Growth device for maintaining aluminum source supply for growing silicon carbide single crystal by liquid phase method
By employing graphite side plates and alternating stacking structures in the liquid-phase silicon carbide single crystal growth device, the problem of uneven crystal doping caused by aluminum source volatilization was solved, improving crystal quality and production efficiency while reducing costs.
Patent Information
- Application Number
- CN202520035660.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2026-01-27
- Estimated Expiration
- 2035-01-07
AI Technical Summary
Existing liquid-phase silicon carbide single crystal growth equipment suffers from inconsistent crystal doping levels due to aluminum source volatilization at high temperatures, resulting in deteriorated crystal quality and impacting yield and cost.
The crucible is divided into two cavities by a graphite side plate, which are used to hold aluminum supplement and silicon material respectively. Gas is supplied to supplement aluminum and carbon elements through a seed crystal rod, and a multi-layer structure of alternating stacked graphite layers and aluminum foil layers is used to maintain a uniform supply of aluminum and carbon.
It significantly improves the quality and surface morphology of silicon carbide single crystals, increases the growth time in a single furnace, reduces production costs, and reduces the failure rate of experiments.
Smart Images
Figure CN223837643U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of silicon carbide single crystal production equipment, and in particular to a growth device for maintaining the supply of aluminum source for growing silicon carbide single crystals by liquid phase method. Background Technology
[0002] Silicon carbide (SiC), as a novel wide-bandgap semiconductor material, exhibits great potential in the manufacture of high-frequency, high-voltage, and high-power power electronic devices due to its high potential, wide bandgap, large breakdown field, high thermal conductivity, excellent radiation resistance, and good chemical stability. It also demonstrates significant application value in electric vehicles, rail transportation, 5G communications, and aerospace. The supply of high-quality, large-size, and low-cost silicon carbide single-crystal substrates is a prerequisite for the large-scale application of silicon carbide single crystals. However, the current production of silicon carbide single-crystal substrates is still affected by problems such as high defect density, low yield, and high cost. This not only affects the application range of silicon carbide single crystals but also limits their promotion in various high-end fields. Liquid phase epitaxy (LPE), due to its advantages such as low dislocation density and low crystal growth cost, has gradually attracted industry attention in recent years and is used to produce high-quality silicon carbide single crystals.
[0003] Liquid-phase growth of silicon carbide single crystals involves dissolving carbon from a graphite crucible using a silicon or silicon alloy melt at high temperatures. Through the combined effects of convective and diffusion mass transfer, recrystallization occurs at the seed crystal growth surface, resulting in the growth of the silicon carbide single crystal. In liquid-phase epitaxy, to maintain a sufficient carbon supply, transition metals or rare earth elements are typically added to the solution to increase carbon solubility. High-concentration p-type doping is achieved by adding aluminum. During silicon carbide single crystal growth, especially at high temperatures, when aluminum is used as the p-type dopant, the aluminum source volatilizes, causing a decrease in aluminum source concentration. This leads to inconsistent doping levels in the crystal, affecting its overall electrical properties and reliability. Furthermore, as the growth time increases, the solution composition gradually deviates from the ideal state, further deteriorating the quality of the silicon carbide single crystal. Therefore, there is an urgent need for a device or method that can maintain a stable aluminum source concentration within the growth chamber.
[0004] This invention provides a growth device for maintaining the supply of aluminum source in liquid phase growth of silicon carbide single crystals, in order to solve the problems of inconsistent crystal doping levels and crystal quality degradation caused by the volatilization of aluminum source at high temperatures in existing growth devices. Utility Model Content
[0005] The purpose of this invention is to provide a growth device for maintaining the supply of aluminum source for growing silicon carbide single crystals in the liquid phase method, so as to solve the problems of inconsistent crystal doping levels and crystal quality deterioration caused by the volatilization of aluminum source at high temperatures in existing growth devices.
[0006] The technical solution of this utility model is: a growth device for maintaining the supply of aluminum source for growing silicon carbide single crystals by liquid phase method, comprising an external heating crucible with an insulation layer and a heater on its outer side, a seed crystal assembly, and a graphite crucible assembly; the graphite crucible assembly is disposed inside the external heating crucible; the seed crystal assembly is disposed above the graphite crucible assembly and extends into the graphite crucible assembly;
[0007] The graphite crucible assembly includes a crucible body with a top opening, a top cover sealing the crucible body, and a graphite side plate disposed inside the crucible body. The graphite side plate is coaxially arranged with the crucible body, and the graphite side plate divides the interior of the crucible body into two chambers. The two chambers include an inner growth chamber for accommodating silicon material used for silicon carbide single crystal growth and an Al clamping chamber for accommodating Al supplement material.
[0008] Preferably, the periphery of one end of the graphite side plate is connected to the bottom of the crucible body, so that the inner side surface of the graphite side plate and the bottom of the crucible body form the inner growth cavity, and the outer side surface of the graphite side plate and the inner sidewall of the crucible body form the Al clamping cavity; the periphery of the other end abuts against the top cover.
[0009] Preferably, the width of the Al clamping cavity is 5-15 mm;
[0010] The Al supplement is prepared from aluminum carbide powder through mixing, molding, pressing and sintering;
[0011] The Al supplement material is in the shape of a ring; the inner wall of the Al supplement material is in contact with the outer side of the graphite side plate, and the outer wall of the Al supplement material is in contact with the inner wall of the crucible body.
[0012] Preferably, the graphite side plate is a multi-layer structure with alternating stacked graphite layers and aluminum foil layers;
[0013] The thickness of the graphite side plate is 3-5 mm; the thickness of the crucible body is 10-15 mm.
[0014] Preferably, the top cover is provided with a through hole;
[0015] The seed crystal assembly includes a seed crystal rod and a silicon carbide seed crystal; one end of the seed crystal rod extends through the through hole into the inner growth cavity inside the crucible body, and the silicon carbide seed crystal is disposed on the end face.
[0016] Preferably, the seed crystal rod has an internal gas delivery channel.
[0017] Preferably, the seed crystal rod extends to one end inside the crucible body, and a plurality of vent holes are provided through it within a range of 7-17 cm from the end face where the silicon carbide seed crystal is located; the diameter of the plurality of vent holes is 0.1-0.5 mm.
[0018] Compared with the prior art, the advantages of this utility model are:
[0019] (1) This utility model provides a growth device for maintaining the supply of aluminum source for liquid phase growth of silicon carbide single crystals. The growth device divides the crucible body into two cavities by using graphite side plates, which are used to contain Al supplement and silicon material components respectively. This effectively separates the supply stages of aluminum and carbon, ensuring that sufficient carbon and aluminum can be supplied as needed at different stages of crystal growth. At the same time, the supplemented aluminum and carbon can be relatively uniformly distributed in the molten silicon material and transported to the crystal growth interface through diffusion and convection. This significantly improves the quality and surface morphology of silicon carbide single crystals during long-term growth, and helps to increase the total growth time in a single furnace, improve the utilization efficiency of raw materials, and further reduce production costs. This solves the problems of inconsistent crystal doping levels and crystal quality deterioration caused by the volatilization of aluminum source at high temperatures in existing devices.
[0020] (2) The present invention provides a growth device for maintaining the supply of aluminum source for growing silicon carbide single crystals by liquid phase method. The growth device can also deliver the gas required for single crystal growth to the interior of the inner growth cavity through the gas delivery channel on the seed crystal rod without interfering with the crystal growth thermal field. At the same time, several ventilation holes are set at appropriate positions on the seed crystal rod to allow the gas to be released evenly into the interior of the inner growth cavity to replenish aluminum, carbon and other elements, ensuring that the replenishment process will not have a negative impact on the solution temperature and thermal stability, thereby maintaining high-quality crystal growth conditions and reducing the experimental failure rate caused by insufficient aluminum supply. Attached Figure Description
[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments:
[0022] Figure 1 This is a cross-sectional view of the graphite crucible assembly described in this utility model;
[0023] Figure 2 This is a cross-sectional view of the growth apparatus described in this utility model;
[0024] The components are: 1. Crucible body; 2. Graphite side plate; 3. Top cover; 4. Inner growth cavity; 41. Silicon material; 5. Al clamping cavity; 51. Al supplement material; 6. Through hole; 7. External heating crucible; 8. Seed crystal assembly; 81. Seed crystal rod; 82. Silicon carbide seed crystal; 83. Gas delivery channel; 84. Vent hole. Detailed Implementation
[0025] The present invention will be further described in detail below with reference to specific embodiments:
[0026] Implementation Method 1
[0027] A growth apparatus for maintaining the supply of aluminum source for growing silicon carbide single crystals in liquid phase includes an external heating crucible 7 disposed on its outer side, a graphite crucible assembly disposed inside the external heating crucible 7, and a seed crystal assembly 8. The outer surface of the external heating crucible 7 is covered with a heat insulation layer, and a heater is disposed on the outer side of the heat insulation layer. The heater heats the external heating crucible 7, and the heat insulation layer serves to keep the external heating crucible 7 warm. The seed crystal assembly 8 is disposed above the graphite crucible assembly and extends into the graphite crucible assembly. During long-term crystal growth, using graphite crucible components as a carbon source can lead to gradual consumption of the graphite crucible components under continuous high temperatures, potentially resulting in melt-through. Once the graphite crucible components melt through, the molten metal flows into the furnace, damaging the single crystal furnace, potentially interrupting the experiment, and causing significant economic losses. By placing the graphite crucible components in an externally heated crucible 7, which effectively transfers heat to the graphite crucible components under the action of a heater, the stability of the entire heating system can be effectively ensured. Even if the graphite crucible components are partially damaged, a constant heating effect can be maintained, supporting continuous crystal growth. This improves the efficiency and economy of the entire silicon carbide single crystal growth process. It also provides flexibility in experimental operation and the ability of the liquid phase growth device to adapt to different growth requirements of silicon carbide single crystals.
[0028] like Figure 1 As shown, the graphite crucible assembly includes a crucible body 1 with a top opening, a top cover 3, and a graphite side plate 2. The top cover 3 seals the crucible body 1 and has a through hole 6 through which the seed crystal assembly 8 passes. The graphite side plate 2 has a ring-shaped structure and is coaxially arranged with the crucible body 1. The periphery of one end of the graphite side plate 2 is connected to the bottom of the crucible body 1, dividing the interior of the crucible body 1 into two chambers: an inner growth cavity 4 formed between the inner side of the graphite side plate 2 and the bottom of the crucible body 1, and an Al cavity 5 formed between the outer side of the graphite side plate 2 and the inner wall of the crucible body 1. The inner growth cavity 4 is used to accommodate the silicon material 41 required for silicon carbide single crystal growth, and the Al cavity 5 is used to accommodate the Al supplement material 51. The periphery of the other end of the graphite side plate 2 abuts against the top cover 3. The seed crystal assembly 8 includes a seed crystal rod 81 and a silicon carbide seed crystal 82; one end of the seed crystal rod 81 extends through the through hole 6 and into the inner growth cavity 4 inside the crucible body 1, and a silicon carbide seed crystal 82 is provided on the end face of this end of the seed crystal rod 81.
[0029] Since the melting point of aluminum (Al) is actually about 660.3℃, while the temperature required for crystal growth in the inner growth cavity 4 is usually above 1800℃, a large amount of aluminum in the solution will volatilize under this high temperature condition. Therefore, without additional treatment, after 10-20 hours of silicon carbide single crystal growth, the Al concentration in the solution in the inner growth cavity 4 will decrease to half or less of the original raw material concentration. In order to reduce crystal defects caused by uneven doping and unstable material supply, it is necessary to supplement the aluminum source in the solution in the inner growth cavity 4 during the middle and later stages of crystal growth. At the same time, since the melting point of Al4C3 (aluminum carbide) is about 2100℃, this means that aluminum carbide will melt at a very high temperature, indicating that it has good thermal stability and is suitable as a supplementary aluminum source for high-temperature crystal growth in the later stage. Therefore, in this embodiment, aluminum carbide material is used as Al supplement material 51. The purpose of this design is to utilize the high melting point of aluminum carbide to ensure that aluminum is effectively supplemented during the critical stage of crystal growth.
[0030] In this embodiment, under high-temperature conditions, to ensure that the supplemented aluminum source is uniformly dispersed in the molten silicon material 41 to significantly improve the quality of crystal growth, it is necessary to ensure that aluminum carbide is uniformly distributed in the Al supplement 51. Therefore, the Al supplement 51 is formed into a ring structure by mixing, molding, pressing, and sintering aluminum carbide powder. Furthermore, the inner wall of the Al supplement 51 is attached to the outer side of the graphite side plate 2, and the outer wall of the Al supplement 51 is attached to the inner wall of the crucible body 1, so that the Al supplement 51 is fixedly placed in the Al cavity 5. This ensures that the Al supplement 51 will not move randomly during the early stage of growing P-type silicon carbide single crystals, thereby avoiding its impact on the growth quality of silicon carbide crystals. The width of the Al cavity 5, i.e., the distance between the outer side of the graphite side plate 2 and the inner wall of the crucible body 1, should be controlled within the range of 5-15 mm; correspondingly, the thickness of the Al supplement 51 should match the width of the Al cavity 5. However, during the growth of silicon carbide crystals, insufficient carbon source supply may occur. Therefore, in other embodiments, in order to supplement the carbon source while supplementing the aluminum source to the molten silicon material 41, the Al supplement 51 may also include other carbon-containing materials, such as graphite or silicon carbide. Furthermore, in other embodiments, the Al supplement 51 may also take other shapes, as long as it can ensure that it can provide a continuous aluminum source for the silicon carbide crystal growth stage.
[0031] In this embodiment, the graphite side plate 2 is composed of several graphite layers. During the growth of silicon carbide crystals, most of the carbon source is provided by the graphite side plate 2 and the crucible body 1. The thickness of the graphite side plate 2 is usually set in the range of 3-5 mm, and the thickness of the crucible body 1 is usually set in the range of 10-15 mm. In the early stage of crystal growth, the focus is on melting the silicon material 41 in the inner growth cavity 4. The graphite side plate 2, as a carbon source, will be gradually melted to supply carbon source into the inner growth cavity 4. As the crystal growth enters the middle and later stages, the graphite side plate 2 will be melted through first. After that, the melt in the inner growth cavity 4 begins to contact the Al supplement material 51 in the Al cavity 5. At this time, aluminum source is added to the melt that has been depleted due to long-term single crystal growth, thereby maintaining the component concentration required for single crystal growth. In other embodiments, the graphite side plate 2 can also be a multilayer structure with alternating stacked graphite layers and aluminum foil layers. Under high-temperature conditions, the aluminum foil layer gradually releases aluminum, which reacts with graphite to form aluminum carbide. This helps maintain chemical equilibrium during growth and reduces crystal defects caused by uneven doping and unstable material supply. Furthermore, the aluminum foil layer is positioned in the middle of the graphite layer to prevent premature volatilization of aluminum due to direct contact between the aluminum foil layer and silicon material 41 in the early stages of crystal growth. In addition, at approximately 700°C, the aluminum foil can react with graphite within the graphite layer to generate aluminum carbide. The alternating stacking of aluminum foil layers and graphite layers forms a multilayer structure, which increases the contact area between aluminum and graphite, reduces local overheating or undercooling areas, ensures the thermal stability of crystal growth, and ensures a uniform supply of aluminum and carbon throughout the crystal growth process. This helps achieve more uniform P-type doping, thereby improving the electrical performance of the final SiC single crystal. At the same time, mechanical compaction and other methods can be used to ensure a tight bond between the aluminum foil and the graphite layer, preventing aluminum foil displacement during growth.
[0032] Implementation Method 2
[0033] The difference between this implementation method and implementation method one is that: Figure 2 As shown, the seed crystal rod 81 is designed as a hollow structure, forming a gas delivery channel 83 inside, which is used to deliver the gas required for single crystal growth, such as aluminum-containing gas and carbon-containing gas, into the inner growth chamber 4. Furthermore, on one end of the seed crystal rod 81 extending into the crucible body 1, several vent holes 84 are provided within a range of 7-17 cm from the end face where the silicon carbide seed crystal 82 is located. The several vent holes 84 are evenly arranged along the circumference of the seed crystal rod 81 to uniformly release the gas into the single crystal growth environment. The diameter of each of the several vent holes 84 is 0.1-0.5 mm. The setting of these small-diameter and numerous vent holes 84 can not only reduce the local disturbance caused by a single hole and increase the uniformity of gas diffusion, but also avoid the gas directly impacting the growth interface and affecting the thermal stability of the solution, and avoid local oversaturation or undersaturation of the solution system.
[0034] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. It is obvious to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and therefore, all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within this utility model.
Claims
1. A growth apparatus for maintaining the supply of aluminum source in liquid-phase silicon carbide single crystal growth, characterized in that, The system includes an external heating crucible (7) with an insulation layer and a heater on its outer surface, a seed crystal assembly (8), and a graphite crucible assembly; the graphite crucible assembly is disposed inside the external heating crucible (7); the seed crystal assembly (8) is disposed above the graphite crucible assembly and extends into the graphite crucible assembly; The graphite crucible assembly includes a crucible body (1) with a top opening, a top cover (3) covering the crucible body (1), and a graphite side plate (2) disposed inside the crucible body (1). The graphite side plate (2) is coaxially disposed with the crucible body (1), and the graphite side plate (2) divides the interior of the crucible body (1) into two chambers. The two chambers include an inner growth chamber (4) for accommodating silicon material (41) used for silicon carbide single crystal growth and an Al clamping chamber (5) for accommodating Al supplement material (51).
2. The growth apparatus for maintaining aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 1, characterized in that: The periphery of one end of the graphite side plate (2) is connected to the bottom of the crucible body (1), so that the inner side surface of the graphite side plate (2) and the bottom of the crucible body (1) form the inner growth cavity (4), and the outer side surface of the graphite side plate (2) and the inner side wall of the crucible body (1) form the Al clamping cavity (5); the periphery of the other end abuts against the top cover (3).
3. The growth apparatus for maintaining the aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 2, characterized in that: The width of the Al clamping cavity (5) is 5-15mm; The Al supplement (51) is prepared by mixing, molding, pressing and sintering aluminum carbide powder; The Al supplement (51) is in the shape of a ring; the inner wall of the Al supplement (51) is attached to the outer side of the graphite side plate (2), and the outer wall of the Al supplement (51) is attached to the inner wall of the crucible body (1).
4. The growth apparatus for maintaining the aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 2, characterized in that: The graphite side plate (2) is a multi-layer structure with alternating stacked graphite layers and aluminum foil layers; The thickness of the graphite side plate (2) is 3-5 mm; the thickness of the crucible body (1) is 10-15 mm.
5. The growth apparatus for maintaining the aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 2, characterized in that: The top cover (3) is provided with a through hole (6); The seed crystal assembly (8) includes a seed crystal rod (81) and a silicon carbide seed crystal (82); one end of the seed crystal rod (81) extends through the through hole (6) and into the inner growth cavity (4) inside the crucible body (1), and the silicon carbide seed crystal (82) is provided on the end face.
6. The growth apparatus for maintaining aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 5, characterized in that: The seed crystal rod (81) is provided with a gas delivery channel (83).
7. The growth apparatus for maintaining aluminum source supply in liquid-phase silicon carbide single crystal growth according to claim 6, characterized in that: The seed crystal rod (81) extends to one end inside the crucible body (1), and a plurality of ventilation holes (84) are provided through it within a range of 7-17 cm from the end face where the silicon carbide seed crystal (82) is located; the diameter of the plurality of ventilation holes (84) is 0.1-0.5 mm.