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 Cl 2 etching. At room temperature, etching conditions with a higher chiorine pressure of about 10 -3 Torr provide no significant etching rate, whereas etching conditions at a lower chlorine pressure of (4±1)×10 -5 Torr provide a moderately slow etching rate (40 Å/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 the Cl radicals is clearly demonstrated, but this cleaning does not occur when using Cl 2 molecules. When the GaAs surface is not covered with such contaminants, both the Cl-RE and the Cl 2 etching progress. The roughness of the Cl-radical-etched surface is as low as 50 Å after etching to a depth of 2640 Å. After heat treatment of the Cl-radical-etched sample at 400°C, an atomically ordered and stoichiometric GaAs surface is obtained.