Patent Application
20250102911
This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2023-158300 filed in Japan on Sep. 22, 2023, the entire contents of which are hereby incorporated by reference.
This invention relates to a resist composition and a patterning process using the composition.
To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. As the use of 5G high-speed communications and artificial intelligence (AI) is widely spreading, high-performance devices are needed for their processing. As the advanced miniaturization technology, manufacturing of microelectronic devices at the 5-nm node by the lithography using EUV of wavelength 13.5 nm has been implemented in a mass scale. Studies are made on the application of EUV lithography to 3-nm node devices of the next generation and 2-nm node devices of the next-but-one generation. IMEC in Belgium announced its successful development of 1-nm and 0.7-nm node devices.
As the feature size reduces, image blurs due to acid diffusion become a problem. For acquiring a resolution for fine patterns with a size of 45 nm et seq., not only an improvement in dissolution contrast is important as previously reported, but the control of acid diffusion is also important as reported in Non-Patent Document 1. Since chemically amplified resist compositions are designed such that sensitivity and contrast are enhanced by acid diffusion, an attempt to minimize acid diffusion by reducing the temperature and/or time of post-exposure bake (PEB) fails, resulting in drastic reductions of sensitivity and contrast.
The EUV resist material must meet high sensitivity, high resolution and low LWR at the same time. As the acid diffusion distance is reduced, LWR or CDU is improved, but sensitivity becomes lower. For example, as the PEB temperature is lowered, the outcome is an improved LWR or CDU, but a lower sensitivity. As the amount of quencher added is increased, the outcome is an improved LWR or CDU, but a lower sensitivity. It is necessary to overcome the tradeoff relation between sensitivity and LWR.
Patent Documents 1 to 4 disclose resist compositions comprising an onium salt having an iodized or brominated anion as an acid generator. Due to inclusion of iodine having substantial absorption of EUV or bromine having a high ionization efficiency, the decomposition efficiency of an acid generator during light exposure is increased, leading to a high sensitivity. As the number of photons absorbed increases, physical contrast is enhanced.
Non-Patent Document 2 describes the acid-generating mechanism that an acid is generated by exposure to high-energy radiation such as EB or EUV. Upon EB or EUV exposure, a polymer is ionized to generate secondary electrons whose energy is transferred to the acid generator to generate an acid as they diffuse. From the result of resist pattern transfer and simulation, the distance from a light absorbing point to an acid generating point is estimated to be 2.4 nm (see Non-Patent Document 3). This distance is inclusive of the diffusion distance of secondary electrons. Non-Patent Document 3 describes that the total of the acid diffusion distance and the diffusion distance from the light absorbing point to the acid generating point is 4 to 8 nm when the PEB temperature is changed. When the acid diffusion is reduced by low-temperature PEB or application of an anion-bound PAG polymer, one half of the diffusion distance is occupied by the diffusion from the light absorbing point to the acid generating point. Differently stated, it is crucial for miniaturization to control not only acid diffusion, but also the diffusion from the light absorbing point to the acid generating point, that is, the diffusion of secondary electrons.
It is desired to develop a resist composition exhibiting a higher sensitivity than prior art resist compositions and capable of reducing the LWR of line patterns or improving the CDU of hole patterns.
An object of the invention is to provide a resist composition which achieves a high sensitivity, minimal LWR and improved CDU independent of whether it is of positive or negative tone, and a pattern forming process using the resist composition.
The inventors have found that when a sulfonium or iodonium salt containing an aromatic sulfone anion having a linkage of two iodized or brominated aromatic groups is used as an acid generator, the acid generator is directly excited by exposure to radiation so that the influence of diffusion of secondary electrons is eliminated. Then a resist composition having a high sensitivity, improved LWR or CDU, high contrast, high resolution and wide process margin is obtained.
In one aspect, the invention provides a resist composition comprising an acid generator containing an onium salt of aromatic sulfonic acid having a linkage of two iodized or brominated aromatic groups.
In a preferred embodiment, the onium salt has the formula (1).
Herein m is an integer of 1 to 5, n is an integer of 0 to 4, m+n is from 1 to 5, p is an integer of 1 to 4, q is an integer of 0 to 3, p+q is from 1 to 4, r is an integer of 0 to 6,
The resist composition may further comprise a base polymer.
In a preferred embodiment, the base polymer comprises repeat units having the formula (a1) or (a2).
Herein RA is each independently hydrogen or methyl,
The resist composition in this embodiment is a chemically amplified positive resist composition.
In another embodiment, the base polymer is free of an acid labile group. The resist composition in this embodiment is a chemically amplified negative resist composition.
The resist composition may further comprise an organic solvent, a quencher, and/or a surfactant.
In another aspect, the invention provides a pattern forming process comprising the steps of applying the resist composition defined herein 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.
In a preferred embodiment, the high-energy radiation is ArF excimer laser of wavelength 193 nm, KrF excimer laser of wavelength 248 nm, EB or EUV of wavelength 3 to 15 nm.
An onium salt containing an aromatic sulfonic acid anion having a linkage of two iodized or brominated aromatic groups is characterized by remarkable absorption of EUV radiation and substantial control of acid diffusion. Using the onium salt as an acid generator, a lowering of resolution due to blur by acid diffusion is prevented. A resist composition having a high sensitivity and reduced LWR or improved CDU is thus constructed.
As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. The notation (Cn-Cm) means a group containing from n to m carbon atoms per group. As used herein, the terms “group” and “moiety” are interchangeable. In chemical formulae, the broken line designates a valence bond or point of attachment. The term “brominated” refers to a bromine-substituted or bromine-containing compound or group, and “iodized” refers to an iodine-substituted or iodine-containing compound or group.
The abbreviations and acronyms have the following meaning.
One embodiment of the invention is a resist composition comprising an acid generator containing an onium salt containing an aromatic sulfonic acid anion having a linkage of two iodized or brominated aromatic groups. The onium salt in which the absorption ability of iodine or the ionization ability of bromine cooperates with the high reactivity of sulfonic acid has advantages including a high contrast and low acid diffusion. Then LWR or CDU is improved.
The acid generator exerts the effect of improving LWR or CDU, which is valid in positive or negative pattern formation through aqueous alkaline development and in negative pattern formation through organic solvent development.
In a preferred embodiment, the onium salt containing an aromatic sulfonic acid anion having a linkage of two iodized or brominated aromatic groups has the formula (1).
In formula (1), m is an integer of 1 to 5, n is an integer of 0 to 4, m+n is from 1 to 5; p is an integer of 1 to 4, q is an integer of 0 to 3, p+q is from 1 to 4; r is an integer of 0 to 6.
In formula (1), XBI is bromine or iodine.
In formula (1), R1 and R2 are each independently hydroxy, carboxy, fluorine, chlorine, amino, a C1-C20 hydrocarbyl group, C1-C20 hydrocarbyloxy group, C2-C20 hydrocarbyloxycarbonyl group, C2-C20 hydrocarbylcarbonyloxy group, —N(Ra)—C(═O)—Rb, —N(Ra)—C(═O)—O—Rb, or —N(Ra)—S(═O)2—Rb. The hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylcarbonyloxy groups may contain at least one moiety selected from fluorine, chlorine, bromine, iodine, hydroxy, amino, ester bond, and ether bond. Ra is hydrogen or a C1-C6 saturated hydrocarbyl group which may contain halogen, hydroxy, C1-C6 saturated hydrocarbyloxy moiety, C2-C6 saturated hydrocarbylcarbonyl moiety, or C2-C6 saturated hydrocarbylcarbonyloxy moiety. Rb is a C1-C1-6 aliphatic hydrocarbyl group or C6-C12 aryl group, which may contain halogen, hydroxy, C1-C6 saturated hydrocarbyloxy moiety, C2-C6 saturated hydrocarbylcarbonyl moiety, or C2-C6 saturated hydrocarbylcarbonyloxy moiety.
The hydrocarbyl group and hydrocarbyl moiety in the hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylcarbonyloxy groups, represented by R1 and R2, may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl; C3-C20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; C2-C20 alkenyl groups such as vinyl, propenyl, butenyl and hexenyl; C2-C20 alkynyl groups such as ethynyl, propynyl and butynyl; C3-C20 cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl and norbornenyl; C6-C20 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; C7-C20 aralkyl groups such as benzyl and phenethyl; and combinations thereof.
In formula (1), R3 is a single bond or C1-C28 hydrocarbylene group which may contain at least one moiety selected from oxygen, nitrogen, sulfur and halogen. The hydrocarbylene group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C28 alkanediyl groups such as ethane-1,1-diyl, ethane-1,2-diyl, 1-methylethane-1,2-diyl, 1-ethylethane-1,2-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,3-diyl, butane-1,4-diyl, 1,1-dimethylpropane-1,3-diyl, 2,2-dimethylpropane-1,3-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl, octadecane-1,18-diyl, nonadecane-1,19-diyl, and icosane-1,20-diyl; C3-C28 cyclic saturated hydrocarbylene groups such as cyclopentanediyl, cyclohexanediyl, bicyclo[2.2.2]octanediyl, norbornanediyl and adamantanediyl; C2-C28 alkenediyl groups such as ethenediyl, propenediyl and butenediyl; C2-C28 alkynediyl groups such as ethynediyl, propynediyl and butynediyl; C3-C28 cyclic unsaturated aliphatic hydrocarbylene groups such as cyclohexenediyl, bicyclo[2.2.2]octenediyl, and norbornenediyl; C6-C28 arylene groups such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, tert-butylnaphthylene, and anthracenediyl; and combinations thereof.
R3 is preferably a C1-C28 alkanediyl group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen, or a C6-C28 arylene group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen; more preferably a C1-C12 alkanediyl group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen, or a C6-C12 arylene group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen; even more preferably a C1-C6 alkanediyl group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen, or a C6-C10 arylene group which may contain at least one atom selected from oxygen, nitrogen, sulfur and halogen.
In formula (1), R4 is a C1-C6 saturated hydrocarbyl group, nitro, cyano, fluorine, iodine, trifluoromethyl or trifluoromethoxy group. Inter alia, fluorine, trifluoromethyl and trifluoromethoxy group are preferred, with fluorine being more preferred.
In formula (1), X1 and X2 are each independently a single bond, ether bond, ester bond, sulfonate ester bond, amide bond, urethane bond, urea bond, carbonate bond, sulfonamide bond, or C1-C6 alkanediyl group. The alkanediyl group may contain an ether bond and/or ester bond. Preferably, at least one of X1 and X2 is an amide bond, urethane bond, urea bond, carbonate bond, or sulfonamide bond. More preferably, both X1 and X2 are an amide bond, urethane bond, urea bond, carbonate bond, or sulfonamide bond. Notably, X1 and X2 may be identical or different.
In formula (1), X3 is a single bond, ether bond, ester bond, or C1-C6 alkanediyl group. The alkanediyl group may contain an ether bond and/or ester bond.
In formula (1), Ar is a C6-C10 (r+2)-valent aromatic hydrocarbon group. Examples of the (r+2)-valent aromatic hydrocarbon group include groups obtained by removing (r+2) number of hydrogen atoms from aromatic hydrocarbons such as benzene and naphthalene.
Examples of the anion in the salt having formula (1) are shown below, but not limited thereto.
In formula (1), M+ is a sulfonium or iodonium cation, preferably sulfonium cation having the formula (2) or iodonium cation having the formula (3).
In formulae (2) and (3), R4 to R8 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine.
The C1-C20 hydrocarbyl group represented by R4 to R8 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl; C3-C20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; C2-C20 alkenyl groups such as vinyl, allyl, butenyl, and hexenyl; C2-C20 alkynyl groups such as ethynyl, propynyl and butynyl; C3-C20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl and norbornenyl; C6-C20 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; C7-C20 aralkyl groups such as benzyl and phenethyl, and combinations thereof.
In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, mercapto, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl moiety.
Also, R4 and R5 may bond together to form a ring with the sulfur atom to which they are attached. Exemplary structures of the ring are shown below.
Examples of the sulfonium cation M+ are shown below, but not limited thereto.
Examples of the iodonium cation M+ are shown below, but not limited thereto.
The onium salt can be synthesized, for example, by salt exchange between a sulfonium or iodonium salt containing a halide anion and an ammonium salt containing an aromatic sulfonic acid anion having a linkage of two iodized or brominated aromatic groups.
In the resist composition, the sulfonium or iodonium salt having formula (1) is preferably present in an amount of 0.01 to 1,000 parts by weight, and more preferably 0.05 to 500 parts by weight per 100 parts by weight of a base polymer to be described just below, as viewed from sensitivity and acid diffusion suppressing effect.
In a preferred embodiment, the resist composition contains a base polymer. In the case of a positive resist composition, the base polymer comprises repeat units containing an acid labile group. The preferred repeat units containing an acid labile group are repeat units having the formula (a1) or repeat units having the formula (a2). These repeat units are also referred to as repeat units (a1) and (a2).
In formulae (a1) and (a2), RA is each independently hydrogen or methyl. Y1 is a single bond, phenylene group, naphthylene group, or a C1-C12 linking group containing at least one moiety selected from ester bond, ether bond and lactone ring. Y2 is a single bond or ester bond. Y3 is a single bond, ether bond or ester bond. R11 and R12 are each independently an acid labile group. R13 is a C1-C4 saturated hydrocarbyl group, halogen, C2-C5 saturated hydrocarbylcarbonyl group, cyano, or C2-C5 saturated hydrocarbyloxycarbonyl group. R14 is a single bond or C1-C6 alkanediyl group which may contain an ether bond or ester bond. The subscript “a” is an integer of 0 to 4.
Examples of the monomer from which repeat units (a1) are derived are shown below, but not limited thereto. Herein RA and R11 are as defined above.
Examples of the monomer from which repeat units (a2) are derived are shown below, but not limited thereto. Herein RA and R12 are as defined above.
The acid labile groups represented by R11 and R12 in formulae (a1) and (a2) may be selected from a variety of such groups, for example, the groups described in U.S. Pat. No. 8,574,817 (JP-A 2013-080033) and U.S. Pat. No. 8,846,303 (JP-A 2013-083821).
Typical acid labile groups have the following formulae (AL-1) to (AL-3).
In formula (AL-1) and (AL-2), RL1 and RL2 are each independently a C1-C40 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. As the hydrocarbyl group, C1-C40, especially C1-C20 saturated hydrocarbyl groups are preferred.
In formula (AL-1), b is an integer of 0 to 10, preferably 1 to 5.
In formula (AL-2), RL3 and RN are each independently hydrogen or a C1-C20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. As the hydrocarbyl group, C1-C20 saturated hydrocarbyl groups are preferred. Any two of RL2, RL3 and RN may bond together to form a C3-C20 ring with the carbon atom or the carbon and oxygen atoms to which they are attached. Rings of 4 to 16 carbon atoms are preferred, with aliphatic rings being more preferred.
In formula (AL-3), RL5, RL6 and RL7 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. As the hydrocarbyl group, C1-C20 saturated hydrocarbyl groups are preferred. 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. Rings of 4 to 16 carbon atoms are preferred, with aliphatic rings being more preferred.
The base polymer may comprise repeat units (b) having a phenolic hydroxy group as an adhesive group. Examples of the monomer from which repeat units (b) are derived are shown below, but not limited thereto. Herein RA is as defined above.
The base polymer may further comprise repeat units (c) having another adhesive group. The other adhesive group is selected from hydroxy (other than phenolic hydroxy), lactone ring, sultone ring, ether bond, ester bond, sulfonate ester bond, carbonyl, sulfonyl, cyano, and carboxy groups. Examples of the monomer from which repeat units (c) are derived are given below, but not limited thereto. Herein RA is as defined above.
The base polymer may further comprise repeat units (d) which are derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene, and derivatives thereof. Examples of the monomer from which repeat units (d) are derived are given below, but not limited thereto.
The base polymer may further comprise repeat units (e) which are derived from styrene, vinylnaphthalene, vinylanthracene, vinylpyrene, methyleneindene, vinylpyridine, and vinylcarbazole compounds.
The base polymer may further comprise repeat units (f) derived from an onium salt having a polymerizable unsaturated bond. JP-A 2005-084365 discloses a sulfonium or iodonium salt containing a polymerizable olefin capable of generating a specific sulfonic acid. JP-A 2006-178317 discloses a sulfonium salt having a sulfonic acid directly attached to the backbone.
The preferred repeat units (f) include repeat units having the following formulae (f1), (f2) and (f3). These units are simply referred to as repeat units (f1), (f2) and (f3), which may be used alone or in combination of two or more types.
In formulae (f1) to (f3), RA is each independently hydrogen or methyl. Z1 is a single bond, C1-C6 aliphatic hydrocarbylene group, phenylene group, naphthylene group, or C7-C18 group obtained by combining the foregoing, —O—Z11—, —C(═O)—O—Z11—, or —C(═O)—NH—Z11—. Z11 is a C1-C6 aliphatic hydrocarbylene group, phenylene group, naphthylene group, or C7-C18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety. Z2 is a single bond or ester bond. Z3 is a single bond, —Z31—C(═O)—O—, —Z31—O— or —Z31—O—C(═O)—. Z31 is a C1-C12 aliphatic hydrocarbylene group, phenylene group or C7-C18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond, iodine or bromine. Z4 is methylene, 2,2,2-trifluoro-1,1-ethanediyl, or carbonyl. Z5 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, —O—Z51—, —C(═O)—O—Z51—, or —C(═O)—NH—Z51—. Z51 is a C1-C6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond, hydroxy moiety or halogen.
In formulae (f1) to (f3), R21 to R28 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl groups R4 to R1 in formulae (2) and (3). In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl. A pair of R23 and R24, or R26 and R27 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the ring are as exemplified above for the ring that R4 and R5 in formula (2), taken together, form with the sulfur atom to which they are attached.
In formula (f1), M− is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride and bromide ions; fluoroalkylsulfonate ions such as triflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate; arylsulfonate ions such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate; alkylsulfonate ions such as mesylate and butanesulfonate; imide ions such as bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide and bis(perfluorobutylsulfonyl)imide; methide ions such as tris(trifluoromethylsulfonyl)methide and tris(perfluoroethylsulfonyl)methide.
Also included are sulfonate ions having fluorine substituted at α-position as represented by the formula (f1-1), and sulfonate ions having fluorine substituted at α-position and trifluoromethyl at β-position as represented by the formula (f1-2).
In formula (f1-1), R31 is hydrogen, or a C1-C20 hydrocarbyl group which may contain at least one moiety selected from ether bond, ester bond, carbonyl, lactone ring, and fluorine.
In formula (f1-2), R32 is hydrogen, or a C1-C30 hydrocarbyl group or C2-C30 hydrocarbylcarbonyl group, which may contain at least one moiety selected from ether bond, ester bond, carbonyl and lactone ring.
The hydrocarbyl group and hydrocarbyl moiety in the hydrocarbylcarbonyl group, represented by R31 and R32, may be saturated or unsaturated and straight, branched or cyclic. Examples of the hydrocarbyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl, heptadecyl, and icosyl; cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbornylmethyl, tricyclodecanyl, tetracyclododecanyl, tetracyclododecanylmethyl, and dicyclohexylmethyl; alkenyl groups such as allyl; cyclic unsaturated hydrocarbyl groups such as 3-cyclohexenyl; aryl groups such as phenyl, 1-naphthyl, 2-naphthyl; and aralkyl groups such as benzyl and diphenylmethyl.
In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, cyano, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl moiety. Examples of the heteroatom-containing hydrocarbyl group include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl.
Examples of the cation in the monomer from which repeat units (f1) are derived are shown below, but not limited thereto. Herein RA and M− are as defined above.
Examples of the cation in the monomer from which repeat units (f2) or (f3) are derived are as exemplified above for the sulfonium cation M+ in formula (1).
Examples of the monomer from which repeat units (f2) are derived are shown below, but not limited thereto. Herein RA as
Examples of the monomer from which repeat units (0) are derived are shown below, but not limited thereto. Herein RA is as defined above.
The repeat units (f1) to (f3) function as an acid generator. The attachment of an acid generator to the polymer backbone is effective in restraining acid diffusion, thereby preventing a reduction of resolution due to blur by acid diffusion. Also, LWR or CDU is improved since the acid generator is uniformly distributed.
The base polymer for formulating the positive resist composition comprises repeat units (a1) or (a2) having an acid labile group as essential component and additional repeat units (b), (c), (d), (e), and (f) as optional components. A fraction of units (a1), (a2), (b), (c), (d), (e), and (f) is: preferably 0≤a1<1.0, 0≤a2<1.0, 0<a1+a2<1.0, 0≤b≤0.9, 0≤c≤0.9, 0≤d≤0.8, 0≤e≤0.8, and 0≤f≤0.5; more preferably 0≤a1≤0.9, 0≤a2≤0.9, 0.1≤a1+a2≤0.9, 0≤b≤0.8, 0≤c≤0.8, 0≤d≤0.7, 0≤e≤0.7, and 0≤f≤0.4; and even more preferably 0≤a1≤0.8, 0≤a2≤0.8, 0.1≤a1+a2≤0.8, 0≤b≤0.75, 0≤c≤0.75, 0≤d≤0.6, 0≤e≤0.6, and 0≤f≤0.3. Notably, f=f1+f2+f3, meaning that unit (f) is at least one of units (f1) to (f3), and a1+a2+b+c+d+e+f=1.0.
For the base polymer for formulating the negative resist composition, an acid labile group is not necessarily essential. The base polymer comprises repeat units (b), and optionally repeat units (c), (d), (e), and/or (f). A fraction of these units is: preferably 0<b≤1.0, 0≤c≤0.9, 0≤d 0.8, 0≤e≤0.8, and 0≤f≤0.5; more preferably 0.2≤b≤1.0, 0≤c≤0.8, 0≤0≤d≤0.7≤e≤0.7, and 0≤f≤0.4; and even more preferably 0.3≤b≤1.0, 0≤c≤0.75, 0≤d≤0.6, 0≤e≤0.6, and 0≤f≤0.3. Notably, f=f1+f2+f3, meaning that unit (f) is at least one of units (f1) to (f3), and b+c+d+e+f=1.0.
The base polymer may be synthesized by any desired methods, for example, by dissolving one or more monomers selected from the monomers corresponding to the foregoing repeat units in an organic solvent, adding a radical polymerization initiator thereto, and heating for polymerization. Examples of the organic solvent which can be used for polymerization include toluene, benzene, tetrahydrofuran (THF), diethyl ether, and dioxane. Examples of the polymerization initiator used herein include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. Preferably, the reaction temperature is 50 to 80° C. and the reaction time is 2 to 100 hours, more preferably 5 to 20 hours.
Where a monomer having a hydroxy group is copolymerized, the hydroxy group may be replaced by an acetal group susceptible to deprotection with acid, typically ethoxyethoxy, prior to polymerization, and the polymerization be followed by deprotection with weak acid and water. Alternatively, the hydroxy group may be replaced by an acetyl, formyl, pivaloyl or similar group prior to polymerization, and the polymerization be followed by alkaline hydrolysis.
When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, an alternative method is possible. Specifically, acetoxystyrene or acetoxyvinylnaphthalene is used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy group is deprotected by alkaline hydrolysis, for thereby converting the polymer product to hydroxystyrene or hydroxyvinylnaphthalene. For alkaline hydrolysis, a base such as aqueous ammonia or triethylamine may be used. Preferably the reaction temperature is −20° C. to 100° C., more preferably 0° C. to 60° C., and the reaction time is 0.2 to 100 hours, more preferably 0.5 to 20 hours.
The base polymer should preferably have a weight average molecular weight (Mw) in the range of 1,000 to 500,000, and more preferably 2,000 to 30,000, as measured by GPC versus polystyrene standards using tetrahydrofuran (THF) solvent. A Mw in the range ensures that the resist film has heat resistance and high solubility in alkaline developer.
If a base polymer has a wide molecular weight distribution or dispersity (Mw/Mn), which indicates the presence of lower and higher molecular weight polymer fractions, there is a possibility that foreign matter is left on the pattern or the pattern profile is degraded. The influences of Mw and Mw/Mn become stronger as the pattern rule becomes finer. Therefore, the base polymer should preferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially 1.0 to 1.5, in order to provide a resist composition suitable for micropatterning to a small feature size.
It is understood that a blend of two or more polymers which differ in compositional ratio, Mw or Mw/Mn is acceptable.
An organic solvent may be added to the resist composition. The organic solvent used herein is not particularly limited as long as the foregoing and other components are soluble therein. Examples of the organic solvent are described in JP-A 2008-111103, paragraphs [0144]-[0145](U.S. Pat. No. 7,537,880). Exemplary solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone and 2-heptanone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol (DAA); 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 propylene glycol monomethyl ether acetate (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; and lactones such as γ-butyrolactone, which may be used alone or in admixture.
In the resist composition, the organic solvent is preferably present in an amount of 100 to 10,000 parts, and more preferably 200 to 8,000 parts by weight per 100 parts by weight of the base polymer.
The resist composition may further comprise a quencher. As used herein, the quencher refers to a compound capable of trapping the acid generated by the PAG to prevent the acid from diffusing into the unexposed region of the resist film.
The quencher is typically selected from conventional basic compounds. Conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds with carboxy group, nitrogen-containing compounds with sulfonyl group, nitrogen-containing compounds with hydroxy group, nitrogen-containing compounds with hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives, imide derivatives, and carbamate derivatives. Also included are primary, secondary, and tertiary amine compounds, specifically amine compounds having a hydroxy group, ether bond, ester bond, lactone ring, cyano group, or sulfonate ester bond as described in JP-A 2008-111103, paragraphs [0146]-[0164], and compounds having a carbamate bond as described in JP 3790649. Addition of a basic compound may be effective for further suppressing the diffusion rate of acid in the resist film or correcting the pattern profile.
Suitable quenchers also include onium salts such as sulfonium, iodonium and ammonium salts of sulfonic acids which are not fluorinated at α-position, carboxylic acids, and fluorinated alkoxides, as described in U.S. Pat. No. 8,795,942 (JP-A 2008-158339). While an α-fluorinated sulfonic acid, imide acid, and methide acid are necessary to deprotect the acid labile group of carboxylic acid ester, an α-non-fluorinated sulfonic acid, carboxylic acid or fluorinated alcohol is released by salt exchange with the onium salt. An α-non-fluorinated sulfonic acid, carboxylic acid or fluorinated alcohol functions as a quencher because they do not induce deprotection reaction.
Exemplary quenchers include a compound having the formula (4) which is an onium salt of α-non-fluorinated sulfonic acid, a compound having the formula (5) which is an onium salt of carboxylic acid, and a compound having the formula (6) which is an onium salt of alkoxide.
In formula (4), R101 is hydrogen or a C1-C40 hydrocarbyl group which may contain a heteroatom, exclusive of the hydrocarbyl group in which the hydrogen bonded to the carbon atom at α-position of the sulfo group is substituted by fluorine or fluoroalkyl moiety.
The C1-C40 hydrocarbyl group R101 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C40 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl and n-decyl; C3-C40 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.02,6]decyl, adamantyl, and adamantylmethyl; C2-C40 alkenyl groups such as vinyl, allyl, propenyl, butenyl and hexenyl; C3-C40 cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl; C6-C40 aryl groups such as phenyl, naphthyl, alkylphenyl groups (e.g., 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-ethylphenyl, 4-tert-butylphenyl, 4-n-butylphenyl), di- or trialkylphenyl groups (e.g., 2,4-dimethylphenyl and 2,4,6-triisopropylphenyl), alkylnaphthyl groups (e.g., methylnaphthyl and ethylnaphthyl), dialkylnaphthyl groups (e.g., dimethylnaphthyl and diethylnaphthyl); and C7-C40 aralkyl groups such as benzyl, 1-phenylethyl and 2-phenylethyl.
In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy moiety, cyano moiety, carbonyl moiety, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—), or haloalkyl moiety. Suitable heteroatom-containing hydrocarbyl groups include heteroaryl groups such as thienyl, 4-hydroxyphenyl, alkoxyphenyl groups such as 4-methoxyphenyl, 3-methoxyphenyl, 2-methoxyphenyl, 4-ethoxyphenyl, 4-tert-butoxyphenyl, 3-tert-butoxyphenyl; alkoxynaphthyl groups such as methoxynaphthyl, ethoxynaphthyl, n-propoxynaphthyl and n-butoxynaphthyl; dialkoxynaphthyl groups such as dimethoxynaphthyl and diethoxynaphthyl; and aryloxoalkyl groups, typically 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl, 2-(1-naphthyl)-2-oxoethyl and 2-(2-naphthyl)-2-oxoethyl.
In formula (5), R102 is a C1-C40 hydrocarbyl group which may contain a heteroatom. Examples of the hydrocarbyl group R102 are as exemplified above for the hydrocarbyl group R101. Also included are fluorinated alkyl groups such as trifluoromethyl, trifluoroethyl, 2,2,2-trifluoro-1-methyl-1-hydroxyethyl, 2,2,2-trifluoro-1-(trifluoromethyl)-1-hydroxyethyl, and fluorinated aryl groups such as pentafluorophenyl and 4-trifluoromethylphenyl.
In formula (6), R103 is a C1-C8 saturated hydrocarbyl group or C6-C10 aryl group, which contains at least 3 fluorine atoms and optionally contains a nitro moiety.
In formulae (4), (5) and (6), Mq+ is an onium cation. The onium cation is preferably a sulfonium, iodonium or ammonium cation, with the sulfonium cation being more preferred. Suitable sulfonium cations are as exemplified above for the sulfonium cation M+ in formula (1).
A sulfonium salt of iodized benzene ring-containing carboxylic acid having the formula (7) is also useful as the quencher.
In formula (7), x is an integer of 1 to 5, y is an integer of 0 to 3, and z is an integer of 1 to 3.
In formula (7), R111 is hydroxy, fluorine, chlorine, bromine, amino, nitro, cyano, or a C1-C6 saturated hydrocarbyl, C1-C6 saturated hydrocarbyloxy, C2-C6 saturated hydrocarbylcarbonyloxy, or C1-C4 saturated hydrocarbylsulfonyloxy group, in which some or all hydrogen may be substituted by halogen, or —N(R111A)—C(═O)—R111B, or —N(R111A) C(═O)—O—R111B. R111A is hydrogen or a C1-C6 saturated hydrocarbyl group and R111B is a C1-C6 saturated hydrocarbyl or C2-C8 unsaturated aliphatic hydrocarbyl group. A plurality of R111 may be identical or different when y and/or z is 2 or 3.
In formula (7), L1 is a single bond, or a C1-C20 (z+1)-valent linking group which may contain at least one moiety selected from ether bond, carbonyl, ester bond, amide bond, sultone ring, lactam ring, carbonate bond, halogen, hydroxy and carboxy moiety. The saturated hydrocarbyl, saturated hydrocarbyloxy, saturated hydrocarbylcarbonyloxy and saturated hydrocarbylsulfonyloxy groups may be straight, branched or cyclic.
In formula (7), R112, R113 and R114 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl group represented by R4 to R8 in formulae (2) and (3).
Examples of the compound having formula (7) include those described in U.S. Pat. No. 10,295,904 (JP-A 2017-219836) and US 20210188770 (JP-A 2021-091666).
Quenchers of polymer type as described in U.S. Pat. No. 7,598,016 (JP-A 2008-239918) are also useful. The polymeric quencher segregates at the resist film surface and thus enhances the rectangularity of resist pattern. When a protective film is applied as is often the case in the immersion lithography, the polymeric quencher is also effective for preventing a film thickness loss of resist pattern or rounding of pattern top.
Other useful quenchers include sulfonium salts of betaine type as described in JP 6848776 and JP-A 2020-037544, fluorine-free methide acids as described in JP-A 2020-055797, sulfonium salts of sulfonamide as described in JP 5807552, sulfonium salts of iodized sulfonamide as described in JP-A 2019-211751, or acid generators capable of generating phenols, halogen or carbonic acid.
In the resist composition, the quencher is preferably added in an amount of 0 to 5 parts, more preferably 0 to 4 parts by weight per 100 parts by weight of the base polymer. The quencher may be used alone or in admixture.
In addition to the foregoing components, the resist composition may further contain other components such as an acid generator other than the onium salt having formula (1), surfactant, dissolution inhibitor, crosslinker, water repellency improver, and acetylene alcohol. Each additional component may be used alone or in admixture of two or more.
The other acid generator is typically a compound (PAG) capable of generating an acid upon exposure to actinic ray or radiation. Although the PAG used herein may be any compound capable of generating an acid upon exposure to high-energy radiation, those compounds capable of generating sulfonic acid, imide acid (imidic acid) or methide acid are preferred. Suitable PAGs include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acid generators. Exemplary PAGs are described in JP-A 2008-111103, paragraphs [0122]-[0142](U.S. Pat. No. 7,537,880), JP-A 2018-005224, and JP-A 2018-025789. The other acid generator is preferably added in an amount of 0 to 200 parts, more preferably 0.1 to 100 parts by weight per 100 parts by weight of the base polymer.
Exemplary surfactants are described in JP-A 2008-111103, paragraphs [0165]-[0166]. Inclusion of a surfactant may improve or control the coating characteristics of the resist composition. The surfactant is preferably added in an amount of 0.0001 to 10 parts by weight per 100 parts by weight of the base polymer.
In the case of positive resist compositions, inclusion of a dissolution inhibitor may lead to an increased difference in dissolution rate between exposed and unexposed areas and a further improvement in resolution. The dissolution inhibitor which can be used herein is a compound having at least two phenolic hydroxy groups on the molecule, in which an average of from 0 to 100 mol % of all the hydrogen atoms on the phenolic hydroxy groups are replaced by acid labile groups or a compound having at least one carboxy group on the molecule, in which an average of 50 to 100 mol % of all the hydrogen atoms on the carboxy groups are replaced by acid labile groups, both the compounds having a molecular weight of 100 to 1,000, and preferably 150 to 800. Typical are bisphenol A, trisphenol, phenolphthalein, cresol novolac, naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic acid derivatives in which the hydrogen atom on the hydroxy or carboxy group is replaced by an acid labile group, as described in U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs [0155]-[0178]).
In the positive resist composition, the dissolution inhibitor is preferably added in an amount of 0 to 50 parts, more preferably 5 to 40 parts by weight per 100 parts by weight of the base polymer.
In the case of negative resist compositions, a negative pattern may be formed by adding a crosslinker to reduce the dissolution rate of exposed area. Suitable crosslinkers which can be used herein include epoxy compounds, melamine compounds, guanamine compounds, glycoluril compounds and urea compounds having substituted thereon at least one group selected from among methylol, alkoxymethyl and acyloxymethyl groups, isocyanate compounds, azide compounds, and compounds having a double bond such as an alkenyloxy group. These compounds may be used as an additive or introduced into a polymer side chain as a pendant. Hydroxy-containing compounds may also be used as the crosslinker.
Suitable epoxy compounds include tris(2,3-epoxypropyl) isocyanurate, trimethylolmethane triglycidyl ether, trimethylolpropane triglycidyl ether, and triethylolethane triglycidyl ether. Examples of the melamine compound include hexamethylol melamine, hexamethoxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups methoxymethylated and mixtures thereof, hexamethoxyethyl melamine, hexaacyloxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups acyloxymethylated and mixtures thereof. Examples of the guanamine compound include tetramethylol guanamine, tetramethoxymethyl guanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethoxyethyl guanamine, tetraacyloxyguanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the glycoluril compound include tetramethylol glycoluril, tetramethoxyglycoluril, tetramethoxymethyl glycoluril, tetramethylol glycoluril compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethylol glycoluril compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the urea compound include tetramethylol urea, tetramethoxymethyl urea, tetramethylol urea compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, and tetramethoxyethyl urea.
Suitable isocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and cyclohexane diisocyanate. Suitable azide compounds include 1,1′-biphenyl-4,4′-bisazide, 4,4′-methylidenebisazide, and 4,4′-oxybisazide. Examples of the alkenyloxy-containing compound include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, trimethylol propane trivinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitol pentavinyl ether, and trimethylol propane trivinyl ether.
In the negative resist composition, the crosslinker is preferably added in an amount of 0.1 to 50 parts, more preferably 1 to 40 parts by weight per 100 parts by weight of the base polymer.
To the resist composition, a water repellency improver may also be added for improving the water repellency on surface of a resist film. The water repellency improver may be used in the topcoatless immersion lithography. Suitable water repellency improvers include polymers having a fluoroalkyl group and polymers having a specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue and are described in JP-A 2007-297590 and JP-A 2008-111103, for example. The water repellency improver to be added to the resist composition should be soluble in alkaline developers and organic solvent developers. The water repellency improver of specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue is well soluble in the developer. A polymer comprising repeat units having an amino group or amine salt serves as the water repellency improver and is effective for preventing evaporation of acid during PEB, thus preventing any hole pattern opening failure after development. An appropriate amount of the water repellency improver is 0 to 20 parts, preferably 0.5 to 10 parts by weight per 100 parts by weight of the base polymer.
Also, an acetylene alcohol may be blended in the resist composition. Suitable acetylene alcohols are described in JP-A 2008-122932, paragraphs [0179]-[0182]. An appropriate amount of the acetylene alcohol blended is 0 to 5 parts by weight per 100 parts by weight of the base polymer.
The resist composition is used in the fabrication of various integrated circuits. Pattern formation using the resist composition may be performed by well-known lithography processes. The process generally involves the steps of applying the resist composition 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. If necessary, any additional steps may be added.
Specifically, the resist composition is first applied onto a substrate on which an integrated circuit is to be formed (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrate on which a mask circuit is to be formed (e.g., Cr, CrO, CrON, MoSi2, or SiO2) by a suitable coating technique such as spin coating, roll coating, flow coating, dipping, spraying or doctor coating. The coating is prebaked on a hotplate preferably at a temperature of 60 to 150° C. for 10 seconds to 30 minutes, more preferably at 80 to 120° C. for 30 seconds to 20 minutes. The resulting resist film is generally 0.01 to 2 μm thick.
The resist film is then exposed to a desired pattern of high-energy radiation such as UV, deep-UV, EB, EUV of wavelength 3 to 15 nm, x-ray, soft x-ray, excimer laser light, γ-ray or synchrotron radiation. When UV, deep-UV, EUV, x-ray, soft x-ray, excimer laser light, γ-ray or synchrotron radiation is used as the high-energy radiation, the resist film is exposed thereto directly or through a mask having a desired pattern in a dose of preferably about 1 to 200 mJ/cm2, more preferably about 10 to 100 mJ/cm2. When EB is used as the high-energy radiation, the resist film is exposed thereto directly or through a mask having a desired pattern in a dose of preferably about 0.1 to 300 μC/cm2, more preferably about 0.5 to 200 μC/cm2. It is appreciated that the inventive resist composition is suited in micropatterning using KrF excimer laser, ArF excimer laser, EB, EUV, x-ray, soft x-ray, γ-ray or synchrotron radiation, especially in micropatterning using EB or EUV.
After the exposure, the resist film may be baked (PEB) on a hotplate or in an oven preferably at 30 to 150° C. for 10 seconds to 30 minutes, more preferably at 50 to 120° C. for 30 seconds to 20 minutes.
After the exposure or PEB, the resist film is developed in a developer in the form of an aqueous base solution for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes by conventional techniques such as dip, puddle and spray techniques. A typical developer is a 0.1 to 10 wt %, preferably 2 to 5 wt % aqueous solution of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), or tetrabutylammonium hydroxide (TBAH). In the case of a positive resist composition, the resist film in the exposed area is dissolved in the developer whereas the resist film in the unexposed area is not dissolved. The desired positive pattern is formed on the substrate. In the case of a negative resist composition, inversely, the resist film in the exposed area is insolubilized whereas the resist film in the unexposed area is dissolved away.
In an alternative embodiment, a negative pattern can be obtained from the resist composition comprising a base polymer containing acid labile groups by effecting organic solvent development. The developer used herein is preferably selected from among 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, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate, and mixtures thereof.
At the end of development, the resist film is rinsed. As the rinsing liquid, a solvent which is miscible with the developer and does not dissolve the resist film is preferred. Suitable solvents include alcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbon atoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, and aromatic solvents. Specifically, suitable alcohols of 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, t-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-s-butyl ether, di-n-pentyl ether, diisopentyl ether, di-s-pentyl ether, di-t-pentyl ether, and di-n-hexyl ether. Suitable alkanes of 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, and cyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atoms include hexyne, heptyne, and octyne. Suitable aromatic solvents include toluene, xylene, ethylbenzene, isopropylbenzene, t-butylbenzene and mesitylene.
Rinsing is effective for minimizing the risks of resist pattern collapse and defect formation. However, rinsing is not essential. If rinsing is omitted, the amount of solvent used may be reduced.
A hole or trench pattern after development may be shrunk by the thermal flow, RELACS® or DSA process. A hole pattern is shrunk by coating a shrink agent thereto, and baking such that the shrink agent may undergo crosslinking at the resist surface as a result of the acid catalyst diffusing from the resist layer during bake, and the shrink agent may attach to the sidewall of the hole pattern. The bake is preferably at a temperature of 70 to 180° C., more preferably 80 to 170° C., for a time of 10 to 300 seconds. The extra shrink agent is stripped and the hole pattern is shrunk.
Examples of the invention are given below by way of illustration and not by way of limitation. All parts are by weight (pbw).
Acid generators PAG-1 to PAG-16 in the form of sulfonium or iodonium salts having the structure shown below were used in resist compositions.
Base polymers (Polymers P-1 to P-4) of the construction shown below were synthesized by combining selected monomers, and effecting copolymerization reaction in THF solvent. The reaction solution was poured into methanol for precipitation, after which the solid precipitate was washed with hexane, isolated, and dried. The base polymers were analyzed for composition by 1H-NMR spectroscopy and for Mw and Mw/Mn by GPC versus polystyrene standards using THF solvent.
Resist compositions were prepared by dissolving components in a solvent in accordance with the recipe shown in Table 1, and filtering the solution through a filter having a pore size of 0.2 μm.
The components in Table 1 are identified below.
Organic solvents:
Comparative acid generators: cPAG-1 and cPAG-2
Quenchers: Q-1 and Q-2
Each of the resist compositions in Table 1 was spin coated on a silicon substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 (Shin-Etsu Chemical Co., Ltd., Si content 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 (ASML, NA 0.33, σ 0.9/0.6, quadrupole illumination), the resist film was exposed to EUV through a mask bearing a hole pattern at a pitch 40 nm (on-wafer size) and +20% bias. The resist film was baked (PEB) on a hotplate at the temperature shown in Table 1 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 20 nm in Examples 1 to 18 and Comparative Examples 1 and 2 or a dot pattern having a size of 20 nm in Example 19 and Comparative Example 3.
The resist pattern was observed under CD-SEM (CG6300, Hitachi High-Technologies Corp.). The exposure dose that provides a hole or dot pattern having a size of 20 nm is reported as sensitivity. The size of 50 holes or dots was measured, from which a 3-fold value (36) of the standard deviation (6) was computed and reported as size variation, i.e., CDU.
The resist compositions are shown in Table 1 together with the sensitivity and CDU of EUV lithography.
It is demonstrated in Table 1 that resist compositions comprising an onium salt of aromatic sulfonic acid having a linkage of two iodized or brominated aromatic groups offer a high sensitivity and improved CDU.
Japanese Patent Application No. 2023-158300 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 |
|---|---|---|---|
| 2023-158300 | Sep 2023 | JP | national |
