Study on advanced multilayered magnetostrictive thin film coating techniques for MEMS application

This paper is to investigate the multilayer deposition technique with selective DC magnetron sputtering for the fabrication of partially film deposited magnetostrictive actuator. The multilayer of this study was consisted of TbDyFe and Ni layers. The magneto-mechanical characteristics of TbDyFe (called as Terfenol-D) and Ni multilayered thin films with different thickness ratios of TbDyFe/Ni/TbDyFe (0.2/0.1/0.2, 0.2/0.1/0.1, 0.2/0.1/0.0 μm) were considered and the magnetostrictive multilayers were deposited on two kinds of micro-multi-body actuator systems to check the size effect. To fabricate the multilayered film on Si based micro-frame, micromachining process and selective DC magnetron sputtering techniques were combined. The deposited film thicknesses were measured by X-ray diffraction (XRD). To characterize the magneto-mechanical properties of the TbDyFe/Ni/TbDyFe film, the magnetization of the film on the fabricated actuator was observed using vibrating sample magnetometer (VSM) and the magnetostriction of the actuator was determined by measuring the differences of the curvature of the coated silicon substrates using the optical cantilever method. For the application to a micro-actuator, the maximum deflection of the actuator under 0.5 T was 280 ppm. The results indicate that the Ni layer makes 3–5% lower coercive force and 10–15% enhancement of magnetostriction in low magnetic field (<0.5 T).