Photoresist shrinkage observation by a metrological tilting-AFM

Abstract

Scanning electron microscopy (SEM) is commonly used for line edge roughness (LER) measurement; however, it is difficult to achieve high-precision LER measurement of photoresists because exposure to an electron beam (EB) causes shrinkage of the materials. The differences in the 3D sidewall shape before and after shrinkage have not been investigated in detail. In this study, EB-induced photoresist shrinkage was observed by employing the atomic force microscopy with tip-tilting technique (tilting-AFM), which enables high-precision observation of the vertical sidewall of the pattern. In the experiment, the shrinkage deformation was observed by measuring the same photoresist pattern with the tilting-AFM before and after EB exposure (by SEM observation) on the pattern. The results show that the sidewall was smoothed by EB exposure. Further, the tendency of changes in LER (roughness parameters) was observed. This measurement technique can be used to better understand photoresist materials and to improve the LER measurement by SEM.