Characterization of a multi-layered MEMS pressure sensor using piezoresistive silicon nanowire within large measurable strain range

Multilayered pressure sensors using piezoresistive silicon nanowires (SiNWs) are characterized using center displacement loading approach. The silicon nanowire (SiNW) is embedded in a multilayered diaphragm structure comprising of silicon nitride and silicon oxide. By leveraging the high fracture stress and intrinsic tensile stress of silicon nitride layer to produce a flat diaphragm, we can create compressive strain to the SiNW as large as 1.7% without damaging the diaphragm. The equivalent pressure to break the diaphragm is derived as high as above 500 psi. The sensitivity at low pressure application region (<45 psi) is derived as around 0.25% psi^-1. The relationship between SiNW resistance change and applied strain is measured and investigated with 2 μm and 5 μm SiNWs for both scientific and practical points of view. This approach also demonstrates the validity to reveal the SiNW properties under large strain and the exploration provides a good reference for future SiNW based MEMS sensor design.