Diffusion and Solubility of Iridium in Silicon

摘要

Diffusion of Ir into Si was investigated by annealing of front-side deposited floating-zone Si wafers at temperatures between 1000 and 1200℃. Concentration-depth profiles were measured by means of neutron activation analysis in conjunction with mechanical sectioning. The observed deep penetrations strongly indicate that interstitial Ir_I is involved as highly mobile species. The profile shape changes from erfc-type at 1200℃ to anomalously convex at lower temperatures. This can be rationalized within the framework of the kick-out mechanism in which interstitial(Ir_I)-substitutional(Ir_s) exchange produces excess self-interstitials (Ⅰ). Specifically, Ir appears to be the first impurity in Si for which a gradual transition from Ir_I-controlled to I-controlled kick-out diffusion with (decreasing) temperature is found.