Polyacetal-based resin, composition for lithography film formation, resist film, and method for forming resist pattern

Abstract

To provide a polyacetal-based resin exhibiting superior resist sensitivity characteristics and excellent solvent solubility, heat resistance, and film-forming performance, and also to provide a composition for lithography film formation containing the polyacetal-based resin, a resist film, and a method for forming a resist pattern, all of which features excellent resist sensitivity characteristics.SOLUTION: There are provided a polyacetal-based resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound, a composition for lithography film formation containing the polyacetal-based resin, and a method for forming a resist pattern using the composition for lithography film formation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyacetal resin, a composition for forming a lithography film, a resist film, and a method for forming a resist pattern. [Background technology]

[0002] In the manufacture of semiconductor devices, microfabrication is carried out using lithography with photoresist materials, but in recent years, with the increasing integration and speed of LSIs (large-scale integrated circuits), there is a demand for further miniaturization using pattern rules. Conventional resist materials have been polymeric resist materials capable of forming amorphous thin films, such as polymethyl methacrylate, polyhydroxystyrene or polyalkyl methacrylate having an acid-dissociable group, etc. Therefore, lithography materials (photoresist materials) that can accommodate further miniaturization of patterns are being developed. For example, Patent Document 1 discloses a composition containing a resin having structural units derived from an ascorbic acid derivative as a composition for a resist film that has high sensitivity and high solubility in a solvent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 049472 Summary of the Invention [Problem to be solved by the invention]

[0004] Lithography materials are required to satisfy not only sensitivity to radiation but also other physical properties. For example, in semiconductor manufacturing processes, solubility in highly safe solvents used is required, while heat resistance is also required. Furthermore, film-forming properties are also required. Therefore, lithography materials that can simultaneously satisfy these properties are in demand. Furthermore, previously developed high-sensitivity lithography materials have problems such as insufficient pattern quality, including large pattern defects and roughness, and insufficient etching resistance. In light of these circumstances, there is a demand for lithography materials with even higher sensitivity that can address the above-mentioned problems. Therefore, an object of the present invention is to provide a polyacetal resin that has excellent resist sensitivity characteristics, solvent solubility, heat resistance, and film-forming properties, as well as a lithography film-forming composition, a resist film, and a method for forming a resist pattern that contain the polyacetal resin, all of which have excellent resist sensitivity characteristics. [Means for solving the problem]

[0005] The present inventors have found that a polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound can solve the above problems, and have completed the present invention.

[0006] That is, the present invention is as follows. <1> A polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound. <2> The polycarboxylic acid compound contains a benzenedicarboxylic acid compound. <1> The polyacetal resin according to claim 1. <3> The benzenedicarboxylic acid compound is at least one selected from the group consisting of isophthalic acid and phthalic acid. <2> The polyacetal resin according to claim 1. <4> The polycarboxylic acid compound further contains a benzenetricarboxylic acid compound. <2> or <3> The polyacetal resin according to claim 1. <5> A polyacetal resin containing a structural unit represented by the following formula (1): [ka] (In the formula, X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-; Y is a hydrogen atom or a chlorine atom; and Z is at least one group selected from the group consisting of formula (2) and formula (3).) [ka] <6> The above-mentioned compound further contains a structural unit represented by the following formula (4): <5> The polyacetal resin according to claim 1. [ka] <7> The aforementioned <1> ~ <6> A lithography film-forming composition comprising the polyacetal resin according to any one of the above items. <8> The above further contains a solvent. <7> The lithography film-forming composition according to claim 1. <9> The composition further contains at least one selected from the group consisting of an acid generator and a crosslinking agent. <7> or <8> The lithography film-forming composition according to claim 1. <10> The resist film-forming composition <7> ~ <9> 10. The lithography film-forming composition according to claim 9, wherein the lithography film-forming composition is a lithography film-forming composition. <11> The aforementioned <7> ~ <10> A resist film formed from the composition for forming a lithographic film according to any one of the above items. <12> On the substrate, <7> ~ <10> 10. A method for forming a resist pattern, comprising using the composition for lithography film formation according to any one of the above items. <13> On the substrate, <7> ~ <10> 1. A method for forming a resist pattern, comprising: forming a resist film using the composition for lithography film formation according to any one of 1 to 8; and exposing and developing the resist film. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a polyacetal resin having excellent resist sensitivity characteristics, solvent solubility, heat resistance, and film-forming properties, and a lithography film-forming composition containing the polyacetal resin having excellent resist sensitivity characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Polyacetal resin] The polyacetal resin of the present invention is a polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound. Such a polyacetal resin has an acetal structure in the main chain and an ester bond with the polycarboxylic acid compound, and therefore is characterized by being easily decomposable with an acid and having excellent developability with an alkaline developer, and is thought to have excellent resist sensitivity characteristics. Furthermore, it is believed that the presence of the above structure results in excellent solubility in solvents, excellent film-forming properties when forming a resist film, and excellent heat resistance.

[0009] <Polycarboxylic acid compounds> The polycarboxylic acid compound used as a raw material for the polyacetal resin of the present invention is preferably at least one selected from the group consisting of dicarboxylic acid compounds, tricarboxylic acid compounds, and polycarboxylic acid compounds having four or more carboxy groups, more preferably at least one selected from the group consisting of dicarboxylic acid compounds and tricarboxylic acid compounds, and even more preferably a dicarboxylic acid compound.

[0010] The polycarboxylic acid compound is preferably at least one selected from the group consisting of aromatic polycarboxylic acid compounds and aliphatic polycarboxylic acid compounds, more preferably an aromatic polycarboxylic acid compound, and even more preferably a benzene polycarboxylic acid. The aromatic polycarboxylic acid is preferably at least one selected from the group consisting of aromatic dicarboxylic acid compounds, aromatic tricarboxylic acid compounds, and aromatic polycarboxylic acid compounds having four or more carboxy groups, more preferably at least one selected from the group consisting of aromatic dicarboxylic acid compounds and aromatic tricarboxylic acid compounds, and even more preferably an aromatic dicarboxylic acid compound. The benzenepolycarboxylic acid is preferably at least one selected from the group consisting of a benzenedicarboxylic acid compound, a benzenetricarboxylic acid compound, and a polyvalent benzenecarboxylic acid compound having four or more carboxy groups, more preferably at least one selected from the group consisting of a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and even more preferably a benzenedicarboxylic acid compound.

[0011] That is, the polycarboxylic acid compound used as a raw material for the polyacetal resin of the present invention preferably contains a benzenedicarboxylic acid compound. Use of a benzenedicarboxylic acid compound makes it possible to obtain a polymer having an acetal structure and an ester bond in the main chain with a high degree of polymerization, and the obtained polymer is easily decomposable with an acid and has excellent developability with an alkaline developer, which is thought to improve resist sensitivity characteristics. The benzenedicarboxylic acid compound is preferably at least one selected from the group consisting of isophthalic acid, phthalic acid, and terephthalic acid, more preferably at least one selected from the group consisting of isophthalic acid and phthalic acid, and even more preferably phthalic acid.

[0012] When the polycarboxylic acid compound contains a benzenedicarboxylic acid compound, the polycarboxylic acid compound preferably further contains a benzenetricarboxylic acid compound. That is, the polyacetal resin of the present invention is preferably a polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound containing a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and a polyfunctional vinyl ether group-containing compound. The use of a benzenetricarboxylic acid compound is preferred because it can impart a branched structure to the polymer and make it possible to adjust the film-forming properties and solubility in a solvent. The benzenetricarboxylic acid compound is preferably at least one selected from the group consisting of trimesic acid (1,3,5-benzenetricarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), and hemimellitic acid (1,2,3-benzenetricarboxylic acid), more preferably at least one selected from the group consisting of trimesic acid and trimellitic acid, and even more preferably trimesic acid.

[0013] <Polyfunctional vinyl ether group-containing compound> The polyfunctional vinyl ether group-containing compound used as a raw material for the polyacetal resin of the present invention is preferably a compound represented by the following formula (5). [ka] (In the formula, W represents an n-valent aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, heterocyclic group, or group in which two or more of these are bonded together, and represents a group having 1 to 120 carbon atoms. The aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, heterocyclic group, or group in which two or more of these are bonded together may have, as a substituent, an alkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, an amino group, a sulfo group, a halogen atom, a cyano group, or a nitro group. n is an integer of 2 to 8.)

[0014] In formula (5), W is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, or a group in which two or more of these are bonded together, and is a group having 1 to 120 carbon atoms. Furthermore, the aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, heterocyclic group, or group in which two or more of these are bonded together that constitutes W may have, as a substituent, an alkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, an amino group, a sulfo group, a halogen atom, a cyano group, or a nitro group. n vinyl ether groups are bonded to W. Therefore, W is an n-valent group. In formula (5), n is an integer of 2 to 8, preferably an integer of 2 to 4, more preferably 2 or 3, and even more preferably 2. n represents the valence of W.

[0015] More specifically, the polyfunctional vinyl ether group-containing compound is preferably at least one selected from the group consisting of compounds represented by the following formula (6) and compounds represented by the following formula (7), and more preferably the compound represented by the following formula (6). [ka] (wherein R is a group represented by formula (8), and R 1 is a hydrogen atom, a methyl group, or an ethyl group, X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, and Y is a hydrogen atom or a chlorine atom.

[0016] In formula (6) and formula (7), Y is a hydrogen atom or a chlorine atom, and is preferably a hydrogen atom. In formula (6), X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, preferably at least one selected from the group consisting of -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, more preferably at least one selected from the group consisting of -S-, -C(CH3)2-, and -C(CF3)2-, and even more preferably -C(CH3)2-. In equation (7), R 1is a hydrogen atom, a methyl group, or an ethyl group, and is preferably a hydrogen atom.

[0017] A specific example of the compound represented by formula (6), from the viewpoints of solubility in a solvent, film-forming ability, heat resistance, and sensitivity, is preferably at least one selected from the group consisting of a compound represented by the following formula (61), a compound represented by the following formula (62), a compound represented by the following formula (63), a compound represented by the following formula (64), a compound represented by the following formula (65), a compound represented by the following formula (66), and a compound represented by the following formula (67), more preferably at least one selected from the group consisting of a compound represented by the following formula (61), a compound represented by the following formula (62), a compound represented by the following formula (63), and a compound represented by the following formula (64), even more preferably at least one selected from the group consisting of a compound represented by the following formula (61), a compound represented by the following formula (62), and a compound represented by the following formula (63), and even more preferably at least one selected from the group consisting of a compound represented by the following formula (61), a compound represented by the following formula (62), and a compound represented by the following formula (63), and even more preferably a compound represented by the following formula (61). [ka]

[0018] There are no limitations on the method for synthesizing the polyfunctional vinyl ether group-containing compound, but it is preferable to synthesize it from the corresponding polyhydric alcohol and chloroethyl vinyl ether by the Williamson synthesis method.

[0019] <Structure of polyacetal resin> The polyacetal resin of the present invention is preferably a polyacetal resin containing a structural unit represented by the following formula (1). [ka] (In the formula, X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-; Y is a hydrogen atom or a chlorine atom; and Z is at least one group selected from the group consisting of formula (2) and formula (3).) [ka]

[0020] In formula (1), Y is a hydrogen atom or a chlorine atom, and is preferably a hydrogen atom. In formula (1), X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, preferably at least one selected from the group consisting of -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, more preferably at least one selected from the group consisting of -S-, -C(CH3)2-, and -C(CF3)2-, and even more preferably -C(CH3)2-.

[0021] Specific examples of the structural unit represented by formula (1), from the viewpoints of solubility in solvents, film-forming properties, heat resistance, and sensitivity, are preferably at least one selected from the group consisting of structural units represented by the following formula (11), structural units represented by the following formula (12), structural units represented by the following formula (13), structural units represented by the following formula (14), structural units represented by the following formula (15), structural units represented by the following formula (16), and structural units represented by the following formula (17), more preferably at least one selected from the group consisting of structural units represented by the following formula (11), structural units represented by the following formula (12), structural units represented by the following formula (13), and structural units represented by the following formula (14), even more preferably at least one selected from the group consisting of structural units represented by the following formula (11), structural units represented by the following formula (12), and structural units represented by the following formula (13), and even more preferably at least one selected from the group consisting of structural units represented by the following formula (11), structural units represented by the following formula (12), and structural units represented by the following formula (13), and even more preferably a structural unit represented by the following formula (11). In the following formulas, Z has the same meaning as Z in formula (1). [ka]

[0022] In formula (1), Z is at least one group selected from the group consisting of groups represented by formula (2) and groups represented by formula (3), and is preferably a group represented by formula (3). The polyacetal resin of the present invention has the above-described structure, and thus has high solubility in solvents, excellent film-forming properties, and high heat resistance.

[0023] Furthermore, when the polyacetal resin of the present invention is used as a material for a lithography film-forming composition, the resulting lithography film-forming composition and lithography film have excellent resist sensitivity, which is thought to be due to the fact that the acetal structure or hemiacetal structure in the main chain is easily decomposed by acid and therefore easily cleaved, and also due to the excellent developability with an alkaline developer.

[0024] The polyacetal resin of the present invention preferably further contains a structural unit represented by the following formula (4). [ka] The polyacetal resin of the present invention can be made into a multi-branched polyacetal resin by further containing a structural unit represented by formula (4). This makes it possible to adjust film-forming ability and solubility in solvents. The polyacetal resin of the present invention, by further containing a structural unit represented by formula (4), has high solubility in solvents, excellent film-forming ability, and higher heat resistance.

[0025] The polyacetal resin of the present invention contains a structural unit represented by formula (1) and further contains a structural unit represented by formula (4), thereby achieving high sensitivity when used as a material for forming a lithography film. Although the reason for this is unclear, it is thought that the high sensitivity is due to the ease of cleavage of the main chain caused by the presence of an acetal structure and a hemiacetal structure in the main chain, and the excellent developability with an alkaline developer caused by the multi-branched structure.

[0026] When the polyacetal resin of the present invention contains a structural unit represented by formula (1) and a structural unit represented by formula (4), it has a structure in which a structural unit represented by formula (6a) is bonded to a structural unit represented by formula (4). It also has a structure in which a structural unit represented by formula (6a) is bonded to a structural unit represented by formula (23). The structure in which a structural unit represented by formula (6a) is bonded to a structural unit represented by formula (23) is a structural unit represented by formula (1). [ka] (In the formula, X is at least one selected from the group consisting of a single bond, -O-, -S-, -SO2-, -C(CH3)2-, and -C(CF3)2-, and Y is a hydrogen atom or a chlorine atom. Formula (23) is either formula (2) or formula (3).)

[0027] Specific examples of the constitutional unit represented by formula (6a) are the moieties in the above formulas (11) to (17) excluding Z. In addition, preferred embodiments are the same as those described above.

[0028] When the polyacetal resin of the present invention contains a structural unit represented by formula (1) and a structural unit represented by formula (4), the molar ratio of the structural unit represented by formula (23) to the structural unit represented by formula (6a) [structural unit represented by formula (23) / structural unit represented by formula (6a)] is preferably 5 / 95 to 40 / 60, more preferably 6 / 94 to 30 / 70, even more preferably 7 / 93 to 20 / 80, and still more preferably 8 / 92 to 10 / 90.

[0029] When the polyacetal resin of the present invention contains a structural unit represented by formula (1) and a structural unit represented by formula (4), the molar ratio of the structural unit represented by formula (4) to the structural unit represented by formula (6a) [structural unit represented by formula (4) / structural unit represented by formula (6a)] is preferably 10 / 90 to 70 / 30, more preferably 20 / 80 to 60 / 40, even more preferably 30 / 70 to 50 / 50, and still more preferably 35 / 65 to 40 / 60.

[0030] When the polyacetal resin of the present invention contains a structural unit represented by formula (1) and a structural unit represented by formula (4), the molar ratio of the structural unit represented by formula (4) to the structural unit represented by formula (23) [structural unit represented by formula (4) / structural unit represented by formula (23)] is preferably 50 / 50 to 98 / 2, more preferably 60 / 40 to 95 / 5, even more preferably 70 / 30 to 92 / 8, and still more preferably 80 / 20 to 90 / 10.

[0031] <Characteristics of polyacetal resin> The number average molecular weight of the polyacetal resin of the present invention is preferably 1000 to 10000, more preferably 2500 to 8000, even more preferably 3000 to 7000, and still more preferably 3000 to 6000. When the number average molecular weight is within the above range, the resin has high solvent solubility, excellent film-forming properties, and high heat resistance. The molecular weight distribution (Mw / Mn) of the polyacetal resin of the present invention is preferably 1.3 to 10.0, more preferably 1.4 to 5.0, even more preferably 1.5 to 4.0, and still more preferably 1.5 to 3.5. When the molecular weight distribution is within the above range, the polyacetal resin has high solvent solubility, excellent film-forming properties, and high heat resistance.

[0032] <Method for producing polyacetal resin> The polyacetal resin of the present invention may be produced by any method without limitation, provided that it is obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound. However, the following method is preferred.

[0033] Specifically, it is more preferable to obtain it by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound in the presence of an acid catalyst such as pyridinium p-toluenesulfonate (PPTS). The amounts of the polycarboxylic acid compound and the polyfunctional vinyl ether group-containing compound used may be adjusted depending on the properties required for the resin, such as molecular weight, but are preferably determined based on the molar ratio of the carboxy groups of the polycarboxylic acid compound to the vinyl groups of the polyfunctional vinyl ether group-containing compound. The molar ratio of the carboxy groups of the polycarboxylic acid compound to the vinyl groups of the polyfunctional vinyl ether group-containing compound [carboxy groups / vinyl groups] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45, and it is even more preferable that the molar ratios are approximately equal.

[0034] When the polycarboxylic acid compound is a benzenedicarboxylic acid compound and the polyfunctional vinyl ether group-containing compound is a bifunctional vinyl ether group-containing compound, the molar ratio of the amount of the benzenedicarboxylic acid compound used to the amount of the bifunctional vinyl ether group-containing compound used [benzenedicarboxylic acid compound / bifunctional vinyl ether group-containing compound] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45, and it is even more preferable that the molar ratios are approximately equal.

[0035] When the polycarboxylic acid compound is a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and the polyfunctional vinyl ether group-containing compound is a bifunctional vinyl ether group-containing compound, the functional group molar ratio of the amount of the benzenedicarboxylic acid compound and the benzenetricarboxylic acid compound used to the amount of the bifunctional vinyl ether group-containing compound used [(benzenedicarboxylic acid compound × 2 + benzenetricarboxylic acid × 3) / (bifunctional vinyl ether group-containing compound × 2)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45, and it is even more preferable that the molar ratios are approximately equal.

[0036] When the polycarboxylic acid compound is a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and the polyfunctional vinyl ether group-containing compound is a bifunctional vinyl ether group-containing compound, the molar ratio of the amount of the benzenedicarboxylic acid compound used to the amount of the bifunctional vinyl ether group-containing compound used [benzenedicarboxylic acid compound / bifunctional vinyl ether group-containing compound] is preferably 5 / 95 to 40 / 60, more preferably 6 / 94 to 30 / 70, even more preferably 7 / 93 to 20 / 80, and still more preferably 8 / 92 to 10 / 90.

[0037] When the polycarboxylic acid compound is a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and the polyfunctional vinyl ether group-containing compound is a bifunctional vinyl ether group-containing compound, the molar ratio of the amount of the benzenetricarboxylic acid compound used to the amount of the bifunctional vinyl ether group-containing compound used [benzenetricarboxylic acid compound / bifunctional vinyl ether group-containing compound] is preferably 10 / 90 to 70 / 30, more preferably 20 / 80 to 60 / 40, even more preferably 30 / 70 to 50 / 50, and still more preferably 35 / 65 to 40 / 60.

[0038] When the polycarboxylic acid compound is a benzenedicarboxylic acid compound and a benzenetricarboxylic acid compound, and the polyfunctional vinyl ether group-containing compound is a bifunctional vinyl ether group-containing compound, the molar ratio of the amount of the benzenetricarboxylic acid compound used to the amount of the benzenedicarboxylic acid compound used [benzenetricarboxylic acid compound / benzenedicarboxylic acid compound] is preferably 50 / 50 to 98 / 2, more preferably 60 / 40 to 95 / 5, even more preferably 70 / 30 to 92 / 8, and still more preferably 80 / 20 to 90 / 10.

[0039] The reaction temperature is preferably 0 to 50°C, more preferably 10 to 50°C, and even more preferably 20 to 40°C, and may be performed at room temperature. The reaction time may be adjusted appropriately depending on the reaction temperature, amount of catalyst, reactivity of the raw materials, target molecular weight, etc., but is preferably 1 to 72 hours, more preferably 2 to 48 hours, and even more preferably 2 to 24 hours.

[0040] The reaction may be carried out in the presence of a solvent. Preferred solvents are those in which the resulting polyacetal resin dissolves, more preferably ether solvents, and even more preferably tetrahydrofuran. When an acid catalyst is used, the reaction is preferably stopped by introducing a basic substance such as triethylamine. The obtained polyacetal resin is preferably purified by a conventional post-treatment. Specifically, it is preferable to remove raw materials and by-products by pouring the reaction mixture into an organic solvent in which the polyacetal resin is insoluble and recovering the precipitate. Alternatively, it is preferable to dissolve the polyacetal resin in an organic solvent in which the polyacetal resin is soluble and then wash with water or the like to remove the catalyst and the like. When the polyacetal resin is obtained as a solution in an organic solvent at the end of the polymerization or purification treatment, it is preferable to concentrate and dry the resulting solution to obtain the polyacetal resin as a solid. The polyacetal resin obtained in this manner has high solubility in solvents, excellent film-forming properties, and high heat resistance.

[0041] [Lithography film-forming composition] The lithography film-forming composition of the present invention is a lithography film-forming composition containing the polyacetal resin. That is, the lithography film-forming composition of the present invention is a lithography film-forming composition containing a polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound, and is preferably a lithography film-forming composition containing a polyacetal resin containing a structural unit represented by the above formula (1). The lithography film-forming composition of the present invention is suitable as a composition for forming a resist film because it contains the polyacetal resin, which has excellent resist sensitivity characteristics, solvent solubility, heat resistance, and film-forming properties. In other words, the lithography film-forming composition of the present invention is preferably a composition for forming a resist film.

[0042] Furthermore, the lithography film-forming composition containing the polyacetal-based resin is considered to have excellent resist sensitivity because the acetal structure or hemiacetal structure in the main chain of the polyacetal-based resin is easily decomposed by acid and therefore easily cleaved, and also because the composition has excellent developability with an alkaline developer.

[0043] <Solvent> The lithography film-forming composition of the present invention may be appropriately adjusted in terms of formulation depending on the intended use, so long as it contains the polyacetal resin, but preferably further contains a solvent as a component other than the polyacetal resin.

[0044] The solvent is not particularly limited, but examples thereof include ethylene glycol monoalkyl ether acetates, ethylene glycol monoalkyl ethers, propylene glycol monoalkyl ether acetates, propylene glycol monoalkyl ethers, lactate esters, aliphatic carboxylic acid esters, esters other than the above esters, aromatic hydrocarbons, ketones, amides, lactones, and ethers, and is preferably at least one selected from the group consisting of propylene glycol monoalkyl ether acetates, propylene glycol monoalkyl ethers, lactate esters, aliphatic carboxylic acid esters, ketones, and ethers, and more preferably at least one selected from the group consisting of propylene glycol monoalkyl ether acetates, propylene glycol monoalkyl ethers, and ketones.

[0045] Examples of ethylene glycol monoalkyl ether acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-propyl ether acetate, and ethylene glycol mono-n-butyl ether acetate. Examples of the ethylene glycol monoalkyl ethers include ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. Examples of propylene glycol monoalkyl ether acetates include propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate (PGMEA), propylene glycol mono-n-propyl ether acetate, and propylene glycol mono-n-butyl ether acetate, with propylene glycol monoethyl ether acetate (PGMEA) being preferred. Examples of propylene glycol monoalkyl ethers include propylene glycol monomethyl ether (PGME) and propylene glycol monoethyl ether, with propylene glycol monomethyl ether (PGME) being preferred.

[0046] Examples of lactate esters include methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and n-amyl lactate, with ethyl lactate being preferred. Examples of the aliphatic carboxylic acid esters include methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, n-amyl acetate, n-hexyl acetate, methyl propionate, and ethyl propionate, with butyl acetate and ethyl propionate being preferred. Examples of esters other than the above-mentioned esters include methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 3-methoxy-2-methylpropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, butyl 3-methoxy-3-methylpropionate, butyl 3-methoxy-3-methylbutyrate, methyl acetoacetate, methyl pyruvate, ethyl pyruvate, and methyl 2-hydroxyisobutyrate (HBM). Examples of aromatic hydrocarbons include toluene and xylene. Examples of ketones include methyl ethyl ketone, 2-heptanone, 3-heptanone, 4-heptanone, cyclopentanone (CPN), cyclohexanone (CHN), and the like, with 2-heptanone, cyclopentanone (CPN), and cyclohexanone (CHN) being preferred. Examples of amides include N,N-dimethylformamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Examples of lactones include γ-lactone. The ethers are preferably anisole. The solvents may be used alone or in combination of two or more.

[0047] The solvent is preferably a safe solvent, and is preferably at least one selected from the group consisting of propylene glycol monoethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), cyclopentanone (CPN), cyclohexanone (CHN), 2-heptanone, anisole, butyl acetate, ethyl propionate, and ethyl lactate, and more preferably at least one selected from the group consisting of propylene glycol monoethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), and cyclohexanone (CHN).

[0048] The content of the solvent is preferably 20 to 99 mass %, more preferably 50 to 99 mass %, even more preferably 60 to 98 mass %, and still more preferably 90 to 98 mass %, based on the total amount of the composition for forming a lithographic film.

[0049] <Other ingredients> The lithography film-forming composition of the present invention may contain the polyacetal resin, and the composition may be adjusted in its formulation depending on the intended use, but may also contain components other than the polyacetal resin and the solvent. Note that the following components are solid components, and are usually dissolved in a solvent and blended into the lithography film-forming composition.

[0050] The lithographic film-forming composition of the present invention may further contain at least one component selected from the group consisting of an acid generator, a crosslinking agent, an acid diffusion controller, and other additives, preferably at least one component selected from the group consisting of an acid generator, a crosslinking agent, and an acid diffusion controller, more preferably at least one component selected from the group consisting of an acid generator and a crosslinking agent, and even more preferably an acid generator and a crosslinking agent.

[0051] The content of the polyacetal resin contained in the lithography film-forming composition of the present invention is preferably 50 to 99.4 mass %, more preferably 55 to 90 mass %, even more preferably 60 to 85 mass %, and still more preferably 65 to 80 mass %, based on the total content of the solid components (total content of the polyacetal resin, acid generator, crosslinking agent, acid diffusion controller, and other additives).Within this range, resolution can be improved and line edge roughness (LER) can be reduced.

[0052] (acid generator) The lithographic film-forming composition of the present invention may further contain an acid generator, and preferably further contains an acid generator.

[0053] The acid generator is preferably an acid generator that generates an acid directly or indirectly when irradiated with any one of visible light, ultraviolet light, excimer laser, electron beam, extreme ultraviolet light (EUV), X-ray, and ion beam. The radiation may be ultraviolet rays such as g-rays or i-rays, and an excimer laser is preferred because it enables fine processing. Furthermore, electron beams, extreme ultraviolet rays, X-rays, or ion beams are also preferred high-energy rays because they also enable fine processing.

[0054] Examples of the acid generator include the compounds disclosed in WO 2017 / 033943. The acid generator is preferably an acid generator having an aromatic ring, more preferably an acid generator having a sulfonate ion with an aryl group. The acid generator is more preferably at least one selected from the group consisting of diphenyltrimethylphenylsulfonium p-toluenesulfonate, triphenylsulfonium p-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoromethanesulfonate, ditertiarybutyldiphenyliodonium nonafluorobutanesulfonate, and pyridinium p-toluenesulfonate. Use of the acid generator can reduce line edge roughness.

[0055] The acid generator may preferably further contain a diazonaphthoquinone photoactive compound. The diazonaphthoquinone photoactive compound is not particularly limited as long as it is generally used as a photosensitive component in positive resist compositions. The diazonaphthoquinone photoactive compound is preferably a polymeric diazonaphthoquinone photoactive compound or a non-polymeric diazonaphthoquinone photoactive compound, more preferably a non-polymeric diazonaphthoquinone photoactive compound, even more preferably a non-polymeric diazonaphthoquinone photoactive compound having a molecular weight of 1500 or less, even more preferably a non-polymeric diazonaphthoquinone photoactive compound having a molecular weight of 1200 or less, and even more preferably a non-polymeric diazonaphthoquinone photoactive compound having a molecular weight of 1000 or less. Specific examples of diazonaphthoquinone photoactive compounds include the non-polymeric diazonaphthoquinone photoactive compounds disclosed in WO 2016 / 158881. The diazonaphthoquinone photoactive compounds can be used alone or in combination.

[0056] The content of the acid generator contained in the lithography film-forming composition of the present invention is preferably 0.001 to 49 mass %, more preferably 1 to 40 mass %, even more preferably 3 to 30 mass %, and still more preferably 5 to 20 mass %, based on the total content of the solid components (total content of the polyacetal resin, acid generator, crosslinking agent, acid diffusion controller, and other additives). Within this range, sensitivity can be increased and edge roughness of the pattern profile can be reduced. The acid generators can be used singly or in combination of two or more.

[0057] (Crosslinking agent) The lithographic film-forming composition of the present invention may further contain a crosslinking agent, and preferably further contains a crosslinking agent. The crosslinking agent contained in the lithographic film-forming composition of the present invention is preferably an acid crosslinking agent. The acid crosslinking agent can crosslink the polyacetal resin intramolecularly or intermolecularly by the acid generated from the acid generator. The inclusion of the crosslinking agent can increase the strength of the resist pattern.

[0058] The crosslinking agent is preferably a compound having a crosslinkable group. The crosslinkable group is not particularly limited, but examples thereof include a hydroxyalkyl group, a carbonyl group, a nitrogen-containing group, a glycidyl-containing group, an aromatic group, a polymerizable multiple bond-containing group, and groups derived therefrom, and preferred are hydroxyalkyl groups and groups derived therefrom. Specifically, examples of hydroxyalkyl groups and groups derived therefrom include hydroxyalkyl groups, alkoxyalkyl groups, and acetoxyalkyl groups, and are preferably at least one selected from the group consisting of hydroxyalkyl groups and alkoxyalkyl groups, and more preferably an alkoxymethyl group. Examples of the carbonyl group and groups derived therefrom include a formyl group and a carboxyalkyl group. Examples of the nitrogen-containing group include a dimethylaminomethyl group, a diethylaminomethyl group, a dimethylolaminomethyl group, a diethylolaminomethyl group, and a morpholinomethyl group. Examples of the glycidyl-containing group include a glycidyl ether group, a glycidyl ester group, and a glycidylamino group. Examples of the aromatic group include a benzyloxymethyl group, a benzoyloxymethyl group, an allyloxyalkyl group, and an aralkyloxyalkyl group. Examples of the polymerizable multiple bond-containing group include a vinyl group and an isopropenyl group. Suitable examples of acid crosslinking agents are listed below in several categories: The type and content of the acid crosslinking agent may be adjusted depending on the type of substrate used when forming the resist pattern.

[0059] Preferred examples of the acid crosslinking agent include methylol group-containing compounds, alkoxyalkyl group-containing compounds, carboxymethyl group-containing compounds, and epoxy compounds. Examples of the methylol group-containing compound include a methylol group-containing melamine compound, a methylol group-containing benzoguanamine compound, a methylol group-containing urea compound, a methylol group-containing glycoluril compound, and a methylol group-containing phenol compound. Examples of the alkoxyalkyl group-containing compound include an alkoxyalkyl group-containing melamine compound, an alkoxyalkyl group-containing benzoguanamine compound, an alkoxyalkyl group-containing urea compound, an alkoxyalkyl group-containing glycoluril compound, and an alkoxyalkyl group-containing phenol compound. Examples of the carboxymethyl group-containing compound include a carboxymethyl group-containing melamine compound, a carboxymethyl group-containing benzoguanamine compound, a carboxymethyl group-containing urea compound, a carboxymethyl group-containing glycoluril compound, and a carboxymethyl group-containing phenol compound. Examples of epoxy compounds include bisphenol A-based epoxy compounds, bisphenol F-based epoxy compounds, bisphenol S-based epoxy compounds, novolac resin-based epoxy compounds, resol resin-based epoxy compounds, and poly(hydroxystyrene)-based epoxy compounds.

[0060] Further examples of the acid crosslinking agent include a compound having a phenolic hydroxyl group, in which the crosslinkable group is introduced into the acidic functional group to impart crosslinkability, and an alkali-soluble resin, in which the crosslinkable group is introduced into the acidic functional group to impart crosslinkability. The introduction rate of the crosslinkable group is preferably 5 to 100 mol %, more preferably 10 to 60 mol %, and even more preferably 15 to 40 mol %, based on the total acidic functional groups in the compound having a phenolic hydroxyl group and the alkali-soluble resin. This range is preferable because it allows the crosslinking reaction to occur sufficiently, preventing a decrease in the residual film rate and the occurrence of swelling and meandering of the resist pattern.

[0061] Further examples of the acid crosslinker include alkoxyalkylated urea compounds or resins thereof, alkoxyalkylated glycoluril compounds or resins thereof, phenol derivatives, and compounds having an α-hydroxyisopropyl group, such as those disclosed in WO 2017 / 033943. The phenol derivative has 1 to 6 benzene rings in the molecule and two or more hydroxyalkyl groups or alkoxyalkyl groups throughout the molecule, and the hydroxyalkyl groups or alkoxyalkyl groups are bonded to any of the benzene rings.

[0062] The content of the crosslinking agent contained in the lithography film-forming composition of the present invention is preferably 0.5 to 49 mass %, more preferably 0.5 to 40 mass %, even more preferably 1 to 30 mass %, and still more preferably 2 to 20 mass %, based on the total content of the solid components (the total content of the polyacetal resin, acid generator, crosslinking agent, acid diffusion controller, and other additives). This range is preferable because it can suppress dissolution of the resist film in a developer, suppress reduction in the residual film rate and swelling and meandering of the resist pattern, and further improve the heat resistance of the resist.

[0063] (acid diffusion controller) The lithographic film-forming composition of the present invention may further contain an acid diffusion controller, and preferably further contains an acid diffusion controller. The acid diffusion controller optionally contained in the lithographic film-forming composition of the present invention controls the diffusion of the acid generated from the acid generator in the resist film upon irradiation with radiation, thereby preventing undesirable chemical reactions in unexposed areas. This improves the storage stability of the lithographic film-forming composition, thereby improving resolution. Furthermore, it can suppress changes in the line width of the resist pattern due to variations in the exposure time before and after radiation exposure, resulting in extremely excellent process stability.

[0064] Examples of the acid diffusion controller include radiolytic basic compounds such as nitrogen atom-containing basic compounds, basic sulfonium compounds, and basic iodonium compounds. Examples of the acid diffusion controller include the compounds disclosed in WO 2017 / 033943. The acid diffusion controller can be used alone or in combination of two or more.

[0065] The content of the acid diffusion controller contained in the lithography film-forming composition of the present invention is preferably 0.001 to 49% by mass relative to the total content of the solid components (the total content of the polyacetal resin, acid generator, crosslinking agent, acid diffusion controller, and other additives). From the viewpoint of preventing deterioration in sensitivity and developability of unexposed areas, the content is more preferably 0.01 to 10% by mass, even more preferably 0.01 to 5% by mass, and even more preferably 0.01 to 3% by mass. Within this range, deterioration in resolution and deterioration in the resist pattern shape and dimensional fidelity can be suppressed. Furthermore, deterioration in the shape of the upper layer of the resist pattern does not occur when the waiting time between electron beam irradiation and post-irradiation heating is long.

[0066] (Other additives) The lithographic film-forming composition of the present invention may further contain other additives within the range that does not impair the effects of the present invention. Examples of other additives include dissolution promoters, dissolution controllers, sensitizers, surfactants, and organic carboxylic acids or phosphorus oxoacids or derivatives thereof, etc. Examples of other additives include the compounds disclosed in WO 2017 / 033943. The total content of other additives contained in the lithography film-forming composition of the present invention is preferably 0 to 49 mass %, more preferably 0 to 5 mass %, even more preferably 0 to 1 mass %, still more preferably 0 mass %, and even more preferably 0 mass %, relative to the total content of the solid components (total content of the polyacetal resin, acid generator, crosslinking agent, acid diffusion controller, and other additives).

[0067] <Method for producing lithography film-forming composition> The method for producing the lithography film-forming composition of the present invention is not particularly limited, but is preferably a method in which the components are dissolved in a solvent to form a homogeneous solution. If necessary, the solution obtained may be filtered to remove impurities. The filter used for filtration preferably has a pore size of about 0.2 μm.

[0068] The lithographic film-forming composition of the present invention may contain a resin within a range that does not impair the effects of the present invention. Examples of the resin include novolac resin, polyvinylphenols, polyacrylic acid, polyvinyl alcohol, and styrene-maleic anhydride resin. The total content of resins contained in the lithography film-forming composition of the present invention is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, still more preferably 0 parts by mass, and even more preferably none, relative to 100 parts by mass of the polyacetal resin.

[0069] [Resist film] The resist film of the present invention is a resist film formed from the above-described composition for forming a lithography film. As described above, the lithography film-forming composition contains the polyacetal resin, and therefore has excellent resist sensitivity characteristics and is an excellent raw material for forming a resist film. The resist film of the present invention can be formed from the composition for forming a lithographic film by the method described below as a method for forming a resist pattern.

[0070] The resist film of the present invention can be obtained as an amorphous film by known methods such as spin coating, and can be made to have either a positive resist pattern or a negative resist pattern depending on the type of developer used.

[0071] In the case of a positive resist pattern, the dissolution rate of the amorphous film formed by spin-coating the lithography film-forming composition in a developer at 23°C is preferably 5 Å / sec or less, more preferably 0.0005 to 5 Å / sec. A dissolution rate within this range allows the resist to be insoluble in the developer, thereby improving resolution. This is presumably because the change in solubility of the polyacetal resin before and after exposure increases the contrast at the interface between the exposed portion, which dissolves in the developer, and the unexposed portion, which does not dissolve in the developer. Furthermore, the composition is effective in reducing line edge roughness and defects.

[0072] In the case of a negative resist pattern, the dissolution rate of the amorphous film formed by spin-coating the lithography film-forming composition in a developer at 23°C is preferably 10 Å / sec or more. A dissolution rate within this range is suitable for the resist and improves resolution. This is presumably because the microscopic surface regions of the polyacetal resin dissolve, reducing line edge roughness. The composition also has the effect of reducing defects. The dissolution rate can be measured by immersing an amorphous film in a developer at 23° C. for a predetermined time, and measuring the film thickness before and after the immersion visually, by an ellipsometer, a QCM method, or the like.

[0073] In the case of a positive resist pattern, the dissolution rate in a developer at 23°C of the portion of the amorphous film formed by spin-coating the lithography film-forming composition, which has been exposed to radiation such as an excimer laser (preferably a KrF excimer laser), extreme ultraviolet light, electron beam, or X-ray, is preferably 10 Å / sec or higher. A dissolution rate within this range is suitable for the resist and improves resolution. This is presumably because the microscopic surface regions of the polyacetal resin dissolve, reducing line edge roughness. It also has the effect of reducing defects.

[0074] In the case of a negative resist pattern, the dissolution rate in a developer at 23°C of the portion of the amorphous film formed by spin-coating the lithography film-forming composition, exposed to radiation such as an excimer laser (preferably a KrF excimer laser), extreme ultraviolet light, electron beam, or X-ray, is preferably 5 Å / sec or less, more preferably 0.0005 to 5 Å / sec. A dissolution rate within this range allows the resist to be insoluble in the developer, thereby improving resolution. This is presumably because the change in solubility of the polyacetal resin before and after exposure increases the contrast at the interface between the exposed portion, which dissolves in the developer, and the unexposed portion, which does not dissolve in the developer. Furthermore, this composition is effective in reducing line edge roughness and defects.

[0075] [Method for forming resist pattern] The method for forming a resist pattern of the present invention is a method for forming a resist pattern using the above-described composition for forming a lithography film. More specifically, the present invention relates to a method for forming a resist pattern, the method comprising the steps of forming a resist film on a substrate using the composition for forming a lithography film, and exposing and developing the resist film. The formed resist pattern can also be used as an upper layer resist in a multi-layer process.

[0076] <Step of forming a resist film> The method for forming a resist pattern of the present invention includes a step of forming a resist film on a substrate using the composition for forming a lithographic film. Examples of a method for forming a resist film include a method in which the lithography film-forming composition is applied onto a substrate by a coating means such as spin coating, casting coating, or roll coating. The substrate may be a conventionally known substrate, and examples thereof include substrates for electronic components and substrates on which wiring patterns are formed. Examples of the substrate include a silicon wafer, a substrate made of a metal such as copper, chromium, iron or aluminum, and a glass substrate. Examples of materials for the wiring pattern include copper, aluminum, nickel, and gold. The substrate may also have an inorganic or organic film provided thereon. Examples of inorganic films include inorganic anti-reflective coatings (inorganic BARCs). Examples of organic films include organic anti-reflective coatings (organic BARCs). The substrate may be surface-treated with hexamethyldisilazane (1,1,1,3,3,3-hexamethyldisilazane) or the like.

[0077] The substrate coated with the lithography film-forming composition may be heated. The heating conditions may be adjusted appropriately depending on the components of the composition, but are preferably 20 to 250° C., more preferably 20 to 150° C. Heating is preferred because it improves the adhesion of the resist film to the substrate.

[0078] <Exposure process> The method for forming a resist pattern of the present invention includes a step of exposing the formed resist film to light, whereby the resist film is exposed to light in a desired pattern. The exposure is performed using a type of radiation selected from the group consisting of visible light, ultraviolet light, excimer laser, electron beam, extreme ultraviolet (EUV), X-ray, and ion beam. The exposure conditions may be appropriately adjusted depending on the formulation of the lithography film-forming composition.

[0079] After irradiation, it is preferable to heat the substrate having the resist film. The heating conditions may be adjusted appropriately depending on the formulation of the composition for forming a lithographic film, but are preferably 20 to 250° C., more preferably 20 to 150° C. Heating allows for stable formation of a highly accurate fine pattern during exposure.

[0080] <Developing process> The method for forming a resist pattern of the present invention includes a step of exposing a formed resist film to light and developing it. This step is a step of developing the exposed resist film with a developer. By this step, a desired resist pattern is formed.

[0081] The developer is preferably a solvent whose solubility parameter (SP value) is close to the solubility parameter (SP value) of the polyacetal resin. The solvent is preferably a polar solvent, a hydrocarbon solvent, or an alkaline aqueous solution, and depending on the type of developer, a positive resist pattern or a negative resist pattern can be produced. Generally, a polar solvent or a hydrocarbon solvent produces a negative resist pattern, while an alkaline aqueous solution produces a positive resist pattern. Examples of the polar solvent include ketone-based solvents, ester-based solvents, alcohol-based solvents, amide-based solvents, and ether-based solvents. The developer preferably contains a polar solvent, and even more preferably contains at least one solvent selected from ketone solvents, ester solvents, alcohol solvents, amide solvents, and ether solvents. Developers containing such solvents are preferred because they can improve resist performance such as the resolution and roughness of the resist pattern. Examples of ketone-based solvents, ester-based solvents, alcohol-based solvents, amide-based solvents, ether-based solvents, hydrocarbon-based solvents, and aqueous alkaline solutions include those disclosed in WO 2017 / 033943.

[0082] The solvent may be a mixture of two or more of the solvents, and may contain water or other solvents as long as the effects of the present invention are not impaired. When an organic solvent (a polar solvent or a hydrocarbon solvent) is used in the developer, the water content of the developer is preferably less than 70% by mass, more preferably less than 50% by mass, even more preferably less than 30% by mass, still more preferably less than 10% by mass, and even more preferably substantially free of water.

[0083] The content of organic solvents (polar solvents and hydrocarbon-based solvents) in the developer is preferably 30% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, even more preferably 70% by mass or more and 100% by mass or less, still more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0084] The vapor pressure of the developer at 20°C is preferably 5 kPa or less, more preferably 3 kPa or less, and even more preferably 2 kPa or less. When the vapor pressure of the developer is within this range, evaporation of the developer on the substrate or in the developing cup is suppressed, improving temperature uniformity within the wafer surface and, as a result, improving dimensional uniformity within the wafer surface. Examples of developers having such vapor pressure include the developer disclosed in International Publication No. 2017 / 033943.

[0085] The developer may contain a surfactant. The surfactant may be a nonionic surfactant or an ionic surfactant, with a nonionic surfactant being preferred. The surfactant is preferably at least one selected from the group consisting of a fluorine-based surfactant and a silicone-based surfactant, and more preferably at least one selected from the group consisting of a nonionic fluorine-based surfactant and a nonionic silicone-based surfactant. Examples of fluorine-based surfactants and silicone-based surfactants include surfactants described in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988, U.S. Pat. Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511, and 5,824,451.

[0086] The amount of the surfactant used is preferably 0.001 to 5% by mass, more preferably 0.005 to 2% by mass, and even more preferably 0.01 to 0.5% by mass, based on the total amount of the developer.

[0087] Examples of the developing method include a dipping method, a puddle method, a spray method, and a dynamic dispensing method. The dip method is a method in which a substrate is immersed in a tank filled with developer for a certain period of time, the puddle method is a method in which developer is piled up on the surface of the substrate by surface tension and left to stand for a certain period of time to develop, the spray method is a method in which developer is sprayed onto the surface of the substrate, and the dynamic dispense method is a method in which developer is continuously dispensed by scanning a developer dispensing nozzle at a constant speed over a substrate that is rotating at a constant speed. The development time is not particularly limited, but is preferably 10 to 90 seconds.

[0088] <Other processes> The method for forming a resist pattern of the present invention may include the following steps in addition to the steps described above.

[0089] After the development step, a step of stopping the development while replacing the solvent with another solvent may be carried out.

[0090] After the development step, it is preferable to include a step of washing with a rinse liquid containing an organic solvent (rinsing step). The rinse liquid is preferably a solvent that does not dissolve the resist pattern, and more preferably a solution containing an organic solvent or water. The rinse liquid preferably contains at least one organic solvent selected from the group consisting of hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, amide solvents, and ether solvents, more preferably contains at least one organic solvent selected from the group consisting of ketone solvents, ester solvents, alcohol solvents, and amide solvents, even more preferably contains at least one organic solvent selected from the group consisting of alcohol solvents and ester solvents, still more preferably contains a monohydric alcohol, and even more preferably contains a monohydric alcohol having 5 or more carbon atoms.

[0091] The monohydric alcohol may be linear, branched, or cyclic. Preferably, the monohydric alcohol is at least one selected from the group consisting of 1-butanol, 2-butanol, 3-methyl-1-butanol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 1-hexanol, 4-methyl-2-pentanol, 1-heptanol, 1-octanol, 2-hexanol, cyclopentanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, and 4-octanol. More preferably, the monohydric alcohol is 1-hexanol, 2-hexanol, 4-methyl-2-pentanol, 1-pentanol, or 3-methyl-1-butanol. The organic solvents may be used in combination, or may contain an organic solvent other than those mentioned above.

[0092] The water content in the organic solvent-based rinse liquid is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. If the water content is within this range, better development characteristics can be obtained. The rinse liquid may contain a surfactant. The vapor pressure of the rinse liquid at 20° C. is preferably 0.05 to 5 kPa, more preferably 0.1 to 5 kPa, and even more preferably 0.12 to 3 kPa. When the vapor pressure of the rinse liquid is within this range, the temperature uniformity within the wafer surface is further improved, and swelling due to penetration of the rinse liquid is further suppressed, resulting in improved dimensional uniformity within the wafer surface.

[0093] The cleaning method is preferably a spin coating method, a dipping method, or a spray method, more preferably a spin coating method. It is more preferable to perform cleaning by a spin coating method, and then rotate the substrate at a rotation speed of 2000 rpm to 4000 rpm to remove the rinse liquid from the substrate. The spin coating method is a method in which the rinse solution is continuously applied onto a substrate rotating at a constant speed, the dipping method is a method in which the substrate is immersed in a tank filled with the rinse solution for a certain period of time, and the spray method is a method in which the rinse solution is sprayed onto the surface of the substrate. There is no particular limitation on the time for rinsing the pattern, but it is preferably 10 to 90 seconds.

[0094] After forming the resist pattern, a patterned wiring substrate can be obtained by etching, which can be performed by a known method such as dry etching using plasma gas or wet etching using an alkaline solution, cupric chloride solution, ferric chloride solution, or the like.

[0095] After forming the resist pattern, plating may be performed. The plating method is not particularly limited, but examples thereof include copper plating, solder plating, nickel plating, and gold plating.

[0096] The remaining resist pattern after etching can be stripped using an organic solvent. Examples of the organic solvent include, but are not limited to, PGMEA (propylene glycol monomethyl ether acetate), PGME (propylene glycol monomethyl ether), and ethyl lactate. Examples of the stripping method include, but are not limited to, a dipping method and a spray method. The wiring board on which the resist pattern is formed may be a multilayer wiring board and may have small-diameter through-holes. The wiring substrate may be formed by a lift-off method, in which a resist pattern is formed, a metal is evaporated in a vacuum, and then the resist pattern is dissolved in a solution. [Example]

[0097] The present invention will be specifically described based on the following examples, but the present invention is not limited to these examples.

[0098] [analysis] Fourier transform infrared spectroscopy (FT-IR) spectra were measured using a JASCO FT / IR4200 (manufactured by JASCO Corporation). 1 H-NMR spectrum and 13C-NMR spectra were measured using an ECS-400K (manufactured by JEOL Ltd.) at frequencies of 400 MHz and 100 MHz, respectively, using CDCl3 as a solvent and Me4Si(TMS) as an internal standard. The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the resin were measured by size exclusion chromatography (SEC) under the following conditions. Standard polystyrene (narrow molecular weight distribution, 0.5 to 1000 kg / mol) was used for calibration. (Measurement conditions: Apparatus: HLC-8220 SEC apparatus, manufactured by Tosoh Corporation; Columns: TSKgel Super AW3000, AW2500 x 2; Detection: RI; Eluent: DMF solution of LiBr and phosphoric acid (20 mM); Flow rate: 0.6 mL / min)

[0099] [Rating 1] <Solubility> The solubility of the resin was confirmed in the following solvents at room temperature (25°C). The solvents tested were NMP (N-methylpyrrolidone), DMSO (dimethyl sulfoxide), DMF (N,N-dimethylformamide), ethyl acetate, acetone, chloroform, PGMEA, and MEK (methyl ethyl ketone). For these solvents, the solubility was evaluated as "good (◯)" when 2 mg or more of the resin dissolved in 2 g of the solvent.

[0100] <Thermal stability (heat resistance)> The thermal stability was evaluated using a thermogravimetric analyzer (TGA) TGA-50 / 50H (Shimadzu Corporation) by heating at a heating rate of 10°C / min under nitrogen. The higher the initial decomposition temperature (Tdi), the more excellent the thermal stability. Since the polyacetal resin of the present invention has excellent thermal stability as described below, when used as a photoresist material, it can withstand high temperatures during pre-baking and post-baking (PEB).

[0101] <Film-forming and film-removing properties> A methyl ethyl ketone (MEK) solution of polyacetal resin (60 mg of resin, 2.0 g of MEK) was spin-coated onto a silicon wafer treated with hexamethyldisilazane (HMDS) to form a thin film approximately 100 nm thick. The film thickness was measured using a film thickness measuring device (Ellipsometer SE-101 (manufactured by Photonic Lattice Co., Ltd.), surface profiling system Dektak-XT (manufactured by Bruker)) (measurement wavelength: 636 nm). The film-forming properties were evaluated as "good" when a thin film could be formed. Next, the film was immersed in a 2.38 mass % aqueous solution of TMAH (Tetramethyl ammonium hydroxide) and then the thickness of the film was measured. The difference between the film thickness before and after immersion in the TMAH aqueous solution was determined, and the value (%) obtained by dividing the difference by the film thickness before immersion in the TMAH aqueous solution was used to evaluate the thickness loss property. The smaller this value, the more suppressed the film loss, and the more preferable it is. This is an evaluation of the usefulness of a positive resist material, particularly when used with an alkaline developer. The value is preferably 40% or less, more preferably 30% or less, and even more preferably 10% or less, and the closer to zero, the better. As will be described later, the polyacetal resin of the present invention has excellent adhesion and is suppressed from film loss.

[0102] [Raw materials] The raw materials used in the examples and evaluations and their abbreviations are as follows: <Benzenedicarboxylic acid compounds> PA: Phthalic acid (Tokyo Chemical Industry Co., Ltd.) IPA: Isophthalic acid (Tokyo Chemical Industry Co., Ltd.) <Benzenetricarboxylic acid compounds> TCA: 1,3,5-benzenetricarboxylic acid <Polyfunctional vinyl ether group-containing compound> BPA-CEVE: 2,2-Bis[4-{2-(vinyloxy)ethoxy}phenyl]propane (synthesized from bisphenol A and chloroethyl vinyl ether by the Williamson synthesis method.) <Other ingredients> MA: methacrylic acid (Tokyo Chemical Industry Co., Ltd., distilled before use) ST: styrene (Tokyo Chemical Industry Co., Ltd., distilled before use) AIBN:2,2'-Azobis(isobutyronitrile) PPTS: pyridinium p-toluenesulfonate (Tokyo Chemical Industry Co., Ltd.) THF: tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.; distilled and dried from sodium benzophenone before use) TMAH aqueous solution: Tetramethyl ammonium hydroxide aqueous solution (2.38% by mass aqueous solution) (manufactured by Tama Chemical Industry Co., Ltd.)

[0103] [Production of linear polyacetal resin] Example 1 (Production of poly(BPA-CEVE-co-PA)) [ka] A mixture of PA (10.0 mmol, 1.66 g), BPA-CEVE (10.0 mmol, 3.68 g), PPTS (0.20 mmol, 50 mg) as a catalyst, and THF (10 mL) was stirred at 25 °C for 5 h. Then, a small amount of triethylamine was added, and the resulting mixture was poured into a large amount of methanol to precipitate a solid. The solid was recovered by decantation. The recovered solid was dissolved in CHCl3 and washed three times with water. The resulting solution was dried over anhydrous magnesium sulfate and concentrated using a rotary evaporator to obtain a residue. The residue was dried under vacuum at room temperature (20-30°C) for 24 hours to obtain poly(BPA-CEVE-co-PA) as a white solid. The analytical results are shown below. Yield: 5.24g, 98% Mn=5,150, Mw / Mn=1.84 FT-IR (KBr, cm -1 ): 3628 (νO-H), 2937 (νC-H), 1718 (νC=O of ester), 1455 (νC=C of aromatic), 1248 (νC-O of ether), 1144 (νC-O of acetal), 729 (νC-H of aromatic) 1 H-NMR (400 MHz, CDCl3, TMS)δ(ppm): 1.51~1.62 (br m, -CH3), 3.96~4.14 (m, -CH2-), 6.20~6.28 (m, >CH- of methine), 6.74~7.13 (m, aromatic H), 7.49~7.76 (m, aromatic H).

[0104] Example 2 (Preparation of poly(BPA-CEVE-co-IPA)) [ka] Except for replacing PA with IPA, the same procedure as in Example 1 was carried out to obtain poly(BPA-CEVE-co-IPA) as a white solid. The analytical results are shown below. Yield: 86% Mn=3,570, Mw / Mn=1.54 FT-IR (KBr, cm -1 ): 3542 (νO-H), 2937 (νC-H), 1717 (νC=O of ester), 1498 (νC=C of aromatic), 1249 (νC-O of ether), 1177 (νC-O of acetal), 743 (νC-H of aromatic) 1H-NMR (400 MHz, CDCl3, TMS)δ(ppm): 1.56~1.63 (br m, -CH3), 3.95~4.14 (m, -CH2-), 6.27~6.33 (m, >CH- of methine), 6.75~7.12 (m, aromatic H), 7.51~8.76 (m, aromatic H).

[0105] [Production of branched polyacetal resin] Example 3 (Preparation of poly(BPA-CEVE-co-PA-co-TCA)) [ka] Poly(BPA-CEVE-co-PA-co-TCA) was obtained as a white solid in the same manner as in Example 1, except that TCA was further added, the charge ratio was BPA-CEVE / PA / TCA = 1 / 0.1 / 0.6 (molar ratio), and the reaction time was changed to 13 hours. The analytical results are shown below. Yield 46% Mn=3,800, Mw / Mn=3.34

[0106] Example 4 (Preparation of poly(BPA-CEVE-co-IPA-co-TCA)) [ka] Poly(BPA-CEVE-co-IPA-co-TCA) was obtained as a white solid in the same manner as in Example 3, except that PA was replaced with IPA. The analytical results are shown below. Yield 47% Mn=3,000, Mw / Mn=1.67

[0107] [Production of side-chain polyacetal resin] Comparative example 1(poly(MA-CHVE 25 -co-ST 75 ) Production [ka] A mixture of MA-CHVE (7.5 mmol, 2.03 g), ST (22.5 mmol, 2.34 g), AIBN (0.90 mmol, 0.15 g), and DMF (15 mL) was stirred at 60 °C for 20 hours. The resulting mixture was then poured into a large amount of methanol to precipitate a solid, which was then collected using a membrane filter. The collected solid was dried at room temperature (20-30°C) for 24 hours to obtain poly(MA-CHVE) as a white solid. 25 -co-ST 75 The analysis results are shown below. Yield 73% Mn=7,700, Mw / Mn=1.30 FT-IR (KBr, cm -1 ): 2920 (νC-H), 1600 (νC=O of ester), 1492 (νC=C of aromatic), 1248 (νC-O of ether), 1153 (νC-O of acetal), 756 (νC-H of aromatic), 697 (ν-CH2-). 1 H-NMR (400 MHz, CDCl3, TMS)δ(ppm): 0.88~3.65 (br, -CH2- of polymer skeleton, -CH2of cyclohexane, and -CH3of acetal), 4.91~5.93 (m, >CH- of methine), 6.38~7.23 (m, aromatic H).

[0108] [Table 1]

[0109] The results in Table 1 show that the polyacetal resins of the examples all have high solubility in solvents and excellent heat resistance and film-forming properties. They also have good film-removal properties in developing solutions. Therefore, the polyacetal resins of the present invention are excellent materials for forming lithography films, and are particularly excellent materials for forming resist films.

[0110] [Rating 2] <Resist sensitivity> The types and amounts of acid generators shown in Tables 2 and 3 were dissolved in methyl ethyl ketone (MEK) solutions of the polyacetal resins of the Examples or the resins of the Comparative Examples (60 mg of resin, 2.0 g of MEK), and the resulting solution was filtered through a 0.20 μm PTFE syringe filter to obtain evaluation solutions. The obtained evaluation solution was spin-coated on a hexamethyldisilazane (HMDS)-treated silicon wafer at 2500 rpm for 30 seconds to form a thin film, which was then pre-baked at 90°C for 60 seconds to obtain a film for evaluation. The acid generators shown in Tables 2 and 3 are as follows: TPS-109: Triphenylsulfonium trifluoromethanesulfonate (TPS-109 (trade name), manufactured by Midori Chemical Co., Ltd.) TPS-Nf: Triphenylsulfonium nonafluorobutanesulfonate The amount of acid generator shown in Tables 2 and 3 is the amount relative to the polyacetal resin (amount when the polyacetal resin is taken as 100% by mass).

[0111] (EB sensitivity evaluation) The obtained evaluation film was exposed using an electron beam lithography system (EB lithography) (EB-ENGINE System, manufactured by Hamamatsu Photonics KK) (accelerating voltage 50 keV, exposed area size 1 cm x 1 cm). The exposed silicon wafer was then subjected to post-exposure baking (PEB) at 90°C for 30 seconds, and then developed by immersing the post-exposure baked silicon wafer in a 2.38% by mass aqueous TMAH solution at room temperature for 30 seconds, rinsing with deionized water for 10 seconds, and drying. The film thickness was measured using an ellipsometer (SE-101, manufactured by Photonic Lattice Co., Ltd.), and a sensitivity curve was calculated. The lower the exposure dose at which the film thickness becomes zero, the better the resist sensitivity. Table 2 shows E0 (the exposure dose at which the film thickness becomes zero (μC / cm 2 )) is shown.

[0112] [Table 2]

[0113] (EUV sensitivity evaluation) The obtained evaluation film was irradiated with EUV using an EUV exposure device (EUVES-7000, manufactured by Litho Tech Japan Co., Ltd.), and then developed by immersing in ion-exchanged water for 30 seconds. The film thickness was measured using an ellipsometer (SE-101, manufactured by Photonic Lattice Co., Ltd.), and a sensitivity curve was calculated. The lower the exposure dose at which the film thickness becomes zero, the better the resist sensitivity. Table 3 shows E0 (the exposure dose at which the film thickness becomes zero (mJ / cm 2 )) is shown.

[0114] [Table 3]

[0115] The results in Tables 2 and 3 show that the polyacetal resins of the examples also have excellent resist sensitivity. These results show that the polyacetal resins of the present invention have excellent resist sensitivity characteristics, solvent solubility, heat resistance, and film-forming properties. Furthermore, it is clear that the lithography film-forming composition containing the polyacetal resin has excellent resist sensitivity characteristics.

Claims

1. A polyacetal resin obtained by addition polymerization of a polycarboxylic acid compound and a polyfunctional vinyl ether group-containing compound.

2. The polyacetal resin according to claim 1 , wherein the polycarboxylic acid compound contains a benzenedicarboxylic acid compound.

3. 3. The polyacetal resin according to claim 2, wherein the benzenedicarboxylic acid compound is at least one selected from the group consisting of isophthalic acid and phthalic acid.

4. The polyacetal resin according to claim 2 or 3, wherein the polycarboxylic acid compound further contains a benzenetricarboxylic acid compound.

5. A polyacetal resin containing a structural unit represented by the following formula (1): 【Chemistry 1】 (wherein X is a single bond, —O—, —S—, —SO ２ -, -C(CH ３ ) ２ -, and -C(CF ３ ) ２ -, Y is a hydrogen atom or a chlorine atom, and Z is at least one group selected from the group consisting of formula (2) and formula (3). 【Chemistry 2】

6. The polyacetal resin according to claim 5, further comprising a structural unit represented by the following formula (4): 【Transformation 3】

7. A lithography film-forming composition comprising the polyacetal resin according to any one of claims 1 to 6.

8. The lithographic film-forming composition according to claim 7 , further comprising a solvent.

9. The lithographic film-forming composition according to claim 7 or 8, further comprising at least one selected from the group consisting of an acid generator and a crosslinking agent.

10. The composition for forming a lithography film according to any one of claims 7 to 9, which is a composition for forming a resist film.

11. A resist film formed from the composition for forming a lithographic film according to any one of claims 7 to 10.

12. A method for forming a resist pattern, which comprises using the composition for forming a lithographic film according to any one of claims 7 to 10.

13. A step of forming a resist film on a substrate using the composition for lithography film formation according to any one of claims 7 to 10; and a step of exposing the resist film to light and developing it; A method for forming a resist pattern, comprising:

Images