I forgot to mention that an easy way to check issues with your
exposure/contact parameters is to look at some of your delaminated
structures end-on under a microscope so you can see the side wall
profile and thickness at the bottom.

I suspect you may have mushrooming/"T-topping" and a negative sidewall slope.
If the thickness at the base of your structure is thinner than your
mask then you don't have enough exposure energy. A mushroom / T-topped
profile could indicate poor mask contact and/or poor filtering of deep UV.

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.