A method for fabricating a multicolor transmission grating

Abstract

This invention relates to the field of transmissive grating technology, specifically to a method for fabricating a multicolor transmissive grating. This method involves depositing narrow bands of specific colors of light sequentially in corresponding areas of the grating through multiple photolithography overlays and vacuum evaporation coating on the basis of a striped grating. This ensures that only specific colors of light are transmitted in specific areas, thereby producing a multicolor transmissive grating with high grating strip width accuracy.

Description

Technical Field

[0001] This invention relates to the field of transmissive grating technology, and more specifically to a method for manufacturing a multicolor transmissive grating. Background Technology

[0002] Gratings are an important tool in modern optics, an optical element that exhibits periodic transmission or reflection of light. Multicolor (chromatic) gratings possess unique properties different from monochrome gratings, thus finding wide application in color measurement, optical microscopy, and laser detection. A multicolor grating is an optical element composed of multiple gratings of different wavelengths, capable of simultaneously displaying multiple different colored fringes after the complex white light has been dispersed. Current methods for manufacturing multicolor gratings primarily involve screen printing with optical inks in different areas. However, this method suffers from the following problems: the optical inks exhibit poor stability and weak adhesion, and the lack of clear zoning leads to alternating influences between different colors. Summary of the Invention

[0003] This invention provides a method for fabricating a multicolor transmissive grating. The method involves depositing narrow bands of specific colors of light sequentially in the corresponding areas of the grating through multiple photolithography overlays and vacuum evaporation coating on the basis of a striped grating. This ensures that only specific colors of light are transmitted in specific areas, thereby producing a multicolor transmissive grating with high grating strip width accuracy.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A method for fabricating a multicolor transmission grating includes the following steps:

[0006] S1. Take a clean and dry optical glass substrate and deposit a metal light-shielding film layer on the surface of the optical glass substrate.

[0007] S2. Photolithography is performed on the surface of the metal light-shielding film to form equidistant alternating light and dark grating stripes;

[0008] S3. On an optical glass substrate with grating stripes, a narrow band coating capable of transmitting specific colors of light is formed by photolithography overlay and partitioning. The wavelength range of the specific color of light transmitted by the narrow band is consistent after each photolithography overlay and coating process. The specific steps of photolithography overlay and coating are as follows:

[0009] S3.1. Coat the side of the optical glass substrate with grating stripes with photoresist and dry it;

[0010] S3.2 Remove the photoresist from the surface of the grating area where a specific color narrow band is to be deposited by exposure and development. Use a photoresist mask to cover the remaining areas, and then dry.

[0011] S3.3. Deposit a light-transmitting film layer of the corresponding color light in the grating area where a narrow band of a specific color light is to be deposited. The light-transmitting film layer satisfies the transmittance T > 90% in the wavelength range of the specific color light, and the light in other areas is cut off.

[0012] S3.4 Remove and peel off the remaining photoresist, and clean and dry it;

[0013] S4. Then, according to the method in step S3, photolithography is performed on the optical glass substrate with grating stripes to form and coat a narrow band that can transmit another specific color of light. This process continues until all the narrow bands that can transmit color light are pre-set on the grating and photolithography is completed, thus obtaining a multicolor transmissive grating.

[0014] In step S1, the metal light-shielding film is a chromium film, which satisfies the requirement of transmittance T < 0.1% in the wavelength range of 400-700nm.

[0015] The photolithography process in step S2 includes: coating photoresist on the surface of a metal light-shielding film layer, followed by mask exposure, development, wet etching, and stripping of the remaining photoresist.

[0016] The wet etching solution used in wet etching is a mixed solution prepared by pure water, glacial acetic acid and cerium ammonium nitrate in a ratio of 30 mL:(0.8-1.2) mL:(5-8) g.

[0017] The photoresist is SUN-115P UV positive photoresist.

[0018] The developing solution used is a 2.2% - 2.5% TMAH solution.

[0019] The adhesive removal solution used in the adhesive removal process is a KOH solution with a mass concentration of 10%-15%.

[0020] The drying process in step S3.2 is to bake at 100℃ for 10-15 minutes.

[0021] The coating process in step S3.3 is vacuum evaporation coating using a vacuum evaporation coating machine.

[0022] The width of the narrow band in steps S3 and S4 is the same as the width of the alternating bright and dark grating stripes in step S2.

[0023] Compared with the prior art, the beneficial effects of the present invention are: (1) Based on the alternating light and dark striped grating, the present invention sequentially deposits narrow bands of specific colors of light in the corresponding areas of the grating through multiple photolithography overlays and vacuum evaporation coating, ensuring that only specific colors of light are transmitted in specific areas, thereby producing a multicolor transmission grating. This multicolor transmission grating can achieve different transmission effects in different segments and positions of the visible light band of 400nm-700nm.

[0024] (2) The different light transmission zones of the multicolor transmissive grating prepared by the present invention are partitioned by photolithography, which avoids the problem of mutual influence during the partitioning process, and the accuracy of the grating strip width can reach ±0.5μm.

[0025] (3) The present invention produces grating stripes by deposition and etching of chromium. Chromium metal is stable and not easily damaged, ensuring the stability of the grating shading area under various conditions for a long time.

[0026] (4) The multicolor transmissive grating prepared by the present invention can be applied to the field of medical endoscopy. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the equidistant alternating bright and dark grating stripes obtained in step S2 of the present invention.

[0028] Figure 2 This is a schematic diagram of the invention after sequentially photolithographically etching a narrow band of blue light transmittance and a narrow band of green light transmittance onto equidistant alternating light and dark grating stripes. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] The method for fabricating a multicolor transmissive grating provided by this invention includes the following steps:

[0031] S1. Take a clean and dry optical glass substrate and deposit a metal light-shielding film layer on the surface of the optical glass substrate using a magnetron sputtering coating equipment.

[0032] The present invention preferably selects a suitable optical glass substrate based on the optical performance and external dimensions required by the corresponding product, for specific optical performance requirements;

[0033] Specifically, before depositing the metal light-shielding film layer, the optical glass substrate is ultrasonically cleaned and dried; further, it is first ultrasonically cleaned with a solvent and then rinsed with pure water. The solvent used for ultrasonic cleaning is preferably a strong alkaline solution. After cleaning, the cleaned optical glass substrate is preferably evaporated with IPA to ensure that the optical glass substrate is clean and dry.

[0034] Preferably, the metal light-shielding film is a chromium film, which satisfies a transmittance T < 0.1% in the wavelength range of 400-700 nm. Preferably, the thickness of the chromium film is 120 nm. Preferably, the magnetron sputtering conditions include: a Cr target sputtering power of 5 kW and an Ar gas flow rate of 30 sccm / s during Cr film sputtering. After depositing the metal light-shielding film, ultrasonic cleaning is performed again.

[0035] S2. Photolithography is performed on the surface of the metal light-shielding film to form equidistant, alternating bright and dark grating stripes, such as... Figure 1 As shown;

[0036] Specifically, the photolithography process includes: coating a metal light-shielding film layer with photoresist, followed by mask exposure, development, wet etching, and residual photoresist stripping. Preferably, the photoresist is SUN-115P UV positive photoresist with a viscosity of 25 CP. Preferably, the development solution is a 2.38% TMAH solution. Preferably, the wet etching solution used in the wet etching process is a mixed solution prepared from pure water, glacial acetic acid, and cerium ammonium nitrate in a ratio of 30 mL: 1.1 mL: 6 g. Preferably, the stripping solution used in the stripping process is a 10% KOH solution. The invention preferably also includes cleaning the optical glass substrate after stripping, preferably by sequentially immersing in concentrated sulfuric acid and ultrasonic cleaning.

[0037] S3. After the film performance is tested and approved by the Olympus reflectivity tester, a narrow band coating capable of transmitting specific colors of light is formed on an optical glass substrate with grating stripes through photolithography, and in the designated grating area. The wavelength range of the specific colors of light that can be transmitted by the narrow band is consistent after each photolithography and coating process; specifically, the width of the narrow band is consistent with the width of the alternating bright and dark grating stripes in step S2; the specific steps of photolithography and coating are as follows:

[0038] S3.1. Coat the side of the optical glass substrate with grating stripes with photoresist and dry it;

[0039] Preferably, the photoresist is SUN-115P UV positive photoresist with a viscosity of 25 CP; the thickness of the photoresist coating is preferably 1 μm; the coating process is preferably spin coating, and the spin coating speed is preferably 2500 rpm / min.

[0040] S3.2 Remove the photoresist from the surface of the grating area to be plated with a specific color narrow band by exposure and development, exposing the grating strip area to be plated with a specific color narrow band. Cover the remaining areas with a photoresist mask and then dry.

[0041] The preferred exposure method is ultraviolet (UV) exposure; the UV light source wavelength is 365nm, the preferred exposure intensity is 12mW / cm², and the preferred exposure time is 10s; preferably, the developing solution is a 2.38% TMAH solution, and the immersion time is 30s. Preferably, the drying process is baking at 100℃ for 10 minutes; during exposure, the photomask and the optical glass substrate with grating stripes have alignment marks, and exposure is performed after alignment.

[0042] S3.3. Deposit a light-transmitting film layer of the corresponding color light in the grating area where a narrow band of a specific color light is to be deposited. The light-transmitting film layer satisfies the transmittance T > 90% in the wavelength range of the specific color light, and the light in other areas is cut off.

[0043] Preferably, the coating process is vacuum evaporation coating using a vacuum evaporation coating machine;

[0044] S3.4 Remove and peel off the remaining photoresist, then clean and dry it, leaving only the light-transmitting film layer coated on the optical glass;

[0045] Preferably, the degumming solution used in the degumming process is a 10% KOH solution.

[0046] S4. Then, according to the method in step S3, photolithography is performed on the optical glass substrate with grating stripes to complete the narrow band coating that can transmit another specific color of light, until all the narrow bands that can transmit color light are pre-set on the grating are photolithographically etched, thus obtaining a multicolor transmissive grating.

[0047] In this embodiment, the multicolor transmissive grating has pre-set narrow bands that can transmit visible light (white light), blue light, and green light respectively. The equidistant, alternating bright and dark grating stripes obtained in step S2 can transmit visible light. Figure 1 In step S3, a narrow band that transmits blue light is photolithographically overlaid on the grating that transmits visible light. In step S4, a narrow band that transmits green light is photolithographically overlaid on the grating that transmits both visible and blue light, thus obtaining a three-color transmission grating that transmits visible, blue, and green light respectively. Figure 2 As shown. Specifically, the light-transmitting film layer deposited on the narrow band that transmits blue light satisfies a transmittance T > 90% in the blue light wavelength range (450±12nm), while light in other regions is cut off; the light-transmitting film layer deposited on the narrow band that transmits green light satisfies a transmittance T > 90% in the green light wavelength range (550±12nm), while light in other regions is cut off. If, in actual production, a color-transmitting grating that transmits visible light, blue light, green light, and orange light is required, then a narrow band that transmits orange light is photolithographically overlaid on the grating that transmits visible light, blue light, and green light. The accuracy of the grating strip width of the multicolor transmitting grating obtained by the above method in this invention can reach ±0.5μm.

Claims

1. A method for fabricating a multicolor transmission grating, characterized in that... Includes the following steps: S1. Take a clean and dry optical glass substrate, and deposit a metal light-shielding film layer on the surface of the optical glass substrate; the metal light-shielding film layer is a chromium film, which satisfies the requirement of transmittance T < 0.1% in the wavelength range of 400-700nm; S2. Photolithography is performed on the surface of the metal light-shielding film to form equidistant alternating light and dark grating stripes; S3. On an optical glass substrate with grating stripes, a narrow band coating capable of transmitting specific colors of light is formed by photolithography overlay and partitioning. The wavelength range of the specific color of light transmitted by the narrow band is consistent after each photolithography overlay and coating process. The specific steps of photolithography overlay and coating are as follows: S3.

1. Coat the side of the optical glass substrate with grating stripes with photoresist and dry it; S3.2 Remove the photoresist from the surface of the grating area where a specific color narrow band is to be deposited by exposure and development. Use a photoresist mask to cover the remaining areas, and then dry. S3.

3. Deposit a light-transmitting film layer of the corresponding color light in the grating area where a narrow band of a specific color light is to be deposited. The light-transmitting film layer satisfies the transmittance T > 90% in the wavelength range of the specific color light, and the light in other areas is cut off. S3.4 Remove and peel off the remaining photoresist, and clean and dry it; S4. Then, according to the method in step S3, photolithography is performed on the optical glass substrate with grating stripes to form and coat the narrow band that can transmit another specific color of light, until all the narrow bands that can transmit color light are pre-set on the grating are photolithographically formed and coated, thus obtaining a multicolor transmissive grating. The width of the narrow band in steps S3 and S4 is the same as the width of the alternating bright and dark grating stripes in step S2.

2. The method for manufacturing a multicolor transmission grating according to claim 1, characterized in that: The photolithography process in step S2 includes: coating photoresist on the surface of a metal light-shielding film layer, followed by mask exposure, development, wet etching, and stripping of the remaining photoresist.

3. The method for manufacturing a multicolor transmission grating according to claim 2, characterized in that: The wet etching solution used in wet etching is a mixed solution prepared by pure water, glacial acetic acid and cerium ammonium nitrate in a ratio of 30 mL:(0.8-1.2) mL:(5-8) g.

4. The method for manufacturing a multicolor transmission grating according to claim 1 or 2, characterized in that: The photoresist is SUN-115P UV positive photoresist.

5. The method for manufacturing a multicolor transmission grating according to claim 1 or 2, characterized in that: The developing solution used is a 2.2% - 2.5% TMAH solution.

6. The method for manufacturing a multicolor transmission grating according to claim 1 or 2, characterized in that: The adhesive removal solution used in the adhesive removal process is a KOH solution with a mass concentration of 10%-15%.

7. The method for manufacturing a multicolor transmission grating according to claim 1, characterized in that: The drying process in step S3.2 is to bake at 100℃ for 10-15 minutes.

8. The method for manufacturing a multicolor transmission grating according to claim 1, characterized in that: The coating process in step S3.3 is vacuum evaporation coating using a vacuum evaporation coating machine.

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