Negative bias temperature instability modeling for pure-SiO2

Abstract

Negative Bias Temperature Instability (NBTI) is a serious degradation mechanism in nanoscale devices and circuits. It impacts mainly P-channel devices by generating traps at the Si/SiO2 interface as well as in the oxide bulk. These generated traps cause the degradation of the most important transistor parameters such as threshold voltage, saturation current and channel mobility. Since the improvement of devices and circuit performance is the main target in Nanotechnology, investigating the physics of the NBTI and its modeling is essential and highly useful. In this thesis, the study of NBTI degradation for pure-SiO2 is undertaken and it is demonstrated that for pure-SiO2 only one mechanism is behind the degradation. This mechanism is related to Pbcenters creation and hydrogen species diffusion into the oxide. The Reaction-diffusion framework which is widely used for modeling NBTI is investigated. Nevertheless the validity of R-D model is put under question by many researchers due to its failure in predicting some important NBTI behavior. The proposed model is an amelioration of the classical R-D by modifying some assumptions used in the classical R-D. The proposed model takes into consideration the non-instantaneous transformation of H to H2as well as the diffusion of the latter into the polysilicon gate. COMSOL Multiphysics is used to simulate the model and the obtained results demonstrate the validity of the model