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

Abstract

The invention provides a radiation-sensitive composition, a pattern forming method and an onium salt which can form a resist film or pattern with excellent sensitivity or LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern roundness, EL performance and pattern collapse resistance. A radiation-sensitive composition containing an onium salt represented by formula (1), a polymer containing a structural unit (I) having an acid-dissociable group, and a solvent (in formula (1), Q1 and Q2 are each independently a carbon atom or a nitrogen atom; wherein at least one of Q1 and Q2 is a carbon atom; w represents a monocyclic or polycyclic non-aromatic ring structure having 3-40 ring members, which is configured together with Q1 and Q2 in the formula; in the formula, the following formula between Q1 and Q2 represents a single bond or a double bond; (AAA) R1 is a monovalent organic group having 1-20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; when a plurality of R1 are present, the plurality of R1 are the same as or different from each other; m1 is an integer of 0-4; and Z + represents a monovalent onium cation). # imgabs0 #

Description

Technical Field

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

[0002] Photolithography using a resist composition is utilized to form fine circuits in semiconductor devices. A typical process involves exposing a film of the resist composition to radiation through a mask pattern to generate an acid. This acid acts as a catalyst for a reaction that creates a difference in the solubility of the polymer in an alkaline or organic developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] In the above-mentioned photolithography technology, pattern miniaturization is promoted by using short-wavelength radiation such as ArF excimer laser, or using a liquid immersion exposure method (liquid immersion lithography) in which exposure is performed while the space between the lens and the resist film of the exposure device is filled with a liquid medium.

[0004] In an effort to further advance this technology, a technique has been proposed: adding a quencher (acid diffusion controller) to the resist composition to trap the acid that diffuses into the unexposed areas through a salt exchange reaction, thereby improving the performance of ArF-based lithography (Japanese Patent No. 5556765). Furthermore, lithography using shorter wavelength radiation, such as electron beams, X-rays, and extreme ultraviolet (EUV), is also being studied as a next-generation technology.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5556765 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In the efforts towards this next-generation technology, the resist performance is required to be equal to or better than before in terms of sensitivity or line width roughness (LWR) performance that represents the deviation of the line width of the resist pattern, depth of focus (DOF) performance, pattern rectangularity that represents the rectangularity of the cross-sectional shape of the resist pattern, critical dimension uniformity (CDU) performance that is an indicator of the uniformity of the line width or pore size, pattern circularity that represents the circularity of the pore shape, exposure latitude (EL) performance, and resistance to pattern collapse.

[0010] The present invention aims to provide a radiation-sensitive composition, a pattern forming method, and an onium salt capable of forming a resist film or pattern having excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance.

[0011] Technical means to solve the problem

[0012] The present inventors have diligently studied to solve the problem and, as a result, have found that the object can be achieved by adopting the following structure, thereby completing the present invention.

[0013] That is, the present invention, in one embodiment, relates to a radiation-sensitive composition comprising:

[0014] Onium salt represented by the following formula (1) (hereinafter also referred to as "onium salt (1)"),

[0015] A polymer containing a structural unit (I) having an acid-dissociable group, and

[0016] solvent.

[0017] [Chemistry 1]

[0018]

[0019] (In formula (1),

[0020] Q 1 and Q 2 are independently a carbon atom or a nitrogen atom; wherein, Q 1 and Q 2 At least one of is a carbon atom;

[0021] W is the Q in the formula 1 and Q 2 Together they form a monocyclic or polycyclic non-aromatic ring structure with 3 to 40 ring members;

[0022] Q in the formula1 With Q 2 The following formula between represents a single bond or a double bond;

[0023] [Chemistry 2]

[0024]

[0025] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; in R 1 When there are multiple R 1 the same as or different from each other;

[0026] m1 is an integer from 0 to 4;

[0027] Z + is a monovalent onium cation)

[0028] The radiation-sensitive composition contains an onium salt (1) as a quencher (acid diffusion controller), and therefore can exhibit excellent sensitivity or various resist properties such as LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance when forming a resist pattern. The reason for this is not limited by any theory, but is speculated as follows. Due to the structural proximity between the carboxyl group and its anion respectively present on two adjacent carbon atoms in the onium salt (1), the hydrogen bonding ability between the two is reduced. As a result, compared with the case where the carboxyl group and its anion are present on the same carbon, the basicity of the onium salt (1) is enhanced, and the acid capture ability at the unexposed part can be improved. In addition, by introducing a structure with relatively high polarity of the carboxyl group and its anion, the dissolution contrast between the exposed part and the unexposed part can be improved. Furthermore, by adopting a non-aromatic ring structure as the main skeleton, compared with the case of adopting an aromatic ring structure or a chain structure, the dispersibility and compatibility in the resist film can be improved while ensuring transparency (non-absorptivity) to the exposure light. It is speculated that these factors work together to exert the various properties of the resist. In addition, the so-called organic group is a group containing at least one carbon atom. Among them, the functional group or characteristic group (cyano group, carboxyl group, carbonyl group, etc.) containing carbon atoms itself is not included in the organic group.

[0029] In another embodiment, the present invention relates to a method for forming a pattern, comprising:

[0030] a step of directly or indirectly coating the radiation-sensitive composition on a substrate to form a resist film;

[0031] a step of exposing the resist film to light; and

[0032] A step of developing the exposed resist film using a developer.

[0033] In the pattern forming method, a high-quality resist pattern can be efficiently formed by using the radiation-sensitive composition capable of forming a resist film or pattern having excellent sensitivity or LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance.

[0034] In another embodiment, the present invention relates to an onium salt represented by the following formula (1).

[0035] [Chemistry 3]

[0036]

[0037] (In formula (1),

[0038] Q 1 and Q 2 are independently a carbon atom or a nitrogen atom; wherein, Q 1 and Q 2 At least one of is a carbon atom;

[0039] W is the Q in the formula 1 and Q 2 Together they form a monocyclic or polycyclic non-aromatic ring structure with 3 to 40 ring members;

[0040] Q in the formula 1 With Q 2 The following formula between represents a single bond or a double bond;

[0041] [Chemistry 4]

[0042]

[0043] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; in R 1 When there are multiple R 1 the same as or different from each other;

[0044] m1 is an integer from 0 to 4;

[0045] Z + It is a monovalent onium cation.)

[0046] The onium salt (1) can exert good basicity, polarity and transparency in the resist film. Therefore, when formulated in a radiation-sensitive composition, it can exert excellent sensitivity or LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance during resist pattern formation. DETAILED DESCRIPTION

[0047] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In addition, combinations of preferred aspects in the embodiments are also preferred.

[0048] <Radiation-sensitive composition>

[0049] The radiation-sensitive composition of this embodiment (hereinafter also referred to as "composition") comprises an onium salt (1), a polymer, and a solvent. Furthermore, a radiation-sensitive acid generator may be optionally included. The composition may also include any other components as long as the effects of the present invention are not impaired. The radiation-sensitive composition, by including the prescribed onium salt (1), can exhibit excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance during resist pattern formation.

[0050] (Onium salt (1))

[0051] The onium salt (1) can function as a quencher (also referred to as a "photodegradable base" or "acid diffusion controller") that captures acid before exposure or in unexposed areas. The onium salt (1) is represented by the formula (1).

[0052] In the formula (1), Q 1 and Q 2 Preferably, they are all carbon atoms.

[0053] In the formula (1), W represents the same as Q in the formula 1 and Q 2 The non-aromatic ring structure of the monocyclic or polycyclic ring with 3 to 40 ring members constituted together, as long as it is a non-aromatic (not having aromatic) ring structure of 3 to 40 ring members, can be any structure of monocyclic or polycyclic, or can be any saturated or unsaturated. As a polycyclic structure, it can be a condensed ring structure in which two adjacent rings have one edge (bond between two adjacent atoms), or it can be a bridged ring structure formed by bonding two carbon atoms that are not adjacent to each other in the carbon atoms constituting the ring through a linking group containing more than one atom, or it can be a ring structure in which two adjacent rings utilize single bond bonding, or it can be a spirocyclic structure in which two adjacent rings have one carbon atom. The combination of two adjacent rings can be any one of a combination of monocyclic and monocyclic, a combination of monocyclic and polycyclic, or a combination of polycyclic and polycyclic. As a ring-constituting atom, in addition to carbon atoms, heteroatoms can also be included. As heteroatoms, oxygen atoms, sulfur atoms, nitrogen atoms, etc. can be listed. The number of ring members is the number of rings containing Q in W. 1 and Q 2 The total number of atoms in the inner ring.

[0054] The non-aromatic ring structure is preferably a monocyclic or polycyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms, a monocyclic or polycyclic aliphatic heterocyclic structure having 3 to 20 carbon atoms, or a combination thereof.

[0055] Examples of the monocyclic or polycyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms include monocyclic or polycyclic cycloalkane structures, or monocyclic or polycyclic cycloolefin structures. Monocyclic cycloalkane structures are preferably cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Polycyclic cycloalkane structures are preferably bridged ring structures such as norbornane, adamantane, tricyclodecane, and tetracyclododecane. Monocyclic cycloolefin structures include monocyclic cycloalkenyl groups such as cyclopropene, cyclobutene, cyclopentene, and cyclohexene. Polycyclic cycloolefin structures include norbornene, tricyclodecene, and tetracyclododecene.

[0056] Examples of the monocyclic or polycyclic aliphatic heterocyclic structure having 3 to 20 carbon atoms include structures in which a portion of the carbon atoms constituting the ring of the monocyclic or polycyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms are substituted with -CO-, -CS-, -O-, -S-, -SO2-, -NR'-, or a divalent heteroatom-containing group formed by combining two or more of these groups. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0057] Examples of the aliphatic heterocyclic structure include:

[0058] Aliphatic heterocyclic structures containing oxygen atoms, such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane (e.g., cyclic acetal);

[0059] Aliphatic heterocyclic structures containing nitrogen atoms such as aziridine, pyrrolidine, piperidine, and piperazine;

[0060] Aliphatic heterocyclic structures containing sulfur atoms such as thietane, thiolane, and thiazane;

[0061] Aliphatic heterocyclic structures containing two or more heteroatoms, such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane;

[0062] Lactone structure, cyclic carbonate structure, sultone structure, cyclic acetal structure, etc.

[0063] The non-aromatic ring structure is preferably a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornane ring, a tricyclodecane ring, a tetracyclododecane ring, an adamantane ring, a ring structure (cyclic ether structure, cyclic ketone structure, lactone structure, cyclic acetal structure) in which a part of the carbon atoms constituting these ring structures are substituted by -O-, -CO- or a combination thereof, or a combination thereof.

[0064] As R 1 The monovalent organic group having 1 to 20 carbon atoms represented by the group is preferably, for example, a substituted or unsubstituted monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof. Examples include groups in which some or all of the hydrogen atoms contained in these chain, alicyclic, and aromatic hydrocarbon groups are substituted with substituents, and groups containing the aforementioned divalent heteroatom-containing group between carbon atoms of these groups or at the ends of the groups.

[0065] Examples of the substituent that replaces a part or all of the hydrogen atoms possessed by the organic group include: a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; a hydroxyl group; a carboxyl 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 a halogen atom; a pendant oxy group (=O), and the like.

[0066] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include 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.

[0067] As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a group obtained by removing one hydrogen atom from the monocyclic or polycyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms in W can be preferably used.

[0068] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthracenyl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0069] m1 is preferably an integer of 0-3, more preferably an integer of 0-2.

[0070] The anion portion of the onium salt (1) represented by the formula (1) is not particularly limited, and examples thereof include structures represented by the following formulas (1-1-1) to (1-1-33).

[0071] [Chemistry 5]

[0072]

[0073] [Chemistry 6]

[0074]

[0075] In the formula (1), Z +The monovalent onium cation represented by Z includes, for example, onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. As the onium cation, a radiation-decomposable onium cation is preferred. As the radiation-decomposable onium cation, for example, sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, and pyridinium cations can be mentioned. Among them, sulfonium cations or iodonium cations are preferred. + It is preferably a monovalent sulfonium cation containing at least one aromatic ring, more preferably a monovalent sulfonium cation containing at least one aromatic ring or a monovalent iodonium cation containing at least one aromatic ring.

[0076] The sulfonium cation or iodonium cation is preferably represented by the following formula (X-1) to formula (X-6).

[0077] [Chemistry 7]

[0078]

[0079] In the formula (X-1), R a1 、R a2 and R a3 are independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxyl group, a halogen atom, -OSO2-R P 、-SO2-R Q or -SR T , or represents a ring structure formed by combining two or more of these groups. The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton. P 、R Q and R T Each of k1, k2 and k3 is independently an integer from 0 to 5. In R a1 ~R a3 and R P 、R Q and R T In the case of multiple R a1 ~R a3 and R P 、R Q and R T They may be the same or different.

[0080] In the formula (X-2), Rb1 It is a substituted or unsubstituted linear or branched alkyl group having 1 to 20 carbon atoms, or an alkoxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. k is 0 or 1. k When n is 0, k4 is an integer from 0 to 4. k When is 1, k4 is an integer from 0 to 7. b1 In the case of multiple R b1 Can be the same or different. In addition, multiple R b1 It can also be expressed as a ring structure formed by mutual combination. b2 L is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. C is a single bond or a divalent linking group. k5 is an integer from 0 to 4. b2 In the case of multiple R b2 Can be the same or different. In addition, multiple R b2 It can also be expressed as a ring structure formed by mutual bonding. q is an integer from 0 to 3. + The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton.

[0081] In the formula (X-3), R c1 、R c2 and R c3 Each independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0082] In the formula (X-4), R g1 It is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. k2 is 0 or 1. k2 When n is 0, k10 is an integer from 0 to 4. k2 When it is 1, k10 is an integer from 0 to 7. g1 In the case of multiple R g1 Can be the same or different. In addition, multiple R g1 It can also be expressed as a ring structure formed by mutual combination. g2 and R g3Each of k11 and k12 is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxyl group, a halogen atom, or a ring structure formed by combining these groups. k11 and k12 are each independently an integer from 0 to 4. In R g2 and R g3 In the case of multiple R g2 and R g3 They may be the same or different.

[0083] In the formula (X-5), R d1 and R d2 Each of k6 and k7 is 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, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are independently an integer from 0 to 5. In R d1 and R d2 In the case of multiple R d1 and R d2 They may be the same or different.

[0084] In the formula (X-6), R e1 and R e2 Each of k8 and k9 is independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

[0085] Specific examples of the radiation-decomposable onium cation include, but are not limited to, structures represented by the following formulae (1-2-1) to (1-2-54).

[0086] [Chemistry 8]

[0087]

[0088] [Chemistry 9]

[0089]

[0090] [Chemistry 10]

[0091]

[0092] The onium salt (1) can be formed by any combination of the anion portion in the formula (1) and the monovalent onium cation. Specific examples of the onium salt (1) are not particularly limited, but include structures represented by the following formulas (1-1) to (1-36).

[0093] [Chemistry 11]

[0094]

[0095] [Chemistry 12]

[0096]

[0097] [Chemistry 13]

[0098]

[0099] [Chemistry 14]

[0100]

[0101] The content of the onium salt (1) in the radiation-sensitive composition can be appropriately selected depending on the type of polymer used, exposure conditions or required sensitivity, and the type and content of the radiation-sensitive acid generator described below.

[0102] The lower limit of the content of the onium salt (1) (the total of these when multiple onium salts are used in combination) relative to 100 parts by mass of the polymer described later is preferably 0.1 parts by mass, more preferably 0.3 parts by mass, and further preferably 0.5 parts by mass. The upper limit of the content is preferably 30 parts by mass, more preferably 28 parts by mass, and further preferably 25 parts by mass. By setting the content of the onium salt (1) to the above range, the excellent sensitivity or LWR performance, DOF performance, pattern rectangularity, CDU performance, pattern circularity, EL performance, and pattern collapse resistance as described above can be exerted when forming a resist pattern.

[0103] (Synthesis Method of Onium Salt (1))

[0104] According to the following scheme, the target onium salt (1) can be synthesized by using a dicarboxylic acid (i) having the anion portion of the target onium salt (1) as a raw material and reacting it with an onium cation halide corresponding to the onium cation portion to form a carboxylate.

[0105] [Chemistry 15]

[0106]

[0107] (In the process, Q 1 , Q 2 , W, Q in the formula 1 With Q 2The bonding form between 1 , Z + and m1 have the same meaning as in formula (1); D - is a halide ion)

[0108] (polymer)

[0109] The polymer is an aggregate of polymer chains (hereinafter also referred to as the "base polymer") having a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). The "acid-dissociable group" refers to a group that replaces a hydrogen atom possessed by a carboxyl group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfonic group, or the like, and that dissociates upon the action of an acid. The radiation-sensitive composition has excellent pattern-forming properties due to the presence of structural unit (I) in the polymer.

[0110] The base polymer preferably has, in addition to the structural unit (I), a structural unit (II) comprising at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, as described below, but may also have structural units other than the structural units (I) and (II). Each structural unit is described below.

[0111] [Structural unit (I)]

[0112] Structural unit (I) is a structural unit having an acid-dissociable group. Structural unit (I) is not particularly limited as long as it contains an acid-dissociable group. Examples thereof include structural units having a tertiary alkyl ester moiety, structural units having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and structural units having an acetal bond. From the perspective of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0113] [Chemistry 16]

[0114]

[0115] In the formula (3), R 17 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. 18 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. 19 and R 20 Each independently represents a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or represents a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with each other and the carbon atoms to which they are bonded.

[0116] As the R 17From the viewpoint of improving the copolymerizability of the monomer of the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0117] As the R 18 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 10 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.

[0118] As the R 18 ~R 20 Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms include a monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a monovalent linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0119] As the R 18 ~R 20 The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by 1 The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0120] As the R 18 The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) may preferably be R 1 A monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0121] As the R 18 , preferably a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0122] The R 19 and R 20 The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these carbon atoms, is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom of a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. It can be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group. As a polycyclic hydrocarbon group, it can be either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group, and it can be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. In addition, the so-called condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group composed of multiple alicyclic rings sharing a common edge (a bond between two adjacent carbon atoms).

[0123] As the saturated hydrocarbon group in the monocyclic alicyclic hydrocarbon group, cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, cyclooctanediyl and the like are preferred, and as the unsaturated hydrocarbon group, cyclopentendiyl, cyclohexendiyl, cycloheptenediyl, cyclooctendiyl, cyclodecenediyl and the like are preferred. As the polycyclic alicyclic hydrocarbon group, a bridged alicyclic saturated hydrocarbon group is preferred, for example, bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, tricyclo[3.3.1.1 3,7 ]Decan-2,2-diyl (adamantane-2,2-diyl), etc.

[0124] Among these, R 18 is an alkyl group with 1 to 4 carbon atoms, R 19 and R 20 The alicyclic structure formed by combining these carbon atoms with each other is a polycyclic or monocyclic cycloalkane structure.

[0125] Examples of the structural unit (I-1) include structural units represented by the following formulae (3-1) to (3-8) (hereinafter also referred to as “structural units (I-1-1) to (I-1-8)”).

[0126] [Chemistry 17]

[0127]

[0128] In the above formulas (3-1) to (3-8), R 17 ~R 20 It has the same meaning as in the above formula (3). h is an integer of 1 to 4. i and j are each independently an integer of 1 to 4. k and l are 0 or 1.

[0129] i and j are preferably 1. 18 , preferably methyl, ethyl, isopropyl or cyclopentyl. 19 and R 20 , preferably methyl or ethyl.

[0130] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0131] The lower limit of the content ratio of the structural unit (I) relative to all the structural units constituting the base polymer (the total content ratio when multiple structural units are included) is preferably 10 mol%, more preferably 20 mol%, further preferably 30 mol%, and particularly preferably 35 mol%. Furthermore, the upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, further preferably 70 mol%, and particularly preferably 60 mol%. By setting the content ratio of the structural unit (I) within the above range, the pattern forming properties of the radiation-sensitive composition can be further improved.

[0132] [Structural unit (II)]

[0133] Structural unit (II) is a structural unit comprising at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further comprising structural unit (II), the base polymer can adjust its solubility in a developer, resulting in improved lithographic performance, such as resolution, of the radiation-sensitive composition. Furthermore, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0134] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-11).

[0135] [Chemistry 18]

[0136]

[0137] In the formula, R L1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L2 ~R L5 R is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, or a dimethylamino group. L4 and R L5 It may also be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining with each other and with these bonded carbon atoms. 2 is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0138] As the R L4 and R L5 The divalent alicyclic group having 3 to 8 carbon atoms formed by combining with each other and with these carbon atoms to which they are bonded includes R in the above formula (3): 19 and R 20 A group having 3 to 8 carbon atoms in a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these carbon atoms with each other. One or more hydrogen atoms in the alicyclic group may be substituted with a hydroxyl group.

[0139] As the L 2 Examples of the divalent linking group include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one of -CO-, -O-, -NH-, and -S-.

[0140] Among these, the structural unit (II) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and still more preferably a structural unit derived from norbornane lactone-based (meth)acrylate.

[0141] The lower limit of the content ratio of the structural unit (II) relative to all the structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, further preferably 30 mol%, and particularly preferably 35 mol%. Furthermore, the upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, further preferably 70 mol%, and particularly preferably 65 mol%. By setting the content ratio of the structural unit (II) within the above range, the radiation-sensitive composition can further improve lithographic performance such as resolution and adhesion between the formed resist pattern and the substrate.

[0142] [Structural unit (III)]

[0143] In addition to the structural units (I) and (II), the base polymer may optionally have other structural units. Examples of the other structural units include structural units (III) containing polar groups (excluding those corresponding to structural units (II)). By further including structural units (III), the base polymer can adjust its solubility in the developer, thereby improving the lithographic performance of the radiation-sensitive composition, such as the resolution. Examples of the polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0144] Examples of the structural unit (III) include structural units represented by the following formula.

[0145] [Chemistry 19]

[0146]

[0147] In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0148] When the base polymer contains the structural unit (III) having the polar group, the lower limit of the content ratio of the structural unit (III) relative to all the structural units constituting the base polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. Furthermore, the upper limit of the content ratio is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content ratio of the structural unit (III) within the above range, the lithographic performance such as resolution of the radiation-sensitive composition can be further improved.

[0149] [Structural unit (IV)]

[0150] As other structural units, in addition to the structural unit (III) having the polar group, the base polymer optionally contains a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)"). Structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility between the exposed portion and the unexposed portion (solution contrast). In particular, it is preferably applicable to pattern formation using exposure based on radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In such a case, the polymer preferably contains structural unit (IV) together with structural unit (I).

[0151] The structural unit having a phenolic hydroxyl group is represented by, for example, the following formula (4-1) to formula (4-6).

[0152] [Chemistry 20]

[0153]

[0154] In the above formulas (4-1) to (4-6), R 41 Each of the Y groups is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 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. When there are multiple Y groups, the multiple Y groups may be the same or different. t is an integer from 0 to 4.

[0155] When obtaining structural unit (IV), it is preferred to polymerize monomers while protecting the phenolic hydroxyl group with a protecting group such as an alkali-dissociable group (e.g., an acyl group) during polymerization, followed by hydrolysis and deprotection to obtain structural unit (IV). Alternatively, monomers may be polymerized without protecting the phenolic hydroxyl group.

[0156] In the case of a polymer for exposure to radiation with a wavelength of 50 nm or less, the lower limit of the content ratio of the structural unit (IV) relative to all the structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%. In addition, the upper limit of the content ratio is preferably 70 mol%, more preferably 60 mol%.

[0157] [Other structural units]

[0158] The base polymer may contain a structural unit having an alicyclic structure represented by the following formula (6) as a structural unit other than the structural units listed above.

[0159] [Chemistry 21]

[0160]

[0161] (In the formula (6), R 1α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R 2α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms)

[0162] In the formula (6), R 2α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by 1 The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0163] When the base polymer contains the structural unit having an alicyclic structure, the lower limit of the content ratio of the structural unit having an alicyclic structure relative to all the structural units constituting the base polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content ratio is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0164] (Method for synthesizing base polymer)

[0165] The base polymer can be synthesized by, for example, polymerizing monomers providing each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0166] Examples of the radical polymerization initiator include azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, with AIBN being more preferred. These radical initiators may be used alone or in combination of two or more.

[0167] Examples of the solvent used in the polymerization include:

[0168] Alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane;

[0169] Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decahydronaphthalene, and norbornane;

[0170] Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene;

[0171] Halogenated hydrocarbons such as chlorobutanes, brominated hexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene;

[0172] Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate;

[0173] γ-butyrolactone and other cyclic esters;

[0174] Ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone;

[0175] Ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and some polyol ethers;

[0176] Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol, etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0177] 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.

[0178] The molecular weight of the base polymer is not particularly limited. The lower limit of the polystyrene-equivalent weight average molecular weight (Mw) obtained by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, and even more preferably 4,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 10,000. When the Mw of the base polymer is within this range, good heat resistance and developability can be obtained in the resulting resist film.

[0179] The ratio (Mw / Mn) of the base polymer Mw to the polystyrene-equivalent number average molecular weight (Mn) obtained by GPC is usually 1 to 5, preferably 1 to 3, and more preferably 1 to 2.

[0180] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0181] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh)

[0182] Column temperature: 40°C

[0183] Solvent: Tetrahydrofuran

[0184] Flow rate: 1.0 mL / min

[0185] Sample concentration: 1.0 mass%

[0186] Sample injection volume: 100 μL

[0187] Detector: Differential refractometer

[0188] Standard material: monodisperse polystyrene

[0189] The content of the base polymer is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0190] (Other polymers)

[0191] The radiation-sensitive composition of this embodiment may also contain, as an additional polymer, a polymer having a higher fluorine atom mass content 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 polymer can be preferentially present in the surface layer of the resist film relative to the base polymer. This can improve the surface water repellency of the resist film during immersion exposure, improve the surface properties of the resist film during EUV exposure, and control the distribution of the composition within the film.

[0192] The high fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may optionally have structural unit (I) or structural unit (III) in the base polymer.

[0193] [Chemistry 22]

[0194]

[0195] In the formula (5), R 13 is a hydrogen atom, a methyl group or a trifluoromethyl group. L R is a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH-, -OCONH-, or a combination thereof. 14It 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.

[0196] As the R 13 From the viewpoint of improving the copolymerizability of the monomer of the structural unit (V), a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0197] As the G L From the viewpoint of improving the copolymerizability of the monomer of the structural unit (V), a single bond and -COO- are preferred, and -COO- is more preferred.

[0198] As the R 14 Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include a group in which a part or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0199] As the R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include a group in which a part or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0200] As the R 14 , preferably a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and still more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0201] When the high fluorine content polymer has a structural unit (V), the lower limit of the content ratio of the structural unit (V) relative to all the structural units constituting the high fluorine content polymer is preferably 50 mol%, more preferably 60 mol%, and further preferably 70 mol%. In addition, the upper limit of the content ratio is preferably 95 mol%, more preferably 90 mol%, and further preferably 85 mol%. By setting the content ratio of the structural unit (V) within the above range, the mass content of fluorine atoms in the high fluorine content polymer can be more appropriately adjusted, further promoting the partial presence of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during liquid immersion exposure can be further improved.

[0202] The high fluorine content polymer may also have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to structural unit (V) or in place of structural unit (V). When the high fluorine content polymer has structural unit (f-2), its solubility in alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0203] [Chemistry 23]

[0204]

[0205] Structural unit (VI) can be broadly divided into two types: one having (x) an alkali-soluble group and one having (y) a group that dissociates by the action of an alkali and increases solubility in an alkaline developer (hereinafter also referred to as an "alkali-dissociable group"). Both (x) and (y) are common. In the above formula (f-2), R C 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 in the hydrocarbon group E The end of the side is bonded with oxygen atoms, sulfur atoms, -NR dd -, carbonyl, -COO-, -OCO- or -CONH-, or a structure in which a part of the hydrogen atoms possessed by the above hydrocarbon group is substituted by an organic group having a heteroatom. dd is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0206] When the structural unit (VI) has (x) an alkali-soluble group, R F A is a hydrogen atom, 1 It is an oxygen atom, -COO-* or -SO2O-*. * indicates that it is bonded to R F W 1 is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. 1 When W is an oxygen atom, 1 For A 1 A fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which it is bonded. E is a single bond or a divalent organic group having 1 to 20 carbon atoms. E 、W 1 、A 1 and R F The structural unit (VI) having an alkali-soluble group (x) can improve the affinity for alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A is particularly preferred. 1 is an oxygen atom and W 1 This is the case of 1,1,1,3,3,3-hexafluoro-2,2-methanediyl.

[0207] When the structural unit (VI) has (y) an alkali-dissociable group, R F A is a monovalent organic group with 1 to 30 carbon atoms, 1 is an oxygen atom, -NR aa -, -COO-*, -OCO-* or -SO2O-*. R aaIt is a hydrogen atom or a monovalent hydrocarbon group with 1 to 10 carbon atoms. * indicates a bond to R F W 1 R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. E It is a single bond or a divalent organic group with 1 to 20 carbon atoms. 1 In the case of -COO-*, -OCO-* or -SO2O-*, W 1 or R F In with A 1 There is a fluorine atom on the carbon atom to which the bond is made or on the carbon atom adjacent to it. 1 When W is an oxygen atom, 1 、R E is a single bond, R D R is a hydrocarbon group having 1 to 20 carbon atoms E The structure formed by the carbonyl group bonded to the end of the side, 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 They may be the same or different. When the structural unit (VI) has the (y) alkali dissociating group, the surface of the resist film changes from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer can be greatly improved, and development defects can be suppressed more efficiently. As the structural unit (VI) having the (y) alkali dissociating group, A is particularly preferred. 1 is -COO-* and R F or W 1 or both of them have fluorine atoms.

[0208] As R C From the viewpoint of improving the copolymerizability of the monomer of the structural unit (VI), a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0209] When the high fluorine content polymer has the structural unit (VI), the lower limit of the content ratio of the structural unit (VI) relative to all the structural units constituting the high fluorine content polymer is preferably 40 mol%, more preferably 50 mol%, and further preferably 55 mol%. In addition, the upper limit of the content ratio is preferably 95 mol%, more preferably 90 mol%, and further preferably 85 mol%. By setting the content ratio of the structural unit (VI) within the above range, the water repellency of the resist film during immersion exposure can be further improved, and the occurrence of development defects can be suppressed.

[0210] [Other structural units]

[0211] The high fluorine content polymer may contain a structural unit having an alicyclic structure represented by the above formula (6) as a structural unit other than the structural units listed above.

[0212] When the high fluorine content polymer includes the structural unit having an alicyclic structure, the content ratio of the structural unit having an alicyclic structure relative to all the structural units constituting the high fluorine content polymer is preferably 10 mol%, more preferably 20 mol%, and further preferably 30 mol%. In addition, the upper limit of the content ratio is preferably 60 mol%, more preferably 50 mol%, and further preferably 45 mol%.

[0213] The lower limit of the Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, further preferably 4,000, and particularly preferably 5,000. The upper limit of the Mw is preferably 30,000, more preferably 20,000, further preferably 10,000, and particularly preferably 8,000.

[0214] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0215] When the radiation-sensitive composition includes a high-fluorine content polymer, 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. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 5 parts by mass.

[0216] By setting the content of the high-fluorine-content polymer within the above range, the high-fluorine-content polymer can be more effectively localized in the surface layer of the resist film. As a result, the water repellency of the resist film surface during immersion exposure can be further improved, and the surface of the resist film can be modified or the distribution of the composition within the film can be controlled during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine-content polymers.

[0217] (Synthesis Method of High Fluorine Content Polymer)

[0218] The high fluorine content polymer can be synthesized using the same method as the synthesis method of the base polymer.

[0219] (Radiosensitive acid generator)

[0220] The radiation-sensitive composition of this embodiment preferably further comprises a radiation-sensitive acid generator that generates an acid having a lower pKa than the acid generated by the onium salt (1), i.e., a relatively strong acid, upon irradiation (exposure) with radiation. When the polymer includes a structural unit (I) having an acid-dissociable group, the acid generated by the radiation-sensitive acid generator upon exposure can dissociate the acid-dissociable group of the structural unit (I), thereby generating a carboxyl group or the like. This function differs from that of the onium salt (1). Under the pattern forming conditions using the radiation-sensitive composition, the onium salt (1) does not substantially dissociate the acid-dissociable group of the structural unit (I) or the like in the polymer, thereby suppressing the diffusion of the acid generated by the radiation-sensitive acid generator in unexposed areas. The difference in function between the onium salt (1) and the radiation-sensitive acid generator is determined by the energy required to dissociate the acid-dissociable group of the structural unit (I) or the like in the polymer, and the acidity of the acid generated by the radiation-sensitive acid generator. The radiation-sensitive acid generator in the radiation-sensitive composition may be present as a single compound (free from the polymer), incorporated as part of the polymer, or both. However, it is preferably present as a single compound.

[0221] When the radiation-sensitive composition contains the radiation-sensitive acid generator, the polarity of the polymer in the exposed portion increases, and the polymer in the exposed portion becomes soluble in the developer during development with an alkaline aqueous solution, but becomes poorly soluble in the developer during development with an organic solvent.

[0222] Examples of the radiation-sensitive linear acid generator include onium salts (excluding the onium salt (1) above), sulfonimide compounds, halogen-containing compounds, and diazoketone compounds. Examples of the onium salt include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts. Among these, sulfonium salts and iodonium salts are preferred.

[0223] Examples of acids generated by exposure include those that generate sulfonic acids. Examples of such acids include compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are substituted on carbon atoms adjacent to a sulfonic group. Among these, those having a cyclic structure are particularly preferred as radiation-sensitive acid generators.

[0224] These sensitive radiation linear acid generators can be used alone, and also can be used in combination with two or more.Relative to described base polymer 100 mass parts, the lower limit of the content of sensitive radiation linear acid generator (being these totals when using multiple sensitive radiation linear acid generators) is preferably 2 mass parts, more preferably 5 mass parts.In addition, relative to described base polymer 100 mass parts, the upper limit of described content is preferably 60 mass parts, more preferably 50 mass parts, and then is preferably 45 mass parts.Thus, when resist pattern is formed, can bring into play excellent resist all performances as above.

[0225] (Solvent)

[0226] The radiation-sensitive composition of the present embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the compound (1) and the polymer, and optionally the radiation-sensitive acid generator, etc.

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

[0228] Examples of the alcoholic solvent include:

[0229] Monohydric alcohol solvents with 1 to 18 carbon atoms, such as isopropyl alcohol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol;

[0230] Polyol 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;

[0231] Polyol partial ether solvents obtained by etherifying part of the hydroxyl groups of the polyol solvents, and the like.

[0232] In the present embodiment, alcoholic acid esters such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvent.

[0233] Examples of the ether solvent include:

[0234] Dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether;

[0235] Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;

[0236] Ether solvents containing aromatic rings such as diphenyl ether and anisole (methyl phenyl ether);

[0237] Polyol ether solvents obtained by etherifying the hydroxyl groups of the polyol solvents mentioned above.

[0238] Examples of the ketone solvent include chain ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone;

[0239] Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone;

[0240] 2,4-pentanedione, acetonylacetone, acetophenone, etc.

[0241] Examples of the amide solvent include cyclic amide solvents such as N,N′-dimethylimidazolidinone and N-methylpyrrolidone;

[0242] Chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0243] Examples of the ester solvent include:

[0244] Monocarboxylic acid ester solvents such as n-butyl acetate;

[0245] Polyol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate;

[0246] Lactone solvents such as γ-butyrolactone and valerolactone;

[0247] Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate;

[0248] Polycarboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0249] Examples of hydrocarbon solvents include:

[0250] Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;

[0251] Aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-pentylnaphthalene.

[0252] Among these, alcohol solvents and ester solvents are preferred, polyol partial ether solvents, polyol partial ether acetate solvents, lactone solvents, and monocarboxylic acid ester solvents are more preferred, and propylene glycol monomethyl ether, ethyl lactate, propylene glycol monomethyl ether acetate, and γ-butyrolactone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0253] (Other optional ingredients)

[0254] In addition to the aforementioned components, the radiation-sensitive composition may also contain other optional components. Examples of such other optional components include crosslinking agents, polarization accelerators, surfactants, compounds containing alicyclic skeletons, and sensitizers. These other optional components may be used alone or in combination of two or more. The content of these other optional components is typically 5 parts by mass or less per 100 parts by mass of the polymer.

[0255] <Method for preparing radiation-sensitive composition>

[0256] The radiation-sensitive composition can be prepared, for example, by mixing an onium salt (1), a polymer, a solvent, and, if necessary, a radiation-sensitive acid generator, a high-fluorine content polymer, etc., in a predetermined ratio. The radiation-sensitive composition is preferably filtered, for example, using a filter having a pore size of about 0.1 μm to 0.5 μm after mixing. The solid content concentration of the radiation-sensitive composition is generally 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0257] <Pattern Formation Method>

[0258] A pattern forming method according to one embodiment of the present invention includes:

[0259] Step (1) (hereinafter also referred to as "resist film forming step") is to directly or indirectly apply the radiation-sensitive composition on a substrate to form a resist film;

[0260] Step (2) (hereinafter also referred to as "exposure step"), exposing the resist film; and

[0261] In step (3) (hereinafter also referred to as "development step"), the exposed resist film is developed.

[0262] According to the pattern forming method, a high-quality resist pattern can be formed by using the radiation-sensitive composition having excellent resist properties.

[0263] [Resist Film Formation Step]

[0264] In this step (the step (1)), a resist film is formed using the radiation-sensitive composition. Examples of substrates for forming the resist film include silicon wafers, silicon dioxide, and aluminum-coated wafers. Alternatively, an organic or inorganic antireflection film disclosed in, for example, 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, cast coating, and roll coating. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. PB temperature is typically 60°C to 150°C, preferably 80°C to 140°C. PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film to be formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0265] In the case of immersion exposure, regardless of the presence or absence of a hydrophobic polymer additive such as the high fluorine content polymer in the radiation-sensitive composition, a liquid immersion protective film that is insoluble in the immersion liquid may be provided on the formed resist film for the purpose of avoiding direct contact between the immersion liquid and the resist film. As the liquid immersion protective film, a solvent-peelable protective film that is peeled off using a solvent before the development process (for example, see Japanese Patent Laid-Open No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with the development of the development process (for example, see WO2005-069076 and WO2006-035790) may be used. Among them, from the perspective of production output, it is preferred to use a developer-peelable liquid immersion protective film.

[0266] When the subsequent exposure step is performed using radiation having a wavelength of 50 nm or less, it is preferred to use a polymer having the structural unit (I) and the structural unit (IV) as the base polymer in the composition.

[0267] [Exposure process]

[0268] In this step (the step (2)), the resist film formed in the step (1), i.e., the resist film forming step, is exposed to radiation through a photomask (optionally via an immersion medium such as water). Examples of the radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the target pattern. Of these, far ultraviolet light, electron beams, and EUV are preferred, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred.

[0269] In the case of exposure by immersion exposure, the immersion liquid used may include, for example, water, a fluorine-based inert liquid, etc. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index that is as small as possible to minimize the deformation of the optical image projected onto the film, particularly when the exposure light source is ArF excimer laser light (wavelength 193nm). Based on the above viewpoint, water is preferably used in terms of ease of acquisition, ease of operation, etc. When water is used, an additive that reduces the surface tension of the water and increases the surface activity may be added in a slight proportion. The additive preferably does not dissolve the resist film on the wafer, and its effect on the optical coating on the lower surface of the lens is negligible. Distilled water is preferably used as the water used.

[0270] After the exposure, a post-exposure bake (PEB) is preferably performed. In the exposed portions of the resist film, the acid generated by the radiation-sensitive acid generator during exposure promotes the dissociation of acid-dissociable groups in the polymer, etc. This PEB creates a difference in solubility in the developer between the exposed and unexposed areas. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0271] [Development Process]

[0272] In this step (step (3)), the resist film exposed in step (2), i.e., the exposure step, is developed. This forms a predetermined resist pattern. Generally, after development, the resist film is rinsed with a rinse solution such as water or alcohol and then dried.

[0273] In the case of alkali development, examples of the developer used for the development include alkaline aqueous solutions 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, a TMAH aqueous solution is preferred, and a 2.38% by mass TMAH aqueous solution is more preferred.

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

[0275] As described above, the developer may be an alkaline developer or an organic solvent developer. Preferably, the developer contains an organic solvent, and the obtained pattern is a negative pattern.

[0276] Examples of the developing method include: a method of immersing a substrate in a tank filled with a developer for a fixed period of time (immersion method); a method of performing development by utilizing surface tension to deposit the developer on the surface of the substrate and allowing the developer to remain stationary for a fixed period of time (puddle method); a method of spraying the developer onto the surface of the substrate (spray method); a method of continuously spraying the developer onto the substrate rotating at a fixed speed while scanning a developer spray nozzle at a fixed speed (dynamic distribution method), etc.

[0277] <Onium salt (1)>

[0278] The onium salt according to another embodiment of the present invention is represented by the following formula (1).

[0279] [Chemistry 24]

[0280]

[0281] (In formula (1),

[0282] Q 1 and Q 2 are independently a carbon atom or a nitrogen atom; wherein, Q 1 and Q 2 At least one of is a carbon atom;

[0283] W is the Q in the formula 1 and Q 2 Together they form a monocyclic or polycyclic non-aromatic ring structure with 3 to 40 ring members;

[0284] Q in the formula1 With Q 2 The following formula between represents a single bond or a double bond;

[0285] [Chemistry 25]

[0286]

[0287] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; in R 1 When there are multiple R 1 the same as or different from each other;

[0288] m1 is an integer from 0 to 4;

[0289] Z + is a monovalent onium cation)

[0290] As the onium salt represented by the formula (1) in this embodiment, the onium salt (1) contained in the radiation-sensitive composition can be preferably used.

[0291] Example

[0292] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples. The following describes the measurement methods of various physical properties.

[0293] [Weight average molecular weight (Mw) and number average molecular weight (Mn)]

[0294] The Mw and Mn of the polymer were measured under the above-mentioned conditions. The dispersion degree (Mw / Mn) was calculated based on the measurement results of Mw and Mn.

[0295] [ 13 C-NMR ( 13 C-Nuclear Magnetic Resonance, 13 C-NMR) analysis]

[0296] polymeric 13 C-NMR analysis was performed using a nuclear magnetic resonance apparatus ("JNM-Delta400" manufactured by JEOL Ltd.).

[0297] Synthesis of polymers and high-fluorine polymers

[0298] The monomers used in the synthesis of each polymer and high-fluorine content polymer in each Example and each Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is taken as 100 parts by mass, and mole % refers to the value when the total number of moles of the monomers used is taken as 100 mole %.

[0299] [Chemistry 26]

[0300]

[0301] [Synthesis example 1]

[0302] (Synthesis of Polymer (A-1))

[0303] Monomers (M-1), (M-4), (M-5), (M-11), and (M-14) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 40 / 10 / 20 / 20 / 10 (mol%). A monomer solution was prepared by adding azobisisobutyronitrile (AIBN) as an initiator (3 mol% relative to the total 100 mol% of the monomers used). 2-Butanone (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. The reaction vessel was then set to 80°C and the monomer solution was added dropwise over 3 hours while stirring. The polymerization reaction was initiated by the start of the addition, and the reaction was continued for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was added to methanol (2,000 parts by mass), and the precipitated white powder was separated by filtration. The white powder separated by filtration was washed twice with methanol, separated by filtration, and dried at 50°C for 24 hours to obtain a white powder polymer (A-1) (yield: 80%). The Mw of polymer (A-1) was 9,100, and the Mw / Mn was 1.54. 13 As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-4), (M-5), (M-11), and (M-14) were 40.6 mol%, 9.7 mol%, 21.1 mol%, 20.5 mol%, and 8.1 mol%, respectively.

[0304] [Synthesis Examples 2 to 11]

[0305] (Synthesis of Polymers (A-2) to (A-11))

[0306] Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the monomers of the types and blending ratios shown in Table 1 were used. The content ratios (mol %) of the structural units and the physical properties (Mw and Mw / Mn) of the resulting polymers are shown in Table 1. "-" in Table 1 indicates that the corresponding monomer was not used (the same applies to the following tables).

[0307] [Table 1]

[0308]

[0309] [Synthesis Example 12]

[0310] (Synthesis of Polymer (A-12))

[0311] The monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) at a molar ratio of 50 / 50 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 1-methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. The reaction vessel was then set to 80°C and the monomer solution was added dropwise over 3 hours while stirring. The start of the addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled to below 30°C. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was separated by filtration. The separated white powder was washed twice with hexane, separated by filtration, and dissolved in 1-methoxy-2-propanol (300 parts by mass). Then, methanol (500 parts by mass), triethylamine (50 parts by mass) and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours while stirring. After the reaction was completed, the residual solvent was distilled off, and the obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The obtained solid was separated by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 79%). The Mw of the polymer (A-12) was 5,200, and the Mw / Mn was 1.60. In addition, 13 As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-18) were 51.3 mol% and 48.7 mol%, respectively.

[0312] [Synthesis Examples 13 to 15]

[0313] (Synthesis of Polymers (A-13) to (A-15))

[0314] Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that the monomers of the types and blending ratios shown in Table 2 were used. The content ratios (mol %) of the structural units and the physical properties (Mw and Mw / Mn) of the obtained polymers are shown in Table 2.

[0315] [Table 2]

[0316]

[0317] [Synthesis Example 16]

[0318] (Synthesis of High Fluorine Content Polymer (E-1))

[0319] Monomer (M-1), monomer (M-14) and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 20 / 10 / 70 (mol%), and AIBN (4 mol%) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after nitrogen flushing for 30 minutes, the temperature in the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the addition was set as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled and cooled to below 30°C. After the solvent was replaced with acetonitrile (400 parts by mass), hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered. This operation was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of high fluorine content polymer (E-1) was obtained (yield: 72%). The high fluorine content polymer (E-1) had an Mw of 6,500 and an Mw / Mn of 1.62. 13 As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1), (M-14), and (M-20) were 20.1 mol%, 9.6 mol%, and 70.3 mol%, respectively.

[0320] [Synthesis Examples 17 to 20]

[0321] (Synthesis of High Fluorine Content Polymers (E-2) to (E-5))

[0322] High fluorine content polymers (E-2) to (E-5) were synthesized in the same manner as in Synthesis Example 16, except that the monomers of the types and blending ratios shown in Table 3 were used. The content ratios (mol %) of the structural units and the physical properties (Mw and Mw / Mn) of the obtained high fluorine content polymers are shown in Table 3.

[0323] [Table 3]

[0324]

[0325] <Synthesis of Acid Diffusion Controller C>

[0326] [Example C1]

[0327] (Synthesis of Compound (C-1))

[0328] Compound (C-1) was synthesized according to the following synthesis scheme.

[0329] [Chemistry 27]

[0330]

[0331] Compound (C-1-1) (20.0 mmol) and 50 g of saturated sodium bicarbonate aqueous solution were added to a reaction vessel and stirred at room temperature for 24 hours. The reaction was stopped by adding 1 M hydrochloric acid, followed by extraction with ethyl acetate and separation of the organic layer. After drying over sodium sulfate, the solvent was distilled off to obtain the dicarboxylic acid (C-1-2) in good yield.

[0332] To the dicarboxylic acid, 20.0 mmol of sodium bicarbonate and 20.0 mmol of triphenylsulfonium chloride were added, along with a mixture of water and dichloromethane (1:3 by mass) to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the compound (C-1) represented by Formula (C-1) in a good yield.

[0333] [Examples C2 to C7]

[0334] (Synthesis of Compounds (C-2) to (C-7))

[0335] Onium salts represented by the following formulae (C-2) to (C-7) were synthesized in the same manner as in Example C1 except that the raw materials and precursors were appropriately changed.

[0336] [Chemistry 28]

[0337]

[0338] [Example C8]

[0339] (Synthesis of Compound (C-8))

[0340] Compound (C-8) was synthesized according to the following synthesis scheme.

[0341] [Chemistry 29]

[0342]

[0343] 20.0 mmol of dimethyl tartrate, 20.0 mmol of acetone, 2.0 mmol of sulfuric acid, and 50 g of chloroform were added to a reaction vessel and stirred at 60°C for 4 hours. After completion of the reaction, saturated aqueous sodium bicarbonate solution was added to the reaction solution, followed by extraction with ethyl acetate, and the organic layer was separated. The resulting organic layer was washed sequentially with saturated aqueous sodium chloride solution and water. After drying over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain an acetal in good yield.

[0344] 50 g of a 1M aqueous sodium hydroxide solution was added to the acetal, and the mixture was stirred at room temperature for 4 hours. 1M hydrochloric acid was added to stop the reaction, followed by extraction with ethyl acetate and separation of the organic layer. After drying over sodium sulfate, the solvent was distilled off to obtain the dicarboxylic acid in good yield.

[0345] To the dicarboxylic acid, 20.0 mmol of sodium bicarbonate and 20.0 mmol of triphenylsulfonium chloride were added, along with a mixture of water and dichloromethane (1:3 by mass) to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the compound (C-8) represented by the formula (C-8) in good yield.

[0346] [Examples C9 to C11]

[0347] (Synthesis of Compounds (C-9) to (C-11))

[0348] Onium salts represented by the following formulae (C-9) to (C-11) were synthesized in the same manner as in Example C8 except that the raw materials and precursors were appropriately changed.

[0349] [Chemistry 30]

[0350]

[0351] [Example C12]

[0352] (Synthesis of Compound (C-12))

[0353] Compound (C-12) was synthesized according to the following synthetic scheme.

[0354] [Chemistry 31]

[0355]

[0356] 20.0 mmol of 5-norbornene-2,3-dicarboxylic anhydride, 20 g of methanol, and 20 g of 12 M hydrochloric acid were added to a reaction vessel and stirred at 65°C for 4 hours. Saturated aqueous sodium bicarbonate solution was then added to the reaction solution to complete the reaction. Ethyl acetate was then added for extraction, and the organic layer was separated. The resulting organic layer was washed sequentially with saturated aqueous sodium chloride solution and water. After drying over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain a diester in good yield.

[0357] To the diester, 30.0 mmol of potassium permanganate and a mixture of water and dichloromethane (1:1 (mass ratio)) were added to prepare a 0.5 M solution, which was then stirred at 55°C for 10 hours. After impurities were removed by filtration through celite, ethyl acetate was added for extraction, and the organic layer was separated. The resulting organic layer was washed sequentially with saturated sodium chloride solution and water. After drying over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the diol in good yield.

[0358] To the diol, 20.0 mmol of acetone, 2.0 mmol of sulfuric acid, and 50 g of chloroform were added, and the mixture was stirred at 80°C for 10 hours. Saturated aqueous sodium bicarbonate solution was then added to the reaction solution to complete the reaction. Ethyl acetate was then added for extraction, and the organic layer was separated. The resulting organic layer was washed sequentially with saturated aqueous sodium chloride solution and water. After drying over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the acetal in a good yield.

[0359] 50 g of a 1M aqueous sodium hydroxide solution was added to the acetal, and the mixture was stirred at 50°C for 5 hours. The reaction was stopped by adding 1M hydrochloric acid, followed by extraction with ethyl acetate. The organic layer was separated and dried over sodium sulfate. The solvent was then distilled off to obtain the dicarboxylic acid in good yield.

[0360] To the dicarboxylic acid, 20.0 mmol of sodium bicarbonate and 20.0 mmol of triphenylsulfonium chloride were added, along with a mixture of water and dichloromethane (1:3 by mass) to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the compound (C-12) represented by Formula (C-12) in good yield.

[0361] [Examples C13 to C15]

[0362] (Synthesis of Compounds (C-13) to (C-15))

[0363] Onium salts represented by the following formulae (C-13) to (C-15) were synthesized in the same manner as in Example C12 except that the raw materials and precursors were appropriately changed.

[0364] [Chemistry 32]

[0365]

[0366] [Example C16]

[0367] (Synthesis of Compound (C-16))

[0368] Compound (C-16) was synthesized according to the following synthetic scheme.

[0369] [Chemistry 33]

[0370]

[0371] 20.0 mmol of diphenyl sulfoxide, 40.0 mmol of 2,6-dimethylphenol, 30.0 mmol of trifluorosulfonic anhydride (Tf2O) and 50 g of dichloromethane were added to the reaction vessel and stirred at 0°C for 4 hours. After that, a saturated aqueous sodium bicarbonate solution was added to the reaction solution to complete the reaction, and dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and water in sequence. After drying with sodium sulfate, the solvent was distilled off and purified by column chromatography to obtain compound (C-16-1) in good yield.

[0372] Potassium carbonate 20.0mmol, tert-butyl bromoacetate 30.0mmol and dimethylformamide 50g are added to the compound (C-16-1), and stirred at room temperature for 4 hours. Afterwards, saturated ammonium chloride aqueous solution is added in the reaction solution and after the reaction is completed, dichloromethane is added for extraction, and the organic layer is separated. Saturated sodium chloride aqueous solution and water are used to clean the obtained organic layer. After being dried using sodium sulfate, the solvent is distilled off and refined using column chromatography, thus obtaining compound (C-16-2) with good yield.

[0373] To compound (C-16-2) were added 50 g of a 1 M aqueous sodium iodide solution and 50 g of dichloromethane, and the mixture was stirred at 50°C for 12 hours. Dichloromethane was then added to the reaction solution for extraction, and the organic layer was separated. The solvent in the obtained organic layer was distilled off, thereby obtaining compound (C-16-3) in a good yield.

[0374] To the compound (C-16-3) were added 20.0 mmol of compound (C-1-2), 20.0 mmol of sodium bicarbonate, 50 g of dichloromethane, and 50 g of water, and the mixture was stirred at room temperature for 4 hours. Dichloromethane was added to the reaction solution for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the compound (C-16) represented by the formula (C-16) in a good yield.

[0375] [Examples C17-C18]

[0376] (Synthesis of Compounds (C-17) to (C-18))

[0377] Onium salts represented by the following formulae (C-17) and (C-18) were synthesized in the same manner as in Example C16 except that the raw materials and precursors were appropriately changed.

[0378] [Chemistry 34]

[0379]

[0380] [Onium salts other than compounds (C-1) to (C-18)]

[0381] CC-1 to CC-8: Compounds represented by the following formulas (CC-1) to (CC-8) (hereinafter, the compounds represented by formulas (CC-1) to (CC-8) may be referred to as "Compound (CC-1)" to "Compound (CC-8)", respectively)

[0382] [Chemistry 35]

[0383]

[0384] [[B]Radiosensitive acid generator]

[0385] B-1 to B-8: Compounds represented by the following formulae (B-1) to (B-8) (hereinafter, compounds represented by formulae (B-1) to (B-8) may be referred to as "compound (B-1)" to "compound (B-8)," respectively)

[0386] [Chemistry 36]

[0387]

[0388] [[D]Solvent]

[0389] D-1: Propylene glycol monomethyl ether acetate

[0390] D-2: Propylene glycol monomethyl ether

[0391] D-3: γ-butyrolactone

[0392] D-4: Ethyl lactate

[0393] [Preparation of positive-type radiation-sensitive composition for ArF exposure]

[0394] [Example 1]

[0395] 100 parts by mass of (A-1) as the polymer [A], 12.0 parts by mass of (B-1) as the radiation-sensitive acid generator [B], 8.0 parts by mass of (C-1) as the acid diffusion controller [C], 3.0 parts by mass of (E-1) as the high fluorine content polymer [E] (solid content), and 3,400 parts by mass of a mixed solvent of (D-1) / (D-2) / (D-3) as the solvent [D] were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0396] [Examples 2 to 45, Examples 60 to 62, and Comparative Examples 1 to 8]

[0397] Radiation-sensitive compositions (J-2) to (J-45), (J-60) to (J-62), and (CJ-1) to (CJ-8) were prepared in the same manner as in Example 1 except that the types and contents of the components shown in Table 4 below were used.

[0398] [Table 4]

[0399]

[0400]

[0401] <Formation of a Resist Pattern Using a Positive-Tone Radiation-Sensitive Composition for ArF Exposure>

[0402] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 100 nm. The prepared positive-type radiation-sensitive composition for ArF exposure was then applied to the lower antireflective film using the spin coater and prebaked (PB) at 100°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 110 nm. Next, the resist film was exposed using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and dipole (σ = 0.9 / 0.7) through a mask pattern of 55 nm lines and spaces. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. Thereafter, the resist film was alkaline developed using a 2.38% by mass aqueous TMAH solution as an alkaline developer. After development, the film was rinsed with water and dried to form a positive resist pattern (55 nm line and space pattern).

[0403] <Evaluation>

[0404] The resist patterns formed using the positive-type radiation-sensitive composition for ArF exposure were evaluated for sensitivity, LWR performance, DOF performance, pattern rectangularity, EL performance, and pattern collapse resistance (minimum collapse size) according to the following methods. The results are shown in Table 5. Furthermore, a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the resist patterns.

[0405] [sensitivity]

[0406] In forming a resist pattern using the positive-type radiation-sensitive composition for ArF exposure, the exposure dose for forming a 55 nm line and space pattern was defined as the optimum exposure dose, and the optimum exposure dose was defined as the sensitivity (mJ / cm 2 ). Regarding sensitivity, 30mJ / cm 2 The following cases are evaluated as "good" and will exceed 30mJ / cm 2 The situation was rated as “poor”.

[0407] [LWR performance]

[0408] The optimal exposure amount obtained in the sensitivity evaluation is irradiated to form a resist pattern of 55nm lines and spaces. Using the scanning electron microscope, the formed resist pattern is observed from the top of the pattern. The deviation of the line width at a total of 500 points is measured, and the 3 sigma value is calculated based on the distribution of the measured values, and the 3 sigma value is set to LWR (nm). The smaller the LWR value, the smaller the roughness of the line and the better. Regarding the LWR performance, the case below 2.5nm is evaluated as "good", and the case exceeding 2.5nm is evaluated as "poor".

[0409] [DOF performance]

[0410] Using the method described in the sensitivity measurement, the depth of focus (DOF) range was measured for a line width of 45 nm to 65 nm, using a mask having a line-and-space pattern (1L1S) with a line width of 55 nm. DOF performance was evaluated as "good" for a line width of 150 nm or greater, and "poor" for a line width of less than 150 nm.

[0411] [Pattern rectangularity]

[0412] A 55 nm line and space resist pattern formed by irradiating the optimal exposure dose determined in the sensitivity evaluation was observed using the scanning electron microscope to evaluate the cross-sectional shape of the line and space pattern. Regarding the rectangularity of the resist pattern, an "A" (excellent) rating was assigned if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape was greater than 1 and less than 1.05; a "B" (good) rating was assigned if it exceeded 1.05 and less than 1.10; and a "C" (poor) rating was assigned if it exceeded 1.10.

[0413] [EL performance (exposure latitude)]

[0414] In the range of exposure amount including the optimum exposure amount, the exposure time is 1 mJ / cm 2 The exposure amount is changed for each unit, and resist patterns are formed separately. The line widths of each line are measured using the scanning electron microscope. Based on the relationship between the obtained line width and the exposure amount, the exposure amount E(60) for a line width of 60 nm and the exposure amount E(50) for a line width of 50 nm are calculated, and the exposure latitude (%) is calculated according to the formula: exposure latitude (EL) = (E(50) - E(60)) × 100 / (optimum exposure amount). The larger the value of the exposure latitude, the smaller the change in the size of the pattern obtained when the exposure amount changes, which can improve the yield rate during device production. Regarding the EL performance, the case of 13% or more is evaluated as "good", and the case of less than 13% is evaluated as "poor".

[0415] [Pattern collapse resistance (minimum collapse size)]

[0416] The mask pattern separating the 55nm lines and spaces was used to expose the film at a dose of 1mJ / cm 2 The exposure was carried out at the same time while changing the unit. The exposure dose was measured by the scanning electron microscope to be less than 1 mJ / cm2 which caused the line collapse. 2 The line width of the pattern formed by the exposure amount is set as the minimum collapse size (nm). The smaller the value, the higher the resistance to pattern collapse.

[0417] [Table 5]

[0418]

[0419]

[0420] The results in Table 5 clearly show that the radiation-sensitive compositions of the Examples, when used for ArF exposure, exhibit excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, EL performance, and minimum collapse size. In contrast, the Comparative Examples exhibited inferior properties compared to the Examples. Therefore, when the radiation-sensitive compositions of the Examples were used for ArF exposure, resist patterns with high sensitivity, excellent LWR performance, DOF performance, and EL performance, and excellent pattern shape and collapse resistance could be formed.

[0421] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure]

[0422] [Example 46]

[0423] 100 parts by mass of (A-12) as the polymer [A], 40.0 parts by mass of (B-1) as the radiation-sensitive acid generator [B], 25.0 parts by mass of (C-1) as the acid diffusion controller [C], 3.0 parts by mass of (E-5) as the high fluorine content polymer [E] (solid content), and 6,550 parts by mass of a mixed solvent of (D-1) / (D-2) / (D-4) as the solvent [D] were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-46).

[0424] [Examples 47 to 57 and Comparative Examples 9 to 13]

[0425] Radiation-sensitive compositions (J-47) to (J-57) and (CJ-9) to (CJ-13) were prepared in the same manner as in Example 46, except that the types and contents of the components shown in Table 6 below were used.

[0426] [Table 6]

[0427]

[0428] <Formation of a Resist Pattern Using a Positive-Tone Radiation-Sensitive Composition for EUV Exposure>

[0429] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 30 nm. The prepared positive-tone radiation-sensitive composition for EUV exposure was applied to the lower antireflective film using the spin coater and subjected to photopolymerization (PB) at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 40 nm. Next, the resist film was exposed using an EUV exposure system (ASML's "NXE3300") with an NA of 0.33, conventional illumination conditions (s=0.89), and an imecDEFECT32FFR02 mask. After exposure, photopolymerization (PEB) was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkali development using a 2.38% by mass TMAH aqueous solution as an alkaline developer, and after development, it was washed with water and dried to form a positive resist pattern (27 nm line and space pattern).

[0430] <Evaluation>

[0431] The sensitivity and LWR performance of the resist pattern formed using the positive-tone radiation-sensitive composition for EUV exposure were evaluated according to the following method. The results are shown in Table 7. The length of the resist pattern was measured using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation).

[0432] [sensitivity]

[0433] In forming a resist pattern using the positive radiation-sensitive composition for EUV exposure, the exposure dose for forming a 27 nm line and space pattern was defined as the optimal exposure dose, and the optimal exposure dose was defined as the sensitivity (mJ / cm 2 ). Regarding sensitivity, 50mJ / cm 2 The following cases are evaluated as "good" and will exceed 50mJ / cm 2 The situation was rated as “poor”.

[0434] [LWR performance]

[0435] The optimal exposure amount obtained in the evaluation of the sensitivity is irradiated, and the mask size is adjusted in a manner to form a 27nm line and space pattern to form a resist pattern. Using the scanning electron microscope, the formed resist pattern is observed from the top of the pattern. The deviation of the line width at a total of 500 points is measured, and the 3 sigma value is calculated based on the distribution of the measured values, and the 3 sigma value is set to LWR (nm). The smaller the value of LWR, the smaller the line shake and the better. Regarding the LWR performance, the case below 3.0nm is evaluated as "good", and the case exceeding 3.0nm is evaluated as "poor".

[0436] [Pattern collapse resistance (minimum collapse size)]

[0437] The mask pattern separating the 27nm lines and spaces was used to expose the film at a dose of 1mJ / cm 2 The exposure was carried out at the same time while changing the unit. The exposure was measured by the scanning electron microscope to be less than 1 mJ / cm2 which caused the line collapse. 2 The line width of the pattern formed by the exposure amount is set as the minimum collapse size (nm). The smaller the value, the higher the resistance to pattern collapse.

[0438] [Table 7]

[0439]

[0440] The results in Table 7 clearly show that the radiation-sensitive compositions of Examples have good sensitivity, LWR performance, and pattern collapse resistance when used for EUV exposure, whereas the Comparative Examples are inferior in various properties compared to the Examples.

[0441] [Preparation of Negative-Tone Radiation-Sensitive Composition for ArF Exposure, Formation and Evaluation of Resist Pattern Using the Composition]

[0442] [Example 58]

[0443] 100 parts by mass of (A-1) as the polymer [A], 10.0 parts by mass of (B-3) as the radiation-sensitive acid generator [B], 4.0 parts by mass of (C-1) as the acid diffusion controller [C], 4.0 parts by mass of (E-4) as the high fluorine content polymer [E] (solid content), and 3,230 parts by mass of a mixed solvent of (D-1) / (D-2) / (D-3) (mass ratio 2240 / 960 / 30) as the solvent [D] were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-58).

[0444] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 100 nm. The prepared negative-type radiation-sensitive composition for ArF exposure (J-58) was applied to the lower antireflective film using the spin coater and prebaked (PB) at 100°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 90 nm. Next, the resist film was exposed using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 60 nm holes and 120 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. The resist film was then organically developed using n-butyl acetate as an organic solvent developer and dried to form a negative-tone resist pattern (60 nm holes, 120 nm pitch).

[0445] The sensitivity of the resist pattern using the negative-type radiation-sensitive composition for ArF exposure was evaluated in the same manner as the evaluation of the resist pattern using the positive-type radiation-sensitive composition for ArF exposure. In addition, the CDU performance and pattern circularity were evaluated according to the following methods.

[0446] [CDU performance]

[0447] The optimal exposure dose determined in the sensitivity evaluation was used to form contact holes with a 60 nm hole and a 120 nm pitch. The resulting resist pattern was observed from the top of the pattern using the scanning electron microscope. The contact hole deviations at a total of 500 locations were measured, and a 3 sigma value was calculated based on the distribution of the measured values. This 3 sigma value was defined as CDU (nm). A smaller CDU value indicates a smaller and better hole roughness. Regarding CDU performance, a value less than 3.5 nm was evaluated as "good," and a value greater than 3.5 nm was evaluated as "poor."

[0448] [Circularity of pattern]

[0449] The 60 nm hole and the 120 nm pitch contact hole formed by irradiating with the optimal exposure dose determined in the sensitivity evaluation were observed from above using the scanning electron microscope, and the longitudinal and lateral dimensions were measured. If the ratio of longitudinal dimension to lateral dimension was 0.95 or greater and less than 1.05, the evaluation was "A" (extremely good); if it was 0.90 or greater and less than 0.95, or 1.05 or greater and less than 1.10, the evaluation was "B" (good); and if it was less than 0.90 or 1.10 or greater, the evaluation was "C" (poor).

[0450] As a result, the radiation-sensitive composition of Example 58 exhibited good sensitivity, CDU performance, and pattern circularity even when a negative-type resist pattern was formed by ArF exposure.

[0451] [Preparation of Negative-Tone Radiation-Sensitive Composition for EUV Exposure, Formation and Evaluation of Resist Pattern Using the Composition]

[0452] [Example 59]

[0453] 100 parts by mass of (A-14) as the polymer [A], 30.0 parts by mass of (B-2) as the radiation-sensitive acid generator [B], 20.0 parts by mass of (C-8) as the acid diffusion controller [C], 2.0 parts by mass of (E-5) as the high fluorine content polymer [E] (solid content), and 6,000 parts by mass of a mixed solvent of (D-1) / (D-2) (mass ratio 4000 / 2000) as the solvent [D] were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-59).

[0454] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 30 nm. The prepared negative-type radiation-sensitive composition for EUV exposure (J-59) was applied to the lower antireflective film using the spin coater and subjected to PB at 130°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 30 nm. The resist film was then exposed using an EUV exposure system (ASML's "NXE3300") with an NA of 0.33, conventional illumination conditions of s = 0.89, and an imecDEFECT32FFR15 mask. After exposure, PEB was performed for 60 seconds at 120° C. Then, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (contact hole pattern with 20 nm holes and 40 nm pitch).

[0455] Resist patterns formed using the negative-working radiation-sensitive composition for EUV exposure were evaluated in the same manner as the resist patterns formed using the negative-working radiation-sensitive composition for ArF exposure. The results showed that the radiation-sensitive composition of Example 59 exhibited excellent sensitivity, CDU performance, and pattern circularity even when forming a negative-working resist pattern using EUV exposure.

[0456] Industrial applicability

[0457] The radiation-sensitive composition, pattern forming method, and onium salt described above can form a resist pattern that exhibits good sensitivity to exposure light and excellent LWR performance, DOF performance, pattern rectangularity, EL performance, pattern collapse resistance, CDU performance, and pattern circularity. Therefore, these compositions are preferably used in processes for semiconductor devices, which are expected to continue to be miniaturized.

Claims

1. A radiation-sensitive composition comprising: Onium salt represented by the following formula (1), A polymer containing a structural unit (I) having an acid-dissociable group, and solvent. [Chemistry 1] (In formula (1), Q 1 and Q 2 are independently a carbon atom or a nitrogen atom. Q 1 and Q 2 At least one of them is a carbon atom. W is the same as Q in the formula 1 and Q 2 Together they constitute a monocyclic or polycyclic non-aromatic ring structure having 3 to 40 ring members. Q in the formula 1 With Q 2 The following formula between represents a single bond or a double bond. [Chemistry 2] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; in R 1 When there are multiple R 1 Same as or different from each other. m1 is an integer from 0 to 4. Z + is a monovalent onium cation).

2. The radiation-sensitive composition according to claim 1, wherein The non-aromatic ring structure is a monocyclic or polycyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms, a monocyclic or polycyclic aliphatic heterocyclic structure having 3 to 20 carbon atoms, or a combination thereof.

3. The radiation-sensitive composition according to claim 1, wherein The non-aromatic ring structure is a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornane ring, a tricyclodecane ring, a tetracyclododecane ring, an adamantane ring, a ring structure in which a portion of the carbon atoms constituting these ring structures are substituted by -O-, -CO- or a combination thereof, or a combination thereof.

4. The radiation-sensitive composition according to any one of claims 1 to 3, wherein Z + is a monovalent sulfonium cation containing at least one aromatic ring or a monovalent iodonium cation containing at least one aromatic ring.

5. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The content of the onium salt is 0.1 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the polymer.

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The structural unit (I) is represented by the following formula (3). [Chemistry 3] (In formula (3), R 17 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 18 It is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R 19 and R 20 are independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R 19 and R 20 (a divalent alicyclic group having 3 to 20 carbon atoms that is bonded to each other and formed together with these bonded carbon atoms).

7. The radiation-sensitive composition according to any one of claims 1 to 3, wherein In formula (3), R 18 、R 19 and R 20 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; or R 18 is a monovalent hydrocarbon group having 1 to 20 carbon atoms and R 19 and R 20 It represents a divalent polycyclic aliphatic hydrocarbon group having 5 to 20 carbon atoms formed by combining with each other and with these bonded carbon atoms.

8. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The content ratio of the structural unit (I) in all the structural units constituting the polymer is 10 mol% or more and 90 mol% or less.

9. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The polymer further includes a structural unit (II) containing at least one selected from the group consisting of a polycyclic lactone structure, a cyclic carbonate structure, and a sultone structure.

10. The radiation-sensitive composition according to claim 7, wherein The content ratio of the structural unit (II) in all the structural units constituting the polymer is 10 mol% or more and 90 mol% or less. 11 . The radiation-sensitive composition according to claim 1 , further comprising a radiation-sensitive acid generator that generates an acid having a lower pKa than the acid generated from the onium salt upon irradiation with radiation.

12. A pattern forming method comprising: A step of directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 3 on a substrate to form a resist film; a step of exposing the resist film to light; and A step of developing the exposed resist film using a developer.

13. The pattern forming method according to claim 12, wherein: The exposure is performed by ArF excimer laser or extreme ultraviolet rays.

14. An onium salt represented by the following formula (1). [Chemistry 4] (In formula (1), Q 1 and Q 2 are independently a carbon atom or a nitrogen atom; wherein, Q 1 and Q 2 At least one of them is a carbon atom. W is the same as Q in the formula 1 and Q 2 Together they constitute a monocyclic or polycyclic non-aromatic ring structure having 3 to 40 ring members. Q in the formula 1 With Q 2 The following formula between represents a single bond or a double bond. [Chemistry 5] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a nitro group, a hydroxyl group, an amino group, a thiol group, a cyano group, a carboxyl group or a halogen atom; in R 1 When there are multiple R 1 Same as or different from each other. m1 is an integer from 0 to 4. Z + is a monovalent onium cation).

15. The pattern forming method according to claim 14, wherein Z + is a monovalent sulfonium cation containing at least one aromatic ring or a monovalent iodonium cation containing at least one aromatic ring.

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