DRY-ETCHING TECHNIQUES AND CHEMISTRIES FOR III-V-SEMICONDUCTORS

Dry etching of III-V materials using both chlorine-based (CCl2F2, SiCl4, BCl3 and Cl2) and CH4-H-2 discharges is briefly reviewed. The etch rates using chlorine-based mixtures are generally faster than those utilizing CH4-H-2, but the latter gives smoother surface morphologies for indium-containing compounds. The use of microwave (2.45 GHz) electron cyclotron resonance (ECR) discharges minimizes the depth of lattice disorder resulting from dry etching, relative to conventional r.f. (13.56 MHz) discharges. Recent results on the systematics of ECR plasma etching of both indium- and gallium-based III-V semiconductors using CCl2F2-O2 and CH4-H2 mixtures will be discussed, including the determination of the maximum self-biases allowable which do not induce near-surface damage in the semiconductor. A further key issue is the prevention of changes in the surface stoichiometry of materials such as InP, where the lattice constituents may have considerably different volatilities in the particular discharge.