Bonding method and bonding device for 8-12-inch large-size silicon carbide seed crystals

Abstract

The invention provides a bonding method and a bonding device for 8-12-inch large-size silicon carbide seed crystals, and belongs to the technical field of silicon carbide bonding. The method specifically comprises the following steps of: uniformly coating an adhesive on the large-size silicon carbide by using a spin coater or a spraying machine, pressing on graphite paper or a graphite support, putting the adhered seed crystal between two graphite discs, screwing the edges by using a circle of screws, putting into a heating furnace, heating under vacuum to achieve a hot pressing effect, cooling after the adhesion is finished, and taking the discs to finish the adhesion of the seed crystal. According to the bonding method, the incompatibility of large-size seed crystal bonding to bonding equipment can be reduced, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide bonding, and in particular to a bonding method and a bonding device for 8-12 inch large-size silicon carbide seed crystals. Background Art

[0002] Silicon carbide (SiC) material, with its exceptional physical properties—including a wide bandgap, high critical breakdown field strength, high electron mobility, and high thermal conductivity—has become an ideal choice for manufacturing high-temperature, high-frequency, high-power, radiation-resistant, short-wavelength luminescence and optoelectronic integrated devices. These unique properties give SiC material broad application potential in key areas such as satellites, rocket propulsion systems, radar technology, communications equipment, fighter aircraft systems, interference-free electronic ignition devices, and jet engine sensors. Consequently, major developed countries worldwide have invested substantial resources in the in-depth research and development of SiC material-related technologies.

[0003] Because silicon carbide does not exist in a stoichiometric melt at room temperature and pressure, it cannot be prepared and produced using the mature and efficient Czochralski method. Currently, the most commonly used and established method for preparing silicon carbide single crystals both domestically and internationally is physical vapor transport (PVT). Under the protection of a high-purity dynamic inert gas, in a suitable temperature field established by induction heating or graphite resistance heating, high-purity silicon carbide powder decomposes and sublimates in the high-temperature source region of the growth chamber. Then, under the influence of the thermal field temperature gradient and the gas phase concentration gradient, it is transported to the low-temperature seed crystal guidance region, where it rearranges itself into a regular atomic-level arrangement and crystallizes.

[0004] In addition to selecting high-quality, low-defect wafers, the connection and placement of the top-guided seed crystal and the top cavity are also crucial factors in determining process success. Common methods for bonding wafers of the same diameter include: 1. Directly bonding the seed crystal to the graphite holder using high-temperature adhesive. Even with a graphite cap with similar thermal expansion coefficients, achieving a good bond is difficult due to machining variations between the wafer and the graphite holder. 2. Bonding the seed crystal to the graphite holder twice using flexible graphite paper. This two-step bonding method is cumbersome and complex, requiring significant time and effort.

[0005] The utility model patent with authorization announcement number CN204530015U and authorization announcement date of August 5, 2015 discloses a sintering seed crystal pressing device, which uses an air bag to evenly disperse the contact, and then uses multiple pressure blocks above to adjust the pressure on the seed crystal. The operation is very cumbersome and laborious, and the air bag is prone to rupture during operation due to the lack of spatial positioning restrictions, which can easily cause air exhaust to be blocked during the subsequent seed crystal hot pressing process.

[0006] The utility model patent with authorization announcement number CN210683993U and authorization announcement date June 5, 2020 discloses a three-station silicon carbide seed crystal bonding furnace, which uses a cylinder to hard-press and bond the workpiece with three independent upper and lower heating plates between the upper and lower pressure plates. Although the upper pressure unit adopts a two-stage spherical movable connection structure, the pressure is not easy to control, and the processing deviation of the seed crystal and the graphite support or the matching deviation between the two will also have a great impact on the bonding effect. At the same time, the plane hard pressing has very high requirements on the height of the three groups of workpieces, and it is difficult to achieve a good bonding effect.

[0007] Authorization announcement number CN118516768B provides a multi-station high-efficiency seed crystal bonding furnace and its bonding method. This multi-station high-efficiency seed crystal bonding furnace is simple to operate and can perform efficient and dense hot pressing bonding on multiple graphite trays and seed crystal sheets at the same time. Although it can improve the bonding efficiency, that is, the bonding yield, the bonding equipment suitable for this bonding process is relatively complex and is only suitable for the bonding of small-sized seed crystals. For the bonding of 8-12 inch seed crystals, the furnace chamber that meets the requirements of this process needs to be very large, and the equipment cost is relatively high.

[0008] Based on the shortcomings of the above-mentioned various solutions, the present invention provides a new hot-press bonding method, which places the seed crystal to be bonded in the middle of a graphite disc, then tightens the graphite disc with a graphite nut and places it in a vacuum heating furnace chamber to bond large-sized seed crystals. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and to propose a bonding method and a bonding device for large-sized silicon carbide seed crystals of 8-12 inches.

[0010] In order to achieve the above object, a technical solution adopted by the present invention is: a method for bonding large-sized silicon carbide seed crystals of 8-12 inches, the specific steps of which are as follows: S1. Apply adhesive evenly; Specifically, use a glue spreader or sprayer to evenly apply a high-temperature adhesive (such as a high-temperature resistant inorganic adhesive or a carbon-based adhesive) to the surface to be bonded of the 8-12 inch silicon carbide seed crystal; control the coating thickness to 1-20μm, and ensure that there are no bubbles, no impurities, and the thickness is uniform.

[0011] S2. Pre-pressed graphite carrier; Specifically, the seed crystal coated with the adhesive is pressed onto the surface of the pretreated graphite paper or graphite support with the adhesive surface facing up; an initial pressure of 0.1-1 MPa is applied and maintained for 10-60 seconds to allow the adhesive to initially infiltrate the surface of the graphite support.

[0012] S3. Assemble hot pressing fixture; Specifically, a graphite carrier with seed crystals is placed in the center of the lower graphite disc, and then covered with an upper graphite disc to form a "sandwich" structure; it is tightened and fixed with screws (6-12) evenly distributed on the edge to ensure uniform pressure distribution and avoid seed crystal displacement or local stress concentration.

[0013] S4. Vacuum hot pressing bonding; Place the components assembled in step S3 in a vacuum heating furnace and evacuate to 10 -2 Pa; heat up to 300-1000℃ at a rate of 5-10℃ / min and keep warm for 30-120 minutes to pyrolyze and carbonize the adhesive or melt and bond; after tightening with screws, the pressure between the two graphite sheets is greater than 50MPa, which promotes interface densification.

[0014] S5. Cooling and removal; Specifically, the heating system is turned off and the mixture is naturally cooled to room temperature; the screws are released and the graphite disc is separated to obtain a firmly bonded silicon carbide seed crystal-graphite carrier assembly.

[0015] Preferably, a pre-tightening force of 1000-5000N is applied by the edge screws, and a tightening torque of 10Nm-50Nm is applied to meet production requirements.

[0016] The present invention also provides another technical solution: a bonding device for large-sized silicon carbide seed crystals of 8-12 inches, comprising graphite paper or a graphite holder and two graphite discs, wherein the graphite paper or the graphite holder is bonded to the seed crystal, and the assembly after the graphite paper or the graphite holder and the seed crystal are bonded is arranged between the two graphite discs, and a plurality of pre-tightening screws are arranged on the edge of the graphite disc, and the pre-tightening screws fasten the upper and lower graphite discs.

[0017] Compared with existing technologies, this invention achieves the following technical benefits: The bonding method reduces the incompatibility of bonding equipment with large-sized seed crystals. Through adjustable preload and a graphite disc structure, it effectively suppresses warping of 8-12 inch seed crystals. The bonding device is simple in structure, eliminating the need for complex equipment, and the graphite components are reusable, reducing production costs and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For ease of explanation, the present invention is described in detail with reference to the following specific embodiments and accompanying drawings.

[0019] Figure 1 Schematic diagram of the size seed crystal sizing / spraying adhesive of the present invention.

[0020] Figure 2 This is a schematic diagram of the seed crystal overpowering the graphite paper / graphite support of the present invention.

[0021] Figure 3 This is a schematic diagram of fixing the seed crystal in the middle of the graphite disk in the present invention. DETAILED DESCRIPTION

[0022] The following are specific embodiments of the present invention and are combined with the attached Figure 1-3 , further describing the technical solutions of the present invention, but the present invention is not limited to these embodiments; in the following description, specific details such as specific configurations are provided only to facilitate a comprehensive understanding of the embodiments of the present invention. Therefore, it should be apparent to those skilled in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention.

[0023] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0024] Example 1 Bonding method A method for bonding large-sized silicon carbide seed crystals of 8-12 inches, the specific steps are as follows: S1. Apply adhesive evenly; like Figure 1 As shown, use a glue spreader or sprayer to evenly apply a high-temperature adhesive (such as a high-temperature resistant inorganic adhesive or a carbon-based adhesive) to the surface to be bonded of the 8-12 inch silicon carbide seed crystal; control the coating thickness to 1-20μm, and ensure that there are no bubbles, impurities, and the thickness is uniform.

[0025] S2. Pre-pressed graphite carrier; like Figure 2 As shown, the seed crystal coated with the adhesive is pressed with its adhesive surface facing the surface of the pretreated graphite paper or graphite support; an initial pressure of 0.1-1 MPa is applied and maintained for 10-60 seconds to allow the adhesive to initially infiltrate the surface of the graphite support.

[0026] S3. Assemble hot pressing fixture; like Figure 3 As shown, the graphite carrier with the seed crystal is placed in the center of the lower graphite disk, and then covered with the upper graphite disk to form a "sandwich" structure; it is tightened and fixed by 12 screws evenly distributed on the edge to ensure uniform pressure distribution and avoid seed crystal displacement or local stress concentration.

[0027] S4. Vacuum hot pressing bonding; Specifically, the components assembled in step S3 are placed in a vacuum heating furnace and evacuated to 10 -2 Pa; heat up to 300-1000℃ at a rate of 5-10℃ / min and keep warm for 30-120 minutes to pyrolyze and carbonize the adhesive or melt and bond; after tightening with screws, the pressure between the two graphite sheets is greater than 50MPa, which promotes interface densification.

[0028] S5. Cooling and removal; Specifically, the heating system is turned off and the mixture is naturally cooled to room temperature; the screws are released and the graphite disc is separated to obtain a firmly bonded silicon carbide seed crystal-graphite carrier assembly.

[0029] Preferably, a pre-tightening force of 1000-5000N is applied by the edge screws, and a tightening torque of 10Nm-50Nm is applied to meet production requirements.

[0030] Example 2 Adhesive device A bonding device for large-sized silicon carbide seed crystals of 8-12 inches includes graphite paper or a graphite holder and two graphite discs. The graphite paper or the graphite holder is bonded to the seed crystal. The assembly after the graphite paper or the graphite holder and the seed crystal are bonded is arranged between the two graphite discs, and a plurality of pre-tightening screws are arranged on the edges of the graphite discs to fasten the upper and lower graphite discs.

[0031] Those skilled in the art to which this application relates may make various modifications or additions to the described specific embodiments or replace them in a similar manner, but they will not deviate from the inventive concept of this application or exceed the scope defined by the appended claims.

Claims

1. A method for bonding large-sized silicon carbide seed crystals of 8-12 inches, characterized in that: The specific steps are as follows: S1. Apply adhesive evenly; S2. Pre-pressed graphite carrier; S3. Assemble hot pressing fixture; S4. Vacuum hot pressing bonding; S5. Cool down and take out.

2. A method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 1, characterized in that: The step S1 specifically comprises: using a coating machine or a sprayer to evenly coat the high-temperature adhesive on the surface to be bonded of the 8-12 inch silicon carbide seed crystal; controlling the coating thickness to be 1-20 μm, ensuring that there are no bubbles, no impurities and the thickness is uniform.

3. A method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 2, characterized in that: The step S2 specifically comprises: pressing the adhesive-coated seed crystal bonding surface onto the pretreated graphite paper or graphite support surface; applying an initial pressure of 0.1-1 MPa and maintaining it for 10-60 seconds to allow the adhesive to initially infiltrate the surface of the graphite support.

4. The method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 3, characterized in that: The step S3 is specifically as follows: placing the graphite carrier with the seed crystal attached to the center of the lower graphite disc, and then covering it with the upper graphite disc to form a "sandwich" structure; and tightening and fixing it with 12 screws evenly distributed on the edge.

5. A method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 4, characterized in that: The step S4 is specifically as follows: placing the components assembled in step S3 in a vacuum heating furnace, evacuating the furnace to 10 -2 Pa or less; heat to 300-1000°C at a rate of 5-10°C / min and keep warm for 30-120 minutes to pyrolyze and carbonize the adhesive or melt and bond; After being tightened by screws, the pressure between the two graphite sheets is greater than 50 MPa, which promotes interface densification.

6. The method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 5, characterized in that: The step S5 specifically includes: turning off the heating system and naturally cooling to room temperature; releasing the screws and separating the graphite disc to obtain a firmly bonded silicon carbide seed crystal-graphite carrier assembly.

7. A method for bonding large-sized silicon carbide seed crystals of 8-12 inches according to claim 6, characterized in that: A pre-tightening force of 1000-5000N is applied through the edge pre-tightening screws, and a tightening torque of 10Nm-50Nm is applied to meet production requirements.

8. A bonding device for 8-12 inch large-sized silicon carbide seed crystals, characterized in that: It includes graphite paper or graphite holder and two graphite discs. The graphite paper or graphite holder is bonded to the seed crystal. The assembly after bonding of the graphite paper or graphite holder and the seed crystal is set between the two graphite discs. Several pre-tightening screws are set on the edges of the graphite discs to fasten the upper and lower graphite discs.

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