A double crucible assembly and a method of crystal growth

Abstract

The application belongs to the technical field of crystal growth, and discloses a double-layer crucible assembly and a crystal growth method. The double-layer crucible assembly comprises an outer-wall crucible (1) and a coaxially nested inner-wall crucible (2). The inner space of the inner-wall crucible (2) constitutes a crystal growth cavity. An annular first slit (3) is formed between the inner side wall of the outer-wall crucible (1) and the outer side wall of the inner-wall crucible (2). A second slit (4) is formed in the side wall of the inner-wall crucible (2) and extends along the axial direction of the inner-wall crucible (2) and penetrates the wall thickness of the inner-wall crucible (2). A flow-through structure (5) is arranged at the bottom of the inner-wall crucible (2). The melt in the crystal growth cavity can enter the first slit (3) through the flow-through structure (5) and climb up under the capillary action, permeate to the inner circumferential surface of the inner-wall crucible (2), and form a dynamic melt liquid film that separates the crystal from the inner-wall crucible (2), thereby avoiding the introduction of crystal cracking and dislocation and preventing the deformation of the crucible caused by the thermal shrinkage deformation of the single crystal.

Description

Technical Field

[0001] This invention belongs to the field of crystal growth technology, and in particular relates to a double-layer crucible assembly and a crystal growth method. Background Technology

[0002] In high-temperature melt crystal growth processes such as the Czochralski method, the EFG method, and directional solidification casting, the noble metal iridium (Ir) is favored for growing high-melting-point gallium oxide due to its excellent high-temperature chemical stability, extremely high melting point (approximately 2446℃), and superior resistance to oxidation and corrosion. Suitable crucible materials for single crystals. In the current directional solidification casting growth process, the raw material is filled into the crucible cavity of a traditional single-layer iridium crucible. After the raw material is completely melted by an induction coil, it spontaneously nucleates on the surface of the melt. Then, the temperature is controlled by a very slow linear power decrease. Since this process does not involve conventional pulling, rotating and detaching movements, the crystal crystallizes in situ and gradually fills the entire crucible cavity. The crystal directly contacts and is fixed to the inner wall of the crucible.

[0003] However, due to the anisotropic shrinkage mismatch, there is a significant difference in the coefficient of thermal expansion between gallium oxide single crystals and metallic iridium. Specifically, the coefficient of linear expansion of gallium oxide is approximately... to The coefficient of linear expansion of metallic iridium is approximately... Furthermore, it exhibits anisotropy. Once a solid-solid rigid bond forms between the crystal and the crucible wall, the enormous thermal stress cannot be released during the cooling process after growth, potentially leading to two adverse consequences: first, the grown single crystal may suffer severe cracking and introduce dislocations, rendering the entire crystal unusable; second, the high-hardness single crystal exerts enormous mechanical restraint on the iridium crucible wall during thermal shrinkage, causing irreversible deformation and topological damage to the extremely expensive iridium crucible, thus shortening its lifespan. The root cause of this problem lies in the following inherent defects of existing single-layer iridium crucibles: first, they cannot actively prevent solid-solid contact because the inner wall of traditional single-layer crucibles is a rigid, hard iridium surface; once the crystal grows... The first problem is that the contact between the crystal and iridium forms a solid-solid physical bond. The crucible wall itself has no blocking or buffering mechanism. Secondly, the thermal stress cannot be released. The shrinkage of the crystal and iridium during cooling is mismatched. The huge rigid mechanical stress generated after the bond cannot be released, which leads to crystal cracking. At the same time, it may also cause deformation and damage to the crucible body. Thirdly, the crucible structure is inelastic and cannot adapt to thermal shrinkage. Because the rigidity of traditional integral seamless cylindrical crucibles is extremely high, they cannot provide deformation space in the radial direction, nor can they absorb the uneven stress generated by the anisotropic thermal shrinkage of the crystal. The crucible is very easy to crack or undergo irreversible plastic deformation, resulting in the permanent scrapping of high-cost crucibles and causing a lot of losses.

[0004] Therefore, how to avoid solid-solid adhesion between the crystal and the inner wall of the iridium crucible, and effectively release the rigid mechanical restraint thermal stress during the cooling stage, so as to prevent crystal cracking and protect the crucible from irreversible deformation, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a double-layer crucible assembly and a crystal growth method. During the casting process of gallium oxide crystal growth, it avoids solid-solid adhesion between the crystal and the inner wall of the crucible, and actively releases the rigid mechanical constraint thermal stress generated during the cooling stage due to the anisotropic mismatch of the thermal expansion coefficients of the single crystal and the metal. This prevents crystal cracking and the introduction of dislocations, while also preventing irreversible deformation of the crucible caused by the thermal shrinkage deformation of the high-hardness single crystal, thus reducing production costs.

[0006] The present invention provides a double-layer crucible assembly comprising an outer wall crucible and an inner wall crucible coaxially nested inside the outer wall crucible, wherein the bottom surface of the inner wall crucible is disposed on the inner bottom surface of the outer wall crucible, and the internal space of the inner wall crucible constitutes a crystal growth cavity.

[0007] An annular first slit is formed between the inner wall of the outer wall crucible and the outer wall of the inner wall crucible, and the first slit constitutes a capillary channel for the capillary climb of the melt.

[0008] A second slit is provided on the side wall of the inner wall crucible, extending along the axial direction of the inner wall crucible and penetrating the wall thickness of the inner wall crucible. The second slit connects the first slit with the crystal growth cavity.

[0009] The bottom of the inner wall crucible is provided with a flow structure that connects the crystal growth cavity and the first slit;

[0010] The melt in the crystal growth chamber can enter the first slit through the flow structure and climb under capillary action, and then flow back and / or penetrate through the second slit to the inner circumferential surface of the inner wall crucible, forming a dynamic melt liquid film on the inner circumferential surface of the inner wall crucible that isolates the crystal from the inner wall crucible.

[0011] Preferably, in the above-described double-layer crucible assembly, the width of the first slit is configured such that the height of the melt in the first slit rising under capillary action is greater than the vertical height difference between the melt surface and the top edge of the inner wall crucible, so that the melt in the first slit can flow back over the top edge of the inner wall crucible to the inner circumferential surface of the inner wall crucible.

[0012] Preferably, in the above-mentioned double-layer crucible assembly, there are multiple second slits, and the multiple second slits are distributed at intervals along the circumference of the inner wall crucible;

[0013] The second slit extends upward from the bottom edge of the inner wall crucible, and there is a gap between the top of the second slit and the top opening of the inner wall crucible so that the top of the inner wall crucible remains continuous.

[0014] Multiple second slits discretize the sidewall of the inner wall crucible into multiple arc-shaped elastic blades capable of radial elastic deformation.

[0015] Preferably, in the above-mentioned double-layer crucible assembly, the wall thickness of the inner wall crucible is set to be thinner at the top and thicker at the bottom along the axial direction, and the inner circumferential surface of the inner wall crucible is an inverted conical slope surface that is wider at the top and narrower at the bottom.

[0016] Preferably, in the above-mentioned double-layer crucible assembly, both the outer wall crucible and the inner wall crucible are made of iridium, and the outer wall crucible is the direct heating object of the induction coil and constitutes the active heat source of the crystal growth thermal field.

[0017] Preferably, in the above-mentioned double-layer crucible assembly, the flow structure is a plurality of flow gaps opened at the bottom of the inner wall crucible, and the plurality of flow gaps are evenly distributed along the circumference of the inner wall crucible so that the melt in the crystal growth cavity can flow laterally into the first slit.

[0018] Preferably, in the above-mentioned double-layer crucible assembly, when the crystal cools and shrinks, the plurality of arc-shaped elastic blades can radially elastically retract toward the first slit side to release the thermal stress between the crystal and the inner wall crucible.

[0019] The present invention provides a crystal growth method using a double-layer crucible assembly as described in any of the above claims, comprising:

[0020] S1: The inner wall crucible is nested axially inside the outer wall crucible, so that the bottom surface of the inner wall crucible is attached to the inner bottom surface of the outer wall crucible. The assembled double-layer crucible assembly is placed in the hot field of the induction furnace and aligned with the induction coil. Raw materials are filled into the crystal growth chamber, a vacuum is drawn, and protective gas is introduced to positive pressure.

[0021] S2: Heating completely melts the raw material. The melt in the crystal growth chamber enters the first slit through the flow structure and rises and flows back under capillary action, forming a dynamic melt film on the inner circumferential surface of the inner wall crucible.

[0022] S3: Reduce the heating power to control the cooling, so that the melt surface in the crystal growth chamber nucleates and crystallizes downward in situ. As the melt is consumed, the melt surface in the crystal growth chamber drops. The melt in the first slit permeates through the second slit to replenish the inner circumferential surface of the inner wall crucible, maintaining the coverage of the dynamic melt film on the side of the crystallization front.

[0023] S4: After the melt has completely crystallized, it is cooled down. The sidewall of the inner wall crucible undergoes radial elastic yielding under the discrete action of the second slit, releasing the thermal stress generated by the cooling and shrinkage of the crystal. After cooling to room temperature, it is demolded and the crystal is taken out.

[0024] Preferably, in the above crystal growth method, in step S2, the melt in the first slit, under capillary action, crosses the top edge of the inner wall crucible and flows back, merging with the melt spread through the second slit, forming a continuous dynamic melt film on the inner circumferential surface of the inner wall crucible; in step S3, as the melt level in the crystal growth cavity drops, after the backflow that crosses the top edge of the inner wall crucible is interrupted, the melt in the first slit changes to being laterally replenished through the second slit at the current liquid level, so that the dynamic melt film dynamically tracks and covers the side of the crystallization front.

[0025] Preferably, in the above crystal growth method, the inner circumferential surface of the inner wall crucible is an inverted conical slope surface that is wider at the top and narrower at the bottom; in step S4, after cooling to room temperature, a vertically upward pulling force is applied to the crystal to form a gap between the outer circumferential surface of the crystal and the inner circumferential surface of the inner wall crucible, so that the entire crystal is lifted out of the inner wall crucible in situ without damage.

[0026] As described above, the double-layer crucible assembly provided by the present invention includes an outer wall crucible and an inner wall crucible coaxially nested inside the outer wall crucible. An annular first slit is formed between the inner sidewall of the outer wall crucible and the outer sidewall of the inner wall crucible, constituting a capillary channel for the capillary ascent of the melt. A second slit extending axially along the inner wall crucible and penetrating its wall thickness is provided on the sidewall of the inner wall crucible, connecting the first slit and the crystal growth chamber. A flow structure connecting the crystal growth chamber and the first slit is provided at the bottom of the inner wall crucible. The melt in the crystal growth chamber can pass through the... The flow structure enters the first slit and rises under capillary action, then flows back and / or permeates through the second slit to the inner circumferential surface of the inner wall crucible. A dynamic melt film is formed on the inner circumferential surface of the inner wall crucible, isolating the crystal from the inner wall crucible. Therefore, this dynamic melt film can prevent solid-solid adhesion between the crystal and the inner wall of the crucible during the casting process of gallium oxide crystal growth, and actively release the rigid mechanical constraint thermal stress caused by the anisotropic mismatch of the thermal expansion coefficients of the single crystal and the metal during the cooling stage. This avoids crystal cracking and the introduction of dislocations, while also preventing irreversible deformation of the crucible caused by the thermal shrinkage deformation of the high-hardness single crystal, thus reducing production costs. The crystal growth method provided by this invention has the same advantages. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 A structural cross-sectional view of an embodiment of a double-layer crucible assembly provided by the present invention;

[0029] Figure 2 This is a schematic diagram of an embodiment of a crystal growth method provided by the present invention. Detailed Implementation

[0030] The core of this invention is to provide a double-layer crucible assembly and a crystal growth method, which can avoid solid-solid adhesion between the crystal and the inner wall of the crucible during the casting process of gallium oxide crystal growth, and actively release the rigid mechanical constraint thermal stress caused by the anisotropic mismatch of the thermal expansion coefficients of the single crystal and the metal during the cooling stage, thereby avoiding crystal cracking and the introduction of dislocations, while preventing irreversible deformation of the crucible caused by thermal shrinkage deformation of high-hardness single crystal, and reducing production costs.

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0032] An embodiment of the double-layer crucible assembly provided by the present invention is as follows: Figure 1 As shown, Figure 1 This is a structural cross-sectional view of an embodiment of a double-layer crucible assembly provided by the present invention. The double-layer crucible assembly may include an outer wall crucible 1 and an inner wall crucible 2 coaxially nested inside the outer wall crucible 1. This coaxial nesting method can ensure the consistency of the thermal field of the two crucibles in the 360° direction. The bottom surface of the inner wall crucible 2 is set on the inner bottom surface of the outer wall crucible 1. In actual operation, the inner wall crucible 2 can be stably placed on the bottom surface inside the outer wall crucible 1. It is necessary to ensure that the two remain relatively stationary during the crystal growth process. The internal space of the inner wall crucible 2 constitutes a crystal growth cavity. That is to say, crystal growth is only carried out inside this inner wall crucible 2. Moreover, both the outer wall crucible 1 and the inner wall crucible 2 can preferably be iridium crucibles.

[0033] An annular first slit 3 is formed between the inner wall of the outer wall crucible 1 and the outer wall of the inner wall crucible 2. The first slit 3 constitutes a capillary channel for the capillary climbing of the melt. The first slit 3 must have a sufficiently small width to generate capillary climbing force, allowing the melt to climb upward along the first slit 3 and eventually cross over the top of the inner wall crucible 2. Then, under the action of gravity, it flows downward to form a flowing liquid film, preventing the grown crystal from directly contacting the inner circumferential surface of the inner wall crucible 2, thus forming a buffer layer.

[0034] A second slit 4 is provided on the side wall of the inner wall crucible 2, extending along the axial direction of the inner wall crucible 2 and penetrating through the wall thickness of the inner wall crucible 2. The second slit 4 connects the first slit 3 with the crystal growth chamber. In this case, the melt can pass through this second slit 4 and enter the inner circumferential surface of the inner wall crucible 2 to form a flowing liquid film. This can combine with the flowing liquid film introduced by the capillary channel to form a buffer between the crystal and the crucible. The spacing and number of such second slits 4 can be selected according to actual needs and are not limited here.

[0035] The bottom of the inner wall crucible 2 is provided with a flow structure 5 that connects the crystal growth chamber and the first slit 3. In this case, the melt can pass through the inner wall crucible 2 through the flow structure 5 and then enter the first slit 3 for capillary ascent. The number, shape, size and spacing of such flow structures 5 can be selected according to actual needs and are not limited here.

[0036] The melt in the crystal growth chamber can enter the first slit 3 through the flow structure 5 and climb up under capillary action, and then flow back and / or penetrate through the second slit 4 to the inner circumferential surface of the inner wall crucible 2, forming a dynamic melt liquid film on the inner circumferential surface of the inner wall crucible 2 that isolates the crystal from the inner wall crucible 2.

[0037] It should be noted that the double-layer crucible assembly in this invention is a crucible assembly composed of an outer wall crucible 1 and an inner wall crucible 2 coaxially nested. The outer wall crucible 1 is responsible for induction heating, the inner wall crucible 2 constitutes the crystal growth cavity, and the first slit 3 is an annular capillary gap formed between the inner side wall of the outer wall crucible 1 and the outer side wall of the inner wall crucible 2, which constitutes a capillary liquid flow channel. The flow structure 5 serves as the total fluid inlet of the first slit 3, which breaks the rigid seal at the bottom of the inner wall crucible 2, allowing the liquid melt in the crystal growth cavity to flow laterally and overflow into the first slit 3, providing a continuous supply of melt with reduced flow resistance for the longitudinal capillary climbing and lateral film formation circuits.

[0038] It should also be noted that the high surface tension gallium oxide melt exhibits strong micro-wetting properties towards iridium, even under capillary-driven pressure differential. Under the influence of γ, where γ is the surface tension of the melt, θ is the contact angle, and d1 is the width of the first slit 3, the melt can spontaneously climb upwards along the first slit 3 and fill the entire annular channel, then flow back to the inner side of the inner wall crucible 2 to form a liquid film. This dynamic melt liquid film changes the contact between the crystal solid phase and the iridium crucible wall from a solid-solid hard contact to a solid-liquid fluid soft contact, physically isolating the rigid contact between the crystal and the crucible wall, thus achieving the purpose of preventing adhesion. Of course, the melt in this invention can be gallium oxide melt, or other melts of high-melting-point crystals that require growth using an iridium crucible; there are no limitations here.

[0039] As described above, in the embodiments of the double-layer crucible assembly provided by the present invention, since it includes an outer wall crucible 1 and an inner wall crucible 2 coaxially nested inside the outer wall crucible 1, an annular first slit 3 is formed between the inner sidewall of the outer wall crucible 1 and the outer sidewall of the inner wall crucible 2, the first slit 3 constitutes a capillary channel for capillary climbing of the melt; a second slit 4 is provided on the sidewall of the inner wall crucible 2, extending axially along the inner wall crucible 2 and penetrating the wall thickness of the inner wall crucible 2, the second slit 4 connects the first slit 3 and the crystal growth cavity; a flow structure 5 is provided at the bottom of the inner wall crucible 2, connecting the crystal growth cavity and the first slit 3; the melt in the crystal growth cavity can flow through the first slit 3. The crystal enters the first slit 3 through the through structure 5 and rises under capillary action, then flows back and / or penetrates through the second slit 4 to the inner circumferential surface of the inner wall crucible 2, forming a dynamic melt film on the inner circumferential surface of the inner wall crucible 2 that isolates the crystal from the inner wall crucible 2. Therefore, by using this dynamic melt film, solid-solid adhesion between the crystal and the inner wall of the crucible can be avoided during the casting process of gallium oxide crystal growth, and the rigid mechanical constraint thermal stress caused by the anisotropic mismatch of the thermal expansion coefficients of the single crystal and the metal during the cooling stage can be actively released, thereby avoiding crystal cracking and the introduction of dislocations. At the same time, it can prevent irreversible deformation of the crucible caused by the thermal shrinkage deformation of the high-hardness single crystal, thus reducing production costs.

[0040] In a specific embodiment of the above-mentioned double-layer crucible assembly, the width of the first slit 3 can be configured such that the height of the melt in the first slit 3 rising under capillary action is greater than the vertical height difference between the melt surface and the top edge of the inner wall crucible 2, so that the melt in the first slit 3 can flow back over the top edge of the inner wall crucible 2 to the inner circumferential surface of the inner wall crucible 2.

[0041] It should be noted that only when the capillary climb height is greater than the vertical height difference between the melt surface and the top edge of the inner wall crucible 2 at the initial melt level can the melt within the first slit 3 spontaneously climb over the top edge and form an initial liquid film on the inner circumferential surface of the inner wall crucible 2. Specifically, the width d1 of the first slit 3 can preferably be 0.2 mm to 1.5 mm, for example, 0.8 mm, at which point the maximum capillary climb height can reach 15 mm to 18 mm. Those skilled in the art can precisely design d1 according to the surface tension and contact angle parameters of the target melt. For melts with higher surface tension, d1 can be appropriately increased, which is not limited here.

[0042] In another specific embodiment of the above-mentioned double-layer crucible assembly, there are multiple second slits 4, and the multiple second slits 4 are distributed at intervals along the circumference of the inner wall crucible 2;

[0043] The second slit 4 extends upward from the bottom edge of the inner wall crucible 2, and there is a gap between the top of the second slit 4 and the top opening of the inner wall crucible 2 so that the top of the inner wall crucible 2 remains continuous.

[0044] Multiple second slits 4 discretize the sidewall of the inner crucible 2 into multiple arc-shaped elastic blades capable of radial elastic deformation.

[0045] It should be noted that the second slit 4 has a dual function: on the one hand, it is a key liquid distribution channel connecting the first slit 3 and the crystal growth cavity, enabling the melt to spread and distribute from the first slit 3 to the inner circumferential surface of the inner wall crucible 2 in all directions; on the other hand, multiple second slits 4 discretize the sidewall of the inner wall crucible 2 into multiple arc-shaped elastic blades, giving the inner wall crucible 2 radial flexibility, while the continuous part at the top of the inner wall crucible 2 forms a reinforcing ring, which forms an elastic constraint on the top of each arc-shaped elastic blade.

[0046] Specifically, the number of second slits 4 can be selected from 2 to 8, preferably 8. When the number is 2, liquid film coverage can still be achieved, and there are 2 elastic blades. When the number is 8, the liquid film distribution is more uniform, the blades are finer and the elasticity is stronger. The specific number can be optimized according to the crucible size, crystal size and material properties. The slit width d2 of the second slit 4 can be 0.1 mm to 0.8 mm, for example, 0.5 mm. The second slit 4 extends upward from the bottom edge of the inner wall crucible 2 to a height of 70 mm to 90 mm, that is, its top end is about 10 mm from the bottom edge of the top opening of the inner wall crucible 2. In addition, the cross-sectional shape of the second slit 4 is not limited to a rectangular straight slit, and can also be designed as a wedge, elliptical or other cross-sections to further optimize the fluid spreading rate and the stiffness characteristics of the elastic blades. There is no limitation here.

[0047] In another specific embodiment of the above-mentioned double-layer crucible assembly, the wall thickness of the inner wall crucible 2 is set to be thinner at the top and thicker at the bottom along the axial direction, and the inner circumferential surface of the inner wall crucible 2 is an inverted conical slope surface that is wider at the top and narrower at the bottom.

[0048] Specifically, the upper wall thickness of the inner crucible 2 can be 1mm to 2mm, for example, 1.5mm, and the lower wall thickness can be 1.5mm to 2.5mm, for example, 2mm, with the lower wall thickness being greater than the upper wall thickness. The axial height can be 80mm to 100mm. The purpose of this design is twofold: firstly, the inverted conical slope, wider at the top and narrower at the bottom, can weaken the gravitational downward force of the liquid film flowing along the inner circumferential surface, which is beneficial for the spreading and retention of the liquid film on the inner circumferential surface; secondly, the outer contour of the crystallized single crystal will naturally present an inverted funnel shape, wider at the top and narrower at the bottom. When demolding, only a small vertical upward pulling force needs to be applied to the single crystal, and a physical gap can be formed between the outer wall of the crystal and the inner circumferential surface of the inner crucible 2, thereby achieving in-situ, non-destructive demolding of the entire single crystal.

[0049] In a preferred embodiment of the above-mentioned double-layer crucible assembly, both the outer wall crucible 1 and the inner wall crucible 2 are made of iridium. The outer wall crucible 1 is the direct heating object of the induction coil and constitutes the active heat source of the crystal growth thermal field.

[0050] It should be noted that iridium has a melting point of approximately 2446℃ and possesses excellent high-temperature chemical stability and resistance to oxidation and corrosion, making it an indispensable crucible material for growing high-melting-point gallium oxide single crystals. The outer crucible 1, as the direct heating object of the induction coil, is the active heat source for the entire thermal field. Utilizing the skin effect of mid-frequency induction heating, a specific radial thermal field is established, ensuring that the temperature of the outer crucible 1 > the temperature of the melt within the first slit 3 > the temperature of the inner crucible 2 > the temperature of the dynamic melt film > the temperature of the main melt at the center of the crystal growth cavity on any radial cross-section. Therefore, as the crystal at the center of the melt gradually grows outwards with a uniform diameter and the crystallization front continuously approaches the crucible wall, the melt within the first slit 3 and the second slit 4 remains in a liquid state without premature crystallization and blockage. The dynamic melt film continuously receives melt replenishment and maintains full coverage of the inner wall without additional control until crystal growth is complete. Specifically, the wall thickness of the outer wall crucible 1 can be 1.5mm to 3mm, the axial height can be 90mm to 110mm, and the inner diameter of the straight cylinder can be 110mm to 130mm; the axial height of the inner wall crucible 2 is less than the axial height of the outer wall crucible 1, for example, the inner wall crucible 2 is about 10mm lower than the outer wall crucible 1, which serves as a safety boundary so that the melt that crosses the top edge of the inner wall crucible 2 is blocked by the outer wall crucible 1 and will not overflow outward.

[0051] In another preferred embodiment of the above-mentioned double-layer crucible assembly, the above-mentioned flow structure 5 is a plurality of flow gaps opened at the bottom of the inner wall crucible 2. The plurality of flow gaps are evenly distributed along the circumference of the inner wall crucible 2 so that the melt in the crystal growth cavity can flow laterally into the first slit 3.

[0052] Specifically, multiple flow gaps can be formed at the outer edge of the arc-shaped corner of the bottom surface of the inner wall crucible 2, for example, eight arc-shaped flow gaps with identical geometric dimensions. The flow cross-sectional height d3 of a single flow gap can be 0.5 mm to 1.5 mm, for example, 1 mm, and they are evenly and centrally symmetrically arranged along the circumferential direction at the bottom edge of the inner wall crucible 2, thereby breaking the rigid seal at the bottom of the inner wall crucible 2 and allowing the melt in the crystal growth cavity to flow laterally into the first slit 3. Of course, in addition to the directly open flow gaps mentioned above, the flow structure 5 can also be designed as a flow guide groove or a directional aperture array, etc., to optimize the uniformity of the flow distribution of the melt entering the first slit 3, which is not limited here.

[0053] In another preferred embodiment of the above-mentioned double-layer crucible assembly, when the crystal cools and shrinks, multiple arc-shaped elastic blades can radially elastically retract toward the first slit 3 side to release the thermal stress between the crystal and the inner wall crucible 2.

[0054] Specifically, taking the opening of eight second slits 4 as an example, the original continuous cylindrical rigid structure of the inner wall crucible 2 is discretized in cross-section into eight arc-shaped elastic blades with extremely high radial flexibility. During the final cooling and shrinkage stage, when severe anisotropic compressive stress is generated due to the mismatch of the linear expansion coefficients of the crystal and iridium, each arc-shaped elastic blade undergoes a slight radial retreat and elastic displacement in the space towards the first slit 3 under the elastic constraint of the top reinforcing ring, or actively dissipates and releases the destructive mechanical constraint thermal stress through the closing or opening displacement of the second slit 4 itself. This can greatly reduce the single crystal cracking rate. Furthermore, since the stress is released through elastic deformation rather than transferred to the crucible material body, the possibility of plastic deformation damage to the expensive iridium crucible can be reduced, thus improving the service life.

[0055] An embodiment of the crystal growth method provided by this invention is as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of an embodiment of a crystal growth method provided by the present invention, employing a double-layer crucible assembly as described in any of the above claims. The method may include the following steps:

[0056] S1: The inner wall crucible 2 is nested axially inside the outer wall crucible 1, so that the bottom surface of the inner wall crucible 2 is attached to the inner bottom surface of the outer wall crucible 1. The assembled double-layer crucible assembly is placed in the hot field of the induction furnace and aligned with the induction coil. Raw materials are filled into the crystal growth chamber, a vacuum is drawn and protective gas is introduced to positive pressure.

[0057] Specifically, in step S1, before assembly, the outer wall crucible 1 and inner wall crucible 2 can be cleaned and dried to remove surface oil and adsorbed moisture, avoiding contamination of the melt at high temperatures. Then, using tooling, the inner wall crucible 2 can be precisely embedded into the cavity of the outer wall crucible 1 along the vertical axis, so that the bottom surface of the inner wall crucible 2 directly adheres to and is located on the inner bottom surface of the outer wall crucible 1 by its own weight. At this time, the flow structure 5 at the bottom edge of the inner wall crucible 2 connects the crystal growth cavity with the first slit 3, providing a channel for the subsequent lateral flow of the melt. When placing the assembled double-layer crucible assembly into the hot zone of the induction furnace, strict... The induction coil is aligned with the grid to ensure the geometric symmetry of electromagnetic induction heating in the circumferential direction, avoiding local overheating or uneven temperature. The filling material can be sintered gallium oxide blocks. The filling amount should be such that the initial height of the main melt surface in the crystal growth cavity is accurately and stably stabilized at a predetermined position (e.g., 85 mm) after complete melting. This initial liquid level determines whether the subsequent capillary reflux can be successfully established. Finally, a vacuum is drawn and a protective gas (e.g., carbon dioxide) is introduced to positive pressure. This can not only remove air from the furnace and suppress the volatilization and decomposition of gallium oxide melt at high temperature, but the positive pressure environment is also conducive to maintaining the stability of the melt.

[0058] S2: Heating completely melts the raw material. The melt in the crystal growth chamber enters the first slit 3 through the flow structure 5 and rises and flows back under capillary action, forming a dynamic melt film on the inner circumferential surface of the inner wall crucible 2.

[0059] Specifically, in step S2, a medium-frequency power supply can be started to control the heating program to linearly increase the temperature at a rate of 5°C / min to 10°C / min to above the melting point of the raw material (the melting point of gallium oxide is approximately 1800°C), and after establishing an initial superheat of 10°C to 30°C, the material is allowed to stand and stabilize for 1 to 2 hours to allow it to completely melt and fully degas. After melting, the main melt flows outward instantaneously through the flow structure 5 under the influence of gravity and the principle of communicating vessels, filling the first slit 3. Because the gallium oxide melt has a strong affinity for iridium... With strong micro-wetting properties, under the action of capillary-driven pressure difference, the melt in the first slit 3 spontaneously rises upward and over the top edge of the inner wall crucible 2. After being blocked by the outer wall crucible 1, it is turned back and flows downward along the inner circumference of the inner wall crucible 2, merging with the melt that is simultaneously spreading laterally through the second slit 4. This spontaneously forms a continuous dynamic melt film on the inner circumference of the inner wall crucible 2. The thickness of the melt film can reach more than 1 mm, laying the foundation for the soft physical isolation between the subsequent crystallization front and the crucible wall.

[0060] S3: Reduce heating power to control cooling, so that the melt surface in the crystal growth chamber nucleates and crystallizes downward in situ. As the melt is consumed, the melt surface in the crystal growth chamber drops. The melt in the first slit 3 is supplied to the inner circumferential surface of the inner wall crucible 2 through the second slit 4, maintaining the dynamic melt film covering the side of the crystallization front.

[0061] Specifically, in step S3, a gradual linear power reduction program can be applied to the induction coil, for example, controlling the heating power to continuously decrease at a rate of 1.0 W / min to 2.0 W / min (typically 1.0 W / min), to achieve extremely slow directional solidification. Based on the fact that the heat source is on the outside and at the natural heat dissipation boundary, the core area of ​​the main melt surface, located at the farthest end of the heat source center and with the fastest heat dissipation, reaches the crystallization point first, thus achieving seedless surface self-nucleation. Subsequently, the crystallization front expands radially around the perimeter in an umbrella shape, while simultaneously monotonically advancing downwards. Throughout the growth process, the thermal field maintains a radial temperature gradient of: temperature of the outer wall crucible 1 > temperature of the melt inside the first slit 3 > temperature of the inner wall crucible 2 > temperature of the dynamic melt film > temperature of the central main melt, so that... The melt within the first slit 3 and the second slit 4 remains in a liquid state and does not prematurely crystallize and block the flow. As crystallization proceeds downwards in situ, the melt level in the crystal growth chamber continuously decreases due to material consumption. When the melt level in the crystal growth chamber drops below a predetermined critical height (e.g., 72mm to 75mm), the melt in the first slit 3 overturns the backflow interruption at the top edge of the inner wall crucible 2. The melt in the first slit 3 then transitions to in-situ infiltration and replenishment by passing laterally through the second slit 4 at the current dynamic liquid level. Wherever the crystallization front descends, the second slit 4 immediately releases liquid to form a film at its corresponding axial height section, dynamically tracking and protecting the active crystallization interface. The solid side of the crystal is separated from the inner wall of the iridium by a liquid film from beginning to end, and the thickness of the liquid film can be stably maintained above 1mm.

[0062] S4: After the melt has completely crystallized, it is cooled down. The sidewall of the inner crucible 2 undergoes radial elastic yielding under the dispersion action of the second slit 4, releasing the thermal stress generated by the cooling and shrinkage of the crystal. After cooling to room temperature, it is demolded and the crystal is taken out.

[0063] Specifically, in step S4, when the power is reduced to the point where the main material in the entire crucible is completely transformed into a solid crystal, and the thin layer of melt within the outermost first slit 3 also enters the crystallization stage, the in-situ growth ends. Subsequently, the system enters the forced annealing solid-phase cooling stage. At this time, due to the mismatch in the linear expansion coefficients of the crystal and iridium, severe anisotropic compressive stress will occur. The multiple arc-shaped elastic blades formed by the second slit 4, under the elastic constraint of the top reinforcing ring, can undergo slight radial retreat and elastic displacement towards the space on one side of the first slit 3. Dynamic decompression releases destructive mechanical constraint thermal stress, reducing the single crystal cracking rate by more than 90%. At the same time, the expensive crucible will not be damaged by plastic deformation, thus extending its reuse life. After cooling to room temperature and demolding, since the inner circumferential surface of the inner wall crucible 2 is an inverted conical slope that is wider at the top and narrower at the bottom, the outer contour of the crystallized single crystal naturally has an inverted funnel shape that is larger at the top and smaller at the bottom. Only a small vertical upward pulling force needs to be applied to the single crystal to form a physical gap between the outer wall of the crystal and the inner circumferential surface of the inner wall crucible 2, thereby achieving the in-situ, non-destructive, and integral removal of the entire single crystal.

[0064] Of course, the crystal growth method provided by this invention is not only applicable to the growth of gallium oxide single crystals, but also to the growth of various doped gallium oxide crystals, or other high-melting-point crystals suitable for iridium crucibles, and is not limited here.

[0065] In a specific embodiment of the above crystal growth method, in step S2, the melt in the first slit 3 is flipped over the top edge of the inner wall crucible 2 under capillary action and flows back, merging with the melt spread through the second slit 4, forming a continuous dynamic melt film on the inner circumferential surface of the inner wall crucible 2; in step S3, as the melt level in the crystal growth cavity drops, after the backflow over the top edge of the inner wall crucible 2 is interrupted, the melt in the first slit 3 is replaced by lateral permeation and replenishment through the second slit 4 at the current liquid level, so that the dynamic melt film dynamically tracks and covers the side of the crystallization front.

[0066] It should be noted that this is a dual-track fluid relay mechanism: In the initial stage of operation after the material is melted, the main liquid level is high, and the second slit 4 is submerged below the melt surface line in the crystal growth chamber. The melt in the first slit 3, under capillary action, rolls over the top edge of the inner wall crucible 2, but is blocked by the outer wall crucible 1 and cannot overflow. It is forced to turn back and flow down the slope of the inner circumference of the inner wall crucible 2, merging with the melt that spreads laterally through the second slit 4, forming a complete encapsulation. A continuous initial reflux liquid film is formed. As crystallization consumes material, the melt level in the crystal growth chamber decreases monotonically. When the vertical height difference between the melt level in the crystal growth chamber and the top edge of the inner wall crucible 2 exceeds the capillary climb limit, the top overflows the reflux channel and remains dry. At this time, the melt in the first slit 3, which is filled by capillary force, no longer climbs upwards, but directly passes through the second slit 4 at the current dynamic liquid level, overflows on the spot, and spreads on the inner circumference of the inner wall crucible 2. This constructs an adaptive dynamic tracking loop: wherever the crystallization front drops, the melt level in the crystal growth chamber drops, and the second slit 4 immediately releases liquid to form a film at its corresponding height section. The area above that has crystallized and detached from the liquid film dries naturally, while the side of the active crystallization front that needs protection below is constantly replenished with melt, thus achieving uninterrupted soft physical barrier at all liquid levels and throughout the entire cycle. The liquid film thickness can be stably maintained above 1 mm.

[0067] In another specific embodiment of the above crystal growth method, the inner circumferential surface of the inner wall crucible 2 is an inverted conical slope surface that is wider at the top and narrower at the bottom; in step S4, after cooling to room temperature, a vertical upward pulling force is applied to the crystal to form a gap between the outer circumferential surface of the crystal and the inner circumferential surface of the inner wall crucible 2, so that the entire crystal is lifted away from the inner wall crucible 2 in situ without damage.

[0068] It should be noted that, since the inner circumferential surface of the inner wall crucible 2 is an inverted conical slope that is wider at the top and narrower at the bottom, the outer contour of the crystallized single crystal naturally presents an inverted funnel shape that is larger at the top and smaller at the bottom. Therefore, when demolding, only an extremely small vertical upward linear pulling force needs to be applied. A physical gap will be generated between the outer wall of the crystal and the inner circumferential surface of the inner wall crucible 2 in a very short time. Without knocking or damaging the crucible, the entire single crystal can be lifted out in situ without damage, avoiding damage to the crystal and crucible during the demolding process.

[0069] The following example illustrates the double-layer crucible assembly and crystal growth method provided by this invention through a complete gallium oxide crystal growth process, so that those skilled in the art can more clearly understand the technical solution of this invention. However, the following process is only an example and should not be construed as a limitation on the scope of protection of this invention.

[0070] (1) Loading the furnace: Clean and dry the double-layer crucible assembly; use tooling to precisely embed the inner wall crucible 2 into the cavity of the outer wall crucible 1 along the vertical axis, so that its bottom surface is directly attached to the inner bottom surface of the outer wall crucible 1 by its own weight. At this time, the eight arc-shaped flow gaps at the bottom edge of the inner wall crucible 2 connect the crystal growth cavity with the first slit 3; place the assembled assembly into the hot field of the medium frequency induction heating furnace, strictly center the induction coil, and ensure the geometric symmetry of electromagnetic induction heating in the circumferential direction; fill the sintered gallium oxide material block into the crystal growth cavity inside the inner wall crucible 2, so that the initial height of the melt surface of the main cavity after complete melting is accurately stabilized at 85mm, evacuate and introduce carbon dioxide to positive pressure.

[0071] (2) Material preparation: Start the intermediate frequency power supply and control the heating program to linearly heat up to above 1800℃ (gallium oxide melting point) at a rate of 5℃ / min to 10℃ / min, establish an initial superheat of 10℃ to 30℃ and let it stand for 1h to 2h to allow the material to melt completely and exhaust the gas fully; the main melt flows outward instantaneously through the flow gap at the bottom edge under the principle of gravity and communicating vessels, filling the first slit 3; driven by capillary pressure difference, the melt spontaneously rises significantly upward in the first slit 3, with a maximum rise height of 15mm to 18mm; due to the distance between the melt liquid surface (85mm) in the initial crystal growth cavity and the top edge of the inner wall crucible 2 ( With only about 5mm of axial height difference remaining (90mm), the capillary-suctioned fluid rushes over the top edge in a very short time. It is forced to turn back due to the obstruction of the outer wall crucible 1 (about 100mm in height) and flows down the inner circumference of the inner wall crucible 2 in a waterfall-like manner. It can accurately cover and protect the top reinforcing ring of the 80mm to 90mm section. At the same time, the second slit 4 (0 to 80mm section) submerged below the liquid level performs lateral hydraulic distribution and merges with the backflow flowing down from the top. Under the synergistic effect of the inverted conical slope weakening the downward force of gravity, a continuous dynamic melt film layer with a thickness of not less than 1mm is spontaneously constructed on the inner circumference of the inner wall crucible 2.

[0072] (3) Growth control: Apply a gradual linear power reduction program to the induction coil to control the heating power to continuously decrease at a rate of 1.0W / min to 2.0W / min; the core area at the center of the main melt surface reaches the crystallization point first, realizing self-nucleation of the seedless crystal surface, and then the crystallization front expands radially in an umbrella shape and simultaneously grows monotonically downward; when the melt level in the crystal growth chamber drops below the critical height of 72mm to 75mm, the power of the melt in the first slit 3 to overcome gravity and cross the top edge is exhausted, the top overturning backflow is interrupted and dried up, at this time the melt accumulated in the first slit 3 no longer climbs upward on the current low liquid level reference, but directly passes through the second slit 4 (the slit width can be 0.5mm) at the current dynamic liquid level height, and performs in-situ lateral penetration replenishment; wherever the crystallization front drops, the second slit 4 immediately vents liquid to form a film on its corresponding axial height section, separating the solid side of the crystal from the inner wall of the iridium with a liquid film from beginning to end, and the thickness of the liquid film is stably maintained above 1mm.

[0073] (4) End of growth and cooling demolding: When the power is reduced to the point that the main material of the whole pot is completely transformed into solid crystal and the thin layer of melt in the outermost first slit 3 also enters the crystallization stage, the in-situ growth ends; the system enters the forced annealing solid phase cooling stage. Under the elastic constraint of the top reinforcing ring, the 8 arc-shaped elastic blades make slight radial retreat and elastic displacement to the space on one side of the first slit 3, actively eliminating and releasing the destructive mechanical restraint thermal stress, which is beneficial to reducing the risk of single crystal cracking; after cooling to room temperature, the mold is demolded. Since the inner circumferential surface of the inner wall crucible 2 is an inverted conical slope surface that is wider at the top and narrower at the bottom, only a small vertical upward linear pulling force needs to be applied to the single crystal. The outer wall of the crystal and the inner circumferential surface of the inner wall crucible 2 will generate a physical gap in a very short time, realizing the whole single crystal in-situ non-destructive overall removal.

[0074] It should be noted that the specific dimensions, liquid level height and process parameters described in steps (1) to (4) above are only a preferred example of the present invention. Those skilled in the art can make adaptive adjustments according to the crucible size, crystal size and material properties, which are not limited here.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A double-layer crucible assembly, characterized in that, It includes an outer wall crucible (1) and an inner wall crucible (2) coaxially nested inside the outer wall crucible (1). The bottom surface of the inner wall crucible (2) is located on the inner bottom surface of the outer wall crucible (1). The internal space of the inner wall crucible (2) constitutes a crystal growth cavity. An annular first slit (3) is formed between the inner wall of the outer wall crucible (1) and the outer wall of the inner wall crucible (2), and the first slit (3) constitutes a capillary channel for capillary climbing of the melt. The inner wall crucible (2) has a second slit (4) extending along the axial direction of the inner wall crucible (2) and penetrating the wall thickness of the inner wall crucible (2). The second slit (4) connects the first slit (3) with the crystal growth cavity. The bottom of the inner wall crucible (2) is provided with a flow structure (5) that connects the crystal growth cavity with the first slit (3). The melt in the crystal growth chamber can enter the first slit (3) through the flow structure (5) and climb up under capillary action, and then flow back and / or penetrate through the second slit (4) to the inner circumferential surface of the inner wall crucible (2), forming a dynamic melt liquid film on the inner circumferential surface of the inner wall crucible (2) that isolates the crystal from the inner wall crucible (2).

2. The double-layer crucible assembly according to claim 1, characterized in that, The width of the first slit (3) is configured such that the height of the melt in the first slit (3) rising under capillary action is greater than the vertical height difference between the melt surface and the top edge of the inner wall crucible (2), so that the melt in the first slit (3) can flow back to the inner circumferential surface of the inner wall crucible (2) over the top edge of the inner wall crucible (2).

3. The double-layer crucible assembly according to claim 1 or 2, characterized in that, The second slit (4) consists of multiple slits, which are distributed at intervals along the circumference of the inner wall crucible (2). The second slit (4) extends upward from the bottom edge of the inner wall crucible (2), and there is a gap between the top of the second slit (4) and the top opening of the inner wall crucible (2) so that the top of the inner wall crucible (2) remains continuous. Multiple second slits (4) discretize the sidewall of the inner wall crucible (2) into multiple arc-shaped elastic blades capable of radial elastic deformation.

4. The double-layer crucible assembly according to claim 1, characterized in that, The inner wall crucible (2) has a wall thickness that is thinner at the top and thicker at the bottom along the axial direction, and the inner circumferential surface of the inner wall crucible (2) is an inverted conical slope surface that is wider at the top and narrower at the bottom.

5. The double-layer crucible assembly according to claim 1, characterized in that, Both the outer wall crucible (1) and the inner wall crucible (2) are made of iridium. The outer wall crucible (1) is the direct heating object of the induction coil and constitutes the active heat source of the crystal growth thermal field.

6. The double-layer crucible assembly according to claim 1, characterized in that, The flow structure (5) consists of multiple flow gaps at the bottom of the inner wall crucible (2), which are evenly distributed along the circumference of the inner wall crucible (2) so that the melt in the crystal growth cavity can flow laterally into the first slit (3).

7. The double-layer crucible assembly according to claim 3, characterized in that, When the crystal cools and shrinks, the multiple arc-shaped elastic blades can radially elastically retract toward the first slit (3) to release the thermal stress between the crystal and the inner wall crucible (2).

8. A crystal growth method, employing the double-layer crucible assembly as described in any one of claims 1 to 7, characterized in that, include: S1: The inner wall crucible (2) is nested axially inside the outer wall crucible (1), so that the bottom surface of the inner wall crucible (2) is attached to the inner bottom surface of the outer wall crucible (1). The assembled double-layer crucible assembly is placed in the hot field of the induction furnace and aligned with the induction coil. Raw materials are filled into the crystal growth chamber, a vacuum is drawn, and protective gas is introduced to positive pressure. S2: Heating causes the raw material to melt completely. The melt in the crystal growth cavity enters the first slit (3) through the flow structure (5) and rises and flows back under capillary action, forming a dynamic melt film on the inner circumferential surface of the inner wall crucible (2). S3: Reduce the heating power to control the cooling, so that the melt surface in the crystal growth chamber nucleates and crystallizes downward in situ. As the melt is consumed, the melt surface in the crystal growth chamber drops. The melt in the first slit (3) is supplied to the inner circumferential surface of the inner wall crucible (2) through the second slit (4) to maintain the coverage of the dynamic melt film on the side of the crystallization front. S4: After the melt is completely crystallized, it is cooled down. The side wall of the inner wall crucible (2) undergoes radial elastic yielding under the discrete action of the second slit (4), releasing the thermal stress generated by the cooling and shrinkage of the crystal. After cooling to room temperature, it is demolded and the crystal is taken out.

9. The crystal growth method according to claim 8, characterized in that, In step S2, the melt in the first slit (3) is flipped over the top edge of the inner wall crucible (2) under capillary action and flows back, merging with the melt spread through the second slit (4) to form a continuous dynamic melt film on the inner circumferential surface of the inner wall crucible (2); in step S3, as the melt level in the crystal growth cavity drops, after the backflow over the top edge of the inner wall crucible (2) is interrupted, the melt in the first slit (3) is replaced by lateral permeation and replenishment through the second slit (4) at the current liquid level, so that the dynamic melt film dynamically tracks and covers the side of the crystallization front.

10. The crystal growth method according to claim 8 or 9, characterized in that, The inner circumferential surface of the inner wall crucible (2) is an inverted conical slope surface that is wider at the top and narrower at the bottom. In step S4, after cooling to room temperature, a vertical upward pulling force is applied to the crystal to form a gap between the outer circumferential surface of the crystal and the inner circumferential surface of the inner wall crucible (2), so that the entire crystal is lifted out of the inner wall crucible (2) in situ without damage.

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