Micromachining of a Bimorph Pb(Zr,Ti)O-3 (PZT) Cantilever Using a Micro-Electromechanical Systems (MEMS) Process for Energy Harvesting Application

Abstract

We designed and fabricated a bimorph Pb(Zr,Ti)O-3 (PZT) cantilever with an integrated Si proof mass to obtain a low resonant frequency for an energy harvesting application. The cantilevers were fabricated on the micro-electromechanical systems (MEMS) scale. A mode of piezoelectric conversions were d31 and d33 mode in cantilever vibration Therefore, we designed and fabricated a single cantilever with d31 unimorph, d31 bimorph, d33 unimorph, and d33 bimorph modes. Finally, we fabricated a device with beam dimensions of about 5,400 mu m x 480 mu m x 14 mu m (< +/- 5%), and an integrated Si proof mass with dimensions of about 1,481 mu m x 988 mu m x 450 mu m (< +/- 5%). In order to measure the d31 and d33 modes, we fabricated top and bottom electrodes. The distance between the top electrodes was 50 mu m and the resonant frequency was 89.4 Hz. The average powers of the d31 unimorph, d31 bimorph, d33 unimorph, and d33 bimorph modes were 3.90, 9.60, 21.42, and 22.47 nW at 0.8 g (g = 9.8 m/s(2)) and optimal resistance, respectively.