request to use PDMS in P5000

Jim McVittie mcvittie at
Wed Jan 4 13:24:23 PST 2006


I guess I did not notice that she had 500um of PDMS.  You are correct. This
thickness will affect the etching characrtistics. If Pt is the only metal of
significance, then metal contamination will not be a big issue.


Mary Tang wrote:

> Hi Alissa, Jim --
> I think I have this information somewhere, from a previous request.  As
> I vageuly recall, PDMS (Dow Corning Sylgard 182 or 184) is based on a
> Pt-catalyzed reaction, although very little Pt is actually present.
> Other metals and impurities, such as sulfur, will prevent
> polymerization.  So, other than the Pt, PDMS is actually pretty clean --
> although perhaps not by electronics-grade standards, it's cleaner than
> your ordinary plastics.  I'll see if I can find the info.  I think that
> Claudia Richter provided it, so I'll also check with her.
> Just on a side note, I'm personally less concerned about the potential
> contamination than the process flow itself (Alissa, perhaps you've got
> experience or references on this already.)  500 microns of PDMS is
> pretty thick...  It's got a high thermal expansion coefficient, so I'm
> not entirely sure that you could put 0.5 microns of Al on it without
> having it peel off due to stress differences, even with an adhesion
> layer (although having thin lines might help).   I think Claudia or
> Neville Mehenti may have experience in depositing metals on PDMS in our
> lab (although I'm pretty sure they would have used metalica or
> innotec.)  By the way, does your request entail using gryphon for Al
> deposition?
> Also, PDMS is a darn good insulator -- I think the Al etch rates and
> profiles may be very different than they would be on silicon due to
> differences in plasma behavior (at least, I understand that P5000
> etching of films on quartz is very different from etching on silicon.)
> I would suggest that if you have problems, a thinner PDMS layer (tens of
> microns -- you may have to dilute and spin coat) might help.
> Constrained PDMS (by adhesion at the Si/PDMS interface) won't expand as
> much and electronic effects on plasma *might* be reduced.
> Again, I'll if I still have the purity info, and if not, I'll drop a
> note to Claudia.  I think that Dow provided this info to Claudia (or
> whomever it was who gave it to me) so you might try asking them.
> Mary
> Jim McVittie wrote:
> >Hi Alissa,
> >
> >During the overetch, the Al etch chamber will be contaminated by the
> >decomposition products of the PDMS. So the important question what is in
> >PDMS and is it a problem to other users of the chamber. My concern is
> >what metals at in PDMS and at what level. Can you find a purity analysis
> >for PDMS?
> >
> >    Thanks, Jim
> >
> >"Alissa M. Fitzgerald" wrote:
> >
> >
> >
> >>   Part 1.1    Type: Plain Text (text/plain)
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> >
> >
> >
> --
> Mary X. Tang, Ph.D.
> Stanford Nanofabrication Facility
> CIS Room 136, Mail Code 4070
> Stanford, CA  94305
> (650)723-9980
> mtang at

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