Graphite crucible and liquid phase method silicon carbide crystal growth furnace

Abstract

The invention provides a graphite crucible and a liquid phase method silicon carbide crystal growth furnace, and relates to the technical field of silicon carbide crystal growth. The step structure is arranged along the inner wall of the crucible body, the stacking structure is arranged on the bottom surface of the groove, and step shapes in contact with a solution are formed on the side wall and the bottom of the graphite crucible, so that the contact area between the solution and the graphite crucible is increased, the dissolving speed of carbon and the conveying efficiency of the carbon are improved, and the conveying distance of the carbon is reduced; even at a relatively low temperature, sufficient carbon sources can be obtained for growth of the silicon carbide crystals, and the growth quality of the silicon carbide single crystals is improved. The graphite crucible forms a W shape in contact with a solution due to the shapes of the stepped structure and the laminated structure, and the distribution mode of the multi-stage inner wall steps and the multi-stage bottom surface steps is opposite to the liquid flow direction of the solution, so that the impact of the solution on the inner wall of the graphite crucible is stronger, and the carbon dissolving efficiency and the carbon conveying efficiency are further improved; and deposition of silicon carbide polycrystals at the bottom of the graphite crucible is inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon carbide crystal growth, more particularly to a graphite crucible and a liquid phase method silicon carbide crystal growth furnace. BACKGROUND

[0002] As a third-generation semiconductor material, silicon carbide single crystal has a higher band gap than traditional semiconductors, and has significant advantages in high-temperature, high-frequency and high-power application fields. At present, the growth methods of silicon carbide single crystal mainly include physical vapor transport method, high-temperature chemical vapor deposition method and liquid phase method. The physical vapor transport method is relatively mature, but it has limitations such as low yield, difficulty in expanding the diameter and high cost. The high-temperature chemical vapor deposition method is also limited in development due to expensive equipment and high material cost. The liquid phase method can realize the growth of silicon carbide single crystal at a lower temperature and in a near thermodynamic equilibrium state, and it is theoretically easier to obtain high-quality silicon carbide single crystal.

[0003] The liquid phase method for growing silicon carbide single crystal is to dissolve high-purity graphite crucible in a high-temperature liquid composed of silicon and a cosolvent, so that the solution obtains carbon elements; then the carbon elements are transported to the silicon carbide growth interface by solution convection; because the temperature at the silicon carbide growth interface is lower, the carbon elements are in a supersaturated state and precipitate at the silicon carbide growth interface, carrying out silicon atoms under the action of the lattice coulomb field, to realize the growth of silicon carbide single crystal. In the process of growing silicon carbide single crystal, as the carbon elements continuously precipitate at the growth interface, the solution needs to continuously dissolve high-purity graphite crucible to supplement carbon elements. In the prior art, the crucible of the liquid phase method silicon carbide crystal growth furnace generally adopts a cylindrical crucible, which results in poor crystal growth effect. SUMMARY

[0004] Therefore, the present application provides a graphite crucible and a liquid phase method silicon carbide crystal growth furnace, which effectively solves the technical problems existing in the prior art and improves the crystal growth effect of the liquid phase method silicon carbide crystal growth furnace.

[0005] To achieve the above-mentioned purpose, the technical solutions provided by the present application are as follows:

[0006] A graphite crucible is applied to a liquid phase method silicon carbide crystal growth furnace, and the graphite crucible comprises:

[0007] A crucible body, wherein the crucible body comprises a groove;

[0008] A stepped structure is arranged in the groove and along the inner wall of the crucible body, the stepped structure has a plurality of inner wall steps towards the center side of the groove; in the depth direction from the opening top surface of the groove to the bottom surface of the groove, the stepped structure extends from the set depth of the groove to the bottom surface of the groove towards the center side of the groove;

[0009] A layer stack structure is arranged on the bottom surface of the groove, the layer stack structure comprises a plurality of single layers arranged in a stack along the depth direction, the cross-sectional area of the single layers increases layer by layer along the depth direction, and the layer stack structure is a multi-stage bottom surface step towards the inner wall side of the crucible body.

[0010] Optionally, the crucible body, the step structure and the layer stack structure are an integral forming structure.

[0011] Optionally, the inner diameter of the crucible body ranges from 150 to 400 mm, the sidewall thickness of the crucible body ranges from 10 to 40 mm, the depth of the groove ranges from 150 to 200 mm, and the bottom thickness of the crucible body ranges from 10 to 50 mm.

[0012] Optionally, the step height of the inner wall step ranges from 0.1 to 10 mm, and the step width of the inner wall step ranges from 0.1 to 10 mm.

[0013] Optionally, the step height of the bottom surface step ranges from 0.1 to 10 mm, and the step width of the bottom surface step ranges from 0.1 to 10 mm.

[0014] Optionally, the graphite crucible further comprises:

[0015] An isolation ring is arranged on the bottom of the crucible body away from the groove, and a surrounding area of the isolation ring is formed with a heat preservation cavity; wherein, the heat preservation cavity is used for arranging a heat preservation layer.

[0016] Optionally, the isolation ring and the crucible body are an integral forming structure.

[0017] Optionally, the heat preservation layer comprises a gas heat preservation layer or a heat preservation felt layer.

[0018] Optionally, the gas heat preservation layer comprises an Ar gas heat preservation layer, an He gas heat preservation layer or an Ar and He mixed gas heat preservation layer.

[0019] Based on the same inventive concept, the application further provides a liquid phase method silicon carbide crystal growing furnace, which comprises:

[0020] A heating bucket;

[0021] A graphite crucible arranged in the heating bucket, wherein the graphite crucible is the graphite crucible described above.

[0022] Compared with the prior art, the technical solution provided by the application has at least the following advantages:

[0023] This application provides a graphite crucible and a liquid-phase silicon carbide crystal growth furnace. The graphite crucible includes: a crucible body, the crucible body including a groove; a stepped structure disposed within the groove and along the inner wall of the crucible body, the stepped structure having multiple inner wall steps on the side facing the center of the groove; in the depth direction from the top surface of the groove opening to the bottom surface of the groove, the stepped structure extends from a set depth of the groove towards the center of the groove to the bottom surface of the groove; and a stacked structure located on the bottom surface of the groove, the stacked structure including multiple single layers stacked along the depth direction, the cross-sectional area of ​​the single layer increasing layer by layer along the depth direction, the stacked structure having multiple bottom surface steps on the side facing the inner wall of the crucible body.

[0024] As described above, the technical solution provided in this application, by setting a stepped structure along the inner wall of the crucible body and a stacked structure on the bottom surface of the groove, forms a stepped shape on the side wall and bottom of the graphite crucible that contacts the solution. This increases the contact area between the solution and the graphite crucible, improves the carbon dissolution rate and carbon transport efficiency, and reduces the carbon transport distance. Even at lower temperatures, sufficient carbon source can be obtained for silicon carbide crystal growth, improving the growth quality of silicon carbide single crystals and enhancing the crystal growth effect of the phase-method silicon carbide crystal growth furnace. Furthermore, the shape presented by the stepped and stacked structures forms a W-shape in the graphite crucible that contacts the solution. Simultaneously, the distribution of the multi-level inner wall steps and multi-level bottom steps is opposite to the liquid flow direction of the solution, resulting in a stronger impact of the solution on the inner wall of the graphite crucible, further improving the carbon dissolution efficiency and carbon transport efficiency, and also suppressing the deposition of polycrystalline silicon carbide at the bottom of the graphite crucible. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of a graphite crucible provided in an embodiment of this application;

[0027] Figure 2 This is a schematic diagram of another graphite crucible provided in an embodiment of this application;

[0028] Figure 3 A partial structural schematic diagram of a liquid-phase silicon carbide crystal growth furnace provided in this application embodiment;

[0029] Figure 4A partial structural schematic diagram of another liquid-phase silicon carbide crystal growth furnace provided in this application embodiment;

[0030] Figure 5 A partial structural schematic diagram of another liquid-phase silicon carbide crystal growth furnace provided in an embodiment of this application;

[0031] Figure 6 A partial structural schematic diagram of another liquid-phase silicon carbide crystal growth furnace provided in an embodiment of this application;

[0032] Figure 7 This is a schematic diagram of the silicon carbide single crystal corresponding to Example 1;

[0033] Figure 8 This is a schematic diagram of the silicon carbide single crystal corresponding to Comparative Example 1;

[0034] Figure 9 This is a schematic diagram of the silicon carbide single crystal corresponding to Comparative Example 2;

[0035] Figure 10 This is a schematic diagram of the silicon carbide single crystal corresponding to Comparative Example 3.

[0036] Figure label:

[0037] 10-Graphite crucible; 110-Cruise body; 111-Groove; 120-Stepped structure; 121-Inner wall step; 130-Layered structure; 131-Single layer; 132-Bottom step; 140-Isolation ring; 141-Insulation cavity; 20-Heating barrel; 30-Auxiliary isolation ring; 40-Auxiliary insulation layer; 51-Top insulation felt; 52-Side wall insulation felt; 53-Bottom insulation felt; 61-Graphite seed crystal rod; 62-Graphite support; 63-SiC seed crystal; 71-Cruise shaft; 72-Cruise tray; 80-Induction coil; 90-Furnace body; 100-Alloy solution; Y-Depth direction. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] As described in the background section, liquid-phase silicon carbide single crystal growth involves dissolving a high-purity graphite crucible in a high-temperature liquid composed of silicon and a flux, thereby introducing carbon into the solution. The carbon is then transported to the silicon carbide growth interface via solution convection. Because the temperature at the silicon carbide growth interface is lower, the carbon is in a supersaturated state and precipitates at the interface. Under the influence of the coulomb field of the crystal lattice, it carries silicon atoms, thus achieving silicon carbide single crystal growth. During the silicon carbide single crystal growth process, as carbon continuously precipitates at the growth interface, the solution needs to continuously dissolve the high-purity graphite crucible to replenish the carbon. In existing technologies, the crucibles in liquid-phase silicon carbide crystal growth furnaces are generally cylindrical, resulting in poor crystal growth performance.

[0040] Based on this, the present application provides a graphite crucible and a liquid-phase silicon carbide crystal growth furnace, which effectively solves the technical problems existing in the prior art and improves the crystal growth effect of the liquid-phase silicon carbide crystal growth furnace.

[0041] To achieve the above objectives, the technical solutions provided in this application are as follows, in specific combination with... Figures 1 to 10 The technical solutions provided in the embodiments of this application will be described in detail.

[0042] refer to Figure 1 The diagram shown is a structural schematic of a graphite crucible provided in an embodiment of this application. The graphite crucible 10 provided in this embodiment is applied in a liquid-phase silicon carbide crystal growth furnace. The graphite crucible 10 includes: a crucible body 110, which includes a groove 111; a stepped structure 120 disposed within the groove 111 and along the inner wall of the crucible body 110; the stepped structure 120 having multiple inner wall steps 121 on the side facing the center of the groove 111; and extending from a predetermined depth of the groove 111 towards the center of the groove 111 to the bottom surface of the groove 111 in the depth direction Y from the top surface of the opening of the groove 111 to the bottom surface of the groove 111. The stacked structure 130 is located on the bottom surface of the groove 111. The stacked structure 130 includes a plurality of single layers 131 stacked along the depth direction Y. The cross-sectional area of ​​the single layer 131 increases layer by layer along the depth direction Y. The side of the stacked structure 130 facing the inner wall of the crucible body 110 has a multi-level bottom step 132.

[0043] Understandably, in the technical solution provided in this application embodiment, the groove 111 is used to hold the solution. By setting a stepped structure 120 along the inner wall of the crucible body 110 and a stacked structure 130 on the bottom surface of the groove 111, a stepped shape that contacts the solution is formed on the side wall and bottom of the graphite crucible 10. This increases the contact area between the solution and the graphite crucible 10, improves the dissolution rate of carbon and the carbon conveying efficiency, and reduces the carbon conveying distance. Even at lower temperatures, silicon carbide crystal growth can obtain sufficient carbon source, improving the growth quality of silicon carbide single crystals and improving the crystal growth effect of the phase-method silicon carbide crystal growth furnace. Furthermore, the shapes presented by the stepped structure 120 and the stacked structure 130 make the graphite crucible 10 form a W shape that contacts the solution. At the same time, the distribution of the multi-level inner wall steps 121 and the multi-level bottom surface steps 132 is opposite to the liquid flow direction of the solution, which makes the solution impact the inner wall of the graphite crucible 10 more powerful, further improving the carbon dissolution efficiency and carbon transport efficiency, and also suppressing the deposition of silicon carbide polycrystalline at the bottom of the graphite crucible 10.

[0044] The graphite crucible 10 provided in this embodiment is made of graphite, meaning that the crucible body 110, the stepped structure 120, and the stacked structure 130 are all made of graphite. In some embodiments, the crucible body 110, the stepped structure 120, and the stacked structure 130 provided in this embodiment are integrally formed, thereby improving the strength and properties of the graphite crucible 10. Optionally, the inner diameter h1 of the crucible body 110 provided in this embodiment ranges from 150 to 400 mm, the sidewall thickness h2 of the crucible body 110 ranges from 10 to 40 mm, the depth h3 of the groove 111 ranges from 150 to 200 mm, and the bottom thickness h4 of the crucible body 110 ranges from 10 to 50 mm. Furthermore, the step height h5 of the inner wall step 121 provided in this embodiment ranges from 0.1 to 10 mm, and the step width h6 of the inner wall step 121 ranges from 0.1 to 10 mm. Furthermore, the step height h8 of the bottom step 132 provided in this application embodiment is 0.1-10mm, and the step width h9 of the bottom step 132 is 0.1-10mm.

[0045] refer to Figure 2The diagram shows another graphite crucible structure provided in this application embodiment. The graphite crucible 10 provided in this application embodiment further includes an isolation ring 140, which is disposed at the bottom of the crucible body 110 on the side opposite to the groove 111. A heat-insulating cavity 141 is formed around the isolation ring 140; wherein a heat-insulating layer is disposed in the heat-insulating cavity 141. The heat-insulating layer can provide heat preservation, thereby preventing the solution at the bottom of the graphite crucible 10 from becoming too cold, which would reduce the carbon dissolution rate and carbon transport efficiency, further improving the crystal growth effect of the liquid-phase silicon carbide crystal growth furnace. Optionally, the isolation ring 140 and the crucible body 110 provided in this application embodiment can be an integrally formed structure, thereby improving the overall strength of the graphite crucible 10. Furthermore, the heat-insulating layer provided in this application embodiment can include a gas heat-insulating layer or a heat-insulating felt layer; when the heat-insulating layer is a gas heat-insulating layer, a corresponding gas is continuously introduced during the operation of the liquid-phase silicon carbide crystal growth furnace. The gas insulation layer provided in this application embodiment includes an Ar gas insulation layer, a He gas insulation layer, or a mixed Ar and He gas insulation layer; and the insulation felt layer can be a graphite insulation felt layer, which is not specifically limited in this application.

[0046] Based on the same inventive concept, this application also provides a liquid-phase silicon carbide crystal growth furnace. (Reference) Figure 3 The diagram shown is a partial structural schematic of a liquid-phase silicon carbide crystal growth furnace provided in an embodiment of this application. The liquid-phase silicon carbide crystal growth furnace provided in this embodiment includes: a heating chamber 20; and a graphite crucible 10 disposed within the heating chamber 20, wherein the graphite crucible 10 is any of the graphite crucible 10 provided in the above embodiments. During the operation of the liquid-phase silicon carbide crystal growth furnace, the heating chamber 20 transfers heat to the graphite crucible 10 to heat the solution within the groove 111 of the graphite crucible 10. In the graphite crucible 10 provided in this embodiment, a stepped structure 120 is provided along the inner wall of the crucible body 110, and a stacked structure 130 is provided on the bottom surface of the groove 111, thereby forming a stepped shape that contacts the solution on the side wall and bottom of the graphite crucible 10. This increases the contact area between the solution and the graphite crucible 10, improves the dissolution rate and carbon transport efficiency of carbon, and reduces the carbon transport distance. Even at lower temperatures, sufficient carbon source can be obtained for silicon carbide crystal growth, improving the growth quality of silicon carbide single crystals and enhancing the crystal growth effect of the phase-method silicon carbide crystal growth furnace. Furthermore, the shapes presented by the stepped structure 120 and the stacked structure 130 make the graphite crucible 10 form a W shape that contacts the solution. At the same time, the distribution of the multi-level inner wall steps 121 and the multi-level bottom surface steps 132 is opposite to the liquid flow direction of the solution, which makes the solution impact the inner wall of the graphite crucible 10 more powerful, further improving the carbon dissolution efficiency and carbon transport efficiency, and also suppressing the deposition of silicon carbide polycrystalline at the bottom of the graphite crucible 10.

[0047] refer to Figure 4 The diagram shows a partial structural schematic of another liquid-phase silicon carbide crystal growth furnace provided in this application embodiment. The liquid-phase silicon carbide crystal growth furnace provided in this application embodiment further includes: an auxiliary isolation ring 30, which is disposed within the heating chamber 20 and on the side of the graphite crucible 10 facing the bottom of the heating chamber 20; wherein, the surrounding area of ​​the auxiliary isolation ring 30 forms an auxiliary insulation cavity, and an auxiliary insulation layer 40 is disposed in the auxiliary insulation cavity. The auxiliary insulation layer 40 can play a role in heat preservation, thereby preventing the solution at the bottom of the graphite crucible 10 from becoming too cold, which would lead to a decrease in the carbon dissolution rate and carbon transport efficiency, further improving the crystal growth effect of the liquid-phase silicon carbide crystal growth furnace. Optionally, the auxiliary insulation layer 40 provided in this application embodiment may include a gas-assisted insulation layer or an auxiliary insulation felt layer; when the auxiliary insulation layer 40 is a gas-assisted insulation layer, a corresponding gas is continuously introduced during the operation of the liquid-phase silicon carbide crystal growth furnace. In this application, the gas-assisted insulation layer includes an Ar gas-assisted insulation layer, a He gas-assisted insulation layer, or a mixed Ar and He gas-assisted insulation layer; and the auxiliary insulation felt layer can be a graphite auxiliary insulation felt layer, which is not specifically limited in this application. Furthermore, at least one of the heating element 20 and the auxiliary isolation ring 30 provided in this application is a graphite structure. When the heating element 20 and the auxiliary isolation ring 30 are made of the same material, they can be an integrally formed structure, which is not specifically limited in this application.

[0048] It should be noted that when the graphite crucible 10 provided in this embodiment does not include the isolation ring 140, the graphite crucible 10 can be placed in a heating chamber 20 without the auxiliary isolation ring 30 for subsequent crystal growth processes, such as... Figure 3 The liquid-phase silicon carbide crystal growth furnace shown. Alternatively, when the graphite crucible 10 provided in this embodiment does not include the isolation ring 140, the graphite crucible 10 can be placed in the heating chamber 20 with the auxiliary isolation ring 30 for subsequent crystal growth processes, such as... Figure 4 The liquid-phase silicon carbide crystal growth furnace shown is illustrated. Furthermore, when the graphite crucible 10 provided in this embodiment includes an isolation ring 140, the graphite crucible 10 can also be placed in a heating chamber 20 with an auxiliary isolation ring 30 for subsequent crystal growth processes. Alternatively, when the graphite crucible 10 provided in this embodiment includes an isolation ring 140, the graphite crucible 10 can be placed in a heating chamber 20 without an auxiliary isolation ring 30 for subsequent crystal growth processes. This application does not impose specific limitations on this, such as... Figure 5 The liquid-phase silicon carbide crystal growth furnace shown.

[0049] refer to Figure 6The diagram shown is a partial structural schematic of another liquid-phase silicon carbide crystal growth furnace provided in this application embodiment. The liquid-phase silicon carbide crystal growth furnace provided in this application embodiment includes: insulation felt surrounding the heating chamber 20, such as a top insulation felt 51 located on the top side of the heating chamber 20, a sidewall insulation felt 52 located on the side wall of the heating chamber 20, and a bottom insulation felt 53 located on the bottom side of the heating chamber 20; a device for supporting the SiC seed crystal 63, such as a graphite seed crystal rod 61, and a graphite support 62 connected to and fixing the SiC seed crystal 63; a device for supporting the side components of the graphite crucible 10, such as a crucible shaft 71, and a crucible tray 72 connected to the crucible shaft 71 and supporting the bottom insulation felt 53; an induction coil 80 located on the side of the heating chamber 20 and surrounding the insulation felt; and a furnace body 90 providing the furnace cavity for the crystal growth furnace. When growing silicon carbide single crystals using a liquid-phase silicon carbide crystal growth furnace, an alloy solution 100 is placed inside the graphite crucible 10. The corresponding structure of this liquid-phase silicon carbide crystal growth furnace is the same as that of the prior art, so this application will not elaborate further.

[0050] The following steps are included when growing silicon carbide single crystals using a liquid-phase silicon carbide crystal growth furnace:

[0051] Step 1: Loading the furnace. After uniformly mixing the Si-Cr-Al raw materials of a specific composition, place them in a graphite crucible 10 with a stepped structure 120, a layered structure 130, and an isolation ring 140; place the graphite crucible 10 inside the heating chamber 20. Fix the SiC seed crystal 63 on the graphite support 62, and connect the graphite seed crystal rod 61 to the upper rotating shaft of the equipment (not shown). After placing the insulation felt, close the furnace.

[0052] Step 2: Vacuuming and Material Preparation. The liquid-phase silicon carbide crystal growth furnace is evacuated and the material is prepared.

[0053] Step 3: Seed crystal remelting. The SiC seed crystal 63 is remelted to eliminate processing damage and adhering volatiles on the surface of the SiC seed crystal 63, making the surface of the SiC seed crystal 63 smoother and creating the steps required for growth.

[0054] Step 4: Crystal Growth. After the SiC seed crystal 63 has been remelted, the meniscus is pulled upwards. The SiC seed crystal 63 is pulled upwards at a slow speed to achieve stable crystal growth. For example... Figure 4 As shown, the distribution of the multi-level inner wall steps 121 and multi-level bottom surface steps 132 of the graphite crucible 10 is related to the liquid flow direction of the alloy solution 100 (e.g., Figure 4 The flow direction (indicated by the middle arrow) is opposite, thus making the impact of the solution on the inner wall of the graphite crucible 10 stronger, further improving the carbon dissolution efficiency and carbon transport efficiency, and also inhibiting the deposition of silicon carbide polycrystalline material at the bottom of the graphite crucible 10.

[0055] Step 5: Cooling. After the silicon carbide single crystal growth is completed, the crystal and solution are separated by pulling the graphite seed rod 61, and then the temperature is slowly lowered to room temperature.

[0056] The following describes the relevant growth process of the liquid-phase silicon carbide crystal growth furnace provided in the embodiments of this application, with reference to specific growth parameters. The liquid-phase silicon carbide crystal growth furnace provided in Embodiment 1 includes the graphite crucible 10 provided in any of the above embodiments, wherein the inner diameter of the crucible body 110 of the graphite crucible 10 is 230 mm, the sidewall thickness of the crucible body 110 is 20 mm, the depth of the groove 111 is 150 mm, the height of the inner wall step 121 and the bottom step 132 is 1 mm, and the width of the inner wall step 121 and the bottom step 132 is 2 mm. Furthermore, the liquid-phase silicon carbide crystal growth furnace provided in Embodiment 1 includes a heat insulation layer 40. The corresponding growth process in Embodiment 1 includes:

[0057] Step 1: Loading the furnace. After uniformly mixing the Si-Cr-Al raw materials with a composition ratio of 45:55:5, place them in a graphite crucible 10 with a stepped structure 120, a layered structure 130, and an isolation ring 140. Place the graphite crucible 10 inside the heating chamber 20. Fix the 6-inch 0° semi-insulating D-grade SiC seed crystal 63 (0.5mm thick) to the graphite support 62 using graphite paper, and connect the graphite seed crystal rod 61 to the upper rotating shaft of the equipment (not shown). After placing the insulation felt, close the furnace.

[0058] Step 2: Evacuation and Material Processing. Evacuate the furnace to 10 Pa, backfill with Ar gas to a furnace pressure of 50 kPa (wash gas), and evacuate again to a furnace pressure of 1 × 10⁻⁶ kPa. -3 Pa, then backfill with Ar gas to a furnace pressure of 50 kPa. The furnace temperature is then increased to 1800 °C at a heating rate of 300 °C / h.

[0059] Step 3: Seed Crystal Remelting. After the raw material has completely melted, the SiC seed crystal 63 is brought into contact with the alloy solution 100 and penetrates into the higher temperature region of the alloy solution 100 to eliminate processing damage and adhering volatiles on the surface of the SiC seed crystal 63, making the surface of the SiC seed crystal 63 smoother. The remelting time of the SiC seed crystal 63 is 60 minutes.

[0060] Step 4: Crystal Growth. At 1850℃, with a meniscus of 1 mm, the SiC seed crystal 63 rotates at 150 rpm using ACRT (Accelerated Crucible Rotation Technique), while the graphite crucible 10 remains stationary. The graphite seed crystal rod 61 is pulled upwards at a uniform speed of 20 μm / h for stable growth over 40 hours. The constant rotation speed period is 20 minutes, and the variable speed period is 10 minutes.

[0061] Step 5: Cooling. After the silicon carbide single crystal growth is complete, the crystal is pulled upwards by 20 mm at a rate of 10 mm / h to separate the crystal from the alloy solution. Then, the furnace temperature is cooled to room temperature at a rate of 50℃ / h. This yields... Figure 7 The silicon carbide single crystal shown exhibits a smooth and flat crystal interface with minimal steps, and no step clustering or metal encapsulation. The silicon carbide single crystal provided in Example 1 was grown for 40 hours, achieving a thickness of 3.0-3.2 mm and a growth rate of 75-80 μm / h.

[0062] To demonstrate that the silicon carbide single crystals grown using the liquid-phase silicon carbide crystal growth furnace provided in this application have higher performance, several comparative methods for preparing silicon carbide single crystals are provided below for comparison.

[0063] Comparative Example 1:

[0064] The liquid phase silicon carbide crystal growth furnace provided in Comparative Example 1 has basically the same structural parameters as the liquid phase silicon carbide crystal growth furnace provided in Example 1 of this application. The difference is that the crucible of the liquid phase silicon carbide crystal growth furnace provided in Comparative Example 1 has no stepped structure 120, and the inner wall of the crucible of the liquid phase silicon carbide crystal growth furnace provided in Comparative Example 1 is a flat inner wall.

[0065] Based on the liquid-phase silicon carbide growth furnace provided in Comparative Example 1, and using the same growth process as provided in Example 1, silicon carbide crystals were grown to obtain... Figure 8 The silicon carbide single crystal shown has a smooth and flat interface, but exhibits macroscopic defects such as localized metal inclusions and cracks. The crystal in Comparative Example 1 shows more metal inclusions because its carbon dissolution rate is lower than that of Example 1. The silicon carbide single crystal provided in Comparative Example 1 was grown for 40 hours, achieving a thickness of 2.8-3.0 mm and a growth rate of 70-85 μm / h. Compared to Example 1, the silicon carbide single crystal grown in Comparative Example 1 is of lower quality.

[0066] Comparative Example 2:

[0067] The liquid phase silicon carbide crystal growth furnace provided in Comparative Example 2 has basically the same structural parameters as the liquid phase silicon carbide crystal growth furnace provided in Example 1 of this application. The difference is that the crucible of the liquid phase silicon carbide crystal growth furnace provided in Comparative Example 2 does not have an isolation ring 140.

[0068] Based on the liquid-phase silicon carbide growth furnace provided in Comparative Example 2, and using the same growth process as provided in Example 1, silicon carbide crystals were grown to obtain... Figure 9The silicon carbide single crystal shown has no grooves or metal encapsulation on its surface, but microcracks are present, indicating insufficient carbon supply during crystal growth. Comparative Example 2 shows a silicon carbide single crystal grown for 40 hours, with a thickness of 3.2-3.4 mm and a growth rate of 80-85 μm / h. Cutting the crucible of Comparative Example 2 vertically along its center reveals a layer of polycrystalline SiC deposited at the bottom. This is because the bottom of the crucible in Comparative Example 2 is in direct contact with the heating element, resulting in a lower solution temperature at the bottom and thus the polycrystalline SiC deposition.

[0069] Comparative Example 3:

[0070] The liquid phase silicon carbide crystal growth furnace provided in Comparative Example 3 has basically the same structural parameters as the liquid phase silicon carbide crystal growth furnace provided in Example 1 of this application. The difference is that the crucible in the liquid phase silicon carbide crystal growth furnace provided in Comparative Example 2 does not have a stepped structure 120, a stacked structure 130, or an isolation ring 140.

[0071] Based on the liquid-phase silicon carbide growth furnace provided in Comparative Example 3, and using the same growth process as provided in Example 1, silicon carbide crystals were grown to obtain... Figure 10 The silicon carbide single crystal shown exhibits microcracks on its surface, with metal inclusions within the microcracks and deep trenches containing substantial metal inclusions. This is a clear indication of insufficient carbon supply during crystal growth. Comparative Example 3, with a silicon carbide single crystal grown for 40 hours, has a thickness of 4.0-4.2 mm and a growth rate of 100-102 μm / h. The higher growth rate of this crystal is attributed to the presence of numerous metallic impurities within it.

[0072] Therefore, by comparing Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, the silicon carbide single crystals grown by the liquid phase silicon carbide crystal growth furnace provided in the embodiments of this application have smooth and flat crystal interfaces, very small steps, and no step clustering or metal encapsulation, which improves the growth effect of silicon carbide single crystals.

[0073] In summary, this application provides a graphite crucible and a liquid-phase silicon carbide crystal growth furnace. The graphite crucible includes: a crucible body, the crucible body including a groove; a stepped structure disposed within the groove and along the inner wall of the crucible body, the stepped structure having multiple inner wall steps on the side facing the center of the groove; in the depth direction from the top surface of the groove opening to the bottom surface of the groove, the stepped structure extends from a set depth of the groove towards the center of the groove to the bottom surface of the groove; and a stacked structure located on the bottom surface of the groove, the stacked structure including multiple single layers stacked along the depth direction, the cross-sectional area of ​​the single layer increasing layer by layer along the depth direction, the stacked structure having multiple bottom surface steps on the side facing the inner wall of the crucible body. As can be seen from the above, the technical solution provided in this application, by setting a stepped structure along the inner wall of the crucible body and a stacked structure on the bottom surface of the groove, forms a stepped shape on the side wall and bottom of the graphite crucible that contacts the solution. This increases the contact area between the solution and the graphite crucible, improves the carbon dissolution rate and carbon transport efficiency, and reduces the carbon transport distance. Even at lower temperatures, sufficient carbon source can be obtained for silicon carbide crystal growth, improving the growth quality of silicon carbide single crystals and enhancing the crystal growth effect of the phase-method silicon carbide crystal growth furnace. Furthermore, the shape presented by the stepped and stacked structures makes the graphite crucible form a W shape that contacts the solution. At the same time, the distribution of the multi-level inner wall steps and multi-level bottom steps is opposite to the liquid flow direction of the solution, thereby making the impact of the solution on the inner wall of the graphite crucible stronger, further improving the carbon dissolution efficiency and carbon transport efficiency, and also suppressing the deposition of silicon carbide polycrystals at the bottom of the graphite crucible.

[0074] In the description of the embodiments of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and other terms indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0076] In the embodiments of this application, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0077] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0078] In the embodiments of this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A graphite crucible used in a liquid-phase silicon carbide crystal growth furnace, characterized in that, The graphite crucible includes: A crucible body, the crucible body including a groove; A stepped structure is provided within the groove and along the inner wall of the crucible body. The stepped structure has multiple inner wall steps on the side facing the center of the groove. In the depth direction from the top surface of the groove opening to the bottom surface of the groove, the stepped structure extends from a set depth of the groove towards the center of the groove to the bottom surface of the groove. A stacked structure is located on the bottom surface of the groove. The stacked structure includes multiple single layers stacked along the depth direction. The cross-sectional area of ​​each single layer increases progressively along the depth direction. The side of the stacked structure facing the inner wall of the crucible body has multiple bottom steps.

2. The graphite crucible according to claim 1, characterized in that, The crucible body, the stepped structure, and the stacked structure are integrally formed.

3. The graphite crucible according to claim 1, characterized in that, The inner diameter of the crucible body ranges from 150 to 400 mm, the sidewall thickness of the crucible body ranges from 10 to 40 mm, the depth of the groove ranges from 150 to 200 mm, and the bottom thickness of the crucible body ranges from 10 to 50 mm.

4. The graphite crucible according to claim 1, characterized in that, The height of the inner wall step ranges from 0.1 to 10 mm, and the width of the inner wall step ranges from 0.1 to 10 mm.

5. The graphite crucible according to claim 1, characterized in that, The height of the bottom step ranges from 0.1 to 10 mm, and the width of the bottom step ranges from 0.1 to 10 mm.

6. The graphite crucible according to claim 1, characterized in that, The graphite crucible also includes: An isolation ring is disposed at the bottom of the crucible body on the side opposite to the groove, and a heat-insulating cavity is formed in the surrounding area of ​​the isolation ring; wherein, a heat-insulating layer is disposed in the heat-insulating cavity.

7. The graphite crucible according to claim 6, characterized in that, The isolation ring and the crucible body are integrally formed.

8. The graphite crucible according to claim 6, characterized in that, The insulation layer includes a gas insulation layer or an insulation felt layer.

9. The graphite crucible according to claim 7, characterized in that, The gas insulation layer includes an Ar gas insulation layer, a He gas insulation layer, or a mixed Ar and He gas insulation layer.

10. A liquid-phase silicon carbide crystal growth furnace, characterized in that, The liquid-phase silicon carbide crystal growth furnace includes: Heating bucket; The graphite crucible disposed within the heating chamber is the graphite crucible as described in any one of claims 1-9.

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