I am looking for a mask material for use with planar etchant consisting
of hydrofluoric ; nitric; acetic acid ( 8% HF / 75% HNO3 / 17% CH3OOH )
on [100] Si.  I am trying to define features which are 300 microns deep
so I need a selectivity x achievable thickness product equal to this.
Any help would be greatly appreciated.

>Pete