Effect of resist surface characteristics on film-pulling velocity in immersion lithography

Abstract

In an immersion lithography system, liquid loss may occur at the receding contact line associated with the free surface of the liquid that is confined between the stationary lens apparatus and the moving wafer (or substrate). This deposited liquid may lead to defects in the printed features. The critical velocity for liquid loss is a function of the substrate surface properties, the geometry of the immersion lens, and the properties of the immersion liquid. This article investigates the effect of both the fluid properties of the immersion liquid and surface characteristics of the substrate on liquid loss velocity. Specifically, glycerine-water mixtures of varying viscosities were tested to determine the effect on critical velocity. In this article the authors experimentally investigate the impact of the partition coefficient or logP, which is a measure of the relative hydrophobicity of different surfaces. The correlation is used to approximately isolate the effect of the static, receding contact angle fro...