Plasma Quest update ...

John Shott shott at
Fri Aug 22 15:44:37 PDT 2008

Plasma Quest community:

This afternoon Elmer and I spent some time trying to resolve some of the 
outstanding issues on the Plasma Quest.

In particular, we changed the clamping springs to a weaker set that, we 
believe, still clamp hard limit helium blow by, but won't clamp so hard 
that we break wafers.

We also worked to treat the O-ring in an oxygen plasma in hopes that 
this will tend to limit wafer sticking to the O-ring and the subsequent 
drop off the pins.

We have put everything back together and a releasing things for the 
weekend with the following cautions:

1. Please keep an eye on your wafers during load and unload to watch for 
wafers falling off pins and other things that might result in wafer 

2. Please try to note helium flow to maintain 10 Torr backside pressure 
and the bias observed during your process.  While we think that the 
helium flow is behaving pretty well, bias may still be somewhat low.

3. If you run into problems and get a trapped wafer, send me email.  I 
should be available many times during the weekend to extract wafers, etc.

Note: if the oxygen-plasma-treated O-ring doesn't reduce sticking 
problems, I've also got a couple of spare O-rings that I can try Elmer's 
special bead-blasting-to-reduce-sticking treatment.

So best of luck this weekend .... and let me know if you encounter problems.


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