Sulfonium compound, positive resist composition, and pattern forming method

Abstract

The invention relates to a sulfonium compound, a positive resist composition and a pattern forming method. The sulfonium compound has a structure represented by formula (1): # imgabs0 #, in the formula (1), X and T are each independently a linear chain, branched chain or cyclic C1-C20 divalent hydrocarbon group, and can contain a heteroatom-containing structural part; y is a divalent linking group; z is a group represented by formula (1-1); n1 is 0 or a positive integer; # imgabs 1 # wherein R is a linear, branched or cyclic C1-C20 monovalent hydrocarbon, alcohol or phenol, which may contain a heteroatom moiety, n2 and n3 are each independently 0 or a positive integer, and n1 + n2 + n3 > = 1. The positive resist composition comprising a sulfonium compound of a specific structure as PAG has excellent lithographic performance factors such as high sensitivity, improved LWR and DOF, and is a quite effective resist material for precise micropatterning.

Description

Technical Field

[0001] The present invention relates to a sulfonium compound, a positive resist composition and a pattern forming method. Background Art

[0002] Driven by higher integration and operation speed in LSI devices, many efforts have been made in recent years to achieve finer pattern rules, and DUV and EUV lithography are considered particularly promising as next-generation microfabrication technologies. In particular, lithography using ArF excimer lasers is indispensable for enabling micropatterning technology with feature sizes below 0.13μm.

[0003] ArF lithography has been partially used since the manufacture of devices at the 130nm node and has become the main lithography method since the 90nm node devices. ArF immersion lithography has suddenly received a lot of attention, which introduces a liquid with a higher refractive index than air (e.g., water, ethylene glycol, glycerin) between the projection lens and the wafer, allowing the projection lens to be designed with a numerical aperture (NA) of more than 1.0 and achieve higher resolution. ArF immersion lithography is now implemented in the commercial arena. Immersion lithography requires a resist material that is essentially insoluble in water.

[0004] In order to meet the current rapid development of micro-manufacturing technology, development is devoted not only to methods but also to resist materials, and various studies have been conducted on photoacid generators. In this case, a photoacid generator that generates alkane or aromatic sulfonic acid, which is used in conventional chemically amplified resist materials using KrF excimer laser as a light source, is used as a component of ArF chemically amplified resist materials. It was found that when this resin is used, the acid strength is not enough to cleave the acid-labile groups of the resin, and resolution cannot be achieved at all, or the sensitivity is low, which is not suitable for device manufacturing.

[0005] For this reason, triphenylsulfonium cations and sulfur salts of perfluoroalkanesulfonic acid anions are generally used as photoacid generators for ArF chemically amplified resist materials. Among perfluoroalkanesulfonic acids, perfluorooctanesulfonic acid (PFOS) has problems such as persistence, bioaccumulation, and toxicity. Although a generator is used, the generated acid has a large diffusion rate when used in resist materials, making it difficult to achieve high resolution.

[0006] Introducing bulky substituents or polar groups into PAGs effectively inhibits acid diffusion, however, resist compositions containing such PAGs are still insufficient in precisely controlling acid diffusion and their lithographic performance is unsatisfactory when evaluated overall with respect to LWR (as an index of pattern roughness) and resolution.

[0007] As PAGs that effectively control acid diffusion, the prior art describes betaine-structured sulfonium compounds. However, betaine-type sulfonium compounds have a huge molecular structure and can form dimers in the resist film. They therefore have high acid diffusion control capabilities, but have low solvent solubility, which may lead to coating defects and post-development defects. Because betaine-type sulfonium compounds have low solubility in resist solvents and a structure that can form dimers, partial aggregation may occur in the resist film, thereby reducing its uniform dispersibility within the resist film, resulting in degradation of LWR and CDU. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a positive resist composition with high sensitivity, excellent PED stability, excellent DOF characteristics, and good LWR, and a pattern forming method using the positive resist composition.

[0009] To achieve the above object, the first aspect of the present invention provides a sulfonium compound having a structure shown in the following formula (1):

[0010]

[0011] In formula (1), X and T are each independently a linear, branched or cyclic C1-C20 divalent hydrocarbon group, which may contain a structural part containing a heteroatom; Y is a divalent linking group; Z is a group represented by the following formula (1-1); n1 is 0 or a positive integer;

[0012]

[0013] Wherein, R is a straight chain, branched chain or cyclic C1-C 20 A monovalent hydrocarbon, alcohol or phenol, which may contain a heteroatom structure, wherein n2 and n3 are each independently 0 or a positive integer, and n1+n2+n3≥1.

[0014] A second aspect of the present invention provides a positive resist composition comprising (A) a photoacid generator in the form of a sulfonium compound having a structure of formula (1) as an essential component, and further comprising: (B) a base polymer containing an acid-labile group, and (C) an organic solvent.

[0015] The base polymer (B) contains at least a repeating unit containing an acid-labile group represented by the following formula (a) and, if necessary, a repeating unit containing an acid-labile group represented by the following formula (b), and its alkali solubility is improved by acid. If a repeating unit containing an acid-labile group represented by the following formula (b) is contained, the acid-labile group having 14 or more carbon atoms should account for 5 mol% or less of all the repeating units.

[0016]

[0017] In the formula, R A is a hydrogen atom or a methyl group; R 21 is a linear or branched alkyl group having 1 to 8 carbon atoms; p is an integer of 1 to 3; X A It is an acid-labile group other than the group represented by the following formula (b1).

[0018]

[0019] In the formula, R 21 and p are the same as above.

[0020] Furthermore, the X A The acid-labile group represented is a group represented by any one of the following formulae (L1) to (L2).

[0021]

[0022] In the formula, R L01 ~R L03 Each independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R L04 It is a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms.

[0023] Preferably, the sulfonium compound is one or more combinations represented by the following structural formula (2):

[0024]

[0025] Furthermore, the sulfonium compound is preferably one or more combinations represented by the following structural formula (3):

[0026]

[0027] Preferably, the sulfonium compound is used in an amount of 5-20 parts by mass relative to 80 parts by mass of the base polymer.

[0028] Preferably, the base polymer further contains at least one repeating unit selected from the group consisting of the following formulae (c) to (e):

[0029]

[0030] In the formula, R A are each independently a hydrogen atom or a methyl group; R 23 and R 24 are each independently a hydrogen atom or a hydroxyl group; R 25 is a substituent containing a lactone structure; R 26 and R 27 Each is independently a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, at least one of which is an alkyl group having 1 to 15 carbon atoms; R 26 With R 27They can also bond to each other and form a ring together with the carbon atoms to which they are bonded. In this case, R 26 With R 27 The group formed by the bond is an alkanediyl group having 2 to 15 carbon atoms. 28 It is a divalent hydrocarbon group having 1 to 20 carbon atoms, wherein -CH2- constituting the divalent hydrocarbon group may be substituted with -O- or -C(=O)-. 29 It is -CH2-, -CH2CH2- or -O-, or two -Hs separated from each other; the dotted line represents a single bond bonding the norbornane ring, bicyclo[2.2.2]octane ring, 7-oxanorbornane ring or cyclohexane ring structure to the γ-butyrolactone ring structure, a divalent organic group, or a structure in which one or two constituent carbon atoms are shared between these two ring structures.

[0031] A third aspect of the present invention provides a pattern forming method, characterized in that it comprises the following steps:

[0032] Using the positive resist composition to form a resist film on a substrate;

[0033] Exposing the resist film to light using ArF excimer laser;

[0034] The exposed resist film is developed using a developer.

[0035] Furthermore, the exposure is immersion exposure performed by inserting a liquid having a refractive index of 1.0 or more between the resist film and the projection lens.

[0036] Furthermore, a protective film is further formed on the resist film, and the liquid is inserted between the protective film and the projection lens to perform immersion exposure.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) Compared with the photoacid generator with separated anions and cations, the betaine-type sulfonium compound of the present invention has a larger molecular volume and the ability to control acid diffusion, which is beneficial to reducing the line width roughness of the photolithographic pattern.

[0039] (2) The sulfonium compound of the present invention has a phenolic hydroxyl group structure, which increases the dissolution rate in an alkaline developer, and can construct a pattern profile with improved DOF, reduced LWR, and excellent PED stability. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In the chemical formula, the dotted lines represent valence bonds; Me represents methyl, Ac represents acetyl, and Ph represents phenyl. It is understood that for some structures represented by chemical formulas, enantiomers and diastereomers may exist due to the presence of asymmetric carbon atoms. In such cases, a single formula uniformly represents all such isomers. The isomers may be used alone or in admixture.

[0042] <Sulfonium compounds>

[0043] The present invention provides a sulfonium compound having the structure of formula (1).

[0044]

[0045] In formula (1), X and T are each independently a linear, branched or cyclic C1-C20 divalent hydrocarbon group, which may contain a structural part containing a heteroatom; Y is a divalent linking group; Z is a group represented by the following formula (1-1); n1 is 0 or a positive integer;

[0046]

[0047] Wherein, R is a straight chain, branched chain or cyclic C1-C 20 A monovalent hydrocarbon, alcohol or phenol, which may contain a heteroatom structure, wherein n2 and n3 are each independently 0 or a positive integer, and n1+n2+n3≥1.

[0048] The sulfonium compound of the present invention has a fluorine structure at the α-position of the sulfonic group, and since the acid generated therefrom has a higher acidity, the acid generated by the corresponding sulfonium compound has a higher acidity sufficient to effectively cleave the acid-labile groups on the base resin.

[0049] Examples of the sulfonium compound having the structure of formula (1) include one or more combinations shown in formula (2), but are not limited thereto.

[0050]

[0051] The sulfonium compound of the present invention is characterized in that it has a betaine structure and a phenolic hydroxyl unit. Because of the betaine structure, a bulky structure is retained even after acid generation, indicating that acid diffusion is controllable at a high level. Generally, when the generated acid has a bulky structure, acid diffusion is reduced. In addition, due to the highly compatible phenolic hydroxyl unit, the sulfonium compound has a higher solubility in resist solvents and developers, resulting in fewer defects.

[0052] In addition, the sulfonium compound of the present invention has a phenolic hydroxyl unit, which contributes to the improvement of solvent solubility on the one hand, and on the other hand, the hydroxyl group in the structure forms a hydrogen bond with the acid generated during exposure, resulting in acid diffusion inhibition. Therefore, the sulfonium compound is uniformly dispersed in the resist composition, which may lead to improvements in PED stability, DOF and LWR.

[0053] Preferably, the sulfonium compound having the structure of formula (1) of the present invention is selected from one or more combinations of the compounds shown below:

[0054]

[0055] The sulfonium compound of the present invention, as a photoacid generator, is preferably a structure having a small amount of benzene rings. That is, a sulfonium compound having a diphenyl skeleton is more preferred than a triphenyl skeleton, because the sulfonium compound having a diphenyl skeleton has higher transparency under a 193nm light source, and in addition to the synergistic effect of the betaine structure and the phenolic hydroxyl unit, the sulfonium compound can be used to construct a pattern profile with high sensitivity and reduced LWR in a small amount, and the desired DOF characteristics can be easily obtained.

[0056] <Positive Resist Composition>

[0057] Another embodiment of the present invention is a resist composition comprising (A) a photoacid generator in the form of a sulfonium compound having the formula (1) as an essential component. The resist composition may further comprise: (B) a polymer containing an acid-labile group, and (C) an organic solvent.

[0058] In the positive resist composition of the present invention, the content of component (A) is 5 to 20 parts by mass, preferably 5 to 15 parts by mass, relative to 80 parts by mass of the base polymer of component (B). As long as the amount is within the above range, component (A) imparts all the functions of the photoacid generator and eliminates any performance degradation including reduced sensitivity, insufficient solubility and foreign particles. Component (A) can be used alone or in combination of two or more.

[0059] <(B) Base polymer containing an acid-labile group>

[0060] The acid-labile group-containing base polymer of the component (B) is a polymer containing a repeating unit represented by the following formula (a) (hereinafter, also referred to as repeating unit a).

[0061]

[0062] In formula (a), R A R is a hydrogen atom or a methyl group, preferably a methyl group. 21 It is a linear or branched alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl.

[0063] In formula (a), p is an integer of 1 to 3, preferably 1 or 2.

[0064] The repeating unit a may include the following, but is not limited thereto. In the following formula, RA is the same as described above.

[0065]

[0066] The base polymer may further contain a repeating unit represented by the following formula (b) (hereinafter, also referred to as repeating unit b).

[0067] As a unit containing an acid-labile group.

[0068]

[0069] In formula (b), R A X is a hydrogen atom or a methyl group. A It is an acid-labile group other than the group represented by the following formula (b1).

[0070]

[0071] In the formula, R 21 and p are the same as above.

[0072] Dashed lines are covalent bonds.

[0073] X A The number of carbon atoms in the acid-labile group represented by is preferably 13 or less. If the number of carbon atoms is 13 or less, the desired DOF characteristics are easily obtained, which is preferred. A The acid-labile group having 14 or more carbon atoms may be contained as long as the amount thereof is within 5 mol% of all repeating units of the base polymer.

[0074] Acid labile group X A There is no particular limitation, and examples thereof include groups represented by the following formulae.

[0075]

[0076] In the formula, the dashed lines represent covalent bonds.

[0077] The content of the units containing acid unstable groups (repeating units a and b) in the above-mentioned component (B) base polymer is preferably 25 to 70 mol% of all repeating units, and more preferably 40 to 60 mol%. The repeating unit a is preferably 50 mol% or more of the units containing acid unstable groups, and more preferably 80 mol% or more. The repeating unit b is preferably 50 mol% or less of the units containing acid unstable groups, and more preferably 20 mol% or less.

[0078] The above-mentioned base polymer of component (B) may further contain at least one selected from the group consisting of a repeating unit represented by the following formula (c) (hereinafter, also referred to as repeating unit c), a repeating unit represented by the following formula (d) (hereinafter, also referred to as repeating unit d), and a repeating unit represented by the following formula (e) (hereinafter, also referred to as repeating unit e).

[0079]

[0080] In formulas (c) to (e), R A Each is independently a hydrogen atom or a methyl group. 23 and R 24 Each is independently a hydrogen atom or a hydroxyl group. 25 is a substituent containing a lactone structure. 26 and R 27 Each independently represents a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, and at least one of them is an alkyl group having 1 to 15 carbon atoms. 26 With R 27 They can also bond to each other and form a ring together with the carbon atoms to which they are bonded. In this case, R 26 With R 27 The group formed by the bond is an alkanediyl group having 2 to 15 carbon atoms. 28 It is a divalent hydrocarbon group having 1 to 20 carbon atoms, wherein -CH2- constituting the divalent hydrocarbon group may be substituted with -O- or -C(=O)-. 29 It is -CH2-, -CH2CH2- or -O-, or two -Hs separated from each other. The dotted line represents a single bond that bonds a norbornane ring, a bicyclo[2.2.2]octane ring, a 7-oxanorbornane ring or a cyclohexane ring structure to a γ-butyrolactone ring structure, a divalent organic group, or a structure in which one or two constituent carbon atoms are shared between these two ring structures.

[0081] The repeating unit c is not particularly limited, and is preferably as shown below. A Same as above.

[0082]

[0083] The repeating unit d is not particularly limited, and is preferably as shown below. A Same as above.

[0084]

[0085] The repeating unit e is not particularly limited, and is preferably as shown below. A Same as above.

[0086]

[0087] When the above-mentioned base polymer contains repeating unit c, its content is preferably 25 mol% or less of all repeating units, and more preferably 15 mol% or less. When the above-mentioned base polymer contains repeating unit d, its content is preferably 75 mol% or less of all repeating units, and more preferably 60 mol% or less. When the above-mentioned base polymer contains repeating unit e, its content is preferably 40 mol% or less of all repeating units, and more preferably 25 mol% or less. The total amount of repeating units c, d and e is preferably 30 to 75 mol%, and more preferably 40 to 60 mol%.

[0088] If the base polymer further contains repeating unit c, a resist film having excellent etching resistance can be formed. If the base polymer further contains repeating unit d, a resist film having even better LWR can be provided. If the base polymer further contains repeating unit e, a pattern having an excellent shape with suppressed tailing can be formed on the lower antireflection film.

[0089] The weight average molecular weight (Mw) of the base polymer of the above-mentioned (B) component is preferably 5,000 to 30,000, and more preferably 5,000 to 20,000. In addition, Mw in the present invention is a polystyrene conversion measurement value obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent. As long as Mw is within this range, sufficient etching resistance can be obtained, and any reduction in resolution due to the inability to establish a difference in dissolution rate before and after exposure is avoided.

[0090] The dispersion degree (Mw / Mn) of the base polymer of the component (B) is preferably 1.0 to 3.0, more preferably 1.0 to 2.0. When the dispersion degree is within this range, a resist composition suitable for fine-scale pattern formation can be prepared.

[0091] The synthesis method of the base polymer may be a conventional preparation method in the art, for example, a method in which one or more desired monomers among monomers providing various repeating units are added to an organic solvent, a free radical polymerization initiator is added, and the mixture is heated to polymerize.

[0092] The base polymer of the component (B) may be used alone or in combination of two or more.

[0093] <(C) Organic Solvent>

[0094] The positive resist composition of the present invention contains an organic solvent as component (C). The organic solvent is not particularly limited as long as it can dissolve the aforementioned essential components and the optional components described below. By containing an organic solvent, for example, the coating properties of the resist composition on a substrate or the like can be improved.

[0095] Examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-pentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; and lactones such as γ-butyrolactone, but are not limited thereto. The organic solvent may be used alone or in combination of two or more.

[0096] Among these organic solvents, diethylene glycol dimethyl ether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, cyclohexanone, γ-butyrolactone, and mixed solvents thereof are preferred because they have the best solubility for the acid generator.

[0097] The amount of the organic solvent (C) used is preferably 500 to 4500 parts by mass, more preferably 500 to 4000 parts by mass, based on 80 parts by mass of the base polymer of the component (B).

[0098] <(F) Fluorine-containing polymer>

[0099] The positive resist composition of the present invention further comprises at least one fluorine-containing polymer selected from the group consisting of a repeating unit represented by the following formula (f1), a repeating unit represented by the following formula (f2), and a repeating unit represented by the following formula (f3).

[0100]

[0101] In formulas (f1) to (f3), R B Rf1 and R f2 Each R is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. f3 R is a single bond or a linear or branched divalent hydrocarbon group having 1 to 5 carbon atoms. f4is a hydrogen atom, a monovalent hydrocarbon group having 1 to 15 carbon atoms, a fluorinated monovalent hydrocarbon group having 1 to 15 carbon atoms, or an acid-labile group, R f4 When it is a monovalent hydrocarbon group or a fluorinated monovalent hydrocarbon group, an ether bond or a carbonyl group may be inserted between carbon-carbon bonds. f5 and R f6 Each is independently a fluorinated monovalent hydrocarbon group having 1 to 10 carbon atoms. L is an (r+1)-valent hydrocarbon group having 1 to 15 carbon atoms or an (r+1)-valent fluorinated hydrocarbon group having 1 to 15 carbon atoms. r is an integer of 1 to 3.

[0102] R f1 and R f2 The monovalent hydrocarbon group represented by may be any of straight chain, branched, and cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, adamantyl, norbornyl, etc. Among them, the one having 1 to 6 carbon atoms is preferred.

[0103] R f3 The divalent hydrocarbon group represented by may be any of linear, branched, and cyclic, and specific examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.

[0104] R f4 The monovalent hydrocarbon group represented by may be any of straight chain, branched, and cyclic, and specific examples thereof include alkyl, alkenyl, alkynyl, etc., preferably alkyl. f1 and R f2 In addition to the monovalent hydrocarbon groups exemplified by , n-undecyl, n-dodecyl, tridecyl, tetradecyl, pentadecyl and the like can be mentioned. f4 The fluorinated monovalent hydrocarbon group represented by : may be a group in which a part or all of the hydrogen atoms bonded to the carbon atoms of the monovalent hydrocarbon group are substituted with fluorine atoms. As described above, such a carbon-carbon bond may contain an ether bond or a carbonyl group.

[0105] R f4 The acid-labile groups represented by the present invention include: the acid-labile groups contained in the aforementioned base polymer; tertiary alkyl groups having 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms; trialkylsilyl groups in which each alkyl group is an alkyl group having 1 to 6 carbon atoms; oxoalkyl groups having 4 to 20 carbon atoms, etc.

[0106] R f5 and R f6The fluorinated monovalent hydrocarbon group having 1 to 10 carbon atoms represented by EMI15.1 may be any of a linear, branched, or cyclic group, and specific examples thereof include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoro-1-propyl group, a 3,3,3-trifluoro-2-propyl group, a 2,2,3,3-tetrafluoropropyl group, a 1,1,1,3,3,3-hexafluoroisopropyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 2,2,3,3,4,4,5,5-octafluoropentyl group, a 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, a 2-(perfluorobutyl)ethyl group, a 2-(perfluorohexyl)ethyl group, a 2-(perfluorooctyl)ethyl group, and a 2-(perfluorodecyl)ethyl group.

[0107] The (r+1)-valent hydrocarbon group having 1 to 15 carbon atoms represented by L may be any of linear, branched, and cyclic, and specific examples thereof include groups formed by further removing r hydrogen atoms from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, adamantyl, norbornyl, etc. Furthermore, the aforementioned (r+1)-valent fluorinated hydrocarbon group having 1 to 15 carbon atoms may be any of linear, branched, and cyclic, and specific examples thereof include groups formed by replacing a part or all of the hydrogen atoms of the aforementioned (r+1)-valent hydrocarbon group with fluorine atoms.

[0108] As for the fluorinated polymer of component (F), when a resist protective film is not used in ArF immersion exposure, it has the function of reducing water penetration and leaching by being aligned on the surface of the resist film. When the aforementioned fluorinated polymer is contained, its content is preferably 1 to 12 parts by mass, and more preferably 3 to 8 parts by mass relative to 80 parts by mass of the base polymer of component (B). By containing the aforementioned fluorinated polymer, a resist pattern with further reduced pattern defects can be formed. The aforementioned fluorinated polymers can be used alone or in combination of two or more.

[0109] <(Q) Quencher>

[0110] The positive resist composition of the present invention may further include (Q) a quencher. As used herein, "quencher" refers to a compound capable of capturing the acid generated by the PAG. The quencher can suppress the acid diffusion rate when the acid generated by the PAG diffuses in the resist film.

[0111] The positive resist composition of the present invention may also contain a basic compound as a quencher. By adding a basic compound, the resolution can be further improved. Examples of the basic compound include primary, secondary or tertiary amine compounds, amine compounds having a hydroxyl group, an ether bond, an ester bond, a lactone ring, a cyano group or a sulfonate bond, and compounds having a carbamate group.

[0112] When the above-mentioned basic compound quencher is contained, its content is preferably 0.05 to 3 parts by mass relative to 80 parts by mass of the base polymer of component (B). The above-mentioned quencher can be used alone or in combination of two or more. The inclusion of the quencher promotes the adjustment of the resist sensitivity and suppresses the acid diffusion rate within the resist film, resulting in better resolution. In addition, it suppresses changes in sensitivity after exposure and reduces dependence on the substrate and the environment, as well as improves exposure margin and pattern profile. The quencher is also effective in improving adhesion to the substrate.

[0113] <Other additives>

[0114] The positive resist composition of the present invention may contain an acid proliferation compound, a dissolution inhibitor, a surfactant, etc. as other components.

[0115] The acid multiplication compound is a compound that decomposes with acid and generates acid. When the acid multiplication compound is contained, its content is preferably 1.6 parts by mass or less, and more preferably 0.8 parts by mass or less, relative to 80 parts by mass of the base polymer of component (B). If the content of the acid multiplication compound is within the above range, acid diffusion can be easily controlled, and there is no risk of resolution degradation or pattern shape degradation, so it is preferred. The acid multiplication compound may be used alone or in combination of two or more.

[0116] As the dissolution inhibitor, compounds with a weight average molecular weight of 3,500 or less, whose solubility in alkaline developer changes due to the action of organic acid derivatives and acids, can be cited. The content of the dissolution inhibitor is preferably 12 parts by mass or less relative to 80 parts by mass of the base polymer of component (B). By containing the dissolution inhibitor in the above range, the difference in dissolution rate between the exposed part and the unexposed part can be further increased, so that the resolution is further improved. The dissolution inhibitor can be used alone or in combination of two or more.

[0117] Examples of the surfactant include FC-4430 (manufactured by 3M Co., Ltd.), surflon (registered trademark) S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), OLFINE (registered trademark) E1004 (manufactured by Nissin Chemical Co., Ltd.), KH-20 and KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), and an oxetane ring-opening polymer represented by the following formula (surf-1).

[0118]

[0119] Here, R, Rf, A, B, C, m, and n are not limited to the above descriptions and are applicable only to formula (surf-1). R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. As for the aforementioned aliphatic group, examples of the divalent aliphatic group include ethylene, 1,4-butylene, 1,2-propylene, 2,2-dimethyl-1,3-propylene, and 1,5-pentylene.

[0120] The surfactant may be used alone or in combination of two or more. The surfactant preferably has an Mw of 1,000 to 30,000, which is measured by GPC relative to a polystyrene standard. A surfactant having an Mw within the range may be effective for surface modification and does not cause development defects; the amount of the surfactant used is preferably 0.001 to 10 parts by mass, preferably 0.01 to 10 parts by mass, relative to 80 parts by mass of the base polymer of component (B). By adding a surfactant, the coating properties of the resist composition can be further improved or controlled.

[0121] <Pattern Formation Method>

[0122] The pattern forming method of the present invention comprises the following steps: forming a resist film on a substrate using the positive resist composition of the present invention; exposing the resist film using a KrF excimer laser; and developing the exposed resist film using a developer.

[0123] As a substrate, for example, a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, a substrate with an organic anti-reflection film, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) can be used.

[0124] As for the resist film, for example, the positive resist composition of the present invention can be applied on a substrate by spin coating or the like so that the film thickness becomes 0.05 to 2 μm, and the resist film is heat-treated (pre-baked) on a heating plate at preferably 60 to 150° C. for 1 to 10 minutes, and more preferably 80 to 140° C. for 1 to 5 minutes.

[0125] When the resist film is exposed using a KrF excimer laser, the exposure can be performed by irradiating the resist film using a mask for forming a target pattern so that the exposure amount is preferably 1 to 200 mJ / cm 2 , more preferably 10 to 100 mJ / cm 2 .

[0126] In addition to the usual exposure method, the exposure may be performed by an immersion method in which a liquid having a refractive index of 1.0 or more, such as water, is inserted between the resist film and the projection lens. In this case, a water-insoluble protective film may be used.

[0127] After exposure, a post-exposure bake (PEB) may be performed. PEB can be performed, for example, by heating on a hot plate at preferably 60 to 150° C. for 1 to 5 minutes, more preferably 80 to 140° C. for 1 to 3 minutes.

[0128] As for development, for example, a developer such as an alkaline aqueous solution of tetramethylammonium hydroxide (TMAH) with a concentration of preferably 0.1 to 5% by mass, more preferably 2 to 3% by mass, can be used, and development can be carried out by conventional methods such as dipping, puddle, and spraying for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes.

[0129] Regarding the pattern forming method, pure water rinsing (postsoak) may be performed after the resist film is formed to extract the acid generator from the film surface or to wash away particles, or rinsing (postsoak) may be performed after exposure to remove water remaining on the film.

[0130] The above and other advantages of the present invention may be better understood through the following examples, but the following examples are not intended to limit the scope of the present invention.

[0131] Example

[0132] The present invention is described below with reference to the following examples, but the present invention is not limited to the following examples.

[0133] <Sulfonium compounds>

[0134] Synthesis example 1

[0135] Synthesis of PAG-1

[0136]

[0137] 45g of compound 1-1 (4,4'-dihydroxydiphenyl sulfoxide) was dissolved in a mixture of 25g of diisopropylethylamine and 150g of acetonitrile. In an ice-water bath, 10g of chloromethyl methyl ether was added dropwise to the solution and then aged overnight at room temperature. It was then combined with 200g of water and 200g of toluene and then separated. The organic layer was washed once with water, washed with 1wt% ammonia water and then washed again with water. The solution was further washed with 1wt% hydrochloric acid and then washed with water. The organic layer was taken out and concentrated under reduced pressure, and the concentrate was dried under vacuum to obtain white crystals, which were compound intermediate 1-2.

[0138] 40 g of compound intermediate 1-2 was dissolved in 200 g of THF, and a freshly prepared THF solution of Grignard reagent A (equivalent to 5 times the molar number of intermediate 1-2) was added dropwise to the solution in an ice-water bath, and then 35 g of chlorotrimethylsilane was added dropwise to the solution, and then aged overnight at room temperature. In an ice-water bath, 200 g of 10 wt% aqueous ammonium chloride solution, 200 g of MIBK and 100 g of water were added to the above solution in sequence, and then the organic layer containing compound intermediate 1-3 was taken out and transferred to the subsequent reaction.

[0139] 50g of compound 1,1,2,2-tetrafluoro-4-hydroxybutane-1-sodium sulfonate and 100g of water were added to the organic layer obtained above, and then a separation operation was performed. The organic layer was taken out, washed 3 times with an aqueous solution of 2.5wt% of compound 1,1,2,2-tetrafluoro-4-hydroxybutane-1-sodium sulfonate, and then washed 3 times with deionized water. The organic layer was concentrated under reduced pressure to obtain an oily product. DIPE was added to the product for precipitation, and then concentrated under reduced pressure to obtain an intermediate product; below 5°C, a solution containing 2.5g of sodium hydride and 125g of THF was added dropwise to a solution containing 45g of the intermediate product and 100g of THF, and then aged overnight at room temperature. Thereafter, water and 300g of MIBK were added to the solution in sequence below 5°C, and then a separation operation was performed. The organic layer was taken out and washed with water, and then washed with 1wt% hydrochloric acid and washed with water again. The organic layer was taken out and concentrated under reduced pressure to obtain an oily product. DIPE was added to the oily product for precipitation, and the solid was collected by filtration and dried in vacuo to obtain white crystals, which were compound Intermediate 1-4.

[0140] Dissolve 15g of intermediate 1-4 and 1.2g of 35wt% hydrochloric acid in a solvent mixture containing 60g of methanol and 15g of deionized water, stir and heat to 50°C for 20 hours. Then add 150g of MIBK and 150g of deionized water to the solution, stir and take out the organic layer. Wash the organic layer twice with 200g of 33wt% methanol aqueous solution and once with 150g of deionized water, and then concentrate under reduced pressure. Dilute the concentrate with MIBK to form a 50wt% solution, add 100g of DIPE for crystallization, collect the precipitate by filtration and vacuum dry to obtain white crystals, namely PAG-1.

[0141] Synthesis example 2

[0142] Synthesis of PAG-2

[0143]

[0144] The 4,4'-dihydroxydiphenyl sulfoxide in Synthesis Example 1 was replaced with Compound 2-1, and the synthesis was carried out according to the synthesis steps of PAG-1 to obtain Synthetic PAG-2.

[0145] Synthesis example 3

[0146] Synthesis of PAG-3

[0147]

[0148] 40g of 10 mass% benzyltrimethylammonium chloride aqueous solution was stirred and added to a solution containing 5g of compound 3-1 and 100g of THF, and then a solution containing 1.5g of sodium hydride and 100g of THF was added dropwise to the mixed solution below 5°C, and then aged overnight at room temperature. Water and 150g of MIBK were then added to the solution in sequence below 5°C, and then a separation operation was performed. The organic layer was taken out and washed with water, then washed with 1wt% hydrochloric acid and washed with water again. The organic layer was taken out and concentrated under reduced pressure to obtain an oily product. DIPE was added to the oily product for precipitation, and the solid was collected by filtration and dried in a vacuum to obtain white crystals, which were the compound intermediate ammonium salt 3-2.

[0149] The above-mentioned compound intermediate ammonium salt 3-2 is used to replace the 1,1,2,2-tetrafluoro-4-hydroxybutane-1-sodium sulfonate in Synthesis Example 2, and the synthesis is carried out according to the synthesis steps of PAG-2 to obtain synthetic PAG-3.

[0150] Synthesis example 4

[0151] Synthesis of PAG-4

[0152]

[0153] 59g of compound 4-1 bis(4-hydroxyphenyl)iodonium bromide was dissolved in a mixture of 35g of diisopropylethylamine and 150g of acetonitrile. In an ice-water bath, 15g of chloromethyl methyl ether was added dropwise to the solution, and then aged overnight at room temperature. It was then combined with 150g of water and 100g of toluene, and then separated. The organic layer was washed once with water, washed with 1wt% ammonia water, and then washed again with water. The solution was further washed with 1wt% hydrochloric acid and then washed with water. The organic layer was taken out and concentrated under reduced pressure, and the concentrate was dried under vacuum to obtain white crystals, which were compound intermediate 4-2;

[0154] Add 28g of intermediate 4-2 to 250mL of chlorobenzene, add 8g of compound A, stir at 25°C for half an hour, add 0.3g of copper benzoate, raise the temperature to 105°C, stir and react at 105°C for 1.5-2 hours, add 100g of water to the reaction solution, separate the liquids, extract with 250mL of dichloromethane, wash the organic phase with deionized water, concentrate, add 150mL of n-hexane, stir, let stand, filter, and dry the solid to obtain intermediate 4-3;

[0155] The intermediate 4-3 was substituted for the compound 2-3 in Synthesis Example 3, and the synthesis was carried out according to the synthesis steps of PAG-3 to obtain synthetic PAG-4.

[0156] Synthesis example 5

[0157] Synthesis of PAG-5

[0158]

[0159] The intermediate 4-3 was substituted for 1-3 in Synthesis Example 1, and the synthesis was carried out according to the synthesis steps of PAG-1 to obtain synthetic PAG-5.

[0160] <Synthesis of base polymer>

[0161] Synthesis Example 6-7

[0162] The monomers were combined in a composition ratio as shown in Table 1 below, and copolymerization was carried out in a nitrogen atmosphere using butanone and 2,2'-azobis(methyl 2-methylpropionate) as solvent and initiator, respectively, to synthesize base polymers P-1 and P-2 with compositions as shown in Table 1. The product was precipitated with methanol, and after repeated washing with hexane, separated and dried, the molecular weight of which was confirmed by GPC (solvent: tetrahydrofuran; standard: polystyrene).

[0163] Table 1

[0164]

[0165] The structures of the units in Table 1 are shown in Table 2.

[0166] Table 2

[0167]

[0168] <Preparation of Resist Composition>

[0169] Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-2

[0170] Each component was dissolved in a solvent according to the composition ratio shown in Table 3 (all parts by mass), and after the dissolution, the mixture was filtered using a Teflon filter (pore size 0.2 μm) to prepare a resist composition.

[0171] Table 3

[0172]

[0173]

[0174] In Table 3, the photoacid generator (PAG-A to PAG-B), the quencher Q-1, the fluorinated polymer F-1, the surfactant S-1, and the solvent are as follows.

[0175] Solvent: PGMEA (propylene glycol monomethyl ether acetate)

[0176] GBL (γ-butyrolactone)

[0177] Photoacid generator: PAG-A~PAG-B

[0178]

[0179] Amine quencher: Q-1

[0180]

[0181] Fluoropolymer: F-1

[0182]

[0183] Surfactant: S-1 (3-methyl-3-(2,2,2-trifluoroethoxymethyl)oxetane)·THF·2,2-dimethyl-1,3-propanediol copolymer (manufactured by Omnova)

[0184]

[0185] a:(b+b'):(c+c')=1:4~7:0.01~1 (molar ratio)

[0186] Mw=1500

[0187] <Evaluation of Resist Composition>

[0188] Examples 2-1 to 2-8, Comparative Examples 2-1 to 2-2

[0189] An antireflection film solution (ARC-29A manufactured by Nissan Chemical Co., Ltd.) was coated on a silicon substrate and baked at 180°C for 60 seconds to form an antireflection film (100 nm film thickness). Each resist composition (R-1 to R-8, CR-1 to CR-2) was spin-coated on the aforementioned antireflection film and baked at 100°C for 60 seconds using a hot plate to form a resist film with a film thickness of 90 nm. Immersion exposure was performed using an ArF excimer laser scanning exposure machine (NSR-S610C manufactured by Nikon Co., Ltd., NA=1.30, σ0.94 / 0.74, Dipole-35deg illumination, binary mask). In addition, water was used as the immersion liquid. Thereafter, baking (PEB) was performed at 85°C for 60 seconds, and development was performed for 60 seconds using a 2.38 mass % TMAH aqueous solution to form a line and space (L / S) pattern.

[0190] Regarding the evaluation of the resist composition, LWR, DOF, and PED stability were evaluated according to the following methods.

[0191] An 82nm pitch, 37nm chromium pattern was observed using an electron microscope, and the exposure obtained with a pitch width of 45nm was taken as the optimum exposure (Eop, mJ / cm2). The smaller this value, the higher the sensitivity.

[0192] As for DOF, the focus range of the LS pattern analyzed at the target size of 45nm±10% (i.e. 40.5-49.5nm) is obtained by shifting the focus up and down in the above-mentioned optimal exposure, and this is defined as DOF ​​(nm). The larger the value, the wider the tolerance for focus shift, which can be regarded as good performance.

[0193] As for LWR, the dimension of 60 points in the long side direction of the pitch width of the L / S pattern irradiated at Eop is measured, and the value (3σ) three times the standard deviation (σ) is calculated as LWR. The smaller this value is, the more likely it is that a pattern with less roughness and uniform pitch width can be obtained.

[0194] Regarding PED stability, the line width dimension (CD0) when PEB was performed immediately after exposure with an exposure amount of 52 nm line / 104 nm pitch to make the line width dimension of the pattern 52 nm, and the line width dimension (CD90) when PEB was performed 90 minutes after exposure were measured, and the line width change (%) was calculated according to the following formula, which was defined as PED stability. The smaller the line width change, the better.

[0195] Line width change (%) = 100 × |CD90-CD0| / 52

[0196] The results are shown in Table 4.

[0197] Table 4

[0198]

[0199] As shown in Table 4, the positive resist composition containing the sulfonium compound of the present invention as a photoacid generator has high sensitivity, good DOF, LWR and PED stability. The DOF characteristics, LWR characteristics and PED stability of the comparative example are relatively poor. These data show that the resist composition of the present invention is suitable for ArF immersion lithography.

[0200] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A sulfonium compound, characterized in that It has the structure shown in the following formula (1): In formula (1), X and T are each independently a linear, branched or cyclic C1-C 20 A divalent hydrocarbon group, which may contain a structural part containing a heteroatom; Y is a divalent linking group; Z is a group represented by the following formula (1-1); n1 is 0 or a positive integer; Wherein, R is a straight chain, branched chain or cyclic C1-C 20 A monovalent hydrocarbon, alcohol or phenol, which may contain a heteroatom structure, wherein n2 and n3 are each independently 0 or a positive integer, and n1+n2+n3≥1.

2. A positive resist composition, characterized in that: Contains the sulfonium compound as claimed in claim 1.

3. A positive resist composition as claimed in claim 2, characterized in that: It also contains (B) a base polymer containing an acid-labile group, and (C) an organic solvent; The base polymer (B) contains at least a repeating unit containing an acid-labile group represented by the following formula (a), or further contains a repeating unit containing an acid-labile group represented by the following formula (b) having 14 or more carbon atoms, the amount of which should be 5 mol% or less in all the repeating units; In the formula, R A is a hydrogen atom or a methyl group; R 21 is a linear or branched alkyl group having 1 to 8 carbon atoms; p is an integer of 1 to 3; X A An acid-labile group other than the group represented by the following formula (b1); In the formula, R 21 and p are the same as above.

4. A positive resist composition as claimed in claim 2, characterized in that: The X A The acid-labile group represented is a group represented by any one of the following formulae (L1) to (L2). In the formula, R L01 ~R L03 Each independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R L04 It is a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms.

5. A positive resist composition according to claim 2 or 3, characterized in that: The sulfonium compound is one or more combinations of the following structural formula (2):

6. A positive resist composition according to claim 2 or 3, characterized in that: The sulfonium compound is preferably one or more combinations of the following structural formula (3):

7. A positive resist composition according to claim 2 or 3, characterized in that: The sulfonium compound is used in an amount of 5 to 20 parts by mass relative to 80 parts by mass of the base polymer.

8. A pattern forming method, characterized in that: The following steps are included: forming a resist film on a substrate using the positive resist composition according to any one of claims 2 to 7; Exposing the resist film to light using ArF excimer laser; The exposed resist film is developed using a developer.

9. A pattern forming method as claimed in claim 8, characterized in that: The exposure is immersion exposure performed by inserting a liquid having a refractive index of 1.0 or more between the resist film and the projection lens.

10. A pattern forming method according to claim 8, characterized in that: A protective film is further formed on the resist film, and the aforementioned liquid is inserted between the protective film and the projection lens to perform immersion exposure.

Images