Fabrication and performance of a micromachined 3-D solenoid inductor

A high-Q and fres (self-resonant frequency)solenoid inductor was fabricated by using the microelectromechanical systems(MEMS) technology with air-core structure. This inductor has an air core and an electroplated copper coil to reduce the series resistance, and the solenoid structure with laterally laid out structure saves the chip area significantly. The measurement results show that this inductor has high Q-factor and stable inductance over wide range of operating frequency. The maximum Q-factor of this inductor is 38 and the inductance is 1.78 nH at 5 GHz with an air core of 45 μm. Moreover, the Q-factor and the inductance grow with the increasing of the air core.