STS2 Update

Jim McVittie mcvittie at cis.Stanford.EDU
Sun May 2 21:01:27 PDT 2010

STS2 Users,

The good news is the recent turbo pump problem was less of an issue than 
expected. The bad news is there is still an intermittent problem with high 
reflected power causing the rf power to drop out.

Since last week the turbo pump shut down 3 times from overheating. At 
first Elmer thought the problem was due to a bad bearing in the pump. 
However, on further inspection he found that the cooling water was dirty 
and had to be flushed. The pump now appears to be working fine. I did at 
least 5 hrs of runs on the tool with no pump problems since the flushing.
Before the flushing this problem would have shutdown the pump after an few 
hours of use.

Regarding the high reflective power problem, I have learn a lot of things
we should be doing differently but there is still an intermittent problem
characterized by a sudden drops in the forward power after switching from
an dep to an etch step. The dropouts appear to be due a cut back in the
forward power when the reflected power suddenly goes out of control and
excesses a limit value. I am consulting the with STS but so far we have
not determined the cause. When the dropout start occurring repeatedly in a
run, the only solution so far is to stop your run and let the tool sit
unused for a while. Continuing run with lots of dropouts is not a good
idea since they degrade the etch process and are hard on the 3 KW coil

The following items MUST be done to minimize the dropout problem and to 
reduce stress on the coil generator:  

1. Run a 10 min O2 clean step before your run. 

2. Make sure your recipe starts with a 10s stabilization period so the gas 
flows, pressure and matching network positions are stabilize before the 
plasma comes on. 

2. Your recipe should have the "Tolerance Recipe" box selected. This 
insures that the process will quickly fault out if there is a problem with 
excessive reflected power or other condition, which will damage tool or 
your wafer.

3. Do not start with a etch (SF6) step for a switched process. 

5. Check your tune and load matching network preset positions. I or some 
knowledgeable can help you do this. I will leave a note on the tool for 
typical preset values. 

6. We still have not corrected the initial rf generator fault, which 
occurs each time the coil generator turns on after a new wafer has been 
loaded. You need to use the retry button at the bottom of the error page.

       Thanks,  Jim 

James (Jim) P. McVittie, Ph.D.	        Sr. Research Scientist 
Paul G. Allen Building                  Electrical Engineering
Stanford Nanofabrication Facility       jmcvittie at
Stanford University             	Office: (650) 725-3640
Rm. 336X, 330 Serra Mall		Lab: (650) 721-6834
Stanford, CA 94305-4075			Fax: (650) 723-4659 

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