A method for preparing a large-size single crystal by a crucible-free method
By using a multi-seed crystal splicing and iterative growth method, the problem of difficult diameter expansion in crucible-free methods has been solved, enabling the preparation of low-cost, large-size, high-quality gallium oxide single crystals and providing a completely new technical path.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU FUJIA GALLIUM TECH CO LTD
- Filing Date
- 2026-03-25
- Publication Date
- 2026-06-05
AI Technical Summary
Existing crucibleless methods face challenges in expanding the diameter of large-size gallium oxide single crystals, limiting crystal size and increasing the cost of obtaining large-size seed crystals, thus creating technical and cost bottlenecks.
Multiple small-sized seed crystals are spliced together to form a large-sized composite seed crystal. Through crystal orientation competition and directional thermal field control, the dominant single crystal region is expanded during the single crystal growth process. Grain boundaries are gradually eliminated through iterative growth, and finally a large-sized single crystal is obtained.
This method enables the low-cost preparation of high-quality large-size single crystals that are much larger than the initial seed crystal size, breaking through the diameter expansion limitations of the traditional crucibleless method and reducing the preparation cost.
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Figure CN122147543A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor material preparation technology, and in particular to a crucible-free method for preparing large-size single crystals. Background Technology
[0002] Gallium oxide (Ga2O3), as an ultrawide bandgap semiconductor material, has shown great application potential in power electronic devices, deep ultraviolet optoelectronic devices, and other fields. The fabrication of high-quality, large-size gallium oxide single crystals is key to its industrial application. Currently, mainstream single crystal growth methods include the EFG (Extended-Fed Growth) method, the Czochralski (CZ) method, and the crucible-drop (VB) method. In recent years, a crucible-free top-fed growth method (DG) has attracted attention due to its ability to effectively avoid crucible contamination and reduce costs.
[0003] The core feature of the DG method is the use of two temperature zones within the growth chamber: an upper zone for melting the raw material and a lower zone for crystal growth. Induction heating is used to achieve both the melting of the raw material and the growth of the crystal. While this method avoids the use of expensive and easily contaminated iridium crucibles, it has inherent challenges in crystal diameter expansion (shoulder formation), specifically as follows: 1. Difficulty in diameter expansion and limitation of crystal size: Due to the lack of constraint from the crucible sidewalls, the melt relies mainly on surface tension to maintain its position on the seed crystal surface, making it difficult to achieve stable and significant diameter expansion. Therefore, to grow a 4-inch crystal, a seed crystal of nearly 4 inches is usually required, which greatly limits further breakthroughs in crystal size.
[0004] 2. High cost of obtaining large-size seed crystals: Due to the difficulty of diameter expansion, there is a strong dependence on large-size seed crystals. However, the preparation of large-size, high-quality seed crystals is difficult and costly, forming a bottleneck in both technology and cost. Therefore, there is an urgent need for a new method that can overcome the limitations of existing crucibleless diameter expansion methods and achieve low-cost, large-size, high-quality gallium oxide single crystal preparation. Summary of the Invention In view of the shortcomings of the prior art, the purpose of this invention is to provide a crucible-free method for preparing large-size single crystals, which aims to solve the problems of difficulty in diameter expansion, limited crystal size, and high cost of obtaining large-size seed crystals in the existing crucible-free method.
[0005] The technical solution of the present invention is as follows: A crucibleless method for preparing large-size single crystals, comprising the following steps: a. Provide multiple small-sized seed crystals, wherein the seed crystals are single-crystal seed crystals; b. The multiple small-sized seed crystals are spliced together to form a large-sized composite seed crystal; c. Single crystal growth is performed on the composite seed crystal. During the single crystal growth process, the single crystal region with growth advantage gradually expands and occupies a dominant position through crystal orientation competition. d. The grown single crystal, whose single crystal region has expanded and become dominant, is processed into a new seed crystal for the next round of splicing and growth; e. Repeat steps bd to obtain a large-size single crystal.
[0006] The crucibleless method for preparing large-size single crystals is described above, wherein the multiple small-size seed crystals have the same thickness, which is 5-20 mm.
[0007] The crucibleless method for preparing large-size single crystals is described in which the large surface of each small-size seed crystal is the same crystal plane, and the splicing surface of two small-size seed crystals is flat and is the same crystal plane.
[0008] The crucibleless method for preparing large-size single crystals involves splicing together multiple fan-shaped small-size seed crystals to form a circular large-size composite seed crystal. Alternatively, a small circular seed crystal and multiple fan-shaped small seed crystals surrounding the small circular seed crystal can be spliced together to form a large circular composite seed crystal.
[0009] The crucibleless method for preparing large-size single crystals, wherein, The region where the single crystal region expands and dominates is defined as the target region, and the region outside the target region is defined as the non-target region. A heat-insulating baffle is installed above the side of the non-target area to suppress the growth of single crystals in the non-target area.
[0010] The crucibleless method for preparing large-size single crystals is described above, wherein the region in which the single crystal region is expanded and dominates is defined as the target region; Cooling gas is concentrated and blown toward the upper or side surface of the target area by an airflow guiding device to promote the growth of single crystals in the target area.
[0011] In the crucibleless method for preparing large-size single crystals, the temperature of the target region is lower than the temperature of the non-target region, and the temperature difference between the non-target region and the target region is controlled within 5°C.
[0012] The crucibleless method for preparing large-size single crystals involves splicing a small circular seed crystal and four fan-shaped small seed crystals surrounding the small circular seed crystal to form a large circular composite seed crystal. During the single crystal growth process, cooling gas is concentrated and blown onto the upper surface of the central circular region through an airflow guiding device to promote single crystal growth in the central circular region.
[0013] The method for preparing large-size single crystals without a crucible, wherein the single crystal is a gallium oxide single crystal, a sapphire single crystal, or a silicon carbide single crystal.
[0014] The crucibleless method for preparing large-size single crystals, wherein the large-size single crystal is a single crystal larger than 4 inches.
[0015] Beneficial Effects: This invention splices multiple small-sized seed crystals into a large-sized composite seed crystal, and then performs single-crystal growth on the composite seed crystal. Utilizing the minute crystal orientation differences between the spliced seed crystals, the single-crystal region with growth advantage gradually encroaches upon and covers other regions, thus expanding the area of the advantageous single crystal. The crystal with the expanded single-crystal region after a single growth is processed into a new seed crystal, and the splicing-growth process is repeated. Through multiple iterations, grain boundaries are gradually squeezed out, ultimately obtaining a large-sized single crystal without splicing defects, achieving a leap from small seed crystals to large-sized single crystals. This method of the present invention employs a "divide and conquer, iterative optimization" strategy, cleverly avoiding the difficulties of traditional diameter expansion processes. It can prepare high-quality single crystals much larger than the initial seed crystal size based on low-cost small-sized seed crystals, providing a new and effective technical path for breakthroughs in single crystal size (such as gallium oxide single crystals). Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the sector splicing method.
[0017] Figure 2 This is a schematic diagram of the central circle + ring splicing method.
[0018] Figure 3 This is a schematic diagram illustrating the competition during the growth of multiple seed crystals.
[0019] Figure 4 This is a schematic diagram illustrating the adjustment of heat dissipation pathways using localized heat insulation baffles.
[0020] Figure 5 This is a schematic diagram of a heat dissipation process achieved through airflow regulation.
[0021] Figure 6 This is a schematic diagram of the gas flow channel and nozzle for gas delivery during crystal growth.
[0022] Figure 7 This is a schematic diagram of the nozzle air delivery structure during crystal growth.
[0023] Figure 8 This is a schematic diagram showing the increase in size of the single crystal region after growth. Detailed Implementation
[0024] This invention provides a crucible-free method for preparing large-size single crystals. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0025] In recent years, a crucible-free top-fed growth method (DG) has attracted attention due to its ability to effectively avoid crucible contamination and reduce costs. The core feature of the DG method is the establishment of two temperature zones within the growth chamber: an upper zone for raw material melting and a lower zone for crystal growth. Induction heating is used to achieve both raw material melting and crystal growth. While this method avoids the use of expensive and easily contaminated iridium crucibles, it presents inherent challenges in crystal diameter expansion (shoulder formation), with the following specific drawbacks: 1. Difficulty in diameter expansion and limitation of crystal size: Due to the lack of constraint from the crucible sidewalls, the melt relies mainly on surface tension to maintain its position on the seed crystal surface, making it difficult to achieve stable and significant diameter expansion. Therefore, to grow a 4-inch crystal, a seed crystal of nearly 4 inches is usually required, which greatly limits further breakthroughs in crystal size.
[0026] 2. High cost of obtaining large-size seed crystals: Due to the difficulty of diameter expansion, there is a strong dependence on large-size seed crystals. However, the preparation of large-size, high-quality seed crystals is difficult and costly, forming a bottleneck in both technology and cost. Therefore, there is an urgent need for a new method that can overcome the limitations of existing crucibleless diameter expansion methods and achieve low-cost, large-size, high-quality gallium oxide single crystal preparation.
[0027] Based on this, embodiments of the present invention provide a crucible-free method for preparing large-size single crystals, comprising the following steps: a. Provide multiple small-sized seed crystals, wherein the seed crystals are single-crystal seed crystals; b. The multiple small-sized seed crystals are spliced together to form a large-sized composite seed crystal; c. Single crystal growth is performed on the composite seed crystal. During the single crystal growth process, the single crystal region with growth advantage gradually expands and occupies a dominant position through crystal orientation competition. d. The grown single crystal, whose single crystal region has expanded and become dominant, is processed into a new seed crystal for the next round of splicing and growth; e. Repeat steps bd to obtain a large-size single crystal.
[0028] This embodiment avoids the reliance on large initial seed crystals by splicing multiple small seed crystals into a large composite seed crystal, eliminating the need for a large initial seed crystal. Single crystal growth is then performed on the composite seed crystal. Utilizing the slight crystal orientation differences between the spliced seed crystals, the dominant single crystal region gradually encroaches upon and covers other regions, expanding the area of the dominant single crystal. The crystal with the expanded single crystal region after a single growth is processed into a new seed crystal. The splicing-growth process is repeated, gradually extruding grain boundaries through multiple iterations, ultimately obtaining a large single crystal without splicing defects, achieving a leap from small seed crystals to large single crystals.
[0029] This embodiment cleverly bypasses the difficulties of traditional diameter expansion processes by adopting a strategy of "breaking down the whole into parts and iterative optimization". It can prepare high-quality single crystals (sizes can reach more than 4 inches) that are much larger than the initial seed crystals based on low-cost small-sized seed crystals, providing a new and effective technical path for breakthroughs in the size of single crystals (such as gallium oxide single crystals).
[0030] In one implementation, step a specifically includes: Provide single crystals (such as gallium oxide single crystals); The single crystal is cut to obtain multiple small-sized seed crystals.
[0031] Furthermore, the multiple small seed crystals have the same thickness, ranging from 5 to 20 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, etc.
[0032] Furthermore, during the cutting process, an orientation tester is used to ensure that the large surface of each small seed crystal is the same crystal plane, and the splicing surface of each pair of small seed crystals is flat and is the same crystal plane. This ensures that the physical gap between each seed crystal is as small as possible during subsequent splicing, preferably less than 0.5 mm, while ensuring that the internal crystal orientation deviation of each seed crystal is as small as possible, preferably less than 2°.
[0033] After cutting, the splicing surfaces of the seed crystals are finely ground and polished to make them flat. This ensures that the seed crystals fit together tightly during the subsequent splicing process, minimizing the physical gaps between them and improving the splicing quality. This lays the foundation for obtaining high-quality, large-size single crystals.
[0034] In one embodiment, step b specifically includes: splicing the plurality of small-sized seed crystals according to a preset geometric configuration to form a large-sized composite seed crystal. This eliminates the need for a large-sized initial seed crystal, thus avoiding the reliance on large seed crystals in traditional crucible-free methods from the outset.
[0035] Among them, "multiple" can refer to two or more, such as two, three, four, five, six, etc.
[0036] The preset geometric configurations include, but are not limited to, the fan-shaped splicing method and the central circle + ring splicing method.
[0037] The aforementioned sector-shaped splicing method refers to splicing multiple small-sized seed crystals in a sector shape to form a large-sized circular composite seed crystal. In practice, the central angle and arc length of each small-sized seed crystal in a sector must be precisely calculated based on the diameter of the desired large-sized composite seed crystal to ensure a tight fit between the seed crystals after splicing, without gaps or misalignments. By sequentially splicing the various small-sized seed crystals in a sector shape to form a complete large-sized circular composite seed crystal, the foundation for subsequent crucible-free growth of large-sized single crystals is laid. Specifically, this can be achieved by dividing a circular region into N equal parts, and then piecing together N small-sized fan-shaped seed crystals to form a large-sized circular composite seed crystal, where N is an integer greater than or equal to 2. For example, prepare four small-sized circular seed crystals, and cut and process 90° fan-shaped seed crystals from each of the four small-sized circular seed crystals; then piece together the four 90° fan-shaped seed crystals to form a large-sized circular composite seed crystal, as shown below. Figure 1 As shown. The central circle + ring splicing method refers to splicing a small circular seed crystal with multiple fan-shaped small seed crystals surrounding it to form a large circular composite seed crystal. This method is beneficial for preferentially expanding the single crystal in the central region. In practice, the diameter of the desired large circular composite seed crystal is first determined. Based on this, a suitable small circular seed crystal is selected as the central circle. Then, according to the size relationship between the central circle and the large composite seed crystal, the number, central angle, and arc length of the fan-shaped small seed crystals required around the central circle are precisely calculated. The small circular seed crystal is placed at the predetermined center position, and multiple fan-shaped small seed crystals are sequentially spliced around the central circle, ensuring a tight fit between the seed crystals without gaps or misalignments. This ultimately forms a complete large circular composite seed crystal, creating conditions for subsequent crucible-free growth of large single crystals.
[0038] For example, prepare five small circular seed crystals, and cut out fan-shaped small seed crystals from four of them; then, splice the central small circular seed crystal with the four surrounding fan-shaped small seed crystals to form a large circular composite seed crystal, such as... Figure 2 As shown.
[0039] In this embodiment, when splicing seed crystals, a small amount of catalyst or crystal orientation inducer that can promote the growth of a specific crystal orientation can be pre-placed at the splicing seam, thereby more actively controlling the result of crystal orientation competition.
[0040] In this way, crystals can be guided to grow along specific crystal orientations during the growth process, reducing the generation of grain boundaries and defects and improving the quality of large-size single crystals. Furthermore, the selection of catalysts or crystal orientation inducers can be optimized based on specific materials and growth conditions to achieve the best growth results.
[0041] In step c, the composite seed crystal is placed on the support shaft of the growth device for single crystal growth. For example... Figure 3 As shown, during the single crystal growth process, due to the various seed crystals (such as...) Figure 3 The crystal orientations of seed crystals 1, 2, and 3 in the single crystal grow slightly (usually less than 2°), forming grain boundaries at the seams. As the single crystal grows upwards, competition for crystal orientation occurs between crystal crystals with different orientations. Under specific thermodynamic conditions (including temperature gradient, heat flow direction, and supercooling), the crystal orientation with growth advantage will grow faster, and its corresponding single crystal region will gradually encroach on and cover other regions, resulting in the continuous expansion of the area of the dominant single crystal region and its dominance.
[0042] To accelerate and guide the expansion of the dominant single-crystal region, an active thermal field control mechanism can be introduced. By employing various methods to create an asymmetric temperature field in the growth region, the direction of heat flow can be adjusted, and the shape of the solid-liquid growth interface can be altered, thereby promoting the expansion of the target single-crystal region.
[0043] In one implementation, the region where the single-crystal region is expanded and dominates is defined as the target region, and the region outside the target region is defined as the non-target region. A heat-insulating baffle is installed above the side of the non-target area to suppress the growth of single crystals in the non-target area.
[0044] like Figure 4 As shown, a heat-insulating baffle (material such as high-temperature ceramic zirconia or alumina) is placed above and to the side of the non-target area (i.e., the area where growth is to be inhibited). The baffle hinders heat dissipation from this area (i.e., heat dissipation is blocked in the non-target area), making its temperature relatively high; while the target area has a relatively low temperature due to normal heat dissipation. This temperature difference drives the solid-liquid interface to tilt, thereby accelerating the expansion of the target area.
[0045] Specifically, the size, shape, and placement of the heat insulation baffle can be precisely designed based on the actual size of the single crystal growth furnace, the shape and size of the single crystal, and the size of the target area. For example, the length of the baffle should be sufficient to cover the sides of the non-target area to ensure effective heat isolation; the shape of the baffle can be rectangular, trapezoidal, etc., depending on the spatial layout and heat flow distribution within the single crystal growth furnace; and the placement should be as close as possible to the non-target area to minimize heat loss through radiation. By rationally designing the heat insulation baffle, precise control of the target single crystal growth process can be achieved, improving the efficiency and quality of large-size single crystal preparation.
[0046] Taking gallium oxide single crystal growth as an example, the heat insulation baffle can be a zirconia material heat insulation baffle, and the thickness of the heat insulation baffle can be 2-5mm.
[0047] Zirconia heat insulation baffles possess high thermal resistance and excellent chemical stability, enabling them to operate stably for extended periods at high temperatures without deformation or damage. Their thickness, set at 2-5mm, effectively prevents heat loss from non-target areas without compromising the overall thermal field distribution and the normal growth process within the single crystal growth furnace due to excessive thickness. In practical applications, this thickness can be fine-tuned according to the specific process requirements of gallium oxide single crystal growth to achieve optimal growth results.
[0048] In another implementation, the region where the single-crystal region expands and becomes dominant is defined as the target region; Cooling gas is concentrated and blown toward the upper or side surface of the target area by an airflow guiding device to promote the growth of single crystals in the target area.
[0049] like Figures 5-7 As shown, by designing specific airflow channels and / or nozzles, cooling gases (such as nitrogen or argon) are concentrated and blown onto the upper surface or side of the target area, enhancing heat dissipation efficiency and making the temperature of the target area lower than that of the non-target area, forming a local low-temperature zone, thereby greatly promoting the lateral growth of the target area. Since the crystal growth process is sensitive to temperature and supercooling, excessively low temperatures can lead to the formation of impurities. Therefore, the temperature difference between the non-target area and the target area is controlled within 5°C.
[0050] For the growth of gallium oxide single crystals, the airflow channel or nozzle can use high-temperature ceramic materials, such as fused zirconium or high-purity alumina; the flow rate of the cooling gas can be controlled within 1L / min-10L / min, such as 1L / min, 2L / min, 5L / min, 1L / min, 8L / min, 10L / min, etc., to avoid overcooling leading to the formation of impurity crystals.
[0051] The shape of the airflow guiding channel can be straight, curved, or branched, depending on the location and shape of the target area, to ensure that the cooling gas is blown evenly and concentratedly onto the target area. The design of the nozzles is also important; their orifice size, shape, and arrangement all affect the gas flow rate and distribution. By optimizing the design of the airflow guiding device, the temperature distribution in the target area can be precisely controlled, thereby achieving fine-grained control of the single-crystal growth process in the target area.
[0052] In another implementation, an asymmetric temperature field that is conducive to the expansion of the target area can be created by setting auxiliary heaters in non-target areas or using insulation materials with adjustable thickness / density.
[0053] The power and location of the auxiliary heater can be adjusted according to actual needs to achieve precise temperature control in non-target areas. Variations in the thickness and density of the insulation material can also optimize the temperature in non-target areas. These measures help create an asymmetric temperature field conducive to the expansion of the target area, thereby promoting single-crystal growth in the target region.
[0054] In a preferred embodiment, a small circular seed crystal and four fan-shaped small seed crystals surrounding the small circular seed crystal are spliced together to form a large circular composite seed crystal; and during the single crystal growth process, cooling gas is concentrated and blown onto the upper surface of the central circular region through an airflow channel or nozzle to promote the single crystal growth in the central circular region.
[0055] The assembled circular large-size composite seed crystal is placed on the support shaft of the crucibleless growth apparatus. The airflow channel or nozzle is opened, allowing cooling gas to be precisely and stably concentrated and blown onto the upper surface of the central circular region at a set flow rate, as mentioned above. During single crystal growth, the temperature of the central circular region and surrounding areas is continuously monitored. The flow rate of the cooling gas is adjusted in a timely manner according to temperature changes to ensure that the temperature difference between the central circular region and the non-target areas is always controlled within 5°C. This ensures the quality and stability of single crystal growth and effectively promotes single crystal growth in the central circular region.
[0056] In step e, through multiple iterations, a breakthrough in size is achieved, ultimately resulting in a large-size single crystal.
[0057] The core of this embodiment lies in "iteration". After one growth cycle, the obtained single crystal may still contain some grain boundaries, but the area of a certain single crystal region is significantly larger than the initial single seed crystal, such as... Figure 8 As shown. Next, this single crystal will be used as a new "raw material" to cut out multiple new seed crystals with larger areas for the next round of splicing and growth.
[0058] Each growth cycle is optimized based on the results of the previous cycle. Through continuous iteration, grain boundaries are gradually eliminated, and the target single-crystal region is expanded. With the increase in the number of iterations, the size and quality of the single crystal are significantly improved. This iterative method not only improves the growth efficiency of single crystals but also reduces the fabrication cost, providing strong support for the production of large-size single crystals.
[0059] Besides extracting the dominant single crystal grown and expanded into a seed crystal for the next round, a regional melting recrystallization method can also be used. That is, after one growth cycle, instead of removing the single crystal, the grain boundary region is locally melted, and then the dominant single crystal region is expanded into the melted region by controlling the cooling process, thereby repairing the grain boundary and expanding the single crystal region.
[0060] In zone melting recrystallization, precise control of the melting range and depth is crucial. Appropriate melting parameters, such as heating temperature and time, must be set based on the specific structure of the single crystal and the distribution of grain boundaries. During the cooling process, a slow and uniform cooling method should be adopted to ensure that the dominant single crystal region can steadily expand into the melting zone, avoiding the formation of new defects due to excessively rapid or uneven cooling. This approach effectively repairs grain boundaries, further expands the single crystal region, and provides a more reliable method for preparing large-size single crystals.
[0061] The crucible-free method for preparing large-size single crystals provided in this invention is universal and not limited to gallium oxide single crystals. It can also be applied to other crystal material systems that are grown using the crucible-free method and face the challenge of diameter expansion, such as sapphire single crystals and silicon carbide single crystals.
[0062] This method allows for the preparation of large-size single crystals by simply adjusting parameters such as heating power, temperature gradient, and gas flow rate according to the specific characteristics of different crystal material systems, including melting point and crystal growth habit. This significantly expands the application scope of crucible-free large-size single crystal preparation technology and provides an effective solution for the large-size preparation of various crystal materials. The crystal growth apparatus for implementing the above method in this embodiment of the invention is basically the same as the traditional crucible-free top-feed pull-down method apparatus, except that: based on the traditional crucible-free top-feed pull-down method apparatus, a local heat insulation baffle or gas guiding device (i.e., gas flow guiding channel and / or nozzle) for asymmetric thermal field control is added.
[0063] Localized heat insulation baffles can be designed in different shapes and sizes according to actual needs, and their installation positions are precisely calculated to achieve precise control of the thermal field. The gas guiding device, through a rationally designed layout of airflow channels and nozzles, can guide the cooling gas to flow in a specific direction, thereby optimizing the thermal field distribution. This unique design helps to create an asymmetric temperature field conducive to the expansion of the target area, thus promoting single crystal growth in the target area and improving the growth quality and efficiency of large-size single crystals.
[0064] In summary, this invention addresses the technical challenges of existing crucible-free methods in terms of diameter expansion and crystal size limitations. It provides a crucible-free method for preparing large-size single crystals, the core of which lies in the combination of multi-seed crystal splicing and multi-round iterative growth, supplemented by directional thermal field control to accelerate and guide this process. The main steps are as follows: 1. Multi-seed crystal splicing: splicing multiple small-sized seed crystals into a large-sized composite seed crystal according to a preset geometric configuration; 2. Iterative growth and crystal orientation competition: By utilizing the slight crystal orientation differences between different seed crystals, during the crystal growth process, crystal orientation competition causes the single crystal region with growth advantage to continuously expand, while other regions gradually shrink or are eliminated. 3. Directional thermal field control: By introducing local baffles and controlling airflow organization, the temperature distribution at the growth interface is actively controlled to guide and accelerate the expansion of the target single crystal region. 4. Multiple iterations: The grown crystal with expanded single-crystal regions is processed again into new seed crystals for the next round of splicing and growth. Through multiple iterations, the splicing grain boundaries are gradually "squeezed out" of the crystal, eventually obtaining a complete large-size single crystal.
[0065] This invention cleverly bypasses the difficulties of traditional diameter expansion processes by adopting a strategy of "breaking down the whole into parts and iterative optimization". It can prepare high-quality single crystals with a size much larger than the initial seed crystal based on low-cost small-sized seed crystals, providing a new and effective technical path for the size breakthrough of gallium oxide single crystals.
[0066] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A method for preparing large-size single crystals without a crucible, characterized in that, Including the following steps: a. Provide multiple small-sized seed crystals, wherein the seed crystals are single-crystal seed crystals; b. The multiple small-sized seed crystals are spliced together to form a large-sized composite seed crystal; c. Single crystal growth is performed on the composite seed crystal. During the single crystal growth process, the single crystal region with growth advantage gradually expands and occupies a dominant position through crystal orientation competition. d. The grown single crystal, whose single crystal region has expanded and become dominant, is processed into a new seed crystal for the next round of splicing and growth; e. Repeat steps bd to obtain a large-size single crystal.
2. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The multiple small seed crystals have the same thickness, ranging from 5 to 20 mm.
3. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The large surface of each small seed crystal is the same crystal plane, and the splicing surface of two small seed crystals is flat and is the same crystal plane.
4. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, Multiple small, fan-shaped seed crystals are spliced together to form a large, circular composite seed crystal; Alternatively, a small circular seed crystal and multiple fan-shaped small seed crystals surrounding the small circular seed crystal can be spliced together to form a large circular composite seed crystal.
5. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The region where the single crystal region expands and dominates is defined as the target region, and the region outside the target region is defined as the non-target region. A heat-insulating baffle is installed above the side of the non-target area to suppress the growth of single crystals in the non-target area.
6. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The target region is defined as the area where the single crystal region expands and becomes dominant. Cooling gas is concentrated and blown toward the upper or side surface of the target area by an airflow guiding device to promote the growth of single crystals in the target area.
7. The method for preparing large-size single crystals without a crucible according to claim 6, characterized in that, The temperature of the target area is lower than that of the non-target area, and the temperature difference between the non-target area and the target area is controlled within 5°C.
8. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, A small circular seed crystal and four fan-shaped small seed crystals surrounding the small circular seed crystal are spliced together to form a large circular composite seed crystal. During the single crystal growth process, cooling gas is concentrated and blown onto the upper surface of the central circular region through an airflow guiding device to promote single crystal growth in the central circular region.
9. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The single crystal is gallium oxide single crystal, sapphire single crystal, or silicon carbide single crystal.
10. The method for preparing large-size single crystals without a crucible according to claim 1, characterized in that, The large-size single crystal refers to a single crystal larger than 4 inches.