JP2006201402A - Positive resist composition and resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition having high resolution and capable of enhancing DOF. <P>SOLUTION: In the positive resist composition, a resin component (A) whose alkali solubility is increased by the action of an acid has at least one constitutional unit (a1) selected from the group consisting of constitutional units represented by a general formula (a1-01) and constitutional units represented by a general formula (a1-02), and an acid generator component (B) which generates an acid upon exposure contains an onium salt-based acid generator (B1) having an anionic moiety represented by a general formula (b-3) or (b-4). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positive resist composition and a resist pattern forming method.

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, miniaturization has rapidly progressed due to advances in lithography technology. As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, in the past, ultraviolet rays typified by g-line and i-line were used, but now KrF excimer laser (248 nm) is the center of mass production, and ArF excimer laser (193 nm) is mass-produced. It has begun to be introduced.
Such a resist for a short wavelength light source is required to have high resolution capable of reproducing a pattern with a fine dimension and high sensitivity to such a short wavelength light source. As one of the resists that satisfy such conditions, a chemically amplified resist containing a base resin and an acid generator (PAG) that generates an acid upon exposure is known. There are a positive type in which the alkali solubility of the portion increases and a negative type in which the alkali solubility of the exposed portion decreases.

There is an onium salt as a PAG used in the chemically amplified positive resist composition, and various types have been proposed so far. For example, the following Patent Document 1 describes a PAG composed of a triphenylsulfonium onium salt. Among them, a fluorinated alkyl sulfonate ion such as triphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS) is anion (acid). An onium salt-based acid generator is most commonly used.
JP 2003-167347 A

  By the way, it is important to improve the depth of focus (DOF) in order to realize a resist pattern with a fine dimension, but it is not easy to improve the DOF while achieving high resolution.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a positive resist composition and a resist pattern forming method capable of obtaining high resolution and improving DOF. .

［上記式中、Ｙは脂肪族環式基を表し；ｎは０または１〜３の整数を表し；ｍは０または１を表し；Ｒはそれぞれ独立して水素原子、炭素数１〜５の低級アルキル基、フッ素原子または炭素数１〜５のフッ素化低級アルキル基を表し；Ｒ^１、Ｒ^２はそれぞれ独立して水素原子または炭素数１〜５の低級アルキル基を表す。］
からなる群から選択される少なくとも１種の構成単位（ａ１）を有し、かつ
前記（Ｂ）成分が、下記一般式（ｂ−３）又は（ｂ−４）

［式中、Ｘ”は、少なくとも１つの水素原子がフッ素原子で置換された炭素数２〜６のアルキレン基を表し；Ｙ”、Ｚ”は、それぞれ独立に、少なくとも１つの水素原子がフッ素原子で置換された炭素数１〜１０のアルキル基を表す。］
で表されるアニオン部を有するオニウム塩系酸発生剤（Ｂ１）を含有することを特徴とする。 In order to achieve the above object, the present invention employs the following configuration.
A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) that generates an acid upon exposure,
The component (A) is a structural unit represented by the following general formula (a1-01) and a structural unit represented by the following general formula (a1-02)

[In the above formula, Y represents an aliphatic cyclic group; n represents an integer of 0 or 1 to 3; m represents 0 or 1; and R independently represents a hydrogen atom or a carbon number of 1 to 5] A lower alkyl group, a fluorine atom or a fluorinated lower alkyl group having 1 to 5 carbon atoms; R ¹ and R ² each independently represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; ]
And at least one structural unit (a1) selected from the group consisting of: and the component (B) is represented by the following general formula (b-3) or (b-4)

[Wherein X ″ represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y ″ and Z ″ each independently represent at least one hydrogen atom as a fluorine atom; Represents an alkyl group having 1 to 10 carbon atoms and substituted with
An onium salt acid generator (B1) having an anion moiety represented by the formula:

  The present invention also includes a step of forming a resist film on a substrate using the positive resist composition of the present invention, a step of exposing the resist film, and a step of developing the resist film to form a resist pattern. A resist pattern forming method is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the formation method of the positive resist composition which can obtain high resolution and can improve DOF, and a resist pattern is provided.

The “structural unit” in the claims and the specification means a monomer unit (monomer unit) constituting the resin.
The “structural unit derived from an acrylate ester” in the claims and the specification means a structural unit formed by cleavage of an ethylenic double bond of an acrylate ester.
The “structural unit derived from an acrylate ester” is a structural unit in which a hydrogen atom bonded to a carbon atom at the α-position is substituted with another substituent such as a halogen atom, an alkyl group, a halogenated alkyl group, or the like. And a structural unit derived from an acrylate ester in which a hydrogen atom is bonded to a carbon atom.
In the “structural unit derived from an acrylate ester”, the term “α-position (α-position carbon atom)” means a carbon atom to which a carboxy group is bonded, unless otherwise specified.
Further, the “alkyl group” includes a linear, cyclic or branched alkyl group unless otherwise specified.

<Positive resist composition>
The positive resist composition of the present invention contains the resin component (A) (hereinafter sometimes referred to as the component (A)) and an acid generator (hereinafter referred to as an acid generator) that generates an acid upon irradiation (exposure) of radiation. (B) component)).
Since the component (A) has a structural unit (a1) having an acid dissociable, dissolution inhibiting group, it is alkali-insoluble before exposure, and when an acid generated from the component (B) by exposure acts, acid dissociable dissolution The inhibitory group is dissociated, whereby the whole component (A) is increased from alkali-insoluble to alkali-soluble. Therefore, in the formation of a resist pattern, when selective exposure is performed on the resist, or when post-exposure heating (PEB) is performed in addition to exposure, the exposed portion turns into alkali-soluble while the unexposed portion is alkali-insoluble. Thus, a positive resist pattern can be formed by alkali development.

<(A) component>
[Structural unit (a1)]
The component (A) is at least one structural unit (a1) selected from the group consisting of the structural unit represented by the general formula (a1-01) and the structural unit represented by the general formula (a1-02). ).
The structural unit (a1) is a structural unit derived from an acrylate ester, and an acetal group (alkoxyalkyl) is bonded to the terminal oxygen atom of a carbonyloxy group (—C (O) —O—) derived from a carboxy group. Group) type acid dissociable, dissolution inhibiting group [—C (R ¹ R ² ) —O— (CH ₂ ) _n —Y]. Therefore, when an acid acts, a bond is cut between the acid dissociable, dissolution inhibiting group and the terminal oxygen atom.

In general formulas (a1-01) and (a1-02), R represents a hydrogen atom, a lower alkyl group having 1 to 5 carbon atoms, a fluorine atom, or a fluorinated lower alkyl group having 1 to 5 carbon atoms.
The fluorinated lower alkyl group is a group in which part or all of the hydrogen atoms in the alkyl group are substituted with fluorine atoms, and any of them may be used, but it is preferable that all are fluorinated.
Preferable examples of the lower alkyl group as R include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
The fluorinated lower alkyl group having 1 to 5 carbon atoms is preferably a trifluoromethyl group, a hexafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, or the like, and more preferably a trifluoromethyl group.

In general formulas (a1-01) and (a1-02), at least one of R ¹ and R ² is preferably a hydrogen atom, more preferably a hydrogen atom.
n is preferably 0 or 1, more preferably 0.

Y is an aliphatic cyclic group, which may or may not have a substituent on the ring skeleton.
Here, “aliphatic” in the claims and the specification is a relative concept with respect to aromatics, and is defined to mean a group, a compound, or the like that does not have aromaticity. The “aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity.
The basic ring structure excluding the substituent of the “aliphatic cyclic group” in the present invention is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but may be a hydrocarbon group. preferable. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. A polycyclic group is preferred.
Specific examples of such aliphatic cyclic groups include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as monocycloalkane, bicycloalkane, tricycloalkane, and tetracycloalkane. .
Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Y is particularly preferably a group obtained by removing one or more hydrogen atoms from adamantane (which may have a substituent).
When the aliphatic cyclic group as Y has a substituent on the ring skeleton, the substituent is preferably a polar group, particularly in order to suppress pattern collapse. Specific examples of the polar group include a hydroxyl group, a carboxy group, a cyano group, and an oxygen atom (═O). Of these, an oxygen atom (= O) is preferable.

  Specific examples of the structural unit represented by the general formula (a1-01) are shown below.

  Specific examples of the structural unit represented by the general formula (a1-02) are shown below.

As the structural unit (a1), any one selected from the group consisting of the structural unit represented by the general formula (a1-01) and the structural unit represented by the general formula (a1-02) is used. Two or more kinds may be used.
It is preferable from the viewpoint of resolution that the structural unit (a1) includes the structural unit represented by the general formula (a1-01). The proportion of the structural unit represented by the general formula (a1-01) in (a1) is preferably 50 mol% or more, more preferably 80 mol% or more, and 100 Most preferably, it is mol%.

  The proportion of the structural unit (a1) in the component (A) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, and more preferably 25 to 50 mol% with respect to all the structural units in the component (A). Further preferred. By setting it to the lower limit value or more, a good resist pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, a balance with other structural units can be achieved.

[Structural unit (a2)]
In addition to the structural unit (a1), the component (A) preferably has a structural unit (a2) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group.
The lactone-containing monocyclic or polycyclic group of the structural unit (a2) increases the adhesion of the resist film to the substrate or has an affinity for a developer when the component (A) is used for forming a resist film. It is effective in raising
Here, the lactone-containing monocyclic or polycyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring, and when it is only the lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.

As the structural unit (a2), any structural unit can be used without particular limitation as long as it has both such a lactone structure (—O—C (O) —) and a cyclic group.
Specifically, examples of the lactone-containing monocyclic group include groups in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the lactone-containing polycyclic group include groups in which one hydrogen atom has been removed from a lactone ring-containing bicycloalkane, tricycloalkane, or tetracycloalkane. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula is advantageous in that it is easily available industrially.

  More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

[Wherein, R is the same as defined above, R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms, and m is 0 or 1. ]

In general formulas (a2-1) to (a2-5), the lower alkyl group for R ′ is the same as the lower alkyl group for R in the structural unit (a1).
In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.

  Specific structural units of the general formulas (a2-1) to (a2-5) are exemplified.

  As the structural unit (a2), it is preferable to use at least one selected from the general formulas (a2-1) to (a2-5), and the structural unit (a2) is selected from the general formulas (a2-1) to (a2-3). It is more preferable to use one or more. Among them, chemical formulas (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3-2) , (A2-3-9) and (a2-3-10) are preferably used.

In the component (A), as the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
When the structural unit (a2) is contained in the component (A), the content of the structural unit (a2) is preferably 10 to 80 mol% with respect to the total of all the structural units in the component (A). 50 mol% is more preferable, and 25-50 mol% is further more preferable. By making it the lower limit value or more, the effect of containing the structural unit (a2) can be sufficiently obtained, and by making it the upper limit value or less, it is possible to balance with other structural units.
In the present invention, the component (A) is preferably a copolymer having the structural units (a1) and (a2) because the effects of the present invention are excellent.

[Structural unit (a3)]
The structural unit (a3) is a structural unit other than the structural unit (a1) and the structural unit (a2), includes an aliphatic cyclic group-containing non-acid dissociable, dissolution inhibiting group, and does not include a polar group. , A structural unit derived from an acrylate ester.
The aliphatic cyclic group-containing non-acid dissociable, dissolution inhibiting group is a group having a cyclic group (aliphatic cyclic group) that does not have aromaticity, and is dissociated by an acid generated from the component (B). It is a group (non-acid dissociable, dissolution inhibiting group) that does not occur. As the structural unit (a3), for example, a unit in which the aliphatic cyclic group-containing non-acid dissociable, dissolution inhibiting group is bonded to the ester portion of an acrylate ester, or the like can be given.
That is, the structural unit (a3) reduces the alkali solubility of the entire component (A) before exposure, and does not dissociate by the action of an acid generated from the component (B) after exposure. Group having a solubility inhibiting property that reduces the alkali solubility of the entire component (A) when the entire component (A) is changed to alkali-soluble by dissociation of the acid dissociable dissolution inhibiting group of Is a structural unit including Accordingly, the structural unit (a3) has a function of suppressing the alkali solubility by increasing the hydrophobicity of the entire component (A) before and after exposure. Specifically, it is a structural unit that can improve the contact angle with respect to pure water rinse after PEB (post-exposure heat treatment) (improve hydrophobicity).
Further, the structural unit (a3) needs to contain no polar group. The polar group here is a hydroxyl group, a cyano group, a carboxy group, a “hydroxyalkyl group in which a part of the hydrogen atoms of the alkyl group are substituted with fluorine atoms” or the like.
The structural unit (a3) preferably does not contain an acid dissociable, dissolution inhibiting group.

  The structural unit (a3) is preferably the following general formula (a3)

[Wherein, R is the same as defined above. Z represents an aliphatic cyclic group having 4 to 15 carbon atoms in the basic ring, which may have 1 to 3 alkyl groups having 1 to 10 carbon atoms. ]
It is a structural unit indicated by.

Z is an aliphatic cyclic group (which may be monocyclic or polycyclic) having 4 to 15 carbon atoms in the basic ring (ring structure excluding a substituent), and the aliphatic cyclic group has a carbon number You may have 1-3 alkyl groups of 1-10.
When Z has an alkyl group, the alkyl group is an alkyl group having 1 to 10 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms is particularly preferable. Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a pentyl group, an isopentyl group, and a neopentyl group. In Z, the number of the alkyl group is preferably 0 or 1, and more preferably 0.

The structural unit (a3) does not overlap with the structural unit (a1) and the structural unit (a2). That is, neither the specific acid dissociable, dissolution inhibiting group in the structural unit (a1) nor the lactone-containing group in the structural unit (a2) is retained.
In the structural unit (a3), as the cyclic group constituting the basic skeleton of the aliphatic cyclic group, a monocyclic or polycyclic aliphatic cyclic group conventionally known as an ArF positive resist material is used. Is possible.
Examples of the monocyclic aliphatic cyclic group include groups in which one or two or more hydrogen atoms have been removed from a monocycloalkane such as cyclohexane or cyclopentane.
Examples of the polycyclic aliphatic cyclic group include groups in which one or two or more hydrogen atoms have been removed from a polycycloalkane such as bicycloalkane, tricycloalkane, and tetracycloalkane. Specifically, And groups obtained by removing one or more hydrogen atoms from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Among these, a cyclohexyl group, a cyclopentyl group, an adamantyl group, a norbornyl group, an isobornyl group, a tricyclodecanyl group, and a tetracyclododecanyl group are preferable from the viewpoint of easy industrial availability.

  The following general formulas (a3-1) to (a3-5) are preferred examples of the structural unit (a3).

[Wherein, R is the same as defined above. ]
Among these, the structural unit represented by the general formula (a3-1) is preferable because the shape of the obtained resist pattern, for example, rectangularity is particularly good. Moreover, it is preferable from the point of pattern collapse suppression.

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
(A) When making a structural unit (a3) contain in a component, 3-50 mol% is preferable with respect to the sum total of all the structural units of (A) component, and the content rate of a structural unit (a3) is 5-35. More preferred is mol%, and most preferred is 15 to 30 mol%. By setting it to the lower limit value or more, the effect of the present invention is excellent, and by setting the upper limit value or less, it is possible to balance with other structural units.

[Structural unit (a4)]
The component (A) may have a structural unit (a4) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group in addition to the structural units (a1) to (a3). Good. By having the structural unit (a4), the hydrophilicity of the component (A) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved. .
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, a “hydroxyalkyl group in which a part of the hydrogen atoms of the alkyl group are substituted with fluorine atoms”, and the like, and a hydroxyl group is particularly preferable.

Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, it contains an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom, and is derived from an acrylate ester. A structural unit is more preferable. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed polymers (resin components) for resist compositions for ArF excimer lasers. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  The structural unit (a4) is derived from a hydroxyethyl ester of acrylic acid when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms. When the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a4-1), a structural unit represented by (a4-2), (a4-3) The structural unit represented by is mentioned as a preferable thing.

(Wherein R is the same as above, j is an integer of 1 to 3, k is an integer of 1 to 3, t 'is an integer of 1 to 3, and l is an integer of 1 to 5) And s is an integer of 1 to 3.)

In formula (a4-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that the hydroxyl group is bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that the hydroxyl group is bonded to the 3-position of the adamantyl group.
j is preferably 1, and a hydroxyl group bonded to the 3rd position of the adamantyl group is particularly preferred.

  In formula (a4-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

  In formula (a4-3), t ′ is preferably 1. l is preferably 1. s is preferably 1. These preferably have a 2-norbornyl group or a 3-norbornyl group bonded to the terminal of the carboxy group of acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a4), one type may be used alone, or two or more types may be used in combination.
When (A) component has structural unit (a4), the content rate of structural unit (a4) in (A) component is 5-50 mol% with respect to all the structural units in the said (A) component. More preferably, it is more preferably 15 to 45 mol%, and most preferably 15 to 35 mol%.

[Other structural units]
Further, in the positive photoresist composition of the present invention, as the component (A), a conventional chemically amplified positive resist other than the structural units (a1) to (a4) is used as long as the effects of the present invention are not impaired. Known acrylic acid derivatives, methacrylic acid derivatives, acrylic acid, methacrylic acid, maleic acid, carboxylic acid having an ethylenic double bond to make it soluble in alkali, fumaric acid, etc., known monomers used for the production of acrylic resins Etc. can be appropriately combined and copolymerized as necessary.

The component (A) can be obtained, for example, by polymerizing a monomer related to each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN).
In addition, the component (A) is used in combination with a chain transfer agent such as, for example, HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH at the time of the polymerization. A —C (CF ₃ ) ₂ —OH group may be introduced into the. As described above, a copolymer introduced with a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group is substituted with a fluorine atom reduces development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

The mass average molecular weight (Mw) of the component (A) (polystyrene conversion standard by gel permeation chromatography) is not particularly limited, but is preferably 3000 to 50000, more preferably 3000 to 30000, and most preferably 5000 to 20000. preferable. When it is smaller than the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and the dry etching resistance and resist pattern cross-sectional shape that are larger than the lower limit of this range are good.
Further, the dispersity (Mw / Mn) of the component (A) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.0 to 2.5.

<Acid generator component (B)>
[(B1) component]
In the present invention, as the component (B), the onium salt acid generator (B1) having an anion moiety represented by the general formula (b-3) or (b-4) is used as an essential component.
In the general formula (b-3), X ″ is a linear or branched alkylene group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkylene group has 2 to 6 carbon atoms. , Preferably 3 to 5 carbon atoms, most preferably 3 carbon atoms.
In the general formula (b-4), Y ″ and Z ″ are each independently a linear or branched alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and the carbon of the alkyl group The number is 1 to 10, preferably 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms.
The carbon number of the alkylene group of X ″ or the carbon number of the alkyl group of Y ″ and Z ″ is preferably as small as possible because the solubility in the resist solvent is good within the above carbon number range.
In addition, in the alkylene group of X ″ or the alkyl group of Y ″ and Z ″, it is preferable that the number of hydrogen atoms substituted with fluorine atoms is higher because the strength of the acid becomes stronger. The fluorine of the alkylene group or alkyl group The conversion ratio is preferably 70 to 100%, more preferably 90 to 100%, and most preferably a perfluoroalkylene group or a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms.

  As the anion moiety of the component (B1), an anion moiety represented by the general formula (b-3) is preferable, and X ″ is more preferably a perfluoroalkylene group.

The cation moiety in the component (B1) is not particularly limited, and what is known as the anion moiety of the onium salt acid generator can be appropriately used.
Among these, it is preferable to have a cation part represented by the following general formula (b-1) or (b-1) ′.

［式中、Ｒ^１”〜Ｒ^３”，Ｒ^５”〜Ｒ^６”は、それぞれ独立に、アリール基またはアルキル基を表し；Ｒ^１”〜Ｒ^３”のうち少なくとも１つはアリール基を表し、Ｒ^５”〜Ｒ^６”のうち少なくとも１つはアリール基を表す。］

[Wherein, R ¹ ″ to R ³ ″ and R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group; at least one of R ¹ ″ to R ³ ″ represents an aryl group. , R ⁵ ″ to R ⁶ ″ each represents an aryl group. ]

In formula (b-1), R ¹ ″ to R ³ ″ each independently represents an aryl group or an alkyl group. At least one of R ¹ ″ to R ³ ″ represents an aryl group. Of R ¹ ″ to R ³ ″, two or more are preferably aryl groups, and most preferably all R ¹ ″ to R ³ ″ are aryl groups.
The aryl group for R ¹ ″ to R ³ ″ is not particularly limited, and is, for example, an aryl group having 6 to 20 carbon atoms, in which part or all of the hydrogen atoms are alkyl groups, alkoxy groups It may or may not be substituted with a group, a halogen atom or the like. The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples include a phenyl group and a naphthyl group.
As the aryl group for R ¹ ″ to R ³ ″, at least one is most preferably a naphthyl group. By using a naphthyl group, transparency with respect to ArF excimer laser light is improved, and lithography properties such as resolution and DOF are improved.
The alkyl group that may be substituted for the hydrogen atom of the aryl group is preferably an alkyl group having 1 to 5 carbon atoms, and is a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group. Is most preferred.
The alkoxy group that may be substituted for the hydrogen atom of the aryl group is preferably an alkoxy group having 1 to 5 carbon atoms, and most preferably a methoxy group or an ethoxy group.
The halogen atom that may be substituted for the hydrogen atom of the aryl group is preferably a fluorine atom.
The alkyl group for R 1 ^{"~R 3",} is not particularly limited, for example, a straight, include alkyl groups such as branched or cyclic. It is preferable that it is C1-C5 from the point which is excellent in resolution. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group. A methyl group is preferable because it is excellent in resolution and can be synthesized at low cost.

In formula (b-1) ′, R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group. At least one of R ⁵ ″ to R ⁶ ″ represents an aryl group. Of R ⁵ ″ to R ⁶ ″, two or more are preferably aryl groups, and most preferably R ⁵ ″ to R ⁶ ″ are all aryl groups.
As the aryl group for R ⁵ ″ to R ⁶ ″, the same as the aryl groups for R ¹ ″ to R ³ ″ can be used.
Examples of the alkyl group for R ⁵ ″ to R ⁶ ″ include the same as the alkyl group for R ¹ ″ to R ³ ″.
Among these, it is most preferable that all of R ⁵ ″ to R ⁶ ″ are phenyl groups.

  Preferred specific examples of the component (B1) are listed below.

Among these, the acid generator represented by the chemical formula (b1-07) or (b108) is particularly preferable.
As the component (B1), any one type may be used, or two or more types may be used in combination.
The proportion of the component (B1) in the entire component (B) is preferably 50% by mass or more, and may be 100% by mass. A more preferable range is 60 to 90% by mass, and 70 to 85% by mass is most preferable.

[(B2) component]
The component (B) preferably contains an acid generator (B2) represented by the following general formula (b-2) in addition to the component (B1). The component (B2) does not overlap with the component (B1).

[Wherein R ⁴ ′ ″ is a linear, branched or cyclic alkyl group or fluorinated alkyl group; R ¹ ′ ″ to R ³ ′ ″ each independently has a substituent. An aryl group or an alkyl group which may be substituted, and at least one of R ¹ ′ ″ to R ³ ′ ″ represents an aryl group. ]

In formula (b-2), R ′ ″ ^{1 to} R ³ ′ ″ each independently represents an aryl group or an alkyl group which may have a substituent. .
At least one of R ¹ ′ ″ to R ³ ′ ″ represents an aryl group. Of R ¹ ′ ″ to R ³ ′ ″, two or more are preferably aryl groups, and most preferably R ¹ ′ ″ to R ³ ′ ″ are all aryl groups.
The aryl group as R ¹ ′ ″ to R ³ ′ ″ is, for example, an aryl group having 6 to 20 carbon atoms. , It may or may not be substituted with a halogen atom or the like. The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples include a phenyl group and a naphthyl group.
The alkyl group as a substituent for the hydrogen atom of the aryl group is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group. .
The alkoxy group as a substituent for the hydrogen atom of the aryl group is preferably an alkoxy group having 1 to 5 carbon atoms, and most preferably a methoxy group or an ethoxy group.
The halogen atom as a substituent for the hydrogen atom of the aryl group is preferably a fluorine atom.

The alkyl group as R ¹ ′ ″ to R ³ ′ ″ is not particularly limited, and examples thereof include linear, branched or cyclic alkyl groups having 1 to 10 carbon atoms. It is preferable that it is C1-C5 from the point which is excellent in resolution. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group. A methyl group is preferable because it is excellent in resolution and can be synthesized at low cost.
Among these, it is most preferable that R ¹ ′ ″ to R ³ ′ ″ are all phenyl groups.

R ⁴ ′ ″ represents a linear, branched or cyclic alkyl group or a fluorinated alkyl group.
The linear or branched alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.
The cyclic alkyl group is a cyclic group as represented by R ¹ ′ ″, preferably having 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, It is most preferable that it is several 6-10.
The fluorinated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. Also. The fluorination rate of the fluorinated alkyl group is preferably from 10 to 100%, more preferably from 50 to 100%, and in particular, those in which all hydrogen atoms are substituted with fluorine atoms are preferable because the strength of the acid becomes strong.
R ⁴ ″ is most preferably a linear or cyclic alkyl group or a fluorinated alkyl group.

  Specific examples of the component (B2) include triphenylsulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its Nonafluorobutane sulfonate, trifluorone sulfonate of monophenyldimethylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, trifluoromethane sulfonate of diphenyl monomethylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, (4- Methylphenyl) diphenylsulfonium trif Oromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, (4-methoxyphenyl) diphenylsulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-tert-butyl) phenyl Examples thereof include trifluoromethane sulfonate of sulfonium, its heptafluoropropane sulfonate, its nonafluorobutane sulfonate, and the like. Moreover, the onium salt which replaced the anion part of these onium salts by methanesulfonate, n-propanesulfonate, n-butanesulfonate, and n-octanesulfonate can also be used.

As the component (B2), any one type may be used, or two or more types may be used in combination.
When the component (B2) is used, the proportion of the component (B2) in the entire component (B) is preferably 10 to 40% by mass, more preferably 15 to 30% by mass, and 15 to 25% by mass. Most preferred.

[Other acid generators (B3)]
The component (B) may further contain a known acid generator (hereinafter sometimes referred to as other acid generator (B3)) that has been used in conventional chemically amplified resist compositions. For the effect of the present invention, the total ratio of the component (B1) and the component (B2) in the entire component (B) is preferably 80% by mass or more, and more preferably 100% by mass.

Other acid generators (B3) include onium salt acid generators other than the onium salt acid generators (B1) and (B2) (for example, iodonium salts), oxime sulfonate acid generators, bisalkyls. Or diazomethane acid generators such as bisarylsulfonyldiazomethanes and poly (bissulfonyl) diazomethanes, nitrobenzyl sulfonate acid generators, iminosulfonate acid generators, disulfone acid generators, etc. An acid generator can be appropriately used.
Other acid generators (B3) may be used alone or in combination of two or more.

  The content of the component (B) in the positive resist composition of the present invention is preferably 2 to 20 parts by mass, more preferably 5 to 15 parts by mass, and 5 to 13 parts by mass with respect to 100 parts by mass of the component (A). Most preferably. By setting it within the above range, pattern formation is sufficiently performed and good characteristics are obtained. Moreover, since a uniform solution is obtained and storage stability becomes favorable, it is preferable.

<Nitrogen-containing organic compound (D)>
The positive resist composition of the present invention can further contain a nitrogen-containing organic compound (D) as an optional component in order to improve the resist pattern shape, the stability over time, and the like.
Since a wide variety of component (D) has already been proposed, any known one may be used, but aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred. .
Examples of the aliphatic amine include amines (alkyl amines or alkyl alcohol amines) in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms. Specific examples thereof include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di-n-heptylamine, Dialkylamines such as di-n-octylamine and dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptyl Trialkylamines such as amine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n-dodecylamine; diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n -Ok Noruamin, alkyl alcohol amines such as tri -n- octanol amine. Among these, alkyl alcohol amines and trialkyl amines are preferable, and alkyl alcohol amines are most preferable. Of the alkyl alcohol amines, triethanolamine and triisopropanolamine are most preferred.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

<(E) component>
In addition, the positive resist composition of the present invention further includes an organic component as an optional component for the purpose of preventing sensitivity deterioration due to the blending of the component (D) and improving the resist pattern shape and stability with time. Carboxylic acid or phosphorus oxo acid or derivative thereof (E) (referred to herein as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid- Like phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and derivatives thereof, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
(E) A component is used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

<Organic solvent>
The positive resist composition of the present invention can be produced by dissolving the material in an organic solvent.
Any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and one or two kinds of conventionally known solvents for chemically amplified resists can be used. These can be appropriately selected and used.
For example, lactones such as γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate Polyhydric alcohols such as dipropylene glycol or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof, cyclic ethers such as dioxane, Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, pyruvate Le, methyl methoxypropionate, esters such as ethyl ethoxypropionate can be exemplified.

These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
A mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2.
In addition, as the organic solvent, a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.
Although the amount of the organic solvent used is not particularly limited, it is a concentration that can be applied to a substrate and the like, and is appropriately set according to the coating film thickness. In general, the solid content concentration of the resist composition is 2 to 20 mass. %, Preferably 5-15% by mass.

<Other optional components>
The positive resist composition of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coating properties, dissolution inhibitors, Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added and contained as appropriate.

<Resist pattern formation method>
The resist pattern forming method of the present invention can be performed, for example, as follows.
That is, first, the positive resist composition is coated on a substrate such as a silicon wafer with a spinner and prebaked for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. A film is formed.
Next, the resist film is selectively exposed with ArF excimer laser light through a desired mask pattern by, for example, an ArF exposure apparatus, and then subjected to PEB (post-exposure heating) at a temperature of 80 to 150 ° C. It is applied for 40 to 120 seconds, preferably 60 to 90 seconds.
Subsequently, this is developed using an alkaline developer, for example, an aqueous 0.1 to 10% by mass tetramethylammonium hydroxide solution. You may post-bake after image development processing as needed.
In this way, a resist pattern faithful to the mask pattern can be obtained.
An organic or inorganic antireflection film can be provided between the substrate and the coating layer of the resist composition.

The wavelength used for the exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be done using radiation. In particular, the positive resist composition according to the present invention is effective for an ArF excimer laser.

According to the positive resist composition of the present invention, high resolution can be obtained and DOF can be improved. In addition, the resist pattern is less likely to fall and the exposure margin can be improved. The reason is not clear, but is presumed as follows.
Since the component (B1), which is an essential component of the positive resist composition of the present invention, has a skeleton represented by the general formula (b-3) or (b-4) in the anion part, a fluorinated alkyl Compared to an acid generator component composed of an onium salt having a sulfonate ion as an anion portion, the acid diffusion length is expected to be short. The structural unit (a1) of the component (A) has an acetal group (alkoxyalkyl group) type acid dissociable, dissolution inhibiting group. Since the deprotection energy of the acid dissociable, dissolution inhibiting group of the acetal group type is lower than that of the tertiary ester type acid dissociable, dissolution inhibiting group, the structural unit (a1) It is presumed that the acid dissociable, dissolution inhibiting group can be eliminated to increase alkali solubility and resolve a fine pattern.
In the present invention, by using a combination of the component (B1) and the component (A), the above-described plurality of good characteristics such as high resolution and improved DOF can be achieved by the synergistic effect of the two. It can be achieved at the same time.

[Synthesis Example 1] Synthesis of (2-adamantyloxymethyl) methacrylate 6.9 g of methacrylic acid was dissolved in 200 mL of tetrahydrofuran, and 8.0 g of triethylamine was added. After stirring at room temperature, 100 mL of tetrahydrofuran in which 15 g of 2-adamantyl chloromethyl ether was dissolved was added dropwise. After stirring for 12 hours at room temperature, the precipitated salt was filtered off. The obtained filtrate was evaporated, dissolved in 200 mL of ethyl acetate, washed with pure water (100 mL × 3), and evaporated. A white solid was obtained after standing under ice cooling.
The obtained compound 1 ((2-adamantyloxymethyl) methacrylate) is represented by the following chemical formula.
Infrared absorption spectrum (IR), showing the results of measurement of the proton nuclear magnetic resonance spectra ⁽¹ H-NMR). IR (cm ⁻¹ ): 2907, 2854 (C—H stretch), 1725 (C═O stretch), 1638 (C═C stretch) ¹ H-NMR (CDCl ₃ , internal standard: tetramethylsilane) ppm: 1 .45-2.1 (m, 17H), 3.75 (s, 1H), 5.45 (s, 2H), 5.6 (s, 1H), 6.12 (s, 1H)

[Synthesis Example 2] Synthesis of Resin Component (A1) 20.0 g of (2-adamantyloxymethyl) methacrylate obtained in Synthesis Example 1 above, 13.6 g of γ-butyrolactone methacrylate (GBLMA), and tricyclodeca 8.8 g of nyl methacrylate was dissolved in 200 ml of tetrahydrofuran, and 1.64 g of azobisisobutyronitrile was added. After refluxing for 12 hours, the reaction solution was added dropwise to 1 L of n-heptane. The precipitated resin was separated by filtration and dried under reduced pressure to obtain a white powder resin. The structural formula of this resin 1 is shown below.
Resin 1 had a weight average molecular weight (Mw) of 7000 and a dispersity (Mw / Mn) of 2.2.
Further, as a result of measuring carbon 13 nuclear magnetic resonance spectrum ( ¹³ C-NMR), the composition ratio of each structural unit shown in the following structural formula was m: n: l = 0.4: 0.4: 0.2 (mol). Ratio).

[Example 1] Preparation and Evaluation of Positive Resist Composition Positive Resist Composition by Mixing Resin 1 Synthesized in Synthesis Example 2, Acid Generators 1 and 2, Nitrogen-Containing Organic Compound, and Solvent shown below A product was prepared.
Resin 1: 100 parts by mass,
Acid generator 1: 6.0 parts by mass,
Acid generator 2: 1.6 parts by mass,
As a nitrogen-containing organic compound, triethanolamine: 0.38 parts by mass,
PGMEA: EL = 8: 2 (mass ratio) mixed solvent as organic solvent: 750 parts by mass.

The acid generator 1 is a compound represented by the chemical formula (b1-08), and the acid generator 2 is (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate.
“PGMEA” represents propylene glycol monomethyl ether acetate. “EL” represents ethyl lactate.

A resist pattern was formed using the positive resist composition obtained above.
That is, first, an organic antireflection film composition “ARC-29A” (trade name, manufactured by Brewer Science) was applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 90 seconds. By drying, an organic antireflection film having a thickness of 90 nm was formed.
Next, the positive resist composition obtained above was applied onto an antireflection film using a spinner, pre-baked (PAB) at 105 ° C. for 90 seconds on a hot plate, and dried to obtain a film having a thickness of 180 nm. A resist film was formed.
Subsequently, an ArF excimer laser (193 nm) was applied to the resist film with an ArF exposure apparatus NSR-S306C (Nikon Corp .; NA (numerical aperture) = 0.78, 2/3 ring zone) with 6% halftone. Selective exposure was performed by selective irradiation through a reticle.
Thereafter, PEB treatment was performed at 105 ° C. for 90 seconds, and further paddle development was performed at 23 ° C. with a 2.38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution for 60 seconds, followed by washing with water for 20 seconds, followed by shaking and drying. Went. Further, the film was heated at 100 ° C. for 60 seconds and dried to form a 1: 1 90 nm line and space pattern (hereinafter referred to as L / S pattern).
Let the exposure amount (sensitivity) when the 90 nm L / S pattern is formed 1: 1 be Eop.

The positive resist composition was evaluated as follows. The results are shown in Table 1 below.
<DOF>
In Eop, the focus was shifted appropriately up and down, and the depth of focus (DOF) range in which the 90 nm L / S pattern was obtained within the range of the dimensional change rate of ± 10% was determined in nm units.

<LER>
For the 90 nm L / S pattern (1: 1) obtained in Eop, 3σ, which is a measure indicating LER, was obtained as an evaluation of line edge roughness (LER) at which the surface of the side wall of the line pattern becomes non-uniform. 3σ is a side length SEM (manufactured by Hitachi, Ltd., trade name “S-9220”). The width of the resist pattern of the sample is measured at 32 locations, and the standard deviation (σ) calculated from the result is 3 times the value (3σ ). This 3σ means that the smaller the value, the smaller the roughness and the uniform width resist pattern was obtained. Measurement was performed at two measurement voltages of 800V and 300V.

<Exposure margin>
Obtained from the exposure amount (sensitivity) (Eop) for resolving 90 nm L / S pattern accurately at 1: 1 and the exposure amount variation range (sensitivity variation range) for resolving 90 nm ± 10% L / S pattern The obtained exposure margin was calculated from the following equation.
Exposure margin (%) = [E (81 nm) −E (99 nm)] × 100 / Eop
In the formula, E (99 nm) is a sensitivity (mJ / cm ² ) when obtaining a 99 nm L / S pattern,
E (81 nm) is the sensitivity (mJ / cm ² ) when obtaining an L / S pattern of 81 nm.

<Pattern collapse>
When the exposure time in the selective exposure was lengthened, and the width of the pattern gradually narrowed along with it, it was observed by SEM (scanning electron microscope) at which point the pattern collapsed.

[Comparative Example 1]
In Example 1, 3.5 parts by mass of triphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS) was used in place of the acid generators 1 and 2, and the blending amount of triethanolamine was changed to 0.35 parts by mass. In the same manner as in Example 1, a positive resist composition was prepared, and a resist pattern was formed using the resist composition.
A 90 nm L / S pattern was resolved. The exposure amount (sensitivity) when the 90 nm L / S pattern was formed 1: 1 was set to Eop, and the characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

As can be seen from these results, both Example 1 and Comparative Example 1 have better resolution, and LER is slightly superior in Example 1. Regarding DOF, Example 1 is greatly improved as compared with Comparative Example 1. The first embodiment is also superior in terms of exposure margin and pattern collapse.

Claims (6)

A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) that generates an acid upon exposure,
The component (A) is a structural unit represented by the following general formula (a1-01) and a structural unit represented by the following general formula (a1-02)

[In the above formula, Y represents an aliphatic cyclic group; n represents an integer of 0 or 1 to 3; m represents 0 or 1; and R independently represents a hydrogen atom or a carbon number of 1 to 5] A lower alkyl group, a fluorine atom or a fluorinated lower alkyl group having 1 to 5 carbon atoms; R ¹ and R ² each independently represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; ]
And at least one structural unit (a1) selected from the group consisting of: and the component (B) is represented by the following general formula (b-3) or (b-4)

[Wherein X ″ represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y ″ and Z ″ each independently represent at least one hydrogen atom as a fluorine atom; Represents an alkyl group having 1 to 10 carbon atoms and substituted with
A positive resist composition comprising an onium salt acid generator (B1) having an anion moiety represented by the formula:   The positive resist composition according to claim 1, wherein the component (A) has a structural unit (a2) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group.   The component (A) is a structural unit other than the structural unit (a1) and the structural unit (a2), includes an aliphatic cyclic group-containing non-acid dissociable, dissolution inhibiting group, and does not include a polar group. The positive resist composition according to claim 1, comprising a structural unit (a3) derived from an acrylate ester. The component (B) is represented by the following general formula (b-2)

[Wherein R ⁴ ′ ″ is a linear, branched or cyclic alkyl group or fluorinated alkyl group; R ¹ ′ ″ to R ³ ′ ″ each independently has a substituent. An aryl group or an alkyl group which may be substituted, and at least one of R ¹ ′ ″ to R ³ ′ ″ represents an aryl group. ]
The positive resist composition according to any one of claims 1 to 3, further comprising an onium salt-based acid generator (B2) other than the component (B1).   The positive resist composition as described in any one of Claims 1-4 containing a nitrogen-containing organic compound (D). A step of forming a resist film on a substrate using the positive resist composition according to claim 1, a step of exposing the resist film, and developing the resist film to form a resist pattern A resist pattern forming method including the step of: