JP2002107925A - Phenolic resin for photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phenolic resin for photoresist having high heat resistance, high resolution and high sensitivity. SOLUTION: The phenolic resin is a novolak type phenolic resin obtained by reacting phenols (P) comprising 30-70 wt.% m-cresol, 5-40 wt.% p-cresol and 5-50 wt.% xylenol and/or trimethylphenol with aldehydes (F) comprising formaldehyde (f1) and aromatic aldehydes (f2) in an f1 to f2 weight ratio of (1:9) to (9:1). The inertial radius (molecular size) of the novolak type phenolic resin is 1.50-2.50 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, a positive photoresist is composed of a sensitizer having a quinonediazide group such as a naphthoquinonediazide compound and an alkali-soluble resin (for example, a novolak-type phenol resin).
Resin) is used. 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 the manufacture of 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.

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. Alkyl phenols such as xylenol and trimethylphenol have been studied to improve heat resistance. Although an 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, such as a high-ortho-modified resin. However, it has not been put to practical use due to poor heat resistance. In addition, various monomers
There are cases where the types have been studied, but all have their advantages and disadvantages and have not yet been put to practical use.

[0005]

DISCLOSURE OF THE INVENTION The present invention has a high heat resistance.
It is an object of the present invention to provide a phenol resin that enables the production of a photoresist having both high resolution and high sensitivity.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a metacreso-
30-70% by weight and para-cresol 5-40% by weight,
Xylenol and / or trimethylphenol 5-50
And aldehydes (F) consisting of formaldehyde (f1) and aromatic aldehydes (f2) at a weight ratio (f1 / f2) of 1 / 9-9 / 1. A phenolic resin for a photoresist, characterized in that the radius of inertia (molecular size) of the novolak phenolic resin is 1.50-2.50 nm. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the raw materials used in the present invention will be described.
Phenols include meta-cresol and para-cresol.
, Xylenol and trimethylphenol can be used. Xylenol includes 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. They may be used alone or in combination of two or more. Trimethylphenol is 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 3,4,5
-Trimethylphenol can be used, and it may be used alone or as a mixture of two kinds. Metacresol in phenols
The proportion of toluene is 30-70% by weight, and particularly preferably 35-65% by weight. If the amount of meta-cresol is less than 30% by weight, the sensitivity is impaired, and if it exceeds 70% by weight, the resolution is reduced.
The proportion of paracresol is 10-35 at 5-40% by weight.
% By weight is particularly preferred. If it is less than 5% by weight, the pattern shape is deteriorated, and if it exceeds 40% by weight, the sensitivity is reduced.
The proportion of xylenol and / or trimethylphenol is preferably 5 to 50% by weight and particularly preferably 10 to 45% by weight. 5 xylenol and / or trimethylphenol
If the amount is less than 50% by weight, heat resistance decreases, and if it exceeds 50% by weight, sensitivity decreases.

As aldehydes, formaldehyde (f1) and aromatic aldehydes (f2) are mixed and used, and their ratio is 9 / 1-1 / 1 in weight ratio (f1 / f2).
9, particularly preferably 8 / 2−2 / 8. Formaldehyde may be either formalin (aqueous solution) or paraformaldehyde (solid), and may be used alone or in combination. If the weight ratio of formaldehyde (f1) exceeds 9, the heat resistance will decrease, and if it is less than 1, the sensitivity will decrease. Examples of aromatic aldehydes include, but are not limited to, salicylaldehyde (o-hydroxybenzaldehyde), p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, benzaldehyde, vanillin, thymol, anethole, eugenol, safrole, naphthaldehyde, and the like. However, any aromatic aldehyde can be used. Salicylaldehyde is most preferred as the aromatic aldehyde from the viewpoint of reactivity as a monomer and improvement in resolution, but is not particularly limited. The molar ratio between aldehydes and phenols is 0.1-0.9, preferably 0.2-0.8.

As the acid catalyst used for synthesizing the phenolic resin for a photoresist of the present invention, organic sulfonic acids such as benzenesulfonic acid, paratoluenesulfonic acid and methanesulfonic acid, and inorganic acids such as hydrochloric acid and sulfuric acid are used. There is no particular limitation, and any material capable of reacting an aromatic aldehyde with phenols can be used. The amount used is from 0.01% by weight to 5% by weight based on the phenols, but is preferably as small as possible because of the properties of the photoresist resin.
Since residual acid catalyst in the resin adversely affects the properties of the photoresist, it is preferable to use an amine to neutralize the acid catalyst. As amines for neutralization, trimethylamine, triethylamine, diethylamine, tributylamine and the like can be used, but there is no particular limitation, and a salt that neutralizes an acid catalyst and becomes soluble in water is used. Any material that can be formed can be used. The amount used depends on the amount of the acid catalyst, but the acid catalyst is neutralized and the pH in the reaction system is reduced.
Is preferably used in such an amount that falls within the range of 4-7. 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 and the radius of gyration of the resin according to the present invention will be described. The weight average molecular weight is determined by gel permeation chromatography (G
PC measurement) based on a calibration curve prepared using a polystyrene standard substance. The radius of inertia is calculated using a Mark-Houwink Plot created from the measurement results of the differential pressure viscosity, refraction and light scattering detectors, with a weight average molecular weight of 1,000 to 40000 as a calculation range. The GPC measurement was performed using tetrahydrofuran as an elution solvent under the conditions of a flow rate of 1.0 ml / min and a column temperature of 40 ° C. Body: HLC made by TOSOH
-8120, detector: TDA-30 manufactured by VISCOTEK
0 triple detector (differential pressure viscosity detector, refraction detector, light scattering detector), analytical column: TSKOH-GE TSK-GE
L One G1000HXL, Two G2000HXL,
One G3000HXL was used.

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 1500-15000 in view of the performance of the photoresist and the handling property in production. preferable.
If the weight average molecular weight is less than 1500, the sensitivity may be too high to form an image, and if it exceeds 15,000, the pattern shape may be deteriorated. As a method for controlling the weight average molecular weight, the molar ratio (A / P) of aldehydes and phenols is most suitable and can be appropriately set according to the target molecular weight. .2
-0.8 is particularly preferred. The radius of inertia is usually preferably 1.50 to 2.50, particularly preferably 1.80 to 2.40. If the ratio is less than 1.50, the resin structure becomes two-dimensional, and there is a possibility that the heat resistance is reduced. Also 2.
If it exceeds 50, the resin structure will have an excessive three-dimensional structure, interaction with the photosensitive agent cannot be effectively performed due to three-dimensional factors, and the resolution tends to decrease.

Further, the present invention will be described along the reaction procedure. In the reaction, a phenol, an aromatic aldehyde, and an acid catalyst are charged into a reactor equipped with a stirrer, a thermometer, and a heat exchanger to start a primary reaction. The reaction temperature and time can be appropriately set depending on the reactivity of the monomer. However, it is particularly preferable that the reaction time is 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. After completion of the reaction, formaldehyde (formalin and / or paraformaldehyde) is added to perform a secondary reaction. The method of adding formaldehyde can be either a sequential addition method or a batch method, and can be selected according to the degree of heat generated when formaldehyde is added. The reaction temperature and time of the secondary reaction can be appropriately selected depending on the properties of the resin to be produced and the reactivity of the monomer. However, the reaction time is 1 to 10 hours and the reaction temperature is 50 and 50 as stable and economical production levels. -150 ° C is particularly preferred. In the primary reaction and the secondary reaction, a reaction solvent can be added and used if necessary. The type of the solvent is not particularly limited, but a solvent that dissolves the phenol resin is particularly preferable.

After the completion of the washing, dehydration and de-monomerization are carried out under normal pressure and reduced pressure to obtain a phenol resin for photoresist. The temperature at which the resin is taken out of the reaction vessel after dehydration and demonomerization can be appropriately set depending on the characteristics of the phenol resin, the viscosity of the resin, and the like.
It is particularly preferred to carry out at 50 ° C. Although the degree of pressure reduction can be set as appropriate, it is particularly preferable to perform the pressure reduction at about 0.1 to 200 torr.

After the completion of the reaction, amines are added to neutralize the acid catalyst, and water is added, followed by washing with water. Although the amount and the number of times of washing water are not particularly limited, it is particularly preferable from the economical viewpoint that the number of times of washing is reduced to a level at which about 1 to 5 times does not substantially affect the washing. The washing temperature is not particularly limited, but may be 40 or less from the viewpoint of the efficiency of removing the catalyst species and the workability.
It is preferably carried out at -95 ° C. 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. The type 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.

[0015]

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. The weight average molecular weight and the radius of gyration were determined by GPC measurement as described above.

Example 1 Metacresol 850 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, 510 parts of paracresol, 340 parts of 2,3,5-trimethylphenol, 152 parts of salicylaldehyde and 17 parts of paratoluenesulfonic acid, and after reacting at 88 to 92 ° C. for 5 hours, ethyl cellosolve was added. 680 parts were added and the mixture was cooled to an internal temperature of 60 ° C, and 823 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 increased stepwise, and finally the reaction was carried out at a reflux temperature (97-103 ° C) for 3 hours.
After completion of the reaction, the mixture was cooled to 90 ° C. and triethylamine 11
Of acetone, 170 parts of acetone and 6 parts of ion-exchanged water.
80 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 7.0, and the separated water was removed. Acetone 170
And 680 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 under reduced pressure to 195 ° C. at 80 torr.
De-monomerize, phenol resin for photoresist 1
650 g were obtained. The weight average molecular weight of the obtained resin is 35.
The free monomer was 2.8%. The radius of inertia was 1.88 nm.

Example 2 Metacresol 520 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, paracresol 300 parts, 3,5-xylenol 4
50 parts, 90 parts of salicylaldehyde and 18 parts of paratoluenesulfonic acid were charged and reacted at 98 to 102 ° C. for 4 hours.
After cooling to 0 ° C., 600 parts of 37% formalin were successively added at 58-62 ° C. for 1.5 hours, followed by a further reaction 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 12 parts of triethylamine,
Further, 300 parts of acetone and 900 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 7.0, and the separated water was removed. This washing operation was repeated once using 300 parts of acetone and 900 parts of ion-exchanged water, and then dehydrated under normal pressure to an internal temperature of 170 ° C.
Dehydration and demonomerization were performed under reduced pressure at 195 ° C. at Torr to obtain 1400 g of a phenol resin for photoresist. The weight average molecular weight of the obtained resin was 4000, and the free monomer was 4.0%. The radius of inertia is 1.91.
nm.

Example 3 Metacresol 600 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, paracresol 600 parts, 2,5-xylenol 3
After 100 parts of salicylaldehyde, 160 parts of salicylaldehyde and 18 parts of p-toluenesulfonic acid were charged and reacted at 98 to 102 ° C. for 3 hours, 750 parts of ethyl cellosolve was added to cool to an internal temperature of 60 ° C., and then 37% formalin was added. 800 parts were added successively at 98-102 ° C. for 2 hours, and the mixture was further reacted for 30 minutes. Thereafter, the reaction was carried out at a reflux temperature (97-103 ° C.) for 2 hours. After the completion of the reaction, the mixture was cooled to 90 ° C., 13 parts of triethylamine was added, 150 parts of acetone and 550 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
Adjusted to -7.0, and separated water was removed. This washing operation was repeated once using 150 parts of acetone and 550 parts of ion-exchanged water.
At 195 ° C. under reduced pressure 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 7,200, and the free monomer was 2.5%.
The radius of inertia was 2.24 nm.

Example 4 Metacresol 1120 was placed in a 5 L four-necked flask equipped with a stirrer, thermometer and heat exchanger.
Parts, 280 parts of paracresol, 220 parts of 2,3,6-trimethylphenol, 320 parts of naphthaldehyde and 16 parts of paratoluenesulfonic acid, and after reacting at 98 to 102 ° C. for 4 hours, ethyl cellosolve was added. 650 parts were added and the mixture was cooled to an internal temperature of 60 ° C., and 730 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 5
300, 1.8% free monomer. The radius of inertia was 2.04 nm.

Comparative Example 1 400 parts of meta-cresol, 600 parts of para-cresol, 3 parts of the same reactor as in Example 1
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 to 102 ° C. for 4 hours, dehydration is performed under normal pressure to raise the internal temperature to 140 ° C., and then dehydration is performed under a reduced pressure of 80 Torr to remove the monomer at the internal temperature. 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%. The radius of inertia was 1.52 nm.

Comparative Example 2 400 parts of meta-cresol, 600 parts of para-cresol and 3 parts of the same reactor were used 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%. The radius of inertia was 2.78 nm.

Comparative Example 3 1020 parts of meta-cresol, 250 parts of para-cresol and the same reactor as in Example 1 were used.
After 210 parts of 2,3,5-trimethylphenol, 200 parts of salicylaldehyde and 16 parts of paratoluenesulfonic acid were charged and reacted at 98 to 102 ° C. for 4 hours, 700 parts of ethyl cellosolve was added and the mixture was heated at an internal temperature. After cooling to 60 ° C., 970 parts of 37% formalin were successively added at 58-62 ° C. for 1.5 hours, and the reaction was further performed for 30 minutes. Thereafter, the temperature is raised stepwise, and finally the reflux temperature (97-10
(3 ° C.) for 2 hours. After completion of the reaction, the mixture was cooled to 90 ° C., 11 parts of triethylamine was added, and 150 parts of acetone and 1200 parts of ion-exchanged water were added.
The mixture was stirred and allowed to stand at ℃. The pH of the separated water separated by standing was adjusted to 5.5 to 7.0, and the separated water was removed. 150 parts of acetone, 1200 parts of deionized water
After repeating this washing operation again using
Dehydrate to 140 ° C under normal pressure, and further 80 torr
Then, dehydration and demonomerization were performed under reduced pressure to 195 ° C. to obtain 1900 g of a phenol resin for photoresist. The weight average molecular weight of the obtained resin was 16,800, and the free monomer was
Was 0.7%. The radius of inertia was 2.91 nm.

Evaluation Example 1 Evaluation Method of Heat Resistance 100 parts of a novolak phenol resin and 30 parts of 2,3,4-trihydroxybenzophenone ester of naphthoquinone 1,2-diazido-5-sulfonic acid were mixed with ethyl lactate. And a resist solution was prepared. These are 0.2
The solution was filtered through a micron membrane filter to obtain a resist solution. This was applied by information 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 allowed to stand on a hot plate at a varied temperature for 30 minutes, and the change in the shape of the resist pattern on the silicon wafer was observed with a scanning electron microscope to evaluate the heat resistance.

<< Evaluation Example 2 >> Evaluation method of critical resolution / 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 measured with a scanning electron microscope. Was observed. The depth of focus is 0.
A photograph when the focal point was changed at a line width of 30 μm was visually observed, and the resolvable focal point fluctuation width was measured. Also,
The limit resolution was visually determined and measured for the limit that can be resolved from a photograph under optimal exposure and development conditions.

[0026]

[Table 1]

[0027]

According to the present invention, it has become possible to provide a phenolic resin for a 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 increasing the integration of semiconductors in the future.

Claims (4)

[Claims] 1. A phenol (P) comprising 30-70% by weight of meta-cresol, 5-40% by weight of para-cresol, 5-50% by weight of xylenol and / or trimethylphenol, formaldehyde (f1) and an aromatic aldehyde. A novolak phenol resin obtained by reacting an aldehyde (F) having a weight ratio (f1 / f2) of 1 / 9-9 / 1 with the aldehyde (f2), wherein the novolak phenol resin Radius of gyration (molecular size)
Is 1.50 to 2.50 nm. 2. The phenolic resin for a photoresist according to claim 1, wherein the trimethylphenol is 2,3,5-trimethylphenol. 3. The method according to claim 1, wherein the aromatic aldehyde is 2-hydroxybenzaldehyde (salicylaldehyde).
Or a phenolic resin for photoresist according to 2 above. 4. The phenolic resin for a photoresist according to claim 1, wherein the weight-average molecular weight of the novolak type phenolic resin is 1500-15000.