Crucible structure for growth of low-carbon inclusion low-stress silicon carbide single crystal and growth method

Abstract

The invention relates to a crucible structure for growth of a low-carbon inclusion low-stress silicon carbide single crystal and a growth method, a seed crystal support, a TaC isolating ring and a flow guide filtering assembly are sequentially arranged at the upper part in the crucible from top to bottom, and the flow guide filtering assembly is composed of multiple layers of TaC microporous rings, a TaC microporous plate and a TaC flow guide cylinder from bottom to top; the multi-layer TaC microporous ring comprises at least two annular microporous rings which are coaxially arranged, and the inner diameter and the outer diameter of the lower-layer microporous ring are larger than those of the upper-layer microporous ring. The crucible structure disclosed by the invention is provided with the flow guide filtering assembly, the flow guide filtering assembly changes an edge flow field, carbon particles from powder graphitization are concentratedly deposited in an edge polycrystalline deposition area, the carbon particles in the powder are prevented from participating in crystal growth, and the silicon carbide single crystal with a low-carbon inclusion is obtained.

Description

A crucible structure and growth method for low-carbon inclusion, low-stress silicon carbide single crystal growth Technical Field

[0001] This invention relates to a crucible structure and growth method for growing low-carbon inclusion, low-stress silicon carbide single crystals, belonging to the field of crystal growth technology. Background Technology

[0002] Silicon carbide possesses many excellent properties such as a large bandgap, high thermal conductivity, and high breakdown field strength, and has broad application prospects in the fields of high-temperature, high-power, and high-frequency electronic devices.

[0003] Currently, the mainstream technology for silicon carbide single crystal growth is physical vapor deposition transport (PVT). This technology heats the silicon carbide powder at the bottom using an induction coil or resistor, causing it to sublimate. Subsequently, the gaseous silicon carbide condenses at the top seed crystal, thus growing a silicon carbide single crystal. However, due to the non-uniform thermal field in the powder, graphitized regions are concentrated at the powder edges. Under the combined action of the thermal field and the flow field, carbon particles in the graphitized regions overcome gravity and enter the silicon carbide single crystal growth region with the flow field, existing in the crystal as carbon inclusions. This leads to defects such as micropipes and dislocations, severely affecting the quality of the silicon carbide crystal.

[0004] N117737858A discloses a growth apparatus and method for low-inclusion-density silicon carbide crystals. It employs a flat-topped, pyramidal-shaped corrosion-resistant filter assembly, adjusts the airflow direction to concentrate carbon inclusions at the crystal ingot edge region, and finely refines the crystal edge contour to obtain low-inclusion-density SiC crystals. However, due to the change in airflow direction, the growth rate at the crystal edge is significantly higher than in the central region. This method struggles to obtain low-stress crystals with a central micro-convex interface, resulting in higher stress at the crystal edge, which can lead to crystal cracking. Furthermore, the processing workload at the crystal edge is substantial.

[0005] CN113151897B discloses a crucible structure. By setting two flow guiding components and a flow splitting component, carbon inclusions in the powder are deposited on the upper surface of the first flow guiding component, thereby reducing the carbon inclusion density in the crystal. In addition, the flow splitting component reduces the generation of inter-lattice internal stress by shielding the thermal radiation of the material surface. However, this crucible structure cannot avoid the corrosive effect of a large amount of silicon component in the growth chamber on the graphite component, thereby introducing carbon inclusions outside the powder.

[0006] CN212610986U discloses a crucible for reducing carbon inclusions in silicon carbide single crystals. By setting multiple sets of homogenizing elements and a cover plate, and providing through holes in the sidewalls of the assembly, the airflow transmission changes from a convection-dominated mode to a diffusion-dominated mode. Low-speed airflow struggles to overcome the weight of carbon particles, thus reducing the introduction of carbon particles into the powder and consequently reducing carbon inclusions in the silicon carbide single crystal. However, this invention severely limits the crystal growth rate, hindering the improvement of production efficiency.

[0007] CN212223148U discloses a crucible for reducing carbon inclusions in silicon carbide single crystals. By providing an annular crucible attachment on the inner wall of the crucible body, with a groove on its bottom surface, excess silicon near the crucible body's sidewall enters the groove, helping to reduce carbon inclusions in the SiC single crystal. Simultaneously, after a period of single crystal growth, carbon from the remaining polycrystalline material near the crucible body's sidewall also enters the groove of the crucible attachment, further reducing carbon inclusions in the silicon carbide single crystal. However, excessive crystallization at the groove can lead to significant stress at the edges of the silicon carbide single crystal; during the growth of large-size silicon carbide single crystals, carbon particles are transported to the crystal center region in the middle and later stages under the influence of a large radial temperature gradient.

[0008] Given the aforementioned drawbacks, there is an urgent need for a new growth technology to reduce stress and carbon inclusions in the crystal, thereby improving the overall quality of silicon carbide single crystals. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention relates to a crucible structure and growth method for growing low-carbon inclusion, low-stress silicon carbide single crystals.

[0010] The growth apparatus of the present invention can construct a growth structure with low stress and low carbon inclusions, and can keep the silicon carbide crystal growth process stable.

[0011] Terminology Explanation:

[0012] Porosity refers to the ratio of the total volume of pores inside silicon carbide powder to the total volume of the powder. If the grown silicon carbide powder undergoes sublimation, the excessive sublimation of silicon components results in more residual carbon in the powder, increasing the porosity. A decrease in porosity indicates that the sublimated gaseous components were not effectively transported to the growth chamber, leading to secondary crystallization within the powder.

[0013] Powder graphitization: This refers to the process where, after powder participates in single crystal growth, the Si component preferentially escapes, and the remaining C component transforms into graphite in the source region, which is called powder graphitization.

[0014] This invention is achieved through the following technical solution:

[0015] A crucible structure for low-carbon inclusion low-stress silicon carbide single crystal growth is characterized in that, from top to bottom, a seed crystal holder, a TaC isolation ring, and a flow guiding and filtering assembly are arranged sequentially inside the crucible. The flow guiding and filtering assembly is composed of multiple TaC microporous rings, a TaC microporous plate, and a TaC flow guiding cylinder from bottom to top. The multiple TaC microporous rings include at least two coaxially arranged annular microporous rings, and the inner and outer diameters of the lower microporous rings are both larger than those of the upper microporous rings.

[0016] The crucible of the present invention is provided with a flow guiding and filtering component. During the growth process, the flow guiding and filtering component generates a driving force due to the difference in porosity, which causes the part containing carbon inclusions to grow in the polycrystalline deposition zone, while maintaining the crystal center as a micro-convex interface. The seed crystal holder with a certain thickness can avoid contact between the polycrystalline and silicon carbide single crystal, thereby reducing the risk of crystal cracking.

[0017] According to a preferred embodiment of the present invention, the multilayer TaC microporous ring comprises two levels of microporous rings: a first-diameter microporous ring and a second-diameter microporous ring. Both the first-diameter and second-diameter microporous rings comprise 2-4 layers of microporous rings, stacked from top to bottom, forming a topless tower shape. The inner and outer diameters of the lower-layer microporous rings are larger than those of the upper-layer microporous rings. The outer periphery of the bottommost microporous ring is disposed on the crucible. Both the first-diameter and second-diameter microporous rings have penetrating holes on their annular surfaces. The porosity of the second-diameter microporous ring is greater than or equal to that of the first-diameter microporous ring.

[0018] According to a preferred embodiment of the present invention, the first-diameter microporous ring and the second-diameter microporous ring have the same thickness, which is 1-5 mm.

[0019] According to a preferred embodiment of the present invention, a TaC microporous plate is disposed on top of a first-diameter microporous ring, and the diameter of the TaC microporous plate is larger than the inner diameter of the first-diameter microporous ring.

[0020] According to a preferred embodiment of the present invention, the TaC microporous plate is provided with through holes, the porosity is 0.2-0.6, the thickness of the TaC microporous plate is 1-5 mm, and the porosity of the second pore size microporous ring, the first pore size microporous ring and the TaC microporous plate decreases sequentially.

[0021] According to a preferred embodiment of the present invention, the TaC guide tube includes a cylindrical sidewall and a top wall disposed on the top of the cylindrical sidewall. The top wall is recessed into the cylinder in the shape of an inverted frustum. The top wall is provided with small holes and has a porosity of 0.1-0.5.

[0022] According to a preferred embodiment of the present invention, the TaC flow guide tube is disposed at the center of the TaC microporous plate, and the outer diameter of the TaC flow guide tube is smaller than the diameter of the TaC microporous plate.

[0023] According to a preferred embodiment of the present invention, the height of the TaC guide tube is 10-20 mm.

[0024] According to a preferred embodiment of the present invention, the porosity of the top wall of the TaC guide tube is less than or equal to the porosity of the TaC microporous plate, and less than the porosity of the multilayer TaC microporous ring.

[0025] According to a preferred embodiment of the present invention, the top end of the TaC isolation ring is fixed on the seed crystal holder, the bottom end of the TaC isolation ring is disposed on the second aperture microporous ring, and the inner wall of the TaC isolation ring is in contact with the first aperture microporous ring.

[0026] According to a preferred embodiment of the present invention, the TaC isolation ring is cylindrical, the outer diameter of the TaC isolation ring is the same as the diameter of the seed crystal holder, and is 0.5-1.2 mm larger than the inner diameter of the second aperture microporous ring in the top layer, the outer diameter of the isolation ring is equal to the diameter of the seed crystal holder, and the height of the TaC isolation ring is 20-60 mm.

[0027] According to a preferred embodiment of the present invention, the seed crystal holder, the TaC isolation ring, the microporous ring, and the crucible enclose a polycrystalline deposition region.

[0028] According to a preferred embodiment of the present invention, the TaC isolation ring is closely attached to the seed crystal holder and the TaC microporous ring. This isolates the polycrystalline deposition region and the single-crystal growth region to avoid defects caused by carbon particles participating in single-crystal growth.

[0029] According to a preferred embodiment of the present invention, the diameter of the seed crystal is 156-310 mm. This ensures that the diameter of the grown crystal is larger than the target crystal diameter.

[0030] According to a preferred embodiment of the present invention, the thickness of the seed crystal holder is greater than the thickness of the silicon carbide polycrystalline deposition, and its diameter is equal to the outer diameter of the isolation ring. This is to avoid crystal cracking caused by polycrystalline deposition on the outer edge of the TaC isolation ring.

[0031] The present invention also provides a method for growing low-carbon inclusion single crystals.

[0032] A method for growing low-carbon inclusion single crystals, using the aforementioned crucible structure for silicon carbide single crystal growth, includes the following steps:

[0033] 1) Place the above-mentioned crucible structure for silicon carbide single crystal growth into the growth chamber of the growth equipment, seal the single crystal growth equipment, and perform vacuum treatment on the growth chamber of the growth equipment.

[0034] 2) The single crystal growth equipment is heated by an induction coil, and a carrier gas is introduced into the growth chamber to make the temperature inside the single crystal growth equipment reach 2000~2400℃ and the pressure reach 1~30 mbar;

[0035] 3) The growth is carried out by holding the temperature for 100~200 h, growing silicon carbide single crystals on the seed crystal, and condensing silicon carbide polycrystalline in the polycrystalline deposition zone.

[0036] 4) After the crystal growth is completed, the inside of the single crystal growth equipment is cooled down, and the carrier gas is introduced to 150 ~ 250 mbar. After cooling to room temperature, silicon carbide single crystal is obtained.

[0037] The grown silicon carbide single crystals are ground to remove residual graphite or carbon inclusions at the edges using an external cylindrical grinder, resulting in a standard silicon carbide ingot with low stress and low carbon inclusion density. After cutting, polishing, and cleaning, a silicon carbide substrate wafer with low stress and low carbon inclusions is obtained. The processed SiC wafers are tested for inclusion quantity using a CS8520, and stress magnitude and uniformity are characterized using a stress meter.

[0038] The stacked arrangement of TaC microporous rings with different porosities utilizes the porosity difference between the central and edge materials to adjust the airflow direction. Under high temperature, graphitization preferentially occurs at the edge of the silicon carbide powder. Under the action of thermal and flow fields, tiny carbon particles are transported upward from the edge, escaping gravity. With the help of the flow guiding and filtering components, the carbon particles are guided to the polycrystalline deposition area. At the same time, it is ensured that the microporous components of each layer are tightly fitted without gaps. Through porosity design, the carbon particles in the airflow are effectively filtered.

[0039] As shown in Figure 4, due to the emissivity of TaC material and the influence of the primary flow guidance without the flow guidance filter component, the center and edge temperatures of the crystal surface are relatively higher, making it easy to obtain low-quality silicon carbide single crystals with a concave surface. The crucible structure of the present invention, through the TaC flow guide tube at the top of the flow guidance filter component, adjusts the flow field in the growth chamber a second time. With the design of the inverted frustum microporous surface, it can compensate for the phenomenon of weak central flow field caused by the primary flow field adjustment and the characteristics of TaC material itself, thereby obtaining high-quality silicon carbide single crystals with microconvex interfaces.

[0040] In addition, TaC material has high temperature corrosion resistance. It will not decompose or corrode under the extreme high temperature and low pressure environment of silicon carbide single crystal growth. No granulation will occur on the surface of TaC module, ensuring that no encapsulation caused by module corrosion will be introduced into the growth chamber.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. The crucible structure of the present invention is provided with a flow guiding and filtering component. The flow guiding and filtering component changes the edge flow field and concentrates the carbon particles from the graphitization of the powder into the edge polycrystalline deposition region, thereby avoiding the carbon particles in the powder from participating in crystal growth, and thus obtaining silicon carbide single crystals with low carbon inclusions.

[0043] 2. The crucible structure of the present invention is provided with a flow guiding and filtering component. Through the TaC flow guiding tube of the flow guiding and filtering component, the direction of the central airflow is readjusted, the overall flow field uniformity is improved, which is conducive to obtaining a crystal surface with a slightly convex center, thereby obtaining a low-stress silicon carbide single crystal.

[0044] 3. The crucible structure of the present invention, in which the seed crystal holder, TaC isolation ring, microporous ring and crucible enclose a polycrystalline deposition zone, isolates the polycrystalline containing a large amount of carbon inclusions from the silicon carbide single crystal through the polycrystalline deposition zone, effectively avoiding the risk of crystal cracking caused by a large number of edge polycrystalline / polymorphic crystals, which is conducive to obtaining low-stress silicon carbide crystals and improving the growth yield of silicon carbide single crystals.

[0045] 4. The crucible structure of the present invention, wherein the seed crystal holder, TaC isolation ring, microporous ring and crucible enclose a polycrystalline deposition region, through which most of the components containing carbon inclusions are deposited into the polycrystalline deposition region, and a very small portion is deposited at the edge of the silicon carbide single crystal. This helps to reduce the difficulty of the subsequent silicon carbide single crystal edge removal process and effectively improves the substrate production efficiency. Attached Figure Description

[0046] The accompanying drawings, which constitute a part of this invention, are used to provide a further understanding of the invention. The illustrative examples and descriptions of the invention are used to explain the invention and do not constitute an improper limitation of the invention.

[0047] Figure 1 is a schematic diagram of the crucible structure for low-stress silicon carbide single crystal growth of low-carbon inclusions of the present invention placed in the growth equipment.

[0048] Figure 2 is a schematic diagram of the flow guiding and filtering component in the crucible structure of the present invention;

[0049] Figure 3 is a schematic diagram of the silicon carbide single crystal growth apparatus in Comparative Example 1.

[0050] Figure 4 is a schematic diagram of the component flow field of the single crystal growth device in Comparative Example 1.

[0051] Figure 5 is a schematic diagram of the TaC guide tube;

[0052] Figure 6 is a schematic diagram of the structure of the TaC microplate;

[0053] Figure 7 is a schematic diagram of the structure of the TaC microporous ring with the first pore size;

[0054] Figure 8 is a schematic diagram of the structure of the second-diameter TaC microporous ring;

[0055] Figure 9 shows the test results of CS8520 inclusions on a substrate grown in Example 1;

[0056] Figure 10 shows the instrumental characteristics of a substrate grown in Example 1 under stress testing.

[0057] Figure 11 shows the test results of CS8520 inclusions on a substrate grown in Example 2;

[0058] Figure 12 shows the instrumental characteristics of a substrate grown in Example 2 under stress testing.

[0059] Figure 13 shows the test results of CS8520 inclusions on a substrate grown in Comparative Example 1.

[0060] Figure 14 shows the instrumentation characteristics of a substrate grown in Comparative Example 1 under stress testing.

[0061] Figure 15 shows the test results of CS8520 inclusions on a substrate grown in Comparative Example 2.

[0062] Figure 16 shows the instrumentation characteristics of a substrate grown in Comparative Example 2 under stress testing.

[0063] Figure 17 shows the test results of CS8520 inclusions on a substrate grown in Comparative Example 3.

[0064] Figure 18 shows the instrumentation characteristics of a substrate grown in Comparative Example 3 under stress testing.

[0065] Figure 19 shows the test results of CS8520 inclusions on a substrate grown in Comparative Example 4.

[0066] Figure 20 shows the instrumentation characteristics of a substrate grown in Comparative Example 4 under stress testing.

[0067] The labels for the attached figures are as follows:

[0068] 1. Insulation component; 2. Crucible; 3. Seed crystal holder; 4. Seed crystal; 5. TaC isolation ring; 6. Flow guiding and filtering component; 61. TaC flow guiding cylinder; 62. TaC microporous plate; 63. First aperture microporous ring; 64. Second aperture microporous ring; 7. Silicon carbide powder; 8. Induction coil. Detailed Implementation

[0069] To further understand the content of this invention, a detailed description is provided in conjunction with the accompanying drawings.

[0070] The present application will now be described in further detail with reference to the accompanying drawings. It is understood that the terms "microporous ring," "isolation ring," and "microporous plate" used in the drawings are for the convenience of describing the technical solution of this application and have no specific limiting effect; they are all general terms and do not constitute a limitation on the technical solution of this application.

[0071] Example 1

[0072] A crucible structure for low-carbon inclusion low-stress silicon carbide single crystal growth is shown in Figures 1-2. The crucible has a seed crystal holder 3, a TaC isolation ring 5 and a flow guiding and filtering component 6 arranged from top to bottom inside the upper part. The flow guiding and filtering component 6 (Figure 2) is composed of a multilayer TaC microporous ring, a TaC microporous plate 62 and a TaC flow guiding cylinder 61 from bottom to top.

[0073] The multilayer TaC microporous ring includes two coaxially arranged annular microporous rings, namely a first-diameter microporous ring and a second-diameter microporous ring. Both the first-diameter microporous ring and the second-diameter microporous ring include two layers of microporous rings, which are stacked from top to bottom and have a topless tower shape. The first-diameter microporous ring and the second-diameter microporous ring are provided with penetrating holes on their annular rings.

[0074] Two layers of second-diameter microporous rings 64 (see Figure 7) are stacked sequentially from bottom to top in order of decreasing inner diameter; the inner and outer diameters of the lower layer of second-diameter microporous rings are 88 mm and 100 mm, respectively, and the inner and outer diameters of the upper layer of second-diameter microporous rings are 77 mm and 89 mm, respectively. The porosity of both is 0.6 and the thickness of both is 2 mm. The outer periphery of the lower layer of second-diameter microporous rings is set on the crucible.

[0075] Two layers of first-diameter microporous rings 63 (see Figure 8) are stacked sequentially from bottom to top in order of decreasing inner diameter; the inner diameter and outer diameter of the lower first-diameter microporous ring are 66 mm and 77 mm, respectively, and the inner diameter and outer diameter of the upper second-diameter microporous ring are 56 mm and 67 mm, respectively. The porosity of both is 0.4 and the thickness of both is 2 mm.

[0076] A TaC microporous plate (see Figure 6) 62 is disposed on top of a first-diameter microporous ring 63. The diameter of the TaC microporous plate 62 is larger than the inner diameter of the first-diameter microporous ring 63. The radius of the TaC microporous plate is 56 mm. The TaC microporous plate has through holes and a porosity of 0.3. The thickness of the TaC microporous plate is 2 mm. The porosities of the second-diameter TaC microporous ring, the first-diameter TaC microporous ring, and the TaC microporous plate decrease sequentially.

[0077] The TaC flow guide tube 61 is located at the center of the TaC microporous plate 62, and the outer diameter of the TaC flow guide tube 61 is smaller than the diameter of the TaC microporous plate 62. The structure of the TaC flow guide tube 61 is shown in Figure 5. It includes a cylindrical sidewall and a top wall located at the top of the cylindrical sidewall. The top wall is concave inward into the cylinder in the shape of an inverted frustum. The top wall has small holes. The inner diameter and outer diameter of the TaC flow guide tube are 40 mm and 42 mm, respectively, and the height is 14 mm. The porosity of the top wall is 0.3.

[0078] The top of the TaC isolation ring 5 is fixed to the seed crystal holder 4, and the bottom of the TaC isolation ring 5 is set on the second aperture microporous ring 64, with the inner wall of the TaC isolation ring 5 fitting against the first aperture microporous ring 63. The TaC isolation ring 5 is cylindrical, with an inner diameter of 78 mm, an outer diameter of 80 mm, a thickness of 2 mm, and a height of 40 mm. The seed crystal is fixed to the top of the crucible by the seed crystal holder, with the edge of the seed crystal just in contact with the TaC isolation ring. The radius of the seed crystal is 78 mm, the radius of the seed crystal holder is 80 mm, and the thickness is 33 mm.

[0079] The method for growing low-carbon inclusion single crystals, using the aforementioned crucible structure for silicon carbide single crystal growth, includes the following steps:

[0080] 1) Spread silicon carbide powder evenly on the bottom of the crucible; wherein the silicon carbide powder has a height of 60mm, a porosity of 0.8, and a mass of 1210 g; place the crucible structure into the growth chamber of the growth equipment, seal the single crystal growth equipment, and perform vacuum treatment on the growth chamber of the growth equipment.

[0081] 2) The single crystal growth equipment is heated using an induction coil. Carrier gas is introduced into the growth chamber to a growth pressure of 10 mbar. The graphite crucible is then heated to 2200℃ for crystal growth.

[0082] 3) The growth process involves holding the temperature for 100 h to grow silicon carbide single crystals on the seed crystal and condensing silicon carbide polycrystalline in the polycrystalline deposition zone.

[0083] 4) After the crystal growth is completed, the inside of the single crystal growth equipment is cooled down, and the carrier gas is introduced to 200 mbar. After cooling to room temperature, silicon carbide single crystal is obtained. The graphite or carbon inclusions remaining at the edge of the silicon carbide are removed by an external cylindrical grinding machine to obtain a standard silicon carbide ingot with low stress and low carbon inclusion density.

[0084] The silicon carbide crystal obtained in this embodiment has a central micro-convex interface. After cutting, polishing, and cleaning, a SiC substrate wafer is obtained. The number of inclusions in the wafer is tested using a CS8520, as shown in Figure 9. There is only one inclusion in the substrate, and the substrate as a whole has an extremely low carbon inclusion density. The stress magnitude and uniformity are characterized using a stress tester, as shown in Figure 10. The average stress of the substrate is 1.54 MPa, and the difference between the edge stress and the center stress is 0.12~0.25 MPa. The substrate as a whole has low stress and good stress uniformity.

[0085] Example 2

[0086] Example 1: Crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth.

[0087] The method for growing single crystals with low-carbon inclusions is carried out according to Example 1, with the following differences:

[0088] Step 2) The single crystal growth equipment is heated using an induction coil. Carrier gas is introduced into the growth chamber to a growth pressure of 5 mbar. The graphite crucible is heated to 2100℃ for crystal growth.

[0089] 3) The growth process involves holding the silicon carbide crystal at a temperature of 150 h to grow a single silicon carbide crystal on the seed crystal and condensing polycrystalline silicon carbide in the polycrystalline deposition zone. The graphite or carbon inclusions remaining at the edge of the silicon carbide are removed by an external cylindrical grinding machine to obtain a standard silicon carbide ingot with low stress and low carbon inclusion density.

[0090] The silicon carbide crystal obtained in this embodiment has a central micro-convex interface. After cutting, polishing, and cleaning, a SiC substrate wafer is obtained. The number of inclusions in the wafer is tested using a CS8520, as shown in Figure 11. There are only 11 inclusions in the substrate, and the substrate as a whole has an extremely low carbon inclusion density. The stress magnitude and uniformity are characterized using a stress tester, as shown in Figure 12. The average stress of the substrate is 1.71 MPa, and the difference between the edge stress and the center stress is 0.57~1.11 MPa. The substrate as a whole has low stress and good stress uniformity.

[0091] Comparative Example 1

[0092] The crucible structure for low-stress silicon carbide single crystal growth with low-carbon inclusions described in Example 1 is different in that: the inside of the crucible is arranged from top to bottom as follows: seed crystal holder 3, TaC isolation ring 5 and flow guiding filter assembly 6. The flow guiding filter assembly 6 (Figure 3) is composed of multiple layers of TaC microporous rings and TaC microporous plates from bottom to top. Compared with Example 1, no TaC flow guiding cylinder is provided.

[0093] The growth conditions were exactly the same as in Example 1, and silicon carbide single crystals were grown. The graphite or carbon inclusions remaining at the edge of the silicon carbide were removed by an external cylindrical grinding machine to obtain a standard silicon carbide ingot with low stress and low carbon inclusion density.

[0094] The silicon carbide ingot obtained in this comparative example has a concave central interface. After cutting, polishing, and cleaning, a SiC substrate wafer was obtained. The number of inclusions in the wafer was tested using a CS8520, as shown in Figure 13. There were 19 carbon inclusions in the substrate, although the overall carbon inclusion density of the substrate was relatively low. The stress magnitude and uniformity were characterized using a stress meter, as shown in Figure 14. The average stress of the substrate was 6.76 MPa, and the difference between the edge stress and the center stress was 19.36 ~ 20.26 MPa. The stress at the edge of the substrate was significantly higher than that in the center region, and the overall stress was very high and the stress uniformity was very poor, which could easily lead to crystal cracking.

[0095] Figure 4 is a schematic diagram of the flow field of the single crystal growth device in this embodiment. Without the TaC guide tube, the central flow field is weak, which eventually leads to the phenomenon of concave center of the crystal surface. At the same time, the large amount of polycrystalline material deposited at the edges in conjunction with the cooling stage causes a large amount of stress to accumulate at the crystal edges.

[0096] Comparative Example 2

[0097] The crucible structure for low-stress silicon carbide single crystal growth with low-carbon inclusions is the same as that in Example 1, except that a seed crystal holder and a flow guiding and filtering component are arranged sequentially from top to bottom inside the crucible. The flow guiding and filtering component is the same as that in Example 1, but TaC isolation ring is not provided compared to Example 1.

[0098] Other growth conditions are exactly the same as in Example 1.

[0099] The silicon carbide ingot obtained in this comparative example has a concave central interface. After cutting, polishing, and cleaning, a SiC substrate wafer was obtained. The number of inclusions in the wafer was tested using a CS8520, as shown in Figure 15. There were 16 inclusions in the substrate, and the overall substrate had a low carbon inclusion density. The stress magnitude and uniformity were characterized using a stress meter, as shown in Figure 16. The average stress of the substrate was 3.11 MPa, and the difference between the edge stress and the center stress was 3.68 ~ 6.86 MPa. The stress at the edge of the substrate was significantly higher than that in the center region. Although the overall stress and stress uniformity were improved compared to Comparative Example 1, the overall stress of the crystal obtained in this comparative example was still very high and the stress uniformity was very poor compared to the results of Example 1.

[0100] Comparative Example 3

[0101] The crucible structure for low-stress silicon carbide single crystal growth with low-carbon inclusions is the same as that described in Example 1, except that: the crucible is provided with a seed crystal holder, a TaC isolation ring and a flow guiding filter assembly from top to bottom. The flow guiding filter assembly is composed of multiple layers of TaC microporous rings and TaC flow guiding cylinders from bottom to top. Compared with Example 1, no TaC microporous plate is provided.

[0102] The growth conditions were exactly the same as in Example 1.

[0103] Silicon carbide single crystals are obtained, and graphite or carbon inclusions remaining at the edges of the silicon carbide are removed by an external cylindrical grinding machine to obtain a standard silicon carbide ingot with low stress and low carbon inclusion density.

[0104] The silicon carbide ingot obtained in this comparative example has a centrally convex interface. After cutting, polishing, and cleaning, a SiC substrate wafer was obtained. The number of inclusions in the wafer was tested using a CS8520, as shown in Figure 17. There were 12 inclusions in the substrate, and the overall substrate had a low carbon inclusion density. The stress magnitude and uniformity were characterized using a stress meter, as shown in Figure 18. The average stress of the substrate was 3.52 MPa, and the difference between the edge stress and the center stress was 7.30 ~ 8.25 MPa. The stress at the edge of the substrate was significantly higher than that in the center region. Although the overall stress and stress uniformity were improved compared to Comparative Example 1, the overall stress of the crystal obtained in this comparative example was still very high and the stress uniformity was very poor compared to the results of Example 1.

[0105] Comparative Example 4

[0106] The crucible structure for low-stress silicon carbide single crystal growth with low-carbon inclusions is the same as that described in Example 1, except that: a seed crystal holder and a TaC isolation ring are arranged sequentially from top to bottom inside the crucible, and the polycrystalline deposition area and the single crystal growth area are separated only by the TaC isolation ring, without a flow guiding filter component.

[0107] The growth conditions were exactly the same as in Example 1.

[0108] Silicon carbide single crystals are obtained, and graphite or carbon inclusions remaining at the edges of the silicon carbide are removed by an external cylindrical grinding machine to obtain a standard silicon carbide ingot with low stress and low carbon inclusion density.

[0109] The silicon carbide ingot obtained in this comparative example has a centrally convex interface. After cutting, polishing, and cleaning, a SiC substrate wafer was obtained. The number of inclusions in the wafer was tested using a CS8520, as shown in Figure 19. There were 697 inclusions in the substrate, and the substrate as a whole had an extremely high carbon inclusion density. The stress magnitude and uniformity were characterized using a stress tester, as shown in Figure 20. The average stress of the substrate was 2.12 MPa, and the difference between the edge stress and the center stress was 1.75 ~ 4.74 MPa. Although the overall stress and stress uniformity of the substrate were improved, the carbon inclusion density was still extremely high.

Claims

1. A crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth, characterized in that, Inside the crucible, from top to bottom, a seed crystal holder, a TaC isolation ring, and a flow guiding and filtering assembly are arranged sequentially. The flow guiding and filtering assembly consists of multiple layers of TaC microporous rings, a TaC microporous plate, and a TaC flow guiding cylinder from bottom to top. The multiple layers of TaC microporous rings include at least two coaxially arranged annular microporous rings, with the inner and outer diameters of the lower microporous ring being larger than those of the upper microporous ring.

2. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 1, characterized in that, The multilayer TaC microporous ring includes two levels of microporous rings: a first-pore-size microporous ring and a second-pore-size microporous ring. Both the first-pore-size microporous ring and the second-pore-size microporous ring consist of 2-4 layers of microporous rings, stacked from top to bottom, with a topless tower-like shape.

3. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 2, characterized in that, The inner and outer diameters of the lower microporous ring are both larger than those of the upper microporous ring. The outer periphery of the bottom microporous ring is set on the crucible. The first and second diameter microporous rings are both provided with penetrating holes. The porosity of the second diameter microporous ring is greater than or equal to that of the first diameter microporous ring. The first and second diameter microporous rings have the same thickness, which is 1-5 mm.

4. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 2, characterized in that, The TaC microporous plate is placed on top of the first-diameter microporous ring. The diameter of the TaC microporous plate is larger than the inner diameter of the first-diameter microporous ring. The TaC microporous plate has through holes with a porosity of 0.2-0.6 and a thickness of 1-5 mm. The porosity of the second-diameter microporous ring, the first-diameter microporous ring, and the TaC microporous plate decreases sequentially.

5. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 2, characterized in that, The TaC flow guide tube includes a cylindrical sidewall and a top wall located at the top of the cylindrical sidewall. The top wall is recessed into the cylinder in the shape of an inverted frustum. Small holes are provided on the top wall, and the porosity of the top wall is 0.1-0.

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6. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 2, characterized in that, The TaC guide tube is located at the center of the TaC microporous plate. The outer diameter of the TaC guide tube is smaller than the diameter of the TaC microporous plate. The height of the TaC guide tube is 10-20mm. The porosity of the top wall of the TaC guide tube is less than or equal to the porosity of the TaC microporous plate and less than the porosity of the multilayer TaC microporous ring.

7. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 1, characterized in that, The top of the TaC isolation ring is fixed on the seed crystal holder, the bottom of the TaC isolation ring is set on the second aperture microporous ring, and the inner wall of the TaC isolation ring is in contact with the first aperture microporous ring.

8. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 1, characterized in that, The TaC isolation ring is cylindrical. The outer diameter of the TaC isolation ring is the same as the diameter of the seed crystal holder, and it is 0.5-1.2 mm larger than the inner diameter of the second aperture micro-perforated ring in the top layer. The outer diameter of the isolation ring is equal to the diameter of the seed crystal holder, and the height of the TaC isolation ring is 20-60 mm.

9. The crucible structure for low-carbon inclusion, low-stress silicon carbide single crystal growth according to claim 1, characterized in that, The seed crystal has a diameter of 156-310 mm to ensure that the diameter of the grown crystal is larger than the target crystal diameter. The thickness of the seed crystal holder is greater than the thickness of the silicon carbide polycrystalline deposition, and its diameter is equal to the outer diameter of the isolation ring. This is to avoid crystal cracking caused by polycrystalline deposition on the outer edge of the TaC isolation ring.

10. A method for growing a low-carbon inclusion single crystal, using the crucible structure for silicon carbide single crystal growth as described in claim 1, comprising the following steps: 1) placing the crucible structure for silicon carbide single crystal growth as described in claim 1 into the growth chamber of a growth device, sealing the single crystal growth device, and evacuating the growth chamber; 2) heating the single crystal growth device using an induction coil, and filling the growth chamber with carrier gas to bring the temperature inside the single crystal growth device to 2000~2400℃ and the pressure to 1~30 mbar; 3) maintaining the temperature for 100~200 h for growth, growing a silicon carbide single crystal on a seed crystal, and condensing silicon carbide polycrystalline in the polycrystalline deposition zone; 4) after the crystal growth is completed, cooling the inside of the single crystal growth device, filling it with carrier gas to 150~250 mbar, and cooling it to room temperature to obtain a silicon carbide single crystal.

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