STSetch back alive, and not breaking wafers

[Eric Perozziello]

Hi All,

As you might know, the stsetch was effectively "down"
for a repeated wafer-breaking problem.

I think that problem is resolved now, as I executed
dozens of transfers last night on a dummy wafer with no
breaking/chipping.  I cleared the broken wafer, and I think
identified the root cause.

The machine was down all day today because I couldn't get it
to pump down.  I finally managed to get past that
problem, and measured the leakrate at <0.25 millitorr
per minute, which is by far the lowest I've ever seen it.  (Mainly
because I first thought the pumpdown might be a leak
caused by the chamber service, so I went through the whole
chamber to make better seals).

In going through the chamber in detail, I did notice is that
seals inside are getting
eaten fast, probably due to excessively long O2 cleans.
We should probably limit these cleans to ~20 minutes in a
given day of etching.

Also, the screw caps are pretty much completely gone (again,
due to a lot of "cleaning"), and we have no replacements in
stock.  We need to order more, but in the meantime, I don't
expect the wafers coming out to be "iron free".

So, I believe the machine is ok to use now.  It's still
listed as a "problem" from Ed, but I believe that is now
completely resolved.  The only (minor) issue that I noticed
is that the loader is loading the wafer a little "deep"
into the chamber.  Keep an eye on the position.

Happy Etching.
-Eric