Development of a displacement sensor with a sidewall piezoresistor and its typical application

For improving displacement sensor sensitivity to detect the motion in-plane and to improve the vertical sidewall surface, a new displacement sensor used for detecting motion in-plane is proposed. Piezoresistor technology is compatible with the other micromachining technology. This sensor can be integrated with other devices easily and fabricated with ion implantation technology combined with deep reactive ion etching technology. This design doubles the sensitivity compared with the conventional design because it puts the piezoresistor on the surface of the vertical sidewall of the detection beam. Besides using vertical sidewall piezoresistor technology, this displacement sensor has been applied to a micro xy-stage to detect the stage motion successfully. The experimental results verify that the sensitivity of the fabricated displacement sensors is better than 0.903 mV/μm, the linearity is better than 0.814%, and the displacement resolution is better than 12.3 nm.