PROJECT TITLE :

Residual Stress Extraction of Surface-Micromachined Fixed-Fixed Nickel Beams Using a Wafer-Scale Technique

ABSTRACT:

This paper reports on the extraction of residual stress in surface-micromachined nickel skinny films of electrostatically actuated fastened-fastened beams employing a wafer-scale technique. The distribution of residual stress for 87 beams on a four-in quarter wafer piece is presented. The residual stress ( $sigma _0$ ) is determined from the simplest match of the displacement-voltage curves predicted by a computationally economical model to the experimental data. The nondestructive and automated measurements are taken at room temperature and directly at the beam itself without any extra check structures. The model utilized incorporates the nonideal effects of inclined supports, nonflat initial beam profiles, and fringing fields. The extracted residual stress values vary between −12.eight and 13.vi MPa (negative values are for compressive stresses and positive ones for tensile stresses). The residual stresses for these eighty seven beams follow an almost traditional distribution with a mean price of −one.seven MPa and a commonplace deviation of five.9 MPa, which represents the variability of the residual stresses across the wafer. Detailed uncertainty analysis has been conducted, and it reveals that wrong modeling of the nonideal effects will result in vital errors in the extracted residual stress. Though demonstrated on nickel thin films, this system can be applied to different metallic thin films. [2014-0344]