Bipolar transistor with polysilicon stringer base contact

Details Bipolar transistor with polysilicon stringer base contact Bipolar transistor with polysilicon stringer base contact

1988-09-21

1990-11-27

Jackson, Jr., Jerome

357 59, H01L 2972, H01L 2904

Patent

active

049740466

ABSTRACT:
There is disclosed herein a base and emitter contact structure for a bipolar transistor which is comprised of a polysilicon stripe over an isolation island which stripe extends to a position external to the position of the isolation island and assumes the shape of an emitter contact pad. The emitter contact stripe has a layer of self aligned silicide formed thereover to lower its resistance, and this silicide is doped with both N and P type impurities one of which is selected to have a higher rate of diffusion than the other. A layer of self aligned insulating material is formed over the silicide and polysilicon of the emitter contact stripe. There are anisotropically etched insulating spacers formed on the sides of the emitter contact stripe, and there are silicide base contact stringers formed beside the spacers by anisotropic etching of a layer of doped silicide. A heat drive in step in the process used to make the structure, also disclosed herein, causes the impurities from the two silicide layers to diffuse into the emitter contact polysilicon and into the epitaxially grown silicon in the isolation island. An emitter and a base are and the the attendant base-emitter and base-collector junctions are formed because the faster diffusing impurity overtakes the slower diffusion impurity and passes it to thereby form the base region. The impurities from the base contact stringers also diffuse into the epitaxially grown silicon and their lateral diffusion causes them to link up with the base impurities which have diffused into the epitaxially grown silicon from the silicide over the emitter contact polysilicon.

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