mcvittie at cis.Stanford.EDU
Tue Apr 20 16:58:48 PDT 2010
As most of you know, we lost the 3KW source RF generator a week or so ago.
To speed the repair we purchased a used generator, but we unable able to
use it because firmware was not programmed to work with the DeviceNet
communication which the STS2 uses. In parallel we sent the broken
generator back to its manufacturer (MKS/ENI) to do an expedited repair. On
getting the generator the first thing ENI told us was that the unit was a
prototype and would need a number of upgrades beside replacing the shorted
output transistors. Being a prototype unit is surprising since it came
from STS on a new etcher. We received the repaired unit this morning. It
has been installed and it is working. However, its characteristics are a
bit different in that the plasma appears to be more stable. Before the
light emission was constantly changing for a 3s/2s etch/dep process
whereas now it is more like 2 levels of brightness, as you would expect
for a two step process. In addition, the reflected power, as the process
switches, appears to be less.
I would like to hold off opening up the tool to users for a day, so I can
improve the matching. My reasons are follows:
1. The recent generator failure was caused by excessive reflected power.
Lowering the reflected power transients with better matching will keep us
from experiencing the same problem.
2. Six months ago when I came back to working on the STS2, I detuned the
matching network to eliminate a blinking problem we were having at the
time. With the improvement to the generator, I think blinking will be less
of a problem and we would be better off with better matching.
3. I expect the improved performance of the generator may affect current
processes so now is the time to tweak the matching phase/mag detector
since users will already have to tweak their processes.
4. I want to work out a procedure for setting better initial matching
positions (tune and load) in our recipes to reduce initial reflected power
at the start of runs and when process conditions are changed or stopped in
the middle of a run.
James (Jim) P. McVittie, Ph.D. Sr. Research Scientist
Paul G. Allen Building Electrical Engineering
Stanford Nanofabrication Facility jmcvittie at stanford.edu
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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