Percolation resistance evolution during progressive breakdown in narrow MOSFETs

A method has been developed to determine the effective resistance of a conductive breakdown (BD) path formed in ultrathin gate dielectric. Based on this method, the evolution of the percolation resistance (R_perc) during progressive BD (PBD) is studied in details. It is found that R_perc rapidly degrades in the initial stage of PBD with the rate of 0.1-0.2 dec/s. As PBD continues to evolve, the R_perc degradation drastically slows down, and the parasitic resistance becomes increasingly significant. In the later stage of PBD, R_perc degrades with a very slow rate, leading to the saturation of R_perc. Additionally, the temperature and the voltage dependence of R_perc suggest that the mechanism responsible in governing the PBD growth under normal operations could be different from that during accelerated stressing.