The replacement of poly-silicon by metallic compounds in the gate stack leads to the search of metals with suitable work function. However, it is observed that thermal budget has a large influence on the effective work functions of several metals, In this paper, we investigated the possible modification of the chemical states by physical analysis techniques (XPS, XRR, MEIS, TOF-SIMS) by studying the chemistry of the high-k oxide/metal interface. We show that in the case of the TiN/TaN/HfO2/SiO2/Si stack, several modifications occur upon 1000C N2annealing: Increase of the nitrogen content of the TaN, interdiffusion of the Ti and TaN, and formation of Ta2O5at the TaN/HfO2interface.
Conard, T., Franquet, A., Vandervorst, W., Reading, M., Van Den Berg, J. A., Van Elshocht, S., ... De Gendt, S. (2008). Physical Characterization of the Metal/High-k Layer Interaction upon Annealing. ECS Transactions, 16(5), 433-442. https://doi.org/10.1149/1.2981624