JP2013068675A - Photoresist composition and method for forming negative pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoresist composition which suppresses thickness reduction of a resist film in a pattern formation step and is excellent in resolution and LWR.SOLUTION: There is provided a photoresist composition for forming a negative pattern using a developer containing an organic solvent, wherein the photoresist composition contains [A] a polymer having (I) a structural unit including a group which is converted into a hydroxyl group by an action of an acid and [B] an acid generator. In addition, [A] the polymer preferably is a polymer which shows increased solubility in an aqueous alkali solution and decreased solubility in a developer containing an organic solvent.

Description

  The present invention relates to a photoresist composition and a negative pattern forming method.

  With the miniaturization of various electronic device structures such as semiconductor devices and liquid crystal devices, pattern miniaturization in the lithography process is required. At present, it is possible to form a fine pattern having a line width of about 90 nm using, for example, an ArF excimer laser, but in the future, a finer pattern formation is required.

  In response to the above requirements, a technique using an organic solvent having a polarity lower than that of an alkaline aqueous solution as a developing solution is known as a technique for increasing the resolution of a conventional chemically amplified photoresist composition without increasing the number of steps using an existing apparatus. (See JP 2000-199953 A). In other words, when forming a pattern using an alkaline aqueous solution as a developer, it is difficult to form a fine pattern due to poor optical contrast, whereas when an organic solvent is used with this technique, Since the optical contrast can be increased, a fine pattern can be formed.

  However, when an organic solvent is used as a developer with respect to the conventional photoresist composition, there is a disadvantage that the film thickness of the resist film is reduced, whereby the etching resistance is lowered and a desired pattern cannot be obtained. In addition, according to the above technique, there is a disadvantage that the desired pattern cannot be obtained because the line width roughness (LWR) of the obtained pattern is large. In recent years, in particular, as the miniaturization of patterns has progressed, the resist film has become thinner. Therefore, improvement of the film reduction is strongly desired.

JP 2000-199953 A

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a photoresist composition that can suppress a decrease in the thickness of the resist film and is excellent in LWR and resolution. .

The invention made to solve the above problems is
A photoresist composition for forming a negative pattern using a developer containing an organic solvent,
[A] A polymer having a structural unit (I) containing a group that becomes a hydroxyl group by the action of an acid (hereinafter also referred to as “[A] polymer”), and [B] an acid generator. A photoresist composition.

  The photoresist composition of the present invention contains a [A] polymer and a [B] acid generator. The [A] polymer has the structural unit (I) containing a group that becomes a hydroxyl group instead of an acid such as a carboxy group by the action of an acid generated from the [B] acid generator upon exposure, whereby the photoresist composition Things can suppress film loss. In addition, the photoresist composition is excellent in resolution and LWR because the dissolution contrast between the unexposed area and the exposed area in the development process is improved.

  [A] The polymer may be a polymer whose solubility in an aqueous alkali solution increases due to the action of an acid and whose solubility in a developer containing an organic solvent decreases. [A] Since the polymer is such a polymer, the photoresist composition can be suitably used for forming a negative pattern.

  The hydroxyl group is preferably an alcoholic hydroxyl group or a phenolic hydroxyl group. [A] When the polymer contains a group that becomes an alcoholic hydroxyl group or a phenolic hydroxyl group instead of an acid such as a carboxy group by the action of an acid, the photoresist composition can further suppress film loss. In addition, the resolution and LWR are also excellent. Here, the alcoholic hydroxyl group means a hydroxyl group bonded to a hydrocarbon group. Moreover, a phenolic hydroxyl group means the hydroxyl group couple | bonded directly on the aromatic ring.

（式（１）中、Ｒ^１は、２価の炭化水素基である。Ｒ^２及びＲ^３は、それぞれ独立して、水素原子又は１価の有機基である。Ｒ^４は、酸解離性基である。但し、Ｒ^１〜Ｒ^４のいずれかが互いに結合して、環構造を形成してもいてもよい。
式（２）中、Ｒ^５は、２価の炭化水素基である。ｍは、０〜３の整数である。
式（３）中、Ｒ^６は、１価の有機基である。ｎは、０〜４の整数である。但し、ｎが２以上である場合、複数のＲ^６は、それぞれ同一でも異なっていてもよい。Ｒ^７は、酸解離性基である。
式（４）中、Ｒ^８は、２価の有機基である。Ｒ^９は、酸解離性基である。） The structural unit (I) preferably contains at least one group selected from the group consisting of groups represented by the following formulas (1) to (4).

(In Formula (1), R ¹ is a divalent hydrocarbon group. R ² and R ³ are each independently a hydrogen atom or a monovalent organic group. R ⁴ is an acid dissociative property. However, any of R ^{1 to} R ⁴ may be bonded to each other to form a ring structure.
In formula (2), R ⁵ is a divalent hydrocarbon group. m is an integer of 0-3.
In formula (3), R ⁶ is a monovalent organic group. n is an integer of 0-4. However, when n is 2 or more, the plurality of R ⁶ may be the same or different. R ⁷ is an acid dissociable group.
In formula (4), R ⁸ is a divalent organic group. R ⁹ is an acid dissociable group. )

  Since the structural unit (I) includes a group having the specific structure, an alcoholic hydroxyl group or a phenolic hydroxyl group is generated by the action of an acid. Therefore, the photoresist composition can further suppress film loss. Also, the resolution and LWR are more excellent. Here, the “acid-dissociable group” refers to a group that substitutes a hydrogen atom of a polar group such as a carboxy group, a hydroxyl group, an amino group, or a sulfo group, and dissociates by the action of an acid.

（式（５）中、Ｒ^１０〜Ｒ^１２は、それぞれ独立して、炭素数１〜４の直鎖状若しくは分岐状のアルキル基又は炭素数４〜２０の脂環式基である。但し、Ｒ^１０〜Ｒ^１２の何れか２つが互いに結合して、それらが結合している炭素原子と共に２価の脂環式基を形成していてもよい。また、上記アルキル基及び脂環式基が有する水素原子の一部又は全部は置換されていてもよい。） [A] The polymer preferably further has a structural unit (II) containing a group represented by the following formula (5).

(In Formula (5), R < ¹⁰ > -R < ¹² > is respectively independently a C1-C4 linear or branched alkyl group or a C4-C20 alicyclic group, provided that Any two of R ^{10 to} R ¹² may be bonded to each other to form a divalent alicyclic group together with the carbon atom to which they are bonded, and the alkyl group and the alicyclic group are Some or all of the hydrogen atoms possessed may be substituted.)

  [A] When the polymer further has a structural unit (II) containing an acid-dissociable group having the above specific structure, fine adjustment of the dissolution contrast between the unexposed part and the exposed part becomes possible. Thereby, the photoresist composition can suppress film loss and is more excellent in resolution and LWR.

（式（６）中、Ｒ^１３は、フッ素原子を有さない１価の有機基である。Ｍ^＋は、１価のオニウムカチオンである。） [B] The acid generator is preferably a compound represented by the following formula (6).

(In formula (6), R ¹³ is a monovalent organic group having no fluorine atom. M ⁺ is a monovalent onium cation.)

  [B] When the acid generator has the specific structure not containing a fluorine atom, the acid generated by exposure becomes a weak acid. When the acid generated from the acid generator is a weak acid, the influence of acid diffusion to the unexposed area is reduced, so that the LWR value of the resulting pattern can be reduced. [A] Since the acid-dissociable group contained in the polymer is easily dissociated by the action of an acid, it can be sufficiently dissociated even by the weak acid. As a result, the photoresist composition can suppress film loss and is further excellent in resolution and LWR.

The negative pattern forming method of the present invention is
(1) A step of applying a photoresist composition of the present invention on a substrate to form a resist film,
(2) a step of exposing the resist film; and (3) a step of developing the exposed resist film using a developer containing an organic solvent.

  According to the negative pattern forming method, it is possible to suppress a reduction in the thickness of the resist film and to form a pattern having excellent resolution and LWR.

  The photoresist composition of the present invention can suppress a decrease in the thickness of the resist film in the negative pattern forming method, and is excellent in resolution and LWR.

<Photoresist composition>
The photoresist composition of the present invention is for forming a negative pattern using a developer containing an organic solvent, and contains a [A] polymer and a [B] acid generator. Moreover, the said photoresist composition contains a [C] fluorine atom containing polymer, a [D] acid diffusion control body, and a [E] solvent as a suitable component. Furthermore, unless the effect of this invention is impaired, the said photoresist composition may contain another arbitrary component. Hereinafter, each component will be described in detail. The negative pattern forming method will be described later.

<[A] polymer>
[A] The polymer is a polymer having a structural unit (I) containing a group that becomes a hydroxyl group by the action of an acid. The [A] polymer has the structural unit (I) containing a group that becomes a hydroxyl group instead of an acid such as a carboxy group by the action of an acid generated from the [B] acid generator upon exposure, whereby the photoresist composition Things can suppress film loss. In addition, since the dissolution contrast between the unexposed area and the exposed area is improved, the photoresist composition is also excellent in resolution and LWR.

  [A] The polymer is preferably a polymer whose solubility in an aqueous alkali solution is increased by the action of an acid and whose solubility in a developer containing an organic solvent is decreased. [A] When the polymer has such properties, the photoresist composition can be suitably used for forming a negative pattern. In addition, the [A] polymer needs to have structural unit (I) in a ratio sufficient to have the said property.

  [A] In addition to the structural unit (I), the polymer includes a structural unit (II) containing a group represented by the above formula (5), a structural unit (III) containing a lactone group, a cyclic carbonate group or a sultone group. It is preferable to have. In addition to the structural unit (I), the structural unit (II), and the structural unit (III), the [A] polymer may have other structural units as long as the effects of the present invention are not impaired. In addition, the [A] polymer may have each structural unit independently, and may use 2 or more types together. Hereinafter, each structural unit will be described in detail.

[Structural unit (I)]
The structural unit (I) is a structural unit containing a group that becomes a hydroxyl group by the action of an acid. A photoresist composition for negative pattern formation using a developer containing an organic solvent generates an acid such as a carboxy group by the action of an acid generated from an acid generator, as in the case of positive pattern formation by alkali development. That is not essential. The photoresist composition can suppress a decrease in the thickness of the resist film by including a group that becomes a hydroxyl group rather than an acid such as a carboxy group by the action of an acid. That is, the hydroxyl group is preferably an alcoholic hydroxyl group or a phenolic hydroxyl group.

  The structural unit (I) preferably contains at least one group selected from the group consisting of groups represented by the above formulas (1) to (4). When the structural unit (I) has such a group, an alcoholic hydroxyl group or a phenolic hydroxyl group can be generated by the action of an acid. As a result, the [A] polymer can have the property that the solubility in an aqueous alkali solution increases and the solubility in a developer containing an organic solvent decreases due to the action of an acid.

(Group represented by the above formula (1))
When the structural unit (I) includes a group having an acetal structure represented by the above formula (1), [B] a hydroxyl group can be generated even if the acid generated from the acid generator is a weak acid. Reduction can be further suppressed.

In formula (1), R ¹ is a divalent hydrocarbon group. R ² and R ³ are each independently a hydrogen atom or a monovalent organic group. R ⁴ is an acid dissociable group. However, any of R ^{1 to} R ⁴ may be bonded to each other to form a ring structure.

Examples of the divalent hydrocarbon group represented by R ¹ include a linear or branched hydrocarbon group having 1 to 10 carbon atoms, an alicyclic group having 4 to 20 carbon atoms, and 6 to 20 carbon atoms. The aromatic group etc. are mentioned.

  Examples of the linear or branched hydrocarbon group having 1 to 10 carbon atoms include methylene group, ethanediyl group, n-propanediyl group, i-propanediyl group, n-butanediyl group, i-butanediyl group, n -A pentanediyl group, i-hexanediyl group, etc. are mentioned.

  Examples of the alicyclic group having 4 to 20 carbon atoms include a cyclobutanediyl group, a cyclopentanediyl group, a cyclohexanediyl group, an adamantanediyl group, and a norbornanediyl group.

  Examples of the aromatic group having 6 to 20 carbon atoms include a phenylene group, a naphthalenylene group, and an anthracenylene group.

Examples of the monovalent organic group represented by R ² and R ³ include a linear or branched alkyl group having 1 to 10 carbon atoms, an alicyclic group having 4 to 20 carbon atoms, and 6 to 20 carbon atoms. And aromatic hydrocarbon groups.

  As said C1-C10 linear or branched alkyl group, a methyl group, an ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group etc. are mentioned, for example.

  Examples of the alicyclic group having 4 to 20 carbon atoms include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group.

  Examples of the aromatic hydrocarbon group having 6 to 20 carbon atoms include phenyl group, naphthalenyl group, phenanthrenyl group, anthracenyl group, tetracenyl group, pentacenyl group, toluenyl group, xylenyl group, ethylbenzyl group, and mesityrenyl group. It is done.

The acid dissociable group represented by R ⁴ is not particularly limited as long as it is a group dissociated by the action of an acid generated from the [B] acid generator upon exposure, but for example, represented by R ² and R ³ above. Examples thereof include the same groups as those exemplified as the monovalent organic group. Among these, an acid dissociable group represented by the following formula (7) is preferable. An alcoholic hydroxyl group can be generated by the dissociation of the acid-dissociable group by the action of an acid.

In the above formula ^{(7), R} 14 ~R ¹⁶ is a cycloaliphatic radical of linear or branched alkyl group or 4 to 20 carbon atoms having 1 to 4 carbon atoms. However, one part or all part of the hydrogen atom which the said alkyl group and alicyclic group have may be substituted. Further, any two of R ^{14 to} R ¹⁶ may be bonded to each other to form a divalent alicyclic group together with the carbon atom to which they are bonded.

Examples of the linear or branched alkyl group having 1 to 4 carbon atoms represented by R ^{14 to} R ¹⁶ include a methyl group, an ethyl group, an n-propyl group, and an i-propyl group.

Said ^R 14 4 to 20 carbon atoms represented by ^{to R 16} cycloaliphatic radicals, and attached any two from each other of said ^R 14 ^{to R 16,} alicyclic together with the carbon atoms to which they are attached Examples of the group include the same groups as those exemplified as the alicyclic group having 4 to 20 carbon atoms represented by R ¹ and R ² above.

(Group represented by the above formula (2))
In the formula (2), ^{R 5} represents a divalent hydrocarbon group. m is an integer of 0-3.

Examples of the divalent hydrocarbon group represented by R ⁵ include the same groups as those exemplified as the divalent hydrocarbon group represented by R ¹ . Among these, alicyclic groups such as ethanediyl group, i-propanediyl group, i-butanediyl group, i-pentanediyl group, cyclobutanediyl group, cyclopentanediyl group, cyclohexanediyl group, adamantanediyl group, norbornanediyl group, etc. An ethanediyl group, an i-propanediyl group, an i-butanediyl group, an i-pentanediyl group, and an adamantanediyl group are more preferable.

  As said m, 0-2 are preferable and 0 or 1 is more preferable.

  When the structural unit (I) contains a group represented by the above formula (2), two alcoholic hydroxyl groups can be generated by the action of an acid. Thereby, the photoresist composition can suppress a decrease in the thickness of the resist film, and is excellent in resolution and LWR.

(Group represented by the above formula (3))
In the above formula (3), R ⁶ is a monovalent organic group. n is an integer of 0-4. However, when n is 2 or more, the plurality of R ⁶ may be the same or different. R ⁷ is an acid dissociable group.

Examples of the monovalent organic group represented by R ⁶ include the same groups as those exemplified as the monovalent organic group represented by R ² and R ³ .

  As said n, 0-2 are preferable and 0 or 1 is more preferable.

The acid dissociable group represented by R ⁷ is not particularly limited as long as it is a group dissociated by the action of an acid generated from the [B] acid generator upon exposure, but for example, represented by R ² and R ³ above. Examples thereof include the same groups as those exemplified as the monovalent organic group. Among these, an acid dissociable group represented by the above formula (7) is preferable. The acid dissociable group is dissociated by the action of an acid, whereby a phenolic hydroxyl group can be generated.

(Group represented by the above formula (4))
In the above formula (4), R ⁸ is a divalent organic group. R ⁹ is an acid dissociable group.

Examples of the divalent organic group represented by R ⁸ include a divalent hydrocarbon group.

Examples of the divalent hydrocarbon group include the same groups as those exemplified as the divalent hydrocarbon group represented by R ¹ .

The acid dissociable group represented by R ⁹ is not particularly limited as long as it is a group that can be dissociated by the action of an acid generated from the [B] acid generator upon exposure, but for example, represented by R ² and R ³ above. Examples thereof include the same groups as those exemplified as the monovalent organic group. Among these, an acid dissociable group represented by the above formula (7) is preferable. It is considered that the acid dissociable group is dissociated by the action of an acid to generate a —R ⁸ —O (CO) OH group, and carbon dioxide is released to eventually generate a —R ⁸ —OH group. It is done.

  Examples of the structural unit (I) include a structural unit represented by the following formula.

In the above formula, R ^a is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^b and R ^c are each independently a hydrocarbon group having 1 to 20 carbon atoms. R ^d is a methylene group which may have a substituent. p and q are each independently an integer of 0 to 4. R < ² > -R < ⁴ > is synonymous with the said Formula (1). R ⁵ has the same meaning as the above formula (2). R ⁶ has the same meaning as the above formula (3). R ⁹ has the same meaning as in the above formula (4).

  Among these, the structural unit represented by the following formula is preferable.

In the above formula, R ^a is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. p is an integer of 0-4. R ⁶ and n are synonymous with the above formula (3).

  [A] In the polymer, the content of the structural unit (I) is preferably 10 mol% or more and 80 mol% or less, and more preferably 30 mol% or more and 70 mol% or less. By setting the content of the structural unit (I) in the above range, film loss can be effectively suppressed while maintaining other performance.

  As a monomer which gives structural unit (I), the compound represented by a following formula is mentioned, for example.

[Structural unit (II)]
The structural unit (II) includes a group represented by the above formula (5). [A] The polymer may have a structural unit (II) in addition to the structural unit (I) for the purpose of fine adjustment of the dissolution contrast between the unexposed area and the exposed area in the development step.

In said formula (5), R < ¹⁰ > -R < ¹² > is respectively independently a C1-C4 linear or branched alkyl group or a C4-C20 alicyclic group. However, any two of R ^{10 to} R ¹² may be bonded to each other to form a divalent alicyclic group together with the carbon atom to which they are bonded. Moreover, one part or all part of the hydrogen atom which the said alkyl group and alicyclic group have may be substituted.

Linear or branched alkyl group having 1 to 4 carbon atoms represented by ^R 10 ^{to R 12,} alicyclic group having 4 to 20 carbon ^atoms, although any two of R 10 ^{to R 12} bond to each other For the divalent alicyclic group formed together with the carbon atom to which they are bonded, the explanation of the group represented by R ^{14 to} R ¹⁶ in the above formula (7) in the structural unit (I) is applied. can do.

  Examples of the structural unit (II) include a structural unit represented by the following formula.

In the above formula, R ¹⁷ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ¹⁸ is an alkyl group having 1 to 4 carbon atoms. r is an integer of 1-6.

  Among these, preferred structural units include structural units represented by the following formulas (2-1) to (2-22).

In the above formula, R ¹⁷ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

  Among these, the structural unit represented by the above formula (2-4) is more preferable.

  [A] In the polymer, the content of the structural unit (II) is preferably 5 mol% to 50 mol%, and preferably 10 mol% to 45 mol%, based on all structural units constituting the [A] polymer. Is more preferable, and 15 mol% to 40 mol% is more preferable. By making the content rate of structural unit (II) into the said range, the said photoresist composition is excellent in resolution and LWR.

  Monomers that give structural unit (II) include monomers containing an acid-dissociable group having a monocyclic alicyclic group such as 1-alkyl-cycloalkyl ester, 2-alkyl-2-dicycloalkyl, etc. And monomers containing an acid dissociable group having a polycyclic alicyclic group such as an ester.

[Structural unit (III)]
[A] The polymer preferably has a structural unit (III) containing a lactone group, a cyclic carbonate group or a sultone group. [A] When the polymer further has the structural unit (III), the resist film formed from the photoresist composition can improve the adhesion to the substrate. Here, the lactone group refers to a group containing one ring (lactone ring) including a structure represented by —O—C (O) —. Moreover, a cyclic carbonate group means group containing one ring (cyclic carbonate ring) containing the structure represented by -OC (O) -O-. The sultone group refers to a group containing one ring (sultone ring) including a structure represented by —O—SO ₂ —. Note that the lactone ring, cyclic carbonate ring or sultone ring is counted as the first ring. If only the lactone ring, cyclic carbonate ring or sultone ring is a monocyclic group, and if it has another ring structure, the structure is Regardless, it is called a polycyclic group.

  Examples of the structural unit (III) include a structural unit represented by the following formula.

In the above formula, R ¹⁹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

  Among these, from the viewpoint of improving the adhesion of the resist film, the structural unit represented by the above formula (3-1) is preferable.

  As a monomer compound which gives structural unit (III), the compound represented by a following formula is mentioned, for example.

  [A] The content of the structural unit (III) in the polymer is preferably 10 mol% or more and 80 mol% or less, and more preferably 20 mol% or more and 70 mol% or less. By making the content rate of structural unit (III) into the said range, the resist film obtained from the said photoresist composition can improve the adhesiveness to a board | substrate etc.

[Other structural units]
[A] The polymer may further have a structural unit containing a polar group as a structural unit other than the structural units (I) to (III) as long as the effects of the present invention are not impaired. Since the [A] polymer further has a structural unit containing a polar group, the compatibility between the [A] polymer and other components such as the [B] acid generator is improved. The resolution and LWR can be made excellent values.

<[A] Polymer Synthesis Method>
[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, and n-decane;
Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, norbornane;
Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, cumene;
Halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, chlorobenzene;
Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate and methyl propionate;
Ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone;
Ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes;
Examples include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. These solvents may be used alone or in combination of two or more.

  Although the reaction temperature in the said polymerization should just be suitably determined according to the kind of radical initiator, it is 40 to 150 degreeC normally, and 50 to 120 degreeC is preferable. The reaction time is usually 1 hour to 48 hours, preferably 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 target resin 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] As a weight average molecular weight (Mw) by the gel permeation chromatography (GPC) of a polymer, 1,000-100,000 are preferable, 2,000-50,000 are more preferable, 3,000-30 Is more preferred. [A] By making Mw of a polymer into the above-mentioned specific range, film loss can be suppressed and LWR of the pattern obtained can be made an excellent value.

  [A] The ratio (Mw / Mn) of Mw and number average molecular weight (Mn) of the polymer is usually 1 to 5, preferably 1 to 3, and more preferably 1 to 2. By making Mw / Mn into such a specific range, film loss can be suppressed and the LWR of the resulting pattern can be made an excellent value.

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

<[B] Acid generator>
[B] The acid generator is a compound that generates an acid upon irradiation with radiation in the exposure step of the pattern forming method. By the action of the acid, the acid dissociable group of the structural unit (I) present in the [A] polymer is dissociated to generate a hydroxyl group. Further, the acid dissociable group of the structural unit (II) is dissociated to generate a polar group such as a carboxy group. As a result, the [A] polymer becomes hardly soluble or insoluble in a developer containing an organic solvent. As the form of inclusion of the [B] acid generator in the photoresist composition, the form of a compound as described later (hereinafter also referred to as “[B] acid generator” as appropriate) is incorporated as part of the polymer. Either of these forms may be used.

  [B] Examples of the acid generator include onium salt compounds, sulfonimide compounds, halogen-containing compounds, diazoketone compounds, and the like. Of these [B] acid generators, onium salt compounds are preferred.

  Examples of the onium salt compounds include sulfonium salts represented by the above formula (6), other sulfonium salts (including tetrahydrothiophenium salts) shown below as specific examples, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts. Etc.

In the above formula (6), R ¹³ is a monovalent organic group having no fluorine atom. M ⁺ is a monovalent onium cation.

  Examples of the onium salt represented by the above formula (6) include triphenylsulfonium camphorsulfonate, 4-cyclohexylphenyldiphenylsulfonium camphorsulfonate, 4-methanesulfonylphenyldiphenylsulfonium camphorsulfonate, and the like.

  Examples of the other sulfonium salts include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, and triphenylsulfonium 2-bicyclo [2.2.1]. ] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1-difluoroethanesulfonate, 4-cyclohexylphenyl Diphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium perful Rho-n-octanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium trifluoro L-methanesulfonate, 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, triphenylphosphonium 1,1,2,2-tetrafluoro-6- (1-adamantane carbonilo Sheet) - hexane-1-sulfonate, triphenylsulfonium norbornyl - difluoroethanesulfonate the like.

  Of these, triphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1-difluoroethanesulfonate is preferred.

  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. Of these tetrahydrothiophenium salts, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) Tetrahydrothiophenium perfluoro-n-octane sulfonate and 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butane sulfonate are preferred.

  Examples of the iodonium salt include diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium perfluoro-n-octanesulfonate, diphenyliodonium 2-bicyclo [2.2.1] hept-2-yl- 1,1,2,2-tetrafluoroethanesulfonate, diphenyliodonium camphorsulfonate, bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, Bis (4-t-butylphenyl) iodonium perfluoro-n-octanesulfonate, bis (4-t-butylphenyl) iodonium 2-bicyclo [2.2 1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, bis (4-t- butylphenyl) iodonium camphorsulfonate, and the like. Of these iodonium salts, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate is preferred.

  [B] The acid generator is more preferably triphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1-difluoroethanesulfonate.

  These [B] acid generators may be used alone or in combination of two or more. [B] The content when the acid generator is an acid generator is usually 0.1 mass with respect to 100 parts by mass of the polymer [A] from the viewpoint of ensuring sensitivity and developability as a resist. Part to 30 parts by mass, preferably 0.5 part to 20 parts by mass. [B] When the usage-amount of an acid generator is the said specific range, the said photoresist composition is excellent in resolution and LWR.

<[C] Fluorine atom-containing polymer>
The photoresist composition preferably contains a [C] fluorine atom-containing polymer (hereinafter also referred to as “[C] polymer”). When the photoresist composition contains the [C] polymer, the distribution tends to be unevenly distributed on the surface of the resist film due to the water-repellent characteristics of the [C] polymer when the resist film is formed. Therefore, at the time of immersion exposure, elution of the acid generator and the acid diffusion controller in the film into the immersion medium can be suppressed. As the [C] polymer, a polymer corresponding to the [A] polymer is excluded.

  [C] The polymer can be usually formed by polymerizing one or more monomers containing fluorine atoms in the structure.

  [C] The polymer preferably has a structural unit (FI) represented by the following formula (8).

In the formula (8), R ²⁰ represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. A is a single bond or a divalent linking group. R ²¹ is a linear or branched alkyl group having 1 to 6 carbon atoms having at least one fluorine atom, or a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof. .

  Examples of the divalent linking group represented by A include an oxygen atom, a sulfur atom, a carbonyloxy group, an oxycarbonyl group, an amide group, a sulfonylamide group, and a urethane group.

Preferred monomers that give the structural unit (FI) include trifluoromethyl (meth) acrylic acid ester, 2,2,2-trifluoroethyl (meth) acrylic acid ester, and perfluoroethyl (meth) acrylic. Acid ester, perfluoro n-propyl (meth) acrylic acid ester, perfluoro i-propyl (meth) acrylic acid ester, perfluoro n-butyl (meth) acrylic acid ester, perfluoro i-butyl (meth) acrylic acid ester , Perfluoro t-butyl (meth) acrylate, 2- (1,1,1,3,3,3-hexafluoropropyl) (meth) acrylate, 1- (2,2,3,3, 4,4,5,5-octafluoropentyl) (meth) acrylic acid ester, perfluorocyclohexylmethyl (meth) ) Acrylic acid ester, 1- (2,2,3,3,3-pentafluoropropyl) (meth) acrylic acid ester, 1- (3,3,4,4,5,5,6,6,7, 7,8,8,9,9,10,10,10-heptadecafluorodecyl) (meth) acrylic acid ester, 1- (5-trifluoromethyl-3,3,4,4,5,6,6
9,6-octafluorohexyl) (meth) acrylic acid ester.

  [C] The content of the structural unit (FI) in the polymer is usually 5 mol% or more, preferably 10 mol% or more, and more preferably 15 mol% or more. If the content of the structural unit (FI) is less than 5 mol%, the receding contact angle becomes less than 70 degrees, and there is a possibility that inconveniences such as inability to suppress the elution of the acid generator from the resist film may occur. . In addition, the [C] polymer may have only 1 type of structural unit (FI), and may have 2 or more types.

  In addition to the structural unit having the above-described fluorine atom in the structure, the polymer [C] includes, for example, a structural unit containing an acid-dissociable group, a lactone group, a cyclic carbonate group in order to control the dissolution rate in the developer. Or, a structural unit containing a sultone group, a structural unit containing a hydroxyl group, a structural unit containing an alicyclic group, etc., a structural unit derived from an aromatic compound to suppress light scattering due to reflection from the substrate, etc. One or more “structural units” can be contained.

  Examples of the structural unit containing the dissociable group include the same structural unit as the structural unit (II) of the [A] polymer. Examples of the structural unit containing the lactone group, cyclic carbonate group or sultone group include the same structural unit as the structural unit (III) of the polymer [A].

  [C] In the polymer, the content of these other structural units is usually 80 mol% or less, preferably 75 mol% or less, and more preferably 70 mol% or less.

<[C] Polymer Synthesis Method>
[C] The polymer can be synthesized, for example, by polymerizing a monomer corresponding to each predetermined structural unit in a suitable solvent using a radical polymerization initiator. In addition, as a polymerization initiator, a solvent, etc. which are used for the synthesis | combination of a [C] polymer, the thing similar to what was illustrated in the said synthesis method of a [A] polymer can be mentioned.

  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.

  [C] The polystyrene-reduced weight average molecular weight (Mw) of the polymer by gel permeation chromatography (GPC) is preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and 3,000. ˜30,000 is particularly preferred. [C] When the Mw of the polymer is in the specific range, the developability when the resist is formed is excellent.

  [C] 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 2.5.

<[D] Acid diffusion controller>
[D] The acid diffusion controller is a component that controls the diffusion phenomenon in the resist film of the acid generated from the [B] acid generator by exposure and suppresses an undesirable chemical reaction in the unexposed area. When the photoresist composition contains the [D] acid diffusion controller, the storage stability of the resulting photoresist 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. The content of the [D] acid diffusion controller in the photoresist composition of the present invention may be a free compound (hereinafter also referred to as “[D] acid diffusion controller” as appropriate). It may be a form incorporated as part of the coalescence or both forms.

  [D] 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; di (cyclo) alkylamines; tri (cyclo) alkylamines; substituted alkylanilines or derivatives thereof; ethylenediamine, N, N, N ′, N′-tetra Methylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 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) propane, 2- (4-amino) Phenyl) -2- (4-hydroxyphenyl) propane, 1, -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 can be mentioned.

  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, 4-hydroxy-N-amyloxycarbonylpiperidine, piperidineethanol, 3-piperidino- 1,2-propanediol, morpholine, 4-methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine, 3- (N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane, Nt-butoxycarbonyl-4-hydroxypiperidine and the like can be mentioned.

  Further, as the [D] acid diffusion control agent, a photodisintegratable base that is exposed to light and generates a weak acid by exposure can also be used. The photodegradable base generates an acid in the exposed portion to increase the insolubility of the [A] polymer in the developer, and as a result, suppresses the roughness of the exposed portion surface after development. 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 (D1) and an iodonium salt compound represented by the following formula (D2).

In the formula (D1) and Formula ^{(D2), R} 22 ~R ²⁶ independently represent a hydrogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom or _-SO 2 -R ^C. R ^C is an alkyl group, a cycloalkyl group, an alkoxy group or an aryl group. Z ⁻ is OH ⁻ , R ²⁷ —COO ⁻ , R ^D —SO ₂ —N ^— —R ²⁷ , R ²⁷ —SO ₃ ^— or an anion represented by the following formula (D3). R ²⁷ is a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an alkaryl group having 7 to 30 carbon atoms. Some or all of the hydrogen atoms of the alkyl group, cycloalkyl group, aryl group and alkaryl group may be substituted. ^RD is a C1-C10 linear or branched alkyl group or a C3-C20 cycloalkyl group 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 (D3), R < ²⁸ > is a C1-C12 linear or branched alkyl group by which a part 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.

  The content of the [D] acid diffusion controller in the photoresist composition used in the pattern forming method is preferably less than 10 parts by mass with respect to 100 parts by mass of the [A] polymer. When the total amount used is less than 10 parts by mass, the sensitivity as a resist is easily maintained. These [D] acid diffusion inhibitors may be used alone or in combination of two or more.

<[E] solvent>
The photoresist composition usually contains an [E] solvent. [E] The solvent is not particularly limited as long as it can dissolve at least the [A] polymer, the [B] acid generator, the preferred component [C] polymer, the [D] acid diffusion controller and the optional component. [E] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and mixed solvents thereof.

Examples of alcohol solvents include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, 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-tetradecyl alcohol, sec-heptadeci Monoalcohol solvents such as 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 -Polyhydric alcohol solvents such as ethyl-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.

  Examples of ether solvents include diethyl ether, dipropyl ether, dibutyl ether, diphenyl ether and the like.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-i-butyl ketone, methyl-n-pentyl ketone, ethyl-n-butyl ketone, methyl-n- Examples include ketone solvents such as hexyl ketone, di-i-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 ester solvents include diethyl carbonate, propylene carbonate, methyl acetate, ethyl acetate, γ-butyrolactone, γ-valerolactone, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-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 Non-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, glycol diacetate Methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, Examples include diethyl malonate, dimethyl phthalate, and diethyl phthalate.

Examples of hydrocarbon solvents include n-pentane, i-pentane, n-hexane, i-hexane, n-heptane, i-heptane, 2,2,4-trimethylpentane, n-octane, i-octane, and cyclohexane. , Aliphatic hydrocarbon solvents such as methylcyclohexane;
Fragrances such as benzene, toluene, xylene, mesitylene, ethylbenzene, trimethylbenzene, methylethylbenzene, n-propylbenzene, i-propylbenzene, diethylbenzene, i-butylbenzene, triethylbenzene, di-i-propylbenzene, n-amylnaphthalene Group hydrocarbon solvents and the like.

  Of these, propylene glycol monomethyl ether acetate, cyclohexanone, and γ-butyrolactone are preferable, and propylene glycol monomethyl ether acetate is more preferable. These solvents may be used alone or in combination of two or more.

<Other optional components>
The photoresist composition can contain a surfactant, an alicyclic skeleton-containing compound, a sensitizer, and the like as other optional components. In addition, the said photoresist composition may contain only 1 type of said other arbitrary 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 photoresist composition used in the 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 photoresist composition used in the pattern forming method.

[Sensitizer]
The sensitizer exhibits the effect of increasing the amount of acid generated from the [B] acid generator, and has the effect of improving the “apparent sensitivity” of the photoresist composition used in the pattern forming method. .

<Method for preparing photoresist composition>
The photoresist composition used in the pattern forming method includes, for example, an [A] polymer, a [B] acid generator, a [C] polymer, a [D] acid diffusion controller and an optional component in a [E] solvent. It can be prepared by mixing at a predetermined ratio. Moreover, the said composition can be prepared and used in the state melt | dissolved or disperse | distributed to the appropriate [E] solvent.

<Negative pattern forming method>
The pattern forming method of the present invention comprises:
(1) A step of applying the photoresist composition on a substrate to form a resist film,
(2) A negative pattern forming method including a step of exposing the resist film, and (3) a step of developing the exposed resist film using a developer containing an organic solvent. Hereinafter, each process is explained in full detail.

[(1) Process]
In this step, the photoresist composition is applied onto a substrate to form a resist film. 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.

  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 0.01 micrometer-1 micrometer normally, and 0.01 micrometer-0.5 micrometer are preferable.

  After apply | coating the said photoresist composition, you may volatilize the solvent in a coating film by prebaking (PB) as needed. The heating conditions for PB are appropriately selected depending on the composition of the photoresist composition, but are usually about 30 ° C to 200 ° C, preferably 50 ° C to 150 ° C.

  In order to prevent the influence of basic impurities contained in the environmental atmosphere, a protective film disclosed in, for example, Japanese Patent Laid-Open No. 5-188598 can be provided on the resist layer. Furthermore, in order to prevent the acid generator and the like from flowing out of the resist layer, a liquid immersion protective film disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-352384 can be provided on the resist layer. These techniques can be used in combination.

[(2) Process]
In this step, exposure is performed by reducing and projecting a desired pattern of the resist film formed in step (1) through a mask of a specific pattern and, if necessary, an immersion liquid. For example, an isoline pattern can be formed by performing reduced projection exposure on a desired region through an isoline pattern mask. Similarly, a hole pattern can be formed by performing reduced projection exposure through a dot pattern mask. Moreover, you may perform exposure twice or more with a desired pattern and a 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. Examples of the immersion liquid used for exposure include water and a fluorine-based inert liquid. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a refractive index temperature coefficient that is as small as possible so as to minimize distortion of the optical image projected onto the film. In the case of excimer laser light (wavelength 193 nm), it is preferable to use water from the viewpoints of availability and easy handling in addition to the above-described viewpoints.

  The radiation used for the exposure is appropriately selected according to the type of the [B] acid generator, and examples thereof include ultraviolet rays, far ultraviolet rays, X-rays, and charged particle beams. Among these, far ultraviolet rays represented by ArF excimer laser and KrF excimer laser (wavelength 248 nm) are preferable, and ArF excimer laser is more preferable. The exposure conditions such as the exposure amount are appropriately selected according to the composition of the photoresist composition and the type of additive. In the resist pattern forming method, the exposure process may be performed a plurality of times as described above, and the same light source or different light sources may be used in the plurality of times of exposure. However, it is preferable to use ArF excimer laser light for the first exposure.

  In addition, post exposure baking (PEB) is preferably performed after exposure. By performing PEB, the dissociation reaction of the acid dissociable group in the photoresist composition can proceed smoothly. As a heating condition of PEB, it is 30 degreeC-200 degreeC normally, and 50 degreeC-170 degreeC is preferable.

[(3) Process]
In this step, the resist film exposed in step (2) is developed with the developer of the present invention to form a pattern. The developer is a negative developer containing an organic solvent. Here, the negative developer is a developer that selectively dissolves and removes the low-exposed portion and the unexposed portion. As content of the organic solvent in a developing solution, 80 mass% or more is preferable, 90 mass% or more is more preferable, and 99 mass% or more is further more preferable. By setting the content of the organic solvent in the developer to the above specific range, the dissolution contrast between the exposed and unexposed areas can be improved, and as a result, a pattern with excellent LWR can be formed. . Examples of components other than the organic solvent include water and silicone oil.

  Examples of the organic solvent include alcohol solvents, ether solvents, ketone organic solvents, amide solvents, ester organic solvents, hydrocarbon solvents, and the like. As each solvent, the solvent similar to the solvent illustrated as a [E] solvent etc. can be mentioned.

  Of these, ether solvents, ketone solvents, and ester solvents are preferable, butyl acetate, isopropyl acetate, amyl acetate, anisole, methyl ethyl ketone, methyl-n-butyl ketone, and methyl-n-amyl ketone are preferable, and butyl acetate is more preferable. . These organic solvents may be used alone or in combination of two or more.

  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 negative pattern forming method preferably includes a rinsing step of washing the resist film with a rinsing liquid after the step (3). An organic solvent can be used as the rinsing liquid in the rinsing step. By using an organic solvent as the rinsing liquid, the generated scum can be efficiently washed.

  As the organic solvent used as the rinsing liquid, hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, amide solvents and the like are preferable. Of these, alcohol solvents and ester solvents are more preferable, and alcohol solvents are more preferable. Among the alcohol solvents, monovalent alcohol solvents having 6 to 8 carbon atoms are more preferable.

  Each component of the said rinse liquid may be used independently and may use 2 or more types together. The water content in the rinse liquid is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. By setting the water content in the rinse liquid to 10% by mass or less, good development characteristics can be obtained. A surfactant can be added to the rinse liquid.

  Examples of the cleaning treatment using the rinsing liquid include, for example, a method of continuously applying the rinsing liquid onto a substrate rotating at a constant speed (rotary coating method), and immersing the substrate in a tank filled with the rinsing liquid for a predetermined time. Examples thereof include a method (dip method) and a method (spray method) of spraying a rinsing liquid on the substrate surface.

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

[Weight average molecular weight (Mw), number average molecular weight (Mn) and dispersity (Mw / Mn)]
Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using Tosoh GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) under the following conditions. The degree of dispersion (Mw / Mn) was calculated from the measurement results of Mw and Mn.
Eluent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Column temperature: 40 ° C
Detector: Differential refractometer Standard material: Monodisperse polystyrene

[Low molecular weight component content]
[A] The content (mass%) of the low molecular weight component (component having a molecular weight of less than 1,000) in the polymer was determined by high performance liquid chromatography (HPLC) using an Intersil ODS-25 μm column (4.6 mmφ manufactured by GL Sciences). × 250 mm) was used, and the measurement was performed under the following conditions. The low molecular weight component is a component having a monomer as a main component, and more specifically, a component having a molecular weight of 500 or less.
Elution solvent: Acrylonitrile / 0.1% phosphoric acid aqueous solution Flow rate: 1.0 mL / min Sample concentration: 1.0 mass%
Sample injection volume: 100 μL
Detector: Differential refractometer

[ ¹³ C-NMR analysis]
^{The 13} C-NMR analysis was performed using JNM-EX270 manufactured by JEOL Ltd. and DMSO-d ₆ as a measurement solvent. The content rate of each structural unit in a polymer was computed from the area ratio of the peak corresponding to each structural unit in the spectrum obtained by < ¹³ > C-NMR.

<[A] Synthesis of polymer>
The monomers used for the synthesis of the [A] polymer and the later-described [C] polymer are shown below.

[Synthesis Example 1]
9.48 g (50 mol%) of the compound (M-3) giving the structural unit (I) and 10.52 g (50 mol%) of the compound (M-2) giving the structural unit (III) are dissolved in 40 g of 2-butanone. Further, a monomer solution in which 0.78 g (5 mol%) of azobisisobutyronitrile (AIBN) was added as an initiator was prepared. Next, 20 g of 2-butanone was charged into a 100 mL three-necked flask equipped with a thermometer and a dropping funnel, and the inside of this three-necked flask was purged with nitrogen for 30 minutes. After purging with nitrogen, the inside of the three-necked flask was heated to 80 ° C. while stirring with a magnetic stirrer, and the monomer solution prepared in advance was maintained for 3 hours using a dropping funnel while maintaining the temperature. It was dripped over. The polymerization reaction was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization solution was cooled to 30 ° C. or less by water cooling. After cooling, it was poured into 400 g of methanol, and the precipitated white powder was filtered off. The filtered white powder was washed twice with 80 g of methanol as a slurry, filtered, and dried at 50 ° C. for 17 hours to obtain a white powder copolymer (A-1) (11. 1 g, yield 56%). This copolymer has Mw of 7,240 and Mw / Mn of 1.64. As a result of ¹³ C-NMR analysis, each structure derived from compound (M-1) and compound (M-2) The unit content was 50.3: 49.7 (mol%). Moreover, content of the low molecular weight component in this copolymer was 0.04 mass%.

[Synthesis Examples 2 to 4]
Polymers (A-2) to (A-3) and (a-1) were obtained in the same manner as in Synthesis Example 1 except that a predetermined amount of the monomers listed in Table 1 were blended. Table 1 shows the content of each structural unit, Mw, Mw / Mn ratio, yield (%), and low molecular weight component content of each polymer obtained.

<Synthesis of [C] fluorine atom-containing polymer>
[Synthesis Example 5]
Compound (M-6) 79.9 g (70 mol%) and compound (M-7) 20.91 g (30 mol%) were dissolved in 100 g of 2-butanone to obtain dimethyl 2,2′-azobisisobutyrate. 4.77 g was added to prepare a monomer solution. A 1,000 mL three-necked flask containing 100 g of 2-butanone was purged with nitrogen for 30 minutes, and then the monomer solution prepared by heating to 80 ° C. with stirring was added dropwise using a dropping funnel over 3 hours. The dripping start was set as the polymerization reaction start time, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water and cooled to 30 ° C. or lower. After transferring the reaction solution to a 2 L separatory funnel, the polymerization solution was uniformly diluted with 150 g of n-hexane, and 600 g of methanol was added and mixed. Next, 30 g of distilled water was added, and the mixture was further stirred and allowed to stand for 30 minutes. Thereafter, the lower layer was recovered to obtain a propylene glycol monomethyl ether acetate solution (yield 60%). Mw of the obtained polymer (C-1) was 7,200, Mw / Mn was 2.00, and low molecular weight component content was 0.07 mass%. As a result of ¹³ C-NMR analysis, the content of the structural unit derived from the compound (M-6) and the structural unit derived from the compound (M-7) in the polymer (C-1) was 71.1 mol%: It was 28.9 mol%.

<Preparation of photoresist composition>
The [B] acid generator, [D] acid diffusion controller, and [E] solvent used for the preparation of the photoresist composition are shown below.

([B] acid generator)
Compound represented by the following formula (B-1): triphenylsulfonium 2- (bicyclo [2.2.1] hept-2-yl) -1,1-difluoroethanesulfonate

([D] acid diffusion controller)
Compound represented by the following formula (D-1): Nt-butoxycarbonyl-4-hydroxypiperidine

([E] solvent)
(E-1): Propylene glycol monomethyl ether acetate

[Example 1]
100 parts by weight of polymer (A-1), 3 parts by weight of polymer (C-1), 7.87 parts by weight of acid generator (B-1), 0.945 parts by weight of acid diffusion controller (D-1) And 3,500 parts by mass of the solvent (E-1) were mixed, and the resulting mixed solution was filtered through a filter having a pore size of 0.20 μm to prepare a photoresist composition (J-1).

[Examples 2-3 and Synthesis Example 6]
The photoresist compositions (J-2) to (J-3) and (j-1) were prepared in the same manner as in Example 1 except that the components of the types and blending amounts described in Table 2 were mixed. did.

<Formation of resist pattern>
[Examples 4 to 6 and Comparative Examples 1 to 3]
A lower antireflection film (ARC66, manufactured by Brewer Science) was applied on a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron), and then heated at 205 ° C. for 60 seconds to have a film thickness of 105 nm. A lower antireflection film was formed. Next, using the spin coater, each photoresist composition shown in Table 3 was applied, and PB was performed at 90 ° C. for 60 seconds. Thereafter, it was cooled at 23 ° C. for 30 seconds to form a resist film having a thickness of 90 nm. Next, using an ArF immersion exposure apparatus (NSR-S610C, manufactured by Nikon Seiki Company) under the optical conditions of NA = 1.3 and dipole (Sigma 0.977 / 0.782), through the mask pattern, Exposure was performed under conditions of best focus. Thereafter, PEB was carried out at 85 ° C. for 60 seconds, developed using the developer shown in Table 3 at 23 ° C. for 30 seconds, and dried to form a resist pattern. The following evaluation was performed about the formed pattern. A scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, CG4000) was used for length measurement in each evaluation.

<Evaluation>
Various physical properties of the resist pattern formed as described above were evaluated as follows. The results are shown in Table 3. In Table 3, “-” indicates that the pattern could not be evaluated because no pattern was formed. “TMAH” indicates 2.38% tetramethylammonium hydroxide.

[Resolution (nm)]
The exposure amount at which the pattern formed by the pattern forming method is a line-and-space pattern with a line width of 80 nm is set as the optimal exposure amount, and the minimum resist pattern dimension resolved at this optimal exposure amount is set as the resolution ( nm). When the resolution was less than 35 (nm), the resolution was good, and when the resolution was 35 (nm) or more, it was judged that the resolution was poor.

[LWR: Line Width Roughness (nm)]
A line-and-space pattern with a line width of 80 nm resolved at the optimum exposure dose was observed from above the pattern using a scanning electron microscope (CG-4000, manufactured by Hitachi High-Technologies Corporation). Then, a total of 50 points were measured for the line width at an arbitrary point, and the value calculated with the measurement variation as 3 sigma was defined as LWR (nm). The case where the value of LWR was less than 4.5 (nm) was judged as good, and the case where it was 4.5 (nm) or more was judged as bad.

[Film reduction (nm)]
First, a resist film having a thickness of 120 nm is formed on each of the above photoresist compositions on an 8-inch silicon wafer on which a 77 nm-thick lower layer antireflection film (ARC29A, manufactured by Brewer Science Co., Ltd.) is formed. PB was performed for 60 seconds. Next, this resist film was subjected to 25 mJ / cm without using a mask under the conditions of NA = 0.78, sigma = 0.90, Annular using an ArF excimer laser exposure apparatus (NSR S306C, manufactured by NIKON). ^The entire wafer surface was exposed with an exposure amount of ² . After exposure, PEB was performed at 85 ° C. for 60 seconds. The film thickness (F1) at this time was measured. Thereafter, development was performed with butyl acetate at 23 ° C. for 30 seconds, and the film thickness (F2) was measured. A value obtained by subtracting F2 from F1 (F1-F2) was obtained. This was measured at 10 points, and the average value was defined as film thickness reduction (nm). In addition, the optical interference type film thickness measuring apparatus (Lambda ace, Dainippon Screen Mfg. Co., Ltd.) was used for the film thickness measurement. The film thickness was judged to be good when it was less than 5.0 nm and bad when it was 5.0 nm or more.

  From the results shown in Table 3, it was found that the radiation-sensitive resin composition of the present invention was excellent in resolution and LWR and suppressed film loss in a negative pattern forming method using an organic solvent developer.

  The photoresist composition of the present invention can suppress film loss in the negative resist pattern forming step, and is excellent in resolution and LWR. Therefore, the photoresist composition 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 (6)

A photoresist composition for forming a negative pattern using a developer containing an organic solvent,
[A] A polymer having a structural unit (I) containing a group that becomes a hydroxyl group by the action of an acid, and [B] an acid generator.   [A] The photoresist composition according to claim 1, wherein the polymer has increased solubility in an aqueous alkali solution and decreased solubility in a developer containing an organic solvent due to the action of an acid.   The photoresist composition according to claim 1, wherein the hydroxyl group is an alcoholic hydroxyl group or a phenolic hydroxyl group. The structural unit (I) contains at least one group selected from the group consisting of groups represented by the following formula (1) to the following formula (4): The photoresist composition as described.

(In Formula (1), R ¹ is a divalent hydrocarbon group. R ² and R ³ are each independently a hydrogen atom or a monovalent organic group. R ⁴ is an acid dissociative property. However, any of R ^{1 to} R ⁴ may be bonded to each other to form a ring structure.
In formula (2), R ⁵ is a divalent hydrocarbon group. m is an integer of 0-3.
In formula (3), R ⁶ is a monovalent organic group. n is an integer of 0-4. However, when n is 2 or more, the plurality of R ⁶ may be the same or different. R ⁷ is an acid dissociable group.
In formula (4), R ⁸ is a divalent organic group. R ⁹ is an acid dissociable group. ) [A] The photoresist composition according to any one of claims 1 to 4, wherein the polymer further comprises a structural unit (II) containing a group represented by the following formula (5).

(In Formula (5), R < ¹⁰ > -R < ¹² > is respectively independently a C1-C4 linear or branched alkyl group or a C4-C20 alicyclic group, provided that Any two of R ^{10 to} R ¹² may be bonded to each other to form a divalent alicyclic group together with the carbon atom to which they are bonded, and the alkyl group and the alicyclic group are Some or all of the hydrogen atoms possessed may be substituted.) (1) A step of coating the photoresist composition according to any one of claims 1 to 5 on a substrate to form a resist film;
(2) A negative pattern forming method including a step of exposing the resist film, and (3) a step of developing the exposed resist film using a developer containing an organic solvent.