Time-dependent degradation due to negative bias temperature instability of p-MOSFET with an ultra-thin SiON gate dielectric

This paper presents the time-dependence of the negative bias temperature instability (NBTI) degradation of p-MOSFETs with an ultra-thin silicon oxynitride gate dielectric. The concentrations of nitrogen in the gate dielectric were approximately 3% and 10%. The device with 10% nitrogen concentration had unique time-dependent degradation characteristics due to the nitrogen enhanced NBTI effect. It degraded significantly just after application of an NBTI stress. After this initial degradation, a fast and slow degradation followed in sequence. The initial, fast, and slow degradations appear to be associated with the deep donor effect of nitrogen, the diffusion of ionic and neutral hydrogen combined with Si–H bond breaking, and the diffusion of neutral hydrogen combined with O–H bond breaking, respectively. Owing to the slow down of the NBTI degradation after the initial and fast degradations, the lifetime for the device with 10% nitrogen concentration was three times longer than that with 3% nitrogen concentration.