A method for preparing a deep ultraviolet gray-tone mask based on a blue print process

Abstract

The present application relates to the technical field of optical information storage, and particularly relates to a preparation method of a deep ultraviolet gray-tone mask based on a blue printing process, which comprises the following steps: mixing a blue printing aqueous solution and a gelatin aqueous solution according to a volume ratio of 2:5-4:5 to obtain a blue printing photosensitive agent solution; uniformly covering the blue printing photosensitive agent solution on the surface of a quartz substrate by using a drop coating method or a spin coating method; controlling the exposure dose distribution of the blue printing photosensitive solution on the surface of the quartz by using the light transmittance difference of a gray-tone film mask; placing the quartz in ice water after ultraviolet exposure; removing the unexposed soluble iron salt by washing with water; developing the blue image; adding hydrogen peroxide aqueous solution to enhance the contrast of the Prussian blue pattern; forming a light shielding layer gradient; drying; and obtaining the deep ultraviolet gray-tone mask based on the blue printing process. The method combines the light shielding layer gradient of the blue printing process with the ultraviolet light transmittance of the quartz substrate, and realizes the preparation of the ultraviolet gray-tone mask with low cost and high flexibility.

Description

Technical Field

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

[0002] In the ultraviolet band, traditional photomasks are typically binary (fully transparent and 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. In existing methods, halftone masks require multi-step etching and deposition processes (such as two photolithography and coating processes), while grayscale lithography may rely on complex electron beam direct writing or multiple overlay processes.

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

[0004] Film masks are based on synthetic resin, which is low in cost and suitable for medium to low precision applications. However, synthetic resin materials have severe absorption in the deep ultraviolet band (such as 254nm), with a transmittance of less than 5%, making it impossible to achieve deep ultraviolet light storage and grayscale image writing. They are mainly used in fields with low resolution requirements, such as printed circuit boards and liquid crystal displays.

[0005] Stainless steel photomasks, using a metal substrate, possess high durability and mechanical strength, making them suitable for processes such as electron beam evaporation and magnetron sputtering. Based on their fabrication processes, they can be divided into two categories: laser cutting and chemical etching. Laser cutting achieves rapid processing using high-energy lasers, but is affected by thermal deformation, making it difficult to handle complex patterns at the micrometer level; it is typically suitable for applications with linewidths greater than 1 mm. Chemical etching selectively removes metal using chemical reactions, enabling the fabrication of micropores and complex structures at the 50 μm level; however, the process is highly complex and cannot control the light transmission gradient, supporting only binary imaging with full transmission / full obscuration. Neither of these fabrication processes can achieve grayscale imaging.

[0006] Photolithography masks use quartz glass as a substrate with a chromium-plated surface to form a light-shielding layer, offering high precision (minimum linewidth 2μm) and long lifespan. Through electron beam lithography and wet etching processes, complex integrated circuit patterns with line pitches below 130nm can be fabricated. However, their drawbacks include: heavy metal contamination from chromium layer processing, complex processes requiring multiple exposures for grayscale masks, and high costs associated with the quartz substrate and manufacturing processes. They are primarily used in high-end manufacturing fields such as semiconductor devices.

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

[0008] Therefore, there is an urgent need for a low-cost, wide UV-compatible, and simple grayscale mask fabrication 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 at least solve one of the technical problems existing in related technologies. Therefore, the object of the present invention is to provide a method for preparing a deep ultraviolet grayscale mask based on an cyanotype process.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a deep ultraviolet grayscale mask based on cyanotype printing includes the following steps: S100. Mix the cyan photosensitive agent solution and the gelatin solution in a volume ratio of 2:5 to 4:5 to obtain the cyan photosensitive agent solution. The concentration of the gelatin aqueous solution is 10–20% (w / v); The cyanophthalic acid aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) ferric ammonium citrate aqueous solution, and solution B is a 5-10% (w / v) potassium ferricyanide aqueous solution. The volume ratio of solution A to solution B is 2:3 to 3:2. S200: Using drop coating or spin coating, the blue photosensitive agent solution is evenly coated on the surface of the quartz substrate and dried in the dark to obtain the photosensitive layer. S300: The grayscale film with the target pattern is attached to the surface of the photosensitive layer. After ultraviolet exposure, it is placed in ice water at a temperature of 0-4℃. Unexposed soluble iron salts are removed by washing with water, and a blue image is developed. Hydrogen peroxide aqueous solution is added to enhance the contrast of the Prussian blue pattern. After drying, a deep ultraviolet grayscale mask based on the cyanotype process is obtained. The core of the cyanotype process lies in the photosensitizing iron salts, primarily ferric ammonium citrate and potassium ferricyanide. Ferric ammonium citrate is a photosensitizer; under ultraviolet excitation, ferric ions are reduced to ferrous ions. Potassium ferricyanide reacts with ferrous ions to form water-insoluble ferrous ferrocyanide, i.e., Prussian blue precipitate. The simplified chemical reaction formula is shown below: ; The amount of Prussian blue precipitate formed is controlled by adjusting the exposure intensity, as follows: High exposure area (film transparent area) → high light intensity → high Prussian blue production → low ultraviolet transmittance (strong light blocking). Low exposure area (high density area of ​​film) → low light intensity → less Prussian blue formation → high ultraviolet transmittance (weak shading).

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

[0012] Further, in step S100, solutions A and B in the cyano solution are mixed in equal volumes.

[0013] Furthermore, in step S100, the concentration of the ferric ammonium citrate aqueous solution 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] Further, 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 in the deep ultraviolet (DUV) range of 100–300 nm, and has a low coefficient of thermal expansion, which can ensure the stability of the mask during ultraviolet exposure.

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

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

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

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

[0021] The above-described 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 fabricating a deep ultraviolet grayscale mask based on cyanophotography. This method combines the light-shielding layer gradient of the cyanophotography process with the ultraviolet transmittance of the quartz substrate, achieving low-cost and highly flexible fabrication of ultraviolet grayscale masks. This fabrication method is simple, low-cost, and environmentally friendly, breaking through the dependence of traditional technologies on complex equipment and specialized materials. Its core innovation lies in integrating classical photography with modern mask requirements, providing a new solution for the fields of ultraviolet light storage and patterned display.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

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

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

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

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0027] A method for preparing a deep ultraviolet grayscale mask based on cyanotype printing includes the following steps: S100. Mix the cyan photosensitive agent solution and the gelatin solution in a volume ratio of 2:5 to 4:5 to obtain a cyan photosensitive agent solution. The concentration of the gelatin aqueous solution is 10–20% (w / v); The cyanophthalic acid aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) ferric ammonium citrate aqueous solution, and solution B is a 5-10% (w / v) potassium ferricyanide aqueous solution. The volume ratio of solution A to solution B is 2:3 to 3:2. S200: Using a drop-coating or spin-coating method, the blue photosensitive agent solution is evenly covered on the substrate surface and dried in the dark to obtain a photosensitive layer. S300: The grayscale film with the target pattern is attached to the surface of the photosensitive layer. After ultraviolet exposure, it is placed in ice water at a temperature of 0-4℃. Unexposed soluble iron salts are removed by washing with water, and a blue image is developed. Hydrogen peroxide aqueous solution is added to enhance the contrast of the Prussian blue pattern. After drying, a deep ultraviolet grayscale mask based on the cyanotype process is obtained.

[0028] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0029] Example 1 I. Preparation of solution: Take 1.5 g of gelatin granules, add an appropriate amount of deionized water, bring the volume to 10 ml, transfer to a 60℃ water bath and heat, stirring continuously until completely dissolved, to finally obtain a 15% (w / v) gelatin aqueous solution.

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

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

[0032] Mix solution A, solution B, and gelatin aqueous solution in a volume ratio of 3:3:10 to obtain a cyanotype photosensitive agent solution.

[0033] II. Pretreatment of the quartz substrate, the process is as follows: The quartz substrate was placed in ethanol, sonicated for 5 minutes, rinsed repeatedly with deionized water, and dried to obtain a clean quartz substrate.

[0034] 3. Apply the blue photosensitive agent solution evenly to the surface of a clean quartz substrate. Manually shake the substrate horizontally to assist in spreading the liquid film, utilizing the surface tension of the liquid to allow it to spread naturally into a uniform film on the quartz substrate surface. Pour excess liquid into a waste liquid tank along one corner of the quartz substrate, and gently wipe the edges of the substrate with a lint-free cloth to prevent accumulation at the edges after drying. Tilt the substrate at a 15-degree angle and let it stand for 2 minutes, then place it horizontally in a light-proof drying oven and dry at room temperature (25℃) for 24 hours to obtain a uniform photosensitive layer.

[0035] 4. Attach the grayscale film with the target pattern to the surface of the photosensitive layer, cover it with a quartz plate to ensure no gap between the film and the photosensitive layer, and clamp the two quartz plates together for ultraviolet exposure. Expose to direct sunlight for 5 minutes to trigger the photochemical reaction of iron salts. Immerse the exposed quartz substrate with the photosensitive layer attached in ice water at 0-4°C, wash away unexposed soluble iron salts, develop a blue image, add hydrogen peroxide solution to enhance the contrast of the Prussian blue pattern, and dry to obtain a grayscale mask with controllable transmittance gradient in the deep ultraviolet band based on the cyanotype process.

[0036] This invention utilizes the photochemical conversion mechanism of the blue exposure process to transform the light distribution density of the grayscale film into the gradient of the Prussian blue light-blocking layer on the surface of the quartz glass. By leveraging its ultraviolet absorption characteristics, the transmittance of the quartz mask can be continuously controlled in the ultraviolet band (100-400nm), thereby forming an ultraviolet grayscale mask.

[0037] like Figure 1As shown, regions 1 to 6 were set on a deep ultraviolet grayscale mask based on cyanotype to create a gradient of film masking layers with different grayscale levels. The photosensitive liquid reaction dosage was controlled by ultraviolet exposure. After the exposure of regions 1 to 6 was 98%, 90%, 80%, 70%, 50%, and 40%, respectively, the transmittance of each region was measured. The measurement process is as follows: Light source and probe: A 254nm ultraviolet light source was used to test the transmittance. The ultraviolet light was irradiated onto the surface of the mask to ensure that the light was uniform and free from scattering interference. Different grayscale areas were precisely located, and an optical fiber probe was placed at the incident light position on the other side of the mask.

[0038] Reference and Measurement: The ultraviolet light was calibrated using the undeveloped transparent area as the full transmittance reference. Then, the ultraviolet light was moved to different transmittance areas in sequence, and the transmittance of the ultraviolet band under different Prussian blue shading layer gradients was measured by a spectrometer to calculate the ultraviolet transmittance.

[0039] Error control: Each region was randomly tested three times, and the average value was taken to reduce random error. The results are as follows: Figure 2 As shown in the figure, the ultraviolet transmittance of regions 1 to 6 are 1.5%, 10.1%, 18.4%, 29.1%, 46.8% and 64.5% respectively, achieving a gradient distribution of the Prussian blue shading layer on the quartz surface.

[0040] The application of writing patterns onto a photosensitive medium using a deep ultraviolet grayscale mask based on cyanophotography is illustrated in the following examples: Figure 3 As shown.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a deep ultraviolet grayscale mask based on cyanotype process, characterized in that, Includes the following steps: S100. Mix the cyan photosensitive agent solution and the gelatin solution in a volume ratio of 2:5 to 4:5 to obtain the cyan photosensitive agent solution. The concentration of the gelatin aqueous solution is 10–20% (w / v); The cyanophthalic acid aqueous solution includes solution A and solution B. Solution A is a 15-25% (w / v) ferric ammonium citrate aqueous solution, and solution B is a 5-10% (w / v) potassium ferricyanide aqueous solution. The volume ratio of solution A to solution B is 2:3 to 3:

2. S200: Using drop coating or spin coating, the blue photosensitive agent solution is evenly coated on the surface of the quartz substrate and dried in the dark to obtain the photosensitive layer. S300: The grayscale film with the target pattern is attached to the surface of the photosensitive layer. After ultraviolet exposure, it is placed in ice water at a temperature of 0-4℃. Unexposed soluble iron salts are removed by washing with water, and a blue image is developed. Hydrogen peroxide aqueous solution is added to enhance the contrast of the Prussian blue pattern. After drying, a deep ultraviolet grayscale mask based on the cyanotype process is obtained.

2. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, 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 cyanotype as described in claim 1, characterized in that, In step S100, solutions A and B in the cyano solution are mixed in equal volumes.

4. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, In step S100, the concentration of the ferric ammonium citrate aqueous solution is 19-20% (w / v).

5. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, 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 cyanotype as described in claim 1, characterized in that, In step S200, the substrate is selected from a quartz glass substrate.

7. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, In step S200, the drying temperature is 10–50°C.

8. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, In step S300, the transmittance of ultraviolet light during ultraviolet exposure is 40-98%.

9. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, In step S300, the ultraviolet exposure time is 2 to 60 minutes.

10. The method for preparing a deep ultraviolet grayscale mask based on cyanotype as described in claim 1, characterized in that, In step S300, the wavelength range of ultraviolet light during the ultraviolet exposure process is 100–400 nm.

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