Iron precipitation at oxygen related bulk defects in Czochralski silicon

Behavior of iron atoms in silicon during a simulated integrated circuit device fabrication process was examined. The results from the electron microscopic and deep-level transient spectroscopic analysis indicate that iron at concentrations below the solubility limit precipitates at a bulk stacking fault containing an oxide precipitate. Based upon the defect morphology and the eutectoid temperature of the α-FeSi2 phase, it is suggested that iron precipitation occurs during the cooling down period after a high-temperature treatment. The result shows that iron may react with oxygen atoms in the oxide precipitate via a Fe2O3 phase transformation which in turn causes a change in the precipitate morphology. In this study, it is suggested that iron precipitation at the bulk defects is fundamentally different from that of other transition metals such as nickel and copper where the precipitation occurs either along the Frank partial dislocations of the bulk stacking fault or at the punch-out dislocation loops originating at the oxide precipitate interface.