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

Abstract

Provided are: a radiation-sensitive composition that can exhibit sensitivity, LWR, CDU, pattern rectangularity, depth of focus (DOF), pre- and post-exposure storage stability, and development defect suppression at sufficient levels during pattern formation; a pattern formation method; and an onium salt compound. This radiation-sensitive composition comprises an onium salt compound represented by formula (1), a polymer, and a solvent. (In the formula, R1 is -CN, -NO2, -SO2-R11, -F, a C1-10 monovalent hydrocarbon group, or a C1-20 monovalent fluorinated hydrocarbon group. R2 is -CN, -NO2, -CF2H, or -SO2-R21. R11 and R21 are C1-20 monovalent hydrocarbon groups. R3 and R4 are hydrogen atoms or C1-20 monovalent organic groups. X is -O-, -S-, -SO-, -SO2-, or -NR'-. Wa is a hydrogen atom or a C1-40 monovalent organic group. Z+ is an organic cation.)

Description

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

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

[0002] Photolithography, 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 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 KrF excimer lasers and ArF excimer lasers, and further employ liquid immersion lithography, a method in which exposure is performed with a liquid medium filling the space between the lens of the exposure apparatus and the resist film. As next-generation technologies, lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered.

[0004] Regarding photoacid generators, which are the main components of resist compositions, perfluoroalkyl sulfonic acid, which can impart strong acid, is widely used to improve sensitivity and resolution. On the other hand, in recent years, due to growing environmental awareness, photoacid generators with reduced fluorine atom content are being investigated (see Japanese Patent Publication No. 7015295).

[0005] Patent No. 7015295

[0006] As pattern miniaturization progresses, resist compositions are required to have resist performance equivalent to or better than conventional ones in terms of sensitivity, LWR, CDU, pattern rectangularity, depth of field (DOF), storage stability before and after exposure, and development defect suppression, while also being environmentally conscious.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern forming method, and an onium salt compound that can exhibit sufficient levels of sensitivity, LWR, CDU, pattern rectangularity, depth of focus (DOF), storage stability before and after exposure, and development defect suppression properties during pattern formation.

[0008] As a result of intensive studies to solve the present problem, the present inventors have found that the above object can be achieved by adopting the following constitution, and have completed the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: an onium salt compound represented by the following formula (1); a polymer; and a solvent. (In formula (1), R １ is -CN, -NO ２ , -SO ２ -R １１ , -F, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R １１ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ２ is -CN, -NO ２ , -CF ２ H or -SO ２ -R ２１ . R ２１ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ３ and R ４ are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. When a plurality of R ３ and R ４ are present, the plurality of R ３ and R ４ are each the same or different from each other. n is an integer of 0 to 8. X is -O-, -S-, -SO-, -SO ２ - or -NR'-, and R' is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. W ａ is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. Z ＋ is an organic cation.)

[0010] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the 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.

[0011] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1). (In formula (1), R １ -CN, -NO ２ , -SO ２ -R １１ -F is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. １１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ２ -CN, -NO ２ , -CF ２ H or -SO ２ -R ２１ That is. R ２１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ３ and R ４ Each of these is independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ and R ４ If multiple R ３ and R ４ These are either identical or different from each other. n is an integer from 0 to 8. X is -O-, -S-, -SO-, -SO ２ - or -NR'-. R' is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. W ａ This is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. ＋ (This is an organic cation.)

[0012] In this specification, "organic group" means a group containing at least one carbon atom. However, cyano groups (-CN), carboxyl groups (-COOH), formyl groups (-CHO), carbonyl groups (-CO-:-(C=O)-), etc., which can function or be characteristic groups on their own, are excluded as organic groups. A "fused ring" means a polycyclic structure in which any two adjacent rings share two consecutive atoms. A "bridged ring" means a polycyclic structure in which any two adjacent rings share three or more consecutive atoms. When three or more atoms are shared between two adjacent rings, the atoms or atomic chains excluding the atoms at both ends of the three or more shared atoms are called "bridges." As abbreviations for substituents, "Me" represents a methyl group and "Ph" represents a phenyl group.

[0013] 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.

[0014] Radiation-sensitive composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains an onium salt compound, a polymer, and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0015] According to this composition, sensitivity, LWR, CDU, pattern rectangularity, depth of field (DOF), pre- and post-exposure storage stability, and development defect suppression can be achieved at a sufficient level during pattern formation. Although the reason for this is not clear, it is presumed to be as follows.

[0016] Firstly, the composition uses an onium salt compound with a low fluorine content and heteroatoms in its molecular chain as a radiation-sensitive acid generator. This increases compatibility with polymers having many (meth)acrylic and phenolic moieties, improving uniform dispersibility in the film, and also shortens the diffusion length of the generated acid by increasing its interaction ability with the polymer.

[0017] Secondly, because the sulfonate anion has one or two electron-withdrawing groups at the α-carbon, the generated acid can exhibit sufficient acidity. The combination of low fluorine content, the ability to control the diffusion length of the generated acid, and the ability to make the generated acid highly acidic allows for efficient progress of desired acid reactions (such as the dissociation reaction of acid-dissociable groups or polymer crosslinking reactions by crosslinking agents) only in the exposed area, thereby increasing the dissolution contrast between the exposed and unexposed areas while suppressing swelling.

[0018] Thirdly, the radiation-sensitive acid generator contains -CO-CH ２ -C (CN) ２ -SO ３ - or -CO-CH ２ -CH(CN)-C(CN) ２ -SO ３ - When a structure like this is present, the hydrogen atoms of the methylene group in the structure become active protons due to the electron-withdrawing properties of the carbonyl and dicyano structures, causing the adjacent cyano group to be eliminated and generating hydrogen cyanide while simultaneously forming an acrylic structure (-CO-CH=C(CN)-SO ３ - (and so on) can occur. Since this side reaction is accelerated in the presence of acid, it not only reduces storage stability when stored after exposure, but also leads to contamination of the exposure machine itself. The onium salt compound of this composition employs a structure that does not generate such active protons, thus providing good storage stability after exposure.

[0019] These effects occur synergistically, allowing the composition to exhibit the desired resist properties.

[0020] <Onium Salt Compounds> Onium salt compounds are represented by the above formula (1) and are compounds that generate acid upon irradiation with radiation. If the above polymer contains structural units having acid-dissociable groups, the acid generated from the onium salt compound can dissociate the above acid-dissociable groups.

[0021] In the above formula (1), R １ -SO ２ -R １１ In R １１Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms, as represented by , include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or groups combining these.

[0022] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0023] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 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.

[0024] Examples of monovalent aromatic hydrocarbon groups having 6 to 20 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.

[0025] R １１ The group is preferably an alkyl group having 1 to 5 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms, more preferably a methyl group, an ethyl group, a cyclopentyl group, or a cyclohexyl group, and even more preferably a methyl group.

[0026] R １ As a monovalent hydrocarbon group having 1 to 10 carbon atoms, R １１ Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by , groups corresponding to 1 to 10 carbon atoms can be suitably adopted. １ Preferably, the alkyl group has 1 to 5 carbon atoms, and more preferably, a methyl group or an ethyl group.

[0027] R １Examples of monovalent fluorinated hydrocarbon groups having 1 to 20 carbon atoms, represented by the formula, include monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms and monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms.

[0028] Examples of the above-mentioned monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms include fluorinated alkyl groups such as trifluoromethyl group, difluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, heptafluoron-propyl group, heptafluoroisopropyl group, nonafluoron-butyl group, nonafluoroisobutyl group, nonafluorot-butyl group, 2,2,3,3,4,4,5,5-octafluoron-pentyl group, tridecafluoron-hexyl group, and 5,5,5-trifluoro-1,1-diethylpentyl group; fluorinated alkenyl groups such as trifluoroethenyl group and pentafluoropropenyl group; and fluorinated alkynyl groups such as fluoroethynyl group and trifluoropropynyl group.

[0029] Examples of the above-mentioned monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as fluorocyclopentyl group, difluorocyclopentyl group, nonafluorocyclopentyl group, fluorocyclohexyl group, difluorocyclohexyl group, undecafluorocyclohexylmethyl group, fluoronorbornyl group, fluoroadamantyl group, fluorobornyl group, fluoroisobornyl group, and fluorotricyclodecyl group; and fluorinated cycloalkenyl groups such as fluorocyclopentenyl group and nonafluorocyclohexenyl group.

[0030] R １ For example, -CN, -SO ２ -R １１ It is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, and more preferably -CN. １１ As stated above,

[0031] In the above formula (1), R ２ -SO ２ -R２１ In R ２１ As a monovalent hydrocarbon group having 1 to 20 carbon atoms, R １１ The above monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by [formula], can be suitably used.

[0032] R ２ It is preferable that it is -CN.

[0033] R １ and R ２ Preferably, all of these are -CN. This overcomes the weakness of low-fluorine type radiation-sensitive acid generators, which is that the acidity of the generated acid cannot be increased, thus enabling high levels of uniform dispersibility and acid-induced reactions (such as dissociation reactions of acid-dissociable groups and polymer crosslinking reactions by crosslinking agents). As a result, improvements in sensitivity and roughness, and suppression of development defects can be achieved.

[0034] In the above formula (1), R ３ and R ４ Examples of monovalent organic groups having 1 to 20 carbon atoms represented by include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups having a divalent heteroatom-containing linking group between carbon atoms of the hydrocarbon group or at the terminal end of the hydrocarbon group (hereinafter also referred to as "group (α)"), groups in which some or all of the hydrogen atoms of the hydrocarbon group or group (α) are replaced with monovalent heteroatom-containing substituents, or groups that combine these.

[0035] As a monovalent hydrocarbon group having 1 to 20 carbon atoms, R in formula (1) above is an example. １１ A monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably used.

[0036] Examples of heteroatoms that constitute a divalent heteroatom-containing linking group or a monovalent heteroatom-containing substituent include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0037] Examples of divalent heteroatom-containing linking groups include -CO-, -CS-, -NR'-, -O-, -S-, -SO-, and -SO ２- and combinations thereof are examples. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0038] Examples of monovalent heteroatom-containing substituents include hydroxyl groups, sulfanyl groups, cyano groups, nitro groups, amino groups, and halogen atoms. The halogen atoms are as described above.

[0039] R ３ and R ４ Preferably, the group is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; more preferably, a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; even more preferably, a hydrogen atom, a methyl group, or an ethyl group; and particularly preferably, a hydrogen atom.

[0040] In formula (1) above, n is preferably an integer from 1 to 8, more preferably an integer from 1 to 5, even more preferably an integer from 1 to 4, and particularly preferably an integer from 1 to 3. By setting n within the above range, the effect of increased steric hindrance near the sulfonic acid can be reduced, and the decrease in reaction efficiency in the film as an generated acid can be suppressed. This allows the desired roughness performance and development defect performance to be suitably exhibited.

[0041] In formula (1) above, the monovalent organic group having 1 to 10 carbon atoms represented by R' in -NR'- as X is R ３ Of the monovalent organic groups having 1 to 20 carbon atoms represented by the above, groups corresponding to 1 to 10 carbon atoms can be suitably adopted. In particular, R' is preferably a monovalent organic group having 2 to 10 carbon atoms having -CO- at the hydrogen atom or nitrogen atom end, and more preferably a hydrogen atom, a 2 to 10 carbon atom alkoxycarbonyl group, or a 2 to 10 carbon atom acyl group. The alkoxy group in the above alkoxycarbonyl group is preferably a methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, or t-butoxy group, and more preferably a t-butoxy group. The above acyl group is preferably an acetyl group or a propionyl group.

[0042] X is preferably -O-.

[0043] In the above formula (1), Wａ As a monovalent organic group having 1 to 40 carbon atoms, R ３ The monovalent organic group having 1 to 20 carbon atoms, as represented by the above, can be suitably adopted as a group having 1 to 40 carbon atoms.

[0044] W ａ It is preferable that the ring structure includes a ring structure. The ring structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the ring structure may be alicyclic, aromatic, or a combination thereof. In the case of a combination, the ring structures may be linked by a chain structure, and two or more ring structures may form a fused ring structure or a ring aggregate structure. A ring aggregate structure is a structure in which two adjacent rings are linked by a single bond. These structures are preferably included as the smallest basic skeleton of the ring structure. The number of ring structures may be one or two or more. The above-mentioned divalent heteroatom-containing linking groups may be present between carbon atoms or at the ends of carbon chains forming the skeleton of the ring or chain structure, and hydrogen atoms on carbon atoms of the ring or chain structure may be substituted with other substituents.

[0045] The above alicyclic structure is R in formula (1) above. １ Structures corresponding to monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, as shown in [reference], can be suitably adopted.

[0046] The above aromatic ring structure is R in formula (1) above. １ In addition to the ring structures corresponding to the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms shown above, aromatic heterocycles having 3 to 20 carbon atoms, such as triazole rings, imidazole rings, furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, indole rings, benzimidazole rings, benzofuran rings, quinoline rings, and carbazole rings, can be suitably adopted.

[0047] The above chain-like structure includes the divalent heteroatom-containing linking group and the R of formula (1) above. １Structures corresponding to monovalent chain hydrocarbon groups having 1 to 20 carbon atoms as shown above, or structures containing divalent heteroatom-containing linking groups between carbon atoms in said structure, or combinations thereof, can be suitably adopted.

[0048] Aliphatic heterocyclic structures can also be used as the alicyclic structures described above. Examples of such aliphatic heterocyclic structures include oxygen-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0049] Aliphatic heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetal structures, cyclic imide structures, lactam structures, or combinations thereof.

[0050] W ａ It is preferable that it contains the above-mentioned alicyclic structure.

[0051] Examples of substituents that substitute hydrogen atoms on carbon atoms in the above-mentioned ring or chain structure include halogen atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, cycloalkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; or groups that combine these groups; oxo groups (=O), etc. The halogen atoms are as described above.

[0052] W ａ It is preferable that this is a monovalent organic group having 2 to 40 carbon atoms and having -CO- at the X end. ａ The portion of the X-side terminal other than -CO- is as described above. ａWhen has -CO- at the X-side terminal and X is -O-, an ester bond (-CO-O-) is formed by both groups. This improves the ease of synthesis of the onium salt compound, enables appropriate control of the molecular polarity and interaction with the polymer, and can improve the various performances of the resist described above.

[0053] Specific examples of the anion of the onium salt compound represented by the above formula (1) include structures represented by the following formulae, for example.

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] Z ＋ The organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the onium cation include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, ammonium cations, and the like.

[0060] Z ＋ is preferably a radiation-sensitive onium cation. Examples of the radiation-sensitive onium cation include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, and the like. Among these, radiation-sensitive sulfonium cations or radiation-sensitive iodonium cations are preferred, and radiation-sensitive sulfonium cations are more preferred.

[0061] The radiation-sensitive onium cation may have at least one selected from the group consisting of an iodo group and a fluoro group. The organic cation preferably includes an iodo group-containing aromatic ring structure as an embodiment containing the iodo group. The iodo group-containing aromatic ring structure is a structure in which part or all of the hydrogen atoms of the aromatic ring are substituted with iodo groups. In the organic cation, the fluoro group is preferably contained in the form of a fluoro group-containing aromatic ring structure. The fluoro group-containing aromatic ring structure is a structure in which part or all of the hydrogen atoms of the aromatic ring are substituted with fluoro groups. As the aromatic ring in the iodo group-containing aromatic ring structure and the fluoro group-containing aromatic ring structure, W of the above formula (1) ａ The aromatic ring structure shown in can be suitably employed. The introduction of an iodo group or a fluoro group increases radiation absorption efficiency, thereby improving sensitivity.

[0062] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0063]

[0064] In the above formula (X-1), R ａ１ , R ａ２ and R ａ３ each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ , -O-, -CO- or a combination thereof, or a ring structure formed by combining two or more of these groups with each other. The ring structure may contain a heteroatom such as O or S between carbon-carbon bonds forming the skeleton. R Ｐ , R Ｑ and R ＴEach 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.

[0065] In the above equation (X-2), R ｂ１ This refers to a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. 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.

[0066] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0067] In the above equation (X-4), R ｇ１ This refers to a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, halogen atom, or hydroxyl group having 6 to 8 carbon atoms. 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 ｇ３ Each 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.

[0068] In the above equation (X-5), R ｄ１ and R ｄ２Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyl 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 having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are each independently 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.

[0069] In the above formula (X-6), R ｅ１ and R ｅ２ Each of these is independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are independently integers from 0 to 4.

[0070] Specific examples of the above-mentioned radiation-sensitive onium cation include, but are not limited to, structures represented by the following formula.

[0071]

[0072]

[0073]

[0074]

[0075] Onium salt compounds can be obtained by appropriately combining the above-mentioned anion and organic cation (the anion and organic cation are not limited to the structures specifically shown). Specific examples, though not limited to specific examples, include structures represented by the following formula.

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] The onium salt compound may be used alone or in combination of two or more types. The lower limit of the onium salt compound content (total in the case of multiple types) is preferably 0.1 parts by mass, more preferably 1 part by mass, and still more preferably 2 parts by mass, per 100 parts by mass of the base polymer described later. The upper limit of the above content is preferably 100 parts by mass, more preferably 80 parts by mass, and still more preferably 60 parts by mass. This allows for the excellent resist properties described above to be exhibited.

[0083] <Synthesis Method for Onium Salt Compounds> It is clear that onium salt compounds can be synthesized based on the description in the examples and common technical knowledge. In formula (1) above, R １ and R ２ is -CN, R ３ and R ４ As a representative example, the molecule can be synthesized using the following scheme, where is a hydrogen atom, n is 2, and X is -O-.

[0084] (In the scheme, Z ＋ This is equivalent to equation (1) above. Each X is an independent halogen atom. - This is a halide ion. ａ１ (This is a monovalent organic group.)

[0085] Onium salt compounds can be synthesized by reacting a halogenated alcohol with malononitrile to form a dicyano compound, introducing a sulfonic acid group by reacting with a halogenated sulfonic acid, and finally performing a salt exchange with the target radiation-sensitive onium cation halide. Furthermore, the structure of the onium salt compound can be further modified by reacting it with a substrate having a group that can react with the hydroxyl group of the onium salt compound (such as a carboxyl group). Other structures can also be synthesized by appropriately selecting the type of starting material and reaction substrate. In addition, for the introduction of the sulfonic acid group, it is also effective to use other common sulfonic acid introducing agents or to use a base in combination, and it can also be induced by converting the active proton between the dicyano groups to a halogen before converting it to a sulfonic acid group.

[0086] <Polymers> A polymer (i.e., a base polymer) is preferably an aggregate of polymerization chains containing at least one structural unit. The main structural units that a polymer may contain include a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (I)"), a structural unit containing at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures (hereinafter also referred to as "structural unit (II)"), a structural unit containing a polar group (hereinafter also referred to as "structural unit (III)") (however, different from structural units (I) and (II)), a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)"), and the like.

[0087] The structural units incorporated into the polymer can be appropriately selected according to various conditions in the pattern formation process to which the composition is applied, particularly the exposure conditions. The following describes each structural unit.

[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 that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (I).

[0089] Structural unit (I) is not particularly limited as long as it has an acid-dissociable group. Examples include structural units having a tertiary alkyl ester moiety, a structure in which an aromatic group and an aliphatic hydrocarbon group are bonded to a secondary carbon atom in a secondary carboxylic acid ester structure, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with 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, a 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 substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups 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. １１ａMethylene groups and ethanediyl groups are preferred as the base group.

[0094] L １１ａ Examples of the arenediyl group 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 or arenediyl group represented by the above formula (1) may have are W ａ The substituents shown in can be suitably adopted.

[0096] The above R １８ Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms, represented by [the formula], include monovalent linear hydrocarbon groups having 1 to 10 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, and monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

[0097] The above R １８ ~R ２０ Examples of monovalent linear hydrocarbon groups having 1 to 10 carbon atoms represented by include monovalent linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms, or monovalent linear or branched unsaturated hydrocarbon groups having 1 to 10 carbon atoms.

[0098] The above R １８ ~R ２０ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R １１ The monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown in the above can be suitably used.

[0099] The above R １８ As a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the above formula (1), R １１ Monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, as shown in the above, can be suitably used.

[0100] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0101] The above R １９and R ２０ The divalent alicyclic groups having 3 to 20 carbon atoms, which are formed by combining these atoms with the carbon atoms to which they are bonded, can preferably be groups obtained by removing one hydrogen atom from the above-mentioned monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms.

[0102] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these atoms with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure or an aliphatic heterocyclic structure. As the aliphatic heterocyclic structure, a cyclic ether structure containing an ether bond between the carbon atoms of the cycloalkane is preferred.

[0103] The above R １８ ~R ２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0104] 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)").

[0105]

[0106]

[0107] 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. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0108] i and j are preferably 1 or 2. １８ Preferred groups include methyl group, ethyl group, isopropyl group, t-butyl group, cyclopentyl group, ethenyl group, phenyl group, (di)iodophenyl group, methoxyphenyl group, and (di)iodomethoxyphenyl group. 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).

[0109] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0110]

[0111] 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. h1 is an integer from 1 to 4.

[0112] The above R βｆ Preferably, the element is a hydrogen atom, a methyl group, or an ethyl group. H1 is preferably 1 or 2.

[0113] 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 25 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 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.

[0114] [Structural Unit (II)] Structural Unit (II) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. By further comprising Structural Unit (II), the solubility of the base polymer in the developer can be adjusted, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. Furthermore, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0115] Examples of structural units (II) include structural units represented by the following formulas (T-1) to (T-11).

[0116]

[0117] 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. Ｅ 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.

[0118] 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 R ２０ 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.

[0119] The above L ＥExamples 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-.

[0120] Among these, structural units (II) 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.

[0121] When the base polymer has structural unit (II), the lower limit of the content of structural unit (II) (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. The upper limit of the above content is preferably 85 mol%, more preferably 80 mol%, and even more preferably 75 mol%. By setting the content of structural unit (II) 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.

[0122] [Structural Unit (III)] The base polymer optionally has structural unit (III) containing a polar group (however, it is different from structural units (I) and (II)). By further having structural unit (III), the solubility in the developer can be adjusted, 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 hydroxyl group, carboxyl group, cyano group, nitro group, sulfonamide group, etc. Among these, hydroxyl group and carboxyl group are preferred, and hydroxyl group is more preferred.

[0123] Examples of structural units (III) include structural units represented by the following formula.

[0124]

[0125]

[0126] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0127] When the base polymer has structural unit (III) having the polar group described above, the lower limit of the content of structural unit (III) (total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (III) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0128] [Structural Unit (IV)] The base polymer optionally contains structural units having phenolic hydroxyl groups (hereinafter also referred to as "structural unit (IV)"). Structural unit (IV) 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 wavelengths of 50 nm or less, such as electron beams and EUV, in addition to KrF excimer lasers.

[0129] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0130] (In the above formula (4), R β 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, alkoxy 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.)

[0131] The above R β From the viewpoint of copolymerization of the monomer that gives the structural unit (IV), it is preferable that it be a hydrogen atom or a methyl group.

[0132] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0133] R １０２ Fluorine atoms and iodine atoms are preferred as halogen atoms in this mixture.

[0134] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0135] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0136] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0137] When obtaining structural unit (IV), polymerization may be carried out without protecting the phenolic hydroxyl group of the corresponding monomer. Alternatively, the monomer may be polymerized with the phenolic hydroxyl group protected by a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then hydrolysis may be performed to deprotect it and obtain structural unit (IV).

[0138] The lower limit of the content of structural unit (IV) (total content if multiple types are included) is preferably 15 mol%, and more preferably 25 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content may be 70 mol%, or 60 mol%.

[0139] [Other structural units] The base polymer 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 (VII)"). (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.)

[0140] In the above formula (6), R ２α As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R １１ The monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown in the above can be suitably used.

[0141] When the base polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0142] (Method for synthesizing base polymers) Base polymers 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.

[0143] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate (MAIB); 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.

[0144] Solvents used in the above polymerization include, for example, 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, methyl propionate, and propylene glycol monomethyl ether acetate; and ketones such as acetone, 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.

[0145] 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.

[0146] The molecular weight of the base polymer 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 2,000, more preferably 3,000, and even more preferably 4,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 18,000. By keeping the Mw of the base polymer within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0147] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0148] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0149] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh) 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

[0150] The base polymer content is preferably 40% by mass or more, and more preferably 50% by mass or more, relative to the total solid content of the radiation-sensitive composition.

[0151] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer that is more hydrophobic than the base polymer (hereinafter also referred to as a "highly hydrophobic polymer"). The highly hydrophobic polymer is a polymer that has a higher mass content of fluorine atoms or a higher introduction rate of hydrocarbon groups compared to the base polymer. When the radiation-sensitive composition contains a highly hydrophobic polymer, it can be made to be unevenly distributed on the surface of the resist film relative to the base polymer, and as a result, the water repellency of the surface of the resist film during immersion exposure can be improved, and the surface modification of the resist film and the distribution of the composition within the film can be controlled during EUV exposure.

[0152] As a highly hydrophobic polymer, it may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)").

[0153]

[0154] 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 -SO２ 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.

[0155] The above R １３ From the viewpoint of copolymerizability of the monomer that gives the structural unit (V), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0156] The above G Ｌ From the viewpoint of copolymerization of monomers that provide structural units (V), single bonds and -COO- are preferred, and -COO- is more preferred.

[0157] 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.

[0158] 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.

[0159] The above R １４ Preferably, 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.

[0160] When the highly hydrophobic polymer has structural units (V), the lower limit of the content of structural units (V) is preferably 15 mol%, more preferably 25 mol%, and even more preferably 35 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural units (V) within the above range, the mass content of fluorine atoms in the highly hydrophobic 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.

[0161] The highly hydrophobic polymer may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (VI)) represented by the following formula (f-2), either together with or in place of structural unit (V). By having structural unit (VI), the highly hydrophobic polymer can improve its solubility in alkaline developers and suppress the occurrence of development defects.

[0162]

[0163] Structural units (VI) 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 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.

[0164] If structural unit (VI) 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 an alkali-soluble group in structural unit (VI) increases its affinity for alkaline developers and suppresses development defects. A structural unit (VI) having an alkali-soluble group is A 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.

[0165] If the structural unit (VI) has an alkali-dissociable group (y), 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. １ R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -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, W１ , 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 (VI) 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 units (VI) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0166] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural unit (VI), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0167] R Ｅ When the group is a divalent organic group, a group having a lactone structure is preferred, a group having a polycyclic lactone structure is more preferred, and a group having a norbornane lactone structure is even more preferred.

[0168] When the highly hydrophobic polymer has structural units (VI), the lower limit of the content of structural units (VI) is preferably 5 mol%, and more preferably 15 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 95 mol%, and more preferably 85 mol%. By setting the content of structural units (VI) 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 to suppress the occurrence of development defects.

[0169] [Other structural units] A highly hydrophobic polymer containing the above structural unit (V) or structural unit (VI) may, if necessary, also contain structural units other than those listed above, such as structural unit (I), structural unit (III), and structural unit (VII) in the base polymer.

[0170] When a highly hydrophobic polymer contains structural unit (I), the lower limit of the content of structural unit (I) is preferably 10 mol%, and more preferably 20 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 90 mol%, and more preferably 80 mol%.

[0171] When a highly hydrophobic polymer contains structural unit (III), the lower limit of the content of structural unit (III) is preferably 2 mol%, and more preferably 4 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0172] When the highly hydrophobic polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, and more preferably 5 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 20 mol%, and more preferably 15 mol%.

[0173] The highly hydrophobic polymer may have a structural unit having a primary, secondary, or tertiary hydrocarbyl ester structure (however, different from structural unit (I) in the base polymer; hereinafter also referred to as "structural unit (VIII)") instead of the above structural units (V) and (VI). In this case, it is preferable that the highly hydrophobic polymer does not contain fluorine atoms. It is preferable that structural unit (VIII) has a secondary hydrocarbyl ester structure. It is preferable that structural unit (VIII) is a structural unit represented by the following formula (VIII-1). (In formula (VIII-1), R γ R is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ３１ and R ３２Each of these is independently a monovalent linear hydrocarbon group having 3 to 10 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a group in which some or all of the hydrogen atoms of the alicyclic hydrocarbon group are substituted with alkyl groups, or R ３１ and R ３２ This represents a monovalent alicyclic group having 3 to 20 carbon atoms, which can be combined with the carbon atoms to which they are bonded, or a group in which some or all of the hydrogen atoms of the alicyclic group are replaced with alkyl groups.

[0174] R γ The alkyl group having 1 to 10 carbon atoms represented by the above formula (1) is R １１ Among the alkyl groups shown, groups corresponding to those with 1 to 10 carbon atoms can be preferably adopted.

[0175] R ３１ and R ３２ As a monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by the above formula (1), R １１ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms shown above, groups corresponding to 3 to 10 carbon atoms can be suitably adopted. In particular, R ３１ and R ３２ The monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by isopropyl, isobutyl, t-butyl, and n-hexyl groups are preferred.

[0176] R ３１ and R ３２ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R １１ The monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown above can be suitably adopted. The alkyl group that substitutes some or all of the hydrogen atoms of the alicyclic hydrocarbon group is R γ A C1 to C10 alkyl group represented by [the formula shown] can be preferably used.

[0177] R ３１ and R ３２ The monovalent alicyclic group having 3 to 20 carbon atoms, formed by combining these elements, is R in formula (1) above. １１ The monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown above can be suitably adopted. In particular, R３１ and R ３２ As a monovalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups, monocyclic or polycyclic cycloalkyl groups are preferred, and cyclopentyl, cyclohexyl, and norbornyl groups are more preferred. As an alkyl group that substitutes some or all of the hydrogen atoms of the above monovalent alicyclic group, R γ C1 to C10 alkyl groups represented by can be suitably used. In particular, the alkyl group used as a substituent is preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group.

[0178] When a highly hydrophobic polymer has structural unit (VIII), the content of structural unit (VIII) (total content if multiple types are included) is preferably 5 mol%, more preferably 15 mol%, and even more preferably 20 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of structural unit (VIII) 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 to suppress the occurrence of development defects.

[0179] If the highly hydrophobic polymer has structural unit (VIII), it may optionally include structural unit (I) in the base polymer as a structural unit other than structural unit (VIII).

[0180] When the highly hydrophobic polymer contains structural unit (I), the content of structural unit (I) is preferably 60 mol%, and more preferably 70 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 95 mol%, and more preferably 85 mol%.

[0181] The lower limit of Mw for the highly hydrophobic polymer is preferably 3,000, and more preferably 4,000. The upper limit of Mw is preferably 20,000, and more preferably 14,000.

[0182] The lower limit of Mw / Mn for a highly hydrophobic polymer is usually 1, with 1.1 being more preferred. The upper limit of Mw / Mn is usually 5, with 3 being preferred, and 2 being more preferred.

[0183] If the radiation-sensitive composition contains a highly hydrophobic polymer, the lower limit of the content of the highly hydrophobic polymer 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. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 5 parts by mass.

[0184] By setting the content of the highly hydrophobic polymer within the above range, the highly hydrophobic polymer can be more effectively localized to the surface layer of the resist film. As a result, it is possible to enhance 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 highly hydrophobic polymers.

[0185] (Method for synthesizing highly hydrophobic polymers) Highly hydrophobic polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0186] <Acid Diffusion Control Agent> The radiation-sensitive composition may optionally contain an acid diffusion control agent. The acid diffusion control agent controls the diffusion phenomenon of the acid generated from the onium salt compound in the resist film upon exposure, and has the effect of suppressing undesirable chemical reactions in unexposed areas. In addition, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the holding time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0187] Examples of acid diffusion control agents include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

[0188]

[0189] In the above formula (7), R ２２ , R ２３ and R ２４ Each of these is independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0190] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0191] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0192] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0193] Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0194] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0195] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0196] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0197] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as an acid diffusion control agent. The acid generated from the above-mentioned radiation-sensitive weak acid generator is a weak acid that does not dissociate the acid-dissociable groups in the polymer under conditions that cause the acid-dissociable groups to dissociate.

[0198] Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Also, examples include compounds containing a sulfonium cation and anion in the same molecule, represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, represented by the following formula (8-4).

[0199]

[0200] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. ＋ Examples of sulfonium cations represented by the above formulas (X-1) to (X-4) include U ＋Examples of iodonium cations represented by the above formulas (X-5) to (X-6) include iodonium cations represented by E. - and Q - Each of them is independent of OH - , R α -COO - , R α -SO ３ - This is an anion represented by R. α R is a single bond or a monovalent organic group having 1 to 30 carbon atoms. α As a monovalent organic group having 1 to 30 carbon atoms represented by the above formula (1), R ３ A monovalent organic group having 1 to 20 carbon atoms, as represented by the above, can be suitably used, or a group that has been extended to have 1 to 30 carbon atoms. Furthermore, if radiation sensitivity is not required, an organic ammonium cation can be used instead of the sulfonium cation or iodonium cation mentioned above.

[0201] Examples of anions for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also given as examples. The iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0202]

[0203]

[0204] As the onium cation in the above-mentioned acid diffusion control agent, the organic cation of the above-mentioned onium salt compound can be suitably used.

[0205] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0206] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 0.1 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 70 parts by mass, more preferably 60 parts by mass, and even more preferably 55 parts by mass.

[0207] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the onium salt compound, the base polymer, and any optional components that may be included.

[0208] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0209] Examples of alcohol-based solvents include monoalcohol 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, such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether), which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents. 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether ester solvents such as diethylene glycol acetate mono-n-butyl ether, propylene glycol acetate monomethyl ether, and dipropylene glycol acetate monomethyl ether; 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.

[0214] 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.

[0215] Among these, alcohol-based solvents and ester-based solvents are preferred, with monoalcohol-based solvents having 1 to 18 carbon atoms, polyhydric alcohol partial ether-based solvents, polyhydric alcohol partial ether acetate-based solvents, and lactone-based solvents being more preferred, and diacetone alcohol, propylene glycol acetate monomethyl ether, propylene glycol monomethyl ether, and γ-butyrolactone being even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0216] (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 promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0217] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared by mixing, for example, an onium salt compound, a polymer, and optionally additives, as well as a solvent, in predetermined proportions. After mixing, it is preferable to filter the above radiation-sensitive composition using, for example, a filter with a pore size of about 0.05 μm to 0.40 μm.

[0218] <Pattern Forming Method> The pattern forming method according to this embodiment includes a step (1) (hereinafter also referred to as the "resist film forming step") of applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film, a step (2) (hereinafter also referred to as the "exposure step") of exposing the resist film, and a step (3) (hereinafter also referred to as the "developing step") of developing the exposed resist film with a developer.

[0219] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, LWR, CDU, pattern rectangularity, depth of field (DOF), pre- and post-exposure storage stability, and development defect suppression is used during pattern formation, high-quality resist patterns can be efficiently formed. Each step will be described below.

[0220] [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, such as those disclosed in 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.

[0221] The lower limit of the thickness of the formed resist film is preferably 10 nm, more preferably 20 nm, and even more preferably 30 nm. The upper limit of the thickness is preferably 500 nm, more preferably 300 nm, and even more preferably 200 nm.

[0222] When performing immersion exposure, regardless of whether or not the above-mentioned hydrophobic polymer additive is present in the radiation-sensitive composition, a protective immersion film insoluble in the immersion liquid may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the protective immersion 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, Japanese Patent Application Publication Nos. WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective immersion film.

[0223] [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; for example, electron beams and charged particle beams such as alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, and KrF excimer laser light (wavelength 248 nm), ArF excimer laser light (wavelength 193 nm), electron beams, and EUV are more preferred.

[0224] 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.

[0225] 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., by the acid generated from the onium salt compound during exposure in the exposed portion of the resist film. 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.

[0226] [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.

[0227] 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.

[0228] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, etc., 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.

[0229] 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.

[0230] 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 leaving it 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).

[0231] Onium Salt Compounds The onium salt compound according to this embodiment is a compound represented by the following formula (1). (In formula (1), R １ -CN, -NO ２ , -SO ２ -R １１ -F is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. １１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ２ -CN, -NO ２ , -CF ２ H or -SO ２ -R ２１ That is. R ２１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ３ and R ４ Each of these is independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ and R ４ If multiple R ３ and R ４ These are either identical or different from each other. n is an integer from 0 to 8. X is -O-, -S-, -SO-, -SO ２ - or -NR'-. R' is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. W ａ This is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. ＋(This is an organic cation.)

[0232] As such an onium salt compound, the onium salt compound in the above-mentioned radiation-sensitive composition can be suitably used.

[0233] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0234] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0235] [ １３ [C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0236] <Synthesis of Polymers> The monomers used in the synthesis of each polymer in each example and comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is 100 mol%.

[0237]

[0238] [Synthesis Example 1] (Synthesis of Polymer (A-1)) Monomers (M-1), (M-3), (M-5), (M-10) and (M-14) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 35 / 5 / 45 / 10 / 5 (mol%), and MAIB (dimethyl 2,2'-azobisisobutyrate) (10 mol% relative to 100 mol% of the total monomers used) as an initiator was added to prepare a monomer solution. 2-butanone (100 parts by mass) was charged into a reaction vessel, after nitrogen purging for 30 minutes, the inside of the reaction vessel was set to 80°C, and the above monomer solution was added dropwise over 3 hours while stirring. The start of dropping was taken as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to 30°C or lower. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was collected by filtration. After the filtered white powder was washed twice with methanol, it was collected by filtration and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 80%). The Mw of the polymer (A-1) was 5,100, and Mw / Mn was 1.62. Further, １３ as a result of 13C-NMR analysis, the content ratios of respective structural units derived from (M-1), (M-3), (M-5), (M-10) and (M-14) were 35.1 mol%, 4.8 mol%, 45.3 mol%, 10.2 mol% and 4.6 mol%, respectively.

[0239] [Synthesis Examples 2 to 11] (Synthesis of Polymers (A-2) to (A-11)) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that monomers of the types and blending ratios shown in Table 1 below were used. The content ratios (mol%) of each structural unit and the physical property values (Mw and Mw / Mn) of the obtained polymers are also shown in Table 1 below. In addition, "-" in Table 1 below indicates that the corresponding monomer was not used (the same applies to the following tables).

[0240]

[0241] (Synthesis of Polymer (A-12)) Monomers (M-4), (M-5) and (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) such that the molar ratio was 60 / 10 / 30 (mol%), and MAIB (10 mol%) was added as an initiator to prepare a monomer solution. 1-methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel, purged with nitrogen for 30 minutes, then the inside of the reaction vessel was heated to 80°C, and the above monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was taken as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to 30°C or lower. The cooled polymerization solution was poured into hexane (2,000 parts by mass), the precipitated white powder was collected by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 90%). The Mw of the polymer (A-12) was 4,800 and Mw / Mn was 1.55. Furthermore, １３ As a result of C-NMR analysis, the content ratios of each structural unit derived from (M-4), (M-5) and (M-18) were 59.3 mol%, 9.4 mol% and 31.3 mol%, respectively.

[0242] [Synthesis Examples 13 to 15] (Synthesis of Polymers (A-13) to (A-15)) Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that monomers of the types and blending ratios shown in Table 2 below were used. The content ratios (mol%) of each structural unit and the physical property values (Mw and Mw / Mn) of the obtained polymers are also shown in Table 2 below.

[0243]

[0244] [Synthesis Example 16] (Synthesis of highly hydrophobic polymer (F-1)) Monomer (M-4) and monomer (M-21) were dissolved in 2-butanone (200 parts by mass) in a molar ratio of 45 / 55 (mol%), and AIBN (2,2'-azobisisobutyronitrile) (5 mol%) was added as an initiator to prepare monomer solutions. 2-butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours 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. A solution of the highly hydrophobic polymer (F-1) was obtained by substituting the solvent with propylene glycol monomethyl ether acetate (yield: 75%). The Mw of the highly hydrophobic polymer (F-1) was 8,700, and the Mw / Mn ratio was 1.67. １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from (M-4) and (M-21) was 44.9 mol% and 55.1 mol%, respectively.

[0245] [Synthesis Examples 17-23] (Synthesis of highly hydrophobic polymers (F-2) to (F-8)) Highly hydrophobic polymers (F-2) to (F-8) 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 highly hydrophobic polymers are shown in accordance with Table 3 below.

[0246]

[0247] <Synthesis of Onium Salt Compound B> [Examples B1 and B2] (Synthesis of Onium Salt Compounds (B-1) and (B-2)) Onium salt compounds (B-1) and (B-2) were synthesized as radiation-sensitive acid generators according to the following synthesis scheme.

[0248]

[0249] 20.0 mmol of 2-bromoethanol, 20.0 mmol of malononitrile, 30.0 mmol of potassium carbonate, and 50 g of acetone were added to a reaction vessel and stirred at 50°C for 12 hours. Then, saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, and ethyl acetate was added for extraction, separating the organic layer. The obtained organic layer was washed with saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the dicyano compound was obtained in good yield by column chromatography.

[0250] 30.0 mmol of chlorosulfonic acid, 3.0 mmol of potassium carbonate, and 50 g of dichloromethane were added to the above dicyano compound and the mixture was stirred at room temperature for 12 hours. Then, 30.0 mmol of triphenylsulfonium bromide and 50 g of water were added to the reaction solution and the mixture was stirred at room temperature for 1 hour. Dichloromethane was then 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 (B-1) represented by the above formula (B-1) was purified by column chromatography to obtain compound (B-1) in good yield.

[0251] To the above compound (B-1), 30.0 mmol of adamantanecarboxylic acid, 3.0 mmol of sulfuric acid, and 50 g of acetonitrile were added and the mixture was stirred at 100°C for 12 hours. Then, 50 g of saturated sodium bicarbonate aqueous solution was added to the reaction solution to stop the reaction, and dichloromethane was added for extraction, after which the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-2) represented by the above formula (B-2) was obtained in good yield by purification by column chromatography.

[0252] [Example B21] (Synthesis of Onium Salt Compound (B-21)) An onium salt compound (B-21) was synthesized as a radiation-sensitive acid generator according to the following synthesis scheme.

[0253]

[0254] 20.0 mmol of compound (B-21-1), 20.0 mmol of 1,3-propanediol, 30.0 mmol of triethylamine, and 50 g of dichloromethane were added to a reaction vessel and stirred at 50°C for 12 hours. Then, 1 M hydrochloric acid was added to the reaction solution to terminate the reaction, and dichloromethane 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 over sodium sulfate, the solvent was removed by distillation, and the compound (B-21-2) was obtained in good yield by purification by column chromatography.

[0255] To the above compound (B-21-2), 20.0 mmol of phosphorus tribromide and 50 g of toluene were added and the mixture was stirred at room temperature for 12 hours. Then, the reaction solution was diluted with water, 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 over sodium sulfate, the solvent was removed by distillation, and the compound (B-21-3) was obtained in good yield by purification by column chromatography.

[0256] To the above compound (B-21-3), 20.0 mmol of malononitrile, 30.0 mmol of potassium carbonate, and 50 g of acetone were added and the mixture was stirred at 50°C for 12 hours. Then, saturated ammonium chloride aqueous solution was added to the reaction solution to terminate 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 over sodium sulfate, the solvent was removed by distillation, and the compound (B-21-4) was obtained in good yield by purification by column chromatography.

[0257] To the above compound (B-21-4), 30.0 mmol of potassium tert-butoxide and 50 g of tetrahydrofuran were added and the mixture was stirred at room temperature for 1 hour. Then, 30.0 mmol of sulfur trioxide dimethylformamide complex was added to the reaction solution and the mixture was stirred at room temperature for 12 hours. Then, 30.0 mmol of compound (B-21-5), 50 g of dichloromethane, and 50 g of water were added to the reaction solution and the mixture was stirred at room temperature for 1 hour. Dichloromethane was then 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 (B-21) represented by the above formula (B-21) was purified by column chromatography to obtain compound (B-21) in good yield.

[0258] [Examples B3 to B22] (Synthesis of onium salt compounds (B-3) to (B-22)) Onium salt compounds represented by the following formulas (B-3) to (B-22) were synthesized as radiation-sensitive acid generators in the same manner as in Examples B1, B2, and B21, except that the raw materials and precursors were appropriately changed.

[0259]

[0260]

[0261] [Radiation-sensitive acid generators other than onium salt compounds (B-1) to (B-13)] b-1 to b-13: Compounds represented by the following formulas (b-1) to (b-13)

[0262]

[0263] [[D] Compounds as acid diffusion control agents] D-1 to D-7: Compounds represented by the following formulas (D-1) to (D-7) were used as acid diffusion control agents.

[0264]

[0265] [E] Solvents E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-Butyrolactone E-4: Diacetone alcohol

[0266] [Preparation of positive-type radiation-sensitive composition for ArF immersion exposure] [Example 1] A radiation-sensitive composition (J-1) was prepared by mixing 100 parts by mass of (A-1) as a polymer, 2.0 parts by mass (solids) of (F-1) as a highly hydrophobic polymer, 12.0 parts by mass of (B-2) as an onium salt compound, 10.0 parts by mass of (D-1) as an acid diffusion control agent, and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0267] [Examples 2-40, 101-109 and Comparative Examples 1-7] Radiation-sensitive compositions (J-2) to (J-40), (J-101) to (J-109), and (CJ-1) to (CJ-7) 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.

[0268]

[0269]

[0270] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Immersion Exposure> A composition for forming an underlayer antireflective coating ("ARC66" from Brewer Science) was coated onto a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), followed by heating at 205°C for 60 seconds to form an underlayer antireflective coating with an average thickness of 100 nm. The prepared positive radiation-sensitive composition for ArF immersion exposure was coated onto this underlayer antireflective coating using the above spin coater, and PB (prebaking) was performed at 100°C for 60 seconds. Thereafter, cooling was performed at 23°C for 30 seconds to form a resist film with an average thickness of 120 nm. Next, the resist film was exposed via a mask pattern for a 50 nm line-and-space resist pattern using an ArF excimer laser immersion exposure apparatus ("TWINSCAN XT-1900i" from ASML) under optical conditions of NA=1.35 and Dipole (σ=0.9 / 0.7). After exposure, PEB (post-exposure baking) was performed at 100°C for 60 seconds. Thereafter, the above resist film was subjected to alkali development using a 2.38 mass% TMAH aqueous solution as an alkali developer, washed with water after development, and further dried to form a positive resist pattern (a resist pattern with 50 nm lines and 110 nm pitch).

[0271] <Evaluation> For the resist pattern formed using the above positive radiation-sensitive composition for ArF immersion exposure, sensitivity, LWR, pattern rectangularity, depth of focus, storage stability before and after exposure, and the number of development defects were evaluated according to the methods below. The results are shown in the following Tables 5-1 and 5-2. A scanning electron microscope ("CG-5000" from Hitachi High-Technologies Corporation) was used for measuring the dimensions of the resist pattern.

[0272] [Sensitivity] In the formation of a resist pattern using the above positive radiation-sensitive composition for ArF immersion exposure, the exposure amount for forming a resist pattern with 50 nm lines and 110 nm pitch is taken as the optimal exposure amount, and this optimal exposure amount is defined as sensitivity in mJ / cm ２ . Sensitivity is rated "Good" when it is 40 mJ / cm ２ or less, and 40 mJ / cm ２If it exceeded this value, it was rated as "poor."

[0273] [LWR] A resist pattern with 50 nm lines and a 110 nm pitch 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 2.5 nm or less was evaluated as "good," and an LWR greater than 2.5 nm was evaluated as "poor."

[0274] [Pattern Rectangularity] The resist patterns with 50 nm lines and 110 nm pitch, formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, were observed using the scanning electron microscope described above, and the cross-sectional shape of the line patterns was evaluated. The rectangularity of the resist pattern was evaluated as follows: if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape was 1.00 or more and 1.05 or less, it was evaluated as "A" (excellent); if it was greater than 1.05 and 1.10 or less, it was evaluated as "B" (good); and if it was greater than 1.10, it was evaluated as "C" (poor).

[0275] [Depth of Focus] In the resist pattern resolved at the optimal exposure amount determined in the sensitivity evaluation above, the dimensions were observed when the focus was changed in the depth direction. The margin in the depth direction where the pattern dimensions fall within 90% to 110% of the standard without bridging or residue was measured, and this measured value was defined as the depth of focus (nm). A larger depth of focus indicates a better result. A depth of focus of 70 nm or more is evaluated as "good," and a depth of focus of less than 70 nm is evaluated as "poor."

[0276] [Storage Stability Before Exposure] The above ArF immersion lithography positive-type radiation-sensitive composition was stored at 35°C for 30 days, and then the optimal exposure amount, i.e., sensitivity, for forming a resist pattern with 50 nm holes and a 110 nm pitch was measured again. The sensitivity before storage (S), expressed by the following formula, was measured again. ０ Sensitivity (S) after 30 days of storage for ) ３０If the rate of change of ) was between 0% and 1.0%, it was evaluated as "A" (excellent); if it was between 1.0% and 2.0%, it was evaluated as "B" (good); and if it was above 2.0%, it was evaluated as "C" (poor). Rate of change of sensitivity (%) = | (S ３０ -S ０ ) / S ０ | × 100

[0277] [Storage Stability After Exposure (PED Storage Stability)] The optimal exposure amount determined in the sensitivity evaluation above was applied, and PEB was performed at 100°C for 60 seconds. After that, the material was stored at room temperature for 12 hours before proceeding with the development process. After storage, the resist film was alkaline developed, washed with water after development, and then dried to form a positive-type resist pattern, and the line width was measured. The line width L in the normal development process is expressed by the following formula. ０ Line width L after 12 hours of storage at room temperature following PEB １２ If the rate of change was between 0% and 5.0%, it was evaluated as "A" (excellent); if it was between 5.0% and 7.5%, it was evaluated as "B" (good); and if it was above 7.5%, it was evaluated as "C" (poor). Rate of change of line width (%) = |(L １２ -L ０ ) / L ０ | × 100

[0278] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a resist pattern with 50 nm lines and a 110 nm pitch, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 5 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 150 or less, and as "poor" if it exceeded 150.

[0279]

[0280]

[0281] As is clear from the results in Tables 5-1 and 5-2, the radiation-sensitive compositions of the examples exhibited good sensitivity, LWR, pattern rectangularity, depth of field, pre- and post-exposure storage stability, and development defect count when used in ArF immersion lithography, whereas the comparative examples failed to satisfy all of these characteristics. Therefore, when the radiation-sensitive compositions of the examples are used in ArF immersion lithography, it is possible to form a resist pattern with optimal sensitivity, excellent roughness performance, pattern shape, and various margins.

[0282] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 41] A radiation-sensitive composition (J-41) was prepared by mixing 100 parts by mass of (A-12) as a polymer, 2.0 parts by mass (solids) of (F-5) as a highly hydrophobic polymer, 60.0 parts by mass of (B-15) as an onium salt compound, 50.0 parts by mass of (D-3) as an acid diffusion control agent, and 6,300 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-4) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0283] [Examples 42-50 and Comparative Examples 8-12] Radiation-sensitive compositions (J-42) to (J-50) and (CJ-8) to (CJ-12) were prepared in the same manner as in Example 41, except that the components of the types and amounts shown in Table 6 below were used.

[0284]

[0285] <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 prepared positive-type radiation-sensitive composition for EUV exposure 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 50 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. After development, it was washed with water and then dried to form a positive-type resist pattern (20 nm line, 40 nm pitch pattern).

[0286] <Evaluation> The resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated for sensitivity, LWR, storage stability after exposure, and number of development defects according to the method described below. 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.

[0287] [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 20 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" and 30 mJ / cm². ２ If it exceeded this value, it was rated as "poor."

[0288] [LWR] A resist pattern was formed by adjusting the mask size to create a 20 nm line and 40 nm pitch pattern using 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 jaggedness in the lines and a better result. An LWR of 2.5 nm or less was evaluated as "good," and an LWR greater than 2.5 nm was evaluated as "poor."

[0289] [Storage Stability After Exposure (PED Storage Stability)] The optimal exposure amount determined in the sensitivity evaluation above was applied, and PEB was performed at 100°C for 60 seconds. After that, the material was stored at room temperature for 12 hours before proceeding with the development process. After storage, the resist film was alkaline developed, washed with water after development, and then dried to form a positive-type resist pattern, and the line width was measured. The line width L in the normal development process is expressed by the following formula. ０ Line width L after 12 hours of storage at room temperature following PEB １２ If the rate of change was between 0% and 5.0%, it was evaluated as "A" (excellent); if it was between 5.0% and 7.5%, it was evaluated as "B" (good); and if it was above 7.5%, it was evaluated as "C" (poor). Rate of change of line width (%) = |(L １２ -L ０ ) / L ０ | × 100

[0290] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a resist pattern with 20 nm lines and a 40 nm pitch, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 5 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 100 or less, and as "poor" if it exceeded 100.

[0291]

[0292] As is clear from the results in Table 7, the radiation-sensitive composition of the example showed good sensitivity, LWR, post-exposure storage stability, and development defect performance when used in EUV exposure, whereas the comparative example failed to satisfy all of these characteristics. Therefore, when the radiation-sensitive composition of the example is used in EUV exposure, it is possible to form a resist pattern with optimal sensitivity, good LWR, storage stability, and defect performance.

[0293] [Preparation of a negative-type radiation-sensitive composition for ArF exposure, formation and evaluation of a resist pattern using this composition] [Example 51] A radiation-sensitive composition (J-51) was prepared by mixing 100 parts by mass of (A-8) as a polymer, 3.0 parts by mass of (F-3) as a highly hydrophobic polymer (solids), 3.0 parts by mass of (B-2) and 3.0 parts by mass of (B-3) as onium salt compounds, 3.0 parts by mass of (D-4) and 0.5 parts by mass of (D-7) as acid diffusion control agents, and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-4) (2240 / 960 / 30 parts by mass) as a solvent and filtering through a membrane filter with a pore size of 0.2 μm.

[0294] 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-51) 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 135 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 70 nm holes and a 130 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 70 nm holes and a 130 nm pitch).

[0295] The sensitivity and depth of field of the resist pattern using the above-mentioned ArF exposure negative-type radiation-sensitive composition were 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.

[0296] [CDU] The optimal exposure dose determined in the sensitivity evaluation above was used to form 70 nm holes and 130 nm pitch contact holes. The formed resist pattern was observed from the top using the scanning electron microscope described above. The variation in contact hole diameter 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 CDU (nm). A smaller CDU value indicates less roughness and better quality of the holes. A CDU of less than 3.0 nm was evaluated as "good," and a CDU of 3.0 nm or more was evaluated as "poor."

[0297] As a result, the radiation-sensitive composition of Example 51 exhibited good sensitivity, depth of field, and CDU even when a negative-type resist pattern was formed by ArF exposure.

[0298] The radiation-sensitive composition, pattern formation method, and onium salt compound described above provide excellent storage stability before and after exposure, good sensitivity to exposure light, and enable the formation of resist patterns with excellent LWR, CDU, pattern rectangularity, depth of focus (DOF), and development defect suppression. 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 comprising an onium salt compound represented by the following formula (1), a polymer, and a solvent. In the formula (1), R １ is -CN, -NO ２ , -SO ２ -R １１ , -F, a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R １１ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ２ is -CN, -NO ２ , -CF ２ H or -SO ２ -R ２１ R ２１ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ３ and R ４ are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ３ and R ４ when a plurality of R ３ and R ４ are each the same as or different from each other. n is an integer of 0 to 8. X is -O-, -S-, -SO-, -SO ２ - or -NR'-, wherein R' is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. W ａ is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. Z ＋ is an organic cation.) 2. In the above formula (1), R ２ The radiation-sensitive composition according to claim 1, wherein is -CN.

3. The radiation-sensitive composition according to claim 1, wherein in formula (1) above, X is -O-.

4. In the above formula (1), W ａ The radiation-sensitive composition according to any one of claims 1 to 3, wherein is a monovalent organic group having 2 to 40 carbon atoms and having -CO- at the X end.

5. In the above formula (1), R ３ and R ４ The radiation-sensitive composition according to any one of claims 1 to 3, wherein is a hydrogen atom.

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein n is an integer from 1 to 5 in formula (1) above.

7. In the above equation (1), Z ＋ The radiation-sensitive composition according to any one of claims 1 to 3, wherein is a sulfonium cation or an iodonium cation.

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

9. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer comprises a structural unit having an acid-dissociable group.

10. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer comprises a structural unit comprising at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.

11. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer comprises a structural unit having a phenolic hydroxyl group.

12. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 3 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.

13. The pattern formation method according to claim 12, wherein the exposure is performed using a KrF excimer laser, an ArF excimer laser, or extreme ultraviolet light.

14. An onium salt compound represented by the following formula (1). (In formula (1), R １ -CN, -NO ２ , -SO ２ -R １１ -F is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. １１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ２ -CN, -NO ２ , -CF ２ H or -SO ２ -R ２１ That is. R ２１ R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ３ and R ４ Each of these is independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ and R ４ If multiple R ３ and R ４ These are either identical or different from each other. n is an integer from 0 to 8. X is -O-, -S-, -SO-, -SO ２ - or -NR'-. R' is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. W ａ This is a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. ＋ (This is an organic cation.)

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