Surface photovoltage minority carrier lifetime / diffusion length analysis of copper contaminated silicon was performed. It was observed that copper and copper associated defects degrade minority carrier lifetime more in n-type than in p-type silicon. In n-type silicon the copper associated defect exhibits strong hole capture and thus minority carrier lifetimes are greatly reduced. There are few electron traps reported in p-type silicon and the Cu_s-Cu_i pair is only a weak electron recombination center. Further in copper contaminated p-type silicon, an optical or thermal activation procedure is shown to significantly degrade the minority carrier diffusion length. A process similar to that of Fe-B in p-type silicon is proposed. The activation process dissociates the Cu-Cu pairs and forms extended substitutional defects in silicon, which have much greater recombination activity. No recovery of diffusion length was observed following such an activation procedure. The change in phase of copper with low temperature thermal annealing is shown to follow an Arrhenius relationship. The dissociation has an activation energy of 0.419eV. The difference in diffusion length recovery properties in copper and iron contaminated silicon, after optical/thermal activation is used to differentiate and delineate iron contamination from copper contamination and allows for detection and assessment of interstitial copper contamination in silicon.
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