Pquest up for some cautious testing ....

John Shott shott at stanford.edu
Tue Aug 5 16:17:59 PDT 2008

Plasma Quest community:

After some careful alignment, Elmer has finally cleared the shutdown on 
the pquest.  We believe that we are ready for some cautious testing .... 
let me explain a bit more about what was done to the machine so that you 
understand why we need to proceed with caution.

We are now using a clamp plate that holds the wafer completely around 
the perimeter rather than simply pressing down at 5 points.  This clamp, 
however, will likely affect etch rates particularly near the edge of the 
wafer which is one of our causes of recommending cautious testing before 
you commit any valuable wafers.

Elmer has carefully aligned this clamp and has also reduced the overall 
clamping pressure in hopes that we will see fewer broken wafers.  
However, because we are not clamping with great force, the helium 
leakage that we see to maintain a backside pressure of 10 Torr is higher 
somewhat than we would like.  We felt, however, that erring on the side 
of less clamping pressure was better than trying to clamp harder only to 
break wafers.

Thus far, we have test loaded/clamped/unloaded a number of wafers and 
have also run them under oxygen plasma.  We have not yet had time to 
actually do process testing.  However, I know that a number of you .... 
particularly Li-Wen and Shabbir and probably others ..... are anxious to 
begin to test.  I also know that there has been discussion of the 
fluorine vs chlorine status of the machine.  While I do not know where 
that discussion ended, I trust that Li-Wen, Shabbir and other anxious 
users will be able to resolve this amongst yourselves .... and will let 
others know which mode is in use.

Now, here is my offer: if anyone is willing to do some testing of this 
tool that will help us to check out etch rates, adequate clamping, and 
adequate cooling, and proper unloading  ..... ideally on expendable test 
wafers in case something goes amiss .... I will make sure that you do 
not get charged for that equipment time as long as you communicate your 
findings to us and the rest of this community.

I apologize for the extended downtime that this tool has experienced, 
but am hopeful that some cautious testing of both clamping and etching 
characteristics are now in order and that we will soon be getting useful 
etch results out of this tool.

Let us know if you encounter any problems.



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