| 摘要 |
PROBLEM TO BE SOLVED: To obtain a single crystal ingot and wafer excellent in electrical characteristics by suppressing the formation of agglomerate of hole-type point defects and interstitial silicon-type point defects and lowering the contamination concentration of iron to be not more than a specific value in a Czochralski method. SOLUTION: Silicon molten liquid is obtained by washing, preferably at least two times, source silicon with an aqueous solution containing dissolved ozone and then hydrofluoric acid or nitrohydrofluoric acid, and, after finally washing with ultra-pure water, melting the source silicon in a furnace based on a Czochralski method. The ratio of solidification is preferably set to be not less than 0.9 at initial pulling-up and the ratio of solidification is set to be not more than 0.9, preferably not more than 0.8 when the single crystal is pulled up after remelting. Thereby, the contamination concentration of iron element becomes not more than 2×109 atoms/cm3. When the rate of pulling-up an ingot is set as V (mm/min) and the temp. gradient at the interface between the ingot and the silicon molten liquid is set to be G( deg.C/mm), the value of V/G (mm2/min. deg.C) is determined over whole length of the ingot by simulation, and the ingot is grown, thereby a crystal free from defects can be obtained.
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