Hi;

Try to use

Cl2/O2/SF6 /CBrF3/CHF3

To etch deeply you mast use Cl2 in the main RECIPE

To have a good sélectivité about oxyde you should use O2 with Br
and also CHF3


Regards

anaitbouda@cdta.dz
Process Engineer in the Dry etch area
of the Clean Room of the CDTA
Centre de Developpement des Technologies Avancées
Cite du 20 Aout 1956 Baba Hassen,Alger,Algerie