Forming a Rounded Convex Corner by Using Two-Step Anisotropic KOH Wet Etching

Abstract

Anisotropic etchants produce a hole consisting of (100) and (111) planes onto a (100) silicon wafer through a rectangular opening in a mask. In this case the upper corner of the hole is sharp. If the whole surface is etched by maskless wet anisotropic etching process the upper corners become rounded. The corner round up is essential for example in case of realization of wafer through — hole interconnects. The sharp corner increases the risk of a photoresist break up which is used for patterning of the metal underneath. Therefore it is important to know the etching behaviour of the most common anisotropic etchants — KOH and the shape of the rounded convex corners. This paper explains the rounding effect of KOH at the convex corners by the etching rate distribution of the etchant for the different crystal planes. To determine the fast-etched plane simulation of the shape of the corner round up has been made. The performed experimental results are very similar to the simulated shape of the etched corner.