Dear MEMS experts: I have etched bulk-silicon with RIE technology using SF6 and CF2Cl2 as etching gas without O2 gas. The side wall is perfect, while the bottom appears black. There are innumerable micro holes in the bottom of the silicon trench. How can i avoid these holes? Welcome your reply. My email address: xgxiongc@online.sh.cn Best Regards. Xiong