Omega-Scan: an X-ray tool for the characterization of crystal properties

The X-ray diffractometric X-Scan method needs only one measuring circle to determine the lattice geometry of single crystals. From the angular positions of at least two reflection pairs the orientation in a certain range can be precisely determined. For cubic crystals the lattice parameter related to a reference crystal can be calculated additionally. The method is applied to the adjustment of crystal ingots for the succeeding processing and to the characterization of wafers. By means of an x-y table the distribution of the structural parameters over the wafer surface can be mapped with a lateral resolution of about 1 mm. In a Si(1-x)Ge(x) sample, characteristic concentric distributions have been found with orientation changes up to 3 arc minutes and lattice-parameter differences up to 2.8 x 10(-5) nm, corresponding to differences of the Ge content up to 1.4 at%.