A compact SPICE model for statistical post-breakdown gate current increase due to TDDB

Abstract

We developed a compact SPICE model capable of modeling the increases in post-breakdown (BD) gate current (IG_BD) due to time-dependent dielectric breakdown (TDDB), for circuit level simulations. IG_BD is determined by the random shape of the BD path given by the percolation model and the location of BD path. The statistical nature of our analysis provides different IG_BD for each transistor and hence, can be efficient for statistical circuit simulation. The generated gate current is fed into the proposed SPICE model incorporating transistor threshold voltage shift (VTH-SHIFT) due to bias temperature instability (BTI). We present simulation results of a ring oscillator using our model and compare the results to experimental data from an ultrathin CMOS technology. We also show that IDDQ is a more representative signature of TDDB degradation than the delay of a ring oscillator.