Seed crystal bonding adhesive and seed crystal bonding method

Abstract

The present application relates to a seed crystal adhesive and a seed crystal bonding method, wherein the seed crystal adhesive comprises a carbon nanotube material and an adhesive, wherein the aspect ratio of the carbon nanotube material is ≥1000, and the mass ratio of the carbon nanotube material to the volume ratio of the adhesive is (0.1-0.3) g:1 mL. By using the carbon nanotube material as the skeleton, on the one hand, the overall strength and toughness of the carbonized layer formed after the seed crystal adhesive is carbonized can be effectively enhanced, thereby effectively reducing the brittleness of the carbonized layer and effectively avoiding the risk of shedding and cracking of the carbonized layer, thereby effectively avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to cracks; on the other hand, the carbon nanotube material has a hollow pipe structure, and by controlling the aspect ratio of the carbon nanotube material, the external exhaust capacity can be enhanced, and the generation of microbubbles can be suppressed, thereby further avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to microbubbles.

Description

Technical Field

[0001] The present application relates to the field of material technology, and in particular to a seed crystal bonding glue and a seed crystal bonding method. Background Art

[0002] Compared to silicon and gallium arsenide, silicon carbide (SiC) boasts high thermal conductivity, high breakdown field strength, and high saturated electron drift velocity. It is a third-generation semiconductor material, following silicon and gallium arsenide, and is widely used in high-temperature, high-frequency, high-power, and radiation-resistant devices. Since traditional silicon-based power electronic devices are approaching the limits of silicon material due to parasitic effects, the development of semiconductor devices using wide-bandgap materials such as SiC has become a trend. The saturated electron drift velocity of 4H-SiC material is twice that of silicon, enabling higher current density and transconductance in SiC devices. These high breakdown characteristics give SiC power and switching devices a breakdown voltage 3-4 times higher than that of silicon and GaAs devices. The high thermal conductivity and high-temperature resistance ensure that SiC devices offer high power density and reliable operation at high temperatures.

[0003] The traditional method for preparing silicon carbide single crystals is physical vapor transport (PVT). Silicon carbide powder is placed in a sealed graphite crucible, and a silicon carbide seed crystal is placed on the top of the crucible. The thermal field distribution of the single crystal furnace is designed so that the temperature of the powder source area is higher than that of the seed crystal area, and the powder source area reaches the sublimation temperature point of the silicon carbide powder source. The Si, C, Si2C, SiC2, SiC and other molecules generated by the sublimation of the silicon carbide powder source are transported to the vicinity of the seed crystal area through diffusion or convection effects. Due to the low temperature of the seed crystal area, the above-mentioned atmosphere forms a certain degree of supercooling and crystallizes into silicon carbide crystals on the surface of the seed crystal. Among them, the method of placing the silicon carbide seed crystal on the top of the crucible includes the use of a seed crystal bonding method. The seed crystal bonding method refers to a method of bonding the initial seed crystal used for crystal growth (silicon carbide seed crystal) to the relevant components of the single crystal growth system (generally graphite material). However, traditional seed crystal bonding methods usually use adhesives for bonding, and the formed carbonized layer will crack or the seed crystal will fall off. The cracking of the carbonized layer will cause ablation along the cracks on the back of the seed crystal and induce the formation of macroscopic crystal defects such as micropipes, hexagonal holes and dislocations.

[0004] Therefore, it is of great significance to provide a seed crystal bonding method with strong bonding and no cracks in the carbonized layer.

[0005] Application Contents

[0006] Based on this, the present application provides a seed crystal adhesive and a seed crystal bonding method that have strong bonding and a crack-free carbonized layer formed after carbonization.

[0007] The technical solution of this application to solve the above technical problems is as follows.

[0008] A seed crystal bonding glue comprises a carbon nanotube material and an adhesive, wherein the aspect ratio of the carbon nanotube material is ≥1000, and the mass ratio of the carbon nanotube material to the volume ratio of the adhesive is (0.1-0.3) g:1 mL.

[0009] In some embodiments, in the seed crystal adhesive, the diameter of the carbon nanotube material is 2 nm to 20 nm.

[0010] In some embodiments, in the seed crystal adhesive, the ratio of the mass of the carbon nanotube material to the volume of the adhesive is (0.2-0.3) g:1 mL.

[0011] In some embodiments, in the seed crystal adhesive, the adhesive is selected from at least one of epoxy resin, phenolic resin, silicone resin, carbon adhesive and carbohydrate adhesive.

[0012] In some embodiments, in the seed crystal adhesive, the viscosity of the seed crystal adhesive is 500 mPa·s to 2500 mPa·s.

[0013] In some embodiments, in the seed crystal adhesive, the aspect ratio of the carbon nanotube material is 1000-5000.

[0014] In some embodiments, in the seed crystal adhesive, the carbon nanotube material is a carbon nanotube material that has been subjected to high-temperature treatment, and the temperature of the high-temperature treatment is 1800° C. to 2400° C.

[0015] The present application also provides a seed crystal bonding method, comprising the following steps:

[0016] After the above-mentioned seed crystal adhesive and base material are sequentially arranged on the back of the seed crystal, hot pressing curing and carbonization are sequentially performed.

[0017] In some embodiments, in the seed crystal bonding method, the pressure of the hot pressing curing is 100 kg to 2000 kg.

[0018] In some embodiments, in the seed crystal bonding method, the carbonization temperature is 400° C. to 800° C., and the time is 1 hour to 5 hours.

[0019] Compared with the prior art, the seed crystal adhesive of the present application has the following beneficial effects:

[0020] The above-mentioned seed crystal adhesive includes a specific proportion of carbon nanotube material and adhesive, and uses the carbon nanotube material as the skeleton. On the one hand, it can effectively enhance the overall strength and toughness of the carbonized layer formed after the seed crystal adhesive is carbonized, that is, effectively reduce the brittleness of the carbonized layer, thereby effectively avoiding the risk of falling off and cracking of the carbonized layer, and thus effectively avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to cracks; on the other hand, the carbon nanotube material has a hollow pipe structure, and by controlling the aspect ratio of the carbon nanotube material, the external exhaust capacity can be enhanced and the generation of microbubbles can be suppressed, thereby further avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to microbubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 This is a microscopic image of the carbon nanotube material in Example 1;

[0023] Figure 2 This is a macroscopic image of the carbon nanotube material in Example 1;

[0024] Figure 3 This is a photograph of the seed crystal after bonding and carbonization in Example 1;

[0025] Figure 4 This is a back photograph of a SiC ingot grown using the seed crystal of Example 1;

[0026] Figure 5 This is a partial photograph of the back of a SiC ingot grown using the seed crystal of Example 1;

[0027] Figure 6 This is a photograph of the seed crystal after bonding and carbonization in Example 6;

[0028] Figure 7 This is a back photograph of a SiC ingot grown using the seed crystal of Example 6;

[0029] Figure 8 This is a microscopic image of the carbon nanotube material in Comparative Example 1;

[0030] Figure 9 This is a macroscopic image of the carbon nanotube material in Comparative Example 1;

[0031] Figure 10 This is a backside photograph of a SiC ingot grown using the seed crystal of Comparative Example 1;

[0032] Figure 11 A partial photograph of the back of a SiC ingot grown using the seed crystal of Comparative Example 1;

[0033] Figure 12 This is a micrograph of the seed crystal adhesive obtained in step (3) of Comparative Example 2;

[0034] Figure 13 This is a micrograph of the carbonized layer obtained after the seed crystal adhesive is carbonized in step (5) of comparative example 2;

[0035] Figure 14 This is the microscopic morphology of the seed crystal adhesive in Comparative Example 3;

[0036] Figure 15 This is a photograph of the seed crystal after bonding and carbonization in Comparative Example 3;

[0037] Figure 16 A partial photograph of the back of a SiC ingot grown using the seed crystal of Comparative Example 3;

[0038] Figure 17 This is a photograph of the seed crystal after bonding and carbonization in Comparative Example 4;

[0039] Figure 18 A partial photograph of the back of a SiC ingot grown using the seed crystal of Comparative Example 4;

[0040] Figure 19 This is a photograph of the seed crystal after bonding and carbonization in Comparative Example 5;

[0041] Figure 20 This is a partial photograph of the back side of a SiC ingot grown using the seed crystal of Comparative Example 5. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0044] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0045] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the weights described in the examples of this application may be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0046] After research and analysis, the technical personnel of this application have found that the reasons why the carbonized layer cracks or the seed crystal falls off in the traditional seed crystal bonding method are as follows:

[0047] The materials of traditional seed crystal bonding technology usually include silicon carbide layer, carbide layer and substrate (graphite, graphite paper or other high-temperature resistant materials, such as tungsten, tantalum carbide, etc.). The carbide layer is an organic material (glue) as an adhesive, which undergoes a carbonization reaction at high temperature to form an adhesive layer connecting the silicon carbide seed crystal and the substrate material; the carbide layer formed by the carbonization of traditional adhesives is generally brittle, and with the continuous development of the growth of large-sized silicon carbide single crystals, large-sized seed crystals are prone to uneven bonding during the use of traditional bonding processes. Due to increased warping or mismatched thermal expansion, problems such as cracking of the carbide layer and seed crystal falling occur.

[0048] Furthermore, there is a problem of thermal expansion matching between various materials in traditional seed crystal bonding technology. Although the use of materials such as flexible graphite paper as a transition layer can solve the thermal expansion mismatch problem between the graphite substrate and the silicon carbide seed crystal, there is still a thermal mismatch problem between the adhesive and the silicon carbide crystal. It can also cause the carbonized layer formed later to form microcracks under the high temperature environment of crystal growth (greater than 2000 degrees Celsius), which is very obvious when the thickness of the carbonized layer is large. The microcracks cause ablation along the cracks on the back of the seed crystal and induce crystal defects such as microtubes, hexagonal holes and dislocations.

[0049] Moreover, the adhesive will inevitably produce volatile gases during the subsequent high-temperature carbonization process; and the carbonized layer formed by the carbonization of the adhesive has the characteristics of high density, which may cause the gas generated by the adhesive during the carbonization process to be difficult to discharge from the carbonized layer. On the one hand, it will reduce the bonding strength. On the other hand, the gas will accumulate at the local bonding weak points of the seed crystal back to form microbubbles, which will cause local ablation of the seed crystal back, thereby inducing defects such as hexagonal holes and microtubes.

[0050] One embodiment of the present application provides a seed crystal adhesive, comprising a carbon nanotube material and an adhesive, wherein the aspect ratio of the carbon nanotube material is ≥1000, and the mass ratio of the carbon nanotube material to the volume ratio of the adhesive is (0.1-0.3) g:1 mL.

[0051] The above-mentioned seed crystal adhesive uses carbon nanotube material as the skeleton and controls the amount of carbon nanotube material added. On the one hand, it can effectively enhance the overall strength and toughness of the carbonized layer formed after the seed crystal adhesive is carbonized, that is, effectively reduce the brittleness of the carbonized layer, thereby effectively avoiding the risk of falling off and cracking of the carbonized layer, and thus effectively avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to cracks; on the other hand, the carbon nanotube material has a hollow pipe structure, and by controlling the aspect ratio of the carbon nanotube material, the external exhaust capacity can be enhanced and the generation of microbubbles can be suppressed, thereby further avoiding crystal defects such as microtubes, hexagonal holes and dislocations induced by burning due to microbubbles.

[0052] The seed crystal bonding adhesive is evenly and firmly bonded, and the carbonized layer formed after carbonization is dense and free of cracks.

[0053] It can be understood that the aspect ratio of the carbon nanotube material refers to the ratio of the length of the carbon nanotube material to the tube diameter.

[0054] It will be further understood that the aspect ratio of the carbon nanotube material includes but is not limited to 1000, 1050, 1100, 1200, 1250, 1500, 2000, 2500, 3000, 3500, 4000, 5000, and 6000, and the volume ratio of the mass of the carbon nanotube material to the adhesive includes but is not limited to 0.1 g:1 mL, 0.12 g:1 mL, 0.15 g:1 mL, 0.16 g:1 mL, 0.18 g:1 mL, 0.2 g:1 mL, 0.22 g:1 mL, 0.24 g:1 mL, 0.25 g:1 mL, 0.26 g:1 mL, 0.28 g:1 mL, and 0.3 g:1 mL.

[0055] In some of these examples, the aspect ratio of the carbon nanotube material in the seed bonding paste is 1000 to 5000.

[0056] In some of the examples, the ratio of the mass of the carbon nanotube material to the volume of the adhesive in the seed crystal adhesive is (0.2-0.3) g:1 mL.

[0057] In some of the examples, the diameter of the carbon nanotube material in the seed crystal adhesive is 2 nm to 20 nm.

[0058] It can be understood that the diameter of the carbon nanotube material includes but is not limited to 2nm, 2.5nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 15nm, 18nm, and 20nm.

[0059] In some examples, in the seed crystal adhesive, the adhesive is selected from at least one of epoxy resin, phenolic resin, silicone resin, carbon adhesive, and carbohydrate adhesive.

[0060] It can be understood that epoxy resins include but are not limited to bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester epoxy resin; phenolic resins include but are not limited to thermoplastic phenolic resin and thermosetting phenolic resin; silicone resins include but are not limited to methylphenyl silicone resin, methyl silicone resin, polymethyl silicone resin, amino silicone resin, fluorosilicone resin, methyl MQ silicone resin, vinyl MQ silicone resin; carbon glue includes but is not limited to TiB2 carbon glue and SPI conductive carbon glue; carbohydrate adhesives include but are not limited to glucose, sucrose, fructose, etc.

[0061] In some of these examples, the seed attach paste also includes a solvent.

[0062] It is understood that the solvent includes but is not limited to ethanol, acetone, isopropanol, ethyl acetate, etc.

[0063] In some of the examples, the carbon nanotube material in the seed crystal adhesive is a carbon nanotube material that has been treated at high temperature.

[0064] Furthermore, the temperature of the high temperature treatment is 1800°C to 2400°C.

[0065] It can be understood that the temperature of high temperature treatment includes but is not limited to 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, and 2400°C.

[0066] In some examples, in the seed crystal adhesive, the viscosity of the seed crystal adhesive is 500 mPa·s to 2500 mPa·s.

[0067] It can be understood that the viscosity of the seed crystal adhesive includes but is not limited to 500mPa·s, 600mPa·s, 700mPa·s, 800mPa·s, 1000mPa·s, 1200mPa·s, 1500mPa·s, 1800mPa·s, 2000mPa·s, 2100mPa·s, 2200mPa·s, and 2500mPa·s.

[0068] An embodiment of the present application provides a method for preparing a seed crystal adhesive, including step S10.

[0069] Step S10: mixing the adhesive, the carbon nanotube material and the solvent.

[0070] In some examples, step S10 includes steps S11 to S12:

[0071] Step S11: mixing the adhesive and the solvent to obtain an adhesive mixed liquid;

[0072] Step S12: mixing the adhesive mixture with the carbon nanotube material.

[0073] In some examples, after the adhesive, the carbon nanotube material, and the solvent are mixed in step S10 , a stirring step is further included.

[0074] In some examples, in step S10 , the stirring speed is 10 rpm to 1500 rpm, and the stirring time is 60 min to 120 min.

[0075] It will be understood that the stirring speed includes but is not limited to 10rpm, 50rpm, 100rpm, 200rpm, 500rpm, 1000rpm, and 1500rpm; and the stirring time includes but is not limited to 60min, 80min, 100min, 110min, and 120min.

[0076] In some examples, before the step of mixing the adhesive, the carbon nanotube material, and the solvent in step S10, the step S01 of pre-treating the carbon nanotube material is also included:

[0077] The carbon nanotubes are sequentially acid-washed, water-washed and dried.

[0078] In some examples, in step S01 , the acid solution used in pickling is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0079] In some examples, in step S01 , the drying temperature is 95° C. to 250° C., and the drying time is 4 hours to 6 hours.

[0080] It is understood that the drying temperature includes but is not limited to 95°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 230°C, and 250°C, and the drying time includes but is not limited to 4h, 4.5h, 5h, 5.5h, and 6h.

[0081] An embodiment of the present application provides a seed crystal bonding method, including steps S100 to S200.

[0082] Step S100: placing the seed crystal adhesive and the base material on the back of the seed crystal in sequence to obtain a precursor.

[0083] In some examples, in step S100 , when the seed crystal adhesive is provided on the back side of the seed crystal, manual coating or use of a glue spreader can be selected.

[0084] It can be understood that the base material covers the above-mentioned adhesive.

[0085] Furthermore, the base material is a graphite base material.

[0086] Step S200: hot pressing and carbonizing the precursor in sequence.

[0087] It can be understood that the above-mentioned seed crystal adhesive is set on the back of the seed crystal in step S100, and a carbonized layer is formed after hot pressing and carbonization in step S200, wherein the adhesive and the carbon nanotube material are cured into a whole, and finally the entire back of the seed crystal is tightly connected to the base material.

[0088] It can be further understood that when the above-mentioned seed crystal adhesive is provided on the back side of the seed crystal, only the above-mentioned seed crystal adhesive can be provided, or other seed crystal adhesives can be provided.

[0089] In some examples, in step S200 , the pressure of the hot pressing curing is 100 kg to 2000 kg.

[0090] It can be understood that the pressure of hot pressing curing includes but is not limited to 100kg, 200kg, 500kg, 800kg, 1000kg, 1500kg, and 2000kg.

[0091] In some examples, in step S200 , the carbonization temperature is 400° C. to 800° C., and the time is 1 hour to 5 hours.

[0092] It can be understood that the carbonization temperature includes but is not limited to 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, and 800°C, and the carbonization time includes but is not limited to 1h, 2h, 2.5h, 3h, 4h, and 5h.

[0093] In some examples, in step S200 , carbonization is performed under a vacuum environment.

[0094] In some examples, in step S200 , the temperature is raised to the carbonization temperature at a rate of 2° C. / min to 10° C. / min for carbonization.

[0095] It will be appreciated that the rate of increasing the temperature to the carbonization temperature includes, but is not limited to, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, and 10°C / min.

[0096] The above-mentioned seed crystal bonding method effectively solves the problems of cracking of the carbonized layer or falling of the seed crystal in the traditional seed crystal bonding method by adopting the above-mentioned seed crystal bonding glue. After carbonization, the carbonized layer does not crack, and there is no macroscopic ablation and microscopic small bubble ablation on the back of the growing crystal.

[0097] The following examples are given based on the seed crystal adhesive and the seed crystal bonding method of the present application. It can be understood that the seed crystal adhesive and the seed crystal bonding method of the present application are not limited to the following embodiments.

[0098] Example 1

[0099] (1) Select carbon nanotubes with a diameter of about 10 nanometers and a length of about 15 microns, which have been treated at high temperature, and then pickle them to remove impurities, wash them with water, and dry them for use;

[0100] (2) Diluting the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0101] (3) mixing 10 mL of the diluted adhesive obtained in step (2) with 2 g of carbon nanotubes and treating the mixture in a blender for 1 hour to obtain a seed crystal adhesive;

[0102] (4) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (3) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0103] (5) Place the precursor obtained in step (4) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0104] The microscopic image of the carbon nanotube material selected in step (1) is as follows: Figure 1 As shown, the macroscopic image of carbon nanotube material is as follows Figure 2 As shown, Figure 3 This is a photo of the seed crystal after bonding and carbonization. Figure 4 This is a backside photo of a SiC ingot grown using this seed crystal. Figure 5 A partial backside photo of a SiC ingot grown using this seed crystal ( Figure 4 partial photo).

[0105] from Figure 3 It can be seen that the seed crystal adhesive prepared in Example 1 has no cracks after carbonization; Figures 4 and 5 It can be seen that there is no macroscopic ablation and microscopic small bubble ablation on the back of the growing crystal.

[0106] Example 2

[0107] The method is basically the same as Example 1, except that the aspect ratio of the carbon nanotube material is different. Specifically, the diameter of the carbon nanotube material is about 10 nanometers and the length is about 12 micrometers.

[0108] Example 3

[0109] The method is basically the same as Example 1, except that the aspect ratio of the carbon nanotube material is different. Specifically, the diameter of the carbon nanotube material is about 10 nanometers and the length is about 15 micrometers.

[0110] Example 4

[0111] The method is basically the same as Example 1, except that the aspect ratio of the carbon nanotube material is different. Specifically, the diameter of the carbon nanotube material is about 10 nanometers and the length is about 20 micrometers.

[0112] Example 5

[0113] The method is basically the same as Example 1, except that step (3) is as follows:

[0114] (3) 10 mL of the diluted adhesive obtained in step (2) and 3 g of carbon nanotubes were mixed and treated in a blender for 1 hour to obtain a seed crystal adhesive.

[0115] The seed crystal adhesives prepared in Examples 2 to 5 did not crack after carbonization, and there was no macroscopic ablation and microscopic small bubble ablation on the back of the growing crystal.

[0116] Example 6

[0117] The method is basically the same as Example 1, except that step (3) is as follows:

[0118] (3) 10 mL of the diluted adhesive obtained in step (2) and 1 g of carbon nanotubes were mixed and treated in a blender for 1 hour to obtain a seed crystal adhesive.

[0119] in, Figure 6 This is a photo of the seed crystal after bonding and carbonization in step (5). Figure 7 This is a backside photograph of a SiC ingot grown using this seed crystal.

[0120] from Figures 6-7It can be seen that the seed crystal adhesive prepared in Example 6 does not crack after carbonization, and there is no macroscopic ablation and microscopic small bubble ablation phenomenon on the back of the growing crystal.

[0121] Comparative Example 1

[0122] The method is basically the same as Example 1, except that the aspect ratio of the carbon nanotube material is different, as follows:

[0123] (1) Select carbon nanotubes with a diameter of about 10 nanometers and a length of about 2 micrometers, which have been treated at high temperature, and then pickle them to remove impurities, wash them with water, and dry them for use;

[0124] (2) Diluting the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0125] (3) mixing 10 mL of the diluted adhesive obtained in step (2) with 2 g of carbon nanotubes and treating the mixture in a blender for 1 hour to obtain a seed crystal adhesive;

[0126] (4) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (3) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0127] (5) Place the precursor obtained in step (4) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0128] The microscopic image of the carbon nanotube material selected in step (1) is as follows: Figure 8 As shown, the macroscopic image of carbon nanotube material is as follows Figure 9 As shown, Figure 10 This is a back photo of the SIC ingot grown using this seed crystal. Figure 11 This is a partial photo of the back of the SIC ingot grown using this seed crystal ( Figure 10 partial photo).

[0129] Depend on Figures 10 and 11 It can be seen that in Comparative Example 1, which also uses carbon nanotube material as an additive, there is no macroscopic ablation on the back of the grown crystal, but there are microscopic bubble ablation points; this indicates that when the aspect ratio of carbon nanotubes is insufficient, the exhaust capacity is reduced, and microbubbles are generated to a certain extent.

[0130] Comparative Example 2

[0131] The method is basically the same as Example 1, except that the carbon nanotube material is replaced with a carbon powder material with a particle size of 5 microns, as follows:

[0132] (1) Select carbon powder material with a particle size of 5 μm and treat it in a graphitization furnace at 2400°C for 10 hours;

[0133] (2) Diluting the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0134] (3) Mixing 10 mL of the diluted adhesive obtained in step (2) with 2 g of carbon powder material, and treating the mixture in a blender for 2 hours to obtain a seed crystal adhesive;

[0135] (4) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (3) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0136] (5) Place the precursor obtained in step (4) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0137] in, Figure 12 is a microscopic image of the seed crystal adhesive obtained in step (3), Figure 13 This is a microscopic image of the carbonized layer obtained after the seed crystal adhesive is carbonized in step (5).

[0138] from Figures 12-13 It can be seen that in Comparative Example 2, the carbon powder material used is spherical and irregular in shape. When it is used as a skeleton reinforcement material, the aspect ratio is insufficient and the toughness and mechanical strength of the carbonized rubber layer cannot be effectively enhanced. Cracks still exist in the carbonized layer.

[0139] Comparative Example 3

[0140] The method is basically the same as Example 1, except that the carbon nanotube material is replaced with carbon fiber material, as follows:

[0141] (1) The T300 standard carbon fiber material is woven into carbon fiber cloth. After impregnation molding, the long fibers are cut into short fibers of about 30 microns in length by mechanical cutting. After soaking, cleaning and drying in sequence, the fibers are treated in a graphitization furnace at 2600°C for 2 hours to increase mechanical toughness.

[0142] (2) Diluting the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0143] (3) Mixing 10 mL of the diluted adhesive obtained in step (2) with 2 g of short fibers and treating in a blender for 1 hour to obtain a seed crystal adhesive;

[0144] (4) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (3) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0145] (5) Place the precursor obtained in step (4) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0146] in, Figure 14 This is the microscopic morphology of the seed crystal adhesive of comparative example 3. Figure 15 This is a photo of the seed crystal after bonding and carbonization in step (5). Figure 16 This is a partial photo of the back of the SIC ingot grown using this seed crystal.

[0147] from Figures 15-16 It can be seen that carbon fiber material, as a skeleton reinforcement material, enhances the mechanical strength, there are no cracks in the carbonized layer, and no seed crystal shedding phenomenon, but seed crystal back ablation caused by tiny bubbles was found.

[0148] Comparative Example 4

[0149] The method is basically the same as Example 1, except that the carbon nanotube material is replaced with graphene material, as follows:

[0150] (1) Dilute the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0151] (2) mixing 10 mL of the diluted adhesive obtained in step (1) with 2 g of graphene material, and treating the mixture in a blender for 1 hour to obtain a seed crystal adhesive;

[0152] (3) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (2) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0153] (4) Place the precursor obtained in step (3) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0154] in, Figure 17 This is a photo of the seed crystal after bonding and carbonization in step (4) of Comparative Example 4. Figure 18 This is a partial photo of the back of the SIC ingot grown using this seed crystal.

[0155] from Figures 17-18 It can be seen that there are no cracks in the carbonized layer on the back of the seed crystal. After the growth is completed, micron-scale ablation pits caused by very few tiny bubbles are found on the back.

[0156] Comparative Example 5

[0157] The method is basically the same as Example 1, except that in step (3), the ratio of the mass of carbon nanotubes to the volume of the adhesive is 1 g / 1 mL, as follows:

[0158] (1) Select carbon nanotubes with a diameter of about 10 nanometers and a length of about 15 microns, which have been treated at high temperature, and then pickle them to remove impurities, wash them with water, and dry them for use;

[0159] (2) Diluting the adhesive phenolic resin with ethanol to a viscosity of about 1000 mPa·s;

[0160] (3) mixing 10 mL of the diluted adhesive obtained in step (2) with 10 g of carbon nanotubes and treating the mixture in a blender for 1 hour to obtain a seed crystal adhesive;

[0161] (4) using a knife edge ruler to evenly apply the seed crystal adhesive obtained in step (3) to the surface of the seed crystal, and then covering it with a graphite base material to obtain a precursor;

[0162] (5) Place the precursor obtained in step (4) in a hot press furnace, apply a pressure of 1500 kg on the base material to provide bonding pressure; in a vacuum environment, heat it to 500°C at a rate of 2°C / min, keep it constant for 8 hours, and then cool it down and take it out.

[0163] in, Figure 19 This is a photograph of the seed crystal after bonding and carbonization in step (5) of comparative example 5. Figure 20 This is a partial photo of the back of a SIC ingot grown using this seed crystal.

[0164] from Figures 19-20 It can be seen that when the ratio of carbon nanotube material to adhesive is not appropriate, there may be a situation where the backing is partially weakly bonded, resulting in severe local ablation.

[0165] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0166] The embodiments described above only express several implementation methods of the present application, which are convenient for understanding the technical solutions of the present application in a specific and detailed manner, but they cannot be understood as limiting the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent application of this application shall be based on the content of the attached claims, and the description and drawings can be used to interpret the content of the claims.

Claims

1. A seed crystal adhesive, characterized in that: The invention comprises a carbon nanotube material and an adhesive, wherein the aspect ratio of the carbon nanotube material is ≥1000, the mass of the carbon nanotube material and the volume ratio of the adhesive is (0.1-0.3) g:1 mL, the carbon nanotube material is a carbon nanotube material after high-temperature treatment, and the temperature of the high-temperature treatment is 1800°C-2400°C; the adhesive is selected from at least one of epoxy resin, phenolic resin, silicone resin, carbon glue and carbohydrate adhesive, and the viscosity of the seed crystal adhesive is 500mPa·s-2500mPa·s.

2. The seed crystal adhesive according to claim 1, wherein: The diameter of the carbon nanotube material is 2nm to 20nm.

3. The seed crystal adhesive according to any one of claims 1 to 2, characterized in that: The mass ratio of the carbon nanotube material to the volume ratio of the adhesive is (0.2-0.3) g:1 mL.

4. The seed crystal adhesive according to any one of claims 1 to 2, characterized in that: The aspect ratio of the carbon nanotube material is 1000-5000.

5. A seed crystal bonding method, characterized in that: The following steps are involved: After the seed crystal adhesive according to any one of claims 1 to 4 and the base material are sequentially arranged on the back of the seed crystal, hot pressing curing and carbonization are sequentially performed.

6. The seed crystal bonding method according to claim 5, wherein: The pressure of the hot pressing curing is 100kg to 2000kg.

7. The seed crystal bonding method according to claim 5 or 6, wherein: The carbonization temperature is 400° C. to 800° C., and the carbonization time is 1 hour to 5 hours.

Images