Dual Metal Gates with Band-Edge Work Functions on Novel HfLaO High-K Gate Dielectric

In this work, by using a novel HfLaO high-kappa (HK) gate dielectric, we show for the first time that with a thermal budget of 1000 degC, Fermi-Pinning in the HK-metal gate (MG) stack can be released. The effective metal work function (EWF) can be tuned by a wide range more than the requirement of bulk CMOSFETs, and also fits the future UTB-SOI CMOSFETs when Si body thickness is approaching 3 nm or less. As prototype examples, TaN gate with EWF ~3.9-4.4 eV and TaN/Pt gate with EWF ~5.5 eV are shown. In addition, by replacing HfO₂ with HfLaO, high k value and low gate tunneling are maintained, BTI V_th instability is improved by one order. These new findings are correlated to the enhanced thermal stability and significantly reduced oxygen vacancy density in HfLaO compared to HfO ₂ as estimated by the first-principles calculations