> I'm looking for details concerning the etching speed of
> thermal SiO2 (especially
> burried SiO2 specific to SOI wafers) by using 49% HF.
>
> Could you give me any references or brief informations about this?


I have measured an etch rate of 2.3 um/min for thermal oxide in 49% HF.
For a reference, see
Williams and Muller, "Etch Rates for Micromachining Processing,"
J. Microelectromechanical Systems, vol. 5, no. 4, Dec. 1996.

The buried oxide in bonded SOI wafers is normally thermal oxide
and should have the same etch rate. It is possible that it is slightly
different,
however, as the SOI wafers have undergone a high-temperature anneal for bonding.

        --Kirt Williams Agilent Technologies