Very thin SiC membranes for micromachined vacuum sensors

Very thin (20-200 nm) SiC membranes with controlled composition and thickness, low tensile stress, layer continuity and etching selectivity are fabricated using a specially developed LPCVD process. These characteristics are necessary for their application in vacuum sensors, especially for operation in harsh environment. The continuity, low stress (180 MPa) and etching selectivity in combination with the reduced thickness increase the sensor sensitivity. Full characterization of these membranes is performed to investigate their structural and mechanical properties and fine tune them according to the application specific requirements. The fabricated membranes have undergone a bulge test in a system that can generate up to 1bar pressure. The largest size tested (800 mum times 600 mum) can withstand a maximum pressure of 780 mbar, while the smaller membranes did not break even for the maximum pressure our test system supplies.