Crucible, silicon carbide crystal growth equipment and crucible preparation method

Abstract

The invention relates to a crucible, silicon carbide crystal growth equipment and a crucible preparation method. In one aspect, there is provided a crucible comprising: a crucible body made of graphite; the composite material layer is arranged on the inner surface of the crucible body, the composite material layer is made of carbon and silicon and releases the carbon and the silicon in the growth process of the silicon carbide crystals, and the composite material layer is configured to enable the carbon released in the early stage of release to be more than the released silicon and the carbon released in the later stage of release to be less than the released silicon. Therefore, the quality of the grown silicon carbide crystal can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor manufacturing technology, and in particular, to a crucible, a silicon carbide crystal growth device, and a crucible preparation method. Background Art

[0002] As a third-generation semiconductor material, silicon carbide (SiC) has the advantages of large bandgap, high electron saturation rate, and high thermal conductivity. It can be widely used in automobiles, communications, photovoltaic power generation and other fields.

[0003] Physical Vapor Transport (PVT) is a common method for growing SiC crystals. In the PVT method, SiC powder is placed at the bottom of a graphite crucible and sublimated into gaseous Si and Si by heating. 2 C. SiC 2 These gaseous components will then condense on the surface of the SiC seed crystal with a lower temperature fixed on the top of the graphite crucible and grow to form SiC crystals.

[0004] However, during the growth of SiC crystals, Si will be released into the growth environment. At the same time, since the PVT method uses a graphite crucible to provide a heat field, C will also be released from the graphite crucible into the growth environment. This may cause the growth environment of the SiC crystal to be Si-rich or C-rich, which will have an adverse effect on the growth of the SiC crystal. Summary of the invention

[0005] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0006] The present disclosure aims to provide a crucible, a SiC crystal growth apparatus and a crucible preparation method capable of reducing the influence of Si-rich or C-rich in the growth environment of SiC crystal on the quality of the grown Si crystal.

[0007] In order to achieve the above object, according to one aspect of the present disclosure, a crucible is provided for growing SiC crystals using a PVT method, comprising: Crucible body, made of graphite; A composite material layer is provided on the inner surface of the crucible body, the composite material layer is made of C and Si, and releases C and Si during the growth of SiC crystals, The composite material layer is configured such that the C released is more than the Si released in the early stage of release, and the C released is less than the Si released in the late stage of release.

[0008] In some embodiments, the carbon-silicon ratio of the composite material layer may gradually decrease from the inside to the outside of the crucible.

[0009] In some embodiments, the density of the composite material layer may gradually increase from the inside to the outside of the crucible.

[0010] In some embodiments, the composite material layer may include a plurality of material layers sequentially arranged from the inside toward the outside of the crucible.

[0011] In some embodiments, the thickness of each material layer may be in the range of 0.5 mm to 1 mm, and the thickness of the composite material layer may be in the range of 5 mm to 10 mm.

[0012] In some embodiments, the composite material layer may include multiple material layers arranged sequentially from the inside to the outside of the crucible, wherein the carbon-silicon ratio of one material layer close to the inside of the crucible among each two adjacent material layers may be greater than the carbon-silicon ratio of the other material layer away from the inside of the crucible.

[0013] In some embodiments, the density of the one material layer may be less than the density of the other material layer.

[0014] In some embodiments, the composite material layer may be in a cylindrical shape, wherein the top end of the cylinder is open and the bottom end is closed, so as to accommodate SiC powder for growing SiC crystals inside the cylinder.

[0015] According to another aspect of the present disclosure, there is also provided a crucible for growing SiC crystals using a PVT method, comprising: Crucible body; A composite material layer is provided on the inner surface of the crucible body, the composite material layer is made of C and Si, and releases C and Si during the growth of SiC crystals, The carbon-silicon ratio of the side of the composite material layer close to the inner side of the crucible is the largest and greater than 1, and the carbon-silicon ratio of the other side of the composite material layer opposite to the side is the smallest and less than 1.

[0016] According to yet another aspect of the present disclosure, there is provided a SiC crystal growth device, comprising the crucible according to any one of the above embodiments.

[0017] According to another aspect of the present disclosure, a method for preparing a crucible is provided. The crucible is used for growing SiC crystals using a PVT method. The method for preparing a crucible comprises: A plurality of material layers are sequentially coated from the inside to the outside on the inner surface of a crucible body made of graphite using a mixed slurry, wherein the mixed slurry includes C powder and Si powder, and the carbon-silicon ratio of the mixed slurry corresponding to the outermost layer of the plurality of material layers is the largest and greater than 1, and the carbon-silicon ratio of the mixed slurry corresponding to the innermost layer of the plurality of material layers is the smallest and less than 1.

[0018] In some embodiments, corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, the carbon-silicon ratios of the corresponding plurality of mixed slurries may gradually decrease.

[0019] In some embodiments, corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, the particle sizes of the C powder and the Si powder in the corresponding plurality of mixed slurries may gradually decrease.

[0020] In some implementations, the process may further include sintering the crucible body coated with the plurality of material layers.

[0021] In some embodiments, the purity of the C powder and the Si powder in the mixed slurry may be greater than 99.999%, and the particle size may be between 30 mesh and 300 mesh.

[0022] According to the above technical solution, by arranging a composite material layer on the inner surface of the crucible body made of graphite, and making the composite material layer release more C than Si in the early stage of release, and release less C than Si in the later stage of release, the surplus C will be added to the Si-rich growth environment in the early stage of SiC crystal growth, and the surplus Si will be added to the C-rich growth environment in the later stage of SiC crystal growth, thereby improving the inappropriate carbon-silicon ratio in the early and later stages of the growth environment, thereby reducing the defects in the grown SiC crystal caused by too small and too large carbon-silicon ratio, and improving the quality of the grown Si crystal. In addition, the SiC crystal is maintained for a long time to maintain stable growth, so as to achieve a larger crystal thickness, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The features and advantages of the embodiments of the present disclosure will become more easily understood through the following description with reference to the accompanying drawings. The drawings are not drawn to scale and some features may be enlarged or reduced to show details of specific parts. In the drawings: Figure 1 Schematic diagram of the structure of a silicon carbide crystal growth device according to the related art.

[0024] Figure 2 It is a schematic structural diagram of a crucible according to an embodiment of the present disclosure.

[0025] Figure 3 The release of C and Si in the early stages of SiC crystal growth is schematically shown.

[0026] Figure 4 Schematic diagram showing the release of C and Si in the later stages of SiC crystal growth.

[0027] Figure 5 Schematic diagram of the structure of a crucible according to another embodiment of the present disclosure.

[0028] Figure 6 It is a schematic structural diagram of a crucible according to another embodiment of the present disclosure.

[0029] Figure 7 It is a schematic structural diagram of a silicon carbide crystal growth device according to an embodiment of the present disclosure.

[0030] Figure 8 is a flow chart of a method for preparing a crucible according to an embodiment of the present disclosure.

[0031] In the drawings, the same or corresponding technical features, parts or components are represented by the same or corresponding reference numerals. DETAILED DESCRIPTION

[0032] The present disclosure is described in detail below with reference to the accompanying drawings by means of exemplary embodiments. It should be noted that the following detailed description of the present disclosure is only for illustrative purposes and is by no means a limitation of the present disclosure.

[0033] It should be noted that, for the sake of clarity, not all features of a specific implementation are described and illustrated in the specification and drawings. Furthermore, in order to avoid unnecessary details that obscure the technical solution focused on by the present disclosure, only the device structures and parts closely related to the technical solution of the present disclosure are described and illustrated in the specification and drawings, while other details that are not closely related to the technical content of the present disclosure and are known to those skilled in the art are omitted.

[0034] As mentioned above, during the growth of SiC crystals, the growth environment of the crystals may be Si-rich and C-rich, which may have an adverse effect on the growth of SiC crystals. This will be described in detail below in conjunction with a SiC crystal growth device according to the related art.

[0035] It should be noted that the SiC crystal growth apparatus according to the related art described herein does not necessarily belong to the scope of the prior art.

[0036] First, refer to Figure 1 , which shows a SiC crystal growth apparatus 1 ′ according to the related art.

[0037] The SiC crystal growth apparatus 1 ′ includes a graphite crucible 10 ′, a heat-insulating felt 20 ′, and a heating device 30 ′.

[0038] The graphite crucible 10' is used to accommodate SiC powder 2' inside it, and can conduct heat to provide a high temperature environment during the crystal growth process. Generally, the graphite crucible 10' can be cylindrical, however, it can also be any other suitable shape. A SiC seed crystal 40' is also arranged inside the graphite crucible 10' and at its top. The SiC seed crystal 40' has the same crystal structure as the SiC crystal to be grown, so that the desired SiC crystal can be grown on the SiC seed crystal 40'.

[0039] The insulation felt 20' is arranged to surround the graphite crucible 10' to reduce the energy loss of the graphite crucible 10' and thereby maintain the stability of the temperature field in the graphite crucible 10'. The insulation felt 20' is provided with a temperature measuring hole 201' at its top to allow a temperature measuring device such as an infrared thermometer to monitor the temperature inside the graphite crucible 10', in particular, to monitor the temperature of the area where the SiC seed crystal 40' disposed at the top of the graphite crucible 10' is located.

[0040] The heating device 30' may be, for example, an induction coil. Figure 1 As shown in FIG. 1 , an induction coil is disposed around the insulation felt 20 ′ and on the outside of the insulation felt 20 ′, so as to heat the graphite crucible 10 ′ to a temperature capable of sublimating the SiC powder 2 ′ by means of induction heating.

[0041] In the SiC crystal growth process using the SiC crystal growth apparatus 1', the graphite crucible 10' is heated by the heating device 30', for example, the temperature inside the graphite crucible 10' reaches above 2000°C, and the SiC powder 2' contained in the graphite crucible 10' decomposes and sublimates into gaseous Si, Si 2 C. SiC 2 etc. (these gaseous components are Figure 1 The specific chemical formula is as follows: SiC(s)=Si(g)+C(s) 2SiC(s)=Si(g)+SiC 2 (g) 2SiC(s)=Si 2 C(g)+C(s) Wherein, s represents solid, and g represents gas. Since the SiC powder 2' is located in the high temperature region of the graphite crucible 10', and the SiC seed crystal 40' is located in the relatively low temperature region, these gaseous components will be transferred to the SiC seed crystal 40' in the low temperature region under the action of the temperature gradient, and grow on the SiC seed crystal 40' to form SiC crystal according to the following chemical formula. The specific chemical formula is as follows: Si(g) +SiC 2(g) =2SiC(s) Si 2 C(g) = SiC(s)+Si(g) Here, s represents a solid, and g represents a gas.

[0042] Therefore, in the above reaction of SiC crystal growth, Si is released into the growth environment. In addition, since the heat field is provided by the graphite crucible 10 ′ in the PVT method, C is also released from the graphite crucible 10 ′ into the growth environment.

[0043] Although the C released from the graphite crucible 10' into the growth environment can absorb a portion of Si, however, in the early stage of SiC crystal growth, due to the large amount of SiC powder 2' in the graphite crucible 10', the Si released into the growth environment will be more abundant than C, so that the crystal growth is in a Si-rich growth environment, which will cause phase change, microtubes, Si droplets, dislocations and other defects in the grown SiC crystal, resulting in a decrease in crystal quality. On the other hand, with the consumption of SiC powder 2', the C released from the graphite crucible 10' into the growth environment becomes relatively more, resulting in the crystal growth in a C-rich growth environment in the later stage of SiC crystal growth, which will not only cause C packaging, microtubes, dislocations and other defects in the grown SiC crystal, but also make the SiC crystal unable to grow for a long time, and even cause growth stagnation, resulting in insufficient thickness of the prepared SiC crystal, thereby increasing production costs.

[0044] In this regard, the present disclosure attempts to solve the above-mentioned problem by providing a composite material layer composed of C and Si on the inner surface of a graphite crucible, and allowing the composite material layer to release more C in the early stage of SiC crystal growth and more Si in the later stage of SiC crystal growth, so as to maintain a reasonable carbon-silicon ratio throughout the entire process of SiC crystal growth by supplementing C in the early stage and Si in the later stage.

[0045] To this end, according to an embodiment of the present disclosure, a crucible for SiC crystal growth using a PVT method is proposed. Figures 2 to 4 , the crucible 10 according to an embodiment of the present disclosure will be described in detail.

[0046] It should be noted that only the crucible is described here. As for other parts of the SiC crystal growth device, they are applicable to the above description of other parts of the SiC crystal growth device according to the related art, and will not be repeated here.

[0047] First, refer to Figure 2 The crucible 10 includes a crucible body 110 and a composite material layer 120 .

[0048] The crucible body 110 is made of graphite and is used to contain SiC powder 2 (see Figure 3 and Figure 4 ), and can conduct heat to provide a high temperature environment during crystal growth. The crucible body 110 can be cylindrical, or in any other suitable shape. The SiC seed crystal 40 (see Figure 3 , Figure 4 and Figure 7 ) may be disposed inside the crucible body 110 and at the top end thereof.

[0049] The composite material layer 120 is disposed on the inner surface 111 of the crucible body 110, and the composite material layer 120 is made of C and Si, and releases C and Si during the growth of the SiC crystal, wherein the composite material layer 120 is configured such that the C released in the early stage of the release is more than the Si released, and the C released in the later stage of the release is less than the Si released. It should be noted that the C released here is more or less than the Si released in terms of the number of atoms, that is, the number of the released C atoms is more or less than the number of the released Si atoms.

[0050] Specifically, the inner surface 111 of the crucible body 110 is the surface of the crucible body 110 that is close to or in contact with the growth environment of the SiC crystal. By arranging the composite material layer 120 on the inner surface 111 of the crucible body 110, when the composite material layer 120 begins to release C and Si in the high temperature environment of the SiC crystal growth, the released C and Si can enter the growth environment of the SiC crystal, that is, enter the interior of the crucible 10.

[0051] Reference Figure 3 and Figure 4 , C is schematically shown as solid dots, and Si is schematically shown as hollow dots. Figure 3 As shown in , when the composite material layer 120 releases more C than Si in the early stage of the above release, the surplus C will be added to the Si-rich growth environment in the early stage of SiC crystal growth, thereby improving the too small carbon-silicon ratio of the growth environment in the early stage. As the crystal grows, the composite material layer 120 is continuously consumed, such as Figure 4 As shown in , when the C released by the composite material layer 120 in the later stage of the above release is less than the Si released, the surplus Si will be added to the C-rich growth environment in the later stage of SiC crystal growth, thereby reducing the excessive carbon-silicon ratio of the growth environment in the later stage. It should be noted that the carbon-silicon ratio here refers to the number of atoms, that is, the ratio of the number of C atoms to the number of Si atoms.

[0052] In this way, defects such as phase change, C packaging, micropipes, Si droplets, dislocations, etc. in the grown SiC crystal caused by too small or too large carbon-silicon ratio can be reduced, thereby improving the quality of the grown Si crystal. In addition, the SiC crystal can maintain stable growth for a long time to achieve a larger crystal thickness, thereby reducing production costs.

[0053] Regarding the manner in which the composite material layer 120 releases C and Si during SiC crystal growth, it can be imagined that the carbon-silicon ratio of the side 121 of the composite material layer 120 close to the inner side of the crucible 10 can be maximized and greater than 1, and the carbon-silicon ratio of the other side 122 of the composite material layer 120 opposite to the side 121 can be minimized and less than 1.

[0054] In this case, the side 121 of the composite material layer 120 is close to the inner side of the crucible 10, while the other side 122 is far from the inner side of the crucible 10. Therefore, during the growth of the SiC crystal in a high-temperature environment, the side 121 of the composite material layer 120 will first release its components into the growth environment of the SiC crystal, while the side 122 will finally release its components into the growth environment.

[0055] By making the carbon-silicon ratio of the side portion 121 of the composite material layer 120 the largest and greater than 1, the C released by the composite material layer 120 will be greater than the released Si in the early release period when the growth environment has the most surplus Si, thereby improving the excessively small carbon-silicon ratio of the growth environment in the early period. By making the carbon-silicon ratio of the other side portion 122 of the composite material layer 120 the smallest and less than 1, the C released by the composite material layer 120 will be less than the released Si in the late release period when the growth environment has the most surplus C, thereby reducing the excessively large carbon-silicon ratio of the growth environment in the late period.

[0056] In some embodiments, the carbon-silicon ratio of the composite material layer 120 may gradually decrease from the inside to the outside of the crucible 10 .

[0057] The inner side of the crucible 10 is a side of the crucible 10 close to the growth environment of the SiC crystal, and the outer side of the crucible 10 is a side of the crucible 10 far from the growth environment of the SiC crystal.

[0058] During the growth of SiC crystals, as the SiC powder 2 loaded inside the crucible 10 is consumed, the carbon-silicon ratio in the growth environment of the SiC crystals will gradually increase, from an excessively small carbon-silicon ratio in the early Si-rich period to an excessively large carbon-silicon ratio in the later C-rich period. In response to the trend of the carbon-silicon ratio in the growth environment gradually increasing, in this embodiment, the carbon-silicon ratio of the composite material layer 120 is correspondingly gradually reduced from the inside to the outside of the crucible 10. As a result, the amount of C added to the growth environment of the SiC crystal by the composite material layer 120 in the early stage will gradually decrease, and the amount of Si added to the growth environment of the SiC crystal in the later stage will gradually increase, so that by controlling the speed of adding C in the early stage and adding Si in the later stage, the carbon-silicon ratio in the growth environment is always kept within a suitable range during the entire growth process of the SiC crystal.

[0059] In this way, defects in the grown SiC crystal caused by an inappropriate carbon-silicon ratio can be better reduced, thereby further improving the quality of the grown Si crystal, and enabling the SiC crystal to maintain stable growth for a longer period of time to achieve a greater crystal thickness, thereby further reducing production costs.

[0060] In some embodiments, the density of the composite material layer 120 may gradually increase from the inside to the outside of the crucible 10 .

[0061] The density reflects the compactness of the components within the composite material layer 120. For example, generally, the composite material layer 120 composed of C and Si with smaller particle sizes has a greater density than the composite material layer 120 composed of C and Si with larger particle sizes. The speed at which the composite material layer 120 releases C and Si can be controlled by the density. For example, when the density of the composite material layer 120 is greater, the speed at which the composite material layer 120 releases C and Si during the growth of SiC crystals is lower, and when the density of the composite material layer 120 is lower, the speed at which the composite material layer 120 releases C and Si during the growth of SiC crystals is higher.

[0062] When in a high-temperature growth environment, the entire composite material layer 120 will be affected by the temperature and release components. When the carbon-silicon ratio of the composite material layer 120 gradually decreases from the inside to the outside of the crucible 10, by gradually increasing the density of the composite material layer 120 from the inside to the outside of the crucible 10, the release rate of C and Si can be controlled to gradually decrease from the side of the composite material layer 120 close to the growth environment of the SiC crystal to the other side away from the growth environment, so that the composite material layer 120 releases components successively from the above-mentioned one side to the above-mentioned other side, thereby allowing the carbon-silicon ratio in the growth environment of the SiC crystal to remain in a suitable range for a longer time, thereby obtaining a larger crystal thickness, thereby further reducing production costs.

[0063] In some embodiments, Figure 5 As shown in FIG. 1 , the composite material layer 120 may include a plurality of material layers 1200 sequentially arranged from the inside toward the outside of the crucible 10 .

[0064] By making the composite material layer 120 include a plurality of material layers 1200, the composite material layer 120 can be manufactured more flexibly and conveniently by configuring each material layer 1200 separately. For example, it can be more flexibly and conveniently realized that the C released by the composite material layer 1200 in the early stage of release is more than the Si released, and the C released in the later stage of release is less than the Si released; and the carbon-silicon ratio of the composite material layer 120 is gradually reduced from the inside to the outside of the crucible 10; and the density of the composite material layer 120 is gradually increased from the inside to the outside of the crucible 10.

[0065] In some embodiments, the carbon-silicon ratio of one of every two adjacent material layers 1200 , which is closer to the inner side of the crucible 10 , may be greater than the carbon-silicon ratio of the other material layer, which is farther from the inner side of the crucible 10 .

[0066] In this way, the carbon-silicon ratio of the composite material layer 120 can be gradually reduced from the inside to the outside of the crucible 10 according to the different carbon-silicon ratios of the plurality of material layers 1200. Thus, the carbon-silicon ratio can be gradually reduced from the inside to the outside of the crucible 10 in a simpler way.

[0067] It is conceivable that the one of the plurality of material layers 1200 closest to the inner side of the crucible 10 may be a pure carbon layer, and the one of the plurality of material layers 1200 farthest from the inner side of the crucible 10 may be a pure silicon layer.

[0068] In this way, as much C as possible can be provided to the growth environment of the SiC crystal in the initial stage of release, and as much Si as possible can be provided to the growth environment in the final stage of release, so that the carbon-silicon ratio in the growth environment reaches the expected appropriate range.

[0069] In some embodiments, Figure 6 As shown in , the density of one of every two adjacent material layers 1200 , which is closer to the inner side of the crucible 10 , may be smaller than the density of the other material layer, which is farther from the inner side of the crucible 10 .

[0070] Figure 6 , the composite material layer 120 includes three material layers 1200 , and the three material layers 1200 have different densities, wherein denser points are used to represent a greater density, and looser points are used to represent a smaller density.

[0071] In this way, the density of the composite material layer 120 can be gradually increased from the inside to the outside of the crucible 10 according to the different densities of the plurality of material layers 1200. Thus, the density can be gradually increased from the inside to the outside of the crucible 10 in a simpler way.

[0072] In some embodiments, the thickness of each material layer 1200 may be in the range of 0.5 mm to 1 mm, and the thickness of the composite material layer 120 may be in the range of 5 mm to 10 mm.

[0073] When the thickness of the material layer 1200 is less than 0.5 mm, the manufacturing process of the material layer will be too complicated, and when the thickness of the material layer 1200 is greater than 1 mm, the bonding effect between the material layers 1200 is poor and cracks are likely to occur. When the thickness of the composite material layer 120 is less than 5 mm, the release rate of C or Si in the composite material layer 120 cannot be maintained for a long time, and when the thickness of the composite material layer 120 is greater than 10 mm, the strength of the crucible will be reduced, and thus the service life of the crucible will be reduced.

[0074] In some embodiments, for example, referring to Figure 6 The composite material layer 120 may be in a cylindrical shape, wherein the top end of the cylinder is open and the bottom end is closed, so as to accommodate SiC powder inside the cylinder.

[0075] By setting the composite material layer 120 in the above-mentioned cylindrical shape, C and Si can be supplemented to the growth environment of the SiC crystal from the entire circumference of the crucible 10 and from the entire bottom of the crucible 10, making the supplement more uniform. Thus, a better supplement effect and thus a better crystal quality can be obtained.

[0076] According to another aspect of the present disclosure, referring to Figure 7 , a SiC crystal growth device 1 is also provided, which includes a crucible 10.

[0077] Similar to the SiC crystal growth apparatus 1' according to the related art, the SiC crystal growth apparatus 1 further includes a heat preservation felt 20 and a heating device 30. The heat preservation felt 20 is arranged to surround the crucible 10, and the heat preservation felt 20 is provided with a temperature measuring hole 201 at the top thereof. The heating device 30 may be, for example, an induction coil, and Figure 7 As shown in FIG. 1 , the induction coil is arranged around the thermal insulation felt 20 and on the outside of the thermal insulation felt 20 .

[0078] Below, refer to Figure 8 , and combined with Figure 7 , a crucible preparation method for preparing the crucible 10 is described in detail.

[0079] The crucible preparation method comprises: using a mixed slurry to sequentially coat multiple material layers from the inside to the outside on the inner surface 111 of a crucible body 110 made of graphite, wherein the mixed slurry comprises C powder and Si powder, and the carbon-silicon ratio of the mixed slurry corresponding to the outermost layer of the multiple material layers is the largest and greater than 1, and the carbon-silicon ratio of the mixed slurry corresponding to the innermost layer of the multiple material layers is the smallest and less than 1. It should be noted that the carbon-silicon ratio here is still in terms of the number of atoms, that is, the ratio of the number of C atoms to the number of Si atoms.

[0080] Exemplarily, the mixed slurry may include C powder and Si powder with a purity greater than 99.999% and a particle size of 30 to 300 mesh. Specifically, the mixed slurry may be prepared by mixing a mixture of C powder and Si powder with phenolic resin and alcohol, for example, in a mass ratio of 90:5:5. By controlling the ratio of C powder to Si powder, a mixed slurry with different carbon-silicon ratios may be obtained.

[0081] By coating a layer of mixed slurry on the inner surface 111 of the crucible body 110, a material layer can be obtained, which corresponds to the material layer 1200 of the crucible 10. Thus, the multiple material layers can be obtained by coating the mixed slurry layer by layer from the inside to the outside on the inner surface 111. By controlling the ratio of C powder and Si powder in the mixed slurry, the carbon-silicon ratio of the mixed slurry corresponding to the outermost layer can be maximized and greater than 1, and the carbon-silicon ratio of the mixed slurry corresponding to the innermost layer can be minimized and less than 1, thereby, the carbon-silicon ratio of the outermost layer can be maximized and greater than 1, and the carbon-silicon ratio of the innermost layer can be minimized and less than 1, and thereby, the composite material layer formed by the multiple material layers can release more C than the released Si in the early stage of release, and release less C than the released Si in the later stage of release, that is, the crucible 10 is prepared.

[0082] In some embodiments, corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, the carbon-silicon ratio of the corresponding plurality of mixed slurries may be gradually reduced. Thus, the carbon-silicon ratio of the composite material layer formed by the plurality of material layers may be gradually reduced from the inside to the outside of the crucible.

[0083] In some embodiments, corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, the particle sizes of the C powder and the Si powder in the corresponding plurality of mixed slurries may be gradually reduced.

[0084] By controlling the particle sizes of the C powder and the Si powder in the mixed slurry, the density of the material layer formed by coating the mixed slurry can be controlled. Therefore, a corresponding plurality of mixed slurries including C powder and Si powder of different particle sizes can be prepared to obtain material layers of different densities. Therefore, in the above manner, the density of the composite material layer formed by the plurality of material layers can be gradually increased from the inside to the outside of the crucible.

[0085] In some embodiments, Figure 8 As shown in , the crucible preparation method may further include sintering the crucible body 110 coated with the multiple material layers.

[0086] Exemplarily, the crucible body 110 coated with the multiple material layers can be maintained at a temperature greater than 2000° C. for more than 12 hours under an inert atmosphere such as argon at a pressure close to one atmosphere to complete sintering and solidification of the crucible body 110 coated with the multiple material layers.

[0087] In the present disclosure, although the present disclosure has been described with reference to exemplary embodiments, it should be understood that the present disclosure is not limited to the specific embodiments described and shown in detail herein. Those skilled in the art may make various changes to the exemplary embodiments without departing from the scope defined by the claims of the present disclosure.

[0088] The features mentioned and / or shown in the above description of the exemplary embodiments of the present disclosure may be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or substituted for the corresponding features in other embodiments. The technical solutions obtained by these combinations or substitutions shall also be deemed to be included in the protection scope of the present disclosure.

Claims

1. A crucible for growing silicon carbide crystals using a PVT method, characterized in that: include: Crucible body, made of graphite; a composite material layer, disposed on the inner surface of the crucible body, the composite material layer being made of carbon and silicon and releasing carbon and silicon during the growth of the silicon carbide crystal, The composite material layer is configured such that the carbon released is greater than the silicon released in the early stage of release, and the carbon released is less than the silicon released in the late stage of release.

2. The crucible according to claim 1, characterized in that The carbon-silicon ratio of the composite material layer gradually decreases from the inside to the outside of the crucible.

3. The crucible according to claim 2, characterized in that The density of the composite material layer gradually increases from the inside to the outside of the crucible.

4. The crucible according to any one of claims 1 to 3, characterized in that The composite material layer includes a plurality of material layers sequentially arranged from the inside to the outside of the crucible.

5. The crucible according to claim 4, characterized in that The thickness of each material layer is in the range of 0.5 mm to 1 mm, and the thickness of the composite material layer is in the range of 5 mm to 10 mm.

6. The crucible according to claim 1, characterized in that The composite material layer includes a plurality of material layers arranged sequentially from the inside to the outside of the crucible, wherein the carbon-silicon ratio of a material layer close to the inside of the crucible of each two adjacent material layers is greater than the carbon-silicon ratio of the other material layer away from the inside of the crucible.

7. The crucible according to claim 6, characterized in that The density of the one material layer is lower than the density of the other material layer.

8. The crucible according to any one of claims 1 to 3, characterized in that The composite material layer is in a cylindrical shape, wherein the top end of the cylinder is open and the bottom end is closed, so as to accommodate silicon carbide powder for growing silicon carbide crystals inside the cylinder.

9. A crucible for growing silicon carbide crystals using a PVT method, characterized in that: include: Crucible body; a composite material layer, disposed on the inner surface of the crucible body, the composite material layer being made of carbon and silicon and releasing carbon and silicon during the growth of the silicon carbide crystal, The carbon-silicon ratio of the side of the composite material layer close to the inner side of the crucible is the largest and greater than 1, and the carbon-silicon ratio of the other side of the composite material layer opposite to the side is the smallest and less than 1.

10. A silicon carbide crystal growth device, characterized in that: Comprising the crucible according to any one of claims 1 to 9.

11. A method for preparing a crucible, wherein the crucible is used for growing silicon carbide crystals using a PVT method, characterized in that: The crucible preparation method comprises: A plurality of material layers are sequentially coated from the inside to the outside on the inner surface of a crucible body made of graphite using a mixed slurry, wherein the mixed slurry includes carbon powder and silicon powder, and the carbon-silicon ratio of the mixed slurry corresponding to the outermost layer of the plurality of material layers is the largest and is greater than 1, and the carbon-silicon ratio of the mixed slurry corresponding to the innermost layer of the plurality of material layers is the smallest and is less than 1.

12. The method for preparing a crucible according to claim 11, characterized in that: Corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, carbon-silicon ratios of the corresponding plurality of mixed slurries gradually decrease.

13. The method for preparing a crucible according to claim 12, characterized in that: Corresponding to the plurality of material layers sequentially arranged from the inside to the outside of the crucible, the particle sizes of the carbon powder and the silicon powder in the corresponding plurality of mixed slurries gradually decrease.

14. The method for preparing a crucible according to any one of claims 11 to 13, characterized in that: The method also includes sintering the crucible body coated with the plurality of material layers.

15. The method for preparing a crucible according to any one of claims 11 to 13, characterized in that: The purity of the carbon powder and silicon powder in the mixed slurry is greater than 99.999%, and the particle size is between 30 mesh and 300 mesh.

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