Nitrogen is released when the resist is exposed. If your rather high temp softbake creates a crust on the resist surfaces, the nitrogen might not have a way to escape. You might want to reduce the SB temp to 95 deg. -----Original Message----- From: mems-talk-bounces+shay=mizur.com@memsnet.org [mailto:mems-talk-bounces+shay=mizur.com@memsnet.org] On Behalf Of Wei Cheng Sent: Friday, February 01, 2013 6:25 AM To: General MEMS discussion Subject: [mems-talk] AZ5218 PR issue in Metal Lift off process I use AZ5218 in metal lift off process. I have seen lots of bubbles in the PR sometimes. See pictures below. Lots of bubbles form a line in the center of the scribe-line. The bubble line lies at exactly where two exposure fields overlap. So the PR in this 10um width strip sees double exposure. And this strip is where I can find most of the bubbles. This bubble issue does not happen always. On some other wafers or even some other portion of the same wafer, I can only find much less bubble. One time I did inspection right after post exposure bake (PEB) I saw the bubbles on the wafer already. This is a mystery to me. Anyone has any idea what could be wrong? Spin speed of ~1000rpm=20 Soft bake: 110C/90"=20 ~3.7um film thickness Exposure: 55~70mj in Canon i1 stepper PEB: 115C / 75"~90" Flood exposure 300" in Quintel aligner Develop: diluted AZ400K / 100" _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk