JP2009271540A - Positive resist composition and pattern forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resist composition which has a wide process window in contact hole formation, and can suppress pit formation during flow baking, and to provide a pattern forming method using the same. <P>SOLUTION: The positive resist composition comprises: (A) a resin that increases the solubility to developer by the action of an acid and includes (a) a repeating unit containing a group that is decomposed by the action of an acid to become alkali-soluble, (b) a repeating unit containing an alicyclic lactone structure, (c) a repeating unit containing an alicyclic structure substituted with a hydroxy group and (d) a methacrylic acid repeating unit, wherein the amount of the methacrylic acid repeating unit is from 5 to 18% by mole based on the total repeating units of the resin; and (B) a compound that generates an acid upon exposure to active ray or radiant ray. The pattern forming method uses the composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positive resist composition for microfabrication such as a semiconductor element sensitive to far ultraviolet rays and a pattern forming method using the same.

In recent years, the degree of integration of integrated circuits has been increasing, and in the manufacture of semiconductor substrates such as VLSI, processing of ultra-fine patterns having a line width of less than half a micron has been required. In order to satisfy this need, the wavelength used by exposure apparatuses used in photolithography has become increasingly shorter, and now it is considered to use excimer laser light (XeCl, KrF, ArF, etc.) having a short wavelength among far ultraviolet rays. It is becoming.
A chemical amplification type resist is used for lithography pattern formation in this wavelength region.

As a resist composition for an ArF light source, a resin having an alicyclic hydrocarbon moiety introduced therein has been proposed for the purpose of imparting dry etching resistance.
Patent Document 1 discloses a resist using an acid-sensitive compound containing an alkali-soluble group protected with a structure containing an alicyclic group, and a structural unit in which the alkali-soluble group is eliminated by an acid to make it alkali-soluble. The materials are listed.

Patent Document 2 and Patent Document 3 describe resist compositions containing a copolymer containing methacrylic acid or acrylic acid repeating units and acid-decomposable repeating units.
Patent Documents 4 and 5 describe resist compositions containing a copolymer containing a repeating unit having an alicyclic lactone structure.
Patent Document 6 and Patent Document 7 describe resist compositions containing a copolymer containing a repeating unit having an alicyclic group substituted with a hydroxyl group.
Patent Document 8 and Patent Document 9 describe combining an acid-decomposable repeating unit, a repeating unit having an alicyclic lactone structure, and a repeating unit having an alicyclic group substituted with a hydroxyl group.

In general, the resin containing an acid-decomposable group used for the photoresist for exposure to far ultraviolet rays as described above contains an aliphatic cyclic hydrocarbon group in the molecule at the same time.
With respect to the application of these conventional alicyclic hydrocarbon moiety-introduced resins as resist compositions, further improvements in various performances are desired. Among these, further expansion of the process window for contact hole resists has been demanded.

Further, exposure used for photolithography A reduction projection exposure method using resist light (g-line, i-line, KrF excimer laser light) has been used so far. In general, the resolution R of the lens is expressed by the following equation according to Rayleigh's theoretical equation.
R = k [λ / (NA)]
Here, λ is the exposure wavelength, N.A. is the numerical aperture of the lens (Numerical Aparture), and N.A. = sin θ, where θ is the opening angle incident on the wafer. k indicates a different value depending on the resist, and is often used as a characteristic parameter indicating the performance of the resist. Based on experience with i-line resist, it can only be reduced to about 0.5 even if the resist is improved.
Increasing the resolving power is to reduce R, as is clear from the above equation. For this purpose, NA is increased or λ is decreased, but k must be decreased. However, NA has also increased to a value approaching 0.8, and k has reached the limit of 0.5. From the viewpoint of further shortening the wavelength, 248 nm of KrF excimer laser light to 193 nm of ArF excimer laser light has been studied, but even with this ArF excimer laser light, it is theoretically difficult to form a pattern of 100 nm or less. .

Therefore, a resist material and a pattern forming method that can form a finer pattern with a current exposure apparatus have been desired. As a technique corresponding to the above method, the wafer is heated (flow bake) while irradiating ultraviolet rays (UV) in vacuum disclosed in Patent Document 10, and the resist shape is changed (flowed). Although a method for adjusting the contact hole diameter of a semiconductor device capable of reducing the size is promising, development of a resist material suitable for the method has been insufficient. Further, since the process of flow baking the wafer while irradiating with UV in a vacuum is complicated, a resist material that can obtain the same effect only by flow baking in air has been desired. However, when the flow bake process is applied to the resist materials known so far, the problem is that the flow rate is high and the hole size is difficult to control, and that the flow does not flow sufficiently even at a practical flow temperature (180 ° C or lower). was there.
More recently, it has been found that pits frequently occur in the film during the flow bake stage. Since this pit formation is concerned about adverse effects on the subsequent etching process (pattern transfer property deterioration after etching, etching resistance deterioration, etc.), it has been desired to prevent the generation of pits.

JP-A-9-73173 JP 2000-214588 A JP 2000-321771 A JP 2001-188351 A JP 2000-26446 A JP 7-252324 A JP-A-11-109632 JP 2001-109154 A Japanese Patent Laid-Open No. 2002-296783 JP-A-6-37071

  An object of the present invention is to provide a positive resist composition that solves the problems in the above-described performance improvement technology inherent to microphotofabrication using far ultraviolet light, particularly ArF excimer laser light, and a pattern forming method using the same. Accordingly, it is an object of the present invention to provide a positive resist composition having a wide process window in forming contact holes and suppressing pit formation during flow baking, and a pattern forming method using the same.

  As a result of intensive studies on the constituent materials of the positive chemically amplified resist composition, the present inventors have found that the object of the present invention can be achieved by the following constitution, and have reached the present invention.

(1) A repeating unit (a) containing a group that decomposes by the action of an acid and becomes alkali-soluble, a repeating unit (b1) having an alicyclic lactone structure represented by the following general formula (V1), and a fat substituted with a hydroxyl group Repeating unit (c) having a ring structure and repeating unit of methacrylic acid (d)
A resin (A1) that has a methacrylic acid repeating unit (d) ratio of 5 to 18 mol% in all repeating units and that has increased solubility in a developer by the action of an acid, and actinic rays or radiation. A positive resist composition comprising a compound (B) that generates an acid upon irradiation.

In general formula (V1), R _b0 represents a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.
A ′ represents a single bond, an ether group, an ester group, a carbonyl group, an alkylene group, or a divalent group obtained by combining these.
B ₂ represents a group represented by any one of the following general formulas (a-1) to (a-3).

In General Formulas (a-1) to (a-3), R _{1 to} R ₆ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, or —COORa. Here, Ra represents an alkyl group. Two of R _{1 to} R ₆ may combine to form a ring.

  (2) The resin (A1) is characterized in that the content of the repeating unit (a) containing a group that decomposes by the action of an acid and becomes alkali-soluble is 23 to 45 mol% in all repeating units. The positive resist composition according to (1).

  (3) In the resin (A1), the repeating unit (c) having an alicyclic structure substituted with a hydroxyl group is a repeating unit (c1) represented by the following general formula (IIa) ( The positive resist composition as described in 1) or (2).

In general formula (IIa), R ₃₀ represents a hydrogen atom or a methyl group.
R _{31 to} R ₃₃ each independently represents a hydrogen atom, a hydroxyl group or an alkyl group. However, two of R _{31 to} R ₃₃ represent a hydroxyl group.

  (4) Any one of (1) to (3), wherein the repeating unit (a) containing a group that decomposes by the action of an acid of the resin (A1) and becomes alkali-soluble contains an alicyclic structure. The positive resist composition as described in 1. above.

  (5) The repeating unit (a) containing a group that decomposes by the action of an acid of the resin (A1) and becomes alkali-soluble is represented by the following general formula (I): Positive resist composition.

In general formula (I),
R ₂ represents a hydrogen atom or a methyl group.
A represents a single bond or a linking group.
ALG is a group containing an alicyclic hydrocarbon represented by the following general formulas (pI) to (pV).

In the formulas (pI) to (pV),
R ₁₁ represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a sec-butyl group.
Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with a carbon atom.
R _{12 to} R ₁₆ each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms or an alicyclic hydrocarbon group. However, at least one of R _{12 to} R ₁₄ and any one of R ₁₅ and R ₁₆ represents an alicyclic hydrocarbon group.
R _{17 to} R ₂₁ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{17 to} R ₂₁ Represents an alicyclic hydrocarbon group. Further, either R ₁₉ or R ₂₁ represents a linear or branched alkyl group or alicyclic hydrocarbon group having 1 to 4 carbon atoms.
R _{22 to} R ₂₅ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{22 to} R ₂₅ Represents an alicyclic hydrocarbon group. R ₂₃ and R ₂₄ may be bonded to each other to form a ring.

  (6) The positive resist composition according to any one of (1) to (5), wherein the acid value of the resin (A1) is 0.2 to 0.9 meq / g.

  (7) A pattern forming method comprising: forming a resist film from the positive resist composition according to any one of (1) to (6); and exposing and developing the resist film.

  (8) A method for forming a contact hole pattern, comprising: forming a resist film from the positive resist composition according to any one of (1) to (6); and exposing and developing the resist film. .

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a resist composition that has a wide process window in forming contact holes and can suppress pit formation during flow baking, and a pattern forming method using the same.

Hereinafter, the components used in the present invention will be described in detail.
In the present invention, in the notation of a group (atomic group), when substituted or unsubstituted is not particularly described, both substituted and unsubstituted are included. For example, when it is simply described as “alkyl group”, it may be an unsubstituted alkyl or an alkyl group having a substituent.

[1] Resin whose solubility in a developer increases by the action of an acid The positive resist composition of the present invention comprises:
A repeating unit (a) containing a group that decomposes by the action of an acid and becomes alkali-soluble,
A repeating unit (b1) having an alicyclic lactone structure represented by the general formula (V1);
A repeating unit (c) having an alicyclic structure substituted with a hydroxyl group, and
Methacrylic acid repeating unit (d)
And a resin (A1) that has a methacrylic acid repeating unit (d) ratio of 5 to 18 mol% in all repeating units and that increases the solubility in a developing solution by the action of an acid.

  The resin (A1) preferably has no aromatic group. The aromatic group is a compound such as a benzene ring, naphthalene, anthracene, etc., and is a residue having a cyclic π electron cloud delocalized above and below the electron plane, and the π electron cloud has a total of 4n + 2 It is characterized in that (n is 0 or a natural number) π electrons are included.

(A) Repeating unit containing a group that decomposes by the action of an acid and becomes alkali-soluble Resin (A1) is a resin (acid-decomposable resin) whose solubility in an alkaline developer is increased by the action of an acid. It contains a repeating unit (a) having a group (acid-decomposable group) that decomposes by action and becomes alkali-soluble.

When an ArF excimer laser is used as a light source for exposure, it is preferable to use a group represented by —C (═O) —X ₁ —R ₀ as a group that is decomposed by the action of an acid. Here, as R ₀ , tertiary alkyl groups such as t-butyl group and t-amyl group, isobornyl group, 1-ethoxyethyl group, 1-butoxyethyl group, 1-isobutoxyethyl group, 1-cyclohexyloxy 1-alkoxyethyl group such as ethyl group, 1-methoxymethyl group, alkoxymethyl group such as 1-ethoxymethyl group, tetrahydropyranyl group, tetrahydrofuranyl group, trialkylsilyl group, 3-oxocyclohexyl group, the above lactone group Etc. X ₁ represents an oxygen atom or a sulfur atom, preferably an oxygen atom.

The repeating unit (a) having an acid-decomposable group preferably has an alicyclic hydrocarbon structure. As the alicyclic hydrocarbon structure (alicyclic structure), structures represented by formulas (pI) to (pV) described later are preferable.
More preferably, it contains a repeating unit represented by the following general formula (I).

In the general formula (I), R ₂ represents a hydrogen atom or a methyl group, A represents a single bond or a linking group, and ALG includes an alicyclic hydrocarbon represented by the following general formulas (pI) to (pV). It is a group.

The linking group of A is selected from the group consisting of an alkylene group, an ether group, a thioether group, a carbonyl group, an ester group, an amide group, a sulfonamide group, a urethane group, or a urea group, or a combination of two or more groups Represents. Examples of the alkylene group in A include groups represented by the following formulas.
− [C (R _b ) (R _c )] _r −
In the formula, R _b and R _c represent a hydrogen atom, an alkyl group, a halogen atom, a hydroxyl group and an alkoxy group, and both may be the same or different. The alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, and more preferably selected from a methyl group, an ethyl group, a propyl group, and an isopropyl group. Examples of the alkoxy group include those having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom. The alkyl group and alkoxy group may have a substituent. Examples of the substituent for the alkyl group and alkoxy group include a hydroxyl group, a halogen atom, and an alkoxy group (preferably having 1 to 4 carbon atoms). r represents an integer of 1 to 10.

In the formula, R ₁₁ represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a sec-butyl group, and Z forms an alicyclic hydrocarbon group together with a carbon atom. Represents the atomic group necessary to do.
R _{12 to} R ₁₆ each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms or an alicyclic hydrocarbon group. However, at least one of R _{12 to} R ₁₄ and any one of R ₁₅ and R ₁₆ represents an alicyclic hydrocarbon group.
R _{17 to} R ₂₁ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{17 to} R ₂₁ Represents an alicyclic hydrocarbon group. Further, either R ₁₉ or R ₂₁ represents a linear or branched alkyl group or alicyclic hydrocarbon group having 1 to 4 carbon atoms.
R _{22 to} R ₂₅ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{22 to} R ₂₅ Represents an alicyclic hydrocarbon group. R ₂₃ and R ₂₄ may be bonded to each other to form a ring.

In the general formulas (pI) to (pV), the alkyl group in R _{12 to} R ₂₅ may be either substituted or unsubstituted, and a linear or branched alkyl group having 1 to 4 carbon atoms Represents. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group.
Further, the further substituent of the alkyl group includes an alkoxy group having 1 to 4 carbon atoms, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an acyl group, an acyloxy group, a cyano group, a hydroxyl group, A carboxy group, an alkoxycarbonyl group, a nitro group, etc. can be mentioned.

The alicyclic hydrocarbon group in R _{11 to} R _{25 or} the alicyclic hydrocarbon group formed by Z and a carbon atom may be monocyclic or polycyclic. Specific examples include groups having a monocyclo, bicyclo, tricyclo, tetracyclo structure or the like having 5 or more carbon atoms. The carbon number is preferably 6-30, and particularly preferably 7-25. These alicyclic hydrocarbon groups may have a substituent.
Below, the structural example of an alicyclic part (alicyclic structure) is shown among alicyclic hydrocarbon groups.

  In the present invention, preferred examples of the alicyclic moiety include adamantyl group, noradamantyl group, decalin residue, tricyclodecanyl group, tetracyclododecanyl group, norbornyl group, cedrol group, cyclohexyl group, cycloheptyl. Group, cyclooctyl group, cyclodecanyl group and cyclododecanyl group. More preferred are an adamantyl group, a decalin residue, a norbornyl group, a cedrol group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecanyl group, a cyclododecanyl group, and a tricyclodecanyl group.

Examples of the substituent for these alicyclic hydrocarbon groups include an alkyl group, a halogen atom, a hydroxyl group, an alkoxy group, a carboxyl group, and an alkoxycarbonyl group.
The alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, and more preferably a substituent selected from the group consisting of a methyl group, an ethyl group, a propyl group, and an isopropyl group. To express. Examples of the alkoxy group include those having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. The alkyl group and alkoxy group may have a substituent. Examples of the substituent for the alkyl group and alkoxy group include a hydroxyl group, a halogen atom, and an alkoxy group.

In addition, it is preferable that A is a single bond and ALG contains the repeating unit represented by the formula (I) which is a group represented by the general formula (pI) or (pII).
In addition, from the point that variation in pattern size during observation with a scanning electron microscope is small (SEM resistance), in general formula (I), A is a single bond, and ALG is a group represented by the following: Particularly preferred.

R ₂₆ and R ₂₇ each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms.

  Specific examples of the monomer corresponding to the repeating unit represented by the general formula (I) are shown below.

(B) Repeating unit having alicyclic lactone structure The resin (A1) contains a repeating unit (b1) having an alicyclic lactone structure represented by the general formula (V1) as a repeating unit having an alicyclic lactone structure. To do.
In the repeating unit (b1) having an alicyclic lactone structure represented by the general formula (V1), any one of the general formulas (a-1) to (a-3) in which B ₂ in the general formula (V) described later is used. In the case of representing a group represented by formula (V), it is a repeating unit represented by formula (V).
In addition, resin (A1) may contain the repeating unit which has another alicyclic lactone structure.
By containing a repeating unit having an alicyclic lactone structure, it is possible to expect an effect of improving pattern collapse prevention performance and suppressing SEM shrinkage (pattern size shrinkage during observation with a scanning electron microscope).
Examples of the repeating unit having an alicyclic lactone structure include a repeating unit having cyclohexanelactone, norbornanelactone, or adamantanelactone.

For example, as a repeating unit having norbornane lactone, the following general formula (a-1)
The (meth) acrylic repeating unit having a group represented by (a-3) and the repeating unit having cyclohexanelactone have groups represented by the following general formulas (a-4) and (a-5) ( Examples of the repeating unit having a (meth) acrylic repeating unit and adamantanelactone include a (meth) acrylic repeating unit having a group represented by the following general formula (VI).
In particular, a (meth) acrylic repeating unit having a group represented by any of the following general formulas (a-1) to (a-3) is particularly preferable.

In General Formulas (a-1) to (a-5), R _{1 to} R ₆ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, or —COORa. Here, Ra represents an alkyl group. Two of R _{1 to} R ₆ may combine to form a ring.
In addition, about each of R < ₁ > -R < ₆ >, the case where it is a hydrogen atom means that it is unsubstituted. For example, the cyclic structure in the general formula (a-1) can have a maximum of five substituents (an alkyl group, a cycloalkyl group, or an alkenyl group) as R _{1 to} R ₅ .

The alkyl group as R _{1 to} R ₆ or Ra may have a substituent and is a linear or branched alkyl group.
The linear or branched alkyl group is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear or branched alkyl group having 1 to 10 carbon atoms, still more preferably a methyl group, An ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

The cycloalkyl group as R _{1 to} R ₆ may have a substituent, and those having 3 to 8 carbon atoms, such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. preferable.
The alkenyl group as R _{1 to} R ₆ may have a substituent, and those having 2 to 6 carbon atoms such as vinyl group, propenyl group, butenyl group and hexenyl group are preferable.
Examples of the ring formed by combining two of R _{1 to} R ₆ include 3- to 8-membered rings such as cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring, and cyclooctane ring.
In the general formulas (a-1) to (a-5), R _{1 to} R ₆ may be connected to any carbon atom constituting the cyclic skeleton.

  Moreover, as a preferable substituent which the said alkyl group, a cycloalkyl group, and an alkenyl group may have, a C1-C4 alkoxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), Examples thereof include an acyl group having 2 to 5 carbon atoms, an acyloxy group having 2 to 5 carbon atoms, a cyano group, a hydroxyl group, a carboxy group, an alkoxycarbonyl group having 2 to 5 carbon atoms, and a nitro group.

  Examples of the repeating unit having a group represented by general formulas (a-1) to (a-5) include a repeating unit represented by the following general formula (V).

In general formula (V), _Rb0 represents a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.
As a preferable substituent which the alkyl group of R _b0 may have, as a preferable substituent which the alkyl group as R ₁ in the general formulas (a-1) to (a-5) may have. What was illustrated previously is mentioned.
Examples of the halogen atom for R _b0 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R _b0 is preferably a hydrogen atom.
A ′ represents a single bond, an ether group, an ester group, a carbonyl group, an alkylene group, or a divalent group obtained by combining these.
B ₂ represents a group represented by any one of the general formulas (a-1) to (a-5). In A ′, examples of the combined divalent group include those represented by the following formulae.

In the above formula, R _ab and R _bb represent a hydrogen atom, an alkyl group, a halogen atom, a hydroxyl group, and an alkoxy group, and both may be the same or different.
The alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, and more preferably selected from a methyl group, an ethyl group, a propyl group, and an isopropyl group. Examples of the alkoxy group include those having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom. The alkyl group and alkoxy group may have a substituent. Examples of the substituent for the alkyl group and alkoxy group include a hydroxyl group, a halogen atom, and an alkoxy group having 1 to 4 carbon atoms. r1 represents an integer of 1 to 10, preferably an integer of 1 to 4. m represents an integer of 1 to 3, preferably 1 or 2.

Specific examples of the repeating unit represented by the general formula (V) are shown below, but the contents of the present invention are not limited to these.

  Examples of the repeating unit having adamantane lactone include the repeating unit represented by the following general formula (VI).

In the general formula (VI), A ₆ represents a single bond, an alkylene group, a cycloalkylene group, an ether group, a thioether group, a carbonyl group, or a group of two or more groups selected from the group consisting of ester groups.
R _6a represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, or a halogen atom.

In the general formula (VI), examples of the alkylene group represented by A ₆ include groups represented by the following formulae.
-[C (Rnf) (Rng)] r-
In the above formula, Rnf and Rng represent a hydrogen atom, an alkyl group, a halogen atom, a hydroxyl group, and an alkoxy group, and both may be the same or different.
The alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, and more preferably selected from a methyl group, an ethyl group, a propyl group, and an isopropyl group. Examples of the alkoxy group include those having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. The alkyl group and alkoxy group may have a substituent. Examples of the substituent for the alkyl group and alkoxy group include a hydroxyl group, a halogen atom, and an alkoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom. r is an integer of 1-10.

In the general formula (VI), examples of the cycloalkylene group represented by A ₆ include those having 3 to 10 carbon atoms, and examples thereof include a cyclopentylene group, a cyclohexylene group, and a cyclooctylene group.

The bridged alicyclic ring containing Z ₆ may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (preferably having 1 to 4 carbon atoms), an alkoxycarbonyl group (preferably having 1 to 5 carbon atoms), an acyl group (for example, a formyl group and a benzoyl group), an acyloxy group ( Examples thereof include a propylcarbonyloxy group, a benzoyloxy group), an alkyl group (preferably having 1 to 4 carbon atoms), a carboxyl group, a hydroxyl group, and an alkylsulfonylsulfamoyl group (such as —CONHSO ₂ CH ₃ ). In addition, the alkyl group as a substituent may be further substituted with a hydroxyl group, a halogen atom, an alkoxy group (preferably having 1 to 4 carbon atoms), or the like.

In the general formula (VI), the oxygen atom of the ester group bonded to A ₆ may be bonded at any position of the carbon atom constituting the bridged alicyclic ring structure containing Z ₆ .

  Although the specific example of the repeating unit represented by general formula (VI) below is given, it is not limited to these.

(C) Repeating unit having an alicyclic structure substituted with a hydroxyl group The resin (A1) contains a repeating unit (c) having an alicyclic structure substituted with a hydroxyl group. As the repeating unit (c), a repeating unit represented by the general formula (II) is preferable.

In the general formula (II), R ₃ represents a hydrogen atom or a methyl group.
A ₃ represents a single bond or a divalent linking group.
Z ₃ represents a p + 1 valent alicyclic hydrocarbon group.
p represents an integer of 1 to 3.
That, -Z ₃ - (OH) p is a hydroxyl group in the alicyclic hydrocarbon group representing the number p substituted group.

Examples of the divalent linking group for A ₃ include the same groups as those for A in formula (I), and the same applies to the preferred groups.
Examples of the alicyclic hydrocarbon group of Z _3, the general formula can be exemplified an alicyclic hydrocarbon group as R ₁₁ to R ₂₅ for ALG in (I), The same applies to the preferred group.
The p hydroxyl groups may be substituted with any of the alicyclic hydrocarbon group of Z ₃ itself and the substituent portion of the alicyclic hydrocarbon.

  In addition, the repeating unit represented by the following general formula (IIa) is preferable as the repeating unit represented by the general formula (II) in that a wide exposure margin can be obtained when forming a line pattern by underexposure.

In general formula (IIa), R ₃₀ represents a hydrogen atom or a methyl group.
R _{31 to} R ₃₃ each independently represents a hydrogen atom, a hydroxyl group or an alkyl group, provided that at least one represents a hydroxyl group.

Further, in forming a hole pattern by underexposure, it is more preferable that two of R _{31 to} R ₃₃ are hydroxyl groups in the repeating unit represented by the general formula (IIa) in that a wide exposure margin is obtained. .

  Specific examples of the repeating unit represented by the general formula (II) are shown below, but are not limited thereto.

(D) Methacrylic acid repeating unit The resin (A1) of the present invention contains a methacrylic acid repeating unit. In the present invention, the methacrylic acid repeating unit is a repeating unit represented by the following formula.

  The resin (A1) can further contain a repeating unit having a lactone structure represented by the following general formula (IV).

In general formula (IV), R _1a represents a hydrogen atom or a methyl group.
W ₁ represents a single bond, an alkylene group, an ether group, a thioether group, a carbonyl group, or a group of two or more groups selected from the group consisting of an ester group.
R _a1 , R _b1 , R _c1 , R _d1 and R _e1 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. m and n each independently represents an integer of 0 to 3, and m + n is 2 or more and 6 or less.

_Examples of the alkyl group having 1 to 4 carbon atoms of R _{a1 to} R _e1 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. Can do.

In the general formula (IV), examples of the alkylene group represented by W ₁ include groups represented by the following formulae.
− [C (Rf) (Rg)] r ₁ −
In the above formula, Rf and Rg represent a hydrogen atom, an alkyl group, a halogen atom, a hydroxyl group or an alkoxy group, and both may be the same or different.
The alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, and more preferably selected from a methyl group, an ethyl group, a propyl group, and an isopropyl group. Examples of the alkoxy group include those having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom. r ₁ is an integer of 1 to 10.

  The alkyl group and alkoxy group may have a substituent. Further substituents in the alkyl group and alkoxy group include a carboxyl group, an acyloxy group, a cyano group, a halogen atom, a hydroxyl group, an alkoxy group, an acetylamide group, an alkoxycarbonyl group, and an acyl group.

  Hereinafter, although the specific example of the monomer corresponding to the repeating unit shown by general formula (IV) is shown, it is not limited to these.

  In the specific example of the general formula (IV), (IV-17) to (IV-36) are preferable because the exposure margin becomes better.

The resin (A1) may further have a repeating unit based on other acrylate esters.
The repeating unit based on other acrylates that the resin (A1) may have is preferably a repeating unit based on an alkyl acrylate having an alkyl group having 1 to 10 carbon atoms, such as methyl acrylate, ethyl acrylate, Propyl acrylate, amyl acrylate, cyclohexyl acrylate, ethyl hexyl acrylate, octyl acrylate, tert-octyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate, 2,2-dimethylhydroxypropyl acrylate, 5-hydroxypentyl Acrylate, trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate Mention may be made of a repeating unit by over door or the like.

The resin (A1) may further have a repeating unit of other methacrylic acid esters.
The repeating unit of other methacrylic acid esters that the resin (A1) may have is preferably a repeating unit of an alkyl methacrylate having an alkyl group having 1 to 10 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl. Methacrylate, isopropyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate, 2,2-dimethyl-3- Hydroxypropyl methacrylate, trimethylolpropane monomethacrylate, pentaerythritol monomethacrylate DOO, may be mentioned furfuryl methacrylate, a repeating unit by tetrahydrofurfuryl methacrylate.

  The resin (A1) can be synthesized according to a conventional method (for example, radical polymerization). For example, as a general synthesis method, monomer species are charged into a reaction vessel in a batch or in the course of reaction, and if necessary, a reaction solvent such as ethers such as tetrahydrofuran, 1,4-dioxane, diisopropyl ether, methyl ethyl ketone, Dissolve in a solvent that can dissolve various monomers, such as ketones such as methyl isobutyl ketone, ester solvents such as ethyl acetate, and propylene glycol monomethyl ether acetate described later, and then use nitrogen, argon, etc. Polymerization is started using a commercially available radical initiator (azo initiator, peroxide, etc.) as necessary under an active gas atmosphere. If desired, an initiator is added or added in portions, and after completion of the reaction, it is put into a solvent and a desired polymer is recovered by a method such as powder or solid recovery. The concentration of the reaction is 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. The reaction temperature is 10 ° C to 150 ° C, preferably 30 ° C to 120 ° C, more preferably 50-100 ° C.

In resin (A1),
The content of the repeating unit (a) having an acid-decomposable group is preferably 18 to 55 mol%, more preferably 20 to 50 mol%, still more preferably 23 to 45 mol% as a total amount in all repeating units. is there.
The content of the repeating unit (b1) having an alicyclic lactone structure represented by the general formula (V1) is preferably 15 to 60 mol%, more preferably 20 to 55 mol%, still more preferably 25 in all repeating units. ˜50 mol%.
The content of the repeating unit (c) having an alicyclic structure substituted with a hydroxyl group is preferably 5 to 40 mol%, more preferably 10 to 35 mol%, still more preferably 15 to 30 mol% in all repeating units. is there.
The content of the methacrylic acid repeating unit (d) is 5 to 18 mol%, preferably 7 to 17 mol%, more preferably 8 to 16 mol% in all repeating units.
The total amount of the four types of repeating units is usually 70 mol% or more, preferably 80 to 100, more preferably 90 to 100, in all repeating units.
The content of the repeating unit represented by the formula (IV) having a lactone structure in the side chain is preferably 1 to 30 mol%, more preferably 3 to 20 mol%, still more preferably 5 to 10 mol in all repeating units. %.
The amount of the resin (A1) added is usually 50 to 99% by mass, preferably 60 to 98% by mass, based on the total solid content of the positive resist composition.

  In the present invention, the acid value of the resin as the component (A1) is preferably 0.2 to 0.9 meq / g. More preferably, it is 0.3-0.8 meq / g. The acid value can be calculated by titrating the resin solution with an alkaline solution. In the titration, the neutralization point is generally determined by titration indicator such as phenolphthalein or potential difference measurement.

[2] Compound that generates acid upon irradiation with actinic rays or radiation (component B)
The positive resist composition of the present invention contains a compound that generates an acid upon irradiation with actinic rays or radiation (photoacid generator, component B).
As the photoacid generator, a photoinitiator for photocationic polymerization, a photoinitiator for photoradical polymerization, a photodecoloring agent for dyes, a photochromic agent, or a microresist is preferably used. Acid is generated by irradiation with light of a wavelength (specifically, KrF excimer laser (248 nm), ArF excimer laser (193 nm), F ₂ excimer laser (157 nm)), X-ray, electron beam or the like. Known compounds and mixtures thereof can be appropriately selected and used.

Examples thereof include diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonates, oxime sulfonates, diazodisulfones, disulfones, and o-nitrobenzyl sulfonates.
Particularly preferred are sulfonium salts, and triarylsulfonium salts, phenacylsulfonium salts, and sulfonium salts having a 2-oxoalkyl group are most preferred.

  Further, a group that generates an acid upon irradiation with these actinic rays or radiation, or a compound in which a compound is introduced into the main chain or side chain of the polymer, for example, US Pat. No. 3,849,137, German Patent No. 3914407. JP, 63-26653, JP, 55-164824, JP, 62-69263, JP, 63-146038, JP, 63-163452, JP, 62-153853, The compounds described in JP-A 63-146029 can be used.

  Furthermore, compounds capable of generating an acid by light as described in US Pat. No. 3,779,778, European Patent 126,712 and the like can also be used.

  Among the compounds that decompose upon irradiation with actinic rays or radiation to generate an acid, compounds represented by the following general formulas (ZI), (ZII), and (ZIII) can be exemplified.

In the above general formula (ZI), R ₂₀₁ , R ₂₀₂ and R ₂₀₃ each independently represents an organic group.
The carbon number of the organic group as R ₂₀₁ , R ₂₀₂ and R ₂₀₃ is generally 1-30, preferably 1-20.
Two of R _{201 to} R ₂₀₃ may be bonded to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group.
The two of the group formed by bonding of the R ₂₀₁ to R _203, there can be mentioned an alkylene group (e.g., butylene, pentylene).
X ⁻ represents a non-nucleophilic anion.

Examples of the non-nucleophilic anion as X ⁻ include a sulfonate anion, a carboxylate anion, a sulfonylimide anion, a bis (alkylsulfonyl) imide anion, and a tris (alkylsulfonyl) methyl anion.

  A non-nucleophilic anion is an anion that has an extremely low ability to cause a nucleophilic reaction, and is an anion that can suppress degradation over time due to an intramolecular nucleophilic reaction. This improves the temporal stability of the resist.

  Examples of the sulfonate anion include an alkyl sulfonate anion, an aryl sulfonate anion, and a camphor sulfonate anion.

  Examples of the carboxylate anion include an alkylcarboxylate anion, an arylcarboxylate anion, and an aralkylcarboxylate anion.

  The alkyl moiety in the alkyl sulfonate anion may be an alkyl group or a cycloalkyl group, and preferably an alkyl group having 1 to 30 carbon atoms and a cycloalkyl group having 3 to 30 carbon atoms, such as a methyl group or an ethyl group. Group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group Tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, adamantyl group, norbornyl group, boronyl group and the like.

  The aryl group in the aryl sulfonate anion is preferably an aryl group having 6 to 14 carbon atoms, such as a phenyl group, a tolyl group, and a naphthyl group.

  The alkyl group, cycloalkyl group, and aryl group in the alkyl sulfonate anion and aryl sulfonate anion may have a substituent.

  Examples of such substituents include nitro groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), carboxyl groups, hydroxyl groups, amino groups, cyano groups, and alkyl groups (preferably having 1 to 5 carbon atoms). ), An alkoxy group (preferably 1 to 5 carbon atoms), a cycloalkyl group (preferably 3 to 15 carbon atoms), an aryl group (preferably 6 to 14 carbon atoms), an alkoxycarbonyl group (preferably 2 to 7 carbon atoms). ), An acyl group (preferably 2 to 12 carbon atoms), an alkoxycarbonyloxy group (preferably 2 to 7 carbon atoms), an alkylthio group (preferably 1 to 5 carbon atoms), and the like. About the aryl group and ring structure which each group has, an alkyl group (preferably C1-C15) can further be mentioned as a substituent.

Examples of the alkyl moiety in the alkylcarboxylate anion include those similar to the alkyl group and cycloalkyl group in the alkylsulfonate anion.

  Examples of the aryl group in the arylcarboxylate anion include the same aryl groups as in the arylsulfonate anion.

  The aralkyl group in the aralkyl carboxylate anion is preferably an aralkyl group having 6 to 12 carbon atoms, such as a benzyl group, a phenethyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylmethyl group.

  The alkyl group, cycloalkyl group, aryl group and aralkyl group in the alkylcarboxylate anion, arylcarboxylate anion and aralkylcarboxylate anion may have a substituent. Examples of the substituent include an arylsulfonate anion. And the same halogen atom, alkyl group, cycloalkyl group, alkoxy group, alkylthio group and the like as in.

  Examples of the sulfonylimide anion include saccharin anion.

  The alkyl group in the bis (alkylsulfonyl) imide anion and tris (alkylsulfonyl) methyl anion is preferably an alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, An isobutyl group, a sec-butyl group, a pentyl group, a neopentyl group, and the like can be given. These alkyl groups may have a substituent, and examples of the substituent include a halogen atom, an alkyl group substituted with a halogen atom, an alkoxy group, an alkylthio group, and the like, which are substituted with a fluorine atom. Alkyl groups are preferred.

  Examples of other non-nucleophilic anions include fluorinated phosphorus, fluorinated boron, and fluorinated antimony.

As the non-nucleophilic anion of X ⁻ , an alkanesulfonic acid anion in which the α-position of the sulfonic acid is substituted with a fluorine atom, an arylsulfonic acid anion substituted with a fluorine atom or a group having a fluorine atom, and an alkyl group having a fluorine atom And a tris (alkylsulfonyl) methide anion in which the alkyl group is substituted with a fluorine atom. The non-nucleophilic anion is particularly preferably a perfluoroalkanesulfonic acid anion having 4 to 8 carbon atoms, a benzenesulfonic acid anion having a fluorine atom, most preferably nonafluorobutanesulfonic acid anion, perfluorooctanesulfonic acid anion, penta Fluorobenzenesulfonate anion, 3,5-bis (trifluoromethyl) benzenesulfonate anion.

Specific examples of the organic group as R ₂₀₁ , R ₂₀₂ and R ₂₀₃ include corresponding groups in the compounds (Z1-1), (Z1-2) and (Z1-3) described later.

In addition, the compound which has two or more structures represented by general formula (ZI) may be sufficient. For example, the general formula at least one of R ₂₀₁ to R ₂₀₃ of a compound represented by (ZI) is, at least one bond with structure of R ₂₀₁ to R ₂₀₃ of another compound represented by formula (ZI) It may be a compound.

  More preferable examples of the (ZI) component include compounds (Z1-1), (Z1-2), and (Z1-3) described below.

Compound (Z1-1) is at least one of the aryl groups R ₂₀₁ to R ₂₀₃ in formula (ZI), arylsulfonium compound, i.e., a compound having arylsulfonium as a cation.

In the arylsulfonium compound, all of R _{201 to} R ₂₀₃ may be an aryl group, or a part of R _{201 to} R ₂₀₃ may be an aryl group with the remaining being an alkyl group or a cycloalkyl group.

  Examples of the arylsulfonium compound include triarylsulfonium compounds, diarylalkylsulfonium compounds, aryldialkylsulfonium compounds, diarylcycloalkylsulfonium compounds, aryldicycloalkylsulfonium compounds, and the like.

  The aryl group of the arylsulfonium compound is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group. When the arylsulfonium compound has two or more aryl groups, the two or more aryl groups may be the same or different.

  The alkyl group or cycloalkyl group that the arylsulfonium compound has as necessary is preferably a linear or branched alkyl group having 1 to 15 carbon atoms and a cycloalkyl group having 3 to 15 carbon atoms, such as a methyl group, Examples thereof include an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a t-butyl group, a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group.

Aryl group, alkyl group of R ₂₀₁ to R _203, cycloalkyl group, an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (for example, 6 to 14 carbon atoms) , An alkoxy group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, or a phenylthio group may be substituted. Preferred substituents are linear or branched alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, and linear, branched or cyclic alkoxy groups having 1 to 12 carbon atoms, most preferably carbon. An alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. The substituent may be substituted with any one of the three R _{201 to} R ₂₀₃ , or may be substituted with all three. When R _{201 to} R ₂₀₃ are an aryl group, the substituent is preferably substituted at the p-position of the aryl group.

Next, the compound (Z1-2) will be described.
Compound (Z1-2) is a compound in the case where R _{201 to} R ₂₀₃ in formula (ZI) each independently represents an organic group not containing an aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.

The organic group having no aromatic ring as R ₂₀₁ to R ₂₀₃ generally has 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms.

R _{201 to} R ₂₀₃ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a linear or branched 2-oxoalkyl group, 2-oxocycloalkyl group, alkoxy group. A carbonylmethyl group, most preferably a linear or branched 2-oxoalkyl group.

The alkyl group and cycloalkyl group of R ₂₀₁ to R _203, preferably a linear or branched alkyl group having 1 to 10 carbon atoms (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group), carbon Examples thereof include cycloalkyl groups of several 3 to 10 (cyclopentyl group, cyclohexyl group, norbornyl group). More preferred examples of the alkyl group include a 2-oxoalkyl group and an alkoxycarbonylmethyl group. More preferred examples of the cycloalkyl group include a 2-oxocycloalkyl group.

The 2-oxoalkyl group may be either linear or branched, and a group having> C = O at the 2-position of the above alkyl group is preferable.
The 2-oxocycloalkyl group is preferably a group having> C═O at the 2-position of the cycloalkyl group.

  The alkoxy group in the alkoxycarbonylmethyl group is preferably an alkyl group having 1 to 5 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group).

R _{201 to} R ₂₀₃ may be further substituted with a halogen atom, an alkoxy group (for example, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

Two members out of R _{201 to} R ₂₀₃ may combine to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. The two of the group formed by bonding of the R ₂₀₁ to R _203, there can be mentioned an alkylene group (e.g., butylene, pentylene).

  The compound (Z1-3) is a compound represented by the following general formula (Z1-3), and is a compound having a phenacylsulfonium salt structure.

R _{1c to} R _5c each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group or a halogen atom.
R _6c and R _7c represent a hydrogen atom, an alkyl group, or a cycloalkyl group.
Rx and Ry each independently represents an alkyl group, a cycloalkyl group, an allyl group or a vinyl group.

Any two or more of R _{1c to} R _5c , and R _x and R _y may be bonded to each other to form a ring structure, and this ring structure includes an oxygen atom, a sulfur atom, an ester bond, and an amide bond. May be included.

Zc ⁻ represents a non-nucleophilic anion, and examples thereof include the same as the non-nucleophilic anion of X ^{− in} formula (ZI).

The alkyl group as R _{1c to} R _7c may be either linear or branched, for example, an alkyl group having 1 to 20 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms ( Examples thereof include a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, and a linear or branched pentyl group.
Examples of the cycloalkyl group include a cyclic alkyl group having 3 to 8 carbon atoms (for example, a cyclopentyl group and a cyclohexyl group).

The alkoxy group as R _{1c to} R _{5c may} be linear, branched or cyclic, for example, an alkoxy group having 1 to 10 carbon atoms, preferably a linear or branched alkoxy group having 1 to 5 carbon atoms. (For example, methoxy group, ethoxy group, linear or branched propoxy group, linear or branched butoxy group, linear or branched pentoxy group), C3-C8 cyclic alkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) ).

Preferably, any one of R _{1c to} R _5c is a linear or branched alkyl group, a cycloalkyl group, or a linear, branched or cyclic alkoxy group, and more preferably a sum of carbon numbers of R _{1c to} R _5c is 2 to 2. 15. Thereby, solvent solubility improves more and generation | occurrence | production of a particle is suppressed at the time of a preservation | save.

_Examples of the alkyl group and cycloalkyl group as R _x and R _y include the same alkyl groups and cycloalkyl groups as R _{1c to} R _{7c, such} as a 2-oxoalkyl group and a 2-oxocycloalkyl group. An alkoxycarbonylmethyl group is more preferable.

Examples of the 2-oxoalkyl group and 2-oxocycloalkyl group include a group having> C═O at the 2-position of the alkyl group or cycloalkyl group as R _{1c to} R _7c .

Examples of the alkoxy group in the alkoxycarbonylmethyl group include the same alkoxy groups as R _{1c to} R _5c .

Examples of the group formed by combining R _x and R _y include a butylene group and a pentylene group.

R _x and R _y are preferably an alkyl group or cycloalkyl group having 4 or more carbon atoms, more preferably 6 or more, and still more preferably 8 or more alkyl groups or cycloalkyl groups.

In formula (ZII), (ZIII), R 204 ~R 207 each independently represents an aryl group, an alkyl group or a cycloalkyl group.

Phenyl group and a naphthyl group are preferred as the aryl group of R ₂₀₄ to R _207, more preferably a phenyl group.

Alkyl group and cycloalkyl group as R ₂₀₄ to R ₂₀₇ is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group), carbon A cyclic alkyl group (cyclopentyl group, cyclohexyl group, norbornyl group) of several 3 to 10 can be exemplified.

The R ₂₀₄ to R ₂₀₇ are substituents which may have, for example, an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (e.g., 6 carbon atoms 15), alkoxy groups (for example, having 1 to 15 carbon atoms), halogen atoms, hydroxyl groups, phenylthio groups and the like.

X ⁻ represents a non-nucleophilic anion, and examples thereof include the same non-nucleophilic anion as X ^{− in} formula (ZI).

  Examples of particularly preferable photoacid generators are given below.

The addition amount of these photo-acid generators is normally used in the range of 0.001 to 30% by mass, preferably 0.3 to 20% by mass, more preferably 0.8%, based on the solid content in the composition. It is used in the range of 5 to 10% by mass.
The addition amount of the photoacid generator is preferably 0.001% by mass or more from the viewpoint of sensitivity, and the addition amount of 30% by mass or less keeps the light absorption of the resist low, the profile and the process ( In particular, it is preferable in terms of baking margin.
In the present invention, a compound that decomposes upon irradiation with actinic rays or radiation to generate sulfonic acid is preferable.

[3] Other additives In the positive resist composition of the present invention, a surfactant, an organic basic compound, an acid-decomposable dissolution inhibiting compound, a dye, a plasticizer, a photosensitizer, and A compound or the like that promotes solubility in a developer can be contained.

(A) Surfactant The positive resist composition of the present invention is any one of surfactants, particularly fluorine surfactants, silicon surfactants, and surfactants containing both fluorine atoms and silicon atoms, Or it is preferable to contain 2 or more types.
By containing the surfactant, the positive resist composition of the present invention is particularly effective when the line width of the pattern is narrower, and development defects are further improved.

As these fluorine-based and / or silicon-based surfactants, for example, JP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950 are disclosed. JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988, JP-A-2002-277862, US Pat. Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511, 5,824,451 The following commercially available surfactants can also be used as they are.
Examples of commercially available fluorine-based and / or silicon-based surfactants that can be used include F-top EF301, EF303 (manufactured by Shin-Akita Kasei Co., Ltd.), Florard FC430, 431 (manufactured by Sumitomo 3M Co., Ltd.), Megafac F171 F173, F176, F189, R08 (Dainippon Ink Chemical Co., Ltd.), Surflon S-382, SC101, 102, 103, 104, 105, 106 (Asahi Glass Co., Ltd.), Troisol S-366 (Troy Chemical) Fluorine-based surfactants or silicon-based surfactants such as those manufactured by K.K. Polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used as a silicon-based surfactant.

In addition to the known surfactants shown above, fluorine-based and / or silicon-based surfactants can be produced by a telomerization method (also referred to as a telomer method) or an oligomerization method (also referred to as an oligomer method). A surfactant using a polymer having a fluoroaliphatic group derived from a fluoroaliphatic compound can be used. The fluoroaliphatic compound can be synthesized by the method described in JP-A-2002-90991.
As the polymer having a fluoroaliphatic group, a copolymer of a monomer having a fluoroaliphatic group and (poly (oxyalkylene)) acrylate and / or (poly (oxyalkylene)) methacrylate is preferable and distributed irregularly. Or may be block copolymerized. Examples of the poly (oxyalkylene) group include a poly (oxyethylene) group, a poly (oxypropylene) group, a poly (oxybutylene) group, and the like, and a poly (oxyethylene, oxypropylene, and oxyethylene group). A unit having different chain lengths in the same chain length, such as a block link) or poly (block link of oxyethylene and oxypropylene) may be used. Furthermore, a copolymer of a monomer having a fluoroaliphatic group and (poly (oxyalkylene)) acrylate (or methacrylate) is not only a binary copolymer but also a monomer having two or more different fluoroaliphatic groups, Further, it may be a ternary or higher copolymer obtained by simultaneously copolymerizing two or more different (poly (oxyalkylene)) acrylates (or methacrylates).
For example, as a commercially available fluorine-based and / or silicon-based surfactant, Megafac F178, F-470, F-473, F-475, F-476, F-472 (manufactured by Dainippon Ink & Chemicals, Inc.) Can be mentioned. Further, a copolymer of an acrylate (or methacrylate) having a C ₆ F ₁₃ group and (poly (oxyalkylene)) acrylate (or methacrylate), an acrylate (or methacrylate) having a C ₆ F ₁₃ group and (poly (oxy) (Ethylene)) acrylate (or methacrylate) and (poly (oxypropylene)) acrylate (or methacrylate) copolymer, acrylate (or methacrylate) and (poly (oxyalkylene)) acrylate having C ₈ F ₁₇ groups (or Copolymer of acrylate (or methacrylate), (poly (oxyethylene)) acrylate (or methacrylate), and (poly (oxypropylene)) acrylate (or methacrylate) having a C ₈ F ₁₇ group Coalesce, etc. Can.

  The amount of the surfactant used is preferably 0.0001 to 2% by mass, more preferably 0.001 to 1% by mass, and particularly preferably 0.01 to the total amount of the positive resist composition (excluding the solvent). It is mass%-1 mass%.

Specific examples of surfactants that can be used other than the above include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether. , Polyoxyethylene alkyl allyl ethers such as polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether, polyoxyethylene / polyoxypropylene block copolymers, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan Sorbitan fatty acid esters such as monooleate, sorbitan trioleate, sorbitan tristearate, polyoxyethylene sorbitan Nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters such as laurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate Etc.

(B) Organic basic compound The positive resist composition of the present invention preferably contains an organic basic compound. A preferable organic basic compound is a compound having a stronger basicity than phenol. Of these, nitrogen-containing basic compounds are preferable, and examples thereof include structures represented by the following (A) to (E).

Here, R ²⁵⁰ , R ²⁵¹ and R ²⁵² each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. R ²⁵¹ and R ²⁵² may combine with each other to form a ring. The alkyl group, cycloalkyl group, and aryl group may have a substituent. Examples of the alkyl group having a substituent include an aminoalkyl group having 1 to 20 carbon atoms and a hydroxyalkyl group having 1 to 20 carbon atoms. Examples of the cycloalkyl group having a substituent include an aminocycloalkyl group having 3 to 20 carbon atoms and a hydroxycycloalkyl group having 3 to 20 carbon atoms.

In the formula, R ²⁵³ , R ²⁵⁴ , R ²⁵⁵ and R ²⁵⁶ each independently represent an alkyl group having 1 to 20 carbon atoms.
Further preferred compounds are nitrogen-containing basic compounds having two or more nitrogen atoms of different chemical environments in one molecule, and particularly preferably both a substituted or unsubstituted amino group and a ring structure containing a nitrogen atom. Or a compound having an alkylamino group. Preferred examples include substituted or unsubstituted guanidine, substituted or unsubstituted aminopyridine, substituted or unsubstituted aminoalkylpyridine, substituted or unsubstituted aminopyrrolidine, substituted or unsubstituted indazole, substituted or unsubstituted Pyrazole, substituted or unsubstituted pyrazine, substituted or unsubstituted pyrimidine, substituted or unsubstituted purine, substituted or unsubstituted imidazoline, substituted or unsubstituted pyrazoline, substituted or unsubstituted piperazine, substituted or unsubstituted amino Examples include morpholine and substituted or unsubstituted aminoalkylmorpholine. Preferred substituents are amino group, aminoalkyl group, alkylamino group, aminoaryl group, arylamino group, alkyl group, alkoxy group, acyl group, acyloxy group, aryl group, aryloxy group, nitro group, hydroxyl group, cyano group It is.

  Preferable specific examples of the nitrogen-containing basic compound include guanidine, 1,1-dimethylguanidine, 1,1,3,3-tetramethylguanidine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2- Dimethylaminopyridine, 4-dimethylaminopyridine, 2-diethylaminopyridine, 2- (aminomethyl) pyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-6-methylpyridine, 3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine, piperazine, N- (2-aminoethyl) piperazine, N- (2-aminoethyl) piperidine, 4- Amino-2,2,6,6-tetramethylpiperidine, 4-piperidinopiperidine, 2- Minopiperidine, 1- (2-aminoethyl) pyrrolidine, pyrazole, 3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine, 2- (aminomethyl) -5 Methylpyrazine, pyrimidine, 2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine, N- (2-aminoethyl) morpholine, 1,5-diazabicyclo [ 4.3.0] non-5-ene, 1,8-diazabicyclo [5.4.0] undec-7-ene, 1,4-diazabicyclo [2.2.2] octane, 2,4,5- Triphenylimidazole, N-methylmorpholine, N-ethylmorpholine, N-hydroxyethylmorpholine, N-benzylmorpholine, cyclohexane Examples include tertiary morpholine derivatives such as silmorpholinoethylthiourea (CHMETU), hindered amines described in JP-A-11-52575 (for example, those described in the publication [0005]), and the like. Absent.

Particularly preferred examples are 1,5-diazabicyclo [4.3.0] non-5-ene, 1,8-diazabicyclo [5.4.0] undec-7-ene, 1,4-diazabicyclo [2. 2.2] Octane, 4-dimethylaminopyridine, hexamethylenetetramine, 4,4-dimethylimidazoline, pyrroles, pyrazoles, imidazoles, pyridazines, pyrimidines, tertiary morpholines such as CHMETU, bis (1, 2,2,6,6-pentamethyl-4-piperidyl) sebagate and other hindered amines, N, N-dihydroxyethylaniline, N, N-dibutylaniline, trioctylamine, triphenylimidazole, antipyrine, 2,6-diisopropyl And aniline.
Among them, 1,5-diazabicyclo [4.3.0] non-5-ene, 1,8-diazabicyclo [5.4.0] undec-7-ene, 1,4-diazabicyclo [2.2.2] Octane, 4-dimethylaminopyridine, hexamethylenetetramine, CHMETU, bis (1
, 2,2,6,6-pentamethyl-4-piperidyl) sebagate, N, N-dihydroxyethylaniline, N, N-dibutylaniline, trioctylamine, triphenylimidazole, antipyrine, 2,6-diisopropylaniline are preferred. .

  These nitrogen-containing basic compounds are used alone or in combination of two or more. The usage-amount of a nitrogen-containing basic compound is 0.001-10 mass% normally with respect to solid content of the whole composition of the resist composition of this invention, Preferably it is 0.01-5 mass%. The above range is suitable from the viewpoints of sufficient effects of addition of the nitrogen-containing basic compound and balance with sensitivity and developability of the non-exposed area.

[4] Solvent The positive resist composition of the present invention is dissolved in a solvent that dissolves each of the above components and coated on a support. Solvents used here include ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, γ-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate , Propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), ethylene carbonate, toluene, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, pyruvin Ethyl acetate, propyl pyruvate, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl Pyrrolidone, tetrahydrofuran and the like are preferable to use these solvents singly or in combination.

  Among these, preferable solvents include propylene glycol monomethyl ether acetate, 2-heptanone, γ-butyrolactone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether , Ethylene carbonate, butyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, N-methylpyrrolidone and tetrahydrofuran.

  The resist composition prepared by dissolving each component in a solvent is preferably 3 to 25% by mass, more preferably 5 to 22% by mass, and 7 to 20% by mass as the total solid concentration. % Is more preferable.

Such a positive resist composition of the present invention is applied onto a substrate to form a thin film. The film thickness of this coating film is preferably 0.2 to 1.2 μm.
Examples of the substrate that can be used include a normal BareSi substrate, an SOG substrate, and a substrate having an inorganic antireflection film described below.
If necessary, a commercially available inorganic or organic antireflection film can be used.

As the antireflection film, an inorganic film type such as titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, α-silicon, and an organic film type made of a light absorber and a polymer material can be used. The former requires equipment such as a vacuum deposition apparatus, a CVD apparatus, and a sputtering apparatus for film formation. Examples of the organic antireflection film include a condensate of a diphenylamine derivative and a formaldehyde-modified melamine resin described in JP-B-7-69611, an alkali-soluble resin, a light absorber, and maleic anhydride copolymer described in US Pat. No. 5,294,680. A reaction product of a coalescence and a diamine type light absorbing agent, a resin binder described in JP-A-6-186863 and a methylolmelamine thermal crosslinking agent, a carboxylic acid group, an epoxy group and a light-absorbing group described in JP-A-6-118656. An acrylic resin-type antireflection film in the same molecule, a composition comprising methylol melamine and a benzophenone-based light absorber described in JP-A-8-87115, and a low-molecular light absorber added to a polyvinyl alcohol resin described in JP-A-8-179509 And the like.
Further, as the organic antireflection film, DUV30 series, DUV-40 series, ARC25, AC-2, AC-3, AR19, AR20, etc., manufactured by Brewer Science can be used.

Appropriate use of the resist solution on a substrate (eg, silicon / silicon dioxide coating) used for the manufacture of precision integrated circuit elements (on a substrate provided with the antireflection film if necessary), spinner, coater, etc. A good resist pattern can be obtained by applying by a proper coating method and drying to form a resist film, then exposing through a predetermined mask, baking and developing. Here, the exposure light is preferably light having a wavelength of 150 nm to 250 nm. Specific examples include a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), an F ₂ excimer laser (157 nm), an X-ray, and an electron beam.

Examples of the developer include inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia, primary amines such as ethylamine and n-propylamine, diethylamine, and di-n. -Secondary amines such as butylamine; tertiary amines such as triethylamine and methyldiethylamine; alcohol amines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide. An alkaline aqueous solution (usually 0.1 to 10% by mass) of cyclic amines such as pyrrole and pihelidine can be used.
Furthermore, an appropriate amount of alcohol or surfactant may be added to the alkaline aqueous solution.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
In the following synthesis examples, unless otherwise specified, ratio and% mean mass ratio and mass%.

Synthesis Example (1) Synthesis of Resin (1) 2-Adamantyl-2-propyl methacrylate, 3,5-dihydroxy-1-adamantyl methacrylate, norbornane lactone acrylate and methacrylic acid were charged at a ratio of 30/20/40/10. It was dissolved in propylene glycol monomethyl ether acetate / propylene glycol monomethyl ether = 70/30 (mass ratio) to prepare 450 g of a solution having a solid content concentration of 22%. To this solution was added 1 mol% of W-601 made by Wako Pure Chemical as a polymerization initiator, and this was heated to 100 ° C. over 6 hours in a nitrogen atmosphere, and a mixture of propylene glycol monomethyl ether acetate / propylene glycol monomethyl ether = 70/30 It was dripped at 50g of solutions. The reaction liquid was stirred for 2 hours after completion | finish of dripping. After completion of the reaction, the reaction solution was cooled to room temperature, crystallized in 5 L of a mixed solvent of hexane / ethyl acetate = 9/1, and the precipitated white powder was collected by filtration to recover the target resin (1).
^The polymer composition ratio (molar ratio) determined from ¹³ C NMR was 2-adamantyl-2-propyl methacrylate / 3,5-dihydroxy-1-adamantyl methacrylate / norbornane lactone acrylate / methacrylic acid = 32/21/37/10 (mass ratio). ), The acid value was 0.45. Moreover, the weight average molecular weight of standard polystyrene conversion calculated | required by GPC measurement was 7800, and dispersion degree was 2.0.
Resin (1 ′), resin (1 ″), resins (2) to (15), (Comparative 1A) and (Comparative 1B) were synthesized in the same manner as in Synthesis Example (1). Resin (1 ′), Resin (1 ″), (Comparative 1A) and (Comparative 1B) have the same repeating units as resin (1), but differ in composition ratio and the like.
The structure, monomer composition ratio, weight average molecular weight, dispersity, and acid value of each resin are shown below.

Examples 1-9, 12-21, Reference Examples 10 and 11, and Comparative Examples 1-2
(Preparation and evaluation of positive resist composition)
As shown in Table 2,
Resin synthesized in the above synthesis example (2 g),
Acid generator (the amount is shown in Table 2),
Organic basic compound (4 mg),
Surfactant (10mg)
And dissolved in the solvent shown in Table 2 so as to have a solid content of 10% by mass, and then filtered through a 0.1 μm polyethylene filter. Examples 1 to 9, 12 to 21, Reference Examples 10 and 11 and The positive resist compositions of Comparative Examples 1 and 2 were prepared. In addition, the ratio in the case of using two or more about each component in Table 2 is a mass ratio.

[Evaluation]
First, ARC-29 manufactured by Brewer Science Co., Ltd. was applied as a reflection preventing film to a thickness of 85 nm on a silicon wafer using a spin coater, dried, and then the positive resist composition obtained thereon was applied thereto. A positive resist film having a thickness of 280 nm was formed by drying at a temperature (PB) shown in 2 for 90 seconds, and then exposed to an ArF excimer laser ((ASML PAS5500 / 1100 stepper (NA0 / 75)). The heat treatment was performed at the temperature (PEB) shown in Table 2 for 90 seconds, developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution, and rinsed with distilled water to obtain a resist pattern profile.

[Process window]
Using a halftone phase shift mask having a transmittance of 6%, exposure was performed with an exposure amount at which a line pattern having a mask size of 140 nm (280 nm pitch) was reproduced at 120 nm as an optimal exposure amount E ₀ . The process window is defined as follows, assuming that E _{1 is} the maximum exposure and E ₂ is the minimum exposure to reproduce the line width of 120 nm ± 10% under the condition of ± 0.3 μm defocus with respect to the best focus. did.
Process window (%) = (E ₁ −E ₂ ) × 100 / E ₀
The results are shown in Table 2.

[Pit formation during flow baking]
Using a hole / duty ratio contact hole pattern (mask size 140 nm), a pattern with a hole size of 120 nm was formed.
Each wafer is divided into 8 parts and heated for 90 seconds on a hot plate heated to 150 ° C., 155 ° C., 160 ° C., 165 ° C., 170 ° C., 175 ° C., 180 ° C., and 185 ° C. Observation with a microscope and the presence or absence of pit formation were confirmed. It is most preferable that there is no pit formation, and among those in which pit formation has been confirmed, a higher pit formation start temperature is preferable. Table 8 shows the lowest temperature at which pit formation was observed among eight samples in each example. In addition, “None” is described in Table 2 for an example in which pit formation was not observed under all flow baking conditions.

The symbol of each component in Table 2 shows the following.
[Acid generator]
The symbols in Table 2 correspond to specific examples of the acid generator (PAG) exemplified above.
[Surfactant]
1: MegaFuck F176 (Dainippon Ink Chemical Co., Ltd.) (Fluorine)
2: Megafuck R08 (Dainippon Ink Chemical Co., Ltd.)
(Fluorine and silicone)
3: Polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.)
4: Polyoxyethylene nonylphenyl ether 5: Troisol S-366 (manufactured by Troy Chemical Co., Ltd.)

[Basic compounds]
1: N, N-dihydroxyethylaniline 2: N, N-dibutylaniline 3: trioctylamine 4: triphenylimidazole 5: antipyrine 6: 2,6-diisopropylaniline.

〔solvent〕
S1: Propylene glycol monomethyl ether acetate S2: Propylene glycol monomethyl ether S3: γ-butyrolactone S4: Cyclohexanone S5: Ethyl lactate S6: Butyl acetate

  From Table 2, it can be seen that the composition of the present invention has a wide process window in forming contact holes and suppresses pit formation during flow baking.

Claims (8)

A repeating unit (a) containing a group that decomposes by the action of an acid and becomes alkali-soluble, a repeating unit (b1) having an alicyclic lactone structure represented by the following general formula (V1), and an alicyclic structure substituted with a hydroxyl group It contains a repeating unit (c) having methacrylic acid and a repeating unit (d), and the ratio of the repeating unit of methacrylic acid (d) is 5 to 18 mol% in all repeating units. A positive resist composition comprising a resin (A1) having increased properties and a compound (B) that generates an acid upon irradiation with actinic rays or radiation.

In general formula (V1), R _b0 represents a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.
A ′ represents a single bond, an ether group, an ester group, a carbonyl group, an alkylene group, or a divalent group obtained by combining these.
B ₂ represents a group represented by any one of the following general formulas (a-1) to (a-3).

In General Formulas (a-1) to (a-3), R _{1 to} R ₆ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, or —COORa. Here, Ra represents an alkyl group. Two of R _{1 to} R ₆ may combine to form a ring.   In the resin (A1), the content of the repeating unit (a) containing a group that decomposes by the action of an acid and becomes alkali-soluble is 23 to 45 mol% in all repeating units. 2. The positive resist composition according to 1. In the resin (A1), the repeating unit (c) having an alicyclic structure substituted with a hydroxyl group is a repeating unit (c1) represented by the following general formula (IIa): 2. The positive resist composition according to 2.

In general formula (IIa), R ₃₀ represents a hydrogen atom or a methyl group.
R _{31 to} R ₃₃ each independently represents a hydrogen atom, a hydroxyl group or an alkyl group. However, two of R _{31 to} R ₃₃ represent a hydroxyl group.   The positive unit according to any one of claims 1 to 3, wherein the repeating unit (a) containing a group that decomposes by the action of an acid of the resin (A1) and becomes alkali-soluble contains an alicyclic structure. Resist composition. The positive resist according to claim 4, wherein the repeating unit (a) containing a group that decomposes by the action of an acid of the resin (A1) and becomes alkali-soluble is represented by the following general formula (I): Composition.

In general formula (I),
R ₂ represents a hydrogen atom or a methyl group.
A represents a single bond or a linking group.
ALG is a group containing an alicyclic hydrocarbon represented by the following general formulas (pI) to (pV).

In the formulas (pI) to (pV),
R ₁₁ represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a sec-butyl group.
Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with a carbon atom.
R _{12 to} R ₁₆ each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms or an alicyclic hydrocarbon group. However, at least one of R _{12 to} R ₁₄ and any one of R ₁₅ and R ₁₆ represents an alicyclic hydrocarbon group.
R _{17 to} R ₂₁ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{17 to} R ₂₁ Represents an alicyclic hydrocarbon group. Further, either R ₁₉ or R ₂₁ represents a linear or branched alkyl group or alicyclic hydrocarbon group having 1 to 4 carbon atoms.
R _{22 to} R ₂₅ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an alicyclic hydrocarbon group, provided that at least one of R _{22 to} R ₂₅ Represents an alicyclic hydrocarbon group. R ₂₃ and R ₂₄ may be bonded to each other to form a ring.   The positive resist composition according to claim 1, wherein the acid value of the resin (A1) is 0.2 to 0.9 meq / g.   A pattern forming method comprising the steps of: forming a resist film from the positive resist composition according to claim 1; and exposing and developing the resist film.   A method for forming a contact hole pattern, comprising: forming a resist film from the positive resist composition according to claim 1; and exposing and developing the resist film.