my last etch info

Luigi Scaccabarozzi scaccag at
Tue Jun 24 07:50:20 PDT 2003

Hi all,
I would like to share some info about my last etch (last sunday) that may
help writing the new policy or other users to get consistent results.
Last sunday I did first O2 cleaning (30 min) and then run my recipe
(GIGI2, Ar:BCl3:Cl2) for 45 min on a dummy.
Then I etched my samples (GaAs with Ni mask) for 5 min. each (all details
are in the logbook).
Though I'm not sure yet about the etch quality,I found exceptionally good
etch rates (1.3 um / 5  min or 2600 A/min which is even higher  than what
I expect <~ 2000 A/min) and   the interesting thing is that the last user
before me was Carl (according  to history, logbook and last run recipe),
etching with SF6. Even more  interesting is the fact that Carl's etch was
run  24 hrs earlier and  nobody used the machine in between (and it has
not been manually cleaned, up to my knowledge).
Moreover, I remember Ali noticed that his best etch was after a weekend,
when nobody has used the machine.
Maybe this is a coincidence or maybe the fact that the machine is left in
pumpdown for enough time after a supposed "dirty" etch (I mean with
fluorine) contributes to the cleaning process (or simply that Carl's
recipe is compatible with mine).
I ask Jim, or others more expert than me, if this is possible and/or if it
makes sense.
Hope this will help.

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