| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method of producing a sapphire single crystal which suppresses bubble groups in the latter half part of the straight cylindrical body, in growing sapphire ingot whose straight cylindrical body has diameter of 150 mm or greater and length of 200 mm or greater by the Czochralski method and provide a sapphire single crystal whose shoulder part and straight cylindrical part have a very low probability of formation of bubble groups and which improves the yield of a sapphire single crystal substrate for LED.SOLUTION: A method of producing a c-axis sapphire single crystal by the Czochralski method is based on growing a single crystal body having a straight cylindrical body of diameter of 150 mm or greater and is characterized by varying the crystal pulling speed in growing the straight cylindrical body so as to be lower immediately after completion of the growing than at the start of growing, in growing sapphire ingot having length of the straight cylindrical body of 300 mm or greater. Before the solidification ratio becomes 28% or higher, the pulling speed is decreased. The initial pulling speed is 2-5 mm/h, and the pulling speed immediately before completion is 50-80% of the initial pulling speed.</p> |
