Study On A Latching Electrothermal Bistable Microswitch

MEMS relay or switch has a series of advantages, such as good linearity, fast response time, small size, high integration, easy batch manufacturing, and so on. In view of this, we propose a bimorph electrothermal actuated microswitch, with a dual beam staggered locking latch mechanism, which can maintain the steady state without continued power. This design takes advantages of the electrothermal micro-actuator, such as high driving force, high energy density, and compatibility with IC manufacturing. By a combination of diverse materials, we successfully achieved the microswitch via integrated manufacturing, and tested its performance. The main work and the conclusions of this dissertation are as follows:This paper proposes a microswitch using dual beam staggered locking latch mechanism, which can maintain the steady state without continued power. We design the prototype of the device and optimize the structure parameters, and this design is proved reasonable and feasible via the theoretical analysis of the micro-switch. We propose two kinds of fabrication processes, one is based on silicon and the combination of nickel and silica, the other is based on polymer and the combination of nickel and electrophoretic paint. We have successfully completed the integrated manufacturing of the microswitch via bulk silicon etching and copper sacrificial layer surface micromachining technology respectively. Overall, the advantages and disadvantages of both ways are obvious, silicon-based devices, yield of silicon dioxide beams is low, but the device match well with the design, polymer-based device is easy to be fabricated, but the bimorph is prone to delamination and control of internal stress is very hard.We also focus on the some of the individual micromachining steps in the preparation of microswitch, mainly of which are zinc sacrificial layer technique and polymer pattern via through-mask electrophoretic deposition. We study the zinc plating from the sulfate, chloride and alkaline zinc bathes, mainly focus on surface morphology, internal stress, throwing power and micro-throwing power. Through-mask plating of acid zinc solution is firstly studied, we utilize the FEM simulation and electrochemical impedance spectroscopy (EIS) to analyse the mechanism from the view of electric field. Electrophoretic deposition process as a polymer deposition and pattern method in micromachining is explored, and study includes the deposition parameters of electrophoretic paint, polymer pattern techniques via through-mask electrophoretic deposition, multi-surface coating properties, and the adhesive properties with nickel, the bond strength of electrophoretic paint and nickel is 10 times of SU-8 and nickel.Finally, we utilize the optical microscope, scanning electron microscopy (SEM), and Veeco optical profiler to observe the static characteristics of the microswitch. We utilize Veeco and pulse power supply to test the microswitch, and utilize Bond tester to test the mechanical properties of the microswitch. The test results show that the dual beam locking latch mechanism can achieve designed bistable properties.