Seed crystal bonding method

Abstract

The invention provides a seed crystal bonding method. The seed crystal bonding method comprises the following steps: arranging a first non-high-temperature-resistant organic self-adhesive film between a non-growth surface of a seed crystal and graphite paper; carrying out primary hot pressing to enable the graphite paper to be adhered to the non-growth surface of the seed crystal so as to form a graphite layer on the seed crystal, and then carrying out primary cooling; paving a second non-high-temperature-resistant organic self-adhesive film on a seed crystal support, and placing the seed crystal on the seed crystal support according to a mode that the graphite layer is in contact with the second non-high-temperature-resistant organic self-adhesive film; and carrying out secondary hot pressing to enable the seed crystal to be bonded on the seed crystal support, and then carrying out secondary cooling. The method disclosed by the invention is simple to operate, low in cost and good in bonding quality, and effectively solves the problem of non-uniform colloid coating caused by the increase of the size of the seed crystal.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material processing. Specifically, the present invention relates to a method for bonding a seed crystal. Background Art

[0002] Aluminum nitride (AlN) crystal is an inorganic non-metallic material with various excellent properties and has important applications in many fields. The bandgap of AlN is about 6.2 eV and it is a direct bandgap, with good chemical stability and high thermal conductivity. AlN can be used to fabricate high-frequency, high-voltage, and high-temperature electronic devices; due to its good light transmittance in the ultraviolet band, it can be used to manufacture ultraviolet optoelectronic devices.

[0003] Silicon carbide (SiC) is also a wide-bandgap semiconductor material with high thermal conductivity, large bandgap, suitable for high-temperature high-power fields; its critical breakdown field strength is high, suitable for high-voltage fields; its saturated electron drift velocity is large, suitable for high-frequency fields. Silicon carbide can be applied to extreme environments that silicon-based semiconductors are not suitable for and is an ideal material for fabricating high-frequency, high-voltage, and high-power devices.

[0004] Whether it is aluminum nitride or silicon carbide, crystal growth requires a seed crystal to obtain large-size and high-quality single crystals. During crystal growth, a homoepitaxial seed crystal is the most ideal seed crystal. If a homoepitaxial seed crystal is lacking, a heteroepitaxial seed crystal can also be selected. Since the lattice mismatch between silicon carbide and aluminum nitride is small, silicon carbide can be used as a seed crystal for aluminum nitride crystal growth. Especially, the technology for growing silicon carbide crystals has developed rapidly, and large-size silicon carbide seed crystals are easily obtained. Using a silicon carbide seed crystal to grow large-size aluminum nitride crystals is a feasible technical route. During single crystal growth, the seed crystal needs to be fixed on a seed crystal holder and placed above the raw material. The seed crystal can be fixed by mechanical methods, but usually, the bonding method is adopted. Seed crystal bonding is a crucial step in crystal growth and directly affects the quality of the crystal. Currently, the conventional seed crystal bonding method is to coat an organic glue between the seed crystal and the seed crystal holder. Organic glues such as epoxy resin, phenolic resin, photoresist, glucose, etc. This bonding method has the disadvantages of uneven coating, shrinkage and outgassing of the colloid when heated, and it is very easy to form bubbles on the back of the seed crystal, resulting in uneven heat conduction of the seed crystal and easily causing problems such as seed crystal ablation and uneven growth.

[0005] The diameter of silicon carbide seed crystals has gradually developed from 4 inches to 12 inches, and the difficulty of seed crystal bonding increases exponentially with the increase in size. The main reason is that as the size increases, the unevenness of glue coating becomes more prominent. Therefore, there is an urgent need for a new seed crystal bonding method. Summary of the Invention

[0006] Therefore, the purpose of the present invention is to provide a method for bonding a seed crystal. This seed crystal bonding method is simple, fast, easy to operate, and has good bonding quality, does not fall off at high temperatures, and there are no bubbles on the back of the seed crystal.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] The present invention provides a method for bonding a seed crystal, which comprises the following steps:

[0009] (1) A first non-high-temperature-resistant organic self-adhesive film is provided between the non-growth surface of the seed crystal and the graphite paper;

[0010] (2) A first hot pressing is carried out to bond the graphite paper to the non-growth surface of the seed crystal, thereby forming a graphite layer on the seed crystal, and then a first temperature reduction is carried out;

[0011] (3) A second non-high-temperature-resistant organic self-adhesive film is laid flat on the seed crystal holder, and the seed crystal is placed on the seed crystal holder in such a way that the graphite layer is in contact with the second non-high-temperature-resistant organic self-adhesive film;

[0012] (4) A second hot pressing is carried out to bond the seed crystal to the seed crystal holder, and then a second temperature reduction is carried out.

[0013] According to some embodiments of the present invention, the seed crystal is a silicon carbide seed crystal or an aluminum nitride seed crystal.

[0014] According to some embodiments of the present invention, the size (i.e., diameter) of the seed crystal is 2 inches to 12 inches.

[0015] Preferably, the size of the seed crystal is 4 inches to 8 inches.

[0016] According to some embodiments of the present invention, the thickness of the first non-high-temperature-resistant organic self-adhesive film is 1 μm to 100 μm.

[0017] Preferably, the thickness of the first non-high-temperature-resistant organic self-adhesive film is 20 μm to 50 μm.

[0018] According to some embodiments of the present invention, the highest heat-resistant temperature of the first non-high-temperature-resistant organic self-adhesive film is not higher than 400 °C.

[0019] Preferably, the first non-high-temperature-resistant organic self-adhesive film is an organic polymer thin film.

[0020] More preferably, the first non-high-temperature-resistant organic self-adhesive film is selected from the group consisting of polyethylene (PE) thin film, polypropylene (PP) thin film, polyvinyl chloride (PVC) thin film, polyethylene terephthalate (PET) thin film, polyvinylidene fluoride (PVDF) thin film, polysulfone (PS) thin film, and polytetrafluoroethylene (PTFE) thin film.

[0021] According to some embodiments of the present invention, the thickness of the second non-high-temperature-resistant organic self-adhesive film is 1 μm to 100 μm.

[0022] Preferably, the second non-high temperature resistant organic self-adhesive film has a thickness of 20 μm to 50 μm.

[0023] According to some embodiments of the present invention, the maximum heat-resistant temperature of the second non-high-temperature-resistant organic self-adhesive film is not higher than 400°C.

[0024] Preferably, the second non-high temperature resistant organic self-adhesive film is an organic high molecular polymer film.

[0025] More preferably, the second non-high temperature resistant organic self-adhesive film is selected from one of polyethylene (PE) film, polypropylene (PP) film, polyvinyl chloride (PVC) film, polyethylene terephthalate (PET) film, polyvinylidene fluoride (PVDF) film, polysulfone (PS) film and polytetrafluoroethylene (PTFE) film.

[0026] According to some embodiments of the present invention, the thickness of the graphite paper is 0.05 mm to 1 mm.

[0027] Preferably, the thickness of the graphite paper is 0.3 mm to 0.5 mm.

[0028] In the present invention, the graphite paper (graphite layer) is arranged between the seed crystal holder and the seed crystal, which can play a buffering role, so that the seed crystal is evenly stressed during hot pressing and is not easy to break, thereby ensuring that the seed crystal is firmly bonded.

[0029] According to some embodiments of the present invention, the pressure of the first hot pressing is 500N to 5000N.

[0030] Preferably, the pressure of the first hot pressing is 1000N to 3000N.

[0031] According to some embodiments of the present invention, the temperature of the first hot pressing is increased from room temperature to 500° C. at a heating rate of 1° C. / min to 10° C. / min.

[0032] Preferably, during the heating process, when the temperature reaches 100° C., 200° C., 300° C., 400° C. and 500° C., the temperature is maintained for 0.5 hour to 1 hour respectively.

[0033] In the method of the present invention, heat preservation at different temperature points is beneficial to discharge bubbles introduced during bonding between the seed crystal and the graphite paper.

[0034] According to some embodiments of the present invention, the pressure of the second hot pressing is 500N to 5000N.

[0035] Preferably, the pressure of the second hot pressing is 1000N to 3000N.

[0036] According to some embodiments of the present invention, the temperature of the second hot pressing is raised from room temperature to 500 °C at a heating rate of 1 °C / min to 10 °C / min.

[0037] Preferably, during the heating process, when the temperature reaches 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C, heat preservation is carried out for 0.5 hour to 1 hour respectively.

[0038] In the method of the present invention, by performing heat preservation at different temperature points, it is beneficial to discharge the air bubbles introduced during the bonding between the graphite paper and the seed crystal holder.

[0039] According to some embodiments of the present invention, the first cooling is carried out at a cooling rate of 1 °C / min to 5 °C / min to room temperature.

[0040] According to some embodiments of the present invention, the second cooling is carried out at a cooling rate of 1 °C / min to 5 °C / min to room temperature.

[0041] In the method of the present invention, slow cooling at a cooling rate of 1 °C / min to 5 °C / min is beneficial to release thermal stress.

[0042] According to some embodiments of the present invention, the material of the seed crystal holder is a high melting point material with a melting point above 2000 °C.

[0043] Preferably, the material of the seed crystal holder is graphite, tantalum carbide, or tungsten.

[0044] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0045] The method of the present invention performs two hot pressings to bond the graphite paper and the seed crystal, and bond the graphite paper and the seed crystal holder respectively, so that the fitting between the graphite paper and the seed crystal, and the fitting between the graphite paper and the seed crystal holder are tighter, and the thermal stress is smaller.

[0046] The method of the present invention is simple to operate, low in cost, good in bonding quality, the seed crystal does not fall off at a high temperature of 2000 °C, and there are no air bubbles on the back of the seed crystal.

[0047] The method of the present invention effectively avoids the problem of uneven colloidal coating caused by the increase in the size of the seed crystal, and also avoids the formation of air bubbles between the seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder due to the heat shrinkage of the colloid and the outgassing at high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings, wherein:

[0049] Figure 1Schematic diagram of the seed crystal bonded by using the method of the present invention; wherein: 1-seed crystal; 2-first non-high-temperature-resistant organic self-adhesive film; 3-graphite paper; 4-second non-high-temperature-resistant organic self-adhesive film; 5-seed crystal holder.

[0050] Figure 2 Shows the bonded seed crystal in Example 1 of the present invention.

[0051] Figure 3 Shows the bonded seed crystal in Example 2 of the present invention.

[0052] Figure 4 Shows the bonded seed crystal in Example 3 of the present invention.

[0053] Figure 5 Shows the bonded seed crystal in Example 4 of the present invention.

[0054] Figure 6 Shows the bonded seed crystal in Comparative Example 1 of the present invention.

[0055] Figure 7 Shows the bonded seed crystal in Comparative Example 2 of the present invention.

[0056] Figure 8 Shows the bonded seed crystal in Comparative Example 3 of the present invention. Detailed implementation manners

[0057] The present invention will be further described in detail below in conjunction with the detailed implementation manners. The examples given are only for clarifying the present invention, rather than limiting the scope of the present invention.

[0058] Example 1

[0059] This example provides a method for bonding a seed crystal for the growth of aluminum nitride single crystal or silicon carbide single crystal. For the schematic diagram of the structure of the bonded seed crystal, see Figure 1 . The seed crystal in this example is a 4-inch silicon carbide seed crystal, the non-high-temperature-resistant organic self-adhesive film is polyethylene (PE) with a thickness of 1 μm, and the thickness of the graphite paper is 0.1 mm.

[0060] The method for bonding the 4-inch silicon carbide seed crystal in this example includes the following steps:

[0061] (1) Lay a layer of polyethylene (PE) self-adhesive film between the 4-inch silicon carbide seed crystal and the graphite paper;

[0062] (2) Perform hot pressing on the seed crystal and the graphite paper, the pressure is 500 N, heat from room temperature to 500 °C, the heating rate is 1 °C / min, and keep warm for 0.5 h at the temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool down to room temperature, and the cooling rate is 1 °C / min;

[0063] (3) Lay a layer of polyethylene (PE) self-adhesive film flat on the seed crystal holder, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (self-adhesive film facing up);

[0064] (4) Apply hot pressing again, with a pressure of 500 N, heat from room temperature to 500 °C at a heating rate of 1 °C / min, and hold for 0.5 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; Slowly cool down to room temperature at a cooling rate of 1 °C / min.

[0065] After hot pressing and carbonization of the self-adhesive film, a bonding layer is formed between the 4-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, firmly bonding the seed crystal and the graphite paper, and the graphite paper and the seed crystal holder together, and the 4-inch silicon carbide seed crystal is successfully bonded. The bonding effect is as Figure 2 shown. It can be seen from Figure 2 that the fit between the graphite paper and the seed crystal and the fit between the seed crystal and the seed crystal holder are very tight, without bubbles, and the color is uniform.

[0066] Example 2

[0067] Similar to the seed crystal bonding process in Example 1, in Example 2, the size of the SiC seed crystal, the composition of the non-high-temperature-resistant organic self-adhesive film, the thickness of the graphite paper, the magnitude of the hot pressing pressure, the heating rate, and the holding time at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C have all changed.

[0068] The seed crystal bonding method in Example 2 includes the following steps:

[0069] (1) Lay a layer of polypropylene (PP) self-adhesive film flat between the 6-inch silicon carbide seed crystal and the graphite paper with a thickness of 0.2 mm;

[0070] (2) Apply hot pressing to the seed crystal and the graphite paper, with a pressure of 1000 N, heat from room temperature to 500 °C at a heating rate of 2 °C / min, and hold for 1 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; Slowly cool down to room temperature at a cooling rate of 1 °C / min;

[0071] (3) Lay a layer of polypropylene (PP) self-adhesive film flat on the seed crystal holder, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (self-adhesive film facing up);

[0072] (4) Apply hot pressing again, with a pressure of 1000 N, heat from room temperature to 500 °C at a heating rate of 2 °C / min, and hold for 1 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; Slowly cool down to room temperature at a cooling rate of 1 °C / min.

[0073] After hot pressing and carbonization, an adhesive layer is formed between the 6-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, firmly bonding the seed crystal to the graphite paper and the graphite paper to the seed crystal holder. The 6-inch silicon carbide seed crystal is successfully bonded. The bonding effect is as shown in Figure 3 shown. It can be seen from Figure 3 that the fit between the graphite paper and the seed crystal and the fit between the seed crystal and the seed crystal holder are very tight, without bubbles, and the color is uniform.

[0074] Example 3

[0075] Similar to the seed crystal bonding process in Example 1, in Example 3, the size of the SiC seed crystal, the composition of the non-high-temperature-resistant organic self-adhesive film, the thickness of the graphite paper, the magnitude of the hot pressing pressure, the heating rate, and the holding time at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C are all changed.

[0076] The seed crystal bonding method in Example 3 includes the following steps:

[0077] (1) Lay a layer of polyethylene terephthalate (PET) self-adhesive film with a thickness of 30 μm between the 8-inch silicon carbide seed crystal and the graphite paper with a thickness of 0.3 mm;

[0078] (2) Hot press the seed crystal and the graphite paper, with a pressure magnitude of 2000 N, heat from room temperature to 500 °C, with a heating rate of 5 °C / min, and hold for 0.8 h at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool down to room temperature, with a cooling rate of 1 °C / min;

[0079] (3) Lay a layer of polyethylene terephthalate (PET) self-adhesive film with a thickness of 30 μm on the seed crystal holder, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (self-adhesive film facing up);

[0080] (4) Hot press again, with a pressure magnitude of 2000 N, heat from room temperature to 500 °C, with a heating rate of 5 °C / min, and hold for 0.8 h at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool down to room temperature, with a cooling rate of 1 °C / min.

[0081] After hot pressing and carbonization, an adhesive layer is formed between the 8-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, firmly bonding the seed crystal to the graphite paper and the graphite paper to the seed crystal holder. The 8-inch silicon carbide seed crystal is successfully bonded. The bonding effect is as shown in Figure 4 shown. It can be seen from Figure 4 that the fit between the graphite paper and the seed crystal and the fit between the seed crystal and the seed crystal holder are very tight, without bubbles, and the color is uniform.

[0082] Example 4

[0083] Similar to the seed crystal bonding process in Example 1, in Example 4, the seed crystal is a 2-inch AlN seed crystal, and the composition of the non-high-temperature-resistant organic self-adhesive film, the thickness of the graphite paper, the magnitude of the hot pressing pressure, the heating rate, the holding time at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C, and the cooling rate have all changed.

[0084] The seed crystal bonding method in Example 4 includes the following steps:

[0085] (1) Lay a 100-μm-thick polyvinylidene fluoride (PVDF) self-adhesive film flat between the 2-inch AlN seed crystal and the 1-mm-thick graphite paper;

[0086] (2) Perform hot pressing on the seed crystal and the graphite paper, with a pressure magnitude of 500 N, heat from room temperature to 500 °C, a heating rate of 10 °C / min, hold for 0.6 h at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool to room temperature, with a cooling rate of 5 °C / min;

[0087] (3) Lay a layer of polyvinylidene fluoride (PVDF) self-adhesive film flat on the seed crystal holder, and then place the previously graphite paper-bonded seed crystal (graphite paper facing down) on the seed crystal holder (self-adhesive film facing up);

[0088] (4) Perform hot pressing again, with a pressure magnitude of 500 N, heat from room temperature to 500 °C, a heating rate of 10 °C / min, hold for 0.6 h at each temperature point of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool to room temperature, with a cooling rate of 5 °C / min.

[0089] After the self-adhesive film is hot-pressed and carbonized, a bonding layer is formed between the 2-inch aluminum nitride seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, firmly bonding the seed crystal and the graphite paper, and the graphite paper and the seed crystal holder together. The 2-inch aluminum nitride seed crystal is successfully bonded. The bonding effect is as Figure 5 shown. It can be Figure 5 seen that the fit between the graphite paper and the seed crystal and the fit between the seed crystal and the seed crystal holder are very tight, without bubbles, and the color is uniform.

[0090] Comparative Example 1

[0091] Similar to the seed crystal bonding process in Example 3, in Comparative Example 1, the two hot pressings are changed to one hot pressing. The seed crystal bonding method in Comparative Example 1 includes the following steps:

[0092] (1) Lay a 30-μm-thick polyethylene terephthalate (PET) self-adhesive film flat between an 8-inch silicon carbide seed crystal and a 0.3-mm-thick graphite paper.

[0093] (2) Lay a 30-μm-thick polyethylene terephthalate (PET) self-adhesive film flat on the seed crystal holder, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (self-adhesive film facing up).

[0094] (4) Hot press with a pressure of 2000 N. Heat from room temperature to 500 °C at a heating rate of 5 °C / min, and hold for 0.8 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Slowly cool down to room temperature at a cooling rate of 1 °C / min.

[0095] After the self-adhesive film is hot-pressed and carbonized, a bonding layer is formed between the 8-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, bonding the seed crystal and the graphite paper, and the graphite paper and the seed crystal holder together. The bonding effect of the 8-inch silicon carbide seed crystal is as Figure 6 shown. Since only one hot press is performed and the two adhesive films are carbonized simultaneously during the hot press, compared with two hot presses, the deformation caused by carbonization increases, resulting in uneven pressure and thus introducing air bubbles.

[0096] Comparative Example 2

[0097] Similar to the seed crystal bonding process in Example 3, in Comparative Example 2, the self-adhesive film becomes a 914B glue (epoxy resin glue) film. The seed crystal bonding method in Comparative Example 2 includes the following steps: (1) Uniformly coat the non-growth surface of an 8-inch silicon carbide seed crystal with 914B glue, and attach a 0.3-mm-thick graphite paper to the glue film.

[0098] (2) Hot press the seed crystal and the graphite paper with a pressure of 2000 N. Heat from room temperature to 500 °C at a heating rate of 5 °C / min, and hold for 0.8 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Slowly cool down to room temperature at a cooling rate of 1 °C / min;

[0099] (3) Uniformly coat the seed crystal holder with 914B glue, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (914B glue facing up).

[0100] (4) Hot press again with a pressure of 2000 N. Heat from room temperature to 500 °C at a heating rate of 5 °C / min, and hold for 0.8 h at temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Slowly cool down to room temperature at a cooling rate of 1 °C / min.

[0101] After hot pressing and carbonization of the 914B glue, a bonding layer is formed between the 8-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, bonding the seed crystal and the graphite paper, and the graphite paper and the seed crystal holder together. The bonding effect is as Figure 7 shown. Since the 914B glue has the properties of flowing and outgassing at high temperatures, the glue film is uneven, introducing air bubbles.

[0102] Comparative Example 3

[0103] Similar to the seed crystal bonding process in Comparative Example 2, in Comparative Example 3, the 914B glue film is pre-baked. The seed crystal bonding method in Comparative Example 3 includes the following steps:

[0104] (1) Uniformly coat the 914B glue on the non-growth surface of the 8-inch silicon carbide seed crystal, heat the glue film to 50 °C and keep it warm for 30 min, and attach the graphite paper with a thickness of 0.3 mm to the glue film;

[0105] (2) Hot press the seed crystal and the graphite paper, with a pressure of 2000 N, heat from room temperature to 500 °C, and the heating rate is 5 °C / min. Keep it warm for 0.8 h at the temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool down to room temperature, and the cooling rate is 1 °C / min;

[0106] (3) Uniformly coat the 914B glue on the seed crystal holder, heat the glue film to 50 °C and keep it warm for 30 min, and then place the aforementioned seed crystal with the graphite paper attached (graphite paper facing down) on the seed crystal holder (914B glue facing up);

[0107] (4) Hot press again, with a pressure of 2000 N, heat from room temperature to 500 °C, and the heating rate is 5 °C / min. Keep it warm for 0.8 h at the temperature points of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C; slowly cool down to room temperature, and the cooling rate is 1 °C / min.

[0108] After hot pressing and carbonization of the 914B glue, a bonding layer is formed between the 8-inch silicon carbide seed crystal and the graphite paper, and between the graphite paper and the seed crystal holder, bonding the seed crystal and the graphite paper, and the graphite paper and the seed crystal holder together. The bonding effect is as Figure 8 shown. Even though the 914B glue has been pre-baked, since the 914B glue still has the properties of flowing and outgassing at high temperatures above 200 °C, the glue film is uneven, introducing air bubbles.

[0109] The above are only several exemplary embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any equivalent or equivalent embodiments obtained by making some changes or modifications using the disclosed technical content by any person skilled in the relevant art within the scope of the technical solution of the present invention fall within the scope of the present invention.

Claims

1. A seed crystal bonding method, which comprises the following steps: (1) Set a first non-high-temperature-resistant organic self-adhesive film between the non-growth surface of the seed crystal and the graphite paper; (2) Conduct the first hot pressing to bond the graphite paper to the non-growth surface of the seed crystal, thereby forming a graphite layer on the seed crystal, and then conduct the first temperature reduction; (3) Lay a second non-high-temperature-resistant organic self-adhesive film on the seed crystal holder, and place the seed crystal on the seed crystal holder in a manner that the graphite layer is in contact with the second non-high-temperature-resistant organic self-adhesive film; (4) Conduct the second hot pressing to bond the seed crystal to the seed crystal holder, and then conduct the second temperature reduction.

2. The seed crystal bonding method according to claim 1, wherein, The seed crystal is a silicon carbide seed crystal or an aluminum nitride seed crystal; Preferably, the size of the seed crystal is 2 inches to 12 inches; more preferably, the size of the seed crystal is 4 inches to 8 inches.

3. The seed crystal bonding method according to claim 1, wherein, The highest heat-resistant temperature of the first non-high-temperature-resistant organic self-adhesive film is not higher than 400 °C; Preferably, the first non-high-temperature-resistant organic self-adhesive film is an organic polymer thin film; More preferably, the first non-high-temperature-resistant organic self-adhesive film is selected from one of polyethylene thin film, polypropylene thin film, polyvinyl chloride thin film, polyethylene terephthalate thin film, polyvinylidene fluoride thin film, polysulfone thin film, and polytetrafluoroethylene thin film.

4. The seed crystal bonding method according to claim 1, wherein, The highest heat-resistant temperature of the second non-high-temperature-resistant organic self-adhesive film is not higher than 400 °C; Preferably, the second non-high-temperature-resistant organic self-adhesive film is an organic polymer thin film; More preferably, the second non-high-temperature-resistant organic self-adhesive film is selected from one of polyethylene thin film, polypropylene thin film, polyvinyl chloride thin film, polyethylene terephthalate thin film, polyvinylidene fluoride thin film, polysulfone thin film, and polytetrafluoroethylene thin film.

5. The seed crystal bonding method according to claim 1, wherein, The thickness of the first non-high-temperature-resistant organic self-adhesive film is 1 μm to 100 μm, preferably 20 μm to 50 μm; The thickness of the second non-high-temperature-resistant organic self-adhesive film is 1 μm to 100 μm, preferably 20 μm to 50 μm; The thickness of the graphite paper is 0.05 mm to 1 mm, preferably 0.3 mm to 0.5 mm.

6. The seed crystal bonding method according to claim 1, wherein, The pressure of the first hot pressing is 500 N to 5000 N, preferably 1000 N to 3000 N; The temperature of the first hot pressing is raised from room temperature to 500 °C at a heating rate of 1 °C / min to 10 °C / min; preferably, during the heating process, when the temperature reaches 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C, it is respectively kept warm for 0.5 hour to 1 hour.

7. The seed crystal bonding method according to claim 1, wherein, The pressure of the second hot pressing is 500 N to 5000 N, preferably 1000 N to 3000 N; The temperature of the second hot pressing is raised from room temperature to 500 °C at a heating rate of 1 °C / min to 10 °C / min; preferably, during the heating process, when the temperature reaches 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C, it is respectively kept warm for 0.5 hour to 1 hour.

8. The seed crystal bonding method according to claim 1, wherein, The first temperature reduction is to reduce the temperature to room temperature at a cooling rate of 1 °C / min to 5 °C / min; The second temperature reduction is to reduce the temperature to room temperature at a cooling rate of 1 °C / min to 5 °C / min.

9. The seed crystal bonding method according to claim 1, wherein, The material of the seed crystal holder is a high melting point material with a melting point above 2000 °C; preferably, the material of the seed crystal holder is graphite, tantalum carbide or tungsten.

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