Temperature coefficients of material properties for electrodeposited MEMS

This paper presents the use of micromachined differential capacitive strain sensors to investigate mechanical properties of electroplated Ni deposited under two different conditions on Si and glass substrates. The thermal expansion coefficient (/spl alpha/), Young's modulus, and residual strain were studied as a function of temperature. The measured a was 8-16 ppm/K over 23-150/spl deg/C; the residual strain changed from neutral to -880 microstrain over 23-100/spl deg/C in one case and +68.5 microstrain to -420 microstrain over 23-130/spl deg/C in another case; and the Young's modulus ranged from 115-135 GPa at room temperature. The sensitivity of the device to structural non-idealities was evaluated by numerical modeling.