POLYCRYSTALLINE SILICON MASS AND PROCESS FOR PRODUCING POLYCRYSTALLINE SILICON MASS
First Claim
1. A polycrystalline silicon mass, wherein a sum of concentrations of chromium, iron, nickel, copper, and cobalt impurities detected from a bulk is not more than 150 ppta.
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Abstract
The present invention provides a clean and high-purity polycrystalline silicon mass having a small content of chromium, iron, nickel, copper, and cobalt in total, which are heavy metal impurities that reduce the quality of single-crystal silicon. In the vicinity of an electrode side end of a polycrystalline silicon rod obtained by the Siemens method, the total of the chromium, iron, nickel, copper, and cobalt concentrations is high. Accordingly, before a crushing step of a polycrystalline silicon rod 100, a removing step of removing at least 70 mm of a polycrystalline silicon portion from the electrode side end of the polycrystalline silicon rod 100 extracted to the outside of a reactor is provided. Thereby, the polycrystalline silicon portion in which the total of the chromium, iron, nickel, copper, and cobalt concentrations in a bulk is not less than 150 ppta can be removed.
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Citations
20 Claims
- 1. A polycrystalline silicon mass, wherein a sum of concentrations of chromium, iron, nickel, copper, and cobalt impurities detected from a bulk is not more than 150 ppta.
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7. A process for producing a polycrystalline silicon mass, the process comprising:
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vapor depositing silicon on a core wire to obtain a polycrystalline silicon rod, one end of the core wire being connected to a first electrode and the other end thereof being connected to a second electrode; extracting the polycrystalline silicon rod to an outside of a reactor; removing at least 70 mm of a polycrystalline silicon portion from an electrode side end of the polycrystalline silicon rod extracted to the outside of the reactor; and crushing the polycrystalline silicon rod into polycrystalline silicon masses. - View Dependent Claims (8, 9, 10, 11, 12, 15, 16, 17, 18, 19, 20)
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Specification