Cationic two-photon photoresist based on ternary polymer and patterning method thereof

Abstract

This invention discloses a cationic two-photon photoresist based on a ternary polymer and its patterning method. The cationic two-photon photoresist comprises 6-30 wt% of a ternary polymer film-forming resin, 0-9 wt% of an active monomer, 0.5-5 wt% of a photoacid-type initiator, and 65-89.5 wt% of a solvent. The ternary polymer film-forming resin has the structural formula shown in Formula (I), and is synthesized via free radical polymerization using styrene, adamantyl methyl methacrylate (as shown in Formula (II)), and glycidyl methacrylate as reactive monomers, with the addition of an initiator. This invention improves the adhesion and etching resistance of the cationic photoresist by introducing groups such as phenyl, hydroxyl, and adamantane into the polymer, thereby increasing the pattern resolution to meet the requirements of patterned manufacturing. Furthermore, the introduction of small molecule monomers into the photoresist system increases the degree of crosslinking, giving the photoresist stronger mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of photoresist, and particularly relates to a cationic two-photon photoresist and its patterning method. Background Technology

[0002] With the rapid development of the microelectronics industry, photolithography technology is an indispensable and crucial step in the fabrication of large-scale integrated circuits, attracting significant attention due to its strategic importance in economic and defense fields. Photoresist, also known as photoresist, is the core material in the photolithography process and is a type of photosensitive composition. Photoresist generally consists of a photoinitiator, film-forming resin, solvent, and some additives. After exposure to a light source, the photoresist in the exposed area undergoes a photochemical reaction, changing its solubility in the developer to achieve patterning.

[0003] Based on their polymerization mechanism, photoresists can be classified into free radical, cationic, and free radical-cationic hybrid types. Cationic photoresists offer advantages such as oxygen-free polymerization inhibition and low volume shrinkage. They are primarily composed of epoxides and possess high mechanical properties and low curing shrinkage. However, cationic photoresists often use photoacid initiators, which are prone to diffusion during post-exposure baking, leading to reduced resolution and difficulty in obtaining high-resolution patterns. Furthermore, acrylic polymers are commonly used photoresist film-forming resin systems due to their simple synthesis and wide variety. However, their simple linear molecular chain structure results in poor etching resistance, easily damaging the substrate surface during subsequent etching processes. They also exhibit poor adhesion, easily causing high-precision patterns to detach, making it difficult to obtain high-resolution photolithographic patterns.

[0004] Therefore, we provide a cationic two-photon photoresist based on ternary polymers and its patterning method to improve the polymer's etch resistance and adhesion, thereby solving the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a ternary polymer-based cationic two-photon photoresist and its patterning method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a cationic two-photon photoresist based on a ternary polymer, comprising, by weight percentage, 6-30 wt% of a ternary polymer film-forming resin, 0-9 wt% of an active monomer, 0.5-5 wt% of a photoacid initiator and 65-89.5 wt% of a solvent.

[0008] The ternary polymer film-forming resin has the structural formula shown in formula (I). It is synthesized by free radical polymerization using styrene, adamantyl methyl methacrylate (as shown in formula (II)) and glycidyl methacrylate as monomers, with the addition of an initiator. The chemical reaction formula is shown below:

[0009]

[0010] Furthermore, the preparation method of the ternary polymer film-forming resin includes the following steps: styrene, adamantyl methyl methacrylate and glycidyl methacrylate are dissolved in a solvent under an inert gas atmosphere. After all the raw materials are dissolved, an initiator is added, and the mixture is heated to 60-80℃ under stirring for 8-48 hours. After the reaction is completed, the mixture is cooled to room temperature. The solution is added dropwise to a precipitant to remove the solvent and obtain a solid product.

[0011] Furthermore, in the reactive monomers of the ternary polymer film-forming resin, the mass percentage of styrene is 10%-30%, the mass percentage of adamantyl methyl methacrylate is 30%-60%, and the mass percentage of glycidyl methacrylate is 30%-60%.

[0012] Furthermore, when the content of active monomer in the cationic two-photon photoresist is not zero, the active monomer is selected from at least one of the following small molecule compounds containing epoxy groups: bisphenol A diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, and trimethylolpropane triglycidyl ether. Even further, in the ternary polymer-based cationic two-photon photoresist, the mass percentage of the active monomer is 3-9 wt%.

[0013] Furthermore, the photoacid initiator exhibits nonlinear absorption of femtosecond lasers and can initiate two-photon polymerization, specifically selected from at least one of the following: triarylsulfonium hexafluoroantimonate, isopropylphenylcyclopentadiene iron hexafluorophosphate, diphenyliodonium hexafluorophosphate, dialkylbenzoylmethylthiodonium salt, and ferrocene salt.

[0014] Further, the solvent is selected from at least one of the following: propylene glycol methyl ether acetate, toluene, dichloromethane, chloroform, acetone, ethanol, isopropanol, γ-butyrolactone, 2-ethoxyethanol, methyl 3-methoxypropionate, di(ethylene glycol) diethyl ether, and ethylene glycol monomethyl ether.

[0015] Furthermore, the ternary polymer-based cationic two-photon photoresist is made of 6-30 wt% ternary polymer film-forming resin, 3-9 wt% active monomer, 0.5-5 wt% photoacid initiator and 65-89.5 wt% solvent.

[0016] The cationic two-photon photoresist based on ternary polymer described in this invention is simple to prepare. The cationic two-photon photoresist based on ternary polymer can be obtained by mixing the raw material components in proportion and uniformly in a photoluminescence chamber, and filtering (preferably using a filter membrane with a pore size of 0.22-0.45 micrometers) to remove impurities.

[0017] Secondly, the present invention also provides a patterning method for cationic two-photon photoresist based on ternary polymers, comprising the following steps:

[0018] (1) Silicon wafer processing: The silicon wafer is cleaned to improve the uniformity of photoresist distribution and prevent the formation of voids;

[0019] (2) Spin coating: Cationic two-photon photoresist based on ternary polymer is dropped onto a spin coating substrate and a photoresist film is obtained by spin coating using a spin coater;

[0020] (3) Soft baking: The photoresist film obtained in step (2) is placed on a baking device for baking;

[0021] (4) Writing: The photoresist is exposed using a femtosecond laser direct writing device;

[0022] (5) Post-baking: The exposed film is baked on a drying equipment;

[0023] (6) Development: The photoresist is immersed in the developing solution to develop and obtain the photolithographic pattern.

[0024] Further, the cleaning process in step (1) is carried out as follows: the silicon wafer is cleaned with acetone or isopropanol, heated and dried, and then treated with a plasma cleaner for a certain period of time.

[0025] Further, the spin coating in step (2) is carried out as follows: first spin coating at a low rotation speed of 500-1000 rpm for 5-20 s, and then spin coating at a high rotation speed of 2000-5000 rpm for 30-60 s to control the thickness of the photoresist film.

[0026] Further, in step (3), the silicon wafer coated with photoresist wet film is placed on a baking device and heated to 70-95°C for 40-60 seconds.

[0027] Furthermore, in step (4), the wavelength of the femtosecond laser is between 500-800nm, the power of the femtosecond laser is 1-30mW, and the writing speed is 0.1-100mm / s.

[0028] Furthermore, in step (5), the exposed photoresist film is heated to 90-105°C on a baking device, and the holding time of the temperature is determined according to the required photoresist thickness.

[0029] Further, in step (6), the developing solution is selected from one or more of propylene glycol methyl ether acetate, acetone, N-methylpyrrolidone, ethanol and isopropanol, and the developing time is 1-10 min.

[0030] Compared with existing technologies, the advantages of this invention are as follows: This invention utilizes free radical polymerization to synthesize ternary polymer film-forming resins, which has the advantages of simple synthesis and high yield; by introducing groups such as phenyl, hydroxyl, and adamantane into the polymer, it is beneficial to improve the adhesion and etching resistance of cationic photoresists, and can improve the resolution of patterns to meet the needs of patterned manufacturing. In addition, the introduction of small molecule monomers into the photoresist system increases the degree of crosslinking, giving the photoresist stronger mechanical properties. Attached Figure Description

[0031] Figure 1 This is a SEM image of the line obtained by photoresist femtosecond laser direct writing photoresist processing according to Embodiment 4 of the present invention;

[0032] Figure 2 This is a SEM image of the lines obtained by photoresist femtosecond laser direct writing photoresist processing according to Embodiment 5 of the present invention;

[0033] Figure 3 This is a SEM image of the lines obtained by photoresist femtosecond laser direct writing photoresist processing according to Embodiment 6 of the present invention;

[0034] Figure 4 This is a SEM image of the line obtained by photoresist femtosecond laser direct writing photoresist processing according to Embodiment 7 of the present invention;

[0035] Figure 5 This is a SEM image obtained from the photoresist femtosecond laser direct writing photoresist processing according to Comparative Example 1 of the present invention.

[0036] Figure 6 This is a schematic diagram of the femtosecond laser direct writing device used in an embodiment of the present invention, wherein 1-femtosecond laser, 2-galvanometer, 3-objective lens, 4-displacement stage, and 5-photoresist. Detailed Implementation

[0037] The present invention will be further illustrated below with examples. The specific details described in the following embodiments are illustrative rather than restrictive, and will help those skilled in the art to further understand the present invention, but should not be construed as limiting the invention in any way. It should be noted that those skilled in the art can make some adjustments and improvements without departing from the basic concept and method of the present invention.

[0038] A schematic diagram of the femtosecond laser direct writing device used in this embodiment of the invention is shown below. Figure 6As shown, unless specific conditions are specified in the examples, they should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified can be purchased by those skilled in the art through conventional technical means or commercial channels.

[0039] Example 1

[0040] The preparation of a ternary polymer film-forming resin includes the following steps:

[0041] Under a nitrogen atmosphere, 2 g of styrene, 2.27 g of 3-hydroxy-1-adamantyl methacrylate and 2.73 g of glycidyl methacrylate were dissolved in 35 mL of N,N-dimethylformamide solvent. After all the raw materials were dissolved, 0.23 g of benzoyl peroxide initiator was added, and the mixture was stirred and heated to 80 °C for 8 h. After the reaction was completed, the mixture was cooled to room temperature. The solution was added dropwise to ethanol, and the solvent was removed by filtration to obtain a white powdery solid product.

[0042] Example 2

[0043] The preparation of a ternary polymer film-forming resin includes the following steps:

[0044] Under a nitrogen atmosphere, 1 g of styrene, 4.54 g of 3-hydroxy-1-adamantyl methacrylate and 2.73 g of glycidyl methacrylate were dissolved in 40 mL of acetonitrile. After all the raw materials were dissolved, 0.27 g of benzoyl peroxide initiator was added, and the mixture was stirred and heated to 60 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature. The solution was added dropwise to diethyl ether, and the solvent was removed by filtration to obtain a white powdery solid product.

[0045] Example 3

[0046] The preparation of a ternary polymer film-forming resin includes the following steps:

[0047] Under a nitrogen atmosphere, 1 g of styrene, 2.27 g of 3-hydroxy-1-adamantyl methacrylate and 4.10 g of glycidyl methacrylate were dissolved in 35 mL of acetonitrile. After all the raw materials were dissolved, 0.24 g of benzoyl peroxide initiator was added, and the mixture was stirred and heated to 60 °C for 48 h. After the reaction was completed, the mixture was cooled to room temperature. The solution was added dropwise to methanol, and the solvent was removed by filtration to obtain a white powdery solid product.

[0048] Example 4

[0049] A cationic two-photon photoresist based on a ternary polymer and its patterning method, comprising the following steps:

[0050] First, 0.3g of ternary polymer film-forming resin (Example 3), 0.05g of photoacid initiator triarylsulfonium hexafluoroantimonate and 0.65g of propylene glycol methyl ether acetate were mixed evenly in a photoluminescence chamber. Then, impurities were removed by filtration through a filter membrane with a pore size of 0.22 micrometers to obtain a ternary polymer-based cationic two-photon photoresist.

[0051] After cleaning the silicon wafer with isopropanol or acetone solution, it was heat-treated at 120℃ for 5 min, followed by plasma cleaning for 10 min to obtain the treated silicon wafer. A ternary polymer-based cationic two-photon photoresist was dropped onto the treated silicon substrate and spin-coated using a spin coater at 500 rpm for 20 s and 5000 rpm for 30 s to obtain a photoresist film. The obtained film was then soft-baked at 95℃ for 40 s. The photoresist was then exposed using a 532 nm femtosecond laser direct writing device with a femtosecond laser power of 20 mW and a writing speed of 10 mm / s. The exposed film was then baked at 105℃ for 60 s. Finally, it was immersed in propylene glycol methyl ether acetate developer for 5 min, then transferred to ethanol for 5 min, and allowed to dry to obtain the photolithographic pattern. The results show that the limiting precision of this photoresist formulation is 240 nm.

[0052] Example 5

[0053] A cationic two-photon photoresist based on a ternary polymer and its patterning method, comprising the following steps:

[0054] First, 0.07g of ternary polymer film-forming resin (Example 2), 0.03g of bisphenol A diglycidyl ether, 0.005g of photoacid initiator triarylsulfonium hexafluoroantimonate and 0.895g of acetone were mixed evenly in a photoluminescence chamber. Then, impurities were removed by filtration through a filter membrane with a pore size of 0.45 micrometers to obtain a ternary polymer-based cationic two-photon photoresist.

[0055] After cleaning the silicon wafer with isopropanol or acetone solution, it was heat-treated at 120℃ for 5 min, followed by plasma cleaning for 10 min to obtain the treated silicon wafer. A ternary polymer-based cationic two-photon photoresist was dropped onto the treated silicon substrate and spin-coated using a spin coater at 1000 rpm for 5 s and 2000 rpm for 60 s to obtain a photoresist film. The obtained film was then soft-baked at 90℃ for 60 s. The photoresist was then exposed using a 532 nm femtosecond laser direct writing device with a femtosecond laser power of 20 mW and a writing speed of 10 mm / s. The exposed film was then baked at 105℃ for 45 s. Finally, it was immersed in N-methylpyrrolidone developer for 1 min and allowed to dry to obtain the photolithographic pattern. The results show that the limiting precision of this photoresist formulation is 165 nm.

[0056] Example 6

[0057] A cationic two-photon photoresist based on a ternary polymer and its patterning method, comprising the following steps:

[0058] First, 0.1g of ternary polymer film-forming resin (Example 2), 0.09g of trimethylolpropane triglycidyl ether, 0.02g of photoacid initiator diphenyliodonium hexafluorophosphate and 0.79g of toluene were mixed evenly in a photoluminescence chamber. Then, impurities were removed by filtration through a filter membrane with a pore size of 0.22 micrometers to obtain a ternary polymer-based cationic two-photon photoresist.

[0059] After cleaning the silicon wafer with isopropanol or acetone solution, it was heat-treated at 120℃ for 5 min, followed by plasma cleaning for 10 min to obtain the treated silicon wafer. A ternary polymer-based cationic two-photon photoresist was dropped onto the treated silicon substrate and spin-coated using a spin coater at 1000 rpm for 10 s and 3000 rpm for 40 s to obtain a photoresist film. The obtained film was then soft-baked at 70℃ for 45 s. The photoresist was then exposed using a 532 nm femtosecond laser direct writing device with a femtosecond laser power of 20 mW and a writing speed of 10 mm / s. The exposed film was then baked at 95℃ for 60 s. After immersion in acetone developer for 2 min, it was transferred to isopropanol for 1 min and allowed to dry to obtain the photolithographic pattern. The results show that the limiting precision of this photoresist formulation is 190 nm.

[0060] Example 7

[0061] A cationic two-photon photoresist based on a ternary polymer and its patterning method, comprising the following steps:

[0062] First, 0.06g of ternary polymer film-forming resin (Example 1), 0.04g of resorcinol diglycidyl ether, 0.01g of photoacid initiator dialkylbenzoyl methyl thioonium salt and 0.89g of di(ethylene glycol) diethyl ether were mixed evenly in a photoluminescence chamber. Then, impurities were removed by filtration through a filter membrane with a pore size of 0.22 micrometers to obtain a ternary polymer-based cationic two-photon photoresist.

[0063] After cleaning the silicon wafer with isopropanol or acetone solution, it was heat-treated at 120℃ for 5 min, followed by plasma cleaning for 10 min to obtain the treated silicon wafer. A ternary polymer-based cationic two-photon photoresist was dropped onto the treated silicon substrate and spin-coated using a spin coater at 800 rpm for 10 s and 3000 rpm for 40 s to obtain a photoresist film. The obtained film was then soft-baked at 90℃ for 60 s. The photoresist was then exposed using a 532 nm femtosecond laser direct writing device with a femtosecond laser power of 20 mW and a writing speed of 10 mm / s. The exposed film was then baked at 105℃ for 45 s. Finally, it was immersed in propylene glycol methyl ether acetate developer for 3 min, then transferred to isopropanol for 2 min, and allowed to dry to obtain the photolithographic pattern. The results show that the limiting precision of this photoresist formulation is 210 nm.

[0064] Comparative Example 1

[0065] To demonstrate the advantages of this invention, a comparative experiment was conducted using commonly used epoxy-type cationic two-photon photoresists. The photoresist and its patterning method include the following steps: First, the silicon wafer is cleaned with isopropanol or acetone solution, then heat-treated at 120°C for 5 minutes, followed by plasma cleaning for 10 minutes to obtain the treated silicon wafer. In a photolithography chamber, photoresist SU82000.5 is dropped onto the treated silicon substrate, and a spin coater is used to obtain a photoresist film by rotating at 1000 rpm for 5 seconds and then at 2000 rpm for 60 seconds. The obtained film is then placed on a baking device for soft baking at 90°C for 60 seconds. The photoresist is then exposed using a 532nm femtosecond laser direct writing device with a femtosecond laser power of 20mW and a writing speed of 10mm / s. Next, the exposed film is baked on a baking device at 105°C for 45 seconds. Finally, the film is immersed in propylene glycol methyl ether acetate developer for 3 minutes, then transferred to isopropanol for 2 minutes, and allowed to dry to obtain the photolithographic pattern. The results show that the limiting precision of this photoresist formulation is 630 nm.

[0066] Therefore, it can be seen that the commonly used epoxy-type cationic two-photon photoresist SU82000.5 (Comparative Example 1) has a processing precision of 630nm, and from the attached... Figure 5It can be observed that the lines exhibit significant distortion and detachment, indicating poor adhesion. In contrast, the lines processed by the ternary polymer-based cationic two-photon photoresist provided by this invention exhibit high quality and strong adhesion. With increasing adamantyl methyl methacrylate content, adhesion increases and processing precision improves (Examples 5 and 7). Furthermore, the lines obtained from the ternary polymer photoresist alone show slight distortion (Example 4), while the introduction of small molecule epoxy groups increases the mechanical strength of the lines, resulting in more regular lines. This demonstrates that the ternary polymer-based two-photon photoresist provided by this invention has significant advantages over traditional photoresists.

Claims

1. A cationic three-component polymer-based two-photon photoresist, characterized in that: By mass percentage, it contains 6-30 wt% ternary polymer film-forming resin, 0-9 wt% active monomer, 0.5-5 wt% photoacid initiator and 65-89.5 wt% solvent; The ternary polymer film-forming resin has the structural formula shown in formula (I). It uses styrene, adamantyl methyl methacrylate (as shown in formula (II), and glycidyl methacrylate) as reacting monomers. In the reacting monomers of the ternary polymer film-forming resin, the mass percentage of styrene is 10%-30%, the mass percentage of adamantyl methyl methacrylate is 30%-60%, and the mass percentage of glycidyl methacrylate is 30%-60%. It is synthesized by adding an initiator through free radical polymerization. The chemical reaction formula is shown below: (II) (I).

2. The cationic two-photon photoresist according to claim 1, wherein: The preparation method of the ternary polymer film-forming resin includes the following steps: under an inert gas atmosphere, styrene, adamantyl methyl methacrylate and glycidyl methacrylate are dissolved in a solvent. After all the raw materials are dissolved, an initiator is added, and the mixture is heated to 60-80℃ under stirring for 8-48 h. After the reaction is completed, the mixture is cooled to room temperature. The reaction solution is added dropwise to a precipitant, the solvent is removed, and a solid product is obtained, which is the ternary polymer film-forming resin.

3. The cationic two-photon photoresist as described in claim 1, characterized in that: When the content of active monomer in the cationic two-photon photoresist is not 0, the active monomer is selected from at least one of the following small molecule compounds containing epoxy groups: bisphenol A diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, and trimethylolpropane triglycidyl ether.

4. The cationic two-photon photoresist as described in claim 3, characterized in that: In the ternary polymer-based cationic two-photon photoresist, the active monomer has a mass percentage content of 3-9 wt%.

5. The cationic two-photon photoresist as described in claim 1, characterized in that: The photoacid initiator is selected from at least one of the following: triarylsulfonium hexafluoroantimonate, isopropylphenylcyclopentadiene iron hexafluorophosphate, diphenyliodonium hexafluorophosphate, dialkylbenzoylmethylthiodonium salt, and ferrocene salt.

6. The cationic two-photon photoresist as described in claim 1, characterized in that: The solvent is selected from at least one of the following: propylene glycol methyl ether acetate, toluene, dichloromethane, chloroform, acetone, ethanol, isopropanol, γ-butyrolactone, 2-ethoxyethanol, methyl 3-methoxypropionate, di(ethylene glycol) diethyl ether, and ethylene glycol monomethyl ether.

7. The cationic two-photon photoresist as described in claim 4, characterized in that: The ternary polymer-based cationic two-photon photoresist is made of 6-30 wt% ternary polymer film-forming resin, 3-9 wt% active monomer, 0.5-5 wt% photoacid initiator and 65-89.5 wt% solvent.

8. A patterning method for a ternary polymer-based cationic two-photon photoresist as described in claim 1, comprising the following steps: (1) Silicon wafer processing: Cleaning the silicon wafers; (2) Spin coating: The cationic two-photon photoresist based on ternary polymer as described in claim 1 is dropped onto a spin coating substrate, and a photoresist film is obtained by spin coating using a spin coater; (3) Soft baking: Place the photoresist film obtained in step (2) on a baking device for baking; (4) Writing: The photoresist is exposed using a femtosecond laser direct writing device; (5) Post-baking: The exposed film is baked on a baking device; (6) Development: Immerse the photoresist in the developing solution to develop it and obtain the photolithographic pattern.

9. The patterning method as described in claim 8, characterized in that: In step (4), the wavelength of the femtosecond laser is between 500-800nm, the power of the femtosecond laser is 1-30mW, and the writing speed is 0.1-100mm / s; In step (6), the developing solution is selected from one or more of propylene glycol methyl ether acetate, acetone, N-methylpyrrolidone, ethanol and isopropanol, and the developing time is 1-10 min.

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