Mechanical Properties of Sputtered Silicon Oxynitride Films by Nanoindentation

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1049-AA05-17

Mechanical Properties of Sputtered Silicon Oxynitride Films by Nanoindentation Yan Liu, I-Kuan Lin, and Xin Zhang Department of Manufacturing Engineering, Boston University, 15 St. Mary's Street, Brookline, MA, 02446 ABSTRACT Silicon oxynitride (SiON) films with different oxygen and nitrogen content were deposited by RF magnetron sputtering. Fourier-transform infrared (FT-IR) spectroscopy study revealed that co-sputtered SiON films were composed of one homogeneous phase of random bonding O-Si-N network. Time-dependent plastic deformation (creep) of SiON films were investigated by depth-sensing nanoindentation at room temperature. Results from nanoindentation creep indicated that plastic flow was relatively less homogenous with increasing nitrogen content in film composition. 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. INTRODUCTION Silicon oxynitride (SiON) has been under extensive investigation as a promising material system for the development of optics, photonics and microelectronics applications. SiON demonstrates unique tunability in optical and electronic properties when changing the chemical composition of oxygen and nitrogen, from silicon dioxide (SiO2) to silicon nitride (Si3N4). The flexibility in mechanical properties allows SiON films with low residual stress and high thermal stability to be integrated into the micro-electro-mechanical systems (MEMS) [1]. However, only a few attempts have been made to study the mechanical properties of SiON thin films. And even more, time-dependent plastic deformation (creep) behavior of SiON thin film at room temperature has not been reported previously in literature. Depthsensing nanoindentation is a powerful technique for studying the mechanical properties of materials in micro- or nano-scaled dimensions. Upon precisely recording the loaddisplacement data and constructing relevant analysis models, nanoindentation has been used to reveal and interpret the mechanisms of various mechanical properties [2]. In the present work, SiON films with different composition of oxygen and nitrogen content were deposited by RF magnetron sputtering. Creep behaviors of sputtered SiON films have been investigated by depth-sensing nanoindentation with constant-load controlled experiments carried out at room temperature. Energy dispersive X-ray (EDX) spectroscopy and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize SiON films with respect to stoichiometric composition and atomic bonding structure. A deformation mechanism based on chemical bonding structure and shear transformation zone (STZ) amorphous plasticity theory was proposed to interpret nanoindentation creep properties of SiON films. EXPERIMENT Silicon oxynitride films with a thickness of approximately 1 ┬Ám were deposited on silicon wafer substrates at room temperature by a Discovery 18 RF magnetron sputtering system. Among five sputtered SiON specimens, si