A fine pattern GTO thyristor fabricated using a self-aligned process

Abstract

GTO thyristors with a 2 cm2 active area and small rectangular 40 * 40 μm emitters were fabricated using a specially developed self-aligned process based entirely on reactive ion etching, RIE, technology. Each device consists of 176 1 mm2 segments containing 100 individual emitters. The devices were electrically evaluated and compared to standard, wet etched mesa, GTO devices of comparable size having 3000 * 200 μm large emitters. Simulations were carried out to analyse specific features of the new devices. In particular the influence of the surface quality on the gate trigger current and on-state voltage was investigated. It was demonstrated that it is possible to reduce significantly the GTO unit cell dimensions without sacrificing the yield. 23% of the cm2 devices out of a lot containing 50 devices could be accepted without repair while the overall segment yield was 97%. The dynamic performance of the devices under both snubbered and snubberless conditions compares well to that of the reference devices.