Patent ID: 8795432

Claim:
An apparatus for pulling a silicon single crystal, comprising: a crucible that stores a silicon melt; a heater that heats the crucible; a crucible driving unit for rotating and/or lifting up and down the crucible; a chamber that holds the crucible and the heater; and a magnetic field applying unit that is provided outside the chamber and applies a magnetic field to the chamber, wherein: the magnetic field applying unit is formed along an outer peripheral surface of the chamber to have a substantially ring-like shape surrounding the chamber, and has a ring-shaped case and at least two magnetic coils attached to a cylindrical wall of the case in an opposite arrangement, where each coil of the at least two magnetic coils is deformed to have an elongated shape and is further deformed such that the longitudinal axis has a radius of curvature matching a radius of curvature of the cylindrical wall of the case; substantially concentric circle-shaped equi-strength lines of a magnetic field are formed about a center axis of the crucible by the magnetic field applying unit in a horizontal direction relative to the center axis; the magnetic field applying unit is configured to generate the magnetic field such that the strength of the magnetic field in the horizontal direction gradually decreases from a highest value towards the upward direction along the center axis and towards the downward direction along the center axis; the magnetic field applying unit is configured such that a strength of the magnetic field selectively monotonously decreases or monotonously increases from a melt surface of the silicon melt to a bottom face of the crucible; a variation range of the strength of the magnetic field selectively monotonously decreasing or monotonously increasing from the melt surface of the silicon melt to the bottom face of the crucible is controlled by a controller having a programmable memory with a program, to be within the range of 0.6 to 0.9 times a maximum strength of the magnetic field applied to the chamber by the magnetic field applying unit; and the at least two magnetic coils installed in the ring-shaped case consist of a pair of coils axisymmetrically arranged in the ring-shaped case.