Patent Application
20250053087
This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2023-127895 filed in Japan on Aug. 4, 2023, the entire contents of which are hereby incorporated by reference.
The present invention relates to an onium salt, a chemically amplified resist composition, and a pattern forming process.
While miniaturization of a pattern rule is required as an LSI advances toward higher integration and higher processing speed in recent years, far ultraviolet lithography and extreme ultraviolet (EUV) lithography are thought to hold particular promise as the next generation in microfabrication technology. In particular, photolithography using ArF excimer laser is requisite to the micropatterning technology capable of achieving a feature size of 0.13 μm or less.
The ArF lithography started partial use from the fabrication of 130-nm node devices and became the main lithography technology since 90-nm node devices. Although lithography technology using F2 laser (157 nm) was initially thought promising as the next lithography for 45-nm node devices, its development was retarded by several problems, and thus a highlight is suddenly placed on ArF immersion lithography that introduces a liquid having a higher refractive index than air, such as water, ethylene glycol, or glycerol, between the projection lens and the wafer, allowing the projection lens to be designed to a numerical aperture (NA) of 1.0 or higher and achieving a higher resolution (Non-Patent Document 1), and is in a practical stage. This immersion lithography requires a resist composition which is substantially non-leachable in water.
In the ArF lithography, a high sensitivity resist composition capable of exhibiting sufficient resolution with a small exposure dose is required in order to prevent deterioration of a precise and expensive optical system material. As a method for realizing this, it is most common to select a highly transparent component at a wavelength of 193 nm as a component thereof. For example, as the base polymer, polyacrylic acid and a derivative thereof, norbornene-maleic anhydride alternating copolymers, polynorbornene, ring-opening metathesis polymers, ring-opening metathesis polymer hydrogenated product, and the like have been proposed, and this choice is effective to some extent in that the transparency of a resin alone is increased.
Recently, a highlight is put on the negative tone resist adapted for organic solvent development as well as the positive tone resist adapted for alkaline aqueous solution development. Since a very fine hole pattern, which is not achievable with the positive tone, is resolvable through negative tone exposure, a negative pattern is formed by developing with an organic solvent using a positive resist composition having high resolution. An attempt to double a resolving power by combining two developments of alkaline aqueous solution development and organic solvent development. As the ArF resist composition for negative tone development with an organic solvent, a conventional positive ArF resist composition can be used, and a pattern forming process using the same is described in Patent Documents 1 to 3.
To meet the current rapid progress of microfabrication technology, development efforts are put on not only the process technology, but also the resist composition. Various studies have also been made on photoacid generators, and sulfonium salts comprising a triphenylsulfonium cation and a perfluoroalkanesulfonic acid anion are generally used. However, perfluoroalkanesulfonic acid as an acid to be generated, in particular, perfluorooctanesulfonic acid (PFOS) is considered problematic with respect to its non-degradability, biological concentration, and toxicity, and is difficult to apply this acid to the resist composition, and a photoacid generator capable of generating perfluorobutanesulfonic acid is currently used. However, when this acid is used for the resist composition, diffusion of the acid to be generated is large, and it is difficult to achieve high resolution. To address the problem, various partially fluorinated alkanesulfonic acids and salts thereof have been developed, and for example, Patent Document 1 describes a photoacid generator capable of generating α,α-difluoroalkanesulfonic acid by exposure to light, specifically, a photoacid generator capable of generating di(4-tert-butylphenyl)iodonium 1,1-difluoro-2-(1-naphthyl)ethanesulfonate or α,α,β,β-tetrafluoroalkanesulfonic acid. Despite a reduced degree of fluorine substitution, these photoacid generators still have the following problems: since they do not have a decomposable substituent such as an ester structure, they are unsatisfactory from the viewpoint of environmental safety due to ease of decomposition; the molecular design to change the size of alkanesulfonic acid is limited; and a fluorine atom-containing starting material is expensive.
As the circuit line width is reduced, the degradation of contrast by acid diffusion becomes more serious for the resist composition. The reason is that the pattern feature size is approaching the diffusion length of acid, and this invites a lowering of mask fidelity and a degradation of pattern rectangularity because a dimensional shift on a wafer (mask error factor (MEF)) relative to a dimensional shift value on the mask is exaggerated. Therefore, in order to sufficiently obtain benefits of shortening the wavelength of a light source and increasing NA, it is necessary to increase dissolution contrast or restrain acid diffusion, as compared with the conventional materials. As one of improvement measures, when the bake temperature is lowered, the acid diffusion is reduced, and as a result, MEF can be improved, but the sensitivity is inevitably lowered.
Incorporating a bulky substituent or polar group into a photoacid generator is effective for suppressing acid diffusion. Patent Document 4 describes a photoacid generator having 2-acyloxy-1,1,3,3,3-pentafluoropropane-1-sulfonic acid which is excellent in solubility and stability in a solvent and allows for a wide span of molecular design, and particularly, a photoacid generator having 2-(1-adamantyloxy)-1,1,3,3,3-pentafluoropropane-1-sulfonic acid into which a bulky substituent is introduced has small acid diffusion. Patent Documents 5 to 7 describe photoacid generators in which condensed ring lactone, sultone, or thiolactone is introduced as a polar group. Although it has been confirmed that the performance is improved to some extent due to the effect of suppressing acid diffusion by introduction of a polar group, it is still insufficient for advanced control of acid diffusion, and the lithographic performances are not satisfactory in comprehensive view of MEF, a pattern shape, sensitivity, and the like.
Incorporating a polar group into the anion of the photoacid generator is effective for suppressing acid diffusion, but is disadvantageous from the viewpoint of solvent solubility. In Patent Documents 8 and 9, in order to improve solvent solubility, an attempt has been made to secure solvent solubility by introducing an alicyclic group into a cation moiety of a photoacid generator, and specifically, a cyclohexane ring or an adamantane ring is introduced. Although the solubility is improved by introduction of such an alicyclic group, a certain number of carbon atoms is required in order to secure the solubility, and as a result, the molecular structure of the photoacid generator becomes bulky, so that lithographic performances such as linewidth roughness (LWR) and dimensional uniformity (CDU) deteriorate at the time of fine pattern formation.
Patent Document 10 describes a photoacid generator capable of generating a fluoroalkanesulfonic acid having an aromatic condensed ring derived from anthracene in an anion. As a result, although improvement in lithographic performances to some extent has been confirmed, when the number of fluorine atoms bonded to the alkanesulfonic acid structure is 2 to 4, the organic solvent solubility is not sufficiently high, and there is a concern about deposition in the solvent. In order to meet the demand for further miniaturization, development of a novel photoacid generator is important, and it is desired to develop a photoacid generator in which acid diffusion is sufficiently controlled, solvent solubility is excellent, and lithographic performances are improved.
With respect to the recent demand for high resolution of resist patterns, a resist composition using a conventional onium salt type photoacid generator cannot sufficiently suppress acid diffusion, and as a result, contrast and lithographic performances such as MEF and LWR may be deteriorated.
It is an object of the present invention to provide an onium salt which is used for a chemically amplified resist composition having excellent solvent solubility, high sensitivity, high contrast, and excellent lithographic performances such as exposure latitude (EL) and LWR particularly in photolithography using high-energy radiation such as KrF excimer laser, ArF excimer laser, electron beam (EB), and EUV, a chemically amplified resist composition comprising the onium salt as a photoacid generator, and a pattern forming process using the chemically amplified resist composition.
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that an onium salt including a ring-condensed structure having a substituent and an alkanesulfonic acid structure containing a trifluoromethyl group and having 5 or more fluorine atoms in an anion is excellent in solvent solubility, and a chemically amplified resist composition using the onium salt as a photoacid generator has high sensitivity, high contrast, excellent lithographic performances such as EL and LWR and is extremely effective for fine pattern formation, thereby completing the present invention.
That is, the present invention provides the following onium salt, chemically amplified resist composition, and pattern forming process.
When a pattern is formed using a chemically amplified resist composition comprising the onium salt of the present invention as a photoacid generator, sensitivity is high, an acid diffusion control ability is excellent, lithographic performances such as MEF and LWR are improved, so that resist patterns can be prevented from collapsing at the time of fine pattern formation.
An onium salt of the present invention has the following formula (1).
In formula (1), R1 to R12 are each independently a hydrogen atom, a halogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom. One of R13 and R14 is a group having a partial structure of formula (1a) described below, and the other one is a hydrogen atom, a halogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C20 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-hexyl group, a n-octyl group, a n-nonyl group, a n-decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group; C3-C20 cyclic saturated hydrocarbyl groups such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group, and an adamantyl group; C2-C20 alkenyl groups such as a vinyl group, an allyl group, a propenyl group, a butenyl group, and a hexenyl group; C3-C20 cyclic unsaturated hydrocarbyl groups such as a cyclohexenyl group; C6-C20 allyl groups such as a phenyl group and a naphthyl group; C7-C20 aralkyl groups such as a benzyl group, a 1-phenylethyl group, and a 2-phenylethyl group; and groups obtained by combining these. Of these, an aryl group is preferable. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like.
At least two of R1 to R14 may bond together to form a ring with the carbon atom to which they are attached or with the carbon atom to which they are attached and the carbon atom therebetween. Specific examples of the ring formed at this time include alicyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a norbornane ring, and an adamantane ring, and aromatic rings such as a benzene ring, a naphthalene ring, and an anthracene ring. Some or all of the hydrogen atoms in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by R1. The ring is preferably an aromatic ring and more preferably a benzene ring.
In formula (1), any one of R13 and R14 is a group having a partial structure of the following formula (1a). Of these, from the viewpoint of synthesis, R14 is preferably a group having a partial structure of the following formula (1a).
In formula (1a), LA and LB are each independently a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond. Of these, a single bond, an ether bond, or an ester bond is preferable.
In formula (1a), XL is a single bond or a C1-C40 hydrocarbylene group which may contain a heteroatom. The hydrocarbylene group may be straight, branched, or cyclic, and specific examples thereof include an alkanediyl group and a cyclic saturated hydrocarbylene group. Specific examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.
Specific examples of the C1-C40 hydrocarbylene group, which may contain a heteroatom, represented by XL are shown below, but not limited thereto. In the following formula, * designates a point of attachment to LA and LB.
Of these, XL-0 to XL-22 and XL-47 to XL-58 are preferable.
In formula (1a), Q1 to Q3 are each independently a hydrogen atom, a fluorine atom, or a C1-C6 fluorinated saturated hydrocarbyl group. The fluorinated saturated hydrocarbyl group is preferably a trifluoromethyl group.
In formula (1a), when both of Q1 and Q2 are a hydrogen atom, Q3 is a fluorine atom or a C1-C6 fluorinated saturated hydrocarbyl group. The fluorinated saturated hydrocarbyl group is preferably a trifluoromethyl group.
In formula (1a), the number of fluorine atoms in Q1 to Q3 has to be two or more in total. Thus, the solvent solubility of the onium salt is improved, and the onium salt is uniformly dissolved in a resist solvent, so that various lithographic performances can be improved.
Specific examples of the partial structure of —C(CF3)(Q3)—C(Q1)(Q2)-SO3— in formula (1a) are preferably shown below, but not limited thereto. In the following formula, * designates a point of attachment to LB.
Of these, from the viewpoint of synthesis, Acid-1 and Acid-3 are preferable. In Acid-1, since a carbon atom to which a trifluoromethyl group is bonded is an asymmetric carbon, a diastereomer is generated in an anion structure, and the solvent solubility is improved. Acid-2 does not produce a diastereomer like Acid-1, but the solvent solubility is improved as the number of fluorine atoms increases.
The onium salt having formula (1) preferably has the following formula (1A).
The onium salt having formula (1A) preferably has the following formula (1B).
In formula (1B), R15 and R16 are each independently a hydrogen atom, a halogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom. Specific examples of the halogen atom and the hydrocarbyl group are as exemplified above for the halogen atom and the hydrocarbyl group represented by R1 to R14.
In formula (1B), n1 and n2 are each independently an integer of 0 to 4. Among them, from the viewpoint of raw material availability, both of n1 and n2 are preferably 0 to 2.
In formula (1B), when n1 and n2 are 2 or more, a plurality of R15's and R16's may bond together to form a ring with the carbon atom to which they are attached or with the carbon atom to which they are attached and the carbon atom therebetween. Specific examples of the ring formed at this time include as exemplified above for the ring that at least two of R1 to R14 may bond together to form.
The onium salt having formula (1B) preferably has the following formula (1C).
Specific examples of the anion of the onium salt having formula (1) are shown below, but not limited thereto. In the following formula, Me is a methyl group.
In formula (1), Z+ is an onium cation. The onium cation is preferably a sulfonium cation having the following formula (cation-1) or an iodonium cation having the following formula (cation-2).
In formulae (cation-1) and (cation-2), Rct1 to Rct5 are each independently a halogen atom or a C1-C30 hydrocarbyl group which may contain a heteroatom.
Examples of the halogen atom represented by Rct1 to Rct5 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The hydrocarbyl group represented by Rct1 to Rct5 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C30 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group; C3-C30 cyclic saturated hydrocarbyl groups such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group, and an adamantyl group; C2-C30 alkenyl groups such as a vinyl group, an allyl group, a propenyl group, a butenyl group, and a hexenyl group; C3-C30 cyclic unsaturated hydrocarbyl groups such as a cyclohexenyl group; C6-C30 aryl groups such as a phenyl group, a naphthyl group, and a thienyl group; C7-C30 aralkyl groups such as a benzyl group, a 1-phenylethyl group, and a 2-phenylethyl group; and groups obtained by combining these, and an aryl group is preferable. Some of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like.
Rct1 and Rct2 may bond together to form a ring with the sulfur atom to which they are attached. In this case, examples of the structure of the ring at this time are those having the following formula.
Specific examples of the sulfonium cation having formula (cation-1) are shown below, but not limited thereto.
Specific examples of the iodonium cation having formula (cation-2) are shown below, but not limited hereto.
Specific examples of the onium salt of the present invention include arbitrary combinations of anions with cations, both as exemplified above.
The onium salt of the present invention can be synthesized by a known method. As an example, a method for producing an onium salt having the following formula (PAG-1-ex) is described, but the synthesis method is not limited thereto.
The first step is to produce Intermediate In-1 by reaction between Raw Material SM-1 and Raw Material SM-2, which is commercially available or can be obtained by a known synthesis method. Various condensing agents can be used when an ester bond is formed directly from the carboxy group in Raw Material SM-1 and the hydroxy group in Raw Material SM-2. Examples of the condensing agent to be used include N,N′-dicyclohexylcarbodiimide, N,N′-diisopropylcarbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and from the viewpoint of easy removal of a urea compound formed as the by-product after the reaction, it is preferred to use 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The reaction is performed by dissolving Raw Material SM-1 and Raw Material SM-2 in a halogen-based solvent such as methylene chloride and adding a condensing agent. The reaction rate can be improved by adding 4-dimethylaminopyridine (DMAP) as a catalyst. The reaction time is determined as appropriate by monitoring the reaction process by silica gel thin layer chromatography (TLC) because it is desirable from the yield percentage aspect to drive the reaction to completion, but the reaction time is usually about 12 to 24 hours. After stopping the reaction, if necessary, the urea compound produced as a by-product is removed by filtration or water washing, and then the reaction solution is subjected to ordinary aqueous work-up, whereby Intermediate In-1 can be obtained. The resulting Intermediate In-1 may be purified by a conventional method such as chromatography, or recrystallization, if necessary.
The second step is to obtain an onium salt (PAG-1-ex) by subjecting the resulting Intermediate In-1 to salt exchange with an onium salt (Raw Material SM-3) represented by Z+X−. As X−, a chloride ion, a bromide ion, an iodide ion, or a methylsulfate anion is preferable because the exchange reaction easily proceeds in a quantitative manner. The progress of the reaction is desirably confirmed by TLC in terms of yield percentage. An onium salt (PAG-1-ex) can be obtained by subjecting the reaction mixture to ordinary aqueous work-up. The resulting onium salt can be purified by a conventional method such as chromatography, or recrystallization, if necessary.
In the above scheme, the ion exchange in the second step may be readily performed by a known method, for example, with reference to JP-A 2007-145797.
The producing method is merely exemplary and the method for producing an onium salt of the present invention is not limited thereto.
As a structural feature of the onium salt of the present invention, there are mentioned a ring-condensed structure having a substituent and an alkanesulfonic acid structure containing a trifluoromethyl group and having 5 or more fluorine atoms are introduced into an anion. The ring-condensed structure having a substituent has a large excluded volume, functions as a bulky substituent, and highly suppresses diffusion of the generated acid. The ring-condensed structure having a substituent has resistance to an alkaline developer to reduce film loss of a pattern of an unexposed area. Meanwhile, the alkanesulfonic acid structure containing a trifluoromethyl group and having 5 or more fluorine atoms increases the acidity of the generated acid to deprotect an acid labile group of a base polymer, and the carbon atom to which the trifluoromethyl group is bonded becomes an asymmetric carbon, thereby generating an isomer in the anion. The generation of the isomer lowers the crystallization ability of a target product, and an increase in the number of fluorine atoms improves the solvent solubility. Since the fluorine atom is an element having a high EUV light absorption effect although not as high as the iodine atom, the generation amount of secondary electrons increases as the number of fluorine atoms increases, and the decomposition of cations is promoted, which contributes to high sensitivity. JP 7109178 proposes alkanesulfonic acid type photoacid generators having 2 to 4 fluorine atoms, but since these photoacid generators do not produce isomers and have poor solvent solubility, there is a concern of development defects, and since the number of fluorine atoms is smaller than that of the photoacid generator of the present invention, it is expected that these photoacid generators contribute less to higher sensitivity. Due to these synergistic effects, the resist composition containing the onium salt of the present invention has high sensitivity and low acid diffusibility, and thus is excellent in LWR of a line pattern and CDU of a hole pattern, and enables pattern formation resistant to pattern collapse, and thus is suitable for fine pattern formation.
The onium salt can be suitably used as a photoacid generator.
A chemically amplified resist composition of the present invention comprises (A) a photoacid generator comprising the onium salt having formula (1) as an essential component.
In the chemically amplified resist composition of the present invention, the content of the photoacid generator comprising the onium salt having formula (1) of the component (A) is preferably 0.1 to 40 parts by weight and more preferably 0.5 to 30 parts by weight per 80 parts by weight of a base polymer described below. When the content of the component (A) is in the above range, the sensitivity and resolution are favorable, and there is no possibility that a problem of foreign matter occurs after development or peeling of the resist film, which is preferable. The photoacid generator of the component (A) may be used alone or in combination of two or more kinds thereof.
The chemically amplified resist composition of the present invention may comprise a base polymer as a component (B). The base polymer (B) comprises repeat units having the following formula (a1) (also referred to as repeat units a1, hereinafter).
In formula (a1), RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.
In formula (a1), X1 is a single bond, a phenylene group, a naphthylene group, or *—C(═O)—O—X11—, the phenylene group or the naphthylene group may be substituted with a C1-C10 alkoxy group which may contain a fluorine atom, or a halogen atom. X11 is a C1-C10 saturated hydrocarbylene group, a phenylene group, or a naphthylene group, the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * designates a point of attachment to the carbon atom in the backbone.
In formula (a1), AL1 is an acid labile group. Examples of the acid labile group include those groups described in JP-A 2013-80033 and JP-A 2013-83821.
Typical examples of the acid labile group include groups having the following formulae (AL-1) to (AL-3).
In formulae (AL-1) and (AL-2), RL1 and RL2 are each independently a C1-C40 hydrocarbyl group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. The hydrocarbyl group is preferably a C1-C20 saturated hydrocarbyl group.
In formula (AL-1), k is an integer of 0 to 10 and preferably an integer of 1 to 5.
In formula (AL-2), RL3 and RL4 are each independently a hydrogen atom or a C1-C20 hydrocarbyl group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. The hydrocarbyl group is preferably a C1-C20 saturated hydrocarbyl group. Any two of RL2, RL3, and RL4 may bond together to form a C3-C20 ring with the carbon atom or carbon and oxygen atoms to which they are attached. The ring is preferably a C4-C16 ring and particularly preferably an alicyclic ring.
In formula (AL-3), RL5, RL6, and RL7 are each independently a C1-C20 hydrocarbyl group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. The hydrocarbyl group is preferably a C1-C20 saturated hydrocarbyl group. Any two of RL5, RL6, and RL7 may bond together to form a C3-C20 ring with the carbon atom to which they are attached. The ring is preferably a C4-C16 ring and particularly preferably an alicyclic ring.
Specific examples of the repeat units a1 are shown below, but not limited thereto. In the following formula, RA and AL1 are as defined above.
The base polymer may further comprise repeat units having the following formula (a2) (also referred to as repeat units a2, hereinafter).
In formula (a2), RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X2 is a single bond or *—C(═O)—O—. * designates a point of attachment to the carbon atom in the backbone. R11 is a halogen atom, a cyano group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. AL2 is an acid labile group. Examples of the acid labile group are as exemplified above for the acid labile group represented by AL1. a is an integer of 0 to 4, preferably 0 or 1.
Specific examples of the repeat units a2 are shown below, but not limited thereto. In the following formula, RA and AL2 are as defined above.
The base polymer preferably further comprises repeat units having the following formula (b1) (also referred to as repeat units b1, hereinafter) or repeat units having the following formula (b2) (also referred to as repeat units b2, hereinafter).
In formulae (b1) and (b2), RA is each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y1 is a single bond or *—C(═O)—O—. * designates a point of attachment to the carbon atom in the backbone. R21 is a hydrogen atom or a C1-C20 group containing at least one or more structures selected from a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (—C(═O)—O—C(═O)—). R22 is a halogen atom, a hydroxy group, a nitro group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. b is an integer of 1 to 4. c is an integer of 0 to 4. Provided that b+c is from 1 to 5.
Specific examples of the repeat units b1 are shown below, but not limited thereto. In the following formula, RA is as defined above.
Specific examples of the repeat units b2 are shown below, but not limited thereto. In the following formula, RA is as defined above.
As the repeat units b1 or b2, those units having a lactone ring as a polar group are particularly preferred in the case of ArF lithography, and those units having a phenol site as a polar group are preferred in the case of KrF lithography, EB lithography, and EUV lithography.
The base polymer may further include at least one selected from repeat units having the following formula (c1) (also referred to as repeat units c1, hereinafter), repeat units having the following formula (c2) (also referred to as repeat units c2, hereinafter), repeat units having the following formula (c3) (also referred to as repeat units c3, hereinafter), and repeat units having the following formula (c4) (also referred to as repeat units c4, hereinafter).
In formulae (c1) to (c4), RA is each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z1 is a single bond or a phenylene group. Z2 is *—C(═O)—O—Z21—, *—C(═O)—NH—Z21—, or *—O—Z21—. Z21 is a C1-C6 aliphatic hydrocarbylene group, a phenylene group, or a divalent group obtained by combining the foregoing, which may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z3 is each independently a single bond, a phenylene group, a naphthylene group, or *—C(═O)—O—Z31. Z31 is a C1-C10 aliphatic hydrocarbylene group, a phenylene group, or a naphthylene group, the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z4 is each independently a single bond, **—Z41—C(═O)—O—, **—C(═O)—NH—Z41, or **—O—Z41. Z41 is a C1-C20 hydrocarbylene group which may contain a heteroatom. Z5 is each independently a single bond, *—Z51—C(═O)—O—, *—C(═O)—NH—Z51—, or *—O—Z51—. Z51 is a C1-C20 hydrocarbylene group which may contain a heteroatom. Z6 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a trifluoromethyl group-substituted phenylene group, *—C(═O)—Z61—, *—C(═O)—N(H)—Z61—, or *—O—Z61. Z61 is a C1-C6 aliphatic hydrocarbylene group, a phenylene group, a fluorinated phenylene group, or a trifluoromethyl group-substituted phenylene group, which may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * designates a point of attachment to the carbon atom in the backbone. ** designates a point of attachment to Z3.
The aliphatic hydrocarbylene group represented by Z21, Z31, and Z61 may be straight, branched, or cyclic, and specific examples thereof include alkanediyl groups such as a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-2,3-diyl group, a butane-1,4-diyl group, a 1,1-dimethylethane-1,2-diyl group, a pentane-1,5-diyl group, a 2-methylbutane-1,2-diyl group, and a hexane-1,6-diyl group; cycloalkanediyl groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these.
The hydrocarbylene group represented by Z41 and Z51 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are shown below, but not limited thereto.
In formula (c1), R31 and R32 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C20 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group; C3-C20 cyclic saturated hydrocarbyl groups such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group, and an adamantyl group; C2-C20 alkenyl groups such as a vinyl group, an allyl group, a propenyl group, a butenyl group, and a hexenyl group; C3-C20 cyclic unsaturated hydrocarbyl groups such as a cyclohexenyl group; C6-C20 aryl groups such as a phenyl group, a naphthyl group, and a thienyl group; C7-C20 aralkyl groups such as a benzyl group, a 1-phenylethyl group, and a 2-phenylethyl group; and groups obtained by combining these, and an aryl group is preferable. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like.
R31 and R32 may bond together to form a ring with the sulfur atom to which they are attached. In this case, examples of the ring are as exemplified above for the ring that Rct1 and Rct2 in the description of formula (cation-1) may bond together to form with the sulfur atom to which they are attached.
Specific examples of the cation of the repeat units c1 are shown below, but not limited thereto. In the following formula, RA is as defined above.
In formula (c1), M− is a non-nucleophilic counter ion. The non-nucleophilic counter ion is preferably a halide ion, a sulfonic acid anion, an imidic acid anion, and a methidate anion. Specific examples of the halide ion include a chloride ion and a bromide ion. Specific examples of the sulfonic acid anion (sulfonate ion) include fluoroalkyl sulfonate ions such as a triflate ion, a 1,1,1-trifluoroethane sulfonate ion, and a nonafluorobutane sulfonate ion; aryl sulfonate ions such as a tosylate ion, a benzene sulfonate ion, a 4-fluorobenzenesulfonate ion, and a 1,2,3,4,5-pentafluorobenzenesulfonate ion; and alkyl sulfonate ions such as mesylate ions and butanesulfonate ions. Specific examples of the imidic acid anion (imide ion) include a bis(trifluoromethylsulfonyl)imide ion, a bis(perfluoroethylsulfonyl)imide ion, and a bis(perfluorobutylsulfonyl)imide ion. Specific examples of the methidate anion (methide ion) include imide ions such as a bis(trifluoromethylsulfonyl)imide ion, a bis(perfluoroethylsulfonyl)imide ion, and a bis(perfluorobutylsulfonyl)imide ion; a tris(trifluoromethylsulfonyl)methide ion, and a tris(perfluoroethylsulfonyl)methide ion.
Other examples of the non-nucleophilic counter ion include anions having any one of the following formulae (c1-1) to (c1-4).
In formula (c1-1), Rfa is a fluorine atom, or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by Rfa1 in formula (c1-1-1) described below.
The anion having formula (c1-1) preferably has the following formula (c1-1-1).
In formula (c1-1-1), Q11 and Q12 are each independently a hydrogen atom, a fluorine atom, or a C1-C6 fluorinated saturated hydrocarbyl group, but at least one of Q11 and Q12 is preferably a trifluoromethyl group for improving solvent solubility. m is an integer of 0 to 4, but is particularly preferably 1. Rfa1 is a C1-C35 hydrocarbyl group which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, and more preferably an oxygen atom. The hydrocarbyl group is particularly preferably a C6-C30 hydrocarbyl group from the viewpoint of obtaining a high resolution in fine pattern formation.
In formula (c1-1-1), the C1-C35 hydrocarbyl group represented by R11 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C35 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, a nonyl group, an undecyl group, a tridecyl group, a pentadecyl group, a heptadecyl group, and an icosyl group; C3-C35 cyclic saturated hydrocarbyl groups such as a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a 1-adamantylmethyl group, a norbornyl group, a norbornylmethyl group, a tricyclodecyl group, a tetracyclododecyl group, a tetracyclododecylmethyl group, and a dicyclohexylmethyl group; C2-C35 unsaturated aliphatic hydrocarbyl groups such as an allyl group and a 3-cyclohexenyl group; C6-C35 aryl groups such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and a 9-fluorenyl group; C7-C35 aralkyl groups such as a benzyl group and a diphenylmethyl group; and groups obtained by combining these.
Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like. Examples of the heteroatom-containing hydrocarbyl group include a tetrahydrofuryl group, a methoxymethyl group, an ethoxymethyl group, a methylthiomethyl group, an acetamidomethyl group, a trifluoroethyl group, a (2-methoxyethoxy)methyl group, an acetoxymethyl group, a 2-carboxy-1-cyclohexyl group, a 2-oxopropyl group, a 4-oxo-1-adamantyl group, and a 3-oxocyclohexyl group.
In formula (c1-1-1), L1 is a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond, and from the viewpoint of synthesis, is preferably an ether bond or an ester bond and more preferably an ester bond.
Specific examples of the anion having formula (c1-1) are shown below, but not limited thereto. In the following formula, Q11 is as defined above, and Ac is an acetyl group.
In formula (c1-2), Rfb1 and Rfb2 are each independently a fluorine atom, or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by Rfa1 in formula (c1-1-1). Preferably, Rfb1 and Rfb2 each are a fluorine atom or a straight C1-C4 fluorinated alkyl group. Rfb1 and Rfb2 may bond together to form a ring with the group (—CF2—SO2—N—SO2—CF2—) to which they are attached, and in this case, the group obtained by bonding Rfb1 and Rfb2 to each other is preferably a fluorinated ethylene group or a fluorinated propylene group.
In formula (c1-3), Rfc1, Rfc2, and Rfc3 are each independently a fluorine atom, or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by Rfa1 in formula (c1-1-1). Preferably, Rfc1, Rfc2, and Rfc3 each are a fluorine atom or a straight C1-C4 fluorinated alkyl group. Rfc1 and Rfc2 may bond together to form a ring with the group (—CF2—SO2—C—SO2—CF2—) to which they are attached, and in this case, the group obtained by bonding Rfc1 and Rfc2 to each other is preferably a fluorinated ethylene group or a fluorinated propylene group.
In formula (c1-4), Rfd is a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by Rfa1 in formula (c1-1-1).
Specific examples of the anion having formula (c1-4) are shown below, but not limited thereto.
Examples of the non-nucleophilic counter ion further include an anion having an aromatic ring substituted with an iodine atom or a bromine atom. Specific examples of such an anion include those having the following formula (c1-5).
In formula (c1-5), x is an integer satisfying 1≤x≤3. y and z are integers satisfying 1≤y≤5, 0≤z≤3, and 1≤y+z≤5. y is preferably an integer satisfying 1≤y≤3 and more preferably 2 or 3. z is preferably an integer satisfying 0≤z≤2.
In formula (c1-5), XBI is an iodine atom or a bromine atom, and may be the same or different when x and/or y is 2 or more.
In formula (c1-5), L11 is a single bond, an ether bond, an ester bond, or a C1-C6 saturated hydrocarbylene group which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be straight, branched, or cyclic.
In formula (c1-5), L12 is a single bond or a C1-C20 divalent linking group when x is 1, and a C1-C20 (x+1)-valent linking group which may contain an oxygen atom, a sulfur atom, or a nitrogen atom when x is 2 or 3.
In formula (c1-5), Rfe is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a C1-C20 hydrocarbyl group, C1-C20 hydrocarbyloxy group, C2-C20 hydrocarbylcarbonyl group, C2-C20 hydrocarbyloxycarbonyl group, C2-C20 hydrocarbylcarbonyloxy group, or C1-C20 hydrocarbylsulfonyloxy group, which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group, or an ether bond, or —N(RfeA)(RfeB), —N(RfeC)—C(═O)—RfeD, or —N(RfeC)—C(═O)—O—RfeD. RfeA and RfeB are each independently a hydrogen atom or a C1-C6 saturated hydrocarbyl group. RfeC is a hydrogen atom or a C1-C6 saturated hydrocarbyl group, which may contain a halogen atom, a hydroxy group, a C1-C6 saturated hydrocarbyloxy group, a C2-C6 saturated hydrocarbylcarbonyl group, or a C2-C6 saturated hydrocarbylcarbonyloxy group. RfeD is a C1-C16 aliphatic hydrocarbyl group, a C6-C12 aryl group, or a C7-C15 aralkyl group, which may contain a halogen atom, a hydroxy group, a C1-C6 saturated hydrocarbyloxy group, a C2-C6 saturated hydrocarbylcarbonyl group, or a C2-C6 saturated hydrocarbylcarbonyloxy group. The aliphatic hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. The hydrocarbyl group, the hydrocarbyloxy group, the hydrocarbylcarbonyl group, the hydrocarbyloxycarbonyl group, the hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be straight, branched, or cyclic. When x and/or z is 2 or more, respective Rfe may be the same as or different from each other.
Of these, Rfe is preferably a hydroxy group, —N(RfeC)—C(═O)—RfeD, —N(RfeC)—C(═)—O—RfeD, a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, or the like.
In formula (c1-5), Rf11 to Rf14 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of Rf11 to Rf14 is a fluorine atom or a trifluoromethyl group. Rf11 and Rf12, taken together, may form a carbonyl group. Particularly, both Rf11 and Rf14 are preferably a fluorine atom.
Specific examples of the anion having formula (c1-5) are shown below, but not limited thereto. In the following formula, XBI is as defined above.
Other useful examples of the non-nucleophilic counter ion include fluorobenzenesulfonic acid anions having an iodized aromatic ring bonded thereto as described in JP 6648726, anions having an acid-catalyzed decomposition mechanism as described in WO 2021/200056 and JP-A 2021-70692, anions having a cyclic ether group as described in JP-A 2018-180525 and JP-A 2021-35935, and anions as described in JP-A 2018-92159.
Further useful examples of the non-nucleophilic counter ion include an anion of a bulky fluorine-free benzenesulfonic acid derivative as described in JP-A 2006-276759, JP-A 2015-117200, JP-A 2016-65016, and JP-A 2019-202974, and fluorine-free benzenesulfonic acid or alkylsulfonic acid anions having an iodized aromatic group bonded thereto as described in JP 6645464.
Also useful examples of the non-nucleophilic counter ion include bissulfonic acid anions as described in JP-A 2015-206932, sulfonamide or sulfonimide anions having sulfonic acid side and different side as described in WO 2020/158366, and anions having a sulfonic acid side and a carboxylic acid side as described in JP-A 2015-24989.
In formulae (c2) and (c3), L1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond. Of these, from the viewpoint of synthesis, an ether bond, an ester bond, and a carbonyl group are preferable, and an ester bond and a carbonyl group are more preferable.
In formula (c2), Rf1 and Rf2 are each independently a fluorine atom or a C1-C6 fluorinated saturated hydrocarbyl group. Of these, Rf1 and Rf are each preferably a fluorine atom in order to increase the acid strength of the generated acid. Rf3 and Rf4 are each independently a hydrogen atom, a fluorine atom, or a C1-C6 fluorinated saturated hydrocarbyl group. Of these, at least one of Rf3 and Rf4 is preferably a trifluoromethyl group for improving solvent solubility.
In formula (c3), Rf and Rf are each independently a hydrogen atom, a fluorine atom, or a C1-C6 fluorinated saturated hydrocarbyl group. Provided that all Rf and Rf6 are not a hydrogen atom at the same time. Of these, at least one of Rf5 and Rf is preferably a trifluoromethyl group for improving solvent solubility.
In formulae (c2) and (c3), d is an integer of 0 to 3, preferably 1.
Specific examples of the anion of the repeat units c2 are shown below, but not limited thereto. In the following formula, RA is as defined above, and Me is a methyl group.
Specific examples of the anion of the repeat units c3 are shown below, but not limited thereto. In the following formula, RA is as defined above.
Specific examples of the anion of the repeat units c4 are shown below, but not limited thereto. In the following formula, RA is as defined above.
In formulae (c2) to (c4), A+ is an onium cation. Examples of the onium cation include an ammonium cation, a sulfonium cation, and an iodonium cation, and a sulfonium cation and an iodonium cation are preferable. Specific examples thereof include, but are not limited to, as exemplified above for the sulfonium cation having formula (cation-1) and the iodonium cation having formula (cation-2), and as exemplified above for the ammonium cation having formula (cation-3) described below.
Specific structures of the repeat units c1 to c4 include arbitrary combinations of anions with cations, both as exemplified above.
Of the repeat units c1 to c4, from the viewpoint of controlling acid diffusion, the repeat units c2, c3, and c4 are preferable, from the viewpoint of the acid strength of the generated acid, the repeat units c2 and c4 are more preferable, and from the viewpoint of solvent solubility, the repeat unit c2 is still more preferable.
The base polymer may further comprise repeat units having a structure having a hydroxy group protected with an acid labile group (also referred to as repeat units d, hereinafter). The repeat unit d is not particularly limited as long as the unit includes one or two or more structures having a hydroxy group protected with a protective group such that the protective group is decomposed to generate the hydroxy group under the action of acid, but repeat units having the following formula (d1) are preferable.
In formula (d1), RA is as defined above. R41 is a C1-C30 (e+1)-valent hydrocarbon group which may contain a heteroatom. R42 is an acid labile group. e is an integer of 1 to 4.
In formula (d1), the acid labile group represented by R42 may be any group that is deprotected under the action of acid so that a hydroxy group is generated. The structure of R42 is not particularly limited, an acetal structure, a ketal structure, an alkoxycarbonyl group, an alkoxymethyl group having the following formula (d2), and the like are preferable, and an alkoxymethyl group having the following formula (d2) is particularly preferable.
Specific examples of the acid labile group represented by R42, the alkoxymethyl group having formula (d2), and the repeat units d are as exemplified for the repeat units d described in JP-A 2020-111564.
The base polymer may further include repeat units e derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene, or derivatives thereof. Specific examples of the monomer from which repeat units e are derived are shown below, but not limited thereto.
The base polymer may further comprise repeat units f derived from indane, vinylpyridine, or vinylcarbazole.
In the polymer of the present invention, the repeat units a1, a2, b1, b2, c1 to c4, d, e, and f are incorporated in a ratio of preferably 0<a1≤0.8, 0≤a2≤0.8, 0≤b1≤0.6, 0≤b2≤0.6, 0≤c1≤0.4, 0≤c2≤0.4, 0≤c3≤0.4, 0≤c4≤0.4, 0≤d≤0.5, 0≤e≤0.3, and 0≤f≤0.3, more preferably 0<a1≤0.7, 0≤a2≤0.7, 0≤b1≤0.5, 0≤b2≤0.5, 0≤c1≤0.3, 0≤c2≤0.3, 0≤c3≤0.3, 0≤c4≤0.3, 0≤d≤0.3, 0≤e≤0.3, and 0≤f≤0.3.
The weight average molecular weight (Mw) of the polymer is preferably 1,000 to 500,000 and more preferably 3,000 to 100,000. When Mw is in this range, sufficient etching resistance is obtained, and there is no possibility of degradation of resolution due to a failure to acquire a difference in dissolution rate before and after exposure. In the present invention, Mw is a value measured by gel permeation chromatography (GPC) with THF or N,N-dimethylformamide (DMF) as a solvent, and calculated as polystyrene.
Since the influence of the molecular weight distribution (Mw/Mn) becomes stronger as the pattern rule becomes finer, the Mw/Mn of the polymer preferably has narrow dispersity of 1.0 to 2.0 in order to obtain a resist composition suitable for micropatterning to a small feature size. Within the above range, there is little polymer having a low molecular weight or a high molecular weight, and there is no possibility that foreign matter is observed on the pattern or the shape of the pattern is deteriorated after exposure.
In order to synthesize the polymer, for example, a monomer from which the foregoing repeat units are derived may be heated in an organic solvent with a radical polymerization initiator added thereto to perform polymerization.
Examples of the organic solvent used during polymerization include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1′-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The initiator is preferably added in an amount of 0.01 to 25 mol % based on the total of monomers to be polymerized. The reaction temperature is preferably 50 to 150° C., more preferably 60 to 100° C. The reaction time is preferably 2 to 24 hours, more preferably 2 to 12 hours from the viewpoint of production efficiency.
The polymerization initiator may be fed to the reactor either by adding the initiator to the monomer solution and feeding the solution to the reactor, or by dissolving the initiator in a solvent to form an initiator solution and feeding the initiator solution and the monomer solution independently to the reactor. Because of a possibility that in the standby duration, the initiator generates a radical which triggers polymerization reaction to form an ultra high-molecular-weight polymer, it is preferred from the viewpoint of quality control to prepare the monomer solution and the initiator solution separately and add them dropwise. The acid labile group that has been incorporated in the monomer may be kept as such, or polymerization may be followed by protection or partial protection. Any known chain transfer agent such as dodecyl mercaptan or 2-mercaptoethanol may be used in combination for molecular weight control purpose. In this case, these chain transfer agents are preferably added in an amount of 0.01 to 20 mol % based on the total of monomers to be polymerized.
In the case of a monomer containing a hydroxy group, the hydroxy group may be substituted with an acetal group susceptible to deprotection with an acid such as an ethoxyethoxy group during polymerization, and then deprotected by a weak acid and water, or may be substituted with an acetyl group, a formyl group, a pivaloyl group, or the like, and then alkaline hydrolysis may be performed after polymerization.
When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, hydroxystyrene or hydroxyvinylnaphthalene and another monomer may be heated and polymerized by adding a radical polymerization initiator in an organic solvent, but acetoxystyrene or acetoxyvinylnaphthalene may be used, and the acetoxy group may be deprotected by alkaline hydrolysis after polymerization to obtain polyhydroxystyrene or hydroxypolyvinylnaphthalene.
As a base during the alkaline hydrolysis, aqueous ammonia, triethylamine, or the like can be used. The reaction temperature is preferably −20 to 100° C. and more preferably 0 to 60° C. The reaction time is preferably 0.2 to 100 hours and more preferably 0.5 to 20 hours.
The amount of each monomer in the monomer solution may be appropriately set, for example, so as to have a preferred content ratio of the repeat units.
Regarding the polymer obtained by the production method, a reaction solution resulting from polymerization reaction may be used as a final product, or a powder obtained through a purifying step such as re-precipitation method in which a polymerization liquid is added to a poor solvent to obtain a powder may be used as a final product, but from the viewpoints of operation efficiency and consistent quality, it is preferable to use a polymer solution obtained by dissolving the powder resulting from the purifying step in a solvent as a final product.
Specific examples of the solvent used at that time 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 (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, 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 mono-tert-butyl ether acetate; lactones such as GBL; alcohols such as diacetone alcohol (DAA); high-boiling-point alcohol-based solvents such as diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol; and a mixed solvent thereof, which are described in JP-A 2008-111103, paragraphs [0144] to [0145].
The polymer solution preferably has a polymer concentration of 0.01 to 30 wt %, more preferably 0.1 to 20 wt %.
The reaction solution or polymer solution is preferably filtered through a filter. Filtration is effective in terms of consistent quality because foreign matter and gel which may cause defects can be removed.
Examples of the material for the filter used for the filter filtration include fluorocarbon-based, cellulose-based, nylon-based, polyester-based, and hydrocarbon-based materials, and in the filtration step of the resist composition, a filter formed of a fluorocarbon-based material called Teflon®, a hydrocarbon-based material such as polyethylene and polypropylene, or nylon is preferable. While the pore size of the filter may be selected appropriate to comply with the desired cleanness, the filter preferably has a pore size of 100 nm or less, more preferably 20 nm or less. A single filter may be used or a plurality of filters may be used in combination. Although the filtering method may be single pass of the solution, more preferably the filtering step is repeated by flowing the solution in a circulating manner. In the polymer production step, the filtration step may be carried out any times, in any order and in any stage, but the reaction solution after the polymerization reaction or the polymer solution may be filtered, preferably both are filtered.
The base polymer (B) may be used alone or in combination of two or more polymers which are different in compositional ratio, Mw and/or Mw/Mn. The base polymer (B) may contain a hydrogenated ring-opened metathesis polymer in addition to the polymer, and as the hydrogenated ring-opened metathesis polymer, a polymer described in JP-A 2003-66612 can be used.
The chemically amplified resist composition of the present invention may comprise an organic solvent as a component (C). The organic solvent (C) is not particularly limited as long as each component described above and each component described below can be dissolved. Examples of such an organic solvent include ketones such as cyclopentanone, 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; ketoalcohols such as DAA; ethers such as PGME, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, 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 mono-tert-butyl ether acetate; lactones such as GBL, and mixed solvents thereof.
Of the foregoing organic solvents, it is recommended to use 1-ethoxy-2-propanol, PGMEA, cyclohexanone, GBL, DAA, and mixed solvents thereof because the base polymer of the component (B) is most soluble therein.
The content of the organic solvent (C) in the chemically amplified resist composition of the present invention is preferably 200 to 5000 parts by weight and more preferably 400 to 3500 parts by weight per 80 parts by weight of the base polymer (B). The organic solvent (C) may be used alone or in admixture of two or more kinds thereof.
The chemically amplified resist composition of the present invention may comprise a quencher as a component (D). In the present invention, the quencher is a material capable of trapping the acid generated by the photoacid generator in the chemically amplified resist composition to prevent the acid from diffusing to the unexposed area, for thereby forming a desired pattern.
Examples of the quencher (D) include an onium salt having the following formula (2) or (3).
In formula (2), Rq1 is a hydrogen atom or a C1-C40 hydrocarbyl group which may contain a heteroatom, exclusive of the hydrocarbyl group in which the hydrogen atom bonded to the carbon atom at α-position of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group. In formula (3), Rq2 is a hydrogen atom or a C1-C40 hydrocarbyl group which may contain a heteroatom.
Specific examples of the C1-C40 hydrocarbyl group represented by Rq1 include C1-C40 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, a sec-propyl group, a n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, a tert-pentyl group, a n-hexyl group, a n-octyl group, a 2-ethylhexyl group, a n-nonyl group, and a n-decyl group; C3-C40 cyclic saturated hydrocarbyl groups such as a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, a tricyclo[5.2.1.02,6]decyl group, and an adamantyl group; and C6-C40 aryl groups such as a phenyl group, a naphthyl group, and an anthracenyl group. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like.
Specific examples of the hydrocarbyl group represented by Rq2 include, in addition to the substituents exemplified as specific examples of Rq1, fluorinated saturated hydrocarbyl groups such as a trifluoromethyl group and a trifluoroethyl group, and fluorinated aryl groups such as a pentafluorophenyl group and a 4-trifluoromethylphenyl group.
Specific examples of the anion of the onium salt having formula (2) are shown below, but not limited thereto.
Specific examples of the anion of the onium salt having formula (3) are shown below, but not limited thereto.
In formulae (2) and (3), Mq+ is an onium cation. The onium cation is preferably a sulfonium cation having formula (cation-1) described above, an iodonium cation having formula (cation-2) described above, or an ammonium cation having the following formula (cation-3).
In formula (cation-3), Rct6 to Rct9 are each independently a C1-C40 hydrocarbyl group which may contain a heteroatom. Rct6 and Rct7 may bond together to form a ring with the nitrogen atom to which they are attached. Examples of the hydrocarbyl group are as exemplified above for the hydrocarbyl group represented by Rct1 to Rct5 in the description of formulae (cation-1) and (cation-2).
Specific examples of the ammonium cation having formula (cation-3) are shown below, but not limited thereto.
Specific examples of the onium salt having formula (2) or (3) include arbitrary combinations of anions with cations, both as exemplified above. These onium salts are easily prepared by an ion exchange reaction using a known organic chemical method. For the ion exchange reaction, for example, JP-A 2007-145797 can be referred to.
The onium salt having formula (2) or (3) acts as a quencher in the chemically amplified resist composition of the present invention. This is because each counter anion of the onium salt is a conjugate base of a weak acid. The weak acid as used herein means an acid having an acidity at which the acid labile group of the acid labile group-containing unit used for the base polymer cannot be deprotected. The onium salt having formula (2) or (3) functions as a quencher when used in combination with an onium salt type photoacid generator having a conjugate base of a strong acid such as a sulfonic acid whose α-position is fluorinated as a counter anion. That is, in the case of mixing an onium salt generating a strong acid such as a sulfonic acid whose α-position is fluorinated and an onium salt generating a weak acid such as a sulfonic acid or a carboxylic acid that is not fluorinated for use, when the strong acid generated from the photoacid generator by irradiation with high-energy radiation collides with an unreacted onium salt having a weak acid anion, the strong acid is released by salt exchange to produce an onium salt having a strong acid anion. In this process, the strong acid is exchanged to a weak acid having lower catalytic ability, so that the acid is apparently deactivated and acid diffusion can be controlled.
As the quencher (D), the onium salt having a sulfonium cation and a phenoxide anion moiety within one molecule described in JP 6848776, the onium salts having a sulfonium cation and a carboxylate anion moiety within one molecule described in JP 6583136 and JP-A 2020-200311, and the onium salt having an iodonium cation and a carboxylate anion moiety within one molecule described in JP 6274755 can also be used.
When the photoacid generator capable of generating a strong acid is an onium salt, an exchange from the strong acid generated by irradiation with high-energy radiation to a weak acid as described above can take place; however, it is considered that the weak acid generated by irradiation with high-energy radiation collides with the unreacted onium salt generating a strong acid, so that it is difficult to perform a salt exchange. This is due to the phenomenon that the onium cation easily forms an ion pair with an anion of a stronger acid.
When the chemically amplified resist composition of the present invention comprises the onium salt having formula (2) or (3) as the quencher (D), the content thereof is preferably 0.1 to 20 parts by weight and more preferably 0.1 to 10 parts by weight per 80 parts by weight of the base polymer (B). When the content of the onium salt type quencher of the component (D) is in the above range, the resolution is favorable, and the sensitivity is not significantly lowered, which is preferable. The onium salt having formula (2) or (3) can be used alone or in combination of two or more kinds thereof.
The chemically amplified resist composition of the present invention may comprise a nitrogen-containing compound as the quencher (D). Examples of the nitrogen-containing compound of the component (D) include primary, secondary, and tertiary amine compounds, specifically amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonic acid ester bond as described in JP-A 2008-111103, paragraphs [0146] to [0164]. As in the compound described in JP 3790649, a compound in which a primary or secondary amine is protected with a carbamate group can also be mentioned.
A sulfonium sulfonate having a nitrogen-containing substituent may be used as the nitrogen-containing compound. Such a compound functions as a quencher in the unexposed area, and the exposed area functions as a so-called photodegradable base that loses quencher capability by neutralization with its own generated acid. By using the photodegradable base, the contrast between the exposed area and the unexposed area can be further enhanced. As the photodegradable base, for example, JP-A 2009-109595, JP-A 2012-46501, and the like can be referred to.
When the chemically amplified resist composition of the present invention comprises the nitrogen-containing compound as the quencher (D), the content thereof is preferably 0.001 to 12 parts by weight and more preferably 0.01 to 8 parts by weight per 80 parts by weight of the base polymer (B). The nitrogen-containing compound may be used alone or in combination of two or more kinds thereof.
The chemically amplified resist composition of the present invention may comprise a photoacid generator other than the component (A) (also referred to as other photoacid generator, hereinafter) as a component (E). The other photoacid generator is not particularly limited as long as it is a compound capable of generating an acid by irradiation with high-energy radiation. Examples of suitable other photoacid generators include those having the following formula (4) or (5).
In formula (4), R101 to R105 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom. Any two of R101, R102, and R103 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the hydrocarbyl group are as exemplified above for the hydrocarbyl group represented by Rct1 to Rct5 in the description of formulae (cation-1) and (cation-2).
Specific examples of the cation of the sulfonium salt having formula (4) are exemplified above for the sulfonium cation having formula (cation-1). Specific examples of the cation of the iodonium salt having formula (5) are exemplified above for the iodonium cation having formula (cation-2).
In formulae (4) and (5), Xa− is an anion of a strong acid. Examples of the anion of the strong acid include those having any one of formulae (c1-1) to (c1-5).
The other photoacid generator of the component (E) preferably has the following formula (6).
In formula (6), R201 and R202 are each independently a C1-C30 hydrocarbyl group which may contain a heteroatom. R203 is a C1-C30 hydrocarbylene group which may contain a heteroatom. Any two of R201, R202, and R203 may bond together to form a ring with the sulfur atom to which they are attached.
The C1-C30 hydrocarbyl group represented by R201 to R202 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C30 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a tert-pentyl group, a n-pentyl group, a n-hexyl group, a n-octyl group, a 2-ethylhexyl group, a n-nonyl group, and a n-decyl group; C3-C30 cyclic saturated hydrocarbyl groups such as a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, an oxanorbornyl group, a tricyclo[5.2.1.02,6]decyl group, and an adamantyl group; C6-C30 aryl groups such as a phenyl group, a methylphenyl group, an ethylphenyl group, a n-propylphenyl group, an isopropylphenyl group, a n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, a n-propylnaphthyl group, an isopropylnaphthyl group, a n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, a tert-butylnaphthyl group, and an anthracenyl group; and groups obtained by combining these. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like.
The C1-C30 hydrocarbylene group represented by R203 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include C1-C30 alkanediyl groups such as a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, and a heptadecane-1,17-diyl group; C3-C30 cyclic saturated hydrocarbylene groups such as a cyclopentanediyl group, a cyclohexanediyl group, a norbornanediyl group, and an adamantanediyl group; and arylene groups such as a phenylene group, a methylphenylene group, an ethylphenylene group, a n-propylphenylene group, an isopropylphenylene group, a n-butylphenylene group, an isobutylphenylene group, a sec-butylphenylene group, a tert-butylphenylene group, a naphthylene group, a methylnaphthylene group, an ethylnaphthylene group, a n-propylnaphthylene group, an isopropylnaphthylene group, a n-butylnaphthylene group, an isobutylnaphthylene group, a sec-butylnaphthylene group, and a tert-butylnaphthylene group. Some or all of the hydrogen atoms in the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, some of —CH2— in the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, so that the group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (—C(═O)—O—C(═O)—), a haloalkyl group, or the like. The heteroatom is preferably an oxygen atom.
In formula (6), LA is a single bond, an ether bond, or a C1-C20 hydrocarbylene group which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbylene group represented by R203.
In formula (6), Xa, Xb, Xc, and Xd are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group. Provided that at least one of Xa, Xb, Xc, and Xd is a fluorine atom or a trifluoromethyl group.
The photoacid generator having formula (6) preferably has the following formula (6′).
In formula (6′), LA is as defined above. Xe is a hydrogen atom or a trifluoromethyl group and preferably a trifluoromethyl group. R301, R302, and R303 are each independently a hydrogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof are as exemplified above for the hydrocarbyl group represented by Rfa1 in formula (c1-1-1). p and q are each independently an integer of 0 to 5, and r is an integer of 0 to 4.
Examples of the photoacid generator having formula (6) are as exemplified for the photoacid generator having formula (2) in JP-A 2017-26980.
Of the foregoing other photoacid generators, those having an anion of formula (c1-1-1) or (c1-4) are particularly preferred because of reduced acid diffusion and high solubility in the solvent. Those having formula (6′) are particularly preferred because of extremely reduced acid diffusion.
When the chemically amplified resist composition of the present invention comprises the other photoacid generator (E), the content thereof is preferably 0.1 to 40 parts by weight and more preferably 0.5 to 20 parts by weight per 80 parts by weight of the base polymer (B). When the added amount of the photoacid generator of the component (E) is in the above range, the resolution is favorable, and there is no possibility that a problem of foreign matter occurs after development or peeling of the resist film, which is preferable. The other photoacid generator (E) may be used alone or in combination of two or more kinds thereof.
The chemically amplified resist composition of the present invention may further comprise a surfactant as a component (F). The surfactant (F) is preferably a surfactant insoluble or sparingly soluble in water and soluble in an alkaline developer, or a surfactant insoluble or sparingly soluble in water and an alkaline developer. As such a surfactant, those described in JP-A 2010-215608 and JP-A 2011-16746 can be referred to.
As the surfactant insoluble or sparingly soluble in water and an alkaline developer, among the surfactants described in the above publication, FC-4430 (manufactured by 3M), SURFLON® S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), OLFINE® E1004 (manufactured by Nissin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), an oxetane ring-opening polymer having the following formula (surf-1), and the like are preferable.
R, Rf, A, B, C, m, and n apply only to formula (surf-1), regardless of the foregoing description. R is a di- to tetra-valent C2-C5 aliphatic group. Examples of the divalent aliphatic group include an ethylene group, a 1,4-butylene group, a 1,2-propylene group, a 2,2-dimethyl-1,3-propylene group, and a 1,5-pentylene group, and examples of the tri- and tetra-valent aliphatic group are shown below.
Of these, a 1,4-butylene group, a 2,2-dimethyl-1,3-propylene group, and the like are preferable.
Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer of 0 to 3, n is an integer of 1 to 4, and the sum of n and m, which represents the valence of R, is an integer of 2 to 4. A is 1. B is an integer of 2 to 25, preferably an integer of 4 to 20. C is an integer of 0 to 10, preferably 0 or 1. Each constituent unit in formula (surf-1) does not prescribe the arrangement thereof, and may be arranged either blockwise or randomly. For the preparation of surfactants in the form of partially fluorinated oxetane ring-opened polymers, reference should be made to U.S. Pat. No. 5,650,483 and the like.
When a resist protective film is not used in ArF immersion lithography, the surfactant insoluble or sparingly soluble in water and soluble in an alkaline developer has a function of minimizing water penetration or leaching by being oriented on the surface of the resist film. Therefore, the surfactant is useful for preventing water-soluble components from being leached out of the resist film for minimizing any damage to the exposure tool, and is also useful because it becomes solubilized during alkaline aqueous solution development after exposure or after post exposure bake (PEB), and thus forms few or no foreign matter which become defects. Such a surfactant has a property of being insoluble or sparingly soluble in water and being soluble in an alkaline developer, is also called a polymeric surfactant, and is particularly preferably a surfactant having high water repellency and improving lubricity.
Specific examples of such a polymeric surfactant include those containing at least one selected from repeat units having any one of the following formulae (7A) to (7E).
In formulae (7A) to (7E), RB is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. W1 is —CH2—, —CH2CH2—, —O—, or two separate —H. Rs1 is each independently a hydrogen atom or a C1-C10 hydrocarbyl group. Rs2 is a single bond or a C1-C5 straight or branched hydrocarbylene group. Rs3 is each independently a hydrogen atom, a C1-C15 hydrocarbyl group or fluorinated hydrocarbyl group, or an acid labile group. When Rs3 is a hydrocarbyl group or fluorinated hydrocarbyl group, an ether bond or a carbonyl group may intervene in a carbon-carbon bond. Rs4 is a C1-C20 (u+1)-valent hydrocarbon group or fluorinated hydrocarbon group. u is an integer of 1 to 3. Rs5 is each independently a hydrogen atom or a group having —C(═O)—O—Rsa. Rsa is a C1-C20 fluorinated hydrocarbyl group. Rs6 is a C1-C15 hydrocarbyl group or fluorinated hydrocarbyl group, and an ether bond or a carbonyl group may intervene in a carbon-carbon bond thereof.
The C1-C10 hydrocarbyl group represented by Rs1 is preferably a saturated hydrocarbyl group and may be straight, branched, or cyclic. Specific examples thereof include C1-C10 alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, and a n-decyl group; and C3-C10 cyclic saturated hydrocarbyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group, and a norbornyl group. Of these, C1-C6 groups are preferable.
The hydrocarbylene group represented by Rs2 is preferably a saturated hydrocarbylene group and may be straight, branched, or cyclic. Specific examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.
The hydrocarbyl group represented by Rs3 or Rs6 may be saturated or unsaturated and straight, branched, or cyclic. Specific examples thereof include aliphatic unsaturated hydrocarbyl groups such as a saturated hydrocarbyl group, an alkenyl group, and an alkynyl group, and a saturated hydrocarbyl group is preferable. Examples of the saturated hydrocarbyl group include an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group in addition to those exemplified as the hydrocarbyl group represented by Rs1. Examples of the fluorinated hydrocarbyl group represented by Rs3 or Rs6 include groups in which some or all hydrogen atoms bonded to carbon atoms of the foregoing hydrocarbyl group are substituted by fluorine atoms. As described above, an ether bond or a carbonyl group may be interposed between these carbon-carbon bonds.
Specific examples of the acid labile group represented by Rs3 include the groups having formulae (AL-3) to (AL-5) described above, trialkylsilyl groups in which each alkyl group is a C1-C6 alkyl group, and C4-C20 oxo group-containing alkyl groups.
The (u+1)-valent hydrocarbon or fluorinated hydrocarbon group represented by Rs4 may be straight, branched, or cyclic, and specific examples thereof include the foregoing hydrocarbyl or fluorinated hydrocarbyl groups from which “u” number of hydrogen atoms are eliminated.
The fluorinated hydrocarbyl group represented by Rsa is preferably saturated and may be straight, branched, or cyclic. Specific examples thereof include the foregoing hydrocarbyl groups in which some or all hydrogen atoms are substituted by fluorine atoms, 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.
Specific examples of the repeat units having any one of formulae (7A) to (7E) are shown below, but not limited thereto. In the following formula, RB is as defined above.
The polymeric surfactant may further contain repeat units other than the repeat units having formulae (7A) to (7E). Examples of the other repeat units include repeat units derived from methacrylic acid, an α-trifluoromethylacrylic acid derivative, or the like. In the polymeric surfactant, the content of the repeat units having formulae (7A) to (7E) is preferably 20 mol % or more, more preferably 60 mol % or more, and still more preferably 100 mol % of the overall repeat units.
The Mw of the polymeric surfactant is preferably 1,000 to 500,000, more preferably 3,000 to 100,000. Mw/Mn is preferably 1.0 to 2.0, more preferably 1.0 to 1.6.
Examples of the method for synthesizing the polymeric surfactant include a method of dissolving an unsaturated bond-containing monomer providing repeat units having formulae (7A) to (7E) and optionally other repeat units in an organic solvent, adding a radical initiator, and heating for polymerization. Examples of the organic solvent used in the polymerization include toluene, benzene, THF, diethyl ether, and dioxane. Examples of the polymerization initiator include AIBN, 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 100° C. The reaction time is preferably 4 to 24 hours. The acid labile group that has been incorporated in the monomer may be kept as such, or polymerization may be followed by protection or partial protection.
In the case of synthesizing the polymeric surfactant, any known chain transfer agent such as dodecyl mercaptan or 2-mercaptoethanol may be used for molecular weight control purpose. In this case, these chain transfer agents are preferably added in an amount of 0.01 to 10 mol % based on the total number of moles of monomers to be polymerized.
When the chemically amplified resist composition of the present invention comprises the surfactant (F), the content thereof is preferably 0.1 to 50 parts by weight and more preferably 0.5 to 10 parts by weight per 80 parts by weight of the base polymer (B). When the content of the surfactant (F) is 0.1 parts by weight or more, the receding contact angle with water of the resist film at its surface is sufficiently improved, and when the content thereof is 50 parts by weight or less, the dissolution rate of the resist film at its surface in the developer is low, and the height of the formed fine pattern is sufficiently maintained. The surfactant (F) may be used alone or in combination of two or more kinds thereof.
The chemically amplified resist composition of the present invention may comprise a compound which is decomposed with an acid to generate another acid (acid amplifier compound), an organic acid derivative, a fluorinated alcohol, a compound having a Mw of 3,000 or less which changes its solubility in a developer under the action of acid (dissolution inhibitor), and the like as other components (G). As the acid amplifier compound, a compound described in JP-A 2009-269953 or JP-A 2010-215608 can be referred to. When the chemically amplified resist composition comprises the acid amplifier compound, the content thereof is preferably 0 to 5 parts by weight and more preferably 0 to 3 parts by weight per 80 parts by weight of the base polymer (B). When the content thereof is too large, it is difficult to control acid diffusion, and resolution and pattern profile may be deteriorated. As the organic acid derivative, the fluorinated alcohol, and the dissolution inhibitor, compounds described in JP-A 2009-269953 or JP-A 2010-215608 can be referred to.
A pattern forming process of the present invention comprises the steps of: applying the chemically amplified resist composition defined above onto a substrate to form a resist film thereon; exposing the resist film to high-energy radiation; and developing the exposed resist film in a developer.
As the substrate, for example, substrates for integrated circuit fabrication (such as Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, and organic antireflective coating), or substrates for mask circuit fabrication (such as Cr, CrO, CrON, MoSi2, and SiO2) can be used.
The resist film can be formed by, for example, applying the chemically amplified resist composition onto a substrate by a method such as spin coating so that the film thickness is preferably 0.05 to 2 μm, and prebaking the chemically amplified resist composition on a hotplate at preferably 60 to 150° C. for 1 to 10 minutes, more preferably 80 to 140° C. for 1 to 5 minutes.
Examples of the high-energy radiation used for exposure of the resist film include KrF excimer laser, ArF excimer laser, EB, and EUV. In the case of using KrF excimer laser, ArF excimer laser, or EUV, exposure can be performed by using a mask for forming a target pattern and performing irradiation so that the exposure dose is preferably 1 to 200 mJ/cm2, more preferably 10 to 100 mJ/cm2. In the case of using EB, irradiation is performed using a mask for forming a target pattern or directly so that the exposure dose is preferably 1 to 300 μC/cm2, more preferably 10 to 200 μC/cm2.
In addition to a normal exposure method, it is also possible to use an immersion method in which exposure is performed by interposing a liquid having a refractive index of 1.0 or more between a resist film and a projection lens. In this case, it is also possible to use a water-insoluble protective film.
The water-insoluble protective film is used to prevent an eluate from the resist film and to increase the lubricity of the film surface, and is generally divided into two types. The first type is an organic solvent-strippable protective film in which peeling is required before alkaline aqueous solution development by an organic solvent that does not dissolve a resist film, and the second type is an alkaline aqueous solution-soluble protective film which is soluble in an alkaline developer so that the protective film is removed simultaneously with the removal of solubilized regions of the resist film. The protective film of the second type is particularly preferably of a material comprising a polymer having a 1,1,1,3,3,3-hexafluoro-2-propanol residue, which is insoluble in water and soluble in an alkaline developer, as a base and dissolved in an alcohol-based solvent of 4 or more carbon atoms, an ether-based solvent of 8 to 12 carbon atoms, and a mixed solvent thereof. A material obtained by dissolving the surfactant, which is insoluble in water and soluble in an alkaline developer, in an alcohol-based solvent of 4 or more carbon atoms, an ether-based solvent of 8 to 12 carbon atoms, or a mixed solvent thereof can also be used.
After the exposure, PEB may be performed. PEB can be performed, for example, by heating on a hotplate at preferably 60 to 150° C. for 1 to 5 minutes, more preferably 80 to 140° C. for 1 to 3 minutes.
For example, the resist film is developed with a developer in the form of an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH) in an amount of preferably 0.1 to 5 wt %, more preferably 2 to 3 wt % for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes by conventional techniques such as dip, puddle, and spray techniques. In this way, the exposed area is dissolved and a target pattern is formed on the substrate.
After the resist film is formed, the acid generator or the like may be extracted from the film surface by performing rinsing with pure water, or particles may be washed off, or rinsing for removing water remaining on the film after exposure may be performed.
Pattern formation may be performed by a double patterning process. Examples of the double patterning process include a trench process of processing an underlay to 1:3 trench pattern by a first step of exposure and etching, shifting the position, and forming a 1:3 trench pattern by a second step of exposure, for forming a 1:1 pattern, and a line process of processing a first underlay to a 1:3 isolated left pattern by a first step of exposure and etching, shifting the position, processing a second underlay formed below the first underlay by a second step of exposure through the 1:3 isolated left pattern, for forming a half-pitch 1:1 pattern.
In the pattern forming process of the present invention, a method of negative tone development in which an organic solvent is used instead of the alkaline aqueous solution as the developer for dissolving away the unexposed area may be used.
For the organic solvent development, as the developer, 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, 2-phenylethyl acetate, and the like can be used. These organic solvents may be used alone or in admixture of two or more kinds thereof.
Hereinafter, the present invention is specifically described with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples. The devices used are as follows.
In a nitrogen atmosphere, a reaction vessel was charged with Raw Material SM-1 (10.0 g), Raw Material SM-2 (15.9 g), DMAP (0.5 g), and methylene chloride (100 g), and cooled in an ice bath. 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (9.2 g) was added as a powder while the temperature in the reaction vessel was kept at 20° C. or lower. After addition, the reaction mixture was warmed up to room temperature, and aged for 12 hours. After aging, water was added to stop the reaction, ordinary aqueous work-up was performed, the solvent was distilled off, then diisopropyl ether was added thereto, and the residue was washed, thereby obtaining 23.9 g (yield percentage: 98%) of Intermediate In-1 as oily matter.
In a nitrogen atmosphere, Intermediate In-1 (9.2 g), Raw Material SM-3 (6.6 g), methylene chloride (50 g), and water (30 g) were added, the mixture was stirred for 15 minutes, and then the organic layer was taken out, washed with water, and concentrated under reduced pressure. Methyl isobutyl ketone (50 g) was added to the concentrate to perform azeotropic dehydration, and diisopropyl ether was further added to wash the residue, thereby obtaining 11.3 g (yield percentage: 97%) of PAG-1 of a target product as oily matter.
The IR spectrum data and results of TOF-MS of PAG-1 are shown below. The results of the nuclear magnetic resonance spectrum (1H-NMR/DMSO-d6) is shown in
IR(D-ATR): ν=3101, 3061, 2971, 1769, 1708, 1587, 1492, 1468, 1459, 1407, 1371, 1329, 1247, 1186, 1171, 1161, 1130, 1113, 1072, 1009, 992, 930, 912, 887, 874, 838, 763, 736, 703, 642, 607, 577, 553, 519, 438 cm−1.
MALDI TOF-MS:
POSITIVE M+317 (corresponding to C18H12F3S+)
NEGATIVE M-461 (corresponding to C20H14F5O5S−)
Onium Salts PAG-2 to PAG-9 having the following formulae were synthesized using corresponding raw materials and known organic synthesis reactions.
Base polymers (P-1 to P-5) of the composition shown below were synthesized by combining respective monomers, effecting copolymerization reaction in MEK as a solvent, charging the reaction solution into hexane, washing the solid precipitate with hexane, isolation, and drying. The obtained base polymers were analyzed for composition by 1H-NMR spectroscopy and for Mw and Mw/Mn by GPC versus polystyrene standards using THF solvent.
Chemically amplified resist compositions (R-1 to R-30 and CR-1 to CR-20) were prepared by dissolving the onium salt (PAG-1 to PAG-9) of the present invention, a comparative photoacid generator (PAG-A to PAG-E), other photoacid generator (PAG-X, PAG-Y), a base polymer (P-1 to P-5), and a quencher (Q-1 to Q-4) in a solvent containing 0.01 wt % of a surfactant A (OMNOVA Solutions Inc.) in accordance with the formulation shown in Tables 1 and 2 below to prepare a solution, and filtering the solution through a 0.2 μm Teflon® filter.
In Tables 1 and 2, the solvents, the other photoacid generators PAG-X, PAG-Y, the comparative photoacid generators PAG-A to PAG-E, the quenchers Q-1 to Q-4, and the surfactant A are as follows.
Mw=1,500
Each chemically amplified resist composition (R-1 to R-30 and CR-1 to CR-20) shown in Tables 1 to 3 was spin coated on a Si substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 manufactured by Shin-Etsu Chemical Co., Ltd. (content of silicon: 43 wt %) and prebaked on a hotplate at 100° C. for 60 seconds to form a resist film of 50 nm thick. Using an EUV scanner NXE3400 (NA 0.33, a 0.9/0.6, dipole illumination) manufactured by ASML, the resist film was exposed to EUV through a LS pattern having a size of 18 nm and a pitch of 36 nm (on-wafer size) while varying the exposure dose and focus (exposure dose pitch: 1 mJ/cm2, focus pitch: 0.020 μm), and after the exposure, the resist film was subjected to PEB at the temperature shown in Tables 4 and 5 for 60 seconds. Thereafter, the resist film was puddle developed in a 2.38 wt % TMAH aqueous solution for 30 seconds, rinsed with a surfactant-containing rinse material, and spin-dried to obtain a positive pattern.
The obtained LS pattern was observed with a critical dimension SEM (CG6300) manufactured by Hitachi High-Tech Corporation and evaluated for sensitivity, EL, LWR, depth of focus (DOF), and collapse limit by the following methods. The results are shown in Tables 3 and 4.
An optimum exposure dose Eop (mJ/cm2) which provided a LS pattern with a line width of 18 nm and a pitch of 36 nm was determined and taken as sensitivity. A smaller value indicates higher sensitivity.
EL (unit: %) was determined from the exposure dose which provided a LS pattern with a space width of 18 nm±10% (16.2 to 19.8 nm) according to the following equation. A greater value indicates better performance.
For the LS pattern formed by exposure at the optimum dose Eop, the line width was measured at 10 longitudinally spaced apart points, from which a 3-fold value (3σ) of the standard deviation (σ) was determined as LWR. As this value is smaller, a pattern having small roughness and uniform line width can be obtained.
As evaluation of the depth of focus, a range of focus which provided a LS pattern with a size of 18 nm±10% (16.2 to 19.8 nm) was determined. A greater value indicates a wider depth of focus.
For the LS pattern formed by exposure at the exposure dose corresponding to the optimum focus, the line width was measured at 10 longitudinally spaced apart points. The minimum line size above which lines could be resolved without collapse was determined and reported as collapse limit. A smaller value indicates better collapse limit.
From the results shown in Tables 3 and 4, it was confirmed that the chemically amplified resist composition comprising a photoacid generator composed of the onium salt of the present invention has favorable sensitivity and is excellent in EL, LWR, and DOF. It was confirmed that the value of the collapse limit was small and the pattern was resistant to collapse even in fine pattern formation. Therefore, it was shown that the chemically amplified resist composition of the present invention is suitable as a material for EUV lithography.
Each chemically amplified resist composition (R-1 to R-30 and CR-1 to CR-20) shown in Tables 1 to 3 was spin coated on a Si substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 manufactured by Shin-Etsu Chemical Co., Ltd. (content of silicon: 43 wt %) and prebaked on a hotplate at 105° C. for 60 seconds to form a resist film of 50 nm thick. Using an EUV scanner NXE3400 (NA 0.33, a 0.9/0.6, quadrupole illumination, mask bearing a hole pattern at a pitch 46 nm (on-wafer size) and +20% bias) manufactured by ASML, the resist film was exposed to EUV, the resist film was baked (PEB) on a hotplate at the temperature shown in Tables 7 and 8 for 60 seconds and developed in a 2.38 wt % TMAH aqueous solution for 30 seconds to form a hole pattern having a size of 23 nm.
The exposure dose that provides a hole pattern having a size of 23 nm was measured using a critical dimension SEM (CG6300) manufactured by CG6300, Hitachi High-Technologies Corp. and taken as sensitivity, the size of 50 holes at that dose was measured, from which a 3-fold value (3σ) of the standard deviation (σ) was computed and taken as critical dimension uniformity (CDU). The results are shown in Tables 5 and 6.
From the results shown in Tables 5 and 6, it was confirmed that the chemically amplified resist composition comprising a photoacid generator composed of the onium salt of the present invention has favorable sensitivity and is excellent in CDU.
Japanese Patent Application No. 2023-127895 is incorporated herein by reference. Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-127895 | Aug 2023 | JP | national |
