JP4406727B2 - Magnetic field applied single crystal manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The magnetic field application type single crystal production apparatus of the present invention is an apparatus for growing single crystals of large diameter oxides, metals, semiconductors, etc. by a floating zone method with a strong magnetic field applied. It is suitable for producing a single crystal of a material that easily reacts with a generally used crucible material such as platinum.
Furthermore, it is expected that a high quality single crystal can be produced stably and at high speed by applying a strong magnetic field and by applying a strong magnetic field effect such as a forced stirring effect and a magnetic levitation effect.
In particular, the present invention is useful in the field of manufacturing single crystals applicable to the present invention for manufacturing high-quality single crystals of materials that are essential for the information and communication industry, such as optical materials, superconductors, ferroelectrics, and semiconductors.
[0002]
[Prior art]
As a conventional single crystal manufacturing apparatus, a pulling method single crystal manufacturing apparatus is known, and it is known that application of a magnetic field is effective in suppressing convection of silicon raw material in a quartz crucible in manufacturing a silicon single crystal. . However, the pulling method single crystal growing apparatus is not suitable for a material that easily reacts with a high melting point material or a crucible material, and further has a problem that a growing atmosphere cannot be freely selected.
[0003]
In the floating zone method, a part of the raw material is melted to form a melting zone between the raw material and the seed crystal, and then the melting zone is moved, or the raw material and the seed crystal are simultaneously moved downward. Known as a method of growing a single crystal through melting and solidification of the raw material by moving the melting zone relatively, and a single crystal such as a high melting point material or a material that easily reacts with the crucible material because no crucible is used. Suitable for training.
[0004]
In the single crystal growth apparatus for the floating zone method, a high-frequency heating type and an infrared condensing heating type are generally known as a heating source, and the high-frequency heating type is a single unit of a material having good conductivity such as metal or semiconductor. Limited to crystal growth. On the other hand, the infrared heating type has a wide range of applications such as insulating oxides in addition to metals and semiconductors. An example of a conventional infrared heating type single crystal growing apparatus is shown in FIG. As shown in FIG. 5, in a conventional infrared heating type single crystal growth apparatus, one or more ellipsoidal mirrors having a diameter of 150 mm or more are combined to collect infrared rays from a lamp at one focal point at the other focal point. I am making it light. Therefore, an infrared heating device cannot be incorporated in a narrow cylindrical space having a diameter of 150 mm or less such as an electromagnet bore. In addition, halogen lamps and xenon lamps become unstable in heating at a magnetic field of 70 gauss or more.
[0005]
A laser heating pedestal method is known as a method for producing a single crystal by locally heating a part of a narrow cylindrical space having a diameter of 150 m or less such as an electromagnet bore. An example of a laser heating pedestal device is shown in FIG. This method uses a carbon dioxide laser or Nd ³⁺ : YAG solid-state laser as a heating source, and condenses the laser light at one point by combining a conical mirror, a conical mirror, a plane mirror, and a parabolic mirror. This is a method of growing a single crystal by melting and forming a melting zone between a seed crystal and a raw material, and single crystals having a diameter of 3 mm or less such as sapphire, YAG, LiNbO ₃ have been grown so far (example: M M. Fejer et al., Proc. SPIE, Advances in Infrared Fibers II, VOL.32, PP.50 (1982)). In addition, a single crystal growing apparatus in which a similar optical system using laser light as a heat source is incorporated in a superconducting magnet has been reported (see Japanese Patent Application Laid-Open No. 2001-261478 ).
[0006]
These laser heating methods are suitable for growing fiber crystals because of their high condensing efficiency due to the high directivity of laser light, but the condensing density extremely decreases as the crystal diameter increases, There is a problem that it becomes difficult to form a sufficiently large melting zone necessary for crystal growth, and when a high-power laser is used, the temperature gradient of the melting zone is too large due to the high directivity of the laser. There arises a problem that the evaporation of the melting zone component becomes intense.
[0007]
In the conventional single crystal growth apparatus, the crystal growth part is shielded from the outside air by a transparent quartz tube so that various growth atmosphere gases can flow. The transparent quartz tube could be installed by raising the lower rotation shaft and lowering the lower rotating shaft. However, if the crystal growth part is installed in the bore of the electromagnet for applying the magnetic field, there is a problem that the conventional method cannot insert the transparent quartz tube. .
[0008]
[Problems to be solved by the invention]
Recently, a small helium-free superconducting magnet has been developed, and it has become possible to generate a strong magnetic field relatively easily. Therefore, research on the development of materials using the strong magnetic field effect and the search for a new strong magnetic field effect is active. Has been done. In the field of single crystal growth, a strong magnetic field has been applied to semiconductors such as silicon, but it has been found that forced convection occurs even in melts of non-conductive materials such as oxides. In the growth of single crystals of oxides, some magnetic field effect is expected, and research on single crystal growth in the application of a strong magnetic field has attracted attention (Y. Miyazawa et al., Journal of Crystal Growth, Vol. 166, pp. 286 (1996)).
[0009]
Of the single crystal growth methods described above, the floating zone method is maintained by surface tension with the melting zone sandwiched between the raw material rod and the seed crystal, and is expected to be particularly susceptible to strong magnetic fields. It is considered suitable for studying the effect, and the development of a magnetic field application type floating zone single crystal growth device was desired.
[0010]
In order to overcome the above-mentioned problems while taking advantage of the above-mentioned conventional technology and develop a device for growing a large-diameter single crystal under the application of a strong magnetic field, a halogen lamp or a xenon lamp is used as a heating light source. It is necessary to efficiently extract infrared rays radiated from the light source as parallel light, introduce them into the bores of the electromagnet with a plane mirror, and collect them with a parabolic mirror. In view of this, a magnetic field application type single crystal manufacturing apparatus to which a conventional technique is applied has been considered. FIG. 7 is a diagram showing this principle, and the structure and principle are as follows. The lamp 1 is arranged outside the bore of the electromagnet, and a part of the infrared rays emitted radially from the lamp 1 is reflected by the parabolic mirror 3 to become parallel light, reflected by the plane mirror 6 and introduced into the bore of the electromagnet. Then, it is reflected by the parabolic mirror 7 and collected. However, in this heating method, the light collection efficiency is low, and even if the diameter of the parabolic mirror 7 is larger than the bore diameter of the electromagnet, the light collection efficiency is not improved, so that a high temperature of 1500 ° C. or higher cannot be obtained.
[0011]
Here, the spheroid mirror has the property that when the lamp is placed at one focal position, the light emitted from the lamp is condensed at the other focal position. When the emitted light is reflected by a parabolic mirror, it has the property of becoming parallel light. Therefore, the light emitted from the lamp at the focal position of the spheroid mirror is reflected by the parabolic mirror and directed more by matching the focal position of the spheroid mirror with the focal position of the parabolic mirror. Focusing on the fact that highly parallel light can be obtained, the inventors have invented a magnetic field application type floating zone single crystal growth apparatus.
[0012]
[Means for Solving the Problems]
That is, the magnetic field application type single crystal manufacturing apparatus of this invention is
A floating zone type single crystal manufacturing device that heats and melts in a transparent quartz tube installed in a vertical direction,
An infrared light source arranged at a position not affected by the leakage magnetic field of the magnetic application means arranged around the floating zone ;
A spheroid mirror disposed around an infrared light source, a parabolic mirror that collimates reflected light from the spheroid mirror, and a cylindrical mirror that guides the light toward a transparent quartz tube A first optical system that converts the light composed of infrared rays into parallel light with directivity;
A second optical system for reflecting the parallel light as hollow cylindrical light along the transparent quartz tube and irradiating the reflected hollow cylindrical light from the periphery of the floating zone;
The magnetic application means is provided around the floating zone.
[0013]
The magnetic field application type single crystal manufacturing apparatus of the present invention is also characterized in that the magnetic application means is a superconducting magnet.
[0014]
A magnetic field application type single crystal manufacturing apparatus according to the present invention includes a lower rotating shaft moving mechanism that slides a lower rotating shaft and a quartz tube support tube in a lateral direction as a driving system. After moving to the position, slide the quartz tube support tube to the side along with the lower rotation axis moving mechanism, insert the transparent quartz tube into the floating zone, and then return the quartz tube support tube to its original position. It is also characterized in that it is fixed on a quartz tube support tube.
[0015]
The secondary features of the present invention are as follows.
(1) The light collection efficiency is increased by increasing the size of the spheroid mirror.
(2) The area around the melting zone can be heated uniformly.
(3) Since the lamp can be separated from the electromagnet by 150 cm or more by reflecting the parallel light with a flat mirror, the single crystal can be grown even in a strong magnetic field of 10T.
(4) Since the position of the parabolic mirror in the bore can be moved up and down, crystals can be grown under magnetic field conditions with different magnetic field distributions and magnetic field strengths.
(5) Since the crystal growth region can be blocked from the outside air by the transparent quartz tube, various atmospheric gases can be flowed and the magnetic Archimedes effect can be tested.
(6) Since the condensing region is 5 mm or more, a single crystal having a large diameter of 5 mm or more can be grown.
(7) By attaching a cylindrical mirror, infrared rays other than parallel light are also introduced into the bore to bring about a heat retaining effect around the crystal and to play a role of safety protection against damage to eyes caused by infrared irradiation.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a magnetic field application type single crystal manufacturing apparatus according to the present invention will be described below in detail with reference to the drawings and examples.
[0017]
One embodiment of a single crystal manufacturing apparatus according to the present invention is shown in FIG. A xenon lamp or a halogen lamp is used as the heating light source 1. The optical system includes a first optical system that converts light made of infrared rays into parallel light with directivity, and a second optical system that reflects the parallel light as hollow cylindrical light along the transparent quartz tube. And a third optical system for irradiating the hollow cylindrical light reflected by the second optical system from the periphery of the floating zone.
The first optical system includes a spheroid mirror 2, a parabolic mirror 3, a plane mirror 4, and a cylindrical mirror 5. The second optical system includes a plane mirror 6 disposed around a transparent quartz tube, and a floating zone. And a parabolic mirror 7 disposed around the periphery.
In the first optical system, the heating light source 1 is arranged at one focal position of the spheroid mirror 2 so that the other focal position of the spheroid mirror 2 and the focal position of the parabolic mirror 3 coincide. A paraboloidal mirror 3 is arranged. Infrared radiation emitted from the heating light source 1 passes through another focal point of the spheroid mirror 2 and is reflected by the parabolic mirror 3 to become ring-shaped parallel light. The parallel light is reflected by the plane mirror 4 and the plane mirror 6 inclined by 45- and introduced into the bore of the electromagnet 13. The infrared light directly reflected from the heating light source 2 to the parabolic mirror 3 passes through the cylindrical mirror 5 from the plane mirror 4 and is sent to the plane mirror 6.
The infrared light that has passed through the cylindrical mirror 5 is reflected by the plane mirror 6 constituting the second optical system and introduced into the bore of the electromagnet 13. The infrared light introduced into the bore is reflected by the parabolic mirror 7 and collected.
[0018]
Here, the distance between the plane mirror 4 and the plane mirror 6 sandwiching the cylindrical mirror 5 can be changed according to the capacity of the electromagnet 13 used so that the leakage magnetic field from the electromagnet does not affect the heating light source. Specifically, it is as follows. The leakage magnetic field in the case of a 10 Tesla superconducting magnet is shown in FIG. In the case of a 5 kW xenon lamp, it does not light up with a leakage field of 70 gauss, so the heating light source 1 of the xenon lamp or halogen lamp needs to be separated from the magnetic field center of the electromagnet 13 by 150 cm or more according to this figure. In consideration, the distance between the plane mirror 4 and the plane mirror 6 sandwiching the cylindrical mirror 5 is adjusted so that the distance between the center of the magnetic field of the heating light source 1 and the electromagnet 13 is 150 cm to 200 cm.
[0019]
Further, the diameter of the spheroid mirror 2 can be made larger than the bore diameter of the electromagnet 13, and the reflection efficiency of infrared rays can be increased by making the spheroid mirror 2 larger. Further, the lamp 1, the ellipsoidal mirror 2, and the parabolic mirror 3 may be arranged vertically without using the plane mirror 4.
[0020]
Next, an enlarged view around the crystal growth of the embodiment of the single crystal manufacturing apparatus according to the present invention is shown in FIG. The parabolic mirror 7 is fixed by a parabolic mirror support tube 8, and a small CCD camera 17 and a plane mirror 18 are fixed to the parabolic mirror support tube 8. Since the parabolic mirror support tube 8 is configured to be driven up and down independently of the upper rotary shaft 9 and the lower rotary shaft 10, the paraboloid mirror support tube 8 is moved up and down to move the electromagnet 13. Crystal growth can be performed by changing the magnetic field distribution and the magnetic field strength. 14 is a raw material rod attached to the lower end of the upper rotary shaft 9, 16 is a seed crystal, and 15 is a melting zone that is condensed and heated. The state of crystal growth is reflected by the plane mirror 18 and can be observed through the small CCD camera 17.
[0021]
The drive system includes an upper rotary shaft moving mechanism 20, a quartz tube support tube moving mechanism 21, a lower rotary shaft moving mechanism 22, and a parabolic mirror support bar moving mechanism 23. These drive systems are operated independently. Alternatively, the three moving mechanisms of the upper rotating shaft moving mechanism 20, the quartz tube fixed shaft moving mechanism 21, and the lower rotating shaft moving mechanism 22 can be operated in conjunction with each other. The lower rotating shaft 10 and the quartz tube support tube 12 are attached to the lower rotating shaft moving mechanism 22 and have a function of sliding in the lateral direction.
[0022]
The length of the transparent quartz tube can be shortened by making the quartz tube support tube 12 long. For example, when the bore length of the electromagnet 13 is 60 cm, the length of the quartz tube support tube 12 is preferably not less than 20 cm and not more than 60 cm. By setting the length to 40 cm, the length of the transparent quartz tube 11 becomes 1 m or less, and a commercially available standard transparent quartz tube can be used. When attaching the transparent quartz tube 11, first, the lower rotary shaft moving mechanism 22 is moved to the lowest position, and then the quartz tube support tube 12 is slid sideways to insert the transparent quartz tube 11 into the bore of the electromagnet 13. Then, the quartz tube support tube 12 is returned, and the transparent quartz tube 11 is placed on the quartz tube support tube 12 and fixed. Next, the lower rotary shaft moving machine 22 is raised to pass the transparent quartz tube 11 through the upper part of the bore, and further through the plane mirror 6, and then the quartz tube fixing shaft moving mechanism 21 is lowered and fixed to the upper end of the transparent quartz tube 11. To do. In subsequent operations, the quartz tube support tube moving mechanism 21 and the lower rotating shaft moving mechanism 22 are moved up and down in conjunction with each other.
[0023]
A water cooling jacket is attached along the inner wall of the bore of the electromagnet 13 to prevent the electromagnet 13 from being heated by introducing infrared rays and to obtain a stable magnetic field for a long time.
[0024]
FIG. 4 shows another embodiment of the single crystal manufacturing apparatus according to the present invention. In this embodiment, the optical system is composed of a spheroid mirror 2, a parabolic mirror 3, a cylindrical mirror 5, a plane mirror 6, and a parabolic mirror 7. The horizontal structure in which the plane mirror 4 is removed from the first embodiment. It has become. In this embodiment, the infrared light emitted from the heating light source 1 passes through another focal point of the spheroid mirror 2 and is reflected by the parabolic mirror 3 to become ring-shaped parallel light. The parallel light is reflected by the plane mirror 6 inclined at 45- and introduced into the bore of the electromagnet. The infrared light directly reflected from the heating light source 1 to the parabolic mirror 3 passes through the cylindrical mirror 5 and is then reflected by the plane mirror 6 and introduced into the bore of the electromagnet 13. The infrared light introduced into the bore is reflected by the parabolic mirror 7 and collected.
[0025]
In this case, the distance between the parabolic mirror 3 and the plane mirror 6 is separated from 150 cm to 200 cm so that the leakage magnetic field from the electromagnet 13 does not affect the heating light source 1 according to the capacity of the electromagnet 13 to be used.
[0026]
In each embodiment of the single crystal manufacturing apparatus according to the present invention, the infrared rays radiated from the heating light source 1 such as a xenon lamp or a halogen lamp are reflected by the spheroid mirror 2 and the parabolic mirror 3 so that the ring-shaped parallel light is reflected. Then, the parallel light is reflected by two plane mirrors 4 and 6 inclined by 45 ° or only by the plane mirror 6 and introduced into the bore of the electromagnet 13. And the infrared rays introduced into the bore are reflected by the parabolic mirror 7 and condensed, whereby the entire circumference of the melting zone can be heated uniformly.
[0027]
Further, in the first embodiment, the distance between the two plane mirrors 4 and 6 is changed. In the second embodiment, the distance between the paraboloidal mirror 3 and the plane mirror 6 is changed. Can be prevented. Furthermore, the diameter of the spheroid mirror 2 can be made larger than the bore diameter of the electromagnet 13, and the infrared reflection efficiency can be increased by increasing the size of the spheroid mirror 2.
[0028]
Since the parabolic mirror 7 in the bore of the electromagnet 13 has a structure that can move up and down, crystal growth can be performed at the maximum magnetic field position and the maximum magnetic force position of the electromagnet 13. The state of crystal growth is reflected by the plane mirror 18 and can be observed through the small CCD camera 17.
[0029]
In each embodiment, the drive system includes an upper rotary shaft moving mechanism 20, a quartz tube support tube moving mechanism 21, a lower rotary shaft transfer mechanism 22, and a parabolic mirror support bar moving mechanism 23, and these drive systems are independent. Thus, it is possible to adopt a structure that moves up and down, or moves up and down in conjunction with the three moving mechanisms of the upper rotating shaft moving mechanism 20, the quartz tube support tube moving mechanism 21, and the lower rotating shaft moving mechanism 22. Further, the lower rotary shaft 10 and the quartz tube support tube 12 are attached to the lower rotary shaft moving mechanism 22 and have a function of sliding in the horizontal direction. Therefore, after the quartz tube support tube 12 is slid horizontally, it is transparent. The quartz tube 11 can be inserted into the bore of the electromagnet 13. By incorporating such a quartz tube support tube 12, a standard transparent quartz tube 11 having a length of 1 m or less can be used.
[0030]
【The invention's effect】
According to the magnetic field application type single crystal manufacturing apparatus of the present invention, infrared light emitted from a heating light source such as a xenon lamp or a halogen lamp is converted into a ring-shaped parallel light, and then along the outer periphery of the crystal growth axis in the bore of the electromagnet. By introducing the ring-shaped parallel light and condensing with a parabolic mirror in the bore, the entire circumference of the melting zone can be heated uniformly. Here, since the infrared rays emitted radially from the heating light source are changed to parallel light, the light collection efficiency does not decrease even if the heating light source is moved away from the electromagnet, and the influence of the leakage magnetic field from the electromagnet on the heating light source is prevented. be able to. Therefore, a stable single crystal can be grown under a strong magnetic field, and a new magnetic field effect in melting → solidification can be investigated. In addition, since the position of the melting zone can be changed along the vertical direction of the electromagnet, single crystal growth is possible with various magnetic field distributions and magnetic field strengths, especially single crystal growth under maximum magnetic field and maximum magnetic force. It can be performed.
[0031]
In addition, the quartz tube support tube and the rotating shaft are provided with a function of sliding horizontally from the crystal growth axis, and the transparent quartz tube can be inserted into the bore of the electromagnet. Moreover, a transparent quartz tube of 1 m or less can be used by fixing the transparent quartz tube to the quartz tube support tube. Therefore, the height of the single crystal manufacturing apparatus can be lowered to 3 m or less, and it can be installed in a laboratory for research. In addition, by attaching a transparent quartz tube in this way, the crystal growth part can be shut off from the outside air and various gases can be flowed, and the difference in magnetic field effect due to the atmospheric gas in single crystal growth can be investigated.
[Brief description of the drawings]
FIG. 1 is a plan view showing Example 1 of a magnetic field application type single crystal manufacturing apparatus of the present invention.
FIG. 2 is a relationship diagram between a distance from a 10 Tesla superconducting magnet and a leakage magnetic field.
FIG. 3 is an enlarged view of a crystal growth region of a magnetic field application type single crystal manufacturing apparatus of the present invention.
FIG. 4 is a plan view showing Example 2 of the magnetic field application type single crystal manufacturing apparatus of the present invention.
FIG. 5 is an explanatory view of a conventional infrared intensive heating floating zone single crystal growing apparatus.
FIG. 6 is an explanatory diagram of a conventional laser heating pedestal device.
FIG. 7 is a principle view of a magnetic field application type single crystal manufacturing apparatus to which a conventional technique is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating light source 2 Rotating ellipsoidal mirror 3 Parabolic mirror 4 Plane mirror 5 Cylindrical surface mirror 6 Plane mirror 7 Parabolic mirror 8 Parabolic mirror support tube 9 Upper rotating shaft 10 Lower rotating shaft 11 Transparent quartz tube 12 Quartz tube supporting tube 13 Electromagnet 17 Small CCD camera 18 Plane mirror 20 Upper rotation shaft moving mechanism 21 Quartz tube support tube moving mechanism 22 Lower rotation shaft moving mechanism 23 Parabolic mirror support bar moving mechanism

Claims (3)

A floating zone type single crystal manufacturing device that heats and melts in a transparent quartz tube installed in a vertical direction,
An infrared light source arranged at a position not affected by the leakage magnetic field of the magnetic application means arranged around the floating zone ;
A spheroid mirror disposed around an infrared light source, a parabolic mirror that collimates reflected light from the spheroid mirror, and a cylindrical mirror that guides the light toward a transparent quartz tube A first optical system that converts the light composed of infrared rays into parallel light with directivity;
A second optical system for reflecting the parallel light as hollow cylindrical light along the transparent quartz tube and irradiating the reflected hollow cylindrical light from the periphery of the floating zone;
A magnetic field application type single crystal manufacturing apparatus comprising magnetic application means arranged around a floating zone. 2. The magnetic field application type single crystal manufacturing apparatus according to claim 1, wherein the magnetic application means comprises a superconducting magnet. The drive system of the single crystal manufacturing apparatus includes a lower rotating shaft moving mechanism that slides the lower rotating shaft and the quartz tube support tube in the horizontal direction, and after moving the lower rotating shaft moving mechanism to the lowest position, the lower rotating shaft moving mechanism At the same time, slide the quartz tube support tube horizontally, insert the transparent quartz tube into the floating zone, return the quartz tube support tube to its original position, and place the transparent quartz tube on the quartz tube support tube and fix it. The magnetic field application type single crystal manufacturing apparatus according to claim 1 or 2 .

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