Pulse-Reverse Electrodeposited Nanograinsized CoNiP Thin Films and Microarrays for MEMS Actuators

Abstract

This paper reports on a low residual stress hard magnetic CoNiP alloyelectrodeposition technique for microelectromechanical systems (MEMS)applications based on techniques previously developed for CoNiP thinfilms for perpendicular magnetic recording. Besides electrolytechemicals, various processing parameters including applied currentdensity, film thickness, electrolyte agitation, electrolyte pH, andtemperature are optimized to provide thick films with low residualstress. The resulting hard magnetic CoNiP alloy exhibits a relativelyhigh perpendicular coercivity (H-c) of around 700-1200 Oe and a highsaturation magnetization (M-s) of 0.41-0.52 kG. Thick films up to 52 mmwith a low residual stress have been realized using this CoNiPelectrodeposition technique. In addition, CoNiP microarrays 22.5 mu mthick are surface micromachined for the integrations with magnetic MEMSdevices. Experimental results confirm that these microarrayconfigurations have a higher coercivity and maximum magnetic energydensity, (BH)(max), than thin films in the perpendicular direction. (c)2005 The Electrochemical Society. All rights reserved.