Silicon oxynitride films (SiOxNy) are of great importance for opto-electronic applications and art promising for the development of microelectromechanical systems (MEMS). This work presents a theoretical model to determine: the modulus of elasticity, the thermal expansion coefficient, and the thermal conductivity of rf-plasma enhanced CVD SiOxNy films using suspended micromachined beams. The model predicts the occurrence of well-defined deformations (buckling) of a fixed-end microbeam when this microbeam is subjected to controlled thermal compression forces. The mechanical and thermophysical properties are obtained through the measurement of the beam deflection. The results show that microbeams with a 20 mum width and a 1000 mum length readily exhibit observable buckling when electrical voltages in the range of 0.1-0.3 V tine applied to the resistor. This confirms the feasibility of fabricating SiOxNy microbeams and the use of these microstructures for its mechanical and thermophysical characterization.