JPH01293338A - Negative type photoresist composition - Google Patents

Abstract

PURPOSE:To improve transparency and the allowability of alkaline development by incorporating such a copolymer which contains two kinds of specific constitutional units in which the ratio of the respective constitutional units has a specific relation and a bisazide photosensitive agent added thereto at need into the above compsn. CONSTITUTION:This compsn. consists of the copolymer contg. the constitutional unit (I) expressed by the formula (I) and the constitutional unit (II) expressed by the formula II and the bisazide photosensitive agent added thereto at need. In the formula, n denotes 1-5 integer. This copolymer is obtd. by condensation reaction of, for example, polyvinyl phenol and halogenated epoxide such as epichlorohydrin. The ratio of the constitutional units (I) and (II) is preferably 0.1<=m/m+k<=0.5 when the number of the constitutional unit (I) is designated as m and the number of the constitutional unit (II) as k. Adverse influence is exerted on sensitivity and development conditions if the value is below 0.1. Alkaline solubility is degraded if the value exceeds 0.5. The transparency and the allowability of the alkaline development are thereby improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a photoresist composition suitable for forming a fine resist pattern, and more specifically to lithography using deep ultraviolet rays and excimer laser as a light source.
The present invention relates to a negative photoresist composition that has high sensitivity and resolution, and has excellent alkaline development tolerance. The negative photoresist composition of the present invention is used in the production of high-density integrated circuits such as LSI and VLSI, as well as in the production of photomasks used in their production. Widely used in the field of

[Prior Art] In recent years, semiconductors have become increasingly highly integrated, and the demands for miniaturization are becoming more and more severe.

Therefore, in terms of manufacturing, it is becoming difficult to cope with conventional processes, and the introduction of new technologies is being considered. Efforts are being made to establish ultra-fine pattern processing technology by using deep ultraviolet rays with shorter wavelengths and excimer lasers instead of conventional ultraviolet rays as light sources used in lithography. Along with these changes in light sources, resists now have conventional RI resistance.
In addition to properties such as E properties and heat resistance, the following properties are newly required.

b) High sensitivity to deep ultraviolet rays and excimer lasers.

Mouth) Excellent transparency in the deep ultraviolet region and excimer laser wavelength region.

c) High resolution.

A photosensitive composition prepared by mixing a vinylphenol homopolymer and a photosensitizer has been proposed as a negative photoresist that meets these requirements (Japanese Patent Publication No. 56-29261).
. However, although the base resin of these compositions, polyvinylphenol, has excellent transparency in the deep ultraviolet and excimer laser wavelength regions, the photosensitizers used together have poor transparency after exposure, and furthermore, the alkali dissolution rate of polyvinylphenol is low. Since this is relatively fast, it is necessary to add a considerable amount of the above-mentioned photosensitizer in order to obtain a resist pattern with little film burr due to the alkaline phenomenon after exposure, and as a result, the transparency of the composition itself in this region becomes considerably low. . Therefore, the cross section of the resist pattern obtained by development after exposure exhibits a strong inverted trapezoidal shape, and there is a problem in that it is not possible to resolve a fine pattern in which the side surfaces of the pattern are perpendicular to the substrate.

Furthermore, in order to solve the above problems, when the concentration of the photosensitizer in the composition is lowered and used, in addition to the decrease in resist sensitivity, the difference in solubility between exposed and unexposed areas becomes smaller, resulting in fine resist patterns. In order to obtain this, it is necessary not only to dilute the concentration of the developer, but also to maintain the temperature and development time of the developer very strictly. When this setting is made, there is a problem in that resist residue is likely to be generated in the punched pattern area, making it extremely difficult to set development conditions that will give good results for both the punched pattern and the leftover pattern.

[Problems to be Solved by the Invention] As described above, it is difficult to say that conventional negative photoresist compositions are still practical in terms of transparency and development conditions.

Therefore, the present invention has been made to solve the above-mentioned problems, and the purpose of the present invention is to provide a negative type that has high transparency in the deep ultraviolet and excimer laser wavelength ranges and has excellent alkali development tolerance after exposure. An object of the present invention is to provide a photoresist composition.

[Means for Solving the Problems] In view of the above circumstances, the present inventors have conducted extensive studies and have introduced a group containing an epoxy group active against photoreaction into the phenol side chain of polyvinylphenol. As a result, the amount of photosensitizer used in conventional compositions can be significantly reduced or eliminated without impairing the transparency of polyvinylphenol in the deep ultraviolet and excimer laser regions. The transparency of the resist composition is significantly improved in this wavelength range, and at the same time, since some of the phenolic OH groups are protected by the above-mentioned groups, the alkali dissolution rate of the resist during development after exposure is reduced. The present inventors have discovered that, as a result, the setting range of alkaline development conditions is expanded and the tolerance of development conditions is improved, and the present invention has been completed. That is, the negative photoresist composition of the present invention is a copolymer containing a structural unit represented by the following general formula (I) (wherein n represents an integer of 1 to 5) and a structural unit represented by the following formula (II). The object of the present invention is to provide a photosensitive composition comprising the combination and a bisazide photosensitizer added as necessary.

The negative photoresist composition of the present invention will be explained in detail below. The polymer used in the negative photoresist composition of the present invention is a copolymer having structural units represented by the above formulas (I) and (n), such as polyvinylphenol and halogenated epoxide such as epichlorohydrin. It can be obtained by a condensation reaction with In the core copolymer, the epoxy group-containing group and the OH group may be located at either the 〇-position, the 1m-position or the p-position with respect to the polyvinyl skeleton, but the p-position is most preferred, followed by the m-position. −
Preferably. In addition, the ratio of the structural units represented by formula (I) and the structural units represented by formula (n) in the former copolymer is determined when the number of structural units (I) is m1 and the number of structural units (n) is k. It is preferable that 0.1≦□≦0.5 m+. If this value is less than 0.1, it is undesirable because it adversely affects the sensitivity and development conditions of the resist, and if it exceeds 0.5, it is undesirable because the alkali solubility of the resist decreases.

Further, the copolymer has a weight average molecular weight (Mw) of 1.000 to 1 as determined by gel permeation chromatography (GPC method) using monodisperse polystyrene as a standard.
00,000 preferably 2,000 to 50,000
Use the one. Outside the above range, sensitivity, resolution, heat resistance, film performance, adhesion to the substrate, etc. will be adversely affected.

In addition, since the negative photoresist composition of the present invention has a photosensitive group in the polymer itself constituting the composition,
Although it can be used alone as a photoresist composition, a photosensitizer can be added as necessary for the purpose of improving the sensitivity of the resist. Preferred examples of such photosensitizers include aromatic azide compounds and aliphatic azide compounds, and particularly preferred examples include aromatic azide compounds. Specifically, 4-azidobenzalacetophenone, 4-azidobenzal-4
'-Methoxyacetophenoenone, 4-azidobenzalacetone, 3-[4-(p-azidophenyl)-1゜3
-butadienyl]-5,5-dimethyl-2-cyclohexen-1-one, 3-(p-azidostyryl)-5,5
-dimethyl-2-cyclohexen-1-one, 1-azidopyrene, 4,4'-diazidochalcone, 2,6-bis(4'-azidobenzal)cyclohexanone, 1,3-
Bis(4'-azidobenzal)-2-propanone, 1.
3-bis(4'-azidobenzal)-2-propanone-
2'-Sulfonic acid, 2.6-bis(4'-azidocinnamylidene)-4-methylcyclohexanone, 2.6-bis(4'-azidocinnamylidene)-4-methoxycyclohexanone, 2.6- Bis(4'-azidocinnamylidene)-4-hydroxycyclohexanone, 2,6-bis(4'-azidocinnamylidene)cyclohexanone,
2.6-bis(4′-azidocinnamylidene)4-hydroxymethylcyclohexanone, 2.6-bis(4′-
azidocinnamylidene) 4-trimethylsilylcyclohexanone, 2,6-bis(4'-azidocinnamylidene)cyclohexanone-4-carboxylic acid, 2,6-bis(4'-azidocinnamylidene)cyclohexanone-4-carboxylic acid,
4'-azidocinnamylidene)cyclohexanone-4-
Sulfonic acid, 4,4'-diazidiphenylmethane, 4
．． 4'-Diazidiphenyl ether, 4.4'-Diazidobenzophenone, 4.4'-Diazidiphenyl sulfide, 4.4'-Diazidiphenyl sulfone, 3
．． 3'-Diazido diphenyl sulfone, 4.4'-Diazido diphenyl, 4.4'-Diazido stilbene, 2.
2'-diazidostilbene, 4.4'-diazidodiphenylamine, 4.4'-diazidophenylazobenzene, 4.4'-diazidophenylazonaphthalene, 4.4
'-Diazidostilbene-2,2'-dicarboxylic acid, polyvinyl azidophthalate, azidobenzaldehyde-phenol resin, 4-7didodiphenylamine-2-carboxylic acid-formaldehyde resin, polyvinyl-p-azidobenzal resin, etc. These include, but are not limited to: Further, these photosensitizers can be used alone or in combination of two or more.

The blending ratio of the copolymer and the photosensitizer is 0.1 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the copolymer. If it deviates from the above range, pattern shape and resolution will be adversely affected.

The negative photoresist composition according to the present invention is soluble in organic solvents, and when used in the production of integrated circuits, it is usually used in the form of a solution (resist solution). In this case, the composition is generally prepared by dissolving it in an organic solvent in a proportion of 1 to 50% by weight, preferably 5 to 30% by weight. In this case, the solvent to be used is one that uniformly dissolves each component of the negative photoresist composition of the present invention, and that contains silicon,
It is preferable that a uniform and smooth coating film can be obtained by evaporating the organic solvent after coating the surface of a substrate such as aluminum. Specifically, acetone, methyl ethyl ketone,
Ketone solvents such as cyclopentanone, cyclohexanone, cellosolve solvents such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, ether solvents such as tetrahydrofuran, diethylene glycol dimethyl ether, ethylene glycol monoethyl ester, acetic acid Examples include, but are not limited to, ester solvents such as ethylene glycol monomethyl ester. The above organic solvents may be used alone or in combination of two or more.

In addition to the above-mentioned components, the negative photoresist composition of the present invention may also contain sensitizers, dyes, plasticizers, other resins, various inhibitors such as thermal reaction inhibitors, adhesion improvers, etc. You can. The negative photoresist composition of the present invention can be prepared by adjusting the resist solution as described above.
The relief pattern can be formed using conventional photoresist techniques.

The method for forming this relief parallax will be explained below.

First, a resist solution prepared as described above is applied to a substrate. This application to the substrate can be performed using, for example, a spinner. This is then heated to a temperature of 60 to 120°C, preferably 80°C.
Dry at ~100°C for 20-60 minutes. After drying, the coated film is irradiated with deep ultraviolet rays and excimer laser through a negative photomask chart. Next, a relief pattern is obtained by washing away the unexposed areas with a developer.

As the developer, a weak alkaline aqueous solution of sodium hydroxide, potassium hydroxide, sodium metasilicate, tetramethylammonium hydroxide, etc., having a concentration of 5% by weight or less, can be used. The relief pattern thus formed has good resolution and contrast.

Furthermore, a substrate can be etched using the negative photoresist composition of the present invention and the pattern formed as described above as a mask.

[Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Synthesis Example 1 12.0 g of polyvinylphenol with a molecular weight of 6000 and 4.8 g of triethylamine were dissolved in 30 Gml of THF, and epichlorohydrin 2 was dissolved at 15°C while stirring well.
．． A mixed solution of 8 g and 2 Q ml of THF was added dropwise over 1 hour. After the dropwise addition was completed, the mixture was further stirred at room temperature for 5 hours, and then the reaction solution was added to 32x water, and the precipitated polymer was collected by filtration. This polymer was purified by repeating THF dissolution and water reprecipitation several times, and vacuum-dried at 80° C. for 6 hours to obtain the desired polymer EP-1 (14.8 g). The introduction rate of epoxy substituents in this polymer was determined by elemental analysis.
It was 15%.

Synthesis Example 2 12.0 g of polyvinylphenol with a molecular weight of about 6000 and 4.8 g of triethylamine were dissolved in 300 ml of THF, and a mixture of 6.9 g of epichlorohydrin and 20 ml of THF was added to the solution over 1 hour while stirring well at 15°C. dripped. After the addition was completed, the mixture was further stirred at room temperature for 5 hours,
The reaction solution was 3 i! The precipitated polymer added to the water in Z was collected by filtration. This polymer was purified by repeating THF dissolution and water reprecipitation several times, and vacuum-dried at 80° C. for 6 hours to obtain the desired polymer EP-2 (16.3 g). The introduction rate of epoxy substituents into this polymer was found to be 31% by elemental analysis.

Synthesis Example 3 1240 g of polyvinylphenol with a molecular weight of about 6000 and 4.8 g of triethylamine were dissolved in 300 ml of THF, and a mixed solution of 13.7 g of shrimp chlorohydrin and 30 ml of THF was added dropwise over 1 hour while stirring well at 15°C. . After the dropwise addition was completed, the reaction solution was further stirred at room temperature for 5 hours, and then the reaction solution was diluted with 3% The precipitated polymer added to the water of z was collected by filtration. This polymer was purified by repeating THF dissolution and water reprecipitation several times, and vacuum-dried at 80° C. for 6 hours to obtain the desired polymer EP-2 (ILSg). The rate of introduction of epoxy substituents into this polymer was found to be 48% by elemental analysis. Example 1 110 g of EP-1 obtained in Synthesis Example 1 was dissolved in 22 ml of ethyl cellolub acetate to prepare a resist solution. This resist solution was coated onto a silicon wafer using a spin coater at 2300 rpm, and prebaked at 80° C. for 40 minutes to obtain a coating thickness of about 1.0 μm.

Next, this resist film was irradiated with light using a KrF excimer laser stepper. After irradiating with varying exposure doses, immersing in a 2.3% tetramethylammonium hydroxide aqueous solution for 60 seconds to develop, and rinsing by immersing in water for 30 seconds, the remaining film is plotted against the exposure dose. The sensitivity curve was defined as a sensitivity curve, and the exposure amount at which the residual film rate after development was 80% was defined as the sensitivity. The sensitivity of this resist is 3
It was 20mj. Furthermore, using this resist, in the same manner as above, a resist film with a thickness of lμ- was formed on a silicon wafer, and a chromium mask having a pattern was passed through this, using a KrF excimer laser stepper.
Reduction projection exposure was performed. Further, this resist film was developed by treating it with a 2.3% aqueous solution of tetramethylammonium hydroxide (20° C.) for 60 seconds, and was washed with water for 30 seconds to form a resist pattern.

As a result of observing the pattern thus formed using an electron microscope, it was found that both the cut-out pattern and the left-over pattern did not have steep cross-sectional profiles and were well resolved as fine patterns of 0.5 μl.

Example 2 A resist solution was prepared by dissolving 0 g of EP-2 obtained in Synthesis Example 2 in 22 ml of ethyl cellolub acetate. This resist solution was coated onto a silicon wafer using a spin coater at 2100 rpm, and prebaked at 80° C. for 40 minutes to obtain a coating of about 1.0 μm. Next, the sensitivity of this resist film was measured in the same manner as in Example 1, and it was found that it had a sensitivity of 270 mj. Furthermore, using this resist, a resist pattern was formed on a silicon wafer in the same manner as in Example 1.

As a result of observing the pattern thus formed using an electron microscope, it was found that both the cutout pattern and the remaining pattern had good resolution of fine patterns of 0.5 μm without having steep cross-sectional profiles.

Example 3 A resist solution was prepared by dissolving 0 g of EP-38 obtained in Synthesis Example 3 in 22 ml of ethyl cellulose acetate. This resist solution was coated onto a silicon wafer using a spin coater 1,800,800 times, and prebaked at 80° C. for 40 minutes to obtain a coating of about 1.0 μm. next,
The sensitivity of this resist film was measured in the same manner as in Example 1 and was found to have a sensitivity of 250 mj. Furthermore, using this resist, in the same manner as in Example 1,
A resist pattern was formed on a silicon wafer.

As a result of observing the pattern thus formed using an electron microscope, it was found that both the cutout pattern and the remaining pattern had good resolution of fine patterns of 0.5 .mu.I without having steep cross-sectional profiles.

Example 4 EP-18.0g and 3.3'- obtained in Synthesis Example 1
A resist solution was prepared by dissolving 1.2 g of diazidodiphenylsulfone in 22 ml of ethyl cellolub acetate. This resist solution was applied to a silicon wafer using a spin coater at 1800 rpm, and then heated to 80°C for 400 min.
Brebake was performed for a minute to obtain a coating of approximately 1.0 μm.
Next, the sensitivity of this resist film was measured in the same manner as in Example 1, and it was found that it had a sensitivity of 250 mj.

Furthermore, using this resist, a resist pattern was formed on a silicon wafer in the same manner as in Example 1. As a result of observing the pattern thus formed using an electron microscope, it was found that both the cutout pattern and the remaining pattern had good resolution of fine patterns of 0.5 μm without having steep cross-sectional profiles.

Comparative Example 1 EP-18.0g and 3.3'- obtained in Synthesis Example 1
A resist solution was prepared by dissolving 2.4 g of diazide diphenyl sulfone in 22 ml of ethyl cellolub acetate. This resist solution was coated onto a silicon wafer using a spin coater at 2,600 rpm, and prebaked at 80° C. for 40 minutes to obtain a coating of about 1.0 μl. Next, the sensitivity of this resist film was measured in the same manner as in Example 1, and it was found that it had a sensitivity of 115 mj.

Furthermore, using this resist, a resist film with a thickness of 1 μm was formed on a silicon wafer in the same manner as in Example 1, and then exposed to light. )in
It was processed for 60 seconds, developed, and washed with water for 30 seconds to form a resist pattern. As a result of observing the pattern thus formed using an electron microscope, the cross-sectional shape of the pattern showed a strong inverse taper, and fine patterns of 0.8 μm or less could not be resolved.

Comparative Example 2 Using the resist solution used in Comparative Example 1, a resist film with a thickness of 1 μm was formed on a silicon wafer in the same manner as in Example 1, and then exposed to light. Oxide 0.8% aqueous solution (
20° C.) for 120 seconds to develop, and wash with water for 30 seconds to form a resist pattern. As a result of observing the pattern thus formed using an electron microscope, it was found that undeveloped portions were generated in the punched pattern portion, and fine patterns of 0.8 μm or less could not be resolved.

〔Effect of the invention〕

As explained above, the negative photoresist composition of the present invention has high transparency in the deep ultraviolet and excimer laser wavelength regions. As a result, sensitivity, resolution, and contrast can be significantly improved in lithography using the above-mentioned light beam as a light source, which is necessary for work to improve the resolution of resists.Furthermore, since the alkali developability is good,
There is no risk of pattern swelling or development residue, etc.
It is possible to form fine photoresist patterns with high precision. Therefore, the requirements for resolution of these compositions will become stricter in the future.
In addition to being used as a resist for producing high-density integrated circuits such as SI, it can also be used in a wide range of fields in the electronic industry, such as for producing photomasks used in the production of such circuits.

Claims (1)

[Claims] (1) (A) The following general formula (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) (In the formula, n represents an integer from 1 to 5) The structural unit shown by the following formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Contains the structural unit shown by (II), and the ratio of the structural unit shown by formula (I) to the structural unit shown by formula (II) is the number of structural units (I) A copolymer such that 0.1≦(m)/(m+k)≦0.5 where m is the number of structural units (II) and k is the number of structural units (II), and (b) a bisazide system that is added as necessary. A negative photoresist composition containing a photosensitizer. (2) The negative photoresist composition of the present invention is characterized in that the proportion of the bisazide photosensitizer added as needed is 0.1 to 20 parts by weight based on 100 parts by weight of the copolymer. A negative photoresist composition according to claim 1.