Cathode Electron Injection Breakdown Model and Time Dependent Dielectric Breakdown Lifetime Prediction in High-k/Metal Gate Stack p-Type Metal–Oxide–Silicon Field Effect Transistors

Abstract

We have investigated the time dependent dielectric breakdown (TDDB) for a high-k/metal gate p-type metal–oxide–semiconductor field effect transistors (pMOSFETs) under inversion stress. We have found that electrons, injected from the cathode, are minority carriers in the gate leakage current and play an important role in determining TDDB lifetime and that the existence of oxygen vacancies in HfSiON, decide the electron current mechanism in HfSiON. Since electrons from the cathode flow as a tunneling current with the effective barrier height determined by the energy level of the oxygen vacancies in the HfSiON, electron current is strongly dependent on the effective work function of the metal gate. That implies that a higher work function should be effective to suppress of electron current, due to the elevated barrier height for electrons. Therefore, the formation of a high work function metal gate is essential, not only for low threshold voltage of pMOSFETs but also to achieve long TDDB lifetimes.