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

Abstract

Provided are: a radiation-sensitive composition that makes it possible to achieve substantial sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity when a resist pattern is formed; a pattern formation method; and an onium salt compound. A radiation-sensitive composition according to the present invention includes an onium salt compound represented by formula (1), a polymer that includes a structural unit that has an acid-dissociable group, and a solvent.　(In formula (1), A is a C1–40 monovalent organic group, R1 and R2 are each independently a hydrogen atom, a C1–20 monovalent fluorine-free organic group, a cyano group, a nitro group, a hydroxyl group, or an amino group, each of the R1s and R2s being the same or different when there are a plurality of R1s and R2s, m1 is an integer from 1 to 8, inclusive, and Z+ is a monovalent radiation-sensitive onium cation.)

Description

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

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

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

[0003] The photolithography technology described above is promoting pattern miniaturization by using short-wavelength radiation such as ArF excimer lasers, and further by using liquid immersion lithography, in which exposure is performed with the space between the lens of the exposure device and the resist film filled with a liquid medium. Lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation technology.

[0004] As for the photoacid generator, which is a main component of a resist composition, perfluoroalkylsulfonic acids capable of imparting strong acidity are often used in order to improve sensitivity, resolution, etc. Meanwhile, due to the recent increase in environmental awareness, photoacid generators with reduced fluorine atom content have been investigated (see Japanese Patent No. 7015295).

[0005] Patent No. 7015295

[0006] Even with a photoacid generator having a reduced content of fluorine atoms, resist performance equivalent to or better than conventional ones is required in terms of sensitivity, LWR (Line Width Roughness) performance indicating variations in line width and line width of the resist pattern, DOF (Depth Of Focus) performance, pattern rectangularity indicating the rectangularity of the cross-sectional shape of the resist pattern, critical dimension uniformity (CDU) performance which is an index of the uniformity of line width and hole diameter, pattern circularity indicating the circularity of the hole shape, and the like.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern formation method, and an onium salt compound that are capable of exhibiting sufficient levels of sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity during resist pattern formation.

[0008] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0009] That is, in one embodiment, the present invention provides a radiation-sensitive composition comprising: an onium salt compound represented by the following formula (1) (hereinafter also referred to as “onium salt compound (1)”); a polymer including a structural unit having an acid-dissociable group; and a solvent. (In formula (1), A is a monovalent organic group having 1 to 40 carbon atoms. R １ and R ２ are each independently a hydrogen atom, a monovalent non-fluorine-containing organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxy group, or an amino group. １ and R ２ If there are multiple R １ and R ２ are the same or different. １ is an integer from 1 to 8. ＋ is a monovalent radiation-sensitive onium cation.

[0010] The radiation-sensitive composition contains the onium salt compound (1) as a radiation-sensitive acid generator, and therefore can exhibit excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity during pattern formation. The reason for this is presumed to be as follows, without being bound by any theory.

[0011] In onium salt compound (1), a sulfonyl group is contained in the anion backbone chain at an appropriate distance from the sulfonate anion. This electron-withdrawing property allows onium salt compound (1) to generate a sufficiently strong acid, and its polarity appropriately controls solubility and interactions with other components. As a result, it is believed that the desired resist performance can be achieved. Furthermore, reducing the fluorine atom content can also limit environmental impact. The term "organic group" refers to a group containing at least one carbon atom (but does not include an ionic structure). Structures that are themselves functional or characteristic groups, such as a cyano group or a carbonyl group, are not included in the organic group.

[0012] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film.

[0013] The pattern formation method uses the radiation-sensitive composition, which exhibits excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity during pattern formation, and therefore can efficiently form a high-quality resist pattern.

[0014] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1): (In formula (1), A is a monovalent organic group having 1 to 40 carbon atoms. R １ and R ２ are each independently a hydrogen atom, a monovalent non-fluorine-containing organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxy group, or an amino group. １ and R ２ If there are multiple R １ and R ２ are the same or different. １ is an integer from 1 to 8. ＋ is a monovalent radiation-sensitive onium cation.

[0015] The onium salt compound has a characteristic structure containing a sulfonyl group in the backbone chain of the anionic structure, and therefore can be suitably used as a radiation-sensitive acid generator in a radiation-sensitive composition.

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

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains an onium salt compound (1), a polymer containing a structural unit having an acid-dissociable group, and a solvent. It may further contain an acid diffusion controller as needed. The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0018] (Onium Salt Compound (1)) The onium salt compound is represented by the above formula (1) and functions as a radiation-sensitive acid generator that generates an acid upon irradiation with radiation.

[0019] The monovalent organic group having 1 to 40 carbon atoms represented by A is not particularly limited, and may be a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group in which some or all of the hydrogen atoms contained in the hydrocarbon group have been substituted with substituents (hereinafter also referred to as "group (α)"), or a group in which -CO-, -CS-, -O-, -S-, -SO ２ -, -NR'-, a group containing a combination of two or more of these (hereinafter also referred to as "group (β)"), or a combination of these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0020] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and combinations thereof.

[0021] 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.

[0022] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic cycloalkyl groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl groups. A bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0023] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0024] The group (β) is also preferably a group containing a heterocyclic group containing a heteroatom between carbon atoms constituting the ring. Examples of the heterocyclic group include a group in which one hydrogen atom has been removed from an aromatic heterocyclic structure and a group in which one hydrogen atom has been removed from an aliphatic heterocyclic structure. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0025] Examples of the aromatic heterocyclic structure include: oxygen atom-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0026] Examples of the aliphatic heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0027] The aliphatic heterocyclic structure also includes a lactone structure, a cyclic carbonate structure, a sultone structure, and a structure containing a cyclic acetal, such as those represented by the following formulas (H-1) to (H-12).

[0028]

[0029] In the above formula, γ is an integer of 1 to 3.

[0030] Examples of the substituent that substitutes some or all of the hydrogen atoms of the organic group include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; hydroxy groups; carboxy groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and oxo groups (═O).

[0031] In the above formula (1), A is preferably a monovalent chain organic group having 1 to 20 carbon atoms, or a monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure. Examples of the cyclic structure include a structure corresponding to the above monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a structure corresponding to the above monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, a structure corresponding to the above heterocyclic group, or a combination thereof. Examples of combinations include fused rings in which two adjacent rings share one side (a bond between two adjacent atoms), ring assemblies in which two adjacent rings are bonded by a single bond, and spiro rings in which two adjacent rings share one carbon atom.

[0032] The monovalent organic group having 1 to 40 carbon atoms represented by A, whether in a chain or a cyclic structure, preferably contains at least one of an ester bond, an amide bond, an ether bond, and an acetal structure, from the viewpoints of molecular design, solubility, control of acid diffusion length, and the like.

[0033] R １ and R ２ As the monovalent fluorine-free organic group having 1 to 20 carbon atoms represented by the formula (I), a group corresponding to a carbon number of 1 to 20 among the monovalent organic groups having 1 to 40 carbon atoms represented by A can be suitably used, except that it does not contain a fluorine atom.

[0034] R １ and R ２ is preferably a hydrogen atom in terms of acid diffusibility due to flexibility.

[0035] m １ is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 1 or 2.

[0036] Specific examples of the anion moiety of the onium salt compound (1) include, but are not limited to, structures of the following formulae (1-1-1) to (1-1-45).

[0037]

[0038]

[0039] In the formula (1), the Z ＋ Examples of the monovalent radiation-sensitive onium cation represented by the formula (I) include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the radiation-decomposable onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Among these, sulfonium cation or iodonium cation is preferred. Z ＋preferably contains at least one aromatic ring, and more preferably is a monovalent sulfonium cation containing at least one aromatic ring or a monovalent iodonium cation containing at least one aromatic ring. The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0040]

[0041] In the above formula (X-1), R ａ１ , R ａ２ and R ａ３ are each 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 hydroxy group, a halogen atom, or —OSO ２ -R Ｐ , -SO ２ -R Ｑ or -S-R Ｔ or a ring structure formed by combining two or more of these groups. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton. R Ｐ , R Ｑ and R Ｔ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ If there are multiple R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ may be the same or different.

[0042] In the above formula (X-2), R ｂ１is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ is 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ may be the same or different, and multiple R ｂ１ may represent a ring structure formed by combining with each other. ｂ２ 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 of 0 to 4. R ｂ２ If there are multiple R ｂ２ may be the same or different, and multiple R ｂ２ may represent a ring structure formed by combining with each other, and q is an integer of 0 to 3. ＋ The ring structure containing the following may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton.

[0043] In the above formula (X-3), R ｃ１ , R ｃ２ and R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms. ｃ１ , R ｃ２ and R ｃ３ At least one selected from the group consisting of is a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0044] In the above formula (X-4), R ｇ１is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ２ is 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ may be the same or different, and multiple R ｇ１ may represent a ring structure formed by combining with each other. ｇ２ and R ｇ３ are each 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 hydroxy group, a halogen atom, or a ring structure formed by combining these groups together. k11 and k12 are each independently an integer of 0 to 4. R ｇ２ and R ｇ３ If there are multiple R ｇ２ and R ｇ３ may be the same or different.

[0045] In the above formula (X-5), R ｄ１ and R ｄ２ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, 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 each independently an integer of 0 to 5. R ｄ１ and R ｄ２ If there are multiple R ｄ１ and R ｄ２ may be the same or different.

[0046] In the above formula (X-6), R ｅ１ and R ｅ２ are each 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.

[0047] Specific examples of the radiation-sensitive onium cation include, but are not limited to, structures of the following formulae (1-2-1) to (1-2-59).

[0048]

[0049]

[0050]

[0051] The onium salt compound (1) can be obtained by appropriately combining the above-mentioned anion moiety with the above-mentioned radiation-sensitive onium cation. Specific examples include, but are not limited to, structures of the following formulae (1-1) to (1-45):

[0052]

[0053]

[0054]

[0055]

[0056]

[0057] The lower limit of the content of onium salt compound (1) (when multiple types of onium salt compound (1) are contained, the total amount thereof) is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, per 100 parts by mass of the polymer described below. The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass. The content of onium salt compound (1) is appropriately selected depending on the type of polymer used, exposure conditions, desired sensitivity, and the like. This allows the composition to exhibit excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity during resist pattern formation.

[0058] (Method for synthesizing onium salt compound (1)) As a method for synthesizing the onium salt compound (1), １ is 2, and two R １ and two R ２ A typical scheme is shown below, where each of the is a hydrogen atom.

[0059]

[0060] In the above scheme, A and Z ＋ has the same meaning as in formula (1). １ and X ２ is a halogen atom.

[0061] A thioether-containing onium salt is obtained by reacting a halogenated sulfonate with a thiol having a structure corresponding to A, followed by reaction with an onium cation halide salt corresponding to the onium cation moiety to allow salt exchange to proceed. Finally, the thioether moiety of the thioether-containing onium salt is oxidized with an oxidizing agent (hydrogen peroxide in the scheme), thereby synthesizing the desired onium salt compound (1) represented by formula (1α). The desired onium salt compound (1) represented by formula (1α) may also be synthesized by salt exchange of a sulfonyl group-containing sulfonate. Onium salt compounds (1) having other structures can also be synthesized by appropriately selecting starting materials or precursors corresponding to the anion moiety and onium cation moiety.

[0062] In addition to the above scheme, the target onium salt compound (1) can also be synthesized by reacting a raw material compound capable of providing an active methylene structure at the α-position of the sulfonyl group with a sulfonating agent to sulfonate the compound, and then reacting the compound with an onium cation halide salt to cause salt exchange.

[0063] (Polymer) The polymer is an aggregate of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)") (hereinafter this polymer will also be referred to as "base polymer"). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The radiation-sensitive composition has excellent pattern formability because the polymer contains the structural unit (I).

[0064] In addition to the structural unit (I), the base polymer preferably contains a structural unit (II) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, which will be described later, and may contain structural units other than the structural units (I) and (II). Each structural unit will be described below.

[0065] [Structural Unit (I)] The structural unit (I) is a structural unit containing an acid-dissociable group. The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability 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.

[0066]

[0067] In the above 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 ２０are each 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 a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded.

[0068] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0069] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) 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.

[0070] The above R １８ ~R ２０ As the chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (1), a group corresponding to the number of carbon atoms of the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms represented by A in the formula (1) can be suitably used.

[0071] The above R １８ ~R ２０ As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) can be suitably used.

[0072] The above R １８ As the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1), the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) can be suitably used.

[0073] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0074] The above R １９ and R ２０The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group in which two hydrogen atoms have been removed from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0075] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７ ] Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0076] Among these, R １８ is an alkyl group having 1 to 4 carbon atoms, and R １９ and R ２０ The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0077] Examples of the structural unit (I-1) include structural units represented by the following formulas (3-1) to (3-8) (hereinafter also referred to as "structural units (I-1-1) to (I-1-8)").

[0078]

[0079] In the above formulas (3-1) to (3-8), R １７ ~R ２０ has the same meaning as in 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.

[0080] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, or a cyclopentyl group. １９ and R ２０ As the alkyl group, a methyl group or an ethyl group is preferred.

[0081] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0082] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, and particularly preferably 35 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, even more preferably 60 mol%, and particularly preferably 55 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0083] [Structural Unit (II)] The structural unit (II) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (II), the base polymer can adjust its solubility in a developer, thereby improving the lithography 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.

[0084] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-11).

[0085]

[0086] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５are each 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 hydroxy group, a hydroxymethyl group, or a dimethylamino group. Ｌ４ and R Ｌ５ may be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining together with the carbon atoms to which they are attached. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0087] The above R Ｌ４ and R Ｌ５ Examples of the divalent alicyclic group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded include R １９ and R ２０ Among divalent alicyclic groups having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, groups having 3 to 8 carbon atoms are exemplified. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0088] The above L ２ Examples of the divalent linking group represented by the formula (I) 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 group selected from -CO-, -O-, -NH-, and -S-.

[0089] Of 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 even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0090] The lower limit of the content of the structural unit (II) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 15 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0091] [Structural Unit (III)] The base polymer optionally has other structural units in addition to the structural units (I) and (II). Examples of the other structural units include a structural unit (III) containing a polar group (excluding those corresponding to the structural unit (II)). By further including the structural unit (III), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as the resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0092] Examples of the structural unit (III) include structural units represented by the following formula:

[0093]

[0094] In the above formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0095] When the base polymer has the structural unit (III) having the polar group, the lower limit of the content of the structural unit (III) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of the structural unit (III) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0096] [Structural Unit (IV)] The base polymer optionally has, as another structural unit, a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)") in addition to the structural unit (III) having the polar group. The structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, it is suitable for pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beams or EUV. In this case, it is preferable that the polymer has structural unit (I) in addition to structural unit (IV).

[0097] The structural unit having a phenolic hydroxyl group is represented by, for example, the following formulas (4-1) to (4-6).

[0098]

[0099] In the above formulas (4-1) to (4-6), R ４１ are each 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, acyloxy group, or alkoxycarbonyl group having 2 to 7 carbon atoms. When there are multiple Ys, the multiple Ys may be the same or different. t is an integer of 0 to 4.

[0100] In order to obtain the structural unit (IV), it is preferable to carry out polymerization in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group) during polymerization, and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis. Alternatively, a monomer that gives the structural unit (IV) may be polymerized without protecting the phenolic hydroxyl group.

[0101] In the case of a polymer for exposure to radiation having a wavelength of 50 nm or less, the lower limit of the content of the structural unit (IV) is preferably 10 mol %, more preferably 20 mol %, based on all structural units constituting the polymer, and the upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0102] [Other Structural Units] The base polymer may contain a structural unit having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)") as a structural unit other than the structural units listed above. (In the above formula (6), R １α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0103] In the above formula (6), R ２α As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) can be suitably used.

[0104] When the base polymer contains the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to all structural units constituting the base polymer, and the upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%.

[0105] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0106] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0107] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; cyclic esters such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and partial ethers of polyhydric alcohols; Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol, etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0108] 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.

[0109] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 4,500. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 10,000, and particularly preferably 8,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0110] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0111] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0112] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40°C Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0113] The content of the base polymer is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0114] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer. As a result, it is possible to increase the water repellency of the surface of the resist film during immersion exposure, and to modify the surface of the resist film during EUV exposure and control the distribution of composition within the film.

[0115] 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 have the structural unit (I) or the structural unit (III) of the base polymer, as necessary.

[0116]

[0117] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. １４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0118] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0119] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and —COO— are preferred, and —COO— is more preferred.

[0120] The above R １４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0121] The above R １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0122] The above R １４As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 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 are even more preferable.

[0123] When the high-fluorine content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content 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 uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0124] The high-fluorine content polymer may 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 or instead of the structural unit (V). By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0125]

[0126] The structural unit (VI) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ 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 Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄR has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0127] When the structural unit (VI) has an alkali-soluble group (x), R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VI) has an alkali-soluble group (x), it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0128] When the structural unit (VI) has an alkali-dissociable group (y), R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VI) has an alkali-dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. Examples of the structural unit (VI) having an alkali-dissociable group (y) include A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0129] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0130] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and even more preferably a group having a norbornane lactone structure.

[0131] When the high-fluorine-content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (VI) within the above range, it is possible to increase the water repellency of the resist film during immersion exposure and to improve the solubility in an alkaline developer, thereby suppressing the occurrence of development defects.

[0132] [Other Structural Units] The high fluorine content polymer may contain, as a structural unit other than the structural units listed above, the structural unit (VII) in addition to the structural unit (I) and the structural unit (III) in the base polymer.

[0133] When the high-fluorine content polymer contains the structural unit (I), the structural unit (III), or the structural unit (VII), the content ratio of each structural unit in the high-fluorine content polymer can suitably be the content ratio described for the base polymer.

[0134] The lower limit of Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 10,000, and particularly preferably 8,000.

[0135] 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.

[0136] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 6 parts by mass or less, and particularly preferably 4 parts by mass or less.

[0137] 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, which results in improving the water repellency of the surface of the resist film during immersion lithography, and enabling control of the surface modification of the resist film and the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more high fluorine content polymers.

[0138] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0139] (Acid Diffusion Controller) The radiation-sensitive composition may contain an acid diffusion controller, if necessary. The acid diffusion controller controls the diffusion phenomenon in the resist film of the acid generated from the onium salt compound (1) upon exposure, thereby suppressing undesirable chemical reactions in unexposed areas. The storage stability of the resulting radiation-sensitive composition is also improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the incubation time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0140] Examples of the acid diffusion controller include a compound represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compound (I)"), a compound having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compound (II)"), a compound having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compound (III)"), an amide group-containing compound, a urea compound, and a nitrogen-containing heterocyclic compound.

[0141]

[0142] In the above formula (7), R ２２ , R ２３ and R ２４ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0143] Examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0144] Examples of the nitrogen-containing compound (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0145] Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0146] Examples of the amide group-containing compound include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0147] Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0148] Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; pyrazine, pyrazole, and the like.

[0149] Furthermore, a compound having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of such nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0150] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can also be suitably used as the acid diffusion controller. The acid generated by the radiation-sensitive weak acid generator is a weak acid that does not induce dissociation of the acid-dissociable group in the polymer under conditions that dissociate the acid-dissociable group. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

[0151] Examples of the radiation-sensitive weak acid generator include onium salt compounds that decompose upon exposure to light and lose their ability to control acid diffusion. Examples of the onium salt compound include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Other examples include compounds containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule represented by the following formula (8-4).

[0152]

[0153] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. ＋Examples of the sulfonium cation represented by the formula (X-1) to (X-4) include sulfonium cations represented by the formula (X-1) to (X-4), and U ＋ Examples of the iodonium cation represented by the formula (X-5) to (X-6) include the iodonium cation represented by the formula (X-6). － and Q － are each independently OH － , R α -COO － , R α -SO ３ － It is an anion represented by R α is a single bond or a monovalent organic group having 1 to 30 carbon atoms. Examples of this organic group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of this hydrocarbon group or at the carbon chain end, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0154] As the monovalent hydrocarbon group having 1 to 20 carbon atoms, the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by A in the above formula (1) can be suitably used.

[0155] Examples of heteroatoms constituting the divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, etc. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0156] Examples of the divalent heteroatom-containing group include -CO-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ -, or a group in which these are combined.

[0157] Examples of the monovalent heteroatom-containing group include a hydroxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0158] Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula:

[0159]

[0160]

[0161] Of these, the radiation-sensitive weak acid generator is preferably a sulfonium salt, more preferably a triarylsulfonium salt, and even more preferably triphenylsulfonium salicylate or triphenylsulfonium 10-camphorsulfonate.

[0162] The lower limit of the content of the acid diffusion controller relative to 100 parts by mass of the polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, and the upper limit of the content is preferably 30 parts by mass, more preferably 25 parts by mass, and even more preferably 20 parts by mass.

[0163] By setting the content of the acid diffusion controller within the above range, the lithography performance of the radiation-sensitive composition can be further improved. The radiation-sensitive composition may contain one or more types of acid diffusion controller.

[0164] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt compound (1) and the polymer, as well as an optional acid diffusion controller and the like.

[0165] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0166] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0167] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0168] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0169] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0170] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0171] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0172] Among these, alcohol-based solvents, ester-based solvents, and ether-based solvents are preferred, alcohol acid ester-based solvents, polyhydric alcohol partial ether-based solvents, polyhydric alcohol partial ether acetate-based solvents, lactone-based solvents, monocarboxylic acid ester-based solvents, and ketone-based solvents are more preferred, and propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, γ-butyrolactone, ethyl lactate, and cyclohexanone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0173] (Other Optional Components) The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0174] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the onium salt compound (1), a polymer, and, if necessary, a high-fluorine-content polymer, and a solvent in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.40 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0175] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention includes the steps of: applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); exposing the resist film (hereinafter also referred to as an "exposing step"); and developing the exposed resist film (hereinafter also referred to as a "developing step").

[0176] According to the pattern formation method, the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity during pattern formation, and therefore a high-quality resist pattern can be efficiently formed. Each step will be described below.

[0177] [Resist Film Formation Step] In this step, a resist film is formed from the radiation-sensitive composition. Examples of substrates on which this resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 70°C to 150°C, preferably 90°C to 140°C. The PB time is typically 5 to 600 seconds, preferably 10 to 300 seconds.

[0178] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 20 nm, and even more preferably 30 nm, and the upper limit of the thickness is preferably 400 nm, more preferably 300 nm, and even more preferably 250 nm.

[0179] When performing immersion exposure, regardless of whether the radiation-sensitive composition contains a water-repellent polymer additive such as a high-fluorine-content polymer, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-peelable protective film that is peeled off with a solvent before the development step (see, for example, JP-A 2006-227632), or a developer-peelable protective film that is peeled off simultaneously with development in the development step (see, for example, WO 2005-069076 and WO 2006-035790). However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective film for immersion exposure.

[0180] When the next exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural units (I) and (IV) as the base polymer in the composition.

[0181] [Exposure Step] In this step, the resist film formed in the resist film formation step is exposed to radiation through a photomask (or, in some cases, through an immersion liquid such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0182] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser beam (wavelength 193 nm), water is preferred from the above-mentioned viewpoints, as well as from the viewpoints of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0183] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 160°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0184] [Development Step] In this step, the resist film exposed in the exposure step is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0185] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0186] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0187] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0188] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispense method).

[0189] <Onium Salt Compound> The onium salt compound according to this embodiment is represented by the following formula (1). (In formula (1), A is a monovalent organic group having 1 to 40 carbon atoms. R １ and R ２ are each independently a hydrogen atom, a monovalent non-fluorine-containing organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxy group, or an amino group. １ and R ２ If there are multiple R １ and R ２ are the same or different. １ is an integer from 1 to 8. ＋ is a monovalent radiation-sensitive onium cation.

[0190] As the onium salt compound, the onium salt compound (1) in the radiation-sensitive composition can be suitably used.

[0191] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0192] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0193] [ １３C-NMR analysis of polymer １３ C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0194] <Synthesis of Polymer> The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value when the total mass of the monomers used is taken as 100 parts by mass, and mol % refers to a value when the total number of moles of the monomers used is taken as 100 mol %.

[0195]

[0196] Synthesis Example 1 Synthesis of Polymer (A-1) Monomer (M-1), monomer (M-2), monomer (M-5), monomer (M-10), and monomer (M-14) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 40 / 10 / 20 / 20 / 10 (mol %), and AIBN (azobisisobutyronitrile) (5 mol % relative to 100 mol % of the total monomers used) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerized solution was cooled to below 30°C with water. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered off, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 89%). The Mw of the polymer (A-1) was 7,100, and the Mw / Mn was 1.61. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-2), (M-5), (M-10) and (M-14) were 40.3 mol%, 9.2 mol%, 20.5 mol%, 19.8 mol% and 10.2 mol%, respectively.

[0197] Synthesis Examples 2 to 11 (Synthesis of Polymers (A-2) to (A-11)) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Table 1 below were used. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymers are also shown in Table 1 below. In Table 1 below, "-" indicates that the corresponding monomer was not used (the same applies to the following tables).

[0198]

[0199] Synthesis Example 12 Synthesis of Polymer (A-12) Monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to a molar ratio of 50 / 50 (mol %), and AIBN (7 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 after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to below 30°C. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The white powder separated by filtration was washed twice with hexane, filtered off, and dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, 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 with stirring. After completion of the reaction, the residual solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to coagulate the polymer. The resulting solid was filtered and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 81%). The Mw of the polymer (A-12) was 5,500, and the Mw / Mn was 1.62. １３ As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-18) were 50.2 mol % and 49.8 mol %, respectively.

[0200] [Synthesis Examples 13 to 15] (Synthesis of Polymers (A-13) to (A-15)) Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that the types and blending ratios of monomers shown in Table 2 below were used. Note that the monomer that gives the structural unit (IV) is １３ C-NMR analysis confirmed that the peaks of the carbonyl groups of the acetyl groups had disappeared, and that substantially all of the alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymer are also shown in Table 2 below.

[0201]

[0202] Synthesis Example 16 Synthesis of High Fluorine Content Polymer (F-1) Monomer (M-4), monomer (M-15), and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) to give 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 purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerized solution was cooled to 30°C or below with water. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered. This process was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate to obtain a solution of high fluorine content polymer (F-1) (yield: 80%). The high fluorine content polymer (F-1) had an Mw of 6,500 and an Mw / Mn ratio of 1.71. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-4), (M-15) and (M-20) were 19.8 mol %, 9.7 mol % and 70.5 mol %, respectively.

[0203] Synthesis Examples 17 to 20 (Synthesis of high fluorine content polymer (F-2) to high fluorine content polymer (F-5)) High fluorine content polymer (F-2) to high fluorine content polymer (F-5) were synthesized in the same manner as in Synthesis Example 16, except for using monomers of the types and blending ratios shown in Table 3 below. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained high fluorine content polymers are also shown in Table 3 below.

[0204]

[0205] <Synthesis of Onium Salt Compound (1) [B]> Onium salt compound (1) [B], which is a radiation-sensitive acid generator, was synthesized by the following procedure.

[0206] Example B1 Synthesis of Onium Salt Compound (B-1) Onium salt compound (B-1) as the onium salt compound (1) [B] was synthesized according to the following synthesis scheme.

[0207]

[0208] 20.0 mmol of sodium 2-bromoethanesulfonate, 30.0 mmol of sodium hydroxide, 40.0 mmol of adamantane-1-thiol, and 30 g of water were added to a reaction vessel and stirred at 80°C for 3 hours. 70 g of water was then added for dilution, and then 20.0 mmol of triphenylsulfonium bromide and 100 g of methylene chloride were added and stirred vigorously at room temperature for 3 hours. Dichloromethane was then added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain an onium salt in good yield.

[0209] A mixed solution of acetonitrile and water (3:1 (mass ratio)) was added to the onium salt to prepare a 0.5 M solution. 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. Acetonitrile was then added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the onium salt compound (B-1) represented by the above formula (B-1) in good yield.

[0210] Examples B2 to B23 Synthesis of Onium Salt Compounds (B-2) to (B-23) Onium salt compounds as radiation-sensitive acid generators represented by the following formulas (B-2) to (B-23) were synthesized in the same manner as in Example B1, except that the raw materials and precursors were appropriately changed.

[0211]

[0212]

[0213]

[0214] Example B24 Synthesis of Onium Salt Compound (B-24) Onium salt compound (B-24) as the onium salt compound (1) [B] was synthesized according to the following synthesis scheme.

[0215]

[0216] 20.0 mmol of 2-(methylsulfonyl)acetophenone, 30.0 mmol of chlorosulfuric acid, and 30 g of dichloromethane were added to a reaction vessel and stirred at 50°C for 3 hours. Then, 100 g of saturated aqueous sodium bicarbonate solution was added, followed by 20.0 mmol of triphenylsulfonium bromide and 100 g of methylene chloride, and the mixture was vigorously stirred at room temperature for 3 hours. Dichloromethane was then added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the onium salt compound (B-24) represented by the above formula (B-24) in good yield.

[0217] Examples B25 to B32 Synthesis of Onium Salt Compounds (B-25) to (B-32) Onium salt compounds as radiation-sensitive acid generators represented by the following formulas (B-25) to (B-32) were synthesized in the same manner as in Example B24, except that the raw materials and precursors were appropriately changed.

[0218]

[0219] The following compounds were used as components other than the components synthesized above.

[0220] [Radiation-sensitive acid generators other than onium salt compounds (B-1) to (B-32)] b-1 to b-9: Compounds represented by the following formulas (b-1) to (b-9) (hereinafter, the compounds represented by formulas (b-1) to (b-9) may be referred to as "compound (b-1)" to "compound (b-9)," respectively).

[0221]

[0222] [[D] Acid Diffusion Controller] D-1 to D-7: Compounds represented by the following formulas (D-1) to (D-7).

[0223]

[0224] [[E] Solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Cyclohexanone E-3: γ-butyrolactone E-4: Ethyl lactate E-5: Propylene glycol monomethyl ether

[0225] [Preparation of positive-tone radiation-sensitive composition for ArF immersion exposure] [Example 1] 100 parts by mass of [A] polymer (A-1), [B] onium salt compound (1) (B-1) 6.0 parts by mass, [D] acid diffusion controller (D-1) 3.0 parts by mass, [F] high-fluorine content polymer (F-1) 3.0 parts by mass (solids content), and [E] solvent (E-1) / (E-2) / (E-3) mixed solvent 3,230 parts by mass were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare radiation-sensitive composition (J-1).

[0226] [Examples 2 to 59 and Comparative Examples 1 to 5] Radiation-sensitive compositions (J-2) to (J-59) and (CJ-1) to (CJ-5) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 4 below were used.

[0227]

[0228] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Immersion Exposure> A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 100 nm. The positive radiation-sensitive composition for ArF exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 110 nm. Next, this resist film was exposed through a 65 nm line and space mask pattern 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). After exposure, a PEB (post-exposure bake) was performed at 100°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (65 nm line and space pattern).

[0229] <Evaluation> The resist patterns formed using the above-described positive radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity, LWR performance, DOF performance, and pattern rectangularity according to the methods described below. The results are shown in Table 5. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0230] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for ArF immersion exposure, the exposure dose required to form a 65 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ The sensitivity was 35 mJ / cm ２ The following cases are considered "good" and 35 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0231] [LWR Performance] A 65 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. The LWR performance was evaluated as "good" when it was 3.0 nm or less, and as "poor" when it exceeded 3.0 nm.

[0232] [DOF Performance] According to the method for measuring sensitivity, a mask having dimensions such that the line width of the formed line and space pattern (1L1S) is 65 nm was used, and the range of depth of focus (DOF) in which the line width of the line and space pattern formed as described above is 55 nm to 75 nm was measured. The DOF performance was evaluated as "good" when it was 100 nm or more, and as "poor" when it was less than 100 nm.

[0233] [Pattern rectangularity] A 65 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation was observed using the scanning electron microscope, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the bottom side to the length of the top side in the cross-sectional shape was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0234]

[0235] As is clear from the results in Table 5, when the radiation-sensitive compositions of the Examples were used in ArF immersion exposure, they exhibited good sensitivity, LWR performance, DOF performance, and pattern rectangularity, whereas the Comparative Examples were inferior in each of the properties to the Examples. Therefore, when the radiation-sensitive compositions of the Examples are used in ArF immersion exposure, resist patterns with high sensitivity and good LWR performance, DOF performance, and pattern rectangularity can be formed.

[0236] [Preparation of positive radiation-sensitive composition for ArF-dry exposure] [Example 60] [A] 100 parts by mass of (A-1) as a polymer, [B] 6.0 parts by mass of (B-1) as an onium salt compound (1), [D] 6.0 parts by mass of (D-1) as an acid diffusion controller, and [E] 3,200 parts by mass of a mixed solvent of (E-1) / (E-5) / (E-3) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-60).

[0237] Examples 61 to 73 and Comparative Examples 6 to 7 Radiation-sensitive compositions (J-61) to (J-73) and (CJ-6) to (CJ-7) were prepared in the same manner as in Example 48, except that the types and amounts of each component shown in Table 6 below were used.

[0238]

[0239] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF-Dry Exposure> A composition for forming a bottom antireflective coating ("ARC29" from Brewer Science) was applied to an 8-inch silicon wafer using a spin coater ("CLEAN TRACK ACT8" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 77 nm. The positive radiation-sensitive composition for ArF-Dry exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 200 nm. Next, a resist pattern with a line width of 90 nm, line-and-space, was formed on this resist film using an ArF excimer laser exposure device (Nikon Corporation's "S306C") under optical conditions of NA = 0.75 and annular (σ = 0.8 / 0.6). After exposure, PEB (post-exposure bake) was performed at 100 ° C. for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass % TMAH aqueous solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (90 nm line-and-space resist pattern).

[0240] <Evaluation> The resist patterns formed using the above-described positive radiation-sensitive composition for ArF-Dry exposure were evaluated for sensitivity, LWR performance, DOF performance, and pattern rectangularity according to the methods described below. The results are shown in Table 7 below. The resist patterns were measured using a scanning electron microscope ("S-9380" manufactured by Hitachi High-Technologies Corporation).

[0241] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for ArF-Dry exposure, the exposure dose required to form a 90 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ The sensitivity was 30 mJ / cm ２ The cases below are "good" and 30 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0242] [LWR Performance] A 90 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. The LWR performance was evaluated as "good" when it was 4.5 nm or less, and as "poor" when it exceeded 4.5 nm.

[0243] [DOF Performance] According to the method for measuring sensitivity, a mask having dimensions such that the line width of the formed line and space pattern (1L1S) is 90 nm was used, and the depth of focus (DOF) range in which the line width of the line and space pattern formed as described above is 80 nm to 100 nm was measured. The DOF performance was evaluated as "good" when it was 200 nm or more, and as "poor" when it was less than 200 nm.

[0244] [Pattern rectangularity] A 90 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation was observed using the scanning electron microscope, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the bottom side to the length of the top side in the cross-sectional shape was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0245]

[0246] As is clear from the results in Table 7, when the radiation-sensitive compositions of the Examples were used for ArF-dry exposure, the sensitivity, LWR performance, DOF performance, and pattern rectangularity were good, whereas in the Comparative Examples, each property was inferior to that of the Examples. Therefore, when the radiation-sensitive compositions of the Examples are used for ArF-dry exposure, resist patterns with high sensitivity and good LWR performance, DOF performance, and pattern rectangularity can be formed.

[0247] [Preparation of positive-tone radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 74] [A] 100 parts by mass of (A-12) as a polymer, [B] 30.0 parts by mass of (B-1) as an onium salt compound (1), [D] 20.0 parts by mass of (D-1) as an acid diffusion controller, [F] 3.0 parts by mass (solids content) of (F-5) as a high fluorine content polymer, and [E] 6,100 parts by mass of a mixed solvent of (E-1) / (E-5) / (E-4) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-74).

[0248] Examples 75 to 83 and Comparative Examples 8 and 9 Radiation-sensitive compositions (J-75) to (J-83) and (CJ-8) to (CJ-9) were prepared in the same manner as in Example 63, except that the types and amounts of each component shown in Table 8 below were used.

[0249]

[0250] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for EUV Exposure> A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The positive radiation-sensitive composition for EUV exposure prepared above was applied to this bottom antireflective coating using the spin coater, and then subjected to PB at 130°C for 60 seconds. Subsequently, the wafer was cooled at 23°C for 30 seconds to form a resist film with an average thickness of 40 nm. Next, this resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (20 nm line and space pattern).

[0251] <Evaluation> The resist patterns formed using the above-described positive radiation-sensitive composition for EUV exposure were evaluated for sensitivity, LWR performance, and pattern rectangularity according to the methods described below. The results are shown in Table 9. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0252] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for EUV exposure, the exposure dose required to form a 20 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ The following cases are considered "good" and 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0253] [LWR Performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 20 nm line-and-space pattern. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line chatter and the better the result. The LWR performance was evaluated as "good" when it was 3.0 nm or less, and as "poor" when it exceeded 3.0 nm.

[0254]

[0255] As is clear from the results in Table 9, the radiation-sensitive compositions of the Examples exhibited good sensitivity and LWR performance when used for EUV exposure, whereas the Comparative Examples were inferior in each property to the Examples.

[0256] [Preparation of Negative Radiation-Sensitive Composition for ArF Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 84] 100 parts by mass of [A] (A-7) as a polymer, [B] 5.0 parts by mass of (B-1) as an onium salt compound (1), [D] 2.0 parts by mass of (D-1) as an acid diffusion controller, [F] 5.0 parts by mass (solids content) of (F-3) as a high fluorine content polymer, and [E] 3,300 parts by mass of a mixed solvent of (E-1) / (E-5) / (E-3) (mass ratio 2,500 / 700 / 100) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-84).

[0257] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating having an average thickness of 100 nm. The negative radiation-sensitive composition for ArF exposure (J-84) prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film having an average thickness of 90 nm. Next, this resist film was exposed to light using an ArF excimer laser immersion exposure 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 45 nm holes and a 90 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. Thereafter, the resist film was developed using n-butyl acetate as an organic solvent developer, and dried to form a negative resist pattern (a contact hole pattern with 45 nm holes and a 90 nm pitch).

[0258] The resist patterns prepared using the negative-working radiation-sensitive composition for ArF exposure were evaluated for sensitivity in the same manner as in the evaluation of the resist patterns prepared using the positive-working radiation-sensitive composition for ArF exposure. The CDU performance and pattern circularity were also evaluated according to the following methods.

[0259] [CDU Performance] Contact holes with a 45 nm hole and a 90 nm pitch were formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The variation in the diameter of the contact holes was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as CDU (nm). The smaller the CDU value, the smaller the hole roughness and the better the result. CDU performance was evaluated as "good" when it was less than 4.0 nm, and as "poor" when it was 4.0 nm or more.

[0260] [Pattern circularity] The 45 nm holes and 90 nm pitch contact holes formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation were observed in plan view using the scanning electron microscope described above, and their vertical and horizontal sizes were measured. A ratio of vertical size to horizontal size of 0.95 or more and less than 1.05 was evaluated as "A" (very good), a ratio of 0.90 or more and less than 0.95, or 1.05 or more and less than 1.10 was evaluated as "B" (good), and a ratio of less than 0.90 or more than 1.10 was evaluated as "C" (poor).

[0261] As a result, the radiation-sensitive composition of Example 84 exhibited good sensitivity, CDU performance, and pattern circularity even when a negative resist pattern was formed by ArF exposure.

[0262] [Preparation of Negative Radiation-Sensitive Composition for EUV Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 85] 100 parts by mass of [A] (A-15) as a polymer, [B] 30.0 parts by mass of (B-11) as an onium salt compound (1), [D] 30.0 parts by mass of (D-3) as an acid diffusion controller, [F] 1.0 part by mass (solids content) of (F-5) as a high fluorine content polymer, and [E] 6,030 parts by mass of a mixed solvent of (E-1) / (E-5) (mass ratio 4,500 / 1,530) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-85).

[0263] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The negative radiation-sensitive composition for EUV exposure (J-85) prepared above was applied to this bottom antireflective coating using the spin coater, and baked 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 45 nm. Next, this resist film was exposed to light using an EUV exposure system ("NXE3300" from ASML) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR15. After the exposure, PEB was performed for 60 seconds at 120° C. Thereafter, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 20 nm holes and a 40 nm pitch).

[0264] The resist pattern formed using the negative-tone radiation-sensitive composition for EUV exposure was evaluated in the same manner as the evaluation of the resist pattern formed using the negative-tone radiation-sensitive composition for ArF exposure. As a result, the radiation-sensitive composition of Example 85 exhibited good sensitivity, CDU performance, and pattern circularity, even when a negative-tone resist pattern was formed by EUV exposure.

[0265] The radiation-sensitive composition, pattern forming method, and onium salt compound (1) described above can form a resist pattern that has good sensitivity to exposure light and is excellent in LWR performance, DOF performance, pattern rectangularity, CDU performance, and pattern circularity. Therefore, these can be suitably used in processing processes for semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: an onium salt compound represented by the following formula (1); a polymer including a structural unit having an acid-dissociable group; and a solvent. (In formula (1), A is a monovalent organic group having 1 to 40 carbon atoms. R １ and R ２ R are each independently a hydrogen atom, a monovalent non-fluorine-containing organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxyl group, or an amino group. １ and R ２ When there are multiple R １ and R ２ are the same or different. １ is an integer from 1 to 8. ＋ is a monovalent radiation-sensitive onium cation.

2. m １ The radiation-sensitive composition according to claim 1, wherein is an integer of 1 to 3.

3. R １ and R ２ The radiation-sensitive composition according to claim 1 , wherein is a hydrogen atom.

4. The radiation-sensitive composition according to claim 1, wherein A is a monovalent chain organic group having 1 to 20 carbon atoms, or a monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure.

5. The radiation-sensitive composition according to claim 1, wherein the content of the onium salt compound is from 1 part by mass to 30 parts by mass per 100 parts by mass of the polymer.

6. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the structural unit having an acid-dissociable group is represented by the following formula (3): (In formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ are each independently a monovalent linear 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 represent a divalent alicyclic group having 3 to 20 carbon atoms formed by combining with each other and the carbon atom to which they are bonded.

7. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the polymer further comprises a structural unit containing at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.

8. The radiation-sensitive composition according to any one of claims 1 to 5, further comprising an acid diffusion controller.

9. A pattern forming method comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 5 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film.

10. The method for forming a pattern according to claim 9, wherein the exposure is carried out with an ArF excimer laser or extreme ultraviolet light.

11. An onium salt compound represented by the following formula (1): (In formula (1), A is a monovalent organic group having 1 to 40 carbon atoms. R １ and R ２ R are each independently a hydrogen atom, a monovalent non-fluorine-containing organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxyl group, or an amino group. １ and R ２ When there are multiple R １ and R ２ are the same or different. １ is an integer from 1 to 8. ＋ is a monovalent radiation-sensitive onium cation.