Analytical and numerical analyses of the delay time of BiCMOS structures

Analytical expressions for the transient response of BiCMOS structures have been derived. The analysis is performed on conventional structures and structures employing short-channel MOSFETs. The equations relate the delay time to key device and technology parameters. In deriving the time response, the two basic conduction regions (linear and saturation) for the MOSFET have been considered. A numerical algorithm for solving for the delay time of BiCMOS structures taking into account high-level injection effects, base resistance, doping-dependent mobilities, and bandgap narrowing is presented. A figure of merit for the speed is derived and scaling the supply voltage is considered