Silicon carbide single crystal growth device and silicon carbide single crystal growth method

Abstract

The invention discloses a silicon carbide single crystal growth apparatus and a silicon carbide single crystal growth method. The silicon carbide single crystal growth device comprises a growth system, the growth system comprises a graphite crucible, a seed crystal support and a crucible support, the crucible support is arranged on the lower side of the graphite crucible, the graphite crucible is used for containing a growth solution, and the seed crystal support is arranged above the growth solution; wherein one side, close to the growth solution, of the seed crystal support is provided with at least one seed crystal bonding area, the seed crystal bonding area is used for bonding off-axis seed crystals, and the center of the seed crystal bonding area does not coincide with the center of the seed crystal support. The off-axis seed crystal is eccentrically arranged on the seed crystal support, so that the step flow direction of single crystal growth can be effectively controlled to be opposite to the solution convection direction, complete reverse step growth of the solution in the single flow direction in the seed crystal range is realized, the crystal quality can be effectively improved, and the growth efficiency is improved. Meanwhile, the off-axis seed crystal is adopted, so that the cost is greatly reduced.

Description

Technical Field

[0001] This application belongs to the technical field of growing silicon carbide single crystals by the solution method, and particularly relates to a silicon carbide single crystal growth device and a silicon carbide single crystal growth method. Background Art

[0002] Growing silicon carbide (SiC) single crystals by the solution method is regarded as a potential direction to reduce the cost of silicon carbide because of its advantages such as high quality, easy diameter expansion, stable P-type doping, and observable crystal growth process. However, the industry still faces problems such as high cost, low efficiency, and poor crystallization quality in growing silicon carbide single crystals by the solution method. Summary of the Invention

[0003] This application aims to solve at least one of the technical problems in the related art to some extent. For this purpose, the purpose of this application is to provide a silicon carbide single crystal growth device and a silicon carbide single crystal growth method.

[0004] In one aspect of this application, a silicon carbide single crystal growth device is provided. According to an embodiment of this application, the silicon carbide single crystal growth device includes:

[0005] A growth system, the growth system includes a graphite crucible, a seed crystal holder, and a crucible holder. The crucible holder is arranged on the lower side of the graphite crucible. The graphite crucible is used to contain a growth solution, and the seed crystal holder is arranged above the growth solution;

[0006] Wherein, at least one seed crystal bonding area is arranged on one side of the seed crystal holder close to the growth solution. The seed crystal bonding area is used to bond an off-axis seed crystal, and the center of the seed crystal bonding area does not coincide with the center of the seed crystal holder.

[0007] According to the silicon carbide single crystal growth device of the embodiment of this application, by setting the center of the seed crystal bonding area not to coincide with the center of the seed crystal holder, that is, the off-axis seed crystal is eccentrically arranged on the seed crystal holder, the direction of the step flow during single crystal growth can be effectively controlled to be opposite to the direction of solution convection, realizing a completely inverse step growth with a single flow direction of the solution within the range of the seed crystal. The growth interface of the single crystal is continuously scoured by the solution, suppressing the bunching of growth steps, suppressing macroscopic steps, and reducing the inclusion of flux, thereby effectively improving the crystal quality and growth efficiency. At the same time, this application uses an off-axis seed crystal, which significantly reduces the cost compared with the situation of widely using on-axis seed crystals (generally semi-insulating substrates, which are expensive) in the industry; and the silicon carbide single crystal ingot grown by the solution method is further processed into an off-axis seed crystal, which can greatly increase the effective thickness of the crystal and improve the wafer yield.

[0008] In addition, the silicon carbide single crystal growth device according to the above embodiment of this application may further have the following additional technical features:

[0009] In some embodiments of the present application, the center of the seed crystal holder is located outside the seed crystal bonding area.

[0010] In some embodiments of the present application, the edge of the seed crystal bonding area is in contact with the edge of the seed crystal holder.

[0011] In some embodiments of the present application, the seed crystal holder is circular, the seed crystal bonding area is circular, and the edge of the seed crystal bonding area is internally tangent to the edge of the seed crystal holder.

[0012] In some embodiments of the present application, the minimum distance h between the edge of the seed crystal bonding area and the center of the seed crystal holder is greater than 20 mm.

[0013] In some embodiments of the present application, the off-axis angle of the off-axis seed crystal ranges from 0° to 8°, and is not equal to 0°; and / or, the thickness of the off-axis seed crystal is 350 μm to 1000 μm; and / or, the seed crystal bonding area is a seed crystal bonding step, and the height of the seed crystal bonding step is 0.5 mm to 2 mm.

[0014] In some embodiments of the present application, on the side of the seed crystal holder close to the growth solution, a coating is provided in the area except the seed crystal bonding area, and the coating includes at least one of silicon carbide, tantalum carbide, and tungsten carbide.

[0015] In some embodiments of the present application, a hollow chamber is provided in the crucible holder, and a graphite felt is provided in the hollow chamber.

[0016] In some embodiments of the present application, it further includes: a heating system, the heating system includes an induction heating unit and a resistance heating unit; a heat preservation system, the heat preservation system includes an upper heat preservation felt, a lower heat preservation felt, a heat preservation barrel, and a heating cylinder, the upper heat preservation felt is provided above the heat preservation barrel, the lower heat preservation felt is provided below the heat preservation barrel, and the upper heat preservation felt, the lower heat preservation felt, and the heat preservation barrel enclose a closed space, the growth system is provided in the closed space, the heating cylinder is provided on the side of the heat preservation barrel close to the growth system; the induction heating unit is provided outside the heat preservation barrel; a rotation and lifting system, the rotation and lifting system includes an upper transmission mechanism, a seed crystal shaft, a lower transmission mechanism, and a lower graphite shaft, the lower end of the seed crystal shaft is provided on the side of the seed crystal holder away from the growth solution, and the upper end of the seed crystal shaft passes through the upper heat preservation felt and is connected to the upper transmission mechanism, the seed crystal holder is provided above the growth solution through the seed crystal shaft; the upper part of the lower graphite shaft is connected to the crucible holder, and the lower part of the lower graphite shaft is connected to the lower transmission mechanism; the resistance heating unit is provided between the crucible holder and the lower heat preservation felt, and is provided on the lower graphite shaft.

[0017] In the second aspect of the present application, a method for single crystal growth using the silicon carbide single crystal growth apparatus described in the above embodiments is proposed. According to an embodiment of the present application, the method includes:

[0018] Bond an off-axis seed crystal to the seed crystal bonding area;

[0019] Place the raw material of the growth solution in a graphite crucible, evacuate the air, and heat the raw material to a solution state to form a growth solution;

[0020] Lower the seed crystal holder until the off-axis seed crystal on the seed crystal holder contacts the surface of the growth solution, and rotate to perform non-axisymmetric crystal growth;

[0021] After crystal growth is completed, separate the crystal from the growth solution and enter the cooling section. After cooling to room temperature, open the furnace to take out the crystal.

[0022] According to the method for single crystal growth using the above-mentioned silicon carbide single crystal growth apparatus according to an embodiment of the present application, since the center of the seed crystal bonding area does not coincide with the center of the seed crystal holder, that is, the off-axis seed crystal is eccentrically arranged on the seed crystal holder, the direction of the step flow during single crystal growth can be effectively controlled to be opposite to the direction of solution convection, realizing a completely reverse step growth in which the solution maintains a single flow direction within the range of the seed crystal, so that the growth interface of the single crystal is continuously scoured by the solution, suppressing the bunching of growth steps, suppressing macroscopic steps, reducing the inclusion of flux, thereby effectively improving the crystal quality and growth efficiency. At the same time, this method uses an off-axis seed crystal, which significantly reduces the cost compared with the situation where a large number of on-axis seed crystals (generally semi-insulating substrates, which are expensive) are used in the industry; and the silicon carbide single crystal ingot grown by the solution method is further processed into an off-axis seed crystal, which can greatly increase the effective thickness of the crystal and improve the wafer yield.

[0023] Additional aspects and advantages of the present application will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0025] Figure 1 is a schematic structural diagram of a silicon carbide single crystal growth apparatus according to an embodiment of the present application;

[0026] Figure 2 is a schematic structural diagram of a crucible holder according to some embodiments of the present application;

[0027] Figure 3 is a top view of a crucible holder according to some embodiments of the present application;

[0028] Figure 4Top view of the crucible support for some other embodiments of the present application;

[0029] Figure 5 Top view of the crucible support for some other embodiments of the present application;

[0030] Figure 6 Top view of the crucible support for some other embodiments of the present application;

[0031] Figure 7 Top view of the crucible support of Comparative Example 1;

[0032] Figure 8 Schematic diagram of the solution flow direction after the seed crystal is offset in the embodiment of the present application;

[0033] Figure 9 Schematic diagram of the solution flow direction in the conventional central layout of the seed crystal in the prior art;

[0034] Figure 10 Crystal diagram of non-axisymmetric growth with the seed crystal offset layout in Example 1;

[0035] Figure 11 Optical microscope image of the central region of the crystal of non-axisymmetric growth with the seed crystal offset layout in Example 1;

[0036] Figure 12 XRD rocking curve diagram of the crystal of non-axisymmetric growth with the seed crystal offset layout in Example 1;

[0037] Figure 13 Crystal diagram of symmetric growth with the conventional seed crystal layout in Comparative Example 1;

[0038] Figure 14 Optical microscope image of the central region of the crystal of symmetric growth with the conventional seed crystal layout in Comparative Example 1 of Comparative Example 1;

[0039] Figure 15 XRD rocking curve diagram of the crystal of symmetric growth with the conventional seed crystal layout in Comparative Example 1 of Comparative Example 1.

[0040] Reference numerals:

[0041] 1 - Seed crystal axis, 2 - Seed crystal support, 2-1 - Seed crystal bonding area, 2-2 - Off-axis seed crystal, 3 - Graphite crucible, 4 - Growth solution, 5 - Crucible support, 6 - Resistance heating unit, 7 - Lower heat insulation felt, 8 - Upper heat insulation felt, 9 - Heat insulation barrel, 10 - Induction heating unit, 11 - Heating cylinder, 12 - Hollow chamber, 13 - Lower graphite shaft. Detailed implementation manners

[0042] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals designate like or similar elements or elements having like or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and should not be construed as limiting the present application.

[0043] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.

[0044] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0045] In the present application, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "connected to", "fixed" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0046] In the present application, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature has a lower horizontal height than the second feature.

[0047] The prior art still faces the problems of high cost, low efficiency, and poor crystallization quality in growing silicon carbide single crystals by the solution method. Through research, the inventors found that a large part of the reason is that the seed crystal is arranged at the center of the thermal field in an axisymmetric manner. Based on the existing thermal field process, reverse step growth cannot be fully achieved, and the solution cannot flow in a single direction within the range of the seed crystal, resulting in problems such as step bunching, flux inclusion, and macroscopic defects that affect crystal quality, and ultimately the obtained crystal has poor crystallization quality. At the same time, the practice of using ortho-axis seed crystals in the solution method for growing silicon carbide single crystals in the prior art also greatly increases the cost because the price of ortho-axis semi-insulating seed crystals is much higher than that of off-axis seed crystals.

[0048] Specifically, the conventional seed crystal bonding method is to bond the seed crystal to the center of a circular seed crystal holder (refer to the appendix Figure 7 ). Since the thermal field is axisymmetrically distributed, the entire seed crystal growth interface is at the exact center of the thermal field and is regarded as axisymmetric growth. The inventors found that the drawback of axisymmetric growth is that the solution cannot completely flow in a single direction within the range of the seed crystal growth interface (refer to the appendix Figure 9 ), that is, the solution flow direction is the same as or opposite to the step flow growth direction in some areas, which will cause problems such as flux inclusion and poor crystallization quality. Especially in the case of using an off-axis seed crystal, due to the existence of the seed crystal offset angle, the growth steps bunch together, the surface roughness of the growth surface is greatly increased, it is easy to wrap the flux into the crystal interior, and the single flow direction of the solution in the seed crystal growth area cannot be fully achieved, and it is impossible to reverse-scour the growth steps or the relatively rough growth surface in a timely manner, resulting in difficulty in suppressing the generation of flux inclusion, and macroscopic defects such as solution wrapping and grooves appear on the surface of the grown crystal, leading to the direct scrapping of the crystal. Therefore, the industry mainly uses ortho-axis seed crystals as the seed crystals for growing silicon carbide single crystals by the solution method in order to obtain high-quality crystals, but the improvement effect is limited, and at the same time, the cost is greatly increased. Therefore, the present application proposes a solution method silicon carbide single crystal growth device with a seed crystal offset (eccentric arrangement) and a method for growing single crystals by the off-axis seed crystal non-axisymmetric solution method, which can well solve this problem.

[0049] In view of this, in one aspect of the present application, the present application proposes a silicon carbide single crystal growth device. According to an embodiment of the present application, refer to the appendix Figure 1 , the above-mentioned silicon carbide single crystal growth device includes: a growth system, the growth system includes a graphite crucible 3, a seed crystal holder 2, and a crucible holder 5. The crucible holder 5 is arranged on the lower side of the graphite crucible 3. The graphite crucible 3 is used to hold the growth solution 4, and the seed crystal holder 2 is arranged above the growth solution 4; wherein, at least one seed crystal bonding area 2-1 is arranged on the side of the seed crystal holder 2 close to the growth solution 4. The seed crystal bonding area 2-1 is used to bond the off-axis seed crystal 2-2, and the center of the seed crystal bonding area 2-1 does not coincide with the center of the seed crystal holder 2.

[0050] The beneficial effects that can be achieved by the silicon carbide single crystal growth device proposed in this application will be described in detail below:

[0051] In this application, by setting the center of the seed crystal bonding area 2-1 not to coincide with the center of the seed crystal holder 2, that is, the off-axis seed crystal 2-2 is eccentrically arranged on the seed crystal holder 2, the direction of the step flow during single crystal growth can be effectively controlled to be opposite to the direction of solution convection, realizing a completely reverse step growth with a single flow direction of the solution within the range of the seed crystal (refer to the appendix Figure 8 ), so that the growth interface of the single crystal is continuously scoured by the solution, inhibiting the bunching of growth steps, suppressing macroscopic steps, and reducing the inclusion of flux, thereby effectively improving the crystal quality and growth efficiency. At the same time, in this application, the off-axis seed crystal 2-2 is adopted, which greatly reduces the cost compared with the situation of widely using on-axis seed crystals (generally semi-insulating substrates, which are relatively expensive) in the industry; and the silicon carbide single crystal ingot grown by the solution method is further processed into the off-axis seed crystal 2-2, which can greatly increase the effective thickness of the crystal and improve the wafer yield.

[0052] It should be noted that the seed crystal holder 2 is arranged in the central area of the growth device. When the off-axis seed crystal 2-2 is eccentrically arranged on the seed crystal holder 2, it is equivalent to the off-axis seed crystal 2-2 being eccentrically arranged in the thermal field formed by the growth device.

[0053] According to some specific embodiments of this application, referring to the appendix Figures 2 - 6 , the center of the seed crystal holder 2 is located outside the seed crystal bonding area 2-1, that is, the seed crystal bonding area 2-1 does not cover the center of the seed crystal holder 2. Thus, it is further ensured that the off-axis seed crystal 2-2 is eccentrically arranged on the seed crystal holder 2, which can further ensure that the solution flows unidirectionally at the growth interface of the single crystal to achieve complete reverse step growth, and further ensure the improvement of the crystallization quality of the crystal.

[0054] According to some other specific embodiments of this application, referring to the appendix Figures 2 - 6 , the edge of the seed crystal bonding area 2-1 is in contact with the edge of the seed crystal holder 2. Thus, it is further ensured that the off-axis seed crystal is eccentrically arranged on the seed crystal holder 2, which can further ensure that the solution flows unidirectionally at the growth interface of the single crystal to achieve complete reverse step growth, and further ensure the improvement of the crystallization quality of the crystal.

[0055] According to some other specific embodiments of this application, referring to the appendix Figures 2 - 6 , the seed crystal holder 2 is circular, the seed crystal bonding area 2-1 is circular, and the edge of the seed crystal bonding area 2-1 is internally tangent to the edge of the seed crystal holder 2. Thus, it is further ensured that the off-axis seed crystal is eccentrically arranged on the seed crystal holder 2, which can further ensure that the solution flows unidirectionally at the growth interface of the single crystal to achieve complete reverse step growth, and further ensure the improvement of the crystallization quality of the crystal.

[0056] According to some other specific embodiments of this application, referring to the appendix Figure 5, the minimum distance h between the edge of the seed crystal bonding area 2-1 and the center of the seed crystal holder 2 is greater than 20 mm. Thus, it is further ensured that the off-axis seed crystal is eccentrically arranged on the seed crystal holder 2, which can further ensure the unidirectional flow of the solution at the growth interface of the single crystal to achieve complete inverse step growth, and further ensure the improvement of the crystallization quality of the crystal.

[0057] In the embodiments of the present application, the number of the seed crystal bonding areas 2-1 provided on the above-mentioned seed crystal holder 2 is not particularly limited, and those skilled in the art can design according to actual needs. For example, one seed crystal bonding area 2-1 can be provided (as shown in the attached Figure 5 figure), or two seed crystal bonding areas 2-1 can be provided (as shown in the attached Figure 6 figure), three seed crystal bonding areas 2-1 (as shown in the attached Figure 2 and 3 figures), four seed crystal bonding areas 2-1 (as shown in the attached Figure 4 figure).

[0058] According to some other specific embodiments of the present application, the off-axis angle range of the off-axis seed crystal is 0° to 8°, and not equal to 0°, for example, it can be 0.5°, 1°, 1.5°, 2°, 2.5°, 3°, 3.5°, 4°, 5°, 6°, 7°, 8°, etc., preferably 1° to 4°. As some specific embodiments, an off-axis seed crystal with an off-axis angle of 1° to 4° and an n-type conductivity type of 6 inches or 8 inches can be selected.

[0059] According to some other specific embodiments of the present application, the thickness of the above-mentioned off-axis seed crystal is 350 μm to 1000 μm, for example, the thickness of the off-axis seed crystal is 350 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, etc. In addition, the growth surface of the above-mentioned off-axis seed crystal is the C plane or the Si plane.

[0060] According to some other specific embodiments of the present application, the seed crystal bonding area 2-1 is a seed crystal bonding step, and the seed crystal bonding step is used to bond the off-axis seed crystal. Therefore, the diameter of the seed crystal bonding step is equal to the diameter of the off-axis seed crystal. As some specific examples, the height of the seed crystal bonding step is 0.5 mm to 2 mm, for example, it can be 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, etc. Thus, it is convenient to bond the off-axis seed crystal on the seed crystal bonding step.

[0061] In the embodiments of the present application, the above-mentioned growth solution is mainly a cosolvent system composed of silicon-transition metal, and its main function is to dissolve and transport the carbon component to the surface of the seed crystal for precipitation and crystallization.

[0062] According to some further specific embodiments of the present application, on the side of the seed crystal holder 2 close to the growth solution, a coating is provided in the area except the seed crystal bonding area 2-1. The coating includes at least one of silicon carbide (SiC), tantalum carbide, and tungsten carbide, thereby providing a C source, Si source, etc. for the growth system, compensating for the instability of the solution caused by component volatilization, and ensuring a long-term stable growth environment.

[0063] According to some further specific embodiments of the present application, referring to the attached Figure 1 , a hollow chamber 12 is provided in the crucible holder 5, and a graphite felt is provided in the hollow chamber 12, which can be used for heat preservation. Thus, the problem of uneven radial temperature gradient caused by the increase in the size of the seed crystal holder 2 due to the eccentric arrangement of the seed crystal can be solved, and the radial temperature difference can be reduced.

[0064] According to some further specific embodiments of the present application, referring to the attached Figure 1 , the above-mentioned silicon carbide single crystal growth device further includes: a heating system, a heat preservation system, and a rotation and pulling system.

[0065] According to some further specific embodiments of the present application, referring to the attached Figure 1 , the above-mentioned heating system includes an induction heating unit 10 and a resistance heating unit 6. The induction heating unit 10 can be an induction coil, which is placed on the side of the thermal field as the main heating system, and the frequency of the induction coil is less than 7 kHz. The above-mentioned resistance heating unit 6 can be an auxiliary resistance heater, which is placed below the crucible holder 5 and above the lower heat preservation felt, as the auxiliary heating system.

[0066] According to some further specific embodiments of the present application, referring to the attached Figure 1 , the above-mentioned heat preservation system includes an upper heat preservation felt 8, a lower heat preservation felt 7, a heat preservation barrel 9, and a heating cylinder 11. The upper heat preservation felt 8 is arranged above the heat preservation barrel 9, the lower heat preservation felt 7 is arranged below the heat preservation barrel 9, and the upper heat preservation felt 8, the lower heat preservation felt 7, and the heat preservation barrel 9 enclose a closed space. The growth system is arranged in the closed space, and the heating cylinder 11 is arranged on the side of the heat preservation barrel 9 close to the growth system; the induction heating unit 10 is arranged outside the heat preservation barrel 9. As some specific examples, the above-mentioned upper heat preservation felt 8, lower heat preservation felt 7, and heat preservation barrel 9 can be made of graphite soft felt or hard felt respectively, and the above-mentioned heating cylinder 11 can be a graphite heating cylinder. In addition, the above-mentioned heat preservation system further includes a graphite felt placed in the hollow chamber 12 of the crucible holder 5.

[0067] As some specific embodiments, the inner diameter of the graphite crucible 3 can be 400 mm to 450 mm, for example, it can be 400 mm, 410 mm, 420 mm, 430 mm, 440 mm, 450 mm, etc. As some further specific embodiments, the distance between the graphite crucible 3 and the heating cylinder can be 25 mm to 40 mm, for example, it can be 25 mm, 30 mm, 35 mm, 40 mm, etc.

[0068] In some specific embodiments, the diameter of the seed crystal holder 2 may be 310 mm to 420 mm, for example, it may be 310 mm, 320 mm, 340 mm, 360 mm, 380 mm, 400 mm, 420 mm, etc. In still some other specific embodiments, the distance between the edge of the seed crystal holder 2 and the inner wall of the crucible may be 25 mm to 60 mm, for example, it may be 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, etc.

[0069] In some specific embodiments, the diameter of the hollow chamber 12 provided in the crucible holder 5 may be 150 mm to 200 mm, for example, it may be 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, etc.

[0070] According to still some other specific embodiments of the present application, referring to the attached Figure 1 , the above-mentioned rotation and pulling system includes an upper transmission mechanism, a seed crystal shaft 1, a lower transmission mechanism and a lower graphite shaft 13. The lower end of the seed crystal shaft 1 is arranged on the side of the seed crystal holder 2 away from the growth solution, and the upper end of the seed crystal shaft 1 passes through the upper heat insulation felt 8 and is connected to the upper transmission mechanism. The seed crystal holder 2 is arranged above the growth solution through the seed crystal shaft 1; the upper part of the lower graphite shaft 13 is connected to the crucible holder 5, and the lower part of the lower graphite shaft 13 is connected to the lower transmission mechanism; the resistance heating unit 6 is arranged between the crucible holder 5 and the lower heat insulation felt 7 and is arranged on the lower graphite shaft 13. The above-mentioned upper transmission mechanism and lower transmission mechanism are inherent to the crystal growth furnace equipment. The above-mentioned seed crystal shaft 1 may be a graphite shaft, and the lower part of the seed crystal shaft 1 and the seed crystal holder 2 may be connected by threads. The above-mentioned transmission mechanism can drive the seed crystal holder 2 and the crucible to move up and down and rotate.

[0071] It should be noted that the seed crystal shaft 1 may be arranged at the central position of the seed crystal holder 2 (as shown in the attached Figure 1 ), or may be arranged at the edge position of the seed crystal holder 2 (as shown in the attached Figure 2 ).

[0072] In the second aspect of the present application, the present application proposes a method for growing a single crystal by using the silicon carbide single crystal growth device of the above embodiments. According to the embodiments of the present application, the above method includes:

[0073] S100: Bond the off-axis seed crystal to the seed crystal bonding area;

[0074] In this step, a specific number of off-axis seed crystals are bonded to the seed crystal bonding area according to actual requirements.

[0075] S200: Place the raw material of the growth solution in the graphite crucible, evacuate, and heat the raw material to a solution state to form a growth solution;

[0076] In this step, the raw materials of the growth solution are placed in a graphite crucible, and the vacuum is pumped down to below 10 -4 Pa, then heating is started until the melting temperature is reached and held constant for 20 min to 40 min to form the growth solution.

[0077] S300: Lower the seed crystal holder until the off-axis seed crystal on the seed crystal holder contacts the surface of the growth solution, and rotate it to perform non-axisymmetric crystal growth;

[0078] In this step, lower the seed crystal holder until the off-axis seed crystal on the seed crystal holder contacts the surface of the growth solution, start the rotation mechanism, and only keep the crucible or the seed crystal holder rotating at a speed of 10 rpm to 100 rpm and start non-axisymmetric crystal growth.

[0079] S400: After crystal growth is completed, separate the crystal from the growth solution and move it into the cooling section. After cooling to room temperature, open the furnace to take out the crystal.

[0080] According to the method for growing single crystals using the above silicon carbide single crystal growth device according to the embodiments of the present application, since the center of the seed crystal bonding area does not coincide with the center of the seed crystal holder, that is, the off-axis seed crystal is eccentrically arranged on the seed crystal holder, it is possible to effectively control the direction of the step flow of single crystal growth to be opposite to the direction of solution convection, realize the completely inverse step growth with a single flow direction of the solution within the range of the seed crystal, continuously wash the growth interface of the single crystal by the solution, inhibit the clustering of growth steps, inhibit macroscopic steps, reduce the inclusion of flux, thereby effectively improving the crystal quality and growth efficiency. At the same time, this method uses an off-axis seed crystal, which greatly reduces the cost compared with the situation where a large number of on-axis seed crystals (generally semi-insulating substrates, which are relatively expensive) are used in the industry; and the silicon carbide single crystal ingot grown by the solution method is further processed into an off-axis seed crystal, which can greatly increase the effective thickness of the crystal and improve the wafer yield.

[0081] Furthermore, the above non-axisymmetric growth can also be achieved by adjusting the relative position of the seed crystal rod or the seed crystal holder in the thermal field, so that it deviates from the center of the thermal field, and the result is that the seed crystal grows around the solution rather than at the center of the solution.

[0082] The embodiments of the present application will be described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. Additionally, if not explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also easily obtainable by those skilled in the art.

[0083] Example 1

[0084] This embodiment provides a silicon carbide single crystal growth device. Referring to the attached Figure 1 , this silicon carbide single crystal growth device includes:

[0085] Growth system, which includes a graphite crucible, a seed crystal holder, and a crucible support. The crucible support is arranged on the lower side of the graphite crucible. The graphite crucible is used to hold the growth solution, and the seed crystal holder is arranged above the growth solution. Among them, three seed crystal bonding areas are arranged on the side of the seed crystal holder close to the growth solution, and the seed crystal bonding areas are used to bond off-axis seed crystals. The center of the seed crystal holder is located outside the seed crystal bonding areas, and the seed crystal holder is circular, the seed crystal bonding areas are circular, the edge of the seed crystal bonding area is internally tangent to the edge of the seed crystal holder, and the closest distance h from the edge of the seed crystal bonding area to the center of the seed crystal holder is 25 mm. And, the above-mentioned seed crystal bonding areas are seed crystal bonding steps, the diameter of the seed crystal bonding step is equal to the diameter of the off-axis seed crystal, and the height of the seed crystal bonding step is 1 mm. In addition, the off-axis angle of the above-mentioned off-axis seed crystal is 2° n-type conductive 6-inch seed crystal. The thickness of the above-mentioned off-axis seed crystal is 500 μm, and the growth surface of the off-axis seed crystal is the C plane.

[0086] In addition, on the side of the seed crystal holder close to the growth solution, an SiC coating is provided in the area except the seed crystal bonding areas. A hollow chamber is provided in the crucible support, and a graphite felt is arranged in the hollow chamber, and the graphite felt can be used for heat preservation, and the diameter of the hollow chamber can be 180 mm.

[0087] The above-mentioned silicon carbide single crystal growth device further includes: a heating system, a heat preservation system, and a rotation and lifting system. The heating system is mainly a combination of an induction heating system and a resistance heating system. The induction heating system is an induction coil, which is placed on the side of the heat field as the main heating system, and the frequency of the induction coil is less than 7 kHz. The above-mentioned resistance heating system is an auxiliary resistance heater, which is placed below the crucible support and above the lower heat preservation felt as the auxiliary heating system.

[0088] The above-mentioned heat preservation system includes an upper heat preservation felt, a lower heat preservation felt, a heat preservation barrel, and a heating cylinder. The upper heat preservation felt is arranged above the heat preservation barrel, the lower heat preservation felt is arranged below the heat preservation barrel, and the upper heat preservation felt, the lower heat preservation felt, and the heat preservation barrel enclose a closed space, and the growth system is arranged in the closed space. The heating cylinder is arranged on the side of the heat preservation barrel close to the growth system. The above-mentioned upper heat preservation felt, lower heat preservation felt, and heat preservation barrel are respectively made of graphite soft felt or hard felt, and the above-mentioned heating cylinder is a graphite heating cylinder. In addition, the above-mentioned heat preservation system further includes a graphite felt placed in the hollow chamber of the crucible support. Among them, the inner diameter of the graphite crucible is 420 mm, the distance between the graphite crucible and the heating cylinder is 30 mm, and the diameter of the seed crystal holder can be 370 mm. The distance between the edge of the seed crystal holder and the inner wall of the crucible can be 25 mm.

[0089] The above-mentioned rotation and lifting system includes an upper transmission mechanism, a seed crystal shaft, a lower transmission mechanism, and a lower graphite shaft. The lower end of the seed crystal shaft is arranged on the side of the seed crystal holder away from the growth solution, and the upper end of the seed crystal shaft passes through the upper heat insulation felt and is connected to the upper transmission mechanism. The seed crystal holder is arranged above the growth solution through the seed crystal shaft; the upper part of the lower graphite shaft is connected to the crucible holder, and the lower part of the lower graphite shaft is connected to the lower transmission mechanism. The above-mentioned upper transmission mechanism and lower transmission mechanism are inherent to the crystal growth furnace equipment. The above-mentioned seed crystal shaft is a graphite shaft, and the lower part of the seed crystal shaft and the seed crystal holder can be connected by threads. The above-mentioned transmission mechanism can drive the seed crystal holder and the crucible to move up and down and rotate.

[0090] Using the silicon carbide single crystal growth device of the above embodiment for single crystal growth, the following steps are included:

[0091] Bond the off-axis seed crystal to the seed crystal bonding area.

[0092] Place the raw material of the growth solution in a graphite crucible, evacuate to 10 -4 Pa, start heating to the melting temperature and keep it constant for 30 minutes to form a growth solution, which is mainly a solvent system composed of silicon-transition metal.

[0093] Lower the seed crystal holder until the off-axis seed crystal on the seed crystal holder contacts the surface of the growth solution, start the rotation mechanism, and only keep the crucible rotating at a speed of 50 rpm and start non-axisymmetric crystal growth.

[0094] After crystal growth is completed, separate the crystal from the growth solution and enter the cooling section. After cooling to room temperature, open the furnace and take out the crystal.

[0095] Comparative Example 1

[0096] This comparative example is basically the same as Example 1, and the only difference is:

[0097] There is 1 seed crystal bonding area arranged on the side of the seed crystal holder close to the growth solution, and the center of the seed crystal holder coincides with the center of the seed crystal bonding area, that is, the seed crystal is centered. Refer to the appendix Figure 7 . And, the on-axis seed crystal is bonded to the seed crystal bonding area.

[0098] Optical microscopy and XRD tests were respectively carried out on the silicon carbide single crystals prepared in Example 1 and Comparative Example 1, and the results are as shown in the appendix Figures 10 - 15 shown. Among them, the appendix Figure 10 is the crystal diagram of the off-axis layout and non-axisymmetric growth of the seed crystal in Example 1, and the appendix Figure 11 is the optical microscopy image of the central area of the crystal of the off-axis layout and non-axisymmetric growth of the seed crystal in Example 1, and the appendix Figure 12 is the XRD rocking curve diagram of the crystal of the off-axis layout and non-axisymmetric growth of the seed crystal in Example 1, and the appendix Figure 13 is the crystal diagram of the conventional layout and symmetric growth of the seed crystal in Comparative Example 1, and the appendixFigure 14 Optical microscope image of the central region of a crystal grown symmetrically with the conventional layout of the seed crystal of Comparative Example 1 for Comparative Example 1, attached Figure 15 XRD rocking curve of a crystal grown symmetrically with the conventional layout of the seed crystal of Comparative Example 1 for Comparative Example 1.

[0099] As can be seen from the attached Figures 10 - 15 The surface of the crystal grown non-axisymmetrically with the offset layout of the seed crystal in Example 1 is smooth and flat, while the center of the crystal grown symmetrically with the conventional layout of the seed crystal in Comparative Example 1 is rough and solvent-included. There is no clustering of growth steps in the central region of the crystal grown non-axisymmetrically with the offset layout of the seed crystal in Example 1, while the growth steps in the center of the crystal grown symmetrically with the conventional layout of the seed crystal in Comparative Example 1 are clustered. The full width at half maximum (FWHM) value of the XRD rocking curve of the crystal grown non-axisymmetrically with the offset layout of the seed crystal in Example 1 is 37.5 arcsec, indicating high crystallization quality; while the full width at half maximum (FWHM) value of the XRD rocking curve of the crystal grown symmetrically with the conventional layout of the seed crystal in Comparative Example 1 is 67.1 arcsec, indicating low crystallization quality.

[0100] In summary, for Comparative Example 1 with the conventional central arrangement of the seed crystal, the growth interface steps are clustered, the surface of the crystal center is rough, solvent-included, and the crystallization quality is not high (FWHM 67.1 arcsec). For Example 1 with the offset layout of the seed crystal, there is no agglomeration of the growth interface steps, the surface of the crystal center is smooth and flat, there is no solvent inclusion, and the crystallization quality is high (FWHM 37.5 arcsec).

[0101] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0102] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A silicon carbide single crystal growth apparatus, characterized in that, Comprising: A growth system, the growth system including a graphite crucible, a seed crystal holder, and a crucible holder, the crucible holder being disposed on the lower side of the graphite crucible, the graphite crucible being used to contain a growth solution, and the seed crystal holder being disposed above the growth solution; Wherein, at least one seed crystal bonding area is disposed on a side of the seed crystal holder close to the growth solution, the seed crystal bonding area being used to bond an off-axis seed crystal, and the center of the seed crystal bonding area does not coincide with the center of the seed crystal holder.

2. The silicon carbide single crystal growth apparatus according to claim 1, wherein, The center of the seed crystal holder is located outside the seed crystal bonding area.

3. The silicon carbide single crystal growth apparatus according to claim 2, wherein, The edge of the seed crystal bonding area is in contact with the edge of the seed crystal holder.

4. The silicon carbide single crystal growth apparatus according to claim 3, wherein The seed crystal holder is circular, the seed crystal bonding area is circular, and the edge of the seed crystal bonding area is internally tangent to the edge of the seed crystal holder.

5. The silicon carbide single crystal growth apparatus according to claim 2, wherein The minimum distance h between the edge of the seed crystal bonding area and the center of the seed crystal holder is greater than 20 mm.

6. The silicon carbide single crystal growth apparatus according to claim 1, wherein The off-axis angle range of the off-axis seed crystal is 0° to 8°, and is not equal to 0°; And / or, the thickness of the off-axis seed crystal is 350 μm to 1000 μm; And / or, the seed crystal bonding area is a seed crystal bonding step, and the height of the seed crystal bonding step is 0.5 mm to 2 mm.

7. The silicon carbide single crystal growth apparatus according to any one of claims 1 to 6, characterized in that, On a surface of the seed crystal holder close to the growth solution, a coating is disposed on an area other than the seed crystal bonding area, and the coating includes at least one of silicon carbide, tantalum carbide, and tungsten carbide.

8. The silicon carbide single crystal growth apparatus according to any one of claims 1 to 6, characterized in that, A hollow chamber is disposed in the crucible holder, and a graphite felt is disposed in the hollow chamber.

9. The silicon carbide single crystal growth apparatus according to any one of claims 1 to 6, characterized in that Also comprising: A heating system, the heating system including an induction heating unit and a resistance heating unit; A heat preservation system, the heat preservation system including an upper heat preservation felt, a lower heat preservation felt, a heat preservation barrel, and a heating cylinder, the upper heat preservation felt being disposed above the heat preservation barrel, the lower heat preservation felt being disposed below the heat preservation barrel, and the upper heat preservation felt, the lower heat preservation felt, and the heat preservation barrel enclose a closed space, the growth system being disposed in the closed space, and the heating cylinder being disposed on a side of the heat preservation barrel close to the growth system; the induction heating unit is disposed outside the heat preservation barrel; A rotation and lifting system, the rotation and lifting system including an upper transmission mechanism, a seed crystal shaft, a lower transmission mechanism, and a lower graphite shaft, the lower end of the seed crystal shaft being disposed on a side of the seed crystal holder away from the growth solution, and the upper end of the seed crystal shaft passing through the upper heat preservation felt and being connected to the upper transmission mechanism, and the seed crystal holder being disposed above the growth solution through the seed crystal shaft; the upper part of the lower graphite shaft is connected to the crucible holder, and the lower part of the lower graphite shaft is connected to the lower transmission mechanism; The resistance heating unit is disposed between the crucible holder and the lower heat preservation felt, and is disposed on the lower graphite shaft.

10. A method for growing a single crystal using the single crystal growth apparatus according to any one of claims 1 to 9, characterized in that, Comprising: Bonding an off-axis seed crystal to the seed crystal bonding area; Placing raw materials of the growth solution into the graphite crucible, evacuating, and heating the raw materials to a solution state to form a growth solution; Lowering the seed crystal holder until the off-axis seed crystal on the seed crystal holder contacts the surface of the growth solution, rotating, and performing non-axisymmetric crystal growth; After crystal growth is completed, separating the crystal from the growth solution and entering a cooling section, and after cooling to room temperature, opening the furnace to take out the crystal.

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