Sumitomo Metal Industries, Inc.

Masahiko Mizuta

Masato Tabuchi

Tokuji Maeda

In pulling a single crystal by CZ method, stable pulling up is carried out in a pulling rate as fast as possible while a crystal deformation is controlled to an aimed value and density of grown-in defects is suppressed to a value below an upper limit value. As an index of deformation of the single crystal from a perfect circle, the aimed value of the crystal deformation is previously determined. The upper limit value of a pulling rate necessary to suppress a defect density to an allowable range is previously calculated from distribution of grown-in defects in the crystal section, the single crystal is pulled up according to a predetermined pulling rate, and then deviation of the achieved value from the aimed value of the crystal deformation in pulling is calculated. The deviation is converted to a correction of the pulling rate. This correction is added to a set value of the pulling rate in the pulling and the result is used as a temporary set value of the pulling rate in the next pulling. The temporary set value is compared with the upper limit value of the above described pulling rate and the smaller value is determined as the pulling rate in the next runs.

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Hyogo, Japan

Masahiko Mizuta