Determination of Work Functions in the Ta1-xAlxNy/HfO2 Advanced Gate Stack Using Combinatorial Methodology
Kao-Shuo Chang, Martin L. Green, Jason Hattrick-Simpers, John S. Suehle, Ichiro Takeuchi, Ozgur Celik, S De Gendt
Combinatorial methodology enables the generation of comprehensive and uniform samples, and therefore data sets, compared to the one-composition-at-a-time approach. We demonstrate the efficacy of combinatorial methodology applied to Ta1-xAlxNy alloys as metal gates on HfO2 for CMOS applications, for the first time. The equivalent oxide thickness (EOT) maps indicate that only limited interaction between the gate stack layers takes place below 950 C RTA. The work function (Fm) of the Ta1-xAlxNy libraries was systematically mapped over a wide (0.05 x 0.50) composition range, after forming gas and rapid thermal anneals. Fm can be tuned as a function of gate metal composition as well as annealing condition. Our results suggest that Ta1-xAlxNy gate metal electrodes may be useful as a replacement for polycrystalline Si for p-MOS applications; they are thermally stable up to 950 C, possess a reasonably high Fm. and a relatively small SiO2/Si interfacial fixed oxide charge.