Thank you all for your generous helps.

After the expose, PEB and developing, should I do some further bake ? Since I
the SU-8 100 to stay as the mechanical structure and  it needs to have some
robustness.

Thanks
J.J. Wang

Florian Herrault  wrote: Is it 250F or 250C ?
If it is celcius, it is way too high !
use a leveled hotplate and put your sample on it at RT. ramp it up to 95C for
about 4-5hrs and ramp it down ! wait for 1 hr, expose, postbake from 25 to 95
for 1 hr and ramp it down again. wait 3hrs and develop
200 um thick is not that thick. you should not have any problem with it !

florian