On-chip RF power inductors with nanogranular magnetic cores using prism-assisted UV-LED lithography

This paper presents a CMOS-compatible microfabrication process for on-silicon racetrack power inductors using prism-assisted lithography with an ultraviolet light-emitting diode (UV-LED) array as a light source. This combination of lithographic techniques was applied in making 60-μm-tall SU-8 structures with 45° sidewalls to achieve high performance from a sputtered nanogranular magnetic core material, Co-Zr-O. Microfabricated magnetic components with Co-Zr-O cores were designed, built, and tested for use in a 25-W dc-dc power converter operating at a switching frequency between 5-30 MHz. Fabricated inductors achieved a peak quality factor of 18 and an inductance of 660 nH at 15 MHz.