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 Y
2
O
3
-layers on HfSiON films, V
th
fluctuations are the same as with non-capped samples, while maintaining excellent V
th
controllability (|ΔV
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 µA/µm) at an I
off
value of 100 nA/µm.