The Czochralski method has been conventionally widely adopted for growth of a silicon single crystal. Among others, the MCZ method (the magnetic field applied Czochralski method) for applying a magnetic field to a silicon melt in order to suppress a convection current of a silicon melt in a quartz crucible has been known. In the MCZ method, a silicon single crystal is grown by performing a melting step of accommodating polycrystalline silicon in a quartz crucible and melting the polycrystalline silicon in the quartz crucible with use of a heater and a pulling step of bringing a seed crystal into contact with a melt surface of the silicon melt from above, rotating and moving up and down the seed crystal and the quartz crystal while applying a magnetic field to the silicon melt with use of a coil, and pulling the seed crystal.
The quartz crucible configured to accommodate the silicon melt therein is made of amorphous SiO2 (quartz glass) having an amorphous structure. The quartz crucible reacts with the silicon melt, and a cristobalite crystal layer, which is crystalline SiO2, is formed on a SiO2/Si interface, i.e., an inner surface of the quartz crucible that is in contact with the silicon melt. In some cases, the cristobalite crystal layer is exfoliated during pulling up the silicon single crystal, liberated or allowed to fall into the silicon melt from the quartz crucible, and reaches a growth interface of a silicon single crystal that is being pulled up. As a result, the cristobalite crystal layer enters the silicon single crystal that is being pulled up, and it may cause dislocation generation of the silicon single crystal.
Thus, to prevent exfoliation of cristobalite from the inner surface of the quartz crucible during the silicon single crystal pulling step and avoid the dislocation generation of the silicon single crystal, various methods have been suggested. For example, Patent Literature 1 discloses a method for growing a silicon single crystal while applying a magnetic field to a silicon melt with use of a quartz crucible having an aluminum low concentration layer on an inner surface side.
However, according to the method disclosed in Patent Literature 1, a problem lies in that the aluminum low concentration layer (an impurity layer) is formed in the quartz crucible and hence this impurity is contained in the silicon single crystal. If the impurity is contained in the silicon single crystal, an influence on a device is a concern, and hence forming the impurity layer on an inner surface of the quartz crucible is not preferable. Especially, this is particularly undesirable solving means for a next-generation device that is expected to achieve high purity.
Further, Patent Literature 2 discloses intermittently applying a magnetic field to a silicon melt to control a size of cristobalite. However, to intermittently apply a magnetic field to the silicon melt more than once, magnetization and demagnetization of a coil must be repeated, this operation is troublesome, and a risk of operational errors is increased. Furthermore, when the magnetization and the demagnetization of the coil are repeated, a dead time that the silicon single crystal is not manufactured is increased, which is inefficient.