I have always been told that vacuum vapor prime will not help.  In 30
years experience I have yet to find a surface and organic that is not
helped by a vacuum dehydration and the right chemistry for the adhesion
promoter.  I have the equipment and lots of different adhesion promoters
if you want to experiment.  Bill Moffat

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Dhananjay Dendukuri
Sent: Wednesday, October 22, 2008 11:19 PM
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