A MEMS Capacitive Resonator as an Acoustic Sensor for Photoacoustic Spectroscopy

This paper presents the design of a MEMS resonator with capacitive transduction as an acoustic sensor, intended for cantilever-enhanced photoacoustic spectroscopy. The sensor employs area-variable capacitive detection by surrounding the silicon resonator with dense comb teeth. To reduce gas damping effects on the resonator motion, the anchor height is increased to 260 $\mu\mathrm{m}$ . This approach successfully resolves the capacitance detection sensitivity and motion damping trade-off commonly seen in acoustic detection. Experimental results exhibit a maximum sensitivity of 3749 mV/Pa at the resonant frequency of 1870 Hz with a 15 V bias voltage. The equivalent noise has a peak value of 7.9 $\mu \text{Pa}/\text{Hz}^{1/2}$ and the noise sources are analyzed.