Electrical Characteristics of Piezoelectric RF-MEMS Tunable Capacitor

Abstract

Piezoelectric RF-MEMS tunable capacitors are useful components for realizing reconfigurable RF circuits for multi-band mobile terminals. In this paper, we describe fabrication process of an AlN RF-MEMS tunable capacitor and electrical characteristics of the tunable capacitor. We chose AlN as piezoelectric material and Al as electrode material, because these materials are compatible with conventional CMOS processes. The tunable capacitor utilized the piezoelectric bimorph actuator with folded beam structure. The structure of the actuator can cancel curling of the beam due to residual stress of the AlN piezoelectric actuator. After subtraction of parasitic components, net capacitance of the tunable capacitor changed from 0.20pF to 0.51pF with drive voltage ranging from 0V to 8V. The tuning ratio was 2.6. Q factor of the capacitor varied 29 to 11 at the same voltage range.