Radiation-sensitive composition and pattern forming method

Abstract

The present invention provides: a radiation-sensitive composition which is excellent in terms of sensitivity, CDU, and process margin during the formation of a pattern; and a pattern forming method. This radiation-sensitive composition contains a solvent and a polymer which has an iodine group and contains a structural unit (I) that has an acid dissociable group. At least the radiation-sensitive composition contains a radiation-sensitive acid generator which includes a partial structure represented by formula (a), or the polymer contains a structural unit (II) that includes a partial structure represented by formula (a). (In formula (a), R1 is a nitro group, a cyano group, a carboxy group, an iodine atom, an amino group, an alkyl group, an acyl group, or an alkoxycarbonyl group; in cases where there are a plurality of R1 moieties, the plurality of R1 moieties are the same as or different from each other; L1 is -O-, -S-, -SO-, or -SO2-;　m is 0 or 1; n1 is an integer of 1 to (2m + 4), and n2 is an integer of 0 to (2m + 3), wherein the relationship n1 + n 2 ≤ 2m + 4 is satisfied; * is an atomic bond in the corresponding polymer or radiation-sensitive acid generator to another moiety; and Z+ is a monovalent onium cation.)

Description

Radiation-sensitive composition and pattern forming method

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

[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 polymer 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. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] As patterns become finer, there is a demand for highly precise control of acid diffusion, and development of acid generators, which are components of resist materials, is also progressing (Japanese Patent Application Laid-Open No. 2023-109701).

[0005] Japanese Patent Application Laid-Open No. 2023-109701

[0006] Recently, in photolithography using EUV or the like, there is a demand for an expansion of the process window. This demand is particularly strong in the formation of hole patterns, but there is a risk of holes connecting to each other on the high exposure dose side, and of holes shrinking in size or becoming filled in on the low exposure dose side. In other words, there is a demand for radiation-sensitive compositions that have improved CDU on both the high and low exposure dose sides and are excellent in process margin.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that are excellent in sensitivity, CDU, and process margin during pattern formation.

[0008] 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.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer having an iodine group and including a structural unit (I) having an acid-dissociable group; and a solvent, wherein the radiation-sensitive composition contains at least a radiation-sensitive acid generator having a partial structure represented by the following formula (a) (hereinafter also referred to as "partial structure (a)"), or the polymer contains a structural unit (II) having a partial structure represented by the following formula (a): (In formula (a), R １ R is a nitro group, a cyano group, a carboxy group, an iodine atom, an amino group, an alkyl group, an acyl group, or an alkoxycarbonyl group. １ If there are multiple R １ are the same or different. １ represents -O-, -S-, -SO- or -SO ２ -. m is 0 or 1. n １ is an integer from 1 to (2m+4). ２ is an integer from 0 to (2m+3), where n １ +n ２ The relationship of ≦2m+4 is satisfied. * represents a bond to another moiety in the corresponding polymer or radiation-sensitive acid generator. Z ＋ is a monovalent onium cation.

[0010] The radiation-sensitive composition can exhibit excellent sensitivity, CDU, and process margin during resist pattern formation. Although the reason for this is not clear, it is presumed to be as follows.

[0011] The iodine groups contained in the polymer have a high absorption of radiation such as EUV having a wavelength of 13.5 nm, which increases the efficiency of secondary electron generation and makes the resulting resist film highly sensitive.

[0012] The present inventors have found that -SO ３ －The present inventors have discovered that resist patterns with good CDUs can be formed at high exposure doses when using an acid generator that generates an acid with lower acidity than acid generators in which a fluorine atom or a fluorinated hydrocarbon group is bonded to a carbon atom to which the fluorine atom is bonded. Furthermore, when the polymer contains an iodine group, resist patterns with good CDUs can be formed at low exposure doses. One of the reasons for this is thought to be that the weak acidity of the generated acid suppresses dissociation of excess acid-dissociable groups at high exposure doses, while the high secondary electron generation efficiency generates sufficient acid for pattern formation at low exposure doses. In this radiation-sensitive composition, the partial structure (a) is incorporated into the polymer or radiation-sensitive acid generator as an acid-generating structure that generates acid upon exposure. The acid generated from the partial structure (a) has appropriate acidity, resulting in excellent CDUs at high exposure doses. Furthermore, the inclusion of an iodine group in the polymer results in excellent CDUs at low exposure doses. This allows the radiation-sensitive composition to exhibit excellent CDUs over a wide range of exposure doses during pattern formation.

[0013] It is presumed that the above resist performance can be achieved by the combined effects of these factors.

[0014] In the above formula (1), R １ , L １ , S.O. ３ － and F may be bonded to the other ring instead of only to one of the rings to which they are bonded. For example, in the case of a naphthalene ring where m is 1, the naphthalene ring can be considered as a ring in which two benzene rings are condensed. In the above formula (1), R １ and L １ is bonded to the left benzene ring among the benzene rings constituting the naphthalene ring, but may also be bonded to the right benzene ring. ３ － and similarly for F.

[0015] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

[0016] This pattern formation method uses the above-mentioned radiation-sensitive composition, which is capable of exhibiting excellent sensitivity, CDU, and process margin when forming a resist pattern, and therefore can efficiently form a high-quality resist pattern.

[0017] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0018] Radiation-Sensitive Composition The radiation-sensitive composition (hereinafter also simply referred to as the "composition") according to this embodiment contains a polymer (hereinafter also referred to as the "base polymer") and a solvent. The composition satisfies at least the following condition (α) or (β): Condition (α): The composition contains a radiation-sensitive acid generator containing the partial structure (a). Condition (β): The base polymer contains a structural unit (II) containing the partial structure (a). In other words, when the composition does not contain a radiation-sensitive acid generator, the partial structure (a) is contained as part of the base polymer. When the composition contains a radiation-sensitive acid generator, the partial structure (a) may be contained as part of the radiation-sensitive acid generator, as part of the base polymer, or as part of both the radiation-sensitive acid generator and the base polymer. The composition may contain other optional components as long as the effects of the present invention are not impaired. Hereinafter, an embodiment in which the composition contains a radiation-sensitive acid generator and the partial structure (a) is contained as part of both the radiation-sensitive acid generator and the base polymer will be described.

[0019] <Polymer> The polymer (i.e., base polymer) is an assembly of polymer chains having an iodine group and further including the structural unit (I), the structural unit (II), and the structural unit (III). In addition to these structural units, the base polymer may also include a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (III)") and a structural unit containing a lactone structure or the like (hereinafter also referred to as "structural unit (IV)").

[0020] By incorporating iodine groups into the base polymer, the radiation absorption efficiency increases, and the secondary electron generation efficiency increases, thereby improving sensitivity.

[0021] The form in which the base polymer contains an iodine group is not particularly limited, but in the base polymer, the acid-dissociable group preferably contains an iodine group.

[0022] The base polymer preferably contains an iodo group in the form of an iodo group-containing aromatic ring structure. The iodo group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in an aromatic ring are substituted with iodo groups. One or more of the structural units constituting the base polymer may contain an iodo group-containing aromatic ring structure.

[0023] In particular, the acid-dissociable group preferably contains an iodine group-containing aromatic ring structure. Generally, the introduction of an iodine group tends to reduce removability with a developer. In contrast, the acid-dissociable group dissociates with acid upon exposure to generate an acid group, which is easily removed during development. By introducing an iodine group or an iodine group-containing aromatic ring structure into the acid-dissociable group that is easily removed during development, good development defect suppression properties can be achieved.

[0024] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0025] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0026] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The acid generated from the structural unit (II) of the polymer upon exposure dissociates the acid-dissociable group in the structural unit (I), generating a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0027] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. In the base polymer, it is preferable that the acid-dissociable group contains the above-mentioned iodine group-containing aromatic ring structure. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0028] (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a divalent linking group. １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a 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 together with the carbon atoms to which they are bonded. １Ａ and R １Ｂ There is no case where both of Ar and Ar are hydrogen atoms. １ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１are the same or different. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p+q is 5 or less.

[0029] L １ Examples of the divalent linking group represented by the formula (I) include a divalent hydrocarbon group such as an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, or an arenediyl group, a divalent heteroatom-containing group, a group in which the divalent heteroatom-containing group is incorporated between the carbon-carbon bonds of the divalent hydrocarbon group, or a group combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the divalent heteroatom-containing group include -CO-, -CS-, -O-, -S-, and -SO ２ -, -NR'-, or a combination of two or more of these. Some or all of the hydrogen atoms of these groups may be substituted with 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 atoms of these groups are substituted with halogen atoms.

[0030] L １Examples of the alkyl group as a substituent include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group.

[0031] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0032] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0033] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0034] Examples of the arenediyl group include a phenylene group, a tolylene group, a naphthylene group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0035] L １ The divalent linking group represented by the formula (I) is preferably an alkanediyl group or an arenediyl group, more preferably an alkanediyl group having 1 to 4 carbon atoms or an arenediyl group having 6 to 10 carbon atoms, and even more preferably a methanediyl group or a benzenediyl group.

[0036] R １Ａ and R １Ｂ Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 10 carbon atoms include alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0037] R １Ａ and R １ＢExamples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups are cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic cycloalkyl groups are bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl groups. Note that a 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 linking group containing one or more carbon atoms.

[0038] R １Ａ and R １Ｂ As the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0039] R １Ａ and R １Ｂ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R １Ａ and R １Ｂ are combined together together with the carbon atoms to which they are bonded, a divalent alicyclic group having 3 to 20 carbon atoms is preferred, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms is more preferred, and a methyl group, an ethyl group, a cyclopentanediyl group, or a cyclohexanediyl group is even more preferred.

[0040] Ar １ As the aromatic ring in the above, the aromatic ring in the iodo group-containing aromatic ring structure can be suitably used. １ The aromatic ring in Ar is preferably a benzene ring, a thiophene ring or a furan ring, and more preferably a benzene ring.１ The aromatic ring having 5 to 20 ring members and a valence of (p+q+1) is represented by the above Ar １ A group in which (p+q+1) hydrogen atoms have been removed from the aromatic ring of the formula (I) can be suitably used.

[0041] R １０１ The alkoxy group represented by the formula (1) is １ Examples of the alkoxy groups include those shown as the substituents of the above.

[0042] p is preferably 1 or 2. q is preferably 0 or 1.

[0043] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0044]

[0045] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0046] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0047] Specific examples of the structural unit (I) (including the structural unit (I-1)) are not particularly limited, but include structures represented by the following formulae (1-1) to (1-51).

[0048]

[0049]

[0050]

[0051]

[0052] In the formula, R α is synonymous with the above formula (1).

[0053] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved. When the acid-dissociable group has an iodine group, sensitivity can be further improved.

[0054] (Structural Unit (II)) The structural unit (II) contains the partial structure (a). The partial structure (a) has an onium salt structure formed from a sulfonate anion and an onium cation, and generates an acid that dissociates the acid-dissociable group upon exposure. That is, the partial structure (a) functions as a radiation-sensitive acid-generating structure. When the base polymer contains the partial structure (a), the polarity of the base polymer in the exposed area increases, making it soluble in the developer in the case of aqueous alkaline development, but sparingly soluble in the developer in the case of organic solvent development.

[0055] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0056] R in the above formula (a) １ The alkyl group, acyl group and alkoxycarbonyl group represented by the formula (1) are each １ The alkyl group, acyl group and alkoxycarbonyl group shown as the substituents in the above can be preferably used.

[0057] L １ is preferably —O— or —S—, and more preferably —O—.

[0058] When m is 0, n １ is preferably an integer of 2 to 4, more preferably 3 or 4, and even more preferably 4.

[0059] When m is 0, n ２is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0060] When m is 1, n １ is preferably an integer of 4 to 6, more preferably 5 or 6, and even more preferably 6.

[0061] When m is 1, n ２ is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0062] In particular, in the above formula (a), m is 0, and n １ is 4, and n ２ is preferably 0.

[0063] In the above formula (a), m is 0, and -L １ -Ha-SO ３ － It is preferred that the amino acid be present in the p-position of

[0064] The monovalent onium cation may be a radioactive onium cation. Examples of the radioactive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0065] The onium cation preferably has an iodo group. The onium cation preferably contains the iodo group-containing aromatic ring structure.

[0066] The onium cation in the structural unit (II) is preferably a fluoro-group-containing onium cation having a fluoro group. The fluoro-group-containing onium cation preferably has a fluoro-group-containing aromatic ring structure. The fluoro-group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. As the aromatic ring in the fluoro-group-containing aromatic ring structure, an aromatic ring in an iodine-group-containing aromatic ring structure can be suitably used. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0067] Although the form of inclusion of the partial structure (a) in the structural unit (II) of the base polymer is not particularly limited, from the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer has the above-mentioned sulfonate anion as a side chain moiety. "Having as a side chain moiety" means that the corresponding sulfonate anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. In this case, the onium cation is ionic bonded to the sulfonate anion as a counter ion of the sulfonate anion.

[0068] The structural unit (II) is preferably a structural unit represented by the following formula (A1).

[0069] (In formula (A1), R Ｍ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １１ is a divalent linking group. １ , L １ , Z ＋ , m, n １ and n ２ has the same meaning as the above formula (1).

[0070] L １１ The divalent linking group represented by the formula (1) is L １ Among them, divalent linking groups represented by the following formula (I) can be preferably used. １１ The divalent linking group represented by the formula (I) is preferably an alkanediyl group, an arenediyl group, —CO—, —O—, or a combination thereof.

[0071] Examples of the sulfonate anion of the monomer that provides the structural unit (II) include, but are not limited to, the structures shown in the following formulae (A1-1) to (A1-18). Ｍ is synonymous with the above.

[0072]

[0073]

[0074] The onium cation of the above formula (A1) is preferably represented by the following formula (Q-1):

[0075]

[0076] 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 substituent. 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.

[0077] The substituents represented by Ra1, Ra2 and Ra3 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.

[0078] 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.

[0079] The cycloalkyl group of Ra1 and Ra2 includes a monocyclic or polycyclic cycloalkyl group (preferably a cycloalkyl group 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.

[0080] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl groups 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.

[0081] 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.

[0082] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy group of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0083] 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 of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups.

[0084] 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.

[0085] 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 and an iodine atom being preferred.

[0086] The halogenated hydrocarbon group of Ra1 and Ra2 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0087] 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 are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２-, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable that they form - or a single bond. Among these, it is more preferable that they form -O-, -S- or a single bond, and it is particularly preferable that they form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0088] Ra3 is preferably a fluorine atom, an iodine 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, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ are particularly preferred.

[0089] Ra3 is a fluorine atom, an iodine atom, or CF ３ is preferred, and a fluorine atom or an iodine atom is more preferred.

[0090] n1 and n2 each independently represent preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

[0091] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0092] (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, n3=1 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0093] Specific examples of such onium cations represented by the above formula (Q-1) include the following: The fluorine atom or iodine atom in the onium cations below may be substituted with a hydrogen atom or another substituent.

[0094]

[0095]

[0096]

[0097]

[0098] The monovalent onium cation may be a substituted or unsubstituted diaryl iodonium cation. The aryl group is Ar in the above formula (1). １ The aryl group is preferably a phenyl group. When the aryl group has a substituent, the substituent may be L in the above formula (1). １ The aryl group preferably has one or more fluorine atoms or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluoro group-containing aromatic ring structure or an iodo group-containing aromatic ring structure.

[0099] Specific examples of such iodonium cations include the following:

[0100]

[0101] The structural unit (II) having the above structures in combination can efficiently exhibit the above functions.

[0102] When the base polymer contains the structural unit (II), the lower limit of the content of the structural unit (II) (when multiple types are contained, the total content) is preferably 1 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 content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.By setting the content of the structural unit (II) within the above range, it can fully exhibit its function as an acid generating structure and exhibit the above resist properties.

[0103] The monomer that provides the structural unit (II) 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.

[0104] (Structural Unit (III)) The structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to the structural unit (I)). When the polymer contains the structural unit (III), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (III) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (III) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beams or EUV. The structural unit (III) is preferably represented by the following formula (2):

[0105] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０２R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0106] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (III), it is preferable that the alkyl group is a hydrogen atom or a methyl group.

[0107] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0108] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the formula (1) is preferably L １ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0109] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0110] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0111] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0112] The structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-20) (hereinafter also referred to as "structural unit (III-1) to structural unit (III-20)").

[0113]

[0114]

[0115] In the above formulas (2-1) to (2-20), R β is the same as the above formula (2).

[0116] The lower limit of the content of the structural unit (III) (total content when multiple types of structural unit (III) are present) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can further improve the sensitivity and development contrast.

[0117] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (III) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0118] (Structural Unit (IV)) The structural unit (IV) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (IV), the base polymer can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0119] When the base polymer contains the structural unit (IV), the lower limit of the content of the structural unit (IV) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of the structural unit (IV) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0120] (Structural Unit (V)) The base polymer optionally has other structural units. Examples of the other structural units include a structural unit (V) containing a polar group (excluding those corresponding to the structural units (I) to (IV)). By further including the structural unit (V), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Of these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0121] Examples of the structural unit (V) include structural units represented by the following formula:

[0122]

[0123] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0124] When the base polymer has the structural unit (V) having the polar group, the lower limit of the content of the structural unit (V) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content of the structural unit (V) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0125] (Structural Unit (VI)) The polymer may further contain a structural unit derived from substituted or unsubstituted styrene (hereinafter also referred to as "structural unit (VI)") (excluding those corresponding to the structural units (I) to (VI)). When the structural unit (VI) has a substituent, examples of the substituent include L in the above formula (1). １ The substituent is preferably a halogen atom or an alkoxy group, more preferably an iodine atom or a methoxy group.

[0126] Examples of the monomer that provides the structural unit (VI) include compounds represented by the following formula:

[0127]

[0128] When the base polymer has the structural unit (VI) having the polar group, the lower limit of the content of the structural unit (VI) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on the total structural units constituting the base polymer, and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0129] The base polymer contains an iodine group. The iodine group may be contained in one or more of the structural units (I) to (VI). When the base polymer contains an iodine group, it is possible to exhibit excellent sensitivity, CDU, and process margin.

[0130] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0131] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0132] As the solvent used in the polymerization, the solvents described below can be suitably used. These solvents used in the polymerization may be used alone or in combination of two or more kinds.

[0133] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0134] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured 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 10,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0135] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0136] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0137] The lower limit of the content of the base polymer is preferably 50% by mass, more preferably 60% by mass, and even more preferably 70% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 98% by mass, more preferably 95% by mass, and even more preferably 92% by mass.

[0138] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having 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, the high-fluorine-content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to desired states.

[0139] The high-fluorine content polymer preferably has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). In addition, for example, the high-fluorine content polymer may have at least one of the structural units (I) and (III) to (V) in the base polymer, if necessary.

[0140] In the above formula (6), R ７３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an oxygen atom, a sulfur atom, -COO-, or -SO ２ ONH-, -CONH- or -OCONH-. ７４ 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.

[0141] The above R ７３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0142] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a single bond and —COO— are preferred, and —COO— is more preferred.

[0143] The above R ７４Examples 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.

[0144] The above R ７４ 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.

[0145] The above R ７４ As 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.

[0146] When the high-fluorine-content polymer has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 100 mol%, more preferably 95 mol%, and even more preferably 90 mol%. By setting the content of the structural unit (VII) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, thereby further promoting uneven distribution of fluorine atoms in the surface layer of the resist film.

[0147] The lower limit of Mw of the high fluorine content polymer is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 5,000. The upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 20,000, and particularly preferably 15,000.

[0148] The Mw / Mn of the high fluorine content polymer 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.

[0149] The lower limit of the content of the high-fluorine content polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, relative to 100 parts by mass of the base polymer, and the upper limit of the content is preferably 10 parts by mass, more preferably 8 parts by mass, and even more preferably 5 parts by mass.

[0150] The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0151] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0152] <Radiation-Sensitive Acid Generator> The radiation-sensitive composition according to this embodiment contains a radiation-sensitive acid generator containing a partial structure (a). As described above, the partial structure (a) forms an onium salt structure with a sulfonate anion and an onium cation. The radiation-sensitive acid generator containing the partial structure (a) is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer to generate a carboxyl group or the like. The radiation-sensitive acid generator exists alone as a low-molecular-weight compound (free from the polymer), and is different from a radiation-sensitive acid-generating structure in which the partial structure (a) is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure, such as the structural unit (II) in the base polymer.

[0153] Details of the partial structure (a) are as explained above in relation to the structural unit (II) in the base polymer.

[0154] At least one selected from the group consisting of the sulfonate anion and the onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0155] The radiation-sensitive acid generator is preferably a compound represented by the following formula (A2). (In formula (A2), R Ａ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. １ , L １ , Z ＋ , m, n １ and n ２ has the same meaning as the above formula (1).

[0156] R Ａ２ Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the terminal of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, and combinations thereof.

[0157] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R １Ａ and R １Ｂ In addition to monovalent chain hydrocarbon groups having 1 to 10 carbon atoms and monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, examples of the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include: monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as aryl groups, including phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups, including benzyl, phenethyl, and naphthylmethyl. Examples of the divalent heteroatom-containing group include L in the above formula (1). １ It is possible to suitably employ a divalent heteroatom-containing group in a divalent linking group represented by the following formula: Examples of monovalent heteroatom-containing groups include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0158] Examples of the sulfonate anion in the partial structure (a) of the radiation-sensitive acid generator include, but are not limited to, those shown below.

[0159]

[0160]

[0161]

[0162] The onium cation structure of the partial structure (a) of the radiation-sensitive acid generator can suitably be the onium cation structure of the structural unit (II) in the base polymer.

[0163] The above-mentioned radiation-sensitive acid generator can be synthesized by a known method, particularly by a salt exchange reaction. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0164] These radiation-sensitive acid generators may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total content when multiple types are used) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 100 parts by mass, more preferably 60 parts by mass, and even more preferably 40 parts by mass. This allows the resist pattern to exhibit excellent sensitivity, CDU, and process margin during formation.

[0165] <Acid Diffusion Controller> The radiation-sensitive composition may contain an acid diffusion controller. The acid diffusion controller preferably contains an organic acid anion and an onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The acid diffusion controller does not substantially dissociate the acid-dissociable group of the base polymer under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange.

[0166] By including the acid diffusion controller in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern with superior resolution and development contrast.

[0167] Examples of the acid diffusion controller include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), etc. Further examples include a compound containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and a compound containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4).

[0168]

[0169] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. － and Q － are each independently OH － and R α -COO － , R α -SO ３ － In the above formulas (8-1) and (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. α is a single bond or a divalent organic group having 1 to 30 carbon atoms. The monovalent organic group having 1 to 30 carbon atoms is R Ａ２ It is possible to suitably employ a group in which the monovalent organic group having 1 to 20 carbon atoms, represented by the following formula, is extended to have 1 to 30 carbon atoms. Examples of the divalent organic group having 1 to 30 carbon atoms include groups in which one hydrogen atom has been removed from the monovalent organic group having 1 to 30 carbon atoms.

[0170] Examples of organic acid anions of the acid diffusion controller include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As organic acid anions that do not have an iodo group-containing aromatic ring structure, structures in which the iodo group in the following formula is substituted with an atom or group other than an iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0171]

[0172]

[0173] As the onium cation in the acid diffusion controller, the structure of the onium cation of the structural unit (II) in the base polymer can be suitably adopted.

[0174] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0175] The acid diffusion controller may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (total when multiple types are used) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol% based on the total content of the monomer corresponding to the content ratio of the structural unit (II) of the base polymer and the content of the radiation-sensitive acid generator. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%.

[0176] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer and, optionally, the radiation-sensitive acid generator, additives, and the like.

[0177] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0178] Examples of alcohol-based solvents include monoalcohol-based 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-based 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-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0179] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0180] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0181] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0182] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0183] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0184] Among these, ester-based solvents and ether-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.

[0185] <Other Optional Components> The radiation-sensitive composition may contain other optional components in addition to the components described above. 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.

[0186] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a solvent, and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of approximately 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0187] <Pattern Forming Method> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to 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 an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0188] According to the pattern formation method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, CDU, and process margin during pattern formation. Each step will be described below.

[0189] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive 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 JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, soft baking (SB) may be performed, if necessary, to volatilize the solvent in the coating film. The SB temperature is typically 60°C to 160°C, and preferably 80°C to 140°C. The SB 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.

[0190] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0191] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like due to the acid generated from the structural unit (II) or the radiation-sensitive acid generator in the exposed portions of the resist film. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0192] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. 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.

[0193] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, 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.

[0194] 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 an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive 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.

[0195] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0196] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" are based on mass unless otherwise specified. The measurement methods for each physical property value are shown below.

[0197] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymer] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer were measured by gel permeation chromatography (GPC) using Tosoh GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following conditions: Eluent: tetrahydrofuran (Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40°C Detector: differential refractometer Standard material: monodisperse polystyrene

[0198] <Synthesis of Compound (M) Containing Partial Structure (a)> [Synthesis Example 1-1] (Synthesis of Monomer (M-16)) Monomer (M-16) was synthesized according to the following reaction scheme.

[0199]

[0200] 10 mmol of sodium 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonate, 60 mL of acetone, 12 mmol of methacryloyl chloride, and 13 mmol of triethylamine were added to a reaction vessel and stirred at room temperature for 1 hour. 250 mL of dichloromethane (DCM), 250 mL of ultrapure water, and 11 mmol of tris(4-fluorophenyl)sulfonium bromide were added and stirred at room temperature for 1 hour. The organic layer was separated and washed with 200 mL of ultrapure water. Purification by silica gel column chromatography yielded (M-16).

[0201] <Synthesis of Compound (B) Containing Partial Structure (a)> [Synthesis Example 1-2] (Synthesis of Radiation-Sensitive Acid Generator (B-1)) Radiation-sensitive acid generator (B-1) was synthesized according to the following reaction scheme.

[0202]

[0203] A reaction vessel was charged with 5.0 mmol of sodium 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonate, 30 mL of acetone, 6.0 mmol of acetyl chloride, and 6.5 mmol of triethylamine, and the mixture was stirred at room temperature for 1 hour. 125 mL of dichloromethane, 125 mL of ultrapure water, and 5.5 mmol of triphenylsulfonium bromide were added, and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed with 100 mL of ultrapure water. Purification by silica gel column chromatography yielded (B-1).

[0204] [Synthesis Examples 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11] (Synthesis of Radiation-Sensitive Acid Generators (B-3), (B-8), (B-9), (B-10), (B-11), (B-13), (B-14), (B-17), and (B-20)) Radiation-sensitive acid generators (B-3), (B-8), (B-9), (B-10), (B-11), (B-13), (B-14), (B-17), and (B-20) were synthesized in the same manner as in Synthesis Example 1-2, except that the substrates used in Synthesis Example 1-2 were appropriately selected.

[0205]

[0206] Synthesis Example 1-12 (Synthesis of Radiation-Sensitive Acid Generator (B-2)) A radiation-sensitive acid generator (B-2) was synthesized according to the following reaction scheme.

[0207]

[0208] To a reaction vessel were added 5.0 mmol of sodium 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonate, 15 mmol of potassium carbonate, and 50 mL of acetone. After stirring for 1 hour, 10 mmol of 1-bromobutane was added dropwise, and the mixture was stirred at 55°C for 5 hours. After cooling to room temperature, 125 mL of dichloromethane, 125 mL of ultrapure water, and 5.5 mmol of tris(4-fluorophenyl)sulfonium bromide were added, and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed with 100 mL of ultrapure water. Purification by silica gel column chromatography yielded (B-2).

[0209] Synthesis Example 1-13 (Synthesis of Radiation-Sensitive Acid Generator (B-4)) Radiation-sensitive acid generator (B-4) was synthesized according to the following reaction scheme.

[0210]

[0211] To a reaction vessel were added 5.0 mmol of sodium 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonate, 15 mmol of potassium carbonate, and 50 mL of acetone. After stirring for 1 hour, 10 mmol of methyl bromoacetate was added dropwise, and the mixture was stirred at 55°C for 5 hours. After cooling to room temperature, 125 mL of dichloromethane, 125 mL of ultrapure water, and 5.5 mmol of bis(3,4-difluorophenyl)(4-fluorophenyl)sulfonium bromide were added, and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed with 100 mL of ultrapure water. Purification by silica gel column chromatography yielded (pB-4).

[0212] 4 mmol of (pB-4), 30 mL of tetrahydrofuran, and 30 mL of ultrapure water were added to a reaction vessel and stirred at room temperature for 3 hours. The organic layer was separated and washed three times with 50 mL of ultrapure water to obtain (B-4).

[0213] [Synthesis Examples 1-14, 1-15, 1-16, 1-17, 1-18, and 1-19] (Synthesis of Radiation-Sensitive Acid Generators (B-5), (B-6), (B-7), (B-12), (B-15), and (B-16))

[0214] Radiation-sensitive acid generators (B-5), (B-6), (B-7), (B-12), (B-15), and (B-16) were synthesized in the same manner as in Synthesis Example 1-13, except that the substrates used were appropriately selected.

[0215]

[0216] Synthesis Example 1-20 (Synthesis of Radiation-Sensitive Acid Generator (B-18)) Radiation-sensitive acid generator (B-18) was synthesized according to the following reaction scheme.

[0217]

[0218] To a reaction vessel were added 5.0 mmol of sodium 2,3,5,6-tetrafluoro-4-mercaptobenzenesulfonate, 15 mmol of potassium carbonate, and 50 mL of acetone. After stirring for 1 hour, 10 mmol of 4-iodobenzyl bromide was added dropwise, and the mixture was stirred at 55°C for 5 hours. After cooling to room temperature, 125 mL of dichloromethane, 125 mL of ultrapure water, and 5.5 mmol of tris(4-fluorophenyl)sulfonium bromide were added, and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed with 100 mL of ultrapure water. Purification by silica gel column chromatography yielded (pB-18).

[0219] A reaction vessel was charged with 4.0 mmol of (pB-18) and 20 mL of dichloromethane, and the mixture was cooled to 0°C. 5.2 mmol of metachloroperbenzoic acid (mCPBA) was added, and the mixture was stirred for 2 hours. 20 mL of saturated aqueous sodium bicarbonate solution was added, and the organic layer was separated to obtain (B-18).

[0220] Synthesis Example 1-21 (Synthesis of Radiation-Sensitive Acid Generator (B-19)) A radiation-sensitive acid generator (B-19) was synthesized according to the following reaction scheme.

[0221]

[0222] To a reaction vessel were added 5.0 mmol of sodium 2,3,5,6-tetrafluoro-4-mercaptobenzenesulfonate, 15 mmol of potassium carbonate, and 50 mL of acetone. After stirring for 1 hour, 10 mmol of 4-iodobenzyl bromide was added dropwise, and the mixture was stirred at 55°C for 5 hours. After cooling to room temperature, 125 mL of dichloromethane, 125 mL of ultrapure water, and 5.5 mmol of (4-fluorophenyl)bis(4-(trifluoromethyl)phenyl)sulfonium bromide were added, and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed with 100 mL of ultrapure water. Purification by silica gel column chromatography gave (pB-19).

[0223] A reaction vessel was charged with 4.0 mmol of (pB-19), 20 mL of acetonitrile, and 2 mL of ultrapure water, and the mixture was cooled to 0°C. 4.8 mmol of oxone was added, and the mixture was warmed to room temperature and stirred for 6 hours. The solid was removed by suction filtration, and the filtrate was concentrated, and then 20 mL of ethyl acetate was added. After washing three times with ultrapure water, the organic layer was separated to obtain (B-19).

[0224] <Synthesis of Base Polymers> [Synthesis Examples 2-1 to 2-21] Synthesis of Base Polymers Each monomer was combined according to the composition shown in Table 1 below, and a copolymerization reaction was carried out in tetrahydrofuran (THF) solvent. The polymer was crystallized in methanol, and after repeated washing with hexane, it was isolated and dried to obtain base polymers A-1 to A-21. In the table, "-" indicates that the corresponding component was not used. The same applies to the following tables.

[0225]

[0226] The monomers used in the synthesis of the base polymer are shown below.

[0227]

[0228] <Preparation and Evaluation of Radiation-Sensitive Composition> The components used in preparing the radiation-sensitive composition are shown below.

[0229] <[A] Polymer (Base Polymer)> A-1 to A-21: Polymers obtained in Synthesis Examples 2-1 to 2-21

[0230] <[B] Radiation-sensitive acid generators> B-1 to B-25: Compounds represented by the following formulas (B-1) to (B-20), respectively, obtained in Synthesis Examples 1-2 to 1-21, and compounds represented by the following formulas (B-21) to (B-25), respectively.

[0231]

[0232]

[0233]

[0234] <[Z] Acid diffusion controller> Z-1 to Z-4: Compounds represented by the following formulas (Z-1) to (Z-4), respectively

[0235]

[0236] [D] Solvent D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether

[0237] <Preparation of Radiation-Sensitive Composition> [Example 1] A radiation-sensitive composition (R-1) was prepared by blending [A] 100 parts by mass of polymer (A-1) as a base polymer, [B] 30 parts by mass of radiation-sensitive acid generator (B-1), [Z] 50 mol % of compound (Z-1) as an acid diffusion controller based on the amount of radiation-sensitive acid generator (B-1), and [D] 2,000 parts by mass of compound (D-1) and 4,800 parts by mass of compound (D-2) as solvents.

[0238] Examples 2 to 39 and Comparative Examples 1 to 10 Radiation-sensitive compositions (R-2) to (R-39) and (CR-1) to (CR-10) were prepared in the same manner as in Example 1, except that the types and amounts of each component were changed as shown in Table 2. In Example 36 and Comparative Example 10, the acid diffusion controller [Z] was added in an amount of 50 mol % relative to the amount of the monomer providing the structural unit (II) contained in 100 parts by mass of the base polymer [A].

[0239]

[0240] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 40-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron Ltd.). Soft baking was performed at 130°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a 50-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400," ASML, NA=0.33, illumination conditions: Conventional s=0.89, mask: NALA DF). The resist film was then subjected to PEB at 110°C for 60 seconds. Next, development was carried out using a 2.38% by mass aqueous solution of TMAH at 23° C. for 30 seconds to form a positive 23 nm contact hole pattern.

[0241] <Evaluation> The sensitivity, CDU performance, and process margin of each radiation-sensitive composition were evaluated by measuring each resist pattern formed as described above according to the methods below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-4100") was used to measure the resist patterns. The evaluation results are shown in Table 3 below.

[0242] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 23 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the sensitivity value, the better, since the desired resist pattern can be formed with a smaller amount of exposure.

[0243] [CDU Performance] The resist pattern formed above was observed using the scanning electron microscope. Hole widths were measured at 50 random locations, and the 3 sigma value was calculated from the distribution of the measured values, which was used as the CDU (unit: nm). The smaller the CDU value, the smaller the hole rattle, and the better the CDU performance.

[0244] [Max CD] In forming the resist pattern, the hole width was measured while increasing the exposure dose, and the maximum hole width at which the holes did not cross-link (referring to the phenomenon in which the resist film between adjacent holes is removed after development, causing the holes to connect) was defined as Max CD (unit: nm). The larger the value of Max CD, the wider and more favorable the process margin for forming contact holes.

[0245] [Min CD] In forming the resist pattern, the hole width was measured while decreasing the exposure dose, and the minimum hole width at which a hole could be formed was defined as Min CD (unit: nm). The smaller the Min CD value, the wider and more favorable the process margin for forming a contact hole.

[0246]

[0247] As is clear from the results in Table 3, the sensitivity, CDU, Max CD, and Min CD were all at sufficient levels for the radiation-sensitive compositions of Examples 1 to 39. The radiation-sensitive compositions of Comparative Examples 1 to 10 were inferior to the examples in one or more of sensitivity, CDU, Max CD, and Min CD.

[0248] The above results demonstrate that the radiation-sensitive composition of the present invention, which contains a polymer having an iodine group and in which the partial structure (a) is introduced into at least the radiation-sensitive acid generator or the polymer, has good sensitivity to exposure light, excellent CDU performance, and a wide process margin.

[0249] The radiation-sensitive composition and pattern forming method described above can form a resist pattern that has good sensitivity to exposure light and is excellent in CDU and process margin, and can therefore be suitably used in the fabrication processes of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer having an iodine group and including a structural unit (I) having an acid-dissociable group; and a solvent, wherein the radiation-sensitive composition contains at least a radiation-sensitive acid generator including a partial structure represented by the following formula (a), or the polymer includes a structural unit (II) including a partial structure represented by the following formula (a): (In formula (a), R １ R is a nitro group, a cyano group, a carboxy group, an iodine atom, an amino group, an alkyl group, an acyl group, or an alkoxycarbonyl group. １ If there are multiple R １ are the same or different. １ represents -O-, -S-, -SO- or -SO ２ -. m is 0 or 1. n １ is an integer from 1 to (2m+4). ２ is an integer from 0 to (2m+3), where n １ +n ２ The relationship of ≦2m+4 is satisfied. * represents a bond to another moiety in the corresponding polymer or radiation-sensitive acid generator. Z ＋ is a monovalent onium cation.

2. In the above formula (a), m is 0 and n １ is 4, and n ２ The radiation-sensitive composition according to claim 1 , wherein is 0.

3. In the above formula (a), m is 0, and -L １ -Ha-SO ３ － The radiation-sensitive composition according to claim 1 , wherein the alkyl group is present at the p-position of 4. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive composition contains the radiation-sensitive acid generator, and the content of the radiation-sensitive acid generator is 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the polymer.

5. The radiation-sensitive composition according to claim 1, wherein the polymer contains the structural unit (II), and the content of the structural unit (II) in all structural units constituting the polymer is 1 mol % or more and 30 mol % or less.

6. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group has the iodine group.

7. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group contains an aromatic ring structure containing an iodine group.

8. The radiation-sensitive composition according to claim 7, wherein the aromatic ring in the iodo group-containing aromatic ring structure is a benzene ring, a thiophene ring, or a furan ring.

9. The radiation-sensitive composition according to claim 6, wherein the number of iodo groups in the acid-dissociable group is one, two or three.

10. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) is represented by the following formula (1): (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a divalent linking group. １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a 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 together with the carbon atoms to which they are bonded. １Ａ and R １Ｂ There is no case where both of Ar and Ar are hydrogen atoms. １ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１ are the same or different. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p+q is 5 or less.

11. The radiation-sensitive composition according to any one of claims 1 to 10, wherein the content of the structural unit (I) in all structural units constituting the polymer is 10 mol % or more and 70 mol % or less.

12. The radiation-sensitive composition according to any one of claims 1 to 10, wherein the polymer further comprises a structural unit (III) having a phenolic hydroxyl group.

13. The radiation-sensitive composition according to any one of claims 1 to 10, further comprising an acid diffusion controller.

14. The radiation-sensitive composition according to claim 13, wherein the acid diffusion controller has an iodine group.

15. The radiation-sensitive composition according to any one of claims 1 to 10, further comprising a high-fluorine content polymer having a higher mass content of fluorine atoms than the polymer.

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

17. The pattern forming method according to claim 16, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

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