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 result in rough surfaces and undercutting. The etching results can be improved by adding BCl3 to the CCl2F2 /Ar discharges. The process of reactive 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 AlGaAs, gasous mixtures containing CC12F2 are often used. Fluorine from the glow discharge promotes the formation of AlF3, responsible for the selectivity of the etching process. Furthermore, selective and nonselective etching can be achieved in the CCl2F2/BCl3/Ar discharge by varying the proportion of the CCl2F2. High selective etching can be accomplished at low radio-frequency (r.f.) power and low d.c. bias when the CCl2F2 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. Silicon dioxide can be removed in situ by the CF4 plasma and the SiO2 mask is better than photoresist for its low etching rate and low sputtering rate.