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1 March 1974 Accurate Measurement Of Slitwidths In Microphoto Fabrication Based On Lateral Interferometry
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An accurate electro-optical method was developed to measure slitwidths in the 0.5 to 400 micron range. A prototype instrument was built that gave experimental evidence of accuracy, resolution and reproducibility of measured data. The present setup covers a width range between 40 and 260 microns. Throughout this range a better than 1 percent resolution was demonstrated. The Atlantic Research technique uses a laterally moving optical fringe pattern, that is generated by two laser beams, converging at a small angle. The two laser beams are identical in intensity, derived from the same laser by using a Bragg cell as a beamsplitter. One of the two laser beams is shifted in frequency by an amount determined by the ultrasonic frequency of the Bragg cell, which causes the fringes to move in a direction perpendicular to their plane. Since the fringe spacing in the interference zone is constant (determined by the laser wavelength and the converging angle of the two laser beams), it can be used as a "yardstick" to compare its length to dimensions such as width of a slit. When the fringe spacing equals the slitwidth, the RF component of the transmitted radiation becomes zero. Accurate positioning of the slit (to be measured) in the fringe field is not necessary; however, a good angular alignment with the fringes is desired to obtain good signal-to-noise ratios.
© (1974) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sandor Holly "Accurate Measurement Of Slitwidths In Microphoto Fabrication Based On Lateral Interferometry", Proc. SPIE 0055, Technological Advances in Micro and Submicro Photofabrication Imagery, (1 March 1974);


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