Wednesday  |  Conference Center A  |  04:20 PM–04:40 PM

#13391, High-throughput Bend Strengths of Polysilicon MEMS Components

A critical element in mechanical design is the prediction of the load-bearing capacity of structural components from strength information derived from test coupons. For commercial reasons, such coupons are usually smaller, less complicated in shape, and fewer in number than the intended components, so that extrapolation is inevitable. For microelectromechanical systems (MEMS), the extrapolation and inherent information leverage are very large, as billions of small-scale components are manufactured and sold commercially and yet only thousands of test coupons are examined mechanically. There is, thus, an ongoing need for the development and verification of procedures that predict the load carrying capability of MEMS components from the limited coupon or test specimen strength data. In this work, sophisticated MEMS design and processing were used to fabricate and test ultra-small bend beams and tensile bars in a high-throughput manner. Imaging of the beams via scanning electron microscopy (SEM) and implementation of finite element analysis (FEA) simulations enabled the maximum tensile stress in as-processed specimens to be determined, revealing microscopic and macroscopic deviations from a simple continuum beam theory estimate. A stochastic extreme-value analysis was used to predict the beam strength distribution from tests on identically-fabricated tensile bars. The stress localization inferred from the FEA, previous estimates of strength-controlling flaw density, quantitative comparison of the tensile and bending strength distributions, and SEM observations all combine to suggest that the beams were at or near the limit of size extrapolation and accessed the flaw population directly. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Frank DelRio   Sandia National Laboratories
Brad Boyce   Sandia National Laboratories
Lawrence Friedman   National Institute of Standards and Technology
Robert Cook   Independent Scientist