An investigation of nonideal base currents in advanced self-aligned 'etched-polysilicon' emitter bipolar transistors

The authors report a physical analysis of nonideal base currents in advanced self-aligned etched-polysilicon emitter bipolar transistors. By studying the dependence of the leakage currents on bias voltage, temperature, device geometry, and process parameters, the authors identify the nature of these currents and isolate the main critical fabrication steps. The abnormal base current at forward bias is found to be a generation-recombination current involving defects along the spacer oxides. These defects also control the reverse base characteristics through a trap-assisted tunneling current mechanism. A simple modification of the spacer structure is shown to result in high-performance emitter/base junction properties.>