Advances in Planar Coil Processing for Improved Microinductor Performance

This paper examines the process challenges in developing high aspect-ratio copper structures for improving microinductor performance. With increased miniaturization, increasing windings losses become a major challenge limiting the microinductor efficiency. It was also identified that within constraint footprints coil thickness to spacing ratio increase can reduce dc resistance significantly. In this paper, we present a reliable process for developing high aspect ratio (~5.8) resist moulds for copper electrodeposition. This resist provided coil spacings 10 μm for 58 μm resist thickness; this in turn reduces the dc resistance of a typical microinductor by more than 17% when compared with a similar device reported previously.