I did a significant amount of work with PI2611 and PI2721, both of which
readily absorb water from the atmosphere.  The best method I found for
getting other things such as PECVD oxide or nitride, metal, or other
polymers to stick to it, is to bake it out under vacuum.  If you are doing
this in an evaporator, the best method is to heat the film under vacuum,
then cool it before you deposit the metal, all without breaking
vacuum.  Since some evaporators have substrate heaters, this is easy.  If I
remember correctly, you do not want to take the film above 300C or the
highest temp that it was cured at.  Since I did not have a substrate
heater, I used a vacuum hot plate and after it cooled, I vented it with dry
N2.  I immediately loaded the sample into the evaporator and pulled
vacuum.  This worked most of the time.  But, I was not doing a lift-off
which could provide some trouble.  Good Luck.



At 12:33 PM 6/23/2005, you wrote:
>Hi everyone,
>     I am trying to lift-off about 0.2 microns of e-beamed Pt (20 nm Cr
> adhesion layer) from a 3 micron polyimide (PI-2611) layer but keep
> finding cracks occuring in the metal on the photoresist and polyimide.
> The deposition is started after reaching a pressure ~1 x 10-6 Torr. I
> have tried this deposition using both a water cooled platen and an
> uncooled platen with the same results.  For the lift-off we are using LOR
> A (Lift-Off Resist) and 1813.