ROBUST REACTIVE ION ETCHING PROCESSES FOR GAAS/ALGAAS/ALAS BY APPLICATION OF STATISTICAL CONCEPTS

Reactive ion etching of AlGaAs/GaAs was investigated using chlorine-containing gases. We defined a remarkably stable process exhibiting very good process parameters: smooth surfaces, rectangular side walls, and good selectivity against photoresist, but almost no difference in etch rates due to a different aluminum content. These response variables depend on the process parameters RF power, total gas pressure, total gas flow, and mixing ratio of reactive to nonreactive gases. The etch rate mainly depends linearly on dc-bias and the flow of BCl3. The deviation from linearity for bias is attributed to the chemical part of material removal. About three quarters of the observed response variables can be explained by the chosen model. The inclination angle of the side walls which are free of redeposits is almost rectangular to the etched surfaces, which are extremely smooth. This is compared with glow discharges of neutral atoms.