Development of High-Performance Solenoid-Type RF Chip Inductors Utilizing Low-Loss Al2O3 Core Materials

Abstract

In this study, small size, high-performance, solenoid-type RF chip inductors utilizing low-loss Al2O3 core materials were investigated. Copper coils with a diameter of 40 µm were used and the dimensions of the RF chip inductors fabricated were 2.1×1.5×1.0 mm3. The high-frequency characteristics of the inductance, quality factor, and impedance of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with a HP16193A test fixture). The developed inductors have a self-resonant frequency of 1 to 3.5 GHz and exhibit an inductance of 22 to 150 nH. The inductors have a quality factor of 60 to 90 over the frequency ranges of 500 MHz to 1.5 GHz. The capacitance–frequency data is well described in the experimental data. It was suggested that reducing the number of turns of the coil and increasing the space between the coils are important measures for improving the high-frequency limit of the RF chip inductors.