A flexible support seed holder for pvt aluminum nitride crystal growth

Abstract

The utility model discloses a kind of elastic support seed crystal holder for PVT aluminum nitride crystal growth, the device includes pedestal body, fixed on pedestal body elastic support component and lap on elastic support component elastic buffer layer, it is also equipped with annular rigid support platform, spring positioning seat and the guiding column of buffer layer radial positioning and the like auxiliary structure.Elastic support component adopts variable diameter variable pitch tungsten alloy spring, cooperate elastic buffer layer to realize heat stress efficient release;Guiding column bottom is connected with pedestal body, top is equipped with disc limit structure, annular rigid support platform and guiding column collaborative control inverted state under seed crystal total floating amount≤0.1mm.The utility model effectively solves the problem of traditional seed crystal holder heat stress concentration, gravity subsidence, spring contraction and high temperature deformation, make large size seed crystal cracking rate from 40% to 10% below, significantly improve the quality and stability of aluminum nitride single crystal growth, applicable to large-scale aluminum nitride single crystal preparation scene.

Description

Technical Field

[0001] This invention belongs to the technical field of aluminum nitride single crystal growth equipment, specifically relating to an elastic support seed crystal seat for growing aluminum nitride single crystals by physical vapor transport (PVT) method. Background Technology

[0002] Aluminum nitride single crystals are ultra-wide bandgap semiconductor materials with a high bandgap (6.2 eV), high thermal conductivity (340 W / (m∙K)), high breakdown field strength (11.7 MV / cm), and excellent ultraviolet transmittance. They have irreplaceable application value in optoelectronic fields such as high-temperature electronic devices, deep-ultraviolet LEDs, and ultraviolet detectors. Currently, physical vapor transport (PVT) is the mainstream technology for preparing high-quality aluminum nitride single crystals. Its core principle is to sublimate aluminum nitride raw materials into vapor in a high-temperature, high-vacuum environment of 1800-2200℃, and then deposit the vapor on the surface of the seed crystal to grow into a single crystal.

[0003] As a key component supporting the seed crystal in the PVT growth system, the performance of the seed crystal directly determines the stability of the seed crystal and the quality of single crystal growth. Existing seed crystal holders suffer from the following core defects, severely hindering the industrialization of aluminum nitride single crystals: (1) Thermal stress concentration problem: Traditional seed crystal bases mostly adopt rigid structures (such as integrated silicon carbide bases), which cannot alleviate the difference in thermal expansion coefficients between the seed crystal and the supporting structure (the thermal expansion coefficient of aluminum nitride is about 4.9×10). -6 / ℃, silicon carbide approximately 4.5×10 -6 At high temperatures (°C), stress concentration can easily form inside the seed crystal, resulting in a cracking rate of over 40% for large-sized (≥40mm) seed crystals.

[0004] (2) Floating problem caused by gravity sinking and spring contraction: In the PVT method, the seed crystal is often arranged "downward" to optimize the vapor deposition path. However, the supporting components (such as ordinary metal springs) are prone to creep under high temperature environment, which causes the seed crystal position to shift, destroys the stability of the temperature field gradient, and thus causes the single crystal growth interface to be uneven.

[0005] (3) Problem of insufficient high temperature stability: Ordinary metal springs (such as stainless steel springs) are prone to oxidation and creep at high temperatures above 2000℃, resulting in failure of elastic function and inability to stably support seed crystals for a long time, leading to interruption of growth process or decline in crystal quality.

[0006] Therefore, developing a seed crystal holder that combines thermal stress buffering capability, floating control function, and high-temperature stability is of great significance for breaking through the industrialization bottleneck of aluminum nitride single crystals. Summary of the Invention

[0007] This invention aims to overcome the three major defects of existing seed crystal seats: insufficient thermal stress release, excessive vertical fluctuation, and unstable high-temperature structure. It provides an elastic support seed crystal seat that can significantly reduce the cracking rate of large-size seed crystals, ensure the accuracy of seed crystal growth position, and work stably for a long time at a high temperature of 2200℃.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0009] This invention provides an elastic support seed crystal base for PVT aluminum nitride crystal growth, achieving a performance breakthrough through the coordinated design of "main functional components" and "auxiliary structures". The elastic support seed crystal base includes at least three main functional components: a base body, an elastic support assembly, and an elastic buffer layer; and auxiliary structures consisting of guide posts, an annular rigid support platform, and a spring positioning seat. The specific structure of each component and their interconnections are as follows.

[0010] (1) Base body: As the main support of the entire seed crystal holder device, it is a circular block with a thickness of 12~15mm. Its diameter is matched according to the size of the seed crystal it supports. Assuming the diameter of the supported seed crystal is d, the diameter of the base body is preferably d+26~30mm. The base body is made of high-density graphite composite material or tungsten carbide alloy, which has both high strength and high temperature resistance, and provides stable support for other components. An annular groove is provided on the base body along one circumference of the center of the base body. The annular groove is used to fit and fix the annular rigid support platform. Several internal threaded holes are evenly pre-set on the base body along another circumference of the center of the base body. The internal threaded holes are used to connect with the guide post. The number of internal threaded holes is the same as the number of guide posts, preferably 3-6; more preferably M3-M4 internal threaded holes.

[0011] (2) Elastic support assembly: This consists of multiple identical tungsten alloy springs fixedly connected to the surface of the base body. These springs are evenly distributed circumferentially along the center of the base body. The tungsten alloy springs employ a "variable diameter, variable pitch" design, meaning the upper and lower sections of the spring have different pitches and wire thicknesses; the upper section has a thinner wire and a larger pitch, while the lower section has a thicker wire and a smaller pitch. The lower section of the spring refers to the end connected to the base body, and the upper section refers to the end away from the base body. This "variable diameter, variable pitch" design simultaneously meets the requirements of "sensitive response to low stress" and "stable load-bearing under high gravity." The tungsten alloy springs are made of W-Re-HfC alloy and coated with a boron nitride coating to enhance their high-temperature oxidation resistance and creep resistance. Furthermore, the tungsten alloy springs are welded to the surface of the base body. Preferably, the upper and lower sections of the tungsten alloy spring have the same natural elongation length, with the upper section having an inner diameter of 0.4-0.6 mm and a pitch of 0.8-1.2 mm, and the lower section having an inner diameter of 0.8-1.2 mm and a pitch of 0.4-0.6 mm.

[0012] Furthermore, the tungsten alloy spring is made of W-Re-HfC alloy, wherein the Re (rhenium) content is 5-10%, the HfC (hafnium carbide) content is 0.5-1%, and the remainder is W, and the spring surface is provided with a 5-10μm boron nitride coating.

[0013] Furthermore, the tungsten alloy spring undergoes aging treatment at 2100-2300℃ for 15-25 hours in a nitrogen atmosphere, and the deformation after pretreatment is ≤0.04mm.

[0014] (3) Elastic buffer layer: This is a thin, circular block, coaxially positioned above the base body. Its lower surface overlaps the upper surface of the elastic support assembly. Several guide holes are provided on this layer, each corresponding to a specific internal thread hole on the base body. The guide post passes through these guide holes to radially position the elastic buffer layer. During operation, an aluminum nitride seed crystal is bonded and fixed to the upper surface of the elastic buffer layer. The elastic buffer layer is made of flexible molybdenum alloy or high-purity flexible graphite. Radial micro-deformation helps release the thermal stress of the seed crystal, preventing stress concentration at the interface between the seed crystal and the support structure. Preferably, the thickness of the elastic buffer layer is 0.1-2.1 mm. The seed crystal is fixed to the elastic buffer layer using an aluminum nitride adhesive ≤5 μm thick, ensuring bonding strength while reducing stress transmission.

[0015] (4) Auxiliary structure: ① Guide post: Made of boron nitride ceramic, with an external thread at the bottom that matches the internal thread on the base body, and an integrally formed disc-shaped limiting structure at the top; the disc-shaped limiting structure has a diameter of 5-8mm and a thickness of 1-2mm; the guide post is detachably connected to the base body via the bottom external thread and the internal thread on the base body, and passes through a guide hole set in the elastic buffer layer, with a clearance of 0.03-0.12mm between the post body and the guide hole to achieve radial limiting; during initial installation, the lower surface of the disc-shaped limiting structure is in contact with the upper surface of the elastic buffer layer, and the lower surface of the elastic buffer layer is exactly overlapping the top of each tungsten alloy spring when it is naturally extended, thus achieving axial positioning of the elastic buffer layer and limiting the top of the tungsten alloy spring; furthermore, the number of guide posts is preferably 3-6, and the diameter of the post body is 3-4mm.

[0016] ② Annular Rigid Support Platform: Made of high-density tungsten carbide, it is rigidly fixed to the base body via an interference fit and a pre-set annular groove. Its height protruding from the upper surface of the base body is 0.08-0.22mm lower than the top of the tungsten alloy spring when it naturally elongates. When the spring contracts slightly due to high-temperature creep, the annular rigid support platform can promptly support the elastic buffer layer, preventing excessive floating of the seed crystal and controlling the total floating amount to ≤0.1mm. Therefore, the distance from the annular groove to the center of the base body is less than the radius of the elastic buffer layer, ensuring that the annular rigid support platform can support the elastic buffer layer when the spring contracts due to high-temperature creep.

[0017] ③ Spring positioning seat: Fixedly mounted on the upper surface of the base body, corresponding one-to-one with each tungsten alloy spring, cylindrical in shape, its outer diameter matching the inner diameter of the lower section of the tungsten alloy spring, allowing the cylindrical spring positioning seat to be inserted into the tungsten alloy spring for positioning and auxiliary support, preventing radial displacement of the spring. The height of the spring positioning seat is at least 0.1mm lower than the height of the tungsten alloy spring, preferably approximately equal to the length of the lower section of the tungsten alloy spring. The material is high-density tungsten carbide or high-density graphite composite material.

[0018] The core innovation of this utility model lies in solving the existing technical problems through the synergistic optimization of structural design and material selection: (1) Spring-buffer layer composite buffer structure: Breaking through the limitations of traditional single rigid or elastic support, the thermal stress is released in layers through the synergistic effect of the "radial deformation" of the elastic buffer layer and the "axial elasticity" of the variable diameter spring, reducing the stress level by more than 50% compared with the traditional rigid structure.

[0019] (2) Gravity-creep synergistic control mechanism: The height difference design of the ring rigid support platform is 0.08-0.22mm lower than the natural height of the spring, which precisely matches the maximum creep of the spring at 2200℃, forming a dual guarantee of "spring elastic support + support platform limit", which strictly controls the seed crystal floating amount within 0.1mm and solves the position displacement problem caused by high temperature creep.

[0020] (3) High temperature stable material system: Customized W-Re-HfC alloy spring (Re improves high temperature toughness, HfC enhances creep resistance) combined with boron nitride coating, so that the spring can maintain stable elasticity at a high temperature of 2200℃, and its service life is more than 3 times longer than that of ordinary metal springs.

[0021] (4) Precise positioning design of spring positioning seat: The newly added spring positioning seat can accurately position the spring one-to-one, avoid the radial displacement of the spring caused by high temperature vibration or assembly error, improve the uniformity of spring force, and further reduce the risk of seed crystal cracking.

[0022] (5) Integrated guide post limiting structure: The bottom of the guide post is fixed by a thread and the top is limited by a disc, which simultaneously achieves radial limiting and axial fixing, solving the problem that the buffer layer is easy to detach in the inverted state.

[0023] The workflow of this utility model's elastic support seed crystal seat in the aluminum nitride single crystal PVT growth process is as follows: The seed crystal is fixed to the central area of ​​the elastic buffer layer with aluminum nitride adhesive. The buffer layer is attached to the top of the elastic support component (i.e., tungsten alloy spring). The spring positioning seat is fixed to the base body. The tungsten alloy springs are inserted outside the spring positioning seat and the bottom of the spring is fixed to the base body. The guide post passes through the guide hole of the buffer layer and is fixed to the base body by the bottom thread. The top disc structure realizes the axial positioning of the buffer layer. The annular rigid support platform is fixed in the annular groove of the base body by interference fit. The assembled seed crystal holder is installed upside down in the PVT growth system, with the seed crystal facing downwards. (3) When the growth system is heated to 1800-2200℃, the stress generated by the thermal expansion of the seed crystal is first transferred to the elastic buffer layer, and the buffer layer initially releases 30%-40% of the stress through radial micro-deformation. (4) The remaining stress is transferred to the elastic support component. The variable diameter and variable pitch spring further absorbs the stress through axial expansion and contraction. The upper section with a fine pitch structure responds sensitively to small stresses, while the lower section with a coarse pitch structure ensures the load-bearing strength and structural stability.

[0024] (5) In a high-temperature environment, if the spring undergoes slight creep (deformation ≤0.04mm after pretreatment, deformation ≤0.08mm after long-term use), when the total floating amount approaches 0.1mm, the lower surface of the elastic buffer layer contacts the annular rigid support platform, and the support platform restricts the further floating of the buffer layer and the seed crystal; at the same time, the disc-shaped limiting structure at the top of the guide column forms a reverse limiting, providing double protection for position accuracy.

[0025] (6) The guide column ensures that the buffer layer and the seed crystal move only along the axial direction, avoiding the seed crystal tilting and damaging the temperature field; the boron nitride coating on the spring surface prevents the spring from sticking to the buffer layer and the base body, while protecting the spring from oxidation, ensuring that the entire device works stably during the growth cycle (more than 200 hours).

[0026] This invention achieves significant performance improvements in the growth of aluminum nitride single crystals through synergistic optimization of structure and materials, with the following specific beneficial effects: (1) Significant stress relief effect: The cracking rate of large-size (≥40mm) seed crystals has been reduced from 40% in the traditional structure to below 10%, a reduction of ≥30%, which greatly improves the utilization rate of seed crystals.

[0027] (2) Precise position control: The center of the seed crystal floats ≤0.1mm, and the height difference between the edge and the center is ≤0.03mm, ensuring a stable temperature gradient and avoiding unevenness of the single crystal growth interface due to position offset.

[0028] (3) Excellent high temperature stability: During the growth cycle of 2200℃ and 200 hours, the deformation of the tungsten alloy spring is ≤0.08mm and the elastic coefficient decay rate is ≤5%, which can meet the requirements of long-term continuous growth.

[0029] (4) Significant improvement in crystal quality: The electrical and optical properties of single crystals are better, ensuring the use of aluminum nitride single crystals and meeting the requirements for deep ultraviolet device fabrication.

[0030] (5) Stable spring positioning: The spring positioning seat effectively avoids radial displacement of the spring and improves the overall stability of the device.

[0031] (6) Reliable axial fixation: The bottom threaded connection of the guide column and the top disc limit solve the problem of the buffer layer easily detaching in the inverted state, and the overall stability of the device is improved by more than 60%. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an elastic support seed crystal seat structure according to various embodiments of the present invention.

[0033] In the figure: 1-base body, 2-tungsten alloy spring with boron nitride coating, 3-annular rigid support platform, 4-guide column, 5-elastic buffer layer, 6-seed crystal, 7-spring positioning seat.

[0034] In various embodiments of the utility model, before entering the PVT device, the assembly relationship of the components of the elastic support seed crystal seat is as follows: Figure 1 As shown in the figure: the seed crystal (6) is fixed to the center of the upper surface of the elastic buffer layer (5) by aluminum nitride adhesive; the spring positioning seat (7) is fixedly installed on the base body (1), the bottom end of the tungsten alloy spring (2) is fixed on the base body (1) and inserted outside the spring positioning seat (7); the elastic buffer layer (5) is placed on the tungsten alloy spring (2), and the lower surface of the elastic buffer layer (5) is in contact with the top end of the tungsten alloy spring (2); the guide post (4) passes through the preset guide hole on the elastic buffer layer (5), and the bottom is fixed to the base body (1) by thread, the post body realizes the radial limit of the elastic buffer layer (5), and the top disc structure integrally formed on the guide post (4) realizes the axial positioning of the elastic buffer layer (5); the annular rigid support platform (3) is fixed in the preset annular groove on the base body (1) by interference fit, and is arranged around the outside of the tungsten alloy spring (2), with the top end height being 0.08-0.22mm lower than the natural support height of the spring (2). During operation, the assembled elastic support seed crystal seat is inverted and installed in the PVT device to grow aluminum nitride crystals. Detailed Implementation

[0035] The following is a more detailed description in conjunction with the embodiments and accompanying drawings. Example

[0036] The elastic support seed crystal holder of this embodiment is suitable for aluminum nitride crystal growth by the PVT method using aluminum nitride seed crystals with a diameter of 40 mm.

[0037] The assembly structure of the elastic support seed crystal seat in this embodiment is as follows: Figure 1 The parameters for each component are selected as follows: Base body (1): The material is high-density graphite composite material, with a diameter of 68mm and a thickness of 12mm; an annular groove is pre-set on the upper surface of the base body, with an inner diameter of 52mm, an outer diameter of 62mm and a depth of 2mm; M3 internal thread holes are provided at the positions corresponding to the installation of 3 guide columns on the base body.

[0038] Tungsten alloy spring (2): In this embodiment, 8 tungsten alloy springs are used, which are evenly distributed around the circumference of the base body (1) with a circumference radius of 15mm. The material is W-Re-HfC alloy, with a Re content of 8% and an HfC content of 0.8%. A variable diameter and variable pitch structure is adopted. The upper section of the spring has an inner diameter of 0.5mm, a length of 5mm, and a pitch of 1.0mm. The lower section of the spring has an inner diameter of 1.0mm, a length of 5mm, and a pitch of 0.5mm. The total length of the spring is 10mm. The surface is coated with an 8μm thick boron nitride coating. The spring is aged at 2200℃ for 20 hours in a nitrogen atmosphere. After pretreatment, the deformation is 0.02mm.

[0039] Spring positioning seat (7): made of high-density graphite composite material, 8 in number, set along the circumference of the base corresponding to the spring installation position, cylindrical in shape, with a diameter of 0.8mm and a height of 2mm.

[0040] Elastic buffer layer (5): The material is flexible molybdenum alloy, with a diameter of 56mm and a thickness of 0.6mm; a 40mm diameter seed crystal (6) is fixed at the center of its upper surface by a 5μm thick aluminum nitride adhesive; guide holes are set on the elastic buffer layer (5) at the installation positions of each guide post (4).

[0041] Guide post (4): made of boron nitride ceramic, 3 in number, 3mm in diameter, with M3 external thread at the bottom, and the top disc-shaped limiting structure integrally formed on the guide post (4) has a diameter of 6mm and a thickness of 1mm; the fit clearance between the guide post (4) and the guide hole of the elastic buffer layer (5) is 0.08mm, and the position of the top disc-shaped limiting structure on the guide post (4) satisfies the following: the seed crystal seat is installed and placed upside down in the initial position of the PVT equipment, the spring is in natural extension, the top of the spring just overlaps with the lower surface of the buffer layer, and the lower surface of the top disc-shaped limiting structure just contacts the upper surface of the buffer layer.

[0042] Annular rigid support platform (3): made of high-density tungsten carbide, with an inner diameter of 52mm, an outer diameter of 62mm, and a height of 11.85mm (after being placed in the pre-set annular groove of the base body, it is 0.15mm lower than the natural height of the spring), and is interference-fitted with the pre-set annular groove of the base body (fit tolerance -0.02~-0.01mm).

[0043] Installation steps: Step 1: Fix 8 spring positioning seats (7) to the preset position on the upper surface of the base body (1), then insert 8 tungsten alloy springs (2) outside the spring positioning seats (7), and then fix the springs to the preset position on the upper surface of the base body (1) by high temperature welding (2000℃ argon atmosphere).

[0044] Step 2: Press the annular rigid support platform (3) into the pre-set annular groove on the base body (1) by interference fit, ensuring that its top height is 0.15mm lower than the natural height of the spring (2).

[0045] Step 3: Align the guide hole of the elastic buffer layer (5) with the guide post installation position on the base body (1) and place it on the spring. Then, pass the three sets of guide posts (4) through the guide hole of the buffer layer and tighten them with the M3 internal thread hole of the base body through the bottom M3 external thread to ensure that the gap between the guide post body and the buffer layer is uniform.

[0046] Step 4: Apply a 5μm thick layer of aluminum nitride adhesive to the center of the upper surface of the elastic buffer layer (5), and attach and fix the 40mm diameter aluminum nitride seed crystal (6) to complete the assembly.

[0047] Step 5: Place the assembled seed crystal holder upside down in the PVT growth system, and incubate at 2050℃ and 1×10⁻⁶ ℃. -5 A 100-hour aluminum nitride single crystal growth experiment was conducted under a vacuum environment. Experimental results: The seed crystal (6) was crack-free with a cracking rate of 0%; the center float of the seed crystal was 0.07 mm; the height difference between the edge and center of the grown aluminum nitride crystal was 0.02 mm; the deformation of the tungsten alloy spring (2) was 0.17 mm; the elastic coefficient decay rate was 3%; the electrical and optical properties of the grown aluminum nitride single crystal met the requirements for deep ultraviolet device fabrication. Example

[0048] The elastic support seed crystal holder in this embodiment is suitable for aluminum nitride crystal growth using the PVT method with aluminum nitride seed crystals of 60 mm diameter.

[0049] The assembly structure of the elastic support seed crystal seat in this embodiment is as follows: Figure 1 The parameters for each component are selected as follows.

[0050] Base body (1): The material is tungsten carbide alloy, with a diameter of 88mm and a thickness of 15mm. The upper surface has a pre-set annular groove (inner diameter 72mm, outer diameter 82mm, depth 2.5mm), and there are 4 M4 internal thread holes corresponding to the guide post positions. Tungsten alloy springs (2): 12 springs, evenly distributed around the circumference of the base body (1) (distribution radius is 20mm); the material is W-Re-HfC alloy (where Re content is 10% and HfC content is 1%); a variable diameter and variable pitch structure is adopted, the upper section of the spring has an inner diameter of 0.6mm, a length of 6mm and a pitch of 1.2mm, and the lower section of the spring has an inner diameter of 1.2mm, a length of 6mm and a pitch of 0.6mm; the spring length is 12mm, and the surface is coated with a 10μm thick boron nitride coating; the spring is aged at 2300℃ for 25 hours in a nitrogen atmosphere, and the deformation after pretreatment is 0.03mm.

[0051] Spring positioning seat (7): made of high-density tungsten carbide, 12 in number, set along the circumference of the base corresponding to the spring position, cylindrical in shape, with a diameter of 1mm and a height of 2.5mm.

[0052] Elastic buffer layer (5): The material is high-purity flexible graphite, with a diameter of 76mm and a thickness of 1.2mm; a 60mm diameter seed crystal (6) is fixed at the center of its upper surface by a 4μm thick aluminum nitride adhesive; guide holes are set on the elastic buffer layer (5) at the installation positions of each guide post (4).

[0053] Guide post (4): made of boron nitride ceramic, 4 posts, 4mm in diameter, with M4 external thread at the bottom, and a top disc-shaped limiting structure integrally formed on the guide post (4) with a diameter of 7mm and a thickness of 1.5mm; the fit clearance between the guide post (4) and the guide hole on the elastic buffer layer (5) is 0.10mm, and the position of the top disc-shaped limiting structure on the guide post (4) satisfies the following: the seed crystal seat is installed and placed upside down in the initial position of the PVT equipment, the spring is in natural extension, the top of the spring just overlaps with the lower surface of the buffer layer, and the lower surface of the top disc-shaped limiting structure just contacts the upper surface of the buffer layer.

[0054] Annular rigid support platform (3): made of high-density tungsten carbide, with an inner diameter of 72mm, an outer diameter of 82mm, and a height of 14.3mm (after being placed in the pre-set annular groove of the base body, it is 0.2mm lower than the natural height of the spring), and is interference-fitted with the pre-set annular groove of the base body (fit tolerance -0.02~-0.01mm).

[0055] Operating steps: Steps 1-4 are the same as in Example 1, except that the assembly positioning accuracy is adjusted according to the component size (such as spring distribution radius, guide post spacing, etc.).

[0056] Step 5: Invert the assembled seed crystal holder in the PVT growth system and incubate at 2100℃ and 1×10⁻ 5 A 150-hour aluminum nitride single crystal growth experiment was conducted under a vacuum environment.

[0057] Experimental results: Only one seed crystal (6) showed a microcrack (out of a total of 10 crystals tested), with a cracking rate of 10%; the center float of the seed crystal was 0.09 mm, and the height difference between the edge and center of the aluminum nitride crystal was 0.03 mm; the deformation of the tungsten alloy spring (2) was 0.24 mm, and the elastic coefficient decay rate was 5%; the electrical and optical properties of the grown aluminum nitride single crystal met the requirements for deep ultraviolet device fabrication.

[0058] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. It should be noted that for those skilled in the art, the component parameters of this utility model (such as the number of springs, the height of the buffer layer, etc.) can be adjusted without departing from the principle of this utility model, and such adjustments all fall within the protection scope of the claims of this utility model.

Claims

1. An elastic support seed crystal holder for PVT aluminum nitride crystal growth, characterized in that: The elastic support seed crystal base includes: a base body, an elastic support assembly connected to the base body, and an elastic buffer layer supported on the elastic support assembly; the elastic support assembly includes multiple sets of tungsten alloy springs evenly distributed along the circumference of the base body and fixed to the base body; spring positioning seats are provided on the base body, corresponding one-to-one with the tungsten alloy springs; the seed crystal is bonded and fixed to the upper surface of the elastic buffer layer; the base body and the elastic buffer layer are connected by guide posts: the elastic buffer layer is provided with several guide holes, the bottom of the guide post is detachably connected to the base body, and the guide post passes vertically through the guide holes to radially position the elastic buffer layer; the top of the guide post is provided with a disc-shaped limiting structure to achieve axial positioning of the elastic buffer layer and prevent excessive floating of the seed crystal; the base body is also pre-set with an annular groove, the distance from the annular groove to the center of the base body is less than the radius of the elastic buffer layer; an annular rigid support platform is placed in the annular groove, and the height of the annular rigid support platform above the surface of the base body is 0.08-0.22 mm less than the natural elongation height of the tungsten alloy spring.

2. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 1, characterized in that: The base body is a circular block, and the elastic buffer layer is a circular thin block, coaxially positioned directly above the base body, with its lower surface overlapping the elastic support assembly. The annular groove is provided along a circumference at the center of the base body, and the annular groove is interference-fitted to fix the annular rigid support platform. On the base body, along another circumference at the center of the base body, there are a plurality of internally threaded holes that are detachably connected to the guide posts, the number of which is the same as the number of guide posts. The bottom of the guide post is provided with an external thread, and the guide post is detachably connected to the base body through the external thread and the internal thread on the base body.

3. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 2, characterized in that: The spring positioning seat is fixedly installed on the upper surface of the base body. It is cylindrical and its outer diameter is adapted to the inner diameter of the lower section of the tungsten alloy spring, so that the cylindrical spring positioning seat can be inserted into the tungsten alloy spring to position and provide auxiliary support for the tungsten alloy spring and prevent the spring from radially shifting. The height of the spring positioning seat is at least 0.1 mm lower than the height of the tungsten alloy spring.

4. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 2, characterized in that: The disc-shaped limiting structure at the top of the guide post is integrally formed with the guide post. During initial installation, the lower surface of the disc-shaped limiting structure just contacts the upper surface of the elastic buffer layer, and the lower surface of the elastic buffer layer just overlaps the top of each tungsten alloy spring when it naturally extends, thus achieving axial positioning of the elastic buffer layer and limiting the top of the tungsten alloy spring.

5. An elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 4, characterized in that: The disc-shaped limiting structure has a diameter of 5-8mm and a thickness of 1-2mm.

6. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 1, characterized in that: The tungsten alloy spring adopts a "variable diameter and variable pitch" design, that is: the upper and lower sections of the spring have different pitches and different wire thicknesses; the upper section has a thinner wire and a larger pitch, while the lower section has a thicker wire and a smaller pitch; the lower section of the spring refers to the end connected to the base body, and the upper section refers to the end away from the base body; the inner diameter of the upper section is 0.4-0.6mm and the pitch is 0.8-1.2mm, while the inner diameter of the lower section is 0.8-1.2mm and the pitch is 0.4-0.6mm.

7. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 1, characterized in that: The guide posts are 3-6 in number; the diameter of the post body is 3-4mm, and the clearance between the guide post body and the guide hole is 0.03-0.12mm.

8. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 1, characterized in that: The thickness of the base body is 12~15mm; its diameter is matched according to the size of the supported seed crystal. Assuming the diameter of the supported seed crystal is d, the diameter of the base body is d+26~30mm.

9. The elastic support seed crystal holder for PVT aluminum nitride crystal growth according to claim 1, characterized in that: The thickness of the elastic buffer layer is 0.1-2.1 mm.

10. An elastic support seed crystal holder for PVT aluminum nitride crystal growth according to any one of claims 1-9, characterized in that: The seed crystal size is ≥40mm.

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