JP2000264941A - Production of novolak resin for photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a novolak resin for a positive-type photoresist, capable of sufficiently controlling its dissolving speed in alkali, and consequently forming such an extremely fine pattern that the line width is 0.30 μm. SOLUTION: This method for producing a novolak resin for a photoresist comprises reacting a phenol with an aldehyde using an aromatic hydrocarbon or an aliphatic hydrocarbon as a solvent at a temperature of >=150 deg.C in a pressure vessel, then subjecting the reaction product to crosslinking reaction using a crosslinking agent, such as the aldehyde or a dimethylol compound derived from the phenol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a novolak resin for a photoresist, and more particularly to a method for producing a novolak resin for a photoresist having high sensitivity and high resolution.

[0002]

2. Description of the Related Art A positive photoresist using an i-line (wavelength: 365 nm) as an exposure light source is composed of an alkali-soluble novolak resin (base resin) and a photodegradable photosensitive agent such as naphthoquinonediazidesulfonic acid ester. And is used as an etching protection film in photolithography when manufacturing semiconductor integrated circuits such as ICs and LSIs.

[0003] As a base resin for a positive type photoresist, as disclosed in JP-A-62-35349,
Representative examples are a cresol novolak resin from m-cresol and p-cresol, and a xylenol-modified novolak resin as disclosed in Japanese Patent Publication No. 6-90441.

However, in recent years, in the production of semiconductor integrated circuits, the integration of ICs, LSIs, etc. has been increasingly advanced, and finer pattern formation has been required. Higher performance is essential. For i-line exposure light sources, a technique called super-resolution technology has been developed,
At the same time, photoresists are required to be capable of forming patterns with a line width of 0.30 μm. In order to realize an extremely fine pattern with a line width of 0.30 μm, very high performance is required for the photoresist. To satisfy this performance, novolak resin as a base resin has been used. There has been a search for improvements and photosensitizers.

Among them, Japanese Patent Application Laid-Open No. 60-159846 discloses the addition condensation of phenols and formaldehyde under conditions of pH = 4 to 7 using an organic acid salt of a divalent metal such as zinc as a catalyst. By using a novolak resin (high orthonovolak resin) having a high ratio of ortho bonds / para bonds of internuclear methylene bonds synthesized as a base resin of a photoresist, high performance is achieved.
However, a positive photoresist containing a high-ortho novolak resin as a base resin has a large difference in the alkali dissolution rate between an exposed part and an unexposed part, but the alkali dissolution rate largely depends on the molecular weight of the resin. Therefore, it is difficult to control the dissolution rate.

In order to control the alkali dissolution rate, it is necessary to synthesize a high-ortho novolak resin having a predetermined molecular weight and a predetermined molecular weight distribution. However, in practice, its synthesis is difficult and is disclosed in Japanese Patent Application Laid-Open No. 60-159846. However, it has not yet been possible to sufficiently control the alkali dissolution rate.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a novolak resin for a positive type photoresist, in which the alkali dissolution rate is sufficiently controlled, and as a result, an extremely fine pattern having a line width of 0.30 μm can be formed. The purpose is to provide.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of intensive studies to achieve the above object, and as a result, a product obtained by reacting a phenol and an aldehyde in a nonpolar solvent at high temperature and high pressure. And a cross-linking reaction using a cross-linking agent to obtain a novolak resin for a positive photoresist, which enables formation of an extremely fine pattern with a line width of 0.30 μm. The present invention has been completed.

That is, the present invention provides a product obtained by reacting a phenol and an aldehyde with an aromatic or aliphatic hydrocarbon as a solvent at a temperature of 150 ° C. or more in a pressure vessel. A method for producing a novolak resin for a photoresist, which comprises performing a crosslinking reaction using a crosslinking agent.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, first, a phenol and an aldehyde are reacted in a non-polar solvent under high temperature and high pressure to form a linear or very branched highly orthonovolak resin. And then cross-linking and branching the high-ortho novolak resin using a dimethylol of an aldehyde or a phenol to form a pattern having a line width of 0.30 μm with high sensitivity. Obtain novolak resin for resist. The method of synthesizing a high-ortho novolak, whose alkali dissolution rate is difficult to control, once into a linear or less branched structure, and then cross-linking and branching it, makes the structure more conventional than a conventional photoresist resin. It is presumed that the degree of control could be controlled to a high degree, and as a result, the alkali dissolution rate could be controlled.

The phenols used in the present invention include phenol, cresol, xylenol, ethylphenol, t-butylphenol, trimethylphenol, resorcinol and the like. Among them, m-cresol, p-cresol, 3,5-xylenol It is preferable that a substituent is not introduced at the two ortho positions as described above.

As the aldehydes, formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, crotonaldehyde and the like can be used. In particular, those having no bulky substituent such as formaldehyde and paraformaldehyde are preferable.

As the nonpolar solvent, aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene, and aliphatic hydrocarbons such as hexane, heptane and cyclohexane can be used.

The temperature during the high-temperature and high-pressure reaction in the nonpolar solvent is 150 ° C. or higher, preferably 180 to 220 ° C.
The pressure is preferably the saturated vapor pressure of the solvent at the reaction temperature. If necessary, the pressure may be higher than the saturated vapor pressure of the solvent. The molar ratio of the aldehyde to the phenol is 0.5 to 1.2, preferably 0.85 to 1.2.
It is better to be in the range of 0.9. The weight ratio of the solvent to the phenol may be 0.1 or more, but is preferably 3 to 15.

In the resin produced according to the present invention, the ratio of ortho-bond / para-bond of methylene bond between nuclei is preferably 2.5 or more, and the weight average molecular weight is 3500 to 200.
00 is preferred.

On the other hand, examples of the crosslinking agent used in the present invention include the above-mentioned aldehydes and phenols such as 2,6-bis (hydroxymethyl) -p-cresol (dimethylol of p-cresol). Those having a plurality of substituents that cause an electrophilic substitution reaction or a nucleophilic substitution reaction on an aromatic ring can be given. Regarding the amount of the crosslinking agent to be added,
The molar ratio is from 0.01 to 0.5, preferably from 0.05 to 0.2. A catalyst can be added as needed to accelerate the crosslinking reaction. The temperature during the crosslinking reaction is 150
° C or less, and room temperature to 100 ° C is preferred.

A quinonediazide compound is used as a photosensitive component. Although the kind of the quinonediazide compound is not particularly limited, for example, 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-5 -Sulfonic acid esters and the like. It is preferable to use the quinonediazide compound and the novolak resin in a mixing ratio of 1: 1 to 1: 6.

The photoresist solution using the phenolic resin of the present invention is prepared by mixing and dissolving the novolak resin and the quinonediazide compound in a solvent that provides a uniform and smooth coating film so that the concentration of the quinonediazide compound is 5 to 50% by weight. Do. Suitable solvents for the preparation of the resist include ethyl lactate, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, methoxypropyl acetate, l-n-butyl lactate, methyl isobutyl ketone, xylene and the like. . In addition, a surfactant, a storage stabilizer, a dye, and the like can be added as necessary.

[0019]

The present invention will be described below in detail with reference to examples, but the present invention is not limited by these examples.

Example 1 400 parts of m-cresol, 100 parts of p-cresol, and paraformaldehyde (88% purity) were placed in an autoclave having a capacity of 10 L and equipped with a stirrer, a heat exchanger, a temperature sensor, a pressure gauge, and a safety valve.
138 parts and 5000 parts of xylene were charged to give 20
The temperature was raised to 0 ° C. ± 2 ° C. and maintained at that temperature for 6 hours.
After cooling the reaction solution to 80 ° C., 14 parts of paraformaldehyde and 5 parts of oxalic acid were added, and the mixture was kept at 80 ° C. ± 2 ° C. for 3 hours. Xylene and unreacted cresol are distilled off under reduced pressure,
A novolak resin was obtained. The ratio of ortho / para bonds in the internuclear methylene bonds determined by NMR was 4.4. The weight average molecular weight determined by GPC is 470.
0, molecular weight distribution was 2.7.

Example 2 In the same autoclave as in Example 1, 200 parts of m-cresol, 226 parts of 3,5-xylenol, 100 parts of p-cresol, 138 parts of paraformaldehyde (88% purity), and xylene 5000
The temperature was raised to 200 ° C. ± 2 ° C. and maintained at that temperature for 6 hours. After cooling the reaction solution to 80 ° C., 14 parts of paraformaldehyde and 5 parts of oxalic acid were added, and the mixture was added at 80 ° C. ±
It was kept at 2 ° C. for 3 hours. Xylene, unreacted cresol and unreacted xylenol were distilled off under reduced pressure to obtain a novolak resin. The ratio of ortho-bond / para-bond of the internuclear methylene bond determined by NMR was 4.5. The weight average molecular weight determined by GPC is 6,400, and the molecular weight distribution is 3.
It was 2.

Example 3 400 parts of m-cresol and 100 parts of p-cresol were placed in the same autoclave as in Example 1.
Parts, 138 parts of paraformaldehyde (88% purity), and 5000 parts of xylene were charged, the temperature was raised to 200 ° C. ± 2 ° C., and the temperature was maintained for 6 hours. After cooling the reaction solution to 80 ° C., 2,6-bis (hydroxymethyl)
-Add 78 parts of p-cresol and 5 parts of oxalic acid, and add
C. for 3 hours. Xylene and unreacted cresol were distilled off under reduced pressure to obtain a novolak resin. The ratio of ortho-bond / para-bond of the internuclear methylene bond determined by NMR was 4.7. The weight average molecular weight determined by GPC was 5,600, and the molecular weight distribution was 2.9.

Comparative Example 1 400 parts of m-cresol, 100 parts of p-cresol, and 1 part of oxalic acid were charged into a 3 L four-necked flask equipped with a stirrer, a thermometer, a reflux tube, and an adding device. After heating to 100 ° C., 37%
After 308 parts of formalin were successively added for 1.5 hours using an adding apparatus, the mixture was reacted at a reflux temperature for 1 hour. After dehydration by heating to 130 ° C. under normal pressure, unreacted cresol was removed under reduced pressure to obtain a novolak resin. The ratio of ortho / para bonds in the internuclear methylene bonds determined by NMR was 1.5. The weight average molecular weight determined by GPC was 4,600, and the molecular weight distribution was 4.1.

Comparative Example 2 200 parts of m-cresol, 226 parts of 3,5-xylenol, 100 parts of p-cresol and 1 part of oxalic acid were charged into the same three-liter four-necked flask as in Comparative Example 1, and 100 parts of oxalic acid were added. After the temperature was raised to 0 ° C, 308 parts of 37% formalin was added successively for 1.5 hours using an adding device, and then reacted at reflux temperature for 1 hour. 1 under normal pressure
After dehydration by heating to 30 ° C., unreacted cresol and unreacted xylenol were removed under reduced pressure to obtain a novolak resin. The ratio of ortho-bond / para-bond of the internuclear methylene bond determined by NMR was 1.6. The weight average molecular weight determined by GPC is 5,300, and the molecular weight distribution is 4.3.
Met.

Comparative Example 3 400 parts of m-cresol, 100 parts of p-cresol, and 1 part of zinc acetate were charged into the same three-liter four-necked flask as in Comparative Example 1, and heated to 100 ° C. After 308 parts of 37% formalin were successively added for 1.5 hours using an adding apparatus, the mixture was reacted at a reflux temperature for 1 hour. After dehydration by heating to 130 ° C. under normal pressure, unreacted cresol was removed under reduced pressure to obtain a novolak resin. The ratio of ortho / para bonds in the internuclear methylene bonds determined by NMR was 2.5. The weight average molecular weight determined by GPC was 4,900, and the molecular weight distribution was 4.1.

100 parts by weight of the novolak resin obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were mixed with naphthoquinone 1,
A resist solution was prepared by dissolving together with 30 parts by weight of 2,3,4-trihydroxybenzophenone ester of 2-diazide-5-sulfonic acid in 400 parts by weight of ethyl cellosolve acetate. Each of these compositions was filtered using a 0.2 μm membrane filter to obtain a resist solution sample.

This was applied to a silicon wafer that had been washed by a conventional method so as to have a dry coating thickness of 1.0 μm using a spin coater. Next, this silicon wafer was
Dry on a hot plate at 0 ° C. for 90 seconds. Thereafter, exposure was performed through a test chart mask using a reduction projection exposure apparatus, development was performed for 50 seconds using a developing solution (2.38% tetraammonium aqueous solution), washed with water, and dried.

After these silicon wafers with the developed resist pattern are left in a clean oven set at 130 ° C. for 30 minutes, the resist pattern is observed with a scanning electron microscope to determine the resolution, sensitivity and exposure. The light tolerance was evaluated. Table 1 summarizes the evaluation results
It was shown to.

[0029]

[Table 1]

As can be seen from the results in Table 1, the photoresist of the embodiment using the phenolic resin according to the present invention is:
All of the resolution, sensitivity, and exposure latitude showed excellent values as compared with the comparative example.

[0031]

The positive photoresist containing the novolak resin obtained by the production method of the present invention can form an extremely fine pattern with high sensitivity, excellent resolution and a line width of 0.30 μm. This is useful for further increasing the degree of integration of a semiconductor integrated circuit and is useful.

Continued on front page F-term (reference) 2H025 AA00 AA01 AA02 AB16 AC01 AD03 BE01 CB29 CB51 CB56 4J031 CA06 CA12 CA13 4J032 CA03 CA04 CA06 CE03 CE06 CE12 CG01 4J033 CA01 CA02 CA03 CA05 CA11 CA12 CA13 CB02 HA23 HA25

Claims (3)

[Claims] 1. A product obtained by reacting a phenol with an aldehyde in a nonpolar solvent under high temperature and pressure.
A method for producing a novolak resin for a photoresist, wherein a crosslinking reaction is carried out using a crosslinking agent. 2. A phenol and an aldehyde, wherein an aromatic hydrocarbon or an aliphatic hydrocarbon is used as a solvent,
A method for producing a novolak resin for a photoresist, comprising subjecting a product obtained by reacting at a temperature of 150 ° C. or more in a pressure vessel to a crosslinking reaction using a crosslinking agent. 3. The method for producing a photoresist novolak resin according to claim 1, wherein the crosslinking agent is a dimethylol of an aldehyde or a phenol.