JP2012162419A - Apparatus and method for producing single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for producing a single crystal, wherein optimum magnetic fields can be formed on upper and lower sides of a coil, respectively, in an induction-heating coil.SOLUTION: The induction-heating coil 24 and a current-supplying unit are provided, wherein: the induction-heating coil consists of an upper surface-side coil 24a and a lower surface-side coil 24b, and heats and melts a silicon-material bar 12 to grow a silicon single crystal 32; and the current-supplying unit supplies high-frequency currents independently to the upper surface-side coil 24a and the lower surface-side coil 24b, respectively. Then the high-frequency currents are supplied independently to the upper surface-side coil 24a and the lower surface-side coil 24b, respectively, in the induction-heating coil 24, thereby growing the silicon single crystal 32 by heating and melting the silicon material bar 12.

Description

  The present invention relates to a single crystal manufacturing apparatus and a single crystal manufacturing method, and in particular, for growing a single crystal by heating and melting a raw material rod such as silicon using an induction heating coil by an FZ method (floating zone method). The present invention relates to a suitable manufacturing apparatus and manufacturing method.

  Conventionally, a single crystal manufacturing apparatus and a single crystal manufacturing method for growing a silicon single crystal by heating and melting a silicon raw material rod using an induction heating coil by the FZ method are known (for example, see Patent Document 1). This single crystal manufacturing apparatus includes an upper shaft for holding a silicon raw material rod, an upper shaft for holding a seed crystal, and a heating device for heating and melting the silicon raw material rod. The heating device has an annular induction heating coil that heats and melts one end of a silicon raw material rod held on the upper shaft.

  When manufacturing a silicon single crystal from a silicon raw material rod using the manufacturing apparatus described above, first, by supplying a high-frequency current to the induction heating coil, the lower end of the silicon raw material rod held on the upper shaft is heated and melted. After the fusion zone is fused to the seed crystal held on the lower shaft, the silicon raw material rod and the seed crystal are integrated while the diameter is reduced by the seed drawing to eliminate dislocation. Next, the silicon raw material rod held on the upper shaft is relatively moved in the axial direction while rotating relative to the induction heating coil, so that the molten zone is removed from the fusion portion between the silicon raw material rod and the seed crystal. Gradually move toward the other end of the bar. The melted and melted zone is gradually cooled while generating radiant heat in the process of leaving the induction heating coil, and single-crystallized according to the crystal orientation of the seed crystal. Therefore, according to the manufacturing apparatus described above, a rod-shaped silicon single crystal can be obtained from a silicon raw material rod.

JP-A-8-104590

  By the way, in the above-described single crystal manufacturing apparatus, in order to heat and melt the silicon raw material rod, it is necessary to flow a high-frequency current through an annular induction heating coil via a power supply terminal. When a high frequency current is supplied to the induction heating coil, a magnetic field is formed on each of the coil upper surface side and the coil lower surface side of the induction heating coil. When the silicon raw material rod is disposed in the magnetic field region on the upper surface of the coil, the silicon raw material rod is heated and melted to form the melting zone. Therefore, in order to heat and melt the silicon raw material rod, it is important to form a magnetic field for heating and melting the silicon raw material rod on the upper surface side of the induction heating coil. On the other hand, the magnetic field formed on the lower surface side of the induction heating coil causes Lorentz force that does not cause dripping in the melt in the melt zone. Therefore, in order to hold the molten liquid in the molten zone so as not to cause liquid dripping, it is important to form a magnetic field on the lower surface side of the induction heating coil for applying Lorentz force to the molten liquid. .

  However, in the above-described single crystal manufacturing apparatus, the magnetic field formed on the upper surface of the coil and the magnetic field formed on the lower surface of the coil are formed by supplying high-frequency current to one induction heating coil. There is a possibility that the magnetic field for heating and melting one end of the silicon raw material rod to be formed and the magnetic field for applying Lorentz force to the melt formed on the lower surface side of the coil may not be optimal.

  The present invention has been made in view of the above points, and provides a single crystal manufacturing apparatus and a single crystal manufacturing method capable of forming an optimum magnetic field on the coil upper surface side and the coil lower surface side of the induction heating coil. The purpose is to do.

  The above object is composed of an upper surface side coil and a lower surface side coil, an induction heating coil for heating and melting a raw material rod to grow a single crystal, and an independent high frequency current for each of the upper surface side coil and the lower surface side coil. And a current supply means for supplying the current.

  Also, the above object is to heat and melt the raw material rod by supplying independent high frequency currents to the upper surface side coil and the lower surface side coil of the induction heating coil constituted by the upper surface side coil and the lower surface side coil. This is achieved by a single crystal manufacturing method including a growth process for growing a single crystal.

  According to the present invention, an optimum magnetic field can be formed on the coil upper surface side and the coil lower surface side of the induction heating coil.

It is a block diagram of the single crystal manufacturing apparatus which is one Example of this invention. It is principal part sectional drawing of the single crystal manufacturing apparatus which is one Example of this invention. It is a figure showing the voltage waveform supplied to the upper surface side coil and lower surface side coil of the induction heating coil with which the single crystal manufacturing apparatus which is one Example of this invention is provided. It is principal part sectional drawing of the single crystal manufacturing apparatus which is the 1st modification of this invention. It is principal part sectional drawing of the single crystal manufacturing apparatus which is the 2nd modification of this invention. It is principal part sectional drawing of the single crystal manufacturing apparatus which is the 3rd modification of this invention.

  Hereinafter, specific embodiments of a single crystal manufacturing apparatus and a single crystal manufacturing method according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a single crystal manufacturing apparatus (hereinafter simply referred to as a manufacturing apparatus) 10 according to an embodiment of the present invention. 1A is a vertical cross-sectional view of the manufacturing apparatus 10, and FIG. 1B is a cross-sectional view of the manufacturing apparatus 10 taken along the line AA ′ in FIG. 1A. Show. Moreover, FIG. 2 shows the principal part block diagram of the manufacturing apparatus 10 of a present Example. The manufacturing apparatus 10 of the present embodiment is an apparatus for growing a silicon single crystal from a silicon raw material rod by a floating zone method (FZ method).

  The manufacturing apparatus 10 includes an upper shaft 14 for holding a polycrystalline silicon raw material rod 12, a lower shaft 18 for holding a seed crystal 16 made of silicon, and a heating device 20 for heating and melting the silicon raw material rod 12. I have. The heating device 20 includes a growth furnace 22 and an induction heating coil 24 disposed in the growth furnace 22. The silicon raw material rod 12 and the seed crystal 16 are accommodated in a growth furnace 22. Each of the upper shaft 14 and the lower shaft 18 can move in the vertical direction and rotate relative to the growth furnace 22 while holding the silicon raw material rod 12 or the seed crystal 16.

  The silicon raw material rod 12 has a predetermined diameter. The induction heating coil 24 is an annular member made of metal and disposed coaxially with the silicon raw material rod 12 in the growth furnace 22. The induction heating coil 24 has an inner diameter smaller than the diameter of the silicon raw material rod 12 and is arranged so as to surround the silicon raw material rod 12. The induction heating coil 24 is formed so that the inner diameter side is thin and the outer diameter side is thick in the axial direction.

  A controller 28 is connected to the induction heating coil 24 via a power supply terminal 26. The controller 28 generates a high frequency voltage to be applied to the induction heating coil 24. A high frequency voltage generated by the control of the controller 26 is applied to the induction heating coil 24 via the power supply terminal 26. The induction heating coil 24 forms a magnetic field in which a magnetic flux change occurs on the upper surface side in the axial direction and a magnetic field in which a magnetic flux change occurs on the lower surface side in the axial direction when a high frequency current flows by applying a high frequency voltage.

  In the manufacturing apparatus 10 described above, when growing the silicon single crystal 30 from the silicon raw material rod 12, the controller 28 generates a high frequency voltage and supplies the high frequency current to the induction heating coil 24 via the power supply terminal 26. When a high-frequency current is supplied to the induction heating coil 24, a magnetic field in which a magnetic flux change is generated around the induction heating coil 24 (both on the upper surface side and the lower surface side). When such a magnetic field is formed, an eddy current is generated in the direction of preventing the magnetic flux change in the silicon raw material rod 12 held on the upper shaft 14 by the action of the magnetic field by the induction heating coil 24. The tip (lower end) of the silicon raw material rod 12 is heated and melted. At this time, a melted zone 32 heated and melted is formed on the tip side of the silicon raw material rod 12. The melt zone 32 is fused to the seed crystal 16 held on the lower shaft 18 and then the diameter of the melt zone 32 is reduced by the seed drawing so as to be dislocation-free. As a result, the silicon raw material rod 12 and the seed crystal 16 are integrated.

  Next, the silicon raw material rod 12 is relatively moved in the axial direction while rotating relative to the induction heating coil 24. In this case, the melting zone 32 is gradually moved from the fused portion between the silicon raw material rod 12 and the seed crystal 16 toward the other end (upper end) of the silicon raw material rod 12. The heated and melted melting zone 32 is gradually cooled while generating radiant heat in the process of leaving the induction heating coil 24, and is single-crystallized according to the crystal orientation of the main crystal 16. Therefore, according to the manufacturing apparatus 10, the rod-shaped silicon single crystal 30 can be obtained from the silicon raw material rod 12 using the induction heating coil 24.

  FIG. 3 is a diagram illustrating voltage waveforms supplied to the upper surface side coil 24a and the lower surface side coil 24b of the induction heating coil 24 included in the manufacturing apparatus 10 of the present embodiment. 3A shows a voltage waveform to the upper surface side coil 24a, and FIG. 3B shows a voltage waveform to the lower surface side coil 24b.

  In the manufacturing apparatus 10 of the present embodiment, the induction heating coil 24 includes an upper surface side coil 24a and a lower surface side coil 24b separated in the axial direction, as shown in FIG. Both the upper surface side coil 24a and the lower surface side coil 24b are formed in an annular shape, and have a cross-sectional taper shape from the center to the radially outer side. The inner diameter of the upper surface side coil 24a and the inner diameter of the lower surface side coil 24b are substantially the same, and the outer diameter of the upper surface side coil 24a and the outer diameter of the lower surface side coil 24b are approximately the same. Each of the outermost diameter portion of the upper surface side coil 24a and the outermost diameter portion of the lower surface side coil 24b has a predetermined thickness in the axial direction. The upper surface side coil 24a and the lower surface side coil 24b are wound in the same direction with respect to the axial direction.

  The upper surface side coil 24a and the lower surface side coil 24b are opposed to each other via the insulating member 34 in the axial direction. The insulating member 34 has substantially the same planar shape as the planar shape of the upper surface side coil 24a and the lower surface side coil 24b when viewed from above or below, and is substantially the same as the inner diameter of the upper surface side coil 24a and the lower surface side coil 24b. In addition to having the same inner diameter, the outer diameter of the upper surface side coil 24a and the lower surface side coil 24b is substantially the same. The insulating member 34 is made of a material having a relatively low dielectric constant, and has a predetermined thickness in the axial direction from the inner diameter side to the outer diameter side. The insulating member 34 has a function of blocking a magnetic field generated between the upper surface side coil 24a and the lower surface side coil 24b.

  Further, a controller 28 is connected to the upper coil 24a via a power supply terminal 26a, and a controller 28 is connected to the lower coil 24b via a power supply terminal 26b. The controller 28 independently generates a high frequency voltage to be applied to the upper surface side coil 24a and a high frequency voltage to be applied to the lower surface side coil 24b. Specifically, as shown in FIG. 3, the controller 28 generates a high frequency voltage to be applied to the upper surface side coil 24a and a high frequency voltage to be applied to the lower surface side coil 24b so that a shift of half a wavelength occurs between them. To do. Then, the high-frequency voltage in which the shift of half wavelength is generated is applied to the upper surface side coil 24a and the lower surface side coil 24b through the power supply terminals 26a and 26b. At this time, the application of the high frequency voltage is performed such that the magnetic field on the upper surface side coil 24a side and the magnetic field on the lower surface side coil 24b side cancel each other. Thus, the application of the high frequency voltage from the controller 28 to the induction heating coil 24 is performed using two high frequency power supplies.

  When a high frequency voltage is applied to the upper surface side coil 24a, a high frequency current flows through the upper surface side coil 24a, whereby a magnetic field for heating and melting the lower end of the silicon raw material rod 12 on the upper surface side in the axial direction of the upper surface side coil 24a. Therefore, an eddy current is generated inside the silicon raw material rod 12 by the action of the magnetic field, and the silicon raw material rod 12 is heated and melted to form a melting zone 32. In addition, when a high frequency voltage is applied to the lower surface side coil 24b, a high frequency current flows through the lower surface side coil 24b, thereby causing dripping in the melt of the melting zone 32 on the lower surface side in the axial direction of the lower surface side coil 24b. Since a magnetic field for applying a Lorentz force that is not to be generated is formed, a Lorentz force that does not cause dripping in the melt of the melt zone 32 is applied by the action of the magnetic field.

  In the present embodiment, the high frequency voltage or high frequency current applied or supplied to the upper surface side coil 24a and the high frequency voltage or high frequency current applied or supplied to the lower surface side coil 24b are independently controlled by the controller 28. Therefore, the magnetic field formed on the upper surface side of the induction heating coil 24 can be optimized for heating and melting the silicon raw material rod 12, and formed on the lower surface side of the induction heating coil 24. The magnetic field to be applied can be optimized for applying a Lorentz force that does not cause dripping in the melt in the melt zone 32.

  Further, the high-frequency voltage or high-frequency current on the upper surface side coil 24a side and the high-frequency voltage or high-frequency current on the lower surface side coil 24b side are shifted from each other by a half wavelength, and therefore, between the upper surface side coil 24a and the lower surface side coil 24b. In addition, the magnetic field generated based on the high frequency current supplied to the upper surface side coil 24a and the magnetic field generated based on the high frequency current supplied to the lower surface side coil 24b act so as to cancel each other. In this regard, according to this embodiment, the formation of a non-uniform magnetic field around the induction heating coil 24 is suppressed.

  An insulating material 34 having a low dielectric constant is interposed between the upper surface side coil 24a and the lower surface side coil 24b. The insulating material 34 has a function of blocking a magnetic field to pass therethrough. For this reason, the presence of the insulating material 34 suppresses the magnetic field generated based on the high-frequency current supplied to the upper surface side coil 24a from reaching the lower surface side coil 24b, and conversely, the lower surface side coil 24b. The magnetic field generated based on the supplied high-frequency current is prevented from reaching the upper surface side coil 24a side. In this regard, according to the present embodiment, the magnetic field for heating and melting the silicon raw material rod 12 and the magnetic field for applying Lorentz force that does not cause dripping in the melt in the melting zone 32 affect each other. Is suppressed.

  Therefore, according to the manufacturing apparatus 10 of the present embodiment, the optimum magnetic field for heating and melting the silicon raw material rod 12 around the induction heating coil 24 by using the two coils 24 a and 24 b as the induction heating coil 24. It is possible to form an optimum magnetic field region for forming a region and applying a Lorentz force that does not cause sag in the melt in the melt zone 32, and thereby the silicon single crystal 30 can be formed from the silicon raw material rod 12. It is possible to easily set production conditions necessary for growth.

  In the above embodiment, the controller 28 supplies independent high-frequency currents to the upper surface side coil 24a and the lower surface side coil 24b of the induction heating coil 24, respectively, so that “current supply means” and "Growth process" has been realized.

  By the way, in the above embodiment, the upper surface side coil 24a and the lower surface side coil 24b of the induction heating coil 24 are formed so as to have substantially the same inner diameter and substantially the same outer diameter. It is not limited and it is good also as making an inside diameter and / or an outside diameter different.

  That is, as shown in FIG. 4, the inner diameter of the lower surface side coil 24b of the induction heating coil 24 may be larger than the inner diameter of the upper surface side coil 24a. In the configuration of such a modified example, it is difficult to cause the magnetic field on the lower surface side coil 24b side to act on the melting column of the melting zone 32 where the silicon raw material rod 12 is heated and melted, and the magnetic field acting on the melting column is applied to the upper surface side coil 24a. Therefore, the controllability in the manufacturing process of obtaining the silicon single crystal 30 from the silicon raw material rod 12 can be enhanced.

  In addition, as shown in FIG. 5, the outer diameter of the lower surface side coil 24b of the induction heating coil 24 may be different from the outer diameter of the upper surface side coil 24a (for example, larger than the outer diameter of the upper surface side coil 24a). Good. In the configuration of such a modified example, even when the outer diameter of the silicon single crystal 30 to be manufactured is different from the outer diameter of the silicon raw material rod 12 held on the upper shaft 14, the lower surface side is matched to the difference in the outer diameter. If the outer diameter of the coil 24 b is set, the magnetic field generated by the lower surface side coil 24 b can be formed so as to apply a Lorentz force that forms a desired outer diameter without causing dripping in the melt of the melt zone 32. Therefore, the silicon single crystal 30 obtained from the silicon raw material rod 12 can be formed into a desired shape.

  Further, as shown in FIG. 6, the configuration shown in FIG. 4 may be combined with the configuration shown in FIG. In the configuration of such a modification, both the effect of the configuration shown in FIG. 4 and the effect of the configuration shown in FIG.

  Further, the above embodiment is an example of the manufacturing apparatus 10 for growing a silicon single crystal from a silicon raw material rod by the floating zone method (FZ method), but the present invention is not limited to this, and other materials are used. It is good also as applying to the manufacturing apparatus which grows a single crystal from the raw material stick | rod consisting of.

DESCRIPTION OF SYMBOLS 10 Single crystal manufacturing apparatus 12 Silicon raw material rod 16 Seed crystal 24 Induction heating coil 24a Upper surface side coil 24b Lower surface side coil 28 Controller 30 Silicon single crystal 32 Melting zone

Claims (2)

An induction heating coil that is composed of an upper surface side coil and a lower surface side coil, and heats and melts the raw material rod to grow a single crystal;
Current supply means for supplying independent high frequency currents to the upper surface side coil and the lower surface side coil;
An apparatus for producing a single crystal, comprising: Growth in which a raw material rod is heated and melted to grow a single crystal by supplying independent high frequency currents to the upper surface side coil and the lower surface side coil of the induction heating coil constituted by the upper surface side coil and the lower surface side coil. A method for producing a single crystal comprising the steps.

Images