Vth fluctuation suppression and high performance of HfSiON/metal gate stacks by controlling capping-Y2O3 layers for 22nm bulk devices

We have succeeded in suppressing random threshold voltage (V_th) fluctuations by controlling capping-layers and high-k materials with metal gate first stacks for 22 nm-node devices. By employing 1-2 mono Y₂O₃-layers on HfSiON films, V_th fluctuations are the same as with non-capped samples, while maintaining excellent V_th controllability (|¿V_th| > 180 mV). Furthermore, the devices exhibit high device performance because ultra-thin equivalent-oxide-thickness (EOT: 0.74 nm) can be achieved with high electron carrier mobility, and very high drain current (I_on > 1060 ¿A/¿m) at an I_off value of 100 nA/¿m.