STS2 Status Update

Jim McVittie mcvittie at
Tue Jul 28 17:51:01 PDT 2009

STS2 Users,

The top section of the etcher has been thoroughly cleaned and the ICP coil
ceramic and all the o-rings in this section have been replaced. In
addition, a manufacturing defect in the positioning of the ICP coil, which
was causing sputtering, has been corrected. These changes should improve
the etch performance and control. An initial test done yesterday shows a
about a 15 increase in etch rate use an SOI process.  Unfortunately, the
air leak rate into the chamber is still around 10 mT/min, which is the
same as before the shutdown. Elmer and Mike have determined that the
o-ring between the middle and bottom sections of the etch chamber is
leaking.  Replacing this o-ring is very complicated. A procedure for
replacing this o-ring has been requested but has not been forth coming
from STS. STS has offered to replace this o-ring and those in the bottom
section of the chamber for $12,000 but they can not do it until late

We have been requested to take the tool off shutdown while we wait for the
leak repair.  While the present leak rate may have subtle effects on the
etch performance, it is unlikely to have major effects on the processes.
In particular, it is unlikely that this leak rate contributed to the
resist burning problem seen before the shutdown. It was more likely to
have been caused by the helium lip seal, which has been replaced. Although
we are not going to work on improving the etch processes until the leak is
repaired, the initial SOI process test results for a 20 um deep etch for
widths between 1 and 50 ums showed typical results similar to what was
seen before the shut down but with the higher etch rate.

For now we are taking the system off shutdown but are not making any
guarantees about the tool's performance. Once the leak has been repaired,
we will be doing of series of qualification tests ( etch rates, dep rates,
wafer temperature) to compare the tool^Rs performance to when the system
was new.  If problems are found, they will be addressed. We are planning
on installing an enhanced radical transfer funnel STS.  The roll of this
Teflon funnel is to reduce the loss of active radicals from the ICP plasma
zone to the wafer. The goal of the tunnel in to increase etch rate without
increasing ion bombardment which contributes to resist heating and loss.


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