Void properties in silicon heavily doped with arsenic and phosphorus



Grown-in voids in silicon are strongly affected by donor dopants. For As-doped wafers, voids (revealed as light-scattering surface defects observed after cleaning) show a pronounced increase in their density up to [As] = 1.7 × 1019 cm−3, but at higher [As] the void density drops sharply. A similar behaviour was found for P-doped wafers where a sharp drop occurs at [P] > 2.9 × 1019 cm−3. Such a dependence is accounted for by an effect of minor impurity species: vacancy-impurity complexes (trapped vacancies) and interstitial impurity atoms (trapped self-interstitials). The total incorporated concentration of the vacancy species is first incremented due to the trapped vacancies. At higher impurity concentrations, it is reduced due to an increased contribution of negatively charged interstitial impurity species. The simulated dependence of void density and size on the impurity concentration is well consistent with the experimental data.