Radiation-sensitive composition, pattern formation method, and radiation-sensitive acid generator

Abstract

Provided are: a radiation-sensitive composition capable of exhibiting sensitivity, CDU, and development defect suppressing properties at sufficient levels when forming a pattern; a pattern formation method; and a radiation-sensitive acid generator. This radiation-sensitive composition comprises: a radiation-sensitive acid generator having an organic acid anion and an organic cation; a polymer which contains a structural unit having an acid-dissociable group; and a solvent, wherein at least one selected from the group consisting of the organic acid anion and the organic cation includes a partial structure (i) represented by formula (i). (In formula (i), R1 is a hydrogen atom or a substituted or unsubstituted C1-C10 monovalent hydrocarbon group. * is a bond with a portion other than the partial structure (i) in the radiation-sensitive acid generator.)

Description

Radiation-sensitive composition, pattern-forming method, and radiation-sensitive acid generator

[0001] The present invention relates to a radiation-sensitive composition, a pattern-forming method, and a radiation-sensitive acid generator.

[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] In order to improve sensitivity, resolution, and other properties, various photoacid generators have been investigated for the photoacid generators that are the main components of the resist composition (Japanese Patent Publication No. 5703702).

[0005] Patent No. 5703702

[0006] With the miniaturization of patterns using next-generation technologies, resist compositions are required to have resist performance equivalent to or better than conventional ones in terms of sensitivity, CDU, and development defect suppression.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, and a radiation-sensitive acid generator that can exhibit sufficient levels of sensitivity, CDU, and development defect suppression during pattern formation.

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

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising a radiation-sensitive acid generator having an organic acid anion and an organic cation, a polymer containing a structural unit having an acid-dissociable group, and a solvent, wherein at least one selected from the group consisting of the above organic acid anion and the above organic cation comprises a substructure (i) represented by the following formula (i). (In formula (i), R １ (i) is a hydrogen atom, or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. (*) is a bond with a part other than the above substructure (i) in the radiation-sensitive acid generator.

[0010] The radiation-sensitive composition exhibits excellent sensitivity, CDU (Cell Degradation Unit), and suppression of development defects during pattern formation. Although the reason for this is not entirely clear, it is presumed to be as follows: The radiation-sensitive acid generator incorporates a substructure (i) corresponding to phosphonic acid, which increases hydrophilicity and improves developer solubility. Furthermore, the interaction between the substructure (i) of the radiation-sensitive acid generator and the polymer increases the glass transition temperature (Tg) of the resist film, allowing for appropriate control of the diffusion length of the generated acid. It is presumed that these combined effects enable the resist to exhibit the aforementioned properties.

[0011] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

[0012] In this pattern formation method, since the above-mentioned radiation-sensitive composition is used, which exhibits excellent sensitivity, CDU, and development defect suppression during pattern formation, high-quality resist patterns can be efficiently formed.

[0013] In yet another embodiment, the present invention relates to a radiation-sensitive acid generator represented by the following formula (1). (In formula (1), R １Each of these is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. １ If multiple R １ These are either identical or different from each other. W is a p+q valent organic group with 1 to 40 carbon atoms. M ＋ is an organic cation having bonds with r phosphorus atoms in the formula. p is an integer from 0 to 3. q is an integer from 1 to 3. r is an integer from 0 to 3. If there are multiple r values, they can be either identical or distinct from one another. However, the sum of p and the q r values ​​must be 1 or greater.

[0014] Because this radiation-sensitive acid generator exhibits excellent developer solubility and acid diffusion length control, it is suitable as an acid generator in radiation-sensitive compositions.

[0015] In this specification, the definitions of terms are as follows: "Organic group" means a group containing at least one carbon atom. However, cyano groups, carboxyl groups, formyl groups, carbonyl groups, carbamoyl groups, etc., which can function or be characteristic groups on their own as organic groups are excluded. "Fused ring" means a ring structure in which two adjacent rings share one edge (two adjacent atoms). "Bridged ring" means a polycyclic structure in which two non-adjacent carbon atoms constituting an aliphatic cyclic structure that does not have aromaticity are bonded together by a bridge containing one or more atoms. "Ring assembly" means a ring structure in which two adjacent rings are bonded by a single bond. "Spiro ring" means a ring structure in which two adjacent rings share one carbon atom. As abbreviations for substituents, "Me" represents a methyl group, "Et" represents an ethyl group, "t-Bu" represents a t-butyl group, and "Ph" represents a phenyl group.

[0016] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Preferred combinations of embodiments are also preferred.

[0017] Radiation-sensitive composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a radiation-sensitive acid generator, a 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.

[0018] <Radiation-sensitive acid generator> The radiation-sensitive acid generator has an organic acid anion and an organic cation, and has the function of generating an acid that dissociates an acid-dissociable group upon exposure. At least one selected from the group consisting of the above organic acid anion and the above organic cation contains a substructure (i) represented by the above formula (i). That is, embodiments of the substructure (i) include an embodiment in which the organic acid anion contains substructure (i) and the organic cation does not contain substructure (i), an embodiment in which the organic acid anion does not contain substructure (i) and the organic cation contains substructure (i), and an embodiment in which both the organic acid anion and the organic cation contain substructure (i).

[0019] In the above formula (i), R １ Examples of monovalent hydrocarbon groups having 1 to 10 carbon atoms represented by this formula include monovalent linear hydrocarbon groups having 1 to 10 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 10 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 10 carbon atoms, or combinations thereof.

[0020] Examples of monovalent chain hydrocarbon groups having 1 to 10 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.

[0021] Examples of monovalent alicyclic hydrocarbon groups having 3 to 10 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.

[0022] Examples of the monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms include aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, and aralkyl groups such as benzyl group and phenethyl group.

[0023] R １ Examples of the substituent when R has a substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; hydroxy group; carboxy group; cyano group; nitro group; amino group; alkoxy group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group, acyloxy group or a group combining these groups or a group in which a hydrogen atom of these groups is substituted with a halogen atom; oxo group (=O), etc.

[0024] Examples of the alkoxy group as the above-mentioned substituent include linear or branched alkoxy groups having 1 to 8 carbon atoms such as methoxy group, ethoxy group, and propoxy group. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 1 to 6 carbon atoms of alkoxy groups such as methoxycarbonyl group and ethoxycarbonyl group. Examples of the alkoxycarbonyloxy group include chain or alicyclic alkoxycarbonyloxy groups having 2 to 8 carbon atoms such as methoxycarbonyloxy group, butoxycarbonyloxy group, and cyclopentylmethyloxycarbonyloxy group. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 8 carbon atoms such as acetyl group, propionyl group, benzoyl group, and acryloyl group. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 8 carbon atoms such as acetyloxy group, propionyloxy group, benzoyloxy group, and acryloyloxy group.

[0025] R １ is preferably a hydrogen atom or a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrogen atom or a monovalent chain saturated hydrocarbon group having 1 to 6 carbon atoms, still more preferably a hydrogen atom or a monovalent linear saturated hydrocarbon group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom.

[0026] The organic acid anion has, as the acid anion part, a sulfonic acid anion (-SO ３ -) and sulfonimide anions (-SO ２ -N - -SO ２ It is preferable to have at least one selected from the group consisting of -), and more preferably to have a sulfonic acid anion. Examples of acids generated by exposure include sulfonic acid and sulfonimide, corresponding to the above acid anion portion.

[0027] The above-mentioned organic acid anion can suitably employ structures other than the acid anion portion, such as a ring structure, a chain structure, a structure combining a ring structure and a chain structure, or a structure combining at least one selected from the group consisting of a ring structure and a chain structure with a divalent heteroatom-containing linking group.

[0028] As for the ring structure, R １ Examples of aliphatic heterocyclic structures include structures corresponding to groups that extend the monovalent alicyclic hydrocarbon group having 3 to 10 carbon atoms to 20 carbon atoms as shown above, aliphatic heterocyclic structures, aromatic ring structures, or combinations thereof. Examples of aliphatic heterocyclic structures include oxygen atom-containing aliphatic heterocyclic structures such as oxiranes, tetrahydrofurans, tetrahydropyrans, dioxolanes, and dioxanes; nitrogen atom-containing aliphatic heterocyclic structures such as aziridines, pyrrolidines, piperidines, and piperazines; sulfur atom-containing aliphatic heterocyclic structures such as thiethanes, thiolanes, and thianes; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholines, 1,2-oxathiolanes, and 1,3-oxathiolanes. Examples of the above aliphatic heterocyclic structures include structures containing lactones, cyclic carbonates, sultones, cyclic acetals, and cyclic ketones. Examples of aromatic ring structures 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, pyridine rings, pyridazine rings, triazine rings, carbazole rings, and dibenzofuran rings; or combinations thereof. The combination of ring structures may be fused rings, bridged rings, ring aggregates, or spiro rings.

[0029] The above chain structure is R １ Examples of structures that correspond to groups obtained by extending the monovalent chain hydrocarbon group having 1 to 10 carbon atoms shown above up to 20 carbon atoms.

[0030] Examples of divalent heteroatom-containing linking groups include -CO-, -CS-, -NR'-, -O-, -S-, and -SO ２ -Examples of groups combining these elements are shown. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0031] If the above ring structure or chain structure has substituents, R １ The substituents that it may have can be suitably adopted.

[0032] When the above organic acid anion has a sulfonic acid anion as the acid anion portion, it is preferable that an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom in the sulfonic acid anion. When the above organic acid anion has a sulfonimide anion as the acid anion portion, it is preferable that an electron-withdrawing group is bonded to the sulfur atom in the sulfonimide anion. This allows the radiation-sensitive acid generator to efficiently exhibit the above functions. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, and cyano groups. As fluorinated hydrocarbon groups, perfluoroalkyl groups having 1 to 5 carbon atoms and difluoromethyl groups are preferred. When the acid anion portion is a sulfonimide anion, a fluorinated hydrocarbon group is preferred as the electron-withdrawing group.

[0033] The above-mentioned radiation-sensitive acid generator is preferably a compound represented by the following formula (1). (In formula (1), W is a p+q valent organic group having 1 to 40 carbon atoms. M ＋ R is an organic cation having bonds with r phosphorus atoms in the formula. p is an integer from 0 to 3. q is an integer from 1 to 3. r is an integer from 0 to 3. If there are multiple r values, they can be either identical or distinct from one another. However, the sum of p and the q r values ​​is 1 or greater. １ This is equivalent to equation (i) above. R １ If multiple R１ They are either identical or different from one another.

[0034] As the p+q valent organic group having 1 to 40 carbon atoms represented by W, a group obtained by removing p+q-1 hydrogen atoms from a monovalent organic group having 1 to 40 carbon atoms can be suitably adopted. Examples of monovalent organic groups having 1 to 40 carbon atoms include a monovalent hydrocarbon group having 1 to 40 carbon atoms, a group (a) having a divalent heteroatom-containing linking group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with a monovalent heteroatom-containing group, or combinations thereof.

[0035] As monovalent hydrocarbon groups having 1 to 40 carbon atoms, R １ A monovalent hydrocarbon group having 1 to 10 carbon atoms, represented by [the formula shown], can be suitably adopted, with the carbon number extended up to 40.

[0036] As the divalent heteroatom-containing linking group, the divalent heteroatom-containing linking groups shown in other structures of the above organic acid anion can be suitably adopted.

[0037] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0038] In formula (1) above, W preferably includes a ring structure, a chain structure, a structure combining a ring structure and a chain structure, and a structure combining at least one selected from the group consisting of a ring structure and a chain structure with a divalent heteroatom-containing linking group. As these structures, each of the structures shown as other structures other than the acid anion portion of the above organic acid anion can be suitably adopted. Among these, it is preferable that W includes a ring structure. As the ring structure, aromatic hydrocarbon structures, bridged ring saturated hydrocarbon structures, aliphatic heterocyclic structures or combinations thereof are preferred, and benzene structures, norbornane structures, adamantane structures, cyclic acetal structures or combinations thereof are more preferred.

[0039] Preferably, W includes a ring structure, and the substructure (i) is bonded to the ring structure in W.

[0040] In formula (1) above, W preferably has an iodine group. The iodine group is preferably included in the form of an iodine group-containing aromatic ring structure. 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 by iodine groups. As the aromatic ring, aromatic rings other than the acid anion portion of the above organic acid anion can be suitably adopted.

[0041] In the above formula (1), at least one -SO ３ - It is preferable that the electron-withdrawing group is bonded to the carbon atom in W located at the α or β position relative to the sulfur atom.

[0042] p is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0043] q is preferably 1 or 2, and more preferably 1.

[0044] The organic acid anion of the radiation-sensitive acid generator preferably has a structure represented by the following formula (Aa). (In formula (Aa), R １ And p are equivalent to equation (1) above. Cy １１ and Cy １２ These are, independently, substituted or unsubstituted ring structures. １２ If there are multiple Cy １２ They are either identical or different from each other. １１ , L １２ and L １３ Each of these is independently a single bond, a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent heteroatom-containing linking group, or a combination thereof. １１ and L １２ If there are multiple L １１ and L １２ These are either identical or different from each other. ｆ１ and R ｆ２Each of these is independently a hydrogen atom, a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. However, R ｆ１ and R ｆ２ At least one selected from the group consisting of the following is a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. (z12 is an integer from 0 to 3. z13 is an integer from 1 to 4.)

[0045] L １１ ~L １３ As the divalent heteroatom-containing linking group represented by , the divalent heteroatom-containing linking groups shown in other structures of the above organic acid anion can be suitably adopted.

[0046] L １１ ~L １３ In this, the divalent hydrocarbon group having 1 to 10 carbon atoms is R in formula (i) above. １ A group obtained by removing one hydrogen atom from a monovalent hydrocarbon group having 1 to 10 carbon atoms, represented by the formula (i), can be suitably adopted. The substituents that the hydrocarbon group may have include R in the above formula (i). １ The substituents that it may have can be suitably adopted.

[0047] Cy １１ and Cy １２ As the ring structure represented by the above formula (i), ring structures other than the acid anion portion of the above organic acid anion can be suitably adopted. Substituents that the cyclic structure may have include R of the above formula (i). １ The substituents that it may have can be suitably adopted.

[0048] R ｆ１ and R ｆ２ The fluorinated hydrocarbon group represented by is preferably a perfluoroalkyl group having 1 to 5 carbon atoms or a difluoromethyl group.

[0049] z11 is preferably 1. z12 is preferably an integer between 0 and 2, and more preferably 0 or 1. z13 is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0050] Specific examples of organic acid anions include structures represented by the following formula.

[0051]

[0052]

[0053]

[0054] In the above formula (1), M ＋ The organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, and ammonium cations.

[0055] M ＋ It is preferable that the cation is a radiation-sensitive onium cation. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, radiation-sensitive sulfonium cations or radiation-sensitive iodonium cations are preferred, and radiation-sensitive sulfonium cations are more preferred.

[0056] M ＋ It is preferable that the compound contains an iodine group or a fluoro group. The iodine group or fluoro group is preferably included in the form of an iodine group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure. As the iodine group-containing aromatic ring structure, the iodine group-containing aromatic ring structure shown in W of formula (1) above can be suitably adopted. The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by fluoro groups. As the aromatic ring in the fluoro group-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be suitably adopted. By introducing an iodine group or a fluoro group, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0057] r is preferably an integer between 0 and 2, more preferably 0 or 1, and even more preferably 0.

[0058] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-2).

[0059]

[0060] In the above equations (X-1) to (X-2), R １ This is equivalent to equation (i) above. L ｘ１ Each of these independently corresponds to L in the above formula (Aa). １１ This is synonymous with R. １ and L ｘ１ If each of them is multiple, then multiple R １ and L ｘ１ These may be the same or different.

[0061] In the above equation (X-1), R ａ１ , R ａ２ and R ａ３ Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom, or -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ This represents a ring structure consisting of -O-, -CO-, or a combination thereof, or two or three or more of these groups combined with each other. The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton. Ｐ , R Ｑ and R ＴEach of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. c1, c2, and c3 are each independently integers from 0 to 3. If the organic cation has substructure (i), c1 + c2 + c3 is 1 or greater. k1, k2, and k3 are each independently integers from 0 to 5. c1 + k1, c2 + k2, and c3 + k3 are each 5 or less. ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0062] In the above equation (X-2), R ｄ１ and R ｄ２ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by two or more of these groups combined. d1 and d2 are each independently integers from 0 to 3. If the organic cation has a substructure (i), d1 + d2 is 1 or greater. k6 and k7 are each independently integers from 0 to 5. d1 + k6 and d2 + k7 are each 5 or less. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0063] Specific examples of organic cations as the above-mentioned radiation-sensitive onium cation include, but are not limited to, the structure shown in the following formula. The following formula shows both the structure with substructure (i) and the structure without substructure (i).

[0064]

[0065]

[0066]

[0067]

[0068] A radiation-sensitive acid generator can be obtained by appropriately combining the above-mentioned organic acid anion and organic cation (the organic acid anion and organic cation are not limited to the structures specifically shown). Specific examples, though not limited to those shown, include the structure of the following formula.

[0069]

[0070]

[0071]

[0072]

[0073] The above-mentioned radiation-sensitive acid generator may be used alone or in combination of two or more types. The lower limit of the content of the radiation-sensitive acid generator (total in the case of multiple types) is preferably 5 parts by mass, more preferably 8 parts by mass, even more preferably 12 parts by mass, and particularly preferably 16 parts by mass, per 100 parts by mass of the base polymer described later. The upper limit of the above content is preferably 50 parts by mass, more preferably 40 parts by mass, even more preferably 30 parts by mass, and particularly preferably 25 parts by mass. This makes it possible to exhibit the above-mentioned excellent resist properties.

[0074] <Synthesis Method for Radiation-Sensitive Acid Generators> It is clear that radiation-sensitive acid generators can be synthesized based on the descriptions in the examples and common technical knowledge. Typically, a compound having partial structure (i) or its precursor structure is obtained by reacting a phosphorous acid derivative with a compound having a halogen group (e.g., aryl halides), or by reacting a phosphoric acid halide with a nucleophile (e.g., a compound containing a hydroxyl group). An organic acid anion is synthesized by reacting this compound with a compound having an acid anion moiety (e.g., a sulfonic acid anion) or a salt of this compound with an organic cation by known methods, and finally, if necessary, a salt exchange is performed with a compound having an organic cation to synthesize the compound. If the phosphorous acid derivative is an ester, it is also possible to convert it to a phosphonic acid structure by performing a dealkylation reaction at any stage (e.g., after the salt exchange reaction). Other structures can also be synthesized by appropriately selecting the type of starting material and reaction substrate.

[0075] <Polymers> A polymer (i.e., a base polymer) is an aggregate of polymer chains having structural units containing acid-dissociable groups (hereinafter also referred to as "structural unit (I)"). 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)"), lactone structures, cyclic carbonate structures, and sultone structures (hereinafter also referred to as "structural unit (III)"). Each structural unit will be described below.

[0076] [Structural Unit (I)] Structural unit (I) is a structural unit having an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer has structural unit (I).

[0077] As the structural unit (I), there is no particular limitation as long as it has an acid dissociable group. For example, a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which an aromatic group and an aliphatic group are bonded to a secondary carbon constituting a secondary alkyl ester moiety, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, etc. can be mentioned. From the viewpoint of improving the pattern formation property of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter, also referred to as "structural unit (I-1)") is preferable.

[0078]

[0079] In the above formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R １８ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. R １９ and R ２０ are each independently a substituted or unsubstituted monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted monovalent 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 atom to which they are bonded. L １１ is ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ COO- represents. L １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is a bond with the carbon atom to which R １７ is bonded.

[0080] As the above R １７ From the viewpoint of the copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable.

[0081] As the alkanediyl group represented by L １１ａ Examples thereof include alkanediyl groups having 1 to 10 carbon atoms such as a methylene group, an ethanediyl group, a 1,3-propanediyl group, and a 2,2-propanediyl group. L １１ａMethylene groups and ethanediyl groups are preferred as the base group.

[0082] L １１ａ Examples of allenediyl groups 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.

[0083] L １１ａ The substituents that the arenediyl group represented by the above formula (i) may have include R １ The substituents that it may have can be suitably adopted.

[0084] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (i), R １ A monovalent hydrocarbon group having 1 to 10 carbon atoms, represented by [the formula shown], can be suitably adopted, with the carbon number extended up to 20.

[0085] 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.

[0086] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these atoms with the carbon atoms to which they are bonded, is R in formula (i) above. １ A group obtained by extending the monovalent alicyclic hydrocarbon group having 3 to 10 carbon atoms shown above up to 20 carbon atoms, and then removing one hydrogen atom from that group, can be suitably adopted.

[0087] 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.

[0088] The above R １８ ~R ２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0089] 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)").

[0090]

[0091]

[0092] 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.

[0093] i and j are preferably 1 or 2. 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).

[0094] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0095]

[0096] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms.１ is an integer between 1 and 4.

[0097] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0098] The lower limit of the content of structural unit (I) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 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.

[0099] [Structural Unit (II)] Structural unit (II) is a structural unit having a phenolic hydroxyl group. Structural unit (II) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0100] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0101] (In the above formula (4), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ Or -O-. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxy 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 m is an integer between 0 and 8, where 1 ≤ m ３ +m４ ≤ 2n ３ (Saves +5.)

[0102] 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.

[0103] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0104] R １０２ In this mixture, fluorine or iodine atoms are preferred as halogen atoms.

[0105] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0106] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0107] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0108] When the base polymer contains structural unit (II), the lower limit of the content of structural unit (II) in relation to the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 10 mol%, and more preferably 20 mol%. The upper limit of the above content is preferably 80 mol%, and more preferably 70 mol%.

[0109] [Structural Unit (III)] Structural unit (III) 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 (III), 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. Furthermore, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0110] Examples of structural units (III) include those represented by the following formulas (T-1) to (T-11).

[0111]

[0112] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ These are, independently, a hydrogen atom, a C1-C4 alkyl group, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, and a dimethylamino group. Ｌ４ and R Ｌ５ These may be divalent alicyclic groups having 3 to 8 carbon atoms, which can be combined with each other and bonded together with the carbon atoms. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0113] The above R Ｌ４ and R Ｌ５ When these are combined with each other, the divalent alicyclic group having 3 to 8 carbon atoms, formed together with the carbon atoms to which they are bonded, is R in formula (3) above. １９ and R ２０ Examples include divalent alicyclic groups with 3 to 20 carbon atoms, where these groups are combined with each other and formed together with the carbon atoms to which they are bonded, specifically groups with 3 to 8 carbon atoms. One or more hydrogen atoms on these alicyclic groups may be substituted with hydroxyl groups.

[0114] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0115] Among these, structural units (III) are preferably those containing a lactone structure, more preferably those containing a γ-butyrolactone structure or a norbornane lactone structure, and even more preferably those derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl(meth)acrylate.

[0116] When the base polymer contains structural unit (III), the lower limit of the content of structural unit (III) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 4 mol%, more preferably 8 mol%, and even more preferably 12 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By setting the content of structural unit (III) 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.

[0117] [Structural Unit (IV)] The base polymer may have structural unit (IV) containing a polar group (excluding those corresponding to structural units (I) to (III)). By further having structural unit (IV), the solubility of the base polymer in the developer can be adjusted, and as a result, the lithographic performance such as resolution of the radiation-sensitive composition can be improved. Examples of the above polar group include a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxyl group and a carboxyl group are preferred, and a hydroxyl group is more preferred.

[0118] Examples of structural units (IV) include structural units represented by the following formula.

[0119]

[0120]

[0121] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0122] When the base polymer has a structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of structural unit (IV) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0123] [Structural Unit (V)] The base polymer may have a structural unit (V) that includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and 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-generating structure) functions as a radiation-sensitive acid-generating structure. By containing the above radiation-sensitive acid-generating structure in the base polymer, 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 sparingly soluble in the developer in the case of organic solvent development.

[0124] Although the form in which the first organic acid anion and the first onium cation are contained in the structural unit (V) of the base polymer is not particularly limited, it is preferable that the base polymer has the first organic acid anion as a side chain portion from the viewpoint of controlling the acid diffusion length. Having it as a side chain portion means that the first organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0125] The above-mentioned first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions as the acid anion portion. As for the acid generated by exposure, sulfonic acid, carboxylic acid, and sulfonimide can be cited, corresponding to the above-mentioned acid anion portion.

[0126] The above-mentioned first organic acid anion can suitably employ structures other than the acid anion portion, such as a ring structure or a structure combining at least one of a ring structure or a chain structure with a divalent heteroatom-containing linking group. These structures can suitably employ the structures shown as other structures besides the acid anion portion in the organic acid anion of the radiation-sensitive acid generator.

[0127] 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 of the sulfur atom in the sulfonic acid anion. This allows the first acid generation structure to efficiently perform the above-described function. As the electron-withdrawing group, the electron-withdrawing group shown in the organic acid anion of the above-described radiation-sensitive acid generator can be suitably adopted.

[0128] 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.

[0129] Examples of the first onium cation mentioned above include radiation-sensitive onium cations. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0130] The first onium cation described above preferably has an iodine group or a fluoro group. The first onium cation preferably contains an iodine group-containing aromatic ring structure as an iodine group-containing configuration. The first onium cation preferably contains a fluoro group-containing aromatic ring structure as an fluoro group-containing configuration. These configurations increase radiation absorption efficiency, thereby improving sensitivity.

[0131] The structural unit (V) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0132] The structural unit (V) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (V-1)").

[0133]

[0134] 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, an amide bond, or a linear or branched alkylene group having 1 to 12 carbon atoms, a cyclic cycloalkylene group having 3 to 12 carbon atoms, or a combination thereof, and some 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 ２ Each 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. X １ ＋ This is a sulfonium cation or an iodonium cation.

[0135] V ２ and V ３Some or all of the hydrogen atoms in the C1-C12 alkyl group, C3-C12 cycloalkyl group, and C6-C20 aryl group in the above 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, and 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.

[0136] Preferably, the structural unit (V-1) is a structural unit represented by the following formula (a1-1).

[0137]

[0138] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ ,kk and X 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.

[0139] Examples of the first organic acid anion of the monomer that gives structural unit (V) (including structural unit (V-1)) include, but are not limited to, the structure shown in the following formula. In the following, the iodine group of the iodine group-containing aromatic ring structure may be substituted with a hydrogen atom or a substituent that the above-mentioned bridged alicyclic ring may have. In the following formula, R Ｖ This is synonymous with the above.

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] In the above formula, R Ｖ This is equivalent to equation (a1) above.

[0146] X in the above formula (a1) １ ＋ As for M in the above formula (1) ＋ A sulfonium cation or an iodonium cation can be suitably used in the organic cation represented by [the formula].

[0147] 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 4 mol%, and more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 20 mol%, and more preferably 16 mol%. By setting the content of structural units (V) within the above range, the function as an acid-generating structure can be fully exhibited, and the above-mentioned resist properties can be achieved.

[0148] [Structural Unit (VI)] The base polymer may include structural unit (VI), which has a second organic acid anion and a second onium cation, and contains a second acid generating structure that generates an acid by exposure without dissociating the 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 acid generated from the above-mentioned radiation-sensitive acid generating agent or structural unit (V) (if included) in the unexposed area by salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the above-mentioned radiation-sensitive acid generating agent or structural unit (V). 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] Regarding the inclusion of the second organic acid anion and the second onium cation in the structural unit (VI) of the base polymer, from the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

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

[0151] The above-mentioned second organic acid anion can preferably employ the structure shown as the structure other than the acid anion portion of structural unit (V).

[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, an organic cation of a radiation-sensitive acid generator 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 (VI) preferably has the above-mentioned fluorogroup-containing aromatic ring structure. This can improve sensitivity by increasing the radiation absorption efficiency.

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

[0157] The structural unit (VI) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (VI-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. ２ The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3- Examples include C1-C12 alkanediyl groups such as diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, heptane-1,7-diyl groups, octane-1,8-diyl groups, nonane-1,9-diyl groups, and decane-1,10-diyl groups; C3-C12 cyclic saturated hydrocarbylene groups such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; and groups obtained by combining these.

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

[0163] In formula (p1), X1 ~X ２ Some or all of the hydrogen atoms in the bridged alicyclic ring may be substituted with substituents. Preferably, substituents that the bridged alicyclic ring may have can be used. 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), R ｘ These are halogen atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0165] In formula (p1), Z ２ ＋ This is a secondary onium cation. As the above secondary onium cation, the organic cation shown in the radiation-sensitive acid generator can be suitably used.

[0166] Examples of monomeric second organic acid anions that give structural unit (VI) (including structural unit (VI-1)) include, but are not limited to, those listed below. In the following formulas, the iodine group or hydroxyl group is a hydrogen atom or the R in formula (i) above. １ It may be substituted with substituents that it may have. 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] When the base polymer contains structural unit (VI), the lower limit of the content of structural unit (VI) (or the total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of structural unit (VI) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0170] [Other structural units] The base polymer may also contain structural units other than those listed above, such as structural units having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). (In the above formula (6), R １α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α (It is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.)

[0171] In the above formula (6), R ２α As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (i), R １ A monovalent alicyclic hydrocarbon group having 3 to 10 carbon atoms, as shown above, can be suitably adopted, with the carbon number extended up to 20.

[0172] When the base polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0173] (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.

[0174] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(isobutyrate)dimethyl (MAIB), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0175] Solvents used in the above polymerization include, for example, alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; and ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone. Examples include linear ethers such as dimethoxyethanes and diethoxyethanes; cyclic ethers such as tetrahydrofurans and 1,4-dioxanes; polyhydric alcohol partial ethers such as 1-methoxy-2-propanol (propylene glycol monomethyl ether); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0176] 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.

[0177] The molecular weight of the base polymer is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 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.

[0178] 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.

[0179] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0180] The base polymer content is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0181] <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.

[0182] High-fluorine-content polymers may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VIII)").

[0183]

[0184] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. ＬIt 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.

[0185] The above R １３ From the viewpoint of copolymerization of monomers that give structural unit (VIII), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0186] The above G Ｌ From the viewpoint of copolymerization of monomers that give structural unit (VIII), single bonds and -COO- are preferred, and -COO- is more preferred.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] When a high-fluorine-content polymer has structural unit (VIII), the lower limit of the content of structural unit (VIII) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%. By setting the content of structural unit (VIII) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the film quality controllability of the resist film can be further improved.

[0191] High-fluorine-content polymers may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (IX)) represented by the following formula (f-2), either together with or in place of structural unit (VIII). The presence of structural unit (IX) in high-fluorine-content polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0192]

[0193] Structural units (IX) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in 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.

[0194] If the structural unit (IX) has (x) an alkali-soluble group, RＦ A is a hydrogen atom, １ The oxygen atom is -COO-* or -SO ２ It is O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having an alkali-soluble group in the structural unit (IX) increases its affinity for alkaline developer and suppresses development defects. A structural unit (IX) having an alkali-soluble group is A １ is an oxygen atom and W １ It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0195] If the structural unit (IX) has an alkali-dissociable group (y), R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ It is O-*. ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. 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.１ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in the structural unit (IX) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural units (IX) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0196] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural units (IX), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0197] When a high-fluorine-content polymer has structural units (IX), the lower limit of the content of structural units (IX) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of structural units (IX) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers, thereby suppressing the occurrence of development defects.

[0198] [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 (IV) in the base polymer.

[0199] When a high-fluorine-content polymer contains structural unit (I), the lower limit of the content of structural unit (I) is preferably 4 mol%, and more preferably 8 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 30 mol%, and more preferably 15 mol%.

[0200] When a high-fluorine-content polymer contains structural units (IV), the lower limit of the structural unit (IV) content is preferably 10 mol%, and more preferably 20 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 50 mol%, and more preferably 40 mol%.

[0201] The lower limit of Mw for the high-fluorine-content polymer is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 10,000, and even more preferably 7,000.

[0202] 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.

[0203] If the radiation-sensitive composition contains a high-fluorine-content polymer, the lower limit of the high-fluorine-content polymer content is preferably 0.1 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 10 parts by mass, and even more preferably 8 parts by mass.

[0204] 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.

[0205] (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.

[0206] <Acid Diffusion Control Agent> The radiation-sensitive composition may optionally contain an acid diffusion control agent. The acid diffusion control agent controls the diffusion phenomenon of the acid generated from the radiation-sensitive acid generator or structural unit (V) in the resist film upon exposure, and has the effect of suppressing undesirable chemical reactions in unexposed areas. In addition, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the setting time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0207] Examples of acid diffusion control agents include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

[0208]

[0209] In the above formula (7), R ２２ , R ２３ and R ２４ Each of these is independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0210] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0211] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0212] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0213] Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0214] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0215] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0216] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0217] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as an acid diffusion control agent. The acid generated from the above-mentioned radiation-sensitive weak acid generator is a weak acid that does not dissociate the acid-dissociable groups in the polymer under conditions that cause the acid-dissociable groups to dissociate.

[0218] Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Also, examples include compounds containing a sulfonium cation and anion in the same molecule, represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, represented by the following formula (8-4).

[0219]

[0220] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. ＋ Examples of sulfonium cations represented by the above formulas (X-1) to (X-4) include U ＋ Examples of iodonium cations represented by the above formulas (X-5) to (X-6) include iodonium cations represented by E. - and Q - Each of them is independent of OH - , R α -COO - , R α -SO ３ - This is an anion represented by R. α R is a single bond or a monovalent organic group having 1 to 30 carbon atoms. α As the monovalent organic group having 1 to 30 carbon atoms represented by the above formula (1), groups corresponding to 1 to 30 carbon atoms can be suitably adopted from among the monovalent organic groups having 1 to 40 carbon atoms shown in W of formula (1). The anion is R α -SO ３ - When expressed as R α SO in３ - Neither the α-position nor the β-position carbon atom has an electron-withdrawing group bonded to it. The electron-withdrawing groups shown in the organic acid anion of the above-mentioned radiation-sensitive acid generator can be suitably adopted as electron-withdrawing groups.

[0221] Examples of anions for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also given as examples. The iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0222]

[0223]

[0224] As the onium cation in the above-mentioned acid diffusion control agent, the structure of the organic cation of the above-mentioned radiation-sensitive acid generator can be suitably adopted.

[0225] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0226] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%, relative to the total number of moles of the radiation-sensitive acid generator and the first organic acid anion monomer that gives structural units (V) of the base polymer (collectively referred to as the "acid generator"). The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%.

[0227] (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 radiation-sensitive acid generator, the base polymer, and any optional components that may be included.

[0228] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0229] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether), which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0230] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents in which the hydroxyl groups of the above-mentioned polyhydric alcohol solvents, such as propylene glycol monomethyl ether, have been etherified.

[0231] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0232] 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.

[0233] 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.

[0234] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0235] Among these, alcohol-based solvents and ester-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0236] (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.

[0237] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared by mixing, for example, a radiation-sensitive acid generator, a polymer, and additives as needed, along with a solvent, in predetermined proportions. After mixing, the above radiation-sensitive composition is preferably filtered using, for example, a filter with a pore size of about 0.05 μm to 0.40 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0238] <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").

[0239] According to the pattern formation method described above, since the above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, CDU, and development defect suppression, is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0240] [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 150°C, with 80°C to 120°C being preferred. The SB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0241] 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 500 nm, more preferably 350 nm, and even more preferably 200 nm.

[0242] 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.

[0243] [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 are even more preferred.

[0244] 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.

[0245] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups in the polymer, etc., in the exposed portion of the resist film by using a radiation-sensitive acid generator or, optionally, an acid generated from structural units (V) contained in the polymer due to the exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 150°C, with 80°C to 120°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0246] [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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] 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).

[0251] 《Radiation-sensitive acid generator》 The radiation-sensitive acid generator is a compound represented by the following formula (1). (In formula (1), R １ Each of these is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. １ If multiple R １ These are either identical or different from each other. W is a p+q valent organic group with 1 to 40 carbon atoms. M ＋ is an organic cation having bonds with r phosphorus atoms in the formula. p is an integer from 0 to 3. q is an integer from 1 to 3. r is an integer from 0 to 3. If there are multiple r values, they can be either identical or distinct from one another. However, the sum of p and the q r values ​​must be 1 or greater.

[0252] As such compounds, the radiation-sensitive acid generator in the above-mentioned radiation-sensitive composition can be suitably used.

[0253] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0254] [Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "G2000HXL" columns, one "G3000HXL" column, and one "G4000HXL" column) under the following conditions: Elution solvent: Tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Column temperature: 40°C Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0255] <Synthesis of Radiation-Sensitive Acid Generator (A)> [Example A-3: Synthesis of Compound (A-3)] Compound (A-3) was synthesized as a radiation-sensitive acid generator according to the reaction scheme below.

[0256]

[0257] In a round-bottom flask under an argon atmosphere, palladium(II) acetate (2 mmol), triphenylphosphine (4 mmol), and toluene (40 mL) were added and stirred at room temperature for 30 minutes. Compound (A-3-a) (40 mmol), compound (A-3-b) (48 mmol), and triethylamine (80 mmol) were added and heated under reflux for 3 hours. After filtering the reaction mixture, it was washed with 2 mol / L hydrochloric acid aqueous solution and ultrapure water. The organic layer was dried over sodium sulfate and filtered. After removing the solvent by distillation, compound (A-3-c) was obtained in good yield by silica gel column chromatography.

[0258]

[0259] Compound (A-3-c) (30 mmol), compound (A-3-d) (25 mmol), p-toluenesulfonic acid monohydrate (TsOH) (5 mmol), and toluene (150 mL) were added to a round-bottom flask and heated under reflux for 5 hours in a Dean-Stark apparatus. The solvent was removed by distillation and ethyl acetate was added. The organic layer was washed with aqueous sodium carbonate solution and ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation and compound (A-3-e) was obtained in good yield by purification by silica gel column chromatography.

[0260]

[0261] Compound (A-3-e) (15 mmol), acetonitrile (30 mL), and bromotrimethylsilane (TMS-Br) (75 mmol) were added to a round-bottom flask and stirred at room temperature for 48 hours. The solvent was removed by distillation, and acetonitrile (15 mL) and ultrapure water (15 mL) were added and stirred for 1 hour. The solvent was removed by distillation to obtain compound (A-3) in good yield.

[0262] [Example A-13: Synthesis of Compound (A-13)] Compound (A-13) was synthesized according to the following reaction scheme.

[0263]

[0264] Compound (A-13-a) (20 mmol), compound (A-13-b) (24 mmol), and dichloromethane (100 mL) were added to a round-bottom flask placed in an ice bath. Triethylamine (40 mmol) was added, and the mixture was stirred at room temperature for 8 hours. The reaction mixture was diluted with dichloromethane and washed with 2 mol / L hydrochloric acid aqueous solution and ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation, and compound (A-13-c) was obtained in good yield by purification by silica gel column chromatography.

[0265]

[0266] Compound (A-13-c) (18 mmol), dichloromethane (100 mL), and 1,1'-carbonyldiimidazole (18 mmol) were added to a round-bottom flask and stirred at room temperature for 1 hour. Compound (A-13-d) (15 mmol) and triethylamine (23 mmol) were added and stirred at room temperature for 3 hours. The reaction mixture was diluted with dichloromethane and washed with 2 mol / L hydrochloric acid aqueous solution and ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation, and compound (A-13-e) was obtained in good yield by purification by silica gel column chromatography.

[0267]

[0268] Compound (A-13-e) (10 mmol) and dichloromethane (200 mL) were added to a round-bottom flask. Trifluoroacetic acid (50 mmol) was added and the mixture was stirred at room temperature for 18 hours. The solvent was removed by distillation, and the mixture was washed with ultrapure water after adding dichloromethane. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation, and compound (A-13) was obtained in good yield by purification using silica gel column chromatography.

[0269] [Example A-19: Synthesis of Compound (A-19)] Compound (A-19) was synthesized according to the following reaction scheme.

[0270]

[0271] Compound (A-19-a) (20 mmol), phenol (60 mmol), and dichloromethane (40 mL) were added to a round-bottom flask. After cooling to -40°C, trifluoromethanesulfonic anhydride (Tf ２ 24 mmol of (O) was added and the mixture was stirred at room temperature for 8 hours. The reaction mixture was diluted with dichloromethane and washed with ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation and the compound (A-19-b) was purified by silica gel column chromatography to obtain compound (A-19-b) in good yield. Subsequently, 15 mmol of compound (A-19-b) was dissolved in dichloromethane, passed through an ion exchange resin (SEPHADEX A-25), and the solvent was removed by distillation to obtain compound (A-19-c) in good yield.

[0272]

[0273] Compound (A-19-c) (12 mmol), compound (A-19-d) (15 mmol), and dichloromethane (60 mL) were added to a round-bottom flask placed in an ice bath. Triethylamine (24 mmol) was added, and the mixture was stirred at room temperature for 8 hours. The reaction mixture was diluted with dichloromethane and washed with 2 mol / L hydrochloric acid aqueous solution and ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was removed by distillation, and compound (A-19-e) was obtained in good yield by purification by silica gel column chromatography.

[0274]

[0275] A compound (A-19-e) (12 mmol), a compound (A-19-f) (12 mmol), dichloromethane (30 mL), and ultrapure water (30 mL) were added to a eggplant flask and stirred at room temperature for 2 hours. Ultrapure water was added for dilution, and extraction was performed with dichloromethane. The organic layer was dried over sodium sulfate and filtered. The solvent was distilled off, and the compound (A-19-g) was obtained in a good yield by purification using silica gel column chromatography. Subsequently, the compound (A-19-g) (10 mmol) was dissolved in dichloromethane (200 mL). Trifluoroacetic acid (50 mmol) was added and stirred at room temperature for 18 hours. The solvent was distilled off, dichloromethane was added, and washing was performed with ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was distilled off, and the compound (A-19) was obtained in a good yield by purification using silica gel column chromatography.

[0276] Referring to the above synthesis method, the following compounds (A-1) to (A-22) and comparative compounds (CA-1) to (CA-2) were synthesized.

[0277]

[0278]

[0279] <Synthesis of Polymer (P)> Polymers (P-1) to (P-21) as polymer (P) were synthesized according to the following method. The following monomers (M-1) to (M-20) were used for the synthesis of the polymer.

[0280]

[0281] [Synthesis Examples P-1 to P-21: Synthesis of Polymers (P-1) to (P-21)] Each monomer was combined and a copolymerization reaction was carried out under a tetrahydrofuran solvent. Crystallization occurred in methanol, and washing was further repeated with hexane. Isolation and drying were performed to obtain polymers (P-1) to (P-21) having the compositions shown in Table 1. The composition of the obtained polymer was １ By 1H-NMR, Mw and the dispersity (Mw / Mn) were confirmed under the above GPC conditions. The Mw and Mw / Mn of the obtained polymers are shown in Table 1 together with the types and amounts of use of each monomer. In Table 1, "mol%" means the value when the total number of moles of the monomers used is 100 mol%.

[0282]

[0283] <Preparation of Radiation-Sensitive Compositions> The polymer (P), radiation-sensitive acid generator (A), acid diffusion control agent (Q), and solvent (E) used in the preparation of the radiation-sensitive compositions in the following examples and comparative examples are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" means the value when the mass of the polymer (P) used is set to 100 parts by mass, and "mol%" means the value when the total number of moles of the first organic acid anions in the radiation-sensitive acid generator (A) and, if present, the polymer (P) is set to 100 mol%.

[0284] [Polymer (P)] As polymers, polymers (P-1) to (P-21) synthesized in the above synthesis example were used.

[0285] [Radiation-sensitive acid generator (A)] As radiation-sensitive acid generators, compounds (A-1) to (A-22) synthesized in the above examples and comparative compounds (CA-1) to (CA-2) were used.

[0286] [Acid diffusion control agent (Q)] As the acid diffusion control agent, compounds represented by the following formulas (Q-1) to (Q-6) were used.

[0287]

[0288] [Solvent (E)] The following solvents were used as solvent (E): E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[0289] [Example 1: Preparation of Radiation-Sensitive Composition (R-1)] 100 parts by mass of (P-1) as a polymer (P), 20 parts by mass of (A-1) as a radiation-sensitive acid generator (A), 30 mol% of (Q-1) as an acid diffusion control agent (Q), 5,000 parts by mass of (E-1) and 1,500 parts by mass of (E-2) as solvents (E) were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare the radiation-sensitive composition (R-1).

[0290] [Examples 2-47 and Comparative Examples 1-2: Preparation of Radiation-Sensitive Compositions (R-2)-(R-47) and Radiation-Sensitive Compositions (CR-1)-(CR-2)] Radiation-sensitive compositions (R-2)-(R-47) and radiation-sensitive compositions (CR-1)-(CR-2) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Tables 2-1 and 2-2 below were used.

[0291]

[0292]

[0293] <Formation of Resist Pattern> On the surface of a 12-inch silicon wafer with a 20 nm thick underlayer (AL412 (manufactured by Brewer Science)) formed on it, each of the radiation-sensitive compositions prepared above was applied using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After performing a soft bake (SB) at 100°C for 60 seconds, it was cooled at 23°C for 30 seconds to form a 40 nm thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The above resist film was subjected to a post-exposure bake (PEB) at 100°C for 60 seconds. Next, the film was developed using a 2.38 wt% TMAH aqueous solution at 23°C for 30 seconds to form a positive-type 50 nm pitch, 25 nm contact hole pattern.

[0294] <Evaluation> For each resist pattern formed as described above, the sensitivity, CDU, and number of development defects were evaluated according to the following method. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The evaluation results are shown in Table 3 below.

[0295] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 25 nm contact hole pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 40 mJ / cm². A smaller value indicates better sensitivity. ２ If the value is less than 40 mJ / cm², it is classified as "A" (very good) and 40 mJ / cm². ２More than 42mJ / cm ２ In the following cases, the rating is "B" (good), and the temperature is 42 mJ / cm². ２ If the value exceeded this, it was rated as "C" (poor).

[0296] [CDU] A 25 nm contact hole pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in hole diameter was measured at a total of 600 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as the CDU (nm). A smaller CDU value indicates that the variation in hole diameter over long periods is small and the result is good. A CDU of less than 2.8 nm was judged as "A" (excellent), a CDU of 2.8 nm or more and less than 3.0 nm was judged as "B" (good), and a CDU of 3.0 nm or more was judged as "C" (poor).

[0297] [Development Defect Count] A 25 nm contact hole pattern was formed by exposing a resist film with the optimal exposure dose, and this was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). The measured defects were then classified into those determined to be from the resist film and those determined to be from external foreign matter. The development defect count was determined as follows: if the number of defects determined to be from the resist film was less than 30, it was judged as "A" (very good); if it was between 30 and 50, it was judged as "B" (good); and if it was more than 50, it was judged as "C" (poor).

[0298]

[0299] As is clear from the results in Table 3, all of the radiation-sensitive compositions in the examples showed good performance in terms of sensitivity, CDU, and number of development defects.

[0300] The radiation-sensitive composition pattern formation method and radiation-sensitive acid generator of the present invention can improve sensitivity, CDU (Chronic Development Unit), and the number of development defects 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

1. A radiation-sensitive composition comprising a radiation-sensitive acid generator having an organic acid anion and an organic cation, a polymer containing a structural unit having an acid-dissociable group, and a solvent, wherein at least one selected from the group consisting of the above organic acid anion and the above organic cation comprises a substructure (i) represented by the following formula (i). (In formula (i), R １ (i) is a hydrogen atom, or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. (*) is a bond with a part other than the above substructure (i) in the radiation-sensitive acid generator.

2. In the above equation (i), R １ The radiation-sensitive composition according to claim 1, wherein is a hydrogen atom.

3. The radiation-sensitive composition according to claim 1 or 2, wherein the above-mentioned radiation-sensitive acid generator is a compound represented by the following formula (1). (In formula (1), W is a p+q valent organic group having 1 to 40 carbon atoms. M ＋ R is an organic cation having bonds with r phosphorus atoms in the formula. p is an integer from 0 to 3. q is an integer from 1 to 3. r is an integer from 0 to 3. If there are multiple r values, they can be either identical or distinct from one another. However, the sum of p and the q r values ​​is 1 or greater. １ This is equivalent to equation (i) above. R １ If multiple R １ They are either identical or different from one another.

4. The radiation-sensitive composition according to claim 3, wherein q is 1 in formula (1) above.

5. The radiation-sensitive composition according to claim 3, wherein in formula (1) above, p is 1 or 2 and r is 0.

6. The radiation-sensitive composition according to claim 3, wherein W in formula (1) above comprises a ring structure.

7. In formula (1) above, at least one -SO ３ - The radiation-sensitive composition according to claim 3, wherein an electron-withdrawing group is bonded to the carbon atom of W located at the α or β position relative to the sulfur atom.

8. In the above formula (1), at least one selected from the group consisting of W and M ＋ has an iodine group, and the radiation-sensitive composition according to claim 3.

9. M ＋ The radiation-sensitive composition according to claim 1 or 2, wherein is a radiation-sensitive sulfonium cation or a radiation-sensitive iodonium cation.

10. The radiation-sensitive composition according to claim 1 or 2, wherein the content of the above-mentioned radiation-sensitive acid generator is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the above-mentioned polymer.

11. The radiation-sensitive composition according to claim 1 or 2, wherein the polymer further comprises structural units having phenolic hydroxyl groups.

12. The radiation-sensitive composition according to claim 1 or 2, 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.

13. A pattern forming method comprising the steps of: applying the radiation-sensitive composition described in claim 1 or 2 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.

14. The pattern forming method according to claim 13, wherein the exposure is performed using extreme ultraviolet light or an electron beam.

15. A radiation-sensitive acid generator represented by the following formula (1). (In formula (1), R １ Each of these is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. １ If multiple R １ These are either identical or different from each other. W is a p+q valent organic group with 1 to 40 carbon atoms. M ＋ is an organic cation having bonds with r phosphorus atoms in the formula. p is an integer from 0 to 3. q is an integer from 1 to 3. r is an integer from 0 to 3. If there are multiple r values, they can be either identical or distinct from one another. However, the sum of p and the q r values ​​must be 1 or greater.

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