Dhananjay,

The cause of your issue is most likely a humidity one. I would suggest
performing a dehydration bake after your piranha clean. This should
resolve your issue...

Good luck.

Regards,
Bruce


________________________________

From: mems-talk-bounces@memsnet.org on behalf of Dhananjay Dendukuri
Sent: Thu 2008.10.23 02:18
To: mems-talk@memsnet.org
Subject: [mems-talk] SU-8 delamination problem


Dear all,

I have a severe problem of SU8 delamination. Please go through my
process below and advise

I am fabricating an array of 100 microchannels of 50 micron width and 40
micron depth (the gap between two channels is 100 micron) on a 4 inch
silicon wafer using *Su8 2035* negative resist. The process flow is
given below.

1. Hard bake - 150 C for 20 min (after cleaning silicon wafer in Piranha
solution).
2. Spin coat - 15 sec at 400 rpm followed by 30 sec at 2000 rpm.
3. Soft bake - 3 min at 65 C and 5 min at 95 C. (wait for 10 min)
4. UV expose - 28 sec to get an exposure energy of 220 mJ/cm2.
5. PEB - 30 min at lower initial temperature of 65 C and ramping up the
temperature to 95 C in every 15 min with every 10 C increase. (Wait for 10
min)
6. Development - In ultrasonic bath (without sonicator SU8 in the channel
path is not possible to remove completely).

Within 1 min of development, all the channels are completely
delaminated.  We
tried the process on many wafers by changing different soft bake and PEB
timings, but nothing is working.  Any suggestions to avoid delamination
problem are deeply appreciated.

Thank you

Dhananjay