Co-optimization of the metal gate/high-k stack to achieve high-field mobility >90% of SiO2 universal mobility with an EOT=∼1 nm

HfO₂ and HfSiON gate dielectrics with high-field electron mobility greater than 90% of the SiO₂ universal mobility and equivalent oxide thickness (EOT) approaching 1 nm are successfully achieved by co-optimizing the metal gate/high-k/bottom interface stack. Besides the thickness of the high-κ dielectrics, the thickness of the ALD TiN metal gate and the formation of the bottom interface also play an important role in scaling EOT and achieving high electron mobility. A phase transformation is observed for aggressively scaled HfO₂ and HfSiON, which may be responsible for the high mobility and low charge trapping of the optimized HfO₂ gate stack.