Dear Daniel;

For the safe material I think it is best for your substrate holder and for the
silicon etch process to use ceramic materials like alcatel deep silicon etcher.

For the best recipe of aluminum Al2o3 etching is to use chlorine gaze specially
:  BCl3 with high power.

regards

naitbouda abdelyaminea
naitbouda@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