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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]

Dielectric breakdown mechanism of gate dielectrics has been reconsidered with SiO2 films of various thicknesses ranging from 3.6 to 9.5 nm. Careful time-dependent dielectric breakdown (TDDB) measurements have realized the detection of anomalous lifetime (TBD) lowering than the expectation from generally accepted power-law (PL) model at relatively low-voltage region in 6- and 6.5-nm-thick films. Analysis from the viewpoint of the hole and electron fluence to breakdown (QBD,hole and QBD,el) has demonstrated the dominant carrier change(DCC) from hole to electron with the lowering of the stress voltage. These results strongly support the DCC model. The DCC model provides stress voltage-independent defect generation efficiencies of electron and of hole at the stress voltage region where each carrier dominates the breakdown, while the PL model provides the stress voltage-dependent efficiency. The DCC model is also capable to explain the empirically reported linear electric field (E) dependence of TBD in a wide range of stress voltage which supports the thermochemical model (E-model). Therefore, it is expected that the DCC model can also be employed in the lifetime prediction of gate dielectrics thicker than ~5 nm, where the E-model is generally employed in the lifetime insurance of actual market products. The DCC model is expected to give longer predicted TDDB lifetimes at the actual device operating conditions in most devices than the E-model and other models and, hence, more aggressive usage of gate dielectric films can be realized. [ABSTRACT FROM AUTHOR]