Impact of Mixed Negative Bias Temperature Instability and Hot Carrier Stress on MOSFET Characteristics—Part II: Theory

摘要

In this paper, we examine the interplay of two serious reliability issues in MOSFET devices, namely, bias temperature instability (BTI) and hot-carrier degradation (HCD). Most publications are devoted to the characterization of either BTI or HCD, and complex models have been developed to independently describe each degradation mode. However, very limited data are available on the interplay of both degradation regimes, particularly the effect of a drain bias onto the charging and discharging dynamics of oxide traps. Part I of this paper provides an extensive experimental study toward the impact of mixed-mode stress conditions on the dynamics of oxide defects. Here, we present the first microscopic modeling approach beyond a simple electrostatic approximation. We extend the existing nonradiative multiphonon theory by taking nonequilibrium processes such as full carrier distribution functions which include the effect impact ionization along the channel into account. To ultimately validate our framework, we compare simulation results and experimental data for a single-oxide defect as well as a large ensemble of traps in a MOSFET device. We show that our modeling approach accurately captures the rather puzzling measurement trends for a broad stress regime and allows developing the knowledge on how oxide defects can be affected by an increased drain stress.