Field of the Invention
The present invention relates to a resist pattern formation method and a resist composition.
Related Art
In the lithography technology, there is, for example, performed a process in which a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure and development treatment, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which an exposed area becomes soluble in a developing solution is called a positive type, and a resist material in which an exposed area becomes insoluble in a developing solution is called a negative type.
In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, advances in the lithography technology have led to rapid progress in the field of pattern miniaturization. As a method of miniaturization, in general, shortening (generation of high energy) of an exposure light source is performed. Specifically, ultraviolet rays typified by g-line and i-line have been conventionally used. But, at present, mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser is now started. In addition, research is also being made regarding the lithography technology using an exposure light source having a wavelength shorter (higher energy) than these excimer lasers, such as EUV (extreme ultraviolet ray), EB (electron beam), and an X ray.
The resist material is required to have sensitivity to these exposure light sources, high resolution capable of reproducing a pattern with minute dimensions, and lithography properties such as mask reproducibility and also have a satisfactory resist pattern shape.
As a resist material that satisfies these requirements, a chemically amplified resist composition containing a base material component whose solubility in a developing solution changes by the action of an acid and an acid generator component that generates an acid upon exposure has been conventionally used.
For example, in the case where the developing solution is an alkali developing solution (alkali development process), a resist composition containing a resin component (base resin) whose solubility in an alkali developing solution increases by the action of an acid and an acid generator component is generally used as a positive-type chemically amplified resist composition. In a resist film which is formed using such a resist composition, when selective exposure is performed at the time of forming a resist pattern, an acid is generated from the acid generator component in an exposed area, and the polarity of the base resin increases by the action of the acid, whereby the exposed area becomes soluble in the alkali developing solution. Accordingly, by performing the alkali development, a positive-type pattern in which an unexposed area remains as a pattern is formed.
On the other hand, in the case where such a chemically amplified resist composition is applied to a solvent development process using a developing solution containing an organic solvent (organic developing solution), when the polarity of the base resin increases, the solubility in the organic developing solution is relatively lowered. Thus, a negative-type resist pattern in which an unexposed area of the resist film is dissolved in the organic developing solution and removed, whereas an exposed area remains as a pattern is formed. The solvent development process for forming such a negative-type resist pattern is sometimes referred to as a negative-type development process (see, for example, Patent Document 1).
In general, the base resin which is used in the chemically amplified resist composition has plural constituent units for the purpose of enhancing lithography properties and the like. For example, in the case of a resin component whose solubility in an alkali developing solution increases by the action of an acid, a constituent unit containing an acid decomposable group whose polarity increases upon decomposition by the action of an acid generated from an acid generator or the like is used. Besides, a constituent unit containing a lactone-containing cyclic group, a constituent unit containing a polar group such as a hydroxyl group, and the like are used (see, for example, Patent Document 2).
In addition, a resin having a constituent unit containing a cyclic group containing an —SO2— structure is proposed as the base resin. It is said that such a base resin contributes to enhancements of a resist pattern shape as well as mask reproducibility and lithography properties such as reduction of roughness.
Now, this roughness means roughness of the resist pattern surface and causes a defective shape of the resist pattern. For example, a roughness of line width (line width roughness (LWR)) causes a defective shape typified by ununiformity of line width in a line-and-space pattern. There is a concern that the defect of the resist pattern shape adversely affects the formation of a minute semiconductor element, or the like, and when the pattern is finer, its improvement becomes important.
Furthermore, with advances of miniaturization of the pattern, in addition to the above-described problem of roughness, problems such as attachment of extraneous matters onto the pattern surface at the time of development and pattern collapse become visualized. In order to solve such problems, a pattern formation method in which a resist film composed of a resist material is formed on a substrate and subjected to selective exposure and development treatment, followed by a rinse treatment with a rinse solution is proposed (see, for example, Patent Document 3).
Patent Document 1: JP-A-2009-025723
Patent Document 2: JP-A-2003-241385
Patent Document 3: JP-A-2007-219009