Positive resist composition and photosensitizers

Abstract: A positive photoresist composition comprising, as a photosensitizer, a quinonediazide sulfonic acid ester of a phenol compound represented by the following formula (I): wherein Q 1 , Q 2 , Q 3 , Q 4 , Q 5 , Q 6 , Q 7 , Q 8 , Q 9 and Q 10 independently represent hydrogen, alkyl having 1-6 carbon atoms or phenyl, or Q 1 and Q 2 , Q 3 and Q 4 , Q 5 and Q 6 , Q 7 and Q 8 , or Q 9 and Q 10 may form a cycloalkane ring having 6 or less carbon atoms together with a carbon atoms to which they are connected, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 and R 16 independently represent hydrogen, hydroxyl, alkyl having 1-6 carbon atoms or phenyl; and m and n independently represent a number of 0 or 1; and an alkali soluble resin; and a quinonediazide sulfonic acid ester of a phenol compound of formula (I).

Description: The present invention relates to photosensitive resin compositions, particularly positive photoresist compositions which give a positive pattern by irradiation with a radiation such as near ultra-violet ray and deep ultra-violet ray including excimer laser. It has been generally known that quinonediazide sulfonic acid esters of compounds having a phenolic hydroxyl group are used as photosensitizers in photosensitive resin composition for minute processing for semiconductors. These compositions are used as positive resists utilizing the fact that when a composition comprising a compound having a quinonediazide group and a novolak resin is applied on a substrate, and is then irradiated with a light of 300 - 500 nm, the quinonediazide group is decomposed to form a carboxyl group, allowing to change the composition from an alkali-insoluble state to an alkali-soluble state. Since such positive resists are characterized in that they are excellent in resolution as compared with negative resists, they found utilization in producing various kinds of integrated circuits for semiconductors. In recent years, the integrated circuits in the semi-conductor industries have gone on increasing minuteness with a progress of the level of integration and now formation of a pattern in submicron order is demanded. Especially, the lithographic process occupies an important position in the production of integrated circuits and a more excellent resolution (high γ-value) is required for the positive resists. Many combinations of ingredients have been proposed for resist materials containing a quinonediazide compound and a novolak resin. For example, JP-A-1-189644 (corr. to US-A-5,153,096) has disclosed a use of quinonediazide sulfonic acid esters of triphenylmethane compounds having at least two phenolic hydroxyl groups as photosensitizers. When these known sensitizers were used, however, there was a limit in improvement of the γ-value as the resist for the ultra minute processing currently used in the production of ultrahigh integrated circuits or for so-called submicron lithography. Therefore, various researches have been carried out in order to improve properties as the resist such as sensitivity, resolution, heat resistance and the like. For example, JP-A-6-167805 (corr. to EP-A-573,056) has disclosed a use of quinonediazide sulfonic acid esters of compounds having four or more phenol nuclei as photosensitizers. EP-A-731 074, a document under Art. 54(3) EPC, discloses a photosensitive resin composition comprising an alkali-soluble novolac resin and a photosensitizer comprising a tetraphenol compound represented by the formula: wherein one of R 1 , R 2 , R 3 and R 4 represents 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl and the reminder represent, independently of one another, hydrogen, 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl. An object of the present invention is to provide photosensitive resin compositions, particularly positive photoresist compositions which are well balanced among various properties as the resist such as high sensitivity, high resolution, high heat resistance, good profile, good forcus latitude and little development residue using such compounds. Another object of the present invention is to provide novel phenol compounds which can be used as a photosensitiser for photosensitive resin compositions such as positive photoresist. These objects could be achieved on the basis of the finding that positive photoresist compositions which are more balanced among various properties as the resists compared to known positive photoresist compositions can be obtained by using specific phenol compounds having groups derived from para-cresol at their both ends. The present invention provides phenol compounds represented by the following formulae VII or X wherein i) Y 1 =Y 2 = -CH 3 , A= -OR, B=D=E= -H or ii) Y 1 =Y 2 = -H, A= -OR, B=E= -H, D= -CH 3 or iii) Y 1 =Y 2 = -H, A= -OR, B=D=E= -H or iv) Y 1 =Y 2 = -CH 3 , A= -OR, B=E= CH 3 , D=-H or v) Y 1 =Y 2 = -H or -CH 3 , A= -CH 3 , B=E=-H, D= -OR and wherein each R independently represents hydrogen, 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl, with the proviso that at least one R is 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl; wherein R 33 , R 34 , R 35 , R 36 , R 37 and R 38 independently represent hydrogen, 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl provided that at least one of R 33 , R 34 , R 35 , R 36 , R 37 and R 38 is 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl. In the above-mentioned formulae VII, or X, 1,2-naphthoquinonediazide-4-sulfonyl is represented by the following formula VIII and 1,2-naphthoquinonediazide-5-sulfonyl is represented by the following formula IX. The compound represented by the above-mentioned formulae VII or X which has at least one naphthoquinone sulfonyl group in the molecule can be used as a photosensitizer for the positive resist composition of the present invention. The phenol compound of formula VII or X wherein R, R 33 , R 34 , R 35 , R 36 , R 37 , and R 38 are hydrogen can be produced, for example, by reacting para-cresol with 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol, 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol, or a compound represented by the following formula XV: wherein R 56 represents hydrogen or methyl respectively. The dimethylol compounds, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol, 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol and a compound of formula XV, (Hereinafter, these six dimethylol compounds are referred to as Dimethylol compound A") can be obtained, for example, by reacting 2,6-bis(4-hydroxy-2,5-dimethylbenzyl)-4-methylphenol, 4,4'-methylenebis[2-(4-hydroxy-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-2,3,6-trimethylbenzyl)-4-methylphenol, or a compound represented by the following formula XVI: wherein R 56 is same as defined above, respectively, (Hereinafter, these six compounds are referred to as Starting compound B") with formaldehyde in the presence of an alkaline catalyst. 2,6-Bis(4-hydroxy-2,5-dimethylbenzyl)-4-methylphenol can be obtained, for example, by a condensation reaction of 2,6-bis(hydroxymethyl)-4-methylphenol and 2,5-xylenol. 2,6-Bis(hydroxymethyl)-4-methylphenol can be obtained by reacting para-cresol with formaldehyde. 4,4'-Methylenebis[2-(4-hydroxy-2,5-dimethylbenzyl)-3,6-dimethylphenol], which is described in JP-A-6-167805(=US-A-5,407,779), can be obtained, for example, by a condensation reaction of 4,4'-methylenebis(2-hydroxymethyl-3,6-dimethylphenol) and 2,5-xylenol. 4,4'-Methylenebis(2-hydroxymethyl-3,6-dimethylphenol) can be obtained by reacting 2,5-xylenol with formaldehyde. 2,6-Bis(4-hydroxy-3-methylbenzyl)-3,4-dimethylphenol can be obtained, for example, by a condensation reaction of 2,6-bis(hydroxymethyl)-3,4-dimethylphenol and ortho-cresol. 2,6-Bis(hydroxymethyl)-3,4-dimethylphenol can be obtained by reacting 3,4-xylenol with formaldehyde. 2,6-Bis(4-hydroxy-3-methylbenzyl)-4-methylphenol can be obtained, for example, by a condensation reaction of 2,6-bis(hydroxymethyl)-4-methylphenol and ortho-cresol. 2,6-Bis(4-hydroxy-2,3,6-trimethylbenzyl)-4-methylphenol can be obtained, for example, by a condensation reaction of 2,6-bis(hydroxymethyl)-4-methylphenol and 2,3,5-trimethylphenol. A compound of formula XVI can be obtained, for example, by a condensation reaction of 2,4-bis(hydroxymethyl)-3,6-dimethylphenol with ortho-cresol or 2,5-xylenol. 2,4-Bis(hydroxymethyl)-3,6-dimethylphenol can be obtained by reacting 2,5-xylenol with formaldehyde. In the reaction of Starting compound B with formaldehyde to produce Dimethylol compound A, the molar ratio of Starting compound B and formaldehyde is usually 1 : 2-10, preferably 1 : 4-8. For the production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol, the ratio of 1 : 5-6 is more preferred. This reaction is carried out in the presence of an alkaline catalyst. Although, either an inorganic base or an organic base can be used, an inorganic base such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate are preferred as the alkaline catalyst, Particularly, sodium hydroxide is preferred. The amount of the alkaline catalyst is preferably 0.5 - 5 mol, more preferably 1 - 4 mol, further more preferably 2 - 3 mol, for the production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol; and preferably 0.5 - 8 mol, more preferably 1 - 5 mol, for the production of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol and a compound of formula XV, per 1 mol of Starting compound B. This reaction is usually carried out in an solvent. As the solvent, a polar solvent such as tetrahydrofuran, dioxane, water and methanol are preferred and, particularly, a mixed solvent of tetrahydrofuran and water is preferred. The amount of the reaction solvent is preferably 1 - 10 parts by weight, more preferably 3 - 6 parts by weight, further more preferably 4 - 5 parts by weight, for the production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol; and is preferably 2 - 30 parts by weight, for the production of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol and a compound of formula XV, per 1 part by weight of Starting compound B. When a mixed solvent of tetrahydrofuran and water is used, the amount of tetrahydrofuran is preferably 0.05 - 1 parts by weight, more preferably 0.1 - 0.5 parts by weight, particularly preferably 0.1 - 0.2 parts by weight, per 1 part by weight of water. This reaction is usually carried out within a temperature range of 10 - 60 °C. For the production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol, this reaction is preferably carried out at 30 - 50 °C, particularly preferably 35 - 45 °C. For this reaction, adding formaldehyde to a mixture of Starting compound B, an alkaline catalyst and a solvent over a period of time is preferred in order to avoid generation of too much heat. Preferably, as the formaldehyde, an aqueous solution of formaldehyde is used. For the production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol, for example, the reaction mass is neutralized with acid to precipitated the reaction product and it is filtered to obtain the reaction product of high purity in high yield. In the reaction of Dimethylol A with para-cresol, para-cresol is used in an amount generally of 2 - 50 moles, preferably of 4 - 20 moles, per 1 mole of Dimethylol compound A. For the reaction of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol with para-cresol, the amount of 8 - 20 moles per 1 mole of Dimethylol compound A is more preferred. It is preferred that an acid catalyst is present in this reaction. The acid catalyst may be either an inorganic acid such as hydrochloric acid and sulfuric acid or an organic acid such as formic acid, acetic acid, propionic acid and paratoluene sulfonic acid. Among them, a mineral acid such as hydrochloric acid and sulfuric acid and paratoluene sulfonic acid is preferred, and among them, paratoluene sulfonic acid is particularly preferred. The acid catalyst is used in an amount usually of 1 equivalent or less and preferably within a range of 0.1 - 0.5 equivalent based on Dimethylol compound A. The reaction is preferably carried out in a solvent. Aromatic solvents, water or alcohols can be used as the reaction solvent for the reaction of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol], 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol, 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol or a compound of formula XV with para-cresol. For the reaction of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol with para-cresol, aromatic solvents, particularly aromatic hydrocarbon solvents, are preferred. Examples of the alcohols include lower alcohols such as methanol, ethanol, propanol and butanol, among which methanol is preferred. Examples of the aromatic hydrocarbon solvents include benzene, toluene and xylene, among which toluene is preferred. The reaction solvent is used in an amount generally within a range of 0.5- to 5-fold weight, preferably 1- to 3-fold weight, based on the total amount of Dimethylol compound A and p-cresol. The reaction is carried out at a temperature usually within a range of 10 °C to the boiling temperature, preferably within a range of 15 - 60°C, more preferably within a range of 40 - 60°C. The reaction is usually carried out under atmospheric pressure. The reaction product crystallizes as the reaction proceeds when the reaction is carried out around room temperature. When the reaction is carried out at a higher temperature, the reaction product crystallizes upon cooling to room temperature after completion of the reaction. A crude product can be obtained by isolating the crystals and may be subjected to an optional purification step. For example, the compound can be purified by crystallization from an aromatic solvent or by repetition thereof as desired. The crystallizing solvent may be the same as or different from that used in the reaction. The phenol compounds of the present invention, reaction products of the above-mentioned reactions, can be isolated by crystallization from an aromatic solvent such as benzene, toluene and xylene, preferably toluene. It is preferred to decrease the metal content of the phenol compounds of the present invention by dissolving the crude product in a solvent having a solubility of 9 g / 100 g or less in water, then washing the resulting solution with water and separating. A solubility of 9 g / 100 g or less means that the maximum amount of the solvent soluble in 100 g of water at 20°C is 9 g or less. Further, it is preferred to use a solvent in which the phenol compounds of the present invention have a solubility of 1 g / 100 g or more at a temperature of 20°C. Such solvent includes, for example, acetic acid esters such as ethyl acetate, n-butyl acetate and isoamyl acetate, ketones such as methyl isobutyl ketone and 2-heptanone, among which ethyl acetate is preferred. The phenol compounds of the present invention thus obtained can be converted into a quinonediazide sulfonic acid ester, which can be used as a photosensitizer. In the esterification, various kinds of sulfonic acid derivatives having a 1,2-quinonediazide structure such as 1,2-benzoquinonediazide-4- or -5-sulfonylhalide and 1,2-naphthoquinonediazide-4- or -5-sulfonyl halide can be used as an esterifying agent. Among them, 1,2-naphthoquinonediazide-4- or -5-sulfonyl halide is preferred. The halogen in the sulfonyl halide may be, for example, chlorine and bromine, among which chlorine is usually preferred. Hence, as the sulfonic acid derivatives, 1,2-naphthoquinonediazide-4- or -5-sulfonyl chloride is more preferred as an esterifying agent. Also, a mixture of 1,2-naphthoquinonediazide-4-sulfonyl halide and 1,2-naphthoquinonediazide-5-sulfonyl halide can be used. In the esterification reaction, quinonediazide sulfonyl halide is used in a molar ratio usually of 1.2 per 1 mole of the phenol compounds of the present invention. The reaction is usually conducted in the presence of a dehydrohalogenating agent. The dehydrohalogenating agent includes generally basic compounds, for example, inorganic bases such as sodium carbonate and sodium hydrogen carbonate and amines such as ethylamine, ethanolamine, diethylamine, diethanolamine, triethylamine, N,N-dimethylaniline and N,N-diethylaniline. The dehydrohalogenating agent is used in a molar ratio usually of 1.05 - 1.5, preferably of 1.05 - 1.2 and more preferably of 1.1 - 1.2, per 1 mole of 1,2-naphthoquinonediazide-4- or -5-sulfonyl halide. The esterification reaction is usually conducted in a solvent. The solvent for the reaction includes ethers, lactones, and aliphatic ketones and is preferably selected from dioxolane, 1,4-dioxane, tetrahydrofuran, γ-butyrolactone, acetone and 2-heptanone. These can be used alone or in combination of two or more. Among them, 1,4-dioxane is preferred. The solvent for reaction is used in an amount usually within a range of 2- to 6-fold weight, preferably 3- to 5- fold weight and more preferably 4- to 5-fold weight based on the total amount of the phenol compounds of the present invention and quinonediazide sulfonyl halide. The esterification reaction well proceeds under an ordinary pressure and around an ordinary temperature but generally conducted at a temperature of 20 - 30°C for 2 - 10 hours. After completion of the reaction, the objective ester crystallizes out when the reaction mixture is neutralized with an acid such as acetic acid, followed by filtering off solid substance and mixing of the filtrate with a diluted aqueous acid solution, for example, an aqueous acetic acid solution of about 1 % by weight. The ester can be isolated from the resulting mixture by filtration, washing and drying. By the esterification reaction, usually, a mixture of two or more of the quinonediazide sulfonyl esters of a phenol compound of the present invention wherein a part of the phenolic hydroxyl groups is converted into quinonediazide sulfonyl and all of the phenolic hydroxyl groups are converted into quinonediazide sulfonyl is produced, depending on the molar ratio of 1,2-naphthoquinone-diazide sulfonyl halide used. This mixture can usually be used as it is for a photosensitizer. A mixture of the quinonediazide sulfonyl esters produced from two or more kind of a phenol compound of the present invention can also be used. The esterified compounds may advantageously be used for photosensitizers sensitive to radiation such as ultraviolet rays and far ultraviolet rays (including excimer lasers). For a photosensitizer, if desired, the esterified compounds may be used in combination with a quinonediazide sulfonyl esters of another phenol compound. Examples of the quinonediazide sulfonyl esters of another phenol compound includes a compound described in JP-A-5-204148, a compound described in JP-A-5-323597(=EP-A-570,884), a compound described in JP-A-6-167805(=EP-A-573,056), and a compound represented by the following formula(VI): wherein one of R 21 and R 22 represents -OX 4 ; the other one of R 21 and R 22 , R 23 , R 24 and R 25 independently represent hydrogen, alkyl having 6 or less carbon atoms, cycloalkyl having 6 or less carbon atoms, alkenyl having 6 or less carbon atoms, alkoxy having 6 or less carbon atoms or halogen; R 26 and R 27 independently represent hydrogen, alkyl having 6 or less carbon atoms, alkenyl having 6 or less carbon atoms, or R 26 and R 27 form a cycloalkane ring having 6 or less carbon atoms together with a carbon atom to which they are connected; and X 1 , X 2 , X 3 and X 4 independently represent hydrogen or quinonediazide sulfonyl provided that at least one of X 1 , X 2 , X 3 and X 4 is quinonediazide sulfonyl (This compound is described in Japanese patent application No. 7-58826). In the present invention, the photosensitizer, including other quinonediazide sulfonic acid esters if used, is preferably contained in an amount within a range of 10 - 50 % by weight based on the total solid amount in the resist composition. The alkali-soluble novolak resins as a constituent of the positive resist composition are resins obtained by condensing a compound having at least one phenolic hydroxyl group with an aldehyde in the presence of an acid catalyst. They are not limited in their kind and may be any one usable in the field of resist. The phenol compounds as the starting material for the novolak resins include, for example, meta-cresol, para-cresol, ortho-cresol, 2,5-xylenol, 3,5-xylenol, 3,4-xylenol, 2,3,5-trimethylphenol, 2-t-butyl-5-methylphenol and t-butylhydroquinone. The aldehydes as the other starting material for the novolak resins include formaldehyde, acetaldehyde, benzaldehyde, glyoxal and salicylaldehyde. Particularly, formaldehyde is industrially mass-produced in the form of a 37 % aqueous solution and is suitable for use. The novolak resins are obtained by condensing one, two or more of the phenol compounds with one, two or more of the aldehydes in the presence of an acid catalyst. As the acid catalyst, an organic acid, an inorganic acid or a salt of bivalent metal may be used. Specific examples include oxalic acid, acetic acid, para-toluene sulfonic acid, hydrochloric acid, sulfuric acid, phosphoric acid and zinc acetate. The condensation reaction can be conducted according to the ordinary method, for example, at a temperature within a range of 60 - 120°C for about 2 - 30 hours. The reaction may be carried out without diluent or in a suitable solvent. The obtained novolak resin is preferably treated, for example by fractionation, to form a resin which has a ratio of an area in a pattern of gel-permeation chromatography (GPC, using a UV254 nm detector ) for a portion having a molecular weight converted into polystyrene of 900 or less being 25 % or less based on the total area in the pattern except an area in the pattern for unreacted phenol compound, for purposes such as minimization of undeveloped residue of the resist. Further, it is more preferred to adjust the ratio of area for the portion having a molecular weight converted into polystyrene of 900 or less to 20 % or less. Methods for the fractionation include a method in which the novolak resin is dissolved in a good solvent, for example, an alcohol such as methanol and ethanol, a ketone such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, an ethylene glycol ether such as ethyl cellosolve, an ethylene glycol ether ester such as ethyl cellosolve acetate or a cyclic ether such as tetrahydrofuran, and then the solution is poured into water to precipitate high molecular weight components; and a method in which the above solution is mixed with a poor solvent such as pentane, hexane and heptane, followed by phase separation. It is also effective to add an alkali-soluble phenol compound having a molecular weight of 900 or less to the novolak resin which is made rich in high molecular weight components by a fractionation treatment such as those mentioned above. The alkali-soluble phenol compounds having a molecular weight of 900 or less preferably have two or more phenolic hydroxyl groups in the molecular structure and include, for example, those described in JP-A-2-275955 (EP-A-358,871) or JP-A-2-2560. The alkali-soluble phenol compound having a molecular weight of 900 or less, when used, is preferably contained in an amount within a range of 3 - 40 % by weight based on the total solid amount in the resist composition. Preparation of a resist solution is carried out by mixing and dissolving a photosensitizer, an alkali soluble resin and further, if necessary, an alkali-soluble phenol compound having a molecular weight of 900 or less in a solvent. As the solvent, one which has a suitable drying rate and which gives a uniform and flat membrane after evaporation is preferred. Such solvents include glycol esters such as propylene glycol monomethyl ether acetate, ethyl cellosolve acetate and methyl cellosolve acetate, esters such as ethyl pyruvate, n-amyl acetate and ethyl lactate, ketones such as 2-heptanone, cyclic esters such as γ-butyrolactone, and further solvents described in JP-A-2-220056, those described in JP-A-4-362645 and those described in JP-A-4-367863. These solvents can be used singly or in combination of two or more. The obtained resist solution or photosensitive resin composition may further contain a small amount of resin or dye as required. EXAMPLES The present invention will be described in more detail with Examples which should not be construed as a limitation to the scope of the present invention. In the Examples, % and parts used for showing contained or added amount are weight based unless otherwise specified. Example 1 (1)Production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol Into a 3 liter four-necked flask were charged 263.6 g of 2,6-bis(4-hydroxy-2,5-dimethylbenzyl)-4-methylphenol, 67.2 g of sodium hydroxide, 1169.3 g of water and 107.5 g of tetrahydrofuran and they were completely dissolved. While stirring at 40°C, 340.9 g of 37% formaldehyde was added dropwise thereto over 1 hour, and the reaction was conducted for 2 more hours. After completion of the reaction, 134.4 g of 90 % aqueous acetic acid solution was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 g of deionized water. The resulting product was dried a whole day and night under reduced pressure at 45°C to obtain 265 g of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol Purity measured by liquid chromatography(LC): 80% Mass spectrum: MS 436 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.95 (s, 3H); 2.05 (s, 6H); 2.10 (s, 6H); 3.78 (S, 4H); 4.65 (s, 4H); 5.23 (brs, 2H); 6.31 (s, 2H); 6.70 (s, 2R); 8.18 (brs, 1H); 8.60 (brs, 2H). (2) Production of 2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl]-4-methylphenol (hereinafter referred to as compound 1) Into a 1 liter of four-necked flask were charged 1.90 g of para-toluene sulfonic acid, 86.51 g of para-cresol and 176.83g of toluene. Further, keeping the temperature at 30°C, 21.83 g of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol obtained above and having a purity of 80 % was added in ten portions over 1 and half hours. The mixture was stirred at the same temperature for three more hours. After completion of the reaction, the mixture was filtered and rinsed with 200 g of toluene. The filter cake was added to a mixed solvent of 200 g of toluene and 400 g of ethyl acetate and dissolved at 60 °C. Thereafter, 400 g of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Then, metal content was removed by adding 400 g of 1% aqueous oxalic acid solution, followed by stirring the mixture and by carrying out a phase separation. Thereafter, washing with 400g of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 200g of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200g of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 22.87 g of compound 1. Purity(LC) : 94.6% Mass spectrum: MS 616 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.88 (s, 6H); 1.95 (s, 3H); 2.03 (s, 6H); 2.13 (s, 6H); 3.78 (s, 4H); 3.88 (s, 4H); 6.28 (s, 2H); 6.32 (s, 2H); 6.68 (d, J = 8.2 Hz, 2H); 6.70 (s, 2H); 6.74 (d, J = 8.2 Hz, 2H); 7.95 (brs, 2H); 8.12 (brs, 1H); 9.20 (brs, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 1 Into a 100 ml four-necked flask were charged 1.85 g of compound 1 obtained above, 1.61 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 17.33 g of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 0.73 g of triethylamine was added dropwise over 1 hour. After addition was completed, the mixture was stirred for 3 hours. Thereafter,. 0.18 g of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to a mixture of 0.8g of acetic acid and 80 g of deionized water. The resulting mixture was stirred for 1 hour, filtered and washed. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 3.23 g of the ester (hereinafter referred to as Photosensitizer I). Mass spectrum of the main component : MS 1080 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.70 (s, 6H); 1.95 (s, 3H); 2.05 (s, 6H); 2.13 (s, 6H); 3.75 (s, 4H); 3.86 (s, 4H); 6.22 (s, 2H); 6.40 (s, 2H); 6.65 (d, J = 8.2 Hz, 2H); 6.72 (s, 2H); 6.88 (d, J = 8.2 Hz, 2H); 7.42 (d, J = 7.9 Hz, 2H); 7.64 (t, J = 7.9 Hz, 2H); 7.75 (d, J = 7.9 Hz, 2H); 8.04(s, 2H); 8.15 (s, 1H); 8.25 (d, J = 7.9 Hz, 2H); 8.62 (d, J = 7.9 Hz, 2H). Formula of the compound 1 is shown below. Example 2 (1)Production of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol] Into a four-necked flask were charged 78.7 parts of 4,4'-methylenebis[2-(4-hydroxy-2,5-dimethylbenzyl)-3,6-dimethylphenol], 28.8 parts of sodium hydroxide, 850 parts of water and 150 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 45.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45°C to obtain 71.9 parts of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol] (2) Production of 4,4'-methylenebis[2-{4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl}-3,6-dimethylphenol](hereinafter referred to as compound 2) Into a four-necked flask were charged 3.80 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 216 parts of toluene. Further, keeping the temperature at 40°C, 58.5 parts of 4,4'-methylenebis[2-(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol] obtained above was added. The mixture was stirred at the same temperature for three more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 26.9 parts of compound 2. Mass spectrum: MS 764 1 H-NMR (dimethylsulfoxide) δ(ppm): 1.88 (s, 6H); 1.98 (s, 6H); 2.03 (s, 6H); 2.10 (s, 6H); 2.12 (s, 6H); 3.71 (s, 4H); 3.83 (s, 4H); 3.90 (s, 48); 6.14 (s, 2H); 6.40 (s, 2H); 6.53 (s, 2H); 6.70 (d, J = 8.2 Hz, 2H); 6.75 (d, J = 8.1 Hz, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 2 Into a four-necked flask were charged 7.7 parts of compound 2 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 65 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 770 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.7 parts of the ester (hereinafter referred to as Photosensitizer N). Mass spectrum of the main component : MS 1228 Example 3 (1)Production of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol Into a four-necked flask were charged 54.4 parts of 2,6-bis(4-hydroxy-3-methylbenzyl)-3,4-dimethylphenol, 21.6 parts of sodium hydroxide, 900 parts of water and 100 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 36.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45 °C to obtain 57.1 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol. (2) Production of 2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-5-methylbenzyl]-3,4-dimethylphenol(hereinafter referred to as compound 3) Into a four-necked flask were charged 3.80 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 216 parts of toluene. Further, keeping the temperature at 40°C, 42.3 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,4-dimethylphenol obtained above was added. The mixture was stirred at the same temperature for three more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 25.6 parts of compound 3. Mass spectrum: MS 602 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.95 (s, 3H); 2.02 (s, 3H); 2.06 (s, 3H); 2.07 (s, 3H); 2.10 (s, 6H); 3.70 (s, 2H); 3.72 (s, 2H); 3.75 (s, 2H); 3.83 (s, 2H); 6.56 (s, 1H); 6.60 (s, 1H); 6.69 (m, 5H); 6.76 (m, 4H); 7.69 (s, 1H); 7.88 (brs, 2H); 9.12 (brs, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 3 Into a four-necked flask were charged 6.0 parts of compound 3 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 57 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 780 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.6 parts of the ester (hereinafter referred to as Photosensitizer O). Mass spectrum of the main component : MS 1066 Example 4 (1)Production of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol Into a four-necked flask were charged 52.3 parts of 2,6-bis(4-hydroxy-3-methylbenzyl)-4-methylphenol, 21.6 parts of sodium hydroxide, 900 parts of water and 100 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 36.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45 °C to obtain 55.1 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol. (2) Production of 2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-5-methylbenzyl]-4-methylphenol(hereinafter referred to as compound 4) Into a four-necked flask were charged 3.8 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 216 parts of toluene. Further, keeping the temperature at 40°C, 40.8 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-4-methylphenol obtained above was added. The mixture was stirred at the same temperature for three more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 24.5 parts of compound 4. Mass spectrum: MS 588 1 H-NMR (dimethylsulfoxide) δ (ppm): 2.02 (s, 3H); 2.10 (s, 12H); 3.68 (s, 4H); 3.74 (s, 4H); 6.51 (s, 2H); 6.68 (d, J = 7.9 Hz, 2H); 6.70 (s, 2H); 6.74 (s, 4H); 6.78 (d, J = 7.9 Hz, 2H); 8.01 (s, 1H); 8.07 (brs, 2H); 9.37 (brs, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 4 Into a four-necked flask were charged 5.9 parts of compound 4 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 56 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 780 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.5 parts of the ester (hereinafter referred to as Photosensitizer P). Mass spectrum of the main component : MS 1052 Example 5 (1)Production of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol Into a four-necked flask were charged 60.7 parts of 2,6-bis(4-hydroxy-2,5,6-trimethylbenzyl)-4-methylphenol, 21.6 parts of sodium hydroxide, 900 parts of water and 100 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 36.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45 °C to obtain 65.6 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol. (2) Production of 2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5,6-trimethylbenzyl]-4-methylphenol(hereinafter referred to as compound 5) Into a four-necked flask were charged 3.8 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 324 parts of toluene. Further, keeping the temperature at 40°C, 46.5 parts of 2,6-bis(4-hydroxy-3-hydroxymethyl-2,5,6-trimethylbenzyl)-4-methylphenol obtained above was added. The mixture was stirred at the same temperature for 3 more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 23.3 parts of compound 5. Mass spectrum: MS 644 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.85 (s, 3H); 1.88 (s, 6H); 2.01 (s, 6H); 2.03 (s, 6H); 2.14 (s, 6H); 3.88 (s, 8H); 5.99 (s, 2H); 6.31 (s, 2H); 6.67 (d, J = 7.6 Hz, 2H); 6.74 (d, J = 7.6 Hz, 2H); 7.87 (s, 2H); 8.31 (s, 1H); 9.21 (s, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 5 Into a four-necked flask were charged 6.4 parts of compound 5 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 59 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 780 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.8 parts of the ester (hereinafter referred to as Photosensitizer Q). Mass spectrum of the main component : MS 1108 Example 6 (1)Production of 2,4-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol Into a four-necked flask were charged 58.6 parts of 2,4-bis(4-hydroxy-2,5-dimethylbenzyl)-3,6-dimethylphenol, 21.6 parts of sodium hydroxide, 900 parts of water and 100 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 36.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45 °C to obtain 59.5 parts of 2,4-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol. (2) Production of 2,4-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl]-3,6-dimethylphenol(hereinafter referred to as compound 6) Into a four-necked flask were charged 3.8 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 216 parts of toluene. Further, keeping the temperature at 40°C, 45.1 parts of 2,4-bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-3,6-dimethylphenol obtained above was added. The mixture was stirred at the same temperature for 3 more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 20.8 parts of compound 6. Mass spectrum: MS 630 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.86 (s, 3H); 1.93 (s, 3H); 1.98 (s, 3H); 2.02 (s, 6H); 2.09 (s, 3H); 2.10 (s, 3H); 2.11 (s, 3H); 3.69 (s, 2H); 3.82 (s, 2H); 3.88 (s, 2H); 3.89 (s, 2H); 6.13 (s, 1H); 6.33 (s, 1H); 6.39 (s, 1H); 6.47 (s, 1H); 6.53 (s, 1H); 6.69 (d, J = 8.1 Hz, 2H); 6.75 (d, J = 8.1 Hz, 2H); 7.86 (s, 1H); 7.87 (s, 1H); 7.93 (s, 1H); 9.23 (s, 1H); 9.25 (s, 1H); (3) Production of quinonediazide sulfonic acid ester of compound 6 Into a four-necked flask were charged 6.3 parts of compound 6 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 58.5 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 780 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.4 parts of the ester (hereinafter referred to as Photosensitizer R). Mass spectrum of the main component : MS 1094 Example 7 (1)Production of 2,4-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,6-dimethylphenol Into a four-necked flask were charged 54.4 parts of 2,4-bis(4-hydroxy-3-methylbenzyl)-3,6-dimethylphenol, 21.6 parts of sodium hydroxide, 900 parts of water and 100 parts of tetrahydrofurane and they were completely dissolved. While stirring at 40°C, 73.0 parts of 37% formaldehyde was added dropwise thereto and the reaction was conducted for 6 hours. After completion of the reaction, 36.0 parts of acetic acid was added for neutralization and then the mixture was cooled to 25 °C. Thereafter, the precipitated crystalline product was filtered out and rinsed with 1000 parts of deionized water. The filtered product was dried a whole day and night under reduced pressure at 45 °C to obtain 56.4 parts of 2,4-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,6-dimethylphenol. (2) Production of 2,4-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-5-methylbenzyl]-3,6-dimethylphenol(hereinafter referred to as compound 7) Into a four-necked flask were charged 3.8 parts of para-toluene sulfonic acid, 108.1 parts of para-cresol and 216 parts of toluene. Further, keeping the temperature at 40°C, 42.3 parts of 2,4-bis(4-hydroxy-3-hydroxymethyl-5-methylbenzyl)-3,6-dimethylphenol obtained above was added. The mixture was stirred at the same temperature for 3 more hours. After completion of the reaction, the mixture was cooled to 20°C and filtered, and the filter cake was rinsed with 400 parts of toluene. The filter cake was added to a mixed solvent of 400 parts of toluene and 600 parts of ethyl acetate and dissolved at 60 °C. Thereafter, 400 parts of deionized water was added thereto and the resulting mixture was stirred and a phase separation was carried out. Thereafter, washing with 400 parts of deionized water was repeated four times, and the oil phase was concentrated. To the concentrated mass, 400 parts of toluene was added and the resulting solution was cooled to 20 °C and filtered. The filter cake was rinsed with 200 parts of toluene and dried a whole day and night under reduced pressure at 45°C to obtain 18.1 parts of compound 7. Mass spectrum: MS 602 1 H-NMR (dimethylsulfoxide) δ (ppm): 1.91 (s, 3H); 1.99 (s, 3H); 2.04 (s, 3H); 2.07 (s, 3H); 2.08 (s, 3H); 2.10 (s, 3H); 3.61 (s, 2H); 3.70 (s, 2H); 3.71 (s, 2H); 3.80 (s, 2H); 6.55 (s, 2H); 6.65 (d, J = 8.2 Hz, 2H); 6.66 (s, 2H); 6.69 (s, 4H); 6.78 (d, J = 8.2 Hz, 2H); 7.89 (s, 1H); 8.02 (brs, 2H); 9.34 (brs, 2H). (3) Production of quinonediazide sulfonic acid ester of compound 7 Into a four-necked flask were charged 6.0 parts of compound 7 obtained above, 5.4 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 57 parts of 1,4-dioxane and the temperature was adjusted to 25°C. Thereto, 2.4 parts of triethylamine was added dropwise. After addition was completed, the mixture was stirred for 3 hours. Thereafter, 0.6 part of acetic acid was added for neutralization and the reaction mixture was filtered. The filtrate was added to 780 parts of 1 % aqueous acetic acid solution. The resulting mixture was stirred for 1 hour, filtered and washed with deionized water. The finally obtained filter cake was dried a whole day and night at 45°C under reduced pressure to obtain 10.2 parts of the ester (hereinafter referred to as Photosensitizer S). Mass spectrum of the main component : MS 1066 Reference Example: Production of novolak resin Into a 1000 ml four-necked flask were charged 148.5 g of meta-cresol, 121.5 g of para-cresol, 252 g of methyl isobutyl ketone, 37.0 g of 10 % oxalic acid and 84.8 g of 90 % aqueous acetic acid solution. Heating the mixture in an oil bath at 100°C with stirring, 129.5 g of 37 % formaldehyde solution was added dropwise thereto over 40 minutes and reaction was effected for further 15 hours. Then, the mixture was washed with water and water was removed to obtain 466 g of a methyl isobutyl ketone solution containing 42.3 % of novolak resin. The resin had a weight average molecular weight, converted into polystyrene, of 4300 as determined by GPC. Into a 5 litter bottom-discharging separable flask was charged 450 g of the above obtained solution and 909.6 g of methyl isobutyl ketone and 996.1 g of n-heptane were added thereto. After stirring at 60°C for 30 minutes, the mixture was left still and subjected to a phase-separation. To the lower layer mass obtained by the separation was added 380 g of 2-heptanone, and methyl isobutyl ketone and n-heptane were removed therefrom by an evaporator to obtain a 2-heptanone solution of a novolak resin. The resin had a weight average molecular weight, converted into polystyrene, of 9000 as determined by GPC, and a ratio of an area for a portion having a molecular weight converted into polystyrene of 900 or less was 14 % based on the total area in the pattern. Examples 8 - 14 A 15 parts portion, converted into solid weight, of a solution of the novolak resin in 2-heptanone obtained in Reference Example, 3.9 parts of 1,3-bis[1-(2,4-dihydroxyphenyl)-1-methylethyl]benzene as an additive, 5 parts of Photosensitizer shown in Table I, 1 part of a condensation product, in a molar ratio of 1:4, of 1,2,3-trihydroxy-4-(4-hydroxy-2,5-dimethylbenzyl)benzene and 1,2-naphthoquinonediazide-5-sulfonylchloride, as the other photosensitizer, and 2-heptanone were mixed in such manner that the total amount of 2- heptanone became 50 parts and they were dissolved. The solution was filtered through a fluorine resin filter having a pore size of 0.2 µm to give a resist solution. The above resist solution was coated onto silicone wafers, using a spin coator so that the resist film thickness after dried become 1.1 µm, and the wafers were washed by conventional means and were baked on a hot plate at 90°C for 1 minute. Then, they were exposed to irradiation with a reduced projection exposing machine (manufactured by Nikon Kabushiki Kaisha, NSR 1755i 7A, NA = 0.5) having an exposing wave length of 365 nm (i-line) changing the exposure amount in steps. Then, the wafers were baked on a hot plate at 110°C for 1 minute and developed with a developing solution "SOPD" (manufactured by Sumitomo Chemical Company, Limited) for 1 minute to give positive patterns. Each of the positive patterns were evaluated in the following manner. The results are shown in Table 1. Effective sensitivity: This was expressed in terms of the exposure amount at which the 0.50 µm line and space pattern became 1 : 1. Resolution: The size of the line and space pattern separable without loss of film was measured with a scanning electron microscope at an exposure amount at which the line and space pattern became 1 : 1 (effective sensitivity). Profile: The shape of cross-section of 0.45 µm line and space pattern at the effective sensitivity was observed with a scanning electron microscope. Focus (Depth of focus): The depth of focus where 0.40 µ m line and space pattern was separable without loss of film at the effective sensitivity was measured with a scanning electron microscope. Scum: Presence or absence of scum (undeveloped residue) was observed with a scanning electron microscope. γ-value: The ascent  of a line obtained by plotting normalized thickness of resist film(= residual thickness of resist film / original thickness of resist film) with respect to the logarithm of exposure amount was measured and tan  was taken as the γ-value. Properties Example No. Photosensitizer Effective Sensitivity msec Resolution µm Depth of Focus µm Scum γ-value 8 I 230 0.375 1.5 none 6.82 9 N 420 0.34 - none 5.43 10 O 130 0.35 - none 3.39 11 P 112 0.39 - none 4.11 12 Q 167 0.32 - none 4.53 13 R 198 0.34 - none 4.06 14 S 142 0.37 - none 3.71 Profile in Example 9 - 14 The naphthoquinonediazide sulfonic acid ester of polyphenol compounds of the present invention are useful as a photosensitizer for a photosensitive resin composition. The positive photo resist of the present invention is well balanced among various properties as the resist for minute processing of semiconductors such as high sensitivity, high resolution (γ-value), high heat resistance, good profile, good focus allowance, and little development residue.

Claims: A phenol compound represented by the following formula VII. wherein i) Y 1 =Y 2 = -CH 3 , A= -OR, B=D=E= -H or ii) Y 1 =Y 2 = -H, A= -OR, B=E= -H, D= -CH 3 or iii) Y 1 =Y 2 = -H, A= -OR, B=D=E= -H or iv) Y 1 =Y 2 = -CH 3 , A= -OR, B=E= CH 3 , D=-H or v) Y 1 =Y 2 = -H or -CH 3 , A= -CH 3 , B=E=-H, D= -OR and wherein each R independently represents hydrogen, 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl, with the proviso that at least one R is 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl. A phenol compound represented by the following formula X wherein R 33 , R 34 , R 35 , R 36 , R 37 and R 38 independently represent hydrogen, 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl provided that at least one of R 33 , R 34 , R 35 , R 36 , R 37 and R 38 is 1,2-naphthoquinonediazide-4-sulfonyl or 1,2-naphthoquinonediazide-5-sulfonyl. 2,6-Bis(4-hydroxy-3-hydroxymethyl-2,5-dimethylbenzyl)-4-methylphenol. Use of the phenol compounds of any of claims 1 to 3 in positive photoresist compositions.

Inventors: ICHIKAWA KOJI, INOUE HIROKI, OSAKI HARUYOSHI, ICHIKAWA, KOJI, INOUE, HIROKI, OSAKI, HARUYOSHI
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1996
Main classification: C07C39
IPC codes: C07C39, G03F7, C07C309