Radiation-sensitive composition, pattern formation method, and onium salt compound

Abstract

Provided is a radiation-sensitive composition or the like having excellent sensitivity, excellent CDU, and an excellent process window. This radiation-sensitive composition comprises: an onium salt compound represented by formula (1); a polymer that includes a structural unit having an acid-dissociable group; and a solvent. (In the formula, X represents a halogeno group. When X includes an iodo group, the iodo group is bound to the p-position of the COO- group in the formula. R1 represents a hydrocarbon group, a group (α) having, between carbon-carbon in said group, a divalent heteroatom-containing group, or a group (β) obtained by substituting a hydrogen atom of said group (α) or said hydrocarbon group with a chloro group, a bromo group, an iodo group, a hydroxy group, a nitro group, an amino group, a carboxy group, or a cyano group. When h is 2 or more, the two R1s may be combined to form a ring structure having 5-20 member rings. R2 represents a monovalent hydrocarbon group having 1-5 carbon atoms, a cyano group, a nitro group, or a hydroxy group. Z+ represents an organic cation including an aromatic ring substituted with an electron-withdrawing group.)

Description

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

[0001] The present invention relates to a radiation-sensitive composition, a pattern-forming method, and an onium salt compound.

[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 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, and further advance pattern miniaturization by employing liquid immersion lithography, a method in which exposure is performed with the space between the lens of the exposure apparatus and the resist film filled with a liquid medium. As next-generation technologies, lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered.

[0004] Various structures have been investigated for quenchers, which are also a major component of resist compositions (see Japanese Patent Publication No. 2024-67732).

[0005] Japanese Patent Publication No. 2024-67732

[0006] As patterns become finer, resist compositions are required to have resist performance characteristics equivalent to or better than conventional ones in terms of sensitivity, CDU, process window, etc., during pattern formation.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, and an onium salt compound that exhibit excellent sensitivity, CDU, and process window 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] That is, in one embodiment, the present invention relates to a radiation-sensitive composition containing an onium salt compound represented by the following formula (1) (hereinafter also referred to as "onium salt compound (1)"), a polymer containing a structural unit having an acid dissociable group, and a solvent. (In formula (1), g, h, and i are each independently an integer of 0 to 3. However, g + h + i is 3 or less. When X, R １ and R ２ are present in plural, the plural X, R １ and R ２ are each the same as or different from one another. X is a halogeno group. When an iodine group is included in X, one iodine group is bonded to the p-position of the COO - group in the above formula (1). R １ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having 1 to 20 carbon atoms (α) having a divalent heteroatom-containing group between carbon-carbon atoms of the hydrocarbon group, or a group having 1 to 20 carbon atoms (β) in which part or all of the hydrogen atoms of the above hydrocarbon group or the above group (α) are substituted with a chloro group, a bromo group, an iodine group, a hydroxy group, a nitro group, an amino group, a carboxy group or a cyano group. However, when h is 2 or more, the plural R １ are each the above hydrocarbon group, the above group (α) or the above group (β), or two of the plural -OR １ Among them, two R １ in two -OR １ are combined with each other and are a divalent organic group constituting a part of a ring structure having 5 to 20 ring members together with the carbon atom to which -OR １ is bonded. R ２ is a monovalent hydrocarbon group having 1 to 5 carbon atoms, a cyano group, a nitro group or a hydroxy group. Z ＋ is an organic cation containing an aromatic ring substituted with an electron-withdrawing group.)

[0010] Since the radiation-sensitive composition contains the onium salt compound (1) as a quencher (acid diffusion control agent), it can exhibit excellent sensitivity, CDU and process window during pattern formation. Although not bound by any theory, the reason is presumed as follows.

[0011] Because the carboxylate anion is located between bulky iodine groups that are at an m-position relative to each other, the plane formed by one carbon atom and two oxygen atoms of the carboxylate anion does not align with the plane formed by the carbon atoms of the benzene ring. This weakens the electron-withdrawing effect of the benzene ring on the carboxylate anion, improving the basicity of the carboxylate anion.

[0012] Since the anionic portion of the onium salt compound (1) has at least two iodine groups with high EUV absorption efficiency, the secondary electron generation efficiency is increased, and sensitivity can be improved.

[0013] Because organic cations contain aromatic rings substituted with electron-withdrawing groups, the energy of the lowest unoccupied molecular orbital (LUMO) in the entire organic cation is reduced, increasing its reactivity to exposure and improving sensitivity.

[0014] It is presumed that these combined effects enable the resist to exhibit the aforementioned properties.

[0015] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the 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.

[0016] In this pattern formation method, since the above-mentioned radiation-sensitive composition, which has excellent sensitivity, CDU, and process window, is used during pattern formation, high-quality resist patterns can be efficiently formed.

[0017] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1). (In equation (1), g, h, and i are each independent integers between 0 and 3, where g + h + i is less than or equal to 3. X, R １ and R ２ If multiple X and R exist, １ and R ２Each of these is either identical or different from the others. X is a halogeno group. If X contains an iodine group, one of the iodine groups is the COO in formula (1) above. - It binds to the p-position of the group. １ This is a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (α) having 1 to 20 carbon atoms having a divalent heteroatom-containing group between the carbon atoms of the hydrocarbon group, or a group (β) having 1 to 20 carbon atoms in which some or all of the hydrogen atoms of the hydrocarbon group or the group (α) are replaced with a chloro group, bromo group, iodo group, hydroxyl group, nitro group, amino group, carboxyl group, or cyano group. However, if h is 2 or more, multiple R １ These are, respectively, the hydrocarbon group, the group (α), or the group (β), or a plurality of -OR １ Two of the -OR １ Two R's in １ They can be combined with each other - OR １ It is a divalent organic group that forms part of a ring structure with 5 to 20 members, which is formed together with the carbon atom to which it is bonded. ２ This is a monovalent hydrocarbon group, cyano group, nitro group, or hydroxyl group having 1 to 5 carbon atoms. ＋ This is an organic cation containing an aromatic ring substituted with an electron-withdrawing group.

[0018] Because the onium salt possesses the aforementioned high basicity, high secondary electron generation efficiency, and high reactivity, it is suitable as an acid diffusion control agent for radiation-sensitive compositions.

[0019] In this specification, "organic group" means a group containing at least one carbon atom (excluding groups that constitute a functional or characteristic group on their own, such as cyano groups and ketone groups). "Fused ring structure" means a structure in which adjacent rings share one edge (two adjacent atoms). "Bridged ring hydrocarbon group" means a polycyclic cyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the ring are bonded together by a linking group containing one or more carbon atoms.

[0020] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. A combination of preferred embodiments is also preferable.

[0021] <Radiation-sensitive composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") comprises an onium salt compound (1), a polymer containing a structural unit having an acid-dissociable group (hereinafter also referred to as "base polymer"), and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0022] (Onium salt compound (1)) Onium salt compound (1) consists of an organic acid anion (i.e., a carboxylic acid anion) and an organic cation represented by the above formula (1), and functions as an acid diffusion control agent.

[0023] In formula (1) above, examples of halogen groups represented by X include fluoro groups, chloro groups, bromo groups, and iodine groups. If one or more X groups contain iodine groups, one iodine group is the COO in formula (1) above. - It bonds to the p-position of the group. That is, when g is 1 and X is an iodine group, the iodine group is the COO of formula (1) above. - It bonds to the p-position of the group. When g is 2 or more and multiple X contain iodine groups, one iodine group is the COO in formula (1) above. - It bonds to the p-position of the group.

[0024] g is preferably an integer between 1 and 3, more preferably 1 or 2, and even more preferably 1.

[0025] X is preferably an iodine group, a fluoro group, or a bromo group, more preferably an iodine group or a fluoro group, and even more preferably an iodine group. If X contains an iodine group, it is preferable that the iodine groups are not adjacent to each other in order to suppress hydrophobicity. That is, even if there are multiple X groups, the COO of formula (1) above... - It is preferable that only X bonded at the p-position of the group is an iodine group.

[0026] In the above formula (1), R １ Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms, as represented by , 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.

[0027] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0028] 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.

[0029] 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.

[0030] In the above formula (1), R １ Examples of divalent heteroatom-containing groups in this context include -CO-, -O-, -NR'-, -S-, and -SO ２ Examples include groups such as -, -CS-, or combinations thereof. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Epoxy groups are also included as forms of hydrocarbon groups having a divalent heteroatom-containing group between carbon atoms.

[0031] R １ Preferably, the hydrocarbon group is a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a group having 1 to 10 carbon atoms with -CO-, -O-, or a combination thereof between the carbon atoms of the hydrocarbon group; more preferably, the hydrocarbon group is a monovalent hydrocarbon group having 1 to 4 carbon atoms, or a group having 1 to 4 carbon atoms with -CO-, -O-, or a combination thereof between the carbon atoms of the hydrocarbon group; and even more preferably, an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, or an acylalkyl group having 1 to 4 carbon atoms.

[0032] If h is 2 or greater, two R １ When these groups combine to form a ring structure with 5 to 20 members, the divalent organic group can preferably be a group obtained by removing one hydrogen atom from the hydrocarbon group, a group obtained by removing one hydrogen atom from group (α), or a group obtained by removing one hydrogen atom from group (β) (provided that a fluoro group is included as a substituent substituting the hydrogen atom of group (β)). １ The divalent organic group formed by combining these groups is preferably a hydrocarbon group from which one hydrogen atom has been removed, more preferably a divalent hydrocarbon group having 1 to 5 carbon atoms, even more preferably an alkanediyl group having 1 to 5 carbon atoms, and particularly preferably a methanediyl group or an ethanediyl group.

[0033] h is preferably an integer between 1 and 3, more preferably 1 or 2, and even more preferably 1.

[0034] R ２ As a monovalent hydrocarbon group having 1 to 5 carbon atoms, R １ Examples include monovalent hydrocarbon groups with 1 to 20 carbon atoms represented by , specifically those corresponding to groups with 1 to 5 carbon atoms.

[0035] R ２ Preferably, the group is a hydroxyl group or a cyano group, with the cyano group being more preferred.

[0036] i is preferably an integer between 0 and 2, more preferably 0 or 1, and even more preferably 0.

[0037] Specific examples of the carboxylic acid anion of the onium salt compound (1) include, but are not limited to, structures represented by the following formulas (a-1) to (a-22).

[0038]

[0039]

[0040] Z ＋The organic cation represented by is not particularly limited as long as it contains an aromatic ring substituted with an electron-withdrawing group, 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.

[0041] Z ＋ It is preferable that is a radiation-sensitive onium cation containing an aromatic ring substituted with an electron-withdrawing group. Examples of the above radiation-sensitive onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, etc. Among these, Z ＋ Preferably, this is a radiation-sensitive sulfonium cation containing an aromatic ring substituted with an electron-withdrawing group, or a radiation-sensitive iodonium cation containing an aromatic ring substituted with an electron-withdrawing group.

[0042] The aromatic ring described above is not particularly limited as long as it has 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.

[0043] Examples of the electron-withdrawing groups mentioned above include halogeno groups, halogenated hydrocarbon groups, nitro groups, cyano groups, carbonyl-containing groups, sulfonyl-containing groups, amide-containing groups, and halogenated sulfanyl groups.

[0044] Examples of halogen groups include fluoro groups, chloro groups, bromo groups, and iodine groups.

[0045] Examples of halogenated hydrocarbon groups include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are replaced with halogen atoms. The above monovalent hydrocarbon group having 1 to 20 carbon atoms is R in formula (1) above. １ A monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by , can be suitably used. A fluorine atom is preferred as the halogen atom. As the halogenated hydrocarbon group, a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms is preferred, a monovalent fluorinated linear hydrocarbon group having 1 to 10 carbon atoms is more preferred, a perfluoroalkyl group having 1 to 10 carbon atoms is even more preferred, and a trifluoromethyl group is particularly preferred.

[0046] A carbonyl-containing group is a monovalent group that contains a carbonyl group (-CO-) in its structure. Ｙ１ It is preferable to represent it as R. Ｙ１ Examples include hydrogen atoms, hydroxyl groups, alkyl groups, and alkoxy groups.

[0047] Sulfonyl-containing groups are groups containing sulfonyl (-SO) in their structure. ２ It is a monovalent group containing -). The sulfonyl-containing group is -SO ２ -R Ｙ２ It is preferable to represent it as R. Ｙ2 Examples include alkyl groups and alkoxy groups.

[0048] The amide-containing group is an amide group (-CONR) in the structure. Ｙ３ It is a monovalent group containing -). The carbonyl-containing group is -CON(R Ｙ３ ) R Ｙ４ It is preferable to represent it as R. Ｙ３ and R Ｙ４ Examples of these elements, independently, include hydrogen atoms, alkyl groups, and the like.

[0049] Examples of sulfanyl halides include groups in which one to (valence-1) halogen atoms are bonded to a divalent, tetravalent, or hexavalent sulfur atom. Pentafluorosulfanil groups are preferred as sulfanyl halides.

[0050] The above organic cation is preferably a sulfonium cation represented by the following formula (z1) or an iodonium cation represented by the following formula (z2). (In formulas (z1) and (z2), Ar is independently a (p+q+1) valence group obtained by removing (p+q) hydrogen atoms from a phenyl group or a naphthyl group. ３ and R ４ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms, or R ３ and R ４ These can be combined to form a ring structure with 4 to 12 carbon atoms, along with the sulfur atoms to which they are bonded. ５ Each of these is independently a hydroxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. ５ If multiple R ５ They are either identical or different from each other. ６ is a monovalent organic group having 1 to 20 carbon atoms. Y is independently selected from the group consisting of halogen groups, halogenated hydrocarbon groups, nitro groups, cyano groups, carbonyl-containing groups, sulfonyl-containing groups, amide-containing groups, and halogenated sulfanyl groups. If multiple Y groups exist, they are either identical or distinct from one another. p is independently an integer from 1 to 5. q is independently an integer from 0 to 3.

[0051] Ar is preferably a group with a (p+q+1) valency, obtained by removing (p+q) hydrogen atoms from a phenyl group.

[0052] R ３ ~R ６ Examples of monovalent organic groups having 1 to 20 carbon atoms represented by include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups (γ) having 1 to 20 carbon atoms having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the terminal end of the hydrocarbon group, groups having 1 to 20 carbon atoms in which some or all of the hydrogen atoms of the hydrocarbon group or the group (γ) are replaced with a monovalent heteroatom-containing group, or combinations thereof.

[0053] R ３ ~R ６In this, the monovalent hydrocarbon group having 1 to 20 carbon atoms is R in formula (1) above. １ A monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably used.

[0054] R ３ ~R ６ The divalent heteroatom-containing group in is R in formula (1) above. １ A divalent heteroatom-containing group can be suitably adopted in this material.

[0055] R ３ ~R ６ Examples of monovalent heteroatom-containing groups include hydroxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms. Examples of halogen atoms include the atoms mentioned above.

[0056] R ３ and R ４ Examples of C4-C12 ring structures formed by combining these elements with the sulfur atoms to which they bond include C4-C12 sulfur atom-containing aliphatic heterocyclic structures and C4-C12 sulfur atom-containing aromatic heterocyclic structures. Examples of the above sulfur atom-containing aliphatic heterocyclic structures include thiethane, tetrahydrothiophene, oxathiolane, thiane, dithiane, thiomorpholine, and thioxane. Examples of the above sulfur atom-containing aromatic heterocyclic structures include thiophene, thiazole, benzothiophene, dibenzothiophene, and phenoxathiin. Among these, R ４ and R ５ Tetrahydrothiophene, thioxane, thian, dibenzothiophene, and phenoxathiin are more preferred as the ring structure composed of the above.

[0057] R ３ , R ４ and R ６ Each of these preferably independently contains an aromatic ring. ３ , R ４ and R ６ The aromatic ring in this is Z in the above formula (1). ＋ The aromatic ring shown in can be suitably adopted. ３ , R ４ and R ６The aromatic ring in has a group corresponding to R or Y as a substituent. R, R, and R are each independently preferably a substituted or unsubstituted phenyl group. Examples of the substituent include a group corresponding to R or Y; an oxo group (=O), etc. ５ or may have a group corresponding to Y. ３ , R ４ and R ６ are each independently preferably a substituted or unsubstituted phenyl group. Examples of the substituent include a group corresponding to R or Y; an oxo group (=O), etc. ５ or may have a group corresponding to Y.

[0058] R ５ is preferably a monovalent organic group having 1 to 20 carbon atoms with an ether bond on the bonding side, more preferably an alkoxy group, and even more preferably a methoxy group or an ethoxy group.

[0059] Each of the electron-withdrawing groups represented by Y can preferably adopt a corresponding group among the electron-withdrawing groups shown in Z in the above formula (1). ＋ in the above formula (1).

[0060] Y is preferably each independently a halogeno group or a halogenated hydrocarbon group. The halogen atom constituting Y is preferably at least one selected from the group consisting of a fluorine atom and an iodine atom. Preferred examples of Y include a fluoro group, an iodo group, and a trifluoromethyl group.

[0061] p is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 1 or 2. The same applies when R, R, and R have a group corresponding to Y. ３ , R ４ and R ６ have a group corresponding to Y.

[0062] q is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 0 or 1. The same applies when R, R, and R have a group corresponding to R. ３ , R ４ and R ６ have a group corresponding to R. ５ in the above formula (1).

[0063] Specific examples of the organic cation of the onium salt compound (1) include, but are not limited to, structures represented by the following formulas (z1-1) to (z1-18), (z2-1) to (z2-9), etc.

[0064]

[0065]

[0066]

[0067] The onium salt compound (1) can be obtained by arbitrarily combining the above carboxylic acid anion and the above organic cation (not limited to the exemplified structure). Specific examples, though not limited to them, include structures represented by the following formulas (1-1) to (1-26).

[0068]

[0069]

[0070]

[0071]

[0072] The lower limit of the onium salt compound (1) content (total if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total amount of the monomer that gives the above structural unit (III) in the base polymer described later and the radiation-sensitive acid generator described later (if both are included). The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. As a result, the composition can exhibit excellent sensitivity, CDU, and process window during pattern formation.

[0073] As long as the effects of the present invention are not impaired, the composition may contain, together with the onium salt compound (1), a known acid diffusion control agent other than the onium salt compound (1).

[0074] (Synthesis Method for Onium Salt Compound (1)) A known method can be used to synthesize the onium salt compound (1), and it can typically be synthesized according to the following scheme. The case in formula (1) above where g, h, and i are all 1 will be explained.

[0075] (In the scheme, X, R１ , R ２ and Z ＋ This is equivalent to equation (1) above. Xa - (This is a halide ion.)

[0076] Onium salt compound (1) can be produced by performing a salt exchange between an iodobenzoic acid derivative having the desired carboxylic acid anion structure and a halide salt having the desired organic cation. Other structures can also be produced by appropriately changing the starting materials and reaction substrates.

[0077] (Polymer) A polymer (i.e., a base polymer) is an aggregate of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group, which dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (I).

[0078] In addition to structural unit (I), the base polymer may also contain structural units having phenolic hydroxyl groups (hereinafter also referred to as "structural unit (II)"), structural units containing onium salt structures that function as radiation-sensitive acid-generating structures (hereinafter also referred to as "structural unit (III)"), structural units containing onium salt structures that function as acid diffusion-controlling structures (hereinafter also referred to as "structural unit (IV)"), structural units containing lactone structures, etc. (hereinafter also referred to as "structural unit (V)"), structural units containing polar groups (hereinafter also referred to as "structural unit (VI)"), and the like. Each structural unit will be described below.

[0079] (Structural Unit (I)) Structural Unit (I) 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, which dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (I).

[0080] Structural unit (I) 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 secondary alkyl ester moiety derived from a secondary alcohol having an aromatic group and an aliphatic group, structural units having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, structural units having an acetal bond, etc. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0081]

[0082] 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. 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.

[0083] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (I-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0084] L １１ａ 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. １１ａMethylene groups and ethanediyl groups are preferred as the base group.

[0085] L １１ａ 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. １１ａ A benzenediyl group is preferred as the group.

[0086] L １１ａ The substituents that the arenediyl group represented by can have include, for example, halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino 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; oxo groups (=O), etc.

[0087] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (1), R １ Monovalent hydrocarbon groups having 1 to 20 carbon atoms can be suitably used in this material.

[0088] 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.

[0089] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed when these are combined with the carbon atoms to which they are bonded, is R in formula (1) above. １ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown above, can be suitably adopted.

[0090] 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.

[0091] The above R １８ ~R２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0092] Examples of structural units (I-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (I-1-1) to (I-1-15)").

[0093]

[0094]

[0095] 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.

[0096] i and j are preferably 1. １８ Preferred 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 the structural unit (I).

[0097] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0098]

[0099] In the above equations (1f) to (2f), R αｆEach 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-like alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0100] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0101] The lower limit of the content of structural unit (I) in the total structural units constituting the polymer (the total content if multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%. 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 (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0102] (Structural Unit (II)) Structural unit (II) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to structural unit (I)). By including structural unit (II) in the polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the above-mentioned radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, etc. are used as the radiation irradiated in the exposure step in the resist pattern formation method, structural unit (II) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as electron beams and EUV. Structural unit (II) is preferably represented by the following formula (2).

[0103] (In the above formula (2), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ , -O- or -CONH- ＊* indicates a bond on the aromatic ring side. 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.)

[0104] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (II), it is preferable that it be a hydrogen atom or a methyl group.

[0105] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0106] R １０２ In this mixture, iodine or fluorine atoms are preferred as halogen atoms, with iodine atoms being more preferred.

[0107] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0108] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0109] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0110] The above structural unit (II) is preferably a structural unit represented by the following formulas (2-1) to (2-25) (hereinafter also referred to as "structural unit (II-1) to structural unit (II-25)").

[0111]

[0112]

[0113] In the above equations (2-1) to (2-25), R β This is the same as equation (2) above.

[0114] When the base polymer has structural unit (II), 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 25 mol% relative to the total structural units constituting the polymer. The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural unit (II) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0115] (Structural Unit (III)) The base polymer may also contain structural unit (III) which has a first organic acid anion and a first onium cation and includes a first acid generation structure that generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid generation structure) functions as a radiation-sensitive acid generation structure.

[0116] Because the base polymer contains the above-mentioned radiation-sensitive acid-generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer in the case of alkaline aqueous solution development, while it becomes poorly soluble in the developer in the case of organic solvent development.

[0117] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (III) of the base polymer is not particularly limited, and the base polymer may have the first organic acid anion as a side chain portion, or it may have the first onium cation as a side chain portion. Having it as a side chain portion means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the first organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the first onium cation is ionically bonded to the first organic acid anion as its counterion. On the other hand, when the first onium cation is bonded to the main chain as a side chain structure of the base polymer, the first organic acid anion is ionically bonded to the first onium cation as its counterion. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer has the first organic acid anion as a side chain portion.

[0118] The above-mentioned first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions and sulfonimide anions as the acid anion portion. As the acid generated by exposure, sulfonic acid and sulfonimide can be given, corresponding to the above-mentioned acid anion portion.

[0119] The above-mentioned first organic acid anion preferably includes, as a structure other than the acid anion portion, -O-, -CO-, a cyclic structure, or a combination thereof. This combination also includes structures (heterocyclic structures) in which -O- or -CO- are incorporated as ring-forming parts within the cyclic structure.

[0120] The cyclic structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be alicyclic, aromatic, heterocyclic, or a combination thereof. In the case of a combination, the cyclic structures may be linked by chain structures, and two or more cyclic structures may form fused ring structures, bridged ring structures, or spiro-ring structures. Divalent heteroatom-containing groups may be present between carbon atoms forming the skeleton of the cyclic or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0121] As a divalent heteroatom-containing group, R in formula (1) above is １ The divalent heteroatom-containing group shown can be suitably adopted.

[0122] A substituent that replaces some or all of the hydrogen atoms on the carbon atoms of the above cyclic or chain structure is L of formula (3) above. １１ａ The substituents shown in can be suitably adopted.

[0123] In the above-described first acid generation structure, the first organic acid anion preferably has a sulfonic acid anion as the acid anion portion, and an electron-withdrawing group is preferably bonded to the carbon atom at the α or β position relative to the sulfur atom in the sulfonic acid anion. This allows the first acid generation structure to efficiently perform the above function. The electron-withdrawing group is Z in formula (1) above. ＋ Electron-withdrawing groups can be suitably employed in this material.

[0124] The first organic acid anion described above preferably has an iodine group. The first organic acid anion preferably contains the iodine group-containing aromatic ring structure described above as the form in which the iodine group is contained.

[0125] Examples of the first onium cation mentioned above include radiodegradable onium cations. Examples of radiodegradable 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.

[0126] The above-mentioned first onium cation preferably has an iodine group. The above-mentioned first onium cation preferably contains an iodine group-containing aromatic ring structure as the form of iodine group content. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced with iodine groups. The aromatic ring of the iodine group-containing aromatic ring structure is Z of formula (1) above. ＋ The aromatic ring shown can be suitably adopted.

[0127] The first onium cation in structural unit (III) may be a fluorogroup-containing onium cation having a fluorogroup. The fluorogroup-containing onium cation preferably has a fluorogroup-containing aromatic ring structure. The fluorogroup-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by fluorogroups. As the aromatic ring in the fluorogroup-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be suitably adopted. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0128] The structural unit (III) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0129] The structural unit (III) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (III-1)").

[0130]

[0131] In the formula, R Ｖ This is a hydrogen atom or a methyl group. V １ This is a single bond or an ester group. V ２ This is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, or an amide bond, and a portion of the methylene groups constituting the alkylene group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ This is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in the compound may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. Rf １ ~Rf ２Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer from 1 to 4. Z １ ＋ This is a sulfonium cation or an iodonium cation.

[0132] V ２ and V ３ The C1-C20 monovalent hydrocarbon group in this is preferably a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C6-C20 aryl group. Some or all of the hydrogen atoms in these groups may be substituted with heteroatom-containing groups such as hydroxyl groups, carboxyl groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, alkoxy groups, or alkoxycarbonyl groups. Some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonic acid ester groups.

[0133] Preferably, the structural unit (III-1) is the structural unit represented by the following formula (a1-1).

[0134]

[0135] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ ,kk and Z １ ＋ This is equivalent to the above formula (a1). R ４８ m is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxyl group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer from 0 to 4. n is an integer from 0 to 3.

[0136] Examples of the first organic acid anion of the monomer that gives structural unit (III) (including structural unit (III-1)) are, but are not limited to, those listed below. In the following, the iodine group of the iodine group-containing aromatic ring structure is a hydrogen atom or L of formula (3) above. １１ａ Substitutions may be made with the substituents shown in [reference].

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] In the above formula, R Ｖ This is equivalent to equation (a1) above.

[0144] Z １ ＋ As the sulfonium cation and iodonium cation represented by the above formula (z1) and iodonium cation represented by the above formula (z2), the sulfonium cation and iodonium cation represented by the above formula (z2) can be suitably used.

[0145] In this configuration, a first onium cation is bonded to the main chain as the side chain structure of the base polymer, and a first organic acid anion is ionically bonded to the first onium cation as its counterion. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in formula (a1) is formed. ２ From SO ３ - It is preferable that the structure up to this point is ionically bonded to the first onium cation as a counterion. The divalent linking group is V of formula (a1) above. ２ The group represented by , the above-mentioned divalent heteroatom-containing group, or a combination thereof can be suitably adopted.

[0146] When the base polymer has structural unit (III), the lower limit of the content of structural unit (III) (total content if multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 12 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 40 mol%, more preferably 30 mol% or less, and even more preferably 20 mol% or less. By setting the content of structural unit (III) within the above range, it is possible to fully exhibit its function as an acid-generating structure and exhibit the above-mentioned resist properties.

[0147] The monomer that gives structural unit (III-1) can be synthesized, for example, by the same method as the sulfonium salt having a polymerizable anion described in Japanese Patent Publication No. 5201363.

[0148] (Structural Unit (IV)) The base polymer may include structural unit (IV) which has a second organic acid anion and a second onium cation, and which generates an acid by exposure that does not dissociate 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 (I), and has the function of suppressing the diffusion of the acid generated from the above-mentioned radiation-sensitive acid-generating structure or radiation-sensitive acid generator (if both are 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 the above-mentioned radiation-sensitive acid-generating structure. 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.

[0149] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (IV) of the base polymer is not particularly limited. The base polymer may have the second organic acid anion as a side chain portion, or it may have the second onium cation as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the second organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the second onium cation is ionically bonded to the second organic acid anion as its counterion. On the other hand, when the second onium cation is bonded to the main chain as a side chain structure of the base polymer, the second organic acid anion is ionically bonded to the second onium cation as its counterion. From the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion.

[0150] 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 has 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. The electron-withdrawing group is Z in formula (1) above. ＋ Examples include electron-withdrawing groups as shown above. The acid generated by exposure is a carboxylic acid or sulfonic acid, corresponding to the acid anion portion mentioned above.

[0151] The above-mentioned second organic acid anion preferably includes -O-, -CO-, a cyclic structure, or a combination thereof as a structure other than the acid anion portion. Such a structure can preferably be the one represented by the sulfonic acid anion of structural unit (III).

[0152] The above-mentioned second organic acid anion preferably has an iodine group or a hydroxyl group. The above-mentioned second organic acid anion preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0153] As the second onium cation mentioned above, the organic cation shown in onium salt compound (1) can be suitably used.

[0154] The above-mentioned second onium cation preferably has an iodine group. The above-mentioned second onium cation preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0155] The secondary onium cation in structural unit (IV) preferably has the above-mentioned fluorogroup-containing aromatic ring structure. This can improve sensitivity by increasing the radiation absorption efficiency.

[0156] The structural unit (IV) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0157] The structural unit (IV) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (IV-1)").

[0158]

[0159] In formula (p1), R A This is either a hydrogen atom or a methyl group.

[0160] In formula (p1), X 1 These are single bonds, ester bonds, ether bonds, phenylene groups, naphthylene groups, or combinations thereof.

[0161] In formula (p1), X ２ This 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. ２The 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.

[0162] In formula (p1), X 3 These are single bonds, ester bonds, or ether bonds.

[0163] In formula (p1), X 1 ~X ２ Some or all of the hydrogen atoms in may be substituted with substituents. The substituents shown in the above-mentioned cyclic structure, etc., 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.

[0164] In formula (p1), Z ２ ＋ This is Z in equation (1) above. ＋ It is synonymous with [the above].

[0165] An iodonium cation can also be used as the second onium cation in the above formula (p1). The diaryliodonium cation shown as the onium cation of the onium salt compound (1) can be suitably adopted as the iodonium cation.

[0166] Examples of the second organic acid anion of the monomer that gives structural unit (IV) (including structural unit (IV-1)) are, but are not limited to, those listed below. The iodine group or hydroxyl group in the following formula may be substituted with a hydrogen atom or a substituent as shown in the above cyclic structure, etc. In the following formula, R 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.

[0167]

[0168]

[0169]

[0170]

[0171] As the second onium cation of structural unit (IV), the sulfonium cation of formula (1) above can be suitably adopted.

[0172] 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 the second onium cation as a counterion. As the divalent linking group, the above-mentioned divalent linking group shown when the first onium cation of structural unit (III) is bonded to the main chain can be suitably adopted.

[0173] When the base polymer contains structural units (IV), the lower limit of the content of structural units (IV) (or the total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content of structural units (IV) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0174] (Structural Unit (V)) Structural unit (V) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. By further comprising structural unit (V), the solubility of the base polymer in the developer can be adjusted, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0175] Among these, structural units (V) that include a lactone structure are preferred, and structural units that include a γ-butyrolactone structure, norbornane lactone structure, or adamantane lactone structure are more preferred.

[0176] When the base polymer has structural units (V), the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 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 units (V) 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.

[0177] (Structural Unit (VI)) Structural unit (VI) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (V)). The solubility of the base polymer in the developer can be adjusted by further containing structural unit (VI). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0178] Examples of structural units (VI) include structural units represented by the following formula.

[0179]

[0180]

[0181] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0182] When the base polymer has structural units (VI) having the polar group described above, the lower limit of the content of structural units (VI) (total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 20 mol%, more preferably 12 mol%, and even more preferably 8 mol%. By setting the content of structural units (VI) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0183] (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.

[0184] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 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.

[0185] 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 ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and 1,4-dioxanes; polyhydric alcohol partial ethers such as propylene glycol monomethyl ether (1-methoxy-2-propanol); 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.

[0186] 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.

[0187] 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 2,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 12,000, and even more preferably 8,000. 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.

[0188] 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.

[0189] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0190] 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.

[0191] (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.

[0192] High-fluorine-content polymers may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (i)").

[0193]

[0194] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ It consists of a single bond, an alkanediyl group with 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, and -SO ２ ONH-, -CONH-, -OCONH-, or a combination thereof. １４ This is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0195] The above R １３ From the viewpoint of copolymerization of the monomer that gives structural unit (i), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0196] The above G Ｌ From the viewpoint of copolymerization of monomers that provide structural unit (i), single bonds and -COO- are preferred, and -COO- is more preferred.

[0197] The above R １４ Examples of monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0198] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0199] The above R １４ Preferably, 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.

[0200] When a high-fluorine-content polymer has structural unit (i), the lower limit of the content of structural unit (i) 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 (i) 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.

[0201] High-fluorine polymers may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (ii)) represented by the following formula (f-2), either together with or in place of structural unit (i). The presence of structural unit (f-2) in high-fluorine polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0202]

[0203] Structural units (ii) 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 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.

[0204] If structural unit (ii) has (x) an alkali-soluble group, R ＦA 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 (x) in structural unit (ii) increases its affinity for alkaline developer and suppresses development defects. A is an example of a structural unit (ii) having an alkali-soluble group. 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.

[0205] If structural unit (ii) 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. １ R 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. １If 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 structural unit (ii) 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 unit (ii) 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.

[0206] R Ｃ From the viewpoint of copolymerizability of monomers that give structural unit (ii), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0207] When a high-fluorine-content polymer has structural unit (ii), the content of structural unit (ii) (total content if multiple types are included) 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 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural unit (ii) 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 to suppress the occurrence of development defects.

[0208] [Other structural units] High-fluorine polymers may, if necessary, include structural units other than those listed above, such as structural unit (I) and structural unit (VI) in the base polymer.

[0209] When a high-fluorine-content polymer contains structural unit (I), the content of structural unit (I) 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 70 mol%, and more preferably 60 mol%.

[0210] When a high-fluorine-content polymer contains structural units (VI), the content of structural units (VI) 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%.

[0211] 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 14,000, and even more preferably 9,000.

[0212] 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.

[0213] If the radiation-sensitive composition contains a high-fluorine-content polymer, the lower limit of the high-fluorine-content polymer content is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 15 parts by mass, more preferably 8 parts by mass, and even more preferably 5 parts by mass.

[0214] 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.

[0215] (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.

[0216] (Radiation-sensitive acid generator) The radiation-sensitive composition may contain a radiation-sensitive acid generator. If the base polymer does not contain structural unit (III), it is preferable that the composition contains a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates acid upon exposure. The acid generated upon exposure has the function of dissociating the acid-dissociable groups of the base polymer and generating carboxyl groups, etc. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low molecular weight compound (liberated from the polymer), and is different from the radiation-sensitive acid generation structure in which the first organic acid anion or the first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer, as in structural unit (III) of the base polymer.

[0217] At least one selected from the group consisting of the above-mentioned third organic acid anion and third onium cation preferably has an iodine group, and more preferably has the above-mentioned iodine group-containing aromatic ring structure.

[0218] The structure of the third organic acid anion in the radiation-sensitive acid generator is V in formula (a1) of the base polymer. ２ From SO ３ - The following structures can be suitably adopted.

[0219] Examples of radioactive acid-sensitive third organic acid anions include, but are not limited to, those listed below. Furthermore, structures in which the iodine group in the following formula is replaced with a hydrogen atom or other substituents can also be suitably adopted instead of the iodine group-containing aromatic ring structure in the third organic acid anion.

[0220]

[0221]

[0222]

[0223] The structure of the third onium cation of the radiation-sensitive acid generator can preferably be the sulfonium cation or iodonium cation structure shown in the above onium salt compound (1), except that it does not need to contain an electron-withdrawing group.

[0224] The above-mentioned radiation-sensitive acid generator can also be synthesized by known methods, particularly by salt exchange reactions.

[0225] These radiation-sensitive acid generators may be used individually or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total in the case of multiple types) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 80 parts by mass, more preferably 60 parts by mass, and even more preferably 40 parts by mass. This allows for excellent sensitivity during resist pattern formation.

[0226] (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 optionally contained additives.

[0227] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0228] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, 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 propylene glycol monomethyl ether (1-methoxy-2-propanol), in which some of the hydroxyl groups of the above-mentioned polyhydric alcohol solvents are etherified. 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.

[0229] 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 obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0230] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, methyl isobutyl ketone, and 4-hydroxy-4-methyl-2-pentanone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0231] 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.

[0232] 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.

[0233] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbencene, and n-amylnaphthalene.

[0234] Among these, ester solvents, ether solvents, alcohol solvents, and ketone solvents are preferred, polyhydric alcohol partial ether acetate solvents, polyhydric alcohol partial ether solvents, alcoholic acid ester solvents, and linear ketone solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, methyl 2-hydroxyisobutyrate, and 4-hydroxy-4-methyl-2-pentanone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0235] (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.

[0236] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing an onium salt compound (1), a polymer, and other additives as needed, and a solvent in a predetermined proportion. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 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.

[0237] <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").

[0238] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, CDU, and process window is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0239] [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, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The SB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The SB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0240] The lower limit of the thickness of the formed resist film is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 300 nm, more preferably 200 nm, and even more preferably 150 nm.

[0241] 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.

[0242] [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.

[0243] 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.

[0244] 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., by the acid generated from the radiation-sensitive acid generator or radiation-sensitive acid-generating structure in the exposed portion of the resist film. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 180°C, with 80°C to 130°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0245] [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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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 puddling the developer solution onto the substrate surface using surface tension and leaving it 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).

[0250] <Onium Salt Compound> The onium salt compound is a compound represented by the following formula (1). The onium salt compound (1) and its synthesis method used in the above-mentioned radiation-sensitive composition can be suitably employed as such an onium salt compound and its manufacturing method. (In equation (1), g, h, and i are each independent integers between 0 and 3, where g + h + i is less than or equal to 3. X, R １ and R ２ If multiple X and R exist, １ and R ２ Each of these is either identical or different from the others. X is a halogeno group. If X contains an iodine group, one of the iodine groups is the COO in formula (1) above. - It binds to the p-position of the group. １ This is a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (α) having 1 to 20 carbon atoms having a divalent heteroatom-containing group between the carbon atoms of the hydrocarbon group, or a group (β) having 1 to 20 carbon atoms in which some or all of the hydrogen atoms of the hydrocarbon group or the group (α) are replaced with a chloro group, bromo group, iodo group, hydroxyl group, nitro group, amino group, carboxyl group, or cyano group. However, if h is 2 or more, multiple R １ These are, respectively, the hydrocarbon group, the group (α), or the group (β), or a plurality of -OR １ Two of the -OR １ Two R's in １They can be combined with each other - OR １ It is a divalent organic group that forms part of a ring structure with 5 to 20 members, which is formed together with the carbon atom to which it is bonded. ２ This is a monovalent hydrocarbon group, cyano group, nitro group, or hydroxyl group having 1 to 5 carbon atoms. ＋ This is an organic cation containing an aromatic ring substituted with an electron-withdrawing group.

[0251] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. Various physical properties in the examples and comparative examples were obtained by the measurement methods shown below.

[0252] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] These were measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard, using Tosoh GPC columns (G2000HXL: 2, G3000HXL: 1, G4000HXL: 1), under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0% by mass, sample injection volume: 100 μL, column temperature: 40°C, and detector: differential refractometer. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0253] [ １ H-NMR analysis and １３ C-NMR analysis] １ H-NMR analysis and １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0254] <[Q] Acid diffusion control agent> Acid diffusion control agents (Q-1) to (Q-23) represented by the following formulas (Q-1) to (Q-23) were synthesized according to the following procedure.

[0255]

[0256]

[0257]

[0258] [Example Q-1: Synthesis of Acid Diffusion Control Agent (Q-1)] The acid diffusion control agent (Q-1) was synthesized according to the following synthesis scheme. In the scheme, ｔ "Bu" represents the tert-butyl group.

[0259]

[0260] 35.0 mmol of the compound represented by (Z-1), 52.5 mmol of iodomethane, 69.9 mmol of potassium carbonate, and 200 mL of acetone were added to a reaction vessel and stirred at room temperature for 5 hours. Then, methylene chloride was added and the mixture was washed with water and saturated brine. The resulting organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound represented by formula (Z-2) was purified by silica gel column chromatography.

[0261] Compound (Z-2) (20.5 mmol), trifluoroacetic acid (163 mmol), and methylene chloride (120 mL) were added to a reaction vessel and stirred at room temperature for 5 hours. Then, 100 mL of water was added and the organic layer was washed three times. After drying the organic layer over sodium sulfate, the solvent was removed and the mixture was purified by silica gel column chromatography to obtain the compound represented by the above formula (Z-3).

[0262] Compound (Z-3) (10.0 mmol), sodium bicarbonate (15.0 mmol), phenylbis(4-(trifluoromethyl)phenyl)sulfonium chloride (10.0 mmol), water (100 mL), and dichloromethane (100 mL) were added to a reaction vessel and stirred at room temperature. The organic layer was washed twice with water, and the solvent was removed by distillation to obtain the target compound represented by the above formula (Q-1).

[0263] [Examples Q-2 to Q-11] Acid diffusion control agents (Q-2) to (Q-11) were obtained in the same manner as in Example Q-1, except that the substrate was appropriately selected.

[0264] [Example Q-12: Synthesis of Compound (Q-12)] The acid diffusion control agent (Q-12) was synthesized according to the following synthesis scheme.

[0265]

[0266] Compound (Z-4) (10.0 mmol), sodium bicarbonate (15.0 mmol), phenylbis(4-(trifluoromethyl)phenyl)sulfonium chloride (10.0 mmol), water (100 mL), and dichloromethane (100 mL) were added to a reaction vessel and stirred at room temperature. The organic layer was washed twice with water, and the solvent was removed by distillation to obtain the target compound represented by the above formula (Q-12).

[0267] [Examples Q-13 to Q-19 and Comparative Examples Q-20 to Q-23] Acid diffusion control agents (Q-13) to (Q-23) were obtained in the same manner as in Example Q-12, except that the substrate was appropriately selected.

[0268] <[P] Synthesis of Polymers> [Synthesis Example P: Synthesis of Polymers (P-1) to (P-15)] Each monomer was combined and copolymerized under 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) solvent. The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, filtered, and dissolved in 1-methoxy-2-propanol (300 parts by mass). The polymer was added dropwise to 500 parts by mass of water to coagulate, and the obtained solid was filtered off. The polymers (P-1) to (P-15) were dried at 50°C for 12 hours to obtain white powder polymers. The composition of the obtained polymers is １ Mw and dispersion (Mw / Mn) were confirmed by 1H-NMR under the GPC conditions described above. The types and amounts of each monomer are shown in Table 1. In Table 1, "-" indicates that the corresponding component was not used. The same applies to subsequent tables.

[0269]

[0270]

[0271] <[A] Radiation-sensitive acid generator> As a radiation-sensitive acid generator, compounds represented by the following formulas (A-1) to (A-5) were used.

[0272] <[S] Solvent> S-1: Propylene glycol monomethyl ether acetateS-2: Propylene glycol monomethyl ether S-3: Methyl 2-hydroxyisobutyrate S-4: 4-Hydroxy-4-methyl-2-pentanone

[0273] <Preparation of Radiation-Sensitive Composition> [Examples 1 to 57 and Comparative Examples 1 to 4](P-1) to (P-15) as polymers, (A-1) to (A-5) as radiation-sensitive acid generators, (Q-1) to (Q-23) as acid diffusion inhibitors, and (S-1) to (S-4) as solvents were combined and mixed. By filtering this through a membrane filter with a pore size of 0.2 μm, radiation-sensitive compositions (R-1) to (R-57) and (CR-1) to (CR-4) were prepared. The types and amounts of each component are shown in Tables 2-1 to 2-2 below. The content of the acid diffusion control agent is shown as a molar ratio to the amount of the monomer that gives the structural unit (III) in the base polymer or the amount of the radiation-sensitive acid generator.

[0274]

[0275]

[0276] <Formation of Resist Pattern> On the surface of a 12-inch silicon wafer on which a lower layer film (AL412 (manufactured by Brewer Science)) with a film thickness of 20 nm was formed, each of the above-prepared radiation-sensitive compositions was applied using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After performing SB (soft bake) at 100°C for 60 seconds, it was cooled at 23°C for 30 seconds to form a resist film with a film thickness of 30 nm. This resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination condition: Conventional s = 0.89). The above resist film was subjected to PEB (post-exposure bake) at 100°C for 60 seconds. Then, development was carried out at 23°C for 30 seconds using a 2.38 wt% aqueous TMAH solution to form a positive 36-nm contact hole pattern.

[0277] <Evaluation> For each of the above-formed resist patterns, the sensitivity, CDU, and process window of each radiation-sensitive composition were evaluated by measuring according to the following method. A scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation) was used for measuring the length of the resist pattern. The evaluation results are shown in Table 3-1 and Table 3-2 below.

[0278] [Sensitivity] In the formation of the above EUV resist pattern, the exposure dose for forming a 36 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ ). When the sensitivity was less than 40 mJ / cm ２ , it was determined as "A", when it was 40 mJ / cm ２ or more and less than 45 mJ / cm ２ , it was determined as "B", when it was 45 mJ / cm ２ or more and less than 47 mJ / cm ２ , it was determined as "C", and when it was 47 mJ / cm ２ or more, it was determined as "D".

[0279] [CDU] In the formation of the above resist pattern, a 36 nm contact hole pattern was formed. The formed resist pattern was observed from the top of the pattern using the above scanning electron microscope. The variation in the hole diameter was measured at a total of 600 points, and the 3-sigma value was obtained from the distribution of the measured values, and this 3-sigma value was defined as the CDU (nm). A smaller CDU value indicates a smaller variation in the hole diameter in the long period and better performance. When the CDU was less than 2.8 nm, it was determined as "A" (extremely good), when it was 2.8 nm or more and 3.2 nm or less, it was determined as "B" (good), and when it exceeded 3.2 nm, it was determined as "C" (bad).

[0280] [Process Window (CD Margin)] Patterns were formed from low to high exposure levels using a mask that forms a 36 nm contact hole pattern. Generally, pattern disappearance is observed at low exposure levels, and defects such as pattern continuity are observed at high exposure levels. The difference between the upper and lower limits of the resist dimensions where these defects are not observed was defined as the CD margin (nm). A larger CD margin indicates better results. CD margins were judged as "A" (excellent) if 2.0 nm or more, "B" (good) if 1.6 nm or more and less than 2.0 nm, and "C" (poor) if less than 1.6 nm.

[0281]

[0282]

[0283] As is clear from the results in Tables 3-1 and 3-2, the radiation-sensitive compositions of the examples showed good sensitivity, CDU, and process window when used in EUV exposure, whereas the comparative examples exhibited inferior characteristics compared to the examples.

[0284] The radiation-sensitive composition, pattern-forming method, and onium salt compound of the present invention can improve sensitivity, CDU, and process margin compared to conventional methods. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

An onium salt compound represented by the following formula (1), A polymer containing a structural unit having an acid-dissociable group, Solvent and A radiation-sensitive composition containing the following: (In formula (1), g, h, and i are each independent integers between 0 and 3, where g + h + i is less than or equal to 3. X, R １ and R ２ If multiple X and R exist, １ and R ２ They are either identical or different from one another. X is a halogeno group. If X contains an iodine group, one iodine group is the COO in formula (1) above. - It bonds to the p-position of the group. R １ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (α) having 1 to 20 carbon atoms with a divalent heteroatom-containing group between carbon-carbon atoms of the hydrocarbon group, or a group having 1 to 20 carbon atoms (β) in which some or all of the hydrogen atoms of the hydrocarbon group or the group (α) are substituted with a chloro group, a bromo group, an iodo group, a hydroxy group, a nitro group, an amino group, a carboxy group or a cyano group. However, when h is 2 or more, a plurality of R １ are each the hydrocarbon group, the group (α) or the group (β), or two of the plurality of -OR １ Among them, two -OR １ In two R １ are combined with each other and are a divalent organic group constituting a part of a ring structure having 5 to 20 ring members formed together with the carbon atom to which -OR １ is attached. R ２ This is a monovalent hydrocarbon group, cyano group, nitro group, or hydroxyl group having 1 to 5 carbon atoms. Z ＋ This is an organic cation containing an aromatic ring substituted with an electron-withdrawing group. 　 The radiation-sensitive composition according to claim 1, wherein in formula (1) above, g is an integer from 1 to 3 and X is an iodine group. 　 The radiation-sensitive composition according to claim 1, wherein g is 1 in the above formula (1). 　 The radiation-sensitive composition according to claim 1, wherein in formula (1) above, h is 1. 　 In the above formula (1), R １ The radiation-sensitive composition according to claim 1, wherein is a monovalent hydrocarbon group having 1 to 4 carbon atoms. 　 The radiation-sensitive composition according to claim 1, wherein i is 0 in the above formula (1). Z ＋ The radiation-sensitive composition according to any one of claims 1 to 6, wherein is a radiation-sensitive sulfonium cation containing an aromatic ring substituted with an electron-withdrawing group, or a radiation-sensitive iodonium cation containing an aromatic ring substituted with an electron-withdrawing group. 　 The above organic cation is represented by the following formula (z1) or (z2), and is a radiation-sensitive composition according to any one of claims 1 to 6. (In equations (z1) and (z2), Ar is a (p+q+1) valence group obtained by removing (p+q) hydrogen atoms from a phenyl group or a naphthyl group, independently of each other. R ３ and R ４ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms, or R ３ and R ４ These can be combined to form a ring structure with 4 to 12 carbon atoms, along with the sulfur atoms to which they bond. R ５ Each of these is independently a hydroxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. ５ If multiple R ５ They are either identical or different from one another. R ６ It is a monovalent organic group having 1 to 20 carbon atoms. Each Y is an electron-withdrawing group independently selected from the group consisting of halogen groups, halogenated hydrocarbon groups, nitro groups, cyano groups, carbonyl-containing groups, sulfonyl-containing groups, amide-containing groups, and halogenated sulfanyl groups. If multiple Ys exist, they are either identical or different from one another. Each of the values ​​of p is an independent integer between 1 and 5. q is an independent integer between 0 and 3. 　 The radiation-sensitive composition according to claim 8, wherein Y in formulas (z1) and (z2) above is independently a halogeno group or a halogenated hydrocarbon group. 　 The radiation-sensitive composition according to claim 8, wherein in the above formulas (z1) and (z2), the halogen atom constituting Y is at least one selected from the group consisting of fluorine atoms and iodine atoms. 　 The radiation-sensitive composition according to claim 8, wherein in the above formulas (z1) and (z2), r is 0. 　 In the above equations (z1) and (z2), R ３ , R ４ and R ６ The radiation-sensitive composition according to claim 8, comprising an aromatic ring. 　 The radiation-sensitive composition according to any one of claims 1 to 6, wherein the polymer further comprises a structural unit having a phenolic hydroxyl group. 　 The radiation-sensitive composition according to any one of claims 1 to 6, wherein the polymer further comprises a structural unit having a first organic acid anion and a first onium cation, and including a first acid generating structure that generates an acid that dissociates the acid-dissociable group upon exposure. 　 A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 6 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following. 　 The pattern forming method according to claim 15, wherein the exposure is performed using extreme ultraviolet light or an electron beam. 　 An onium salt compound represented by the following formula (1). (In formula (1), g, h, and i are each independent integers between 0 and 3, where g + h + i is less than or equal to 3. X, R １ and R ２ If multiple X and R exist, １ and R ２ They are either identical or different from one another. X is a halogeno group. If X contains an iodine group, one iodine group is the COO in formula (1) above. - It bonds to the p-position of the group. R １ This is a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (α) having 1 to 20 carbon atoms having a divalent heteroatom-containing group between the carbon atoms of the hydrocarbon group, or a group (β) having 1 to 20 carbon atoms in which some or all of the hydrogen atoms of the hydrocarbon group or the group (α) are replaced with a chloro group, bromo group, iodo group, hydroxyl group, nitro group, amino group, carboxyl group, or cyano group. However, if h is 2 or more, multiple R １ These are, respectively, the hydrocarbon group, the group (α), or the group (β), or a plurality of -OR １ Two of the -OR １ Two R's in １ They can be combined with each other - OR １ It is a divalent organic group that forms part of a ring structure with 5 to 20 members, which is formed together with the carbon atom to which it is bonded. R ２ This is a monovalent hydrocarbon group, cyano group, nitro group, or hydroxyl group having 1 to 5 carbon atoms. Z ＋ This is an organic cation containing an aromatic ring substituted with an electron-withdrawing group.

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