Self-measuring Method and Experiment of Residual Stress of Grating Moving Light Modulator

Most of the measuring methods of residual stress of devices of micro-electro-mechanical systems(MEMS) need standard test structures. The structures will take up a lot of space on the chip, and enhance the complication and difficulty of measuring. Aiming at a grating moving light modulator (GMLM) based on micro-opto-electro-mechanical systems (MOEMS), a measuring method is proposed. It directly utilizes the structural characteristics of GMLM to obtain the residual stress without needing addition of measuring structure. This measuring method utilizes the relationship between residual stress and GMLM pull-in voltage, and the value of residual stress of material can be calculated from the measured value of pull-in voltage. The relationship equation between GMLM residual stress and GMLM pull-in voltage is derived, and it is modified in consideration of the fringe effects of parallel-plate capacitance. The residual stress of Al-1%Si film of GMLM is measured as 99 MPa by experiment. This method makes GMLM not only an actuator, but also a measuring structure. By integrating them all in one structure, the method decreases the price and complexity of the measurement of residual stress.