Nonlinear piezoresistance of silicon at large stresses

This paper reports on the piezoresistive characterization of low-doped crystalline silicon using the wafer-scale microtensile technique. Multiple test structures composed of <;110>; and <;100>; specimens bridging the gap between movable and fixed micromachined frames are processed in a single wafer and sequentially measured. In addition to the extraction of elastic and fracture parameters, the method allows to obtain the piezoresistance behavior of silicon samples at large applied stresses. This is realized by defining longitudinal and transversal resistors on the specimens by ion implantation and monitoring the respective resistances until fracture occurs. For sufficiently large loads, resistivity variations clearly deviate from the expected linear dependence on stress and become non-monotonic. These findings are particularly relevant for the application of crystalline silicon in piezoresistive sensing devices subjected to large stress levels.