JP7089140B2 - Resin for photoresist, method for producing resin for photoresist and photoresist composition - Google Patents

Description

The present invention relates to a photoresist resin, a method for producing a photoresist resin, and a photoresist composition.

In recent years, the line width of circuit patterns of integrated circuit semiconductors has been steadily becoming finer as the degree of integration has increased. Further, in the case of liquid crystal display elements and the like, the wiring width is also narrowed, and there is a tendency for the wiring width to be miniaturized. As display panels become larger and cheaper, there is a need for technology to stably form wiring on large substrates in a simple process.
Conventionally, in the photolithography technique used in the semiconductor field, a step of patterning a resist film and then forming wiring by a wet etching method or a dry etching method is widespread. The photolithography technique is also being applied in the manufacturing process of liquid crystal display elements.
Along with this, the required performance of resin materials for photoresists has become more sophisticated and diversified. It is necessary to have excellent high developability such as sensitivity and resolution, and excellent etching resistance such as wet etching resistance and dry etching resistance.

Phenol resins are used for photoresist applications, and the cresol novolac type phenol resin is the most widely used. The cresol novolak type phenol resin is obtained by reacting cresol (ortho, meta, para) with formaldehyde in the presence of an acid catalyst. In order to adjust or improve the characteristics of the photoresist, the ratio and molecular weight of cresol (ortho, meta, para) are being investigated. Further, the cresol novolak resin having a reduced content of low molecular weight below the dimer is attracting attention as a resin having an excellent balance of sensitivity and resolution.
As such a cresol novolak type phenol resin, a cresol novolak type phenol resin containing orthocresol as an essential component has been studied (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-115728

However, it becomes difficult to stably obtain a cresol novolak type phenol resin containing orthocresol as an essential component as described in Patent Document 1 at a high molecular weight when the usage ratio of low-reactivity orthocresol is increased. .. In addition, the conventional cresol novolac type phenol resin cannot meet the performance required by the market in recent years, which is becoming more sophisticated and diversified, and its etching resistance is not sufficient.

Therefore, an object of the present invention is to provide a photoresist composition having high sensitivity and resolution and excellent dry etching resistance, a photoresist resin used in this photoresist composition, and a method for producing the same. ..

As a result of diligent studies to solve the above problems, the present inventors have high sensitivity and resolution by using a condensed polymer of an orthocresol novolak resin and a phenol compound having at least two methylol groups in the molecule. , And have found that a photoresist composition having excellent dry etching resistance can be obtained, and have reached the present invention.

That is, the present invention is a photoresist resin containing a polycondensation polymer of a novolak resin containing orthocresol as a main component and a phenol compound having at least two methylol groups in the molecule.

INDUSTRIAL APPLICABILITY According to the present invention, a photoresist composition having high sensitivity and resolution and excellent dry etching resistance, a photoresist resin used in this photoresist composition, and a method for producing the same are provided.

[Resin for photoresist]
The photoresist resin of the present invention contains a polycondensation polymer of an orthocresol novolak resin and a phenolic compound having at least two methylol groups in the molecule.

<Novolak resin containing orthocresol as the main component>
The novolak resin containing orthocresol as a main component (hereinafter, also simply referred to as “orthocresol novolak resin”) is a polycondensate of orthocresol and formaldehyde.

Orthocresol suppresses the formation of the binuclear component of the orthocresol novolak resin obtained by polycondensation. Thereby, the binuclear body content of the photoresist resin of the present invention can be suppressed.
Other phenols may be contained as long as the action of orthocresol is not impaired. The other phenols are not particularly limited, but for example, phenol, p-cresol, m-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xyleno-. 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, trimethylphenol -Le, naphthol, allylphenol, catechol, resorcinol, hydroquinone and the like are exemplified. It is desirable that the amount of other phenols is about 5% by mass or less of orthocresol.

Formaldehyde can be used in any form and polycondensed with orthocresol. For example, an aqueous solution of formaldehyde and a polymer such as paraformaldehyde and trioxane that decomposes in the presence of an acid to form formaldehyde can be preferably used.
The binuclear body content of the orthocresol novolak resin is not particularly limited, but is preferably 15% or less of the total resin. When the binuclear body content of the orthocresol novolak resin is 15% or less of the total resin, the binuclear body content of the obtained photoresist resin is also suppressed, and etching resistance can be ensured when the photoresist composition is prepared. .. The binuclear body content of the orthocresol novolak resin is more preferably 12% or less, further preferably 10% or less, and most preferably 5% or less.
The binuclear body content of the orthocresol novolak resin can be measured by gel permeation chromatography (GPC) measurement, for example, by the method described in Examples described later.

The weight average molecular weight (Mw) of the orthocresol novolak resin is not particularly limited, but is preferably 1000 to 40,000 from the viewpoint of the performance of the photoresist composition and the handleability in production. By using an orthocresol novolak resin having a weight average molecular weight of 1000 to 40,000, a resin for a photoresist having desired characteristics can be obtained. The weight average molecular weight of the orthocresol novolak resin is more preferably 1500 to 30,000, even more preferably 1500 to 25,000. By controlling the weight average molecular weight (Mw) of the orthocresol novolak resin, the weight average molecular weight of the photoresist resin of the present invention can be easily adjusted.
The weight average molecular weight of the orthocresol novolak resin is a weight average molecular weight in terms of standard polystyrene by gel permeation chromatography (GPC) measurement, and can be measured by, for example, the method described in Examples described later.

（ここで、ｐは１～１００の整数を表す。） One of the preferred embodiments of the orthocresol novolak resin is a polycondensate obtained by reacting orthocresol and formaldehyde under an acid catalyst, and is represented by the following general formula (AA).

(Here, p represents an integer from 1 to 100.)

In the orthocresol novolak resin represented by the above general formula (AA), p is a repetition number and represents an integer of 1 or more and 100 or less. Since the orthocresol novolak resin is an aggregate of molecules having various repetition numbers p, it can be expressed as an average value p'. Here, the average value p'is a value such that the above-mentioned weight average molecular weight (Mw) is preferably 1000 or more and 40,000 or less, and more preferably a weight average molecular weight (Mw) of 1500 or more and 30,000 or less. The weight average molecular weight (Mw) is more preferably 1500 or more and 25,000 or less.

<Phenol compound>
The phenolic compound used in the present invention is a phenolic compound in which at least two methylol groups (-CH ₂ OH) are bonded to the same benzene nucleus in the molecule, and the methylol group is bonded to a plurality of benzene nuclei existing in the molecule to form the entire molecule. A phenolic compound having at least two methylol groups, or a mixture thereof.
The methylol group is a reactive group. Such a phenol compound having at least two methylol groups stably reacts with the orthocresol novolak resin to efficiently increase the weight average molecular weight of the photoresist resin of the present invention. Thereby, the weight average molecular weight can be easily adjusted. In addition, the binuclear body content of the photoresist resin of the present invention can be reduced.

（式中、Ｒ_１、Ｒ_２及びＲ_３はそれぞれ独立に、炭素数が１～６のアルキル基または水酸基を表す。）

（式中、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８及びＲ_９はそれぞれ独立に、炭素数が１～６のアルキル基または水酸基を表す。） Examples of preferred phenolic compounds are shown below.

(In the formula, R ₁ , R ₂ and R ₃ independently represent an alkyl group or a hydroxyl group having 1 to 6 carbon atoms.)

(In the formula, R ₄ , R ₅ , R ₆ , R ₇ , R ₈ and R ₉ each independently represent an alkyl group or a hydroxyl group having 1 to 6 carbon atoms.)

Specifically, examples of the phenol compound include m-cresol, p-cresol, o-cresol, 2,3-xylenoyl, 2,4-xylenoyl, 2,5-xylenol, and the like. 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, and 4-t -Dimethylol compounds such as butylcatechol can be preferably mentioned.

Examples of more preferred phenolic compounds are shown below.

Examples of more preferred phenolic compounds are shown below.

<Mass ratio ( _MA / _MB )>
The polycondensation product in the photoresist resin of the present invention is obtained by a polycondensation reaction between an orthocresol novolak resin and a phenol compound. The ratio ( _MA / _MB ) of the mass _MA of the _orthocresol novolak resin to the mass MB of the phenol compound is 50/50 to 95/5, preferably 70/30 to 95/5, and more. It is preferably 80/20 to 95/5, and more preferably 80/20 to 90/10.
The mass ratio ( _MA / MB) of the _orthocresol novolak resin and the phenol compound in the polycondensation product is determined by adjusting the ratio of the orthocresol novolak resin and the phenol compound used in the polycondensation reaction, as described later. Can be controlled.

When the mass ratio ( _MA / _MB ) is 50/50 to 95/5, the weight average molecular weight of the photoresist resin of the present invention can be efficiently increased, and the weight average molecular weight can be easily adjusted. can. In addition, the binuclear body content of the photoresist resin of the present invention can be reduced. By using the photoresist resin of the present invention, a photoresist composition having an excellent balance between high etching resistance and other performance can be obtained.

If the orthocresol novolak resin occupies 50% by mass or more of the photoresist resin of the present invention, it dissolves in an alkaline solution at an appropriate rate and exhibits sufficient etching resistance when made into a photoresist composition. On the other hand, if the phenol compound occupies 5% by mass or more of the photoresist resin of the present invention, the weight average molecular weight of the photoresist resin of the present invention is efficiently increased. Such a photoresist resin can be dissolved in an alkaline solution at an appropriate rate to ensure sufficient etching resistance when the photoresist composition is obtained.

<2 Nucleolus content>
The binuclear body content of the photoresist resin of the present invention is not particularly limited, but is preferably 5% or less of the total resin. When the binuclear body content of the photoresist resin of the present invention is 5% or less, sufficient etching resistance is ensured when the photoresist composition is prepared. In the photoresist resin of the present invention, the binuclear body content is more preferably 3% or less of the total resin, and most preferably 2% or less.

The binuclear body content of the photoresist resin can be reduced, for example, by reacting the orthocresol novolak resin of the present invention with a phenol compound having at least two methylol groups in the molecule, and has heat resistance and alkali dissolution. A phenolic resin having particularly good properties can be obtained. In addition, it can be adjusted by, for example, a method such as solvent fractionation or removal by steam distillation. Further, the binuclear body content of the photoresist resin can be measured by gel permeation chromatography (GPC), for example, by the method described in Examples described later.

<Block Polymer>
The photoresist resin of the present invention comprises a first segment derived from an orthocresol novolak resin and a second segment derived from a phenolic compound having at least two methylol groups in the molecule, the first segment and the first segment. It is preferable that the two segments are blocked.
As the photoresist resin of the present invention, a novolak type phenol resin obtained by a two-step reaction of the reaction represented by the following formula 1 and the reaction represented by the formula 2 can be exemplified.

First, the reaction of the formula 1 gives an orthocresol novolak resin in which orthocresols are bonded to each other by a methylene group ( _-CH2- ). This is referred to as the first segment S1. By reacting the orthocresol novolak resin obtained by this reaction with the phenol compound as shown in the formula 2, the first segment S1 derived from the orthocresol novolak resin and the second segment derived from the phenol compound are obtained. A novolak-type phenolic resin in which the first segment S1 and the second segment S2 are blocked can be obtained.

（ただし、ｐは１から１００の整数を示し、ｑはセグメント（Ｓ２）同士が縮重合した場合の重合度を示し、ｒはセグメント（Ｓ１）とセグメント（Ｓ２）とが縮重合した重合度を示し、ｑ、ｒはそれぞれ独立に１から１００の整数を示す。）

(However, p indicates an integer from 1 to 100, q indicates the degree of polymerization when the segments (S2) are polycondensed, and r indicates the degree of polymerization in which the segment (S1) and the segment (S2) are polycondensed. Indicated, q and r each independently indicate an integer from 1 to 100.)

The photoresist resin of the present invention has a structure such as, for example, S1S2S1S2S1S2 ..., S1S2S1S2S2S1 ... For example, when phenols containing orthocresol and paracresol and formaldehyde are subjected to a random polycondensation reaction in one step, such a structure cannot be obtained. The photoresist resin of the present invention has a chemical structure different from that of the conventional novolak type phenol resin.

Since the reaction proceeds as described above, the distribution of the degree of polymerization of each polymerization unit existing in a block is narrowed, and the molecular weight can be easily controlled. Phenolic compounds having at least two methylol groups in the molecule are reliably consumed and incorporated into the resin. In this way, the polycondensation reaction is completed, and the novolak type phenol resin of the present invention is produced. By using the novolak type phenol resin of the present invention, a photoresist composition having high sensitivity, high resolution, wet etching resistance, and dry etching resistance can be obtained.

<Additional polymerization unit>
The block polymer described above may contain yet another polymerization unit. Examples of the further polymerization unit include aldehydes derived from formaldehyde used for polycondensation of orthocresol novolak resin.

<Weight average molecular weight (Mw)>
The weight average molecular weight (Mw) of the photoresist resin of the present invention is not particularly limited, but is preferably more than 3000 to 50,000 from the viewpoint of performance when the photoresist composition is obtained and handling in manufacturing. When the weight average molecular weight is in the range of 3000 to 50,000, the desired sensitivity and resolution can be obtained when the photoresist composition is prepared. The weight average molecular weight of the photoresist resin is more preferably 5000 to 30,000, still more preferably 5000 to 20000.

<Softening point>
The softening point of the photoresist resin of the present invention is preferably 140 ° C. or higher, more preferably 150 ° C. or higher, and most preferably 160 ° C. or higher. When the softening point is 140 ° C. or higher, it has sufficient heat resistance for use as a photoresist.

[Manufacturing of resin for photoresist]
The method for producing a photoresist resin of the present invention includes two steps, a first step and a second step. In the first step, an orthocresol novolak resin is obtained by a polycondensation reaction between orthocresol and formaldehyde. In the second step, the orthocresol novolak resin and the phenol compound having at least two methylol groups in the molecule are subjected to a polycondensation reaction.

In the present invention, as a first step, an orthocresol novolak resin is obtained in advance by a polycondensation reaction between orthocresol and formaldehyde. As a result, in the subsequent second step, when the phenol compound having at least two methylol groups in the molecule is subjected to a polypolymer reaction, at least the first segment derived from the orthocresol novolak resin and the second segment derived from the phenol compound are derived. It is possible to produce a novolak-type phenolic resin containing the above-mentioned segment and blocking the first segment and the second segment.

<First step>
The first step in the method for producing a photoresist resin of the present invention is a step of subjecting orthocresol and formaldehyde to a shrink polymerization reaction to obtain an orthocresol novolak resin. The polycondensation reaction here can be carried out under conventionally known conditions applied when preparing a normal phenol resin as shown below.

<Mole ratio of orthocresol and formaldehyde>
In the reaction of orthocresol and formaldehyde, the amount of formaldehyde is preferably 0.2 to 1.5 mol, more preferably 0.7 to 1.2 mol, based on 1 mol of orthocresol.

<Acid catalyst>
An acid catalyst can be used in the first step. The acid catalyst is not particularly limited as long as it is an acid that promotes the reaction between orthocresol and formaldehyde, and is, for example, organic sulfonic acid such as oxalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and methanesulfonic acid, and hydrochloric acid. , Inorganic acids such as sulfuric acid can be used alone or in combination of two or more. In particular, sulfuric acid, oxalic acid or p-toluenesulfonic acid is preferable.

The amount of the acid catalyst can be about 0.01 to 1% by mass of orthocresol. In order to prevent the acid catalyst remaining in the resin from affecting the characteristics of the photoresist, it is preferable that the amount of the acid catalyst used is as small as possible. The preferred amount used depends on the type. In the case of oxalic acid, it is preferably 0.3 to 1.0% by mass, in the case of sulfuric acid, it is preferably 0.05 to 0.1% by mass, and in the case of p-toluenesulfonic acid, it is preferably about 0.1 to 0.5% by mass.

<Reaction solvent>
When the raw material formaldehyde contains water, the water acts as a reaction solvent. An organic solvent that does not affect the reaction may be used as the reaction solvent. Examples of the organic solvent include ethers such as diethylene glycol dimethyl ether, 1,2-dimethoxyethane and 1,2-diethoxyethane; esters such as propylene glycol monomethyl ether acetate; and cyclic ethers such as tetrahydrofuran and dioxane.
The amount of the reaction solvent used can be 20 to 1000 parts by mass per 100 parts by mass of the reaction raw material.

<Reaction temperature>
The reaction temperature of the polycondensation reaction in the first step is not particularly limited, and is preferably 50 to 200 ° C. Within this temperature range, the reaction can be allowed to proceed while being controlled, so that the desired orthocresol novolak resin can be stably obtained. The reaction temperature is more preferably 70 to 180 ° C, particularly preferably 80 to 170 ° C.

<Reaction time, reaction pressure>
The reaction time of the polycondensation reaction in the first step depends on the reaction temperature, but is usually about 0.1 to 20 hours. The reaction pressure of the polycondensation reaction is usually carried out under normal pressure, but may be carried out under pressure or reduced pressure.

<Second step>
The second step in the method for producing a photoresist resin of the present invention is a step of shrinking and reacting the orthocresol novolak resin obtained as described above with a phenol compound having at least two methylol groups in the molecule. be.
The second step may be continuously performed in the same reaction system as the first step. When the second step is performed following the first step, a method can be taken in which a phenol compound is added to the orthocresol novolak resin obtained in the first step, uniformly mixed, and then subjected to a polycondensation reaction.

Further, in the second step, the orthocresol novolak resin obtained in the first step may be taken out once and carried out in a reaction system different from that in the first step.
The orthocresol novolak resin is preferably recovered as follows. Specifically, after the completion of the first step, a base is added to remove the acid catalyst, and water is added to wash with water. The temperature of the reaction system is raised to 130 to 230 ° C., and volatile components such as unreacted raw materials and organic solvents remaining in the reaction mixture are distilled off under a reduced pressure of, for example, 20 to 50 torr. The orthocresol novolak resin thus recovered.

At that time, the amount of orthocresol (monomer), which is an unreacted raw material contained in the orthocresol novolak resin, is preferably 5% by mass or less. When the content of orthocresol (monomer) in the orthocresol novolak resin is 5% by mass or less, the weight average molecular weight of the photoresist resin obtained by the reaction with the phenol compound is efficiently increased, and the weight average molecular weight is increased. It can be easily adjusted. Further, the effect of suppressing the binuclear body content of the photoresist resin can be obtained. The content of the unreacted monomer is more preferably 3% by mass or less, further preferably 1% by mass or less, and most preferably 0.5% by mass or less.

<Method of adding phenol compound>
In the second step of the method for producing a photoresist resin of the present invention, a solid or liquid raw material can be added at once to a phenol compound having at least two methylol groups in the molecule (collective addition). Phenolic compounds may be added sequentially. When the phenol compound is a liquid raw material, it can be added by dropping as it is. On the other hand, when the phenol compound is a solid raw material, it is used by dissolving it in an organic solvent as needed. Examples of the organic solvent include ethers such as propylene glycol monomethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, and 1,2-diethoxyethane; esters such as propylene glycol monomethyl ether acetate; tetrahydrofuran, dioxane, and the like. Cyclic ethers and the like can be used.

<Mass ratio ( _MA / _MB )>
In the second step of the method for producing a photoresist resin of the present invention, the ratio ( _MA / _MB ) of the mass _MA of the _orthocresol novolak resin to the mass MB of the phenol compound is 50/50 to 95/5. It is preferably 70/30 to 95/5, more preferably 80/20 to 95/5, and even more preferably 80/20 to 90/10.
When the mass ratio ( _MA / _MB ) is 50/50 to 95/5, the weight average molecular weight of the photoresist resin of the present invention can be efficiently increased, and the weight average molecular weight can be easily adjusted. can. In addition, the binuclear body content of the photoresist resin of the present invention can be reduced. By using the photoresist resin of the present invention, a photoresist composition having an excellent balance between high etching resistance and other performance can be obtained.

If the orthocresol novolak resin occupies 50% by mass or more of the photoresist resin of the present invention, it dissolves in an alkaline solution at an appropriate rate and exhibits sufficient etching resistance when made into a photoresist composition. On the other hand, if the phenol compound occupies 5% by mass or more of the photoresist resin of the present invention, the weight average molecular weight of the photoresist resin of the present invention is efficiently increased. Such a photoresist resin can be dissolved in an alkaline solution at an appropriate rate to ensure sufficient etching resistance when the photoresist composition is obtained.

<Acid catalyst>
In the second step of the method for producing a photoresist resin of the present invention, an acid catalyst can be used for the polycondensation reaction, if necessary. The acid catalyst is not particularly limited as long as it is an acid capable of reacting the orthocresol novolak resin with the methylol group of the phenol compound. The acid catalyst can be selected from organic sulfonic acids such as oxalic acid, benzenesulfonic acid, paratoluenesulfonic acid and methanesulfonic acid, and inorganic acids such as hydrochloric acid and sulfuric acid. The acid catalyst can be used alone or in combination of two or more.

The amount of the acid catalyst used in the second step varies depending on the type, but in the case of oxalic acid, it is about 0.3 to 1.0% by mass, in the case of sulfuric acid, it is about 0.05 to 0.1% by mass, and para. In the case of toluene sulfonic acid, it is preferable to use about 0.1 to 0.5% by mass. It is preferable to use sulfuric acid or p-toluenesulfonic acid.

<Reaction solvent>
In the second step of the method for producing a photoresist resin of the present invention, a reaction solvent can be used if necessary. As the reaction solvent, an organic solvent that does not affect the reaction can also be used. Examples of the organic solvent include ethers such as propylene glycol monomethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, and 1,2-diethoxyethane; esters such as propylene glycol monomethyl ether acetate; and cyclic ethers such as tetrahydrofuran and dioxane. Kind and the like.
The amount of the reaction solvent used can be usually 20 to 1000 parts by mass per 100 parts by mass of the reaction raw material.

<Reaction temperature>
In the second step of the method for producing a photoresist resin of the present invention, the reaction temperature in the polycondensation reaction is not particularly limited, but if it is 50 to 200 ° C., the polymerization reaction is controlled and allowed to proceed to obtain the desired photo. A resin for resist can be stably obtained. The reaction temperature is preferably 60 to 160 ° C, more preferably 80 to 140 ° C.

<Reaction time, reaction pressure>
The reaction time in the second step of the method for producing a photoresist resin of the present invention depends on the reaction temperature, but is usually within 20 hours. The reaction pressure is usually carried out under normal pressure, but may be carried out under slight pressurization or reduced pressure.

<Post-processing>
After the completion of the polycondensation reaction, it is preferable to perform post-treatment to neutralize and remove the acid catalyst. The acid catalyst can be neutralized by adding a base and then removed by washing with water.
The base is not particularly limited, and any base that neutralizes the acid catalyst and forms a salt that is soluble in water can be used. Examples of the base include inorganic bases such as metal hydroxides and metal carbonates, and organic bases such as amines and organic amines. Specific examples of the inorganic base include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium hydrogencarbonate, and calcium carbonate. Specific examples of the amine of the organic base or the organic amine include ammonia, trimethylamine, triethylamine, diethylamine, tributylamine and the like. Preferably organic amines are used. The base is preferably used in an amount that neutralizes the acid catalyst so that the pH in the reaction system becomes 4 to 8.

The amount of water washed and the number of times of washing are not particularly limited. Usually, the acid catalyst can be removed to an amount that does not affect the actual use as a photoresist resin by washing with water about 1 to 5 times.
The washing temperature is not particularly limited, but is preferably 40 to 95 ° C. from the viewpoint of catalyst removal efficiency and workability. During washing with water, a solvent that reduces the viscosity of the resin can be added in order to promote the separation of the resin and the washing water. It is also effective to raise the washing temperature. Such a solvent can be used without particular limitation as long as it dissolves the phenol resin and lowers the viscosity.
After removing the acid catalyst by neutralization and washing with water, for example, the temperature of the reaction system is raised to 130 ° C. to 230 ° C., and the unreacted raw materials and organic solvents existing in the reaction system are volatilized under a reduced pressure of 20 to 50 toor. Neutralize the minute. In this way, the photoresist resin of the present invention can be obtained.

[Photoresist composition]
The photoresist composition of the present invention contains the photoresist resin of the present invention. The content of the photoresist resin in the photoresist composition is preferably 5 to 40% by mass, more preferably 10 to 25% by mass. The rest of the photoresist composition of the present invention includes a photosensitive agent described later, a stabilizer such as an antioxidant, which is a conventional component of the photoresist composition, a plasticizer, a surfactant, an adhesion improver, and a dissolution promotion. It can be an agent, a dissolution inhibitor, or the like.

The photoresist composition of the present invention may further contain a photosensitive agent. Examples of the photosensitive agent include those generally used as a photosensitive agent for a photoresist composition containing a novolak type phenol resin. As the photosensitizer, a quinone diazide compound having a quinone diazide group is preferable, and a 1,2-quinone diazide compound or a derivative thereof is particularly preferable as a photosensitizer.

The quinone diazide compound changes the solubility of the photoresist composition in an alkaline solution when exposed. Therefore, when a photoresist composition containing a quinonediazide compound is formed and exposed, the alkali dissolution rate of the exposed portion increases and the alkali dissolution rate of the unexposed portion decreases. By increasing the difference in dissolution rate between the exposed portion and the unexposed portion in this way, it is possible to obtain a sharp resist pattern having high contrast.

As the quinone diazide compound, a known compound conventionally used in a quinone diazido-novolak-based photoresist composition can be used. Examples of the compound containing such a quinone diazide group include a compound obtained by reacting a naphthoquinone diazide sulfonic acid chloride, a benzoquinone diazido sulfonic acid chloride, or the like with a compound having a functional group capable of a condensation reaction with these acid chlorides. preferable.

Examples of the functional group that can be condensed with the acid chloride include a hydroxyl group and an amino group, and a hydroxyl group is particularly preferable. Examples of the compound having a hydroxyl group capable of condensing with acid chloride include hydroquinone, resorcin, 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,4,6-trihydroxybenzophenone, 2,4,4. '-Trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,2', 3,4,6'-pentahydroxybenzophenone, etc. Hydroxyphenyl alkanes such as hydroxybenzophenones, bis (2,4-dihydroxyphenyl) methane, bis (2,3,4-trihydroxyphenyl) methane, bis (2,4-dihydroxyphenyl) propane, 4,4' , 3 ", 4" -Tetrahydroxy-3,5,3', 5'-Tetramethyltriphenylmethane, 4,4', 2 ", 3", 4 "-Pentahydroxy-3,5,3', Hydroxytriphenylmethanes such as 5'-tetramethyltriphenylmethane can be mentioned. These may be used alone or in combination of two or more.

Specific examples of the acid chloride such as naphthoquinone diazide sulfonic acid chloride and benzoquinone diazido sulfonic acid chloride are preferably 1,2-naphthoquinone diazide-5-sulfonyl chloride, 1,2-naphthoquinone diazido-4-sulfonyl chloride and the like. Is mentioned as.

The blending amount of the photosensitive agent is preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the photoresist resin of the present invention. Higher sensitivity can be obtained by containing 5 parts by mass of the photosensitive agent. If the blending amount of the photosensitive agent is 50 parts by mass or less, precipitation of the components can be avoided.

In addition to the above-mentioned photoresist resin and photosensitive agent of the present invention, the photoresist composition of the present invention comprises a stabilizer such as an antioxidant, a plasticizer, and a surfactant, which are conventional components of the photoresist composition. Adhesion improvers, dissolution accelerators, dissolution inhibitors and the like can be added. Other novolak resins may be contained in the photoresist composition of the present invention as long as the effects of the present invention are not impaired.

[Use]
The photoresist composition using the photoresist resin of the present invention of the present invention can be used as a thin film transistor (TFT) material for lithography and liquid crystal in manufacturing a highly integrated semiconductor.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
<Resin for photoresist>
First, an example of a novolak type phenol resin as a photoresist resin will be shown. The resin analysis method and evaluation method are as follows.

(1) Weight average molecular weight (Mw)
GPC measurement was performed under the following conditions, and the weight average molecular weight in terms of polystyrene was determined.
Equipment used: Waters Alliance 2695 (gel permeation chromatograph analysis)
Column: SHODEX LF-804
Guard column: KF-G made by SHODEX
Column oven temperature: 40 ° C
Solvent: Tetrahydrofuran (THF)
Flow rate: 1.00 mL / min Detector: Waters 2487 Dual λAbsorbance Detector
Detection wavelength: 254 nm

(2) Alkaline dissolution rate (DR)
3 g of novolak type phenol resin was dissolved in 9 g of propylene glycol monomethyl ether acetate (PGMEA) to prepare a resin solution. The obtained resin solution was filtered through a 0.2 micron membrane filter. This was applied on a 4-inch silicon wafer with a spin coater to a thickness of about 15,000 Å (angstrom), and dried on a hot plate at 110 ° C. for 60 seconds.
Then, a developer (1.60% tetramethylammonium hydrooxide aqueous solution) was used to measure the time until the film completely disappeared. The value (Å / s) obtained by dividing the initial film thickness by the time until dissolution was defined as the dissolution rate.

(3) Binuclear content The binuclear content of the photoresist resin was determined by gel permeation chromatography (GPC) analysis. Specifically, the area ratio (area%) of the obtained two nuclei was calculated using the analysis software Emper3 (manufactured by Japan Waters Corp.). In the calculation of the area ratio (area%) of the two nucleoli, the straight line portion before and after the peak was used as the baseline (0 value), and the peaks were divided by vertical cutting at the lowest point between the peaks of each component. The area ratio (area%) of the obtained binuclear body was defined as the content of the binuclear body.
Equipment used: Waters Alliance 2695 (gel permeation chromatograph analysis)
Columns: The following five SHODEX columns were connected in series from upstream to downstream in the following order.
KF-804 x 1
KF-803 x 1
KF-802.5 x 1
KF-802 x 1
KF-801 x 1
In addition, one KF-G manufactured by SHODEX was used as a guard column.
Column oven temperature: 40 ° C
Solvent: Tetrahydrofuran (THF)
Flow rate: 1.00 mL / min Detector: Waters 2487 Dual λAbsorbance Detector
Detection wavelength: 254 nm

In the example, the target novolak type phenol resin is produced by two-step polymerization. First, as the first-stage polymerization, orthocresol and formalin as raw materials are housed in a glass flask having a capacity of 500 parts and equipped with a thermometer, a charging / distilling outlet, and a stirrer, and reacted, as shown below. Two kinds of orthocresol novolak resins (A-1) and (A-2) were obtained.
[Synthesis Example 1]
о 100 parts (0.93 mol) of cresol, 52.31 parts (0.74 mol) of 42% formalin and 1.0 part of oxalic acid were placed in a glass flask and reacted at 100 ° C. for 5 hours. Then, the temperature was raised to 185 ° C. and dehydrated, and then vacuum distillation at 30 torr was carried out for 2 hours to obtain a novolak type cresol resin. This resin had a weight average molecular weight of 1150 and a binuclear body content of 11.9% based on GPC analysis. The obtained resin is referred to as orthocresol novolak resin (A-1).

[Synthesis Example 2]
A novolak-type cresol resin was obtained in the same manner as in Synthesis Example 1 except that the amount of 42% formalin was changed to 78.47 parts (1.11 mol). This resin had a weight average molecular weight of 2500 and a binuclear body content of 3.1% based on GPC analysis. The obtained resin is referred to as orthocresol novolak resin (A-2).

The orthocresol novolak resin (A-1) or the orthocresol novolak resin (A-2) is used for the second-stage polymerization to produce the novolak-type phenol resin which is the resin for the photoresist of the present invention.

[Example 1]
In a glass flask similar to the above, 80 parts of the orthocresol novolak resin (A-1) obtained in Synthesis Example 1, 20 parts (0.12 mol) of 2,6-dimethylol-p-cresol as a phenol compound, and 0.1 part of paratoluenesulfonic acid was contained as an acid catalyst, and the reaction was carried out at 100 ° C. for 6 hours. After completion of the reaction, the mixture was cooled to 90 ° C., and 0.1 g of triethylamine as a base was added to neutralize the acid catalyst.

Then, 100 g of ion-exchanged water was added, and the mixture was stirred and then allowed to stand. The pH of the aqueous layer separated by standing was adjusted to 5.5 to 7.0, and the separated water was removed. This operation was performed twice. Then, after the temperature was raised to 185 ° C. and dehydrated, unreacted raw materials and the like were removed by performing vacuum distillation at 30 torr for 2 hours to obtain the novolak type phenol resin of Example 1.
The novolak-type phenol resin of Example 1 had a weight average molecular weight of 4550 and a binuclear body content of 1.6% based on GPC analysis. The alkali dissolution rate obtained by the above-mentioned method was 794 Å / s.

[Example 2]
In a glass flask similar to the above, 95 parts of the orthocresol novolak resin (A-2) obtained in Synthesis Example 2, 5 parts of 2,6-dimethylol-p-cresol (0.03 mol) as a phenol compound, and 0.1 part of paratoluenesulfonic acid was contained as an acid catalyst, and the reaction was carried out in the same manner as in Example 1. Further, the same operation as in Example 1 was carried out to obtain a novolak type phenol resin of Example 2.
The novolak-type phenol resin of Example 2 had a weight average molecular weight of 4370 and a binuclear body content of 1.6% based on GPC analysis. The alkali dissolution rate obtained by the above-mentioned method was 1706 Å / s.

[Example 3]
In a glass flask similar to the above, 90 parts of the orthocresol novolak resin (A-2) obtained in Synthesis Example 2, 10 parts (0.06 mol) of 2,6-dimethylol-p-cresol as a phenol compound, and 0.1 part of paratoluenesulfonic acid was contained as an acid catalyst, and the reaction was carried out in the same manner as in Example 1. Further, the same operation as in Example 1 was carried out to obtain a novolak type phenol resin of Example 3.
The novolak-type phenol resin of Example 3 had a weight average molecular weight of 10840 and a binuclear body content of 1.8% based on GPC analysis. The alkali dissolution rate obtained by the above-mentioned method was 232 Å / s.

[Comparative Example 1]
80 g (0.74 mol) of m-cresol, 120 g (1.11 mol) of p-cresol, 80.8 g of 42% formalin in a glass flask with a capacity of 1000 parts equipped with a thermometer, a charging / distilling outlet and a stirrer. (1.15 mol) and 0.7 g of oxalic acid were contained and reacted at 100 ° C. for 10 hours. Then, after the temperature was raised to 185 ° C. and dehydrated, unreacted raw materials and the like were removed by performing vacuum distillation at 30 torr for 2 hours to obtain a novolak type phenol resin of Comparative Example 1.
The novolak-type phenol resin of Comparative Example 1 is a general-purpose novolak-type phenol resin. This resin had a weight average molecular weight of 5700 and a binuclear body content of 8.3%. The alkali dissolution rate obtained by the above-mentioned method was 380 Å / s.

[Comparative Example 2]
In the same glass flask as in Comparative Example 1, 216 parts (2.00 mol) of m-cresol, 314 parts (3.00 mol) of p-cresol, and 213.8 parts (2.99 mol) of 42% formalin. And 1.9 parts of oxalic acid were housed and reacted at 100 ° C. for 5 hours. After completion of the reaction, the temperature was raised to 180 ° C. for dehydration, and the temperature was further raised to 210 ° C. The novolak type cresol resin of Comparative Example 2 was obtained by distillation under reduced pressure for 9 hours under steam conditions at 40 torr under reduced pressure.
The novolak-type cresol resin of Comparative Example 2 is a general-purpose dimerless novolak-type cresol resin. This resin had a weight average molecular weight of 9500 and a binuclear body content of 4.0%. The alkali dissolution rate obtained by the above-mentioned method was 250 Å / s.

[Comparative Example 3]
In a glass flask similar to that of Comparative Example 1, 75 g (0.69 mol) of о-cresol, 25 g (0.23 mol) of p-cresol, 65.3 g (0.93 mol) of 42% formalin and 1 oxalic acid 1 .0 g was housed and reacted at 100 ° C. for 10 hours. Then, after the temperature was raised to 185 ° C. and dehydrated, unreacted raw materials and the like were removed by performing vacuum distillation at 30 torr for 2 hours to obtain a novolak type phenol resin of Comparative Example 3.
The novolak-type phenol resin of Comparative Example 3 is a novolak-type phenol containing orthocresol as a main component. This resin had a weight average molecular weight of 1900 and a binuclear body content of 4.6%. The alkali dissolution rate obtained by the above-mentioned method was 4024 Å / s.

[Comparative Example 4]
In a glass flask similar to that of the example, 80 parts of the orthocresol novolak resin (A-1) obtained in Synthesis Example 1, 5 parts of 42% formalin (0.07 mol) and 1.0 part of oxalic acid were placed. It was housed and reacted at 100 ° C. for 18 hours. After completion of the reaction, the temperature was raised to 185 ° C. and dehydrated, and then vacuum distillation at 30 torr was carried out for 2 hours to remove unreacted raw materials and the like to obtain a novolak-type phenol resin of Comparative Example 4.
The novolak-type cresol resin of Comparative Example 4 had a weight average molecular weight of 2100 and a binuclear body content of 5.0% based on GPC analysis. The alkali dissolution rate obtained by the above-mentioned method was 2300 Å / s.

Table 1 below summarizes the weight average molecular weight, alkali dissolution rate, and binuclear body content of the photoresist resins of Examples 1 to 3 and Comparative Examples 1 to 4.

The novolak-type phenol resin of Examples 1 to 3 has a larger weight average molecular weight than the novolak-type phenol resin containing orthocresol as a main component of Comparative Example 3. Further, the novolak type phenol resin of the example has a low binuclear body content of 1.8%. It can be seen that the production method of the present invention can easily adjust the weight average molecular weight of the novolak-type phenol resin and can significantly suppress the formation of binuclear bodies.

[Photoresist composition]
Next, an example of the photoresist composition using the novolak type phenol resin of the present invention will be shown.
The characteristics of the photoresist composition were evaluated by forming a resist pattern as follows. In forming the resist pattern, first, the photoresist composition was applied on a 4-inch silicon wafer with a spin coater and dried on a hot plate at 110 ° C. for 60 seconds to form a resist film having a thickness of 15,000 Å.

Then, using a reduced projection exposure apparatus, the exposure time was changed stepwise to confirm the optimum exposure amount, and then the exposure was performed so as to obtain the optimum exposure amount. The resist film after exposure was developed with a developing solution (2.38% tetramethylammonium hydrooxide aqueous solution) for 60 seconds, rinsed and dried to obtain a positive resist pattern.

(1) Sensitivity The pattern shape of the obtained pattern was observed with a scanning electron microscope, and the sensitivity was evaluated according to the following criteria.
AA: A pattern can be formed at less than 3 mJ / cm ² .
A: A pattern can be formed at less than 5 mJ / cm ² .
B: A pattern can be formed at 5 to 60 mJ / cm ² .

(2) Resolution A pattern was formed on the resist film formed in the same manner as described above using a test chart mask, and the resolution was evaluated according to the following criteria.
⊚: 1.5 μ line & space can be resolved.
◯: 2.0 μ line & space can be resolved.
X: 2.0 μ line & space cannot be resolved.

(3) Dry etching resistance The resist pattern formed in the same manner as described above was dry-etched using an etching apparatus, and the film thickness before and after etching was measured to determine the etching rate of the resist pattern. The etching conditions were 0.7 sccm and 80 W, and CF ₄ was used as the etching gas. The etching rate of the photoresist composition when only the phenol resin of Comparative Example 2 was used as the photoresist resin was used as a reference value, and the obtained results were compared with the reference values.
The ratio of the etching rate of the photoresist composition to the reference value ([etching rate of the photoresist composition] / [reference value]) was evaluated according to the following criteria.
AA: When the reference value is less than 0.75 A: When the reference value is 0.75 or more and 0.90 or less B: When the reference value exceeds 0.90 C: Equivalent to or less than the reference value

[Example 4]
The novolak-type phenol resin of Example 1 was used as the resin for the photoresist, and a photoresist composition was prepared by the following method. That is, 20 g of novolak-type phenol resin and 5 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved in 75 g of PGMEA, filtered through a 0.2 micron membrane filter, and the photoresist of Example 4 was used. The composition was obtained.

[Examples 5 to 6, Comparative Examples 5 to 8]
The photoresist compositions of Examples 5 to 6 and Comparative Examples 5 to 8 were prepared by the same method as in Example 4 except that the photoresist resin was changed to the resins of Examples 2 to 3 and Comparative Examples 1 to 4. Obtained.
The results of evaluating the properties of the photoresist compositions of Examples 5 to 6 and Comparative Examples 5 to 8 are summarized in Table 2 below.

The photoresist compositions of Examples 4 to 6 have good sensitivity and resolution, as well as excellent dry etching resistance. In Examples 4 to 6, the photoresist resin of the present invention containing a polycondensation polymer of an orthocresol novolak resin and a phenol compound having at least two methylol groups in the molecule is used, and thus has high sensitivity. It has high resolution and high dry etching resistance.

All of the photoresist compositions of the comparative examples have poor dry etching resistance. In Comparative Example 2, the sensitivity is inferior in addition to the dry etching resistance, and in Comparative Examples 3 and 4, the resolution is also inferior in addition to the dry etching resistance.

Claims (1)

The first step of polymerizing orthocresol and formaldehyde to obtain an orthocresol novolak resin having a binuclear body content of 10% or less.
The second step of polycondensing the orthocresol novolak resin and the phenol compound having at least two methylol groups in the molecule in the presence of an acid catalyst.
A post-treatment step for neutralizing the acid catalyst is provided.
_A method for producing a resin for a photoresist in which the ratio ( _MA / _MB ) of the mass _MA of the orthocresol novolak resin to the mass MB of the phenol compound is 80/20 to 90/10.