Seed crystal bonding device and method

Abstract

The invention provides a seed crystal bonding device and method, and relates to the technical field of silicon carbide crystal growth, the device comprises a seed crystal support, a seed crystal, a first buffer piece and a pressure applying device, the seed crystal is bonded to the surface of the seed crystal support; the first buffer piece is arranged on the surface, away from the seed crystal support, of the seed crystal, the thickness of the first buffer piece is sequentially reduced from the center to the outside, and the center of the first buffer piece covers the center of the seed crystal; the pressure applying device is used for sequentially applying pressure to the seed crystal from the center to the outside. According to the application, the first buffer part is arranged, when pressure is applied to the seed crystal, the center of the seed crystal is firstly stressed, at the moment, the seed crystal on the periphery is not extruded, gas in the middle can be smoothly discharged outwards, pressure is continuously applied, the first buffer part is sequentially stressed from the center to the outside, and in the whole pressure applying process, the seed crystal is sequentially stressed from the center to the outer edge; and the generated gas is gradually discharged outwards from the central position, so that the problem that the gas is sealed in the middle of the seed crystal and cannot be discharged is solved, and the growth quality of the seed crystal is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide crystal growth, and particularly to a seed crystal bonding device and method. Background Art

[0002] With the development of technology, more and more fields require materials with high working frequency, high power density, high temperature resistance, good chemical stability, and the ability to work in a strong radiation environment. Due to its high electron mobility, critical breakdown electric field, larger bandgap width, good thermal conductivity, good chemical stability, and high radiation resistance, SiC crystals have attracted great attention and are expected to become excellent third-generation semiconductor materials.

[0003] Generally, the growth of SiC crystals is divided into physical vapor transport method, liquid phase method, etc. Among them, the physical vapor transport method is carried out at a high temperature of 2200 °C. A certain temperature gradient needs to be formed inside the graphite crucible. The silicon carbide seed crystal is fixed on the seed crystal holder and placed at the top of the crucible, and the silicon carbide powder is placed at the bottom of the crucible. Through the sublimation of the powder, it is deposited at the seed crystal and initially grows into a SiC crystal with a certain thickness. The growth of SiC crystals by the liquid phase method is to melt silicon in a high-purity graphite crucible by heating to form a carbon supersaturated solution, and then insert a graphite shaft with a seed crystal attached to the head into the solution. By controlling an appropriate temperature gradient, the temperature at the seed crystal is slightly lower than the solution temperature, so that SiC gradually grows on the surface of the seed crystal to form a SiC crystal with a certain thickness.

[0004] However, whether it is the physical vapor transport method or the liquid phase method for growing SiC crystals, it is necessary to bond the seed crystal to the seed crystal holder in advance and then place it at the top of the crucible or in the solution for growth. The bonding quality between the seed crystal and the seed crystal holder is directly related to crystal growth. If the bonding quality is poor, the heat conduction between the seed crystal and the seed crystal holder will be uneven, resulting in defects such as microtubes and dislocations in the crystal, thus affecting the crystal quality.

[0005] In the prior art, the bonding method between the seed crystal and the seed crystal holder is as follows: A layer of organic glue is coated on the back surface of the seed crystal and the surface of the seed crystal holder. After preliminary curing, the seed crystal and the seed crystal holder are bonded together. Finally, the bonded sample is placed in a carbonization furnace for curing and carbonization. During the curing and carbonization process, a large amount of gas will be released by the organic glue. During this process, due to the different curing times of the organic glue, the gas discharge path at the edge part of the sample is shorter and it is relatively easy to discharge, but the gas discharge path at the central part is relatively long and it is very difficult to completely discharge. Moreover, if the organic glue at the edge of the seed crystal cures first, it will block the gas discharge channel at the central part, resulting in a phenomenon where the edge is firmly bonded but there are bubbles in the middle. During the growth process of such a seed crystal with bubbles, due to the presence of gas between the seed crystal and the seed crystal holder, thermal expansion will occur, leading to the detachment of the seed crystal or excessive stress resulting in crystal cracking. Therefore, how to completely discharge the bubbles generated during the bonding process of the seed crystal is an urgent problem to be solved in the field of silicon carbide crystal growth. Summary of the Invention

[0006] The purpose of the present application is to provide a seed crystal bonding device and method to solve the technical problem that the bubbles generated during the bonding process of the seed crystal in the prior art cannot be completely discharged.

[0007] To achieve the above purpose, the technical solution adopted in the present application is: In the first aspect, the present application provides a seed crystal bonding device, including: a seed crystal holder, a seed crystal, a first buffer member, and a pressing device. The seed crystal is bonded to the surface of the seed crystal holder; the first buffer member is disposed on the surface of the seed crystal facing away from the seed crystal holder, the thickness of the first buffer member decreases sequentially from the center to the outside, and the center of the first buffer member covers the center of the seed crystal; the pressing device is disposed above the first buffer member for applying pressure to the seed crystal sequentially from the center to the outside through the first buffer member.

[0008] In some embodiments, on the side surface of the first buffer member facing the seed crystal, the center of the first buffer member protrudes towards the seed crystal, and / or On the side surface of the first buffer member facing away from the seed crystal, the center of the first buffer member protrudes towards the pressing device.

[0009] In some embodiments, on the side surface of the first buffer member facing the seed crystal, the center of the first buffer member protrudes towards the seed crystal, and the side surface of the first buffer member facing away from the seed crystal is a planar structure, or On the side surface of the first buffer member facing away from the seed crystal, the center of the first buffer member protrudes towards the pressing device, and the side surface of the first buffer member facing the seed crystal is a planar structure.

[0010] In some embodiments, the first buffer member is in a conical shape, or a frustum shape, or a spherical crown shape.

[0011] In some embodiments, the pressing device includes: a driving mechanism and a pressing block mechanism; the pressing block mechanism is connected to the driving end of the driving mechanism and is located above the first buffer member, and the projection area of the pressing block mechanism on the surface of the first buffer member covers the surface of the first buffer member.

[0012] In some embodiments, the pressing block mechanism includes a pressing plate, an airbag, and a pressing unit arranged in sequence from top to bottom. Among them, the pressing plate is connected to the driving end of the driving mechanism, the upper surface of the airbag is fixed to the pressing plate, the lower surface of the airbag is connected to the pressing unit, the airbag is connected to a compressed air source, the pressing unit includes a plurality of pressing members sleeved in sequence along its radial direction, and two adjacent pressing members can slide relative to each other.

[0013] In some embodiments, the plurality of pressing members include a pressing plate located at the center and a plurality of pressing rings sleeved outside the pressing plate in sequence. Among them, the pressing plate is circular and is arranged corresponding to the center of the first buffer member, and the pressing ring is circular and coaxial with the pressing plate.

[0014] In some embodiments, it further includes: a cavity, a heating base is provided at the bottom of the cavity, a limiting groove is provided on the heating base, and the seed crystal holder is limited in the limiting groove.

[0015] In some embodiments, it further includes: a second buffer member, and the second buffer member is bonded between the seed crystal holder and the seed crystal.

[0016] In a second aspect, the present application provides a method for bonding a seed crystal. The bonding method is realized by the seed crystal bonding device according to any one of the first aspect, and includes the following steps: Start the driving mechanism, drive the pressing block mechanism to press down, apply a pressure of 140 - 160 kg to the first buffer member, the seed crystal, and the seed crystal holder, start the heating program of the heating base, set the heating rate to 2 - 3 °C / min, when the temperature reaches 70 °C, maintain for 8 - 15 min; maintain a pressure of 140 - 160 kg, continue heating to 110 °C, the heating rate is 1.5 - 2 °C / min, maintain for 10 - 20 min, continue to maintain a pressure of 140 - 160 kg, continue heating to 140 °C, the heating rate is 1 - 1.5 °C / min, maintain for 50 - 70 min; Start the vacuum pump to pump out the air in the cavity. When the pressure in the cavity drops below 100 pa, start heating the heating base, raise the temperature at a rate of 1 - 2 °C / min, and at the same time, maintain the applied pressure of 140 - 160 kg; when the temperature rises to 300 °C, maintain this temperature for 60 - 120 min; when most of the released gas is discharged, continue to heat at a heating rate of 1.5 - 3 °C / min to gradually raise the temperature to 800 °C. At the same time, during the temperature rise process, the driving mechanism applies pressure to the first buffer member, the seed crystal, and the seed crystal holder at a rate of 2 - 4 kg / min. After the applied pressure reaches 500 - 600 kg, maintain this pressure until the end; After the above process is completed, stop heating and naturally cool to room temperature while maintaining negative pressure in the cavity to complete the bonding of the seed crystal.

[0017] Based on the above technical solution, the seed crystal bonding device and method provided by this application at least have the following beneficial technical effects: The seed crystal bonding device provided by this application is provided with a first buffer member on the surface of the seed crystal facing away from the seed crystal holder. The thickness of the first buffer member decreases sequentially from the center to the outside, and the center of the first buffer member covers the center of the seed crystal. Therefore, when pressure is applied to the seed crystal by the pressing device, the center of the seed crystal is stressed first. At this time, the surrounding seed crystals have not been squeezed, so the gas in the middle can be discharged smoothly. As the pressing device continues to apply pressure, the first buffer member is sequentially pressed from the center to the outside. In this way, during the entire pressing process, the seed crystal is stressed sequentially from the center to the outer edge, and the generated gas can be gradually discharged from the center position, solving the problem that the gas is sealed in the middle of the seed crystal and cannot be discharged, and greatly improving the growth quality of the seed crystal.

[0018] On the other hand, the seed crystal bonding device provided by the embodiment of this application further includes a pressing block mechanism. The pressing block mechanism includes a pressing plate, an airbag and a pressing unit arranged sequentially from top to bottom. Among them, the pressing plate is connected to the driving end of the driving mechanism. The upper surface of the airbag is fixed to the pressing plate, the lower surface of the airbag is connected to the pressing unit, and the airbag is connected to a compressed air source. The pressing unit includes a plurality of pressing members sleeved sequentially along its radial direction, and two adjacent pressing members can slide relative to each other. Considering the material of the first buffer member, when the plastic deformation amount during the compression process is small, after the gas is released, the pressure on the edge of the seed crystal is less than the pressure on the center, resulting in the bonding strength of the edge being less than the bonding strength of the center. Therefore, by setting the pressing block mechanism to include an airbag and a plurality of pressing members sleeved sequentially along its radial direction, after the gas is released, compressed air can be introduced into the airbag, and the airbag can press each pressing member respectively. Each pressing member can fit the surface of the first buffer member under the action of pressure, so that the area where the pressure is small near the edge continues to be pressed, ensuring that the entire surface of the seed crystal receives sufficient pressure and guaranteeing the bonding effect. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of a seed crystal bonding device according to one or more embodiments of this application.

[0021] Figure 2 is Figure 1 An exploded structural schematic diagram of some components in the seed crystal bonding device of the illustrated embodiment.

[0022] Figure 3 A structural schematic diagram of the seed crystal bonding device of another embodiment or multiple embodiments of the present application.

[0023] Figure 4 is Figure 3 An exploded structural schematic diagram of some components in the seed crystal bonding device of the illustrated embodiment.

[0024] Figure 5 A longitudinal sectional view of an embodiment of the first buffer member in the seed crystal bonding device of the present application.

[0025] Figure 6 A longitudinal sectional view of another embodiment of the first buffer member in the seed crystal bonding device of the present application.

[0026] Figure 7 A longitudinal sectional view of yet another embodiment of the first buffer member in the seed crystal bonding device of the present application.

[0027] Figure 8 A longitudinal sectional view of yet another embodiment of the first buffer member in the seed crystal bonding device of the present application.

[0028] Figure 9 A structural diagram of the pressure block mechanism in the seed crystal bonding device of the present application and a top view of the pressure application unit.

[0029] Figure 10 A schematic diagram showing the action of the pressure application unit of the pressure block mechanism on the first buffer member in the seed crystal bonding device of the present application.

[0030] Figure 11 A top view of the heating base in the seed crystal bonding device of the present application.

[0031] In the figure: 1 - cavity; 2 - heating base; 3 - seed crystal holder; 4 - second buffer member; 5 - seed crystal; 6 - first buffer member; 7 - vacuum pump; 10 - pressure block mechanism; 11 - pressure plate; 12 - airbag; 13 - pressure application unit; 20 - drive mechanism; 21 - drive motor; 22 - drive rod; 71 - corrugated pipeline; 130 - pressing plate; 131 - pressing ring; 211 - limiting groove. Detailed implementation manners

[0032] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0036] The technical solution of the present application will be described in detail below with reference to the accompanying drawings of the specification.

[0037] As Figures 1 to 4 shown, a seed crystal bonding device provided by the present application includes a seed crystal holder 3, a seed crystal 5, a first buffer member 6, and a pressing device. Among them, the function of the seed crystal holder 3 is to fix the seed crystal 5, and the shape of the seed crystal holder 3 is the same as that of the seed crystal 5. The seed crystal 5 can be directly or indirectly bonded to the surface of the seed crystal holder 3. In some embodiments, the seed crystal 5 is bonded to the surface of the seed crystal holder 3 by an organic glue. The first buffer member 6 is disposed on the surface of the seed crystal 5 facing away from the seed crystal holder 3. The thickness of the first buffer member 6 decreases sequentially from the center to the outside, and the center of the first buffer member 6 covers the center of the seed crystal 5. In some embodiments, the orthographic projection area of the first buffer member 6 on the surface of the seed crystal 5 covers the surface of the seed crystal 5. The first buffer member 6 can be a layered structural member with certain plasticity. For example, the first buffer member 6 can be a dense graphite paper or graphite felt so that it can undergo a certain deformation when pressed. The pressing device is disposed above the first buffer member 6 and is used to apply pressure to the seed crystal 5 sequentially from the center to the outside through the first buffer member 6.

[0038] In the technical solution of the embodiment of the present application, by providing a first buffer member 6 on the surface of the seed crystal 5 facing away from the seed crystal holder 3, the thickness of the first buffer member 6 decreases successively from the center to the outside, and the center of the first buffer member 6 covers the center of the seed crystal 5. Then, when a pressure applying device applies pressure to the seed crystal 5, the center of the seed crystal 5 is the first to be stressed. At this time, the surrounding seed crystals 5 have not been squeezed yet. Therefore, the gas in the middle can be smoothly discharged outward. Since the first buffer member 6 has a certain plasticity, as the pressure applying device continues to apply pressure, the first buffer member 6 is slowly flattened, and the area from its center to the outside begins to be stressed in turn. In this way, during the entire pressure application process, the seed crystal is stressed successively from the center to the outer edge, and the generated gas can be discharged gradually from the center position outward, solving the problem that the gas is sealed in the middle of the seed crystal and cannot be discharged, and greatly improving the growth quality of the seed crystal.

[0039] Preferably, in order to achieve that the thickness of the first buffer member 6 decreases successively from the center to the outside, as Figure 5 shown, on the side of the first buffer member 6 facing the seed crystal 5, the center of the first buffer member 6 protrudes toward the seed crystal 5, and on the side of the first buffer member 6 facing away from the seed crystal 5, the center of the first buffer member 6 protrudes toward the pressure applying device. Thus, the first buffer member 6 forms a structure with a thick center and thin periphery.

[0040] In some other embodiments, as Figure 6 shown, on the side of the first buffer member 6 facing the seed crystal 5, the center of the first buffer member 6 protrudes toward the seed crystal 5, and the side of the first buffer member 6 facing away from the seed crystal 5 has a planar structure. Of course, in other embodiments, as Figure 10 shown, on the side of the first buffer member 6 facing away from the seed crystal 5, the center of the first buffer member 6 protrudes toward the pressure applying device, and the side of the first buffer member 6 facing the seed crystal 5 has a planar structure.

[0041] Specifically, as Figures 6 to 8 shown, the first buffer member 6 can be conical, frustum-shaped, or spherical-crowned.

[0042] In the technical solution of the embodiment of the present application, through the above settings, the thickness of the first buffer member 6 decreases successively from the center to the outside. In this way, when the pressure applying device acts on the first buffer member 6, the center of the first buffer member 6 corresponding to the center of the seed crystal 5 is the first to be stressed, and then as the pressure applying device continues to apply pressure, the first buffer member 6 is stressed successively from the center to the outside, enabling the gas to be discharged gradually from the center to the outside.

[0043] In some embodiments, the thickness of the first buffer member 6 is 0.1 - 1 mm. Preferably, the thickness of the first buffer member 6 is 0.3 - 0.6 mm. The height difference between the position with the maximum thickness and the position with the minimum thickness of the first buffer member 6 is 50 - 100 μm.

[0044] Due to processing reasons, the surface of the seed crystal holder 3 is uneven. Therefore, a second buffer member 4 is bonded between the seed crystal holder 3 and the seed crystal 5. An organic glue with a certain thickness is coated between the seed crystal holder 3 and the second buffer member 4 and between the second buffer member 4 and the seed crystal 5, so that the seed crystal holder 3, the second buffer member 4 and the seed crystal 5 are bonded and fixed. The second buffer member 4 can be a graphite paper or a graphite felt with a certain thickness. In some embodiments, the thickness of the second buffer member 4 is 0.1~0.3 mm.

[0045] In the technical solution of the embodiment of the present application, the second buffer member 4 can effectively fill the pores between the seed crystal holder 3 and the seed crystal 5, making the bonding of the seed crystal more firm, improving the heat conduction effect during the crystal growth process, and being conducive to growing high-quality crystals.

[0046] In some embodiments, please refer to Figure 1 and Figure 2 , the pressing device includes: a driving mechanism 20 and a pressing block mechanism 10; the driving mechanism 20 includes a driving motor 21 and a driving rod 22. The pressing block mechanism 10 is connected to the driving end of the driving mechanism 20 and is located above the first buffer member 6. The projection area of the pressing block mechanism 10 on the surface of the first buffer member 6 covers the surface of the first buffer member 6. The pressing block mechanism 10 is connected to the driving rod 22 of the driving mechanism 20.

[0047] In the technical solution of the embodiment of the present application, through the above settings, when pressure needs to be applied, by turning on the driving mechanism 20, the driving rod 22 of the driving mechanism 20 drives the pressing block mechanism 10 to move towards the first buffer member 6 and press on the upper surface of the first buffer member 6. The upper surface of the first buffer member 6 is the first to be stressed, and then the center of the corresponding seed crystal 5 is the first to be stressed. At this time, the surrounding seed crystals 5 have not been squeezed yet, so the gas in the middle can be smoothly discharged. Since the first buffer member 6 has a certain plasticity, as the driving mechanism 20 continues to apply pressure, the first buffer member 6 is slowly flattened, and the area from its center to the outside starts to be stressed in turn. In this way, during the entire pressing process, the seed crystal 5 is stressed gradually from the center to the outer edge in turn, and the generated gas can be discharged from the center position, solving the problem that the gas is sealed in the middle of the seed crystal and cannot be discharged, and greatly improving the growth quality of the seed crystal.

[0048] Considering that when the first buffer member 6 is made of graphite paper or graphite felt, its plastic deformation amount may be small, so that after the gas release is completed, the pressure on the edge of the seed crystal 5 is less than that in the middle, and then the bonding strength of the edge may be less than that in the middle, affecting the bonding effect of the seed crystal, as Figure 3 , Figure 4 , Figure 9 and Figure 10As shown in the figure, the pressing block mechanism 10 of the seed crystal bonding device of the present application includes a pressing plate 11, an airbag 12, and a pressing unit 13 arranged in sequence from top to bottom. Among them, the pressing plate 11 can be a circular plate. The pressing plate 11 is connected to the driving end of the driving mechanism 20. It can be understood that the pressing plate 11 is connected to the driving rod 22 of the driving mechanism 20. The upper surface of the airbag 12 is fixed to the pressing plate 11, and the lower surface of the airbag 12 is connected to the pressing unit 13. The airbag 12 is connected to a compressed air source so that compressed air can be introduced into the airbag 12 through the compressed air source when needed. The pressing unit 13 includes a plurality of pressing members sleeved in sequence along its radial direction, and two adjacent pressing members can slide relative to each other.

[0049] In the technical solution of the embodiment of the present application, through the above settings, after the gas is released, compressed air can be introduced into the airbag 12 through the compressed air source. The airbag 12 can press each of the pressing members respectively. Each pressing member can fit the surface of the first buffer member 6 under the action of the pressure, so that the area with less pressure near the edge continues to be pressed, ensuring that the entire seed crystal surface receives sufficient pressure and guaranteeing the bonding effect.

[0050] Please refer to Figure 9 , in some embodiments, the plurality of pressing members include a pressing plate 130 located at the center and a plurality of pressing rings 131 sleeved outside the pressing plate 130 in sequence. Among them, the pressing plate 130 is circular and is arranged corresponding to the center of the first buffer member 6. The pressing rings 131 are circular rings coaxial with the pressing plate 130. The materials of the pressing plate 130 and the pressing rings 131 can be 304 stainless steel.

[0051] In some embodiments, the number of the pressing rings 131 can be set as needed. It can be three, four, five, six or even more. The more the number of the pressing rings 131, the more uniform the pressure control on the first buffer member 6 and the better the bonding effect.

[0052] In some embodiments, the airbag 12 can be connected to each pressing member by screws, and the connection between the screws and the airbag 12 is sealed by an O-ring. As Figure 10 shown, the function of the airbag 12 is to make the pressing ring 131 tilt and deform to fit the surface of the first buffer member 6 after compressed air is introduced, and at the same time apply pressure to the first buffer member 6, so as to continue to press the area with less pressure at the contact edge between the first buffer member 6 and the seed crystal 5, ensuring that the entire seed crystal surface finally receives sufficient pressure and guaranteeing the bonding effect.

[0053] As Figures 1 to 4 and Figure 11As shown in the figure, the seed crystal bonding device of the present application further includes: a cavity 1, a heating base 2 is provided at the bottom of the cavity 1, a limiting groove 211 is provided on the heating base 2, and the seed crystal holder 3 is limited in the limiting groove 211. The limiting groove 211 is provided at the central position of the heating base 2. The limiting groove 211 is a circular groove formed by the surface of the heating base 2 being recessed inward. Its cross-sectional shape and size can be consistent with the cross-sectional shape and size of the seed crystal holder 3. The bottom of the seed crystal holder 3 is fixed in the limiting groove 211 to realize the fixation of the seed crystal holder 3. In some embodiments, the groove depth of the limiting groove 211 is 2-5 mm.

[0054] In some embodiments, a heater is provided inside the heating base 2 for heating the bonding sample. The bonding sample includes a seed crystal holder 3, a second buffer 4, and a seed crystal 5. The heating of the heater is controlled by a heating control system, and the heater can achieve continuous control from room temperature to 800 °C. The material of the heating base 2 is high-purity graphite. High-purity graphite has good thermal conductivity and can quickly conduct the temperature generated by the heater to the bonding sample. A temperature-measuring thermocouple is provided near the heater for monitoring and controlling the heating temperature.

[0055] In some embodiments, the driving rod 22 of the driving mechanism 20 passes through the cavity 1 such that the pressing block mechanism 10 is located above the first buffer 6. The driving motor 21 drives the driving rod 22 and the pressing block mechanism to move up and down to complete the pressing and pressure relief of the seed crystal 5.

[0056] In some embodiments, a movable door is provided on the side of the cavity 1 for conveniently taking and placing the bonding sample. The cavity 1 and the movable door can be sealed by a sealing rubber strip so that a sealed space is formed inside the cavity 1. The cavity 1 is connected to a vacuum pump 7 through a corrugated pipe 71 so that a negative pressure can be formed inside the cavity 1 after the vacuum pump 7 is started.

[0057] The specific process of the seed crystal bonding method of the present application can be referred to as follows: The present invention also includes a seed crystal bonding method, and the specific process is as follows: (1) Take one piece of seed crystal, one piece of graphite paper, and one seed crystal holder. Carefully wipe the surface with alcohol to ensure that the stains on the surface (such as dust, grease, etc.) are removed completely. Then place them on the heating platform and bake for 2-5 minutes to allow the alcohol and moisture left by the wiping to volatilize sufficiently. The temperature of the heating platform is set at 120-150 °C. After baking, take them down and cool for standby.

[0058] (2) Uniformly apply an adhesive organic glue on the back of the seed crystal and one side of the graphite paper. The method of applying the glue can be spin coating, scraping, or a combination of both. After applying the glue, place it on a heating platform and bake for 2 - 5 minutes to initially cure the organic glue under heat and release the air trapped in the glue. The baking temperature is 120 - 150 °C. In addition to the above initial curing method, a baking lamp can also be used for photocatalytic curing of the organic glue. Or, a combination of a heating platform and a baking lamp can be used for initial curing of the organic glue.

[0059] (3) Bond the seed crystal coated with glue in step (2) and the graphite paper together. When bonding, try to minimize the air sealed by the glue on the bonding surface. After bonding well, use a knife to cut off the excess graphite paper so that the graphite paper has the same size as the seed crystal.

[0060] (4) Uniformly apply glue and initially cure it on the non-bonding surface of the graphite paper in step (3). The method of applying glue and initial curing is the same as that in step (2). After initial curing, bond it to the seed crystal holder. When bonding, the main reference edges and secondary reference edges of the seed crystal and the seed crystal holder need to be aligned respectively. In this step, a layer of glue can also be applied on the surface of the seed crystal holder and then bonded to the graphite paper after initial curing.

[0061] (5) Place the bonded sample obtained in step (4) (including the seed crystal, graphite paper, and seed crystal holder) into the seed crystal bonding device of the present application, and then run the program. This program includes two processes: thermal curing and carbonization. The function of thermal curing is to expel the air contained in the bonding surface under pressure, and then let the organic glue thermally decompose and expel the released gas. The function of the carbonization process is to completely convert the organic glue applied in the sample into a carbon network and firmly fix the seed crystal on the seed crystal holder.

[0062] Specifically, the specific process of thermal curing is as follows: (1) Start the drive motor 21 to lower the pressing block mechanism 10 and apply a pressure of 140 - 160 kg, preferably 150 kg, to the first buffer member 6 and the bonded sample. Start the heating program for the heating base 2, set the heating rate to 2 - 3 °C / min, and when the temperature reaches 70 °C, maintain for 8 - 15 minutes to fully preheat the bonded sample.

[0063] (2) Maintain a pressure of 140 - 160 kg, preferably 150 kg, continue heating to 110 °C, maintain for 10 - 20 minutes, and the heating rate is 1.5 - 2 °C / min.

[0064] (3) Continue to maintain a pressure of 140 - 160 kg, preferably 150 kg, and continue heating to 140 °C, maintaining for 50 - 70 min, with a heating rate of 1 - 1.5 °C / min. During this process, the air wrapped in the organic glue is discharged outward from the bonding surface under the action of pressure and temperature. In the bonding device of the present application, since a first buffer member 6 with a middle-high and surrounding-low shape is provided between the seed crystal 5 and the press block mechanism 10, the pressure received by the periphery of the bonding surface is less than that of the middle part, and the gas can be smoothly discharged outward.

[0065] The above heat curing process can be carried out in an air environment or in a negative pressure (pressure less than 100 pa) environment.

[0066] Specifically, the specific process of the above carbonization process is as follows: (1) Start the vacuum pump 7 to pump out the air in the cavity 1. When the pressure in the cavity 1 drops below 100 pa, start heating the heating base 2 and increase the temperature at a rate of 1 - 2 °C / min. At the same time, maintain a pressure of 140 - 160 kg, preferably 150 kg.

[0067] (2) When the temperature rises to 300 °C, maintain this temperature for 60 - 120 min. During this process, the organic glue decomposes and releases a large amount of gas. At this temperature, maintaining for a period of time can allow the released gas to have enough time to discharge outward. Start the compressed air source to introduce compressed air into the airbag 12.

[0068] (3) After most of the gas released by the colloid is discharged, continue heating at a heating rate of 1.5 - 3 °C / min to gradually increase the temperature to 800 °C. Under the action of high temperature during this process, the organic glue is fully carbonized to form a uniform carbon network structure, firmly bonding the seed crystal and the seed crystal holder together. At the same time, during the heating process, the driving device applies pressure to the seed crystal at a rate of 2 - 4 kg / min. After the applied pressure reaches 500 - 600 kg, maintain this pressure until the program runs to the end. During this process, due to the increasing pressure applied to the seed crystal surface, the middle-thicker position of the first buffer member 6 provided between the press block mechanism 10 and the seed crystal 5 deforms and is gradually flattened. The pressure ring 131 can fit on the surface of the first buffer member 6 under the action of the airbag 12 and apply pressure to the first buffer member 6, so that the periphery also begins to receive sufficient pressure, making the entire seed crystal surface closely fit with the seed crystal holder.

[0069] (4) After the above steps are completed, stop heating and naturally cool to room temperature while maintaining the negative pressure in the cavity. Thus, the bonding of the seed crystal is completed.

[0070] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A seed crystal bonding device, characterized in that, Comprising: A seed crystal holder (3); A seed crystal (5) bonded to the surface of the seed crystal holder (3); A first buffer member (6) disposed on the surface of the seed crystal (5) facing away from the seed crystal holder (3), the thickness of the first buffer member (6) decreasing successively from the center outwards, and the center of the first buffer member (6) covering the center of the seed crystal (5); A pressing device disposed above the first buffer member (6) for applying pressure to the seed crystal (5) successively from the center outwards through the first buffer member (6).

2. The seed crystal bonding device according to claim 1, wherein On the side of the first buffer member (6) facing the seed crystal (5), the center of the first buffer member (6) protrudes towards the seed crystal (5), and / or, On the side of the first buffer member (6) facing away from the seed crystal (5), the center of the first buffer member (6) protrudes towards the pressing device.

3. The seed crystal bonding device according to claim 2, characterized in that, On the side of the first buffer member (6) facing the seed crystal (5), the center of the first buffer member (6) protrudes towards the seed crystal (5), and the side of the first buffer member (6) facing away from the seed crystal (5) has a planar structure, or, On the side of the first buffer member (6) facing away from the seed crystal (5), the center of the first buffer member (6) protrudes towards the pressing device, and the side of the first buffer member (6) facing the seed crystal (5) has a planar structure.

4. The seed crystal bonding device according to claim 3, characterized in that The first buffer member (6) is in a conical shape, or a frustum shape, or a spherical crown shape.

5. The seed crystal bonding device according to any one of claims 1 to 4, characterized in that The pressing device includes: A driving mechanism (20); A pressing block mechanism (10) connected to the driving end of the driving mechanism (20) and located above the first buffer member (6), the projection area of the pressing block mechanism (10) on the surface of the first buffer member (6) covering the surface of the first buffer member (6).

6. The seed crystal bonding device according to claim 5, characterized in that, The pressing block mechanism (10) includes a pressing plate (11), an airbag (12), and a pressing unit (13) arranged successively from top to bottom. Among them, the pressing plate (11) is connected to the driving end of the driving mechanism (20), the upper surface of the airbag (12) is fixed to the pressing plate (11), the lower surface of the airbag (12) is connected to the pressing unit (13), the airbag (12) is connected to a compressed air source, and the pressing unit (13) includes a plurality of pressing members sleeved successively along its radial direction, and two adjacent pressing members can slide relative to each other.

7. The seed crystal bonding device according to claim 6, characterized in that, The plurality of pressing members include a pressing plate (130) located at the center and a plurality of pressing rings (131) sleeved successively outside the pressing plate (130). Among them, the pressing plate (130) is circular and is arranged corresponding to the center of the first buffer member (6), and the pressing rings (131) are in a circular ring shape coaxial with the pressing plate (130).

8. The seed crystal bonding device according to claim 1, characterized in that, Further comprising: A cavity (1), a heating base (2) is provided at the bottom of the cavity (1), a limiting groove (211) is provided on the heating base (2), and the seed crystal holder (3) is limited in the limiting groove (211).

9. The seed crystal bonding device according to claim 1, characterized in that, Further comprising: A second buffer member (4) bonded between the seed crystal holder (3) and the seed crystal (5).

10. A seed crystal bonding method, characterized in that, The method is implemented by the seed crystal bonding device according to any one of claims 1 to 9, and includes the following steps: Start the driving mechanism (20) to drive the pressing block mechanism (10) to press down, applying a pressure of 140 - 160 kg on the first buffer (6), the seed crystal (5) and the seed crystal holder (4). Start the heating program for the heating base (2), set the heating rate to 2 - 3 °C / min. When the temperature reaches 70 °C, hold for 8 - 15 min; maintain the pressure of 140 - 160 kg, continue heating to 110 °C, with a heating rate of 1.5 - 2 °C / min, hold for 10 - 20 min, continue to maintain the pressure of 140 - 160 kg, continue heating to 140 °C, with a heating rate of 1 - 1.5 °C / min, hold for 50 - 70 min; Start the vacuum pump (7) to pump out the air in the cavity (1). After the pressure in the cavity (1) drops below 100 Pa, start heating the heating base (2), increasing the temperature at a rate of 1 - 2 °C / min. At the same time, maintain the applied pressure of 140 - 160 kg; when the temperature rises to 300 °C, hold this temperature for 60 - 120 min; after most of the released gas is discharged, continue heating at a heating rate of 1.5 - 3 °C / min to gradually raise the temperature to 800 °C. During the heating process, the driving mechanism (20) applies pressure on the first buffer (6), the seed crystal (5) and the seed crystal holder (4) at a rate of 2 - 4 kg / min. After the applied pressure reaches 500 - 600 kg, maintain this pressure until the end; After the above process is completed, stop heating and naturally cool to room temperature while maintaining the negative pressure in the cavity (1) to complete the bonding of the seed crystal.

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