Hi,

 I have a problem with the bilayer liftoff process with
AZ7220(positive PR) and LOR5A.

Although I used higher temperature for longer time for baking AZ7220
then single layer process, the upper 7220 layer seems to desolve
faster than or similar to the undercut rate of LOR during developing.

 I suspect that the upper 7220 layer is not hardened enough.
 I'm thinking of two possible ways to circumvent problems and I'd like
to get any feedback on these.

1. I can use oven instead of hot plate for baking 7220 (LOR
underneath) before exposure.  Any recommendations for oven temperature
and time?

2. Two step developing.
   I can probably stop developing when the patterns in 7220 are
developed and LORs are not or a little bit affected.  Then, I might
bake the sample at higher temperature (between baking temperatures for
LOR only and 7220/LOR) to harden
7220 layer.  Then, proceed with short develop to achieve undercut in LOR layer.

Any experience or comment can be helpful for me.

Thank you very much.

J. Park