A study of reactive ion etching of gallium arsenide in mixtures of methane and hydrogen plasmas

The aim of this research was to investigate the reactive ion etching (RIE) of gallium arsenide (GaAs) in mixtures of methane and hydrogen (CH ₄H₂) plasma and to evaluate thier advantages over chlorinated plasmas. This was performed in order to find the optimum etching conditions for GaAs such as, the best etch rate with greatest degree of anisotropy, the finest smooth side walls and the lowest surface roughness. The induced damage to GaAs due to RIE was investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. From a study of the behaviour of the DC self bias voltage and an analysis of electrical characterization, a possible model of the mechanism of etching GaAs in methane and hydrogen mixtures was proposed. The main contributions of this research are as follows:
Etching of GaAs while maintaining the total flow rate of the gas mixture and its residence time in the chamber constant.
Studying the effect of the physical component of the etching
mechanism on GaAs by investigating the variation in the DC self bias voltage for all process parameters.
Analyzing the effect of process parameters on the deposition rate of carbon polymers on the surface of the inorganic mask during GaAs etching.
Investigating the effect of process parameters and carbon polymer deposition on SiO ₂mask erosion during GaAs etching.
Examining the electrical characteristics of highly doped p-GaAs following RIE in CH ₄/H₂ plasma and comparing with those of H ₂ etched samples.