Laser interferometry for the determination of thickness distributions of low absorbing films and their spatial and thickness resolutions.
New laser interferometry has been developed, based on the principle that a 2-D fringe pattern can be produced by interference of spatially coherent light beams. To avoid the effect of reflection from the back surface of the substrate, the Brewster angle of incidence is adopted; to suppress the effect of diffraction, a lens or a lens system is used. This laser interferometry is an efficient nondestructive technique for the determination of thickness distributions or uniformities of low absorbing films on transparent substrates over a large area without involving laborious computations. The limitation of spatial resolution, thickness resolution, and visibility of fringes is fully analyzed.
Mishima
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University of Manitoba, Department of Electrical Engineering, Materials & Devices Research Laboratory, Winnipeg, Manitoba R3T 2N2.
Kao
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