A micro strain gauge with mechanical amplifier

• Published in: Journal of microelectromechanical systems 1997-12, Vol.6 (4), p.313-321
• Main Authors: Liwei Lin, Pisano, A.P., Howe, R.T.
• Format: Article
• Language: English
• Subjects: Capacitive sensors; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Gain measurement; Measurement and testing methods; Measurement methods and techniques in continuum mechanics of solids; Mechanical and acoustical properties; Mechanical variables measurement; Optical amplifiers; Optical films; Optical microscopy; Physical properties of thin films, nonelectronic; Physics; Semiconductor optical amplifiers; Solid mechanics; Strain measurement; Structural and continuum mechanics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tensile strain; Testing
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/84.650128

A passive micro strain gauge with a mechanical amplifier has been designed, analyzed, and tested. The mechanical amplifier provides a high gain such that residual strain in thin films can be directly measured under an optical microscope. This strain gauge can be in situ fabricated with active micro sensors or actuators for monitoring residual strain effects, and both tensile and compressive residual strains can be measured via the strain gauge. It is shown that a very fine resolution of 0.001% strain readouts can be achieved for a micro strain gauge with a 500 /spl mu/m-long indicator beam. Beam theories have been used to analyze the strain gauge with a mechanical amplifier, and the results were verified by a finite-element analysis. Experimental measurements of both polysilicon and silicon-riched silicon-nitride thin films fabricated by surface micromachining processes are presented.