Anisotropy and selectivity control of TMAH

Abstract

A new approach to control the characteristics of TMAH silicon anisotropic etchant is proposed. The effects of potassium ions on TMAH etching characteristics at a concentration of 20 wt.% and temperature of 80/spl deg/C were investigated. A K/sub 2/CO/sub 3/ additive to the TMAH was used as a potassium ion source. The SiO/sub 2/ etching rate increased with increasing the amount of added K/sub 2/CO/sub 3/. Anisotropic etching characteristics were measured using a wagon wheel pattern. It was observed that the etched wagon wheel pattern changed with increasing the amount of added K/sub 2/CO/sub 3/. This change was caused by a decrease in the etching rate in the silicon <014> direction. From these results, it is concluded that important characteristics of silicon anisotropic etching, such as selectivity to silicon dioxide and anisotropy, can be controlled by adding potassium ions to TMAH solution.