Hi can be done. you have to get good control over the rate so you know when to stop. if you do a whole wafer, have ready something to 'fish' it with from the koh and transfter to DI water for rinsing. also, you should float it on IPA after rinsing so it wouldn't stick and let dry over a piece of paper. id you do only 1mm islands in a wafer there is no problem. you can go down to 0.5u for this size. shay Original Message: ----------------- From: Chin-Jen Chiang chinjen_chiang@yahoo.com.tw Date: Tue, 6 Nov 2007 02:33:50 +0800 (CST) To: mems-talk@memsnet.org Subject: [mems-talk] a question about KOH etch back Hi guys, I am trying to etch back a Si bulk with KOH to remain a ~10 um thick membrace wirh an area of 0.5mm x 0.5mm. I am concerned if such a thin membrance with such a big area is very fragile and if it is achievable. Someone told me such a thin Si layer is not flexible as a thin nitride layer. Is that true? I appreciate your advices. Lawrence