Hello!

I am trying to estimate stress of dielectric thin film by measuring the
curvature of Si wafer (001) , either by Flexus of by an optical set-up.
Somehow in most of the measurements I obtain that the radius of
curvature measured along the axis ,which is going through the center of
the wafer and is parallel to the flat, is higher  than the radius
measured along the axis which is perpendicular to the flat. This
phenomenon is very consistent for all the wafers, with no connection to
their history and to the deposited layers.
Did anyone also observed this result? Can it be that the presence of the
flat somehow changes the boundary conditions near the edges of wafer and
makes the stress distribution asymmetric to the wafer center.
Thanks
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Mark Schvartzman
Process engineer
GWS Photonics Inc.
Paz Towers, 33, Bezalel st.
Ramat-Gan, 52581, Israel
Tel. 972-3-7534440
Cell. 972-51-722389
E-mail: mark@gws-photonics.com