White X‐ray beam topography and radiography of Si1–xGex crystals bonded to silicon

The defect structure of Si 1– x Ge x wafers with 4% of germanium and their interfaces with Si wafers were studied using white radiation topography and phase‐sensitive radiography. The heterostructures were manufactured by direct bonding of Si 1– x Ge x and Si crystalline wafers made of bulk crystals that were grown by the Czochralski technique. In Si 1– x Ge x crystals, the segregations of Ge act as dislocation nucleation sites. In Si 1– x Ge x /Si bonded structures, the segregation of Ge as well as the accumulation of dislocations induce elastic strain and plastic deformation during high‐temperature bonding annealing. With the topography–radiography combination, we are able not only to detect microcracks, indicating nonbonded areas, by radiography, but also to reveal dislocations and long‐range strain fields by topography at the same time. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)