Cusp-magnetic-field process window optimization for oxygen and vacancy–oxygen defect control in photovoltaic Czochralski silicon growth

High-quality Czochralski silicon (CZ-Si) for photovoltaic applications requires coordinated control of oxygen incorporation, interfacial transport, and vacancy-oxygen defect evolution during crystal growth. In this work, a coupled thermo-flow-oxygen-defect multiphysics model incorporating a cusp magnetic field was developed to investigate oxygen transport and the evolution of VO and VO 2 during 300 mm n-type CZ-Si growth. A two-factor full-factorial design with three magnetic-field intensities (0.15 - 0.45 T) and four zero magnetic surface (ZMS) positions (0 - 0.75H) was employed to quantify the effects of magnetic damping and ZMS location on melt convection, interfacial transport, oxygen incorporation, and VOx behavior. The interfacial oxygen concentration varied from 3.71 to 7.34 ppma, while the interfacial thermal stress ranged from 3.08 × 10 7 to 5.31 × 10 7 Pa. A statistical VOx reference interval of 1.012 - 1.138 × 10 14 cm −3 was constructed from the investigated cases for relative comparison, and a six-metric CRITIC evaluation framework was established. The highest-ranked condition was obtained at ZMS = 0.25H and B = 0.30 T, with a composite score of 0.60914. FTIR measurements quantitatively supported the simulated interstitial-oxygen levels under the tested conditions, whereas lifetime, PL, and metallographic observations provided qualitative evidence of subsequent oxygen-related defect evolution. These findings provide a quantitative basis for magnetic-field optimization in photovoltaic CZ-Si growth and offer practical guidance for improving wafer quality in high-efficiency silicon solar-cell manufacturing.