A carbon-based material for crystal growth and preparation method thereof

Abstract

The present invention relates to the technical field of silicon carbide crystal preparation, and in particular to a carbon-based material for crystal growth and a preparation method thereof. The carbon-based material for crystal growth comprises a carbon matrix and a composite layer; the carbon matrix has pores, and the porosity of the carbon matrix is ​​5-55%; the composite layer is filled in the pores of the carbon matrix and is close to the surface side of the carbon matrix. When the carbon-based material is used as a reaction container for crystal growth, it can not only reduce the amount of carbon encapsulation in the crystal, prevent the generation of defects such as edge polycrystalline, and improve the quality of the crystal; it can also provide a partial carbon source for crystal growth to ensure the growth rate of the crystal; it solves the problem that the use of a graphite crucible coated with a TaC coating as a container for crystal growth in the prior art will reduce the crystal growth rate, thereby increasing the cost of silicon carbide ingot production.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide crystal preparation, and in particular to a carbon-based material for crystal growth and a preparation method thereof. Background Art

[0002] With the rapid development of the integrated circuit field in recent years, the performance of traditional single crystal silicon materials has limitations. Therefore, in the fields of high frequency, high voltage, high temperature power and radio frequency semiconductors, the third-generation semiconductor material with better performance, silicon carbide (SiC), has a broader application prospect. Silicon carbide is a representative of new wide bandgap semiconductor materials. Compared with the first generation of semiconductor silicon, silicon carbide has about 3 times the bandgap width, 2 times the saturated electron drift rate, 3 times the thermal conductivity and 10 times the breakdown field strength. It also has high critical breakdown field strength, high thermal conductivity, high electron saturation drift rate, excellent mechanical properties and physical and chemical stability. It can be used to make high voltage, high temperature and other high power devices. At present, the mainstream silicon carbide single crystal growth on the market is achieved by physical vapor transport (PVT), and the process temperature is as high as 2200℃. Physical vapor transport (PVT) is usually used to grow silicon carbide single crystals. High-purity isostatic graphite materials are usually selected as containers for heat generation, heat transfer and crystal growth.

[0003] Graphite materials have high melting points, high purity, stable chemical properties, low prices, and certain structural strength at high temperatures. They are commonly used reaction vessels in the semiconductor field, especially graphite crucibles. However, when growing silicon carbide single crystals using the physical vapor transport method (PVT), due to the strong corrosiveness of the Si-containing atmosphere at high temperatures to the graphite matrix, the carbon particles on the inside of the graphite crucible are easily detached and enter the growing crystal with the airflow to form carbon encapsulation, which in turn produces defects such as micropipe dislocations. In addition, due to the close contact between the graphite crucible and the silicon carbide ingot, it is also easy to form polycrystalline edges of the ingot. Therefore, in order to promote high-quality growth of silicon carbide, a layer of TaC coating is often needed to be added to the part of the inside of the graphite crucible that contacts the crystal growth area.

[0004] However, due to the mismatch of carbon-silicon ratio in the atmosphere during the growth of silicon carbide ingots, the carbon required for silicon carbide growth comes not only from silicon carbide powder, but also partly from the graphite crucible; it can be seen that using a graphite crucible coated with TaC coating as a container for crystal growth can improve the growth quality of the crystal, but it will also simultaneously reduce the crystal growth rate, thereby increasing the cost of silicon carbide ingot production. Therefore, it is of great significance to develop a graphite material for crystal growth that can ensure both the growth quality of silicon carbide crystals and the crystal growth rate, as well as a method for preparing the graphite material for crystal growth.

[0005] The present invention provides a carbon-based material for crystal growth and a preparation method thereof, so as to solve the problem in the prior art that using a graphite crucible coated with a TaC coating as a container for crystal growth will reduce the crystal growth rate and thus increase the cost of silicon carbide ingot production. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon-based material for crystal growth and a preparation method thereof, so as to solve the problem in the prior art that using a graphite crucible coated with a TaC coating as a container for crystal growth will reduce the crystal growth rate and thus increase the cost of silicon carbide ingot production.

[0007] The technical solution of the present invention is: a carbon-based material for crystal growth, comprising: a carbon matrix and a composite layer; the carbon matrix has pores, and the porosity of the carbon matrix is ​​5-55%; the composite layer is filled in the pores of the carbon matrix and is close to the surface side of the carbon matrix.

[0008] Preferably, the composite layer comprises at least two phases; the first phase of the composite layer is carbon, and the remaining phases include one or more phases of a substance composed of any two elements of Ta, C, and Si;

[0009] The thickness of the composite layer is 0.01-8 mm.

[0010] Preferably, the material of the remaining phases includes Ta element.

[0011] Preferably, the volume proportion of the remaining phases in the composite layer is less than 50%.

[0012] Preferably, the porosity of the carbon matrix is ​​10-50%; and the thickness of the composite layer is 0.01-5 mm.

[0013] The present invention also provides a method for preparing the above-mentioned carbon-based material for crystal growth, comprising the following steps:

[0014] a. Place the carbon substrate into an oxidation furnace for pore increase, the temperature of the oxidation furnace is 400-1200 ° C, the atmosphere is air or oxygen; the pore increase time is 5-20min;

[0015] b. Place the porous carbon substrate into a high-temperature furnace and prepare the composite layer using a chemical vapor infiltration process; the temperature in the high-temperature furnace is 1000-1500°C; the pressure in the high-temperature furnace is 1-650mbar; the infiltration atmosphere is TaCl 5 、SiCl 4 、Ta、C、C 3 H 6 , H 2 , Ar, and any three or more of them form a mixed gas, and the mixed gas includes TaCl 5and / or SiCl 4 ;

[0016] c. After the composite layer is prepared, the temperature change curve is controlled so that the dense TaC coating on the surface falls off, thereby obtaining a carbon-based material for crystal growth having a composite layer.

[0017] Preferably, during the chemical vapor infiltration process, the pressure in the high-temperature furnace is a continuously changing value within a range of 1-500 mbar.

[0018] Preferably, the temperature control curve may be a single-stage cooling-heating-cooling process or a multi-stage cooling-heating-cooling process.

[0019] Preferably, the infiltrating atmosphere is TaCl 5 , H 2 , Ar, and a mixed gas formed by the combination of the three; H 2 、Ar、TaCl 5 The flow ratio is (0.5-2):10:10.

[0020] Preferably, the infiltrating atmosphere is H 2 、Ar、TaCl 5 、SiCl 4 The mixed gas is formed by the combination of four kinds of gases; TaCl 5 、SiCl 4 , H 2 , and the flow ratio of Ar is (0.5-2):(1-3):10:10.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) The present invention provides a carbon-based material for crystal growth and a preparation method thereof, wherein the pores of the carbon-based material are filled with a composite layer, and the first phase of the composite layer is carbon, and the remaining phases contain Ta elements; when the carbon-based material is used as a reaction container for crystal growth, it can not only reduce the amount of carbon encapsulation in the crystal, prevent the formation of defects such as edge polycrystalline, and improve the quality of the crystal; it can also provide a partial carbon source for crystal growth to ensure the growth rate of the crystal; and solve the problem in the prior art that using a graphite crucible coated with a TaC coating as a container for crystal growth will reduce the crystal growth rate, thereby increasing the cost of producing silicon carbide ingots.

[0023] (2) The present invention provides a carbon-based material for crystal growth, wherein the pores of the carbon-based material are filled with a composite layer, and the composite layer is close to the surface side of the carbon matrix; during crystal growth, the Si-containing atmosphere can be effectively prevented from entering the pores of the carbon-based material for corrosion, so that the Si-containing atmosphere can only start to corrode from the surface side of the carbon-based material; and, although the Si-containing atmosphere will preferentially corrode the connection points between carbon particles, due to the binding of the composite layer to the carbon particles, the carbon particles will not fall with the flow of the atmosphere, which can effectively reduce the carbon encapsulation in the crystal; as the corrosion proceeds, the composite layer particles will fall, but due to the high density of the composite layer particles, they will fall directly and will not exist in the SiC crystal in the form of encapsulation, further preventing the formation of defects such as carbon encapsulation in the crystal and edge polycrystalline, thereby improving the quality of the crystal. In addition, the pores of the carbon-based material are filled with a composite layer, and its surface is exposed, so that the carbon-based material can provide part of the carbon source for the growth of the crystal, thereby ensuring the growth rate of the crystal and effectively reducing the production cost of the crystal ingot.

[0024] (3) The present invention provides a method for preparing the carbon-based material for crystal growth, which can adjust the thickness of the composite layer by controlling the range of pressure change in the high-temperature furnace or the porosity of the carbon-based material, thereby enabling the carbon-based material to achieve the supply of carbon atmosphere while preventing the formation of defects such as carbon encapsulation and edge polycrystalline. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0026] Figure 1 This is a schematic diagram of the cross-sectional morphology of the carbon-based material for crystal growth prepared in Example 1 of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the cross section of the carbon-based material for crystal growth prepared in Example 3 of the present invention;

[0028] Wherein: 1. Carbon matrix; 2. Composite layer. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments: Example 1

[0030] S1. Put the carbon matrix with an initial porosity of 20% into an oxidation furnace for pore increase. The temperature of the oxidation furnace is set to 600°C. The pore increase time is 10 minutes. The atmosphere used for pore increase is air or oxygen. After the pore increase is completed, a carbon matrix with a porosity of 30% is obtained.

[0031] S2, placing the pore-enlarged carbon matrix in a high-temperature furnace, and using a chemical vapor infiltration process to prepare a carbon matrix with a composite layer 2; during the infiltration, the selected infiltration atmosphere is TaCl 5 , H 2 , Ar mixed gas, and the mixed gas contains TaCl 5 , H 2 The flow ratio of Ar is 1:10:10; during infiltration, the temperature in the furnace is 1200°C, the pressure in the furnace is 1-10 mbar, and the infiltration time is 10 hours. The first phase of the composite layer 2 is carbon, and the second phase is TaC.

[0032] S3. After the infiltration is completed, the temperature in the high-temperature furnace is cooled to room temperature at a cooling rate of 10°C / min, and then the temperature is increased and decreased at the same temperature change rate to make the dense TaC coating on the surface of the carbon matrix fall off, and finally a carbon-based material with a composite layer 2 thickness of 0.1 mm is obtained.

[0033] In this embodiment, the pressure in the high temperature furnace in step S2 is a continuous and regularly changing value, so that the flow field in the furnace is in a chaotic state, and then the infiltrating atmosphere is dynamically infiltrated into the pores, so that the composite layer 2 is filled in the pores of the carbon matrix and close to the surface side of the carbon matrix. In this embodiment or other embodiments, the carbon-based material includes a graphite material.

[0034] In this embodiment, when the composite layer is prepared by chemical vapor infiltration process in step S2, since the progress of the chemical vapor infiltration process is difficult to accurately control, a TaC coating will be formed on the surface of the carbon matrix immediately after the pore filling is completed, that is, a dense TaC coating may be formed on the inner surface of the pores of the carbon matrix and the surface of the carbon matrix. In order to enable the carbon-based material to provide a carbon source for crystal growth to ensure the crystal growth rate while improving the growth quality of the crystal, the TaC coating formed on the surface of the carbon matrix needs to be removed; step S3 removes the TaC coating formed on the surface of the carbon matrix through a continuous cooling-heating-cooling process.

[0035] In this embodiment, if Figure 1 As shown, the volume proportion of the second phase in the composite layer 2 on the carbon substrate 1 is less than 50%, so that the carbon-based material can be used as a reaction vessel for crystal growth, which can not only realize the supply of carbon source atmosphere but also prevent the generation of defects such as carbon encapsulation; if the volume proportion of the second phase in the composite layer 2 is greater than 50%, the TaC coating on the inner surface of the pores of the carbon substrate 1 and the surface of the carbon substrate 1 is not dense and is very easy to fall off; when the TaC coating falls off, the Si-containing atmosphere will corrode the graphite substrate, which will lead to a large number of carbon encapsulations in the crystal, poor crystal quality and other problems. In other embodiments, such as Figure 1 As shown, the volume proportion of the second phase in the composite layer 2 should also be less than 50%.

[0036] In other embodiments, when the TaC coating formed on the surface of the carbon substrate is removed through a continuous cooling-heating-cooling process in step S3, the temperature change rates of heating and / or cooling may be different and irregular changes; the continuous cooling-heating-cooling may also be a temperature change process repeated multiple times. Example 2

[0037] S1. Put the carbon matrix with an initial porosity of 20% into an oxidation furnace for pore increase. The temperature of the oxidation furnace is set to 600°C. The pore increase time is 10 minutes. The atmosphere used for pore increase is air. After the pore increase is completed, a carbon matrix with a porosity of 30% is obtained.

[0038] S2. The carbon matrix with increased pores is placed in a high temperature furnace and a carbon matrix with a composite layer is prepared by chemical vapor infiltration process. During the infiltration, the infiltration atmosphere selected is TaCl 5 , H 2 , Ar mixed gas, and the mixed gas contains TaCl 5 , H 2 The flow ratio of Ar is 1:10:10; during infiltration, the temperature in the furnace is 1200℃, the pressure in the furnace is 1-50mbar; the infiltration time is 10h. Among them, the first phase of the composite layer is carbon, and the second phase is TaC.

[0039] S3. After the infiltration is completed, the temperature in the high-temperature furnace is cooled to room temperature at a cooling rate of 10°C / min, and then the temperature is increased and decreased at the same temperature change rate to make the dense TaC coating on the surface of the carbon matrix fall off, and finally a carbon-based material with a composite layer thickness of 0.5 mm is obtained.

[0040] In this embodiment, the pressure in the high-temperature furnace in step S2 changes continuously and irregularly, making the flow field in the furnace more chaotic, so that the infiltrating atmosphere has more sufficient power to penetrate into the pores of the carbon matrix, so that the composite layer is filled in the pores of the carbon matrix and close to the surface side of the carbon matrix. Example 3

[0041] S1. Put the carbon matrix with an initial porosity of 20% into an oxidation furnace for pore increase. The temperature of the oxidation furnace is set to 600°C. The pore increase time is 10 minutes. The atmosphere used for pore increase is oxygen. After the pore increase is completed, a carbon matrix with a porosity of 30% is obtained.

[0042] S2. The carbon matrix with increased pores is placed in a high temperature furnace and a carbon matrix with a composite layer is prepared by chemical vapor infiltration process. During the infiltration, the infiltration atmosphere selected is TaCl 5 , H 2 , Ar mixed gas, and the mixed gas contains TaCl 5 , H2 , the flow ratio of Ar is 1:10:10; during infiltration, the temperature in the furnace is 1200°C, the pressure in the furnace is 1-100 mbar; and the infiltration time is 10 h.

[0043] S3. After the chemical vapor infiltration process is completed, the temperature in the high-temperature furnace is cooled to room temperature at a cooling rate of 10°C / min, and then the temperature is raised and lowered at the same temperature change rate to make the dense TaC coating on the surface of the carbon matrix fall off, and finally a carbon-based material with a composite layer thickness of 1mm is obtained. The first phase of the composite layer is carbon, and the second phase is TaC.

[0044] Take a small piece of the carbon-based material prepared in Example 3 and crush it, and perform electron microscope scanning on the cross section of one of the fragments. Figure 2 As shown, the black part at the bottom is the first phase in the composite layer: carbon, and the bright part is the remaining phases in the composite layer; thus, it can be seen that the composite layer is filled in the pores of the carbon matrix and is close to the surface side of the carbon matrix.

[0045] In this embodiment, the pressure in the high-temperature furnace in step S2 is a continuously and irregularly changing value; the larger the range of pressure change in the high-temperature furnace, the more chaotic the flow field in the furnace, which is more conducive to the infiltration of the infiltrating atmosphere into the pores and forming a composite layer on the inner surface of the pores, thereby making the thickness of the formed composite layer thicker. Example 4

[0046] S1. Put the carbon matrix with an initial porosity of 20% into an oxidation furnace for pore increase. The temperature of the oxidation furnace is set to 600°C, the pore increase time is 15 minutes, and the atmosphere used for pore increase is air. After the pore increase is completed, a carbon matrix with a porosity of 40% is obtained.

[0047] S2. The carbon matrix with increased pores is placed in a high temperature furnace and a carbon matrix with a composite layer is prepared by chemical vapor infiltration process. During the infiltration, the infiltration atmosphere selected is TaCl 5 , H 2 、Ar、SiCl 4 A mixed gas containing TaCl 5 、SiCl 4 , H 2 , the flow ratio of Ar is 1:2:10:10; during infiltration, the temperature in the furnace is 1200℃, the pressure in the furnace is 1-100mbar; the infiltration time is 10h.

[0048] S3. After the infiltration is completed, the temperature in the high-temperature furnace is cooled to room temperature at a cooling rate of 10°C / min, and then the temperature is increased and decreased at the same temperature change rate, so that the dense TaC coating and SiC coating on the surface of the carbon matrix fall off, and finally a carbon-based material with a composite layer thickness of 1.5 mm is obtained. Among them, the first phase of the composite layer is carbon, and the remaining phases are a composite of TaC phase and SiC phase.

[0049] In this embodiment, the pressure in the high temperature furnace in step S2 changes continuously and irregularly. Example 5

[0050] S1. Put the carbon matrix with an initial porosity of 20% into an oxidation furnace for pore increase. The temperature of the oxidation furnace is set to 600°C, the pore increase time is 15 minutes, and the atmosphere used for pore increase is air. After the pore increase is completed, a carbon matrix with a porosity of 40% is obtained.

[0051] S2. The carbon matrix with increased pores is placed in a high temperature furnace and a carbon-based material body with a composite layer is prepared by chemical vapor infiltration process; during infiltration, the infiltration atmosphere selected is TaCl 5 , H 2 , Ar mixed gas, and the mixed gas contains TaCl 5 , H 2 The flow ratio of Ar is 1:10:10; during infiltration, the temperature in the furnace is 1200℃, the pressure in the furnace is 1-100mbar; the infiltration time is 10h. The first phase of the composite layer is carbon, and the second phase is TaC.

[0052] S3. After the infiltration is completed, the temperature in the high-temperature furnace is cooled to room temperature at a cooling rate of 10°C / min, and then the temperature is increased and decreased at the same temperature change rate to make the dense TaC coating on the surface of the carbon matrix fall off, and finally a carbon-based material with a composite layer thickness of 1.5 mm is obtained.

[0053] In this embodiment, the pressure in the high temperature furnace in step S2 changes continuously and irregularly.

[0054] Comparative Example 1

[0055] S1. Place the graphite part in a high-temperature furnace and use chemical vapor deposition to prepare the TaC coating; the atmosphere selected for deposition is TaCl 5 , C 3 H 6 , H 2 , Ar mixed gas, TaCl in the mixed gas 5 , C 3 H 6 , H 2, Ar flow ratio is 3:1:30:10, the deposition time is 10h; the furnace temperature is 1200℃, and the furnace pressure is 10mbar.

[0056] S2. After the deposition is completed, the temperature in the furnace is lowered to room temperature at a cooling rate of 2°C / min to obtain a graphite part with a TaC coating thickness of 30um.

[0057] Comparative Example 2

[0058] Purified carbon-based materials.

[0059] In order to verify the role of the carbon-based materials prepared in the above Examples 1-5 and Comparative Examples 1-2 in the crystal growth process, the carbon-based materials prepared in the above Examples 1-5 and Comparative Examples 1-2 were used as reaction containers, respectively, and crystal growth verification was carried out under the same conditions, and the verification results were compared and analyzed. During the crystal growth, the crystal growth temperature was 2200°C and the crystal growth time was 100h. After the crystal growth was completed, the thickness of the ingot was measured respectively; then, the ingot was sliced, the number of carbon packages on each chip was observed with the naked eye, and the average area occupied by the carbon packages on the chip was calculated; the statistical results are shown in Table 1.

[0060] Table 1: Crystal growth verification results of carbon-based materials prepared in Examples 1-5 and Comparative Examples 1-2

[0061]

[0062] The effective effects of the carbon-based materials prepared in the above embodiments 1-5 and the carbon-based materials prepared in comparative example 1 in the crystal growth process are compared. It can be seen from Table 1 that, although the average carbon coating area occupied by the crystals cultured using the carbon-based materials prepared in the above embodiments 1-5 and the carbon-based materials prepared in comparative example 1 as reaction containers is similar, the crystals cultured using the carbon-based materials prepared in the above embodiments 1-5 as reaction containers for crystal growth have a higher ingot thickness. It can be seen that in Comparative Example 1, a dense TaC coating is prepared on the surface of the carbon-based material, which can effectively reduce the corrosion of the Si-containing atmosphere to the graphite matrix under high temperature environment, reduce the shedding of carbon particles inside the carbon-based material, and then reduce the number of carbon packages formed in the crystal, reduce the generation of defects such as micropipe dislocation and edge polycrystalline, and improve the quality of the crystal; however, the thickness of the crystal ingot of the crystal grown under the same conditions is significantly reduced, which further illustrates that part of the carbon source required for crystal growth is provided by the carbon-based material as a reaction vessel; a dense TaC coating is prepared on the surface of the carbon-based material, and the carbon-based material cannot provide a carbon source, the carbon source in the atmosphere required for crystal growth is insufficient, and the carbon-silicon ratio is not matched, resulting in a significant decrease in the crystal growth rate, thereby increasing the production cost of the crystal ingot. The carbon-based material prepared in Examples 1-5 is a crystal cultured in a reaction vessel, which can not only improve the growth quality of the crystal, but also provide part of the carbon source for crystal growth to ensure the crystal growth rate and reduce the production cost of the crystal ingot.

[0063] The effective effects of the carbon-based materials prepared in Examples 1-5 and the carbon-based materials prepared in Comparative Example 2 in the crystal growth process are compared. It can be seen from Table 1 that although the thickness of the crystal ingots cultured using the carbon-based materials prepared in Examples 1-5 and the carbon-based materials prepared in Comparative Example 2 as reaction vessels are comparable, the average carbon-encapsulated area of ​​the crystals cultured using the carbon-based materials prepared in Examples 1-5 as reaction vessels for crystal growth is significantly lower, which further illustrates that the crystals cultured using the carbon-based materials prepared in Examples 1-5 as reaction vessels can provide a partial carbon source for crystal growth to ensure the crystal growth rate while improving the crystal growth quality, thereby reducing the production cost of the crystal ingots. In Comparative Example 2, the purified carbon-based material is directly used as a reaction container for crystal growth. Since the carbon-based material has a porosity of 10%-25%, during the crystal growth process, the Si-containing atmosphere will enter the pores of the carbon matrix and corrode it. The carbon-based material is formed by bonding carbon particles to each other with a binder. The connection points between the carbon particles are more easily corroded than the carbon particles themselves. The Si-containing atmosphere will preferentially corrode the connection points between the carbon particles, which will cause a large amount of carbon powder to fall from the surface of the carbon-based material crucible. The fallen carbon powder will enter the growing crystal with the airflow to form carbon encapsulation, which will then cause the crystal to have defects such as microtubules, dislocations, polymorphism, and polycrystals, affecting the quality of crystal growth. The carbon-based materials prepared in Examples 1-5 have a surface porosity of 25%-50% by increasing the pores, and then a composite layer is filled in the pores of the carbon matrix and close to the surface of the carbon matrix, wherein the first phase of the composite layer is carbon, and the remaining phases are single-phase TaC, Ta, or the remaining phases are a composite of any two phases or a composite of multiple phases such as TaC, Ta, silicon carbide, and tantalum silicide; when the composite layer is used to fill the pores of the carbon matrix, during crystal growth, the Si-containing atmosphere will corrode the carbon substrate layer by layer from the outside to the inside, so that carbon powder will not fall off, thereby affecting the quality of crystal growth; as the corrosion proceeds, the composite layer particles will also fall off, but due to the high density of the composite layer particles, they will fall directly and will not exist in the crystal in the form of a package; therefore, the carbon-based materials prepared in Examples 1-5 can both realize the supply of carbon atmosphere and prevent the formation of defects such as carbon packaging and edge polycrystalline.

[0064] The effective effects of the carbon-based materials prepared in Example 1, Example 2 and Example 3 in the crystal growth process are compared. It can be seen from Table 1 that the crystals cultured in the reaction vessels using the carbon-based materials prepared in Example 1, Example 2 and Example 3 have similar ingot thicknesses, but the average carbon package area occupied by the crystals cultured in the reaction vessel using the carbon-based material prepared in Example 3 is significantly smaller. It can be seen that under the conditions of the same porosity, the same infiltration atmosphere and flow ratio, and the same temperature and infiltration time in the high-temperature furnace during infiltration, the greater the range of continuous pressure changes in the high-temperature furnace, the more chaotic the flow field in the furnace, the more sufficient the infiltration atmosphere has to penetrate into the pores, and the more conducive it is to fill the pores of the carbon matrix with a thicker composite layer. The thicker the composite layer, the smaller the average carbon package area occupied by the crystals cultured in the reaction vessel. At the same time, due to the close contact between the carbon-based material and the ingot, the thicker the composite layer, the more conducive it is to prevent the formation of edge polycrystals.

[0065] The effective effects of the carbon-based materials prepared in Example 3 and Example 5 in the crystal growth process are compared. It can be seen from Table 1 that the crystals cultured in reaction vessels using the carbon-based materials prepared in Example 3 and Example 5 have similar ingot thicknesses and similar average carbon encapsulation area in the crystals. It can be seen that under the conditions of the same infiltration atmosphere and flow ratio, the same temperature and pressure continuous change range in the high-temperature furnace during infiltration, and the same infiltration time, the higher the porosity, the more conducive it is to filling the pores of the carbon matrix with a thicker composite layer.

[0066] The effective effects of the carbon-based materials prepared in Example 4 and Example 5 in the crystal growth process are compared. It can be seen from Table 1 that the crystals cultured using the carbon-based materials prepared in Example 4 and Example 5 as reaction vessels, the ingot thickness of the crystals cultured using the carbon-based materials prepared in Example 5 as reaction vessels is thicker than the ingot thickness of the crystals cultured using the carbon-based materials prepared in Example 4 as reaction vessels, but the difference is small. The average carbon encapsulation area in the crystals is comparable. It can be seen that the composite layer filled in the pores of the carbon matrix, when the remaining phases of the composite layer are a composite of TaC phase and SiC phase, the carbon-based material is used as a reaction vessel for crystal growth, which can also provide part of the carbon source for crystal growth to ensure the crystal growth rate, reduce the production cost of the ingot, and at the same time reduce the amount of carbon encapsulation in the crystal and improve the growth quality of the crystal.

[0067] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A carbon-based material for crystal growth, characterized in that: include: A carbon matrix and a composite layer; the carbon matrix has pores, and the porosity of the carbon matrix is ​​5-55%; the composite layer is filled in the pores of the carbon matrix and is close to the surface side of the carbon matrix; The first phase of the composite layer is carbon, and the remaining phases are single-phase TaC or Ta, or the remaining phases are a composite of any two phases or a composite of multiple phases among TaC, Ta, silicon carbide, and tantalum silicide; the volume proportion of the remaining phases in the composite layer is less than 50%; The method for preparing the carbon-based material for crystal growth comprises the following steps: a. Place the carbon substrate into an oxidation furnace for pore increase, the temperature of the oxidation furnace is 400-1200 ° C, the atmosphere is air or oxygen; the pore increase time is 5-20min; b. Place the pore-increased carbon matrix into a high-temperature furnace and prepare a carbon matrix with a composite layer by a chemical vapor infiltration process; the temperature in the high-temperature furnace is 1000-1500°C; the pressure in the high-temperature furnace is a continuously changing value, and the range of change is 1-500mbar; the infiltration atmosphere is a mixed gas formed by any three or more combinations of TaCl5, SiCl4, C3H6, H2, and Ar, including at least TaCl5; c. After the chemical vapor infiltration process is completed, the temperature change curve is controlled so that the dense TaC coating on the surface falls off, and a carbon-based material for crystal growth with a composite layer is obtained.

2. A carbon-based material for crystal growth according to claim 1, characterized in that: The porosity of the carbon matrix is ​​10-50%; the thickness of the composite layer is 0.01-5 mm.

3. The carbon-based material for crystal growth according to claim 1, characterized in that: The controlled temperature change curve is a single-stage cooling-heating-cooling process or a multi-stage cooling-heating-cooling process.

4. The carbon-based material for crystal growth according to claim 1, characterized in that: The infiltration atmosphere is a mixed gas formed by a combination of TaCl5, H2 and Ar; the flow ratio of H2, Ar and TaCl5 in the mixed gas is (0.5-2):10:

10.

5. The carbon-based material for crystal growth according to claim 1, characterized in that: The infiltration atmosphere is a mixed gas formed by a combination of H2, Ar, TaCl5 and SiCl4; the flow ratio of TaCl5, SiCl4, H2 and Ar in the mixed gas is (0.5-2): (1-3): 10:10.

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