Self-aligned process using indium gallium arsenide etching to form reentry feature in heterojunction bipolar transistors
AssigneeAgilent Technologies, Inc.
InventorsScott A. McHugo, Gregory N. DeBrabander
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Abstract
A method for forming a heterojunction bipolar transistor (HBT) includes forming an etch mask a top layer of the HBT to expose a portion of the emitter cap layer, and selectively etching the exposed portion of the emitter cap layer to (1) form a reentry feature and (2) to expose a portion of the emitter layer. The method further includes selectively etching the exposed portion of the emitter layer to expose a portion of the base layer, and forming a metal layer over the exposed portion of the base layer and the exposed portion of the emitter cap layer.
Claims12
A method for forming a heterojunction bipolar transistor, comprising:
- forming a sub-collector layer;
- forming a collector layer atop the sub-collector layer;
- forming a base layer atop the collector layer;
- forming an emitter layer atop the collector layer;
- forming a cap layer atop the emitter layer, wherein the base layer comprises a different material than at least one of the emitter layer and the collector layer;
- forming an etch mask atop the cap layer to expose a portion of the cap layer;
- selectively etching the exposed portion of the cap layer to form a sidewall with at reentry feature comprising an undercut profile and to expose a portion of the emitter layer;
- selectively etching the exposed portion of the emitter layer to expose a portion of the base layer;
- and
- forming metal contacts on the exposed portion of the base layer and the exposed portion of the cap layer.
A method for forming a heterojunction bipolar transistor, comprising:
- forming a sub-collector layer;
- forming a collector layer atop the sub-collector layer;
- forming a base layer atop the collector layer;
- forming an emitter layer atop the collector layer;
- forming a cap layer atop the emitter layer, wherein the base layer comprises a different material than at least one of the emitter layer and the collector layer;
- forming an etch mask atop the cap layer to expose a portion of the emitter layer;
- selectively etching the exposed portion of the cap layer to form a sidewall with a reentry feature and to expose a portion of the emitter layer;
- selectively etching the exposed portion of the emitter layer to expose a portion of the base layer;
- forming a second etch mask atop the exposed portion of the base layer to expose a second portion of the base layer;
- selectively etching the second exposed portion of the base layer to form a second sidewall and to expose a portion of the collector layer;
- and
- forming metal contacts on the exposed portion of the base later and the exposed portion of the cap layer.
Dependencies are inferred from the claim text.