I used shipley 1813 and the spin speed is 4000rpm (thickness of
photoresist is about 1.3um). After spin coating the wafer is softbaked
in oven at 90C for 30min. But after the wafer is developed in MIF 319,
there is always some photoresist left in the exposed area with 10um in
width but the photoresist was removed in the exposed area of 100um by
100um. I tried to increase the exposure time, but the problem still
exist? Could that possibly because the mask and wafer are not contacted?
Thanks.

Laura