NONCONTACT CHARACTERIZATION FOR GROWN-IN DEFECTS IN CZOCHRALSKI SILICON-WAFERS WITH A LASER MICROWAVE PHOTOCONDUCTANCE METHOD

Minority-carrier recombination lifetime mapping has been performed wit h a noncontact laser/microwave photoconductance method for as-polished wafers containing a ring-shaped distribution of embryonic defects whi ch form stacking faults during subsequent heat treatment. Using an alg orithm for the separation of bulk and surface components of the recomb ination lifetime, four regions, which cannot be distinguished with oth er techniques such as x-ray topography and preferential chemical etchi ng, were clearly observed in the maps as those with different lifetime s. The result can be attributed to the inhomogeneous distribution of g rown-in defects, most likely intrinsic point defects and/or oxygen rel ated defects. Moreover, the lifetime was correlated to the surface mic roroughness of the polished wafers.