Jordan:

Have you tried a downstream asher like a Gasonics or Matrix system for this
process. Either process is very isotropic but I don't know how much 10 microns
 it will actually undercut. I have a Gasonics 3510 system set up and I could
process some wafers for you but you would have to send them by next week and
they can have no gold on the substrate. Call me at 602-206-6154 for further
details.  Bob Henderson