A device and method for liquid phase growth of silicon carbide crystals

Abstract

The present invention provides a device and method for liquid phase growth of silicon carbide crystals, belonging to the field of crystal growth technology, the device includes a crucible assembly, a seed crystal rod assembly, a heating assembly located outside the crucible assembly, and a heat preservation assembly wrapping the crucible assembly, the seed crystal rod assembly and the heating assembly; the crucible assembly includes a first crucible and a second crucible arranged in sequence from outside to inside; the first crucible is provided with a detachable crucible cover, and the crucible cover is provided with a fixing component for fixing the seed crystal rod assembly; the inner bottom surface of the first crucible is provided with a boss; the outer bottom of the second crucible is provided with a groove matching the shape of the boss, and the middle of the groove is provided with a pushing assembly for pushing, pulling and rotating the second crucible; the pushing assembly passes through the bottom of the first crucible, the heating assembly and the heat preservation assembly in sequence. The device provided by the present invention can ensure the temperature stability of the silicon carbide crystal growth process, while avoiding the problem of excessive jitter during the seed crystal pulling and rotation process.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal growth, and in particular to a device and method for growing silicon carbide crystals in liquid phase. Background Art

[0002] In recent years, SiC, as a typical third-generation semiconductor material, has developed rapidly. Due to its excellent physical properties such as large bandgap, high critical breakdown field strength, high saturated electron velocity, high thermal conductivity, and stable chemical properties, SiC material is considered to be an ideal material for preparing high-temperature, high-frequency, and high-power semiconductor devices. Due to the different stacking and circulation modes of Si-C diatomic layers, there are many crystal structures in SiC, such as 4H, 6H, 15R, and 3C. Compared with the most widely studied 4H- and 6H- SiC, 3C-SiC (cubic silicon carbide) has higher carrier mobility (2-4 times), lower interface defect state density (1 order of magnitude lower), and higher electron affinity (3.7 eV). The use of 3C-SiC crystals to prepare field-effect transistors can effectively solve problems such as poor device reliability caused by many gate oxide interface defects. However, the existing 3C-SiC crystal growth method mainly grows 3C-SiC crystals by pulling and rotating a seed rod. During the growth process, the seed rod is very likely to produce large vibrations when it rotates, resulting in defects such as large bubbles on the surface of the grown cubic silicon carbide crystal, affecting the quality of the cubic silicon carbide crystal. Summary of the invention

[0003] In response to one or more technical problems existing in the prior art, the present invention provides a device and method for liquid phase growth of silicon carbide crystals. The device provided by the present invention can ensure the temperature stability of the silicon carbide crystal growth process, while avoiding the problem of excessive vibration of the seed rod during the pulling and rotation process of the silicon carbide crystal growth process, thereby growing large-sized, high-quality cubic silicon carbide crystals.

[0004] In a first aspect, the present invention provides a device for liquid phase growth of silicon carbide crystals, the device comprising a crucible assembly, a seed crystal rod assembly, a heating assembly located outside the crucible assembly, and a heat preservation assembly wrapping the crucible assembly, the seed crystal rod assembly and the heating assembly;

[0005] The crucible assembly comprises a first crucible and a second crucible which are arranged in sequence from the outside to the inside;

[0006] The first crucible is provided with a detachable crucible cover, and the crucible cover is provided with a fixing portion for fixing the seed crystal rod assembly;

[0007] The inner bottom surface of the first crucible is provided with a boss;

[0008] The outer bottom of the second crucible is provided with a groove matching the boss, and the middle of the groove is provided with a pushing component for pushing, pulling and rotating the second crucible;

[0009] The pushing component sequentially passes through the bottom of the first crucible, the heating component and the heat-insulating component.

[0010] Preferably, the melting point of the first crucible is higher than the growth temperature of silicon carbide crystals and does not react with graphite;

[0011] The second crucible is a high purity graphite crucible; and / or

[0012] The heating component is made of graphite.

[0013] Preferably, the first crucible is made of one or more materials selected from the group consisting of metals and metal oxides.

[0014] Preferably, the device further comprises an induction coil arranged outside the heat preservation component.

[0015] Preferably, a plurality of temperature monitoring components are provided on the outer wall of the heating component.

[0016] Preferably, the device further comprises a fixed cover arranged outside the heat preservation component.

[0017] Preferably, the seed rod assembly is provided with threads, and the fixing portion is a threaded hole matching the threads.

[0018] In a second aspect, the present invention provides a method for growing cubic silicon carbide crystals in a liquid phase, which is implemented by the device described in the aspect, and the growth method comprises the following steps:

[0019] Putting a mixture of flux and silicon into a second crucible, and heating the second crucible by a heating component to melt the mixture to obtain a melt; the flux is an alloy containing rare earth metals, transition metals and carbon;

[0020] The melt is brought into contact with the silicon carbide seed crystal fixed on the seed crystal rod assembly by pushing the assembly, so that cubic silicon carbide crystals are grown to obtain cubic silicon carbide crystals.

[0021] Preferably, the growth temperature of the silicon carbide crystal is 1300-1400° C.; and / or

[0022] The molar ratio of the rare earth metal to the transition metal is not less than 7:3.

[0023] Preferably, during the growth of the cubic silicon carbide crystal, the second crucible rises or falls at a speed of 5 to 20 μm / h; and / or

[0024] During the growth of the cubic silicon carbide crystal, the second crucible rotates at a speed of 5-60 r / h.

[0025] Preferably, after the growth of the cubic silicon carbide crystal, the method further includes a step of removing residues on the surface of the cubic silicon carbide crystal by using a mixed acid and water; the mixed acid contains HNO3 and HF.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The device for growing silicon carbide crystals in liquid phase provided by the present invention adopts a double crucible design, and a pushing assembly is arranged at the bottom of the second crucible, which is used to push, pull and rotate the second crucible during the growth of silicon carbide crystals. During the growth of silicon carbide crystals, the second crucible is moved up by the pushing assembly to contact with the silicon carbide seed crystal to start crystal growth. At the same time, the boss on the inner bottom surface of the first crucible and the groove design on the outer bottom of the second crucible can limit the second crucible during the crystal growth process, avoiding shaking when pushing, pulling and rotating the second crucible to affect crystal growth, solving the problem that the existing seed crystal rod is prone to large shaking, causing defects such as large bubbles on the surface of the silicon carbide crystal, and affecting the quality of the silicon carbide crystal. In addition, the crucible with a cover design has a good heat preservation effect to provide a stable temperature for the growth of silicon carbide crystals, which can avoid the problem that the temperature at the seed crystal end of the open crucible design diffuses faster during the growth of silicon carbide crystals, the temperature gradient changes greatly, and it is difficult to maintain the temperature stability during the growth of silicon carbide crystals, thereby affecting the stability and growth quality of silicon carbide crystals. At the same time, the double crucible design can also effectively avoid the problem of the second crucible melting through and causing damage to the heating component, and realize the repeated reuse of the raw materials for the growth of silicon carbide crystals. The device provided by the present invention can ensure the temperature stability of the silicon carbide crystal growth process, while avoiding the problem of excessive vibration during the seed crystal pulling and rotation process, and grow large-sized, high-quality cubic silicon carbide crystals.

[0028] The present invention uses an alloy including rare earth metals, transition metals and carbon as a flux, which can reduce the melting temperature of the raw materials for preparing silicon carbide crystals, realize the growth of cubic silicon carbide crystals at low temperatures, and avoid the influence of excessive temperature on the stability and growth quality of cubic silicon carbide crystals; at the same time, it can increase the solubility of carbon in the melt, increase the carbon concentration in the melt in the early stage of cubic silicon carbide crystal growth, and increase the growth rate of cubic silicon carbide crystals. Under the premise of ensuring the growth quality of cubic silicon carbide crystals, the growth time of cubic silicon carbide crystals is shortened, and the growth efficiency of cubic silicon carbide crystals is improved. Compared with the use of traditional fluxes, the temperature of growing high-quality and large-sized silicon carbide crystals using the flux provided by the present invention is lower, the efficiency is higher (the growth time is shorter), and there is no other generation between the flux and silicon and carbon, which is beneficial to improving the quality of silicon carbide single crystals. In addition, during the growth process of cubic silicon carbide crystals, the rare earth metals and transition metals in the flux are not consumed, and can be continuously reused, which is beneficial to reducing the cost of crystal growth.

[0029] The cubic silicon carbide crystal growth method provided by the present invention has a simple process, low growth temperature and high growth efficiency, and can achieve lower temperature and more efficient growth of high-quality, large-sized cubic silicon carbide crystals, thereby overcoming the problems of the existing large-sized cubic silicon carbide crystal growth process, poor crystal stability, a long preparation process and low production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a schematic structural diagram of a device for liquid phase growth of silicon carbide crystals provided by the present invention;

[0032] Figure 2 It is a structural schematic diagram of a crucible assembly and a seed crystal rod assembly in a device for liquid phase growth of silicon carbide crystals provided by the present invention;

[0033] Figure 3 is a physical picture of the cubic silicon carbide crystal grown in Example 2 of the present invention;

[0034] Figure 4 is the Raman spectrum of the cubic silicon carbide crystal grown in Example 2 of the present invention;

[0035] Figure 5 is the rocking curve of the cubic silicon carbide crystal grown in Example 2 of the present invention;

[0036] Figure 6 Schematic diagram of the structure of the silicon carbide crystal growth device used in Comparative Example 1 of the present invention;

[0037] Figure 7 It is a schematic diagram of the second crucible melting through after the cubic silicon carbide crystal is grown in Comparative Example 1 of the present invention;

[0038] Figure 8 This is a physical picture of the cubic silicon carbide crystal grown in Comparative Example 1 of the present invention (with bubbles on the surface).

[0039] Reference numerals:

[0040] 1- Crucible assembly;

[0041] 11-first crucible; 111-crucible cover; 112-boss;

[0042] 12-second crucible; 121-groove; 122-pushing assembly;

[0043] 2-seed crystal rod assembly;

[0044] 21-seed crystal rod; 22-seed crystal holder;

[0045] 3-Heating components;

[0046] 31- Temperature monitoring component;

[0047] 4- Insulation components;

[0048] 5-Fixed hood;

[0049] 6- Induction coil. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0051] like Figure 1-2 As shown, the present invention provides, in a first aspect, a device for growing silicon carbide crystals in liquid phase, the device comprising a crucible assembly 1, a seed crystal rod assembly 2, a heating assembly 3 located outside the crucible assembly 1, and a heat preservation assembly 4 wrapping the crucible assembly 1, the seed crystal rod assembly 2 and the heating assembly 3;

[0052] The crucible assembly 1 includes a first crucible 11 and a second crucible 12 arranged in sequence from the outside to the inside;

[0053] The first crucible 11 is provided with a detachable crucible cover 111, and the crucible cover 111 is provided with a fixing component for fixing the seed rod assembly 2;

[0054] The inner bottom surface of the first crucible 11 is provided with a boss 112;

[0055] The outer bottom of the second crucible 12 is provided with a groove 121 matching the shape of the boss 112, and a pushing component 122 for pushing, pulling and rotating the second crucible 12 is provided in the middle of the groove 121;

[0056] The pushing component 122 sequentially passes through the bottom of the first crucible 11 , the heating component 3 , and the heat-insulating component 4 .

[0057] The device for growing silicon carbide crystals in liquid phase provided by the present invention adopts a double crucible design, and a pushing assembly is arranged at the bottom of the second crucible, which is used to push, pull and rotate the second crucible during the growth of silicon carbide crystals. During the growth of silicon carbide crystals, the second crucible is moved up by the pushing assembly to contact with the silicon carbide seed crystal to start crystal growth. At the same time, the boss on the inner bottom surface of the first crucible and the groove design on the outer bottom of the second crucible can limit the second crucible during the crystal growth process, avoiding shaking when pushing, pulling and rotating the second crucible to affect crystal growth, solving the problem that the existing seed crystal rod is prone to large shaking, causing defects such as large bubbles on the surface of the silicon carbide crystal, and affecting the quality of the silicon carbide crystal. In addition, the design of the crucible with a lid has a good heat preservation effect and provides a stable temperature for the growth of silicon carbide crystals, which can avoid the problem that the temperature at the seed crystal end of the open crucible design diffuses faster during the growth of silicon carbide crystals, the temperature gradient changes greatly, and it is difficult to maintain the temperature stability during the growth of silicon carbide crystals, thereby affecting the stability and growth quality of silicon carbide crystals. At the same time, the double crucible design can also effectively avoid the problem of the second crucible melting through and causing damage to the heating component, and realize the repeated reuse of the raw materials for the growth of silicon carbide crystals. The device provided by the present invention can ensure the temperature stability of the silicon carbide crystal growth process, while avoiding the problem of excessive vibration during the seed crystal pulling and rotation process, and grow large-sized, high-quality cubic silicon carbide crystals.

[0058] It should be noted that the push assembly of the present invention pushes, pulls and rotates the second crucible through an external drive device. The height of the boss and the depth of the groove are greater than the rising height of the second crucible during the growth of the silicon carbide crystal.

[0059] According to some preferred embodiments, the melting point of the first crucible 11 is higher than the growth temperature of cubic silicon carbide crystals and does not react with graphite; the material of the first crucible is a high-melting-point oxide or a metal crucible whose melting point is higher than the growth temperature of silicon carbide crystals and does not easily react with graphite at the growth temperature of silicon carbide crystals.

[0060] According to some preferred embodiments, the second crucible 12 is a high-purity graphite crucible. The second crucible is a high-purity graphite crucible with a purity of not less than 99.9999 wt %, which not only serves as a container for the growth raw materials of cubic silicon carbide crystals, but also provides a carbon source for the later growth of cubic silicon carbide crystals.

[0061] According to some preferred embodiments, the thickness of the second crucible 12 is 5-10 mm.

[0062] According to some preferred embodiments, the outer diameter of the first crucible 11 is the same as the inner diameter of the heating component 3 .

[0063] According to some preferred embodiments, the heating component 3 is made of graphite; the heating component is preferably a graphite heating tube.

[0064] According to some preferred embodiments, the first crucible 11 is made of one or more metals and metal oxides, preferably one or more of aluminum oxide, zirconium oxide, magnesium oxide, tantalum crucible, and niobium crucible. The first crucible is located between the second crucible and the heating component, which can prevent the second crucible from melting through and causing the melt to penetrate into the heating component (heating tube) and damage the heating component.

[0065] According to some preferred embodiments, the device further comprises an induction coil 6 disposed outside the heat preservation component. The graphite heating component (graphite heating tube) generates Joule heat under the frequency change of the induction coil, thereby providing the required stable heat source for the growth of cubic silicon carbide crystals.

[0066] According to some preferred embodiments, the outer wall of the heating component 3 is provided with a plurality of temperature monitoring components 31, and the temperature monitoring components 31 are preferably type B thermocouples. The present invention provides a plurality of temperature monitoring components on the outer wall of the heating component, preferably the plurality of temperature monitoring components are evenly arranged, to ensure accurate monitoring of the growth temperature of the cubic silicon carbide crystal.

[0067] According to some preferred embodiments, the thickness of the first crucible 11 is 5-20 mm.

[0068] According to some preferred embodiments, the device further comprises a fixed cover 5 arranged outside the heat preservation component. The heat preservation component of the present invention is a heat preservation felt, and the fixed cover is a quartz cover.

[0069] According to some preferred embodiments, the inner diameter of the fixed cover 5 is the same as the outer diameter of the thermal insulation component.

[0070] According to some preferred embodiments, the seed crystal rod assembly 2 is provided with threads, and the fixing portion is a threaded hole matching the threads, and preferably the fixing portion is arranged at the center of the crucible cover. The seed crystal rod assembly 2 of the present invention comprises a seed crystal rod 21 and a seed crystal holder 22, the silicon carbide seed crystal is fixed on the seed crystal holder 22, the crystal rod 21 is provided with threads, and a threaded hole (fixing portion) matching the threads on the seed crystal rod is arranged on the crucible cover for fixing the seed crystal rod assembly, so as to avoid the seed crystal rod assembly from shaking during the growth of the cubic silicon carbide crystal, which affects the growth quality and stability of the cubic silicon carbide crystal.

[0071] According to some preferred embodiments, the diameter of the threaded hole is 20-50 mm.

[0072] In a second aspect, the present invention provides a method for growing cubic silicon carbide crystals in a liquid phase, which is implemented by the device described in the aspect, and the growth method comprises the following steps:

[0073] Putting a mixture of flux and silicon into a second crucible, and heating the second crucible by a heating component to melt the mixture to obtain a melt; the flux is an alloy containing rare earth metals, transition metals and carbon;

[0074] The melt is brought into contact with the silicon carbide seed crystal fixed on the seed crystal rod assembly by pushing the assembly, so that cubic silicon carbide crystals are grown to obtain cubic silicon carbide crystals.

[0075] The present invention uses an alloy including rare earth metals, transition metals and carbon as a flux, which can reduce the melting temperature of the raw materials for preparing silicon carbide crystals, realize the growth of cubic silicon carbide crystals at low temperatures, and avoid the influence of excessive temperature on the stability and growth quality of cubic silicon carbide crystals; at the same time, it can increase the solubility of carbon in the melt, increase the carbon concentration in the melt in the early stage of cubic silicon carbide crystal growth, and increase the growth rate of cubic silicon carbide crystals. Under the premise of ensuring the growth quality of cubic silicon carbide crystals, the growth time of cubic silicon carbide crystals is shortened, and the growth efficiency of cubic silicon carbide crystals is improved. Compared with the use of traditional fluxes, the temperature of growing high-quality and large-sized silicon carbide crystals using the flux provided by the present invention is lower, the efficiency is higher (the growth time is shorter), and no other substances are generated between the flux and silicon and carbon, which is beneficial to improving the quality of silicon carbide single crystals. In addition, during the growth process of cubic silicon carbide crystals, the rare earth metals and transition metals in the flux are not consumed, and can be continuously reused, which is beneficial to reducing the cost of crystal growth.

[0076] The cubic silicon carbide crystal growth method provided by the present invention has a simple process, low growth temperature and high growth efficiency, and can achieve lower temperature and more efficient growth of high-quality, large-sized cubic silicon carbide crystals, thereby overcoming the problems of the existing large-sized cubic silicon carbide crystal growth process, poor crystal stability, a long preparation process and low production efficiency.

[0077] According to some preferred embodiments, the growth temperature of the silicon carbide crystal is 1300-1400°C (for example, it can be 1300°C, 1310°C, 1320°C, 1330°C, 1340°C, 1350°C, 1360°C, 1370°C, 1380°C, 1390°C or 1400°C); during the growth process of cubic silicon carbide crystals, the crystal stability is low, and the crystal transformation is prone to occur when the temperature is too high, affecting the quality and performance of the crystal. The above-mentioned flux used in the present invention can reduce the melting temperature of the raw materials for preparing cubic silicon carbide crystals (as low as 1300°C), thereby reducing the growth temperature of cubic silicon carbide crystals, achieving the growth of cubic silicon carbide crystals at lower temperatures, avoiding the influence of excessive temperature on the stability and growth quality of cubic silicon carbide crystals, and obtaining high-quality cubic silicon carbide crystals.

[0078] According to some preferred embodiments, the molar ratio of the rare earth metal to the transition metal is not less than 7:3.

[0079] The inventors of the present invention have found that when the molar ratio of the rare earth metal to the transition metal is ≥7:3, high-quality cubic silicon carbide crystals can be grown at 1300°C.

[0080] According to some preferred embodiments, the silicon carbide seed crystal is a silicon carbide wafer. The silicon carbide seed crystal of the present invention is one of a 3C-SiC wafer, a 4H-SiC wafer, and a 6H-SiC wafer; during the growth process, the Si face of the silicon carbide seed crystal, i.e., the (0001) face, serves as the growth face of the silicon carbide seed crystal.

[0081] According to some preferred embodiments, during the growth of the cubic silicon carbide crystal, the second crucible rises or falls at a speed of 5-20 μm / h (for example, 5 μm / h, 6 μm / h, 7 μm / h, 8 μm / h, 9 μm / h, 10 μm / h, 11 μm / h, 12 μm / h, 13 μm / h, 14 μm / h, 15 μm / h, 16 μm / h, 17 μm / h, 18 μm / h, 19 μm / h or 20 μm / h).

[0082] According to some preferred embodiments, during the growth of the cubic silicon carbide crystal, the second crucible rotates at a speed of 5 to 60 r / h (for example, 5 r / min, 10 r / min, 15 r / min, 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, 45 r / min, 50 r / min, 55 r / min or 60 r / min).

[0083] In the process of growing cubic silicon carbide crystals, the second crucible is rotated at a speed of 5-60 r / h and descended at a speed of 5-20 μm / h by pushing the assembly, so as to ensure smooth growth of the cubic silicon carbide crystals.

[0084] According to some preferred embodiments, the rare earth metal is a lanthanide metal, preferably one or more of La, Ce, and Pr. The types of rare earth metals of the present invention include but are not limited to the above types.

[0085] According to some preferred embodiments, the transition metal is at least one of Ni and Co.

[0086] According to some preferred embodiments, the method for preparing the flux includes: mixing rare earth metals, transition metals and carbon, and performing arc melting to obtain the flux; it should be noted that the arc melting uses a water-cooled copper crucible as an electrode and a tungsten needle as an electrode, and during the arc melting process, a mixture of rare earth metals, transition metals and carbon blocks is placed in a water-cooled copper crucible, and the arc melting process is carried out under an inert gas protective atmosphere.

[0087] In some specific embodiments of the present invention, the method for preparing the flux comprises: RE )、Transition metals( M ) and carbon mixture is placed in a water-cooled copper crucible, the water-cooled copper crucible is used as an electrode, a tungsten needle is used as an electrode, and alloying melting is performed by arc melting in an inert gas atmosphere to obtain the flux ( RE - M -C), wherein the ratio of the total molar number of rare earth metals and transition metals to the molar number of carbon is 2:3; the molar ratio of rare earth metals to transition metals is not less than 7:3; the purity of rare earth metals, transition metals and carbon are all ≥99.9 wt%; and the arc melting method is used to prepare the flux, and the melting needs to be repeated several times to ensure uniform mixing.

[0088] According to some preferred embodiments, after the growth of the cubic silicon carbide crystal, the process further includes a step of removing residues on the surface of the cubic silicon carbide crystal using a mixed acid and water; the mixed acid contains HNO3 and HF.

[0089] After growing the silicon carbide crystal, the present invention first treats it with a mixed acid solution containing HNO3 and HF (the volume ratio of HNO3 and HF is 2:1) to remove small droplets (residues) on the surface of the crystal, and then rinses it with clean water to clean the acid solution on the surface to obtain a high-purity cubic silicon carbide crystal.

[0090] In some specific embodiments of the present invention, the method for growing cubic silicon carbide crystals comprises the following steps: (1) in a protective atmosphere, placing a mixture of flux and silicon (with a purity of not less than 99.9999 wt%) into a high-purity dense graphite crucible (a second crucible) and compacting the mixture to keep the surface flat, and evacuating the mixture until the vacuum reaches 10 -4 Pa ~10 -3 When the temperature is 0.0400 Pa, the heating component is heated by the induction coil to heat the second crucible to melt the mixture and obtain a melt; wherein the heating temperature is 1300-1400°C. (2) The melt is brought into contact with the silicon carbide seed crystal fixed on the seed crystal rod component by pushing the component to grow a cubic silicon carbide crystal, thereby obtaining a cubic silicon carbide crystal; the second crucible is pushed upward by the pushing component to bring the melt into contact with the silicon carbide seed crystal fixed on the seed crystal rod component to start the growth of the cubic silicon carbide crystal. During the growth of the cubic silicon carbide crystal, the second crucible is rotated at a speed of 5-60 r / h and descended at a speed of 5-20 μm / h by pushing the component; (3) After the growth is completed, the cubic silicon carbide crystal is quickly removed from the solution, first treated with a mixed acid solution containing HNO3 and HF (the volume ratio of HNO3 and HF is 2:1), and then rinsed with clean water to obtain a cubic silicon carbide crystal.

[0091] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and the reagents can be directly purchased or synthesized by themselves.

[0092] The testing method for the performance data of the cubic silicon carbide crystals grown in the embodiments of the present invention and the comparative examples is as follows:

[0093] Crystal size and quality measurement: Place the processed crystal on standard coordinate paper or standard caliper to confirm the size; Use laser confocal Raman scattering to measure the crystal form; Use XRD diffractometer to measure the rocking curve of the crystal to determine its crystalline quality.

[0094] Example 1

[0095] like Figure 1-2 As shown, a device for liquid phase growth of silicon carbide crystals, comprising:

[0096] A crucible assembly 1, a seed crystal rod assembly 2, a heating assembly 3 located outside the crucible assembly 1, a heat preservation assembly 4 wrapping the crucible assembly 1, the seed crystal rod assembly 2 and the heating assembly 3, and a fixed cover 5 and an induction coil 6 arranged outside the heat preservation assembly 4;

[0097] The crucible assembly 1 includes a first crucible 11 and a second crucible 12 arranged in sequence from the outside to the inside; wherein the first crucible 11 is an alumina crucible, and the second crucible 12 is a high-purity graphite crucible (purity not less than 99.9999 wt%)); a boss 112 is provided on the inner bottom surface of the first crucible 11; a groove 121 matching the shape of the boss 112 is provided on the outer bottom of the second crucible 12, and a pushing component 122 for pushing, pulling and rotating the second crucible is provided in the middle of the groove 121; the pushing component 122 passes through the bottom of the first crucible 11, the heating component 3 and the insulation component 4 in sequence; wherein the heating component 3 is a graphite heating tube, the insulation component 4 is a graphite insulation hard felt, and the fixed cover 5 is a quartz cover; the seed crystal rod assembly 2 includes a seed crystal rod 21 and a seed crystal holder 22, and the seed crystal rod 21 is provided with a thread; the first crucible 11 is provided with a detachable crucible cover 112, and the crucible cover 112 is provided with a fixing part for fixing the seed crystal rod assembly 2, and the fixing part is a threaded hole matching the thread on the seed crystal rod 21; the outer wall of the heating component 3 is provided with a plurality of temperature monitoring components 31, and the temperature monitoring components 31 are thermocouples.

[0098] Example 2

[0099] A method for liquid phase growth of cubic silicon carbide crystals is implemented by the device for liquid phase growth of silicon carbide crystals of embodiment 1, comprising:

[0100] (1) Place the mixture of flux and silicon chunks into the second crucible and compact it to make the surface flat. Evacuate the crucible until the vacuum reaches 10 -4 When Pa, the induction coil starts to heat (the heating temperature is 1300℃) to melt the mixture to obtain a melt; wherein, the preparation method of the flux includes: under the protection of argon gas, rare earth metal (La), transition metal (Ni) and carbon are mixed in a molar ratio of 7:3:15 and put into a water-cooled copper base crucible, and arc melting is carried out in an arc furnace with a water-cooled copper base crucible as an electrode and a tungsten probe as an electrode to obtain a flux (La-Ni-C alloy).

[0101] (2) In a protective atmosphere, place a mixture of flux and silicon (purity not less than 99.9999 wt%) into a high-purity dense graphite crucible (the second crucible) and compact it to keep the surface flat. Evacuate the crucible until the vacuum reaches 10 -4 When the pressure is 0.04 Pa, the heating component is heated by the induction coil to heat the crucible to melt the mixture and obtain a melt; wherein the heating temperature is 1300°C.

[0102] (3) While keeping the temperature constant, a driving device is used to drive the pushing assembly to move the crucible upward, so that the melt contacts the silicon carbide seed crystal and the growth of the cubic silicon carbide crystal begins. The growth temperature of the cubic silicon carbide crystal is 1300°C. During the growth of the cubic silicon carbide crystal, the crucible rotates at a speed of 60 r / h and descends at a speed of 10 μm / h. After the growth is completed, the cubic silicon carbide crystal is pulled out of the solution, and the heating power is reduced to 0. The solution is cooled to room temperature and the furnace is opened to obtain a cubic silicon carbide crystal.

[0103] The 4-inch large cubic silicon carbide crystal (3C-SiC single crystal) grown in this embodiment is as follows Figure 3 As shown in the figure, it can be observed that the crystal surface is flat and there are no macro defects such as bubbles. It should be noted that SiC crystal growth is a step flow growth, and the lines on the crystal surface are the growth steps of the SiC crystal. The small amount of white spots on the crystal surface are residual flux. The obtained SiC crystal is first treated with a mixed acid solution of HNO3 and HF to remove the flux on the crystal surface, and then rinsed with clean water several times to clean the surface acid, and finally rinsed with alcohol several times to obtain high-purity cubic silicon carbide crystals.

[0104] The Raman spectrum of the crystal (such as Figure 4 ) It can be seen that the Raman peak shift is 796 cm -1 It shows that the crystal form is 3C crystal form. It should be noted that the Raman spectrum ( Figure 4 ) represents the Raman shift, and the ordinate represents the Raman peak intensity.

[0105] The rocking curve of the crystal (such as Figure 5 ) shows that the half-height width is 32.4 arcsec, indicating that the crystal is of high quality. It should be noted that the rocking curve ( Figure 5 ) represents the angle on the horizontal axis and the intensity on the vertical axis.

[0106] It should be noted that the present invention has been verified through experiments that when the flux is La-Co-C, La-Co-Ni-C, Ce-Ni-C, Ce-Co-C, Ce-Ni-Co-C, Pr-Ni-C, Pr-Co-Ni-C and Pr-Co-C, large-sized, high-quality cubic silicon carbide crystals with a size and quality close to those of Example 1 can also be grown, which are not listed one by one here.

[0107] Comparative Example 1

[0108] It is basically the same as Example 2, except that: Figure 6The silicon carbide crystal growth device shown is implemented, and the silicon carbide crystal growth device includes: a crucible assembly 1, a seed crystal rod assembly 2, a heating assembly 3, a heat preservation assembly 4, a fixed cover 5 and an induction coil 6. Among them, the crucible assembly 1 is a high-purity graphite crucible with a purity of not less than 99.9999 wt%, which is used as a container for holding the raw materials for the growth of cubic silicon carbide crystals and provides a carbon source for the later growth of cubic silicon carbide crystals. The seed crystal rod assembly 2 is used to fix the silicon carbide seed crystal, and during the growth of the silicon carbide crystal, the seed crystal rod assembly 2 is driven by a driving device to pull and rotate to achieve the growth of the crystal. The heating assembly 3 is a graphite heating cylinder, the heat preservation assembly 4 is a graphite heat preservation hard felt, and the fixed cover 5 is a quartz cover. The heating assembly 3 (graphite heating cylinder) generates Joule heat under the frequency change of the induction coil 6, providing the required stable heat source for the growth of cubic silicon carbide crystals.

[0109] The silicon carbide crystal growth device used in Comparative Example 1 only includes a graphite crucible (the second crucible). After a long period of crystal growth, the surface of the high-temperature solution inside the graphite crucible is melted through by the graphite crucible wall due to the consumption of carbon (e.g. Figure 7 As shown in the figure, the risk of damaging the heating tube is reduced, which increases the service life of the heating tube. The crucible cover of the silicon carbide crystal growth device used in Example 1 adopts an open design, which makes the temperature diffusion at the seed crystal end faster and the temperature gradient changes greatly, seriously affecting the growth quality of the crystal. Example 1 adopts a process design of seed crystal rotation and pulling. Under high-speed rotation and pulling, it is easy to produce large crystal jitter, which in turn causes large bubbles and other defects on the crystal surface (such as Figure 8 seriously affects the crystal quality.

[0110] Comparative Example 2

[0111] It is basically the same as Example 2, except that no carbon is added during the preparation of the flux, that is, the flux is La-Ni alloy.

[0112] The flux is an alloy containing only La and Ni. During the crystal growth process, it takes a long time to dissolve a large amount of carbon in the melt. The insufficient carbon concentration in the early stage leads to low crystal quality. The inventors also found that the situation is similar when using La-Co alloy, Ce-Ni alloy, Ce-Co alloy, Pr-Ni alloy, Pr-Co alloy and other flux systems, which are not listed here one by one.

[0113] Comparative Example 3

[0114] It is basically the same as Example 2, except that the flux is Ce-Cr-Si alloy, wherein the molar ratio of Ce, Cr and Si is 7:3:15.

[0115] Comparative Example 4

[0116] It is basically the same as Example 2, and the only difference is that the flux is a Cr-Si alloy, wherein the molar ratio of Cr to Si is 2:3.

[0117] Comparative Example 5

[0118] It is basically the same as Example 2, and the only difference is that the flux is a Ti-Si alloy, wherein the molar ratio of Ti to Si is 2:3.

[0119] The inventors found that the growth temperature of cubic silicon carbide crystal (3C-SiC crystal) using the flux system of Comparative Examples 3-5 is as high as over 1600°C, and cubic silicon carbide crystal (3C-SiC crystal) cannot be grown at 1300°C.

[0120] Comparative Example 6

[0121] It is basically the same as Example 2, except that the flux is a La-Fe-C alloy, wherein the molar ratio of La, Fe and C is 7:3:15).

[0122] Comparative Example 7

[0123] It is basically the same as Example 2, except that the flux is La-Cr-C alloy, wherein the molar ratio of La, Cr and C is 7:3:15.

[0124] The inventors found that the growth temperature of cubic silicon carbide crystal (3C-SiC crystal) using the flux system of Comparative Examples 6-7 is as high as over 1600°C, and cubic silicon carbide crystal (3C-SiC crystal) cannot be grown at 1300°C.

[0125] Comparative Example 8

[0126] The method is basically the same as Example 2, except that: in step (1), the flux does not contain carbon, that is, the flux is La-Ni alloy;

[0127] In step (2), the La-Ni alloy, carbon powder and excess silicon obtained in step (1) are placed in a high-purity graphite crucible (purity ≥ 99.9999 wt%), and argon is used as a protective gas. The mixture is heated to a molten state at 1300° C. and then kept warm for 2 h to obtain a melt.

[0128] The inventors found that when carbon powder was added during the preparation of the melt, the carbon powder was not easily dissolved in the melt, and the concentration of carbon in the silicon melt in the early stage of crystal growth was not significantly increased (not much different from Comparative Example 2), and the quality of the obtained crystals was low.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for growing cubic silicon carbide crystals in liquid phase, characterized in that: The method comprises the following steps: Putting a mixture of flux and silicon into a second crucible, heating the second crucible by a heating component to melt the mixture to obtain a melt; the flux is an alloy containing rare earth metal, transition metal and carbon; the rare earth metal is one or more of La, Ce and Pr; the transition metal is at least one of Ni and Co; the molar ratio of the rare earth metal to the transition metal is not less than 7:3; The melt is brought into contact with the silicon carbide seed crystal fixed on the seed crystal rod assembly by pushing the assembly to grow a cubic silicon carbide crystal to obtain a cubic silicon carbide crystal; the growth temperature of the cubic silicon carbide crystal is 1300-1400° C.; The method is implemented by a device for growing silicon carbide crystals in liquid phase, the device comprising a crucible assembly, a seed crystal rod assembly, a heating assembly located outside the crucible assembly, and a heat preservation assembly wrapping the crucible assembly, the seed crystal rod assembly and the heating assembly; The crucible assembly comprises a first crucible and a second crucible which are arranged in sequence from the outside to the inside; The first crucible is provided with a detachable crucible cover, and the crucible cover is provided with a fixing portion for fixing the seed crystal rod assembly; The inner bottom surface of the first crucible is provided with a boss; The outer bottom of the second crucible is provided with a groove matching the boss, and the middle of the groove is provided with a pushing component for pushing, pulling and rotating the second crucible; The pushing component sequentially passes through the bottom of the first crucible, the heating component and the heat-insulating component.

2. The method according to claim 1, characterized in that The melting point of the first crucible is higher than the growth temperature of the silicon carbide crystal and does not react with graphite; The second crucible is a high purity graphite crucible; and / or The heating component is made of graphite.

3. The method according to claim 2, characterized in that The first crucible is made of one or more materials selected from metals and metal oxides.

4. The method according to claim 2, characterized in that: The device further comprises an induction coil arranged outside the heat preservation component; and / or The outer wall of the heating component is provided with a plurality of temperature monitoring components.

5. The method according to claim 1, characterized in that The device also includes a fixed cover arranged outside the heat preservation component.

6. The method according to claim 5, characterized in that The seed crystal rod assembly is provided with threads, and the fixing portion is a threaded hole matching the threads.

7. The method according to claim 1, characterized in that During the growth of the cubic silicon carbide crystal, the second crucible rises or falls at a speed of 5 to 20 μm / h; and / or During the growth of the cubic silicon carbide crystal, the second crucible rotates at a speed of 5 to 60 r / h.

8. The method according to claim 1, characterized in that After the cubic silicon carbide crystal is grown, the method further includes a step of removing residues on the surface of the cubic silicon carbide crystal by using a mixed acid and water; the mixed acid contains HNO3 and HF.

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