JPH1055070A - Resist pattern forming method and production of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make patternability almost independent of a humid environment at the time of patterning by forming a film of a photoresist contg. a poly(hydroxystyrene) deriv. and an acid generating agent which generates an acid when irradiated with light on a base and carrying out heat treatment and development. SOLUTION: A film of a photoresist compsn. contg. a poly(hydroxystyrene) deriv. having hydroxyl groups each protected with an acetal group releasable by an acid and an acid generating agent which generates the acid when irradiated with light is formed on a base, patternwise exposed, heat-treated and developed. The film is formed by dissolving the photoresist compsn. in a proper solvent and coating the top of the base such as a silicon substrate with the resultant coating soln. by spin coating or other method. The film is baked before and after the selective exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for forming a resist pattern used for manufacturing a semiconductor device and the like, and a method for manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art As one of methods for forming a resist pattern with high resolution and high throughput, there is a method using a chemically amplified photoresist composition. As a conventional example, there is a method disclosed in JP-A-63-292128.

In the method disclosed in Japanese Patent Application Laid-Open No. 63-292128, a photoresist composition comprising silylated poly (hydroxystyrene), ie, silylated poly (vinylphenol), and a compound which generates an acid upon irradiation with light is disclosed. Is formed on the base. Next, this film is heat-treated, then exposed to light having a wavelength of 240 to 260 nm, then heat-treated, and then developed to form a resist pattern.

The principle of pattern formation is as follows. An acid is generated in the light-irradiated portion of the silylated poly (vinylphenol). Then, the light-irradiated portion of the silylated poly (vinyl phenol) returns to the phenol resin again by the catalytic action of the acid, and thus becomes soluble in the alkali developing solution. Therefore, a resist pattern is formed by development. According to the method disclosed in JP-A-63-292128, a resist film having a
It is said that a desired resist pattern can be obtained with an exposure amount of mJ / cm ² .

[0005]

However, in the photoresist composition disclosed in JP-A-63-292128, after the exposure, the sample is immersed in water and then developed with an alkali developing solution. When not immersed in water, the development time becomes longer, and the resolution of the pattern is reduced. That is, in the case of this photoresist composition, when the film thickness was 1 μm or more, it was necessary to immerse the sample in water during development.

[0006] This means that water is required for the reaction of regenerating poly (hydroxystyrene) by elimination of silyl groups by an acid, and therefore, it is necessary to control moisture during the production process. . However, such water management is not preferable because it is complicated and increases the cost.

Therefore, a method for forming a resist pattern using a photoresist composition which becomes soluble in a developing solution by the action of an acid, wherein the patterning characteristics are less affected by the moisture environment during patterning, is desired. .

[0008]

According to the resist pattern forming method of the present invention, a poly (hydroxystyrene) derivative in which a hydroxyl group is protected by an acetal group which is eliminated by an acid is used to achieve this object. A first step of forming a film of a photoresist composition containing an acid generator that generates an acid upon irradiation on a base, and a second step of selectively exposing the film to an intended pattern in accordance with a target pattern And a fourth step of heat-treating the exposed film and a fourth step of developing the heat-treated film.

In the practice of the present invention, the poly (hydroxystyrene) derivative is preferably represented by the following formula or the formula (where R ¹ , R ² and R ³ are , Hydrogen, an alkyl group or an aryl group, which may be the same or partially or entirely different, X is O (oxygen) or S (sulfur), and n is a positive integer In the formula, R ⁴ is hydrogen, an alkyl group or an aryl group, R ⁵ is a substituted or unsubstituted alkylene group having 2 or 3 carbon atoms, and X is O (oxygen). Or S (sulfur), and n is a positive integer.)

[0010]

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The poly (hydroxystyrene) derivative represented by the above formula, that is, acetalized poly (hydroxystyrene) is, for example, as shown in the following reaction formula (I):
It is obtained by reacting poly (hydroxystyrene) with an alkyl vinyl ether using an acid catalyst (provided that R ² , R ³ and R ⁶ in the formula (I) are hydrogen or an alkyl group and are the same. And some or all may be different, and R ¹ is an alkyl group.
Is a positive integer. )

[0012]

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The poly (hydroxystyrene) derivative represented by the formula can also be obtained by a method according to the synthesis method of the formula. Here, regarding the degree of acetalization of poly (hydroxystyrene) with respect to phenolic hydroxyl groups (acetalization rate), there is a sufficient difference in the dissolution rate of both the exposed part and the unexposed part of the photoresist composition in an alkali developing solution. Any degree is acceptable. It is desirable that the film loss of the unexposed portion after development is substantially 0,
Considering this point, the acetalization rate is at least 80.
% Is preferable. However, the acetalization rate at which the unexposed portion can be made insoluble in the developer varies depending on the degree of hydrophobicity depending on the type of acetal, and controlling the acetalization rate in a narrow range is not preferable in terms of synthesis itself. Therefore, acetalization is almost 10
Performing 0% is preferable from the viewpoint of synthesis and prevention of film loss.

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

[0015]

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Specific examples of the substance represented by the formula include, but are not limited to, 2-tetrahydrothiofuranyl ether of poly (hydroxystyrene) represented by the following formula; (Hydroxystyrene), tetrahydropyranyl ether of poly (hydroxystyrene) represented by the following formula, 4-methoxytetrahydropyranyl ether of poly (hydroxystyrene) represented by the following formula, poly (hydroxystyrene) represented by the following formula )) Tetrahydrothiopyranyl ether.

[0017]

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[0018]

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In practicing the present invention, the above-mentioned acid generator is preferably a sulfonium salt or an iodonium salt, and more preferably a triarylsulfonium salt or a diaryliodonium salt. It is conceivable to use a diazonium salt as the acid generator, but this is unsuitable due to poor thermal stability.

Suitable iodonium salts to be used are not limited to these, but include those represented by the following formulas (a) to (d).

[0021]

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Suitable sulfonium salts to be used are not limited to these, but include those represented by the following formulas (e) to (i).

[0023]

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The lower limit of the content of the acid generator with respect to the poly (hydroxystyrene) derivative is that the lower limit is such that a catalytic reaction (reaction described later with reference to the formula (II)) can be caused. The upper limit is mainly determined by the amount which does not impair the film formability of the photoresist. Specifically, it is preferable to include the acid generator in an amount of 1 to 50 parts by weight based on 100 parts by weight of the poly (hydroxystyrene) derivative.

In the actual use of the photoresist composition of the present invention, the photoresist composition is dissolved in an appropriate solvent to prepare a coating solution, and the coating solution is further placed on a base such as a silicon substrate. Coating is performed by a spin coating method, and thereafter, baking before exposure, exposure, baking after exposure, and development are sequentially performed. At this time, the sensitivity of the photoresist composition depends on the rate 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, since the rate of this desorption reaction depends on the catalytic reaction (Equation II) described later, if other conditions than the temperature of the post-exposure bake in the lithography process are kept constant, the sensitivity of this photoresist becomes It will depend on the temperature of the post-exposure bake. Therefore, the post-bake temperature needs to be higher than the temperature at which a catalytic reaction in the acetal desorption reaction can occur and lower than the temperature at which the generator in the unexposed portion is decomposed. Specifically, 60 ° C. or more and 15
A temperature within the range of 0 ° C. or less is good. However, considering that the acetal elimination reaction is caused promptly and that the risk of cross-linking of a part of poly (hydroxystyrene) to make patterning impossible is reduced, 80 ° C. or more
More preferably, the temperature is 0 ° C. or lower.

According to the invention of the method of manufacturing a semiconductor device of the present application, in the method of manufacturing a semiconductor device including a step of forming a resist pattern on a base, the resist pattern is formed by forming the resist pattern of the invention of the present application. It is characterized by being formed by a method.

According to each invention of the present application, in the light-irradiated portion of the photoresist composition, the protecting group protecting the hydroxyl group of poly (hydroxystyrene) is changed by the acid generated from the acid generator. Pulled out. As a result, since this portion is soluble in an alkali developing solution, patterning can be performed. In addition, this protective group can be extracted without requiring special water.

Particularly, in the case of a structure using a poly (hydroxystyrene) derivative represented by the formula or the formula,
Since the hydroxyl-protecting group is an acetal having at least one hydrogen on a carbon atom adjacent to the acetal carbon, the E1 reaction (elimination reaction) is performed chemically at room temperature under acidic conditions of about 0.01 N hydrochloric acid or 5% acetic acid. ) Easily occurs, and the acetal serving as a protecting group is easily eliminated from the poly (hydroxystyrene) derivative. The acid generator contained in the photoresist composition generates an acid having sufficient strength for desorption of the acetal by light irradiation, specifically, a Lewis acid (Lewis acid). In the above, the above elimination reaction easily occurs. The state of the reaction is shown in the following formula (II). In the formula (II), E is a Lewis acid generated by decomposition of the acid generator by light irradiation. Nu is a Lewis base (Lewis base) similarly generated by decomposition or an oxygen atom constituting a functional group of the resin.

[0029]

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According to the reaction of the formula (II), the Lewis acid E is regenerated at the same time that the phenol resin is finally formed. In addition, the reaction proceeds catalytically as the regenerated Lewis acid E acts again on the poly (hydroxystyrene) derivative in the photoresist composition. Since the catalyst (Lewis acid) may be formed in a small amount in the film of the photoresist composition, the amount of exposure to the acid generator to generate the catalyst is small, and high sensitivity is secured. .

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention of the method of forming a resist pattern and the invention of the method of manufacturing a semiconductor device of the present application will be described together. The materials used and numerical conditions described in the following description of the embodiments are merely preferred examples within the scope of the present invention. Therefore, it should be understood that the present invention is not limited only to these materials and numerical conditions.

1. Example 1 1-1. Synthesis Example First, one kind of a poly (hydroxystyrene) derivative in which a hydroxyl group is protected by a protecting group released by an acid is synthesized as described below.

[0033] (manufactured by Maruzen Petrochemical Co.) poly a weight average molecular weight M _W 11,000 (hydroxystyrene) 1.
2 g and 0.06 g of paratoluenesulfonic acid are dissolved in 50 ml of tetrahydrofuran, and this is cooled to 0 ° C.

Next, 1.16 g of methyl vinyl ether is added to this solution and reacted for 8 hours.

Next, the mixture after the completion of the reaction is added to 200 ml of cold methanol. As a result, a white precipitate is generated. The white precipitate is collected by filtration and dried in vacuo at 25 ° C. overnight to obtain 1.0 g of a dried resin.

This dry resin corresponds to 1-methyl-1-methoxymethyl ether of poly (hydroxystyrene) (shown by the above formula).

This dry resin has no ether absorption in the IR (infrared) spectrum, and has an etherification ratio based on the integrated intensity ratio between the aromatic proton and the 1-position methyl group in the NMR (nuclear magnetic resonance) spectrum. Is 90% or more.

1-2. Preparation of coating solution Next, 5 g of 1-methyl-1-methoxymethyl ether of poly (hydroxystyrene) obtained by synthesis as described above,
Diphenyliodonium hexafluoroantimonate (shown in the above formula (b)) as an acid generator
05 g of the photoresist composition was dissolved in 15 ml of methoxyethyl acetate, and this solution was filtered through a Teflon filter to prepare a coating solution of the photoresist composition of Example 1.

1-3. Patterning Experiment Next, the coating solution of the photoresist composition prepared above was applied to a 2-inch (1 inch: about 2.54 cm) silicon substrate that had been subjected to a hydrophobic treatment with HMDS (hexamethyldisilazane), at a rotation speed of 2500 / It is applied by a spin coating method under the condition of minutes. Next, the silicon substrate is baked at a temperature of 80 ° C. for 1 minute using a hot plate. The film thickness of the photoresist composition after baking in Example 1 was 1.10 μm.

Next, chromium masks having line and space (L / S) patterns of various dimensions are brought into close contact with the silicon substrate, and are exposed with a Xe-Hg lamp. Next, the exposed silicon substrate is baked at 100 ° C. for 1 minute using a hot plate.

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

Such a resist pattern forming operation is performed a plurality of times while changing the exposure amount.

Next, the resist pattern of each sample with the changed exposure amount was observed with a scanning electron microscope (SEM), and a 1.0 μm L / S pattern was formed from these samples in accordance with the mask pattern. When a sample was searched, a sample having an exposure amount of 40 mJ / cm ² corresponded to this.
Further, when the cross section of the resist pattern of this sample was observed by SEM, the L / S pattern of 0.5 μm showed a taper angle (an angle formed between the resist side wall and the substrate surface) of about 7 μm.
It was found that the film was formed in a state having 0 degrees.

2. 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 0.1 g of diphenyliodonium hexafluoroantimonate as an acid generator is used. That is, a coating solution of a photoresist composition in which the content of the acid generator is twice that of the photoresist composition of Example 1 is prepared.

Next, using this coating solution, a patterning experiment is performed in the same procedure as in the patterning experiment of Example 1.
As a result, it was found that the exposure amount for resolving the pattern according to the mask pattern was 25 mJ / cm ² .

As is clear from a comparison between Example 1 and Example 2, it can be seen that the sensitivity increases with an increase in the content of the acid generator. However, according to another experiment, if the amount of the acid generator is too large, the film formability of the photoresist composition deteriorates.

3. Example 3 Next, poly (hydroxystyrene) synthesized in Example 1
Of 5 g of 1-methyl-1-methoxymethyl ether and 0.5 g of diphenyliodonium hexafluoroantimonate as an acid generator in 15 ml of methoxyethyl acetate
And the solution is filtered through a Teflon filter to prepare a coating solution of the photoresist composition of Example 3.

Next, using this coating solution, a patterning experiment is performed in the same procedure as in the patterning experiment of Example 1.
In this patterning experiment, the development was performed with 0.11 N tetramethylammonium hydroxide,
Difference between when developed with 12N tetramethylammonium hydroxide and when the exposed sample is immersed in pure water before development and then developed with 0.12N tetramethylammonium hydroxide (detailed conditions will be described later) Also check.

As a result, when the developing solution of 0.11 N was used, the developing time required 7 minutes.

When a 0.12N developing solution is used, the developing time is 140 seconds, and the exposure for resolving the pattern according to the mask pattern is 20 mJ / cm ² . It was found that a 5 μmL / S pattern could be resolved. In general, when the concentration of the developer is increased, both the sensitivity and the resolution are decreased. However, as can be seen from Example 3, such a phenomenon does not occur in the photoresist composition of the present invention.

The exposed sample is placed in pure water before development.
Immersion for 1 minute, air-dried, baked at 100 ° C. for 1 minute, and then developed with 0.12 N tetramethylammonium hydroxide, the exposure dose for resolving the pattern according to the mask pattern is 25 mJ / cm ² , and it was found that a 0.5 μmL / S pattern could be resolved, and it was found that almost the same characteristics as in normal development were obtained. Therefore, it can be seen that the photoresist composition of the present invention can perform desired patterning without being affected by the moisture environment during patterning.

4. Fourth Embodiment Next, a fourth embodiment will be described.

4-1. Synthesis Example First, in the same manner as in Example 1 the weight average molecular weight M _W is 11,0
First, 1.2 g of poly (hydroxystyrene) No. 00 is prepared. Next, this, 1.47 g of 2-chlorotetrahydrothiophene, and 1.21 g of triethylamine were put in 100 ml of tetrahydrofuran.
Incubate for 6 hours. In addition, 2-chlorotetrahydrothiophene is described in the literature (J. Org. Chem. 43, p. 3).
548 (1978)).

The obtained reaction product was cooled in 300 ml of cooled methanol.
to obtain a precipitate. The precipitate is vacuum dried overnight at 25 ° C. to give 0.9 g of dry resin.

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

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

4-2. Preparation of coating solution Next, 7 g of 2-tetrahydrothiofuranyl ether of poly (hydroxystyrene) obtained by synthesis as described above,
As an acid generator, 0.05 g of diphenyliodonium hexafluoroantimonate as in Example 1 was dissolved in 15 ml of methoxyethyl acetate, and this solution was filtered through a Teflon filter to prepare a coating solution of the photoresist composition of Example 4. .

4-3. Patterning experiment Next, using this coating solution, a patterning experiment is performed in the same procedure as the patterning experiment of Example 1.

As a result, the exposure amount for resolving the pattern according to the mask pattern was 60 mJ / cm ² ,
It was found that a 5 μmL / S pattern could be resolved.

The present invention is not limited to the above-described embodiment, and many modifications or changes can be made.

[0061] For example, in the above embodiments, the poly (hydroxystyrene) derivative in which a hydroxyl group is protected by a protecting group released by an acid is, M _W 11,000 of poly (hydroxystyrene) synthesized as the starting material However, it is clear that the same effect as in the example can be obtained when the photoresist composition obtained by changing the starting material to one having a molecular weight usable as a resist is used.

[0062]

As is apparent from the above description, according to the method for forming a resist pattern and the method for manufacturing a semiconductor device of the present invention, the base resin, one of the components of the photoresist composition, is made of an acid. A resist pattern is formed using a photoresist composition which is a poly (hydroxystyrene) derivative in which a hydroxyl group is protected by an acetal group released by the above method. Specifically, using a photoresist composition containing, as a resin, a poly (hydroxystyrene) derivative in which a hydroxyl group is protected by an acetal protecting group having a structure having at least one hydrogen on a carbon atom adjacent to the acetal carbon, A resist pattern is formed. Then, the protecting group can be eliminated by the action of an acid without the aid of moisture. For this reason, it is less affected by the atmosphere in the lithography process than in the related art.

Therefore, it is expected that the requirement for controlling the atmosphere in the resist processing step can be relaxed, and that the variation of the quality of the resist-coated sample over time can be reduced. Therefore, a semiconductor device can be manufactured at a lower cost and a higher yield than in the conventional case.

Claims (7)

[Claims] 1. A film of a photoresist composition containing a poly (hydroxystyrene) derivative in which a hydroxyl group is protected by an acetal group released by an acid and an acid generator that generates an acid by light irradiation, is coated on a substrate. A step of selectively exposing the film according to a target pattern; a step of heat-treating the exposed film; and a step of developing the heat-treated film. A method for forming a resist pattern. 2. A method of forming a resist pattern according to claim 1, a resist pattern forming method, which comprises using those represented by the following formula as the poly (hydroxystyrene) derivatives (wherein, R ¹ , R ² and R ³ are hydrogen, an alkyl group or an aryl group, which may be the same or different, X is O (oxygen) or S (sulfur), and n is positive. Is an integer.). Embedded image 3. A method of forming a resist pattern according to claim 1, a resist pattern forming method, which comprises using those represented by the following formula as the poly (hydroxystyrene) derivatives (wherein, R ⁴ Is hydrogen, an alkyl group or an aryl group, R ⁵ is a substituted or unsubstituted alkylene group having 2 or 3 carbon atoms, and X is O (oxygen) or S (sulfur). n is a positive integer.). Embedded image 4. The method for forming a resist pattern according to claim 1, wherein a triarylsulfonium salt or a diaryliodonium salt is used as the acid generator. 5. The method for forming a resist pattern according to claim 1, wherein the acid generator is used in an amount of 1 to 50 parts by weight based on 100 parts by weight of the poly (hydroxystyrene) derivative. A method of forming a resist pattern. 6. The method for forming a resist pattern according to claim 1, wherein the temperature during the heat treatment is in a range of 60 ° C. to 150 ° C. 7. A method for manufacturing a semiconductor device including a step of forming a resist pattern on an underlayer, wherein the step of forming the resist pattern is performed.
7. A method for manufacturing a semiconductor device, comprising the step of forming a resist pattern according to any one of the above items.