Fabrication of thin film inductors using FeTaN soft magnetic films

Planar-type thin film inductors were fabricated using FeTaN soft magnetic films. It was found that excellent soft magnetic properties (coercivity of 0.1–0.2 Oe, effective permeability of 4000, and saturation magnetization of 15 kG) could be obtained in the Fe78.8Ta8.5N12.7 films after anneals at 400–500 °C. The initial permeability of the films was constant up to 20 MHz. Internal-coil inductors, in which Cu coils were sandwiched by SiO2 insulator/FeTaN magnetic layers, were fabricated and their characteristics were compared with air-core inductors. The inductance was increased by a factor of 4 compared to air-core inductors. However, the high frequency characteristic was degraded due to a frequency-limited permeability of FeTaN magnetic layers.