Structural Design of Thin-Film Spiral Inductors for MHz Devices.

A method for structural design of thin-film spiral inductors was studied, using FEM electromagnetic field simulation. By analyzing the direction of the eddy current, we found that specific divisions of magnetic layers effectively reduced the electric power loss in magnetic layers. A 3 mm x 13 mm thin-film inductor for which L = 0.9 μH Q = 14.5 and Ibias = 0.55 A at 5 MHz was developed, based on an analysis of the electromagnetic field simulation. With this structure, a thin-film inductor of Q = 20 was achieved by increasing the coil thickness.