On-Chip High- Variable Inductor Using Wafer-Level Chip-Scale Package Technology

In this paper, the authors propose an on-chip high-Q variable inductor embedded in wafer-level chip-scale package (WL-CSP). The variable inductor has a metal plate and a spiral inductor fabricated by the WL-CSP technology. The metal plate can be moved by a microelectromechanical systems (MEMS) actuator, and the inductance is varied according to the position of the metal plate. At the present time, the MEMS actuator has not been implemented yet. In this paper, the authors present a feasibility study on the proposed variable inductor. The inductor is evaluated with measurement results using a metal plate moved by a micromanipulator instead of the MEMS actuator. At 2 GHz, the measured inductance is varied from 4.80 to 2.27 nH, i.e., the variable ratio is 52.6%. The maximum value of quality factor is 50.1