Microfabricated V-Groove Power Inductors Using Multilayer Co–Zr–O Thin Films for Very-High-Frequency DC–DC Converters

V-groove microinductors are designed, fabricated, and tested for operation above 10 MHz. Multilayer nanogranular Co-Zr-O/ZrO₂ magnetic thin films are used as the core material of these 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 in a Si substrate based on optimization results for 7 to 3.3-V, 1-A dc-dc buck converters. The inductors exhibit an inductance of 3.4 nH from 10 to 100 MHz, a dc resistance of 3.83 mΩ, and a quality factor of up to at least 50. 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 to 3.3-V, 1-A converter exhibiting a power density of 2.5 W/mm² and an efficiency of 86% at 100 MHz; or a power density of 0.36 W/mm² and an efficiency of 91% at 11 MHz.