Reliability Characteristics Of SiO_xN_y Gate Dielectrics

Negative bias temperature instability (NBTI) and stress-induced leakage current (SILC) in p-MOS devices has become a significant reliability issue in the advanced CMOS technology. When CMOS technology scaled down to very deep sub-micro technology node. SiO_xN_y has been widely applied in CMOS as the gate dielectrics instead of SiO₂. In this paper, NBTI characteristics of nanoscale pMOS devices with SiO_xN_y gate dielectrics were investigated systematically including the frequency dependence of NBTI under dynamic NBT stresses and the source/drain bias dependence of NBTI. Some interesting results have been achieved as follows:1) Analysis of leakage current conduction mechanisms of ultra-thin oxynitride dielectric films shows that, with the increase of new traps, both Frenkel-Poole emission and Schottky emission mechanism may contribute to the SILC effect.2) The influence of positive bias temperature instability (PBTI) can also be neglected compared to the effect of NBTI for ultra-thin oxynitride dielectric films, so that the research of BTI can be concentrated on NBTI.3) Dynamic NBTI characteristics of pMOS devices with ultra thin SiO_xN_y gate dielectrics fabricated using plasma nitridation process (DPN) are addressed. The results indicate that: the degradation under dynamic stress is less than that under static stress with the same effective stress time, which is due to the recovery effect at the "off" state of dynamic stress.The achievements in this study on NBTI degradation will be helpful to further understand the NBTI mechanism and make correct lifetime prediction in the real CMOS circuits.