Fabrication and investigation of low actuation voltage curved beam bistable MEMS switch

Abstract

Fabrication and characterization of a novel bistable MEMS (MicroElectroMechanical Systems)-based switch is reported in this paper. The bistable switch is fabricated on SOI wafer with 10 µm thick device Si layer using Silicon-On-Insulator Multi User MEMS Process with three masks. The proposed device is comprised of a centrally clamped parallel curved beams (switching element) and a pair of electrothermal V-beam microactuators (actuating element). The bistability is achieved through the buckling of centrally clamped parallel curved beams and the critical buckling load is provided by the electro-thermal expansion of the V-beam microactuators. Hinges, latches, membranes are not used in the proposed design and thus the fabrication complexity is reduced to a greater extent. A maximum displacement of 20.7 µm is achieved at 14 V DC supply for the V-beam microactuator and this thermal expansion of the V-beam microactuator acted as the critical buckling load for the centrally clamped parallel curved beam. Electrical and mechanical characterization of switch is performed and after the analysis, it is verified that the nonlinear property (elasticity) of silicon material is poor and that is the reason for comparatively higher actuation voltage to simulation results. A novel optimized redesign for the electrothermal V-beam microactuator based on POLYMUMPs process is proposed in order to overcome the uncertainties endured.