Subsurface Micro-Lattice Strain Mapping
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SUBSURFACE MICRO-LATTICE STRAIN MAPPING T.S. Ananthanarayanan, R.G. Rosemeier, W.E. Mayo*
and P. Becla**
Brimrose Corporation of America 7720 Belair Road Baltimore, MD 21236 (301) 668-5800 * Rutgers University Piscataway, NJ 08854 ** MIT,
Francis Bitter National Magnet Lab Cambridge, MA 02139
Synopsis Defect morphology and distribution up to depths of 20um have been shown to be critical to device performance in micro-electronic applications. A unique and novel x-ray diffraction method called DARC (Digital Automated Rocking Curve) topography has been effectively various to map crystalline micro-lattice strains in utilized The spatial resolution of this substrates and epitaxial films. is in the the order of 100um and the analysis time for a technique DARC topography incorporates state-of2cm2 area is about 10 secs. the-art 1-dimensional and 2-dimensional X-ray detectors to modify a conventional Double Crystal Diffractometer to obtain color x-ray rocking curve topographs. This technique, being non-destructive and non-intrusive in nature, is an invaluable tool in materials' quality control for IR detector The DARC topographs clearly delineate areas of microfabrication. plastic strain inhomogeniety. Materials analyzed using this technique include HgMnTe, HgCdTe, BaF2 , PbSe, PbS both substrates and epitaxial By varying the incident x-ray beam wavelength the depth of films. penetration can be adjusted from a 1-2 micron up to 15-20um. This can easily be achieved in a synchrotron. Background : II-VI Characterization and Use II-VI compound semiconductors form a major family of compounds for These include both active (laser advanced IR device applications. generators) and passive (detector) devices. The compounds of interest may vary anywhere from a binary alloys to complicated multiThe metallurgy involved constituent epitaxies and heterostructures. in the crystallization of many of these multi-constituent, multi-layer Consequently, these materials materials is extremely complicated. tend to have higher defect structures than a single element material. Nevertheless, the consistency of any microscopic (electrical and mechanical) property is directly a function of the microlattice strain state. Hence there is increasing need for a quantitative, nondestructive microstructural characterization technique.
Mat. Res. Soc. Symp. Proc. Vol. 90. ý 1987 Materials Research Society
210
Over the past three decades X-ray diffraction and topography techniques have emerged as sturdy tools for rapid quality control of crystalline materials(l). X-ray reflection topography has regained prominence in the recent past(2). This technique lacked quantification. Several attempts were made to digitize the photographic records of the diffraction events. Although these efforts yielded excellent results, they were unsuitable for rapid surface characterization required under production environments. This limitation affects the data collection abilities for research environments as well. The use of electronic X-ray detectors is becoming increasingly
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