The influence of the wafer surface material and wafer bias voltage on the Br radical density in HBr/Ar and HBr/Ar/O2 inductively coupled plasmas was investigated by appearance mass spectrometry. By increasing the bias voltage, a monotonic decrease in the Br radical density was observed irrespective of the surface material (Si, Al2O3) of the wafer. A drastic increase in Br radical density was observed after O2 addition to HBr/Ar plasma in the case of a bare Si wafer, whereas almost the same density was observed in the case of an Al2O3-sputtered Si wafer. X-ray photoelectron spectroscopy (XPS) analysis indicated that O2 addition promotes oxide formation on the Si surface. Measurement of the decay time constant for a Br radical after turning off the plasma indicated that O2 addition results in a longer decay time constant, suggesting the decrease of the surface loss probability of Br radicals for the surface-oxidized Si surface.