Development of GHz-Drive Magnetic Thin Film Inductors for Integrated Circuits

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A new GHz-band permeameter has been developed to find out the CoNbZr, FeAlO and (CoFeB)SiO_2 Thin-film materials as the possible candidates for GHz-drive inductors. A new technique on raise the ferromagnetic resonance (FMR) frequency has also been developed; Microfabricate narrow slits along the easy axis of magnetization and apply RE magnetic field along the hard axis. Then magnetic losses at 2GHz can be negligible through the optimum slit design method we established.An integrated spiral inductor with 0.1-1.0μm-thick silted CoNbZr film on the top exhibited L=8nH and Q=5 at 2GHz, Its size was 330x330μm^2. Provided that the silted CoNbZr magnetic film are installed below and on the spiral (sandwich type inductor), L=7.9nH and Q=13 has been achieved is the 200x400μm^2 size. This is worth achieving main objective of this work.An RE magnetic near field probe has been developed to analyze leakage flux from the integrated inductor to semiconductor circuit. The probe exhibited world-highest spatial resolution of 40μm at 1GHz. It is estimated that the electromagnetic interference to the integrated circuit would be negligible.An extensive application of integrated ferromagnetic film has been proposed to suppress RF in-line electromagnetic noise by means of FMR losses. Insertion loss at 1GHz was only 0.4dB while is reached 15dB as 20GHz.Thus this work has been concluded, showing a practical possibility of ferromagnetic integrated inductors as well as to pioneering a new technology field of "soft magnetic applications in the GHz range for IT." The first and second international symposium on "High Frequency Micromagnetic Devices and Materials" has been initiated by the investigators.