Inclusion-related ridge breakage in large-diameter floating-zone silicon

Large-diameter Floating-zone (FZ) silicon, particularly 8-inch crystals, is essential for high-voltage devices like insulated gate bipolar transistors (IGBTs) and fast recovery diodes (FRDs), yet its production is hindered by low crystal growth yield due to ridge breakage defects. This study investigates inclusion-induced ridge breakage mechanisms in mass-produced 8-inch FZ silicon, using 8-inch (100) and 5-inch (111) crystals, with the latter employed to study bulk defect propagation. Through scanning electron microscopy, energy-dispersive spectroscopy, and mechanochemical polishing, we identified two mechanisms: surface-origin carbon inclusions, likely silicon carbide particles from graphite wear at the initial heating stage, induce twin formation, while bulk-origin microcrystalline silicon inclusions trigger dislocations and cracks. Numerical simulations revealed that central and edge high-stress zones amplify inclusion effects, with stress scaling linearly with diameter, exacerbating breakage in 8-inch crystals. A stress-inclusion interaction model explains how inclusions narrow the tolerable stress window. These findings advocate optimizing preform rod preparation and heating processes to minimize inclusions, enhancing yield for 8-inch FZ silicon in high-performance electronics.