Subsurface Micro-Lattice Strain Mapping

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 utilized to map crystalline micro-lattice strains in various substrates and epitaxial films. The spatial resolution of this technique is in the the order of 100um and the analysis time for a 2cm2 area is about 10 secs. DARC topography incorporates state-ofthe- 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 fabrication. The DARC topographs clearly delineate areas of microplastic strain inhomogeniety. Materials analyzed using this technique include HgMnTe, HgCdTe, BaF2, PbSe, PbS both substrates and epitaxial films. By varying the incident x-ray beam wavelength the depth of penetration can be adjusted from a 1–2 micron up to 15–20um. This can easily be achieved in a synchrotron.