Use of synchrotron white beam X-ray topography to characterize IR detector manufacturing processes

It has been have demonstrated that synchrotron white beam x-ray topography can be used to characterize IR detector materials at nearly every stage in the manufacturing cycle, including: as-grown CdZnTe single crystal boules; substrate wafers cut from different positions in the boules; thin films grown on characterized wafers; and HgCdTe focal plane array structures. Special diffraction geometries have been developed, taking advantage of the broad wavelength spectrum, large beam size, and high intensity of the synchrotron radiation source, to enable rapid and non-destructive assessment of defect densities and strain distributions after each processing step. This diagnostic method has important implications for increasing the producibility of focal plane arrays. Boule characterization can reveal defects, grain orientation, interfaces and strains, and provides guidance for optimal slicing. Wafer characterization produces multiple topographic images, providing both defect mapping and depth profiling in a single exposure. Finally, x-ray topography of HgCdTe focal plane array test articles reveals subsurface damage not observable by optical or IR microscopy. The applicability of this technique to evaluate yield, quality, and reproducibility will be discussed.