Mechanical properties of sputtered silicon oxynitride films by nanoindentation

Silicon oxynitride (SiON) has received a great deal of attention in micro-electro-mechanical system (MEMS) integration due to its composition-dependent tunability in optical, electronic and mechanical properties. In this work, silicon oxynitride films with different oxygen and nitrogen content were deposited by RF magnetron sputtering. Energy dispersive X-ray (EDX) spectroscopy and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize the SiON films with respect to stoichiometric composition and atomic bonding structure. Time-dependent plastic deformation (creep) of SiON films were investigated by depth-sensing nanoindentation at room temperature. Young's modulus and indentation-hardness were found correlated with the nitrogen/oxygen ratio in SiON films. Results from nanoindentation creep indicated that plastic flow was less homogenous with increasing nitrogen content in film composition. Correspondingly, a deformation mechanism based on atomic bonding structure and shear transformation zone (STZ) plasticity theory was proposed to interpret creep behaviors of sputtered SiON films.