Enhanced etching of InP by cycling with sputter etching and reactive ion etching

A new etch technique which oscillates between sputter etching and RIE modes of etching was investigated. Extensive studies for InP using BCl₃/Ar and Cl₂/BCl₃/Ar gas systems were performed with standard RIE equipment. The etching sequence was performed with a programmable controller which automates the cycling sequence. The time period and sputter duty cycle or percent sputter time are two important factors that were studied in these experiments. Using this cyclic technique, an etch rate of 300 angstrom/min was obtained which is an order of magnitude higher than our standard RIE etch rate for InP. Standard optical photoresists can be used as masks for this technique although metal masks are more feasible. The resulting wall shape is vertical with smooth morphology. Etch enhancements may be explained by the removal of an indium chloride layer. Surface analysis was performed to verify that chlorine is forming on the surface.