Hot carrier induced degradation in mesa-isolated n-channel SOI MOSFETs operating in a Bi-MOS mode

A thorough investigation of hot carrier effects is made in mesa-isolated SO I nMOSFETs operating in the Bi-MOS mode (abbreviated as Bi-nMOSFETs). As a result of its unique hybrid operation mechanism, significant reduction of h ot carrier induced maximum transconductance degradation and threshold volta ge shift in the Bi-nMOSFET is observed in comparison with that in the conve ntional SOI nMOSFETs, Device lifetime of SOI Bi-nMOSFETs and conventional S OI nMOSFETs was roughly estimated for comparison. In view of the analysis o f the degradation mechanism, the devices were stressed under different cond itions. The post-stress body current and stress body current in Bi-nMOSFETs as a function of the stress time and stress drain voltage were evaluated a s further proofs of the aging reasons. The hot electron injection is found to be the dominant degradation process in the SOI Bi-nMOSFETs. Compared wit h SOI nMOSFETs, SOI Bi-nMOSFETs show better immunity to the parasitic bipol ar transistor action due to the body contact. In addition, the positive bod y bias can result in lowered hot hole injection into the gate oxide due to the provision of the generated hole leakage path, and thus decreased interf ace traps.