Hello

To use
KOH  silicon etch  ; You can protect the back side of the
wafer by the LPCVD nitride who is better than PECVD .and then use these
three methods :

1.
Protective Tapes

2.
Wafer Holder

3.
Black Wax

The best
option for frontside protection is  a coat of Black Wax to prevent
 from broken   and contamination wafer ,after etching silicon
with KOH you can remove the wax with Toluène solution very easy .

Naitbouda
abdelyamine

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