Dimension effect on mechanical behavior of silicon micro-cantilever beams

The bulk micro-machining technique is commonly applied to fabricate the silicon micro-cantilever beam. With a micro-probe and special designed fixtures a micro-force testing machine can effectively apply mechanical loading on the beams by bending. This paper is thus aimed at studying the mechanical behavior of single crystal silicon (SCS) micro-cantilever beams by the specific method. The focus is at elucidating failure mechanisms of bent beams since limited studies have been conducted concerning its impact on reliability evaluation. We have fabricated various types of samples that have different lengths and thickness. With various beams in micro-scale, not only the stress–strain relationship can be achieved, but dimension effects on flexural strength, Young’s modulus, and failure strain of MEMS devices can also be precisely evaluated. In addition, locations and failure modes of bent beams are detected by SEM. Based on the microscopic analysis, failure mechanisms are determined for various beams. For reliability analysis purposes it is crucial to determine the location and cause of failure. Data on strength and failure strain as found in the study can be very important for reliability evaluation of SCS such as fatigue life. The testing method can also be easily extended to nano-scale specimens by adding a force magnification lever mechanism.