Defect engineering in Czochralski silicon through tin-doping: A perspective from tin-vacancy-oxygen interactions

Grown-in defects such as voids and oxide precipitates critically affect the performance of Czochralski (CZ) silicon wafers. In this work, the effects of tin (Sn)-doping on vacancy-related defect evolution in CZ silicon are investigated using first-principles calculations, molecular dynamics simulations, rapid thermal annealing, gold diffusion, and deep-level transient spectroscopy. The results show that Sn-doping fundamentally alters the kinetic evolution pathways of vacancy-related defects during crystal cooling under low intrinsic vacancy concentrations relevant to practical CZ growth. Substantial SnV complex formation initiates within the temperature range of 1100–1080 °C and continues down to ∼1030 °C. Since this temperature window substantially overlaps with the regime for vacancy aggregation and void evolution, the continuous trapping of mobile vacancies by substitutional Sn atoms kinetically competes with void nucleation and growth during cooling. As the temperature further decreases below ∼1030 °C, part of the SnV complexes react with interstitial oxygen atoms to form relatively stable SnVO complexes. Importantly, although SnVO complexes contain vacancy constituents, they exhibit negligible binding affinity for additional oxygen atoms and, therefore, cannot act as effective heterogeneous nucleation centers for oxygen precipitation. Meanwhile, the reduced population of mobile free vacancies further suppresses the formation of conventional VO2 complexes acting as oxygen precipitation nuclei. Consequently, the formation of both voids and grown-in oxide precipitates is significantly suppressed in Sn-doped CZ silicon. This work reveals a thermodynamic-kinetic decoupling in vacancy behavior induced by Sn-doping: although Sn-doping lowers the vacancy formation energy, it simultaneously redirects mobile vacancies into kinetically inactive configurations through competing kinetic pathways. More broadly, this work establishes a kinetic framework for understanding impurity-mediated vacancy evolution and defect engineering in CZ silicon under realistic crystal growth conditions.