Abstract
In this work, we demonstrate the simple fabrication process of AlN-based piezoelectric energy harvesters (PEH), which are made of cantilevers consisting of a multilayer ion beam-assisted deposition. The preferentially (001) orientated AlN thin films possess exceptionally high piezoelectric coefficients d33 of (7.33 ± 0.08) pC∙N−1. The fabrication of PEH was completed using just three lithography steps, conventional silicon substrate with full control of the cantilever thickness, in addition to the thickness of the proof mass. As the AlN deposition was conducted at a temperature of ≈330 °C, the process can be implemented into standard complementary metal oxide semiconductor (CMOS) technology, as well as the CMOS wafer post-processing. The PEH cantilever deflection and efficiency were characterized using both laser interferometry, and a vibration shaker, respectively. This technology could become a core feature for future CMOS-based energy harvesters.
Highlights
Energy harvesting has recently attracted significant attention as a key power source where changing batteries in applications is not practical, or in low-power autonomous sensors and micro-devices, as a replacement of electrochemical batteries.Several methods of harvesting ambient energies have been investigated, including solar energy, wind, flowing water, waste heat, electromagnetic waves, or vibrations [1,2]
The utilization of mechanical vibrations represent a suitable alternative for any environment, including indoors, as well as low-power autonomous sensors and microdevices [3]
Electrostatic and electromagnetic induction, and piezoelectricity can all typically be exploited as transducing mechanisms to convert mechanical energy into electrical [4]
Summary
Energy harvesting has recently attracted significant attention as a key power source where changing batteries in applications is not practical, or in low-power autonomous sensors and micro-devices, as a replacement of electrochemical batteries. Piezoelectric materials have an inherent capability to directly convert mechanical stress/strain energy into electrical energy, such devices are compact and possess simpler designs, compared to their electromagnetic and electrostatic counterparts Such devices can be fabricated by micromachining techniques and directly integrated into monolithic, micro-electro-mechanical systems (MEMS) [6]. AlN, prepared by sputtering, can be implemented in standard complementary metal oxide semiconductor (CMOS) technology, as well as the CMOS wafer post-processing [12], thereby, enabling the integration of PEH with active devices Other piezoelectric materials such as PZT, ZnO, and PVDF possess contamination risks for CMOS processing lines [13], while AlN, deposited by the metal-organic chemical vapor deposition (MOCVD) technique, requires high temperature, which prohibits its integration with CMOS devices. We show a simple method to prepare PEH with a high value of piezoelectric coefficients of (7.33 ± 0.08) pC·N−1, using low temperature ion-assisted deposition, making it fully CMOS-compatible, including the CMOS wafer post-processing
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