Dear John,
What kind of glass are you using?
Is it the same glass as the 4" wafers?
Is it thermally matched with silicon?
Borosilicate float glass is considered to be a good match with Si. Or at
least, it was.
With the larger wafers, you're going to have a larger absolute expansion
of the materials, so CTE's will have to better match.

HTH,
Jesse



>From "John Dangtran" 
Subject [mems-talk] Metallization Peel on Anodic Bonded Glass Wafer

Dear all,

Could anyone shed us a light to the problem?  I use Ti-Pt-Au on glass,
which
is anodically bonded to silicon substrate with bad results, the metal
adhesion failed.  In the past, we had good results on the 4" wafers until
we
switched to the 6".  We sputter- etched 500A of glass before depositing
Ti-Pt-Au.