A MICRO STRAIN-GAUGE WITH MECHANICAL AMPLIFIER

A passive micro strain gauge with a mechanical amplifier has been desi gned, analyzed, and tested, The mechanical amplifier provides a high g ain such that residual strain in thin films can be directly measured u nder an optical microscope, This strain gauge can be in situ fabricate d with active micro sensors or actuators for monitoring residual strai n effects, and both tensile and compressive residual strains can be me asured via the strain gauge, It is shown that a very fine resolution o f 0.001% strain readouts cad be achieved for a micro strain gauge with a 500-mu m-long indicator beam, Beam theories have been used to analy ze the strain gauge with a mechanical amplifier, and the results were verified by a finite-element analysis. Experimental measurements of bo th polysilicon and silicon-riched silicon-nitride thin films fabricate d by surface micromachining processes are presented.