SECONDARY DEFECT FORMATION IN SELF-ION IRRADIATED SILICON

A detailed experimental study has been made of the evolution of extend ed secondary defects which form during rapid thermal anneals of 0.5 Me V energy self-ion irradiated silicon. The implant fluence (2 x 10(15) ions/cm(2)), flux and substrate temperature (91 degrees C) were chosen so that primary damage levels were well below saturation. Cross-secti onal transmission electron microscopy (X-TEM), Rutherford backscatteri ng-channeling spectroscopy (RBS-C) and variable-energy positron annihi lation techniques (VEP) have been used to allow partial discrimination between vacancy- and interstitial-type defects. The growth and develo pment of the defect band and of specific types of extended defects wit hin the band has been followed up to anneal temperatures of 1000 degre es C, where the majority are shown to have dissipated. X-TEM has revea led the formation of a previously unreported tubular defect which is f ound in a narrow temperature range of 700-765 degrees C. The occurrenc e of this defect correlates with the positron annihilation analysis wh ich shows that a small concentration of defects with vacancy character is present after annealing in the same temperature range. In addition , positron annihilation analysis has allowed an assessment of the role played by defects lying in regions appearing defect-free by the other techniques (RBS-C and TEM). The implications of these findings to exi sting models involving secondary defect production are discussed.