Hi Scott,

We are using the ASTM reference (ASTM F534 3.1.2) for the definition of
measuring bow and warp on a wafer after backgrind.  The ASTM document was
originally written for bare wafers, not wafers after backgrind.  Do you know of
a standard document for bow and warp definitions for wafers after backgrind?  We
would especially be interested if there is any discussion of the surface
reference plane established by three points equally spaced on a circle near the
wafer edge. Our thought is that very thin wafers (50 micrometer) could easily
move on these three points resulting in an measurement errors for the bow.

Thanks for any information you could provide.

Best regards,

Tom Bristow
Chapman Instruments


-----Original Message-----
From: smcwilliams@photodigm.com [mailto:smcwilliams@photodigm.com]
Sent: Tuesday, May 23, 2006 9:43 AM
To: mems-talk@memsnet.org
Subject: RE: [mems-talk] stress induced by backgrinding

Hi Cla, usually people measure stress by how much the substrate bows.  We
studied backgrinding stress by grinding to 80 microns thick and using a long
scan profilometer scan to measure the bow.  An inferometer can also be used.

Scott

-----Original Message-----
From: cla rai [mailto:fromsingawithlove@yahoo.it]
Sent: Tuesday, May 23, 2006 1:15 AM
To: General MEMS discussion
Subject: [mems-talk] stress induced by backgrinding


hi!!

  i want to study the stressed induced by backgrinding in a silicon
wafer..do somebody have an idea on how can i do that?