Effective work function engineering for a TiN/XO(X = La, Zr, Al)/SiO2 stack structures

In this study, we demonstrated that work function engineering is possible over a wide range (+200 mV to −430 mV) in a TiN/XO (X = La, Zr, or Al)/SiO2 stack structures. From ab initio simulations, we selected the optimal material for the work function engineering. The work function engineering mechanism was described by metal diffusion into the TiN film and silicate formation in the TiN/SiO2 interface. The metal doping and the silicate formation were confirmed by transmission electron microscopy and energy dispersive spectroscopy line profiling, respectively. In addition, the amount of doped metal in the TiN film depended on the thickness of the insertion layer XO. From the work function engineering technique, which can control a variety of threshold voltages (Vth), an improvement in transistors with different Vth values in the TiN/XO/SiO2 stack structures is expected.