JP6060577B2 - Negative resist pattern forming method - Google Patents

Description

  The present invention relates to a protective film forming composition and a negative resist pattern forming method.

  Along with miniaturization of various electronic device structures such as semiconductor devices and liquid crystal devices, miniaturization of resist patterns in lithography processes is required. At present, a fine resist pattern having a line width of about 90 nm can be formed using, for example, an ArF excimer laser. However, in the future, a finer resist pattern will be required.

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

  In the development using such an organic solvent, immersion exposure is used to form a finer resist pattern, and a protective film (top coat) is formed on the resist film during the immersion exposure. (See JP 2008-309878).

  However, when an organic solvent is used as a developer as described above, there is a disadvantage in that the resist film is reduced in the pattern forming step, thereby reducing the etching resistance and a desired fine pattern cannot be obtained. Further, in the above immersion exposure, immersion defects generated due to the remaining immersion liquid on the resist film, blob defects generated due to insufficient rinsing on the resist film, and undissolved resist film remain. There is an inconvenience that various defects such as a bridge defect generated due to the occurrence.

  With the use of the conventional protective film forming composition, the above-described film reduction cannot be suppressed, and in recent years when the pattern is further miniaturized, The requirements for the suppression of occurrence and the rectangularity of the cross-sectional shape of the resist pattern are not satisfied.

JP 2000-199953 A JP 2008-309878 A

  The present invention has been made based on the circumstances as described above, and its purpose is to suppress film loss and generation of defects in the formation of a negative resist pattern using a developer containing an organic solvent, and to have a cross-sectional shape. An object of the present invention is to provide a protective film forming composition capable of forming a resist pattern having excellent rectangularity.

The invention made to solve the above problems is
A protective film forming composition for a negative pattern forming method using a developer containing an organic solvent,
[A] a fluorine atom-containing polymer, and [B] a solvent,
[B] The protective film-forming composition, wherein the solvent contains at least one selected from the group consisting of a chain ether solvent, a hydrocarbon solvent, and an alcohol solvent having 5 or more carbon atoms.

The negative resist pattern forming method of the present invention,
(1) a step of forming a resist film using a photoresist composition;
(2) A step of laminating a protective film on the resist film using the protective film-forming composition,
(3) a step of immersion exposure of the resist film on which the protective film is laminated; and (4) a step of developing the immersion exposed resist film using a developer containing an organic solvent.

  According to the protective film forming composition and the negative resist pattern forming method of the present invention, in the negative pattern formation using a developer containing an organic solvent, film loss and the occurrence of defects are suppressed, and the cross-sectional shape is rectangular. It is possible to form a resist pattern that is excellent in resistance. Therefore, according to the protective film forming composition and the negative resist pattern forming method, the protective film forming composition and the negative resist pattern forming method can be suitably used for pattern formation in the field of semiconductor devices and the like that will require further miniaturization and higher quality in the future.

<Protective film forming composition>
The protective film forming composition is a protective film forming composition for a negative pattern forming method using a developer containing an organic solvent, and contains [A] a fluorine atom-containing polymer and [B] a solvent, [B] The solvent includes at least one selected from the group consisting of a chain ether solvent, a hydrocarbon solvent, and an alcohol solvent having 5 or more carbon atoms.

According to the protective film forming composition, in the negative pattern formation using a developer containing an organic solvent, it is possible to form a resist pattern that suppresses film loss and generation of defects and is excellent in cross-sectional rectangularity. it can. The reason why the protective film-forming composition has the above-described configuration provides the above-mentioned effects is not necessarily clear, but can be inferred as follows, for example.
By using the specific solvent as the solvent for the protective film-forming composition, the intermixing that occurs between the resist film and the protective film formed by the protective film-forming composition on the resist film is made moderate. be able to. As a result, the intermixing is suppressed more than before, and the occurrence of defects and the rectangularity of the cross-sectional shape of the resist pattern are improved.

  The protective film-forming composition is used in a negative resist pattern forming method using a developer containing an organic solvent. According to the negative resist pattern forming method using a developer containing an organic solvent, the optical contrast can be increased as compared with the positive resist pattern forming method using a developer such as an alkaline aqueous solution. A resist pattern can be formed.

  The protective film-forming composition contains [A] a fluorine atom-containing polymer and a [B] solvent, and includes [C] a basic compound as a preferred component and a compound that forms a basic compound by the action of an acid. At least one selected (hereinafter also referred to as “[C] compound”) may be contained, and other optional components may be contained within a range not impairing the effects of the present invention. Hereinafter, each component will be described.

<[A] Fluorine atom-containing polymer>
[A] The fluorine atom-containing polymer is a polymer containing fluorine atoms. The said protective film formation composition can form the protective film excellent in surface water repellency and elution suppression property by containing [A] fluorine atom containing polymer, As a result, it uses suitably for immersion exposure be able to.

  [A] The fluorine atom-containing polymer is not particularly limited as long as it is a polymer containing a fluorine atom, but as a structural unit containing a fluorine atom, a group represented by the above formula (1) (hereinafter referred to as “group (1)”) The structural unit (I) including at least one selected from the group consisting of a group represented by the above formula (2) (hereinafter also referred to as “group (2)”) and a fluorinated alkyl group. It is preferable. [A] The fluorine atom-containing polymer is a structural unit other than the structural unit (I) in addition to the structural unit (I), and includes a structural unit containing a hydrocarbon group having 4 to 20 carbon atoms ( II), a structural unit (III) represented by the formula (3) described later, a structural unit (IV) containing a basic group, and the like. [A] The fluorine atom-containing polymer may have one or more of each of these structural units. Hereinafter, each structural unit will be described.

[Structural unit (I)]
The structural unit (I) is a structural unit containing at least one selected from the group consisting of the group (1), the group (2) and the fluorinated alkyl group (hereinafter, the structural unit containing each group is referred to as “structural unit”). (I-1) "," Structural Unit (I-2) "and" Structural Unit (I-3) ").

(Structural unit (I-1))
The structural unit (I-1) is a structural unit containing a group represented by the following formula (1). [A] A fluorine atom containing polymer can improve the solubility to the developing solution containing an organic solvent by having a structural unit (I-1). As a result, the protective film formed from the protective film-forming composition is more excellent in water repellency and removability.

In the above formula (1), ^{R 1} is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R ² is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.

Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by R ¹ include:
Fluoromethyl group, difluoromethyl group, trifluoromethyl group, fluoroethyl group, difluoroethyl group, trifluoroethyl group, pentafluoroethyl group, fluoro-n-propyl group, difluoro-n-propyl group, trifluoro-n- Propyl group, pentafluoro-n-propyl group, heptafluoro-n-propyl group, trifluoro-i-propyl group, hexafluoro-i-propyl group, heptafluoro-i-propyl group, trifluoro-n-butyl group , Fluorinated alkyl groups such as pentafluoro-n-butyl group, heptafluoro-n-butyl group, nonafluoro-n-butyl group, undecafluoro-n-pentyl group;
Fluorinated cycloalkyl groups such as a fluorocyclopentyl group, a difluorocyclopentyl group, an undecafluorocyclopentyl group, a fluorocyclohexyl group, and a tridecafluorocyclohexyl group;
Examples thereof include fluorinated aryl groups such as a fluorophenyl group, a difluorophenyl group, a trifluorophenyl group, a pentafluorophenyl group, a fluorotolyl group, and a trifluorotolyl group.
Among these, from the viewpoint of increasing the fluorine atom content of the [A] fluorine atom-containing polymer, a fluorinated alkyl group is preferable, a perfluoroalkyl group is more preferable, and carbon is preferable from the viewpoint of ease of synthesis. A perfluoroalkyl group having 1 to 4 is more preferable, and a trifluoromethyl group is particularly preferable.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ² include a monovalent chain hydrocarbon group, a monovalent alicyclic hydrocarbon group, and a monovalent aromatic hydrocarbon group. A substituted hydrocarbon group obtained by substituting a hydrogen atom of the chain hydrocarbon group, alicyclic hydrocarbon group and aromatic hydrocarbon group with a substituent, the chain hydrocarbon group, alicyclic hydrocarbon group, aromatic And a group having a divalent group containing a hetero atom between carbon and carbon of the aromatic hydrocarbon group and the substituted hydrocarbon group.

Examples of the monovalent chain hydrocarbon group include:
Alkyl groups such as methyl, ethyl, propyl and butyl groups;
An alkenyl group such as an ethenyl group, a propenyl group, a butenyl group;
Examples thereof include alkynyl groups such as ethynyl group, propynyl group, and butynyl group.

Examples of the monovalent alicyclic hydrocarbon group include:
Monocyclic cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, cyclodecyl group;
A polycyclic cycloalkyl group such as a norbornyl group, an adamantyl group, a tricyclodecyl group, a tetracyclododecyl group;
And cycloalkenyl groups such as cyclopentenyl group and cyclohexenyl group.

Examples of the monovalent aromatic hydrocarbon group include:
Aryl groups such as phenyl group, tolyl group, xylyl group, mesityl group, naphthyl group;
Examples thereof include aralkyl groups such as a benzyl group, a phenylethyl group, and a naphthylmethyl group.

  Examples of the substituent that may substitute the hydrogen atom of the chain hydrocarbon group, alicyclic hydrocarbon group and aromatic hydrocarbon group include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom Hydroxy group, carboxy group, amino group, alkoxy group, alkoxycarbonyl group, acyl group, acyloxy group and the like.

  Examples of the divalent group containing a heteroatom that may be present between carbon-carbons of the chain hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, and substituted hydrocarbon group include -O -, -S-, -NR "-, -CO-, -CS-, groups in which two or more of these are combined, and the like. R" is a monovalent hydrocarbon group having 1 to 10 carbon atoms. It is.

  Examples of the group (1) include groups represented by the following formulas (1-1) to (1-8) (hereinafter also referred to as “groups (1-1) to (1-8)”). It is done.

  As the group (1), a hydroxybis (perfluoroalkyl) methyl group is preferable, groups (1-1) to (1-3) are more preferable, and a group represented by the group (1-1) is more preferable.

  As the structural unit (I-1), the structural unit represented by the following formula (1-1a) from the viewpoint of copolymerization of the monomer that gives the structural unit (I-1), etc. I-1a) ”) is preferred.

In the above formula (1-1a), R ^A represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^B is a divalent linking group.

R ^A is preferably a hydrogen atom or a methyl group, and more preferably a methyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1a).

Examples of the divalent linking group represented by R ^B, for example, a divalent chain hydrocarbon group having 1 to 6 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, said chain A group containing a group consisting of —O—, —S—, —CO—, —CS—, or a combination thereof, between carbon-carbons of the hydrocarbon group and the alicyclic hydrocarbon group.

Examples of the divalent chain hydrocarbon group having 1 to 6 carbon atoms include:
Methanediyl group, 1,1-ethanediyl group, 1,2-ethanediyl group, 1,1-propanediyl group, 1,2-propanediyl group, 1,3-propanediyl group, 2,2-propanediyl group, 1 , 4-propanediyl group, 1,5-pentanediyl group, 1,6-hexanediyl group, 1-methyl-1,3-propanediyl group, 2-methyl-1,3-propanediyl group, 2-methyl- Alkanediyl groups such as 1,2-propanediyl group, 1-methyl-1,4-butanediyl group, 2-methyl-1,4-butanediyl group;
Alkenediyl groups such as 1,2-ethenediyl group, 1,3-propenediyl group, 1,2-propenediyl group;
Examples include alkynediyl groups such as 1,2-ethynediyl group and 1,3-propynediyl group.
Among these, an alkanediyl group is preferable, a methanediyl group, an ethanediyl group, and a propanediyl group are more preferable, and a methanediyl group, 1,1-ethanediyl group, 1,2-ethanediyl group, 1,2-propanediyl group, 1 1,3-propanediyl group is more preferable, and 1,2-propanediyl group is particularly preferable.

Examples of the divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms include:
Cyclobutanediyl group such as 1,3-cyclobutanediyl group, cyclopentanediyl group such as 1,3-cyclopentanediyl group, cyclohexanediyl group such as 1,4-cyclohexanediyl group, 1,2-cyclohexanediyl group, 1 Cyclooctanediyl group such as 1,5-cyclooctanediyl group, 1,1-cyclopentylethanediyl group, cyclopentylethanediyl group such as 1,2-cyclopentylethanediyl group, 1,1-cyclohexylethanediyl group, 1,2 A monocyclic cycloalkanediyl group such as a cyclohexylethanediyl group such as a cyclohexylethanediyl group;
1,4-norbornanediyl group, norbornanediyl group such as 2,5-norbornanediyl group, 1,3-adamantanediyl group, adamantanediyl group such as 2,4-adamantanediyl group, 2,7-tetracyclododecanediyl And a polycyclocycloalkanediyl group such as a tetracyclododecanediyl group, a norbornylmethanediyl group, an adamantylmethanediyl group, and the like.
Among these, norbornanediyl group, tetracyclododecanediyl group, and cyclohexylethanediyl group are preferable, and 2,5-norbornanediyl group, 2,7-tetracyclododecanediyl group, and 1,2-cyclohexylethanediyl group are more preferable. A 1,2-cyclohexylethanediyl group is more preferable.

  Examples of the structural unit (I-1a) include structural units represented by the following formulas (1-1a-1) to (1-1a-8) (hereinafter referred to as “structural units (I-1a-1) to ( I-1a-8) ”) and the like.

In the formulas (1-1a-1) to (1-1a-8), R ^A has the same meaning as the formula (1-1a).

  Among these, the structural unit (1-1a-4) and the structural unit (I-1a-8) are preferable.

  As the structural unit (I), a structural unit represented by the following formula (1-1b) (hereinafter also referred to as “structural unit (I-1b)”) is also preferable.

In the above formula (1-1b), R ^C is a single bond or a divalent linking group. ^RD is a hydrogen atom or a monovalent organic group.

Examples of the divalent linking group represented by ^RC include, for example, a divalent chain hydrocarbon group having 1 to 20 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and the above chain. And a group in which one or more of a hydrocarbon group and an alicyclic hydrocarbon group are combined with —O—.

  Examples of the divalent chain hydrocarbon group having 1 to 20 carbon atoms include a methanediyl group, an ethanediyl group, a propanediyl group, a butanediyl group, a pentanediyl group, a hexanediyl group, an octanediyl group, a decandidiyl group, a dodecandiyl group, Examples thereof include a tetradecanediyl group, a hexadecanediyl group, an octadecanediyl group, and an icosanediyl group.

  Examples of the divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, a cyclohexanediyl group, a cyclooctanediyl group, and a cyclodecandidiyl group. .

  Examples of the group in which one or more of the chain hydrocarbon group and the alicyclic hydrocarbon group are combined with -O- include, for example, a methanediyloxy group, an ethanediyloxy group, and a propanediyloxy group. , Butanediyloxy group, pentanediyloxy group, hexanediyloxy group, octanediyloxy group and other alkanediyloxy groups; methanediyloxymethanediyl group, methanediyloxyethanediyl group, methanediyloxy (1,2-propane) A group containing one —O— such as a diyl) group, a methanediyloxybutanediyl group, a methanediyloxycyclohexanediyl group; a group containing two or more —O— such as a propanediyloxyethanediyloxyethanediyl group Etc.

Among them, R ^C is preferably a single bond, a methanediyl group, an alkanediyloxy group having 2 to 4 carbon atoms, or a cycloalkanediyloxy group having 7 to 10 carbon atoms. -Ethanediyloxy group, 1,2-propanediyloxy group, and 2,6-norbornanediyloxy group are more preferable, and 1,2-ethanediyloxy group is more preferable.

Examples of the monovalent organic group represented by ^RD include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and the number of carbon atoms. 6-20 monovalent aromatic hydrocarbon groups or one or more of them and a hetero atom such as -O-, -CO-, -OCO-, -COO-, -S- Examples include a group combined with a linking group. Some or all of the hydrogen atoms of these groups may be substituted with a fluorine atom, a hydroxy group, a carboxy group, an amino group, a cyano group, or the like.

As ^RD , a hydrogen atom, a monovalent chain hydrocarbon group, a monovalent alicyclic hydrocarbon group, a monovalent fluorinated chain hydrocarbon group, a monovalent fluorinated alicyclic hydrocarbon group, A monovalent hydroxy chain hydrocarbon group, a group containing a hydroxybis (perfluoroalkyl) methyl group, and a group having a monovalent lactone structure are preferred, and a hydrogen atom, a methyl group, an ethyl group, an i-propyl group, n- Butyl group, cyclohexylmethyl group, hexafluoro-2-propyl group, 2-hydroxyethyl group, hydroxybis (perfluoroalkyl) butyl group, hydroxybis (perfluoroalkyl) methylnorbornyl group, α-butyrolactone-yl group , Norbornanelactone-yl group and trifluoromethylnorbornanelactone-yl group are more preferable, and methyl group and ethyl group are more preferable.

  Examples of the structural unit (I-1b) include structural units represented by the following formulas (1-1b-1) to (1-b-18) (hereinafter referred to as “structural units (I-1b-1) to ( I-1b-18) ”) and the like.

  Among these, the structural units (I-1b-1) to (I-1b-9), the structural unit (I-1b-13), and the structural unit (I-1b-16) are preferable, and the structural unit (I— 1b-1) and the structural unit (I-1b-2) are more preferable.

Process for preparing a compound which gives the structural unit (I-1b) may, ^{R C _{is, -R C '-O- (CH 2}} ) n - (n is an integer from 1 to 4) in which the following formula (1 1b-m) (hereinafter also referred to as “compound (1-1b-m)”), for example, it can be produced by the following method. As the compound that gives the structural unit (I-1b) in which R ^C is other than —RC ^{′ ′ —} O— (CH ₂ ) _n —, a known compound can be used. Examples of the known compound include compounds described in JP-A No. 2002-220420, JP-A No. 2002-155112, JP-A No. 2005-107476, and the like.

In the above formulas (ia), (ib), and (1-1b-m), R ^{C ′} is a divalent chain hydrocarbon group having 1 to 16 carbon atoms, or this chain hydrocarbon group. And —O— group. ^RD is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. X is a halogen atom. n is an integer of 1 to 4.

The dihydroxy compound represented by the above formula (ia) and the haloalkyl acrylate compound represented by the above formula (ib) are reacted in a solvent such as dichloromethane in the presence of a base compound such as triethylamine. To give compound (1-1b-m). In the compound represented by the formula (ia), since the reactivity of the hydroxy group bonded to the carbon atom adjacent to the CF ₃ group out of the two hydroxy groups is low, the compound (1-1b- m) can be obtained.

  Examples of the halogen atom represented by X include a fluorine atom, a halogen atom, a bromine atom, and an iodine atom. Among these, a bromine atom is preferable from the viewpoint of reaction yield.

  [A] As a content rate of the structural unit (I-1) in a fluorine atom containing polymer, 10 mol%-90 mol% are preferable with respect to all the structural units which comprise a [A] fluorine atom containing polymer, 20 mol%-80 mol% are more preferable, 35 mol%-75 mol% are further more preferable, and 45 mol%-60 mol% are especially preferable. [A] By making the content rate of the structural unit (I-1) in a fluorine atom containing polymer into the said range, the water-repellent property and removability of the protective film formed from the said protective film formation composition further improve.

[Structural unit (I-2)]
The structural unit (I-2) is a structural unit containing the group (2). The group (2) is a group represented by the following formula (2). [A] A fluorine atom containing polymer can improve the solubility to the developing solution containing an organic solvent by having a structural unit (I-2). As a result, the protective film formed from the protective film-forming composition is more excellent in water repellency and removability.

In the above formula (2), ^{R 3} is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms.

The monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by R ^3, for example, like same groups as exemplified fluorinated hydrocarbon group as R ¹ above can be mentioned.

Examples of the group (2) include a fluoromethylsulfonamide group, a difluoromethylsulfonamide group, a trifluoromethylsulfonamide group, a difluoroethylsulfonamide group, a trifluoroethylsulfonamide group, a pentafluoroethylsulfonamide group, Fluoro-n-propylsulfonamide group, heptafluoro-n-sulfonamide group, trifluoro-i-propylsulfonamide group, hexafluoro-i-propylsulfonamide group, nonafluoro-n-butylsulfonamide group, undecafluoro -N-pentylsulfonamide group etc. are mentioned.
Among these, a perfluoroalkylsulfonamide group is preferable, a trifluoromethylsulfonamide group, a pentafluoroethylsulfonamide group, a trifluoro-n-propylsulfonamide group, and a nonafluoro-n-butylsulfonamide group are more preferable. A trifluoromethylsulfonamide group is more preferred.

  As the structural unit (I-2), from the viewpoint of copolymerization of the monomer that gives the structural unit (I-2), a structural unit represented by the following formula (1-2a) (hereinafter “structural unit ( I-2a) ”) is preferred.

In the above formula (1-2a), R ^E is a hydrogen atom, a methyl group, a fluorine atom or a trifluoromethyl group. R ^F is a divalent linking group. R ³ has the same meaning as the above formula (2).

The above-mentioned R ^E, from the viewpoint of copolymerizability and the like of the monomer giving the structural unit (I-2a), a hydrogen atom, preferably a methyl group, more preferably a methyl group.

Examples of the divalent linking group represented by R ^F include, for example, a divalent chain hydrocarbon group having 1 to 6 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, and the number of carbon atoms. 6 to 14 divalent aromatic hydrocarbon group, a group in which the chain hydrocarbon group and -O- are combined, or a hydrogen atom in the group in which the chain hydrocarbon group and -O- are combined is oxo. And a group substituted with a group.

Examples of the divalent chain hydrocarbon group having 1 to 6 carbon atoms include:
Methanediyl group, 1,2-ethanediyl group, 1,1-ethanediyl group, 1,3-propanediyl group, 1,2-propanediyl group, 1,1-propanediyl group, 2,2-propanediyl group, 1 , 4-propanediyl group, 1,5-pentanediyl group, 1,6-hexanediyl group, 1-methyl-1,3-propanediyl group, 2-methyl-1,3-propanediyl group, 2-methyl- Alkanediyl groups such as 1,2-propanediyl group, 1-methyl-1,4-butanediyl group, 2-methyl-1,4-butanediyl group;
Examples include alkenediyl groups such as 1,2-ethenediyl group, 1,3-propenediyl group, and 1,2-propenediyl group.

Examples of the divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms include a cyclobutanediyl group such as a 1,3-cyclobutanediyl group; a cyclopentanediyl group such as a 1,3-cyclopentanediyl group; Cyclohexanediyl groups such as 1,4-cyclohexanediyl group and 1,2-cyclohexanediyl group; monocyclic cycloalkanediyl groups such as cyclooctanediyl group such as 1,5-cyclooctanediyl group;
1,4-norbornanediyl group, norbornanediyl group such as 2,5-norbornanediyl group, polycyclic alkanediyl group such as adamantanediyl group such as 1,3-adamantanediyl group, 2,4-adamantanediyl group, etc. Can be mentioned.

Examples of the divalent aromatic hydrocarbon group having 6 to 14 carbon atoms include:
Arenediyl groups such as benzenediyl group, toluenediyl group, naphthalenediyl group;
Arenediylalkanediyl groups such as benzenediylmethanediyl group, naphthalenediylmethanediyl group;
Examples include alkanediylarenediylalkanediyl groups such as methanediylbenzenediylmethanediyl group and methanediylnaphthalenediylmethanediyl group.

  Examples of the group obtained by combining the chain hydrocarbon group and —O— include ethanediyloxy, ethanediyl group, and propanediyloxypropanediyl group.

  Examples of the group obtained by substituting a hydrogen atom of a group in which the chain hydrocarbon group and —O— are combined with an oxo group include methanediylcarbonylmethanediylcarbonyloxyethanediyl group, ethanediylcarbonylmethanediylcarbonyloxypropane A diyl group etc. are mentioned.

Among these, R ^F includes a divalent chain hydrocarbon group having 1 to 3 carbon atoms, a divalent alicyclic hydrocarbon group having 5 to 8 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Group is preferable, 1,2-ethanediyl group, 1,3-propanediyl group, 1,6-cyclohexanediyl group, methanediylbenzenediylmethanediyl group are more preferable, and 1,2-ethanediyl group is more preferable.

  Examples of the structural unit (I-2a) include structural units represented by the following formulas (1-2a-1) to (1-2a-8) (hereinafter referred to as “structural units (I-2a-1) to ( I-2a-8) ”) and the like.

In the above formulas (1-2a-1) to (1-2a-8), R ^E has the same meaning as the above formula (1-2a).

  Among these, the structural units (I-2a-1) to (I-2a-4) are preferable, the structural units (I-2a-1) to (I-2a-3) are more preferable, and the structural unit (I-2a-3) is preferable. -2a-1) is more preferred.

  [A] As a content rate of the structural unit (I-2) in a fluorine atom containing polymer, 10 mol%-90 mol% are preferable with respect to all the structural units which comprise a [A] fluorine atom containing polymer, 20 mol%-80 mol% are more preferable, 35 mol%-75 mol% are further more preferable, and 45 mol%-60 mol% are especially preferable. [A] By making the content rate of the structural unit (I-2) in a fluorine atom containing polymer into the said range, the water-repellent property and removability of the protective film formed from the said protective film formation composition further improve.

[Structural unit (I-3)]
The structural unit (III) is a structural unit containing a fluorinated alkyl group. [A] A fluorine atom containing polymer can improve hydrophobicity by having structural unit (III). As a result, the protective film formed from the protective film-forming composition has higher water repellency.

  Examples of the fluorinated alkyl group include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, a fluoro-n-propyl group, and a difluoro- n-propyl group, trifluoro-n-propyl group, pentafluoro-n-propyl group, heptafluoro-n-propyl group, fluoro-i-propyl group, trifluoro-i-propyl group, hexafluoro-i-propyl Group, fluoro-n-butyl group, octafluoro-n-butyl group, nonafluoro-n-butyl group, undecafluoro-n-pentyl group, heptadecafluoro-n-decyl group and the like.

  As the structural unit (I-3), from the viewpoint of copolymerization of the monomer that gives the structural unit (I-3), a structural unit represented by the following formula (1-3a) (hereinafter, “structural unit ( I-3a) ”) is preferred.

In said formula (1-3a), ^RG is a hydrogen atom, a methyl group, a fluorine atom, or a trifluoromethyl group. ^RH is a monovalent fluorinated alkyl group.

The above ^RG is preferably a hydrogen atom or a methyl group, more preferably a methyl group, from the viewpoint of copolymerization of the monomer that gives the structural unit (I-2a).

Examples of the monovalent fluorinated alkyl group represented by ^RH include the groups exemplified as the above-described fluorinated alkyl group.

  Examples of the structural unit (I-3a) include structural units represented by the following formulas (1-3a-1) to (1-3a-6) (hereinafter referred to as “structural units (I-3a-1) to ( I-3a-6) ”) and the like.

In the above formulas (1-3a-1) to (1-3a-6), R ^G has the same meaning as the above formula (1-3a).

  Among these, the structural units (I-3a-1) to (I-3a-3) are preferable, the structural unit (I-3a-1) and the structural unit (I-3a-3) are more preferable, and back contact The structural unit (I-3a-3) is more preferable from the viewpoints of improving the angle and further suppressing immersion defects.

  [A] The content ratio of the structural unit (I-3) in the fluorine atom-containing polymer is preferably 10 mol% to 90 mol% with respect to all the structural units constituting the [A] fluorine atom-containing polymer, 20 mol%-80 mol% are more preferable, 25 mol%-75 mol% are further more preferable, and 35 mol%-65 mol% are especially preferable. [A] By making the content rate of the structural unit (I-3) in a fluorine atom containing polymer into the said range, the protective film formed from the said protective film formation composition further improves water repellency.

  [A] The content ratio of the structural unit (I) in the fluorine atom-containing polymer (the total content ratio of the structural units (I-1), (I-2) and (I-3)) is [A] fluorine atom 40 mol% to 100 mol% is preferable, 60 mol% to 100 mol% is more preferable, 80 mol% to 100 mol% is further preferable, and 90 mol% to 100 mol% is based on all structural units constituting the containing polymer. Mole% is particularly preferred. [A] By making the content rate of structural unit (I) in a fluorine atom containing polymer into the said range, the protective film formed from the said protective film formation composition is further excellent in water repellency and removability.

[Structural unit (II)]
The structural unit (II) is a structural unit other than the structural unit (I) and includes a hydrocarbon group having 4 to 20 carbon atoms. The said protective film formation composition can improve the inhibitory property of blob defect, and peeling resistance because a [A] fluorine atom containing polymer has structural unit (II).

Examples of the hydrocarbon group having 4 to 20 carbon atoms include:
Alkyl groups such as butyl, pentyl, hexyl, octyl and decyl;
A cycloalkyl group such as cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, norbornyl group, adamantyl group, tricyclodecyl group, tetracyclododecyl;
Examples thereof include aryl groups such as phenyl group, tolyl group, xylyl group, mesityl group, naphthyl group and anthryl group.

  Among these, an alkyl group and a cycloalkyl group are preferable, an alkyl group having 4 to 10 carbon atoms and a cycloalkyl group having 6 to 12 carbon atoms are more preferable, and an n-pentyl group, an n-hexyl group, a cyclohexyl group, and a norbornyl group. An adamantyl group and a tricyclodecyl group are more preferable, and an n-pentyl group and a tricyclodecyl group are particularly preferable.

  As the structural unit (II), from the viewpoint of copolymerizability of the monomer that gives the structural unit (II), a structural unit represented by the following formula (2-a) (hereinafter referred to as “structural unit (II-a)”) Are also preferred).

In said formula (2-a), R ^<I> is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ^J is a hydrocarbon group having 4 to 20 carbon atoms.

The above R ^I is preferably a hydrogen atom or a methyl group, more preferably a methyl group, from the viewpoint of copolymerization of the monomer that gives the structural unit (II-a).

Examples of the hydrocarbon group having 4 to 20 carbon atoms represented by R ^J include the groups exemplified above as the hydrocarbon group having 4 to 20 carbon atoms.

  As the structural unit (II-a), for example, structural units represented by the following formulas (2-a-1) to (2-a-8) (hereinafter referred to as “structural units (II-a-1) to ( II-a-8) ”) and the like.

  Among these, the structural units (II-a-1) to (II-a-7) are preferable, and the structural unit (II-a-2), the structural unit (II-a-3), and the structural unit (II- a-5) to (II-a-7) are more preferable, and the structural unit (II-a-2) and the structural unit (II-a-7) are more preferable.

  The content ratio of the structural unit (II) is preferably 0 mol% to 60 mol%, more preferably 10 mol% to 50 mol%, based on all the structural units constituting the [A] fluorine atom-containing polymer. 20 mol%-40 mol% are more preferable. By making the content rate of structural unit (II) into the said range, the removability and peeling resistance of the protective film formed from the said protective film formation composition can be improved more. When the content rate of structural unit (II) exceeds the said upper limit, the water repellency of the protective film formed from the said protective film formation composition may fall.

[Structural unit (III)]
The structural unit (III) is a structural unit containing a group represented by the following formula (3) (hereinafter also referred to as “group (3)”). The said protective film formation composition can improve the inhibitory property of blob defect, and peeling resistance because [A] fluorine atom containing polymer has structural unit (III).

In the above formula (3), R ⁴ is a hydrogen atom, a halogen atom, a nitro group, an alkyl group, a monovalent alicyclic hydrocarbon group, an alkoxy group, an acyl group, an aralkyl group or an aryl group. Some or all of the hydrogen atoms of the alkyl group, alicyclic hydrocarbon group, alkoxy group, acyl group, aralkyl group and aryl group may be substituted. R ⁵ is —C (═O) —R ⁶ , —S (═O) ₂ —R ⁷ , —R ⁸ —CN or —R ⁹ —NO ₂ . R ⁶ and R ⁷ are each independently a hydrogen atom, alkyl group, fluorinated alkyl group, monovalent alicyclic hydrocarbon group, alkoxy group, cyano group, cyanomethyl group, aralkyl group or aryl group. However, R ⁶ or R ⁷ and R ⁴ may be bonded to each other to form a ring structure. R ⁸ and R ⁹ are each independently a single bond, a methylene group or an alkylene group having 2 to 5 carbon atoms.

Examples of the halogen atom represented by R ⁴ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom and a chlorine atom are preferable.

Examples of the alkyl group represented by R ⁴ include linear alkyl groups such as methyl group, ethyl group, n-propyl group, and n-butyl group; i-propyl group, i-butyl group, sec- Examples thereof include branched alkyl groups such as a butyl group and a t-butyl group. As said alkyl group, a C1-C20 alkyl group is preferable.

Examples of the monovalent alicyclic hydrocarbon group represented by R ⁴ include a monocyclic alicyclic hydrocarbon group such as a cyclopentyl group and a cyclohexyl group; an adamantyl group, a norbornyl group, a tetracyclodecanyl group, and the like. And the polycyclic alicyclic hydrocarbon group. As said alicyclic hydrocarbon group, a C3-C20 alicyclic hydrocarbon group is preferable.

Examples of the alkoxy group represented by R ⁴ include a methoxy group and an ethoxy group. As said alkoxy group, a C1-C20 alkoxy group is preferable.

Examples of the acyl group represented by R ⁴ include an acetyl group and a propionyl group. As said acyl group, a C2-C20 acyl group is preferable.

Examples of the aralkyl group represented by R ⁴ include a benzyl group, a phenethyl group, and a naphthylmethyl group. As said aralkyl group, a C7-C12 aralkyl group is preferable.

Examples of the aryl group represented by R ⁴ include a phenyl group, a tolyl group, a dimethylphenyl group, a 2,4,6-trimethylphenyl group, and a naphthyl group. As said aryl group, a C6-C10 aryl group is preferable.

Examples of the substituent that the alkyl group, monovalent alicyclic hydrocarbon group, alkoxy group, acyl group, aralkyl group and aryl group represented by R ⁴ may have include a fluorine atom and a chlorine atom. And halogen atoms such as hydroxyl group, nitro group, cyano group and the like.

As R ⁴ , among these, from the viewpoint of balancing developer solubility and peeling resistance of the protective film formed from the protective film-forming composition, among them, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, and a carbon number A 1-5 alkoxy group and a C2-C5 acyl group are preferable, and a hydrogen atom, a methyl group, an ethyl group, and an acetyl group are more preferable.

When R ⁵ is —C (═O) —R ⁶ and —S (═O) ₂ —R ⁷ , an alkyl group represented by R ⁶ and R ⁷ , a monovalent alicyclic hydrocarbon group, an alkoxy group Examples of the aralkyl group and aryl group include the same groups as those exemplified as the respective groups for R ⁴ . Examples of the fluorinated alkyl group represented by R ⁶ and R ⁷ include a group in which at least one hydrogen atom of the group exemplified as the alkyl group for R ⁴ is substituted with a fluorine atom. Among these, as R ⁶ and R ⁷ , a hydrogen atom and an alkyl group are preferable, and a hydrogen atom, a methyl group, and an ethyl group are more preferable.

The group containing a ring structure formed by bonding R ⁶ or R ⁷ and R ⁴ to each other includes the carbon atom to which R ⁶ or R ⁷ and R ⁴ are bonded, and having an oxo group. A divalent alicyclic hydrocarbon group of 5 to 12 is preferred.

When R ⁵ is —R ⁸ —CN and —R ⁹ —NO ₂ , R ⁸ and R ⁹ are preferably a single bond, a methanediyl group or an ethanediyl group.

  As the group (3), groups represented by the following formulas (3-1) to (3-8) (hereinafter also referred to as “groups (3-1) to (3-8)”) are preferable.

  In the above formulas (3-1) to (3-8), * represents a binding site.

  Examples of the structural unit (III) include (meth) acrylic acid ester derivatives having a group (3), (meth) acrylamide derivatives, vinyl ether derivatives, olefin derivatives, structural units derived from styrene derivatives, and the like. In this, the structural unit derived from the (meth) acrylic acid ester derivative which has group (3) from a copolymerizable viewpoint of the monomer which gives structural unit (III) is preferable. That is, the structural unit (III) is preferably a structural unit represented by the following formula (3-a) (hereinafter also referred to as “structural unit (III-a)”).

In said formula (3-a), ^RK is a hydrogen atom, a methyl group, a fluorine atom, or a trifluoromethyl group. R ^L is an (m + 1) -valent linking group. R ⁴ and R ⁵ are as defined in the above formula (3). m is an integer of 1-3. When R ⁴ and R ⁵ is plural, respectively, it may be different in each of a plurality of R ⁴ and R ⁵ are the same.

Examples of the R ^K, from the viewpoint of copolymerizability and the like of the monomer giving the structural unit (3-a), a hydrogen atom, preferably a methyl group, more preferably a methyl group.

Examples of the (m + 1) -valent linking group represented by ^RL include, for example, an alkanediyl group, a divalent alicyclic hydrocarbon group, and an alkenediyl group as a divalent linking group (when n is 1). And arenediyl groups. Note that some or all of the hydrogen atoms contained in these groups may be substituted with a halogen atom such as a fluorine atom or a chlorine atom, a cyano group, or the like.

  Examples of the alkanediyl group include methanediyl group, ethanediyl group, propanediyl group, butanediyl group, hexanediyl group, and octanediyl group. As said alkanediyl group, a C1-C8 alkanediyl group is preferable.

  Examples of the divalent alicyclic hydrocarbon group include monocyclic alicyclic hydrocarbon groups such as cyclopentanediyl group and cyclohexanediyl group; and polycyclic alicyclic groups such as norbornanediyl group and adamantanediyl group. A hydrocarbon etc. are mentioned. As said bivalent alicyclic hydrocarbon group, a C5-C12 alicyclic hydrocarbon group is preferable.

  Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, and a butenediyl group. As said alkenediyl group, a C2-C6 alkenediyl group is preferable.

  Examples of the arenediyl group include a phenylene group, a tolylene group, and a naphthylene group. As the above arenediyl group, an arenediyl group having 6 to 15 carbon atoms is preferable.

Among these, ^RL is preferably an alkanediyl group, a divalent alicyclic hydrocarbon group, an alkanediyl group having 1 to 4 carbon atoms, or a divalent alicyclic hydrocarbon group having 6 to 11 carbon atoms. Is more preferable. When ^RL is a divalent alicyclic hydrocarbon group, it is preferable from the viewpoint of improving the water repellency of the resulting protective film.

  As the structural unit (III-a), structural units represented by the following formulas (3-a-1) to (3-a-10) (hereinafter referred to as “structural units (III-a-1) to (III- a-10) ") is preferred.

In the above formulas (3-a-1) to (3-a-10), ^RK has the same meaning as the above formula (3-a).

  The content ratio of the structural unit (III) is preferably 0 mol% to 60 mol%, more preferably 10 mol% to 50 mol%, based on all the structural units constituting the [A] fluorine atom-containing polymer. 20 mol%-40 mol% are more preferable. By making the content rate of structural unit (III) into the said range, the removability and peeling resistance of the protective film formed from the said protective film formation composition can be improved more. When the content rate of structural unit (III) exceeds the said upper limit, the water repellency of the protective film formed from the said protective film formation composition may fall.

[Structural unit (IV)]
The structural unit (IV) is at least one selected from the group consisting of a structural unit containing a basic group and a structural unit containing a group that generates a basic group by the action of an acid. [A] Since the fluorine atom-containing polymer has the structural unit (IV), deprotection (generation of acidic groups due to dissociation of acid dissociable groups) is suppressed by the action of the basic group, and as a result, the resist film In the exposed portion, film loss can be suppressed.

  The basic group is not particularly limited as long as it is a basic group. Examples thereof include an amino group, a monohydrocarbon group-substituted amino group, a dihydrocarbon group-substituted amino group, a cyclic amino group, and an amide group. It is done.

Examples of the monohydrocarbon group-substituted amino group include:
Monoalkylamino groups such as methylamino group, ethylamino group, propylamino group;
A monocycloalkylamino group such as a cyclopentylamino group and a cyclohexylamino group;
Monoarylamino groups such as a phenylamino group and a naphthylamino group;
Examples thereof include monoaralkylamino groups such as benzylamino group and phenethylamino group.

As the dihydrocarbon group-substituted amino group, for example,
Dialkylamino groups such as dimethylamino group, methylethylamino group, diethylamino group, dipropylamino group;
A dicycloalkylamino group such as a dicyclopentylamino group, a dicyclohexylamino group, a dinorbornylamino group;
Diarylamino groups such as diphenylamino group, ditolylamino group, dinaphthylamino group, phenyltolylamino group;
Examples thereof include diaralkylamino groups such as dibenzylamino group, diphenethylamino group, and di (naphthylmethyl) amino group.

  Examples of the cyclic amino group include an azacyclopentyl group (pyrrolidinyl group), an azacyclohexyl group (piperidinyl group), an azacyclooctyl group, and the like.

  Examples of the amide group include a dimethylamide group and a diethylamide group.

  Among these, the basic group is preferably a dihydrocarbon-substituted amino group, more preferably a dialkylamino group, and even more preferably a dimethylamino group.

  Examples of the group that generates a basic group by the action of an acid include a group obtained by substituting a hydrogen atom of the basic group with an alkoxycarbonyl group. As the group that generates basicity by the action of the acid, a t-alkoxycarbonylmonohydrocarbon group-substituted amino group and a t-alkoxycarbonyl-substituted cyclic amino group are preferable, a t-alkoxycarbonyl-substituted cyclic amino group is more preferable, and N- A t-alkoxycarbonyl azacycloalkyl group is more preferable, and an Nt-butoxycarbonyl azacyclohexyl group is particularly preferable.

  The structural unit (IV) is a structural unit represented by the following formula (4-a) (hereinafter referred to as “structural unit (IV-a)” from the viewpoint of copolymerization of the monomer that gives the structural unit (IV). Are also preferred).

In the above formula (4-a), R ^M represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. ^RN is a group containing a group containing a basic group or a group that generates a basic group by the action of an acid.

Examples of the R ^M, from the viewpoint of copolymerizability of the monomer giving the structural unit (IV), a hydrogen atom, preferably a methyl group, more preferably a methyl group.

The group containing a group resulting basic groups by the action of radicals and an acid containing a basic group represented by R ^N, for example, groups bonded to produce a basic group by the action of a basic group and an acid of the above And monovalent hydrocarbon groups.
Among these, a dihydrocarbon group-substituted amino hydrocarbon group and an Nt-alkoxycarbonyl-substituted cyclic amino group are preferable, a dialkylaminoalkyl group and an Nt-alkoxycarbonylazacycloalkyl group are more preferable, and dimethylaminoethyl And the group Nt-butoxycarbonyl azacyclohexyl is more preferred.

  Examples of the structural unit (IV) include structural units represented by the following formulas (4-a-1) to (4-a-8) (hereinafter referred to as “structural units (IV-a-1) to (IV- a-8) ")) and the like.

In the above formulas (4-a-1) to (4-a-8), ^RM has the same meaning as the above formula (4-a).

  Among these, the structural units (IV-a-1) to (IV-a-5) and the structural unit (IV-a-8) are preferable, and the structural units (IV-a-1) to (IV-a) are preferable. a-5) is more preferable, and the structural unit (IV-a-1) and the structural unit (IV-a-5) are more preferable.

  The content ratio of the structural unit (IV) is preferably 0 mol% to 60 mol%, more preferably 10 mol% to 50 mol%, based on all structural units constituting the [A] fluorine atom-containing polymer. 20 mol%-40 mol% are more preferable. By making the content rate of structural unit (IV) into the said range, the film loss in the resist pattern formed from the said protective film formation composition can be suppressed more. When the content ratio of the structural unit (IV) exceeds the above upper limit, the pattern formability of the resist pattern may be deteriorated.

[Other structural units]
[A] The fluorine atom-containing polymer may have other structural units other than the structural units (I) to (IV). Examples of other structural units include a structural unit containing a carboxy group and a structural unit containing a sulfo group. The content ratio of the other structural units is preferably 20 mol% or less, more preferably 10 mol% or less, based on all the structural units constituting the [A] fluorine atom-containing polymer.

  The protective film-forming composition may have one or more [A] fluorine atom-containing polymers. [A] As a fluorine atom-containing polymer, in addition to the polymer containing the structural unit (I), the polymer containing the structural unit (I) and the structural unit (II) and / or the structural unit (III) is used in combination. By this, peeling resistance and blob defect suppression can be improved. [A] In addition to the polymer containing the structural unit (I) as the fluorine atom-containing polymer, the polymer containing the structural unit (I) and the structural unit (IV) is used in combination to suppress blob defects. Can be improved.

<[A] Method for Synthesizing Fluorine Atom-Containing Polymer>
The [A] fluorine atom-containing polymer is synthesized, for example, by polymerizing a predetermined monomer in a polymerization solvent in the presence of a suitably selected polymerization initiator or chain transfer agent. be able to.

As the polymerization solvent, for example,
Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol, diethylene glycol, propylene glycol;
Cyclic ethers such as tetrahydrofuran and dioxane;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl Alkyl ethers of polyhydric alcohols such as ethers;
Alkyl ether acetates of polyhydric alcohols such as ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate;
Aromatic hydrocarbons such as toluene and xylene;
Ketones such as acetone, 2-butanone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol;
Ethyl acetate, butyl acetate, methyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, 2-hydroxy-3-methylbutane And esters such as methyl acid, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, and the like. Of these, cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones or esters are preferred. In addition, the said polymerization solvent can use 1 type (s) or 2 or more types.

  [A] The weight average molecular weight (Mw) in terms of polystyrene by gel permeation chromatography (GPC) of the fluorine atom-containing polymer is preferably 2,000 to 50,000, more preferably 3,000 to 30,000, 4,000 to 20,000 is more preferable, and 5,000 to 9,000 is particularly preferable. [A] By making Mw of the fluorine atom-containing polymer above the lower limit, water resistance and mechanical properties as a protective film can be improved, and by making Mw below the upper limit, [A] fluorine atom containing The solubility with respect to the [B] solvent of a polymer can be improved.

  [A] The ratio (Mw / Mn) of the Mw of the fluorine atom-containing polymer to the number average molecular weight (Mn) in terms of polystyrene by GPC is preferably 1 to 5, more preferably 1 to 3, and more preferably 1 to 2.5. Is more preferable, and 1-2 is particularly preferable.

  The said protective film formation composition is so preferable that there are few impurities, such as a halogen ion and a metal. By reducing the impurities, it is possible to improve the coating property as the protective film-forming composition and the uniform solubility of the protective film in the developer containing the organic solvent. Examples of methods for purifying [A] fluorine atom-containing polymer in order to reduce impurities include chemical purification methods such as water washing, liquid-liquid extraction, and demetalization filter passage, and these chemical purification methods and ultrafiltration. And a combination with a physical purification method such as centrifugation.

  [A] The content of the fluorine atom-containing polymer is preferably 90% by mass to 100% by mass, more preferably 95% by mass to 100% by mass with respect to the total solid content in the protective film-forming composition. 99 mass%-100 mass% are still more preferable.

[[B] solvent]
[B] The solvent includes at least one selected from the group consisting of a chain ether solvent, a hydrocarbon solvent, and an alcohol solvent having 5 or more carbon atoms (hereinafter also referred to as “specific alcohol solvent”). Here, the “chain ether solvent” refers to a solvent that does not contain ether —O— in the ring structure, that is, a solvent that is not a cyclic ether solvent. The protective film-forming composition contains a [B] solvent together with the [A] fluorine atom-containing polymer, so that the protective film is formed between the resist film and the protective film formed thereon by the protective film-forming composition. Intermixing that occurs can be moderated. As a result, in forming a negative pattern using a developer containing an organic solvent, it is possible to form a resist pattern that suppresses film loss and generation of defects and is excellent in rectangular cross-sectional shape. [B] The solvent may contain one or more chain ether solvents, hydrocarbon solvents and specific alcohol solvents.

As the chain ether solvent, for example,
Diethyl ether, ethyl n-propyl ether, di n-propyl ether, di i-propyl ether, di n-butyl ether, di i-butyl ether, disec-butyl ether, di-t-butyl ether, methyl t-butyl ether, ethyl t-butyl ether Di-aliphatic ether solvents such as di-n-amyl ether, diisoamyl ether, methyl n-hexyl ether, di n-hexyl ether, methyl n-octyl ether, di n-octyl ether;
Alicyclic hydrocarbon group-containing ether solvents such as dicyclopentyl ether, dicyclohexyl ether, dicyclooctyl ether, methylcyclopentyl ether, methylcyclohexyl ether, ethylcyclooctyl ether;
Aliphatic-aromatic ether solvents such as anisole and phenylethyl ether;
Examples thereof include alkyl ether solvents of polyhydric alcohols such as ethylene glycol dimethyl ether, ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.
Among these, dialiphatic ether solvents are preferable, dialiphatic ether solvents having 8 to 12 carbon atoms are more preferable, di n-butyl ether, diisobutyl ether, di n-pentyl ether, diisoamyl ether, di n -Hexyl ether and diisohexyl ether are more preferable, and diisoamyl ether is particularly preferable.

Examples of the hydrocarbon solvent include:
lower hydrocarbon solvents such as n-hexane, cyclohexane, n-heptane;
Examples include higher hydrocarbon solvents such as n-decane, n-undecane, and n-dodecane.
Among these, higher hydrocarbon solvents are preferable, n-decane, n-undecane, and n-dodecane are more preferable, and n-decane is more preferable.

As the specific alcohol solvent, for example,
Chain monohydric alcohol solvents such as 1-pentanol, 2-hexanol, 4-methyl-2-pentanol, 2-heptanol, 2-octanol, 2-ethylhexanol, 2-decanol; cyclopentanol, cyclohexanol Monohydric alcohol solvents having 5 or more carbon atoms, such as cyclic monohydric alcohol solvents such as cycloheptanol and cyclooctanol;
Polyhydric alcohol solvents having 5 or more carbon atoms such as pentanediol, hexanediol and dipropylene glycol;
Partial alkyl ether solvents of polyhydric alcohols having 5 or more carbon atoms such as ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, etc. Can be mentioned.
Among these. A monohydric alcohol solvent is preferred, a chain monohydric alcohol solvent is more preferred, a chain monohydric alcohol solvent having 5 to 7 carbon atoms is more preferred, 1-pentanol, 2-hexanol, 4-methyl-2 -Pentanol and 2-heptanol are particularly preferred, and 4-methyl-2-pentanol and 2-heptanol are particularly preferred.

  [B] The solvent is preferably a chain ether solvent or a specific alcohol solvent, and more preferably includes both a chain ether solvent and a specific alcohol solvent. [B] By using a chain ether solvent as the solvent, the protective film-forming composition can make intermixing between the protective film to be formed and the resist film more appropriate. As a result, the suppression of film loss and the rectangular shape of the cross-sectional shape in resist pattern formation are improved. Moreover, by using a specific alcohol solvent as the [B] solvent, the suppression of bridge defects and the suppression of nozzle drying in the pattern forming apparatus are improved. [B] By including both the chain ether solvent and the specific alcohol solvent as the solvent, it is possible to improve both of these performances.

  [B] As a solvent, the mixing ratio (i / ii) when the specific alcohol solvent (i) and the chain ether solvent and / or hydrocarbon solvent (ii) are used in combination is 1/99 to 60/40 is preferable, 5/95 to 40/60 is more preferable, and 10/90 to 30/70 is still more preferable. By making the said mixing ratio into the said range, the film | membrane reduction inhibitory property of the said protective film formation composition, the rectangularity of a cross-sectional shape, and bridge | bridging defect inhibitory property can be improved more.

The protective film-forming composition may contain a solvent other than the [B] solvent.
Examples of the other solvent include ester solvents, ketone solvents, amide solvents, cyclic ether solvents, alcohol solvents having 4 or less carbon atoms, and the like.

As the ester solvent, for example,
Alkyl ether acetate solvents of polyhydric alcohols such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate;
Acetate solvents such as ethyl acetate and butyl acetate;
Lactone solvents such as butyrolactone and valerolactone;
Examples include carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate.

Examples of the ketone solvent include:
Chain ketone solvents such as acetone and 2-butanone;
Examples thereof include cyclic ketone solvents such as cyclopentanone and cyclohexanone.

As the amide solvent, for example,
Chain amide solvents such as formamide, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide;
Examples thereof include cyclic amide solvents such as pyrrolidone, N-methylpyrrolidone and N-ethylpyrrolidone.

As the cyclic ether solvent, for example,
Tetrahydrofuran, tetrahydropyran, dioxane, perfluoro-2-butyltetrahydrofuran and the like can be mentioned.

Examples of the alcohol solvent having 4 or less carbon atoms include, for example,
Monohydric alcohol solvents such as methanol, ethanol, propanol, butanol;
Dihydric alcohol solvents such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol;
Examples thereof include partial alkyl ether solvents of polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether.

  The content of the solvent [B] in the solvent contained in the protective film-forming composition is usually 40% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more. More preferred is 100% by mass.

<Optional component>
The protective film-forming composition may contain an optional component in addition to the [A] fluorine atom-containing polymer and the [B] solvent. Examples of optional components include [C] basic compounds and surfactants.

[[C] Compound]
The compound [C] is at least one selected from the group consisting of a basic compound and a compound that generates a basic compound by the action of an acid. The compound [C] acts on the exposed portion of the resist film under the protective film to be formed, thereby suppressing deprotection, thereby further reducing film loss in resist pattern formation. Moreover, the inhibitory property of the blob defect in a resist pattern can be improved.

  Examples of the basic compound include (cyclo) alkylamine compounds, nitrogen-containing heterocyclic compounds, amide group-containing compounds, urea compounds, and photodegradable basic compounds.

  Examples of the (cyclo) alkylamine compound include compounds having one nitrogen atom, compounds having two nitrogen atoms, and compounds having three or more nitrogen atoms.

Examples of the compound having one nitrogen atom include mono (cyclo) alkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, 1-aminodecane, and cyclohexylamine;
Di-n-butylamine, di-n-pentylamine, di-n-hexylamine, di-n-heptylamine, di-n-octylamine, di-n-nonylamine, di-n-decylamine, cyclohexylmethylamine, Di (cyclo) alkylamines such as dicyclohexylamine;
Triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri -Tri (cyclo) alkylamines such as n-decylamine, cyclohexyldimethylamine, methyldicyclohexylamine, tricyclohexylamine;
Substituted alkylamines such as triethanolamine and tri (n-hexyloxyethyl) amine;
Aniline, N-methylaniline, N, N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, N, N-dibutylaniline, 4-nitroaniline, diphenylamine, triphenylamine, naphthylamine, 2 , 4,6-tri-tert-butyl-N-methylaniline, N-phenyldiethanolamine, 2,6-diisopropylaniline, 2- (4-aminophenyl) -2- (3-hydroxyphenyl) propane, 2- ( And aromatic amines such as 4-aminophenyl) -2- (4-hydroxyphenyl) propane.

  Examples of the compound having two nitrogen atoms include ethylenediamine, tetramethylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and 4,4′-diaminobenzophenone. 4,4′-diaminodiphenylamine, 2,2-bis (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 1,4-bis [1- ( 4-aminophenyl) -1-methylethyl] benzene, 1,3-bis [1- (4-aminophenyl) -1-methylethyl] benzene, bis (2-dimethylaminoethyl) ether, bis (2-diethylamino) Ethyl) ether, 1- (2-hydroxyethyl) -2-imidazolide Down, 2-quinoxalinium linoleic, N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine, and the like.

  Examples of the compound having three or more nitrogen atoms include polyethyleneimine, polyallylamine, 2-dimethylaminoethylacrylamide polymer, and the like.

  Examples of the nitrogen-containing heterocyclic compound include nitrogen-containing aromatic heterocyclic compounds and nitrogen-containing aliphatic heterocyclic compounds.

Examples of the nitrogen-containing aromatic heterocyclic compound include:
Imidazoles such as imidazole, 4-methylimidazole, 4-methyl-2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-methyl-1H-imidazole;
Pyridine, 2-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 4-ethylpyridine, 2-phenylpyridine, 4-phenylpyridine, 2-methyl-4-phenylpyridine, nicotine, nicotinic acid, nicotinamide, Examples thereof include pyridines such as quinoline, 4-hydroxyquinoline, 8-oxyquinoline, acridine, and 2,2 ′: 6 ′, 2 ″ -terpyridine.

Examples of the nitrogen-containing aliphatic heterocyclic compound include:
Piperazines such as piperazine and 1- (2-hydroxyethyl) piperazine;
Pyrazine, pyrazole, pyridazine, quinosaline, purine, pyrrolidine, proline, piperidine, piperidine ethanol, 3-piperidino-1,2-propanediol, morpholine, 4-methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine , 3- (N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane, and the like.

  Examples of the amide group-containing compound include formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, benzamide, pyrrolidone, N-methylpyrrolidone, N-acetyl-1-adamantylamine, isocyanuric acid tris (2-hydroxyethyl) and the like can be mentioned.

  Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tri-n-butyl. Examples include thiourea.

  As a compound which produces | generates a basic compound by the effect | action of the said acid, the compound etc. which substituted the hydrogen atom couple | bonded with the nitrogen atom of the said basic compound with the t-alkoxycarbonyl group etc. are mentioned, for example. Can be mentioned.

Examples of the compound that generates a basic compound by the action of the acid include Nt-butoxycarbonyldi-n-octylamine, Nt-butoxycarbonyldi-n-nonylamine, and Nt-butoxycarbonyldi-n. -Decylamine, Nt-butoxycarbonyldicyclohexylamine, Nt-butoxycarbonyl-1-adamantylamine, Nt-butoxycarbonyl-2-adamantylamine, Nt-butoxycarbonyl-N-methyl-1-adamantyl Amine, (S)-(−)-1- (t-butoxycarbonyl) -2-pyrrolidinemethanol, (R)-(+)-1- (t-butoxycarbonyl) -2-pyrrolidinemethanol, Nt- Butoxycarbonyl-4-hydroxypiperidine, Nt-butoxycarbonylpyrrolidine, Nt-butoxycarbonylpiperazine, N, N-di-t-butoxycarbonyl-1-adamantylamine, N, N-di-t-butoxycarbonyl-N-methyl-1-adamantylamine, Nt-butoxycarbonyl -4,4'-diaminodiphenylmethane, N, N'-di-t-butoxycarbonylhexamethylenediamine, N, N, N ', N'-tetra-t-butoxycarbonylhexamethylenediamine, N, N'-di -T-butoxycarbonyl-1,7-diaminoheptane, N, N'-di-t-butoxycarbonyl-1,8-diaminooctane, N, N'-di-t-butoxycarbonyl-1,9-diaminononane, N, N′-di-t-butoxycarbonyl-1,10-diaminodecane, N, N′-di-t-butoxycarbonyl-1,12-diamino Decane, N, N′-di-t-butoxycarbonyl-4,4′-diaminodiphenylmethane, Nt-butoxycarbonylbenzimidazole, Nt-butoxycarbonyl-2-methylbenzimidazole, Nt-butoxycarbonyl N-t-alkoxycarbonyl group-substituted nitrogen-containing compounds such as 2-phenylbenzimidazole and the like, and their t-amyloxycarbonyl-substituted products.

  The photodegradable basic compound is a compound having basicity, and is a compound that is exposed to light upon exposure to produce a weak acid and the basicity is lowered. Examples of the photodegradable base compound include onium salt compounds. Examples of the onium salt compound include a sulfonium salt compound represented by the following formula (K1) and an iodonium salt compound represented by the following formula (K2).

In the above formulas (K1) and (K2), R ^{6 to} R ¹⁰ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, or a halogen atom. Z ^{- is, OH -, R 12 -COO -} , R 13 -SO 2 -N - -R 12, R 12 -SO 3 - or an anion represented by the following formula (K3). R ¹² is a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Some or all of the hydrogen atoms of the alkyl group, cycloalkyl group, aryl group and aralkyl group may be substituted. R ¹³ is a C 1-10 linear or branched alkyl group or a C 3-20 cycloalkyl group which may have a substituent. Some or all of the hydrogen atoms of the alkyl group and cycloalkyl group may be substituted with fluorine atoms. However, when Z ⁻ is R ¹² —SO ₃ ^— , a fluorine atom is not bonded to a carbon atom to which SO ₃ ^— is bonded.

In said formula (K3), R < ¹⁴ > is a C1-C12 linear or branched alkyl group by which a part or all of a hydrogen atom may be substituted by the fluorine atom, or C1-C12 These are linear or branched alkoxy groups. u is an integer of 0-2.

  As said photodegradable base, the compound etc. which are represented by a following formula are mentioned, for example.

  [C] The compound is preferably a (cyclo) alkylamine compound, a nitrogen-containing heterocyclic compound, a compound that produces a (cyclo) alkylamine compound by the action of an acid, or a compound that produces a nitrogen-containing heterocyclic compound by the action of an acid. , (Cyclo) alkylamine compounds, compounds that generate nitrogen-containing heterocyclic compounds by the action of an acid are more preferable, substituted alkylamines, Nt-alkoxycarbonyl-substituted nitrogen-containing aliphatic heterocyclic compounds are more preferable, tri ( n-hexyloxyethyl) amine and Nt-amyloxycarbonyl-4-hydroxypiperidine are particularly preferred.

  As content of the [C] compound in the said protective film formation composition, 0 mass part-10 mass parts are preferable with respect to 100 mass parts of [A] fluorine atom containing polymers, 0.01 mass part-5 masses Part is more preferable, 0.1 part by weight to 3 parts by weight is further preferable, and 0.2 part by weight to 2 parts by weight is particularly preferable. By setting the content of the [C] compound within the above range, film loss in resist pattern formation can be further reduced. If the content of the [C] compound exceeds the above upper limit, the pattern formability of the formed resist pattern may be lowered. [C] A compound can be used individually by 1 type or in mixture of 2 or more types.

[Surfactant]
Examples of the surfactant include commercially available fluorine-based surfactants such as BM-1000, BM-1100 (above, manufactured by BM Chemie), MegaFuck F142D, F172, F173, F183 (above, manufactured by DIC). Agents and the like. As content of the said surfactant, 5 mass parts or less are preferable with respect to 100 mass parts of [A] fluorine atom containing polymers.

<Method for preparing protective film-forming composition>
The protective film-forming composition can be prepared by, for example, mixing [A] a fluorine atom-containing polymer and, if necessary, optional components such as a [C] compound with a [B] solvent and dissolving them. it can. As solid content concentration of the said protective film formation composition, it is 0.1 mass%-30 mass% normally, 0.3 mass%-20 mass% are preferable, and 0.5 mass%-10 mass% are more. preferable.

<Negative resist pattern forming method>
The negative resist pattern forming method of the present invention,
(1) a step of forming a resist film using a photoresist composition;
(2) A step of laminating a protective film on the resist film using the protective film-forming composition,
(3) a step of immersion exposure of the resist film on which the protective film is laminated; and (4) a step of developing the immersion exposed resist film using a developer containing an organic solvent.

  According to the negative resist pattern forming method, since the protective film forming composition is used, it is possible to form a resist pattern that suppresses film loss and generation of defects and is excellent in rectangular shape in cross section. Hereinafter, each step will be described.

[(1) Process]
In step (1), a photoresist film is used to form a resist film. As a substrate to be used, a silicon wafer, a silicon wafer coated with aluminum, and the like are usually mentioned. In order to maximize the characteristics of the resist film to be formed, an organic or inorganic antireflection film described in, for example, Japanese Patent Publication No. 6-12452 is formed on the surface of the substrate in advance. It is preferable to keep it.

  The type of the photoresist composition is not particularly limited, and it is appropriately selected from the photoresist compositions conventionally used for forming a resist film according to the intended use of the resist. be able to. Among these, a photoresist composition containing a polymer (P) containing an acid dissociable group and an acid generator (Q) is preferable.

  In the polymer (P), examples of the structural unit containing an acid dissociable group (hereinafter also referred to as “structural unit (p)”) include a structural unit represented by the following formula (5).

In said formula (5), ^RP is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ^p1 is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms. R ^p2 and R ^p3 are monovalent chain hydrocarbon groups having 1 to 10 carbon atoms or monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, or these groups are bonded to each other. A ring structure having 3 to 20 carbon atoms is formed together with the carbon atoms to which they are bonded.

Examples of the R ^P, from the viewpoint of copolymerizability of the monomer giving the structural units (p), a hydrogen atom, preferably a methyl group, more preferably a methyl group.

Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by R ^p1 , R ^p2 and R ^p3 include a methyl group, an ethyl group, an n-propyl group, an i-butyl group, an n- Examples thereof include alkyl groups such as a butyl group.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ^p2 and R ^p3 include monocyclic cycloalkyl groups such as a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; a norbornyl group and an adamantyl group And a polycyclic cycloalkyl group such as a group.

  Examples of the ring structure having 3 to 20 carbon atoms formed together with the carbon atom to which these groups are bonded to each other include monocyclic cycloalkane structures such as a cyclopentane structure and a cyclohexane structure; a norbornane structure; Examples include polycyclic cycloalkane structures such as an adamantane structure.

  Examples of the structural unit (p) include 1-alkyl-1-monocyclic cycloalkyl (meth) acrylates such as 1-ethyl-1-cyclopentyl (meth) acrylate; 2-i-propyl-2-adamantyl (meth) Examples include structural units derived from 2-alkyl-2-polycyclic cycloalkyl (meth) acrylates such as acrylate.

  In addition to the structural unit (p), the polymer (P) includes at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure and a sultone structure (hereinafter also referred to as “structural unit (q)”). ).

As the structural unit (q), for example,
As lactone structure, norbornane lactone structure, butyrolactone structure, etc .;
As cyclic carbonate structure, ethylene carbonate structure, propylene carbonate structure, etc .;
Examples of the sultone structure include a structural unit derived from a (meth) acrylic acid ester including a norbornane sultone structure, a propane sultone structure, and the like.

  Moreover, the polymer (P) may have other structural units other than the structural unit (p) and the structural unit (q). Examples of the other structural unit include a structural unit containing a hydrocarbon group having 4 to 20 carbon atoms (hereinafter also referred to as “structural unit (r)”), a structural unit containing a polar group such as a hydroxy group, and the like. It is done. Examples of the structural unit (r) include those similar to the structural unit (II) of the [A] fluorine atom-containing polymer of the protective film-forming composition.

  As a content rate of a structural unit (p), 30 mol%-60 mol% are preferable with respect to all the structural units which comprise a polymer (P). By making the content rate of a structural unit (p) into the said range, the resolution of the said photoresist composition can be improved. When the content ratio of the structural unit (p) is less than the lower limit, the pattern forming property of the photoresist composition may be deteriorated. When the content ratio of the structural unit (p) exceeds the upper limit, the resist film thickness after the protective film is peeled may be extremely reduced.

  As a content rate of a structural unit (q), 20 mol%-60 mol% are preferable with respect to all the structural units which comprise a polymer (P). By setting the content ratio of the structural unit (q) in the above range, the solubility of the resist film formed from the photoresist composition in a developer containing an organic solvent can be appropriately adjusted, and the resist The adhesion of the film to the substrate can be improved. When the content ratio of the structural unit (q) is less than the lower limit, the adhesion of the photoresist composition to the substrate may be lowered. When the content ratio of the structural unit (q) exceeds the upper limit, the pattern forming property of the photoresist composition may be deteriorated.

  As a content rate of the said other structural unit, 20 mol% or less is preferable with respect to all the structural units which comprise a polymer (P), and 15 mol% or less is more preferable.

  The acid generator (Q) is a substance that generates an acid by radiation irradiation (exposure). Due to the action of the generated acid, the acid-dissociable group protecting the acidic group such as the carboxy group of the polymer (P) is dissociated in the exposed portion to generate an acidic group. As a result, the polymer (P) has a reduced solubility in a developer containing an organic solvent in the exposed portion, and a negative resist pattern is formed.

  Examples of the acid generator (Q) include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, onium salts such as phosphonium salts, diazonium salts, pyridinium salts, N-sulfonyloxyimide compounds, halogen-containing compounds, and diazoketone compounds. Etc.

Examples of the sulfonium salt include triphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, and triphenylsulfonium 2- (bicyclo [2.2.1] hepta-2. '-Yl) -1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2- (bicyclo [2.2.1] hepta-2'-yl) -1,1-difluoroethanesulfonate, and the like. .
Examples of the tetrahydrothiophenium salt include 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (4-n-butoxynaphthyl) tetrahydrothiophene. Examples include nitro 2- (bicyclo [2.2.1] hepta-2'-yl) -1,1,2,2-tetrafluoroethane sulfonate.

  In addition to the polymer (P) and the acid generator (Q), the photoresist composition may contain other components such as an acid diffusion controller (R) and a surfactant. Examples of the acid diffusion controller (R) include amine compounds such as trioctylamine and triethanolamine; R-(+)-(t-butoxycarbonyl) -2-piperidinemethanol, Nt-butoxycarbonyl- Examples include Nt-alkoxycarbonyl-containing amide compounds such as 4-hydroxypiperidine; photodegradable bases such as triphenylsulfonium 10-camphor sulfonate and triphenylsulfonium salicylate.

  The photoresist composition is prepared, for example, by dissolving the polymer (P), the acid generator (Q), and, if necessary, the acid diffusion controller (R) in a solvent. The photoresist composition is usually filtered through a filter having a pore diameter of about 30 nm. The total solid concentration of the photoresist composition is preferably 0.2% by mass to 20% by mass from the viewpoint of ease of application.

  Examples of the method for applying the photoresist composition include conventionally known coating methods such as spin coating, cast coating, and roll coating. After applying on the substrate, pre-baking (PB) may be performed to volatilize the solvent.

[(2) Process]
In the step (2), the protective film forming composition is used, and a protective film is laminated on the resist film formed in the step (1). Examples of the method for applying the protective film-forming composition include the same method as the method for applying the photoresist composition in the step (1). In this step, it is preferable to perform pre-baking (PB) after applying the protective film-forming composition. By forming a protective film on the resist film, the immersion liquid and the resist film are not in direct contact with each other, so that the lithography performance of the resist film is reduced due to the immersion liquid penetrating the resist film, Contamination of the lens of the projection exposure apparatus due to components eluted from the resist film into the immersion liquid is effectively suppressed.

  The thickness of the protective film to be formed is preferably as close as possible to an odd multiple of λ / 4m (λ: wavelength of radiation, m: refractive index of the protective film). By doing in this way, the reflection suppression effect in the upper interface of a resist film can be enlarged.

[(3) Process]
(3) In the step, the resist film on which the protective film is laminated is subjected to immersion exposure. This immersion exposure is performed by placing an immersion liquid on the protective film and exposing through the immersion liquid.

  As the immersion liquid, a liquid having a refractive index higher than that of air is usually used. As the immersion liquid, water is preferably used, and pure water is more preferably used. Note that the pH of the immersion liquid may be adjusted as necessary. In a state where the immersion liquid is interposed, that is, in a state where the immersion liquid is filled between the lens and the protective film of the exposure apparatus, exposure light is irradiated from the exposure apparatus and is passed through a mask having a predetermined pattern. To expose the resist film.

  The exposure light used for this immersion exposure can be appropriately selected according to the type of the resist film or the protective film. For example, visible light; ultraviolet rays such as g rays and i rays; far ultraviolet rays such as excimer laser light; X-rays such as tron radiation; charged particle beams such as electron beams. Among these, far ultraviolet rays are preferable, ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm) are more preferable, and ArF excimer laser light is more preferable. Moreover, the exposure light irradiation conditions, for example, the exposure amount and the like can be appropriately set according to the composition of the photoresist composition and the protective film-forming composition, the type of additives contained therein, and the like.

  After the immersion exposure, post-exposure baking (PEB) is preferably performed in order to improve the resolution, pattern shape, developability, and the like of the resulting resist pattern. Although it can set suitably as a PEB temperature according to the kind etc. of the photoresist composition used or the protective film formation composition, it is 30 to 200 degreeC normally, and 50 to 150 degreeC is preferable. The PEB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds.

[(4) Process]
In the step (4), the resist film subjected to the immersion exposure is developed using a developer containing an organic solvent. Thereby, a desired negative resist pattern can be obtained. According to the negative resist pattern forming method, since the protective film is formed using the protective film forming composition, the developing solution is used during the development, or in the case of performing the cleaning after the development, the cleaning solution during the cleaning. Thus, the protective film can be easily removed. That is, no separate peeling process is required to remove the protective film.

  Examples of the developer containing the organic solvent include alcohol solvents, ether solvents, ketone organic solvents, amide solvents, ester organic solvents, hydrocarbon solvents, and the like.

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

  Examples of the ether solvent include anisole, diethyl ether, dipropyl ether, dibutyl ether, tetrahydrofuran, dioxane, diphenyl ether and the like.

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

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

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

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

  Among these, ether solvents, ketone solvents, and ester solvents are preferable, and n-butyl acetate, isopropyl acetate, amyl acetate, anisole, 2-butanone, methyl-n-butyl ketone, and methyl-n-amyl ketone are more preferable. These organic solvents may be used alone or in combination of two or more.

  The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. By setting the content of the organic solvent in the developer within the above range, the dissolution contrast between the exposed part and the unexposed part can be improved, and as a result, a resist pattern having excellent lithography characteristics can be formed. . Examples of components other than the organic solvent include water, silicon oil, and the like.

  The developer may contain a nitrogen-containing compound. When the developer contains a nitrogen-containing compound, film loss of the formed resist pattern can be further reduced.

  As said nitrogen-containing compound, the compound etc. which were illustrated as a [C] compound of the said protective film formation composition mentioned above are mentioned, for example.

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

  As a developing method, for example, a method in which a substrate is immersed in a tank filled with a developer for a certain period of time (dip method), a method in which the developer is raised on the surface of the substrate by surface tension and is left stationary for a certain time (paddle method) ), A method of spraying the developer on the substrate surface (spray method), a method of continuously applying the developer while scanning the developer coating nozzle on the substrate rotating at a constant speed (dynamic dispensing method) Etc.

  (4) It is preferable to include a rinsing step of washing the resist film with a rinsing liquid after the step. An organic solvent can be used as the rinsing liquid in the rinsing step. By using an organic solvent as the rinsing liquid, the generated scum can be efficiently washed.

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

  Examples of the monovalent alcohol solvent having 6 to 8 carbon atoms include linear, branched or cyclic monohydric alcohols, and specifically, 1-hexanol, 1-heptanol, 1-octanol. 4-methyl-2-pentanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, benzyl alcohol and the like. Of these, 1-hexanol, 2-hexanol, 2-heptanol, and 4-methyl-2-pentanol are preferable.

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

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

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The measuring method of various physical property values is shown below.

[Mw and Mn measurement]
Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) under the following conditions.
GPC column: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (manufactured by Tosoh)
Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Column temperature: 40 ° C
Standard material: Monodisperse polystyrene Detector: Differential refractometer

[ ¹³ C-NMR analysis and ¹⁹ F-NMR analysis]
For the ¹³ C-NMR analysis and ¹⁹ C-NMR analysis of the polymer, a nuclear magnetic resonance apparatus (JNM-ECX400, manufactured by JEOL Ltd.) was used, CDCl ₃ was used as a measurement solvent, and tetramethylsilane (TMS) was used as an internal standard. As measured.

<[A] Synthesis of Fluorine Atom-Containing Polymer>
[A] Monomers used for the synthesis of the fluorine atom-containing polymer are shown below.

  Monomers (M-1) to (M-7) are structural units (I), monomers (M-8) and (M-9) are structural units (II), M-10) gives structural unit (III), and monomers (M-11) and (M-12) give structural unit (IV).

[Synthesis Example 1]
A polymerization initiator solution was prepared by dissolving 6.1 g of dimethyl 2,2-azobis (2-methylpropionate) as a polymerization initiator in 6.1 g of 2-butanone. On the other hand, in a 200 mL three-necked flask equipped with a thermometer and a dropping funnel, 48 g (30 mol%) of the monomer (M-1), 52 g (70 mol%) of the monomer (M-6) and 2-butanone. 94 g was charged and purged with nitrogen for 30 minutes. After purging with nitrogen, the flask was heated to 75 ° C. while stirring with a magnetic stirrer. Subsequently, using the dropping funnel, the polymerization initiator solution prepared above was dropped over 5 minutes and aged for 6 hours. Then, it cooled to 30 degrees C or less, and obtained the polymerization reaction liquid.

Subsequently, 2-butanone was added to the resulting polymerization reaction solution to dilute to 222 g, and then transferred to a separatory funnel. The separatory funnel was charged with 222 g of methanol and 1,111 g of n-hexane to carry out separation purification. After separation, 168 g of the lower layer liquid was recovered. 168 g of methanol and 842 g of n-hexane were added to the recovered lower layer liquid, and liquid separation purification was performed. After separation, 219 g of the lower layer liquid was recovered. 109 g of 2-butanone and 656 g of n-hexane were added to the recovered lower layer liquid, and liquid separation purification was performed. After separation, 806 g of the upper layer liquid was recovered. The recovered upper layer liquid was replaced with 4-methyl-2-pentanol to obtain 400 g of a solution containing a fluorine atom-containing polymer. Next, the obtained solution was transferred to a separatory funnel, and 400 g of water was added to the separatory funnel, and after separation purification, 440 g of the upper layer liquid was recovered. The recovered upper layer liquid was replaced with 4-methyl-2-pentanol, and 104 g of a solution containing the fluorine atom-containing polymer (A-1) was obtained. The solution containing the fluorine atom-containing polymer (A-1) is solidified from the mass of the residue after 0.5 g of the solution containing the polymer is placed on an aluminum dish and heated on a hot plate heated to 155 ° C. for 30 minutes. The partial concentration was calculated, and the solid concentration value was used for the subsequent preparation of the protective film-forming composition and the yield calculation. The obtained fluorine atom-containing polymer (A-1) had an Mw of 8,100, an Mw / Mn of 1.5, and a yield of 30%. As a result of ¹⁹ F-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-6) were 29 mol% and 71 mol%, respectively.

[Synthesis Examples 2 to 13]
Fluorine atom-containing polymers (A-2) to (A-13) were synthesized in the same manner as in Example 1 except that the types and amounts of monomers listed in Table 1 were used. The total mass of the monomers used was 100 g. In Table 1, “-” indicates that the corresponding component was not used. The content ratio, yield, Mw, and Mw / Mn of each structural unit of the obtained [A] fluorine atom-containing polymer are shown in Table 1.

<Preparation of protective film forming composition>
The [B] solvent and [C] basic compound used for the preparation of the protective film-forming composition are shown below.

[[B] solvent]
B-1: 4-methyl-2-pentanol B-2: 2-heptanol B-3: Diisoamyl ether B-4: n-decane b-1: 1-butanol

[[C] basic compound]
C-1: Tri (n-hexyloxyethyl) amine (compound represented by the following formula (C-1))
C-2: Nt-amyloxycarbonyl-4-hydroxypiperidine (compound represented by the following formula (C-2))

[Example 1]
[A] 100 parts by mass of (A-1) as a fluorine atom-containing polymer and (B-1) 980 parts by mass and (B-3) 3,920 parts by mass of a solvent as a solvent are protected. A film-forming composition (J-1) was prepared.

[Examples 2 to 21 and Comparative Example 1]
Protective film forming compositions (J-2) to (J-21) and (CJ-1) were prepared in the same manner as in Example 1 except that the components of the types and blending amounts shown in Table 2 below were used. .

<Preparation of photoresist composition>
A photoresist composition for forming a resist film was prepared by the following method.

[[P] Synthesis of polymer for photoresist composition]
[P] Monomers used for the synthesis of the polymer for the photoresist composition are shown below.

[Synthesis Example 14]
Monomer (r-1) 53.93 g (50 mol%), monomer (r-2) 35.38 g (40 mol%) and monomer (r-3) 10.69 g (10 mol%) ) Was dissolved in 200 g of 2-butanone, and a monomer solution in which 5.58 g of dimethyl 2,2′-azobis (2-methylpropionate) was further dissolved was prepared. A 500 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After the nitrogen purge, the reaction kettle was heated to 80 ° C. with stirring, and the monomer solution prepared above was added dropwise over 3 hours using a dropping funnel. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization reaction liquid was cooled to 30 ° C. or lower by water cooling, and then poured into 2,000 g of methanol, and the precipitated white powder was filtered off. The filtered white powder was washed twice by slurrying with 400 g of methanol each time, separated, and then dried at 50 ° C. for 17 hours to obtain a white powder polymer (P-1). (74 g, 74% yield). This polymer (P-1) had Mw of 6,900 and Mw / Mn of 1.70. In addition, as a result of ¹³ C-NMR analysis, the content ratios of the structural units derived from (r-1), (r-2), and (r-3) were 53.0, 37.2, and 9. 8 (mol%).

<Preparation of photoresist composition (α)>
The [Q] acid generator, [R] acid diffusion controller and [S] solvent used for the preparation of the photoresist composition (α) are shown below.

[[Q] acid generator]
Q-1: Triphenylsulfonium nonafluoro-n-butanesulfonate Q-2: 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate

[[R] acid diffusion controller]
R-1: R-(+)-(t-butoxycarbonyl) -2-piperidinemethanol

[[S] solvent]
S-1: Propylene glycol monomethyl ether acetate S-2: Cyclohexanone S-3: γ-butyrolactone

[Synthesis Example 15]
[P] 100 parts by mass of (P-1) polymer, (Q-1) 1.5 parts by mass and (Q-2) 6 parts by mass of [Q] acid generator, [R] acid diffusion control (R-1) 0.65 parts by mass as an agent is mixed, and (S-1) 2,900 parts by mass, (S-2) 1,250 parts by mass as (S) solvent, and (S) S-3) A photoresist composition (α) was prepared by adding 100 parts by mass, adjusting the total solid content concentration to 5% by mass, and filtering through a filter having a pore diameter of 30 nm.

<Evaluation>
Various evaluations shown below were performed on the protective film forming compositions of the above Examples and Comparative Examples. The evaluation results are shown in Table 3 below.

[Composition stability]
The presence or absence of white turbidity of the protective film forming composition over time was evaluated.
After stirring the protective film-forming composition for 30 minutes, the presence or absence of cloudiness was visually observed. The composition stability was evaluated as “◎” when no white turbidity was observed, “◯” when slightly white turbidity was observed, and “x” when white turbidity was significantly observed.

[Protective film removal]
The removability of the protective film with a developer containing an organic solvent was evaluated.
A protective film forming composition was spin-coated on an 8-inch silicon wafer with a coating / developing apparatus (CLEAN TRACK ACT8, manufactured by Tokyo Electron), and PB was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 90 nm. . The film thickness was measured using a film thickness measuring device (Lambda Ace VM90, manufactured by Dainippon Screen). This protective film was subjected to paddle development for 60 seconds using methyl pentyl ketone as a developer in the coating / developing apparatus, spin-dried by shaking off, and the wafer surface was observed. The protective film removal property was evaluated as “◎” when no residue was observed, “◯” when a little residue was observed, and “×” when the residue was observed remarkably.

[Backward contact angle]
The receding contact angle of water on the protective film surface was measured.
A protective film-forming composition was spin-coated on an 8-inch silicon wafer, and PB was performed on a hot plate at 90 ° C. for 60 seconds to form a protective film having a thickness of 30 nm. Thereafter, using a contact angle meter (DSA-10, manufactured by KRUS), the receding contact angle was quickly measured according to the following procedure in an environment of room temperature 23 ° C., humidity 45%, and normal pressure.
First, the wafer stage position of the contact angle meter was adjusted, and the wafer was set on the adjusted stage. Next, water was injected into the needle, and the position of the needle was finely adjusted to an initial position where water droplets could be formed on the set wafer. Thereafter, water was discharged from the needle to form a 25 μL water droplet on the wafer. The needle was once withdrawn from the water droplet, and again pulled down to the initial position and placed in the water droplet. Subsequently, a water droplet was sucked with a needle at a speed of 10 μL / min for 90 seconds, and at the same time, the contact angle was measured once per second for a total of 90 times. Among these, the average value for the contact angle for 20 seconds from the time when the measured value of the contact angle was stabilized was calculated and set as the receding contact angle (unit: degree (°)). The receding contact angle was evaluated as “◎” when 75 ° or more, “◯” when 70 ° or more and less than 75 °, and “×” when less than 70 °.

[Elution suppression]
The elution amount of the resist film component from the resist film on which the protective film was formed was measured, and the elution suppression property was evaluated.
Silicon centered on an 8-inch silicon wafer that has been subjected to hexamethyldisilazane (HMDS) treatment (100 ° C. for 60 seconds) with the above coating / development apparatus, and the center is cut into a circular shape with a diameter of 11.3 cm A rubber sheet (made of Kureha elastomer, thickness 1.0 mm, square of 30 cm on one side) was placed. Next, 10 mL of ultrapure water was filled in the hollowed out portion at the center of the silicon rubber using a 10 mL hole pipette.
On the other hand, separately from the silicon wafer, an 8-inch silicon wafer having a lower antireflection film, a resist film, and a protective film is prepared, and the 8-inch silicon wafer is placed so that the protective film is positioned on the silicon rubber sheet side, that is, Then, the protective film and the ultrapure water were brought into contact with each other while being placed so that the ultrapure water did not leak.
The silicon wafer on which the lower antireflection film, the resist film and the protective film are formed is prepared by applying the lower antireflection film composition (ARC29A, manufactured by Brewer Science) on the 8-inch silicon wafer and applying the coating / developing apparatus. The lower antireflection film having a film thickness of 77 nm is formed by spin coating, and then the photoresist composition (α) is spin coated on the lower antireflection film using the coating / developing apparatus. A resist film having a thickness of 120 nm is formed by baking at 115 ° C. for 60 seconds, and then a protective film-forming composition is applied onto the resist film and PB is performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 30 nm. It was obtained by doing.

  After placing the protective film, the state was kept for 10 seconds. Thereafter, the other 8-inch silicon wafer was removed, and ultrapure water was collected with a glass syringe, which was used as a sample for analysis. Note that the recovery rate of ultrapure water after the experiment was 95% or more.

Subsequently, the peak intensity of the anion part of the photoacid generator in the ultrapure water obtained above was measured using a liquid chromatograph-mass spectrometer (LC-MS) (LC part: SERIES 1100 (manufactured by AGILENT), MS part: Mariner. (Perseptive Biosystems, Inc.)) under the following measurement conditions. At that time, a calibration curve was prepared by measuring the peak intensity of the 1 ppb, 10 ppb, and 100 ppb aqueous solutions of the [Q] acid generator used in the photoresist composition (α) under the following measurement conditions. The amount of elution was calculated from the peak intensity. The amount of elution was also measured in the same manner for the [R] acid diffusion controller. The elution inhibitory property of the resist film component exceeds “×” and 5.0 × 10 ⁻¹³ mol / cm ² when the measured elution amount is 5.0 × 10 ⁻¹³ mol / cm ² or less. When it was 1.0 × 10 ⁻¹² mol / cm ² or less, “◯” was evaluated, and when it exceeded 1.0 × 10 ⁻¹² mol / cm ² , “×” was evaluated.

(Measurement condition)
Column used: 1 CAPCELL PAK MG (manufactured by Shiseido) Flow rate: 0.2 mL / min Eluent: Water / methanol (volume ratio: 3/7) with 0.1% by mass of formic acid Measurement temperature: 35 ° C.

[Peeling resistance]
The difficulty of peeling off the protective film from the substrate was evaluated.
As the substrate, an 8-inch silicon wafer not subjected to HMDS treatment was used. A protective film forming composition was spin-coated on the substrate using the coating / developing apparatus, and then PB was performed at 90 ° C. for 60 seconds to form a coating film (protective film) having a thickness of 30 nm. Thereafter, rinsing with pure water was performed for 60 seconds in the coating / developing apparatus, followed by drying by shaking. The peeling resistance is visually observed after rinsing with “◎” when no peeling of the protective film is observed, and “○” when peeling is observed only at the edge, and the protective film is peeled off on the entire wafer surface. When evaluated, it was evaluated as “×”.

[Membrane loss suppression]
The amount of reduction of the resist film was measured and its inhibitory property was evaluated.
First, a resist film having an initial film thickness of 120 nm is formed by using a photoresist composition (α) on an 8-inch silicon wafer on which a 77 nm-thick lower layer antireflection film (ARC29A, manufactured by Brewer Science) is formed. PB was carried out at 60 ° C. for 60 seconds. Next, this resist film was formed by using an ArF excimer laser exposure apparatus (NSR S306C, manufactured by NIKON Corp.) with a NA of 0.78, a sigma = 0.90, and a 40 nm line / The entire surface of the wafer was exposed with an optimal exposure amount (Eop) for forming a line pattern with a pitch of 80 nm. After exposure, PEB was performed at 115 ° C. for 60 seconds. Thereafter, development was performed at 23 ° C. for 30 seconds using methylpentyl ketone as a developer, and after rinsing with 4-methyl-2-pentanol for 7 seconds, drying was performed. After completion of the series of processes, the film thickness of the remaining resist film was measured, and a value obtained by subtracting the remaining film thickness from the initial film thickness was defined as a film reduction amount (nm). In addition, the optical interference type film thickness measuring device (Lambda Ace, manufactured by Dainippon Screen Manufacturing Co., Ltd.) was used for the film thickness measurement. The film loss suppression property was evaluated as “◎” when the measured film loss amount was less than 30 nm, “◯” when it was 30 nm or more and less than 40 nm, and “X” when it was 40 nm or more.

[Rectangularity of the cross-sectional shape]
The rectangularity of the cross-sectional shape of the resist pattern formed from the resist film on which the protective film was formed was evaluated.
On the 12-inch silicon wafer substrate, the lower-layer antireflection film-forming composition (ARC29A, manufactured by Brewer Science) is applied to form a lower-layer antireflection film having a film thickness of 77 nm using the above coating / developing apparatus. After spin-coating the resist composition (α), a resist film having a film thickness of 120 nm is formed by PB at 115 ° C. for 60 seconds, and then a protective film forming composition is applied onto the resist film at 90 ° C. A protective film having a thickness of 30 nm was formed by performing PB for 60 seconds.
Next, the formed resist film is exposed through a mask pattern for forming a line-and-space pattern (1L / 1S) with a line width of 90 nm using an ArF excimer laser immersion exposure apparatus (S610C, manufactured by NIKON). went. Next, after performing PEB at 115 ° C. for 60 seconds, using methyl pentyl ketone as a developer, developing at 23 ° C. for 60 seconds, rinsing with 4-methyl-2-pentanol, drying, and negative-type A resist pattern was formed. At this time, an exposure amount at which a line and space pattern (1L / 1S) having a line width of 90 nm was formed was determined as the optimum exposure amount.
The cross-sectional shape of the resist pattern formed with this optimum exposure dose is observed with a scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies), and the line width Lb in the middle in the height direction of the resist pattern and the upper part of the pattern The line width La was measured and the ratio (La / Lb) was calculated. When the (La / Lb) is 0.95 ≦ (La / Lb) ≦ 1.05, the rectangular shape of the cross-sectional shape is “◎” and 0.9 ≦ (La / Lb) <0.95. Or, when 1.05 <(La / Lb) ≦ 1.1, “◯” and 0.85 ≦ (La / Lb) <0.9 or 1.1 <(La / Lb) ≦ 1.15 Was evaluated as “×” and when (La / Lb) <0.85 or 1.15 <(La / Lb), “XX” was evaluated.

[Immersion defect suppression]
The number of immersion defects in the resist pattern obtained by developing the resist film on which the protective film was formed was measured.
An underlayer antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) is spin-coated on a 12-inch silicon wafer surface using a coating / developing apparatus (Lithius Pro-i, manufactured by Tokyo Electron), and then PB is performed to obtain a film thickness of 105 nm. The coating film was formed. Next, the photoresist composition (α) was spin-coated using a coating / developing apparatus (CLEAN TRACK ACT12, manufactured by Tokyo Electron), PB at 115 ° C. for 60 seconds, and then cooled at 23 ° C. for 30 seconds to form a film. A 120 nm thick photoresist film was formed. Thereafter, a protective film-forming composition was spin-coated on this resist film, and PB was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 30 nm.

Next, using an ArF immersion exposure apparatus (S610C, manufactured by NIKON), exposure was performed through a pattern forming mask having a 45 nm line / 90 nm pitch under the optical conditions of NA: 1.30 and Crosspore. Next, PEB is performed at 115 ° C. for 60 seconds on the “Lithius Pro-i” hot plate, cooled at 23 ° C. for 30 seconds, and then paddled for 10 seconds using methyl pentyl ketone as a developer at the GP nozzle of the developing cup. Development was performed and rinsed with 4-methyl-2-pentanol. Thereafter, spin drying was performed by shaking off at 2,000 rpm for 15 seconds to obtain a substrate on which a resist pattern was formed. At this time, the exposure amount at which a resist pattern having a 45 nm line / 90 nm pitch was formed was determined as the optimum exposure amount. The substrate on which the obtained resist pattern is formed is subjected to defect inspection using an inspection apparatus (2810, manufactured by KLA-Tencor), and observed using a scanning electron microscope (RS6000, manufactured by Hitachi High-Technologies). The number of defects was measured.
The immersion defect suppression property is “◎” when the measured number of immersion defects is 20 / cm ² , “O” when the number exceeds 20 / cm ² and less than 50 / cm ² , and 50 When it exceeded the piece / cm < ² >, it evaluated as "x".

[Blob defect suppression]
The number of occurrences of blob defects in the resist pattern obtained by developing the resist film on which the protective film was formed was measured.
An underlayer antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) is spin-coated on a 12-inch silicon wafer surface using a coating / developing apparatus (Lithius Pro-i, manufactured by Tokyo Electron), and then PB is performed to obtain a film thickness of 105 nm. The coating film was formed. Next, a photoresist composition (α) is spin-coated using the above-mentioned “CLEAN TRACK ACT12”, PB is applied at 115 ° C. for 60 seconds, and then cooled at 23 ° C. for 30 seconds to form a photoresist film having a thickness of 120 nm. Formed. Thereafter, a protective film-forming composition was spin-coated on this resist film, and PB was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 30 nm.

  Next, using an ArF immersion exposure apparatus (S610C, manufactured by NIKON), exposure was performed through a pattern forming mask having a 45 nm line / 90 nm pitch under the optical conditions of NA: 1.30 and Crosspore. Next, PEB is performed at 115 ° C. for 60 seconds on the “Lithius Pro-i” hot plate, cooled at 23 ° C. for 30 seconds, and then paddled for 10 seconds using methyl pentyl ketone as a developer at the GP nozzle of the developing cup. Development was performed and rinsed with 4-methyl-2-pentyl ketone. Thereafter, spin drying was performed by shaking off at 2,000 rpm for 15 seconds to obtain a substrate on which a resist pattern was formed. At this time, the exposure amount at which a resist pattern having a 45 nm line / 90 nm pitch was formed was determined as the optimum exposure amount. The substrate on which the obtained resist pattern is formed is subjected to defect inspection using an inspection apparatus (2810, manufactured by KLA-Tencor), and observed using a scanning electron microscope (RS6000, manufactured by Hitachi High-Technologies) to detect blob defects. Number was measured. Blob defect suppression is "◎" when the number of blob defects measured is 200 or less per wafer, "○" when it exceeds 200 and less than 500 per wafer, and exceeds 500 Was evaluated as “×”.

[Bridge defect suppression]
The number of occurrences of bridge defects in the resist pattern obtained by developing the resist film on which the protective film was formed was measured.
An underlayer antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) is spin-coated on a 12-inch silicon wafer surface using a coating / developing apparatus (Lithius Pro-i, manufactured by Tokyo Electron), and then PB is performed to obtain a film thickness of 105 nm. The coating film was formed. Next, a photoresist composition (α) is spin-coated using the above-mentioned “CLEAN TRACK ACT12”, PB is applied at 115 ° C. for 60 seconds, and then cooled at 23 ° C. for 30 seconds to form a photoresist film having a thickness of 120 nm. Formed. Thereafter, a protective film-forming composition was spin-coated on this resist film, and PB was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 30 nm.

  Next, using an ArF immersion exposure apparatus (S610C, manufactured by NIKON), exposure was performed through a pattern forming mask having a 45 nm line / 90 nm pitch under the optical conditions of NA: 1.30 and Crosspore. Next, PEB is performed at 115 ° C. for 60 seconds on the “Lithius Pro-i” hot plate, cooled at 23 ° C. for 30 seconds, and then paddled for 10 seconds using methyl pentyl ketone as a developer at the GP nozzle of the developing cup. Development was performed and rinsed with 4-methyl-2-pentanol. Thereafter, spin drying was performed by shaking off at 2,000 rpm for 15 seconds to obtain a substrate on which a resist pattern was formed. At this time, the exposure amount at which a resist pattern having a 45 nm line / 90 nm pitch was formed was determined as the optimum exposure amount. The substrate on which the obtained resist pattern is formed is subjected to defect inspection using an inspection apparatus (2810, manufactured by KLA-Tencor), and observed using a scanning electron microscope (RS6000, manufactured by Hitachi High-Technologies), and bridge defects Number was measured. When the number of bridge defects measured is 200 or less per wafer, the bridge defect suppression property is “◎”, and when the number exceeds 200 and less than 500, “◯”, and when the number exceeds 500. Was evaluated as “×”.

[Nozzle drying suppression]
In the nozzle of the apparatus used for forming the resist pattern, the degree to which the protective film forming composition was dried and foreign matter was generated was evaluated.
Using a coating nozzle that has not been subjected to dummy dispensing for 1 hour in an application / development apparatus (Lithius Pro-i, manufactured by Tokyo Electron), a protective film forming composition is spin-coated on the surface of a 12-inch silicon wafer and heated at 90 ° C. for 60 hours. A protective film having a thickness of 30 nm was formed by performing PB for 2 seconds. About the formed protective film, the coating defect number was measured using the inspection apparatus (2810, product made from KLA-Tencor). Nozzle drying suppression is "「 "when the number of coating defects measured is 150 or less per wafer, and" ○ "when 150 or more and 300 or less per wafer, and 300 per wafer. In the case of exceeding 500 and not more than 500, “Δ” was evaluated, and in the case of exceeding 500 per wafer, “×” was evaluated.

  As a reference example, in Example 2 above, instead of methylpentyl ketone, which is an organic solvent, a 2.38 mass% tetramethylammonium hydroxide aqueous solution, which is an alkaline developer, is used as a developing solution. Table 3 shows the evaluation results when resist pattern formation is performed using ultrapure water instead of 4-methyl-2-pentanol.

  From the results of Table 3, according to the protective film-forming composition of the present invention, while maintaining performances such as composition stability, protective film removability, receding contact angle, elution suppression, peeling resistance, and nozzle drying suppression. It is possible to suppress film loss in resist pattern formation, to improve the rectangularity of the cross-sectional shape of the resist pattern, and to suppress the occurrence of defects such as immersion defects, blob defects, bridge defects, etc. It was shown that it can.

  According to the protective film forming composition and the negative resist pattern forming method of the present invention, it is possible to form a resist pattern with few development defects, reduced film thickness reduction, and excellent cross-sectional rectangularity. Therefore, according to the said protective film formation composition and the negative resist pattern formation method using the same, it can use suitably for the semiconductor device manufacture from which refinement | miniaturization is anticipated further from now on.

Claims (4)

(1) a step of forming a resist film using a photoresist composition;
(2) A step of laminating a protective film on the resist film using the protective film-forming composition,
(3) a step of immersion exposure of the resist film on which the protective film is laminated, and (4) a step of developing the immersion exposed resist film using a developer containing an organic solvent,
The protective film forming composition is
[A] a fluorine atom-containing polymer, and [B] a solvent,
[B] the solvent comprises a carbon number of 5 or more alcohol Solvent,
[A] A structural unit in which the fluorine atom-containing polymer contains at least one selected from the group consisting of a group represented by the following formula (1), a group represented by the following formula (2), and a fluorinated alkyl group ( A negative resist pattern forming method comprising I) and a structural unit other than the structural unit (I) and a structural unit (II) containing a hydrocarbon group having 5 to 20 carbon atoms.

(In Formula (1), R ¹ is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R ² is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.
In Formula (2), R ³ is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ) (1) a step of forming a resist film using a photoresist composition;
(2) A step of laminating a protective film on the resist film using the protective film-forming composition,
(3) immersion exposure of the resist film on which the protective film is laminated; and
(4) A step of developing the immersion-exposed resist film using a developer containing an organic solvent.
Have
The protective film forming composition is
[A] a fluorine atom-containing polymer, and
[B] Solvent
Containing
[B] The solvent includes a chain ether solvent and an alcohol solvent having 5 or more carbon atoms,
[A] A structural unit in which the fluorine atom-containing polymer contains at least one selected from the group consisting of a group represented by the following formula (1), a group represented by the following formula (2), and a fluorinated alkyl group ( A negative resist pattern forming method comprising I) and a structural unit other than the structural unit (I) and a structural unit (II) containing a hydrocarbon group having 5 to 20 carbon atoms.

(In formula (1), R ¹ Is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R ² Is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.
In formula (2), R ³ Is a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ) [A] a fluorine atom-containing polymer, according to claim 1 or claim further comprising at least one selected from the group consisting of structural units containing a group resulting basic groups by the action of the structural units and acid containing a basic group negative resist pattern forming method as described in 2. The said protective film formation composition further contains at least 1 sort (s) chosen from the group which consists of a compound which produces | generates a basic compound by the effect | action of a [C] basic compound and an acid , Claim 2 or Claim 3 2. A negative resist pattern forming method as described in 1.