Silicon carbide crystal growth apparatus and preparation method

Abstract

The present application relates to a silicon carbide crystal growth device and preparation method. The silicon carbide crystal growth device includes a crucible and an atmosphere adjustment structure. The crucible has a crystal growth chamber, the bottom of the crystal growth chamber is a raw material holding chamber, and the top of the crystal growth chamber has a crystal growth substrate. The atmosphere adjustment structure is disposed between the crystal growth substrate and the raw material holding chamber, and the material of the atmosphere adjustment structure includes silicon nitride. The silicon carbide crystal growth device can provide sufficient nitrogen doping and silicon-carbon ratio control throughout the crystal growth cycle, thereby optimizing the silicon-carbon ratio in the gas phase components, preventing silicon component deficiency, reducing carbon component excess, and thereby suppressing the occurrence of carbon encapsulation, thereby promoting the growth of high-quality silicon carbide crystals.

Description

Technical Field

[0001] This application relates to the field of crystal growth technology, and in particular to a silicon carbide crystal growth apparatus and preparation method. Background Art

[0002] Silicon carbide (SiC), as a wide-bandgap semiconductor material, is widely used in high-power, high-frequency, and high-temperature electronic devices due to its superior physical and chemical properties, such as high thermal conductivity, high breakdown electric field, and high electron saturation velocity. Among these, N-type silicon carbide crystals exhibit particularly outstanding electrical and thermal properties. Currently, the physical vapor transport (PVT) method is the most commonly used method for growing silicon carbide single crystals. However, in traditional PVT crystal growth techniques, carbon encapsulation easily forms on the crystal surface, leading to a decrease in crystal quality. Summary of the Invention

[0003] Therefore, it is necessary to provide silicon carbide crystal growth apparatus and preparation method that can reduce carbon encapsulation and improve crystal quality.

[0004] One aspect of this application provides a silicon carbide crystal growth apparatus, the silicon carbide crystal growth apparatus including a crucible and an atmosphere conditioning structure, the crucible having a crystal growth cavity, the bottom of the crystal growth cavity being a raw material receiving cavity, the top of the crystal growth cavity having a crystal growth substrate, the atmosphere conditioning structure being disposed between the crystal growth substrate and the raw material receiving cavity, the material of the atmosphere conditioning structure including silicon nitride.

[0005] The aforementioned silicon carbide crystal growth apparatus incorporates an atmosphere conditioning structure between the crystal growth substrate and the raw material container. This atmosphere conditioning structure is made of silicon nitride, meaning it is positioned along the gas phase transport path where the raw material transforms from powder to gas. This structure prevents the silicon nitride and silicon carbide raw material from rapidly decomposing at high temperatures within the raw material container, thus avoiding the complete decomposition of silicon nitride in the early stages of crystal growth and consequently reducing crystal quality. Furthermore, the aforementioned silicon carbide crystal growth apparatus provides sufficient nitrogen doping and silicon-to-carbon ratio control throughout the entire crystal growth cycle, thereby optimizing the silicon-to-carbon ratio in the gas phase composition, preventing insufficient silicon content, reducing excess carbon content, suppressing carbon encapsulation, and promoting high-quality silicon carbide crystal growth.

[0006] In some embodiments, the cross-sectional area of ​​the atmosphere conditioning structure decreases from the raw material receiving cavity to the crystal growth substrate.

[0007] In some embodiments, the atmosphere conditioning structure is a hollow structure, and the wall thickness of the hollow structure decreases from the raw material receiving cavity to the crystal growth substrate.

[0008] In some embodiments, the silicon carbide crystal growth apparatus satisfies at least one of the following conditions:

[0009] (1) The ratio of the maximum to the minimum wall thickness of the hollow structure is 5~10:1;

[0010] (2) The maximum wall thickness of the hollow structure is 5mm~10mm;

[0011] (3) The minimum wall thickness of the hollow structure is 1mm to 5mm;

[0012] (4) The wall thickness of the hollow structure decreases by 1 mm for every 10 mm distance from the raw material receiving cavity to the crystal growth substrate.

[0013] In some embodiments, the outer wall of the atmosphere conditioning structure is fitted to the inner wall of the crystal growth chamber.

[0014] In some embodiments, the atmosphere conditioning structure is cylindrical, and the outer wall of the cylindrical atmosphere conditioning structure is attached to the inner wall of the crystal growth cavity; and / or,

[0015] The atmosphere conditioning structure includes multiple strip plates, each strip plate being fixed to the inner wall of the crystal growth chamber to form a hollow structure; and / or,

[0016] The atmosphere conditioning structure is made of silicon nitride ceramic, and the porosity of the atmosphere conditioning structure is ≤1%.

[0017] In some embodiments, the silicon carbide crystal growth apparatus further includes a first heater located outside the raw material receiving chamber, and a second heater located outside the crystal growth chamber for heating the atmosphere conditioning structure.

[0018] In some embodiments, the silicon carbide crystal growth apparatus further includes a support plate fixed to the inner wall of the crystal growth chamber, and the atmosphere conditioning structure is disposed on the support plate.

[0019] A second aspect of this application provides a method for preparing silicon carbide crystals, comprising the following steps:

[0020] Silicon carbide crystals are prepared using silicon carbide powder as raw material via physical vapor transport; wherein an atmosphere conditioning structure is provided along the vapor transport path from powder to gas, and the material of the atmosphere conditioning structure includes silicon nitride.

[0021] In some of these embodiments, the silicon carbide crystal growth apparatus described in the first aspect is used. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a silicon carbide crystal growth apparatus according to one embodiment.

[0023] Figure 2 This is a schematic diagram of an atmosphere conditioning structure according to one embodiment.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Crucible; 10. Crystal growth chamber; 101. Raw material receiving chamber; 2. Atmosphere conditioning structure; 3. Tray; 4. First heater; 5. Second heater; 6. Top heater; 7. Bottom heater; 8. Crystal growth substrate. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] In the preparation of silicon carbide crystals using the physical vapor transport method, the silicon component in the silicon carbide raw material preferentially decomposes, especially the silicon carbide powder near the bottom and inner wall of the crucible. This rapid graphitization of the raw material leads to an imbalance in the Si / C ratio in the gas phase composition. Furthermore, the carbon particles generated after graphitization are carried to the crystal surface by the gas flow, forming carbon encapsulation, which directly degrades crystal quality. Therefore, optimizing the silicon-to-carbon ratio in the gas phase composition is crucial. Traditional techniques sometimes control the silicon-to-carbon ratio by adjusting process parameters, but these parameters are numerous and interact with each other, making effective control difficult. Other methods involve adding silicon nitride powder to the silicon carbide powder to control the gas phase composition. While this method can prevent carbon encapsulation to some extent, the sublimation temperature of silicon nitride is lower than that of silicon carbide raw material. This causes the silicon nitride powder to sublimate completely in the early stages of crystal growth, hindering later control of the silicon-to-carbon ratio and failing to suppress carbon encapsulation formation.

[0029] Based on this, the first aspect of this application, one embodiment, provides a silicon carbide crystal growth apparatus, please refer to... Figure 1The silicon carbide crystal growth apparatus includes a crucible 1 and an atmosphere conditioning structure 2. The crucible 1 has a crystal growth chamber 10, the bottom of which is a raw material receiving chamber 101. Figure 1 The raw materials contained therein are shown in the diagram. The top of the crystal growth cavity 10 has a crystal growth substrate 8, and an atmosphere conditioning structure 2 is disposed between the crystal growth substrate 8 and the raw material containing cavity 101. The material of the atmosphere conditioning structure 2 includes silicon nitride.

[0030] The atmosphere regulating structure 2 is located between the crystal growth substrate 8 and the raw material receiving cavity 101; that is, the atmosphere regulating structure 2 is located in the space between the raw material in the crystal growth substrate 8 and the raw material in the raw material receiving cavity 101. Thus, the raw material in the raw material receiving cavity 101 is heated and transformed from powder into a gas phase, which is then transported from the bottom to the crystal growth substrate 8 via the atmosphere regulating structure 2; that is, the atmosphere regulating structure 2 is located on the gas phase transport path of the raw material transforming from powder into a gas phase. Silicon nitride in the atmosphere regulating structure 2 can decompose upon heating to generate nitrogen gas.

[0031] The aforementioned silicon carbide crystal growth apparatus includes an atmosphere conditioning structure 2 between the crystal growth substrate 8 and the raw material receiving chamber 101. The material of the atmosphere conditioning structure 2 includes silicon nitride. This atmosphere conditioning structure 2 is located on the gas phase transport path where the raw material is converted from powder to gas phase. This avoids the problem of rapid high-temperature decomposition of silicon nitride and silicon carbide raw materials mixed in the raw material receiving chamber 101 in the traditional method, which leads to the complete decomposition of silicon nitride in the early stage of crystal growth, resulting in an inability to effectively improve crystal quality. The aforementioned silicon carbide crystal growth apparatus can provide sufficient nitrogen doping and more sustained control of the silicon-carbon ratio throughout the entire crystal growth cycle, thereby optimizing the silicon-carbon ratio in the gas phase composition, compensating for silicon composition, reducing excess carbon composition, and thus suppressing the generation of carbon encapsulation phenomenon, promoting the growth of high-quality silicon carbide crystals.

[0032] The silicon carbide ingots grown using the aforementioned silicon carbide crystal growth apparatus can effectively reduce carbon encapsulation defects, reducing the wafer scrap rate caused by carbon encapsulation defects by more than 30%, and maintaining resistivity uniformity within 4%.

[0033] Understandably, when the material of the atmosphere conditioning structure 2 is silicon nitride, the atmosphere conditioning structure 2 decomposes upon heating to produce nitrogen and silicon components, providing nitrogen doping and silicon-to-carbon ratio control, thus preparing N-type silicon carbide.

[0034] Understandably, when crystal growth begins, the silicon carbide raw material at the bottom of crucible 1 will preferentially decompose, and the silicon component within the raw material will preferentially sublimate. This leads to graphitization of the raw material, resulting in carbon particles being trapped in the upward-transporting gaseous material. The gaseous material will be transported along the inner wall of crucible 1 to the crystal growth substrate 8. The atmosphere regulating structure 2 of the silicon nitride material is located in the gas transport path. The atmosphere regulating structure 2 will decompose at high temperature to release nitrogen and gaseous silicon. When the gaseous material with carbon particles is transported to the vicinity of the atmosphere regulating structure 2, the gaseous silicon produced by the decomposition of the atmosphere regulating structure 2 will react with the carbon in the gaseous material, thereby achieving the purpose of controlling the carbon-silicon ratio in the gaseous material and reducing carbon encapsulation defects on the crystal growth surface. At the same time, the nitrogen produced by the decomposition of the atmosphere regulating structure 2 can be doped into the crystal, thereby preparing an N-type silicon carbide crystal.

[0035] Understandably, the top of the atmosphere conditioning structure 2 can contact the top of the crystal growth chamber 10, or it can be left at a distance; the bottom of the atmosphere conditioning structure 2 can contact the raw material, or it can be left at a distance; the outer wall of the atmosphere conditioning structure 2 can fit against the inner wall of the crystal growth chamber 10, or it can have a gap.

[0036] In some embodiments, the bottom of the atmosphere conditioning structure 2 is 30mm to 50mm away from the upper surface of the raw material in the raw material receiving cavity 101.

[0037] In some embodiments, the cross-sectional area of ​​the atmosphere conditioning structure 2 decreases from the raw material receiving chamber 101 to the crystal growth substrate 8. The silicon component in the silicon carbide raw material will preferentially decompose. The reaction in the crystal growth chamber 10 near the raw material receiving chamber 101 requires more silicon component for regulation. More silicon component can be decomposed in areas with larger cross-sectional areas than in areas with smaller cross-sectional areas. This type of atmosphere conditioning structure 2 can better meet the silicon-to-carbon ratio regulation requirements.

[0038] Understandingly, the direction from the raw material receiving cavity 101 to the crystal growth substrate 8 is a gas phase transport method, that is, the gas phase transport direction in which the raw material is transformed from powder into gas. Figure 1 In a specific example, that is Figure 1 The middle direction is from bottom to top.

[0039] In some of these implementations, please refer to Figure 2 The atmosphere conditioning structure 2 is a hollow structure, and the wall thickness of the hollow structure decreases from the raw material receiving cavity 101 to the crystal growth substrate 8. The hollow structure of the atmosphere conditioning structure 2 can reduce the interference of airflow during the gas phase transport process, and the decreasing wall thickness from the raw material receiving cavity 101 to the crystal growth substrate 8 can better adapt to the gas phase's demand for silicon components.

[0040] In some embodiments, the ratio of the maximum to the minimum wall thickness of the hollow structure is 5 to 10:1. Carbon particles embedded in the upward-transported gaseous material react with the gaseous silicon generated by the thermal decomposition of the atmosphere conditioning structure 2 on its surface. Within this ratio range, the hollow structure provides a larger reaction contact area and a better silicon-to-carbon ratio for the aforementioned reaction, further improving the removal efficiency of carbon particles embedded in the gaseous material, ultimately reducing the crystal scrap rate and resulting in better resistivity uniformity of the crystal.

[0041] Furthermore, the ratio of the maximum to the minimum wall thickness of the hollow structure is preferably 5 to 8:1.

[0042] exist Figure 2 In a specific example, the maximum wall thickness is... Figure 2 The minimum wall thickness at the bottom of the middle cylinder is... Figure 2 The wall thickness at the top of the middle cylinder.

[0043] In some embodiments, the maximum wall thickness of the hollow structure is 5mm to 10mm.

[0044] In some embodiments, the minimum wall thickness of the hollow structure is 1mm to 5mm.

[0045] In some embodiments, the maximum wall thickness of the hollow structure is 5mm to 10mm, and the minimum wall thickness is 1mm to 5mm. Within this wall thickness range, the decomposition rate of the hollow structure matches the crystal growth rate well, providing an appropriate amount of nitrogen gas in real time throughout the entire crystal growth cycle, further promoting the growth of high-quality silicon carbide crystals.

[0046] In some embodiments, the wall thickness of the hollow structure decreases by 1 mm for every 10 mm distance from the raw material receiving cavity 101 to the crystal growth substrate 8. This decrease in wall thickness significantly reduces carbon encapsulation and improves the resistivity uniformity of the crystal.

[0047] In some embodiments, the outer diameter of the hollow structure is 160mm to 220mm.

[0048] In some embodiments, the silicon carbide crystal growth apparatus further includes a support plate 3, which is fixed on the inner wall of the crystal growth chamber 10, and the atmosphere adjustment structure 2 is disposed on the support plate 3.

[0049] Understandably, the atmosphere conditioning structure 2 made of silicon nitride is placed on the tray 3 and is located in the upper part of the crucible 1, which is a relatively cool area of ​​the thermal field, thus avoiding a large amount of decomposition on the surface of the silicon nitride ceramic in the early stage.

[0050] In some embodiments, the tray 3 is an annular plate.

[0051] Furthermore, the tray 3 is fixedly connected to the inner wall of the crucible 1 by threads.

[0052] In some embodiments, the support plate 3 is a plurality of symmetrically arranged convex plates.

[0053] Understandably, the size of the pallet 3 is as small as possible while maintaining the stability of the atmosphere conditioning structure 2.

[0054] Furthermore, the material of pallet 3 is graphite.

[0055] In some embodiments, the outer wall of the atmosphere conditioning structure 2 is attached to the inner wall of the crystal growth cavity 10. Attaching the outer wall of the atmosphere conditioning structure 2 to the inner wall of the crystal growth cavity 10 results in higher heat transfer efficiency, smoother gas phase transport, and avoids additional carbon deposition that could affect crystal quality.

[0056] Furthermore, the outer wall of the hollow structure is attached to the inner wall of the crystal growth cavity 10.

[0057] In some embodiments, the atmosphere conditioning structure 2 is cylindrical, and the outer wall of the cylindrical atmosphere conditioning structure 2 is attached to the inner wall of the crystal growth cavity 10.

[0058] Further, please refer to Figure 2 The atmosphere conditioning structure 2 is cylindrical, and the wall thickness of the cylinder decreases from the raw material receiving cavity 101 to the crystal growth substrate 8. Specifically, the outer diameter of the atmosphere conditioning structure 2 is constant, and the inner diameter is variable. Specifically, the inner diameter of the atmosphere conditioning structure 2 increases from the raw material receiving cavity 101 to the crystal growth substrate 8, thus achieving a decrease in the wall thickness of the cylinder from the raw material receiving cavity 101 to the crystal growth substrate 8.

[0059] Understandably, the atmosphere regulating structure 2 is cylindrical in shape, and the sidewalls constituting the cylindrical atmosphere regulating structure 2 can be a single unit or formed by multiple relatively independent components surrounding each other. Furthermore, when the sidewalls constituting the cylindrical atmosphere regulating structure 2 are a single unit, they can be either a perforated structure or a non-perforated structure.

[0060] In some embodiments, the atmosphere conditioning structure 2 is a solid cylinder.

[0061] Understandably, the atmosphere regulating structure 2 is a solid cylinder, meaning that the sidewall of the atmosphere regulating structure 2 is a single, solid, and non-perforated unit.

[0062] In some embodiments, the atmosphere conditioning structure 2 is composed of multiple strip plates, each strip plate being fixed to the inner wall of the crystal growth cavity 10 to form a hollow structure, such as a cylindrical hollow structure. Furthermore, the strip plates are uniformly fixed to the inner wall of the crystal growth cavity 10 at equal intervals.

[0063] Furthermore, one end of each strip plate abuts against the top of the crystal growth cavity 10, and the other end abuts against the upper surface of the support plate 3. Each strip plate is embedded and attached to the inner wall of the crystal growth cavity 10.

[0064] In some embodiments, the atmosphere conditioning structure 2 is fixed in a fence-like shape on the inner wall of the crystal growth chamber 10.

[0065] To put it simply, the fence-like structure is composed of multiple interconnected strips.

[0066] In some embodiments, the atmosphere conditioning structure 2 is made of silicon nitride ceramic, and the porosity of the atmosphere conditioning structure 2 is ≤1%.

[0067] As an example, the porosity of the atmosphere conditioning structure 2 is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%, or it can be within the range defined by any two of the above point values ​​as endpoints. The porosity of the silicon nitride ceramic is preferably 0.5% to 0.8%.

[0068] In some embodiments, the atmosphere conditioning structure 2 is made of silicon nitride ceramic, and the porosity of silicon nitride ceramic is ≤1%. The atmosphere conditioning structure 2 is made of silicon nitride ceramic, which not only has a high decomposition temperature and a slow decomposition rate that is easy to control, but also can stably decompose to produce nitrogen gas.

[0069] In some embodiments, the crystal growth substrate 8 is a seed crystal holder.

[0070] In some embodiments, the silicon carbide crystal growth apparatus further includes a first heater 4 located outside the raw material receiving chamber 101, and a second heater 5 located outside the crystal growth chamber 10 for heating the atmosphere conditioning structure 2. The placement of the first heater 4 and the second heater 5 outside the crystal growth chamber 10 allows for a better formation of a temperature gradient in the gas phase transport direction, facilitating the control of the decomposition rate of the atmosphere conditioning structure 2 through temperature changes.

[0071] As an example, in the early stage of crystal growth, the first heater 4 can be turned on and the second heater 5 can be turned off, so that the atmosphere conditioning structure 2 is in a cooler region of the thermal field, and the atmosphere conditioning structure 2 maintains a low decomposition rate, avoiding a large amount of decomposition of the atmosphere conditioning structure 2 in the early stage; in the later stage of crystal growth, as the graphitization of the raw materials intensifies, it is necessary to increase the decomposition rate of the atmosphere conditioning structure 2. At this time, the second heater 5 is turned on to provide more gaseous silicon to remove carbon particles.

[0072] Furthermore, during the preparation process, the power of the first heater 4 is greater than the power of the second heater 5.

[0073] As an example, in the early stage of crystal growth, the first heater 4 and the second heater 5 can be turned on simultaneously. The second heater 5 operates at a lower power than the first heater 4, so that the atmosphere conditioning structure 2 is in a cooler region of the thermal field.

[0074] In some embodiments, the second heater 5 includes multiple sub-heaters. This structural form is beneficial for controlling the temperature gradient of the atmosphere conditioning structure 2, enabling the layer-by-layer decomposition of the atmosphere conditioning structure 2, thereby ensuring that the atmosphere conditioning structure 2 can provide sufficient nitrogen doping and silicon-carbon ratio control throughout the entire crystal growth cycle, making the silicon-carbon ratio in the gas phase composition closer to the stoichiometry, and further improving the crystal quality.

[0075] As an example, in the later stages of crystal growth, as the graphitization of the raw materials intensifies, it is necessary to increase the decomposition rate of the atmosphere conditioning structure 2. At this time, the sub-heaters can be turned on. Because the lower layer reaction requires a large amount of gaseous silicon, the bottommost sub-heater can be turned on first. As the atmosphere conditioning structure 2 decomposes from bottom to top, the corresponding sub-heaters are turned on sequentially from bottom to top. The direction from bottom to top is from the raw material receiving chamber 101 to the crystal growth substrate 8.

[0076] Furthermore, the second heater 5 includes a plurality of sub-heaters arranged in the direction from the raw material receiving cavity 101 to the crystal growth substrate 8, and the power of the plurality of sub-heaters decreases in the direction from the raw material receiving cavity 101 to the crystal growth substrate 8.

[0077] As an example, in the later stage of crystal growth, as the graphitization of the raw material intensifies, it is necessary to increase the decomposition rate of the atmosphere conditioning structure 2. At this time, all sub-heaters can be turned on, and each sub-heater operates at a different power, with the power decreasing from the raw material receiving chamber 101 to the crystal growth substrate 8.

[0078] In some embodiments, the silicon carbide crystal growth apparatus further includes a top heater 6 and a bottom heater 7, with the top heater 6 located on the top outer side of the crystal growth chamber 10 and the bottom heater 7 located on the bottom outer side of the raw material receiving chamber 101.

[0079] A second aspect of this application provides a method for preparing silicon carbide crystals, comprising the following steps:

[0080] Silicon carbide crystals are prepared using silicon carbide powder as raw material through a physical vapor transport method; wherein, an atmosphere conditioning structure 2 is set in the vapor transport path from powder to gas phase, and the material of the atmosphere conditioning structure 2 includes silicon nitride.

[0081] When preparing silicon carbide crystals using silicon carbide powder as raw material via physical vapor transport, an atmosphere conditioning structure 2 is set along the vapor transport path from powder to gas phase. The material of the atmosphere conditioning structure 2 includes silicon nitride. This method can avoid the rapid high-temperature decomposition of silicon nitride and silicon carbide raw material together, which would lead to the complete decomposition of silicon nitride in the early stage of crystal growth and thus a decrease in crystal quality. This method can provide sufficient nitrogen doping and silicon-carbon ratio control throughout the entire crystal growth cycle, thereby optimizing the silicon-carbon ratio in the gas phase composition, preventing insufficient silicon composition, reducing excess carbon composition, and thus suppressing the occurrence of carbon encapsulation phenomenon and promoting the growth of high-quality silicon carbide crystals.

[0082] In some of these embodiments, the silicon carbide crystal growth apparatus described in the first aspect is used.

[0083] In some of these embodiments, heating is used to maintain the temperature of the silicon carbide powder at 2100°C to 2500°C at the start of growth.

[0084] In some embodiments, the growth time is 200h to 400h.

[0085] In some embodiments, at the start of growth, argon gas with a flow rate of 130 sccm to 160 sccm is introduced into the crystal growth chamber 10.

[0086] In some implementations, the growth environment pressure is controlled to be 200 Pa to 300 Pa.

[0087] The following are specific examples.

[0088] Example 1

[0089] Adopting such Figure 1 The silicon carbide crystal growth apparatus shown is used for N-type silicon carbide crystal growth, wherein the atmosphere conditioning structure 2 adopts... Figure 2 The silicon nitride ceramic cylinder shown specifically includes the following steps:

[0090] 6 kg of silicon carbide powder is loaded into the raw material receiving cavity 101 at the bottom of the crucible 1. A silicon carbide seed crystal is placed below the crystal growth substrate 8, and a silicon nitride ceramic cylinder is placed on a graphite support plate 3 inside the crystal growth cavity 10. The atmosphere conditioning structure 2 uses a silicon nitride ceramic cylinder with a mass of 400 g, a height of 50 mm, an outer diameter of 220 mm, and a porosity of 0.6%. The wall thickness of the silicon nitride ceramic cylinder decreases uniformly along the gas phase transport direction at a rate of 1 mm every 10 mm, with a top wall thickness of 1 mm and a bottom wall thickness of 5 mm.

[0091] At the start of growth, argon gas with a flow rate of 150 sccm is introduced into the crystal growth chamber 10, and the growth environment pressure is maintained at 280 Pa. The top heater 6, the first heater 4, and the bottom heater 7 are turned on to heat the crucible 1, maintaining the temperature of the silicon carbide powder at 2350℃. At this time, the silicon carbide powder decomposes and sublimates, and the upward-transporting gaseous material reacts with the gaseous silicon produced by the decomposition of silicon nitride on the surface of the silicon nitride ceramic cylinder, thereby eliminating carbon particles trapped in the gaseous material and reducing carbon encapsulation defects. As crystal growth progresses, after 150 hours of growth, the second heater 5 is turned on to further enhance the growth of the entire crystal. During the growth process, the silicon nitride ceramic cylinder is heated to maintain the surface temperature of the silicon nitride ceramic cylinder at 2000℃~2100℃, causing the silicon nitride ceramic cylinder to gradually decompose and produce nitrogen gas and gaseous silicon. As the crystal growth progresses, the graphitization of the silicon carbide raw material intensifies. Turning on the second heater 5 can increase the decomposition rate of silicon nitride. At the same time, by controlling the power of the second heater 5, the decomposition rate of the silicon nitride ceramic cylinder is uniformly controlled, thereby achieving stable nitrogen doping. Meanwhile, the gaseous silicon produced by the decomposition of the silicon nitride ceramic cylinder reacts with the carbon particles embedded in the gaseous material, which more effectively reduces carbon encapsulation. After the crystal growth is completed, all heaters are turned off.

[0092] Comparative Example 1

[0093] Comparative Example 1 is basically the same as Example 1, except that the silicon nitride ceramic cylinder is replaced with an equal mass of silicon nitride powder, and the silicon nitride powder is mixed into silicon carbide raw material for crystal growth.

[0094] The crystals prepared in Example 1 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1 below.

[0095] Resistivity uniformity refers to the degree of uniformity of resistivity distribution at various locations within a material. Resistivity uniformity is measured using a four-probe tester.

[0096] Table 1

[0097]

[0098] As shown in Table 1 above, silicon carbide ingots grown using the silicon carbide crystal growth apparatus of this application can effectively reduce carbon encapsulation defects, reduce the wafer scrap rate caused by carbon encapsulation defects by 35%, and maintain resistivity uniformity within 4%.

[0099] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, The silicon carbide crystal growth apparatus includes a crucible and an atmosphere conditioning structure. The crucible has a crystal growth cavity, the bottom of which is a raw material receiving cavity, and the top of which is a crystal growth substrate. The atmosphere conditioning structure is located between the crystal growth substrate and the raw material receiving cavity. The material of the atmosphere conditioning structure is silicon nitride ceramic. The atmosphere conditioning structure is a hollow structure, and the wall thickness of the hollow structure decreases from the raw material receiving cavity to the crystal growth substrate. The ratio of the maximum to the minimum wall thickness of the hollow structure is 5 to 10:

1.

2. The silicon carbide crystal growth apparatus as described in claim 1, characterized in that, The wall thickness of the hollow structure decreases by 1 mm for every 10 mm distance from the raw material receiving cavity to the crystal growth substrate.

3. The silicon carbide crystal growth apparatus as described in claim 2, characterized in that, At least one of the following conditions must be met: (1) The maximum wall thickness of the hollow structure is 5mm~10mm; (2) The minimum wall thickness of the hollow structure is 1mm to 5mm.

4. The silicon carbide crystal growth apparatus according to any one of claims 1 to 3, characterized in that, The outer wall of the atmosphere conditioning structure is attached to the inner wall of the crystal growth chamber.

5. The silicon carbide crystal growth apparatus according to any one of claims 1 to 3, characterized in that, The atmosphere conditioning structure is cylindrical, and its outer wall is attached to the inner wall of the crystal growth chamber; and / or, The atmosphere conditioning structure includes multiple strip plates, each strip plate being fixed to the inner wall of the crystal growth chamber to form a hollow structure; and / or, The porosity of the atmosphere conditioning structure is ≤1%.

6. The silicon carbide crystal growth apparatus according to any one of claims 1 to 3, characterized in that, The silicon carbide crystal growth apparatus further includes a first heater located outside the raw material receiving chamber, and a second heater located outside the crystal growth chamber for heating the atmosphere conditioning structure.

7. The silicon carbide crystal growth apparatus according to any one of claims 1 to 3, characterized in that, The silicon carbide crystal growth apparatus also includes a support plate, which is fixed on the inner wall of the crystal growth chamber, and the atmosphere adjustment structure is disposed on the support plate.

8. The silicon carbide crystal growth apparatus according to any one of claims 1 to 3, characterized in that, The distance between the bottom of the atmosphere conditioning structure and the upper surface of the raw material in the raw material receiving cavity is 30mm~50mm.

9. A method for preparing silicon carbide crystals, characterized in that, Includes the following steps: The silicon carbide crystal growth apparatus according to any one of claims 1 to 7 is used to prepare silicon carbide crystals using silicon carbide powder as raw material via physical vapor transport; wherein, an atmosphere conditioning structure is provided on the vapor transport path in which the raw material is converted from powder to gas, and the material of the atmosphere conditioning structure includes silicon nitride.

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