Double-layer stripping process based on alkali-soluble metal stripping adhesive

Abstract

The invention discloses a double-layer stripping process based on alkali-soluble metal stripping glue, and belongs to the technical field of microelectronic manufacturing. The method is used for solving the problems that in a traditional double-layer lift-off metal stripping process, a cross-linked and cured adhesive film is difficult to thoroughly remove by using a conventional organic solvent / alkaline solution, and adhesive residues are extremely easy to generate; and a single-layer negative photoresist lift-off metal stripping process is difficult to obtain good undercutting. The invention solves the technical problems in the prior art. The double-layer stripping process based on the alkali-soluble metal stripping adhesive comprises the following steps: S1, pretreating a substrate to obtain a pretreated substrate; spin-coating an alkali-soluble metal stripping adhesive on the pretreated substrate to obtain an upper-layer adhesive substrate; s2, continuing to spin-coat the negative photoresist on the upper-layer photoresist substrate, pre-baking, carrying out ultraviolet lithography, exposing and developing to obtain a developed substrate; s3, metal layer deposition / dry etching / ion implantation and alkaline leaching reaction are carried out on the developed substrate, and finally a target pattern is formed. The stripping process provided by the invention has the advantages of complete undercut structure and no adhesive residue phenomenon.

Description

Technical Field

[0001] This invention relates to the field of microelectronics manufacturing technology, and more specifically to a two-layer release process based on alkali-soluble metal release adhesive. Background Technology

[0002] In the manufacturing of semiconductors, microelectromechanical systems, superconducting devices, and high-frequency devices, lift-off metal stripping is a key technology for forming fine metal patterns (such as electrodes, leads, antennas, etc.). The specific process of lift-off metal stripping includes: first, defining the pattern by photolithography, then depositing metal, and finally removing the photoresist, leaving only the metal structure corresponding to the pattern.

[0003] In traditional lift-off metal removal processes, dual-layer assisted lift-off utilizes the synergistic effect of two adhesive systems to form a good undercut structure, thereby enabling precise lift-off of metal or non-metal films. Negative photoresists, in particular, offer significant advantages in dual-layer assisted lift-off processes due to their higher photosensitivity, better etching resistance, and superior pattern fidelity. However, negative photoresists also have significant drawbacks in lift-off processes: the cross-linked and cured film is difficult to completely remove with conventional organic solvents or alkaline solutions, easily resulting in severe photoresist residue. These residues directly affect the electrical performance, reliability, and long-term stability of devices, leading to a substantial decrease in product yield.

[0004] Existing single-layer negative photoresist lift-off metal stripping processes or double-layer photoresist processes struggle to achieve good undercut while ensuring clean, thorough, and damage-free removal of the photoresist layer. Therefore, there is an urgent need for a lift-off metal stripping process specifically designed for negative photoresists that can perfectly solve the problem of photoresist residue during removal.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a two-layer lift-off process based on alkali-soluble metal release adhesive, which solves the technical problems in the existing two-layer lift-off metal release process, where the cross-linked and cured adhesive film is difficult to remove completely with conventional organic solvents / alkaline solutions, and adhesive residue is easily generated; and the single-layer negative adhesive lift-off metal release process is difficult to obtain good undercut.

[0007] The objective of this invention can be achieved through the following technical solutions: A two-layer release process based on alkali-soluble metal release adhesive includes the following steps: S1. Substrate pretreatment to obtain a pretreated substrate; spin-coating the pretreated substrate with alkali-soluble metal release adhesive and baking to obtain the upper adhesive substrate; S2. The upper substrate is further spin-coated with negative photoresist and baked to obtain a substrate coated with negative photoresist; the substrate coated with negative photoresist is then subjected to ultraviolet lithography, exposure and development to obtain a developed substrate; S3. After development, the substrate is deposited with a metal layer / dry etching / ion implantation, alkaline immersion reaction, washed, and dried with nitrogen to form the target pattern.

[0008] The pretreatment steps for the substrate include washing it sequentially with deionized water, isopropanol, and acetone, and then baking it in a hot plate or oven to remove impurities such as metal residues, particles, and organic matter from the substrate surface, thereby enhancing its adhesion.

[0009] The pre-treated substrate is spin-coated with alkali-soluble metal release agent and negative photoresist, followed by exposure and development processes. During this process, the developer penetrates the negative photoresist window in the developed area above and isotropically and slightly etches the underlying alkali-soluble release agent. After development, the crucial undercut structure is formed. A metal layer is then deposited, followed by alkali dissolution of the upper structure (negative photoresist + metal covering it), ultimately leaving only the target metal pattern on the substrate.

[0010] Further, in step S1, the substrate is made of any one of bare silicon, gallium arsenide, indium antimonide, indium phosphide, gallium nitride, silicon carbide, zinc oxide, and diamond; in step S1, the spin coating speed is 500-6000 rpm, the spin coating thickness is 0.05-1 μm, the baking temperature is 150-200℃, and the baking time is 2-5 minutes.

[0011] Furthermore, the spin coating speed is preferably 1000-5000 rpm, the spin coating thickness is 0.1-0.5 μm, the baking temperature is 160-190℃, and the baking time is 3-4 minutes.

[0012] Further, in step S1, the preparation process of the alkali-soluble metal stripping adhesive includes the following steps: A1. Ethylene glycol methyl ether acetate is added to the reaction vessel, followed by divinylbenzene, ethylene glycol dimethacrylate, and dielyl itaconic acid. Acrylic monomers are then added dropwise and mixed thoroughly to obtain a mixed monomer solution. An initiator solution is added dropwise to the mixed monomer solution to form reactants. A2. Heat the reactants to 80-90℃ and maintain the temperature for 80-100 minutes to obtain the product; cool the product to 35-45℃ and adjust the pH to 7-8 to obtain the spherical crosslinked comonomer. A3. Mix 20-30 parts by weight of polymer resin, 50-60 parts by weight of solvent and 1-5 parts by weight to obtain the alkali-soluble metal stripping adhesive.

[0013] Further, in step A1, the ratio of ethylene glycol methyl ether acetate, divinylbenzene, ethylene glycol dimethacrylate, diallyl itaconic acid, acrylate monomers, and initiator solution is 100-200 mL: 100-120 mL: 50-60 mL: 20-30 mL: 20-30 mL: 5-10 mL; the acrylate monomers are any one of methyl methacrylate, ethyl methacrylate, methyl acrylate, tert-butyl methacrylate, and tert-butyl acrylate.

[0014] Further, in step A3, the solvent is one or more of ethylene glycol methyl ether acetate, ethylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl lactate, ethylene glycol monomethyl ether, cyclohexanone, cyclopentanone, butyl acetate, anisole, and N-methylpyrrolidone; the additive is an organic compound containing a phenolic structure, a diazonaphthoquinone sulfonic acid structure, or a coumarin structure.

[0015] Further, in step A3, the additive is preferably 2,1,4-trihydroxybenzophenone diaminonaphthoquinone sulfonate, 2,1,5-trihydroxybenzophenone diaminonaphthoquinone sulfonate, or coumarin 6,7-amino-4-methylcoumarin.

[0016] Furthermore, in step S2, the spin coating speed of the negative photoresist is 500-6000 rpm, the spin coating thickness is 1-100 μm; the baking temperature is 90-150℃, the baking time is 1-5 minutes; the exposure and development temperature is 23-25℃, and the development time is 60-120 s.

[0017] Further, in step S3, the preferred exposure wavelengths are g-line (436nm), i-line (365nm), and KrF (248nm); the developer is an alkaline system: tetramethylammonium hydroxide, tetraethylammonium hydroxide, potassium hydroxide, or sodium hydroxide aqueous solution; the organic system is one or more of n-butyl acetate, n-pentyl acetate, toluene, xylene, PGMEA, and cyclopentanone; the development temperature is 23-25℃, and the development time is 60-120 seconds; the material of the deposited metal layer is Au, Ag, Ti, Al, Ni, or Cu; in the dry etching process, the etching material is bare silicon, gallium arsenide, indium antimonide, indium phosphide, gallium nitride, silicon carbide, zinc oxide, or diamond; the ion implanted element is boron, phosphorus, arsenic, antimony, fluorine, or nitrogen.

[0018] Furthermore, in step S3, the stripping solution used in the alkaline leaching reaction is any one of the aqueous solutions of N-methylpyrrolidone, tetramethylammonium hydroxide, tetraethylammonium hydroxide, potassium hydroxide, and sodium hydroxide; the temperature of the alkaline leaching reaction is 60-80℃, and the duration is 5-10 min.

[0019] The present invention has the following beneficial effects: 1. This invention provides a metal stripping process. An alkali-soluble metal stripping adhesive and a negative photoresist are sequentially spin-coated onto a substrate, followed by photolithography patterning, metal deposition, and pattern transfer processes to ultimately form the target metal pattern. The alkali-soluble metal stripping adhesive is a mixture of polymer resin, solvent, and additives. The polymer resin is a product obtained by free radical polymerization and reaction of divinylbenzene, ethylene glycol dimethacrylate, and diallyl itaconic acid monomers. On one hand, the polymer resin has a large specific surface area, increasing its contact opportunity with the alkaline solution and thus accelerating dissolution; on the other hand, the polymer resin contains abundant carboxyl, hydroxyl, and ester functional groups, which can be rapidly dissolved by the alkaline solution. Testing has shown that the alkali-soluble metal stripping adhesive can be completely removed by conventional strippers. 2,1,4-Trihydroxybenzophenone diaminonaphthoquinone sulfonate and 2,1,5-Trihydroxybenzophenone diaminonaphthoquinone sulfonate, etc., are used as photosensitizers to enhance the sensitivity of the photoresist by increasing its light absorption efficiency, thereby optimizing the precision and efficiency of the metal stripping process.

[0020] 2. The negative photoresist itself is insoluble in alkaline solutions, but the alkaline-soluble metal stripper underneath can be rapidly dissolved by the stripper solvent (as shown in the examples and comparative examples, the stripper solvent includes KOH solution, TMAH aqueous solution, and conventional stripper solvents for rapid dissolution). The stripping process does not rely on dissolving the difficult-to-remove negative photoresist itself, but rather "removes the root cause" by dissolving the underlying "sacrificial layer"—the alkaline-soluble metal stripper—allowing the entire upper structure (negative photoresist + the metal covering it) to detach as a whole. This fundamentally eliminates the problems of photoresist residue and carbonization residue caused by the difficulty in removing the negative photoresist. In the specific process, the thickness of the lower alkaline-soluble metal stripper layer is precisely controlled at 0.1-0.5 μm to ensure the formation of a moderately sized and uniform undercut structure during development. This is crucial for ensuring the integrity of the metal pattern and the success rate of stripping. This process is stable and reliable, and can significantly improve the production yield of devices. The entire stripping process is carried out in an alkaline aqueous solution, avoiding the use of irritating organic solvents or plasma adhesives that may cause physical or chemical damage to sensitive substrates and metal structures. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the stripping process of the present invention.

[0022] Wherein, 100: substrate; 200: release adhesive; 300: negative photoresist; 400: exposure mask; 500: deposited metal; 501: etched substrate, forming an etched pattern; 502: ion implantation layer. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This embodiment provides a method for preparing an alkali-soluble metal release adhesive for a two-layer release process based on an alkali-soluble metal release adhesive, comprising the following steps: A1. Select a 500mL laboratory reactor equipped with a thermometer, stirrer, titrator, and oil-water separator. Add 100mL of ethylene glycol methyl ether acetate, then add 100mL of divinylbenzene, 50mL of ethylene glycol dimethacrylate, and 20mL of diallyl itaconic acid to the reactor. Next, add 20mL of methyl methacrylate to the reactor using the titrator and stir to obtain a mixed monomer solution. Continue titrating the reactor with 5mL of a 1wt% ammonium persulfate aqueous solution over 20 minutes.

[0025] A2. The reaction mixture was heated to 80°C in a laboratory reactor and kept at this temperature for 80 minutes to obtain the reactants. The reactants were then cooled to 35°C, and 30wt% NaOH solution was added dropwise to adjust the pH of the reactants to 7.5, which yielded the prepared spherical crosslinked copolymer.

[0026] A3. By weight, mix 20 parts of polymer resin, 50 parts of ethylene glycol methyl ether acetate and 1 part of 2,1,4-trihydroxybenzophenone diaminonaphthoquinone sulfonate to obtain the prepared alkali-soluble metal release adhesive.

[0027] Example 2 This embodiment provides a method for preparing an alkali-soluble metal release adhesive for a two-layer release process based on an alkali-soluble metal release adhesive, comprising the following steps: A1. Select a 500mL laboratory reactor equipped with a thermometer, stirrer, titrator, and oil-water separator. Add 150mL of ethylene glycol methyl ether acetate, then add 110mL of divinylbenzene, 55mL of ethylene glycol dimethacrylate, and 25mL of diallyl itaconic acid to the reactor. Next, add 30mL of ethyl methacrylate to the reactor using a titrator, and mix thoroughly with a stirrer to obtain a mixed monomer solution. Continue to add 6mL of a 2wt% ammonium persulfate aqueous solution to the reactor using a titrator, completing the addition within 25 minutes.

[0028] A2. The temperature of the reaction mixture was raised to 85°C in a laboratory reactor and maintained at this temperature for 90 minutes to obtain the reactants. The reactants were then cooled to 40°C, and 35 wt% NaOH solution was added dropwise to adjust the pH of the reactants to 7.8, which yielded the prepared spherical crosslinked copolymer.

[0029] A3. By weight, mix 15 parts of polymer resin, 65 parts of propylene glycol methyl ether acetate and 3 parts of 2,1,5-trihydroxybenzophenone diaminonaphthoquinone sulfonate to obtain the prepared alkali-soluble metal release adhesive.

[0030] Example 3 This embodiment provides a method for preparing an alkali-soluble metal release adhesive for a two-layer release process based on an alkali-soluble metal release adhesive, comprising the following steps: A1. Select a 500mL laboratory reactor equipped with a thermometer, stirrer, titrator, and oil-water separator. Add 200mL of ethylene glycol methyl ether acetate, then add 120mL of divinylbenzene, 60mL of ethylene glycol dimethacrylate, and 30mL of diallyl itaconic acid. Then, add 40mL of tert-butyl methacrylate to the reactor via titration, stirring to obtain a mixed monomer solution. Continue titrating 10mL of a 3wt% ammonium persulfate aqueous solution to the reactor within 30 minutes to form the reactants.

[0031] A2. The reaction mixture was heated to 90°C in a laboratory reactor and kept at this temperature for 100 minutes to obtain the product. The product was cooled to 45°C, and then 40wt% NaOH solution was added dropwise to adjust the pH of the reactants to 8, which yielded the prepared spherical crosslinked copolymer.

[0032] A3. By weight, mix 10 parts of polymer resin, 80 parts of ethyl lactate and 5 parts of 7-amino-4-methylcoumarin to obtain the prepared alkali-soluble metal stripping adhesive.

[0033] Example 4 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, isopropanol, and acetone, then transfer it to an oven and bake it at 100°C for 60 minutes to obtain a pre-treated substrate.

[0034] S2. The alkali-soluble metal release adhesive prepared in Example 1 is spin-coated onto the pretreated substrate at a spin speed of 5000 rpm and a coating thickness of 0.5 μm. Then, it is baked on a hot plate at 150°C for 2 minutes to obtain the upper adhesive substrate. The preferred baking temperature is 160°C, and the preferred baking time is 3 minutes.

[0035] S3. The upper substrate is then spin-coated with negative photoresist at a spin speed of 5000 rpm and a coating thickness of 1 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at a temperature of 110°C for 3 minutes, resulting in a substrate with a negative photoresist film covering its surface.

[0036] S4. The substrate with a negative photoresist film on its surface is patterned using an ultraviolet lithography machine; then, a 2.38wt% tetramethylammonium hydroxide developer is used to develop the substrate.

[0037] S5. A 50nm / 300nm Ti / Au metal layer was deposited on the developed substrate using an electron beam evaporation stage to obtain the deposited substrate. The deposited substrate was then immersed in a 3wt% KOH solution and heated to 70℃ for 10 minutes. The metal film on the substrate was observed to wrinkle rapidly and completely peel off. The substrate was then washed with deionized water and dried with nitrogen. A clear, clean gold electrode pattern without any residue was observed on the silicon wafer. Microscopic and scanning electron microscopic examination revealed no adhesive residue, meeting the cleanliness standard and forming the target metal pattern.

[0038] Example 5 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% KOH solution, and then transfer it to an oven to dry at 105℃ for 54 minutes to obtain a surface-pretreated substrate.

[0039] S2. The alkali-soluble metal release adhesive prepared in Example 2 was spin-coated onto the pretreated substrate at a spin speed of 4000 rpm and a thickness of 0.2 μm. Then, it was baked on a hot plate at a temperature of 180°C for 3 min to obtain the upper adhesive substrate.

[0040] S3. Continue spin-coating the upper substrate with negative photoresist SU8 at a spin speed of 2000 rpm and a coating thickness of 20 μm to obtain a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at a temperature of 95°C for 3.5 minutes to obtain a substrate with a negative photoresist film covering its surface.

[0041] S4. The substrate with a negative photoresist film on its surface is patterned using a UV lithography machine; then it is developed sequentially using PGMEA developer and 2.38wt% tetramethylammonium hydroxide developer to obtain the developed substrate. The developed substrate is then etched with pure O2 as the etching gas to obtain the etched sample.

[0042] S5. The etched sample was immersed in N-methylpyrrolidone and left to stand at room temperature for 10 minutes, with ultrasonic assistance for 2 minutes during this period. It was observed that the metal film layer quickly wrinkled and completely peeled off. After rinsing with deionized water, a gold electrode pattern with clear outlines and a clean surface without any residue was revealed on the silicon wafer. Microscopic and scanning electron microscopic examination showed no adhesive residue, meeting the cleanliness standard and forming the target pattern.

[0043] Example 6 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 108℃ for 52 minutes to obtain a surface-pretreated substrate.

[0044] S2. Spin-coat the alkali-soluble metal release adhesive prepared in Example 3 onto the pretreated substrate. The preferred spin-coating speed is 2000 rpm and the preferred spin-coating thickness is 0.3 μm. Then, bake the substrate with a hot plate at a temperature of 190°C for 3 min to obtain the upper adhesive substrate.

[0045] S3. The upper substrate is then spin-coated with SEPR-I382 negative photoresist at a spin speed of 2000 rpm to a thickness of 20 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at 110℃ for 3 minutes, resulting in a substrate with a negative photoresist film covering its surface.

[0046] S4. The substrate with a negative photoresist film on its surface is exposed using a UV lithography machine, and then developed using a 2.38wt% tetramethylammonium hydroxide developer for 30 seconds to obtain the developed substrate. The developed substrate is then hardened to form a hardened substrate. The hardened substrate is then placed in an ion implanter to implant ions, obtaining the sample.

[0047] S5. The sample was immersed in N-methylpyrrolidone and left to stand at room temperature for 10 minutes, with ultrasonic assistance for 2 minutes during this period. The metal film was observed to wrinkle rapidly and completely peel off. After rinsing with deionized water, a clear, clean gold electrode pattern without any residue was revealed on the silicon wafer. Microscopic and scanning electron microscopic examination showed no adhesive residue, achieving complete cleanliness and forming the target pattern.

[0048] Example 7 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 50-60 minutes to obtain a pre-treated substrate.

[0049] S2. The alkali-soluble metal release adhesive prepared in Example 3 was spin-coated onto the pretreated substrate at a spin speed of 6000 rpm and a thickness of 0.05 μm. Then, it was baked on a hot plate at a temperature of 180°C for 4 min to obtain the upper adhesive substrate.

[0050] S3. The upper substrate is then spin-coated with negative photoresist AZ nLOF 2070 at a spin speed of 1000 rpm to a thickness of 100 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at 100°C for 4 minutes, yielding a substrate with a surface covered by a negative photoresist film.

[0051] S4. The substrate with a negative photoresist film on its surface is exposed using a UV lithography machine, followed by development with a 2.38 wt% tetraethylammonium hydroxide developer for 120 seconds to obtain the developed substrate. The developed substrate is then immersed in N-methylpyrrolidone stripping solution at 60°C for 10 minutes, after which it is removed. The stripping effect is observed; microscopic and scanning electron microscopic examination shows no photoresist residue, achieving complete cleanliness and forming the target pattern.

[0052] Example 8 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0053] S2. The alkali-soluble metal release adhesive prepared in Example 3 was spin-coated onto the pretreated substrate at a spin speed of 5000 rpm and a thickness of 0.1 μm. Then, it was baked on a hot plate at a temperature of 190°C for 4 min to obtain the upper adhesive substrate.

[0054] S3. The upper substrate is then spin-coated with AZ nLOF 2070 photoresist at a spin speed of 1000 rpm to a thickness of 100 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at a temperature of 110°C for 5 minutes, resulting in a substrate with a negative photoresist film covering its surface.

[0055] S4. The substrate with a negative photoresist film on its surface is exposed using a UV lithography machine, followed by development with potassium hydroxide solution for 100 seconds to obtain the developed substrate. The developed substrate is then immersed in TechniStrip NI555 resist remover for 10 minutes at a temperature of 80°C. After removal, the substrate is examined under a microscope and scanning electron microscope, and no resist residue is found, achieving complete cleanliness and forming the target metallic pattern.

[0056] Example 9 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0057] S2. Spin-coat the alkali-soluble metal release adhesive prepared in Example 3 onto the pretreated substrate at a spin speed of 4000 rpm and a coating thickness of 0.2 μm. Then, bake the substrate with a hot plate at a temperature of 200°C for 5 min to obtain the upper adhesive substrate.

[0058] S3. Spin-coat the upper substrate with negative photoresist NR9 at a spin speed of 6000 rpm and a coating thickness of 20 μm. Then bake with a hot plate at a temperature of 120℃ for 3 minutes to obtain a substrate with a negative photoresist film covering its surface.

[0059] S4. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, and then developed using a sodium hydroxide aqueous solution for 60 seconds to obtain the developed substrate. The developed substrate was then immersed in N-methylpyrrolidone stripping solution at 80℃ for 10 minutes. After the experiment, the substrate was removed and observed. Microscopic and scanning electron microscopic examination showed no photoresist residue, achieving complete cleanliness and forming the target pattern.

[0060] Example 10 This embodiment provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0061] S2. Spin-coat the alkali-soluble metal release adhesive prepared in Example 3 onto the pretreated substrate at a spin speed of 500 rpm and a coating thickness of 1 μm. Then, bake the substrate with a hot plate at a temperature of 180°C for 4 min to obtain the upper adhesive substrate.

[0062] S3. Continue spin-coating the upper substrate with photoresist SU8 at a spin speed of 3000 rpm and a coating thickness of 100 μm to obtain a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at a temperature of 150℃ for 4 minutes to obtain a substrate with a negative photoresist film covering its surface.

[0063] S4. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, followed by development with PGMEA developer and 2.38wt% tetramethylammonium hydroxide developer for 60s each, to obtain the developed substrate. The developed substrate was then immersed in Remover PG stripper at 80℃ for 10 minutes. After the experiment, the substrate was removed and observed. Microscopic and scanning electron microscopic examination showed no photoresist residue, achieving complete cleanliness and forming the target pattern.

[0064] Comparative Example 1 This comparative example provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0065] S2. Spin-coat a negative photoresist AZ nLOF 2070 onto the pre-treated substrate at a spin speed of 1000 rpm to a thickness of 100 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at 110°C for 3 minutes, resulting in a substrate with a negative photoresist film covering its surface.

[0066] S3. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, followed by development with a 2.38 wt% tetramethylammonium hydroxide developer for 60 seconds to obtain the developed substrate. The developed substrate was then immersed in NMP stripping solution at 60°C for 10 minutes, after which it was removed. Observation of the stripping effect revealed a small amount of residual photoresist on the substrate surface, indicating that the stripping effect did not meet the cleanliness standard.

[0067] Comparative Example 2 This comparative example provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0068] S2. Spin-coat a negative photoresist AZ nLOF 2070 onto the pre-treated substrate at a spin speed of 3000 rpm to a thickness of 70 μm, resulting in a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at 100°C for 5 minutes, resulting in a substrate with a negative photoresist film covering its surface.

[0069] S3. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, followed by development with potassium hydroxide solution for 30 seconds to obtain the developed substrate. The developed substrate was then immersed in TechniStrip NI555 resist remover for 10 minutes at a temperature of 80°C. After removal, the substrate was observed to have a small amount of resist residue on its surface, indicating that the resist removal effect did not meet the cleanliness standard.

[0070] Comparative Example 3 This comparative example provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0071] S2. Spin-coat negative photoresist NR9 onto the pretreated substrate at a spin speed of 6000 rpm and a coating thickness of 20 μm. Then bake on a hot plate at a temperature of 120℃ for 3 minutes to obtain a substrate with a negative photoresist film covering its surface.

[0072] S3. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, and then developed using a sodium hydroxide aqueous solution for 60 seconds to obtain the developed substrate. The developed substrate was then immersed in N-methylpyrrolidone stripping solution at a temperature of 80℃ for 10 minutes. After the experiment, the substrate was removed. Upon observation, a small amount of photoresist residue was found on the surface of the substrate, indicating that the stripping effect did not meet the cleanliness standard.

[0073] Comparative Example 4 This comparative example provides a two-layer release process based on alkali-soluble metal release adhesive, including the following steps: S1. Select a 4-inch silicon substrate. Wash the silicon substrate sequentially with deionized water, anhydrous ethanol and 5wt% NaOH solution, and then transfer it to an oven to dry at 120℃ for 60 minutes to obtain a surface-pretreated substrate.

[0074] S2. Continue spin-coating photoresist SU8 onto the pre-treated substrate at a spin speed of 3000 rpm and a coating thickness of 100 μm to obtain a substrate coated with negative photoresist. The substrate coated with negative photoresist is then baked on a hot plate at a temperature of 150°C for 4 minutes to obtain a substrate with a negative photoresist film covering its surface.

[0075] S3. The substrate with a negative photoresist film on its surface was exposed using a UV lithography machine, followed by development with PGMEA developer and 2.38wt% tetramethylammonium hydroxide developer for 60s each, to obtain the developed substrate. The developed substrate was then immersed in Remover PG stripper for 10 minutes at a temperature of 80℃. After the experiment, the substrate was removed and observed. It was found that a large amount of photoresist residue remained on the substrate surface, and the stripping effect did not meet the cleanliness standard.

[0076] Performance testing: The adhesive removal effect of the double-layer peeling process in Examples 4-10 and Comparative Examples 1-4 was summarized and analyzed to determine whether the complete cleanliness standard was achieved. Specific observation results are shown in Table 1.

[0077] Table 1. Sample Performance Test Data Group Project Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Adhesive removal effect No glue residue was found, meeting cleanliness standards. No glue residue was found, meeting cleanliness standards. There is no glue residue, achieving complete cleanliness standards. There is no glue residue, achieving complete cleanliness standards. There is no glue residue, achieving complete cleanliness standards. There is no glue residue, achieving complete cleanliness standards. There is no glue residue, achieving complete cleanliness standards. A small amount of adhesive residue remains; the adhesive removal effect has not met the cleanliness standard. A small amount of adhesive residue remains; the adhesive removal effect has not met the cleanliness standard. A small amount of adhesive residue remains; the adhesive removal effect has not met the cleanliness standard. There is a large amount of glue residue, and the glue removal effect does not meet the cleanliness standard. Data Analysis: According to the data in Table 1, Examples 4-6 of this invention employ a two-layer adhesive system, first spin-coating an alkali-soluble metal release adhesive, then spin-coating a negative photoresist, followed by dissolution with a resist remover, all achieving the desired resist removal effect. In particular, Example 6 shows no resist residue on the substrate and achieves a completely clean standard. Examples 7-10, like Example 6, all use the alkali-soluble metal release adhesive prepared in Example 3, achieving the same resist removal effect as Example 6, reaching a completely clean standard. Therefore, the alkali-soluble metal release adhesives prepared in Examples 1-3 of this invention can be easily removed by the resist remover; among them, the alkali-soluble metal release adhesive prepared in Example 3 shows the best resist removal effect.

[0078] However, in Comparative Examples 1-4, single-layer spin-coated substrates were used. After dissolution with resist remover, none met the cleanliness standard, indicating poor resist removal. Therefore, it can be concluded that the two-layer resist system can fundamentally eliminate the resist residue problem caused by the difficulty in removing negative photoresist.

[0079] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0080] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A two-layer release process based on alkali-soluble metal release adhesive, characterized in that, Includes the following steps: S1. Substrate preprocessing to obtain a preprocessed substrate; The pretreated substrate is spin-coated with an alkali-soluble metal release adhesive and baked to obtain the upper adhesive substrate; S2. The upper substrate is further spin-coated with negative photoresist and baked to obtain a substrate coated with negative photoresist; the substrate coated with negative photoresist is then subjected to ultraviolet lithography, exposure and development to obtain a developed substrate; S3. After development, the substrate is deposited with a metal layer / dry etching / ion implantation, alkaline immersion reaction, washed, and dried with nitrogen to form the target pattern.

2. The preparation process of the alkali-soluble metal stripping adhesive according to claim 1, characterized in that, In step S1, the substrate is made of any one of bare silicon, gallium arsenide, indium antimonide, indium phosphide, gallium nitride, silicon carbide, zinc oxide, and diamond; in step S1, the spin coating speed is 500-6000 rpm, the spin coating thickness is 0.05-1 μm, the baking temperature is 150-200℃, and the baking time is 2-5 minutes.

3. The preparation process of an alkali-soluble metal stripping adhesive according to claim 2, characterized in that, The preferred spin coating speed is 1000-5000 rpm, and the preferred spin coating thickness is 0.1-0.5 μm; the baking temperature is 160-190℃, and the baking time is 3-4 minutes.

4. The preparation process of an alkali-soluble metal stripping adhesive according to claim 1, characterized in that, In step S1, the preparation process of the alkali-soluble metal stripping adhesive includes the following steps: A1. Ethylene glycol methyl ether acetate is added to the reaction vessel, followed by divinylbenzene, ethylene glycol dimethacrylate, and dielyl itaconic acid. Acrylic monomers are then added dropwise and mixed thoroughly to obtain a mixed monomer solution. An initiator solution is added dropwise to the mixed monomer solution to form reactants. A2. Heat the reactants to 80-90℃ and maintain the temperature for 80-100 minutes to obtain the product; cool the product to 35-45℃ and adjust the pH to 7-8 to obtain the spherical crosslinked comonomer. A3. Mix 20-30 parts by weight of polymer resin, 50-60 parts by weight of solvent and 1-5 parts by weight to obtain the alkali-soluble metal stripping adhesive.

5. The preparation process of an alkali-soluble metal stripping adhesive according to claim 4, characterized in that, In step A1, the ratio of ethylene glycol methyl ether acetate, divinylbenzene, ethylene glycol dimethacrylate, diallyl itaconic acid, acrylate monomers, and initiator solution is 100-200 mL: 100-120 mL: 50-60 mL: 20-30 mL: 20-30 mL: 5-10 mL; the acrylate monomers are any one of methyl methacrylate, ethyl methacrylate, methyl acrylate, tert-butyl methacrylate, and tert-butyl acrylate.

6. The preparation process of an alkali-soluble metal stripping adhesive according to claim 4, characterized in that, In step A3, the solvent is one or more of ethylene glycol methyl ether acetate, ethylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl lactate, ethylene glycol monomethyl ether, cyclohexanone, cyclopentanone, butyl acetate, anisole, and N-methylpyrrolidone; the additive is an organic compound containing a phenolic structure, a diazonaphthoquinone sulfonic acid structure, or a coumarin structure.

7. The preparation process of an alkali-soluble metal stripping adhesive according to claim 4, characterized in that, In step A3, the additive is preferably 2,1,4-trihydroxybenzophenone diaminonaphthoquinone sulfonate, 2,1,5-trihydroxybenzophenone diaminonaphthoquinone sulfonate, or coumarin 6,7-amino-4-methylcoumarin.

8. The preparation process of an alkali-soluble metal stripping adhesive according to claim 1, characterized in that, In step S2, the spin coating speed of the negative photoresist is 500-6000 rpm, the spin coating thickness is 1-100 μm; the baking temperature is 90-150℃, the baking time is 1-5 minutes; the exposure and development temperature is 23-25℃, and the development time is 60-120 s.

9. The preparation process of an alkali-soluble metal stripping adhesive according to claim 1, characterized in that, In step S3, the preferred exposure wavelengths are g-line (436nm), i-line (365nm), and KrF (248nm); the developer is an alkaline system: tetramethylammonium hydroxide, tetraethylammonium hydroxide, potassium hydroxide, or sodium hydroxide aqueous solution; the organic system is one or more of n-butyl acetate, n-pentyl acetate, toluene, xylene, PGMEA, and cyclopentanone; the development temperature is 23-25℃, and the development time is 60-120 seconds; the deposited metal layer is made of Au, Ag, Ti, Al, Ni, or Cu; in the dry etching process, the etching material is bare silicon, gallium arsenide, indium antimonide, indium phosphide, gallium nitride, silicon carbide, zinc oxide, or diamond; the ion implantation element is boron, phosphorus, arsenic, antimony, fluorine, or nitrogen.

10. The preparation process of an alkali-soluble metal stripping adhesive according to claim 1, characterized in that, In step S3, the stripping solution used in the alkaline leaching reaction is any one of the aqueous solutions of N-methylpyrrolidone, tetramethylammonium hydroxide, tetraethylammonium hydroxide, potassium hydroxide, and sodium hydroxide; the temperature of the alkaline leaching reaction is 60-80℃, and the duration is 5-10 min.

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