Radiation-sensitive composition, pattern forming method, polymer, and onium salt

Abstract

The present invention provides: a radiation-sensitive composition which has excellent sensitivity, CDU, LWR, and excellent post-development defect suppressing properties when a pattern is formed; a pattern forming method; a polymer; and an onium salt. The radiation-sensitive composition contains: a polymer which has a structural unit (I) derived from an onium salt that has a partial structure represented by formula (i), and a structural unit (II) containing an acid-dissociable group; and a solvent.　(In formula (i), X1 - is S- or O-. X2 and X3 are each independently S or O. However, S is included in at least one selected from the group consisting of X1 -, X2, and X3. Z+ is an organic cation. Each * is a bond to another atom in the onium salt. However, the onium salt contains one or more polymerizable groups in a portion other than the partial structure.)

Description

Radiation-sensitive composition, pattern-forming method, polymer, and onium salt

[0001] The present invention relates to radiation-sensitive compositions, pattern-forming methods, polymers, and onium salts.

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic solvent-based developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, or combine this radiation with liquid immersion lithography to advance pattern miniaturization. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] As pattern refinement progresses, techniques have been proposed to introduce acid-generating structures into polymers for the purpose of improving roughness, etc. (for example, Japanese Patent Publication No. 2013-195844).

[0005] Japanese Patent Publication No. 2013-195844

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance equivalent to or better than conventional resists in terms of sensitivity, CDU, LWR, and development defect suppression during pattern formation.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, a polymer, and an onium salt that exhibit excellent sensitivity, CDU, LWR, and suppression of development defects during pattern formation.

[0008] The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition containing a structural unit (I) derived from an onium salt having a partial structure represented by the following formula (i) (hereinafter also referred to as "partial structure (i)"), a polymer having a structural unit (II) containing an acid dissociable group, and a solvent. (In formula (i),

[0010] - X - is S - or O ２ X ３ and X １ - are each independently S or O. However, at least one selected from the group consisting of X ２ , X ３ contains S. ＋ Z is an organic cation. * is a bond with other atoms in the above onium salt. However, the onium salt contains one or more polymerizable groups in a portion other than the above partial structure.) According to the radiation-sensitive composition, excellent sensitivity, CDU, LWR, and development defect suppression can be exhibited during pattern formation. Although the reason for this is not clear, it is speculated as follows.

[0011] The partial structure (i) of the structural unit (I) possessed by the polymer is an acid generation structure that generates an acid for dissociating an acid dissociable group upon exposure. The partial structure (i) contains a sulfonic acid anion (-SO ３ -A structure is introduced in which at least one of the three oxygen atoms constituting the thiosulfonic acid anion is substituted with a sulfur atom (hereinafter, regardless of the number or position of the sulfur atoms, this will also be called a "thiosulfonic acid anion" or "thiosulfonic acid anion structure," and the corresponding acid structure will also be called a "thiosulfonic acid" or "thiosulfonic acid structure"). This improves the acidity of the generated acid, increases the dissolution contrast between the exposed and unexposed areas, and improves roughness. Furthermore, since the acid-generating substructure (i) is incorporated as a structural unit (1) of the polymer, the diffusion length of the generated acid is appropriately controlled. This also contributes to the improvement of roughness. In addition, by improving the acidity of the acid generated from the thiosulfonic acid anion compared to the sulfonic acid anion, the dissociation of acid-dissociable groups in the exposed area is sufficiently promoted, reducing highly hydrophobic regions in the polymer, and as a result, development defects can be suppressed. It is presumed that the above-mentioned unique performance can be achieved through the combined effects of these factors.

[0012] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

[0013] In this pattern formation method, since the above-mentioned radiation-sensitive composition is used, which exhibits excellent sensitivity, CDU, LWR, and development defect suppression during pattern formation, high-quality resist patterns can be efficiently formed.

[0014] In another embodiment, the present invention relates to a polymer having a structural unit (I) derived from an onium salt having a substructure represented by the following formula (i), and a structural unit (II) containing an acid-dissociable group. (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X２ , and X ３ S is included in at least one of the groups selected from Z. ＋ is an organic cation. * represents the bonding site with other atoms in the onium salt described above. However, the onium salt contains one polymerizable group in the portion other than the substructure described above.

[0015] Since the polymer has a structural unit (I) containing the specific substructure (i) described above, it can contribute to improving sensitivity, CDU, LWR, and development defect suppression when used in a radiation-sensitive composition.

[0016] In one embodiment, the present invention relates to an onium salt represented by the following formula (A1) (hereinafter also referred to as "onium salt (A1)"). (In formula (A1), W is a polymerizable group. R １ａ n, which has 1 to 40 carbon atoms. １ It is an organic group with a +m valency. Here, m is 1 and n １ is 1, n ２ If R is 0, １ａ Excluding methylene groups or benzenediyl groups. １ ＋ is, n ２ It is a valence organic cation. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of n. １ and n ２ Each of these is independently either 0 or 1. However, n １ and m pieces of n ２ The sum of these is 1. m is an integer from 1 to 3. If m is 2 or greater, multiple X １ - , X ２ , X ３ Z １＋ and n ２ (These are either identical or different from each other.)

[0017] In a further embodiment, the present invention relates to an onium salt represented by the following formula (B) (hereinafter also referred to as "onium salt (B)"). (In formula (B), W is a polymerizable group. Z ２ ＋ is 1 + n １ It is a valence organic cation. Ａ２ This is a single bond, or 2+n ２ It is a valence linking group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of n. １ and n ２ Each of these is independently either 0 or 1. However, n １ to n ２ The sum of these is 1.

[0018] Since the onium salt (A1) and onium salt (B) have the above-described specific substructure (i), when incorporated as structural units (I) of polymers in a radiation-sensitive composition, they can contribute to improving sensitivity, CDU, LWR, and development defect suppression.

[0019] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Preferred combinations of embodiments are also preferred.

[0020] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") contains a polymer (hereinafter also referred to as "base polymer") having a structural unit (I) derived from an onium salt having a partial structure (i) and a structural unit (II) containing an acid-dissociable group, and a solvent. The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0021] (Polymer) A polymer (i.e., a base polymer) is an aggregate of polymerization chains having structural units (I) derived from an onium salt having substructure (i) (hereinafter also referred to as "onium salt (i)") and structural units (II) containing acid-dissociable groups. In addition to structural units (I) and (II), the base polymer may also contain structural units (III) having phenolic hydroxyl groups, structural units (IV) containing at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures, structural units (V) containing polar groups, etc. Each structural unit will be described below.

[0022] [Structural Unit (I)] Structural unit (I) is a structural unit derived from onium salt (i) having a substructure represented by the following formula (i). Onium salt (i) has a salt structure formed by an organic acid anion (thiosulfonic acid anion) and an organic cation, and substructure (i) is incorporated into this salt structure. (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ is an organic cation. * represents a bond with another atom in the onium salt described above. However, the onium salt contains one or more polymerizable groups in parts other than the substructure described above.

[0023] The structure of the entire onium salt is not particularly limited as long as it includes the partial structure (i) and the polymerizable group. The structure of the entire onium salt is roughly classified into two types according to the bonding mode between the organic acid anion (thiosulfonic acid anion) and the organic cation. The first is a mode in which, in the onium salt molecule, the organic acid anion and the organic cation exhibit a salt structure by ionic bonding (hereinafter, the onium salt according to this mode is also referred to as "onium salt (A)"). The second is a mode in which, in the onium salt molecule, the organic acid anion and the organic cation linked to each other by a covalent bond locally exhibit a salt structure (hereinafter, the onium salt according to this mode is also referred to as "onium salt (B)"). Further, the onium salt (A) may be in a form in which the organic acid anion is introduced as a side chain portion of the base polymer, or may be in a form in which the organic cation is introduced as the side chain portion. Having as a side chain portion means that the corresponding organic acid anion or organic cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0024] The structures of the organic acid anion, the organic cation, and the polymerizable group will be described later together with specific structural formulas.

[0025] In the above formula (i), X １ - is S - and it is preferable that both X ２ and X ３ are O.

[0026] The number of polymerizable groups in the above onium salt is preferably 1.

[0027] The above onium salt (A) is preferably a compound represented by the following formula (A). (In formula (A), W is a polymerizable group. R １ is a single bond or an n １ + m-valent organic group having 1 to 40 carbon atoms. Z １ ＋ is an n ２ -valent organic cation. n １ and n ２ are each independently 0 or 1. However, n １ and m n ２The sum of these is 1. m is an integer from 1 to 3. If m is 2 or greater, multiple X １ - , X ２ , X ３ Z １ ＋ and n ２ These are either identical or different from one another. １ - , X ２ and X ３ This is equivalent to equation (i) above.

[0028] In formula (A) above, the polymerizable group represented by W can be, for example, a group containing a carbon-carbon double bond. Typical structures include an ethylenically unsaturated double bond, or a structure containing an ethylenically unsaturated double bond as a substructure constituting a ring. The polymerizable group may have substituents.

[0029] Examples of substituents when the polymerizable group has substituents include halogen atoms, monovalent organic groups having 1 to 20 carbon atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, oxo groups (=O), and the like.

[0030] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0031] Examples of the monovalent organic groups having 1 to 20 carbon atoms include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups (a) having a divalent heteroatom-containing group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with monovalent heteroatom-containing groups, or combinations thereof.

[0032] Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof.

[0033] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0034] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl groups; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and bridged ring unsaturated hydrocarbon groups such as norbornyl and tricyclodecenyl groups.

[0035] Examples of monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0036] Examples of heteroatoms that constitute a divalent or monovalent heteroatom-containing group include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0037] Examples of divalent heteroatom-containing groups include -CO-, -CS-, -NR'-, -O-, -S-, and combinations thereof. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0038] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0039] Specific examples of the polymerizable group mentioned above include, but are not limited to, structures represented by the following formula.

[0040] (In the formula, * represents R) １ or Z １ ＋ (This is a bonding bond with the constituent atoms.)

[0041] In the above formula (A), R １ n, which has 1 to 40 carbon atoms, is represented by １ As for the +m-valent organic group, the monovalent organic group with 1 to 20 carbon atoms shown in W is extended up to 40 carbon atoms, and then n １ A group with +m-1 hydrogen atoms removed can be suitably adopted.

[0042] R １ It is preferable that the group includes at least one structure selected from the group consisting of a cyclic structure, -CO-, -O-, and -NR'-. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. The cyclic structure may be monocyclic, polycyclic, or a combination thereof. The cyclic structure may also be an alicyclic structure, an aromatic ring structure, or a combination thereof. In the case of a combination, the cyclic structures may be linked by a chain structure, or two or more cyclic structures may form a fused ring structure. These structures are preferably included as the smallest basic skeleton of the cyclic structure. The number of cyclic structures as the basic skeleton in the organic group may be one or two or more. The divalent heteroatom-containing group may be present between carbon atoms or at the ends of carbon chains forming the skeleton of the cyclic or chain structure, and hydrogen atoms on carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0043] As the above alicyclic structure, a structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown in W of formula (A) above, can be suitably adopted.

[0044] The above aromatic ring structure is not particularly limited as long as it is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, perylene rings, and coronene rings; aromatic heterocycles such as furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, carbazole rings, and dibenzofuran rings; or combinations thereof. Among these, benzene rings are preferred as aromatic rings.

[0045] As the above-mentioned chain structure, a structure corresponding to a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, as shown in W of formula (A), can be suitably adopted.

[0046] Aliphatic heterocyclic structures can also be used as the alicyclic structures described above. Examples of such aliphatic heterocyclic structures include oxygen-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0047] Aliphatic heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetal structures, cyclic imide structures, or combinations thereof.

[0048] Examples of substituents that substitute hydrogen atoms on carbon atoms in the above-mentioned cyclic or chain structures include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and oxo groups (=O).

[0049] The above cyclic structure preferably includes an iodine group-containing aromatic ring structure. As the iodine group-containing aromatic ring structure, a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by iodine groups can be suitably adopted.

[0050] In the above formula (A), R １ In this case, it is preferable that a fluorine atom, a monovalent fluorinated hydrocarbon group, or a cyano group is bonded to the carbon atom at the α or β position relative to S in formula (i) above. This makes it possible to further improve the acidity of the thiosulfonic acid generated by exposure.

[0051] Examples of the above-mentioned monovalent fluorinated hydrocarbon groups include monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms and monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms.

[0052] Examples of the above-mentioned monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms include fluorinated alkyl groups such as trifluoromethyl group, difluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, heptafluoron-propyl group, heptafluoroisopropyl group, nonafluoron-butyl group, nonafluoroisobutyl group, nonafluorot-butyl group, 2,2,3,3,4,4,5,5-octafluoron-pentyl group, tridecafluoron-hexyl group, and 5,5,5-trifluoro-1,1-diethylpentyl group; fluorinated alkenyl groups such as trifluoroethenyl group and pentafluoropropenyl group; and fluorinated alkynyl groups such as fluoroethynyl group and trifluoropropynyl group.

[0053] Examples of the above-mentioned monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as fluorocyclopentyl group, difluorocyclopentyl group, nonafluorocyclopentyl group, fluorocyclohexyl group, difluorocyclohexyl group, undecafluorocyclohexylmethyl group, fluoronorbornyl group, fluoroadamantyl group, fluorobornyl group, fluoroisobornyl group, and fluorotricyclodecyl group; and fluorinated cycloalkenyl groups such as fluorocyclopentenyl group and nonafluorocyclohexenyl group.

[0054] The above-mentioned fluorinated hydrocarbon group is preferably a monovalent fluorinated linear hydrocarbon group having 1 to 8 carbon atoms, and more preferably a monovalent fluorinated linear hydrocarbon group having 1 to 5 carbon atoms.

[0055] In the above formula (A), m is preferably 1 or 2, and more preferably 1.

[0056] In the above formula (A), n １ is 1, and n ２ It is preferable that this value is 0.

[0057] The organic acid anion of the onium salt (A) preferably has a structure represented by the following formula (Aa). (In equation (Aa), W, X １ - , X ２ and X ３ This is equivalent to the above formula (A). L １１ This is a single bond or a divalent heteroatom-containing group. Cy １１ and Cy １２ These are, independently, substituted or unsubstituted cyclic structures. １２ If there are multiple Cy １２ They are either identical or different from each other. １２ and L １３ Each of these is independently a single bond, a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent heteroatom-containing group, or a combination thereof. １２ If there are multiple L １２ They are either identical or different from each other. ｆ１ and Rｆ２ Each of these is independently a hydrogen atom, a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. However, R ｆ１ and R ｆ２ At least one selected from the group consisting of the following is a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. z11 is 0 or 1. z12 is an integer from 0 to 3. z13 is an integer from 1 to 4.

[0058] L １１ ~L １３ As the divalent heteroatom-containing group represented by the above formula (A), the divalent heteroatom-containing group shown in W can be suitably adopted.

[0059] Cy １１ and Cy １２ The cyclic structure represented by the above formula (A) is R １ The cyclic structure shown in can be suitably adopted. The substituents that the cyclic structure may have include R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0060] L １２ and L １３ As the divalent hydrocarbon group having 1 to 10 carbon atoms in the above-mentioned polymerizable group of the onium salt (i), a group obtained by removing one hydrogen atom from the group corresponding to 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms shown above can be suitably adopted. Substituents that the hydrocarbon group may have include, the R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0061] R ｆ１ and R ｆ２ As the fluorinated hydrocarbon group represented by the above formula (A), the fluorinated hydrocarbon group shown can be suitably adopted.

[0062] z11 is preferably 1. z12 is preferably an integer between 0 and 2, and more preferably 0 or 1. z13 is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0063] Specific examples of the organic acid anion of the onium salt (A) include, but are not limited to, structures represented by the following formulas (A-1-1) to (A-1-38) (including the structure represented by the above formula (Aa)). Although the following formulas all show structures in which polymerizable groups have been introduced into the organic acid anion, the formulas are not limited to these, and organic acid anions without polymerizable groups are also suitable. In this case, in the following formulas, W-L in the above formula (Aa) １１ -corresponding structure (CH ２ = CH-, CH ２ = C(CH ３ )-, CH ２ = CH-COO- or CH ２ = C(CH ３ The )-COO-) group can be replaced with a hydrogen atom or other substituent, and a polymerizable group can be introduced to the organic cation. Other substituents include R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] Z ＋ The organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, and ammonium cations. Z of formula (A) above １ ＋ n represented by ２ As for valence organic cations, Z ＋ From the organic cation represented by n ２A group from which one hydrogen atom has been removed can be suitably adopted.

[0070] Z ＋ It is preferable that the cation is a radiation-sensitive onium cation. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0071] The above organic cation preferably has at least one selected from the group consisting of an iodine group and a fluoro group. By introducing an iodine group or a fluoro group, the sensitivity can be improved by increasing the radiation absorption efficiency. The above organic cation preferably contains the above iodine group-containing aromatic ring structure as the form of the iodine group. In the organic cation, the fluoro group is preferably in the form of a fluoro group-containing aromatic ring structure. As the fluoro group-containing aromatic ring structure, a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced with fluoro groups can be suitably adopted.

[0072] The sulfonium cation or iodonium cation containing the polymerizable group described above is preferably represented by the following formulas (X-1) to (X-6).

[0073]

[0074] In the above formulas (X-1) to (X-6), W is independently a polymerizable group. Ｘ Each of these is independently a single bond or a divalent heteroatom-containing group. The polymerizable groups represented by W can preferably be any of the above polymerizable groups. Ｘ As the divalent heteroatom-containing group represented by the above formula (A), the divalent heteroatom-containing group shown in W can be suitably adopted.

[0075] In the above equation (X-1), R ａ１ , R ａ２ and R ａ３Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom, or -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ It represents a ring structure consisting of -O-, -CO-, or a combination thereof, or two or more of these groups combined with each other. The ring structure contains W-L in formula (X-1) above. Ｘ - may be bonded. The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds that form the skeleton. Ｐ , R Ｑ and R Ｔ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently integers from 0 to 5. R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0076] In the above equation (X-2), R ｂ１ This refers to a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. ｋ n is either 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋWhen k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O and S between the carbon-carbon bonds that form the skeleton.

[0077] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0078] In the above equation (X-4), R ｇ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, halogen atom, or hydroxyl group having 6 to 8 carbon atoms. ｋ２ n is either 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0079] In the above equation (X-5), R ｄ１ and R ｄ２ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by two or more of these groups combined. k6 and k7 are each independently integers from 0 to 5. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0080] In the above formula (X-6), R ｅ１ and R ｅ２ k8 and k9 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0081] Specific examples of radiation-sensitive onium cations as organic cations containing the polymerizable group mentioned above include, but are not limited to, the structures shown in formulas (1-2-1) to (1-2-46) below. Although the following formulas all show structures in which a polymerizable group has been introduced into the organic cation, organic cations without a polymerizable group are also suitable. In this case, in the following formulas, W-L in formulas (X-1) to (X-6) above. Ｘ -corresponding structure (CH ２ = CH-, CH ２ = C(CH ３ )-, CH ２ = CH-COO- or CH ２ = C(CH ３ The )-COO-) group can be replaced with a hydrogen atom or other substituent, and a polymerizable group can be introduced to the organic acid anion. Other substituents include R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] The organic cation of structural unit (I) may be a diaryliodonium cation. The diaryliodonium cation preferably has one or more fluorine or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluorogroup-containing aromatic ring structure or an iodogroup-containing aromatic ring structure. A phenyl group is preferred as the aryl group. A polymerizable group may be bonded to the aryl group.

[0088] Specific examples of such iodonium cations are listed below. Although the following formulas all show structures in which the organic cation does not have polymerizable groups, organic cations with polymerizable groups are also suitable, not limited to these. In this case, the W-L in formulas (X-1) to (X-6) above is on the aryl group in the following formulas. Ｘ -corresponding structure (CH ２ = CH-, CH ２ = C(CH ３ )-, CH ２ = CH-COO- or CH ２ = C(CH ３ The )-COO-) can be introduced, and the polymerizable group of the organic acid anion can be replaced with a hydrogen atom or other substituent. Other substituents include R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0089]

[0090] The onium salt (A) can be obtained by combining the above-mentioned organic acid anion and the above-mentioned sulfonium cation (however, neither is limited to the above-mentioned exemplified structures). Specific examples, though not limited to them, include structures represented by the following formulas (A-1) to (A-40).

[0091]

[0092]

[0093]

[0094]

[0095]

[0096] The above onium salt (B) is preferably a compound represented by the following formula (B). (In formula (B), W is a polymerizable group. Z ２ ＋ is 1 + n １ It is a valence organic cation. Ａ２ This is a single bond, or 2+n ２ It is a valence linking group.１ and n ２ Each of these is independently either 0 or 1. However, n １ to n ２ The sum of these is 1. １ - , X ２ and X ３ This is equivalent to equation (i) above.

[0097] In formula (B) above, the polymerizable group represented by W can preferably be the polymerizable group represented by W in formula (A) above.

[0098] Z ２ ＋ 1+n １ As a valence organic cation, Z in the above formula (A) is １ ＋ n represented by ２ In the valence of an organic cation, n ２ From the structure where is 0, 1 + n １ A structure with a hydrogen atom removed can be suitably adopted.

[0099] L Ａ２ 2+n ２ As the valence linking group, 1 + n are selected from the monovalent organic groups having 1 to 20 carbon atoms shown in W in formula (A) above. ２ A group from which one hydrogen atom has been removed can be suitably adopted. Ａ２ Preferably, it includes at least one structure selected from the group consisting of an aromatic ring and an ester bond.

[0100] In the above formula (B), L Ａ２ and Z ２ ＋ Preferably, at least one selected from the group consisting of the above contains an iodine group. Preferably, the iodine group is incorporated in the form of the above iodine group-containing aromatic ring structure.

[0101] In the above formula (B), n １ is 1, and n ２ It is preferable that this value is 0.

[0102] Specific examples of onium salt (B) include, but are not limited to, structures represented by the following formulas (B-1) to (B-4).

[0103]

[0104] The lower limit of the content of the above structural unit (I) in the total structural units constituting the base polymer (total percentage if multiple types exist) is preferably 1 mol%, more preferably 2 mol%, and still more preferably 3 mol%. The upper limit of the above content is preferably 30 mol%, more preferably 25 mol%, and still more preferably 20 mol%. As a result, the composition can exhibit excellent sensitivity, CDU, LWR, and development defect suppression during pattern formation.

[0105] As long as the effects of the present invention are not impaired, the base polymer may contain known structural units having an onium salt structure as an acid-generating structure, in addition to structural unit (I).

[0106] (Synthesis method of onium salts) Onium salts can typically be synthesized according to the following scheme. In formula (A) above, X １ - S - X ２ and X ３ All of them are O, n １ is 1, and n ２ We will now explain the case where is 0 and m is 1. However, we are not limited to this case, and known methods can be used.

[0107]

[0108] In the scheme, W and Z １ ＋ This is equivalent to the above formula (A). X Ａ - R is a halide ion. １１ and R １２ These are, independently, divalent organic groups. ｐ ＋ It is a monovalent cation.

[0109] A salt exchange is performed between the halide salt of an organic cation and a sulfonate to produce a salt of a sulfonate anion and an organic cation. Then, a polymerizable group is introduced into the salt by an appropriate reaction (esterification reaction in the above scheme) between this salt and a compound having a polymerizable group. Furthermore, the sulfonate anion is halogenated (chlorinated in the above scheme), and finally reacted with a thiol group to form a thiosulfonate anion, thereby synthesizing the desired onium salt. Other structures can also be synthesized by appropriately changing the starting materials and intermediate components.

[0110] [Structural Unit (II)] Structural unit (II) is a structural unit containing an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (II).

[0111] Structural unit (II) is not particularly limited as long as it has an acid-dissociable group, and examples include structural units having a tertiary alkyl ester moiety, structural units having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, and structural units having an acetal bond. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, the structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (II-1)") is preferred.

[0112]

[0113] In the above formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. ３１ teeth,＊ -COO-, ＊ -L ３１ａ COO- or ＊ -COOL ３１ａ Represents COO-. ３１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0114] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (II-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0115] L ３１ａ Examples of alkanediyl groups represented by include methylene groups, ethanediyl groups, 1,3-propanediyl groups, and 2,2-propanediyl groups, which have 1 to 10 carbon atoms. ３１ａ Methylene groups and ethanediyl groups are preferred as the base group.

[0116] L ３１ａ Examples of the arenediyl group represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. ３１ａ A benzenediyl group is preferred as the group.

[0117] L ３１ａ The substituents that the arenediyl group represented by can have include halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkyl groups, fluorinated alkyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and alkoxy groups.

[0118] The above R １８ As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (A), the monovalent hydrocarbon group having 1 to 20 carbon atoms shown in W can be suitably adopted.

[0119] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0120] The above R １９ and R ２０The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these atoms with the carbon atoms to which they are bonded, can preferably be a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in W of formula (A) above.

[0121] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0122] The above R １８ ~R ２０ The substituents that can be present are L ３１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0123] Examples of structural units (II-1) include the structural units represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (II-1-1) to (II-1-15)").

[0124]

[0125]

[0126] In the above equations (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R is a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently integers from 1 to 4. k and l are 0 or 1. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0127] i and j are preferably 1 or 2. １８Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into structural unit (II).

[0128] Furthermore, the polymer may contain structural units represented by the following formulas (1f) to (2f) as structural units (II).

[0129]

[0130] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0131] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0132] The lower limit of the content of structural unit (II) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural unit (II) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0133] [Structural Unit (III)] Structural unit (III) is a structural unit having a phenolic hydroxyl group. Structural unit (III) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0134] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0135] (In the above formula (4), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ Or -O-. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ Each of these is an independent integer between 0 and 8, where 1 ≤ m. ３ +m ４ ≤ 2n ３ (Saves +5.)

[0136] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (III), it is preferable that the atom is a hydrogen atom or a methyl group.

[0137] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0138] R １０２ In this case, an iodine atom is preferred as the halogen atom.

[0139] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0140] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0141] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0142] When the base polymer contains structural unit (III), the lower limit of the content of structural unit (III) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 10 mol%, and more preferably 20 mol%. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0143] [Structural Unit (IV)] Structural unit (IV) is a structural unit that includes at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures (excluding those corresponding to structural unit (I)). The base polymer can have its solubility in the developer adjusted by further including structural unit (IV), and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. It can also improve the adhesion between the resist pattern formed from the base polymer and the substrate.

[0144] Examples of structural units (IV) include those represented by the following formulas (T-1) to (T-11).

[0145]

[0146] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ These are, independently, a hydrogen atom, a C1-C4 alkyl group, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, and a dimethylamino group. Ｌ４ and R Ｌ５ These may be divalent alicyclic groups having 3 to 8 carbon atoms, which can be combined with each other and bonded together with the carbon atoms. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0147] The above R Ｌ４ and R Ｌ５ When these are combined with each other, the divalent alicyclic group having 3 to 8 carbon atoms, formed together with the carbon atoms to which they are bonded, is R in formula (3) above.１９ and R ２０ Examples include divalent alicyclic groups with 3 to 20 carbon atoms, where these groups are combined with each other and formed together with the carbon atoms to which they are bonded, specifically groups with 3 to 8 carbon atoms. One or more hydrogen atoms on these alicyclic groups may be substituted with hydroxyl groups.

[0148] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0149] Among these, structural units (IV) are preferably those containing a lactone structure, more preferably those containing a γ-butyrolactone structure or a norbornane lactone structure, and even more preferably those derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl(meth)acrylate.

[0150] When the base polymer contains structural unit (IV), the lower limit of the content of structural unit (IV) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural unit (II) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0151] [Structural Unit (V)] Structural unit (V) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (IV)). The base polymer can have its solubility in the developer adjusted by further containing structural unit (V), and as a result, the lithographic performance such as resolution of the radiation-sensitive composition can be improved. Examples of the above polar group include a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxyl group and a carboxyl group are preferred, and a hydroxyl group is more preferred.

[0152] Examples of structural units (V) include structural units represented by the following formula.

[0153]

[0154]

[0155] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0156] When the base polymer has a structural unit (V) having the polar group, the lower limit of the content of the structural unit (V) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and still preferably 3 mol%. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and still preferably 8 mol%. By setting the content of structural unit (V) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0157] [Structural Unit (VI)] The base polymer may include structural unit (VI), which has a second organic acid anion and a second onium cation, and contains a second acid generating structure that generates an acid by exposure without dissociating the above-mentioned acid-dissociable group. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid generating structure substantially prevents the dissociation of the acid-dissociable group of structural unit (II), and has the function of suppressing the diffusion of acid generated from structural unit (I) (the onium salt incorporated into structural unit (I)) or the radiation-sensitive acid generating agent (if included) in the unexposed area by salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from structural unit (I) (the onium salt incorporated into structural unit (I)) or the radiation-sensitive acid generating agent. Whether an onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable groups of the base polymer, and the acidity of the onium salt structure or the generated acid.

[0158] Regarding the inclusion of the second organic acid anion and the second onium cation in the structural unit (VI) of the base polymer, from the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0159] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion, and more preferably a carboxylic acid anion. However, when the above-mentioned second organic acid anion has the above-mentioned sulfonic acid anion, no electron-withdrawing group is bonded to either the α-position or the β-position carbon atom of the sulfur atom in the sulfonic acid anion. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, cyano groups, etc. The acid generated by exposure corresponds to the above-mentioned acid anion portion and is a carboxylic acid or sulfonic acid.

[0160] The above second organic acid anion preferably contains -O-, -CO-, a cyclic structure or a combination thereof as a structure other than the acid anion moiety. As such a structure, the structure represented by the organic acid anion of the onium salt (A) can be preferably adopted.

[0161] The above second organic acid anion preferably has an iodine group or a hydroxy group. As a mode of containing the iodine group, the above second organic acid anion preferably contains the iodine group-containing aromatic ring structure.

[0162] As the above second onium cation, the organic cation shown in the structural unit (I) (however, not containing a polymerizable group) can be preferably adopted.

[0163] The above second onium cation preferably has an iodine group. As a mode of containing the iodine group, the above second onium cation preferably contains the iodine group-containing aromatic ring structure.

[0164] The second onium cation in the structural unit (VI) preferably has the above fluorine group-containing aromatic ring structure. Thereby, the sensitivity can be improved by increasing the radiation absorption efficiency.

[0165] By having the structural unit (VI) in combination with the above structures, the above functions can be efficiently exhibited.

[0166] The structural unit (VI) is preferably a structural unit represented by the following formula (p1) (hereinafter, also referred to as "structural unit (VI-1)").

[0167]

[0168] In the formula (p1), R A is a hydrogen atom or a methyl group.

[0169] In the formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group, a naphthylene group or a combination thereof.

[0170] In the formula (p1), X ２This is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may include an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3- Examples include C1-C12 alkanediyl groups such as diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, heptane-1,7-diyl groups, octane-1,8-diyl groups, nonane-1,9-diyl groups, and decane-1,10-diyl groups; C3-C12 cyclic saturated hydrocarbylene groups such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; and groups obtained by combining these.

[0171] In formula (p1), X 3 These are single bonds, ester bonds, or ether bonds.

[0172] In formula (p1), X 1 ~X ２ Some or all of the hydrogen atoms in may be substituted with substituents. Examples of substituents include R in formula (A) above. １ The substituents shown in can be suitably adopted. 1 ~X ２ If the compound has a phenylene group, it is preferable that some or all of the hydrogen atoms of the phenylene group are substituted with fluorine atoms or iodine atoms.

[0173] In formula (p1), R ｘ These are halogen atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0174] In formula (p1), Z ２ ＋ This is a secondary onium cation. As the secondary onium cation, the organic cation shown in structural unit (I) (however, without polymerizable groups) can be suitably used.

[0175] In the above formula (p1), an iodonium cation can also be used as the second onium cation. As the iodonium cation, the diaryliodonium cation shown as the onium cation of structural unit (I), except that it does not contain a polymerizable group, can be suitably adopted.

[0176] Examples of monomeric second organic acid anions that give structural unit (VI) (including structural unit (VI-1)) include, but are not limited to, those listed below. In the following formulas, the iodine group or hydroxyl group is a hydrogen atom or R in formula (A) above. １ Substitutions may be made with the substituents shown in the following formula. Ａ The same applies as described above. It is preferable that the second organic acid anion has a carboxylate anion and a hydroxyl group. In this case, it is preferable that the carboxylate anion and the hydroxyl group are bonded to the same aromatic ring in the second organic acid anion, and it is more preferable that the carbon atom to which the carboxylate anion is bonded and the carbon atom to which the hydroxyl group is bonded are directly connected to each other on the same aromatic ring.

[0177]

[0178]

[0179]

[0180]

[0181] In this configuration, a secondary onium cation is bonded to the main chain as the side chain structure of the base polymer, and a secondary organic acid anion is ionically bonded to the secondary onium cation as its counterion. In this case, the secondary onium cation is bonded to the main chain via a divalent linking group or a single bond, and X in formula (p1) above is formed. １ From COO- It is preferable that the structure up to this point is ionically bonded to a second onium cation as a counterion. As the above divalent linking group, the above divalent heteroatom-containing group shown in W of formula (A) can be suitably adopted.

[0182] When the base polymer contains structural unit (VI), the lower limit of the content of structural unit (VI) (or the total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of structural unit (VI) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0183] [Other structural units] The base polymer may also contain structural units other than those listed above, such as structural units having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). (In the above formula (6), R １α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α (It is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.)

[0184] In the above formula (6), R ２α As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (A), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in W can be suitably adopted.

[0185] When the base polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0186] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0187] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(isobutyrate)dimethyl (MAIB), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0188] Solvents used in the above polymerization include, for example, alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; and ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone. Examples include linear ethers such as dimethoxyethanes and diethoxyethanes; cyclic ethers such as tetrahydrofurans and 1,4-dioxanes; polyhydric alcohol partial ethers such as 1-methoxy-2-propanol (propylene glycol monomethyl ether); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0189] The reaction temperature in the polymerization described above is usually 40°C to 150°C, with 50°C to 120°C being preferred. The reaction time is usually 1 hour to 48 hours, with 1 hour to 24 hours being preferred.

[0190] The molecular weight of the base polymer is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 12,000. By keeping the Mw of the base polymer within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0191] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0192] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0193] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh) Column temperature: 40°C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0194] The base polymer content is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0195] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer, and as a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, or to modify the surface of the resist film and control the distribution of the composition within the film during EUV exposure.

[0196] As the high-fluorine content polymer, for example, it may have a structural unit represented by the following formula (5) (hereinafter, also referred to as "structural unit (VIII)").

[0197]

[0198] In the above formula (5), R １３ is a hydrogen atom, a methyl group or a trifluoromethyl group. G Ｌ is a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. R １４ is a monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0199] Regarding the above R １３ From the viewpoint of the copolymerizability of the monomer that gives the structural unit (VIII), a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable.

[0200] Regarding the above G Ｌ From the viewpoint of the copolymerizability of the monomer that gives the structural unit (VIII), a single bond and -COO- are preferable, and -COO- is more preferable.

[0201] Regarding the above R １４ Examples of the monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms represented by the above R

[0202] include those in which some or all of the hydrogen atoms of a linear or branched alkyl group having 1 to 20 carbon atoms are substituted by fluorine atoms. １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above R

[0203] Regarding the above R １４Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0204] When a high-fluorine-content polymer has structural unit (VIII), the lower limit of the content of structural unit (VIII) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural unit (VIII) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0205] High-fluorine polymers may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (IX)) represented by the following formula (f-2), either together with or in place of structural unit (VIII). The presence of structural unit (f-2) in high-fluorine polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0206]

[0207] Structural units (IX) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In common to both (x) and (y), in the above formula (f-2), R Ｃ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ-A structure to which a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms of this hydrocarbon group are substituted by an organic group having a heteroatom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0208] If the structural unit (IX) has (x) an alkali-soluble group, R Ｆ A is a hydrogen atom, １ The oxygen atom is -COO-* or -SO ２ It is O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having an alkali-soluble group in the structural unit (IX) increases its affinity for alkaline developer and suppresses development defects. A structural unit (IX) having an alkali-soluble group is A １ is an oxygen atom and W １ It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0209] If the structural unit (IX) has an alkali-dissociable group (y), R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ It is O-*. ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. １R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom. １ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in the structural unit (IX) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural units (IX) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0210] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural units (IX), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0211] When a high-fluorine-content polymer has structural units (IX), the content of structural units (IX) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural units (IX) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers, thereby suppressing the occurrence of development defects.

[0212] [Other structural units] High-fluorine polymers may, if necessary, include structural units other than those listed above, such as structural unit (II) and structural unit (V) in the base polymer.

[0213] When a high-fluorine-content polymer contains structural unit (II), the content of structural unit (II) is preferably 30 mol%, and more preferably 40 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0214] When a high-fluorine-content polymer contains structural units (V), the content of structural units (V) is preferably 1 mol%, and more preferably 3 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 15 mol%, and more preferably 8 mol%.

[0215] The lower limit of Mw for the high-fluorine-content polymer is preferably 4,000, more preferably 5,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 10,000, and even more preferably 8,000.

[0216] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0217] If the radiation-sensitive composition contains a high-fluorine content polymer, the lower limit of the high-fluorine content polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass.

[0218] By setting the content of the high-fluorine polymer within the above range, the high-fluorine polymer can be more effectively distributed to the surface layer of the resist film. As a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, and to control the surface modification of the resist film and the distribution of the internal composition during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine polymers.

[0219] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0220] (Radiation-sensitive acid generator) The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator is a compound having an organic acid anion and an onium cation, which generates an acid that dissociates the above-mentioned acid-dissociable group upon exposure. Unlike onium salts that give structural unit (I) incorporated as part of a polymer, the radiation-sensitive acid generator is a compound that exists as a compound on its own (liberated from the polymer).

[0221] Examples of organic acid anions include sulfonate anions, sulfonimide anions, and sulfonmethide anions.

[0222] Examples of such acids include: (1) compounds in which one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups are substituted on the α or β carbon atoms of a sulfo group, or in which an ester bond is interposed between carbon atoms; (2) compounds having a sulfonimide structure containing a fluorine atom; and (3) compounds having a sulfonemethide structure containing a fluorine atom.

[0223] The radiation-sensitive acid generator is preferably a compound represented by the following formula (z-a). (In formula (z-a), R ４ｚ It is a monovalent organic group having 2 to 40 carbon atoms. However, -SO ３ - A fluorine atom or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α or β position. ＋ (This is a monovalent onium cation.)

[0224] R ４ｚ As the monovalent organic group having 2 to 40 carbon atoms represented by the above formula (A), a group obtained by extending the monovalent organic group having 1 to 20 carbon atoms shown in W of the above formula (A) to have 2 to 40 carbon atoms can be suitably adopted.

[0225] R ４ｚ It is preferably a monovalent organic group having 4 to 40 carbon atoms that includes at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond. As for the cyclic structure, R in formula (A) above is preferable. １ The annular structure shown can be suitably adopted.

[0226] The above monovalent fluorinated hydrocarbon group is R of formula (A) above. １ The monovalent fluorinated hydrocarbon group shown in [reference] can be suitably used.

[0227] Za ＋ As the monovalent onium cation represented by , the sulfonium cation or iodonium cation shown in the onium salt that gives structural unit (I) can be suitably used (however, neither contains a polymerizable group).

[0228] Specific examples of radiation-sensitive acid generators include, but are not limited to, structures represented by the following formulas (1B-1) to (1B-24).

[0229]

[0230]

[0231]

[0232] In addition to the above, compounds in which an organic acid anion and an onium cation are covalently bonded can also be used as radiation-sensitive acid generators.

[0233] When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total if multiple types are included) is preferably 1 part by mass, and more preferably 3 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 15 parts by mass, and more preferably 10 parts by mass. As a result, the composition can exhibit excellent sensitivity, CDU, LWR, and development defect suppression when forming resist patterns.

[0234] <Acid Diffusion Control Agent> The radiation-sensitive composition may contain an acid diffusion control agent. The acid diffusion control agent preferably contains an organic acid anion and an onium cation, and generates an acid with a higher pKa than the acid generated from the above structural unit (I) (the onium salt incorporated into structural unit (I)) upon exposure. Under pattern-forming conditions using the radiation-sensitive composition, the acid diffusion control agent has the function of substantially preventing the dissociation of the acid-dissociable groups of the base polymer and suppressing the diffusion of the acid generated from the above structural unit (I) and the radiation-sensitive acid generator in the unexposed areas by salt exchange.

[0235] By including the above-mentioned acid diffusion control agent in the radiation-sensitive composition, acid diffusion in unexposed areas can be suppressed, enabling the formation of a resist pattern with superior resolution and development contrast.

[0236] Examples of acid diffusion control agents include sulfonium salt compounds represented by the following formula (8-1), iodonium salt compounds represented by the following formula (8-2), and so on. Also included are compounds containing both a sulfonium cation and anion within the same molecule, represented by the following formula (8-3), and compounds containing both an iodonium cation and anion within the same molecule, represented by the following formula (8-4).

[0237]

[0238] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋This is an iodonium cation. E - and Q - Each of them is independent of OH - It may be R α -COO - , R α -SO ３ - It may also be an organic acid anion represented by the above formulas (8-1) to (8-2), α R is a monovalent organic group having 1 to 30 carbon atoms. In the above formulas (8-3) to (8-4), α This is a single bond or a divalent organic group having 1 to 30 carbon atoms. As the monovalent organic group having 1 to 30 carbon atoms, a group obtained by extending the monovalent organic group having 1 to 20 carbon atoms shown in W of formula (A) to 1 to 30 carbon atoms can be suitably adopted. As the divalent organic group having 1 to 30 carbon atoms, a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 30 carbon atoms can be mentioned. α -SO ３ - In the case of an anion represented by R, α SO in ３ - The electron-withdrawing group is not bonded to either the α- or β-carbon atom of the sulfur atom.

[0239] The above acid diffusion control agent preferably contains an iodine group. The iodine group in the above acid diffusion control agent preferably contains the above iodine group-containing aromatic ring structure.

[0240] Examples of organic acid anions for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also examples. As organic acid anions that do not have an iodine group-containing aromatic ring structure, structures in which the iodine group in the following formula is replaced with an atom or group other than an iodine group, such as a hydrogen atom or other substituent, can be suitably adopted.

[0241]

[0242]

[0243] As the onium cation in the above-mentioned acid diffusion control agent, the structure of the onium cation of the onium salt that gives structural unit (I) (however, without polymerizable groups) can be suitably adopted.

[0244] As acid diffusion control agents, for example, primary to tertiary amine compounds (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), nitrogen-containing heterocyclic compounds, onium salts having a quaternary ammonium cation, etc., can also be suitably used.

[0245] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0246] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0247] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0248] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0249] Furthermore, compounds having acid-dissociable groups can also be used as the nitrogen-containing organic compounds mentioned above. Examples of nitrogen-containing organic compounds having such acid-dissociable groups include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-pentyloxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0250] As the quaternary ammonium cation, a tetraalkylammonium cation is preferred. As the anion of the onium salt having a quaternary ammonium cation, the structures exemplified as organic acid anions of the acid diffusion control agent described above can be suitably adopted. Among these, cyclobutanedicarboxylic acid mono(tetrabutylammonium), tetrabutylammonium salicylate, and tetrabutylammonium benzoate are preferred.

[0251] Acid diffusion control agents may be used alone or in combination of two or more types.

[0252] If the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 2 parts by mass, more preferably 4 parts by mass, and still more preferably 6 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 60 parts by mass, more preferably 50 parts by mass, and still more preferably 40 parts by mass.

[0253] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the base polymer and any optional components that may be included.

[0254] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0255] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 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, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether), which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0256] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents in which the hydroxyl groups of the above-mentioned polyhydric alcohol solvents, such as propylene glycol monomethyl ether, have been etherified.

[0257] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0258] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0259] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0260] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0261] Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferred, alcoholic acid ester-based solvents, C1-C18 monoalcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, and lactone-based solvents are more preferred, and methyl 2-hydroxyisobutyrate, diacetone alcohol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and γ-butyrolactone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0262] (Other optional components) The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0263] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared by mixing, for example, a polymer, and optionally a high-fluorine-content polymer, and a solvent in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using, for example, a filter with a pore size of about 0.05 μm to 0.40 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0264] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention includes a step (1) of applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as the "resist film forming step"), a step (2) of exposing the resist film (hereinafter also referred to as the "exposure step"), and a step (3) of developing the exposed resist film with a developer solution (hereinafter also referred to as the "development step").

[0265] According to the pattern formation method described above, since the above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, CDU, LWR, and development defect suppression, is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0266] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film, such as those disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, pre-baking (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 170°C, with 80°C to 150°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0267] The lower limit of the thickness of the resist film formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 350 nm, and even more preferably 200 nm.

[0268] When performing immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer in the above-mentioned radiation-sensitive composition, an immersion-insoluble protective film may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the immersion-protective film, either a solvent-peelable protective film that is peeled off with a solvent before the development process (see, for example, Japanese Patent Application Publication No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development process (see, for example, Japanese Patent Application Publication Nos. WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable immersion-protective film.

[0269] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask (and, in some cases, through an immersion liquid such as water). The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; for example, electron beams and charged particle beams such as alpha rays. 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 wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0270] When exposure is performed by immersion lithography, the immersion liquid used can be, for example, water or a fluorine-based inert liquid. The immersion liquid is preferably transparent to the exposure wavelength and has the smallest possible temperature coefficient of refractive index to minimize distortion of the optical image projected onto the film. In particular, when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above considerations, water is preferred due to its availability and ease of handling. When water is used, a small amount of an additive that reduces the surface tension of the water and increases its surfactant properties may be added. This additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0271] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the structural unit (I-1) or the radiation-sensitive acid generator due to the exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0272] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0273] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing 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, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0274] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, etc., or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As for ether solvents, glycol ether solvents are preferred, and ethylene glycol monomethyl ether and propylene glycol monomethyl ether are more preferred. As for ester solvents, acetate ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvents in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0275] As mentioned above, either an alkaline developer or an organic solvent developer may be used as the developer. The appropriate choice can be made depending on whether a positive or negative pattern is desired.

[0276] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by piling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0277] <Polymer> The polymer in question is a polymer having a structural unit (I) derived from an onium salt having a substructure represented by the following formula (i), and a structural unit (II) containing an acid-dissociable group. (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ is an organic cation. * represents the bonding site with other atoms in the onium salt described above. However, the onium salt contains one polymerizable group in the portion other than the substructure described above.

[0278] As such a polymer, the polymer (base polymer) in the above-mentioned radiation-sensitive composition can be suitably used.

[0279] <Onium Salt> The onium salt in question is a compound represented by the following formula (A1). (In formula (A1), W is a polymerizable group. R １ａ n, which has 1 to 40 carbon atoms. １ It is an organic group with a +m valency. Here, m is 1 and n１ is 1, n ２ If R is 0, １ａ Excluding methylene groups or benzenediyl groups. １ ＋ is, n ２ It is a valence organic cation. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of n. １ and n ２ Each of these is independently either 0 or 1. However, n １ and m pieces of n ２ The sum of these is 1. m is an integer from 1 to 3. If m is 2 or greater, multiple X １ - , X ２ , X ３ and Z １ ＋ (These are either identical or different from each other.)

[0280] As such a compound, an onium salt (A) that gives structural unit (I) in the polymer (base polymer) of the above-mentioned radiation-sensitive composition can be suitably used. However, m is 1 and n １ is 1, n ２ If R is 0, １ａ Excluding methylene groups or benzenediyl groups.

[0281] <Onium Salt> The onium salt in question is a compound represented by the following formula (B). (In formula (B), W is a polymerizable group. Z ２ ＋ is 1 + n １ It is a valence organic cation. Ａ２ This is a single bond, or 2+n ２ It is a valence linking group. １ - is, S- or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of n. １ and n ２ Each of these is independently either 0 or 1. However, n １ to n ２ The sum of these is 1.

[0282] As such a compound, an onium salt (B) that provides structural unit (I) in the polymer (base polymer) of the above-mentioned radiation-sensitive composition can be suitably adopted.

[0283] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0284] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0285] [ １３ [C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0286] <Synthesis of Compound (Monomer)> [Example A1] (Synthesis of Monomer (A-1)) Compound (A-1) was synthesized according to the following synthesis scheme.

[0287] 20.0 mmol of compound (A-1-a), 20.0 mmol of compound (A-1-b), 50 g of dichloromethane, and 50 g of water were added to a reaction vessel and stirred at room temperature for 4 hours. Dichloromethane was added to the reaction mixture for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain compound (A-1-c), represented by the above formula (A-1-c), in good yield.

[0288] To the above compound (A-1-c), 20.0 mmol of 3-iodo-4-vinylbenzoic acid, 30.0 mmol of 1,1'-carbonylbis-1H-imidazole, and 100 g of dichloromethane were added and the mixture was stirred at room temperature for 12 hours. After adding saturated ammonium chloride aqueous solution to terminate the reaction, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (A-1-d) represented by the above formula (A-1-d) was obtained in good yield by purification by column chromatography.

[0289] The above compound (A-1-d) contains SOCl ２ 20.0 mmol of NaSH and 100 g of dichloromethane were added, and the mixture was stirred at room temperature for 4 hours. After the solvent was removed by distillation, 20.0 mmol of NaSH and 200 g of methanol were added, and the mixture was stirred at room temperature for a further 4 hours. After the reaction was complete, the solvent was removed by distillation, and the compound (A-1) represented by the above formula (A-1) was obtained in good yield by purification by column chromatography.

[0290] [Examples A2 to A31] (Synthesis of monomers (A-2) to (A-31)) Monomers represented by the following formulas (A-2) to (A-31) were synthesized in the same manner as in Example A1, except that the raw materials and precursors were appropriately changed.

[0291]

[0292]

[0293]

[0294] The monomers other than monomers (A-1) to (A-31) used in the synthesis of each polymer are shown below. Hereafter, compounds represented by formulas (M-1) to (M-23) may be referred to as "compound (M-1)" to "compound (M-23)" or "monomer (M-1)" to "monomer (M-23)," respectively.

[0295]

[0296]

[0297] <Synthesis of Polymers> In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is set to 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is set to 100 mol%.

[0298] [Example P1] (Synthesis of Polymer (P-1)) Monomer (A-1), monomer (M-1), and monomer (M-9) were dissolved in 1-methoxy-2-propanol (200 parts by mass) in a molar ratio of 15 / 40 / 45 (mol%), and AIBN (azobisisobutyronitrile) (5 mol% relative to the total 100 mol% of monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 1-methoxy-2-propanol was placed in an empty reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered again, and dried at 50°C for 10 hours to obtain a white powdery polymer (P-1) (yield: 85%). The Mw of polymer (P-1) was 7,500, and the Mw / Mn ratio was 1.50. １３ ¹³C-NMR analysis revealed that the content percentages of each structural unit derived from monomer (A-1), monomer (M-1), and monomer (M-9) were 16.0 mol%, 41.5 mol%, and 42.5 mol%, respectively.

[0299] [Examples P2-44 and Comparative Examples CP1-3] (Synthesis of polymers (P-2) to polymer (P-44) and polymers (CP-1) to polymer (CP-3)) ​​Polymers (P-2) to polymer (P-44) and polymers (CP-1) to polymer (CP-3) were synthesized in the same manner as in Example P1, except that monomers of the types and blending ratios shown in Tables 1-1 and 1-2 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are shown in Table 1 below.

[0300]

[0301]

[0302] [Synthesis Example F1] (Synthesis of High Fluorine-Content Polymer (F-1)) Monomers (M-9), (M-17), and (M-18) were dissolved in 2-butanone (200 parts by mass) in a molar ratio of 45 / 50 / 5 (mol%), and MAIB (5 mol%) was added as an initiator to prepare a monomer solution. The subsequent procedure was the same as in Example P1 to synthesize the high fluorine-content polymer (F-1). The Mw of the high fluorine-content polymer (F-1) was 7,500, and the Mw / Mn was 1.70. １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from (M-9), (M-17), and (M-18) was 45.6 mol%, 49.3 mol%, and 5.1 mol%, respectively.

[0303] [C] Radiation-sensitive acid generators C-1 to C-3: Compounds represented by the following formulas (C-1) to (C-3)

[0304]

[0305] [D] Acid diffusion control agents D-1 to D-9: Compounds represented by the following formulas (D-1) to (D-9)

[0306]

[0307] [Solvents] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Methyl 2-hydroxyisobutyrate E-4: Diacetone alcohol E-5: γ-Butyrolactone

[0308] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 1] Radiation-sensitive composition (J-1) was prepared by mixing 100 parts by mass of (P-1) as polymer (A), 35.0 parts by mass of (D-1) as acid diffusion control agent (D), 5.0 parts by mass (solids) of (F-1) as high-fluorine-content polymer (F), and 7,000 parts by mass of a mixed solvent of (E-1) / (E-2) as solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0309] [Examples 2-51 and Comparative Examples 1-2] Radiation-sensitive compositions (J-2) to (J-51) and (CJ-1) to (CJ-2) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Table 2 below were used.

[0310]

[0311] <Formation of a resist pattern using a positive-type radiation-sensitive composition for EUV exposure> An anti-reflective underlayer film (ARC66 from Brewer Sciences) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 105 nm. The prepared positive-type radiation-sensitive composition for EUV exposure was applied to this anti-reflective underlayer film using the spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 65 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an EUV lithography system (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (30 nm contact hole pattern).

[0312] <Evaluation> The sensitivity, CDU, and number of development defects of the resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated according to the following method. The results are shown in Table 3 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0313] [Sensitivity] In forming a resist pattern using the above-mentioned positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 30 nm contact hole pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２The sensitivity was set to 40 mJ / cm². ２ In the following cases, it is considered "good" and 40 mJ / cm². ２ If it exceeded this value, it was rated as "poor."

[0314] [CDU] The mask size was adjusted to form a 30 nm contact hole pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The hole diameter was measured at 16 points in the range of 500 nm and the average value was calculated. This average value was then measured at a total of 500 points at arbitrary points, and the 3-sigma value was calculated from the distribution of the measured values, which was defined as CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and is therefore better. A CDU of 3.0 nm or less was evaluated as "good," and a value greater than 3.0 nm was evaluated as "poor."

[0315] [Development Defect Count] A 30 nm contact hole pattern was formed by exposing a resist film with the optimal exposure dose, and this was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 50 or less, and as "poor" if it exceeded 50.

[0316]

[0317] As is clear from the results in Table 3, the radiation-sensitive composition of the example showed good sensitivity, CDU, and development defect performance when used in EUV exposure, whereas the comparative example exhibited inferior characteristics compared to the example.

[0318] [Preparation of positive-type radiation-sensitive composition for ArF immersion exposure] [Example 52] 100 parts by mass of (P-28) as polymer (P), 8.0 parts by mass of (D-2) as acid diffusion control agent (D), 3.0 parts by mass of (F-1) as high-fluorine-content polymer (F) (solids), and 2,730 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent (E) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-52).

[0319] [Examples 53-58 and Comparative Example 3] Radiation-sensitive compositions (J-53) to (J-58) and (CJ-3) were prepared in the same manner as in Example 52, except that the components of the types and amounts shown in Table 4 below were used.

[0320]

[0321] <Formation of a resist pattern using a positive-type radiation-sensitive composition for ArF immersion lithography> An anti-reflective underlayer film formation composition ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 100 nm. The positive-type radiation-sensitive composition for ArF lithography prepared above was applied to this anti-reflective underlayer film using the same spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 120 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed to a 50 nm line-and-space pattern using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Dipole (σ = 0.9 / 0.7). After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (50 nm line-and-space pattern).

[0322] <Evaluation> The sensitivity, LWR, and number of development defects of the resist patterns formed using the above ArF immersion exposure positive-type radiation-sensitive composition were evaluated according to the following method. The results are shown in Table 5 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0323] [Sensitivity] In forming a resist pattern using the above ArF immersion lithography positive-type radiation-sensitive composition, the exposure amount used to form a 50 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 30 mJ / cm². ２ The following conditions are considered "good": 30 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0324] [LWR] A 50 nm line-and-space resist pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better quality. An LWR of 3.5 nm or less was evaluated as "good," and an LWR greater than 3.5 nm was evaluated as "poor."

[0325] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a 50 nm line-and-space pattern, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 50 or less, and as "poor" if it exceeded 50.

[0326]

[0327] As is clear from the results in Table 5, the radiation-sensitive composition of the example showed good sensitivity, LWR, and development defect count when used in ArF exposure, whereas the comparative example exhibited inferior characteristics compared to the example.

[0328] The radiation-sensitive composition and pattern formation method described above allow for the formation of resist patterns that exhibit good sensitivity to exposure light and excellent CDU, LWR, and development defect suppression. Therefore, these can be suitably used in semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

1. A radiation-sensitive composition containing a structural unit (I) derived from an onium salt having a partial structure represented by the following formula (i), a polymer having a structural unit (II) containing an acid dissociable group, and a solvent. (In formula (i), １ - X - is S - or O ２ X ３ and X １ - are each independently S or O. However, at least one selected from the group consisting of X ２ , X ３ contains S. ＋ Z is an organic cation. * is a bond with another atom in the above onium salt. However, the above onium salt contains one or more polymerizable groups in the portion other than the above partial structure.) 2. The radiation-sensitive composition according to claim 1, wherein the onium salt is a compound represented by the following formula (A) or formula (B). (In formula (A), W is a polymerizable group. R １ This refers to a single bond or a n-bond with 1 to 40 carbon atoms. １ It is an organic group with a positive (m) valency. Z １ ＋ is, n ２ It is a valence organic cation. １ and n ２ Each of these is independently either 0 or 1. However, n １ and m pieces of n ２ The sum of these is 1. m is an integer from 1 to 3. If m is 2 or greater, multiple X １ - , X ２ , X ３ Z １ ＋ and n ２ These are either identical or different from one another. １ - , X ２ and X ３ This is equivalent to equation (i) above. (In formula (B), W is a polymerizable group. Z ２ ＋ is 1 + n １ It is a valence organic cation. Ａ２ This is a single bond, or 2+n ２ It is a valence linking group. １ and n ２ Each of these is independently either 0 or 1. However, n １ to n ２ The sum of these is 1. １ - , X ２ and X ３ This is equivalent to equation (i) above.

3. The radiation-sensitive composition according to claim 2, wherein m is 1 in formula (A) above.

4. In the above formula (A), R １ The radiation-sensitive composition according to claim 2, wherein is comprised of at least one structure selected from the group consisting of a cyclic structure, -CO-, -O-, and -NR'-, and R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

5. The radiation-sensitive composition according to claim 4, wherein the above cyclic structure includes an iodine group-containing aromatic ring structure.

6. In the above formula (A), R １ The radiation-sensitive composition according to claim 2, wherein a fluorine atom or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α or β position of S in formula (i) above.

7. In the above formula (B), L Ａ２ and Z ２ ＋ The radiation-sensitive composition according to claim 2, wherein at least one selected from the group consisting of the following is an iodine group.

8. In the above formula (B), L Ａ２ The radiation-sensitive composition according to claim 2, wherein the composition comprises at least one structure selected from the group consisting of an aromatic ring and an ester bond.

9. In the above formula (A), n １ is 1, and n ２ The radiation-sensitive composition according to claim 2, wherein is 0.

10. In the above formula (B), n １ is 1, and n ２ The radiation-sensitive composition according to claim 2, wherein is 0.

11. The radiation-sensitive composition according to claim 2, wherein in formula (A) and formula (B), the organic cation is independently a sulfonium cation or an iodonium cation.

12. X １ - is, S - X ２ and X ３ The radiation-sensitive composition according to any one of claims 1 to 11, wherein all of the elements are O.

13. The radiation-sensitive composition according to any one of claims 1 to 11, wherein the polymerizable group is a group containing a carbon-carbon double bond.

14. The radiation-sensitive composition according to any one of claims 1 to 11, wherein the content of the structural unit (I) in relation to the total structural units constituting the polymer is 1 mol% or more and 30 mol% or less.

15. The radioactive composition according to any one of claims 1 to 11, wherein the above-mentioned structural unit (II) having an acid-dissociable group is represented by the following formula (3). (In formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these is independently either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ These elements combine with each other to form a divalent alicyclic group with 3 to 20 carbon atoms, which is then bonded to the carbon atoms. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

16. The radiation-sensitive composition according to any one of claims 1 to 11, wherein the polymer further comprises a structural unit (III) having a phenolic hydroxyl group.

17. The radiation-sensitive composition according to any one of claims 1 to 11, further comprising an acid diffusion control agent.

18. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 11 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

19. The pattern formation method according to claim 18, wherein the above exposure is performed by an ArF excimer laser or extreme ultraviolet light.

20. A polymer having a structural unit (I) derived from an onium salt having a substructure represented by the following formula (i), and a structural unit (II) containing an acid-dissociable group. (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ is an organic cation. * represents the bonding site with other atoms in the onium salt described above. However, the onium salt contains one polymerizable group in the portion other than the substructure described above.

21. An onium salt represented by the following formula (A1). (In formula (A1), W is a polymerizable group. R １ａ is an organic group having n １ + m valences with 1 to 40 carbon atoms. However, when m is 1, n １ is 1, and n ２ is 0, R １ａ excludes a methylene group or a benzenediyl group. Z １ ＋ is an organic cation having n ２ valences. X １ - is S - or O - X ２ and X ３ are each independently S or O. However, X １ - X ２ and X ３ includes S in at least one selected from the group consisting of. n １ and n ２ are each independently 0 or 1. However, the sum of n １ and m n ２ is 1. m is an integer from 1 to 3. When m is 2 or more, a plurality of X １ - X ２ X ３ Z １ ＋ and n ２ are each the same as or different from each other.) 22. An onium salt represented by the following formula (B). (In formula (B), W is a polymerizable group. Z ２ ＋ is 1 + n １ It is a valence organic cation. Ａ２ This is a single bond, or 2+n ２ It is a valence linking group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of n. １ and n ２ Each of these is independently either 0 or 1. However, n １ to n ２ The sum of these is 1.

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