Microfabricated ultrasensitive piezoresistive cantilevers for torque magnetometry

New types of piezoresistive cantilevers for torque magnetometry have been m icrofabricated and tested. The design is optimized to detect the flexion an d torsion of the cantilever corresponding to a torque in two directions, wh ich is induced by a microscopic magnetic sample mounted on the lever surrou nded by an external magnetic field. The high sensitivity (up to approximate to 10(-14) N m) of the device is achieved by its special geometrical desig n featuring cantilever legs with only 3-mu m-wide beams. The microfabricati on process makes use of silicon-on-insulator wafers for precise etch-stop o f a novel deep-trench etch process from the backside to fabricate the indiv idual chips. One cantilever version has an integrated metal loop for absolu te calibration of the sensor within 1%. The loop can also be used to actuat e the lever mechanically. Owing to their small dimension and mass, the new devices feature ultrahigh sensitivity combined with short response time, wh ich allows the characterization of microscopic magnetic samples with very h igh resolution. (C) 1999 Elsevier Science B.V. All rights reserved.