Isotropic etching is known to cause rounding off of etch profile. Anisotropic etching, though it yields better  defined shapes, can only form pyramidal openings. determine (a) The approximate shape of the mask (b) the type of etch (c) etch stop material and (d) a typical etchant required to form a triangular opening for a cavity formed on a 100 silicon wafer by wet etching.