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2D global transient model for generation‐six (G6) GT‐style furnace and upgraded generation‐seven (G7) ALD‐style furnace in which all types of heat transfer and flow are included is established to investigate the thermal field, melt convection, melt–crystal (m–c) interface shape, thermal stress, growth rate, and Voronkov ratios in the growing silicon ingot. The modeling is verified by the heater power and temperature experiment. Simulation results show that the melt flow is relatively stronger as the furnace upgrades. For G7, a relatively higher thermal stress and growth rate are found due to the higher temperature gradient both in the horizontal and axial directions. Furthermore, unlike the optimized G6, G7 shows the overly convex m–c interface in the initial stage and edge nucleation throughout crystal growth stage. [ABSTRACT FROM AUTHOR]

Transient global simulations were carried out to investigate the effect of argon flow on oxygen and carbon coupled transport in an industrial directional solidification furnace for quasi-single crystalline silicon ingots. Global calculation of impurity transport in the argon gas and silicon melt was based on a fully coupled calculation of the thermal and flow fields. Numerical results show that the argon flow rate affects the flow intensity along the melt–gas surface, but has no significant effect on the flow patterns of silicon melt and argon gas above the melt–gas surface. It was found that the evaporation flux of SiO along the melt–gas surface decreases with the increasing argon flow rate during the solidification process. However, the net flux of oxygen atoms (SiO evaporation flux minus CO dissolution flux) away from the melt–gas surface increases with the increasing argon flow rate, leading to a decrease in the oxygen concentration in the grown ingot. The carbon concentration in the grown ingot shows an exponential decrease with the increase of the argon flow rate, owing to the fact that the dissolution flux of CO significantly decreases with the increasing argon flow rate. The numerical results agree well with the experimental measurements. [ABSTRACT FROM AUTHOR]

• Gas flow and impurity transport in DS furnace are studied by numerical modeling. • Backflow at crucible outlet is caused by buoyancy convection. • Backflow induces impurities accumulation and affects the reaction intensity. • For high flow rate, backflow is restrained and CO concentration is decreases. • With new susceptor, backflow almost disappears and CO concentration is lower. In order to study the mechanisms of gas flow and impurity transport in an industrial directional solidification furnace for producing multi-crystalline silicon (mc-Si), a 3D global modeling, including argon flow, thermal conduction, thermal radiation, chemical reaction, and mass transfer was established. Simulation results show that the backflow at crucible outlet near the midcourt plane is mainly attributed to buoyancy, which will induce SiO and CO impurities accumulation and affect the chemical reaction intensity on the graphite components. With the increasing of argon flow rate, the backflow is restrained, and the CO concentration at the melt free surface decreases exponentially. When the flow rate is exceed 30 L/min, the benefit is limited. An argon gas guidance system was designed and numerically analyzed, it is found that when the ratio a/b = 0.5, the backflow at crucible outlet almost disappears and the impurity concentration further decreases. According to the newly discovered mechanisms of the flow, chemical reaction and impurity transport, the new designed argon gas guidance system will beneficial for improving the quality of mc-Si. [ABSTRACT FROM AUTHOR]