Steven Yang wrote:
> 1) Hotplate: 150C to dehydrate 15mins
>
I would increase this (~200C for 1hour) to be sure. (Or use Bill's
priming method to remove moisture).

> 2) Spin coat SU-8 2050: 500/100/5s, and then 4000/1000/45s, suppose to
> be 40um thick.
> 3) Softbake: 65C for 3mins, and cool down to room temperature, then
> 95C for 30mins.

Are you cooling down in-between 65C and 95C or is that a typo? Ramp from
65C to 95C - do not allow it to cool in-between.

> 4) Exposure: MA8 CI1 7mw/cm2 35s

Don't believe the dosage quoted in the datasheets. IMO this is the most
likely reason your structure peels off as the SU-8 may not be fully
crosslinked at the bottom and thus suffer poor adhesion. Try doubling it
and see if it has an effect.

> 5) PEB: 65C for 3mins then raise the temperature up to 95C and stay for
10mins.

PEB is the second most likely reason your structure peels off especially
if you are exposing a large area. You can try a lower temperature bake
for longer. This will reduce the stress which can cause peel off.