Self-protection against breakover turn-on failure in thyristors through selective base lifetime control

摘要

A thyristor is protected against voltage breakover turn-on failure by selective control of the minority charge carrier lifetime in the base region and in the gate region to establish a predictable location of the voltage breakover turn-on in the gate region. Carrier lifetime modification in the selected gate region is achieved by shielding the gate region during electron irradiation of the high- lifetime silicon substrate to protect against lifetime-killing radiation defect centers, by annealling the gate region after electron irradiation to a temperature threshold known to eliminate the radiation-induced defects, or by introducing lifetime killing defects, such as gold or platinum, external to the gate region, typically by selective diffusion or localized ion implantation. As a result, a locally higher gate sub- transistor gain thyristor is attained, so that the turn-on criterion, the unity product of the base transport factor and the avalanche multiplication factor, is established at a lower voltage in the gate region than elsewhere in the thyristor device.