JPH11349653A - Photoresist phenolic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoresist phenolic resin having higher heat resistance and higher resolution and higher sensitivity than conventional photoresist phenolic resins. SOLUTION: The objective photoresist phenolic resin is obtained by reacting a phenolic composition comprising 55-98 wt.% m-cresol, 1-20 wt.% p-cresol, and 1-25 wt.% xylenol and/or trimethylphenol with an aldehyde composition comprising formaldehyde and an aldehyde having an alkenyl group at a weight ratio of the formaldehyde to the aldehyde of 1/9 to 9/1 in the presence of an acid catalyst, where the amount of the catalyst remaining in the phenolic resin is small to adversely affect practical use and the amount of impurities of metals as to all elements is not more than 1 ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoresist having high heat resistance, high residual film ratio, high sensitivity and high resolution, which is used for a photoresist used for lithography in manufacturing semiconductors and LCDs. A phenolic resin which enables the production of

[0002]

2. Description of the Related Art In general, a positive photoresist is made of a photosensitive agent having a quinonediazide group such as a naphthoquinonediazide compound and an alkali-soluble resin (for example, a novolak phenol resin). Positive photoresists having such a composition exhibit high resolving power upon development with an alkaline solution, and are used in the manufacture of semiconductors such as ICs and LSIs and circuit substrates such as LCDs. In addition, novolak type phenolic resin also has high heat resistance to plasma dry etching after exposure due to the structure having many aromatic rings, so far novolak type phenolic resin and naphthoquinonediazide-based photosensitizer Numerous positive-type photoresists containing have been developed and put into practical use, and have achieved great results.

In general, a phenol resin obtained by reacting meta-cresol / para-cresol with formaldehyde in the presence of an acid catalyst is used as a phenol resin for a photoresist. In order to adjust or improve the characteristics of the photoresist, the ratio and molecular weight of meta-paracresol have been studied and applied to lithography techniques such as semiconductors and LCDs. Photoresists for semiconductors are required to have properties such as high heat resistance, high resolution and high sensitivity. To improve heat resistance, alkylphenols such as xylenol and trimethylphenol and aromatic aldehydes are required. There is an example in which a monomer was studied, and hydroxybenzaldehyde and the like were examined for higher sensitivity. In each case, although a slight improvement effect was obtained, a sufficient effect was not obtained.

In recent years, there has been an extremely high demand for high integration of semiconductors, and accordingly, there has been an extremely high demand for high resolution of photoresists. In order to improve the resolution, a phenolic resin to be used has been studied to improve the phenolic resin, for example, a high ortho-modified resin has been studied. However, it has not been put to practical use due to poor heat resistance. In addition, there are examples in which various monomers have been studied, but all of them have advantages and disadvantages and have not been put to practical use.

A phenolic resin for a photoresist is obtained by reacting a phenol with an aldehyde in the presence of an acid catalyst. However, since the remaining acid catalyst greatly affects the performance of the photoresist, it is removed. Oxalic acid is generally used as an acid catalyst which is easy to be used. However, when a special aldehyde other than formaldehyde is applied for the purpose of improving performance, the reaction does not proceed with a weak acid such as oxalic acid,
Strong acids such as organic sulfonic acids and inorganic acids are used. When an organic sulfonic acid or the like is used as an acid catalyst, it is difficult to be removed by decomposition and sublimation like oxalic acid, so that a large amount thereof remains in the phenol resin, hindering the production of the phenol resin, and deteriorating the performance of the photoresist. It becomes a factor that greatly reduces. In addition, because of its strong corrosiveness, impurities such as metal from the phenol resin reaction vessel also increase, and only those that are not suitable as phenol resin for photoresist can be obtained. Not practical.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a high heat resistance.
An object of the present invention is to provide a phenolic resin for a photoresist which enables the production of a photoresist having both high resolution and high sensitivity.

[0007]

According to the present invention, the composition of the phenols (P) is 55-98% by weight of meta-cresol, 1-20% by weight of para-cresol, xylenol and / or trimethylphenol. The aldehyde (A) is an aldehyde containing formaldehyde and an alkenyl group at a weight ratio of 1 / 9-9 / 1,
A phenolic resin for photoresists, characterized in that the catalyst remaining in the resin is so small that it does not affect practical use, and the metal impurities are 1 ppm or less for each element. It is a phenolic resin that enables the production of photoresists having high sensitivity.

Hereinafter, the present invention will be described in detail. First, the phenol resin of the present invention will be described in accordance with the synthesis procedure. In the synthesis reaction, a phenol (P), an aldehyde containing an alkenyl group, and an acid catalyst are charged into a reactor equipped with a stirrer, a thermometer, and a heat exchanger, and a primary reaction is started. The reaction temperature and time can be appropriately set depending on the reactivity of the monomer, but the reaction time is preferably 2 to 10 hours and the reaction temperature is preferably 70 to 150 ° C. as a stable and economical level. After completion of the primary reaction, a secondary reaction is performed by adding formaldehyde (formalin and / or paraformaldehyde). The formaldehyde may be added in its entirety initially or may be added dropwise over time, and may be selected according to the degree of heat generated when formaldehyde is added. The reaction temperature and time for the secondary reaction
It can be appropriately selected depending on the characteristics of the resin to be produced and the reactivity of the monomer, but the stable and economical production is preferably carried out at a reaction time of 1 to 10 hours and a reaction temperature of 50 to 150 ° C. At the time of the primary reaction and the secondary reaction, a reaction solvent can be added and used as necessary. The type of the solvent is not particularly limited, but a solvent that dissolves the phenol resin is preferable. Generally, ketones such as acetone and methyl ethyl ketone, ether alcohols such as ethyl cellosolve, alcohols such as methanol, ethanol, propanol and butanol, and tetrahydrofuran And cyclic ethers such as dioxane and esters such as ethyl acetate and butyl acetate.

After completion of the reaction, amines are added to stop the reaction to neutralize the acid catalyst, and then water is added to remove the acid catalyst, followed by washing with water. Although the amount and the number of times of washing water are not particularly limited, the number of times of washing to remove the acid catalyst to an amount that does not affect actual use is preferably about 1 to 5 times from the viewpoint of economy. The amount that the acid catalyst does not affect the actual use is an amount that does not adversely affect the performance of the photoresist when the phenolic resin is used for the photoresist, and the amount of the acid catalyst does not affect the actual use.
5,000p, although it depends on how the resin is used)
pm or less can be used for photoresist,
Especially preferably, it is 1000 ppm or less. Further, the temperature at the time of washing with water is not particularly limited, but it is preferable to perform the washing at 40 to 95 ° C from the viewpoint of the efficiency of removing the acid catalyst and the workability. If the separation of the resin and the washing water is poor during washing, it is effective to add a solvent that reduces the viscosity of the resin or to increase the washing temperature. At this time, the kind of the solvent is not particularly limited, but any solvent can be used as long as it dissolves the phenol resin and lowers the viscosity. Generally, ketones such as acetone and methyl ethyl ketone, ether alcohols such as ethyl cellosolve, methanol
And alcohols such as toluene, ethanol, propanol and butanol, cyclic ethers such as tetrahydrofuran and dioxane, and esters such as ethyl acetate and butyl acetate.

After completion of the washing, dehydration and demonomerization are performed under normal pressure and reduced pressure to obtain a phenolic resin for a photoresist. Although the degree of pressure reduction can be set as appropriate, it is preferable to perform the pressure reduction at about 0.1 to 200 torr. The temperature at which the phenol resin is taken out of the reaction vessel after the dehydration and de-monomerization can be appropriately set depending on the properties and viscosity of the phenol resin, but from the viewpoint of the stability of the resin, the temperature is preferably from 150 to 250 ° C. . In some cases, it can be dissolved in a solvent used for a photoresist and discharged as a liquid.

Next, the raw materials used in the present invention will be described. As phenols (P), metacresol
Phenol, paracresol, xylenol and trimethylphenol are used, and xylenol is 2,3-xylenol, 2,4-xylenol, 2,5-xylenol.
2,6-xylenol, 3,4-xylenol,
3,5-xylenol can be used, and it may be used alone or in combination of two or more. Trimethylphenol is 2,
3,5-trimethylphenol and 2,3,6-trimethylphenol can be used, and they may be used alone or as a mixture of two kinds. The proportion of metacresol in the phenols (P) is from 55 to 98% by weight, particularly preferably from 70 to 95% by weight. If the amount is less than 55% by weight, the sensitivity of the photoresist becomes too low and 98% by weight. On the other hand, if it is more than%, the sensitivity is too high and the resolution is lowered, so that it is not suitable for actual use. The ratio of paracresol is 1-20
%, Particularly preferably 3 to 15% by weight, and if it is more than 20% by weight, the sensitivity of the photoresist decreases,
If it is less than 1%, the resolution decreases. Xyleno
Of trimethylphenol and / or trimethylphenol is 1-25
% By weight, with 3-20% by weight being particularly preferred. Also,
Xylenol and trimethylphenol may be used alone or in combination. If the amount of xylenol and / or trimethylphenol is more than 25% by weight, the sensitivity of the photoresist will be low. If the amount is small, the heat resistance and the resolution will be reduced, which is not suitable for practical use.

As the aldehyde (A), formaldehyde and an aldehyde containing an alkenyl group are mixed and used.
Since the effect of improving the characteristics of the photoresist can be obtained by introducing a double bond into the molecule and restricting the movement of the molecule in terms of the structure, the ratio is 9/1/1/9 by weight and 8 / 2-. 2
/ 8 is particularly preferred. As formaldehyde, either formalin (aqueous solution) or paraformaldehyde (solid) may be used, and it may be used alone or in combination. Examples of the aldehyde containing an alkenyl group include propenal (acrolein), butenal (crotonaldehyde and the like), pentenal, hexenal, heptenal, octenal, cinnamaldehyde, and the like.
It is not limited to these, and any aldehyde containing an alkenyl group can be used. Also, the molar ratio of aldehydes (A) to phenols (P) (A / P)
Is 0.1-0.9, preferably 0.2-0.8. When it is lower than 0.1, the weight average molecular weight is small and the sensitivity is too high to obtain heat resistance. When it is higher than 0.9, the weight average molecular weight is large, and the sensitivity is too low to be suitable for practical use.

[0013] The acid catalyst is not particularly limited,
Any alkenyl-containing aldehyde and phenols (P) can be used as long as they have the ability to react. Organic carboxylic acids such as acetic acid and oxalic acid do not have the ability to react aldehydes containing an alkenyl group with phenols (P). Therefore, benzenesulfonic acid, paratoluenesulfonic acid, methanesulfonic acid and the like are generally used. It is preferable to use inorganic acids such as organic sulfonic acid, hydrochloric acid and sulfuric acid. The amount used is generally preferably from 0.01% by weight to 5% by weight based on the phenols (P), but is preferably 5% by weight.
If the amount is too large, the reaction will proceed too sharply, making it difficult to control. If the amount is less than 0.1% by weight, the reaction will proceed slowly, which is not economically preferable. However, for the characteristics of the photoresist resin, it is preferable that the amount is as small as possible even within the above range. As amines for neutralizing the acid catalyst, trimethylamine, triethylamine, diethylamine, tributylamine and the like can be used, but there is no particular limitation, and the acid catalyst is neutralized and soluble in water. Any substance that forms a salt can be used.
The amount used depends on the amount of the acid catalyst, but is preferably used in such an amount that the acid catalyst is neutralized and the pH in the reaction system falls within the range of 4-8.

Next, the characteristics of the phenol resin of the present invention will be described. The weight average molecular weight is measured by gel permeation chromatography (GPC) and calculated based on a calibration curve prepared using a polystyrene standard substance. For GPC measurement, tetrahydrofuran was used as the eluting solvent, the flow rate was 1.0 ml / min, and the column temperature was 4
The test was performed at 0 ° C. Body: HLC-8 made by TOSOH
020, detector: TOSO set at a wavelength of 280 nm
H-8011, Analytical column: Showa Denko SHO
DEX KF-802 1 pc, KF-8031 pc, KF
-805 One each was used.

The weight-average molecular weight of the phenolic resin for photoresist of the present invention is not particularly limited.
Preferably it is 5000. Weight average molecular weight is 150
If it is smaller than 0, the sensitivity is too high and the heat resistance is poor, and 1
If it is larger than 5000, the sensitivity is too low to be suitable for actual use. The easiest way to control the weight average molecular weight is to change the molar ratio (A / P) of the aldehyde (A) and the phenol (P) depending on the target molecular weight. , A / P are appropriately selected within the range of 0.1-0.9, but are preferably 0.2-0.8. The amount of free phenols remaining in the phenol resin is not particularly limited, but is preferably 5% or less, more preferably 3% or less, in terms of the peak area of GPC from the viewpoint of handling and the properties of the photoresist. % Or less. It is easiest to control free phenols when dehydrating and de-monomerizing under reduced pressure, depending on the degree of reduced pressure and the termination temperature.

The smaller the amount of metal impurities in the phenolic resin for photoresist, the better, but it is necessary that the content be 1 ppm or less. A phenol resin containing a metal impurity exceeding 1 ppm cannot be used because the amount of the metal impurity that can be used as a phenol resin for a photoresist cannot be reduced by any treatment after the synthesis. It is. When producing a phenol resin having a metal impurity content of 1 ppm or less, a glass lining and / or
Alternatively, use a manufacturing apparatus using a metal material made of a metal selected from tantalum, hafnium, zirconium, niobium, titanium and / or an alloy thereof and containing substantially no other material as a reaction facility material, or using glass. It is preferable to use a lining manufacturing device, and any device may be used.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.
All “parts” and “%” described herein indicate “parts by weight” and “% by weight”, and the present invention is not limited by these examples.

Example 1 In a 5 L four-neck flask made of zirconium equipped with a stirrer, thermometer and heat exchanger, 1470 parts of metacresol, 82 parts of paracresol, 2,3,3
82 parts of 5-trimethylphenol, 128 parts of crotonaldehyde and 16 parts of p-toluenesulfonic acid were charged, and 9
After performing the reaction at 8 to 102 ° C for 4 hours, 650 parts of ethyl cellosolve was added and the mixture was cooled to an internal temperature of 60 ° C, and then 690 parts of 37% formalin was added dropwise at 58 to 62 ° C for 1.5 hours. The reaction was performed for 30 minutes. The molar ratio between the aldehyde (A) and the phenol (P) is 0.690.
It is. Thereafter, the temperature was raised stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 2 hours. After the reaction,
Cool to 90 ° C. and add 11 parts of triethylamine,
Further, 170 parts of acetone and 1100 parts of ion-exchanged water were added, and the mixture was stirred and allowed to stand at about 70 ° C. The pH of the separated water separated by standing was adjusted to 5.5 to 7.5 with triethylamine and paratoluenesulfonic acid,
Separated water was removed. 170 parts of acetone, deionized water 1
This washing operation was repeated once using 100 parts, and then dehydrated to an internal temperature of 140 ° C. under normal pressure.
Dehydration and demonomerization were performed at rr under reduced pressure to 195 ° C to obtain 1650 g of a phenol resin for photoresist. The obtained resin had a weight average molecular weight of 3,500, a free monomer of 2.0%, an iron impurity of 100 ppb, and a residual acid catalyst amount of 3,500 ppm.

Example 2 A 5-liter tantalum four-necked flask equipped with a stirrer, a thermometer and a heat exchanger was supplied with meta-cresol.
1306 parts of paracresol, 82 parts of paracresol, 245 parts of 2,5-xylenol, 132 parts of crotonaldehyde, and 16 parts of paratoluenesulfonic acid.
After reacting for an hour, 650 parts of butyl acetate was added and cooled to an internal temperature of 60 ° C., and then 37% formalin 712 was added.
The mixture was added dropwise at 58-62 ° C. for 1.5 hours, and the mixture was further reacted for 30 minutes. Aldehydes (A) and phenols (P)
Is 0.718. Thereafter, the temperature was raised stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., 11 parts of triethylamine was added, 170 parts of acetone and 1100 parts of ion-exchanged water were added, and the mixture was stirred and allowed to stand at about 70 ° C. 4. the pH of the separated water separated by standing
The mixture was adjusted to 5-7.5 with triethylamine and paratoluenesulfonic acid, and the separated water was removed. This washing operation was repeated once using 170 parts of acetone and 1100 parts of ion-exchanged water.
And then dehydrated and de-monomerized under reduced pressure at 195 ° C. at 80 torr to obtain phenol for photoresist.
Thus, 1750 g of resin was obtained. The weight average molecular weight of the obtained resin was 4230, the free monomer was 2.9%, and the iron impurity was 3%.
5 ppb and the amount of the remaining acid catalyst was 2500 ppm.

Example 3 In a 5 L four-necked niobium flask equipped with a stirrer, thermometer and heat exchanger, 1150 parts of metacresol, 200 parts of paracresol, 300 parts of 2,5-xylenol, croton 132 parts of aldehyde and 16 parts of p-toluenesulfonic acid are charged,
After reacting for an hour, 650 parts of ethyl cellosolve was added and the mixture was cooled to an internal temperature of 60 ° C. Then, 812 parts of 37% formalin was added dropwise at 58-62 ° C for 1.5 hours, and further reacted for 30 minutes. The molar ratio between the aldehyde (A) and the phenol (P) is 0.796. Thereafter, the temperature was raised stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., and 11 parts of triethylamine was added.
And 1100 parts of ion-exchanged water, and the mixture was stirred and allowed to stand at about 70 ° C. PH of separated water separated by standing
Was adjusted with triethylamine and p-toluenesulfonic acid so as to be 5.5 to 7.5, and separated water was removed. Using 170 parts of acetone and 1100 parts of ion-exchanged water,
After repeating this washing operation once again, the internal temperature was reduced to 1 at normal pressure.
After dehydration to 40 ° C, dehydration and demonomerization were performed at 80 torr under reduced pressure to 195 ° C to obtain 1650 g of a phenol resin for photoresist. The obtained resin had a weight average molecular weight of 9000, a free monomer of 2.5%, an iron impurity of 25 ppb, and a residual acid catalyst amount of 800 ppm.

Example 4 1320 parts of metacresol, 180 parts of paracresol, 2,3,5 were placed in a 5 L four-neck hafnium flask equipped with a stirrer, thermometer and heat exchanger.
-120 parts of trimethylphenol, 320 parts of crotonaldehyde and 16 parts of paratoluenesulfonic acid were charged, and 9 parts of
After reacting at 8 to 102 ° C. for 4 hours, 650 parts of methyl isobutyl ketone was added, and the mixture was cooled to an internal temperature of 60 ° C.
Then 330 parts of 37% formalin at 58-62 ° C.
The mixture was added dropwise over 5 hours, and the reaction was further performed for 30 minutes. The molar ratio between the aldehyde (A) and the phenol (P) is 0.58
5 Thereafter, the temperature was raised stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., 11 parts of triethylamine was added, 150 parts of acetone and 1100 parts of ion-exchanged water were added, and the mixture was stirred and allowed to stand at about 70 ° C. The pH of the separated water separated by standing was adjusted to 5.5 to 7.5 with triethylamine and paratoluenesulfonic acid, and the separated water was removed. This washing operation was repeated once using 150 parts of acetone and 1100 parts of ion-exchanged water, and then dehydrated to an internal temperature of 140 ° C. under normal pressure.
Dehydration and de-monomerization were performed at 195 ° C. under reduced pressure at 0 torr to obtain 1600 g of a phenol resin for photoresist. The obtained resin had a weight average molecular weight of 2,000, a free monomer of 1.8%, an iron impurity of 45 ppb, and a residual acid catalyst amount of 4,200 ppm.

Example 5 Meta-cresol was placed in a 5 L glass four-necked flask equipped with a stirrer, thermometer and heat exchanger.
After 1000 parts, 300 parts of paracresol, 300 parts of 3,5-xylenol, 250 parts of acrolein and 16 parts of paratoluenesulfonic acid were charged and reacted at 98 to 102 ° C. for 4 hours, butanol 780 was obtained. Add 6 parts of internal temperature
After cooling to 0 ° C., 330 parts of 37% formalin was added dropwise at 58-62 ° C. over 1.5 hours, and the mixture was further reacted for 30 minutes. The molar ratio between the aldehyde (A) and the phenol (P) is 0.589. Thereafter, the temperature was raised stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., 11 parts of triethylamine was added, 300 parts of acetone and 1100 parts of ion-exchanged water were added, and the mixture was stirred and allowed to stand at about 70 ° C. The pH of the separated water separated by standing is 5.5
The mixture was adjusted to -7.5 with triethylamine and p-toluenesulfonic acid, and the separated water was removed. Acetone 3
This water washing operation was repeated once again using 00 parts and 1100 parts of ion-exchanged water, followed by dehydration to an internal temperature of 170 ° C. under normal pressure, and further dehydration and de-monomerization under reduced pressure at 195 ° C. at 80 torr. 1600 g of a phenol resin for a photoresist was obtained. The obtained resin had a weight average molecular weight of 12,000, a free monomer of 3.5%, an iron impurity of 80 ppb, and a residual acid catalyst amount of 180 ppm.

Comparative Example 1 400 parts of meta-cresol, 600 parts of para-cresol, 412.9 parts of 37% formalin (412.9 parts of charged mole ratio: 0.55) were prepared in the same reactor as in Example 1 except that the material was stainless steel. Charge 2 parts of oxalic acid, 98 ~
After a reflux reaction at 102 ° C. for 4 hours, dehydration was performed under normal pressure to raise the internal temperature to 140 ° C., and then dehydration was performed under a reduced pressure of 80 Torr, and demonomerization was performed until the internal temperature reached 195 ° C. -Resin was obtained. The obtained product had a weight average molecular weight of 2,200 and a free monomer of 3.
3%, the iron impurity was 5000 ppb, and the amount of the remaining acid catalyst was 3800 ppm.

Comparative Example 2 400 parts of meta-cresol, 600 parts of para-cresol, 563.1 parts of 37% formalin (charged molar ratio 0.75) were prepared in the same reactor as in Example 1 except that the material was stainless steel. 9 parts of oxalic acid, 96 ~
After performing a reflux reaction at 100 ° C. for 5 hours, dehydration is performed under normal pressure, the internal temperature is raised to 150 ° C., and then 300 Torr
Dehydration and de-monomerization were performed under a reduced pressure of r until the internal temperature reached 165 ° C. to obtain a phenol resin for photoresist. The obtained product had a weight average molecular weight of 9,300, a free monomer of 10.6%, an iron impurity of 6,800 ppb, and a residual acid catalyst amount of 800 ppm.

Comparative Example 3 400 parts of metacresol, 600 parts of paracresol, 600 parts of 2,5-xylenol and 600 parts of croton were placed in a 5-liter zirconium four-necked flask equipped with a stirrer, a thermometer, and a heat exchanger. 5 parts of aldehyde and 16 parts of paratoluenesulfonic acid were charged,
After reacting for an hour, 780 parts of ethyl cellosolve was added and the mixture was cooled to an internal temperature of 60 ° C. Then, 712 parts of 37% formalin was added dropwise at 58 to 62 ° C for 1.5 hours, and the reaction was further performed for 30 minutes. The molar ratio of aldehydes (A) to phenols (P) is 0.624 and the weight ratio of formaldehyde to crotonaldehyde is 52.5 / 1.
Thereafter, the temperature is increased stepwise, and finally the reflux temperature (97-
(103 ° C.) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., 11 parts of triethylamine was added, 170 parts of acetone and 1100 parts of ion-exchanged water were added, and the mixture was stirred and allowed to stand at about 70 ° C. The pH of the separated water separated by standing was adjusted to 5.5 to 7.5 with triethylamine and paratoluenesulfonic acid, and the separated water was removed. This washing operation was repeated once again using 170 parts of acetone and 1100 parts of ion-exchanged water, followed by dehydration under normal pressure to an internal temperature of 140 ° C., and further dehydration and de-monomerization under reduced pressure at 195 ° C. at 80 torr. Thus, 1600 g of a phenol resin for photoresist was obtained. The weight average molecular weight of the obtained resin was 5,100, and the free monomer was 2.
5%, iron impurities 50 ppb, remaining acid catalyst amount 90
It was 00 ppm.

The properties of the phenolic resin obtained as described above as a photoresist were measured, and are shown in Table 1 together with the weight average molecular weight and the amount of free monomer.
Table 2 shows the amounts of metal impurities.

[Evaluation Method 1: Evaluation Method for Heat Resistance] 100 parts of the phenol resin obtained in each of the above examples and 2,3,4-trihydroxybenzophenone ester of naphthoquinone 1,2-diazide-5-sulfonic acid 30 parts were dissolved in ethyl lactate to prepare a resist solution. These are 0.2
The solution was filtered through a micron membrane filter to obtain a resist solution. This was applied by a conventional method and dried on a hot plate at 110 ° C. for 90 seconds. Thereafter, exposure was performed through a test chart mask using a reduction projection exposure apparatus, and development was performed for 50 seconds using a developing solution (2.38% aqueous solution of tetramethylammonium hydroxide). The obtained silicon wafer was left for 30 minutes on a hot plate where the temperature was changed, and the shape change of the resist pattern on the silicon wafer was observed with a scanning electron microscope to evaluate the heat resistance.

[Evaluation Method 2: Evaluation Method of Critical Resolution and Depth of Focus] In the same manner as in Evaluation Example 1, solution preparation, pretreatment, coating, exposure and development using a test chart mask were performed, and the resist pattern shape was changed to a scanning electron beam. Observed under a microscope. The depth of focus was obtained by visually observing a photograph when the focus was changed at a line width of 0.30 μm, and measuring a resolvable focus variation width. The limit resolution was determined and measured by visually observing the limit that could be resolved from a photograph under optimal exposure and development conditions.

[Evaluation Method 3: Method for Measuring Sensitivity Stability] A phenol resin was dissolved in ethyl lactate to prepare a sample solution. These were filtered through a 5B filter paper, applied to a silicon wafer by a conventional method, and dried on a hot plate at 110 ° C. for 90 seconds. Thereafter, it was immersed in a developing solution (2.38% aqueous solution of tetramethylammonium hydroxide), and the time required for the phenol resin to completely dissolve was measured. The measurement was performed at n = 5, and the sensitivity stability was evaluated based on the variation in the dissolution time.

[0030]

[Table 1]

[Evaluation Method 4: Measurement Method of Metal Impurity Amount]
Metal impurities were measured using a frameless atomic absorption spectrophotometer.

[0032]

[Table 2]

[0033]

According to the present invention, it is possible to provide a phenolic resin for photoresist which has high heat resistance, high resolution and high sensitivity, which cannot be obtained by the conventional method. The photoresist obtained by using the phenolic resin of the present invention is used for lithography when manufacturing a highly integrated semiconductor, and is expected to be useful for further high integration of semiconductors in the future.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Osamu Onishi 2-5-2-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Durez Corporation

Claims (9)

[Claims] The composition of phenols (P) is 55-98% by weight of meta-cresol, 1-20% by weight of para-cresol, xylenol and / or trimethylphenol 1-.
25% by weight, the composition of the aldehyde (A) is an aldehyde containing formaldehyde and an alkenyl group, the weight ratio of which is 1 / 9-9 / 1, and the phenol and the aldehyde are acid catalyzed. Wherein the amount of acid catalyst remaining in the phenolic resin is small enough not to affect practical use, and metal impurities are 1 ppm or less in each element. resin. 2. The phenolic resin for a photoresist according to claim 1, wherein the molar ratio (A / P) of the aldehyde (A) and the phenol (P) is 0.1-0.9. 3. The phenolic resin for a photoresist according to claim 1, wherein the weight average molecular weight in terms of polystyrene by GPC is from 1500 to 15000. 4. The phenolic resin for a photoresist according to claim 1, wherein the amount of free phenols is 5% or less in a peak area of GPC. 5. Xylenol is 2,3-xylenol
2,4-xylenol, 2,5-xylenol, 3,
5. The phenolic resin for a photoresist according to claim 1, which is one or more of 4-xylenol and 3,5-xylenol. 6. The photoresist phenolic resin according to claim 1, wherein the trimethylphenol is 2,3,5-trimethylphenol. 7. A phenolic resin for a photoresist according to claim 1, wherein the aldehyde containing an alkenyl group is propenal (acrolein) or 2-butenal (crotonaldehyde). 8. The phenolic resin for a photoresist according to claim 1, wherein the amount of the acid catalyst remaining in the phenolic resin is 5000 ppm or less. 9. Lithium, sodium, potassium, calcium, magnesium, barium in a phenol resin,
Iron, nickel, chromium, aluminum, zinc, tin, copper,
2. The phenolic resin for a photoresist according to claim 1, wherein the contents of each element of lead, manganese and silicon are 1 ppm or less.