Acrylic resin positive photoresist as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of manufacturing of polymer materials and semiconductor chemicals, and particularly relates to an acrylic resin positive photoresist as well as a preparation method and application thereof. The preparation method comprises the following steps: dropwise adding an intermediate polymerization raw material consisting of methyl methacrylate, styrene, acrylic acid, hydroxyethyl methylacrylate, n-butyl acrylate and an initiator DTBP into a reaction kettle containing an organic solvent A, and reacting at 155-165 DEG C under closed conditions to obtain an acrylic resin intermediate A; then carrying out catalytic grafting reaction on the acrylic resin A and isocyano ethyl methacrylate to obtain acrylic resin B; and uniformly mixing the acrylic resin B with a photoacid generator, a photobase generator, an epoxy silane coupling agent and an organic solvent B to obtain the acrylic resin positive photoresist. By improving the preparation process of the acrylic resin and introducing the isocyano ethyl methacrylate grafted monomer, the sensitivity and resolution of the obtained photoresist can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and semiconductor chemical manufacturing technology, specifically relating to an acrylic resin positive photoresist, its preparation method, and its application. Background Technology

[0002] Existing high-resolution positive photoresists (minimum linewidth / line spacing (L / S) below 10μm / 10μm) are generally manufactured using linear phenolic resins combined with photoacid-generating agents. Linear phenolic resins require a narrow molecular weight distribution and low metal impurity content. Therefore, the source of the matrix resin required for high-precision photoresists is limited. It is necessary to develop a high-precision photoresist system that departs from this approach. Acrylic resins are characterized by fast drying and good chemical corrosion resistance. The main application of acrylic resins is as coating resins, which has low added value. Utilizing the characteristics of acrylic resins, developing a high-resolution positive photoresist based on acrylic resin has broad market prospects and economic significance.

[0003] To manufacture high-resolution positive photoresists using acrylic resins, the following issues need to be addressed:

[0004] 1. To manufacture resins with a narrow molecular weight distribution, it is best to control the molecular weight distribution index (weight-average molecular weight M(w) / number-average molecular weight M(n)) D≤1.3, and the number-average molecular weight is optimally in the range of 10000±2000.

[0005] 2. The resin film must have post-crosslinking groups after it is formed, so that it can be post-crosslinked and resistant to chemical corrosion.

[0006] 3. The resin must contain an appropriate amount of carboxyl groups to participate in exposure and development.

[0007] 4. The resin should have good adhesion to the substrate and be able to pass the cross-cut adhesion test (ASTM D3359). Summary of the Invention

[0008] To address the aforementioned technical problems, the primary objective of this invention is to provide a method for preparing positive acrylic resin photoresist.

[0009] Another object of the present invention is to provide an acrylic resin positive photoresist prepared by the above method.

[0010] Another object of the present invention is to provide the application of the above-mentioned acrylic resin positive photoresist in semiconductor photolithography.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing an acrylic resin positive photoresist includes the following preparation steps:

[0013] (1) Methyl methacrylate, styrene, acrylic acid, hydroxyethyl methacrylate and n-butyl acrylate are mixed with the initiator di-tert-butyl peroxide (DTBP) to obtain intermediate polymerization raw materials;

[0014] (2) Add organic solvent A to the reaction vessel after nitrogen purging, heat to 155~165℃ under sealed conditions, then add intermediate polymerization raw material dropwise and keep warm while stirring to react. Control the dropwise addition time to 3~4h. After the dropwise addition is complete, add initiator DTBP and continue to keep warm for 1~3h. After the reaction is complete, cool down to obtain acrylic resin intermediate A.

[0015] (3) The mixture of acrylic resin intermediate A, isocyanate methacrylate, organic bismuth catalyst and polymerization inhibitor is heated to 60~80℃ and kept at the temperature until the mass percentage of NCO group is less than 0.03%. The mixture is then cooled and discharged to obtain acrylic resin B.

[0016] (4) Mix acrylic resin B with photoacid generator, photoalkali generator, epoxy silane coupling agent (KH560) and organic solvent B evenly to obtain acrylic resin positive photoresist.

[0017] Further, the mass ratio of methyl methacrylate, styrene, acrylic acid, hydroxyethyl methacrylate and n-butyl acrylate in step (1) is (75~85):(35~45):(15~25):(5~15):(45~55).

[0018] Under the above monomer ratio, the resulting photoresist can simultaneously achieve good resolution, corrosion resistance and adhesion.

[0019] Furthermore, the amount of DTBP used in step (1) is 1 to 3% of the mass of the intermediate polymerization raw material.

[0020] Furthermore, the organic solvent A mentioned in step (2) is xylene, and the amount of organic solvent A is 4 to 6 times the mass of the intermediate polymerization raw material.

[0021] Furthermore, the amount of DTBP initiator added in step (2) is 0.05 to 0.2% of the mass of the intermediate polymerization raw material.

[0022] Furthermore, the amount of isocyanate methacrylate used in step (3) is 20-35% of the mass of the intermediate polymerization raw materials.

[0023] This invention introduces isocyanate methacrylate monomers that can react with isocyanate methacrylate in acrylic resin intermediate A, introducing highly polar urethane groups that can effectively inhibit acid diffusion. Under the action of photoacid-generating agents, this significantly increases the polymer polarity in the exposed area and neutralizes and "captures" excess acid that diffuses into the unexposed area, thereby enhancing the solubility difference between the exposed and unexposed areas, sharpening the pattern, and ultimately improving the sensitivity and resolution of the photoresist.

[0024] Furthermore, the organic bismuth catalyst mentioned in step (3) is a conventional organic bismuth catalyst for polyurethane reaction, such as bismuth naphthenate, bismuth isooctanoate, bismuth laurate, etc., and its mass concentration in the mixed system is 0.005%~0.02%.

[0025] Further, the polymerization inhibitor mentioned in step (3) is p-hydroxyanisole, and the mass concentration of the polymerization inhibitor in the mixed system is 0.01%~0.02%.

[0026] Further, the photoacid-producing agent in step (4) is diazonaphthoquinone (DNQ), and the photoalkali-producing agent is a cobalt-amine complex or a carbamate.

[0027] Furthermore, the epoxy silane coupling agent described in step (4) serves to improve adhesion and, in the post-baking stage after exposure and development, to increase etching resistance through organosilicon crosslinking.

[0028] Further, the organic solvent B mentioned in step (4) is a mixed solvent of propylene glycol methyl ether acetate and isopropanol.

[0029] Furthermore, the mass fraction of each material in step (4) is as follows:

[0030] Acrylic resin B 400~600 parts, photoacid generator 4~6 parts, photoalkali generator 0.1~0.3 parts, epoxy silane coupling agent 5~15 parts, organic solvent B 80~120 parts.

[0031] An acrylic resin positive photoresist is prepared by the above method.

[0032] The above-mentioned positive acrylic photoresist is used in semiconductor photolithography. The application method is as follows: the prepared positive acrylic photoresist is coated on the substrate, baked and cured at 80~100℃, exposed to light with a wavelength of 395nm, developed with sodium carbonate aqueous solution, and after development, the substrate is baked and cured at 140~160℃, and then etched.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] (1) By controlling the copolymerization of acrylic monomers using high temperature and high pressure, and by synthesizing acrylic resin using the starvation drop method, the final product solid content is controlled at around 20%, avoiding the widening of molecular weight distribution caused by bimolecular termination. This effectively controls the molecular weight distribution index D≤1.3 and the number average molecular weight of the product in the range of 10000±2000. This significantly improves its resolution as a positive photoresist.

[0035] (2) By introducing isocyanate methacrylate monomer, it can react directionally with isocyanate methacrylate in acrylic resin intermediate A, and introduce urethane groups with strong polarity and effective ability to inhibit acid diffusion. Under the action of photoacid generator, the polymer polarity of the exposed area is significantly improved, and the excess acid diffused into the non-exposed area can be neutralized and "captured", thereby enhancing the solubility difference between the exposed and unexposed areas, sharpening the pattern, and ultimately improving the sensitivity and resolution of the photoresist.

[0036] (3) Adhesion is improved by using epoxy silane coupling agent, and etching resistance is increased by cross-linking with organosilicon during the post-baking stage after exposure and development. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0038] Example 1

[0039] A method for preparing an acrylic resin positive photoresist includes the following preparation steps:

[0040] (1) Mix 80g methyl methacrylate, 40g styrene, 20g acrylic acid, 10g hydroxyethyl methacrylate and 50g n-butyl acrylate with 4g initiator di-tert-butyl peroxide (DTBP) to obtain intermediate polymerization raw materials.

[0041] (2) Add 1000g of xylene to the reaction vessel after nitrogen purging. Under sealed conditions, heat to 160℃ and pressure inside the vessel to about 300kPa. Then, use a special pressure pump to drop the intermediate polymerization raw material into the reaction vessel and keep it warm while stirring. Control the dropping time to 3.5h. After the dropping is completed, add 0.2g of initiator DTBP and continue to keep it warm for 2h. After the reaction is completed, cool down to 80℃ to obtain acrylic resin intermediate A.

[0042] (3) The mixture of acrylic resin intermediate A, 59.6 g of isocyanate methacrylate, 0.1 g of organobismuth catalyst, and 0.2 g of p-hydroxyanisole was heated to 70 °C and reacted for 5 h until the mass percentage of NCO groups was less than 0.03%. The mixture was then cooled and discharged to obtain acrylic resin B. The number average molecular weight of the obtained acrylic resin B was 10,500, and the molecular weight distribution index D = 1.17.

[0043] (4) Take 500g of acrylic resin B, 5g of photoacid generator DNQ, 0.2g of photoalkali generator cobalt hexamine nitrate complex, 10g of epoxy silane coupling agent (KH560), 50g of propylene glycol methyl ether acetate, and 50g of isopropanol and mix them evenly. Note that the operation should be carried out under yellow light conditions and avoid sunlight exposure to obtain positive acrylic resin photoresist. The obtained positive acrylic resin photoresist has an adhesion grade of 5B after a cross-cut adhesion test.

[0044] The application method of the acrylic resin positive photoresist obtained in this embodiment is as follows:

[0045] The prepared photoresist was coated onto a 0.1 mm thick substrate, with the coating thickness controlled at 3 μm. After coating, it was baked at 90 °C for 30 min, then exposed to light with a wavelength of 395 nm, and developed with a 1% sodium carbonate aqueous solution. After development, the substrate was baked at 150 °C for 40 min, and then etched.

[0046] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 56 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 1.8μm / 1.8μm.

[0047] Example 2

[0048] A method for preparing an acrylic resin positive photoresist includes the following preparation steps:

[0049] (1) Mix 75g methyl methacrylate, 35g styrene, 15g acrylic acid, 5g hydroxyethyl methacrylate and 45g n-butyl acrylate with 3g initiator di-tert-butyl peroxide (DTBP) to obtain intermediate polymerization raw materials.

[0050] (2) Add 1000g of xylene to the reaction vessel after nitrogen purging. Under sealed conditions, heat to 155℃ and pressure inside the vessel to about 260kPa. Then, use a special pressure pump to drop the intermediate polymerization raw material into the reaction vessel and keep it warm while stirring. Control the dropping time to 3h. After the dropping is completed, add 0.15g of initiator DTBP and continue to keep it warm for 2h. After the reaction is completed, cool down to 80℃ to obtain acrylic resin intermediate A.

[0051] (3) The mixture of acrylic resin intermediate A, 36g of isocyanate methacrylate, 0.1g of organobismuth catalyst, and 0.2g of p-hydroxyanisole was heated to 60°C and reacted for 5h until the NCO group mass percentage was less than 0.03%. The mixture was then cooled and discharged to obtain acrylic resin B. The number average molecular weight of the obtained acrylic resin B was 9600, and the molecular weight distribution index D=1.24.

[0052] (4) Take 400g of acrylic resin B, 4g of photoacid generator DNQ, 0.1g of photoalkali generator cobalt hexamine nitrate complex, 5g of epoxy silane coupling agent (KH560), 50g of propylene glycol methyl ether acetate, and 50g of isopropanol and mix them evenly. Note that the operation should be carried out under yellow light conditions and avoid sunlight exposure to obtain positive acrylic resin photoresist. The obtained positive acrylic resin photoresist has an adhesion grade of 5B after a cross-cut adhesion test.

[0053] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 68 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 2.1μm / 2.1μm.

[0054] Example 3

[0055] A method for preparing an acrylic resin positive photoresist includes the following preparation steps:

[0056] (1) Mix 85g of methyl methacrylate, 45g of styrene, 25g of acrylic acid, 15g of hydroxyethyl methacrylate and 55g of n-butyl acrylate with 5g of initiator di-tert-butyl peroxide (DTBP) to obtain intermediate polymerization raw materials.

[0057] (2) Add 1000g of xylene to the reaction vessel after nitrogen purging. Under sealed conditions, heat to 165℃ and pressure inside the vessel to about 350kPa. Then, use a special pressure pump to drop the intermediate polymerization raw material into the reaction vessel and keep it warm while stirring. Control the dropping time to 4h. After the dropping is completed, add 0.25g of initiator DTBP and continue to keep it warm for 2h. After the reaction is completed, cool down to 80℃ to obtain acrylic resin intermediate A.

[0058] (3) The mixture of acrylic resin intermediate A, 75g of isocyanate methacrylate, 0.1g of organobismuth catalyst, and 0.2g of p-hydroxyanisole was heated to 80°C and reacted for 5 hours until the mass percentage of NCO groups was less than 0.03%. The mixture was then cooled and discharged to obtain acrylic resin B. The number average molecular weight of the obtained acrylic resin B was 11200, and the molecular weight distribution index D = 1.12.

[0059] (4) Take 600g of acrylic resin B, 6g of photoacid generator DNQ, 0.2g of photoalkali generator cobalt hexamine nitrate complex, 15g of epoxy silane coupling agent (KH560), 50g of propylene glycol methyl ether acetate, and 50g of isopropanol and mix them evenly. Note that the operation should be carried out under yellow light conditions and avoid sunlight exposure to obtain positive acrylic resin photoresist. The obtained positive acrylic resin photoresist has an adhesion grade of 5B after a cross-cut adhesion test.

[0060] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 42 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 2.5μm / 2.5μm.

[0061] Comparative Example 1

[0062] A method for preparing an acrylic resin positive photoresist, compared with Example 1, the reaction in step (2) is carried out under normal pressure (about 100 kPa) and reflux at 140°C, and the rest is the same.

[0063] The obtained acrylic resin B had a number-average molecular weight of 8350 and a molecular weight distribution index D of 1.57.

[0064] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 85 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 5.4μm / 5.4μm.

[0065] The results of this comparative example show that the present invention can significantly reduce the molecular weight distribution index of the obtained acrylic resin and significantly improve the sensitivity and resolution of the obtained positive photoresist by using high temperature and high pressure reaction conditions.

[0066] Comparative Example 2

[0067] A method for preparing an acrylic resin positive photoresist, compared with Example 1, step (2) of the reaction is replaced by adding intermediate polymer raw materials at once and stirring for 3.5h while keeping the reaction at a constant temperature. The rest is the same.

[0068] The obtained acrylic resin B had a number-average molecular weight of 11,800 and a molecular weight distribution index D of 1.72.

[0069] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 104 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 7.0μm / 7.0μm.

[0070] The results of this comparative example show that the starvation drop method used in this invention to synthesize acrylic resin can significantly reduce the molecular weight distribution index of the obtained acrylic resin and significantly improve the sensitivity and resolution of the obtained positive photoresist.

[0071] Comparative Example 3

[0072] A method for preparing an acrylic resin positive photoresist, compared with Example 1, the amount of xylene solvent added in step (2) is reduced to 600g, and the rest are the same.

[0073] The obtained acrylic resin B had a number-average molecular weight of 19,300 and a molecular weight distribution index D of 1.45.

[0074] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 76 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 4.4μm / 4.4μm.

[0075] The results of this comparative example show that by controlling the concentration of the polymerizable monomer in a low range (below 20%), the present invention can significantly reduce the molecular weight and molecular weight distribution index of the obtained acrylic resin, and significantly improve the sensitivity and resolution of the obtained positive photoresist.

[0076] Comparative Example 4

[0077] A method for preparing an acrylic resin positive photoresist, compared with Example 1, lacks step (3) of the reaction process with isocyanate methacrylate, and specifically includes the following preparation steps:

[0078] Steps (1) and (2) are the same as in Example 1. The number average molecular weight of the obtained acrylic resin intermediate A is 10200 and the molecular weight distribution index D=1.16.

[0079] (3) Take 500g of acrylic resin intermediate A, 5g of photoacid generator DNQ, 0.2g of photoalkali generator cobalt hexamine nitrate complex, 10g of epoxy silane coupling agent (KH560), 50g of propylene glycol methyl ether acetate, and 50g of isopropanol and mix them evenly. Note that the operation should be carried out under yellow light conditions and avoid sunlight exposure to obtain positive acrylic resin photoresist. The obtained positive acrylic resin photoresist has an adhesion grade of 5B after cross-cut adhesion test.

[0080] The minimum exposure energy of the obtained acrylic resin positive photoresist, as determined by sensitivity testing (no photoresist residue after full-page exposure and development), is 120 mJ / cm². 2 The minimum line width / line spacing (L / S) of the resolution test results is 10.5μm / 10.5μm.

[0081] The results of this comparative example show that the grafting reaction between isocyanate methacrylate monomer and acrylic resin intermediate A introduced in this invention can significantly improve the sensitivity and resolution of the resulting acrylic resin positive photoresist.

[0082] Comparative Example 5

[0083] A method for preparing an acrylic resin positive photoresist, which is the same as in Example 1 except that an epoxy silane coupling agent (KH560) is not added.

[0084] The resulting acrylic resin positive photoresist showed an adhesion grade of 4B in the cross-cut adhesion test.

[0085] The results of this comparative example show that the introduction of epoxy silane coupling agent in this invention can significantly improve adhesion.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an acrylic resin positive photoresist, characterized by: The preparation steps include: (1) methyl methacrylate, styrene, acrylic acid, hydroxyethyl methacrylate and n-butyl acrylate are stirred and mixed with initiator DTBP to obtain intermediate polymer raw material; (2) organic solvent A is added to the reaction kettle after nitrogen replacement, and the temperature is raised to 155-165℃ under closed condition, then the intermediate polymer raw material is added dropwise and stirred, the dropwise time is controlled for 3-4h, after the dropwise addition is completed, the initiator DTBP is added and the reaction is continued for 1-3h, and then the reaction is completed, and the temperature is lowered to obtain acrylic resin intermediate A; (3) the mixture of acrylic resin intermediate A, isocyanatoethyl methacrylate, organic bismuth catalyst and polymerization inhibitor is heated to 60-80℃, and the reaction is continued until the mass percentage of NCO group is less than 0.03%, then the temperature is lowered to obtain acrylic resin B; (4) acrylic resin B is mixed with photoacid generator, photoalkali generator, epoxy silane coupling agent and organic solvent B to obtain acrylic resin positive photoresist.

2. The method of claim 1, wherein the method is characterized by: The mass ratio of methyl methacrylate, styrene, acrylic acid, hydroxyethyl methacrylate and n-butyl acrylate in step (1) is (75-85):(35-45):(15-25):(5-15):(45-55).

3. The method for preparing an acrylic resin positive photoresist according to claim 1, characterized in that: The organic solvent A in step (2) is xylene, and the amount of organic solvent A is 4-6 times the mass of the intermediate polymer raw material.

4. The method of claim 1, wherein the method is characterized by: The amount of isocyanatoethyl methacrylate in step (3) is 20-35% of the mass of the intermediate polymer raw material.

5. The method of claim 1, wherein the method is characterized by: The organic bismuth catalyst in step (3) is naphthenic acid bismuth, isooctanoic acid bismuth or lauric acid bismuth, and the mass concentration of the catalyst in the mixed system is 0.005%-0.02%; the polymerization inhibitor is p-hydroxyanisole, and the mass concentration of the polymerization inhibitor in the mixed system is 0.01%-0.02%.

6. The method of claim 1, wherein the method is characterized by: The photoacid generator in step (4) is diazonium naphthoquinone, and the photoalkali generator is cobalt ammine complex or carbamate.

7. The method of claim 1, wherein the method is characterized by: The organic solvent B in step (4) is a mixed solvent of propylene glycol methyl ether acetate and isopropyl alcohol.

8. The method of claim 1, wherein the method is characterized by: The mass ratio of each material in step (4) is as follows: Acrylic resin B 400-600 parts, photoacid generator 4-6 parts, photoalkali generator 0.1-0.3 parts, epoxy silane coupling agent 5-15 parts, and organic solvent B 80-120 parts.

9. An acrylic resin positive photoresist, characterized by: Prepared by the method of any one of claims 1-8.

10. Use of the acrylic resin positive photoresist according to claim 9 in semiconductor lithography, characterized in that: The application method is: the prepared acrylic resin positive photoresist is coated on the substrate, and then the substrate is baked and cured at 80-100℃, exposed to light with a wavelength of 395nm, developed with sodium carbonate aqueous solution, and then baked and cured at 140-160℃ after development, and then etched.