From sylviajs at stanford.edu  Mon Jul  3 15:52:51 2000
From: sylviajs at stanford.edu (S. J. Smullin)
Date: Mon, 3 Jul 2000 15:52:51 -0700 (PDT)
Subject: streaks on wafers
Message-ID: <Pine.GSO.4.21.0007031550200.390-100000@elaine10.Stanford.EDU>

In recent nitride etches using electrodes 2-5, my wafers have come out of
the machine with radial streaks or scratches (can't tell which) on the 
unetched side that do not disappear after a dip in the piranha bath. The
backsides are unpatterned, no resist. Has anyone else had similar
problems? The electrodes show no obvious "dirt".

-Sylvia



From lian at Stanford.EDU  Tue Jul  4 10:19:06 2000
From: lian at Stanford.EDU (Lian Zhang)
Date: Tue, 4 Jul 2000 10:19:06 -0700 (PDT)
Subject: streaks on wafers
In-Reply-To: <Pine.GSO.4.21.0007031550200.390-100000@elaine10.Stanford.EDU> from "S. J. Smullin" at Jul 03, 2000 03:52:51 PM
Message-ID: <200007041719.KAA05788@myth2.Stanford.EDU>

Hi Sylvia,

I had the problem two months ago.  The streaks come from the traces of
photoresist/developer after you pattern the front side.  If you check the
backside after developing, you'll see it's actually quite dirty.  So you
might want to dump rinse and spin dry the wafers (sometimes I even have to
use acetone to manually wipe the backside) before you put them into
drytek2--it's recommended because photoresist and developer are corrosive
to electrodes.  Another effective way is to add a backing wafer to protect
the backside.  But again, please make sure the backing wafer is clean.

Hope this helps,
Lian

> 
> In recent nitride etches using electrodes 2-5, my wafers have come out of
> the machine with radial streaks or scratches (can't tell which) on the 
> unetched side that do not disappear after a dip in the piranha bath. The
> backsides are unpatterned, no resist. Has anyone else had similar
> problems? The electrodes show no obvious "dirt".
> 
> -Sylvia
> 
>