Misfit strain of oxygen precipitates in Czochralski silicon studied with energy-dispersive X-ray diffraction

Abstract

Annealed Czochralski Silicon wafers containing SiOx precipitates have been studied by high energy X-ray diffraction in a defocused Laue setup using a laboratory tungsten tube. The energy dispersive evaluation of the diffracted Bragg intensity of the 220 reflection within the framework of the statistical dynamical theory yields the static Debye-Waller factor E of the crystal, which gives access to the strain induced by the SiOx precipitates. The results are correlated with precipitate densities and sizes determined from transmission electron microscopy measurements of equivalent wafers. This allows for the determination of the constrained linear misfit ε between precipitate and crystal lattice. For samples with octahedral precipitates the values ranging from ε = 0.39 (+0.28/−0.12) to ε = 0.48 (+0.34/−0.16) indicate that self-interstitials emitted into the matrix during precipitate growth contribute to the lattice strain. In this case, the expected value calculated from literature values is ε = 0.26 ± 0.05. Further, the precise evaluation of Pendellösung oscillations in the diffracted Bragg intensity of as-grown wafers reveals a thermal Debye-Waller parameter for the 220 reflection B220(293 K) of 0.5582 ± 0.0039 Å2 for a structure factor based on spherically symmetric scattering contributions.