Dear Xiaohui,

You might consider a bilayer resist approach: first use a soft-baked and spun-on
'lift-off' resist such as LOR-10A, followed by a spun-on soft-baked and exposed
thicker positive resist, with a post-bake for image reversal, and finally flood
expose and develop. I've had easy lift-offs with this approach when I needed
thicker sputtered metallization.

Best of luck,

Thomas