Radiation-sensitive resin composition and pattern forming method

Abstract

Provided are a radiation-sensitive resin composition and a pattern formation method, which enable exertion of sufficient levels of sensitivity and CDU performance when next generation technology is applied. This radiation-sensitive resin composition contains: at least one onium salt including an anion part of an organic acid and a cation part of an onium; a compound having a structure in which an alkoxycarbonyl group is bound to a nitrogen atom; and a solvent. At least a portion of the anion part of the organic acid in the onium salt includes an iodine-substituted aromatic ring structure. At least a portion of the cation part of the onium includes a fluorine-substituted aromatic ring structure.

Description

[Technical Field]

[0001] The present invention relates to a radiation-sensitive resin composition and a pattern forming method. [Background technology]

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the resin in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above uses short-wavelength radiation such as ArF excimer lasers, or combines this radiation with liquid immersion lithography to promote pattern miniaturization. Next-generation technologies are being developed that utilize even shorter-wavelength radiation such as electron beams, X-rays, and extreme ultraviolet (EUV), and resist materials containing acid generators with benzene rings that have improved radiation absorption efficiency are also being investigated (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-5224 Summary of the Invention [Problem to be solved by the invention]

[0005] The next-generation technologies mentioned above also require resist performance that is equal to or better than conventional ones in terms of sensitivity as well as critical dimension uniformity (CDU) performance, which is an index of uniformity in line width and hole diameter.

[0006] An object of the present invention is to provide a radiation-sensitive resin composition and a pattern forming method that can exhibit sufficient levels of sensitivity and CDU performance when next-generation technology is applied. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0008] In one embodiment, the present invention provides a composition comprising one or more onium salts containing an organic acid anion moiety and an onium cation moiety; a compound having a structure in which an alkoxycarbonyl group is bonded to a nitrogen atom; Solvent and Including, The present invention relates to a radiation-sensitive resin composition in which at least a portion of the organic acid anion moiety in the onium salt contains an iodine-substituted aromatic ring structure, and at least a portion of the onium cation moiety contains a fluorine-substituted aromatic ring structure.

[0009] This radiation-sensitive resin composition allows the construction of a resist film that satisfies the required sensitivity and CDU performance. While the reason for this is unclear, it is presumed to be as follows: Radiation such as EUV with a wavelength of 13.5 nm is highly absorbed by iodine atoms and fluorine atoms, thereby enhancing the sensitivity of the radiation-sensitive resin composition. Furthermore, the iodine-substituted aromatic ring structure contained in at least a portion of the organic acid anion moiety in the onium salt can reduce acid diffusion due to the large molecular weight of the iodine atom. Furthermore, compounds having a structure in which an alkoxycarbonyl group is bonded to a nitrogen atom exhibit an appropriate quencher function and can control acid diffusion. It is presumed that these combined effects enable the aforementioned resist performance to be achieved.

[0010] In another embodiment, the present invention provides a step of directly or indirectly applying the radiation-sensitive resin composition onto a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; The present invention relates to a pattern forming method comprising the steps of:

[0011] In this pattern formation method, the radiation-sensitive resin composition having excellent sensitivity and CDU performance is used, and therefore a high-quality resist pattern can be efficiently formed. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0013] 《Radiation-sensitive resin composition》 The radiation-sensitive resin composition according to this embodiment (hereinafter also simply referred to as the "composition") contains one or more specific onium salts, and further contains a compound and a solvent. It also contains a resin, if necessary. The composition may contain other optional components as long as they do not impair the effects of the present invention. By including the specific onium salt and compound, the radiation-sensitive resin composition can be endowed with high levels of sensitivity and CDU performance.

[0014] <Onium salt> The onium salt is a component that contains an organic acid anion moiety and an onium cation moiety and generates acid upon exposure. At least a portion of the organic acid anion moiety in the onium salt contains an iodine-substituted aromatic ring structure, and at least a portion of the onium cation moiety in the onium salt contains a fluorine-substituted aromatic ring structure, thereby achieving high sensitivity due to improved acid generation efficiency and excellent CDU performance due to acid diffusion controllability.

[0015] Although the form of the onium salt contained in the radiation-sensitive resin composition is not particularly limited, the onium salt is preferably at least one selected from the group consisting of a radiation-sensitive acid-generating resin containing a structural unit having the organic acid anion moiety and the onium cation moiety, a radiation-sensitive acid generator containing the organic acid anion moiety and the onium cation moiety, and an acid diffusion controller containing the organic acid anion moiety and the onium cation moiety and generating an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The different functions of these are explained below.

[0016] The acid generated by exposure of an onium salt is thought to have two functions in the radiation-sensitive resin composition, depending on the strength of the acid. The first function is to dissociate the acid-dissociable group of a structural unit of the resin containing the acid-dissociable group, thereby generating a carboxyl group or the like. An onium salt having this first function is called a radiation-sensitive acid generator. The second function is to inhibit the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas by salt exchange without substantially dissociating the acid-dissociable group of the resin under pattern formation conditions using the radiation-sensitive resin composition. An onium salt having this second function is called an acid diffusion controller. The acid generated from the acid diffusion controller can be said to be a relatively weaker acid (having a higher pKa) than the acid generated from the radiation-sensitive acid generator. Whether an onium salt functions as a radiation-sensitive acid generator or an acid diffusion controller depends on the energy required to dissociate the acid-dissociable group of the resin and the acidity of the onium salt. The radiation-sensitive acid generator may be contained in the radiation-sensitive resin composition in a form in which the onium salt structure exists as a compound by itself (isolated from a polymer), in which the onium salt structure is incorporated as part of a polymer, or in both of these forms. The form in which the onium salt structure is incorporated as part of a polymer is particularly referred to as a radiation-sensitive acid-generating resin.

[0017] When the radiation-sensitive resin composition contains the radiation-sensitive acid generator or the radiation-sensitive acid-generating resin, the polarity of the resin in the exposed area increases, and the resin in the exposed area becomes soluble in the developer in the case of development with an aqueous alkaline solution, while becoming poorly soluble in the developer in the case of development with an organic solvent.

[0018] Furthermore, by including the acid diffusion controller in the radiation-sensitive resin composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern that is superior in pattern developability and CDU performance.

[0019] In the radiation-sensitive resin composition, the organic acid anion moiety in at least one selected from the group consisting of the radiation-sensitive acid-generating resin, the radiation-sensitive acid generator, and the acid diffusion controller may contain the iodine-substituted aromatic ring structure. Furthermore, the onium cation moiety in at least one selected from the group consisting of the radiation-sensitive acid-generating resin, the radiation-sensitive acid generator, and the acid diffusion controller may contain the fluorine-substituted aromatic ring structure. Therefore, the iodine-substituted aromatic ring structure and the fluorine-substituted aromatic ring structure may be present in the same compound or in different compounds.

[0020] Regardless of the onium salt's incorporation form, the organic acid anion portion preferably has at least one anion selected from the group consisting of sulfonate anions, carboxylate anions, and sulfonimide anions. The onium cation preferably has at least one anion selected from the group consisting of sulfonium cations and iodonium cations. The onium salt can efficiently exhibit the above-described functions by combining these structures.

[0021] The acid generated upon exposure includes those which generate sulfonic acid, carboxylic acid, and sulfonimide upon exposure, corresponding to the above organic acid anions.

[0022] For example, the onium salt that gives a sulfonic acid upon exposure is (1) A compound having one or more fluorine atoms or fluorinated hydrocarbon groups bonded to a carbon atom adjacent to a sulfonate anion, (2) Compounds in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfonate anion Examples include:

[0023] Examples of onium salts that give carboxylic acids upon exposure include: (3) A compound having one or more fluorine atoms or fluorinated hydrocarbon groups bonded to a carbon atom adjacent to a carboxylate anion. (4) Compounds in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the carboxylate anion Examples include:

[0024] Among these, the radiation-sensitive acid generator or radiation-sensitive acid-generating resin is preferably one that falls under the above category (1), and the acid diffusion controller is preferably one that falls under the above category (2), (3), or (4), with the category (2) or (4) being particularly preferred.

[0025] <Radiation-sensitive acid-generating resin> The radiation-sensitive acid-generating resin contains a structural unit having an organic acid anion moiety and an onium cation moiety. The radiation-sensitive acid-generating resin preferably contains a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit a1") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit a2").

[0026] [ka]

[0027] In the formula, R A is a hydrogen atom or a methyl group. 1 is a single bond or an ester group. 2X is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. 2 X contains an iodine-substituted aromatic ring structure. 3 Rf is a single bond, an ether group, an ester group, or a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. 1 ~Rf 4 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. 3 ~R 7 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R 3 and R 4 and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 3 ~R 5 and at least one of R 6 ~R 7 At least one of each contains a fluorine-substituted aromatic ring structure.

[0028] R 3 ~R 7 In the formula (I), the monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonate ester groups.

[0029] The structural unit a1 and the structural unit a2 are preferably represented by the following formulae (a1-1) and (a2-1), respectively.

[0030] [ka]

[0031] In the formula, R A , R 3 ~R 7 , Rf 1 ~Rf 4 and X 1 has the same meaning as in formula (a1) or (a2). 8 is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy 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 of 0 to 4. n is an integer of 0 to 3.

[0032] Examples of the organic acid anion moiety of the monomer that gives the structural unit a1 or a2 include, but are not limited to, those shown below. Note that all of the organic acid anion moieties shown below have an iodine-substituted aromatic ring structure, but as an organic acid anion moiety that does not have an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] The onium cation portion of the structural unit a1 is preferably represented by the following formula (Q-1).

[0041] [ka]

[0042] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra3 represents a fluorine atom or a group having one or more fluorine atoms. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring. When n1 is 1 or greater and n2 is 1 or greater, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom).

[0043] The substituents represented by Ra1 and Ra2 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom, or a halogenated hydrocarbon group.

[0044] The alkyl groups of Ra1 and Ra2 may be linear or branched. The alkyl groups preferably have 1 to 10 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl. Of these, methyl, ethyl, n-butyl, and t-butyl are particularly preferred.

[0045] The cycloalkyl groups of Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0046] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl group of Ra1 and Ra2. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0047] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0048] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy groups of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0049] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred examples of these alkylsulfonyl groups or cycloalkylsulfonyl groups include a methanesulfonyl group, an ethanesulfonyl group, an n-propanesulfonyl group, an n-butanesulfonyl group, a cyclopentanesulfonyl group, and a cyclohexanesulfonyl group.

[0050] Each of the groups Ra1 and Ra2 may further have a substituent, such as a halogen atom such as a fluorine atom (preferably a fluorine atom), a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0051] Examples of the halogen atom for Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.

[0052] The halogenated hydrocarbon groups of Ra1 and Ra2 are preferably halogenated alkyl groups. Examples of the alkyl groups and halogen atoms constituting the halogenated alkyl groups are the same as those described above. Among these, fluorinated alkyl groups are preferred, and CF3 is more preferred.

[0053] As described above, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 be bonded to each other to form a single bond or a divalent linking group. Examples of divalent linking groups include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO2-, alkylene groups, cycloalkylene groups, alkenylene groups, or combinations of two or more of these, and those having a total carbon number of 20 or less are preferred. When Ra1 and Ra2 are bonded to each other to form a ring, it is preferable that Ra1 and Ra2 be bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO2-, or a single bond. Among these, it is more preferable to form -O-, -S-, or a single bond, and it is particularly preferable to form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1s may be bonded to each other to form a ring, and when n2 is 2 or more, multiple Ra2s may be bonded to each other to form a ring. An example of such a case is when two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are attached.

[0054] Ra3 is a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, such as CF3, C2F5, C3F7, C4F9, and C5F 11 , C6F 13 , C7F 15 , C8F 17 , CH2CF3, CH2CH2CF3, CH2C2F5, CH2CH2C2F5, CH2C3F7, CH2CH2C3F7, CH2C4F9 and CH2CH2C4F9 are more preferred, and CF3 is particularly preferred.

[0055] Ra3 is preferably a fluorine atom or CF3, more preferably a fluorine atom.

[0056] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0057] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0058] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, it is preferable that n3=1 and Ra3 is a fluorine atom or CF3. When (n1+n2+n3) is 2, it is preferable that n1=n3=1 and Ra1 and Ra3 are each independently a fluorine atom or CF3, and it is preferable that n3=2 and Ra3 is a fluorine atom or CF3. When (n1+n2+n3) is 3, it is preferable that n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom or CF3. When (n1+n2+n3) is 4, it is preferable that n1=n3=2 and Ra1 and Ra3 are each independently a fluorine atom or CF3. When (n1+n2+n3) is 5, the following combinations are preferred: n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom or CF3; n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom or CF3; and n3=5, and Ra3 are each independently a fluorine atom or CF3. When (n1+n2+n3) is 6, the following combinations are preferred: n1=n2=n3=2, and Ra1 to Ra3 are each independently a fluorine atom or CF3.

[0059] Specific examples of such onium cation moieties represented by the above formula (Q-1) include the following: All of the following are sulfonium cation moieties having a fluorine-substituted aromatic ring structure, but as onium cation moieties that do not have a fluorine-substituted aromatic ring structure, structures in which the fluorine atom or CF3 in the following formula is substituted with an atom or group other than a fluorine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0060] [ka]

[0061] [ka]

[0062] When the onium cation moiety of the structural unit a2 contains a fluorine-substituted aromatic ring structure, the onium cation moiety is preferably a diaryliodonium cation having one or more fluorine atoms, and is particularly preferably represented by the following formula (Q-2):

[0063] [ka]

[0064] In the formula, R d1 and R d2 R are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a nitro group. d3 and R d4 are each independently a fluorine atom or a group having a fluorine atom. k1 and k2 are each independently an integer of 0 to 5. k3 and k4 are each independently an integer of 0 to 5, provided that (k1+k3) and (k2+k4) are each 5 or less, and (k3+k4) is an integer of 1 to 10. R d1 ~R d4 If there are multiple R d1 ~R d4 may be the same or different.

[0065] R d1 and R d2 Alkyl groups, alkoxy groups and alkoxycarbonyl groups represented by the formula: d3 and R d4 Examples of the group having a fluorine atom represented by the formula (Q-1) include the same as those represented by the formula (Q-1) above.

[0066] Examples of the monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl and phenethyl.

[0067] Examples of the substituent on each group include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or a group in which the hydrogen atom of any of these groups has been substituted with a halogen atom; and an oxo group (=O).

[0068] Each of k1 and k2 is preferably 0 to 2, and more preferably 0 or 1. Each of k3 and k4 is preferably 1 to 3, and more preferably 1 or 2. (k3+k4) is an integer of 1 to 10, preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and even more preferably 1 or 2.

[0069] Specific examples of such onium cation moieties represented by the above formula (Q-2) include the following: All of the following are iodonium cation moieties having a fluorine-substituted aromatic ring structure, but as onium cation moieties that do not have a fluorine-substituted aromatic ring structure, structures in which the fluorine atom or CF3 in the following formula is substituted with an atom or group other than a fluorine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0070] [ka]

[0071] The content of the structural unit a1 or the structural unit a2 (the total content when multiple types are included) is preferably 2 mol% or more, more preferably 3 mol% or more, even more preferably 4 mol% or more, and particularly preferably 5 mol% or more, based on all structural units constituting the radiation-sensitive acid-generating resin. Also, it is preferably 30 mol% or less, more preferably 25 mol% or less, even more preferably 20 mol% or less, and particularly preferably 15 mol% or less. By keeping the content of the structural unit a1 or the structural unit a2 within the above range, the function as an acid generator can be fully exhibited.

[0072] The monomer that provides the structural unit a1 or a2 can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0073] The radiation-sensitive acid-generating resin can also function as a base resin. In this case, the radiation-sensitive acid-generating resin preferably contains a structural unit having an acid-dissociable group. The structural unit having an acid-dissociable group is preferably a structural unit represented by the following formula (b1) (hereinafter also referred to as structural unit b1) or a structural unit represented by the following formula (b2) (hereinafter also referred to as structural unit b2).

[0074] [ka]

[0075] In the formula, R A are each independently a hydrogen atom or a methyl group. 1 Y is a single bond, a phenylene group, a naphthylene group, or a linking group having 1 to 12 carbon atoms and containing at least one selected from an ester group and a lactone ring. 2 is a single bond or an ester group. 11 and R 12 R is each independently an acid-dissociable group. 13 R is a halogen atom, a trifluoromethyl group, a cyano group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an acyl group, an acyloxy group or an alkoxycarbonyl group having 2 to 7 carbon atoms.14 represents a single bond or an alkylene group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether group or an ester group. p is 1 or 2. q is an integer of 0 to 4.

[0076] Examples of the structural unit b1 include, but are not limited to, those shown below. A and R 11 is the same as above.

[0077] [ka]

[0078] Examples of the structural unit b2 include, but are not limited to, those shown below. A and R 12 is the same as above.

[0079] [ka]

[0080] In formulas (b1) and (b2), R 11 and R 12 Examples of the acid-dissociable group represented by the formula (I) include those described in JP-A Nos. 2013-80033 and 2013-83821.

[0081] Typical examples of the acid-dissociable group include those represented by the following formulae (AL-1) to (AL-3).

[0082] [ka]

[0083] In formulas (AL-1) and (AL-2), R 21 and R 24R is a monovalent hydrocarbon group having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, such as a branched or cyclic alkyl group, and may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. 22 and R 23 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, such as a linear, branched, or cyclic alkyl group, and may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. 22 , R 23 and R 24 Any two of the above may be bonded to each other to form a ring, particularly an alicyclic ring, having 3 to 20 carbon atoms, preferably 4 to 16 carbon atoms, together with the carbon atom or the carbon atom and oxygen atom to which they are bonded. k is an integer of 1 to 5.

[0084] In formula (AL-3), R 25 , R 26 and R 27 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, such as a linear, branched, or cyclic alkyl group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. 25 , R 26 and R 27 Any two of these may be bonded to each other to form, together with the carbon atom to which they are bonded, a ring, particularly an alicyclic ring, having 3 to 20 carbon atoms, preferably 4 to 16 carbon atoms.

[0085] The content of the structural unit b1 or the structural unit b2 (the total content when multiple types are included) is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, and particularly preferably 35 mol% or more, based on all structural units constituting the radiation-sensitive acid-generating resin. Also, it is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less. By setting the content of the structural unit b1 or the structural unit b2 within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0086] When the radiation-sensitive acid-generating resin also functions as a base resin, it preferably further contains a structural unit c having a phenolic hydroxyl group. Examples of monomers that provide the structural unit c include, but are not limited to, the following. In the following formula, R A is the same as above.

[0087] [ka]

[0088] The content of structural unit c (the total content when multiple types are included) is preferably 5 mol% or more, more preferably 8 mol% or more, even more preferably 10 mol% or more, and particularly preferably 15 mol% or more, based on all structural units constituting the radiation-sensitive acid-generating resin. Also, it is preferably 50 mol% or less, more preferably 45 mol% or less, even more preferably 40 mol% or less, and particularly preferably 35 mol% or less. By setting the content of structural unit c within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0089] When the radiation-sensitive acid-generating resin also functions as a base resin, it may further contain a structural unit d containing an alcoholic hydroxyl group, a carboxyl group, a lactone ring, a sultone ring, an ether group, an ester group, a carbonyl group, or a cyano group as an adhesive group. Examples of monomers that provide the structural unit d include, but are not limited to, those shown below. In the following formula, R A is the same as above.

[0090] [ka]

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] [ka]

[0098] [ka]

[0099] The content of structural unit d (the total content when multiple types are included) is preferably 5 mol% or more, more preferably 8 mol% or more, even more preferably 10 mol% or more, and particularly preferably 15 mol% or more, based on the total structural units constituting the radiation-sensitive acid-generating resin. Also, it is preferably 60 mol% or less, more preferably 50 mol% or less, even more preferably 40 mol% or less, and particularly preferably 35 mol% or less. By keeping the content of structural unit d within the above range, pattern adhesion can be further improved.

[0100] The radiation-sensitive acid-generating resin can be synthesized, for example, by polymerizing a monomer that provides the structural unit described above in an organic solvent with a radical polymerization initiator by heating. Known polymerization initiators can be used for the polymerization.

[0101] When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, acetoxystyrene or acetoxyvinylnaphthalene may be used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy groups may be deprotected by the alkaline hydrolysis to form hydroxystyrene units or hydroxyvinylnaphthalene units.

[0102] The radiation-sensitive acid-generating resin preferably has a weight-average molecular weight (Mw) of 1,000 or more, more preferably 2,000 or more, as measured by gel permeation chromatography (GPC) using THF as a solvent, relative to polystyrene standards. The weight-average molecular weight (Mw) is also preferably 50,000 or less, more preferably 30,000 or less. When the Mw is within the above range, the resist material exhibits good pattern formability and heat resistance.

[0103] Furthermore, if the molecular weight distribution (Mw / Mn) of the radiation-sensitive acid-generating resin is broad, the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the pattern shape may be deteriorated. As the pattern rule becomes finer, the effects of Mw and molecular weight distribution tend to become greater. Therefore, in order to obtain a resist material that is suitable for fine pattern dimensions, it is preferable that the molecular weight distribution of the radiation-sensitive acid-generating resin is narrow, i.e., 1.0 to 2.0, and particularly 1.0 to 1.7.

[0104] The radiation-sensitive acid-generating resin may contain two or more polymers having different composition ratios, Mws, and molecular weight distributions.

[0105] When the radiation-sensitive resin composition contains a radiation-sensitive acid-generating resin, the content of the radiation-sensitive acid-generating resin is preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the amount of the components other than the solvent contained in the radiation-sensitive resin composition. The content is preferably 99% by mass or less, more preferably 95% by mass or less.

[0106] <Radiation-sensitive acid generator> The radiation-sensitive acid generator contains an organic acid anion moiety and an onium cation moiety and is preferably represented by the following formula (A-1) or (A-2).

[0107] [ka]

[0108] In formulas (A-1) and (A-2), L 1 is a single bond, an ether bond or an ester bond, or an alkylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The alkylene group may be linear, branched or cyclic.

[0109] R 1 is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or is an alkyl group having 1 to 20 carbon atoms, an alkoxy ...carbonyl group having 2 to 10 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, or an alkylsulfonyloxy group having 1 to 20 carbon atoms, which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group, or an alkoxy group having 1 to 10 carbon atoms, or -NR 8 -C(=O)-R 9 or -NR 8 -C(=O)-OR 9 and R 8 is a hydrogen atom, or an alkyl group having 1 to 6 carbon atoms which may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms, and R 9 is an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms. The alkyl group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group, and alkenyl group may be linear, branched, or cyclic.

[0110] Of these, R 1 Examples include hydroxy groups, -NR 8 -C(=O)-R 9 fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0111] R 2 represents a single bond or a divalent linking group having 1 to 20 carbon atoms when p is 1, and represents a trivalent or tetravalent linking group having 1 to 20 carbon atoms when p is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0112] Rf 1 ~Rf 4 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. 1 and Rf 2 may combine to form a carbonyl group. 3 and Rf 4 are preferably both fluorine atoms.

[0113] R 3 , R 4 , R 5 , R 6 and R 7 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. When the onium cation moiety of the radiation-sensitive acid generator has fluorine, R 3 , R 4 and R 5 At least one of R contains one or more fluorine atoms, 6 and R 7 At least one of R contains one or more fluorine atoms. 3 , R 4 and R 5Any two of the above may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, alkynyl groups having 2 to 12 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms in these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0114] p is an integer that satisfies 1≦p≦3. q and r are integers that satisfy 0≦q≦5, 0≦r≦3, and 0≦q+r≦5. q is preferably an integer that satisfies 1≦q≦3, more preferably 2 or 3. r is preferably an integer that satisfies 0≦r≦2.

[0115] Examples of the organic acid anion moiety of the radiation-sensitive acid generator represented by the above formulas (A-1) and (A-2) include, but are not limited to, the following: All of the following are organic acid anion moieties having an iodine-substituted aromatic ring structure, but as organic acid anion moieties not having an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0116] [ka]

[0117] [ka]

[0118] [ka]

[0119]

change

[0120]

change

[0121]

change

[0122]

change

[0123]

change

[0124]

change

[0125]

change

[0126]

change

[0127]

change

[0128]

change

[0129]

change

[0130]

change

[0131]

change

[0132]

change

[0133]

change

[0134]

change

[0135]

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[0136]

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[0137]

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[0138]

change

[0139] As the onium cation moiety in the radiation-sensitive acid generator represented by the above formula (A-1) or (A-2), the onium cation moiety in the structural unit a1 and the structural unit a2 of the radiation-sensitive acid-generating resin can be suitably used.

[0140] The radiation-sensitive acid generators represented by the formulas (A-1) and (A-2) can be synthesized by known methods, particularly by salt exchange reactions. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0141] These radiation-sensitive acid generators may be used alone or in combination of two or more. The content of the radiation-sensitive acid generator is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the base resin (total amount when including the radiation-sensitive acid-generating resin and the resin described below). Furthermore, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 13 parts by mass or less, per 100 parts by mass of the resin. This allows for excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0142] <Acid diffusion control agent> The acid diffusion controller contains an organic acid anion moiety and an onium cation moiety, and upon irradiation with radiation, generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator. The acid diffusion controller is preferably represented by the following formula (S-1) or (S-2):

[0143] [ka]

[0144] In formulas (S-1) and (S-2), R 1 represents a hydrogen atom, a hydroxy group, a fluorine atom, a chlorine atom, an amino group, a nitro group, a cyano group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, or an alkylsulfonyloxy group having 1 to 4 carbon atoms, which may be substituted with a halogen atom, or -NR1A -C(=O)-R 1B or -NR 1A -C(=O)-OR 1B R 1A is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1B is an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 8 carbon atoms.

[0145] The alkyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, and cyclohexyl. Examples of the alkyl moiety of the alkoxy group having 1 to 6 carbon atoms, the acyloxy group having 2 to 7 carbon atoms, and the alkoxycarbonyl group having 2 to 7 carbon atoms include the same alkyl groups as those described above. Examples of the alkyl moiety of the alkylsulfonyloxy group having 1 to 4 carbon atoms include the alkyl groups described above with 1 to 4 carbon atoms. The alkenyl group having 2 to 8 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include vinyl, 1-propenyl, and 2-propenyl. Among these, R 1 Examples of the alkyl group include a fluorine atom, a chlorine atom, a hydroxy group, an amino group, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, and -NR 1A -C(=O)-R 1B , -NR 1A -C(=O)-OR 1B etc. are preferred.

[0146] R 3 , R 4 , R 5 , R 6 and R 7 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. When the onium cation moiety of the acid diffusion controller has a fluorine atom, R 3 , R 4 and R 5At least one of R contains one or more fluorine atoms, 6 and R 7 At least one of R contains one or more fluorine atoms. 3 , R 4 and R 5 Any two of the above may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, alkynyl groups having 2 to 12 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms in these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0147] L 1 is a single bond or a divalent linking group having 1 to 20 carbon atoms, which may contain an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, or a carboxy group.

[0148] m and n are integers that satisfy 0≦m≦5, 0≦n≦3, and 0≦m+n≦5, but are preferably integers that satisfy 1≦m≦3 and 0≦n≦2.

[0149] Examples of the organic acid anion moiety of the acid diffusion controller represented by the above formula (S-1) or (S-2) include, but are not limited to, those shown below. Note that all of the organic acid anion moieties shown below have an iodine-substituted aromatic ring structure, but as an organic acid anion moiety that does not have an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0150] [ka]

[0151] [ka]

[0152] [ka]

[0153] [ka]

[0154] [ka]

[0155] As the onium cation moiety in the acid diffusion controller represented by the above formulae (S-1) and (S-2), the onium cation moiety in the structural unit a1 and the structural unit a2 of the radiation-sensitive acid-generating resin can be suitably used.

[0156] The acid diffusion controllers represented by the formulas (S-1) and (S-2) can be synthesized by known methods, particularly by salt exchange reactions. Known acid diffusion controllers can also be used as long as they do not impair the effects of the present invention.

[0157] These acid diffusion controllers may be used alone or in combination of two or more. The content of the acid diffusion controller is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the content of the radiation-sensitive acid generator (when a radiation-sensitive acid-generating resin is included, the total content of the structural units a1 and a2 per 100 parts by mass of the radiation-sensitive acid-generating resin). Furthermore, the above content is preferably 100% by mass or less, more preferably 80% by mass or less, and even more preferably 60% by mass or less. This allows for excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0158] <Resin> When the onium salt is at least one selected from the group consisting of a radiation-sensitive acid generator and an acid diffusion controller, the resin is a component included as a base resin in the radiation-sensitive resin composition. The resin contains a structural unit having a phenolic hydroxyl group and a structural unit having an acid-dissociable group. The resin may further contain a structural unit containing a hydroxy group, a carboxy group, a lactone ring, an ether group, an ester group, a carbonyl group, or a cyano group other than the phenolic hydroxyl group. Specific examples of the structural units contained in the resin include structural units b1 and b2 other than the structural units a1 and a2 having an organic acid anion moiety and an onium cation moiety in the radiation-sensitive acid-generating resin, as well as structural units c and d. The content ratio of each structural unit in the resin is the same as that of the radiation-sensitive acid-generating resin, except that the structural units a1 and a2 of the radiation-sensitive acid-generating resin are not included.

[0159] The content of the resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the amount of the radiation-sensitive resin composition excluding the solvent.

[0160] (Method of synthesizing resin) The resin can be synthesized by the same method as used for synthesizing the radiation-sensitive acid-generating resin as the base resin.

[0161] <Other resins> The radiation-sensitive resin composition of this embodiment may contain, as another resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter also referred to as a "high-fluorine content resin"). When the radiation-sensitive resin composition contains a high-fluorine content resin, the high-fluorine content resin can be unevenly distributed in the surface layer of the resist film relative to the base resin, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to a desired state.

[0162] The high-fluorine content resin preferably has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit e"). In addition, for example, the resin may have structural units b1, b2, structural unit c, and even structural unit d of the base resin, as needed. [ka]

[0163] In the above formula (6), R 13 is a hydrogen atom, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH-, or -OCONH-. R 14 is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0164] Above R 13 As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit e, a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0165] Above G L As the group, from the viewpoint of copolymerizability of the monomer that provides the structural unit e, a single bond and -COO- are preferred, and -COO- is more preferred.

[0166] Above R 14 Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0167] Above R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0168] Above R 14As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a 5,5,5-trifluoro-1,1-diethylpentyl group, and a 1,1,1,2,2,3,3-heptafluoro-6-methylheptan-4-yl group are even more preferable.

[0169] When the high-fluorine-content resin has the structural unit e, the content of the structural unit e is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more, based on all structural units constituting the high-fluorine-content resin. Furthermore, the content is preferably 100 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less. By setting the content of the structural unit e within the above range, the mass content of fluorine atoms in the high-fluorine-content resin can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film.

[0170] The high-fluorine content resin may have a fluorine atom-containing structural unit represented by the following formula (f-1) (hereinafter also referred to as structural unit f) in addition to the structural unit e. By having the structural unit f, the high-fluorine content resin has improved solubility in an alkaline developer, and can suppress the occurrence of development defects. [ka]

[0171] The structural unit f is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R C R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. D is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R of this hydrocarbon group E Oxygen atom, sulfur atom, -NR ddR is a structure in which -, a carbonyl group, -COO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. dd is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0172] When the structural unit f has (x) an alkali-soluble group, R F is a hydrogen atom, and A 1 is an oxygen atom, -COO-* or -SO2O-*. * is R F The binding site of W is shown. 1 A is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. 1 is an oxygen atom, W 1 is A 1 is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R 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 may be the same or different. When the structural unit f has (x) an alkali-soluble group, it is possible to increase the affinity for an alkaline developer and suppress development defects. As the structural unit f having (x) an alkali-soluble group, A 1 is an oxygen atom and W 1 It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0173] When the structural unit f has (y) an alkali-dissociable group, R F is a monovalent organic group having 1 to 30 carbon atoms, and A 1 is an oxygen atom, -NR aa -, -COO-* or -SO2O-*. R aa is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R F The binding site of W is shown. 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 When is -COO-* or -S02O-*, W 1 or R F is A 1 A has a fluorine atom on the carbon atom bonded to or adjacent to A. 1 is an oxygen atom, W 1 , R E is a single bond, and R D R is a hydrocarbon group with 1 to 20 carbon atoms E A carbonyl group is bonded to the end of the 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 may be the same or different. When the structural unit f has (y) an alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkaline development step. As a result, the affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit f having (y) an alkali-dissociable group, A 1 is -COO-* and R F Or W 1 It is particularly preferred that both of them have a fluorine atom.

[0174] R C As the structural unit f, a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred, from the viewpoint of copolymerizability of the monomer that gives the structural unit f.

[0175] R E When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and more preferably a group having a norbornane lactone structure.

[0176] When the high-fluorine-content resin has the structural unit f, the content of the structural unit f is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, and particularly preferably 35 mol% or more, based on the total structural units constituting the high-fluorine-content resin. The content is preferably 90 mol% or less, more preferably 75 mol% or less, and even more preferably 60 mol% or less. By setting the content of the structural unit f within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0177] The Mw of the high fluorine content resin is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and particularly preferably 5,000 or more. The Mw is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and particularly preferably 15,000 or less.

[0178] The Mw / Mn of the high fluorine content resin is usually at least 1, and more preferably at least 1.1. The Mw / Mn is usually at most 5, preferably at most 3, more preferably at most 2.5, and even more preferably at most 2.2.

[0179] The content of the high-fluorine-content resin is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the base resin (total amount when including the radiation-sensitive acid-generating resin and the resin). The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. By setting the content of the high-fluorine-content resin within the above range, the high-fluorine-content resin can be more effectively distributed unevenly in the surface layer of the resist film, thereby suppressing elution from the upper part of the pattern during development and improving the rectangularity of the pattern. The radiation-sensitive resin composition may contain one or more high-fluorine-content resins.

[0180] (Method for synthesizing high fluorine content resin) The high fluorine content resin can be synthesized by the same method as the above-mentioned method for synthesizing the base resin.

[0181] <Compound> The radiation-sensitive resin composition preferably contains, as a quencher, a compound having a structure in which an alkoxycarbonyl group is bonded to a nitrogen atom, which can appropriately control the diffusion length of the generated acid and improve pattern formability and CDU performance.

[0182] The compound is preferably represented by the following formula (1): [ka] (In the above formula (1), R 1 is a branched alkyl group having 4 to 20 carbon atoms. R 2 and R 3 are each independently a hydrocarbon group having 1 to 20 carbon atoms, or R 2 and R 3 are combined together and together with the nitrogen atom to which they are attached represent a heterocyclic ring having 3 to 20 ring members.

[0183] R 1 The branched alkyl group having 4 to 20 carbon atoms represented by the formula (I) is preferably a tertiary alkyl group having 4 to 10 carbon atoms, more preferably a t-butyl group or a t-pentyl group.

[0184] R 2 and R 3 Examples of the hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0185] The chain hydrocarbon group having 1 to 20 carbon atoms includes a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 20 carbon atoms.

[0186] The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms includes a monocyclic or polycyclic saturated hydrocarbon group, or a monocyclic or polycyclic unsaturated hydrocarbon group. Preferred examples of the monocyclic saturated hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Preferred examples of the polycyclic cycloalkyl group include a bridged alicyclic hydrocarbon group such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are linked by a bond chain containing one or more carbon atoms.

[0187] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0188] R 2 and R 3 and the nitrogen atom to which they are bonded, may be combined, and examples of the heterocyclic ring having 3 to 20 ring members include an aziridine ring, an azirine ring, a diaziridine ring, an azetidine ring, a diazetidine ring, a pyrrolidine ring, a pyrrole ring, an imidazolidine ring, a pyrazolidine ring, an imidazole ring, a pyrazole ring, an oxazolidine ring, an isoxazolidine ring, an oxazole ring, an isoxazole ring, a thiazolidine ring, an isothiazolidine ring, a thiazole ring, an isothiazole ring, a piperidine ring, a pyridine ring, a piperazine ring, a diazine ring, a morpholine ring, an oxazine ring, a thiomorpholine ring, a thiazine ring, an azepane ring, an azepine ring, an indole ring, an isoindole ring, a benzimidazole ring, a benzotriazole ring, a quinoline ring, an isoquinoline ring, an acridine ring, and a carbazole ring, regardless of whether they are saturated or unsaturated.

[0189] Some or all of the hydrogen atoms in the heterocycle may be substituted with a substituent, such as a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group, or a group in which the hydrogen atoms of these groups are substituted with halogen atoms; a hydroxyalkyl group; or an oxo group (═O).

[0190] Examples of the compound represented by the above formula (1) include compounds represented by the following formulas (1-1) to (1-50).

[0191] [ka]

[0192] [ka]

[0193] [ka]

[0194] [ka]

[0195] The content of the compound is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, based on the content of the radiation-sensitive acid generator (when a radiation-sensitive acid-generating resin is included, the total content of the structural units a1 and a2 in 100 parts by mass of the radiation-sensitive acid-generating resin). The content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. By setting the content of the compound within the above range, appropriate acid diffusion controllability can be obtained, and CDU performance can be improved.

[0196] <Solvent> The radiation-sensitive resin composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt and base resin (at least one of the radiation-sensitive acid-generating resin and the resin), as well as optional additives.

[0197] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0198] Examples of alcohol-based solvents include: Monoalcohol solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents 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; Examples of suitable polyhydric alcohol solvents include partially etherified polyhydric alcohol solvents in which some of the hydroxy groups of the above polyhydric alcohol solvents have been etherified.

[0199] Examples of ether 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 (methyl phenyl ether); Examples of the polyhydric alcohol solvent include polyhydric alcohol ether solvents obtained by etherifying the hydroxy groups of the above polyhydric alcohol solvents.

[0200] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone: Examples include 2,4-pentanedione, acetonylacetone, and acetophenone.

[0201] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; Examples of the solvent include chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0202] Examples of ester solvents include: Monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate; 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; Examples of the solvent include polycarboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

[0203] Examples of hydrocarbon solvents include Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0204] Among these, ester-based solvents and ketone-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, cyclic ketone-based solvents and lactone-based solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone and γ-butyrolactone are even more preferred. The radiation-sensitive resin composition may contain one or more solvents.

[0205] <Other optional ingredients> The radiation-sensitive resin composition may contain other optional components in addition to the above components. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0206] <Method for preparing radiation-sensitive resin composition> The radiation-sensitive resin composition can be prepared, for example, by mixing an onium salt, a base resin (at least one of a radiation-sensitive acid-generating resin and a resin), a solvent, and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.2 μm. The solids concentration of the radiation-sensitive resin composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0207] <Pattern formation method> The pattern forming method in this embodiment includes: a step (1) of directly or indirectly applying the radiation-sensitive resin composition onto a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); A step (2) of exposing the resist film to light (hereinafter also referred to as the "exposure step"); and The method includes a step (3) of developing the exposed resist film (hereinafter also referred to as the "developing step").

[0208] According to the pattern forming method, a high-quality resist pattern can be formed because the radiation-sensitive resin composition has excellent sensitivity and CDU performance in the exposure step. Each step will be described below.

[0209] [Resist film formation process] In this step (step (1) above), a resist film is formed from the radiation-sensitive resin composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Application Laid-Open No. 59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 140°C, and preferably 80°C to 120°C. The PB time is typically 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0210] When performing immersion exposure, regardless of whether the radiation-sensitive resin composition contains a water-repellent polymer additive such as a high-fluorine-content resin, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-removable protective film that is removed with a solvent before the development step (see, for example, JP-A No. 2006-227632), or a developer-removable protective film that is removed simultaneously with development in the development step (see, for example, WO2005-069076 and WO2006-035790). However, from the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion exposure.

[0211] When the next exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a resin having the structural units b1, b2 and c, and optionally the structural unit d, as the base resin in the composition.

[0212] [Exposure process] In this step (step (2) above), the resist film formed in step (1), the resist film formation step, is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). The radiation used for exposure may be, depending on the line width of the desired pattern, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; or charged particle beams such as electron beams and alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0213] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser (wavelength 193 nm), water is preferred for its availability and ease of handling, in addition to the above considerations. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power 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.

[0214] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the resin or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 180°C, preferably 80°C to 130°C. The PEB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0215] [Development process] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0216] In the case of alkaline development, the developer used for the development may be, for example, 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, or 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, a TMAH aqueous solution is preferred, and a 2.38 mass % TMAH aqueous solution is more preferred.

[0217] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive resin composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent 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 the organic solvent in the developer include water and silicone oil.

[0218] Examples of development methods include a method in which a substrate is immersed in a tank filled with developer for a certain period of time (dip method), a method in which developer is piled up on the surface of the substrate by surface tension and left to stand for a certain period of time (puddle method), a method in which developer is sprayed onto the surface of the substrate (spray method), and a method in which developer is continuously dispensed onto a substrate rotating at a constant speed while a developer dispensing nozzle is scanned at a constant speed (dynamic dispense method). [Example]

[0219] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0220] The structures of onium salts 1 to 15 (hereinafter also referred to as "PAG1") used as radiation-sensitive acid generators (PAGs) in the radiation-sensitive resin compositions are shown below. PAGs 1 to 15 were synthesized by ion exchange between the ammonium salt of an iodinated aromatic ring structure-containing fluorinated sulfonic acid, which provides the organic acid anion moiety shown below, and a sulfonium chloride or iodonium chloride, which provides the onium cation moiety shown below.

[0221] [ka]

[0222] [ka]

[0223] [Synthesis Example] Synthesis of base resins (P-1 to P-7) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent, crystallized in methanol, and then repeatedly washed with hexane, isolated, and dried to obtain base resins P-1 to P-7 with the following compositions. 1 Mw and dispersity (Mw / Mn) were confirmed by H-NMR and GPC (solvent: THF, standard: polystyrene). In the formula below, the number attached to each structural unit indicates the content ratio of that structural unit (molar ratio; the total is 1). P-1: Mw=7,600, Mw / Mn=1.7 P-2: Mw=7,600, Mw / Mn=1.7 P-3: Mw=8,600, Mw / Mn=1.7 P-4: Mw=9,300, Mw / Mn=1.8 P-5: Mw=8,000, Mw / Mn=1.7 P-6: Mw=7,600, Mw / Mn=1.7 P-7: Mw=7,600, Mw / Mn=1.7

[0224] [ka]

[0225] [ka]

[0226] [Examples and Comparative Examples] A radiation-sensitive resin composition was prepared by dissolving each component in the composition shown in Table 1 in a solvent containing 100 ppm of FC-4430 (manufactured by 3M) as a surfactant, and filtering the resulting solution through a 0.2 μm filter. The components in Table 1 are as follows.

[0227] Organic solvents: PGMEA (Propylene Glycol Monomethyl Ether Acetate) GBL (γ-butyrolactone) CHN (cyclohexanone) PGME (Propylene Glycol Monomethyl Ether) DAA (diacetone alcohol)

[0228] Acid diffusion control agents Q-1 to Q-11 [ka]

[0229] [ka]

[0230] Compounds B-1~B-7 [ka]

[0231] High fluorine content resin F-1: Mw=8,900, Mw / Mn=2.0 [ka]

[0232] [EUV exposure evaluation] [Examples 1 to 16, Comparative Examples 1 to 4] Each radiation-sensitive resin composition listed in Table 1 was spin-coated onto a Si substrate on which a 20-nm-thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed. This was pre-baked for 60 seconds at 105°C using a hot plate to produce a 60-nm-thick resist film. This was then exposed using an ASML EUV scanner NXE3300 (NA 0.33, σ 0.9 / 0.6, quadruple-pole illumination, a mask with a hole pattern with a 46-nm pitch on the wafer and a +20% bias). PEB was performed for 60 seconds on a 100°C hot plate. Development was performed for 30 seconds using a 2.38% by mass TMAH aqueous solution to obtain a hole pattern with a dimension of 23 nm. The exposure dose required to form a hole with a dimension of 23 nm was measured, and this was used as the sensitivity. Furthermore, the dimensions of 50 holes were measured using a critical dimension SEM (CG5000) manufactured by Hitachi High-Technologies Corporation, and CDU (dimensional variation 3σ) was calculated. The results are shown in Table 1.

[0233] [Table 1]

[0234] The resist patterns formed through the above-described EUV exposure were evaluated, and as a result, the radiation-sensitive resin compositions of the examples were found to have good sensitivity and CDU performance. [Industrial Applicability]

[0235] The radiation-sensitive resin composition and the method for forming a resist pattern described above can form a resist pattern that has good sensitivity to exposure light and excellent CDU performance, and therefore can be suitably used in the fabrication processes of semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. one or more onium salts containing an organic acid anion moiety and an onium cation moiety; a compound having a structure in which an alkoxycarbonyl group is bonded to a nitrogen atom; Solvent and Including, at least one of the onium salts is a radiation-sensitive acid generator containing the organic acid anion moiety and the onium cation moiety; At least a portion of the organic acid anion moiety in the onium salt contains an iodine-substituted aromatic ring structure, and at least a portion of the onium cation moiety contains a fluorine-substituted aromatic ring structure; the content of the compound is 5% by mass or more and 50% by mass or less relative to the content of the radiation-sensitive acid generator, The radiation-sensitive resin composition is characterized in that the compound is represented by the following formula (1): 【Chemistry 1】 (In the above formula (1), R １ is a branched alkyl group having 4 to 20 carbon atoms. R ２ and R ３ are each independently a hydrocarbon group having 1 to 20 carbon atoms, or R ２ and R ３ are taken together and together with the nitrogen atom to which they are attached represent a heterocyclic ring having 3 to 20 ring members.

2. The onium salt is a radiation-sensitive acid-generating resin containing a structural unit having the organic acid anion moiety and the onium cation moiety; and an acid diffusion controller which contains the organic acid anion moiety and the onium cation moiety, and which generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation; 2. The radiation-sensitive resin composition according to claim 1, wherein the radiation-sensitive resin composition is at least one selected from the group consisting of:

3. 3. The radiation-sensitive resin composition according to claim 2, wherein the radiation-sensitive acid-generating resin further comprises a structural unit having a phenolic hydroxyl group and a structural unit having an acid-dissociable group.

4. 3. The radiation-sensitive resin composition according to claim 2, wherein the onium salt is at least one selected from the group consisting of the radiation-sensitive acid generator and the acid diffusion controller, and the radiation-sensitive resin composition further comprises a resin including a structural unit having a phenolic hydroxyl group and a structural unit having an acid-dissociable group.

5. the organic acid anion moiety in at least one selected from the group consisting of the radiation-sensitive acid-generating resin, the radiation-sensitive acid generator, and the acid diffusion controller contains the iodine-substituted aromatic ring structure; 3. The radiation-sensitive resin composition according to claim 2, wherein the onium cation moiety in at least one selected from the group consisting of the radiation-sensitive acid-generating resin, the radiation-sensitive acid generator, and the acid diffusion controller includes the fluorine-substituted aromatic ring structure.

6. The radiation-sensitive resin composition according to any one of claims 1 to 5, wherein the organic acid anion moiety has at least one anion selected from the group consisting of a sulfonate anion, a carboxylate anion, and a sulfonimide anion.

7. 7. The radiation-sensitive resin composition according to claim 1, wherein the onium cation is at least one selected from the group consisting of a sulfonium cation and an iodonium cation.

8. when the onium salt is at least one selected from the group consisting of the radiation-sensitive acid-generating resin and the radiation-sensitive acid generator, the organic acid anion moiety has a sulfonate anion, 8. The radiation-sensitive resin composition according to claim 2, wherein a fluorine atom or a fluorinated hydrocarbon group is bonded to a carbon atom adjacent to the sulfonate anion.

9. The organic acid anion portion of the acid diffusion controller has a sulfonate anion or a carboxylate anion (provided that, when the organic acid anion has the sulfonate anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfonate anion).

8. The radiation-sensitive resin composition according to any one of claims 2 to 7.

10. a step of directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 9 onto a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; A pattern forming method comprising:

11. The pattern forming method according to claim 10, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

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