Time-resolved local-stress measurement of MEMS resonating structure using micro Raman spectroscopy

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A pull-in type electrostatic optical chopper using silicon-on-glass (SOG) wafer was proposed, fabricated, and tested to develop time-resolved micro-Raman spectroscopy for measuring local dynamic stress of silicon micro-electro-mechanical system (MEMS) resonators. The moving mass of electrostatic actuator made of the silicon device layer of SOG wafer is used as an optical chopper. The silicon mass has many slits where the incident laser light penetrates. At the OFF-state, the penetrated light terminated at aluminum shields on the glass substrate. By actuating the mass by electrostatic parallel plate electrodes, the penetrated light goes through the chopper (ON-state). Inserting the chopper to the micro Raman spectroscope, time-resolved analysis will be realized. The mechanical and optical responses of the chopper were measured. The double-side-drive type of chopper has a response time of around 50 us, which is good enough for the application.