US 2022/0190145 A1 · HETEROJUNCTION BIPOLAR TRANSISTORS WITH UNDERCUT EXTRINSIC BASE REGIONS

Abstract

Device structures and fabrication methods for heterojunction bipolar transistors. Trench isolation regions are positioned in a semiconductor substrate to define active regions. A base layer includes first sections that are respectively positioned over the active regions and second sections that are respectively positioned over the trench isolation regions. Emitter fingers are respectively positioned on the first sections of the base layer. The first sections of the base layer include single-crystal semiconductor material, and the second sections of the base layer include polycrystalline semiconductor material. The second sections of the base layer are spaced in a vertical direction from the trench isolation regions to define a first cavity that extends about a perimeter of the base layer and second cavities that are connected to the first cavity.

Claims20

Dependent claims

A device structure for a heterojunction bipolar transistor, the device structure comprising:

a semiconductor substrate;
a plurality of trench isolation regions positioned in the semiconductor substrate to define a plurality of active regions;
a base layer including a plurality of first sections that are respectively positioned over the active regions and a plurality of second sections that are respectively positioned over the trench isolation regions, the first sections of the base layer including single-crystal semiconductor material, the second sections of the base layer including polycrystalline semiconductor material, and the second sections of the base layer spaced in a vertical direction from the trench isolation regions to define a first cavity that extends about a perimeter of the base layer and a plurality of second cavities surrounded by the first cavity;
and
a plurality of emitter fingers respectively positioned on the first sections of the base layer adjacent to the second cavities.

2 more elements

A method of forming a heterojunction bipolar transistor, the method comprising:

forming a plurality of trench isolation regions in a semiconductor substrate that define a plurality of active regions;
forming a base layer that includes a plurality of first sections including single-crystal semiconductor material that are respectively positioned over the active regions and a second plurality of sections including polycrystalline semiconductor material that are respectively positioned over the trench isolation regions;
removing a first semiconductor layer of each of the second sections of the base layer selective to a second semiconductor layer of each of the second sections of the base layer to define a first cavity and a plurality of second cavities that are positioned in a vertical direction between the second semiconductor layer and the trench isolation regions, wherein the first cavity extends about a perimeter of the base layer and the second cavities are connected to the first cavity;
and
forming a plurality of emitters respectively positioned on the first sections of the base layer.

2 more elements

Dependencies are inferred from the claim text.

Heterojunction bipolar transistors with undercut extrinsic base regions

Life of this patent

Heterojunction bipolar transistors with undercut extrinsic base regions

Life of this patent

Abstract

Claims20