Design optimization of semiconductor piezoresistors with Schottky diode contacts.

A modeling theory is developed to predict the performance of piezoresistors which incorporate Schottky diode electrical contacts. This new theory allows the design of high performance gauges which can be fabricated using Non-Lithographically-Based Microfabrication (NLBM) techniques. These semiconductor piezoresistors can be designed in customizable sizes and fabricated in parallel in order to integrate position sensing into MEMS flexural positioners. Customizable sensing for nanopositioning platforms will enable advances in a range of nano-scale fabrication and metrology applications. A semiconductor piezoresistor with Schottky diode contacts was fabricated and attached to a titanium flexure. This device is shown to match predicted electrical performance within about 8% and to show a gauge factor of 116, within 2% of the predicted value. Optimized performance limits for Schottky diode semiconductor piezoresistors are identified to be about 127 dB full noise dynamic range for a quarter bridge over a 10 kHz sensor bandwidth on a 600 μm width titanium flexure, making them ideal for sensing on meso-/micro-scale flexural positioners. Methods are suggested for achieving the performance limits indicated above and the impact of these methods on the sensor dynamic range are studied. • A new model is presented for nonlinear semiconductor piezoresistors, and enable them to be analyzed using the standard optimization framework. • The model incorporates voltage drops, excess resistances, and barrier-based flicker noise, which apply to a wide range of gauge materials. • A gauge is fabricated and the gauge performance is shown to match the modeled performance within 2%. • The optimization theory is used to suggest performance capabilities and limitations of customized silicon piezoresistors. [ABSTRACT FROM AUTHOR]