Dear all,

As mentioned in many papers, several organic materials could be used as
sacrifical layer, including photoresist, polyimide etc. I suppose it is a
mature
process both in academic an industry field. However, I found some problems
when I doing these process.

First, I spin HPR 204 on the wafers, then pattern the 204. After the general
developing process, the 204 was baked in oven at 120 degree for 30mins.
After that, 2um Al was sputtered on the patterned 204. Till now, no problems
happened. When I spined the second 204 on the sputtered Al, some happend.
After the 110 degree prebake, I found the Al on large area photoresist 204
formed
ripples. I thought it was due to the thermal expansion of Al cause this
problem.

Maybe I can solve this problem by baking the 1st 204 in higher temperature,
or
use high temperature photoresist and cured photosensitive polyimide as the
sacrificial layer. If that, I have to use O2 plasma etch the sacrifical
layer, because
it is difficult for MS2001 or Acetone to solve the high temperature baked PR
or
cured polyimide. However, the O2 plasma could damage the CMOS transistor
due to the charge accumulation. As we all know, PR or polyimide do be
sacrificial
layers on top of CMOS circuits, such as TI's DMD and INTEGRAM's MPK process
in industry.

I don't know how they solve this problem. Is there any other dry etching
method
to avoid the cmos circuit damage?  UV-ozone?

Any suggestions will be appriciated greatly.

Regards,

Li