Dual nature of metal gate electrode effects on BTI and dielectric breakdown in TaC/HfSiON MISFETs

We investigated bias temperature instability (BTI) and time dependent dielectric breakdown (TDDB) in TaCx/HfSiON MOSFETs in terms of the effects of TaCx metal gate electrode, using various Ta composition and TaCx thickness. We find a dual nature of TaCx metal gate electrode effects on the reliability. The gate electrode has both positive and negative influence on BTI and TDDB. Though various TaCx layers were deposited on the same HfSiON layer, high composition of Ta in the TaCx layer and thick TaCx layer improve BTI and mobility, while they deteriorate time to breakdown (Tbd) because of the effects of metal gate induced defects.