Reliability issues for electrostatically actuated MEMS switch

Microelectromechanical systems (MEMS) switches are attractive for radio frequency and microwave systems due to outstanding performance, but low reliability limits application of these devices. To date, a number of reliability problems are overcome, but some of them get little attention. This work describes the first experimental results on a novel failure mechanism of the MEMS switch with electrostatic actuation. The device is fabricated on a thermally oxidized silicon wafer with chromium adhesive layer. After several thousand working cycles, nanostructures containing adhesive material emerge at the gate. They coalesce into micron-sized defects that touch the beam during actuation and disturb normal operation. The material transfer also takes place at the substrate around the gate. This phenomenon was not reported in the literature, although Cr is widely used for microfabrication. The reasons for material transfer must be revealed in order to exclude this failure mechanism for MEMS devices.