Controllability of flatband voltage in high-k gate stack structures - remarkable advantages of La/sub 2/O/sub 3/ over HfO/sub 2/

The authors have achieved a remarkably wide range (~1.2 V) of differences in flatband voltage (V
_fb
) by using a combination of metal alloy (Pt-W)/La2O3 gate stacks. The controllable range is about 3 times greater than that of Hf-based gate stacks. The wide range of V
_fb
can be maintained even after annealing in forming gas and oxidizing gas ambients. The authors consider that this is attributed to charge transfer at the Pt/La
₂
O
₃
interfaces inducing increase in the effective work functions, especially at high Pt composition ratios. The authors believe that La
₂
O
₃
is one of the most promising high-k dielectric materials for future CMOS devices in 32nm-node and beyond