Inline characterization of SiGe structures on 8 inch Si wafers using the Bede QC200 x-ray diffractometer

Inline characterization of SiGe and SiGe:C heterobipolar transistors places stringent requirements on x-ray diffraction set-ups: (i) precise mounting and positioning of 8 inch wafers for single position scans and area mapping; (ii) high beam intensity in a small spot; and (iii) low background to realize a dynamic range better than five orders of magnitude for precise rocking curve simulation. The Bede QC200 x-ray diffractometer, which applies a novel micro-focus x-ray source and a novel beam conditioning optics to a double-crystal x-ray diffraction system, meets these requirements. Data collected on SiGe structures with the QC200 are compared with data collected at a synchrotron source. We demonstrate that reliable depth profiles of Ge content can be obtained in structures of 500 × 500 µm 2 size in an automatic operation mode at different positions over an 8 inch wafer in a well defined grid. Two automatic fitting programs, one involving a genetic algorithm, are used to extract material information from simulation of the high-resolution diffraction scans. Rapid, reliable convergence on the global minimum gives objective fitting, suitable for quality control in a SiGe technology. Finally, we show how the lateral distribution of Ge content and layer thickness can be mapped over an 8 inch wafer.