A method of crystal growth that avoids the formation of gallium oxide poly crystalline shoulders

Abstract

The application discloses a crystal growth method for avoiding polycrystalline shoulder formation of gallium oxide, and belongs to the technical field of crystal growth. The length of a slit on the surface of a mold is designed to be less than one third of the length of the mold, the supply of melt is strictly limited to the local area of the slit in the seeding stage, and the accurate starting of a single crystal is realized. Then, in the lateral expansion stage of the crystal, the interval between the upper surface of the mold and the growth interface of the crystal is actively controlled, and the melt layer in the interval is used as a dynamic and expandable raw material supply channel. Therefore, the technical prejudice of the traditional guide mold method relying on the full-length entity slit supply of the mold is broken, the melt exposure area is reduced to the vicinity of the growth interface, the spontaneous nucleation of the melt in the non-target area is fundamentally inhibited, the formation of the polycrystalline shoulder (flat shoulder) is effectively avoided, the raw material volatilization is significantly reduced, the thermal field uniformity is improved, and the crystal quality, the growth stability and the process efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and more specifically, to a crystal growth method that avoids the formation of gallium oxide polycrystalline shoulders. Background Technology

[0002] Currently, the mode-guided method is the mainstream method for growing gallium oxide crystals. However, in the early stage of crystal growth (mid-stage of shoulder formation), gallium oxide crystals are prone to developing a horizontal polycrystalline shoulder, which is referred to as a flat shoulder in the industry. This phenomenon occurs about 30% of the time when the main face is (100) and even more than 70% when the main face is (001). The larger the size of the grown crystal, the more likely this problem will occur. Once a flat shoulder appears, the entire crystal needs to be remelted. After remelting, the phenomenon is usually more likely to occur again. If the flat shoulder cannot be resolved after multiple remeltings, the crystal growth in the furnace will completely fail. This seriously reduces the efficiency and yield of gallium oxide crystal growth.

[0003] In traditional mold-guided growth processes, the feed slit on the mold surface is typically designed to be the same length as or slightly shorter than the mold itself. This design is effective for the growth of many crystal materials, but not for gallium oxide (GaO). The fundamental reason is that GaO crystals exhibit extremely significant anisotropy in their three main crystal orientations (a, b, and c). Especially when growing the (001) principal face, the process window is very narrow, and the supercooling required for shoulder formation is very close to the critical temperature for spontaneous nucleation of the melt within the mold slit. Therefore, during shoulder formation, a large amount of melt within the mold slit is highly susceptible to unexpected spontaneous nucleation and rapid growth into bulk polycrystalline material, leading to the formation of flat shoulders during GaO crystal growth.

[0004] Therefore, there is an urgent need for a technical solution to address the flat shoulder problem that occurs during gallium oxide crystal growth. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a crystal growth method that avoids the formation of polycrystalline shoulders in gallium oxide.

[0006] This invention provides a crystal growth method to avoid the formation of gallium oxide polycrystalline shoulders, comprising:

[0007] S1: Provides a crucible and a mold disposed inside the crucible, wherein the interior of the mold is provided with at least one internal slit for the melt to rise, and the upper surface of the mold is provided with a connecting surface slit for each internal slit, and the length of the surface slit is 5 mm to no more than 1 / 3 of the mold length;

[0008] S2: Place the gallium oxide raw material in a crucible and heat the crucible until the gallium oxide raw material melts to form a melt. The melt rises through the internal slit to the area where the surface slit is located via capillary action.

[0009] S3: Lower the seed crystal so that the seed crystal comes into contact with and fuses with the melt in the area where the surface slit is located;

[0010] S4: The seed crystal is pulled using a pulling device to achieve diameter reduction growth;

[0011] S5: Gradually reduce the heating power to allow the gallium oxide crystal to grow shoulder-like until it fills the area of ​​the mold along the length of the surface slit;

[0012] S6: Continue gallium oxide crystal growth. By controlling the process parameters, adjust the melt layer between the upper surface of the mold and the crystal growth interface as a raw material supply channel, so that the gallium oxide crystal can expand and grow to the mold area on both sides of the surface slit until it covers the entire upper surface of the mold.

[0013] S7: Grow gallium oxide crystals with a constant diameter. After the melt in the crucible is exhausted, the gallium oxide crystal separates from the mold. At this point, stop pulling the seed crystal and gradually reduce the heating power of the crucible. After the crucible cools to room temperature, the growth of the gallium oxide crystal ends.

[0014] Optionally, in step S6, by monitoring the melt traction force on the gallium oxide crystal, feedback control is performed on the gap between the upper surface of the mold and the crystal growth interface to maintain and adjust the raw material supply channel.

[0015] Optionally, in step S6, the molten pulling force on the gallium oxide crystal is monitored by a first load sensor set on the lifting device or by a second load sensor set below the crucible;

[0016] Furthermore, the preset threshold for melt traction force is set to 2% to 20% of the weight of gallium oxide crystal; when the melt traction force detected by the first load sensor or the second load sensor is greater than the preset threshold, the cooling rate is reduced to increase the interval; when the detected melt traction force is less than the preset threshold, the cooling rate is increased to decrease the interval.

[0017] Optionally, in step S6, a first load cell mounted on the lifting device and a second load cell mounted below the crucible are used simultaneously to monitor the molten traction force on the gallium oxide crystal.

[0018] Furthermore, the preset threshold for the melt traction force is set to 2% to 20% of the weight of the gallium oxide crystal; based on the comparison results between the monitoring values ​​of the first load sensor and the second load sensor and the preset threshold, the corresponding first cooling rate adjustment amount and second cooling rate adjustment amount are calculated, and the average value of the first cooling rate adjustment amount and the second cooling rate adjustment amount is used as the final cooling rate adjustment value to control the interval.

[0019] Optionally, the upper surface of the mold is a plane.

[0020] Optionally, the upper surface of the mold is curved, and the middle of the curved surface is recessed towards the bottom of the mold.

[0021] Optionally, the length of the internal slit is greater than the length of the surface slit it communicates with.

[0022] Optionally, a groove is provided below the internal slit to guide and collect the melt.

[0023] Optionally, the surface slits are multiple and arranged in parallel to each other.

[0024] Optionally, in step S2, the heating rate of the crucible is 300-1000 W / h; in step S4, the pulling speed of the pulling device is 10-20 mm / h; in step S5, the heating power is reduced at a rate of 50-150 W / h; and in step S7, after the gallium oxide crystal is separated from the mold, the heating power of the crucible is gradually reduced at a rate of 500-1000 W / h.

[0025] This invention creatively designs the length of the slit on the mold surface to be no more than one-third of the mold length, thereby strictly limiting the melt supply within this local slit area during the crystal initiation stage, achieving precise initiation of single crystals. Subsequently, during the lateral crystal growth stage, by actively controlling the interval between the upper surface of the mold and the crystal growth interface, the interstitial melt layer formed between the two serves as a dynamic and controllable main channel for raw material supply, ensuring that the melt supply range during lateral crystal growth is synchronized and precisely matched with the growth interface. This invention overcomes the technical bias of traditional mold-guided methods that rely on a full-length solid slit penetrating the mold for material feeding. It innovatively reduces the exposed area of ​​the melt from the entire mold surface to a microscopic scale close to the growth interface. This not only significantly suppresses spontaneous nucleation of the melt in non-target areas, fundamentally avoiding the formation of polycrystalline shoulders (flat shoulders), but also significantly reduces raw material volatilization, preventing contamination of the crystal surface by volatiles. Furthermore, since the surface slit exists only locally, the majority of the mold surface in contact with the crystal growth interface has continuous thermal conductivity, thus eliminating thermal field distortion and localized stress caused by the alternation of "slit" and "no-slit" areas, improving the uniformity and stability of crystallization. Therefore, this invention completely solves the flat shoulder defect in gallium oxide crystals while simultaneously improving crystal quality and the stability of the growth process. Thus, it effectively solves the technical problem of flat shoulders that occur during gallium oxide crystal growth. Attached Figure Description

[0026] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0027] Figure 1 This is a schematic flowchart of a crystal growth method for avoiding the formation of gallium oxide polycrystalline shoulders according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a crucible and a mold disposed inside the crucible according to an embodiment of the present invention;

[0029] Figure 3 yes Figure 2 A cross-sectional view of the crucible and the mold placed inside the crucible shown;

[0030] Figure 4 This is another schematic diagram of the crucible and the mold disposed inside the crucible according to an embodiment of the present invention;

[0031] Figure 5 yes Figure 4 The cross-sectional view of the crucible and the mold placed inside the crucible is shown. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0033] The description of this invention assumes that the mainstream growth crystal plane (001) of gallium oxide is used, but the apparatus and method can still be used for the growth of gallium oxide on other crystal planes.

[0034] Combination Figures 1 to 4 As shown, embodiments of the present invention propose a crystal growth method to avoid the formation of gallium oxide polycrystalline shoulders, comprising the following steps:

[0035] Step S1: Provide a crucible 10 and a mold 20 disposed inside the crucible 10. The mold 20 has at least one internal slit 22 for the melt to rise. The upper surface of the mold 20 is provided with a surface slit 21 that connects to each internal slit 22. The length of the surface slit 21 is 5 mm to no more than 1 / 3 of the mold length.

[0036] Specifically, through in-depth research into the causes of the flat shoulder problem in gallium oxide crystals, the inventors discovered a deeply ingrained technical paradigm in the mold design of the traditional guided mold method: to ensure a continuous and sufficient supply of melt, the solid slit of the mold not only extends throughout the entire thickness of the mold (the channel for melt to rise), but its opening on the upper surface is also typically designed to traverse the entire length of the mold (where the mold length direction is the direction of the main face of the grown crystal), and the internal channel and the surface opening are consistent in size and orientation (i.e., a full-length slit consistent on both the surface and the interior). This design concept has long been considered an inherent characteristic of the guided mold method and has not been questioned. However, for materials like gallium oxide, it is precisely this full-length and consistent slit design that provides a large, continuous melt exposure area below the crystal growth interface, becoming the fundamental structural cause of uncontrolled nucleation (i.e., flat shoulder) and non-uniform thermal field. This invention creatively challenges and breaks with this traditional paradigm by drastically shortening the length of the surface slit, thus differentiating its function from that of the internal feeding channel: the internal channel remains responsible for efficiently transporting the melt from the crucible, while the ultra-short surface opening serves only as a precise crystal-guiding window. This non-uniform design of a short surface slit and an independent internal feeding channel is one of the essential characteristics that distinguishes it from traditional technical solutions, and it is also key to achieving precise confinement and controllable expansion of the melt region.

[0037] Based on this groundbreaking understanding, the inventors creatively limited the length of the surface slit 21 of the mold 20 to no more than one-third of the mold length (for example, for a mold 30 mm long, the length of the surface slit 21 is only 5-10 mm). This design physically alters the state of the melt on the surface of the mold 20, strictly confining it to a very small local area during the critical crystal initiation stage. This eliminates the possibility of a large area of ​​melt existing simultaneously and spontaneously nucleating, creating the necessary conditions for the precise initiation and stable growth of a single crystal nucleus.

[0038] Furthermore, compared to the traditional mold-guided method where the surface slit runs across the entire mold, the localized short slit design of this invention (i.e., the length of the surface slit 21 is limited to no more than one-third of the mold length) has a significant advantage in improving crystal quality. In traditional designs, the slit region and the slitless solid mold region, due to differences in heat capacity, thermal conductivity, and the degree of disturbance to melt convection, will form periodic or regional temperature field distortions below the crystal growth interface. This inherent thermal field inhomogeneity introduces additional thermal stress into the grown crystal, affecting the crystal integrity and material uniformity. This invention, by strictly limiting the surface slit 21 to a very small local area, ensures that most of the mold surface covered by the crystal growth interface is a continuous and uniform solid material, thereby fundamentally eliminating the source of thermal field differences caused by the alternation of "slit" and "slitless" structures. Therefore, this solution successfully suppresses the formation of polycrystalline shoulders while also contributing to obtaining gallium oxide single crystals with lower thermal stress and better crystal quality.

[0039] In some embodiments of the present invention, such as Figure 2 and Figure 3 As shown, the upper surface of mold 20 is flat. The flat upper surface of the mold is easy to process, and the thermal field distribution is relatively easy to predict and control, which is conducive to achieving stable initial thermal contact and melt spreading.

[0040] In some embodiments of the present invention, such as Figure 4 and Figure 5 As shown, the upper surface of mold 20 is curved, and the middle of the curved surface is concave towards the bottom of mold 20. This concave arc-shaped surface helps to more naturally gather and confine the melt from the internal slit to the central region in the early stage of crystal growth, which is more beneficial to the positioning and stability of the initial crystal nucleus. In addition, the arc surface makes the stability of the internal feeding channel easier to control.

[0041] In some embodiments of the present invention, such as Figure 3 and 5 As shown, the length of the internal slit 22 is greater than the length of the surface slit 21 that it communicates with. The longer size of the internal slit 22 (e.g., the length of the internal slit 22 is 1.5 to 3 times that of the surface slit 21) can significantly reduce the flow resistance of the melt rising in the slit, ensuring that the melt can be adequately and rapidly transported to the growth interface even when the raw materials are consumed in the later stages of crystal growth, thus compensating for the limitation of the small cross-sectional area of ​​the surface slit.

[0042] Furthermore, the length of the internal slit 22 can also be equal to the length of the surface slit 21 it connects to. This equal-width design simplifies the mold manufacturing process, reducing complexity and cost. In certain applications where crystal growth is not particularly sensitive to melt flow resistance, or where raw material supply pressure is sufficient (e.g., growing small crystals), the equal-width internal slit is sufficient to ensure that the melt rises stably to the surface slit region through capillary action. This design retains the core advantage of the short surface slit limiting the initial melt region while providing a more easily implemented process option.

[0043] In some embodiments of the present invention, such as Figure 3 and 5 As shown, a groove 23 is provided below the internal slit 22 for guiding and collecting the melt. This groove 23 acts as a small melt buffer zone, which can more effectively collect the melt flowing from the crucible and smoothly guide it into the internal slit above, further optimizing the continuity and stability of the feeding.

[0044] In some embodiments of the present invention, such as Figure 2 and Figure 4 As shown, there are multiple surface slits 21, which are arranged in parallel to each other.

[0045] Specifically, two or more parallel short surface slits 21 can be set, and each surface slit 21 is independently connected to the inner slit 22 below. This can increase the total cross-sectional area of ​​the melt transported upward from the inner slit 22. Thus, while maintaining the core principle of limiting the exposed area of ​​the melt, the melt supply capacity can be improved by increasing the total cross-sectional area of ​​the supply channel to meet the needs of larger size or higher growth rate crystals.

[0046] Step S2: Place the gallium oxide raw material in the crucible 10, heat the crucible 10 until the gallium oxide raw material melts to form a melt, and the melt rises through the internal slit 22 to the area where the surface slit 21 is located through capillary action.

[0047] Specifically, this step is a key physical process for achieving precise definition of the melt region. After the raw material is completely melted, the melt is transported upwards along the internal slit 22 of the mold 20 under capillary force. Because the opening on the upper surface of the mold 20 is intentionally designed as a short slit (i.e., surface slit 21, not exceeding 1 / 3 of the mold length), the lateral spread of the melt after rising to the upper surface of the mold 20 is strictly limited within the geometric boundary of this short slit (i.e., the area where surface slit 21 is located), and cannot freely spread across the entire length of the mold as in a traditional full-length slit. Thus, before the crystal growth begins, a small melt region with controlled size and defined position is actively created, laying a decisive foundation for the subsequent precise contact between the seed crystal and the melt, and for the fixed-point and oriented initiation of the single crystal.

[0048] In some embodiments of the present invention, in step S2, the heating rate of the heating crucible 10 is 300-1000 w / h.

[0049] Specifically, a heating rate of 300-1000 W / h is used to steadily heat the gallium oxide material to above its melting point (approximately 1740°C), avoiding damage to the crucible or mold caused by severe thermal stress due to excessively rapid heating. This also ensures uniform and complete melting of the material, reducing the formation of unmelted slag. After the melt forms, under capillary action, it rises along the internal slit 22 of the mold 20, eventually filling the area of ​​the surface slit 21 on the upper surface.

[0050] Step S3: Lower the seed crystal so that it comes into contact with and fuses with the melt in the area where the surface slit 21 is located.

[0051] Specifically, the seed crystal (whose main growth surface is usually set as the (001) surface) is slowly lowered until its lower end contacts the melt in the short slit on the upper surface of the mold 20. After contact, it is usually kept in contact briefly or slightly remelted (e.g., remelted for 1-3 mm) to allow the front end of the seed crystal to achieve full atomic bonding with the melt, forming a stable solid-liquid interface, completing the fusion process, and laying the foundation for crystal growth.

[0052] Step S4: Use a pulling device to pull the seed crystal for diameter reduction growth.

[0053] In some embodiments of the present invention, in step S4, the lifting speed of the lifting device is 10-20 mm / h.

[0054] Specifically, after fusion, the seed crystal is slowly pulled upwards at a speed of 10-20 mm / h to grow a narrower neck. The purpose of this stage is to grow a narrow neck with a diameter much smaller than the original diameter of the seed crystal. This process helps to eliminate defects such as dislocations in the seed crystal and prepare a suitable crystal seed for the subsequent growth of a high-quality single crystal.

[0055] Step S5: Gradually reduce the heating power to allow the gallium oxide crystal to grow shoulder-like until it covers the area of ​​the mold 20 along the length of the surface slit 21.

[0056] In some embodiments of the present invention, in step S5, the rate of decrease of heating power is 50-150 w / h.

[0057] Specifically, after the necking growth is completed, the heating power is gradually reduced at a rate of 50-150 W / h. According to Bravais's law and experimental verification, the gallium oxide crystal will first grow along its inherent crystallographic direction (for the (001) principal face, usually along the

[001] direction). During this stage, the crystal diameter gradually increases, first growing along the

[001] direction (i.e., the direction at 76.2° with the principal face) until it fills the mold thickness direction, and then maintaining this cross-sectional size for growth. When the supercooling reaches the threshold for growth in the

[100] direction, shoulder growth begins along the

[100] direction until the width of the crystal (in the slit length direction) completely covers and slightly exceeds the area of ​​the surface slit 21. At this time, the crystal appears as a narrow and long single crystal strip on the upper surface of the mold 20.

[0058] Step S6: Continue gallium oxide crystal growth. By controlling the process parameters, adjust the melt layer between the upper surface of the mold 20 and the crystal growth interface as a raw material supply channel, so that the gallium oxide crystal can expand and grow to the mold area on both sides of the surface slit 21 until it covers the entire upper surface of the mold 20.

[0059] Specifically, this step represents a core innovation in the mechanism for achieving lateral crystal expansion. The inventors of this application discovered that in traditional mold-guided growth, an extremely thin melt layer formed by melt surface tension always exists between the crystal and the upper surface of the mold. However, traditional understanding completely ignores the crucial role of this melt layer in raw material transport, simply assuming that a solid slit penetrating the mold must be designed to ensure melt supply. This invention breaks through this limitation. After using a short surface slit to complete crystal initiation and initial longitudinal growth, it actively utilizes this existing, dynamic melt layer as the main raw material supply channel for lateral crystal expansion. By precisely controlling process parameters such as temperature, the thickness, fluidity, and coverage of this melt layer can be altered, making it a virtual supply slit that extends synchronously with the crystal growth interface. This innovative method strictly confines the melt to a microscopic region closely adhering to the growth interface. The remaining portion of the mold surface, lacking melt exposure, completely eliminates the possibility of spontaneous polycrystalline nucleation, thus ensuring that the crystal maintains its monocrystalline characteristics throughout the entire process of safely expanding laterally until it covers the entire mold surface.

[0060] In some embodiments of the present invention, in step S6, the gap between the upper surface of the mold and the crystal growth interface is controlled by monitoring the melt traction force on the gallium oxide crystal in order to maintain and adjust the raw material supply channel.

[0061] Specifically, when the crystal needs to expand to both sides of the surface slit (i.e., along the mold's length) to fill the entire mold, the pulling force exerted by the melt layer on the crystal (manifested as a change in the apparent weight of the crystal or crucible) is a sensitive function of its state (such as thickness and meniscus curvature). By monitoring this pulling force in real time with sensors and comparing it with an ideal threshold set based on the crystal weight, a closed-loop feedback control system can be constructed. This system can automatically adjust the heating power (manifested as controlling the cooling or heating rate), thereby precisely and dynamically stabilizing the state of the melt layer and ensuring the continuity, stability, and efficiency of this virtual raw material supply channel.

[0062] In some embodiments of the present invention, in step S6, the molten traction force on the gallium oxide crystal is monitored by a first load-bearing sensor provided on the lifting device or by a second load-bearing sensor provided below the crucible; and a preset threshold for the molten traction force is set to 2% to 20% of the weight of the gallium oxide crystal; when the molten traction force detected by the first load-bearing sensor or the second load-bearing sensor is greater than the preset threshold, the cooling rate is reduced to increase the interval; when the detected molten traction force is less than the preset threshold, the cooling rate is increased to decrease the interval.

[0063] Specifically, the traction force of the melt on the crystal (manifested as a change in the crystal's apparent weight) is a sensitive indicator of the gap size between the upper surface of the mold and the crystal growth interface. A preset threshold for the melt traction force is set between 2% and 20% of the gallium oxide crystal weight, providing a precise and stable process target range for closed-loop control. The lower limit (2%) ensures sufficient adhesion and support of the melt layer to the crystal, preventing instability at the growth interface or interruption of material supply due to insufficient traction force; the upper limit (20%) prevents excessive mechanical stress within the crystal or undesirable deformation of the growth interface due to excessive traction force, thus ensuring crystal quality while maintaining stable material supply.

[0064] When using the first load cell to monitor the pulling force, an increase in traction force usually indicates a smaller gap and increased pull of the melt on the crystal. In this case, the cooling rate should be reduced to increase melt fluidity and widen the gap, thereby reducing the traction force. The reverse is also true. When using the second load cell to monitor the crucible weight change, the traction force it experiences is in the opposite direction to that of the first load cell. The logic is similar: an increase in traction force usually indicates a smaller gap and increased pull of the melt on the crystal. In this case, the cooling rate should be reduced to increase melt fluidity and widen the gap, thereby reducing the traction force. The reverse is also true.

[0065] It should be noted that the calculation process of the melt traction force monitored by the first load sensor is as follows: the actual value detected by the first load sensor is subtracted from the load below it (including the crystal and its fixing device and driving device), and the absolute value of the result is taken as the melt traction force monitored by the first load sensor.

[0066] The calculation process of the melt traction force monitored by the second load sensor is as follows: subtract the actual value detected by the second load sensor from the load above it (including the crucible, mold, melt and the crucible fixing device and driving device), and take the absolute value of the subtraction result as the melt traction force monitored by the second load sensor.

[0067] In some embodiments of the present invention, in step S6, a first load-bearing sensor disposed on the lifting device and a second load-bearing sensor disposed below the crucible are used simultaneously to monitor the melt traction force on the gallium oxide crystal; and a preset threshold for the melt traction force is set to 2% to 20% of the weight of the gallium oxide crystal; based on the comparison results between the monitoring values ​​of the first load-bearing sensor and the second load-bearing sensor and the preset threshold, the corresponding first cooling rate adjustment amount and second cooling rate adjustment amount are calculated, and the average value of the first cooling rate adjustment amount and the second cooling rate adjustment amount is used as the final cooling rate adjustment value to control the interval.

[0068] Specifically, using two load cells simultaneously provides a more comprehensive and interference-resistant measurement signal. The control system reads data from both load cells and independently calculates a final power adjustment based on their respective preset logic (as described above). For example, when the actual gap between the crystal and the mold is too small, the first load cell (monitoring the lifting force) will detect an increased traction force, and its control logic will indicate that the cooling rate needs to be reduced to increase the gap, thus calculating a recommended adjustment ΔT1 of -18 W / h (i.e., a power reduction of 18 W / h). At the same time, the second load cell (monitoring the weight of the crucible system) will detect a decrease in traction force due to the reduced weight of the lifted melt, and its control logic will also indicate that the cooling rate needs to be reduced, thus calculating a recommended adjustment ΔT2 of -12 W / h. The system averages these two independent recommended values ​​to obtain a final power adjustment command of a reduction of 15 W / h (i.e., (-18 W / h) + (-12 W / h) / 2 = -15 W / h), and executes it accordingly.

[0069] This data fusion method, through cross-validation and integration of different representations of the same physical phenomenon by two independent sensors, can effectively offset the drift, random errors or local interference that may exist in a single sensor, thereby reflecting the state of the growth interface more realistically and robustly, and significantly improving the accuracy of control and the robustness of the system.

[0070] Step S7: Grow gallium oxide crystals with constant diameter. After the melt in the crucible is exhausted, the gallium oxide crystal separates from the mold. At this point, stop pulling the seed crystal and gradually reduce the heating power of the crucible. After the crucible cools to room temperature, the growth of the gallium oxide crystal ends.

[0071] In some embodiments of the present invention, in step S7, after the gallium oxide crystal is separated from the mold, the heating power of the crucible is gradually reduced at a rate of 500-1000 W / h.

[0072] Specifically, once the crystal diameter reaches the target value and enters the constant diameter growth stage, stable process conditions are maintained until the raw materials are exhausted. After the crystal naturally separates from the mold, the power is reduced at a relatively fast rate (500-1000 w / h), which allows the crystal to quickly pass through the dangerous temperature range that is prone to plastic deformation or cracking, reducing residual thermal stress, and finally cooling smoothly to room temperature to complete the entire growth process.

[0073] In summary, by creatively designing the length of the slit on the mold surface to not exceed one-third of the mold length, the melt supply is strictly limited to this local slit area during the crystal initiation stage, achieving precise single crystal initiation. Subsequently, during the lateral crystal growth stage, by actively controlling the interval between the upper surface of the mold and the crystal growth interface, the interstitial melt layer formed between them serves as a dynamic and controllable main channel for raw material supply, ensuring that the melt supply range during lateral crystal growth is synchronized and precisely matched with the growth interface. This invention overcomes the technical bias of traditional mold-guided methods that rely on a full-length solid slit penetrating the mold for material feeding. It innovatively reduces the exposed area of ​​the melt from the entire mold surface to a microscopic scale close to the growth interface. This not only significantly suppresses spontaneous nucleation of the melt in non-target areas, fundamentally avoiding the formation of polycrystalline shoulders (flat shoulders), but also significantly reduces raw material volatilization, preventing contamination of the crystal surface by volatiles. Furthermore, since the surface slit exists only locally, the majority of the mold surface in contact with the crystal growth interface has continuous thermal conductivity, thus eliminating thermal field distortion and localized stress caused by the alternation of "slit" and "no-slit" areas, improving the uniformity and stability of crystallization. Therefore, this invention completely solves the flat shoulder defect in gallium oxide crystals while simultaneously improving crystal quality and the stability of the growth process. Thus, it effectively solves the technical problem of flat shoulders that occur during gallium oxide crystal growth.

[0074] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are merely illustrative of selected implementations based on combinations of all possible embodiments. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A crystal growth method for avoiding the formation of gallium oxide polycrystalline shoulders, characterized in that, include: S1: Provides a crucible and a mold disposed inside the crucible, wherein the interior of the mold is provided with at least one internal slit for the melt to rise, and the upper surface of the mold is provided with a connecting surface slit for each internal slit, and the length of the surface slit is 5 mm to no more than 1 / 3 of the mold length; S2: Place the gallium oxide raw material in a crucible and heat the crucible until the gallium oxide raw material melts to form a melt. The melt rises through the internal slit to the area where the surface slit is located via capillary action. S3: Lower the seed crystal so that the seed crystal comes into contact with and fuses with the melt in the area where the surface slit is located; S4: The seed crystal is pulled using a pulling device to achieve diameter reduction growth; S5: Gradually reduce the heating power to allow the gallium oxide crystal to grow shoulder-like until it fills the area of ​​the mold along the length of the surface slit; S6: Continue gallium oxide crystal growth. By controlling the process parameters, adjust the melt layer between the upper surface of the mold and the crystal growth interface as a raw material supply channel, so that the gallium oxide crystal can expand and grow to the mold area on both sides of the surface slit until it covers the entire upper surface of the mold. S7: Grow gallium oxide crystals with constant diameter. After the melt in the crucible is exhausted, the gallium oxide crystal separates from the mold. At this point, stop pulling the seed crystal and gradually reduce the heating power of the crucible. After the crucible cools to room temperature, the growth of the gallium oxide crystal ends. In step S6, the molten traction force on the gallium oxide crystal is monitored by a first load-bearing sensor on the lifting device or a second load-bearing sensor below the crucible. A preset threshold for the molten traction force is set to 2% to 20% of the weight of the gallium oxide crystal. Based on the comparison between the monitored values ​​of the first and second load-bearing sensors and the preset threshold, the corresponding first and second cooling rate adjustment amounts are calculated. The average of the first and second cooling rate adjustment amounts is used as the final cooling rate adjustment value to control the interval. Alternatively, when the molten traction force monitored by the first or second load-bearing sensor is greater than the preset threshold, the cooling rate is reduced to increase the interval; when the monitored molten traction force is less than the preset threshold, the cooling rate is increased to decrease the interval.

2. The method according to claim 1, characterized in that, In step S6, by monitoring the melt traction force on the gallium oxide crystal, feedback control is used to control the gap between the upper surface of the mold and the crystal growth interface, so as to maintain and adjust the raw material supply channel.

3. The method according to claim 1, characterized in that, The upper surface of the mold is flat.

4. The method according to claim 1, characterized in that, The upper surface of the mold is curved, and the middle of the curved surface is concave towards the bottom of the mold.

5. The method according to claim 1, characterized in that, The length of the internal slit is greater than the length of the surface slit it connects to.

6. The method according to claim 1, characterized in that, A groove is provided below the internal slit to guide and collect the melt.

7. The method according to claim 1, characterized in that, The surface has multiple slits, which are arranged in parallel to each other.

8. The method according to claim 1, characterized in that, In step S2, the heating rate of the crucible is 300-1000 W / h; in step S4, the pulling speed of the pulling device is 10-20 mm / h; in step S5, the heating power is reduced at a rate of 50-150 W / h; in step S7, after the gallium oxide crystal is separated from the mold, the heating power of the crucible is gradually reduced at a rate of 500-1000 W / h.

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