Intrinsic Threshold Voltage Instability of the HFO2 NMOS Transistors

Electron trapping in high-k gate dielectrics under constant voltage stress is investigated. It is suggested that the electron trapping occurs through a two-step process: resonant tunneling of the injected electron into the pre-existing defects (fast trapping) and temperature-activated migration of trapped electrons to unoccupied traps (slow trapping). The proposed model successfully describes low temperature threshold voltage instability in NMOS transistors with HfO
₂
/TiN gate stacks