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X-ray diffraction topography is a powerful tool for observing defects in crystals which are harmful for device performance. In order to overcome the tedious procedure of the photographic method, a technique for the direct viewing of topographic images was developed based on a television system using an X-ray-sensing lead oxidevidicon camera tube (resolution 25 μm). The diffracted intensity necessary for direct viewing was estimated by considering photon noise. The required intensity was obtained with a rotating molybdenum target X-ray generator which is operated at 60 kVp and 0.5 A with a focal spot size of 0.5 by 10 mm. In transmission topography, two regions of the crystal, each having a width of 1 mm, are seen on the picture monitor due to the Kα1 and Kα2 radiation. By moving both the crystal and the TV camera and storing the Kα1 images consecutively in an image storage tube, a topograph with an area of 13 by 9 mm can be synthesized in 3 to 10 s. This storage improves the image quality and results in a signal-to-noise ratio of about 10 for individual dislocation images in silicon crystals. For low-intensity images, as observed for higher-order reflections, the signal-to-noise ratio of the images was improved by the storage of images on the target layer of the vidicon tube. Alignment of the specimen can be made easily and safely with remote control by viewing the TV images. It is possible to perform all procedures from specimen setting to image recording within a few minutes. The imaging system is applicable to dynamic investigation of defect generation. The capability is demonstrated by some observations of moving dislocations and growth processes of silicon crystals.
crystal growth, dislocations, high-power X-ray generator, image quality, semiconductor device inspection, signal-to-noise ratio, silicon, vidicon camera tube (lead oxide), X-ray diffraction topography, X-ray TV system
Senior research scientist, NHK Broadcasting Science Research Laboratories, Tokyo,