Single crystal fiber manufacturing device and method for manufacturing single crystal fiber

Abstract

The present invention provides a single crystal fiber manufacturing apparatus and a single crystal fiber manufacturing method. The single crystal fiber manufacturing apparatus does not require the high precision control required in conventional single crystal manufacturing apparatus, and can easily maintain a stable state for a long time, and can stably manufacture single crystal fibers with a length of hundreds of meters or more. The single-crystal fiber manufacturing apparatus of the present invention manufactures single-crystal fibers by irradiating the upper surface of a raw material rod with laser light in a chamber to form a molten liquid, impregnating a single crystal seed in the molten liquid, and pulling it upwards. The apparatus includes: a laser light source that irradiates the raw material rod with parallel light; a pulling device configured to move vertically while holding the single crystal seed; and a plane mirror that reflects the laser light so that it is incident vertically onto the upper surface of the raw material rod. Furthermore, the apparatus is configured to irradiate the upper surface of the raw material rod with laser light in a manner that creates a circular temperature distribution in the molten liquid.

Description

Technical Field

[0001] The present invention relates to a single crystal manufacturing apparatus and a single crystal manufacturing method, and more particularly, to a manufacturing apparatus and a manufacturing method for single crystal fibers having an extremely fine diameter of several tens of μm and a length of at least several hundreds of m or more (preferably several km). Prior Art

[0002] In the past, in order to realize the development of novel electronic devices, miniaturization and high performance of electronic components, etc., a manufacturing method for high-quality ultra-fine single crystal fibers has been developed. In the 1980s, centered around Stanford University in the United States, a manufacturing method for single crystal fibers with a diameter of several tens of μm was developed using laser light, and it was named the Laser Heated Pedestal Growth (LHPG) method (Non-Patent Document 1, etc.). However, as will be described later, since the LHPG method must be a method of extremely high-precision control, it has not been put into practical use to date.

[0003] Therefore, for a method with even higher controllability, a pulling method or a μ-PD method, etc., has been developed in which a raw material melt is gradually dropped little by little from a nozzle using a container such as a crucible and solidified below to manufacture a single crystal fiber.

[0004] However, in the methods using such containers, there are often cases where a suitable container material cannot be found depending on the material, or cases where contamination of the raw material melt by the container cannot be ignored, which hinders practical use. Therefore, there is a desire to develop a novel manufacturing method that does not require the use of a container and can stably and cheaply manufacture high-purity and high-quality single crystal fibers. [Prior Art Documents] [Non-Patent Documents]

[0005] [Non-Patent Document 1] R.S. Feigelson, "Pulling optical fibers", Journal of Crystal Growth 79 (1986) 669-680 Summary of the Invention Problems to be Solved by the Invention

[0006] FIG. 5 is a schematic diagram of a single crystal fiber manufacturing apparatus using the conventional LHPG method. As shown in Figure 5, in the single crystal fiber manufacturing apparatus 100, the laser light irradiated from the laser light source 102 is focused onto the upper surface 106a of the raw material rod 106 by the parabolic mirror 104 and melted. After the target single crystal seed 108 with a small diameter is immersed in the obtained melt, it is pulled upward using the pulling device 110.

[0007] Furthermore, the heat of the molten liquid can be absorbed by the seed crystal 108, causing the molten liquid in contact with the seed crystal 108 to solidify and be pulled up. In this way, a single-crystal fiber 112 with the desired diameter can be manufactured. At this time, for continuous and stable manufacturing, as shown in Figure 6, it has been reported that it is preferable to set the ratio of the radius rf of the single-crystal fiber 112 to the radius Rs of the raw material rod 106 to be approximately 1:3.

[0008] When manufacturing single-crystal fibers 112 using a single-crystal fiber manufacturing apparatus 100 operating according to the conventional LHPG method, in order to ensure the stable growth of the single-crystal fibers 112, it is necessary to correctly and precisely control all control factors related to the melting and solidification of the raw material rod, that is, (1) Intensity of laser light irradiation, (2) Laser light irradiation distribution, (3) The location of the laser beam irradiation, (4) Vertical position of the front end of the raw material bar (5) Position of the front end of the raw material bar in the horizontal plane. (6) The upward movement speed of the raw material rod caused by the pulling action of the single crystal fiber. (7) Position of the single crystal fiber in the horizontal plane (8) All factors, including the pulling speed of the single crystal fiber pulled upwards.

[0009] For example, when manufacturing single-crystal fibers with a diameter of 20 μm, the control accuracy of the aforementioned positions must be at least ±2 μm, preferably ±0.2 μm. However, meeting this requirement is extremely difficult and will drive up the price of single-crystal fiber manufacturing equipment to an exorbitant level.

[0010] In view of the current situation, the present invention aims to provide a single crystal fiber manufacturing apparatus and a single crystal fiber manufacturing method. The single crystal fiber manufacturing apparatus does not require high-precision control of the control factors required by the conventional LHPG method, and can easily maintain a stable state for a long time, and can stably manufacture single crystal fibers with a length of hundreds of meters or more. The means to solve the problem

[0011] This invention was invented to solve the problem of "the need for extremely high-precision control of position control in the conventional LHPG method as described above." The single-crystal fiber manufacturing apparatus of the present invention involves irradiating the upper surface of a raw material rod with laser light in a chamber to form a molten liquid, immersing a single crystal seed in the molten liquid, and pulling it upwards to manufacture single-crystal fibers; the single-crystal fiber manufacturing apparatus comprises: The laser light source illuminates the aforementioned laser light in the form of parallel light; The lifting device is configured to move vertically upwards while maintaining the aforementioned single crystal seed; and The plane mirror reflects the aforementioned laser light so that it is incident perpendicularly onto the upper surface of the aforementioned raw material rod; The single-crystal fiber manufacturing apparatus is configured to irradiate the upper surface of the raw material rod with laser light in such a way that the temperature of the melt is distributed in a circular shape.

[0012] In such a single-crystal fiber manufacturing apparatus, it is preferable that the aforementioned laser light has a circular intensity distribution. Furthermore, it is preferable that the radius of the aforementioned raw material rod is more than 10 times the radius of the single crystal fiber to be manufactured. Furthermore, it is preferable that when the radius of the single crystal fiber to be manufactured is less than 100μm, the radius of the aforementioned raw material rod is set to the range of 2mm to 5mm.

[0013] Furthermore, it may also include: a light guide device, which is a laser light guide window that houses the aforementioned chamber and the aforementioned plane mirror.

[0014] In this case, it can also be configured such that ambient gas is introduced into the aforementioned cavity from the aforementioned light guide device.

[0015] Furthermore, it can also possess: position control means, which are used to control the position of the aforementioned single crystal fiber in the horizontal plane within a predetermined limit range.

[0016] Furthermore, the single-crystal fiber manufacturing method of the present invention involves irradiating the upper surface of a raw material rod with a parallel laser light to form a molten liquid, impregnating a single crystal seed in the molten liquid and pulling it upward to manufacture a single-crystal fiber; wherein the laser light is irradiated onto the upper surface of the raw material rod in such a way that the temperature of the aforementioned molten liquid becomes a circular temperature distribution.

[0017] In such a method for manufacturing a single crystal fiber, preferably, the laser light is laser light having an annular intensity distribution. Also, preferably, the radius of the raw material rod is 10 times or more the radius of the single crystal fiber to be manufactured.

[0018] Further, more preferably, when the radius of the single crystal fiber to be manufactured is 100 μm or less, the radius of the raw material rod is set in the range of 2 mm to 5 mm. Advantages of the Invention

[0019] According to the present invention, during the manufacturing process of a single crystal fiber, even if the raw material rod is consumed, the vertical position of the front end portion of the raw material rod only slightly changes. For example, when manufacturing a single crystal fiber with a radius of 10 μm and a length of 100 m using a raw material rod with a radius of 3 mm, the length by which the raw material rod is consumed is only about 1.1 mm.

[0020] Furthermore, since the laser light is perpendicularly irradiated onto the upper surface of the raw material rod from above while maintaining a certain shape, even if the vertical position of the front end portion of the raw material rod slightly decreases, the shape and intensity of the irradiated laser light still remain constant. Therefore, even when manufacturing a single crystal fiber and causing the vertical position of the front end portion of the raw material rod to decrease, it is not necessary to control the position of the raw material rod (the vertical position and the position in the horizontal plane of the front end portion of the raw material rod), and it can be kept fixed.

[0021] Therefore, it is possible to extremely easily maintain a stable state for a long time, and it is possible to stably manufacture a single crystal fiber with a length of several hundred meters or more. Brief Explanation of the Drawings

[0022] FIG. 1 is a schematic diagram for explaining the configuration of the single crystal fiber manufacturing apparatus of the present embodiment. FIG. 2 is a chart showing the intensity distribution of laser light. FIG. 3 is a schematic diagram showing the configuration of the position control means. FIG. 4 is a chart showing the temperature distribution of the melt. FIG. 5 is a schematic diagram of a single crystal fiber manufacturing apparatus using the conventional LHPG method. FIG. 6 is a schematic diagram for explaining the relationship between the radius of the single crystal fiber and the radius of the raw material rod when manufacturing a single crystal fiber using the single crystal fiber manufacturing apparatus shown in FIG. 5. Embodiment

[0023] The following describes in more detail the embodiments (examples) of the present invention, using the manufacturing of lithium fluoride single crystal fibers as an example, based on the drawings. Figure 1 is a schematic diagram illustrating the structure of the monocrystalline fiber manufacturing apparatus of this embodiment.

[0024] As shown in Figure 1, the single-crystal fiber manufacturing apparatus 10 of this embodiment includes: a carbon dioxide gas laser light source 12 for irradiating laser light; an optical system 13 for adjusting the shape of the laser light to the most appropriate diameter and annular intensity distribution; a plane mirror 14 for reflecting the horizontally incident laser light at a right angle so that the laser light irradiates the upper surface 16a of the raw material rod 16; and a winding device 20 for immersing the single crystal seed 18 in the molten liquid formed by melting the upper surface 16a of the raw material rod 16, pulling it upward and winding it onto a drum.

[0025] Furthermore, the raw material rod 16 or single crystal seed 18 is disposed in the chamber 26, and a gas suitable for the target material is introduced into the chamber 26. For example, when manufacturing lithium fluoride single crystal fibers, an ambient gas such as tetrafluoromethane is introduced through the ambient gas introduction device 30. The manufacturing of single crystal fibers 22 is carried out in this chamber 26.

[0026] Furthermore, a laser light guide window (window 26a) is provided in the chamber 26, which is used to guide the parallel laser light irradiated by the external laser light source 12 into the chamber 26.

[0027] In this embodiment, the laser light source 12 is configured to illuminate a parallel laser beam with an annular intensity distribution as shown in FIG2 via the optical system 13. Furthermore, in this embodiment, the optical system 13 includes a beam expander 13a and an axicon lens 13b.

[0028] Furthermore, as shown in Figure 1, the plane mirror 14 is configured to enclose the single crystal seed 18 and is set to reflect the parallel laser light that is horizontally irradiated from the laser light source 12 at a right angle and be incident perpendicularly onto the upper surface 16a of the raw material rod 16.

[0029] The winding device 20 is configured to connect the single crystal seed 18 to a metal wire, for example, with a diameter of 15 μm, and to move the single crystal seed 18 vertically while holding the metal wire. Furthermore, after immersing the single crystal seed in the molten liquid (raw material molten liquid) formed on the upper surface 16a of the raw material rod 16 melted by laser irradiation, it is pulled upward at a predetermined speed and the manufactured single crystal fiber 22 is wound onto a roller at the same time.

[0030] Furthermore, in this embodiment, it is preferable to house the plane mirror 14 and the window 26a located in the chamber 26 within the light guide device 24. In this way, by arranging the plane mirror 14 and the window 26a within the light guide device 24 and allowing ambient gas to be introduced into the light guide device 24, contamination of the plane mirror 14 and the window 26a due to the adhesion of evaporates from the molten metal (raw material molten metal) can be prevented.

[0031] Furthermore, there are no particular limitations on the material used to form the light guide device 24; for example, transparent quartz or stainless steel can be used.

[0032] Furthermore, when configured in this way, it is preferable that the ambient gas is introduced into the light guide device 24 through the inlet hole 24a from the ambient gas inlet device 30 near the window 26a of the chamber 26, and the ambient gas is released into the chamber 26 from the light guide device 24 at a position about 10mm to 20mm above the molten material bar 16.

[0033] The chamber 26 is configured such that a discharge port 24b is provided near the side of the molten material rod 16, and ambient gas is discharged from the discharge port 24b to the outside of the chamber 26. In this way, the chamber 26 can be maintained in a state of ambient gas suitable for manufacturing single crystal fibers 22.

[0034] Furthermore, in this embodiment, a position control means 17 is provided to suppress the swaying of the manufactured single crystal fiber 22 in the horizontal plane. The position control means 17 is not particularly limited as long as it is configured to control the swaying of the single crystal fiber 22 in the horizontal plane within a predetermined limit range.

[0035] The position control means 17 is configured, for example, to arrange the circular ring 17a as shown in FIG3(a) or the four fine lines 17b as shown in FIG3(b) orthogonally at a predetermined interval. By allowing the single crystal fiber 22 to pass through the inner side of such a circular ring 17a or the area surrounded by the lines 17b, the swaying of the single crystal fiber 22 can be suppressed by the circular ring 17a or the lines 17b.

[0036] Furthermore, when manufacturing single-crystal fibers 22 with a diameter of approximately tens of μm, it is preferable that the diameter of the circular rings 17a or the spacing between the arranged lines 17b be approximately 100 μm.

[0037] In the monocrystalline fiber manufacturing apparatus 10 configured in this embodiment, a raw material rod 16 with a radius at least 10 times the radius of the monocrystalline fiber 22 to be manufactured is used. In particular, when the radius of the monocrystalline fiber 22 to be manufactured is 100 μm or less, the radius of the raw material rod is preferably set to the range of 2 mm to 5 mm. By irradiating the upper surface 16a of such a raw material rod 16 with laser light, the irradiated area of ​​the raw material rod 16 is melted and liquefied. Furthermore, the outer diameter of the laser light is preferably set to be almost the same as or slightly larger than the diameter of the raw material rod 16. By optimizing the outer diameter of the laser light in this way, the entire upper surface 16a of the raw material rod 16 can be stably melted to obtain a molten liquid.

[0038] At this time, the temperature distribution of the molten material formed on the upper surface 16a of the raw material rod 16 is as shown in Figure 4, with the temperature at the outer periphery slightly higher than that at the center (in this specification, such a temperature distribution is referred to as "annular temperature distribution"). This is because a laser light with an annular intensity distribution as shown in Figure 2 is irradiated, and the intensity distribution of the laser light is stronger at the periphery than near the center. Therefore, near the center of the molten material (raw material molten material) formed by irradiating the upper surface 16a of the raw material rod 16, the amount of laser light irradiation is less, and the heating is also less. Furthermore, the molten material (raw material molten material) near the center is heated by heat conduction from the molten material at the periphery, which has become high-temperature due to irradiation by high-intensity laser light, so its temperature is lower than that of the periphery.

[0039] Furthermore, the temperature of the melt near the center of the upper surface of the raw material rod 16 constructed in this way can be reduced even if the intensity of laser light irradiation changes slightly, and the temperature of the raw material melt can be stably maintained.

[0040] If the seed crystal 18 is attached to the molten material rod 16 in this state, heat will be taken away by the seed crystal 18 due to thermal conduction, so the molten material in contact with the seed crystal 18 will solidify and can be pulled up. At this time, although the manufactured single crystal fiber 22 is impregnated in the molten material with a diameter that is sufficiently larger than the diameter of the single crystal fiber 22 to be manufactured, the temperature of the interface between the single crystal fiber 22 and the molten material is lowered by the thermal conduction of the manufactured single crystal fiber 22, so single crystallization can continue.

[0041] Furthermore, the heat conducted to the single-crystal fiber 22 is dissipated from the surroundings in the form of radiated heat, and the single-crystal formation continues. In this way, when the thermal conductivity of the single-crystal fiber 22 material is high, the pulling speed can be increased. Even with raw materials with low thermal conductivity, when the single-crystal fiber 22 has a small diameter, the surface area ratio is high. Therefore, by means of heat radiation from the surface, compared with conventional bulk single-crystal manufacturing methods, such as the pulling method commonly used in industry, it is possible to pull at a much higher speed and manufacture high-quality single-crystal fibers 22 at a lower cost.

[0042] Furthermore, when the temperature of the molten liquid is distributed in a circular pattern, even if the positional accuracy of the seed crystal 18 is not precise, the temperature of the part of the molten liquid in contact with the raw material rod 16 will hardly change, thus having almost no impact on the growth of the single crystal.

[0043] Furthermore, in this invention, since the laser light is directly and perpendicularly irradiated onto the upper surface 16a of the raw material rod 16 without focusing, even if the raw material rod 16 is consumed and shortened during the manufacturing process of the single crystal fiber 22, the radius of the raw material rod 16 is still very large compared to the radius of the single crystal fiber 22, so the length by which the raw material rod 16 shortens is limited. Therefore, the intensity of the laser light irradiating the upper surface 16a of the raw material rod 16 is always constant, and the amount of molten liquid formed on the upper surface 16a of the raw material rod 16 does not change. Therefore, even if the manufacturing of the single crystal fiber 22 continues, if the length (change) due to the consumption of the raw material rod 16 is within about 20 mm, it is not necessary to change the vertical position of the front end of the raw material rod 16.

[0044] Therefore, according to the single crystal fiber manufacturing apparatus 10 of the present invention, it is not necessary to control the irradiation position of the laser light, or the vertical and horizontal positions of the front end of the raw material rod. Furthermore, compared to the conventional LHPG method, it is not necessary to have high-precision control over the irradiation intensity of the laser light or the horizontal position of the single crystal seed.

[0045] Furthermore, according to the single-crystal fiber manufacturing apparatus 10 of the present invention, even when using decomposed and melted substances or solid solution substances as single-crystal materials, high-precision control is not required, and stable continuous manufacturing can be carried out over a long period of time.

[0046] When using a decomposed molten material or a solid solution material as the single crystal material, the melt is adjusted to a composition in which the solid components of the single crystal fiber 22 to be manufactured coexist in equilibrium with the liquid phase (hereinafter referred to as the "solvent"). In this case, generally speaking, the melting point of the solvent is mostly tens of degrees lower than the melting point of the material of the single crystal fiber 22 to be manufactured.

[0047] Even in such a case, by using a raw material rod 16 with a very large radius relative to the radius of the single crystal fiber 22 to be manufactured, that is, by manufacturing the single crystal fiber 22 from a solvent with a large diameter, even if the position of the single crystal fiber 22 (that is, the position of the single crystal seed 18) changes by tens of μm, the temperature of the solvent hardly changes, so the degree of influence on the growth of the single crystal can be ignored.

[0048] Furthermore, when using decomposed and melted substances or solid solutions as single-crystal materials, the radius of the raw material rod 16 is preferably more than 100 times the radius of the single-crystal fiber 22 to be manufactured, and more preferably around 2 mm to 5 mm. This is because, as the single crystal grows, it is better to stably maintain the range in which the more concentrated component (boundary region) of the solvent emitted from the solid-liquid interface due to solution diffusion is homogenized, and this also stabilizes the growth of the single crystal.

[0049] As the single-crystal fiber 22 grows, although the composition and amount of the solvent may change, the composition tends to shift towards lower melting points. If the amount of solvent decreases, the solvent will pass through, and the amount of laser light reaching the interface between the solvent and the raw material rod will increase, thus promoting the dissolution of the raw material rod in the solvent. Therefore, the composition and amount of the solvent are usually kept constant. As a result, the composition and diameter of the grown single-crystal fiber 22 are usually constant, and single-crystal fibers 22 of a certain diameter can be manufactured according to a predetermined composition.

[0050] The above describes a preferred embodiment of the present invention, but the invention is not limited thereto. For example, in the above embodiment, a laser with a circular intensity distribution is used to set the temperature of the molten material bar 16 to a circular temperature distribution. However, the laser light may also have a Gaussian intensity distribution. When using a laser with a Gaussian intensity distribution, a light shield may be placed along the optical path of the laser light to reduce the temperature near the center. Thus, various modifications can be made without departing from the purpose of the present invention.

[0051] 10,100: Single-crystal fiber manufacturing equipment 12,102: Laser source 13: Department of Optics 13a: Beam expander 13b: Conical lens 14: Plane mirror 16,106: Raw material bars 16a, 106a: Upper surface 17: Position control methods 17a: Circular ring 17b: Line 18,108: Single crystal seed 20: Winding device 22,112: Monocrystalline fiber 24: Light guides 24a: Inlet hole 24b: Discharge port 26: Chamber 26a: Window 30: Ambient gas introduction device 104: Parabolic mirror 110: Pulling device

Claims

1. A single-crystal fiber manufacturing apparatus, comprising: irradiating the upper surface of a raw material rod with laser light in a chamber to form a molten liquid; immersing a single crystal seed in the molten liquid and pulling it upwards to manufacture a single-crystal fiber; the apparatus comprising: a laser light source for irradiating the laser light in the form of parallel light; a pulling device configured to move vertically upwards while holding the single crystal seed; and a plane mirror for reflecting the laser light so that it is incident vertically onto the upper surface of the raw material rod; wherein... The single-crystal fiber manufacturing apparatus is configured to irradiate the upper surface of the aforementioned raw material rod with laser light in such a way that the temperature of the aforementioned melt is in a ring-shaped temperature distribution such that the temperature of the peripheral part of the melt is higher than that of the center part.

2. The monocrystalline fiber manufacturing apparatus as described in claim 1, wherein, The aforementioned laser light is a circular intensity distribution laser light in which the intensity of the peripheral portion of the laser light is stronger than the intensity of the central portion of the laser light.

3. The monocrystalline fiber manufacturing apparatus as described in claim 1 or 2, wherein, The radius of the aforementioned raw material rod is more than 10 times the radius of the single crystal fiber to be manufactured.

4. The monocrystalline fiber manufacturing apparatus as described in claim 3, wherein, When the radius of the single crystal fiber to be manufactured is less than 100μm, the radius of the aforementioned raw material rod is set to be in the range of 2mm to 5mm.

5. The monocrystalline fiber manufacturing apparatus as described in claim 1 further comprises: a light guide device, which is a laser light guide window that houses the aforementioned chamber and the aforementioned planar reflector.

6. The monocrystalline fiber manufacturing apparatus as described in claim 5 is configured to introduce ambient gas from the aforementioned light guide into the aforementioned chamber.

7. The monocrystalline fiber manufacturing apparatus as described in claim 1 further comprises: a position control means for controlling the position of the aforementioned monocrystalline fiber in a horizontal plane within a predetermined limit range.

8. A method for manufacturing single-crystal fibers, comprising irradiating the upper surface of a raw material rod with parallel laser light to form a molten liquid, impregnating a single-crystal seed in the molten liquid and pulling it upwards to manufacture single-crystal fibers; wherein, The laser light is irradiated onto the upper surface of the aforementioned raw material rod in such a way that the temperature of the aforementioned melt is in a ring-shaped temperature distribution such that the temperature of the peripheral part of the melt is higher than that of the center part.

9. The method for manufacturing single-crystal fibers as described in claim 8, wherein, The aforementioned laser light is a circular intensity distribution laser light in which the intensity of the peripheral portion of the laser light is stronger than the intensity of the central portion of the laser light.

10. The method for manufacturing single-crystal fibers as described in claim 8 or 9, wherein, The radius of the aforementioned raw material rod is more than 10 times the radius of the single crystal fiber to be manufactured.

11. The method for manufacturing single-crystal fibers as described in claim 10, wherein, When the radius of the single crystal fiber to be manufactured is less than 100μm, the radius of the aforementioned raw material rod is set to be in the range of 2mm to 5mm.

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