Polycrystalline silicon-germanium heating layer for phase-change memory applications

Abstract

This letter reports on the performance improvement of phase-change memory (PCM) cells by applying silicon-germanium (SiGe) alloys as resistive heating layers. The in situ doped polycrystalline Si0.75Ge0.25 films, lying under holes filled with a Ge2Sb2Te5 (GST) phase-change material in a pore-style configuration, promoted the temperature rise and phase transition in the GST. The SiGe heating layer caused drastic reduction in both set and reset currents compared to a conventional TiN heater material. The threshold voltages of the PCM cells were almost uniform irrespective of the kind of heating layers. It is considered that this beneficial effect of the SiGe heating layer originates from the high electrical resistivity and low thermal conductivity of a SiGe alloy.