Silicon carbide crystal growth device and preparation method

Abstract

The invention relates to a silicon carbide crystal growth device and a preparation method.The silicon carbide crystal growth device comprises a crucible and an atmosphere adjusting structure, the crucible is provided with a crystal growth cavity, the bottom of the crystal growth cavity is a raw material containing cavity, and the top of the crystal growth cavity is provided with a crystal growth base body; the atmosphere adjusting structure is arranged between the crystal growth substrate and the raw material accommodating cavity, and the material of the atmosphere adjusting structure comprises silicon nitride. The silicon carbide crystal growth device can provide sufficient nitrogen doping and silicon-carbon ratio regulation and control in the whole growth period of the crystal, so that the silicon-carbon ratio in a gas-phase component is optimized, the silicon component is prevented from being insufficient, the excess of the carbon component is reduced, the carbon wrapping phenomenon is further inhibited, and the growth of the high-quality silicon carbide crystal is promoted.

Description

Technical Field

[0001] The present application relates to the technical field of crystal growth, and particularly to a silicon carbide crystal growth apparatus and a preparation method thereof. Background Art

[0002] Silicon carbide (SiC), as a wide-bandgap semiconductor material, is widely used in the fields of high-power, high-frequency, and high-temperature electronic devices due to its excellent physical and chemical properties, such as high thermal conductivity, high breakdown electric field, and high electron saturation velocity. Among them, the electrical and thermal conductivity of N-type silicon carbide crystals are particularly prominent. Currently, the physical vapor transport method (PVT) is the most commonly used method for growing silicon carbide single crystals. However, in the traditional technology of growing crystals by the physical vapor transport method, carbon encapsulation is likely to form on the crystal surface, which in turn leads to a decline in crystal quality. Summary of the Invention

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

[0004] In one aspect of the present application, a silicon carbide crystal growth apparatus is provided. The silicon carbide crystal growth apparatus includes a crucible and an atmosphere adjustment structure. The crucible has a crystal growth cavity, the bottom of the crystal growth cavity is a raw material accommodation cavity, the top of the crystal growth cavity has a crystal growth substrate, the atmosphere adjustment structure is disposed between the crystal growth substrate and the raw material accommodation cavity, and the material of the atmosphere adjustment structure includes silicon nitride.

[0005] The above-mentioned silicon carbide crystal growth apparatus is provided with an atmosphere adjustment structure between the crystal growth substrate and the raw material accommodation cavity, and the material of the atmosphere adjustment structure includes silicon nitride, that is, this atmosphere adjustment structure is disposed on the gas-phase transport path where the raw material is converted from powder to gas phase. This structural form can avoid the rapid decomposition of silicon nitride and the silicon carbide raw material together at high temperature in the raw material accommodation cavity, resulting in the exhaustion of silicon nitride at the initial stage of crystal growth and further leading to a decline in crystal quality; the above-mentioned silicon carbide crystal growth apparatus can provide sufficient nitrogen doping and silicon-carbon ratio regulation throughout the crystal growth cycle, thereby optimizing the silicon-carbon ratio in the gas phase components, preventing insufficient silicon components, reducing the excess of carbon components, and further inhibiting the generation of carbon encapsulation phenomenon and promoting the growth of high-quality silicon carbide crystals.

[0006] In some embodiments, the cross-sectional area of the atmosphere adjustment structure decreases in the direction from the raw material accommodation cavity to the crystal growth substrate.

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

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

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

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

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

[0012] (4) The decreasing amplitude of the wall thickness of the hollow structure per 10 mm distance in the direction from the raw material accommodating cavity to the crystal growth substrate is 1 mm.

[0013] In some of these embodiments, the outer sidewall of the atmosphere regulating structure fits against the inner sidewall of the crystal growth chamber.

[0014] In some of these embodiments, the atmosphere regulating structure is cylindrical, and the outer sidewall of the cylindrical atmosphere regulating structure fits against the inner sidewall of the crystal growth chamber; and / or,

[0015] The atmosphere regulating structure includes a plurality of strip-shaped plates, and each strip-shaped plate is fixed on the inner sidewall of the crystal growth chamber to form a hollow structure; and / or,

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

[0017] In some of these embodiments, the silicon carbide crystal growth device further includes a first heater, the first heater is disposed outside the raw material accommodating cavity, and a second heater for heating the atmosphere regulating structure is disposed outside the crystal growth chamber.

[0018] In some of these embodiments, the silicon carbide crystal growth device further includes a tray, the tray is fixed on the inner sidewall of the crystal growth chamber, and the atmosphere regulating structure is disposed on the tray.

[0019] In a second aspect of the present application, a method for preparing a silicon carbide crystal is provided, including the following steps:

[0020] Using physical vapor transport method to prepare silicon carbide crystal with silicon carbide powder as raw material; wherein, an atmosphere regulating structure is disposed on the gas transport path where the raw material is converted from powder to gas phase, and the material of the atmosphere regulating structure includes silicon nitride.

[0021] In some of these embodiments, it is carried out using the silicon carbide crystal growth device described in the first aspect. Description of the Drawings

[0022] Figure 1 Schematic structural diagram of a silicon carbide crystal growth device according to an embodiment.

[0023] Figure 2 Schematic structural diagram of an atmosphere regulation structure according to an embodiment.

[0024] Description of reference numerals:

[0025] 1, crucible; 10, crystal growth chamber; 101, raw material accommodation chamber; 2, atmosphere regulation structure; 3, tray; 4, first heater; 5, second heater; 6, top heater; 7, bottom heater; 8, crystal growth substrate. Specific embodiments

[0026] For ease of understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] In the process of preparing silicon carbide single crystal by physical vapor transport method, since the silicon component in the silicon carbide raw material decomposes preferentially, especially the silicon carbide powder near the bottom and inner wall of the crucible decomposes preferentially, the raw material is rapidly graphitized, and the Si / C ratio in the gas phase components will also be imbalanced. Moreover, the carbon particles generated after the raw material is graphitized will be carried to the crystal surface by the gas flow to form carbon encapsulation, and the formation of carbon encapsulation will directly lead to the decline of crystal quality. Therefore, optimizing the silicon-carbon ratio in the gas phase components is crucial. In the traditional technology, some adjust the silicon-carbon ratio by adjusting process parameters, but there are many process parameters and they affect each other, making it difficult to achieve effective control; some add silicon nitride powder to the silicon carbide powder to regulate the gas phase components. Although this method can prevent the generation of carbon encapsulation to a certain extent, since the sublimation temperature of silicon nitride is lower than that of the silicon carbide raw material, this will cause the silicon nitride powder to sublimate completely at the initial stage of crystal growth, which is not conducive to the control of the silicon-carbon ratio in the later stage and cannot inhibit the generation of carbon encapsulation in the later stage of the crystal.

[0029] Based on this, in the first aspect of the present application, an embodiment provides a silicon carbide crystal growth device. Please refer to Figure 1, the silicon carbide crystal growth apparatus includes a crucible 1 and an atmosphere regulating structure 2. The crucible 1 has a crystal growth chamber 10, and the bottom of the crystal growth chamber 10 is a raw material accommodating chamber 101 ( Figure 1 The raw materials accommodated therein are shown). The top of the crystal growth chamber 10 has a crystal growth substrate 8, and the atmosphere regulating structure 2 is provided between the crystal growth substrate 8 and the raw material accommodating chamber 101. The material of the atmosphere regulating structure 2 includes silicon nitride.

[0030] Wherein, the atmosphere regulating structure 2 is provided between the crystal growth substrate 8 and the raw material accommodating chamber 101; that is, the atmosphere regulating structure 2 is provided in the space between the crystal growth substrate 8 and the raw materials in the raw material accommodating chamber 101. Thus, the raw materials in the raw material accommodating chamber 101 are heated and transformed from powder into gas phase and transmitted from the bottom to the crystal growth substrate 8, passing through the atmosphere regulating structure 2; that is, the atmosphere regulating structure 2 is provided on the gas phase transmission path when the raw materials are transformed from powder into gas phase. Nitrogen can be generated by the decomposition of the silicon nitride in the atmosphere regulating structure 2 when heated.

[0031] The above-mentioned silicon carbide crystal growth apparatus is provided with an atmosphere regulating structure 2 between the crystal growth substrate 8 and the raw material accommodating chamber 101, and the material of the atmosphere regulating structure 2 includes silicon nitride, that is, the atmosphere regulating structure 2 is provided on the gas phase transmission path when the raw materials are transformed from powder into gas phase, which can avoid the problem that the traditional mixing of silicon nitride and silicon carbide raw materials in the raw material accommodating chamber 101 decomposes rapidly at high temperature, resulting in the exhaustion of silicon nitride at the initial stage of crystal growth and unable to effectively improve the crystal quality; the above-mentioned silicon carbide crystal growth apparatus can provide relatively sufficient nitrogen doping and relatively persistent regulation of the silicon-carbon ratio throughout the entire crystal growth cycle, so as to optimize the silicon-carbon ratio in the gas phase components, make up for the silicon component, reduce the excess of the carbon component, and further inhibit the generation of carbon encapsulation phenomenon, and promote the growth of high-quality silicon carbide crystals.

[0032] The silicon carbide ingot grown by using the above-mentioned silicon carbide crystal growth apparatus can effectively reduce carbon encapsulation defects, the wafer scrap rate caused by carbon encapsulation defects is reduced by more than 30%, and the resistivity uniformity is maintained within 4%.

[0033] It can be understood that when the material of the atmosphere regulating structure 2 is silicon nitride, the atmosphere regulating structure 2 decomposes when heated to generate nitrogen and silicon components, providing nitrogen doping and silicon-carbon ratio regulation to prepare N-type silicon carbide.

[0034] Understandably, when crystal growth begins, the silicon carbide raw material at the bottom of the crucible 1 will decompose preferentially, and the silicon component in the raw material will sublime preferentially, which will lead to the graphitization of the raw material, resulting in carbon particles being mixed in the upwardly transported gas-phase substances. The gas-phase substances will be transported along the inner wall of the crucible 1 towards the crystal growth substrate 8; the atmosphere regulating structure 2 made of silicon nitride material is on the gas transmission path. At high temperatures, the atmosphere regulating structure 2 will decompose into nitrogen gas and gaseous silicon. When the gas-phase substances mixed with carbon particles are transported near the atmosphere regulating structure 2, the gaseous silicon decomposed by the atmosphere regulating structure 2 at this time will react with the carbon in the gas-phase substances, thereby achieving the purpose of regulating the carbon-silicon ratio in the gas-phase substances and reducing the carbon-wrapping defect on the crystal growth surface; at the same time, the nitrogen gas decomposed on the surface of the atmosphere regulating structure 2 can be doped into the crystal, thereby preparing N-type silicon carbide crystals.

[0035] Understandably, the top of the atmosphere regulating structure 2 can be in contact with the top of the crystal growth chamber 10, or there can be a distance left. The bottom of the atmosphere regulating structure 2 can be in contact with the raw material, or there can be a distance left; the outer sidewall of the atmosphere regulating structure 2 can be attached to the inner sidewall of the crystal growth chamber 10, or there can be a gap left.

[0036] In some embodiments, the distance between the bottom of the atmosphere regulating structure 2 and the upper surface of the raw material in the raw material accommodating cavity 101 is 30 mm to 50 mm.

[0037] In some embodiments, the cross-sectional area of the atmosphere regulating structure 2 decreases in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8. The silicon component in the silicon carbide raw material will decompose preferentially. The reaction in the crystal growth chamber 10 near the raw material accommodating cavity 101 requires more silicon components for regulation. More silicon components can be decomposed at the place with a larger cross-sectional area than at the place with a smaller cross-sectional area. The atmosphere regulating structure 2 in this structural form can better meet the requirements for regulating the silicon-carbon ratio.

[0038] Understandably, the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8 is the gas-phase transmission direction, that is: the gas-phase transmission direction in which the raw material is converted from powder to gas phase. In Figure 1 the specific example of Figure 1 it is the upward direction from bottom to top.

[0039] In some embodiments, please refer to Figure 2 , the atmosphere regulating structure 2 is a hollow structure, and the wall thickness of the hollow structure decreases in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8. The atmosphere regulating structure 2 in the shape of a hollow structure can reduce the interference with the gas flow during the gas-phase transmission process. The decreasing wall thickness in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8 can better adapt to the gas-phase demand for silicon components.

[0040] In some of these embodiments, the ratio of the maximum wall thickness to the minimum wall thickness of the hollow structure is 5 to 10:1. The carbon particles mixed in the upwardly transported gaseous substances will react with the gaseous silicon generated by the thermal decomposition of the atmosphere regulating structure 2 on the surface of the atmosphere regulating structure 2. The hollow structure within this ratio range can provide a larger reaction contact surface and a better silicon-carbon ratio for the aforementioned reaction, further improving the removal efficiency of the carbon particles mixed in the gaseous substances, ultimately reducing the crystal scrap rate, and making the resistivity uniformity of the crystal better.

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

[0042] In Figure 2 the specific example of Figure 2 the maximum wall thickness is the Figure 2 wall thickness at the bottommost part of the middle cylinder, and the minimum wall thickness is the

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

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

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

[0046] In some of these embodiments, the decreasing amplitude of the wall thickness of the hollow structure per 10 mm distance from the raw material containing cavity 101 to the crystal growth substrate 8 is 1 mm. With this decreasing amplitude of the wall thickness of the hollow structure, the inhibition of the carbon wrapping phenomenon and the improvement effect of the resistivity uniformity of the crystal are particularly obvious.

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

[0048] In some of these embodiments, the silicon carbide crystal growth device further includes a support plate 3, the support plate 3 is fixed on the inner side wall of the crystal growth chamber 10, and the atmosphere regulating structure 2 is arranged on the support plate 3.

[0049] Understandably, the atmosphere regulating structure 2 made of silicon nitride is placed on the support plate 3 and is located in the upper half part inside the crucible 1, which is a relatively cold area of the thermal field, and can avoid a large amount of decomposition on the surface of the silicon nitride ceramic in the initial stage.

[0050] In some of these embodiments, the pallet 3 is an annular plate.

[0051] Further, the pallet 3 is fixedly connected to the inner sidewall of the crucible 1 by a thread.

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

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

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

[0055] In some of these embodiments, the outer sidewall of the atmosphere regulating structure 2 fits against the inner sidewall of the crystal growth chamber 10. Fitting the outer sidewall of the atmosphere regulating structure 2 against the inner sidewall of the crystal growth chamber 10 makes the heat transfer efficiency higher, the gas phase transmission process smoother, and avoids the generation of additional carbon deposition that affects the crystal quality.

[0056] Further, the outer sidewall of the hollow structure fits against the inner sidewall of the crystal growth chamber 10.

[0057] In some of these embodiments, the atmosphere regulating structure 2 is in a cylindrical shape, and the outer sidewall of the cylindrical atmosphere regulating structure 2 fits against the inner sidewall of the crystal growth chamber 10.

[0058] Further, please refer to Figure 2 , the atmosphere regulating structure 2 is in a cylindrical shape, and the wall thickness of the cylinder decreases from the raw material accommodation chamber 101 to the crystal growth substrate 8 direction. Specifically, the outer diameter of the atmosphere regulating structure 2 is of equal diameter, the inner diameter of the atmosphere regulating structure 2 is of variable diameter. Specifically, the inner diameter of the atmosphere regulating structure 2 increases from the raw material accommodation chamber 101 to the crystal growth substrate 8 direction, so as to achieve the wall thickness of the cylinder decreasing from the raw material accommodation chamber 101 to the crystal growth substrate 8 direction.

[0059] Understandably, the atmosphere regulating structure 2 is integrally in a cylindrical shape, and the sidewall of the cylindrical atmosphere regulating structure 2 can be a whole or formed by a plurality of relatively independent components surrounding. Further, when the sidewall of the cylindrical atmosphere regulating structure 2 is a whole, it can be a hollow structure or a non - hollow structure.

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

[0061] Understandably, the atmosphere regulating structure 2 being a solid cylinder means that the sidewall of the atmosphere regulating structure 2 is a whole and solid without being hollowed out.

[0062] In some of these embodiments, the atmosphere regulating structure 2 is composed of multiple strip-shaped plates, and each strip-shaped plate is fixed on the inner sidewall of the crystal growth chamber 10 to form a hollow structure, such as a cylindrical hollow structure. Further, each strip-shaped plate is evenly fixed on the inner sidewall of the crystal growth chamber 10 at equal intervals.

[0063] Furthermore, one end of each strip-shaped plate abuts against the top of the crystal growth chamber 10, and the other end abuts against the upper surface of the support plate 3. Each strip-shaped plate is embedded and fitted on the inner sidewall of the crystal growth chamber 10.

[0064] In some of these embodiments, the atmosphere regulating structure 2 is fixed on the inner sidewall of the crystal growth chamber 10 in a fence shape.

[0065] Understandably, the fence shape is composed of multiple interconnected strip-shaped plates.

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

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

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

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

[0070] In some of these embodiments, the silicon carbide crystal growth device further includes a first heater 4. The first heater 4 is arranged outside the raw material accommodation chamber 101, and a second heater 5 for heating the atmosphere regulating structure 2 is arranged outside the crystal growth chamber 10. Arranging the first heater 4 and the second heater 5 outside the crystal growth chamber 10 can better form a temperature gradient in the gas phase transmission direction, which is convenient for regulating the decomposition rate of the atmosphere regulating structure 2 through temperature changes.

[0071] As an example, at the initial 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 regulating structure 2 is in a relatively cold region of the thermal field, keeping the decomposition rate of the atmosphere regulating structure 2 low and avoiding a large amount of decomposition of the atmosphere regulating structure 2 at the initial stage; at 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 regulating structure 2. At this time, the second heater 5 is turned on to provide more gaseous silicon to remove carbon particles.

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

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

[0074] In some of the embodiments, the second heater 5 includes a plurality of sub-heaters. This structural form is conducive to controlling the temperature gradient of the atmosphere regulating structure 2, enabling layer-by-layer decomposition of the atmosphere regulating structure 2, and further promoting the atmosphere regulating structure 2 to provide sufficient nitrogen doping and silicon-carbon ratio regulation throughout the entire crystal growth cycle, making the silicon-carbon ratio in the gas phase closer to the stoichiometric ratio and further improving the crystal quality.

[0075] As an example, at 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 regulating structure 2. At this time, the sub-heaters can be turned on. Since the reaction demand in the lower layer is large and more gaseous silicon is required, the lowermost sub-heater can be turned on first. As the atmosphere regulating 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 accommodating cavity 101 to the crystal growth substrate 8.

[0076] Further, the second heater 5 includes a plurality of sub-heaters arranged in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8, and the powers of the plurality of sub-heaters decrease in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8.

[0077] As an example, at 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 regulating structure 2. At this time, all the sub-heaters can be turned on, and each sub-heater operates at a different power, and the power decreases in the direction from the raw material accommodating cavity 101 to the crystal growth substrate 8.

[0078] In some of the embodiments, the silicon carbide crystal growth device further includes a top heater 6 and a bottom heater 7. The top heater 6 is disposed outside the top of the crystal growth cavity 10, and the bottom heater 7 is disposed outside the bottom of the raw material accommodating cavity 101.

[0079] The second aspect of the present application provides a method for preparing a silicon carbide crystal, comprising the following steps:

[0080] Using physical vapor transport method, silicon carbide powder is used as raw material to prepare silicon carbide crystal; wherein, an atmosphere regulating structure 2 is arranged on the gas phase transport path where the raw material is converted from powder to gas phase, and the material of the atmosphere regulating structure 2 includes silicon nitride.

[0081] When using physical vapor transport method to prepare silicon carbide crystal with silicon carbide powder as raw material, an atmosphere regulating structure 2 is arranged on the gas phase transport path where the raw material is converted from powder to gas phase, and the material of the atmosphere regulating structure 2 includes silicon nitride. This method can avoid the high-temperature rapid decomposition of silicon nitride together with the silicon carbide raw material, resulting in the complete decomposition of silicon nitride at the initial stage of crystal growth, and then leading to the decline of crystal quality; this method can provide sufficient nitrogen doping and silicon-carbon ratio regulation throughout the crystal growth cycle, so as to optimize the silicon-carbon ratio in the gas phase components, prevent the shortage of silicon components, reduce the excess of carbon components, and then inhibit the generation of carbon encapsulation phenomenon, and promote the growth of high-quality silicon carbide crystals.

[0082] In some embodiments, it is carried out by using the silicon carbide crystal growth device described in the first aspect.

[0083] In some embodiments, at the beginning of growth, the temperature of the silicon carbide powder is maintained at 2100°C - 2500°C by heating.

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

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

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

[0087] The following are specific examples.

[0088] Example 1

[0089] Adopt the Figure 1 shown silicon carbide crystal growth device to carry out the growth of N-type silicon carbide crystal, and the atmosphere regulating structure 2 therein adopts the Figure 2 shown silicon nitride ceramic cylinder, specifically including the following steps:

[0090] 6 kg of silicon carbide powder is loaded into the raw material containing chamber 101 at the bottom of the crucible 1, a silicon carbide seed crystal is placed under the crystal growth substrate 8, and a silicon nitride ceramic tube is placed on a graphite support plate 3 in the crystal growth chamber 10; wherein, the atmosphere adjustment structure 2 adopts a silicon nitride ceramic tube 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 tube decreases uniformly along the gas phase transmission direction with a decreasing amplitude of 1 mm for every 10 mm distance, the top wall thickness is 1 mm, and the bottom wall thickness is 5 mm;

[0091] At the beginning of growth, argon gas with a gas flow rate of 150sccm is introduced into the crystal growth chamber 10, the growth environment pressure is set to be maintained at 280pa, the top heater 6, the first heater 4 and the bottom heater 7 are turned on to heat the crucible 1 to maintain the temperature of the silicon carbide powder at 2350°C, at which time the silicon carbide powder decomposes and sublimates, and the gas phase material transmitted upward will react with the gas phase silicon produced by the decomposition of silicon nitride on the surface of the silicon nitride ceramic tube, thereby eliminating the carbon particles contained in the gas phase material and reducing the carbon encapsulation defects; as the crystal growth progresses, after 150h of growth, the second heater 5 is turned on in the subsequent entire crystal During the growth process, the silicon nitride ceramic tube is heated to keep the surface temperature of the silicon nitride ceramic tube at 2000°C~2100°C, so that the silicon nitride ceramic tube is gradually decomposed to produce nitrogen and gaseous silicon. As the crystal growth progresses, the graphitization of the silicon carbide raw material increases. Turning on the second heater 5 can increase the decomposition rate of silicon nitride. At the same time, the decomposition speed of the silicon nitride ceramic tube is uniformly controlled by controlling the power of the second heater 5, thereby achieving stable nitrogen doping. At the same time, the gaseous silicon produced by the decomposition of the silicon nitride ceramic tube reacts with the carbon particles contained in the gas phase material to more effectively reduce carbon encapsulation. After the crystal growth is completed, all heaters are turned off.

[0092] Comparative Example 1

[0093] Comparative Example 1 is substantially the same as Example 1, except that the silicon nitride ceramic tube is replaced with silicon nitride powder of equal mass, 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 uniformity of the resistivity distribution at each location within the material. Resistivity uniformity is measured using a four-probe tester.

[0096] Table 1

[0097]

[0098] As can be seen from Table 1 above, the silicon carbide ingot grown by the silicon carbide crystal growth device of the present application can effectively reduce carbon inclusion defects, the wafer scrap rate caused by carbon inclusion defects is reduced by 35%, and the resistivity uniformity is maintained within 4%.

[0099] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0100] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, The silicon carbide crystal growth device includes a crucible and an atmosphere regulating structure. The crucible has a crystal growth chamber, the bottom of the crystal growth chamber is a raw material accommodating chamber, the top of the crystal growth chamber has a crystal growth substrate, the atmosphere regulating structure is arranged between the crystal growth substrate and the raw material accommodating chamber, and the material of the atmosphere regulating structure includes silicon nitride.

2. The silicon carbide crystal growth apparatus according to claim 1, wherein, The cross-sectional area of the atmosphere regulating structure decreases in the direction from the raw material accommodating chamber to the crystal growth substrate.

3. The silicon carbide crystal growth apparatus according to claim 1, wherein, The atmosphere regulating structure is a hollow structure, and the wall thickness of the hollow structure decreases in the direction from the raw material accommodating chamber to the crystal growth substrate.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, Meet at least one of the following conditions: (1) The ratio of the maximum value to the minimum value of the wall thickness of the hollow structure is 5-10:1; (2) The maximum value of the wall thickness of the hollow structure is 5 mm - 10 mm; (3) The minimum value of the wall thickness of the hollow structure is 1 mm - 5 mm; (4) The decreasing amplitude of the wall thickness of the hollow structure per 10 mm distance in the direction from the raw material accommodating chamber to the crystal growth substrate is 1 mm.

5. The silicon carbide crystal growth apparatus according to any one of claims 1 to 4, characterized in that, The outer wall of the atmosphere regulating structure fits the inner wall of the crystal growth chamber.

6. The silicon carbide crystal growth apparatus according to any one of claims 1 to 4, characterized in that, The atmosphere regulating structure is cylindrical, and the outer wall of the cylindrical atmosphere regulating structure fits the inner wall of the crystal growth chamber; and / or, The atmosphere regulating structure includes a plurality of strip-shaped plates, and each strip-shaped plate is fixed on the inner wall of the crystal growth chamber to form a hollow structure; and / or, The material of the atmosphere regulating structure is silicon nitride ceramic, and the porosity of the atmosphere regulating structure ≤ 1%.

7. The silicon carbide crystal growth apparatus according to any one of claims 1 to 4, characterized in that, The silicon carbide crystal growth device further includes a first heater, the first heater is arranged outside the raw material accommodating chamber, and a second heater for heating the atmosphere regulating structure is arranged outside the crystal growth chamber.

8. The silicon carbide crystal growth apparatus according to any one of claims 1 to 4, characterized in that, The silicon carbide crystal growth device further includes a support plate, the support plate is fixed on the inner wall of the crystal growth chamber, and the atmosphere regulating structure is arranged on the support plate.

9. A method for preparing a silicon carbide crystal, characterized in that, Including the following steps: Using physical vapor transport method to prepare silicon carbide crystal with silicon carbide powder as raw material; wherein, an atmosphere regulating structure is arranged on the gas transport path where the raw material is converted from powder to gas phase, and the material of the atmosphere regulating structure includes silicon nitride.

10. The method for preparing a silicon carbide crystal according to claim 9, wherein, Carry out by using the silicon carbide crystal growth device according to any one of claims 1 to 8.

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