Reliability scaling issues for nanoscale devices

We discuss two specific scaling issues that can result in qualitative changes in device reliability prediction for nanoscale devices. The first of these involves a rapid increase in early failures due to a distribution of activation energies of defect precursors. We show that the slopes of the failure functions for hot carrier interface state generation (HCI) and time-dependent dielectric breakdown (TDDB) have simple physical interpretations in terms of a geometrical factor and the activation energy distribution width. The second issue involves a transition from single to multiple electrons causing individual defects. This picture allows simple physical explanations for the larger HCI damage in NMOS versus PMOS, the anomalous isotope effect of activation energies for HCI in the lucky electron model, and the observed power law dependence of the time to breakdown versus voltage for TDDB for ultrathin oxides.