On the mechanical properties of ultrathin titanium nitride films under different gas ratios of PVD process

Titanium Nitride (TiN_x) thin film has numerous applications in semiconductors, nanotechnology, and various aspects of daily life. This study presents an approach to adjusting the mechanical properties of TiN_x ultrathin films, including Young's modulus, residual stress, and coefficients of thermal expansion (CTE), by varying the gas ratio of N₂ and Ar during the Physical Vapor Deposition (PVD) process (DC magnetron sputtering). In the experiment, TiN_x films with three different gas ratios R_N (= N₂/(N₂ + Ar)) were investigated. To demonstrate the feasibility of this approach, TiN_x films with different R_N values (0.3, 0.5, and 0.8) were deposited on SiO₂ beams to form composite test cantilevers. Measurements reveal significant changes (ranging from 33 % to 2-fold) in Young's modulus, residual stress, and CTE of the TiN_x films by varying the gas ratio during the PVD process. As a result, this study provides a straightforward approach and guidelines for users to tailor TiN_x films according to specific application requirements.