Electrodeposition of CoNiFeX magnetic Films with Low Magnetic Losses for Power Applications



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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 IC devices, we have developed solution chemistry for electrodeposition of CoNiFeX (X=S,P,B,V) thin films with high magnetic moment (HMM) and permeability with higher than 100μΩ-cm resistivity; higher than 1.7 T magnetic moment. CoNiFeX alloys are fully compatible with existing manufacturing concepts in semiconductor industry. Direct current (DC) and pulse current (PC) deposition methods to produce CoNiFeX alloys is employed to demonstrate control over BCC crystal structure by tuning transport conditions during electrodeposition. The BCC structure of CoNiFeX alloys is characterized with average grain size of 10-20 nm which consequently yields coercivity values of CoNiFeX alloys between 8-15 Oe at 500 nm film thickness. CoNiFe alloys produced by DC and PC deposition have magnetic moment higher than 1.7 T, which is not significantly diminished with addition of X (X=S,P,B,V) as resistivity controlling phase. More than 100% increase in the resistivity of deposited CoNiFeX alloys is demonstrated with controlled concentration of X burring molecules and Fe3+ ions as hydroxide precipitating agent without deterioration in magnetic properties. All samples exhibit shiny surface finish and low stress. Electrodeposition process is scaled up with customized setup to build thin film inductor devices on 4 in wafer, fabricated at Nanofabrication Facility at the University of Houston. Thin film inductor devices with CoNiFeX cores are tested at Intel Corporation facility in wide frequency range (1 MHz to 1 GHz). More than 70% improvement in induction efficiency compared to air core devices is observed when CoNiFeX magnetic cores of various geometry are introduced in device design. Direct measurement of permeability and losses for DC deposited CoNiFeX alloys is performed by resonant cavity setup, which illustrate reduction in losses at 100 MHz frequency due to resistivity improvement by incorporation of X phase in CoNiFeX alloys.



CoNiFe, Thin film inductor