Hi Le Hong,


I'm also new to SU-8. I think we are facing similar problems. I got some craters
in softbake. I kinda overcame it by relaxing the my sample after spin coating
for more than 1hr (for 100um thick layer). At the same time, I started to bake
the sample from room temp with an increment of 120C/hr. I also lowered the soft
bake temperature from 95C to 85C. From my observation, this helped and no
craters formed in the softbake. In my opinion, the problem may be caused by the
environmental differences between our lab and the manufacturer's. The fume hood
temp of
ours is below 15C and thereby a quick heat to 65C may be culprit that generates
bubbles/craters.

Although I do not see those craters anymore,the surface is not as flat as I
expected. The SU-8 can be pulled back from the edge of substrate and the center
becomes thicker than the rest after a long relaxation time before softbake.

I would also like to hear you guys suggestions to help me improve my work as
well.

Cheers