Fracture testing of silicon microelements in situ in a scanning electron microscope

This paper describes a simple method for the evaluation of fracture properties of micromachined silicon cantilever beams. In this technique, bend testing is performed in situ in a scanning electron microscope, using specially designed equipment. Silicon cantilever beams of various sizes and orientations, manufactured in Si (100) wafers by two different micromachining procedures, were tested by simple bending to fracture, and the fundamental fracture parameters were determined using an analytical model of elastic fracture. Fracture limits, fracture strains, and initiating flaw sizes were determined, and fracture surfaces resulting from high- and low-strength fractures were examined. It was found that smooth or facetted fracture surfaces usually occur in cases of low fracture limits, indicating that the failure was initiated by a serious strength- reducing flaw. A hackled fracture, occurring in cases of high fracture limits, indicates that the initiating flaw must have been very small. (I.S.)