Preparation method of deep ultraviolet grayscale mask based on blue drying process

Abstract

The invention relates to the technical field of optical information storage, in particular to a preparation method of a deep ultraviolet gray mask based on a blue-basking process, which comprises the following steps: mixing a blue-basking aqueous solution and a gelatin aqueous solution according to a volume ratio of 2: 5-4: 5 to obtain a blue-basking photosensitizer solution; a dispensing method or a spin coating method is adopted, the surface of a quartz substrate is evenly covered with the blue-basking photosensitizer solution, the exposure dose distribution of the blue-basking photosensitizer solution on the surface of the quartz substrate is controlled by means of the light transmittance difference of a gray-scale film plate, after ultraviolet exposure, the quartz substrate is placed in ice water and washed to remove unexposed soluble ferric salt, a blue image is developed, and the gray-scale film plate is obtained. The preparation method comprises the following steps: adding an aqueous hydrogen peroxide solution to enhance the contrast ratio of a Prussian blue pattern, forming a shading layer gradient, and drying to obtain the deep ultraviolet gray scale mask plate based on the blue drying process, and by combining the shading layer gradient of the blue drying process with the ultraviolet light transmittance of a quartz substrate, the preparation of the ultraviolet gray scale mask plate with low cost and high flexibility is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optical information storage, and in particular to a method for preparing a deep ultraviolet grayscale mask based on a cyanotype process. Background Art

[0002] In the UV range, traditional photomasks are typically binary (fully transparent or opaque), while grayscale masks achieve multi-level grayscale effects through spatially distributed differences in transmittance. For example, halftone masks achieve multi-level grayscale through partially transparent areas, while grayscale lithography can achieve grayscale control through sub-pixel encoding (adjusting the proportion of transparent area) or variable dose exposure. Existing methods require multi-step etching and deposition processes (such as two photolithography steps and coating), while grayscale lithography may rely on complex electron beam direct writing or multiple overlays.

[0003] Currently commonly used templates mainly include film masks, stainless steel masks and photolithography masks.

[0004] Film masks, based on synthetic resin, are low-cost and suitable for low- to medium-precision applications. However, synthetic resins strongly absorb deep UV wavelengths (such as 254nm), resulting in a transmittance of less than 5%, making them incapable of deep UV storage and grayscale image writing. Consequently, they are primarily used in applications requiring lower resolution, such as printed circuit boards and liquid crystal displays.

[0005] Stainless steel masks use a metal substrate, which offers high durability and mechanical strength, making them suitable for processes such as electron beam evaporation and magnetron sputtering. They can be categorized by their preparation process: laser cutting and chemical etching. Laser cutting uses high-energy lasers to achieve rapid processing, but is affected by thermal deformation and has difficulty processing complex micron-level patterns. It is generally suitable for scenarios with line widths greater than 1mm. Chemical etching uses chemical reactions to selectively remove metals, enabling the processing of 50μm-level micropores and complex structures. However, the process is highly complex and cannot control the transmittance gradient, supporting only full-transmittance / full-blocking binary imaging. Both preparation processes are unable to achieve grayscale imaging.

[0006] Photolithography masks use a quartz glass substrate with a chrome-plated light-shielding layer. They offer high precision (minimum line width 2μm) and a long service life. Through electron beam lithography and wet etching processes, they can produce complex integrated circuit patterns with line pitches below 130nm. However, these masks have drawbacks: heavy metal contamination from chromium layer processing, the complex process required for multiple exposures of grayscale masks, and the high cost of quartz substrates and manufacturing processes. Consequently, they are primarily used in high-end manufacturing applications such as semiconductor devices.

[0007] Patent (CN117826521A) discloses a grayscale mask and a method for manufacturing the same, but the manufacturing process of the grayscale mask is complicated and cannot be used for complex patterns.

[0008] Therefore, there is an urgent need for a low-cost, broad UV-compatible, and simple process grayscale mask preparation method to support the demand for grayscale patterning in emerging fields such as optical information storage. Summary of the Invention

[0009] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention aims to provide a method for preparing a deep ultraviolet grayscale mask based on a cyanotype process.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing a deep ultraviolet grayscale mask based on a cyanotype process comprises the following steps: S100, uniformly mixing the blue-printing aqueous solution and the gelatin aqueous solution in a volume ratio of 2:5 to 4:5 to obtain a blue-printing sensitizer solution; wherein the concentration of the gelatin aqueous solution is 10-20% (w / v); The cyanotype aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) aqueous solution of ammonium ferric citrate, and solution B is a 5-10% (w / v) aqueous solution of potassium ferricyanide. The volume ratio of solution A to solution B is 2:3 to 3:2. S200, using a drop coating method or a spin coating method to evenly cover the surface of the quartz substrate with a blue-printing sensitizer solution, and drying in the dark to obtain a photosensitive layer; S300, laminating a grayscale film plate with a target pattern to the surface of the photosensitive layer, and after ultraviolet exposure, placing it in ice water at a temperature of 0 to 4°C, removing unexposed soluble iron salts by water washing, developing a blue image, adding a hydrogen peroxide solution to enhance the contrast of the Prussian blue pattern, and drying to obtain a deep ultraviolet grayscale mask plate based on the cyanotype process; The core of the cyanotype process lies in photosensitizing iron salts, primarily ammonium ferric citrate and potassium ferrocyanide. Ammonium ferric citrate is a photosensitizer. Under ultraviolet light, ferric ions are reduced to ferrous ions. Potassium ferrocyanide reacts with ferrous ions to form water-insoluble ferric ferrocyanide, the precipitate of Prussian blue. The simplified chemical reaction formula is as follows: ; The amount of Prussian blue precipitate formed can be controlled by controlling the exposure intensity as follows: High exposure area (film transparent area) → high light intensity → high Prussian blue production → low UV transmittance (strong light-blocking property); Low exposure area (high film density area) → low light intensity → less Prussian blue generated → high UV transmittance (weak light-blocking property).

[0011] Furthermore, in step S100, the concentration of the gelatin aqueous solution is 14-16% (w / v).

[0012] Furthermore, in step S100, equal volumes of solution A and solution B in the blue-printing aqueous solution are mixed.

[0013] Furthermore, in step S100, the concentration of the aqueous solution of ammonium ferric citrate is 19-20% (w / v).

[0014] Furthermore, in step S100, the concentration of the potassium ferricyanide aqueous solution is 7.5-8.5% (w / v).

[0015] Furthermore, in step S200, the substrate is selected from a quartz glass substrate.

[0016] Quartz glass (SiO2) has high transmittance (>90%) in the ultraviolet band, especially the deep ultraviolet (DUV) 100-300nm, and a low thermal expansion coefficient, which can ensure the stability of the mask during UV exposure.

[0017] Furthermore, in step S200, the drying temperature is 10-50°C.

[0018] Furthermore, in step S300 , the transmittance of ultraviolet rays during the ultraviolet exposure process is 40-98%.

[0019] Furthermore, in step S300, the UV exposure time is 2 to 60 minutes.

[0020] Furthermore, in step S300 , the wavelength range of ultraviolet rays during the ultraviolet exposure process is 100 to 400 nm.

[0021] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: This invention provides a method for preparing a deep UV grayscale mask based on a cyanotype process. By combining the gradient of the cyanotype light-shielding layer with the UV transmittance of a quartz substrate, this method achieves low-cost, highly flexible UV grayscale mask production. This method is simple, low-cost, and environmentally friendly, breaking away from the traditional reliance on complex equipment and specialized materials. Its core innovation lies in integrating classical photography with modern mask requirements, providing a new solution for UV storage and patterned display.

[0022] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram showing areas 1 to 6 set on a deep ultraviolet grayscale mask based on a cyanotype process provided in Example 1 of the present invention.

[0024] Figure 2 This is a statistical diagram of the transmittance of areas 1 to 6 set on the deep ultraviolet grayscale mask based on the cyanotype process provided in Example 1 of the present invention.

[0025] Figure 3 This is an example diagram of an application scenario of the deep ultraviolet grayscale mask based on the cyanotype process provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0027] A method for preparing a deep ultraviolet grayscale mask based on a cyanotype process comprises the following steps: S100, mixing the blue-printing aqueous solution and the gelatin aqueous solution in a volume ratio of 2:5 to 4:5 to obtain a blue-printing sensitizer solution; wherein the concentration of the gelatin aqueous solution is 10-20% (w / v); The cyanotype aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) aqueous solution of ammonium ferric citrate, and solution B is a 5-10% (w / v) aqueous solution of potassium ferricyanide. The volume ratio of solution A to solution B is 2:3 to 3:2. S200, using a drop coating method or a spin coating method to evenly cover the surface of the substrate with a blue-printing sensitizer solution, and drying in the dark to obtain a photosensitive layer; S300, attaching a grayscale film plate with a target pattern to the surface of the photosensitive layer, placing it in ice water at a temperature of 0-4°C after ultraviolet exposure, removing unexposed soluble iron salts by water washing, developing a blue image, adding a hydrogen peroxide solution to enhance the contrast of the Prussian blue pattern, and drying to obtain a deep ultraviolet grayscale mask plate based on the cyanotype process.

[0028] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0029] Example 1 1. Prepare the solution: Take 1.5 g of gelatin particles, add appropriate amount of deionized water, dilute to 10 ml, transfer to a 60°C water bath and heat, continue stirring until completely dissolved, and finally obtain a 15% (w / v) gelatin aqueous solution.

[0030] At room temperature (25°C), weigh 2 g of ammonium ferric citrate, add an appropriate amount of deionized water, stir and dissolve, then dilute to 10 ml to obtain a 20% (w / v) ammonium ferric citrate solution, labeled as solution A.

[0031] At room temperature (25°C), weigh 0.8 g of potassium ferrocyanide, add an appropriate amount of deionized water, stir and dissolve, then dilute to 10 ml to obtain an 8% (w / v) potassium ferrocyanide aqueous solution, labeled as solution B.

[0032] Solution A, solution B and gelatin aqueous solution were evenly mixed in a volume ratio of 3:3:10 to obtain a blue-printing sensitizer solution.

[0033] 2. Pretreatment of quartz substrate: The quartz substrate was placed in ethanol, ultrasonicated for 5 minutes, repeatedly rinsed with deionized water, and dried to obtain a clean quartz substrate.

[0034] 3. Apply a droplet of the cyanotype photosensitive solution evenly to the surface of a clean quartz substrate. Manually shake the film horizontally to help it spread, using the surface tension of the liquid to naturally spread it into a uniform film on the surface of the quartz plate. Pour the excess liquid into a waste tank along one corner of the quartz substrate. Gently wipe the edge of the substrate with a dust-free cloth to prevent accumulation at the edge after drying. Tilt the substrate 15 degrees and let it stand for 2 minutes. Then, place it horizontally in a light-proof drying oven and dry it at room temperature (25°C) for 24 hours to obtain a uniform photosensitive layer.

[0035] Fourth, a grayscale film plate bearing the target pattern is bonded to the surface of the photosensitive layer. A quartz plate is placed on top to ensure a gap between the film and the photosensitive layer. The two quartz plates are clamped together and exposed to UV light. Exposure is carried out under direct sunlight for 5 minutes to trigger the photochemical reaction of the iron salt. The exposed quartz substrate with the photosensitive layer attached is immersed in ice water at a temperature of 0-4°C. Unexposed soluble iron salts are removed by washing, and a blue image is developed. Aqueous hydrogen peroxide solution is added to enhance the contrast of the Prussian blue pattern. The mask is then dried to obtain a grayscale mask with a controllable transmittance gradient in the deep UV band, based on the cyanotype process.

[0036] The present invention uses the photochemical conversion mechanism of the cyanotype process to convert the light distribution density of the grayscale film into a Prussian blue light-shielding layer gradient on the surface of the quartz glass. The ultraviolet absorption properties of the layer are utilized to achieve continuous control of the light transmittance of the quartz mask in the ultraviolet band (100-400nm), thereby forming an ultraviolet grayscale mask.

[0037] like Figure 1As shown, areas 1 to 6 are set on a deep UV grayscale mask based on a cyanotype process to form a film-shielding layer gradient with different grayscale levels. The photosensitive liquid reaction dose is controlled by UV exposure. Areas 1 to 6 are exposed to 98%, 90%, 80%, 70%, 50%, and 40% respectively. The transmittance of each area is then tested. The testing process is as follows: Light source and probe: Use a 254nm UV light source to test transmittance. Irradiate the UV light onto the mask surface to ensure uniform light distribution and no scattering interference. Highly accurately locate different grayscale areas and place a fiber optic probe at the incident light position on the other side of the mask.

[0038] Benchmark and measurement: The UV light is calibrated using the undeveloped transparent area as the fully transparent benchmark. The UV light is then moved to different transparent areas in sequence. The UV band transmittance under different Prussian blue light-shielding layer gradients is measured using a spectrometer to calculate the UV transmittance.

[0039] Error control: Each area is randomly tested 3 times and the average value is taken to reduce the random error. The results are as follows Figure 2 As shown in the figure, it can be seen that the ultraviolet transmittances of regions 1 to 6 are 1.5%, 10.1%, 18.4%, 29.1%, 46.8% and 64.5%, respectively, realizing the gradient distribution of the Prussian blue light-shielding layer on the quartz surface.

[0040] Using a deep ultraviolet grayscale mask based on a cyanotype process to write patterns on a photosensitive medium, its application scenarios include: Figure 3 shown.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a deep ultraviolet grayscale mask based on a cyanotype process, characterized in that: The steps include: S100, uniformly mixing the blue-printing aqueous solution and the gelatin aqueous solution in a volume ratio of 2:5 to 4:5 to obtain a blue-printing sensitizer solution; wherein the concentration of the gelatin aqueous solution is 10-20% (w / v); The cyanotype aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) aqueous solution of ammonium ferric citrate, and solution B is a 5-10% (w / v) aqueous solution of potassium ferricyanide. The volume ratio of solution A to solution B is 2:3 to 3:

2. S200, using a drop coating method or a spin coating method to evenly cover the surface of the quartz substrate with a blue-printing sensitizer solution, and drying in the dark to obtain a photosensitive layer; S300, attaching a grayscale film plate with a target pattern to the surface of the photosensitive layer, placing it in ice water at a temperature of 0-4°C after ultraviolet exposure, removing unexposed soluble iron salts by water washing, developing a blue image, adding a hydrogen peroxide solution to enhance the contrast of the Prussian blue pattern, and drying to obtain a deep ultraviolet grayscale mask plate based on the cyanotype process.

2. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S100, the concentration of the gelatin aqueous solution is 14-16% (w / v).

3. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S100, equal volumes of solution A and solution B in the cyanotype aqueous solution are mixed.

4. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S100 , the concentration of the aqueous solution of ammonium ferric citrate is 19-20% (w / v).

5. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S100 , the concentration of the potassium ferricyanide aqueous solution is 7.5-8.5% (w / v).

6. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S200, the substrate is selected from a quartz glass substrate.

7. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S200, the drying temperature is 10-50°C.

8. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S300 , the transmittance of ultraviolet rays during the ultraviolet exposure process is 40-98%.

9. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S300 , the UV exposure time is 2 to 60 minutes.

10. The method for preparing a deep ultraviolet grayscale mask based on a cyanotype process according to claim 1, wherein: In step S300 , the wavelength of ultraviolet light during the ultraviolet exposure process is in the range of 100 to 400 nm.

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