Fabrication of Via Holes in 200 μm Thick GaAs Wafers

Etching of via holes from the back side of is an important processing step for fabrication of monolithic microwave integrated circuits. Normally, via holes are defined in wafers of 100 μm or smaller thickness. In this paper, we describe a process for fabrication of via holes in wafers of 200 μm thickness. A phosphoric acid‐hydrogen peroxide based etch has been used. The etch rate decreases with time after the start of etching due to entrapment of etchant in the via hole.