Design of Piezoresistive Cantilevers for Low Force Electrical Contact Measurements

Abstract Micromachined piezoresistive cantilevers were fabricated to measure contact resistance and force for low force and small area electrical contacts. The intended application is the evaluation of contact tip geometries and metal films manufactured using standard semiconductor processing techniques. Prototype cantilevers are evaluated for force sensitivity, range, and noise as well as for feasibility of 4 wire contact resistance measurements at the end of the cantilever. The piezoresistors have a gage factor of about 35 and noise of about 1mV/Hz at 1Hz (the lowest frequency of intended measurements). Initial measurements of one cantilever design tested indicate sensitivity of 0.24mV/μN and force resolution of about 0.41mN for a piezoresistor drive voltage of about 9V and 100X gain on the bridge output. Force measurements are noise limited at the 5 Hz sampling rates used. 4-wire contact resistance measurements were made synchronously with piezoresistor bridge output voltage measurements.