Abstract:
A method for selectively oxidizing the surface of a III-V compound semiconductor wafer. A photoresist mask is first formed on the surface of the semiconductor leaving exposed the areas to be oxidized. The semiconductor is then made the anode in an electrolytic cell wherein the electrolyte comprises water and a source of ions for adjusting the pH or providing conductivity to the solution. In a preferred embodiment, the wafer is a gallium containing compound semiconductor and in particular GaAs, and the electrolyte is water and an ammonium acid phosphate. The oxide is grown electrolytically only into the exposed areas of the wafer, and the photoresist may then be stripped off leaving the desired oxide pattern.
Abstract:
A method for oxidation and etching of a III-V compound semiconductor in a single solution. The semiconductor is made the anode in an electrolytic cell wherein the electrolyte is water raised to a pH of 8 or above by a source of hydroxyl ions such as NH4OH. When an appropriate electric field is established in the cell, an oxide is grown into the surface of the semiconductor. Then the field is lowered or turned off and the oxide dissolves faster than it is grown resulting in an etching of the semiconductor material previously consumed in forming the oxide. The method permits electrochemical thinning of a semiconductor layer for such uses as FETS and IMPATTS and further allows formation of passivating layers on etched surfaces in situ.