JPH03282550A - Photoresist composition - Google Patents

Abstract

PURPOSE:To form the photoresist compsn. which is made soluble in a developer by the effect of an acid and has the patterning characteristic not affected by moisture environment at the time of patterning by incorporating a polymer deriv. the hydroxyl group of which is protected by an acetal group eliminated by the acid and an acid generating agent which generates the acid when irradiated with light into the above compsn. CONSTITUTION:The resin which is one of the constituting components of the compsn. is the polymer deriv. the hydroxyl group of which is protected by the acetal group eliminated by the acid. More specifically, the resin is constituted of the polymer deriv. the hydroxyl group of which is protected by the acetal protective group of the structure having at least one piece of hydrogen on the adjacent carbon atoms of the acetal carbon and, therefore, the elimination of the protective group is executed by the effect of the acid without the aid of moisture. The photoresist compsn. which is hardly affected by the atmosphere of the lithography stage is thereby obtd. The relieving of the requirement for the atmosphere control of the resist processing stage is consequently expected and the decrease in the fluctuation of the quality of the sample coated with the resist with lapse of time is expected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photoresist composition used for manufacturing semiconductor devices and the like.

(Prior art) Compositions composed of diazonaphthoquinone compounds and phenol novolak resins have been widely used as positive photoresists that become soluble in developing solutions in areas irradiated with visible light or ultraviolet light. Ta. The principle by which the light-irradiated portion of this composition becomes soluble in the developer was based on the reaction described below.

Since the diazonaphthoquinone compound itself in this composition is insoluble in aqueous alkaline solutions, it exhibits an excellent dissolution inhibiting effect on phenol novolak resins that are soluble in aqueous alkaline solutions (hereinafter referred to as alkali-soluble). However, this diazonaphtho-based non-compound becomes indenecarboxylic acid and changes into an alkali-soluble substance when irradiated with light, so in the light-irradiated part of the composition, the effect of inhibiting alkali dissolution on the phenol nopolac resin is lost, and thus , becomes soluble in alkaline developer.

In addition, since the above-mentioned composition uses a phenolic resin as a base resin that exhibits satisfactory resistance to reactive gas plasma for dry etching used in the manufacturing of semiconductor devices, it is also useful in semiconductor device manufacturing in this respect. There were some suitable ones for use.

Positive photoresists composed of such compositions have already been commercialized and sold in various grades and are easily available.

However, as semiconductor devices become more highly integrated, photoresists with high resolution are increasingly desired, and photoresists with high sensitivity that can improve output are also increasingly desired in order to reduce the cost of semiconductor devices. Among these, there is a limit to the ability to increase resolution and sensitivity with the positive type photoresist having the above-mentioned structure. This was for the reasons explained below.

In the case of the photoresist having the above structure, in order to improve the resolution, the content of the diazonaphthoquinone compound is increased. This improves the ability to inhibit dissolution of the resin, significantly increases the dissolution rate difference in the developing solution between the exposed and unexposed areas, and suppresses film loss in the unexposed areas.
Furthermore, since the contrast of light intensity within the photoresist is increased, the resolution is certainly improved. However, as the content of the diazonaphthoquinone compound increases, the amount of exposure required to lose its ability to inhibit dissolution increases, resulting in a decrease in sensitivity. This is because there are contradictory phenomena.

Therefore, there was a composition that attempted to increase the sensitivity of positive photoresists using a completely different method. This method uses a compound whose structure changes due to catalytic action and repeatedly heats the exposed area to make the exposed area soluble in a developer.

An example of this is a composition comprising a phenolic resin, a dissolution inhibiting substance whose structure changes with acid and loses its dissolution inhibiting effect on the phenolic resin, and a substance that generates an acid upon irradiation with light (e.g. , JP-A-63-250
(Disclosed in Japanese Patent Application Laid-Open No. 12995/1983).

An example of this is a composition in which a phenolic resin itself is derivatized and then returned to a phenolic resin by the catalytic action of an acid, thereby making it soluble in an alkaline developer (for example, the composition disclosed in JP-A-63-292128). ).

According to JP-A No. 63-292128, a composition comprising silylated poly(hydroxystyrene) ffI, silylated poly(vinylphenol), and a compound that generates an acid upon irradiation with light is used as a positive photoresist. It has been disclosed that it can be used. This composition has a film thickness of 1 or more when exposed to exposure light having a wavelength of 240 to 260 (nm).
In the case of .degree.Oum, the desired impact was obtained at 60 mJ/cm2, indicating that a highly sensitive positive photoresist could be obtained.

(Problems to be Solved by the Invention) However, in the photoresist composition disclosed in JP-A-63-292128, compared to the case where the sample is immersed in water after exposure and then developed with an alkaline developer, If it is not immersed in water, the development time will be longer and the resolution of the pattern will be lower. KJ Right: In the case of this photoresist composition, if the film thickness was to be 81 um or more, it was necessary to immerse the sample in water during development.

This means that water is required for the reaction in which poly(hydroxystyrene) is regenerated by elimination of the silyl group by acid, and therefore, water must be controlled during the manufacturing process. However, such moisture management is not preferable because it increases costs.

The present invention was made in view of the above points, and therefore, an object of the present invention is to provide a photoresist composition that becomes soluble in a developing solution by the action of an acid, and that has buttering properties that are similar to the moisture environment during buttering. An object of the present invention is to provide a photoresist composition that is not affected by

(Means for Solving the Problems) In order to achieve this object, the photoresist composition of the present invention uses poly(hydroxystyrene) whose hydroxyl groups are protected by acetal groups that are eliminated by acid.
It is characterized by comprising a derivative and an acid generator that generates acid upon irradiation with light.

In carrying out the present invention, it is preferable that the poly(hydroxystyrene) derivative is represented by the following formula (1) or (2) (provided that in formula (1), l: JI
, l: (2 and R3 are hydrogen, an alkyl group, or an aryl group, and may be the same or partially or completely different, and X is O (oxygen) or S (sulfur). Also, n is a positive integer. Also, in formula (■), R
4 is hydrogen, an alkyl group, or an aryl group. Further, day 5 is an alkylene group having 2 or 3 carbon atoms and having a substituent. Moreover, X is 0 (oxygen) or S (sulfur).

Further, n is a positive integer. ).

The poly(hydroxystyrene) derivative represented by the formula (2), that is, the acetalized poly(hydroxystyrene), is, for example,
As shown in reaction formula (I) below, it is obtained by reacting poly(hydroxystyrene) and alkyl beer ether using an acid catalyst (provided that R2 in formula (I)
, R3 and R6 are hydrogen or an alkyl group, and may be the same or partially or completely different. Also, R
- is an alkyl group. Further, n is a positive integer. ) Furthermore, the poly(hydroxystyrene) derivative represented by formula (1) can also be obtained by a method analogous to the synthesis method of formula (0).

Here, regarding the degree of acetalization of the phenol hydroxyl group of poly(hydroxystyrene) (acetalization rate), there is a sufficient difference in the dissolution rate in the alkaline developer of both the exposed and unexposed areas of the photoresist composition. It's fine as long as it's a certain amount. It is desirable that the film loss in the unexposed area after development is substantially O. Considering this point, it is preferable that the acetalization rate is at least 80% or more. However, the rate of acetalization that makes the unexposed area insoluble in the developing solution varies depending on the degree of hydrophobicity depending on the type of acetal, and controlling the rate of acetalization within a narrow gap is itself not preferable in terms of synthesis. Therefore, it is preferable to carry out almost 100% acetalization both from the viewpoint of synthesis and from the viewpoint of preventing film loss.

Specific examples of the substance represented by the formula 0 include, but are not limited to, 1-methyl-1-methoxymethyl ether of boros(hydroxystyrene) represented by the following formula 0, and polyester represented by the following formula 0. (Hydroxystyrene)]
-ethoxyethyl ether and the like.

In addition, specific examples of the substance represented by the formula (2) include, but are not limited to, 2-tetrahydrothiofuranyl ether of poly(hydroxystyrene) represented by the following formula 0, and poly(hydroxystyrene) represented by the following formula 0. hydroxystyrene)
Tetrahydropyranyl ether of poly(hydroxystyrene) represented by the following formula 0, 4-methoxytetrahydropyranyl ether of poly(hydroxystyrene) represented by the following formula 0, poly(hydroxystyrene) represented by the following formula 0 ) tetrahydrothiopyranyl ether, etc.

Further, in carrying out the present invention, it is preferable to use a sulfonium salt or an iodonium salt as the acid generator, more preferably a triarylsulfonium salt or a diaryliodonium salt. Although it is possible to use diazonium salt as an acid generator,
This is unsuitable due to poor thermal stability.

Iodonium salts suitable for use include, but are not limited to, those represented by the following formulas 0 to 0.

Sulfonium salts suitable for use include, but are not limited to, those represented by the following formulas 0 to 0.

Also, the lower limit of the content of acid generator in poly(hydroxystyrene) derivatives depends on the catalytic reaction (
Reaction described later with reference to formula (II). ), and the desired sensitivity can be obtained, and its upper limit is mainly determined by the amount that does not impair the film formation properties of the photoresist. Specifically, the acid generator is preferably included in an amount of 1 to 50 parts by weight per 100 parts by weight of the poly(hydroxystyrene) derivative.

In actual use of the photoresist composition of the present invention, a coating solution is prepared by dissolving it in an appropriate solvent, and the coating solution is applied onto a substrate such as a silicon substrate by, for example, a spin cord method. After that, pre-exposure hake, exposure, post-exposure hake and development are sequentially performed.

At this time, the sensitivity of this photoresist composition depends on the speed of the reaction in which the hydroxyl protecting group of the poly(hydroxystyrene) derivative is eliminated by the acid generated from the acid generator.

However, the rate of this elimination reaction depends on the catalytic reaction (Equation 2) described above, so if other conditions other than the temperature of the hexagon after exposure in the Ringranoy process are held constant, this
The sensitivity of the odoresist will depend on the temperature of the hake after exposure. Therefore, the boiling temperature needs to be higher than the temperature at which the catalytic reaction in the acetal elimination reaction occurs and lower than the temperature at which the acid generator in the unexposed area is decomposed. Specifically, the temperature within the animal's surroundings is preferably 60°C or higher and 150°C or lower. However, in order to quickly cause the acetal elimination reaction and to reduce the risk of cross-linking in a part of the poly(hydroxystyrene) and rendering buttering impossible, the temperature should be 80"C or more and 120"C or less. It is more preferable to set the temperature to .

(Function) According to the configuration of the present invention, in the light-irradiated portion of the photoresist composition, the protecting group protecting the hydroxyl group of poly(hydroxystyrene) is removed by the acid generated from the acid generator. It will be done.

As a result, this portion becomes soluble in alkaline fluorescent solution and can be buttered. Further, this protecting group can be extracted without requiring any special moisture.

In particular, in the case of a structure using a poly(hydroxystyrene) derivative as shown by the formula 0 or the formula ■, the hydroxyl protecting group is present on at least one carbon atom of the acetal carbon.
Chemically, the E1 reaction (elimination reaction) easily occurs even at room temperature under vI conditions such as 0.0 IN hydrochloric acid or 5% acetic acid, and the acetal, which is a protective group, Easily released from (hydroxystyrene) derivatives. The acid generator contained in the photoresist composition is an acid with sufficient strength to eliminate the acetal upon irradiation with light, specifically Lewis acid (Lewis #).
! Therefore, the above-mentioned elimination reaction easily occurs in the photoresist composition. The state of the reaction (
II) is shown in the formula. Incidentally, in formula (II), the ``snake'' is a Lewis acid produced by decomposition of the acid generator by light irradiation. Also,
Nu is a Lewis base produced by decomposition or an oxygen atom constituting a functional group of the resin.

According to the reaction of formula (II), the phenol resin is finally produced and, at the same time, the Lewis acid E is strongly regenerated. Furthermore, the reaction proceeds catalytically as the regenerated Lewis acid E acts again on the poly(hydroxystyrene) derivative in the photoresist composition. This catalyst (Lewis acid) only needs to be generated in a small amount in the film of the photoresist composition, so the amount of exposure to the acid generator to generate this catalyst is small, ensuring high sensitivity. .

(Examples) Examples of the photoresist composition of the present invention will be described below. It should be noted that the materials used and numerical conditions described in the following description of the examples are merely preferred examples within the scope of the present invention. Therefore, it should be understood that the present invention is not limited to these materials or the numerical conditions.

Example 1 First, the photoresist composition of Example 1 will be described.

First, the photoresist composition of Example 1 contains:
One type of poly(hydroxystyrene) derivative whose hydroxyl group is protected by a protecting group that is removed by acid is synthesized as described below.

Poly(hydroxystyrene) with a weight average molecular weight Mw of 11,000 (manufactured by Marutai Petrochemical Co., Ltd.) 1.29 and paratoluenesulfone MO, 06q were dissolved in 50 mβ of tetrahydrofuran, and this was cooled to 0°C. do.

Next, 1°169 of methyl vinyl ether was added to this solution and allowed to react for 8 hours.

The reaction mixture is then added to 200 ml of cold methanol. This produced a white precipitate, which was collected by filtration and vacuum-dried overnight at 25°C to obtain a dry resin of 1.09.

This dry resin corresponds to 1-methyl-1-methoxymethyl ether of poly(hydroxystyrene) (as shown in formula 0 above).

This dry resin has no absorption of hydroxyl groups in the R (infrared) spectrum, and the integrated intensity ratio of aromatic protons and 1-position methyl group in the NMR (nuclear magnetic resonance) spectrum.
It was found that the etherification rate was over 90%.

1-methyl-1-methoxymethylnitrile 59 of poly(hydroxystyrene) synthesized as described above, and diphenyliodonium hexafluoroantimonate (synthesized as described above) as an acid generator. (shown by the formula) 0.
059 in 15rrl of methoxyethyl acetate,
This solution was filtered through a Teflon filter to prepare a coating solution 18:v4 of the photoresist composition of Example 1.

Next, apply the coating solution of the photoresist composition of Example 1 to
The coating is applied to a 2-inch (1 inch is about 2.54 cm) silicon substrate that has been hydrophobized using HMDS (hexamethyldisilazane) using a spin code method at a rotation speed of 2500/min.

Next, this silicon substrate was heated at 80°C using a hot plate.
Hake for 1 minute at a temperature of . The film thickness of the photoresist composition of Example 1 after baking was 1.1 OL 1 m.

Next, 1! on this silicon substrate! A chromium mask having line and space (L/S) buttons of various sizes is placed on a chrome mask and exposed to light using a Xe-H9 lamp.

Next, the exposed silicon substrate is baked at a temperature of 100° C. for 1 minute using a hot plate.

Next, development is performed for 90 seconds using a 0.11N tetramethylammorum hydroxide aqueous solution to form a resist pattern.

Such resist pattern formation and cleaning is performed multiple times by changing the exposure (2).

Next, the resist pattern for each sample with different exposure doses was observed using a scanning electron microscope (SEM), and among these samples, a sample that had a 1.0 um L/S pattern or a sample that was formed according to the mask pattern was searched. However, the exposure amount @ 40
This was the case for the sample with mJ/cm2. Furthermore, a cross section of the resist pattern of this sample! SEM
When observed, the L/S pattern of 0.5 LIm was found to have a taper angle (the angle between the resist side wall and the substrate surface).
It was found that it could be formed with an angle of about 70 degrees.

<Example 2> Next, a coating solution of the photoresist composition of Example 2 is prepared in the same manner as in Example 1 except that diphenyliodonium hexafluoroacythimonate to, 19 is used as the acid generator. . That is, a coating solution of a photoresist composition having twice the acid generator content as that of the photoresist composition of Example 1 is prepared.

Next, a buttering experiment is performed using this coating solution in the same manner as the buttering experiment in Example 1. As a result, the exposure amount to resolve the pattern according to the mask pattern is 25
It turns out that it is mJ/cm2.

As is clear from comparing Example 1 and Example 2 (
It can be seen that the sensitivity improves as the content of the acid generator increases. However, other experiments have shown that if the amount of acid generator is too large, the film forming properties of the photoresist composition deteriorate.

<Example 3> Next, poly(hydroxystyrene) synthesized in Example 1
1 methyl-1-methoxymethyl ether 59 and diphenyliodonium hexafluoroantimonate 0.59 as an acid generator, methoxyethyl acetate 15 mβ
A coating solution of the photoresist composition of Example 3 is prepared by dissolving the photoresist composition in Example 3 and filtering the solution through a Teflon filter.

Next, a buttering experiment is performed using this coating solution in the same manner as the Batang experiment in Example 1.In this buttering experiment, the case where development was performed with 0.11N tetramethylammonium hydroxide, When developed with 0.12N tetramethylammonium hydroxide, and when the exposed sample was immersed in pure water before development and then developed with 0.12N tetramethylammonium hydroxide (
(Detailed conditions will be described later).

As a result, when a 0.11N developer was used, it took 7 minutes to close during development.

Also, when a 0.12N developer is used, the darkness during development is 14
However, the exposure amount to resolve the pattern according to the mask pattern is 20 mJ/cm2, which is roughly 0 seconds.
．． It was found that 5 um L/S Bakun could be resolved. Generally, when the concentration of a developer is increased, both sensitivity and resolution are reduced, but as seen in Example 3, it can be seen that such a problem does not occur with the photoresist composition of the present invention.

In addition, the exposed sample was immersed in pure water for 5 minutes before development.
When this is air-dried, baked at a temperature of 1100°C for 1 minute, and then developed with 0.12N tetramethylammonium hydroxide, the exposure amount to resolve the pattern according to the mask pattern is 25mJ/cm2. In addition, it was found that a 0.5 um L/S pattern could be resolved, and it was found that almost the same characteristics as those obtained during normal development were obtained. Therefore, the photoresist composition of the present invention
It can be seen that the desired patterning can be performed without being affected by the moisture environment during patterning.

<Example 4> Next, the photoresist composition of Example 4 will be explained.

a) First, in Examples, the weight average molecular weight M is T1. O
Next, prepare poly(hydroxystyrene) 1゜29 of OO and 2-chlorotetrahydrothiophene 1.
．． 479 and 1.219 of triethylamine were placed in 100 ml of tetrahydrofuradi, and 1.219 ml of triethylamine were added to
Allow to react for 6 hours. In addition, 2-chlorotetrahydrothiophene is described in the literature (J, Or9. Chem, 43p, 35
48 (1978)) is used.

The resulting reaction product is added to 300 ml of cooled methanol to obtain a precipitate. This precipitate was vacuum-dried overnight at 25°C.
．． 99 dry resin is obtained.

This dry resin corresponds to the 2-tetrahydrothiofuranyl ether of poly(hydroxystyrene) (as shown in formula 0 above).

This dry resin was found to have an etherification rate of 90% or more based on the integrated intensity ratio of protons adjacent to sulfur and aromatic protons in the NMR (nuclear magnetic resonance) spectrum.

Next, 2-tetrahydrothiofuranyl ether 79 of poly(hydroxystyrene) synthesized as described above,
A coating solution of the photoresist composition of Example 4 was prepared by dissolving 0.059 of the same diphenyliodonium hexafluoroantimonate as in Example 1 as an acid generator in 15 ml of methoxyethyl acetate and filtering this solution through a Teflon filter. do.

Next, a patterning experiment was performed using this coating solution in the same manner as the batting experiment in Example 1.

As a result, the exposure amount to resolve the pattern according to the mask pattern was 60 mJ/cm2, and 0.5 umL/S
It turns out that Batashi can be resolved.

In the above description, examples of the photoresist composition of the present invention have been described, but the present invention is not limited to the above-mentioned examples, and modifications as described below can be made.

For example, in the above example, the poly(hydroxystyrene) derivative whose hydroxyl group is protected by a protecting group that is removed by acid was synthesized using poly(hydroxystyrene) with an Mw of 11.00.0 as a starting material. It is clear that a photoresist composition obtained by changing the starting material to one having a molecular weight that can be used as a resist can also produce the same effects as in the examples.

(Effects of the Invention) As is clear from the above description, according to the photoresist composition of the present invention, the resin, which is one of the constituent components of the composition, is removed by the acetal group, which releases 1lI12, by an acid. A protected poly(hydroxystyrene) derivative, specifically a poly(hydroxystyrene) derivative whose hydroxyl group is protected by an acetal protecting group having a structure having at least one hydrogen on every elementary carbon atom of the acetal carbon. Because of the structure, the protecting group can be removed by the action of an acid without the aid of water. For this reason,
It is possible to provide a photoresist composition that is less affected by the atmosphere during the lithography process than conventionally.

Therefore, it can be expected that the requirements for atmosphere control in the resist processing process will be relaxed, and that variations in the quality of resist-coated samples over time will be reduced.

Patent request from Oki Electric Industry Co., Ltd.

Claims (5)

[Claims] (1) A photoresist composition comprising a poly(hydroxystyrene) derivative whose hydroxyl group is protected by an acetal group that is eliminated by an acid, and an acid generator that generates an acid when irradiated with light. (2) The photoresist composition according to claim 1, wherein the poly(hydroxystyrene) derivative is represented by the following formula (1) (provided that R^1, R^
2 and R^3 are hydrogen, an alkyl group, or an aryl group, and may be the same or different, and X is O
(oxygen) or S (sulfur), and n is a positive integer. ). ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) (3) The photoresist composition according to claim 1, wherein the poly(hydroxystyrene) derivative is represented by the following formula (2) (wherein R^4 is hydrogen, an alkyl group, or It is an aryl group. Also, R^5 is an alkylene group having a substituent and having 2 or 3 carbon atoms, X is O (oxygen) or S (sulfur), and n is a positive integer. ). ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(2) (4) The photoresist composition according to claim 1, wherein the acid generator is a triarylsulfonium salt or a diaryliodonium salt. (5) The photoresist composition according to claim 1, wherein the acid generator is contained in 1 to 50 parts by weight based on 100 parts by weight of the poly(hydroxystyrene) derivative.