Low Bias Dry Etching of III-Nitrides in Cl_2-Based Inductively Coupled Plasmas

摘要

Cl_2-based inductively coupled plasmas (ICP) with low additional dc self biases (--100V) produce convenient etch rates (500--1500A·min~-1) for III-nitride elec- tronic device structures. A systematic study of the effects of additive gas (Ar, N_2, H_2), discharge composition, process pressure, and ICP source power and chuck power on etch rate and surface morphology has been performed. The general trends are to go through a maximum in etch rate with percent Cl_2 in the discharge for all three mixtures, and to have an increase (decrease) in etch rate with source power (pressure). Since the etching is strongly ion-assisted, aniso- tropic pattern transfer is readily achieved. Maximum etch selectivities of approximately six for InN over the other nitrides were obtained.