JPH05281744A - Radiation sensitive resin composition - Google Patents

Abstract

PURPOSE:To provide a new radiation sensitive resin compsn. having high sensitivity to radiation. CONSTITUTION:This radiation sensitive resin compsn. is obtd. by mixing 5g of t-butyl phthalate of poly(hydroxystyrene) (having 8500 weight average mol.wt. and 1.2 specific dispersion), 0.5g of triphenylsulfonium trifluoromethane sulfonate, and 20ml of 2-methoxyethyl acetate as a solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used as a constituent material of a resist used in the manufacture of semiconductor devices and the like, and is a novel radiation sensitive material which is sensitive to radiation such as light, electron beam, X-ray or ion beam. Resin composition.

[0002]

2. Description of the Related Art In recent years, processing technology on the order of submicrons has become necessary with the high integration of LSIs. Therefore, for example, in the etching process in the manufacture of LSI, a dry etching technique capable of highly precise and fine processing is adopted.

Here, the dry etching technique means that a substrate to be processed is covered with a resist, the resist is patterned by using light or an electron beam, and the obtained pattern is used as a mask to react the substrate with reactive gas plasma. This is a technique for etching the portion exposed from the mask. Therefore, the resist used in the dry etching technique is composed of a material having a resolution of submicron order and sufficient resistance to reactive gas plasma.

Therefore, at present, as a resist material,
A positive photoresist composed of a diazonaphthoquinone compound and a phenol novolac resin is used, and as an exposure device, a reduction projection exposure device using g-line or i-line of a mercury lamp is used. However, at the stage where it is required to process half-micron or smaller dimensions with high accuracy, high resolution and a large focus margin, which surpass those of current lithography technology, are required. Therefore, reduction projection exposure using a short wavelength light source is required. Law and electron beam exposure are indispensable. Therefore, various resist materials suitable for such a lithography technique have been studied and various proposals have been made.

[0005] For example, Japanese Patent Laid-Open No. 61-240237 discloses a deep U having a wavelength of less than 300 nm.
Techniques relating to lithographic resist compositions that can be used in V are disclosed. According to this, the use of a positive resist composed of a photosensitive solubilizer compound such as trans-2-diazodecalin-1,3-dione and an alkali-soluble matrix such as a novolak resin improves the resolution characteristics. It is stated that it can be achieved.

A technique using a radiation-sensitive polymer is disclosed in Japanese Patent Laid-Open No. 1-1201654.
That is, it is described that the acetoin ester of poly (p-styrenesulfonic acid) can be used as a positive resist as in the technique disclosed above and a high resist contrast can be achieved.

A negative resist has also been proposed. The one disclosed in Japanese Patent Laid-Open No. 62-10644. This is to enhance the sensitivity of a deep UV / EB photosensitive resin composition while maintaining a narrow distribution of substituted poly (styrene) and maintaining high resolution, and developing with an organic solvent using dichlorobenzene as a photosensitizer. This is a type of resist.

Japanese Unexamined Patent Publication No. 1-293338 discloses Kr.
A technique relating to a photosensitive resin composition suitable for F excimer laser exposure is disclosed. According to it, a small amount of glycidyl group is introduced into poly (vinylphenol), and
It is described that by using bis azide as a photosensitizer in combination, the cross-sectional shape of the resist can be improved more than ever before.

[0009]

By the way, when the light in the deep UV region of a mercury lamp is used as a short-wavelength light source, the illuminance thereof is extremely low, so that a resist with extremely high sensitivity is required. Further, even when a KrF excimer laser is used as the light source, a highly sensitive resist is required due to the attenuation of the light intensity in the reduction optical system.

Further, in the electron beam lithography, the pattern forming method is different from the photolithography in that the wafer surface is sequentially drawn by the electron beam, so that it cannot be put to practical use unless the sensitivity of the resist is high. Since the number of beam shots will increase remarkably as the degree of integration of semiconductor devices further increases in the future, the requirement for sensitivity to the resist becomes the most important factor together with the resolution.

However, the above-mentioned conventional radiation-sensitive resin requires at least a considerable light exposure amount or electron beam exposure amount for pattern formation, and cannot meet the above-mentioned demand. Therefore, the advent of highly sensitive resists for short wavelength light sources has been earnestly desired.

The present invention has been made in view of the above points, and therefore, an object of the present invention is to prevent radiation.
It is to provide a novel radiation-sensitive resin composition having high sensitivity.

[0013]

In order to achieve this object, according to the radiation-sensitive resin composition of the present invention, a dicarboxylic acid t-butyl ester of a phenol resin as a first component, and , An acid generator as a second component that decomposes by the action of radiation such as an electron beam, an X-ray, or an ion beam to generate an acid.

The dicarboxylic acid t-butyl ester of poly (hydroxystyrene) of phenol resin, which is the first component, is a typical hydrophobic substance. As it is released, it is converted to a hydrophilic and acidic carboxylic acid (half ester of dicarboxylic acid of phenol resin). The removed t-butyl group becomes isobutylene. Further, the acid generator as the second component generates an acid for removing the t-butyl group from the first component by the action of radiation. Therefore, for example, when a film of the photosensitive resin composition of the present invention is formed on the lower surface of a silicon substrate (a method of forming the film will be described later) and the film is selectively irradiated with radiation, the irradiation part of the film is exposed. Only the first component of is converted to a hydrophilic and acidic carboxylic acid. Therefore, when this coating film that has been selectively irradiated with radiation is developed with an alkali developing solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH), the radiation irradiation portion is dissolved and a positive resist pattern is obtained.
Further, when a non-polar solvent such as cyclohexane is used for development, a non-irradiated portion which is hydrophobic is dissolved, so that a negative resist pattern is obtained.

Since the first component is converted into a hydrophilic and acidic carboxylic acid by the action of a slight amount of acid from the acid generator, the exposure amount when exposing the radiation-sensitive resin composition is Since the exposure amount that can generate a desired acid from the acid generator is sufficient, the composition has high sensitivity.
Further, since the phenol resin is used, the dry etching resistance is also secured.

The phenolic resin which can be used here may be various ones, for example, poly (hydroxystyrene) or novolac resin. Poly (hydroxystyrene) having a relatively wide molecular weight distribution is available from Maruzen Petrochemical Co., Ltd., for example.
Further, those having a narrow molecular weight distribution are disclosed, for example, in Japanese Patent Application No. 59-19
It can be prepared by an anionic polymerization method as described in 9705.

When poly (hydroxystyrene) is used as the phenolic resin, dicarboxylic acid t-butyl ester of poly (hydroxystyrene) represented by the following formula (2) can be used as the first component. However, n in the formula (2) is a positive integer, and R is an alkylene group (including a case where a plurality of the alkylene groups are repeated), for example,-.
(CH _{2) m} - (m is a positive integer), or an arylene group such as those of the formula (I) is represented by the (ii) or (iii).

[0018]

[Chemical 2]

The suitable molecular weight range of the first component can be arbitrarily selected depending on the coating property of the radiation-sensitive resin composition on a substrate. When the radiation-sensitive resin composition is used as a resist, for example, it is possible to form a solid film, be soluble in a solvent for preparing a resist coating solution, obtain a desired resolution, etc. Therefore, the molecular weight is preferably in the range of 500 to 100,000, more preferably 3000 to 50,000. The first component can be synthesized with any suitable molecular weight, but the molecular weight may be determined by the molecular weight of available phenol resin.

As the acid generator which is the second component of the radiation-sensitive resin composition of the present invention, various conventionally known acid generators can be used. However, hydrohalic acid is not very suitable because it has a weak catalytic action. For example, various sulfonium salts represented by the following formula (I) and formula (II), various iodonium salts represented by the following formula (III) and formula (IV), the following formula (V) and formula (V)
Various aromatic compounds represented by I) having at least one trichloromethyl group, various p-toluenesulfonates represented by the following formula (VII), sulfonic acid esters and the like are stronger than hydrohalic acid. It is suitable because it generates an acid.

[0021]

[Chemical 3]

[0022]

[Chemical 4]

However, X in the formulas (I) to (IV)
^- is, for example, _{^{B 4 -, AsF 6 -,}} SbF 6 -, ClO
₄ ^- or CF ₃ SO ₃ ^- represents, R in the formula (V)
Is, for example, CCl ₃ or the following formulas (A), (B),
Represents a group represented by (C), (D) or (E), R ¹ in formula (VI) is, for example, Cl or H, and R ² is, for example, Cl or CCl ₃ ; R in the formula (VII) represents, for example, a group represented by the following formula (F) or formula (G).

[0024]

[Chemical 5]

The above-mentioned acid generators are commercially available or, for example, JV Crivel (JV Cri).
Velo) [Journal of Polymer Science, Polymer Chemistry Edition (J. Polymer Sci., Polymer C
hem. Ed. , 18, 2677 (1980)].

These acid generators are based on the weight of the dicarboxylic acid t-butyl ester of the phenol resin used.
The range of 0.01 to 50% by weight, preferably 0.05 to 3
It is advisable to add it in an amount in the range of 0% by weight. If it is out of this range, the sensitivity of the radiation-sensitive resin composition will be low, or the coating film will be fragile.

When the radiation-sensitive resin composition is used, when the composition is applied onto a substrate by spin coating to form this film on the substrate, a solvent for preparing a coating solution for that purpose is required. Examples of the solvent include methyl isobutyl ketone (MIBK), cellosolve acetate, methyl cellosolve acetate, dioxane, DMSO and the like.

In using the radiation-sensitive resin composition, the film of the composition is irradiated with radiation and then the sample is heat-treated to enhance the action of the acid generator in the radiation-irradiated portion. Can be urged.

[0029]

EXAMPLES Examples of the radiation-sensitive resin composition of the present invention will be described below. Numerical conditions such as materials used and their amounts, processing time, processing temperature, and film thickness, which are mentioned in the following description, are only suitable examples within the scope of the present invention. Therefore, the present invention is not limited to these conditions. In the examples described below, the dicarboxylic acid t-butyl ester of phenol resin is poly (hydroxystyrene) phthalic acid t-butyl ester (shown in (2) above, where R is of the formula (a)). thing.)
And triphenylsulfonium trifluoromethanesulfonate (in formula (I), X ⁻ is CF) as an acid generator.
₃ SO ₃ ^- in which one. ) Is an example using.

1. Synthesis of phthalic acid t-butyl ester of poly (hydroxystyrene) 1-1. Synthesis of poly (hydroxystyrene): commercially available p
-Tert-Butoxystyrene (manufactured by Hokuko Kagaku) was used as a starting material, which was distilled under reduced pressure.
Poly (hydroxystyrene) is synthesized by the method described in Japanese Patent No. 705 as follows.

10 g of monomer obtained by vacuum distillation
And a pentane solution of sec-butyllithium (2.5 ×
10 ⁻³ mol) in 100 ml of benzene obtained by distillation from sodium benzophenone at room temperature. After 4 hours, stop the reaction with methanol,
The reaction product is put into methanol. The polymer obtained is dried under vacuum overnight, then dissolved in 1 l (acetone) of acetone and then heated to 60 ° C. With respect to this solution, while maintaining the temperature of 60 ° C and stirring, 5%
5 ml of hydrobromic acid was added and left for 6 hours. afterwards,
After the acetone is distilled off, the residue is thoroughly washed with water and dried under vacuum overnight.

Thus, 5.0 g of poly (hydroxystyrene) was obtained. Weight average molecular weight (Mw) of this
As a result of measuring the specific dispersion (Mw / Mn), the following values were obtained.

Mw: 5200, Mw / Mn: 1.15.

1-2. Synthesis of phthalic acid t-butyl half-ester chloride: The phthalic acid t-butyl half-ester chloride is also synthesized as follows.

14.8 g of phthalic anhydride, 7.6 g of t-butanol, and 1 g of 4-N, N-dimethylaminopyridine (DMAP) are dissolved in 50 ml of pyridine and reacted overnight at room temperature. The reaction product obtained is diluted with ethyl acetate and then made weakly acidic with 2N hydrochloric acid.
Then the organic phase thereof is separated. The separated product is washed with water, washed with a copper sulfate aqueous solution, washed again with water, further washed with saturated saline, and then dried with copper sulfate. Then, by distilling off the solvent from the organic phase,
18.0 g of phthalic acid t-butyl half ester are obtained.

The phthalic acid t-butyl half ester obtained is dissolved in 200 ml of benzene and cooled with ice.
Next, oxalyl chloride 3 was added to the benzene solution.
0 g and 0.5 ml of dimethylformamide (DMF) are added. After stirring the mixture below 20 ° C. for about 2 hours, benzene and excess oxalyl chloride are distilled off to give 18.2 g of phthalic acid t-butyl half ester chloride.

1-3. Poly (hydroxystyrene) phthalic acid t-butyl ester: 10.0 g of the obtained phthalic acid t-butyl half ester chloride, poly (hydroxystyrene) 5.0 g, and DMAP 1.0 g were dissolved in pyridine 50 ml. And leave it at room temperature overnight. The reaction product is put into water and extracted with ethyl acetate. The organic phase is washed with a saturated aqueous solution of sodium hydrogencarbonate, water, an aqueous solution of copper sulfate, water and a saturated saline solution in that order, and then dried with magnesium sulfate. next,
The solvent of this organic phase is distilled off, the remaining solid is dissolved in a small amount of tetrahydrofuran (THF) and it is poured into methanol. The resulting precipitate is filtered and the precipitate separated by filtration is dried under vacuum overnight. In this way, 12 g of the desired compound is obtained.

The values of the weight average molecular weight and the specific dispersion of the obtained phthalic acid t-butyl ester of poly (hydroxystyrene), and the results of IR analysis and NMR analysis were as follows.

Mw: 8500, Mw / Mn: 1.2.

IR: Absorption of ester at 1740 cm ^-1 .

NMR: 1.15 (t-butyl), 8.0
-7.0 (aromatic ring), 1.2-2.0 (main chain).

From the analysis by NMR, the esterification rate of poly (hydroxystyrene) is 80%. The esterification rate may be any esterification rate such that the unexposed portion of the radiation-sensitive resin composition does not dissolve in the alkali developing solution, and can be changed according to the design.

2. Pattern formation 2-1. In the case of electron beam exposure and alkaline developer: 5 g of phthalic acid t-butyl ester of poly (hydroxystyrene) (weight average molecular weight 8500, specific dispersion 1.2) and 0.5 g of triphenylsulfonium trifluoromethanesulfonate. 2-Methoxyethyl acetate 20 ml
After being dissolved in it, it was filtered with a filter having 0.2 μm pores,
Prepare a resist solution.

Hexamethyldisilazane is spin-coated on a silicon wafer, and then a resist solution is spin-coated. This is baked on a hot plate at about 80 ° C. for about 1 minute to form a resist layer having a thickness of 1.0 μm. An electron beam with an accelerating voltage of 20 kV (Elionix, E
Using LS3300 (trade name), an appropriate number of evaluation figures are drawn by changing the exposure amount. The exposed sample is baked on a hot plate at about 180 ° C. for about 2 minutes.

After that, development is carried out with an aqueous solution of tetramethylammonium hydroxide having a concentration of 0.05 mol / l (hereinafter referred to as an aqueous solution of TMAH), followed by washing with pure water.
As a result, the exposed portion is dissolved and a positive pattern is formed.

Next, the residual film thickness after development is measured. A curve, which is a value obtained by normalizing the value with the initial film thickness, is plotted against the logarithm of the exposure amount, that is, a characteristic curve is created. As a result, when sensitivity and contrast were calculated,
It was 1.2 μC / cm ² and 5.8. Further, when the pattern was observed with a scanning electron microscope (SEM), it was found that a line and space of 0.8 μm was resolved.

2-2. For electron beam exposure and non-polar solvents:
Preparation of the resist solution, formation of the resist layer, and exposure of the resist layer to an electron beam are performed under the same conditions as in Section 2-1. Approximately 180 the exposed sample on a hot plate
Bake at about ℃ for 2 minutes.

Thereafter, development is carried out for about 30 seconds using a mixed solvent of xylene / methylcyclohexane of 1: 4, followed by washing with methanol for about 30 seconds. As a result, the exposed portion remains and a negative resist pattern is formed.

Next, the residual film thickness after development is measured and 2-1
Create a characteristic curve in the same way as in Section. As a result, the sensitivity and contrast were found to be 0.8 μC / c
m ² was 4.0. Further, when the pattern was observed by SEM, it was found that a line and space of 0.8 μm was resolved.

2-3. Exposure with Xe-Hg lamp and alkaline developer: Preparation of a resist solution and formation of a resist layer are performed under the same conditions as in Section 2-1. A Xe-Hg lamp (PLA manufactured by Canon Inc.) is formed on the resist layer.
I attached it to the 501 aligner. ) Was used, and the exposure amount was changed for each wafer, and contact exposure of a chrome mask pattern was performed. The exposed sample is baked on a hot plate at about 140 ° C. for about 2 minutes.

After that, with respect to the processed sample, 0.05 m
Development is performed using an aqueous solution of hydroxylated TMAH having a concentration of ol / l, and then cleaning is performed with pure water. As a result, the exposed portion is dissolved and a positive pattern is formed.

Next, the residual film thickness after development is measured and 2-1
Create a characteristic curve in the same way as the term. As a result, the sensitivity and contrast were calculated to be 3 mJ / c, respectively.
m ² and was 2.5. Further, when the pattern was observed by SEM, it was found that a line and space of 1.0 μm was resolved.

2-4. Exposure with Xe-Hg lamp and non-polar solvent: Preparation of resist solution, formation of resist,
The exposure and the post-exposure bake are performed under the same conditions as in Section 2-3.

Thereafter, the treated sample was treated with a mixed solvent of xylene / methylcyclohexane in a ratio of 1: 4 to obtain about 3 parts thereof.
After development for 0 seconds, washing with methanol is performed for about 30 seconds. As a result, the exposed portion remains and a negative resist pattern is formed.

Next, the residual film thickness after development is measured and 2-1
Create a characteristic curve in the same way as in Section. As a result, the sensitivity and contrast were found to be 1.8 mJ / c, respectively.
m ² and 3.5. Further, when the pattern was observed by SEM, it was found that a line and space of 1.0 μm was resolved.

Although the examples of the radiation-sensitive resin composition of the present invention have been described above, the present invention is not limited to the above-mentioned examples.

For example, in the above-mentioned embodiments, phthalic acid t-butyl ester of poly (hydroxystyrene) is used as the dicarboxylic acid t-butyl ester of phenol resin, and triphenylsulfonium trifluoromethanesulfonate is used as the acid generator. However, this is just one example. Dicarboxylic acid t-butyl ester of phenol resin is used as dicarboxylic acid t-butyl ester of novolak resin, and other suitable ones such as those in which the dicarboxylic acid t-butyl ester residue is represented by the above formula (1) When the acid generator is one represented by the above formulas (I) to (VII) or another suitable one such as a sulfonic acid ester, the same effect as in the above-mentioned embodiment can be obtained. Obtainable.

Further, in the above-mentioned examples, the radiation-sensitive resin composition was exposed using an electron beam and Xe-Hg lamp light as the radiation. The radiation used for this exposure was an electron beam or Xe. -Not limited to Hg lamp light, X
The same effect as in the embodiment can be obtained by using other radiation such as a ray or an ion beam.

[0059]

As is apparent from the above description, in the radiation-sensitive resin composition of the present invention, an acid is generated from the acid generator in a portion irradiated with radiation, and the acid causes the acid to generate that portion. The t-butyl group of the dicarboxylic acid t-butyl ester of the phenol resin of 1 is released. Since this reaction progresses catalytically, the amount of acid may be very small, and therefore, the irradiation dose of the radiation required to generate the acid from the acid generator may be small, and this radiation-sensitive resin composition has The resist is highly sensitive to radiation.

Further, in the radiation-sensitive resin composition of the present invention, the t-butyl group of the dicarboxylic acid t-butyl ester of the phenol resin is acted on by the action of the catalyst generated by the acid from the acid generator in the radiation-irradiated portion. The dicarboxylic acid t-butyl ester of phenol resin, which was originally a hydrophobic substance, is converted into a hydrophilic and acidic carboxylic acid. Therefore, for example, when developing with an alkaline developing solution, the radiation irradiating part dissolves,
This radiation-sensitive resin composition can be used as a positive resist, and when it is developed with a non-polar solvent such as cyclohexane, the unirradiated radiation which is hydrophobic is dissolved, so that the radiation-sensitive resin composition is It can be used as a negative resist.

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Claims (9)

[Claims] 1. A radiation-sensitive resin composition comprising a dicarboxylic acid t-butyl ester of a phenol resin and an acid generator that decomposes to generate an acid by the action of irradiation radiation. 2. The radiation-sensitive resin composition according to claim 1, wherein the phenol resin is a poly (hydroxystyrene) or a novolac resin. 3. The radiation-sensitive resin composition according to claim 1, wherein the dicarboxylic acid t-butyl ester residue in the dicarboxylic acid t-butyl ester of the phenol resin is represented by the formula (1). (In the formula, R is an alkylene group (including a case where a plurality of the alkylene groups are repeated) or an arylene group). [Chemical 1] 4. The radiation-sensitive resin composition according to claim 1, wherein the dicarboxylic acid t-butyl ester of the phenol resin has a molecular weight in the range of 1500 to 100,000. 5. The radiation according to claim 1, wherein the acid generator is a sulfonium salt, and the addition amount thereof is 0.01 to 50% with respect to the weight of the dicarboxylic acid t-butyl ester of the phenol resin. Sensitive resin composition. 6. The radiation according to claim 1, wherein the acid generator is an iodonium salt, and the addition amount thereof is 0.01 to 50% with respect to the weight of the dicarboxylic acid t-butyl ester of the phenol resin. Sensitive resin composition. 7. The aromatic compound having at least one trichloromethyl group as the acid generator, and the addition amount thereof is 0.01 to 50% with respect to the weight of the dicarboxylic acid t-butyl ester of the phenol resin. Claim 1 characterized by
The radiation-sensitive resin composition described. 8. The sulfonic acid ester as the acid generator, and the addition amount thereof is 0.01 to 50% with respect to the weight of the dicarboxylic acid t-butyl ester of the phenol resin. Radiosensitive resin composition. 9. The acid generator is p-toluene sulfonate, and the amount of addition is t-dicarboxylic acid of phenol resin.
The radiation-sensitive resin composition according to claim 1, wherein the weight of the butyl ester is 0.01 to 50%.