A STUDY OF SELECTIVE AND NONSELECTIVE REACTIVE ION ETCHING OF GAAS A1GAAS MATERIALS/

High etching rates of GaAs can be obtained by reactive ion etching of GaAs in CCl2F2/Ar discharges. However high chemical etching rates resu lt in rough surfaces and undercutting. The etching results can be impr oved by adding BCl3 to the CCl2F2 /Ar discharges. The process of react ive ion etching in the BCl3 discharge consists of the BCl(x) (x = 1 or 2) radical species, which react with III V compound semiconductors to form easily sputtered compounds. For selective etching of GaAs on AlG aAs, gasous mixtures containing CC12F2 are often used. Fluorine from t he glow discharge promotes the formation of AlF3, responsible for the selectivity of the etching process. Furthermore, selective and nonsele ctive etching can be achieved in the CCl2F2/BCl3/Ar discharge by varyi ng the proportion of the CCl2F2. High selective etching can be accompl ished at low radio-frequency (r.f.) power and low d.c. bias when the C Cl2F2 is more than 20% and nonselective etching can be reached when it is less than 10%. Photoresist or SiO2 was used as the etching mask. S ilicon dioxide can be removed in situ by the CF4 plasma and the SiO2 m ask is better than photoresist for its low etching rate and low sputte ring rate.