Self-aligned polysilicon base contact structure

Details Self-aligned polysilicon base contact structure Self-aligned polysilicon base contact structure

1986-03-24

1987-09-01

James, Andrew J.

357 59, 357 49, 357 54, 357 50, 357 35, H01L 2972

Patent

active

046912193

ABSTRACT:
An integrated bipolar transistor having a self-aligned polysilicon base contact is formed by depositing a first doped polysilicon layer and a silicon nitride passivating layer on the surface of a semiconductor substrate having an isolated collector region therein. An opening is formed in the first polysilicon and silicon nitride layers over the collector to expose the surface of the semiconductor substrate. The base region is formed through the opening and a conformal silicon nitride coating is then deposited on the wall of the opening and over the surface of the semiconductor substrate within the opening. A second polysilicon layer is formed on the silicon nitride passivating layer. The second polysilicon layer is reactive ion etched, leaving a polysilicon sidewall on the wall of the opening while removing the rest of the second polysilicon layer. The polysilicon sidewall is then oxidized, and an emitter is formed through the opening. The bipolar transistors of the present invention have high density, high speed and improved device to device uniformity because thinning or shorting of the passivating layer on the polysilicon layer is prevented.

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