A seed crystal holder and a method for growing silicon carbide single crystal

Abstract

The present application provides a seed crystal holder and a method for growing a silicon carbide single crystal, wherein a heat-conducting layer is provided in the central region of the seed crystal holder base, and the thermal conductivity of the heat-conducting layer is greater than the thermal conductivity of the seed crystal holder base. When the SiC seed crystal is bonded to the seed crystal holder for single crystal growth, since the thermal conductivity of the heat-conducting layer in the central region of the seed crystal holder is greater than that of the graphite seed crystal holder base, the surface temperature of the seed crystal corresponding to the central region is lower than that of other regions of the seed crystal, and the corresponding growth component concentration is high and the supersaturation is large. When the supersaturation reaches the critical supersaturation, nucleation begins, while the temperature of other regions on the surface of the seed crystal is relatively high and has not reached the critical supersaturation, and spontaneous nucleation is impossible. In this way, the crystal nucleus formed in the above-mentioned central region can be used as the center for slow growth, and the central crystal nucleus advantage can be established, thereby obtaining a silicon carbide single crystal. The present application utilizes the above-mentioned heat-conducting layer to modulate the surface temperature field of the seed crystal, thereby reducing the number of nucleations and improving the quality of the SiC crystal.

Description

Technical Field

[0001] The present disclosure relates to the technical field of silicon carbide crystal preparation, and in particular to a seed crystal holder and a silicon carbide single crystal growth method. Background Art

[0002] Silicon carbide (SiC) is the third generation wide bandgap semiconductor material developed after Si and GaAs. Due to its excellent physical and chemical properties such as large bandgap, high critical breakdown electric field strength, high thermal conductivity, and good chemical stability, the SiC single crystal material and device industry has become a strategic industry in the high-tech field, and has set off a climax in SiC device research worldwide. Among them, large-sized SiC wafers can effectively improve the preparation efficiency of SiC devices, greatly reduce the cost of SiC devices, and are more conducive to the promotion of the practicality of silicon carbide single crystals. For example, the widespread realization of 150mm diameter SiC substrates and future 200mm and 250mm substrates can significantly reduce the cost of SiC-based semiconductor devices.

[0003] At present, the most mature and effective method for growing large-sized bulk SiC single crystals is the physical vapor transport (PVT) method. Its basic principle is to heat SiC polycrystalline powder to a certain temperature or above, and the gas phase components of SiC polycrystalline powder after high-temperature sublimation are transported under the action of concentration gradient, and finally recrystallized on the surface of silicon carbide seed crystal with lower temperature to grow SiC single crystal. In the process of SiC single crystal growth, temperature field control and optimization are the key to growing high-quality crystals. For example, the evolution of crystal growth interface shape and the change of single crystal zone diameter are related to the temperature field of crystal growth. Further, since the convex or concave growth interface leads to step aggregation, stacking faults, polymorphic inclusions and other defects on the growth interface, it is generally believed that the nearly flat and slightly convex growth interface is the most conducive to high crystal quality. In addition, for SiC single crystal growth, it is most reasonable to have only one nucleation growth center, so that the step can be pushed to the edge without obstruction, and then stable growth can be carried out. However, there is often a phenomenon of multi-nuclear competition in the early stage of crystal growth. When one growth center annihilates another growth center or two growth centers meet, a large number of defects will be generated, such as small-angle grain boundaries, micropipes, dislocations and polymorphic inclusions. The reason for the multi-nuclear competition is that the temperature distribution on the surface of the seed crystal is uneven, resulting in uneven distribution of supersaturation of the growth components (Si, Si2C, SiC2, etc.) on the surface of the seed crystal. At low temperatures, the concentration of the growth components is high, the supersaturation is large, and there are a large number of dislocation outcrops on the surface of the seed crystal, which makes it easy for spontaneous nucleation to produce a large number of growth centers.

[0004] In summary, for the growth of large-sized SiC single crystals (diameter greater than 100mm), the requirements for the uniformity of the temperature field on the surface of the seed crystal are extremely high due to the greatly increased seed crystal area. However, in the actual crystal growth process, it is difficult to ensure the absolute uniformity of the temperature field within the large-sized seed crystal area. When there are multiple local low-temperature points on the surface temperature field of the seed crystal at the initial stage of growth, and when the supersaturation at this position reaches the critical value required for nucleation, a multi-nucleation phenomenon will occur, resulting in deterioration of the crystal quality. Therefore, in order to suppress the above-mentioned spontaneous nucleation growth phenomenon, establish the initial central facet nucleation center advantage, and ensure the growth of a single growth center of the single crystal, a large radial temperature gradient needs to be introduced, which is inconsistent with the nearly flat and slightly convex temperature field required for the growth of high-quality silicon carbide single crystals. In addition, for the growth of large-sized single crystals, a large radial temperature gradient will introduce considerable internal stress inside the single crystal, introduce a large number of dislocations, stacking faults and other defects in the crystal, and even directly cause the single crystal to crack directly. Summary of the invention

[0005] The embodiments of the present invention provide a seed crystal holder and a method for growing a silicon carbide single crystal to solve the problem of multi-nucleation phenomenon in single crystal growth in the prior art.

[0006] According to a first aspect of an embodiment of the present invention, a seed crystal holder is provided, the seed crystal holder comprising a seed crystal holder base made of graphite, wherein:

[0007] A heat-conducting layer is provided in the central area of ​​one side of the seed crystal support base for bonding the seed crystal, and the seed crystal is bonded to the heat-conducting layer and the seed crystal support base around the heat-conducting layer by an adhesive;

[0008] The thermal conductivity of the heat-conducting layer is greater than the thermal conductivity of the seed pad base.

[0009] Optionally, the area of ​​the heat-conducting layer accounts for 5% to 10% of the total area of ​​the seed crystal support base.

[0010] Optionally, the heat-conducting layer is a heat-conducting film structure provided on the surface of the seed crystal support base, and the heat-conducting film includes a single-layer film structure or a multi-layer film structure.

[0011] Optionally, a groove is provided in the central area of ​​one side of the seed crystal support base for bonding the seed crystal, and the heat conductive layer is filled in the groove.

[0012] Optionally, a through hole is opened in the central area of ​​the seed crystal support base, and the heat conductive layer is filled in the through hole.

[0013] Optionally, the surface of the heat conducting layer and the surface of the seed crystal support base are at the same level.

[0014] Optionally, the material used for the heat-conducting layer includes high-melting-point metal, carbide of high-melting-point metal or nitride of high-melting-point metal.

[0015] According to a second aspect of an embodiment of the present invention, another seed crystal holder is provided, the seed crystal holder comprising a seed crystal holder base made of graphite, wherein:

[0016] A heat-conducting layer is provided in the central area of ​​the back side of the seed crystal support base, and the front side of the seed crystal support base is used to bond the seed crystal by an adhesive;

[0017] The thermal conductivity of the heat-conducting layer is greater than the thermal conductivity of the seed pad base.

[0018] Optionally, the area of ​​the heat-conducting layer accounts for 5% to 10% of the total area of ​​the seed crystal support base.

[0019] According to a third aspect of an embodiment of the present invention, a method for growing a silicon carbide single crystal is provided. The method uses the seed crystal holder described in any one of the first aspect or the second aspect of the embodiment of the present invention. The method comprises the following steps:

[0020] Adhere the seed crystal to the seed crystal holder by using an adhesive;

[0021] The seed crystal holder bonded with the seed crystal is placed into a growth furnace and vacuumed;

[0022] The growth temperature is controlled at 2000-2100° C. and the temperature field is a nearly flat and slightly convex temperature field, so that the region of the seed crystal provided with the heat conducting layer undergoes nucleation, and the steps formed at the nucleation center of the seed crystal gradually expand outward until they extend to the edge of the seed crystal;

[0023] The temperature is increased and the pressure is decreased to grow, so that the silicon carbide single crystal grows and thickens until the thickness of the silicon carbide single crystal reaches a preset thickness.

[0024] As can be seen from the above embodiments, the seed crystal holder and the method for growing a silicon carbide single crystal provided in this embodiment provide a heat-conducting layer in the central area of ​​the seed crystal holder base. When the SiC seed crystal is bonded to the seed crystal holder for single crystal growth, the thermal conductivity of the heat-conducting layer in the central area of ​​the seed crystal holder is greater than that of the graphite seed crystal holder base. Therefore, the surface temperature of the seed crystal corresponding to the central area is lower than that of other areas of the seed crystal, and the corresponding growth component concentration is high and the supersaturation is large. When the supersaturation reaches the critical supersaturation, nucleation begins. However, other areas on the surface of the seed crystal have relatively high temperatures and low supersaturation, and have not yet reached the critical supersaturation, and cannot spontaneously nucleate. In this way, the crystal nucleus formed in the above central area can be used as the center for slow growth, and the central crystal nucleus advantage can be established. Then, the conditions can be changed for rapid growth to obtain a silicon carbide single crystal. By using the thermal conductive layer in the central area of ​​the seed crystal support base to modulate the surface temperature field of the seed crystal, the SiC single crystal can preferentially form a crystal nucleus in the center of the seed crystal under the condition of a radial temperature gradient close to zero. Therefore, it not only reduces the number of nucleations but also avoids the problem of large internal stress introduced into the single crystal by a large radial temperature gradient, thereby improving the quality of the SiC crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic diagram of the basic structure of a seed crystal holder provided in an embodiment of the present application;

[0028] Figure 2 for Figure 1 Schematic diagram of the upper surface structure of the seed crystal holder;

[0029] Figure 3 for Figure 1 Schematic diagram of the structure after the seed crystal holder is bonded with the silicon carbide seed crystal;

[0030] Figure 4 A schematic diagram of the basic structure of another seed crystal holder provided in an embodiment of the present application;

[0031] Figure 5 A schematic diagram of the basic structure of another seed crystal holder provided in an embodiment of the present application;

[0032] Figure 6A schematic diagram of the basic structure of another seed crystal holder provided in an embodiment of the present application after bonding a silicon carbide seed crystal;

[0033] Figure 7 A schematic flow chart of a method for growing a silicon carbide single crystal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, 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. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] In the prior art, there is a phenomenon of multi-nuclear competition in the early stage of silicon carbide single crystal growth, which leads to the generation of a large number of defects in the crystal, especially the growth of large-sized SiC single crystals (diameter greater than 100mm). However, in order to suppress multi-nuclear competition, the large radial temperature gradient growth method currently used will cause considerable internal stress inside the single crystal, introduce a large number of dislocations, stacking faults and other defects into the crystal, and even directly cause the single crystal to crack directly. This embodiment provides a seed crystal holder and a method for growing silicon carbide single crystals, which prepare high-quality large-diameter SiC crystals by controlling the nucleation process and the number of nuclei on the surface of the seed crystal.

[0036] Embodiment 1

[0037] Figure 1 A schematic diagram of the basic structure of a seed crystal holder provided in an embodiment of the present application. Figure 2 for Figure 1 Schematic diagram of the upper surface structure of the seed crystal holder. Figure 1 and 2 As shown, the seed crystal holder includes a seed crystal holder base 10 made of graphite, wherein a heat-conducting layer 20 is provided in the central area of ​​one side of the seed crystal holder base 10 for bonding the seed crystal, and specifically, the heat-conducting layer 20 is a heat-conducting film structure provided on the surface of the seed crystal holder base 10, and the heat-conducting film includes a single-layer film structure or a multi-layer film structure. At the same time, it is required that the heat-conducting layer 20 and the seed crystal holder base 10 have a certain difference in thermal conductivity, and the thermal conductivity of the heat-conducting layer 20 material is greater than the thermal conductivity of the seed crystal holder base 10.

[0038] The material of the heat-conducting layer 20 can be selected from high melting point metals, carbides of high melting point metals or nitrides of high melting point metals. The high melting point metals described in this embodiment can include high melting point metals such as tungsten, tantalum, niobium, iridium, and titanium. During production, the heat-conducting layer 20 can be formed on the upper surface of the seed crystal support base 10 by film-making methods such as sputtering and evaporation. In addition, when the heat-conducting layer 20 is a multi-layer film structure, each layer of the film can be made of the same or different materials.

[0039] Further, the area of ​​the heat-conducting layer 20 accounts for 5% to 10% of the total area of ​​the seed crystal support base 10, such as its diameter can be Φ20mm, preferably Φ10mm, more preferably Φ5mm or Φ2mm, etc. Because this example needs to perform SiC nucleation in the central area corresponding to the heat-conducting layer 20, theoretically, the smaller the area of ​​this area, the fewer the number of nuclei, and the easier it is to establish the advantage of a single nucleus. Therefore, according to experimental verification, this example sets the lower limit of the area of ​​the heat-conducting layer 20 to the total area of ​​the seed crystal support base 10 to 5%. However, if the area of ​​the central area is too small, it is not easy to establish the advantage of the central nucleus. Therefore, according to experimental verification, the lower limit of the area of ​​the heat-conducting layer 20 to the total area of ​​the seed crystal support base 10 is set to 5%.

[0040] Figure 3 for Figure 1 Schematic diagram of the structure after the seed crystal holder is bonded with the silicon carbide seed crystal. Figure 3 As shown in the figure, when in use, the seed crystal 40 is bonded to the heat conductive layer 20 and the surrounding seed crystal holder base 10 by the adhesive 30. Then, the seed crystal holder bonded with the seed crystal is placed in a SiC single crystal growth furnace to grow a SiC single crystal block on the seed crystal 40 by physical vapor transport.

[0041] Specifically, when the SiC seed crystal 40 is bonded to the seed crystal holder for SiC crystal growth, the thermal conductivity difference between the heat-conducting layer 20 in the center area of ​​the seed crystal holder and the surrounding graphite material is certain, and the thermal conductivity of the material is large and the heat dissipation is fast. Therefore, within a certain temperature and pressure range, the temperature of the center area of ​​the seed crystal surface is lower than that of other areas of the seed crystal, and the corresponding growth component concentration is high and the supersaturation is large. When its supersaturation concentration reaches the critical supersaturation, nucleation begins, while other areas of the seed crystal surface have relatively high temperatures and low supersaturation, and cannot reach the critical supersaturation, so spontaneous nucleation is impossible. It should be noted that the temperature range at this time should fall exactly within the temperature window where the 4H or 6H crystal form is stable, so as to ensure that the central nucleation is the desired crystal form nucleation, and there is no other heterogeneous phase nucleation to produce polymorphic inclusions. In specific implementation, medium-frequency induction heating and infrared pyrometer temperature measurement can be used to control the temperature measurement range within the temperature window where the desired crystal form is stable. Once the central area of ​​the seed crystal surface is nucleated, it grows slowly under this growth condition, allowing the step formed by the nucleation center of the seed crystal to gradually expand outward until it extends to the edge of the large-diameter seed crystal, establishing a central core advantage, wherein the growth rate can be controlled to be below 100μm / h, preferably below 50μm / h, and more preferably below 30μm / h. Finally, the crystal is thickened by increasing the temperature, reducing the pressure, and increasing the growth rate. When the crystal thickness reaches a preset value, the growth is terminated. Among them, the growth rate can be 300μm / h, 500μm / h, or even 1mm / h.

[0042] The seed crystal holder provided in this example utilizes the higher thermal conductivity of the material in the central region compared to the surrounding region to modulate the temperature field on the surface of the seed crystal, thereby enabling the SiC crystal to preferentially form nuclei at the center of the seed crystal under conditions of a radial temperature gradient close to zero (such as a nearly flat and slightly convex temperature field) and with a low nucleus formation density during crystal growth. The optimal situation is that only a single nucleus is formed, thereby avoiding a large number of defects such as small-angle grain boundaries, micropipes, dislocations, and polymorphic inclusions that are generated when multiple growth centers meet or annihilate in the prior art, and also avoiding the problem of large internal stresses introduced into the single crystal by large radial temperature gradients, thereby obtaining high-quality large-size silicon carbide single crystals.

[0043] The seed crystal tray provided in this example is not only applicable to the manufacture of 4H, 6H, and 15R crystal single crystals, but also applicable to n-type and semi-insulating single crystals. The diameter of the seed crystal tray in this embodiment can be 100 mm, 125 mm, 150 mm, 200 mm, or 250 mm, or even larger silicon carbide single crystals, and the larger the size of the single crystal, the more obvious the advantage.

[0044] Embodiment 2

[0045] Since the larger the surface area of ​​the heat conducting layer 20 on the seed crystal holder base 10 is, the more obvious the temperature field control effect on the seed crystal surface is, but the larger the area is, the more nucleation number in the corresponding area will increase. Therefore, based on the first embodiment, this embodiment also provides another seed crystal holder.

[0046] Figure 4 This is a basic structural diagram of another seed crystal holder provided in an embodiment of the present application. Figure 4 As shown, the seed crystal tray provided in this example includes a seed crystal tray base 10, and a groove is provided in the central area of ​​one side of the seed crystal tray base 10 for bonding the seed crystal, and the heat conductive layer 20 is filled in the groove. At the same time, it is required that the heat conductive layer 20 and the seed crystal tray base 10 have a certain difference in thermal conductivity, and the thermal conductivity of the heat conductive layer 20 material is greater than the thermal conductivity of the seed crystal tray base 10.

[0047] Furthermore, in order to ensure the number and quality of nuclei, in this embodiment, the area of ​​the heat conducting layer 20 accounts for 5% to 10% of the total area of ​​the seed crystal support base 10 .

[0048] In this example, the heat conducting layer 20 is embedded in the seed crystal support base 10, which can increase the surface area of ​​the heat conducting layer 20 on the one hand, and make the seed crystal support base 10 corresponding to the area thinner on the other hand, thereby increasing the heat conduction effect and thus achieving a better temperature field on the seed crystal surface.

[0049] Furthermore, in order to facilitate the bonding of the seed crystal to the seed crystal holder and prevent the problem of an air layer existing at the junction of the heat conductive layer 20 and the seed crystal holder base 10 in the surrounding area due to poor filling of the adhesive, the surface of the heat conductive layer 20 and the surface of the seed crystal holder base 10 are designed to be on the same horizontal plane in this embodiment, that is, the surface of the entire seed crystal holder is a flat surface.

[0050] Embodiment 3

[0051] In the above embodiment, the heat conducting layer 20 mainly dissipates heat through heat conduction with the surrounding crystal support base and adhesive to achieve the purpose of temperature field regulation. In order to make the heat conducting layer 20 have a more direct heat dissipation effect, the temperature difference at the center of the seed crystal surface is greater than that at other regions of the seed crystal. This embodiment further provides another seed crystal support based on the above embodiments 1 and 2.

[0052] Figure 5 This is a basic structural diagram of another seed crystal holder provided in the embodiment of the present application. Figure 5 As shown, the seed crystal tray provided in this example includes a seed crystal tray base 10, and a through hole is opened in the central area of ​​the seed crystal tray base 10, and the heat conductive layer 20 is filled in the through hole. At the same time, it is required that the heat conductive layer 20 and the seed crystal tray base 10 have a certain difference in thermal conductivity, and the thermal conductivity of the heat conductive layer 20 material is greater than the thermal conductivity of the seed crystal tray base 10.

[0053] Furthermore, to ensure the number and quality of nucleation, the area of ​​the heat-conducting layer 20 in this embodiment accounts for 5% to 10% of the total area of ​​the seed crystal holder base 10. In addition, in order to facilitate the bonding of the seed crystal to the seed crystal holder, the surface of the heat-conducting layer 20 and the surface of the seed crystal holder base 10 are designed to be at the same level, that is, the surface of the entire seed crystal holder is a flat surface.

[0054] In this embodiment, the heat conducting layer 20 is disposed in the through hole opened on the seed crystal support base 10, and the back surface thereof which is not in contact with the seed crystal can directly dissipate heat by convection with the surrounding air, thus having a more direct heat dissipation effect.

[0055] Embodiment 4

[0056] In the above embodiments, the heat conducting layer 20 is disposed in the seed crystal support base 10 for bonding the front side of the seed crystal. Of course, it can also be designed on the back side.

[0057] Figure 5 This is a basic structural diagram of another seed crystal holder provided in the embodiment of the present application. Figure 5 As shown, the seed crystal tray provided in this example includes a seed crystal tray base 10, a heat-conducting layer 20 is provided in the central area of ​​the back side of the seed crystal tray base 10, and the front side of the seed crystal tray base 10 is used to bond the seed crystal by an adhesive. At the same time, the heat-conducting layer 20 and the seed crystal tray base 10 have a certain difference in thermal conductivity, and the thermal conductivity of the heat-conducting layer 20 material is greater than the thermal conductivity of the seed crystal tray base 10.

[0058] In this way, the heat conductive layer 20 can make the temperature of the central area of ​​the seed crystal support base 10 lower than that of other areas, and further make the temperature of the central area of ​​the seed crystal surface lower than that of other areas of the seed crystal, thereby achieving the effect of temperature field regulation.

[0059] Of course, a groove may also be dug on the back side of the seed crystal support base 10 and the heat conducting layer 20 may be filled in the groove.

[0060] Furthermore, using the seed crystal holder provided in the above embodiment, this example also provides a method for growing a silicon carbide single crystal. Figure 7 The following is a schematic diagram of a process for growing a silicon carbide single crystal provided in an embodiment of the present application. Figure 7 As shown, the method specifically comprises the following steps:

[0061] Step S110: bonding the seed crystal to the seed crystal holder by using an adhesive.

[0062] The seed crystal holder comprises a seed crystal holder base made of graphite material, and a heat-conducting layer is arranged in the central area thereof, wherein the thermal conductivity of the heat-conducting layer material is greater than the thermal conductivity of the seed crystal holder base.

[0063] Step S120: placing the seed crystal holder bonded with the seed crystal into the growth furnace and evacuating the furnace.

[0064] Step S130: Control the growth temperature at 2000-2100° C. and the temperature field to be a nearly flat and slightly convex temperature field, so that the region of the seed crystal where the heat conductive layer is provided is nucleated, and the steps formed at the nucleation center of the seed crystal gradually expand outward until they extend to the edge of the seed crystal.

[0065] The growth pressure can be 200 mbar. By designing insulation, the growth temperature field is made into a nearly flat slightly convex temperature field. The center of the seed crystal is controlled for nucleation. The growth is slow for 10-20 hours, and the step formed by the nucleation center of the seed crystal is gradually expanded outward until it expands to the edge of the large-diameter seed crystal, thereby establishing a central core advantage.

[0066] Furthermore, before this step, the surface of the seed crystal may be etched to remove the stress damage layer.

[0067] Step S140: increasing the temperature and decreasing the pressure to grow the silicon carbide single crystal, until the thickness of the silicon carbide single crystal reaches a preset thickness.

[0068] By utilizing the above steps, under a nearly flat and slightly convex temperature field, the density of nucleation growth centers on the surface of large-sized seed crystals can be greatly reduced. The reduction in the density of growth centers means a reduction in the defect density, which avoids a large number of defects such as small-angle grain boundaries, micropipes, dislocations and polymorphic inclusions generated when multiple growth centers meet or annihilate, thereby helping to improve the quality of the crystal, thereby obtaining high-quality large-sized silicon carbide single crystals.

[0069] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device and system embodiments described above are merely schematic, in which the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative work.

[0070] The above is only a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for growing a silicon carbide single crystal, characterized in that: For growing a silicon carbide single crystal in a temperature field with a near-zero radial temperature gradient, the method comprising: Bonding the seed crystal to the seed crystal holder by means of an adhesive; The seed crystal holder bonded with the seed crystal is placed in a growth furnace and vacuumed; wherein the seed crystal holder comprises a seed crystal holder base made of graphite, a heat-conducting layer is provided in the central area of ​​one side of the seed crystal holder base for bonding the seed crystal, and the seed crystal is bonded to the heat-conducting layer and the seed crystal holder base around the heat-conducting layer by an adhesive; the thermal conductivity of the heat-conducting layer is greater than the thermal conductivity of the seed crystal holder base, and the area of ​​the heat-conducting layer accounts for 5% to 10% of the total area of ​​the seed crystal holder base, so that the surface area of ​​the seed crystal corresponding to the heat-conducting layer preferentially forms a crystal nucleus; The growth temperature is controlled at 2000-2100° C. and the temperature field is a nearly flat and slightly convex temperature field, so that the region corresponding to the heat conductive layer in the seed crystal undergoes nucleation, and the steps formed at the nucleation center of the seed crystal gradually expand outward until they extend to the edge of the seed crystal; The silicon carbide single crystal is grown by increasing the temperature and decreasing the pressure, so that the silicon carbide single crystal grows and thickens until the thickness of the silicon carbide single crystal reaches a preset thickness.

2. The method for growing a silicon carbide single crystal according to claim 1, characterized in that: The heat-conducting layer is a heat-conducting film structure arranged on the surface of the seed crystal support base, and the heat-conducting film includes a single-layer film structure or a multi-layer film structure.

3. The method for growing a silicon carbide single crystal according to claim 1, characterized in that: A groove is provided in the central area of ​​one side of the seed crystal support base for bonding the seed crystal, and the heat conductive layer is filled in the groove.

4. The method for growing a silicon carbide single crystal according to claim 1, characterized in that: A through hole is opened in the central area of ​​the seed crystal support base, and the heat conductive layer is filled in the through hole.

5. The method for growing a silicon carbide single crystal according to claim 3 or 4, characterized in that: The surface of the heat conducting layer and the surface of the seed crystal support base are at the same level.

6. The method for growing a silicon carbide single crystal according to claim 1, characterized in that: The material used for the heat-conducting layer includes high-melting-point metal, carbide of high-melting-point metal or nitride of high-melting-point metal.

7. A method for growing a silicon carbide single crystal, characterized in that: For growing a silicon carbide single crystal in a temperature field with a near-zero radial temperature gradient, the method comprising: Bonding the seed crystal to the seed crystal holder by means of an adhesive; The seed crystal holder bonded with the seed crystal is placed in a growth furnace and vacuumed; wherein the seed crystal holder comprises a seed crystal holder base made of graphite, a heat-conducting layer is provided in the central area of ​​the back side of the seed crystal holder base, and the front side of the seed crystal holder base is used to bond the seed crystal through an adhesive; the thermal conductivity of the heat-conducting layer is greater than the thermal conductivity of the seed crystal holder base, and the area of ​​the heat-conducting layer accounts for 5% to 10% of the total area of ​​the seed crystal holder base, so that the surface area of ​​the seed crystal corresponding to the heat-conducting layer preferentially forms a crystal nucleus; The growth temperature is controlled at 2000-2100° C. and the temperature field is a nearly flat and slightly convex temperature field, so that the region corresponding to the heat conductive layer in the seed crystal undergoes nucleation, and the steps formed at the nucleation center of the seed crystal gradually expand outward until they extend to the edge of the seed crystal; The temperature is increased and the pressure is decreased to grow, so that the silicon carbide single crystal grows and thickens until the thickness of the silicon carbide single crystal reaches a preset thickness.

Images