POLYCRYSTALLINE SILICON MASS AND PROCESS FOR PRODUCING POLYCRYSTALLINE SILICON MASS
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United States of America Patent
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Issued Date -
Jul 12, 2012
app pub date -
Jul 21, 2010
filing date -
Sep 16, 2009
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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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