A kind of ultraviolet positive photoresist based on hexaarylbiimidazole and its use method

Abstract

The present invention belongs to the field of microelectronic processing materials technology, and more specifically, relates to a hexaaryl biimidazole-based ultraviolet positive photoresist and a method for using the same. The photoresist comprises an oligomer diol, a functionalized hexaaryl biimidazole molecular switch cross-linker, a free radical quencher, a catalyst, and a diisocyanate. When the photoresist is used for photolithography, under ultraviolet light, the dynamic C-N covalent bond between the two imidazole rings in the hexaaryl biimidazole unit in the polymer network structure formed in the photoresist responds to light and cleaves to form oligomers; wherein the free radical quencher is used to ensure that the photoresist does not spontaneously recover after being depolymerized by exposure to form oligomers, thereby ensuring that the oligomers formed in the exposed part of the photoresist can be dissolved by a developer, while the unexposed part is insoluble in the developer, and a high-resolution target positive pattern is obtained after development.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic processing materials, and more specifically, relates to a hexaarylbiimidazole-based ultraviolet positive photoresist and a method for using the same. Background Art

[0002] Photolithography is a technique that uses photoresist (photoresist) to transfer a pattern from a mask to a substrate under ultraviolet light. As the most important functional material in the photolithography process, the quality of photoresist directly determines the quality of the final photolithography process. Photoresist is widely used in the fabrication of printed circuit boards (PCBs), liquid crystal displays (LCDs), and integrated circuits.

[0003] The main methods for improving resolution in the photolithography process include increasing the numerical aperture of the lens and shortening the wavelength of the light source. Currently, the wavelength of the exposure light source has evolved through the full UV spectrum (300-450nm), G-line (436nm), I-line (365nm), deep UV (248nm and 193nm), and extreme UV (13.5nm). The ever-shrinking wavelength of the light source has also placed higher demands on the photoresist. Photoresists were invented in the 1950s, with Kodak producing polyvinyl cinnamate UV negative photoresists in 1953 and cyclized rubber-azide negative photoresists in 1958. Although these negative photoresists offer advantages such as good photosensitivity and heat resistance, they often swell in organic developer solutions, failing to meet the resolution requirements of large-scale integrated circuits and, as a result, have not been widely used. The phenolic resin-diazonaphthoquinone (DNQ) system is a widely used commercial photoresist in G-line and I-line photolithography processes. In unexposed areas, DNQ inhibits the resin's dissolution in the developer. In exposed areas, DNQ undergoes a photochemical reaction to form indanone, which is further converted to indenecarboxylic acid in the developer, promoting the dissolution of the phenolic resin. Because this system exhibits no swelling, strong dry-etch resistance, and high resolution, it is widely used in large-scale integrated circuits (SICs) larger than 0.25 μm. However, in deep ultraviolet lithography, phenolic resin-diazonaphthoquinone photoresists have been discontinued due to their strong non-photobleaching properties at 248 nm. Studies have shown that poly(p-hydroxystyrene) resin has a high optical transmittance at 248nm, making it an ideal 248nm photoresist resin. Poly(methacrylate) resin is the main film-forming resin for 193nm photolithography. Its main photochemical reaction principle is that under ultraviolet light, the photoacid generator produces acid to catalyze the shedding of the protecting group, exposing the polar group, which is then dissolved in the alkaline developer. The proton hydrogen can be recycled repeatedly, greatly shortening the exposure dose of the photoresist. Therefore, it is also called chemically amplified photoresist.

[0004] Patent CN113341653A discloses a UV positive photoresist based on a hexaarylbiimidazole molecular switch and its use method. This photoresist uses hexaarylbiimidazole as a crosslinking unit and a photoresponsive unit. Under illumination, the CN covalent bond between the two imidazole rings in the hexaarylbiimidazole is cleaved, causing the polymer to depolymerize into oligomers. A free radical quencher is used to prevent the oligomers generated by depolymerization from spontaneously recovering after exposure, thereby forming an irreversible oligomer structure. This increases the solubility of the exposed portion of the polymer in the developer, while the unexposed portion remains insoluble in the developer. This results in a high-resolution positive pattern after development. However, the patent document uses an unfunctionalized hexaarylbiimidazole molecular switch as a free radical quencher. Experimental results show that this free radical quencher has poor quenching effect in this system, resulting in poor development and residual residues in the exposed area, affecting the photolithography quality. Summary of the Invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a hexaaryl biimidazole-based UV positive photoresist and a method of using the same, so as to solve the technical problems of the prior art of hexaaryl biimidazole-based UV positive photoresist such as poor quenching effect of the free radical quencher leading to development residues.

[0006] To achieve the above objectives, the present invention provides a hexaarylbiimidazole-based UV positive photoresist, comprising an oligomer diol, a functionalized hexaarylbiimidazole molecular switch crosslinker, a free radical quencher, a catalyst, and a diisocyanate; the free radical quencher is one or more of 2,2,6,6-tetramethylpiperidinyl oxide, a phenolic polymerization inhibitor, benzil, and tetrachlorobenzoquinone;

[0007] When in use, the oligomer diol and the functionalized hexaaryl biimidazole molecular switch cross-linking agent can undergo gradual addition polymerization with diisocyanate under the catalytic conditions of the catalyst to form a polymer network structure; when the photoresist is used for photolithography, under ultraviolet light, the dynamic CN covalent bond between the two imidazole rings in the hexaaryl biimidazole unit in the polymer network structure responds to light and cracks to form oligomers; the free radical quencher is used to ensure that the photoresist will not spontaneously recover after being depolymerized by exposure to form oligomers, thereby ensuring that the oligomers formed in the exposed part of the photoresist can be dissolved by the developer, while the unexposed part is insoluble in the developer, and a target positive pattern with high resolution is obtained after development.

[0008] Preferably, the oligomer diol is polyethylene glycol or polyether diol; more preferably polyethylene glycol; the molecular weight of the oligomer diol is 200-1000.

[0009] Preferably, the isocyanate is one or more of hexamethylene diisocyanate, 4,4'-methylene phenyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and toluene diisocyanate. Isocyanate is more preferred. Isocyanate has relatively low reactivity, which prevents monomer polymerization in solution and ensures film formation on silicon wafers.

[0010] Preferably, the functionalized hexaaryl biimidazole molecular switch cross-linker is a molecular switch with a hydroxyl functional group that is modified and designed with hexaaryl biimidazole as the molecular main body, wherein the hexaaryl biimidazole has a structure shown in the following formula (1): The molecule is composed of two triphenylimidazoles covalently connected by a CN bond. Under ultraviolet light, the molecule breaks to form two triphenylimidazole free radicals, accompanied by a color change. After the light is removed, the two free radicals are bonded back to the initial dimer form through the CN bond.

[0011]

[0012] Further preferably, the functionalized hexaarylbiimidazole molecular switch crosslinker is a molecular switch with a hydroxyl functional group obtained by modifying and designing hexaarylbiimidazole as the main molecule, and some hydrogen atoms on the benzene ring in the molecular switch structure are replaced by electron-withdrawing groups, preferably halogen atoms or nitro groups. Further preferably, the structure is shown in the following formula (II) to formula (VII):

[0013]

[0014] In formulas (II) to (VII), R is an alkyl chain with multiple hydroxyl groups, specifically an alkyl chain with 1 to 10 carbon atoms containing 1 to 3 hydroxyl groups, more preferably an alkyl chain with 1 to 5 carbon atoms containing 1 to 2 hydroxyl groups; R is further preferably CH2CHOHCH2OH.

[0015] Preferably, the free radical quencher is 2,2,6,6-tetramethylpiperidinyl oxide as shown in formula (VIII), a phenolic polymerization inhibitor as shown in formula (IX), benzil as shown in formula (X), or tetrachlorobenzoquinone as shown in formula (XI). More preferably, the phenolic polymerization inhibitor is shown in formula (IX), wherein R1 is H or OH, and R2 is -C(CH3)3, -CH3, -CH2CH3, -OCH3, -OH, -Br, -Cl, -NO2, etc.

[0016]

[0017] The phenolic polymerization inhibitor further preferably has a structure represented by the following formula (XII) to formula (XXI).

[0018]

[0019] The phenolic polymerization inhibitor free radical quencher is further preferably tert-butylhydroquinone represented by formula (XX). It should be noted that only a few types of phenolic polymerization inhibitors are listed here, and all other polymerization inhibitors with phenolic structures are within the scope of protection of the present invention.

[0020] Preferably, the photoresist also includes an organic solvent for dissolving the oligomer diol, the functionalized hexaaryl biimidazole molecular switch crosslinker and the free radical quencher. The organic solvent can be anhydrous tetrahydrofuran, ethyl acetate, acetone, acetonitrile, etc., and the organic solvent is further preferably anhydrous ethyl acetate.

[0021] Preferably, the catalyst is bisdimethylaminoethyl ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine or dibutyltin dilaurate, more preferably dibutyltin dilaurate.

[0022] Preferably, the molar ratio of the oligomeric diol to the functionalized hexaarylbiimidazole molecular switch crosslinker is 7:1 to 1:7, more preferably 4:1 to 2:3; the molar amount of the free radical quencher is greater than the molar amount of the functionalized hexaarylbiimidazole molecular switch crosslinker; the molar ratio of the free radical quencher to the functionalized hexaarylbiimidazole molecular switch crosslinker is more preferably 1.5 to 3.5:1; the molar amount of the diisocyanate is greater than or equal to the sum of the molar amounts of the oligomeric diol and the functionalized hexaarylbiimidazole molecular switch crosslinker in the first composition. The molar amount of the catalyst does not exceed 2% of the total molar amount of the monomers involved in the polymerization, where the monomers involved in the polymerization include the oligomeric diol, the functionalized hexaarylbiimidazole molecular switch crosslinker, and the diisocyanate.

[0023] According to another aspect of the present invention, there is provided a method for using the photoresist, characterized in that it comprises the following steps:

[0024] (1) mixing the oligomer diol with a functionalized hexaarylbiimidazole molecular switch crosslinker, a free radical quencher, a catalyst, and a diisocyanate dissolved in an organic solvent, and stirring to cause a preliminary polymerization reaction to obtain a polyurethane prepolymer solution;

[0025] (2) spin coating the polyurethane prepolymer solution into a film, and then performing a pre-baking treatment to further cause addition polymerization to obtain a polyurethane photoresist film with hexaarylbiimidazole as a crosslinking point;

[0026] (3) exposing the polyurethane photoresist film obtained in step (2) to ultraviolet light, so that the dynamic CN covalent bond between the two imidazole rings in the hexaaryl biimidazole unit in the polymer network structure is cleaved in response to light, and the polymer is depolymerized to form oligomers; after the exposure is completed, the photoresist is developed, and the free radical quencher in the photoresist can ensure that the photoresist does not spontaneously recover after being depolymerized to form oligomers, thereby ensuring that the oligomers formed in the exposed part of the photoresist can be quickly dissolved by the developer, while the unexposed part is insoluble in the developer, and a target positive pattern with high resolution is obtained after development.

[0027] Preferably, the mixing time in step (1) is 5 to 30 minutes; more preferably, the mixing time is 8 to 15 minutes.

[0028] Further preferably, the oligomer diol in step (1) is polyethylene glycol, and the polyethylene glycol is obtained after sufficient removal of water under vacuum heating conditions.

[0029] Preferably, the pre-baking temperature in step (2) is lower than or equal to 90° C., and the pre-baking time is not less than 20 minutes; more preferably, the pre-baking temperature is 60-80° C., and the pre-baking time is 30-40 minutes.

[0030] In general, the present invention uses hexaarylbiimidazole as a photosensitive unit to propose a type of polyurethane positive photoresist with superior photosensitivity and resolution. Compared with the existing technology, the above technical solution conceived by the present invention has the following beneficial effects:

[0031] (1) The present invention uses hexaaryl biimidazole as a photosensitive crosslinking point and prepares a type of positive polyurethane photoresist that is sensitive to ultraviolet light by mixing it with oligomer diols, diisocyanates, and free radical quenchers through a one-step method. By pre-baking to remove the solvent and stimulate the polymerization reaction, each monomer is successfully polymerized and connected to the polymer backbone. Under the action of the free radical quencher, a light-controllable cross-linked polyurethane photoresist is obtained. The hexaaryl biimidazole is used as a photosensitive unit and has excellent photosensitivity to both ultraviolet light and deep ultraviolet light sources. It can be used as a photosensitizer for I-line and deep ultraviolet lithography. At the same time, the resin structure of the polyurethane has a series of excellent properties such as good solvent corrosion resistance and etching resistance. The photoresist can be used in ultraviolet and deep ultraviolet lithography in the manufacturing process of printed circuit boards and semiconductor discrete devices.

[0032] (2) In the present invention, the hexaarylbiimidazole serves as both a photosensitive unit and a crosslinking point for the crosslinked polyurethane, allowing changes in the molecular structure of the hexaarylbiimidazole to directly affect the molecular weight and other physical properties of the polymer. In the area irradiated by ultraviolet light, the hexaarylbiimidazole is photo-fragmented into two triphenylimidazole free radicals, which are then quenched by a quencher. This process is accompanied by the opening of the polymer crosslinking points, resulting in the polymer transforming from a crosslinked structure to a linear structure, with a sharp decrease in molecular weight. This enables the system to have very high lithographic resolution, reaching the submicron level.

[0033] (3) In the present invention, the illuminated area is transformed into a linear structure with excellent solubility in the developer, while the unilluminated area maintains a cross-linked structure with minimal solubility in the developer, thereby achieving a film retention rate of nearly 100% in the unilluminated area. Simultaneously, there is a significant difference in solubility between the illuminated and unilluminated areas, resulting in a photolithographic pattern with good contrast.

[0034] (4) In the present invention, the breakage of hexaarylbiimidazole is used as the controlling factor for the transformation of the polymer structure before and after photolithography. Unlike traditional naphthoquinone diazide and chemical amplification systems that require the addition of a photoacid generator as a photosensitizer, the present invention avoids defects such as line broadening caused by acid diffusion.

[0035] (5) Free radical quencher is a key substance in the present invention, and its type directly affects the photosensitivity of the entire photoresist system. Experiments have found that different types of quenchers have different mechanisms and effects in quenching free radicals. It is crucial to select a quencher that has a good quenching effect but does not introduce side reactions. Compared with quenchers that generate free radicals under light, phenolic inhibitors do not absorb photons and therefore do not compete with hexaaryl biimidazole molecules. At the same time, phenolic hydroxyl groups have a very good free radical quenching effect. Among the many phenolic inhibitors, tert-butylhydroquinone, as a common inhibitor in food, has non-toxicity and high free radical quenching efficiency, making it a type of free radical quencher with excellent performance, which greatly improves the photosensitivity of polyurethane photoresists based on hexaaryl biimidazole and obtains very excellent resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the technical roadmap for the positive cross-linked polyurethane photoresist based on hexaarylbiimidazole in Example 1.

[0037] Figure 2 This is a curve showing the change in the optical pattern of the photoresist after photolithography development and the film thickness of the exposed portion after development in Example 1.

[0038] Figure 3 This is a curve showing the change in the optical pattern of the photoresist after photolithography development and the film thickness of the exposed portion after development in Example 2.

[0039] Figure 4 This is a curve showing the change in the optical pattern of the photoresist after photolithography development and the film thickness of the exposed portion after development in Example 3.

[0040] Figure 5 This is a curve showing the change in the optical pattern of the photoresist after photolithography development and the film thickness of the exposed portion after development in Example 4.

[0041] Figure 6 This is a curve showing the change in the optical pattern of the photoresist after photolithography development and the film thickness of the exposed part after development in Comparative Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Some embodiments of the present invention provide a hexaarylbiimidazole-based UV positive photoresist, the main components of which include hexaarylbiimidazole, an oligomer diol, an isocyanate, a free radical quencher, a catalyst (dibutyltin dilaurate), and anhydrous ethyl acetate as solvent. In use, the oligomer diol is first dehydrated under vacuum heating conditions. After cooling to room temperature, the hexaarylbiimidazole, the catalyst (dibutyltin dilaurate), the isocyanate, and the free radical quencher are dissolved in anhydrous ethyl acetate in sequence and added to the solution under a nitrogen atmosphere and protected from light. The solution is then vigorously stirred for 5 to 30 minutes, preferably 10 to 15 minutes. The solution is then removed with a syringe and filtered three times to obtain a prepolymer solution of the polyurethane photoresist. The prepolymer solution is then dropwise added to a cleaned silicon wafer, spin-coated at a constant speed to form a film, and pre-baked at 70°C for 30 to 40 minutes to remove the solvent and stimulate a polymerization reaction between the functional hydroxyl groups on the monomers and the isocyanate groups. Then it is placed on the stage of the photolithography machine so that it contacts the mask and is contact exposed under a 365nm light source. After the exposure is completed, it is placed in tetrahydrofuran for development for 30 seconds, and then the surface solvent is blown dry with nitrogen to obtain a photolithography pattern with a certain resolution.

[0044] During the photolithography process, the hexaarylbiimidazole acts as both a crosslinking unit and a photosensitive unit. In the ultraviolet light irradiation area, the CN bond within the hexaarylbiimidazole unit breaks, forming two triphenylimidazole free radicals. These free radicals are further quenched by the surrounding quencher, preventing them from returning to their initial dimer form. The polymer crosslinking points are opened, and the crosslinked structure is transformed into a linear structure or even shorter molecular residues. This makes the illuminated portion extremely easy to dissolve in organic solvents, while the unilluminated portion maintains the crosslinked structure and is not dissolved by the developer. This results in a significant solubility difference between the illuminated and unilluminated areas, successfully transferring the pattern on the mask to the photoresist film, and making the pattern have high contrast. The hexaarylbiimidazole-based UV positive photoresist provided by the present invention can be used in the fine processing of printed circuit boards and discrete semiconductor devices.

[0045] The functionalized hexaarylbiimidazoles in the embodiments of the present invention are obtained by modifying the parent structure of formula (1). Any of the structures of formulas (2) to (7) can be used. In addition to the structures listed above, electron-withdrawing or electron-donating groups can be introduced into the benzene ring of the hexaarylbiimidazole to change the absorption band of the hexaarylbiimidazole, thereby imparting different photosensitivity properties.

[0046] The present invention uses a one-step process to mix the various photoresist components under a nitrogen atmosphere to obtain a prepolymerized solution of each monomer. The solution is then spin-coated onto a cleaned silicon wafer surface at a predetermined rotational speed. Pre-baking removes the solvent and simultaneously stimulates a cross-linking polymerization reaction, resulting in a polyurethane photoresist film with hexaaryl biimidazole as the photosensitive crosslinking point. Under ultraviolet light irradiation, the CN bonds within the hexaaryl biimidazole units break, forming two triphenylimidazole free radicals. These free radicals are quenched by a free radical quencher, thereby opening the polymer crosslinking points and significantly reducing the molecular weight, allowing it to be dissolved in a developer. This mechanism allows the pattern on the mask to be smoothly transferred to the surface of the photoresist film. Experiments have found that the type and properties of the quencher, a key compound in the present invention, are crucial to the photosensitivity of the photoresist. An inappropriate type or poor photosensitivity can result in oligomers formed in the exposed portion during development that are not rapidly dissolved by the developer, thus affecting the performance of the photoresist. The dynamic CN covalent bond between the two imidazole rings in the hexaarylbiimidazole unit cleaves into two free radicals in response to light. The present invention uses a variety of quenchers that can effectively quench these free radicals. However, when these quenchers are applied to the photoresist system of the present invention, different free radical quenchers exhibit different quenching effects. A comparison of hexaarylbiimidazoles without any functional groups, 2,2,6,6-tetramethylpiperidinium oxide (TEMPO), various phenolic polymerization inhibitors, benzil, and tetrachlorobenzoquinone revealed that phenolic polymerization inhibitors have relatively superior free radical quenching effects, with tert-butylhydroquinone (TBHQ) being further preferred due to its non-toxic and efficient free radical quenching efficiency. The present invention's UV positive photoresist based on the combined action of the hexaarylbiimidazole molecular switch and the free radical quencher has promising application prospects.

[0047] The following are examples:

[0048] Example 1

[0049] The oligomer diol is polyethylene glycol with a molecular weight of 400 (PEG 400 ), isophorone diisocyanate (IPDI) as the isocyanate source, tetrahydroxy-functionalized hexaarylbiimidazole (2-Cl-4-diol-HABI) as the photosensitive unit and crosslinking unit, the catalyst is dibutyltin dilaurate (DBTDL), and the quencher is tert-butylhydroquinone (TBHQ) corresponding to formula (XX). The structure of 2-Cl-4-diol-HABI is shown in formula (XXII):

[0050]

[0051] Figure 1 The invention relates to a preparation technology route of a cross-linked polyurethane positive photoresist using 2-Cl-4-diol-HABI as a photosensitive unit and TBHQ as a quencher.

[0052] Weigh 0.1g PEG 400 Place in a 50ml round bottom flask, vacuum remove water at 75 degrees Celsius for 10 minutes, then switch to nitrogen environment and cool to room temperature. Then weigh 0.079g 2-Cl-4-diol-HABI and dissolve it in 4ml anhydrous ethyl acetate, inject into the PEG 400 Place the mixture in a round-bottom flask and stir vigorously to mix thoroughly. Then, inject a trace amount of dibutyltin dilaurate as a catalyst. Weigh 0.097g of IPDI and inject approximately 0.092ml directly into the reaction system. After thoroughly mixing the monomers under vigorous stirring, weigh 0.047g of TBHQ and dissolve it in 2ml of anhydrous ethyl acetate and inject it into the reaction system. After stirring for approximately 10 minutes, remove the mixture with a 10ml syringe and filter it three times through a 0.22µm pore filter until ready for use. Place the cleaned silicon wafer on a spin coater and set the first step to 1000rpm for 20s; the second step to 8000rpm for 20s. The prepolymer solution was added dropwise onto a silicon wafer, and a photoresist film was obtained by a two-step spin coating method at the above-mentioned rotation speed. The silicon wafer coated with the photoresist was placed on a hot plate at 70 degrees Celsius and baked for 40 minutes to remove the solvent. At the same time, this process was accompanied by polymerization of the monomers in the photoresist film, resulting in a polyurethane positive photoresist with 2-Cl-4-diol-HABI as the crosslinking point and photosensitive unit and TBHQ as the quencher.

[0053] The silicon wafer spin-coated with polyurethane photoresist was placed on the stage of a photolithography machine so that it was in contact with the mask. The mask channel width was 5 μm. Contact exposure was performed for 30 seconds under a 365 nm light source. After the exposure, it was placed in tetrahydrofuran for development for 30 seconds, and then the surface solvent was blown dry with nitrogen to obtain a photolithography pattern with a line width of 5 μm. Figure 2 The following are photos of the photolithographic pattern after photolithography development under an optical microscope and a scanning electron microscope. It can be seen that a pattern with a 5um channel width has been formed on the photoresist surface. At the same time, the residual thickness of the exposed part after development was characterized by a step profiler, and it can be seen that only 256mJ / cm 2 An exposure dose of can make the exposed part completely dissolved by the developer, indicating that TBHQ has a high free radical quenching efficiency, giving the photoresist very excellent photosensitivity.

[0054] Example 2

[0055] The oligomer diol is polyethylene glycol with a molecular weight of 400 (PEG 400), isophorone diisocyanate (IPDI) as the isocyanate source, tetrahydroxy-functionalized hexaarylbiimidazole (2-Cl-4-diol-HABI) as the photosensitive unit and crosslinking unit, the catalyst is dibutyltin dilaurate (DBTDL), and the quencher is 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) corresponding to formula (VIII). The structure of 2-Cl-4-diol-HABI is shown in formula (XXII):

[0056]

[0057] Weigh 0.1g PEG 400 Place in a 50ml round bottom flask, vacuum remove water at 75 degrees Celsius for 10 minutes, then switch to nitrogen environment and cool to room temperature. Then weigh 0.079g 2-Cl-4-diol-HABI and dissolve it in 4ml anhydrous ethyl acetate, inject into the PEG 400 Place the mixture in a round-bottom flask and stir vigorously to mix thoroughly. Then, inject a trace amount of dibutyltin dilaurate as a catalyst. Weigh 0.097g of IPDI and inject approximately 0.092ml directly into the reaction system. After thoroughly mixing the monomers under vigorous stirring, weigh 0.044g of TEMPO and dissolve it in 2ml of anhydrous ethyl acetate and inject it into the reaction system. After stirring for approximately 10 minutes, remove the mixture with a 10ml syringe and filter it three times through a 0.22µm pore filter until ready for use. Place the cleaned silicon wafer on a spin coater and set the first step to 1000rpm for 20s; the second step to 8000rpm for 20s. The prepolymer solution is added dropwise onto a silicon wafer, and a photoresist film is obtained by a two-step spin coating method at the above-mentioned rotation speed. The silicon wafer coated with the photoresist is placed on a hot plate at 70 degrees Celsius and baked for 40 minutes to remove the solvent. At the same time, this process is accompanied by polymerization of the monomers in the photoresist film, resulting in a polyurethane positive photoresist with 2-Cl-4-diol-HABI as the crosslinking point and photosensitive unit and TEMPO as the quencher.

[0058] The silicon wafer with the polyurethane photoresist spin-coated above was placed on the stage of the photolithography machine so that it was in contact with the mask. The mask channel width was 5 μm. The wafer was exposed to a 365 nm light source for 900 s. After the exposure, the wafer was placed in tetrahydrofuran for 30 s and then the surface solvent was blown off with nitrogen. Figure 3 As shown in the figure, a photolithographic pattern with a certain degree of clarity is obtained. However, from the characterization of the residual thickness of the exposed part by the step profiler, it can be seen that even if the exposure dose reaches nearly 8000mJ / cm 2 , a film about 250 nm thick still remains on the substrate in the exposed area, which is far from meeting the requirements of practical applications, indicating that TEMPO does not show an ideal quenching effect in this system.

[0059] Example 3

[0060] The oligomer diol is polyethylene glycol with a molecular weight of 400 (PEG 400 ), isophorone diisocyanate (IPDI) as the isocyanate source, tetrahydroxy-functionalized hexaarylbiimidazole (2-Cl-4-diol-HABI) as the photosensitive unit and crosslinking unit, the catalyst is dibutyltin dilaurate (DBTDL), and the quencher is the benzil corresponding to formula (10). The structure of 2-Cl-4-diol-HABI is shown in formula (22):

[0061]

[0062] Weigh 0.1g PEG 400 Place in a 50ml round bottom flask, vacuum remove water at 75 degrees Celsius for 10 minutes, then switch to nitrogen environment and cool to room temperature. Then weigh 0.079g 2-Cl-4-diol-HABI and dissolve it in 4ml anhydrous ethyl acetate, inject into the PEG 400 Place the mixture in a round-bottom flask and stir vigorously to mix thoroughly. Then, inject a trace amount of dibutyltin dilaurate as a catalyst. Weigh 0.097g of IPDI and inject approximately 0.092ml directly into the reaction system. After thoroughly mixing the monomers under vigorous stirring, weigh 0.059g of benzil, dissolve it in 2ml of anhydrous ethyl acetate, and inject it into the reaction system. After stirring for approximately 10 minutes, remove the mixture with a 10ml syringe and filter it three times through a 0.22µm pore filter. Place the cleaned silicon wafer on a spin coater and set the first step to 1000rpm for 20s; the second step to 8000rpm for 20s. The prepolymer solution is added dropwise onto a silicon wafer, and a photoresist film is obtained by a two-step spin coating method at the above-mentioned rotation speed. The silicon wafer coated with the photoresist is placed on a hot plate at 70 degrees Celsius and baked for 40 minutes to remove the solvent. At the same time, this process is accompanied by polymerization of the monomers in the photoresist film, resulting in a polyurethane positive photoresist with 2-Cl-4-diol-HABI as the crosslinking point and photosensitive unit, and benzil as the quencher.

[0063] The silicon wafer with the polyurethane photoresist spin-coated above was placed on the stage of the photolithography machine so that it was in contact with the mask. The mask channel width was 5 μm. The wafer was exposed to a 365 nm light source for 900 s. After the exposure, the wafer was placed in tetrahydrofuran for 30 s and then the surface solvent was blown off with nitrogen. Figure 4 As shown in the figure, even at high exposure doses, only very blurred lithography patterns can be obtained. From the characterization of the residual thickness of the exposed part by the step profiler, it can be seen that even at an exposure dose of nearly 8000mJ / cm 2, a film about 300 nm thick still remains on the substrate in the exposed area, which is far from meeting the requirements of practical applications, indicating that benzil does not show an ideal quenching effect in this system.

[0064] Example 4

[0065] The oligomer diol is polyethylene glycol with a molecular weight of 400 (PEG 400 ), isophorone diisocyanate (IPDI) as the isocyanate source, tetrahydroxy-functionalized hexaarylbiimidazole (2-Cl-4-diol-HABI) as the photosensitive unit and crosslinking unit, the catalyst is dibutyltin dilaurate (DBTDL), and the quencher is tetrachlorobenzoquinone corresponding to formula (XI). The structure of 2-Cl-4-diol-HABI is shown in formula (XXII):

[0066]

[0067] Weigh 0.1g PEG 400 Place in a 50ml round bottom flask, vacuum remove water at 75 degrees Celsius for 10 minutes, then switch to nitrogen environment and cool to room temperature. Then weigh 0.079g 2-Cl-4-diol-HABI and dissolve it in 4ml anhydrous ethyl acetate, inject into the PEG 400 Place the mixture in a round-bottom flask and stir vigorously to mix thoroughly. Then, inject a trace amount of dibutyltin dilaurate as a catalyst. Weigh 0.097g of IPDI and inject approximately 0.092ml directly into the reaction system. After thoroughly mixing the monomers under vigorous stirring, weigh 0.069g of tetrachlorobenzoquinone, dissolve it in 2ml of anhydrous ethyl acetate, and inject it into the reaction system. After stirring for approximately 10 minutes, remove the mixture with a 10ml syringe and filter it three times through a 0.22µm pore filter. Place the cleaned silicon wafer on a spin coater and set the first step to 1000rpm for 20s; the second step to 8000rpm for 20s. The prepolymer solution was added dropwise onto a silicon wafer, and a photoresist film was obtained by a two-step spin coating method at the above-mentioned rotation speed. The silicon wafer coated with the photoresist was placed on a hot plate at 70 degrees Celsius and baked for 40 minutes to remove the solvent. At the same time, this process was accompanied by polymerization of the monomers in the photoresist film, resulting in a polyurethane positive photoresist with 2-Cl-4-diol-HABI as the crosslinking point and photosensitive unit, and tetrachlorobenzoquinone as the quencher.

[0068] The silicon wafer with the polyurethane photoresist spin-coated above was placed on the stage of the photolithography machine so that it was in contact with the mask. The mask channel width was 5 μm. Contact exposure was performed under a 365 nm light source for 900 s. After the exposure, it was placed in tetrahydrofuran for development for 30 s, and then the surface solvent was blown dry with nitrogen to obtain the following: Figure 5The photolithographic pattern shown has a relatively rough surface and is close to 8000mJ / cm 2 At an exposure dose of 100 nm, a residual film thickness of approximately 280 nm remained in the exposed portion, which is far from sufficient for practical applications. This indicates that chloranil can damage the film's flatness and has a poor effect on quenching free radicals in this system.

[0069] Comparative Example 1

[0070] The oligomer diol is polyethylene glycol with a molecular weight of 400 (PEG 400 ), isophorone diisocyanate (IPDI) as the isocyanate source, tetrahydroxy-functionalized hexaarylbiimidazole (2-Cl-4-diol-HABI) as the photosensitive unit and crosslinking unit, and the catalyst is dibutyltin dilaurate (DBTDL). In this comparative example, 2-Cl-HABI is used as the quencher, and its structure is shown in Formula (XXIII). The structure of 2-Cl-4-diol-HABI is shown in Formula (XXII):

[0071]

[0072] Weigh 0.1g PEG 400 Place in a 50ml round bottom flask, vacuum remove water at 75 degrees Celsius for 10 minutes, then switch to nitrogen environment and cool to room temperature. Then weigh 0.079g 2-Cl-4-diol-HABI and dissolve it in 4ml anhydrous ethyl acetate, inject into the PEG 400 Place the mixture in a round-bottom flask and stir vigorously to mix thoroughly. Then, inject a trace amount of dibutyltin dilaurate as a catalyst. Weigh 0.097g of IPDI and inject approximately 0.092ml directly into the reaction system. After thoroughly mixing the monomers under vigorous stirring, weigh 0.186g of 2-Cl-HABI and dissolve it in 2ml of anhydrous ethyl acetate and inject it into the reaction system. Remove the mixture using a 10ml syringe and filter it three times through a 0.22µm pore filter until ready for use. Place the cleaned silicon wafer on a spin coater and set the first step to 1000rpm for 20s; the second step to 8000rpm for 20s. The prepolymer solution was added dropwise onto a silicon wafer, and a photoresist film was obtained by a two-step spin coating method at the above-mentioned rotation speed. The silicon wafer coated with the photoresist was placed on a hot plate at 70 degrees Celsius and baked for 40 minutes to remove the solvent. At the same time, this process was accompanied by polymerization of the monomers in the photoresist film, resulting in a polyurethane positive photoresist with 2-Cl-4-diol-HABI as the crosslinking point and photosensitive unit and 2-Cl-HABI as the quencher.

[0073] The silicon wafer with the polyurethane photoresist spin-coated above was placed on the stage of the photolithography machine so that it was in contact with the mask. The mask channel width was 5 μm. Contact exposure was performed under a 365 nm light source for 900 s. After the exposure, it was placed in tetrahydrofuran for development for 30 s, and then the surface solvent was blown dry with nitrogen to obtain the following: Figure 6 The photolithographic pattern shown was characterized by a step profiler to measure the thickness of the exposed portion. It was found that when the exposure dose was close to 8000mJ / cm2, there was still a residual film of about 160nm left on the substrate, indicating that the radical quenching efficiency of 2-Cl-HABI in this system was still poor.

[0074] By comparing the photolithography effects and photosensitivity of HABI photoresists corresponding to the above-mentioned quenchers, TBHQ exhibits ultra-high free radical quenching efficiency, giving HABI photoresist excellent photosensitivity, making TBHQ-HABI polyurethane photoresist a highly promising positive photoresist material.

[0075] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A UV positive photoresist based on a hexaarylbiimidazole molecular switch, characterized in that: The invention comprises an oligomeric diol, a functionalized hexaarylbiimidazole molecular switch cross-linker, a free radical quencher, a catalyst and a diisocyanate; The functionalized hexaaryl biimidazole molecular switch cross-linker is a molecular switch with a hydroxyl functional group that is modified and designed with hexaaryl biimidazole as the molecular main body, wherein the hexaaryl biimidazole has a structure shown in the following formula (1): Formula (1); The free radical quencher is a phenolic polymerization inhibitor represented by formula (IX): Formula (9) In formula (9), R1 is H or OH, and R2 is -C(CH3)3, -CH3, -CH2CH3, -OCH3, -OH, -Br, -Cl or -NO2; When used, the oligomer diol and the functionalized hexaaryl biimidazole molecular switch cross-linker can undergo stepwise addition polymerization with diisocyanate under the catalytic conditions of the catalyst to form a polymer network structure; when the photoresist is used for photolithography, under ultraviolet light, the dynamic CN covalent bond between the two imidazole rings in the hexaaryl biimidazole unit in the polymer network structure responds to light and is cleaved to form an oligomer; The free radical quencher is used to ensure that the photoresist will not spontaneously recover after being depolymerized to form oligomers during exposure, thereby ensuring that the oligomers formed in the exposed part of the photoresist can be dissolved by the developer, while the unexposed part is insoluble in the developer, and the target positive pattern is obtained after development.

2. The UV positive photoresist according to claim 1, wherein The oligomer diol is polyethylene glycol or polyether diol; the molecular weight of the oligomer diol is 200-1000.

3. The UV positive photoresist according to claim 1, wherein The functionalized hexaaryl biimidazole molecular switch cross-linker is a molecular switch with a hydroxyl functional group that is modified and designed with hexaaryl biimidazole as the molecular main body, and some hydrogen atoms on the benzene ring in the molecular switch structure are replaced by electron-withdrawing groups.

4. The UV positive photoresist according to claim 3, wherein The electron-withdrawing group is a halogen atom or a nitro group.

5. The UV positive photoresist according to claim 1, wherein Also included is an organic solvent for dissolving the oligomer diol, the functionalized hexaarylbiimidazole molecular switch cross-linker, and the free radical quencher.

6. The UV positive photoresist according to claim 1, wherein The molar ratio of the oligomer diol to the functionalized hexaaryl biimidazole molecular switch cross-linker is 7:1 to 1:7; the molar amount of the free radical quencher is greater than the molar amount of the functionalized hexaaryl biimidazole molecular switch cross-linker; The molar amount of the diisocyanate is greater than or equal to the sum of the molar amounts of the oligomeric diol and the functionalized hexaarylbiimidazole molecular switch cross-linker.

7. The method for using the photoresist according to any one of claims 1 to 6, wherein: The steps include: (1) mixing the oligomer diol with a functionalized hexaarylbiimidazole molecular switch cross-linker, a free radical quencher, a catalyst, and a diisocyanate, and stirring the mixture to cause a preliminary polymerization reaction to obtain a polyurethane prepolymer solution; (2) spin coating the polyurethane prepolymer solution into a film, and then performing a pre-baking treatment to further cause addition polymerization to obtain a polyurethane photoresist film with hexaarylbiimidazole as a crosslinking point; (3) exposing the polyurethane photoresist film obtained in step (2) to ultraviolet light, so that the dynamic CN covalent bond between the two imidazole rings in the hexaaryl biimidazole unit in the polymer network structure is cleaved in response to light, and the polymer is depolymerized to form oligomers; After the exposure is completed, development is performed. The free radical quencher in the photoresist can ensure that the photoresist will not spontaneously recover after being depolymerized to form oligomers during exposure, thereby ensuring that the oligomers formed in the exposed part of the photoresist can be quickly dissolved by the developer, while the unexposed part is insoluble in the developer, and the target positive pattern is obtained after development.

8. The method of use according to claim 7, wherein: The mixing time of step (1) is 5 to 30 minutes.

9. The method of use according to claim 7, wherein: The pre-baking temperature in step (2) is lower than or equal to 90° C., and the pre-baking time is not less than 20 minutes.

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