In the early days of investigations into Bias Temperature Instability (BTI) the most prominent model to describe the observed shifts in threshold voltage of Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) was the Reaction Diffusion (RD) model. This model linked the shifts in threshold voltage in a MOSFET to the creation of interfacial defects between the semiconductor and oxide and the diffusion of hydrogen in the oxide. Recent achievments and detailed investigations have led to the discovery that oxide defects are the main cause of BTI. In an effort to characterize these oxide defects, a new method termed Time Dependent Defect Spectroscopy (TDDS) has been developed and has led to a new oxide defect model for BTI based on Non-radiative MultiPhonon (NMP) theory. To further refine this existing model we have begun to perform self consistent simulations of charge pumping currents and DCIV experiments on undegraded devices followed by degraded devices. This also includes the simulation of inhomogeneous BTI for various device architectures. Finally, by considering BTI degradation in a self-consistent manner, we might be able to make life-time predictions for MOS-devices, as larger defect densities modify the electric field in the MOS-devices.
Interfacial defects between the semiconductor and the oxide in high voltage and scaled devices still play an important role in the description of Hot Carrier (HC) effects, while the diffusion of hydrogen does not play a significant role. In order to test our current models for hot carrier degeneration, self consistent simulations of HC effects are necessary. For such simulations, a replacement for the time consuming Monte Carlo simulator is currently under development using a spherical harmonics expansion of the Boltzmann transport equation. This is essential in order to understand and estimate the accuracy of simplified transport codes based on the drift-diffusion model.