Diffraction grating and analytical apparatus using the same, method for manufacturing diffraction grating

Abstract

To provide a diffraction grating with finer grating grooves than the processing limits of existing semiconductor processes or machining.SOLUTION: A diffraction grating mounted on an analytical apparatus is characterized by that a diffraction grating substrate is fabricated by arranging multiple gratings with approximately rectangular cross-sectional shapes on a silicon substrate, the surface of the diffraction grating substrate is thermally oxidized to shrink the gaps between the gratings, and the thermally oxidized diffraction grating substrate is used as a mold and fabricated by transferring the gap pattern onto transparent resin or glass.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a diffraction grating structure and a manufacturing method thereof, and more particularly to a technique that is effective when applied to a diffraction grating having a finer diffraction grating pattern than can be formed by a semiconductor process. [Background technology]

[0002] Diffraction gratings, which disperse various types of light from soft X-rays to the far-infrared region, are used in many fields as an indispensable optical element in spectroscopic instruments. For example, diffraction gratings installed in spectroscopic analysis equipment disperse light of specific wavelengths and introduce them into a detector. After irradiating a sample with light from a light source, the diffraction grating separates the light into individual wavelengths, and the absorption of light by the sample is detected based on its intensity. Conventionally, such diffraction gratings have been manufactured by transferring a mold made by mechanical ruling or holographic exposure onto resin or metal.

[0003] In recent years, to further improve spectral performance, diffraction gratings have been developed with subwavelength structures that are smaller than the wavelength of light, which are difficult to fabricate by mechanical ruling or holographic exposure. These subwavelength diffraction gratings require structures smaller than the wavelength of the spectral light, but even when semiconductor processes are used, there are still challenges, such as photolithography resolution and etching processing accuracy.

[0004] Background art in this technical field includes, for example, a technique such as that described in Patent Document 1. In Patent Document 1, in order to create a periodic uneven pattern on the surface of a resin film for diffracting transmitted light, an evenly spaced uneven pattern is created on a silicon substrate by semiconductor lithography technology, an oxide film is formed by thermal oxidation to make it easier to peel off, and then a fluorinated polyimide resin is coated and hardened, and then peeled off to form a diffraction grating made of fluorinated polyimide.

[0005] In Patent Document 2, a periodic concave-convex pattern is created on a silicon substrate by photolithography and etching, an oxide film is formed by thermal oxidation, and then the oxide film is removed to create a smaller pattern, which is then transferred to molten glass to create a diffraction grating with fine concave patterns.

[0006] Furthermore, in Patent Document 3, in order to prevent the convex silicon structure from being distorted, tilted, or collapsed when an oxide film is formed by thermal oxidation, a cut portion is provided in the middle of the convex structure, and when an oxide film is formed by thermal oxidation, the structure is connected by the expansion of the film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-275014 [Patent Document 2] US Patent Application Publication No. 2024 / 0004111 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-75550 Summary of the Invention [Problem to be solved by the invention]

[0008] In the case of the above-mentioned diffraction grating, it is difficult to fabricate a diffraction grating having a fine structure using photolithography and etching in the existing semiconductor process due to the resolution limit and processing limit.

[0009] In the above-mentioned Patent Document 1, a periodic uneven pattern with a minimum period of 200 nm can be created on a silicon substrate using two-beam interference, but for spectral analysis in the ultraviolet-visible light region, it is necessary to create an even finer uneven pattern. Furthermore, under the thermal oxidation conditions described in Patent Document 1, a relatively thick thermal oxide film is formed, leaving room for improvement in terms of film thickness control.

[0010] In addition, in Patent Document 2, convex structures on a silicon substrate are thermally oxidized, causing oxygen to diffuse into the silicon and form an oxide film. Removing this oxide film allows the convex silicon structures to be made smaller. This smaller convex structure is then transferred to glass using the silicon substrate as a mold to create a diffraction grating with small concave structures. However, the convex structures required to achieve a refractive index distribution end up being large. Furthermore, because the glass is bonded to the silicon and then transferred, the silicon substrate mold breaks after one transfer.

[0011] In addition, in Patent Document 3, in order to prevent distortion, tilting, or falling of the convex structure of the silicon substrate, cut sections are provided in the convex structure, and the silicon convex structure is enlarged and connected by thermal oxidation. Because this uneven structure is used as an optical element, it is not suitable for mass production.

[0012] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a diffraction grating having grating grooves finer than the processing limits of existing semiconductor processes or mechanical processing, an analytical device using the same, and a method for manufacturing the diffraction grating. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a diffraction grating to be mounted on an analytical device, which is produced by preparing a diffraction grating substrate having a plurality of gratings, each having a substantially rectangular cross-sectional shape, arranged on a silicon substrate, thermally oxidizing the surface of the diffraction grating substrate to shrink the gaps between the gratings, and using the thermally oxidized diffraction grating substrate as a mold to transfer the pattern of the gaps onto a transparent resin or glass.

[0014] The present invention is also characterized by an analytical device equipped with the above-mentioned diffraction grating.

[0015] The present invention is also characterized by comprising the steps of: (a) fabricating a diffraction grating substrate by photolithography and dry etching, on a main surface of a silicon substrate, a plurality of gratings each having a substantially rectangular cross section, arranged thereon; (b) performing a thermal oxidation treatment on the surface of the diffraction grating substrate fabricated in step (a) to shrink gaps between the gratings; and (c) using the diffraction grating substrate thermally oxidized in step (b) as a mold, transferring the pattern of the gaps onto a transparent resin or glass. [Effects of the Invention]

[0016] According to the present invention, it is possible to realize a diffraction grating having grating grooves finer than the processing limits of existing semiconductor processes or mechanical processing, an analytical device using the same, and a method for manufacturing a diffraction grating.

[0017] This makes it possible to improve the diffraction efficiency of the diffraction grating and improve the sensitivity of the analysis device.

[0018] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a schematic configuration of an analysis device according to Example 1 of the present invention. [Figure 2] 1 is a perspective view showing a schematic configuration of a diffraction grating having a substantially rectangular grating with equal intervals according to the present invention; [Figure 3] 1 is a perspective view showing a schematic configuration of a diffraction grating having a non-uniformly spaced, substantially rectangular grating according to the present invention; [Figure 4] 5A to 5C are diagrams illustrating a method for manufacturing a diffraction grating according to a second embodiment of the present invention. [Figure 5] 10A to 10C are diagrams illustrating a method for manufacturing a diffraction grating according to a third embodiment of the present invention. [Figure 6] 10A to 10C are diagrams illustrating a method for manufacturing a diffraction grating according to Example 4 of the present invention. [Figure 7] 10A to 10C are diagrams illustrating a method for manufacturing a diffraction grating according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted. [Example]

[0021] <Analytical device using a transmission diffraction grating> An analytical device using a diffraction grating of the present invention will be described with reference to FIGS.

[0022] Fig. 1 is a diagram showing a schematic configuration of an analysis device 1 according to this embodiment. Fig. 2 is a perspective view showing a schematic configuration of a diffraction grating 2 of the present invention having a grating 21 with equal intervals and a substantially rectangular shape. Fig. 3 is a perspective view showing a schematic configuration of a diffraction grating 2 of the present invention having a grating 21 with unequal intervals and a substantially rectangular shape.

[0023] The analytical device 1 of this embodiment is used for substance identification by detecting light emission from specific substances, such as chemical substances and biological substances. As shown in FIG. 1, the analytical device 1 mainly comprises a light source 11, lenses 12a, 12b, and 12c, a sample chamber 13, a diffraction grating 2, and multiple detectors 15 arranged in a line. Light from the light source 11 is focused by lens 12a and irradiated onto a sample to be measured placed in sample chamber 13. Light emitted from the sample in sample chamber 13 passes through lens 12b and is irradiated onto diffraction grating 2, where it is dispersed along wavelengths to form a spectrum. The formed spectrum is detected by detector 15, such as a photodetector or a CCD (Charge Coupled Device), through lens 12c.

[0024] Diffraction grating 2 of the present invention will be described with reference to Figures 2 and 3. Diffraction grating 2 is configured by arranging gratings 21, each having a substantially rectangular cross section, at equal intervals (Figure 2) or at unequal intervals (Figure 3). Diffraction grating 2 has gratings 21 formed in a material that can transmit light in the ultraviolet and visible light range, such as acrylic or cycloolefin resin. Alternatively, a sol-gel liquid of a glass precursor that transmits light in the ultraviolet and visible light range is applied and thermally cured to transfer it to glass.

[0025] When light passes through the diffraction grating 2, it can be split into light beams at the gratings 21 due to differences in refractive index. The split wavelength can be changed by adjusting the spacing, depth, pitch, etc. of the gratings 21. Furthermore, as shown in Figure 3, by periodically arranging a group of unevenly spaced gratings 21 as units 22, it is possible to impart periodicity to the refractive index, thereby improving spectroscopic performance.

[0026] In the above, an example of a transmission type diffraction grating that uses transmitted diffracted light has been shown as the diffraction grating 2 of the present invention and the analytical device 1 equipped with the same. However, the diffraction grating 2 of the present invention described in each of the following examples can also be applied to a reflection type diffraction grating that uses reflected diffracted light and an analytical device equipped with the same. [Example]

[0027] <Equally spaced diffraction grating> Second Embodiment A diffraction grating according to a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a diagram showing a method for manufacturing the equally spaced diffraction grating 2 as shown in Fig. 2.

[0028] First, as shown in step (a), a silicon substrate 30 is prepared.

[0029] Next, as shown in step (b), a resist is applied to the surface of the silicon substrate 30, and a grating pattern is formed in the resist by photolithography such as ArF immersion exposure in a semiconductor process. After that, a grating 31 having an approximately rectangular cross section and equal intervals is formed by dry etching using the resist with the grating pattern formed as a mask, thereby producing a diffraction grating substrate 3.

[0030] Next, as shown in step (c), the diffraction grating substrate 3 is subjected to a thermal oxidation treatment to form a silicon oxide film 32 on the surface of the diffraction grating substrate 3. At this time, in the cross-sectional shape of the diffraction grating substrate 3, the approximately rectangular gratings 31 expand due to the diffusion of oxygen, and the gaps 33 between the gratings 31 become smaller.

[0031] It is desirable that the gap 33 be 20 nm or more after thermal oxidation, because a diffraction grating pattern with a lower limit of about 20 nm is required to effectively separate light on the low wavelength side.

[0032] Next, as shown in step (d), a transparent resin 4 coated with an organic solvent capable of dissolving the transparent resin or a reagent obtained by diluting the organic solvent with water is brought into contact with the diffraction grating substrate 3 having a silicon oxide film 32 formed on its surface, and a load is applied.

[0033] At this time, by making the solubility parameters of the organic solvent and the transparent resin 4 approximately match, the transparent resin 4 dissolves and enters the gaps 33. The organic solvent in the dissolved transparent resin 4 that has entered the gaps 33 between the gratings 31 of the diffraction grating substrate 3 volatilizes, forming gratings 41 on the surface of the transparent resin 4.

[0034] Finally, as shown in step (e), the transparent resin 4 is peeled off from the diffraction grating substrate 3. The gaps 33 between the gratings 31 of the diffraction grating substrate 3 are transferred onto the surface of the transparent resin 4 as gratings 41.

[0035] The thermal oxidation treatment in step (c) reduces the gaps 33 between the gratings 31 of the diffraction grating substrate 3 fabricated by photolithography and dry etching, and by transferring this, it is possible to create a grating 41 on the surface of the transparent resin 4 that is finer and has equal spacing than the patterns that can be formed by semiconductor processes.

[0036] In addition, the dry etching in step (b) may be performed under high aspect ratio dry etching conditions, and a high aspect ratio structure may be formed by repeating the steps of forming a protective film to protect the side walls of the lattice 31 (gap 33) and etching.

[0037] When a high aspect ratio structure is formed by repeating the steps of forming a protective film and etching, unevenness called scallops is formed on the side surfaces of the lattice 31 (gaps 33). When the silicon substrate 30 with the scallops formed on it is used as a mold to transfer to transparent resin 4, the transparent resin 4 also fills the scallops, and the lattice 41 is damaged when peeled off.

[0038] The thermal oxidation treatment in step (c) smooths the unevenness of the scallops, preventing damage to the grating 41 during the transfer to the transparent resin 4 and peeling process. Furthermore, applying a fluorine-based coating, for example, to the surface of the silicon oxide film 32 formed by the thermal oxidation treatment reduces the surface energy of the silicon oxide film 32, making it easier to peel. Alternatively, the grating 31 of the diffraction grating substrate 3 can be transferred to a metal by plating or the like, and then the metal mold can be transferred, preventing damage to the mold. This manufacturing method using a metal mold will be described later in Examples 4 and 5.

[0039] The thermal oxidation process in step (c) can be wet oxidation, which forms an oxide film by reacting water molecules into silicon, or dry oxidation, which forms an oxide film by diffusing oxygen molecules into silicon. For the thermal oxidation process in the manufacturing process of the diffraction grating 2 of the present invention, it is desirable to use dry oxidation, which has a slow growth rate for silicon oxide films and makes it easy to control the film thickness. For dry oxidation, oxygen or oxygen diluted with an inert gas is used.

[0040] As described above, the diffraction grating of this embodiment is a diffraction grating 2 to be mounted on the analytical device 1, and is produced by preparing a diffraction grating substrate 3 having a plurality of gratings 31, each having a substantially rectangular cross-sectional shape, arranged on a silicon substrate 30, thermally oxidizing the surface of the diffraction grating substrate 3 to shrink the gaps 33 between the gratings 31, and then using the thermally oxidized diffraction grating substrate 3 as a mold to transfer the pattern of the gaps 33 onto a transparent resin 4 (or glass).

[0041] By thermally oxidizing the surface of the diffraction grating substrate 3 to shrink the gaps 33 between the gratings 31, it is possible to fabricate a diffraction grating 2 having grating grooves that are finer than the processing limits of existing semiconductor processes or mechanical processing.

[0042] The gratings 31 are fabricated by dry etching the surface of the silicon substrate 30. By using dry etching, it is possible to form gratings 31 with a substantially rectangular cross section that has a high anisotropy (aspect ratio).

[0043] Moreover, it is desirable to use acrylic or cycloolefin as the material for the transparent resin 4, as described in Example 1. By using acrylic or cycloolefin, light on the short wavelength side can be transmitted efficiently.

[0044] Furthermore, the aspect ratio (depth / width), which is the ratio of the depth to the width of the gap 33, is preferably 10 or more. This is because if the aspect ratio (depth / width) of the gap 33 is less than 10, the diffraction efficiency of the diffraction grating 2 decreases. [Example]

[0045] <Diffraction grating with uneven spacing> Third Embodiment A diffraction grating according to a third embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a diagram showing a method for manufacturing the non-uniformly spaced diffraction grating 2 as shown in Fig. 3.

[0046] First, as shown in step (a), a silicon substrate 30 is prepared.

[0047] Next, as shown in step (b), a resist is applied to the surface of the silicon substrate 30, and a grating pattern is formed in the resist by photolithography such as ArF immersion exposure in a semiconductor process. After that, the resist with the grating pattern formed on it is used as a mask to form irregularly spaced gratings 31 with a substantially rectangular cross section by dry etching, thereby producing the diffraction grating substrate 3. Here, a group of multiple irregularly spaced gratings 31 is formed as a unit 34 and is periodically arranged.

[0048] Next, as shown in step (c), the diffraction grating substrate 3 is subjected to a thermal oxidation treatment to form a silicon oxide film 32 on the surface of the diffraction grating substrate 3. At this time, in the cross-sectional shape of the diffraction grating substrate 3, the approximately rectangular gratings 31 expand due to the diffusion of oxygen, and the gaps 33 between the gratings 31 become smaller.

[0049] It is desirable that the gap 33 be 20 nm or more after thermal oxidation. This is because a diffraction grating pattern with a lower limit of about 20 nm is required to effectively separate light on the low wavelength side. On the other hand, to ensure the function as diffraction grating 2, a diffraction grating pattern with an upper limit of about 200 nm is required, so it is desirable that the gap 33 be 200 nm or less after thermal oxidation.

[0050] Next, as shown in step (d), a transparent resin 4 coated with an organic solvent capable of dissolving the transparent resin or a reagent obtained by diluting the organic solvent with water is brought into contact with the diffraction grating substrate 3 having a silicon oxide film 32 formed on its surface, and a load is applied.

[0051] At this time, by making the solubility parameters of the organic solvent and the transparent resin 4 approximately match, the transparent resin 4 dissolves and enters the gaps 33. The organic solvent in the dissolved transparent resin 4 that has entered the gaps 33 between the gratings 31 of the diffraction grating substrate 3 volatilizes, forming gratings 41 on the surface of the transparent resin 4.

[0052] Finally, as shown in step (e), the transparent resin 4 is peeled off from the diffraction grating substrate 3. The gaps 33 between the gratings 31 of the diffraction grating substrate 3 are transferred onto the surface of the transparent resin 4 as gratings 41.

[0053] The thermal oxidation treatment in step (c) reduces the gaps 33 between the gratings 31 of the diffraction grating substrate 3 fabricated by photolithography and dry etching, and by transferring this, it is possible to fabricate on the surface of the transparent resin 4 gratings 41 that are arranged at irregular intervals and are finer than the patterns that can be formed by semiconductor processes. [Example]

[0054] <Equally spaced diffraction grating> A diffraction grating according to Example 4 of the present invention will be described with reference to Fig. 6. Fig. 6 is a diagram showing a method for manufacturing an equally spaced diffraction grating 2 as shown in Fig. 2, and corresponds to a modified example of Example 2 (Fig. 4). In this example, a manufacturing method using a metal mold will be described.

[0055] Steps (a) to (c) are the same as those in Example 2 (FIG. 4), and therefore repeated explanations will be omitted.

[0056] As shown in step (d), a resin 35 coated with an organic solvent capable of dissolving the resin or a reagent obtained by diluting an organic solvent with water is brought into contact with the diffraction grating substrate 3 having a silicon oxide film 32 formed on its surface, and a load is applied. Unlike the transparent resin 4, this resin 35 does not need to be transparent.

[0057] At this time, by making the solubility parameters of the organic solvent and the resin 35 approximately the same, the resin 35 dissolves and enters the gaps 33. The dissolved resin 35 that has entered the gaps 33 between the gratings 31 of the diffraction grating substrate 3 volatilizes the organic solvent, forming a grating 41 on the surface of the resin 35.

[0058] The resin 35 may be made of polystyrene, for example, and may be dissolved in an organic solvent or softened by heating, and then brought into contact with the diffraction grating substrate 3 and a load applied thereto.

[0059] Next, as shown in step (e), the resin 35 is peeled off from the diffraction grating substrate 3. The gaps 33 between the gratings 31 of the diffraction grating substrate 3 are transferred as gratings 41 onto the surface of the resin 35.

[0060] Next, as shown in step (f), the surface of the resin 35 including the grid 41 is plated to form a metal 36. Examples of materials for the metal 36 include nickel.

[0061] Since the spacing between the grids 41 is small, if a solvent is not used during plating, the plating solution will not penetrate between the grids 41, and there is a high possibility that the plating will not be transferred properly. Therefore, it is desirable to first form a seed on the surface of the resin 35 including the grids 41 by electroless plating or the like, and then form the metal 36 by electrolytic plating.

[0062] Thereafter, as shown in step (g), the resin 35 is removed by dissolving or the like, and a mold for the metal 36 is formed.

[0063] By transferring this metal 36 mold to a transparent resin 4 in a manner similar to steps (d) and (e) of Example 2 (Figure 4), it is possible to create a grating 41 with equal spacing that is finer than the patterns that can be formed by semiconductor processes.

[0064] As described above, the diffraction grating of this embodiment is fabricated by using the thermally oxidized diffraction grating substrate 3 as a mold to transfer the pattern of the gaps 33 onto the metal 36, and then transferring the metal mold onto which the pattern of the gaps 33 has been transferred onto the transparent resin 4 (or glass).

[0065] By temporarily transferring the pattern of the gaps 33 of the thermally oxidized diffraction grating substrate 3 to the metal 36, damage to the mold of the diffraction grating substrate 3 can be suppressed. [Example]

[0066] <Diffraction grating with uneven spacing> A diffraction grating according to a fifth embodiment of the present invention will be described with reference to Fig. 7. Fig. 7 is a diagram showing a method for manufacturing the diffraction grating 2 having irregular intervals as shown in Fig. 3, and corresponds to a modified example of the third embodiment (Fig. 5). In this embodiment, a manufacturing method using a metal mold will be described.

[0067] Steps (a) to (c) are the same as those in Example 3 (FIG. 5), and therefore repeated explanations will be omitted.

[0068] As shown in step (d), a resin 35 coated with an organic solvent capable of dissolving the resin or a reagent obtained by diluting an organic solvent with water is brought into contact with the diffraction grating substrate 3 having a silicon oxide film 32 formed on its surface, and a load is applied. Unlike the transparent resin 4, this resin 35 does not need to be transparent.

[0069] At this time, by making the solubility parameters of the organic solvent and the resin 35 approximately the same, the resin 35 dissolves and enters the gaps 33. The dissolved resin 35 that has entered the gaps 33 between the gratings 31 of the diffraction grating substrate 3 volatilizes the organic solvent, forming a grating 41 on the surface of the resin 35.

[0070] The resin 35 may be made of polystyrene, for example, and may be dissolved in an organic solvent or softened by heating, and then brought into contact with the diffraction grating substrate 3 and a load applied thereto.

[0071] Next, as shown in step (e), the resin 35 is peeled off from the diffraction grating substrate 3. The gaps 33 between the gratings 31 of the diffraction grating substrate 3 are transferred as gratings 41 onto the surface of the resin 35.

[0072] Next, as shown in step (f), the surface of the resin 35 including the grid 41 is plated to form a metal 36. Examples of materials for the metal 36 include nickel.

[0073] Since the spacing between the grids 41 is small, if a solvent is not used during plating, the plating solution will not penetrate between the grids 41, and there is a high possibility that the plating will not be transferred properly. Therefore, it is desirable to first form a seed on the surface of the resin 35 including the grids 41 by electroless plating or the like, and then form the metal 36 by electrolytic plating.

[0074] Thereafter, as shown in step (g), the resin 35 is removed by dissolving or the like, and a mold for the metal 36 is formed.

[0075] By transferring this metal 36 mold to a transparent resin 4 in a manner similar to steps (d) and (e) of Example 3 (Figure 5), it is possible to create a grating 41 that is arranged at irregular intervals and is finer than the patterns that can be formed by semiconductor processes.

[0076] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0077] 1…Analyzer 2...Diffraction grating 3... Diffraction grating substrate 4...Transparent resin 11...Light source 12, 12a, 12b, 12c...Lens 13...Sample chamber 15...Detector 21,31,41...lattice 22, 34... units 30...Silicon substrate 32...Silicon oxide film 33...Gap 35...Resin 36...Metal.

Claims

1. A diffraction grating mounted on an analytical device, A diffraction grating substrate is fabricated on a silicon substrate, in which a plurality of gratings each having a substantially rectangular cross section are arranged; The surface of the diffraction grating substrate is thermally oxidized to shrink the gaps between the gratings; A diffraction grating characterized in that it is produced by using the thermally oxidized diffraction grating substrate as a mold to transfer the pattern of the gaps onto a transparent resin or glass.

2. 2. The diffraction grating of claim 1, A diffraction grating, wherein the plurality of gratings are fabricated by dry etching the surface of the silicon substrate.

3. 2. The diffraction grating of claim 1, A diffraction grating, wherein the gap after thermal oxidation is 20 nm or more.

4. 2. The diffraction grating of claim 1, the thermally oxidized diffraction grating substrate is used as a mold to transfer the pattern of the gaps onto a transparent resin, A diffraction grating characterized in that the transparent resin material is acrylic or cycloolefin.

5. 2. The diffraction grating of claim 1, A diffraction grating characterized in that the aspect ratio (depth / width), which is the ratio of the depth to the width of the gap, is 10 or more.

6. 2. The diffraction grating of claim 1, A diffraction grating, wherein the plurality of gratings are arranged at equal intervals on the silicon substrate.

7. 2. The diffraction grating of claim 1, A diffraction grating, wherein the plurality of gratings are arranged at irregular intervals on the silicon substrate.

8. 8. The diffraction grating of claim 7, A diffraction grating, wherein the gap after thermal oxidation is 20 nm or more and 200 nm or less.

9. 2. The diffraction grating of claim 1, The diffraction grating is characterized in that the thermal oxidation is dry oxidation using oxygen or oxygen diluted with an inert gas.

10. 2. The diffraction grating of claim 1, using the thermally oxidized diffraction grating substrate as a mold to transfer the gap pattern onto a metal; A diffraction grating characterized in that a metal mold onto which the pattern of the gaps is transferred is transferred onto the transparent resin or glass.

11. An analytical instrument equipped with the diffraction grating according to any one of claims 1 to 10.

12. A method of manufacturing a diffraction grating, comprising the steps of: (a) producing a diffraction grating substrate by photolithography and dry etching, in which a plurality of gratings each having a substantially rectangular cross section are arranged on a main surface of a silicon substrate; (b) performing a thermal oxidation treatment on the surface of the diffraction grating substrate fabricated in the step (a) to shrink the gaps between the gratings; (c) A step of transferring the pattern of the gaps onto a transparent resin or glass using the diffraction grating substrate thermally oxidized in the step (b) as a mold.

13. 13. A method for manufacturing a diffraction grating according to claim 12, comprising the steps of: a step (c) of transferring the gap pattern to a metal using the thermally oxidized diffraction grating substrate as a mold, and then transferring the metal mold onto which the gap pattern has been transferred to the transparent resin or the glass.

14. 13. A method for manufacturing a diffraction grating according to claim 12, comprising the steps of: A method for manufacturing a diffraction grating, wherein the plurality of gratings are arranged at equal intervals on the silicon substrate.

15. 13. A method for manufacturing a diffraction grating according to claim 12, comprising the steps of: A method for manufacturing a diffraction grating, wherein the plurality of gratings are arranged at irregular intervals on the silicon substrate.

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