Apparatus and method for dynamically adjusting axial temperature gradient during crystal growth

Abstract

The application provides a device and method for dynamically adjusting an axial temperature gradient in a crystal growth process, and belongs to the technical field of silicon carbide crystal production. The device comprises a crucible main body, a crucible cover provided with an opening, a seed crystal rod, and a temperature adjusting device; one end of the seed crystal rod is connected to a seed crystal holder for carrying a seed crystal, the seed crystal holder is placed in the crucible main body during the growth process, and the other end is sleeved with the temperature adjusting device; the temperature adjusting device comprises an adjusting assembly, a connecting assembly, and a transmission assembly; the adjusting assembly is made of graphite soft felt and is provided with a through hole in the center, and the seed crystal rod passes through the through hole; the transmission assembly is connected to the adjusting assembly through the connecting assembly and controls the adjusting assembly to move up and down along the seed crystal rod to realize axial temperature regulation; the adjusting assembly is in a contracted state during the up and down movement, and is expanded through the transmission assembly when being in contact with the crucible cover or the seed crystal holder. The scheme realizes axial temperature regulation in the crystal growth process.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal production technology, and in particular to a device and method for dynamically adjusting the axial temperature gradient during crystal growth. Background Technology

[0002] Silicon carbide, as one of the most important third-generation semiconductor materials, has unique characteristics such as a large bandgap and a high critical breakdown field strength, making it an ideal material for manufacturing high-frequency, high-power, radiation-resistant and light-resistant integrated devices. It is currently widely used in many fields such as new energy vehicles, 5G communications, and aerospace.

[0003] For liquid-phase silicon carbide single crystal growth technology, the required axial temperature gradient varies throughout the entire crystal growth process, depending on the specific crystal growth requirements. A larger axial temperature gradient is needed during the growth stage to increase the crystal growth rate; a smaller temperature gradient is needed during the cooling stage to allow the crystal to cool slowly and uniformly, reducing internal stress differences and thus lowering the cracking rate. However, because the crystal growth system is located inside a "black box" at high temperatures, dynamic control of the temperature field has always been a challenge in liquid-phase silicon carbide single crystal growth. Therefore, there is an urgent need to develop a device and method for dynamically adjusting the axial temperature gradient during crystal growth. Summary of the Invention

[0004] This invention provides a device and method for dynamically adjusting the axial temperature gradient during crystal growth, thereby achieving axial temperature control during crystal growth, reducing the probability of crystal cracking, and improving crystal quality.

[0005] In a first aspect, the present invention provides a device for dynamically adjusting the axial temperature gradient during crystal growth, the device comprising a crucible body, a crucible lid with an opening, a seed crystal rod, and a temperature adjustment device;

[0006] One end of the seed crystal rod is connected to the seed crystal holder that carries the seed crystal. During the growth process, the seed crystal holder is placed inside the crucible body. The other end is fitted with the temperature regulation device.

[0007] The temperature regulating device includes a regulating component, a connecting component, and a transmission component;

[0008] The adjusting component is made of graphite felt and has a through hole in the center, through which the seed crystal rod passes. The transmission component is connected to the adjusting component through the connecting component and controls the adjusting component to move up and down along the seed crystal rod to achieve axial temperature control. The adjusting component is in a contracted state during the up and down movement. When the adjusting component moves to the crucible cover or the seed crystal holder, the transmission component unfolds the adjusting component so that the adjusting component is laid flat on the upper surface of the crucible cover or the seed crystal holder.

[0009] Preferably, the thickness of the adjustment component is 2~30mm;

[0010] The diameter of the through hole is 20~100mm, and the diameter of the through hole is larger than the diameter of the seed crystal rod.

[0011] Preferably, the width of the adjustment component after unfolding is 25~250mm.

[0012] Preferably, when the adjusting component can be laid flat on the upper surface of the crucible lid, the unfolded width is greater than the opening size of the crucible lid; when the adjusting component can be laid flat on the upper surface of the seed crystal holder, the unfolded width is the same as the size of the seed crystal holder.

[0013] Preferably, the connecting assembly includes a mechanical connecting rope and a collar; one end of the mechanical connecting rope is fixedly connected to the outer edge of the adjusting assembly, and the other end is connected to the collar; the collar is used to pass through the seed crystal rod and is connected to the transmission assembly.

[0014] Preferably, the adjustment component is connected to at least eight mechanical connecting ropes, and the connection points of the mechanical connecting ropes are evenly distributed on the outer edge of the adjustment component.

[0015] Preferably, the mechanical connecting rope is a molybdenum wire with a purity greater than 99.5% or a tungsten wire with a purity greater than 99.5%; wherein, the length of the mechanical connecting rope is greater than 1 / 2 of the opening size of the crucible lid;

[0016] The collar is made of silicon carbide, molybdenum, or tungsten.

[0017] Preferably, the transmission assembly achieves the raising, lowering, and lowering of the mechanical connecting rope by moving and / or rotating.

[0018] Preferably, the transmission assembly includes a robotic arm or a transmission rod.

[0019] Preferably, the device further includes: a rotating turntable; the rotating turntable includes several different adjustment components for axial temperature control by rotating to select the desired adjustment component.

[0020] Preferably, the device further includes: a heating device, a heat insulation layer, and a lifting device; the crucible body is placed inside the heating device, and the heating device is placed inside the heat insulation layer; the lifting device is used to control the lifting and rotation of the seed crystal rod.

[0021] Preferably, the insulation layer has a channel in the middle, through which the seed crystal rod enters the interior of the crucible body via the channel and the crucible cover; wherein, the width of the adjustment component in the contracted state is smaller than the diameter of the channel; and the diameter of the channel is larger than the diameter of the seed crystal holder.

[0022] In a second aspect, the present invention also provides a method for dynamically adjusting the axial temperature gradient during crystal growth, employing any of the apparatus described in the first aspect above, comprising:

[0023] (1) The growth material is placed in the crucible body and heated to obtain a melt;

[0024] (2) The seed crystal holder carrying the seed crystal is placed inside the crucible body and in contact with the melt to grow silicon carbide;

[0025] (3) During the growth process, the transmission component drives the connection component to move, thereby controlling the adjustment component, which is in a contracted state, to move downward along the seed crystal rod until it contacts the crucible cover or the seed crystal holder, thereby controlling the transmission component to unfold and achieving axial temperature control.

[0026] Preferably, the method further includes:

[0027] Based on the detected temperature of the seed crystal holder, determine the target temperature required for the current growth stage;

[0028] The adjustment component is selected from the rotating dial based on the target temperature.

[0029] Preferably, step (3) further includes:

[0030] The transmission assembly controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be in a retracted state. Then, the transmission assembly moves the retracted adjustment assembly downwards along the seed crystal rod, passing through the holes of the insulation layer and the crucible cover until it contacts the seed crystal holder. The transmission assembly then controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be laid flat on the upper surface of the seed crystal holder.

[0031] Compared with the prior art, the present invention has at least the following advantages:

[0032] The present invention provides a device for dynamically adjusting the axial temperature gradient during crystal growth. This device, by adding a temperature control mechanism, can precisely control the temperature difference between the upper surface of the seed crystal holder and the seed crystal, and between the seed crystal and the raw material. This achieves dynamic and precise adjustment of the axial temperature field at the crystal end during growth, thereby reducing the risk of crystal cracking and improving crystal quality and the yield of complete finished products. Thus, the device provided by the present invention has excellent heat preservation capabilities and can reduce the heating power required to maintain high temperatures, significantly reducing energy consumption. Furthermore, the stable thermal field and higher crystal quality improve raw material utilization, thereby reducing production costs and bringing significant economic benefits. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a device for dynamically adjusting the axial temperature gradient during crystal growth, provided in an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of a planar structure of an adjustment component provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of another device for dynamically adjusting the axial temperature gradient during crystal growth, provided in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of the retraction and extension process of an adjustment component provided in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a planar structure of a rotating turntable according to an embodiment of the present invention;

[0039] Figure 6 This is a flowchart of a method for dynamically adjusting the axial temperature gradient during crystal growth, provided by an embodiment of the present invention;

[0040] Reference numerals: 10-Cruise body, 20-Cruise lid with opening, 30-Seed crystal rod, 301-Seed crystal holder, 40-Temperature regulating device, 400-Regulating component, 401-Connecting component, 4011-Mechanical connecting rope, 4012-Loop, 402-Transmission component, 50-Growth raw material, 60-Rotating turntable, 70-Heating device, 80-Insulation layer, 90-Induction coil. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] The following describes the specific implementation of the concept in this application.

[0043] Please refer to Figure 1 The present invention provides a device for dynamically adjusting the axial temperature gradient during crystal growth. The device includes a crucible body 10, a crucible cover 20 with an opening, a seed crystal rod 30, and a temperature adjustment device 40.

[0044] One end of the seed crystal rod 30 is connected to the seed crystal holder 301 that carries the seed crystal. During the growth process, the seed crystal holder 301 is placed inside the crucible body 10, and the other end is fitted with the temperature regulating device 40.

[0045] The temperature regulating device 40 includes an regulating component 400, a connecting component 401, and a transmission component 402;

[0046] The adjusting component 400 is made of graphite felt and has a through hole in the center, through which the seed crystal rod 30 passes. The transmission component 402 is connected to the adjusting component 400 through the connecting component 401 and controls the adjusting component 400 to move up and down along the seed crystal rod 30 to achieve axial temperature control. The adjusting component 400 is in a retracted state during the up and down movement. When the adjusting component 400 moves to the crucible cover 20 or the seed crystal holder 301, the transmission component 402 unfolds the adjusting component 400 so that the adjusting component 400 is laid flat on the upper surface of the crucible cover 20 or the seed crystal holder 301.

[0047] The present invention provides a device for dynamically adjusting the axial temperature gradient during crystal growth. This device, by adding a temperature regulating mechanism, can precisely control the temperature difference between the upper surface of the seed crystal holder and the seed crystal, and between the seed crystal and the raw material. This achieves dynamic and precise adjustment of the axial temperature field at the crystal end during growth, thereby reducing the risk of crystal cracking and improving crystal quality and the yield of complete finished products. Thus, the device provided by the present invention has excellent heat preservation capabilities and can reduce the heating power required to maintain high temperatures, significantly reducing energy consumption. Furthermore, the stable thermal field and higher crystal quality improve raw material utilization, thereby reducing production costs and bringing significant economic benefits.

[0048] It should be noted that the crucible body 10 and the crucible lid 20 can be connected, for example, by a threaded connection. Specifically, the crucible lid 20 is screwed onto the upper edge of the crucible body 10. In this invention, the crucible body 10 and the crucible lid 20 are made of graphite. During the liquid-phase growth of silicon carbide, the growth raw material 50 is contained inside the crucible body 10. The crucible body 10 provides space for the growth of silicon carbide crystals and also serves as a carbon source to provide the carbon required for the reaction of silicon carbide crystal growth. Figure 1 The diagram shows a scenario where the adjustment component 400 is positioned above the seed crystal rod and in a retracted state. When the connecting component lifts the adjustment component, because the adjustment component is made of graphite felt, it automatically retracts due to gravity, presenting the following position. Figure 1The contraction state is shown.

[0049] In a preferred embodiment, the thickness of the adjustment component is 2 to 30 mm (for example, it can be 2 mm, 3 mm, 5 mm, 8 mm, 10 mm, 15 mm, 18 mm, 20 mm, 22 mm, 25 mm, 26 mm, 28 mm or 30 mm).

[0050] The diameter of the through hole is 20~100mm (for example, it can be 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm or 100mm), and the diameter of the through hole is larger than the diameter of the seed crystal rod.

[0051] In a preferred embodiment, the width of the adjustable component after unfolding is 25~250mm (for example, it can be 25mm, 30mm, 40mm, 50mm, 60mm, 80mm, 100mm, 120mm, 150mm, 160mm, 180mm, 200mm, 220mm or 250mm).

[0052] In this invention, the adjusting component can be made of graphite soft felt, but its ash content should be less than 100 ppm to avoid excessive impurities affecting the crystal growth quality. The thickness of the adjusting component is set between 2 and 30 mm, and can be adjusted according to actual needs. The adjusting component can be composed of multiple layers of graphite soft felt stacked together, and its thermal insulation performance can be changed according to different stacking thicknesses and stacking methods; the specific selection depends on process requirements. The diameter of the through-hole in the adjusting component, provided it is larger than the diameter of the seed crystal rod and can pass through the seed crystal rod for vertical movement, can be adjusted together with the thickness of the adjusting component according to thermal insulation requirements; the smaller the through-hole diameter, the better the thermal insulation performance.

[0053] In one specific implementation, the adjustment component can be a graphite felt with uniform thickness or a graphite felt with gradient thickness. In this way, the temperature difference between the crystal center and the edge can be precisely controlled by designing the thickness and the through-hole size, so as to achieve dynamic and precise adjustment of the radial temperature field at the crystal end during the growth process, and further improve the crystal quality.

[0054] In a preferred embodiment, such as Figure 3 As shown, the connecting assembly 401 includes a mechanical connecting rope 4011 and a collar 4012; one end of the mechanical connecting rope 4011 is fixedly connected to the outer edge of the adjusting assembly 400, and the other end is connected to the collar 4012; the collar 4012 is used to pass through the seed crystal rod 30 and is connected to the transmission assembly 402.

[0055] In a preferred embodiment, the adjustment component 400 is connected to at least eight (e.g., eight, ten, twelve, etc.) mechanical connecting ropes 4011, and the connection points of the mechanical connecting ropes 4011 are evenly distributed on the outer edge of the adjustment component 400.

[0056] In this invention, the adjusting component includes, but is not limited to, a circular (i.e., ring) or square shape with a through hole in the center. For example... Figure 2 As shown, the adjustment component is a circle with a through hole in the center and has 8 evenly distributed connection points for connecting to, for example... Figure 3 The mechanical connecting rope shown. Figure 3 The illustration shows the scene where the adjustment assembly is fitted onto the seed crystal rod and unfolds flat on the crucible lid as it moves down to the lid.

[0057] In a preferred embodiment, the mechanical connecting rope 4011 is a molybdenum wire with a purity greater than 99.5% or a tungsten wire with a purity greater than 99.5%; wherein the length of the mechanical connecting rope 4011 is greater than 1 / 2 of the opening size of the crucible lid 20.

[0058] In this embodiment of the invention, by uniformly connecting at least eight mechanical connecting ropes along the outer edge of the adjusting component, not only is a tight connection between the adjusting component and the connecting component ensured, but the multiple mechanical connecting ropes also ensure stable and smooth up-and-down movement of the adjusting component, thereby ensuring that the adjusting component can be smoothly placed on the upper surface of the crucible lid or seed crystal holder. The length of the mechanical connecting ropes is greater than 1 / 2 of the opening size of the crucible lid to ensure that the adjusting device can be smoothly deployed. It should be noted that the mechanical connecting ropes can be metal wires made of high-temperature resistant materials with high purity and no volatile impurities, thus not affecting the quality of the silicon carbide crystal.

[0059] In a preferred embodiment, the collar 4012 is made of silicon carbide, molybdenum, or tungsten.

[0060] It should be noted that the diameter of the collar is larger than the diameter of the seed crystal rod to allow it to be fitted onto the seed crystal rod. The purity of the materials used for the collar is greater than 99.5%.

[0061] In a preferred embodiment, the transmission assembly 402 achieves the raising, lowering, and retraction of the mechanical connecting rope 4011 by moving and / or rotating. For example, raising and lowering the transmission assembly can raise and lower the mechanical connecting rope, while rotating the transmission assembly or a combination of rotation and raising and lowering can achieve the retraction and retraction of the mechanical connecting rope.

[0062] In a preferred embodiment, the transmission assembly 402 includes a robotic arm or a transmission rod.

[0063] In this invention, both the collar and the adjusting component are sleeved on the seed crystal rod, and the collar is directly connected to the transmission component. Therefore, by controlling the transmission component to perform actions such as clamping, releasing, and rotating, the collar is driven to move up and down along the seed crystal rod, thereby realizing the release and lifting of the mechanical connecting rope, and finally realizing the lifting and releasing of the adjusting component.

[0064] In a preferred embodiment, such as Figure 3 As shown, when the adjusting component 400 can be laid flat on the upper surface of the crucible lid 20, its unfolded width is greater than the opening size of the crucible lid 20. When the adjusting component 400 can be laid flat on the upper surface of the seed crystal holder 301, its unfolded width is the same as the size of the seed crystal holder 301.

[0065] In this invention, Figure 4 The diagram shows, from left to right, the adjustment components transitioning from a contracted state to an unfolded state (i.e., after being laid flat).

[0066] In a preferred embodiment, such as Figure 5 As shown, the device also includes a rotating turntable 60; the rotating turntable 60 includes several different adjustment components 400, which are used to select the desired adjustment component 400 by rotation for axial temperature control.

[0067] It should be noted that different adjustment components have different insulation capabilities. Preferably, each adjustment component in the rotating turntable corresponds to one transmission component, that is, the number of adjustment components is the same as the number of transmission components. For the rotating turntable, when an adjustment component is selected and moves downwards along the seed crystal rod, the remaining unselected adjustment components remain above the seed crystal rod or outside the insulation layer.

[0068] In a preferred embodiment, such as Figure 3 As shown, the device also includes: a heating device 70, a heat insulation layer 80, and a lifting device; the crucible body 10 is placed inside the heating device 70, and the heating device 70 is placed inside the heat insulation layer 80; the lifting device is used to control the lifting and rotation of the seed crystal rod 30.

[0069] In a preferred embodiment, the insulation layer 80 has a channel in the middle, through which the seed crystal rod 30 enters the interior of the crucible body 10 via the channel and the crucible cover 20; wherein, the width of the adjusting component 400 in the contracted state is smaller than the diameter of the channel; and the diameter of the channel is larger than the diameter of the seed crystal holder 301. Preferably, the diameter of the channel is 30~200mm.

[0070] like Figure 6 As shown, the present invention also provides a method for dynamically adjusting the axial temperature gradient during crystal growth, comprising:

[0071] (1) The growth material is placed in the crucible body and heated to obtain a melt;

[0072] (2) The seed crystal holder carrying the seed crystal is placed inside the crucible body and in contact with the melt to grow silicon carbide;

[0073] (3) During the growth process, the transmission component drives the connection component to move, thereby controlling the adjustment component, which is in a contracted state, to move downward along the seed crystal rod until it contacts the crucible cover or the seed crystal holder, thereby controlling the transmission component to unfold and achieving axial temperature control.

[0074] It should be noted that the growth process includes a heating stage, a crystal growth stage, and a cooling stage, and the adjustment component can be applied in any stage or throughout the entire growth process.

[0075] In a preferred embodiment, after step (2) and before step (3), the method further includes:

[0076] Based on the detected temperature of the seed crystal holder, determine the target temperature required for the current growth stage;

[0077] The adjustment component is selected from the rotating dial based on the target temperature.

[0078] In this embodiment of the invention, the heat preservation capacity and applicable growth stage of each regulating component are determined in advance through test experiments and stored in a database. That is, the database stores regulating components suitable for the target temperature required for the growth stage. In this way, the corresponding regulating component can be accurately selected directly from the database during the silicon carbide crystal growth process.

[0079] In a preferred embodiment, step (3) further includes:

[0080] The transmission assembly controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be in a retracted state. Then, the transmission assembly moves the retracted adjustment assembly downwards along the seed crystal rod, passing through the holes of the insulation layer and the crucible cover until it contacts the seed crystal holder. The transmission assembly then controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be laid flat on the upper surface of the seed crystal holder.

[0081] In a preferred embodiment, step (3) further includes:

[0082] The transmission assembly controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be in a retracted state. Then, the transmission assembly moves the retracted adjustment assembly downwards along the seed crystal rod, passing through the holes in the insulation layer. When it reaches the position of the crucible lid, the transmission assembly controls the movement of the collar again to retract the mechanical connecting rope, causing the adjustment assembly to be laid flat on the upper surface of the crucible lid.

[0083] In a preferred embodiment, a device for dynamically adjusting the axial temperature gradient during crystal growth further includes a sensor module;

[0084] For step (3), the control component, which is in a contracted state, moves downward along the seed crystal rod until it reaches the position of the crucible lid or contacts the seed crystal holder, including:

[0085] Step (31): Obtain the current position of the adjustment component detected by the sensor module;

[0086] Step (32): Based on the furnace pressure and airflow speed detected in real time by the sensor module, dynamically adjust the descent speed of the regulating component until the target surface is reached; wherein, the target surface is the upper surface of the crucible lid or the upper surface of the seed crystal holder.

[0087] It should be noted that the sensor module includes a high-temperature vision camera for detecting the location of the adjustment component, a laser rangefinder for measuring the distance between the adjustment component and the seed crystal holder or crucible cover, an infrared sensor for acquiring the temperature of the upper surface of the seed crystal holder, and at least two high-frequency pressure sensors set in the growth environment.

[0088] In one specific implementation, dynamically adjusting the descent speed of the regulating component includes:

[0089] Determine the current distance based on the current location and the target surface;

[0090] When the current distance is greater than 100mm, adjust the descent speed to 50~80mm / min (for example, it can be 50mm / min, 52mm / min, 55mm / min, 60mm / min, 65mm / min, 70mm / min, 75mm / min or 80mm / min).

[0091] When the current distance is between 10mm and 100mm (e.g., 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm or 100mm), adjust the descent speed to 10~20mm / min (e.g., 10mm / min, 12mm / min, 14mm / min, 15mm / min, 16mm / min, 18mm / min or 20mm / min).

[0092] When the current distance is less than 10mm, adjust the descent speed to 0.5~2mm / min (for example, it can be 0.5mm / min, 0.6mm / min, 0.8mm / min, 1mm / min, 1.2mm / min, 1.5mm / min, 1.8mm / min or 2mm / min).

[0093] At the moment of contact until the adjustment component is laid flat on the target surface, the descent speed is adjusted to 0.1~0.2 mm / min (for example, it can be 0.1 mm / min, 0.15 mm / min or 0.2 mm / min) to achieve quasi-static bonding.

[0094] In this embodiment of the invention, when the current distance is greater than 100mm, the distance between the adjusting component and the crucible lid is greater than 100mm. The airflow velocity in this area is low, so a faster descent speed in this initial stage will not cause significant pressure fluctuations. In the transition stage (10mm to 100mm), the adjusting component enters the mainstream airflow zone. To avoid generating a tail vortex that affects the flow field at the top of the crucible, a descent speed of 10~20mm / min is selected. Subsequently, in the fine-tuning stage (less than 10mm to contact), since the adjusting component will compress the gas below, a slower descent speed is required to allow the gas sufficient time to escape laterally, thereby preventing local high-pressure areas. Finally, from the moment of contact until final bonding, a quasi-static bonding speed of 0.1~0.2mm / min is used to avoid pressure pulses caused by the piston effect and uneven heat preservation or gas leakage caused by local suspension, thereby improving the coverage accuracy of the adjusting component and ensuring the stability and controllability of the silicon carbide crystal growth interface, thus ensuring the quality of the silicon carbide crystal.

[0095] Specifically, the descent speed of the regulating component is dynamically adjusted, including: when an airflow disturbance exceeding a preset allowable value is detected, the component continues to descend by rotation (preferably 1-2 rpm), and pauses descent when the current distance meets a preset critical distance. Thus, when a large airflow disturbance is detected, the system automatically initiates compensation, converting the piston effect caused by axial descent into a more uniform spiral flow through rotational descent, and pausing at the critical position until the real-time furnace pressure data stabilizes. The preset allowable value is the permissible pressure disturbance threshold, which is dynamically adjusted according to the current stage of crystal growth, with a stricter threshold used during the isothermal crystal growth stage. This further reduces airflow disturbance at the growth interface, ensuring the stability and controllability of the growth interface.

[0096] After step (31) and before step (32), in addition to including an airflow control unit in the device, the following further applies: when the current position is a preset distance above the target surface, the airflow control unit is activated to allow inert gas to flow out, forming a gas film between the adjustment component and the target surface. It should be noted that the preset distance is 100mm. The airflow control unit can be located outside the crucible, but the airflow outlet of its high-temperature gas delivery pipe is located near the seed crystal rod guide mechanism or on the back of the seed crystal rod or on the back of the seed crystal support.

[0097] In this embodiment of the invention, the airflow control unit is activated to form an air film, which can make minor posture adjustments through airflow regulation before final bonding, achieving non-contact fine adjustment; it can also blow away volatile deposits on the surface of the seed crystal holder through airflow, improving contact thermal conductivity; at the same time, it can also buffer the instantaneous thermal shock when the air film adjustment component comes into contact with the high-temperature target surface.

[0098] In this invention, by employing a phased descent speed and adjusting the descent speed, pressure pulses and airflow turbulence caused by the piston effect are avoided, ensuring a continuous and stable gas phase concentration and temperature field near the crystal growth interface. This ensures that the crystal growth rate does not fluctuate during the up-and-down movement of the regulating component, avoiding growth streaks or defects introduced by this operation. Secondly, by using phased descent speed in conjunction with a gas film, the gas gap between the regulating component and the high-temperature target surface gradually decreases, and heat exchange gradually increases, thereby avoiding sudden local temperature changes caused by sudden contact and protecting the seed crystal and the grown crystal portion from thermal shock. Thus, this operation improves the coverage success rate and accuracy of the regulating component, and enhances crystal quality while protecting crystal growth.

[0099] The method for dynamically adjusting the axial temperature gradient during crystal growth provided in this embodiment of the invention can be implemented by software, hardware, or a combination of software and hardware.

[0100] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0101] Example 1

[0102] A device for dynamically adjusting the axial temperature gradient during crystal growth, such as... Figure 3 As shown, the device includes a crucible body 10, a crucible lid 20 with an opening, a seed crystal rod 30, a temperature regulating device 40, growth raw material 50, a rotating turntable 60, a heating device (heating barrel) 70, a heat insulation layer 80, and an induction coil 90. The temperature regulating device 40 includes an adjusting component 400, a connecting component 401, and a transmission component 402. The connecting component 401 includes a mechanical connecting rope 4011 and a collar 4012. The induction coil 90 is located outside the heat insulation layer 80 and is used for induction heating of the entire growth system. The heat insulation layer 80 is divided into three parts: lower heat insulation of the heating barrel, edge heat insulation of the heating barrel, and upper heat insulation of the heating barrel. The upper heat insulation has an opening in the middle, through which the seed crystal rod 30 and the retracted adjusting component 400 can pass. The heating device (heating barrel) 70 is the heating element of the growth system, and it is magnetically heated by the induction coil. The crucible body 10 is used to hold the growth material 50, providing space for the growth of silicon carbide single crystals and supplying carbon (C) for the growth. The growth material 50 is an essential raw material for silicon carbide single crystal growth, containing silicon and other fluxing metals. The crucible lid 20 is connected to the crucible body 10. The upper end of the lid 20 is threaded, allowing the entire crucible body 10 and lid 20 to be lifted and lowered using a handle. The adjustment component 400 is used to adjust the axial temperature gradient at the crystal end; its lifting and lowering process is described below. Figure 4 The seed crystal holder 301 is a graphite holder, with its lower end connected to the seed crystal. After contacting the growth material, crystal growth occurs. Its upper end is connected to the seed crystal rod, which can move the seed crystal up, down, and rotate. The mechanical connecting rope 4011 connects the adjusting component 400 and the collar 4012. Each adjusting component 400 has eight mechanical connecting ropes 4011, which can be extended and retracted to achieve the contraction and expansion of the adjusting component 400. The mechanical connecting rope 4011 is made of a high-temperature resistant material with high purity and no volatile impurities. The collar 4012 passes through the seed crystal rod 30 and connects the mechanical connecting rope 4011 to the transmission component 402. It is used to fix the position of the mechanical connecting rope 4011 and indirectly control the mechanical connecting rope 4011 through the transmission component 402. The transmission component 402 connects to the collar 4012 and can move or rotate to achieve the extension, retraction, and raising / lowering of the mechanical connecting rope 4011. The rotating turntable 60 is connected to multiple adjustment components 400, allowing rotation to select the appropriate adjustment component 400 for subsequent experiments. It should be noted that... Figure 3 The rotating turntable is not shown.

[0103] Adopting such Figure 3 The device shown is for dynamically adjusting the axial temperature gradient during crystal growth to grow silicon carbide single crystals using the liquid phase method. The specific operation is as follows:

[0104] S1. Preparation Stage: a. Determine the experimental scheme to determine the adjustment components to be used; in this embodiment, the crucible lid opening is 100mm, and the selected adjustment component is a graphite soft felt with a through hole diameter of 50mm, an unfolded diameter of 150mm, and a thickness of 10mm; b. Assemble the materials according to the experimental ratio; c. Place the graphite support (i.e., seed crystal support) connected to the graphite rod (i.e., seed crystal rod) into the crucible body, and the seed crystal is connected on the graphite support; d. Drive the graphite rod through the crystal growth furnace and place it in a suitable position inside the crucible;

[0105] S2. Heating stage: a. Evacuate the furnace, then fill it with an inert gas (such as argon), and then turn on the power to heat up, so that the growth material in the crucible body melts to obtain a melt; b. After the temperature reaches 1700℃, insert the seed crystal into the melt;

[0106] S3, Crystal growth stage: Control the rotation of the seed crystal and crucible to make the melt composition uniform, and at the same time control the lifting or lowering of the seed crystal and crucible to ensure a suitable growth environment;

[0107] S4. Cooling Stage: a. Pull out the crystal and place the graphite rod in the preset cooling position; b. Rotate the rotating turntable to the adjustment component selected in S1; c. Control the collar through the transmission component to indirectly control the mechanical connecting rope to retract, and the retracted adjustment component can pass through the pre-reserved opening in the middle of the insulation layer; d. Control the transmission component to lower the adjustment component until it enters the heating chamber; e. Control the collar through the transmission component to indirectly control the mechanical connecting rope to unfold, and the unfolded adjustment component is laid flat on the back of the crucible lid to achieve axial temperature control of the crystal end; f. Reduce the power and wait for the temperature to drop to room temperature;

[0108] Specifically, the descent speed of the descent component is dynamically adjusted during the descent process. When the distance between the adjustment component and the back of the crucible lid is greater than 100 mm, the descent speed is adjusted to 50~80 mm / min; when the distance between the adjustment component and the back of the crucible lid is between 10 mm and 100 mm, the descent speed is adjusted to 10~20 mm / min; when the distance between the adjustment component and the back of the crucible lid is less than 10 mm, the descent speed is adjusted to 0.5~2 mm / min; and at the moment of contact, the descent speed is adjusted to 0.1~0.2 mm / min.

[0109] S5. Sampling stage: Separate the graphite rod from the crystal growth furnace, open the furnace lid, remove the upper insulation layer, remove the crucible, and take out the silicon carbide crystal.

[0110] Example 2

[0111] The device for dynamically adjusting the axial temperature gradient during crystal growth, as described in Example 1, was used for liquid-phase growth of silicon carbide single crystals. The specific operation is as follows:

[0112] S1. Preparation Stage: a. Determine the experimental scheme to determine the adjustment components to be used; in this embodiment, the crucible lid opening is 100mm, and the selected adjustment component is a graphite soft felt with a through hole diameter of 50mm, an unfolded diameter of 150mm, and a thickness of 10mm; b. Assemble the materials according to the experimental ratio; c. Place the graphite support (i.e., seed crystal support) connected to the graphite rod (i.e., seed crystal rod) into the crucible body, and the seed crystal is connected on the graphite support; d. Drive the graphite rod through the crystal growth furnace and place it in a suitable position inside the crucible;

[0113] S2, Heating Stage: a. Evacuate the furnace, then fill it with an inert gas (such as argon), and then turn on the power to heat up, melting the growth material inside the crucible body to obtain a melt; b. Rotate the rotating turntable to the adjustment component selected in S1; c. Control the collar through the transmission component to indirectly control the mechanical connecting rope to retract, and the retracted adjustment component can pass through the pre-reserved opening in the middle of the insulation layer; d. Control the transmission component to lower the adjustment component until it enters the heating barrel; e. Control the collar through the transmission component to indirectly control the mechanical connecting rope to unfold, and the unfolded adjustment component is laid flat on the back of the crucible lid to achieve axial temperature control of the crystal end; f. After the temperature reaches 1700℃, insert the seed crystal into the melt;

[0114] S3, Crystal Growth Stage: After the seed crystal is inserted into the melt for 2 hours, the mechanical connecting rope is indirectly controlled by manipulating the collar through the transmission component to retract. The retracted adjustment component can pass through the pre-reserved opening in the middle of the insulation layer; b. The transmission component is raised to adjust the component until the adjustment component returns to the rotating turntable; c. During the crystal growth stage, the rotation of the seed crystal and crucible is controlled to make the melt composition uniform, and the lifting or lowering of the seed crystal and crucible is controlled to ensure a suitable growth environment;

[0115] S4. Cooling Stage: a. Pull out the crystal and place the graphite rod in the preset cooling position; b. Rotate the rotating turntable to the adjustment component selected in S1; c. Control the collar through the transmission component to indirectly control the mechanical connecting rope to retract, and the retracted adjustment component can pass through the pre-reserved opening in the middle of the insulation layer; d. Control the transmission component to lower the adjustment component until it enters the heating chamber; e. Control the collar through the transmission component to indirectly control the mechanical connecting rope to unfold, and the unfolded adjustment component is laid flat on the back of the crucible lid to achieve axial temperature control of the crystal end; f. Reduce the power and wait for the temperature to drop to room temperature;

[0116] In steps S2 and S4, the descent speed of the lowering component is dynamically adjusted. When the distance between the adjusting component and the back of the crucible lid is greater than 100 mm, the descent speed is adjusted to 50-80 mm / min; when the distance between the adjusting component and the back of the crucible lid is between 10 mm and 100 mm, the descent speed is adjusted to 10-20 mm / min; when the distance between the adjusting component and the back of the crucible lid is less than 10 mm, the descent speed is adjusted to 0.5-2 mm / min; and at the moment of contact, the descent speed is adjusted to 0.1-0.2 mm / min.

[0117] S5. Sampling stage: Separate the graphite rod from the crystal growth furnace, open the furnace lid, remove the upper insulation layer, remove the crucible, and take out the silicon carbide crystal.

[0118] Comparative Example 1

[0119] In the conventional liquid-phase method for growing silicon carbide single crystals, this apparatus, compared to Example 1, does not include a temperature control device. However, it is necessary to pre-insulate the crucible lid to reduce the axial temperature gradient before placing the growth crucible in the crystal furnace for heating. The specific method is as follows:

[0120] S1. Place the graphite felt in the crucible lid in advance;

[0121] S2. Prepare the raw materials and put them into the growth crucible, then place the crucible in the crystal furnace;

[0122] S3. Place the seed crystal in the crucible using the seed crystal rod;

[0123] S4. After pretreatment, the mixture is heated and then allowed to grow in liquid.

[0124] S5. Cool down the grown crystal and pull it out.

[0125] Comparative Example 2

[0126] In the conventional liquid-phase method for growing silicon carbide single crystals, this apparatus, compared to Example 1, does not include a temperature control device. The growth crucible is placed in a crystal furnace for heating, and the specific method is as follows:

[0127] S1. Prepare the raw materials and put them into the growth crucible, then place the crucible in the crystal furnace;

[0128] S2. Place the seed crystal in the crucible using the seed crystal rod;

[0129] S3. After pretreatment, heating is performed, followed by liquid-in-liquid growth;

[0130] S4. Cool the grown crystal and pull it out.

[0131] It should be noted that the only difference between Example 1, Example 2, Comparative Example 1, and Comparative Example 2 is the apparatus; the process parameters (such as heating power) used in the growth process are the same.

[0132] By observing the growth process of the above embodiments and comparative examples, and by conducting quality tests on the prepared silicon carbide crystals, it was found that Comparative Example 2 used a traditional liquid-phase silicon carbide growth apparatus. This apparatus had an excessively large axial temperature gradient in the crystal, resulting in a fast crystal growth rate, but it was prone to crystal cracking during the cooling stage. Compared with Comparative Example 2, under the same conditions, Example 1 used the apparatus of the present invention to grow silicon carbide single crystals using the liquid-phase method. An adjustment component was placed during the cooling stage after crystal growth, reducing the axial temperature gradient at the crystal end and thus reducing the cracking rate by approximately 35%. In Example 2, the apparatus of the present invention was used to grow silicon carbide single crystals using the liquid-phase method. Different adjustment components were adjusted during the crystal growth process to improve quality and reduce the cracking rate: in the initial crystal growth stage, the axial temperature gradient was reduced by increasing the heat preservation, thus increasing the crystal growth quality; after stable growth, the adjustment component was removed to increase the stable crystal growth rate; and during the cooling stage, heat preservation was increased to reduce the axial temperature gradient and reduce the crystal cracking rate. Compared to Comparative Example 2, under the same conditions, Example 2 showed a reduction of approximately 20% in crystal inclusion density, a reduction of approximately 3% in average crystal growth rate, and an increase of approximately 35% in crystal crack resistance. Compared to Comparative Example 2, Comparative Example 1 used graphite felt to insulate the crucible lid, which was not removed during the heating, crystal growth, and cooling stages. Although this reduced the axial temperature gradient to some extent and increased the crystal crack resistance by approximately 35% compared to Comparative Example 2, the crystal growth rate was approximately 50% slower.

[0133] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on a device for dynamically adjusting the axial temperature gradient during crystal growth. In other embodiments of the present invention, a device for dynamically adjusting the axial temperature gradient during crystal growth may include more or fewer components than illustrated, or combine some components, or split some components, or arrange different components. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0134] The information interaction and execution process between the modules in the above-mentioned device are based on the same concept as the method embodiment of the present invention, and the specific details can be found in the description of the method embodiment of the present invention, and will not be repeated here.

[0135] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0136] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium, etc. Those skilled in the art can understand the specific meaning of this term in this invention depending on the specific circumstances.

[0137] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for dynamically adjusting the axial temperature gradient during crystal growth, characterized in that, The device includes a crucible body, a crucible lid with an opening, a seed crystal rod, a temperature regulating device, a rotating disk, and a sensor module; One end of the seed crystal rod is connected to the seed crystal holder that carries the seed crystal. During the growth process, the seed crystal holder is placed inside the crucible body. The other end is fitted with the temperature regulation device. The temperature regulating device includes a regulating component, a connecting component, and a transmission component; The adjusting component is made of graphite felt and has a through hole in the center, through which the seed crystal rod passes. The transmission component is connected to the adjusting component through the connecting component and controls the adjusting component to move up and down along the seed crystal rod to achieve axial temperature control. The adjusting component is in a contracted state during the up and down movement. When the adjusting component moves to the crucible cover or the seed crystal holder, the transmission component unfolds the adjusting component so that the adjusting component is laid flat on the upper surface of the crucible cover or the seed crystal holder. When the adjusting component can be laid flat on the upper surface of the crucible lid, its unfolded width is greater than the opening size of the crucible lid; when the adjusting component can be laid flat on the upper surface of the seed crystal holder, its unfolded width is the same as the size of the seed crystal holder; the connecting component includes a mechanical connecting rope and a collar; one end of the mechanical connecting rope is fixedly connected to the outer edge of the adjusting component, and the other end is connected to the collar; the collar is used to pass through the seed crystal rod and is connected to the transmission component; The rotating turntable includes several different adjustment components, which are used to select the desired adjustment component by rotation for axial temperature control; The process involves acquiring the current position of the adjustment component detected by the sensor module; dynamically adjusting the descent speed of the adjustment component based on the furnace pressure and airflow speed detected in real time by the sensor module until the target surface is reached; where the target surface is the upper surface of the crucible lid or the upper surface of the seed crystal holder.

2. The apparatus according to claim 1, characterized in that, The thickness of the adjustment component is 2~30mm; The diameter of the through hole is 20~100mm, and the diameter of the through hole is larger than the diameter of the seed crystal rod.

3. The apparatus according to claim 1, characterized in that, The width of the adjustment component after unfolding is 25~250mm.

4. The apparatus according to claim 1, characterized in that, The adjustment assembly is connected to at least eight mechanical connecting ropes, and the connection points of the mechanical connecting ropes are evenly distributed on the outer edge of the adjustment assembly.

5. The apparatus according to claim 1, characterized in that, The mechanical connecting rope is a molybdenum wire with a purity greater than 99.5% or a tungsten wire with a purity greater than 99.5%; wherein the length of the mechanical connecting rope is greater than 1 / 2 of the opening size of the crucible lid; The collar is made of silicon carbide, molybdenum, or tungsten.

6. The apparatus according to claim 4, characterized in that, The transmission component achieves the raising, lowering, and winding of the mechanical connecting rope by moving and / or rotating.

7. The apparatus according to claim 4, characterized in that, The transmission assembly includes a robotic arm or a transmission rod.

8. The apparatus according to any one of claims 1 to 7, characterized in that, Also includes: The device includes a heating element, an insulation layer, and a lifting device; the crucible body is placed inside the heating element, which is placed inside the insulation layer; the lifting device is used to control the lifting and rotation of the seed crystal rod.

9. The apparatus according to claim 8, characterized in that, Also includes: The insulation layer has a channel in the middle, through which the seed crystal rod enters the interior of the crucible body via the channel and the crucible cover; wherein, the width of the adjustment component in the contracted state is smaller than the diameter of the channel; the diameter of the channel is larger than the diameter of the seed crystal holder.

10. A method for dynamically adjusting the axial temperature gradient during crystal growth, characterized in that, The apparatus according to any one of claims 1 to 9 comprises: (1) The growth material is placed in the crucible body and heated to obtain a melt; (2) The seed crystal holder carrying the seed crystal is placed inside the crucible body and in contact with the melt to grow silicon carbide; (3) During the growth process, the transmission component drives the connection component to move, thereby controlling the adjustment component, which is in a contracted state, to move downward along the seed crystal rod until it contacts the crucible cover or the seed crystal holder, thereby controlling the transmission component to unfold and achieving axial temperature control.

11. The method according to claim 10, characterized in that, The device also includes a rotating turntable; the rotating turntable includes several different adjustment components for axial temperature control by rotating to select the desired adjustment component; the method further includes: Based on the detected temperature of the seed crystal holder, determine the target temperature required for the current growth stage; The adjustment component is selected from the rotating dial based on the target temperature.

12. The method according to claim 10 or 11, characterized in that, The connecting assembly includes a mechanical connecting rope and a collar; one end of the mechanical connecting rope is fixedly connected to the outer edge of the adjusting assembly, and the other end is connected to the collar. The collar is used to pass through the seed crystal rod and connect to the transmission assembly; the device also includes: a heating device, a heat insulation layer, and a lifting device; the crucible body is placed inside the heating device, and the heating device is placed inside the heat insulation layer; the lifting device is used to control the lifting and rotation of the seed crystal rod; in step (3), it also includes: The transmission assembly controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be in a retracted state. Then, the transmission assembly moves the retracted adjustment assembly downwards along the seed crystal rod, passing through the holes of the insulation layer and the crucible cover until it contacts the seed crystal holder. The transmission assembly then controls the movement of the collar to retract the mechanical connecting rope, causing the adjustment assembly to be laid flat on the upper surface of the seed crystal holder.

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