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

Abstract

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.