request to use PDMS in P5000/gryphon

Alissa M. Fitzgerald amf at
Wed Jan 4 14:13:50 PST 2006

Hi Mary, Jim,

Thanks for the info.  Based on your information, and Jim's most recent
email, does this mean it is approved for use in the P5000?  (Also, as a side
note, based on the number of inquiries I get regarding PDMS, SpecMat may
want to consider and publicize a general policy with regards to this
material.  I think it's an important material that is gaining popularity in
MEMS, esp. with regards to medical and biotech applications.)

The process is aggressive and experimental.  Honestly, I am not sure this it
is going to work, but the customer is interested in trying it out. We may
need to start with different PDMS thickness, bigger CD's, etc. 

We will need permission to put PDMS in the gryphon, too.  We need to use


> -----Original Message-----
> From: Mary Tang [mailto:mtang at] 
> Sent: Wednesday, January 04, 2006 7:47 AM
> To: Jim McVittie
> Cc: Alissa M. Fitzgerald; SpecMat at
> Subject: Re: request to use PDMS in P5000
> 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:
> >
> >  
> >
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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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