Double self-aligned fabrication process for making a bipolar transistor structure having a small polysilicon-to-extrinsic base contact area

摘要

A bipolar transistor device is disclosed having a structure wherein a layer of insulating material extends over and covers the structure substrate up to the region of the extrinsic base around the emitter. A very small area conductive base contact is provided to the extrinsic base, and a protective wall of insulating material is located on the sidewall of the base contact to isolate it from the emitter contact. This structure is made possible by a fabrication process incorporating a double-self-alignment technique wherein the base is self-aligned to a window in the insulating material and the emitter is self-aligned to the base.