Plasma etching of InGaP, AlInP and AlGaP in BCl3 environments

The etch rates of InGaP, AlInP and AlGaP are more than an order of magnitude larger in microwave-enhanced BCl3/Ar discharges relative to conventional reactive ion etch (RIE) conditions. This is due to the increased atomic radical and ion densities. While RIE discharges produce rough, non-stoichiometric surfaces of InGaP and AlInP due to the formation of an InCl3 selvedge layer, the surfaces of samples etched under ECR conditions are generally smooth and stoichiometric. This difference is found to be due to the efficient ion-assisted desorption of InCl3 under high ion density conditions. The advantage of this process is that simple BCl3-based plasma chemistries can be employed for all III-V semiconductors, whereas previously CH4/H-2 was used for In-containing materials and chlorine chemistries for Ga-containing materials. The etch rate of AlGaP is substantially slower than the other two materials, which can be explained on the basis of the bonding differences.