Hi memstalk members,

I hope you guys can help me with this.
I am trying to make a 2 level su-8 structure.
the bottom layer is 5um su-8 2005 and top layer is 50 um su-8 50.
after the postbake of the bottom layer, i spin deposit the top layer and
prebake,
in the first minute of the 65C stage, the su-8 starts to wrinkle and  it affect
the exposure process.
i have tried developing the bottom layer before depositing the top, and it
improves a little but there are still wrinkles on the surface.
I have also tried depositing the top layer immediately after exposing the bottom
layer and prebake, so that the postbake of the bottom layer and prebake of the
top layer is done at the same time. But it made it even worse, the su-8 becomes
puddle-like.

any comments are welcomed

thanks in advance

chenhan