JP5312136B2 - Terminal-modified polyfunctional vinyl aromatic copolymer and resist composition - Google Patents

Description

  The present invention relates to a terminal-modified polyfunctional vinyl aromatic copolymer having improved alkali solubility and heat resistance, and a resist composition using the same.

  In recent years, with the higher integration and higher speed of LSI, deep ultraviolet lithography has been put into practical use in response to the demand for finer pattern rules. Far-ultraviolet lithography can process 0.3 μm or less, and when a resist material with low light absorption is used, it is possible to form a pattern having sidewalls that are nearly perpendicular to the substrate.

  As a high-resolution resist corresponding to these short-wavelength radiations, for example, an acid-catalyzed chemically amplified negative resist material uses a high-brightness KrF excimer laser as a far-ultraviolet light source, and has sensitivity and resolution. It is known that the dry etching resistance is high and has excellent characteristics (Patent Documents 1 to 3). For example, Patent Document 2 discloses a negative resist composition containing an alkali-soluble polymer obtained using allylphenol as a monomer component and a radiation-sensitive acid forming agent.

  Such a chemically amplified negative resist material is very useful in deep ultraviolet lithography, but in recent years, there are problems such as an increase in the number of processes accompanying the miniaturization of the lithography pattern, and the improvement of LSI productivity. It is desired to further improve the lithography pattern formation, etching resistance, heat resistance and the like.

  On the other hand, in Patent Document 5, divinyl aromatic compound (a) and monovinyl aromatic compound (b) are polymerized in an organic solvent at a temperature of 20 to 100 ° C. in the presence of a Lewis acid catalyst and an initiator having a specific structure. Discloses a soluble polyfunctional vinyl aromatic copolymer. Patent Document 6 discloses a monomer component containing 20 to 100 mol% of a divinyl aromatic compound (a) in the presence of a quaternary ammonium salt with a Lewis acid catalyst and an initiator having a specific structure. A method for producing a soluble polyfunctional vinyl aromatic copolymer having a controlled molecular weight distribution by cationic polymerization at a temperature of ˜120 ° C. is disclosed. The soluble polyfunctional vinyl aromatic copolymer obtained by the techniques disclosed in these two patents is excellent in solvent solubility and processability, and by using this, a cured product having a high glass transition temperature and excellent heat resistance can be obtained. Can be obtained. However, the soluble polyfunctional vinyl aromatic copolymer obtained by these techniques has a problem that the adhesion is not sufficient because it does not have a polar group that gives adhesion to a metal or the like. .

  In order to solve the above problem, Patent Document 4 discloses a pendant vinyl group obtained from a divinyl aromatic compound, a monovinyl aromatic compound and a phenol compound, having a phenolic hydroxyl group at a terminal and derived from the divinyl aromatic compound. A polyfunctional vinyl aromatic copolymer soluble in an organic solvent is disclosed. However, since the phenolic compound used here has only one hydroxy group, the resulting polyfunctional vinyl aromatic copolymer has excellent adhesion and high glass transition temperature and heat resistance. Although it was a product, it was poor in solubility in an alkaline solution and could not be used as a resist material.

JP-A-1-293339 Japanese Patent Laid-Open No. 5-134411 JP 2000-131843 A JP 2008-189745 A JP 2004-123873 A Japanese Patent Laid-Open No. 2005-213443

  The present invention has been made in view of the above circumstances, and has a development property and process adaptability that exceed those of conventional resist materials, a good pattern shape after exposure, and an excellent heat-resistant pattern shape retainability. It is an object of the present invention to provide a chemically amplified negative resist composition.

  The present invention is a copolymer comprising a structural unit (a) derived from a divinyl aromatic compound and a structural unit (b) derived from a monovinyl aromatic compound, and has an average of one or more of the following It has a terminal group derived from a catechol-based compound represented by the formula (1), has a number average molecular weight Mn of 500 to 10,000, and acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, ethanol or isopropanol. It is a polyfunctional vinyl aromatic copolymer that is soluble and soluble in a 15% tetramethylammonium hydroxide aqueous solution.

ここで、Ｒ₁は酸素原子及び窒素原子を含んでもよい炭素数１〜１８の炭化水素基であり、ｎは０〜３の整数を表す。

Wherein, R ₁ is a hydrocarbon group having 1 to 18 carbon atoms which may contain an oxygen atom and a nitrogen atom, n represents an integer of 0 to 3.

The polyfunctional vinyl aromatic copolymer has a // when the existing mole fractions of the structural unit (a) derived from the divinyl aromatic compound and the structural unit (b) derived from the monovinyl aromatic compound are a and b, respectively. (a + b) = 0.4 to 0.95 is satisfied, and the content of the terminal vinyl group is 0.5 to 20 mol% of the total structural units.

  Examples of the monovinyl aromatic compound that gives the structural unit (b) derived from the monovinyl aromatic compound include styrene, ethylvinylbenzene, vinylnaphthalene, nucleus-substituted vinylnaphthalene, vinylbiphenyl, nucleus-substituted vinylbiphenyl, acenaphthylene, and nucleus-substituted acenaphthylene. A monovinyl aromatic compound selected from the group consisting of vinyl anthracene, and nucleus-substituted vinyl anthracene is preferred.

  A negative resist composition comprising the polyfunctional vinyl aromatic copolymer and a photosensitive component.

  The polyfunctional vinyl aromatic copolymer of the present invention exhibits alkali solubility because the terminal is modified. Therefore, this copolymer is useful as a curable resin to be blended in the resist composition, and a resist composition excellent in alkali-soluble contrast before and after exposure and having excellent heat resistance can be obtained. In particular, it is excellent as a negative resist composition suitable for ultra-LSI manufacturing and as a photomask fine pattern forming material.

  Hereinafter, the present invention will be described in detail. The polyfunctional vinyl aromatic copolymer of the present invention is a copolymer obtained by reacting a divinyl aromatic compound, a monovinyl aromatic compound and a catechol-based compound, and has a terminal group represented by the above formula (1). Have. It is soluble in at least one organic solvent selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, ethanol and isopropanol. It is also alkali-soluble. Specifically, it is soluble in a 15% tetramethylammonium hydroxide aqueous solution. The polyfunctional vinyl aromatic copolymer of the present invention is modified as described above, is soluble in the solvent, and has a polymerizable unsaturated group in the molecule, and thus has a property of being cured by polymerization. . The polyfunctional vinyl aromatic copolymer of the present invention is a polyfunctional vinyl aromatic copolymer whose terminal is modified and shows solvent solubility. However, when no misunderstanding occurs, the copolymer or the copolymer of the present invention is used. Abbreviated.

  By the way, a polyfunctional vinyl aromatic copolymer which is a copolymer obtained by reacting a divinyl aromatic compound and a monovinyl aromatic compound and is soluble in an organic solvent is known from Patent Documents 4 to 6 and the like. It has been. The polyfunctional vinyl aromatic copolymer of the present invention uses a catechol compound together with a divinyl aromatic compound and a monovinyl aromatic compound. Therefore, it can be said that the polyfunctional vinyl aromatic copolymer of the present invention is an improved end group of the polyfunctional vinyl aromatic copolymer known in Patent Documents 4 to 6 and the like.

  The copolymer of the present invention is represented by the above formula (1) derived from a catechol compound in addition to the structural unit (a) derived from a divinyl aromatic compound and the structural unit (b) derived from a monovinyl aromatic compound. Structural unit (hereinafter referred to as structural unit (c)). And the terminal group represented by the said Formula (1) is called terminal group (c). The divinyl aromatic compound and the monovinyl aromatic compound are monomers because they have a vinyl group that is a polymerizable functional group, and the catechol-based compound reacts with the unsaturated group at the end of the copolymer, but as such, Since it has no polymerizable unsaturated group, it is not a monomer but a terminal modifier. The polymer chain (main chain and side chain) of the copolymer of the present invention is generated from a monomer, and a part of the terminal is generated from a catechol-based compound. The term “total structural unit” refers to all structural units of the main chain, side chain, and terminal.

  If the existing mole fraction of each structural unit is a, b and c, a / (a + b) should be in the range of 0.05 to 0.96, preferably 0.4 to 0.95, more preferably 0.50 to 0.90. . Note that b / (a + b) can be calculated from a / (a + b). From another viewpoint, the structural unit (a) is preferably 20 to 60 mol% with respect to 100 mol% in total of all the structural units. The structural unit (b) is preferably 5 to 40 mol% and the structural unit (c) is preferably 10 to 60 mol% with respect to 100 mol% in total of all the structural units.

  The structural unit (a) derived from the divinyl aromatic compound contains a vinyl group as a crosslinking component for developing heat resistance, while the structural unit (b) derived from the monovinyl aromatic compound is involved in the curing reaction. Since it does not have a vinyl group, molecular linearity, that is, solubility is improved. Therefore, if a / (a + b) is less than 0.05, the heat resistance of the cured product is insufficient, and if it exceeds 0.96, the alkali solubility decreases.

  In the copolymer, the structural unit (a) derived from the divinyl aromatic compound is partially crosslinked to give a branched structure, a part remains as a terminal vinyl group, and a part of the terminal vinyl group is Bonded with the terminal structural unit (c), a part remains as an unsaturated group in the polymer chain. Therefore, the structural unit (a) derived from the divinyl aromatic compound branches the copolymer to increase the terminal and gives polymerization curability. However, when many divinyl aromatic compounds are crosslinked, they harden and do not exhibit solvent solubility, and thus are polymerized so as to exhibit solvent solubility. Preferably, the terminal vinyl group is 0.5 to 20 mol%, preferably 1 to 10 mol% of all structural units.

Further, the terminal of the copolymer has a terminal group (c) represented by the above formula (1). The terminal group (c) gives the terminal structural unit (c). The terminal group (c) or terminal structural unit (c) has an average of 1 or more per molecule. Preferably it has 2-5 pieces. From another viewpoint, the molar fraction c of the terminal structural unit (c) satisfies c / (a + b + c) = 0.1 to 0.6, more preferably 0.2 to 0.4, and still more preferably 0.2 to 0.35. It is good. In the above formula (1), R ₁ is a hydrocarbon group having 1 to 18 carbon atoms which may contain an oxygen atom and a nitrogen atom, preferably an alkyl group having 1 to 4 carbon atoms. n represents an integer of 0 to 3, and is preferably 0 or 1.

  By introducing the terminal group (c) at the terminal of the copolymer of the present invention so as to satisfy the above relationship, it has excellent heat resistance and high adhesion even for a high thermal history, and is alkali-soluble. It can be set as the resin composition excellent in. If the amount of the terminal group (c) is small, the alkali solubility is lowered, and if it is too large, the mechanical properties as a polymer cannot be maintained, and the heat resistance is further lowered.

  The copolymer of the present invention has a Mn (wherein Mn is a number average molecular weight in terms of standard polystyrene measured using gel permeation chromatography) of 500 to 10,000, preferably 700 to 5,000. More preferably, it is 1,000 to 4,000. If the Mn is less than 500, the viscosity of the copolymer is too low, making it difficult to form a thick film, resulting in poor processability. If the Mn exceeds 10,000, gel is likely to be formed. When a thin film is formed, the resolution is lowered and the number of terminal functional groups is lowered, so that it is not possible to improve the alkali solubility. The molecular weight distribution (Mw / Mn) is 50.0 or less, preferably 20.0 or less, more preferably 1.5 to 3.0. When Mw / Mn exceeds 50.0, problems such as deterioration of the solubility characteristics of the copolymer and generation of gels occur.

  The copolymer of the present invention is soluble in any one or more organic solvents selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, ethanol and isopropanol, and further a 15% tetramethylammonium hydroxide aqueous solution. But is preferably soluble in any of the above organic solvents. In order to be a copolymer soluble in an organic solvent and an alkaline solution, a part of the vinyl group of the divinyl aromatic compound remains without being cross-linked so as to have an appropriate degree of cross-linking. Here, being soluble means that 1 g or more is dissolved in 100 ml of a solvent such as an organic solvent or an alkaline solution at 25 ° C.

The copolymer of the present invention can be obtained according to the methods described in Patent Documents 4 to 6. Specifically, a divinyl aromatic compound, a monovinyl aromatic compound, and a catechol compound represented by the following formula (5) are used for copolymerization to obtain a copolymer having a terminal group derived from the catechol compound. be able to. In formula (5), R ₁ and n have the same meanings as R ₁ and n of formula 1.

  For example, as a method for producing a copolymer, a divinyl aromatic compound, a monovinyl aromatic compound and a catechol-based compound can be obtained by cationic copolymerization in the presence of a promoter selected from a Lewis acid catalyst and an ester compound. it can.

  The amount of divinyl aromatic compound, monovinyl aromatic compound and catechol compound used is determined so as to give the composition of the copolymer of the present invention. The divinyl aromatic compound is preferably 10 to 90 of all monomers. The mol%, more preferably 40 to 95 mol%, still more preferably 50 to 90 mol% is used. The monovinyl aromatic compound is preferably used in an amount of 90 to 10 mol%, more preferably 5 to 60 mol%, still more preferably 10 to 50 mol% of the total monomers.

  A monomer means a component having a polymerizable unsaturated bond as described above, but other monomers are 50 mol% or less, preferably 10 mol% or less, more preferably 5 mol% or less of the total monomers. May be used. Examples of other monomers include aliphatic vinyl compounds.

  The Lewis acid catalyst used in the production of the copolymer can be used without particular limitation as long as it is a compound comprising a metal ion (acid) and a ligand (base) and can receive an electron pair. From the viewpoints of control of molecular weight and molecular weight distribution and polymerization activity, boron trifluoride ether (diethyl ether, dimethyl ether, etc.) complexes are most preferably used. The Lewis acid catalyst is used in the range of 0.001 to 10 mol, more preferably 0.001 to 0.01 mol, relative to 1 mol of the catechol-based compound. If the use amount of the Lewis acid catalyst is excessive, the polymerization rate becomes too high, so that not only the control of the molecular weight distribution becomes difficult, but also the introduction amount of the phenolic hydroxyl group decreases.

  Examples of the cocatalyst include one or more selected from ester compounds. Among them, an ester compound having 4 to 30 carbon atoms is preferably used from the viewpoint of controlling the polymerization rate and the molecular weight distribution of the copolymer. From the viewpoint of availability, ethyl acetate, propyl acetate and butyl acetate are preferably used. The cocatalyst is used in the range of 0.001 to 10 moles with respect to 1 mole of the catechol-based compound, more preferably 0.01 to 1 mole. When the amount of the cocatalyst used is excessive, the polymerization rate decreases, the yield of the copolymer decreases, and the amount of phenolic hydroxyl group introduced decreases. On the other hand, when the amount of the cocatalyst used is too small, the selectivity of the polymerization reaction is lowered, the molecular weight distribution is increased, the gel is generated, and the polymerization reaction is difficult to control.

  The catechol-based compound is a compound that causes a chain transfer reaction with a polymerization active species during a polymerization reaction and plays a role of introducing a catechol hydroxyl group that enables alkali solubility to be imparted to the terminal of the copolymer. Since the catechol-based compound does not have a polymerizable unsaturated group, it exists only at the terminal. The amount of the catechol-based compound used is preferably in the range of 0.01 to 10 mol, more preferably 0.5 to 5 mol, relative to 1 mol of all monomers. When the amount of the catechol-based compound used is small, the amount of the terminal group (c) introduced decreases, and functions such as alkali solubility and adhesiveness are lowered. On the other hand, if the content is too large, the content of vinyl groups in the copolymer is significantly reduced, making it difficult to cure the copolymer, and the alkali solubility of the cured product obtained from the copolymer is not sufficiently reduced. Heat resistance also decreases. In addition, since a catechol type compound reacts with a part of vinyl group to form a terminal group, an excess of the catechol type compound remains unreacted when used.

  Examples of the catechol-based compound include catechol-based compounds having 6 to 30 carbon atoms such as catechol, alkyl catechol, dialkyl catechol, phenyl catechol, and alkylphenyl catechol. Of these catechol-based compounds, catechol is preferably used from the viewpoint of reactivity and availability.

  The divinyl aromatic compound plays an important role as a crosslinking component for developing heat resistance when the copolymer is thermally cured. Examples of these include divinylbenzene (both isomers of m- and p-), divinylnaphthalene (including each isomer), divinylbiphenyl (including each isomer), and the like. Is not to be done. Moreover, these can be used individually or in combination of 2 or more types.

  The monovinyl aromatic compound has a function of improving the solvent solubility and processability of the polyfunctional vinyl aromatic copolymer of the present invention. Examples of monovinyl aromatic compounds used include, but are not limited to, styrene, nuclear alkyl substituted monovinyl aromatic compounds, α-alkyl substituted monovinyl aromatic compounds, β-alkyl substituted styrenes, alkoxy substituted styrenes, and the like. It is not a thing. In order to prevent polymer gelation and improve solubility in solvents and processability, especially styrene, ethyl vinyl benzene (both isomers of m- and p-), vinyl naphthalene, nucleus-substituted vinyl naphthalene, vinyl biphenyl Nuclear substituted vinyl biphenyl, acenaphthylene, nuclear substituted acenaphthylene, vinyl anthracene, and nuclear substituted vinyl anthracene are preferred and used. Here, an alkyl group having 1 to 6 carbon atoms is preferable as a substituent of a nucleus-substituted compound such as nucleus-substituted vinylnaphthalene.

  The polymerization reaction is preferably performed in one or more solvents having a dielectric constant of 2 to 15 by dissolving the produced polyfunctional vinyl aromatic copolymer. As the solvent, toluene, xylene, n-hexane, cyclohexane, methylcyclohexane and ethylcyclohexane are particularly preferable. Further, the amount of the solvent used is such that the concentration of the copolymer in the polymerization solution at the end of the polymerization is 1 to 80 wt%, preferably 5 to 60 wt%, in consideration of the viscosity of the resulting polymerization solution and ease of heat removal. Particularly preferably, it is determined to be 7 to 50 wt%. The polymerization temperature is in the range of 20 to 120 ° C, preferably 40 to 100 ° C.

  Next, the resist composition of the present invention will be described.

  The copolymer of the present invention can be used as a negative resist in the presence of a photosensitive component. Therefore, when it is a composition with a photosensitive component, it becomes a negative resist in which alkali insolubilization appears only in the exposed portion.

  The resist composition of the present invention can be used as a negative resist material and contains the polyfunctional vinyl aromatic copolymer of the present invention, an organic solvent and a photosensitive component as main components.

  Here, examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amyl ketone, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2- Alcohols such as propanol, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, and other ethers, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether Acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl-3-methoxypropionate, ethyl-3 Include esters such as ethoxypropionate, these can be used one type alone or a mixture of two or more kinds. Of these, diethylene glycol dimethyl ether and 1-ethoxy-2-propanol, which have the highest solubility of the photosensitive component in the resist component, are preferably used.

  The amount of the organic solvent used is 200 to 1,000 parts by weight, preferably 400 to 800 parts by weight, based on 100 parts by weight of the polyfunctional vinyl aromatic copolymer. When the amount is less than 200 parts, the compatibility is lowered and the film formability is inferior. When the amount exceeds 1,000 parts, the resist film is formed into a thin film and cannot be used.

  The photosensitive component is a compound that is decomposed by radiation irradiation to crosslink the polyfunctional vinyl aromatic copolymer that is an alkali-soluble resin, or to increase the acidity and insolubilize in the developer.

  Examples of such a photosensitive component include general photopolymerization initiators and photoacid generators. Examples of the photopolymerization initiator include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, and benzoin isobutyl ether; acetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2 -Phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-phenylpropan-1-one, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl Acetophenones such as 2-morpholinopropan-1-one; ant such as 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-chloroanthraquinone, 2-amylanthraquinone Quinones; thioxanthones such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone; ketals such as acetophenone dimethyl ketal and benzyldimethyl ketal; benzophenone, 4-benzoyl-4′-methyldiphenyl sulfide Benzophenones such as 4,4′-bismethylaminobenzophenone; phosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide It is done.

  As the photoacid generator, an azide group-containing compound is useful. For example, 1-azidopyrene, p-azidobenzophenone, 4′-methoxy-4-azidodiphenylamine, 4-azidobenzal-2′-methoxyacetophenone, 4-azido-4 Monoazide compounds such as' -nitrophenylazobenzene, 4,4'-diazidobenzophenone, 4,4'-diazidobenzomethane, 4,4'-diazidostilbene, 2,2'-di (ethanolsulfonamide)- 4,4′-diazidostilbene, 4,4′-diazidochalcone, 2-diethoxyethylsulfonamide-4,4′-diazidochalcone, 4,4′-diazidodiphenylsulfone, 3,4′- Diazide diphenyl sulfone, 3,3′-diazide diphenyl sulfone, 2,6-di (4′-azidobenzaza) ) Bisazide compounds such as cyclohexane, 2,6-di (4′-azidobenzal) 4-methylcyclohexane, monosulfonyl azide compounds such as sulfonyl azidobenzene, p-sulfonylazidetoluene and p-bis (sulfonylazide) benzene, Bissulfonyl azide compounds such as 4′-bis (sulfonyl azide) benzophenone are mentioned.

  Among these, a bisazide compound is used as a preferable photosensitive component. These photosensitive components are used alone or in combination of two or more. The addition amount of the photosensitive component is usually 0.1 to 40 parts by weight, preferably 1 to 30 parts by weight with respect to 100 parts by weight of the copolymer. If the addition amount of the photosensitive component is less than 0.1 part by weight, the radiation irradiated part is hardly insolubilized in the developer, and if it exceeds 40 parts by weight, the pattern becomes reversely tapered and the pattern shape is deteriorated.

  Furthermore, the resist composition of the present invention includes various (meth) acrylate compounds as other polyfunctional low-molecular monomers to improve sensitivity and curability, and surfactants and diffuse reflection from the substrate to improve coatability. In order to reduce the influence of the light absorbing material, a light absorbing material can be blended.

  In order to form a pattern using the negative resist composition of the present invention, a known lithography technique can be adopted. For example, a resist is applied onto a silicon wafer by a spin coating method and prebaked. A resist film is formed. Then, after irradiating light energy rays, such as a far infrared ray, an electron beam, and an X-ray, and exposing, it can develop by developing with alkaline aqueous solution.

  EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, all the parts in each example are parts by weight. Moreover, the measurement of the softening temperature etc. in an Example performed sample preparation and a measurement with the method shown below.

1) Molecular weight and molecular weight distribution of polymer GPC (Tosoh, HLC-8120GPC) was used for measuring the molecular weight and molecular weight distribution of the soluble polyfunctional aromatic copolymer, tetrahydrofuran as the solvent, flow rate of 1.0 ml / min, column temperature of 38. The measurement was carried out using a calibration curve of monodisperse polystyrene at ° C.

2) Polymer structure Determined by ¹³ C-NMR and ¹ H-NMR analysis using a JNM-LA600 nuclear magnetic resonance spectrometer manufactured by JEOL. Using chloroform -d ₁ as a solvent, was used resonance line of tetramethylsilane as an internal standard.

3) Analysis of terminal groups The calculation of terminal groups is based on the number average molecular weight obtained from the GPC measurement and the amount of derivative used to introduce terminal groups relative to the total amount of monomers obtained from the results of ¹ H-NMR measurement and elemental analysis. From the above, the number of terminal groups contained in one molecule of the soluble polyfunctional vinyl aromatic copolymer having terminal groups was calculated.

4) Sample preparation and measurement for measurement of glass transition temperature (Tg) and softening temperature of cured product Apply soluble polyfunctional vinyl aromatic copolymer solution uniformly to glass substrate so that the thickness after drying is 20 μm. The sample was heated for 30 minutes at 90 minutes using a hot plate and dried. The resin film obtained together with the glass substrate is set in TMA (thermomechanical analyzer), heated to 220 ° C. at a temperature rising rate of 10 ° C./min under a nitrogen stream, and further heat-treated at 220 ° C. for 20 minutes. The remaining solvent was removed and the soluble polyfunctional vinyl aromatic copolymer was cured. After allowing the glass substrate to cool to room temperature, an analytical probe is brought into contact with the sample in the TMA measuring apparatus, and scan measurement is performed from 30 ° C. to 360 ° C. at a temperature rising rate of 10 ° C./min under a nitrogen stream. The softening temperature was determined.

5) Dissolution test in organic solvent and aqueous alkali solution Add 1 g of copolymer to 100 ml of various organic solvents (acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, ethanol and isopropanol) at 25 ° C., and magnetic stirrer. After stirring for 30 minutes, the solubility was visually confirmed. When completely dissolved, it was considered soluble. As a dissolution test in an alkaline aqueous solution, 1.0 g of a copolymer was dissolved in 15 g of ethylene glycol monomethyl ether acetate to form a solution, and a film was formed on a silicone wafer by spin coating. The film thickness was applied at a rotational speed such that the film thickness after drying was about 1 μm. Pre-baking was performed at 80 ° C. for 20 minutes. The copolymer thin film was developed for 25 seconds using a 2.38% tetramethylammonium hydroxide aqueous solution (manufactured by Kao Corporation, Clean Through KS-5020), and the remaining film thickness was measured. The case where the remaining film thickness was zero was considered soluble and the solubility was confirmed.

Example 1
Divinylbenzene 1.701 mol (242.3 mL), ethyl vinylbenzene 0.399 mol (56.8 mL), acenaphthylene 0.900 mol (137.0 g), catechol 3.15 mol (346.8 g), butyl acetate 400 0.0 mL and 800.0 mL of toluene were put into a 3.0 L reactor, 50 mmol of boron trifluoride diethyl ether complex was added at 60 ° C., and the mixture was reacted at 60 ° C. for 1 hour and at 90 ° C. for 3 hours. It was. After stopping the polymerization reaction with methanol, the reaction mixture was poured into a large amount of hexane at room temperature to precipitate a polymer. The obtained polymer was dissolved in methanol and poured into a large amount of water in which a small amount of hydrochloric acid was dissolved to precipitate the copolymer. The copolymer was washed, filtered, dried, and weighed to obtain a copolymer A 311. 12 g was obtained.

Mn of the obtained copolymer A was 906, Mw was 1720, and Mw / Mn was 1.90. By performing ¹³ C-NMR and ¹ H-NMR analyses, in the copolymer A, end group resonance lines derived from catechol were observed. The amount of introduced catechol-derived end groups (c1) of the copolymer A calculated from the elemental analysis results of copolymer A and the number average molecular weight in terms of standard polystyrene is 2.6 (pieces / molecule), It was 31.6 mol%. Moreover, 72.3 mol% of structural units derived from divinylbenzene and 27.7 mol% of structural units derived from acenaphthylene and ethylbenzene were contained (excluding terminal structural units). The vinyl group content contained in the copolymer A was 3.4 mol% (excluding the terminal structural unit). Moreover, the structural unit derived from divinylbenzene with respect to all the structural units was 49.5%. “Excluding the terminal structural unit” means that the total of the structural unit (a) of the divinyl aromatic compound and the structural unit (b) of the monovinyl aromatic compound was calculated as 100 mol%.
Copolymer A was soluble in organic solvents such as methanol, ethanol, THF, acetone, and methyl ethyl ketone. Further, it was soluble in an aqueous solution of 2.38% tetramethylammonium hydroxide and had alkali solubility. No gel formation was observed.

Example 2
Divinylbenzene 2.098 mol (298.8 mL), ethyl vinylbenzene 0.492 mol (70.1 mL), styrene 0.410 mol (47.0 mL), catechol 3.15 mol (346.8 g), butyl acetate 400 0.0 mL and 800.0 mL of toluene were put into a 3.0 L reactor, 50 mmol of boron trifluoride diethyl ether complex was added at 50 ° C., and reacted at 50 ° C. for 3 hours and at 90 ° C. for 3 hours. It was. After stopping the polymerization reaction with methanol, the reaction mixture was poured into a large amount of hexane at room temperature to precipitate a polymer. The obtained polymer was dissolved in methanol and poured into a large amount of water in which a small amount of hydrochloric acid was dissolved to precipitate the polymer. The polymer was washed, filtered, dried, and weighed to obtain 393.78 g of copolymer B. Got.

Mn of the obtained copolymer B was 1260, Mw was 2340, and Mw / Mn was 1.86. By performing ¹³ C-NMR and ¹ H-NMR analyses, in the copolymer B, end group resonance lines derived from catechol were observed. The introduction amount (c1) of terminal groups derived from catechol of the soluble polyfunctional vinyl aromatic copolymer calculated from the elemental analysis result of copolymer B and the number average molecular weight in terms of standard polystyrene is 2.8 (pieces / molecule). And 24.5 mol% of all structural units. Further, it contained 73.1 mol% of structural units derived from divinylbenzene and 26.9 mol% in total of structural units derived from styrene and ethylbenzene (excluding terminal structural units). The vinyl group content contained in the copolymer B was 2.1 mol% (excluding the terminal structural unit). Moreover, the structural unit derived from divinylbenzene with respect to all the structural units was 55.2%.
Copolymer B was soluble in organic solvents such as methanol, ethanol, THF, acetone, and methyl ethyl ketone. Further, it was soluble in an aqueous solution of 2.38% tetramethylammonium hydroxide and had alkali solubility. No gel formation was observed.

Comparative Example 1
Divinylbenzene 2.098 mol (298.8 mL), ethyl vinylbenzene 0.492 mol (70.1 mL), styrene 0.410 mol (47.0 mL), phenol 3.15 mol (346.8 g), butyl acetate 400 0.0 mL and 800.0 mL of toluene were put into a 3.0 L reactor, 50 mmol of boron trifluoride diethyl ether complex was added at 50 ° C., and reacted at 50 ° C. for 3 hours and at 90 ° C. for 3 hours. It was. After stopping the polymerization reaction with methanol, the reaction mixture was poured into a large amount of hexane at room temperature to precipitate a polymer. The obtained polymer was dissolved in methanol and poured into a large amount of water in which a small amount of hydrochloric acid was dissolved to precipitate the polymer. The polymer was washed, filtered, dried and weighed to obtain 339.45 g of copolymer C. Got.

Mn of the obtained copolymer C was 1140, Mw was 2520, and Mw / Mn was 2.21. By performing ¹³ C-NMR and ¹ H-NMR analyses, in the copolymer C, resonance lines of end groups derived from phenol were observed. The introduction amount (c1) of the phenol-derived terminal of the soluble polyfunctional vinyl aromatic copolymer calculated from the elemental analysis result of the copolymer C and the number average molecular weight in terms of standard polystyrene is 2.9 (pieces / molecule). It was 23.9 mol% of all the structural units. Moreover, 72.6 mol% of structural units derived from divinylbenzene and 27.4 mol% of structural units derived from styrene and ethylbenzene were contained in total (excluding terminal structural units). The vinyl group content contained in the copolymer C was 1.6 mol% (excluding the terminal structural unit). Moreover, the structural unit derived from divinylbenzene with respect to all the structural units was 55.2%.
Copolymer C was soluble in organic solvents such as methanol, ethanol, THF, acetone, and methyl ethyl ketone. However, when a 2.38% tetramethylammonium hydroxide aqueous solution is used, the remaining film rate is 80%, and even when a stronger 15.0% tetramethylammonium hydroxide aqueous solution is used, the remaining film rate is 30%. There was no alkali-solubility capable of pattern formation. On the other hand, the formation of gel was not recognized.

Example 3
A negative resist composition was obtained by dissolving 0.2 g of 3,3′-diazidodiphenylsulfone and 1.0 g of copolymer A obtained in Example 1 in 13.7 g of ethylene glycol monomethyl ether acetate. This negative resist composition was formed on a silicone wafer by spin coating, and prebaked at 80 ° C. for 20 minutes. The thickness of the obtained resist film was 0.56 μm.
Next, a test mask was placed on the wafer using an exposure machine (manufactured by HI-TECH Co. Ltd., HTE-505S), and exposure was performed at an exposure amount of 60 mJ / cm ² . The development was performed using a 2.38% tetramethylammonium hydroxide aqueous solution (manufactured by Kao Corporation, Clean-Through KS-5020) for 25 seconds, and immersed in deionized water for 80 seconds for rinsing.

  As a result of observing the developed pattern with a scanning electron microscope, a good pattern was obtained with no particular taper. Furthermore, the developed silicone wafer was baked at a high temperature of 130 ° C. for 5 minutes, and the state of pattern deterioration was similarly observed with a scanning electron microscope, and it was visually confirmed that there was no change in the pattern shape before and after heating. .

Example 4
A negative resist composition was obtained in the same manner as in Example 3 except that the copolymer B obtained in Example 2 was used. Using this negative resist composition, a resist film is prepared by the same method as in Example 3, and exposure, development and pattern observation after development are performed, and a good pattern can be obtained with no particular taper. I confirmed that it was possible. Further, the developed silicone wafer was baked at a high temperature of 130 ° C. for 5 minutes, and the state of pattern deterioration was similarly observed with a scanning electron microscope, and it was confirmed that there was no change in the pattern shape before and after heating. .

Comparative Example 2
Except that the copolymer C obtained in Comparative Example 1 was used, a negative resist composition was obtained by the same method as in Example 3, a resist film was prepared, and the pattern after exposure, development and development As a result of observation, only a slight taper indicating a photo pattern was observed, and it was confirmed that the pattern could not be formed.

Claims (4)

A copolymer comprising a structural unit (a) derived from a divinyl aromatic compound and a structural unit (b) derived from a monovinyl aromatic compound, wherein one or more of the following formula (1)

(Here, R ₁ is a C 1-18 hydrocarbon group that may contain an oxygen atom and a nitrogen atom, and n represents an integer of 0-3)
And the existing mole fractions of the structural unit (a) derived from the divinyl aromatic compound and the structural unit (b) derived from the monovinyl aromatic compound are represented by a and b, respectively. When a / (a + b) satisfies 0.4 to 0.95, the content of terminal vinyl groups satisfies 0.5 to 20 mol% of the total structural units, and the number average molecular weight is 500 to 10 , 000, soluble in acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, ethanol or isopropanol, and soluble in 15% tetramethylammonium hydroxide aqueous solution Group copolymer. 2. The polyfunctional vinyl aromatic copolymer according to claim 1, wherein a / (a + b) satisfies 0.50 to 0.90, and the content of terminal vinyl groups satisfies 1 to 10 mol% of all structural units .   Monovinyl aromatic compounds that give structural units (b) derived from monovinyl aromatic compounds are styrene, ethyl vinyl benzene, vinyl naphthalene, nucleus substituted vinyl naphthalene, vinyl biphenyl, nucleus substituted vinyl biphenyl, acenaphthylene, nucleus substituted acenaphthylene, vinyl anthracene, The polyfunctional vinyl aromatic copolymer according to claim 1 or 2, which is a monovinyl aromatic compound selected from the group consisting of a nucleus-substituted vinyl anthracene.   A negative resist composition comprising the polyfunctional vinyl aromatic copolymer according to claim 1 and a photosensitive component.