Improved iron gettering of contaminated multicrystalline silicon by high-temperature phosphorus diffusion

D. P. Fenning, A. S. Zuschlag, Mariana Bertoni, B. Lai, G. Hahn, T. Buonassisi

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51 Scopus citations

Abstract

The efficacy of higher-temperature gettering processes in reducing precipitated iron concentrations is assessed by synchrotron-based micro-X-ray fluorescence. By measuring the same grain boundary before and after phosphorus diffusion in a set of wafers from adjacent ingot heights, the reduction in size of individual precipitates is measured as a function of gettering temperature in samples from the top of an ingot intentionally contaminated with iron in the melt. Compared to a baseline 820 °C phosphorus diffusion, 870 °C and 920 °C diffusions result in a larger reduction in iron-silicide precipitate size. Minority carrier lifetimes measured on wafers from the same ingot heights processed with the same treatments show that the greater reduction in precipitated metals is associated with a strong increase in lifetime. In a sample contaminated with both copper and iron in the melt, significant iron gettering and complete dissolution of detectable copper precipitates is observed despite the higher total metal concentration. Finally, a homogenization pre-anneal in N2 at 920 °C followed by an 820 °C phosphorus diffusion produces precipitate size reductions and lifetimes similar to an 870 °C phosphorus diffusion without lowering the emitter sheet resistance.

Original languageEnglish (US)
Article number214504
JournalJournal of Applied Physics
Volume113
Issue number21
DOIs
StatePublished - Jun 7 2013

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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