Self-assembled silicon membrane resonator for high vacuum pressure sensing

Abstract

In this paper, a mechanical vacuum gauge based on a circular membrane resonator is proposed and its high responsivity is verified in high vacuum down to a pressure of similar to 6 x 10(-7) mbar. A silicon-on-nothing (SON) resonator with a self-sealed cavity having a diameter of 150 mu m and a thickness of 1.55 mu m is fabricated through a high vacuum annealing process. After the fabricated membrane resonator is placed inside a custom vacuum chamber, its resonant characteristics are measured with a frequency sweep, and the vibration amplitudes are measured by resonance feedback using a laser and photodiodes at various vacuum pressures. Using quality factor (Q factor) measurement, the SON resonator shows a high responsivity (delta Q/delta P) of up to similar to 3.7 x 10(8 )mbar(-1) in the high vacuum range. Both quality factor and amplitude are found to be effective vacuum indicators, and amplitude measurement is specifically useful for real-time vacuum monitoring.