Chemical Request

Mary Tang mtang at
Tue Mar 2 07:25:16 PST 2004

Hi all --

This seems OK to me, as long as the actual mixing of the silicone rubbers are done outside the lab.  They can then be brought in and used.  The mesitylene can be added to the silicone at the solvent benches -- although you might want to do this outside the lab as well, if you plan to degas the silicones after dilution.   (The silicone monomer is basically silicone oil, and it can easily migrate between surfaces -- if it gets on processing glassware, it can prevent resist adhesion.  The mixed silicone cures into something that's inert and easily peeled off.  So, as a rule, it's best to keep
mixing of silicones outside the lab.)  The trimethylbenzene, like all aromatics, is probably a carcinogen and smells strongly, so extra care should be taken to ensure that this solvent and the silicone rubbers diluted with this solvent should be handled only in exhausted areas and tightly covered whenever transporting outside the exhausted areas.

People have routinely used toluene to dilute PDMS for spin at the headway.  This is very much the same, although the trimethylbenzene is probably even safer.

Unless other SpecMat'ers weigh in on this, I think we can consider this approved.


Claudia Richter wrote:

> Specmat Committee:
> I've spoken to Mahnaz regarding the use of silicone rubbers (PDMS, and OE4100) in the photolithography area. We plan to spin-coat these silicones on 4 inch silicon wafers and plan to do this using the Headway manual coater and curing using the hotplates. I believe Dien (coral: adnguyen) has submitted the information for the OE4100 elastomer, but we would like to add a solvent to dilute the elastomer to get thinner coats. We plan on diluting the elastomer with a solvent recommended by the manufacturer called mesitylene (1,3,5-trimethylbenzene). Attached is the MSDS sheet for this chemical.
> We plan on bringing in the OE4100 and mesitylene mixture in a vial to the Headway to spin-coat wafers and cure it in the photolithography room. The amount of mesitylene in elastomer shall be about 10% by weight.
> If there is any further information needed to complete this request or concerns please contact me at crichter at or Dien at adnguyen at
> Best regards,
> Claudia
> Claudia Richter
> Senior Staff Engineer
> Los Gatos Research Inc.
> 67 E. Evelyn Ave. Ste.3
> Mountain View, CA. 94040
>   ------------------------------------------------------------------------
>                                  Name: mesitylene-MSDS.pdf
>    mesitylene-MSDS.pdf           Type: Portable Document Format (application/pdf)
>                              Encoding: base64
>                       Download Status: Not downloaded with message

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

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