Temperature influence on etching deep holes with SF6/O2 cryogenic plasma

Abstract

A cryogenic SF6/O2 plasma process has been used to investigate the etching of deep holes in silicon wafers. The influence of crystallographic and aspect ratio dependence of the etch rate on the holes profile have been explored. It was found that wafer temperature, during the etching process, played a crucial role in controlling the anisotropy and deteriorative faceting due to crystal orientation dependent etching. High anisotropy and switching of the process to crystallographic independent etching was achieved by controlling the temperature. Aspect ratio dependent etching was also identified as a serious limitation for the required homogeneity in etched depth.