Silicon carbide single crystal growth device

Abstract

This utility model relates to the field of semiconductor technology, specifically to a silicon carbide single crystal growth apparatus. The silicon carbide single crystal growth apparatus includes a crucible with a receiving cavity; a seed crystal holder disposed on top of the receiving cavity; and a carbon felt layer disposed between the seed crystal holder and the top wall of the crucible. The silicon carbide single crystal growth apparatus provided in this application, by setting the carbon felt layer between the seed crystal holder and the top wall of the crucible, effectively reduces the heat transferred to the seed crystal by thermal radiation when the seed crystal is fixed inside the seed crystal holder. This structure optimizes the axial temperature gradient, making the temperature distribution at the crystal growth interface more uniform, which is beneficial for suppressing dislocation defect aggregation, reducing crystal defects caused by thermal stress, and improving the quality of the single crystal.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor technology, and more specifically, to a silicon carbide single crystal growth apparatus. Background Technology

[0002] Silicon carbide (SiC) single crystals, as a third-generation semiconductor material, possess irreplaceable advantages in high-voltage, high-frequency, high-temperature, and high-power fields such as new energy vehicles, rail transportation, smart grids, 5G communications, and aerospace due to their wide bandgap, high breakdown field strength, high thermal conductivity, and high electron saturation drift velocity. Physical vapor transport (PVT) remains the mainstream technology for the industrial growth of large-size, high-quality SiC single crystals due to its relative maturity and controllable cost.

[0003] However, the PVT method for growing SiC single crystals still faces severe defect challenges. Among them, dislocation defects (such as base plane dislocations (BPD), screw dislocations (TSD), and edge dislocations (TED)) are key bottlenecks affecting crystal quality and limiting the performance and reliability of devices (especially high-blocking-voltage MOSFETs). These defects are difficult to completely eliminate in subsequent epitaxy and device fabrication processes, and may multiply or transform into more fatal stacking faults, leading to premature device failure.

[0004] Root cause analysis of dislocation defect aggregation indicates that thermal stress during growth is one of the main contributing factors. In the PVT thermal field, SiC powder in the high-temperature region (approximately 2100-2400℃) sublimates, and the gaseous components are transported to the seed crystal at a slightly lower temperature for crystallization. To maintain the necessary supersaturation to drive crystal growth, a high thermal conductivity material (such as high-strength graphite) is usually directly connected or in close contact with the seed crystal. This connection method creates a steep axial temperature gradient (dT / dz) at the crystal growth interface. The drastic change in axial temperature generates enormous thermoelastic stress inside the crystal, especially in the early growth region near the seed crystal. When this stress exceeds the critical shear stress of the SiC crystal at that temperature, dislocation slip and multiplication are induced. Utility Model Content

[0005] The purpose of this invention is to provide a silicon carbide single crystal growth device that helps reduce the axial temperature gradient at the growth interface and suppress the accumulation of dislocation defects.

[0006] The embodiments of this utility model are implemented as follows:

[0007] This invention provides a silicon carbide single crystal growth apparatus, comprising: a crucible having a receiving cavity; a seed crystal holder disposed on top of the receiving cavity; and a carbon felt layer disposed between the seed crystal holder and the top wall of the crucible. By setting up the crucible, seed crystal holder, and carbon felt layer, a stable single crystal growth environment is formed. The carbon felt layer effectively insulates heat and reduces heat radiation loss, improving the uniformity and stability of crystal growth. This structure optimizes the axial temperature gradient, making the temperature distribution at the crystal growth interface more uniform, which is beneficial for suppressing dislocation defect aggregation, reducing crystal defects caused by thermal stress, and improving single crystal quality.

[0008] In an optional embodiment, the seed crystal holder is a ring-shaped structure, and the radial outer edge of the carbon felt layer is coplanar with the radial inner edge of the ring-shaped structure. The ring-shaped seed crystal holder and the coplanar arrangement of the outer and inner edges of the carbon felt layer ensure a symmetrical thermal field distribution, avoid crystal defects caused by uneven edge thermal stress, and improve the quality of the single crystal.

[0009] In an optional embodiment, the carbon felt layer includes a first carbon felt portion and a second carbon felt portion surrounding the first carbon felt portion, wherein the density of the first carbon felt portion is greater than the density of the second carbon felt portion. Employing a composite carbon felt layer structure with a high-density center and a low-density periphery can adjust the thermal field distribution and compensate for excessively rapid heat dissipation at the edges. The high-density central region enhances axial thermal insulation, while the low-density peripheral region reduces radial heat loss, thereby optimizing radial temperature uniformity during crystal growth and reducing dislocation density.

[0010] In an optional embodiment, the density of the first carbon felt portion is 0.12–0.15 g / cm³. 3 The density of the second carbon felt portion is 0.10–0.11 g / cm³. 3 The density of the first carbon felt portion is limited to 0.12–0.15 g / cm³. 3 The density of the second carbon felt portion is 0.10–0.11 g / cm³. 3 This design ensures higher thermal resistance in the central region, reducing axial heat conduction, while maintaining appropriate thermal conductivity in the edge regions to prevent sudden temperature drops. This density gradient design significantly improves the thermal stability of the crystal growth interface and reduces microtube defects.

[0011] In optional embodiments, the carbon felt layer has a thickness of 5–15 mm, and / or, the ash content of the carbon felt layer is less than 100 ppm, and / or, the carbon felt layer is a porous fiber structure with a porosity >90%. A carbon felt layer thickness of 5–15 mm provides sufficient thermal insulation while avoiding excessive obstruction of necessary heat conduction. An ash content <100 ppm ensures high material purity, prevents impurities from volatilizing and contaminating the crystal at high temperatures, and improves the chemical stability and electrical properties of the SiC single crystal. The porous fiber structure (porosity >90%) of the carbon felt layer transforms the radiative heat transfer from the high-temperature region (>2000℃) to the seed crystal holder into a combined solid-state thermal conductivity and gas convection heat transfer.

[0012] In an optional embodiment, the thickness of the carbon felt layer is 8–12 mm. Further optimizing the carbon felt layer thickness to 8–12 mm ensures thermal insulation while avoiding excessive thermal inertia due to excessive thickness, which could affect crystal growth rate control. This thickness range has been experimentally verified to effectively balance the axial thermal gradient and growth kinetics requirements.

[0013] In an optional embodiment, a tantalum sheet cover is further included, disposed between the carbon felt layer and the top wall of the crucible. The tantalum sheet cover has a main body covering the top surface of the carbon felt layer and a side portion extending axially downward from the edge of the main body, the side portion covering the side wall of the carbon felt layer. The design of the tantalum sheet cover (covering the top surface and side wall of the carbon felt layer) effectively prevents the high-temperature volatilization of carbon fibers from contaminating the crystal, while reducing heat radiation loss. The high-temperature resistance of tantalum (melting point > 3000℃) ensures its stability at the SiC growth temperature, avoiding reaction with the carbon felt layer.

[0014] In an optional embodiment, the radial outer edge of the tantalum sheet cover is coplanar with the radial outer edge of the seed crystal holder. This design better covers the top surface and sidewalls of the carbon felt layer, effectively preventing the high-temperature volatilization of carbon fibers from contaminating the crystal, while also reducing heat radiation loss.

[0015] In an optional embodiment, the thickness of the tantalum sheet cover is 0.05–0.15 mm, such as 0.1 mm. A tantalum sheet cover thickness of 0.05–0.15 mm ensures mechanical strength while minimizing interference with the thermal distribution. Too thin a sheet is prone to breakage, while too thick a sheet increases heat capacity; this range, when optimized, balances protection and thermal performance.

[0016] In an optional embodiment, a conical guide tube is included, the larger diameter end of which is connected to the side wall of the crucible, and the smaller diameter end of which is connected to the seed crystal holder. The conical guide tube connects the crucible side wall and the seed crystal holder, guiding the gas phase transport path and optimizing raw material transport efficiency. Its conical structure helps to form a stable convection field, reducing compositional fluctuations caused by turbulence and improving crystal compositional uniformity.

[0017] In an optional embodiment, the conical flow guide is made of tantalum carbide. The flow guide, made of tantalum carbide (TaC), possesses both a high melting point (3880°C) and chemical inertness, preventing reaction with SiC vapor. Its thermal conductivity (20–25 W / (m·K)) falls between that of graphite and carbon felt, which helps regulate local heat flow distribution.

[0018] In an optional embodiment, the crucible is a graphite crucible, which provides excellent high-temperature stability and thermal uniformity. Its high thermal conductivity (80–100 W / (m·K)) ensures rapid response in the thermal field. This complements the low thermal conductivity of the carbon felt layer, together constructing a controllable gradient thermal field, suitable for the PVT method to grow large-size, low-defect SiC single crystals.

[0019] The beneficial effects of the silicon carbide single crystal growth apparatus of this utility model embodiment include: the silicon carbide single crystal growth apparatus provided in this application, by setting a carbon felt layer sandwiched between the seed crystal holder and the top wall of the crucible, can effectively reduce the heat transferred to the seed crystal by thermal radiation when the seed crystal is fixed in the seed crystal holder. This structure optimizes the axial temperature gradient, making the temperature distribution at the crystal growth interface more uniform, which is beneficial to suppressing the aggregation of dislocation defects, reducing crystal defects caused by thermal stress, and improving the quality of single crystals. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the silicon carbide single crystal growth apparatus in an embodiment of the present invention.

[0022] icon:

[0023] 1-Crucible 2-Seed crystal holder 3-Seed crystal

[0024] 4-First carbon felt section; 5-Second carbon felt section; 6-Tantalum sheet cover

[0025] 7-Conical guide tube; 8-Silicon carbide raw material Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use. They are only for the convenience of describing this utility model 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 utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0031] Please refer to Figure 1 Some embodiments of this application provide a silicon carbide single crystal growth apparatus, including: a crucible 1 having a receiving cavity; a seed crystal holder 2 disposed on top of the receiving cavity; and a carbon felt layer disposed between the seed crystal holder 2 and the top wall of the crucible 1. The receiving cavity is used to hold silicon carbide raw material 8, and the seed crystal holder 2 can be a columnar support made of high-strength graphite, used to fix the seed crystal 3.

[0032] In at least one of the above embodiments, the thermal conductivity of the carbon felt layer is low, much lower than that of graphite (80-100 W / (m·K). By setting the carbon felt layer between the seed crystal holder 2 and the top wall of the crucible 1, not only is the axial temperature gradient reduced, but the lateral thermal conductivity is also reduced. Thus, a controllable thermal resistance channel is constructed through the carbon felt layer, avoiding dislocation slip accumulation caused by steep axial temperature gradient and reducing the probability of dislocation convergence towards the center caused by growth interface depression.

[0033] By constructing a controllable thermal resistance channel using a carbon felt layer, axial heat conduction is effectively weakened, significantly reducing the axial temperature gradient near the seed crystal / crystal growth interface and suppressing the generation and aggregation of thermal stress-induced dislocations. Compared to graphite pads, the carbon felt layer exhibits significantly lower thermal conductivity; compared to air gap insulation, it improves mechanical stability and prevents thermal field oscillations. This design is simple in structure, highly compatible, and provides an effective solution for improving SiC crystal quality.

[0034] As can be seen from the above, the silicon carbide single crystal growth apparatus provided in the embodiments of this application, by setting a carbon felt layer between the seed crystal holder 2 and the top wall of the crucible 1, and fixing the seed crystal 3 inside the seed crystal holder 2, can effectively reduce the heat transferred to the seed crystal 3 by thermal radiation. This structure optimizes the axial temperature gradient, making the temperature distribution at the crystal growth interface more uniform, which is beneficial to suppressing the aggregation of dislocation defects, reducing crystal defects caused by thermal stress, and improving the quality of single crystals.

[0035] In some embodiments of this application, the seed crystal holder 2 is a ring-shaped structure, and the radial outer edge of the carbon felt layer is coplanar with the radial inner edge of the ring-shaped structure, that is, the radial outer edge of the carbon felt layer is coplanar with the radial outer edge of the seed crystal 3 disposed within the seed crystal holder 2. This ensures a symmetrical thermal field distribution, avoids heat leakage at the outer edge of the carbon felt layer, and also avoids crystal defects caused by uneven edge thermal stress, thereby improving the quality of the single crystal.

[0036] In some embodiments of this application, the carbon felt layer is a disk-shaped structure with dimensions consistent with the seed crystal 3. The axial thermal conductivity of the carbon felt layer is ≤1.5 W / (m·K), and the carbon felt layer is a porous fiber structure with a porosity >90%. By placing the carbon felt layer between the seed crystal holder 2 and the top wall of the crucible 1: 1. It blocks radiative heat transfer: the porous fiber structure (porosity >90%) of the carbon felt layer converts the radiative heat transfer from the high-temperature zone (>2000℃) to the seed crystal holder 2 into a composite heat transfer of solid conduction and gas convection; 2. It smooths the gradient: the temperature of the upper surface of the seed crystal holder 2 increases due to the effect of the heat insulation layer, reducing the temperature difference between it and the crystal growth interface; the axial gradient is significantly smoothed from the seed crystal 3 to the crystal direction; 3. It suppresses defects: the low dislocation density crystal continues to grow under low stress.

[0037] In some embodiments of this application, the carbon felt layer includes a first carbon felt portion 4 and a second carbon felt portion 5 surrounding the first carbon felt portion 4, wherein the density of the first carbon felt portion 4 is greater than the density of the second carbon felt portion 5. Employing a composite carbon felt layer structure with a high density at the center and a low density at the periphery can adjust the thermal field distribution and compensate for the problem of excessively rapid heat dissipation at the edges. The high-density central region enhances axial thermal insulation, while the low-density peripheral region reduces radial heat loss, thereby optimizing the radial temperature uniformity during crystal growth and reducing dislocation density.

[0038] In some embodiments of this application, the density of the carbon felt layer is 0.1-0.15 g / cm³. 3 .

[0039] In some embodiments of this application, the density of the first carbon felt portion 4 is 0.12–0.15 g / cm³. 3 The density of the second carbon felt portion 5 is 0.10–0.11 g / cm³. 3 The density of the first carbon felt portion 4 is limited to 0.12–0.15 g / cm³. 3 The density of the second carbon felt part 5 is 0.10–0.11 g / cm³. 3 This design ensures higher thermal resistance in the central region, reducing axial heat conduction, while maintaining appropriate thermal conductivity in the edge regions to prevent sudden temperature drops. This density gradient design significantly improves the thermal stability of the crystal growth interface and reduces microtube defects.

[0040] In some embodiments of this application, the thickness of the carbon felt layer is 5–15 mm, and the ash content of the carbon felt layer is less than 100 ppm. This application embodiment introduces a high-purity carbon felt layer of a specific thickness between the seed crystal holder 2 and the crucible 1 as a controllable thermal resistance. This structure effectively weakens axial heat conduction, significantly reduces the axial temperature gradient near the seed crystal 3 / crystal growth interface, thereby suppressing the generation and aggregation of thermal stress-induced dislocations. This design is simple, highly compatible, and provides an effective solution for improving the quality of SiC crystals. A carbon felt layer thickness of 5–15 mm provides sufficient thermal insulation while avoiding excessive obstruction of necessary heat conduction. An ash content of <100 ppm ensures high material purity, prevents impurities from volatilizing and contaminating the crystal at high temperatures, and improves the chemical stability and electrical properties of SiC single crystals.

[0041] In some embodiments of this application, the thickness of the carbon felt layer is 8–12 mm. Further optimizing the carbon felt layer thickness to 8–12 mm ensures thermal insulation while avoiding excessive thermal inertia due to excessive thickness, which could affect crystal growth rate control. This thickness range has been experimentally verified to effectively balance the axial thermal gradient and growth kinetics requirements.

[0042] In some embodiments of this application, a tantalum sheet cover 6 is further included. The radial outer edge of the tantalum sheet cover 6 is coplanar with the radial outer edge of the seed crystal holder 2. The tantalum sheet cover 6 is disposed between the carbon felt layer and the top wall of the crucible 1. The tantalum sheet cover 6 has a main body covering the top surface of the carbon felt layer and a covering portion extending axially downward from the edge of the main body. The covering portion covers the sidewall of the carbon felt layer. The covering design of the tantalum sheet cover 6 (covering the top surface and sidewall of the carbon felt layer) can effectively prevent the high-temperature volatilization of carbon fibers from contaminating the crystal, while reducing heat radiation loss. The high-temperature resistance of tantalum (melting point > 3000℃) ensures its stability at the SiC growth temperature, avoiding reaction with the carbon felt layer.

[0043] In some embodiments of this application, the thickness of the tantalum sheet cover 6 is 0.05–0.15 mm, such as 0.1 mm. The thickness of the tantalum sheet cover 6, 0.05–0.15 mm, ensures mechanical strength while minimizing interference with the thermal field distribution. Too thin a layer is prone to breakage, while too thick a layer increases heat capacity; this range, when optimized, balances protection and thermal performance.

[0044] In some embodiments of this application, a conical guide tube 7 is included. The large-diameter end of the conical guide tube 7 is connected to the side wall of the crucible 1, and the small-diameter end of the conical guide tube 7 is connected to the seed crystal holder 2. The conical guide tube 7 connects the side wall of the crucible 1 and the seed crystal holder 2, which can guide the gas phase transport path and optimize the raw material transport efficiency. Its conical structure helps to form a stable convection field, reduce compositional fluctuations caused by turbulence, and improve the uniformity of crystal composition.

[0045] In some embodiments of this application, the conical flow guide 7 is made of tantalum carbide. The flow guide 7 uses tantalum carbide (TaC), which combines a high melting point (3880°C) and chemical inertness, preventing reaction with SiC vapor. Its thermal conductivity (20–25 W / (m·K)) is between that of graphite and carbon felt, which helps to regulate the local heat flow distribution.

[0046] In some embodiments of this application, the crucible 1 is a graphite crucible 1, which provides excellent high-temperature stability and thermal uniformity. Its high thermal conductivity (80–100 W / (m·K)) ensures rapid response in the thermal field. It complements the low thermal conductivity of the carbon felt layer, together constructing a controllable gradient thermal field, suitable for the growth of large-size, low-defect SiC single crystals by the PVT method.

[0047] In summary, the silicon carbide single crystal growth apparatus provided in the embodiments of this application, by setting a carbon felt layer between the seed crystal holder 2 and the top wall of the crucible 1, and fixing the seed crystal 3 inside the seed crystal holder 2, can effectively reduce the heat transferred to the seed crystal 3 by thermal radiation. This structure optimizes the axial temperature gradient, making the temperature distribution at the crystal growth interface more uniform, which is beneficial for suppressing the aggregation of dislocation defects, reducing crystal defects caused by thermal stress, and improving the quality of single crystals.

[0048] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A silicon carbide single crystal growth apparatus, characterized in that, include: A crucible (1) having a receiving cavity; Seed crystal holder (2), which is disposed at the top of the receiving cavity; A carbon felt layer is disposed between the seed crystal holder (2) and the top wall of the crucible (1).

2. The silicon carbide single crystal growth apparatus of claim 1, wherein The seed crystal holder (2) has a ring structure, and the radial outer edge of the carbon felt layer and the radial inner edge of the ring structure are coplanar.

3. The silicon carbide single crystal growth apparatus according to claim 1, characterized in that, The carbon felt layer includes a first carbon felt portion (4) and a second carbon felt portion (5) disposed around the first carbon felt portion (4), wherein the density of the first carbon felt portion (4) is greater than the density of the second carbon felt portion (5).

4. The silicon carbide single crystal growth apparatus according to claim 3, characterized in that, The density of the first carbon felt portion (4) is 0.12–0.15 g / cm³. 3 The density of the second carbon felt portion (5) is 0.10–0.11 g / cm³. 3 .

5. The silicon carbide single crystal growth apparatus according to claim 1, characterized in that, The carbon felt layer has a thickness of 5–15 mm, and / or the ash content of the carbon felt layer is less than 100 ppm, and / or the carbon felt layer is a porous fiber structure with a porosity > 90%.

6. The silicon carbide single crystal growth apparatus of claim 5, wherein The thickness of the carbon felt layer is 8–12 mm.

7. The silicon carbide single crystal growth apparatus of any of claims 1-6, wherein, It also includes a tantalum sheet cover (6), which is disposed between the carbon felt layer and the top wall of the crucible (1). The tantalum sheet cover (6) has a main body covering the top surface of the carbon felt layer and a side portion extending axially downward from the edge of the main body, the side portion covering the side wall of the carbon felt layer.

8. The silicon carbide single crystal growth apparatus of claim 7, wherein The thickness of the tantalum sheet cover (6) is 0.05 to 0.15 mm, and / or the radial outer edge of the tantalum sheet cover (6) is coplanar with the radial outer edge of the seed crystal holder (2).

9. The silicon carbide single crystal growth apparatus of any of claims 1-6, wherein, It includes a conical guide tube (7), the large-diameter end of which is connected to the side wall of the crucible (1), and the small-diameter end of which is connected to the seed crystal holder (2).

10. The silicon carbide single crystal growth apparatus according to claim 9, characterized in that, The conical guide tube (7) is made of tantalum carbide material, and / or the crucible (1) is a graphite crucible.

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