Physical origin of SILC and noisy breakdown in very thin silicon nitride gate dielectric

As the equivalent oxide thickness of the MOSFET gate dielectric continues to shrink, the transition to a material with a higher dielectric constant, such as Si/sub 3/N/sub 4/, seems imminent. It is well-recognized that stress-induced leakage current (SILC) and noisy (or soft) breakdown have become very important degradation phenomena in ultra-thin gate dielectrics. A lot of attention has been recently paid to SILC and soft breakdown in SiO/sub 2/ gate dielectrics, however the physical origins of these phenomena have not been thoroughly investigated. An understanding of the physical mechanisms responsible for the degradation of the ultra-thin gate dielectrics is critical to the development of a reliability model for the future generations of CMOS technology. This paper offers for the first time a detailed examination of SILC and noisy breakdown in Si/sub 3/N/sub 4/ demonstrating that these two degradation phenomena have a common origin. The nature of the traps responsible for SILC and noisy breakdown is revealed. The proposed degradation mechanism also provides a key to understanding and modeling of the dielectric reliability in the ultra-thin SiO/sub 2/ and new high-K gate materials.