Bipolar transistor process using sidewall spacer for aligning base insert.

摘要

An improved method for fabricating a bipolar transistor reduces base current resistance. The transistor base (208) and emitter (206) are formed by diffusion through an emitter contact pedestal (204) formed on an epitaxial layer over a substrate (214). Access to the n-type emitter (206) is through the emitter contact pedestal (204) and the base insert (216) is ensured by forming oxide sidewall spacers (226) on the emitter contact pedestal (204) during the implant used to form the base insert (216). Defining the isolation with sidewall spacers permits reliable isolation of emitter (206) and base insert (216) while minimising their physical separation. The minimised physical separation provides a base current path with considerably less total resistance than is found in the background art in which the isolation is defined photo-lithographically.