High-Quality Factor Ni-Zn Ferrite Planar Inductor

Abstract

Ferrite and air-core planar inductor arrays were fabricated on 4 inch Si wafer to characterize inductor performance. Three micron thick Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> film was deposited by a low temperature electrophoresis ferrite deposition process. All ferrite inductors in the array showed 35% higher inductance ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> ) and 130% higher quality factor ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ) than air-core inductor. The maximum <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> of ferrite inductor was found to be 53 at 2 MHz. The superimposed DC current and the rated power were measured to be about 3 A and 15 W, respectively, for a 5% drop in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> . The fabricated ferrite inductor has a higher current capability than the air-core inductor. In addition, the power efficiency of the buck DC-DC converter was predicted to be 94.3% at 1.93 W.