Immersion exposure process-use resist protection film forming material, composite film, and resist pattern forming method

Abstract

Provided are a material for forming a resist protecting film which is for use in a liquid immersion lithography process and which is formed on a resist film, wherein the material has the following properties of: being transparent with respect to exposure light; having substantially no compatibility with a liquid for liquid immersion lithography; and causing no mixing with the resist film, a composite film comprising a protective film formed from the material and a resist film, and a method for forming a resist pattern using them. These can prevent both the resist film and the liquid used from changing in properties during the liquid immersion lithography, so that a resist pattern with high resolution can be formed using the liquid immersion lithography.

Description

TECHNICAL FIELD [0001] The present invention relates to a material for forming a resist protecting film which is advantageously used in a liquid immersion lithography process, especially in a liquid immersion lithography process of the construction in which a resist film is exposed with lithographic exposure light through a liquid present at least on the resist film in a path of the exposure light toward the resist film wherein the liquid has a predetermined thickness and has a refractive index higher than that of air and lower than that of the resist film, thus improving the resolution of a resist pattern. The present invention also relates to a resist film having thereon a protective film formed from the material for forming a protecting film, and to a method for forming a resist pattern using the protective film. BACKGROUND ART [0002] In the fabrication of a variety of electronic devices with microstructures, such as semiconductor devices and liquid crystal devices, a lithography...

AI Technical Summary

Benefits of technology

[0020] The present invention has been achieved in view of the above problems accompanying the conventional technique, and an object of the invention is to provide a technique for applying a resist film obtained from the conventional resist composition established by spending considerable resources on the development to the liquid immersion lithography. Specifically, an object the invention is to provide a specific protective film temporarily formed on the surface of a conventional resist film, thus making it possible not only to prevent both the resist film and the liquid used from changing in properties during the liquid immersion lithography but also to form a resist pattern with high resolution using the liquid immersion lithography.

[0024] Among the above-mentioned constructions, the liquid immersion lithography process preferably is of the construction in which the resist film is exposed with lithographic exposure light through a liquid for liquid immersion lithography present at least on the resist film in a path of the exposure light toward the resist film, wherein the liquid has a predetermined thickness and has a refractive index larger than that of air and smaller than that of the resist film, thus improving the resolution of a resist pattern.

Problems solved by technology

However, the light source having a shorter wavelength has a problem in that it requires a new expensive exposure system, and the increase of NA has a problem in that since there is a trade-off between the resolution and the depth of focus, the increase in the resolution lowers the depth of focus.

However, in the liquid immersion lithography process, the resist film is directly in contact with the refractive index liquid (immersion liquid) during the exposure, and hence the resist film is vulnerable to invasion by the liquid.

On the other hand, it has been confirmed that there are a number of resist compositions which cannot achieve satisfactory resolution of pattern in the liquid immersion lithography due to a change in their properties by the liquid, but which exhibit fine and high resolution in ordinary lithography employing the exposure through a layer of air.

These resist compositions include a number of compositions which are poor only in the resistance to the immersion liquid.

It has also been confirmed that, even when the resist film suitable for the liquid immersion lithography is used in the liquid immersion lithography, the quality and non-defective yield are slightly poor, as compared to those obtained in the exposure through a layer of air.

Theoretically, when the refractive index of the immersion liquid changes, the optical resolution of the pattern exposure is sure to change, and experiments are unnecessary.

However, it is difficult to judge whether the resolution is affected by the change of properties of the immersion liquid or the change of properties of the resist material or both.

In this point, in the test in which the resist film completely immersed in the liquid is exposed, it is difficult to judge whether the resolution is changed by the change of properties of the immersion liquid, the change of properties of the resist composition due to the immersion liquid, or both.

It has also been confirmed that there are a number of resist films which cannot achieve satisfactory resolution of pattern in the liquid immersion lithography due to the change of properties by the immersion liquid, but which exhibit fine and high resolution in ordinary lithography employing the exposure through a layer of air.

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