Base-contact proximity effects in bipolar transistors with nitride-spacer technology

NPN-BJT´s with spacer separated Al/Si emitter and base contacts are fabricated and characterized. Due to the proximity of the base contact to the emitter-base junction, the base current is increased by two peripheral effects: an increased, but ideal electron current to the base contact and a non-ideal current through a parasitic channel confined under the spacer. The parasitic channel is induced by a positive charge in the silicon nitride spacers that reduces the effective acceptor concentration under the spacer. With the reduction of this concentration, also the associated high-doping effects are reduced.