Hi, guys

I have tried a series of experiments these two days. At first I thought the
cracks are due to high tensile stress as Michael said. So I tied to coat su8
with decreased exposure dose(down to 150mJ/cm2),  with increased cool down
time(up to 1 and half hours), I also tried to bake by oven. The result is quite
frustrating: cracks are still everywhere. But I noticed that the cracks appear
during developing. When su8 is developed for 60s, no cracks are observed. 90s
developing, few cracks can be seen. 120s and longer developing, cracks are
everywhere. It seems my su8 is under-exposed.

Today I tried exposure dose 400mJ/cm2. This time most of the cracks disappeared
with 120s developing. And the feature looks very nice. After 140c 60s hard bake,
all cracks disappeared.  Hence I believe Kevin gets the point, under-exposure
leads to the cracks in my case!

Sonic