Void properties in silicon heavily doped with arsenic and phosphorus

Abstract

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.

Impact of heavy doping with donors on CZ silicon properties

“…This explains the increase in void counts with increasing doping concentration observed for all three dopants. The sharp reduction of void formation at even higher donor concentration (here observed only for As and P) can be explained assuming that, above a certain concentration, the trapping of interstitials by interstitial‐donor atoms starts dominating over the trapping of vacancies . Other mechanisms, invoking Coulomb repulsive forces between charged vacancies, have also been proposed to explain the suppression of void formation at very high doping concentrations .…”

“…Our results have shown that all three donors (P, As, Sb) shift the critical V/G to lower values, moving the point defect equilibrium towards the vacancy‐regime. The increase in vacancy concentration with increasing donor doping can be explained by the formation of dopant‐vacancy complexes, such as SbV or AsV , which act as trapped vacancies and preserve them from annihilation with interstitials, making them available for void formation . This explains the increase in void counts with increasing doping concentration observed for all three dopants.…”

“…This work reports recent results on the impact of a high concentration of donor atoms on the properties of 200 mm diameter Czochralski‐grown silicon crystals, in particular on the formation of point defect‐ and of oxygen‐related microdefects. The impact on the type and concentration of intrinsic point defects – vacancies and self interstitials – and on the formation of related grown‐in microdefects is characterized by several experimental techniques (copper decoration and preferential etching, Atomic Force Microscope, flow pattern defects, surface laser inspection) and discussed in the light of recently published mechanisms . The behaviour of oxygen precipitation is investigated as a function of the oxygen content after submitting the samples to a stabilization and growth thermal treatment followed by defect counting on cleaved and etched cross sections.…”

Czochralski Growth of Silicon Crystals

“…It is also discussed in literature that the occurrence of structure loss during Cz growth of heavily doped silicon crystals can be affected by oxygen or intrinsic point defects, e.g., [80,84]. High doping concentrations of B, P, and As can have considerable influence on the formation of voids, oxygen precipitates, and the position of the oxidation-induced stacking fault (OSF) ring [84].…”

“…At high concentrations (10 18 -10 19 atoms/cm 3 ), doping elements such as boron, arsenic, and phosphorus exhibit similar effects on the intrinsic point defect aggregation as nitrogen [84,168,169]. In the case of boron, it was found that the void region as well as the diameter of the OSF ring starts to shrink when the boron content exceeds a level of 5$10 18 atoms/cm 3 .…”