrasive.

  At this time, in the loading area A of the photomask substrate 9, as described above, more weights W are placed in the vicinity of the central portion 9d than in the vicinity of the peripheral edge portion 9a of the photomask substrate 9. The lower surface 9c of the substrate 9 is removed by this primary creation process as the distance from the peripheral edge 9a to the center 9d of the photomask substrate 9 increases. As a result, a concave surface is formed on the lower surface 9 c of the photomask substrate 9.

  Thereafter, the process proceeds to the second bottom surface shape measurement step, and in the same manner as step S2, the photomask substrate 9 is set upright, and the flatness measuring device is used to measure the current state of the bottom surface 9c of the photomask substrate 9 (that is, The shape of the lower surface 9c of the photomask substrate 9 is measured immediately after the primary creation process (step S5).

  Next, the process proceeds to the lower surface shape determination step, where a difference between the target shape of the lower surface 9c of the photomask substrate 9 and the current shape is obtained, and it is determined whether or not this difference is within a predetermined allowable range ( Step S6).

  As a result, if this difference is not within the predetermined allowable range, steps S3 to S6 are repeated. When this difference falls within a predetermined allowable range, a concave surface having a predetermined target value (for example, 30 μm) is formed on the lower surface 9c of the photomask substrate 9.

  Next, a convex surface having a predetermined curvature is formed on the upper surface 9b of the photomask substrate 9 (steps S7 to S12).

  Therefore, first, in the upper surface target shape calculation step, the target shape of the upper surface 9b of the photomask substrate 9 is calculated on the condition of the substrate characteristics relating to the specifications of the exposure apparatus and the deflection amount (step S7).

  Next, the process proceeds to the first upper surface shape measurement step, and the photomask substrate 9 is set upright, and the flatness measuring device is used to measure the current upper surface 9b of the photomask substrate 9 (that is, the photomask substrate 9). The shape of the upper surface 9b before processing is measured (step S8).

  Thereafter, the process proceeds to an upper surface load distribution determining step, and the distribution of the weight W placed on each loading area A of the photomask substrate 9 based on the difference between the target shape of the upper surface 9b of the photomask substrate 9 and the current shape. Is determined (step S9).

  Here, in order to form a convex surface on the upper surface 9b of the photomask substrate 9, in order to increase the amount of processing in the vicinity of the peripheral portion 9a than in the vicinity of the central portion 9d of the photomask substrate 9, in contrast to step S3 described above, The distribution of the weight W is determined so that a larger load acts on the weight 9 in the vicinity of the peripheral portion 9a than in the vicinity of the center portion 9d of the photomask substrate 9. For example, as shown in FIG. 3, among the 36 loading areas A, 20 loading areas A1 corresponding to the vicinity of the peripheral edge 9a of the photomask substrate 9 (portions lightly displayed in FIG. 3A). Four weights W are respectively mounted, and two weights W are respectively mounted on four loading areas A2 (parts darkly shown in FIG. 3A) corresponding to the vicinity of the center portion 9d of the photomask substrate 9. The distribution of the weights W is determined so that the three weights W are placed on the remaining twelve loading areas A3 (portions indicated by intermediate darkness in FIG. 3A).

  Next, the process proceeds to the upper surface generation processing step, and the same procedure as step S4 described above is performed with the photomask substrate 9 turned upside down and the upper surface 9b in contact with the polishing surface 7a of the lower surface plate 7 of the single-side polishing apparatus 8. Thus, primary generation processing is performed on the upper surface 9b of the photomask substrate 9 using the single-side polishing apparatus 8 (step S10).

  At this time, in the loading area A of the photomask substrate 9, as described above, more weights W are placed in the vicinity of the peripheral portion 9a than in the vicinity of the center portion 9d of the photomask substrate 9. The amount of the upper surface 9b of the substrate 9 removed by the primary creation process increases as the distance from the central portion 9d of the photomask substrate 9 toward the peripheral portion 9a increases. As a result, a convex surface is formed on the upper surface 9 b of the photomask substrate 9.

  Thereafter, the process proceeds to the second upper surface shape measurement step, and in the same manner as in step S8, the photomask substrate 9 is set up vertically, and the flatness measuring device is used to measure the current upper surface 9b of the photomask substrate 9 (that is, The shape of the upper surface 9b of the photomask substrate 9 is measured (immediately after the primary creation process) (step S11).

  Next, the process proceeds to an upper surface shape determination step, where a difference between the target shape of the upper surface 9b of the photomask substrate 9 and the current shape is obtained, and it is determined whether or not this difference is within a predetermined allowable range ( Step S12).

  As a result, if this difference is not within the predetermined allowable range, steps S9 to S12 are repeated. If this difference falls within a predetermined allowable range, a convex surface having a predetermined target value (for example, 30 μm) is formed on the upper surface 9b of the photomask substrate 9.

  Finally, the process proceeds to the substrate finishing step, and the upper and lower surfaces (upper surface 9b and lower surface 9c) of the photomask substrate 9 are finish-polished using a predetermined double-side polishing apparatus (not shown), and then the photomask The substrate 9 is cleaned (step S13).

Here, the creation process of the photomask substrate 9 is completed, and the photomask 1 is completed.
[Other Embodiments of the Invention]

  In the first embodiment described above, the case where 36 loading areas A are formed on the photomask substrate 9 has been described, but the number of loading areas A is not limited to 36.

  In the above-described first embodiment, the case where the weight W having a predetermined size is used has been described. However, if the weight W is reduced, the number of the loading areas A can be increased. As a result, the flatness of the photomask substrate 9 can be further improved by finely determining the distribution of the weights W.

  Moreover, although Embodiment 1 mentioned above demonstrated the case where the weight W which consists of rectangular plate-shaped brass was used, the shape and material of the weight W are not necessarily limited. For example, a container (not shown) corresponding to each loading area A may be prepared, and powder, liquid, or the like may be put in the container as a weight W.

  Further, in the above-described first embodiment, the case where the lower surface 9c and the upper surface 9b of the photomask substrate 9 are finished to have an uneven surface has been described. However, in addition to finishing the uneven surface, high-accuracy polishing with high-precision flatness exceeding the flatness of the lower surface plate 7 of the single-side polishing device 8 (for example, less than 10 μm) is also possible.

  Further, in the first embodiment described above, a case where primary generation processing is performed on the photomask substrate 9 using the single-side polishing apparatus 8 in the lower surface generation processing step (step S4) and the upper surface generation processing step (step S10). explained. However, it is of course possible to substitute polishing means other than the single-side polishing apparatus 8 (for example, a lapping apparatus).

  Furthermore, in the first embodiment described above, the case where the optical element is the photomask 1 has been described. However, an optical element other than the photomask 1 (for example, a reticle mask for semiconductor, a wavefront forming optical element for radiation, a projection / illumination system, etc.) as long as the peripheral edge 1a is bent substantially horizontally while being supported. The present invention can be similarly applied to a lens distortion correction optical element or the like.

Examples of the present invention will be described below. In addition, this invention is not limited to an Example.
<Example 1>

  5 to 8 are diagrams according to Embodiment 1 of the present invention.

  A photomask substrate 9 made of quartz glass having a rectangular plate shape with a length of 1220 mm, a width of 1400 mm, and a thickness of 13 mm was prepared, and the photomask 1 was manufactured according to the procedure of the first embodiment described above.

  At this time, in the lower surface load distribution determining step (step S3) and the upper surface load distribution determining step (step S9), software S that supports the determination of the weight W distribution was used. As shown in FIG. 5, the software S takes in the difference between the target shape of the lower surface 9c and the upper surface 9b of the photomask substrate 9 and the current shape as input data, and flatness data based on the difference is obtained. Displayed in the first display area D1 due to the difference in color. Then, after calculating the number of weights W placed on each loading area A of the photomask substrate 9 based on this input data, the output data includes the second number of weights W for each loading area A in a different color. Displayed in the display area D2. The output data displayed in this way can be changed manually by the operator's judgment if necessary.

  The target values for the lower surface 9c and the upper surface 9b of the photomask substrate 9 were both 30 μm. Therefore, the primary creation of the photomask substrate 9 is performed 8 times for each of the lower surface 9c and the upper surface 9b. Further, the final polishing of the photomask substrate 9 was performed seven times for each of the lower surface 9c and the upper surface 9b.

  In manufacturing the photomask 1, the transition of the flatness of the lower surface 9c and the upper surface 9b of the photomask substrate 9 was examined.

  As a result, as shown in FIG. 6, it was confirmed that the lower surface 9c of the photomask substrate 9 approaches a concave surface having a predetermined curvature as the primary creation process and the finish polishing process proceed. That is, in the state before processing, although the color scheme deviated from the concentric color scheme corresponding to the concave surface of the predetermined curvature is displayed in the first display area D1 of the software S as shown in FIG. On the other hand, in the state after the primary creation process and the finish polishing process, as shown in FIGS. 6B to 6D, a color scheme close to the concentric color scheme corresponding to the concave surface having a predetermined curvature is obtained by the software S. Displayed in the first display area D1.

  Further, as shown in FIG. 7, it was confirmed that the upper surface 9b of the photomask substrate 9 approaches a convex surface having a predetermined curvature as the primary creation process and the finish polishing process proceed. That is, in the state before processing, although the color scheme deviated from the concentric color scheme corresponding to the convex surface having a predetermined curvature is displayed in the first display area D1 of the software S as shown in FIG. On the other hand, in the state after the primary creation process and the finish polishing process, as shown in FIGS. 7B to 7D, a color scheme close to the concentric color scheme corresponding to the convex surface having a predetermined curvature is obtained from the software S. Displayed in the first display area D1.

The line graph of FIG. 8 shows finely the transition of the flatness of the lower surface 9c and the upper surface 9b of the photomask substrate 9. In this line graph, the horizontal axis represents time (the number of machining operations), and the vertical axis represents flatness (unit: μm). As is apparent from the line graph, in the photomask substrate 9, the flatness approaches the target value of 30 μm as the lower surface 9 c and the upper surface 9 b are repeatedly subjected to the primary creation process, and the target value is obtained by finish polishing. Was observed to be maintained.
<Modification>

  In the first embodiment described above, when the photomask 1 is manufactured, the flatness data is stored in the first display area D1 in the lower surface load distribution determining step (step S3) and the upper surface load distribution determining step (step S9). The case of displaying is described. However, instead of displaying the flatness data as it is in the first display area D1, for example, the data from the target values set in the lower surface shape determining step (step S6) and the upper surface shape determining step (step S12). A value obtained by subtracting may be displayed. In this way, although it is actually finished with an uneven surface, it is displayed on the software S in the same way as normal polishing for flat finishing. It is possible to avoid the situation where the work is confused and the work is lost.

  The present invention can be widely applied when manufacturing an optical element such as a photomask used in an exposure apparatus.

1 ... Photomask (optical element)
DESCRIPTION OF SYMBOLS 1a ... Peripheral part 1b ... Upper surface 1c ... Lower surface 1d ... Center part 2 ... Exposure apparatus 5 ... Machine body 6 ... Carrier 6a ... Guide hole 7 ... Lower surface plate 7a ... Polishing surface 8 ... One side Polishing device (polishing means)
9 …… Photomask substrate (Optical element substrate)
9a: Peripheral part 9b: Upper surface 9c: Lower surface 9d: Center part A: Loading area W: Weight (load)

Claims (5)

A method of manufacturing an optical element that creates and molds both surfaces of a substrate for an optical element that is used while being arranged substantially horizontally with a peripheral edge supported,
The optical element substrate is in a state before the peripheral portion is supported by the creation processing so that when the peripheral portion is supported, the vicinity of the central portion hangs down by its own weight and the both surfaces become flat. Then, one surface becomes a predetermined convex surface and the other surface is formed so as to be a predetermined concave surface,
The creation process is
A target shape calculating step for calculating the shape of the predetermined convex surface or the predetermined concave surface of the optical element substrate;
A shape measuring step for measuring a current shape of the optical element substrate;
Based on the difference between the shape of the predetermined convex surface or the predetermined concave surface of the optical element substrate calculated in the target shape calculation step and the current shape of the optical element substrate measured in the shape measurement step, A load distribution determining step for determining a distribution of loads to be applied to a plurality of loading regions of the optical element substrate;
The optical element substrate is placed on the upper side of the polishing surface of the polishing means, and a load is applied to the load region according to the load distribution determined in the load distribution determination step, with respect to the optical element substrate. And a substrate creating process step of creating the one surface or the other surface of the optical element substrate by relatively moving the polishing surface. A method of manufacturing an optical element that creates and molds both surfaces of a substrate for an optical element that is used while being arranged substantially horizontally with a peripheral edge supported,
The optical element substrate is in a state before the peripheral portion is supported by the creation processing so that when the peripheral portion is supported, the vicinity of the central portion hangs down by its own weight and the both surfaces become flat. Then, one surface is a convex surface having a predetermined curvature and the other surface is formed to be a concave surface having a predetermined curvature,
The creation process is
A target shape calculating step for calculating the shape of the convex surface of the predetermined curvature or the concave surface of the predetermined curvature of the optical element substrate;
A shape measuring step for measuring a current shape of the optical element substrate;
The shape of the convex surface of the predetermined curvature or the concave surface of the predetermined curvature calculated in the target shape calculation step and the current shape of the optical element substrate measured in the shape measurement step A load distribution determining step for determining a distribution of a load to be applied to a plurality of loading regions of the optical element substrate based on the difference;
The optical element substrate is placed on the upper side of the polishing surface of the polishing means, and a load is applied to the load region according to the load distribution determined in the load distribution determination step, with respect to the optical element substrate. And a substrate creating process step of creating the one surface or the other surface of the optical element substrate by relatively moving the polishing surface.   The load is applied to the load area so that the magnitude of the load acting on the load area increases and decreases between a central portion and a peripheral edge of the optical element substrate in the substrate generation processing step. Item 3. A method for producing an optical element according to Item 1 or 2.   4. The substrate creation processing step of creating a bottom surface of the optical element substrate in a state where a load is applied to the loading region by placing a weight on the loading region. The manufacturing method of the optical element in any one of.   5. The method for manufacturing an optical element according to claim 1, wherein the optical element substrate is a photomask substrate.