On-Chip Variable Inductor Using Microelectromechanical Systems Technology

Abstract

We have proposed and evaluated the novel three-dimensional on-chip variable inductor that is fabricated using microelectromechanical systems technology. The variable inductor was made of thin film metallic glass, Pd76Cu7Si17, that has high flexibility. Since the thin film metallic glass has high elasticity, the height of the three-dimensional spiral inductor can be changed, resulting in the change of inductance. The fabricated inductor has the inductance of 3.64–3.74 nH due to the change in the spiral height with a Q-factor of 2.0 at 2 GHz. The variable range of inductance is 0.1 nH, and the ratio is 3%. Simulation results have shown that the Q-factor is increased by coating with a low-resistivity metal; when the inductor is coated with Au, the Q-factor is increased to 7.2 at 2 GHz. Furthermore, the several-nH inductor with a variable range of 10% is designed.