Bipolar transistor with a silicon germanium base and an ultra small self-aligned polysilicon emitter and method of forming the transistor

摘要

A low-power bipolar transistor is formed to have a silicon germanium base region, an intrinsic emitter region with a sub-lithographic width, and an oxide layer that is self aligned to an overlying extrinsic emitter. The silicon germanium base region increases the speed of the transistor, while the small extrinsic emitter region reduces the maximum current that can flow through the transistor, and the self-aligned oxide layer and extrinsic emitter reduces the base-to-emitter junction size and device performance variability across the wafer.