Volatile solvent-free photoresist and preparation method thereof

Abstract

The invention relates to the technical field of photoresists, in particular to a volatile solvent-free photoresist and a preparation method thereof. According to the invention, the problem of poor stability of the existing photoresist is overcome. The synthetic raw materials of the photoresist comprise composite resin, a modified photoinitiator, a composite cross-linking agent, a modified curing agent, fluorine-containing siloxane nanoparticles, polyimide microspheres and a composite dispersant. The materials are stirred and ultrasonically mixed to obtain a precursor solution, and then the precursor solution is degassed to obtain the photoresist. According to the invention, the monofunctional resin is introduced into the multifunctional resin to adjust the viscosity, and the monofunctional resin and the modified photoinitiator cooperate to improve the adhesive force of the photoresist; the prepared modified curing agent and the composite cross-linking agent are added into the photoresist, so that the tensile strength of the photoresist is improved; the acid and alkali resistance of the photoresist is improved by adding the prepared fluorine-containing siloxane nanoparticles and polyimide microspheres; the uniformity of the photoresist is improved by controlling the dosage of the composite dispersing agent and the ultrasonic stirring time.

Description

Technical Field

[0001] The present invention relates to the technical field of photoresists, and specifically to a photoresist without volatile solvents and a preparation method thereof. Background Art

[0002] Photoresist is a core material for manufacturing semiconductor devices such as chips and integrated circuits, and is used to transfer the designed circuit pattern onto a semiconductor wafer. With the continuous improvement of chip integration, the performance requirements for photoresist, such as resolution, sensitivity, and corrosion resistance, are getting higher and higher, which has promoted the continuous innovation of photoresist technology.

[0003] Negative photoresist is an important material in the lithography process. After exposure, the unexposed area can be dissolved and removed by the developer, while the exposed area is retained due to crosslinking and other reactions, thereby forming the required pattern on the substrate. Negative photoresists mostly use macromolecular resins as the main resin. Due to the uneven molecular weight distribution and composition differences of the resin, the uniformity is not high, resulting in poor stability of the photoresist. In addition, the molecular weight of the macromolecular resin is usually large, the resolution is low, and it is difficult to ensure the sensitivity of photocuring and the development speed. However, using small molecule resins has a high processing cost, requires controlling its purity during the synthesis process, and the price is relatively expensive. More importantly, small molecule resins are difficult to prepare liquids with high viscosity, which easily causes peeling and missing of the photoresist, thus affecting the quality of the entire semiconductor device.

[0004] Currently, most of the widely used negative photoresists are solvent-based. Solvents are volatile, and the toxicity and flammability of such volatile solvents are high. Special equipment is required for both production and use to ensure safety. In addition, volatile solvents are removed during use rather than participating in the lithography process as part of the photoresist, which also increases costs and is harmful to workers and the environment in the long term, and is not conducive to the sustainable development of the economy and the environment.

[0005] In summary, the current negative photoresists still have disadvantages such as high shrinkage rate and poor adhesion, resulting in poor stability of the photoresist, and there are certain safety hazards in the production process of volatile solvents. Therefore, it is urgent to solve the above problems.

[0006] Therefore, a photoresist without volatile solvents and a preparation method thereof are proposed. Summary of the Invention

[0007] The purpose of the present invention is to design a photoresist without volatile solvents and a preparation method thereof. The synthetic raw materials of the present invention include composite resin, modified photoinitiator, composite crosslinking agent, modified curing agent, fluorinated silicone nanoparticles, polyimide microspheres and composite dispersant; the above materials are stirred and ultrasonically mixed to obtain a precursor solution, and then degassing treatment is performed to obtain a photoresist. The present invention adjusts the viscosity by introducing a monofunctional resin into a multifunctional resin, and prepares a modified photoinitiator to improve the adhesion of the photoresist; the tensile strength of the photoresist is improved and the shrinkage rate is reduced by preparing a modified curing agent and adding it to the photoresist with a composite crosslinking agent; the acid and alkali resistance and adhesion of the photoresist are improved by adding the prepared fluorinated silicone nanoparticles and polyimide microspheres; the uniformity of the photoresist is improved by controlling the amount of the composite dispersant and the time of ultrasonic stirring.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing a photoresist without volatile solvents. The method comprises the following steps by weight:

[0010] S1: adding 40-60 parts of the composite resin into a reaction vessel, slowly adding 5-9 parts of the modified photoinitiator at a rotation speed of 500 rpm, and continuously stirring for 1 h-2 h to form a uniform mixed solution;

[0011] S2: 1-3 parts of a composite crosslinking agent, 0.5-0.9 parts of a modified curing agent, 0.1-0.5 parts of fluorinated silicone nanoparticles, 0.1-0.3 parts of polyimide microspheres, and 0.2-0.4 parts of a composite dispersant are added one by one to the mixed solution at a rotation speed of 500 rpm, and ultrasonically treated at 20 kHz for 10 min-30 min in an ultrasonic machine, followed by stirring at 800 rpm for 2 h-4 h to obtain a photoresist precursor solution;

[0012] S3 degasses the photoresist precursor solution, evacuates the reaction container to a vacuum, and slowly stirs at a rotation speed of 50 rpm for 20 minutes to 60 minutes to eliminate bubbles. After the treatment, a photoresist is obtained.

[0013] Preferably, the preparation method of the composite resin is: adding 19-24 parts of pentaerythritol triacrylate to a three-necked flask, then slowly adding 8 parts of isobornyl acrylate, while turning on the agitator, setting the stirring speed to 300 rpm, placing the three-necked flask in a constant temperature water bath, controlling the temperature at 60°C, and continuing to stir for 90 minutes to obtain a mixture; while stirring, slowly adding 0.1 parts of p-hydroxyanisole to the mixture, and continuing to stir for 60 minutes to obtain a composite resin.

[0014] Preferably, the preparation method of the modified photoinitiator is as follows: Add 8 - 12 parts of ethyl 2,4,6 - trimethylbenzoyl phenylphosphinate and 10 parts of toluene into a reaction kettle. After stirring for 30 min, add 1 part of ethylenediamine and 0.2 part of triethylamine. Heat the reaction system to 80 °C and stir - react for 8 h under heating conditions. After the reaction is completed, cool the reaction solution to room temperature, remove the organic solvent by distillation, and then dry it in a vacuum drying oven at 60 °C for 12 h to obtain the modified photoinitiator.

[0015] Preferably, the composite cross - linker is composed of γ - methacryloxypropyltrimethoxysilane and hexamethoxymethylmelamine, and the weight ratio of γ - methacryloxypropyltrimethoxysilane to hexamethoxymethylmelamine is 1 - 5:1.

[0016] Preferably, the preparation method of the modified curing agent is as follows: Put 3 - 7 parts of benzoin dimethyl ether and 20 parts of absolute ethanol into a flask and stir for 30 min at room temperature to form a transparent solution; put 2 parts of β - cyclodextrin and 20 parts of deionized water into another flask and stir for 40 min at 60 °C to form a clear solution; under the condition of continuous stirring and at 60 °C, slowly drop the transparent solution into the clear solution, control the dropping speed at 2 drops per second. After dropping, continue to stir - react at 60 °C for 2 h - 6 h to obtain a reaction solution; naturally cool the reaction solution to room temperature, then refrigerate and stand at 4 °C for 12 h; after standing, centrifuge the reaction solution at a speed of 4000 rpm for 15 min to separate the precipitate, wash the precipitate 5 times with deionized water, and then put the precipitate into a vacuum drying oven and dry it at 50 °C for 24 h to obtain the modified curing agent.

[0017] Preferably, the preparation method of the fluorosiloxane nanoparticles is as follows: Mix 1 part of heptadecafluorodecyltrimethoxysilane and 1 - 5 parts of tetraethyl orthosilicate, then add 10 parts of ethanol and stir for 60 min to obtain a mixed solution A; slowly drop 1 part of 0.1 mol / L ammonia water solution into the mixed solution A and continuously stir for 2 h - 4 h. After the reaction is completed, let the mixed solution A stand and age for 2 h, then wash out the precipitate by centrifugation, and vacuum - dry the precipitate at 60 °C for 12 h to obtain the fluorosiloxane nanoparticles.

[0018] Preferably, the method for preparing polyimide microspheres is as follows: Dissolve 1-3 parts of pyromellitic dianhydride in 5 parts of N,N-dimethylformamide to obtain solution A; dissolve 3 parts of 4,4'-diaminodiphenyl ether in 5 parts of N,N-dimethylformamide to obtain solution B; slowly drop solution A into solution B to form a prepolymer solution; then add 0.2 part of sodium dodecyl sulfate to the prepolymer solution and continue stirring for 30 min to form a stable emulsion; add 0.1 part of potassium persulfate to the emulsion, stir for 1 h, and then react at 100 °C for 4-8 h. After the reaction, centrifuge and wash the precipitate, and finally dry it in a vacuum drying oven at 60 °C for 12 h to obtain polyimide microspheres.

[0019] Preferably, the composite dispersant is composed of a mixture of fatty alcohol polyoxyethylene ether and sodium dodecylbenzenesulfonate, and the weight ratio of fatty alcohol polyoxyethylene ether to sodium dodecylbenzenesulfonate is 1-3:2.

[0020] On the other hand, the present invention provides a photoresist without volatile solvents. The synthesis raw materials of the photoresist include a composite resin, a modified photoinitiator, a composite crosslinking agent, a modified curing agent, fluorosiloxane nanoparticles, polyimide microspheres, and a composite dispersant;

[0021] The composite resin includes pentaerythritol triacrylate and isobornyl acrylate;

[0022] The modified photoinitiator includes ethyl 2,4,6-trimethylbenzoyl phenylphosphinate and ethylenediamine;

[0023] The modified curing agent includes benzoin dimethyl ether and β-cyclodextrin;

[0024] The fluorosiloxane nanoparticles include heptadecafluorodecyltrimethoxysilane and tetraethyl orthosilicate;

[0025] The polyimide microspheres include pyromellitic dianhydride and 4,4'-diaminodiphenyl ether.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The present invention adjusts the viscosity by introducing monofunctional resin into the multifunctional resin and prepares a modified photoinitiator to improve the adhesion of the photoresist. Pentaerythritol triacrylate provides a high crosslinking density, taking into account fluidity and curing speed. Isobornyl acrylate adjusts the viscosity of the system, facilitating uniform coating in the later stage. The two are prepared into a composite resin, and the carboxyl group therein can undergo an esterification reaction with the silanol group in the substrate material to form a stable ester bond, thereby firmly connecting the photoresist to the substrate and significantly enhancing the adhesion between the photoresist and the substrate. The modified photoinitiator introduced with amino groups has a higher photoinitiating efficiency and can rapidly generate a large number of active species such as free radicals or cations under light irradiation. These active species can not only initiate the crosslinking reaction within the composite resin itself but also promote the crosslinking between the composite resin and other components in the photoresist, thereby enhancing the overall cohesion of the photoresist and its adhesion to the substrate, improving the stability of the photoresist. Through comparison, it is found that the photoresist using a volatile solvent has relatively poor adhesion and cannot effectively improve the stability of the photoresist.

[0028] 2. The present invention improves the tensile strength of the photoresist and reduces the shrinkage rate by preparing a modified curing agent and adding a composite crosslinking agent to the photoresist. Benzoin dimethyl ether and β-cyclodextrin are compounded to form a modified curing agent, which can undergo a chemical reaction with the composite resin to form a more stable, uniform, and dense three-dimensional crosslinking network, thereby improving the tensile strength of the photoresist. The modified curing agent can also reduce the internal stress generated due to the rapid crosslinking of molecules, thereby reducing the shrinkage rate of the photoresist. The modified curing agent can provide a suitable environment and conditions for the reaction of the composite crosslinking agent, and the composite crosslinking agent can further enhance and expand the crosslinking network formed by the modified curing agent, thereby improving the tensile strength of the photoresist. In terms of reducing the shrinkage rate, the modified curing agent reduces the shrinkage rate by controlling the reaction rate and compensating for shrinkage, while the composite crosslinking agent reduces shrinkage by forming a flexible structure and dispersing stress, improving the stability of the photoresist.

[0029] 3. The present invention improves the acid and alkali resistance of the photoresist by adding prepared fluorosiloxane nanoparticles and polyimide microspheres. The fluorine atoms in the fluorosiloxane nanoparticles have extremely high electronegativity, and the formed C-F bond has a high bond energy and good chemical stability. This property enables the nanoparticles themselves to have strong resistance to acids and bases, thereby protecting the main structure of the photoresist from being eroded by acids and bases. The polyimide microspheres form a physical barrier network in the photoresist. Acid or base molecules will be blocked by the microspheres during the diffusion process, increasing the path and difficulty of their diffusion in the photoresist and reducing the erosion rate and degree of the acids and bases on the photoresist. The nanoparticles provide a chemically stable barrier at the micro level, while the microspheres form a physical barrier network at the macro level. This composite structure can resist the erosion of acids and bases from different scales and angles, further improving the acid and alkali resistance of the photoresist and enhancing the stability of the photoresist.

[0030] 4. The present invention improves the uniformity of the photoresist by controlling the dosage of the composite dispersant and the time of ultrasonic stirring. The composite dispersant can reduce the surface tension between the components in the photoresist, enabling the components to be uniformly dispersed in the system. In the photoresist, the composite dispersant molecules will adsorb on the surface of solid particles, forming a protective film that keeps the particles at a certain distance from each other and maintains the dispersed state. During the synthesis of the photoresist, the power of ultrasound can break the agglomeration structure between various particles in the photoresist, dispersing large particles into small particles, which is beneficial to improving the uniformity of the photoresist. The shear force generated during the stirring process can also disperse larger particle aggregates to a certain extent, assisting in improving the ultrasonic dispersion effect and thus enhancing the stability of the photoresist. Description of the Drawings

[0031] Figure 1 It is a graph showing the uniformity of the photoresist in Example 21 and Comparative Examples 17 - 21 of the present invention. Detailed Embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

[0033] Specifically refer to Figure 1 , the present invention provides a photoresist without volatile solvents and its preparation method, and the technical solutions are as follows:

[0034] Example 1

[0035] Prepare the composite resin:

[0036] Add 19 parts of pentaerythritol triacrylate into a three - necked flask, then slowly add 8 parts of isobornyl acrylate, and at the same time start the stirrer, set the stirring speed to 300 rpm, place the three - necked flask in a constant temperature water bath, control the temperature at 60 °C, and continue stirring for 90 min to obtain a mixture; under the stirring state, slowly add 0.1 part of p - methoxyphenol to the mixture, and continue stirring for 60 min to obtain the composite resin.

[0037] Prepare the modified photoinitiator:

[0038] Add 8 parts of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate and 10 parts of toluene into a reaction kettle. After stirring for 30 min, add 1 part of ethylenediamine and 0.2 part of triethylamine. Heat the reaction system to 80 °C and stir the reaction for 8 h under heating conditions. After the reaction is completed, cool the reaction solution to room temperature, remove the organic solvent by distillation, and then dry it in a vacuum drying oven at 60 °C for 12 h to obtain the modified photoinitiator.

[0039] Prepare the modified curing agent:

[0040] Put 3 parts of benzoin dimethyl ether and 20 parts of absolute ethanol into a flask and stir at room temperature for 30 min to form a transparent solution; put 2 parts of β-cyclodextrin and 20 parts of deionized water into another flask and stir at 60 °C for 40 min to form a clear solution; under the condition of continuous stirring and at 60 °C, slowly drop the transparent solution into the clear solution, control the dropping speed at 2 drops per second. After the dropping is completed, continue to stir the reaction at 60 °C for 2 h to obtain the reaction solution; naturally cool the reaction solution to room temperature, then refrigerate and stand at 4 °C for 12 h; after standing, centrifuge the reaction solution at 4000 rpm for 15 min to separate out the precipitate, wash the precipitate with deionized water 5 times, and then put the precipitate into a vacuum drying oven and dry it at 50 °C for 24 h to obtain the modified curing agent.

[0041] Prepare fluorosiloxane nanoparticles:

[0042] Mix 1 part of heptadecafluorodecyltrimethoxysilane and 1 part of tetraethyl orthosilicate, then add 10 parts of ethanol, and stir for 60 min to obtain a mixed solution A; slowly drop 1 part of 0.1 mol / L ammonia water solution into the mixed solution A, continuously stir for 2 h. After the reaction is completed, let the mixed solution A stand for aging for 2 h, then wash out the precipitate by centrifugation, and vacuum dry the precipitate at 60 °C for 12 h to obtain fluorosiloxane nanoparticles.

[0043] Prepare polyimide microspheres:

[0044] Dissolve 1 part of pyromellitic dianhydride in 5 parts of N,N-dimethylformamide to obtain solution A; dissolve 3 parts of 4,4'-diaminodiphenyl ether in 5 parts of N,N-dimethylformamide to obtain solution B; slowly drop solution A into solution B to form a prepolymer solution; then add 0.2 part of sodium dodecyl sulfate to the prepolymer solution and continue to stir for 30 min to form a stable emulsion; add 0.1 part of potassium persulfate to the emulsion, stir for 1 h and then react at 100 °C for 4 h. After the reaction is completed, wash the precipitate by centrifugation, and finally dry it in a vacuum drying oven at 60 °C for 12 h to obtain polyimide microspheres.

[0045] Prepare the photoresist:

[0046] S1 Add 40 parts of composite resin into the reaction vessel. While rotating at a speed of 500 rpm, slowly add 5 parts of the modified photoinitiator and continuously stir for 1 h to form a uniform mixed solution;

[0047] S2 Add 1 part of composite crosslinking agent, 0.5 part of modified curing agent, 0.1 part of fluorosiloxane nanoparticles, 0.1 part of polyimide microspheres and 0.2 part of composite dispersant into the mixed solution one by one while rotating at a speed of 500 rpm. Ultrasonically treat for 10 min at 20 kHz in an ultrasonic machine, and then stir at 800 rpm for 2 h to obtain a photoresist precursor solution;

[0048] S3 Degas the photoresist precursor solution. Pump the reaction vessel to vacuum and slowly stir at 50 rpm for 20 min to eliminate bubbles. After the treatment, a photoresist is obtained.

[0049] Examples 2 - 6 Refer to the parameter conditions in Example 1, and the specific differences are shown in Table 1.

[0050] Comparative Example 1 Refer to the parameter conditions in Example 1, and the difference is that only pentaerythritol triacrylate is used as the matrix resin.

[0051] Comparative Example 2 Refer to the parameter conditions in Example 1, and the difference is that only isobornyl acrylate is used as the matrix resin.

[0052] Comparative Example 3 Refer to the parameter conditions in Example 1, and the difference is that ethyl 2,4,6 - trimethylbenzoyl phenylphosphinate is used as the photoinitiator.

[0053] Comparative Example 4 Refer to the parameter conditions in Example 1, and the difference is that the modified photoinitiator is not added.

[0054] Comparative Example 5 Refer to the parameter conditions in Example 1, and the difference is that the stirring time is 5 h.

[0055] Comparative Example 6 Refer to the parameter conditions in Example 1, and the difference is that the stirring time is 0.2 h.

[0056] Comparative Example 7 Refer to the parameter conditions in Example 1, and the difference is that ethylene glycol monoethyl ether acetate is added as a volatile solvent to participate in the reaction in S1.

[0057] Experimental Example 1 Adhesion test

[0058] Perform adhesion tests on Examples 1 - 6 and Comparative Examples 1 - 7 according to the international standard ISO 2409. The rating standard is from 0 to 5 levels. Level 0 means that there is no coating or photoresist peeling off in the grid area, and the adhesion is the best; Level 5 means that the peeling area of the coating or photoresist in the grid area exceeds 65%, and the adhesion is the worst. The obtained results are shown in Table 1.

[0059] Table 1 Parameter conditions and adhesion tests of Examples 1-6 and Comparative Examples 1-7

[0060]

[0061]

[0062] It can be found from Table 1 that in Comparative Examples 1-2, when only trimethylolpropane triacrylate or isobornyl acrylate is used as the matrix resin, its adhesion is lower than that of Examples 1-6. This is because the too high crosslinking density of trimethylolpropane triacrylate may cause large internal stress in the photoresist during the curing process. When the internal stress exceeds the adhesion between the photoresist and the substrate, the photoresist will peel off from the substrate, reducing the adhesion; while isobornyl acrylate has relatively few functional groups and a relatively low crosslinking density, and the cohesive force of the photoresist may be weak. When subjected to a large external force, the photoresist is prone to deformation or damage, thus reducing its adhesion to the substrate; when the two are compounded, the carboxyl group in the composite resin can react with the silanol group in the matrix material to form stable ester bonds, thereby firmly connecting the photoresist to the substrate and significantly enhancing the adhesion between the photoresist and the substrate. In Comparative Examples 3-4, when only ethyl 2,4,6-trimethylbenzoyl phenylphosphinate is used as the photoinitiator or no modified photoinitiator is used, the adhesion of the photoresist is significantly worse than that of the Examples. By introducing an amino group into ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, during the curing process of the photoresist, the amino group can chemically react with the groups on the substrate to form hydrogen bonds, thereby enhancing the adhesion between the photoresist and the substrate; and the introduction of the amino group makes the modified photoinitiator have higher photoinitiating activity. Under light irradiation conditions, the modified photoinitiator can generate active species such as free radicals or cations more quickly and efficiently, and crosslink with the resin components, making the photoresist form a more compact and stable network structure, enhancing the internal cohesion of the photoresist and the interaction with the substrate. In Comparative Examples 5-6, the control of the stirring time also has a certain influence on the adhesion of the photoresist. Too long or too short stirring time will affect the internal crosslinking process, thereby affecting the adhesion. There is also a certain synergistic effect between the composite resin and the modified photoinitiator. The free radicals generated by the modified photoinitiator can initiate the polymerization reaction between acrylate groups, and at the same time can also crosslink the composite resin with other additives containing polymerizable groups to form a three-dimensional network structure, thereby enhancing the overall internal cohesion of the photoresist and the adhesion to the substrate, and thus improving the stability of the photoresist. In Comparative Example 7, a volatile solvent is used, and its effect is lower than that of the Examples. The toxicity and flammability of this volatile solvent are high, which instead reduces the stability of the photoresist.

[0063] Examples 7 - 12 refer to the parameter conditions in Example 4, with the difference being the control of the dosages of the composite crosslinking agent and the modified curing agent and the parameter changes therein, as specifically shown in Table 2.

[0064] Comparative Example 8 refers to the parameter conditions in Example 4, with the difference being that only γ - methacryloxypropyltrimethoxysilane is used as the crosslinking agent.

[0065] Comparative Example 9 refers to the parameter conditions in Example 4, with the difference being that only hexamethoxymethylmelamine is used as the crosslinking agent.

[0066] Comparative Example 10 refers to the parameter conditions in Example 4, with the difference being that the composite crosslinking agent is not added.

[0067] Comparative Example 11 refers to the parameter conditions in Example 4, with the difference being that only benzoin dimethyl ether is used as the curing agent.

[0068] Comparative Example 12 refers to the parameter conditions in Example 4, with the difference being that the modified curing agent is not used.

[0069] Experimental Example 2 Tensile Strength and Shrinkage Rate Test

[0070] The tensile strength of Example 4, Examples 7 - 12, and Comparative Examples 8 - 12 was tested using a single - column servo - controlled computer - system tensile testing machine; a metal mold with a size of 10 * 10 * 1 mm and a polytetrafluoroethylene coating was taken, and after filling the mold with photoresist and curing it by UV, the shrinkage rate of the four sides of the formed photoresist was measured, which is the shrinkage rate of the photoresist. The obtained results are shown in Table 2.

[0071] Table 2 Parameter Conditions, Tensile Strength, and Shrinkage Rate Test of Example 4, Examples 7 - 12, and Comparative Examples 8 - 12 As can be seen from Table 2, in Comparative Examples 8-10, the tensile strength of the photoresist was significantly lower than that of Examples 4 and 7-12, and the shrinkage rate was significantly higher than that of Examples 4 and 7-12. Mixing γ-methacryloxypropyltrimethoxysilane and hexamethoxymethylmelamine in proportion to form a composite crosslinking agent can make the crosslinking reaction of certain components in the photoresist more sufficient and efficient, enabling the structure of the crosslinking network to be further optimized, improving the tensile strength of the photoresist. γ-Methacryloxypropyltrimethoxysilane has a crosslinking structure with a certain flexibility, and this flexible structure can absorb and buffer the shrinkage stress generated by the crosslinking reaction during the curing process of the photoresist, reducing the degree of shrinkage. In Comparative Examples 11-12, only benzoin dimethyl ether was used as the curing agent or no modified curing agent was used, and the stability of the photoresist was significantly lower than that of the Examples. This is because the modified curing agent is a composite of benzoin dimethyl ether and β-cyclodextrin, which can chemically react with the composite resin to form a more stable, uniform and dense three-dimensional crosslinking network, thereby improving the tensile strength of the photoresist; and the modified curing agent can control the curing reaction rate of the photoresist by adjusting its molecular structure and reactivity. A slower curing rate allows the photoresist to have more time for molecular rearrangement during the curing process, reducing the internal stress generated by the rapid crosslinking of molecules, thereby improving the stability of the photoresist. The modified curing agent and the composite crosslinking agent cooperate with each other during the curing process of the photoresist to jointly construct a more perfect crosslinking network. The modified curing agent can provide a suitable environment and conditions for the reaction of the composite crosslinking agent, while the composite crosslinking agent can further enhance and expand the crosslinking network formed by the modified curing agent, showing a higher tensile strength; in terms of reducing the shrinkage rate, the modified curing agent reduces the shrinkage rate by controlling the reaction rate and compensating for shrinkage, while the composite crosslinking agent reduces shrinkage by forming a flexible structure and dispersing stress, improving the stability of the photoresist.

[0072] Examples 13-18 refer to the parameter conditions in Example 9, except that the amounts of fluorosiloxane nanoparticles and polyimide microspheres and the parameter changes therein are controlled, as specifically shown in Table 3.

[0073] Table 3 Parameter Conditions of Example 9 and Examples 13-18

[0074]

[0075] Comparative Example 13 refers to the parameter conditions in Example 9, except that only heptadecafluorodecyltrimethoxysilane is used and no nanoparticles are prepared.

[0076] Comparative Example 14 refers to the parameter conditions in Example 9, except that no fluorosiloxane nanoparticles are added.

[0077] Comparative Example 15 Refer to the parameter conditions in Example 9, the difference is that only pyromellitic dianhydride is used and polyimide microspheres are not prepared.

[0078] Comparative Example 16 Refer to the parameter conditions in Example 9, the difference is that polyimide microspheres are not added.

[0079] Experimental Example 3 Acid and alkali resistance and adhesion test

[0080] Acid etching resistance test: After drying the developed substrate, immerse it in 3% hydrochloric acid, take it out after etching for 30 min, wash it with water, dry it with air, and observe the change of the surface of the photoresist film; Alkali etching resistance test: After drying the developed substrate, immerse it in 30% sodium hydroxide aqueous solution, take it out after etching for 30 min, wash it with water, dry it with air, and observe the change of the surface of the photoresist film; The adhesion test is carried out according to the test method in Experimental Example 1. The obtained results are shown in Table 4.

[0081] Table 4 Acid and alkali resistance and adhesion test of Example 9, Examples 13 - 18 and Comparative Examples 13 - 16

[0082] Example Acid etching resistance Alkali etching resistance Adhesion / level Example 9 No change after 72h No change after 72h 1 Example 13 No change after 72h No change after 72h 1 Example 14 No change after 96h No change after 96h 1 Example 15 No change after 96h No change after 96h 0 Example 16 No change after 96h No change after 72h 0 Example 17 No change after 72h No change after 72h 1 Example 18 No change after 72h No change after 72h 1 Comparative example 13 Peeled off after 72h Peeled off after 72h 2 Comparative example 14 Peeled off after 48h Peeled off after 48h 3 Comparative example 15 Peeled off after 72h Peeled off after 72h 2 Comparative example 16 Peeled off after 48h Peeled off after 48h 3

[0083] It can be found from Table 4 that in Comparative Examples 13-14, the acid and alkali resistance of the photoresist is significantly worse than that of Examples 9 and 13-18, and the adhesion is also lower than that of the examples, indicating that the fluorine-containing silicone nanoparticles play an important role in the photoresist, because the fluorine atoms in the fluorine-containing silicone nanoparticles have extremely high electronegativity, and the formed CF bonds have high bond energy and good chemical stability. This characteristic makes the nanoparticles themselves highly tolerant to acids and alkalis. When they are uniformly dispersed in the photoresist, they can form a chemically stable barrier inside the photoresist to prevent acid or alkali molecules from penetrating into the photoresist, thereby protecting the photoresist from being corroded by acids and alkalis; and the fluorine-containing silicone nanoparticles have a large specific surface area and a high surface activity. During the photoresist coating process, these nanoparticles can react chemically with atoms or groups on the surface of the substrate, making the connection between the photoresist and the substrate tighter, thereby improving the adhesion of the photoresist and the stability is also improved. In Comparative Examples 15-16, the acid and alkali resistance and adhesion of the photoresist are also significantly lower than those of the embodiments. This is because the polyimide microspheres form a physical barrier network in the photoresist, and the acid or alkali molecules will be blocked by the microspheres during the diffusion process, which increases the path and difficulty of their diffusion in the photoresist, reduces the speed and degree of acid and alkali erosion on the photoresist, and plays a role in protecting the photoresist; and the polyimide microspheres have a certain rigid structure. During the curing process of the photoresist, the microspheres will be partially embedded in the microscopic pores or roughness structure on the surface of the substrate, forming a mechanical interlocking effect, firmly fixing the photoresist on the substrate, and greatly improving the adhesion between the photoresist and the substrate. Fluorosilicone nanoparticles and polyimide microspheres cooperate with each other in the photoresist to form a composite protective structure. Nanoparticles provide a chemically stable barrier at the microscopic level, while microspheres form a physical barrier network at the macroscopic level. This composite structure can resist acid and alkali corrosion from different scales and angles, further improving the acid and alkali resistance of the photoresist. The two also have a synergistic effect in enhancing adhesion. The nanoparticles are tightly bonded to the substrate through surface activity and improved interface properties, and the microspheres fix the photoresist to the substrate through mechanical intercalation and improved stress distribution. Their combined effect makes the connection between the photoresist and the substrate stronger and the adhesion is significantly improved, thereby improving the stability of the photoresist.

[0084] Examples 19-24 refer to the parameter conditions in Example 15, except that the amount of the composite dispersant is controlled and the parameter conditions for preparing the photoresist are specifically shown in Table 5.

[0085] Comparative Example 17 refers to the parameter conditions in Example 15, except that only fatty alcohol polyoxyethylene ether is used as the dispersant.

[0086] Comparative Example 18 refers to the parameter conditions in Example 15, except that only sodium dodecylbenzene sulfonate is used as the dispersant.

[0087] Comparative Example 19 referred to the parameter conditions in Example 15, with the difference that no composite dispersant was added.

[0088] Comparative Example 20 referred to the parameter conditions in Example 15, with the difference that the ultrasonic treatment time in S2 was 2 h and the stirring time was 8 h; the stirring time in S3 was 4 h.

[0089] Comparative Example 21 referred to the parameter conditions in Example 15, with the difference that the ultrasonic treatment time in S2 was 5 min and the stirring time was 0.5 h; the stirring time in S3 was 10 min.

[0090] Experimental Example 4 Homogeneity Test

[0091] The photoresist was spin-coated on a 6-inch silicon wafer at 1200 rpm for 90 s, and then baked at 120 °C for 5 min. The film thickness at 20 points was measured. The homogeneity = (maximum film thickness - minimum film thickness) / (2 × average film thickness) × 100%. The results are shown in Table 5. The photoresist homogeneities of Example 21 and Comparative Examples 17-21 are as Figure 1 shown.

[0092] Table 5 Parameter Conditions and Homogeneity Tests of Example 15, Examples 19-24 and Comparative Examples 17-21

[0093]

[0094]

[0095] From Table 5 and Figure 1It can be found that in Comparative Examples 17-19, using a single dispersant or not adding a composite dispersant will have an adverse effect on the uniformity of the photoresist, resulting in a decrease in the stability of the photoresist. In the examples, a composite dispersant is added, and the overall uniformity is better. The composite dispersant can reduce the surface tension between the components in the photoresist, enabling the components to be uniformly dispersed in the system. In the photoresist, the composite dispersant molecules will adsorb on the surface of solid particles, forming a protective film that keeps the particles at a certain distance from each other and maintains the dispersed state. In Comparative Examples 20-21, whether the ultrasonic and stirring time is too long or too short will affect the uniformity of the photoresist. If the ultrasonic stirring time is too long, it may damage the components in the photoresist. The high-intensity ultrasonic action may cause the degradation of the polymer, change the chemical structure and properties of the photoresist, and may also lead to too high a temperature in the photoresist system, triggering the premature decomposition of the photoinitiator and reducing the stability of the photoresist. If the ultrasonic stirring time is too short, it is difficult to completely disperse the particle aggregates, and the components cannot be fully mixed, which will result in large-size particle clusters and unevenly distributed regions in the photoresist, affecting the uniformity of the photoresist. During lithography, these non-uniform regions will lead to inconsistent exposure and development effects, and the formed pattern will have defects such as uneven line thickness and holes. In the examples, controlling the ultrasonic and stirring time can make the photoresist have good uniformity. The ultrasonic force can break the agglomeration structure between various particles in the photoresist, dispersing large particles into small particles, which is beneficial to improving the uniformity of the photoresist. The shear force generated during the stirring process can also disperse larger particle aggregates to a certain extent, assisting the ultrasonic dispersion effect, thereby improving the stability of the photoresist.

[0096] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a photoresist without volatile solvents, characterized in that: The preparation method comprises the following steps by weight: S1: adding 40-60 parts of the composite resin into a reaction vessel, slowly adding 5-9 parts of the modified photoinitiator at a rotation speed of 500 rpm, and continuously stirring for 1 h-2 h to form a uniform mixed solution; S2: 1-3 parts of a composite crosslinking agent, 0.5-0.9 parts of a modified curing agent, 0.1-0.5 parts of fluorinated silicone nanoparticles, 0.1-0.3 parts of polyimide microspheres, and 0.2-0.4 parts of a composite dispersant are added one by one to the mixed solution at a rotation speed of 500 rpm, and ultrasonically treated at 20 kHz for 10 min-30 min in an ultrasonic machine, followed by stirring at 800 rpm for 2 h-4 h to obtain a photoresist precursor solution; S3: degassing the photoresist precursor solution, evacuating the reaction container to a vacuum, and slowly stirring at a rotation speed of 50 rpm for 20 min-60 min to eliminate bubbles, and obtaining the photoresist after the treatment.

2. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The preparation method of the composite resin is as follows: 19-24 parts of pentaerythritol triacrylate are added into a three-necked flask, then 8 parts of isobornyl acrylate are slowly added, and at the same time, a stirrer is turned on and a stirring speed is set to 300 rpm, the three-necked flask is placed in a constant temperature water bath, the temperature is controlled at 60°C, and stirring is continued for 90 minutes to obtain a mixture; while stirring, 0.1 parts of p-hydroxyanisole is slowly added into the mixture, and stirring is continued for 60 minutes to obtain the composite resin.

3. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The preparation method of the modified photoinitiator is as follows: 8-12 parts of ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 10 parts of toluene are added into a reaction kettle, and after stirring for 30 minutes, 1 part of ethylenediamine and 0.2 parts of triethylamine are added, the reaction system is heated to 80°C, and the reaction is stirred for 8 hours under the heating condition. After the reaction is completed, the reaction solution is cooled to room temperature, the organic solvent is removed by distillation, and then dried in a vacuum drying oven at 60°C for 12 hours to obtain the modified photoinitiator.

4. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The composite crosslinking agent is prepared by mixing γ-methacryloxypropyltrimethoxysilane and hexamethoxymethylmelamine, and the weight ratio of the γ-methacryloxypropyltrimethoxysilane to the hexamethoxymethylmelamine is 1-5:

1.

5. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The preparation method of the modified curing agent is as follows: 3-7 parts of benzoin dimethyl ether and 20 parts of anhydrous ethanol are placed in a flask, and stirred at room temperature for 30 minutes to form a transparent solution; 2 parts of β-cyclodextrin and 20 parts of deionized water are placed in another flask, and stirred at 60° C. for 40 minutes to form a clear solution; Under the conditions of continuous stirring and 60° C., the transparent solution is slowly added dropwise to the clear solution, and the dropping speed is controlled at 2 drops per second. After the dropping is completed, the reaction is continued to be stirred at 60° C. for 2 h-6 h to obtain a reaction solution; the reaction solution is naturally cooled to room temperature, and then refrigerated and allowed to stand at 4° C. for 12 h; after the standing, the reaction solution is centrifuged at a speed of 4000 rpm for 15 min to separate the precipitate, and the precipitate is washed 5 times with deionized water, and then the precipitate is placed in a vacuum drying oven and dried at 50° C. for 24 h to obtain the modified curing agent.

6. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The preparation method of the fluorinated siloxane nanoparticles is as follows: 1 part of heptadecafluorodecyltrimethoxysilane and 1-5 parts of tetraethyl orthosilicate are mixed, then 10 parts of ethanol are added, and the mixture is stirred for 60 minutes to obtain a mixed solution A; 1 part of a 0.1 mol / L ammonia solution is slowly added dropwise to the mixed solution A, and the mixture is stirred for 2 hours to 4 hours. After the reaction is completed, the mixed solution A is allowed to stand for 2 hours, and then a precipitate is washed out by centrifugation, and the precipitate is vacuum dried at 60° C. for 12 hours to obtain the fluorinated siloxane nanoparticles.

7. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The preparation method of the polyimide microspheres is as follows: dissolving 1-3 parts of pyromellitic anhydride in 5 parts of N,N-dimethylformamide to obtain solution A; dissolving 3 parts of 4,4'-diaminodiphenyl ether in 5 parts of N,N-dimethylformamide to obtain solution B; slowly dropping the solution A into the solution B to form a prepolymer solution; then adding 0.2 parts of sodium dodecyl sulfate to the prepolymer solution, and continuing to stir for 30 minutes to form a stable emulsion; adding 0.1 parts of potassium persulfate to the emulsion, stirring for 1 hour, and reacting at 100°C for 4 hours to 8 hours. After the reaction is completed, the precipitate is centrifuged and washed, and finally dried at 60°C in a vacuum drying oven for 12 hours to obtain the polyimide microspheres.

8. The method for preparing a volatile solvent-free photoresist according to claim 1, characterized in that: The composite dispersant is prepared by mixing fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate, and the weight ratio of the fatty alcohol polyoxyethylene ether to the sodium dodecylbenzene sulfonate is 1-3:

2.

9. A photoresist without volatile solvents, characterized in that: The photoresist is prepared by the preparation method according to any one of claims 1 to 8; the synthetic raw materials of the photoresist include composite resin, modified photoinitiator, composite cross-linking agent, modified curing agent, fluorinated silicone nanoparticles, polyimide microspheres and composite dispersant; The composite resin includes pentaerythritol triacrylate and isobornyl acrylate; The modified photoinitiator includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate and ethylenediamine; The modified curing agent includes benzoin dimethyl ether and β-cyclodextrin; The fluorine-containing siloxane nanoparticles include heptadecafluorodecyltrimethoxysilane and tetraethyl orthosilicate; The polyimide microspheres include pyromellitic anhydride and 4,4'-diaminodiphenyl ether.

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