Wide Controllability of Flatband Voltage in La{sub}2O{sub}3 Gate Stack Structures - Remarkable Advantages of La{sub}2O{sub}3 over HfO{sub}2

摘要

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