For those interested in dry etching PDMS, I did finally find a way to
dry-etch through a 10micron layer of PDMS on gold film in such a way
that (1) the thin gold film underneath was unaffected and (2) the etch
was clean (bare gold was left with no significant film on top of it).
The method in this paper:
Biomed Microdevices. 2007 Oct 4
A lithographically-patterned, elastic multi-electrode array for surface
stimulation of the spinal cord.
Meacham KW, Giuly RJ, Guo L, Hochman S, Deweerth SP.
-Rick
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This was my orginial question:
[mems-talk] Selective, clean PDMS etch
Rick Giuly
Mon Apr 18 00:37:17 EDT 2005
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.
Richard J. Giuly
Bioengineering Graduate Student
National Center for Microscopy and Imaging Research (NCMIR)
University of California, San Diego
rgiuly at ucsd dot edu
