Positive resist composition

Abstract

Disclosed is an improved, chemically-amplifying positive resist composition for radiations, especially UV rays, deep-UV rays, excimer laser beams, X-rays, electron beams. The composition comprises (A) a resin component whose solubility in an alkaline aqueous solution is increased by the action of acids, (B) a chemical compound which generates an acid when exposed to radiations, and (C) an organic carboxylic acid compound and (D) an amine, in which said resin component (A) is a mixture comprising (a) a polyhydroxystyrene having a weight-average molecular weight of from 8,000 to 25,000 and a molecular weight distribution (Mw / Mn) of 1.5 or less where from 10 to 60 mol % of the hydroxyl groups have been substituted by residues of a general formula (I): wherein R1 represents a hydrogen atom or a methyl group, R2 represents a methyl group or an ethyl group, and R3 represents a lower alkyl group having 1 to 4 carbon atoms; and (b) a polyhydroxystyrene having a weight-average molecular weight of from 8,000 to 25,000 and a molecular weight distribution (Mw / Mn) of 1.5 or less where from 10 to 60 mol % of the hydroxyl groups have been substituted by tert-butoxycarbonyloxy groups. The composition has a high sensitivity, a high resolution, high heat resistance, good width characteristic in focus depth and good post-exposure storage stability, has good storage stability as a resist solution, and gives resist patterns with good profiles, without depending on the substrate to which it is applied. The composition is useful for forming fine patterns in producing ultra-LSIs.

Description

FIELD OF THE INVENTIONThe present invention relates to a positive resist composition and, more precisely, to a chemically-amplifying positive resist composition sensitive to radiation such as UV rays, deep-UV rays, KrF or Arf excimer laser beams, X-rays, electron beams, etc., which has a high sensitivity, a high resolution, high heat resistance, good width characteristic in focus depth and good post-exposure storage stability, has good storage stability as a resist solution, and gives resist patterns with good profiles on substrates without depending on substrates to which it is applied.BACKGROUND OF THE INVENTIONSemiconductor devices such as ICs, LSIs, etc. have heretofore been produced by repeating several times a series of processes comprising photolithography using photoresist compositions, etching, diffusion of impurities and wiring. Concretely, in the photolithographic process, a thin film of a photoresist composition is formed on a silicon wafer by means of, for example, spin...

AI Technical Summary

Benefits of technology

One object of the present invention is to provide a positive resist composition which is sensitive to radiations, especially deep-UV rays and excimer laser beams (such as KrF laser, ArF laser, etc.) and which has a high sensitivity, a high resolution, high heat resistance, good width characteristic in focus depth and good post-exposure storage stability and, furthermore, which has good storage stability when it is prepared in a resist solution.

Problems solved by technology

However, the conventional positive photoresist composition comprising, as basic components, an alkali-soluble novolak resin and a quinonediazido group-containing compound hardly gives such an ultra-fine patterning as mentioned above.

However, the above-mentioned, known chemically-amplifying positive resist was not satisfactory in practical use, since the resolution and the width characteristic in focus depth are not satisfactory, and since it may cause a problem so-called bridging that the crosssectional profile of the patterns to be made of the resist is often broadened upward like eaves.

Concretely, when the chemically-amplifying positive resist coated on a substrate are exposed, stored for a while, followed by heating treatment and then developed to give patterns, the patterns cannot have good profiles since the acids generated by the exposure are inactivated while the exposed resist films are stored.

The problem of post-exposure storage stability is peculiar to chemically-amplifying positive resists.

When such bridging occurs, a desired wiring pattern cannot be given, which is a serious problem for the production of semiconductor devices.

In this method, however, the production steps are increased, which leads the decrease in throughput and high production cost as well.

From these reasons, this method is unfavorable.

The above-mentioned chemically-amplifying positive resist has another problem that it characteristically depended on substrates to which they are applied, and some of them, when applied on a substrate such as a substrate coated with an insulating film such as silicon nitride (SiN), boron-phosphorus-silicate glass (BPSG) or the like film or on a substrate coated with titanium nitride (TiN), often formed resist patterns with poor profiles expanding downward to the substrates (which is referred to as "substrate dependency", hereinafter).

In this method, however, the production steps are increased, which leads the decrease in throughput and high production cost as well.

From these reasons, this method is also unfavorable.

In addition to the above-mentioned problems, the conventional resist compositions have still another problem.

That is, a patterned resist layer has not high heat resistance and when the resist compositions are prepared in solutions, they have such a poor storage stability that the solutions often generate solid substances while the solutions are stored.

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