Hello Hafizah, In here we also use hot H3PO4 (160°C). Etchrate on LPCVD SiN is app. 3nm/min Another method we use is etching in HF[48%], etchrate is also app. 4nm/min Regards, Peter Kuijpers MiPlaza Technology Laboratories Philips Research Europe High Tech Campus 04 Postbox HTC-4-1 5656 AE Eindhoven The Netherlands Tel.: +31 402743667 +31 612507027 Email: p.e.m.kuijpers@philips.com -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Nor Hafizah Ngajikin Sent: Friday 30 October 2009 7:36 To: mems-talk@memsnet.org Subject: [mems-talk] wet etch of 2um Si3N4 Dear all, I've tried to etch 2 micron thickness of Si3N4 using hot H3PO4. The concentration of H3PO4 is 85w%. I heat the H3PO4 at 150 degree celcius for 1 hour. Unfortunately, this experiment didn't work as expected. None of the nitride is etch away. Can anybody share with me your experience on nitride etch using H3PO4. Thank you. Hafizah