Optimizing the Epilayer Doping Concentration with Respect to Bipolar Transistor Performance in a Low-Power UHF-Process

The performance of bipolar devices (NPN-transistors, lateral PNP-transistors and IIL-gates) in a low-power UHF-process at varying epilayer doping concentration is discussed on the basis of both two-dimensional device simulation and experimental data. While IIL-gates and lateral PNP-transistors would benefit by an increased doping, the observed strong decrease of the NPNs' forward Early Voltage Veaf inmposes a severe restriction on a choice towards raised doping concentrations, since Veaf is an important electrical device parameter in linear analog bipolar processes. The presented results help to find a reasonable, application orientated trade-off between the various electrical device parameters.