Dual lift-off self aligning process for making heterojunction bipolar transistors

摘要

A dual lift-off technique is used to provide self-alignment of the emitter area, the emitter contact, and the base contact of a heterojunction, bipolar transistor. A photoresist pattern which defines an emitter adjacent a base contact is formed on a suitable heterojunction bipolar semiconductor wafer. A base contact is formed by etching through the first semiconductor to the heterojunction and depositing metal on the second semiconductor. Dielectric is then deposited on the base contact. The photoresist is then lifted off with its dual covering of dielectric and metal. The emitter contact metal can then be deposited without requiring critical alignment because the base contact is covered with dielectric.