Microfabrication and calibration of a single-polarity piezoresistive three-dimensional stress sensing chip

A single-polarity (n-type) piezoresistive sensing chip for three-dimensional (3D) stress sensing has been microfabricated and fully calibrated. The sensing chip, which is capable of extracting the six stress components, is prototyped using bulk microfabrication techniques on a (1 1 1) crystalline silicon. A full calibration procedure employing uniaxial, thermal and hydrostatic loading has been conducted. The calibration results confirm the feasibility of our proposed technique of using single-polarity (n-type) sensing elements to develop 3D stress sensors. Preliminary testing results are presented to demonstrate the operation of our developed sensing chip.