Dry etch damage in inductively coupled plasma exposed GaAs/AlGaAs heterojunction bipolar transistors

Abstract

The dc current gain and emitter and base sheet resistance of C-doped GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have been used to measure damage introduced by exposure to Ar inductively coupled plasmas (ICP). As the ICP source power is increased at fixed rf chuck power, the damage-induced changes in device characteristics are reduced due to a reduction in ion energy. Beyond a particular ICP source power (∼1000 W for 50 W rf chuck power), the damage increases due to the increase in ion flux, even though the ion energy is low (<30 eV). These results are a clear demonstration of the advantage of high ion density plasmas for pattern transfer in damage-sensitive minority carrier devices such as HBTs.