An apparatus and method for reducing the density of threading dislocation defects in silicon carbide crystals

Abstract

This application provides an apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals. The apparatus includes an insulation component formed by an upper insulation layer, a first outer insulation layer, and a lower insulation layer. The insulation component is provided with gas exchange channels. By placing a crucible containing a silicon carbide seed crystal and silicon carbide raw material into the insulation component and placing them together into a single crystal growth furnace, silicon carbide crystal is grown according to the parameters set for each growth stage to obtain an N-type silicon carbide crystal. When in the isothermal section, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to a first flow rate state and a second flow rate state. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to basal plane dislocations and stacking faults in the N-type silicon carbide crystal. This solves the problem of high dislocation density in SiC single crystals grown by the current PVT method.

Description

Technical Field

[0001] This application relates to the field of semiconductor materials technology, and in particular to an apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals. Background Technology

[0002] In the current booming semiconductor industry, silicon carbide (SiC) materials, with their superior properties such as wide bandgap, high breakdown electric field, and high electron mobility, have shown enormous application potential in high-end fields such as new energy vehicles, 5G communications, and smart grids, becoming one of the key materials driving technological upgrades in these fields. As a crucial upstream link in the industry chain, the quality of domestically produced commercial silicon carbide single crystals directly determines the performance and application range of downstream epitaxy and devices.

[0003] Currently, the main method for growing commercial silicon carbide single crystals in China is physical vapor deposition (PVT). This method involves sublimating silicon carbide powder at high temperatures and then recrystallizing it on a seed crystal to grow a single crystal. It has advantages such as relatively simple equipment and fast growth rate, and is currently a relatively mature and widely used silicon carbide single crystal growth technology.

[0004] However, SiC single crystals grown by the PVT method exhibit high dislocation densities. Dislocation densities in crystals include various types, such as screw dislocations (TSD), edge dislocations (TED), base-plane dislocations (BPD), and mixed dislocations (TMD). Different dislocation types can affect the subsequent epitaxial quality of the crystal to varying degrees, thereby impacting the performance of the corresponding devices, such as causing leakage current and reduced breakdown voltage. Summary of the Invention

[0005] This application provides an apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals, in order to solve the technical problem of high dislocation density in SiC single crystals grown by the PVT method.

[0006] The first aspect of this application provides an apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals, used in the PVT method for growing N-type silicon carbide crystals, comprising: An insulation component consisting of an upper insulation layer, a first outer insulation layer, and a lower insulation layer; the insulation component has an internal receiving space for fixing a crucible containing a silicon carbide seed crystal and silicon carbide raw material; the insulation component is provided with a gas exchange channel; one end of the gas exchange channel is connected to the receiving space, and the other end of the gas exchange channel is connected to the external space of the insulation component; The process involves placing a crucible containing a silicon carbide seed crystal and silicon carbide raw material into an insulating container and then placing them together into a single crystal growth furnace. Silicon carbide crystals are grown according to the parameters set for each growth stage to obtain N-type silicon carbide crystals. The growth stages, based on the silicon carbide crystal growth temperature, include a first heating stage, a constant temperature stage, a second heating stage, a high-temperature growth stage, and a cooling stage. The gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, with different N2 flow rates in the first and second flow rate states. During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

[0007] In some embodiments, the top of the lower insulation layer is provided with a first fixing groove and a second fixing groove, the first fixing groove being used to fix the crucible; the second fixing groove being used to fix the first outer insulation layer; and the top of the first outer insulation layer is provided with a third fixing groove, the third fixing groove being used to fix the upper insulation layer. Wherein, when the crucible is fixed to the lower insulation layer through the first fixing groove, there is a gap between the crucible and the first outer insulation layer and the upper insulation layer.

[0008] In some embodiments, the apparatus further includes: The second external insulation layer is disposed outside the first external insulation layer and the lower insulation layer, and there is a gap between the second external insulation layer and the first external insulation layer and the lower insulation layer; the projection of the second external insulation layer onto the first external insulation layer and the lower insulation layer completely covers the first external insulation layer and the lower insulation layer.

[0009] In some embodiments, the first external insulation layer is provided with a first gas exchange channel, the openings of the first gas exchange channel being respectively located on the upper surface and the inner sidewall of the first external insulation layer; one end of the first gas exchange channel is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component. The lower insulation layer is provided with a second gas exchange channel, the openings of which are respectively located on the upper surface and the outer wall of the lower insulation layer; one end of the second gas exchange channel is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component.

[0010] In some embodiments, during the process from the first heating stage to the constant temperature stage, the single crystal growth furnace is heated from room temperature to 1900°C-2000°C and then held at that temperature. During the process from the second heating stage to the high temperature growth stage, the single crystal growth furnace is heated from 1900°C-2000°C to 2000°C-2200°C and then silicon carbide crystals are grown. After obtaining N-type silicon carbide crystals, the furnace enters the cooling stage. In the cooling stage, the single crystal growth furnace is cooled from 2000°C-2200°C to room temperature.

[0011] In some embodiments, the pressure inside the single crystal growth furnace in the first heating stage is 40 mbar-800 mbar, the pressure inside the single crystal growth furnace in the isothermal stage is 20 mbar-40 mbar, the pressure inside the single crystal growth furnace in the second heating stage is 5 mbar-20 mbar, the pressure inside the single crystal growth furnace in the high-temperature growth stage is 0.5 mbar-5 mbar, and the pressure inside the single crystal growth furnace in the cooling stage is 0.5 mbar-800 mbar.

[0012] In some embodiments, the Ar flow rate of the single crystal growth furnace in the first heating stage is 100-700 sccm, and the N2 flow rate is 0 sccm; the Ar flow rate of the single crystal growth furnace in the second heating stage is 100-300 sccm, and the N2 flow rate is 1-20 sccm; the Ar flow rate of the single crystal growth furnace in the high-temperature growth stage is 50-200 sccm, and the N2 flow rate is 1-10 sccm; and the Ar flow rate of the single crystal growth furnace in the cooling stage is 100-700 sccm, and the N2 flow rate is 0 sccm.

[0013] In some embodiments, when the isothermal section is in the first flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 1-8 sccm; when the isothermal section is in the second flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 0 sccm.

[0014] The second aspect of this application provides a method for reducing the density of through-type dislocation defects in a silicon carbide crystal, applied to the apparatus for reducing the density of through-type dislocation defects in a silicon carbide crystal as described in any one of the first aspects above, comprising: A crucible containing silicon carbide seed crystals and silicon carbide raw materials is placed inside an insulating component and then placed together into a single crystal growth furnace; the insulating component is provided with gas exchange channels; According to the parameters set for each growth stage, silicon carbide crystals are grown to obtain N-type silicon carbide crystals; the growth stages include: a first heating stage, a constant temperature stage, a second heating stage, a high temperature growth stage, and a cooling stage; the gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, and the N2 flow rate in the first flow rate state and the second flow rate state are different. During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

[0015] This application provides an apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals, used for the growth of N-type silicon carbide crystals via PVT. The apparatus includes: an insulation component formed by an upper insulation layer, a first outer insulation layer, and a lower insulation layer; the insulation component has an internal receiving space for fixing a crucible containing a silicon carbide seed crystal and silicon carbide raw material; the insulation component is provided with gas exchange channels; one end of the gas exchange channels is connected to the receiving space, and the other end of the gas exchange channels is connected to the external space of the insulation component; wherein, by placing the crucible containing the silicon carbide seed crystal and silicon carbide raw material into the insulation component and placing them together into a single crystal growth furnace, silicon carbide crystals are grown according to the parameters set for each growth stage to obtain N-type silicon carbide crystals; The growth stages, based on the silicon carbide crystal growth temperature, include a first heating stage, a constant temperature stage, a second heating stage, a high-temperature growth stage, and a cooling stage. The gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, with different N2 flow rates in the first and second flow rate states. Specifically, in the constant temperature stage, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first and second flow rate states. Nitrogen is intentionally doped into the silicon carbide crystal during growth through the gas exchange channels to increase the conversion probability and ejection probability of through-hole dislocations to plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1, thereby reducing the dislocation density in the SiC single crystal obtained by the PVT method. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram of the device structure for reducing the density of through-type dislocation defects in silicon carbide crystals according to this application.

[0018] Explanation of reference numerals in the attached figures: 1-Upper insulation layer; 2-First external insulation layer; 21-First gas exchange channel; 3-Lower insulation layer; 31-Second gas exchange channel; 4-Silicon carbide seed crystal; 5-Silicon carbide raw material; 6-Crucible; 61-Crucible cover; 7-Second external insulation layer. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0020] Because SiC single crystals grown by the PVT method exhibit high dislocation density in some technologies, this application provides an apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals to address this technical problem. The apparatus and method for reducing the density of through-type dislocation defects in silicon carbide crystals are described below: like Figure 1 The diagram shown is a schematic of the device structure for reducing the density of through-type dislocation defects in silicon carbide crystals according to this application.

[0021] The first aspect of this application provides an apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals, used in the PVT method for growing N-type silicon carbide crystals, comprising: An insulation component is formed by an upper insulation layer 1, a first outer insulation layer 2, and a lower insulation layer 3; the insulation component has an internal receiving space for fixing a crucible 6 containing a silicon carbide seed crystal 4 and a silicon carbide raw material 5; the insulation component is provided with a gas exchange channel; one end of the gas exchange channel is connected to the receiving space, and the other end of the gas exchange channel is connected to the external space of the insulation component; the silicon carbide seed crystal 4 has a deflection angle of 4°.

[0022] Specifically, the first external insulation layer 2 is provided with a first gas exchange channel 21, and the openings of the first gas exchange channel 21 are respectively located on the upper surface and the inner sidewall of the first external insulation layer 2; one end of the first gas exchange channel 21 is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component.

[0023] The lower insulation layer 3 is provided with a second gas exchange channel 31, the openings of which are respectively located on the upper surface and the outer wall of the lower insulation layer 3; one end of the second gas exchange channel 31 is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component.

[0024] It is worth noting that the design of the aforementioned gas exchange channels enables communication between the interior and exterior spaces of the insulation component, improving the exchange efficiency between the gas inside the crystal growth furnace and the crystal growth components in the crucible during the growth process (the gas introduced into the crystal growth furnace can enter the internal space of the insulation component more quickly). The gas exchange channels also allow for precise, delay-free control of the intentional nitrogen doping process, providing a foundation for subsequent periodic nitrogen doping.

[0025] Specifically, the top of the lower insulation layer 3 is provided with a first fixing groove and a second fixing groove. The first fixing groove is used to fix the crucible 6, and the bottom of the crucible 6 is used to fill the silicon carbide raw material 5. The top of the crucible 6 is equipped with a crucible cover 61. The bottom of the crucible cover 61 is equipped with a silicon carbide seed crystal 4. The second fixing groove is used to fix the first external insulation layer 2. The top of the first external insulation layer 2 is provided with a third fixing groove, which is used to fix the upper insulation layer 1.

[0026] When the crucible 6 is fixed to the lower insulation layer 3 through the first fixing groove, there is a gap between the crucible 6 and the first external insulation layer 2 and the upper insulation layer 1, so that N2 introduced into the single crystal growth furnace enters the gap between the first external insulation layer 2 and the upper insulation layer 1 through the gas exchange channel, thereby intentionally doping the nitrogen element in the growth of silicon carbide crystal.

[0027] In this process, a crucible 6 containing a silicon carbide seed crystal 4 and a silicon carbide raw material 5 is placed inside an insulating component and then placed together in a single crystal growth furnace. According to the parameters set for each growth stage, silicon carbide crystals are grown to obtain N-type silicon carbide crystals. The growth stages include a first heating stage, a constant temperature stage, a second heating stage, a high-temperature growth stage, and a cooling stage, depending on the silicon carbide crystal growth temperature. The gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, and the N2 flow rate in the first flow rate state and the second flow rate state are different.

[0028] For example, the process parameters for each growth stage are as follows: During the process from the first heating stage to the constant temperature stage, the single crystal growth furnace is heated from room temperature to 1900°C-2000°C and then held at that temperature for 40 hours. During the process from the second heating stage to the high temperature growth stage, the single crystal growth furnace is heated from 1900°C-2000°C to 2000°C-2200°C and then silicon carbide crystals are grown. After obtaining N-type silicon carbide crystals, the furnace enters the cooling stage. During the cooling stage, the single crystal growth furnace is cooled from 2000°C-2200°C to room temperature.

[0029] The pressure inside the single crystal growth furnace in the first heating stage is 40 mbar-800 mbar, the pressure inside the single crystal growth furnace in the constant temperature stage is 20 mbar-40 mbar, the pressure inside the single crystal growth furnace in the second heating stage is 5 mbar-20 mbar, the pressure inside the single crystal growth furnace in the high temperature growth stage is 0.5 mbar-5 mbar, and the pressure inside the single crystal growth furnace in the cooling stage is 0.5 mbar-800 mbar.

[0030] In the first heating stage, the Ar flow rate of the single crystal growth furnace is 100-700 sccm, and the N2 flow rate is 0 sccm; in the second heating stage, the Ar flow rate of the single crystal growth furnace is 100-300 sccm, and the N2 flow rate is 1-20 sccm; in the high-temperature growth stage, the Ar flow rate of the single crystal growth furnace is 50-200 sccm, and the N2 flow rate is 1-10 sccm; in the cooling stage, the Ar flow rate of the single crystal growth furnace is 100-700 sccm, and the N2 flow rate is 0 sccm.

[0031] Specifically, in the first heating stage, the Ar flow rate of the single crystal growth furnace is 400 sccm and the N2 flow rate is 0 sccm; in the second heating stage, the Ar flow rate of the single crystal growth furnace is 200 sccm and the N2 flow rate is 1 sccm; in the high-temperature growth stage, the Ar flow rate of the single crystal growth furnace is 100 sccm and the N2 flow rate is 6 sccm; and in the cooling stage, the Ar flow rate of the single crystal growth furnace is 400 sccm and the N2 flow rate is 0 sccm.

[0032] During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

[0033] When the isothermal section is in the first flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 1-8 sccm; when the isothermal section is in the second flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 0 sccm.

[0034] Specifically, when the isothermal zone is in the first flow rate state, the Ar flow rate of the single crystal growth furnace is 395 sccm and the N2 flow rate is 5 sccm; when the isothermal zone is in the second flow rate state, the Ar flow rate of the single crystal growth furnace is 400 sccm and the N2 flow rate is 0 sccm. The first and second flow rate states constitute one cycle, and when the single crystal growth furnace is in the isothermal zone, the gas introduction operation is performed according to n cycles.

[0035] For example, periodic nitrogen doping has the following advantages: Growth interface step widening: Periodic nitrogen doping leads to step widening at the growth interface of silicon carbide crystals, which helps to change the growth kinetics of the crystal and promotes the transformation and removal of dislocations.

[0036] Increased shear stress: The change in nitrogen doping concentration gradient increases the shear stress at the doping interface in the crystal grown under the off-angle seed. This stress change helps to activate the movement of dislocations and increases their probability of transformation into basal plane dislocations and stacking faults.

[0037] The formation energy of stacking faults is reduced: Nitrogen doping also reduces the formation energy of stacking faults, making it easier for stacking faults to form and spread in the crystal, thereby absorbing and annihilating through-type dislocations and reducing their density.

[0038] Periodic variations in lattice strain and stacking fault energy: Periodic nitrogen doping leads to periodic variations in lattice strain and stacking fault energy in silicon carbide crystals. These variations provide the impetus for the transformation and expulsion of through-type dislocations, ultimately achieving the goal of reducing the density of through-type dislocations in silicon carbide crystals.

[0039] The device further includes: The second external insulation layer 7 is disposed outside the first external insulation layer 2 and the lower insulation layer 3, and there is a gap between the second external insulation layer 7 and the first external insulation layer 2 and the lower insulation layer 3; the projection of the second external insulation layer 7 toward the first external insulation layer 2 and the lower insulation layer 3 completely covers the first external insulation layer 2 and the lower insulation layer 3.

[0040] For example, the second external insulation layer 7 is disposed outside the first external insulation layer 2 and the lower insulation layer 3, forming an insulation barrier. A certain gap exists between its inner wall and the outer wall of the first external insulation layer 2, which not only enhances the overall insulation effect of the insulation component but also provides space for gas exchange. The second external insulation layer 7 completely covers the outer walls of the upper insulation layer 1, the first external insulation layer 2, and the lower insulation layer 3, ensuring that heat is not easily lost and improving the overall insulation performance of the thermal field.

[0041] In this embodiment, the second external insulation layer 7 makes the insulation component more heat-insulating: As the outermost layer of the thermal field structure, the second external insulation layer 7 serves one of its main functions: providing an additional thermal barrier. By reducing heat loss to the external environment, the second external insulation layer 7 helps maintain a stable temperature distribution within the thermal field, which is crucial for the uniform growth of silicon carbide crystals. Furthermore, the second external insulation layer 7 effectively reduces temperature fluctuations within the thermal field, providing a more stable environment for crystal growth and contributing to improved crystal quality and yield.

[0042] Establish gas exchange channels: Although gas exchange channels are located in the upper insulation layer 1 and the lower insulation layer 3, the second outer insulation layer 7 provides the necessary space and path for gas exchange. The gap between its inner wall and the outer wall of the first outer insulation layer 2 indirectly promotes the flow and exchange of gas within the thermal field, preventing gas stagnation and accumulation within the thermal field, thereby ensuring that doped gases such as nitrogen can accurately control the growth process of silicon carbide crystals without delay.

[0043] Protect the inner wall of the single crystal growth furnace from high-temperature corrosion by components spilling out during the crystal growth process: During the growth of silicon carbide crystals, some spilled components or volatiles are generated. These substances may corrode the inner wall of the single crystal growth furnace at high temperatures. The second external insulation layer 7, acting as an isolation layer between the thermal field and the inner wall of the single crystal growth furnace, effectively prevents direct contact with these corrosive substances, thus protecting the inner wall of the furnace from damage. Simultaneously, the high-temperature stability and chemical stability of the second external insulation layer 7 ensure that it will not fail due to high temperatures or chemical corrosion during long-term use, providing durable and reliable protection for crystal growth.

[0044] To address the issue of high density of through-hole dislocations in silicon carbide substrates produced during the current PVT method for growing silicon carbide single crystals, due to inheritance of through-hole dislocations from the silicon carbide seed crystal or early inclusions during growth, this application proposes to achieve timely and accurate control of the nitrogen doping process during silicon carbide crystal growth by adding gas exchange channels in the silicon carbide crystal growth thermal field. Then, by adding a periodic N2 doping process in the early stage of crystal growth, the conversion probability and ejection probability of through-hole dislocations to basal plane dislocations and stacking faults are increased, thereby reducing the density of through-hole dislocations in the silicon carbide crystal. This method is low-cost, highly feasible, and compatible with most current PVT silicon carbide crystal growth processes.

[0045] This application proposes a device for reducing the density of through-type dislocation defects in silicon carbide crystals. It enables precise, delay-free control of the intentional and unintentional nitrogen doping process during silicon carbide crystal growth by adding gas exchange channels to the thermal field structure corresponding to the silicon carbide crystal growth. Furthermore, by adding periodic N2 doping in the early growth stage, it utilizes the widening of the growth interface steps caused by periodic nitrogen doping in the silicon carbide crystal, the increased shear stress at the doped interface in the crystal grown under the off-angle seed crystal due to changes in nitrogen doping concentration gradient, and the reduction in stacking fault formation energy. This achieves periodic changes in lattice strain and stacking fault energy, increasing the probability of through-type dislocations transforming into plane dislocations and stacking faults, and ultimately solving the problem of excessive dislocation density in the resulting silicon carbide substrate due to the high density and poor quality of through-type dislocations in the silicon carbide seed crystal itself, thereby improving the quality of the obtained N-type silicon carbide crystal.

[0046] A second aspect of this application provides a method for reducing the density of through-type dislocation defects in a silicon carbide crystal, applied to the apparatus for reducing the density of through-type dislocation defects in a silicon carbide crystal described in any of the above embodiments, comprising: A crucible containing silicon carbide seed crystals and silicon carbide raw materials is placed inside an insulating component and then placed together into a single crystal growth furnace; the insulating component is provided with gas exchange channels; According to the parameters set for each growth stage, silicon carbide crystals are grown to obtain N-type silicon carbide crystals; the growth stages include: a first heating stage, a constant temperature stage, a second heating stage, a high temperature growth stage, and a cooling stage; the gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, and the N2 flow rate in the first flow rate state and the second flow rate state are different. During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

[0047] It is worth noting that the effects of the above method embodiments can be found in the effects of the above device embodiments, and will not be repeated here.

[0048] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. An apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals, used for the growth of N-type silicon carbide crystals via PVT, characterized in that, include: An insulation component consisting of an upper insulation layer (1), a first external insulation layer (2), and a lower insulation layer (3); The insulation component has an internal accommodating space for fixing a crucible (6) containing a silicon carbide seed crystal (4) and a silicon carbide raw material (5); the insulation component is provided with a gas exchange channel; one end of the gas exchange channel is connected to the accommodating space, and the other end of the gas exchange channel is connected to the external space of the insulation component. In this process, a crucible (6) containing a silicon carbide seed crystal (4) and a silicon carbide raw material (5) is placed inside a heat-insulating component and then placed together in a single crystal growth furnace. According to the parameters of each growth stage, silicon carbide crystal is grown to obtain an N-type silicon carbide crystal. The growth stages include a first heating stage, a constant temperature stage, a second heating stage, a high-temperature growth stage, and a cooling stage, depending on the silicon carbide crystal growth temperature. The gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, and the N2 flow rate in the first flow rate state and the second flow rate state are different. During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

2. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, The top of the lower insulation layer (3) is provided with a first fixing groove and a second fixing groove. The first fixing groove is used to fix the crucible (6); the second fixing groove is used to fix the first outer insulation layer (2); the top of the first outer insulation layer (2) is provided with a third fixing groove, which is used to fix the upper insulation layer (1). When the crucible (6) is fixed to the lower insulation layer (3) through the first fixing groove, there is a gap between the crucible (6) and the first external insulation layer (2) and the upper insulation layer (1).

3. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, The device further includes: The second external insulation layer (7) is disposed outside the first external insulation layer (2) and the lower insulation layer (3), and there is a gap between the second external insulation layer (7) and the first external insulation layer (2) and the lower insulation layer (3); the projection of the second external insulation layer (7) toward the first external insulation layer (2) and the lower insulation layer (3) completely covers the first external insulation layer (2) and the lower insulation layer (3).

4. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, The first external insulation layer (2) is provided with a first gas exchange channel (21), and the openings of the first gas exchange channel (21) are respectively located on the upper surface and the inner sidewall of the first external insulation layer (2); one end of the first gas exchange channel (21) is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component; The lower insulation layer (3) is provided with a second gas exchange channel (31), the opening of the second gas exchange channel (31) is respectively located on the upper surface and the outer wall of the lower insulation layer (3); one end of the second gas exchange channel (31) is connected to the interior of the accommodating space, and the other end is connected to the external space of the insulation component.

5. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, During the process from the first heating stage to the constant temperature stage, the single crystal growth furnace is heated from room temperature to 1900°C-2000°C and then held at that temperature. During the process from the second heating stage to the high temperature growth stage, the single crystal growth furnace is heated from 1900°C-2000°C to 2000°C-2200°C and then silicon carbide crystals are grown. After obtaining N-type silicon carbide crystals, the furnace enters the cooling stage. During the cooling stage, the single crystal growth furnace is cooled from 2000°C-2200°C to room temperature.

6. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, The pressure inside the single crystal growth furnace in the first heating stage is 40 mbar-800 mbar, the pressure inside the single crystal growth furnace in the constant temperature stage is 20 mbar-40 mbar, the pressure inside the single crystal growth furnace in the second heating stage is 5 mbar-20 mbar, the pressure inside the single crystal growth furnace in the high temperature growth stage is 0.5 mbar-5 mbar, and the pressure inside the single crystal growth furnace in the cooling stage is 0.5 mbar-800 mbar.

7. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, In the first heating stage, the Ar flow rate of the single crystal growth furnace is 100-700 sccm, and the N2 flow rate is 0 sccm; in the second heating stage, the Ar flow rate of the single crystal growth furnace is 100-300 sccm, and the N2 flow rate is 1-20 sccm; in the high-temperature growth stage, the Ar flow rate of the single crystal growth furnace is 50-200 sccm, and the N2 flow rate is 1-10 sccm; in the cooling stage, the Ar flow rate of the single crystal growth furnace is 100-700 sccm, and the N2 flow rate is 0 sccm.

8. The apparatus for reducing the density of through-type dislocation defects in silicon carbide crystals according to claim 1, characterized in that, When the isothermal section is in the first flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 1-8 sccm; when the isothermal section is in the second flow rate state, the Ar flow rate of the single crystal growth furnace is 200-600 sccm and the N2 flow rate is 0 sccm.

9. A method for reducing the density of through-type dislocation defects in a silicon carbide crystal, applied to the apparatus for reducing the density of through-type dislocation defects in a silicon carbide crystal as described in any one of claims 1 to 8, characterized in that, include: A crucible containing silicon carbide seed crystals and silicon carbide raw materials is placed inside an insulating component and then placed together into a single crystal growth furnace; the insulating component is provided with gas exchange channels; According to the parameters set for each growth stage, silicon carbide crystals are grown to obtain N-type silicon carbide crystals; the growth stages include: a first heating stage, a constant temperature stage, a second heating stage, a high temperature growth stage, and a cooling stage; the gas flow rate in the constant temperature stage is set to a first flow rate state and a second flow rate state, and the N2 flow rate in the first flow rate state and the second flow rate state are different. During the isothermal phase, N2 is introduced into the single crystal growth furnace in a cycle of n periods according to the first flow rate and the second flow rate. Nitrogen is intentionally doped into the silicon carbide crystal during the growth process through the gas exchange channels to increase the conversion probability and ejection probability of through-type dislocations to ground plane dislocations and stacking faults in the N-type silicon carbide crystal; n≥1.

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