Monolithic double rectangular spiral thin-film inductors implemented with NiFe magnetic cores for on-chip dc-dc converter applications

摘要

This paper describes a simple, on-chip complimentary metal oxide semiconductor (CMOS) compatible thin-film inductor applied for the dc-dc converters. The double rectangular spiral types of the thin-film inductors were implemented with 15 μm-thick copper films upon 2.5 μm thick of the NiFe magnetic core. Prior to fabricating a high-voltage CMOS dc-dc converter circuit, the NiFe magnetic core was deposited on the polyimide film. Adapting a double-rectangular structure, the fabricated monolithic inductor exhibited not only high inductance of 1.6 μH but also high quality factor of 11.2 at 5 MHz. To simplify the integration process, the planarization process for the top magnetic core was eliminated. The performance of the dc-dc converter which combined with our proposed inductors was evaluated at a high power efficiency of 81% when the converter operated at a frequency of 5 MHz corresponding to input and output voltages of 3.3 V and 8.1 V, respectively.