Characterization of Nickel Contamination in Float Zone and Czochralsky Silicon Wafers by Using Electrolytic Metal Tracer or Microwave Photoconductivity Decay Measurement

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Abstract
The influence of nickel contamination on the free carrier recombination lifetime and on the electrolytic diodes reverse dark current of electrolytic metal tracer (ELYMAT) have been studied on both float zone (FZ) and Czochralsky Conductivity Decay (CZ) wafers. The reverse currents of the ELYMAT electrolytic cell's measured on moderately doped FZ wafers are clearly increasing with nickel concentration. The recombination lifetime in both FZ wafers, and CZ wafers after oxygen precipitation (Internal gettering) treatments is influenced by nickel contamination. In CZ wafers with oxygen precipitation nickel contamination causes a drop of the lifetime which is directly related to the oxygen precipitate density. The characteristic variation of recombination lifetime dominated by oxygen precipitates as a function of injection level changes significantly after intentional nickel contamination. All these results bring new insights for the fast identification of Ni contamination in device fabrication lines.