Direct visualization and in-depth physical study of metal filament formation in percolated high-κ dielectrics

The migration of Ta atoms from a transistor gate electrode into the percolated high-$\kappa$ (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-$\kappa$ (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.