Wide range work function modulation of TiN for complementary field effect transistor: A first-principles study

Complementary field-effect transistor technology enhances integration density and reduces power consumption by vertically stacking n-MOS and p-MOS transistors. However, the three-dimensional (3D) architecture poses challenges in threshold voltage control when depositing metal with distinct work function (WF) for the gates. Using first-principles calculations, we explore wide-range WF modulation (3.20–5.25 eV) of defective TiN widely used in industry for 3D integration, enabling its application for both n- and p-MOS gates. Compared with bulk defects, WF is strongly affected by the surface defect types and their concentrations. Surface N adsorption can increase TiN WF from 4.73 to 5.25 eV when the concentration is within 12.5%–62.5%. In contrast, surface Ti vacancies can reduce the WF to 3.20 eV at a concentration of 62.5%. In addition, the stress effect indicates that WF increases under compressive stress and conversely for tensile stress. The above phenomenon can be attributed to the charge transfer and charge redistribution by different defects. This WF modulation technique in this work has the potential to meet the requirements of next-generation 3D architecture.