Negative resist material and pattern forming method

Abstract

To provide a negative resist material that has a higher resolution than that of the conventional negative resist material and also has reduced edge roughness, and a pattern forming process.SOLUTION: A negative resist material comprises a base polymer comprising repeat units a derived from a triple bond-containing maleimide compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a negative resist material and a pattern forming method. [Background technology]

[0002] As LSIs become more highly integrated and faster, pattern rules are becoming finer at a rapid pace. This is because 5G high-speed communications and artificial intelligence (AI) are becoming more widespread, and high-performance devices are needed to process these. The most advanced miniaturization technology is extreme ultraviolet (EUV) lithography with a wavelength of 13.5 nm, which is used to mass-produce 5 nm node devices. Furthermore, studies are underway to use EUV lithography for next-generation 3 nm node devices and the next-next generation 2 nm node devices.

[0003] In mask pattern production, resist patterns are formed by electron beam (EB) writing. In order to improve the throughput of EB writing, chemically amplified resist materials are generally used. Examples of the chemically amplified resist materials include those in which a polymer in which a part of the hydroxyl groups of polyhydroxystyrene is substituted with an acid labile group is used as a base polymer, to which an acid generator, a quencher for controlling the diffusion of acid, a surfactant, and an organic solvent are blended. Chemically amplified resist materials have the advantage of high sensitivity, but on the other hand, they also have the disadvantage that the resolution and pattern accuracy are reduced due to the blurring of the image caused by acid diffusion.

[0004] Resolution can be improved by narrowing the beam radius or increasing the acceleration voltage from 50 kV to 100 kV. However, in the former case, the drawing area becomes smaller, and in the latter case, the scattering of electrons in the resist film becomes smaller, decreasing the sensitivity of the resist film, and in either case, the drawing time becomes longer. Furthermore, the progress of miniaturization and the increase in the number of drawing patterns also lengthen the drawing time.

[0005] To overcome the trade-off between improving resolution and shortening the writing time, a multi-beam EB writing system has been developed that uses multiple small focused EBs to write simultaneously, thereby shortening the writing time while improving the resolution.

[0006] As the resolution of the resist pattern by EB drawing improves, the aspect ratio of the resist pattern increases, which causes the problem of the pattern collapsing due to stress during rinsing and drying after development. In order to prevent this, the resist film is being made thinner. In addition, it is necessary to improve the dry etching resistance, and in order to improve the dry etching resistance of the resist film, a positive resist material using a base polymer obtained by copolymerizing polyhydroxystyrene substituted with an acid labile group with indene (Patent Document 1) or acenaphthylene (Patent Document 2) has been proposed. By copolymerizing indene or acenaphthylene, not only is the dry etching resistance improved, but there is also the advantage of controlling acid diffusion, which contributes to improving the resolution.

[0007] A negative resist material has been proposed in which the polarity changes from hydrophilic to hydrophobic through a dehydration reaction caused by an acid catalyst, etc. (Patent Document 3). Since this does not involve a crosslinking reaction, it has the characteristic that it swells less in a developer than conventional negative resist materials that contain a crosslinking agent, and therefore pattern collapse is less likely to occur.

[0008] Not only for negative resist materials using base polymers containing crosslinking agents or crosslinking units, but also for negative resist materials in which hydrophilicity is reduced by a dehydration reaction with acid, polymers containing repeating units derived from indene or acenaphthylene have been proposed (Patent Document 4).

[0009] In recent years, oxide film-based hard masks have come to be used as mask substrates, and excessive improvement in the dry etching resistance of resist films is no longer necessary. Rather than improving dry etching resistance, resist materials with excellent resolution are now required, and in addition to improving resolution, reducing edge roughness (LER, LWR) has become important in recent years.

[0010] In order to improve resolution and reduce edge roughness, it is important to reduce acid diffusion, improve dissolution contrast, and reduce swelling. Although the introduction of bulky repeating units having polar groups such as vinyl anthraquinone is effective in reducing acid diffusion (Patent Document 5), there is a demand for the development of materials with even lower acid diffusion. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2004-115630 A [Patent Document 2] JP 2006-169302 A [Patent Document 3] U.S. Patent No. 7,300,739 [Patent Document 4] JP 2013-164588 A [Patent Document 5] JP 2017-222832 A Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a negative resist material having a resolution superior to that of conventional negative resist materials and having small edge roughness, and a pattern formation method. [Means for solving the problem]

[0013] The present inventors have conducted extensive research in order to obtain a negative resist material that meets the recent demand for high resolution and small edge roughness, and have discovered that it is extremely effective to achieve this by using a polymer that contains a specific repeating unit as the base polymer of the negative resist material.

[0014] The polymers containing repeating units derived from indene or acenaphthylene described in Patent Document 4 have 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, the glass transition point of the polymer becomes high, and the acid diffusion distance becomes short. The copolymer has a higher acid diffusion control effect than a styrene copolymer. On the other hand, since indene and acenaphthylene are hydrophobic aromatic compounds, hydrophilic and hydrophobic parts are mixed in the polymer, which causes uneven solubility in an alkaline developer, which causes swelling and leads to deterioration of edge roughness.

[0015] Means for Solving the Problems The present inventors have conducted extensive research to suppress acid diffusion, improve alkaline dissolution uniformity, and reduce edge roughness. As a result, they have found that by using a polymer containing a repeating unit derived from maleimide having a triple bond as a base polymer, a negative resist material can be obtained which has a high alkaline dissolution rate contrast before and after exposure, a high effect of suppressing acid diffusion, high resolution, and good pattern shape and edge roughness after exposure, and is particularly suitable as a fine pattern forming material for use in the manufacture of VLSIs or photomasks, and have completed the present invention.

[0016] That is, the present invention provides the following negative resist material and pattern forming method. 1. A negative resist material comprising a base polymer containing a repeating unit a derived from a maleimide compound having a triple bond. 2. The negative resist material of 1, wherein the repeating unit a is a repeating unit a1 represented by the following formula (a1) or a repeating unit a2 represented by the following formula (a2): [ka] (In the formula, R 1 and R 2 are each independently a hydrogen atom or a methyl group. X 1A and X 1B are each independently a single bond, a saturated hydrocarbylene group having 1 to 6 carbon atoms, or a phenylene group. X 2A and X 2B are each independently a single bond, an ester bond, or an ether bond. 3. The negative resist material of 1 or 2, wherein the base polymer further contains a repeating unit b having a phenolic hydroxy group. 4. A negative resist material according to claim 3, wherein the repeating unit b is represented by the following formula (b): [ka] (In the formula, R A is a hydrogen atom or a methyl group. R 11 represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom. Y 1 is a single bond, an ester bond or an amide bond. a is an integer of 0 to 4, and b is 1 or 2, provided that 1≦a+b≦5. 5. The negative resist material of any one of 1 to 4, wherein the base polymer further contains a repeating unit c represented by the following formula (c): [ka] (In the formula, R A is a hydrogen atom or a methyl group. R 12 is an alkyl group having 1 to 6 carbon atoms or a halogen atom. R 13 and R 14 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms; R 13 and R 14may be bonded to each other to form a ring together with the carbon atoms to which they are attached. Y 2 is a single bond or an ester bond. c is an integer of 0 to 4. d is 1 or 2, provided that 1≦c+d≦5. 6. The negative resist material of any one of 1 to 5, wherein the base polymer further contains a repeating unit represented by any one of the following formulas (d1) to (d3): [ka] (In the formula, R A are each independently a hydrogen atom or a methyl group. Z 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups, or -OZ 11 -, -C(=O)-OZ 11 - or -C(=O)-NH-Z 11 -It is. 11 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group obtained by combining these and having 7 to 18 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 2 is a single bond or an ester bond. Z 3 is a single bond, -Z 31 -C(=O)-O-, -Z 31 -O- or -Z 31 -OC(=O)-. Z 31 represents an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group obtained by combining these and having 7 to 18 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom. Z 4 is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group, or a carbonyl group. Z 5is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -OZ 51 -, -C(=O)-OZ 51 - or -C(=O)-NH-Z 51 -It is. 51 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, a halogen atom, or a hydroxy group. R 21 ~R 28 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 23 and R 24 or R 26 and R 27 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. M - is a non-nucleophilic counterion. 7. A negative resist material according to any one of 1 to 6, further comprising an organic solvent. 8. A negative resist material according to any one of 1 to 7, further comprising an acid generator. 9. A negative resist material according to any one of 1 to 8, further comprising a quencher. 10. A negative resist material according to any one of 1 to 9, further comprising a surfactant. 11. A pattern forming method comprising the steps of forming a resist film on a substrate using a negative resist material according to any one of claims 1 to 10, exposing the resist film to high-energy radiation, and developing the exposed resist film using a developer. 12. The pattern forming method of 11, wherein the substrate is a photomask blank. 13. The pattern formation method according to 11 or 12, wherein the high-energy radiation is ultraviolet radiation having a wavelength of 180 to 400 nm. 14. The pattern formation method according to 11 or 12, wherein the high energy radiation is EB or EUV having a wavelength of 3 to 15 nm. A photomask blank coated with any of the negative resist materials 15.1 to 10. Effect of the Invention

[0017] The negative resist material of the present invention has a significantly high alkali dissolution rate contrast before and after exposure when made into a resist film, has high resolution, has exposure margin, is excellent in process adaptability, has good pattern shape and edge roughness after exposure, and can suppress acid diffusion rate.Therefore, it is particularly suitable as a fine pattern forming material for VLSI manufacturing or photomask, or a pattern forming material for EB exposure, EUV exposure, or ArF excimer laser exposure.In addition, the negative resist material of the present invention can be applied not only to lithography in semiconductor circuit formation, but also to the formation of mask circuit patterns, or to micromachines, thin film magnetic head circuit formation, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Base polymer] The negative resist material of the present invention is characterized by comprising a base polymer that includes a repeating unit a derived from a maleimide compound having a triple bond.

[0019] The repeating unit a is preferably a repeating unit a1 represented by the following formula (a1) or a repeating unit a2 represented by the following formula (a2). [ka]

[0020] In formulas (a1) and (a2), R 1 and R 2 are each independently a hydrogen atom or a methyl group. 1A and X 1B are each independently a single bond, a saturated hydrocarbylene group having 1 to 6 carbon atoms, or a phenylene group. 2A and X 2B are each independently a single bond, an ester bond or an ether bond.

[0021] X 1A and X 1B The saturated hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic. Specific examples thereof include alkanediyl groups having 1 to 6 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3-diyl group, pentane-1,5-diyl group and hexane-1,6-diyl group; cyclic saturated hydrocarbylene groups having 3 to 6 carbon atoms, such as cyclopropanediyl group, cyclobutanediyl group, cyclopentylene group and cyclohexylene group; and groups obtained by combining these groups.

[0022] Examples of monomers that provide the repeating unit a1 include, but are not limited to, those shown below. [ka]

[0023] [ka]

[0024] Examples of monomers that provide the repeating unit a2 include, but are not limited to, those shown below. [ka]

[0025] [ka]

[0026] The maleimide compound can be synthesized, for example, by reacting maleic anhydride or itaconic anhydride with an amine compound having an ethynyl group, or by reacting maleimide or itaconimide with a halogen compound having an ethynyl group.

[0027] The repeating units a1 and a2 have a maleimide group containing a nitrogen atom, and have the ability to control acid diffusion. In addition, the main chain becomes rigid, which also reduces acid diffusion. Furthermore, the triple bond is acidic, so it has moderate alkali solubility and can reduce swelling. This makes it possible to simultaneously achieve low acid diffusion, low swelling, high alkali solubility contrast, high resolution, low LER, and improved CDU.

[0028] The base polymer may further contain a repeating unit b having a phenolic hydroxy group. As the repeating unit b, one represented by the following formula (b) is preferable. [ka]

[0029] In formula (b), R A R is a hydrogen atom or a methyl group. 11 Y is an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom. 1 is a single bond, an ester bond or an amide bond. a is an integer of 0 to 4. b is 1 or 2, provided that 1≦a+b≦5.

[0030] Examples of monomers that provide the repeating unit b include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0031] [ka]

[0032] [ka]

[0033] The base polymer may further include a repeating unit c represented by the following formula (c): The repeating unit c is a unit whose polarity changes from hydrophilic to hydrophobic by a dehydration reaction or the like in the presence of an acid catalyst. [ka]

[0034] In formula (c), R A R is a hydrogen atom or a methyl group. 12 R is an alkyl group having 1 to 6 carbon atoms or a halogen atom. 13 and R 14 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms; R 13 and R 14 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached. 2 is a single bond or an ester bond. c is an integer of 0 to 4. d is 1 or 2, provided that 1≦c+d≦5.

[0035] Examples of monomers that provide the repeating unit c include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0036] [ka]

[0037] [ka]

[0038] The base polymer may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (d1) (hereinafter also referred to as repeating unit d1), a repeating unit represented by the following formula (d2) (hereinafter also referred to as repeating unit d2), and a repeating unit represented by the following formula (d3) (hereinafter also referred to as repeating unit d3). [ka]

[0039] In formulas (d1) to (d3), R A are each independently a hydrogen atom or a methyl group. 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups, or -OZ 11 -, -C(=O)-OZ 11 - or -C(=O)-NH-Z 11 -It is. 11 Z is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. 2 is a single bond or an ester bond. 3 is a single bond, -Z 31 -C(=O)-O-, -Z 31 -O- or -Z 31 -OC(=O)-. Z 31 Z is an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom. 4 is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group, or a carbonyl group. 5 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -OZ 51 -, -C(=O)-OZ 51- or -C(=O)-NH-Z 51 -It is. 51 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, a halogen atom, or a hydroxyl group. 1 , Z 11 , Z 31 and Z 51 The aliphatic hydrocarbylene group represented by the formula (I) may be saturated or unsaturated and may be linear, branched or cyclic.

[0040] In formula (d1), M - is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride ion and bromide ion, fluoroalkylsulfonate ions such as triflate ion, 1,1,1-trifluoroethanesulfonate ion and nonafluorobutanesulfonate ion, arylsulfonate ions such as tosylate ion, benzenesulfonate ion, 4-fluorobenzenesulfonate ion and 1,2,3,4,5-pentafluorobenzenesulfonate ion, alkylsulfonate ions such as mesylate ion and butanesulfonate ion, imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion and bis(perfluorobutylsulfonyl)imide ion, and methide ions such as tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

[0041] Further examples of the non-nucleophilic counter ion include a sulfonate ion represented by the following formula (d1-1) in which the α-position is substituted with a fluorine atom, and a sulfonate ion represented by the following formula (d1-2) in which the α-position is substituted with a fluorine atom and the β-position is substituted with a trifluoromethyl group. [ka]

[0042] In formula (d1-1), R 31 is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and the hydrocarbyl group may contain an ether bond, an ester bond, a carbonyl group, a lactone ring, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 111 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0043] In formula (d1-2), R 32 is a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbylcarbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group and the hydrocarbylcarbonyl group may contain an ether bond, an ester bond, a carbonyl group, or a lactone ring. The hydrocarbyl group and the hydrocarbylcarbonyl group may have a hydrocarbyl moiety that is saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 111 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0044] Examples of the cation of the monomer that gives the repeating unit d1 include, but are not limited to, those shown below. A is the same as above. [ka]

[0045] Examples of the anion of the monomer that gives the repeating unit d2 include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] Examples of the anion of the monomer that gives the repeating unit d3 include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0057] [ka]

[0058] In formulas (d1) to (d3), R 21 ~R 28 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0059] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0060] R 21 ~R 28The hydrocarbyl group having 1 to 20 carbon atoms represented by the following formula may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples of such alkyl groups include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, or an icosyl group; cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group, or an adamantyl group; alkenyl groups having 2 to 20 carbon atoms, such as a vinyl group, a propenyl group, a butenyl group, or a hexenyl group; and an ethynyl group. alkynyl groups having 2 to 20 carbon atoms, such as a propynyl group or a butynyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclohexenyl group or a norbornenyl group; aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a methylphenyl group, an ethylphenyl group, a n-propylphenyl group, an isopropylphenyl group, a n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, a n-propylnaphthyl group, an isopropylnaphthyl group, a n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group or a tert-butylnaphthyl group; aralkyl groups having 7 to 20 carbon atoms, such as a benzyl group or a phenethyl group; and groups obtained by combining these.

[0061] In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, or the like.

[0062] Also, R 23 and R 24 or R 26 and R 27 However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring is preferably one having the structure shown below. [ka] (In the formula, the dashed line represents R 25 or R 28 It is a bond with .)

[0063] Examples of the cations of the repeating units d2 and d3 include, but are not limited to, those shown below. [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067]

change

[0068]

change

[0069]

change

[0070]

change

[0071]

change

[0072]

change

[0073]

change

[0074]

change

[0075]

change

[0076]

change

[0077]

change

[0078] [ka]

[0079] [ka]

[0080] [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] The repeating units d1 to d3 function as an acid generator. By binding the acid generator to the polymer main chain, acid diffusion is reduced, and a decrease in resolution due to blurring caused by acid diffusion can be prevented. Furthermore, the acid generator is uniformly dispersed, improving LWR and CDU. When a base polymer containing the repeating units d1 to d3 (i.e., a polymer-bound acid generator) is used, the incorporation of an additive acid generator, which will be described later, can be omitted.

[0086] The base polymer may further include a repeating unit e containing an adhesive group selected from a hydroxy group, a lactone ring, an ether bond, an ester bond, a carbonyl group, and a cyano group. Examples of monomers that provide the repeating unit e include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0087] [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] The base polymer may further include a repeating unit f containing an iodine atom. Examples of monomers that provide the repeating unit f include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0096] [ka]

[0097] [ka]

[0098] The base polymer may contain a repeating unit g other than the repeating units described above. Examples of the repeating unit g include those derived from styrene, vinylnaphthalene, indene, acenaphthylene, coumarin, and coumarone.

[0099] In the base polymer, the content ratios of the repeating units a1, a2, b, c, d1, d2, d3, e, f, and g are preferably 0 ≦ a1 < 1.0, 0 ≦ a2 < 1.0, 0 < a1 + a2 < 1.0, 0 < b < 1.0, 0 ≦ c < 1.0, 0 ≦ d1 ≦ 0.4, 0 ≦ d2 ≦ 0.4, 0 ≦ d3 ≦ 0.4, 0 ≦ d1 + d2 + d3 ≦ 0.4, 0 ≦ e ≦ 0.7, 0 ≦ f ≦ 0.5, and 0 ≦ g ≦ 0.5; more preferably 0 ≦ a1 ≦ 0.8, 0 ≦ a2 ≦ 0.8, 0.01 ≦ a1 + a2 ≦ 0.8, 0.1 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.9, 0 ≦ d1 ≦ 0.3, 0 ≦ d2 ≦ 0.3, 0 ≦ d3 ≦ 0.3, 0 ≦ d1 + d2 + d3 ≦ 0.3, 0 ≦ e ≦ 0.5, 0 ≦ f ≦ 0.4, and 0 ≦ g ≦ 0.4; still more preferably 0 ≦ a1 ≦ 0.7, 0 ≦ a2 ≦ 0.7, 0.02 ≦ a1 + a2 ≦ 0.7, 0.2 ≦ b ≦ 0.8, 0.2 ≦ c ≦ 0.8, 0 ≦ d1 ≦ 0.25, 0 ≦ d2 ≦ 0.25, 0 ≦ d3 ≦ 0.25, 0 ≦ d1 + d2 + d3 ≦ 0.25, 0 ≦ e ≦ 0.4, 0 ≦ f ≦ 0.3, and 0 ≦ g ≦ 0.3. However, a1 + a2 + b + c + d + e + f + g ≦ 1. For example, a + b + c = 1 means that in the polymer containing the repeating units a, b, and c, the total amount of the repeating units a, b, and c is 100 mol% in all the repeating units, and a + b + c < 1 means that the total amount of the repeating units a, b, and c is less than 100 mol% in all the repeating units and the polymer contains other repeating units in addition to the repeating units a, b, and c.

[0100] To synthesize the base polymer, for example, the desired monomers among the monomers that provide the repeating units a to g may be heated in an organic solvent with a radical polymerization initiator added thereto to carry out polymerization.

[0101] Examples of the organic solvent used during polymerization include toluene, benzene, tetrahydrofuran (THF), diethyl ether, and dioxane. Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The temperature during polymerization is preferably 50 to 80°C. The reaction time is preferably 2 to 100 hours, and more preferably 5 to 20 hours.

[0102] When a monomer containing a hydroxy group is copolymerized, the hydroxy group may be substituted with an acetal group that is easily deprotected by an acid, such as an ethoxyethoxy group, during polymerization, and then deprotected with a weak acid and water after polymerization; alternatively, the hydroxy group may be substituted with an acetyl group, a formyl group, a pivaloyl group, or the like, and then subjected to alkaline hydrolysis after polymerization.

[0103] When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, acetoxystyrene or acetoxyvinylnaphthalene may be used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy group may be deprotected by the above-mentioned alkaline hydrolysis to give hydroxystyrene or hydroxyvinylnaphthalene.

[0104] As the base for the alkaline hydrolysis, ammonia water, triethylamine, etc. can be used. 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.

[0105] The base polymer has a weight average molecular weight (Mw) of preferably 1,000 to 500,000, more preferably 2,000 to 30,000. If Mw is too small, the resist material will have poor heat resistance, and if Mw is too large, the alkali solubility will decrease, making the base material more susceptible to tailing after pattern formation. Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using THF as a solvent.

[0106] In addition, when the base polymer has a wide molecular weight distribution (Mw / Mn), the presence of low-molecular weight and high-molecular weight polymers may cause foreign matter to be found on the pattern after exposure, or the shape of the pattern may be deteriorated. As the pattern rule becomes finer, the effects of Mw and Mw / Mn tend to become greater, so in order to obtain a resist material that is suitable for fine pattern dimensions, it is preferable that the Mw / Mn of the base polymer has a narrow distribution of 1.0 to 2.0, particularly 1.0 to 1.5.

[0107] The base polymer may include two or more polymers having different composition ratios, Mw, and Mw / Mn. A polymer containing a repeating unit a1 may be blended with a polymer containing a repeating unit a2, or a polymer containing a repeating unit a1 and / or a2 may be blended with a polymer not containing a repeating unit a1 or a2. The polymer of the present invention is suitable as a base polymer for a negative resist material.

[0108] [Organic solvents] The negative resist material of the present invention may contain an organic solvent. The organic solvent is not particularly limited as long as it can dissolve the above-mentioned components and the components described below. Examples of the organic solvent include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs

[0144] to

[0145] of JP-A-2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol Examples of the monoethyl ether include ethers such as propylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as 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, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as γ-butyrolactone.

[0109] In the negative resist composition of the present invention, the content of the organic solvent is preferably 50 to 10,000 parts by mass, more preferably 100 to 5,000 parts by mass, based on 100 parts by mass of the base polymer. The organic solvent may be used alone or in combination of two or more kinds.

[0110] [Acid generator] The negative resist material of the present invention may contain an acid generator (hereinafter, also referred to as an additive acid generator) in order to function as a chemically amplified negative resist material. The additive acid generator may be a compound (photoacid generator) that generates an acid in response to actinic rays or radiation. The photoacid generator is not particularly limited as long as it is a compound that generates an acid when irradiated with high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate type acid generators. Specific examples of acid generators include those described in paragraphs

[0122] to

[0142] of JP 2008-111103 A.

[0111] As the acid generator, an arenesulfonate type acid generator is preferred because it generates an acid of suitable strength to induce a crosslinking reaction or a dehydration reaction. As such an acid generator, a sulfonium salt having a sulfonate anion of the structure shown below can be suitably used. As the counter sulfonium cation, the same as those exemplified as the cations of the repeating units d2 and d3 can be used. [ka]

[0112] [ka]

[0113] [ka]

[0114] [ka]

[0115] [ka]

[0116] [ka]

[0117] When the negative resist material of the present invention contains an additive acid generator, the content thereof is preferably 0.01 to 100 parts by mass, more preferably 0.1 to 80 parts by mass, based on 100 parts by mass of the base polymer. The additive acid generator may be used alone or in combination of two or more types. When the base polymer contains the repeating units d1 to d3 and / or when the additive acid generator is contained, the negative resist material of the present invention can function as a chemically amplified negative resist material.

[0118] [Quencher] The negative resist material of the present invention may contain a quencher. The quencher refers to a compound that can trap the acid generated by the acid generator in the resist material, thereby preventing the acid from diffusing into unexposed areas.

[0119] The quencher may be a conventional basic compound. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxy group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxy group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amides, imides, and carbamates. In particular, the primary, secondary, and tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP-A-2008-111103, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonic acid ester bond, or compounds having a carbamate group described in JP-A-3790649 are preferred. By adding such a basic compound, for example, the diffusion rate of the acid in the resist film can be further suppressed or the shape can be corrected.

[0120] The quencher includes onium salts such as sulfonium salts, iodonium salts, and ammonium salts of sulfonic acids and carboxylic acids not fluorinated at the α-position, as described in JP-A-2008-158339. Sulfonic acids, imide acids, or methide acids fluorinated at the α-position are necessary for deprotecting acid labile groups of carboxylic acid esters, but the sulfonic acids or carboxylic acids not fluorinated at the α-position are released by salt exchange with onium salts not fluorinated at the α-position. Sulfonic acids and carboxylic acids not fluorinated at the α-position do not cause a deprotection reaction, and therefore function as quenchers.

[0121] Moreover, the quencher may be a carboxylate onium salt represented by the following formula (1). [ka]

[0122] In formula (1), R 101 ~R 104 are each independently a hydrogen atom, -L-CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 101 and R 102 And, R 102 and R 103 and, or R 103 and R 104 and may be bonded to each other to form a ring together with the carbon atom to which they are bonded. L is a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a hetero atom. R 105 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom or a heteroatom.

[0123] In formula (1), ring R is a ring containing carbon atoms and nitrogen atoms and having 2 to 6 carbon atoms, and some or all of the hydrogen atoms bonded to the carbon atoms of the ring are hydrocarbyl groups having 1 to 20 carbon atoms, or -L-CO2 -and a part of the carbon atoms of the ring may be substituted with a sulfur atom, an oxygen atom, or a nitrogen atom. The ring may be an alicyclic ring or an aromatic ring, and is preferably a 5-membered or 6-membered ring, and specific examples thereof include a pyridine ring, a pyrrole ring, a pyrrolidine ring, a piperidine ring, a pyrazole ring, an imidazoline ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, an imidazoline ring, an oxazole ring, a thiazole ring, a morpholine ring, a thiazine ring, and a triazole ring.

[0124] The onium carboxylate represented by formula (1) has at least one -L-CO2 - That is, R 101 ~R 104 At least one of the following is -L-CO2 - and / or at least one of the hydrogen atoms bonded to the carbon atom of the ring R is -L-CO2 - is replaced by

[0125] In formula (1), Q + is a sulfonium cation, an iodonium cation or an ammonium cation, preferably a sulfonium cation. Examples of the sulfonium cation include the same as those exemplified as the cations of the repeating units d2 and d3.

[0126] Another example of the quencher is a polymer-type quencher described in JP 2008-239918 A. This quencher enhances the rectangularity of the resist pattern by being oriented on the surface of the resist film. The polymer-type quencher also has the effect of preventing film loss of the pattern and rounding of the pattern top when a protective film for immersion exposure is applied.

[0127] When the negative resist composition of the present invention contains the quencher, the content thereof is preferably 0 to 5 parts by mass, more preferably 0 to 4 parts by mass, relative to 100 parts by mass of the base polymer. The quencher may be used alone or in combination of two or more kinds.

[0128] [Other ingredients] The negative resist composition of the present invention may contain, in addition to the above-mentioned components, a surfactant, a crosslinking agent, a water repellency enhancer, acetylene alcohols, and the like.

[0129] Examples of the surfactant include those described in paragraphs

[0165] to

[0166] of JP 2008-111103 A. The addition of a surfactant can further improve or control the coatability of the resist material. When the negative resist material of the present invention contains the surfactant, the content is preferably 0 to 10 parts by mass, more preferably 0.0001 to 5 parts by mass, per 100 parts by mass of the base polymer. The surfactant may be used alone or in combination of two or more kinds.

[0130] Examples of the crosslinking agent include those described in paragraphs

[0170] to

[0177] of JP 2020-027297 A. Although the difference in dissolution rate between the exposed and unexposed parts can be further increased by adding a crosslinking agent, there is also a risk of increased swelling in the developer. When the negative resist material of the present invention contains the crosslinking agent, the content thereof is preferably 0 to 30 parts by mass, more preferably 0 to 20 parts by mass, relative to 100 parts by mass of the base polymer.

[0131] The water repellency improver improves the water repellency of the resist film surface, and can be used in immersion lithography without using a topcoat. As the water repellency improver, a polymer containing a fluorinated alkyl group, a polymer containing a 1,1,1,3,3,3-hexafluoro-2-propanol residue of a specific structure, and the like are preferred, and those exemplified in JP-A-2007-297590 and JP-A-2008-111103 are more preferred. The water repellency improver needs to be dissolved in an alkaline developer or an organic solvent developer. The water repellency improver having the specific 1,1,1,3,3,3-hexafluoro-2-propanol residue described above has good solubility in the developer. As the water repellency improver, a polymer containing a repeating unit containing an amino group or an amine salt is highly effective in preventing the evaporation of acid during post-exposure baking (PEB) and preventing poor opening of a hole pattern after development. When the negative resist composition of the present invention contains a water repellency improver, the content thereof is preferably 0 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the base polymer. The water repellency improver may be used alone or in combination of two or more kinds.

[0132] The acetylene alcohols include those described in paragraphs

[0179] to

[0182] of JP 2008-122932 A. When the negative resist material of the present invention contains an acetylene alcohol, the content is preferably 0 to 5 parts by mass relative to 100 parts by mass of the base polymer. The acetylene alcohols may be used alone or in combination of two or more kinds.

[0133] [Pattern formation method] When the negative resist material of the present invention is used in various integrated circuit manufacturing, known lithography techniques can be applied.For example, as a pattern forming method, the method includes the steps of forming a resist film on a substrate using the above-mentioned negative resist material, exposing the resist film to high-energy radiation, and developing the exposed resist film using a developer.

[0134] First, the negative resist material of the present invention is applied to a substrate for manufacturing integrated circuits (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective film, etc.) or a substrate for manufacturing mask circuits (Cr, CrO, CrON, MoSi2, SiO2, etc.) by a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc., so that the coating film thickness is 0.01 to 2 μm. This is pre-baked 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, to form a resist film.

[0135] On the resist film, a polythiophene or polyaniline-based antistatic film may be provided, or a top coat film other than this may be formed.

[0136] Next, the resist film is exposed to high-energy radiation. Examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV radiation with a wavelength of 3 to 15 nm, X-rays, soft X-rays, excimer laser light, gamma rays, synchrotron radiation, etc. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, synchrotron radiation, etc. are used as the high-energy radiation, the exposure dose is preferably 1 to 200 mJ / cm2, either directly or using a mask for forming a desired pattern. 2 Approximately, more preferably 10 to 100 mJ / cm 2 When EB is used as the high energy beam, the exposure dose is preferably 0.1 to 100 μC / cm 2 Approximately, more preferably 0.5 to 50 μC / cm 2 The negative resist material of the present invention is most suitable for fine patterning using high energy radiation such as EB, EUV, soft X-rays, X-rays, γ-rays, and synchrotron radiation.

[0137] After the exposure, PEB may be performed on a hot plate or in an oven, 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.

[0138] After exposure or PEB, the exposed resist film is developed using a developer, which is an alkaline aqueous solution of preferably 0.1 to 10 mass %, more preferably 2 to 5 mass %, such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), or the like, for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes, by a conventional method such as a dip method, a puddle method, a spray method, or the like. The irradiated portions do not dissolve in the developer, while the unexposed portions do dissolve, forming the desired negative pattern on the substrate.

[0139] TEAH, TPAH and TBAH, which have longer alkyl chains than the commonly used TMAH aqueous solution, have the effect of reducing swelling during development and preventing pattern collapse. As a TMAH developer, a 2.38% by mass aqueous solution is most widely used. This corresponds to 0.26N, and it is preferable that the TEAH, TPAH or TBAH aqueous solution also has the same normality. The concentrations of TEAH, TPAH and TBAH that give 0.26N are 3.84% by mass, 5.31% by mass and 6.78% by mass, respectively.

[0140] In patterns of 32 nm or less resolved by EB or EUV, there are phenomena in which lines become distorted, lines stick together, and stuck lines collapse. This is thought to be caused by lines swelling in the developer and sticking together. Swollen lines are soft like a sponge because they are saturated with developer, so they are prone to collapse due to the stress of rinsing. Developers containing TEAH, TPAH, and TBAH, which have long alkyl chains, are effective in preventing swelling and pattern collapse.

[0141] Triple bonds have the property of being crosslinked by heat of 200°C or more. After forming a resist pattern by development, heating causes crosslinking, resulting in a pattern with even higher hardness. Increasing the hardness of the pattern can improve dry etching resistance. Furthermore, crosslinking by post-baking reduces moisture permeability and increases the rigidity of the film, thereby increasing the durability of the film when used as a permanent film. EXAMPLES

[0142] The present invention will be specifically described below with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples.

[0143] [1] Synthesis of base polymer Monomers M-1 to M-4, AM-1 to AM-4, and PM-1 to PM-4 used in the synthesis of the base polymer are as follows: The Mw of the polymer is a value measured in terms of polystyrene by GPC using THF as a solvent. [ka]

[0144] [ka]

[0145] [ka]

[0146] [Synthesis Example 1] Synthesis of Polymer P-1 In a 2L flask, 2.4g of monomer M-1, 4.1g of monomer AM-1, 7.2g of 4-hydroxystyrene, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-1. The composition of polymer P-1 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0147] [Synthesis Example 2] Synthesis of Polymer P-2 In a 2L flask, 2.4g of monomer M-1, 3.8g of monomer AM-2, 7.8g of 4-hydroxystyrene, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C, and the reaction was carried out for 15 hours. The reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-2. The composition of polymer P-2 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0148] [Synthesis Example 3] Synthesis of Polymer P-3 In a 2L flask, 2.4g of monomer M-2, 4.0g of monomer AM-3, 6.0g of 4-hydroxystyrene, 3.6g of 4-hydroxyphenyl methacrylate, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. The reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-3. The composition of polymer P-3 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0149] [Synthesis Example 4] Synthesis of polymer P-4 In a 2L flask, 2.7g of monomer M-3, 4.9g of monomer AM-1, 5.4g of 4-hydroxystyrene, 6.8g of monomer PM-1, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-4. The composition of polymer P-4 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0150] [Synthesis Example 5] Synthesis of Polymer P-5 In a 2L flask, 5.1g of monomer M-4, 4.9g of monomer AM-1, 4.8g of 4-hydroxystyrene, 5.9g of monomer PM-2, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-5. The composition of polymer P-5 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0151] [Synthesis Example 6] Synthesis of Polymer P-6 In a 2L flask, 3.2g of monomer M-1, 4.9g of monomer AM-1, 4.8g of 4-hydroxystyrene, 5.6g of monomer PM-3, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-6. The composition of polymer P-6 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0152] [Synthesis Example 7] Synthesis of polymer P-7 In a 2L flask, 1.6g of monomer M-1, 8.3g of monomer AM-4, 6.0g of 3-hydroxystyrene, 7.4g of monomer PM-4, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-7. The composition of polymer P-7 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0153] [Synthesis Example 8] Synthesis of polymer P-8 In a 2L flask, 3.2g of monomer M-1, 4.9g of monomer AM-1, 5.9g of 4-hydroxy-3-methoxystyrene, 5.6g of monomer PM-3, and 40g of THF as a solvent were added. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After heating to room temperature, 1.2g of AIBN was added as a polymerization initiator, and the temperature was raised to 60°C and reacted for 15 hours. This reaction solution was concentrated to 1 / 2 and added to a mixed solvent of 1L of methanol and 0.1L of water, whereupon a white solid precipitated. The white solid was filtered off and then dried under reduced pressure at 60°C to obtain polymer P-8. The composition of polymer P-8 was as follows: 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0154] [Comparative Synthesis Example 1] Synthesis of Comparative Polymer cP-1 Comparative polymer cP-1 was obtained by synthesizing the polymer in the same manner as in Synthesis Example 1, except that 2.3 g of acenaphthylene was used instead of monomer M-1. The composition of comparative polymer cP-1 was 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0155] [Comparative Synthesis Example 2] Synthesis of Comparative Polymer cP-2 Comparative polymer cP-2 was obtained in the same manner as in Synthesis Example 1, except that N-phenylmaleimide was used instead of monomer M-1. The composition of comparative polymer cP-2 was 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0156] [Comparative Synthesis Example 3] Synthesis of Comparative Polymer cP-3 Comparative polymer cP-3 was obtained in the same manner as in Synthesis Example 1, except that N-ethyl itaconimide was used instead of monomer M-1. The composition of comparative polymer cP-3 was 13 C-NMR and 1 Mw and Mw / Mn were confirmed by H-NMR and GPC, respectively. [ka]

[0157] [2] Preparation and evaluation of negative resist materials [Examples 1 to 10, Comparative Examples 1 to 3] (1) Preparation of negative resist material A solution in which each component was dissolved in a solvent containing 50 ppm of Omnova's surfactant PolyFox PF-636 in the composition shown in Table 1 was filtered through a 0.2 μm filter to prepare a negative resist material.

[0158] In Table 1, the components are as follows: Organic solvent: PGMEA (propylene glycol monomethyl ether acetate) EL (Ethyl lactate)

[0159] Acid generator: PAG-1 Quencher: Q-1 [ka]

[0160] Blend polymer: bP-1 [ka]

[0161] (2) EB lithography evaluation Each negative resist material shown in Table 1 was spin-coated using a Cleantrac Mark 5 (Tokyo Electron Ltd.) onto a 6-inch diameter Si substrate that had been vapor primed with hexamethyldisilazane (HMDS) for 60 seconds at 110°C, and pre-baked on a hot plate at 110°C for 60 seconds to produce a resist film of 80 nm. This was then subjected to drawing in a vacuum chamber at a HV voltage of 50 kV using a Hitachi Ltd. HL-800D. Immediately after writing, PEB was performed on a hot plate using Cleantrac Mark 5 (Tokyo Electron Ltd.) at the temperature shown in Table 1 for 60 seconds, and paddle development was performed with a 2.38 mass % TMAH aqueous solution for 30 seconds to obtain a negative pattern. The resulting resist patterns were evaluated as follows. The minimum dimension at the exposure dose that resolves 100 nm lines and spaces at 1:1 was defined as the resolution, and the line edge roughness (LER) of 100 nmLS was measured by SEM. The results are shown in Table 1.

[0162] [Table 1]

[0163] The results shown in Table 1 demonstrate that the negative resist material of the present invention has sufficient resolution and reduced LER.

Claims

1. A negative resist material comprising a repeating unit a, which is a repeating unit a1 represented by the following formula (a1) or a repeating unit a2 represented by the following formula (a2), and a base polymer containing a repeating unit represented by any of the following formulas (d1) to (d3). 【Chemistry 1】 (In the formula, R 1 and R 2 each independently represent a hydrogen atom or a methyl group. X 1A and X 1B each independently represent a single bond, a saturated hydrocarbylene group having 1 to 6 carbon atoms, or a phenylene group. X 2A and X 2B each independently represent a single bond, an ester bond, or an ether bond. 【Chemistry 2】 (In the formula, each R A is independently a hydrogen atom or a methyl group. Z 1 is a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or -O-Z 11 -, -C(═O)-O-Z 11 -, or -C(═O)-NH-Z 11 -. Z 11 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 2 is a single bond or an ester bond. Z 3 is a single bond, -Z 31 -C(═O)-O-, -Z 31 -O-, or -Z 31 -O-C(═O)-. Z 31 is an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom. Z 4 is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group or a carbonyl group. Z 5 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O-Z 51 -, -C(=O)-O-Z 51 - or -C(=O)-NH-Z 51 -. Z 51 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, a halogen atom or a hydroxy group. R 21 to R 28 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. In addition, R 23 and R 24 or R 26 and R 27 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. M- is a non-nucleophilic counter ion.

2. A negative resist material comprising a repeating unit a, which is a repeating unit a1 represented by the following formula (a1) or a repeating unit a2 represented by the following formula (a2), and an acid generator. 【Chemistry 3】 (In the formula, R 1 and R 2 are each independently a hydrogen atom or a methyl group. X 1A and X 1B are each independently a single bond, a saturated hydrocarbylene group having 1 to 6 carbon atoms, or a phenylene group. X 2A and X 2B are each independently a single bond, an ester bond, or an ether bond.

3. 3. The negative resist material according to claim 1, wherein the base polymer further comprises a repeating unit b having a phenolic hydroxy group.

4. 4. The negative resist material according to claim 3, wherein the repeating unit b is represented by the following formula (b): 【Chemistry 4】 (In the formula, R A is a hydrogen atom or a methyl group. R 11 represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acetoxy group, or a halogen atom. Y 1 is a single bond, an ester bond or an amide bond. a is an integer from 0 to 4. b is 1 or 2, provided that 1≦a+b≦5.

5. The negative resist material according to any one of claims 1 to 4, wherein the base polymer further contains a repeating unit c represented by the following formula (c): 【Chemistry 5】 (In the formula, R A is a hydrogen atom or a methyl group. R 12 is an alkyl group having 1 to 6 carbon atoms or a halogen atom. R 13 and R 14 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms; R 13 and R 14 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. Y 2 is a single bond or an ester bond. c is an integer from 0 to 4. d is 1 or 2, provided that 1≦c+d≦5.

6. The negative resist material according to any one of claims 1 to 5, further comprising an organic solvent.

7. 2. The negative resist material according to claim 1, further comprising an acid generator.

8. The negative resist material according to any one of claims 1 to 7, further comprising a quencher.

9. The negative resist material according to any one of claims 1 to 8, further comprising a surfactant.

10. A method for forming a pattern comprising the steps of: forming a resist film on a substrate using the negative resist material according to any one of claims 1 to 9; exposing the resist film to high-energy radiation; and developing the exposed resist film using a developer.

11. The method for forming a pattern according to claim 10, wherein the substrate is a photomask blank.

12. 12. The method for forming a pattern according to claim 10, wherein the high-energy radiation is ultraviolet radiation having a wavelength of 180 to 400 nm.

13. 12. The method for forming a pattern according to claim 10, wherein the high-energy beam is an electron beam or extreme ultraviolet light having a wavelength of 3 to 15 nm.

14. A photomask blank coated with the negative resist material according to any one of claims 1 to 9.

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