A coating process for improving the adhesion of metal oxides to photoresist on a photomask

Abstract

The application belongs to the technical field of photomasks, and particularly relates to a coating process for improving the adhesion of metal oxides on a photomask and photoresist, which comprises the following steps: performing plasma cleaning on a photomask substrate containing a metal oxide film, performing surface treatment to form a modified photomask substrate after the cleaning is completed, and finally coating photoresist on the photomask substrate and drying according to a standard process. The application solves the problem of poor adhesion between the existing metal oxide film and the photoresist, forms an organic functional group exposed surface layer on the metal oxide film by using a modified method, forms physical-chemical crosslinking with photoresist molecules, effectively improves the interfacial adhesion, and can reasonably expect that the photoresist is not easy to peel off in the development and etching process.

Description

Technical Field

[0001] This invention belongs to the field of photomask technology, specifically relating to a coating process that improves the adhesion between metal oxides and photoresists on a photomask. Background Technology

[0002] In photomask manufacturing, a metal oxide film is often deposited on the surface of a glass or quartz substrate, and then photoresist is coated on the metal oxide film for subsequent pattern transfer. Current coating methods use spin coating to uniformly apply photoresist to the metal oxide surface, with only routine cleaning such as deionized water rinsing and UV / O3 treatment before coating, followed by soft baking, exposure, and development. However, metal oxides have low surface energy and weak polarity, while photoresists are generally non-polar or low-polar, resulting in insufficient adhesion between the two. Furthermore, the lack of chemical modification steps for the metal oxide surface leads to a narrow process window and low yield. During development or etching, the photoresist is prone to glass defects, bubbles, or pattern defects. Prolonged exposure or humid environments further degrades the interfacial adhesion of the photoresist, affecting the photomask's lifespan. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a coating process that improves the adhesion between metal oxides and photoresists on a photomask. This process involves coating a metal oxide film to form a surface layer with exposed organic functional groups, which then forms a physical-chemical crosslink with the photoresist molecules. This effectively enhances interfacial adhesion and maintains the adhesion stability of the photoresist in subsequent processes.

[0004] To achieve the above technical objectives, the technical solution of the present invention is as follows: A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: Plasma cleaning is performed on the photomask substrate with deposited metal oxide thin film. The plasma cleaning uses oxygen plasma or argon plasma with a power of 100-300W and a time of 1-5min. This step uses plasma cleaning to remove organic contaminants on the surface of the metal oxide thin film and introduce hydroxyl active groups. Step 2: The cleaned photomask substrate is subjected to surface treatment to obtain a modified photomask substrate; the surface treatment includes coupling agent coating-thermal activation reaction, plasma graft polymerization, self-assembled monolayer treatment, and UV / thermal dual curing. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist is positive photoresist or negative photoresist, specifically including: i-line photoresist, KrF photoresist, and ArF photoresist; the soft baking temperature is 90-110℃ and the time is 60-90s.

[0005] Furthermore, the photomask after soft baking undergoes an overall post-baking process to enhance the cross-linking density of the interface. The post-baking temperature is 120-150℃ and the time is 5-10 minutes.

[0006] The coupling agent coating-thermal activation reaction steps include: adding a silane coupling agent to an isopropanol / water mixed solvent to obtain a silane solution with a concentration of 0.5%-2%, and then uniformly coating it onto the metal oxide surface of the photomask by spin coating or spraying; finally, placing the spin-coated photomask on a hot plate for baking to obtain a modified photomask substrate; this baking can promote the condensation polymerization of the coupling agent with the hydroxyl groups on the metal oxide surface, thereby forming Si-OM covalent bonds, while exposing organic photoenergy groups at the other end. The silane coupling agent includes KH560, KH570, and APTMS; the isopropanol volume percentage of the isopropanol / water solvent is 90-95%; the spin coating speed is 500-3000 rpm, the time is 30-60 s, the coating amount is 1-3 mL / piece; and the baking temperature is 80-120℃, the time is 2-10 min.

[0007] The plasma grafting polymerization involves grafting monomers containing polar functional groups onto the surface of a photomask after plasma cleaning, thereby increasing surface polarity. The monomers include acrylic acid, methacrylic acid, maleic anhydride, or acrylamide, at a concentration of 0.1-10 mmol / L, using argon as the carrier gas. The grafting occurs within a grafting reaction chamber at a pressure of 10-50 Pa, a grafting power of 50-200 W, and a time of 5-20 min. After grafting, the surface is rinsed with deionized water and dried with nitrogen.

[0008] The self-assembled monolayer treatment involves using self-assembled molecules containing phosphate or carboxylic acid groups on the surface of a metal oxide film. The self-assembled molecules are alkyl phosphates or alkyl carboxylic acids, including octadecyl phosphate and hexadecyl phosphate, and octadecanoic acid and hexadecanoic acid, respectively. The self-assembled monolayer treatment involves dissolving the self-assembled molecules in anhydrous ethanol or isopropanol to form a solution, immersing the metal oxide film in the solution for 2-24 hours, rinsing with anhydrous ethanol, and drying at 60-100°C for 10-30 minutes. The concentration of the self-assembled molecules in the solution is 0.5-2 mmol / L, and the immersion temperature is 25-60°C.

[0009] The UV / thermal dual curing process involves adding a silane coupling agent and a photoinitiator to a solvent and stirring until homogeneous. This mixture is then uniformly coated onto the surface of a metal oxide substrate, followed by UV curing and thermal curing to obtain a modified photomask substrate. The silane coupling agent is one or more of KH560, KH570, or APTMS; the photoinitiator is Irgacure 184, Irgacure 651, or Darocur 1173, added at 0.5-2% of the coupling agent's mass; the solvent is one or more of isopropanol, acetone, or ethyl acetate, with the coupling agent's mass concentration in the solvent being 1-5%; the uniform coating process involves a spin coating speed of 500-2000 rpm for 20-40 seconds, with a coating amount of 1-2 mL / sheet; and the UV curing wavelength is 365 nm or 254 nm, with a light intensity of 50-200 mW / cm². 2 The curing time is 1-5 minutes, and the temperature for heat curing is 80-100℃, with a curing time of 3-5 minutes.

[0010] As can be seen from the above description, the present invention has the following advantages: 1. This invention solves the problem of poor adhesion between existing metal oxide films and photoresists. By modifying the metal oxide film to form an exposed organic functional group surface layer, it forms a physical-chemical cross-link with the photoresist molecules, effectively improving the interfacial adhesion. It can be reasonably expected that the photoresist will not be easily peeled off during development and etching.

[0011] 2. Based on the improved adhesion, the edge roughness of the photoresist pattern during development will be reduced, the integrity of the pattern will be improved, and defects or floating adhesive caused by local peeling will be avoided.

[0012] 3. This invention forms covalent bonds between the metal oxide and the photoresist. The energy of covalent bonds is much higher than that of physical adsorption, ensuring that the interface performance degradation is less than that of existing processes when stored in a humid and hot environment for a long time, thus maintaining good adhesion.

[0013] 4. This invention forms hydroxyl groups on the surface of metal oxide thin films through plasma cleaning. It does not depend on specific metal oxide components or specific photoresist systems, has good reactivity, and can be widely used in various mask films such as CrO, MoSiO, and ITO. Detailed Implementation

[0014] A specific embodiment of the present invention will be described in detail with reference to the embodiments, but this does not limit the scope of the claims of the present invention in any way.

[0015] Example 1 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses oxygen plasma with a power of 200W and a time of 3min. Step 2: Perform surface treatment on the cleaned photomask substrate to obtain a modified photomask substrate. The surface treatment includes: adding a silane coupling agent to an isopropanol / water mixed solvent to obtain a 0.5% silane solution, and then uniformly coating it onto the metal oxide surface of the photomask using spin coating. Finally, place the spin-coated photomask on a hot plate for baking to obtain the modified photomask substrate. The silane coupling agent used is KH570, the isopropanol volume ratio of the isopropanol / water solvent is 90%, the spin coating speed is 500 rpm, the time is 60 s, the coating amount is 3 mL / piece, and the baking temperature is 80℃ for 10 min.

[0016] Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is i-line photoresist; the soft baking temperature is 100℃ and the time is 70s.

[0017] Example 2 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses oxygen plasma with a power of 100W and a time of 5min. Step 2: Perform surface treatment on the cleaned photomask substrate to obtain a modified photomask substrate. The surface treatment includes: adding a silane coupling agent to an isopropanol / water mixed solvent to obtain a 1.2% silane solution, and then uniformly coating it onto the metal oxide surface of the photomask using spin coating. Finally, place the spin-coated photomask on a hot plate for baking to obtain the modified photomask substrate. The silane coupling agent used is KH560, the isopropanol volume ratio of the isopropanol / water solvent is 93%, the spin coating speed is 1800 rpm, the time is 45 s, the coating amount is 2 mL / piece, and the baking temperature is 100℃ for 5 min.

[0018] Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is KrF photoresist; the soft baking temperature is 110℃ and the time is 60s.

[0019] Example 3 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 300W and a time of 1min. Step 2: Perform surface treatment on the cleaned photomask substrate to obtain a modified photomask substrate. The surface treatment includes: adding a silane coupling agent to an isopropanol / water mixed solvent to obtain a 2% silane solution, and then uniformly coating it onto the metal oxide surface of the photomask by spin coating or spraying. Finally, place the spin-coated photomask on a hot plate for baking to obtain a modified photomask substrate. The silane coupling agent used is APTMS, the isopropanol volume ratio of the isopropanol / water solvent is 95%, the spin coating speed is 3000 rpm, the time is 30 s, the coating amount is 1 mL / piece, and the baking temperature is 120℃ for 2 min.

[0020] Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is ArF photoresist; the soft baking temperature is 90℃ and the time is 90s.

[0021] Comparative Example 1 is based on Example 1, except that no modification treatment was performed, and only photoresist was applied after plasma cleaning. The specific steps are the same as in Example 1.

[0022] The performance of the products coated in Examples 1-3 and Comparative Example 1 was compared, and the results are as follows:

[0023] The data comparison above shows that the coupling agent coating-thermal activation reaction used in this technical solution can effectively improve the activity of the photomask substrate surface, greatly enhance the adhesion and connection between the photoresist and the photomask substrate, and ensure the stability of the photoresist on the photomask substrate.

[0024] Example 4 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses oxygen plasma with a power of 300W and a time of 1min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs plasma grafting polymerization, which involves grafting a monomer containing polar functional groups onto the plasma-cleaned photomask surface to increase surface polarity. The monomer used is acrylamide at a concentration of 0.1 mmol / L, with argon as the carrier gas. The grafting occurs within a grafting reaction chamber at a pressure of 50 Pa, a grafting power of 50 W, and a time of 20 min. After grafting, the substrate is rinsed with deionized water and dried with nitrogen. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is i-line photoresist; the soft baking temperature is 90℃ and the time is 90s.

[0025] Example 5 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 100W and a time of 5min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs plasma grafting polymerization, which involves grafting monomers containing polar functional groups onto the plasma-cleaned photomask surface to increase surface polarity. The monomer used is acrylic acid at a concentration of 5 mmol / L, with argon as the carrier gas. The grafting occurs within a grafting reaction chamber at a pressure of 10 Pa, a grafting power of 120 W, and a time of 10 min. After grafting, the substrate is rinsed with deionized water and dried with nitrogen. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is KrF photoresist; the soft baking temperature is 110℃ and the time is 60s.

[0026] Example 6 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 200W and a time of 3min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs plasma grafting polymerization, which involves grafting monomers containing polar functional groups onto the plasma-cleaned photomask surface to increase surface polarity. The monomer used is maleic anhydride at a concentration of 10 mmol / L, with argon as the carrier gas. The grafting occurs within a grafting reaction chamber at a pressure of 30 Pa, a grafting power of 200 W, and a time of 5 minutes. After grafting, the substrate is rinsed with deionized water and dried with nitrogen. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is ArF photoresist; the soft baking temperature is 100℃ and the time is 80s.

[0027] Comparative Example 2 is based on Example 4, except that: Comparative Example 2 was not modified, but only photoresist was applied after plasma cleaning, and the specific steps were the same as those in Example 2.

[0028] The performance of the products coated in Examples 4-6 and Comparative Example 2 was compared, and the results are as follows:

[0029] The data comparison above shows that the plasma graft polymerization used in this technical solution can effectively improve the activity of the photomask substrate surface, greatly enhance the adhesion and connection between the photoresist and the photomask substrate, ensure the stability of the photoresist on the photomask substrate, reduce the detachment rate between the two, and improve the surface hydrophilicity.

[0030] Example 7 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses oxygen plasma with a power of 100W and a time of 5min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs a self-assembled monolayer treatment, in which self-assembled molecules are dissolved in anhydrous ethanol to form a solution. The metal oxide film is then immersed in the solution for 24 hours, rinsed with anhydrous ethanol, and dried at 100°C for 10 minutes. The concentration of the self-assembled molecules in the solution is 0.5 mmol / L, and the immersion temperature is 25°C. The self-assembled molecules are hexadecanoic acid. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is i-line photoresist; the soft baking temperature is 90℃ and the time is 90s.

[0031] Example 8 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 300W and a time of 1min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs a self-assembled monomolecular film treatment, in which self-assembled molecules are dissolved in anhydrous isopropanol to form a solution. The metal oxide film is then immersed in the solution for 12 hours, rinsed with anhydrous ethanol, and dried at 60°C for 30 minutes. The concentration of the self-assembled molecules in the solution is 1.2 mmol / L, and the immersion temperature is 45°C. The self-assembled molecules used are octadecyl phosphoric acid. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is KrF photoresist; the soft baking temperature is 110℃ and the time is 60s.

[0032] Example 9 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 200W and a time of 3min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs a self-assembled monolayer treatment, in which self-assembled molecules are dissolved in anhydrous ethanol to form a solution. The metal oxide film is then immersed in the solution for 2 hours, rinsed with anhydrous ethanol, and dried at 80°C for 20 minutes. The concentration of the self-assembled molecules in the solution is 2 mmol / L, and the immersion temperature is 60°C. The self-assembled molecules used are hexadecyl phosphoric acid. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is ArF photoresist; the soft baking temperature is 100℃ and the time is 80s.

[0033] Comparative Example 3 was not modified; it was simply plasma cleaned and then photoresist coated, with the same steps as in Example 7.

[0034] The performance of the products coated in Examples 7-9 and Comparative Example 3 was compared, and the results are as follows:

[0035] The data comparison above shows that the self-assembled monomolecular film treatment used in this technical solution can effectively improve the activity of the photomask substrate surface, greatly enhance the adhesion and connection between the photoresist and the photomask substrate, ensure the stability of the photoresist on the photomask substrate, reduce the detachment rate between the two, and improve the water contact angle.

[0036] Example 10 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses oxygen plasma with a power of 100W and a time of 5min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs UV / thermal dual curing. This UV / thermal dual curing involves adding a silane coupling agent and a photoinitiator to a solvent, stirring until homogeneous, and then uniformly coating the mixture onto the metal oxide surface. After UV curing and thermal curing, the modified photomask substrate is obtained. The silane coupling agent used is KH570, and the photoinitiator is Irgacure 651, added at 0.5% of the coupling agent's mass. The solvent is isopropanol, with a coupling agent concentration of 1% by mass. The uniform coating process involves a spin coating speed of 2000 rpm for 20 seconds, a coating amount of 2 mL / sheet, and a UV curing wavelength of 365 nm with a light intensity of 50 mW / cm². 2 The curing time is 5 minutes, and the temperature for heat curing is 100°C for 3 minutes. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is i-line photoresist; the soft baking temperature is 90℃ and the time is 90s.

[0037] Example 11 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 300W and a time of 1min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs UV / thermal dual curing. This UV / thermal dual curing involves adding a coupling agent and photoinitiator to a solvent, stirring until homogeneous, and then uniformly coating the mixture onto the metal oxide surface. After UV curing and thermal curing, the modified photomask substrate is obtained. The coupling agent used is silane coupling agent KH560, and the photoinitiator is Irgacure 184, added at 1.2% of the coupling agent's mass. The solvent is acetone, with a coupling agent concentration of 3% by mass. The uniform coating process involves spin coating at 500 rpm for 40 seconds, with a coating amount of 1 mL / sheet. The UV curing wavelength is 254 nm, and the light intensity is 120 mW / cm². 2 The curing time is 2 minutes, and the temperature for heat curing is 80°C for 5 minutes. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is KrF photoresist; the soft baking temperature is 110℃ and the time is 60s.

[0038] Example 12 A coating process for improving the adhesion between metal oxides and photoresists on a photomask includes the following steps: Step 1: The photomask substrate with deposited metal oxide thin film is subjected to plasma cleaning. The plasma cleaning uses argon plasma with a power of 200W and a time of 3min. Step 2: The cleaned photomask substrate undergoes surface treatment to obtain a modified photomask substrate. The surface treatment employs UV / thermal dual curing. This UV / thermal dual curing involves adding a coupling agent and photoinitiator to a solvent, stirring until homogeneous, and then uniformly coating the mixture onto the metal oxide surface. After UV curing and thermal curing, the modified photomask substrate is obtained. The coupling agent used is the silane coupling agent Darocur 1173, and the photoinitiator is Darocur 1173, added at 2% of the coupling agent's mass. The solvent is ethyl acetate, with a coupling agent concentration of 5% by mass. The uniform coating process involves spin coating at 1000 rpm for 30 seconds, with a coating amount of 1.5 mL / sheet. The UV curing wavelength is 365 nm, and the light intensity is 200 mW / cm². 2 The curing time is 1 minute, and the temperature for heat curing is 90°C for 4 minutes. Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard process; the photoresist used is ArF photoresist; the soft baking temperature is 100℃ and the time is 80s.

[0039] Comparative Example 4 was not modified; it was simply plasma cleaned and then photoresist coated, with the same steps as in Example 10.

[0040] The performance of the products coated in Examples 10-12 and Comparative Example 4 was compared, and the results are as follows:

[0041] The data comparison above shows that the UV / thermal dual curing method used in this technical solution can effectively improve the activity of the photomask substrate surface, greatly enhance the adhesion and connection between the photoresist and the photomask substrate, ensure the stability of the photoresist on the photomask substrate, reduce the peeling rate between the two, and significantly improve the peel strength. It is understood that the above detailed description of the present invention is for illustrative purposes only and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.

Claims

1. A coating process for improving the adhesion between metal oxides and photoresist on a photomask, characterized in that: Includes the following steps: Step 1: Perform plasma cleaning on the photomask substrate with deposited metal oxide thin film; Step 2: Perform surface treatment on the cleaned photomask substrate to obtain a modified photomask substrate; Step 3: Coat the surface of the modified photomask substrate with photoresist, and then perform soft baking according to standard procedures after coating.

2. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 1, characterized in that: The plasma cleaning in step 1 uses oxygen plasma or argon plasma with a power of 100-300W and a time of 1-5 minutes.

3. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 1, characterized in that: The surface treatment in step 2 includes coupling agent coating-thermal activation reaction, plasma grafting polymerization, self-assembled monolayer treatment, and UV / thermal dual curing.

4. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 3, characterized in that: The steps of the coupling agent coating-thermal activation reaction include: adding silane coupling agent to isopropanol / water mixed solvent to obtain a silane solution with a concentration of 0.5%-2%, and then uniformly coating it onto the metal oxide surface of the photomask by spin coating or spray coating; finally, placing the spin-coated photomask on a hot plate for baking to obtain a modified photomask substrate.

5. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 3, characterized in that: The plasma grafting polymerization involves grafting monomers containing polar functional groups onto the surface of a photomask after plasma cleaning, thereby increasing the surface polarity.

6. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 3, characterized in that: The self-assembled monolayer treatment involves using self-assembled molecules containing phosphate or carboxylic acid groups on the surface of a metal oxide thin film.

7. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 6, characterized in that: The self-assembled monolayer treatment involves dissolving the self-assembled molecules in anhydrous ethanol or isopropanol to form a solution, immersing the metal oxide film in the solution for 2-24 hours, rinsing with anhydrous ethanol after removal, and drying at 60-100℃ for 10-30 minutes. The concentration of the self-assembled molecules in the solution is 0.5-2 mmol / L, and the immersion temperature is 25-60℃.

8. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 3, characterized in that: The UV / thermal dual curing process involves adding a silane coupling agent and a photoinitiator to a solvent and stirring until homogeneous. This mixture is then uniformly coated onto the surface of a metal oxide substrate, followed by UV curing and thermal curing to obtain a modified photomask substrate. The photoinitiator used is Irgacure 184, Irgacure 651, or Darocur 1173, added at 0.5-2% of the silane coupling agent's mass. The solvent used is one or more of isopropanol, acetone, and ethyl acetate, with the coupling agent concentration in the solvent being 1-5% by mass. The uniform coating process involves a spin coating speed of 500-2000 rpm for 20-40 seconds, with a coating amount of 1-2 mL / substrate. The UV curing wavelength is 365 nm or 254 nm, and the light intensity is 50-200 mW / cm². 2 The curing time is 1-5 minutes, and the temperature for heat curing is 80-100℃, with a curing time of 3-5 minutes.

9. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 1, characterized in that: The photoresist used in step 3 is either a positive or negative photoresist, specifically including i-line photoresist, KrF photoresist, and ArF photoresist; the soft baking temperature is 90-110℃ and the time is 60-90s.

10. The coating process for improving the adhesion between metal oxides and photoresist on a photomask according to claim 1, characterized in that: The photomask after soft baking undergoes an overall post-baking process to enhance the cross-linking density of the interface. The post-baking temperature is 120-150℃ and the time is 5-10 minutes.

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