MEMS based electrochemical process for fabrication of laminated micro-inductors on silicon

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Anthony, Ricky
Ó Mathúna, S. Cian
Rohan, James F.
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Soft metallic magnetic alloys (such as Co, Ni and Fe based alloys) have been extensively used as core material in integrated inductors and transformers for DC–DC conversion. Although these materials have excellent soft magnetic properties such as high saturation flux density, low coercivity and high permeability; high electronic conductivity makes them susceptible to eddy current losses. As a result, core material thickness is often limited by the skin depth which in turn reduces the inductance density. Laminated magnetic films, where the active layers are separated by a dielectric film can increase the overall core thickness without compromising on its power handling capability. In this work, a CMOS compatible electrochemical-resist-electrochemical based core lamination deposition technique is demonstrated whereby a laminated top magnetic core is fabricated with a self-assembled and selective metallization process on the top SU-8 passivation layer with 2.5 μm Ni81Fe19. The process is site-selective, shows uniform deposition, has excellent step coverage and ideal for metallization of recessed regions in MEMS devices. Moreover, a high frequency measurement of laminated structure suggests uniform permeability for ~ 500 MHz applications.
Integrated magnetics , Magnetic MEMS , Metallization , Electroless deposition , DC–DC Converter
Anthony, R., O' Mathúna, C. and Rohan, J. F. (2016) 'MEMS based electrochemical process for fabrication of laminated micro-inductors on silicon', Microelectronic Engineering, 155, pp. 33-38. doi:10.1016/j.mee.2016.02.009