Fabrication process for a shallow emitter, narrow intrinsic base transistor.

摘要

A high performance bipolar transistor having a shallow emitter and a narrow intrinsic base region is fabricated by a minimum number of process steps. A silicon semiconductor body 10 is provided with regions of monocrystalline silicon isolated from one another by isolation regions (18) an epitaxial layer (14) and a buried subcollector (12). A layer (24) of polycrystalline silicon is deposited on the body. The surface of the polycrystalline silicon layer (24) is oxidized and the polycrystalline silicon is implanted with a base impurity. Silicon nitride and oxide layers (28, 30) are deposited on the polysilicon layer. An opening is made in the surface oxide layer (28) and the silicon nitride layer (30) to define the emitter area of the transistor. The polycrystalline silicon is thermally oxidized to drive the base impurity into the substrate. The thermal oxide is removed in an isotropic etch to leave an oxide sidewall cover (38) on the polycrystalline silicon. An emitter impurity is ion implanted into the polycrystalline silicon in the emitter area and then driven into the substrate. Collector, base and emitter contact openings are made and conductive metallurgy is formed.