| CPC C30B 15/22 (2013.01) [C30B 29/06 (2013.01)] | 16 Claims |

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1. A method for crystal pulling, comprising:
performing an equal-diameter process, wherein the equal-diameter process is divided into a first equal-diameter stage, a second equal-diameter stage, and a third equal-diameter stage in turn according to a growth length of crystal, and wherein performing the equal-diameter process comprises sequentially adjusting a crystal rotation rate, a crucible rotation rate, a furnace pressure, and an inert gas flow rate, including:
from the first equal-diameter stage to the third equal-diameter stage, increasing the crystal rotation rate after starting at a first initial crystal rotation rate, and keeping the crystal rotation rate at a constant rotation rate after increasing the crystal rotation rate;
increasing the crucible rotation rate from a first initial crucible rotation rate to a maximum crucible rotation rate after starting at the first initial crucible rotation rate in the first equal-diameter stage, keeping the crucible rotation rate at the maximum crucible rotation rate in the second equal-diameter stage, and decreasing the crucible rotation rate after the second equal-diameter stage; and
decreasing the furnace pressure after starting at a first initial furnace pressure, starting at a first initial inert gas flow rate in the first equal-diameter stage and increasing the inert gas flow rate after the first equal-diameter stage; and
performing a cooling process in which a furnace pressure and an inert gas flow rate are sequentially adjusted.
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