James,
It is pretty typical to have problems removing wafers from the platen of
an Autoetch or Rainbow system when the chamber is vented. The service
techs will tell you to put a small fragment of vinyl glove, cleanroom
wipe, or a similar object on the platen when you are aligning the
transport system at atmospheric pressure, to prevent wafer breakage from
stiction. The stiction problem should not be too acute with the chamber
under vacuum, however.
I had a similar problem on my 490 when one lift pin got partially pulled
out, so it contacted the wafer before the other 3. You might try
aligning all four lifter pins with a wafer and a small bubble level.
Make sure the leveling of the wafer when lifted is the same as the
leveling on the platen. Having all 4 hit at the same time seems to help
spread the force over the whole wafer rather than at one single lift
point. The pins are simply pressed into holes in the lifter assembly, so
you can pull them straight out with a pliers, and push them back in the
same way. Just raise the lifter pins in the Macro page, and push or pull
them into the holes in the platen until everything is level. It wouldn't
hurt to check the tips of the pins either to see if they are pointy or
rounded off. They should be flat at the top, without any kinks or bends.
I have successfully run thin quartz wafers without breakage in our
machine, and they seem to break if you barely touch them.
Lam Research does not support this etch platform any more, but Aspect
Semiquip in Phoenix, AZ (USA) provides good support and spares.
http://www.aspectsys.com
No relationship, but I have been pretty happy with them so far.
Al Raisanen
Rochester Institute of Technology
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of James Dekker
Sent: Thursday, March 20, 2003 9:21 AM
To: [email protected]
Subject: [mems-talk] LAM etcher troubles
We are using a somewhat dated Lam etcher (autoetch 490) as an oxide
etcher
and it has developed a peculiar problem. Occasionally, (and it is more
frequent than desired) it will break SOI wafers. The best diagnosis
seems
to be that the wafers are sticking to the platen. This sticking problem
happens to both double side polish (DSP) and SSP SOI wafers, and also to
non-SOI dummy wafers. However, the thin (380 um) SOI seem to be weaker
and
so they break when the lifting fingers try to raise the wafer from the
cathode. (we have manually unloaded some wafers after etching and it
takes
quite a bit of effort to pry them from the cathode). Has anybody
encountered this before and is a solution known?
Thanks
James Dekker, Research Engineer
VTT Microelectronics Research center
Tekniikantie 17, Espoo
P.O.Box 1208, FIN-02044 VTT, FINLAND
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