Hi,everybody;
   I have had hard time to pattern the polyimide with normal positive PR.
I'm using PIX3400 from HD MicroSystem and following the process based on
their info.   But, I found it's hard to pattern the PR on polyimide.
It looks like that some chemical reaction between polyimide and PR layer
was happened and then it was not patterned by PR developer anymore.
If I use negative PR, it's a little easer than positive to pattern but
still not as easy as just pattern PR on wafer.
   If anyone know how to pattern polyimide(PIX 3400)properly with normal PR
process, please let me know and  any information should be welcomed.
Thank you.

   One more thing I'd like to be confirmed is etchant which I use for
both developing the PR and etching the polyimide.   I'm using diluted
MF-319(MF319:DI water=1:1).   Is it O.K. or I need to use something special?


By the way, I have used following process.

1. spin coating the polyimide(2500rpm/30sec for 20um thick)
2. prebake(90C/10min + 130C/30min)
3. spin coating the PR
4. Prebake(90C/30min)
5. Exposure
6. resist development and polyimide etching(immersion)
        30C/10mins