Authors: A. Paranjpye, N.C. MacDonald and G.E. Beltz
Affilation: University of California, Santa Barbara, United States
Pages: 363 - 366
Keywords: MEMS, silicon, damage tolerance, composite
A two-dimensional laminar composite material has been shown to exhibit enhanced damage tolerance due to zones of residual compressive stress. The damage tolerance appears as a threshold stress below which the structure does not fail catastrophically. We utilize this concept at the microscale, towards obtaining fracture resistant MEMS structures. Cantilever beams of this laminar composite material, manufactured by MEMS fabrication methods are deflected to fracture, and the measured fracture strength compared to single crystal silicon beams (SCS) of identical geometry. All structures are made on the same die, so uniform processing damage is likely for all of them. A wide range of fracture strength is seen in both the composite and SCS beams. However, the lowest value of fracture stress for all the composite beams is found to be above the predicted threshold strength, while some of the SCS beams fail at lower stresses. We conclude that this composite offers a useful design alternative as a MEMS material.