Enhanced plasma etching for group III-V semiconductors: Techniques and surface kinetics.

Reactive ion etching has become the preferred method for transferring patterns on semiconductors in device fabrication and the use of Group III-V semiconductors has become more widespread in the semiconductor industry. This research effort focuses on developing new etch techniques for III-V compounds and gaining insight into the etching mechanisms. A new etch technique which oscillates between sputter etching and RIE modes of etching was investigated. Extensive studies for GaAs and InP using a BCl$\sb3$/Ar gas system were performed with standard RIE equipment. The time period and sputter duty cycle are two important factors that were studied in these experiments. Etch rate enhancements of three times for GaAs and seven times for InP were obtained using this cyclic technique. Surface analysis was used to study and characterize the etched InP and GaAs surface. The results show that the primary mechanism for etch enhancement was the removal of the Group III chloride through sputtering. The high temperature (RIE) kinetics of InP were studied using a new etchant chemistry of BCl$\sb3$/Ar and $\rm BCl\sb3/Ar/O\sb2.$ At low oxygen flows the etching was enhanced by more chlorine neutrals produced in the plasma. At high oxygen flows the formation of boron oxide inhibited the etching. Surface analysis and optical emission spectroscopy were used to study both the gas and surface chemistries. Finally, the kinetic modeling for the reactive ion etching of InP with BCl$\sb3$ and argon plasmas was performed. The etch rate was limited by the removal of indium chlorides at low temperatures, and the indium mono-chloride formation was found to be rate limiting step at high temperatures. The kinetic model developed contained chlorine neutral and argon ion terms representing the chemical and physical components of etching. The model compared favorably with experimental etching results for both high and low temperatures.