Microfabricated V-groove power inductors using multilayer Co-Zr-O thin films for very-high-frequency DC-DC converters

Microfabricated V-groove inductors targeted to operate above 10 MHz are fabricated and tested. Multilayer nano-granular Co-Zr-O/ZrO₂ magnetic thin films are used as the core material of the inductors to improve the magnetic performance of the films deposited on the sidewalls of V-grooves and to control eddy-current loss in the core. Prototype V-groove inductors are fabricated based on optimization results for 7-V to 3.3-V, 1-A dc-dc buck converters. The inductors exhibit inductance of 3.4 nH from 10 MHz to 100 MHz, dc resistance of 3.83 mΩ, and quality factor up to 66. The prototype inductors are a promising candidate for high-power-density high-efficiency dc-dc converters. The measured inductor performance indicates that they could be used to make a 7-V to 3.3-V, 1-A converter that would exhibit power density of 2.5 W/mm² and efficiency of 86% at 100 MHz; or power density of 0.36 W/mm² and efficiency of 91% at 11 MHz.