Dear all,

When I peeled off the PDMS, the photoresis was always peeled off
together. The procedure is listed as follow. Please give me some
suggestions about which step might cause this problem.

1. Clean silicon wafer for 5 min using oxygen plasma cleaner.
2. Spin adhesion promoter (HMDS/AP010 or AP020) on wafer at the
speed of 2500 rpm for 30 sec hold 5 sec ramp.
3. Immediately spin photoresist (Shipley 1818) on wafer at the speed
of initial spin=500rpm 125 rpm/sec for 10sec, ramp=3000rpm
600rpm/sec over 5sec, spin=hold at max ramp for 30sec.
4. Soft-bake 3min at 105°C and allow to cool up to 30-50 °C on
hotplate (need 10 min).
5. UV exposure for about 1 min.
6. Develop in 351 develooper for > 1 min.
7. Put ~1mL chlorinated silane (tridecafluoro 1,1,2,2 tetrahydro
octyl)-1-trichlorosilane (Sigma, #448931) in a small glass vial and
put in the vacuum chamber for at least 4hrs.
8. Pour the PDMS on the wafer and remove the air bubbles in vacuum
jar for less than 1.5 hour.
9. Put the wafer in the oven at 70°C for 2-4 hours even to
overnight.

-/Bob