Try an R.C.A. clean first (skip the HF etching step for
the Pyrex).

Ed

>I tried to bond a glass (Pyrex) and si wafer with 1000
>V, 430°C and 30 minutes (point cathode), both wafer cleaned with
>acetone.  Unfortunately it did not work. There was only a vacuum
>between the wafers and it was possible to separate them after the
>bonding.