Equipment and method for growing large-size crystal by TSSG (Triglyceride Sulfonate

Abstract

The invention discloses a device and method for growing large-size crystals through a TSSG method, the device comprises a sleeve layer crucible assembly, the sleeve layer crucible assembly comprises an outer crucible and an inner crucible arranged in the outer crucible, the outer crucible is fixed on the surface of a crucible platform, the bottom of the outer crucible is provided with a convex column, and the convex column is fixed on the surface of the crucible platform. The convex column penetrates through the bottom of the inner crucible and extends into the inner crucible; and the heating piece surrounds the outer portion of the jacket layer crucible assembly, the bottom of the heating piece is fixedly connected with the heat preservation layer, and the top of the heating piece is fixedly connected with the inner crucible. According to the invention, a heat source is generated on the crucible through the heating element, and the outer crucible can rotate relative to the inner crucible, so that the effects of promoting melt convection and ensuring solute transmission in the crystal growth process can be realized, and the growth of high-thickness and large-caliber crystals is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal material preparation, and in particular relates to a device and a method for growing large-size crystals using a TSSG method. Background Art

[0002] The Top Seeded Solution Growth (TSSG) method is a crystal growth method that combines the Czochralski method with the flux method. The TSSG method growth device is similar to the Czochralski method, that is, the seed crystal is fixed at the lower end of the seed crystal rod, and the seed crystal is slowly lowered. When the temperature of the seed crystal is roughly the same as the temperature of the solution, the seed crystal is contacted with the saturated solution in the crucible, and then the solution is slowly cooled, and the seed crystal is slowly pulled upward, and the crystal grows slowly.

[0003] However, the current TSSG method has many problems when growing large-sized crystals: the axial length is not thick and the radial length is not large. Taking silicon carbide crystals as an example, the conventional TSSG method usually uses a high-purity inner crucible as a container and carbon source, and sets the temperature gradient by induction heating. Its growth process includes three steps: dissolving carbon in the high-temperature area of ​​the crucible, transferring carbon atoms from the high-temperature area at the bottom of the crucible to the low-temperature area at the top seed crystal through thermal convection, and crystallizing carbon and silicon atoms on the seed crystal in the low-temperature area to form SiC. However, the conventional TSSG method has certain disadvantages: ① It is impossible to grow thicker SiC crystals; ② It is difficult to ensure the quality of the grown large-sized SiC crystals. This is because, in the conventional TSSG method, as the SiC crystals continue to grow, the ratio of C and Si components in the high-temperature solution will change dynamically. Since the C element comes from the inner crucible, its content in the solution will not change significantly; however, the Si content will continue to decrease, resulting in a significant change in the ratio of the solution components, making it impossible to grow thicker SiC crystals. At the same time, the process of Si and C diffusing to the crystal interface to grow SiC crystals requires controlling the flow of solution to provide Si and C solutes; however, the convection intensity generated by the temperature gradient and the rotation of the crucible is weak, and it is difficult to ensure the quality of growing large-sized SiC crystals. These problems also exist in the process of growing other large-sized crystals (such as β-BaB2O4 crystals or LaBGeO5 crystals) by the TSSG method.

[0004] In summary, it is urgent to find new methods and process conditions to solve the problem that the reduction of some raw materials in the process of growing large-sized crystals by the TSSG method results in their axial length being not thick, and the poor diffusion of solutes in high-temperature solutions results in their radial length being not large, thus making it impossible to prepare large-sized crystals (6-8 inches in diameter, thickness >20mm). Summary of the invention

[0005] In view of this, the primary purpose of the present invention is to provide a device for growing large-sized crystals by the TSSG method. By arranging a jacket crucible with an inner crucible inside an outer crucible, the flow of solution is controlled during crystal growth, melt convection is promoted, and solute transmission is ensured, so that the crystal can grow well in both axial and radial directions, and large-sized crystals with thick thickness and large diameter can be prepared.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention first provides a device for growing large-size crystals using a TSSG method, comprising:

[0008] A heat preservation cylinder, wherein a rotatable crucible platform is arranged in the heat preservation cylinder, and a heat preservation layer is arranged on the inner wall of the heat preservation cylinder;

[0009] A layer crucible assembly, comprising an outer crucible and an inner crucible disposed in and separated from the outer crucible, wherein the outer crucible is fixed to the surface of the crucible platform, and a convex column is disposed at the bottom of the outer crucible, and the convex column penetrates the bottom of the inner crucible and extends into the inner crucible;

[0010] a heating element, the heating element surrounding the outside of the jacket crucible assembly, the bottom of the heating element being fixedly connected to the insulation layer, and the top of the heating element being fixedly connected to the inner crucible;

[0011] And a seed crystal rod, the seed crystal rod extends into the inner crucible, and the end of the seed crystal rod extending into the inner crucible is provided with a seed crystal.

[0012] The crystal growth equipment provided in the present invention can be used for growing crystals by the TSSG method, including but not limited to silicon carbide crystals, β-BaB2O4 crystals or LaBGeO5 crystals. The crystal growth equipment can promote the transport or supply of solutes to the crystallization interface, thereby obtaining large-sized crystals with thick thickness and large diameter.

[0013] Taking the growth of large-sized silicon carbide crystals as an example, the device in the present invention is designed with a layered crucible. When growing SiC crystals, a suitable proportion of Si powder and transition metal element powder are placed in the inner crucible of the inner layer, and Si powder is placed between the outer crucible and the inner crucible. The solution formed by melting the Si powder and transition metal element powder in the inner crucible has a high solubility in graphite (the inner crucible provides a carbon source), which can ensure the supply of solutes for the growth of SiC crystals; at the same time, the Si solution formed by the Si powder between the outer crucible and the inner crucible has a low solubility in graphite, and the Si source can be continuously replenished during the crystal growth process, thereby ensuring that the SiC crystal continues to grow to a certain thickness.

[0014] Furthermore, the present invention designs an outer crucible to be fixed on a crucible platform, and an inner crucible is separated from the outer crucible, so that the outer crucible can rotate relative to the inner crucible. At the same time, a convex column is provided at the bottom of the outer crucible, and the convex column penetrates the bottom of the inner crucible and extends into the inner crucible, so as to mechanically stir the high-temperature solution in the inner crucible; at the same time, the seed crystal is controlled to rotate in the opposite direction to the outer crucible, thereby increasing the convection intensity of the solution, controlling the transport of the solute to the crystallization interface, and ensuring that the crystal grows in the radial direction.

[0015] The device provided in the present invention can be used to prepare crystals with high thickness and large diameter.

[0016] In the present invention, the insulation tube mainly plays the role of insulation and heat preservation, and can be made of any material with insulation, heat preservation and heat insulation in the art. Preferably, the insulation tube is a more conventional quartz insulation tube in the art.

[0017] In the present invention, the thermal insulation layer is a conventional thermal insulation felt in the art.

[0018] In a further embodiment, the heating element described in the present invention can be an induction heating element or a resistance heating element, which can be selected according to the crystal to be grown. In some specific embodiments of the present invention, the heating element is an induction heating element, and an induction coil is arranged outside the heat preservation tube, and an alternating electromagnetic field is generated by the induction coil, and a heat source is generated on the jacket crucible assembly through the induction heating element, thereby achieving the purpose of crystal growth.

[0019] In a further embodiment, the centers of the outer crucible, the protruding column, the inner crucible and the heating element are located on the same axis.

[0020] In a further embodiment, in the invention, the function of the protrusion is to mechanically stir the solution in the inner crucible while the outer crucible rotates relative to the inner crucible. The protrusion may be a triangular prism, a quadrangular prism or a hexagonal prism, or a spiral prism in the shape of a spiral blade, so as to further enhance the stirring effect.

[0021] In some specific embodiments of the present invention, it is understood that the jacket crucible assembly must be located in the central area of ​​the heating during crystal growth, which can be achieved by designing the crucible platform as a lifting platform, for example, in some specific embodiments of the present invention, the crucible platform is a rotatable lifting crucible platform. It can also be achieved by designing the movement of the external induction coil, for example, in other specific embodiments, the external induction coil can be lifted and lowered.

[0022] In the present invention, the shell crucible assembly (outer crucible and inner crucible) and the heating element are different according to the different crystals to be grown, and can be selected according to actual needs. Generally speaking, the shell crucible assembly should have the advantages of high temperature resistance, anti-adhesion and no cracking at high temperature, and can be used repeatedly. For example, in some specific embodiments of the present invention, the grown crystal is a silicon carbide crystal, and the material of the outer crucible, inner crucible and the heating element is graphite; in other specific embodiments, the grown crystal is a β-BaB2O4 crystal or a LaBGeO5 crystal, and the material of the outer crucible, inner crucible and the heating element is platinum.

[0023] The second aspect of the present invention provides a method for growing large-size crystals using a TSSG method, which is based on the above-mentioned equipment and comprises the following steps:

[0024] A portion of raw material powder is placed in the inner crucible, and another portion of raw material powder is placed between the outer crucible and the inner crucible;

[0025] After the furnace is evacuated, it is filled with inert gas and kept at a constant pressure;

[0026] The heating element works to completely melt the powders in the outer crucible and the inner crucible;

[0027] The crucible platform and the seed crystal rod are rotated at the same time, and the two rotate in opposite directions, and the seed crystal is slowly lowered to the surface of the solution in the inner crucible, and the crystal growth begins to obtain a crystal.

[0028] In the present invention, the distribution of raw materials between the inner crucible and the outer crucible and between the inner crucible can be designed according to the different crystals grown. For example, in some specific embodiments of the present invention, the grown crystal is a silicon carbide crystal, then the inner crucible is loaded with Si powder and transition metal M powder, and Si powder is loaded between the outer crucible and the inner crucible. Wherein, the transition metal M is Ti, Cr or Fe. It can be understood that the transition metal M powder and Si powder used are high-purity powders with a purity of not less than 99.9%. Specifically, the mass ratio of Si powder and transition metal M powder in the inner crucible can be confirmed according to actual needs based on methods known in the art. For example, in some specific implementation cases, the mass ratio is (3 to 5): 1, for example, it can be any ratio of 3: 1, 4: 1, 5: 1.

[0029] For other crystals, the technicians in this field will make allocations based on the specific circumstances. The technicians in this field have such ability, so it will not be elaborated here.

[0030] In the present invention, vacuuming means that the vacuum degree is not less than 10 -4 Pa.

[0031] In the present invention, the inert gas refers to an inert or inactive gas that does not participate in the reaction, for example, nitrogen or a rare gas (such as helium, argon, etc.). In some specific implementation cases, the inert gas used is helium. After the inert gas is filled, the constant pressure is 4×10 4 Pa~6×10 4 Pa, for example, it can be 4×10 4 Pa, 4.5×10 4 Pa, 5×10 4 Pa or 6×10 4 Any pressure in Pa.

[0032] It is understandable that the specific heating can be induction heating or resistance heating. For example, induction heating can be achieved by adjusting the current or voltage of the coil. The specific method can be confirmed by methods known in the art and is not specifically limited here.

[0033] In the present invention, the method further comprises a cooling step, wherein the cooling rate is 4 to 8°C / h, for example, any rate of 4°C / h, 5°C / h, 6°C / h, 7°C / h or 8°C / h.

[0034] Beneficial effects of the present invention:

[0035] The equipment for growing large-size crystals by the TSSG method proposed in the present invention adopts a jacketed crucible design, in which an outer crucible located on the outer layer rotates and stirs the solution relative to an inner crucible inside it, controls the flow of the high-temperature solution, promotes solute transmission, and allows the crystal to grow radially to a large diameter; at the same time, a portion of the raw materials is placed in the inner crucible, and another portion of the raw materials is placed between the outer crucible and the inner crucible, thereby promoting melt convection during crystal growth, ensuring solute transmission, and allowing the crystal to grow axially to a thicker crystal.

[0036] The device and method of the present invention can be used to prepare large-sized crystals with thick thickness and large diameter, which promotes the development of large-sized crystal growth technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the internal cross-sectional structure of an apparatus for growing large-size crystals using the TSSG method in a preferred embodiment of the present invention.

[0038] In the figure: 11-outer crucible, 12-convex column, 21-inner crucible, 22-induction heating element, 3-crucible cover, 4-crucible platform, 51-seed crystal rod, 52-seed crystal, 6-insulation layer, 7-insulation cylinder, 8-induction coil. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In addition, unless otherwise specified, methods that do not specifically record conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial sources.

[0041] Example 1

[0042] This embodiment provides a device for growing large-size crystals using the TSSG method, and its structure is as follows: Figure 1 As shown in the figure, it includes a heat preservation tube 7, which defines a containing space for placing components such as a crucible. An induction coil 8 is provided on the outside of the heat preservation tube 7. The induction coil 8 is used to excite and generate an alternating electromagnetic field. Through induction heating, a heat source is generated on the components such as the crucible inside the heat preservation tube 7, thereby achieving the purpose of crystal growth.

[0043] Specifically, a layered crucible assembly is provided in the heat preservation cylinder 7, which includes an outer crucible 11 and an inner crucible 21 provided in the outer crucible 11, wherein the inner crucible 21 and the outer crucible 11 are separated, that is, the two do not contact each other. The outer crucible 11 is fixed on the crucible platform 4, and the crucible platform 4 has lifting and rotating functions, so that the outer crucible 11 can be rotated and lifted under the drive of the crucible platform 4. On the one hand, the position of the outer crucible 11 can be controlled to be in the center position of induction heating, and on the other hand, the outer crucible 11 can rotate relative to the inner crucible 21.

[0044] The outer crucible 11 has the advantages of high temperature resistance, anti-adhesion and no cracking at high temperature, and can be used repeatedly. In this embodiment, the outer crucible 11 and the inner crucible 21 are both made of graphite. Figure 1 A convex column 12 is protruded from the bottom of the outer crucible 11, and the convex column 12 passes through the bottom of the inner crucible 21 and extends into the inner crucible 21. Its function is to exert a mechanical stirring effect while the outer crucible 11 rotates. The shape of the convex column 12 is not particularly limited, and it can be a triangular prism, a quadrangular prism or a hexagonal prism that is more common in the art, and it can also be a spiral prism in the shape of a spiral blade, so as to further improve the effect of mechanical stirring.

[0045] Furthermore, the inner crucible 21 is fixed by an induction heating element 22. In the present embodiment, the induction heating element 22 is a graphite tube. Specifically, the induction heating element 22 is arranged along the inner surface of the insulation tube 7, and the induction heating element 22 surrounds the outside of the outer crucible 11. A circle of flanges is provided at the opening edge of the inner crucible 21, and the flange of the inner crucible 21 is fixed to the top of the induction heating element 22, and the bottom of the induction heating element 22 is fixed to the insulation layer 6. In the present invention, the insulation layer 6 is provided on the inner surface of the insulation tube 7, and its material is insulation felt, which is more common in the art. It can be understood that a crucible cover 3 is also provided at the opening of the inner crucible 21, and an insulation layer 6 is also provided on the surface of the crucible cover 3 to achieve an excellent insulation effect.

[0046] Furthermore, the device of the present invention further comprises a seed crystal rod 51, which penetrates the crucible cover 3 and extends into the inner crucible 21. It is understandable that the seed crystal rod 51 also has the functions of lifting and rotating. Figure 1 A seed crystal 52 is provided at the end of the seed crystal rod 51 extending into the inner crucible 21. The specific connection method can be to glue the seed crystal 52 to the end of the seed crystal rod 51 using conventional high-temperature adhesive bonding in the art; or a seed crystal holder can be provided at the end of the seed crystal rod 51 to fix the seed crystal 52 on the seed crystal holder.

[0047] In addition, the induction coil 8 in this embodiment is a radio frequency power supply coil conventionally used in the art.

[0048] In this embodiment, preferably, the centers of the seed crystal rod 51 , the seed crystal 52 , the inner crucible 21 , the induction heating element 22 , the outer crucible 11 , the protruding column 12 and the crucible platform 4 are all on the same axis.

[0049] During specific operation, a portion of raw material powder is placed in the inner crucible 21, and another portion of raw material powder is placed between the outer crucible 11 and the inner crucible 21. The outer crucible 11 is controlled to be located at the center of the induction coil 8 by lifting and lowering the crucible platform 4. An alternating electromagnetic field is generated by the induction coil 8, and a heat source is generated on the induction heating element 22, the inner crucible 21 and the outer crucible 11 by induction heating, so that the powder inside is melted under the action of high temperature to form a high-temperature solution. During the crystal growth process, the outer crucible 11 rotates driven by the crucible platform 4, and the seed crystal rod 51 drives the seed crystal 52 to rotate in the opposite direction to the outer crucible 11. By growing crystals through the equipment of the present invention, solutes can be continuously replenished during the crystal growth process to ensure that the crystals continue to grow to a certain thickness. At the same time, due to the rotation of the outer crucible 11 relative to the inner crucible 21 and the mechanical stirring effect of the convex column 12, the solution convection intensity is increased, the solute is controlled to be transported to the crystal interface, and the crystal grows in the radial direction, thereby preparing a crystal with thick thickness and large caliber.

[0050] Example 2

[0051] In this embodiment, taking the growth of silicon carbide crystal as an example, a method for growing large-size crystals by a TSSG method is provided. The method is based on the crystal growth equipment in Example 1, and the specific steps are as follows:

[0052] S1. Fix the outer crucible 11 on the crucible platform 4 and install the insulation layer 6; and place the inner crucible 21 in the outer crucible 11, maintaining central symmetry, the inner crucible 21 is fixed to the top of the induction heating element 22, and the bottom of the induction heating element 22 is fixed on the insulation layer 6.

[0053] S2. High-purity Si powder and Cr powder in a mass ratio of 4:1 are placed in the inner crucible 21 , and high-purity Si powder is placed between the inner crucible 21 and the outer crucible 11 .

[0054] S3 . The outer crucible 11 is raised to the center of the induction coil 8 by using the lifting function of the crucible platform 4 .

[0055] S4. Use high temperature glue to stick the seed crystal 52 in the

[0001] direction to the end of the seed crystal rod 51.

[0056] S5. Evacuate the furnace to 10 -4 After the pressure is reduced, high-purity He gas is injected and the pressure is kept constant at 5×10 4 Pa; start the induction coil 8 to heat the outer crucible 11, the induction heating element 22 and the inner crucible 21, so that the high-purity powder raw material in the outer crucible 11 and the inner crucible 21 is completely melted to form a high-temperature solution.

[0057] S6, rotating the crucible platform 4 and the seed crystal 52 in opposite directions, and slowly lowering the seed crystal 52 to the surface of the solution in the inner crucible 12 to start crystal growth.

[0058] S7. After the crystal growth is completed, cool down to room temperature at a rate of 6°C / h and take out the crystal.

[0059] According to tests, the silicon carbide crystal grown by the preparation method in this embodiment has a diameter of 6 to 8 inches and a thickness of more than 20 mm.

[0060] It can be understood that the growth equipment and growth method in the present invention are also applicable to other TSSG crystal growth, such as β-BaB2O4 crystal or LaBGeO5 crystal, etc., without special limitations. The specific condition parameters can be determined by experiments based on methods known in the art, so they will not be elaborated one by one here.

[0061] The device and method of the present invention can be used to prepare large-sized crystals with thick thickness and large diameter, which promotes the development of large-sized crystal growth technology.

[0062] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A device for growing large-size crystals by TSSG method, characterized in that: include: A heat preservation cylinder, wherein a rotatable crucible platform is arranged in the heat preservation cylinder, and a heat preservation layer is arranged on the inner wall of the heat preservation cylinder; A layer crucible assembly, comprising an outer crucible and an inner crucible disposed in and separated from the outer crucible, wherein the outer crucible is fixed to the surface of the crucible platform, and a convex column is disposed at the bottom of the outer crucible, and the convex column penetrates the bottom of the inner crucible and extends into the inner crucible; a heating element, the heating element surrounding the outside of the jacket crucible assembly, the bottom of the heating element being fixedly connected to the insulation layer, and the top of the heating element being fixedly connected to the inner crucible; and a seed crystal rod, wherein the seed crystal rod extends into the inner crucible, and a seed crystal is arranged at the end of the seed crystal rod extending into the inner crucible.

2. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The heat-insulating cylinder is a quartz heat-insulating cylinder.

3. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The thermal insulation layer is thermal insulation felt.

4. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The centers of the outer crucible, the convex column, the inner crucible and the heating element are located on the same axis.

5. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The convex column is a triangular prism, a quadrangular prism, a hexagonal prism or a spiral prism.

6. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The heating element is an induction heating element or a resistance heating element; Preferably, the heating element is an induction heating element, and an induction coil is provided outside the heat preservation cylinder, and induction heating is achieved by the induction coil and the induction heating element.

7. The device for growing large-size crystals by the TSSG method according to claim 1, characterized in that: The outer crucible, the inner crucible and the heating element are made of graphite or platinum.

8. A method for growing large-size crystals by TSSG method, using the device according to any one of claims 1 to 7, characterized in that: The following steps are involved: A portion of raw material powder is placed in the inner crucible, and another portion of raw material powder is placed between the outer crucible and the inner crucible; After the furnace is evacuated, it is filled with inert gas and kept at a constant pressure; The heating element works to completely melt the powders in the outer crucible and the inner crucible; The crucible platform and the seed crystal rod are rotated at the same time, and the two rotate in opposite directions, and the seed crystal is slowly lowered to the surface of the solution in the inner crucible to start crystal growth, thereby obtaining a large-sized crystal; Preferably, the method further comprises a cooling step, and the cooling rate is 4-8°C / h.

9. The method for growing large-size crystals by the TSSG method as claimed in claim 8, characterized in that: The large-size crystal is a silicon carbide crystal, Si powder and transition metal M powder are placed in the inner crucible, and Si powder is placed between the outer crucible and the inner crucible; Preferably, the transition metal M is Ti, Cr or Fe.

10. The method for growing large-size crystals by TSSG method according to claim 8, characterized in that: The inert gas is helium.

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