Suzanne,

I have experience using Polyimide as a sacrificial layer. At first I
tried to use an RIE (Trion type). This did not work. It left material
under the Aluminum bridge.

What you want is an asher, which can produce an isotropic plasma. I use
a plasma which is 70% O2, 30% CF4, by pressure (don't have MFC's on our
asher, so I use the vacuum guage and needle valves to control the flow).
I use 1 Torr pressure. This works quite well. The CF4 increases the etch
rate greatly, and does not attack SiO2 or Si in this system (or I
couldn't measure the etch rate if there was one.)

If you are intersted I can send more details.

Also, Aluminum is not a great material for bridges. I deposited it using
an e-beam, and it had compressive stress, so it tended to buckle, or
look "wavy" after release.


Good Luck,

Rob