Electrothermal Characteristics of Electroplated Ni-Based Tunable MEMS Inductor on High-Resistivity Substrate With Displacement Actuator

In this letter, the design and characterization of an electroplated Ni-based tunable microelectromechanical inductor is presented. The inductor was fabricated on high-resistivity substrate (ρ ~ 5 kΩ·cm) to minimize eddy currents and displaced current-induced substrate related losses. The inductor loop had a nitride-encapsulated polysilicon-based vertical electrothermal displacement actuator attached to the backside, and also two fixed lateral metal shields from the same Ni layer. Inductance tunability is achieved by changing the magnetic flux distribution associated with the loops by causing an out-of-plane movement of the spirals when the electrothermal actuation voltage or ambient temperature is changed. Mechanical and radio-frequency characterization of the inductor was carried out for both electrothermal and thermal actuation, with actuation voltage and chuck temperature ranging from 0 to 8V and 30 °C to 200 °C, respectively. In both cases, the inductance tuning ratio was 53.1% and 15.6%, with self-resonance frequency greater than 10 GHz.