Metal contamination of silicon from the furnace atmosphere after crystallization

The contamination of silicon by the furnace atmosphere is investigated based on lab-scale annealing experiments in a carbon-based furnace. The analysis comprises measurements of charge carrier lifetime and interstitial iron as well as elemental analysis. An approach to obtain information on the concentration of the metal species involved in the contamination process based on charge carrier lifetime profiles is established. A significant reduction of the charge carrier lifetime below the sample surface is observed. This reduction is governed by iron and at least one (cobalt and/or nickel) faster diffusing species. The contributions from the furnace parts and the purging gas are investigated and possibilities to reduce the gas phase contamination are elaborated. The results indicate a possible relevance of gas phase contamination in crystallization experiments.