Compatible field-effect and bipolar transistors

David Kin-Poon Cheung

Four methods for the simultaneous fabrication of field-effect and bipolar transistors have been investigated. The basic process involves obtaining two different junction depths by a single diffusion. This was accomplished by the techniques of (1) partial masking, (2) two depositions, (3) etched channels, and (4) oxide depletion. The first three methods were used for the fabrication of compatible field-effect and bipolar transistors. Each of the methods was evaluated on the basis of reproducibility, uniformity and predictability. The field-effect transistor parameters obtained were comparable for all three methods. However, the two-deposition process was considered to be the best of the three because of its excellent reproducibility and the simplicity in its process steps.