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Degradation mechanism of stacked high-k gate dielectrics has been studied with metal-oxide-semiconductor capacitors having HfAlOX/SiO2 films of various thickness combinations. A large leakage current with a peaked shape, named as the low-voltage peak current (LVPC), has been observed in the low-voltage region even in the initial current–voltage characteristics. It has been shown that a main part of LVPC is the transient current component controlled by the process of hole injection to traps in the vicinity of the HfAlOX/SiO2 interface through the interfacial SiO2 layer. By the electrical stress, both the transient and the steady-state current components monotonically increase with time having different rates. Steady-state component has significantly larger rate than the transient component, and the same rate with the stress-induced leakage current (SILC) observed in the high-voltage region, indicating that the steady-state component of LVPC should be regarded as the SILC in the higher-voltage region extending down to the lower gate voltage region where the LVPC is observed. [ABSTRACT FROM AUTHOR]

Degradation behavior of oxide–nitride–oxide (ONO) stacked gate dielectrics used in metal–oxide–nitride–oxide–silicon (MONOS)-based flash memories has been studied. Occurrence of the soft breakdown (SBD), which is well known in single-layer ultrathin silicon dioxides, has been revealed even in these thick and stacked dielectrics. The SBD of ONO dielectrics shows similar characteristics with that of silicon dioxides in locality, current/voltage fluctuation, and the dependencies of the ratio of SBD on the gate area and stress condition. These findings require the countermeasure for SBD even in MONOS-based flash memories and also give useful information on the reliability of high-k stacked gate dielectrics. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]