The role of the disordered HfO2 network in the high- κ n-MOSFET shallow electron trapping

Abstract

Current understanding of the bias temperature instability degradation usually comprises two parts: (1) shallow-level component that can recover within a short time and (2) deep level traps that the emission time of the trapped carrier is extremely long. Prevenient studies of the positive bias temperature instability degradation in the high-κ n-MOSFET indicate that oxygen vacancy (VO) is the dominant defect type that responds for the shallow electron trapping. However, recent experimental results reveal that the VO defect density required to accommodate the experimental measured recoverable threshold voltage degradation (ΔVth) is much higher than that of the reasonable atomic structure in the amorphous HfO2. On the other hand, investigations on the disordered Hf-O-Hf network in the amorphous HfO2 reveal their capabilities as charge trapping centers; therefore, in this work, atomic simulation work is performed, and our results show that the disordered Hf-O-Hf networks can act as effective electron capture centers with shallow levels near the Si conduction band. Moreover, the high density of the stretched Hf-O-Hf networks in the amorphous HfO2 also significantly enriches the shallow electron traps in the oxide.