Hi Andrea
What is the size of your wafers? Usually the numbers are better than quoted
but you will have to sort thru the wafers to find the best ones.
Usually people worry only about TTV since during lithography, the critical
area, that wafers are vacuum clamped to a flat surface so the warp is
temporarily 'ironed' out. The only way I know to flatten a warped wafer is
to heat it on a flat surface to ~1200C and pray!
The surface must not warp itself at the temperature change - flat quartz
block is good. Very slow heating is required.
Shay

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Andrea Mazzolari
Sent: Tuesday, November 27, 2007 10:27 AM
To: General MEMS discussion
Subject: [mems-talk] Decreasing of TTV and Warp

Hi all,
i need to decrease TTV and warp of some silicon wafers.
Initial ttv<3um, warp<20 um.

I have contacted different manufacturers of silicon wafers, but many does
not focus on warp reduction.

Any suggestion about tecniques to reduce both ttv and warp ?