High-temperature gas-phase chemical crystal growth method and equipment for metal catalyst assisted carbon source cracking

Abstract

The invention provides a high-temperature gas-phase chemical crystal growth method and equipment for metal catalyst assisted carbon source cracking, in the crystal growth method, an efficient metal catalyst for carbon source catalytic cracking is prepared, the carbon cracking temperature can be reduced, the carbon cracking efficiency can be improved, the carbon source and a silicon source gas are cracked at the same time, the energy consumption is reduced, and the crystal growth quality is improved; meanwhile, crystal growth equipment is provided with an independent silicon source gas inlet channel and an independent carbon source gas inlet channel, a metal catalyst and a filtering structure are arranged in the carbon source gas inlet channel, carbon source gas flow can be rapidly and efficiently cracked, the filtering structure is arranged, metal particles are captured, and metal impurity pollution is reduced; the silicon source gas is cracked through the independent channel and then mixed with the cracked carbon source gas, the mixture enters the growth chamber to be deposited on the seed crystal, finally the silicon carbide single crystal substrate is obtained, the crystal growth equipment achieves synchronous cracking of the two gas sources and enters the growth chamber through the mixing area to be deposited on the single crystal substrate, and the deposition quality and efficiency of the substrate are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of crystal manufacturing, and relates to a high-temperature gas phase chemical crystal growth method and a crystal growth device. BACKGROUND

[0002] With the rapid development of modern science and technology, semiconductor materials, as the core component of the information industry and the energy field, have important influence on the development of related technologies. Silicon carbide (SiC), as a third-generation semiconductor material, has advantages such as wide band gap, high critical electric field and high saturation mobility, which makes it show significant advantages in high-temperature, high-frequency and high-power electronic device fields. These characteristics make silicon carbide materials widely used in new energy vehicles, photovoltaic power generation, railway transportation and power systems, and become one of the key materials for promoting the technological innovation of these industries.

[0003] In order to meet the needs of industrial production for high-quality silicon carbide materials, researchers are constantly exploring and developing efficient crystal growth technologies. At present, the physical vapor transport method (Physical Vapor Transport, PVT) and the high-temperature gas phase chemical method (High-Temperature Chemical Vapor Deposition, HT-CVD), among which the high-temperature gas phase chemical method gradually becomes one of the hot research directions in the industry because of its advantages such as fast growth rate, strong controllability of crystal quality, and easy realization of large-size crystal growth.

[0004] In the process of growing silicon carbide substrates by high-temperature gas phase chemical method, silicon source gas needs to be mixed with carbon source gas in the high-temperature reaction chamber and then cracked, and then rises into the reaction chamber through the gas channel, and finally deposits on the surface of the seed crystal to obtain silicon carbide substrates.

[0005] However, because the cracking temperature of silicon source gas (such as SiH4, SiCl4) is low (400-600℃), it begins to crack before entering the high-temperature zone, while the thermal cracking temperature of carbon source gas (such as propane, acetylene, methane, etc.) is relatively high, usually needs to be decomposed at >700℃ to form reactive carbon species, which will cause the imbalance of the mixing ratio of silicon source gas and carbon source gas in the crystal growth process, the stoichiometric ratio of the crystal deviates (Si:C≠1:1), and the silicon carbide crystal formed finally causes polymorphism mixing (such as 3C-SiC and 4H-SiC coexist) or dislocation proliferation, and the crystal quality decreases.

[0006] In summary, in the process of high-temperature gas phase chemical crystal growth, the silicon source gas cracking temperature is low, and the carbon source gas cracking temperature is high, and the two cannot be cracked at the same time, which leads to an imbalance in the mixing ratio during the crystal growth process. In order to improve the process efficiency and the activity degree of carbon atoms, the existing methods generally rely on high temperature and long time heating, resulting in high energy consumption, unstable reaction, low gas utilization rate and other problems. Current research shows that some transition metals (such as Ni, Fe, Co, Pt) have excellent carbon source catalytic cracking performance. However, how to systematically combine metal catalysts with gas cracking paths to form a stable, controllable and engineering applicable catalytic cracking method still lacks mature solutions. SUMMARY

[0007] In view of the problems in the prior art, the purpose of the present application is to provide a metal catalyst assisted carbon source cracking high-temperature gas phase chemical crystal growth method and equipment. The crystal growth method introduces a metal catalyst suitable for catalyzing carbon source gas cracking, matches the catalyst carrier structure, and prepares a high-efficiency carbon source catalytic cracking metal catalyst. The use of the catalyst can reduce the carbon cracking temperature, improve the carbon cracking efficiency, enable the carbon source and silicon source gas to crack at the same time, reduce the energy consumption, and improve the crystal growth quality. At the same time, an independent silicon source gas inlet channel and a carbon source gas inlet channel are provided in the crystal growth equipment, and a metal catalyst and a filtering structure are provided in the carbon source gas inlet channel. The cracking temperature is controlled at 500-650℃. The carbon source gas stream passes through the catalytic cracking zone to improve the cracking activity, and can be cracked quickly and efficiently after entering the cracking zone. At the same time, the filtering structure is provided to capture metal particles and reduce metal impurity pollution. At the same time, the silicon source gas is cracked through the independent channel and mixed with the cracked carbon source gas, and then enters the growth chamber to deposit on the seed crystal, and finally obtains a silicon carbide single crystal substrate. The crystal growth equipment realizes the synchronous cracking of the two gas sources by providing a carbon source gas catalytic zone and separate cracking zones for silicon source and carbon source, and deposits a single crystal substrate in the growth chamber through the mixing zone, thereby improving the deposition quality and efficiency of the substrate.

[0008] To achieve this purpose, the following technical solutions are adopted in the present application:

[0009] In a first aspect, the present application provides a metal catalyst assisted carbon source cracking high-temperature gas phase chemical crystal growth method, which comprises the following steps:

[0010] S1 Preparation of metal catalyst:

[0011] Carrier pretreatment: immerse the high-purity high-temperature resistant inert carrier in a 5-10% acid solution and ultrasonically clean for 20-40min, and then calcine at 1000-1200℃ for 1-3h after removing the surface impurities;

[0012] Active component loading: immerse the carrier into the ethanol solution containing metal nitrate, impregnate for 10-30 min; centrifuge to remove the excess solution after impregnation, and dry at 50-70℃;

[0013] Catalytic structure forming: calcine at 280-300℃ for 1-3h in air atmosphere; continue to reduce at 600-650℃ for 1-3h in H2 / N2 mixed gas; finally, pass O2 / Ar mixed gas to passivate the surface to form an oxide film.

[0014] S2 carbon source gas and silicon source gas cracking and mixing:

[0015] Carbon source gas cracking: the carbon source gas passes through an independent metal catalyst catalytic cracking zone and a filter structure; the catalytic cracking zone temperature is controlled at 500-650℃; the carbon source gas flow rate is 20-200sccm;

[0016] Silicon source gas cracking: the silicon source gas passes through an independent cracking zone, the temperature of which is controlled at 500-650℃, and the silicon source gas flow rate is 20-200sccm;

[0017] Carbon source gas and silicon source gas mixing: the carbon atom molar number and the silicon atom molar number of the carbon source gas and the silicon source gas are in a 1:1 ratio, and after passing through the respective independent cracking zones, they are mixed, and the mixing zone temperature is controlled at 1000-1500℃.

[0018] S3 crystal growth process: after the carbon source gas and the silicon source gas are mixed, they enter the growth zone and complete the growth of the silicon carbide substrate on the surface of the seed crystal after temperature and pressure rising; the growth temperature is 2100-2500℃, and the growth pressure is 10-90kPa.

[0019] Preferably, in step S1, the high-temperature inert carrier material is selected from one of Al2O3, SiO2, and ZrO2;

[0020] Preferably, in step S1, the structure of the high-temperature inert carrier can be one of a flake, a circular ring, a foam ceramic, a honeycomb block, a porous sheet, and a nickel mesh structure;

[0021] Preferably, in step S1, the metal nitrate contains one or two of Ni(NO3)2, Co(NO3)2, Fe(NO3)3, and H2Pt(NO3)6;

[0022] Preferably, in step S1, the metal-containing nitrate is a mixture of two metal-containing nitrates, which can be a mixture of Ni(NO3)2 and Co(NO3)2, a mixture of Fe(NO3)3 and H2Pt(NO3)6, a mixture of Ni(NO3)2 and Fe(NO3)3, a mixture of Ni(NO3)2 and H2Pt(NO3)6, a mixture of Co(NO3)2 and Fe(NO3)3, or a mixture of Co(NO3)2 and H2Pt(NO3)6.

[0023] Preferably, in step S1, the mixing ratio of the two metal-containing nitrates is a molar ratio of 5:5 to 7:3 of the two metal elements.

[0024] Preferably, in step S2, a filter structure is provided in the carbon source gas cracking, which is a ceramic filter structure with a ZrO2 coating on a MgO-Al2O3 substrate with a pore density of 350-400 cpsi.

[0025] The present application provides a high-temperature gas-phase chemical crystal growth method assisted by metal catalysts for carbon source cracking,

[0026] By preparing metal catalysts for catalyzing carbon source gas cracking, the carbon source gas cracking temperature is reduced, the carbon cracking efficiency is improved, the carbon source gas and the silicon source gas are cracked and mixed at the same time, the energy consumption is reduced, and the crystal growth quality is improved.

[0027] The metal in the metal catalyst is selected as a double metal complex, which has a synergistic effect, can further reduce the cracking temperature, improve the cracking efficiency, and prolong the service life of the catalyst.

[0028] The metal catalyst is passivated to form an oxide film, which inhibits high-temperature metal evaporation and reduces metal pollution, and at the same time, the oxide film isolates adjacent metal particles to prevent metal crystallites from migrating and agglomerating (sintering) at high temperatures, maintain high specific surface area active sites, and efficiently maintain the catalytic activity and stability of the catalyst.

[0029] After the carbon source gas is cracked, a ceramic filter structure is provided to further filter metal particles, reduce metal pollution, and further improve the crystal growth quality.

[0030] In a second aspect, the present application provides a high-temperature gas-phase chemical crystal growth device assisted by metal catalysts for carbon source cracking, which comprises a heating device, a growth furnace cavity, a heat preservation layer, a growth crucible, a seed crystal pulling device, a gas inlet channel, and a gas inlet assembly.

[0031] The heating device is arranged outside the growth furnace cavity, and the heating mode of the heating device is coil heating.

[0032] The growth furnace cavity comprises a quartz tube, a growth furnace cover and a sealing bottom cover, and the growth furnace cover and the sealing bottom cover are respectively arranged at the upper and lower ends of the quartz tube.

[0033] The growth crucible is a graphite crucible, and the growth crucible is arranged axially at the center of the inner side of the quartz tube, and the heat preservation layer is arranged at the gap between the outside of the growth crucible and the quartz tube.

[0034] The seed crystal pulling device comprises a seed crystal support and a seed crystal holder, the seed crystal support is inserted into the growth furnace cover, and the seed crystal holder is located at the end of the seed crystal support on the side of the growth furnace cavity.

[0035] A through hole one is arranged at the center of the growth furnace cover, and the diameter of the through hole one is D1; the seed crystal support is coaxially arranged at the center of the growth furnace cover through the through hole one, and the diameter of the seed crystal support is D2, and the requirement is D1>D2, and the difference between D1 and D2 is 1-3 mm; the lower end of the seed crystal support is fixedly connected with the seed crystal holder, and the seed crystal support and the seed crystal holder are coaxially inserted into the growth crucible; the upper end of the seed crystal support is connected with a power structure, the power structure is used for rotating and pulling the seed crystal and the seed crystal in the crystal growth process, and the bottom surface of the seed crystal holder is adhered with the seed crystal.

[0036] The gas inlet channel is arranged above the center of the sealing bottom cover; the gas inlet assembly is arranged in the gas inlet channel, and the gas inlet assembly comprises a silicon source gas inlet channel, a carbon source gas inlet channel and a plurality of baffle structures which are arranged in the inner wall of the gas inlet channel in an upper and lower interval along the gas flow direction; the center of the sealing bottom cover is provided with an opening which is connected with the carbon source gas inlet channel and the silicon source gas inlet channel and simultaneously connected with an external gas source;

[0037] The carbon source gas inlet channel is provided with the metal catalyst of the first aspect at the gas inlet, and the filter structure is arranged at the gas outlet, preferably a ceramic filter screen structure, an MgO-Al2O3 substrate with a ZrO2 coating layer, and a pore density of 350-400 cpsi;

[0038] Preferably, the carbon source gas channel is eccentrically arranged at the gas inlet of the gas inlet channel, and the diameter is D3; the silicon source gas channel is arranged in the remaining space of the gas inlet of the gas inlet channel around the carbon source gas channel, and the diameter is D4, and D3>D4;

[0039] Preferably, a plurality of annular steps one are arranged in an upper and lower interval along the vertical direction of the gas flow in the inner wall of the gas inlet channel above the carbon source gas inlet channel and the silicon source gas inlet channel, and the baffle structure is arranged on the annular step one; the vertical distance between the upper and lower baffle structures is 15-20 mm, and the overlapping distance between the baffle structures arranged in an upper and lower interval is 3-5 mm;

[0040] Preferably, the gas outlet of the gas inlet channel is a tapering expanding structure from the low end to the top end;

[0041] Preferably, the outlet of the gas inlet channel is provided with a second annular step, the second annular step is provided with a circular baffle, the circular baffle is provided with a second through hole, the baffle is made of ceramic with a filter structure, an MgO-Al2O3 matrix with a ZrO2 coating, and a pore density of 350-400 cpsi.

[0042] The crystal growth equipment provided by the application is provided with independent silicon source gas inlet channels and carbon source gas inlet channels, the carbon source gas inlet channels are provided with metal catalysts and filter structures, the silicon source gas inlet channels and the carbon source gas inlet channels are independently arranged, so that the silicon source and the carbon source are independently cracked, the cracking temperature is controlled to be 500-650 DEG C, the carbon source gas can be quickly and efficiently cracked through the metal catalysts, and the metal particles can be captured through the filter structures, so that the metal impurity pollution is effectively reduced; during the mixing of the carbon source gas and the silicon source gas, the carbon source gas and the silicon source gas pass through the mixing area composed of the inverted conical outlet and the multi-stage baffle structure, a rotational flow mixing field is formed, the carbon source gas and the silicon source gas after cracking are fully and uniformly mixed, enter the growth chamber, and are deposited on the seed crystal, and finally the silicon carbide single crystal substrate is obtained, the crystal growth equipment realizes the synchronous cracking of the two kinds of gas sources through the arrangement of the carbon source gas catalytic area and the independent cracking area of the silicon source and the carbon source, the single crystal substrate is deposited in the growth chamber through the mixing area, and the deposition quality and efficiency of the substrate are improved. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a structural schematic diagram of the crystal growth equipment of embodiment 1;

[0044] Figure 2 is a schematic diagram of the circular baffle in the device of the crystal growth equipment of embodiment 1;

[0045] In the figure: 10-heating device, 20-growth furnace cavity, 21-quartz tube, 22-growth furnace cover, 23-sealing bottom cover, 30-graphite crucible, 40-heat preservation layer, 51-seed crystal support, 52-seed crystal holder, 53-seed crystal, 61-gas inlet channel, 62-silicon source gas inlet channel, 63-carbon source gas inlet channel, 64-metal catalyst, 65-filter structure, 66-baffle structure, 661-annular step one, 67-circular baffle, 671-second through hole, 672-first through hole, 673-annular step two DETAILED DESCRIPTION

[0046] The technical solutions of the application are further described below through specific embodiments.

[0047] Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0048] Embodiment 1

[0049] A high-temperature gas-phase chemical crystal growth apparatus for carbon source pyrolysis assisted by a metal catalyst is provided. The resulting crystal growth apparatus includes a heating device, a growth furnace chamber, an insulation layer, a growth crucible, a seed crystal pulling device, an air inlet channel, and an air inlet assembly.

[0050] The heating device is located outside the growth furnace cavity, and the heating method of the heating device is coil heating;

[0051] The growth furnace chamber includes a quartz tube, a growth furnace cover, and a sealing bottom cover, with the growth furnace cover and the sealing bottom cover respectively located at the upper and lower ends of the quartz tube;

[0052] The growth crucible is a graphite crucible, which is axially positioned at the center of the inner side of the quartz tube, and the heat insulation layer is positioned in the pore between the outside of the growth crucible and the quartz tube.

[0053] The seed crystal pulling device includes a seed crystal support and a seed crystal holder; the seed crystal support is inserted into the growth furnace cover, and the seed crystal holder is located at the end of the seed crystal support that extends into the growth furnace cavity;

[0054] A through hole with a diameter of D1 is opened at the center of the growth furnace cover; the seed crystal support is coaxially installed at the center of the growth furnace cover through the through hole, and the diameter of the seed crystal support is D2, requiring D1 > D2, with a difference of 1-3mm between D1 and D2; a seed crystal holder is fixedly connected to the lower end of the seed crystal support, and both the seed crystal support and the seed crystal holder are coaxially inserted into the inside of the growth crucible; a power structure is connected to the upper end of the seed crystal support, and the power mechanism is used to rotate and lift the seed crystal and the seed crystal upward during the crystal growth process, with the seed crystal adhering to the bottom surface of the seed crystal holder;

[0055] The air intake channel is located above the center of the sealed bottom cover; the air intake assembly is located inside the air intake channel, and the air intake assembly includes a silicon source gas intake channel, a carbon source gas intake channel, and multiple baffle structures spaced vertically along the gas flow direction on the inner wall of the air intake channel; the center of the sealed bottom cover has an opening that connects the carbon source gas intake channel and the silicon source gas intake channel, and also connects to an external gas source.

[0056] The carbon source gas inlet channel has a metal catalyst as described in the first aspect at the inlet and a filter structure at the outlet. The filter structure is preferably a ceramic filter screen structure with a ZrO2 coating on a MgO-Al2O3 matrix and a pore density of 350-400 cpsi.

[0057] The carbon source gas channel is eccentrically positioned at the air inlet of the air intake channel, with a diameter of D3. The silicon source gas channel is positioned around the carbon source gas channel in the remaining space at the air inlet of the air intake channel, with a diameter of D4, where D3 > D4.

[0058] The inner wall of the gas inlet channel above the carbon source gas inlet channel and the silicon source gas inlet channel is provided with a plurality of annular steps one in the vertical direction along the gas flow direction, and a baffle structure is arranged on the annular step one; the vertical distance between the upper and lower baffle structures is 15-20 mm, and the overlapping distance between the baffle structures arranged in an upper and lower adjacent manner is 3-5 mm;

[0059] The gas outlet of the gas inlet channel is a tapered expanding structure from the low end to the top end; an annular step two is arranged at the gas outlet of the gas inlet channel, a circular baffle is placed on the annular step two, a through hole two is formed in the circular baffle, the baffle is made of a ceramic filter screen structure, an MgO-Al2O3 matrix with a ZrO2 coating, and the hole density is 350-400 cpsi

[0060] Example 2

[0061] A high-temperature gas phase chemical crystal growth method for metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1:

[0062] S1. Preparation of a metal catalyst:

[0063] Carrier pretreatment: immerse a high-purity high-temperature-resistant inert carrier (Al2O3) in a 5% acid solution and ultrasonically clean for 20 min, remove the surface impurities, and then calcine at 1000°C for 1 h;

[0064] Active component loading: immerse the foam ceramic structure carrier in an ethanol solution containing a mixture of metal nitrate Ni(NO3)2 and Co(NO3)2, the molar ratio of the two metal elements Ni(NO3)2 and Co(NO3)2 is 5:5, and the immersion penetration time is 30 min; after immersion, centrifuge to remove excess solution, and dry at 50°C;

[0065] Catalytic structure forming: calcine at 280°C for 3 h in an air atmosphere; continue to reduce at 600°C for 3 h in a H2 / N2 mixed gas; finally, pass an O2 / Ar mixed gas to passivate the surface and form an oxide film.

[0066] S2. Cracking and mixing of carbon source gas and silicon source gas:

[0067] Carbon source gas cracking: the carbon source gas passes through an independent metal catalyst cracking zone and a filter structure; the cracking zone temperature is controlled at 500°C; the filter structure is a ceramic filter screen structure with a hole density of 350 cpsi, and the flow rate of the carbon source gas is 200 sccm;

[0068] Silicon source gas cracking: the silicon source gas passes through an independent cracking zone, and the temperature is controlled at 500°C, and the flow rate of the silicon source gas is 200 sccm;

[0069] Carbon source gas and silicon source gas mixing: the flow ratio of carbon source gas and silicon source gas is 1:1, and after passing through the respective independent cracking zone, they are mixed, and the temperature of the mixing zone is controlled at 1500℃.

[0070] S3 long crystal process: after the carbon source gas and the silicon source gas are mixed, they enter the growth zone and complete the growth of the silicon carbide substrate on the surface of the seed crystal after temperature and pressure rising, the growth temperature is 2100℃, and the growth pressure is 90kPa.

[0071] Example 3

[0072] Using the long crystal equipment provided in Example 1, a high-temperature gas phase chemical long crystal method assisted by metal catalyst for carbon source cracking is provided:

[0073] S1 preparation of metal catalyst:

[0074] Carrier pretreatment: immerse the high-purity high-temperature-resistant inert carrier (SiO2) in an 8% acid solution and ultrasonically clean for 30 min, remove the surface impurities, and then calcine at 1100℃ for 2h;

[0075] Active component loading: immerse the carrier with a nickel mesh structure in an ethanol solution containing a mixture of metal nitrate Fe(NO3)3 and H2Pt(NO3)6, the molar ratio of Fe(NO3)3 to H2Pt(NO3)6 is 6:4, and the impregnation penetration time is 20 min; after impregnation, centrifuge to remove excess solution, and dry at 60℃;

[0076] Catalytic structure forming: calcine at 290℃ for 2h in an air atmosphere; continue to reduce at 630℃ for 2h in H2 / N2 mixed gas; finally, pass O2 / Ar mixed gas to passivate the surface and form an oxide film.

[0077] S2 carbon source gas and silicon source gas cracking and mixing:

[0078] Carbon source gas cracking: the carbon source gas passes through an independent metal catalyst cracking zone and a filter structure; the temperature of the catalytic cracking zone is controlled at 600℃; the filter structure is a ceramic filter mesh structure with a pore density of 380cpsi, and the flow rate of the carbon source gas is 80sccm;

[0079] Silicon source gas cracking: the silicon source gas passes through an independent cracking zone, and the temperature is controlled at 600℃, and the flow rate of the silicon source gas is 80sccm;

[0080] Carbon source gas and silicon source gas mixing: the flow ratio of carbon source gas and silicon source gas is 1:1, and after passing through the respective independent cracking zone, they are mixed, and the temperature of the mixing zone is controlled at 1500℃.

[0081] S3 crystal growth process: after the carbon source gas and the silicon source gas are mixed and enter the growth zone, the silicon carbide substrate is grown on the surface of the seed crystal after temperature and pressure are increased, the growth temperature is 2200°C, and the growth pressure is 40 kPa.

[0082] Example 4

[0083] A high-temperature gas phase chemical crystal growth method for metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1.

[0084] S1 preparation of a metal catalyst:

[0085] Carrier pretreatment: immerse the high-purity high-temperature-resistant inert carrier (ZrO2) in a 10% acid solution and ultrasonically clean for 40 min, remove the surface impurities, and then calcine at 1200°C for 3 h;

[0086] Active component loading: immerse the honeycomb block structure carrier in an ethanol solution containing a mixture of metal nitrate Ni(NO3)2 and Fe(NO3)3, the molar ratio of the two metal elements Ni(NO3)2 and Fe(NO3)3 is 7:3, and the impregnation penetration is 10 min; after impregnation, centrifuge to remove excess solution, and dry at 70°C;

[0087] Catalytic structure forming: calcine at 300°C for 1 h in an air atmosphere; continue to reduce at 650°C for 1 h in H2 / N2 mixed gas; finally, pass O2 / Ar mixed gas to passivate the surface and form an oxide film.

[0088] S2 carbon source gas and silicon source gas cracking and mixing:

[0089] Carbon source gas cracking: the carbon source gas passes through an independent metal catalyst cracking zone and a filter structure; the temperature of the cracking zone is controlled at 650°C; the filter structure is a ceramic filter screen structure with a pore density of 400 cpsi, and the flow rate of the carbon source gas is 20 sccm;

[0090] Silicon source gas cracking: the silicon source gas passes through an independent cracking zone, and the temperature is controlled at 650°C, and the flow rate of the silicon source gas is 20 sccm;

[0091] Carbon source gas and silicon source gas mixing: the flow rate ratio of the carbon source gas and the silicon source gas is 1:1, and after passing through the respective independent cracking zones, they are mixed, and the temperature of the mixing zone is controlled at 1000°C.

[0092] S3 crystal growth process: after the carbon source gas and the silicon source gas are mixed and enter the growth zone, the silicon carbide substrate is grown on the surface of the seed crystal after temperature and pressure are increased, the growth temperature is 2200°C, and the growth pressure is 40 kPa.

[0093] Example 5

[0094] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the metal nitrate contained in the preparation process of the S1 metal catalyst is Ni(NO3)2.

[0095] Comparative Example 1

[0096] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the carrier pretreatment process is removed in the preparation process of the S1 metal catalyst.

[0097] Comparative Example 2

[0098] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the O2 / Ar mixed gas surface passivation process is removed in the preparation process of the S1 metal catalyst.

[0099] Comparative Example 3

[0100] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the carbon source gas is not provided with a filter structure in the cracking and mixing process of the carbon source gas and the silicon source gas.

[0101] Comparative Example 4

[0102] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the carbon source gas and the silicon source gas are not provided with separate cracking channels and are mixed for cracking in the cracking and mixing process of the carbon source gas and the silicon source gas.

[0103] Comparative Example 5

[0104] A high-temperature gas-phase chemical crystal growth method with metal catalyst-assisted carbon source cracking is provided by using the crystal growth equipment provided in Example 1, which is different from Example 2 in that the carbon source gas is not provided with a metal catalyst for cracking in the cracking and mixing process of the carbon source gas and the silicon source gas.

[0105] Characterization and testing:

[0106] The obtained silicon carbide crystals are detected for TSD (screw dislocation), TED (edge dislocation), and BPD (basal plane dislocation). The test results are shown in Table 1.

[0107] Table 1

[0108]

[0109] As can be seen from Table 1:

[0110] As can be seen from the above table, embodiments 2-4 of the present application reduce the carbon cracking temperature, improve the carbon cracking efficiency, make the carbon source and the silicon source gas crack simultaneously, reduce the energy consumption, and improve the crystal growth quality by setting a separate carbon source gas channel, a silicon source gas channel, and a metal catalyst and a filter structure in the carbon source gas channel.

[0111] Compared with example 1, example 5 uses a single metal catalyst, which has lower catalytic activity, resulting in insufficient and slow source gas cracking. When mixed with the fully cracked silicon source gas, the effective carbon-silicon ratio (C / Si) in the mixed gas is lower than the ideal stoichiometric ratio (1:1), which destroys the ordered growth of the crystal lattice and easily introduces defects and dislocations.

[0112] Compared with example 1, the catalyst carrier surface of comparative example 1 is not pretreated, and surface impurities exist on the catalyst carrier surface, which can cause uneven distribution of the subsequently loaded metal active components and weak binding force with the carrier, reduce the catalyst activity, and also cause the carbon source cracking efficiency to decrease, resulting in imbalance of the C / Si ratio and impurity pollution, and high dislocation density caused by the double factors.

[0113] Compared with example 1, comparative example 2 removes the O2 / Ar passivation process, and the metal particles of the catalyst are easily volatilized and agglomerated at high temperature, causing metal pollution and rapid deactivation of the catalyst, which eventually leads to an increase in the dislocation density of the crystal.

[0114] Compared with example 1, comparative example 3 does not set a filter structure in the carbon source gas channel, and the metal catalyst particles directly enter the growth zone, causing physical pollution and thus increasing the dislocation density of the crystal.

[0115] Compared with example 1, comparative example 4 does not set separate channels for cracking the silicon source gas and the carbon source gas, and the two gases are cracked together. The silicon source gas and the carbon source gas are mixed at a low temperature of 500-650℃, which may generate solid silicon carbide (SiC) particles that easily become defect nucleation centers, resulting in an increase in dislocations.

[0116] Compared with example 1, comparative example 5 does not set a metal catalyst for cracking the carbon source gas, and the carbon source cracking temperature is high and the efficiency is low, which cannot synchronize with the silicon source gas cracking, resulting in a serious imbalance of the C / Si ratio and easily producing defects during the crystal growth process.

[0117] The above describes the preferred embodiments of the present application in detail, but the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

[0118] It should be noted that various technical features described in the above detailed description are capable of being combined in any suitable manner, and that the application is not limited to the specific combinations described in the above detailed description, which are provided for illustrative purposes only.

[0119] Furthermore, the various embodiments of the application can also be combined with each other, as long as it does not violate the spirit of the application, it should also be considered as disclosed by the present application.

Claims

1. A high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst, wherein the crystal growth method comprises the following steps: S1. Preparation of metal catalysts: Carrier pretreatment: Immerse the high-purity, high-temperature resistant inert carrier in a 5-10% acid solution and ultrasonically clean for 20-40 minutes to remove surface impurities, then calcine at 1000-1200℃ for 1-3 hours. Active component loading: Immerse the carrier in an ethanol solution containing metal nitrates for 10-30 min; after immersion, centrifuge to remove excess solution and dry at 50-70℃; Catalytic structure forming: The support is calcined in air at 280-300℃ for 1-3 hours; then reduced in H2 / N2 mixed gas at 600-650℃ for 1-3 hours; finally, O2 / Ar mixed gas is introduced to passivate the surface and form an oxide film. S2, a mixture of carbon source gas and silicon source gas after pyrolysis: Carbon source gas cracking: The carbon source gas passes through an independent metal catalyst catalytic cracking zone and a filtration structure; the temperature of the catalytic cracking zone is controlled at 500-650℃; the flow rate of the carbon source gas is 20-200 sccm. Silicon source gas pyrolysis: Silicon source gas passes through an independent pyrolysis zone, with the temperature controlled at 500-650℃ and the flow rate of silicon source gas at 20-200 sccm. Mixing of carbon source gas and silicon source gas: The ratio of the number of carbon atoms to the number of silicon atoms in the carbon source gas and silicon source gas is 1:

1. After passing through their respective independent pyrolysis zones, they are mixed. The temperature of the mixing zone is controlled at 1000-1500℃. S3 crystal growth process: After the carbon source gas and silicon source gas are mixed and enter the growth region, the silicon carbide substrate is grown on the seed crystal surface after heating and pressurization; the growth temperature is 2100-2500℃ and the growth pressure is 10-90kPa.

2. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 1, characterized in that, In step S1, the high-temperature inert support material is selected from one of Al2O3, SiO2, and ZrO2.

3. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 1, characterized in that, In step S1, the structure of the high-temperature inert carrier can be one of the following: thin sheet, ring, foam ceramic, honeycomb block, porous sheet, or nickel mesh structure.

4. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 1, characterized in that, In step S1, the metal nitrate is selected from one or two of Ni(NO3)2, Co(NO3)2, Fe(NO3)3, and H2Pt(NO3)6.

5. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 1, characterized in that, In step S1, the metal nitrate is preferably a mixture of two metal nitrates, specifically a mixture of Ni(NO3)2 and Co(NO3)2, a mixture of Fe(NO3)3 and H2Pt(NO3)6, a mixture of Ni(NO3)2 and Fe(NO3)3, a mixture of Ni(NO3)2 and H2Pt(NO3)6, a mixture of Co(NO3)2 and Fe(NO3)3, or a mixture of Co(NO3)2 and H2Pt(NO3)6.

6. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 5, characterized in that, In step S1, the mixing ratio of the two metal-containing nitrates is the molar ratio of their metal elements, which is 5:5 to 7:

3.

7. The high-temperature vapor-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst according to claim 1, characterized in that, In step S2, during the carbon source gas cracking, the filtration structure is set as a ceramic filter structure, with a MgO-Al2O3 matrix coated with ZrO2 and a pore density of 350-400 cpsi.

8. A crystal growth apparatus for a high-temperature gas-phase chemical crystal growth method for carbon source pyrolysis assisted by a metal catalyst as described in claim 1, wherein the crystal growth apparatus comprises a heating device, a growth furnace chamber, a heat insulation layer, a growth crucible, a seed crystal pulling device, an air inlet channel, and an air inlet assembly; The heating device is located outside the growth furnace cavity, and the heating method of the heating device is coil heating; The growth furnace chamber includes a quartz tube, a growth furnace cover, and a sealing bottom cover, with the growth furnace cover and the sealing bottom cover respectively located at the upper and lower ends of the quartz tube; The growth crucible is a graphite crucible, which is axially positioned at the center of the inner side of the quartz tube, and the heat insulation layer is positioned in the pore between the outside of the growth crucible and the quartz tube. The seed crystal pulling device includes a seed crystal support and a seed crystal holder; the seed crystal support is inserted into the growth furnace cover, and the seed crystal holder is located at the end of the seed crystal support that extends into the growth furnace cavity; A through hole is opened at the center of the growth furnace cover. The seed crystal support passes through the through hole and is coaxially mounted at the center of the growth furnace cover. A seed crystal holder is fixedly connected to the lower end of the seed crystal support. Both the seed crystal support and the seed crystal holder are coaxially inserted into the inside of the growth crucible. The upper end of the seed crystal support is connected to a power structure. The power mechanism is used to rotate and lift the seed crystal and the seed crystal upward during the crystal growth process. The seed crystal is adhered to the bottom surface of the seed crystal holder. The air intake channel is located above the center of the sealed bottom cover; the air intake assembly is located inside the air intake channel, and the air intake assembly includes a silicon source gas intake channel, a carbon source gas intake channel, and multiple baffle structures spaced vertically along the gas flow direction on the inner wall of the air intake channel; the center of the sealed bottom cover has an opening that connects the carbon source gas intake channel and the silicon source gas intake channel, and also connects to an external gas source. The carbon source gas inlet channel is equipped with the metal catalyst described in step S1 of claim 1, and the outlet is equipped with a filter structure. The filter structure is preferably a ceramic filter structure with a MgO-Al2O3 matrix coated with ZrO2 and a pore density of 350-400 cpsi.

9. The crystal growth apparatus for a metal catalyst-assisted carbon source pyrolysis crystal growth method as described in claim 8, characterized in that, Preferably, the carbon source gas channel is eccentrically positioned at the inlet of the air intake channel, with a diameter of D3. The silicon source gas channel is positioned around the carbon source gas channel in the remaining space at the inlet of the air intake channel, with a diameter of D4, where D3 > D4. Preferably, the inner walls of the air intake channels above the carbon source and silicon source air intake channels are provided with multiple annular steps at intervals along the vertical direction of the gas flow. Baffle structures are provided on the annular steps. The vertical spacing between the upper and lower baffle structures is 15-20 mm, and the overlap distance between adjacent baffle structures is 3-5 mm.

10. The crystal growth apparatus for a metal catalyst-assisted carbon source cracking crystal growth method as described in claim 8, characterized in that, The air intake channel outlet has a tapered, gradually expanding structure from the bottom to the top; an annular step two is set at the air intake channel outlet, and a circular baffle is placed on the annular step two. The circular baffle has two through holes. The baffle is made of ceramic with a filter structure, MgO-Al2O3 matrix with ZrO2 coating, and a pore density of 350-400cpsi.

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