GAAS SURFACE CLEANING ETCHING USING PLASMA-DISSOCIATED CL RADICAL

Cl radical etching (RE) of GaAs, a previously evaluated dry etching method with very low damage which is suitable for nanometer-scale fabrication, damage removal and surface cleaning, is investigated in comparison with Cl2 etching. At room temperature, etching conditions with a higher chlorine pressure of about 10(-3) Torr provide no significant etching rate, whereas etching conditions at a lower chlorine pressure of (4 +/- 1) x 10(-5) Torr provide a moderately slow etching rate (40 angstrom/min) and precise control of etching depth, both of which are useful for shallow etching of nanometer-scale structures. Effective cleaning of GaAs native oxide and carbon contaminants by thea radicals is clearly demonstrated, but this cleaning does not occur when using Cl2 molecules. When the GaAs surface is not covered with such contaminants, both the Cl-RE and the Cl2 etching progress. The roughness of the Cl-radical-etched surface is as low as 50 angstrom after etching to a depth of 2640 A. After heat treatment of the Cl-radical-etched sample at 400-degrees-C, an atomically ordered and stoichiometric GaAs surface is obtained.