Method for reducing pattern dimension in photoresist layer

Abstract

The invention discloses improvements in the so-called coated thermal flow process for reducing the pattern dimension of a patterned resist layer on a substrate to accomplish increased fineness of resist patterning, in which a coating layer of a water-soluble resin formed on the patterned resist layer is heat-treated to effect thermal shrinkage of the coating layer with simultaneous reduction of the pattern dimension followed by removal of the coating layer by washing with water. The improvement of the process is obtained by using an aqueous coating solution admixed with a water-soluble amine compound such as triethanolamine in addition to a water-soluble resin such as a polyacrylic acid-based polymer. Further improvements can be obtained by selecting the water-soluble resin from specific copolymers including copolymers of (meth)acrylic acid and a nitrogen-containing monomer such as N-vinylpyrrolidone, N-vinylimidazolidinone and N-acryl-oylmorpholine as well as copolymers of N-vinylpyrrolidone and N-vinylimidazolidinone in a specified copolymerization ratio.

Description

[0001] This is a continuation of Ser. No. 10 / 173,880, filed Jun. 19, 2002, now abandoned.BACKGROUND OF THE INVENTION [0002] The present invention relates to improvements in a method for obtaining a patterned photoresist layer of which the resist pattern has a reduced dimension by a post-patterning heat treatment. More particularly, the invention relates to improvements in the method for reducing the pattern dimension in a photolithographically patterned resist layer by a post-patterning procedure in which a patterned resist layer on a substrate is provided thereon with a coating layer of a water-soluble resin and then the thus coated patterned resist layer is subjected to a heat treatment to effect thermal shrinkage of the resist layer resulting in a reduced pattern dimension followed by complete removal of the coating layer of the water-soluble resin by washing with water. [0003] Along with the recent trend in the technology of semiconductor devices toward higher and higher degrees...

AI Technical Summary

Problems solved by technology

This approach, however, cannot be successful without development of a photoresist composition having adaptability to these short-wavelength exposure radiations.

This method, however, has a problem in respect of the relatively large temperature dependency amounting to more than 10 nm / ° C. within the substrate surface.

This disadvantage can hardly be overcome with the heating device currently employed in the manufacture of semiconductor devices due to poor uniformity of the temperature distribution.

Accordingly, the above-described method of post-patterning dimension-reducing method cannot be practiced without substantial variations in the pattern dimensions.

Though advantageous in respect of small temperature dependency of only a few nm / ° C. within the plane of the substrate surface, this method has a problem that, due to the difficulty in controlling mobilization of the photoresist layer by the heat treatment, uniform reduction of the dimension of the photoresist layer can hardly be expected within the substrate surface.

For example, the crosslinking reaction of the overcoating composition may overly proceed to unnecessary portions such as the bottom of the patterned resist layer resulting in an undesirable non-orthogonal cross sectional profile thereof eventually with trailing skirts.

Further, the temperature dependency obtained by these methods is relatively large to be 10 nm / ° C. or larger so that it is very difficult to ensure high uniformity of the pattern dimension within the substrate surface when the substrate has a large size or the patterned resist layer is extremely fine resulting in poor controllability in reduction of the pattern dimension.

This method, however, is defective because products of reproducible quality can hardly be obtained due to the difficulty encountered in controlling the mobility of the resist by means of heat or radiation.

Since the water-soluble resin used in this method, such as polyvinyl alcohols, is insufficient in the solubility in water required in the removal with water and long-term stability, troubles are sometimes caused by the residual resin film remaining unremoved with water.