Hot pressing device, hot pressing equipment and seed crystal bonding hot pressing method

Abstract

The present application provides a hot pressing device, hot pressing equipment and seed crystal bonding hot pressing method, which relates to the field of silicon carbide crystal growth. The hot pressing device is configured by setting a pressure plate assembly to include a first pressure plate, a second pressure plate and a third pressure plate arranged in sequence along the pressure direction. The third pressure plate is formed by a plurality of pressure pieces arranged in sequence along its radial direction. At least one pressure column is connected between each pressure piece and the first pressure plate. The second pressure plate is provided with a guide hole for allowing the pressure column to pass through. The pressure column is provided with an elastic member in the part between the second pressure plate and the third pressure plate, and the stiffness coefficient of the elastic member decreases from the center to the outside in the radial direction of the third pressure plate. So that during hot pressing, the second pressure plate and the elastic member are driven to act on the surface of the material to be pressed with a gradient load decreasing from the center to the outside for the first hot pressing; it is conducive to the smooth discharge of bubbles inside the carbonized layer of the silicon carbide seed crystal from the center to the outside, solving the problem that the internal bubbles cannot be discharged.

Description

Technical Field

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

[0002] Silicon carbide seed crystal bonding plays an important role in the silicon carbide semiconductor industry, and its bonding process is crucial to the quality of crystal growth and production efficiency. The basic principle of silicon carbide crystal growth is the orderly deposition of gas or liquid sources containing carbon and silicon atoms on the surface of silicon carbide seed crystals, that is, the continuous growth of silicon carbide crystals is achieved by continuously replicating the crystal structure of the seed crystal.

[0003] Seed crystal bonding, as the cornerstone, largely determines the quality of subsequent crystal growth. In the seed crystal bonding process, organic glue is generally used as an adhesive to bond the seed crystal, graphite paper, and graphite tray together, and the adhesive is carbonized under a certain pressure and temperature to form a carbonized layer. During the bonding process, the air on the bonding surface and the gas generated during the carbonization of the bonding layer need to be completely discharged. If the bubbles generated locally in the carbonized layer during the bonding of the silicon carbide seed crystal cannot be discharged smoothly, it will affect the growth quality of the silicon carbide crystal in the later stage; and the presence of bubbles on the seed crystal bonding surface can easily lead to impurities, forming serious microscopic and macroscopic defects, which in turn lead to crystal growth failure and low crystal yield; even for long-term crystal growth, the crystal falls off due to weak bonding. Therefore, how to completely discharge the bubbles generated during the seed crystal bonding process is an urgent problem to be solved in the field of silicon carbide crystal growth. Summary of the invention

[0004] The purpose of the present application is to provide a hot pressing device, hot pressing equipment and a seed crystal bonding hot pressing method to solve the technical problem in the prior art that bubbles in the carbonized layer cannot be completely discharged during the seed crystal bonding process.

[0005] To achieve the above purpose, the technical solution adopted in this application is:

[0006] In a first aspect, the present application provides a hot pressing device, comprising:

[0007] A support plate, used for supporting the material to be pressed;

[0008] A pressure plate assembly is arranged opposite to the support plate, and the pressure plate assembly includes a first pressure plate, a second pressure plate and a third pressure plate which are arranged in sequence along the pressure direction, wherein the third pressure plate is arranged close to the support plate, and the third pressure plate is formed by a plurality of pressure pieces which are arranged in sequence along its radial direction, at least one pressure column is connected between the first pressure plate and each pressure piece, the second pressure plate is provided with a guide hole for allowing the pressure column to pass through, and an elastic piece is sleeved on the pressure column between the second pressure plate and the third pressure plate, and the stiffness coefficient of the elastic piece decreases in sequence from the center to the outside along the radial direction of the third pressure plate;

[0009] The driving mechanism comprises at least a first driving rod and a second driving rod, wherein the first driving rod is connected to the first pressure plate, and the second driving rod is connected to the second pressure plate, and the driving mechanism is configured such that after the first driving rod drives the first pressure plate to drive the pressure column and the third pressure plate to move toward the material to be pressed and contact the surface of the material to be pressed, the second driving rod drives the second pressure plate and the elastic member to act on multiple pressure members of the third pressure plate with a decreasing gradient load to perform a first hot pressing on the surface of the material to be pressed; and the driving mechanism is also configured such that after the first hot pressing is completed, after the second driving rod drives the second pressure plate and the elastic member to move away from the third pressure plate and unloads the load on the third pressure plate, the first driving rod drives the first pressure plate and the pressure column to act on multiple pressure members of the third pressure plate with the same load to perform a second hot pressing on the surface of the material to be pressed.

[0010] In one or more embodiments of the present application, the multiple pressure pieces of the third pressure plate include a first pressure piece located at the center and a plurality of second pressure pieces sequentially arranged on the outside of the first pressure piece, wherein the first pressure piece is circular and the second pressure piece is an annular shape coaxial with the first pressure piece.

[0011] In one or more embodiments of the present application, the pressure column is configured to have a pressure column connected between the center of the first pressure piece and the first pressure plate, and the pressure columns are arranged sequentially from the center of the first pressure piece to the outside along the radial direction of the third pressure plate around the pressure column located at the center.

[0012] In one or more embodiments of the present application, the gap between the first pressing member and the second pressing member is G, and the gap distance between two adjacent second pressing members is G, wherein G≤0.5 mm is satisfied.

[0013] In one or more embodiments of the present application, when the elastic members are in a free state, the heights of all the elastic members along the pressure direction are consistent.

[0014] In one or more embodiments of the present application, one end of the elastic member is connected to or abuts against the second pressing plate, and the other end of the elastic member is connected to or abuts against the first pressing member or the second pressing member.

[0015] In one or more embodiments of the present application, the maximum diameter of the third pressing plate is smaller than the diameter of the first pressing plate, and the diameter of the second pressing plate is larger than the diameter of the first pressing plate.

[0016] In one or more embodiments of the present application, the material to be pressed includes a graphite holder and a seed crystal located on a side of the graphite holder away from the support plate, and graphite paper is attached to a surface of the seed crystal close to the graphite holder.

[0017] In a second aspect, the present application provides a hot pressing device, comprising the hot pressing device described in any one of the first aspects.

[0018] In a third aspect, the present application provides a seed crystal bonding hot pressing method, using the hot pressing device described in the second aspect, comprising the following steps:

[0019] Controlling the hot pressing device to perform the first hot pressing in a radial direction of the seed crystal from the center outward so that the surface of the seed crystal presents a decreasing stress gradient distribution;

[0020] After the first hot pressing is completed, the hot pressing device is controlled to perform a second hot pressing in a radial direction of the seed crystal from the center outward so that the stress on the surface of the seed crystal is evenly distributed.

[0021] Based on the above technical solution, the hot pressing device, hot pressing equipment and seed crystal bonding hot pressing method of the present application have at least the following beneficial technical effects:

[0022] The hot pressing device provided in the embodiment of the present application is configured to have a pressure plate assembly including a first pressure plate, a second pressure plate and a third pressure plate arranged in sequence along the pressure direction, the third pressure plate is formed by a plurality of pressure pieces arranged in sequence along its radial direction, at least one pressure column is connected between each pressure piece and the first pressure plate, the second pressure plate is provided with a guide hole allowing the pressure column to pass through, an elastic piece is provided on a portion of the pressure column located between the second pressure plate and the third pressure plate, and the stiffness coefficient of the elastic piece decreases in sequence from the center to the outside along the radial direction of the third pressure plate. Then, when a force is applied to the second pressing plate, the second pressing plate acts on all elastic members, compresses the elastic members and acts on the third pressing plate. Since the stiffness coefficient of the elastic members decreases from the center to the outside in the radial direction of the third pressing plate, after the elastic members are compressed, the loads of all pressing members on the material to be pressed have a gradient distribution that decreases from the center to the outside in the radial direction. Then, the first driving rod of the driving mechanism is connected to the first pressing plate, and the second driving rod is connected to the second pressing plate, so that during hot pressing, the first driving rod drives the first pressing plate to drive the pressure column and the third pressing plate to move toward the material to be pressed and contact the surface of the material to be pressed. Then, the second driving rod drives the second pressing plate and the elastic members to act on multiple pressing members of the third pressing plate with a gradient load that decreases from the center to the outside, so as to perform the first hot pressing on the surface of the material to be pressed, so that the surface stress of the material to be pressed is distributed in a stress decreasing gradient from the center to the outside in the radial direction; performing the first hot pressing operation is conducive to the smooth discharge of bubbles inside the carbonized layer of the material to be pressed, such as silicon carbide seed crystal bonding, from the center to the outside, thereby solving the problem that bubbles inside the carbonized layer cannot be discharged. The driving mechanism is also configured that after the first hot pressing is completed, the second driving rod drives the second pressure plate and the elastic member to move away from the third pressure plate and unloads the load on the third pressure plate, and the first driving rod drives the first pressure plate and the pressure column to act on multiple pressure members of the third pressure plate with the same load to perform a second hot pressing on the surface of the material to be pressed, so that the surface stress of the material to be pressed is evenly distributed radially from the center to the outside, so as to ensure the overall uniformity of the carbonized layer of the seed crystal bonding, thereby improving the quality of the material to be pressed, such as the seed crystal bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative labor.

[0024] Figure 1 It is a structural schematic diagram of a hot pressing device in the related art.

[0025] Figure 2 It is a schematic diagram of relative stress distribution on the surface of a seed crystal during the seed crystal bonding and hot pressing process of a hot pressing device in the related art.

[0026] Figure 3 It is a schematic diagram of the structure of the hot pressing device provided in the embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of the three-dimensional structure of the second pressing plate provided in an embodiment of the present application.

[0028] Figure 5 It is a structural schematic diagram of the arrangement of the third pressure plate, elastic member and pressure column provided in an embodiment of the present application.

[0029] Figure 6 It is a structural schematic diagram of the arrangement of the third pressure plate and the pressure column provided in an embodiment of the present application.

[0030] Figure 7 It is a structural schematic diagram of an arrangement of the third pressure plate provided in an embodiment of the present application.

[0031] Figure 8 It is a structural schematic diagram of another arrangement of the third pressure plate provided in an embodiment of the present application.

[0032] Fig. 9 It is the relative stress distribution on the surface of the seed crystal during the first hot pressing process of the seed crystal bonding performed by the hot pressing device provided in the embodiment of the present application.

[0033] Fig.10 It is the relative stress distribution on the surface of the seed crystal during the second hot pressing process of the seed crystal bonding performed by the hot pressing device provided in the embodiment of the present application.

[0034] In the figure: 11-support plate; 12-material to be pressed; 20-upper pressing plate; 21-third pressing plate; 22-elastic member; 23-second pressing plate; 24-pressing column; 25-first pressing plate; 26-pressing plate assembly; 31-first driving rod; 32-second driving rod; 210-first pressing piece; 211-second pressing piece; 121-graphite support; 122-seed crystal; 231-guide hole. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0037] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] like Figure 1 As shown, for the seed crystal bonding, the hot pressing device in the related art generally includes a support plate 11 and an upper pressing plate 20 located above the support plate 11, a graphite holder 121 is supported on the support plate 11, a seed crystal 122 is attached to the surface of the graphite holder 121, and graphite paper is attached between the seed crystal 122 and the graphite holder 121 by organic glue. The seed crystal 122 is hot pressed by the upper pressing plate 20. Figure 2 A schematic diagram showing relative stress distribution on the surface of a seed crystal during seed crystal bonding and hot pressing by a hot pressing device in the related art is shown. Figure 2 The relative stress on the surface of the seed crystal (S) during the bonding and hot pressing process was analyzed by finite element (FEM) simulation. R , S R =S N / S MAX , S N : actual stress value at each position on the seed crystal surface; S MAX : Maximum stress value of the entire seed crystal surface). Figure 2 It can be seen that there is a very obvious uneven stress gradient distribution along the radial direction of the seed crystal, and the stress at the edge of the seed crystal is relatively large, which is not conducive to the discharge of internal bubbles during the hot pressing carbonization process, resulting in the inability to completely discharge the bubbles generated in the carbonization layer.

[0040] Based on the above considerations, in order to solve the technical problem that bubbles in the carbonized layer cannot be completely discharged during the seed crystal bonding process in the prior art, the present application provides a hot pressing device, including: a support plate, a pressure plate assembly and a driving mechanism, the support plate is used to support the material to be pressed; the pressure plate assembly is arranged relative to the support plate, the pressure plate assembly includes a first pressure plate, a second pressure plate and a third pressure plate arranged in sequence along the pressure direction, wherein the third pressure plate is arranged close to the support plate, the third pressure plate is formed by a plurality of pressure pieces arranged in sequence along its radial direction, at least one pressure column is connected between the first pressure plate and each pressure piece, the second pressure plate is provided with a guide hole for allowing the pressure column to pass through, the pressure column is provided with an elastic piece in the part between the second pressure plate and the third pressure plate, and the stiffness coefficient of the elastic piece increases from the center to the outside along the radial direction of the third pressure plate. Decrease in sequence; the driving mechanism comprises at least a first driving rod and a second driving rod, wherein the first driving rod is connected to the first pressure plate, and the second driving rod is connected to the second pressure plate, and the driving mechanism is configured that after the first driving rod drives the first pressure plate to drive the pressure column and the third pressure plate to move toward the material to be pressed and contact the surface of the material to be pressed, the second driving rod drives the second pressure plate and the elastic member to act on multiple pressure members of the third pressure plate with a gradient load to perform the first hot pressing on the surface of the material to be pressed; and the driving mechanism is also configured that after the first hot pressing is completed, the second driving rod drives the second pressure plate and the elastic member to move away from the third pressure plate and unloads the load on the third pressure plate, and the first driving rod drives the first pressure plate and the pressure column to act on multiple pressure members of the third pressure plate with the same load to perform the second hot pressing on the surface of the material to be pressed.

[0041] In the technical solution of the embodiment of the present application, the hot pressing device provided by the embodiment of the present application is configured to have a pressure plate assembly including a first pressure plate, a second pressure plate and a third pressure plate arranged in sequence along the pressure direction, the third pressure plate is formed by a plurality of pressure pieces arranged in sequence along its radial direction, at least one pressure column is connected between each pressure piece and the first pressure plate, the second pressure plate is provided with a guide hole for allowing the pressure column to pass through, an elastic piece is provided on the part of the pressure column located between the second pressure plate and the third pressure plate, and the stiffness coefficient of the elastic piece decreases sequentially from the center to the outside along the radial direction of the third pressure plate. Then, when a force is applied to the second pressing plate, the second pressing plate acts on all elastic members, compresses the elastic members and acts on the third pressing plate. Since the stiffness coefficient of the elastic members decreases from the center to the outside in the radial direction of the third pressing plate, after the elastic members are compressed, the loads of all pressing members on the material to be pressed have a gradient distribution that decreases from the center to the outside in the radial direction. Then, the first driving rod of the driving mechanism is connected to the first pressing plate, and the second driving rod is connected to the second pressing plate, so that during hot pressing, the first driving rod drives the first pressing plate to drive the pressure column and the third pressing plate to move toward the material to be pressed and contact the surface of the material to be pressed. Then, the second driving rod drives the second pressing plate and the elastic members to act on multiple pressing members of the third pressing plate with a gradient load that decreases from the center to the outside, so as to perform the first hot pressing on the surface of the material to be pressed, so that the surface stress of the material to be pressed is distributed in a stress decreasing gradient from the center to the outside in the radial direction; performing the first hot pressing operation is conducive to the smooth discharge of bubbles inside the carbonized layer of the material to be pressed, such as silicon carbide seed crystal, from the center to the outside, thereby solving the problem that bubbles inside the carbonized layer cannot be discharged. The driving mechanism is also configured that after the first hot pressing is completed, the second driving rod drives the second pressure plate and the elastic member to move away from the third pressure plate and unloads the load on the third pressure plate, and the first driving rod drives the first pressure plate and the pressure column to act on multiple pressure members of the third pressure plate with the same load to perform a second hot pressing on the surface of the material to be pressed, so that the surface stress of the material to be pressed is evenly distributed radially from the center to the outside, so as to ensure the overall uniformity of the seed crystal carbonization layer and improve the quality of the bonding of the material to be pressed, such as the seed crystal.

[0042] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0043] Please also read Figure 2 , Figure 3 and Figure 4 The embodiment of the present application provides a hot pressing device, including: a support plate 11, a pressing plate assembly 26 and a driving mechanism, wherein the support plate 11 is used to support a material to be pressed 12. The support plate 11 may be a structural member for supporting the material to be pressed 12. In some embodiments, the support plate 11 may be cylindrical.

[0044] The pressure plate assembly 26 is arranged opposite to the support plate 11, and the pressure plate assembly 26 includes a first pressure plate 25, a second pressure plate 23 and a third pressure plate 21 which are arranged in sequence along the pressure direction. Among them, the third pressure plate 21 is arranged close to the support plate 11. It can be understood that the third pressure plate 21 is arranged closer to the support plate 11 than the first pressure plate 25 and the second pressure plate 23, so that the load can be applied to the material to be pressed 12 on the support plate 11 through the third pressure plate 21. The third pressure plate 21 is formed by a plurality of pressure pieces arranged in sequence along its radial direction. It can be understood that the third pressure plate 21 is cylindrical formed by a plurality of pressure pieces arranged in sequence. Each pressure piece can move independently and is not affected by adjacent pressure pieces. At least one pressure column 24 is connected between the first pressure plate 25 and each pressure piece, one end of the pressure column 24 is fixedly connected to the first pressure plate 25, and the other end of the pressure column 24 is connected to one of the pressure pieces. Therefore, the first pressure plate 25 can apply the load to each pressure piece through the pressure column 24, and then act on the material to be pressed 12 through each pressure piece. Refer to Figure 4 The second pressing plate 23 is provided with a guide hole 231 that allows the pressing column 24 to pass through, so that the second pressing plate 23 can move up and down along the pressing column 24. The pressing column 24 is sleeved with an elastic member 22 in the portion between the second pressing plate 23 and the third pressing plate 21, and the stiffness coefficient of the elastic member 22 decreases from the center to the outside along the radial direction of the third pressing plate 21. The stiffness coefficient of the elastic member 22 can also be called the elastic coefficient, which refers to the magnitude of the elastic force generated by the elastic member 22 when a unit deformation occurs. It can be understood that the elastic members 22 that are sequentially arranged from the center to the outside along the radial direction of the third pressing plate 21 generate a smaller elastic force when a unit deformation occurs. Furthermore, when a force is applied to the second pressure plate 23, the second pressure plate 23 acts on all the elastic parts 22, compresses the elastic parts 22 and acts on the third pressure plate 21. Since the stiffness coefficient of the elastic parts 22 decreases radially from the center to the outside of the third pressure plate 21, after the elastic parts 22 are compressed, the loads acting on the material to be pressed 12 by all the pressure parts have a gradient distribution that decreases radially from the center to the outside.

[0045] The driving mechanism includes at least a first driving rod 31 and a second driving rod 32, wherein the first driving rod 31 is connected to the first pressure plate 25, and the second driving rod 32 is connected to the second pressure plate 23. The driving mechanism is configured such that after the first driving rod 31 drives the first pressure plate 25 to drive the pressure column 24 and the third pressure plate 21 to move toward the material to be pressed 12 and contact the surface of the material to be pressed 12, the second driving rod 32 drives the second pressure plate 23 and the elastic member 22 to act on multiple pressure members of the third pressure plate 21 with a decreasing gradient load to perform the first hot pressing on the surface of the material to be pressed 12, thereby making the surface stress of the material to be pressed 12 distributed in a decreasing stress gradient from the center to the outside along the radial direction. The first hot pressing is beneficial to the smooth discharge of bubbles inside the carbonized layer of the material to be pressed, such as silicon carbide seed crystal, from the center to the outside in sequence, thereby avoiding the problem that bubbles inside the carbonized layer cannot be discharged. The driving mechanism is also configured such that after the first hot pressing is completed, the second driving rod 32 drives the second pressing plate 23 and the elastic member 22 to move away from the third pressing plate 21 and removes the load from the third pressing plate 21, and then the first driving rod 31 drives the first pressing plate 25 and the pressing column 24 to act on the multiple pressing members of the third pressing plate 21 with the same load to perform the second hot pressing on the surface of the material to be pressed 12. Thus, the surface stress of the material to be pressed is uniformly distributed from the center to the outside in the radial direction, so as to ensure the uniformity of the overall carbonization layer of the seed crystal and improve the bonding quality of the material to be pressed, such as the seed crystal.

[0046] In some embodiments, please refer to Figure 6 or Figure 7 or Figure 8 The multiple pressing pieces of the third pressing plate 21 include a first pressing piece 210 located at the center and a plurality of second pressing pieces 211 sequentially sleeved on the outside of the first pressing piece 210 , wherein the first pressing piece 210 is circular and the second pressing piece 211 is an annular shape coaxial with the first pressing piece 210 .

[0047] It is understandable that the third pressing plate 21 is a circular structure consisting of a first pressing member 210 in the middle and a plurality of second pressing members 211 sequentially arranged around the first pressing member 210. The number of the second pressing members 211 can be one, two, three, four, five, six or even more.

[0048] In some embodiments, the gap between the first pressing member 210 and the second pressing member 211 is G, and the gap distance between two adjacent second pressing members 211 is G, wherein G≤0.5 mm is satisfied. Thus, on the one hand, it can ensure that the adjacent first pressing members 210 and the second pressing members 211 and the adjacent two second pressing members 211 can move independently, and at the same time, the third pressing plate 21 composed of the first pressing member 210 and the plurality of second pressing members 211 forms a compact circular structure, so that the first pressing member 210 and the plurality of second pressing members 211 can apply a decreasing load to the material 12 to be pressed from the center outward.

[0049] In some embodiments, please refer to Figure 6 The pressure column 24 is configured as a pressure column 24 connected between the center of the first pressure piece 210 and the first pressure plate 25, and along the radial direction of the third pressure plate 21, the pressure columns 24 are arranged in sequence from the center of the first pressure piece 210 to the outside around the pressure column 24 located at the center.

[0050] It is understandable that a pressure column 24 is arranged at the center of the first pressure piece 210, and the central axis of the pressure column 24 is coaxially arranged with the central axis of the first pressure piece 210. Other pressure columns 24 can be arranged outward in a ring shape around the central axis of the pressure column 24 located at the center of the first pressure piece 210. The central axes of the pressure columns 24 located on the same ring are equidistant from the central axis of the first pressure piece 210. Two adjacent pressure columns 24 located on the same ring are arranged at equal intervals. The first pressure piece 210 or each second pressure piece 211 can be provided with a ring pressure column 24, or two rings or more than two rings of pressure columns 24 can be provided.

[0051] In the technical solution of the embodiment of the present application, through the above-mentioned arrangement, the first pressing plate 25 and the pressing column 24 can act on multiple pressing members of the third pressing plate 21, thereby applying a decreasing load on the material to be pressed 12 located below the third pressing plate 21.

[0052] In some embodiments, Figure 5 As shown, when all the elastic members 22 are in a free state, the heights of all the elastic members 22 along the pressure direction are consistent. The inner diameters of all the elastic members 22 are consistent. The outer diameters of all the elastic members 22 are consistent.

[0053] In the technical solution of the embodiment of the present application, through the above-mentioned arrangement, it can be achieved that when all the elastic parts 22 are compressed by the second pressure plate 23, the elastic parts 22 can apply a load that decreases successively from the center to the outside along its radial direction to the third pressure plate 21, and then the load that decreases successively from the center to the outside can be applied to the material to be pressed 12, such as a seed crystal, so that the surface stress of the seed crystal is distributed with a stress decreasing gradient from the center to the outside along the radial direction, so as to completely discharge the bubbles generated by the carbonized layer of the seed crystal from the center.

[0054] In some embodiments, one end of the elastic member 22 is connected to or abuts against the second pressing plate 23 , and the other end of the elastic member 22 is connected to or abuts against the first pressing member 210 or the second pressing member 211 .

[0055] In some embodiments, the elastic member 22 may be a mechanical spring or an electromagnetic spring. In some embodiments, one end of the elastic member 22 is threadedly connected or welded to the second pressing plate 23, and the other end may also be threadedly connected or welded to the first pressing member 210 or the second pressing member 211.

[0056] In some embodiments, Figure 5 As shown, the number of the elastic members 22 is consistent with the number of the pressure posts 24 .

[0057] In some embodiments, the maximum diameter of the third pressing plate 21 is smaller than the diameter of the first pressing plate 25 , and the diameter of the second pressing plate 23 is larger than the diameter of the first pressing plate 25 .

[0058] In some embodiments, the diameter of the material 12 to be pressed is D, the diameter of the first pressing plate 25 is D1, D1=D×α (1≤α≤2). The diameter of the second pressing plate 23 is D2, D2=D1×β (1.2<β<2). The maximum diameter of the third pressing plate 21 is D3, D3=D1×δ (1≤δ). The diameter of the support plate 11 is D4, D4=D3×δ (1≤δ).

[0059] In some embodiments, the material to be pressed 12 includes a graphite holder 121 and a seed crystal 122 located on the side of the graphite holder 121 away from the support plate 11. Graphite paper is attached between the seed crystal 122 and the graphite holder 121, that is, the surface of the seed crystal 122 close to the graphite holder 121 by organic adhesive.

[0060] In some embodiments, the driving mechanism may be a hydraulic system or a servo system.

[0061] The working method of the hot pressing device of this application is as follows:

[0062] When hot pressing is performed, the first hot pressing is performed first. Under the drive of the driving mechanism, the first driving rod drives the first pressing plate 25, the pressing column 24 and the third pressing plate 21 to move toward the support plate 11. At this time, the second pressing plate 23 also moves together. When the third pressing plate 21 contacts the surface of the material to be pressed 12 on the support plate 11, the first driving rod stops moving. At this time, the second driving rod drives the second pressing plate 23 to continue to move toward the third pressing plate 21 and compress the elastic member 22, thereby applying a gradient load to the material to be pressed 12, so that the stress on the surface of the material to be pressed 12, such as the seed crystal, is distributed along the radial direction from the center to the outside with a stress decreasing gradient, such as Fig. 9 As shown;

[0063] After the first hot pressing is completed, the second driving rod drives the second pressing plate 23 to move away from the third pressing plate 21 to unload the third pressing plate 21, so that the elastic member 22 returns to the initial position and is in a free state. At this time, the second hot pressing is carried out. Under the drive of the driving mechanism, the first driving rod continues to drive the first pressing plate 25 to move. At this time, the pressure column 24 and the third pressing plate 21 move accordingly, so that the third pressing plate 21 acts on the surface of the material to be pressed 12, such as the seed crystal, to apply a uniform load, so that the stress on the surface of the seed crystal is uniformly distributed from the center to the outside along the radial direction, such as Fig.10As shown, after the second hot pressing is completed, the first driving rod drives the first pressing plate 25 to move upward under the drive of the driving mechanism, and the unloading is completed, thereby completing the seed crystal bonding.

[0064] On the other hand, the present application also provides a hot pressing device, including the hot pressing device. The hot pressing device can be a hot pressing furnace.

[0065] On the other hand, the present application also provides a seed crystal bonding hot pressing method, using the aforementioned hot pressing equipment, comprising the following steps:

[0066] Controlling the hot pressing equipment to perform the first hot pressing in a radial direction of the seed crystal from the center outward so that the surface of the seed crystal presents a decreasing stress gradient distribution;

[0067] After the first hot pressing is completed, the hot pressing equipment is controlled to perform a second hot pressing in a radial direction of the seed crystal from the center outward so that the stress on the surface of the seed crystal is evenly distributed.

[0068] Specific:

[0069] First hot pressing: control the driving mechanism to make the first driving rod 31 drive the first pressing plate 25 to drive the pressing column 24 and the third pressing plate 21 to move toward the material to be pressed 12 and contact the surface of the material to be pressed 12; control the second driving rod 32 to drive the second pressing plate 23 and the elastic member 22 to act on the plurality of pressing members of the third pressing plate 21 with a gradient load to perform the first hot pressing on the surface of the material to be pressed 12;

[0070] Second hot pressing: After the first hot pressing is completed, control the second driving rod 32 to drive the second pressure plate 23 and the elastic member 22 to move away from the third pressure plate 21 and remove the load from the third pressure plate 21; control the first driving rod 31 to drive the first pressure plate 25 and the pressure column 24 to act on multiple pressure pieces of the third pressure plate 21 with the same uniformly distributed load to perform a second hot pressing on the surface of the material 12 to be pressed.

[0071] In some embodiments, the seed crystal bonding and hot pressing method further comprises:

[0072] (1) First, heat the SiC seed crystal, graphite paper and graphite tray on a heating table to 100-150°C;

[0073] (2) Then, a layer of organic glue is coated on the surface of the SiC seed crystal, and graphite paper is attached to the glue-coated surface of the SiC seed crystal, so that the seed crystal and the graphite paper are highly fitted (without bubbles), forming a combination 1;

[0074] (3) Place the combined body 1 on a heating table and heat for 5-10 minutes (maintaining the temperature at 120-150°C);

[0075] (4) Coating a layer of organic glue on the graphite paper surface of the combination 1, and attaching the glue-coated surface of the combination 1 to the graphite holder so that the combination 1 and the graphite holder are highly fitted (without bubbles), thereby forming a combination 2;

[0076] (5) Place the combined body 2 on a heating table and heat for 5-10 minutes (maintaining the temperature at 120-150°C);

[0077] (6) Performing a hot pressing stage, placing the combined body 2 in a hot pressing furnace equipped with the hot pressing device of the present application; evacuating the hot pressing furnace to control the pressure below 10 Pa;

[0078] (7) Perform the first hot pressing, and apply the load in a decreasing gradient load manner. Specifically: control the driving mechanism to make the first driving rod 31 drive the first pressing plate 25 to drive the pressing column 24 and the third pressing plate 21 to move toward the combination 2 and contact the surface of the combination 2; control the second driving rod 32 to drive the second pressing plate 23 and the elastic member 22 to act on the multiple pressing members of the third pressing plate 21 with a gradient load to perform the first hot pressing on the surface of the combination 2; and simultaneously increase the temperature (the first stage temperature needs to reach 200-400°C at 1-6°C / min and be maintained for 30-120min after reaching the temperature; the second stage temperature needs to reach 650-850°C at 1-6°C / min and be maintained for 30-120min after reaching the temperature;

[0079] (8) After the first hot pressing is completed, the second hot pressing is carried out, and the load is applied in a uniform load manner. The second driving rod 32 is controlled to drive the second pressing plate 23 and the elastic member 22 to move away from the third pressing plate 21 and unload the load on the third pressing plate 21; the first driving rod 31 is controlled to drive the first pressing plate 25 and the pressing column 24 to act on the multiple pressing members of the third pressing plate 21 with the same uniform load to perform the second hot pressing on the surface of the combination 2. The temperature is maintained at 650-850℃ for 60-120min;

[0080] (9) Then, while maintaining the uniform load in step (8), turn off the heating power supply and allow the entire system to cool down along with the furnace. After the temperature drops below 150° C., return the pressure in the hot pressing furnace to atmospheric pressure, and finally take out the combined body 2, completing the entire seed crystal bonding process.

[0081] The seed crystal bonding hot pressing method provided in the embodiment of the present application is divided into two hot pressing stages. The first hot pressing stage can effectively discharge the bubbles generated during the carbonization process, and the second hot pressing stage can make the overall uniformity of the seed crystal carbonization layer better. Fig.10As shown, most stress distribution is uniform, and greater edge stress is more conducive to denser edge compression. During the long crystal growth process, the solution will not penetrate into the carbonized layer. The combination of the two hot pressing stages can improve the quality of seed crystal bonding. The hot pressing device of the present application can achieve high-quality silicon carbide seed crystal bonding, provide technical support for high-quality and long-term growth of silicon carbide, and further promote the commercial application of silicon carbide.

[0082] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A hot pressing device, characterized in that: include: A support plate (11) for supporting the material to be pressed (12); A pressure plate assembly (26) is arranged opposite to the support plate (11), and the pressure plate assembly (26) includes a first pressure plate (25), a second pressure plate (23) and a third pressure plate (21) which are arranged in sequence along the pressure direction, wherein the third pressure plate (21) is arranged close to the support plate (11), and the third pressure plate (21) is formed by a plurality of pressure pieces arranged in sequence along its radial direction, and the plurality of pressure pieces of the third pressure plate (21) include a first pressure piece (210) located at the center and a plurality of second pressure pieces (211) which are arranged in sequence on the outside of the first pressure piece (210), wherein the first pressure piece (210) is circular, and the second pressure piece (211) is an annular shape coaxial with the first pressure piece (210), and at least one pressure column (24) is connected between the first pressure plate (25) and each of the pressure pieces, and the pressure column (24) is configured to be located at the center of the first pressure piece (210). A pressure column (24) is connected between the third pressure plate (21) and the first pressure plate (25), and the pressure columns (24) are arranged in sequence from the center of the first pressure member (210) outward around the pressure column (24) located at the center along the radial direction of the third pressure plate (21), and the second pressure plate (23) is provided with a guide hole (231) for allowing the pressure column (24) to pass through, and the pressure column (24) is sleeved with an elastic member (22) in the part located between the second pressure plate (23) and the third pressure plate (21), and when the elastic member (22) is in a free state, the heights of all the elastic members (22) along the pressure direction are consistent, and the stiffness coefficients of the elastic members (22) decrease in sequence from the center to the outside along the radial direction of the third pressure plate (21), and after the elastic member (22) is compressed, the loads of all the pressure members on the material to be pressed (12) have a gradient distribution that decreases in sequence from the center to the outside along the radial direction; The driving mechanism comprises at least a first driving rod (31) and a second driving rod (32), wherein the first driving rod (31) is connected to the first pressing plate (25), and the second driving rod (32) is connected to the second pressing plate (23), and the driving mechanism is configured such that after the first driving rod (31) drives the first pressing plate (25) to drive the pressing column (24) and the third pressing plate (21) to move toward the material to be pressed (12) and contact the surface of the material to be pressed (12), the second driving rod (32) drives the second pressing plate (23) and the elastic member (22) to perform a decreasing gradient load. The plurality of pressing pieces of the third pressing plate (21) are used to perform a first hot pressing on the surface of the material to be pressed (12); and the driving mechanism is further configured such that after the first hot pressing is completed, the second driving rod (32) drives the second pressing plate (23) and the elastic piece (22) to move away from the third pressing plate (21) and removes the load from the third pressing plate (21), and then the first driving rod (31) drives the first pressing plate (25) and the pressing column (24) to act on the plurality of pressing pieces of the third pressing plate (21) with the same load to perform a second hot pressing on the surface of the material to be pressed (12); The working mode of the hot pressing device is: When hot pressing is performed, the first hot pressing is performed first. Under the drive of the driving mechanism, the first driving rod (31) drives the first pressing plate (25), the pressing column (24) and the third pressing plate (21) to move toward the support plate (11). At this time, the second pressing plate (23) also moves together. When the third pressing plate (21) contacts the surface of the material to be pressed (12) on the support plate (11), the first driving rod (31) stops moving. At this time, the second driving rod (32) drives the second pressing plate (23) to continue to move toward the third pressing plate (21) and compress the elastic member (22), thereby applying a gradient load to the material to be pressed (12), so that the stress on the surface of the material to be pressed (12) is distributed in a radial direction from the center to the outside with a decreasing stress gradient. After the first hot pressing is completed, the second driving rod (32) drives the second pressing plate (23) to move in a direction away from the third pressing plate (21) to unload the third pressing plate (21), so that the elastic member (22) returns to the initial position and is in a free state. At this time, the second hot pressing is carried out. Under the drive of the driving mechanism, the first driving rod (31) continues to drive the first pressing plate (25) to move. At this time, the pressing column (24) and the third pressing plate (21) move accordingly, so that the third pressing plate (21) acts on the surface of the material to be pressed (12) to apply a uniform load, so that the stress on the surface of the seed crystal is uniformly distributed from the center to the outside in the radial direction. After the second hot pressing is completed, under the drive of the driving mechanism, the first driving rod (31) drives the first pressing plate (25) to move upward to complete the unloading and complete the seed crystal bonding.

2. The hot pressing device according to claim 1, characterized in that: The gap between the first pressing member (210) and the second pressing member (211) is G, and / or the gap distance between two adjacent second pressing members (211) is G, wherein G≤0.5 mm is satisfied.

3. The hot pressing device according to claim 1, characterized in that: One end of the elastic member (22) is connected to or abuts the second pressing plate (23), and the other end is connected to or abuts the first pressing member (210) or the second pressing member (211).

4. The hot pressing device according to claim 1, characterized in that: The maximum diameter of the third pressing plate (21) is smaller than the diameter of the first pressing plate (25), and the diameter of the second pressing plate (23) is larger than the diameter of the first pressing plate (25).

5. The hot pressing device according to claim 1, characterized in that: The material to be pressed (12) comprises a graphite holder (121) and a seed crystal (122) located on a side of the graphite holder (121) away from the support plate (11), and graphite paper is attached to a surface of the seed crystal (122) close to the graphite holder.

6. A hot pressing device, characterized in that: A hot pressing device comprising any one of claims 1 to 5.

7. A seed crystal bonding hot pressing method, characterized in that: The hot pressing device according to claim 6 comprises the following steps: Controlling the hot pressing device to perform the first hot pressing in a radial direction of the seed crystal from the center outward so that the surface of the seed crystal presents a decreasing stress gradient distribution; After the first hot pressing is completed, the hot pressing device is controlled to perform a second hot pressing in a radial direction of the seed crystal from the center outward so that the stress on the surface of the seed crystal is evenly distributed.

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