Novel screen-printed ceramic MEMS microhotplate for MOS sensors

We developed a new approach to the fabrication of MEMS substrates for MOS gas sensors. This full screen-printing process is based on the application of sacrificial material, which is solid at the near-room temperature of printing and turns to powder after the firing of the elements of the sensor. Therefore, this sacrificial material can be removed from under the suspended elements of the MEMS structure in ultrasonic bath. The glass-ceramic MEMS is a cantilever structure equipped with a Pt-based microheater made of Pt resistive material with sheet resistance of about 4 Ohm/square fabricated using core-shell technology. It is located at the end edge of the cantilever and is isolated from the contacts to the sensing layer by glass-ceramic insulation. Screen-printing provides cheap fabrication, robustness and low power (∼120 mW@450°C) of the sensing element. The functionality of the microhotplate was checked using ZnO nanomaterial deposited by microextruder, it demonstrated high response and selectivity of ZnO material to NO₂ (response 41.6 at 200°C for 10 ppm).