Off-state instabilities in thermally nitrided-oxide n-MOSFETs

Abstract

The significant off-stage gate current of nitrided-oxide n-MOSFETs can be attributed to severe hot-hole injection into the gate oxide during band-to-band (B-B) tunneling due to a nitridation-induced lowering of barrier height for hole injection. Some of the injected holes are even trapped in the gate oxide above the deep-depletion layer of drain and thus decrease the gate-induced drain leakage (GIDL) current. A subsequent hot-electron injection into the gate oxide can neutralize these trapped holes and make the reduced GIDL current recover, even increase beyond the original value. The proposed mechanism of the GIDL degradation and recovery behaviors can be confirmed by the observed change in the ratio of the substrate to source currents, as well as by the field-distribution analysis of the gate oxide under stressing.