Radiation-sensitive resin composition and pattern forming method

Abstract

Provided are: a radiation-sensitive resin composition which can be formed into a resist film having satisfactory levels of sensitivity and CDU performance even when a next-generation technology is applied; and a pattern formation method.　The radiation-sensitive resin composition comprises a resin containing a structural unit represented by formula (1), at least one onium salt having an organic acid anion moiety and an onium cation moiety, and a solvent, in which at least a portion of the organic acid anion moiety in the onium salt contains a iodine-substituted aromatic ring structure.　(In formula (1), R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms; Y1 represents a bivalent linking group; X1 represents an acid-dissociable group; and n represents 0 or 1.)

Description

Technical Field

[0001] The present invention relates to a radiation-sensitive resin composition and a patterning method.

Background Art

[0002] Photolithography technology using a resist composition is used for forming fine circuits in semiconductor elements. As a typical procedure, for example, acid is generated by exposure of a resist composition film through a mask pattern to radiation, and a difference in solubility of the resin in an alkaline or organic solvent-based developer is caused between the exposed portion and the unexposed portion by a reaction using the acid as a catalyst, thereby forming a resist pattern on a substrate.

[0003] In the above photolithography technology, radiation with a short wavelength such as an ArF excimer laser is used, or this radiation is combined with a liquid immersion exposure method (liquid immersion lithography) to promote pattern miniaturization. As a next-generation technology, use of radiation with an even shorter wavelength such as an electron beam, X-ray, and EUV (extreme ultraviolet ray) is being considered, and a resist material containing an acid generator having a benzene ring with enhanced absorption efficiency of such radiation is also being studied (Japanese Patent Application Laid-Open No. 2014-2359).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Even in the above next-generation technology, resist performances equivalent to or better than those of the conventional technology are required in terms of sensitivity and critical dimension uniformity (CDU) performance, which is an index of the uniformity of line width and hole diameter.

[0006] An object of the present invention is to provide a radiation-sensitive resin composition and a patterning method capable of forming a resist film having sufficient sensitivity and CDU performance even when applying next-generation technologies.

Means for Solving the Problems

[0007] As a result of intensive studies to solve this problem, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

[0008] In one embodiment, the present invention a resin containing a structural unit represented by the following formula (1) (hereinafter, also referred to as "structural unit (I)"); one or more onium salts containing an organic acid anion moiety and an onium cation moiety; a solvent and relates to a radiation-sensitive resin composition in which at least a part of the organic acid anion moiety in the onium salt contains an iodine-substituted aromatic ring structure.

[0009]

Chemical formula

[0010]

Chemical formula

[0011] According to the above radiation-sensitive resin composition, a resist film satisfying sensitivity and CDU performance can be constructed. Although the reason for this is not clear, it is presumed as follows. The absorption of radiation such as EUV with a wavelength of 13.5 nm by iodine atoms and fluorine atoms is very large, whereby the radiation-sensitive resin composition is made highly sensitive. In addition, the iodine-substituted aromatic ring structure contained in at least a part of the organic acid anion moiety in the onium salt can reduce acid diffusion due to the large molecular weight of the iodine atom. It is presumed that these combined actions can exhibit the above resist performance.

[0012] In another embodiment of the present invention, a step of forming a resist film by applying the above radiation-sensitive resin composition directly or indirectly on a substrate; a step of exposing the above resist film; a step of developing the exposed above resist film with a developer and relates to a patterning method including.

[0013] In the above patterning method, since the above radiation-sensitive resin composition excellent in sensitivity and CDU performance is used, a high-quality resist pattern can be efficiently formed.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0015] <Radiation-sensitive resin composition> The radiation-sensitive resin composition according to this embodiment (hereinafter, also simply referred to as "composition") contains one or more predetermined onium salts, and further contains a compound and a solvent. Further, it contains a resin as necessary. The above composition may contain other optional components as long as the effects of the present invention are not impaired. By containing a predetermined onium salt and a compound, the radiation-sensitive resin composition can be imparted with high-level sensitivity and CDU performance.

[0016] <Radiation-sensitive resin> The radiation-sensitive resin (hereinafter, also simply referred to as "resin") is an aggregate of polymers containing a structural unit (I) (hereinafter, this resin is also referred to as "base resin"). In addition to the structural unit (I), the base resin may contain a structural unit having a phenolic hydroxyl group or a structural unit that gives a phenolic hydroxyl group by the action of an acid (hereinafter, both are also collectively referred to as "structural unit (II)"), a structural unit (III) containing a lactone structure, etc. Hereinafter, each structural unit will be described.

[0017] (Structural unit (I)) The structural unit (I) is represented by the following formula (1).

[0018] [Chemical formula] (In the above formula (1), R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, and Y 1 is a divalent linking group, and X 1 is an acid dissociable group. n is 0 or 1.)

[0019] In the above formula (1), the alkyl group having 1 to 5 carbon atoms represented by R is preferably a linear or branched alkyl group. Specifically, examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and the like.

[0020] In the above formula (1), the halogenated alkyl group having 1 to 5 carbon atoms represented by R includes a group in which some or all of the hydrogen atoms of the above alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and a fluorine atom is particularly preferred.

[0021] Y 1 The divalent linking group of is not particularly limited, but examples of suitable ones include a divalent hydrocarbon group which may have a substituent, a divalent linking group containing a heteroatom, and the like.

[0022] That the hydrocarbon group "has a substituent" means that some or all of the hydrogen atoms in the above hydrocarbon group are substituted with substituents (groups or atoms other than hydrogen atoms).

[0023] The above hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

[0024] An aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity.

[0025] The above Y 1 The aliphatic hydrocarbon group as the divalent hydrocarbon group in may be saturated or unsaturated, and is usually preferably saturated.

[0026] More specifically, examples of the above aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, and the like.

[0027] The above linear or branched aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.

[0028] As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specifically, examples include a methylene group [-CH2-], an ethylene group [-(CH2)2-], a trimethylene group [-(CH2)3-], a tetramethylene group [-(CH2)4-], a pentamethylene group [-(CH2)5-], and the like.

[0029] As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable. Specifically, examples include alkylmethylene groups such as -CH(CH3)-, -CH(CH2CH3)-, -C(CH3)2-, -C(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, -C(CH2CH3)2-; alkylethylene groups such as -CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -C(CH3)2CH2-, -CH(CH2CH3)CH2-, -C(CH2CH3)2-CH2-; alkyltrimethylene groups such as -CH(CH3)CH2CH2-, -CH2CH(CH3)CH2-; alkyltetramethylene groups such as -CH(CH3)CH2CH2CH2-, -CH2CH(CH3)CH2CH2-, and other alkylalkylene groups. The alkyl group in the alkylalkylene group preferably has 1 to 5 carbon atoms and is a linear alkyl group.

[0030] The above linear or branched aliphatic hydrocarbon group may or may not have a substituent.

[0031] Examples of the aliphatic hydrocarbon group containing a ring in the above structure include an alicyclic hydrocarbon group (a group obtained by removing two hydrogen atoms from an aliphatic hydrocarbon ring), a group in which an alicyclic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, and a group in which an alicyclic hydrocarbon group is interposed in the middle of a linear or branched aliphatic hydrocarbon group. Examples of the above linear or branched aliphatic hydrocarbon group are the same as those described above.

[0032] The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, more preferably 3 to 12 carbon atoms.

[0033] The alicyclic hydrocarbon group may be polycyclic or monocyclic. As the monocyclic alicyclic hydrocarbon group, a group obtained by removing two hydrogen atoms from monocycloalkane is preferable. The monocycloalkane preferably has 3 to 6 carbon atoms, and specifically, cyclopentane, cyclohexane, etc. can be mentioned. As the polycyclic alicyclic hydrocarbon group, a group obtained by removing two hydrogen atoms from polycycloalkane is preferable. The polycycloalkane preferably has 7 to 12 carbon atoms, and specifically, adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, etc. can be mentioned.

[0034] The alicyclic hydrocarbon group may or may not have a substituent.

[0035] The aromatic hydrocarbon group is a hydrocarbon group having an aromatic ring.

[0036] The aromatic hydrocarbon group as the divalent hydrocarbon group in the above Y 1 preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbon atoms. However, the carbon number does not include the carbon number in the substituent.

[0037] Specific examples of the aromatic ring of the aromatic hydrocarbon group include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom; and the like. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.

[0038] Specific examples of the aromatic hydrocarbon group include a group obtained by removing two hydrogen atoms from the aromatic hydrocarbon ring (arylene group); a group obtained by removing one hydrogen atom from the aromatic hydrocarbon ring (aryl group), in which one hydrogen atom of the aryl group is substituted with an alkylene group (for example, a group obtained by further removing one hydrogen atom from the aryl group in an arylalkyl group such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, etc.). The number of carbon atoms in the alkylene group (alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

[0039] The aromatic hydrocarbon group may or may not have a substituent.

[0040] The above Y 1 The heteroatom in the "divalent linking group containing a heteroatom" of Y is an atom other than a carbon atom and a hydrogen atom, and examples thereof include an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, etc.

[0041] Examples of the divalent linking group containing a heteroatom include -O-, -C(=O)-O-, -C(=O)-, -O-C(=O)-O-, -C(=O)-NH-, -NH- (H may be substituted with a substituent such as an alkyl group, an acyl group, etc.), -S-, -S(=O)2-, -S(=O)2-O-, -NH-C(=O)-, =N-, general formula -Y 21 -O-Y 22 -, -[Y 21 -C(=O)-O] mp -Y 22 - or -Y 21 -O-C(=O)-Y 22 - represented groups [wherein Y 21 and Y 22 are each independently a divalent hydrocarbon group which may or may not have a substituent, O is an oxygen atom, and mp is an integer of 0 to 3.], etc.

[0042] Y 1When it is -NH-, the H may be substituted with a substituent such as an alkyl group or an aryl group (aromatic group). Y 21 and Y 22 are each independently a divalent hydrocarbon group which may have a substituent. As the divalent hydrocarbon group, those similar to those listed as the "divalent hydrocarbon group which may have a substituent" in Y 1 above can be listed.

[0043] Y 21 is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, even more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or an ethylene group.

[0044] Y 22 is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group or an alkylmethylene group.

[0045] As the divalent linking group containing a heteroatom, a linear group having an oxygen atom as the heteroatom, for example, a group containing an ether bond or an ester bond, is preferable, and the above formula -Y 21 -O-Y 22 -, -[Y 21 -C(=O)-O] mp -Y 22 - or -Y 21 -O-C(=O)-Y 22 - represented groups are more preferable.

[0046] Among the above, as the divalent linking group of Y 1 in particular, a linear or branched alkylene group, a divalent alicyclic hydrocarbon group, or a divalent linking group containing a heteroatom is preferable. Among these, a linear or branched alkylene group, or a divalent linking group containing a heteroatom is preferable.

[0047] In the above formula (1), X 1The acid dissociable group represented by is a group having acid dissociability such that, by the action of an acid, at least the bond between the acid dissociable group and the atom adjacent to the acid dissociable group can be cleaved.

[0048] The acid dissociable group is not particularly limited, and examples thereof include a group that forms a cyclic or chain-like tertiary alkyl ester with a carboxy group in (meth)acrylic acid, etc.; an acetal-type acid dissociable group such as an alkoxyalkyl group, etc. which are widely known.

[0049] Here, the "tertiary alkyl ester" means that the hydrogen atom of the carboxy group is substituted with a chain-like or cyclic alkyl group to form an ester, and the tertiary carbon atom of the chain-like or cyclic alkyl group is bonded to the oxygen atom at the terminal of the carbonyloxy group (-C(=O)-O-). In this tertiary alkyl ester, when an acid acts, the bond between the oxygen atom and the tertiary carbon atom is cleaved, and a carboxy group is formed.

[0050] The above chain-like or cyclic alkyl group may have a substituent.

[0051] Hereinafter, for the sake of convenience, the group that becomes acid dissociable by constituting a carboxy group and a tertiary alkyl ester is referred to as a "tertiary alkyl ester type acid dissociable group".

[0052] Examples of the tertiary alkyl ester type acid dissociable group include an aliphatic branched chain acid dissociable group and an acid dissociable group containing an aliphatic cyclic group.

[0053] Here, "aliphatic branched chain" means having a branched chain structure without aromaticity. The structure of the "aliphatic branched chain acid dissociable group" is not limited to a group composed of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. Also, the "hydrocarbon group" may be either saturated or unsaturated, but is usually preferably saturated.

[0054] Examples of the aliphatic branched chain acid dissociable group include, for example, -C(R 71)(R 72 )(R 73 ) groups can be mentioned. In the formula, R 71 ~R 73 are each independently a linear alkyl group having 1 to 5 carbon atoms. -C(R 71 )(R 72 )(R 73 ) group preferably has 4 to 8 carbon atoms, and specifically, tert-butyl group, 2-methyl-2-butyl group, 2-methyl-2-pentyl group, 3-methyl-3-pentyl group, etc. can be mentioned. In particular, the tert-butyl group is preferable.

[0055] "Aliphatic cyclic group" indicates a monocyclic group or a polycyclic group having no aromaticity.

[0056] The aliphatic cyclic group in the "acid dissociable group containing an aliphatic cyclic group" may or may not have a substituent.

[0057] The basic ring structure excluding the substituent of the above aliphatic cyclic group is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. Further, the above hydrocarbon group may be either saturated or unsaturated, but is usually preferably saturated.

[0058] The aliphatic cyclic group may be monocyclic or polycyclic.

[0059] Examples of the aliphatic cyclic group include a group obtained by removing one or more hydrogen atoms from monocycloalkane; a group obtained by removing one or more hydrogen atoms from polycycloalkanes such as bicycloalkane, tricycloalkane, and tetracycloalkane. Further, a part of the carbon atoms constituting the ring of these alicyclic hydrocarbon groups may be substituted with an ether bond (-O-).

[0060] Examples of the acid dissociable group containing an aliphatic cyclic group include groups represented by the following formulas (1-1) to (1-9), groups represented by the following formulas (2-1) to (2-6), etc.

[0061]

Chemical formula

[0062]

Chemical formula

[0063] In formulas (1-1) to (1-9), the alkyl group of R 14 may be linear, branched, or cyclic, and linear or branched is preferred.

[0064] The above linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0065] The above branched alkyl group preferably has 3 to 10 carbon atoms, and more preferably 3 to 5 carbon atoms.

[0066] Examples of the above cyclic alkyl group include those similar to the above aliphatic cyclic group.

[0067] g is preferably an integer from 0 to 4, more preferably an integer from 1 to 4, and even more preferably 1, 2, or 4.

[0068] In formulas (2-1) to (2-6), as the alkyl group of R 15 to R 16 include those similar to the alkyl group of the above R 14 .

[0069] In the above formulas (1-1) to (1-9) and (2-1) to (2-6), a part of the carbon atoms constituting the ring may be substituted with an ether oxygen atom (-O-).

[0070] The "acetal-type acid-dissociable group" is generally bonded to an oxygen atom by substituting a hydrogen atom at the terminal of an OH-containing polar group such as a carboxy group or a hydroxy group. Then, when an acid acts, the bond between the acetal-type acid-dissociable group and the oxygen atom to which the acetal-type acid-dissociable group is bonded is cleaved, and an OH-containing polar group such as a carboxy group or a hydroxy group is formed.

[0071] In the above formula (1), n is 0 or 1.

[0072] X in the above formula (1) 1 is preferably represented by the following formula (s1) or (s2) in addition to the above-mentioned acid-dissociable group. However, X in the above formula (1) 1 when n is 0, X 1 is represented by the following formula (s1) or (s2).

[0073]

Chemical formula

[0074] The aliphatic cyclic group represented by Cy may be a monocyclic group or a polycyclic group. Examples of the monocyclic aliphatic cyclic group include groups obtained by removing one or more hydrogen atoms from monocycloalkanes. The monocycloalkanes are preferably those having 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane. Examples of the polycyclic aliphatic cyclic group include groups obtained by removing one or more hydrogen atoms from polycycloalkanes. Among these, monocyclic aliphatic cyclic groups are preferred, and groups obtained by removing one or more hydrogen atoms from cyclopentane or cyclohexane are more preferred.

[0075] Some or all of the hydrogen atoms of the aliphatic cyclic group may be substituted.

[0076] In formula (s1), Ra 01 ~Ra 03 Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms include alkyl groups having 1 to 10 carbon atoms.

[0077] Ra 01 ~Ra 03 Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups and polycyclic aliphatic saturated hydrocarbon groups.

[0078] Ra 01 ~Ra 03 Among them, from the viewpoint of the ease of synthesis of the monomer compound that induces structural unit (I), a hydrogen atom is particularly preferred.

[0079] Examples of the substituent of the chain saturated hydrocarbon group or aliphatic cyclic saturated hydrocarbon group represented by the above Ra 01 ~Ra 03 include, for example, the same groups as those of the above Ra 05 .

[0080] Ra 01 ~Ra 03Examples of the group containing a carbon-carbon double bond formed by combining two or more of them to form a cyclic structure include, for example, a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, a methylcyclohexenyl group, a cyclopentylideneethenyl group, a cyclohexylideneethenyl group, and the like.

[0081] The aliphatic cyclic group having no crosslinked structure represented by Cy in the formula (s2) is the same as the aliphatic cyclic group represented by Cy in the formula (s1).

[0082] In the formula (s2), Ra 04 Examples of the aromatic hydrocarbon group in include a group obtained by removing one or more hydrogen atoms from an aromatic hydrocarbon ring having 6 to 30 carbon atoms. Among them, Ra 04 is preferably a group obtained by removing one or more hydrogen atoms from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, and most preferably a group obtained by removing one or more hydrogen atoms from benzene.

[0083] Specific examples of the acid dissociable group represented by the above formula (s1) are given below. * indicates a bond.

[0084]

Chemical formula

[0085]

Chemical formula

[0086] Specific examples of the acid dissociable group represented by the above formula (s2) are given below. * indicates a bond.

[0087]

Chemical formula

[0088] Specific examples of the structural unit represented by the above formula (1) are shown below. In each formula, R α represents a hydrogen atom, a methyl group or a trifluoromethyl group.

[0089]

Chem.

[0090]

Chem.

[0091]

Chem.

[0092]

Chem.

[0093] Specific examples of the structural unit (I) having an acid dissociable group represented by the above formula (s1) or (s2) are shown below. In the following formulas, R α represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

[0094]

Chem.

[0095]

Chem.

[0096]

Chem.

[0097] Among the above examples, the structural unit (I) is preferably at least one selected from the group consisting of the structural units represented by the above formulas (a1-3-13) to (a1-3-24), (a1-3-33) to (a1-3-34), formulas (s1-1) to (s1-4), and formulas (s2-1) to (s1-6).

[0098] In the resin, the content ratio of structural unit (I) (when there are multiple types of structural unit (I), the total) is preferably 10 mol% or more, more preferably 20 mol% or more, and still more preferably 30 mol% or more, based on all the structural units constituting the resin. The above content ratio is preferably 70 mol% or less, more preferably 60 mol% or less, and still more preferably 50 mol% or less. By setting the content ratio of structural unit (I) within the above range, the above radiation-sensitive resin composition can further improve sensitivity and CDU performance.

[0099] (Structural unit (II)) Structural unit (II) is a structural unit having a phenolic hydroxyl group or a structural unit that gives a phenolic hydroxyl group by the action of an acid. In the present invention, the phenolic hydroxyl group generated by deprotection by the action of the acid generated by exposure is also included as the phenolic hydroxyl group of structural unit (II). When the resin contains structural unit (II), the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity and the like of the above radiation-sensitive resin composition can be further improved. Further, when KrF excimer laser light, EUV, electron beam, etc. are used as the radiation irradiated in the exposure step in the resist pattern forming method, structural unit (II) contributes to the improvement of etching resistance and the improvement of the difference in developer solubility (dissolution contrast) between the exposed portion and the unexposed portion. In particular, it can be suitably applied to pattern formation using exposure with radiation having a wavelength of 50 nm or less such as an electron beam or EUV. Structural unit (II) is preferably represented by the following formula (2).

[0100] [Chemical formula] (In the above formula (2), R α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L CA is a single bond, -COO- * or -O-. * is a bond on the aromatic ring side. R 101 is a hydrogen atom or a protecting group that is deprotected by the action of an acid. R 101When there are a plurality of them, the plurality of Rs 101 are the same as or different from each other. R 102 is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group or an acyloxy group. When there are a plurality of Rs 102 are the same as or different from each other. 102 are the same as or different from each other. n3 is an integer from 0 to 2, m3 is an integer from 1 to 8, and m4 is an integer from 0 to 8. However, 1 ≦ m3 + m4 ≦ 2n3 + 5 is satisfied.)

[0101] The above R α is preferably a hydrogen atom or a methyl group from the viewpoint of the copolymerizability of the monomer that gives the structural unit (II).

[0102] L CA is preferably a single bond or -COO- * is preferred.

[0103] The above R 101 As the protecting group that is deprotected by the action of the acid represented by, the same ones as the acid dissociable group applied to X in the formula (1) 1 can be mentioned.

[0104] R 102Examples of the alkyl group include linear or branched alkyl groups having 1 to 8 carbon atoms such as methyl group, ethyl group, propyl group and the like. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms such as trifluoromethyl group, pentafluoroethyl group and the like. Examples of the alkoxycarbonyloxy group include chain or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms such as methoxycarbonyloxy group, butoxycarbonyloxy group and adamantylmethyloxycarbonyloxy group. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms such as acetyl group, propionyl group, benzoyl group and acryloyl group. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms such as acetyloxy group, propionyloxy group, benzoyloxy group and acryloyloxy group.

[0105] As for the above n3, 0 or 1 is more preferable, and 0 is even more preferable.

[0106] As for the above m3, an integer of 1 to 3 is preferable, and 1 or 2 is more preferable.

[0107] As for the above m4, an integer of 0 to 3 is preferable, and an integer of 0 to 2 is more preferable.

[0108] As for the above structural unit (II), structural units represented by the following formulas (2a-1) to (2a-10) (hereinafter, also referred to as "structural units (2a-1) to structural units (2a-10)") and the like are preferable.

[0109]

Chemical formula

[0110] In the above formulas (2a-1) to (2a-10), R α is the same as in the above formula (2).

[0111] Among these, the above structural units (2a-1) to (2a-4), (2a-6), (2a-8) and (2a-9) are preferred.

[0112] As the content ratio of the structural unit (II) (when there are multiple types of structural unit (II), the total), 5 mol% or more is preferable, 8 mol% or more is more preferable, 10 mol% or more is further preferable, and 15 mol% or more is particularly preferable with respect to all the structural units constituting the resin. As the above content ratio, 50 mol% or less is preferable, 40 mol% or less is more preferable, 35 mol% or less is further preferable, and 30 mol% or less is particularly preferable. By setting the content ratio of the structural unit (II) within the above range, the above radiation-sensitive resin composition can further improve the sensitivity and CDU performance.

[0113] When polymerizing a monomer having a phenolic hydroxyl group such as hydroxystyrene, it is preferable to polymerize in a state where the phenolic hydroxyl group is protected by a protecting group such as an alkali dissociable group, and then perform hydrolysis for deprotection to obtain the structural unit (II).

[0114] (Structural unit (III)) The structural unit (III) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure and a sultone structure. By further having the structural unit (III), the base resin can adjust the solubility in the developer, and as a result, the above radiation-sensitive resin composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base resin and the substrate can be improved.

[0115] Examples of the structural unit (III) include structural units represented by the following formulas (T-1) to (T-10).

[0116]

Chemical formula

[0117] In the above formula, RL1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R L2 ~R L5 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. R L4 and R L5 may together with the carbon atom to which they are attached form a divalent alicyclic group having 3 to 8 carbon atoms. L 2 is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0118] The above R L4 and R L5 The divalent alicyclic group having 3 to 8 carbon atoms formed together with the carbon atom to which they are attached is not particularly limited as long as it is a group obtained by removing two hydrogen atoms from the same carbon atom constituting the carbon ring of the monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and as the polycyclic hydrocarbon group, either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group may be used, and either a saturated hydrocarbon group or an unsaturated hydrocarbon group may be used. The condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which a plurality of alicyclic rings are formed by sharing a side (bond between two adjacent carbon atoms).

[0119] The above L 2 Examples of the divalent linking group represented by include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH- and -S-.

[0120] Among these, as the structural unit (III), a structural unit containing a lactone structure is preferable, a structural unit containing a norbornane lactone structure is more preferable, and a structural unit derived from norbornane lactone-yl (meth) acrylate is even more preferable.

[0121] The content ratio of structural unit (III) (when there are multiple types of structural unit (III), the total) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more with respect to all the structural units constituting the base resin. As the above content ratio, 50 mol% or less is preferable, 40 mol% or less is more preferable, and 35 mol% or less is even more preferable. By setting the content ratio of structural unit (III) within the above range, the above radiation-sensitive resin composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0122] (Other structural units) In addition to the above structural units (I) to (III), the base resin may optionally have other structural units. Examples of the above other structural units include a structural unit (IV) containing a polar group (however, excluding those corresponding to structural units (II) and (III)), and another structural unit (V) having an acid dissociable group (however, excluding those corresponding to structural unit (I)).

[0123] (Structural unit (IV)) By further having structural unit (IV), the base resin can adjust the solubility in the developer, and as a result, the lithography performance such as resolution of the above radiation-sensitive resin composition can be improved. Examples of the above polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxy group and a carboxy group are preferable, and a hydroxy group is more preferable.

[0124] Examples of structural unit (IV) include structural units represented by the following formula.

[0125]

Chemical formula

[0126] In the above formula, R Ais a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0127] When the base resin has the structural unit (IV), the lower limit of the content ratio of the structural unit (IV) (when there are a plurality of types of structural unit (IV), the total) is preferably 1 mol%, more preferably 5 mol%, still more preferably 10 mol% with respect to all the structural units constituting the base resin. Further, the upper limit of the above content ratio is preferably 40 mol%, more preferably 30 mol%, still more preferably 25 mol%. By setting the content ratio of the structural unit (IV) within the above range, the lithography performance such as the resolution of the above radiation-sensitive resin composition can be further improved.

[0128] (Structural unit (V)) The structural unit (V) is a structural unit containing an acid dissociable group (however, it is different from the structural unit (I) and the structural unit (II)). The structural unit (V) is not particularly limited as long as it contains an acid dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the above radiation-sensitive resin composition, the structural unit represented by the following formula (3) (hereinafter, also referred to as "structural unit (V-1)") is preferable.

[0129]

Chemical formula

[0130] In the above formula (3), R 7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 8 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R 9 and R 10 each independently represent a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or these groups are combined with each other to form a divalent alicyclic group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.

[0131] The above R 7 From the viewpoint of the copolymerizability of the monomer that provides the structural unit (V-1), a hydrogen atom or a methyl group is preferable, and a methyl group is more preferable.

[0132] The above R 8 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above R include a linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0133] The above R 8 ~R 10 Examples of the linear hydrocarbon group having 1 to 10 carbon atoms represented by the above R include a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0134] The above R 8 ~R 10 Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above R include a monocyclic or polycyclic saturated hydrocarbon group, or a monocyclic or polycyclic unsaturated hydrocarbon group.

[0135] The above R 8 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the above R include, for example, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, anthryl group; aralkyl groups such as benzyl group, phenethyl group, naphthylmethyl group, etc.

[0136] The above R 8 Preferably, it is a linear or branched saturated hydrocarbon group having 1 to 5 carbon atoms, a linear or branched unsaturated hydrocarbon group having 1 to 5 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0137] The above R 9 and R 10The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining the groups represented by the following formula and together with the carbon atoms to which they are bonded, may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group.

[0138] Among these, R 8 is an alkyl group having 1 to 4 carbon atoms, and it is preferable that the alicyclic structure formed by combining R 9 and R 10 together with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0139] Examples of the structural unit (V-1) include structural units represented by the following formulas (3-1) to (3-6) (hereinafter, also referred to as "structural units (V-1-1) to (V-1-6)").

[0140]

Chemical formula

[0141] In the above formulas (3-1) to (3-6), R 7 to R 10 have the same meaning as in the above formula (3). i and j are each independently an integer of 1 to 4. k and l are 0 or 1.

[0142] As i and j, 1 is preferable. As R 8 , a methyl group, an ethyl group, or an isopropyl group is preferable. As R 9 and R 10 , a methyl group or an ethyl group is preferable.

[0143] The base resin may contain one or a combination of two or more of the structural units (V).

[0144] When the base resin contains the structural unit (V), the lower limit of the content ratio of the structural unit (V) (when a plurality of types are included, the total content ratio) is preferably 3 mol%, more preferably 5 mol%, and still more preferably 10 mol% with respect to all the structural units constituting the base resin. Further, the upper limit of the above content ratio is preferably 50 mol%, more preferably 40 mol%, and still more preferably 30 mol%. By setting the content ratio of the structural unit (V) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0145] (Synthesis method of resin) The resin as the base resin can be synthesized, for example, by performing a polymerization reaction on monomers that give each structural unit in a suitable solvent using a known radical polymerization initiator or the like.

[0146] The molecular weight of the resin as the base resin is not particularly limited, but the lower limit of the polystyrene-equivalent weight average molecular weight (Mw) by gel permeation chromatography (GPC) is preferably 1,000, more preferably 2,000, still more preferably 3,000, and particularly preferably 4,000. Further, the upper limit of Mw is preferably 50,000, more preferably 30,000, still more preferably 15,000, and particularly preferably 12,000. If the Mw of the resin is within the above range, the heat resistance and developability of the resulting resist film are good.

[0147] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) by GPC of the resin as the base resin is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and still more preferably 1 or more and 2 or less.

[0148] The measurement methods of Mw and Mn of the resin in this specification are according to the description in the examples.

[0149] As the content of the resin, it is preferably 70% by mass or more, more preferably 75% by mass or more, and still more preferably 80% by mass or more with respect to the total solid content of the radiation-sensitive resin composition.

[0150] <Other resins> The radiation-sensitive resin composition of this embodiment may contain, as another resin, a resin having a higher mass content ratio of fluorine atoms than the above base resin (hereinafter, also referred to as "high-fluorine content resin"). When the radiation-sensitive resin composition contains a high-fluorine content resin, it can be unevenly distributed on the surface layer of the resist film with respect to the base resin. As a result, the state of the resist film surface and the component distribution in the resist film can be controlled to a desired state.

[0151] Examples of the high-fluorine content resin preferably include, as necessary, having the structural units (I) to (V) in the base resin alone or in combination, and having a structural unit represented by the following formula (4) (hereinafter, also referred to as "structural unit (VI)").

[0152]

Chemical formula

[0153] In the above formula (4), R 13 is a hydrogen atom, a methyl group or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH- or -OCONH-. R 14 is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0154] When the high-fluorine content resin has the structural unit (VI), the lower limit of the content ratio of the structural unit (VI) is preferably 50 mol%, more preferably 60 mol%, still more preferably 70 mol%, and particularly preferably 80 mol% with respect to all the structural units constituting the high-fluorine content resin. The upper limit of the above content ratio is preferably 100 mol%, more preferably 98 mol%, and still more preferably 95 mol%. By setting the content ratio of the structural unit (VI) within the above range, the mass content ratio of fluorine atoms in the high-fluorine content resin can be adjusted more appropriately to further promote the uneven distribution on the surface layer of the resist film.

[0155] In addition to the structural unit (VI), the high-fluorine content resin may have a structural unit (hereinafter also referred to as structural unit (VII)) having an (x) alkali-soluble group or a group that dissociates by the action of (y) alkali to increase the solubility in an alkali developer. By having the structural unit (VII), the high-fluorine content resin can improve the solubility in an alkali developer and suppress the occurrence of development defects.

[0156] When the high-fluorine content resin has the structural unit (VII), the lower limit of the content ratio of the structural unit (VII) is preferably 10 mol%, more preferably 20 mol%, still more preferably 30 mol%, and particularly preferably 35 mol% with respect to all the structural units constituting the high-fluorine content resin. The upper limit of the above content ratio is preferably 90 mol%, more preferably 75 mol%, still more preferably 60 mol%. By setting the content ratio of the structural unit (VII) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0157] The lower limit of the content of the high-fluorine content resin is preferably 0.1 part by mass, more preferably 0.5 part by mass, still more preferably 1 part by mass, and particularly preferably 1.5 parts by mass with respect to 100 parts by mass of the above base resin. The upper limit of the above content is preferably 12 parts by mass, more preferably 10 parts by mass, still more preferably 8 parts by mass, and particularly preferably 5 parts by mass.

[0158] (Synthesis method of high-fluorine content resin) The high-fluorine content resin can be synthesized by the same method as the synthesis method of the above base resin.

[0159] <onium salt> The onium salt contains an organic acid anion part and an onium cation part and is a component that generates an acid upon exposure. By including at least a part of the organic acid anion part in the onium salt having an iodine-substituted aromatic ring structure, it is possible to achieve high sensitivity due to improved acid generation efficiency and CDU performance due to acid diffusion control.

[0160] Although the form of the onium salt contained in the radiation-sensitive resin composition is not particularly limited, it is preferable that the onium salt is at least one selected from the group consisting of a radiation-sensitive acid-generating resin containing a structural unit having the organic acid anion moiety and the onium cation moiety, a radiation-sensitive acid generator containing the organic acid anion moiety and the onium cation moiety, and an acid diffusion control agent containing the organic acid anion moiety and the onium cation moiety and generating an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The other aspects of these functions will be described below.

[0161] The acid generated by exposure to the onium salt is considered to perform two functions in the radiation-sensitive resin composition depending on the strength of the acid. As the first function, when the resin contains a structural unit having an acid dissociable group, the acid generated by exposure dissociates the acid dissociable group of the structural unit to generate a carboxy group or the like. The onium salt having this first function is called a radiation-sensitive acid generator. As the second function, under the pattern formation conditions using the radiation-sensitive resin composition, the acid dissociable group of the resin is not substantially dissociated, and the diffusion of the acid generated from the radiation-sensitive acid generator in the unexposed portion is suppressed by salt exchange. The onium salt having this second function is called an acid diffusion control agent. It can be said that the acid generated from the acid diffusion control agent is a relatively weak acid (an acid having a high pKa) compared to the acid generated from the radiation-sensitive acid generator. Whether the onium salt functions as a radiation-sensitive acid generator or an acid diffusion control agent is determined by the energy required to dissociate the acid dissociable group of the resin and the acidity of the onium salt. As the form of the radiation-sensitive acid generator contained in the radiation-sensitive resin composition, the onium salt structure may exist as a compound alone (released from the polymer), incorporated as a part of the polymer, or both of these forms. The form in which the onium salt structure is incorporated as a part of the polymer is particularly called a radiation-sensitive acid-generating resin.

[0162] When the radiation-sensitive resin composition contains the radiation-sensitive acid generator or the radiation-sensitive acid-generating resin, the polarity of the resin in the exposed area increases, and the resin in the exposed area becomes soluble in the developer in the case of alkali aqueous solution development, while it becomes hardly soluble in the developer in the case of organic solvent development.

[0163] In addition, when the radiation-sensitive resin composition contains the acid diffusion controller, the diffusion of acid in the unexposed area can be suppressed, and a resist pattern with excellent pattern developability and CDU performance can be formed.

[0164] In the above radiation-sensitive resin composition, the organic acid anion part in at least one selected from the group consisting of the radiation-sensitive acid-generating resin, the radiation-sensitive acid generator, and the acid diffusion controller may contain the iodine-substituted aromatic ring structure. The absorption of radiation such as EUV with a wavelength of 13.5 nm by iodine atoms is very large, which results in higher sensitivity. In addition, when the iodine-substituted aromatic ring structure is included in the organic acid anion part of the onium salt, the acid diffusion can be controlled by the large molecular weight of the iodine atom, and the CDU performance can be improved.

[0165] Regardless of the form of the onium salt, the organic acid anion part preferably has at least one selected from the group consisting of sulfonic acid anion, carboxylic acid anion, and sulfonimide anion. In addition, the onium cation is preferably at least one selected from the group consisting of sulfonium cation and iodonium cation. By combining these structures in the onium salt, the above-mentioned functions can be efficiently exerted.

[0166] Examples of the acid generated by exposure include those that generate sulfonic acid, carboxylic acid, and sulfonimide by exposure corresponding to the above organic acid anion.

[0167] For example, as the onium salt that gives sulfonic acid by exposure, (1) A compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to a carbon atom adjacent to a sulfonic acid anion, (2) A compound in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to a carbon atom adjacent to a sulfonic acid anion can be mentioned.

[0168] As the onium salt that gives a carboxylic acid upon exposure, (3) A compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to a carbon atom adjacent to a carboxylic acid anion, (4) A compound in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to a carbon atom adjacent to a carboxylic acid anion can be mentioned.

[0169] Among these, those corresponding to the above (1) are preferable as the radiation-sensitive acid generator or radiation-sensitive acid-generating resin. Those corresponding to the above (2), (3) or (4) are preferable as the acid diffusion control agent, and those corresponding to (2) or (4) are particularly preferable.

[0170] <Radiation-sensitive acid generator> The onium salt as the radiation-sensitive acid generator contains an organic acid anion moiety and an onium cation moiety. The radiation-sensitive acid generator is preferably represented by the following formula (A-1) or the following formula (A-2).

[0171]

Chemical formula

[0172] In formulas (A-1) and (A-2), L 1 is a single bond, an ether bond or an ester bond, or an alkylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The above alkylene group may be linear, branched or cyclic.

[0173] R 1is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an acyloxy group having 2 to 20 carbon atoms or an alkylsulfonyloxy group having 1 to 20 carbon atoms which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an alkoxy group having 1 to 10 carbon atoms, or -NR 8 -C(=O)-R 9 or -NR 8 -C(=O)-O-R 9 wherein R 8 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms or an acyloxy group having 2 to 6 carbon atoms, and R 9 is an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms or an aryl group having 6 to 12 carbon atoms, which may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms or an acyloxy group having 2 to 6 carbon atoms. The above alkyl group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group and alkenyl group may be linear, branched or cyclic.

[0174] Among these, as R 1 , a hydroxy group, -NR 8 -C(=O)-R 9 , a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group and the like are preferable.

[0175] R 2 is a single bond or a divalent linking group having 1 to 20 carbon atoms when p is 1, and a trivalent or tetravalent linking group having 1 to 20 carbon atoms when p is 2 or 3, and the above linking group may contain an oxygen atom, a sulfur atom or a nitrogen atom.

[0176] Rf 1 ~Rf 4is independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, provided that at least one of these is a fluorine atom or a trifluoromethyl group. Also, Rf 1 and Rf 2 may combine to form a carbonyl group. In particular, it is preferable that both Rf 3 and Rf 4 are fluorine atoms.

[0177] R 3 、R 4 、R 5 、R 6 and R 7 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. R 3 、R 4 and R 5 contain one or more fluorine atoms, and R 6 and R 7 contain one or more fluorine atoms. Also, any two of R 3 、R 4 and R 5 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched or cyclic, and specific examples thereof include an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, and the like. Also, some or all of the hydrogen atoms of these groups may be substituted with a hydroxy group, a carboxy group, a halogen atom, a cyano group, an amide group, a nitro group, a mercapto group, a sultone group, a sulfone group or a sulfonium salt-containing group, and some of the carbon atoms of these groups may be substituted with an ether bond, an ester bond, a carbonyl group, a carbonate group or a sulfonic acid ester bond.

[0178] p is an integer satisfying 1 ≦ p ≦ 3. q and r are integers satisfying 0 ≦ q ≦ 5, 0 ≦ r ≦ 3, and 0 ≦ q + r ≦ 5. It is preferable that q is an integer satisfying 1 ≦ q ≦ 3, and more preferably 2 or 3. It is preferable that r is an integer satisfying 0 ≦ r ≦ 2.

[0179] Examples of the organic acid anion moiety of the radiation-sensitive acid generator represented by the above formulas (A-1) and (A-2) include, but are not limited to, those shown below. Although those shown below are all organic acid anion moieties having an iodine-substituted aromatic ring structure, as the organic acid anion moiety having no iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom such as a hydrogen atom or another substituent can be preferably employed.

[0180]

Chemical formula

[0181]

Chemical formula

[0182]

Chemical formula

[0183]

Chemical formula

[0184]

Chemical formula

[0185]

Chemical formula

[0186]

Chemical formula

[0187]

Chemical formula

[0188] [Chemistry]

[0189] [Chemistry]

[0190] [Chemistry]

[0191] [Chemistry]

[0192] [Chemistry]

[0193] In the radiation-sensitive acid generator represented by the above formula (A-1), the onium cation moiety is preferably represented by the following formula (Q-1).

[0194] [Chemistry]

[0195] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer from 0 to 5, and when n1 is 2 or more, the plurality of Ra1 may be the same or different. n2 represents an integer from 0 to 5, and when n2 is 2 or more, the plurality of Ra2 may be the same or different. n3 represents an integer from 0 to 5, and when n3 is 2 or more, the plurality of Ra3 may be the same or different. Ra3 represents a fluorine atom or a group having one or more fluorine atoms. Ra1 and Ra2 may be linked to each other to form a ring. When n1 is 2 or more, a plurality of Ra1 may be linked to each other to form a ring. When n2 is 2 or more, a plurality of Ra2 may be linked to each other to form a ring.

[0196] As the substituents represented by Ra1 and Ra2, an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom, and a halogenated hydrocarbon group are preferable.

[0197] The alkyl group of Ra1 and Ra2 may be a linear alkyl group or a branched alkyl group. As this alkyl group, those having 1 to 10 carbon atoms are preferable, and a methyl group, an ethyl group, an n-butyl group, and a t-butyl group are particularly preferable.

[0198] Examples of the cycloalkyl group of Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms). Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferable.

[0199] Examples of the alkyl group portion of the alkoxy group of Ra1 and Ra2 include those listed above as the alkyl group of Ra1 and Ra2. As this alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferable.

[0200] Examples of the cycloalkyl group portion of the cycloalkyloxy group of Ra1 and Ra2 include those listed above as the cycloalkyl group of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferable.

[0201] Examples of the alkoxy group portion of the alkoxycarbonyl group of Ra1 and Ra2 include those listed above as the alkoxy group of Ra1 and Ra2. As this alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferable.

[0202] Examples of the alkyl group portion of the alkylsulfonyl groups of Ra1 and Ra2 include those exemplified above as the alkyl groups of Ra1 and Ra2. Examples of the cycloalkyl group portion of the cycloalkylsulfonyl groups of Ra1 and Ra2 include those exemplified above as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred as these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group, n-butanessulfonyl group, cyclopentanesulfonyl group and cyclohexanesulfonyl group.

[0203] Each of the groups Ra1 and Ra2 may further have a substituent. Examples of this substituent include halogen atoms such as a fluorine atom (preferably a fluorine atom), a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0204] Examples of the halogen atoms of Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.

[0205] As the halogenated hydrocarbon group of Ra1 and Ra2, a halogenated alkyl group is preferred. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF3 is more preferred.

[0206] As described above, Ra1 and Ra2 may be connected to each other to form a ring (i.e., a heterocyclic ring containing a sulfur atom). In this case, Ra1 and Ra2 preferably form a single bond or a divalent linking group. Examples of the divalent linking group include, for example, -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO2-, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. Further, when n1 is 2 or more, a plurality of Ra1s may be connected to each other to form a ring, and when n2 is 2 or more, a plurality of Ra2s may be connected to each other to form a ring. Examples of such cases include, for example, a mode in which two Ra1s are connected to each other to form a naphthalene ring together with the benzene ring to which they are attached.

[0207] Ra3 is a fluorine atom or a group having a fluorine atom. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group as Ra1 and Ra2 are substituted with a fluorine atom. Among them, a fluorinated alkyl group can be preferably mentioned, and CF3, C2F5, C3F7, C4F9, C5F 11 、C6F 13 、C7F 15 、C8F 17 、CH2CF3, CH2CH2CF3, CH2C2F5, CH2CH2C2F5, CH2C3F7, CH2CH2C3F7, CH2C4F9, and CH2CH2C4F9 can be more preferably mentioned, and CF3 can be particularly preferably mentioned.

[0208] Ra3 is preferably a fluorine atom or CF3, and more preferably a fluorine atom.

[0209] n1 and n2 are each independently preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0210] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0211] (n1 + n2 + n3) is preferably an integer from 1 to 15, more preferably an integer from 1 to 9, still more preferably an integer from 2 to 6, and particularly preferably an integer from 3 to 6. When (n1 + n2 + n3) is 1, it is preferable that n3 = 1 and Ra3 is a fluorine atom or CF3. When (n1 + n2 + n3) is 2, a combination where n1 = n3 = 1 and Ra1 and Ra3 are each independently a fluorine atom or CF3, and a combination where n3 = 2 and Ra3 is a fluorine atom or CF3 are preferable. When (n1 + n2 + n3) is 3, a combination where n1 = n2 = n3 = 1 and Ra1 to Ra3 are each independently a fluorine atom or CF3 is preferable.

[0212] Specific examples of the onium cation moiety represented by the above formula (Q-1) include the following. Although those shown below are all sulfonium cation moieties containing an aromatic ring structure having a fluorine atom, as an onium cation moiety not containing an aromatic ring structure having a fluorine atom, a structure in which the fluorine atom or CF3 in the following formula is substituted with an atom or group other than a hydrogen atom or a fluorine atom such as another substituent can be preferably adopted.

[0213]

Chemical formula

[0214]

Chemical formula

[0215]

Chemical formula

[0216] When the onium cation moiety in the radiation-sensitive acid generator represented by the above formula (A-2) contains an aromatic ring structure having a fluorine atom, the onium cation moiety is preferably a diaryliodonium cation having one or more fluorine atoms.

[0217] Specific examples of the onium cation moiety represented by the above formula (Q-2) include the following. Although those shown below are all iodonium cation moieties containing an aromatic ring structure having a fluorine atom, as the onium cation moiety not containing an aromatic ring structure having a fluorine atom, a structure in which the fluorine atom or CF3 in the following formula is substituted with an atom or group other than a hydrogen atom or a fluorine atom such as another substituent can be preferably employed.

[0218]

Chemical formula

[0219] The method for synthesizing the radiation-sensitive acid generator represented by the above formulas (A-1) and (A-2) can be a known method, particularly a method of synthesizing by a salt exchange reaction. As long as the effects of the present invention are not impaired, a known radiation-sensitive acid generator can also be used.

[0220] These radiation-sensitive acid generators may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generator is preferably 0.5 part by mass, more preferably 1 part by mass, still more preferably 2 parts by mass, and particularly preferably 4 parts by mass with respect to 100 parts by mass of the base resin. Also, the upper limit of the above content is preferably 20 parts by mass, more preferably 18 parts by mass, still more preferably 15 parts by mass, and particularly preferably 12 parts by mass. Thereby, excellent sensitivity and CDU performance can be exhibited during resist pattern formation.

[0221] <Acid diffusion control agent> The onium salt as an acid diffusion control agent contains an organic acid anion moiety and an onium cation moiety, and generates an acid having a higher pKa than the acid generated from the above radiation-sensitive acid generator by irradiation with radiation. The acid diffusion control agent is preferably represented by the following formula (S-1) or the following formula (S-2).

[0222]

Chemical formula

[0223] In formulas (S-1) and (S-2), R 1 is a hydrogen atom, a hydroxy group, a fluorine atom, a chlorine atom, an amino group, a nitro group or a cyano group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms or an alkylsulfonyloxy group having 1 to 4 carbon atoms, which may be substituted with a halogen atom, or -NR 1A -C(=O)-R 1B or -NR 1A -C(=O)-O-R 1B wherein. R 1A is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1B is an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 8 carbon atoms.

[0224] R 3 , R 4 , R 5 , R 6 and R 7 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom. R 3 , R 4 and R 5 are preferably monovalent hydrocarbon groups containing one or more fluorine atoms or groups having a fluorine atom, and R 6 and R 7 are preferably monovalent hydrocarbon groups containing one or more fluorine atoms or groups having a fluorine atom. Further, any two of R 3 , R 4 and R 5 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The above monovalent hydrocarbon group may be linear, branched or cyclic, and specific examples thereof include an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, and the like.

[0225] L 1is a single bond or a divalent linking group having 1 to 20 carbon atoms, and may contain an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group or a carboxy group.

[0226] m and n are integers satisfying 0 ≦ m ≦ 5, 0 ≦ n ≦ 3, and 0 ≦ m + n ≦ 5, and integers satisfying 1 ≦ m ≦ 3 and 0 ≦ n ≦ 2 are preferred.

[0227] Examples of the anion of the acid diffusion controller represented by the above formula (S-1) or (S-2) include, but are not limited to, those shown below. Note that all of those shown below are organic acid anion moieties having an iodine-substituted aromatic ring structure, and as the organic acid anion moiety not having an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom such as a hydrogen atom or another substituent can be preferably employed.

[0228]

Chemical formula

[0229]

Chemical formula

[0230]

Chemical formula

[0231]

Chemical formula

[0232]

Chemical formula

[0233] As the onium cation moiety in the acid diffusion control agent represented by the above formulas (S-1) and (S-2), the onium cation moiety in the radiation-sensitive acid generator can be preferably adopted.

[0234] The acid diffusion control agent represented by the above formulas (S-1) and (S-2) can also be synthesized by a known method, particularly by a salt exchange reaction. As long as the effects of the present invention are not impaired, a known acid diffusion control agent can also be used. Further, the acid diffusion control agent of the present embodiment also includes the case where the organic acid anion moiety and the onium cation moiety share the same aromatic ring structure.

[0235] These acid diffusion control agents may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion control agent is preferably 0.5 part by mass, more preferably 1 part by mass, and still more preferably 1.5 parts by mass with respect to 100 parts by mass of the base resin. The upper limit of the above content is preferably 15 parts by mass, more preferably 12 parts by mass, and still more preferably 8 parts by mass. Thereby, excellent sensitivity and CDU performance can be exhibited during resist pattern formation.

[0236] <Solvent> The radiation-sensitive resin composition according to the present embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt and the base resin (at least one of the radiation-sensitive acid-generating resin and the resin), and additives contained as desired.

[0237] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

[0238] Examples of the alcohol solvent include monohydric alcohol solvents having 1 to 18 carbon atoms such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; Polyhydric alcohol solvents with 2 to 18 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, etc.; Examples include polyhydric alcohol partial ether solvents in which a part of the hydroxy groups of the above polyhydric alcohol solvents are etherified.

[0239] Examples of ether solvents include, for example, Dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, etc.; Cyclic ether solvents such as tetrahydrofuran, tetrahydropyran, etc.; Aromatic ring-containing ether solvents such as diphenyl ether, anisole (methyl phenyl ether), etc.; Examples include polyhydric alcohol ether solvents in which the hydroxy groups of the above polyhydric alcohol solvents are etherified.

[0240] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, methyl-iso-butyl ketone, etc.: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, methylcyclohexanone, etc.: Examples include 2,4-pentanedione, acetonylacetone, acetophenone, etc.

[0241] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone, N-methylpyrrolidone, etc.; Examples include chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionamide, etc.

[0242] Examples of ester solvents include, for example, Monocarboxylic acid ester solvents such as n-butyl acetate, ethyl lactate, etc.; Polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, etc.; Lactone solvents such as γ-butyrolactone and valerolactone; Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; Examples of polyvalent carboxylic acid diester solvents include propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

[0243] Examples of hydrocarbon solvents include Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; Aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene, etc.

[0244] Among these, ester solvents and ketone solvents are preferred, polyhydric alcohol partial ether acetate solvents, cyclic ketone solvents, and lactone solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone, and γ-butyrolactone are even more preferred. The above radiation-sensitive resin composition may contain one or more solvents.

[0245] <Other optional components> In addition to the above components, the above radiation-sensitive resin composition may also contain other optional components. Examples of the above other optional components include crosslinking agents, segregation promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used in combination of one or more of each.

[0246] <Method for preparing the radiation-sensitive resin composition> The above radiation-sensitive resin composition can be prepared by mixing, for example, an onium salt, a base resin (at least one of a radiation-sensitive acid-generating resin and a resin), and a solvent, and optionally other optional components, in a predetermined ratio. After mixing, the above radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.2 μm. The solid content concentration of the above radiation-sensitive resin composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0247] <Pattern formation method> The pattern formation method in this embodiment is a step (1) of applying the above radiation-sensitive resin composition directly or indirectly onto a substrate to form a resist film (hereinafter, also referred to as the "resist film formation step"), a step (2) of exposing the above resist film (hereinafter, also referred to as the "exposure step"), and a step (3) of developing the exposed resist film with a developer (hereinafter, also referred to as the "development step").

[0248] According to the above pattern formation method, since the above radiation-sensitive resin composition excellent in sensitivity and CDU performance in the exposure step is used, a high-quality resist pattern can be formed. Hereinafter, each step will be described.

[0249] [Resist film formation step] In this step (the above step (1)), a resist film is formed using the above radiation-sensitive resin composition. Examples of the substrate for forming this resist film include conventionally known substrates such as silicon wafers, silicon dioxide, and wafers coated with aluminum. Further, for example, an organic or inorganic antireflection film disclosed in Japanese Patent Publication No. 6-12452, Japanese Patent Application Laid-Open No. 59-93448, etc. may be formed on the substrate. Examples of the coating method include spin coating, casting coating, roll coating, etc. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 140°C, preferably 80°C to 120°C. The PB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The film thickness of the formed resist film is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0250] When performing liquid immersion exposure, regardless of the presence or absence of a water-repellent polymer additive such as the high-fluorine content resin in the above radiation-sensitive resin composition, for the purpose of avoiding direct contact between the liquid immersion liquid and the resist film, a liquid immersion protective film insoluble in the liquid immersion liquid may be provided on the above-formed resist film. As the liquid immersion protective film, a solvent-peeling type protective film that peels off with a solvent before the development process (see, for example, Japanese Patent Application Laid-Open No. 2006-227632), or a developer-peeling type protective film that peels off simultaneously with the development in the development process (see, for example, WO2005-069076, WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peeling type liquid immersion protective film.

[0251] Further, when performing the exposure step, which is the next step, with radiation having a wavelength of 50 nm or less, it is preferable to use a resin having the structural units (I) to (IV) and, if necessary, the structural unit (V) as the base resin in the above composition.

[0252] [Exposure Step] In this step (the above step (2)), radiation is irradiated through a photomask (in some cases, through an immersion medium such as water) onto the resist film formed in the resist film formation step which is the above step (1) for exposure. As the radiation used for exposure, depending on the line width of the target pattern, for example, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, γ-rays; charged particle beams such as electron beams, α-rays, etc. can be mentioned. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with a wavelength of 50 nm or less positioned as the next-generation exposure technology are even more preferred.

[0253] When exposure is performed by immersion exposure, examples of the immersion liquid used include water, fluorine-based inert liquids, etc. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index as small as possible to minimize the distortion of the optical image projected onto the film. Particularly when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above viewpoints, it is preferable to use water in terms of ease of acquisition and ease of handling. When using water, an additive that reduces the surface tension of water and increases the interfacial activity may be added in a small proportion. This additive is preferably one that does not dissolve the resist film on the wafer and has a negligible effect on the optical coating on the lower surface of the lens. Distilled water is preferably used as the water.

[0254] After the above exposure, post-exposure baking (PEB) is performed. It is preferable to promote the dissociation of the acid-dissociable groups of the resin, etc. by the acid generated from the radiation-sensitive acid generator due to exposure in the exposed portion of the resist film. Due to this PEB, a difference in solubility in the developer occurs between the exposed portion and the unexposed portion. The PEB temperature is usually 50°C to 180°C, and 80°C to 130°C is preferable. The PEB time is usually 5 seconds to 600 seconds, and 10 seconds to 300 seconds is preferable.

[0255] [Development Step] In this step (the above step (3)), the resist film exposed in the above exposure step (the above step (2)) is developed with a developer. Thereby, a predetermined resist pattern can be formed. After development, it is generally washed with a rinse liquid such as water or alcohol and dried.

[0256] Examples of the developer used for the above development include, in the case of alkali development, for example, an aqueous alkali solution in which at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. Among these, an aqueous TMAH solution is preferred, and a 2.38 mass% aqueous TMAH solution is more preferred.

[0257] In the case of organic solvent development, examples include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents and other organic solvents, or solvents containing an organic solvent. Examples of the above organic solvents include, for example, one or more of the solvents listed as the solvents of the above radiation-sensitive resin composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, an acetic acid ester solvent is preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, a chain ketone is preferred, and 2-heptanone is more preferred. The content of the organic solvent in the developer is preferably 80 mass% or more, more preferably 90 mass% or more, still more preferably 95 mass% or more, and particularly preferably 99 mass% or more. Examples of the components other than the organic solvent in the developer include, for example, water, silicone oil and the like.

[0258] Examples of the development method include, for example, a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by raising the developer on the substrate surface by surface tension and allowing it to stand for a certain period of time (paddle method), a method of spraying the developer on the substrate surface (spray method), a method of continuously discharging the developer while scanning a developer discharge nozzle at a constant speed on a substrate rotating at a constant speed (dynamic dispense method), and the like.

Example

[0259] Hereinafter, the present invention will be specifically described by showing synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The measurement methods of various physical property values are shown below.

[0260] [Mw and Mn] The Mw and Mn of the polymer were measured under the following conditions using GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") manufactured by Tosoh Corporation by gel permeation chromatography (GPC). Eluent: Tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Column temperature: 40 °C Detector: Differential refractometer Standard substance: Monodisperse polystyrene

[0261] The structures of the radiation-sensitive acid generators PAG1 to PAG9 of the sulfonium salt or iodonium salt used in the radiation-sensitive resin composition of the examples are shown below.

[0262]

Chemical formula

[0263] [Synthesis example] Synthesis of base polymers (P-1) to (P-8) Each monomer was combined and copolymerized under a tetrahydrofuran (THF) solvent, crystallized in methanol, and further washed repeatedly with hexane, followed by isolation and drying to obtain base polymers (P-1) to (P-8) having the following compositions. The compositions of the obtained base polymers were 1 Determined by 1H-NMR, and Mw and dispersity (Mw / Mn) were confirmed by the above-described GPC (solvent: THF, standard: polystyrene). P-1: Mw = 7,800, Mw / Mn = 1.6 P-2: Mw = 7,200, Mw / Mn = 1.7 P-3: Mw = 8,300, Mw / Mn = 1.6 P-4: Mw = 8,200, Mw / Mn = 1.6 P-5: Mw = 7,700, Mw / Mn = 1.7 P-6: Mw = 7,000, Mw / Mn = 1.7 P-7: Mw = 8,500, Mw / Mn = 1.7 P-8: Mw = 9,000, Mw / Mn = 1.6

[0264]

Chemical formula

[0265]

Chemical formula

[0266] [Examples, Comparative Examples] A solution in which each component was dissolved in the composition shown in Table 1 was filtered through a 0.2-μm size filter in a solvent in which 100 ppm of FC-4430 manufactured by 3M was dissolved as a surfactant to prepare a radiation-sensitive resin composition.

[0267] In Table 1, each component is as follows. Organic solvent: PGMEA (propylene glycol monomethyl ether acetate) GBL (γ-butyrolactone) CHN (cyclohexanone) PGME (propylene glycol monomethyl ether) DAA (diacetone alcohol) EL (ethyl lactate)

[0268] Acid diffusion control agents (Q-1) to (Q-6) [Chemical formula]

[0269] High fluorine content resin F-1: Mw = 8,900, Mw / Mn = 2.0 [Chemical formula]

[0270] [Evaluation of sensitivity by EUV exposure] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" by Tokyo Electron Limited), after coating the composition for forming an underlayer antireflection film ("ARC66" by Brewer Science, Inc.), it was heated at 205 °C for 60 seconds to form an underlayer antireflection film with an average thickness of 105 nm. On this underlayer antireflection film, each radiation-sensitive resin composition shown in Table 1 was coated using the above spin coater, and PB was performed at 130 °C for 60 seconds. Then, by cooling at 23 °C for 30 seconds, a resist film with an average thickness of 55 nm was formed. This resist film was exposed using an EUV scanner ("NXE3300" by ASML (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, mask of a hole pattern with a wafer-level dimension of pitch 46 nm, +20% bias)). PEB was performed on a hot plate at 120 °C for 60 seconds, and development was performed for 30 seconds with a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) to form a resist pattern of 23 nm holes and 46 nm pitch. The exposure dose for forming this resist pattern of 23 nm holes and 46 nm pitch was defined as the optimum exposure dose (Eop), and the optimum exposure dose was defined as the sensitivity (mJ / cm 2 ).

[0271] [Evaluation of CDU] The exposure amount of Eop obtained above was irradiated, and the same operations as above were performed to form a resist pattern with a 23 nm hole and a 46 nm pitch. The formed resist pattern was observed from the top of the pattern using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation). The hole diameter was measured at 16 points in the range of 500 nm, and the average value was obtained. Also, the average value was measured at a total of 500 points at arbitrary points. The 3-sigma value was obtained from the distribution of the measured values, and the obtained 3-sigma value was used as the evaluation value (nm) of the CDU performance. The smaller the evaluation value of the CDU performance, the smaller the variation in the hole diameter in the long period and the better the performance. The results are shown in Table 1.

[0272]

Table 1

[0273] As a result of evaluating the resist pattern formed through the above EUV exposure, all of the radiation-sensitive resin compositions of the examples had good sensitivity and CDU performance.

Industrial Applicability

[0274] According to the radiation-sensitive resin composition and the resist pattern forming method described above, a resist pattern having good sensitivity to exposure light and excellent CDU performance can be formed. Therefore, these can be suitably used in the processing process of semiconductor devices and the like, which are expected to further progress in miniaturization in the future.

Claims

1. A resin containing a structural unit represented by the following formula (1), One or more onium salts containing an organic acid anion part and an onium cation part, A solvent And containing A radiation-sensitive resin composition, wherein at least a part of the organic acid anion part in the onium salt contains an iodine-substituted aromatic ring structure. 【Chemical Formula 1】 (In the above formula (1), R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, and Y １ Is a divalent linking group, and X １ Is an acid dissociable group. n is 1, and X1 in the formula (1) is represented by the following formula (s1) or (s2). 【Chemical Formula 2】 (In the above formula (s1), Cy is an aliphatic cyclic group formed together with a carbon atom. Ra01 to Ra03 are each independently a hydrogen atom, a substituted or unsubstituted monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms or a substituted or unsubstituted monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or two or more of these are combined with each other to form an aliphatic cyclic structure, provided that the above aliphatic cyclic structure does not form a cross-linked structure. In the above formula (s2), Cy has the same meaning as in the above formula (s1). Ra04 is a substituted or unsubstituted aromatic hydrocarbon group. In the above formula, * both indicate a bond to an oxygen atom.)

2. The onium salt is A radiation-sensitive acid generator containing the organic acid anion part and the onium cation part, and An acid diffusion control agent that includes the organic acid anion portion and the onium cation portion and generates an acid having a pKa higher than that of the acid generated from the radiation-sensitive acid generator by irradiation with radiation is at least one selected from the group consisting of The radiation-sensitive resin composition according to claim 1, wherein at least one of the organic acid anion portion in the radiation-sensitive acid generator and the organic acid anion portion in the acid diffusion control agent contains the iodine-substituted aromatic ring. **Claim 3** The radiation-sensitive resin composition according to claim 1 or 2, wherein the organic acid anion portion has at least one selected from the group consisting of a sulfonate anion, a carboxylate anion, and a sulfonimide anion. **Claim 4** The radiation-sensitive resin composition according to any one of claims 1 to 3, wherein the resin further includes a structural unit having a phenolic hydroxyl group. **Claim 5** The radiation-sensitive resin composition according to any one of claims 1 to 4, wherein the resin further includes a structural unit including at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. **Claim 6** The radiation-sensitive resin composition according to any one of claims 1 to 5, further including a high fluorine content resin having a higher mass content of fluorine atoms than the resin. **Claim 7** A step of forming a resist film by directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 6 onto a substrate, a step of exposing the resist film, and a step of developing the exposed resist film with a developer and a pattern forming method including the same. **Claim 8** The pattern forming method according to claim 7, wherein the exposure is performed using extreme ultraviolet rays or an electron beam.

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