We performed this study to develop microinductors using CoFeSiB/SiO2 multilayer film with a high quality factor. For a micro dc/dc convertor, efficiency and miniaturization must be improved by incorporating a microinductor. High Q values are compatible with high inductances of the inductors when a three-dimensional helical coil and the multilayer film are used. Furthermore, the decrease of inductor areas and thicknesses contributes to miniaturization, as the polyimide film is used as the substrate of the magnetic core. The microinductors obtained inductances of 3 to 15 μH and quality factors of more than 40 at a frequency of 1 MHz, and displayed a current density of more than 100 A/mm2. We have simulated the magnetic field strength in the magnetic cores using three-dimensional Maxwell simulation tools.
