A Contour-Lithography Method for Etching Nano-dimension and Large-dimension Openings

Abstract

This paper proposes a method for fabricating size-varied structures from nanometer scale to millimeter scale on the same wafer precisely. The advancement in nanometer scale lithography and DRIE have enabled us to develop a lot of applications of high aspect ratio nano structures. However, DRIE conditions optimized for nanometer scale openings are often incompatible with large size openings due to the aspect ratio dependence of optimum conditions. Applying DRIE conditions optimized for small openings to large openings results in lots of silicon pillars in trenches. To solve the problem, this paper proposes a two-step etching method: the etching of nano-structures plus contours of large area patterns followed by the etching of the rest with optimum conditions respectively. The contours etching in the first step enabled us precise alignment of nano-patterns to large patterns. Its capability has been shown by successful fabrication of optical switches which are consisted of large etched areas and fine comb-drive actuators on a 4-inch 25 μm SOI wafer.