Thin Film Inductor with Multilayer Magnetic Core

In this work, thin film microinductors were investigated from the standpoint of increasing the quality factor (Q) and inductance (L). To obtain a high Q, it is important to use a magnetic core with a small iron loss at high frequencies. Thin film microinductors were prepared using multilayered CoNbZr/AlN film. The optimum conditions for a high Q were investigated by changing the size of the magnetic core and the structure of the multilayer film and exciting coil. The Q and L values increased with decreasing thickness of individual magnetic layers and with increasing intermediate layer thickness. The demagnetization of the inductor open magnetic circuit was decreased by using a multilayer magnetic core. The stray capacitance between coil and magnetic core is dominant in these thin film inductors. It was found that multilayer magnetic core is useful for increasing the Q and L values of thin film inductors at high frequencies. An experimental inductor in which iron and copper losses were reduced through the use of a multilayer core and thick coil had an L=120 nH and Q=18 at 50 MHz, and measured 0.5 mm × 2.5 mm × 35 μm.