PECVD-SiOxNy films for large area self-sustained grids applications

Abstract

Abstract In this work we study the structural properties and mechanical stress of silicon oxynitride (SiO x N y ) films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures (320 °C) and report the feasibility of using this material for the fabrication of large area self-sustained grids. The films were obtained at different deposition conditions, varying the gas flow ratio between the precursor gases (N 2 O and SiH 4 ) and maintaining all the other deposition parameters constant. The films were characterized by ellipsometry, by Fourier transform infrared (FT-IR) spectroscopy and by optically levered laser technique to measure the total mechanical stress. The results demonstrate that for appropriated deposition conditions, it is possible to obtain SiO x N y with very low mechanical stress, a necessary condition for the fabrication of mechanically stable thick films (up to ∼10 μm). Since this material (SiO x N y ) is very resistant to KOH wet chemical etching it can be utilized to fabricate, by silicon substrate bulk micromachining, very large self-sustained grids and membranes, with areas up to ∼1 cm 2 and with thickness in the 2–6 μm range. These results allied with the compatibility of the PECVD SiO x N y films deposition with the standard silicon based microelectronic processing technology makes this material promising for micro electro mechanical system (MEMS) fabrication.