A silicon carbide crystal interface control structure, growth apparatus and method of manufacture

Abstract

The application provides a crystal interface control structure of silicon carbide, a growth device and a preparation method, wherein the crystal interface control structure comprises a graphite tray, a plurality of graphite rods distributed on the graphite tray, a plurality of heat exchange pipes connected with the plurality of graphite rods in correspondence and a plurality of electric signal receivers, the heat exchange pipe is provided with a gas inlet pipe, and the gas inlet pipe is provided with a refrigerant gas flow; one end of the electric signal receiver is connected with the heat exchange pipe through a connecting wire, and the other end is connected with the graphite rod through a connecting wire; the graphite rod, the heat exchange pipe and the electric signal receiver form a thermocouple temperature measurement system, and the temperature of the graphite rod can be judged through the electric signal receiver; the temperature distribution of the graphite tray can be adjusted by adjusting the flow of the refrigerant gas, so that the control of the crystal interface is realized. The growth device comprising the crystal interface control structure of the application can obtain a silicon carbide single crystal substrate with low density defects.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal growth technology, specifically to a silicon carbide crystallization interface control device, growth equipment, and preparation method. Background Technology

[0002] As a representative of third-generation semiconductor single crystal materials, silicon carbide (SiC) has the characteristics of wide bandgap, high critical breakdown electric field, high thermal conductivity, high carrier saturation drift velocity and excellent chemical stability. These excellent properties have enabled silicon carbide crystals to be widely used in power electronics, radio frequency devices, optoelectronic devices and other fields, and have an important impact on the development of future electronic information industry technology.

[0003] Silicon carbide wafers, as semiconductor substrate materials, can be manufactured into silicon carbide-based power devices and microwave radio frequency devices through epitaxial growth and device fabrication, making them a crucial foundational material for the development of the third-generation semiconductor industry. Silicon carbide single-crystal substrates are typically grown from bulk crystals using physical vapor transport (PVT) or liquid phase epitaxy (LPE) methods, followed by mechanical processing to obtain the substrate wafer. Therefore, the quality of the bulk crystal directly determines the quality of the silicon carbide single-crystal substrate, and the defects on the bulk crystal determine the order of magnitude of the fundamental defects in the silicon carbide single-crystal substrate.

[0004] Currently, the main methods for controlling defects in silicon carbide single crystals include: repairing defects by lateral growth of the crystal after patterning, such as CN111958070B and JP2006052097A; adding a special atmosphere or adjusting the structure of the seed crystal tray in the growth environment, such as CN112160028A, CN106435734A, and US7501022B2; improving the purity of raw materials by improving the PVT gas phase transport process to avoid defects caused by impurities, such as CN110983434A and US8741413B2; and more often, using chemical vapor deposition (CVD) processes to improve defects, such as CN1926266A and CN111051581A. However, the above-mentioned methods also have many shortcomings. For example, patterned seed crystals or special seed crystal holder structures only fix and change the shape of the crystal growth interface in the initial stage of growth, while the crystallization interface is uncontrolled for most of the crystal growth process. Improvements in the gas phase transport process may improve microtubes or carbon inclusions to some extent, but they cannot improve defects such as stacking faults (SF), screw dislocations (TSD), or basal plane dislocations (BPD). The CVD process can improve the number of defects on the substrate to some extent, but TSD cannot be repaired or only replaced by SF defects during epitaxy. In view of the above, a novel method for controlling defects in silicon carbide single crystal substrates needs to be proposed. Summary of the Invention

[0005] In view of the shortcomings and defects in the prior art, the present invention provides a silicon carbide crystallization interface control structure, growth equipment and preparation method, which are used to control the crystallization interface of silicon carbide to improve the defects inside the silicon carbide single crystal substrate.

[0006] To achieve the above and other related objectives, this invention provides a silicon carbide crystallization interface control structure, comprising a graphite tray, multiple graphite rods, multiple heat exchange tubes, and multiple electrical signal receivers. The graphite tray is used to hold silicon carbide seed crystals, and the multiple graphite rods are installed on the side of the graphite tray facing away from the seed crystals. The multiple heat exchange tubes are respectively connected to the multiple graphite rods, and each heat exchange tube has an inlet pipe through which refrigerant gas flows. The multiple electrical signal receivers are correspondingly arranged with the multiple heat exchange tubes, with one end connected to the heat exchange tube via a connecting wire and the other end connected to the graphite rod via a connecting wire. The graphite rods, the heat exchange tubes, and the electrical signal receivers constitute a thermocouple temperature measurement system, through which the temperature of the graphite rods can be determined. The crystallization interface control device adjusts the temperature distribution of the graphite tray by regulating the flow rate of the refrigerant gas, thereby achieving control of the crystallization interface.

[0007] In one embodiment of the present invention, the heat exchange tube is made of a high-temperature resistant material, which is any one of tantalum (Ta), tantalum carbide (TaC), tungsten (W), molybdenum (Mo), rhenium (Re) or ceramic materials.

[0008] In one embodiment of the present invention, the plurality of graphite rods are evenly distributed on the graphite tray.

[0009] In one embodiment of the present invention, the plurality of graphite rods and the graphite tray are an integral structure, and the ends of the plurality of graphite rods opposite to the graphite tray are connected to the plurality of heat exchange tubes one by one.

[0010] In one embodiment of the present invention, the graphite rod has a hollow structure, the outlet of the air inlet pipe corresponds to the interior of the graphite rod, the refrigerant gas enters the graphite rod through the air inlet pipe to cool it, and is discharged through the heat exchange pipe.

[0011] In one embodiment of the present invention, the graphite rod and the graphite tray are made of high-density graphite material, the density of which is 1.6–1.8 g / cm³. 3 Thermal conductivity is 80–150 W / m -1 K -1 .

[0012] In one embodiment of the present invention, the refrigerant gas is selected from any one of hydrogen (H2), helium (He), and argon (Ar).

[0013] A second aspect of the present invention is to provide a silicon carbide growth apparatus comprising the crystallization interface control structure of the present invention.

[0014] A third aspect of the present invention is to provide a method for controlling defects in a silicon carbide single-crystal substrate, comprising the following steps:

[0015] Provides a silicon carbide growth apparatus incorporating the crystallization interface control structure of the present invention;

[0016] A seed crystal is fixed on the graphite tray of the silicon carbide growth equipment;

[0017] The temperature of the silicon carbide growth equipment is raised to 1600–2500°C, and the pressure is controlled at 0.1–100 mbar.

[0018] The flow rate of the refrigerant gas is adjusted according to the temperature distribution of the graphite tray and the defect distribution in the seed crystal to make the graphite tray achieve the expected temperature distribution and make the growth interface of the seed crystal the expected shape.

[0019] Adjusting the flow rate of the refrigerant gas causes specific crystalline phases of silicon carbide to crystallize preferentially, thus repairing defects;

[0020] Adjust the flow rate of the refrigerant gas to bring the temperature at each location of the graphite tray to a stable growth temperature;

[0021] After stable growth is complete, remove the plant by cooling it down.

[0022] After cooling, silicon carbide crystals are processed to obtain silicon carbide single crystal substrates with low defect density.

[0023] In one embodiment of the present invention, the desired shape of the growth interface of the seed crystal is stepped.

[0024] As described above, this invention provides a crystallization interface control structure. Multiple graphite rods and heat exchange tubes connected to the graphite rods are arranged on a graphite tray. An inlet pipe with refrigerant gas flowing inside the heat exchange tube is provided. The graphite rods, the graphite tray, and an electrical signal receiver constitute a thermocouple temperature measurement system. The temperature of the graphite rods at different positions can be obtained through the electrical signal receiver, thus obtaining the temperature distribution of the graphite tray. The temperature of the graphite rods can be controlled by adjusting the flow rate of the refrigerant gas, thereby achieving the desired temperature distribution of the graphite tray to control the crystallization interface. When this crystallization interface control structure is installed in a growth device, the temperature distribution of the graphite tray can be adjusted by regulating the flow rate of the refrigerant gas, allowing specific crystal phases of silicon carbide to grow preferentially. When defects in different directions meet, they can be eliminated or converge into a single defect. At this point, the temperature distribution of the graphite tray can be readjusted according to product grade requirements until a growth interface with sufficiently low defect density is obtained. This invention also provides a method for controlling defects in a silicon carbide single-crystal substrate. This method can control defects in the silicon carbide single-crystal substrate to obtain a silicon carbide single-crystal substrate with low defect density. Attached Figure Description

[0025] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0026] Figure 1 The diagram shown is a schematic representation of the crystallization interface control structure of the present invention in one embodiment.

[0027] Figure 2 Displayed as Figure 1 Enlarged section view of the central area I.

[0028] Figure 3 The flowchart shown is a preparation method for controlling defects in silicon carbide single crystal substrates according to the present invention.

[0029] Figure 4 Displayed as Figure 3 A schematic diagram of the defect distribution in the seed crystal selected in step S2.

[0030] Figure 5 Displayed as Figure 3 A schematic diagram of the development direction of each defect corresponding to step S4.

[0031] Figure 6 Displayed as Figure 3 A schematic diagram of the structure after defect repair corresponding to step S5.

[0032] Figure 7 Displayed as Figure 3 A schematic diagram of the structure of silicon carbide crystal after stable growth corresponding to step S6.

[0033] Figure 8 The diagram illustrates the process of eliminating defects during silicon carbide growth at a stepped growth interface, as shown in one embodiment of the present invention.

[0034] Figure Labels

[0035] 1. Graphite tray; 2. Graphite rod; 3. Heat exchange tube; 4. Electrical signal receiver; 5. Seed crystal; 6. Inlet pipe; 501. Preferred growth region; 502. Base plane; 503. Seed crystal surface; 504. Defect perpendicular to the base plane; 505. Defect perpendicular to the seed crystal surface; 506. Defect parallel to the base plane; 7. Crystalline plane orientation; 8. Defect; 9. Low-defect growth interface; 10. Seed crystal defect; 101. Top defect; 11. Silicon carbide growth interface; 1101. Sidewall defect. Detailed Implementation

[0036] The following specific examples illustrate embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While the invention may be practiced with any methods and materials similar to or equivalent to those described herein, preferred methods, devices, and materials are described below.

[0040] This invention provides a silicon carbide crystallization interface control structure, growth equipment, and preparation method, which can control the crystallization interface by controlling the temperature distribution of the graphite tray, thereby achieving the purpose of controlling the silicon carbide single crystal substrate.

[0041] Please see Figure 1 and Figure 2 This invention provides a crystallization interface control structure, including a graphite tray 1, multiple graphite rods 2, multiple heat exchange tubes 3, and multiple electrical signal receivers 4. The graphite tray 1 is used to hold a seed crystal 5, and the multiple graphite rods 2 are installed on the side of the graphite tray 1 facing away from the seed crystal 5. The multiple heat exchange tubes 3 are respectively connected to the multiple graphite rods 2, and each heat exchange tube 3 has an inlet pipe 6 through which refrigerant gas flows. The multiple electrical signal receivers 4 are correspondingly arranged with the multiple heat exchange tubes 3. One end of the electrical signal receiver 4 is connected to the heat exchange tube 3 through a connecting wire, and the other end is connected to the graphite rod 2 through a connecting wire. The graphite rods 2, the heat exchange tubes 3, and the electrical signal receivers 4 form a closed loop through the connecting wires to constitute a thermocouple temperature measurement system. The end of the heat exchange tube 3 that is in close contact with the graphite rod 2 generates a thermoelectric potential at high temperature, which is received by the electrical signal receivers 4. The temperature of the graphite tray 1 at this location can be obtained based on the electrical signal received by the electrical signal receivers 4. This crystallization interface control device adjusts the temperature distribution of the graphite tray 1 by adjusting the flow rate of the refrigerant gas, thereby realizing the control of the crystallization interface.

[0042] Please see Figure 1 and Figure 2 The thermocouple temperature measurement system, consisting of heat exchange tube 3, graphite rod 2, and electrical signal receiver 4, requires that heat exchange tube 3 and graphite rod 2 be made of different materials, and that heat exchange tube 3 be made of high-temperature resistant conductor or semiconductor material, such as Ta, TaC, W, Mo, Re, or high-purity dense ceramic material. The end of heat exchange tube 3 in close contact with graphite rod 2 is the hot end of the thermocouple temperature measurement system, while the end connected to electrical signal receiver 4 is the cold end. During crystal growth, the cold end is kept at a constant temperature, while the temperature of the hot end changes with the flow rate of the refrigerant gas. Because a thermoelectric electromotive force is generated in the closed circuit of the thermocouple and is reflected in electrical signal receiver 4, the temperature of graphite tray 1 at that point can be determined based on the electromotive force in electrical signal receiver 4.

[0043] Please see Figure 1 and Figure 2 As an example, multiple graphite rods 2, such as three or more graphite rods 2, are evenly distributed on the side of the graphite tray 1 facing away from the seed crystal 5. The graphite rods 2 and the graphite tray 1 are an integral structure, both made of the same material, for example, a material with a density of 1.6 to 1.8 g / cm³. 3 Thermal conductivity is 80–150 W / m -1 K -1It is made of high-density graphite material. The temperature of the graphite rod 2 is equal to the temperature of the position on the graphite tray 1 where it is connected to the graphite rod 2. Therefore, adjusting the temperature of different graphite rods 2 by means of refrigerant gas is also equivalent to adjusting the temperature distribution of the graphite tray 1.

[0044] Please see Figure 1 and Figure 2 In one embodiment, the graphite rod 2 has a hollow structure, and the heat exchange tube 3 is correspondingly connected to the graphite rod 2 with their interiors interconnected. The inlet of the air inlet pipe 6 inside the heat exchange tube 3 is connected to a refrigerant gas source, and the outlet corresponds to the interior of the graphite rod 2. The refrigerant gas enters the graphite rod 2 from the air inlet pipe 6 to cool it, and then exits through the heat exchange tube 3. The refrigerant gas can be selected from any one of H2, He, Ar, or other inert gases.

[0045] Please see Figures 1 to 3 The present invention also provides a method for controlling defects in a silicon carbide single crystal substrate, comprising at least the following steps:

[0046] S1. A silicon carbide growth apparatus incorporating the crystallization interface control structure of the present invention is provided.

[0047] S2. Fix a seed crystal 5 on the graphite tray 1 of the silicon carbide growth equipment;

[0048] S3. Raise the temperature of the silicon carbide growth equipment to 1600-2500℃ and control the pressure at 0.1-100mbar;

[0049] S4. Adjust the flow rate of the refrigerant gas according to the temperature distribution of the graphite tray 1 and the defect distribution in the seed crystal 5 so that the graphite tray 1 obtains the expected temperature distribution and the growth interface of the seed crystal 5 reaches the expected shape.

[0050] S5. Adjusting the flow rate of the refrigerant gas causes specific crystal phases of silicon carbide to crystallize preferentially, thus repairing defects;

[0051] S6. Adjust the flow rate of the refrigerant gas to stabilize the temperature of each position on the graphite tray 1 to the growth temperature of silicon carbide.

[0052] S7. After stable growth is complete, remove the product by cooling.

[0053] S8. After cooling, the silicon carbide crystal is processed to obtain a silicon carbide single crystal substrate with low defect density.

[0054] Specifically, the silicon carbide growth apparatus in step S1 includes a crucible and a crystallization interface control structure mounted on the crucible, wherein the crystallization interface control structure is the crystallization interface control structure of the present invention, which is sealed at the top of the crucible. Other undisclosed structures of the silicon carbide growth apparatus are conventional structures in the art and will not be described in detail here.

[0055] Please see Figure 1 , Figure 3 and Figure 4 In step S2, the seed crystal 5 is attached to the graphite tray 1. The defect distribution in the seed crystal 5 is known. In one embodiment, the seed crystal surface 503 of the selected seed crystal 5 has a 4° deflection angle θ with the base surface 502, and the seed crystal 5 has a defect 504 perpendicular to the base surface, a defect 505 perpendicular to the seed crystal surface, and a defect 506 parallel to the base surface.

[0056] Please see Figure 3 In step S3, the temperature of the silicon carbide growth equipment is raised to 1600-2500°C, and the pressure is controlled at 0.1-100 mbar. For example, the silicon carbide growth equipment is heated to 2300°C at a heating rate of 200°C / h. Before the temperature inside the equipment reaches 2300°C, the pressure inside the equipment is controlled at 100 mbar. When the temperature approaches 2300°C, the pressure inside the equipment is reduced to 30 mbar.

[0057] Please see Figure 2 , Figure 3 and Figure 5 In step S4, the temperature distribution of the graphite tray 1 is obtained through the electrical signal receiver 4 corresponding to each position, and the defect distribution in the seed crystal 5 can be obtained by detection before the seed crystal 5 is installed. First, the flow rate of the refrigerant gas in the heat exchange tube 3 is adjusted according to the temperature distribution of the graphite tray 1. The refrigerant gas can be selected from any one of H2, He, Ar or other inert gases, so that the seed crystal 5 can grow preferentially to obtain a preferential growth region 501. Then, according to the temperature distribution in the graphite tray 1 and the defect distribution in the seed crystal 5, the flow rate of the refrigerant gas in the heat exchange tube 3 around the defect is adjusted so that the temperature around the defect is lower than the temperature at the defect. For example, the temperature around the defect is adjusted to be more than 5°C lower than the temperature at the defect, so that silicon carbide grows preferentially at the defect to obtain the expected crystallization interface.

[0058] Please see Figure 3 , Figure 5 and Figure 6 In step S5, because the growth rate of silicon carbide in the

[0001] direction is less than... Due to the directional and central heat dissipation effects, defects 504 perpendicular to the base plane, 505 perpendicular to the seed crystal surface, and 506 parallel to the base plane all develop towards the center. The development direction of the defects is not completely perpendicular to the crystallization plane direction 7. When the various defects meet, they will either eliminate or converge to form a converging defect 8 that continues to extend downwards. The temperature at defect 9 is adjusted again according to the product grade requirements, and steps S4 and S5 are repeated to obtain a growth interface 9 with low defect density.

[0059] Please see Figure 3 and Figure 6Step S6: By adjusting the flow rate of the refrigerant gas at each position of the graphite tray 1, the temperature at each point on the graphite tray 1 is raised to the growth temperature of silicon carbide and stabilized for a period of time, such as 80 hours of stable growth to obtain silicon carbide crystals.

[0060] Please see Figure 3 After the stable growth in step S7 is completed, the flow rate of the refrigerant gas is adjusted to ensure that the temperature distribution of the graphite tray 1 is uniform. Then, the crystal temperature is reduced from 2300℃ to room temperature and the crystal is removed.

[0061] The processing of silicon carbide crystals to obtain silicon carbide single crystal substrates in step S8 is a conventional technical operation and will not be described in detail here.

[0062] Please see Figure 8 In one embodiment, a seed crystal 5 is provided, which contains a variety of randomly distributed seed crystal defects 10. Using the method of controlling defects in silicon carbide single crystal substrate of the present invention, in the early stage of crystal growth (corresponding to step S4), a stepped growth interface is obtained by adjusting the flow rate of the refrigerant gas at each position of the graphite tray 1; then the flow rate of the refrigerant gas is adjusted to make the crystal grow rapidly along the direction of the lower step. Some defects extend along the normal direction of the crystal growth interface. However, since the growth rate at the bottom of the step is slow and the growth rate at the top of the step is fast, and the

[0001] directional growth ratio is... The growth rate is slower, so the defect at the bottom step extends more slowly than the crystal growth at the top step. The top crystal covers the bottom defect, while the top defect extends along... Lateral defects 1101 extend towards the crystal sidewalls, and the final crystal retains only the top defect 101 at the top of the step. In subsequent processing, the defect is removed by grinding, thus obtaining a high-quality silicon carbide single crystal substrate.

[0063] The crystallization interface control structure of this application can also be used in chemical vapor deposition equipment. This crystallization interface control structure and CVD epitaxy process can further reduce defects in silicon carbide single crystal substrates.

[0064] In summary, this invention provides a silicon carbide crystallization interface control structure, growth equipment, and preparation method. This crystallization interface control structure regulates the temperature distribution of the graphite tray by adjusting the flow rate of the coolant gas to control the crystallization interface. Silicon carbide crystals grown using the growth equipment incorporating this crystallization interface control structure can yield high-quality silicon carbide single-crystal substrates. Therefore, this invention effectively overcomes some practical problems in the prior art, thus possessing high utilization value and practical significance.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A crystallization interface control structure, characterized in that, include: Graphite tray, used to hold seed crystals; Multiple graphite rods are distributed on the side of the graphite tray opposite to the seed crystal, and the graphite rods are hollow structures; Multiple heat exchange tubes are respectively connected to multiple graphite rods. Each heat exchange tube is provided with an air inlet pipe through which refrigerant gas flows. The heat exchange tubes are connected to the interior of the graphite rods. The air inlet of the air inlet pipe is connected to a refrigerant gas source, and the air outlet of the air inlet pipe corresponds to the interior of the graphite rods. and Multiple electrical signal receivers are provided, corresponding to the multiple heat exchange tubes. One end of each electrical signal receiver is connected to the heat exchange tube via a connecting wire, and the other end is connected to the graphite rod via a connecting wire. The graphite rod, the heat exchange tube, and the electrical signal receiver constitute a thermocouple temperature measurement system, and the temperature of the graphite rod can be determined through the electrical signal receiver. Adjusting the flow rate of the refrigerant gas can regulate the temperature distribution of the graphite tray, thereby controlling the crystallization interface.

2. The crystallization interface control structure according to claim 1, characterized in that, The heat exchange tube is made of a high-temperature resistant material, which is any one of tantalum, tantalum carbide, tungsten, molybdenum, rhenium, or ceramic materials.

3. The crystallization interface control structure according to claim 1, characterized in that, The plurality of graphite rods are evenly distributed on the graphite tray.

4. The crystallization interface control structure according to claim 3, characterized in that, The plurality of graphite rods and the graphite tray are an integral structure, and the ends of the plurality of graphite rods opposite to the graphite tray are connected to the plurality of heat exchange tubes one by one.

5. The crystallization interface control structure according to claim 4, characterized in that, The refrigerant gas enters the graphite rod through the inlet pipe to cool it, and then exits through the heat exchange tube.

6. The crystallization interface control structure according to claim 1, characterized in that, The graphite rod and the graphite tray are made of high-density graphite material, and the density of the graphite tray is 1.6~1.8 g / cm³. 3 Thermal conductivity is 80~150 Wm -1 K -1 .

7. The crystallization interface control structure according to claim 1, characterized in that, The refrigerant gas is selected from any one of hydrogen, helium, and argon.

8. A silicon carbide growth apparatus, characterized in that, Includes the crystallization interface control structure as described in any one of claims 1-7.

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