Onium salt compound, photoacid generator, photoresist composition and pattern forming method

Abstract

The present invention relates to the field of material technology, and more specifically, to an onium salt compound, a photoacid generator, a photoresist composition, and a pattern forming method. The onium salt compound is a salt composed of anions and cations, wherein the cations are sulfonium cations or iodonium cations; the anion general formula is as shown in formula (B): In formula (B), R1 is an ester-containing group that can react with TMAH developer, R2 is a substituted or unsubstituted cycloalkane group with a carbon number of 6 to 10, and n is any integer between 1 and 3. ‑ The combination of fluorine atoms with high electron-withdrawing properties at relatively close positions can enhance the acidity, while introducing a cyclic hydrocarbon group with large spatial volume to reduce the diffusion of the acid; in addition, the addition of a group fragment with an ester group that can be cleaved by an alkaline developer can effectively reduce the development defects. The onium salt compound provided by the present invention is used as a photoacid generator to meet the current demand for high-resolution resist patterns, including low line width roughness (LWR) of the pattern and a smaller mask error enhancement factor (MEEF) of the line pattern, as well as fewer development defects.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to an onium salt compound, a photoacid generator, a photoresist composition and a pattern forming method. Background Art

[0002] In the manufacture of integrated circuits, photoresist is one of the key materials for transferring patterns to substrates. During photolithography, when photoresist is irradiated with light or electron beams of a specific wavelength, its properties change, and a photoresist pattern with a predetermined shape is formed on the photoresist film through development.

[0003] In order to achieve higher integration, ArF immersion lithography technology can achieve higher resolution and has become a research hotspot.

[0004] Photoacid generators are the core components of photoresist materials, and optimizing their structure to improve development performance such as MEEF (mask error enhancement factor) and LWR (line width roughness) is one of the research directions. Photoresists usually use sulfonium salts composed of triphenylsulfonium cations and perfluoroalkylsulfonic acid anions, but the acid diffusion length of the generated perfluoroalkylsulfonic acid is large, and the MEEF and LWR are not ideal. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and to provide an onium salt compound, a photoacid generator, a photoresist composition and a pattern forming method.

[0006] The first aspect of the present invention provides an onium salt compound, which is a salt composed of an anion and a cation, wherein the anion has a general formula as shown in formula (B):

[0007]

[0008] In formula (B), R1 is an ester-containing group that can react with TMAH developer, R2 is a substituted or unsubstituted cycloalkane group having 6 to 10 carbon atoms, and n is any integer between 1 and 3;

[0009] Furthermore, the R1 comprises one or more combinations of the following structures:

[0010]

[0011] Preferably, the R1 is:

[0012]

[0013] Further, the R2 includes one or more combinations of substituted or unsubstituted cyclohexyl, norbornyl, and adamantyl;

[0014] Preferably, said R2 is adamantyl group;

[0015] Further, the cation is a sulfonium cation or an iodonium cation;

[0016] Preferably, a substituted or unsubstituted triphenylsulfonium cation or a substituted or unsubstituted diphenyliodonium cation, wherein the substituent group of the cation is a methyl group;

[0017] A further preferred cation is an unsubstituted triphenylsulfonium cation.

[0018] The second aspect of the present invention provides a photoacid generator comprising the onium salt compound provided by the first aspect of the present invention.

[0019] The third aspect of the present invention provides a photoresist composition, comprising the photoacid generator (B) provided in the second aspect of the present invention, a main resin (A), an acid diffusion controller (C), a fluorine-containing resin (D) and an organic solvent (E). The main resin (A) comprises a structural unit having an acid dissociable group (the following formula A-1) and a structural unit having a lactone skeleton (the following formula A-2):

[0020]

[0021] In formula (A-1) and (A-2), R3 represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R4 represents an acid-labile group, R5 represents a hydrocarbon group having 1 to 10 carbon atoms, X represents an oxygen atom, an ester group, a carbonate group or an imino group, R6 represents a monovalent organic group containing a lactone structure, and n is any integer between 0 and 10;

[0022] Further, the main resin is a ternary or tetrapolymer resin, comprising at least one repeating unit of formula (A-1) and at least one repeating unit of formula (A-2);

[0023] Furthermore, the main resin comprises any one of the following monomer combinations:

[0024] Combination 1:

[0025] Combination 2:

[0026] Combination 3:

[0027] Combination 4:

[0028] Preferably, the main resin comprises any one of the following monomer combinations:

[0029] Combination 2:

[0030] Further, the acid diffuser (C) includes a nitrogen-containing compound (C-1) or a compound (C-2) represented by the following formula, wherein the nitrogen-containing compound includes one or more combinations of amide-containing compounds, urea compounds, and nitrogen-containing heterocyclic compounds, and C-2 is represented by:

[0031] R7-SO3 - M + Formula (C-2)

[0032] In formula (C-2), R7 represents one or more combinations of substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, alicyclic hydrocarbon groups or aryl groups, and M + represents an onium salt cation.

[0033] A fourth aspect of the present invention provides a pattern forming method, comprising the following steps:

[0034] Using the photoresist composition provided by the third aspect of the present invention to form a resist film on a substrate;

[0035] After drying, the resist film is subjected to liquid immersion exposure using ArF excimer laser;

[0036] After baking, the exposed resist film is developed using a developer to obtain a photoresist pattern.

[0037] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a novel onium salt compound, which can be used as a photoacid generator to achieve high photosensitivity of a photoresist composition, and the acid diffusion range can be controlled, which can meet the requirements of high resolution, including low LWR of patterns and smaller MEEF, and can effectively reduce development defects. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] <Onium Salt Compounds>

[0040] The first aspect of the present invention provides an onium salt compound, which is a salt composed of an anion and a cation, wherein the anion has a general formula as shown in formula (B):

[0041]

[0042] In formula (B), R1 is an ester-containing group that can react with TMAH developer, R2 is a substituted or unsubstituted cycloalkane group having 6 to 10 carbon atoms, and n is any integer between 1 and 3.

[0043] R1 includes one or more combinations of the following structures:

[0044]

[0045] Preferably, the R1 is:

[0046]

[0047] R2 includes one or more combinations of substituted or unsubstituted cyclohexyl, norbornyl, and adamantyl:

[0048]

[0049] Preferably, the R2 is:

[0050]

[0051] By irradiation with radiation, the onium salt compound can generate a group fragment having a cyclic hydrocarbon group and an ester group containing an easily breakable bond, thereby increasing the affinity for the alkaline developer, thereby inhibiting the aggregation of the acid in the development process and preventing the occurrence of development defects.

[0052] In addition, since the generated acid has a large cyclic hydrocarbon group with a high carbon content, the diffusion length in the photoresist film is appropriately shortened, which can improve the MEEF and LWR of the pattern. By using a photoacid generator (PAG) containing the above-mentioned onium salt compound, the affinity for the alkaline developer in the development process and the moderately short diffusion length of the acid in the photoresist film are highly balanced, which can further prevent development defects and achieve better MEEF and LWR.

[0053] In addition, by separating SO3 - By combining a fluorine atom or a fluorinated hydrocarbon group with high electron-withdrawing property at a relatively close position, the acid strength can be further increased, thereby further improving the sensitivity as a photoresist.

[0054] Furthermore, the cation is a sulfonium cation or an iodonium cation, preferably a substituted or unsubstituted triphenylsulfonium cation or a substituted or unsubstituted diphenyliodonium cation, and the substituent group of the cation is a methyl group.

[0055] In a specific embodiment of the present invention, the sulfonium cation can be listed as follows:

[0056]

[0057] In a specific embodiment of the present invention, the iodonium cations can be listed as follows:

[0058]

[0059] The preferred cations are:

[0060]

[0061] The present invention also provides a method for preparing the onium salt compound. The synthesis route is not limited. Exemplary synthesis routes that can be listed are as follows:

[0062]

[0063] <Photoacid generator>

[0064] The second aspect of the present invention provides a photoacid generator comprising the onium salt compound provided by the first aspect of the present invention.

[0065] The photoacid generator of the present invention, in addition to the onium salt compounds provided in the first aspect of the present invention, may also include other compounds that can generate acid under ultraviolet rays, far ultraviolet rays, EB, EUV, excimer laser and other rays, including but not limited to one or more of sulfonium salts, iodonium salts, bissulfonyldiazomethane compounds, O-arylsulfonyloxime compounds, and sulfonates.

[0066] <Photoresist composition>

[0067] The third aspect of the present invention provides a photoresist composition, comprising the photoacid generator (B) provided by the second aspect of the present invention, a main resin (A), an acid diffusion controller (C), a fluorine-containing resin (D) and an organic solvent (E). The amount of the photoacid generator added is 0.1 to 30 parts by mass, preferably 0.1 to 20 parts by mass, relative to 100 parts by mass of the main resin.

[0068] Main resin (A)

[0069] The main resin (A) contains a structural unit having an acid-dissociable group (the following formula A-1):

[0070]

[0071] In the formula (A-1), R3 represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, and R4 represents an acid-labile group.

[0072] R4 can be exemplified as follows: substituted or unsubstituted cyclopropane, substituted or unsubstituted cyclobutane, substituted or unsubstituted cyclopentane, substituted or unsubstituted cyclohexane, substituted or unsubstituted cyclopentenyl, substituted or unsubstituted cyclohexenyl, substituted or unsubstituted norbornane, substituted or unsubstituted adamantyl, etc. The substituent is one or more combinations of methyl, cyano or hydroxyl.

[0073] The structural unit (A-1) can be exemplified as follows:

[0074]

[0075] Preferably:

[0076]

[0077] In the present invention, the main resin is a ternary or quaternary copolymer resin, comprising at least one repeating unit described in formula (A-1). Among all the structural units constituting the main resin (A), the lower limit of the content of the structural unit (A-1) is preferably 10 mol%, more preferably 20 mol%, and particularly preferably 30 mol%; the upper limit of the content of the structural unit (A-1) is preferably 90 mol%, more preferably 70 mol%, and particularly preferably 60 mol%. By setting the content of the structural unit (A-1) to the above range, the sensitivity and LWR performance of the photoresist composition can be further improved.

[0078] The main resin (A) further includes a structural unit (A-2) having a lactone skeleton.

[0079]

[0080] In formula (A-2), R3 represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, R5 represents a hydrocarbon group having 1 to 10 carbon atoms, X represents an oxygen atom, an ester group, a carbonate group or an imino group, n is any integer between 0 and 10, and R6 represents a monovalent organic group containing a lactone structure, such as a lactone structural unit, a carbonate structural unit or a sultone structural unit.

[0081] The structural unit (A-2) can be exemplified as follows:

[0082]

[0083] Preferably:

[0084]

[0085] By including the structural unit (A-2), the main resin (A) can adjust its solubility in the developer to an appropriate level, and as a result, the sensitivity and LWR performance of the photoresist composition can be further improved. In addition, the adhesion between the film formed from the photoresist composition and the substrate can be improved.

[0086] In the present invention, the main resin is a ternary or quaternary copolymer resin, comprising at least one repeating unit described in formula (A-2). Among all the structural units constituting the main resin (A), the lower limit of the content of the structural unit (A-2) is preferably 5 mol%, more preferably 15 mol%, and particularly preferably 30 mol%; the upper limit of the content of the structural unit (A-2) is preferably 90 mol%, more preferably 70 mol%, and particularly preferably 60 mol%. By setting the content ratio of the structural unit (A-2) to the above range, the sensitivity and LWR performance of the photoresist composition can be further improved.

[0087] In the present invention, the main resin (A) comprises any one of the following monomer combinations:

[0088] Combination 1:

[0089] Combination 2:

[0090] Combination 3:

[0091] Combination 4:

[0092] Preferably, the main resin comprises any one of the following monomer combinations:

[0093] Give 2:

[0094] Synthesis method of main resin (A)

[0095] The main resin (A) can be synthesized by, for example, polymerizing monomers that provide each structural unit in an appropriate solvent in the presence of a radical polymerization initiator or the like.

[0096] The free radical polymerization initiator includes one or more combinations of azo free radical initiators and peroxide free radical initiators, preferably one or a combination of azobisisobutyronitrile (AIBN) and 2,2'-dimethyl azobisisobutyrate, and more preferably AIBN.

[0097] As the solvent used in the polymerization, the above-mentioned solvent can be cited: straight-chain alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane, cycloalkanes such as cyclohexane, cycloheptane, and cyclooctane, aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, halogenated hydrocarbons such as butyl chloride, hexyl bromide, dichloroethane, hexamethylene dibromide, and chlorobenzene, saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate, ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone, ethers such as tetrahydrofuran, dimethoxyethane, and diethoxyethane, and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. These solvents can be used alone or in combination of two or more.

[0098] The polymerization temperature is preferably 40° C. to 150° C., particularly preferably 50° C. to 120° C. The reaction time is preferably 1 h to 48 h, particularly preferably 1 h to 24 h.

[0099] The weight average molecular weight (Mw) of the polymer is preferably 1000 to 50000, more preferably 1000 to 40000, and particularly preferably 1000 to 30000, as measured by gel permeation chromatography (GPC) in terms of polystyrene. If Mw is less than 1000, a photoresist film having a sufficient receding contact angle may not be obtained. On the other hand, when Mw exceeds 50000, the developability of the photoresist film may deteriorate.

[0100] The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of polystyrene measured by GPC is preferably 1-5, more preferably 1-4.

[0101] Acid diffusion controller (C)

[0102] The photoresist composition of the present invention further comprises an acid diffusion controller as required, wherein the acid diffusion controller comprises a nitrogen-containing compound (C-1) or a compound represented by the following formula (C-2), wherein the nitrogen-containing compound comprises one or more combinations of amide-containing compounds, urea compounds, and nitrogen-containing heterocyclic compounds. The nitrogen-containing compounds can be specifically listed as follows: N-tert-butoxycarbonyl-4-hydroxypiperidine, N-tert-butoxycarbonylpyrrolidine, N-tert-butoxycarbonyl-N', N"-dicyclohexylamine, etc.

[0103] In the present invention, the compound represented by the acid diffusion controller (C-2) is generally represented by:

[0104] R7-SO3 - M + Formula (C-2)

[0105] In formula (C-2), R7 represents one or more combinations of substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, alicyclic hydrocarbon groups or aryl groups, and M + represents an onium salt cation, preferably a sulfonium cation.

[0106] Formula (C-2) can be listed as follows:

[0107]

[0108] The preferred acid diffusion controller (C) is:

[0109]

[0110] The further preferred acid diffusion controller (C) is:

[0111]

[0112] The amount of the acid diffusion controller added in the present invention is preferably 30 parts by mass or less, and more preferably 20 parts by mass or less, relative to 100 parts by mass of the main resin (A). When the amount of the acid diffusion controller added exceeds 30 parts by mass, the sensitivity of the formed photoresist film tends to be significantly reduced.

[0113] Fluorine-containing resin (D)

[0114] The fluorine-containing resin (D) is a polymer having fluorine atoms in the main chain, the side chain, or both the main chain and the side chain. The fluorine-containing resin (D) forms a water-repellent layer near the surface of the photoresist film, inhibiting the dissolution of the acid generator, the acid diffusion controller, etc. from the immersion exposure solution. By reducing the contact angle between the photoresist film and the immersion photoresist, water droplets from the immersion photoresist are less likely to remain on the photoresist film, thereby suppressing defects caused by the immersion photoresist. The following combinations can be listed:

[0115]

[0116]

[0117] The preferred fluorine-containing resin (D) is:

[0118]

[0119] Synthesis method of fluorine-containing resin (D)

[0120] The method for synthesizing the fluorine-containing resin (D) can be suitably applied to the method for producing the main resin (A).

[0121] The Mw of the polystyrene-equivalent fluorinated resin (D) measured by the GPC method is preferably 1000 to 50000, more preferably 1000 to 40000, and particularly preferably 1000 to 30000. If the Mw is less than 1000, a photoresist film having a sufficient receding contact angle may not be obtained. On the other hand, when the Mw exceeds 50000, the developability of the photoresist film may deteriorate. The Mw / Mn of the fluorinated resin (D) is preferably 1 to 5, and more preferably 1 to 4.

[0122] The lower limit of the content of the fluorine-containing resin (D) relative to 100 parts by mass of the main resin (A) is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, more preferably 1 part by mass, and particularly preferably 2 parts by mass; the upper limit of the content of the fluorine-containing resin (D) is preferably 30 parts by mass, more preferably 20 parts by mass, more preferably 15 parts by mass, and particularly preferably 10 parts by mass.

[0123] Solvent (E)

[0124] The organic solvent in the photoresist composition of the present invention is not particularly limited, as long as it can dissolve other components. The solvents that can be cited include ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, 3-methoxypropionic acid methyl ester, 3-ethoxypropionic acid ethyl ester, tert-butyl acetate, tert-butyl propionate, propylene glycol monotert-butyl ether acetate, and γ-butyrolactone; and ketone solvents such as cyclohexanone. These solvents can be used alone or in combination of two or more. The preferred solvent is one or more combinations of PGMEA, cyclohexanone, and γ-butyrolactone. The further preferred solvent is a mixed solution of PGMEA, cyclohexanone, and γ-butyrolactone.

[0125] The amount of the organic solvent added is 200 to 5000 parts by mass, preferably 500 to 3000 parts by mass, based on 100 parts by mass of the main resin.

[0126] <Pattern Formation Method>

[0127] A fourth aspect of the present invention provides a pattern forming method, comprising the following steps:

[0128] (1) forming a resist film on a substrate using the photoresist composition provided by the third aspect of the present invention;

[0129] (2) after drying, the resist film is subjected to liquid immersion exposure using ArF excimer laser;

[0130] (3) After baking, the exposed resist film is developed using a developer to obtain a photoresist pattern.

[0131] Since the pattern forming method uses the composition as a photoresist composition, a resist pattern having good MEEF and LWR can be formed while suppressing development defects in a development step.

[0132] In step (1), a solution of the composition is applied to a substrate such as a silicon wafer or an aluminum-plated wafer by a suitable coating method such as spin coating, cast coating, or roll coating to form a photoresist film. Specifically, after the photoresist composition solution is applied so that the obtained resist film has a predetermined thickness, a pre-baking (SB) is performed to evaporate the solvent in the coating film to form a resist film.

[0133] The thickness of the resist film is preferably 10 nm to 5000 nm, more preferably 10 nm to 2000 nm.

[0134] The heating conditions for the pre-bake vary depending on the composition of the photoresist composition, but are preferably about 30°C to 200°C, more preferably 50°C to 150°C.

[0135] In step (2), an immersion exposure liquid is placed on the photoresist film formed in step (1), and radiation is irradiated through the immersion exposure liquid to perform immersion exposure on the photoresist film.

[0136] An example of the liquid used for the immersion exposure is pure water, and the radiation used is ArF excimer laser light (wavelength: 193 nm).

[0137] Exposure conditions such as exposure amount can be appropriately selected according to the composition of the photoresist composition, the type of additives, etc. In the present invention, it is preferred to perform heat treatment (PEB) after exposure. PEB allows the dissociation reaction of the acid dissociation group in the resin component to proceed smoothly. The heating conditions of PEB are appropriately adjusted according to the composition of the photoresist composition, usually 30°C to 200°C, preferably 50°C to 170°C.

[0138] The developer used in the step (3) development is preferably an alkaline aqueous solution containing tetramethylammonium hydroxide dissolved therein, and the concentration of the alkaline aqueous solution is usually below 10 wt %. After development, the formed photoresist pattern is preferably washed with ultrapure water.

[0139] The above and other advantages of the present invention may be better understood through the following examples, but the following examples are not intended to limit the scope of the present invention.

[0140] Example

[0141] The present invention is described below with reference to the following examples, but the present invention is not limited to the following examples.

[0142] Preparation Example 1

[0143] In this example, the photoacid generator B-1 was prepared according to the following synthetic route:

[0144]

[0145] Preparation Example 2

[0146] According to the same synthetic route as in Preparation Example 1, the corresponding starting materials were selected to prepare the following photoacid generator B-2:

[0147]

[0148] Preparation Example 3

[0149] According to the same synthetic route as in Preparation Example 1, the corresponding starting materials were selected to prepare the following photoacid generator B-3:

[0150]

[0151] Examples and Comparative Examples

[0152] The main resin, fluorine-containing resin, acid diffusion inhibitor and solvent used in the examples and comparative examples are as follows. In the examples and comparative examples, the resins A-1 to A-4 and D-1 to D-2 shown below were used as the main resin (A) and the fluorine-containing resin (D), and they were synthesized using known techniques.

[0153] Main resin (A)

[0154] Resin A-1: ​​weight average molecular weight Mw = 7100, PDI = 1.50

[0155]

[0156] Resin A-2: weight average molecular weight Mw = 6100, PDI = 1.52

[0157]

[0158] Resin A-3: weight average molecular weight Mw = 6500, PDI = 1.42

[0159]

[0160] Resin A-4: weight average molecular weight Mw = 6400, PDI = 1.45

[0161]

[0162] Other acid generators (B)

[0163] B-4: Triphenylsulfonium perfluorobutanesulfonate

[0164] Acid diffusion controller (C)

[0165]

[0166] Fluorine-containing resin (D)

[0167] Resin D-1: weight average molecular weight Mw=7000, PDI=1.6.

[0168]

[0169] Resin D-2: weight average molecular weight Mw = 6000, PDI = 1.4.

[0170]

[0171] Solvent (E)

[0172] E-1: PGMEA

[0173] E-2: Cyclohexanone

[0174] E-3: γ-Butyrolactone

[0175] 100 parts by mass of a main resin (A), 7.8 parts by mass of a photoacid generator (B), 1.6 parts by mass of an acid diffusion inhibitor (C), 3 parts by mass of a fluorine-containing resin (D), and 2220 parts by mass of E-1, 980 parts by mass of E-2, and 30 parts by mass of E-3 as a solvent were mixed according to the components shown in Table 1 to obtain a photoresist composition solution.

[0176] Table 1 Compositions of photoresist compositions of various embodiments and comparative examples

[0177] Example Main resin (A) Photoacid generator (B) Acid diffusion inhibitor (C) Fluorine-containing resin (D) Example 1 A-1 B-1 C-1 D-1 Example 2 A-2 B-2 C-2 D-1 Example 3 A-3 B-3 C-1 D-1 Example 4 A-4 B-1 C-2 D-2 Example 5 A-2 B-3 C-2 D-2 Example 6 A-3 B-2 C-2 D-2 Example 7 A-4 B-3 C-2 D-2 Comparative Example 1 A-1 B-4 C-1 D-1 Comparative Example 2 A-2 B-4 C-1 D-1 Comparative Example 3 A-3 B-4 C-1 D-1

[0178] <Photolithography Characteristics Evaluation>

[0179] Using the resist composition, a resist pattern was formed by the resist pattern forming method described below, and the lithography property was evaluated.

[0180] Using the The silicon wafer with a thick ARC66 (manufactured by Nissan Chemical Industries) film was applied to the substrate by spin coating. Using a Nikon immersion ArF excimer laser exposure system (numerical aperture 1.30), SB was performed at 110°C for 60 seconds on a hot plate to form a photoresist film with a thickness of 0.10μm and a target size of 48nm line width. It was exposed through a line and space pattern (1L / 1S) mask. After that, PEB was performed at 90°C for 60 seconds, and then developed at 23°C for 4 seconds with a 2.38wt% tetramethylammonium hydroxide aqueous solution (TMAH developer), washed with water and dried to form a positive resist pattern.

[0181] LWR

[0182] At this time, the exposure amount used to form a line and space pattern (1L / 1S) with a line width of 48nm and a line width of 1:1 is defined as the optimal exposure amount, and the optimal exposure amount is defined as the sensitivity. When observing the 48nm1L / 1S pattern analyzed with the optimal exposure dose from the top of the pattern using Hitachi CD-SEM: CG4000, observe the line width at any 10 points, and calculate the standard deviation (σ) based on the results, and use 3σ as the measurement value of LWR. The smaller this value is, the better the linearity of the pattern after development.

[0183] MEEF

[0184] The evaluation items of MEEF are the same as those of LWR mentioned above, except that the optimal exposure is set to an exposure with a line width of 50nm formed using a line and space pattern (1L / 1S) mask, where the line and space pattern (1L / 1S) mask has a target size of 50nm line width. The same procedure is used to determine the optimal exposure. At the optimal exposure dose, the line width of the pattern resolved using a line and space pattern mask with a pitch of 100nm is measured, and the target sizes are 46nm, 48nm, 50nm, 52nm and 54nm. The results are plotted on the horizontal axis, with the target size of the mask as the horizontal axis and the line width as the vertical axis, and the slope determined by the least squares method is defined as MEEF. The closer the slope is to 1, the better the mask reproducibility.

[0185] defect

[0186] Same as the above LWR evaluation, except that the entire wafer is exposed using a mask with a target size of 48nm, with a pattern of 1L / 1S so that the distance between one shot and the next is 1mm to form a resist pattern. The unexposed area between shots is inspected using the defect inspection equipment KLA2810, with an inspection area of ​​1cm 2 , evaluates the number of defects per unit. The smaller the number of defects, the more the development defects are suppressed.

[0187] The above evaluation results are shown in Table 2:

[0188] Table 2 Evaluation of photoresist compositions of various examples and comparative examples

[0189] LWR(nm) MEEF <![CDATA[Developing defect (pcs / cm 2 )]]> Example 1 4.7 2.9 5 Example 2 4.4 2.5 3 Example 3 4.6 2.8 6 Example 4 4.7 2.9 5 Example 5 4.6 2.7 4 Example 6 4.5 2.6 4 Example 7 4.8 2.8 5 Comparative Example 1 5.1 3.8 35 Comparative Example 2 5.2 2.9 20 Comparative Example 3 4.9 5.1 21

[0190] As described above, compared with the comparative example, the resist composition obtained by using the photoacid generator provided by the present invention is more excellent in LWR, has a lower line pattern MEEF, and has reduced development defects. This shows that the resist composition obtained by the photoacid generator provided by the present invention has a good line pattern shape. - The combination of highly electron-withdrawing fluorine atoms in a relatively close position can enhance the acidity, while introducing a cyclic hydrocarbon group with a large spatial volume can reduce the diffusion of the acid; in addition, adding a group fragment with an ester group that can be cleaved by TMAH developer can effectively reduce development defects.

[0191] It should be noted that, according to the explanation and elaboration of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention should also be within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the invention.

Claims

1. An onium salt compound, characterized in that: It is a salt composed of anions and cations, and the general formula of the anions is shown in formula (B): In formula (B), R1 is an ester-containing group that can react with TMAH developer, R2 is a substituted or unsubstituted cycloalkane group having 6 to 10 carbon atoms, and n is any integer between 1 and 3; The cation is a sulfonium cation or an iodonium cation.

2. The onium salt compound according to claim 1, characterized in that The R1 includes one or more combinations of the following structures: Preferably, the R1 is:

3. The onium salt compound according to claim 1, characterized in that: The R2 includes one or more combinations of substituted or unsubstituted cyclohexyl, norbornyl, and adamantyl. Preferably, the R2 is adamantyl.

4. The onium salt compound according to claim 1, characterized in that: The cation is a substituted or unsubstituted triphenylsulfonium cation or a substituted or unsubstituted diphenyliodonium cation, the substituent group of the cation is a methyl group, and preferably the cation is an unsubstituted triphenylsulfonium cation.

5. A photoacid generator, characterized in that: Contains the onium salt compound according to any one of claims 1 to 4.

6. A photoresist composition, characterized in that: The invention comprises the photoacid generator (B) according to claim 5, a main resin (A), an acid diffusion controller (C), a fluorine-containing resin (D) and an organic solvent (E), wherein the main resin (A) comprises a structural unit having an acid dissociable group (the following formula A-1) and a structural unit having a lactone skeleton (A-2): In formula (A-1) and (A-2), R3 represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R4 represents an acid-labile group, R5 represents a hydrocarbon group having 1 to 10 carbon atoms, X represents an oxygen atom, an ester group, a carbonate group or an imino group, R6 represents a monovalent organic group containing a lactone structure, and n is any integer between 0 and 10.

7. The photoresist composition according to claim 6, characterized in that The main resin is a ternary or tetrapolymer resin, comprising at least one repeating unit of formula (A-1) and at least one repeating unit of formula (A-2).

8. The photoresist composition according to claim 7, characterized in that The main resin comprises any one of the following monomer combinations: Preferably, the main resin comprises any one of the following monomer combinations:

9. The photoresist composition according to any one of claims 6 to 8, characterized in that: The acid diffuser (C) includes a nitrogen-containing compound (C-1) or a compound (C-2) represented by the following formula, wherein the nitrogen-containing compound includes one or more combinations of amide-containing compounds, urea compounds, and nitrogen-containing heterocyclic compounds, and C-2 is represented by: R7-SO3 - M + Formula (C-2) In formula (C-2), R7 represents one or more combinations of substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, alicyclic hydrocarbon groups or aryl groups, and M + represents an onium salt cation.

10. A pattern forming method, characterized in that: The following steps are involved: Using the photoresist composition according to any one of claims 6 to 9 to form a resist film on a substrate; After drying, the resist film is subjected to liquid immersion exposure using ArF excimer laser; After baking, the exposed resist film is developed using a developer to obtain a photoresist pattern.

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