Evaluation of epitaxial planar transistors based on their double diffused impurity profile distribution

Abstract

A simple procedure is described for the evaluation of large geometry, low frequency and small geometry, high frequency type epitaxial planar transistors in terms of the impurity profile parameters based on their double-diffused impurity profile distribution. The profile parameters: collector doping, base and emitter surface concentrations, emitter and collector junction depths and collector thickness have been obtained from the measurement of the capacitance C( V) of emitter and collector junction, I–V characteristic of emitter-base junction, collector junction breakdown voltage and diffused emitter and base window areas. Making use of the calculated impurity profile distribution the parameters: emitter capacitance and saturation time constant have been calculated for several transistors having f T in the range 300–700 MHz and compared with the corresponding measured values and close agreement has been obtained. Fairly good agreement has also been obtained in calculated and measured junction depths.