If you are defining flatness and thickness variation in a smaller region of the
wafer ( say your device size instead of the whole wafer) then STIR ( Site
specific Total Indicated Reading ) would be a measurement  which is can be 0.2um
over a 22x26 mm location. Those are not exact figures but just for
representation.

Cheers
Ken Smith
Kmbh Technologies - Specialty Silicon Wafers and other materials 510-714-5055

-----Original Message-----
>From: Andrea Mazzolari 
>Sent: Nov 29, 2007 4:01 PM
>To: [email protected]
>Subject: [mems-talk] About flatness of silicon wafers
>
>Hi All,
>I'm interested to flat silicon wafers. Which are the parameters which
>quantify flatness of a silicon wafer ? I know meaning of TTV, warp and Bow.
>Is there something else which is specifing flatness of a silicon wafer ?