Low bias dry etching of III-nitrides in Cl2-based inductively coupled plasmas

Cl2-based inductively coupled plasmas (ICP) with low additional dc self-biases (−100V) produce convenient etch rates (500–1500Å·min−1) for III-nitride electronic device structures. A systematic study of the effects of additive gas (Ar, N2, H2), 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 Cl2 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, anisotropic pattern transfer is readily achieved. Maximum etch selectivities of approximately six for InN over the other nitrides were obtained.