Sandyha:

Do you have enough resist to begin with. Depending on the size of your wafers
you may need enough to do a slow spread program before your final spin speed. By
this I mean spin your chuck at around 400 rpm while you dispense resist from the
middle of the wafer towards the edge. Remember that it requires more resist to
cover the outside diameter due to increased surface area so dispense faster in
the middle and slower on the edge. Once you have covered the wafer from center
to edge then instantly ramp to your final spin speed probably around 3,000 rpm
for that type of resist. If you are using a pipette with a little bulb on it
that makes it more difficult to control bubbles in the resist. Try using a straw
or a longer pipette to insure enough resist and that should help to reduce
bubbles as well. Bob Henderson