Special Request for very limited presence of BISMUTH

Betty Young bayoung at stanford.edu
Fri Jul 20 12:32:12 PDT 2007

Dear All,

Astrid Tomada and I have a few wafers that we need to expose and then  
dry-etch (to define SiN membranes on a Si substrate). These wafers  
have timy patches of Bi on the side we will not etch. We have NEVER  
brought Bi into the lab. We now are in the need to do so, if at all  

(1) To use our own, dedicated, 3" wafer holder to dry-etch through a  
patterned Si wafer. The Bi patches would be on the side of the wafer  
almost entirely coverd by one small cooling-gas hole on the "backside"  
of the 3" adapter plate.

(2) We would also need to do the photolith step ("backside") preceding  
the dry-etch to define the windows for the membranes. We could coat  
the "Bi" side with PR for protection in many of these steps.

Thank you very much for your consideration.
I would appreciate the opportunity to speak with any of you about the  
details of this request, if that would be helpful.

As always, we will ONLY bring the Bi-processed wafers in the lab if we  
receive authorization. Needless to say, we are very eager to meet any  
constraints you may have if it will allow us to do the dry-etch in  
CIS! (We have found no other options for this step.)

Thanks very much,
Betty Young

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