Radiation-sensitive composition, pattern forming method, acid diffusion control agent, and onium salt

Abstract

The objective of the present invention is to provide: a radiation-sensitive composition having excellent sensitivity, LWR, and CDU during pattern formation; a pattern forming method; an acid diffusion control agent; and an onium salt. The radiation-sensitive composition contains an onium salt having a moiety represented by formula (i), a polymer having a structural unit (I) containing an acid-dissociable group, and a solvent. (In formula (i), X1 - is S- or O-. X2 is S or O. S is included in at least one selected from the group consisting of X1 - and X2. Z+ is a monovalent organic cation. * are each a bonding site to another atom in the onium salt.)

Description

Radiation-sensitive composition, pattern-forming method, acid diffusion control agent, and onium salt

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

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic solvent-based developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, or combine this radiation with liquid immersion lithography to advance pattern miniaturization. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] Various structures have also been investigated for quenchers, which are also a major component of resist compositions (see, for example, Japanese Patent Publication No. 2013-125146).

[0005] Japanese Patent Publication No. 2013-125146

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance characteristics equivalent to or better than conventional resists in terms of sensitivity, LWR, CDU, etc., during pattern formation.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, an acid diffusion control agent, and an onium salt that exhibit excellent sensitivity, LWR, and CDU during pattern formation.

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

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition containing an onium salt having a partial structure represented by the following formula (i) (hereinafter also referred to as "partial structure (i)"), a polymer having a structural unit (I) containing an acid dissociable group, and a solvent. (In formula (i), １ - X - is S - or O. ２ X is S or O. However, at least one selected from the group consisting of X １ - and X ２ contains S. ＋ Z is a monovalent organic cation. * is a bond with other atoms in the above onium salt, respectively.)

[0010] According to the radiation-sensitive composition, excellent sensitivity, CDU, and LWR can be exhibited during pattern formation. Although the reason for this is not clear, it is speculated as follows.

[0011] The partial structure (i) possessed by the onium salt is an acid generation structure that generates an acid that does not dissociate the acid dissociable group upon exposure. The partial structure (i) contains a carboxylic acid anion (-CO ２ -A structure is introduced in which at least one of the two oxygen atoms constituting the carboxylate is replaced by a sulfur atom (hereinafter, regardless of the number or position of the sulfur atoms, this will also be called a "thiocarboxylate anion" or "thiocarboxylate anion structure," and the corresponding acid structure will also be called a "thiocarboxylic acid" or "thiocarboxylate structure"). Compared to carboxylate anions, thiocarboxylate anions are stabilized and their basicity is reduced, allowing for appropriate control of the amount of acid captured and improving sensitivity. Furthermore, it is no longer necessary to reduce basicity to prevent a decrease in sensitivity, and a structure to stabilize the anion becomes unnecessary. As a result, depending on the structure of the thiocarboxylate anion, the surface free energy is reduced compared to carboxylate anions, and it becomes easier for the anion to be concentrated on the film surface. Consequently, acid capture efficiency is increased on film surfaces with high exposure and high acid generation, improving roughness. In addition, depending on the structure of the thiocarboxylate anion, transparency is improved compared to carboxylate anions, allowing exposure to the bottom of the film, which also contributes to the improvement of roughness. It is presumed that the above-mentioned unique performance can be achieved through the combined effects of these factors.

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

[0013] This pattern formation method uses the above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, CDU, and LWR during pattern formation, thus enabling the efficient formation of high-quality resist patterns.

[0014] In one embodiment, the present invention relates to an acid diffusion control agent having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２S is included in at least one of the groups selected from Z. ＋ is a monovalent organic cation. * represents the bonding site with other atoms in the acid diffusion control agent described above.

[0015] Since the acid diffusion control agent has the above-described specific substructure (i), when used in a radiation-sensitive composition, it can contribute to improving sensitivity, CDU, and LWR.

[0016] In one embodiment, the present invention relates to an onium salt having a substructure represented by the following formula (ii). (In formula (ii), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ３ ＋ is a monovalent organic cation (excluding monovalent quaternary ammonium cations). * represents the bonding site with other atoms in the onium salt described above.

[0017] Since the onium salt has the above-described specific substructure (i), it can contribute to improving sensitivity, CDU, and LWR when used in a radiation-sensitive composition.

[0018] In this specification, "organic group" means a group containing at least one carbon atom. However, cyano groups, carboxyl groups, formyl groups, carbonyl groups, etc., which can function or be characterized groups on their own as organic groups are excluded. In this specification, "hydrocarbon group" means a group consisting only of carbon and hydrogen atoms, such as a chain hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, but "substituted hydrocarbon group" means a group in which one or more hydrogen atoms of the hydrocarbon group are substituted with a heteroatom-containing group.

[0019] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Preferred combinations of embodiments are also preferred.

[0020] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") contains a polymer (A) having a structural unit (I) containing an acid-dissociable group (hereinafter also referred to as "base polymer (A)"), an onium salt (D), and a solvent (E). The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0021] <Onium salt (D)> The above radiation-sensitive composition contains an onium salt (D) having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ＋ is a monovalent organic cation. * represents the bonding site with other atoms in the onium salt described above.

[0022] The overall structure of onium salt (D) is not particularly limited as long as it has a substructure (i). The overall structure of onium salt (D) can be broadly classified into two types depending on the bonding mode between the organic acid anion (thiocarboxylic acid anion) and the organic cation. The first is a form in which the organic acid anion and the organic cation exhibit a salt structure through ionic bonding in the onium salt molecule (hereinafter, onium salts relating to this form will also be called "onium salt (D1)"). The second is a form in which the organic acid anion and the organic cation, linked to each other by covalent bonds, exhibit a locally formed salt structure in the onium salt molecule (hereinafter, onium salts relating to this form will also be called "onium salt (D2)").

[0023] The above onium salt (D) acts as an acid diffusion control agent that generates an acid with a higher pKa than the acid generated by the radiation-sensitive acid generator (B) described later upon exposure. Under pattern formation conditions using the radiation-sensitive acid generator (B) described later, it has the function of substantially preventing the dissociation of the acid-dissociable groups of the base polymer (A) and suppressing the diffusion of the acid generated by the radiation-sensitive acid generator (B) described later in the unexposed areas through salt exchange.

[0024] The above X １ - , X ２ The combination is X １ - : S - , X ２ : Combinations of O, X １ - : S - 、 X ２ : Combinations of S, X １ - : O - , X ２ There are combinations of S, but among these, X １ - : S - , X ２ : A combination of O or X １ - : O - , X ２ : A combination of S is preferred, X １ - : S - , X ２ The combination of :O is more preferable.

[0025] The above Z ＋ As a monovalent organic cation represented by the formula (D1) described later, Z １ ＋ Examples of monovalent cations can be obtained by removing one hydrogen atom from the organic cation represented by . In this specification, "monovalent organic cation" refers to an organic cation that has one bonding bond with another atom.

[0026] As the onium salt (D), a compound represented by the following formula (D1) (the onium salt (D1)) or a compound represented by the following formula (D2) (the onium salt (D2)) is preferable. Hereinafter, each of the onium salt (D1) and the onium salt (D2) will be described. (In formula (D1), R １ is an n-valent organic group having 1 to 40 carbon atoms. Z １ is an organic cation. n １ ＋ is an integer of 1 to 3. When n １ is 2 or more, a plurality of X １ １ <00,00078>[ ２ １ [ ＋ and Z １ - are the same as or different from each other. X ２ ２ and X ＋ are synonymous with the above formula (i).) (In formula (D2), Z Ａ２ １ is a monovalent organic cation. L - is a single bond or a divalent linking group. X ２ １ and X １ are synonymous with the above formula (i).)

[0027] (Onium salt (D1)) The R in the above formula (D1) １ The n-valent organic group having 1 to 40 carbon atoms represented by can preferably adopt a group obtained by removing (n １ - 1) hydrogen atoms from a monovalent organic group having 1 to 40 carbon atoms.

[0028] [

[0029] Examples of the monovalent organic group having 1 to 40 carbon atoms include, for example, a monovalent hydrocarbon group having 1 to 40 carbon atoms, a group having a divalent heteroatom-containing group between carbon-carbon (between two adjacent or non-adjacent carbons) of this hydrocarbon group or at the end of the hydrocarbon group (a), a group obtained by substituting part or all of the hydrogen atoms of the hydrocarbon group or the group (a) with a monovalent heteroatom-containing group, or a combination thereof.

[0029] Examples of monovalent hydrocarbon groups having 1 to 40 carbon atoms include monovalent linear hydrocarbon groups having 1 to 40 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 40 carbon atoms, or combinations thereof.

[0030] Examples of monovalent chain hydrocarbon groups having 1 to 40 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0031] Examples of monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl groups; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and bridged ring unsaturated hydrocarbon groups such as norbornyl and tricyclodecenyl groups.

[0032] Examples of monovalent aromatic hydrocarbon groups having 6 to 40 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0033] Examples of heteroatoms constituting a divalent or monovalent heteroatom-containing group include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0034] Examples of divalent heteroatom-containing groups include -CO-, -CS-, -NR'-, -O-, -S-, and combinations thereof. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0035] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0036] Also, the above R １ The n-valent organic group having 1 to 40 carbon atoms represented by １ may contain an ionic structure. The ionic structure is not particularly limited, and examples thereof include a structure represented by the following formula (i-a). (In formula (i-a), M １ ＋ is an organic cation. * represents a bond with another atom in R １ .)

[0037] Regarding the above M １ ＋ The organic cation represented by can preferably employ the organic cation represented by Z １ ＋ described later.

[0038] Regarding the above R １ When the n-valent organic group having 1 to 40 carbon atoms represented by contains an ionic structure, the onium salt (D1) is preferably an onium salt (D1-1) represented by the following formula (D1-1). １ (In formula (D1-1), Z １ ＋ , X １ - and X ２ - are synonymous with the above formula (D1). R １１ is a divalent organic group having 1 to 40 carbon atoms. However, a fluorine atom, a cyano group, or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α-position or β-position with respect to the sulfur atom in -SO ３ - . M １ ＋ is synonymous with the above formula (i-a).)

[0039] Regarding the above R １１ As the divalent organic group having 1 to 40 carbon atoms represented by, a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 40 carbon atoms described in the above formula (D1) can be preferably employed.

[0040] As the above monovalent fluorinated hydrocarbon group, those described in the formula (z-a) described later can be preferably employed.

[0041] The above n １ is an integer from 1 to 3, preferably 1 or 2, and more preferably 1.

[0042] In the above formula (D1), n １ If R is 1, １ It is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, n １ If R is 2, １ Preferably, it includes at least one structure selected from the group consisting of a cyclic structure, an alkenediyl group, -CO-, -O-, and -NR'- (R': hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms).

[0043] Specific examples of the organic acid anion of the above onium salt (D1) (including onium salt (D1-1)) are not particularly limited, but for example, a structure represented by the following formula can be cited.

[0044]

[0045]

[0046]

[0047]

[0048] The above Z １ ＋ Examples of organic cations represented by this formula include sulfonium cations, iodonium cations, and quaternary ammonium cations.

[0049] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0050]

[0051] In the above equation (X-1), R ａ１ , R ａ２ and R ａ３Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a hydroxyl group, a nitro group, a halogen atom, or -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ This represents a group formed by combining these groups with -O-, -CO-, or a ring structure formed by combining two or more of these groups. This ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds that form the skeleton. Ｐ , R Ｑ and R Ｔ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently integers from 0 to 5. R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0052] In the above equation (X-2), R ｂ１ These are substituted or unsubstituted linear or branched alkyl or alkoxy groups having 1 to 20 carbon atoms, alkoxyalkyloxy groups, substituted or unsubstituted acyl groups having 2 to 8 carbon atoms, substituted or unsubstituted aromatic hydrocarbon groups having 6 to 8 carbon atoms, nitro groups, cyano groups, and hydroxyl groups. ｂ１ Examples include groups composed of the alkyl group and at least one of the groups -CO-, -O-, -NH-, and -S-. ｋ n is either 0 or 1.ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This 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 k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O and S between the carbon-carbon bonds that form the skeleton.

[0053] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms.

[0054] In the above equation (X-4), R ｇ１ This is 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, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. ｋ２ n is either 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 They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0055] In the above equation (X-5), R ｄ１ and R ｄ２ Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, a hydroxyl group, a cyano group, and a -CO-O-R group. Ｐ１ , -S-R Ｔ１ This represents a ring structure formed by combining two or more of these groups. Ｐ１ and R Ｔ１ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k6 and k7 are each independently integers from 0 to 5. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0056] In the above formula (X-6), R ｅ１ and R ｅ２k8 and k9 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.

[0057] Specific examples of organic cations used as radiation-sensitive onium cations include, but are not limited to, the structure shown in the following formula.

[0058]

[0059]

[0060]

[0061]

[0062] While not particularly limited, examples of quaternary ammonium cations include the organic quaternary ammonium cation represented by the following formula (X-7).

[0063] (In formula (X-7), R ｔ１ , R ｔ２ , R ｔ３ and R ｔ４ These are, independently, organic groups with 1 to 20 carbon atoms.

[0064] The above R ｔ１ , R ｔ２ , R ｔ３ and R ｔ４ As an organic group having 1 to 20 carbon atoms represented by the above formula (D1), R １ Among the monovalent organic groups having 1 to 40 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted, and among these, monovalent chain hydrocarbon groups having 1 to 20 carbon atoms are preferred.

[0065] Specific examples of the above-mentioned quaternary ammonium cations include, for example, tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetrabutylammonium cation, tetraheptylammonium cation, tetrahexylammonium cation, trimethylethylammonium cation, dimethyldiethylammonium cation, dimethylethylpropylammonium cation, methylethylpropylbutylammonium cation, trimethylphenylammonium cation, triethylhexylammonium cation, triethylcyclohexylammonium cation, dodecyltrimethylammonium cation, and the like.

[0066] Any combination of the above-mentioned organic acid anion and organic cation can be used as the onium salt (D1). Specific examples of the onium salt (D1) will be described later.

[0067] (Onium salt (D2)) L in the above formula (D2) Ａ２ Examples of divalent linking groups represented by include divalent hydrocarbon groups having 1 to 10 carbon atoms, and groups composed of one or more divalent hydrocarbon groups having 1 to 10 carbon atoms and at least one group from -CO-, -O-, -NH-, and -S-. Among these, it is preferable that the group includes at least one structure selected from the group consisting of a cyclic structure, -CO-, and -O-.

[0068] As the above-mentioned divalent hydrocarbon group having 1 to 10 carbon atoms, R in formula (D1) is １ In this context, a monovalent hydrocarbon group having 1 to 40 carbon atoms can be suitably adopted, specifically one obtained by removing one hydrogen atom from the corresponding carbon atom group.

[0069] The above-mentioned cyclic structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be alicyclic, aromatic, heterocyclic, or a combination thereof. In the case of a combination, the cyclic structures may be linked by chain structures, and two or more cyclic structures may form a fused ring structure. These structures are preferably included as the smallest basic skeleton of the cyclic structure. The number of cyclic structures as the basic skeleton in the organic group may be one or two or more. The above-mentioned divalent heteroatom-containing group may be present between carbon atoms or at the ends of carbon chains forming the skeleton of the cyclic or chain structure, and hydrogen atoms on carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0070] The above alicyclic structure is R in formula (D1) above. １ Structures corresponding to monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms, as shown in [reference], can be suitably adopted.

[0071] The above aromatic ring structure is R in formula (D1) above. １ A structure corresponding to a monovalent aromatic hydrocarbon group having 6 to 40 carbon atoms can be suitably adopted.

[0072] Examples of the above heterocyclic structures 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 thiethane, thiolane, and thian; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan, benzofuran, and dibenzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, triazine, pyridine, pyrazine, pyrimidine, and pyridazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0073] Heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetal structures, or combinations thereof.

[0074] The above chain structure is R in formula (D1) above. １ Structures corresponding to monovalent chain hydrocarbon groups having 1 to 40 carbon atoms, as shown in [reference], can be suitably adopted.

[0075] Examples of substituents that substitute hydrogen atoms on carbon atoms in the above-mentioned cyclic or chain structures include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and substituents (T) such as oxo groups (=O).

[0076] The above Z ２ ＋ As a monovalent organic cation in the above formula (D1), Z １ ＋ Examples of cations obtained by removing one hydrogen atom from the organic cation represented by can be cited, and monovalent sulfonium cations, monovalent iodonium cations, or monovalent quaternary ammonium cations can be suitably used.

[0077] As for onium salt (D2), Z ２ ＋ However, it is a monovalent triarylsulfonium cation, L Ａ２ Z is an onium salt with a divalent linking group containing a single bond or an ester bond; ２ ＋ However, it is a monovalent diaryliodonium cation, L Ａ２ is an onium salt with a single bond; or Z ２ ＋ However, it is a monovalent quaternary ammonium cation, L Ａ２ It is preferable that the compound is an onium salt, which is a divalent linking group containing an ester bond.

[0078] The above onium salt (D) (including the above onium salt (D1) and onium salt (D2)) can be exemplified by the structure represented by the following formula.

[0079]

[0080]

[0081]

[0082]

[0083]

[0084] The above onium salt (D) can be synthesized by the method described in the examples.

[0085] The above-mentioned radiation-sensitive composition may contain one or more onium salts (D).

[0086] The lower limit of the content of the above onium salt (D) (total if multiple types are included) is preferably 1 part by mass, and more preferably 3 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 60 parts by mass, and more preferably 50 parts by mass. As a result, the composition can exhibit excellent sensitivity, CDU, and LWR when forming a resist pattern.

[0087] <Polymer (A)> Polymer (A) (i.e., base polymer (A)) is an aggregate of polymerization chains having structural units (I) containing acid-dissociable groups. In addition to structural unit (I), base polymer (A) may also contain structural units (II) having phenolic hydroxyl groups, structural units (III) containing at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures, structural units (IV) containing polar groups, and so on. Each structural unit will be described below.

[0088] [Structural Unit (I)] Structural unit (I) is a structural unit containing an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group, which dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because polymer (A) contains structural unit (I).

[0089] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples 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 replaced by a tertiary alkyl group, and a structural unit having an acetal bond. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, the structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0090]

[0091] In the above formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0092] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (I-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0093] L １１ａ Examples of alkanediyl groups represented by include methylene groups, ethanediyl groups, 1,3-propanediyl groups, and 2,2-propanediyl groups, which have 1 to 10 carbon atoms. １１ａ Methylene groups and ethanediyl groups are preferred as the components.

[0094] L １１ａ Examples of allenediyl groups represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the group.

[0095] L １１ａ The substituents that the alkanediyl group and arenediyl group represented by can have include halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkyl groups, fluorinated alkyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and alkoxy groups.

[0096] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (D1), R １ Among the monovalent hydrocarbon groups having 1 to 40 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted.

[0097] The above R １８ Preferably, the group is a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms, and more preferably an alkyl group or adamantyl group having 1 to 4 carbon atoms.

[0098] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed when these are combined with the carbon atoms to which they are bonded, is R in formula (D1) above. １ In this context, a monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms can be suitably adopted, specifically one obtained by removing one hydrogen atom from the corresponding carbon number group.

[0099] The above R １９ and R ２０Each of these is independently an alkyl group having 1 to 4 carbon atoms, or R １９ and R ２０ It is preferable that these are polycyclic or monocyclic cycloalkane structures formed by combining them with carbon atoms to which they are bonded.

[0100] The above R １８ ~R ２０ The substituents that can be present are L １１ａ The substituents that the alkanediyl group and arenediyl group represented by can have can be suitably adopted.

[0101] Examples of structural units (I-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (I-1-1) to (I-1-15)").

[0102]

[0103]

[0104] In the above equations (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R is a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently integers from 1 to 4. k and l are 0 or 1. a3 are each independently integers from 0 to 3. If a3 is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0105] i and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, adamantyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into the structural unit (I).

[0106] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0107]

[0108] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0109] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0110] The base polymer (A) may contain one or more structural units (I) in combination.

[0111] The lower limit of the content of structural unit (I) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural unit (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0112] [Structural Unit (II)] Structural unit (II) is a structural unit having a phenolic hydroxyl group. Structural unit (II) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0113] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0114] (In the above formula (4), Rβ L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ Or -O-. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ m is an integer between 0 and 8, where 1 ≤ m ３ +m ４ ≤ 2n ３ (Saves +5.)

[0115] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (II), it is preferable that it be a hydrogen atom or a methyl group.

[0116] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0117] R １０２ In this mixture, iodine atoms and fluorine atoms are preferred as halogen atoms, with fluorine atoms being more preferred.

[0118] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0119] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0120] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0121] The base polymer (A) may contain one or more structural units (II) in combination.

[0122] When the base polymer (A) contains structural unit (II), the lower limit of the content of structural unit (II) to the total structural units constituting the base polymer (A) (or the total content if multiple types are included) is preferably 10 mol%, and more preferably 20 mol%. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0123] [Structural Unit (III)] Structural unit (III) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. The base polymer (A) can have its solubility in the developer adjusted by further comprising structural unit (III), and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer (A) and the substrate can be improved.

[0124] Examples of structural units (III) include those represented by the following formulas (T-1) to (T-11).

[0125]

[0126] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ These are, independently, a hydrogen atom, a C1-C4 alkyl group, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, and a dimethylamino group. Ｌ４ and R Ｌ５ These may be divalent alicyclic groups having 3 to 8 carbon atoms, which can be combined with each other and bonded together with the carbon atoms. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0127] The above R Ｌ４ and R Ｌ５ When these are combined with each other, the divalent alicyclic group having 3 to 8 carbon atoms, formed together with the carbon atoms to which they are bonded, is R in formula (3) above. １９ and R２０ Examples include divalent alicyclic groups with 3 to 20 carbon atoms, where these groups are combined with each other and formed together with the carbon atoms to which they are bonded, specifically groups with 3 to 8 carbon atoms. One or more hydrogen atoms on these alicyclic groups may be substituted with hydroxyl groups.

[0128] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0129] Among these, structural units (III) are preferably those containing a lactone structure, more preferably those containing a γ-butyrolactone structure or a norbornane lactone structure, and even more preferably those derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl(meth)acrylate.

[0130] The base polymer (A) may contain one or more structural units (III) in combination.

[0131] When the base polymer (A) has structural unit (III), the lower limit of the content of structural unit (III) in the total structural units constituting the base polymer (A) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural unit (III) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0132] [Structural Unit (IV)] Structural unit (IV) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (III)). The base polymer (A) can have its solubility in the developer adjusted by further containing structural unit (IV), and as a result, the lithographic performance such as resolution of the radiation-sensitive composition can be improved. Examples of the above polar group include a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxyl group and a carboxyl group are preferred, and a hydroxyl group is more preferred.

[0133] Examples of structural units (IV) include structural units represented by the following formula.

[0134]

[0135]

[0136] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0137] The base polymer (A) may contain one or more structural units (IV) in combination.

[0138] When the base polymer (A) has a structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) in the total structural units constituting the base polymer (A) (total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and still preferably 3 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and still preferably 25 mol%. By setting the content of structural unit (IV) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0139] [Structural Unit (X)] The base polymer (A) may have a structural unit (X) that includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure. By containing the radiation-sensitive acid-generating structure in the base polymer (A), the polarity of the base polymer in the exposed area increases, making it soluble in the developer in the case of alkaline aqueous solution development, while it becomes sparingly soluble in the developer in the case of organic solvent development.

[0140] Although the form in which the first organic acid anion and the first onium cation are contained in the structural unit (X) of the base polymer (A) is not particularly limited, it is preferable that the base polymer has the first organic acid anion as a side chain portion from the viewpoint of controlling the acid diffusion length. Having it as a side chain portion means that the first organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0141] The above structural unit (X) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (X-1)").

[0142]

[0143] In the formula, R Ｖ This is a hydrogen atom or a methyl group. V １ This is a single bond or an ester group. V ２ This is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, or an amide bond, and a portion of the methylene groups constituting the alkylene group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３This is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in the compound may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. Rf １ ~Rf ２ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer from 1 to 4. X １ ＋ This is a sulfonium cation or an iodonium cation.

[0144] V ２ and V ３ The C1-C20 monovalent hydrocarbon group in this is preferably a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C6-C20 aryl group. Some or all of the hydrogen atoms in these groups may be substituted with heteroatom-containing groups such as hydroxyl groups, carboxyl groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, alkoxy groups, or alkoxycarbonyl groups. Some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonic acid ester groups.

[0145] X in the above formula (a1) １ ＋ As for Z in the above formula (D1) １ ＋ A sulfonium cation or iodonium cation can be suitably used in the monovalent organic cation represented by [formula].

[0146] When the base polymer (A) has structural units (X), the lower limit of the content of structural units (X) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 10 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of structural units (X) within the above range, the function as an acid-generating structure can be fully exhibited, and the above resist properties can be achieved.

[0147] [Structural Unit (XI)] The base polymer (A) may include a structural unit (XI) having a second organic acid anion and a second onium cation, which generates an acid by exposure that does not dissociate the acid-dissociable group. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid-generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid-generating structure substantially prevents the dissociation of the acid-dissociable group of structural unit (I), and has the function of suppressing the diffusion of acid generated from the radiation-sensitive acid generator (B) or the above-mentioned structural unit (X) (if included) in the unexposed area by salt exchange. The acid generated from the second acid-generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the radiation-sensitive acid generator (B) or structural unit (X) described later. Whether an onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable groups of the base polymer, and the acidity of the onium salt structure or the generated acid.

[0148] Regarding the inclusion of the second organic acid anion and the second onium cation in the structural unit (XI) of the base polymer (A), from the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0149] The above structural unit (XI) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (XI-1)").

[0150]

[0151] In formula (p1), R Ａ X is a hydrogen atom or a methyl group. １ This is a single bond, ester bond, ether bond, phenylene group, naphthylene group, or a combination thereof. ２ This is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may include an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3- Examples include C1-C12 alkanediyl groups such as diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, heptane-1,7-diyl groups, octane-1,8-diyl groups, nonane-1,9-diyl groups, and decane-1,10-diyl groups; C3-C12 cyclic saturated hydrocarbylene groups such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; and groups obtained by combining these. ３ These are single bonds, ester bonds, or ether bonds.

[0152] In formula (p1), X １ ~X ２ Some or all of the hydrogen atoms in may be substituted with substituents. The substituent (T) described above can be suitably adopted as the substituent. １ ~X ２If the compound has a phenylene group, it is preferable that some or all of the hydrogen atoms of the phenylene group are substituted with fluorine atoms or iodine atoms.

[0153] In formula (p1), R ｘ These are halogen atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0154] In formula (p1), Z ２ ＋ This is a secondary onium cation. As the secondary onium cation, the organic cation shown in the onium salt (D1) can be suitably used.

[0155] When the base polymer (A) contains structural unit (XI), the lower limit of the content of structural unit (XI) (or the total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of structural unit (XI) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0156] [Other structural units] The base polymer (A) may also contain structural units other than those listed above, such as structural units having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (V)"). (In the above formula (6), R １α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α (It is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.)

[0157] In the above formula (6), R ２α As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (D1), R １ Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted.

[0158] When the base polymer (A) contains structural units (V), the lower limit of the content of structural units (V) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0159] (Method for synthesizing base polymer (A)) Base polymer (A) can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0160] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(isobutyrate)dimethyl (MAIB), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0161] Examples of solvents used in the above 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, isobutyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; and ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone. Examples include linear ethers such as dimethoxyethanes and diethoxyethanes; cyclic ethers such as tetrahydrofurans and 1,4-dioxanes; polyhydric alcohol partial ethers such as 1-methoxy-2-propanol (propylene glycol monomethyl ether); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0162] The reaction temperature in the polymerization described above is usually 40°C to 150°C, with 50°C to 120°C being preferred. The reaction time is usually 1 hour to 48 hours, with 1 hour to 24 hours being preferred.

[0163] The molecular weight of the base polymer (A) is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 15,000. By keeping the Mw of the base polymer (A) within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0164] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) (Mw / Mn) of the base polymer (A) 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.

[0165] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0166] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40°C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0167] The content of the base polymer (A) 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.

[0168] <Other Polymers> The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer (F) (hereinafter also referred to as "high-fluorine content polymer") having a higher mass content of fluorine atoms than the base polymer described above. When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer (A), and as a result, the water repellency of the surface of the resist film during immersion exposure can be enhanced, and the surface modification of the resist film and the distribution of the composition within the film can be controlled during EUV exposure.

[0169] High-fluorine-content polymers may, for example, have structural units represented by the following formula (5) (hereinafter also referred to as "structural unit (VI)").

[0170]

[0171] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ It consists of a single bond, an alkanediyl group with 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, and -SO ２ ONH-, -CONH-, -OCONH-, or a combination thereof. １４ This is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0172] The above R １３ From the viewpoint of copolymerization of monomers that give structural unit (VI), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0173] The above G Ｌ From the viewpoint of copolymerization of monomers that provide structural units (VI), single bonds and -COO- are preferred, and -COO- is more preferred.

[0174] The above R １４ Examples of monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0175] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0176] The above R １４Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0177] When a high-fluorine-content polymer has structural units (VI), the lower limit of the content of structural units (VI) is preferably 50 mol%, more preferably 55 mol%, and even more preferably 60 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural units (VI) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0178] High-fluorine polymers may have fluorine atom-containing structural units represented by the following formula (f-2), either together with or in place of structural unit (VI), structural unit (VI). The presence of structural unit (VII) in high-fluorine polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0179]

[0180] Structural units (VII) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In both (x) and (y), in the above formula (f-2), R Ｃ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the terminal end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ-A structure to which a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms of this hydrocarbon group are substituted by an organic group having a heteroatom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0181] If structural unit (VII) has (x) an alkali-soluble group, R Ｆ A is a hydrogen atom, １ The oxygen atom is -COO-* or -SO ２ It is O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having (x) an alkali-soluble group in structural unit (VII) increases its affinity for alkaline developer and suppresses development defects. A is an example of structural unit (VII) having an alkali-soluble group. １ is an oxygen atom and W １ It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0182] If structural unit (VII) has an alkali-dissociable group, R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ It is O-*. ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. １R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom. １ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in structural unit (VII) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural unit (VII) having a (y) alkali-dissociable group include A １ is -COO-* or -OCO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0183] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural unit (VII), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0184] When a high-fluorine-content polymer has structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural unit (VII) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers, thereby suppressing the occurrence of development defects.

[0185] [Other structural units] High-fluorine polymers may, if necessary, include structural units other than those listed above, such as structural unit (I), structural unit (IV), and structural unit (V) in the base polymer.

[0186] When a high-fluorine-content polymer contains structural unit (I), the lower limit of the content of structural unit (I) is preferably 1 mol%, and more preferably 5 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0187] When a high-fluorine-content polymer contains structural units (IV), the lower limit of the structural unit (IV) content is preferably 1 mol%, and more preferably 3 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 50 mol%, and more preferably 40 mol%.

[0188] When a high-fluorine-content polymer contains structural units (V), the lower limit of the content of structural units (V) is preferably 1 mol%, and more preferably 3 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0189] The lower limit of Mw for the high-fluorine-content polymer is preferably 4,000, more preferably 5,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 10,000, and even more preferably 8,000.

[0190] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0191] If the radiation-sensitive composition contains a high-fluorine-content polymer, the lower limit of the high-fluorine-content polymer content is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass.

[0192] By setting the content of the high-fluorine polymer within the above range, the high-fluorine polymer can be more effectively distributed to the surface layer of the resist film. As a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, and to control the surface modification of the resist film and the distribution of the internal composition during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine polymers.

[0193] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the synthesis method for the base polymer (A) described above.

[0194] <Radiation-sensitive acid generator (B)> The above radiation-sensitive composition preferably contains a radiation-sensitive acid generator (B). The radiation-sensitive acid generator (B) is a compound having an organic acid anion and an onium cation, which generates an acid that dissociates the above acid-dissociable group upon exposure. The acid generated from the radiation-sensitive acid generator (B) can be said to be a relatively stronger acid (an acid with a lower pKa) than the acid generated from the above onium salt (D). The radiation-sensitive acid generator (B) in the radiation-sensitive composition may exist as a compound on its own (liberated from the polymer), as part of the polymer, or in both forms, but it is preferred to exist as a compound on its own.

[0195] Examples of organic acid anions include sulfonic acid anions, sulfonimide anions, and sulfonmethide anions.

[0196] Examples of such acids include: (1) compounds in which one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups are substituted on the α or β carbon atoms of a sulfo group, or in which an ester bond is interposed between carbon atoms; (2) compounds having a sulfonimide structure containing a fluorine atom; and (3) compounds having a sulfonemethide structure containing a fluorine atom.

[0197] The radiation-sensitive acid generator is preferably a compound represented by the following formula (z-a). (In formula (z-a), R ４ｚ It is a monovalent organic group having 2 to 40 carbon atoms. However, -SO ３ - A fluorine atom, a cyano group, or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α or β position relative to the sulfur atom in the molecule. ＋ (This is an onium cation.)

[0198] R ４ｚ As a monovalent organic group having 2 to 40 carbon atoms represented by the above formula (D1), R １ Among the monovalent organic groups having 1 to 40 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted.

[0199] R ４ｚ It is preferable that R is a monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a ring structure, a carbonyl group, and an ether bond. As such an organic group, R of formula (D1) above １ A monovalent organic group having 4 to 40 carbon atoms, including at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond as shown above, can be suitably employed.

[0200] The above monovalent fluorinated hydrocarbon group is R in formula (D1) above. １ In the above example, a monovalent hydrocarbon group having 1 to 40 carbon atoms, in which some or all of the hydrogen atoms are replaced with fluorine atoms, can be suitably adopted.

[0201] Za ＋Examples of onium cations represented by the above formula (D1) include sulfonium cations and iodonium cations. １ ＋ Sulfonium cations and iodonium cations can be suitably used in this.

[0202] Specific examples of the radiation-sensitive acid generator (B) include, but are not limited to, structures represented by the following formula. A configuration in which an organic acid anion and an onium cation are covalently bonded is also shown.

[0203]

[0204]

[0205]

[0206]

[0207] The above-mentioned radiation-sensitive composition may contain one or more radiation-sensitive acid generators (B).

[0208] When the above-mentioned radiation-sensitive composition contains a radiation-sensitive acid generator (B), the lower limit of the content of the radiation-sensitive acid generator (B) (total if multiple types are included) is preferably 1 part by mass, more preferably 3 parts by mass, and still more preferably 5 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 90 parts by mass, more preferably 80 parts by mass, and still more preferably 70 parts by mass. As a result, the composition can exhibit the above-mentioned resist properties.

[0209] <Acid diffusion control agent (d)> The radiation-sensitive composition may contain an acid diffusion control agent (d) other than the onium salt (D). The acid diffusion control agent (d) preferably contains an organic acid anion and an onium cation, and generates an acid having a pKa higher than the acid generated from the radiation-sensitive acid generator (B) by exposure. The acid diffusion control agent (d) does not substantially dissociate the acid dissociable group of the base polymer under the pattern formation conditions using the radiation-sensitive acid generator (B), and suppresses the diffusion of the acid generated from the radiation-sensitive acid generator (B) in the unexposed portion by salt exchange.

[0210] Examples of the acid diffusion control agent (d) include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), and the like. Further, a compound containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and a compound containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4) are included.

[0211]

[0212] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. E - and Q - may each independently be OH - , or an organic acid anion represented by R α -O - , R α -COO - , R α -SO ３ - . In the above formulas (8-1) to (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. In the above formulas (8-3) to (8-4), R α is a single bond or a divalent organic group having 1 to 30 carbon atoms. Examples of the monovalent organic group having 1 to 30 carbon atoms include R of the above formula (D1) １Among the monovalent organic groups having 1 to 40 carbon atoms, those having the corresponding number of carbon atoms can be preferably adopted. Examples of the divalent organic group having 1 to 30 carbon atoms include a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 30 carbon atoms.

[0213] When the radiation-sensitive composition contains an acid diffusion control agent (d), the upper limit of the content of the acid diffusion control agent (d) (total in the case of multiple types) is preferably 10 parts by mass, more preferably 5 parts by mass, and even more preferably 3 parts by mass with respect to 100 parts by mass of the base polymer (A). Also, the lower limit of the above content is not particularly limited and may not be contained.

[0214] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains a solvent (E). The solvent (E) is not particularly limited as long as it is a solvent capable of dissolving or dispersing the base polymer (A), the onium salt (D), and optional components that may be contained as desired.

[0215] Examples of the solvent (E) include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

[0216] Examples of the alcohol solvent include monohydric alcohol solvents having 1 to 18 carbon atoms such as isopropanol, 4-methyl-2-pentanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents obtained by etherifying a part of the hydroxy groups of the above polyhydric alcohol solvents such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether).

[0217] In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0218] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents in which the hydroxyl groups of the above-mentioned polyhydric alcohol solvents, such as propylene glycol monomethyl ether, have been etherified.

[0219] Examples of ketone solvents include linear ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0220] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0221] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0222] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0223] Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferred, alcoholic acid ester-based solvents, C1-C18 monoalcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, and lactone-based solvents are more preferred, and methyl 2-hydroxyisobutyrate, diacetone alcohol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and γ-butyrolactone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0224] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0225] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a polymer (A), an onium salt (D), and optionally a high-fluorine-content polymer (F), a radiation-sensitive acid generator (B), etc., and a solvent (E) in predetermined proportions. After mixing, the above radiation-sensitive composition is preferably filtered using, for example, a filter with a pore size of about 0.05 μm to 0.40 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0226] ≪Pattern Forming Method≫ A pattern forming method according to one embodiment of the present invention includes the steps of: (1) applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as the "resist film forming step"); (2) exposing the resist film (hereinafter also referred to as the "exposure step"); and (3) developing the exposed resist film with a developer (hereinafter also referred to as the "development step").

[0227] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, LWR, and CDU is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0228] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film disclosed in, for example, Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, pre-baking (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 170°C, with 80°C to 150°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0229] The lower limit of the thickness of the formed resist film is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 350 nm, and even more preferably 200 nm.

[0230] When performing immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer in the above-mentioned radiation-sensitive composition, an immersion-insoluble protective film may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the immersion-protective film, either a solvent-peelable protective film that is peeled off with a solvent before the development process (see, for example, Japanese Patent Application Publication No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development process (see, for example, International Publication No. 2005 / 069076 and International Publication No. 2006 / 035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable immersion-protective film.

[0231] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask (and, in some cases, through an immersion liquid such as water). The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; electron beams, alpha rays, and other charged particle beams. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and ArF excimer laser light, electron beams with a wavelength of 50 nm or less (which are positioned as next-generation exposure technologies), and EUV are even more preferred.

[0232] When exposure is performed by immersion lithography, the immersion liquid used can be, for example, water or a fluorine-based inert liquid. The immersion liquid is preferably transparent to the exposure wavelength and has the smallest possible temperature coefficient of refractive index to minimize distortion of the optical image projected onto the film. In particular, when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above considerations, water is preferred due to its availability and ease of handling. When water is used, a small amount of an additive that reduces the surface tension of the water and increases its surfactant properties may be added. This additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0233] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the radiation-sensitive acid generator (B) upon exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0234] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0235] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0236] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As for ether solvents, glycol ether solvents are preferred, and ethylene glycol monomethyl ether and propylene glycol monomethyl ether are more preferred. As for ester solvents, acetate ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvents in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0237] As mentioned above, either an alkaline developer or an organic solvent developer may be used as the developer. The appropriate choice can be made depending on whether a positive or negative pattern is desired.

[0238] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0239] ≪Acid Diffusion Control Agent≫ An acid diffusion control agent according to one embodiment of the present invention has a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ＋ is a monovalent organic cation. * represents the bonding site with other atoms in the acid diffusion control agent described above.

[0240] As such an acid diffusion control agent, the onium salt (D) in the above-mentioned radiation-sensitive composition can be suitably used.

[0241] ≪Onium Salt≫ An onium salt according to one embodiment of the present invention has a substructure represented by the following formula (ii). (In formula (ii), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ３ ＋ is a monovalent organic cation (excluding monovalent quaternary ammonium cations). * represents the bonding site with other atoms in the onium salt described above.

[0242] As such an onium salt, in the onium salt (D) in the above radiation-sensitive composition, an onium salt in which Z １ ＋ is a monovalent organic cation other than a monovalent quaternary ammonium cation can be preferably employed.

[0243] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The measurement methods of various physical property values are shown below.

[0244] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the above-described conditions. Further, the dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0245] １３ 13C-NMR analysis] The １３ 13C-NMR analysis of the polymer was performed using a nuclear magnetic resonance apparatus ("JNM-Delta400" manufactured by JEOL Ltd.).

[0246] <Synthesis of polymer> The monomers used in the synthesis of each polymer in each example and each comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass mean values when the total mass of the monomers used is 100 parts by mass, and mol% means values when the total number of moles of the monomers used is 100 mol%.

[0247]

[0248] [Synthesis Example 1] (Synthesis of Polymer (A-1)) Monomers (M-1), (M-2), (M-5), (M-9), and (M-14) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 40 / 10 / 20 / 20 / 10 (mol%). AIBN (azobisisobutyronitrile) (5 mol% relative to the total 100 mol% of the monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone 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 while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered again, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 87%). The Mw of polymer (A-1) was 7,200, and the Mw / Mn ratio was 1.58. Furthermore, １３ ¹³C-NMR analysis revealed that the content percentages of each structural unit derived from (M-1), (M-2), (M-5), (M-9), and (M-14) were 39.4 mol%, 9.2 mol%, 20.5 mol%, 20.2 mol%, and 10.7 mol%, respectively.

[0249] [Synthesis Examples 2-11] (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 monomers of the types and proportions shown in Table 1 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 1 below. Note that "-" in Table 1 below indicates that the corresponding monomer was not used (the same applies to subsequent tables).

[0250]

[0251] [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 (5 mol%) was added as an initiator to prepare a monomer solution. 100 parts by mass of 1-methoxy-2-propanol was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the temperature inside the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder 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 the hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After the reaction was complete, the residual solvent was removed by distillation, and the obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The obtained solid was filtered off and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 83%). The Mw of polymer (A-12) was 5,400, and the Mw / Mn was 1.63. １３ C-NMR analysis revealed that the content of each structural unit derived from (M-1) and (M-18) was 50.4 mol% and 49.6 mol%, respectively.

[0252] [Synthesis Examples 13-15] (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 monomers of the types and proportions shown in Table 2 below were used. Note that the monomers that give structural unit (II) in the polymer are, １３ 13C-NMR measurements confirmed the disappearance of the carbonyl group peak of the acetyl group, indicating that virtually all alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content (mol%), yield (%), and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymer are shown in Table 2 below.

[0253]

[0254] [Synthesis Example 16] (Synthesis of High Fluorine-Content Polymer (F-1)) Monomer (M-1) and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 20 / 80 (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 temperature inside the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The solvent was replaced with acetonitrile (400 parts by mass), and hexane (100 parts by mass) was added and stirred, and the acetonitrile layer was recovered. This process was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of high fluorine-content polymer (F-1) was obtained (yield: 74%). The Mw of the high-fluorine-content polymer (F-1) was 6,500, and the Mw / Mn ratio was 1.78. １３ 13C-NMR analysis revealed that the content of each structural unit derived from (M-1) and (M-20) was 19.7 mol% and 80.3 mol%, respectively.

[0255] [Synthesis Examples 17-20] (Synthesis of high-fluorine content polymers (F-2) to (F-5)) High-fluorine content polymers (F-2) to (F-5) were synthesized in the same manner as in Synthesis Example 16, except that monomers of the types and proportions shown in Table 3 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained high-fluorine content polymers are shown in accordance with Table 3 below.

[0256]

[0257] [Radiation-sensitive acid generator (B)] Compounds (B-1) to (B-8): Compounds represented by the following formulas (B-1) to (B-8).

[0258]

[0259] <Synthesis of Onium Salt (D) as an Acid Diffusion Control Agent> [Example D1] (Synthesis of Onium Salt (D-1)) Onium salt (D-1) as an acid diffusion control agent was synthesized according to the following synthesis scheme.

[0260]

[0261] 20.0 mmol of compound (D-1-a), 20.0 mmol of sulfur, and 50 g of methanol were added to a reaction vessel and stirred at 60°C for 3 hours. Compound (D-1-b) was obtained in good yield by extraction with acetonitrile and removal of the solvent by distillation.

[0262] To the above compound (D-1-b), 20.0 mmol of triphenylsulfonium bromide and 20.0 mmol of sodium bicarbonate were added, and a 0.5 M solution was prepared by adding a mixture of water and dichloromethane (1:3 by mass ratio). After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-1) in good yield.

[0263] [Examples D2 to D17] (Synthesis of onium salts (D-2) to (D-17)) Onium salts (acid diffusion control agents) represented by the following formulas (D-2) to (D-17) were synthesized in the same manner as in Example D1, except that the raw materials and precursors were appropriately changed.

[0264]

[0265]

[0266] [Example D18] (Synthesis of onium salt (D-18)) Onium salt (D-18) was synthesized according to the following synthesis scheme.

[0267]

[0268] 20.0 mmol of compound (D-18-a), 30.0 mmol of benzene, 30.0 mmol of trifluoromethanesulfonic acid, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (D-18-b) was obtained in good yield by purification by column chromatography.

[0269] Methanol was added to the above compound (D-18-b) to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (D-18-c) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0270] To the above compound (D-18-c), 20.0 mmol of sodium bicarbonate was added, and a mixture of water and dichloromethane (1:3 by mass ratio) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-18) in good yield.

[0271] [Example D19] (Synthesis of onium salt (D-19)) Onium salt (D-19) was synthesized according to the following synthesis scheme.

[0272]

[0273] 20.0 mmol of compound (D-19-a), 20.0 mmol of butyrate chloride, and 50 g of acetonitrile were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and compound (D-19-b) was obtained in good yield by purification by column chromatography.

[0274] Methanol was added to the above compound (D-19-b) to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (D-19-c) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0275] To the above compound (D-19-c), 20.0 mmol of sodium bicarbonate was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-19) in good yield.

[0276] [Example D20] (Synthesis of onium salt (D-20)) Onium salt (D-20) was synthesized according to the following synthesis scheme.

[0277]

[0278] 20.0 mmol of compound (D-20-a), 20.0 mmol of diphenyl sulfoxide, 30.0 mmol of trifluoromethanesulfonic anhydride, and 50 g of acetonitrile were added to a reaction vessel and stirred at -40°C for 3 hours. After dilution with water, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and compound (D-20-b) was obtained in good yield by column chromatography.

[0279] Compound (D-20-b) was mixed with acetonitrile and water (1:1 by mass) to make a 1 M solution, and then 20.0 mmol of sodium hydroxide was added and the mixture was reacted at room temperature for 3 hours. Compound (D-20-c) was obtained by extracting with acetonitrile and removing the solvent by distillation.

[0280] Methanol was added to the above compound (D-20-c) to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. The onium salt (D-20) was obtained in good yield by extraction with acetonitrile and removal of the solvent by distillation.

[0281] [Example D21] (Synthesis of Onium Salt (D-21)) An onium salt (acid diffusion control agent) represented by the following formula (D-21) was synthesized in the same manner as in Example D20, except that the raw materials and precursors were appropriately changed.

[0282]

[0283] [Example D22] (Synthesis of onium salt (D-22)) Onium salt (D-22) was synthesized according to the following synthesis scheme.

[0284]

[0285] 20.0 mmol of compound (D-22-a) and methanol were added to a reaction vessel to make a 0.5 M solution, then 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (D-22-b) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0286] To the above compound (D-22-b), 10.0 mmol of Lawson's reagent was added, and acetonitrile was added to make a 0.5 M solution. After stirring at 100°C for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (D-22-c) was obtained by purification by column chromatography.

[0287] To the above compound (D-22-c), 20.0 mmol of triphenylsulfonium bromide and 20.0 mmol of sodium bicarbonate were added, and a 0.5 M solution was prepared by adding a mixture of water and dichloromethane (1:3 by mass ratio). After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-22) in good yield.

[0288] [Example D23] (Synthesis of Onium Salt (D-23)) An onium salt (acid diffusion control agent) represented by the following formula (D-23) was synthesized in the same manner as in Example D22, except that the raw materials and precursors were appropriately changed.

[0289]

[0290] [Example D24] (Synthesis of onium salt (D-24)) Onium salt (D-24) was synthesized according to the following synthesis scheme.

[0291]

[0292] 20.0 mmol of compound (D-24-a) and 10.0 mmol of Lawson's reagent were added to a reaction vessel, and acetonitrile was added to make a 0.5 M solution. After stirring at 100°C for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (D-24-b) was obtained by purification by column chromatography.

[0293] To the above compound (D-24-b), 20.0 mmol of methoxytriphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-24) in good yield.

[0294] [Example D25] (Synthesis of onium salt (D-25)) Onium salt (D-25) was synthesized according to the following synthesis scheme.

[0295]

[0296] 20.0 mmol of compound (D-25-a), 30.0 mmol of toluene, 30.0 mmol of trifluoromethanesulfonic acid, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (D-25-b) was obtained in good yield by column chromatography.

[0297] To the above compound (D-25-b), 10.0 mmol of Lawson's reagent was added, and acetonitrile was added to make a 0.5 M solution. After stirring at 100°C for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (D-25-c) was obtained by purification by column chromatography.

[0298] To the above compound (D-25-c), 20.0 mmol of sodium bicarbonate was added, and a mixture of water and dichloromethane (1:3 by mass ratio) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt (D-25) in good yield.

[0299] [Example D26] (Synthesis of onium salt (D-26)) Onium salt (D-26) was synthesized according to the following synthesis scheme.

[0300]

[0301] 20.0 mmol of compound (D-26-a), 20.0 mmol of cyclopentadiene, and 50 g of methylene chloride were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, methylene chloride was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution. After drying with sodium sulfate, the solvent was removed by distillation, and compound (D-26-b) was obtained in good yield by purification by column chromatography.

[0302] To the above compound (D-26-b), 40.0 mmol of potassium permanganate and 50 g of acetonitrile were added and the mixture was stirred at 50°C for 10 hours. Then, saturated sodium thiosulfate aqueous solution was added to stop the reaction, and ethyl acetate was added for extraction, separating the organic layer. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (D-26-c) was obtained in good yield by purification by column chromatography.

[0303] To the above compound (D-26-c), 20.0 mmol of 5-acetylsalicylic acid, 2.0 mmol of sulfuric acid, and 50 g of toluene were added and the mixture was stirred at 130°C for 24 hours. After dilution with water, ethyl acetate was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (D-26-d) was obtained in good yield by purification by column chromatography.

[0304] The above compound (D-26-d) was mixed with methanol to make a 0.5 M solution, then 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (D-26-e) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0305] To the above compound (D-26-e), a mixture of acetonitrile and water (1:1 by mass) was added to make a 1 M solution. Then, 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added, and the mixture was reacted at 70°C for 4 hours. After extraction with acetonitrile and removal of the solvent, a mixture of acetonitrile and water (3:1 by mass) was added to make a 0.5 M solution. 60.0 mmol of hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. The sodium sulfonate salt compound was obtained by extraction with acetonitrile and removal of the solvent. To the above sodium sulfonate salt compound, 40.0 mmol of triphenylsulfonium bromide and 20.0 mmol of sodium bicarbonate were added, and a mixture of water and methylene chloride (1:3 by mass) was added to make a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, methylene chloride was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the onium salt (D-26) was purified by column chromatography to obtain it in good yield.

[0306] [Acid diffusion control agents other than (D-1) to (D-26)] Compounds (d-1) to (d-6): Compounds represented by the following formulas (d-1) to (d-6)

[0307]

[0308] [Solvents] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Methyl 2-hydroxyisobutyrate E-4: Diacetone alcohol E-5: γ-Butyrolactone

[0309] [Preparation of positive-type radiation-sensitive composition for ArF immersion exposure] [Example 1] 100 parts by mass of (A-1) as polymer (A), 5.0 parts by mass (solids) of (F-1) as high-fluorine-content polymer (F), 10.0 parts by mass of (B-1) as radiation-sensitive acid generator (B), 4.0 parts by mass of (D-1) as onium salt (D) (acid diffusion control agent), and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent (E) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0310] [Examples 2-45, 62, 63 and Comparative Examples 1-6] Radiation-sensitive compositions (J-2) to (J-45), (J-62), (J-63) and (CJ-1) to (CJ-6) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Tables 4-1 and 4-2 below were used.

[0311]

[0312]

[0313] <Formation of a resist pattern using a positive-type radiation-sensitive composition for ArF immersion lithography> An anti-reflective underlayer film formation composition (ARC66 from Brewer Sciences) 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 an anti-reflective underlayer film with an average thickness of 100 nm. The positive-type radiation-sensitive composition for ArF immersion lithography prepared above was applied to this anti-reflective underlayer film using the spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 90 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed to a 60 nm line-and-space mask pattern using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Dipole (σ = 0.9 / 0.7). After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (60 nm line-and-space pattern).

[0314] <Evaluation> The sensitivity and LWR of the resist patterns formed using the above ArF immersion exposure positive-type radiation-sensitive composition were evaluated according to the following method. The results are shown in Table 5 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The results are shown in Table 5 below.

[0315] [Sensitivity] In forming a resist pattern using the above ArF immersion lithography positive-type radiation-sensitive composition, the exposure amount used to form a 60 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 30 mJ / cm². ２ The following conditions are considered "good": 30 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0316] [LWR] A 60 nm line-and-space resist pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better quality. An LWR of 3.0 nm or less was evaluated as "good," and an LWR greater than 3.0 nm was evaluated as "poor."

[0317]

[0318] As is clear from the results in Table 5, the radiation-sensitive composition of the example showed good sensitivity and LWR when used in ArF immersion lithography, whereas the comparative example exhibited inferior characteristics compared to the example. Therefore, when the radiation-sensitive composition of the example is used in ArF immersion lithography, a resist pattern with optimal sensitivity and good LWR can be formed.

[0319] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 46] A radiation-sensitive composition (J-46) was prepared by mixing 100 parts by mass of (A-12) as polymer (A), 3.0 parts by mass (solids) of (F-5) as high-fluorine-content polymer (F), 60.0 parts by mass of (B-3) as radiation-sensitive acid generator (B), 40.0 parts by mass of (D-5) as acid diffusion control agent (D), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0320] [Examples 47-59, 64 and Comparative Examples 7-8] Radiation-sensitive compositions (J-47)-(J-59), (J-64), and (CJ-7)-(CJ-8) were prepared in the same manner as in Example 46, except that the components of the types and amounts shown in Table 6 below were used.

[0321]

[0322] <Formation of a resist pattern using a positive-type radiation-sensitive composition for EUV exposure> An anti-reflective underlayer film (ARC66 from Brewer Sciences) 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 an anti-reflective underlayer film with an average thickness of 105 nm. The positive-type radiation-sensitive composition for EUV exposure prepared above was applied to this anti-reflective underlayer film using the spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 55 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an EUV lithography system (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. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (25 nm line and space pattern).

[0323] <Evaluation> The sensitivity and LWR of the resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated according to the following method. The results are shown in Table 7 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0324] [Sensitivity] In forming a resist pattern using the above-mentioned positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 25 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 50 mJ / cm². ２ The following conditions are considered "good": 50 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0325] [LWR] The mask size was adjusted to form a 25 nm line-and-space pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements, and this 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line jaggedness and better quality. An LWR of 3.0 nm or less was evaluated as "good," and an LWR greater than 3.0 nm was evaluated as "poor."

[0326]

[0327] As is clear from the results in Table 7, the radiation-sensitive compositions of the examples can form resist patterns with optimal sensitivity and good LWR even when used in EUV positive exposure.

[0328] [Preparation of a negative-type radiation-sensitive composition for ArF exposure, formation and evaluation of a resist pattern using this composition] [Example 60] A radiation-sensitive composition (J-60) was prepared by mixing 100 parts by mass of (A-1) as polymer (A), 2.0 parts by mass (solids) of (F-3) as a high-fluorine-content polymer (F), 12.0 parts by mass of (B-1) as a radiation-sensitive acid generator (B), 10.0 parts by mass of (D-6) as an onium salt (D) (acid diffusion control agent), and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0329] On a 12-inch silicon wafer, a base layer anti-reflective coating composition ("ARC66" from Brewer Science) was applied using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a base layer anti-reflective coating with an average thickness of 100 nm. On this base layer anti-reflective coating, the ArF exposure negative-type radiation-sensitive composition (J-60) prepared above was applied using the same spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 90 nm was formed by cooling at 23°C for 30 seconds. Next, this resist film was exposed using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6) through a mask pattern with 50 nm holes and a 100 nm pitch. After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as the organic solvent developer and dried to form a negative-type resist pattern (a contact hole pattern with 50 nm holes and a 100 nm pitch).

[0330] The sensitivity of the resist pattern using the above-mentioned ArF exposure negative-type radiation-sensitive composition was evaluated in the same manner as the evaluation of the resist pattern using the above-mentioned ArF immersion exposure positive-type radiation-sensitive composition. In addition, the CDU was evaluated according to the method described below.

[0331] [CDU] The optimal exposure dose determined in the sensitivity evaluation above was used to form a contact hole pattern with 50 nm holes and a 100 nm pitch. The formed resist pattern was observed from the top using the scanning electron microscope described above. The variation of the contact holes was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as the CDU (nm). A smaller CDU value indicates less roughness of the holes and a better quality. A CDU of less than 3.5 nm was evaluated as "good," and a CDU of 3.5 nm or more was evaluated as "poor."

[0332] As a result, the radiation-sensitive composition of Example 60 showed good sensitivity and CDU even when a negative-type resist pattern was formed by ArF exposure.

[0333] [Preparation of a negative-type radiation-sensitive composition for EUV exposure, formation and evaluation of a resist pattern using this composition] [Example 61] A radiation-sensitive composition (J-61) was prepared by mixing 100 parts by mass of (A-15) as polymer (A), 5.0 parts by mass (solids) of (F-5) as a high-fluorine-content polymer (F), 60.0 parts by mass of (B-8) as a radiation-sensitive acid generator (B), 40.0 parts by mass of (D-12) as an onium salt (D) (acid diffusion control agent), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as a solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0334] On a 12-inch silicon wafer, a base layer anti-reflective coating composition ("ARC66" from Brewer Science) was applied using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a base layer anti-reflective coating with an average thickness of 105 nm. On this base layer anti-reflective coating, the prepared negative-type radiation-sensitive composition for EUV exposure (J-61) was applied using the same spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 55 nm was formed by cooling at 23°C for 30 seconds. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" from ASML) with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR15. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as the organic solvent developer and dried to form a negative-type resist pattern (a contact hole pattern with 20 nm holes and a 40 nm pitch).

[0335] The resist patterns using the above-mentioned negative-type radiation-sensitive composition for EUV exposure were evaluated in the same manner as the resist patterns using the above-mentioned negative-type radiation-sensitive composition for ArF exposure. As a result, the radiation-sensitive composition of Example 61 showed good sensitivity and CDU even when a negative-type resist pattern was formed by EUV exposure.

[0336] The radiation-sensitive composition and pattern formation method described above allow for the formation of resist patterns with good sensitivity to exposure light and excellent CDU and LWR. Therefore, these can be suitably used in semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

1. A radiation-sensitive composition containing an onium salt having a partial structure represented by the following formula (i), a polymer having a structural unit (I) containing an acid-dissociable group, and a solvent. (In formula (i), １ - X - is S - or O ２ is S or O. However, at least one selected from the group consisting of X １ - and X ２ contains S. ＋ Z is a monovalent organic cation. * is a bond to another atom in the above onium salt, respectively.) 2. The radiation-sensitive composition according to claim 1, wherein the onium salt is a compound represented by the following formula (D1) or (D2). (In formula (D1), R １ n, which has 1 to 40 carbon atoms. １ It is a valence organic group. Z １ ＋ n is an organic cation. １ n is an integer between 1 and 3. １ If there are two or more X １ - , X ２ and Z １ ＋ These are either identical or different from one another. １ - and X ２ This is equivalent to equation (i) above. (In formula (D2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - and X ２ This is equivalent to equation (i) above.

3. In the above formula (D1), n １ The radiation-sensitive composition according to claim 2, wherein is 1.

4. In the above formula (D1), n １ is 1, R １ The radiation-sensitive composition according to claim 2, wherein is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms.

5. In the above formula (D1), n １ R is 2, １ The radiation-sensitive composition according to claim 2, wherein is comprising at least one structure selected from the group consisting of a cyclic structure, an alkenediyl group, -CO-, -O-, and -NR'-, and R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

6. In the above formula (D2), L Ａ２ The radiation-sensitive composition according to claim 2, wherein the composition comprises at least one structure selected from the group consisting of a cyclic structure, -CO-, and -O-.

7. In the above formula (D1), Z １ ＋ The radiation-sensitive composition according to claim 2, wherein is a sulfonium cation, an iodonium cation, or a quaternary ammonium cation.

8. In the above formula (D2), Z ２ ＋ The radiation-sensitive composition according to claim 2, wherein is a monovalent sulfonium cation, a monovalent iodonium cation, or a monovalent quaternary ammonium cation.

9. In the above formula (D2), Z ２ ＋ This is a monovalent triarylsulfonium cation, and L Ａ２ Z is a divalent linking group containing a single bond or an ester bond; ２ ＋ is a monovalent diaryliodonium cation, L Ａ２ is a single bond; or Z ２ ＋ It is a monovalent quaternary ammonium cation, L Ａ２ The radiation-sensitive composition according to claim 2, wherein is a divalent linking group containing an ester bond.

10. X １ - is, S - X ２ A radiation-sensitive composition according to any one of claims 1 to 9, wherein is O.

11. The radiation-sensitive composition according to any one of claims 1 to 9, wherein the content of the onium salt is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the polymer.

12. The radioactive composition according to any one of claims 1 to 9, wherein the above-mentioned structural unit (I) 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 substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these is independently either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ These elements combine with each other to form a divalent alicyclic group with 3 to 20 carbon atoms, which is then bonded to the carbon atoms. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

13. A radiation-sensitive composition according to any one of claims 1 to 9, further comprising a radiation-sensitive acid generator.

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

15. The pattern formation method according to claim 14, wherein the exposure is performed using an ArF excimer laser or extreme ultraviolet light.

16. An acid diffusion control agent having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ＋ is a monovalent organic cation. * represents the bonding site with other atoms in the acid diffusion control agent described above.

17. An onium salt having a substructure represented by the following formula (ii). (In formula (ii), X １ - is, S - or O - That is. X ２ is either S or O. However, X １ - and X ２ S is included in at least one of the groups selected from Z. ３ ＋ is a monovalent organic cation (excluding monovalent quaternary ammonium cations). * represents the bonding site with other atoms in the onium salt described above.

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