MEMS Narrow Gap Electromagnetic Harvester with Mitigation of Curvature Distortion

The narrowing air-gap between coil and magnet of electromagnetic energy harvester is one of the most important parameter to improve the generated power. Because of the sputtering 15 pm thickness NdFeB/Ta multilayer film with high temperature annealing, the large curvature distortion is occurred on Si substrate. In this paper we demonstrate a compensation method for residual stress on the sputtered NdFeB magnetic film on Si wafer. By using both-side sputtering method, we reduced the residual stress, which reduces the reliability of MEMS fabrication and performance of harvesters, from 144 MPa to 9.4 MPa. The electromagnetic type energy harvester with narrow gap of 20 μm was successfully fabricated and evaluated.