Highly efficient piezoelectric micro harvester for low level of acceleration fabricated with a CMOS compatible process

This paper reports on the fabrication and characterization of piezoelectric micro-harvesters vibrating at 200 Hz for acceleration lower than 0.25 g (1 g = 9.81 m s−2). A CMOS compatible process involving Aluminum Nitride (AlN) thin films was developed on Silicon On Insulator (SOI) substrate. A typical device exhibits a volume of 2.8 mm3, harvests 0.62 μW at 214 Hz and 0.25 g as input acceleration. The harvested power reaches the same level under vacuum but at only 0.15 g. This result confirms that using a packaging under vacuum for piezoelectric energy harvesters is very interesting in order to improve the efficiency for a given acceleration. Finally, it turns out that our devices exhibit the highest Mitcheson figure of merit in the 0–1 kHz range, namely 12.2%.