The distribution of dislocations, in Czochralski-grown circular wafers which were thermally deformed into a saddle-shape at 1273K, was investigated by using X-ray topography (for the bulk) and an etching technique (for the surface). In deformed wafers softened by O precipitation (with a density of oxide precipitates of less than 2 x 1015/m3), slip dislocations were preferentially generated and randomly distributed on the concave (compressed) side of the wafer. This preference was attributed to the lattice mismatch between the oxide precipitates and matrix. This caused internal stresses which compressed the matrix and resulted in an externally applied stress on the concave side of the wafer. When the density of micro-defects was less than 2 x 1013/m3, slip dislocations were introduced along the <110> slip direction, in a line which extended from the top surface of the wafer to a neutral plane. At this density, dislocations were nucleated at wafer surfaces, where the thermal stresses were the highest, and then propagated into the neutral plane on both the concave and convex sides.

Dislocations Preferentially Generated in Compressed Regions of Saddle-Shaped Deformed Precipitation-Softened Czochralski-Grown Silicon Wafers. H.Shimizu: Japanese Journal of Applied Physics - 1, 2000, 39[10], 5727-31