Improved quality factor of thin film inductor by application of multilayer film

Recently, thin film inductors are reported by many authors (1-3). These thin film micro inductors are investigated in the point of design of exciting coil and magnetic core. The most difference of electric properties between the thin film inductor and chip inductor is that quality factor (Q) of thin film inductor is lower than that of chip inductor using ferrite magnetic core in same inductance (L). To get the high quality factor, it is important to use the magnetic core in which iron loss is small in high frequency. On the other hand, it is well known that in multilayer magnetic films, generally, the permeability is high and iron loss is small. In this paper, it is proposed that the multilayer magnetic core is useful to increase Q in thin film inductor. The experimental inductor shows L of 100nH, Q=18 at 50 MHz in its size of 0.5x2mm2.