Pattern formation method

Abstract

This invention provides a pattern formation method that uses a (meth)acrylic polymer, which can be used for ArF patterning, as the main framework, and obtains a narrow-pitch fine pattern by dry development without silylation. [Solution] A pattern formation method comprising: forming a multilayer on a substrate to be processed; forming a resist upper layer film using an ArF excimer positive-type chemical amplification resist composition; removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking; performing a hard bake at a higher temperature and shorter time than the post-exposure bake to volatilize the removed acid-unstable groups outside the resist upper layer film, creating a difference in the number of carbon atoms between the unexposed and exposed portions; removing the resist upper layer film from the exposed portion by dry development using an oxygen-containing gas plasma to separate the pattern; and etching the pattern of the resist upper layer film onto the lower multilayer.

Description

[Technical Field]

[0001] The present invention relates to a method for forming a pattern. [Background technology]

[0002] Microfabrication technology has evolved to achieve high integration in semiconductor manufacturing devices. Lithography and dry etching are important manufacturing process technologies that support microfabrication, and the resist materials used in these processes are crucial process materials that determine the processing dimensions.

[0003] For the microfabrication of DRAM (Dynamic Random Access Memory) circuits used in cutting-edge semiconductor devices such as HBM (High Bandwidth Memory), ArF immersion lithography technology with an exposure wavelength of 193 nm is still widely used. In particular, for narrow-pitch patterns of approximately 40 nm line and space (80 nm pattern pitch) or less, so-called double patterning technology is frequently employed, which combines lithography's multi-layer process technology with CVD deposition technology to halve the pattern pitch.

[0004] When forming line and space patterns with a narrow pitch of 40 nm or less, ArF positive-type chemically amplified resists are often used as the resist material, as the exposed areas dissolve in an alkaline aqueous solution to form the pattern. One reason for this is that they offer superior resolution performance compared to ArF negative-type resists, which use organic solvents to leave the exposed areas intact.

[0005] However, even with high-resolution ArF positive resists, the roughness of the pattern edges has become a significant issue, and performance requirements have emerged that cannot be ignored. It is known that one of the causes of this pattern edge roughness is the swelling effect of the resist by the alkaline aqueous solution TMAH (tetramethylammonium hydroxide) developer, and the effects of distortion and wiggling of the resist pattern that occur during the drying process after rinsing the developer.

[0006] Manufacturers of resist materials are working to reduce the pattern edge roughness of ArF resists by developing polymer compositions that are less affected by swelling in aqueous solutions, developing low-diffusion photoacid catalyst materials that improve the resolution of positive resists, and optimizing the composition of these resist materials and their usage conditions.

[0007] On the other hand, in fields of lithography and microfabrication techniques other than ArF immersion lithography, research has been conducted on patterning using dry development to avoid the problem of pattern swelling caused by wet development, which is one of the causes of pattern edge roughness.

[0008] As an example of applying the dry development process, a method has been reported in which patterning is performed by dry development after silylation of chemically amplified positive resist compositions such as styrene and novolac (Patent Documents 1 and 2).

[0009] Furthermore, there are reports of a dry development method for non-chemically amplified resists that reverses the negative-positive state by controlling the temperature of the substrate being dry-developed (Patent Document 3).

[0010] Furthermore, there are reports of resist materials for exposure wavelengths of 300-500 nm that utilize the fact that phenolic hydroxyl groups are replaced with acid-unstable groups, and that the elimination of these acid-unstable groups causes a difference in etching rates between the exposed and unexposed areas during dry development containing oxygen gas (Patent Document 4).

[0011] Furthermore, there are reports that the difference in film thickness between the exposed and unexposed areas, which occurs due to the ideal volume change rate before and after exposure of a chemically amplified resist, can be used for pattern separation (Patent Document 5). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 07-022304 [Patent Document 2] Japanese Patent Publication No. 2004-103926 [Patent Document 3] Japanese Patent Application Publication No. 07-161607 [Patent Document 4] Japanese Patent Publication No. 2018-136536 [Patent Document 5] Japanese Patent Publication No. 2023-157346 [Overview of the project] [Problems that the invention aims to solve]

[0013] However, while silylation technology is an effective method for obtaining selectivity in dry etching, it requires the introduction of dedicated equipment for silylation, and the process is complicated, increasing the risk of defects due to the increased number of steps.

[0014] Furthermore, the negative-positive reversal resist patterning is a research report that focuses on non-chemically amplified resists such as polyvinylphenol and cresol novolac. While there is a mention of PMMA, the method of directly decomposing the main chain of PMMA polymer with energy rays for patterning is difficult to use in current high-productivity mass production technologies due to problems with insufficient etching resistance and exposure sensitivity.

[0015] Furthermore, research on dry development utilizing the ideal volume change rate before and after exposure has reported that a dry-developed pattern can be formed if a film thickness difference of 45% or more is obtained between the unexposed and exposed areas, without the need for special resists or additional steps to obtain a pattern. However, if the base polymer is replaced with a high substitution rate (e.g., protection by acid-degrading groups with a 100% protection rate) to obtain a large ideal volume change, a large exposure is required to obtain the desired high elimination reaction. Alternatively, high-temperature PEB is required to promote deprotection instead of high exposure. However, high-temperature PEB leads to an increase in acid diffusion length, causing problems with reduced microprocessability.

[0016] This invention was made in view of the above circumstances, and aims to provide a pattern forming method that uses a (meth)acrylic polymer, which can be used for ArF patterning, as the main backbone, and obtains a narrow-pitch fine pattern by dry development without silylation. [Means for solving the problem]

[0017] To solve the above problems, the present invention provides a pattern forming method, A process of forming a multilayer on a substrate to be processed, A step of forming a resist upper layer film using an ArF excimer positive chemical amplification resist composition comprising at least a base polymer having a (meth)acrylic structure substituted with an acid-unstable group, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent, A step of removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking, A hard bake is performed at a higher temperature and for a shorter time than the post-exposure bake, to volatilize the detached acid-unstable groups outside the resist upper layer film and create a difference in the number of carbon atoms between the unexposed and exposed areas. A step of removing the resist upper layer film of the exposed area by dry development using an oxygen-containing gas plasma to separate the pattern, The present invention provides a pattern formation method that includes a step of etching and transferring the pattern of the resist upper layer film to the lower layer multilayer.

[0018] With this pattern formation method, a (meth)acrylic polymer suitable for ArF patterning can be used as the main framework, and a narrow-pitch fine pattern can be obtained by dry development without silylation.

[0019] Furthermore, in the present invention, it is preferable to use a base polymer having a (meth)acrylic structure in which the substitution rate of the acid-unstable group is 80% to 100%, and in which the number of carbon atoms of the acid-unstable group is 4 to 9.

[0020] By using a resist composition containing such a base polymer, a predetermined dry development selectivity ratio between the unexposed and exposed areas can be obtained.

[0021] Furthermore, in the present invention, a base polymer that does not have a lactone structure can be used.

[0022] Even when using a resist composition containing such a base polymer, exposure, subsequent baking, dry development, and subsequent dry etching transfer to the underlying multilayer can be performed successfully.

[0023] Furthermore, in the present invention, it is preferable to perform the post-exposure bake at 80°C to 120°C for 40 to 120 seconds, and the hard bake at 130°C or higher for less than 40 seconds.

[0024] By performing post-exposure baking and hard baking at these temperatures and times, the deprotection reaction and volatilization of acid-unstable groups can be carried out more reliably.

[0025] Furthermore, in the present invention, it is preferable to use a resist composition that further contains a surfactant having a topcoat function for ArF immersion lithography, or to include a step of forming a topcoat film before the lithography.

[0026] In this invention, even if a topcoat is applied, pattern separation is possible by dry development, and by using a resist composition containing a surfactant, the topcoat application process can be reduced. [Effects of the Invention]

[0027] As described above, with the pattern formation method of the present invention, since wet development with an alkaline aqueous solution is not performed, pattern roughness due to the swelling effect of the resist during development and pattern roughness due to the waviness and twisting (wiggling) of the resist pattern that occurs during drying after rinsing the development does not occur, and a good pattern with less resist line edge roughness can be obtained.

[0028] Furthermore, because it is a dry development process that does not require silylation, there is no risk of adding dedicated silylation equipment, complicating the process, or increasing the number of process steps, thus reducing the risk of process defects. It is expected to improve the dimensional uniformity of DRAM products and reduce pattern defects caused by roughness. [Brief explanation of the drawing]

[0029] [Figure 1] Figure 1 is an explanatory diagram of an example of the pattern formation method of the present invention (resist film containing a water-repellent agent for liquid immersion). [Figure 2] Figure 2 is an explanatory diagram of another example of the pattern formation method of the present invention (liquid immersion topcoat film formation). [Modes for carrying out the invention]

[0030] As mentioned above, there was a need to develop a patterning method that uses a (meth)acrylic polymer, which can be used for ArF patterning, as the main backbone, and obtains a narrow-pitch fine pattern by dry development without silylation.

[0031] As a result of diligent research into the above-mentioned problems, the present inventors have found that a method can be used in a patterning process to obtain a predetermined separation pattern of the resist upper layer film by (A) forming a resist upper layer film using a resist composition comprising at least a (meth)acrylic base polymer substituted with acid-unstable groups, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent; (B) causing an elimination reaction of the acid-unstable groups by post-exposure baking (PEB); (C) volatilizing the eliminated acid-unstable groups by hard baking at high temperature and for a short time to reduce the carbon content of the exposed area; and (D) dry developing with a gas plasma containing oxygen gas.

[0032] In other words, the present invention is a pattern forming method, A process of forming a multilayer on a substrate to be processed, A step of forming a resist upper layer film using an ArF excimer positive chemical amplification resist composition comprising at least a base polymer having a (meth)acrylic structure substituted with an acid-unstable group, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent, A step of removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking, A hard bake is performed at a higher temperature and for a shorter time than the post-exposure bake, to volatilize the detached acid-unstable groups outside the resist upper layer film and create a difference in the number of carbon atoms between the unexposed and exposed areas. A step of removing the resist upper layer film of the exposed area by dry development using an oxygen-containing gas plasma to separate the pattern, This pattern formation method includes a step of etching and transferring the pattern of the resist upper layer film to the lower multilayer.

[0033] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0034] [Positive-type chemical amplification resist composition for ArF excimers] The ArF excimer positive chemical amplification resist composition used in the pattern formation method of the present invention comprises a base polymer having a (meth)acrylic structure substituted with acid-unstable groups, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent. Other components may be included as needed. Each component will be described in detail below.

[0035] [Base polymer] The base polymer contained in the above resist composition has a (meth)acrylic structure substituted with acid-unstable groups. The structure is not particularly limited, but it is preferable that it contains a repeating unit a1 represented by the following general formula (a1) or a repeating unit a2 represented by the following general formula (a2). [ka]

[0036] In the above general formulas (a1) and (a2), R A is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or (main chain)-C(=O)-O-X 11 -. X 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms which may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or a naphthylene group. X 2 is a single bond or (main chain)-C(=O)-O-. AL 1 and AL 2 are each independently an acid-labile group.

[0037] The carbon number of the above acid-labile group is not particularly limited as long as it volatilizes outside the resist upper layer film by the above hard bake, but 9 or less is preferable, 4 or more and 9 or less is more preferable, and 8 or 9 is still more preferable.

[0038] In addition, the number of oxygen atoms of the acid-labile group that dissociates by PEB and volatilizes by hard bake is preferably 3 or less, and more preferably 2 or less.

[0039] In addition, the smaller the number of hydrogen atoms of the acid-labile group that volatilizes after hard bake, the more preferable, preferably 22 or less, and more preferably 18 or less.

[0040] In the above general formula (a2), R 11 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hetero atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. a is an integer of 0 to 4, preferably 0 or 1.

[0041] Examples of the structure in which X 1 in the above general formula (a1) is changed include, but are not limited to, those shown below. In the following formulas, R A and AL 1 are the same as those described above.

[0042] [ka]

[0043] [ka]

[0044] The base polymer containing repeating unit a1 decomposes upon the action of acid to produce carboxyl groups, making it alkali-soluble.

[0045] AL 1 and AL 2 Examples of acid-unstable groups represented by the formulas (L1) to (L4) below include groups selected from the following general formulas, tertiary hydrocarbyl groups having 4 to 9 carbon atoms, preferably 8 or 9 carbon atoms, or saturated hydrocarbyl groups having 4 to 9 carbon atoms that include a carbonyl group, an ether bond, or an ester bond. [ka]

[0046] In the above general formula (L1), R L01 and R L02 This is a hydrogen atom or a saturated hydrocarbyl group having 1 to 8 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-octyl, and 2-ethylhexyl; and cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, and norbornyl.

[0047] In the above general formula (L1), R L03R is a hydrocarbyl group having 1 to 8 carbon atoms, and may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic, but a saturated hydrocarbyl group is preferred. Furthermore, some or all of the hydrogen atoms of the saturated hydrocarbyl group may be substituted with a hydroxyl group, a saturated hydrocarbyloxy group, an oxo group, an amino group, a saturated hydrocarbylamino group, etc., and some of the -CH2- groups constituting the saturated hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom. The saturated hydrocarbyl group is R L01 and R L02 Examples of saturated hydrocarbyl groups represented by the formula are those similar to those mentioned above. Examples of substituted saturated hydrocarbyl groups include the groups shown below. Note that the dashed lines in the formulas represent bonds.

[0048] [ka]

[0049] R L01 , R L02 and R L03 Any two of these may bond with each other to form a ring with the carbon atom to which they bond, or with a carbon atom and an oxygen atom. If a ring is formed, the R atoms involved in the formation of the ring are also involved. L01 , R L02 and R L03 Preferably, any two of these elements independently have 1 to 8 carbon atoms.

[0050] In the above general formula (L2), R L04 x is a tertiary hydrocarbyl group, or a saturated hydrocarbyl group having 4 to 9 carbon atoms that includes a carbonyl group, an ether bond, or an ester bond, or a group represented by the general formula (L1) above. x is an integer from 0 to 6.

[0051] R L04The tertiary hydrocarbyl group represented by can be branched or cyclic, and specific examples include tert-butyl group, tert-pentyl group, 1,1-diethylpropyl group, 2-cyclopentylpropan-2-yl group, 2-cyclohexylpropan-2-yl group, 1-ethylcyclopentyl group, 1-butylcyclopentyl group, 1-ethylcyclohexyl group, 1-ethyl-2-cyclopentenyl group, and 1-ethyl-2-cyclohexenyl group. Examples of saturated hydrocarbyl groups containing the carbonyl group, ether bond, or ester bond include 3-oxocyclohexyl group, 4-methyl-2-oxooxan-4-yl group, and 5-methyl-2-oxooxolan-5-yl group.

[0052] In the above general formula (L3), R L05 This is a saturated hydrocarbyl group having 1 to 6 carbon atoms, which may be substituted. The substituted saturated hydrocarbyl group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, and n-hexyl; cyclic saturated hydrocarbyl groups such as cyclopentyl and cyclohexyl; and groups in which some or all of the hydrogen atoms are substituted with hydroxyl, saturated hydrocarbyloxy, carboxyl, saturated hydrocarbylcarbonyl, oxo, amino, saturated hydrocarbylamino, cyano, mercapto, saturated hydrocarbylthio, sulfo, etc.

[0053] Furthermore, in the above general formula (L3), y is either 0 or 1, and z is an integer between 0 and 3.

[0054] In the above general formula (L4), R L06 R is a saturated hydrocarbyl group having 1 or 2 carbon atoms, which may be substituted. Also, in the above general formula (L4), L07 ~R L16Each of these is independently a hydrogen atom or a substituted, carbon-1 or carbon-2 hydrocarbyl group. The hydrocarbyl group may be saturated or unsaturated, and examples of the hydrocarbyl group include a methyl group and an ethyl group.

[0055] The following groups are examples of acid-unstable groups represented by the general formula (L1) above, including linear and branched groups. The dashed lines in the formula represent bonds. [ka]

[0056] Among the acid-unstable groups represented by the above general formula (L1), cyclic groups include tetrahydrofuran-2-yl group, 2-methyltetrahydrofuran-2-yl group, tetrahydropyran-2-yl group, and 2-methyltetrahydropyran-2-yl group.

[0057] Examples of acid-unstable groups represented by the above general formula (L2) include tert-butoxycarbonyl group, tert-butoxycarbonylmethyl group, tert-pentyloxycarbonyl group, tert-pentyloxycarbonylmethyl group, 1,1-diethylpropyloxycarbonyl group, 1,1-diethylpropyloxycarbonylmethyl group, 1-ethylcyclopentyloxycarbonyl group, 1-ethylcyclopentyloxycarbonylmethyl group, 1-ethyl-2-cyclopentenyloxycarbonyl group, 1-ethyl-2-cyclopentenyloxycarbonylmethyl group, 1-ethoxyethoxycarbonylmethyl group, 2-tetrahydropyranyloxycarbonylmethyl group, and 2-tetrahydrofuranyloxycarbonylmethyl group.

[0058] Examples of acid-unstable groups represented by the above general formula (L3) include 1-methylcyclopentyl group, 1-ethylcyclopentyl group, 1-n-propylcyclopentyl group, 1-isopropylcyclopentyl group, 1-n-butylcyclopentyl group, 1-sec-butylcyclopentyl group, 1-methylcyclohexyl group, 1-ethylcyclohexyl group, 3-methyl-1-cyclopenten-3-yl group, 3-ethyl-1-cyclopenten-3-yl group, 3-methyl-1-cyclohexen-3-yl group, and 3-ethyl-1-cyclohexen-3-yl group.

[0059] Of the acid-unstable groups represented by the above general formula (L4), the group represented by the following general formula (L4-1) is particularly preferred. [ka]

[0060] In the above general formula (L4-1), the dashed lines indicate the bond position and bond direction. L41 Each of these is independently a hydrocarbyl group having 1 or 2 carbon atoms. The hydrocarbyl group may be saturated or unsaturated. Examples of the hydrocarbyl group include a methyl group and an ethyl group.

[0061] The acid-unstable groups represented by the above general formula (L4) include, but are not limited to, the following groups. In the formula, the dashed lines represent bonds. [ka]

[0062] Also, AL 1 and AL 2 Among the acid-unstable groups represented by , the tertiary hydrocarbyl groups having 4 to 9 carbon atoms and saturated hydrocarbyl groups having 4 to 9 carbon atoms containing a carbonyl group, an ether bond, or an ester bond are, respectively, R L04 Examples similar to those given in the explanation can be cited.

[0063] The repeating unit a1 can be, but is not limited to, the following. Note that in the following formula, R A This is the same as above.

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] Note that these specific examples are X 1 This is the case when it is a single bond, 1 Even when the bond is not a single bond, it can be combined with similar acid-unstable groups. 1 Specific examples of cases where the bond is not a single bond are as described above.

[0070] The base polymer containing repeating unit a2, like repeating unit a1, decomposes under the action of acid to produce hydroxyl groups and becomes alkali-soluble.

[0071] The repeating unit a2 can be, but is not limited to, the following. Note that in the following formula, R A This is the same as above.

[0072] [ka]

[0073] [ka]

[0074] Furthermore, a base polymer without a lactone structure can also be used. Even when using such a base polymer, exposure, subsequent baking, dry development, and subsequent dry etching transfer to the underlying multilayer can be performed successfully.

[0075] Furthermore, the etching selectivity ratio between the unexposed and exposed areas during dry development is highest when 100% substitution is performed with acid-unstable groups.

[0076] In order to obtain a predetermined dry development selectivity ratio between the unexposed and exposed areas, it is preferable that the base polymer has a (meth)acrylic structure in which the substitution rate of the acid-unstable groups (protection rate of the base polymer) is 80% to 100%.

[0077] In other words, it is preferable to use a base polymer having a (meth)acrylic structure in which the substitution rate of the acid-unstable group is 80% to 100%, and in which the number of carbon atoms of the acid-unstable group is 4 to 9.

[0078] The substitution rate of acid-unstable groups was determined using NMR.

[0079] Furthermore, the molecular weight Mw of the above-mentioned base polymer is not particularly limited, but is preferably between 1,000 and 50,000. Note that the molecular weight Mw is the weight-average molecular weight and is measured by gel permeation chromatography (GPC) using tetrahydrofuran as the solvent and polystyrene as the standard substance.

[0080] One example of a method for synthesizing the above-mentioned base polymer is to heat a monomer that provides the repeating units mentioned above in an organic solvent with a polymerization initiator to polymerize it.

[0081] Examples of organic solvents used in the polymerization reaction include toluene, benzene, THF, diethyl ether, and dioxane. Examples of polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 80°C. The reaction time is preferably 2 to 100 hours, more preferably 5 to 20 hours. The acid-unstable group may be used as is after being introduced into the monomer, or it may be protected or partially protected after polymerization.

[0082] [Photoacid Generator] The photoacid generator is not particularly limited as long as it is a compound that generates acid upon irradiation with high-energy rays such as ultraviolet light, far ultraviolet light, EB, EUV, X-rays, excimer laser light, gamma rays, and synchrotron radiation. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxydicarboxyimide, O-allylsulfonyloxime, O-alkylsulfonyloxime, and other photoacid generators. Examples of these photoacid generators are those described in paragraphs

[0102] to

[0113] of Japanese Patent Application Publication No. 2007-145797.

[0083] Preferred photoacid generators include sulfonium salts represented by the following general formula (2). [ka]

[0084] In the above general formula (2), R 101 , R 102 and R 103 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. 101 , R 102 and R 103The C1-C20 hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 2,6 Examples include cyclic saturated hydrocarbyl groups such as decanyl group, adamantyl group, and adamantylmethyl group; aryl groups such as phenyl group, methylphenyl group, ethylphenyl group, n-propylphenyl group, isopropylphenyl group, n-butylphenyl group, isobutylphenyl group, sec-butylphenyl group, tert-butylphenyl group, naphthyl group, methylnaphthyl group, ethylnaphthyl group, n-propylnaphthyl group, isopropylnaphthyl group, n-butylnaphthyl group, isobutylnaphthyl group, sec-butylnaphthyl group, tert-butylnaphthyl group, and anthracenyl group; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups of these groups may have groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms interposed between them, resulting in the presence of hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic acid anhydrides, haloalkyl groups, etc.

[0085] Also, R 101 and R 102 However, they may bond to each other and form a ring with the sulfur atom to which they are bonded. In this case, the ring is preferably structured as shown below. Note that the dashed line in the formula represents R 103This is a combination of the two. [ka]

[0086] The sulfonium cations of the sulfonium salt represented by the above general formula (2) include triphenylsulfonium, 4-hydroxyphenyldiphenylsulfonium, bis(4-hydroxyphenyl)phenylsulfonium, tris(4-hydroxyphenyl)sulfonium, 4-tert-butylphenyldiphenylsulfonium, bis(4-tert-butylphenyl)phenylsulfonium, tris(4-tert-butylphenyl)sulfonium, 4-tert-butoxyphenyldiphenylsulfonium, bis(4-tert-butoxyphenyl)phenylsulfonium, tris(4-tert-butoxyphenyl)sulfonium, 3-tert-butoxyphenyldiphenylsulfonium, bis(3-tert-butoxyphenyl)phenylsulfonium, and tris(3-tert- rt-butoxyphenyl)sulfonium, 3,4-di-tert-butoxyphenyldiphenylsulfonium, bis(3,4-di-tert-butoxyphenyl)phenylsulfonium, tris(3,4-di-tert-butoxyphenyl)sulfonium, diphenyl(4-thiophenoxyphenyl)sulfonium, 4-tert-butoxycarbonylmethyloxyphenyldiphenylsulfonium, tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium, (4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium, tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium, (4-hydroxy-3,5-dimethylphenyl)diphenylsulfonium, (4-n-hexyloxy-3,Examples of cations include 5-dimethylphenyl)diphenylsulfonium, dimethyl(2-naphthyl)sulfonium, 4-hydroxyphenyldimethylsulfonium, 4-methoxyphenyldimethylsulfonium, trimethylsulfonium, 2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, trybenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium, 2-oxo-2-phenylethylthiacyclopentanium, diphenyl2-thienylsulfonium, 4-n-butoxynaphthyl-1-thiacyclopentanium, 2-n-butoxynaphthyl-1-thiacyclopentanium, 4-methoxynaphthyl-1-thiacyclopentanium, and 2-methoxynaphthyl-1-thiacyclopentanium.

[0087] Furthermore, the sulfonium cation of the sulfonium salt represented by the general formula (2) above can be represented by the following formula. In the following formula, Me is a methyl group. [ka]

[0088] Of these, triphenylsulfonium, 4-tert-butylphenyldiphenylsulfonium, 4-tert-butoxyphenyldiphenylsulfonium, tris(4-tert-butylphenyl)sulfonium, tris(4-tert-butoxyphenyl)sulfonium, and dimethylphenylsulfonium are preferred.

[0089] In the above general formula (2), Xa - This is an anion represented by one of the following general formulas (2A) to (2D). [ka]

[0090] In the above general formula (2A), R faThis is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic.

[0091] Among the anions represented by the above general formula (2A), those represented by the following general formula (2A') are particularly preferred. [ka]

[0092] In the above general formula (2A'), R HF R is a hydrogen atom or a trifluoromethyl group. 111 This is a hydrocarbyl group having 1 to 30 carbon atoms, which may contain heteroatoms. The heteroatoms are preferably oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms, with oxygen atoms being more preferred. The hydrocarbyl group is particularly preferred to have 6 to 30 carbon atoms in order to obtain high resolution in fine pattern formation.

[0093] R 111The hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C30 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 eicosanyl; cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, Examples include cyclic saturated hydrocarbyl groups with 3 to 30 carbon atoms, such as norbornylmethyl group, tricyclodecanyl group, tetracyclododecanyl group, tetracyclododecanylmethyl group, and dicyclohexylmethyl group; unsaturated aliphatic hydrocarbyl groups with 2 to 30 carbon atoms, such as allyl group and 3-cyclohexenyl group; aryl groups with 6 to 30 carbon atoms, such as phenyl group, 1-naphthyl group, and 2-naphthyl group; aralkyl groups with 7 to 30 carbon atoms, such as benzyl group and diphenylmethyl group; and groups obtained by combining these.

[0094] Furthermore, some or all of the hydrogen atoms of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the carbon atoms of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, they may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, nitro groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides, haloalkyl groups, etc. Examples of hydrocarbyl groups containing heteroatoms include tetrahydrofuryl groups, methoxymethyl groups, ethoxymethyl groups, methylthiomethyl groups, acetamidomethyl groups, trifluoroethyl groups, (2-methoxyethoxy)methyl groups, acetoxymethyl groups, 2-carboxy-1-cyclohexyl groups, 2-oxopropyl groups, 4-oxo-1-adamantyl groups, and 3-oxocyclohexyl groups.

[0095] The synthesis of sulfonium salts having the anion represented by the above general formula (2A') is described in detail in Japanese Patent Publication No. 2007-145797, Japanese Patent Publication No. 2008-106045, Japanese Patent Publication No. 2009-007327, Japanese Patent Publication No. 2009-258695, etc.

[0096] Examples of anions represented by the above general formula (2A) include, but are not limited to, nonafluorobutanesulfonate, partially fluorinated sulfonates described in paragraphs

[0247] to

[0251] of Japanese Patent Publication No. 2012-189977, partially fluorinated sulfonates described in paragraphs

[0261] to

[0265] of Japanese Patent Publication No. 2013-101271, and those listed below. In the following formula, Ac is an acetyl group.

[0097] [ka]

[0098] [ka]

[0099] [ka]

[0100] In the above general formula (2B), R fb1 and R fb2 Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in the general formula (1A') above. 111 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fb1 and R fb2 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 These are bonded to each other, and the groups to which they bond are (-CF2-SO2-N- It may form a ring with -SO2-CF2-), in which case R fb1 and R fb2 The group obtained by the bonding of these two elements is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0101] In the above general formula (2C), R fc1 , R fc2 and R fc3 Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in the general formula (1A') above. 111 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fc1 , R fc2 and R fc3 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 These are bonded to each other, and the groups to which they bond are (-CF2-SO2-C - It may form a ring with -SO2-CF2-), in which case R fc1 and R fc2 The group obtained by the bonding of these two elements is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0102] In the above general formula (2D), R fd R is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in the general formula (1A') above. 111 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0103] The synthesis of sulfonium salts having the anion represented by the above general formula (2D) is described in detail in Japanese Patent Publication No. 2010-215608.

[0104] The anions represented by the above general formula (2D) include, but are not limited to, those listed below.

[0105] [ka]

[0106] [ka]

[0107] Furthermore, the photoacid generator containing the anion represented by the above general formula (2D) does not have a fluorine atom at the α-position of the sulfo group, but has two trifluoromethyl groups at the β-position, which gives it sufficient acidity to cleave acid-unstable groups in the base polymer. Therefore, it can be used as a photoacid generator.

[0108] Furthermore, as a photoacid generator, one represented by the following general formula (3) is also preferred. [ka]

[0109] In the above general formula (3), R 201 and R 202 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. 203 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. Also, R 201 , R 202 and R 203 Any two of these may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, the ring is defined as R in the explanation of general formula (2) above. 101 and R 102 Examples similar to those exemplified include rings that can be formed when these elements bond to each other, together with the sulfur atoms to which they bond.

[0110] R 201 and R 202The hydrocarbyl group represented by may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, tert-pentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group; cycloalkyl groups having 3 to 20 carbon atoms such as cyclopentyl group, cyclohexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclohexylmethyl group, cyclohexylethyl group, norbornyl group, oxanorbornyl group, tricyclo[5.2.1.0 2,6 decanyl group, adamantyl group; aryl groups having 6 to 20 carbon atoms such as phenyl group, methylphenyl group, ethylphenyl group, n-propylphenyl group, isopropylphenyl group, n-butylphenyl group, isobutylphenyl group, sec-butylphenyl group, tert-butylphenyl group, naphthyl group, methylnaphthyl group, ethylnaphthyl group, n-propylnaphthyl group, isopropylnaphthyl group, n-butylnaphthyl group, isobutylnaphthyl group, sec-butylnaphthyl group, tert-butylnaphthyl group; groups obtained by combining these, etc. Further, some or all of the hydrogen atoms of these groups may be substituted with groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, halogen atom, and some of -CH2- of these groups may be substituted with groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, etc. As a result, it may contain a hydroxy group, fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, carbonyl group, ether bond, ester bond, sulfonic acid ester bond, carbonate bond, lactone ring, sultone ring, carboxylic acid anhydride, haloalkyl group, etc. Among these, R 201 and R 202 are preferably aryl groups in which a hydrogen atom may be substituted.

[0111] R 203The hydrocarbylene group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkane diyl groups with 1 to 20 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, heptadecane-1,17-diyl group, etc.; cyclopentanediyl group, cyclohex Examples include cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as xanediyl, norbornanediyl, and adamantanediyl groups; arylene groups having 6 to 20 carbon atoms, 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, and tert-butylnaphthylene; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of these groups may be substituted with heteroatomic groups such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, they may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, nitro groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides, haloalkyl groups, etc. Among these, R 203 Preferably, it is an arylene group which may have hydrogen atoms substituted on it.

[0112] In the above general formula (3), G is a C1-C20 hydrocarbylene group which may contain single bonds or heteroatoms. The hydrocarbylene group represented by G may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R 203 Examples of hydrocarbylene groups represented by the above are similar to those exemplified. Furthermore, some or all of the hydrogen atoms of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups of these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, they may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, nitro groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides, haloalkyl groups, etc. Of these, G is preferably a methylene group, or a methylene group in which a hydrogen atom is substituted with a fluorine atom or a trifluoromethyl group.

[0113] In the above general formula (3), L x This is a divalent linking group. Examples of such linking groups include ether bonds, ester bonds, thioether bonds, sulfinate ester bonds, sulfonic acid ester bonds, carbonate bonds, and carbamate bonds.

[0114] Examples of photoacid generators represented by the above general formula (3) include those similar to those exemplified as photoacid generators represented by formula (3) in Japanese Patent Publication No. 2018-062503.

[0115] The content of the photoacid generator in the above resist composition is not particularly limited, but is preferably 0 to 40 parts by mass, more preferably 0.1 to 40 parts by mass, and even more preferably 0.1 to 20 parts by mass, per 80 parts by mass of the base polymer. Good resolution is obtained within this range. The photoacid generator may be used alone or in combination of two or more types.

[0116] [Quencher] The above resist composition contains a quencher as an essential component as an acid diffusion control agent. Examples of the quencher include amine compounds and onium salt compounds. Examples of amine compounds include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of Japanese Patent Publication No. 2008-111103, particularly amine compounds having a hydroxyl group, ether linkage, ester linkage, lactone ring, cyano group, or sulfonic acid ester linkage. Also, compounds in which a primary or secondary amine is protected with a carbamate group, such as the compound described in Japanese Patent Publication No. 3790649, can also be cited. Examples of onium salt compounds include those described in Patent Document 1 mentioned above and in Japanese Patent Publication No. 2003-005376, etc.

[0117] Alternatively, a sulfonium sulfonate salt having a nitrogen-containing substituent may be used as a quencher. Such a compound functions as a quencher in the unexposed area and loses its quenching ability in the exposed area through neutralization with its own generated acid, functioning as a so-called photodecayable base. By using a photodecayable base, the contrast between the exposed and unexposed areas can be further enhanced. For example, Japanese Patent Publication No. 2009-109595 and Japanese Patent Publication No. 2012-046501 can be referenced as examples of photodecayable bases.

[0118] The quencher content in the above resist composition is not particularly limited, but is preferably 0.001 to 12 parts by mass, and more preferably 0.01 to 8 parts by mass, per 80 parts by mass of the base polymer. The quencher may be used alone or in combination of two or more types.

[0119] Furthermore, the photoacid generator and quencher included in the above-mentioned resist composition are not particularly limited. For example, the one described in Japanese Patent Publication No. 2010-215608 is one example.

[0120] [Organic solvents] The organic solvent is not particularly limited as long as it has sufficient solubility for the components contained in the resist composition and has good film-forming properties. Examples of such organic solvents include cell-solubilizing solvents such as methyl cell-solubilizing acetate, propylene glycol alkyl ether solvents such as propylene glycol monomethyl ether, propylene glycol alkyl ether acetate solvents such as propylene glycol monomethyl ether acetate, ester solvents such as butyl acetate and ethyl lactate, alcohol solvents such as isopropanol, ketone solvents such as cyclohexanone and methyl isobutyl ketone, ether solvents such as methylphenyl ether, highly polar solvents such as N-methylpyrrolidone, and mixtures thereof.

[0121] [Surfactants] Here, the resist composition may be modified as needed by adding a water-repellent composition (surfactant) that exhibits topcoat functionality to the resist composition in order to reduce the topcoat film formation step during ArF immersion exposure. The water-repellent layer having topcoat functionality is formed with a uniform thickness on the resist upper film during application. The water-repellent layer remains uniformly on the resist upper film after exposure and post-exposure baking. However, since the composition of the water-repellent layer itself does not change before exposure and after post-exposure baking, it is easily removed in the separation step of dry development when separating the exposed and unexposed areas.

[0122] Preferably, the surfactant is one that is insoluble or sparingly soluble in water and alkaline developer, or one that is insoluble or sparingly soluble in water and soluble in alkaline developer. Examples of such surfactants can be found in Japanese Patent Publication No. 2007-297590, Japanese Patent Publication No. 2010-215608, and Japanese Patent Publication No. 2011-016746.

[0123] Examples of surfactants that are insoluble or poorly soluble in the above-mentioned water and alkaline developer include nonionic surfactants such as polyoxyethylene alkyl ethers such as polyoxyethylene olein ether, polyoxyethylene alkyl allyl ethers such as polyoxyethylene nonylphenol ether, polyoxyethylene polyoxypropylene block copolymers, sorbitan fatty acid esters such as sorbitan monostearate, and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate. Among the surfactants described in the above publication, FC-4430 (manufactured by 3M), Surflon® S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Orfin® E1004 (manufactured by Nisshin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), and oxetane ring-opening polymers represented by the following general formula (surf-1) are preferred. [ka]

[0124] Here, R, Rf, A, B, C, m, and n apply only to the above general formula (surf-1), notwithstanding the preceding description. R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. Examples of such aliphatic groups include the divalent ethylene group, 1,4-butylene group, 1,2-propylene group, 2,2-dimethyl-1,3-propylene group, and 1,5-pentylene group, while examples of trivalent or tetravalent groups are listed below. In the formula, the dashed lines represent bonds, which are substructures derived from glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol, respectively. [ka]

[0125] Among these, the 1,4-butylene group and the 2,2-dimethyl-1,3-propylene group are preferred.

[0126] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer from 0 to 3, n is an integer from 1 to 4, and the sum of n and m is the valence of R, which is an integer from 2 to 4. A is 1. B is an integer from 2 to 25, preferably an integer from 4 to 20. C is an integer from 0 to 10, preferably 0 or 1. Also, each structural unit in the general formula (surf-1) does not define its order, and they may be bonded blockwise or randomly. Regarding the production of a surfactant based on a partially fluorinated oxetane ring-opening polymer, it is detailed in US Patent No. 5650483 and the like.

[0127] A surfactant that is insoluble or poorly soluble in water and soluble in an alkaline developer has the function of reducing water seepage and leaching by orienting on the surface of the resist upper layer film when no resist protective film is used in ArF immersion lithography. Therefore, it is useful for suppressing the elution of water-soluble components from the resist upper layer film and reducing damage to the exposure apparatus. Also, after exposure, it becomes solubilized during development with an alkaline developer after post-exposure bake (PEB) and is unlikely to become foreign matter causing defects, so it is useful. Such a surfactant has the property of being insoluble or poorly soluble in water and soluble in an alkaline developer, is a polymer-type surfactant, and is also called a hydrophobic resin. Particularly, those with high water repellency and improved water lubricity are preferred.

[0128] Examples of such polymer-type surfactants include those containing at least one selected from the repeating units represented by any of the following general formulas (4A) to (4E).

Chemical formula

[0129] In the general formulas (4A) to (4E) above, R B is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. W 1 is -CH2-, -CH2CH2-, -O-, or two separated -H's. R s1Each of these is independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. s2 R is a single bond or a linear or branched hydrocarbylene group having 1 to 5 carbon atoms. s3 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group or a fluorinated hydrocarbyl group, or an acid-unstable group. s3 If the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. s4 R is a (u+1) valent hydrocarbon group or fluorinated hydrocarbon group having 1 to 20 carbon atoms. u is an integer from 1 to 3. s5 These are, independently, hydrogen atoms, or -C(=O)-OR s7 It is a group represented by R. s7 This is a fluorinated hydrocarbyl group having 1 to 20 carbon atoms. s6 This is a hydrocarbyl group having 1 to 15 carbon atoms or a fluorinated hydrocarbyl group, and an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds.

[0130] R s1 The hydrocarbyl group represented by can be linear, branched, or cyclic. Specific examples include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, adamantyl, norbornyl, etc. Of these, those with 1 to 6 carbon atoms are preferred.

[0131] R s2 The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene, ethylene, propylene, butylene, and pentylene groups.

[0132] R s3 and R s6The hydrocarbyl group represented by can be linear, branched, or cyclic, and specific examples include alkyl groups, alkenyl groups, and alkynyl groups, but alkyl groups are preferred. The alkyl group is R s1 In addition to the examples given as hydrocarbyl groups represented by , other examples include n-undecyl group, n-dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc. s3 and R s6 Examples of fluorinated hydrocarbyl groups represented by the above-mentioned hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to the carbon atoms are replaced with fluorine atoms. As mentioned above, ether bonds or carbonyl groups may be interposed between these carbon-carbon bonds.

[0133] R s3 Examples of acid-unstable groups represented by the above general formulas (L1) to (L4) include groups represented by the above general formulas (L1) to (L4), tertiary hydrocarbyl groups having 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groups in which each alkyl group has 1 to 6 carbon atoms, and oxoalkyl groups having 4 to 20 carbon atoms.

[0134] R s4 The (u+1) valent hydrocarbon group or fluorinated hydrocarbon group represented by may be linear, branched, or cyclic, and specific examples include groups obtained by further removing u hydrogen atoms from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group.

[0135] R s7The fluorinated hydrocarbyl group represented by can be linear, branched, or cyclic, and specifically, it can be a hydrocarbyl group in which some or all of the hydrogen atoms are substituted with fluorine atoms, and specific examples include trifluoromethyl group, 2,2,2-trifluoroethyl group, 3,3,3-trifluoro-1-propyl group, 3,3,3-trifluoro-2-propyl group, 2,2,3,3-tetrafluoropropyl group, 1,1,1 Examples include 3,3,3-hexafluoroisopropyl group, 2,2,3,3,4,4,4-heptafluorobutyl group, 2,2,3,3,4,4,5,5-octafluoropentyl group, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, 2-(perfluorobutyl)ethyl group, 2-(perfluorohexyl)ethyl group, 2-(perfluorooctyl)ethyl group, and 2-(perfluorodecyl)ethyl group.

[0136] The repeating units that can be represented by any of the above general formulas (4A) to (4E) include, but are not limited to, the following. Note that in the following formulas, R B This is the same as described above.

[0137] [ka]

[0138] [ka]

[0139] [ka]

[0140] The polymer-type surfactant described above may further contain other repeating units other than those represented by the general formulas (4A) to (4E). Examples of other repeating units include those obtained from methacrylic acid and α-trifluoromethylacrylic acid derivatives. The content of the repeating units represented by the general formulas (4A) to (4E) in the polymer-type surfactant is preferably 20 mol% or more, more preferably 60 mol% or more, and even more preferably 100 mol% of the total repeating units.

[0141] The molecular weight Mw of the above polymer-type surfactant is preferably 1,000 to 50,000, and more preferably 2,000 to 20,000. Within this range, the surface modification effect is sufficient, and development defects are less likely to occur.

[0142] One method for synthesizing the above polymer-type surfactant involves polymerizing a monomer containing unsaturated bonds that provide repeating units represented by the above general formulas (4A) to (4E), and optionally other repeating units, by heating it in an organic solvent with a radical initiator. Examples of organic solvents used during polymerization include toluene, benzene, THF, diethyl ether, and dioxane. Examples of polymerization initiators include AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 100°C. The reaction time is preferably 4 to 24 hours. The acid-unstable group may be used as is after being introduced into the monomer, or it may be protected or partially protected after polymerization.

[0143] When synthesizing the above polymer-type surfactants, known chain transfer agents such as dodecyl mercaptan or 2-mercaptoethanol may be used to adjust the molecular weight. In that case, the amount of these chain transfer agents added is preferably 0.01 to 10 mol% relative to the total number of moles of monomers to be polymerized.

[0144] For surfactants that are insoluble or sparingly soluble in water and soluble in alkaline developing solutions, please also refer to Japanese Patent Publication No. 2008-122932, Japanese Patent Publication No. 2010-134012, Japanese Patent Publication No. 2010-107695, Japanese Patent Publication No. 2009-276363, Japanese Patent Publication No. 2009-192784, Japanese Patent Publication No. 2009-191151, Japanese Patent Publication No. 2009-098638, Japanese Patent Publication No. 2010-250105, Japanese Patent Publication No. 2011-042789, etc.

[0145] The surfactant content is preferably 0 to 20 parts by mass per 80 parts by mass of the base polymer. If a surfactant is included, the lower limit is preferably 0.001 parts by mass, and more preferably 0.01 parts by mass. On the other hand, the upper limit is preferably 15 parts by mass, and more preferably 10 parts by mass. The surfactant may be used alone or in combination of two or more types.

[0146] [Pattern formation method] Furthermore, as a patterning method, the aforementioned resist composition is coated onto a workpiece substrate such as a multilayer containing Si elements, ArF immersion exposure and post-exposure baking are performed, and then dry development (dry development) is performed with a gas plasma containing oxygen gas to separate the resist pattern. Next, the resist pattern is transferred to the workpiece substrate under dry etching conditions containing fluorine gas.

[0147] In other words, the present invention provides a pattern forming method, A process of forming a multilayer on a substrate to be processed, A step of forming a resist upper layer film using an ArF excimer positive chemical amplification resist composition comprising at least a base polymer having a (meth)acrylic structure substituted with an acid-unstable group, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent, A step of removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking, A hard bake is performed at a higher temperature and for a shorter time than the post-exposure bake, to volatilize the detached acid-unstable groups outside the resist upper layer film and create a difference in the number of carbon atoms between the unexposed and exposed areas. A step of removing the resist upper layer film of the exposed area by dry development using an oxygen-containing gas plasma to separate the pattern, The present invention provides a pattern formation method that includes a step of etching and transferring the pattern of the resist upper layer film to the lower layer multilayer.

[0148] The substrate to be processed in the pattern formation method of the present invention is not particularly limited, and for example, a wafer substrate on which a film to be processed has been formed can be used. Examples of the film to be processed include silicon oxide films.

[0149] The multilayer formed on the workpiece substrate is not particularly limited as long as it includes two or more layers. The lower layer of the multilayer formed on the workpiece substrate can be, for example, a coated carbon film. The intermediate layer of the multilayer formed on the lower layer can be, for example, a coated Si-containing anti-reflective film.

[0150] Examples of resist compositions for forming the resist upper layer film include the resist compositions described above. Furthermore, the method for forming the resist upper layer film is not particularly limited, and known methods can be used.

[0151] The exposure conditions for the resist upper layer are not particularly limited; for example, when forming a fine line-and-space pattern, a predetermined pattern can be formed using dipole illumination conditions.

[0152] To obtain a predetermined deprotection reaction of acid-unstable groups with a high protection rate of 80% to 100%, and a predetermined volatilization of the acid-unstable groups after elimination, the process is carried out in two stages: a first low-temperature bake (PEB) and a second high-temperature bake (hard bake; this second high-temperature bake determines the quality of the dry-developed pattern). The first low-temperature bake, i.e., the post-exposure bake, is preferably performed for 40 to 120 seconds, more preferably for 60 to 120 seconds, while the second high-temperature bake, i.e., the hard bake, is preferably performed within 40 seconds.

[0153] The first low-temperature bake is preferably performed at 80°C to 120°C. The second high-temperature bake is performed at a higher temperature than the first low-temperature bake. The second high-temperature bake is preferably at 130°C or higher, and more preferably at 150°C or higher.

[0154] Specifically, it is preferable to perform the post-exposure bake at 80°C to 120°C for 40 to 120 seconds, and the hard bake at 130°C or higher for less than 40 seconds. Furthermore, it is more preferable to perform the hard bake at 150°C or higher for less than 40 seconds.

[0155] Any acid-unstable group that undergoes a deprotection reaction at low temperatures in PEB or at high temperatures in PEB can be used, as long as it volatilizes outside the resist upper film by the hard bake described above. In particular, it is preferable that the acid-unstable group has 4 to 9 carbon atoms. Of the acid-unstable groups with 4 to 9 carbon atoms, it is preferable that the acid-unstable group has a cyclic skeleton.

[0156] Furthermore, the base polymer having a (meth)acrylic structure substituted with an acid-unstable group that is eliminated by PEB and volatilized by hard baking is not limited to a single type; base polymers substituted with multiple types of acid-unstable groups can be used.

[0157] Furthermore, it is preferable to use a resist composition that further contains a surfactant having a topcoat function for ArF immersion lithography, or to include a step of forming a topcoat film before the lithography.

[0158] Dry development is not particularly limited as long as it uses an oxygen-containing gas plasma.

[0159] The method for etching and transferring the pattern of the resist upper layer to the lower multilayer is not particularly limited, and known methods can be used.

[0160] An example of the pattern formation method of the present invention will be explained using Figure 1. A multilayer including a coated carbon film 3 and a coated Si-containing anti-reflective film 4 is formed on a wafer substrate 1 on which a film to be processed 2 has been formed, and an ArF positive type chemically amplified resist upper layer film 5 is formed thereon using an ArF positive type chemically amplified resist composition (Figure 1(a)). Next, the ArF positive type chemically amplified resist upper layer film is exposed using a reticle 6 and ArF exposure light 7 (Figure 1(b)). Next, PEB is performed to form a resist exposure area 5a on the ArF positive type chemically amplified resist upper layer film in which the acid-unstable groups have been deprotected (Figure 1(c)). Next, hard bake is performed to volatilize the acid-unstable groups from the resist exposure area 5a in which the acid-unstable groups have been deprotected (Figure 1(d)). Next, the resist exposure area is removed by dry development with an oxygen-containing gas plasma to form a resist pattern 5b (Figure 1(e)). Next, the resist pattern 5b is used as a mask to transfer the pattern to a coated Si-containing anti-reflective film, forming a coated Si-containing anti-reflective film pattern 4a (Figure 1(f)). Next, the coated Si-containing anti-reflective film pattern 4a is used as a mask to transfer the pattern to a coated carbon film, forming a coated carbon film pattern 3a (Figure 1(g)).

[0161] Another example of the pattern formation method of the present invention will be explained using Figure 2. A multilayer including a coated carbon film 23 and a coated Si-containing anti-reflective film 24 is formed on a wafer substrate 21 on which a film to be processed 22 is formed. An ArF positive chemical amplification resist upper layer film 25 is formed thereon using an ArF positive chemical amplification resist composition, and an immersion topcoat film 28 is formed thereon (Figure 2(a)). Next, the ArF positive chemical amplification resist upper layer film is exposed using a reticle 26 and ArF exposure light 27 (Figure 2(b)). Next, PEB is performed to form a resist exposure area 25a on the ArF positive chemical amplification resist upper layer film in which the acid-unstable groups have been deprotected (Figure 2(c)). Next, hard bake is performed to volatilize the acid-unstable groups from the resist exposure area 25a under the immersion topcoat film 28a (Figure 2(d)). Next, the resist exposure area is removed by dry development using an oxygen-containing gas plasma to form a resist pattern 25b (Figure 2(e)). Next, the resist pattern 25b is used as a mask to transfer the pattern to a coated Si-containing anti-reflective film to form a coated Si-containing anti-reflective film pattern 24a (Figure 2(f)). Next, the coated Si-containing anti-reflective film pattern 24a is used as a mask to transfer the pattern to a coated carbon film to form a coated carbon film pattern 23a (Figure 2(g)). [Examples]

[0162] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0163] (Preparation of resist composition) According to a predetermined synthesis method, a base polymer having a predetermined number of carbon atoms and substitution rate was prepared. An acid generator, a quencher, and a water-repellent agent (surfactant) for immersion were dissolved in an organic solvent of PGMEA to prepare a solution. The solution was then filtered through a 0.2 μm Teflon® filter to prepare resist compositions R1-R16, R21-R2C, R31, R32, and R41-R48 (compositions with 4, 5, 8, and 9 carbon atoms in the acid-unstable groups for protection rates of 10%, 30%, 80%, and 100%, respectively; compositions with 4, 5, 8, 9, and 10 carbon atoms in the acid-unstable groups for protection rates of 10% and 90%, respectively; a composition with 9 carbon atoms in the acid-unstable groups for protection rate of 100%, and compositions with 9 carbon atoms in the acid-unstable groups for protection rates of 100%, 90%, 80%, 70%, 60%, 40%, and 10%, respectively). The protection rates were determined using NMR. The structures of each repeating unit from AL1 to AL5, and the structural formulas of the photoacid generator AG1, quencher Q1, and water repellent PF1 are as follows.

[0164] [ka]

[0165] (Resist pattern formation evaluation 1) Table 1 is a list of evaluation samples from an example (resist pattern formation evaluation 1) for investigating the dependence of acid-unstable groups on the protection rate (substitution rate).

[0166] [Table 1]

[0167] First, a multilayer film (a 54nm coated film for the coated carbon film, processed at 250°C for 60 seconds, and an 18nm coated film for the Si-containing anti-reflective film, processed at 220°C for 60 seconds) was formed on the wafer's workpiece film (SiO film). Then, the resist compositions shown in Table 1 were applied to the upper layer by spin coating and pre-baking, respectively. Pre-baking was performed at 120°C for 60 seconds to obtain sample wafers with a resist film thickness of 130nm.

[0168] Next, using an ArF immersion lithography machine, a line and space pattern with a half-pitch of 40 nm was formed on a binary reticle with a lens numerical aperture of 1.35 NA at a rate of 25 mJ / cm². 2 The wafers were exposed under constant exposure conditions. Next, each exposed wafer was subjected to a Post Exposure Bake (PEB) on a hot plate at 90°C for 90 seconds. Then, a hard bake was performed at 150°C for 30 seconds, and the step difference between the exposed and unexposed areas of each sample after the hard bake was measured using an Atomic Force Microscope (AFM). The results are summarized in Table 2.

[0169] [Table 2]

[0170] In resist compositions (R1-R16) of base polymers protected (substituted) with 4-9 carbon atoms, film thinning in the exposed areas was observed after hard baking. The higher the carbon number, the greater the film thinning in the exposed areas after hard baking.

[0171] Next, the evaluation samples in Table 2 were dry-developed, and the residual resist film in the unexposed areas after resist pattern separation was measured. The results are shown in Table 3. The conditions for the dry development were as follows. Chamber pressure: 30mT RF Power (Top): 200W RF Power (lower): 100W O2 gas flow rate: 20 sccm N2 gas flow rate: 290 sccm Etching time: 6 seconds

[0172] [Table 3]

[0173] All evaluation samples from R1 to R16, with 4 to 9 carbon atoms and protection rates of 10% to 100%, were able to retain a resist film in the unexposed areas after dry development. The larger the carbon atom and the higher the protection rate, the larger the residual film in the unexposed areas.

[0174] (Resist pattern formation evaluation 2) Table 4 shows the results of investigating the effect of including non-volatile protective groups in the base polymer on the amount of film loss in the exposed area after hard baking and the remaining film thickness after dry development. Structures with 4 to 9 carbon atoms were used as acid-unstable groups that volatilize during hard baking, and structures with 10 carbon atoms and high-temperature activation energy type acid-unstable groups were used as structures that do not volatilize during hard baking. The protection rate (substitution rate) of the base polymer was set to 10% to 90%.

[0175] [Table 4]

[0176] First, a multilayer film (a 54nm coated carbon film was formed by processing at 250°C for 60 seconds, and an 18nm coated Si-containing anti-reflective film was formed by processing at 220°C for 60 seconds) was formed on the wafer's workpiece film (SiO film). Then, the resist compositions shown in Table 4 were formed on top of these by spin coating and pre-baking, respectively. Pre-baking was performed at 120°C for 60 seconds to obtain sample wafers with a resist film thickness of 130nm.

[0177] Next, using an ArF immersion lithography machine, a line and space pattern with a half-pitch of 40 nm was formed on a binary reticle with a lens numerical aperture of 1.35 NA at a rate of 25 mJ / cm². 2 The wafers were exposed under constant exposure conditions. After exposure, each wafer was subjected to a Post Exposure Bake (PEB) on a hot plate at 90°C for 90 seconds, followed by a hard bake at 150°C for 30 seconds.

[0178] The upper section of Table 5 shows the results of measuring the step difference between the exposed and unexposed areas of each sample after hard baking using an AFM (Atomic Force Microscope). Subsequently, the lower section of the same table shows the results of measuring the remaining film thickness of the unexposed areas after dry development under gas plasma conditions containing oxygen gas. The conditions for the dry development are as follows. Chamber pressure: 30 mT Upper RF power: 200 W Lower RF power: 100 W O2 gas flow rate: 20 sccm N2 gas flow rate: 290 sccm Etching time: 6 seconds

[0179]

Table 5

[0180] For any of the evaluation samples of R21 - R2C with the acid-labile group having 4 to 9 carbon atoms, film loss in the exposed area and resist residue film in the unexposed area after dry development could be confirmed after hard baking. Even when the base polymer contained an acid-labile group with 10 carbon atoms that did not volatilize after hard baking, step difference and pattern separation in dry development could be achieved for the resist evaluation samples with 4 to 9 carbon atoms. However, compared with the resist composition of the base polymer protected by a single acid-labile group, the residual film thickness after dry development was thinner. Also, the greater the protection rate of the acid-labile group that volatilizes during hard baking, the greater the film loss in the exposed area and the thicker the resist residue film in the unexposed area after dry development.

[0181] (Resist pattern formation evaluation 3) Table 6 shows the resist compositions added with a water-repellent agent for ArF immersion and the examples (resist pattern formation evaluation 3) when a coating-type topcoat film was used instead of the water-repellent agent.

[0182]

Table 6

[0183] A multilayer film (the coating-type carbon film was coated with 54 nm at 250 °C for 60 seconds, and the Si-containing antireflection film was coated with 18 nm at 220 °C for 60 seconds) was formed on the processed film (SiO film) of the wafer, and the resist compositions in Table 6 were spin-coated and pre-baked on the upper layer to form coating films. Pre-baking was performed at 120 °C for 60 seconds to obtain each sample wafer with a resist film thickness of 130 nm.

[0184] Next, a topcoat agent composed of an alcohol solvent was spin-coated onto an evaluation resist sample wafer without the addition of a water-repellent agent, and baked at 100°C for 60 seconds to form a topcoat film with a thickness of 30 nm.

[0185] Next, using an ArF immersion lithography machine, a line and space pattern with a half-pitch of 40 nm was formed on a binary reticle with a lens numerical aperture of 1.35 NA at a rate of 25 mJ / cm². 2 The wafers were exposed under constant exposure conditions. After exposure, each wafer was subjected to a Post Exposure Bake (PEB) on a hot plate at 90°C for 90 seconds, followed by a hard bake at 150°C for 30 seconds.

[0186] The step difference between the exposed and unexposed areas of each sample after PEB was measured using an AFM (Atomic Force Microscope). Subsequently, the residual resist film in the unexposed areas was measured after dry development under gas plasma conditions containing oxygen gas. The results are shown in Table 7. The dry development conditions were as follows: Chamber pressure: 30mT RF Power (Top): 200W RF Power (lower): 100W O2 gas flow rate: 20 sccm N2 gas flow rate: 290 sccm Etching time: 6 seconds

[0187] [Table 7]

[0188] Even when a topcoat film was formed on a film created with a resist composition, film thinning in the exposed areas after hard baking and pattern separation due to dry development were observed.

[0189] (Resist pattern formation evaluation 4) Table 8 shows examples for investigating the pattern edge roughness of dry development and the pattern edge roughness of normal alkali wet development (comparative example).

[0190]

Table 8

[0191] A multilayer film (the coating type carbon film is a 54 nm coating film after treatment at 250 °C for 60 seconds, and the Si-containing antireflection film is an 18 nm coating film after treatment at 220 °C for 60 seconds) was formed on the processed film (SiO film) of the wafer, and the resist compositions (SL1 to SL8) in Table 8 and the resist composition (RF1) of the comparative example were spin-coated and pre-baked on the upper layer thereof to form coating films. The pre-baking was performed at 120 °C for 60 seconds to obtain each sample wafer with a resist film thickness of 130 nm.

[0192] Next, for SL1 to SL8 of the examples, using an ArF immersion exposure machine, a line & space pattern with a half pitch of 40 nm formed on a binary reticle with a lens aperture number of 1.35 NA was exposed under constant exposure conditions of 25 mJ / cm 2 Then, each wafer after exposure was subjected to PEB (Post Exposure Bake) treatment at 90 °C for 90 seconds on a hot plate, and then subjected to hot plate baking treatment at 150 °C for 30 seconds as hard baking.

[0193] Next, for SL1 to SL8 of the examples, the exposed portion was etched back under gas plasma conditions containing oxygen gas to separate the resist pattern. The dry conditions at this time are as follows. Chamber pressure: 30 mT Upper RF power: 200 W Lower RF power: 100 W O2 gas flow rate: 20 sccm N2 gas flow rate: 290 sccm Etching time: 6 seconds

[0194] On the other hand, regarding the development of the comparative example, 2.38% TMAH development time was 15 seconds, followed by DIW water washing for 25 seconds, and then spin drying to produce a wafer with a resist pattern.

[0195] Next, the wafers from the example and the comparative example were etched and transferred onto a Si-containing multilayer substrate anti-reflective film under the following dry etching conditions. Chamber pressure: 50mT RF Power (Top): 500W RF Power (lower): 300W CF4 gas flow rate: 150 sccm CHF3 gas flow rate: 50 sccm Etching time: 10 seconds

[0196] The aperture of the Si-containing anti-reflective coating was measured using a low-acceleration voltage measuring SEM. The results are shown in Table 9.

[0197] Next, the pattern of the Si-containing anti-reflective film transfer was used as a mask to etch and transfer onto the underlying coated carbon film. The etching conditions at this time were as follows. Chamber pressure: 30mT RF Power (Top): 200W RF Power (lower): 100W O2 gas flow rate: 30 sccm N2 gas flow rate: 270 sccm Etching time: 15 seconds

[0198] The spatial dimensions of the coated carbon film were measured using a low-acceleration voltage measuring SEM (space dimension measurement). The apertures of the coated carbon film were also measured using a low-acceleration voltage measuring SEM. The results are shown in Table 9.

[0199] [Table 9]

[0200] In the examples with protection rates of 10% to 100% (R41 to R48), etching transfer to the coated carbon film on the underlayer of the multilayer was confirmed. Furthermore, the examples of resist compositions with 80% to 100% substitution (protection) of acid-unstable groups with 9 carbon atoms (R41 to R43) showed better LWR (Line Width Roughness) than the comparative example (RF1).

[0201] In the examples of resist compositions with a protection rate of less than 80% (R44-R48), phenomena such as increased resist dimensions and roughness were observed. However, the results can be improved by optimizing the reticle mask bias amount and etching conditions in each example.

[0202] This specification includes the following embodiments: [1]: A method for forming a pattern, A process of forming a multilayer on a substrate to be processed, A step of forming a resist upper layer film using an ArF excimer positive chemical amplification resist composition comprising at least a base polymer having a (meth)acrylic structure substituted with an acid-unstable group, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent, A step of removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking, A hard bake is performed at a higher temperature and for a shorter time than the post-exposure bake, to volatilize the detached acid-unstable groups outside the resist upper layer film and create a difference in the number of carbon atoms between the unexposed and exposed areas. A step of removing the resist upper layer film of the exposed area by dry development using an oxygen-containing gas plasma to separate the pattern, A pattern formation method characterized by including a step of etching and transferring the pattern of the resist upper layer film to the lower layer multilayer. [2]: The pattern forming method of [1] above, characterized in that the base polymer has a (meth)acrylic structure in which the substitution rate of the acid-unstable group is 80% to 100%, and the number of carbon atoms in the acid-unstable group is 4 to 9. [3]: The pattern forming method according to [1] or [2] above, characterized in that the base polymer does not have a lactone structure. [4]: A pattern formation method according to any one of the above [1] to [3], characterized in that the post-exposure bake is performed at 80°C to 120°C for 40 seconds to 120 seconds, and the hard bake is performed at 130°C or higher for less than 40 seconds. [5]: A pattern formation method according to any one of the above [1] to [4], characterized in that the resist composition further contains a surfactant having a topcoat function for ArF immersion exposure, or includes a step of forming a topcoat film before exposure.

[0203] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0204] 1, 21…wafer substrate 2, 22...Processed film 3, 23…Coated carbon film 3a, 23a... Coated carbon film patterns 4, 24...Coating type Si-containing antireflection coating 4a, 24a... Coated Si-containing anti-reflective coating patterns 5, 25…ArF positive type chemically amplified resist upper layer 5a, 25a... Exposed resist areas where acid-unstable groups have been deprotected. 5b, 25b... Resist pattern (unexposed area) 6, 26... Reticle (photomask) 7, 27…ArF exposure light 28, 28a... Immersion topcoat film

Claims

1. A pattern formation method, A process of forming a multilayer on a substrate to be processed, A step of forming a resist upper layer film using an ArF excimer positive chemical amplification resist composition comprising at least a base polymer having a (meth)acrylic structure substituted with an acid-unstable group, a photoacid generator, a quencher that controls acid diffusion, and an organic solvent, A step of removing acid-unstable groups from the exposed portion of the resist upper layer film by exposure and post-exposure baking, A hard bake is performed at a higher temperature and for a shorter time than the post-exposure bake, to volatilize the detached acid-unstable groups outside the resist upper layer film and create a difference in the number of carbon atoms between the unexposed and exposed areas. A step of removing the resist upper layer film of the exposed area by dry development using an oxygen-containing gas plasma to separate the pattern, A pattern formation method characterized by including a step of etching and transferring the pattern of the resist upper layer film to the lower layer multilayer.

2. The pattern forming method according to claim 1, characterized in that the base polymer used has a (meth)acrylic structure in which the substitution rate of the acid-unstable group is 80% to 100%, and the number of carbon atoms in the acid-unstable group is 4 to 9.

3. The pattern forming method according to claim 1 or 2, characterized in that the base polymer used is one that does not have a lactone structure.

4. The pattern forming method according to claim 1 or 2, characterized in that the post-exposure bake is performed at 80°C to 120°C for 40 seconds to 120 seconds, and the hard bake is performed at 130°C or higher for less than 40 seconds.

5. The pattern forming method according to claim 1 or 2, characterized in that the resist composition further contains a surfactant having a topcoat function for ArF immersion lithography, or includes a step of forming a topcoat film before the lithography.

Images