scholarly journals Control of the Gas Flow in an Industrial Directional Solidification Furnace for Production of High Purity Multicrystalline Silicon Ingots

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Lijun Liu ◽  
Xiaofang Qi ◽  
Wencheng Ma ◽  
Zaoyang Li ◽  
Yunfeng Zhang
Keyword(s):  
Directional Solidification ◽  
High Purity ◽  
Gas Flow ◽  
Multicrystalline Silicon ◽  
Furnace Chamber ◽  
Impurity Transport ◽  
Silicon Melt ◽  
Order Of Magnitude ◽  
Solidification Furnace ◽  
Cover Design

A crucible cover was designed as gas guidance to control the gas flow in an industrial directional solidification furnace for producing high purity multicrystalline silicon. Three cover designs were compared to investigate their effect on impurity transport in the furnace and contamination of the silicon melt. Global simulations of coupled oxygen (O) and carbon (C) transport were carried out to predict the SiO and CO gases in the furnace as well as the O and C distributions in the silicon melt. Cases with and without chemical reaction on the cover surfaces were investigated. It was found that the cover design has little effect on the O concentration in the silicon melt; however, it significantly influences CO gas transport in the furnace chamber and C contamination in the melt. For covers made of metal or with a coating on their surfaces, an optimal cover design can produce a silicon melt free of C contamination. Even for a graphite cover without a coating, the carbon concentration in the silicon melt can be reduced by one order of magnitude. The simulation results demonstrate a method to control the contamination of C impurities in an industrial directional solidification furnace by crucible cover design.

scholarly journals Effect of Argon Flow on Oxygen and Carbon Coupled Transport in an Industrial Directional Solidification Furnace for Crystalline Silicon Ingots

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 421
Author(s):  
Xiaofang Qi ◽  
Yiwen Xue ◽  
Wenjia Su ◽  
Wencheng Ma ◽  
Lijun Liu
Keyword(s):  
Directional Solidification ◽  
Flow Rate ◽  
Crystalline Silicon ◽  
Coupled Transport ◽  
Argon Flow Rate ◽  
Argon Gas ◽  
Argon Flow ◽  
Silicon Melt ◽  
Solidification Furnace ◽  
Evaporation Flux

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.

Temperature Distribution of Multi-Crystalline Silicon Ingots in the Directional Solidification Process

2013 ◽  
Vol 690-693 ◽  
pp. 977-980
Author(s):  
Xiang Rong Ma ◽  
Wu Zan ◽  
Xin Liang Zhang
Keyword(s):  
Temperature Distribution ◽  
Directional Solidification ◽  
Crystalline Silicon ◽  
Solidification Process ◽  
Casting Process ◽  
System Optimization ◽  
Silicon Melt ◽  
Solidification Furnace ◽  
Essential Knowledge ◽  
Melt Solidification

In order to better understand the casting process, we carried out global simulations of heat transfer to investigate the temperature distributions in furnace at 80 mm of insulation cage elevation and 40% of silicon melt solidification for multi-crystalline silicon (mc-Si) ingot using an industrial directional solidification furnace capable of producing 500 kg silicon ingot. The effect of heater position and the crystallization state of silicon melt on temperature distribution and interface shape are discussed as well to provide the essential knowledge for system optimization.

Nucleation of Multicrystalline Silicon during Directional Solidification

2016 ◽  
Vol 847 ◽  
pp. 103-108 ◽  
Author(s):  
Ping Bi ◽  
Xiu Hua Chen ◽  
Wen Hui Ma ◽  
Cong Zhang ◽  
Kui Xian Wei ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Directional Solidification ◽  
Cooling Rate ◽  
Minority Carrier Lifetime ◽  
Multicrystalline Silicon ◽  
X Ray Diffraction ◽  
Average Value ◽  
Initial Nucleation ◽  
Silicon Melt ◽  
Photoconductivity Decay

In this work, directional solidification was performed for multicrystalline silicon (mc-Si) ingot casting. The initial nucleation at the bottom of the silicon melt could be controlled by changing the cooling rate from 9 to 20μm/s. Metallographic microscope, X-Ray Diffraction (XRD), Microwave photoconductivity decay meter (μ-PCD) and four-point probe resistivity tester were used to investigate the microstructure, crystal orientation and electrical properties of the mc-Si ingots. The obtained results showed that cooling rate at 17μm/s is the optimum condition for the mc-Si ingots casting, under which the prepared ingot has lower dislocation density of 6×10-3 cm-2, better electrical properties, more uniformer resistivity distribution with an average value of 0.68 Ω×cm and higher minority carrier lifetime with a maximum value of 1.8 μs than that of in the other cooling rate conditions.

scholarly journals Reduction of Oxygen Impurity in Multicrystalline Silicon Production

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Bing Gao ◽  
Satoshi Nakano ◽  
Koichi Kakimoto
Keyword(s):  
Gas Flow ◽  
Solidification Process ◽  
Unidirectional Solidification ◽  
Multicrystalline Silicon ◽  
Effective Control ◽  
Oxygen Impurity ◽  
High Quality ◽  
Argon Gas ◽  
Oxygen Generation ◽  
Impurity Transport

Effective control of oxygen impurity in multicrystalline silicon is required for the production of a high-quality crystal. The basic principle and some techniques for reducing oxygen impurity in multicrystalline silicon during the unidirectional solidification process are described in this paper. The oxygen impurity in multicrystalline silicon mainly originates from the silica crucible. To effectively reduce the oxygen impurity, it is essential to reduce the oxygen generation and enhance oxygen evaporation. For reduction of oxygen generation, it is necessary to prevent or weaken any chemical reaction with the crucible, and for the enhancement of oxygen evaporation, it is necessary to control convection direction of the melt and strengthen gas flow above the melt. Global numerical simulation, which includes heat transfer in global furnace, argon gas convection inside furnace, and impurity transport in both melt and gas regions, has been implemented to validate the above methods.

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