Selective etching of GaAs over Al_(0.2)Ga_(0.8)As semiconductor in pulsed DC BC1_3/SF_6 plasmas

摘要

Selective dry etching of GaAs over Al_(0.1)Ca_(0.8)As in pulsed DC BCl_3/SF_6 plasmas was studied. The process variable was the composition of SF_6 gas flow rate (0-50% ) in the BCl_3/SF_6 plasmas. The total flow rate of the gases was 20 seem. The other plasma conditions were held constant at 13.33 Pa chamber pressure, 500 V pulsed DC voltage, 200 kHz frequency and 0.7 us reverse time. Only a mechanical pump was used for the processing. Oscilloscope data showed that there was little variation of the input voltage and current on the chuck with the composition change. 10% mixing of SF_6 in the BCl_3/SF_6 plasma produced the highest etch selectivity (48:1) of the GaAs over the Al_(0.2)Ga_(0.8)As. However, further addition of the SF_6 gas to the plasma reduced the etch rate of GaAs and the selectivity. The GaAs and AlGaAs would not etch when the SF_6 composition was >30% in the plasma. The root mean square surface roughness of the GaAs was 0.7-1.3 nm after etching. The overall results indicated that the best selective etching was achieved at 10% SF_6 composition in the pulsed DC BCl_3/SF_6 plasma.