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 Rperc degradation drastic-ally 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 Rperc suggest thal the mechanism responsible in governing the PBD growth under normal operations could be different from that during accelerated stressing.