Improvement of Surface Morphology for InGaP HBT
G.K. Essilfie, T.S. Low, Hengchang Chou, D.K. Kuhn, M. DeLaCruz D.C. D'Avanzo
Agilent Technologies, 1400 Fountaingrove Pkwy., Santa Rose, CA 95403
K.L. Seaward, Elizabeth Carr, Ying-Lan Chang
Electronics Research Lab., Agilent Labs.
An InGap-HBT emitter process with optimized InGaP morphology has been developed. The InGaP-HBT emitter-mesa process presented is a two step process which uses the emitter metal contact as an etch mask. A wet-etch is used to remove the top InGaAs emitter-contact layer, followed by a SiCl4-based RIE of an n+ GaAs contact layer. The RIE terminates on the InGaP emitter which is then passivated by PecVD deposited silicon nitride. The rough and irregular morphology of the passivated InGaP prompted an investigation to identify the cause of the roughness and reduce it through process optimization. A design of experiments was executed to optimize the process, and produce and RIE recipe with lower RF-power, higher SiCl4 partial pressure and ~20 times smoother InGaP surfaces.