Anodic oxidation of GaAs in oxygen plasma

Abstract

This paper deals with the development of a new technology of forming an oxide film on GaAs. It can be used for surface passivation of GaAs or other compound semiconductor devices, for gate insulation of GaAs MISFETs and also for isolation in GaAs IC. A low temperature of below 300°C is required to prevent the evaporation of As during oxidation. This process utilizes the anodic oxidation of GaAs in oxygen plasma, which is a dry process and a process of oxidation in oxygen plasma combined with anodic oxidation. The GaAs chip is placed outside the plasma generating region in order to keep the chip temperature below 300°C and is biased at 10-100V positive with respect to the plasma. Data will be presented on the thickness of grown oxide and the terminal voltage between the anode (GaAs substrate) and the cathode as a function of the oxidation time. It should be pointed out that the oxide with 2000Å in thickness can be grown for 5 minutes even at 80°C. Auger electron spectroscopy revealed the oxide composition as GaAsO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> whose x is less than 4 and the oxide has high electrical resistivity. The capacitance voltage characteristics of an MOS diode have been determined. The authors have succeeded in oxidizing GaAs at room temperature with anodic oxidation in oxygen plasma and obtaining oxide films with good electrical characteristic and with uniform thickness.