JP2003002944A - Resin for photoresist and photoresist composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin for photoresist and a photoresist composition having high sensitivity, high resolution and improving transparency. SOLUTION: This resin for photoresist is obtained by reacting phenolic compounds including a specified quantity of meta-cresol, and aldehydes in the presence of an acidic catalyst and substituting a part or all of the hydroxyl groups in the resin with alkoxyalkyl groups. The photoresist resin composition includes the resin for photoresist and a photoacid generator.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoresist resin and a photoresist composition.

[0002]

2. Description of the Related Art Generally, for a positive photoresist, a sensitizer having a quinonediazide group such as a naphthoquinonediazide compound and an alkali-soluble resin (for example, a novolac phenolic resin) are used. A positive photoresist having such a composition exhibits high resolution when developed with an alkaline solution, and is used in the manufacture of semiconductors such as IC and LSI.
It has been used for manufacturing circuit substrates such as LCDs. Also,
Due to the structure with many aromatic rings, novolac type phenolic resin is suitable for plasma dry etching after exposure.
It had high dry etching resistance and heat resistance.
Up to now, many positive photoresists containing a novolac phenolic resin and a naphthoquinonediazide type photosensitizer have been developed and put into practical use, and great results have been achieved in line width processing up to about 0.3 μm to 2 μm.

However, in recent years, as the demand for higher integration of semiconductors has increased year by year, KrF having a shorter wavelength as a light source,
The use of excimer light such as ArF and F2 is under consideration. These lights are 248 nm, 193 nm and 15
The light has a wavelength of 7 nm, and the phenol resin has poor transparency due to the absorption of light by the aromatic ring of itself, and it is difficult for light to reach the bottom of the resist. Therefore, the amount of exposure at the bottom of the resist is reduced, and only a defective pattern with a taper or the like can be obtained after development. Therefore, application of a chemical amplification system using a acid generated from a photo-acid generator as a catalyst, which is used as a base resin such as polyhydroxystyrene, an acrylic resin, a cycloolefin resin, and a fluorine resin, is under study. The application of polyhydroxystyrene to KrF excimer light has been mainly investigated, but polyhydroxystyrene is not always sufficient in transparency, and it is very expensive, so it is transparent with an inexpensive phenol resin system. There has been a great demand for improvement in sensitivity and resolution.

[0004]

An object of the present invention is to provide a photoresist resin and a photoresist composition having improved transparency, high sensitivity and high resolution.

[0005]

The above objects are achieved by the present invention described in (1) to (10) below. (1) A resin obtained by reacting phenols containing 50% by weight or more of metacresol and aldehydes in the presence of an acid catalyst, wherein a part or all of the hydroxyl groups in the resin are substituted with an alkoxyalkyl group. Resin for photoresist. (2) As phenols other than the meta-cresol,
The photoresist resin according to (1) above, which contains at least one selected from trimethylphenol, xylenol, and orthocresol. (3) The above (1), which contains at least one selected from the above trimethylphenol, xylenol and orthocresol in an amount of 5 to 35% by weight based on the total amount of phenols.
Alternatively, the photoresist resin according to (2). (4) The resin for photoresist as described in (2) or (3) above, wherein the xylenol is 3,5-xylenol. (5) The photoresist resin according to any one of (2) to (4), wherein the trimethylphenol is 2,3,5-trimethylphenol. (6) The photoresist resin according to any one of (1) to (5) above, wherein the alkoxyalkyl group is an alkoxyethyl group. (7) The alkoxyalkyl group is substituted by 5 to 90% of all hydroxyl groups in the resin (1)
The resin for photoresist according to any one of (1) to (6). (8) The weight average molecular weight obtained by GPC measurement is 1,
The photoresist resin according to any one of (1) to (7) above, which is 000 to 50,000. (9) The above (1) to (8), wherein the transmittance of light having a wavelength of 248 nm to a resin having a thickness of 0.5 μm is 10% or more.
The photoresist resin according to any one of 1. (10) A photoresist composition comprising the photoresist resin according to any one of (1) to (9) and a photo-acid generator.

The photoresist resin and photoresist composition of the present invention will be described in detail below. The photoresist resin of the present invention is a resin obtained by reacting a predetermined amount of metacresol-containing phenols and aldehydes in the presence of an acid catalyst, and a part or all of the hydroxyl groups in the resin. It is obtained by substitution with an alkoxyalkyl group. Further, the photoresist composition of the present invention contains a photo-acid generator in the photoresist resin.

The photoresist resin will be described below. The phenols used in the present invention contain 50% by weight or more of metacresol. Cresol includes ortho-cresol, para-cresol, and meta-cresol, and meta-cresol can increase the sensitivity of photoresist. This is because metacresol has a high acidity due to its molecular structure and therefore has a high solubility in alkali. Further, it is considered that the electron density of the aromatic ring is changed in a well-balanced manner by the combination of metacresol and an alkoxyalkyl group described later, and the absorption wavelength of 248 nm of metacresol can be shifted. As a result, the transparency of the photoresist can be improved,
The sensitivity and resolution of the photoresist can be improved. The content of such meta-cresol is 50% by weight
It is above, 60-98 weight% is desirable, especially 65-
95% by weight is preferred. The more the amount of meta-cresol is, the more remarkable the above-mentioned effect is exhibited, but particularly at 50% by weight or more, it shows criticality. Further, by combining meta-cresol with at least one selected from trimethylphenol, xylenol and orthocresol described later, the sensitivity of the photoresist can be increased and the heat resistance can be improved. . When the heat resistance of the photoresist is improved, it is possible to prevent melting of the circuit pattern due to heat generated by plasma dry etching performed in the step of removing the oxide film and the like on the surface of the silicon substrate after development.

Further, the photoresist resin of the present invention is allowed to contain phenols other than metacresol. Examples of such phenols other than the meta-cresol include phenol, orthocresol, para-cresol, 2,3-xylenol, 2,4-
Xylenol such as xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 2,3 , 6-
Trimethylphenol, 2,4,5-trimethylphenol, trimethylphenol such as 3,4,5-trimethylphenol, ethylphenol, propylphenol, butylphenol, octylphenol, nonylphenol, 1-naphthol, 2-naphthol, phenylphenol and the like can be mentioned. To be Among these, it is preferable to contain at least one selected from trimethylphenol, xylenol and orthocresol. Thereby, the heat resistance of the photoresist can be improved. The xylenol is preferably 3,5-xylenol. Further, the trimethylphenol is
2,3,5-Trimethylphenol is preferred. As a result, in addition to the effect of improving the heat resistance, the solubility of alkali can be maintained and the sensitivity of the photoresist can be kept high. Further, it is preferable that at least one selected from the above-mentioned trimethylphenol, xylenol, and orthocresol is contained in an amount of 5 to 35% by weight, and particularly preferably 10 to 30% by weight, based on the whole phenols. When trimethylphenol and the like are within the above range, the sensitivity and heat resistance of the photoresist can be further improved.

Examples of the aldehydes used in the present invention include alkyl aldehydes such as formaldehyde, acetaldehyde, propyl aldehyde and butyraldehyde, and aromatic aldehydes such as benzaldehyde and salicyl aldehyde. Of these, formaldehyde is preferred. Thereby, the sensitivity of the photoresist can be increased. The formaldehyde source is not particularly limited, and examples thereof include formalin (aqueous solution), paraformaldehyde, hemiformal with alcohols, trioxane, and the like. Of these, formalin and paraformaldehyde are preferable. Thereby, workability can be improved. Further, the cost of the photoresist resin can be reduced.

In the present invention, the molar ratio of the aldehydes (F) and the phenols (P) is not particularly limited, but is 0.3 to.
1.2 (F / P) is preferable, and 0.5 to 1.0 is particularly preferable. When the molar ratio is within the above range, the sensitivity and heat resistance of the photoresist can be further improved. Further, the molecular weight of the photoresist resin obtained in the present invention can be controlled.

The photoresist resin of the present invention is a resin obtained by using an acid catalyst for the reaction of phenols and aldehydes. Examples of the acid catalyst include organic carboxylic acids such as oxalic acid and acetic acid, organic sulfonic acids such as benzenesulfonic acid, paratoluenesulfonic acid and methanesulfonic acid, hydrochloric acid,
An inorganic acid such as sulfuric acid may be used. The acid catalysts may be used alone or in admixture of two or more. The addition amount of the acid catalyst is not particularly limited, but is preferably 0.01 to 5 parts by weight, and particularly preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the phenol. When the acid catalyst is within the above range, the stability during resin production is excellent and the residual catalyst of the resin can be reduced.

An example of the reaction between phenols and aldehydes in the present invention will be briefly described. The reaction can be carried out, for example, by adding phenols, aldehydes and an acid catalyst to a reaction vessel equipped with a stirrer, a thermometer and a heat exchanger. The reaction is not particularly limited,
The reaction time is preferably 2 to 10 hours, particularly preferably 3 to 8 hours. The reaction temperature is not particularly limited, but is 70
-150 degreeC is preferable and 80-120 degreeC is especially preferable. In addition, in the reaction, for example, a reaction solvent can be used. As the reaction solvent, for example, a solvent capable of dissolving the resin obtained by the reaction such as ethyl cellosolve and methyl ethyl ketone is preferable.

Further, after completion of the above reaction, for example, in order to remove an acid catalyst, a basic compound may be added to neutralize it to obtain a neutralized salt, and water may be added to wash with 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 economical point of view to remove the neutralized salt in the resin to a level at which there is substantially no effect. Also, the washing temperature is
Although not particularly limited, it is preferably carried out at 40 to 95 ° C. from the viewpoints of neutralizing salt removal efficiency and workability.

Finally, after the reaction or the washing with water is completed, dehydration and demonomerization are carried out under normal pressure and reduced pressure to obtain a photoresist resin. The temperature for taking out from the reaction vessel after dehydration / demonomer is not particularly limited, but can be appropriately set depending on the characteristics of the resin, the viscosity of the resin, and the like, but from the viewpoint of resin stability, it is preferably 150 to 250 ° C.
The degree of reduced pressure is not particularly limited, but is 0.1 torr to 20.
About 0 torr is preferable.

In the present invention, part or all of the hydroxyl groups in the resin obtained by the above reaction are substituted with alkoxyalkyl groups. This makes it possible to decompose by the action of an acid, thereby changing the solubility in an alkali developing solution and imparting a resist function. Conventionally, a tetrahydropyranyl ether group, a t-butoxycarbonyl group, and the like have been known to have the same action, but the resolution of the photoresist is insufficient due to the lack of easy releasability to an acid. It was The alkoxyalkyl group used in the present invention has a low activation energy because of its structure, and is easily desorbed from an acid. As a result, the resolution of the photoresist can be improved. Examples of the alkoxyalkyl group include an alkoxyethyl group such as a methoxyethyl group, an ethoxyethyl group, a propyloxyethyl group, a butyloxyethyl group, a cyclohexyloxyethyl group, an ethoxypropyl group, and an ethoxybutyl group. Among them, the alkoxyethyl group represented by the ethoxyethyl group is preferable. The combination of the alkoxyethyl group and the above-mentioned meta-cresol can improve the adhesiveness between the photoresist resin and the silicon substrate in addition to the effect of improving the transparency, sensitivity and resolution of the photoresist described above.

The alkoxyalkyl group is not particularly limited, but is preferably 5 to 90% substituted, and particularly preferably 10 to 80% substituted with respect to all the hydroxyl groups in the resin. When the substitution of the alkoxyalkyl group is less than the lower limit value, there is a tendency that the function of suppressing solubility in alkali decreases due to the decrease in what can be decomposed by the action of acid, and when the upper limit value is exceeded, the sensitivity of the photoresist is increased. In some cases, the effect of improving heat resistance may decrease. In addition, the substitution amount of the alkoxyalkyl group can be calculated, for example, by using a thermogravimetric analyzer (TG-DTA6300 manufactured by SII), and from the obtained result, the weight reduction corresponding to each substituent. The TG-DTA measurement was performed at a temperature rising rate of 10 ° C / min.

The method of substituting the above-mentioned alkoxyalkyl group with the hydroxyl group in the resin is not particularly limited because the starting material and method used differ depending on the substituting group. For example, in the case of substituting an ethoxyethyl group, a method of adding a predetermined amount of ethyl vinyl ether to the resin obtained in the above reaction at room temperature and reacting for a predetermined time under an acid catalyst, and then adding diethyl ether and washing with water Etc.

The weight average molecular weight of the photoresist resin of the present invention measured by GPC is not particularly limited.
000 to 50,000 is preferable, and 2,000 to 3 is particularly preferable.
10,000 is preferable. If the weight average molecular weight of the photoresist resin is less than the lower limit value, the heat resistance may decrease, and if it exceeds the upper limit value, the effect of improving the sensitivity of the photoresist resin may decrease. The weight average molecular weight of the photoresist resin can be controlled by adjusting the molar ratio of aldehydes to phenols. The weight average molecular weight is calculated based on a calibration curve prepared using a polystyrene standard substance by gel permeation chromatography (GPC) measurement. GPC measurement uses tetrahydrofuran as an elution solvent, a flow rate of 1.0 ml / min, and a column temperature of 40
It was carried out under the condition of ° C. Body: TOSOH HLC-80
20, detector: TOSOH set to a wavelength of 280 nm
UV-8011, Analytical column: Showa Denko SHOD
EX KF-802 1 piece, KF-803 1 piece, KF-
One 805 was used.

Wavelength 248 for 0.5 μm thick resin
The transmittance of nm light is not particularly limited, but is preferably 10% or more, and particularly preferably 20% or more. If the transmittance is less than the above lower limit, the effect of improving the sensitivity of the photoresist resin may be reduced. The transmittance is
For example, it can be evaluated by using a UV spectrophotometer (U-2000 manufactured by Hitachi Ltd.) and measuring the transmittance for light having a wavelength of 248 nm. The evaluation sample was obtained by applying a resin solution dissolved in a solvent on quartz glass by a spin coater and treating it at 90 ° C. for 100 seconds to obtain about 0.5
A resin film may be formed on the quartz glass so as to have a thickness of μm.

Next, the photoresist composition will be described. The photoresist composition of the present invention contains the photoresist resin described above and a photo-acid generator. This makes it possible to generate an acid upon irradiation with light and change the solubility of the photoresist resin in an alkali developing solution. Examples of the photoacid generator used in the present invention include onium salts, organic halogen compounds, compounds having a diazomethanedisulfonyl skeleton, disulfone compounds having an aromatic group, orthoquinonediazide compounds, and sulfonic acid compounds. Among these, onium salts and compounds having a diazomethanedisulfonyl skeleton are preferable.

Further, the photoresist composition of the present invention is
Surfactants, basic compounds and the like can be added within a range that does not deteriorate the characteristics.

[0022]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

Example 1 Production of Resin In a 5 L four-necked flask equipped with a stirrer, a thermometer and a heat exchanger, 1260 g of metacresol and 540 g of 2,3,5-trimethylphenol (metacresol / trimethylphenol = 70/30). , 37% formalin 1141g
(Aldehydes / phenols = 0.90), oxalic acid 9g
Was charged, and after reacting at 98 to 102 ° C. for 4 hours, 650 g of ethyl cellosolve was added to dehydrate at an internal temperature of 170 ° C. under normal pressure, and further dehydration / demonomer was performed at 80 torr under reduced pressure to 200 ° C., Phenolic resin 1850
g was obtained.

546 g of ethyl vinyl ether and 1.8 g of paratoluene sulfonic acid were added to the above resin dissolved in tetrahydrofuran having a substituted alkoxyalkyl group, and the mixture was reacted at room temperature for 4 hours. afterwards,
To neutralize the acid catalyst, triethylamine was added in an equivalent amount,
A predetermined amount of diethyl ether was added, ion-exchanged water was added, and the mixture was washed 3 times with water, and the solvent was removed and dried to obtain 4 of the desired hydroxyl groups of the phenol resin.
A photoresist resin in which 0% was substituted with an ethoxyethyl group was obtained.

Example 2 1530 g of metacresol and 270 g of 3,5-xylenol (metacresol / 3,5-xylenol = 8)
5/15), 1222 g of formalin (aldehydes /
Phenols = 0.92) was added, and 218 g of ethyl vinyl ether (15% of ethoxyethyl group) was added, and the same procedure as in Example 1 was performed.

Example 3 Metacresol was set to 990 g and 3,5 xylenol was set to 810 g (metacresol / 3,5 xylenol = 55).
/ 45), and the same as in Example 1 except that 1153 g of formalin was added.

Example 4 1800 g of meta-cresol and 1216 g of formalin
The same procedure as in Example 1 was carried out except that the other phenols were not used in combination.

Example 5 Example 5 was repeated except that the molar ratio of phenols to aldehydes was 0.45.

Example 6 The same as Example 1 except that the molar ratio of phenols to aldehydes was 1.05.

Example 7 Except that the substitution amount of the alkoxyalkyl group was 95%,
Same as Example 1.

Example 8 Except that the substitution amount of the alkoxyalkyl group was 15%,
Same as Example 1.

Example 9 The procedure of Example 1 was repeated except that an isopropyloxyethyl group was used as the alkoxyalkyl group.

Example 10 Paracresol was used in place of 2,3,5-trimethylphenol, and 1216 g of formalin was added, except that
Same as Example 1.

Comparative Example 1 810 g of meta-cresol and 990 of ortho-cresol
Example 1, except that 1216 g of formalin was added.
Same as.

Comparative Example 2 The procedure of Example 1 was repeated, except that a tetrahydropyranyl group (THP) was used instead of the alkoxyalkyl group.

Comparative Example 3 Metacresol 1530 was prepared by using t-butoxycarbonyl group (t-BOC) instead of the alkoxyalkyl group.
g, 3,5-xylenol 270 g, formalin 119
Same as Example 1 except that 5 g was added.

Comparative Example 4 As a resin, polyhydroxystyrene manufactured by Nippon Soda Co., Ltd. (VP-8000, weight average molecular weight = 12,000)
The same as Example 1 except that was used as it was.

The molecular weight of the obtained photoresist resin and the characteristics of the photoresist are shown in Table 1. The transmittance of the resin was evaluated by using a UV spectrophotometer (U-2000 manufactured by Hitachi, Ltd.) and measuring the transmittance for light having a wavelength of 248 nm. The sample for evaluation was prepared by applying a resin solution dissolved in a solvent on quartz glass with a spin coater and treating it at 90 ° C. for 100 seconds to form a resin film on the quartz glass to a thickness of about 0.5 μm. did. The heat resistance was evaluated by observing the shape of the pattern after heating a photoresist having a pattern with a width of 5 μm for 3 minutes in an oven set to a predetermined temperature of 100 to 150 ° C. with an electron microscope. Table 1 shows the lowest temperature at which the pattern shape does not change.

The characteristics of the photoresist were evaluated as follows. Sample Preparation The resins obtained in Examples and Comparative Examples were dissolved in propylene glycol monomethyl ether acetate so as to have a resin concentration of 15%, and DAM-301 manufactured by Midori Kagaku Co., Ltd. was used as a resin solid content as a compound that generates an acid by light. To 1
% And TPS-105 to 0.19% based on resin solids
Was added to prepare a resist property evaluation sample.

The sample whose development was adjusted was coated on a 5-inch silicon wafer by using a spin coater, and then 90 ° on a hot plate.
Prebaked at 60 ° C. for 60 seconds. The rotation speed of the spin coater was adjusted so that the film thickness of the applied sample was about 0.5 μm. After prebaking, UV made by Litho Tech Japan
Exposure was performed using ES-2000 while changing the light exposure amount at several points, and post-baking was performed on a hot plate at 110 ° C. for 90 seconds. Then, the film thickness of the exposed portion was measured with a film thickness measuring device, and RDA-790 manufactured by Litho Tech Japan was used to measure the developing rate using a 2.38% tetramethylammonium hydroxide aqueous solution.

Characteristic Evaluation of Sensitivity etc. The amount of reduction in film thickness and the speed were measured using RDA-790 manufactured by Lithotec Japan, and based on the measurement results.
The tan θ and the sensitivity (exposure amount) were determined by LeapSet.
In addition, using Prolith / 2 simulation software, the focal depth of the photoresist characteristic value, the limit resolution, and the pattern shape were evaluated under the conditions of 0.18 μm and L & S = 1/1.

[0042]

[Table 1]

As shown in Table 1, all of Examples 1 to 10 have high transmittance, and are excellent in sensitivity and limit resolution.
From this, it was revealed that the photoresist resin and the photoresist composition of the present invention have improved transparency, high sensitivity and high resolution. In particular, Examples 1, 2,
6 and 8 have high heat resistance. In addition, Examples 1 and 2
Has high heat resistance, high sensitivity, and high resolution.

[0044]

Industrial Applicability According to the present invention, it is possible to provide a photoresist resin and a photoresist composition which have improved transparency and enable the production of a photoresist having high sensitivity and high resolution. Further, when at least one selected from trimethylphenol and the like is included as phenols other than metacresol, a resin for photoresist and a photoresist composition having particularly excellent heat resistance can be obtained. Further, when the alkoxyalkyl group is changed to an alkoxyethyl group, the transparency is particularly improved and the adhesion between the photoresist and the silicon substrate can be improved.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Imamura             Sumitomo, 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo             Bakelite Co., Ltd. F-term (reference) 2H025 AA01 AA02 AA10 AB16 AC04                       AC08 AD03 BE00 BE10 CB28                       CB29 CB45 CB51 CB55 CB56                       FA17                 4J033 CA01 CA02 CA05 CA11 CA12                       CA32 CC03 CC08 HA02 HB10

Claims (10)

[Claims] 1. A resin obtained by reacting phenols containing 50% by weight or more of metacresol with aldehydes in the presence of an acid catalyst, wherein a part or all of the hydroxyl groups in the resin are alkoxyalkyl groups. Resin for photoresist replaced with. 2. The resin for photoresist according to claim 1, which contains at least one selected from trimethylphenol, xylenol and orthocresol as the phenols other than the meta-cresol. 3. The photoresist resin according to claim 1, wherein the photoresist resin contains at least one selected from the group consisting of trimethylphenol, xylenol, and orthocresol in an amount of 5 to 35% by weight based on the total amount of phenols. 4. The photoresist resin according to claim 2, wherein the xylenol is 3,5-xylenol. 5. The trimethylphenol is 2,3
The photoresist resin according to claim 2, which is 5-trimethylphenol. 6. The photoresist resin according to claim 1, wherein the alkoxyalkyl group is an alkoxyethyl group. 7. The photoresist resin according to claim 1, wherein the alkoxyalkyl group is substituted with 5 to 90% of all hydroxyl groups in the resin. 8. The weight average molecular weight obtained by GPC measurement is 1,000 to 50,000.
The photoresist resin according to any one of 1. 9. A wavelength of 24 for a resin having a thickness of 0.5 μm.
The photoresist resin according to claim 1, which has a transmittance of 8% light of 10% or more. 10. A photoresist composition containing the photoresist resin according to claim 1 and a photo-acid generator.