Seed crystal bonding device and method for reducing crystal stress

Abstract

The invention discloses a seed crystal bonding device capable of reducing crystal stress, and relates to the technical field of crystal growth, the seed crystal bonding device comprises a seed crystal support, a protruding fixing ring table is arranged on one side, located on a seed crystal, of the seed crystal support, the edge of the seed crystal is bonded to the fixing ring table, a concave stress reduction area is formed in the fixing ring table, and the stress reduction area is located in the seed crystal support. Fixing the middle part of the seed crystal on the seed crystal support in a suspension manner; the device further comprises a pressing block, a protruding pressing ring table is arranged on the side, corresponding to the seed crystal, of the pressing block, and the edge of the seed crystal and the end face of the fixing ring table are pressed and bonded through the pressing ring table. The invention also provides a seed crystal bonding method for reducing the crystal stress. The contact area of the bonding surface and the seed crystal surface is reduced, and the acting force of the seed crystal support on the seed crystal and the growing crystal in the crystal growth and cooling process is reduced, so that the purpose of reducing the internal stress and dislocation of the crystal is achieved, the crystal cracking rate can be effectively reduced, and the crystal growth quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and in particular relates to a seed crystal bonding device and a method for reducing crystal stress. Background Art

[0002] After decades of development of semiconductor materials, the first generation of silicon single crystal semiconductors has approached perfect crystals, and the research on silicon single crystals is also very thorough. The design and development of devices based on silicon materials have also gone through many generations of structural and process optimization and updates, and are gradually approaching the limits of silicon materials. The potential for improving the performance of devices based on silicon materials is getting smaller and smaller. The third generation of semiconductors represented by gallium nitride and silicon carbide have excellent material physical properties, providing greater room for further improving the performance of power electronic devices.

[0003] The third generation of semiconductor high-power power electronic devices represented by SiC is one of the fastest growing power semiconductor devices in the field of power electronics. As a typical representative of the third generation of semiconductor materials, silicon carbide is also one of the wide bandgap semiconductor materials with the most mature crystal production technology and device manufacturing level and the most widely used. At present, a global material, device and application industry chain has been formed. It is an extremely ideal semiconductor material for high temperature, high frequency, radiation resistance and high power applications.

[0004] At present, the preparation of silicon carbide generally adopts the PVT method (physical vapor transport method), which is to sublimate SiC raw materials at a high temperature of more than 2000℃ and decompose them into gas phase substances such as Si, Si2C and SiC2. Driven by the temperature gradient, the above gas phase substances will be transported to the silicon carbide seed crystal with a lower temperature to achieve silicon carbide crystal growth. In the traditional seed crystal preparation process, the difference in thermal expansion coefficient between the seed crystal and the seed crystal holder often causes excessive crystal stress, resulting in excessive crystal dislocation density and even crystal cracking. How to reduce the restriction of the seed crystal holder on the release of crystal stress is a key issue. Reducing the restriction of the seed crystal holder on the release of crystal stress is an important condition for reducing crystal stress and dislocation density and improving crystal quality. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the difference in thermal expansion coefficient between the seed crystal holder and the seed crystal is too large, and excessive stress is accumulated inside the crystal during the growth process and cannot be released, resulting in a high crystal cracking rate and low crystal quality. The present invention proposes a seed crystal bonding device and method for reducing crystal stress. The seed crystal bonding device and method for reducing crystal stress can achieve the purpose of reducing stress and dislocation in the crystal, can effectively reduce the crystal cracking rate, and improve the crystal growth quality.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A seed crystal bonding device for reducing crystal stress is designed, comprising a seed crystal holder, wherein the seed crystal holder is provided with a protruding fixed ring platform on one side of the seed crystal, the edge of the seed crystal is adhered to the fixed ring platform, and a concave stress relief zone is formed inside the fixed ring platform, so that the middle part of the seed crystal is fixed on the seed crystal holder in a suspended manner;

[0008] It also includes a pressing block, and a protruding pressing ring is provided on one side of the pressing block corresponding to the seed crystal. The pressing ring presses and bonds the edge of the seed crystal to the end face of the fixed ring.

[0009] Furthermore, the inner diameter of the fixed ring table is 2-15 mm smaller than the diameter of the seed crystal, and the outer diameter of the fixed ring table is not smaller than the diameter of the seed crystal.

[0010] Furthermore, the inner diameter of the clamping ring is 3-15 mm smaller than the diameter of the seed crystal, and the outer diameter of the clamping ring is 2-10 mm larger than the diameter of the seed crystal.

[0011] Furthermore, the step height of the fixed ring platform is ≥10 mm.

[0012] Furthermore, the step height of the clamping ring is 1-5 mm.

[0013] Furthermore, the seed crystal support includes a support base, a plurality of protrusions are provided on one side of the support base, the plurality of protrusions are fixed on the support base through a translation layer, and are spliced ​​to form a fixed ring platform, and a concave stress relief area is formed between the plurality of protrusions.

[0014] Furthermore, there is a gap between adjacent protrusions, and the gap distance is not less than 2 mm.

[0015] Furthermore, the translation layer is a high temperature resistant silicone layer.

[0016] In order to solve the above technical problems, the present invention further provides a seed crystal bonding method for reducing crystal stress, using the seed crystal bonding device for reducing crystal stress, specifically comprising the following steps:

[0017] Step 1: Make a carbon film on the back of the seed crystal for protection;

[0018] Step 2: Apply special glue on the end surface of the fixed ring table;

[0019] Step 3, stick the back of the seed crystal to the fixed ring stage of the seed crystal holder so that the edge of the seed crystal falls on the end surface of the fixed ring stage;

[0020] Step 4: Use a pressing block to make the end surface of the pressing ring contact the edge of the seed crystal;

[0021] Step 5, placing the assembly of the seed crystal holder, the seed crystal and the pressing block in a hot pressing furnace for pressing and high temperature treatment;

[0022] Step 6: After cooling, remove the compact and clean the seed crystal.

[0023] The invention proposes a seed crystal bonding method for reducing crystal stress, and the beneficial effect is that the invention reduces the contact area between the bonding surface and the seed crystal surface, reduces the force of the seed crystal holder on the seed crystal and the growing crystal during the crystal growth and cooling process, thereby achieving the purpose of reducing the stress and dislocation in the crystal, and can effectively reduce the crystal cracking rate and improve the crystal growth quality. Specifically:

[0024] 1. The present invention adopts a seed crystal holder with a central hollowed-out stress relief zone to greatly reduce the stress release of the crystal during the growth process due to the constraint of the seed crystal holder, thereby reducing the force of the seed crystal holder on the seed crystal and the growing crystal during the crystal growth and cooling process.

[0025] 2. The present invention forms an intermittent fixed ring platform combined with a translation layer by splicing bumps, so that the constraint of the seed crystal holder on the crystal is further reduced during the growth process of the crystal, and the stress of the crystal is further released.

[0026] 3. The crystal prepared by the method of the present invention is easier to separate from the seed crystal holder after growth due to the reduced contact area of ​​the seed crystal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0028] In the attached picture:

[0029] Figure 1 is a structural schematic diagram of a seed crystal bonding device in Example 1 of the present invention;

[0030] Figure 2 is a schematic diagram of the bonding of the seed crystal holder and the seed crystal in Example 1 of the present invention;

[0031] Figure 3 is a schematic diagram of the bonding of the seed crystal holder and the seed crystal in Example 2 of the present invention;

[0032] Figure 4 is a schematic diagram of the three-dimensional structure of the seed crystal holder in Example 2 of the present invention;

[0033] Figure 5 It is a flow chart of a seed crystal bonding method for reducing crystal stress in the present invention;

[0034] The markings in the figure are: 1, seed crystal support; 11, fixed ring platform; 12, stress relief area; 13, bottom support; 14, translation layer; 15, bump; 2, seed crystal; 3, pressure block; 31, clamping ring platform. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", "top / bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] The structural features of the present invention are now described in detail with reference to the accompanying drawings.

[0039] Example 1

[0040] See also Figure 1-Figure 2 A seed crystal bonding device for reducing crystal stress comprises a seed crystal holder 1, wherein the seed crystal holder 1 is provided with a protruding fixed ring platform 11 on one side of a seed crystal 2, the edge of the seed crystal 2 is adhered to the fixed ring platform 11, and a concave stress relief zone 12 is formed inside the fixed ring platform 11, so that the middle part of the seed crystal 2 is fixed on the seed crystal holder 1 in a suspended manner, wherein the inner diameter of the fixed ring platform 11 is 2-15 mm smaller than the diameter of the seed crystal 2, the outer diameter of the fixed ring platform 11 is not less than the diameter of the seed crystal 2, and the step height of the fixed ring platform 11 is ≥10 mm.

[0041] It also includes a pressing block 3, and a protruding pressing ring 31 is provided on one side of the pressing block 3 corresponding to the seed crystal 2. The pressing ring 31 presses and bonds the edge of the seed crystal 2 to the end face of the fixed ring 11, wherein the inner diameter of the pressing ring 31 is 3-15mm smaller than the diameter of the seed crystal 2, the outer diameter of the pressing ring 31 is 2-10mm larger than the diameter of the seed crystal 2, and the step height of the pressing ring 31 is 1-5mm. By adopting a seed crystal holder with a central hollowing-out stress relief zone, the stress release of the crystal during the growth process is greatly reduced due to the constraint of the seed crystal holder, thereby reducing the force of the seed crystal holder on the seed crystal and the growing crystal during the crystal growth and cooling process.

[0042] The seed crystal bonding device for reducing crystal stress of the present invention reduces the contact area between the bonding surface and the seed crystal surface, thereby reducing the force of the seed crystal holder on the seed crystal and the growing crystal during crystal growth and cooling, thereby achieving the purpose of reducing stress and dislocation in the crystal, and can effectively reduce the crystal cracking rate and improve the crystal growth quality.

[0043] See also Figure 5 Specifically, when used, this embodiment proposes a seed crystal bonding method for reducing crystal stress, using a seed crystal bonding device for reducing crystal stress, specifically including the following steps:

[0044] Step 1, forming a carbon film on the back of the seed crystal 2 for protection;

[0045] Step 2: Apply special glue on the end surface of the fixed ring platform 11;

[0046] Step 3, stick the back of the seed crystal 2 to the fixed ring stage 11 of the seed crystal holder 1, so that the edge of the seed crystal 2 falls on the end surface of the fixed ring stage 11;

[0047] Step 4: Use the pressing block 3 to make the end surface of the pressing ring 31 contact the edge of the seed crystal 2;

[0048] Step 5, placing the assembly of the seed crystal holder 1, the seed crystal 2, and the pressing block 3 in a hot pressing furnace for pressing and high temperature treatment;

[0049] Step 6: After cooling, remove the compact 3 and clean the seed crystal 2.

[0050] The crystal prepared by this method has a reduced contact area with the seed crystal surface, so it becomes easier to separate the crystal from the seed crystal holder after growth.

[0051] Example 2

[0052] Reference Figure 3-4As another preferred embodiment of the present invention, the difference from embodiment 1 is that the seed crystal holder 1 includes a base 13, a plurality of protrusions 15 are arranged on one side of the base 13, the plurality of protrusions 15 are fixed on the base 13 through a translation layer 14, and are spliced ​​to form a fixed ring 11, a concave stress relief area 12 is formed between the plurality of protrusions 15, the number of protrusions 15 is not less than four, and there is a gap between adjacent protrusions 15, and the gap distance is not less than 2mm, and the translation layer 14 is a high temperature resistant silicone layer. By splicing the protrusions to form an intermittent fixed ring combined with a translation layer, the constraint of the seed crystal holder on the crystal is further reduced during the growth process, and the crystal stress is further released.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A seed crystal bonding device for reducing crystal stress, comprising a seed crystal holder (1), characterized in that: The seed crystal holder (1) is provided with a protruding fixed ring platform (11) on one side of the seed crystal (2); the edge of the seed crystal (2) is adhered to the fixed ring platform (11); a concave stress relief area (12) is formed inside the fixed ring platform (11), so that the middle part of the seed crystal (2) is fixed on the seed crystal holder (1) in a suspended manner; It also comprises a pressing block (3), wherein a protruding pressing ring platform (31) is provided on one side of the pressing block (3) corresponding to the seed crystal (2), and the pressing ring platform (31) presses and bonds the edge of the seed crystal (2) to the end face of the fixed ring platform (11).

2. A seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The inner diameter of the fixed ring platform (11) is 2-15 mm smaller than the diameter of the seed crystal (2), and the outer diameter of the fixed ring platform (11) is not smaller than the diameter of the seed crystal (2).

3. A seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The inner diameter of the clamping ring (31) is 3-15 mm smaller than the diameter of the seed crystal (2), and the outer diameter of the clamping ring (31) is 2-10 mm larger than the diameter of the seed crystal (2).

4. A seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The step height of the fixed ring platform (11) is ≥10 mm.

5. The seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The step height of the clamping ring platform (31) is 1-5 mm.

6. The seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The seed crystal support (1) comprises a support base (13), a plurality of protrusions (15) are provided on one side of the support base (13), the plurality of protrusions (15) are fixed to the support base (13) via a translation layer (14), and are spliced ​​to form a fixed ring platform (11), and a concave stress relief area (12) is formed between the plurality of protrusions (15).

7. The seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The number of the protrusions (15) is not less than four, and gaps are provided between adjacent protrusions (15), and the gap distance is not less than 2 mm.

8. The seed crystal bonding device for reducing crystal stress according to claim 1, characterized in that: The translation layer (14) is a high temperature resistant silica gel layer.

9. A seed crystal bonding method for reducing crystal stress, characterized in that: The seed crystal bonding device for reducing crystal stress as claimed in any one of claims 1 to 8 specifically comprises the following steps: Step 1, forming a carbon film on the back side of the seed crystal (2) for protection; Step 2, applying special glue on the end surface of the fixed ring platform (11); Step 3, sticking the back of the seed crystal (2) to the fixed ring platform (11) of the seed crystal holder (1) so that the edge of the seed crystal (2) falls on the end surface of the fixed ring platform (11); Step 4: using the pressing block (3), the end surface of the pressing ring (31) is brought into contact with the edge of the seed crystal (2); Step 5, placing the assembly of the seed crystal holder (1), the seed crystal (2) and the pressing block (3) in a hot pressing furnace for pressing and high temperature treatment; Step 6: After cooling, remove the compact (3) and clean the seed crystal (2).

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