Method for manufacturing relief diffraction grating

Abstract

This method for manufacturing a relief diffraction grating (1) comprises: a step for forming a first silicon nitride film (10) on a silicon member (2); a step for oxidizing the silicon member (2) using the first silicon nitride film (10) as a mask, thereby changing a portion of the silicon member (2) into a first silicon oxide film (15); a step for removing the first silicon nitride film (10); and a step for selectively removing the first silicon oxide film (15) and forming a first step part (4a) in the silicon member (2).

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing an embossed diffraction grating. Background Technology

[0002] Japanese Patent Application Publication No. 2000-105307 (Patent Document 1) discloses a method for manufacturing a stepped relief diffraction grating by etching a glass substrate using a photoresist as a mask. Japanese Patent Application Publication No. 2000-155207 (Patent Document 2) discloses a method for manufacturing a stepped relief diffraction grating by etching a laminate of SiO2 and Al2O3 films using a photoresist as a mask.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-105307

[0006] Patent Document 2: Japanese Patent Application Publication No. 2000-155207 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in etching using photoresist, if the convex portion of the periodic uneven structure of the diffraction grating becomes higher, the dimensional accuracy of the diffraction grating decreases. This disclosure was made in view of the above-mentioned problems, and its object is to provide a method for manufacturing an embossed diffraction grating with higher dimensional accuracy.

[0009] Solution for solving the problem

[0010] The method for manufacturing an embossed diffraction grating disclosed herein includes: a step of forming a first silicon nitride film on a silicon component; a step of oxidizing the silicon component by using the first silicon nitride film as a mask to transform a portion of the silicon component into a first silicon oxide film; a step of removing the first silicon nitride film; and a step of selectively removing the first silicon oxide film to form a first step portion on the silicon component.

[0011] The effects of the invention

[0012] By oxidizing a silicon component using a first silicon nitride film as a mask, a first silicon oxide film can be formed with higher dimensional accuracy. Then, by selectively removing the first silicon oxide film, an embossed diffraction grating is manufactured. According to the method for manufacturing an embossed diffraction grating of this embodiment, an embossed diffraction grating with higher dimensional accuracy can be manufactured. Attached Figure Description

[0013] Figure 1This is a schematic partial cross-sectional view of the relief-type diffraction grating of Embodiment 1.

[0014] Figure 2 This is a schematic partial enlarged cross-sectional view of the relief-type diffraction grating of Embodiment 1.

[0015] Figure 3 This is a schematic enlarged cross-sectional view of a step in the manufacturing method of the relief-type diffraction grating according to Embodiment 1.

[0016] Figure 4 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 3 A partial enlarged cross-sectional view of the next process shown.

[0017] Figure 5 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 4 A partial enlarged cross-sectional view of the next process shown.

[0018] Figure 6 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 5 A partial enlarged cross-sectional view of the next process shown.

[0019] Figure 7 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 6 A partial enlarged cross-sectional view of the next process shown.

[0020] Figure 8 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 7 A partial enlarged cross-sectional view of the next process shown.

[0021] Figure 9 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 8 A partial enlarged cross-sectional view of the next process shown.

[0022] Figure 10 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 9 A partial enlarged cross-sectional view of the next process shown.

[0023] Figure 11 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 10 A partial enlarged cross-sectional view of the next process shown.

[0024] Figure 12 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 11 A partial enlarged cross-sectional view of the next process shown.

[0025] Figure 13 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 12 A partial enlarged cross-sectional view of the next process shown.

[0026] Figure 14 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 13 A partial enlarged cross-sectional view of the next process shown.

[0027] Figure 15 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 14 A partial enlarged cross-sectional view of the next process shown.

[0028] Figure 16 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 15 A partial enlarged cross-sectional view of the next process shown.

[0029] Figure 17 This refers to the manufacturing method of the relief-type diffraction grating in Embodiment 1. Figure 16 A partial enlarged cross-sectional view of the next process shown.

[0030] Figure 18 This is a schematic partial cross-sectional view of the relief-type diffraction grating of Embodiment 2.

[0031] Figure 19 This is a schematic partial enlarged cross-sectional view of the relief-type diffraction grating of Embodiment 2.

[0032] Figure 20 This is a schematic enlarged cross-sectional view of a step in the manufacturing method of the relief-type diffraction grating according to Embodiment 2.

[0033] Figure 21 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 20 A partial enlarged cross-sectional view of the next process shown.

[0034] Figure 22 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 21 A partial enlarged cross-sectional view of the next process shown.

[0035] Figure 23 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 22 A partial enlarged cross-sectional view of the next process shown.

[0036] Figure 24 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 23 A partial enlarged cross-sectional view of the next process shown.

[0037] Figure 25 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 24 A partial enlarged cross-sectional view of the next process shown.

[0038] Figure 26 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 25 A partial enlarged cross-sectional view of the next process shown.

[0039] Figure 27 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 26 A partial enlarged cross-sectional view of the next process shown.

[0040] Figure 28 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 27 A partial enlarged cross-sectional view of the next process shown.

[0041] Figure 29 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 28 A partial enlarged cross-sectional view of the next process shown.

[0042] Figure 30 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 29 A partial enlarged cross-sectional view of the next process shown.

[0043] Figure 31 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 30 A partial enlarged cross-sectional view of the next process shown.

[0044] Figure 32 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 31 A partial enlarged cross-sectional view of the next process shown.

[0045] Figure 33 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 32 A partial enlarged cross-sectional view of the next process shown.

[0046] Figure 34This refers to the manufacturing method of the relief-type diffraction grating in embodiment 2. Figure 33 A partial enlarged cross-sectional view of the next process shown.

[0047] Figure 35 This is a schematic partial cross-sectional view of the relief-type diffraction grating of embodiment 3.

[0048] Figure 36 This is a schematic partial enlarged cross-sectional view of the relief-type diffraction grating of embodiment 3.

[0049] Figure 37 This is a schematic enlarged cross-sectional view of a step in the manufacturing method of the relief-type diffraction grating according to Embodiment 3.

[0050] Figure 38 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 37 A partial enlarged cross-sectional view of the next process shown.

[0051] Figure 39 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 38 A partial enlarged cross-sectional view of the next process shown.

[0052] Figure 40 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 39 A partial enlarged cross-sectional view of the next process shown.

[0053] Figure 41 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 40 A partial enlarged cross-sectional view of the next process shown.

[0054] Figure 42 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 41 A partial enlarged cross-sectional view of the next process shown.

[0055] Figure 43 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 42 A partial enlarged cross-sectional view of the next process shown.

[0056] Figure 44 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 43 A partial enlarged cross-sectional view of the next process shown.

[0057] Figure 45 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 44 A partial enlarged cross-sectional view of the next process shown.

[0058] Figure 46 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 45 A partial enlarged cross-sectional view of the next process shown.

[0059] Figure 47 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 46 A partial enlarged cross-sectional view of the next process shown.

[0060] Figure 48 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 47 A partial enlarged cross-sectional view of the next process shown.

[0061] Figure 49 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 3. Figure 48 A partial enlarged cross-sectional view of the next process shown.

[0062] Figure 50 This is a schematic partial cross-sectional view of the relief-type diffraction grating of embodiment 4.

[0063] Figure 51 This is a schematic partial enlarged cross-sectional view of the relief-type diffraction grating of embodiment 4.

[0064] Figure 52 This is a schematic enlarged cross-sectional view of one step in the manufacturing method of the relief-type diffraction grating according to Embodiment 4.

[0065] Figure 53 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 4. Figure 52 A partial enlarged cross-sectional view of the next process shown.

[0066] Figure 54 This refers to the manufacturing method of the relief-type diffraction grating in embodiment 4. Figure 53 A partial enlarged cross-sectional view of the next process shown.

[0067] Figure 55 This is a schematic top view of the optical scanning device in Embodiment 5. Detailed Implementation

[0068] The embodiments of this disclosure will now be described. Furthermore, the same reference numerals will be used to refer to the same structures, and their descriptions will not be repeated.

[0069] Implementation Method 1

[0070] Reference Figure 1 and Figure 2 The relief-type diffraction grating 1 of embodiment 1 is described below. The diffraction wavelength of the relief-type diffraction grating 1 is, for example, in the wavelength region from infrared to far-infrared.

[0071] The relief-type diffraction grating 1 includes a silicon component 2 and a periodic uneven structure 9 formed on the silicon component 2. The relief-type diffraction grating 1 may also include a reflective film (not shown) disposed on the surface of the periodic uneven structure 9. The reflective film is, for example, formed of metal.

[0072] An embossed diffraction grating 1 is formed on a silicon component 2. In this embodiment, the silicon component 2 is a silicon substrate 2a.

[0073] The periodic concave-convex structure 9 includes a plurality of protrusions 3 arranged periodically. Each protrusion 3 includes a side surface 3a, a side surface 3b facing the side surface 3a, and a top surface 4t. The top surface 4t is disposed between the side surface 3a and the side surface 3b, and is connected to the side surface 3a and the side surface 3b.

[0074] In this embodiment, each of the protrusions 3 has multiple height levels. The relief-type diffraction grating 1 is a stepped diffraction grating with multiple height levels. Specifically, each of the protrusions 3 has, for example, four height levels. Each of the protrusions 3 includes stepped portions 4a, 4b, 5a, 5b, 6a, 6b, 7a, and 7b.

[0075] Steps 4a, 5a, 6a, and 7a are provided on side 3a. Step 4a is the uppermost step among steps 4a, 5a, 6a, and 7a. Step 5a is the second uppermost step among steps 4a, 5a, 6a, and 7a. Step 6a is the second lowermost step among steps 4a, 5a, 6a, and 7a. Step 7a is the lowermost step among steps 4a, 5a, 6a, and 7a.

[0076] Steps 4b, 5b, 6b, and 7b are provided on side 3b. Step 4b is the uppermost step among steps 4b, 5b, 6b, and 7b. Step 5b is the second uppermost step among steps 4b, 5b, 6b, and 7b. Step 6b is the second lowermost step among steps 4b, 5b, 6b, and 7b. Step 7b is the lowermost step among steps 4b, 5b, 6b, and 7b.

[0077] The step portion 4b is in the height direction of each of the protrusions 3 ( Figure 2 (up and down direction) in the plane perpendicular to ( Figure 2The top surface 4t faces the step 4a in the left-right direction. The step 5b faces the step 5a in the in-plane direction. The step 6b faces the step 6a in the in-plane direction. The step 7b faces the step 7a in the in-plane direction. The top surface 4t is disposed between the step 4a and the step 4b, and is connected to both the step 4a and the step 4b.

[0078] Step 4a has a smooth edge 4c. Step 4b has a smooth edge 4d. Step 5a has a smooth edge 5c. Step 5b has a smooth edge 5d. Step 6a has a smooth edge 6c. Step 6b has a smooth edge 6d. Step 7a has a smooth edge 7c. Step 7b has a smooth edge 7d. In this specification, a smooth edge refers to an edge whose minimum radius of curvature is more than one-tenth of the diffraction wavelength of the relief diffraction grating 1.

[0079] Reference Figures 3 to 18 This describes the manufacturing method of the relief-type diffraction grating 1 in this embodiment.

[0080] Reference Figure 3 A silicon nitride film 10 is formed on the main surface 2s of the silicon component 2. A portion of the main surface 2s of the silicon component 2 is covered by the silicon nitride film 10. The remaining portion of the main surface 2s of the silicon component 2 is exposed from the silicon nitride film 10.

[0081] For example, a silicon nitride film is formed on the entire surface of the main surface 2s of the silicon component 2 using low-pressure chemical vapor deposition (LPCVD). A photoresist (not shown) is coated onto the silicon nitride film. The photoresist is patterned by exposure and development. The portion of the silicon nitride film exposed from the photoresist is removed by dry etching using a CF-type plasma or wet etching using hot phosphoric acid. The photoresist is removed from the silicon component 2 using oxygen plasma or an organic solvent such as acetone. Thus, a silicon nitride film 10 is formed on a portion of the main surface 2s of the silicon component 2. The silicon nitride film formed by LPCVD can withstand oxidation processes on the silicon component 2 (see reference). Figure 4 The thickness of the silicon nitride film 10 is, for example, in the range of 0.1 μm to 0.3 μm, which is smaller than the thickness of the photoresist (above 1 μm).

[0082] Reference Figure 4The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 10 as a mask, transforming that portion into a silicon oxide film 15. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 10 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 10 become the silicon oxide film 15. The silicon oxide film 15 is formed around the periphery of the silicon nitride film 10, lifting the periphery of the silicon nitride film 10. This bypassing of the silicon oxide film 15 below the periphery of the silicon nitride film 10 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0083] Reference Figure 5 The silicon nitride film 10 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0084] Reference Figure 6 The silicon oxide film 15 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 4a and 4b on the silicon component 2. Stepped portion 4a has a smooth edge 4c. Stepped portion 4b has a smooth edge 4d. This is achieved through a localized oxidation process (see [reference]). Figure 4 ) and the selective removal process of silicon oxide film (refer to Figure 6 The edges 4c and 4d of the stepped portions 4a and 4b become smooth. The top surface 4t is the main surface 2s of the silicon component 2 (see reference). Figure 3 Part of it, and as flat as the main surface 2s.

[0085] Reference Figure 7 A silicon nitride film 11 is formed on the top surface 4t and the step portion 4a of the silicon component 2. The step portion 4b and the silicon component 2 are in the in-plane direction ( Figure 7 The portion of the silicon nitride film 11 located on the opposite side of the top surface 4t relative to the step portion 4a in the left-right direction is exposed. The silicon nitride film 11 is formed by the same method as the silicon nitride film 10. The thickness of the silicon nitride film 11 is, for example, in the range of 0.1 μm to 0.3 μm.

[0086] Reference Figure 8 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 11 as a mask, transforming that portion into a silicon oxide film 16. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 11 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 11 become the silicon oxide film 16. The silicon oxide film 16 is formed around the periphery of the silicon nitride film 11, raising the periphery of the silicon nitride film 11. This bypassing of the silicon oxide film 16 below the periphery of the silicon nitride film 11 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0087] Reference Figure 9 The silicon nitride film 11 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0088] Reference Figure 10 The silicon oxide film 16 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 5a and 5b on the silicon component 2. Stepped portion 5a has a smooth edge 5c. Stepped portion 5b has a smooth edge 5d. This is achieved through a localized oxidation process (see [reference]). Figure 8 ) and the selective removal process of silicon oxide film (refer to Figure 10 The edges of the steps 5a and 5b, 5c and 5d, become smooth.

[0089] Reference Figure 11 A silicon nitride film 12 is formed on the top surface 4t of the silicon component 2 and on the steps 4a and 5a. The steps 4b and 5b and the silicon component 2 are in the in-plane direction ( Figure 11 The portion of the silicon nitride film 12 located on the opposite side of the step portion 5a from the top surface 4t in the left-right direction is exposed. The silicon nitride film 12 is formed by the same method as the silicon nitride film 10. The thickness of the silicon nitride film 12 is, for example, in the range of 0.1 μm to 0.3 μm.

[0090] Reference Figure 12 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 12 as a mask, transforming that portion into a silicon oxide film 17. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 12 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 12 become the silicon oxide film 17. The silicon oxide film 17 is formed around the periphery of the silicon nitride film 12, lifting the periphery of the silicon nitride film 12. This bypassing of the silicon oxide film 17 below the periphery of the silicon nitride film 12 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0091] Reference Figure 13 The silicon nitride film 12 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0092] Reference Figure 14 The silicon oxide film 17 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 6a and 6b on the silicon component 2. Stepped portion 6a has a smooth edge 6c. Stepped portion 6b has a smooth edge 6d. This is achieved through a localized oxidation process (see [reference]). Figure 12 ) and the selective removal process of silicon oxide film (refer to Figure 14 The edges of the steps 6a and 6b, 6c and 6d, become smooth.

[0093] Reference Figure 15 A silicon nitride film 13 is formed on the top surface 4t of the silicon component 2 and on the steps 4a, 5a, and 6a. The steps 4b, 5b, and 6b and the silicon component 2 are in the in-plane direction ( Figure 15 The portion of the silicon nitride film 13 located on the opposite side of the step portion 6a from the top surface 4t in the left-right direction is exposed. The silicon nitride film 13 is formed by the same method as the silicon nitride film 10. The thickness of the silicon nitride film 13 is, for example, in the range of 0.1 μm to 0.3 μm.

[0094] Reference Figure 16 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 13 as a mask, transforming that portion into a silicon oxide film 18. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 13 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 13 become the silicon oxide film 18. The silicon oxide film 18 is formed around the periphery of the silicon nitride film 13, lifting the periphery of the silicon nitride film 13. This bypassing of the silicon oxide film 18 below the periphery of the silicon nitride film 13 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0095] Reference Figure 17 The silicon nitride film 13 is selectively removed by using dry etching such as CF-type plasma or wet etching such as thermal phosphoric acid.

[0096] The silicon oxide film 18 is selectively removed by means of hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 7a and 7b on the silicon component 2 (refer to...). Figure 2 Step 7a has a smooth edge 7c. Step 7b has a smooth edge 7d. This is achieved through a localized oxidation process (see reference). Figure 16 The selective removal process of the silicon oxide film and the steps 7a and 7b results in smooth edges 7c and 7d. This yields... Figure 1 and Figure 2 The relief-type diffraction grating 1 is shown.

[0097] In this embodiment, in order to form four stepped portions 4a, 5a, 6a, 7a and four stepped portions 4b, 5b, 6b, 7b, the local oxidation process and the selective removal process of the silicon oxide film are each performed four times. However, in order to form n stepped portions, the local oxidation process and the selective removal process of the silicon oxide film can be performed n times (where n is a natural number).

[0098] The effects of the manufacturing method of the relief-type diffraction grating 1 in this embodiment will be explained.

[0099] The method for manufacturing the relief-type diffraction grating 1 in this embodiment includes: a step of forming a first silicon nitride film (e.g., silicon nitride film 10) on a silicon component 2; a step of oxidizing the silicon component 2 by using the first silicon nitride film as a mask to transform a portion of the silicon component 2 into a first silicon oxide film (e.g., silicon oxide film 15); a step of removing the first silicon nitride film; and a step of selectively removing the first silicon oxide film to form a first step portion (e.g., step portion 4a) on the silicon component 2.

[0100] By oxidizing (partially oxidizing) the silicon component 2 using a first silicon nitride film as a mask, a first silicon oxide film (e.g., silicon oxide film 15) can be formed with higher dimensional accuracy. Then, by selectively removing the first silicon oxide film, an embossed diffraction grating 1 is manufactured. Therefore, the dimensional accuracy of the diffraction grating in the height direction and the dimensional accuracy of the diffraction grating in the in-plane direction perpendicular to the height direction of the diffraction grating can be improved. According to the method for manufacturing the embossed diffraction grating 1 of this embodiment, an embossed diffraction grating 1 with higher dimensional accuracy can be manufactured.

[0101] If the surface of a diffraction grating is formed by etching or film deposition, the surface of the diffraction grating becomes rough. Light scattering occurs on the surface of the diffraction grating, thereby reducing the diffraction efficiency of the diffraction grating. In contrast, the surface of the silicon component 2 formed by selectively removing the first silicon oxide film (e.g., silicon oxide film 15) as in this embodiment has higher smoothness. Light scattering on the surface of the diffraction grating can be suppressed. According to the method for manufacturing the relief-type diffraction grating 1 of this embodiment, it is possible to manufacture a relief-type diffraction grating 1 with higher diffraction efficiency.

[0102] The relief-type diffraction grating 1 of this embodiment is formed on a silicon component 2 made of a single material such as silicon. Therefore, according to the manufacturing method of the relief-type diffraction grating 1 of this embodiment, it is possible to manufacture a relief-type diffraction grating 1 with superior temperature stability of diffraction efficiency compared to a comparative example relief-type diffraction grating formed of multiple materials with different coefficients of linear expansion.

[0103] In the manufacturing method of the relief diffraction grating 1 in this embodiment, the first step portion (e.g., step portion 4a) has a smooth edge portion (e.g., edge portion 4c).

[0104] Therefore, light scattering at the edge (e.g., edge 4c) can be suppressed. According to the manufacturing method of the relief diffraction grating 1 of this embodiment, it is possible to manufacture a relief diffraction grating 1 with higher diffraction efficiency.

[0105] The manufacturing method of the relief-type diffraction grating 1 in this embodiment further includes: a step of forming a second silicon nitride film (e.g., silicon nitride film 11) on the top surface 4t of the silicon member 2 connected to the first step portion (e.g., step portion 4a) and on the first step portion; a step of oxidizing the silicon member 2 by using the second silicon nitride film as a mask to transform a portion of the silicon member 2 into a second silicon oxide film (e.g., silicon oxide film 16); a step of removing the second silicon nitride film; and a step of selectively removing the second silicon oxide film to form a second step portion (e.g., step portion 5a) connected to the first step portion on the silicon member 2. Each of the protrusions 3 of the relief-type diffraction grating 1 has multiple height levels.

[0106] To form protrusions 3 with multiple height levels through etching using a photoresist as a mask, a relatively thick photoresist with patterning is required. If the thick photoresist is patterned by exposure and development, it cannot be patterned with high precision due to defocusing of the light used for exposure. In contrast, in the method for manufacturing the relief-type diffraction grating 1 of this embodiment, a silicon nitride film thinner than the photoresist is used to form protrusions 3 with multiple height levels. Then, through oxidation (local oxidation) of the silicon component 2 using the silicon nitride film as a mask, the silicon oxide film can be formed with higher dimensional accuracy. By selectively removing the silicon oxide film, the relief-type diffraction grating 1 is manufactured. Therefore, even if each of the protrusions 3 of the relief-type diffraction grating 1 has multiple height levels, a relief-type diffraction grating 1 with higher dimensional accuracy can be manufactured.

[0107] In the manufacturing method of the relief-type diffraction grating 1 in this embodiment, the silicon component 2 is a silicon substrate 2a.

[0108] The relief-type diffraction grating 1 of this embodiment is formed on a silicon substrate 2a made of a single material such as silicon. Therefore, according to the manufacturing method of the relief-type diffraction grating 1 of this embodiment, it is possible to manufacture a relief-type diffraction grating 1 with superior temperature stability of diffraction efficiency compared to a comparative example relief-type diffraction grating formed of multiple materials with different coefficients of linear expansion.

[0109] Implementation Method 2

[0110] Reference Figure 18 and Figure 19 This section describes the relief diffraction grating 1 of Embodiment 2. The relief diffraction grating 1 of this embodiment has the same structure as the relief diffraction grating 1 of Embodiment 1, but differs from the relief diffraction grating 1 of Embodiment 1 in the following aspects.

[0111] In the relief-type diffraction grating 1 of this embodiment, each of the protrusions 3 has a single height level. The relief-type diffraction grating 1 is a diffraction grating with a single height level. Each of the protrusions 3 has smooth sides 3a and 3b. In this specification, a smooth side means that the arithmetic mean roughness Ra of the side is less than one-tenth of the diffraction wavelength of the relief-type diffraction grating 1. The sides 3a and 3b do not have edges.

[0112] Reference Figures 20 to 34 This describes the manufacturing method of the relief-type diffraction grating 1 in this embodiment.

[0113] Reference Figure 20 A silicon nitride film 10 is formed on the main surface 2s of the silicon component 2. A portion of the main surface 2s of the silicon component 2 is covered by the silicon nitride film 10. The remaining portion of the main surface 2s of the silicon component 2 is exposed from the silicon nitride film 10. Figure 20 The process of forming the silicon nitride film 10 shown is similar to Figure 3 The process for forming the silicon nitride film 10 shown is the same.

[0114] Reference Figure 21 A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 10 as a mask, transforming the portion of the silicon component 2 into a silicon oxide film 15. Figure 21 The local oxidation process shown is similar to Figure 4 The local oxidation process shown is the same.

[0115] Reference Figure 22 The silicon nitride film 10 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid. Figure 22 The process of removing the silicon nitride film 10 shown is the same as Figure 5 The process for removing the silicon nitride film 10 shown is the same.

[0116] Reference Figure 23 The silicon oxide film 15 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 4a and 4b on the silicon component 2. The top surface 4t is the main surface 2s of the silicon component 2 (refer to...). Figure 20 Part of it, and is as flat as the main surface 2s. The top surface 4t is disposed between the step portion 4a and the step portion 4b, and is connected to the step portion 4a and the step portion 4b. Figure 23 The process of removing the silicon oxide film 15 shown is similar to Figure 6 The process for removing the silicon oxide film 15 shown is the same.

[0117] Reference Figure 24 A silicon nitride film 11 is formed on the top surface 4t of the silicon component 2. Stepped portions 4a and 4b are exposed from the silicon nitride film 11. The silicon nitride film 11 is formed by the same method as the silicon nitride film 10.

[0118] Reference Figure 25 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 11 as a mask, transforming that portion into a silicon oxide film 16. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 11 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 11 become the silicon oxide film 16. The silicon oxide film 16 is formed around the periphery of the silicon nitride film 11, raising the periphery of the silicon nitride film 11. This bypassing of the silicon oxide film 16 below the periphery of the silicon nitride film 11 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0119] Reference Figure 26 The silicon nitride film 11 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0120] Reference Figure 27 The silicon oxide film 16 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 5a and 5b on the silicon component 2. Figures 24 to 27 The process shown, step 4a (refer to) Figure 23 ) becomes step 5a, step 4b (refer to) Figure 23 Step 5a becomes step 5b. Step 5a is higher or deeper than step 4a. Step 5b is higher or deeper than step 4b. Step 5b is in-plane direction ( Figure 27 The top surface 4t is positioned between the step 5a and the step 5b in the left-right direction and is connected to both the step 5a and the step 5b.

[0121] Reference Figure 28 A silicon nitride film 12 is formed on the top surface 4t of the silicon component 2. Stepped portions 5a and 5b are exposed from the silicon nitride film 12. The silicon nitride film 12 is formed by the same method as the silicon nitride film 10.

[0122] Reference Figure 29 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 12 as a mask, transforming that portion into a silicon oxide film 17. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 12 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 12 become the silicon oxide film 17. The silicon oxide film 17 is formed around the periphery of the silicon nitride film 12, lifting the periphery of the silicon nitride film 12. This bypassing of the silicon oxide film 17 below the periphery of the silicon nitride film 12 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0123] Reference Figure 30The silicon nitride film 12 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0124] Reference Figure 31 The silicon oxide film 17 is selectively removed by hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 6a and 6b on the silicon component 2. Figures 28 to 31 The process shown, step 5a (refer to) Figure 27 ) becomes step 6a, step 5b (refer to) Figure 27 Step 6a becomes step 6b. Step 6a is higher or deeper than step 5a. Step 6b is higher or deeper than step 5b. Step 6b is in-plane direction ( Figure 31 The top surface 4t is positioned between the step portion 6a and the step portion 6b, and is connected to both the step portion 6a and the step portion 6b.

[0125] Reference Figure 32 A silicon nitride film 13 is formed on the top surface 4t of the silicon component 2. Stepped portions 6a and 6b are exposed from the silicon nitride film 13. The silicon nitride film 13 is formed by the same method as the silicon nitride film 10.

[0126] Reference Figure 33 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 13 as a mask, transforming that portion into a silicon oxide film 18. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 13 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 13 become the silicon oxide film 18. The silicon oxide film 18 is formed around the periphery of the silicon nitride film 13, lifting the periphery of the silicon nitride film 13. This bypassing of the silicon oxide film 18 below the periphery of the silicon nitride film 13 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0127] Reference Figure 34 The silicon nitride film 13 is selectively removed by using dry etching such as CF-type plasma or wet etching such as thermal phosphoric acid.

[0128] The silicon oxide film 18 is selectively removed by means of hydrofluoric acid solution or hydrofluoric acid vapor, forming smooth sides 3a and 3b on the silicon component 2 (see reference). Figure 19 Step 6a (refer to) Figure 31 The side surface 3a becomes smooth, and the stepped section 6b (see reference) Figure 31 The smooth side 3a becomes a smooth side 3b. The smooth side 3a is higher or deeper than the step 6a. The smooth side 3b is higher or deeper than the step 6b. The smooth side 3b is in-plane direction ( Figure 19The top surface 4t faces the smooth side surface 3a in the left-right direction. The top surface 4t is positioned between side surface 3a and side surface 3b, and is connected to both side surface 3a and side surface 3b. Thus, we can obtain... Figure 18 and Figure 19 The relief-type diffraction grating 1 is shown.

[0129] In this embodiment, the local oxidation process and the selective removal process of the silicon oxide film are each performed 4 times. However, depending on the height of the protrusion 3, the local oxidation process and the selective removal process of the silicon oxide film can be performed n times (where n is a natural number). The thickness of the silicon oxide film generated in the local oxidation process can also be adjusted.

[0130] In addition to the effects of the manufacturing method of the relief diffraction grating 1 in Embodiment 1, the manufacturing method of the relief diffraction grating 1 in this embodiment also has the following effects.

[0131] The manufacturing method of the relief-type diffraction grating 1 in this embodiment further includes: a step of forming a second silicon nitride film (e.g., silicon nitride film 11) on the top surface 4t of the silicon component 2; a step of oxidizing the silicon component 2 using the second silicon nitride film as a mask to transform a portion of the silicon component 2 into a second silicon oxide film (e.g., silicon oxide film 16); a step of removing the second silicon nitride film; and a step of selectively removing the second silicon oxide film. When selectively removing the first silicon oxide film (e.g., silicon oxide film 15), a second step portion (e.g., step portion 4b) is formed facing the first step portion (e.g., step portion 4a). The top surface 4t of the silicon component 2 is connected to the first step portion and the second step portion. When oxidizing the silicon component 2 using the second silicon nitride film as a mask, the first step portion and the second step portion are exposed from the second silicon nitride film. Each of the protrusions 3 of the relief-type diffraction grating 1 has smooth side surfaces (side surfaces 3a, 3b).

[0132] By using a silicon nitride film as a mask for oxidation (local oxidation) of the silicon component 2, a silicon oxide film can be formed with higher precision. Then, by selectively removing the silicon oxide film, a relief diffraction grating 1 is fabricated. Therefore, even by increasing the height of each of the protrusions 3, a relief diffraction grating 1 with higher dimensional accuracy can be fabricated.

[0133] Furthermore, in the relief-type diffraction grating 1 of this embodiment, each of the protrusions 3 has no edge portions on its side surfaces 3a and 3b, thus eliminating light scattering at the edges. According to the manufacturing method of the relief-type diffraction grating 1 of this embodiment, it is possible to manufacture a relief-type diffraction grating 1 with higher diffraction efficiency.

[0134] Implementation Method 3

[0135] Reference Figure 35 and Figure 36This section describes the relief diffraction grating 1 of Embodiment 3. The relief diffraction grating 1 of this embodiment has the same structure as the relief diffraction grating 1 of Embodiment 1, but differs from the relief diffraction grating 1 of Embodiment 1 in the following aspects.

[0136] In the relief-type diffraction grating 1 of this embodiment, the stepped portion 4a has an edge portion 4c with sharp angles. The stepped portion 5a also has an edge portion 5c with sharp angles. In this specification, an edge portion with sharp angles refers to an edge portion whose minimum radius of curvature is less than one-tenth of the diffraction wavelength of the relief-type diffraction grating 1. The stepped portion 4a has a flat side surface 8a. The stepped portion 5a has a flat side surface 8c. The side surface 3b is a smooth side surface.

[0137] Reference Figures 37 to 49 This describes the manufacturing method of the relief-type diffraction grating 1 in Embodiment 3.

[0138] Reference Figure 37 A photoresist 20 is formed on the main surface 2s of the silicon component 2. A portion of the main surface 2s of the silicon component 2 is covered by the photoresist 20. The remaining portion of the main surface 2s of the silicon component 2 is exposed from the photoresist 20. The thickness of the photoresist 20 is 1 μm or more. The photoresist 20 is formed by coating the entire surface of the main surface 2s of the silicon component 2 with the photoresist and then exposing and developing it.

[0139] Reference Figure 38 Using photoresist 20 as an etching mask, the portion of the silicon component 2 exposed from the photoresist 20 is removed by dry etching such as deep reactive ion etching (DRIE). Step portions 4a and 4b are formed in the silicon component 2. Step portion 4a has a flat side surface 8a and an angular edge portion 4c. Step portion 4b is in the in-plane direction ( Figure 38 The step portion 4b faces the step portion 4a in the left-right direction. The step portion 4b has a flat side surface 8b and an edge portion 4d with sharp edges. The flat side surfaces 8a and 8b may also be perpendicular to the top surface 4t. The top surface 4t is disposed between the step portion 4a and the step portion 4b, and is connected to the step portion 4a and the step portion 4b.

[0140] Reference Figure 39 Photoresist 20 is removed from silicon component 2 using oxygen plasma or organic solvents such as acetone.

[0141] Reference Figure 40 Photoresist 21 is formed on the top surface 4t and the step portion 4a of the silicon component 2. The step portion 4b and the silicon component 2 in the in-plane direction ( Figure 40The portion of the photoresist 21 located on the opposite side of the top surface 4t relative to the step portion 4a in the left-right direction is exposed. The photoresist 21 is thicker than the photoresist 20. The photoresist 21 is formed by the same method as the photoresist 20.

[0142] Reference Figure 41 Using photoresist 21 as an etching mask, the portion of the silicon component 2 exposed from the photoresist 21 is removed by dry etching such as deep reactive ion etching (DRIE). Stepped portions 5a and 5b are formed in the silicon component 2. Stepped portion 5a has a flat side surface 8c and an angular edge portion 5c. Figures 40 to 42 The process shown, step 4b (refer to) Figure 39 Step 5b becomes step 4b. Step 5b is higher or deeper than step 4b. Step 5b is in the in-plane direction ( Figure 41 The step portion 5b faces the steps 4a and 5a in the left and right directions. The step portion 5b has a flat side 8d and an edge portion 4d with sharp edges. The flat side 8c and 8d may also be perpendicular to the top surface 4t. The top surface 4t is disposed between the step portion 4a and the step portion 5b, and is connected to the step portion 4a and the step portion 5b.

[0143] Reference Figure 42 Photoresist 21 is removed from silicon component 2 using oxygen plasma or organic solvents such as acetone.

[0144] Reference Figure 43 A silicon nitride film 10 is formed on the top surface 4t of the silicon component 2 and on the steps 4a and 5a. The step 5b and the silicon component 2 are in the in-plane direction ( Figure 43 The portion of the silicon nitride film 10 exposed on the opposite side of the step portion 5a from the top surface 4t in the left-right direction is exposed. The silicon nitride film 10 of this embodiment is formed by the same method as the silicon nitride film 10 of Embodiment 1. The silicon nitride film 10 is thinner than each of the photoresists 20 and 21. The thickness of the silicon nitride film 10 is, for example, in the range of 0.1 μm to 0.3 μm.

[0145] Reference Figure 44 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 10 as a mask, transforming that portion into a silicon oxide film 15. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 10 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 10 become the silicon oxide film 15. The silicon oxide film 15 is formed around the periphery of the silicon nitride film 10, lifting the periphery of the silicon nitride film 10. This bypassing of the silicon oxide film 15 below the periphery of the silicon nitride film 10 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0146] Reference Figure 45 The silicon nitride film 10 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0147] Reference Figure 46 The silicon oxide film 15 is selectively removed using hydrofluoric acid solution or hydrofluoric acid vapor, forming stepped portions 6a and 6b on the silicon component 2. Stepped portion 6a has a smooth edge 6c. This is achieved through a localized oxidation process (see [reference]). Figure 44 ) and the selective removal process of silicon oxide film (refer to Figure 46 The edge 6c of the stepped portion 6a becomes smooth. Figures 43 to 46 The process shown, step 5b (refer to) Figure 42 Step 6b becomes step 5b. Step 6b is higher or deeper than step 5b. Step 6b is in the in-plane direction ( Figure 46 The top surface 4t faces the steps 4a, 5a, and 6a in the left-right direction. The step 6b has a smooth side surface. The side surface of the step 6b is steeper than that of the step 6a. The top surface 4t is disposed between the step 4a and the step 6b, and is connected to both the step 4a and the step 6b.

[0148] Reference Figure 47 A silicon nitride film 11 is formed on the top surface 4t of the silicon component 2 and on the steps 4a, 5a, and 6a. The step 6b and the silicon component 2 are in the in-plane direction ( Figure 47 The portion of the silicon nitride film 11 located on the opposite side of the step portion 6a from the top surface 4t in the left-right direction is exposed. The silicon nitride film 11 of this embodiment is formed by the same method as the silicon nitride film 10 of this embodiment. The silicon nitride film 11 is thinner than each of the photoresists 20 and 21. The thickness of the silicon nitride film 11 is, for example, in the range of 0.1 μm to 0.3 μm.

[0149] Reference Figure 48 The silicon component 2 is placed in a thermal oxidation furnace (not shown). A portion of the silicon component 2 is oxidized (localized) using a silicon nitride film 11 as a mask, transforming that portion into a silicon oxide film 16. Specifically, the portion of the silicon component 2 exposed from the silicon nitride film 11 and the portion of the silicon component 2 located below the periphery of the silicon nitride film 11 become the silicon oxide film 16. The silicon oxide film 16 is formed around the periphery of the silicon nitride film 11, raising the periphery of the silicon nitride film 11. This bypassing of the silicon oxide film 16 below the periphery of the silicon nitride film 11 can be achieved with high reproducibility and high dimensional accuracy. The silicon component 2 is then removed from the thermal oxidation furnace.

[0150] Reference Figure 49 The silicon nitride film 11 is selectively removed by using dry etching such as CF-type plasma or wet etching such as hot phosphoric acid.

[0151] The silicon oxide film 16 is selectively removed by hydrofluoric acid solution or hydrofluoric acid vapor, forming a step portion 7a on the silicon component 2 (see reference). Figure 36 The stepped portion 7a has a smooth edge portion 7c (see reference). Figure 36 Through a localized oxidation process (refer to...) Figure 48 The selective removal process of the silicon oxide film and the step portion 7a results in a smooth edge portion 7c. Step portion 6b (see reference) Figure 46 ) becomes a smooth side 3b (refer to) Figure 36 Side 3b is higher or deeper than the side of step 6b. Side 3b is in the in-plane direction ( Figure 36 On the left and right sides, it faces steps 4a, 5a, 6a, and 7a. Side 3b is steeper than steps 6a and 7a. Side 3b is gentler than the sides of steps 4a and 5a. Thus, we can obtain... Figure 35 and Figure 36 The relief-type diffraction grating 1 is shown.

[0152] In this embodiment, in order to form two step portions 4a and 5a, the removal process of the silicon component 2 using photoresist is performed twice. Then, in order to form two step portions 6a and 7a, the local oxidation process and the selective removal process of the silicon oxide film are each performed twice. However, in order to form m step portions, the removal process of the silicon component 2 using photoresist is performed m times (where m is a natural number). Then, in order to form n step portions located below the n step portions, the local oxidation process and the selective removal process of the silicon oxide film are each performed n times (where n is a natural number).

[0153] In addition to the effects of the manufacturing method of the relief diffraction grating 1 in Embodiment 1, the manufacturing method of the relief diffraction grating 1 in this embodiment also has the following effects.

[0154] The method for manufacturing the relief-type diffraction grating 1 in this embodiment further includes: a step of forming a photoresist (e.g., photoresist 20) on a silicon component 2; a step of dry etching a portion of the silicon component 2 using the photoresist as an etching mask to form a second step portion (e.g., step portion 4a) on the silicon component 2; and a step of removing the photoresist. A first silicon nitride film (e.g., silicon nitride film 10) is formed on the second step portion and the top surface 4t of the silicon component 2 connected to the second step portion. The first step portion (e.g., step portion 6a) is located below the second step portion. Each of the protrusions 3 of the relief-type diffraction grating 1 has multiple height levels.

[0155] When etching using a photoresist mask to form the upper step portion (e.g., step portions 4a, 5a), the photoresist can be made relatively thin. Therefore, etching using a photoresist mask can also form the upper step portion with relatively high dimensional accuracy. However, when etching using a photoresist mask to form the lower step portion (e.g., step portions 6a, 7a), a thicker photoresist needs to be patterned. If the thicker photoresist is patterned by exposure and development, it is impossible to pattern the thicker photoresist with high accuracy due to the defocusing of the light used for exposure. Therefore, if etching using a photoresist mask to form the lower step portion (e.g., step portions 6a, 7a), the dimensional accuracy of the lower step portion (e.g., step portions 6a, 7a) deteriorates.

[0156] In contrast, in this embodiment, to form the lower stepped portions (e.g., stepped portions 6a, 7a), oxidation (local oxidation) of the silicon component 2 using a silicon nitride film thinner than the photoresist as a mask and selective removal of the silicon oxide film are utilized. Furthermore, by using oxidation (local oxidation) of the silicon component 2 using a silicon nitride film as a mask, the silicon oxide film can be formed with higher dimensional accuracy. By selectively removing the silicon oxide film, an embossed diffraction grating 1 is manufactured. Therefore, the dimensional accuracy of the lower stepped portions (e.g., stepped portions 6a, 7a) is improved. According to the manufacturing method of the embossed diffraction grating 1 of this embodiment, an embossed diffraction grating 1 with higher dimensional accuracy can be manufactured.

[0157] Furthermore, by etching using a photoresist as a mask to form the upper stepped portions (e.g., stepped portions 4a, 5a), the in-plane dimensions of the protrusion 3 can be adjusted. Therefore, the diffraction wavelength of the relief-type diffraction grating 1 can be adjusted.

[0158] In the manufacturing method of the relief-type diffraction grating 1 of this embodiment, when a portion of the silicon member 2 is removed, a flat side surface (e.g., flat side surface 8b) is formed on the silicon member 2 facing the second step portion (e.g., step portion 4a). When the silicon member 2 is oxidized, the flat side surface is exposed from the first silicon nitride film (e.g., silicon nitride film 10). When the first silicon oxide film (e.g., silicon oxide film) is selectively removed, a side surface (e.g., side surface 6b) is formed on the silicon member 2 facing the first step portion (e.g., step portion 6a) and the second step portion and smoother than the first step portion and the second step portion.

[0159] Therefore, the in-plane dimensions of the protrusion 3 can be adjusted. The diffraction wavelength of the relief-type diffraction grating 1 can also be adjusted.

[0160] Implementation Method 4

[0161] Reference Figure 50 and Figure 51 This section describes the relief diffraction grating 1 of Embodiment 4. The relief diffraction grating 1 of this embodiment has the same structure as the relief diffraction grating 1 of Embodiment 1, but differs from the relief diffraction grating 1 of Embodiment 1 in the following aspects.

[0162] In this embodiment, the silicon component 2 is the silicon layer 33 of the silicon-on-insulator (SOI) substrate 30. The SOI substrate 30 includes a silicon substrate 31, a SiO2 insulating layer 32, and the silicon layer 33. The SiO2 insulating layer 32 is located between the silicon substrate 31 and the silicon layer 33. An embossed diffraction grating 1 is formed on the silicon layer 33.

[0163] Each of the protrusions 3 has a flat side 3b facing the stepped portions 4a, 5a, 6a, and 7a 8e. The side 3b may also be perpendicular to the top surface 4t. The side 3b may also extend to the SiO2 insulating layer 32.

[0164] Reference Figures 52 to 54 This describes the manufacturing method of the relief-type diffraction grating 1 in embodiment 4.

[0165] Reference Figure 52 An SOI substrate 30 is prepared. The SOI substrate 30 includes a silicon substrate 31, a SiO2 insulating layer 32, and a silicon layer 33. The SiO2 insulating layer 32 is located between the silicon substrate 31 and the silicon layer 33. The silicon layer 33 has a main surface 2s on the opposite side of the SiO2 insulating layer 32.

[0166] Reference Figure 53 An embossed diffraction grating 1 is formed on a silicon layer 33 using the same manufacturing method as that used in Embodiment 1. The embossed diffraction grating 1 includes a periodic concave-convex structure 9. The periodic concave-convex structure 9 of the embossed diffraction grating 1 includes a plurality of periodically arranged protrusions 3. Each protrusion 3 includes a side surface 3a, a side surface 3b facing the side surface 3a, and a top surface 4t. Stepped portions 4a, 5a, 6a, and 7a are formed on the side surface 3a. Stepped portions 4b, 5b, 6b, and 7b are formed on the side surface 3b.

[0167] Reference Figure 54 Photoresist 35 is formed on the top surface 4t of silicon layer 33 and on the step portions 4a, 5a, 6a, and 7a. The step portions 4b, 5b, 6b, and 7b are exposed from the photoresist 35. The photoresist 35 is thicker than the silicon nitride films 10, 11, 12, and 13 of Embodiment 1. The photoresist 35 is formed using the same method as the photoresist 20 of Embodiment 3.

[0168] Using photoresist 35 as an etching mask, the portion of the silicon layer 33 exposed from the photoresist 35 is removed by dry etching such as deep reactive ion etching (DRIE). Side 3b, forming a flat side 8e, is then formed (see reference). Figure 51 In the etching process of silicon layer 33, SiO2 insulating layer 32 functions as an etching stop layer. Then, photoresist 21 is removed using oxygen plasma or organic solvents such as acetone. Thus, a solution is obtained. Figure 50 and Figure 51 The relief-type diffraction grating 1 is shown.

[0169] In addition to the effects of the manufacturing method of the relief diffraction grating 1 in Embodiment 1, the manufacturing method of the relief diffraction grating 1 in this embodiment also has the following effects.

[0170] The method for manufacturing the relief-type diffraction grating 1 in this embodiment further includes a step of etching a silicon component 2 (e.g., silicon layer 33) to form a flat side surface 8e facing the first step portion (e.g., step portion 4a).

[0171] Therefore, the in-plane dimensions of the protrusion 3 can be adjusted. Therefore, the diffraction wavelength of the relief-type diffraction grating 1 can be adjusted.

[0172] In the manufacturing method of the relief-type diffraction grating 1 in this embodiment, the silicon component 2 is the silicon layer 33 of the silicon substrate 30 on an insulator.

[0173] The relief-type diffraction grating 1 of this embodiment is formed on a silicon layer 33 made of a single material such as silicon. Therefore, according to the manufacturing method of the relief-type diffraction grating 1 of this embodiment, it is possible to manufacture a relief-type diffraction grating 1 with superior temperature stability of diffraction efficiency compared to a comparative example relief-type diffraction grating formed of multiple materials with different coefficients of linear expansion.

[0174] In the etching process of silicon layer 33, the SiO2 insulating layer 32 of the silicon-on-insulator substrate functions as an etching stop layer. Therefore, the height dimension of the protrusion 3 is accurately determined. According to the manufacturing method of relief diffraction grating 1 of this embodiment, relief diffraction grating 1 with higher dimensional accuracy can be manufactured.

[0175] Implementation Method 5

[0176] Reference Figure 55 The optical scanning device 40 of Embodiment 5 is explained. The optical scanning device 40 is an application example of the relief-type diffraction grating 1 of Embodiments 1 to 4.

[0177] The optical scanning device 40 includes an embossed diffraction grating 1, a frame 41, beams 42 and 44, anchors 43, coils 45, and a magnetic field generator 46.

[0178] The relief-type diffraction grating 1 is joined to the frame 41 via beam 42. The frame 41 is joined to the anchor 43 via beam 44. A coil 45 is disposed on the frame 41. The coil 45 is wound around the relief-type diffraction grating 1. A magnetic field generator 46 generates a magnetic field 47. The magnetic field generator 46 is, for example, a permanent magnet.

[0179] When an alternating current is applied to coil 45, an electromagnetic force is applied to frame 41 by the alternating current flowing in the coil and the magnetic field 47 from magnetic field generator 46. This electromagnetic force causes frame 41 to oscillate around beam 44. Relief diffraction grating 1 oscillates together with frame 41, scanning the light incident on relief diffraction grating 1.

[0180] This allows the optical scanning device 40 of this embodiment to achieve its intended effect.

[0181] The optical scanning device 40 includes an embossed diffraction grating 1. Furthermore, the embossed diffraction grating 1 has higher dimensional accuracy. Therefore, the embossed diffraction grating 1 has higher diffraction efficiency. According to this embodiment, the optical scanning device 40 can scan light incident on the embossed diffraction grating 1 with lower optical loss.

[0182] The embodiments 1-5 disclosed herein should be considered illustrative rather than restrictive in all respects. At least two of the embodiments 1-5 may be combined as long as they do not contradict each other. For example, the relief-type diffraction grating of embodiments 1-3 may also be formed on the silicon layer 33 of the SOI substrate 30 as in embodiment 4. The scope of this disclosure is defined not by the foregoing description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0183] Explanation of reference numerals in the attached figures

[0184] 1 Relief-type diffraction grating; 2 Silicon component; 2a Silicon substrate; 2s Main surface; 3 Protrusion; 3a, 3b, 6b Side surfaces; 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b Stepped portions; 4c, 4d, 5c, 5d, 6c, 6d, 7c, 7d Edge portions; 4t Top surface; 8a, 8b, 8c, 8d, 8e Flat side surfaces; 9 Periodic concave-convex structure; 10, 11, 12, 13 Silicon nitride film; 15, 16, 17, 18 Silicon oxide film; 20, 21, 35 Photoresist; 30 Silicon-on-insulator substrate; 31 Silicon substrate; 33 Silicon layer; 32 Insulating layer; 40 Optical scanning device; 41 Frame; 42, 44 Beams; 43 Anchor; 45 Coil; 46 Magnetic field generator; 47 Magnetic field.

Claims

1. A method for manufacturing an embossed diffraction grating, wherein, include: The process of forming a first silicon nitride film on a silicon component; The process of oxidizing the silicon component by using the first silicon nitride film as a mask to transform a portion of the silicon component into the first silicon oxide film; The process of removing the first silicon nitride film; as well as The process of selectively removing the first silicon oxide film to form a first step portion on the silicon component.

2. The method for manufacturing an embossed diffraction grating according to claim 1, wherein, The first stepped portion has smooth edges.

3. The method for manufacturing an embossed diffraction grating according to claim 1 or 2, wherein, Also includes: The process of forming a second silicon nitride film on the top surface of the silicon component connected to the first step portion and on the first step portion; The process of oxidizing the silicon component by using the second silicon nitride film as a mask to transform a portion of the silicon component into the second silicon oxide film; The process of removing the second silicon nitride film; as well as The process of selectively removing the second silicon oxide film and forming a second step portion connected to the first step portion on the silicon component. Each of the protrusions of the relief-type diffraction grating has multiple height levels.

4. The method for manufacturing an embossed diffraction grating according to claim 1 or 2, wherein, Also includes: The process of forming a second silicon nitride film on the top surface of the silicon component; The process of oxidizing the silicon component by using the second silicon nitride film as a mask to transform a portion of the silicon component into the second silicon oxide film; The process of removing the second silicon nitride film; as well as The process of selectively removing the second silicon oxide film, During the selective removal of the first silicon oxide film, a second step portion is formed facing the first step portion. The top surface of the silicon component is connected to the first stepped portion and the second stepped portion. When the silicon component is oxidized using the second silicon nitride film as a mask, the first step portion and the second step portion are exposed from the second silicon nitride film. Each of the protrusions of the relief-type diffraction grating has a smooth side surface.

5. The method for manufacturing an embossed diffraction grating according to claim 1 or 2, wherein, Also includes: The process of forming a photoresist on the silicon component; The process of using the photoresist as an etching mask to dry etch a portion of the silicon component to form a second step portion in the silicon component; as well as The process of removing the photoresist, The first silicon nitride film is formed on the second step portion and the top surface of the silicon component connected to the second step portion. The first step is located below the second step. Each of the protrusions of the relief-type diffraction grating has multiple height levels.

6. The method for manufacturing an embossed diffraction grating according to claim 5, wherein, When removing the portion of the silicon component, a flat side surface is formed on the silicon component facing the second stepped portion. During the oxidation of the silicon component, the flat side is exposed from the first silicon nitride film. When selectively removing the first silicon oxide film, a side surface is formed on the silicon member that faces the first step portion and the second step portion and is smoother than the first step portion and the second step portion.

7. The method for manufacturing an embossed diffraction grating according to any one of claims 1 to 5, wherein, It also includes a process of etching the silicon component to form a flat side facing the first stepped portion.

8. The method for manufacturing an embossed diffraction grating according to any one of claims 1 to 7, wherein, The silicon component is a silicon substrate.

9. The method for manufacturing an embossed diffraction grating according to any one of claims 1 to 7, wherein, The silicon component is a silicon layer on a silicon-on-insulator substrate.

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