Hello All,

I have a 10micron layer of PDMS with a 5000A layer of gold under it. I
want to dry etch completely through the PDMS without damaging the gold.
The etch needs to be clean so that bare gold is exposed to serve as an
electrode.

Here's the recipe I'm using:
CF4+O2 (75:25 ratio)
power: 200w
pressure: 47mTorr

This recipe etches PDMS at about 5microns per hour but:

1. This recipe etches gold also - which means if you etch too long, you
loose the electrode. The PDMS layer is not uniform enough for me to time
its etching perfectly (in hopes that the gold will not be reached), and
our Plasma Therm RIE machine doesn't etch uniformly either.

2. This recipe creates a residue that remains even as it etches through
underlying gold.

Pure oxygen plasma may do the trick - I'm not sure - but I know it would
take an extremely long time. Does anyone know of a PDMS dry etch recipe
that is selective (won't etch gold), clean, and reasonably fast (better
than 2 microns per hour).

After writing this message I'm thinking I could do the CF4+O2 for a while
and then switch to pure O2, but I'm not sure if that's the solution. I
would appreciate some advice - exploring possibilities has been an
extremely time consuming process.

Thanks in advance,

Rick