Work Function Tuning of MoxSiyNz metal gate electrode for Advanced CMOS Technology

Abstract

ABSTRACTDue to continued transistor scaling, the work function tuning of metal gates has become important for advanced CMOS applications. The primary objective of this research is to understand the tuning of the MoxSiyNz (also referred to as MoSiN) gate work function through the incorporation of nitrogen. A molybdenum silicide (MoSi2) target was reactively sputtered in nitrogen (N2) and argon (Ar) plasma. The amount of nitrogen in the MoSiN films was varied by controlling the gas flow ratio, RN = N2/(N2+Ar). Capacitance-voltage (CV) and internal photoemission (IPE) measurements are used to extract the work function (ϕm) of the MoSiN gate. A decrease in the MoSiN work function was observed from ∼4.7eV to ∼4.4eV for an increase in the gas flow ratios from 10% to 40%. The SIMS depth profiles suggested a uniform distribution of nitrogen throughout the films. The XPS surface analysis confirmed a steady increase in the total nitrogen concentration in the MoSiN films as gas flow ratio was increased. The increase in N2 concentration corresponded directly with the lowering of the MoSiN work function. These results clearly demonstrated that the MoSiN work function maybe altered over ∼0.3 eV tuning window by adjusting the N2 concentration in these films.