JP3679404B2 - Chain transfer agent, copolymer and method for producing copolymer using novel thiol compound - Google Patents

Description

  The present invention relates to a novel thiol compound useful as a chain transfer agent, a copolymer obtained by radical copolymerization using the thiol compound as a chain transfer agent, and a method for producing the same. More specifically, the present invention relates to a copolymer suitable as a film-forming polymer such as a resist polymer and an anti-reflection film polymer used in semiconductor lithography, a method for producing the same, and these film-forming polymers. The present invention relates to a novel thiol compound useful as a chain transfer agent in the production of a suitable copolymer.

In lithography used for manufacturing semiconductors, the formation of finer patterns is required as the degree of integration increases. Shortening the wavelength of the exposure light source is indispensable for pattern miniaturization, but now lithography using krypton fluoride (KrF) excimer laser light (wavelength 248 nm) is becoming the mainstream, and argon fluoride (ArF) excimer laser Lithography using light (wavelength 193 nm) with a line width of 100 nm or less is also being put into practical use. Furthermore, a fluorine dimer (F ₂ ) excimer laser beam (wavelength 157 nm)
), Lithography using extreme ultraviolet (EUV), X-rays, electron beams, etc. are in the development stage.

  The resist polymer used in these lithography techniques has a non-polar substituent and a repeating unit having a structure in which the non-polar substituent is decomposed by an acid and a polar group soluble in an alkali developer is expressed, A repeating unit having a polar group for improving adhesion to a semiconductor substrate is an essential component, and a repeating unit having a nonpolar substituent for adjusting the solubility in a resist solvent or an alkaline developer is included as necessary. Consists of. As these repeating units, for example, when using a KrF excimer laser as an exposure source, hydroxystyrenes and derivatives thereof are mainly used. When using an ArF excimer laser, hydroxystyrenes emit light having a wavelength of 193 nm. In order to absorb, (meth) acrylates and derivatives thereof have been studied.

  Specific examples of such a resist polymer include, for example, a copolymer using a (meth) acrylic acid monomer and a styrene monomer (for example, see Patent Documents 1 to 4) or hydroxystyrene in a system using a KrF excimer laser. Polymers partially protected with acetal (for example, see Patent Documents 5 to 8, etc.) are known, and in systems using ArF excimer laser, for example, copolymers of (meth) acrylic acid monomers having a lactone structure (For example, refer to Patent Documents 9 to 10).

  However, even a polymer containing a repeating unit having a polar group for enhancing the adhesion to a semiconductor substrate as described above has a terminal structure derived from a polymerization initiator or a chain transfer agent used during the polymerization reaction. Since the structure is not sufficient, there is a problem that it is impossible to cope with finer pattern formation.

  Also, in the formation of resist patterns, there is a problem that when the washing water volatilizes by drying after development and rinsing, the formed pattern collapses due to the surface tension of the water. Since the area of the contact substrate decreases, pattern collapse is likely to occur. In order to avoid this, it is necessary to keep the pattern aspect ratio (height ÷ width) low. On the other hand, to satisfy the dry etching resistance of the pattern, the coating film is thick, that is, the resist pattern has a high aspect ratio. There is a need to. Therefore, there has been a demand for a resist polymer that can increase the aspect ratio even in the formation of a fine pattern and has higher adhesion to the substrate so that pattern collapse does not occur.

  Therefore, a method has been studied in which a polar group is contained in a polymerization initiator or a chain transfer agent to enhance the substrate adhesion of a resist polymer. For example, as an example of incorporating a polar group into the polymerization initiator, a method using a polymerization initiator having an oxygen atom-containing group or a substituted or unsubstituted amino group in the molecule is known (see, for example, Patent Document 11). However, among the hydroxyl groups, carboxyl groups, substituted oxyl groups, substituted oxycarbonyl groups, acyl groups, substituted or unsubstituted carbamoyl groups, hydroxyimino groups, substituted or unsubstituted oxyimino groups mentioned as oxygen atom-containing groups, carboxyl groups In this method, even if the alkali solubility and the substrate adhesion can be improved, the water absorption of the polymer becomes too strong due to the introduction of the carboxyl group. In lithography, there is a problem that a stable pattern cannot be obtained. In addition, hydroxyl groups, substituted oxyl groups, substituted oxycarbonyl groups, acyl groups, and the like have low polarity and are insufficient to enhance substrate adhesion. Further, oxygen atom-containing groups containing nitrogen atoms such as substituted or unsubstituted carbamoyl groups, hydroxyimino groups, substituted or unsubstituted oxyimino groups, and substituted or unsubstituted amino groups are generated by a photoacid generator when used as a resist. Since the trapped acid is trapped, there is a problem such as a decrease in sensitivity, which is not practical.

  On the other hand, as an example of using a chain transfer agent having a polar group, a method using a carboxyl group-containing thiol such as mercaptoacetic acid or mercaptopropionic acid as a chain transfer agent (see, for example, Patent Document 12), and ester compounds thereof Alternatively, a method using a hydroxyl group-containing thiol such as mercaptoethanol (for example, see Patent Documents 13 to 14) is known. However, also in these methods, as in the case of the above polymerization initiator, the method using a carboxyl group-containing thiol has a problem that swelling easily occurs during alkali development, and an ester compound or a hydroxyl group-containing thiol is used. The method had insufficient substrate adhesion, and none of them reached a practical level.

Further, in lithography using a substrate with high reflectivity, there is a problem that halation occurs in the resist pattern due to the influence of reflected light, and a fine resist pattern cannot be accurately reproduced. In order to solve this problem, it has been proposed to form an antireflection film having a property of absorbing radiation reflected from the substrate under the resist film to be formed on the substrate. In addition to this antireflection film, a polymer for forming a coating film such as a film to be etched having a resolution by dry etching, which is formed in a lower layer of a resist layer in a multilayer resist, etc. Adhesion is important, and a polymer having better adhesion has been demanded.
JP 59-45439 A JP-A-5-113667 JP-A-7-209868 JP 11-65120 A JP 62-115440 A JP-A-4-219757 JP-A-3-223860 JP-A-4-104251 JP-A-9-73173 Japanese Patent Laid-Open No. 10-239846 Japanese Patent Laid-Open No. 2002-20424 Japanese Patent Laid-Open No. 10-55069 JP 2000-19737 A JP 2001-117231 A

  The present invention has been made in view of the background described above, and its purpose is to form a coating film for obtaining a resist pattern having high adhesion to a substrate and less pattern collapse in the formation of an extremely fine pattern in the production of a semiconductor. Provided are a novel copolymer suitable as a polymer, a method for producing the copolymer, and a novel thiol compound useful as a chain transfer agent in the production of a copolymer suitable as a film-forming polymer. There is.

  As a result of intensive studies to solve the above problems, the present inventors have dramatically improved the adhesion of the obtained copolymer to the substrate by using a novel thiol compound having a specific structure as a chain transfer agent. The present invention has been completed.

  That is, the present invention provides the following formula (1):

(Wherein R ¹ Represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms. )
A chain transfer agent useful for the production of a coating film-forming copolymer comprising the thiol compound represented by the formula:

The present invention also provides formula (2)
(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
A terminal structure represented by formula (3) to (9):
Formula (3)

Formula (4)

Formula (5)

Formula (6)

Formula (7)

Formula (8)

Formula (9)

{In the formulas (3) to (9), R ₁ is a hydrogen atom or a methyl group, R ₂ is a group selected from a hydrogen atom, a methyl group, and a trifluoromethyl group, and R is a formula (10) to (15) Is a polar group selected from }
Formula (10)

(Wherein R ₂₁ and R ₂₂ are each independently a hydrogen atom or a methyl group, m and n are each independently 0 or 1, and both are integers that are not 0, and o is a formula (3 ) Represents a bonding site with the repeating unit of (9).
Formula (11)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (12)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (13)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (14)

{In the formula, R ₂₃ represents a divalent alkyl group having 1 to 3 carbon atoms, and o represents a bonding site with the repeating unit of formulas (3) to (9). }
Formula (15)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
A copolymer for forming a coating film comprising a repeating unit (B) having a polar group for enhancing adhesion to a semiconductor substrate represented by formula (2), and a terminal represented by the above formula (2) The structure is represented by at least the above formulas (3) to (9), and R in the formula is an acid-dissociable group selected from formulas (16) to (18). A coating film-forming copolymer comprising a repeating unit (A) having a structure as described above is provided.
Formula (16)

{Wherein R ₁₁ is an alkyl group having 1 to 3 carbon atoms, R ₁₂ and R ₁₃ are both methyl groups, or one of them is a methyl group and the remaining is a 1-adamantyl group, or R ₁₂ and R ₁₃ are bonded to each other. In the alicyclic alkyl group having a monocyclic or bridged ring structure having 5 to 12 carbon atoms formed by o, o represents a bonding site with the repeating unit of the formulas (3) to (9). }
Formula (17)

{In the formula, R ₁₄ represents an alkyl group having 1 to 2 carbon atoms; R ₁₅ represents a chain or alicyclic alkyl group having 1 to 10 carbon atoms; o represents a repeating unit represented by formulas (3) to (9); Represents the bonding site. }
Formula (18)

{ O represents a bonding site with the repeating unit of formulas (3) to (9). }

The present invention further provides formula (1)
(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
The method for producing a coating film-forming copolymer as described above, wherein radical polymerization is performed in the presence of a thiol compound represented by the formula:

  The thiol compound of the present invention is useful as a chain transfer agent for producing a film-forming polymer having excellent substrate adhesion in lithography of semiconductor production, and is obtained by using this as a chain transfer agent. The copolymer of the invention is excellent in adhesion to the substrate, and can be suitably used as a coating film-forming polymer for forming a resist pattern with little pattern collapse particularly in the formation of a very fine pattern. Furthermore, since the terminal structure derived from the thiol compound of the present invention exhibits moderate alkali solubility in the copolymer of the present invention, the resist pattern at the interface between the exposed and unexposed areas is smoothed during pattern formation. Expected to improve edge roughness.

  Hereinafter, the present invention will be described in more detail.

In the novel thiol compound of the present invention, the substituent represented by R ¹ in the formula (1) is a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms. The structure is not particularly limited, and specific examples of R ¹ include the following structures.

Accordingly, specific examples of the novel thiol compound of the present invention represented by the formula (1) include compounds having the following structures, but the thiol compound of the present invention is not limited to these.

  The production method of the novel thiol compound of the present invention is not particularly limited. For example, 4,4-bis (trifluoromethyl) -4-hydroxy-1-butene, 5- (2-hydroxy-1,1,1,3) , 3,3-Hexafluoro-2-propyl) norbornene and other compounds containing 2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl group and having an ethylenic double bond A method of adding hydrogen sulfide; a method of adding a thiocarboxylic acid such as thioacetic acid or thiopropionic acid to the compound having an ethylenic double bond, followed by hydrolysis or alcoholysis; 4-chloro-1,1- Contains 2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl group such as bis (trifluoromethyl) -1-butanol, and contains chlorine or bromine atom Reacted with thiourea to compounds, the resulting thiuronium salts can be readily synthesized by such hydrolyzing under alkaline conditions.

  The copolymer of the present invention is obtained by radical copolymerization of two or more polymerizable compounds having an ethylenic double bond, using the thiol compound represented by the formula (1) as a chain transfer agent. It is done. Further, this copolymer has the following formula (2):

(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
Is included at the end.

  The hydroxyl group contained in the terminal structure has a pKa value smaller than that of a general alcoholic hydroxyl group due to the extremely large electron withdrawing property of the trifluoromethyl group, and has a pKa value equal to or less than that of a phenolic hydroxyl group. Show. For this reason, the copolymer of this invention is excellent in adhesiveness with the board | substrate used for semiconductor lithography, and can be conveniently used as coating-film formation polymers, such as a polymer for resists, and a polymer for antireflection films.

  Furthermore, particularly when used as a resist polymer, this terminal structure exhibits moderate alkali solubility equivalent to that of a phenolic hydroxyl group, so that the resist pattern at the interface between the exposed area and the unexposed area is smoothed. Expected to improve edge roughness. Here, line edge roughness refers to unevenness at the edge part of the line pattern and substrate interface, and is caused by resist characteristics such as diffusion of acid generated by exposure and solubility in an alkaline developer in unexposed areas. It occurs as a result. When this unevenness is transferred by an etching process using a resist as a mask, the electrical characteristics may be deteriorated and the yield may be lowered. The demand for is increasing.

  When the copolymer of the present invention is used as a polymer for forming a coating film in the above semiconductor lithography, if the content of the terminal structure represented by the formula (2) contained in the copolymer is too small, the adhesion to the substrate Such an improvement effect becomes insufficient. Therefore, the content of the terminal structure represented by the formula (2) is preferably 0.1 mol% or more with respect to the total number of monomer units contained in the copolymer, and is 0.5 mol% or more. More preferably.

  In order to make the content of the terminal structure represented by the above formula (2) within the above range, the amount used when the thiol compound of the present invention is used as a chain transfer agent is set to 0.00. The amount is preferably 1 mol or more, more preferably 0.5 mol or more. As the amount of the chain transfer agent used increases, the content of the terminal structure contained in the copolymer increases. On the other hand, the molecular weight of the obtained copolymer decreases, so that the desired average molecular weight is obtained. Select within the range where.

If the weight average molecular weight of the copolymer of the present invention is too high, the solubility in a solvent or an alkali developer used at the time of coating film formation will be low, while if it is too low, the coating film performance will be poor. ,
The range of 000 to 40,000 is preferable, and the range of 3,000 to 30,000 is more preferable.

  The raw material monomer used for radical copolymerization in the production of the copolymer of the present invention can be used without particular limitation as long as it is a polymerizable compound (monomer) having an ethylenic double bond. When a polymer is used as a coating film-forming polymer in semiconductor lithography, the structure required to exert its function varies depending on the specific application.

  First, when the obtained copolymer is used as a resist polymer, the copolymer of the present invention is at least a repeating unit having a structure that is decomposed by an acid and becomes soluble in an alkali developer. Includes a repeating unit (A) having a structure in which a non-polar substituent is decomposed by an acid and a polar group soluble in an alkali developer is expressed, and a repeating unit having a polar group for improving adhesion to a semiconductor substrate (B) is an essential component, and includes a repeating unit (C) having a nonpolar substituent for adjusting the solubility in a resist solvent or an alkaline developer as necessary.

  The repeating unit (A) which is decomposed by an acid and becomes alkali-soluble means a structure generally used as a resist from the past, and a monomer having a structure which is decomposed by an acid and becomes alkali-soluble is polymerized. Alternatively, after polymerizing a monomer having an alkali-soluble structure, the group having an alkali-soluble group (alkali-soluble group) in the alkali-soluble structure is not dissolved in an alkali but is dissociated by an acid (acid-dissociable group) It can obtain by protecting with.

  Examples of the monomer having a structure that is decomposed by an acid to become alkali-soluble include a compound in which an acid-dissociable group is bonded to a polymerizable compound containing an alkali-soluble substituent. And compounds having a phenolic hydroxyl group, a carboxyl group or a hydroxyfluoroalkyl group protected with a group.

Accordingly, specific examples of the polymerizable compound containing an alkali-soluble group include hydroxystyrenes such as p-hydroxystyrene, m-hydroxystyrene, and p-hydroxy-α-methylstyrene; acrylic acid and methacrylic acid. , trifluoromethyl acrylate, 5-norbornene-2-carboxylic acid, 2-trifluoromethyl-5-norbornene-2-carboxylic acid, carboxymethyl tetracyclo [4.4.0.1 ^2,5 .1 ^7,10 Carboxylic acids having an ethylenic double bond such as dodecyl methacrylate; p- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) styrene, 2- (4- (2 -Hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) cyclohexyl) -1,1,1,3,3,3-hexafur Ropropyl acrylate, 2- (4- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) cyclohexyl) -1,1,1,3,3,3-hexafluoro Polymerizable compounds having a hydroxyfluoroalkyl group such as propyltrifluoromethyl acrylate and 5- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) methyl-2-norbornane; Can be mentioned.

Examples of the acid-dissociable group include tert-butyl group, tert-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl 1-cyclohexyl group, 1-ethyl-1-cyclohexyl group. Group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 8-methyl-8-tricyclo [ 5.2.1.0 ^2,6 ] decanyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, 8-methyl-8-tetracyclo [4.4.0. 1 ^2,5 .1 ^7,10] dodecanyl group, 8-ethyl-8-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] saturated hydrocarbon group such as a dodecanyl group; 1-methoxyethyl Group, 1-ethoxyethyl group, 1-iso-propoxyethyl Group, 1-n-butoxyethyl group, 1-tert-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxy Ethyl group, methoxymethyl group, ethoxymethyl group, iso-propoxymethyl group, n-butoxymethyl group tert-butoxymethyl group, cyclopentyloxymethyl group, cyclohexyloxymethyl group, tricyclo [5.2.1.0 ^2,6 An oxygen-containing hydrocarbon group such as a decanyloxymethyl group or a tert-butoxycarbonyl group can be exemplified.

  After polymerizing a monomer having an alkali-soluble structure, when the alkali-soluble group in the alkali-soluble structure is protected with an acid-dissociable group, the compound having the alkali-soluble group is used in the polymerization reaction as it is, An acid dissociable group can be introduced by reacting with a compound that gives a substituent that does not dissolve in an alkali such as vinyl ether or halogenated alkyl ether under an acid catalyst. Examples of the acid catalyst used in the reaction include p-toluenesulfonic acid, trifluoroacetic acid, and strongly acidic ion exchange resin.

  On the other hand, examples of the monomer that gives the repeating unit (B) having a polar group for improving the adhesion to the semiconductor substrate include compounds having a phenolic hydroxyl group, a carboxyl group, or a hydroxyfluoroalkyl group as the polar group. Specifically, for example, as a polymerizable compound containing an alkali-soluble group, the above-described hydroxystyrenes, carboxylic acids having an ethylenic double bond, a polymerizable compound having a hydroxyfluoroalkyl group, and more polar to these In addition to a monomer substituted with a group, a monomer having a polar group bonded to an alicyclic structure such as a norbornene ring or a tetracyclododecene ring can be used.

As the polar group introduced into the repeating unit (B) as a substituent, those having a lactone structure are particularly preferable. For example, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and 1,3-cyclohexanecarbolactone. Examples include substituents containing a lactone structure such as 2,6-norbornanecarbolactone, 4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one, and mevalonic acid δ-lactone. . Examples of polar groups other than the lactone structure include hydroxyalkyl groups such as a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a 3-hydroxy-1-adamantyl group.

Furthermore, as a monomer which gives a repeating unit (C) having a nonpolar substituent for adjusting the solubility in a resist solvent or an alkali developer, which is contained as necessary, for example, a substitution not containing a polar group Or a compound having a polar group protected by an unsubstituted alkyl group or aryl group, or a nonpolar non-acid-decomposable group. Specific examples include styrene, α-methylstyrene, and P-methyl. styrenes such as styrene, acrylic acid, methacrylic acid, trifluoromethyl acrylate, norbornene carboxylic acid, 2-trifluoromethyl-norbornene carboxylic acid, carboxymethyl tetracyclo [4.4.0.1 ^2,5 .1 ^7,10 ] An ester compound in which an acid-stable nonpolar group is substituted for a carboxylic acid having an ethylenic double bond such as dodecyl methacrylate; norbornene, tet Examples thereof include alicyclic hydrocarbon compounds having an ethylenic double bond such as lacyclododecene. Examples of acid-stable nonpolar substituents that are ester-substituted to the carboxylic acid include methyl group, ethyl group, cyclopentyl group, cyclohexyl group, isobornyl group, and tricyclo [5.2.1.0 ^2,6 ] decanyl. group, 2-adamantyl group, and a tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecyl group.

  These monomers can be used by mixing one type or two or more types for each of the repeating units (A), (B) and (C), and the composition ratio of each repeating unit in the resulting resist polymer is The basic performance as a resist can be selected within a range not impairing. That is, in general, the repeating unit (A) is preferably 10 to 70 mol%, and more preferably 10 to 60 mol%. The composition ratio of the repeating unit (B) is preferably 30 to 90 mol%, more preferably 40 to 90 mol%, but for monomer units having the same polar group, 70 mol% or less. It is preferable that Furthermore, the composition ratio of the repeating unit (C) is preferably 0 to 50 mol%, more preferably 0 to 40 mol%.

  In addition, when the copolymer obtained as described above is used as a polymer for a lower layer coating film or an antireflection film of a multilayer resist, it is decomposed with the acid from the resist polymer structure to be alkali-soluble. A polymer having a structure excluding the repeating unit (A) is used. Since the composition ratio of each repeating unit in the copolymer varies depending on the intended use of the coating film, it cannot be defined unconditionally, but in general, the composition ratio of the repeating unit (B) is selected from the range of 10 to 100 mol%, The composition ratio of the repeating unit (C) is selected from the range of 0 to 90 mol%.

  In addition, when using the copolymer of the present invention as an antireflection film, it is necessary to include a crosslinking point and a structure that absorbs radiation irradiated in photolithography. Examples of the crosslinking point include a hydroxyl group, an amino group, A reactive substituent that can be cross-linked by an ester bond, a urethane bond or the like, such as an epoxy group, can be mentioned. Examples of the monomer containing a reactive substituent as a crosslinking point include hydroxystyrenes such as p-hydroxystyrene and m-hydroxystyrene, and the above-described polymerizable compounds such as the hydroxyl group, amino group, and epoxy group. A monomer substituted with a reactive substituent can be used as appropriate.

  Although the structure which absorbs the said radiation changes with wavelengths of the radiation to be used, for example with respect to ArF excimer laser light, the structure containing a benzene ring and its analog is used suitably. Examples of the monomer having such a structure include styrenes such as styrene, α-methylstyrene, p-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, and derivatives thereof; substituted or unsubstituted phenyl (meth) acrylate, Examples thereof include aromatic-containing esters having an ethylenic double bond such as substituted or unsubstituted naphthalene (meth) acrylate and substituted or unsubstituted anthracenemethyl (meth) acrylate. The monomer having a structure that absorbs radiation may be introduced as either the repeating unit (B) or (C) depending on the presence or absence of a polar group, but the composition ratio as a monomer having a structure that absorbs radiation is 10 It is preferably selected from the range of ˜100 mol%.

On the other hand, the method for producing a copolymer of the present invention is a method for producing a copolymer by radical copolymerization of two or more polymerizable compounds having an ethylenic double bond, which is represented by the formula (1). The polymerization initiator used in the polymerization reaction at this time is not particularly limited as long as it is generally used as a radical generator. For example, 2,2 ′ -Azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), dimethyl 2,2'-azobisisobutyrate, 1,1'-azobis (cyclohexane-1-carbonitrile), 4,4 Azo compounds such as' -azobis (4-cyanovaleric acid), decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethylhexanoyl) Peroxide, succinic acid peroxide, a tert- butyl peroxy-2-hexanoate and organic peroxide to ethyl can be used alone or in combination. The amount of the polymerization initiator used depends on the raw material monomer used in the polymerization reaction, the type and amount of the chain transfer agent, and the polymerization conditions such as the polymerization temperature and the polymerization solvent. It is selected from the range of 0.01 to 10 mol, preferably 0.1 to 5 mol, relative to 1 mol.

  As a polymerization method for producing the copolymer of the present invention, solution polymerization is preferable, and radical copolymerization is preferably performed in a state in which a raw material monomer, a polymerization initiator, and a chain transfer agent are dissolved in a polymerization solvent. Solution polymerization can be performed by, for example, a so-called batch polymerization method in which all monomers, initiators, and chain transfer agents are dissolved in a polymerization solvent and heated to the polymerization temperature, or some or all of the monomers, initiators, and chain transfer agents are polymerized at the polymerization temperature. It can carry out by what is called the dropping polymerization method etc. which are dripped in the polymerization system heated to.

  The solvent used in the polymerization reaction is not particularly limited as long as it is a solvent that can stably dissolve the raw material monomer, the obtained copolymer, the polymerization initiator, and the chain transfer agent. Specific examples of the polymerization solvent include ketones such as acetone, methyl ethyl ketone and methyl amyl ketone; ethers such as tetrahydrofuran, dioxane, glyme and propylene glycol monomethyl ether; esters such as ethyl acetate and ethyl lactate; propylene glycol methyl Examples include ether esters such as ether acetate, and lactones such as γ-butyrolactone, and these can be used alone or in combination. Although there is no restriction | limiting in particular in the usage-amount of a polymerization solvent, Usually, it is 0.5-20 weight part with respect to 1 weight part of monomers, Preferably it is 1-10 weight part. If the amount of the solvent used is too small, the monomer or copolymer may be precipitated, and if it is too large, the rate of the polymerization reaction may be insufficient.

  The polymerization reaction conditions are not particularly limited, but in general, the reaction temperature is preferably about 60 ° C to 100 ° C, and the reaction time is preferably about 1 hour to 20 hours.

  The polymer obtained by the above polymerization reaction is prepared by dropping the polymerization reaction liquid into a poor solvent alone or a mixed solvent of a poor solvent and a good solvent, and further washing as necessary to obtain unreacted monomers and oligomers. In addition, unnecessary substances such as a polymerization initiator, a chain transfer agent, and a reaction residue thereof can be removed and purified. The poor solvent is not particularly limited as long as the obtained copolymer does not dissolve in the solvent. For example, water, alcohols such as methanol and isopropanol, and saturated hydrocarbons such as hexane and heptane can be used. . The good solvent is not particularly limited as long as it is a solvent in which a monomer, an oligomer, a polymerization initiator, a chain transfer agent, and these reaction residues are dissolved, but the same solvent as the polymerization solvent is preferable in terms of management of the production process.

  The use form of the copolymer of the present invention obtained as described above is not particularly limited, but when used as a film-forming polymer in semiconductor lithography, it is usually used by dissolving in a solvent for film-forming. Is done. Since the copolymer after purification contains the solvent used for purification, it can be dried under reduced pressure and then dissolved in a solvent for forming a coating film, or a good solvent such as a solvent for forming a coating film or a polymerization solvent as it is Then, the solvent for forming a coating film is supplied as necessary, and the other solvent can be distilled off under reduced pressure to finish the coating film forming solution.

  The solvent for forming the coating film is not particularly limited as long as it dissolves the copolymer. However, usually considering the boiling point, the influence on the semiconductor substrate and other coating films, and the absorption of radiation used in lithography. Selected. Examples of solvents generally used for forming a coating film include solvents such as propylene glycol methyl ether acetate, ethyl lactate, methyl amyl ketone, γ-butyrolactone, and cyclohexanone. Although the usage-amount of a solvent is not restrict | limited in particular, Usually, it is the range of 1 weight part-20 weight part with respect to 1 weight part of copolymers.

  When the copolymer of the present invention is used as a resist polymer, a radiation-sensitive acid generator and a nitrogen-containing compound for preventing acid diffusion to a portion not exposed to radiation are added to the coating film-forming solution. An acid diffusion control agent such as the above can be added to finish the resist composition. As the radiation-sensitive acid generator, those generally used as a resist raw material such as an onium salt compound, a sulfone compound, a sulfonic acid ester compound, a sulfonimide compound, and a disulfonyldiazomethane compound can be used. In addition, compounds that are commonly used as resist additives such as dissolution inhibitors, sensitizers, and dyes can be added to the resist composition as necessary.

The compounding ratio of each component (excluding the resist solvent) in the resist composition is not particularly limited. Generally, the polymer concentration is 10 to 50% by mass, the radiation sensitive acid generator is 0.1 to 10% by mass, and the acid diffusion controller. It is selected from the range of 0.001 to 10% by mass.

  When the obtained copolymer of the present invention is used as an antireflection film, it is used alone or mixed with bifunctional or higher functional isocyanates, amines, epoxides or the like capable of crosslinking between polymers.

EXAMPLES Next, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples. In addition, the average copolymer composition of the obtained copolymer was calculated | required from the measurement result of ¹³ C-NMR. The weight average molecular weight Mw and the degree of dispersion Mw / Mn were determined from the measurement results of gel permeation chromatography (GPC).

Example 1
Preparation of 4-mercapto-1,1-bis (trifluoromethyl) -1-butanol:
A flask equipped with a stirrer, a thermometer, and a condenser was charged with 20 g (96.1 mmol) of 4,4-bis (trifluoromethyl) -4-hydroxy-1-butene and 8.05 g (105. mmol) of thioacetic acid under a nitrogen atmosphere. 7 mmol), 1,4-dioxane 60 g, and 2,2′-azobisisobutyronitrile (hereinafter referred to as “AIBN”) 0.79 g (4.8 mmol) were added and heated to 70 ° C. with stirring. . During the reaction, thioacetic acid and AIBN were added at an appropriate time, and after confirming that the substrate was completely consumed, the reaction solution was distilled under reduced pressure as it was, and the intermediate product 4-acetylthio-1,1-bis (tri 22 g (76.9 mmol) of fluoromethyl) -1-butanol was obtained.

  Next, 14 g (49.3 mmol) of 4-acetylthio-1,1-bis (trifluoromethyl) -1-butanol obtained above was added to a flask equipped with a stirrer, a thermometer, and a condenser under a nitrogen atmosphere. 12.6 g and 2.81 g (30 mol%) of paratoluenesulfonic acid monohydrate were added, and the mixture was stirred under reflux until the substrate was completely consumed. Thereafter, the reaction solution was returned to room temperature, extracted with ethyl acetate, washed with water, then distilled under reduced pressure, and 4-mercapto-1,1-bis (trifluoromethyl)-represented by the following formula (1-c). 10.7 g (44.3 mol) of 1-butanol (hereinafter referred to as “compound (1-c)”) was obtained.

In addition, the structure of the obtained compound (1-c) was confirmed by the following analysis results.
(1) Mass spectrum (GC-MS)
m / z: 242 (M ⁺ ), 209, 190, 171, 155, 139, 121, 91, 69, 47
(2) ¹ H-NMR spectrum (CDCl ₃ solvent)
δ (ppm): 3.48 (1H, br), 2.58 (2H, q like, J = 5.4 Hz, 7.8), 2.10 to 2.05 (2H, m), 1.92 ˜1.85 (2H, m), 1.43 (1H, t, J = 7.8 Hz)
(3) ¹³ C-NMR spectrum (CDCl ₃ solvent)
δ (ppm): 123.1 (CF ₃ , q, J = 287 Hz), 77.4-75.4 ( C —CF ₃ , m), 28.9 (CH ₂ ), 26.1 (CH ₂ ) 24.5 (CH ₂ )

Example 2
Production of copolymer 1 represented by the following structural formula and containing —SC ₃ H ₆ C (CF ₃ ) ₂ OH group at a part of the polymer chain end:

In a container maintained in a nitrogen atmosphere, 150 g of methyl ethyl ketone (hereinafter referred to as “MEK”), 33.2 g of 5-methacryloyloxy-2,6-norbornanecarbolactone (hereinafter referred to as “NLM”), 2-methyl-2- 44.7 g of adamantyl methacrylate (hereinafter referred to as “MAM”) and 1.65 g of the compound (1-c) obtained in Example 1 were charged and dissolved as a chain transfer agent to prepare a monomer feed solution. Moreover, MEK20g and AIBN0.45g as a polymerization initiator were prepared and melt | dissolved in another container kept in nitrogen atmosphere, and the initiator feed liquid was prepared. 65 g of MEK was charged in a polymerization tank maintained in a nitrogen atmosphere and heated to 80 ° C. while stirring, and then the monomer feed liquid and the initiator feed liquid were both fed to the polymerization tank maintained at 80 ° C. for 4 hours for polymerization. It was. The feed ratios of the raw material monomer and the chain transfer agent are shown in Table 1. After feeding, the mixture was aged for 2 hours while maintaining at 80 ° C. After completion of the reaction, the reaction solution was cooled to room temperature, and the polymerization solution was dropped into methanol to cause reprecipitation. The precipitate was filtered, washed with methanol, filtered, and the obtained wet cake was dried with a vacuum dryer to obtain a white polymer powder (Copolymer 1). When the content of the terminal structure derived from the thiol compound in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.5 mol% with respect to the total number of monomer units contained in the polymer.

  Further, the obtained copolymer 1 was dissolved in propylene glycol methyl ether acetate (hereinafter referred to as “PGMEA”) to form a 20% solution, and 1,1,1,3,3,3-hexamethyldisilazane in advance. The treated silicon wafer was spin coated and baked at 110 ° C. for 90 seconds to form a coating film having a thickness of 1.0 μm. About the obtained coating film, the peeling strength and peeling mode of the coating film were measured in the constant load mode using the Daipura-Wintes SAICAS CN-20 type | mold. Table 2 shows the physical properties of the obtained copolymer 1 and the measurement results of the peel strength and peel mode of the coating film.

Example 3
Production of copolymer 2 represented by the following structural formula and containing —SC ₃ H ₆ C (CF ₃ ) ₂ OH group at a part of the polymer chain end:

150 g in a container kept in a nitrogen atmosphere 150 g, γ-butyrolactone-2-yl methacrylate (hereinafter referred to as “GBLM”) 28.9 g, tert-butyl methacrylate (hereinafter referred to as “TBMA”) 24.2 g As a chain transfer agent, 1.65 g of the compound (1-c) obtained in Example 1 was charged and dissolved to prepare a monomer feed solution. Further, 20 g of MEK and 1.5 g of AIBN as a polymerization initiator were charged and dissolved in another container kept in a nitrogen atmosphere to prepare an initiator feed solution. 65 g of MEK was charged in a polymerization tank maintained in a nitrogen atmosphere and heated to 80 ° C. while stirring, and then the monomer feed liquid and the initiator feed liquid were both fed to the polymerization tank maintained at 80 ° C. for 4 hours for polymerization. It was. The feed ratios of the raw material monomer and the chain transfer agent are shown in Table 1. After feeding, the mixture was aged for 2 hours while maintaining at 80 ° C. After completion of the reaction, the reaction solution was cooled to room temperature, and the polymerization solution was dropped into methanol to cause reprecipitation. The precipitate was filtered, washed with methanol, filtered, and the obtained wet cake was dried with a vacuum dryer to obtain a white polymer powder (copolymer 2). When the content of the terminal structure derived from the thiol compound in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.5 mol% with respect to the total number of monomer units contained in the polymer. Table 2 shows the properties of the obtained copolymer 2 and the measurement results of the peel strength and peel mode of the coating film obtained in the same manner as in Example 2.

Comparative Example 1
In Example 2, polymerization was performed in the same manner except that 0.53 g of 2-mercaptoethanol (hereinafter referred to as “MEO”) was used as a chain transfer agent, and Comparative Example 1 was obtained. When the content of the terminal structure derived from MEO in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.5 mol% with respect to the total number of monomer units contained in the polymer. Table 1 shows the charging ratio of the raw material monomer and the chain transfer agent, and Table 2 shows the properties of the copolymer 3 obtained and the measurement results of the peeling strength and peeling mode of the coating film.

Comparative Example 2
In Example 3, polymerization was carried out by the same procedure except that 0.53 g of MEO was used as a chain transfer agent, and Comparative Example 2 was obtained. When the content of the terminal structure derived from MEO in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.5 mol% with respect to the total number of monomer units contained in the polymer. Table 1 shows the charging ratio of the raw material monomer and the chain transfer agent, and Table 2 shows the properties of the copolymer 4 obtained and the measurement results of the peeling strength and peeling mode of the coating film.

Example 4
Preparation of 1,1,1,3,3,3-hexafluoro-2- (5 or 6-mercapto-bicyclo [2.2.1] hept-2-ylmethyl) propan-2-ol:
To a three-necked round bottom flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, 12.21 g (160 mmol) of thioacetic acid was added and heated to 80 ° C. When the internal temperature reached 80 ° C., 0.336 g (1.46 mmol) of dimethyl-2,2′-azobisisobutyrate
1) and 2-bicyclo [2.2.1] hept-5-en-2-ylmethyl-1,1,1,3,3,3-hexafluoropropan-2-ol 40 g (146 mmol) The solution was dropped from the dropping funnel over 2 hours, and the stirring was further continued at 80 ° C. for 2 hours. Thereafter, 19 g of methanol and 3.384 g (17.8 mmol) of paratoluenesulfonic acid monohydrate were added to the reaction solution, followed by stirring for 2 hours under reflux. Next, the reaction solution was returned to room temperature and washed twice with a 7% aqueous sodium hydrogen carbonate solution and water, respectively. The obtained organic phase was distilled under reduced pressure and 1,1,1,3,3,3-hexafluoro-2- (6-mercapto-bicyclo [2.2.1] hept- 2-ylmethyl) propan-2-ol (formula (1-j) below) and 1,1,1,3,3,3-hexafluoro-2- (5-mercapto-bicyclo [
2.2.1] 24.7 g of a mixture of hept-2-ylmethyl) propan-2-ol (the following formula (1-k)) (hereinafter referred to as “compound (1-jk)”) was obtained.

The obtained compound (1-jk) was subjected to structural analysis by the following analysis, and it was confirmed that four kinds of isomers represented by the following formulas were included. The gas chromatographic purity (total of 4 types) was 98%.
(1) Mass spectrum (GC-MS)
m / z: 308 (M ⁺ )
(2) ¹ H-NMR spectrum (DMSO-d ₆ solvent)
δ (ppm): 7.65~7.58 (1H , br), 3.14~2.78 (1H, m), 2.54~2.48 (1H, m, S H), 2.17 ˜1.12 (10H, m), 0.81 to 0.66 (1H, m)
(3) ¹³ C-NMR spectrum (C ₆ D ₆ solvent)
δ (ppm): 128.2 (q, C ₃ F ₃ ), 76.9 (m, C ₃ -CF ₃ ), 53.3 (CH), 51.9 (CH), 47.5 (CH), 47 .2 (CH), 43.5 (CH), 43.0 (CH ₂ ), 42.5 (CH), 42.4 (CH ₂ ), 41.1 (CH ₂ ), 40.5 (CH) 40.3 (CH), 39.5 (CH), 38.8 (CH ₂ ), 38.4 (CH ₂ ), 37.9 (CH), 37.6 (CH ₂ ), 37.3 ( _{CH), 36.9 (CH 2)} , 36.7 (CH 2), 36.6 (CH 2), 36.4 (CH 2), 35.5 (CH), 35.3 (CH 2), 34.8 (CH), 34.0 (CH), 33.9 (CH), 33.0 (CH ₂ ), 32.5 (CH ₂ ), 32.4 (CH), 32.3 (CH ₂ ), 32. _(CH 2)

Example 5 Production of copolymer 5 represented by the following structural formula and containing a terminal structure derived from a thiol compound represented by the following formula (19) at a part of the polymer chain terminal:

In Example 2, polymerization was performed in the same manner except that 2.10 g of the compound (1-jk) obtained in Example 4 was used as the chain transfer agent. When the content of the terminal structure derived from the thiol compound in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.4 mol% with respect to the total number of monomer units contained in the polymer. Table 1 shows the charging ratio of the raw material monomer and the chain transfer agent, and Table 2 shows the properties of the copolymer 5 and the measurement results of the peeling strength and peeling mode of the coating film.

Example 6
Production of copolymer 6 represented by the following structural formula and containing a terminal structure derived from a thiol compound represented by the following formula (19) at a part of the polymer chain terminal:

In Example 3, polymerization was performed in the same manner except that 2.10 g of the compound (1-jk) obtained in Example 4 was used as the chain transfer agent. When the content of the terminal structure derived from the thiol compound in the obtained polymer was determined by ¹³ C-NMR measurement, it was 1.4 mol% with respect to the total number of monomer units contained in the polymer. Table 1 shows the charging ratio of the raw material monomer and the chain transfer agent, and Table 2 shows the properties of the copolymer 6 and the measurement results of the peeling strength and peeling mode of the coating film.

As these results show, the copolymer obtained by using the thiol compound of the present invention as a chain transfer agent has dramatically improved peel strength as compared with the prior art, and has very good substrate adhesion. It turns out that it is excellent.

Claims (4)

Formula (1)

(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
A chain transfer agent useful for the production of a coating film-forming copolymer , characterized by comprising a thiol compound represented by the formula: Formula (2)
(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
A terminal structure represented by formula (3) to (9):
Formula (3)

Formula (4)

Formula (5)

Formula (6)

Formula (7)

Formula (8)

Formula (9)

{In the formulas (3) to (9), R ₁ is a hydrogen atom or a methyl group, R ₂ is a group selected from a hydrogen atom, a methyl group, and a trifluoromethyl group, and R is a formula (10) to (15) Is a polar group selected from }
Formula (10)

(Wherein R ₂₁ and R ₂₂ are each independently a hydrogen atom or a methyl group, m and n are each independently 0 or 1, and both are integers that are not 0, and o is a formula (3 ) Represents a bonding site with the repeating unit of (9).
Formula (11)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (12)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (13)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
Formula (14)

{In the formula, R ₂₃ represents a divalent alkyl group having 1 to 3 carbon atoms, and o represents a bonding site with the repeating unit of formulas (3) to (9). }
Formula (15)

{In the formula, o represents a bonding site with the repeating units of the formulas (3) to (9). }
And a repeating unit (B) having a polar group for enhancing adhesion to a semiconductor substrate represented by the formula: Formula (2)
(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
A terminal structure represented by formula (3) to (9):
Formula (3)

Formula (4)

Formula (5)

Formula (6)

Formula (7)

Formula (8)

Formula (9)

{In Formulas (3) to (9), R ₁ is a hydrogen atom or a methyl group, R ₂ is a group selected from a hydrogen atom, a methyl group, and a trifluoromethyl group, and R is a formula (16) to (18) It is an acid dissociable group selected from }
Formula (16)

{Wherein R ₁₁ is an alkyl group having 1 to 3 carbon atoms, R ₁₂ and R ₁₃ are both methyl groups, or one of them is a methyl group and the remaining is a 1-adamantyl group, or R ₁₂ and R ₁₃ are bonded to each other. In the alicyclic alkyl group having a monocyclic or bridged ring structure having 5 to 12 carbon atoms formed by o, o represents a bonding site with the repeating unit of the formulas (3) to (9). }
Formula (17)

{In the formula, R ₁₄ represents an alkyl group having 1 to 2 carbon atoms; R ₁₅ represents a chain or alicyclic alkyl group having 1 to 10 carbon atoms; o represents a repeating unit represented by formulas (3) to (9); Represents the bonding site. }
Formula (18)

{ O represents a bonding site with the repeating unit of formulas (3) to (9). }
And a repeating unit (A) having a structure which is decomposed by an acid and becomes soluble in an alkali developer. Formula (1)
(In the formula, R ¹ represents a divalent substituent composed of a linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.)
The method for producing a copolymer for forming a coating film according to claim 2, wherein radical polymerization is performed in the presence of a thiol compound represented by the formula: