Characterization and Adhesion of Interacting Surfaces in Capacitive RF MEMS Switches Undergoing Cycling

• Published in: Adhesion Aspects in MEMS/NEMS pp. 297 - 320
• Format: Book Chapter
• Language: English
• Published: CRC Press 2010
• Subjects: Silicon Nitride; Mem Switch; Modulate RF Signal; Adhesion Aspects; Nanomechanical Properties; Stuck Switches; AFM; RF Mem Switch; Mem Device; Beam Surface; Tap Mode AFM; Topmost Surface Layer; RF Mem; PECVD Silicon Nitride; Dielectric Surface; AFM Image; RF Signal Power; RF Signal; Switch Surface; Capacitive Switches; Sim; Contact Surfaces; Dielectric Layer; RMS Roughness; Switch Cycling
• DOI: 10.1201/b12181-22

Commercialization of RF MEMS switches and the substitution for conventional gallium arsenide (GaAs) field-effect transistor (FET) and PIN diode switches is hindered by reliability problems and unpredictable switch failures during operation. Such failures are due partly to the fact that as the surface-to-volume ratio increases in MEMS devices, the surface forces become more dominant than the inertial effects, and thus significantly affect the performance and reliability of MEMS devices. Adhesion of the beam to the bottom dielectric surface (sometimes referred to as stiction in the literature) is the primary failure mechanism in MEMS devices in general and capacitive switches [4] in particular. Adhesion forces are mainly attributed to two phenomena; (1) mechanical deterioration of the contact surface with cycling [5], and (2) electrical charge trapping within the dielectric layer which induces electrostatic attraction [6]. One of the main difficulties in capacitive RF MEMS switch research is that these two effects are coupled and occur at the same time, which makes characterization of adhesion behavior of RF MEMS switches more complex, compared to metal switches, for example. Ref. [7] provides an overview of the major interfacial adhesion and tribological issues in MEMS.