JP5162111B2 - POSITIVE PHOTOSENSITIVE RESIN, PROCESS FOR PRODUCING THE SAME AND RESIST COMPOSITION CONTAINING POSITIVE PHOTOSENSITIVE RESIN - Google Patents

Description

  The present invention relates to a positive photosensitive resin suitably used in semiconductor lithography, a method for producing the same, and a resist composition containing the positive photosensitive resin.

Lithography employed for semiconductor manufacturing requires the formation of finer patterns as the degree of integration increases. Shortening the wavelength of an exposure light source is indispensable for pattern miniaturization. At present, lithography using a KrF excimer laser as a light source is becoming mainstream, and lithography using an ArF excimer laser is also being put into practical use. Furthermore, various types of short-wavelength radiation lithography techniques using F ₂ excimer laser, EUV, X-ray, electron beam, etc. are in the development stage.

  As a photoresist which is a photosensitive resin used in semiconductor lithography, a chemically amplified positive resist developed by Ito et al. Of IBM is now essential. This chemically amplified positive resist is a technique for increasing the sensitivity of a resist by causing an acid-catalyzed deprotection reaction of a protecting group that is dissociated by an acid (acid-dissociable protecting group).

  Further, as specific examples of the resist polymer containing these acid-dissociable protecting groups, in KrF lithography, a copolymer containing a repeating unit derived from hydroxystyrene and a repeating unit derived from acid-dissociable alkoxystyrene is derived from hydroxystyrene. A copolymer containing a repeating unit and a repeating unit derived from an acid dissociable alkyl (meth) acrylate, a polymer obtained by protecting a part of a repeating unit derived from hydroxystyrene with an acetal, etc. are known. ArF lithography contains a lactone structure. A copolymer having a repeating unit derived from (meth) acrylate and a repeating unit derived from acid-dissociable alkyl (meth) acrylate is known.

  These copolymers are all chemically amplified positive resists with high sensitivity, but it is difficult to obtain sufficient resist performance with these protective groups alone, as resist patterns need to be further miniaturized. It is becoming.

  Therefore, a photoresist in which a cross-linking site dissociated by an acid is introduced into a side chain of a copolymer containing a repeating unit having an acid-dissociable protecting group has also been studied (see, for example, Patent Documents 1 to 3).

  This is because the dissolution contrast between the exposed region and the unexposed region is improved by cutting the cross-linking bond with an acid catalyst, but the polymerization of the polymer as the photoresist is difunctional such as diacrylate. Because the molecular weight distribution of the polymer to be produced is extremely large and the solubility is poor, and an ultra-high molecular weight polymer is likely to be produced. However, even after decomposition with an acid, there is a hardly soluble high molecular weight component that is difficult to dissolve in an alkaline developer, and there is a problem that a defect occurs when a fine pattern is formed due to this undissolved residue.

  In addition, in the example (Patent Document 1) in which a cross-linked polymer having a cross-linked site having an acid-unstable acetal skeleton in the polymer side chain is used as a resist polymer, it is very sensitive to acid. There was a tendency that the storage stability was poor, and there was a tendency that the solubility was deteriorated and the undissolved residue was present as described above.

JP 2001-98034 A JP 2000-214587 A JP 2001-106737 A

  The present invention has been made in view of the above-described technical background, and its object is to form a positive photosensitive resin that is used for fine pattern formation in semiconductor manufacturing and has a higher sensitivity than conventional products, its manufacturing method, and the present invention. An object of the present invention is to provide a resist composition containing a positive photosensitive resin.

The invention according to claim 1, which has been made in order to solve the above problems, is a copolymer obtained by polymerizing two or more polymerizable compounds having an ethylenic double bond, which is cleaved by an acid. General formula (2) including a bond

(In the formula, R ₁ represents a single bond, or a linear or branched hydrocarbon having 1 to 5 carbon atoms, and R ₂ may be the same or different independently from each other, and may be a linear chain having 1 to 5 carbon atoms. Or a branched hydrocarbon.)
General formula (1) obtained by polymerizing in the presence of a polyvalent thiol represented by formula (1), which is derived from the polyvalent thiol and contains a bond cleaved by an acid.

(In the formula, R ₁ represents a single bond, or a linear or branched hydrocarbon having 1 to 5 carbon atoms, and R ₂ may be the same or different independently from each other, and may be a linear chain having 1 to 5 carbon atoms. Or a branched hydrocarbon.)
It is a positive photosensitive resin characterized by having an acetal structure represented by

The invention according to claim 2 is the positive photosensitive resin according to claim 1 , which is a copolymer containing at least a repeating unit having a phenolic hydroxyl group.

The invention according to claim 3 is the positive photosensitive resin according to claim 1 , which is a copolymer including a repeating unit in which at least a phenolic hydroxyl group is acetalized.

The invention according to claim 4 is the positive photosensitive resin according to claim 1 , which is a copolymer containing a repeating unit derived from at least a (meth) acrylate derivative having an alicyclic skeleton.

The invention according to claim 5 is the positive photosensitive resin according to claim 1 , which is a copolymer containing at least a repeating unit derived from a (meth) acrylate derivative having a lactone skeleton.

In the invention according to claim 6 , two or more polymerizable compounds having an ethylenic double bond are represented by the general formula (2).

(In the formula, R ₁ is a single bond or represents a linear or branched hydrocarbon of from 1 to carbon atoms 5, R _2, independently of one another, may be identical or different, straight-chain of from 1 to 5 carbon or an branched hydrocarbon.)
And a method for producing a positive photosensitive resin, wherein the polymerization is carried out in the presence of a polyvalent thiol represented by the formula:

The invention according to claim 7 is a resist composition comprising at least the positive photosensitive resin according to any one of claims 1 to 5 and a photoacid generator.

The invention according to claim 8 has the formula

It is a polyvalent thiol characterized by these.

  There are few attempts to introduce an acid-dissociable structure into the main chain of a positive-type photosensitive resin. By introducing an acid-dissociable structure into the main chain, there is no generation of ultra-high molecular weight components, and the positive type has a narrow molecular weight distribution. A photosensitive resin can be obtained. In addition, by using this positive photosensitive resin in semiconductor lithography, defects caused by insoluble components are reduced, and the sensitivity can be greatly improved.

The positive photosensitive resin of the present invention is a copolymer obtained by polymerizing two or more polymerizable compounds having an ethylenic double bond, and has a general formula (2 )

General formula (1) obtained by polymerizing in the presence of a polyvalent thiol represented by formula (1), which is derived from the polyvalent thiol and contains a bond cleaved by an acid.

It is characterized by having an acetal structure represented by

In the above formulas (1) and (2) , R ₁ represents a single bond or a linear or branched hydrocarbon having 1 to 5 carbon atoms. Specific examples other than the single bond include the following structures: However, it is not limited to these.

In the above formulas (1) and (2) , R ₂ may be the same or different independently of each other, and represents a linear or branched hydrocarbon having 1 to 5 carbon atoms . Specific examples are as follows. Examples include, but are not limited to, structures.

  On the other hand, the raw material monomer used in the production of the positive photosensitive resin of the present invention is not particularly limited as long as it is a polymerizable compound (monomer) having an ethylenic double bond. The repeating unit (A) having a structure that increases the solubility in the developer and the repeating unit (B) having a polar group for improving the adhesion to the substrate are essential components, and if necessary, a resist solvent or an alkaline developer. It is comprised including the repeating unit (C) which has a nonpolar structure in order to adjust the solubility to glycerol.

  The repeating unit (A) having a structure that is dissociated by an acid and increases the solubility in an alkali developer means a structure that is conventionally used as a resist, and has a structure that is conventionally dissociated by an acid and has a solubility in an alkali developer. It can be obtained by polymerizing a monomer having an increasing structure or polymerizing a monomer having an alkali-soluble structure and then protecting the alkali-soluble group with an acid-dissociable protecting group.

  Examples of the monomer having a structure that is dissociated by an acid to increase the solubility in an alkali developer include compounds in which an alkali-soluble group is protected with an acid-dissociable protecting group, such as a phenol protected with an acid-dissociable protecting group. And compounds having a functional hydroxyl group, a carboxyl group or a hydroxyfluoroalkyl 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. , Trifluoromethylacrylic acid, 5-nerbornene-2-carboxylic acid, 2-trifluoromethyl-5-norbornene-2-carboxylic acid, carboxytetracyclo [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-hexafluoropropyl acrylate, 2- (4 -(2-hydroxy 1,1,1,3,3,3-hexafluoro-2-propyl) cyclohexyl) -1,1,1,3,3,3-hexafluoropropyl trifluoromethyl acrylate, 5- ( Examples thereof include polymerizable compounds having a hydroxyfluoroalkyl group such as 2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) methyl-2-norbornene. it can.

Examples of the acid dissociable protecting group include t-butyl group, t-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1 -Cyclohexyl 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 dodecanyl group; 1-methoxyethyl group, 2-ethoxyethyl group, 1-iso-propoxyethyl group, 1-n-butoxyethyl group, 1-t-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxyethyl group, 1-methoxymethyl group, 2-
Ethoxymethyl group, 1-iso-propoxymethyl group, 1-n-butoxymethyl group, 1-t
Oxygenated carbonization such as -butoxymethyl group, 1-cyclopentyloxymethyl group, 1-cyclohexyloxymethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxymethyl group, t-butoxycarbonyl group A hydrogen group etc. can be mentioned.

  When a monomer having an alkali-soluble structure is polymerized and then the alkali-soluble group is protected with an acid-dissociable protecting group, the compound having the alkali-soluble group is used in the polymerization reaction as it is, and then the acid catalyst is used. An acid dissociable protecting group can be introduced by reacting with a compound such as vinyl ether or halogenated alkyl ether. 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 enhancing the adhesion to the substrate include compounds having a phenolic hydroxyl group, a carboxyl group, or a hydroxyalkyl 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 further, a polar group is present. In addition to the substituted monomer, a monomer in which a polar group is 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), those having a lactone structure are particularly preferred. For example, γ-butyrolactone, γ-valerolactone, δ-valerolactone, 1,3-cyclohexanecarbolactone, 2, Examples include substituents containing a lactone structure such as 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 hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, 3-hydroxy-1
-Hydroxyalkyl groups, such as an adamantyl group, etc. can be mentioned.

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 an unsubstituted alkyl group or aryl group, a compound having a polar group protected by a nonpolar non-acid-dissociable protecting group, and the like. Specific examples include styrene, α-methylstyrene, p -Styrenes such as methylstyrene; acrylic acid, methacrylic acid, trifluoromethylacrylic acid, norbornenecarboxylic acid, 2-trifluoromethylnorbornenecarboxylic acid, carboxytetracyclo [4.4.0.1 ^2,5 . ^1,7,10 ] ester compounds in which acid-stable nonpolar groups are substituted on carboxylic acids having ethylenic double bonds such as dodecyl methacrylate; alicyclic carbons having ethylenic double bonds such as norbornene and tetracyclododecene A hydrogen compound etc. can be mentioned. 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, tricyclo [5.2.1.0 ^2,6 ] decanyl. Group, 2-adamantyl group, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group and the like.

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 each repeating unit in the resulting positive photosensitive resin of the present invention can be used. The composition ratio of units can be selected within a range that does not impair the basic performance as a resist. 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 the monomer unit having the same polar group, 70 mol% The following is preferable. Furthermore, the composition ratio of the repeating unit (C) is preferably 0 to 50 mol%, more preferably 0 to 40 mol%.

In the positive photosensitive resin of the present invention, if the content of the structure derived from the polyvalent thiol represented by the general formula (1) contained in the polymer main chain is too small, the effect of improving the resist sensitivity is insufficient. Therefore, the content of the structure is preferably 0.1 mol% or more, and more preferably 0.5 mol% or more with respect to the total number of monomer units contained in the resin.

  In order to bring the content of the structure derived from the polyvalent thiol into the above range, the amount of the polyvalent thiol described later, for example, is 0.1 mol or more with respect to 100 mol of the raw material monomer in the polymerization. It is preferable that the amount be 0.5 mol or more. In addition, as the amount of the polyvalent thiol used increases, the content of the structure in the resin increases. On the other hand, the molecular weight of the obtained copolymer decreases, so that a desired average molecular weight can be obtained. select.

  If the weight average molecular weight of the positive photosensitive resin 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 film performance will be poor. The range of 1000-200000 is preferable, and the range of 3000-30000 is more preferable.

Next, the manufacturing method of the positive photosensitive resin of this invention is demonstrated. The positive photosensitive resin of the present invention is obtained by polymerizing two or more polymerizable compounds having an ethylenic double bond in the presence of a polyvalent thiol represented by the following general formula (2), More specifically, the polyvalent thiol represented by the following general formula (2) can be used as a chain transfer agent in radical polymerization or a polymerization initiator in redox polymerization.

In addition, since the definition of R < ₁ >, R < ₂ > in Formula (2) is the same as those in the said Formula (1) or (2) , it abbreviate | omits.

Specific examples of the polyvalent thiol represented by the above formula (2) are shown below, but the polyvalent thiol used in the present invention is not limited thereto. In addition, the polyvalent thiol shown below is a novel compound.

  The polymerization initiator used when the above polyvalent thiol is used as a chain transfer agent and the positive photosensitive resin of the present invention is produced by radical polymerization 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-carbohydrate) Nitrile), azo compounds such as 4,4′-azobis (4-cyanovaleric acid), decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, Organic peroxides such as succinic peroxide and t-butylperoxy-2-ethylhexanoate Ku can be used as a mixture.

  The amount of the polymerization initiator used depends on the raw material monomer used in the polymerization reaction, the type and amount of the polyvalent thiol, the polymerization temperature, and the polymerization conditions of the polymerization solvent. It is selected from the range of 0.01 to 10 mol, preferably 0.1 to 5 mol, relative to mol.

On the other hand, as the polymerization accelerator used when the above polyvalent thiol is used as a polymerization initiator and the positive photosensitive resin of the present invention is produced by redox polymerization, for example, vanadium, chromium, manganese, iron, cobalt, nickel Such metal salts or metal complexes such as vanadium can be used alone or in combination, and a vanadium metal salt or metal complex having a large ionization potential gap is particularly preferable. Examples of the metal salt or metal complex of vanadium include vanadium naphthenate, vanadyl stearate, V (acac) ₃ , and VO (acac) ₂ .

  The amount of polymerization accelerator used varies depending on the raw material monomer used in the polymerization reaction, the type and amount of the polyvalent thiol, and the polymerization conditions such as the polymerization temperature and the polymerization solvent. It is selected from the range of 0.0001 to 1 mol, preferably 0.001 to 0.1 mol, relative to 1 mol.

  As a polymerization method for producing the positive photosensitive resin of the present invention, solution polymerization is preferable, and it is preferable to perform polymerization in a state where raw material monomers and the like are dissolved in a polymerization solvent. This solution polymerization is, for example, a so-called batch polymerization method in which all monomers, initiators, chain transfer agents, etc. are dissolved in a polymerization solvent and heated to the polymerization temperature, or some or all of monomers, initiators, chain transfer agents, etc. Can be carried out by a so-called drop polymerization method or the like in which the solution is dropped into a polymerization system heated to the polymerization temperature.

  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 photosensitive resin, the polymerization initiator, the chain transfer agent, and the like. 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 ether Examples thereof include ether esters such as 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, Comprising: When the usage-amount of a solvent is too little, A monomer or photosensitive resin may precipitate, and when too much, the rate of a polymerization reaction may become inadequate. 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 positive photosensitive resin of the present invention obtained by the above polymerization reaction is deposited by dropping the polymerization reaction solution into a poor solvent alone or a mixed solvent of a poor solvent and a good solvent, and further washing as necessary. , Unreacted monomers, oligomers, polymerization initiators, chain transfer agents, and these reaction residues can be removed and purified. The poor solvent is not particularly limited as long as the obtained photosensitive resin does not dissolve in the solvent. For example, water, alcohols such as methanol and isopropanol, saturated hydrocarbons such as hexane and heptane, etc. may be used alone or in combination. 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.

  In addition, the purified photosensitive resin contains the solvent used at the time of purification, and therefore, after drying under reduced pressure, it is dissolved in a resist solvent or directly as it is in a good solvent such as a resist solvent or a polymerization solvent. After dissolution, the resist solution can be prepared by, for example, distilling off other solvents under reduced pressure while supplying the resist solvent as necessary.

  The solvent for the resist is not particularly limited as long as it dissolves the photosensitive resin, but is usually selected in consideration of the boiling point, the influence on the semiconductor substrate and other coating films, and the absorption of radiation used in lithography. Is done. Examples of solvents generally used for resists 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 photosensitive resin.

  When the positive photosensitive resin of the present invention is used as a resist, a photoacid generator and an acid diffusion control agent such as a nitrogen-containing compound for preventing acid diffusion to a portion not exposed to radiation in the solution. Can be added to finish the resist composition. As the photoacid 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, but in general, the photosensitive resin concentration is 10 to 50% by mass, the radiation sensitive acid generator is 0.1 to 10% by mass, and the acid diffusion. It is selected from the range of 0.001 to 10% by mass of the control agent.

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 photosensitive resin was calculated | required by 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).

Synthesis of trivalent or more polyvalent thiol (3- [1,2,2-tris- (3-mercapto-propoxy) -ethoxy] -propane-1-thiol, hereinafter referred to as TeM12) having a bond cleaved by acid

A 500 cc three-necked flask was charged with 50 g of 3- (1,2,2-tris-allyloxy-ethoxy) -propene and 125 g of 2-butanone, and a cooling tube and a thermometer were attached to the three-necked flask and stirred for 10 minutes. Soaked in an oil bath and heated to 80 ° C. A mixture of 90 g of thioacetic acid and 5 g of 2,2′-azobis (isobutyric acid) dimethyl was added dropwise to the heated reaction solution over 3 hours, and the mixture was stirred and aged for 9 hours while maintaining 80 ° C. Thereafter, 2-butanone and thioacetic acid were removed from the reaction solution with an evaporator to obtain 135 g of a reaction solution. This reaction solution was transferred to a 1 L three-necked flask, 500 g of methanol and 56 g of a 20% aqueous sodium hydroxide solution were added, stirred for 10 minutes, immersed in an oil bath, and reacted at an oil temperature of 80 ° C. for 1.5 hours. . After the reaction, 2N hydrochloric acid 14
After neutralizing with 3 g, the reaction solution was extracted with toluene. Thereafter, toluene was distilled off from the extract with an evaporator to obtain 50.5 g (yield: 66%) of a trivalent or higher polyvalent thiol (TeM12) having a bond cleaved by an acid.

As a result of measuring ¹ H-NMR (solvent: deuterated chloroform) for the obtained polyvalent thiol (TeM12), protons in the structural formulas shown below: 4.35 ppm, b: 3.72 ppm, c: 1.90 ppm, d : Peaks were observed at 2.65 ppm, e: 6.39 ppm, and ¹³ C-NMR was measured. As a result, peaks were observed at carbon a: 102 ppm, b: 65 ppm, c: 34 ppm, d: 21 ppm in the structural formula shown below. And the obtained polyvalent thiol (TeM12) was identified as a compound having the above structure. ^{The 1} H-NMR chart is shown in FIG. 1, and the ¹³ C-NMR chart is shown in FIG.

Example 1
Synthesis of poly (p-hydroxystyrene-co-p-styrene-co-t-butyl acrylate) having a site cleaved by acid in the main chain

Crude p-hydroxystyrene {p-hydroxystyrene (hereinafter referred to as PHS) 23 parts by weight, p-ethylphenol 45 parts by weight, methanol 22 parts by weight obtained by dehydrogenating p-ethylphenol in a 100 cc three-necked flask , 10 parts by weight of water} 10.3 g, 0.56 g of styrene, 1.23 g of t-butyl acrylate (hereinafter referred to as TBA), 120.69 g of TeM, dimethyl-2,2′-azobisisobutyrate (hereinafter referred to as MAIB) 0 .25 g was charged and stirred at room temperature for 20 minutes to completely dissolve. A cooling tube was attached to the three-necked flask, immersed in an oil bath heated to 80 ° C., stirred for 6 hours, and then cooled to room temperature. The obtained polymerization liquid was put into 70 g of toluene to precipitate a polymer (positive photosensitive resin of the present invention), and the supernatant liquid was decanted. Thereafter, the polymer was redissolved with 4.5 g of acetone, the polymer was precipitated again with 70 g of toluene, and the supernatant was decanted. After this operation was performed once again, the polymer was redissolved again with 4.5 g of acetone, the polymer was precipitated with 100 g of hexane, and the supernatant was decanted. The obtained sticky precipitate was dried under reduced pressure at 60 ° C. and 10 torr for 3 days to obtain 5 g of a pale yellow polymer powder. Table 1 shows the dithiol content, average copolymer composition, weight average molecular weight, and polydispersity in the polymer obtained.

Example 2
Synthesis of poly (γ-butyrolactone-2-yl methacrylate-co-methyladamantyl methacrylate) having a site cleaved by acid in the main chain

In a 100cc three-necked flask, γ-butyrolactone-2-yl methacrylate (GBM)
6.01 g, methyl adamantyl methacrylate (hereinafter referred to as MAM) 8.28 g
Then, 14.29 g of methyl ethyl ketone, 1.34 g of TeM12, and 0.19 g of MAIB were added and stirred at room temperature for 20 minutes for complete dissolution. A cooling tube was attached to the three-necked flask, immersed in an oil bath heated to 80 ° C., stirred for 6 hours, and then cooled to room temperature. The obtained polymerization solution was put into 120 g of methanol to precipitate a polymer (positive type photosensitive resin of the present invention), and filtered through a filter paper having 1 micron retained particles. 120 g of the obtained wet cake polymer
Was added to methanol, washed with stirring, and methanol was filtered off. This was performed twice and then dried at 60 ° C. and 10 torr for 3 days to obtain 10.5 g of a white polymer. Table 1 shows the dithiol content, average copolymer composition, weight average molecular weight, and polydispersity in the polymer obtained.

Comparative Example 1
Synthesis of poly (p-hydroxystrene-co-p-styrene-co-t-butyl acrylate having no sites cleaved by acid in the main chain

3,6-Dioxa-1,8-octanedithiol (DOODT) 0.24 as chain transfer agent
Except for changing to g, 7 g of a polymer was synthesized in the same manner as in Example 1. Table 1 shows the DOODT content, average copolymer composition, weight average molecular weight, and polydispersity in the polymer obtained.

Comparative Example 2
Synthesis of poly (γ-butyrolactone-2-yl methacrylate-co-methyladamantyl methacrylate) which does not have a main chain at the site cleaved by acid

4 g of a polymer was synthesized in the same manner as in Example 2 except that the chain transfer agent was changed to 0.22 g of DOODT. Table 1 shows the DOODT content, average copolymer composition, weight average molecular weight, and polydispersity in the polymer obtained.

Example 3
Resist sensitivity evaluation A resist composition having the following composition was prepared.
1 g of the polymer obtained in Example 1 and 0.01 g of a photoacid generator (5-norbornene-2,3-dicarboxyimidyl trifluoromethanesulfonate) were dissolved in 5.8 g of propylene glycol monomethyl ether acetate, The resist composition was prepared by filtration using a 2 μm Teflon (registered trademark) filter. Next, the resist was spin-coated on a silicon wafer having a diameter of 100 mm, which had been previously treated with hexamethyldisilazane, and baked on a hot plate at 130 ° C. for 60 seconds to form a thin film having a thickness of 0.6 μm. Then, this formed wafer was allowed to stand in a contact type exposure experimental machine, a mask having a pattern drawn with chromium on a quartz plate was brought into close contact with the resist film, and ultraviolet rays of 248 nm were irradiated through the mask. Immediately after that, it was post-baked on a hot plate at 150 ° C. for 60 seconds, developed with an aqueous 0.26 mol / l tetraammonium hydroxide (TMAH) solution at a liquid temperature of 23 ° C. for 30 seconds, and then pure for 60 seconds. A rinse treatment was performed with water. As a result, a positive pattern in which only the exposed portion of the resist film was dissolved and removed in the developer was obtained. Similarly, the resists using the resins obtained in Example 2 and Comparative Examples 1 and 2 were also evaluated. Details are shown in Table 2.

  As is clear from the results in Table 2, the resist containing a resin whose main chain is cleaved by an acid obtained in Examples has a significantly improved resist sensitivity compared to a resist containing a resin whose main chain is not cleaved by an acid. Has been.

^{1 is} a ¹ H-NMR chart of an example of a trivalent or higher polyvalent thiol having a bond cleaved by an acid. It is a ¹³ C-NMR chart of an example of a trivalent or higher polyvalent thiol having a bond cleaved by an acid.

Claims (8)

A copolymer obtained by polymerizing two or more polymerizable compounds having an ethylenic double bond, which contains a bond that is cleaved by an acid (2)

(In the formula, R ₁ represents a single bond, or a linear or branched hydrocarbon having 1 to 5 carbon atoms, and R ₂ may be the same or different independently from each other, and may be a linear chain having 1 to 5 carbon atoms. Or a branched hydrocarbon.)
General formula (1) obtained by polymerizing in the presence of a polyvalent thiol represented by formula (1), which is derived from the polyvalent thiol and contains a bond cleaved by an acid.

(In the formula, R ₁ represents a single bond, or a linear or branched hydrocarbon having 1 to 5 carbon atoms, and R ₂ may be the same or different independently from each other, and may be a linear chain having 1 to 5 carbon atoms. Or a branched hydrocarbon.)
A positive photosensitive resin comprising an acetal structure represented by the formula: The positive photosensitive resin according to claim 1 , which is a copolymer containing a repeating unit having at least a phenolic hydroxyl group. The positive photosensitive resin according to claim 1 , which is a copolymer containing a repeating unit in which at least a phenolic hydroxyl group is acetalized. The positive photosensitive resin according to claim 1 , which is a copolymer containing a repeating unit derived from a (meth) acrylate derivative having at least an alicyclic skeleton. The positive photosensitive resin according to claim 1 , which is a copolymer containing at least a repeating unit derived from a (meth) acrylate derivative having a lactone skeleton. Two or more polymerizable compounds having an ethylenic double bond are represented by the general formula (2)

(In the formula, R ₁ is a single bond or represents a linear or branched hydrocarbon of from 1 to carbon atoms 5, R _2, independently of one another, may be identical or different, straight-chain of from 1 to 5 carbon or an branched hydrocarbon.)
A method for producing a positive photosensitive resin, wherein polymerization is carried out in the presence of a polyvalent thiol represented by the formula: A resist composition comprising at least the positive photosensitive resin according to any one of claims 1 to 5 and a photoacid generator. formula

The polyvalent thiol characterized by these.