TMAH @ 80C if the 200A SiO2 is pinhole free. RIE with 200A oxide mask without photoresist. How thick is the silicon? regards, Glenn -----Original Message----- From: Khaled Mohamed Ramadan [mailto:khaled.mohamedramadan@kaust.edu.sa] Sent: Monday, June 06, 2011 7:13 AM To: General MEMS discussion Subject: Re: [mems-talk] RIE Etching SiO2/Si Hi Judith, If you are not concerned with the anisotropy of the etching you can try XeF2 gas etching. It is selective to SiO2 up to 500.