Analysis of the simultaneous fabrication of unipolar and bipolar transistors in a functional block

Abstract

A monolithic functional block containing both unipolar and bipolar transistors was described by K. K. Yu and L. Pollack at the 1961 PGED Meeting. Both unipolar and bipolar transistor structures were fabricated simultaneously by means of double diffusion, as for conventional planar transistors. However, the presence of the unipolar transistors imposes some additional requirements on the controlling parameters. This paper analyzes the problems involved and discusses the compromises and criteria in design. For the unipolar transistors the major considerations are the pinch-off voltage, pinch-off current, the transconductance and the breakdown voltage. For the bipolar transistors, on the other hand, the principal characteristics are the gain and breakdown voltage. In both cases the controlling parameters for these characteristics are the surface concentration, the shape of the impurity profiles, junction depth, etc. The paper analyzes the requirements of these two active devices in the terms of exponential, complementary error function and Gaussian distributions and points the way to an optimum design for both. The analytical results check well with experiments.