Effects of PCl3 addition on ECR CH4/H2 /Ar plasma etching of InP and InGaAs

A hybrid electron cyclotron resonance (ECR)/radiofrequency (RF) plasma etching system used to study the etching characteristics of InP and InGaAs in CH₄H₂-based discharges is described. It was found that the materials retain smooth surface morphologies for microwave powers below 150 W. At higher microwave powers the surface becomes rough due to preferential removal of the group V species. The quality of Au Schottky diode contacts on InP degrades for high-bias etching, but the addition of PCl₃ to the discharge retards this degradation by providing an overpressure of P. The room-temperature photoluminescence intensity of InP is preserved by the PCl₃ addition. The use of CH₃Cl in preference to CH₄ to increase the etch rate of InGaAs was investigated and this appears to have few advantages since the etch rates are comparable to those with CH₄/H₂. The degree of polymer deposition during CH₄/H₂Ar etching on the type of mask used (photoresist, W, or SiO₂) is discussed