Problem stsetch SNF 2010-06-14 14:48:07: More details of etch nonuniformity ....

shott at shott at
Mon Jun 14 14:48:08 PDT 2010

I've followed up a bit more with Mike Tan to get more details about the nonuniformity that he is seeing.  Here is his report:
There is huge etching non-uniformity on a single wafer.  Through
etching 50um sized through holes, I found that the etching time can
differ by as much as 60-90 minutes on the different sides of the
wafer.  Dividing the wafer right through the mid-line, the right side
through holes features experienced much faster etching rates than
those on the left side.  The wafer flat is at the 3 O'clock position.
The reference mid-line is drawn according to the machine.  The right side of the etch would be referred to the right side of the holder when the user is facing the machine.    The etch time for making through holes on the right side is about 210 minutes to 240 minutes for a 300-350um wafer.  The etch rate also differs from run to run.

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