Single crystal extraction method

Abstract

The single crystal extraction method is used for shortening the extraction time from the forming of a straight body part to crystal excision from a meltwater, extracting single crystal and improving a rate of finished products. The method comprises a first process, a second process and a third process. The first process forms the straight body part (C2), and the second process is behind the first process. In the final process of forming the straight body part, a lower protruded shape (C3) protruded downwards is formed at the lower end of the crystal, and the third process is configured to cut the lower protruded shape formed in the second process from the silicon meltwater. In the second process, the field density of the horizontal magnetic field is controlled lower than the first process in the range of 800 to 1000 gausses, the crystal extract speed is controlled lower than the first process in the range of 0.2 to 0.5 mm / min, the crystal rotation speed is controlled lower than the first process in the range of 1 to 3 rpm, and the crucible rotation speed is controlled in the range of 0.5 to 5 rpm.

Description

technical field [0001] The present invention relates to a single crystal extraction method in which a single crystal is grown and a single crystal is extracted according to the Czochralski single crystal growth method (hereinafter referred to as "CZ method"). Background technique [0002] For growing silicon single crystals, the CZ method is widely used. In this method, as Figure 4 As shown, silicon melt M is formed in a quartz glass crucible 50 (hereinafter simply referred to as crucible 50 ) by the heat of a side heater 52 in a melting furnace 55 . Then, within the range surrounded by the radiation shield 51, the seed crystal P is brought into contact with the surface M1 of the molten liquid M, the crucible 50 is rotated, and the seed crystal P is extracted upward while rotating in the opposite direction, thereby A single crystal C is formed at the lower end of the seed crystal P. [0003] Specifically, necking down of the end portion of the melted seed crystal P is per...

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Problems solved by technology

[0011] However, in the single crystal extraction method disclosed in JP-A-2012-36042, in order to form the lower end of the crystal into a convex shape, it is necessary to stop the lifting of the crucible and maintain the state of stopping the crystal extraction for a predetermined time, so it cannot be compared with Significantly shortens the time compared to the case of implementing the conventional tail forming process

[0012] In addition, since the determination of whether an appropriate convex shape is formed at the lower end of the crystal is performed by detecting the change in the apparent weight of the single crystal, if the accuracy of weight measurement is low, an appropriate convex shape cannot be obtained, and there is a risk of dislocation in the crystal.

That is, when the formation of the convex shape is insufficient, a sharp temperature change occurs at the lower end of the crystal, and slip dislocation may occur in the single crystal. In the case of an extremely sharp convex state, the melt is supercooled. risk of dislocation

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