Dear Yilei,
I have obtained good results with a C4F8/CH4/He (17sccm/ 13sccm/ 100sccm)
chemistry. After the process I suggest you to clean the chamber with an Oxygen
plasma in order to avoid cross-contamination.

Fulvio

yilei zhang wrote:

>Dear colleagues,
>Is there a way to get high aspect ratio of silica structures? Like DRIE for
>silicon? Thanks.