Silicon carbide seed crystal bonding device and method

Abstract

The embodiment of the present application discloses a silicon carbide seed crystal bonding device and method. The device includes a graphite substrate, a rotary debonding sleeve, and an upper pressure block. The rotary debonding sleeve is rotatably arranged above the graphite substrate, and is provided with a buffering glue groove and a glue discharge port that are interconnected; the buffering glue groove is filled with granular sugar, which cooperates with the protrusions distributed around it to achieve soft support on the hard surface, preventing the silicon carbide seed crystal from shifting and reducing edge damage. At the same time, the gaps between the granular sugars can discharge gas and glue overflow from the bonding surface, and can increase the flow resistance of the glue to avoid insufficient local glue. During heating and curing, the granular sugar melts, the rotary debonding sleeve rotates, and the protrusions scrape off the glue overflow. At the same time, the granular sugar provides lubrication to reduce damage to the side walls of the seed crystal. In addition, the granular sugar is easily soluble in water and has little residue, which can reduce glue residue, prevent scratches and breakage of the seed crystal, improve the quality of crystal growth, and effectively solve the problems of shift, breakage and glue residue in traditional methods.

Description

Technical Field

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

[0002] Physical vapor transport (PVT) is currently the dominant process technology for growing SiC single crystals. This method involves first placing SiC polycrystalline feedstock at the bottom of a graphite crucible; secondly, precisely bonding a SiC seed crystal to a graphite seed holder; and finally, attaching the graphite seed holder, holding the SiC seed crystal, to the top of the graphite crucible. Throughout the SiC single crystal growth process, the SiC polycrystalline feedstock at the bottom of the graphite crucible is heated, causing it to sublime, thereby gradually growing a SiC single crystal on the SiC seed crystal.

[0003] However, under the existing technical system, the bonding operation of silicon carbide seed crystals generally follows a traditional method: first, adhesive is evenly coated on the bonding surface of the silicon carbide seed crystal, and then a pressure plate is used to apply specific pressure to directly bond and fix the silicon carbide seed crystal to the graphite disk substrate.

[0004] However, many problems are exposed during the actual operation. On the one hand, during the bonding process of applying pressure, the silicon carbide seed crystal often shifts or is misplaced. This disrupts the normal growth process of the silicon carbide single crystal, causing the crystal growth to deviate from the expected trajectory, greatly affecting the crystal quality of the final silicon carbide single crystal, and may even cause the entire single crystal growth process to fail. On the other hand, if the adhesive cannot overflow smoothly during the pressure application process, it will form an uneven distribution on the bonding surface. The uneven distribution of the adhesive will affect the flatness of the seed crystal bonding, resulting in the inability to form a stable and uniform bonding state between the seed crystal and the graphite disk substrate. This further affects key factors such as heat transfer and stress distribution in the silicon carbide growth process, and ultimately has a negative impact on the growth quality of the silicon carbide crystal.

[0005] In order to improve the problems of uneven adhesive distribution and seed crystal offset and misalignment, some existing technologies have attempted to use a technical solution of opening grooves or pits on the seed crystal seat, attempting to design it to accommodate adhesive and serve as a channel for gas overflow. Although this method alleviates the problems of air permeability and adhesive overflow stability to a certain extent, due to the opening of these specific structures on the seed crystal seat, it inevitably causes uneven distribution of adhesive in the area and differences in thermal conductivity. It still has a significant impact on the bonding of the seed crystal, for example, affecting the flatness of the seed crystal bonding, which in turn affects the growth quality of silicon carbide.

[0006] In view of the above problems existing in the prior art, there is an urgent need to develop a silicon carbide seed crystal bonding device that can effectively overcome the above problems to meet the production requirements of high-quality silicon carbide single crystal growth. Summary of the Invention

[0007] In order to solve the problems existing in the prior art of silicon carbide seed crystal bonding process, such as silicon carbide seed crystal bonding offset and misalignment, poor adhesive overflow control, and difficulty in gas overflow, this application proposes a silicon carbide seed crystal bonding device and method. The technical solutions provided in this application are as follows:

[0008] In one aspect, the present application provides a silicon carbide seed crystal bonding device, comprising:

[0009] Graphite substrate, used to support silicon carbide seed crystals;

[0010] A rotary glue removal sleeve is rotatably disposed above the graphite substrate, and has a buffer glue holding groove and a glue discharge port that are interconnected. The buffer glue holding groove is used to accommodate granular sugar, and the glue discharge port is used to discharge the melted granular sugar and excess glue. Bumps are evenly distributed around the buffer glue holding groove to form point contact support with the edge of the silicon carbide seed crystal.

[0011] An upper pressing block is located above the rotating debonding sleeve and is used to press down the silicon carbide seed crystal.

[0012] In some specific embodiments, heat-conducting blocks are arranged around the upper pressing block.

[0013] In some specific embodiments, the device further includes a pressure cover, which covers the top of the buffering glue containing groove and is used to close the buffering glue containing groove.

[0014] In some specific embodiments, the device further comprises a retractable central pressure plate and a liftable annular pressure ring;

[0015] The retractable central pressure plate is installed above the center of the upper pressure block and coincides with the central axis of the upper pressure block, and is used to retract from the center to press down the silicon carbide seed crystal;

[0016] The liftable annular pressure ring is installed above the edge of the upper pressure block and is arranged around the retractable central pressure plate, and is used for pressing down the silicon carbide seed crystal from all sides by lifting.

[0017] In some specific embodiments, a rotating member is provided on the rotary glue removing sleeve, and the rotating member drives the rotary glue removing sleeve to rotate via a driving device.

[0018] In some specific embodiments, the center of the retractable central pressure plate coincides with the center of the silicon carbide seed crystal, and the area of the retractable central pressure plate covers 0.8-0.9 of the area of the silicon carbide seed crystal.

[0019] In some specific embodiments, the relationship between the volume V1 of the buffering tank above the interface reference plane between the upper pressing block and the silicon carbide seed crystal and the volume V2 of the buffering tank below the interface reference plane is V1≥1.1V2.

[0020] In some specific embodiments, the rotary debonding sleeve is coaxially arranged with the graphite substrate.

[0021] On the other hand, the present application also provides a method for bonding a silicon carbide seed crystal, wherein the silicon carbide seed crystal is bonded according to the above-mentioned silicon carbide seed crystal bonding device, comprising the following steps:

[0022] Coating the bonding surface of the silicon carbide seed crystal with adhesive;

[0023] Applying graphite-containing adhesive to the edge of the graphite substrate;

[0024] The silicon carbide seed crystal coated with the adhesive is placed at the center of the graphite substrate and a rotary adhesive removal sleeve is installed; wherein the buffer tank of the rotary adhesive removal sleeve contains granular sugar;

[0025] After applying pressure to the silicon carbide seed crystal by means of an upper pressing block to compact it, the entire assembly is placed in a hot pressing device for pressurized curing.

[0026] In some specific embodiments, the heat bonding is performed in the hot pressing device, comprising:

[0027] The first stage: in a vacuum environment with a pressure of ≤9 Pa, the temperature is raised to 90-100°C at a heating rate of 71-80°C / h and maintained for 5-15 minutes; at the same time, pressure is applied to the center of the silicon carbide seed crystal through a retractable central pressure plate;

[0028] The second stage: increasing the applied pressure of the retractable central pressure plate, heating the temperature to 150-190°C at a heating rate of 30-40°C / h, and maintaining the temperature for 1-1.3 hours; simultaneously starting the rotary rubber removal sleeve and rotating it for 3-5 minutes;

[0029] The third stage: raising the temperature to 400-450°C at a heating rate of 25-35°C / h and maintaining it for 3-4 hours; at the same time, applying pressure to the edge of the silicon carbide seed crystal through a retractable annular pressure ring;

[0030] Stage 4: Heat to 460-499°C at a heating rate of 17-27°C / h until the bond is fully cured.

[0031] In some specific embodiments, the graphite-containing adhesive is coated on the outer edge of the graphite substrate at a position of 1 / 10-1 / 5 of the diameter.

[0032] In some specific embodiments, the adhesive is a phenolic resin adhesive, which comprises a phenolic resin and a propylene glycol methyl ether acetate solvent, wherein the content of the phenolic resin is 13%-17%.

[0033] In some specific embodiments, the graphite-containing adhesive comprises graphite and phenolic resin, the content of the graphite is 10%-40%, and the content of the phenolic resin is 7%-8%.

[0034] In some specific embodiments, the particle size of the granulated sugar is 0.12-0.24 mm.

[0035] By adopting the above technical solution, the silicon carbide seed crystal bonding device and method provided in this application have the following beneficial effects:

[0036] The embodiment of the present application discloses a silicon carbide seed crystal bonding device and method. The device includes a graphite substrate, a rotary debonding sleeve and an upper pressure block. The rotary debonding sleeve can be rotatably arranged above the graphite substrate, and is provided with a buffer glue holding groove and a glue discharge port that are interconnected; the buffer glue holding groove is filled with granular sugar, which cooperates with the protrusions distributed around it to achieve soft support on the hard surface, prevent the silicon carbide seed crystal from shifting, and reduce edge damage. At the same time, the gaps in the granular sugar can discharge gas and glue overflow from the bonding surface, and can increase the flow resistance of the glue to avoid insufficient local glue. During heating and curing, the granular sugar melts, the rotary debonding sleeve rotates, and the protrusions scrape off the glue overflow. At the same time, the granular sugar provides lubrication, reduces damage to the side wall of the seed crystal, improves the quality of crystal growth, and effectively solves the problems of shift, breakage and glue residue in traditional methods. During use, testing revealed that the concentricity between the silicon carbide seed crystal and the graphite substrate 1 was minimal. The single-side offset between the two was less than 0.01 mm, defined as the shortest distance between one side of the silicon carbide seed crystal and the same-side edge of the graphite cover plate. The seed crystal adhesive residue was minimal and easily removed, with no issues such as loose seed crystal adhesion, seed crystal fragmentation, or cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 A front view of a silicon carbide seed crystal bonding device provided in an embodiment of the present application;

[0039] Figure 2 A top view of a silicon carbide seed crystal bonding device provided in an embodiment of the present application;

[0040] Figure 3 This is a flow chart of the silicon carbide seed crystal method provided in an embodiment of the present application.

[0041] The following is a supplementary description of the accompanying drawings:

[0042] 1-graphite substrate; 2-rotating glue removal sleeve; 21-buffer glue tank; 22-bump; 23-glue discharge port; 3-upper pressure block; 4-pressure cover; 5-retractable center pressure plate; 6-liftable annular pressure ring; 7-heat conducting block; 8-rotating part. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0044] References to "one embodiment" or "embodiment" herein refer to specific features, structures, or characteristics that may be included in at least one implementation of the present application. Throughout the description of this application, it should be understood that the terms "upper," "lower," "top," and "bottom," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplification. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, a feature designated "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, the terms "first," "second," etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that such terms are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0045] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein. For example, a specified range from "1 to 10" should be considered to include any and all subranges between a minimum of 1 and a maximum of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0046] See also Figure 1 and Figure 2 , an embodiment of the present application provides a silicon carbide seed crystal bonding device, comprising:

[0047] Graphite substrate 1, used for carrying silicon carbide seed crystals;

[0048] The rotary glue removal sleeve 2 is rotatably arranged above the graphite substrate 1, and is provided with a buffer glue containing groove 21 and a glue discharge port 23 that are interconnected; wherein, the buffer glue containing groove 21 is used to accommodate granular sugar, and the glue discharge port 23 is used to discharge melted granular sugar and excess overflow glue; bumps 22 are evenly distributed around the buffer glue containing groove 21, which are used to form point contact support with the edge of the silicon carbide seed crystal; it can be understood that the buffer glue containing groove 21 is opened on the base of the rotary glue removal sleeve 2, and two adjacent buffer glue containing grooves 21 are separated in the vertical direction by the bumps 22.

[0049] The upper pressing block 3 is located above the rotating debonding sleeve 2 and is used to press down the silicon carbide seed crystal.

[0050] Specifically, the graphite substrate 1 serves as the basic supporting component of the entire silicon carbide seed crystal bonding device, providing stable and reliable support for the silicon carbide seed crystal. During the growth of silicon carbide single crystals, the graphite substrate 1 needs to have good thermal stability, chemical stability and high mechanical strength to ensure that it can maintain its own shape and performance stability under high temperature, complex chemical environment and certain mechanical stress, thereby providing a solid foundation for the bonding and subsequent growth process of the silicon carbide seed crystal. The graphite substrate 1 is usually made of high-purity graphite material to reduce the impact of impurities on the growth of silicon carbide crystals. In addition, the surface of the graphite substrate 1 has been finely processed and has high flatness and smoothness, ensuring good contact between the silicon carbide seed crystal and the graphite substrate 1, avoiding problems such as introducing additional stress or uneven bonding due to surface unevenness.

[0051] The rotary glue removal sleeve 2 is rotatably arranged above the graphite substrate 1, and a buffer glue holding groove 21 is provided inside the rotary glue removal sleeve 2 for accommodating granular sugar. The granular sugar can be white granulated sugar, crystal sugar, etc. There are gaps between the granular sugars. When the bonding surfaces are in contact, the gaps can be used for gas discharge, while also allowing overflowing glue to flow in. In addition, the granular sugars can increase the resistance to the flow of glue on the bonding surface to a certain extent, thereby avoiding problems such as insufficient local glue and insufficient bonding force when the bonding surface is pressed down due to excessive fluidity of the glue on the bonding surface. In addition, when the granular sugars melt into liquid, they can provide lubrication for the rotation of the rotary glue removal sleeve 2, reducing damage to the side walls of the silicon carbide seed crystal. In addition, the granular sugars are easy to remove by water dissolution or other methods, that is, they have the characteristics of being easier to remove and have a small amount of residue. They can greatly reduce defects that affect the quality of the later growth of the silicon carbide seed crystals, such as glue residue, scratches, and breakage when the silicon carbide seed crystals are bonded to the base, thereby improving the quality of crystal growth.

[0052] The glue discharge port 23 is interconnected with the buffer glue holding tank 21 and is used to discharge melted granular sugar, excess glue, etc. Before initial use, melted sugar liquid is injected into the glue discharge port 23, and the glue discharge port 23 is sealed after solidification. Thus, the silicon carbide seed crystal coated with adhesive is placed in the center of the graphite substrate 1, and then the rotary glue removal sleeve 2 is installed. Granular sugar is then added to the buffer glue holding tank 21 of the rotary glue removal sleeve 2, and finally the pressure cover 4 is covered. After completing the above preparations, the upper pressing block 3 is used to slowly apply pressure to the silicon carbide seed crystal so that the silicon carbide seed crystal and the graphite substrate 1 are better fitted through the adhesive. The glue discharge port 23 is sealed to avoid premature loss of granular sugar. During use, as the sugar in the buffer glue holding tank 21 gradually melts, the glue discharge port 23 is connected, and the melted granular sugar and excess glue can be discharged through the glue discharge port 23. During the bonding process, as the temperature rises, the granular sugar continues to melt and flow through the buffer glue tank 21. At this time, part of the excess melted sugar and overflowed glue will be discharged outside the device through the glue discharge port 23.

[0053] The bumps 22 are evenly distributed around the buffering glue groove 21. When the bumps 22 come into contact with the silicon carbide seed crystal, a point contact hard support structure is formed, which, combined with the relatively soft support effect of the granular sugar, realizes point hard support and surface soft support. While providing effective support for the silicon carbide seed crystal, it can effectively reduce the contact area between the silicon carbide seed crystal and the support structure, thereby reducing the possibility of the silicon carbide seed crystal edge being damaged due to force. On the other hand, the point contact support and the buffering effect of the granular sugar cooperate with each other to better prevent the silicon carbide seed crystal from being offset and dislocated during the bonding process, thereby ensuring the position accuracy of the silicon carbide seed crystal during the bonding process. When the bonding surface is heated and cured, the granular sugar melts into a liquid state. At this time, the rotating glue removal sleeve 2 is rotated, and the bumps 22 can play the role of scraping glue to remove the overflow glue adhering to the side wall of the silicon carbide seed crystal.

[0054] The upper pressing block 3 is located above the rotating debonding sleeve 2 and is used to press down the silicon carbide seed crystal to achieve uniform bonding with the base.

[0055] In some specific embodiments, heat conducting blocks 7 are arranged around the upper pressing block 3 .

[0056] Specifically, an annular groove is provided on the four edges of the upper pressing block 3, and the heat-conducting block 7 is arranged in the annular groove and can be fixed by bonding, clamping, etc. The heat-conducting block 7 is made of silicon carbide, while the upper pressing block is made of stainless steel. Due to the high thermal conductivity of the silicon carbide heat-conducting block 7, the heating speed of the edge is faster than that of the center, which helps to accelerate the heating of the graphite adhesive at the edge, promote the rapid generation and discharge of bubbles, and reduce the resistance to bubble discharge, while facilitating the discharge of bubbles generated in the center to the edge. In addition, the rapid heating of the edge can also accelerate the melting of the granular sugar and further optimize the bonding process. The stainless steel material ensures the uniformity of the heating process, avoids local overheating, and thus improves the bonding quality. It effectively solves the problems of difficult bubble discharge, uneven heating, and inconsistent melting rate of granular sugar in the traditional bonding process.

[0057] In some specific embodiments, the device further includes a pressure cover 4 , which covers the buffering and containing glue groove 21 and is used to close the buffering and containing glue groove 21 .

[0058] Specifically, the pressure cap 4 covers the top of the buffering and containing glue groove 21 and is used to close the buffering and containing glue groove 21 when accommodating granular sugar. In some embodiments, the inner wall of the buffering and containing glue groove 21 can be provided with a positioning card slot, and the corresponding position of the edge of the pressure cap 4 is provided with a matching positioning boss. When the pressure cap 4 is installed, the positioning boss can be accurately inserted into the positioning card slot to ensure that the pressure cap 4 and the buffering and containing glue groove 21 are accurately aligned in the horizontal direction. At the same time, the pressure cap 4 is provided with a circle of high-temperature resistant rubber sealing gasket at the edge in contact with the buffering and containing glue groove 21, which can further enhance the sealing effect and prevent the granular sugar from leaking, and can also buffer the impact force of the pressure cap 4 on the buffering and containing glue groove 21. In terms of fixing method, there are multiple threaded holes evenly distributed around the pressure cap 4, and the corresponding position of the buffering and containing glue groove 21 is provided with a matching screw hole. By rotating and tightening the bolts, the pressure cap 4 can be quickly and firmly fixed to the buffering and containing glue groove 21, ensuring that the pressure cap 4 always fits tightly against the buffering and containing glue groove 21 during the process of accommodating granular sugar, achieving reliable closure.

[0059] In some specific embodiments, the device further comprises a retractable central pressure plate 5 and a liftable annular pressure ring 6;

[0060] The retractable central pressure plate 5 is installed above the center of the upper pressure block 3 and coincides with the central axis of the upper pressure block 3, and is used to retract and press the silicon carbide seed crystal downward from the center;

[0061] The elevating annular pressure ring 6 is installed above the edge of the upper pressure block 3 and is arranged around the retractable central pressure plate 5 to press down the silicon carbide seed crystal from all sides by lifting.

[0062] Specifically, a retractable central pressure plate 5 is positioned above the center of the upper pressure block 3. This platen 5 contacts the upper pressure block 3 via guide posts, ensuring stable vertical upward and downward movement. The center of the platen 5 coincides with the central axis of the upper pressure block 3, precisely retracting and pressing the silicon carbide seed crystal downward from the center.

[0063] In addition, a liftable annular pressure ring 6 is provided above the edge of the upper pressure block 3 and is driven by a lifting mechanism such as a hydraulic cylinder or an electric push rod. Limiting devices are provided around the liftable annular pressure ring 6, such as limiting grooves or limiting blocks fixed to a fixed frame, with the edges of the liftable annular pressure ring 6 matching these, ensuring that the ring does not shift during the lifting process. During the high-temperature curing stage, after the bubbles are expelled, the liftable annular pressure ring 6 descends to provide a secondary auxiliary downward pressure on the edge, which helps to improve the overall bonding density and bonding strength.

[0064] In some specific embodiments, a rotating member 8 is provided on the rotary glue removing sleeve 2, and the rotating member 8 drives the rotary glue removing sleeve 2 to rotate through a driving device.

[0065] Specifically, a rotating member 8 is provided on the rotary degumming sleeve 2, and power transmission can be achieved between the rotating member 8 and the rotary degumming sleeve 2 by means of a key connection or a spline connection, thereby driving the rotary degumming sleeve 2 to rotate. The rotating member 8 itself can be powered by a motor or other power source. In some embodiments, the rotating member 8 is rotated by means of gear transmission or the like. For example, the rotating member 8 can be set as a driving gear connected to the power source, and the power is transmitted to the rotary degumming sleeve 2 through a driven gear meshed therewith. In order to ensure the stability of the rotary degumming sleeve 2 during the rotation process, the rotary degumming sleeve 2 can be mounted on a fixed bracket by a bearing. The bearing can effectively reduce the friction resistance during the rotation process and ensure the coaxiality of the rotation. At the same time, a positioning ring or a slot structure can be provided at both ends of the rotary degumming sleeve 2, and a matching positioning protrusion or block is provided on the corresponding fixed component. By this engagement or positioning method, it is further ensured that the rotary degumming sleeve 2 will not have axial movement during rotation, thereby ensuring the accuracy and stability of the entire rotary degumming process.

[0066] In some specific embodiments, the center of the retractable central pressure plate 5 coincides with the center of the silicon carbide seed crystal, and the area of the retractable central pressure plate 5 covers 0.8-0.9 of the area of the silicon carbide seed crystal.

[0067] Specifically, by aligning the center of the retractable center platen 5 with the center of the silicon carbide seed crystal, the area of the retractable center platen 5 covers 0.8-0.9% of the area of the silicon carbide seed crystal. This incomplete coverage arrangement helps to leave a channel for gas to escape at the edge, preventing bubbles from failing to escape or being incompletely escaped, which could affect the bonding quality. If the retractable center platen 5 completely covers the silicon carbide seed crystal, during operations such as heating, the gas generated inside may accumulate between the silicon carbide seed crystal and the adhesive due to nowhere to escape, forming bubbles. If the bubbles cannot be escaped or are incompletely escaped, it will seriously affect the bonding quality, for example, causing defects such as holes and gaps in the adhesive layer, thereby reducing the bonding strength and stability between the silicon carbide seed crystal and other components. By setting the retractable center platen 5 to cover 0.8-0.9% of the area of the silicon carbide seed crystal, a certain amount of space is left at the edge of the silicon carbide seed crystal, thereby forming a channel for gas to escape. The gas generated during the heating process can be smoothly discharged along the channel, avoiding the problem of bubble accumulation.

[0068] In some specific embodiments, the relationship between the volume V1 of the buffering resin containing groove 21 above the interface reference plane between the upper pressing block 3 and the silicon carbide seed crystal and the volume V2 of the lower part is V1≥1.1V2.

[0069] Specifically, the interface between the upper pressing block 3 and the silicon carbide seed crystal is a reference plane, and the volume V1 of the buffering glue holding groove 21 above the reference plane is more than 1.1 times the volume V2 of the buffering glue holding groove 21 below. When heating is carried out, the granular sugar will gradually melt, and its volume will shrink accordingly. At the same time, liquid sugar may flow out under certain conditions. By ensuring that V1 is greater than or equal to 1.1 times V2, sufficient accommodation space and sufficient residence time can be provided for the liquid sugar, so that it can give full play to its lubrication effect. The liquid sugar is able to form a good lubrication effect between the silicon carbide seed crystal and the rotating de-glue sleeve 2, reducing the friction between them, and helping the silicon carbide seed crystal to maintain a stable position and posture during the bonding process, avoiding problems such as position offset or surface damage caused by excessive friction.

[0070] In some specific embodiments, the rotating debonding sleeve 2 is coaxially arranged with the graphite substrate 1 .

[0071] Specifically, during the bonding process of the silicon carbide seed crystal and the graphite substrate, the coaxial arrangement of the rotary debonding sleeve 2 and the graphite substrate 1 effectively prevents the silicon carbide seed crystal from shifting. Because the rotary debonding sleeve 2 and the graphite substrate 1 maintain a precise coaxial relationship, it provides a stable guide frame for the silicon carbide seed crystal, limiting its irregular movement in all directions, thereby ensuring that the silicon carbide seed crystal and the graphite substrate 1 can be precisely coaxially mounted. This, in turn, improves the uniformity of heat transfer and the balance of stress distribution, thereby enhancing the bonding quality.

[0072] See also Figure 3 The present application also provides a method for bonding a silicon carbide seed crystal, wherein the silicon carbide seed crystal is bonded using the above-mentioned silicon carbide seed crystal bonding device, and the method includes the following steps:

[0073] Coating the bonding surface of the silicon carbide seed crystal with adhesive;

[0074] Applying graphite-containing adhesive to the edge of the graphite substrate 1;

[0075] The silicon carbide seed crystal coated with adhesive is placed at the center of the graphite substrate 1 and a rotary adhesive removal sleeve 2 is installed; wherein the buffering adhesive tank 21 of the rotary adhesive removal sleeve 2 contains granular sugar;

[0076] After the silicon carbide seed crystal is pressed by the upper pressing block 3, the entire assembly is placed in a hot pressing device for pressurized curing.

[0077] Specifically, the silicon carbide seed crystal bonding method has the following specific operating steps:

[0078] In step S101 , a layer of adhesive (the adhesive may be phenolic resin adhesive) is evenly coated on the bonding surface of the silicon carbide seed crystal to ensure that the adhesive layer evenly covers the bonding surface.

[0079] In step S102, a graphite-containing adhesive is applied to the edge of the graphite substrate 1. During the bonding process, the gaps between the graphite particles create relatively stable circulation channels for the internal gas, allowing bubbles to be smoothly discharged along these channels. This eliminates the need for dedicated gas discharge channels and allows for rapid removal of bubbles from the graphite-containing adhesive. Furthermore, the graphite-containing adhesive applied to the edge of the graphite substrate 1 also provides excellent bonding to the edges of the silicon carbide seed crystals, enhancing the stability of the bond.

[0080] In step S103 , the silicon carbide seed crystal coated with adhesive is placed at the center of the graphite substrate 1 , and the rotary adhesive removal sleeve 2 is installed. Granular sugar is then added to the adhesive buffer tank 21 of the rotary adhesive removal sleeve 2 , and finally the pressure cover 4 is covered.

[0081] In step S104, after completing the above preparatory steps, the upper pressing block 3 is used to slowly apply pressure to the silicon carbide seed crystal, ensuring a better fit between the silicon carbide seed crystal and the graphite substrate 1 through the adhesive. The entire assembly is then placed in a hot press for pressurized curing. During this step, under the pressure and specific temperature provided by the hot press, the adhesive undergoes a curing reaction, thereby achieving a secure bond between the silicon carbide seed crystal and the graphite substrate 1, ensuring that it will not loosen or separate during subsequent use or processing.

[0082] In some specific embodiments, heat bonding is performed in a hot pressing device, comprising:

[0083] Stage 1: In a vacuum environment with a pressure of ≤9 Pa, the temperature is raised to 90-100°C at a heating rate of 71-80°C / h and maintained for 5-15 minutes. At the same time, pressure is applied to the center of the silicon carbide seed crystal through the retractable center pressure plate 5.

[0084] The second stage: increase the pressure applied by the retractable central pressure plate 5, heat it to 150-190°C at a heating rate of 30-40°C / h, and maintain it for 1-1.3 hours; at the same time, start the rotary rubber removal sleeve 2 and rotate it for 3-5 minutes;

[0085] The third stage: the temperature is raised to 400-450°C at a heating rate of 25-35°C / h and maintained for 3-4 hours; at the same time, pressure is applied to the edge of the silicon carbide seed crystal through the elevating annular pressure ring 6;

[0086] Stage 4: Heat to 460-499°C at a heating rate of 17-27°C / h until the bond is fully cured.

[0087] Specifically, the heating process mainly includes the following four stages:

[0088] During the first stage, the entire heating operation must be performed in a vacuum environment, with the vacuum maintained below 9 Pa to ensure stability and controllability of the heating process. Subsequently, the material is heated at a heating rate of 71-80°C / h until it reaches a temperature range of 90-100°C. This temperature is then maintained at this temperature for 5-15 minutes, with 10 minutes being the preferred duration. Simultaneously, during this process, the retractable center platen 5 begins pressing downward, squeezing the material. At this specific temperature, materials such as the granulated sugar have not yet begun to melt, but some glue may overflow due to thermal expansion and flow into the gaps between the granules. At this point, initial bubbles begin to form within the glue, allowing them to escape preemptively through the gaps between the granules, thus avoiding quality issues that could arise from bubble accumulation during the subsequent heating process. Furthermore, maintaining this temperature for a short period of time allows the glue to be more evenly distributed at a higher temperature for the subsequent heating process, providing a good foundation for the entire heating process and subsequent processing operations, ensuring uniform and stable heating of the material.

[0089] In the second stage, the pressure of the retractable center platen 5 is increased, and the material is then heated at a rate of 30-40°C / h until the temperature reaches 150-190°C, where it is maintained at this temperature for 1-1.3 hours. During this heating phase, the rotary debonding sleeve 2 is simultaneously activated and rotated for 3-5 minutes. Within this temperature range, a large number of bubbles rapidly form and escape from the material. As the reaction proceeds, the rate of bubble escape gradually slows. Increasing the pressure of the retractable center platen 5 further strengthens the bond between the materials. At the same time, as the temperature rises, glue gradually overflows. The rotary motion of the debonding sleeve 2 effectively scrapes away the excess glue. Furthermore, at temperatures between 150-190°C, the granulated sugar melts and is removed, leaving ample channels for bubbles to escape from the material, ensuring smooth bubble discharge and preventing potential quality risks caused by bubble accumulation.

[0090] In the third stage, the temperature is raised to 400-450°C at a heating rate of 25-35°C / h and held constant for 3-4 hours, which helps the remaining tiny bubbles to slowly escape. At the same time, the annular pressure ring 6 can be raised and lowered to apply pressure to the edge to improve the bonding strength without affecting the slow escape of the remaining tiny bubbles.

[0091] In the fourth stage, the temperature is raised to 460-499°C at a heating rate of 17-27°C / h until the adhesive is fully cured. Improper heating control during this stage can lead to incomplete bubble expulsion, resulting in defects such as holes, vortices, and pores, which can affect the growth quality of the SiC seed crystal. Therefore, precise control of the heating rate and temperature range is required to ensure uniform adhesive curing and effective bubble expulsion, thereby improving the bonding strength and growth quality of the SiC seed crystal.

[0092] In some specific embodiments, the graphite-containing adhesive is coated on the outer edge of the graphite substrate 1 at a position of 1 / 10-1 / 5 of the diameter.

[0093] Specifically, the edge of the graphite substrate 1 is coated with a graphite-containing adhesive, preferably at the outermost edge, which is 1 / 10-1 / 5 of the diameter of the graphite substrate 1. Selecting this location effectively disperses external forces applied to the substrate during use, enhancing the structural stability of the edge and preventing damage due to stress concentration. Furthermore, this coating range facilitates precise control of the adhesive dosage, avoiding waste while ensuring optimal bonding between the edge and other components, meeting practical application requirements.

[0094] In some specific embodiments, the adhesive is a phenolic resin adhesive, which comprises a phenolic resin and a propylene glycol methyl ether acetate solvent, wherein the content of the phenolic resin is 13%-17%.

[0095] Specifically, in the preparation process of silicon carbide seed crystals, a uniform layer of adhesive glue will be coated on their bonding surface. The adhesive glue is preferably a phenolic resin glue, which is mainly composed of phenolic resin and propylene glycol methyl ether acetate solvent, wherein the preferred content of phenolic resin is 13%-17%. The use of high-fluidity phenolic resin glue can give full play to the advantages of fluidity, maintain good fluidity, quickly and evenly fill the tiny gaps on the bonding surface, and make the glue more evenly distributed on the bonding surface. Not only can it increase the contact area between the silicon carbide seed crystal and the bonding surface, but it can also effectively avoid problems such as insufficient or excessive local bonding force caused by uneven distribution of glue, thereby significantly improving the bonding stability and reliability of the silicon carbide seed crystal.

[0096] In some specific embodiments, the graphite-containing adhesive includes graphite and phenolic resin, with the graphite content being 10%-40% and the phenolic resin content being 7%-8%.

[0097] Specifically, the edge of the graphite substrate 1 is coated with a graphite-containing adhesive, which is composed of graphite, phenolic resin, and solvent. The graphite content is 10%-40%, preferably 26%-34%; the phenolic resin content is 7%-8%; and the rest is solvent. During the gluing process, bubbles can be quickly removed by heating. The gaps between the graphite particles provide a stable circulation channel for the internal gas, so there is no need to set up a special gas exhaust channel. This not only improves the stability and reliability of the bonding effect, but also provides a better bonding effect for the edge of the silicon carbide seed crystal.

[0098] In some specific embodiments, the particle size of the granulated sugar is 0.12-0.24 mm.

[0099] Specifically, the preferred particle size of granular sugar is 0.12-0.24 mm. Granular sugar within this size range exhibits excellent air permeability, effectively allowing for the effective removal of gas when the bonding surfaces meet while providing a suitable channel for the inflow of excess glue, thereby ensuring a stable and reliable bonding effect. Furthermore, its density is moderate, neither too loose to cause gas accumulation nor too dense to hinder the flow of excess glue, but rather providing a moderate resistance to excess glue.

[0100] The embodiment of the present application discloses a silicon carbide seed crystal bonding device and method. The device includes a graphite substrate, a rotary debonding sleeve and an upper pressure block. The rotary debonding sleeve can be rotatably arranged above the graphite substrate, and is provided with a buffer glue holding groove and a glue discharge port that are interconnected; the buffer glue holding groove is filled with granular sugar, which cooperates with the protrusions distributed around it to achieve soft support on the hard surface, prevent the silicon carbide seed crystal from shifting, and reduce edge damage. At the same time, the gaps in the granular sugar can discharge gas and glue overflow from the bonding surface, and can increase the flow resistance of the glue to avoid insufficient local glue. During heating and curing, the granular sugar melts, the rotary debonding sleeve rotates, and the protrusions scrape off the glue overflow. At the same time, the granular sugar provides lubrication, reduces damage to the side wall of the seed crystal, improves the quality of crystal growth, and effectively solves the problems of shift, breakage and glue residue in traditional methods. During use, testing revealed that the concentricity between the silicon carbide seed crystal and the graphite substrate 1 was minimal. The single-side offset between the two was less than 0.01 mm, defined as the shortest distance between one side of the silicon carbide seed crystal and the same-side edge of the graphite cover plate. The seed crystal adhesive residue was minimal and easily removed, with no issues such as loose seed crystal adhesion, seed crystal fragmentation, or cracking.

[0101] The above are only optional embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A silicon carbide seed crystal bonding device, characterized in that: include: A graphite substrate (1) for carrying silicon carbide seed crystals; A rotary glue removal sleeve (2) is rotatably arranged above the graphite substrate (1), and is provided with a buffer glue holding groove (21) and a glue discharge port (23) that are interconnected; wherein the buffer glue holding groove (21) is used to hold granular sugar, and the glue discharge port (23) is used to discharge the melted granular sugar and excess glue overflow; bumps (22) are evenly distributed around the buffer glue holding groove (21) for forming point contact support with the edge of the silicon carbide seed crystal; An upper pressing block (3) is located above the rotating debonding sleeve (2) and is used to press down the silicon carbide seed crystal; The heat conducting blocks (7) are arranged around the upper pressing block (3).

2. The silicon carbide seed crystal bonding device according to claim 1, characterized in that: The device further comprises a pressure cover (4), wherein the pressure cover (4) covers the upper portion of the buffering glue containing groove (21) and is used for closing the buffering glue containing groove (21).

3. The silicon carbide seed crystal bonding device according to claim 1, characterized in that: The device also includes a retractable central pressure plate (5) and a liftable annular pressure ring (6); The retractable central pressure plate (5) is installed above the center position of the upper pressure block (3) and coincides with the central axis of the upper pressure block (3), and is used to retract from the center to press down the silicon carbide seed crystal; The liftable annular pressure ring (6) is installed above the edge of the upper pressure block (3) and is arranged around the retractable central pressure plate (5) to press down the silicon carbide seed crystal from all sides by lifting.

4. The silicon carbide seed crystal bonding device according to claim 1, characterized in that: The rotary glue removal sleeve (2) is provided with a rotating member (8), and the rotating member (8) drives the rotary glue removal sleeve (2) to rotate via a driving device.

5. The silicon carbide seed crystal bonding device according to claim 3, characterized in that: The center of the retractable central pressure plate (5) coincides with the center of the silicon carbide seed crystal, and the area of the retractable central pressure plate (5) covers 0.8-0.9 of the area of the silicon carbide seed crystal.

6. The silicon carbide seed crystal bonding device according to claim 1, wherein the relationship between the volume V1 of the buffer glue groove (21) above the interface reference plane between the upper pressing block (3) and the silicon carbide seed crystal and the volume V2 of the lower part is V1≥1.1V2.

7. The silicon carbide seed crystal bonding device according to claim 1, characterized in that: The rotating glue removal sleeve (2) is coaxially arranged with the graphite substrate (1).

8. A method for bonding silicon carbide seed crystals, comprising bonding silicon carbide seed crystals using the silicon carbide seed crystal bonding device according to any one of claims 1 to 7, wherein: The following steps are involved: Coating the bonding surface of the silicon carbide seed crystal with adhesive; Applying a graphite-containing adhesive to the edge of the graphite substrate (1); The silicon carbide seed crystal coated with the adhesive is placed at the center of the graphite substrate (1), and a rotating adhesive removal sleeve (2) is installed; wherein the buffering adhesive tank (21) of the rotating adhesive removal sleeve (2) contains granular sugar; After applying pressure to the silicon carbide seed crystal by means of an upper pressing block (3) to compact it, the entire assembly is placed in a hot pressing device for pressurized curing, comprising: The first stage: in a vacuum environment with a pressure of ≤9 Pa, the temperature is raised to 90-100°C at a heating rate of 71-80°C / h and maintained for 5-15 minutes; at the same time, pressure is applied to the center of the silicon carbide seed crystal through a retractable central pressure plate (5); The second stage: increasing the applied pressure of the retractable central pressure plate (5), heating the temperature to 150-190°C at a heating rate of 30-40°C / h, and maintaining the temperature for 1-1.3 hours; simultaneously starting the rotating rubber removal sleeve (2) and rotating it for 3-5 minutes; The third stage: raising the temperature to 400-450°C at a heating rate of 25-35°C / h and maintaining it for 3-4h; at the same time, applying pressure to the edge of the silicon carbide seed crystal through a retractable annular pressure ring (6); Stage 4: Heat to 460-499°C at a heating rate of 17-27°C / h until the bond is fully cured.

9. The method for bonding silicon carbide seed crystals according to claim 8, wherein: The graphite-containing adhesive is applied to the outer edge of the graphite substrate (1) at a diameter of 1 / 10-1 / 5.

10. The method for bonding silicon carbide seed crystals according to claim 8, wherein: The bonding glue is a phenolic resin glue, which comprises a phenolic resin and a propylene glycol methyl ether acetate solvent, wherein the content of the phenolic resin is 13%-17%.

11. The method for bonding silicon carbide seed crystals according to claim 8, wherein: The graphite-containing adhesive comprises graphite and phenolic resin, wherein the content of the graphite is 10%-40%, and the content of the phenolic resin is 7%-8%. 12 . The method for bonding silicon carbide seed crystals according to claim 8 , wherein the particle size of the granular sugar is 0.12-0.24 mm.

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