A Multimetal Surface Micromachining Process for Tunable RF MEMS Passives

摘要

This paper reports on a microfabrication technology for implementing high-performance passive components suitable for advanced RF front-ends. This technology offers three metal layers with different thicknesses, one dielectric, and two sacrificial layers, enabling the fabrication of continuously tuned capacitors, capacitive and ohmic switches, as well as high-$Q$ inductors all on a single chip. To demonstrate the versatility of this technology, several passive components are fabricated on a Borosilicate glass substrate $(varepsilon_{r} = 4.6)$. A high- $Q$ tunable capacitor is fabricated exhibiting an electrostatic tuning range of more than 6 : 1. The temperature variation of capacitance from 223 to 333 K is less than 9%, and the tuning speed is better than 80 $muhbox{s}$. To achieve a higher zero-bias capacitance, a tunable capacitor bank is also implemented, which can be tuned from 2.2 pF to 6.1 pF. In addition, a coupled inductor pair with self-inductances of 15 and 21 nH is implemented showing $Q$s exceeding 40 at 800 MHz. Measurements are compared with high frequency structure simulator (HFSS) electromagnetic simulations, showing good agreement. The technology reported is post-CMOS compatible and low cost.$hfill$[2011-0331]