Thermal Stress Optimization During Industrial Growth of 200 mm Float-Zone Silicon Single Crystals: Numerical Simulation and Experimental Validation

Abstract

Growth of 200 mm float-zone (FZ) silicon single crystals is susceptible to thermal stress, which can promote dislocation generation and crystal cracking. A steady-state global finite-element model was established in CGSim to evaluate the thermal field and thermoelastic stress in an industrial 200 mm FZ silicon growth system. Quartz, graphite, molybdenum, and silicon carbide thermal shields were compared, followed by an assessment of molybdenum-shield lengths of 10, 20, and 30 cm. The numerical results show that the molybdenum shield reduces the crystal-edge temperature gradient and von Mises stress through coupled conductive and radiative heat-transfer effects. The 30 cm molybdenum shield was the best-performing configuration among the investigated lengths. Industrial verification comprised 60 crystals, with 15 crystals in each configuration. For the normal thermal field, the dislocation and cracking rates were 13.3% (2/15) and 20.0% (3/15), respectively. The corresponding rates were 6.6% (1/15) and 6.6% (1/15) for the 10 cm shield, 13.3% (2/15) and 0% (0/15) for the 20 cm shield, and 0% (0/15) and 0% (0/15) for the 30 cm shield. The intermediate groups did not exhibit a strictly monotonic response for every defect indicator, whereas the 30 cm configuration provided the best overall industrial outcome under the investigated conditions.