US 5,665,614 A · Method for making fully self-aligned submicron heterojunction bipolar transistor

Abstract

A submicron emitter heterojunction bipolar transistor and a method for fabricating the same is disclosed. The fabrication process includes lattice matched growth of subcollector, collector, base, emitter, and emitter cap layers in sequential order on a semi-insulating semiconductor substrate. An emitter cap mesa, an emitter/base/collector mesa and a subcollector mesa are formed. Dielectric platforms are formed extending the base/collector layers laterally. Sidewalls are formed on the sides of emitter cap mesa and the sides of the extended base/collector layers and undercuts are etched into the emitter layer and the upper portion of the subcollector layer. This forms an overhang on the emitter cap mesa with respect to the emitter layer and an overhang on the base/collector layers with respect to the upper portion of the subcollector layer. Emitter, base and collector contacts are simultaneously formed, the base contact aligned to the edge of the emitter cap overhang and the collector contact aligned to the edge of the base/collector layer overhang.

Claims18

Dependent claims

A method for forming emitter, base and collector contacts to a heterojunction bipolar transistor which includes, in sequence, subcollector, collector, base, emitter and emitter cap layers, comprising:

forming a first overhang on said emitter cap layer that overhangs said emitter layer,
forming a second overhang on said base and collector layers that overhangs an upper portion of said subcollector layer but is spaced inward from a lower portion of said subcollector layer,
forming an emitter contact to said emitter cap,
forming a base contact to said base layer using said emitter cap layer's first overhang as a mask, and
forming a collector contact to said lower subcollector portion using said base/collector layer second overhang as a mask.

2 more elements

A method for fabricating a heterojunction bipolar transistor, comprising:

providing a substrate with a subcollector layer on one surface, a collector layer on said sub-collector layer, a base layer on said collector layer, an emitter layer with a wider band gap than said base layer on said base layer, and an emitter cap on said emitter layer,
forming said emitter cap into a mesa having a surface width,
forming said emitter, base and collector layers into a mesa having a surface width greater than the surface width of said emitter cap mesa,
forming said sub-collector into a mesa with an upper portion in contact with said collector layer and a lower portion in contact with said substrate,
forming a first overhang on said emitter cap mesa that overhangs said emitter layer,
forming a second overhang on said base and collector layers that overhangs an upper portion of said subcollector layer but is spaced inward from a lower portion of said subcollector layer, and
simultaneously forming emitter cap, base and collector contacts using the edge of said emitter cap mesa's first overhang as a mask so that said base contact is spaced apart from said emitter layer, and using said base/collector layer second overhang as a mask so that said collector contact is made to said lower subcollector layer portion and is discontinuous from said base contact.

4 more elements

Dependencies are inferred from the claim text.

Method for making fully self-aligned submicron heterojunction bipolar transistor

Life of this patent

Method for making fully self-aligned submicron heterojunction bipolar transistor

Life of this patent

Abstract

Claims18