Emitter ballasting by contact area segmentation in ESD bipolar based semiconductor component

摘要

Integrated circuits (ICs) utilize bipolar transistors in electro-static discharge (ESD) protection circuits to shunt discharge currents during ESD events to protect the components in the ICs. Bipolar transistors are subject to non-uniform current crowding across the emitter-base junction during ESD events, which results in less protection for the IC components and degradation of the bipolar transistor. This invention comprises multiple contact islands (126) on the emitter (116) of a bipolar transistor, which act to spread current uniformly across the emitter-base junction. Also included in this invention is segmentation of the emitter diffused region to further improve current uniformity and biasing of the transistor. This invention can be combined with drift region ballasting or back-end ballasting to optimize an ESD protection circuit.

主权项

1. An integrated circuit, comprising an ESD device including:
a semiconductor substrate including an isolated bipolar transistor region; an epitaxial layer of semiconductor material having a given conductivity type formed over the substrate in the isolated region; a buried collector region of the given conductivity type formed in the isolated region in one or both of the epitaxial layer and substrate; a connector region of the given conductivity type formed in the epitaxial layer and extending between a surface of the epitaxial layer and the buried collector region; a collector region of the given conductivity type formed at the surface in the connector region; a base well region of opposite conductivity type formed in the epitaxial layer adjacent the surface at a location different from the location of the collector region; a base region of the opposite conductivity type formed at the surface in the base well region; an emitter region of the given conductivity type formed at the surface in the base well region at a location spaced from the location of the base region; and contacts respectively formed to provide electrical contact to the collector region, the base region and the emitter region; wherein the contacts formed to provide electrical contact to the emitter region comprise a plurality of via clusters to a single diffused region of the emitter region, wherein the via clusters are separated from each other and each of the via clusters provides a multi-dimensional array of vias; and wherein the contacts formed to provide the electrical contact to the emitter region further comprise metal silicide island areas formed in spaced positions over the emitter region offset from edges of the emitter region; and each of said via clusters providing electrical contact to a respective different one of the metal silicide island areas.