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US 5,512,496 AGranted
Method of making collector-up bipolar transistor having improved emitter injection efficiency
AssigneeTexas Instruments Incorporated
InventorsHin F. Chau, Hua Q. Tserng
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Abstract
A collector-up bipolar transistor having an undercut region (522) beneath extrinsic regions of a base layer (510) and an emitter layer (508). The extrinsic emitter region is depleted of charge carriers and provides passivation for the extrinsic portion of the base layer (508). Contact to the emitter layer may be made by forming contacts on the top surface of the substrate (500) or in a recess in the backside of the substrate.
Claims6
A method of forming a bipolar transistor, comprising the steps of:
- forming a collector layer over a base layer;
- forming said base layer over an emitter layer;
- forming said emitter layer over an emitter cap layer;
- removing a portion of said emitter cap layer so that said base and emitter layers extend beyond an edge of said emitter cap layer;
- and
- forming a base contact on a portion of said base layer extending beyond said edge.
3 more elements
Dependencies are inferred from the claim text.