Failure Defects Observed in Post-Breakdown High-κ/Metal Gate Stack Mosfet

Failure defects associated with breakdown of the HfO₂/TaN/TiN gate stack metal-oxide-semiconductor field effect transistor (MOSFET) are studied. Very fast degradation rate in the gate leakage current is attributed to gate material filament of the breakdown path, leading to various degrees of severity in micro structural damages in the narrow width MOSFET structure. This observation is different from that reported for the poly crystalline-silicon (poly-Si) gate MOSFET. On the other hand, some common failure mechanisms driven by gate dielectric breakdown, such as dielectric-breakdown-induced epitaxy (DBIE) and silicide migration i.e. dielectric-breakdown-induced migration (DBIM), previously observed in poly-Si gate MOSFET are still found in metal gate MOSFET