A limiting device for seed crystal hot-pressing process

Abstract

The utility model relates to the technical field of semiconductor, concretely refers to a kind of limiting device for seed crystal hot-pressing process, the device includes the heating disc placed in the upper heating resistance wire, at least one group of seed crystal assembly is arranged in the upper groove of heating disc, two or more seed crystal assemblies can be placed in up-down stack, the uppermost seed crystal assembly is equipped with to top, and the upper part of top is pressed by hot-pressing furnace pressure head to exert pressure;The groove of heating disc is also embedded with the same number of seed crystal assembly limit die group as limit die group. Seed crystal assembly includes seed crystal support, silicon carbide seed crystal piece and graphite paper covered on seed crystal piece, and limit die group is composed of first limit die, second limit die and connecting column. The utility model eliminates the horizontal component of pressure by structural design, avoids the relative sliding of seed crystal and seed crystal support, and prevents adhesive overflow from polluting mould, realizes single group or multiple seed crystal assembly synchronous hot-pressing, improves bonding accuracy, uniformity and efficiency, and meets the needs of scientific research rapid preparation and industrial high-throughput production.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor technology, specifically to a limiting device used in the hot pressing process of seed crystals. Background Technology

[0002] Silicon carbide (SiC), as one of the representatives of third-generation wide-bandgap semiconductor materials, possesses a series of excellent properties, including a wide bandgap, high critical breakdown electric field, excellent intrinsic thermal conductivity, and outstanding chemical stability. Therefore, silicon carbide is particularly suitable for applications in extreme environments such as high temperature, high pressure, high power, and strong radiation. Among the many methods for growing silicon carbide crystals, the liquid-phase method (solution growth method) has received widespread attention and rapid development in recent years due to its ability to produce crystals with high crystallinity while significantly reducing growth costs.

[0003] Unlike the Czochralski method used for silicon single crystal growth, liquid phase epitaxial growth of silicon carbide typically relies on pre-prepared seed crystals. The structural quality and geometric symmetry of these seed crystals have a crucial impact on the stability and uniformity of subsequent crystal growth. Currently, silicon carbide seed crystals are generally fixed using an adhesive bonding process, where the silicon carbide wafer is adhered to a seed crystal holder using an adhesive, and then fixed by hot-pressing carbonization at high temperature. However, due to the fluidity of the adhesive during hot-pressing, and the difficulty in maintaining perfect perpendicularity of the applied external force, relative slippage between the seed crystal and the seed crystal holder is likely to occur.

[0004] If eccentricity or misalignment occurs between the seed crystal and the seed crystal holder during the initial bonding process, it will directly lead to the seed crystal and the melt center not maintaining perpendicular alignment during growth. The resulting solid-liquid interface temperature field will exhibit a non-axisymmetric distribution, affecting not only the stability of crystal growth but also potentially causing non-uniformity in thickness and doping concentration. Furthermore, misalignment between the seed crystal and the seed crystal holder can easily cause melt stagnation in the misaligned area, inducing undesirable phenomena such as polycrystalline adhesion or parasitic crystallization. During subsequent cooling, the presence of these undesirable phases can lead to significant thermal stress within the crystal, causing cracks, structural defects, and other problems, severely impacting the final crystal quality and product yield.

[0005] Therefore, achieving high-precision alignment between the silicon carbide seed and the seed holder to ensure interface stability and symmetry during crystal growth has become a key engineering challenge in liquid phase growth technology. Although various types of seed bonding and positioning molds have been developed, which can suppress relative slippage between the seed and the seed holder to some extent, many shortcomings remain in practical applications, such as uneven adhesive distribution and mold contamination due to adhesive overflow. These problems not only affect alignment accuracy but also increase operational complexity and the risk of contamination. Utility Model Content

[0006] The purpose of this invention is to provide a limiting device that can achieve high-precision positioning and alignment between the silicon carbide seed wafer and the seed wafer holder during the bonding process. This limiting device can effectively suppress relative slippage while optimizing the distribution of the colloid, reducing the risk of mold contamination during the bonding process, thereby improving the accuracy and stability of seed wafer fixation and significantly improving the quality of crystal growth.

[0007] This utility model is achieved through the following technical solution: a limiting device for seed crystal hot pressing process, comprising a heating plate placed above a heating resistance wire, a groove provided on the upper part of the heating plate, at least one set of seed crystal components placed in the groove, two or more sets of seed crystal components stacked one on top of the other, and a top support for pressing the seed crystal components provided on the uppermost seed crystal component, and a hot press furnace head for pressing the top support provided on the top support; a limiting mold group nested outside the seed crystal components and the top support is embedded in the groove of the heating plate, the number of the limiting mold group is the same as the number of seed crystal components, and limits the seed crystal components and the top support.

[0008] The working principle of this technical solution is to ensure that the applied pressure is transmitted only vertically to the seed crystal and the seed crystal holder. The limiting mold assembly fundamentally eliminates the horizontal force component, effectively preventing the relative slippage of the seed crystal during the hot pressing process. In addition, there is a structural gap between the limiting mold assembly and the surface of the seed crystal and its bonding area, so that they do not have direct contact with each other. This achieves high-precision limiting while preventing adhesive overflow and contamination of the mold. The graphite paper laid on the surface of the seed crystal assembly can alleviate the vertical pressure applied to the seed crystal assembly by the upper mold and effectively absorb and disperse the thermal stress caused by uneven thermal expansion, thereby improving the thermal stability and carbon distribution uniformity during the bonding process. The limiting mold assembly can adopt a multi-layer stacked structure and modular combination design. By flexibly replacing, deleting or adding mold components, multiple seed crystal samples can be simultaneously hot-pressed and bonded, which can significantly improve the bonding efficiency.

[0009] To better realize this utility model, the seed crystal assembly further includes a seed crystal holder, on which a silicon carbide seed crystal is bonded and fixed, and on which a graphite paper capable of completely covering the silicon carbide seed crystal is disposed.

[0010] To better realize this utility model, the thickness of the graphite paper is further 0.05mm~2mm.

[0011] To better realize this utility model, the bottom center of the seed crystal holder is provided with a downwardly protruding handle, and the center of the heating plate is provided with a concave hole that matches the lower handle of the seed crystal holder. When there are two or more seed crystal components, the seed crystal holder handle of the lowest seed crystal component is placed in the concave hole in the middle of the heating plate. A tray for placing the seed crystal holder handle is also provided between the upper and lower seed crystal components. The shape of the tray matches the seed crystal holder, and the limiting mold group also limits the tray.

[0012] To better realize this utility model, the limiting mold group further includes a lower first limiting mold and an upper second limiting mold. A cavity is provided between the first limiting mold and the second limiting mold to avoid contact with the graphite paper and the bonding interface between the seed crystal holder and the silicon carbide seed wafer. Both the first limiting mold and the second limiting mold are provided with a number and position matching through holes. A connecting column is vertically inserted into the through hole so that the first limiting mold and the second limiting mold are integrated into one structure. When there are two or more limiting mold groups, the first limiting mold of the lowest limiting mold group is embedded in the upper groove of the heating plate.

[0013] To better realize this utility model, the first limiting mold is a solid disc embedded in the outside of the seed crystal assembly, or a disc with a groove at the bottom, and the second limiting mold is a disc with a groove at the bottom; when there are two or more limiting mold groups, the same connecting column is inserted into the through hole in which the positions of the first limiting mold and the second limiting mold in each limiting mold group match, so that each limiting mold group presents an integral structure.

[0014] To better realize this utility model, a guide pressure plate is further provided between the top support and the pressure head of the hot press furnace. The top of the top support is provided with an upwardly protruding pressure handle. The lower surface of the guide pressure plate is provided with a concave hole that matches the pressure handle of the top support. The pressure handle at the top of the top support is placed in the concave hole on the lower surface of the guide pressure plate.

[0015] To better realize this utility model, a buffer plate is further provided between the guide pressure plate and the hot press head.

[0016] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0017] (1) This utility model optimizes the limiting device in the existing seed crystal hot pressing process so that the external pressure is transmitted to the seed crystal and the seed crystal holder only in the vertical direction, which fundamentally eliminates the force component in the horizontal direction and effectively avoids the relative slippage of the seed crystal during the hot pressing process. In addition, there is a structural gap between the limiting mold assembly body and the surface of the seed crystal and its bonding area, so that they do not have direct contact with each other. Thus, while achieving high-precision limiting, it avoids the overflow of adhesive and contamination of the mold, and improves the uniformity of the adhesive layer distribution and the consistency of quality.

[0018] (2) The limiting mold group in this utility model can adopt a multi-layer stacked structure and modular combination design. By flexibly replacing, deleting or adding mold components, multiple seed crystal samples can be simultaneously hot-pressed and bonded, which can significantly improve the bonding efficiency.

[0019] (3) By adding a limiting mold group, this utility model can effectively achieve precise alignment between the seed crystal and the seed crystal holder, and can also significantly improve the uniformity of adhesive distribution during use, and improve the cleanliness and repeatability of the bonding process. By rationally designing the pressure transmission path, it can effectively eliminate the horizontal component of pressure, so as to solve the problems of seed crystal and seed crystal holder misalignment, uneven distribution of adhesive after carbonization, and adhesive overflow contamination of mold in the prior art. At the same time, it also solves the crystal eccentricity, non-uniform growth and growth defects caused by inaccurate bonding or slippage during hot pressing between the seed crystal and the seed crystal holder. It is suitable for rapid sample preparation in scientific research experiments and high-throughput bonding needs in industrial production, and has obvious industrial promotion potential. Attached Figure Description

[0020] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0021] Figure 1 This is a cross-sectional view of Embodiment 1 of the present invention;

[0022] Figure 2 This is a cross-sectional view of Embodiment 2 of this utility model.

[0023] Wherein: 1—heating plate, 2—seed crystal assembly, 21—seed crystal holder, 22—silicon carbide seed crystal, 23—graphite paper, 3—top support, 4—hot press furnace head, 5—limiting mold assembly, 51—first limiting mold, 52—second limiting mold, 53—connecting column, 6—tray, 7—guide pressure plate, 8—buffer plate. Detailed Implementation

[0024] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0025] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0026] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0027] Example 1:

[0028] This embodiment provides a limiting structure for use in the hot pressing process of seed crystals, such as... Figure 1 As shown, the device includes a heating plate 1 placed above a heating resistance wire. The upper part of the heating plate 1 is provided with a groove, and a set of seed crystal components 2 are placed in the groove. A top support 3 for pressing the seed crystal components 2 is provided on the upper part of the seed crystal components 2, and a hot press furnace head 4 for pressing the top support 3 is provided on the upper part of the top support 3. A limiting mold group 5 is embedded in the groove of the heating plate 1 and nested outside the seed crystal components 2 and the top support 3.

[0029] The seed crystal assembly 2 includes a seed crystal holder 21, on which a silicon carbide seed crystal 22 is bonded and fixed, and on which a graphite paper 23 is provided to completely cover the silicon carbide seed crystal 22.

[0030] The bottom center of the seed crystal holder 21 is provided with a downward protruding handle, and the center of the heating plate 1 is provided with a concave hole that matches the lower handle of the seed crystal holder 21. The handle of the seed crystal holder 21 is placed in the concave hole in the middle of the heating plate 1.

[0031] The limiting mold group 5 consists of a lower first limiting mold 51 and an upper second limiting mold 52. A cavity is provided between the first limiting mold 51 and the second limiting mold 52 to avoid contact with the bonding interface between the graphite paper 23 and the seed crystal holder 21 and the silicon carbide seed wafer 22. The first limiting mold 51 and the second limiting mold 52 are each provided with a number of not less than two through holes, and the through holes are arranged in a ring array around the center of the limiting mold group 5. A connecting post 53 is vertically inserted into the two matching through holes, so that the first limiting mold 51 and the second limiting mold 52 are integrated. The first limiting mold 51 is embedded in the upper groove of the heating plate 1.

[0032] A guide pressure plate 7 is also provided between the top support 3 and the hot press head 4. The top of the top support 3 is provided with an upwardly protruding pressure handle. The lower surface of the guide pressure plate 7 is provided with a concave hole that matches the pressure handle of the top support 3. The pressure handle at the top of the top support 3 is placed in the concave hole on the lower surface of the guide pressure plate 7. A buffer plate 8 is also provided between the guide pressure plate 7 and the hot press head 4.

[0033] In addition, the seed crystal holders in heating plate 1 and seed crystal assembly 2 are both made of graphite, and all structures in this embodiment are circular. The connecting column 53 that fixes the first limiting mold 51 and the second limiting mold 52 is made of high-temperature resistant materials such as alumina ceramic, high-temperature resistant ceramic, and isostatic graphite.

[0034] Its specific usage process is as follows:

[0035] I. Preliminary Preparations and Component Pretreatment

[0036] 1. Component selection and dimensional verification

[0037] Confirm that all circular components are sized correctly: the diameter of the groove in the heating plate 1 is consistent with the outer diameter of the first limiting mold 51; the diameter of the bottom support handle of the seed crystal holder 21 is consistent with the central recess of the heating plate; the diameter of the pressure handle of the top support 3 is compatible with the recess on the lower surface of the guide pressure plate 7; the diameter of the connecting column 53 is consistent with the diameter of the through holes of the first and second limiting molds, and there are at least two of them, arranged in a ring array around the center.

[0038] The diameter of the graphite paper 23 is slightly larger than that of the silicon carbide seed wafer 22 to ensure complete coverage without wrinkles; the diameters of the guide pressure plate 7 and the buffer plate 8 match the outer diameter of the second limiting mold 52 to ensure uniform pressure transmission.

[0039] 2. Cleaning and drying process

[0040] The silicon carbide seed wafer was ultrasonically cleaned in sequence with acetone, anhydrous ethanol, and deionized water to remove surface dust, oil, and residual impurities. It was then placed in a drying oven at 120°C for 30 minutes to avoid contaminating the bonding interface.

[0041] II. Assembly of Seed Crystal Components

[0042] 1. Pre-treatment for bonding seed crystal and seed crystal holder

[0043] Apply a layer of organic adhesive with a thickness of about 0.1~0.3mm evenly to the central area of ​​the upper surface of the graphite seed crystal holder 21, and use a scraper to ensure that the adhesive is evenly distributed.

[0044] The silicon carbide seed wafer 22 is gently placed in the center of the seed wafer holder 21, and a pre-pressure of 0.1 MPa is applied and maintained for 1 minute to allow the adhesive to fully contact and expel air bubbles, forming a pre-positioned seed wafer assembly 2. The assembly is then left to stand at room temperature for 2 hours until the adhesive is semi-cured.

[0045] III. Layer-by-layer assembly of the limiting device

[0046] 1. Positioning of heating plate 1 and seed crystal assembly 2

[0047] Place the graphite heating plate 1 horizontally above the heating resistance wire inside the hot press furnace, and ensure that its central axis coincides with the axis of the hot press furnace pressure head 4 by using the positioning scale inside the furnace.

[0048] Align the bottom handle of the seed crystal holder 21 of the seed crystal assembly 2 with the central recess of the heating plate 1, and vertically place it into the groove of the heating plate, ensuring that the center of the seed crystal assembly 2 is aligned with the center of the heating plate.

[0049] 2. Installation of limit mold assembly 5

[0050] The first limiting mold 51 is embedded in the upper groove of the heating plate 1, so that its central hole is fitted outside the seed crystal holder 21, and the lateral movement of the first limiting mold is restricted by the side wall of the groove.

[0051] Graphite paper 23 is flatly covered on the surface of silicon carbide seed wafer 22 and aligned with the center of silicon carbide seed wafer 22. The edges are gently pressed with tweezers to ensure that there are no wrinkles or offsets, and the seed wafer is completely covered to play a role in buffering and adsorption of excess glue.

[0052] Insert the connecting post 53 vertically into the through hole of the first limiting mold 51, ensuring that the top of the connecting post is 5-10mm above the upper surface of the first limiting mold.

[0053] Align the through hole of the second limiting mold 52 with the top of the connecting post 53 and press it down vertically until it forms a rigid whole with the first limiting mold 51. At this time, a cavity of 2mm to 10mm is left between the two molds to ensure that they do not come into contact with the bonding interface of the graphite paper 23 and the seed crystal assembly.

[0054] 3. Installation of the top support and pressure transmission components

[0055] Place the top support 3 into the center hole of the second limiting mold 52, so that its lower surface lightly presses the graphite paper 23 and the upper surface pressure handle faces upward, ensuring that the axis of the top support coincides with the axis of the seed crystal assembly 2.

[0056] Align the recessed hole on the lower surface of the guide pressure plate 7 with the pressure handle of the top support 3, and place it horizontally on the second limiting mold 52 to ensure that the center of the pressure plate is consistent with the center of the top support.

[0057] A buffer plate 8 is placed horizontally on the upper surface of the guide pressure plate 7 to complete the assembly of the pressure transmission component.

[0058] IV. Implementation of Hot Pressing Process

[0059] 1. Parameter settings

[0060] Based on the adhesive properties and process requirements, the hot pressing temperature is set to 550℃ and the hot pressing time to 6 hours. The vertical pressure is adjusted according to the seed crystal size to ensure uniform pressure transmission.

[0061] 2. Hot pressing process control

[0062] Close the hot press furnace door and start the program: first heat up to the set temperature, and after the temperature stabilizes, apply vertical pressure. The pressure is transferred to the seed crystal module 2 through the hot press furnace head 4 → buffer plate 8 → guide pressure plate 7 → top support 3 → graphite paper 23.

[0063] During the process, the horizontal force is transmitted through the top support 3 to the second limiting mold 52 → connecting column 53 → first limiting mold 51, and is finally absorbed by the groove structure of the heating plate 1, thus preventing the seed crystal and the seed crystal support from sliding relative to each other.

[0064] Graphite paper 23 buffers pressure, isolates silicon carbide seed wafer 22 from contact with other molds, and absorbs overflowing adhesive to prevent mold contamination.

[0065] 3. Cooling and depressurization

[0066] After the hot pressing time is over, keep the pressure constant and slowly cool down to room temperature to avoid thermal stress caused by excessive temperature difference; after cooling is complete, release the pressure and open the furnace door.

[0067] V. Disassembly of the apparatus and removal of samples

[0068] 1. Disassemble the components step by step.

[0069] First, raise the pressure head 4 of the hot press furnace by pressing the button or rotating wheel of the hot press furnace equipment, and then remove the buffer plate 8 and the guide pressure plate 7 in sequence.

[0070] Pull out the alumina ceramic connecting column 53 to separate the second limiting mold 52 from the first limiting mold 51.

[0071] Remove the top support 3, the second limiting mold 52, and the graphite paper 23, and inspect the surface of the silicon carbide seed wafer 22: the silicon carbide seed wafer 22 and the seed wafer support 21 are precisely aligned, with no relative slippage, and there is no excess adhesive contamination at the bonding interface.

[0072] Finally, the second limiting mold 51 is removed from the heating plate 1 to complete the hot pressing limiting process.

[0073] 2. Sample inspection

[0074] Observe the seed crystal component 2: the silicon carbide seed crystal 22 and the seed crystal holder 21 are precisely aligned without any offset; the graphite paper 23 absorbs the excess adhesive, and the mold surface is clean; the bonding interface is free of bubbles and cracks, and the color is consistent, and the carbonized adhesive is evenly distributed.

[0075] It can effectively achieve high-precision bonding of 4-inch seed crystal components, with good centering effect, no glue overflow pollution on the surface, and uniform bonding strength.

[0076] Example 2:

[0077] This embodiment, based on the above embodiment, uses multi-layer stacked seed crystal components 2 for hot pressing, specifically selecting three groups, such as... Figure 2 As shown, it includes a heating plate 1 placed above a heating resistance wire. The upper part of the heating plate 1 is provided with a groove, and three sets of stacked seed crystal components 2 are placed in the groove. The uppermost seed crystal component 2 is provided with a top support 3 to press the seed crystal component 2. The seed crystal component 2 includes a seed crystal support 21, and a silicon carbide seed crystal 22 is bonded and fixed on the upper part of the seed crystal support 21. The silicon carbide seed wafer 22 is provided with a graphite paper 23 on its upper part, which can completely cover the silicon carbide seed wafer 22; the bottom center of the seed wafer holder 21 is provided with a downwardly protruding handle, and the center of the heating plate 1 is provided with a concave hole that matches the lower handle of the seed wafer holder 21. When there are two or more seed wafer assemblies 2, the handle of the seed wafer holder 21 of the lowest seed wafer assembly 2 is placed in the concave hole in the middle of the heating plate 1. A tray 6 for placing the handle of the seed wafer holder 21 is also provided between the upper and lower seed wafer assemblies 2. The shape of the tray 6 matches the seed wafer holder 21. The limiting mold group 5 also limits the tray 6. The seed wafer assembly 2, the top support 3, and the tray 6 are limited by three sets of limiting mold groups 5.

[0078] The limiting mold assembly 5 includes a lower first limiting mold 51 and an upper second limiting mold 52. To prevent contamination caused by contact between the graphite paper 23 and the bonding interface between the seed crystal holder 21 and the silicon carbide seed wafer 22 and the first limiting mold 51 and the second limiting mold 52, a cavity is provided between the first limiting mold 51 and the upper second limiting mold 52. In the uppermost limiting mold assembly 5, the first limiting mold 51 is a solid disc embedded in the outside of the seed crystal assembly 2, and the second limiting mold 52 is a disc with a groove at the bottom. The first limiting mold 51 and the second limiting mold 52 in the lower two layers are both discs with grooves at the bottom. The first limiting mold 51 of the lowermost limiting mold assembly 5 is embedded in the groove at the top of the heating plate 1.

[0079] Each set of limiting mold groups 5 has a first limiting mold 51 and a second limiting mold 52 with a matching number and position of through holes. The same connecting post 53 is inserted into the through holes of the first limiting mold 51 and the second limiting mold 52 in each set of limiting mold groups 5, so that all the limiting mold groups 5 present an integral structure.

[0080] A guide pressure plate 7 is also provided between the top support 3 and the hot press head 4. The top of the top support 3 is provided with an upward protruding pressure handle. The lower surface of the guide pressure plate 7 is provided with a concave hole that matches the pressure handle of the top support 3. The pressure handle at the top of the top support 3 is placed in the concave hole on the lower surface of the guide pressure plate 7.

[0081] The specific implementation process is as follows:

[0082] I. Preliminary Preparations and Component Matching Verification

[0083] 1. Component selection and size matching

[0084] All core components are circular and the materials meet the requirements: heating plate 1, seed crystal holder 21, tray 6, and limiting mold group 5 are made of graphite, and connecting column 53 is made of high-temperature resistant materials such as alumina ceramic, high-temperature resistant ceramic, and isostatic graphite.

[0085] 2. Size matching requirements:

[0086] The diameter of the groove in the heating plate 1 is consistent with the outer diameter of the bottom first limiting mold 51; the diameter of the bottom handle of the seed crystal holder 21 matches the central recess of the heating plate and the central recess of the tray 6.

[0087] The first and second limiting molds 51 and 52 of the lower two-layer limiting mold group 5 are both discs with grooves at the bottom, and the diameter of the grooves is adapted to the outer diameter of the corresponding seed crystal component 2; the uppermost first limiting mold 51 is a solid disc, and its outer diameter matches the groove of the middle layer second limiting mold 52, and the lower groove of the uppermost second limiting mold 52 is adapted to the outer diameter of the top support 3.

[0088] Each set of limiting mold groups has ≥2 through holes distributed in a ring array around the center, and the diameter of the connecting column 53 matches the through holes;

[0089] The diameter of the graphite paper 23 is slightly larger than that of the silicon carbide seed wafer 22. The outer diameter of the tray 6 matches the corresponding limiting mold groove. The diameter of the guide pressure plate 7 is consistent with the outer diameter of the uppermost second limiting mold 52.

[0090] 3. Cleaning treatment

[0091] The silicon carbide seed wafer 22 was ultrasonically cleaned for 15 minutes in sequence with acetone, anhydrous ethanol and deionized water to remove surface impurities, and then dried at 120°C for later use.

[0092] Pretreatment of the second and third sets of seed crystal components

[0093] 1. Bonding of a single seed crystal assembly

[0094] Take three graphite seed crystal holders 21 and apply an organic adhesive of 0.1~0.3mm thickness evenly to their surfaces. Place three silicon carbide seed crystal wafers 22 in the center, press lightly to remove air bubbles, and form three sets of seed crystal components 2. Let stand at room temperature for 2 hours until semi-cured.

[0095] III. Layer-by-layer assembly of multi-layer structures

[0096] 1. Installation of heating plate and bottom base structure

[0097] Place the heating plate 1 horizontally directly above the heating resistance wire of the hot press furnace, and ensure that its center coincides with the axis of the hot press furnace pressure head 4 by using the positioning marks inside the furnace.

[0098] 2. Assembly of the first-layer seed crystal component and the intermediate structure

[0099] Align the bottom handle of the seed crystal holder 21 of the first seed crystal assembly 2 with the central recess of the heating plate 1 to ensure center alignment.

[0100] The first limiting mold 51 of the lowest limiting mold group 5 is installed to limit the first group of seed crystal components 2. The lower part of the limiting mold 51 has a groove that is embedded in the groove of the heating plate 1 to ensure no lateral displacement.

[0101] Graphite paper 23 is laid on the surface of silicon carbide seed wafer 22 to ensure that it is flat and wrinkle-free, completely covering the seed wafer, serving as a buffer, adhesive overflow isolation and adsorption layer.

[0102] A connecting post 53 is inserted into the through hole of the bottom first limiting mold 51, and the bottom second limiting mold 52 with the groove at the bottom is aligned with the connecting post 53 and pressed together to form the first rigid limiting structure. A cavity is left between the two molds so that they do not contact the graphite paper.

[0103] A tray 6 is placed in the groove of the second limiting mold 52 at the bottom layer, with the central concave hole of the tray facing upward, to support the handle of the upper seed crystal holder.

[0104] 3. Assembly of the second-layer seed crystal component and the limiting structure

[0105] The seed crystal holder of the second seed crystal assembly 2 is placed in the recess in the tray 6 above the first seed crystal assembly 2 to achieve fixation.

[0106] The first limiting mold 51 of the intermediate layer limiting mold group 5, with a groove on the lower part, is pressed and placed above the second limiting mold 52 in the bottom limiting mold group 5 to limit the second group of seed crystal components.

[0107] Graphite paper 23 is laid on the surface of the silicon carbide seed crystal 22 of the second seed crystal assembly 2. The size of the graphite paper 23 is slightly larger than the diameter of the seed crystal so as to completely cover the entire surface of the seed crystal.

[0108] The second limiting mold 52 of the intermediate layer, with a groove at the bottom, is aligned with the connecting post 53 and pressed together. Together with the first limiting mold 51 of the intermediate layer, it eliminates the lateral component of the pressure on the second set of seed crystal components during the hot pressing process.

[0109] Another tray 6 is placed in the groove of the second limiting mold 52 in the middle layer.

[0110] 4. Assembly of the third-layer seed crystal component with the upper-layer limiting structure

[0111] The seed crystal holder 21 handle of the third seed crystal assembly 2 is placed in the recess in the tray 6 above the second seed crystal assembly 2 to achieve fixation.

[0112] The first limiting mold 51 of the uppermost limiting mold group 5, with a solid disc aligned with the connecting column 53 and pressed onto the second limiting mold 52 of the middle limiting mold group 5, has the same outer diameter as the second limiting mold 52 of the middle layer.

[0113] Graphite paper 23 is laid on the surface of the silicon carbide seed crystal 22 of the third seed crystal assembly 2. The size of the graphite paper 23 is slightly larger than the diameter of the seed crystal so as to completely cover the entire surface of the seed crystal.

[0114] The uppermost second limiting mold 52, with its lower groove, is aligned with the connecting column and pressed together to form the third rigid limiting structure.

[0115] 5. Installation of the top support and pressure transmission components

[0116] The top support 3 is inserted into the middle of the uppermost second limiting mold 52, and its lower surface is lightly pressed against the graphite paper 23 of the third seed crystal component, with the upper surface pressing handle facing upward.

[0117] Align the recessed hole on the lower surface of the guide pressure plate 7 with the pressure handle of the top support 3 to ensure center alignment.

[0118] IV. Setting and Execution of Hot Pressing Process Parameters

[0119] The specific hot pressing process is the same as in the above embodiments, and will not be repeated here.

[0120] V. Cooling and Equipment Disassembly

[0121] Remove the hot press head 4 and the guide pressure plate 7, pull out the connecting column 53 that connects all the limit mold groups 5, and take out the uppermost second limit mold 52 and the top support 3.

[0122] Remove the third set of seed crystal components 2 and check its bonding alignment accuracy and surface cleanliness; then remove the topmost first limiting mold 51.

[0123] Remove the second limiting mold 52 of the intermediate layer, and then remove the tray 6 of the intermediate layer, the second set of seed crystal components 2 and the graphite paper above them, and the first limiting mold 51 of the intermediate layer in sequence.

[0124] Similarly, disassemble the bottom layer structure and remove the first seed crystal component 2.

[0125] The final result was three sets of bonded seed crystal components 2, all of which achieved precise alignment without slippage or adhesive overflow.

[0126] In actual use, the number of layers of the hot-pressed seed crystal component 2 can be adjusted to achieve hot-pressing processes with different numbers of seed crystals.

[0127] It is understood that the working principle and process of the limiting device structure according to one embodiment of the present utility model, such as the seed crystal holder 21 and the hot press furnace head 4, are existing technologies and are well known to those skilled in the art, and will not be described in detail here.

[0128] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A limiting device for use in the hot pressing process of seed crystals, characterized in that, The heating plate (1) is placed above the heating resistance wire. The upper part of the heating plate (1) is provided with a groove. At least one set of seed crystal components (2) is placed in the groove. Two or more sets of seed crystal components (2) are stacked one on top of the other. The uppermost seed crystal component (2) is provided with a top support (3) that presses the seed crystal component (2). The top support (3) is provided with a hot press furnace head (4) that presses the top support (3). The groove of the heating plate (1) is embedded with a limiting mold group (5) that is nested outside the seed crystal component (2) and the top support (3). The number of limiting mold groups (5) is the same as the number of seed crystal components (2), and they limit the seed crystal component (2) and the top support (3).

2. The limiting device for seed crystal hot pressing process according to claim 1, characterized in that, The seed crystal assembly (2) includes a seed crystal holder (21), on which a silicon carbide seed crystal (22) is bonded and fixed, and on which a graphite paper (23) is provided to completely cover the silicon carbide seed crystal (22).

3. A limiting device for use in the hot pressing process of seed crystals according to claim 2, characterized in that, The thickness of the graphite paper (23) is 0.05mm to 2mm.

4. A limiting device for use in the hot pressing process of seed crystals according to claim 3, characterized in that, The bottom center of the seed crystal holder (21) is provided with a downward protruding handle, and the center of the heating plate (1) is provided with a concave hole that matches the lower handle of the seed crystal holder (21). When there are two or more seed crystal components (2), the handle of the seed crystal holder (21) of the lowest seed crystal component (2) is placed in the concave hole in the middle of the heating plate (1). A tray (6) for placing the handle of the seed crystal holder (21) is also provided between the upper and lower seed crystal components (2). The shape of the tray (6) matches the seed crystal holder (21), and the limiting mold group (5) also limits the tray (6).

5. A limiting device for use in the hot pressing process of seed crystals according to claim 4, characterized in that, The limiting mold group (5) includes a lower first limiting mold (51) and an upper second limiting mold (52). A cavity is provided between the first limiting mold (51) and the second limiting mold (52) to avoid contact with the bonding interface between the graphite paper (23) and the seed crystal holder (21) and the silicon carbide seed wafer (22). The first limiting mold (51) and the second limiting mold (52) are provided with a number and position matching through holes. A connecting column (53) is vertically inserted in the through hole so that the first limiting mold (51) and the second limiting mold (52) are integrated. When there are two or more limiting mold groups (5), the first limiting mold (51) of the lowest limiting mold group (5) is embedded in the upper groove of the heating plate (1).

6. A limiting device for use in the hot pressing process of seed crystals according to claim 5, characterized in that, The first limiting mold (51) is a solid disc embedded in the outside of the seed crystal assembly (2), or a disc with a groove at the bottom. The second limiting mold (52) is a disc with a groove at the bottom. When there are two or more limiting mold groups (5), the same connecting column (53) is inserted into the through hole where the positions of the first limiting mold (51) and the second limiting mold (52) in each limiting mold group (5) match, so that each limiting mold group (5) presents an integral structure.

7. A limiting device for use in the hot pressing process of seed crystals according to any one of claims 1 to 6, characterized in that, A guide pressure plate (7) is also provided between the top support (3) and the hot press head (4). The top of the top support (3) is provided with an upward protruding pressure handle. The lower surface of the guide pressure plate (7) is provided with a concave hole that matches the pressure handle of the top support (3). The pressure handle at the top of the top support (3) is placed in the concave hole on the lower surface of the guide pressure plate (7).

8. A limiting device for use in the hot pressing process of seed crystals according to claim 7, characterized in that, A buffer plate (8) is also provided between the guide pressure plate (7) and the hot press head (4).

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