SiC transient voltage suppressor

摘要

A high power, high current Unidirectional Transient Voltage Suppressor, formed on SiC starting material is disclosed. The device is structured to avalanche uniformly across the entire central part (active area) such that very high currents can flow while the device is reversely biased. Forcing the device to avalanche uniformly across designated areas is achieved in different ways but consistently in concept, by creating high electric fields where the device is supposed to avalanche (namely the active area) and by relaxing the electric field across the edge of the structure (namely in the termination), which in all embodiments meets the conditions for an increased reliability under harsh environments.

主权项

1. A transient voltage suppressor, comprising:
a silicon carbide (SiC) substrate of a first dopant type and a first doping concentration; a backside conductive contact on a backside of the substrate; an epitaxial SiC layer of the first dopant type and a second doping concentration less than the first doping concentration on the substrate; a central active area including one or more regions of a second dopant type opposite the first dopant type forming a PN junction in the epitaxial layer; a frontside conductive contact on an upper side of the epitaxial SiC layer coupled to the one or more regions of the second dopant type; and a peripheral termination area surrounding the central active area and including a termination structure arranged to suppress electric field and avalanche around the central contact area; the central active area being structured to avalanche within the active area under a voltage condition applied across the conductive contacts that exceeds a predetermined breakdown voltage in the central active area that is less than a breakdown voltage of the peripheral termination area; in which: the epitaxial SiC layer has an upper surface; the central active area includes an array of spaced-apart trenches each having a bottom spaced below the upper surface with first implants of the second dopant type in the bottom of each trench; and the peripheral termination area includes an array of second implants of the second dopant type subjacent the upper surface of the epitaxial SiC layer; the first implants extending to a depth in the epitaxial SiC layer greater than a depth of the second implants so as to thereby provide the lower breakdown voltage in the central active area than a breakdown voltage in the peripheral termination area.