JP2000056459A - Resist composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resist composition useful as a negative resist for ArF excimer laser beam exposure by incorporating the polymer of an α-substituted acrylate having a group capable of forming an intramolecular ester by lactonization in the ester part and a photoacid-generator. SOLUTION: This resist composition contains the polymer of an α-substituted acrylate having a group capable of forming an intramolecular ester by lactonization in the ester part and the photoacid-generator, and the polymer has the repeating units of the formula, and the polymer may be a copolymer of the above-mentioned α-substituted acrylate with the other ester, thus permitting the characteristics of the resist composition to be changed in accordance with the use purpose of the resist composition. In the formula, each of R1 and R2 is a 1-6C hydrocarbon group, and it is preferred that each is an alkyl group such as methyl, ethyl, propyl, butyl, and the like; and (m) is 2, 3, or 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a semiconductor integrated circuit (IC), particularly to a fine processing technique. More specifically, the present invention relates to a resist composition that forms a "negative" pattern by photolithography in microfabrication.

[0002]

2. Description of the Related Art In recent years, semiconductor ICs have become increasingly highly integrated, and in photolithography used for microfabrication in the manufacture thereof, the exposure light source has shifted from i-line to KrF excimer laser light (wavelength: 248 nm) having a shorter wavelength. Exposure with ArF excimer laser light (wavelength 193 nm) having a shorter wavelength is being studied for further miniaturization. ArF excimer laser exposure technology is the most promising next-generation exposure technology. However, in resin materials for resists that have been used for exposure at wavelengths prior to KrF excimer laser exposure technology, they are included in molecules to provide etching resistance. Since the benzene ring (phenyl group) has the property of absorbing short-wavelength light, the transmittance to ArF excimer laser light having a shorter wavelength is too low, and the photoreaction does not occur even when exposed to light. (A part very close to), and the pattern could not be formed by development.

Therefore, as a resin material of a resist, an acrylic skeleton having the highest transparency among organic polymers is used as a resin skeleton, and a transmittance to an ArF excimer laser beam becomes almost 0% as an etching resistant group, resulting in a photoreaction. Has been developed using an aliphatic group such as an adamantyl group, which does not reduce the transmittance, in place of the conventional phenyl group, which occurs only on the very surface of the resist layer (JP-A-9-73173). .

[0004]

The resists for ArF excimer laser exposure which have been developed so far have been only positive resists, but no negative resists. When actually performing fine processing using a resist, considering the reflection from the substrate due to the step of the processed substrate and the deterioration of the exposure profile due to the difference in the resist film thickness, the reduction of residues at the time of peeling, etc.
There is a processed layer in which a negative resist having few exposed portions is more advantageous than a positive resist, and it is necessary to develop a negative resist.

Therefore, an object of the present invention is to provide a resist composition useful as a negative resist for ArF excimer laser exposure.

[0006]

Means for Solving the Problems The resist composition of the present invention comprises a polymer of an α-substituted acrylate having a group for forming an intramolecular ester by lactonization in an ester portion, and a photoacid generator. Features.

[0007] The polymer in the resist composition of the present invention may be a homopolymer of an α-substituted acrylate having a group that forms an intramolecular ester by lactonization in the ester portion, It may be a copolymer of an α-substituted acrylate having an ester forming group in the ester portion and another ester. By using a copolymer as the polymer component in the resist composition of the present invention, the characteristics of the resist composition can be changed according to the purpose of use of the resist composition. For example, by using a copolymer with an ester having a structure capable of imparting dry etching resistance, the resist composition of the present invention can be advantageously used in a semiconductor IC manufacturing process involving dry etching.

When the polymer is such a copolymer,
An ester other than the α-substituted acrylate having a group that forms an intramolecular ester by lactonization in the ester portion is
An acrylate having an alicyclic group in the ester portion or an α-substituted acrylate is preferred.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer of an α-substituted acrylate ester having a group for forming an intramolecular ester by lactonization in the ester portion used in the resist composition of the present invention can have a repeating unit represented by the following formula. .

[0010]

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In this formula, R ¹ and R ^{2 each} have 1 to 1 carbon atoms.
And m is an integer of 2 to 4. Preferably, R ¹ and R ² are alkyl groups such as methyl, ethyl, propyl and butyl groups. Further, R ¹ and R ² may be the same or different.

Since such a polymer has a carboxyl group and a hydroxyl group simultaneously in the ester portion, it is easily dissolved in an alkaline solution. On the other hand, such a polymer forms a lactone structure by causing a lactonization (intramolecular esterification) reaction between the carboxyl group and the hydroxyl group of the ester portion by an acid. Then, the polymer having the lactone structure formed by the acid becomes difficult to dissolve in the alkaline solution.

Accordingly, the resist composition of the present invention containing a polymer of an α-substituted acrylate ester having a group which forms an intramolecular ester by lactonization in the ester portion, can form an acid from the acid generator in the composition by exposure. Before being generated, it is soluble in an alkaline solution, but after exposure, the polymer in the exposed area becomes insoluble in the alkaline solution due to the action of the acid generated from the acid generator, so that a negative pattern can be formed by exposure. That is, the resist composition of the present invention can be used as a negative resist.

The polymer used in the resist composition of the present invention may be a copolymer containing a repeating unit of the above formula (1) and another repeating unit. Use of such a copolymer containing a repeating unit having a portion having dry etching resistance particularly provides the resist composition with sufficient resistance to dry etching used in the process of manufacturing a semiconductor IC. It is effective for A typical example of the repeating unit having a portion having dry etching resistance is a repeating unit obtained from an acrylate or an α-substituted acrylate having an alicyclic group in the ester portion, which is represented by the following formula (2) Can be represented by

[0015]

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R ^{A in} this formula is hydrogen, halogen (eg, chlorine, bromine, etc.), or a substituted or unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms (eg, methyl, ethyl, represents a methylol group, etc.), R ^B is alicyclic hydrocarbon group.

[0017] Examples of the alicyclic hydrocarbon group R ^B of the above formula, the following items compound include a monovalent group to the backbone. (1) Adamantane and its derivatives (2) Norbornane and its derivatives (3) Perhydroanthracene and its derivatives (4) Perhydronaphthalene and its derivatives (5) Tricyclo [5.2.1.0 ^2,6 ] decane and (6) Cyclohexane and its derivatives (7) Bicyclohexane and its derivatives (8) Spiro [4,4] nonane and its derivatives (9) Spiro [4,5] decane and its derivatives

Of these, more preferred alicyclic hydrocarbon groups are adamantyl, norbornyl, cyclohexyl, tricyclo [5.2.1.0 ^2,6 ] decanyl and the like, and particularly preferred is adamantyl. It is.

As described above, the resist composition of the present invention having dry etching resistance contains a copolymer represented by the following general formula as a polymer component.

[0020]

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In the formula, R ¹ , R ² , R ^A , R ^B , m
Is as described above, p and q are both integers of 1 or more, and preferably the value of p + q is such that the weight average molecular weight of the copolymer is 1,000 to 35,000. .

When the polymer of the resist composition of the present invention is a copolymer, the intramolecular ester is converted to a lactone to prevent the unexposed portion from being dissolved in an alkaline developer after exposure. The proportion of the α-substituted acrylate having a group to be formed in the ester portion in the copolymer is 3
It is suitable that the content is 5 mol% or more (that is, the proportion of the repeating unit of the formula (1) in the copolymer is 35 mol% or more).

Needless to say, a composition using a polymer of only an α-substituted acrylate ester having a group that forms an intramolecular ester by lactonization in the ester portion is also useful as a negative resist composition. For example, for evaluation of an exposure apparatus, a resist material having no dry etching resistance can be used as long as a resist pattern can be formed, and only an α-substituted acrylate having a group that forms an intramolecular ester by lactonization in an ester portion can be used. The resist composition of the present invention using a polymer can be greatly utilized in such applications.

The polymer used in the resist composition of the present invention, whether it is a homopolymer or a copolymer, can be easily prepared by polymerizing a predetermined monomer using a usual method of organic synthesis. Can be. For example, a solution containing a monomer and a polymerization initiator is heated and polymerized, and the produced polymer can be separated and recovered from the solvent. Examples of the synthesis of the polymer will be more specifically described in the following examples. However, methods for preparing such polymers are well known and need not be elaborated upon further here.

The molecular weight of the polymer contained in the resist composition of the present invention can be appropriately selected according to the purpose of use. However, the polymer in the present invention, whether a homopolymer or a copolymer, has a weight average molecular weight of 1,000.
Those having a range of ~ 35,000 are preferred. I mean,
If the weight average molecular weight is less than 1,000, a resist film may not be formed sufficiently. If the weight average molecular weight is more than 35,000, cracks may occur in the formed film.

The resist composition of the present invention contains an acid generator which is a component for changing the solubility of the exposed portion of the polymer in an alkaline solution to make the portion insoluble in an alkaline developer. . As the acid generator, any substance capable of generating an acid upon exposure (that is, upon irradiation with radiation including ArF excimer laser light), and the generated acid being effective for promoting the above-described lactonization, may be used. Available. As a practical problem, a substance appropriately selected from substances generally used in the field of resist materials can be used. For example, various substances represented by the following formulas (4) to (8) can be used. However, the acid generator of the present invention is not limited to these.

[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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The acid generator is preferably contained in the resist composition of the present invention at a ratio of 1 to 20% by weight based on the weight of the polymer component. When the amount of the acid generator is less than 1% by weight of the polymer, the pattern formed cannot be formed as expected because of insufficient acid generated by exposure. When the amount of the acid generator exceeds 20% by weight, polymer components are contained. The amount is relatively small, which is disadvantageous for the characteristics of the resist film.

The resist composition of the present invention can be used in the same manner as a general resist material. More specifically, a solution dissolved in a suitable solvent is applied to the surface of a substrate on which a resist pattern is to be formed, and then the coating solvent is evaporated to form a resist film, which is then exposed and developed to obtain a predetermined resist. A pattern can be formed. As the solvent, for example, cyclohexanone, propylene glycol methyl ether acetate (PGME
Organic solvents such as A) and lactic acid esters can be mentioned, but the solvent is not limited to these. The use of a light source having an extremely short wavelength such as ArF excimer laser light for exposure is advantageous for forming a fine resist pattern. That said, light sources of other wavelengths can be used. An alkaline developer can be used for development, and typical alkaline developers include tetramethylammonium hydroxide (TMAH) and tetrabutylammonium hydroxide (TBAH).
H), an aqueous solution of tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), or the like.

[0034]

The present invention will be further described with reference to the following examples.
Of course, the invention is not limited to these examples.

Example 1 This example describes the preparation of a base resin for the resist composition of the present invention.

In 1,4-dioxane, adamantyl methacrylate and 3-hydroxy-1-methylcarboxylbutyl methacrylate are mixed at a molar ratio of 3: 7,
The solution was charged in a eggplant-shaped flask as a weight% solution. To this flask, N, N'-azobisisobutyronitrile (AIBN), which is a radical polymerization initiator, was added at 1 mol% of the total number of moles of the monomer, and the flask was immersed in an oil bath at 80 ° C. for 8 hours while stirring. did. Eight hours later, the flask was taken out of the oil bath and allowed to return to room temperature, the contents of the flask were poured into a large amount of diethyl ether, and the resulting precipitate was separated by filtration, collected, and dried. The dried precipitate was dissolved again in tetrahydrofuran (THF) to form a solution. The solution was poured into a large amount of diethyl ether, and the resulting precipitate was separated by filtration, collected, and dried sufficiently.

[0037]

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A 1: 1 copolymer resin of adamantyl methacrylate and 4-hydroxy-1-methylcarboxylbutyl methacrylate represented by the following formula was obtained in a yield of 34% by weight. The determination of the resin composition was performed using ¹³ C-NMR. Also, gel permeation chromatography (GPC)
The resin had a weight average molecular weight (Mw) of 3,400 (dispersion degree 2.24) measured by the method described in (1).

Example 2 3-Hydroxy- of Example 1
Example 1 was repeated except that 1-methylcarboxyl butyl methacrylate was replaced with 4-hydroxy-1-methyl carboxyl pentyl methacrylate. Lower formula

[0040]

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A 1: 1 copolymer resin of adamantyl methacrylate and 4-hydroxy-1-methylcarboxylpentyl methacrylate represented by the following formula was obtained in a yield of 23% by weight. The determination of the resin composition was performed using ¹³ C-NMR. The weight average molecular weight (Mw) of this resin measured by GPC was 2,840 (dispersion degree 3.08).

Example 3 Example 1 was repeated except that the adamantyl methacrylate of Example 1 was replaced with cyclohexyl methacrylate. Lower formula

[0043]

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A 60:40 copolymer resin of cyclohexyl methacrylate and 3-hydroxy-1-methylcarboxylbutyl methacrylate represented by the following formula was obtained in a yield of 42% by weight. The determination of the resin composition was performed using ¹³ C-NMR. The weight average molecular weight (Mw) of this resin measured by GPC is 5,430 (dispersion degree 2.5
6).

Example 4 Example 4 was repeated except that adamantyl methacrylate and 3-hydroxy-1-methylcarboxylbutyl methacrylate of Example 1 were replaced with cyclohexyl methacrylate and 4-hydroxy-1-methylcarboxylpentyl methacrylate. 1 was repeated. Lower formula

[0046]

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A 60:40 copolymer resin of cyclohexyl methacrylate and 4-hydroxy-1-methylcarboxylpentyl methacrylate represented by the following formula was obtained in a yield of 38% by weight. The determination of the resin composition was determined by ¹³ C-NMR
This was performed using The weight average molecular weight (Mw) of this resin measured by GPC was 3,150 (dispersion degree 2.8).
7).

Example 5 As a base resin, adamantyl methacrylate prepared in Example 1 and 3-hydroxy-
A resist composition was prepared using a copolymer resin having a molar composition ratio of 1: 1 with 1-methylcarboxylbutyl methacrylate. In this copolymer resin, as a photoacid generator,
Lower formula

[0049]

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TPS-105 commercially available from Midori Kagaku Co., Ltd. represented by the following formula was added in an amount of 2% by weight of the resin, and this was added to propylene glycol methyl ether acetate (P
GMEA) to prepare a resist solution having a resin amount of 15% by weight. This resist solution is spin-coated on a silicon wafer having enhanced adhesion with hexamethyldisilazane (HMDS), baked on a hot plate at 100 ° C. for 60 seconds to evaporate the coating solvent,
A resist layer having a thickness of 0.50 μm was formed. This wafer is placed on an ArF excimer laser stepper (NA = 0.55)
To expose the electronic circuit pattern on the resist layer by exposure through a reticle, and immediately after exposure, baked on a hot plate at 80 ° C. for 120 seconds. The baked wafer was immersed in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) at 27 ° C. for 120 seconds, developed, washed and dried, and the exposed portion remained as a circuit pattern. It was confirmed that the obtained composition functioned as a negative resist. The minimum resolution line width of this negative resist was 0.1 at an exposure dose of 12 mJ / cm ² .
It was 17 μm.

Example 6 The photoacid generator was represented by the following formula:

[0052]

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Example 5 except that TPS-103 commercially available from Midori Kagaku Co., Ltd. was replaced by
Was repeated, the minimum resolution line width was 10 mJ /
A negative resist pattern of 0.17 μm in cm ² was formed.

Example 7 The adamantyl methacrylate prepared in Example 2 and 4-hydroxy-
Except for using a copolymer resin having a molar composition ratio of 1: 1 with 1-methylcarboxylpentyl methacrylate,
When Example 5 was repeated, the minimum resolution line width was 8
A negative resist pattern of 0.17 μm was formed at mJ / cm ² .

Example 8 Example 7 was repeated, except that the photoacid generator was changed to TPS-103 commercially available from Midori Kagaku Co., Ltd., and the minimum resolution line width was 7.2 m.
A 0.17 μm negative resist pattern was formed at J / cm ² .

[Example 9] Copolymer resin of cyclohexyl methacrylate and 3-hydroxy-1-methylcarboxylbutyl methacrylate prepared in Example 3 having a molar composition ratio of 60:40 was used as a base resin, and Example 5 was repeated except that the immersion time in the 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) was 30 seconds, and the minimum resolution line width was 0.3 mm at an exposure dose of 6 mJ / cm ² . A 175 μm negative resist pattern was formed.

Example 10 Example 9 was repeated, except that the photoacid generator was changed to TPS-103 commercially available from Midori Kagaku Co., Ltd., and the minimum resolution line width was 4.8.
A negative resist pattern of 0.17 μm was formed at mJ / cm ² .

[Example 11] A copolymer resin of cyclohexyl methacrylate and 4-hydroxy-1-methylcarboxylpentyl methacrylate prepared in Example 4 and having a molar composition ratio of 60:40 was used as a base resin.
Example 5 was repeated except that the immersion time in 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution was 30 seconds, and the minimum resolution line width was 5.5 mJ / cm. ² , a negative resist pattern of 0.16 μm was formed.

Example 12 Example 11 was repeated with the photoacid generator replaced by TPS-103 commercially available from Midori Kagaku Co., Ltd., and the minimum resolution line width was 3.
A negative resist pattern of 0.17 μm was formed at 9 mJ / cm ² .

[0060]

As described above, according to the present invention,
The use of a resist composition capable of forming a negative resist pattern by ArF excimer laser exposure becomes possible, greatly contributing to the production of a highly integrated next-generation semiconductor IC that requires finer processing than ever before. .

Claims (6)

[Claims] 1. A resist composition comprising a polymer of an α-substituted acrylate having a group that forms an intramolecular ester by lactonization in an ester portion, and a photoacid generator. 2. The polymer has a repeating unit represented by the following formula:
The resist composition according to claim 1. Embedded image (R ¹ and R ^{2 in} this formula are each a hydrocarbon group having 1 to 6 carbon atoms, and m is an integer of 2 to 4) 3. The resist composition according to claim 1, wherein the polymer is a homopolymer of an α-substituted acrylate ester having a group that forms an intramolecular ester by lactonization in an ester portion. 4. The polymer according to claim 1, wherein the polymer is a copolymer of an α-substituted acrylate ester having a group that forms an intramolecular ester by lactonization in the ester portion and another ester. Resist composition. 5. An acrylate ester or an α-substituted acrylate ester having an alicyclic group in the ester portion other than the α-substituted acrylate ester having a group that forms an intramolecular ester by lactonization in the ester portion. The resist composition according to claim 4, wherein 6. The polymer according to claim 5, wherein the polymer is represented by the following formula.
The resist composition as described in the above. Embedded image (In the formula, R ¹ and R ² are a hydrocarbon group having 1 to 6 carbon atoms, and R ^A is hydrogen, halogen, or a substituted or unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms. R ^B is an alicyclic group, m is an integer of 2 to 4,
p and q are integers of 1 or more)