Mary Tang mtang at stanford.edu
Mon Jan 9 13:32:16 PST 2006

Hi Colin --

Sorry, I've been meaning to post this info on our website for quite some 
time...  We generally do allow Dow Corning Sylgard 182 and 184 into the 
lab, provided the polymer is mixed and degassed outside the lab.  We 
don't allow uncured monomer into the lab because it acts like silicon 
oil and a spill or mess could potentially cause resist lifting problems 
throughout the lab.  Other silicone elastomers have been approved as 
well, but we still do ask that the MSDS and information about each new 
formulation be submitted to SpecMat so that we can keep a record of 
this.  Sygard PDMS can be spun up on the headway2 coater (no other, 
right now) and cured on adjacent hot plates or ovens.  Cured PDMS can 
processed in gold-contaminated equipment (you can coat with resist or 
metals and dry or wet etch).  Sylgard PDMS contains Pt catalyst, I 
believe (the elastomer you are using may be different.)

We generally really don't like having TCE in the lab and try to 
discourage its use.  If you have an alternative solvent you could use, 
it would make us feel better.  Most people seem to use toluene to dilute 
Sylgard PDMS, up to 50% w/w.  Like TCE, toluene is a suspected 
carcinogen, so it's not good stuff, but the maximum recommended OSHA 
exposure levels are about 2X those of TCE...

So...  Let us know which formulation you are using.  If Sylgard 182 or 
184, then it's already approved as per the description you have 
provided.  If not, then please provide us with a description and MSDS.  
If you choose to spin coat your PDMS here, please note that toluene has 
been approved for this purpose, but TCE has not.  If you wish to use TCE 
or other solvent, please do write SpecMat back again with your request.

If you'd like to mix up and degas your PDMS, we have a little area 
outside the lab to do this.  Let me know if you would like to use this 
and I can show you what we've got.



Colin Reese wrote:

> Hello.
> I am :
> Colin Reese
> ccreese
> 650 725 3144
> ccreese at stanford.edu
> PI: Zhenan Bao (chemical engineering)
> Chemical:
> common name: PDMS
> Chemical name: poly(dimethylsiloxane)
> MSDS attached.
> Storage group identifier: G
> Main hazard class: 11
> Vendor:
> Dow Corning
> http://www.dowcorning.com/
> Reason for request:
> There is not an aligner outside of SNF that is of reasonable quality 
> to use.
> Process flow:
> Thin PDMS films (~1um) will be spun onto doped Si wafers, which will 
> then be cured into its elastomer form. This will be followed by 
> photoresist. The resist will then be exposed and dissolved. The 
> aligner will therefore never be directly exposed to the PDMS. Although 
> it is preferred to spincoat the PDMS in SNF, this is not absolutely 
> necessary, and therefore the PDMS would only be present in cured form.
> Form:
> PDMS is formed by adding a base of monomers to a palladium catalyst 
> mixture is a 10:1 w/w mixture. This is then mixed 1:4 w/w in tri
> chloroethylene solvent for spin-coating. Less than 10mL at a time will 
> be necessary to bring into SNF. (If PDMS spincoating is done outside 
> of lab, PDMS would only be present in solid, cured form).
> Storage:
> I will not require SNF storage.
> Disposal:
> This product is highly inert, and will be transported out of SNF and 
> disposed of elsewhere using standard EH&S procedures.
> Thank you,
> Colin Reese

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at stanford.edu

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