TDDB characteristics of ultra-thin HfN/HfO/sub 2/ gate stack

In this paper, the area and electric field dependence of time dependent dielectric breakdown (TDDB) for the ultra thin HfN/HfO/sub 2/ gate stack (EOT/spl sim/9nm) under negative constant voltage stress (CVS) was studied. Area-scaling consistent with Weibull statistics as in SiO/sub 2/ was observed in the HfN/HfO/sub 2/ gate stack, demonstrating that intrinsic effects dominate TDDB characteristics of the ultra thin HfN/HfO/sub 2/ gate stack. A new model on the mechanism of electric-field dependent TDDB was proposed. In this model, the reliability of HfN/HfO/sub 2/ gate stack is dominated by the breakdown of HfO/sub 2/ bulk layer under high electric field stressing and by the breakdown of the interfacial layer (IL) under low electric field stressing, respectively.