Polysilicon-edge, low-power, high-frequency bipolar transistor and method of forming the transistor
AssigneeNational Semiconductor Corporation
InventorsMohamed N. Darwish, Alexei Sadovnikov, Reda Razouk
Life of this patent
Estimating the term…
Abstract
A low-power high-frequency bipolar transistor is formed to have a small self-aligned base region that reduces the base-to-collector capacitance, and small self-aligned base and emitter contacts that reduce the base-to-emitter capacitance and the base resistance. The base and emitter contacts are formed to have sub-lithographic feature sizes.
Claims18
A method for forming a bipolar transistor on a wafer, the wafer having a buried layer and a first epitaxial layer of a first conductivity type, the first epitaxial layer being formed over the buried layer and having a smaller dopant concentration than the buried layer, the method comprising the steps of:
- forming a layer of isolation material on the first epitaxial layer;
- forming an extrinsic base and an extrinsic emitter on the layer of isolation material, the extrinsic base having a second conductivity type and being spaced apart from the extrinsic emitter, the extrinsic emitter having the first conductivity type;
- etching the layer of isolation material to form a first opening in the layer of isolation material, the first opening being between the extrinsic base and the extrinsic emitter, and exposing a surface of the first epitaxial layer;
- forming a first intrinsic base region on the surface of the first epitaxial layer in the first opening;
- forming an isolation region on the first intrinsic base region in the first opening;
- forming a sacrificial material on the isolation region over the first intrinsic base region in the first opening;
- etching the isolation region;
- removing the sacrificial material after the isolation region has been etched;
- forming a base spacer that contacts the extrinsic base and the layer of isolation material formed on the first intrinsic base region, and an emitter spacer that contacts the extrinsic emitter and the layer of isolation material on the first intrinsic base region, the base spacer being spaced apart from the emitter spacer;
- etching the layer of isolation material to form a gap between the base spacer and the first intrinsic base region, and the emitter spacer and the first intrinsic base region;
- and
- forming a second intrinsic base region to fill up the gap so that the second intrinsic base region contacts the first intrinsic base region, the base spacer, and the emitter spacer.
Dependencies are inferred from the claim text.