Wide Controllability of Flatband Voltage by Tuning Crystalline Microstructures in Metal Gate Electrodes

摘要

We propose a novel approach to control the effective workfunction (WF) by taking advantage of crystal structures in metal gate electrodes. The crystal structures determine the predominant material elements at the metal/high-k interface. We have found that, in a Ru-Mo alloy system, a randomly-oriented Ru (fcc) structure promotes the segregation of Mo at the interface, enabling us to achieve a wide controllability of flatband voltage (Vfb) from 0.6-0.8 eV. In addition, the segregation of Mo within a Ru-rich electrode is a key to reducing Fermi level pinning at metal/HfSiON interfaces. Further tunability in Vfb has been examined by employing C-incorporation in the RuMo alloy, thus reducing the crystal grain size and facilitating the control of Vfb for a HfSiON (2nm)/SiO2(0.7nm)/Si capacitor. These results demonstrate that the crystal structure control in metal gates is essential for realizing the MIS-FET devices with a short gate length in the 32-22 nm node and beyond.