A device for removing polycrystalline from the gas-liquid interface of solution-grown crystals

Abstract

The present invention discloses a device for removing polycrystalline at the gas-liquid interface of solution-grown crystals, comprising a lifting control mechanism and a stirring paddle mechanism, wherein the lifting control mechanism is composed of an electromagnet and a spring to control the axial position of the stirring paddle in the crucible, and the stirring paddle is composed of a connecting shaft and a stirring block arranged near the inner wall of the crucible, and its rotation speed is controlled by a motor fixed on a furnace body, and during the crystal growth preparation period, the closed circuit is powered off, and the stirring paddle is away from the solution surface under the action of the spring support force and does not rotate; during the crystal growth process, the electromagnet generates magnetic force to compress the spring, so that the stirring paddle position is lowered, and driven by the motor, it rotates at a certain speed on the solution surface. The present invention can remove the polycrystalline hard interface layer that grows along the inner wall of the crucible toward the center at the gas-liquid interface during the solution-grown crystal process, promote the dissolution of the solute, enhance the mass transfer effect of the solute in the solution, and improve the crystal growth rate and growth quality.

Description

Technical Field

[0001] The invention belongs to the field of solution method crystal growth devices, and in particular relates to a device for removing polycrystals at the gas-liquid interface of solution method crystal growth. Background Art

[0002] Currently, the commonly used crystal growth methods include melt growth, solution growth, vapor phase growth and solid phase growth. Among them, the solution method has the advantages of low growth temperature, large crystal volume and good uniformity, and is widely used in the growth of semiconductor crystals such as silicon carbide and gallium nitride.

[0003] Solution method crystal growth is a method of first dissolving the constituent elements (solutes) of the crystal in another solution (solvent), then obtaining a supersaturated solution by changing state parameters such as temperature and vapor pressure, and finally allowing the solute to precipitate from the solution to form a crystal. During the crystal growth process, due to the influence of factors such as the thermal field, it is easy to cause the solution supersaturation along the inner wall of the crucible at the gas-liquid interface to be relatively large, thereby forming a polycrystalline hard interface layer that grows along the inner wall of the crucible toward the center at the gas-liquid interface. This process not only consumes the solutes in the solution used for crystal growth, but also reduces the contact area between the gas solute and the solution, thereby reducing the crystal growth rate and limiting the crystal growth size. For example, when growing silicon carbide crystals by the solution method, the graphite crucible dissolves in the solution to provide carbon elements for crystal growth. The carbon element concentration at the inner wall of the crucible on the surface of the solution is high, and a polycrystalline hard interface layer is easily formed. Gallium nitride crystals, also a third-generation semiconductor, can be obtained through the flux method. During its growth process, nitrogen dissolves from the surface of the solution into the solution, so the highest concentration of nitrogen in the solution is near the surface of the solution. Therefore, GaN can easily reach supersaturated crystallization in this area, resulting in the formation of a polycrystalline hard interface layer. In order to solve the above problems, there is an urgent need for a simple and controllable device that effectively removes the gas-liquid interface of polycrystalline crystals grown by the solution method.

[0004] Currently, the following patent can be retrieved regarding the removal of polycrystalline at the gas-liquid interface in a solution-based crystal growth device. The Chinese patent with application number CN201510838898.4, authorization publication number CN105256372B, and authorization publication date September 7, 2018, proposes a GaN crystal growth device including a movable seed template driven by a coil, but the main purpose of this patent is to ensure that the seed template is always in the best growth solution environment. The movable seed template proposed can only move in a radial or axial straight line, and cannot remove the polycrystalline hard interface layer generated along the inner wall of the crucible at the gas-liquid interface in the initial stage of the reaction. Summary of the invention

[0005] The purpose of the present invention is to provide a device for removing polycrystals at the gas-liquid interface of solution-grown crystals, which effectively destroys the polycrystal hard interface layer on the surface of the solution by controlling the movement of a stirring paddle on the gas-liquid interface, effectively prevents the consumption of solutes in the solution used for crystal growth, and enhances the mass transfer of solutes in the solution by stirring the liquid; for the crystal growth process that requires the dissolution of gas solutes, the contact area between the gas solute and the solution can be maximized, which helps to further dissolve the gas solute in the solution and improve the growth rate of the crystal in the crucible.

[0006] To achieve the above object, the present invention adopts the following technical scheme to achieve the above object: a device for removing polycrystalline at the gas-liquid interface of solution-grown crystals, comprising a lifting control mechanism and a stirring paddle mechanism, the stirring paddle mechanism is arranged on the axis of the furnace body, and the stirring paddle mechanism comprises a motor, a stirring shaft and a stirring paddle; the motor is arranged on the top of the furnace body, the active end of the stirring shaft is connected to the motor output shaft, the driven end of the stirring shaft is provided with a circular slider, the connecting surface of the stirring shaft and the slider is provided with an anti-rotation structure, the end surface of the driven end of the stirring shaft is provided with a circular support plate, a spring is arranged between the circular slider and the circular support plate, and the circular slider is connected to the stirring paddle; the lifting control mechanism is arranged above the circular slider, the lifting control mechanism comprises a closed loop, a power supply, a first electromagnet, a second electromagnet and a conductive slip ring, coils with opposite spiral directions are arranged on the first electromagnet and the second electromagnet, the coils and the power supply are connected to the closed loop, the coil of the first electromagnet is connected to the stator of the conductive slip ring, the coil of the second electromagnet is connected to the rotor of the conductive slip ring, the second electromagnet is connected to the circular slider, and the first electromagnet is relatively fixedly arranged with the stirring shaft.

[0007] The motor is connected to the frequency converter, and the frequency converter and the power supply of the closed loop are both connected to the output end of the computer system.

[0008] The conductive slip ring is sleeved on the outer side of the stirring shaft, and the first electromagnet and the second electromagnet are symmetrically arranged about the stirring shaft.

[0009] The anti-rotation structure adopts a spline-spline groove.

[0010] The stirring paddles are evenly arranged around the circular slider, and the stirring paddles include a connecting shaft and a stirring block. The connecting shaft connects the circular slider and the stirring block, and a gap is left between the stirring block and the inner wall of the crucible.

[0011] The stirring paddles are V-shaped in the vertical plane and are provided in two groups. The stirring blocks are in the shape of cylinders, and the connecting line thereof forms a straight line intersecting with the axis of the stirring shaft.

[0012] The stirring paddles are arranged in three groups, which are cylindrical in shape, and the connecting line thereof forms a regular triangle plane perpendicular to the axis of the stirring shaft.

[0013] The stirring paddles are V-shaped and are arranged in two groups, and the stirring block is in the shape of a cone.

[0014] The stirring paddle is made of corrosion-resistant metal molybdenum or boron nitride.

[0015] The maximum compression of the spring is less than the distance from the top surface of the stirring block to the surface of the solution.

[0016] Compared with the prior art, the present invention has the following beneficial effects: when the closed circuit is powered on, the first electromagnet generates a magnetic field with an S pole at the top and an N pole at the bottom, and the second electromagnet generates a mutually exclusive magnetic field with an N pole at the top and an S pole at the bottom. The circular slider drives the stirring paddle downward under the action of the repulsive force and compresses the spring. The spring can effectively reduce the impact caused by the descent of the slider, and its maximum compression amount should be less than the distance from the top surface of the stirring block to the surface of the solution. When the closed circuit is powered off, under the action of the spring support force, the circular slider drives the stirring paddle upward and away from the surface of the solution; the position of the stirring paddle is regulated to make the stirring paddle rotate on the surface of the solution to break the stirring paddle. The polycrystalline hard interface layer at the gas-liquid interface during the growth of the ring crystal promotes the dissolution of the solute and enhances the mass transfer of the solute in the solution; while keeping the reaction device sealed, the position and speed of the stirring paddle are changed in real time, which can not only effectively remove the polycrystalline hard interface layer growing toward the center along the inner wall of the crucible, but also enhance the flow below the gas-liquid interface, so that the solute is quickly transferred to the inside of the mixed solution, thereby improving the crystal growth rate and growth quality; at the same time, the upper part of the circular slider is fixedly connected to the second electromagnet, and the second electromagnet is connected to the conductive slip ring rotor. When working, the rotor of the conductive slip ring can rotate at the same speed as the stirring shaft to prevent the line from being entangled.

[0017] Furthermore, the stirring paddle mechanism motor is connected to a frequency converter and a computer system, so that the stirring paddle can be started smoothly during operation, thereby preventing sudden start and stop from causing excessive current and splashing of the mixed solution.

[0018] Furthermore, the stirring paddle is composed of a connecting shaft and a stirring block, has a simple structure, is easy to process, and reduces the processing cost; during use, only the stirring block is immersed in the solution, which effectively reduces the contact area between the stirring paddle and the solution and prevents crystallization on the surface of the stirring paddle.

[0019] Furthermore, the stirring paddle is symmetrically arranged at the bottom of the circular slider. Its material is corrosion-resistant metal molybdenum or boron nitride. It consists of a connecting shaft and a stirring block. The stirring block is arranged near the inner wall of the crucible. The distance between the stirring paddle and the axis of the stirring shaft is slightly smaller than the radius of the crucible, so as to effectively remove the polycrystalline hard interface layer that grows toward the center along the inner wall of the crucible.

[0020] Furthermore, the motor of the stirring paddle mechanism is connected to a frequency converter, and the frequency converter and the closed-loop power supply are connected to a computer system to achieve remote control of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of a device for removing the gas-liquid interface of polycrystals grown by the solution method.

[0022] Figure 2 Schematic diagram of the stirring paddle mechanism.

[0023] Figure 3 Schematic diagram of the lifting control mechanism.

[0024] Figure 4 This is a schematic diagram of the structure of stirring paddle embodiment 1.

[0025] Figure 5 This is a schematic diagram of the structure of stirring paddle embodiment 2.

[0026] Figure 6 This is a schematic diagram of the structure of stirring paddle embodiment 3.

[0027] Explanation of symbols in the figure: 1-stirring paddle mechanism, 101-motor, 102-circular support plate, 103-stirring paddle, 1031-stirring block, 1032-connecting shaft, 104-circular slider, 105-stirring shaft, 2-furnace body, 3-insulation material layer, 4-sleeve, 5-heater, 6-support shaft, 7-support plate, 8-solution, 9-gas solute, 10-crucible, 11-lifting control mechanism, 1101-closed loop, 1102-power supply, 1103-first electromagnet, 1104-second electromagnet, 1105-spring, 1106-conductive slip ring, 12-valve, 13-computer system, 14-inverter. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, the device of the present invention is directed to a device for growing crystals by a solution method, comprising an existing furnace body 2, a heat-insulating material layer 3, a sleeve 4, a heater 5 and a crucible 10, wherein the crucible 10 is arranged at the center of the furnace body 2, and the sleeve 4, the heater 5 and the heat-insulating material layer 3 are arranged in sequence on the outside of the crucible 10, wherein the heat-insulating material layer 3 is fully surrounded, and the crucible 10 is arranged above the support plate 7 through a support shaft 6. The device for removing polycrystalline at the gas-liquid interface of solution-grown crystals of the present invention comprises a lifting control mechanism 11 and a stirring paddle mechanism 1, and the stirring paddle 103 is rotated at a certain speed on the surface of the solution 8 by regulating the position and speed of the stirring paddle 103.

[0030] Provided is a device for removing polycrystalline at the gas-liquid interface of solution-grown crystals, comprising a lifting control mechanism 11 and a stirring paddle mechanism 1, wherein the stirring paddle mechanism 1 is arranged on the axis of a furnace body 2, and the stirring paddle mechanism 1 comprises a motor 101, a stirring shaft 105 and a stirring paddle 103; the motor 101 is arranged on the top of the furnace body 2, the active end of the stirring shaft 105 is connected to the output shaft of the motor 101, a circular slider 104 is arranged at the driven end of the stirring shaft 105, an anti-rotation structure is arranged at the connecting surface of the stirring shaft 105 and the circular slider 104, a circular support plate 102 is arranged at the end surface of the driven end of the stirring shaft 105, a spring 1105 is arranged between the circular slider 104 and the circular support plate 102, and the circular slider 104 The circular slider 104 is connected to the stirring paddle 103; the lifting control mechanism 11 is arranged above the circular slider 104, and the lifting control mechanism 11 includes a closed loop 1101, a power supply 1102, a first electromagnet 1103, a second electromagnet 1104 and a conductive slip ring 1106. Coils with opposite spiral directions are arranged on the first electromagnet 1103 and the second electromagnet 1104, and the coils and the power supply 1102 are connected to the closed loop. The coil of the first electromagnet 1103 is connected to the stator of the conductive slip ring, the coil of the second electromagnet 1104 is connected to the rotor of the conductive slip ring, the second electromagnet 1104 is connected to the circular slider 104, and the first electromagnet 1103 and the stirring shaft 105 are relatively fixed.

[0031] See also Figure 2 The stirring paddle mechanism 1 includes a motor 101, a stirring shaft 105 connected to the motor output shaft, and a stirring paddle 103 connected to the stirring shaft 105 through a circular slider 104. The circular slider 104 is splined to the stirring shaft 105 to achieve the lifting and lowering movement of the slider along the axial direction and the rotational movement with the shaft. The stirring paddle 103 is symmetrically arranged at the bottom of the circular slider 104. The stirring paddle 103 is made of corrosion-resistant metal molybdenum or BN and is composed of a connecting shaft 1032 and a stirring block 1031. The stirring block 1031 is arranged near the inner wall of the crucible 10.

[0032] The stirring paddle mechanism motor 101 is fixed on the top of the furnace body 2, and a protruding circular support plate 102 is provided at the bottom of the stirring shaft 105 connected thereto. Figure 3The spring 1105 fixed on the circular support plate 102 and the first electromagnet 1103 fixed on the top of the sleeve 4 form a lifting control mechanism 11, wherein the spring 1105 is fixedly connected to the circular slider 104, and the second electromagnet 1104 is arranged on the upper part of the circular slider 104. The second electromagnet 1104 is connected to the rotor of the conductive slip ring, and together with the first electromagnet 1103 and the conductive slip ring stator, it forms a closed loop 1101. The stirring paddle mechanism motor 101 is connected to the inverter 14, and the inverter 14 and the closed loop power supply 1102 are connected to the computer system 13. When the closed loop 1101 is passed with current, the first electromagnet 1103 and the second electromagnet 1104 generate mutually repulsive magnetic fields. The circular slider 104 drives the stirring paddle 103 to move downward under the action of repulsion and compresses the spring to reduce the impact. When the stirring block 1031 is on the surface of the solution 8, the motor 101 drives the stirring paddle 103 to rotate to destroy the polycrystalline hard interface layer at the gas-liquid interface. When the closed loop 1101 is powered off, the circular slider 104 moves upward and away from the surface of the solution 8 under the action of the spring support force.

[0033] Regarding the specific structure of the stirring paddle 103, there are three preferred embodiments as follows:

[0034] Example 1

[0035] like Figure 4 As shown, the stirring paddle 103 is V-shaped and symmetrically arranged at the bottom of the circular slider 104. It consists of two sets of connecting shafts 1032 and a stirring block 1031. The stirring block 1031 is in the shape of a cylinder and is arranged near the inner wall of the crucible 10. The connecting line thereof constitutes a straight line intersecting the axis of the stirring shaft 105.

[0036] During the preparation period for crystal growth, the computer system 13 is regulated to keep the closed loop 1101 powered off. At this time, under the action of the spring support force, the circular slider 104 is away from the surface of the solution 8.

[0037] After the preparation is completed, the valve 12 and the heater 5 are controlled, the temperature and pressure are increased to the preset growth conditions, and the crystal begins to grow. During the growth process, since the polycrystalline hard interface layer is easily generated at the gas-liquid interface and grows toward the center along the inner wall of the crucible 10, the solute required for crystal growth is consumed. To this end, the computer system 13 is regulated, and the closed loop 1101 is passed with current, and the first electromagnet 1103 and the second electromagnet 1104 generate mutually repelling magnetic fields. Under the action of repulsive force, the circular slider 104 drives the stirring paddle 103 to move down and compress the spring. When the stirring paddle 103 is on the surface of the solution 8, the computer system 13 is regulated, and the stirring paddle mechanism motor 101 works, driving the stirring paddle 103 to rotate at a certain speed, destroying the polycrystalline hard interface layer on the surface of the solution, strengthening the flow below the gas-liquid interface, and enhancing the mass transfer of the solute in the solution 8, effectively improving the crystal growth rate and growth quality.

[0038] When the growth is completed, the computer system 13 is regulated, the stirring paddle 103 stops rotating, the current of the closed loop 1101 is disconnected, and under the action of the spring support force, the circular slider 104 drives the stirring paddle 103 to move upward and away from the surface of the solution 8, and the temperature and pressure are reduced to remove the crystal.

[0039] Example 2

[0040] like Figure 5 As shown, the stirring paddle 103 is composed of three groups of connecting shafts 1032 and stirring blocks 1031. The stirring blocks 1031 are all arranged near the inner wall of the crucible 10 and are cylindrical in shape. The connecting lines thereof form a regular triangle plane perpendicular to the axis of the stirring shaft 105. The computer system 13 is regulated by the same steps as in Example 1, and the position and speed of the stirring paddle 103 working in the crucible 10 are controlled by the lifting control mechanism 11 and the stirring paddle mechanism 1. The results show that this stirring paddle structure can also effectively remove the polycrystalline hard interface layer growing along the inner wall of the crucible 10 toward the center at the gas-liquid interface, and enhance the mass transfer of the solute in the solution 8.

[0041] Example 3

[0042] like Figure 6 As shown, the stirring paddle 103 is V-shaped and symmetrically arranged at the bottom of the circular slider 104. It is composed of two sets of connecting shafts 1032 and stirring blocks 1031. The stirring blocks 1031 are all arranged near the inner wall of the crucible 10 and are in the shape of a cone. The connecting line forms a straight line intersecting the axis of the stirring shaft 105. The computer system 13 is regulated by taking the same steps as in Example 1, and the position and speed of the stirring paddle 103 working in the crucible 10 are controlled by the lifting control mechanism 11 and the stirring paddle mechanism 1. The results show that this stirring paddle structure can further reduce the contact area between the stirring paddle 103 and the solution 8, prevent crystallization on the surface of the stirring paddle 103, and can also effectively remove the polycrystalline hard interface layer growing along the inner wall of the crucible toward the center at the gas-liquid interface, thereby enhancing the mass transfer of the solute in the solution 8.

[0043] In summary, the device described in the present invention effectively destroys the polycrystalline hard interface layer on the surface of the solution by controlling the movement of the stirring paddle on the gas-liquid interface, effectively prevents the consumption of solutes used for crystal growth in the solution, and enhances the mass transfer of solutes in the solution by stirring the liquid; for the crystal growth process that requires the dissolution of gas solute 9, the contact area between the gas solute and the solution can be maximized, which helps to further dissolve the gas solute in the solution and increase the growth rate of the crystal in the crucible.

[0044] The above description is only a preferred example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the patent application should be included in the protection scope of the present invention.

Claims

1. A device for removing polycrystalline from the gas-liquid interface of solution-grown crystals, characterized in that: The invention comprises a lifting control mechanism (11) and a stirring paddle mechanism (1), wherein the stirring paddle mechanism (1) is arranged on the axis of a furnace body (2), and comprises a motor (101), a stirring shaft (105), and a stirring paddle (103); the motor (101) is arranged on the top of the furnace body (2), the active end of the stirring shaft (105) is connected to the output shaft of the motor (101), a circular slider (104) is arranged at the driven end of the stirring shaft (105), an anti-rotation structure is arranged at the connecting surface of the stirring shaft (105) and the circular slider (104), a circular support plate (102) is arranged at the end surface of the driven end of the stirring shaft (105), a spring (1105) is arranged between the circular slider (104) and the circular support plate (102), and the circular slider (104) is connected to the stirring paddle. (103); the lifting control mechanism (11) is arranged above the circular slider (104), and the lifting control mechanism (11) comprises a closed loop (1101), a power supply (1102), a first electromagnet (1103), a second electromagnet (1104) and a conductive slip ring (1106); coils with opposite spiral directions are arranged on the first electromagnet (1103) and the second electromagnet (1104); the coils and the power supply (1102) are connected to the closed loop, the coil of the first electromagnet (1103) is connected to the stator of the conductive slip ring, the coil of the second electromagnet (1104) is connected to the rotor of the conductive slip ring, the second electromagnet (1104) is connected to the circular slider (104), and the first electromagnet (1103) and the stirring shaft (105) are relatively fixedly arranged.

2. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 1, characterized in that: The motor (101) is connected to the frequency converter (14), and the frequency converter (14) and the closed-loop power supply (1102) are both connected to the output end of the computer system (13).

3. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 1, characterized in that: The conductive slip ring (1106) is sleeved on the outside of the stirring shaft (105), and the first electromagnet (1103) and the second electromagnet (1104) are symmetrically arranged with respect to the stirring shaft (105).

4. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 1, characterized in that: The anti-rotation structure adopts a spline-spline groove.

5. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 1, characterized in that: The stirring paddle (103) is evenly arranged around the circular slider (104), and the stirring paddle (103) comprises a connecting shaft (1032) and a stirring block (1031). The connecting shaft (1032) connects the circular slider (104) and the stirring block (1031), and a gap is left between the stirring block (1031) and the inner wall of the crucible.

6. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 5, characterized in that: The stirring paddles (103) are V-shaped in a vertical plane and are provided in two groups. The stirring blocks (1031) are in the shape of cylinders, and the connecting line thereof forms a straight line intersecting the axis of the stirring shaft (105).

7. The device for removing polycrystals at the gas-liquid interface of solution-grown crystals according to claim 5, characterized in that: Three groups of stirring paddles (103) are provided, each of which is cylindrical in shape, and the connecting line of the stirring paddles (103) forms a regular triangle plane perpendicular to the axis of the stirring shaft (105).

8. The device for removing polycrystals from the gas-liquid interface of solution-grown crystals according to claim 5, characterized in that: The stirring paddles (103) are V-shaped and are provided in two groups, and the stirring block (1031) is in the shape of a cone.

9. The device for removing polycrystals from the gas-liquid interface of solution-grown crystals according to claim 5, characterized in that: The maximum compression amount of the spring (1105) is less than the distance from the top surface of the stirring block (1031) to the surface of the solution.

10. The device for removing polycrystals from the gas-liquid interface of solution-grown crystals according to claim 1, characterized in that: The stirring paddle is made of corrosion-resistant metal molybdenum or boron nitride.

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