Analysis of a Micro-Electrothermal Bimorph Actuator

MEMS actuation, which is the essence of microsensors and micro-actuators, can be achieved through electrothermal actuation, which can produce output actuation force and displacement larger than other actuation mechanisms (e.g. electrostatic and piezoelectric). Another advantage of electrothermal actuation is, it requires less voltage than the above-mentioned counterparts. Most of the electrothermal actuators uses polysilicon and silicon as a base layer because of their well mature fabrication process for MEMS and IC devices. The most common other biomorph material used silicon-base layer is Aluminum (Al). This is due the large difference in the thermal expansion coefficient between Al and Si which can result in higher electrothermal effect. However, there are other metals which has stronger mechanical properties than Al, which could also have large thermal expansion coefficients close to that of Al. Thereby in this article, copper (Cu)/Polysilicon actuator was proposed. The design and analysis of MEMS electrothermal device was carried out. The performance of the proposed device was analyzed in terms of actuation displacement and the actuation force produced. The obtained results demonstrate the ability of the proposed actuator to produce 4 mN force and deflection of $0.5 \mu \mathrm{m}$ at less than the applied 2 mV. Another advantage of the applied approach, is the use of MATLAB/SIMULINK which for the ease of incorporating control actions while optimizing the actuator performance simultaneously.