Microinductor for Flip-Chip Micropower Source

The rapid reduction of line width of large-scale integration (LSI) processes to a width of under 100 nm and the lowering of voltage to below 1 V to drive LSI, in addition to the sharp market growth of personal IT devices using lithium batteries, have seriously raised energy consumption around the world, necessitating the adoption of energy-saving technology using distributed small dc-dc converters. In light of these demands, using new power microelectromechanical system technology and continuous deposition technology, we have developed a new microinductor with a thickness of 300 μm. The magnetic core, consisting of CoFeSiB-Ti-SiO₂ multilayer film on a polyimide sheet, is applicable to a microinductor using a helical coil. In comparison with a mono-layer core such as a ferrite core, due to the magnetic shielding effect of each magnetic layers, a composite multilayer magnetic core is very effective in maintaining inductance up to a high dc current over 1 A. This paper proposes the use of microinductors characterized by high quality, superior dc-biased properties and low height as flip-chip sized micropower sources.