For steep sidewalls, you can also use laser drilling or FIB milling. There are several companies that will do this on an outsource basis. -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Steven Yang Sent: Wednesday, August 01, 2007 6:05 AM To: mems-talk@memsnet.org Subject: [mems-talk] Re: Any suggestions on through holes on Glass pyrex 7740 The thickness of glass wafer is 500 micron. I am wondering how much will the aspect ratio if using HF etching?