JP6729450B2 - Polymer, negative resist material, and pattern forming method - Google Patents

Description

The present invention relates to a polymer, a negative resist material, and a pattern forming method.

Along with the high integration and high speed of LSIs, miniaturization of pattern rules is rapidly progressing. Mass production of 10 nm node logic devices and mass production of DRAM devices of 20 nm or less are imminent. These are formed by double patterning ArF lithography. In addition, studies on extreme ultraviolet (EUV) lithography with a wavelength of 13.5 nm are underway.

On the other hand, the flash memory has been shifting to a three-dimensional memory in which the capacity is increased by three-dimensional stacking after driving the miniaturization up to 15 nm. In this case, an ultra thick film processing technique of more than 10 μm for processing a multi-layer laminated film is required.

In ArF double patterning lithography, as the number of masks increases, it is necessary to improve the alignment accuracy of a plurality of masks and the pattern dimensions. Even in a mask for EUV lithography, it is necessary to form a finer pattern than that for ArF lithography and to improve the accuracy of each pattern.

In the mask pattern production, a resist pattern is formed by electron beam (EB) lithography. Chemically amplified resists are commonly used to improve the throughput of EB lithography. As the chemically amplified resist, for example, a polymer obtained by substituting a part of hydroxy groups of polyhydroxystyrene with an acid labile group is used as a base resin, and an acid generator, a quencher for controlling acid diffusion, and a surfactant are used as the base resin. And those containing an organic solvent. The chemically amplified resist has an advantage of high sensitivity, but has a drawback that the resolution and pattern accuracy are deteriorated due to blurring of the image of acid diffusion.

Along with the improvement of the resolution of the resist pattern by EB lithography, the aspect ratio of the resist pattern increases, which causes a problem that the pattern collapses due to the stress during the rinse drying after development. In order to prevent this, the resist film is being made thinner. At the same time, it is necessary to improve the dry etching resistance, and in order to improve the dry etching resistance of the resist film, polyhydroxystyrene substituted with an acid labile group and indene (Patent Document 1) or acenaphthylene (Patent Document 2) are used. Copolymerized polymer-based positive resists have been proposed. Copolymerization of indene and acenaphthylene not only improved dry etching resistance, but also had the advantage of controlling acid diffusion, which contributed to the improvement of resolution.

Even in the case of a negative resist, not only a negative resist using a base polymer containing a crosslinking agent or a crosslinking unit, but also in a negative resist whose hydrophilicity is reduced by a dehydration reaction by an acid, repeating units derived from indene or acenaphthylene A polymer containing was used (Patent Document 4).

In recent years, oxide film-based hard masks have been used as mask substrates, and it is no longer necessary to excessively improve the dry etching resistance of the resist film. A resist having better resolution than dry etching resistance has been required, and in recent years, in addition to the improvement of resolution, reduction of edge roughness (LER, LWR) has become important. Is coming.

JP, 2004-115630, A JP, 2006-169302, A JP, 2004-61794, A JP, 2013-164588, A

The present invention has been made in view of the above circumstances, a polymer suitable as a base resin for a negative resist material having a high resolution and a small edge roughness that exceeds a conventional negative resist material, a negative resist material using the polymer, In particular, it is an object to provide a negative resist material suitable for i-line, ArF excimer laser, EB, and EUV exposure, and a pattern forming method using the same.

The present inventors have earnestly studied in recent years to obtain a negative resist material having high resolution and small edge roughness, and as a result, a negative resist material containing a polymer containing a specific repeating unit has been found. The inventors have found that it is extremely effective when used as a base resin of, and completed the present invention.

The polymer containing a repeating unit derived from indene or acenaphthylene described in Patent Document 4 has excellent acid diffusion control and reduced edge roughness, but further improvement in performance is required. By copolymerizing indene or acenaphthylene, the main chain becomes rigid, and the glass transition point of the polymer becomes high, which shortens the acid diffusion distance. The copolymer has a higher effect of controlling acid diffusion than the styrene copolymer. On the other hand, since indene and acenaphthylene are hydrophobic aromatic compounds, a hydrophilic part and a hydrophobic part are mixed in the polymer, the solubility of the alkali developer becomes nonuniform, causing swelling, and causing edge roughness deterioration. It becomes a factor.

The copolymer of hydroxystyrene partially substituted with an acid labile group described in Patent Document 3 and coumarin has a lower hydrophobicity than indene or acenaphthylene due to the fact that coumarin has an ester group, and thus alkali development is possible. Swelling in liquid is suppressed and edge roughness is reduced. However, since the polymerizability of coumarin is low, it is difficult to uniformly introduce it into the polymer, and it does not lead to the targeted reduction of edge roughness.

The present inventors further conducted diligent studies in order to suppress acid diffusion, improve alkali dissolution uniformity, and reduce edge roughness, and as a result, a repeating unit derived from vinyl anthraquinone and a hydroxy group-containing tertiary alkyl group were identified. By using a polymer containing a repeating unit containing a bonded benzene ring and a repeating unit derived from hydroxystyrene as a base resin of a negative resist material, the alkali dissolution rate contrast before and after exposure is high, and the effect of suppressing acid diffusion is high. It was found that a negative resist material having a high resolution and a good pattern shape and edge roughness after exposure, which is particularly suitable for a VLSI production or as a fine pattern forming material for a photomask, can be obtained.

Since vinyl anthraquinone has high polymerizability like the styrene derivative, it can be uniformly introduced into the polymer. Since it has two carbonyl groups and has an appropriate hydrophilicity, the difference between the hydrophilicity and the hydrophobicity in the polymer is small, which makes the alkali solubility uniform. The two carbonyl groups also have the property of controlling acid diffusion. With the above characteristics, it is possible to obtain a resist pattern with high resolution and small edge roughness.

The negative resist material of the present invention has a high dissolution contrast when formed into a resist film, has a high effect of suppressing acid diffusion, has a high resolution, has an exposure margin, and is excellent in process adaptability, The pattern shape after exposure is good. Therefore, since they have these excellent characteristics, they are extremely practical and very effective as a resist material mask pattern forming material for VLSI.

（式中、Ｒ^Aは、それぞれ独立に、水素原子又はメチル基である。Ｒ¹は、ヒドロキシ基、直鎖状若しくは分岐状の炭素数１〜４のアルキル基、直鎖状若しくは分岐状の炭素数１〜４のアルコキシ基、アセトキシ基、又はハロゲン原子を表す。Ｒ²及びＲ⁵は、それぞれ独立に、直鎖状若しくは分岐状の炭素数１〜６のアルキル基、又はハロゲン原子である。Ｒ³及びＲ⁴は、それぞれ独立に、炭素数１〜６の直鎖状、分岐状又は環状のアルキル基であり、Ｒ³とＲ⁴とが結合して、これらが結合する炭素原子と共に環を形成していてもよい。Ｘ¹及びＸ²は、それぞれ独立に、単結合又はエステル基である。ｍは、１又は２である。ｐ及びｑは、それぞれ独立に、０又は１である。ｒは、０〜４の整数である。）
２．更に、下記式（ｆ１）〜（ｆ３）で表される繰り返し単位から選ばれる少なくとも１種を含み、その割合が０＜ｆ≦０.３である（ただし、ａ＋ｂ＋ｃ＋ｆ≦１である。）１のポリマー。

（式中、Ｒ^Aは、それぞれ独立に、水素原子又はメチル基である。Ｒ²¹は、単結合、フェニレン基、−Ｏ−Ｒ³¹−、又は−Ｃ(＝Ｏ)−Ｚ¹−Ｒ³¹−であり、Ｚ¹は、−Ｏ−又は−ＮＨ−であり、Ｒ³¹は、直鎖状、分岐状若しくは環状の炭素数１〜６のアルキレン基、直鎖状、分岐状若しくは環状の炭素数２〜６のアルケニレン基、又はフェニレン基であり、カルボニル基、エステル基、エーテル基又はヒドロキシ基を含んでいてもよい。Ｒｆ¹〜Ｒｆ⁴は、それぞれ独立に、フッ素原子、水素原子又はトリフルオロメチル基であるが、Ｒｆ¹〜Ｒｆ⁴のうち少なくとも１つはフッ素原子である。Ｒ²²〜Ｒ²⁹は、それぞれ独立に、カルボニル基、エステル基若しくはエーテル基を含んでいてもよい直鎖状、分岐状若しくは環状の炭素数１〜１２のアルキル基、炭素数６〜１２のアリール基、炭素数７〜２０のアラルキル基、又はメルカプトフェニル基である。Ｙ¹は、単結合、又はエステル基、エーテル基又若しくはラクトン環を含んでいてもよい炭素数１〜１２の連結基である。Ｙ²は、単結合、メチレン基、エチレン基、フェニレン基、フッ素化フェニレン基、−Ｏ−Ｒ³²−、又は−Ｃ(＝Ｏ)−Ｚ²−Ｒ³²−であり、Ｚ²は、−Ｏ−又は−ＮＨ−であり、Ｒ³²は、直鎖状、分岐状若しくは環状の炭素数１〜６のアルキレン基、フェニレン基、又は直鎖状、分岐状若しくは環状の炭素数２〜６のアルケニレン基であり、カルボニル基、エステル基、エーテル基又はヒドロキシ基を含んでいてもよい。Ｍ^-は、非求核性対向イオンである。）
３．１又は２のポリマーを含むベース樹脂を含むネガ型レジスト材料。
４．更に、有機溶剤及び酸発生剤を含む化学増幅レジスト材料である３のネガ型レジスト材料。
５．更に、塩基性化合物を含む３又は４のネガ型レジスト材料。
６．更に、界面活性剤を含む３〜５のいずれかのネガ型レジスト材料。
７．３〜６のいずれかのネガ型レジスト材料を基板上に塗布し、加熱処理をしてレジスト膜を形成する工程と、前記レジスト膜を高エネルギー線で露光する工程と、現像液を用いて露光したレジスト膜を現像する工程とを含むパターン形成方法。
８．前記基板が、フォトマスクブランクである７のパターン形成方法。
９．前記高エネルギー線が、波長１８０〜４００ｎｍの紫外線である７又は８のパターン形成方法。
１０．前記高エネルギー線が、ＥＢ又は波長３〜１５ｎｍのＥＵＶである７又は８のパターン形成方法。
１１．３〜６のいずれかのネガ型レジスト材料を塗布したフォトマスクブランク。 That is, the present invention provides the following polymers, negative resist materials, and pattern forming methods.
1. Repeating unit represented by the following formula (a), the repeating unit represented by the following formula (b), and includes a repeating unit represented by the following formula (c), repeating units represented by the following formula (a) , The proportion of the repeating unit represented by the following formula (b) and the proportion of the repeating unit represented by the following formula (c) are 0.03≦a≦0.5, 0.05≦b≦0.6, and 0.1≦c≦0.9 (provided that a+b+c≦1) and the weight average molecular weight is 1,000 to 500,000.

(In formula, R ^<A> is respectively independently a hydrogen atom or a methyl group. R< ¹ > is a hydroxy group, a linear or branched C1-C4 alkyl group, a linear or branched C1. Represents an alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom, and R ² and R ⁵ are each independently a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. R ³ and R ⁴ are each independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, and R ³ and R ⁴ are bonded to each other, together with the carbon atom to which they are bonded. May form a ring, X ¹ and X ² are each independently a single bond or an ester group, m is 1 or 2. p and q are each independently 0 or 1. Yes, r is an integer of 0 to 4.)
2. Furthermore, look contains at least one selected from the repeating unit represented by the following formula (f1) ~ (f3), the proportion is 0 <f ≦ 0.3 (provided that a + b + c + f ≦ 1.) 1 Polymer of.

(Wherein, R ^A are each independently a hydrogen atom or a methyl group .R ²¹ is a single bond, a phenylene group, -O-R ³¹ -, or ^{-C (= O) -Z 1 -R} 31 - and, Z ¹ is -O- or -NH-, R ³¹ is a linear, branched or cyclic alkylene group having 1 to 6 carbon atoms, a linear, carbon branched or cyclic It is an alkenylene group or a phenylene group having a number of 2 to 6, and may contain a carbonyl group, an ester group, an ether group or a hydroxy group.Rf ^{1 to} Rf ⁴ are each independently a fluorine atom, a hydrogen atom or a triatom. Although it is a fluoromethyl group, at least one of Rf ^{1 to} Rf ⁴ is a fluorine atom, and R ^{22 to} R ²⁹ are each independently a straight chain which may contain a carbonyl group, an ester group or an ether group. , A branched or cyclic alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a mercaptophenyl group, wherein Y ¹ is a single bond or an ester. Group, an ether group, or a linking group having 1 to 12 carbon atoms, which may contain a lactone ring, Y ² is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, or -OR ³² -, or ^{-C (= O) -Z 2 -R} 32 - is and, Z ² is -O- or -NH-, R ³² represents a linear, branched or cyclic carbon atoms 1 6 alkylene group, a phenylene group, or a linear, alkenylene group having 2 to 6 carbon atoms branched or cyclic, may contain a carbonyl group, an ester group, an ether group or a hydroxy group .M ^- Is a non-nucleophilic counterion.)
3. A negative resist material containing a base resin containing the polymer of 1 or 2.
4. Furthermore, the negative resist material of 3 , which is a chemically amplified resist material containing an organic solvent and an acid generator.
5. Furthermore, the negative resist material of 3 or 4 containing a basic compound.
6. Further, any of the negative resist composition of 3 to 5 containing a surfactant.
7. The step of applying the negative resist material of any one of 3 to 6 on a substrate and performing a heat treatment to form a resist film, the step of exposing the resist film with a high energy ray, and the exposure using a developing solution. Forming a patterned resist film.
8. 7. The pattern forming method according to 7, wherein the substrate is a photomask blank.
9. 7. The pattern forming method according to 7 or 8, wherein the high energy rays are ultraviolet rays having a wavelength of 180 to 400 nm.
10. 7. The pattern forming method according to 7 or 8, wherein the high energy ray is EB or EUV having a wavelength of 3 to 15 nm.
11. A photomask blank coated with the negative resist material of any of 11.3 to 6.

The negative resist material containing the polymer of the present invention has a significantly high alkali dissolution rate contrast before and after exposure, has a high resolution, and has a good pattern shape and line edge roughness after exposure, and more particularly, an acid. The diffusion speed can be suppressed. Therefore, it is particularly suitable as a fine pattern forming material for VLSI production or a photomask, a pattern forming material for EUV exposure, and ArF excimer laser exposure. Further, the negative resist material of the present invention can be applied not only to lithography in semiconductor circuit formation, but also to mask circuit pattern formation, micromachines, thin film magnetic head circuit formation, and the like.

[polymer]
The polymer of the present invention has a repeating unit represented by the following formula (a) (hereinafter referred to as repeating unit a), a repeating unit represented by the following formula (b) (hereinafter referred to as repeating unit b), and the following: It contains a repeating unit represented by formula (c) (hereinafter referred to as repeating unit c) and has a weight average molecular weight (Mw) of 1,000 to 500,000.

In the formula, R ^A's are each independently a hydrogen atom or a methyl group. R ¹ represents a hydroxy group, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom. R ² and R ⁵ are each independently a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. R ³ and R ⁴ are each independently a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, and R ³ and R ⁴ are bonded to each other to form a ring together with the carbon atom to which they are bonded. May be formed. X ¹ and X ² are each independently a single bond or an ester group. m is 1 or 2. p and q are 0 or 1 each independently. r is an integer of 0-4.

Examples of the monomer for obtaining the repeating unit a include, but are not limited to, those shown below.

Examples of the monomer for obtaining the repeating unit b include, but are not limited to, those shown below. In the formula below, R ^A is the same as above.

Examples of the monomer for obtaining the repeating unit c include, but are not limited to, those shown below. In the formula below, R ^A is the same as above.

The polymer of the present invention may further contain a repeating unit d containing an adhesive group selected from a hydroxy group, a lactone ring, an ether group, an ester group, a carbonyl group and a cyano group. Examples of the monomer that provides the repeating unit d include, but are not limited to, those shown below. In the formula below, R ^A is the same as above.

In the case of a monomer containing a hydroxy group, the hydroxy group may be replaced with an acetal group that is easily deprotected by an acid such as an ethoxyethoxy group during polymerization, and depolymerization may be performed with a weak acid and water after the polymerization, or an acetyl group, It may be substituted with a formyl group, a pivaloyl group or the like and then subjected to alkali hydrolysis after the polymerization.

The polymer of the present invention may contain a repeating unit f derived from an onium salt containing a polymerizable olefin. JP-A-4-230645, JP-A-2005-84365, and JP-A-2006-045311 propose sulfonium salts and iodonium salts having a polymerizable olefin capable of generating a specific sulfonic acid. Japanese Unexamined Patent Publication No. 2006-178317 proposes a sulfonium salt in which sulfonic acid is directly bonded to the main chain.

Preferred repeating unit f is a repeating unit represented by the following formula (f1) (hereinafter referred to as repeating unit f1), a repeating unit represented by the following formula (f2) (hereinafter referred to as repeating unit f2), and A repeating unit represented by the following formula (f3) (hereinafter, referred to as repeating unit f3) can be given. The repeating units f1 to f3 may be used alone or in combination of two or more.

In the formula, R ^A's are each independently a hydrogen atom or a methyl group. R ²¹ is a single bond, a phenylene group, —O—R ³¹ —, or —C(═O)—Z ¹ —R ³¹ —, Z ¹ is —O— or —NH—, and R ³¹ Is a linear, branched or cyclic alkylene group having 1 to 6 carbon atoms, a linear, branched or cyclic alkenylene group having 2 to 6 carbon atoms, or a phenylene group, a carbonyl group, an ester group, It may contain an ether group or a hydroxy group. Rf ^{1 to} Rf ⁴ are each independently a fluorine atom, a hydrogen atom or a trifluoromethyl group, and at least one of Rf ^{1 to} Rf ⁴ is a fluorine atom. R ^{22 to} R ²⁹ are each independently a linear, branched or cyclic C 1-12 alkyl group which may contain a carbonyl group, an ester group or an ether group, and a C 6-12 aryl. A group, an aralkyl group having 7 to 20 carbon atoms, or a mercaptophenyl group. Y ¹ is a single bond or a linking group having 1 to 12 carbon atoms which may contain an ester group, an ether group or a lactone ring. Y ² represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, -O-R ³² -, or ^{-C (= O) -Z 2 -R} 32 - is and, Z ² is - R ³² is O— or —NH—, and R ³² is a linear, branched or cyclic alkylene group having 1 to 6 carbon atoms, a phenylene group, or a linear, branched or cyclic C 2 to 6 carbon atoms. It is an alkenylene group and may contain a carbonyl group, an ester group, an ether group or a hydroxy group. M ^- is a non-nucleophilic counterion.

Examples of the non-nucleophilic counter ion represented by M ⁻ are halide ions such as chloride ion and bromide ion, triflate, fluoroalkyl sulfonates such as 1,1,1-trifluoroethane sulfonate and nonafluorobutane sulfonate, Aryl sulfonates such as tosylate, benzene sulfonate, 4-fluorobenzene sulfonate, 1,2,3,4,5-pentafluorobenzene sulfonate, alkyl sulfonates such as mesylate and butane sulfonate, bis(trifluoromethylsulfonyl)imide, bis( Examples thereof include imido acids such as perfluoroethylsulfonyl)imide and bis(perfluorobutylsulfonyl)imide, and methide acids such as tris(trifluoromethylsulfonyl)methide and tris(perfluoroethylsulfonyl)methide.

Examples of the non-nucleophilic counter ion further include a sulfonate ion in which the α-position represented by the following formula (K-1) is fluoro-substituted, and α- and β-positions represented by the following formula (K-2) are fluoro. Examples thereof include substituted sulfonate ions.

In formula (K-1), R ¹⁰¹ represents a hydrogen atom, a linear, branched, or cyclic alkyl group having 1 to 30 carbon atoms, a linear, branched, or cyclic acyl group having 2 to 30 carbon atoms. A linear, branched, or cyclic alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aryloxy group, which is an ether group, an ester group, a carbonyl group, a lactone ring, a lactam ring, or a sultone. It may contain a ring, an amino group, a sulfone group, a sulfonate group, a carbonate group, a hydroxy group, a thiol group, a carboxyl group, a carbamate group, an amide group or an imide group.

In formula (K-2), R ¹⁰² represents a hydrogen atom, a linear, branched or cyclic C 1-30 alkyl group, a linear, branched or cyclic C 2-30 acyl group. A linear, branched, or cyclic alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aryloxy group, which is an ether group, an ester group, a carbonyl group, a lactone ring, a lactam ring, or a sultone. It may contain a ring, an amino group, a sulfone group, a sulfonate group, a carbonate group, a hydroxy group, a thiol group, a carboxyl group, a carbamate group, an amide group or an imide group. R ¹⁰³ is a hydrogen atom, a methyl group, an ethyl group or a trifluoromethyl group.

The repeating unit f functions as an acid generator. By binding an acid generator to the polymer main chain, acid diffusion can be reduced, and deterioration of resolution due to blur of acid diffusion can be prevented. Further, the edge roughness is improved by uniformly dispersing the acid generator.

In the polymer of the present invention, the proportion of repeating units a to f is 0<a<1.0, 0<b<1.0, 0<c<1.0, 0≦d≦0.7, 0, respectively. ≤ e ≤ 0.7 and 0 ≤ f ≤ 0.3 are preferred, and 0.03 ≤ a ≤ 0.5, 0.05 ≤ b ≤ 0.6, 0.1 ≤ c ≤ 0.9, 0 ≤ d. ≦0.6, 0≦e≦0.6 and 0≦f≦0.25 are more preferable, and 0.05≦a≦0.4, 0.1≦b≦0.5, 0.2≦c≦ More preferably, 0.8, 0≤d≤0.5, 0≤e≤0.5 and 0≤f≤0.2. When the repeating unit f is at least one kind selected from the repeating units f1 to f3, f=f1+f2+f3. Also, a+b+c+d+e+f≦1. In addition, for example, a+b+c=1 means that in a polymer containing repeating units a, b and c, the total amount of repeating units a, b and c is 100 mol% in all repeating units, and a+b+c<1 Indicates that the total amount of the repeating units a, b and c is less than 100 mol% in all the repeating units and that the repeating units a, b and c contain other repeating units.

The polymer of the present invention has a Mw of 1,000 to 500,000, preferably 2,000 to 30,000. If the Mw is too small, the resist material will be inferior in heat resistance, and if it is too large, the alkali solubility will be lowered, and the footing phenomenon will easily occur after pattern formation. In addition, Mw is a polystyrene conversion measurement value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

Furthermore, in the case where the polymer of the present invention has a wide molecular weight distribution (Mw/Mn), a low molecular weight or high molecular weight polymer is present, so that after exposure, foreign matter is seen on the pattern or the pattern shape deteriorates. There is a risk of Since the influence of Mw and molecular weight distribution tends to increase as the pattern rule becomes finer, the molecular weight distribution of the polymer of the present invention is 1.0 to 1.0 in order to obtain a resist material suitable for use in fine pattern dimensions. A narrow dispersion of 2.0, particularly 1.0 to 1.5 is preferred.

In order to synthesize the polymer of the present invention, for example, a desired monomer among the monomers giving the repeating units a to f may be heated by adding a radical polymerization initiator in an organic solvent to perform polymerization.

Examples of the organic solvent used during the polymerization include toluene, benzene, tetrahydrofuran, diethyl ether, dioxane and the like. As the polymerization initiator, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate) ), benzoyl peroxide, lauroyl peroxide and the like. The temperature at the time of polymerization is preferably 50 to 80°C. The reaction time is preferably 2 to 100 hours, more preferably 5 to 20 hours.

When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, use acetoxystyrene or acetoxyvinylnaphthalene instead of hydroxystyrene or hydroxyvinylnaphthalene.After polymerization, deprotect the acetoxy group by alkaline hydrolysis to remove hydroxystyrene or hydroxyvinylnaphthalene. May be naphthalene.

Ammonia water, triethylamine and the like can be used as the base during the alkali hydrolysis. The reaction temperature is preferably −20 to 100° C., more preferably 0 to 60° C. The reaction time is preferably 0.2 to 100 hours, more preferably 0.5 to 20 hours.

The polymer of the present invention is suitable as a base resin for a negative resist material.

[Negative resist material]
The negative resist material of the present invention contains a base resin containing the above-mentioned polymer. When the polymer is used as a base resin for a negative resist material, the base resin may be a blend of two or more polymers having different composition ratios, molecular weight distributions and molecular weights.

The negative resist composition of the present invention preferably further contains an organic solvent, an acid generator, a dissolution control agent, a basic compound, a surfactant and the like in an appropriate combination according to the purpose. By constructing the negative resist material in this manner, the dissolution rate of the polymer in the developing solution in the exposed portion is accelerated by the catalytic reaction, so that the negative resist material having extremely high sensitivity can be obtained. Therefore, the dissolution contrast and resolution of the resist film are high, the exposure margin is excellent, the process adaptability is excellent, the pattern shape after exposure is good, but the etching resistance is superior, and particularly acid diffusion is suppressed. Because of this, the difference in coarse and fine dimensions is small, and from these facts, it is highly practical and can be made very effective as a resist material for VLSI. In particular, when a chemically amplified negative resist material containing an acid generator and utilizing an acid catalyzed reaction is used, higher sensitivity can be obtained, and various properties are further improved, which is extremely useful. ..

Examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amyl ketone, 3-methoxybutanol, and 3-methyl-, which are described in paragraphs [0144] to [0145] of JP 2008-111103 A. Alcohols such as 3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether , Ethers such as diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, Examples thereof include tert-butyl propionate, esters such as propylene glycol monotert-butyl ether acetate, lactones such as γ-butyrolactone, and mixed solvents thereof. The compounding amount of the organic solvent is preferably 50 to 10,000 parts by mass, and more preferably 100 to 5,000 parts by mass with respect to 100 parts by mass of the base resin.

The negative resist material of the present invention may contain an acid generator to make the chemically amplified negative resist material function. Examples of the acid generator include compounds (photoacid generators) that generate an acid in response to actinic rays or radiation. The component of the photo-acid generator may be any compound as long as it is a compound that generates an acid upon irradiation with high energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonate type acid generators and the like. These can be used alone or in combination of two or more. Specific examples of the acid generator include those described in paragraphs [0122] to [0142] of JP-A-2008-111103. The compounding amount of the acid generator is preferably 0.01 to 100 parts by mass, and more preferably 0.1 to 80 parts by mass with respect to 100 parts by mass of the base resin.

The negative resist composition of the present invention may contain a dissolution control agent. By blending the dissolution control agent, the difference in dissolution rate between the exposed area and the unexposed area can be further increased, and the resolution can be further improved. Specific examples of the dissolution control agent include those described in paragraphs [0155] to [0178] of JP-A-2008-122932. The blending amount of the dissolution control agent is preferably 0 to 50 parts by mass, and more preferably 0 to 40 parts by mass with respect to 100 parts by mass of the base resin.

The negative resist material of the present invention may contain a basic compound. By blending the basic compound, for example, the acid diffusion rate in the resist film can be suppressed and the resolution can be further improved. As the basic compound, a primary, secondary or tertiary amine compound described in paragraphs [0146] to [0164] of JP-A-2008-111103, particularly a hydroxy group, an ether group, an ester group, a lactone Examples thereof include amine compounds having a ring, a cyano group and a sulfonate group, and compounds having a carbamate group described in Japanese Patent No. 3790649. Further, as the basic compound, the polymer type quencher described in JP-A-2008-239918 can also be mentioned. This can enhance the rectangularity of the resist after patterning by orienting on the resist surface after coating. The polymer-type quencher also has an effect of preventing pattern thinning and rounding of the pattern top when a protective film for immersion exposure is applied. The compounding amount of the basic compound is preferably 0 to 100 parts by mass, and more preferably 0.001 to 50 parts by mass with respect to 100 parts by mass of the base resin.

The negative resist material of the present invention may contain a surfactant. By adding a surfactant, the coating property of the resist material can be further improved or controlled.
Specific examples of the surfactant include those described in paragraphs [0165] to [0166] of JP-A-2008-111103. The blending amount of the surfactant is preferably 0 to 10 parts by mass, and more preferably 0.0001 to 5 parts by mass with respect to 100 parts by mass of the base resin.

The resist material of the present invention may further contain acetylene alcohols.
Examples of the acetylene alcohols include those described in paragraphs [0179] to [0182] of JP 2008-122932A. The amount of the acetylene alcohol compounded is preferably 0 to 5 parts by mass with respect to 100 parts by mass of the base resin.

[Pattern formation method]
When the negative resist material of the present invention is used for manufacturing various integrated circuits, known lithography techniques can be applied.

For example, the negative resist material of the present invention is applied to a substrate for manufacturing integrated circuits (Si, SiO ₂ , SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflection film, etc.) or a substrate for manufacturing mask circuits (Cr. , CrO, CrON, MoSi ₂ , SiO ₂ etc.) so that the coating film thickness becomes 0.01 to 2 μm by an appropriate coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc. Apply to. This is prebaked on a hot plate, preferably at 60 to 150°C for 10 seconds to 30 minutes, more preferably at 80 to 120°C for 30 seconds to 20 minutes. Then, a target pattern is directly or directly exposed with high energy rays such as ultraviolet rays, far ultraviolet rays, EB, EUV, X-rays, soft X-rays, excimer lasers, γ rays, and synchrotron radiation. The exposure dose, 1 to 200 mJ / cm ² or so, in particular 10 to 100 mJ / cm ² or so, or 0.1~100μC / cm ² or so, be exposed to particularly a 0.5~50μC / cm ² of about preferable. Next, post-exposure bake (PEB) is preferably performed on a hot plate at 60 to 150° C. for 10 seconds to 30 minutes, more preferably at 80 to 120° C. for 30 seconds to 20 minutes.

An antistatic film based on polythiophene or polyaniline may be provided on the resist film, or a top coat film other than this may be formed.

Further, preferably 0.1 to 5% by mass, more preferably 2 to 10% by mass of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium. Using an alkaline aqueous solution such as hydroxide (TBAH) for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes, a conventional method such as a dipping method, a paddle method, or a spray method. By developing with, a desired negative pattern is formed on the substrate, in which the light-irradiated portion is not dissolved in the developing solution and the unexposed portion is dissolved. The resist material of the present invention is most suitable for fine patterning by EB, EUV, soft X-rays, X-rays, γ-rays and synchrotron radiation, especially among high energy rays.

TEAH, TPAH, and TBAH, which have an alkyl chain longer than that of a widely used TMAH aqueous solution, are effective in reducing swelling during development and preventing pattern collapse. As a TMAH developer, a 2.38 mass% aqueous solution is most widely used. This corresponds to 0.26 N, and TEAH, TPAH or TBAH aqueous solutions preferably have the same normality. The concentrations of TEAH, TPAH, and TBAH that are 0.26 N are 3.84% by mass, 5.31% by mass, and 6.78% by mass, respectively.

In a pattern of 32 nm or less that is resolved by EB or EUV, there are phenomena that the lines are twisted, the lines stick to each other, or the stuck lines fall. It is considered that this is because the swollen lines in the developing solution stick to each other. Since the swollen line contains the developing solution and is soft like a sponge, it is easy to collapse due to the stress of the rinse. The developer containing TEAH, TPAH and TBAH having a long alkyl chain is effective in preventing swelling and pattern collapse.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The weight average molecular weight (Mw) is a polystyrene-converted measurement value by GPC using THF as a solvent. Moreover, the monomers 1 to 3 and the PAG monomers 1 to 4 used in the following examples are as follows.

[1] Synthesis of Polymer [Example 1-1] Synthesis of Polymer 1 To a 2 L flask, 3.5 g of 2-vinylanthraquinone, 4.1 g of Monomer 1, 7.2 g of 4-hydroxystyrene, and 20 g of THF as a solvent were added. .. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After the temperature was raised to room temperature, 1.2 g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, the temperature was raised to 60° C., and the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 1. The composition of polymer 1 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-2] Synthesis of polymer 2 To a 2 L flask, 3.5 g of 2-vinylanthraquinone, 4.1 g of monomer 2, 7.8 g of 4-hydroxystyrene, and 40 g of THF as a solvent were added. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 2. The composition of polymer 2 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-3] Synthesis of polymer 3 In a 2 L flask, 3.5 g of 2-vinylanthraquinone, 5.1 g of monomer 3, 4.2 g of 4-hydroxystyrene, 3.6 g of 4-hydrophenyl methacrylate and 3.6 g of a solvent were used. As a result, 40 g of THF was added. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 3. The composition of polymer 3 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-4] Synthesis of polymer 4 To a 2 L flask, 3.5 g of 2-vinylanthraquinone, 4.9 g of monomer 1, 4.8 g of 4-hydroxystyrene, 6.8 g of PAG monomer 1 and 40 g of THF as a solvent were added. did. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 4. The composition of polymer 4 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-5] Synthesis of polymer 5 To a 2 L flask, 4.5 g of 2-vinylanthraquinone, 4.9 g of monomer 1, 4.8 g of 4-hydroxystyrene, 5.9 g of PAG monomer 2 and 40 g of THF as a solvent were added. did. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 5. The composition of polymer 5 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-6] Synthesis of polymer 6 In a 2 L flask, 4.5 g of 2-vinylanthraquinone, 4.9 g of monomer 1, 5.3 g of 4-hydroxyphenyl methacrylate, and 3-oxo-2,7-methacrylate were used. 2.2 g of dioxatricyclo[4.2.1.0 ^4,8 ]nonan-9-yl, 7.4 g of PAG monomer 3 and 40 g of THF as a solvent were added. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The obtained white solid was separated by filtration and then dried under reduced pressure at 60° C. to obtain a polymer 6. The composition of polymer 6 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Example 1-7] Synthesis of Polymer 7 In a 2 L flask, 2.3 g of 2-vinylanthraquinone, 4.9 g of Monomer 1, 5.3 g of 4-hydroxyphenyl methacrylate, 2.0 g of α-methylene-γ-butyrolactone. , PAG monomer 4 (7.4 g) and THF (40 g) as a solvent were added. The reaction vessel was cooled to −70° C. under a nitrogen atmosphere, and deaeration under reduced pressure and nitrogen blowing were repeated 3 times. After raising the temperature to room temperature, 1.2 g of AIBN was added as a polymerization initiator, and after raising the temperature to 60° C., the reaction was carried out for 15 hours. When the reaction solution was concentrated to 1/2 and added to a mixed solvent of 1 L of methanol and 0.1 L of water, a white solid was precipitated. The white solid obtained was filtered off and dried under reduced pressure at 60° C. to obtain Polymer 7. The composition of polymer 7 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[Comparative Example 1-1] Synthesis of Comparative Polymer 1 Comparative Polymer 1 was obtained by the same method as in Example 1-1, except that 2.3 g of acenaphthylene was used instead of 2-vinylanthraquinone. The composition of Comparative Polymer 1 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

[2] Preparation of Negative Resist Material [Examples 2-1 to 2-9, Comparative Example 2-1]
A negative resist material prepared by dissolving each component having the composition shown in Table 1 in a solvent prepared by dissolving 100 ppm of a surfactant FC-4430 manufactured by 3M Co., Ltd. as a surfactant through a 0.2 μm size filter. Was prepared.
Each component in Table 1 is as follows.
Polymers 1 to 7: Polymers obtained in Examples 1-1 to 1-7 Comparative polymer 1: Polymer obtained in Comparative Example 1 Organic solvent: PGMEA (propylene glycol monomethyl ether acetate)
CyH (cyclohexanone)
-Acid generator: PAG1 (see the structural formula below)
-Basic compound: quencher 1 (see the structural formula below)

[3] EB Lithography Evaluation Each of the negative resist materials prepared in Examples 2-1 to 2-9 and Comparative Example 2-1 was applied to a clean track Mark 5 (Tokyo Electron Ltd.) on a Si substrate having a diameter of 6 inches. )) and spin-coated on a hot plate at 110° C. for 60 seconds to form a 100 nm resist film. HL-800D manufactured by Hitachi, Ltd. was used for this, and drawing was performed in a vacuum chamber at an HV voltage of 50 kV.
Immediately after drawing, PEB was performed on a hot plate at a temperature shown in Table 1 for 60 seconds using a clean track Mark 5 (manufactured by Tokyo Electron Ltd.), and paddle development was performed with a 2.38 mass% TMAH aqueous solution for 30 seconds. , A negative pattern was obtained.
The obtained resist pattern was evaluated as follows.
The minimum dimension in the exposure amount for resolving 100 nm line and space at 1:1 was taken as the resolving power, and the line edge roughness (LER) of 100 nm LS was measured by SEM.
The results are also shown in Table 1.

From the results shown in Table 1, it was found that the resist material using the polymer of the present invention has sufficient resolution and sensitivity, and the LER is reduced.

Claims (11)

Repeating unit represented by the following formula (a), the repeating unit represented by the following formula (b), and includes a repeating unit represented by the following formula (c), repeating units represented by the following formula (a) , The proportion of the repeating unit represented by the following formula (b) and the proportion of the repeating unit represented by the following formula (c) are 0.03≦a≦0.5, 0.05≦b≦0.6, and 0.1≦c≦0.9 (provided that a+b+c≦1) and the weight average molecular weight is 1,000 to 500,000.

(In formula, R ^<A> is respectively independently a hydrogen atom or a methyl group. R< ¹ > is a hydroxy group, a linear or branched C1-C4 alkyl group, a linear or branched C1. Represents an alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom, and R ² and R ⁵ are each independently a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. R ³ and R ⁴ are each independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, and R ³ and R ⁴ are bonded to each other, together with the carbon atom to which they are bonded. May form a ring, X ¹ and X ² are each independently a single bond or an ester group, m is 1 or 2. p and q are each independently 0 or 1. Yes, r is an integer of 0 to 4.) Furthermore, look contains at least one selected from the repeating unit represented by the following formula (f1) ~ (f3), the proportion is 0 <f ≦ 0.3 (provided that a + b + c + f ≦ 1.) Claims Item 2. The polymer according to item 1.

(Wherein, R ^A are each independently a hydrogen atom or a methyl group .R ²¹ is a single bond, a phenylene group, -O-R ³¹ -, or ^{-C (= O) -Z 1 -R} 31 - and, Z ¹ is -O- or -NH-, R ³¹ is a linear, branched or cyclic alkylene group having 1 to 6 carbon atoms, a linear, carbon branched or cyclic It is an alkenylene group or a phenylene group having a number of 2 to 6, and may contain a carbonyl group, an ester group, an ether group or a hydroxy group.Rf ^{1 to} Rf ⁴ are each independently a fluorine atom, a hydrogen atom or a triatom. Although it is a fluoromethyl group, at least one of Rf ^{1 to} Rf ⁴ is a fluorine atom, and R ^{22 to} R ²⁹ are each independently a straight chain which may contain a carbonyl group, an ester group or an ether group. , A branched or cyclic alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a mercaptophenyl group, wherein Y ¹ is a single bond or an ester. Group, an ether group, or a linking group having 1 to 12 carbon atoms, which may contain a lactone ring, Y ² is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, or -OR ³² -, or ^{-C (= O) -Z 2 -R} 32 - is and, Z ² is -O- or -NH-, R ³² represents a linear, branched or cyclic carbon atoms 1 6 alkylene group, a phenylene group, or a linear, alkenylene group having 2 to 6 carbon atoms branched or cyclic, may contain a carbonyl group, an ester group, an ether group or a hydroxy group .M ^- Is a non-nucleophilic counterion.) A negative resist material containing a base resin containing the polymer according to claim 1. The negative resist material according to claim 3, which is a chemically amplified resist material containing an organic solvent and an acid generator. The negative resist material according to claim 3 , further comprising a basic compound. The negative resist material according to claim 3 , further comprising a surfactant. A step of applying the negative resist material according to any one of claims 3 to 6 on a substrate and performing a heat treatment to form a resist film, a step of exposing the resist film with a high energy ray, and a development. And a step of developing a resist film exposed by using a liquid. The pattern forming method according to claim 7, wherein the substrate is a photomask blank. The pattern forming method according to claim 7, wherein the high-energy rays are ultraviolet rays having a wavelength of 180 to 400 nm. The pattern forming method according to claim 7, wherein the high-energy rays are electron rays or extreme ultraviolet rays having a wavelength of 3 to 15 nm. A photomask blank coated with the negative resist material according to claim 3.