An actuator for controlling the area of dielectric layer of the tunable capacitor by commercial CMOS fabrication

This study describes the fabrication of an actuator of controlling the area of a dielectric layer using the commercial 0.35μm Single Polysilicon Four Metals (SPFM) Complementary Metal Oxide Semiconductor (CMOS) process and a post-process. The post-process requires wet and dry etching without using a mask to etch sacrificial layers and release the structures suspended in the actuator. The actuator is composed of a top suspended plate, a bottom fixed plate, and a laterally yielding cantilever beam, and two fixed curved electrodes. One end of the cantilever beam is anchored whereas the other end is connected to the suspended plate. The fixed curved electrodes and the cantilever beam are stacked layers of metals and via layers, formed by the CMOS process. The cantilever beam is deflected over a large distance using electrostatic force and the suspended plate swings laterally to increase or decrease the area of overlap between itself and the bottom fixed plate. The dimensions of the actuator are: suspended plate diameter = 100 μm; cantilever beam width = 2 μm, height = 6 μm, and length = 300 μm. The moved end of the cantilever beam, connected to the suspended plate, is deflected by 25 μm when a dc power supply of 60V is applied to it.