Experimental and theoretical study of heterogeneous iron precipitation in silicon

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School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Journal of Applied Physics, Volume 101, Issue 4
Heterogeneous iron precipitation in silicon was studied experimentally by measuring the gettering efficiency of oxide precipitate density of 1×10exp10cm−3. The wafers were contaminated with varying iron concentrations, and the gettering efficiency was studied using isothermal annealing in the temperature range from 300 to 780°C. It was found that iron precipitation obeys the so called s-curve behavior: if iron precipitation occurs, nearly all iron is gettered. For example, after 30 min annealing at 700°C, the highest initial iron concentration of 8×10exp13cm−3 drops to 3×10exp12cm−3, where as two lower initial iron concentrations of 5×10exp12 and 2×10exp13cm−3 remain nearly constant. This means that the level of supersaturation plays a significant role in the final gettering efficiency, and a rather high level of supersaturation is required before iron precipitation occurs at all. In addition, a model is presented for the growth and dissolution of iron precipitates at oxygen-related defects in silicon during thermal processing. The heterogeneous nucleation of iron is taken into account by special growth and dissolution rates, which are inserted into the Fokker-Planck equation. Comparison of simulated results to experimental ones proves that this model can be used to estimate internal gettering efficiency of iron under a variety of processing conditions.
iron, silicon, heterogeneous iron precipitation, oxide precipitate, gettering efficiency, wafer, isothermal annealing, iron gettering
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Haarahiltunen, Antti & Väinölä, Hele & Anttila, O. & Yli-Koski, Marko. 2007. Experimental and theoretical study of heterogeneous iron precipitation in silicon. Journal of Applied Physics. Volume 101, Issue 4. 0021-8979 (printed). DOI: 10.1063/1.2472271