High-speed growth of Si single bulk crystals by expanding low-temperature region in Si melt using noncontact crucible method

• The noncontact crucible method was used to prepare Si single bulk crystals.
• The growth rate increased to 1.5 mm/min with the cooling rate of 0.4 K/min.
• The growth rate of this method was much higher than that of the cast method.
• The diameter remained constant during crystal growth with high-speed growth.
• An ingot with a constant diameter of 21 cm was grown by a 33 cm diameter crucible.

We propose a high-speed growth based on noncontact crucible method for obtaining large ingots with a constant diameter. In this method, the Si melt used has a large low-temperature region in its central upper part to ensure Si crystal growth inside it. Therefore, this method has the possibility of attaining a high growth rate using a high cooling rate because the growth rate is determined by the rate of expansion of the low-temperature region in the Si melt. The horizontal and vertical growth rates in Si melts were experimentally determined. At a cooling rate of 0.4 K/min, the horizontal growth rate reached 1.5 mm/min in the <110> direction and 1.9 mm/min in the <100> direction. These growth rates are higher than that of the cast method. The growth rate increased with the cooling rate. The vertical growth rate was determined to be 0.3–0.6 mm/min, and it tended to increase with increasing depth of the Si melt. The diameter of an ingot remained constant during pulling due to a high cooling rate of 0.4 K/min because the horizontal growth rate increased as the cooling rate increased and the melt temperature markedly decreased. An ingot with a constant diameter of 21 cm and a height of 7 cm was obtained inside a Si melt by the high speed growth using a crucible with 33 cm diameter.