Abstract
The migration of Ta atoms from a transistor gate electrode into the percolated high-
κ
(HK) gate dielectrics is directly shown using transmission electron microscopy analysis. A nanoscale metal filament that formed under high current injection is identified to be the physical defect responsible for the ultrafast transient breakdown (BD) of the metal-gate/high-
κ
(MG/HK) gate stacks. This highly conductive metal filament poses reliability concerns for MG/HK gate stacks as it significantly reduces the post-BD reliability margin of a transistor.