US 5,961,944 A · Process and apparatus for manufacturing polycrystalline silicon, and process for manufacturing silicon wafer for solar cell

Abstract

An object of the present invention is to provide a process and apparatus for the continuous flow production of polycrystalline silicon from metallic silicon or silicon oxide as a raw material and also for the manufacture of a wafer by using it, which process and apparatus permit the mass production at a low cost. The above object can be attained by the manufacture of polycrystalline silicon and a silicon wafer for a solar cell by the following steps: (A) smelting metallic silicon under reduced pressure, carrying out solidification for the removal of the impurity components from the melt, thereby obtaining a first ingot, (B) removing the impurity concentrated portion from the ingot by cutting, (C) re-melting the remaining portion, removing boron and carbon from the melt by oxidizing under an oxidizing atmosphere, and blowing a mixed gas of argon and water to carry out deoxidization, (D) casting the deoxidized melt into a mold, and carried out directional solidification to obtain a second ingot, and (E) removing the impurity concentrated portion of the ingot obtained by directional solidification by cutting.

Claims20

Dependent claims

A process for manufacturing polycrystalline silicon from metallic silicon, comprising the steps of:

melting metallic silicon under a vacuum to remove the phosphorus contained in said metallic silicon by evaporation, thereby generating a residue containing impurity elements;
carrying out directional solidification by solidifying said residue upwardly from a lower portion of said residue to an upper portion of said residue thereby obtaining a first ingot, wherein said first ingot contains an impurity concentrated portion;
physically removing said impurity concentrated portion of said first ingot, leaving a remaining portion of said first ingot having a reduced impurity concentration;
re-melting said remaining portion of said first ingot, thereby forming a melt;
removing boron and carbon from said melt by oxidizing said melt in an oxidizing atmosphere, and in succession, blowing argon gas or a mixed gas of argon and hydrogen into said melt for deoxidization thereby forming a deoxidized melt;
casting said deoxidized melt in a mold;
subjecting the resulting deoxidized casting to directional solidification wherein said deoxidized casting is solidified upwardly from a lower portion of said deoxidized casting to produce a second ingot wherein said second ingot contains a second impurity concentration portion;
and
physically removing said second impurity concentrated portion of said second ingot to obtain the polycrystalline silicon.

6 more elements

An apparatus for manufacturing polycrystalline silicon, which comprises a retaining container for retaining metallic silicon, heating means for heating said retaining container, thereby maintaining said metallic silicon in a molten state;

a first mold into which said metallic silicon in said molten state is cast from said retaining container;
a vacuum chamber for removing phosphorus from said metallic silicon by evaporation, wherein said vacuum chamber surrounding said retaining container and said first mold;
means for effecting directional solidification of cast metallic silicon, wherein a first cast silicon ingot is formed, said first cast silicon ingot having a first impurity concentrated portion;
means for removing said first impurity concentrated portion of said first cast silicon ingot, leaving a remaining portion of said first cast silicon ingot;
a smelting container positioned to receive said remaining portion of said first cast silicon ingot, said smelting container having a re-melting means for controllably heating at least a portion of said remaining portion of said first cast silicon ingot, thereby forming a re-melt, said smelting container having a spraying means for spraying a gas from a gas source on said re-melt, said gas source comprising a gas selected from the group consisting of an oxidizing gas, a hydrogen gas and a mixed gas of hydrogen and argon, and a second mold positioned to receive said re-melt, means for effecting directional solidification of said re-melt for forming said re-melt into a second cast silicon ingot having a second impurity concentrated portion;
means for removing said second impurity concentrated portion of said second cast silicon ingot.

3 more elements

Dependencies are inferred from the claim text.

Process and apparatus for manufacturing polycrystalline silicon, and process for manufacturing silicon wafer for solar cell

Life of this patent

Process and apparatus for manufacturing polycrystalline silicon, and process for manufacturing silicon wafer for solar cell

Life of this patent

Abstract

Claims20