Novel dual-metal gate technology using Mo-MoSix combination

A novel dual-metal gate technology that uses a combination of Mo-MoSi_x gate electrodes is proposed. An amorphous-Si/Mo stack was fabricated as a gate electrode for the n-channel device. It was thermally annealed to form MoSi_x. Pure Mo served as the gate electrode for the p-channel device. The work functions of MoSi_x and pure Mo gates on SiO₂ are 4.38 and 4.94 eV, respectively, which are appropriate for devices with advanced transistor structures. The small increase in the work function (< 20 meV) and the negligible equivalent oxide thickness variation (< 0.08 nm) after rapid thermal annealing at 950 °C for 30 s also demonstrate the excellent thermal stabilities of Mo and MoSi_x on SiO₂. Additional arsenic ion implantation prior to silicidation was demonstrated further to lower the work function of MoSi_x to 4.07 eV. This approach for modulating the work function makes the proposed combination of Mo-MoSi_x gate electrodes appropriate for conventional bulk devices. The developed dual-metal-gate technology on HfO₂ gate dielectric was also evaluated. The effective work functions of pure Mo and undoped MoSi_x gates on HfO₂ are 4.89 and 4.34 eV, respectively. A considerable work-function shift was observed on the high-κ gate dielectric. The effect of arsenic preimplantation upon the work function of the metal silicide on HfO₂ was also demonstrated, even though the range of modulation was a little reduced.