Try increasing your exposure dose (maybe 2 mins to start with). As has
been discussed before, the datasheet's recommended dosage rarely gives
good adhesion for thicker layers.

If you are having problems with development, this could be due to poor
mask contact or unfiltered UV causing a film to form on the top. You
should probably address this problem first as it will get worse with
increased exposure time.

Cheers

Gareth


On Thu, Oct 23, 2008 at 07:18, Dhananjay Dendukuri
 wrote:
> 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