SURFACE AND BULK POINT-DEFECT GENERATION IN CZOCHRALSKI AND FLOAT-ZONE TYPE SILICON-WAFERS

The origin of the defects which mediate dopant diffusion in silicon ha s never been conclusively established. Two primary theories, one favor ing bulk generation and the other surface generation, have been propos ed to explain the source of point defects. However, the inability to e xperimentally isolate surface effects from bulk effects has presented experimental determination of the dominant point defect source. An exp erimental structure employing multiple box-shaped boron marker layers on a variety of silicon substrates has generated strong evidence for s eparate bulk and surface generation of point defects. A method of usin g dislocations generated by unstably strained SiGe layers as a sink of interstitials allows a determination of the relative magnitude of sur face interstitial generation and bulk interstitial generation. Analysi s reveals that the wafer surface under inert anneals is a significant source of point defects and that the interstitial source in the bulk i s dependent on the oxygen concentration and precipitate size. (C) 1996 American Institute of Physics.