JP2002014465A - Phenolic resin for excimer-photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phenolic resin for a KrF excimer-photoresist excellent in transparency to light of 248 nm wavelength and capable of producing a photoresist having high heat resistance, a high residual film ratio, high sensitivity and high resolution. SOLUTION: The phenolic resin is obtained by polycondensing (1) phenols including 4-100 wt.% m-cresol, 0-30 wt.% p-cresol and 0-30 wt.% xylenol and/or trimethylphenol and (2) aldehydes comprising formaldehyde and a 2-7C linear or cyclic aldehyde in a formaldehyde to 2-7C aldehyde weight ratio of 1:9 to 9:1 in the presence of an acidic catalyst and has >=70% light transmittance at 248 nm wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoresist and a phenol resin used for lithography in the production of semiconductors and the like, which has excellent transparency to light having a wavelength of 248 nm, high heat resistance, and high heat resistance. The present invention relates to a phenolic resin for a KrF excimer photoresist which enables the production of a photoresist having a remaining film ratio, high sensitivity and high resolution.

[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 when developed with an alkaline solution, and are used for manufacturing semiconductors such as ICs and LSIs, LCDs
It is used for the production of circuit substrates such as. 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.

Generally, a phenol resin obtained by reacting meta-paracresol and 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 photoresist, the ratio and molecular weight of meta-paracresol have been studied.
Technology has been applied. In semiconductor photoresists,
Characteristics such as high heat resistance, high resolution and high sensitivity are required, and to improve heat resistance, monomers such as alkylphenols such as xylenol and trimethylphenol and aromatic aldehydes have been studied. There is an example in which hydroxybenzaldehyde and the like have been studied for higher sensitivity. In each of these cases, although a slight improvement effect can be obtained, a sufficient effect has not yet been obtained.

In recent years, as the demand for higher integration of semiconductors has been increasing year by year, there has been a demand for resolution of a region which cannot be theoretically drawn with a wavelength of light such as g-line and i-line. Therefore, KrF excimer light has been used as a light source. KrF excimer laser is
Polyhydroxystyrene has come to be used because it is light having a wavelength of 248 nm and the phenolic resin is inferior in transparency due to light absorption by the aromatic ring of the phenol resin itself. However, the transparency is not sufficient even with polyhydroxystyrene, and it is very expensive. Therefore, there is a great demand for an inexpensive phenol resin-based product with improved transparency.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to the production of photoresists having high heat resistance, high residual film ratio, high sensitivity and high resolution for use in photoresists used in lithography in the production of semiconductors and the like. It is an object of the present invention to provide a phenolic resin for a KrF excimer photoresist having excellent transparency to light having a wavelength of 248 nm, which makes it possible to achieve the above.

[0006]

The resin of the present invention is obtained by polycondensing the above (1) and (2) with an acidic catalyst.
Kr characterized by excellent transmittance at 48 nm
F-Phenol resin for excimer photoresist and 30-1 of phenolic hydroxyl groups in the phenol resin
KrF in which 00 mol% is substituted by an acid-decomposable group
It is a phenolic resin for excimer photoresist.

Hereinafter, the present invention will be described in detail.
The composition of the phenols of (1) is meta-cresol 40-
100% by weight, 0-30% by weight of paracresol, 0-30% by weight of xylenol and / or trimethylphenol
It is. Among the phenols, xylenols include 2,3-xylenol, 2,4-xylenol,
2,5-xylenol, 2,6-xylenol, 3,4
There are -xylenol and 3,5-xylenol, which may be used alone or in combination of two or more. The composition ratio can be adjusted according to the required characteristics of the photoresist. Not done. Also, trimethylpheno-
And the like include 2,3,5-trimethylphenol,
2,3,6-trimethylphenol, 2,3,4-trimethylphenol, 2,4,5-trimethylphenol
And 3,4,5 trimethylphenol. These may be used alone or in combination of two or more. The composition ratio can be adjusted according to the required characteristics of the photoresist, and is not particularly specified. Particularly preferable in terms of characteristics such as resolution, sensitivity and heat resistance of the photoresist are 2,3,5-trimethylphenol and 2,3,6.
-Trimethylphenol.

The composition of the aldehyde (2) is a formaldehyde and a chain or cyclic aldehyde having 2 to 7 carbon atoms, wherein the weight ratio of formaldehyde to the aldehyde having 2 to 7 carbon atoms is 1 / 9-9. / 1. This ratio is 24
It is preferably 2 / 8-8 / 2 from the viewpoint of the transmittance of the resin to light having a wavelength of 8 nm and the solubility to alkali.
For example, acetaldehyde, propanal, butanal, isobutanal, glutaraldehyde, 2-
Butenal, cyclohexanone and the like can be used.
Formaldehyde may be either formalin (aqueous solution) or paraformaldehyde (solid), and may be used alone or in combination. When an aldehyde having more than 7 carbon atoms is used, alkali solubility is reduced, and the sensitivity is insufficient when applied to a photoresist, which is not practical.

As the acid catalyst, organic carboxylic acids such as oxalic acid and acetic acid, organic sulfonic acids such as benzenesulfonic acid, paratoluenesulfonic acid and methanesulfonic acid, and inorganic acids such as hydrochloric acid and sulfuric acid can be used. There is no particular limitation, and it is also possible to use a mixture of two or more of them alone. The amount used is from 0.01% by weight to 5% by weight based on the phenols, but is preferably as small as possible in order to maintain the characteristics of the phenolic resin for photoresist. The reaction solvent can be used if necessary, but the type of the solvent is not particularly limited, and any solvent can be used as long as it dissolves the phenol resin and reduces the viscosity of the resin obtained by the reaction. It is possible.

Next, the weight average molecular weight of the phenolic resin of the present invention will be described. The weight average molecular weight is a value calculated by gel permeation chromatography (GPC) based on a calibration curve prepared using a polystyrene standard substance. GPC measurement uses tetrahydrofuran as an elution solvent, and a flow rate of 1.0 ml /
For 30 minutes at a column temperature of 40 ° C. Body: TOS
OH HLC-8020, detector: TOSOH UV-8011, set at a wavelength of 280 nm, analytical column:
Showa Denko SHOdex KF-802 1 pc., KF-8
03 one and KF-805 one.

The transmittance was evaluated by measuring the transmittance for light having a wavelength of 248 nm using a UV spectrophotometer (U-2000 manufactured by Hitachi, Ltd.). In the measurement, a methanol solution of the resin was used.

Further, the resin of the present invention will be described in accordance with a reaction (production) procedure. The reaction method described below is an example, and is not particularly limited thereto. The reaction is carried out by charging phenols, aldehydes and an acid catalyst into a reaction vessel equipped with a stirrer, thermometer and heat exchanger. The reaction temperature and time can be appropriately set depending on the reactivity of the above-mentioned reaction raw materials, but the reaction time is preferably 2 to 10 hours and the reaction temperature is 70 to 150 ° C. as stable and economical production. If necessary, a reaction solvent can be used. The type of the solvent is not particularly limited, but a solvent that dissolves the phenol resin obtained by the reaction is particularly preferable.

After completion of the reaction, if necessary, a basic compound is added to remove the acid catalyst and neutralized to form a neutralized salt.
Water washing may be performed by adding water. The amount and the number of times of washing water are not particularly limited, but the number of times of washing is preferably about 1 to 5 times from the viewpoint of economically removing the neutralized salt in the resin to a level that does not substantially affect the washing. The washing temperature is not particularly limited, but is preferably 40-95 ° C. from the viewpoint of the removal efficiency of the neutralized salt and the workability. During the washing, if the separation of the washing water from the resin is poor, it is effective to add a solvent or raise the washing temperature to reduce the viscosity of the resin. The type of solvent is not particularly limited, but any solvent can be used as long as it dissolves the phenol resin obtained by the reaction and lowers the viscosity.

After the completion of the reaction or washing with water, dehydration and de-monomerization are performed under normal pressure and reduced pressure to obtain a phenol resin for photoresist. The temperature of taking out of the reaction vessel after the dehydration and de-monomerization can be appropriately set depending on the characteristics of the phenol resin and the viscosity of the resin, but from the viewpoint of the stability of the resin,
It is particularly preferred to work at 150-250 ° C. The degree of decompression is
Can be set as appropriate, but 0.1 torr to 200 torr
It is particularly preferable to perform the reaction at a degree.

The weight average molecular weight of the phenolic resin for a photoresist which can be produced by the present invention is not particularly limited, but is preferably from 1,000 to 20,000 in view of the performance of the photoresist and the handling property in production. , 20
00 to 15000 are particularly preferred. As a method for controlling the weight average molecular weight, it is most appropriate to adjust the molar ratio (2) / (1) of aldehydes and phenols, which can be appropriately set according to the target molecular weight. The range is 0.1 to 1.0, and particularly preferably 0.2 to 0.9 from the viewpoint of the weight average molecular weight, alkali solubility, heat resistance and the like of the obtained resin. The material of the equipment such as a reaction vessel in the production is not particularly limited, but is made of a glass lining, or a metal or an alloy thereof selected from tantalum, hafnium, zirconium, niobium, titanium, and contains substantially no other material. It is preferable to use a manufacturing apparatus using a metal material as a material of a reaction facility.

[0016] The phenolic resin obtained by the method of claim 1 of the present invention is not used as it is, but with respect to the hydroxyl group of the resin.
Those into which a substituent decomposable by an acid is introduced can be used as a phenol resin for KrF excimer.
The substituent to be introduced is not particularly limited, but those which are stable in the absence of an acid and which are easily decomposed by an acid are used, and particularly preferred is t-
Butoxycarbonyl group, tetrahydropyranyl group and ethoxyethyl group. Phenol resins in which 30 to 100% of the hydroxyl groups of the phenolic resin are substituted with these groups exhibit good properties, but from the viewpoint of transmittance for 248 nm light, alkali solubility and heat resistance, particularly preferably 40. ~ 90%.

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 Metacresol 1470 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, 82 parts of paracresol, 82 parts of 2,3,5-trimethylphenol, 128 parts of crotonaldehyde, and 16 parts of paratoluenesulfonic acid.
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, 690 parts of 37% formalin was added successively at 58-62 ° C for 1.5 hours, and further reacted for 30 minutes. . 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, and 170 parts of acetone and 11 parts of ion-exchanged water were added.
After adding 00 parts, 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, and the separated water was removed. Acetone 170
And 1100 parts of ion-exchanged water, this water washing operation was repeated once, then dehydrated under normal pressure to an internal temperature of 140 ° C., and further dehydrated and de-monomerized under reduced pressure at 195 ° C. at 80 torr. 1650 g of a phenol resin for resist was obtained. The weight average molecular weight of the obtained resin is 3
500, 2.0% free monomer.

Example 2 Metacresol 1306 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, paracresol 82 parts, 2,5-xylenol 24
After 5 parts, 132 parts of n-butanal and 16 parts of paratoluenesulfonic acid were charged and reacted at 98-102 ° C for 4 hours, 650 parts of ethyl cellosolve was added, and the internal temperature was 60 ° C.
And then add 712 parts of 37% formalin to 58
The mixture was added successively at -62 ° C for 1.5 hours and reacted for further 30 minutes. Thereafter, the temperature is raised stepwise, and finally the reflux temperature (9
(7-103 ° C) for 2 hours. After the reaction, 90
After cooling to 0 ° 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, 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.
Dehydration and de-monomerization were carried out at 0 torr and 195 ° C. under reduced pressure to obtain 1750 g of a phenol resin for photoresist. The weight average molecular weight of the obtained resin was 4230, and the free monomer was 2.9%.

Example 3 Metacresol 1150 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, 200 parts of paracresol, 2,5-xylenol 3
After adding 100 parts, 132 parts of propanal, and 16 parts of paratoluenesulfonic acid, and performing a reaction at 98-102 ° C for 4 hours, 650 parts of ethyl cellosolve was added and the internal temperature was 60 ° C.
And then add 812 parts of 37% formalin to 58
The mixture was added successively at -62 ° C for 1.5 hours and reacted for further 30 minutes. Thereafter, the temperature is raised stepwise, and finally the reflux temperature (9
(7-103 ° C) for 2 hours. After the reaction, 90
After cooling to 0 ° 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, 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.
Dehydration and demonomerization were carried out at 0 torr at 195 ° C. under reduced pressure to obtain 1650 g of a phenol resin for photoresist. The weight average molecular weight of the obtained resin was 9,000, and the free monomer was 2.5%.

Example 4 Metacresol 1320 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, 180 parts of paracresol, 120 parts of 2,3,5-trimethylphenol, 320 parts of cyclohexanone and 16 parts of paratoluenesulfonic acid, and after reacting at 98-102 ° C. for 4 hours, ethyl cellosolve 650 was added. Then, the mixture was cooled to an internal temperature of 60 ° C., and then 330 parts of 37% formalin were successively added at 58-62 ° C. for 1.5 hours, and further reacted for 30 minutes. 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 triethylamine 11
And 150 parts of acetone and 1 part of ion-exchanged water.
100 parts 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, and the separated water was removed. Acetone 150
And 1100 parts of ion-exchanged water, this water washing operation was repeated once, then dehydrated under normal pressure to an internal temperature of 140 ° C., and further dehydrated and de-monomerized under reduced pressure at 195 ° C. at 80 torr. 1600 g of phenol resin for resist was obtained. The weight average molecular weight of the obtained resin is 2
000, free monomer was 1.8%.

Example 5 Metacresol 1000 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, paracresol 300 parts, 3,5-xylenol 3
After adding 00 parts, 250 parts of isobutanal, and 16 parts of paratoluenesulfonic acid, and performing a reaction at 98-102 ° C. for 4 hours, 780 parts of ethyl cellosolve was added and the internal temperature was adjusted to 60 parts.
C., and 330 parts of 37% formalin in 5 parts
The mixture was successively added at 8-62 ° C for 1.5 hours, and further reacted for 30 minutes. 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, 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 was adjusted to 5.5 to 7.5, and the separated water was removed. This washing operation was repeated once using 300 parts of acetone and 1100 parts of ion-exchanged water, followed by dehydration under normal pressure to an internal temperature of 170 ° C., and dehydration / de-monomerization under reduced pressure at 195 ° C. at 80 torr.
Was carried out to obtain 1600 g of a photoresist phenol resin. The weight average molecular weight of the obtained resin was 16,000, and the free monomer was 3.5%.

<< Examples 6 to 10 >> Di-tert was added to the resins obtained in Examples 1 to 5 dissolved in tetrahydrofuran.
One or more selected from -butyl-dica-carbonate, dihydropyran, and ethylvinylether, and triethylamine were added in an appropriate amount. After reacting at room temperature for 24 hours, diethylether was added. Further, ion-exchanged water was added and the mixture was washed three times with water, and the solvent was removed and dried to obtain a phenol resin for a KrF excimer photoresist having a target acid-decomposable group. The charge composition and properties are summarized in Table 1.

Comparative Example 1 400 parts of meta-cresol, 600 parts of para-cresol and 3 parts of the same reactor as in Example 1 were used.
412.9 parts of 7% formalin (charged molar ratio 0.5
5) After charging 2 parts of oxalic acid and performing a reflux reaction at 98-102 ° 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. The process was continued until the temperature reached 195 ° C. to obtain a phenol resin for photoresist. The obtained product had a weight average molecular weight of 2,200 and a free monomer of 3.3%.

Comparative Example 2 400 parts of meta-cresol, 600 parts of para-cresol, 3 parts of the same reactor as in Example 1
563.1 parts of 7% formalin (charged molar ratio 0.7
5) After charging 7 parts of oxalic acid and performing a reflux reaction at 96 to 100 ° C. for 5 hours, dehydration is performed under normal pressure, the internal temperature is raised to 150 ° C., and then dehydration and demonomerization are performed under a reduced pressure of 80 Torr. The operation was carried out until the internal temperature reached 195 ° C. to obtain a phenol resin for photoresist. The obtained product had a weight average molecular weight of 9,300 and a free monomer of 2.6%.

<< Comparative Examples 3-4 >> Di-tert- was added to the resin obtained in Comparative Examples 1-2 dissolved in tetrahydrofuran.
An appropriate amount of one or more selected from butyl-dicarbonate, dihydropyran, and ethylvinyl ether, and triethylamine were added, and after reacting at room temperature for 24 hours, diethyl ether was added. Further, KrF excimer having a group decomposable by an intended acid is obtained by adding ion-exchanged water, washing with water three times, and removing and drying the solvent.
A phenol resin for photoresist was obtained. The charge composition and properties are summarized in Table 1.

(Measurement of phenolic hydroxyl group substitution ratio) A resin was dissolved in methanol, and the measurement was carried out by titration using a sodium hydroxide / methanol solution. The substitution rate was calculated by setting the titration value of the resin before the substitution reaction to 100 and using the measured value of the resin after the substitution reaction.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, it has become possible to provide a phenol resin having a high transmittance for light having a wavelength of 248 nm, which is the wavelength of a KrF excimer laser. The phenolic resin of the present invention is expected to improve the performance of the KrF excimer photoresist such as resolution and sensitivity, and to be expected to lead to an improvement in the semiconductor industry. In addition, since it can be produced more easily and at lower cost than the currently used polyhydroxystyrene, it is thought to be useful for cost reduction.

Claims (7)

[Claims] 1. A phenol resin obtained by polycondensation of the following (1) and (2) with an acidic catalyst, wherein the phenol resin has a wavelength of 24.
A phenol resin for a KrF excimer photoresist, which has a transmittance of 8% light of 70% or more. (1) phenols which are 40 to 100% by weight of meta-cresol, 0 to 30% by weight of para-cresol, and 0 to 30% by weight of xylenol and / or trimethylphenol;
(2) Aldehydes comprising formaldehyde and a chain or cyclic aldehyde having 2 to 7 carbon atoms, wherein the weight ratio of formaldehyde to the aldehyde having 2 to 7 carbon atoms is 1 / 9-9 / 1. 2. The phenol for KrF excimer photoresist according to claim 1, wherein 30 to 100 mol% of the phenolic hydroxyl groups derived from the phenols are substituted with acid-decomposable groups. resin. 3. The Kr according to claim 2, wherein the group substituted from the phenolic hydroxyl group is a tert-butoxycarbonyl group, an ethoxyethyl group or a tetrahydropyranyl group.
F Excimer Phenol resin for photoresist. 4. The method according to claim 1, wherein the trimethylphenol is 2,3,5-trimethylphenol or 2,3,6-trimethylphenol.
The K according to claim 1, 2 or 3, comprising at least one of
Phenol resin for rF excimer photoresist. 5. A chain or cyclic aldehyde having 2 to 7 carbon atoms, wherein the aldehyde is propanal, butanal, glutaraldehyde,
Claim 1 comprising at least one of crotonaldehyde.
5. The phenolic resin for photoresist according to any one of 4. 6. The phenolic resin for a KrF excimer photoresist according to claim 1, wherein the weight average molecular weight in terms of polystyrene by GPC is from 1,000 to 20,000. 7. The method according to claim 1, wherein the molar ratio (1) / (2) of the phenols (1) to the aldehydes (2) is 0.1 to 1.0. The phenolic resin for the KrF excimer photoresist according to the above.