Electromagnetic continuous casting apparatus for materials possessing high melting temperature and low electric conductance

Abstract

Disclosed is an electromagnetic continuous casting apparatus for a material having a low electric conductivity. The casting apparatus includes a crucible having a vertical axis. The crucible comprises an upper hot crucible and a lower cold crucible. The crucible is surrounded with an induction coil. The hot crucible is formed of a non-metallic material having a high electric conductivity and is not water-cooled. The cold crucible has a cooling structure and is formed of a metallic material having a high thermal conductivity and a high electric conductivity.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electromagnetic continuous casting apparatus for producing a high-purity polycrystalline ingot of semiconductive materials or metallic materials having a high melting temperature and a low electric conductance such as a silicon ingot used for a solar cell substrate. [0003] 2. Background of the Related Art [0004] In general, the aforementioned type silicon ingot is used as a starting material for manufacturing silicon wafers, for example, which are used as photovoltaic elements such as solar cells. [0005] Conventionally, in order to manufacture a polycrystalline silicon wafer for solar cells, firstly, silicon is melted inside a graphite crucible or inside a quartz crucible placed inside a graphite crucible. Thereafter, an ingot is produced by slowly cooling the mold (or crucible) from the bottom thereof such that the melt can be directionally solidified. The ingot is sliced into wa...

AI Technical Summary

Benefits of technology

[0013] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a convenient electromagnetic continuous casting apparatus for producing a high-purity polycrystalline ingot, in which the heating and melting efficiency of a raw material having a high melting point and a low electric conductance can be remarkably improved, and also the electromagnetic pressure can be maintained higher than the hydrostatic pressure due to the melt height throughout the melt region.

Problems solved by technology

This method has been widely used, but embraces some problems in that the silicon ingot is contaminated by carbon and oxygen introduced from the graphite or quartz crucible, and the quartz crucible is fractured during solidification of silicon and must be replaced with a new one every time to thereby increase the manufacturing cost.

On the other hand, the quality and cost of silicon wafers depend on those of the ingot.

However, since the above conventional electromagnetic continuous casting process uses a water-cooled cold crucible, it has difficulties in making a material, which has a high melting temperature and a low electric-conductivity, a high-purity ingot.

Therefore, a great deal of electric power is required for melting the raw materials.

In particular, since silicon is a semiconductive material having a high melting point and a low electric conductivity, a cooling effect by the emission of radiant heat is high, but, in contrast, the induction heating effect is weak.

Thus, it causes difficulties in melting the silicon material continuously and efficiently.

However, this method leads to a high installation cost and also a high production cost disadvantageously.

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