request to use PDMS in P5000/gryphon

Mary Tang mtang at stanford.edu
Wed Jan 4 15:40:22 PST 2006


Hello SpecMat'ers --

I don't know how hot the gryphon can get, but do think that  outgassing 
is likely lot less of a problem for PDMS than for photoresist or 
polyimide tape, if temperatures remain fairly low -- and if the PDMS has 
been sufficiently cured.  Again, I'm not sure of the purity, but I think 
the data exists somewhere...

Mary

Alissa M. Fitzgerald wrote:

>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
>aluminum.
>
>Regards,
>Alissa
>
>  
>
>>-----Original Message-----
>>From: Mary Tang [mailto:mtang at stanford.edu] 
>>Sent: Wednesday, January 04, 2006 7:47 AM
>>To: Jim McVittie
>>Cc: Alissa M. Fitzgerald; SpecMat at snf.stanford.edu
>>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:
>>>
>>> 
>>>
>>>      
>>>
>>>>  Part 1.1    Type: Plain Text (text/plain)
>>>>          Encoding: 7bit
>>>>   
>>>>
>>>>        
>>>>
>>> 
>>>
>>>      
>>>
>>--
>>Mary X. Tang, Ph.D.
>>Stanford Nanofabrication Facility
>>CIS Room 136, Mail Code 4070
>>Stanford, CA  94305
>>(650)723-9980
>>mtang at stanford.edu
>>http://snf.stanford.edu
>>
>>
>>
>>    
>>
>
>
>  
>


-- 
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
(650)723-9980
mtang at stanford.edu
http://snf.stanford.edu





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