Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

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This paper reports on low 1∕f noise, low corner-frequency, piezoresistive microcantilevers suitable for static and slowly time varying, force and displacement sensing applications such as chemical and biosensing. We demonstrate a full bridge, piezoresistive cantilever with greater than 140dB dynamic range, a noise amplitude spectral density floor of 3.7nV∕V√Hz at 0.1Hz. At 1.0Hz, the noise spectral density is 1.2nV∕V√Hz equivalent to 10pN∕√Hz or 5pm∕√Hz. The force resolution over the frequency band of 0.1–100Hz is 100pN.

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