Specmat Request

Mary Tang mtang at stanford.edu
Fri Feb 13 11:44:27 PST 2009

Hi Mikes --

Actually, we have never (as far as I know) approved liquid bromine in 
the lab.  The TWA exposure limit on this is 0.1 ppm.  Compare to 
chlorobenzene which is 10 ppm.  Or HBr, which is 3 ppm.

We've approved HBr solutions as you describe and, in fact, have some 
detailed protocols for this.  But I don't believe I've ever seen Br2 in 
our lab.  I understand it's commonly used as an etchant for certain 
semiconductor films.   But also have heard some horror stories.  I think 
just about any of the old-time GaAs researchers will have bromine 
story.  See the attached.  We did approve dilute HBr solutions for use 
at the wbgaas station with alcohols, but under very specific conditions 
(controlled pH, which I understand is key to keeping things under control.)

I am honestly not sure we could accommodate handling of liquid bromine 
-- not unless we can come up with a really safe way of doing this.  My 
feeling is that this should be done in a proper fume hood (with 
explosion sashes and indescructible/inflammable work surfaces), not the 
wet benches we have at SNF.

But I tend to be conservative on chemical handling.  Other SpecMat'ers 
-- especially those with more experience with this -- what do you think?


Mike Wiemer wrote:
> Hi Ed & Mary,
> Here is a Specmat Request document on Bromine/Methanol etching we want 
> to do at the WBGaAs bench.
> Ed and I spoke about this over the phone. It seems this is an "already 
> approved" chemical in the lab, however, we decided we needed to submit 
> a use/procedure request (see attached).
> Please let me know when we have the green light, or if there are 
> additional issues we need to address.
> Thanks!
> -Mike

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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