Silicon Oxynitride Membrane for Chemical Sensor Application

Tin oxide gas sensor can detect various gases by using the conductivity changes due to adsorption and desorption processes of gaseous molecules on its surface. The reduction of the power consumption especially for batteries back-up operation, is one of the challenge for SnO2 gas sensors. We propose a new solution using a silicon oxynitride membrane (SiOxNy) to reach this objective. Thin films of SiOxNy with different compositions have been studied. Their composition, residual stress, Young modulus and mechanical strength have been evaluated. As a result, we propose an optimized silicon oxynitride membrane with a low residual stress (-50 MPa), giving above 95% fabrication yield and low power consumption (65 mW / 450°C). A new sensors generation has been successfully fabricated and its mechanical strength and thermal performances have been evaluated. Moreover, an equation is derived, which describes the variation of the Young modulus as a function of the silicon oxynitride composition.