JPH0912537A - Sulfonium salt - Google Patents

Abstract

PURPOSE: To obtain a new sulfonium salt having an acid unstable group at the 3-site of the phenyl group of the sulfonium salt and useful as a component of a chemical amplification positive resist material suitable for fine processing technology. CONSTITUTION: This sulfonium salt is expressed by formula I (R<1> is H, an alkyl, etc.; OR<2> is an acid unstable group; Y is an alkylsulfonate, etc.; n is 0, 1 or 2; m is 1, 2 or 3; n+m:3), e.g. trifluoromethanesulfonic acid tris(3-t- butoxyphenyl)sulfonium salt. The exemplified substance of the compound of formula I having t-butyl group at the 3-site of the phenyl group and expressed by formula V can be produced by reacting a sulfoxide compound of formula II with a trialkylsilyl sulfonate compound of formula III (R<3> is methyl or t-butyl) and further reacting with a Grignard reagent of formula IV (X is Br, etc.).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel sulfonium salt suitable as a component of a chemically amplified positive resist material suitable for microfabrication technology.

[0002]

2. Description of the Related Art LSI to be Solved
With the demand for finer pattern rules in accordance with higher integration and higher speed, far-ultraviolet lithography is regarded as promising as a next-generation fine processing technology. The deep ultraviolet lithography can process 0.3 to 0.4 μm, and when a resist material having low light absorption is used, a pattern having a side wall nearly perpendicular to the substrate can be formed. In recent years, high-intensity KrF
Attention has been paid to a technique using an excimer laser. In order to use this technique as a mass production technique, a resist material having low light absorption and high sensitivity is demanded.

From such a viewpoint, a chemically amplified positive resist material using an acid as a catalyst developed in recent years (Japanese Patent Publication No. 2-2
No. 7660, JP-A-63-27829, etc.) have high sensitivity, high resolution, and high dry etching resistance and have excellent characteristics, and are particularly promising resist materials for deep ultraviolet lithography.

In this case, it is known that the compounded acid generator has a particularly large effect on the function of the chemically amplified positive resist material in the chemically amplified positive resist material. Representative examples of such an acid generator include the following onium salts.

[0005]

Embedded image

Since the onium salt itself is an oil-soluble compound, when it is blended as a resist component, it has the effect of reducing the solubility of the resist material in an aqueous alkali solution and suppressing the film loss during development.

However, in the case of a positive resist material, the decomposition product formed by absorbing the high energy rays by the acid generator is also oil-soluble, so that this decomposition product dissolves in the alkaline aqueous solution in the exposed area. It is impossible to reduce the speed and increase the alkali dissolution rate ratio (called dissolution contrast) between the exposed area and the unexposed area. Therefore, the chemically amplified positive resist material using the onium salt has low resolution in alkali development,
Due to the poor removal of the exposed portion, the pattern shape is not rectangular but has a trapezoidal forward taper.

In order to solve this problem, therefore, an tert-butoxy group, which is an acid labile group, is introduced at the p-position of the triphenylsulfonium salt and decomposed by irradiation with high-energy rays, resulting in the action of an acid to produce alkali solubility. It has been carried out to produce a phenol derivative having the formula (1) to increase the dissolution contrast (see Japanese Patent Application No. 6-317626).
However, even if a sulfonium salt that produces such a phenol derivative is used, it is difficult to obtain a satisfactory resolution when exposure is performed on a substrate having a low reflectance.

This is the above sulfonium salt of 250 nm
Since the transmittance in the vicinity is low and the transmittance as a resist film is reduced, the light intensity at the top and bottom of the resist film will differ when exposure is performed using a substrate with a low reflectance, and the amount of acid generated will differ. Appears, which is considered to reduce the resolution.

The conventional chemically amplified positive resist material is exposed to PEB (Post Exposure B) when exposed to deep ultraviolet rays, electron beams and X-ray lithography.
If the standing time until the ake is long, the line pattern becomes a T-top shape when the pattern is formed, that is, the pattern upper portion becomes thicker [PED (PostE
xposure Deley)], which is considered to be because the solubility of the resist film surface is lowered, which is a major drawback in practical use. Due to this drawback, the conventional chemically amplified positive resist material has a problem that it is difficult to control the dimensions in the lithography process and the dimension control is impaired even when the substrate is processed using dry etching [Reference: W. Hinsberg, et. a
l. , J. et al. Photopolym. Sci. Techn
ol. , 6 (4), 535-546 (1993). ,
T. Kumada, et. al. , J. et al. Photopo
lym. Sci. Technol. , 6 (4), 571
-574 (1993). ]. There has not yet been a chemically amplified positive resist material that solves this problem.

In the chemically amplified positive resist material, P
It is believed that basic compounds in air are largely involved in the cause of ED problems. The acid generated on the resist film surface by exposure reacts with a basic compound in the air to be inactivated, and the longer the standing time before PED, the more the amount of inactivated acid increases. Therefore, the acid labile group is decomposed. Is less likely to occur. Therefore, the insolubilized layer is formed on the surface, and the pattern has a T-top shape.

In this case, it is known that the addition of a basic compound can suppress the influence of the basic compound in the air, so that it is also effective for PED (Japanese Patent Laid-Open No. 232706/1993). However, according to the present inventors' investigation, the basic compound used here is not incorporated into the resist film due to volatilization, or has a compatibility with each component of the resist material. It was found that, since the dispersion in the resist film was not uniform, there was a problem in the reproducibility of the effect and the resolution was degraded.

Therefore, it is desired to develop a new component which gives a high-performance chemically amplified positive resist composition free from the above problems.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a novel sulfonium salt suitable as a component of a chemically amplified positive resist material having high resolution suitable for microfabrication technology.

[0015]

Means and Actions for Solving the Problems As a result of earnest studies to achieve the above object, the present inventor has found that a diaryl sulfoxide represented by the following general formula (2) and the following general formula ( By reacting with a trialkylsilyl sulfonate represented by 3) and further reacting with a Grignard reagent represented by the following general formula (4), which can be prepared by a reaction of 3-tert-butoxyphenyl chloride and metallic magnesium, It was found that a novel sulfonium salt having a tert-butoxy group at the 3-position of the phenyl group represented by the general formula (1a) can be obtained. Further, te of the sulfonium salt represented by the following general formula (1a) is
The rt-butoxy group is deprotected with an acid, and te
By substituting the 3-position of the phenyl group with an acid labile group consisting of an rt-butoxycarbonyl group, a tert-butoxycarbonylmethyl group, a trialkylsilyl group, a tetrahydropyranyl group, a methoxymethyl group, etc. A novel sulfonium salt of the following formula (1) having at least one acid labile group is obtained, and the sulfonium salt of the above formula (1) is a chemically amplified positive type having a high resolution suitable for microfabrication technology. It has been found that it is suitable as a component of a resist material and can exert great power particularly in deep ultraviolet lithography.

[0016]

Embedded image (In the formula, R ¹ is a hydrogen atom, an alkyl group, an alkoxy group or a dialkylamino group, OR ² is an acid labile group, and R ³ is a methyl group or a tert-butyl group.
Is a substituted or unsubstituted alkyl sulfonate or aryl sulfonate. n is an integer of 0 to 2, m is an integer of 1 to 3, and the sum of n and m is 3. )

That is, although the sulfonium salt of the above formula (1) of the present invention has a low alkali solubility of the compound itself, an acid produced by decomposition by irradiation with high energy rays, moisture in the resist material and PEB (Post Exposu).
re Bake) efficiently decomposes the acid labile group, resulting in a highly alkaline-soluble phenol moiety or tert.
In the case of having a tertiary carboxylic acid ester group such as -butoxycarbonylmethyloxy group, a carboxylic acid site is generated, so that a larger dissolution contrast can be obtained.

Therefore, the sulfonium salt of the above formula (1) can exhibit excellent performance as an acid generator of a chemically amplified positive resist material, and a resist material containing the sulfonium salt of the above formula (1) can be used. Has a large solubility contrast due to the effect of the acid labile group of the sulfonium salt of the above formula (1), and particularly when a light source near 250 nm is used, the oxygen atom cannot have a resonance structure with the sulfur atom.
By substituting in the position, the transmittance in the vicinity of 250 nm can be increased to a level equal to or higher than that of the non-substitution, and therefore, a resist image having high resolution and a wide range of depth of focus can be obtained. .

That is, the present invention provides (A) the following general formula (1)
And a sulfonium salt having at least one acid labile group at the 3-position of the phenyl group in the molecule.

[0020]

Embedded image (Wherein R ¹ is a hydrogen atom, an alkyl group, an alkoxy group or a dialkylamino group, OR ² is an acid labile group, Y is a substituted or unsubstituted alkyl sulfonate or aryl sulfonate, and n is n An integer from 0 to 2, m
Is an integer of 1 to 3, and the sum of n and m is 3. )

The present invention will be described in more detail below. The novel sulfonium salt of the present invention is represented by the following general formula (1) and has at least one acid labile group at the 3-position of the phenyl group in the molecule. I have.

[0022]

Embedded image (Wherein R ¹ is a hydrogen atom, an alkyl group, an alkoxy group or a dialkylamino group, OR ² is an acid labile group, Y is a substituted or unsubstituted alkyl sulfonate or aryl sulfonate, and n is n An integer from 0 to 2, m
Is an integer of 1 to 3, and the sum of n and m is 3. )

In the above formula (1), R ¹ is a hydrogen atom,
It is an alkyl group, an alkoxy group or a dialkylamino group, and specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, and se.
A C1-butyl group, a tert-butyl group, a hexyl group, a cyclohexyl group and the like having 1 to 8 carbon atoms are preferable, and among them, a methyl group, an ethyl group, an isopropyl group, a tert- group.
Butyl groups are more preferably used. Examples of the alkoxy group include methoxy group, ethoxy group, propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, t.
An ert-butoxy group, a hexyloxy group, a cyclohexyloxy group and the like having 1 to 8 carbon atoms are preferable, and among them, a methoxy group, an ethoxy group, an isopropoxy group, a tert- group.
A butoxy group is more preferably used. As the dialkylamino group, a dimethylamino group, a diethylamino group,
An amino group having an alkyl group having 1 to 4 carbon atoms such as a dipropylamino group is used, and among them, a dimethylamino group is preferable.

OR ² is an acid labile group. Here, as the acid labile group, for example, a tertiary alkoxy group such as tert-butoxy group, a carbonate group such as tert-butoxycarbonyloxy group, a tertiary carboxylic acid ester group such as tert-butoxycarbonylmethyloxy group, Trimethylsilyloxy group, triethylsilyloxy group, ter
Examples thereof include trialkylsilyloxy groups such as t-butyldimethylsilyloxy group, acetals and ketal groups such as tetrahydropyranyloxy group, methoxymethyloxy group, ethoxyethyloxy group and the like.

Y is a substituted or unsubstituted alkyl sulfonate or aryl sulfonate, for example, trifluoromethane sulfonate, nonafluorobutane sulfonate, p-toluene sulfonate are preferable. n
Is an integer of 0 to 2, m is an integer of 1 to 3, and the sum of n and m is 3.

In the present invention, in particular, when a sulfonium salt having a p-toluenesulfonate anion (p-toluenesulfonate) as a counter anion (Y ⁻ ) is used as a component of a resist material, the p-toluenesulfonate anion of the p-toluenesulfonate anion is used. The effect, that is, the effect of acid deactivation by the basic compound in the air on the resist film surface can be made very small, so that the formation of a surface-insoluble layer can be suppressed and the PED stability is good. Thus, the problem of the surface-insoluble layer, which is the cause of the T-top shape, that is, the problem of PED can be sufficiently solved, and a better sensitivity can be obtained.

Specific examples of the sulfonium salt of the above formula (1) include the following. That is, as the sulfonium salt having a tert-butoxy group as an acid labile group, for example, trifluoromethanesulfonic acid (3-tert-butoxyphenyl) diphenylsulfonium, p-toluenesulfonic acid (3-tert-butoxyphenyl) diphenylsulfonium, Nonafluorobutane sulfonic acid (3-tert-butoxyphenyl)
Diphenylsulfonium, bis (3-tert-butoxyphenyl) phenylsulfonium trifluoromethanesulfonate, bis (3-ter) sulfonate p-toluenesulfonate
t-butoxyphenyl) phenylsulfonium, nonafluorobutanesulfonate bis (3-tert-butoxyphenyl) phenylsulfonium, trifluoromethanesulfonate tris (3-tert-butoxyphenyl)
Sulfonium, tris (3-t-p-toluenesulfonate)
ert-butoxyphenyl) sulfonium, tris (3-tert-butoxyphenyl) sulfonium nonafluorobutanesulfonate, trifluoromethanesulfonic acid (3-tert-butoxyphenyl) bis (4-dimethylaminophenyl) sulfonium, p-toluenesulfonic acid (3-tert-butoxyphenyl) bis (4-dimethylaminophenyl) sulfonium, nonafluorobutanesulfonic acid (3-tert-butoxyphenyl) bis (4-dimethylaminophenyl) sulfonium, trifluoromethanesulfonic acid bis (3-tert) -Butoxyphenyl) (4-dimethylaminophenyl) sulfonium, bis (3-tert-butoxyphenyl) p-toluenesulfonate (4-dimethylaminophenyl) sulfonium, nonaf Oro butanoic acid bis (3-t
ert-butoxyphenyl) (4-dimethylaminophenyl) sulfonium and the like.

Examples of the sulfonium salt having a tert-butoxycarbonyloxy group as an acid labile group include bis (3-tert-butoxycarbonyloxyphenyl) phenylsulfonium trifluoromethanesulfonate, p
-Bis (3-tert-butoxycarbonyloxyphenyl) phenylsulfonium toluenesulfonate, tris (3-tert-butoxycarbonyloxyphenyl) sulfonium trifluoromethanesulfonate, tris (3-tert-butoxycarbonyloxyphenyl) p-toluenesulfonate ) Sulfonium, tris (3-tert-butoxycarbonyloxyphenyl) sulfonium nonafluorobutanesulfonate, (3-tert-butoxycarbonyloxyphenyl) bis (4-dimethylaminophenyl) sulfonium trifluoromethanesulfonate, p-toluenesulfonic acid (3-tert-Butoxycarbonyloxyphenyl) bis (4-dimethylaminophenyl) sulfonium, trifluoromethanesulfonic acid bis (3 tert-Butoxycarbonyloxyphenyl) (4-dimethylaminophenyl) sulfonium, bis (3-tert-butoxycarbonyloxyphenyl) (4-dimethylaminophenyl) sulfonium, bis (3-nonafluorobutanesulfonate) tert-butoxycarbonyloxyphenyl) (4-dimethylaminophenyl) sulfonium and the like.

As the sulfonium salt having a tert-butoxycarbonylmethyloxy group as an acid labile group,
Bis (3-tert-butoxycarbonylmethyloxyphenyl) phenylsulfonium trifluoromethanesulfonate, Bis (3-tert-toluenesulfonate)
-Butoxycarbonylmethyloxyphenyl) phenylsulfonium, trifluoromethanesulfonate tris (3-tert-butoxycarbonylmethyloxyphenyl) sulfonium, nonafluorobutanesulfonate tris (3-tert-butoxycarbonylmethyloxyphenyl) sulfonium, trifluoromethanesulfone Acid (3-tert-butoxycarbonylmethyloxyphenyl) bis (4-dimethylaminophenyl) sulfonium, p-toluenesulfonate bis (3-tert-butoxycarbonylmethyloxyphenyl) (4-dimethylaminophenyl) sulfonium and the like. To be

The sulfonium salt having an acetal or ketal group as an acid labile group is a bis (3- (2-tetrahydropyranyl) -oxyphenyl) phenylsulfonium trifluoromethanesulfonate having a tetrahydropyranyl group, Tris (3- (2-tetrahydropyranyl) -oxyphenyl) sulfonium trifluoromethanesulfonate, Tris (3- (2-tetrahydropyranyl) -oxyphenyl) sulfonium nonafluorobutanesulfonate, Trifluoromethanesulfonic acid (3- (2-Tetrahydropyranyl) -oxyphenyl) bis (4-dimethylaminophenyl) sulfonium, p-toluenesulfonate bis (3- (2-tetrahydropyranyl) -oxyphenyl) (4-dimethylaminophenyl) su Honiumu and the like, as having a methoxymethyl group, trifluoromethanesulfonic acid bis (3-methoxymethyl-oxyphenyl) phenyl trifluoromethanesulfonate, tris (3-methoxymethyl-oxyphenyl) sulfonium,
Tris (3-methoxymethyloxyphenyl) sulfonium nonafluorobutanesulfonate, (3-methoxymethyloxyphenyl) bis (4-dimethylaminophenyl) sulfonium trifluoromethanesulfonate, p-
Examples thereof include bis (3-methoxymethyloxyphenyl) (4-dimethylaminophenyl) sulfonium toluenesulfonate.

Examples of the sulfonium salt having a trialkylsilyloxy group as an acid labile group include bis (3-trimethylsilyloxyphenyl) phenylsulfonium trifluoromethanesulfonate and bis (3-triethylsilyloxyphenyl) phenyl bis (3-triethylsilyloxyphenyl) p-toluenesulfonate. Sulfonium, trifluoromethanesulfonate tris (3
-Trimethylsilyloxyphenyl) sulfonium, tris (3-trimethylsilyloxyphenyl) sulfonium nonafluorobutanesulfonate, trifluoromethanesulfonic acid (3-triethylsilyloxyphenyl)
Bis (4-dimethylaminophenyl) sulfonium, p
-Bis (3-trimethylsilyloxyphenyl) (4-dimethylaminophenyl) sulfonium toluenesulfonate and the like.

The sulfonium salt of the above formula (1) of the present invention can be synthesized by the following route. That is, for example, a 3-halogen represented by the following general formula (7) obtained by first condensing a 3-halogenated phenol represented by the following general formula (5) and an isobutene represented by the following general formula (6) with an acid. -Tert-Butoxybenzene is reacted with metallic magnesium in THF by a conventional method to give 3-tert-butoxyphenyl Grignard (Grignear reagent) represented by the following general formula (4). Next, a sulfoxide represented by the following general formula (2) is reacted with a trialkylsilyl sulfonate represented by the following general formula (3) in an organic solvent, and further reacted with a Grignard reagent represented by the following formula (4): A sulfonium salt having a 3-tert-butoxyphenyl group as the acid labile group represented by the following general formula (1a) can be synthesized.

[0033]

[Chemical 6] (However, in the formula, R ¹ , R ² , R ³ , Y, m, and n are the same as described above, and X is a bromine atom or a chlorine atom.)

In the above reaction, the reaction between the 3-halogenated phenol of the above formula (5) and the isobutene of the above formula (6) is described in "Experimental Chemistry Course, Fourth Edition, Organic Synthesis 2, p200, edited by The Chemical Society of Japan, Maruzen." And “J. Holcombe and
T. Livinghouse J. Org. Che
m. , 111-115.51. (1986) ”. In this case, when the 3-halogenated phenol of the formula (5) is reacted with the isobutene of the formula (6), the isobutene of the formula (6) is 1 to 1 relative to the 3-halogenated phenol of the formula (5). 10 mol, particularly 3 to 5 mol, and 0.01 to 0.1 mol, particularly 0.01 to 0.1 mol, relative to the 3-halogenated phenol of the formula (5) using a strong acid such as trifluoromethanesulfonic acid as a catalyst. 0.05
This is preferably added in molar proportions. The reaction is preferably carried out in an organic solvent such as methylene chloride in the temperature range of -40 to -70 ° C for 0.5 to 4 hours.

As the sulfoxide of the above formula (2), diphenyl sulfoxide, bis (3,4-di-tert-butoxyphenyl) sulfoxide represented by the following formula (2a), and bis represented by the following formula (2b). (4-te
rt-butoxyphenyl) sulfoxide, represented by the following formula (2
bis (4-dimethylaminophenyl) sulfoxide represented by c) and bis (3-tert-butoxyphenyl) sulfoxide represented by the following formula (2d), which is a condensation product of the Grignard reagent of the above formula (4) and thionyl chloride. It is desirable to use

[0036]

Embedded image

The synthesis of these sulfoxide compounds can be carried out according to the method described in Japanese Patent Application No. 6-26171.

For example, when the compound of the above formula (2b) is obtained, it can be carried out by a method of reacting p-tert-butoxyphenyl grignia represented by the following formula (A) with thionyl chloride.

[0039]

Embedded image (X represents a chlorine or bromine atom.)

In this case, the reaction is preferably carried out in an organic solvent such as methylene chloride or THF. When reacting thionyl chloride with a Grignard reagent, thionyl chloride is used in an amount of 1/6 to 1/2 mol, preferably 1 /
The reaction was carried out at a rate of -78 ° C.
The temperature is 70C, preferably -60C to 10C, and the dropping time is 10 to 120 minutes, preferably 45 to 90 minutes. After completion of the reaction, the solvent layer is washed with water, dried and concentrated, and then the target compound can be obtained by recrystallization or column chromatography.

In the present invention, the above formulas (2a), (2b),
A novel sulfonium salt having one 3-tert-butoxyphenyl group can be synthesized by using (2c) or a sulfoxide such as diphenyl sulfoxide as a raw material. Moreover, a novel sulfonium salt having three 3-tert-butoxyphenyl groups can be synthesized by using the sulfoxide of the above formula (2d) as a raw material.

A novel sulfonium salt having two 3-tert-butoxyphenyl groups is a bis (3-tert-butoxyphenyl) sulfoxide of the above formula (2d) and an arylglycol represented by the following formula (8). It can be synthesized by reacting with a Niya reagent, for example, phenyl Grignard, 4-tert-butoxyphenyl Grignard, 4-dimethylaminophenyl Grignard and the like.

[0043]

Embedded image (In the above formula, R ¹ , R ³ , Y, X, m and n are the same as above.)

When a sulfoxide having the tert-butoxy group at the 2-position and the 2'-position such as bis (2,4-di-tert-butoxyphenyl) sulfoxide is used as the sulfoxide of the above formula (2), The target compound cannot be obtained due to steric hindrance. The same applies to the case where a compound having a tetrahydropyranyloxy group at the 2-position and the 2'-position is used.

Further, in the conventional method for synthesizing a sulfonium salt or sulfoxide compound by the reaction of phenol or anisole with thionyl chloride, the active site of phenol has two ortho and para positions, and an ortho substitution product depending on the reagent used, It may be different from the para-substitution, especially the meta-substitution cannot be obtained. Further, in this reaction, since hydrogen chloride gas is generated in the reaction system, tert
-It is difficult to synthesize a compound having an acid labile group such as butoxybenzene as a raw material. On the other hand, in the method of the present invention, only the meta-substituted product is obtained quantitatively because the Grignard reagent is used, and only an inorganic salt such as magnesium chloride is generated instead of hydrogen chloride gas. The decomposition of the stable group does not proceed.

In the above synthesis method, 3-tert
-Butoxyphenyl Grignard reagent was used as a raw material for sulfoxide and sulfonium salt, but the protecting group which is inert to Grignard reagent and can be removed by an acid, for example, tetrahydropyranyl group protects the hydroxyl group of 3-halogenated phenol. The sulfonium salt of the above formula (1) can also be synthesized by using a Grignard reagent prepared by reacting with magnesium metal.

In the above reaction, it is preferable to mix the trialkylsilyl sulfonate of the above formula (3) with the sulfoxide of the above formula (2) in an amount of 1 to 5 mol, particularly 2 to 3 mol. Further, it is preferable to add the Grignard reagent of the above formula (4) or the above formula (8) in an amount of 1 to 5 mol, particularly 2 to 3 mol, relative to the sulfoxide of the above formula (2). Furthermore, these reactions prevent elimination of the tert-butoxy group by a slight amount of acidic impurities present in the trialkylsilyl sulfonate of the above formula (3),
In the presence of an organic base such as triethylamine or pyridine, T
It is desirable to carry out in an organic solvent such as HF or methylene chloride. The reaction conditions for these reactions are not particularly limited, but the reaction temperature is preferably 0 to 10 ° C.

Further, in the present invention, the tert-butoxy group of the sulfonium salt of the above formula (1a) is deprotected with an acid,
The hydrogen atom of the phenolic hydroxyl group is tert-
By substituting an acid labile group such as a butoxycarbonyl group, a tert-butoxycarbonylmethyl group, a trialkylsilyl group, a tetrahydropyranyl group, and a methoxymethyl group, the target acid labile group is converted to the 3-position of the phenyl group. A novel sulfonium salt represented by the following general formula (1) can be obtained.

[0049]

Embedded image (However, in the above formula, R ¹ , R ² , Y, n, and m are the same as above.)

The novel sulfonium salt of the above formula (1) of the present invention thus obtained is preferably used as an acid generator for a chemically amplified positive resist composition, and the sulfonium salt of this formula (1) is used. Add salt as an acid generator,
Two-component system (organic solvent, alkali-soluble resin, acid generator)
Alternatively, it can be prepared as a three-component system (organic solvent, alkali-soluble resin, acid generator, dissolution inhibitor) chemically amplified positive resist material, but especially as a three-component chemically amplified positive resist material. Is preferred.

In this case, the above formula (1) as an acid generator is used.
The amount of the sulfonium salt of
0.5 to 15 parts by weight relative to 0 parts by weight (parts by weight, the same applies hereinafter),
Particularly, it is preferably 2 to 8 parts, and if it is less than 0.5 part, the amount of acid generated during exposure may be small and sensitivity and resolution may be inferior, and if it exceeds 15 parts, the transmittance of the resist may be lowered and the resolution may be lowered. May be inferior.

The method of using the resist material in which the sulfonium salt of the above formula (1) is blended, the method of using light and the like can be carried out by adopting a known lithographic technique. In particular, the resist material is 254 to 193 nm. Most suitable for fine patterning with far-ultraviolet light and electron beam.

[0053]

INDUSTRIAL APPLICABILITY The novel sulfonium salt of the above formula (1) of the present invention has an acid labile group introduced at the 3-position of the phenyl group of the sulfonium salt which is an acid generator. The solubility contrast can be increased, and by introducing an oxygen atom at the 3-position so that the resonance structure of the sulfur atom cannot be taken, the transmittance at around 250 nm is equal to or higher than that of the unsubstituted triphenylphosphonium salt. And as a result, the transmittance as a resist material can be increased, which is effective as a component of a chemically amplified positive resist material having a high resolution suitable for a microfabrication technique.

[0054]

[Examples] The present invention will be specifically described below with reference to Examples, Comparative Examples and formulation examples, but the present invention is not limited to the following Examples. All parts in each example are parts by weight.

Example 1 Trifluoromethanesulfonic acid tris (3-tert-)
Synthesis of butoxyphenyl) sulfonium 17.8 g (0.052 mol) of bis (3-tert-butoxyphenyl) sulfoxide was dissolved in 52 g of THF and cooled in an ice water bath. To this was added 5.3 g (0.052 mol) of triethylamine, and 28.6 g (0.1% of trimethylsilyltrifluoromethanesulfonate) was added.
(3 mol) was added dropwise while controlling so as not to exceed 10 ° C, the reaction temperature was adjusted to 0 to 10 ° C, and the reaction was aged for 30 minutes. 24.0 g (0.13 mol) of 3-tert-butoxychlorobenzene, 3.2 g (0.13 mol) of metallic magnesium, and 40 g of THF were used in this solution to control a Grignard reagent prepared by a conventional method so as not to exceed 10 ° C. While dripping. Further, the reaction was ripened for 30 minutes at a reaction temperature of 0 to 10 ° C. After adding 300 g of 20% ammonium chloride aqueous solution to the reaction solution to stop the reaction and perform liquid separation, chloroform 3 was added to the organic layer.
00g was added. After the organic layer was washed twice with 200 g of water, the solvent was distilled off under reduced pressure to obtain an oil. When this oily substance was subjected to column chromatography (silica gel: extract, chloroform-methanol), the yield was 10.
5 g (yield 29%), tris (3-tert-butoxyphenyl) trifluoromethanesulfonate having a purity of 99%
The sulfonium was isolated.

Nuclear magnetic resonance spectrum (NMR), infrared spectrum (IR), elemental analysis value and ultraviolet absorption spectrum (UV) of tris (3-tert-butoxyphenyl) sulfonium trifluoromethanesulfonate obtained.
The results are shown below. As comparative examples, values of ultraviolet absorption spectra of triphenylsulfonium trifluoromethanesulfonate and tris (4-tert-butoxyphenyl) sulfonium trifluoromethanesulfonate are also shown.

[0057]

Embedded image (A) 1.25 singlet 27H (b) 7.05 to 7.06 triplet 3H (c), (e) 7.25 to 7.29 multiplet 6H (d) 7.51 to 7.57 triplet Item 3H IR: (cm ⁻¹ ) 2980, 1587, 1564, 14
77, 1423, 1394, 1369, 1263, 12
59, 1159, 1031, 933, 912, 638. Elemental analysis value: (%) C ₃₁ H ₃₉ O ₆ S ₂ F ₃ theoretical value C: 59.2 H: 6.2 analysis value C: 59.1 H: 6.1

[0058]

[Table 1]

Example 2 A reaction was conducted in the same manner as in Example 1 except that phenyl grignard was used instead of 3-tert-butoxyphenyl Grignard of Example 1, and bis (3) trifluoromethanesulfonate was used. -Tert
-Butoxyphenyl) phenylsulfonium has a purity of 98
%, 35% yield.

Example 3 Example 1 was repeated except that diphenyl sulfoxide was used in place of the sulfoxide of Example 1.
When the reaction was carried out in the same manner as in (3), (3-tert-butoxyphenyl) diphenylsulfonium trifluoromethanesulfonate was obtained with a purity of 98% and a yield of 27%.

Example 4 A reaction was conducted in the same manner as in Example 1 except that bis (4-dimethylaminophenyl) sulfoxide was used instead of the sulfoxide of Example 1, and trifluoromethanesulfonic acid (3-tert −
Butoxyphenyl) bis (4-dimethylaminophenyl) sulfonium was obtained with a purity of 98% and a yield of 27%.

Example 5 A reaction was conducted in the same manner as in Example 1 except that 4-dimethylaminophenyl Grignard was used instead of the Grignard reagent of Example 1, and trifluoromethanesulfonic acid bis (3-tert) was used. -Butoxyphenyl) (4-dimethylaminophenyl) sulfonium was obtained with a purity of 98% and a yield of 33%.

Examples 6 to 10 Trimethylsilyl-p-toluenesulfonate obtained by reacting p-toluenesulfonic acid with trimethylsilylchloride by a conventional method in place of the trimethylsilyltrifluoromethanesulfonate used in Examples 1 to 5 (Boiling point 113-1
The reaction was performed in the same manner as in Examples 1 to 5 except that (17 ° C./0.5 to 0.6 mmHg) was used, whereby sulfonium salts having the following counter anions with p-toluenesulfonic acid were obtained. . Example 6: p-Toluenesulfonic acid tris (3-ter)
t-Butoxyphenyl) sulfonium Purity 99% Yield 35% Example 7: Bis (3-tert-p-toluenesulfonate)
-Butoxyphenyl) phenylsulfonium Purity 99
% Yield 28% Example 8: p-Toluenesulfonic acid (3-tert-butoxyphenyl) diphenylsulfonium Purity 99%
Yield 25% Example 9: p-toluenesulfonic acid (3-tert-butoxyphenyl) bis (4-dimethylaminophenyl)
Sulfonium Purity 97% Yield 31% Example 10: Bis (3-ter) p-toluenesulfonate
t-Butoxyphenyl) (4-dimethylaminophenyl) sulfonium Purity 98% Yield 32%

Examples 11 to 15 Trimethylsilyl nonafluorobutanesulfonate obtained by reacting nonafluorobutanesulfonic acid with trimethylsilyl chloride by a conventional method instead of the trimethylsilyltrifluoromethanesulfonate used in Examples 1 to 5 was obtained. The reaction was performed in the same manner as in Examples 1 to 5 except that the sulfonium salt having nonafluorobutanesulfonic acid in the counter anion as described below was obtained. Example 11: Tris (3) nonafluorobutane sulfonate
-Tert-butoxyphenyl) sulfonium Purity 9
9% Yield 31% Example 12: Bis (3-nonafluorobutane sulfonate)
tert-butoxyphenyl) phenylsulfonium
Purity 99% Yield 28% Example 13: Nonafluorobutanesulfonic acid (3-te
rt-Butoxyphenyl) diphenylsulfonium Purity 99% Yield 18% Example 14: Nonafluorobutanesulfonic acid (3-te
rt-Butoxyphenyl) bis (4-dimethylaminophenyl) sulfonium Purity 98% Yield 27% Example 15: Bis (3-nonafluorobutanesulfonate)
tert-Butoxyphenyl) (4-dimethylaminophenyl) sulfonium Purity 97% Yield 25%

[Examples 16 to 19] The novel sulfonium salt having a tert-butoxy group at the 3-position obtained in Examples 1 to 15 was replaced with the same sulfonic acid as the counter anion (eg, trifluoromethanesulfonate or p-toluenesulfonate). After deprotecting in methanol or ethanol using the compound to obtain the corresponding 3-hydroxyphenylsulfonium salt almost quantitatively, di-tert-butyl-dicarbonate, chloroacetate-tert-butyl, or dihydropyran was obtained by a conventional method. By using it, a sulfonium salt having an acid labile group as shown below at the 3-position of the phenyl group was synthesized. Example 16: Bis (3) nonalifluorobutane sulfonate
-Tert-Butoxycarbonyloxyphenyl) phenylsulfonium Purity 98%, Yield 23% Example 17: Trifluoromethanesulfonic acid (3-te
rt-Butoxycarbonylmethyloxyphenyl) diphenylsulfonium Purity 98%, Yield 25% Example 18: p-toluenesulfonic acid (3-tert-
Butoxycarbonyloxyphenyl) diphenylsulfonium Purity 98%, Yield 19% Example 19: Tris (3) nonafluorobutanesulfonate
-Tert-Butoxycarbonylmethyloxyphenyl) sulfonium Purity 98%, Yield 18%

The 3-position substitution products (3-tert-butoxyphenylsulfonium salts) of the novel sulfonium salts of the above Examples 1 to 10 and 4-position substitution products (4-te) as comparative examples.
rt-butoxyphenylsulfonium salt) 248 nm
Table 2 shows the molar extinction coefficient of the ultraviolet absorption spectrum in.

As is clear from the results shown in Table 2, the sulfonium salt of the present invention has a tert-butoxy group at the 3-position rather than at the 4-position, so that light absorption at 248 nm can be reduced, and the effect is tert-butoxy. It was found that tris (tert-butoxyphenyl) sulfonium salt having a large number of -butoxyphenyl groups appeared most.

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[Table 2]

[Formulation Examples 1 to 14, Comparative Formulation Examples 1 to 5] As shown in Tables 3 and 4, the hydrogen atoms of the partial hydroxyl groups represented by the following formula (Polym.1) are replaced with tert-butoxycarbonyl groups. Protected polyhydroxystyrene, partially represented by the following formula (Polym.2) hydrogen atom of the hydroxyl group protected by tert-butyl group, or partially hydroxyl group represented by the following formula (Polym.3) A polyhydroxystyrene in which a hydrogen atom is protected by a tetrahydropyranyl group, an acid generator selected from onium salts represented by the following formulas (PAG.1) to (PAG.5), and a formula (DRI.1) 2,2′-bis (4-tert-butoxycarbonyloxyphenyl) propane dissolution inhibitor was dissolved in 1-ethoxy-2-propanol. Resist compositions having various compositions shown below were prepared.

A resist solution was prepared by filtering the obtained resist composition through a 0.2 μm Teflon filter, and then the resist solution was spin-coated on a silicone wafer and applied to a thickness of 0.8 μm.

Next, 100 parts of this silicone wafer are prepared.
Baking was performed on a hot plate at 120 ° C. for 120 seconds. Furthermore, an excimer laser stepper (Nikon Corporation, NSR2005
Exposure was performed using EXNA = 0.5), baking was performed at 90 ° C. for 60 seconds, and development was performed with a 2.38% tetramethylammonium hydroxide aqueous solution, whereby a positive pattern could be obtained.

The obtained resist pattern was evaluated as follows. The results are shown in Tables 3 and 4. Resist pattern evaluation method : First, the sensitivity (Eth) was determined. Next, the exposure amount for resolving the top and bottom of a line and space of 0.35 μm at a ratio of 1: 1 is set as the optimum exposure amount (sensitivity: Eop), and the minimum line width of the separated line and space in this exposure amount is set. Was used as the resolution of the evaluation resist. The shape of the resolved resist pattern was observed using a scanning electron microscope.

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[Table 3]

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[Table 4]

[Formulation Examples 15 to 28, Comparative Formulation Examples 5 to 8]
As shown in Tables 5 and 6, the following (PAG.6
.About.8) or the above-mentioned (PAG4,5) was used, and a positive type pattern was obtained in the same manner as in the above formulation example 1. In addition,
A nitrogen-containing compound for PED stability was added to formulation example 28 as an additive.

The obtained resist pattern was evaluated in the same manner as above. Further, the PED stability of the resist is determined by performing PEB after changing the standing time after exposure with the optimum exposure amount, and the time when the change of the resist pattern shape is observed, for example, the line pattern becomes T-top, and the resolution can be resolved. It was evaluated by the time when it disappeared. The longer this time, the better the PED stability. The above results are shown in Tables 5 and 6.

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[Table 5]

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[Table 6]

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Toshinori Ishihara 28-1 Nishi-Fukushima, Nakakubiki-gun, Nakakubiki-gun, Niigata Shin-Etsu Chemical Co., Ltd. Synthetic Technology Laboratory (72) Inventor Shigehiro Nagura Kubiki-mura, Nakakubiki-gun, Niigata Prefecture 28-1 Nishi-Fukushima Shin-Etsu Chemical Co., Ltd. Synthetic Technology Laboratory

Claims (1)

[Claims] 1. A sulfonium salt represented by the following general formula (1), which has at least one acid labile group at the 3-position of the phenyl group in the molecule. Embedded image (Wherein R ¹ is a hydrogen atom, an alkyl group, an alkoxy group or a dialkylamino group, OR ² is an acid labile group, Y is a substituted or unsubstituted alkyl sulfonate or aryl sulfonate, and n is n An integer from 0 to 2, m
Is an integer of 1 to 3, and the sum of n and m is 3. )