Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition which has excellent sensitivity and CDU and good storage stability, and a pattern formation method. This radiation-sensitive composition comprises a polymer which contains a structural unit (I) that has an acid-dissociable group, an acid diffusion control agent which includes a third organic acid anion and a third onium cation and which, when exposed to light, generates an acid that does not dissociate the acid-dissociable group, and a solvent, wherein at least: the polymer includes a structural unit (II) which has a first organic acid anion and an iodonium cation and which includes an acid generation structure that, when exposed to light, generates an acid that dissociates the acid-dissociable group; the radiation-sensitive composition contains a radiation-sensitive acid generation agent which contains a second organic acid anion and an iodonium cation and which, when exposed to light, generates an acid that dissociates the acid-dissociable group; or the third onium cation is an iodonium cation, the third organic acid anion of the acid diffusion control agent includes an aromatic ring, -COO- is bound to one of the ring-forming atoms of the aromatic ring, -OH is bound to each of two ring-forming atoms which are adjacent to the one ring-forming atom, and the solvent includes a compound represented by formula (H). (In formula (H), R1 to R3 are each independently a substituted or unsubstituted C1-20 monovalent aliphatic hydrocarbon group.)

Description

Radiation-sensitive composition and pattern forming method

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

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

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

[0004] As patterns become finer, it is becoming necessary to highly control acid diffusion, and as one measure to achieve this, a resist composition containing a sulfonium salt of a weak acid has been proposed (Japanese Patent No. 7206102).

[0005] Patent No. 7206102

[0006] The present inventors discovered that the acid generation efficiency could be improved by introducing an iodonium cation, which has high decomposition efficiency upon exposure, into a component having an acid generating structure. Expanding on this finding, we have investigated the application of iodonium cations to enhance the sensitivity of resist compositions.

[0007] However, the inventors have found through their investigations that resist compositions that use iodonium cations have reduced storage stability.

[0008] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method which have excellent critical dimension uniformity (CDU), which is an index of sensitivity and uniformity of line width and hole diameter during pattern formation, and which also have good storage stability.

[0009] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0010] In one embodiment, the present invention provides a radiation-sensitive composition comprising: a polymer including a structural unit (I) having an acid dissociable group; an acid diffusion controller that includes a third organic acid anion and a third onium cation and generates, upon exposure, an acid that does not dissociate the acid dissociable group; and a solvent, wherein at least the polymer includes a structural unit (II) having a first organic acid anion and an iodonium cation and including an acid generating structure that generates, upon exposure, an acid that dissociates the acid dissociable group; the radiation-sensitive composition comprises a radiation-sensitive acid generator that includes a second organic acid anion and an iodonium cation and generates, upon exposure, an acid that dissociates the acid dissociable group; or the third onium cation is an iodonium cation; and the third organic acid anion of the acid diffusion controller includes an aromatic ring, and one of the ring-constituting atoms of the aromatic ring has a —COO group. － is bonded to the ring-constituting atom, and —OH is bonded to each of two ring-constituting atoms adjacent to the ring-constituting atom, and the solvent contains a compound represented by the following formula (H): (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0011] The radiation-sensitive composition exhibits excellent sensitivity and CDU during resist pattern formation, and also has good storage stability. Although the reason for this is not clear, it is presumed to be as follows.

[0012] In the radiation-sensitive composition, an iodonium cation is introduced into at least the first acid-generating structure contained in the structural unit (II) in the polymer, the radiation-sensitive acid generator, or the acid diffusion controller, thereby improving the acid generation efficiency and, as a result, achieving high sensitivity. Furthermore, the acid diffusion controller exerts a quencher function, suppressing the diffusion of the generated acid into undesired regions, thereby achieving excellent CDU. In addition, the acid diffusion controller is preferably -COO － The specific structure having —OH on both sides of the compound (I) exhibits weaker basicity than conventional compounds, thereby suppressing decomposition of the iodonium cation. Furthermore, the solvent represented by formula (H) exhibits affinity for and stabilizing action on the iodonium cation. These combined effects enable the radiation-sensitive composition to exhibit good storage stability.

[0013] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

[0014] This pattern formation method uses the radiation-sensitive composition, which is capable of exhibiting excellent sensitivity and CDU during resist pattern formation and has good storage stability, and therefore can efficiently form high-quality resist patterns.

[0015] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0016] Radiation-Sensitive Composition The radiation-sensitive composition (hereinafter simply referred to as the "composition") according to this embodiment contains a polymer (hereinafter simply referred to as the "base polymer"), an acid diffusion controller, and a solvent. Furthermore, the composition optionally contains a radiation-sensitive acid generator. In the composition, an iodonium cation is introduced into at least one of the base polymer (the first acid-generating structure thereof), the optionally added radiation-sensitive acid generator, or the acid diffusion controller. The composition may contain an iodonium cation and a radiation-sensitive acid generator, as illustrated in the following incorporation modes (1) to (10). These incorporation modes are referred to throughout this specification. (1) A mode containing a base polymer into which an iodonium cation has been introduced, no radiation-sensitive acid generator, and an acid diffusion controller into which an iodonium cation has not been introduced. (2) A mode containing a base polymer into which an iodonium cation has not been introduced, no radiation-sensitive acid generator, and an acid diffusion controller into which an iodonium cation has been introduced. (3) An embodiment comprising a base polymer having an iodonium cation introduced therein, no radiation-sensitive acid generator, and an acid diffusion controller having an iodonium cation introduced therein. (4) An embodiment comprising a base polymer having an iodonium cation introduced therein, a radiation-sensitive acid generator having no iodonium cation introduced therein, and an acid diffusion controller having no iodonium cation introduced therein. (5) An embodiment comprising a base polymer having no iodonium cation introduced therein, a radiation-sensitive acid generator having no iodonium cation introduced therein, and an acid diffusion controller having an iodonium cation introduced therein. (6) An embodiment comprising a base polymer having an iodonium cation introduced therein, a radiation-sensitive acid generator having no iodonium cation introduced therein, and an acid diffusion controller having an iodonium cation introduced therein. (7) An embodiment comprising a base polymer having no iodonium cation introduced therein, a radiation-sensitive acid generator having no iodonium cation introduced therein, and an acid diffusion controller having no iodonium cation introduced therein. (8) An embodiment including a base polymer having an iodonium cation introduced therein, a radiation-sensitive acid generator having an iodonium cation introduced therein, and an acid diffusion controller having no iodonium cation introduced therein.(9) An embodiment including a base polymer with no iodonium cations introduced, a radiation-sensitive acid generator with iodonium cations introduced, and an acid diffusion controller with iodonium cations introduced. (10) An embodiment including a base polymer with iodonium cations introduced, a radiation-sensitive acid generator with iodonium cations introduced, and an acid diffusion controller with iodonium cations introduced.

[0017] The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0018] <Polymer> The polymer (i.e., base polymer) is an aggregate of polymer chains containing a structural unit (I) having an acid-dissociable group. In addition to the structural unit (I), the base polymer may also contain a structural unit (II) containing an acid-generating structure, a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (III)"), etc.

[0019] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group (excluding structures corresponding to the structural unit (III)). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. When the base polymer contains the structural unit (II) or when the composition contains a radiation-sensitive acid generator, an acid generated from either component upon exposure dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This creates a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0020] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, etc. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0021]

[0022] In the above formula (1), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ -COO- or ＊ -COO-L １１ａ represents —COO—. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0023] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0024] L １１ａ Examples of the alkanediyl group represented by the formula (I) include divalent alkanediyl groups having 1 to 10 carbon atoms, such as methanediyl, ethanediyl, and propanediyl. １１ａ The alkanediyl group represented by the formula (I) is preferably a methanediyl group or an ethanediyl group.

[0025] L １１ａ Examples of the arenediyl group represented by the formula (I) include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl and naphthalenediyl groups. １１ａ As the arenediyl group represented by the formula:

[0026] L １１ａThe substituents that the alkanediyl group or arenediyl group represented by the formula (I) may have include halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), carboxy groups, cyano groups, nitro groups, hydroxy groups (L １１ａ is an alkanediyl group), an alkyl group, a fluorinated alkyl group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, an alkoxy group, and the like.

[0027] L １１ａ Examples of the alkyl group as a substituent include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms, such as trifluoromethyl and pentafluoroethyl. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, and a propoxy group.

[0028] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof.

[0029] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, and isopentyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0030] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group; monocyclic alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group and a cyclohexenyl group; and polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group.

[0031] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0032] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms is preferred.

[0033] R １９ and R ２０ The monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups having 1 to 10 carbon atoms are exemplified.

[0034] R １９ and R ２０ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula １８ Examples of the monovalent alicyclic hydrocarbon group include those having 3 to 20 carbon atoms.

[0035] The above R １９ and R２０ The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group in which two hydrogen atoms have been removed from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0036] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７ ] Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0037] Among these, R １８ is an alkyl group, an alkenyl group, or a phenyl group having 1 to 4 carbon atoms, and R １９ and R ２０ are combined with each other, and the alicyclic structure formed together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0038] The above R １８ ~R ２０ Examples of the substituent that may be possessed by L include １１ａ The substituents (excluding hydroxy groups) that can be possessed by an alkanediyl group or arenediyl group represented by the following formula can be suitably employed.

[0039] Examples of the structural unit (I-1) include structural units represented by the following formulas (1-1) to (1-11) (hereinafter also referred to as "structural units (I-1-1) to (I-1-11)").

[0040]

[0041] In the above formulas (1-1) to (1-11), R １７ ~R ２０ has the same meaning as in formula (1). Ｌ１１ is a halogen atom, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. h, i, and j each independently represent an integer of 1 to 4. k1, k2, and k3 each independently represent 0 or 1. 3a each independently represent an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other.

[0042] h, i and j are preferably 1 or 2. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, an ethenyl group (vinyl group), a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ is preferably an iodine atom, an alkyl group, or an alkoxy group. １８ An iodophenyl group is used as R Ｌ１１ It is preferable to introduce an iodine group into the structural unit (I) by employing an iodine atom as the ion-exchange group. The introduction of the iodine group increases the radiation absorption efficiency and the secondary electron generation efficiency, thereby improving the sensitivity.

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

[0044]

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

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

[0047] Specific examples of the structural unit (I) (including the structural unit (I-1)) are not particularly limited, but include structures represented by the following formulae (1-1) to (1-28).

[0048]

[0049]

[0050] In the formula, R １７ is synonymous with the above formula (1).

[0051] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved. When the acid-dissociable group has an iodine group, sensitivity can be further improved.

[0052] (Structural Unit (II)) The structural unit (II) includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure.

[0053] In the above-mentioned embodiments (1), (3), (4), (6), (8), and (10), the first onium cation is an iodonium cation. In the other embodiments, the first onium cation is another cation.

[0054] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 100° C. for 60 seconds.

[0055] When the base polymer contains the radiation-sensitive acid generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer when developed with an aqueous alkaline solution, but making it poorly soluble in the developer when developed with an organic solvent.

[0056] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (II) of the base polymer is not particularly limited. The base polymer may have the first organic acid anion as a side chain moiety, or the first onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the first organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the first onium cation is ionically bonded to the first organic acid anion as a counter ion of the first organic acid anion. On the other hand, when the first onium cation is bonded to the main chain of the base polymer as a side chain structure, the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the first organic acid anion as a side chain moiety.

[0057] The first organic acid anion preferably has, as an acid anion moiety, at least one selected from the group consisting of a sulfonate anion, a carboxylate anion, and a sulfonimide anion. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide, corresponding to the acid anion moiety.

[0058] The first organic acid anion preferably includes, as a structure other than the acid anion moiety, —O—, —CO—, a cyclic structure, or a combination thereof. The combination also includes a structure (heterocyclic structure) in which —O— or —CO— is incorporated into the cyclic structure as a ring-forming moiety.

[0059] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0060] The alicyclic structure may be R １８ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0061] Examples of the aromatic ring structure include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, a phenalene ring, a phenanthrene ring, a pyrene ring, a fluorene ring, a perylene ring, and a coronene ring. Of these, a benzene ring is preferred as the aromatic ring.

[0062] Examples of the heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0063] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0064]

[0065] In the above formula, γ is an integer of 1 to 3.

[0066] The chain structure may be R １９ and R ２０ A structure corresponding to the monovalent chain hydrocarbon group having 1 to 10 carbon atoms in the formula (I) can be suitably employed.

[0067] Examples of the divalent heteroatom-containing group include —CO—, —CS—, —NR′—, —O—, —S—, and —SO ２ - or a divalent group formed by combining these groups, etc. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0068] The substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include L １１ａ Substituents that can be possessed by the alkanediyl group or arenediyl group represented by the following formula can be suitably employed.

[0069] In the first acid generating structure, the first organic acid anion preferably has a sulfonate anion as the acid anion moiety, and an electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. This allows the first acid generating structure to efficiently exhibit the above-mentioned function. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, and a cyano group. The fluorinated hydrocarbon group is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0070] The first organic acid anion preferably has an iodine group. The first organic acid anion preferably contains the iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups. Examples of the aromatic ring in the iodine group-containing aromatic ring structure include aromatic hydrocarbon rings such as a benzene ring, a tolyl ring, a naphthalene ring, an anthracene ring, a phenalene ring, a phenanthrene ring, a pyrene ring, a fluorene ring, a perylene ring, and a coronene ring; heteroaromatic rings such as a furan ring, a pyrrole ring, a thiophene ring, a phosphole ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a triazine ring, a carbazole ring, and a dibenzofuran ring; and combinations thereof. Of these, a benzene ring is preferred as the aromatic ring. The number of iodo groups in the iodo group-containing aromatic ring structure is preferably one, two or three.

[0071] As described above, the first onium cation may be an iodonium cation or another cation, depending on whether a radiation-sensitive acid generator is contained, whether an iodonium cation is introduced into the radiation-sensitive acid generator, and whether an iodonium cation is introduced into the acid diffusion controller. Examples of the other cation include a sulfonium cation and a tetrahydrothiophenium cation. Of these, a sulfonium cation is preferred as the other cation.

[0072] The first onium cation preferably has an iodo group. The first onium cation preferably contains the iodo group-containing aromatic ring structure.

[0073] The first onium cation in the structural unit (II) may be a fluoro-group-containing onium cation having a fluoro group. The fluoro-group-containing onium cation preferably has a fluoro-group-containing aromatic ring structure. The fluoro-group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro-group-containing aromatic ring structure can be suitably the aromatic ring in the above-mentioned iodine-group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0074] The first onium cation preferably contains at least one selected from the group consisting of an iodo group-containing aromatic ring structure and a fluoro group-containing aromatic ring structure.

[0075] The structural unit (II) having the above structures in combination can efficiently exhibit the above functions.

[0076] The structural unit (II) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (II-1)").

[0077]

[0078] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkylene group, cycloalkylene group, or arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３Some or all of the hydrogen atoms in Rf may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group.

[0079] X ＋ is a monovalent iodonium cation or sulfonium cation, which will be described in detail later.

[0080] The structural unit (II-1) is preferably represented by the following formula (a1-1).

[0081]

[0082] In the formula, R Ｖ , R ｆ１ ~R ｆ４ , V １ and X ＋ has the same meaning as in formula (a1) above. ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0083] Examples of the first organic acid anion of the monomer that gives the structural unit (II) (including the structural unit (II-1)) include, but are not limited to, those shown below. Note that the iodo group in the structure shown below may be substituted with a hydrogen atom or other substituents. In the following formula, R Ｖ is synonymous with the above.

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] In the above formula, R Ｖ has the same meaning as the above formula (a1).

[0090] The iodonium cation serving as the first onium cation in the structural unit (II-1) is preferably represented by the following formula (P1).

[0091] (In formula (P1), Ar １ is an (a1+1)-valent aromatic ring having 5 to 20 carbon atoms. ２ is an (a2+1)-valent aromatic ring having 5 to 20 carbon atoms. １ and X ２ are each independently a monovalent organic group having 1 to 20 carbon atoms, a nitro group, a hydroxy group, or a halogen atom. １ and X ２ If there are multiple Xs, １ and X ２ are the same or different from each other. a1 and a2 are each independently an integer of 0 to 5.

[0092] As used herein, an "organic group" is a group containing at least one carbon atom.

[0093] Ar １ and Ar ２ As the aromatic ring in Ar, a ring corresponding to a carbon number of 5 to 20 among the aromatic rings in the iodo group-containing aromatic ring structure can be suitably used. １ The (a1+1)-valent aromatic ring having 5 to 20 carbon atoms represented by the formula (Ar) is a structure in which (a1+1) hydrogen atoms have been removed from the above aromatic ring. ２ The (a2+1)-valent aromatic ring having 5 to 20 carbon atoms represented by the formula (Ar) has a structure in which (a2+1) hydrogen atoms have been removed from the aromatic ring. １ and Ar ２ is preferably a benzene ring.

[0094] X １ and X ２Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof. In addition to these, examples of the organic group include a cyano group and a carboxy group.

[0095] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R １８ Preferably, a monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula: can be used. As the divalent heteroatom-containing group, preferably, a divalent heteroatom-containing group in the first organic acid anion of the structural unit (II) of the base polymer can be used. Examples of monovalent heteroatom-containing groups include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0096] X １ and X ２ If there exists X １ and X ２ are each independently preferably an alkoxycarbonyl group or a halogen atom, more preferably a fluorine atom or an iodine atom.

[0097] a1 and a2 are each independently preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 0 or 1.

[0098] Specific examples of such iodonium cations represented by the above formula (P1) include the following.

[0099]

[0100] The sulfonium cation as the first onium cation of the structural unit (II-1) is preferably represented by the following formula (Q-1).

[0101]

[0102] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra3 represents a substituent. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0103] The substituents represented by Ra1, Ra2 and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom or a halogenated hydrocarbon group.

[0104] The alkyl groups of Ra1 and Ra2 are R １８ Examples of the linear or branched alkyl groups include those shown as the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula (1). Of these, methyl, ethyl, n-butyl and t-butyl groups are particularly preferred.

[0105] The cycloalkyl groups of Ra1 and Ra2 are R １８ Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl groups are particularly preferred.

[0106] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0107] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0108] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy group of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0109] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups.

[0110] Each of the groups Ra1 and Ra2 may further have a substituent. The substituent may be any of the groups L in the above formula (1). １１ａ Examples of the substituents that can be possessed by an alkanediyl group or arenediyl group represented by the following formula are given.

[0111] Examples of the halogen atom for Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0112] The halogenated hydrocarbon group of Ra1 and Ra2 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0113] As described above, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable that they form - or a single bond. Among these, it is more preferable that they form -O-, -S- or a single bond, and it is particularly preferable that they form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0114] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF ３ More preferably, the following can be mentioned.

[0115] Ra3 is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0116] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0117] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0118] Specific examples of such onium cations represented by the above formula (Q-1) include the following: The fluorine atom or iodine atom in the onium cations below may be substituted with a hydrogen atom or another substituent.

[0119]

[0120]

[0121]

[0122]

[0123] It is also possible to adopt an embodiment in which a first onium cation is bonded to the main chain as a side chain structure of the base polymer, and a first organic acid anion is bonded to the first onium cation as a counter ion through an ionic bond. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in the above formula (a1) ２ From SO ３ － The structure up to is preferably ionically bonded to the first onium cation as a counter ion. １１ A group represented by the following formula can be preferably used.

[0124] When the base polymer contains the structural unit (II), the lower limit of the content of the structural unit (II) (when multiple types are contained, the total content) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 8 mol% relative to the total structural units constituting the base polymer.The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.By setting the content of the structural unit (II) within the above range, it can fully exhibit its function as an acid generating structure and exhibit the above resist properties.

[0125] The monomer that provides the structural unit (II-1) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0126] (Structural Unit (III)) The structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding the structure corresponding to the structural unit (II)). When the polymer contains the structural unit (III), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (III) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (III) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (III) is preferably represented by the following formula (2):

[0127] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０１ is an acid-dissociable group. １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ and m ５ are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ +m ５ ≦2n ３ Meets +5.)

[0128] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (III), it is preferable that the alkyl group is a hydrogen atom or a methyl group.

[0129] L ＣＡis a single bond or —COO— ＊ is preferred.

[0130] The above R １０１ The acid-dissociable group represented by the formula (I) is not particularly limited, and examples thereof include R １０１ a structure forming a tertiary alkyl ester moiety together with —COO— to which R １０１ a structure that forms, together with —COO— to which —COO— is bonded, a secondary unsaturated alkyl ester moiety having a double bond between the β-position carbon and the γ-position carbon of the terminal oxygen atom of —COO—; １０１ and a structure in which an acetal bond is formed together with —COO— to which —COO— is bonded.

[0131] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the formula (1) is preferably L １ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0132] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0133] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0134] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0135] The above m ５ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0136] The structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-26) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-26)").

[0137]

[0138]

[0139]

[0140] In the above formulas (2-1) to (2-26), R β is the same as the above formula (2).

[0141] The lower limit of the content of the structural unit (III) (total content when multiple types of structural unit (III) are present) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can further improve the sensitivity and development contrast.

[0142] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (III) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0143] (Structural Unit (IV)) The base polymer optionally has other structural units. Examples of the other structural units include structural units (IV) containing a polar group (excluding structural units (III) and structural units (V) described below). By further including the structural unit (IV), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

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

[0145]

[0146] In the above formula, R Ｋis a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0147] When the base polymer has the structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (IV) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0148] (Structural Unit (V)) The structural unit (V) as another structural unit is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (V), the base polymer can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0149] When the base polymer contains the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of the structural unit (V) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0150] The polymer may further contain a structural unit derived from styrene or iodostyrene (hereinafter also referred to as "structural unit (VI)"). When the base polymer contains the structural unit (VI) having the polar group, the lower limit of the content of the structural unit (VI) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%.

[0151] The base polymer preferably contains an iodine group. In this case, the iodine group may be contained in at least one of the structural units (I) to (VI). When the base polymer contains an iodine group, excellent sensitivity and CDU can be exhibited.

[0152] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0153] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0154] As the solvent used in the polymerization, the solvents described below can be suitably used. These solvents used in the polymerization may be used alone or in combination of two or more kinds.

[0155] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0156] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 12,000, and even more preferably 8,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0157] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0158] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0159] The lower limit of the content of the base polymer is preferably 50% by mass, more preferably 60% by mass, and even more preferably 70% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 98% by mass, more preferably 95% by mass, and even more preferably 92% by mass.

[0160] <Other Resins> The radiation-sensitive composition of the present embodiment may contain, as another resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter also referred to as a "high-fluorine-content resin"). When the radiation-sensitive composition contains a high-fluorine-content resin, the high-fluorine-content resin can be unevenly distributed in the surface layer of the resist film relative to the base resin, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to a desired state.

[0161] (Method of synthesizing high-fluorine-content resin) The high-fluorine-content resin can be synthesized by the same method as the above-mentioned method of synthesizing the base resin.

[0162] <Radiation-Sensitive Acid Generator> The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a second organic acid anion and a second onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer and generating a carboxyl group or the like. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low-molecular-weight compound (free from the polymer), and is different from a radiation-sensitive acid-generating structure in which the first organic acid anion or the first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure, such as the structural unit (II) in the base polymer.

[0163] At least one selected from the group consisting of the third organic acid anion and the third onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0164] The structure of the second organic acid anion of the radiation-sensitive acid generator is V in the above formula (a1) of the base polymer. ２ From SO ３ － The above structures can be suitably adopted.

[0165] Examples of the second organic acid anion of the radiation-sensitive acid generator include, but are not limited to, those shown below. Note that, instead of the second organic acid anion having an iodo group-containing aromatic ring structure, a second organic acid anion not having an iodo group-containing aromatic ring structure can suitably employ a structure in which the iodo group in the following formula is substituted with a hydrogen atom or another substituent.

[0166]

[0167]

[0168]

[0169] The structure of the second onium cation in the radiation-sensitive acid generator can suitably be the structure of the first onium cation in the structural unit (II) in the base polymer. In the above-described embodiments (7) to (10), the second onium cation is an iodonium cation. In other embodiments, the second onium cation is another cation.

[0170] The above-mentioned radiation-sensitive acid generator can be synthesized by a known method, particularly by a salt exchange reaction. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0171] These radiation-sensitive acid generators may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total content when multiple types are used) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass, and even more preferably 25 parts by mass. This allows excellent sensitivity to be exhibited during resist pattern formation.

[0172] <Acid Diffusion Controller> The acid diffusion controller contains a third organic acid anion and a third onium cation, and generates an acid that does not dissociate the acid-dissociable group upon exposure. The acid diffusion controller has the function of inhibiting the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange. This makes it possible to inhibit the diffusion of the acid in unexposed areas, thereby forming a resist pattern with excellent resolution and development contrast.

[0173] The third organic acid anion of the acid diffusion controller contains an aromatic ring, and one of the ring-constituting atoms of the aromatic ring has —COO － is bonded to the iodonium cation, and —OH is bonded to each of the two ring atoms adjacent to the ring atom. This makes the acid diffusion controller weakly basic, suppressing decomposition of the iodonium cation. As a result, the storage stability of the radiation-sensitive composition is improved.

[0174] The aromatic ring of the third organic acid anion may be the same as that of the iodo group-containing aromatic ring structure, and preferably is a benzene ring.

[0175] The third organic acid anion of the acid diffusion controller is preferably represented by the following formula (D): (In formula (D), Y is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxy group, or a halogen atom, or when there are multiple Ys, two of the multiple Ys that are located at ortho positions to each other are combined with each other to form a ring structure having 5 to 20 ring members together with the two carbon atoms to which they are bonded. When there are multiple Ys, the multiple Ys are the same or different from each other. b1 is an integer of 0 to 3.)

[0176] The monovalent organic group having 1 to 20 carbon atoms represented by Y is X in the above formula (P1). １ and X ２ A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0177] When there are multiple Ys, two of the multiple Ys that are located at ortho positions to each other are combined with each other to form a 5-20-membered ring structure together with the two carbon atoms to which they are bonded. A ring structure corresponding to the 5-20-membered aromatic ring in the above iodo group-containing aromatic ring structure can be suitably used. The benzene ring in formula (D) and the 5-20-membered ring structure formed by combining the two Ys are condensed. A benzene ring is preferred as the 5-20-membered ring structure.

[0178] b1 is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0179] Examples of the third organic acid anion of the acid diffusion controller include, but are not limited to, those shown below.

[0180]

[0181] The structure of the third onium cation in the acid diffusion controller can suitably be the structure of the first onium cation in the structural unit (II) in the base polymer. In the above-mentioned incorporation modes (2), (3), (5), (6), (9), and (10), the third onium cation is an iodonium cation. In incorporation modes other than these, the second onium cation is another cation. Incorporation modes (2), (3), (5), (6), (9), and (10), the iodonium cation as the third onium cation is preferably not an inner salt. That is, when such an iodonium cation is represented by the above formula (P1), X １ and X ２ Preferably, does not contain anionic groups.

[0182] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0183] These acid diffusion controllers may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (total amount when multiple types are used) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass.

[0184] The lower limit of the content of the acid diffusion controller (total content when multiple types are used) is preferably 5 mol %, more preferably 10 mol %, and even more preferably 15 mol %, based on the total content of the structural unit (II) in the base polymer and the content of the optional radiation-sensitive acid generator, and the upper limit of the content is preferably 40 mol %, more preferably 30 mol %, and even more preferably 25 mol %.

[0185] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer, the acid diffusion controller, and optional additives.

[0186] The solvent contains a compound represented by the following formula (H) (hereinafter also referred to as "compound (H)"). (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0187] R １ ~R ３ The aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) may be any of linear, branched, and cyclic. Specific examples thereof include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an alkynyl group having 2 to 20 carbon atoms. The linear structure may be a linear hydrocarbon group, whether saturated or unsaturated, linear or branched. The cyclic structure may be an alicyclic cyclic hydrocarbon group. In addition, R ２ and R ３ may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. In addition, some or all of the hydrogen atoms of these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0188] The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a cyclopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, an n-pentyl group, a cyclopentyl group, an n-hexyl group, and a cyclohexyl group. The alkenyl group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a vinyl group, a 1-propenyl group, and a 2-propenyl group. The alkynyl group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include an ethynyl group, a propargyl group, and the like.

[0189] As the compound (H), known or novel compounds can be used as appropriate.

[0190] Examples of the compound (H) include methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, n-butyl 2-hydroxyisobutyrate, methyl 2-hydroxy-2-methylbutyrate, etc. These may be used alone or in combination of two or more.

[0191] The compound (H) may be used alone or in combination of two or more. The lower limit of the content of the compound (H) in the solvent (when a plurality of compounds (H) are contained, the total of the compounds) is preferably 5% by mass, more preferably 15% by mass, and even more preferably 30% by mass. The upper limit of the content may be 100% by mass (i.e., the solvent contains only the compound (H)). The upper limit of the content is preferably 90% by mass, more preferably 85% by mass. This allows the composition to exhibit storage stability.

[0192] Examples of other solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0193] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In this embodiment, alcoholic acid ester-based solvents (excluding compound (H)) such as methyl lactate, ethyl lactate, propyl lactate, and butyl lactate are also included in the alcohol-based solvents.

[0194] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0195] Examples of the ketone solvent include chain 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.

[0196] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0197] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0198] 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.

[0199] Among the other solvents, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, and alcohol acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol 1-monomethyl ether, and ethyl lactate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0200] <Other Optional Components> The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0201] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, an acid diffusion controller, and a solvent, and, if necessary, other optional components, in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0202] <Pattern Forming Method> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0203] According to the pattern formation method, a high-quality resist pattern can be efficiently formed because the radiation-sensitive composition has good storage stability and is capable of exhibiting excellent sensitivity and CDU during pattern formation. Each step will be described below.

[0204] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, soft baking (SB) may be performed, if necessary, to volatilize the solvent in the coating film. The SB temperature is typically 60°C to 160°C, and preferably 80°C to 140°C. The SB time is typically 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0205] When the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (III) as the base polymer in the composition.

[0206] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0207] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like due to the acid generated from the radiation-sensitive acid generator or structural unit (II) (if both are included) in the exposed portions of the resist film. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0208] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0209] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0210] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0211] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0212] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties in the examples were measured as follows.

[0213] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] Measurements were performed by gel permeation chromatography (GPC) using Tosoh GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40 ° C., detector: differential refractometer, using monodisperse polystyrene as the standard. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0214] <[A] Synthesis of Polymer> The monomers used in the synthesis of each polymer in each example and comparative example are shown below.

[0215]

[0216] Synthesis Example 1 Synthesis of Polymer (A-1) Compound (M-1) and compound (M-4) were dissolved in propylene glycol 1-monomethyl ether (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 40 / 60. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, propylene glycol 1-monomethyl ether (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then the mixture was heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0217] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution) and then dissolved in propylene glycol 1-monomethyl ether (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring.

[0218] After the reaction was completed, the remaining solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). This solution was added dropwise to 500 parts by mass of water to coagulate the resin, and the resulting solid was filtered off. The resulting mixture was dried at 50°C for 12 hours to obtain a white powdery polymer (A-1).

[0219] [Synthesis Examples 2 to 11] Polymers (A-2) to (A-11) were also synthesized in the same manner as in Synthesis Example 1 above, except that the monomer species and ratios were changed as shown in Table 1 below.

[0220] Synthesis Example 12 Compounds (M-17), (M-4), and (M-3) were dissolved in propylene glycol 1-monomethyl ether (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 30 / 60 / 10. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, propylene glycol 1-monomethyl ether (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then the mixture was heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0221] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution), and then dried at 50°C for 12 hours to obtain a white powdery polymer (A-12).

[0222] Synthesis Examples 13 to 15 Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12 above, except that the monomer species and ratios were changed as shown in Table 1 below.

[0223]

[0224] <[B] Radiation-Sensitive Acid Generator> Compounds represented by the following formulae (B-1) to (B-9) were used as radiation-sensitive acid generators.

[0225]

[0226] <[C] Acid Diffusion Controller> Compounds represented by the following formulae (C-1) to (C-9) were used as acid diffusion controllers.

[0227]

[0228] <[D] Solvent> D-1: Propylene glycol monomethyl ether acetate D-2: Methyl 2-hydroxyisobutyrate D-3: Ethyl 2-hydroxyisobutyrate D-4: Isopropyl 2-hydroxyisobutyrate D-5: Methyl 2-hydroxy 2-methylbutyrate D-6: Propylene glycol 1-monomethyl ether D-7: Ethyl lactate D-8: Diacetone alcohol

[0229] Example 1 100 parts by mass of [A] polymer (A-1), 20 parts by mass of [B] radiation-sensitive acid generator (B-1), [C] acid diffusion controller (C-1) in an amount of 20 mol% relative to (B-1), 2,000 parts by mass of [D] solvent (D-1), and 4,800 parts by mass of (D-2) were blended and mixed, and then filtered through a filter having a pore size of 0.20 μm to prepare a radiation-sensitive composition (R-1).

[0230] [Examples 2 to 36 and Comparative Examples 1 to 4] Radiation-sensitive compositions (R-2) to (R-36) and (CR-1) to (CR-4) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

[0231]

[0232] <Formation of Resist Pattern> (EUV Exposure, Alkali Development) Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 40-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was then post-exposure baked (PEB) at 100°C for 60 seconds. Next, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive-type 50 nm pitch, 25 nm contact hole pattern.

[0233] <Evaluation> The sensitivity, CDU, and storage stability of each radiation-sensitive composition were evaluated by measuring each of the resist patterns formed above according to the methods described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Table 3 below.

[0234] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the value, the better the sensitivity. The sensitivity was 56 mJ / cm ２ If it is less than 56 mJ / cm, it is "S" (very good). ２ More than 58mJ / cm ２ If it is less than 58 mJ / cm, it is "A" (good). ２ More than 61mJ / cm ２ The following cases are "B" (fairly good), 61 mJ / cm ２ If it exceeded this, it was judged as "C" (poor).

[0235] [CDU] Using the scanning electron microscope, a 25 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at random points. The dimensional variation (3σ) was calculated and recorded as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better results. CDU was evaluated as "S" (very good) for values ​​less than 3.4 nm, "A" (good) for values ​​3.4 nm to 3.6 nm, "B" (fair) for values ​​3.6 nm to 3.8 nm, and "C" (poor) for values ​​3.8 nm or greater.

[0236] [Storage Stability] After preparing the radiation-sensitive composition, it was stored at -15°C for 2 weeks or at 35°C for 2 weeks. Thereafter, the optimal exposure dose for forming a 150 nm line and space pattern was determined in resist pattern formation by KrF exposure as described below. Based on the optimal exposure dose of the radiation-sensitive composition stored at 15°C for 2 weeks, if the optimal exposure dose of the radiation-sensitive composition stored at 35°C for 2 weeks increased the sensitivity by 1.0% or more or decreased the sensitivity by 1.0% or more, it was rated as "C." If the optimal exposure dose of the radiation-sensitive composition increased the sensitivity by 0.7% or more but less than 1.0% or decreased the sensitivity by 0.7% or more but less than 1.0%, it was rated as "B." Otherwise, it was rated as "A."

[0237] <Formation of Resist Pattern> (KrF Exposure, Alkali Development) The radiation-sensitive composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (DUV42 (Nissan Chemicals)) had been formed using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After SB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 70-nm-thick resist film. Next, the resist film was irradiated with KrF light using a KrF exposure machine (model "S210D," Nikon, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). The resist film was subjected to PEB at 110°C for 60 seconds. The wafer was then developed at 23°C for 30 seconds using a 2.38 wt% TMAH aqueous solution to form a positive 150-nm line-and-space pattern.

[0238]

[0239] As is clear from the results in Table 3, the radiation-sensitive compositions of the Examples all had good sensitivity and CDU while ensuring storage stability compared to the radiation-sensitive compositions of the Comparative Examples.

[0240] The radiation-sensitive composition and pattern forming method of the present invention can improve sensitivity and CDU while ensuring storage stability, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition comprising: a polymer including a structural unit (I) having an acid dissociable group; an acid diffusion controller including a third organic acid anion and a third onium cation, and generating an acid that does not dissociate the acid dissociable group upon exposure; and a solvent, wherein at least the polymer includes a structural unit (II) having a first organic acid anion and an iodonium cation, and including an acid generating structure that generates an acid that dissociates the acid dissociable group upon exposure; the radiation-sensitive composition includes a radiation-sensitive acid generator including a second organic acid anion and an iodonium cation, and generating an acid that dissociates the acid dissociable group upon exposure; or the third onium cation is an iodonium cation; and the third organic acid anion of the acid diffusion controller includes an aromatic ring, and one of the ring-constituting atoms of the aromatic ring has a -COO group. － is bonded to the ring-constituting atom, and —OH is bonded to each of two ring-constituting atoms adjacent to the ring-constituting atom above, and the solvent contains a compound represented by the following formula (H): (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

2. The radiation-sensitive composition according to claim 1, wherein the iodonium cation is represented by the following formula (P1): (In formula (P1), Ar １ is an aromatic ring having 5 to 20 carbon atoms and a valence of (a1+1). ２ is an (a2+1)-valent aromatic ring having 5 to 20 carbon atoms. １ and X ２ are each independently a monovalent organic group having 1 to 20 carbon atoms, a nitro group, a hydroxyl group, or a halogen atom. １ and X ２ When there are multiple Xs, １ and X ２ are the same or different. a1 and a2 are each independently an integer of 0 to 5.

3. In the above formula (P1), Ar １ and Ar ２ The radiation-sensitive composition according to claim 2 , wherein is a benzene ring.

4. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the third organic acid anion of the acid diffusion controller is represented by the following formula (D): (In formula (D), Y is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a hydroxyl group or a halogen atom, or when there are multiple Ys, two of the multiple Ys that are located at the ortho positions to each other are combined with each other to form a ring structure having 5 to 20 ring members together with the two carbon atoms to which they are bonded. When there are multiple Ys, the multiple Ys are the same or different from each other. b1 is an integer of 0 to 3.) 5. The radiation-sensitive composition according to claim 4, wherein in formula (D), b1 is 0.

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the content of the acid diffusion controller is 5 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the polymer.

7. In the above formula (H), R １ ~R ３ and each independently represent a substituted or unsubstituted monovalent aliphatic chain hydrocarbon group having 1 to 5 carbon atoms.

8. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the content of the compound represented by formula (H) in the solvent is 1% by mass or more and 100% by mass or less.

9. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer further contains a structural unit (III) having a phenolic hydroxyl group.

10. A method for forming a pattern, comprising the steps of: applying the 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.

11. The pattern forming method according to claim 10, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

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