JPH02129641A - Photoresist composition - Google Patents

Abstract

PURPOSE:To obtain a positive photoresist compsn. having high resolution for exposure to short wavelength light by incorporating a copolymer contg. N- substituted maleimide units into the compsn. as polymer binder. CONSTITUTION:An N-substituted maleimide copolymer comprising a copolymer consisting of an N-hydroxyphenyl maleimide unit expressed by the formula I, an N-alkyl maleimide unit expressed by the formula II, a maleic anhydride unit expressed by the formula III, and an alpha-olefin unit expressed by the formula IV, satisfying also the formula V-VII, is incorporated together with a photosensitive agent into a photoresist compsn. In the formulas I-IV, R<1> is 1-16C alkyl group or cycloakyl group; R<2> is H or 1-16C alkyl group or cycloalkyl group; R<3> is H or lower alkyl group. Thus, a photoresist compsn. having high transmittance to exposure with excimer laser light and practically good alkali developing characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive-working photoresist composition, and more particularly, it contains a copolymer containing N-substituted maleimide units as a binder polymer and is suitable for exposure to short wavelength light. The present invention relates to a positive photoresist composition having excellent resolution.

In recent years, the degree of integration of integrated circuits has become significantly higher,
Along with this, the dimensions of photoresist patterns required for microfabrication are becoming increasingly finer. In order to meet these demands, research and development on both exposure equipment and photoresist materials has been carried out intensively.In particular, with regard to exposure equipment, it has been found that shorter exposure wavelengths enable finer processing. Therefore, in place of the conventional high-pressure mercury lamp, exposure apparatuses using an excimer laser as a light source, particularly excimer laser steppers, are being put into practical use. However, compared to the progress of such exposure equipment, the development of suitable photoresist materials has lagged behind. The development of type photoresists is strongly requested.

The excimer laser stepper generally uses a potassium fluoride excimer laser as an exposure light source. Potassium fluoride excimer laser has a wavelength of 248
Generates nm light. However, the novolac resin used in conventional positive photoresists is 248n
Because of the strong absorption of light with a wavelength of m, light with sufficient energy does not reach the bottom of the photoresist layer to sensitize the photoresist, resulting in a loss of resolution and profile of the photoresist.

Although polymethyl methacrylate has relatively good light transmittance on the short wavelength side, it has poor heat resistance and cannot be developed with an alkaline aqueous solution.

On the other hand, various copolymers containing N-substituted maleimide units and their uses are already known. For example, JP-A-6
No. 1-162039 proposes a photoresist TA composition containing a copolymer of N-arylmaleimide units, styrene units and (meth)acrylic acid units, and a sensitizer.

Further, JP-A-62-186253 proposes a positive photoresist composition containing a copolymer of N-hydroxymaleimide units and isobutylene units and a quinonediamide compound.

Although the latter type of positive photoresist has excellent heat resistance, it has low transmittance to excimer laser light at a wavelength of 248 nm and has too high solubility in alkaline developer, so it cannot be used as a positive photoresist for excimer laser. As a type photoresist, there are some drawbacks in its practicality.

The present invention was made in order to solve the above-mentioned problems in conventional positive photoresist compositions, and
In particular, it is an object of the present invention to provide a positive photoresist composition that has high light transmittance and practical alkaline developability for exposure equipment using an excimer laser as a light source.

The positive photoresist composition according to the present invention for i
N-hydroxyphenylmaleimide unit represented by Fukudai; TC) maleic anhydride unit represented by the formula, and +d)-monohydrogen (wherein R2 represents hydrogen or an alkyl group or cycloalkyl group having 1 to 16 carbon atoms, and R3 represents hydrogen or a lower alkyl group It is a copolymer consisting of α-olefin units represented by the following formula, and is characterized by containing an N-substituted maleimide copolymer satisfying k+1 and a photosensitizer.

The N-substituted maleimide copolymer used as the binder polymer in the positive photoresist composition according to the present invention is disclosed in JP-A-62-151408 and JP-A-62-1.
It can be produced according to the methods described in JP-A-51409, JP-A-62-186253, and the like.

That is, maleic anhydride and an α-olefin, such as isobutylene, are copolymerized, and then this copolymer is reacted with an aminophenol and an alkylamine, which is an aliphatic primary amine, in an organic solvent. After converting a part of the maleic anhydride component in the coalescence into an N-hydroxyphenylmaleamic acid component and an N-alkylmaleamic acid component, a cyclization dehydration reaction may be performed. As the amine phenol, 0-aminophenol is preferably used, but it is not limited thereto. Further, a copolymer of maleic anhydride and an α-olefin such as isobutylene is available as a commercial product, and a commercial product related to the above synthesis can be used.

The N-substituted maleimide copolymer used in the present invention is
Consisting of the component unit represented by the above-mentioned - clothing, R1 represents an alkyl group or cycloalkyl group having 1 to 16 carbon atoms,
Preferred alkyl groups include, for example, methyl, ethyl, propyl, butyl, hexyl, decyl, etc., and preferred cycloalkyl groups include cyclohexyl.

In addition, "represents hydrogen, or an alkyl group or cycloalkyl group having 1 to 16 carbon atoms, and P represents hydrogen or a lower alkyl group. When Rlf,!, is an alkyl group or a cycloalkyl group, preferred specific examples include , for example, methyl group, ethyl group, propyl group, butyl group, hexyl group,
Examples include a decyl group, a cyclohexyl group, and when R3 is a lower alkyl group, preferred examples include a methyl group, an ethyl group, a propyl group, a butyl group, and the like. In particular, in the present invention, isobutylene is preferably used as the α-olefin component.

Furthermore, the N-substituted maleimide copolymer is required to satisfy the following, and in particular, preferably satisfies the following.

When the value of n/(k + l +m) exceeds 10, the solubility of the resulting photoresist composition in an alkaline developer decreases, and the heat resistance also decreases. (k
When the value of +1)/(k+1+m) is 0.1 or less, the solubility of the resulting photoresist composition in an alkaline developer decreases. When the value of k/(k+1) is 0.1 or less, the resulting photoresist composition is heat resistant; on the other hand, when it is 1 or more, the photoresist composition is heat resistant.
Transmission at 8 nm is reduced.

In addition, the N-substituted maleimide copolymer used in the present invention has a number average molecular weight (
Mn) is 1000 to 500000, especially 4000 to 1
A value in the range of 00,000 is desirable from the viewpoint of sensitivity, resolution, film performance, adhesion to the substrate, etc. of the resulting photoresist composition.

In the photoresist composition according to the present invention, a quinonediazide compound is used as a photosensitizer. Preferred specific examples include naphthoquinonediazide sulfonic acid ester and benzoquinonediazide sulfonic acid ester.

The photoresist composition according to the present invention comprises 95 to 50 weight percent of the N-substituted maleimide copolymer and 5 to 50 weight percent of the N-substituted maleimide copolymer.
quinonediazide compound. Since the photoresist composition according to the present invention is soluble in an organic solvent, when it is used, it is usually added in an amount of 1 to 50% by weight in an organic solvent.
It is preferably used as a solution in the range of 5 to 30 percent.

Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, and cyclohexanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve,
Preferably used are cellosolves such as methyl cellosolve acetate and ethyl cellosolve acetate, lower fatty acid esters such as butyl acetate, amides such as dimethylformamide and N-methylpyrrolidone, and dimethylformexide. The solvent may be a mixture of two or more.

Furthermore, when preparing the above solution, appropriate additives conventionally used in the preparation of photoresists, such as desensitizers, dyes, and other resins, may be added, if necessary.

The following method may be used to form a fine pattern on a substrate using the photoresist composition according to the present invention. That is, first, the solution as described above is applied onto a substrate by, for example, a spin code method, and then, for example, by hot air,
The organic solvent is removed by drying using an appropriate means such as far infrared rays or a hot plate, preferably at a temperature of 120° C. or lower, particularly preferably 100° C. or lower, to form a film. Next, a mask is brought into close contact with the film, and as described above, the film is exposed to light using an excimer laser stepper and then developed with an alkaline developer to obtain the desired pattern. As the alkaline developer, for example, an aqueous solution of an inorganic alkali such as sodium hydroxide, potassium hydroxide, or sodium silicate, or an organic alkali such as tetramethylammonium hydroxide or trimethyl-2-hydroxyethylammonium hydroxide can be used. . To obtain a practical development speed, for example, when using an aqueous tetramethylammonium hydroxide solution, the concentration is usually 0.1 to 0.
．． A range of 4N is preferred. Alcohols, surfactants, etc. may be added to the developer, if necessary.

Optical Plate ■ As described above, the positive photoresist composition according to the present invention contains an N-779 maleimide copolymer having a predetermined component composition as a binder polymer, and uses an excimer laser as a light source. It has high light transmittance to exposure equipment and practical alkaline developability.

Back Operation The present invention will be explained below with reference to synthesis examples of N-substituted maleimide copolymers and examples of the present invention, but the present invention is not limited in any way by these examples.

Synthesis Example 1 In a reaction vessel, a maleic anhydride-isobutylene copolymer, Isopan-04 manufactured by Kuraray Co., Ltd., with a molecular weight of 5.5 to 6.
5X10') 20g dimethylformamide 100+a
22.7 g of O-aminophenol and 3.8 g of isobutylamine were added thereto, and the mixture was reacted at a temperature of 85° C. under a nitrogen atmosphere for 15 hours to obtain a corresponding maleamic acid copolymer.

Next, 14 g of tri-n-butylamine as a catalyst and 50 ml of toluene as an azeotropic solvent were added to the reaction vessel, and a cyclization dehydration reaction was carried out at 140° C. for 8 hours while blowing nitrogen gas.

After the reaction was completed, the reaction mixture was poured into ethyl ether to precipitate a polymer. The polymer was collected by filtration, dissolved in tetrahydrofuran, and purified by repeated precipitation in ethyl ether to obtain an N-substituted maleimide copolymer having the composition shown in Table 1.

Synthesis Examples 2 to 7 As shown in Table 1, 0-aminophenol and primary amine were used in the same manner as in Synthesis Example 1, respectively.
An N-substituted maleimide copolymer having the composition shown in the table was obtained.

Examples 1-7 The N-substituted maleimide copolymers shown in Table 1 were dissolved in methyl cellosolve acetate to a concentration of 15% by weight to obtain a viscous solution. This solution was applied onto a quartz plate and baked at 100° C. for 2 minutes on a hot plate, and then the transmittance of potassium fluoride excimer laser light at a wavelength of 248 nm was measured.

Further, a solution of the above N-substituted maleimide copolymer was spin-coated onto a silicon wafer, and the solution was coated on a hot plate for 10 min.
The mixture was incubated at 0° C. for 2 minutes, and then the dissolution rate in an alkaline developer consisting of a 0.155 N aqueous solution of tetramethylammonium hydroxide was measured.

The above results are shown in Table 2.

Comparative example I As an N-substituted maleimide copolymer, N-(.

-Hydroxyphenyl)maleimide-isobutylene copolymer was used, but in the same manner as in Example, the transmittance of the copolymer to potassium fluoride excimer laser light at a wavelength of 248 nm and the dissolution rate in an alkaline developer were measured. did. The results are shown in Table 2.

Comparative Example 2 The transmittance of m-talesol-formamide novolac resin to light at a wavelength of 248 nm from a potassium fluoride excimer laser and the dissolution rate in an alkaline developer were measured. The results are shown in Table 2.

Example 8 The N-substituted maleimide copolymer according to Synthesis Example 3 was dissolved in methyl cellosolve acetate to a concentration of 15% by weight, and added with 20% by weight of phenol and 1.2% by weight of the copolymer.
-A homogeneous solution was obtained using an esterified product of naphthoquinone diazide-4-sulfonic acid as a photosensitizer.

This solution was uniformly applied onto a wafer to a thickness of 1 μm, and exposed using a potassium fluoride excimer laser. When developed with a 0.25 N tetramethylammonium hydroxide aqueous solution, a pattern with excellent dimensional accuracy of 0.5 μm was obtained.

Patent applicant: Nagase Electronics Co., Ltd. Agent Patent Attorney Itsu Makino

Claims (1)

[Claims] (1) (a) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ N-hydroxyphenylmaleimide unit represented by (b) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R^1 represents an alkyl group or a cycloalkyl group having 1 to 16 carbon atoms.) N-alkylmaleimide unit represented by formula (c) ▲ Numerical formula, chemical formula, table, etc. ▼ Maleic anhydride unit represented by ( d) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ), and 0.1<n/(k+l+m)≦10, 0.1<(k+l)/(k+l+m)≦1, and 0. 1
A positive photoresist composition comprising an N-substituted maleimide copolymer satisfying <k/(k+l)<1 and a photosensitizer.