Radiation-sensitive composition and method for forming resist pattern

Abstract

This radiation-sensitive composition contains: a polymer whose solubility with respect to a developer changes due to the action of an acid; and a compound having an anion and a radiation-sensitive onium cation, wherein the polymer has a structural unit including a group that generates sulfonic acid due to the action of radiation, the polymer includes an iodine group, and at least one of the anion and the radiation-sensitive onium cation includes an acid-dissociable group.

Description

Radiation-sensitive composition and method for forming resist pattern

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

[0002] Radiation-sensitive compositions used in microfabrication by lithography generate an acid in exposed areas when irradiated with radiation such as far ultraviolet rays such as ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm), electromagnetic waves such as extreme ultraviolet rays (EUV) (wavelength 13.5 nm), or charged particle rays such as electron beams, and a chemical reaction initiated by this acid causes a difference in dissolution rate in a developer between exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] A radiation-sensitive composition is required to have good sensitivity to radiation such as extreme ultraviolet rays and electron beams, as well as excellent CDU (Critical Dimension Uniformity) and development defect suppression properties.

[0004] In response to these requirements, the types, molecular structures, and the like of polymers, acid generators, and other components used in radiation-sensitive compositions have been investigated, and combinations thereof have also been investigated in detail (see JP-A-2010-134279, JP-A-2014-224984, JP-A-2016-047815, and JP-A-2021-009357).

[0005] JP 2010-134279 A JP 2014-224984 A JP 2016-047815 A JP 2021-009357 A

[0006] As resist patterns become finer, the level of performance required is becoming higher and higher, and there is a demand for radiation-sensitive compositions that satisfy these requirements.

[0007] An object of the present invention is to provide a radiation-sensitive composition that is excellent in sensitivity, CDU, and suppression of development defects, and a method of forming a resist pattern using the radiation-sensitive composition.

[0008] The invention made to solve the above problems is a radiation-sensitive composition comprising a polymer whose solubility in a developer changes under the action of an acid, and a compound having an anion and a radiation-sensitive onium cation, wherein the polymer has a structural unit a containing a group that generates a sulfonic acid under the action of radiation, the polymer contains an iodine group, and at least one of the anion and the radiation-sensitive onium cation contains an acid-dissociable group.

[0009] Another invention made to solve the above-mentioned problems is a method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition described above directly or indirectly to a substrate; exposing the resist film formed by the application; and developing the exposed resist film.

[0010] The radiation-sensitive composition of the present invention is excellent in sensitivity, CDU, and development defect suppression. According to the method of forming a resist pattern of the present invention, a resist pattern having good sensitivity and excellent CDU and development defect suppression can be formed.

[0011] The radiation-sensitive composition and method for forming a resist pattern of the present invention will be described in detail below.

[0012] <Radiation-Sensitive Composition> The radiation-sensitive composition contains a polymer whose solubility in a developer changes under the action of an acid (hereinafter also referred to as “polymer [A]”), and a compound having an anion and a radiation-sensitive onium cation (hereinafter also referred to as “compound [Z]”).

[0013] The radiation-sensitive composition contains the polymer [A] and the compound [Z], and by satisfying the following requirements (i) to (iii), which will be described in detail later, the radiation-sensitive composition exhibits excellent sensitivity, CDU, and suppression of development defects. Requirement (i): The polymer [A] has a structural unit a containing a group that generates sulfonic acid when acted on by radiation. Requirement (ii): The polymer [A] contains an iodine group. Requirement (iii): At least one of the anion and the radiation-sensitive onium cation in the compound [Z] contains an acid-dissociable group.

[0014] The reason why the radiation-sensitive composition containing the polymer [A] and the compound [Z] and satisfying the above requirements (i) to (iii) is excellent in sensitivity, CDU, and development defect suppression is not necessarily clear, but it is presumed, for example, as follows: It is thought that the radiation-sensitive composition is excellent in CDU because the requirement (i) controls the diffusion of sulfonic acid generated by exposure. It is thought that the radiation-sensitive composition is excellent in sensitivity and CDU because the requirement (ii) improves the radiation absorption efficiency. It is thought that the radiation-sensitive composition is excellent in sensitivity and CDU because the requirement (iii) improves the solubility in a developer. Therefore, it is thought that the radiation-sensitive composition is excellent in development defect suppression because the requirement (i) to (iii) are satisfied, making it possible to achieve a good balance between the three: sensitivity, CDU, and development defect suppression.

[0015] The radiation-sensitive composition can further improve the sensitivity and CDU by satisfying the following requirement (iv): requirement (iv): at least one of the anion and the radiation-sensitive onium cation in the compound (Z) further contains an iodo group.

[0016] The radiation-sensitive composition usually contains an organic solvent (hereinafter also referred to as "organic solvent [D]"). The radiation-sensitive composition may contain a radiation-sensitive acid generator or an acid diffusion controller other than the compound [Z]. The radiation-sensitive composition may contain a polymer (hereinafter also referred to as "polymer [F]") having a higher fluorine atom content than the polymer [A]. The radiation-sensitive composition may contain other optional components as long as the effects of the present invention are not impaired.

[0017] The radiation-sensitive composition can be prepared, for example, by mixing the polymer [A] and the compound [Z], as well as, if necessary, a radiation-sensitive acid generator, an acid diffusion controller, an organic solvent [D], a polymer [F], and other optional components, in a predetermined ratio, and filtering the resulting mixture through a membrane filter having a pore size of 0.2 μm or less.

[0018] Each component contained in the radiation-sensitive composition will be described below.

[0019] <Polymer [A]> The polymer [A] is a polymer whose solubility in a developer changes under the action of an acid. The polymer [A] has a structural unit a (hereinafter also simply referred to as "structural unit a") containing a group that generates sulfonic acid under the action of radiation. A "polymer" refers to a compound having a structure in which one or more types of monomers are repeatedly bonded. A "structural unit" refers to a partial structure derived from one monomer molecule among the structures that constitute the main chain of the polymer. The radiation-sensitive composition can contain one or more types of polymer [A].

[0020] The polymer [A] preferably has a structural unit b (hereinafter simply referred to as "structural unit b") containing an acid-dissociable group. The polymer [A] preferably has a structural unit c (hereinafter simply referred to as "structural unit c") containing a phenolic hydroxyl group. The polymer [A] may further have a structural unit d (hereinafter simply referred to as "structural unit d") other than the structural units a, b, and c.

[0021] The polymer [A] has an iodine group (requirement (ii)). The polymer [A] has an iodine group, which improves radiation absorption efficiency, and therefore the radiation-sensitive composition has excellent sensitivity and CDU. The polymer [A] may have an iodine group in its main chain or in its side chain. The "main chain" refers to the longest atomic chain among the atomic chains constituting the polymer. The "side chain" refers to an atomic chain other than the main chain among the atomic chains constituting the polymer. The polymer [A] preferably has an iodine group in its side chain, and more preferably, a structural unit contained in the polymer [A] contains an iodine group. The iodine group may be contained in any of the structural units a to d described above. From the viewpoint of further improving radiation absorption efficiency, the iodine group is preferably bonded to an aromatic ring.

[0022] The number of iodo groups in the polymer [A] may be one or more, but is preferably five or more. It is more preferable that the number of iodo groups is 15 or more, as this further improves the sensitivity of the radiation-sensitive composition. It is even more preferable that the number of iodo groups is 30 or more, as this further improves the sensitivity and CDU of the radiation-sensitive composition. It is particularly preferable that the number of iodo groups is 40 or more, as this further improves the sensitivity and CDU of the radiation-sensitive composition. In this specification, the number of iodo groups in the polymer [A] is defined as the number of iodo groups in one structural unit multiplied by the content (mol %) of that structural unit in the polymer [A].

[0023] The lower limit of the content of the polymer (A) in the radiation-sensitive composition is preferably 50% by mass, more preferably 70% by mass, and even more preferably 80% by mass, based on all components other than the organic solvent (D) contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass.

[0024] The lower limit of the weight average molecular weight (Mw) of the polymer [A], as measured by gel permeation chromatography (GPC) in terms of polystyrene, is preferably 1,000, more preferably 2,000, even more preferably 3,000, and still more preferably 5,000. The upper limit of the Mw is preferably 30,000, more preferably 20,000, and even more preferably 10,000. By setting the Mw of the polymer [A] within the above range, the coatability of the radiation-sensitive composition can be improved. The Mw of the polymer [A] can be adjusted, for example, by adjusting the type and amount of polymerization initiator used in the synthesis of the polymer [A].

[0025] The upper limit of the ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer (A) as determined by GPC (hereinafter also referred to as "Mw / Mn") is preferably 2.5, more preferably 2.0, and even more preferably 1.8. The lower limit of the ratio is usually 1.0, preferably 1.1, more preferably 1.2, and even more preferably 1.3.

[0026] [Method for measuring Mw and Mn] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions: GPC columns: two "G2000HXL", one "G3000HXL", and one "G4000HXL" manufactured by Tosoh Corporation Column temperature: 40°C Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0027] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0028] Each structural unit contained in the polymer (A) will be described below.

[0029] [Structural unit a] The structural unit a is a structural unit containing a group that generates sulfonic acid upon the action of radiation (hereinafter also referred to as a "radiation-sensitive sulfonic acid generating group") (requirement (i)). When the polymer [A] contains the structural unit a, the diffusion of sulfonic acid generated by exposure is controlled, and the radiation-sensitive composition has excellent CDU. The polymer [A] can contain one or more types of structural units a.

[0030] Examples of the radiation-sensitive sulfonic acid generating group include a group containing a sulfonate anion and a radiation-sensitive onium cation. Such radiation-sensitive sulfonic acid generating groups are classified into a structure in which a sulfonate anion is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 1") and a structure in which a radiation-sensitive onium cation is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 2"). As the structural unit a, Structure 1 is preferred. Structure 1 is preferred because it further controls the diffusion of sulfonic acid generated by exposure, thereby further improving CDU.

[0031] The polymer [A] functions as a radiation-sensitive acid generator in the radiation-sensitive composition, whereby the sulfonic acid generated by the radiation-sensitive sulfonic acid generating group dissociates the acid-dissociable group contained in the structural unit b described below or the compound [Z]. For example, the structural unit a generates sulfonic acid by the action of radiation, and the sulfonic acid dissociates the acid-dissociable group described below.

[0032] When the radiation-sensitive sulfonic acid generating group corresponds to the above structure 1, examples of the structural unit a include a structural unit represented by the following formula (a).

[0033]

[0034] In the above formula (a), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ and L ２ are each independently a single bond or a divalent linking group. ２ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure having five or more ring members. ０ is 0 or 1. ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. １ is an integer from 0 to 10. ５ and R ６ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ２ is an integer from 1 to 10. ＋ is a monovalent radiation-sensitive onium cation.

[0035] R １ is preferably a hydrogen atom or a methyl group.

[0036] The term "linking group" refers to a group that links two or more structures. The linking group remains in the structure of a compound or polymer due to reasons such as the synthetic materials or synthetic methods, and does not affect the effects of the present invention, or has an extremely small effect on the effects of the present invention. However, this does not mean that all structures other than the linking group contribute to the exertion of the effects of the present invention.

[0037] L １ and L ２ Examples of the divalent linking group represented by １ and L ２ is not particularly limited as long as it is a group that connects two structures to which each of the groups is bonded, and examples thereof include a carbonyl group, an ether group, a carbonyloxy group, a sulfide group, a sulfonyl group, an alkanediyl group having 1 to 10 carbon atoms, or a group combining these.

[0038] R ２ Examples of the ring structure having 5 or more ring members that gives the formula (I) include an aliphatic hydrocarbon ring having 5 or more ring members, an aliphatic heterocycle having 5 or more ring members, an aromatic hydrocarbon ring having 6 or more ring members, and an aromatic heterocycle having 5 or more ring members.

[0039] The "number of ring members" refers to the number of atoms constituting the ring structure, and in the case of a polycyclic ring, it refers to the number of atoms constituting the polycyclic ring. "Polycyclic rings" include not only spiro-type polycyclic rings in which two rings share one shared atom and fused-type polycyclic rings in which two rings share two shared atoms, but also ring assembly-type polycyclic rings in which two rings do not share an atom and are connected by a single bond.

[0040] "Ring structure" includes "alicyclic ring" and "aromatic ring". "Alicyclic ring" includes "aliphatic hydrocarbon ring" and "aliphatic heterocyclic ring". Among alicyclic rings, polycyclic rings containing an aliphatic hydrocarbon ring and an aliphatic heterocyclic ring are considered to be "aliphatic heterocyclic ring". "Aromatic ring" includes "aromatic hydrocarbon ring" and "aromatic heterocyclic ring". Among aromatic rings, polycyclic rings containing an aromatic hydrocarbon ring and an aromatic heterocyclic ring are considered to be "aromatic heterocyclic ring".

[0041] Examples of aliphatic hydrocarbon rings having 5 or more ring members include monocyclic saturated alicyclic rings such as a cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclononane ring, cyclodecane ring, and cyclododecane ring; monocyclic unsaturated alicyclic rings such as a cyclopentene ring, cyclohexene ring, cycloheptene ring, cyclooctene ring, and cyclodecene ring; polycyclic saturated alicyclic rings such as a norbornane ring, adamantane ring, tricyclodecane ring, tetracyclododecane ring, and steroid structure; and polycyclic unsaturated alicyclic rings such as a norbornene ring and tricyclodecene ring. The term "steroid structure" refers to a structure having a basic skeleton (sterane skeleton) in which three 6-membered rings and one 5-membered ring are fused.

[0042] Examples of the aliphatic heterocycle having 5 or more ring members include lactone rings such as a hexanolactone ring and a norbornanelactone ring; sultone rings such as a hexanosultone ring and a norbornanesultone ring; oxygen atom-containing heterocycles such as a dioxolane ring, an oxacycloheptane ring and an oxanorbornane ring; nitrogen atom-containing heterocycles such as an azacyclohexane ring and a diazabicyclooctane ring; and sulfur atom-containing heterocycles such as a thiacyclohexane ring and a thianorbornane ring.

[0043] Examples of aromatic hydrocarbon rings having 6 or more ring members include a benzene ring; condensed polycyclic aromatic hydrocarbon rings such as a naphthalene ring, an anthracene ring, a fluorene ring, a biphenylene ring, a phenanthrene ring, and a pyrene ring; ring-assembly aromatic hydrocarbon rings such as a biphenyl ring, a terphenyl ring, a binaphthalene ring, and a phenylnaphthalene ring; a 9,10-ethanoanthracene ring; and a triptycene ring.

[0044] Examples of aromatic heterocycles having 5 or more ring members include oxygen atom-containing heterocycles such as a furan ring, a pyran ring, a benzofuran ring, and a benzopyran ring; nitrogen atom-containing heterocycles such as a pyridine ring, a pyrimidine ring, and an indole ring; and sulfur atom-containing heterocycles such as a thiophene ring.

[0045] The ring structure is preferably an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring, and more preferably a polycyclic saturated alicyclic ring, a benzene ring, or a condensed polycyclic aromatic hydrocarbon ring.

[0046] The lower limit of the number of ring members in the ring structure is preferably 6, more preferably 8, still more preferably 9, and particularly preferably 10. The upper limit of the number of ring members is preferably 25.

[0047] In the ring structure, some or all of the hydrogen atoms bonded to the atoms constituting the ring structure may be substituted with a substituent, such as a halogeno group such as a fluoro group or an iodo group, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group.

[0048] When the ring structure has an iodo group as a substituent, the above-mentioned requirement (ii) is satisfied.

[0049] n ０ As the number, 1 is preferred.

[0050] R ３ and R ４ Examples of the alkyl group having 1 to 10 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, and a propyl group.

[0051] The term "carbon number" refers to the number of carbon atoms constituting the group. The term "fluorinated alkyl group" refers to a group in which all or some of the hydrogen atoms in an alkyl group have been substituted with fluorine atoms.

[0052] R ３ , R ４ , R ５ and R ６ Examples of the fluorinated alkyl group having 1 to 10 carbon atoms represented by the formula (I) include perfluoroalkyl groups such as trifluoromethyl groups.

[0053] R ３ and R ４ is preferably a hydrogen atom or a fluorinated alkyl group, more preferably a hydrogen atom or a perfluoroalkyl group, and even more preferably a hydrogen atom or a trifluoromethyl group.

[0054] R ５ and R ６ is preferably a fluorine atom.

[0055] n １is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

[0056] n ２ As the number, 1 to 5 is preferable, 1 to 3 is more preferable, and 1 is even more preferable.

[0057] M ＋ The monovalent radiation-sensitive onium cation represented by the formula (I) is not particularly limited as long as it is known as a radiation-sensitive onium cation in an onium salt used as a radiation-sensitive acid generator contained in a radiation-sensitive composition. For example, a sulfonium cation (S ＋ ), iodonium cation (I ＋ ) are listed.

[0058] M ＋ Examples of the monovalent radiation-sensitive onium cation represented by the formula (r-a) include monovalent cations represented by the following formula (r-a):

[0059]

[0060] In the above formula (r-a), Ar Ｂ１ is a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic hydrocarbon ring. Ｂ１ and R Ｂ２ are each independently a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic hydrocarbon ring, or R Ｂ１ and R Ｂ２ are combined with each other to form, together with the sulfur atoms to which they are bonded, a substituted or unsubstituted polycyclic sulfur atom-containing aromatic heterocycle.

[0061] Ar Ｂ１ , R Ｂ１ or R Ｂ２ Examples of the aromatic hydrocarbon ring represented by the formula (a) include R ２ The aromatic hydrocarbon rings exemplified as Ar are the same as those exemplified as Ar. Ｂ１ , R Ｂ１ or R Ｂ２ The aromatic hydrocarbon ring represented by the formula: is preferably a benzene ring.

[0062] R Ｂ１ and R Ｂ２Examples of polycyclic sulfur atom-containing aromatic heterocycles formed by combining these together with the sulfur atoms to which they are bonded include a dibenzothiophene ring.

[0063] At least one hydrogen atom in the aromatic hydrocarbon ring and the polycyclic sulfur atom-containing aromatic heterocycle may be substituted with a substituent. ２ Examples of the substituent include the same as the substituent that may be possessed by the ring structure in the above formula. The substituent is preferably an iodo group, a fluorinated alkyl group, or a fluoro group.

[0064] When the aromatic hydrocarbon ring or the polycyclic sulfur atom-containing aromatic heterocycle has an iodo group as a substituent, the above-mentioned requirement (ii) is satisfied.

[0065] When the aromatic hydrocarbon ring or the polycyclic sulfur atom-containing aromatic heterocycle has a fluoro group as a substituent, the sensitivity of the radiation-sensitive composition can be further improved.

[0066] Examples of the structural unit a include structural units represented by the following formulae (a-1) to (a-4).

[0067]

[0068] In the above formulas (a-1) to (a-4), M ＋ has the same meaning as the above formula (a).

[0069] The lower limit of the content of the structural unit a in the polymer [A] is preferably 1 mol%, more preferably 3 mol%, even more preferably 5 mol%, and particularly preferably 7 mol%, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, even more preferably 20 mol%, and particularly preferably 15 mol%.

[0070] [Structural Unit b] The structural unit b is a structural unit containing an acid-dissociable group. The term "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group or a hydroxy group and dissociates under the action of an acid to give a carboxy group or a hydroxy group.

[0071] When the polymer (A) contains the structural unit b, an acid-dissociable group is dissociated from the structural unit b by the action of an acid generated from the polymer (A), etc., in response to the action of radiation, and this causes a difference in solubility of the polymer (A) in a developer between an exposed portion and a non-exposed portion, thereby enabling the formation of a resist pattern.

[0072] The acid-dissociable group is a group that substitutes a hydrogen atom of a carboxy group or a hydroxy group in the structural unit b. In other words, in the structural unit b, the acid-dissociable group is bonded to the etheric oxygen atom of the carbonyloxy group.

[0073] Examples of the acid-dissociable group include groups represented by the following formulae (s-1) to (s-3).

[0074]

[0075] In the above formulas (s-1) to (s-3), * indicates the bonding site with the etheric oxygen atom of the carboxy group or the oxygen atom of the hydroxy group.

[0076] In the above formula (s-1), R Ｘ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. Ｙ and R Ｚ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or these groups are combined with each other to form a saturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are attached.

[0077] In the above formula (s-2), R Ａ is a hydrogen atom. Ｂ and R Ｃ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ｄ is R Ａ , R Ｂ and R Ｃ are divalent hydrocarbon groups having 1 to 20 carbon atoms which, together with the three carbon atoms to which they are bonded, constitute an unsaturated alicyclic ring having 4 to 20 ring members.

[0078] In the above formula (s-3), R Ｕ and R Ｖare each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R Ｗ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, or R Ｕ and R Ｖ are combined with each other to form a saturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are attached, and R Ｗ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, or R Ｖ and R Ｗ are aligned with each other and R Ｖ and the carbon atom to which R Ｗ together with the oxygen atom to which it is bonded, form an oxygen atom-containing aliphatic heterocyclic ring having 4 to 20 ring members, and R Ｕ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0079] The term "hydrocarbon group" includes "aliphatic hydrocarbon groups" and "aromatic hydrocarbon groups." The term "aliphatic hydrocarbon group" includes "chain hydrocarbon groups" and "alicyclic hydrocarbon groups." From another perspective, the term "aliphatic hydrocarbon group" includes "saturated hydrocarbon groups" and "unsaturated hydrocarbon groups." The term "chain hydrocarbon group" refers to a hydrocarbon group that does not contain a ring structure and is composed only of a chain structure, and includes both straight-chain hydrocarbon groups and branched-chain hydrocarbon groups. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic ring as a ring structure and does not contain an aromatic ring, and includes both monocyclic alicyclic hydrocarbon groups and polycyclic alicyclic hydrocarbon groups. However, it does not have to be composed only of an alicyclic ring, and may contain a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring as a ring structure. However, it does not have to be composed only of an aromatic ring, and may contain a chain structure or an alicyclic ring as part of it.

[0080] R Ｘ , R Ｙ , R Ｚ , R Ｂ , R Ｃ , R Ｕ , R Ｖ or R ＷExamples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives 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, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0081] R Ｘ Examples of the substituent that the hydrocarbon group represented by the formula (a) may have include R ２ The substituents may be the same as those that the ring structure in R Ｘ has an iodo group as a substituent, this is preferred because it tends to further improve the CDU of the radiation-sensitive composition. In this case, the above-mentioned requirement (ii) is satisfied.

[0082] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, isobutyl, and tert-butyl; alkenyl groups such as ethenyl, propenyl, butenyl, and 2-methylprop-1-en-1-yl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0083] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group and a cyclohexyl 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.

[0084] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl.

[0085] R Ｙ and R Ｚ a saturated alicyclic ring having 3 to 20 ring members formed by combining these together with the carbon atoms to which they are attached, and R Ｕ and RＶ Examples of the saturated alicyclic ring having 3 to 20 ring members formed by combining these together with the carbon atoms to which they are bonded include monocyclic saturated alicyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring; and polycyclic saturated alicyclic rings such as a norbornane ring, an adamantane ring, a tricyclodecane ring, and a tetracyclododecane ring.

[0086] R Ｄ Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include groups in which one hydrogen atom has been removed from the groups exemplified above as the monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0087] R Ｄ And, R Ａ , R Ｂ and R Ｃ and three carbon atoms to which each of the carbon atoms is bonded, include, for example, monocyclic unsaturated alicyclic structures such as a cyclobutene structure, a cyclopentene structure, and a cyclohexene structure, and polycyclic unsaturated alicyclic structures such as a norbornene structure.

[0088] R Ｖ and R Ｗ are aligned with each other and R Ｖ and the carbon atom to which R Ｗ Examples of the 4-20-membered oxygen atom-containing aliphatic heterocycle formed together with the oxygen atom to which is bonded include an oxacyclobutane ring, an oxacyclopentane ring, an oxacyclohexane ring, an oxacyclobutene ring, an oxacyclopentene ring, and an oxacyclohexene ring.

[0089] R Ｙ and R Ｚ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, R Ｙ and R Ｚ As R, a chain hydrocarbon group is preferable, an alkyl group is preferable, and a methyl group is more preferable. Ｘ R is preferably a substituted or unsubstituted aromatic hydrocarbon group, more preferably a substituted or unsubstituted aryl group, and even more preferably a phenyl group or an iodophenyl group. Ｘis an aryl group substituted with an iodo group, this is preferred because it tends to further improve the CDU of the radiation-sensitive composition.

[0090] R Ｙ and R Ｚ When R are combined with each other to form a saturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are bonded, the saturated alicyclic ring is preferably a cyclopentane ring, a cyclohexane ring, or an adamantane ring. Ｘ R is preferably a substituted or unsubstituted chain hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group, more preferably an unsubstituted alkyl group or a substituted or unsubstituted aryl group, and even more preferably a methyl group, an ethyl group, a phenyl group or an iodophenyl group. Ｘ is an aryl group substituted with an iodo group, this is preferred because it tends to further improve the CDU of the radiation-sensitive composition.

[0091] Examples of the acid-dissociable group include groups represented by the following formulae (s-1-1) to (s-1-8) and (s-3-1) to (s-3-4).

[0092]

[0093] In the above formulas (s-1-1) to (s-1-8) and (s-3-1) to (s-3-4), * has the same meaning as in the above formulas (s-1) and (s-3).

[0094] Examples of the structural unit b include a structural unit represented by the following formula (b).

[0095]

[0096] In the above formula (b), R ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ３ is a single bond, —COO— or —CONH—. ８ is a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring. ９ is an acid-dissociable group.

[0097] R ７From the viewpoint of copolymerizability of the monomer that gives the structural unit b, a hydrogen atom or a methyl group is preferred.

[0098] L ３ is preferably a single bond.

[0099] R ８ The aromatic hydrocarbon ring that gives ２ The same applies to the substituent. ８ The aromatic hydrocarbon ring that provides the following is preferably a benzene ring.

[0100] When the polymer [A] has the structural unit b, the lower limit of the content of the structural unit b in the polymer [A] is preferably 20 mol%, more preferably 30 mol%, even more preferably 35 mol%, and particularly preferably 40 mol%, based on the total structural units constituting the polymer [A]. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, even more preferably 60 mol%, and particularly preferably 55 mol%.

[0101] [Structural Unit c] The structural unit c is a structural unit containing a phenolic hydroxyl group. The term "phenolic hydroxyl group" refers not only to a hydroxyl group directly bonded to a benzene ring, but also to any hydroxyl group directly bonded to an aromatic ring.

[0102] In the case of KrF exposure, EUV exposure, or electron beam exposure, the sensitivity of the radiation-sensitive composition can be further increased when the polymer [A] contains the structural unit c. Therefore, when the polymer [A] contains the structural unit c, the radiation-sensitive composition can be suitably used as a radiation-sensitive composition for KrF exposure, EUV exposure, or electron beam exposure.

[0103] Examples of the structural unit c include a structural unit represented by the following formula (c).

[0104]

[0105] In the above formula (c), R １０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ４is a single bond, —COO—, —O—, or CONH—. １ represents a group in which (p+1) hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring, where p is an integer of 1 to 3.

[0106] L ４ is preferably a single bond or COO—. ４ When Ar is —COO—, the bond direction of this group is １ When the bonding site is indicated by *, it is preferably --COO--*.

[0107] Ar １ As the aromatic hydrocarbon ring which gives ２ The same applies to the substituent. １ The aromatic hydrocarbon ring giving the formula (I) is preferably a benzene ring or a naphthalene ring.

[0108] Ar ２ In this case, the aromatic hydrocarbon ring having the formula (I) preferably has an iodo group as a substituent, since this tends to further improve the sensitivity of the radiation-sensitive composition. In addition, in this case, the above-mentioned requirement (ii) is satisfied.

[0109] As p, 1 or 2 is preferred.

[0110] Examples of the structural unit c include structural units represented by the following formulae (c-1) to (c-3).

[0111]

[0112] When the polymer [A] has the structural unit c, the lower limit of the content of the structural unit c in the polymer [A] is preferably 20 mol %, more preferably 30 mol %, and even more preferably 35 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 70 mol %, more preferably 60 mol %, and even more preferably 50 mol %.

[0113] [Structural Unit d] The structural unit d is a structural unit other than the structural units a, b, and c. Examples of the structural unit d include a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, a structural unit containing an alcoholic hydroxyl group, and a structural unit derived from a vinyl aromatic compound.

[0114] Examples of the structural unit d include structural units represented by the following formula (d-1) or (d-2).

[0115]

[0116] When the polymer (A) contains the structural unit d, the lower limit of the content of the structural unit d is preferably 1 mol %, more preferably 5 mol %, relative to all structural units constituting the polymer (A), and the upper limit of the content is preferably 20 mol %, more preferably 15 mol %.

[0117] <Compound [Z]> The compound [Z] is a compound having an anion (hereinafter also referred to as "anion (X)") and a radiation-sensitive onium cation (hereinafter also referred to as "cation (Y)").

[0118] Depending on the type of anion group contained in the anion (X), the compound [Z] has the function of generating an acid in the radiation-sensitive composition by the action of radiation, or the function of controlling the diffusion phenomenon of the acid generated by the action of radiation in the resist film, thereby suppressing undesirable chemical reactions in unexposed areas (for example, dissociation reactions of acid-dissociable groups). In other words, depending on the type of anion group, the compound [Z] functions as a radiation-sensitive acid generator (hereinafter also referred to as "acid generator [B]") or an acid diffusion controller (quencher) (hereinafter also referred to as "acid diffusion controller [C]") in the radiation-sensitive composition.

[0119] When the compound [Z] functions as the acid generator [B], an acid dissociable group contained in the structural unit b or the like of the polymer [A] is dissociated by an acid generated from the compound [Z] by the action of radiation, generating an acidic group such as a carboxy group, and this results in a difference in solubility of the resist film in a developer between the exposed and unexposed areas, thereby enabling the formation of a resist pattern.

[0120] When the compound [Z] functions as the acid diffusion controller [C], it generates acid in the exposed area to increase the solubility or insolubility of the polymer [A] in a developer, and in the non-exposed area, it exerts a high acid-scavenging function due to the anion, functions as a quencher, and captures acid diffusing from the exposed area, thereby improving roughness at the interface between the exposed area and the non-exposed area and increasing the difference in solubility in a developer between the exposed area and the non-exposed area, thereby improving resolution.

[0121] The radiation-sensitive composition may contain one or more [Z] compounds. When the radiation-sensitive composition contains both the [Z] compound that functions as the acid generator [B] and the [Z] compound that functions as the acid diffusion controller [C], the radiation-sensitive composition can achieve a good balance between the three factors of sensitivity, CDU, and development defect suppression at a higher level.

[0122] When the compound [Z] functions as the acid generator [B], the lower limit of the amount of the compound [Z] in the radiation-sensitive composition is preferably 1 part by mass, more preferably 5 parts by mass, relative to 100 parts by mass of the polymer [A]. The upper limit of the amount is preferably 20 parts by mass, more preferably 10 parts by mass.

[0123] When the compound [Z] functions as the acid diffusion controller [C], the lower limit of the amount of the compound [Z] in the radiation-sensitive composition is preferably 1 part by mass, more preferably 5 parts by mass, relative to 100 parts by mass of the polymer [A]. The upper limit of the amount is preferably 30 parts by mass, more preferably 20 parts by mass.

[0124] The [Z] compound may be a low molecular weight compound or a polymer. When the [Z] compound is a polymer, the [Z] compound is a polymer different from the [A] polymer. In this specification, "compound" includes "polymer" and "low molecular weight compound." "Polymer" means a compound having a repeating unit, and "low molecular weight compound" means a compound that is not a polymer. More specifically, "low molecular weight compound" refers to a compound having a molecular weight of 2,000 or less.

[0125] In the compound [Z], at least one of the anion (X) and the cation (Y) contains an acid-dissociable group (requirement (iii)). When at least one of the anion (X) and the cation (Y) in the compound [Z] contains an acid-dissociable group, the solubility in a developer is improved, and the radiation-sensitive composition has excellent development defect suppression properties.

[0126] Examples of the acid-dissociable group include the same acid-dissociable groups as those described in the section on [Structural unit b] above, and preferred embodiments are also the same.

[0127] The compound [Z] may contain an acid-dissociable group only in the anion (X), may contain an acid-dissociable group only in the cation (Y), or may contain an acid-dissociable group in both the anion (X) and the cation (Y).

[0128] In the compound [Z], it is preferable that at least one of the anion (X) and the cation (Y) further contains an iodine group (requirement (iv)). In this case, the sensitivity and CDU of the radiation-sensitive composition can be further improved. As in the case of the above-mentioned requirement (i), it is preferable that the iodine group be bonded to an aromatic ring, from the viewpoint of further improving the radiation absorption efficiency.

[0129] When the compound (Z) satisfies the requirement (iii) and the requirement (iv), it is preferable that at least one of the anion (X) and the cation (Y) contains both the acid-dissociable group and the iodine group, thereby further improving the sensitivity, CDU, and suppression of development defects of the radiation-sensitive composition.

[0130] Furthermore, in the compound [Z], the anion (X) preferably contains both the acid-dissociable group and the iodo group, which can further improve the sensitivity, CDU, and development defect suppression ability of the radiation-sensitive composition.

[0131] Each structure of the compound (Z) will be explained below.

[0132] [Anion (X)] The anion (X) has an anionic group. Examples of the anionic group include a monovalent organic acid anionic group. Examples of the monovalent organic acid anionic group include a sulfonic acid anionic group (—SO３ － ), a carboxylate anion group (—COO － ), sulfonimidate anion group (—SO ２ -N － -SO ２ Among these, a sulfonate anion group or a carboxylate anion group is preferred.

[0133] Hereinafter, among the anions (X), an anion having a sulfonate anion group as the monovalent organic acid anion group will be referred to as "anion (X-1)," and an anion having a carboxylate anion group as the monovalent organic acid anion group will be referred to as "anion (X-2)."

[0134] (Anion (X-1)) When the compound [Z] has an anion (X-1), the compound [Z] functions as a radiation-sensitive acid generator. When the compound [Z] functions as a radiation-sensitive acid generator, the radiation-sensitive composition preferably further contains an acid diffusion controller. Examples of the acid diffusion controller include the compound [Z] when it functions as an acid diffusion controller, and acid diffusion controllers other than the compound [Z] described below.

[0135] When the compound [Z] has an anion (X-1), the compound [Z] is preferably a low molecular weight compound.

[0136] The compound [Z] that is a low-molecular-weight compound having an anion (X-1) is not particularly limited as long as it satisfies the requirement (iii) and is usable as a radiation-sensitive acid generator in a radiation-sensitive composition.

[0137] Among the anions (X-1) when the compound [Z] is a low-molecular-weight compound, examples of anions containing an acid-dissociable group (when the requirement (iii) is satisfied) include a sulfonate anion represented by the following formula (X-1a) (hereinafter, also referred to as "anion (X-1a)"):

[0138]

[0139] In the above formula (X-1a), R １０ is an acid-dissociable group. X is —COO—* or O—. * is R １０ The binding site with L５ and L ６ are each independently a single bond or a divalent linking group. １１ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure having five or more ring members. １２ and R １３ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ３ is an integer from 0 to 10. １４ and R １５ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ４ is an integer from 1 to 10.

[0140] R １０ Examples of the acid-dissociable group represented by the formula (I) include the same acid-dissociable groups as those described in the section on [Structural unit b] above, and preferred embodiments are also the same.

[0141] L ５ , L ６ , R １１ , R １２ , R １３ , R １４ , R １５ , n ３ and n ４ are L in formula (a) described in the section [Structural unit a] above. １ , L ２ , R ２ , R ３ R ４ , R ５ , R ６ , n １ and n ２ The same can be mentioned as above, and the preferred embodiments are also the same.

[0142] Specific examples of the anion (X-1) include sulfonate anions represented by the following formulae (X-1-1) to (X-1-8).

[0143]

[0144] The sulfonate anions represented by the above formulae (X-1-1) to (X-1-4), (X-1-6), and (X-1-7) contain an acid-dissociable group and therefore fall under the category of anion (X-1a) (satisfying requirement (iii)). The sulfonate anions represented by the above formulae (X-1-3), (X-1-5), and (X-1-7) contain an iodine group and therefore satisfy requirement (iv).

[0145] (Anion (X-2)) When the compound [Z] has anion (X-2), the compound [Z] functions as an acid diffusion controller. In this case, the polymer [A] functions as a radiation-sensitive acid-generating polymer, and therefore the radiation-sensitive composition may or may not contain a radiation-sensitive acid generator. Examples of the radiation-sensitive acid generator include the compound [Z] when it functions as a radiation-sensitive acid generator, and radiation-sensitive acid generators other than the compound [Z] described below.

[0146] When the compound [Z] has an anion (X-2), the compound [Z] may be a low molecular weight compound or a polymer.

[0147] The compound [Z] that is a low-molecular-weight compound having an anion (X-2) is not particularly limited as long as it satisfies the requirement (iii) and is usable as an acid diffusion controller in the radiation-sensitive composition.

[0148] Among the anions (X-2) when the compound [Z] is a low-molecular-weight compound, examples of anions containing an acid-dissociable group (when the requirement (iii) is satisfied) include a sulfonate anion represented by the following formula (X-2b) (hereinafter, also referred to as "anion (X-2b)").

[0149]

[0150] In the above formula (X-2b), R １０ , X, L ５ , L ６ , R １１ , R １４ , R １５ , n ３ and n ４ has the same meaning as in formula (X-1a) above. １６ and R１７ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, a monovalent fluorinated alkyl group having 1 to 10 carbon atoms, or a group containing an iodo group having 1 to 10 carbon atoms.

[0151] R １６ and R １７ Examples of the iodo group-containing group having 1 to 10 carbon atoms in the formula (I) include groups having an aromatic ring having an iodo group as a substituent.

[0152] Specific examples of the anion (X-2) when the compound [Z] is a low molecular weight compound include carboxylate anions represented by the following formulae (X-2-1) to (X-2-12).

[0153]

[0154] The carboxylate anions represented by the above formulae (X-2-1) to (X-2-4), (X-2-6), (X-2-7), and (X-2-9) to (X-2-11) contain an acid-dissociable group and therefore correspond to the anion (X-2b) (satisfying requirement (iii)). Furthermore, the carboxylate anions represented by the above formulae (X-2-3), (X-2-5), (X-2-7), (X-2-10), and (X-2-11) contain an iodine group and therefore satisfy the above requirement (iv).

[0155] When the compound [Z] is a polymer, it may have a structure (Structure 1) in which the anion (X-2) is bonded to a side chain of the polymer, or a structure (Structure 2) in which the cation (Y) is bonded to a side chain of the polymer, but is preferably Structure 1. When the anion (X-2) is Structure 1, for example, an anion having a structural unit e (cation omitted) represented by the following formula (X-2c) can be mentioned.

[0156]

[0157] In the above formula (X-2c), R １８ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ７ is a single bond or a divalent linking group. ２ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring.

[0158] L ７ is preferably a divalent linking group.

[0159] Ar ２ The aromatic hydrocarbon ring giving the formula (a) described in the section [Structural unit a] above is an aromatic hydrocarbon ring giving the formula (a) ２ The same applies to the substituent. １ The aromatic hydrocarbon ring giving the formula (I) is preferably a benzene ring or a naphthalene ring. When the aromatic hydrocarbon ring has a substituent, the substituent is preferably a hydroxy group.

[0160] When the compound (Z) is a polymer, the content of the structural unit e is the same as the content of the structural unit a in the polymer (A) described above.

[0161] When the compound [Z] is a polymer, the compound [Z] may have a structural unit other than the structural unit e. Examples of the other structural unit include the structural unit b having an acid-dissociable group, the structural unit c having a phenolic hydroxyl group, and the structural unit d, which are described above in the section <Polymer [A]>.

[0162] When the compound [Z] has a structural unit b having an acid-dissociable group as another structural unit, the compound [Z] satisfies requirement (iii).

[0163] [Cation (Y)] The cation (Y) is a radiation-sensitive onium cation. The valence of the cation (Y) is not particularly limited and can be appropriately determined depending on the valence of the anion (X). For example, it is monovalent to trivalent, and monovalent is preferred.

[0164] The cation (Y) is not particularly limited as long as it is known as a radiation-sensitive onium cation in onium salts used as radiation-sensitive acid generators or acid diffusion controllers contained in radiation-sensitive compositions. When the cation (Y) is a monovalent cation, examples of the cation species include sulfonium cations (S ＋ ), iodonium cation (I ＋ ) are listed.

[0165] When the cation (Y) is a sulfonium cation, examples of the cation (Y) include the monovalent cations represented by the formula (r-a) described above in the section on [Structural unit a].

[0166] When the cation (Y) has an acid-dissociable group, the compound (Z) satisfies the requirement (iii).

[0167] Specific examples of the cation (Y) having an acid-dissociable group include cations represented by the following formulae (Y-1) to (Y-5).

[0168]

[0169] As the compound [Z], a compound in which the above-mentioned anion (X) and cation (Y) are appropriately combined can be used as long as the requirement (iii) is satisfied.

[0170] <Organic Solvent (D)> The radiation-sensitive composition usually contains an organic solvent (D). The organic solvent (D) is not particularly limited as long as it can dissolve or disperse at least the polymer (A), the compound (Z), and other optional components contained as needed.

[0171] Examples of the organic solvent (D) include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents. The radiation-sensitive composition may contain one or more organic solvents (D).

[0172] Examples of alcohol-based solvents include aliphatic monoalcohol-based solvents such as 4-methyl-2-pentanol, n-hexanol, diacetone alcohol, and methyl 2-hydroxyisobutyrate; alicyclic monoalcohol-based solvents such as cyclohexanol; polyhydric alcohol-based solvents such as 1,2-propylene glycol; and polyhydric alcohol partial ether-based solvents such as propylene glycol monomethyl ether.

[0173] Examples of ether solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ether solvents such as diphenyl ether and anisole.

[0174] Examples of ketone solvents include chain ketone solvents such as acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl isobutyl ketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone, di-isobutyl ketone, and trimethylnonanone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, and acetophenone.

[0175] 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.

[0176] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate and ethyl lactate; lactone-based solvents such as γ-butyrolactone and valerolactone; polyhydric alcohol carboxylate-based solvents such as propylene glycol acetate; polyhydric alcohol partial ether carboxylate-based solvents such as propylene glycol monomethyl ether acetate; polycarboxylic acid diester-based solvents such as diethyl oxalate; and carbonate-based solvents such as dimethyl carbonate and diethyl carbonate.

[0177] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-pentane and n-hexane; and aromatic hydrocarbon solvents such as toluene and xylene.

[0178] The organic solvent (D) is preferably an alcohol solvent, a ketone solvent, an ester solvent, or a combination thereof, more preferably a polyhydric alcohol partial ether solvent, a cyclic ketone solvent, a polyhydric alcohol partial ether carboxylate solvent, or a combination thereof, and even more preferably propylene glycol monomethyl ether, cyclohexanone, propylene glycol monomethyl ether acetate, or a combination thereof.

[0179] When the radiation-sensitive composition contains the organic solvent (D), the lower limit of the content of the organic solvent (D) is preferably 50 mass %, more preferably 60 mass %, still more preferably 70 mass %, and particularly preferably 80 mass %, based on all components contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99.9 mass %, preferably 99.5 mass %, and more preferably 99.0 mass %.

[0180] <Polymer [F]> The polymer [F] is a polymer different from the polymer [A] and has a higher fluorine atom content than the polymer [A]. Typically, polymers that are more hydrophobic than the base polymer tend to be unevenly distributed in the surface layer of the resist film. The polymer [F] has a higher fluorine atom content than the polymer [A], and due to this hydrophobicity-related property, the polymer [F] tends to be unevenly distributed in the surface layer of the resist film. As a result, when the radiation-sensitive composition contains the polymer [F], it is expected that the cross-sectional shape of the formed resist pattern will be excellent. The radiation-sensitive composition can contain the polymer [F], for example, as a surface conditioner for the resist film. The radiation-sensitive composition can contain one or more types of polymer [F].

[0181] <Other Optional Components> Examples of the other optional components include an acid generator other than the compound [Z], an acid diffusion controller other than the compound [Z], a surfactant, etc. The radiation-sensitive composition may contain one or more of the other optional components.

[0182] Examples of acid generators other than the compound [Z] include N-sulfonyloxyimide compounds, sulfonimide compounds, halogen-containing compounds, and diazoketone compounds.

[0183] Examples of acid diffusion controllers other than the compound [Z] include nitrogen atom-containing compounds, such as amine compounds such as tripentylamine and trioctylamine, amide group-containing compounds such as formamide and N,N-dimethylacetamide, urea compounds such as urea and 1,1-dimethylurea, and nitrogen-containing heterocyclic compounds such as pyridine, N-(undecylcarbonyloxyethyl)morpholine, and N-t-pentyloxycarbonyl-4-hydroxypiperidine.

[0184] <Method of Forming a Resist Pattern> The method of forming a resist pattern includes a step of applying a radiation-sensitive composition directly or indirectly to a substrate (hereinafter also referred to as a "coating step"), a step of exposing the resist film formed in the coating step (hereinafter also referred to as an "exposure step"), and a step of developing the exposed resist film (hereinafter also referred to as a "developing step").

[0185] In the coating step, the radiation-sensitive composition is the radiation-sensitive composition described above. Therefore, according to the method for forming a resist pattern, a resist pattern can be formed that has good sensitivity and excellent CDU and development defect suppression properties.

[0186] Each step of the resist pattern forming method will be described below.

[0187] [Coating Step] In this step, the radiation-sensitive composition is coated directly or indirectly onto a substrate, thereby forming a resist film directly or indirectly on the substrate.

[0188] In this step, the radiation-sensitive composition described above is used as the radiation-sensitive composition.

[0189] Substrates include, for example, silicon wafers, silicon dioxide, and aluminum coated wafers.

[0190] Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (hereinafter also referred to as "PB") may be performed to volatilize the solvent in the coating film. The PB temperature and PB time are not particularly limited, and are, for example, performed at a temperature of 60°C to 150°C for 5 seconds to 300 seconds. The average thickness of the formed resist film is not particularly limited, and is, for example, 10 nm to 1,000 nm.

[0191] [Exposure Step] In this step, the resist film formed in the coating step is exposed to radiation. This exposure is carried out by irradiating the resist film through a photomask (or, in some cases, through an immersion medium such as water). The radiation can be appropriately selected depending on the line width, diameter, etc. of the desired pattern, and examples thereof include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays. Among these, far ultraviolet light, EUV, or electron beams are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV (wavelength 13.5 nm), or electron beams being more preferred, with KrF excimer laser light, EUV, or electron beams being even more preferred, and EUV or electron beams being particularly preferred.

[0192] After the exposure, it is preferable to perform post-exposure baking (hereinafter also referred to as "PEB"). This PEB can increase the difference in solubility in a developer between the exposed and unexposed areas. The PEB temperature and PEB time are not particularly limited, and can be performed, for example, at a temperature of 50°C to 180°C for 5 to 600 seconds.

[0193] [Development Step] In this step, the exposed resist film is developed. This allows a predetermined resist pattern to be formed. The development method in the development step may be alkali development or organic solvent development.

[0194] In the case of alkaline development, examples of the developer used for development include alkaline aqueous solutions containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (hereinafter also referred to as "TMAH"), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, aqueous TMAH solutions are preferred, and 2.38% by mass aqueous TMAH solutions are more preferred.

[0195] In the case of organic solvent development, examples of the developer include the organic solvents exemplified above as the organic solvent (D) of the radiation-sensitive composition.

[0196] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0197] <Synthesis of Polymers> [Synthesis Examples 1 to 18] Various monomers shown below were combined and copolymerized in tetrahydrofuran (THF) solvent, followed by isolation and drying to obtain polymers (P-1) to (P-16), (Pc-1) and (Pc-2) having the compositions shown in Table 1 below. １ The results were confirmed by H-NMR, and Mw and Mw / Mn were confirmed by GPC as described in the above section [Method for measuring Mw and Mn]. Polymers (P-1) to (P-4) and (P-6) to (P-16) are polymers corresponding to the polymer [A]. Polymer (P-5) is a polymer corresponding to the compound [Z]. Polymers (Pc-1) and (Pc-2) are polymers synthesized for comparison.

[0198]

[0199] In Table 1 below, "-" indicates that the corresponding structural unit is not contained, "mol %" indicates the content ratio of each structural unit to all structural units constituting the polymer, and "number of iodine groups" indicates the number of iodine groups in the polymer calculated according to the above definition.

[0200]

[0201] <Preparation of Radiation-Sensitive Composition> The acid generator [B], acid diffusion controller [C], organic solvent [D], and polymer [F] used in the preparation of the radiation-sensitive composition are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" means a value when the mass of the polymer [A] used is taken as 100 parts by mass.

[0202] [[B] Acid Generator] As the acid generator [B], the following acid generators (PAG-1) to (PAG-8), (PAG-A) and (PAG-B) were used. ３ S ＋ " represents a triphenylsulfonium cation. Acid generators (PAG-1) to (PAG-8) correspond to the above-mentioned compound [Z].

[0203]

[0204] [C] Acid Diffusion Controller] As the acid diffusion controller [C], the acid diffusion controllers (Q-1) to (Q-11), (Q-A) and (Q-B) shown below, and the polymer (P-5) synthesized above were used. ３ S ＋ " represents a triphenylsulfonium cation. The acid diffusion controllers (Q-1) to (Q-11) and the polymer (P-5) correspond to the [Z] compound.

[0205]

[0206] [[D] Organic Solvent] The following organic solvents were used as the organic solvent [D]: PGMEA: propylene glycol monomethyl ether acetate PGME: propylene glycol monomethyl ether CHN: cyclohexanone

[0207] [Polymer [F]] Polymer (F-1) shown below was used as polymer [F]. In formula (F-1) below, the numerical value written to the lower right of the structural unit indicates the content ratio (molar ratio) of the structural unit relative to all structural units constituting polymer [F]. Polymer (F-1) had an Mw of 8,900 and an Mw / Mn of 2.0.

[0208]

[0209] [Examples 1 to 29 and Comparative Examples 1 and 2] Each component was dissolved in the organic solvent [D] shown in Table 2 below, in which 100 ppm of a surfactant (3M's "FC-4430") had been dissolved, at the composition shown in Table 2. The resulting solution was filtered through a nylon filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition.

[0210] <Evaluation> The radiation-sensitive compositions prepared above were evaluated for sensitivity, CDU, and development defect suppression ability according to the following methods. The evaluation results are shown in Table 2 below.

[0211] [Sensitivity] A composition for forming a bottom antireflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 10 nm. Each of the radiation-sensitive compositions prepared above was applied to this bottom antireflective coating using the spin coater, and baked at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. This resist film was exposed to light using an EUV scanner (ASML's NXE3300, NA 0.33, σ 0.9 / 0.6, quadrupole pole illumination, a hole pattern mask with a 46 nm pitch on the wafer and +20% bias). The resist pattern (23 nm holes, 46 nm pitch) was formed by PEB on a hot plate at 120°C for 60 seconds and development in a 2.38% by mass TMAH aqueous solution for 30 seconds. The exposure dose required to form this resist pattern was defined as the optimum exposure dose (Eop). The smaller the Eop value, the better the sensitivity, and the optimum exposure dose was 13.0 mJ / cm. ２ When the intensity is less than 13.0 mJ / cm, it is classified as "A".２ 14.0mJ / cm or more ２ "B" indicates a value less than 14.0 mJ / cm ２ 15.0mJ / cm or more ２ If it is less than 15.0 mJ / cm, it is marked "C". ２ 16.0mJ / cm or more ２ If it is less than 16.0 mJ / cm, it is "D". ２ The above cases were evaluated as "E".

[0212] [CDU] A resist pattern (23 nm holes, 46 nm pitch) was formed in the same manner as in the [Sensitivity] section above, using the exposure dose of Eop determined in the [Sensitivity] section above. The formed resist pattern was observed from above the pattern using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation). The hole diameter was measured at 16 points within a 500 nm range, and the average value was calculated. The average value was also measured at a total of 500 points at any desired points. The 3 sigma value was calculated from the distribution of the measured values, and the calculated 3 sigma value was used as the evaluation value of CDU (unit: nm). The smaller the CDU evaluation value, the smaller the variation in hole diameter over a long period, and the better the result. CDU was evaluated as "A" for values ​​less than 2.20 nm, "B" for values ​​2.20 nm or greater but less than 2.25 nm, "C" for values ​​2.25 nm or greater but less than 2.30 nm, "D" for values ​​2.30 nm or greater but less than 2.35 nm, and "E" for values ​​2.35 nm or greater.

[0213] [Development Defect Suppression] Using the spin coater, the composition for forming a lower antireflective coating was applied to a 12-inch silicon wafer, followed by heating at 205°C for 60 seconds to form a lower antireflective coating having an average thickness of 10 nm. Each of the radiation-sensitive compositions prepared above was applied to this lower antireflective coating using the spin coater, followed by PB at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film having an average thickness of 55 nm. Next, this resist film was exposed using the EUV exposure system (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and a mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. The resist film was then alkaline-developed using a 2.38 mass% aqueous TMAH solution as an alkaline developer. After development, the wafer was washed with water and then dried to form a positive resist pattern (32 nm line and space pattern), which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). The development defect suppression ability was evaluated as follows: "A" when the number of defects determined to be derived from the resist film was 10 or less, "B" when it was 11 to 20, "C" when it was 21 to 30, "D" when it was 31 to 50, and "E" when it was more than 50.

[0214] In Table 2 below, "-" indicates that the corresponding component is not contained.

[0215]

Claims

1. A radiation-sensitive composition comprising: a polymer whose solubility in a developer changes due to the action of an acid; and a compound having an anion and a radiation-sensitive onium cation, wherein the polymer has a structural unit a containing a group that generates a sulfonic acid due to the action of radiation, the polymer contains an iodine group, and at least one of the anion and the radiation-sensitive onium cation contains an acid-dissociable group.

2. The radiation-sensitive composition according to claim 1, wherein at least one of said anion and said radiation-sensitive onium cation further comprises an iodo group.

3. The radiation-sensitive composition according to claim 2, wherein at least one of said anion and said radiation-sensitive onium cation contains both said acid-dissociable group and an iodine group.

4. The radiation-sensitive composition according to claim 3, wherein said anion contains both said acid-dissociable group and an iodine group.

5. A method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 4 directly or indirectly to a substrate; exposing a resist film formed by the application; and developing the exposed resist film.