Heterojunction bipolar transistor (HBT) fabrication using a selectively deposited silicon germanium (SiGe)

Abstract

A Heterojunction Bipolar Transistor (HBT) is provided where the SiGe base region is formed through selective deposition, after the formation of the base electrode layer and the emitter window. A sacrificial oxide layer is deposited between the collector and base electrode. The contact to the SiGe base is made at an extrinsic area, underneath the base electrode, after removal of the sacrificial oxide. The SiGe is covered with a temporary oxide layer during further processes, and this protective layer is removed immediately before the deposition of the emitter material. The selective deposition of the SiGe at a relatively late stage of the fabrication process helps insure that the film remains free of the stresses which can degrade electron mobility. A process of fabricating the above-described HBT device is also provided.

Dependencies are inferred from the claim text.