Deformation measurement of a micro-rf capacitive switch membrane using laser interferometry

H. M. Shang National University of Singapore Department of Mechanical Engineering 10 Kent Ridge Crescent 119260 Singapore Abstract. We have developed a measurement method to evaluate deformation of a metallic membrane (thickness 2 mm) in a micro-radiofrequency switch. The method is based on a modified Michelson interferometer incorporated with optoelectronic devices including a He-Ne laser, conventional optics, a CCD sensor, and a photodiode. To detect the deformation of the membrane in the rf switch, a He-Ne laser probe 10 mm in diameter is directed onto the specimen. The laser beam reflected off the membrane is combined with a reference beam. The combined laser beams are regulated to follow a common path. The resulting circular interference fringe pattern is simultaneously recorded by a CCD sensor and a photodiode. The deformation of the membrane is determined from the order of the resulting fringe pattern. As demonstrated by the experimental results, the proposed method is capable of measuring deformation of the rf switch at submicron levels. © 2003 Society of PhotoOptical Instrumentation Engineers. [DOI: 10.1117/1.1525795]