JP2016085382A - Method for forming resist pattern and radiation-sensitive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new pattern forming method, by which LWR that is supposed to be induced by a shot noise of EUV can be suppressed by adjusting a parameter of a radiation-sensitive resin composition without increasing exposure luminous energy.SOLUTION: The pattern forming method includes steps of forming a resist film from a radiation-sensitive resin composition, exposing the resist film to EUV or electron beams, and developing the exposed resist film. The radiation-sensitive resin composition comprises: [A] a polymer satisfying at least one of the conditions that (i) a ClogP value representing hydrophobicity is 2.8 or more and that (ii) when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23°C, the maximum (Rmax) of a dissolution rate is 5.0 μm/s or more; and [B] a radiation-sensitive acid generator satisfying at least one of the conditions that (i) a pKa of an acid generated is -1 or less and that (ii) a diffusion coefficient of the acid generated is 8 to 30 nm/sec at 105°C.SELECTED DRAWING: None

Description

The present invention relates to a resist pattern forming method and a radiation sensitive resin composition.

  Conventionally, in the manufacturing process of semiconductor devices such as IC and LSI, fine processing by lithography using a radiation-sensitive resin composition has been performed. In recent years, with the high integration of integrated circuits, the formation of ultrafine patterns in the submicron region and the quarter micron region has been required. Along with this, the exposure wavelength tends to be shortened from g-line to i-line, KrF excimer laser light, and further ArF excimer laser light. Recently, in addition to excimer laser light, development of lithography technology using EUV, electron beam, etc. has been promoted (Japanese Patent Laid-Open Nos. 2006-171440, 2011-16746, and 2010-204634). No. publication).

  The lithography technique using the EUV or electron beam is expected as a next-generation pattern forming technique capable of forming a pattern in an ultrafine region of 32 nm or less. In general, chemically amplified resists have a trade-off relationship with resolution, sensitivity, and LWR (Line width roughness), and it is necessary to suppress the acid diffusion distance in order to improve the resolution. Will be invited. On the other hand, if the sensitivity is improved, the number of photons required for exposure decreases and the LWR caused by shot noise deteriorates. If the exposure amount is increased, it is possible to suppress the occurrence of LWR caused by shot noise. However, it is not preferable because the throughput is lowered in practice. The LWR deterioration caused by the shot noise is caused by a plurality of intricately entangled factors, and it is considered that there are a plurality of factors in the radiation-sensitive resin composition and the pattern formation process, but it is quantitatively expressed. I can't.

JP 2006-171440 A JP 2011-16746 A JP 2010-204634 A

  The present invention has been made based on the circumstances as described above, and its purpose is to adjust the parameters of the radiation-sensitive resin composition without increasing the exposure amount of LWR, which is considered to be caused by EUV shot noise. It is providing the novel pattern formation method suppressed by this.

The invention made to solve the above problems is
Forming a resist film with a radiation sensitive resin composition;
The step of exposing the resist film with EUV or electron beam, and the step of developing the exposed resist film,
The radiation sensitive resin composition is
[A] a polymer satisfying at least one of the following (i) and (ii):
(I) The value of ClogP representing hydrophobicity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more, and [B] A radiation-sensitive acid generator that satisfies at least one of the following (i) and (ii):
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient D of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.
It is the resist pattern formation method containing this.

Another aspect of the present invention is:
[A] a polymer satisfying at least one of the following (i) and (ii):
(I) The value of ClogP representing hydrophobicity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more, and [B] A radiation-sensitive acid generator that satisfies at least one of the following (i) and (ii):
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient D of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.
And [C] A radiation-sensitive resin composition containing an organic solvent.

  According to the resist pattern forming method of the present invention, LWR can be improved while sufficiently satisfying resist sensitivity. Moreover, the radiation sensitive resin composition of this invention can be used suitably for the said resist pattern formation method. Therefore, they can be suitably used for forming a fine resist pattern in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

It is typical sectional drawing of a trench pattern shape. It is a schematic diagram showing how to obtain an acid diffusion coefficient.

<Resist pattern formation method>
The resist pattern forming method is:
A step of forming a resist film with the radiation-sensitive resin composition (hereinafter, also referred to as “resist film forming step”),
Step of exposing the resist film with EUV or electron beam (hereinafter also referred to as “exposure step”), and step of developing the exposed resist film (hereinafter also referred to as “development step”)
Have
The radiation sensitive resin composition is
[A] a polymer satisfying at least one of the following (i) and (ii):
(I) The value of ClogP representing hydrophobicity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more, and [B] A radiation-sensitive acid generator that satisfies at least one of the following (i) and (ii):
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient D of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.
Containing.

By using the radiation sensitive resin composition, according to the resist pattern forming method, LWR deterioration caused by shot noise can be suppressed.
Hereinafter, each step will be described.

[Resist film forming step]
In this step, a resist film is formed. As the substrate, for example, a conventionally known substrate such as a silicon wafer or a wafer coated with aluminum can be used. Further, for example, an organic or inorganic lower antireflection film disclosed in Japanese Patent Publication No. 6-12452, Japanese Patent Application Laid-Open No. 59-93448, etc. may be formed on the substrate. The radiation sensitive resin composition will be described later.

  Examples of the coating method include spin coating (spin coating), cast coating, and roll coating. In addition, as a film thickness of the resist film formed, it is 10 nm-1,000 nm normally, and 10 nm-500 nm are preferable.

  After apply | coating the said radiation sensitive resin composition, you may volatilize the solvent in a coating film by prebaking (PB) as needed. The PB temperature is appropriately selected depending on the composition of the radiation sensitive resin composition, but is usually 30 ° C to 200 ° C, preferably 50 ° C to 150 ° C. The PB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds.

  Further, in order to prevent the influence of basic impurities contained in the environmental atmosphere, for example, a protective film disclosed in JP-A-5-188598 can be provided on the resist film.

[Exposure process]
In this step, the resist film is exposed. The exposure conditions such as the exposure amount can be appropriately selected according to the composition of the radiation-sensitive resin composition to be used, the type of additive, and the like. Examples of radiation used for exposure include EUV and electron beam.

  In the exposure step, for example, an isotrench pattern can be formed by performing reduced projection exposure through a mask having an isospace pattern in a desired region and developing with an alkaline water-soluble developer. Similarly, a hole pattern can be formed by performing reduced projection exposure through a mask having a dot pattern. Further, the exposure may be performed twice or more by a desired mask pattern. When performing exposure twice or more, it is preferable to perform exposure continuously. In the case of performing multiple exposures, for example, a first reduced projection exposure is performed on a desired area via a line and space pattern mask, and then the second is so that the line intersects the exposed portion where the first exposure has been performed. Reduced projection exposure is performed. The first exposure part and the second exposure part are preferably orthogonal. By being orthogonal, a contact hole pattern can be formed in the unexposed area surrounded by the exposed area. When irradiating an electron beam, for example, exposure is performed by scanning the electron beam to be irradiated.

  In the resist pattern forming method, the exposure process may be performed a plurality of times as described above, and in the plurality of exposures, the same radiation or different radiation may be used.

  In addition, post exposure baking (PEB) is preferably performed after exposure. By performing PEB, the dissociation reaction of the acid dissociable group in the radiation sensitive resin composition can be smoothly advanced. As PEB temperature, it is 30 to 200 degreeC normally, and 50 to 170 degreeC is preferable. The PEB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds.

[Development process]
In this step, the exposed resist film is developed. As the developer used for development, for example, an alkaline aqueous solution can be used, or a liquid containing an organic solvent can be used. The developer can be selected according to the pattern shape to be formed. When a mask pattern is projected onto a resist film by exposure, a positive resist pattern is formed by developing an area with high light irradiation intensity with an alkaline aqueous solution to dissolve and remove the exposed area above a predetermined threshold. Can be formed. On the other hand, when the mask pattern is projected onto the resist film by exposure, an area where the light irradiation intensity is weak is developed with a liquid containing an organic solvent, so that the exposed area below a predetermined threshold is dissolved and removed. A mold resist pattern can be formed. It is also possible to develop by combining these developers depending on the desired resolution and pattern shape. Examples of the alkali used in the alkaline aqueous solution include inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and ammonia; 4 such as tetramethylammonium hydroxide and tetraethylammonium hydroxide. Class ammonium salt etc. are mentioned. In addition, an appropriate amount of a water-soluble organic solvent such as methanol or ethanol or a surfactant can be added to such an alkaline aqueous solution. The concentration of alkali in the aqueous alkali solution is preferably from 0.1% by mass to 5% by mass from the viewpoint of obtaining appropriate developability.

  An appropriate amount of a surfactant can be added to the developer as necessary. As the surfactant, for example, an ionic or nonionic fluorine-based and / or silicon-based surfactant can be used.

  As a developing method, for example, a method in which a substrate is immersed in a tank filled with a developer for a certain period of time (dip method), a method in which the developer is raised on the surface of the substrate by surface tension and is left stationary for a certain time (paddle method) ), A method of spraying the developer on the substrate surface (spray method), a method of continuously applying the developer while scanning the developer coating nozzle on the substrate rotating at a constant speed (dynamic dispensing method) Etc. The development time varies depending on the composition of the radiation sensitive resin composition to be used, but is preferably 10 seconds to 180 seconds.

  The resist pattern forming method preferably includes a rinsing step of washing the resist film with a rinsing liquid after the developing step. By having the rinsing step, the generated scum can be efficiently washed. As the rinsing liquid in the rinsing step, for example, water can be used when the developer is an alkaline aqueous solution.

<Radiation sensitive resin composition>
As a radiation sensitive resin composition used in the resist pattern forming method of the present invention, a conventionally known radiation sensitive resin composition can be used. Among these, a chemically amplified radiation-sensitive resin composition containing a polymer having a structural unit containing an acid-dissociable group (hereinafter also referred to as “[A] polymer”) and [B] a radiation-sensitive acid generator. Things are preferred. The radiation-sensitive resin composition more preferably contains a [C] acid diffusion controller and a [D] solvent. Furthermore, unless the effect of this invention is impaired, the said radiation sensitive resin composition may contain another component. Hereinafter, each component will be described in detail.

<[A] polymer>
[A] The polymer is not particularly limited as long as it is a polymer satisfying at least one of the following (i) and (ii).
(I) The value of ClogP representing polarity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more.

  (I) When the value of ClogP representing polarity is 2.5 or more, the ClogP value of each monomer contained in the polymer in the radiation-sensitive resin composition is determined using Chemdraw (manufactured by CambridgeSoft, Ver 12). Calculated and averaged according to the polymerization composition ratio means that the ClogP of the polymer is 2.8 or more. It can be judged that the higher the ClogP value of this polymer is, the higher the polarity of the radiation-sensitive resin composition containing it. [A] The ClogP value of the polymer is usually 2.5 or more, preferably 2.8 or more, more preferably 3.1 or more, and particularly preferably 3.4 or more.

[A] When the ClogP value of the polymer satisfies the above range, the radiation-sensitive resin composition becomes more polar and has increased solubility in the developer. As a result, exposure partially caused by the influence of shot noise It is considered that the LWR can be suppressed by promoting the dissolution of the low-solubility region in the deficient region or the low-solubility region due to insufficient deprotection of the acid dissociable group described later.

(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more. For example, it means that the maximum value (Rmax) of the dissolution rate that can be determined as follows is 5.0 μm / s or more.
A radiation-sensitive resin composition having the same composition ratio as that of the radiation-sensitive resin composition to be measured for Rmax and having a solid content adjusted so as to obtain a resist film having a thickness of 100 nm is prepared. The prepared radiation-sensitive resin composition is applied on a Si substrate, and heat treatment (PB) is performed under the same conditions as when forming a resist film. Next, irradiation is performed while changing the exposure dose from 1 to 100 (mJ / cm ² ) using a KrF excimer laser (248 nm). Thereafter, heat treatment (PEB) is performed under the same conditions as those for forming the resist pattern to form a resist film having a thickness of about 100 nm. This resist film is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution using a resist development analyzer (RDA, manufactured by RISOTEC Japan), and the maximum value of the dissolution rate at that time is Rmax (μm / second). It is.

[A] Rmax of the polymer is usually 5.0 μm / s or more, preferably 5.5 μm / s or more, more preferably 6.0 μm / s or more.
[A] When the Rmax of the polymer satisfies the above range, the radiation-sensitive resin composition is more soluble in the developer, resulting in an underexposure region partially caused by the influence of shot noise and acid dissociation described later. It is considered that LWR can be suppressed by promoting dissolution of the low solubility region in the developer due to insufficient deprotection of the functional group.

[A] As the structural unit of the polymer, the structural unit (I) having a group dissociated by the action of an acid (hereinafter also referred to as an acid dissociable group), and at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group Carbonized substituted with at least one selected from the structural unit (II) having a selected group, an alcoholic hydroxyl group, a carboxy group, a cyano group, and a sulfo group (including a group that generates a sulfo group by the action of an acid) Examples include at least one structural unit (X) among the structural unit (X1) having at least one structure selected from a structural unit (X1) having a hydrogen group, or a lactone structure, a cyclic carbonate structure, and a sultone structure.
Hereinafter, each structural unit will be described in detail. In addition, the [A] polymer may have only 1 type of each structural unit, and may have 2 or more types.

<Structural unit (I)>
[A] The structural unit (I) having a group dissociating by the action of an acid in the polymer is not particularly limited as long as it has a group dissociating by the action of an acid, but in the following formula (p-1) The group which consists of the structural unit (P-III) derived from the structural unit (P-I) represented, the structural unit (P-II) represented by the following formula (p-2), and the acetalized hydroxystyrenes At least one selected from the above is preferred. Moreover, the [C] polymer may have the structural unit which has other acid dissociable groups other than the said structural unit (PI)-structural unit (P-III). The said radiation sensitive resin composition has a favorable sensitivity because the [C] polymer has such a structural unit.

[Structural unit (PI)]
The structural unit (P-I) is represented by the following formula (p-1).

In the formula (p-1), R ¹⁴ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group or a hydroxymethyl group. R ^{15 to} R ¹⁷ are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 22 carbon atoms, or a monovalent alicyclic carbonization having 4 to 20 carbon atoms. A hydrogen group or a group derived therefrom; However, any two of R ^{15 to} R ¹⁷ may be bonded to each other to form a divalent alicyclic hydrocarbon group or a group derived therefrom together with the carbon atom to which they are bonded.

As a C1-C4 linear or branched alkyl group represented by said R < ¹⁵ > -R < ¹⁷ >, a methyl group, an ethyl group, n-butyl group, i-butyl group etc. are mentioned, for example.

Examples of the aryl group having 6 to 22 carbon atoms represented by ^R 15 ^{to R 17,} a phenyl group, a naphthyl group, and the like.

Examples of the monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms represented by R ^{15 to} R ¹⁷ include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, an adamantyl group, and the like. Is mentioned. Examples of the group derived from these include groups in which some or all of the hydrogen atoms of the alicyclic hydrocarbon group are substituted with substituents.

Examples of the divalent alicyclic hydrocarbon group which may be formed together with the carbon atoms to which any two of R ^{15 to} R ¹⁷ are bonded to each other include, for example, a cyclobutanediyl group and a cyclopentanediyl Group, cyclohexanediyl group and the like. Examples of the group derived from these include groups in which some or all of the hydrogen atoms of the alicyclic hydrocarbon group are substituted with substituents.

  Examples of the structural unit (PI) include structural units represented by the following formulas (p-1-1) to (p-1-7).

In the formulas (p-1-1) to (p-1-7), R ¹⁴ has the same meaning as the formula (p-1). R ¹⁵ is a linear or branched alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 22 carbon atoms.

R ¹⁴ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group, from the viewpoint of the copolymerizability of the monomer that gives the structural unit (PI).
R ¹⁵ is preferably a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably a methyl group, an ethyl group, or an i-propyl group, from the viewpoint of ease of dissociation of the acid dissociable group. A methyl group and an ethyl group are more preferable.

[Structural unit (P-II)]
The structural unit (P-II) is represented by the following formula (p-2).

In the formula (p-2), R ¹⁸ is a hydrogen atom, a methyl group, a trifluoromethyl group or a hydroxymethyl group. R ^{19 to} R ²¹ are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 22 carbon atoms, or a monovalent alicyclic group having 4 to 20 carbon atoms. It is a hydrocarbon group or a group derived therefrom. However, any two of R ^{19 to} R ²¹ may be bonded to each other to form a divalent alicyclic hydrocarbon group or a group derived therefrom with the carbon atom to which they are bonded.

A linear or branched alkyl group having 1 to 4 carbon atoms represented by R ^{19 to} R ²¹ , a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a group derived therefrom, and R ¹⁹ to With respect to the divalent alicyclic hydrocarbon group which may be formed together with the carbon atom to which any two of R ²¹ are bonded to each other or a group derived therefrom, the above formula (p The description of the same group represented by R ^{15 to} R ¹⁷ in -1) can be applied.

[Structural unit (P-III)]
The structural unit (P-III) is a structural unit derived from acetalized hydroxystyrenes. The acetalized hydroxystyrenes have a structure in which an acetal structure is formed from the phenolic hydroxyl group, hydroxy group and carbonyl group of the hydroxystyrenes. Examples of the structural unit (P-III) include structural units represented by the following formulas (p-3-1) to (p-3-4).

  In the above formulas (p-3-1) to (p-3-4), R represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group.

<Structural unit (II)>
As the structural unit (II) having a group in which at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group, structural units represented by the following formulas (C-1-1) to (C-1-4) , Structural units represented by the following formulas (C-2-1) to (C-2-4), and structural units represented by the following formulas (C-4-1) to (C-4-4). be able to.

<Structural unit (X)>
[A] A structure having a hydrocarbon group substituted with at least one selected from the group consisting of an alcoholic hydroxyl group, a carboxy group, a cyano group, and a sulfo group (including a group that generates a sulfo group by the action of an acid) Among the structural units (X2) containing at least one structure selected from the unit (X1) or a lactone structure, a cyclic carbonate structure, and a sultone structure, at least one structural unit (X) is represented by the following formula (C-5). -1) to (C-5-16), structural units derived from compounds represented by the following formulas (C-6-1) to (C-6-6), and the following formula (C -6-7) to (C-6-18), and structural units represented by the following formulas (C-7-1) to (C-7-3).

R ^C in the above formula represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

  In addition, in the [A] polymer, the total content of the structural unit (I) having a group dissociated by the action of an acid is the combination of the other structural units and the above conditions (i) and (ii). However, in order to form a resist pattern that satisfies the litho performance, it is usually preferably 10 mol% to 80 mol%, more preferably 15 mol% to 80 mol%, More preferred is mol% to 70 mol%. By setting the content ratio of the structural unit (I) containing an acid dissociable group within the above range, the radiation-sensitive resin composition can satisfy basic characteristics such as sensitivity and contrast between an exposed area and an unexposed area. .

  In the [A] polymer, the total content of the structural unit (II) having a group in which at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group is determined by combining with other structural units. It may be set so as to satisfy at least one of the above conditions (i) and (ii). However, in order to form a resist pattern satisfying the litho performance, it is usually preferably 10 mol% to 80 mol%, preferably 15 mol. % To 80 mol% is more preferable, and 20 mol% to 70 mol% is more preferable. By making the content ratio of the structural unit (II) having a group in which at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group within the above range, the radiation-sensitive resin composition has solubility in a developer. By providing, LWR resulting from shot noise can be suppressed by compensating for insufficient solubility due to insufficient exposure or insufficient deprotection of the acid dissociable group.

  In the [A] polymer, a hydrocarbon group substituted with at least one selected from an alcoholic hydroxyl group, a carboxy group, a cyano group, and a sulfo group (including a group that generates a sulfo group by the action of an acid) The total content of at least one structural unit (X) in the structural unit (X1) or the structural unit (X2) including at least one structure selected from a lactone structure, a cyclic carbonate structure, and a sultone structure In order to form a resist pattern satisfying the litho performance, it is usually 0 mol, as long as at least one of the above conditions (i) and (ii) is satisfied by combining with other structural units. % To 50 mol% is preferable, 5 mol% to 45 mol% is more preferable, and 5 mol% to 40 mol% is more preferable. By making the content ratio of the structural unit (X) in the above range, the solubility due to insufficient exposure or insufficient deprotection of the acid-dissociable group is imparted to the radiation-sensitive resin composition by providing solubility in a developer. By compensating for the shortage, LWR caused by shot noise can be suppressed.

  [A] The polymer can be produced, for example, by polymerizing a monomer corresponding to each predetermined structural unit in a suitable solvent using a radical polymerization initiator. For example, a method of dropping a solution containing a monomer and a radical initiator into a reaction solvent or a solution containing the monomer to cause a polymerization reaction, a solution containing the monomer, and a solution containing the radical initiator Separately, a method of dropping a reaction solvent or a monomer-containing solution into a polymerization reaction, a plurality of types of solutions containing each monomer, and a solution containing a radical initiator, It is preferable to synthesize by a method such as a method of dropping it into a reaction solvent or a solution containing a monomer to cause a polymerization reaction.

Examples of the solvent used for the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane; cyclohexane, cycloheptane, cyclooctane, decalin, norbornane. Cycloalkanes such as benzene, toluene, xylene, ethylbenzene, cumene and other aromatic hydrocarbons; chlorobutanes, bromohexanes, dichloroethanes, halogenated hydrocarbons such as hexamethylene dibromide, chlorobenzene; ethyl acetate, Saturated carboxylic acid esters such as n-butyl acetate, i-butyl acetate and methyl propionate; ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone and methyl ethyl ketone; tetrahydrofuran, dimethoxyethanes , Diethoxyethane Ethers such as methanol; alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol, and the like. These solvents may be used alone or in combination of two or more.

  As reaction temperature in the said superposition | polymerization, 40 to 150 degreeC and 50 to 120 degreeC are preferable normally. The reaction time is usually preferably 1 hour to 48 hours and 1 hour to 24 hours.

  Examples of the radical initiator used in the polymerization include azobisisobutyronitrile (AIBN), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2 -Cyclopropylpropionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionitrile) and the like. Two or more of these initiators may be mixed and used.

  The polymer obtained by the polymerization reaction is preferably recovered by a reprecipitation method. That is, after completion of the polymerization reaction, the polymer is recovered as a powder by introducing the polymerization solution into a reprecipitation solvent. As the reprecipitation solvent, alcohols or alkanes can be used alone or in admixture of two or more. In addition to the reprecipitation method, the polymer can be recovered by removing low-molecular components such as monomers and oligomers by a liquid separation operation, a column operation, an ultrafiltration operation, or the like.

  [A] The weight average molecular weight (Mw) in terms of polystyrene by gel permeation chromatography (GPC) of the polymer is preferably 1,000 to 50,000, more preferably 1,000 to 30,000, 000 to 10,000 are more preferable.

  [A] The ratio (Mw / Mn) of the polymer Mw to the polystyrene-equivalent number average molecular weight (Mn) by the GPC method is usually 1 to 3, preferably 1 to 2.

<[B] Radiation sensitive acid generator>
The radiation-sensitive resin composition contains [B] a radiation-sensitive acid generator (hereinafter also referred to as an acid generator or PAG) together with the [A] polymer. The acid generator is a compound that generates an acid upon irradiation with radiation in the exposure step of the resist pattern forming method. The acid-dissociable group present in the [A] polymer is dissociated by the action of the acid, and polar groups such as a carboxy group and a phenolic hydroxyl group are generated. As a result, the solubility of the [A] polymer in the developer changes, and it becomes readily soluble in the alkali developer.
[B] The radiation sensitive acid generator of the present invention is a radiation sensitive acid generator that satisfies at least one of the following (i) and (ii).
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.

  (I) The pKa of the generated acid is -1 or less, and the acid dissociation constant pKa of the anionic acid of each PAG contained in the radiation-sensitive resin composition is obtained by using Marvinsketch (Chem Axson). It means that the apparent pKa is −1 or less in the value obtained by averaging each obtained pKa according to the ratio of all PAG species contained in the radiation-sensitive resin composition. For example, the pKa of PAG-A is -1, the pKa of PAG-B is -2, and the apparent pKa in a radiation-sensitive resin composition containing these at a ratio of 50/50 is (-1 × 0.5 ) + (− 2 × 0.5) = − 1.5.

The apparent pKa of the generated acid is usually −1.0 or less, preferably −1.1 or less, more preferably −1.3 or less, and particularly preferably −1.5 or less.
When the apparent pKa of the generated acid satisfies the above range, the deprotection rate of the exposed portion is increased, thereby reducing the low exposure due to the underexposure region partially caused by the influence of shot noise or insufficient deprotection of the acid dissociable group. It is considered that dissolution of the soluble region in the developer is promoted and LWR can be suppressed.

(Ii) The diffusion coefficient of the generated acid at 105 ° C. of 5 to 30 nm ² / sec is determined by the method described in Journal Photopolymer Science Technology, Vol. 17, No. 3, 2004 pp379-384. It means that the value of the coefficient (D) is 5 to 30 nm ² / sec.

A radiation-sensitive resin composition comprising [A] polymer, [B] radiation-sensitive acid generator, and a similar composition ratio contained in the radiation-sensitive resin composition used for pattern formation, and having a resist of about 300 nm A radiation sensitive resin composition ( _RN ) having a solid content adjusted with a solvent [D] so as to obtain a film thickness is prepared. Next, a radiation sensitive resin composition ( _RN-PAG ) is prepared in the same manner except that the [B] radiation sensitive acid generator contained in the radiation sensitive resin composition (R) is not included.
This will be described below with reference to FIG.
A resist film having a film thickness of about 300 nm is applied on a Si wafer by applying a radiation sensitive resin composition ( _RN ) and PB for 60 seconds at the same temperature as the corresponding pattern forming radiation sensitive resin composition. Form. After exposing the resist film (R _N ) with Nikon NSR S203B, the resulting resist film (R _N ) (A in FIG. 2) is scraped off from the Si wafer with a razor to obtain a radiation-sensitive resin powder. It was. This powder was formed into a pellet by press molding (pellet ( _RN )).
Next, it apply | coated on Si wafer using a resin composition ( _RN-PAG ), PB for 60 second at the same temperature as the radiation sensitive resin composition for corresponding pattern formation, and film thickness of about 300 nm The resin film ( _RN-PAG ) (B in FIG. 2) was formed. The pellet carrying (R _N) on the corresponding said resin film (R _N-PAG), and PEB under the same conditions as the radiation-sensitive resin composition for corresponding patterning.
The resin film (R _N-PAG ) after PEB is developed with a 0.26 _N TMAH aqueous solution at 23 ° C.
A difference ΔL between the thickness of the resin film removed by development and the thickness of the unexposed portion was measured by DNS Lambda Ace (λ = 633 nm). The acid diffusion coefficient D can be calculated using the following formula described in Journal Photopolymer Science Technology, Vlo. 17, No. 3, 2004 pp379-384.
ΔL = 2 (D · t _PEB ) ^1/2 erfc ⁻¹ (E _crit ) / E)
[In the above formula, D represents the acid diffusion coefficient, t _PEB represents the PEB time (seconds), erfc represents the error function, E _crit represents the exposure amount when ΔL is first generated, and E represents the exposure amount. ]

The acid diffusion coefficient D is usually 5 to 30 nm ² / sec, preferably 7 to 30 nm ² / sec, and more preferably 10 to 30 nm ² / sec.
When the acid diffusion coefficient D satisfies the above range, the resolution can be maintained without lowering the sensitivity, so that the LWR deterioration due to shot noise can be suppressed.

  Examples of the acid generator include onium salt compounds, N-sulfonyloxyimide compounds, halogen-containing compounds, diazoketone compounds, and the like.

  Examples of the onium salt compounds include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, and the like. Of these, sulfonium salts are preferred.

  Examples of the sulfonium salt include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, triphenylsulfonium 2-bicyclo [2.2.1] hept- 2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium camphorsulfonate, 4-cyclohexylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexyl Phenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-cyclohexylphenyldipheny Sulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium camphorsulfonate, 4-methanesulfonylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium 2-bicyclo [2.2.1] hept-2 -Yl-1,1,2,2-tetrafluoroethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium camphorsulfonate, trifer Rusulfonium 2- (1-adamantyl) -1,1-difluoroethanesulfonate, triphenylsulfonium 6- (1-adamantylcarbonyloxy) -1,1,2,2-tetrafluorohexane-1-sulfonate, triphenylsulfonium 6 -(1-adamantylcarbonyloxy) -1,1,2-trifluorobutane-1-sulfonate, triphenylsulfonium 2- (4-oxo-1-adamantylcarbonyloxy) -1,1,3,3,3- In addition to pentafluoropropane-1-sulfonate, triphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1-difluoroethanesulfonate, and the like, there can be mentioned those represented by the following formula.

  Examples of the tetrahydrothiophenium salt include 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nona. Fluoro-n-butanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophene Ni-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium camphorsulfonate , 1- (6-n-butoxynaphthalen-2-yl) Torahydrothiophenium trifluoromethanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydro Thiophenium perfluoro-n-octanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium 2-bicyclo [2.2.1] hept-2-yl-1,1,2 , 2-tetrafluoroethanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium camphorsulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium trifluoromethanesulfonate , 1- (3,5-dimethyl-4 Hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (3,5-dimethyl- 4-hydroxyphenyl) tetrahydrothiophenium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (3,5-dimethyl-4-hydroxy Phenyl) tetrahydrothiophenium camphorsulfonate and the like.

  The acid generator may be incorporated as a part of the [A] polymer. For example, in the [A] polymer, the above formulas (C-7-1) to (C-7) are used. And those having the structural unit represented by -3).

  [B] The radiation-sensitive acid generator of the present invention may be selected from the above-mentioned acid generator or a combination of two or more acid generators so as to satisfy at least one of the above conditions (i) and (ii). .

As content of the said acid generator in the said radiation sensitive resin composition, in order to form the resist pattern which satisfies litho performance, it is 0.1 mass normally with respect to 100 mass parts of [A] polymers. Part to 40 parts by weight, preferably 0.5 part to 30 parts by weight. By making content of an acid generator into the said range, transparency with respect to radiation can be ensured and LWR deterioration derived from shot noise can be suppressed without lowering sensitivity.
The content ratio when the acid generator is incorporated as a part of the polymer is 0.5 mol% or more and 30 mol% with respect to all structural units constituting the [A] polymer. The following are preferable, and 1 mol% or more and 20 mol% or less are more preferable.

<[C] Acid diffusion controller>
The acid diffusion controller is a component that controls the diffusion phenomenon in the resist film of the acid generated from the acid generator by exposure and suppresses an undesirable chemical reaction in the unexposed area. When the radiation sensitive resin composition contains the acid diffusion controller, the storage stability of the resulting radiation sensitive resin composition is further improved, and the resolution as a resist is further improved. In addition, it is possible to suppress a change in the line width of the resist pattern due to a change in the holding time from exposure to development processing, and a composition having extremely excellent process stability can be obtained. In addition, as a containing form in the radiation sensitive resin composition in the present invention of the acid diffusion controller, a form of a free compound (hereinafter appropriately referred to as “acid diffusion controller”) is incorporated as a part of the polymer. Either of these forms may be used.

  Examples of the acid diffusion controller include amine compounds, amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

Examples of the amine compound include mono (cyclo) alkylamines such as n-butylamine; di (cyclo) alkylamines such as di-n-butylamine; tri (cyclo) alkylamines such as tri-n-butylamine and trioctylamine Substituted alkylaniline or derivatives thereof; ethylenediamine, N, N, N ′, N′-tetramethylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylether, 4, 4′-diaminobenzophenone, 4,4′-diaminodiphenylamine, 2,2-bis (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2- (4 -Aminophenyl) -2- (3-hydroxyphenyl) pro , 2- (4-aminophenyl) -2- (4-hydroxyphenyl) propane, 1,4-bis (1- (4-aminophenyl) -1-methylethyl) benzene, 1,3-bis (1 -(4-aminophenyl) -1-methylethyl) benzene, bis (2-dimethylaminoethyl) ether, bis (2-diethylaminoethyl) ether, 1- (2-hydroxyethyl) -2-imidazolidinone, 2 -Quinoxalinol, N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine, N, N, N ′, N ″ N ″ -pentamethyldiethylenetriamine, triethanolamine and the like.
Of these, tri (cyclo) alkylamines are preferable, and tri-n-butylamine is more preferable.

  Examples of amide group-containing compounds include Nt-butoxycarbonyl group-containing amino compounds, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, Examples thereof include benzamide, pyrrolidone, N-methylpyrrolidone, N-acetyl-1-adamantylamine, and isocyanuric acid tris (2-hydroxyethyl).

  Examples of urea compounds include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, tri-n-butylthiourea and the like. Is mentioned.

Examples of the nitrogen-containing heterocyclic compound include imidazoles; pyridines; piperazines; pyrazine, pyrazole, pyridazine, quinosaline, purine, pyrrolidine, piperidine, N- (t-amyloxycarbonyl) -4-hydroxypiperidine, piperidine ethanol, 3-piperidino-1,2-propanediol, morpholine, N- (t-butoxycarbonyl) -2-hydroxymethylpyrrolidine, 4-methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine, 3- ( N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane, N- (t-butoxycarbonyl) -2-phenylbenzimidazole and the like. It is done.
Among these, N- (t-amyloxycarbonyl) -4-hydroxypiperidine, N- (t-butoxycarbonyl) -2-hydroxymethylpyrrolidine, N- (t-butoxycarbonyl) -2-phenylbenzimidazole, 2 4,5-triphenylimidazole is preferred.

  Further, as the [C] acid diffusion control agent, a photodisintegrable base that is exposed to light and generates a weak acid by exposure can also be used. The photodegradable base can generate an acid in the exposed area to increase the insolubility of the [A] polymer in the developer. On the other hand, in the unexposed area, a high acid capturing function by anions is exhibited and functions as a quencher, and the acid diffused from the exposed area is captured. That is, since it functions as a quencher only in the unexposed area, the contrast of the deprotection reaction is improved, and as a result, the resolution can be further improved. As an example of the photodegradable base, there is an onium salt compound that is decomposed by exposure and loses acid diffusion controllability. Examples of the onium salt compound include a sulfonium salt compound represented by the following formula (4) and an iodonium salt compound represented by the following formula (5).

The formula (4) and the formula ^(5), R 22 ^{to R 26} each independently represent a hydrogen atom, an alkyl group, an alkoxy group, hydroxy group, a halogen atom or _-SO 2 -R ^D. R ^D is an alkyl group, a cycloalkyl group, an alkoxy group or an aryl group. Z ⁻ is OH ⁻ , R ²⁷ —COO ⁻ , R ^E —SO ₂ —N ^— R ²⁷ , R ²⁷ —SO ₃ ^— or an anion represented by the following formula (6). R ²⁷ is a linear or branched alkyl group having 1 to 10 carbon atoms, a linear or branched alkyloxycarbonyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or a carbon number of 3 A cycloalkyloxycarbonyl group having 20 carbon atoms, an aryl group having 6-30 carbon atoms, an aryloxycarbonyl group having 6-30 carbon atoms, and an alkaryl group having 7-30 carbon atoms. Some or all of the hydrogen atoms of the alkyl group, cycloalkyl group, aryl group and alkaryl group may be substituted. R ^E is a linear or branched alkyl group having 1 to 10 carbon atoms or a cycloalkyl group having 3 to 20 carbon atoms which may have a substituent. Some or all of the hydrogen atoms of the alkyl group and cycloalkyl group may be substituted with fluorine atoms. However, when Z ⁻ is R ²⁷ —SO ₃ ^— , a fluorine atom is not bonded to a carbon atom to which SO ₃ ^— is bonded.

In said formula (6), R < ²⁸ > is a C1-C12 linear or branched alkyl group by which some or all of a hydrogen atom may be substituted by the fluorine atom, or C1-C12 These are linear or branched alkoxy groups. u is an integer of 0-2.

  Examples of the photodegradable base include compounds represented by the following formulas.

  The content of the [C] acid diffusion controller in the radiation sensitive resin composition used in the resist pattern forming method is as follows. When the acid diffusion controller is an acid diffusion controller, [A] 100 parts by mass of the polymer 10 parts by mass or less is preferable. When the content exceeds 10 parts by mass, the sensitivity as a resist tends to decrease. These acid diffusion inhibitors may be used alone or in combination of two or more.

<[D] solvent>
The radiation sensitive resin composition used in the resist pattern forming method usually contains a solvent. The solvent is not particularly limited as long as it can dissolve at least the [A] polymer, the [B] acid generator, the [C] acid diffusion controller, and other components described below. Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and mixed solvents thereof.

  Specific examples of the above [D] solvent are not particularly limited as long as they can dissolve the [A] polymer, the [B] radiation-sensitive acid generator, and an optional component. For example, alcohol solvents, ether solvents , Ketone organic solvents, amide solvents, ester solvents, hydrocarbon solvents and the like.

Examples of alcohol solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-pentanol, iso-pentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, 4-methyl-2-pentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol , N-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, 2,6-dimethyl-4-heptanol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec- Monoalcohol solvents such as tetradecyl alcohol, sec-heptadecyl alcohol, furfuryl alcohol, phenol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, diacetone alcohol; ethylene glycol, 1 , 2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1 Polyhydric alcohol solvents such as 1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, polyhydric alcohol partial ether solvents such as dipropylene glycol monopropyl ether. Of these, 4-methyl-2-pentanol is preferred.

  Examples of ether solvents include dipropyl ether, diisopropyl ether, butyl methyl ether, butyl ethyl ether, butyl propyl ether, dibutyl ether, diisobutyl ether, tert-butyl methyl ether, tert-butyl ethyl ether, tert-butyl propyl ether. , Di-tert-butyl ether, dipentyl ether, diisoamyl ether, cyclopentyl methyl ether, cyclohexyl methyl ether, cyclopentyl ethyl ether, cyclohexyl ethyl ether, cyclopentyl propyl ether, cyclopentyl-2-propyl ether, cyclohexyl propyl ether, cyclohexyl-2-propyl Ether, cyclopentyl butyl ether, cyclopentyl-ter - butyl ether, cyclohexyl ether, cyclohexyl -tert- butyl ether, anisole, diethyl ether, diphenyl ether. Examples of cyclic ethers include tetrahydrofuran and dioxane. Of these, diisoamyl ether is preferred.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, methyl-n-amyl ketone, ethyl-n-butyl ketone, methyl-n-hexyl. Examples include ketone solvents such as ketone, di-iso-butyl ketone, trimethylnonanone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, acetophenone, and the like.

  Examples of the amide solvents include N, N′-dimethylimidazolidinone, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, N-methylpyrrolidone and the like can be mentioned.

  Examples of the ester solvents include diethyl carbonate, propylene carbonate, methyl acetate, ethyl acetate, γ-butyrolactone, γ-valerolactone, n-propyl acetate, iso-propyl acetate, n-butyl acetate, iso-butyl acetate, sec sec -Butyl, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, n-nonyl acetate, acetoacetic acid Methyl, ethyl acetoacetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol acetate Cole mono-n-butyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, diacetic acid Glycol, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, iso-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate , Diethyl malonate, dimethyl phthalate, diethyl phthalate and the like.

Examples of the hydrocarbon solvent include n-pentane, iso-pentane, n-hexane, iso-hexane, n-heptane, iso-heptane, 2,2,4-trimethylpentane, n-octane, iso-octane, and cyclohexane. , Aliphatic hydrocarbon solvents such as methylcyclohexane;
Fragrances such as benzene, toluene, xylene, mesitylene, ethylbenzene, trimethylbenzene, methylethylbenzene, n-propylbenzene, iso-propylbenzene, diethylbenzene, iso-butylbenzene, triethylbenzene, di-iso-propylbenzene and n-amylnaphthalene Group hydrocarbon solvents and the like.
Of these, propylene glycol monomethyl ether acetate and ethyl lactate are preferred. These solvents may be used alone or in combination of two or more.

<Other ingredients>
The radiation sensitive resin composition used in the resist pattern forming method can contain a surfactant, an alicyclic skeleton-containing compound, a sensitizer and the like as other components. In addition, the said radiation sensitive resin composition may contain only 1 type of said other components, respectively, and may contain 2 or more types.

[Surfactant]
The surfactant has an effect of improving applicability, striation, developability and the like of the radiation sensitive resin composition used in the resist pattern forming method.

[Alicyclic skeleton-containing compound]
The alicyclic skeleton-containing compound has the effect of improving the dry etching resistance, pattern shape, adhesion to the substrate, and the like of the resist pattern formed from the radiation-sensitive resin composition.

[Sensitizer]
The sensitizer exhibits an action of increasing the amount of acid generated from the acid generator, and has the effect of improving the “apparent sensitivity” of the radiation-sensitive resin composition used in the resist pattern forming method. .

<Method for preparing radiation-sensitive resin composition>
The radiation sensitive resin composition used in the resist pattern forming method includes, for example, [A] polymer, [B] radiation sensitive acid generator, [C] acid diffusion controller and other components in the above solvent. It can prepare by mixing in the ratio. Moreover, the said radiation sensitive resin composition can be prepared and used in the state melt | dissolved or disperse | distributed to the appropriate solvent.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. The measuring method of the physical property value in a present Example is shown below.

[Mw and Mn of polymer]
Mw and Mn of the polymer are GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL, manufactured by Tosoh), flow rate 1.0 mL / min, elution solvent tetrahydrofuran, sample concentration 1.0 mass%, sample Measurement was performed by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard, using a differential refractometer as a detector under the analysis conditions of an injection amount of 100 μL and a column temperature of 40 ° C.

[ ¹³ C-NMR analysis]
The ¹³ C-NMR analysis for determining the content ratio of the structural unit of the polymer uses a nuclear magnetic resonance apparatus (JNM-ECX400, manufactured by JEOL), uses CDCl ₃ as a measurement solvent, and uses tetramethylsilane (TMS). As an internal standard.

<[A] Synthesis of polymer>
[A] Monomers used for polymer synthesis are shown below.

[Synthesis Example 1]
[Synthesis of Polymer (A-1)]
34 g (45 mol%) of the above compound (M-1), 40 g (35 mol%) of the compound (M-4), 25 g (20 mol%) of the compound (M-3), 6.8 g of AIBN, and t-dodecyl mercaptan 2 .6 g was dissolved in 200 g of propylene glycol monomethyl ether, and polymerization was performed for 6 hours while maintaining the reaction temperature at 70 ° C. in a nitrogen atmosphere. After the polymerization, propylene glycol monomethyl ether was distilled off under reduced pressure, and the resulting polymer was dissolved in 100 g of propylene glycol monomethyl ether, and then dropped into 2,000 g of n-hexane to purify and purify the polymer. Next, 150 g of propylene glycol monomethyl ether was added to the polymer again, and then 150 g of methanol, 30 g of triethylamine and 6 g of water were further added, and a hydrolysis reaction was performed for 8 hours while refluxing at the boiling point. After confirming that the deacetylation of the structural unit derived from the compound (M-1) quantitatively proceeds and the structural unit derived from p-hydroxystyrene is generated by infrared spectroscopy, the solvent and triethylamine are produced. Was distilled off under reduced pressure, and the resulting polymer was dissolved in 150 g of acetone, then dropped into 2,000 g of water to solidify, the resulting white powder was filtered, dried at 50 ° C. under reduced pressure overnight, A polymer (A-1) was obtained. The weight average molecular weight of the obtained polymer was Mw = 7200 and Mw / Mn = 1.52.

[Synthesis Examples 2 to 9, 13]
[Synthesis of Polymers (A-2) to (A-9) and (A-13)]
Except having changed the monomer into the thing shown in Table 1, it carried out similarly to the synthesis example 1, and obtained the polymer (A-2)-(A-9) and the polymer (A-13).

[Synthesis Example 10]
[Synthesis of Polymer (A-10)]
After anionic polymerization of p-tert-butoxystyrene, poly (p-hydroxystyrene) was obtained by deprotection with acid. The weight average molecular weight (Mw) determined from GPC (carrier: tetrahydrofuran, in terms of polystyrene) was Mw = 3300, and Mw / Mn was 1.2.
Sufficiently dehydrated poly (p-hydroxystyrene) and propylene glycol monomethyl ether acetate (PGMEA) mixed solution (solid content 20.0 mass%) 50.0 mass parts was added cyclohexyl ethyl vinyl ether 3.21 mass parts. . Subsequently, 1.58 parts by mass of a mixed solution of p-toluenesulfonic acid and PGMEA (solid content: 1.0% by mass) was added and reacted at room temperature with stirring for 1 hour.
After adding 0.99 parts by mass of pyridine, 0.85 parts by mass of acetic anhydride was added, and the mixture was further reacted at room temperature with stirring for 2 hours.
After completion of the reaction, washing with water and concentration were carried out, followed by reprecipitation with a large amount of hexane, filtration and drying to obtain 11.9 parts by mass of a powder of the polymer (A-10). As a result of ¹³ C-NMR analysis, the content ratios of the structural units derived from hydroxystyrene and the structural units derived from (M-1) and (M-8) were 65.0 mol%, 25 mol%, and It was 10 mol%. The weight average molecular weight of the obtained polymer was Mw = 5000 and Mw / Mn = 1.2.

[Synthesis Examples 11 and 12]
[Synthesis of Polymers A-11 and A-12]
4.66 parts by mass of 1-methoxy-2-propanol was heated to 80 ° C. under a nitrogen stream. While stirring this liquid, 4.28 parts by mass of 4-hydroxystyrene, 4.95 parts by mass of compound (M-9), 0.77 parts by mass of compound (M-11), 18.-methoxy-2-propanol 18. A mixed solution of 6 parts by mass and 1.32 parts by mass of dimethyl 2,2′-azobisisobutyrate [V-601, manufactured by Wako Pure Chemical Industries, Ltd.] was dropped over 2 hours. After completion of dropping, the mixture was further stirred at 80 ° C. for 4 hours. The reaction solution was allowed to cool, then reprecipitated with a large amount of hexane / ethyl acetate and vacuum-dried to obtain the resin (A-11) of the present invention.
The weight average molecular weight of the obtained polymer was Mw = 15100 and Mw / Mn = 1.72.

  A-12 polymer was obtained in the same manner as in Synthesis Example 13 except that the monomers were changed to those shown in Table 1.

[Synthesis Example 14]
[Synthesis of Polymer A-14]
Under a nitrogen atmosphere, 146 g of compound (M-1), 11.7 g of compound (M-13), and 8.2 g of 2,2′-azobisisobutyronitrile were dissolved in 550 g of toluene to prepare a solution. The solution was stirred at 50 ° C. for 50 hours under a nitrogen atmosphere and cooled to room temperature. Then, 475 g of methanol and 75 g of water were added to the polymerization solution, and the lower layer of the separated solution was separated and concentrated under reduced pressure. The obtained concentrated solution was used for the hydrolysis reaction in the next step as it was. To the concentrated solution containing the polymer prepared as described above, 290 g of tetrahydrofuran, 260 g of methanol, 90 g of triethylamine and 18 g of water were added and stirred at 60 ° C. for 40 hours, and then the reaction solution was concentrated. 290 g of methanol, 60 g of acetone, and 470 g of hexane were added to the concentrated solution, and the lower layer of the separated solution was collected and concentrated under reduced pressure. 550 g of ethyl acetate was added to the concentrated solution, and this was washed with a 15% aqueous acetic acid solution, then with a 25% aqueous pyridine solution, and further with water, and then concentrated under reduced pressure. After adding 300 g of acetone to the concentrate, this was dropped into 2 liters of water to crystallize the polymer, and the crystallized polymer was filtered and then vacuum dried at 40 ° C. for 20 hours to obtain a white powder solid Jo polymer ^(a 0 -14) was obtained.
Against the polymer ^(A 0 -14) 50g, tetrahydrofuran was added 500g of triethylamine 26 g. To this mixed solution, 7.8 g of 1-chloro-1-methoxy-2-methylpropane was added dropwise and stirred at room temperature for 2 hours. After stirring, 150 g of water was added, the organic layer was separated, concentrated under reduced pressure, and 270 g of ethyl acetate was added to the resulting concentrated solution, and this was washed with 15% acetic acid aqueous solution, then with 25% pyridine aqueous solution, and then with water. Concentration under reduced pressure was performed. After adding 150 g of acetone to the concentrated solution, this was dropped into 2 liters of water to crystallize the polymer, and the crystallized polymer was filtered and then vacuum dried at 40 ° C. for 20 hours to obtain a white powder. A solid polymer (A-14) was obtained. Mw of the obtained polymer was 6000 and Mw / Mn = 1.75.

<Preparation of radiation-sensitive resin composition>
The acid generator, acid diffusion controller and solvent used for the preparation of the radiation sensitive resin composition are shown below.
[Acid generator]

[Acid diffusion control agent]

[solvent]
S-1: Propylene glycol monomethyl ether acetate S-2: Ethyl lactate

[Experiment 1]
[A] Polymer, [B] Radiation-sensitive acid generator, and [C] Acid diffusion control agent shown in Table 2 in types and amounts, and [D] (S-1) 4,280 mass as solvent. And (S-2) 1,830 parts by mass were mixed, and the resulting mixture was filtered through a membrane filter having a pore size of 0.20 μm to prepare a radiation sensitive resin composition (R-1). However, the content ratio of [C] acid diffusion controlling agent shows mol% to [B] radiation sensitive acid generator.

[Experimental Examples 2 to 14]
Radiation sensitivity was obtained by operating in the same manner as in Experimental Example 1 except that the types and amounts of [A] polymer, [B] radiation sensitive acid generator, and [C] acid diffusion controller shown in Table 2 were used. Resin compositions (R-2) to (R-14) were prepared.

<Formation of resist pattern>
A resist film with a film thickness of 50 nm was formed on each 12-inch silicon wafer on which a lower layer film (AL412, manufactured by BSI) was formed, and PB was performed for 60 seconds at the temperature specified in Table 3. Next, using an EUV exposure apparatus (NXE3100, manufactured by ASML), exposure was performed through an isolated trench pattern mask of 24 nm Space 168 nm Pitch under the conditions of NA = 0.25, ratio = 0.81, and conventional. After the exposure, PEB was performed for 60 seconds at the temperature shown in Table 3 for each photoresist composition. Thereafter, the resist film was developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution, washed with water, washed with a washing aqueous solution (FIRM Extreme 10, manufactured by AZEM), and dried to form a positive resist pattern. At this time, the exposure dose (mJ / cm 2) for forming an isolated trench pattern of 21 nm was determined as the optimum exposure dose (Eop). For the measurement, a scanning electron microscope (CG4000, manufactured by Hitachi High-Technologies Corporation) was used.

<Evaluation>
The following evaluation was performed on the formed resist pattern.

[Polymer polarity / ClogP]
The ClogP value of each monomer contained in the polymer in the radiation-sensitive resin composition was calculated using Chemdraw (manufactured by CambridgeSoft, Ver12), and the value averaged according to the polymerization composition ratio was taken as ClogP of the polymer. It can be judged that the higher the ClogP value of this polymer, the higher the polarity of the radiation-sensitive resin composition containing it.

[Rmax evaluation / Rmax]
The radiation-sensitive resin composition used in this evaluation is composed of (S-1) 2,140 parts by mass and (S-2) 915, each component of the radiation-sensitive resin composition shown in Table 2 as the [D] solvent. Except having mixed with the mass part, what was adjusted like the said radiation sensitive resin composition (R-1)-(R-14) was used. These are referred to as (R ⁰ -1) to (R ⁰ -14) to (R-1) to (R-14), respectively. These radiation-sensitive resin compositions were applied onto a Si substrate, PB was applied for 60 seconds at the temperatures shown in Table 3, and the exposure dose was changed from 1 to 100 (mJ / cm ² ) using a KrF excimer laser (248 nm). Irradiation was performed. Thereafter, PEB treatment was performed at a temperature of 60 seconds shown in Table 3 to form a resist film having a thickness of about 100 nm. This resist film is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution using a resist development analyzer (RDA, manufactured by RISOTEC Japan), and the maximum dissolution rate (Rmax, μm / second) at that time Asked.

[PKa of Radiation Sensitive Acid Generator]
The acid dissociation constant pKa of the anionic acid of each PAG contained in the radiation sensitive resin composition was determined using Marvinsketch (Chem Axson). Each obtained pKa was averaged according to the ratio of all PAG species contained in the radiation-sensitive resin composition, and apparent pKa was obtained. For example, the pKa of PAG-A is -1, the pKa of PAG-B is -2, and the apparent pKa in a radiation-sensitive resin composition containing these at a ratio of 50/50 is (-1 × 0.5 ) + (− 2 × 0.5) = − 1.5.

[Acid diffusion coefficient of radiation-sensitive acid generator / D]
[C] A radiation-sensitive resin composition was prepared in the same manner as the composition used for the evaluation of Rmax except that the acid diffusion controller was not used.
These are referred to as (R ¹ -1) to (R ¹ -14), respectively, with respect to the radiation sensitive resin compositions (R ⁰ -1) to (R ⁰ -14).
Next, [B] Resin compositions (R ² -1) to (R ^2- ) are the same as (R ¹ -1) to (R ¹ -14) except that no radiation-sensitive acid generator is used. 14) was adjusted.
On the Si wafer, the radiation sensitive resin compositions (R ¹ -1) to (R ¹ -12), (r ¹ -1), and (r ¹ -2) were respectively applied and shown in Table 3. A resist film having a film thickness of about 300 nm was formed by PB for 60 seconds at the temperature of the corresponding radiation-sensitive resin composition. After exposing the resist film with Nikon NSR S203B, the resulting radiation sensitive resin film (layer A in FIG. 2) was scraped off from the Si wafer with a razor to obtain a radiation sensitive resin powder. This powder was formed into a pellet by press molding.
Next, the resin compositions (R ² -1) to (R ² -14) were applied onto a Si wafer and the corresponding radiation-sensitive resin compositions (R-1) to (R) shown in Table 3 were used. PB was performed for 60 seconds at a temperature of R-14) to form a resin film having a thickness of about 300 nm. The pellets were placed on the corresponding resin film and subjected to PEB under the conditions of the corresponding radiation sensitive resin compositions (R-1) to (R-14) shown in Table 3.
The resin film after PEB was developed with a TMAH aqueous solution at 23 ° C. and 0.26N.
A difference ΔL between the thickness of the resin film removed by development and the thickness of the unexposed portion was measured by DNS Lambda Ace (λ = 633 nm). D was calculated using the following formula described in Journal Photopolymer Science Technology, Vol. 17, No. 3, 2004 pp379-384.
ΔL = 2 (D · t _PEB ) ^1/2 erfc ⁻¹ (E _crit ) / E)

[Bridge resistance / NOK]
The total length used for measuring the trench width of the isolated trench pattern in the above Eop was LCD (nm), and the total length of the bridge occurrence location was Lbridge (nm). The margin (%) was calculated by the following formula using LCD (nm) and Lbridge (nm), and was defined as the bridge occurrence frequency (%). This calculation was repeated at 30 points at different length measurement locations with respect to Eop, and the bridge occurrence frequency was repeated, and the average was defined as the average bridge occurrence frequency (%). It can be determined that the smaller the average bridge occurrence frequency is, the better the bridge resistance is.
Bridge occurrence frequency (%) = NOK (%) = {LCD} / {Lbridge} × 100
[Nano edge roughness / LWR]
The isolated trench pattern was observed using a semiconductor scanning electron microscope (high-resolution FEB measuring device S-9220, manufactured by Hitachi, Ltd.). Arbitrary 50 points of the above pattern are observed, and the observed shape is shown in FIG. 1 at the most marked portion of the unevenness generated along the lateral side surface of the trench portion of the resist film formed on the silicon wafer 1. The difference “ΔCD (nm)” between the line width and the designed trench width of 24 nm was measured by CD-SEM (S-9220, manufactured by Hitachi High-Technologies Corporation). In addition, the unevenness | corrugation shown in FIG. 1 is exaggerated rather than actually.

  From the results of Table 3, it can be seen that according to the resist pattern forming method of the experimental example, it is possible to obtain a pattern in which NOK and LWR are suppressed while maintaining sensitivity.

  According to the present invention, a novel resist pattern forming method that can suppress NOK and LWR, can form a pattern, and sufficiently satisfy the sensitivity, and a radiation-sensitive resin composition used in the resist pattern forming method are provided. Can be provided. Therefore, the radiation sensitive resin composition and the resist pattern forming method using the same of the present invention can be suitably used for forming a resist pattern in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims (9)

Forming a resist film with a radiation sensitive resin composition;
The step of exposing the resist film with EUV or electron beam, and the step of developing the exposed resist film,
The radiation sensitive resin composition is
[A] a polymer satisfying at least one of the following (i) and (ii):
(I) The value of ClogP representing hydrophobicity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in an aqueous 2.38 mass% tetramethylammonium hydroxide solution at 23 ° C. is 5.0 μm / s or more, and [B] A radiation-sensitive acid generator that satisfies at least one of the following (i) and (ii):
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient D of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.
A resist pattern forming method comprising:   [A] The resist pattern forming method according to claim 1, wherein the polymer contains a structural unit (I) having a group capable of dissociating by the action of an acid.   [A] The resist pattern forming method according to claim 1 or 2, wherein the polymer comprises a structural unit (II) having a group in which at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group.   [A] A structure in which the polymer has a hydrocarbon group substituted with at least one selected from an alcoholic hydroxyl group, a carboxy group, a cyano group, and a sulfo group (including a group that generates a sulfo group by the action of an acid) The unit (X1) or the structural unit (X2) comprising at least one structure selected from a lactone structure, a cyclic carbonate structure, and a sultone structure, and comprising at least one structural unit (X). Or the resist pattern formation method of Claim 3.   [A] The resist according to claim 4, wherein the total content of the structural unit (X1) and the structural unit (X2) is 5 to 50 mol% when the structural unit contained in the polymer is 100 mol%. Pattern forming method. [A] a polymer satisfying at least one of the following (i) and (ii):
(I) The value of ClogP representing hydrophobicity is 2.5 or more.
(Ii) The maximum value (Rmax) of the dissolution rate when a resist film having a film thickness of 100 nm is immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. is 5.0 μm / s or more.
[B] A radiation-sensitive acid generator that satisfies at least one of the following (i) and (ii):
(I) The generated acid has a pKa of −1 or less.
(Ii) The diffusion coefficient D of the generated acid at 105 ° C. is 5 to 30 nm ² / sec.
And [C] A radiation sensitive resin composition containing an organic solvent.   [A] The radiation-sensitive resin composition according to claim 6, wherein the polymer contains a structural unit (I) having a group capable of dissociating by the action of an acid.   [A] The radiation-sensitive resin composition according to claim 6 or 7, wherein the polymer comprises a structural unit (II) having a group in which at least one hydrogen atom on the aromatic ring is substituted with a hydroxyl group.   [A] A structure in which the polymer has a hydrocarbon group substituted with at least one selected from an alcoholic hydroxyl group, a carboxy group, a cyano group, and a sulfo group (including a group that generates a sulfo group by the action of an acid) The unit (X1) or the structural unit (X) containing at least one of the structural units (X2) containing at least one structure selected from a lactone structure, a cyclic carbonate structure, and a sultone structure, Item 9. The radiation-sensitive resin composition according to Item 7 or Item 8.

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