Hi Andrea,

I don't do the polishing myself but all my vendors tell me that all you can
do is make the TTV worse after lapping, at least with single side polishing.
Your best bet is a double side polish. Of course, you may produce some
wafers with a lower TTV but it won't be a high yield.

Jeff Besterman
Addison Engineering
150 Nortech Parkway
San Jose, CA 95134
office phone 408-956-5101
office fax 408-956-5111
www.addisonengineering.com

-----Original Message-----
From: Andrea Mazzolari [mailto:mazzolari@fe.infn.it]
Sent: Wednesday, January 31, 2007 9:36 AM
To: 'General MEMS discussion'
Subject: [mems-talk] How to decrease TTV ?

Hi all.
Here i have some silicon wafers with a TTV of 20um.
We also have a bonding unit from Logitech (WSB2 Wafer Substrate Bonding
Unit) and a lapping machine from logitech (PM5 Precision Lapping and
Polishing Machine).
I want to decrease TTV of my wafers. Is there a way to realize this ? It
seams the better way whould be to use a soft-pad grinding. What do you think
about this technique applied to TTV decreasing ? Do you know where i could
find soft-pad grinding tools ?