Electrodeposited Conifex Magnetic Films with Low Magnetic Losses for Power Applications

Abstract

Electromagnetic induction is essential for functioning of the analog circuits used in cell phones, MEMS devices and other power related electronics. In order to meet the demand of higher efficiency and minimum magnetic losses in packaging industry, we have developed solution chemistry1 , 2 for electrodeposition of CoNiFeX (X=S,O,P,B,V) thin films (thickness=500 nm) with high magnetic moment (HMM) and >500 permeability at >500 MHz frequency; >100μΩ-cm resistivity; >1.5 T magnetic moment. The CoNiFeX alloys are fully compatible with existing manufacturing concepts in semiconductor industry. Direct current (DC) and pulse current3 (PC) deposition methods for CoNiFeX alloys is employed to demonstrate control over BCC/FCC crystal structure by tuning transport conditions during electrodeposition. The structure of CoNiFeX alloys is characterized with average grain size of 15-20 nm which consequently yields coercivity values of CoNiFeX alloy films between 8-15 Oe at 500 nm thickness. CoNiFe alloys produced by DC and PC deposition have magnetic moment of 1.8 T, which is optimized to 2.2 T with addition of X (X=S,O,P,B,V) as additives4. More than 100% increase in the resistivity of deposited CoNiFe alloys is demonstrated with controlled concentration of additives and Fe3+ ions as oxide precipitating agent5 without reduction in magnetic properties. All samples exhibit shiny surface finish and low stress. Thin film inductor devices are fabricated with CoNiFeX alloys to test magnetic properties at >500 MHz frequency, which would be discussed with testing data. Brankovic, S. R., Vasiljevic, N., Klemmer, T. J. & Johns, E. C. Influence of additive adsorption on properties of pulse deposited CoFeNi alloys. Journal of the Electrochemical Society 152, C196 (2005).Brankovic, S. R., Sendur, K. & Klemmer, T. J. Magnetic Materials, Processes, and Devices VII and Electrodeposition of Alloys. in Proceedings of the International Symposia 2002, 269 (Electrochemical Society, 2003).Puippe, J.-C. & Leaman, F. Theory and practice of pulse plating. (Amer Electroplaters Soc, 1986).Djokić, S. S. Electrodeposition of amorphous alloys based on the iron group of metals. Journal of the Electrochemical Society 146, 1824 (1999).George, J. et al. Oxide/hydroxide incorporation into electrodeposited CoFe alloys—Consequences for magnetic softness. Electrochimica Acta 110, 411–417 (2013).