A comparative study of CH4 :H2 , and CH4 :H2 :Ar rf-plasma and microwave electron cyclotron resonance (ECR) plasma etching of GaAs and InP is presented. The study is in two parts;
(i) Kinetic studies of GaAs and InP etch rates as a function of the constituent gas flow rates, applied rf and microwave powers, substrate temperature and position. The results indicate that CH4 :H2 :Ar ECR etching of GaAs is 10× more efficient in the utilisation of the CH4 precursor gas than rf-plasmas. However, the absolute etch rates are lower (70 nm min−1 for rf and 25 nm min−1 for rf biassed ECR-plasmas).The effect of etching conditions on InP morphology is also examined.
(ii) The study of electrical “damage” in GaAs/AlGaAs high electron mobility transistor (HEMT) Hall bar structures, was investigated by ECR-plasma etching off the top GaAs capping layer. Results indicate that ECR-plasma etching with an rf-bias between 0V and −30V does not significantly effect the electrical characteristics of such devices at 300K, with some degredation at 1.2 K.