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

Abstract

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.

A Critical Review of The Process and Challenges of Silicon Crystal Growth for Photovoltaic Applications

“…An argon gas purge is used to regulate the atmosphere inside the growth chamber at pressures between 20 and 100 m bar. [15][16][17][18][19][20][21][22][23] A seed crystal with a specified crystallographic orientation is brought into contact with the melt after the feedstock has fully melted. The temperature has been adjusted to nearly the silicon's melting point.…”

“…Finally, they all are segregated in the crystal through the melt. [21,[45][46][47][48][49][50] Melt-Crucible Interface:…”

Numerical Analysis of the Influence of Size Upgrading on Oxygen and Carbon Impurities in Casting Silicon

“…The optimization method through structural design mainly focuses on changing the structure and material of existing components in the furnace, such as cover [8,9], argon tube [10], insulation partition [11], bottom grille [12], heater [13] and so on. The optimization of process parameters mainly focuses on the investigations of argon ow rate [14], furnace pressure [15], thermal stress[16], heater power [17], growth rate[18], and so on. In recent years, the DS furnace has been developing towards the preparation of large size and high-quality silicon ingots, and the size upgrade and hot zone optimization are still widely concerned by researchers.…”

Design and Numerical Study of Argon Gas Diversion System Using Orthogonal Experiment to Reduce Impurities in Large-Sized Casting Silicon

“…This method has the advantages of wider feedstock tolerance, relatively low production costs, higher throughputs, and simpler processes. In addition, the equipment is low cost, high yield, and of simple operation [1][2][3]. However, due to grain boundaries, dislocations, and impurity defects, the quality of the cast silicon ingot is reduced, significantly affecting solar cell performance.…”

“…Some research has focused on suppressing the generation of O and C by controlling the source of pollution, such as by adding an inert material coating to the cover [7], or replacing the graphite cover with a cover made of other materials [8,9] and increasing the thickness of the silicon nitride (Si 3 N 4 ) coating on the surface of the quartz crucible [10,11]. Another important method that cannot be ignored is to decrease the impurity concentration by controlling the transport path of O and C, for example, by increasing furnace pressure [12,13], or increasing the gas flow rate [2,14]. A lot of effort and attempts were also made in furnace structure design and optimization, including the modification and optimization of the cover [15][16][17], the improvement of the graphite heater [18,19], the design of an argon gas guidance structure [20][21][22], etc.…”