CN117587501A

CN117587501A - Seed crystal holder, preparation method thereof, crystal growth device and crystal growth method

Info

Publication number: CN117587501A
Application number: CN202311547649.0A
Authority: CN
Inventors: 邹兴; 万玉喜; 胡浩林; 曾威; 王晓萍
Original assignee: Shenzhen Pinghu Laboratory
Current assignee: Shenzhen Pinghu Laboratory
Priority date: 2023-11-15
Filing date: 2023-11-15
Publication date: 2024-02-23

Abstract

The present disclosure provides a seed crystal holder, a preparation method thereof, a crystal growth apparatus, and a crystal growth method, relates to the technical field of semiconductor chips, and aims to reduce dislocation density in silicon carbide single crystal materials. The seed crystal holder includes a seed crystal holder body and a plurality of filling portions. The first surface of seed crystal holds in palm the main part has seted up a plurality of recesses, and a plurality of recess intervals set up, and the first surface is used for setting up the seed crystal. The filling parts are correspondingly arranged in the grooves. The material of the filling part comprises a first material, the material of the seed crystal holder main body comprises a second material, and the heat conductivity coefficient of the first material is different from that of the second material. The seed crystal holder is applied to a crystal growing device so as to realize the growth of crystals.

Description

Seed crystal holder, preparation method thereof, crystal growth device and crystal growth method

Technical Field

The disclosure relates to the technical field of semiconductor chips, in particular to a seed crystal holder, a preparation method thereof, a crystal growth device and a crystal growth method.

Background

The silicon carbide single crystal material has wide forbidden band, high heat conductivity, high breakdown electric field and high electron saturation migration rate, is one of the most widely applied wide forbidden band semiconductor materials at present, and is a material with mature level in the current crystal growth technology and device manufacturing. Therefore, the high-frequency high-voltage power amplifier is widely applied to high-temperature, high-frequency, radiation-resistant and high-power devices.

At present, the silicon carbide single crystal material is mainly formed by adopting high-purity silicon carbide powder, and the silicon carbide crystal is obtained by high-temperature sublimation under the temperature condition of over 2000 ℃ by a physical vapor transport method (physical vapor transport process, PVT). In the silicon carbide single crystal material prepared by the above-described process, the dislocation density of the silicon carbide crystal is currently at a high level, so that it is necessary to reduce the dislocation density, particularly the density of threading dislocation (Threading screw dislocation, TSD), because threading dislocation belongs to threading dislocation, which can be inherited into the grown crystal by a seed crystal during crystal growth, which leads to an increase in leakage current of a device prepared using the crystal.

Disclosure of Invention

Embodiments of the present disclosure provide a seed holder, a method of manufacturing the seed holder, a crystal growth apparatus, and a crystal growth method, which aim to reduce dislocation density in a silicon carbide single crystal material.

In order to achieve the above object, the embodiments of the present disclosure adopt the following technical solutions:

in one aspect, a seed holder is provided. The seed crystal holder includes a seed crystal holder body and a plurality of filling portions. The first surface of seed crystal holds in palm the main part has seted up a plurality of recesses, and a plurality of recess intervals set up, and the first surface is used for setting up the seed crystal. The filling parts are correspondingly arranged in the grooves. The material of the filling part comprises a first material, the material of the seed crystal holder main body comprises a second material, and the heat conductivity coefficient of the first material is different from that of the second material.

In the seed crystal support provided by the embodiment of the disclosure, the heat conductivity coefficient of the first material is different from that of the second material, so that the heat conductivity of the filling part is different from that of the seed crystal support main body to a certain extent; thus, by modulating the shape and distribution of the plurality of filling portions and the heat conductive property of the first material, the temperature field of the surface of the seed crystal holder on which the seed crystal is arranged can be modulated, and thus, the temperature field of the seed crystal attached to the seed crystal holder can be modulated; in this way, after heat conduction, the temperature distribution (for example, radial temperature distribution) of the region of the growth surface (for example, C-plane of the seed crystal) of the silicon carbide crystal can be changed, a plurality of low-temperature regions are formed on the growth surface (for example, the growth surface of the silicon carbide crystal) of the seed crystal, the crystal is nucleated preferentially in the plurality of low-temperature regions simultaneously, and after nucleation, 0001-oriented crystal growth of a non-preferential growth region (for example, a region located between two low-temperature regions) is blocked by lateral growth perpendicular to the 0001 plane (for example, a plane parallel to and opposite to the C-plane) so that the crystal growth mode is changed, and the TSD density of the grown crystal is reduced. Meanwhile, through the arrangement, the temperature uniformity of the seed crystal holder can be improved, and sublimation of the material of the seed crystal from the back surface can be reduced. Moreover, through the arrangement, the structure and the internal stress of the seed crystal are not influenced, the process is simpler, the feasibility is higher, the prefabrication is convenient, and the large-scale production and popularization and application are facilitated.

In some embodiments, the thermal conductivity of the first material is less than the thermal conductivity of the second material, and the minimum dimension of the bottom surface of the recess has a value in the range of 10-100 μm.

In some embodiments, the thermal conductivity of the first material is greater than the thermal conductivity of the second material, and the minimum spacing between two adjacent grooves is in the range of 10-100 μm.

In some embodiments, the dimension of the recess in the second direction is in the range of 10-500 μm, the second direction being the thickness direction of the seed holder body.

In some embodiments, the plurality of grooves are uniformly distributed along the third direction on the seed holder body; the third direction is the direction in which the geometric center of the seed crystal holder body points to the boundary of the seed crystal holder body.

In some embodiments, the plurality of grooves are distributed on the seed holder body according to a predetermined pattern comprising: the distribution density of the grooves on the seed crystal holder main body is gradually reduced along the third direction; the third direction is the direction in which the geometric center of the seed crystal holder body points to the boundary of the seed crystal holder body.

In some embodiments, the plurality of grooves is divided into a plurality of groove sets, the groove sets including at least one groove. In the case where the groove set includes one groove, the groove is located at the geometric center of the seed holder body. In the case where the groove group includes a plurality of grooves, the plurality of grooves included in the groove group encircle the geometric center of the seed holder body. In the third direction, a first interval is arranged between every two adjacent groove groups. The first intervals are equal; alternatively, the plurality of first intervals are gradually increased in the third direction; the third direction is the direction in which the geometric center of the seed crystal holder body points to the boundary of the seed crystal holder body.

In some embodiments, the ratio between the largest of the first intervals and the smallest of the first intervals is less than or equal to 3.

In some embodiments, a surface of the filling portion remote from the bottom surface of the recess is flush with the first surface; the flatness of the surface of the seed crystal support, on which the seed crystal is arranged, is less than or equal to 150 mu m.

In some embodiments, the first material comprises a combination of any one or more of tantalum, tantalum carbide, and silicon carbide; and/or the second material is graphite.

In some embodiments, the material forming the filler portion further comprises a modified epoxy.

In some embodiments, the mass ratio of the first material to the modified epoxy resin in the material forming the filler ranges from 3:1 to 5:1.

In another aspect, a method of making a seed holder is provided. The preparation method comprises the following steps: an initial seed holder body is provided. Forming a plurality of grooves on a first initial surface of an initial seed holder body; the grooves are arranged at intervals; the first initial surface of the initial seed holder body forms a first surface of the seed holder body, the first surface being for placement of a seed crystal. And filling the plurality of grooves to correspondingly form a plurality of filling parts. The material of the filling part comprises a first material, the material of the initial seed crystal holder main body comprises a second material, and the heat conductivity coefficient of the first material is different from that of the second material.

In some embodiments, the groove is a cylindrical groove; forming a plurality of grooves in a first initial surface of an initial seed holder body includes: and grooving a set area of the first initial surface by utilizing a laser process to form a plurality of grooves.

In some embodiments, the groove is a prismatic mesa groove; forming a plurality of grooves in a first initial surface of an initial seed holder body includes: and grooving a set area of the first initial surface by utilizing an etching process to form a plurality of grooves.

In yet another aspect, a crystal growth apparatus is provided. The crystal growth device comprises the seed crystal support, a crucible main body and a crucible cover arranged on the crucible main body, wherein the seed crystal support is connected to the inner surface of the crucible cover.

In yet another aspect, a method of crystal growth is provided. The crystal growth method is realized based on the crystal growth device.

In some embodiments, the crystal growth method, the crystal growth process comprises: in the first growth stage, nucleating growth is carried out to form crystal nuclei; the growth temperature in the first growth stage is 2150 ℃, and the heat preservation time is 8-12 h. In the second growth stage, continuing the growth of the crystal to form a crystal growth body; the growth temperature in the second growth stage is 2280-2380 deg.C, and the pressure of the growth environment is 400-800 Pa.

It can be appreciated that, the preparation method, the crystal growth apparatus and the crystal growth method of the seed crystal holder provided in the foregoing embodiments of the present disclosure may refer to the beneficial effects of the seed crystal holder described above, and are not described herein.

Drawings

In order to more clearly illustrate the technical solutions of the present disclosure, the drawings that need to be used in some embodiments of the present disclosure will be briefly described below, and it is apparent that the drawings in the following description are only drawings of some embodiments of the present disclosure, and other drawings may be obtained according to these drawings to those of ordinary skill in the art. Furthermore, the drawings in the following description may be regarded as schematic diagrams, not limiting the actual size of the products, the actual flow of the methods, the actual timing of the signals, etc. according to the embodiments of the present disclosure.

FIG. 1 is a schematic structural view of a crystal growth apparatus according to some embodiments;

FIG. 2 is a schematic diagram of a structure of a seed holder according to some embodiments;

FIG. 3 is a schematic view of a structure of a seed holder according to further embodiments;

FIG. 4 is a schematic view of a structure of a seed crystal according to still other embodiments;

FIG. 5 is a schematic view of a structure of a seed crystal according to still other embodiments;

FIG. 6 is a schematic view of a structure of a seed holder according to further embodiments;

FIG. 7 is a schematic view of a structure of a seed holder according to further embodiments;

FIG. 8 is a schematic view of a structure of a seed holder according to further embodiments;

FIG. 9 is a flow chart of a method of preparing a seed holder according to some embodiments;

FIG. 10 is a schematic diagram showing steps S2 in a method of preparing a seed holder according to some embodiments;

FIG. 11 is a schematic structural view of a crystal growing apparatus according to still other embodiments;

FIG. 12 is a flow diagram of a crystal growth method according to some embodiments;

FIG. 13 is a schematic diagram of a structure for forming a crystal growth in a crystal growth method according to some embodiments;

fig. 14 is a metallographic micrograph of a crystal growth according to some embodiments.

Detailed Description

The following description of the embodiments of the present disclosure will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by one of ordinary skill in the art based on the embodiments provided by the present disclosure are within the scope of the present disclosure.

In the description of the present disclosure, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present disclosure and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present disclosure.

Throughout the specification and claims, the term "comprising" is to be interpreted as an open, inclusive meaning, i.e. "comprising, but not limited to, unless the context requires otherwise. In the description of the present specification, the terms "one embodiment," "some embodiments," "example embodiments," "exemplary," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with the embodiment or example is included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The terms "first" and "second" are used below for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present disclosure, unless otherwise indicated, the meaning of "a plurality" is two or more.

At least one of "A, B and C" has the same meaning as at least one of "A, B or C," both include the following combinations of A, B and C: a alone, B alone, C alone, a combination of a and B, a combination of a and C, a combination of B and C, and a combination of A, B and C. "A and/or B" includes the following three combinations: only a, only B, and combinations of a and B.

In addition, the use of "based on" is intended to be open and inclusive in that a process, step, calculation, or other action "based on" one or more of the stated conditions or values may be based on additional conditions or beyond the stated values in practice.

As used herein, "about," "approximately" or "approximately" includes the stated values as well as average values within an acceptable deviation range of the particular values as determined by one of ordinary skill in the art in view of the measurement in question and the errors associated with the measurement of the particular quantity (i.e., limitations of the measurement system).

Exemplary embodiments are described herein with reference to cross-sectional and/or plan views as idealized exemplary figures. In the drawings, the thickness of layers and regions are exaggerated for clarity. Thus, variations from the shape of the drawings due to, for example, manufacturing techniques and/or tolerances, are to be expected. Thus, the exemplary embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments.

As used herein, the term "substrate" refers to a material to which subsequent layers of material may be added. The substrate itself may be patterned. The material added to the substrate may be patterned or may remain unpatterned. In addition, the substrate may include a variety of semiconductor materials such as silicon, germanium, gallium arsenide, indium phosphide, and the like. Alternatively, the substrate may be made of a non-conductive material such as glass, plastic, or sapphire wafer.

Technical terms in the embodiments of the present application are described below:

hexagonal (hexagonal) crystal system refers to crystal attribution in which a characteristic symmetry element of a six-axis or six-axis counter axis exists in the main axis direction of the c-axis having only a higher-order axis. Hexagonal systems, also known as "hexagons", belong to the medium-grade family of crystals. The crystal plane index and the crystal orientation index are usually calibrated by using four crystal axes of a1, a2, a3 and c in the hexagonal system to reflect the crystal orientation and crystal plane of the hexagonal system atoms. The crystal orientation refers to the direction of a dot array in the space lattice (the direction of a straight line connecting any node column in the lattice). The crystal orientation in a hexagonal system is used to denote certain directions in the crystal, involving the position of atoms in the crystal, the direction of the array of atoms, identifying the orientation of a set of straight lines that are parallel to each other, with the directions being identical. The crystal plane refers to a plane passing through any lattice point in the spatial lattice (a plane constituted by nodes in the lattice). The crystal plane in the hexagonal system is used to represent the plane formed by atoms in the crystal.

Note that, in the drawing, "a to B" means that the structure/region a belongs to the structure/region B, that is, the structure referred to by the reference numeral is both the structure a and the structure B, for example, "51 to 50" in fig. 11 means that the structure referred to by the reference numeral is an induction heating coil, and the induction heating coil 51 belongs to the heating unit 50. The reference numerals of "A/B" appearing in the drawings refer to structures/regions A and structures/dimensions B that may be referred to by the same structures/dimensions, e.g., "L1/L1" in FIG. 7 _min "means the minimum L1 of the first interval L1 and the first interval L1 _min May be referred to as this size.

As described in the background, silicon carbide single crystal materials are widely used in high temperature, high frequency, radiation resistant, high power devices. With the demand for enlarging the market scale and reducing the cost, it is currently an urgent need to produce silicon carbide crystals of large size and low defect density. Wherein the defect density of the silicon carbide crystal comprises dislocation defect density and micropipe defect density (Micropipe density, MPD); dislocation defect densities include screw dislocation (Threading screw dislocation, TSD) density, ductile dislocation (Threading edge dislocations, TED) density, and basal vector dislocation (Basal plane dislocations, BPD) density.

In the related art, when a silicon carbide single crystal is formed by a physical vapor transport method, as shown in fig. 1, an intermediate frequency electromagnetic induction heating mode is adopted; the crystal growth apparatus 100 used includes: a crucible 40, a seed holder 10 and an induction heating coil 51. Wherein the crucible 40 includes a crucible body 20 and a crucible cover 30; the seed holder 10 is attached to the inner surface of the crucible cover 30; seed crystal 60 is bonded to seed crystal holder 10; the induction heating coil 51 is wound around the outer peripheral wall of the crucible 40. The heating principle is that after the induction heating coil 51 coaxial with the crucible 40 is energized, an eddy current is generated on the surface of the crucible 40 due to the skin effect, thereby generating joule heat, and heat is supplied to the crystal growing apparatus 100, so that the raw material (for example, the silicon carbide micro powder K) is sublimated at a high temperature, and the sublimated raw material is crystallized on the surface of the seed crystal 60, thereby forming a silicon carbide single crystal.

In the above-mentioned technique, when the induction heating coil 51 provides heat, the temperature required for crystal growth is provided by adopting a peripheral heating mode, and the heat is transferred from outside to inside from the crucible wall, so that an axial temperature gradient is formed in the inner cavity of the crucible 40, and radial temperature gradients distributed along the radial direction of the seed crystal 60, which results in uneven temperature in the crucible 40, and a phenomenon that the temperature at the edge of the seed crystal 60 is higher than the temperature at the center of the seed crystal 60 occurs. In this case, the crystal growth will generally nucleate preferentially in the central region of the seed crystal 60, and defects inherited from the seed crystal 60 will generally extend into the growing crystal, resulting in a grown crystal having a higher dislocation defect density and a dislocation defect density higher than that of micropipe defects. In some examples, micropipe defect densities of less than 1e.a/cm have been achieved on 6 foot silicon carbide single crystals ² Even near zero micropipe defects; micropipe defect densities on 8 feet silicon carbide single crystals are also near the above level; while dislocation defect densities (including TSD density, BPD density, and TED density) are greater than 5000e.a/cm ² . Therefore, as described in the background, it is necessary to reduce the dislocation density, particularly the density of threading dislocations (Threading screw dislocation, TSD), to avoid leakage current in devices fabricated by growing crystals. In addition, since the edge temperature of the seed crystal 60 is higher than the temperature at the center of the seed crystal 60, uniformly distributed high temperature points are easily formed, so that the material of the seed crystal 60 is partially sublimated, the thickness of the seed crystal 60 is partially thinned, and even the melting phenomenon of the seed crystal 60 occurs.

Currently, the growth plane of silicon carbide crystals is mainly the 000-1 plane (which may be referred to as the carbon plane or the C plane). In some implementations, in order to reduce the dislocation density of the silicon carbide single crystal, crystal growth is attempted on different growth planes, for example, 11-20 planes, 1-100 planes, 0001 planes (which may also be referred to as Si planes), etc., which, although giving some crystals with lower TSD density, have adverse effects such as complicated process, higher Stacking Fault (SF), etc.

In still other implementations, as shown in FIG. 4, the axial temperature gradient of the surface of the seed crystal 60 during crystal growth is changed by grooving the back surface 60b of the seed crystal 60 (i.e., the surface opposite the growth surface 60 a) and filling the grooves with a material having a thermal conductivity different from that of silicon carbide, or plating the back surface 60b of the seed crystal 60 directly with a thin film made of a material having a thermal conductivity different from that of silicon carbide; thus, the back surface 60b of the seed crystal 60 has two substances with different heat conductivity coefficients, so that heat dissipation is uneven, and meanwhile, the temperature field on the surface of the seed crystal 60 is unevenly distributed. Therefore, the periodic distribution of two materials with different heat conductivity coefficients positioned at the back of the seed crystal 60 can be utilized to modulate the temperature field distribution of the surface of the seed crystal 60 in the process of growing silicon carbide (SiC) by a physical vapor transport method, so as to force the preferential nucleation in a lower temperature area corresponding to a predefined pattern, select the preferential growth according to the predefined pattern, and then perform lateral growth, thereby achieving the purpose of reducing the threading dislocation density. However, in this implementation, since a groove is formed on the back surface of the seed crystal 60 or a thin film is coated, there is a problem in that the structure and the processing of the seed crystal 60 are complicated.

In other implementations, as shown in FIG. 5, the growth surface 60a of the seed crystal 60 is patterned by photoresist coating and plasma etching to provide a patterned substrate for growing crystals, which is then cleaned and transferred for crystal growth. By this arrangement, the radial temperature distribution of the seed crystal growth surface 60a can be modulated, so that the growth is preferentially started at the groove U during the crystal growth, and the defect growth direction is changed from parallel growth (i.e., longitudinal direction) to transverse growth in the groove U (i.e., the portion between the conical protrusions J), so as to achieve the purpose of reducing the crystal defect density.

Based thereon, as shown in fig. 2, some embodiments of the present disclosure provide a seed holder. The seed holder 10 includes a seed holder body 11 and a plurality of filling portions 12. The first surface 11a of the seed holder body 11 is provided with a plurality of grooves 13, the plurality of grooves 13 are arranged at intervals, and the first surface 11a is used for arranging the seed crystal 60. The filling parts 12 are correspondingly arranged in the grooves 13. The material of the filling portion 12 includes a first material, and the material of the seed holder body 11 includes a second material, where the thermal conductivity of the first material is different from the thermal conductivity of the second material.

The first surface 11a is used for disposing the seed crystal 60, that is, the seed crystal 60 is located on the first surface 11a, and a surface (for example, a Si surface) of the seed crystal 60, which is close to the first surface 11a, is attached to the first surface 11a, thereby realizing connection between the seed crystal 60 and the seed holder body 11. Here, the connection between the seed crystal 60 and the first surface 11a is not limited. For example, the seed crystal 60 may be bonded to the first surface 11a by an adhesive. When the first surface 11a of the seed holder body 11 is provided with the plurality of grooves 13, the surface shared by the seed holder body 11 and the grooves 13 is not the first surface 11a of the seed holder body 11.

The filling parts 12 are correspondingly arranged in the grooves 13. Here, as shown in fig. 2, the number of the filling portions 12 may be equal to the number of the grooves 13, and at this time, a plurality of filling portions 12 are provided in one-to-one correspondence in the plurality of grooves 13; alternatively, the number of the filling portions 12 may be smaller than the number of the grooves 13, and at this time, the filling portions 12 are provided in one-to-one correspondence in one part of the grooves 13, and the filling portions 12 are not provided in the other part of the grooves 13.

Here, the type of the second material is not limited, and is not limited as long as it satisfies the requirement that it can withstand the high-temperature environment at the time of forming the silicon carbide single crystal by the physical vapor transport method. For example, the second material may be graphite.

Here, the type of the first material is not limited, and is not limited as long as it satisfies the requirement that it is different from the second material and can withstand the high-temperature environment when the silicon carbide single crystal is formed by the physical vapor transport method.

As can be appreciated, as shown in fig. 2, when the thermal conductivity of the first material is different from that of the second material, the thermal conductivity of the filling portion 12 is different from that of the seed holder body 11 to some extent; meanwhile, since the first surface 11a of the seed holder body 11 and the surface 12a of the filling portion 12 away from the bottom surface 13a of the recess 13 together form the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed; thus, by modulating the shape, distribution and thermal conductivity of the first material of the plurality of filling portions 12, the temperature field of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed can be modulated, including not only the temperature field of the surface 12a of the filling portion 12 remote from the bottom surface 13a of the recess 13, but also the temperature field of the first surface 11a of the seed holder body 11, so that the temperature field of the seed crystal 60 attached to the seed holder 10 can be modulated; thus, after heat conduction, the temperature distribution (for example, radial temperature distribution) of the growth surface (for example, the C-surface 60a of the seed crystal 60) of the silicon carbide crystal can be changed, compared with the case that the edge temperature of the seed crystal 60 is higher than the temperature at the center of the seed crystal 60 in the related art, a plurality of low-temperature areas Q are formed on the growth surface 60a of the seed crystal 60 (namely, the growth surface of the silicon carbide crystal), so that the crystal is nucleated preferentially in the plurality of low-temperature areas Q at the same time, and after nucleation, according to the silicon carbide crystal growth step flow theory, the step surfaces of a plurality of nucleation centers are simultaneously spread outwards and finally connected into one piece, and in the process, TSD dislocation in the seed crystal 60 is converted into BPD dislocation or disappears due to the transverse growth of the crystal; that is, the TSD density of the grown crystal can be reduced by changing the crystal growth mode by blocking 0001-oriented crystal growth of a non-preferential growth region (e.g., region P located between two low temperature regions Q) by lateral growth perpendicular to the 0001 plane (i.e., perpendicular to the C plane 60 a). Here, 0001-direction crystal growth refers to crystal growth in the second direction Y in fig. 2.

Meanwhile, through the above arrangement, compared with the case of forming uniformly distributed high temperature points on the seed crystal 60 in the related art, the temperature uniformity of the seed crystal holder 10 can be improved, the number of the high temperature points is smaller, the temperature of the high temperature points is lower, and the sublimation of the material of the seed crystal 60 from the back surface can be reduced. Moreover, through the arrangement, compared with the situation that the structure and/or the processing mode of the seed crystal 60 are changed in some implementation modes, the seed crystal support main body 11 made of the second material (such as graphite) is used for grooving and filling, the structure and the internal stress of the seed crystal 60 are not affected, the process is simpler, the feasibility is higher, the prefabrication is convenient, and the large-scale production and popularization and application are facilitated.

It should be noted that, the relative magnitude relation between the thermal conductivity of the first material and the thermal conductivity of the second material is not limited herein.

In some examples, as shown in fig. 2, the thermal conductivity of the first material is greater than that of the second material, and at this time, the thermal conductivity of the first material is better than that of the second material, and the plurality of low temperature regions Q on the growth surface 60a of the seed crystal 60 correspond up and down to the filling portion 12 along the second direction Y. At this time, the first material may be silicon carbide. The second direction Y is the thickness direction of the seed holder body 11.

In other examples, as shown in fig. 3, the thermal conductivity of the first material is smaller than that of the second material, and at this time, the thermal conductivity of the second material is better than that of the first material, and the plurality of low temperature regions Q on the growth surface 60a of the seed crystal 60 correspond to a portion of the first surface 11a of the seed holder body 11 up and down along the second direction Y, i.e., do not correspond to the filling portion 12 up and down along the second direction Y. At this time, the first material may be tantalum or tantalum carbide.

In some embodiments, the thermal conductivity of the first material is smaller than that of the second material, and the minimum dimension of the bottom 13a of the groove 13 is in the range of 10-100 μm.

Here, the size of the bottom surface 13a of the groove 13 refers to the size of a line formed from one boundary point to the other boundary point of the bottom surface 13a of the groove 13 through the geometric center. The minimum dimension of the bottom face 13a of the groove 13 refers to the minimum of the plurality of dimensions of the bottom face 13a of the groove 13.

As described above, in the case where the thermal conductivity of the first material is smaller than that of the second material as shown in fig. 3, the plurality of low temperature regions Q on the growth surface 60a of the seed crystal 60 do not vertically correspond to the filling portion 12 in the second direction Y, so that the filling portion 12 vertically corresponds to a portion (for example, no position shown as P in fig. 3) of the region located between the low temperature regions Q in the second direction Y. Meanwhile, since the filling portion 12 is filled in the groove 13, the size of the groove 13 corresponds to the size of the filling portion 12. Thus, when the minimum dimension of the bottom surface 13a of the groove 13 is in the range of 10 to 100 μm, the distance between the adjacent two low temperature regions Q is small, and thus, after the nucleation of the crystal in the plurality of low temperature regions Q, the effect of blocking 0001-direction crystal growth of the non-preferential growth region by lateral growth is relatively good, and the TSD density of the grown crystal can be reduced.

Preferably, the minimum dimension of the bottom 13a of the recess 13 has a value ranging from 25 to 80 μm.

Illustratively, the minimum dimension of the bottom surface 13a of the groove 13 may be 10 μm, 25 μm, 30 μm, 50 μm, 70 μm, 80 μm, 85 μm, 100 μm, or the like.

In some embodiments, as shown in fig. 2 and 3, the thermal conductivity of the first material is greater than that of the second material, and the minimum distance L2 between two adjacent grooves 13 ranges from 10 μm to 100 μm.

Here, the distance between two adjacent grooves 13 refers to the dimension of a line formed on the reference plane from the boundary point of the first groove 13 to the boundary point of the second groove 13. The reference plane is parallel to the first surface 11a. The minimum pitch L2 between the adjacent two grooves 13 refers to the smallest one of the plurality of pitches between the adjacent two grooves 13.

As described above, as shown in fig. 2, when the thermal conductivity of the first material is greater than that of the second material, the plurality of low temperature regions Q on the growth surface 60a of the seed crystal 60 vertically correspond to the filling portions 12 in the second direction Y, and the regions between the adjacent two low temperature regions Q correspond to the regions between the filling portions 12. Meanwhile, since the filling portions 12 are filled in the grooves 13, the areas between the grooves 13 correspond to the areas between the filling portions 12. Thus, when the minimum distance L2 between the adjacent two grooves 13 is in the range of 10 to 100 μm, the distance between the adjacent two low temperature regions Q is small, and thus, after the nucleation of the crystal in the plurality of low temperature regions Q, the effect of blocking 0001-direction crystal growth of the non-preferential growth region by lateral growth is relatively good, and the TSD density of the grown crystal can be reduced.

Preferably, the minimum distance L2 between two adjacent grooves 13 is in the range of 25 to 80 μm.

Illustratively, the minimum spacing L2 between two adjacent grooves 13 may be 10 μm, 20 μm, 25 μm, 52 μm, 75 μm, 80 μm, 90 μm, 100 μm, or the like.

In some embodiments, as shown in fig. 2 and 3, the dimension H of the recess 13 in the second direction Y is in the range of 10 to 500 μm, and the second direction is the thickness direction of the seed holder body 11.

It will be appreciated that when the dimension H of the recess 13 in the second direction Y is in the range of 10 to 500 μm, the depth of the recess 13 is large, so that the height of the filling portion 12 filled in the recess 13 is high, and the filling amount of the first material located in the filling portion 12 can be made high, and thus the influence of the first material on the temperature field of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is large, and the effect of modulation can be made good when the temperature field of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is modulated by the plurality of filling portions 12.

Preferably, the dimension H of the recess 13 in the second direction Y has a value in the range of 100 to 300. Mu.m.

Illustratively, the dimension H of the groove 13 in the second direction Y may be 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, etc.

In some embodiments, as shown in fig. 2 and 3, the grooves 13 are cylindrical grooves or prismatic grooves. A dimension D1 of the opening 13b of the recess 13 in the first direction X is greater than or equal to a dimension D2 of the bottom surface 13a of the recess 13 in the first direction X; the first direction X is parallel to the first surface 11a.

Here, the first direction X may be any direction parallel to the first surface 11a as long as the dimension D1 of the opening 13b of the groove 13 and the dimension D2 of the bottom surface 13a of the groove 13 are satisfied, and the same first direction X is referred to.

In some examples, as shown in fig. 2, the grooves 13 are cylindrical grooves. The dimension D1 of the opening 13b of the recess 13 in the first direction X is equal to the dimension D2 of the bottom surface 13a of the recess 13 in the first direction X. At this time, the shape of the opening 13b of the groove 13 coincides with the shape of the bottom surface 13a of the groove 13, and in this case, the shape of the opening 13b of the groove 13 (i.e., the shape of the bottom surface 13a of the groove 13) is not limited here.

Illustratively, the opening 13b of the recess 13 may be circular, square, rectangular, triangular, hexagonal, or the like.

Illustratively, in the case where the shape of the opening 13b of the recess 13 is circular, the diameter of the circular shape has a value ranging from 5 to 500 μm, preferably, the diameter of the circular shape has a value ranging from 30 to 50 μm; for example, the diameter of the circle may be 5 μm, 15 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, or the like. In the case where the thermal conductivity of the first material is smaller than that of the second material, the diameter of the circle is the smallest dimension of the bottom 13a of the groove 13, and the preferred value range is 10 to 100 μm.

Illustratively, in the case where the shape of the opening 13b of the recess 13 is square, the side length of the square may be in the range of 10 to 300 μm, for example, the side length of the square may be 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, or the like. When the thermal conductivity of the first material is smaller than that of the second material, the side length of the square is preferably in the range of 10 to 100 μm because the side length of the square is equal to the minimum dimension of the bottom 13a of the groove 13.

Illustratively, in the case where the shape of the opening 13b of the recess 13 is rectangular, the longer side of the rectangle has a value ranging from 100 to 400 μm and the shorter side of the rectangle has a value ranging from 10 to 300 μm, for example, the longer side of the rectangle may have a length ranging from 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, or the like; the shorter sides of the rectangle may have a side length of 10 μm, 50 μm, 80 μm, 100 μm, 160 μm, 200 μm, 240 μm, 300 μm, etc. When the thermal conductivity of the first material is smaller than that of the second material, the side length of the shorter side of the rectangle is preferably in the range of 10 to 100 μm because the side length of the shorter side of the rectangle matches the minimum dimension of the bottom surface 13a of the groove 13.

In other examples, as shown in fig. 3, the grooves 13 are prismatic grooves. The opening 13b of the recess 13 is disposed parallel to and coaxial with the bottom surface 13a of the recess 13. The dimension D1 of the opening 13b of the recess 13 in the first direction X is larger than the dimension D2 of the bottom 13a of the recess 13 in the first direction X, that is, the large mouth end of the recess 13 is located at the opening and the small mouth end is located at the bottom of the recess. At this time, the shape of the opening 13b of the recess 13 may be the same as or different from the shape of the bottom surface 13a of the recess 13, and the present invention is not limited thereto.

Illustratively, in the case where the shape of the opening 13b of the groove 13 is the same as the shape of the bottom surface 13a of the groove 13, the groove 13 may be a truncated cone, a polygonal cone, or the like; the polygonal table can be a triangular table, a square table, a hexagonal table or the like.

Illustratively, in the case where the recess 13 is a circular truncated cone, the diameter of the opening 13b of the recess 13 is in the range of 20 to 500 μm, the diameter of the bottom surface 13a of the recess 13 is in the range of 10 to 200 μm, preferably, the diameter of the opening 13b of the recess 13 is in the range of 50 to 100 μm, and the diameter of the bottom surface 13a of the recess 13 is in the range of 40 to 60 μm; for example, the opening 13b of the recess 13 may have a diameter of 20 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 210 μm, 300 μm, 430 μm, 500 μm or the like; the diameter of the bottom surface 13a of the groove 13 may be 10 μm, 20 μm, 40 μm, 50 μm, 55 μm, 60 μm, 100 μm, 140 μm, 180 μm, 200 μm, or the like. It should be noted that, when the thermal conductivity of the first material is smaller than that of the second material, the diameter of the bottom 13a of the groove 13 is the smallest dimension of the bottom 13a of the groove 13, and the preferred value range is 10-100 μm.

Illustratively, in the case where the recess 13 is a polygonal table, the value of the side length of the opening 13b of the recess 13 ranges from 5 to 100 μm; the side length of the bottom surface 13a of the groove 13 has a value ranging from 3 μm to 50 μm; preferably, the side length of the opening 13b of the recess 13 has a value ranging from 5 to 20 μm; the side length of the bottom surface 13a of the groove 13 is 3-10 mu m; for example, the side length of the opening 13b of the groove 13 may be 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 70 μm, 85 μm, 100 μm, or the like; the bottom 13a of the groove 13 may have a side length of 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 41 μm, 50 μm, or the like.

Illustratively, in the case where the groove 13 is a prismatic table-shaped groove, the dimension H of the groove 13 in the second direction Y has a value ranging from 100 to 300 μm. For example, the dimension of the groove 13 in the second direction Y may be 100 μm, 150 μm, 200 μm, 260 μm, 300 μm, or the like.

It can be appreciated that when the recess 13 is a cylindrical recess or a prismatic recess, firstly, the process feasibility in forming the recess 13 on the first surface 11a of the seed holder body 11 can be improved; secondly, the shape of the recess 13 can be made relatively regular and the distribution area of the first material can be made relatively regular, so that the modulation controllability can be improved when modulating the temperature field of the surface 10a of the seed holder 10 on which the seed crystal 60 is provided by the plurality of filling portions 12.

In some embodiments, as shown in fig. 6 and 8, the plurality of grooves 13 are uniformly distributed on the seed holder body 11 along the third direction Z; the third direction Z is the direction in which the geometric center M of the seed holder body 11 points toward the boundary N of the seed holder body 11.

When the plurality of grooves 13 are uniformly distributed on the seed holder body 11 in the third direction Z, as a possible implementation, as shown in fig. 6, the plurality of grooves 13 are divided into a plurality of groove groups 13G, and the groove groups 13G include at least one groove 13. In the third direction Z, there is a first interval L1 between every adjacent two groove groups 13G. The plurality of first intervals L1 are equal. The third direction Z is a direction in which the geometric center M of the seed holder body 11 points to the boundary N of the seed holder body 11.

It will be appreciated that when the plurality of grooves 13 are uniformly distributed on the seed holder body 11 in the third direction Z, the temperature uniformity of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is improved, the temperature uniformity of the seed holder 10 can be improved, and sublimation of the material of the seed crystal 60 from the back surface can be reduced.

In other embodiments, the plurality of grooves 13 are unevenly distributed on the seed holder body 11.

In some embodiments, as shown in fig. 7, the plurality of grooves 13 are distributed on the seed holder body 11 according to a predetermined rule including: the distribution density of the plurality of grooves 13 on the seed holder body 11 gradually decreases along the third direction Z; the third direction Z is the direction in which the geometric center M of the seed holder body 11 points toward the boundary N of the seed holder body 11.

As a possible implementation, as shown in fig. 7, the plurality of grooves 13 is divided into a plurality of groove groups 13G, and the groove groups 13G include at least one groove 13. In the third direction Z, there is a first interval L1 between every adjacent two groove groups 13G. Along the third direction Z, the plurality of first intervals L1 gradually increases.

It will be appreciated that when the grooves 13 are distributed according to the predetermined rule, the distribution of the grooves 13 on the seed crystal holder body 11 is uneven, and the distribution of the grooves 13 is dense and sparse, so that the structural strength of the seed crystal holder 10 is high.

In some embodiments, as shown in fig. 6-8, the plurality of grooves 13 is divided into a plurality of groove groups 13G, the groove groups 13G including at least one groove 13. In the case where the groove group 13G includes one groove 13, the groove 13 is located at the geometric center M of the seed holder body 11. In the case where the groove group 13G includes a plurality of grooves 13, the plurality of grooves 13 included in the groove group 13G surround the geometric center M of the seed holder body 11. In the third direction Z, there is a first interval L1 between every adjacent two groove groups 13G. The plurality of first intervals L1 are equal; alternatively, the plurality of first intervals L1 gradually increases along the third direction Z; the third direction Z is the direction in which the geometric center M of the seed holder body 11 points toward the boundary N of the seed holder body 11.

Here, as shown in fig. 6 and 7, the recess 13 is located at the geometric center M of the seed holder body 11, meaning that the geometric center of the recess 13 coincides with the geometric center M of the seed holder body 11. In the case where the groove group 13G includes a plurality of grooves 13, as shown in fig. 6 to 8, the plurality of grooves 13 included in the groove group 13G surround the geometric center M of the seed holder body 11, the plurality of grooves 13 are disposed around the geometric center M of the seed holder body 11, and as a possible implementation, the geometric center of the arrangement pattern of the plurality of grooves 13 included in the groove group 13G coincides with the geometric center M of the seed holder body 11.

Here, the plurality of first intervals L1 gradually increase in the third direction Z means that, of any two adjacent first intervals L1 in the third direction Z, the first interval L1 closer to the geometric center M of the seed holder body 11 is larger than the first interval L1 farther from the geometric center M of the seed holder body 11.

It will be appreciated that in the case where the plurality of first intervals L1 are equal, the plurality of grooves 13 are distributed with higher uniformity, so that the temperature uniformity of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is improved, the temperature uniformity of the seed holder 10 can be improved, and sublimation of the material of the seed crystal 60 from the back surface can be reduced. In the case that the plurality of first intervals L1 are gradually increased along the third direction Z, the plurality of grooves 13 are distributed densely inside and sparsely outside, so that the structural strength of the seed holder 10 can be made higher.

In some embodiments, as shown in FIG. 7, the largest L1 of the first intervals L1 _max And the smallest one L1 of the first intervals L1 _mi The ratio between n is less than or equal to 3.

In the case where the plurality of first intervals L1 are equal, the largest one L1 of the first intervals L1 _max And the smallest one L1 of the first intervals L1 _min The ratio between them is equal to 1. In the case where the plurality of first intervals L1 gradually increase in the third direction Z, the largest one L1 of the first intervals L1 _max And the smallest one L1 of the first intervals L1 _min The ratio between them is greater than 1; further, as shown in fig. 7, in the case where the plurality of first intervals L1 gradually increase in the third direction Z, the largest one L1 among the first intervals L1 _max Is the first interval L1 farthest from the geometric center M of the seed holder 10 among the plurality of first intervals L1. The smallest of the first intervals L1 _min Is the first interval L1 closest to the geometric center M of the seed holder 10 among the plurality of first intervals L1.

As can be appreciated, in the case where the crystal growing apparatus 100 supplies heat through the induction heating coil 51, the edge temperature of the seed crystal 60Higher than the temperature at the center of the seed crystal 60 and, correspondingly, the temperature at the edge of the seed holder 10 is higher than the temperature at the center of the seed holder 10. In this case, when the largest L1 of the first intervals L1 _max And the smallest one L1 of the first intervals L1 _min When the ratio is greater than 3, the distribution of the groove groups 13G near the boundary of the seed crystal support 10 is more sparse, so that the influence of the grooves 13 on the temperature field at the boundary of the seed crystal support 10 is smaller, and high-temperature points are easy to exist at the boundary of the seed crystal support 10. Thus, the largest one L1 among the first intervals L1 is passed _max And the smallest one L1 of the first intervals L1 _min The arrangement that the ratio of the two grooves is smaller than or equal to 3 can optimize the distribution of the grooves 13 at the boundary of the seed crystal support 10, and the modulation effect of the grooves 13 on the temperature field at the boundary of the seed crystal support 10 is improved.

Illustratively, the largest L1 of the first intervals L1 _max And the smallest one L1 of the first intervals L1 _min The ratio between them may be 1.0, 1.5, 2.0, 2.5 or 3.0.

In some embodiments, as shown in fig. 2 and 3, a surface 12a of the filling portion 12 remote from the bottom surface 13a of the groove 13 is flush with the first surface 11 a; the flatness of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is 150 μm or less.

In the related art, flatness refers to deviation of a macroscopic relief height of a substrate from an ideal plane, which can be measured by a planar interferometry, a surface-beating measurement, a liquid-plane method, or a beam-plane method.

Here, the flatness of the surface 10a of the seed holder 10 on which the seed crystal 60 is provided refers to the flatness of the surface formed by the first surface 11a of the seed holder body 11 and the surface 12a of the filling portion 12 away from the bottom surface 13a of the recess 13.

As can be appreciated, when the flatness of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is less than or equal to 150 μm, the flatness of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed is high, so that firstly, the connection performance of the seed holder 10 and the seed crystal 60 can be improved; secondly, the seed crystal holder 10 can be attached to the seed crystal 60 more, and when the temperature field of the surface 10a of the seed crystal holder 10 on which the seed crystal 60 is provided is modulated by the plurality of filling portions 12, the modulation effect can be improved.

Illustratively, the flatness of the surface 10a of the seed holder 10 on which the seed crystal 60 is disposed may be 10 μm, 30 μm, 50 μm, 70 μm, 100 μm, 120 μm, 150 μm, or the like.

It will be appreciated that tantalum, tantalum carbide, and silicon carbide are each a high temperature resistant material different from the second material (e.g., graphite), and that the shape and state of the filling portion 12 can be kept unchanged in a high temperature environment (e.g., an environment having a temperature higher than 2000 ℃) when forming a silicon carbide single crystal by a physical vapor transport method, and thus the filling portion 12 can function to modulate the temperature field of the surface 10a of the seed holder 10 where the seed crystal 60 is provided when forming a silicon carbide single crystal by a physical vapor transport method.

In some embodiments, the first material is in the form of a powder, such as a silicon carbide powder, when forming the filler 12. In this case, the first material may be more uniformly distributed by adding an auxiliary material to the material forming the filling portion 12 in addition to the first material to increase the coating uniformity of the material forming the filling portion 12.

In some embodiments, the material forming the filler portion 12 also includes a modified epoxy.

It will be appreciated that in the case where the state of the first material is powder when the filling portion 12 is formed, when the material forming the filling portion 12 further includes a modified epoxy resin, the powder particles of the first material may be uniformly distributed in the modified epoxy resin, and thus, the coating uniformity of the material forming the filling portion 12 may be increased, and the first material may be more uniformly distributed.

Illustratively, the modified epoxy resin may include epoxy resin, phenolic resin, furfuryl alcohol resin, ethylenediamine, thickener, and surfactant; wherein the thickener may be carboxymethyl cellulose. Here, the kind of the surfactant, and the mass ratio of the epoxy resin, the phenolic resin, the furfuryl alcohol resin, the ethylenediamine, the thickener, and the surfactant are not limited, as long as the requirements for achieving the above functions are satisfied.

It will be appreciated that when the mass ratio of the first material to the modified epoxy resin in the material forming the filling portion ranges from 3:1 to 5:1, the mass ratio of the first material to the modified epoxy resin is set appropriately, so that the coating uniformity of the material forming the filling portion 12 can be increased, and the solid content of the first material in the formed filling portion 12 can be made to be higher.

Illustratively, the mass ratio of the first material to the modified epoxy resin in the material forming the filler may be 3:1, 3.5:1, 4:1, 4.2:1, 4.8:1, 5:1, or the like.

Some embodiments of the present disclosure also provide a preparation method of a seed holder, as shown in fig. 9, including S1 to S3:

s1: an initial seed holder body 14 is provided.

Illustratively, the material of the initial seed support body 14 is graphite.

Illustratively, the diameter of the initial seed holder body 14 is slightly larger than the diameter of the seed crystal 60.

S2: as shown in fig. 2, 3 and 10, a plurality of grooves 13 are formed in a first initial surface of the initial seed holder body 14; the plurality of grooves 13 are arranged at intervals; a first initial surface of the initial seed holder body 14 forms a first surface 11a of the seed holder body 11, the first surface 11a being for the placement of a seed crystal 60.

S3: the plurality of grooves 13 are filled, and a plurality of filling portions 12 are formed correspondingly. Wherein the material of the filling portion 12 comprises a first material, and the material of the initial seed holder body 14 comprises a second material, and the thermal conductivity of the first material is different from the thermal conductivity of the second material.

Illustratively, where the material of the filling portion 12 further includes a modified epoxy resin, filling the plurality of grooves 13, the corresponding forming of the plurality of filling portions 12 includes S3.1-S3.3:

s3.1: the grooves 13 are filled with a powder of a first material (hereinafter simply referred to as filler) blended with a modified epoxy resin (for example, silicon carbide), and after removing the excess of the above powder, flattened.

Illustratively, the flattening operation may be to first flatten with a blade and then flatten with a pressing device, with a pressing pressure of 30-50 kg, for example, 30kg, 35kg, 40kg, 45kg, 50kg, or the like; the pressurization time may be 3 hours.

S3.2: the initial seed holder body 14 with the filler is placed in an oven at a preset temperature and held for 4 hours.

The preset temperature is, for example, 300 ℃.

Illustratively, S3.2 may also be replaced by S3.2', S3.2' being specifically: annealing for 2-3 h at 500-800 ℃.

In some examples, the modified epoxy resin may undergo a carbonization reaction at a preset temperature, and the carbonization reaction may be generated to remain in the filling portion 12.

S3.3: the initial seed holder body 14 is removed and the planarity of the surface of the initial seed holder body 14 exposed to the first material is inspected. If the flatness is less than the flatness threshold, the initial seed holder body 14 forms the seed holder body 11, and the material filled in the recess 13 forms the filling portion 12, thereby completing the preparation of the seed holder 10. If the flatness is greater than or equal to the flatness threshold, the surface of the initial seed holder body 14, on which the first material is exposed, is treated with a predetermined number of grinding wheels to remove a certain thickness until the flatness meets the requirements, thereby completing the preparation of the seed holder 10.

Illustratively, the flatness threshold is 150 μm.

Illustratively, the preset mesh grinding wheel is an 800 mesh grinding wheel.

Illustratively, when the surface of the initial seed holder body 14 exposed to the first material is treated with a predetermined number of grinding wheels, the thickness removed may be 5 to 10 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

In some embodiments, the groove 13 is a cylindrical groove; s2 forming a plurality of grooves 13 in a first initial surface of an initial seed holder body 14 includes: a plurality of grooves 13 are formed by grooving a set region of the first initial surface using a laser process.

The laser process may be a green picosecond laser process or an ultraviolet nanosecond laser process, for example.

Illustratively, the cross-sectional pattern of the groove 13 formed parallel to the first surface 11a is a set pattern. The set pattern may be circular, square, rectangular, triangular, hexagonal, or the like.

In some embodiments, after forming the plurality of grooves 13 by grooving the set region of the first initial surface using the laser process, before S3, further comprising: the initial seed crystal support main body 14 provided with the groove 13 is transferred to a cleaning basket for cleaning, and the initial seed crystal support main body 14 is dried for standby after cleaning.

The above-described cleaning process may be accomplished in three steps, for example.

Illustratively, the cleaning agent used in the first step is an SC1 solution, which may be formulated as follows: mixing 27% ammonia water, 30% hydrogen peroxide and water in a volume ratio of 1:1:5; the first cleaning step may be for 5 minutes.

Illustratively, the cleaning agent used in the second step is an SC2 solution, which may be formulated as follows: mixing 37% hydrochloric acid solution, 30% hydrogen peroxide and water in a volume ratio of 1:1:6; the second step of cleaning may take 5 minutes.

Illustratively, the third wash may be performed with a QDR tank, and the third wash may be performed for 3 minutes.

In some embodiments, as shown in fig. 10, the groove 13 is a prismatic mesa groove; s2 forming a plurality of grooves 13 in a first initial surface of an initial seed holder body 14 includes: a plurality of grooves 13 are formed by grooving the set region of the first initial surface 14a using an etching process.

The etching process may be a dry etching process or a wet etching process, for example. The dry etching process is, for example, an inductively coupled plasma (Inductively Coupled Plasma, ICP) -reactive ion etching (reaction ionetching, RIE) dry etching process.

Illustratively, where the etching process is an ICP-RIE dry etching process, as shown in fig. 10, S2 may include S2.1 to S2.6:

s2.1: a photoresist layer W is coated on the first initial surface 14a of the initial seed holder body 14.

Illustratively, the material of the photoresist material layer W may be a photoresist, or may be an inorganic nonmetallic material; for example an acrylate material.

Illustratively, where the material of the photoresist layer W is an acrylate material, coating the first initial surface 14a of the initial seed support body 14 with a layer of photoresist further includes: naturally drying for 10min at room temperature to primarily dry the acrylate material.

S2.2: a plurality of pits 16 are formed in the photoresist layer W using the imprint mold 15.

Illustratively, the imprint mold 15 is a micro-nano imprint mold.

Illustratively, the location of the recess 16 corresponds to the location of the groove 13.

S2.3: the photoresist layer W is cured.

Illustratively, in the case where the material of the photoresist layer W is an acrylate material, the method of curing the photoresist layer W may be: irradiating for 2-3 min under ultraviolet light to make the acrylic ester material undergo the curing reaction to produce acrylic ester cross-linking agent.

S2.4: the residual photoresist material at the bottom of the pit 16 is removed using RIE equipment.

Illustratively, the principle of removing the residual photoresist material at the bottom of the pit 16 may be by chemical reaction using a RIE apparatus.

S2.5: the initial seed holder body 14 with the photoresist is etched using an ICP apparatus to form a plurality of grooves 13.

It will be appreciated that different shapes of the recesses 13 may be formed by selecting different etching ratios due to the different etching rates of the photoresist material and the initial seed holder body 14.

In S2.5, the etching gas may be chlorine (Cl) ₂ ) Hydrogen chloride (HCl) or oxygen (O) ₂ ) Etc.

Illustratively, in S2.5, the flow rate of the etching gas may be 40 to 80sccm, for example 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, or the like.

Illustratively, in S2.5, the dry etch chamber temperature may be 40-120 ℃, e.g., 40 ℃, 60 ℃, 80 ℃, 102 ℃, 120 ℃, or the like. The temperature in the cavity is measured by using a color-changing temperature zone.

Illustratively, in S2.5, the dry etch chamber pressure may be 200-800pa, such as 200pa, 300pa, 400pa, 500pa, 620pa, 700pa, 800pa, or the like.

S2.6: the photoresist material remaining on the first initial surface 14a is removed to form the first surface 11a.

In some embodiments, after forming the plurality of grooves 13 by grooving the set region of the first initial surface 14a of the initial seed holder body 14 using the etching process, before S3, further comprising: the initial seed crystal support main body 14 provided with the groove 13 is transferred to a cleaning basket for cleaning, and the initial seed crystal support main body 14 is dried for standby after cleaning.

The above-described cleaning process may be accomplished in four steps, for example.

Illustratively, the cleaning agent used in the first step of cleaning is an SPM solution, and the formulation thereof may be: mixing a sulfuric acid solution with the mass fraction of 98.3%, hydrogen peroxide with the mass fraction of 35% and water in a volume ratio of 3:1:1-5:1:1; the first cleaning step may be for 5 minutes. In the SPM solution, the volume ratio of the sulfuric acid solution with the mass fraction of 98.3% to the hydrogen peroxide solution with the mass fraction of 35% to the water may be 3:1:1.

Illustratively, the cleaning agent used in the second step is an SC1 solution, which may be formulated as follows: mixing 27% ammonia water, 30% hydrogen peroxide and water in a volume ratio of 1:1:5; the second step of cleaning may take 5 minutes.

Illustratively, the cleaning agent used in the third step is SC2 solution, and the formulation thereof may be: mixing 37% hydrochloric acid solution, 30% hydrogen peroxide and water in a volume ratio of 1:1:6; the third step of cleaning may take 5 minutes.

Illustratively, the fourth cleaning may be accomplished with a QDR tank, and the fourth cleaning may be for a period of 3 minutes.

It can be appreciated that, the beneficial effects achieved by the preparation method of the seed crystal holder provided in the above embodiment of the present disclosure may refer to the beneficial effects of the seed crystal holder described above, and will not be described herein.

Some embodiments of the present disclosure also provide a crystal growth apparatus 100. As shown in fig. 11, the crystal growing apparatus includes a seed holder 10; also comprises a crucible main body 20 and a crucible cover 30 covered on the crucible main body 20; the seed holder 10 is attached to the inner surface of the crucible cover 30.

Here, the fact that the seed holder 10 is coupled to the inner surface of the crucible cover 30 means that the seed holder 10 is coupled to the inner surface of the crucible cover 30, and that no relative movement occurs between the seed holder 10 and the inner surface of the crucible cover 30. The inner surface of the crucible cover 30 is the surface of the crucible cover 30 facing the inner cavity of the crucible main body 20. The connection between the seed holder 10 and the inner surface of the crucible cover 30 is not limited herein.

Illustratively, the manner in which the seed holder 10 is attached to the inner surface of the crucible cover 30 may be: the seed crystal holder 10 is integrated on the inner surface of the crucible cover 30, and then is reinforced by an annealing process; wherein the temperature of the annealing process may be set to 500 ℃.

It will be appreciated that the crucible body 20 and the crucible cover 30 described above may constitute a crucible 40 for containing a feedstock, such as a silicon carbide powder K.

Illustratively, the material of the crucible body 20 may be graphite.

Illustratively, the material of the seed holder 10 may be graphite.

In addition, the crystal growing apparatus 100 may further include a heating assembly 50, wherein the heating assembly 50 is configured to heat the feedstock (e.g., the silicon carbide powder K) within the crucible 40 to cause the feedstock to sublimate at a high temperature.

In some examples, the heating assembly 50 includes an induction heating coil 51 wrapped around the outer peripheral wall of the crucible 40 and disposed coaxially with the crucible 40. Thus, the raw materials can be heated by means of intermediate frequency electromagnetic induction heating. Specifically, after the induction heating coil 51 is energized, an eddy current is generated on the surface of the crucible 40 due to the skin effect, thereby generating joule heat, which is supplied to the crystal growing apparatus 100.

It can be appreciated that the beneficial effects achieved by the crystal growth apparatus provided in the above embodiments of the present disclosure can be referred to the beneficial effects of the seed holder, and will not be described herein.

Some embodiments of the present disclosure also provide a crystal growth method, which is achieved based on the crystal growth apparatus provided by some embodiments of the present disclosure.

It can be appreciated that the beneficial effects of the crystal growth method provided by the above embodiments of the present disclosure can be referred to the beneficial effects of the seed holder, and will not be described herein.

In some embodiments, the crystal growth process includes a first growth stage R1 and a second growth stage R2, as shown in fig. 12.

In the first growth stage R1, nucleating and growing to form a crystal nucleus T; the growth temperature of the first growth stage R1 is 2150 ℃, and the heat preservation time is 8-12 h.

For example, the incubation period of the first growth stage may be 8.0h, 8.5h, 9.0h, 9.4h, 10.0h, 10.5h, 11.0h, 11.5h, or 12.0h.

In some examples, the first growth stage R1 is performed in an argon atmosphere at a pressure of 2000 to 4000Pa, for example, the pressure of the growth atmosphere may be 2000Pa, 2500Pa, 3000Pa, 3600Pa, 4000Pa, or the like.

Illustratively, the manner in which the above-described growth environment is achieved may be: before the first growth stage R1, the single crystal furnace is vacuumized to 10 ^-5 pa; then argon is slowly filled until the pressure reaches a set pressure (for example, 2000-4000 Pa); the crystal growing apparatus 100 is then heated by the heating assembly 50 until the temperature in the cavity of the crucible 40 reaches 2150 ℃.

It is understood that when the growth temperature of the first growth stage R1 is 2150 ℃, the growth temperature is low, and thus crystal polytype growth can be prevented, and thus, the crystal form purity of the grown crystal can be improved.

In the second growth stage R2, as shown in fig. 13, crystal growth is continued to form a crystal growth body E; the growth temperature of the second growth stage R2 is 2280-2380 ℃, and the pressure of the growth environment is 400-800 Pa.

Illustratively, the growth temperature of the second growth stage R2 may be 2280 ℃, 2320 ℃, 2340 ℃, 2360 ℃, 2380 ℃, or the like.

Illustratively, the pressure of the growth environment of the second growth phase R2 may be 400Pa, 510Pa, 600Pa, 700Pa, 800Pa, or the like.

It will be appreciated that the initial growth surface is formed and relatively stable during the second growth phase R2. Moreover, since the growth rate is proportional to the growth temperature over a range of conditions during the growth of a crystal (e.g., a silicon carbide crystal), the growth rate is inversely proportional to the pressure of the growth environment. Therefore, when the growth temperature of the second growth stage R2 is 2280-2380 ℃, and the pressure of the growth environment is 400-800 Pa, the growth temperature is higher, the pressure of the growth environment is lower, the growth rate of the crystal can be faster, and the dislocation density can be reduced.

In order to objectively evaluate the technical effects of the embodiments of the present disclosure, hereinafter, the technical solutions provided by the present disclosure will be exemplarily described in detail by the following experimental examples and comparative examples.

The following examples and comparative examples use different methods to prepare seed holders, crystal growth was performed using a crystal growth apparatus including the seed holders prepared in the examples and comparative examples, and dislocation defect densities of the grown crystals were measured and compared.

In the following comparative examples and examples, the test conditions of screw dislocation (TSD) density, ductile dislocation (TED) density, and basal vector dislocation (BPD) density were the same.

Example 1

The first step: preparing a seed crystal holder.

The method for preparing the seed crystal holder comprises the following steps of V1 to V3:

v1: taking an initial seed crystal support main body 14 made of graphite, and opening a cylindrical groove 13 on a first initial surface 14a of the initial seed crystal support main body by utilizing a laser process, wherein the diameter of the groove 13 is 40 mu m, and the depth of the groove is 300 mu m; furthermore, the minimum distance between two adjacent grooves 13 is 60. Mu.m, and the arrangement of the grooves 13 on the initial seed holder body 14 is shown in FIG. 6.

V2: the initial seed crystal support main body 14 provided with the groove 13 is transferred to a cleaning basket for cleaning, and the initial seed crystal support main body 14 is dried for standby after cleaning. The cleaning process can be completed in three steps: the cleaning agent used in the first step is SC1 solution, and the formula is as follows: mixing 27% ammonia water, 30% hydrogen peroxide and water in a volume ratio of 1:1:5; the washing time may be 5 minutes. The cleaning agent used in the second step is SC2 solution, and the formula is as follows: mixing 37% hydrochloric acid solution, 30% hydrogen peroxide and water in a volume ratio of 1:1:6; the washing time may be 5 minutes. The third step of cleaning is completed by a QDR groove, and the cleaning time can be 3min.

V3: and filling silicon carbide powder (hereinafter referred to as filling material) blended by the modified epoxy resin into the groove 13, removing the redundant filling material, flattening, and then placing into a baking oven at 300 ℃ for heat preservation for 4 hours. The surface of the initial seed holder body 14 exposed to the first material is treated after removal until a flatness of less than 150 μm is achieved.

And a second step of: and the seed crystal support, the seed crystal and the crucible cover are connected.

The connecting method of the seed crystal support, the seed crystal and the crucible cover comprises V4-V5:

v4: and bonding the seed crystal prepared in advance to the seed crystal holder prepared in the first step by using an adhesive, so that the amorphous growth surface-Si surface of the seed crystal is bonded with the surface of the seed crystal holder provided with the filling part.

V5: and integrating the seed crystal holder adhered with the seed crystal with the crucible cover, and then carrying out annealing and reinforcement at the high temperature of 500 ℃.

And a third step of: preparation of the crystal growing apparatus.

First, the crucible cover with the seed crystal holder is adheredIs combined with the crucible main body and seals the crucible. The crucible is installed in a single crystal furnace. Then the single crystal furnace is vacuumized until the vacuum degree reaches 10 ^-5 pa. Then argon is slowly filled until the pressure of the single crystal furnace reaches 2000-4000 pa. The crucible is then heated until the temperature in the cavity of the crucible rises to 2150 ℃.

Fourth step: and (5) crystal growth.

A first growth stage: and (3) carrying out nucleation growth under the condition that the temperature in the cavity of the crucible is 2150 ℃ for 12 hours, and forming crystal nuclei T to obtain a semi-finished product of crystal growth, as shown in figure 2.

And a second growth stage: and reducing the pressure of the single crystal furnace to 800pa, heating the crucible until the temperature in the cavity of the crucible rises to 2280 ℃, and continuing to grow the crystal for 168 hours to form a crystal growth body E. Then, the temperature was lowered to obtain a crystal-grown body as shown in FIG. 13.

Fifth step: dislocation density characterization of the crystal growth.

Taking out the crystal growth body, performing multi-wire cutting, grinding and thinning, performing CMP polishing treatment to obtain a 6-foot substrate slice, and immersing the substrate slice into potassium hydroxide (KOH) melt at 540 ℃ for strong corrosion for 10min. Then, a metallographic microscope is used for representing the dislocation density; wherein The Screw Dislocation (TSD) density is 86e.a/cm ² Dislocation Toughness (TED) density of 2859e.a/cm ² Basal vector dislocation (BPD) density of 1251e.a/cm ² 。

Example 2

The first step: preparing a seed crystal holder.

The method for preparing the seed crystal holder comprises the following steps of V1 '-V3':

v1: an initial seed crystal support body 14 made of a piece of graphite is taken, and a square-table-shaped groove 13 is formed on a first initial surface 14a of the initial seed crystal support body by an etching process. Referring to the steps S2.1 to S2.6, an ICP-RIE dry etching process is used; wherein, the material of the photoresist material layer W is acrylic ester material, and the photoresist material layer W is naturally dried for 10min at room temperature after being coated; the imprinting mold 15 is a micro-nano imprinting mold; the method for curing the photoresist layer W is to irradiate for 2-3 min under ultraviolet light. The bottom 13a of the recess 13 has a side length of 5 μm, the opening 13b of the recess 13 has a side length of 15 μm and a depth of 300 μm, and the arrangement of the recess 13 on the initial seed holder body 14 is shown in FIG. 8.

V2: the initial seed crystal support main body 14 provided with the groove 13 is transferred to a cleaning basket for cleaning, and the initial seed crystal support main body 14 is dried for standby after cleaning. The cleaning process can be completed in four steps: the cleaning agent used in the first step is SPM solution, and the formula is as follows: mixing sulfuric acid solution with the mass fraction of 98.3%, hydrogen peroxide with the mass fraction of 35% and water in a volume ratio of 3:1:1; the washing time may be 5 minutes. The cleaning agent used in the second step is SC1 solution, and the formula is as follows: mixing 27% ammonia water, 30% hydrogen peroxide and water in a volume ratio of 1:1:5; the washing time may be 5 minutes. The cleaning agent used in the third step is SC2 solution, and the formula is as follows: mixing 37% hydrochloric acid solution, 30% hydrogen peroxide and water in a volume ratio of 1:1:6; the washing time may be 5 minutes. The fourth step of cleaning is completed by a QDR groove, and the cleaning time can be 3min.

With reference to the methods of the second to fifth steps, the connection of the seed holder, the seed crystal, and the crucible cover, the preparation of the crystal growing apparatus, the crystal growth, and the dislocation density characterization of the crystal growth body are completed. In the fourth step, the crystal growth semi-finished product obtained in the first growth stage is shown in fig. 3. In the fifth step, the dislocation density was measured to obtain a screw dislocation (TSD) density of 79e.a/cm ² A dislocation Toughness (TED) density of 2231e.a/cm ² Basal vector dislocation (BPD) density of 1315e.a/cm ² . In the fifth step, a metallographic micrograph was also obtained, as shown in FIG. 14.

Comparative example

The first step: preparing a seed crystal holder.

An initial seed holder body 14 made of a piece of graphite is taken and used directly as a seed holder.

With reference to the methods of the second to fifth steps, the connection of the seed holder, the seed crystal, and the crucible cover, the preparation of the crystal growing apparatus, the crystal growth, and the dislocation density characterization of the crystal growth body are completed. Wherein in the fifth step, the dislocation density was measured to give a threading dislocation (TSD) density of 425e.a/cm ² Dislocation Toughness (TED) density of 4288e.a/cm ² The basal vector dislocation (BPD) density was 3218e.a/cm ² 。

To more clearly describe the comparative results of the examples and comparative examples, the dislocation density results measured using the examples and comparative examples are more clearly shown in table 1 below.

TABLE 1

In example 1 and example 2, referring to table 1, the TSD density, BPD density, TED density of example 1 and example 2 are relatively low compared with the comparative examples. This is because the seed holder of embodiment 1 or embodiment 2 includes a filling portion, and the material (first material) of the filling portion has a thermal conductivity different from that of the material (second material) of the seed holder main body, so that the temperature field of the surface of the seed holder on which the seed is disposed can be modulated, and the temperature field of the seed attached to the seed holder can be modulated; in this way, after heat conduction, the temperature distribution (for example, radial temperature distribution) of the region of the growth surface (for example, C-plane of the seed crystal) of the silicon carbide crystal can be changed, a plurality of low-temperature regions are formed on the growth surface (for example, the growth surface of the silicon carbide crystal) of the seed crystal, the crystal is nucleated preferentially in the plurality of low-temperature regions simultaneously, and after nucleation, 0001-oriented crystal growth of a non-preferential growth region (for example, a region located between two low-temperature regions) is blocked by lateral growth perpendicular to the 0001 plane (for example, a plane parallel to and opposite to the C-plane) so that the crystal growth mode is changed, and the TSD density of the grown crystal is reduced. When the TSD density is reduced, the conversion of TSD to BPD and TSD to TED is relatively less, resulting in a reduction in the BPD density and TED density.

As can be seen from the above embodiments and comparative examples, the present disclosure can reduce dislocation density in a silicon carbide single crystal material by providing a plurality of grooves on a first surface of a seed holder body and providing a filling portion in the grooves, such that a thermal conductivity of a material (first material) of the filling portion is different from a thermal conductivity of a material (second material) of the seed holder body.

The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A seed holder, comprising:

the seed crystal support comprises a seed crystal support main body, wherein a plurality of grooves are formed in the first surface of the seed crystal support main body, the grooves are arranged at intervals, and the first surface is used for setting seed crystals;

the filling parts are correspondingly arranged in the grooves;

the material of the filling part comprises a first material, the material of the seed crystal support main body comprises a second material, and the heat conductivity coefficient of the first material is different from that of the second material.

2. The seed holder of claim 1 wherein the first material has a thermal conductivity less than the thermal conductivity of the second material, and wherein the minimum dimension of the bottom surface of the recess has a value in the range of 10-100 μm.

3. The seed holder of claim 1 wherein the first material has a thermal conductivity greater than that of the second material, and wherein the minimum spacing between adjacent ones of the grooves has a value in the range of 10-100 μm.

4. The seed holder of claim 1 wherein the dimension of the recess in a second direction is in the range of 10 to 500 μm, the second direction being the thickness direction of the seed holder body.

5. The seed holder of any one of claims 1-4 wherein the plurality of grooves are uniformly distributed on the seed holder body along a third direction; the third direction is the direction that the geometric center of the seed crystal support body points to the boundary of the seed crystal support body.

6. The seed holder of any one of claims 1-4 wherein the plurality of grooves are distributed on the seed holder body according to a predetermined pattern, the predetermined pattern comprising: the distribution density of the grooves on the seed crystal holder main body is gradually reduced along a third direction; the third direction is the direction that the geometric center of the seed crystal support body points to the boundary of the seed crystal support body.

7. The seed holder of any one of claims 1 to 4, wherein the plurality of grooves is divided into a plurality of groove groups, the groove groups including at least one groove;

in the case where the groove set includes one groove, the groove is located at the geometric center of the seed holder body;

in the case where the groove group includes a plurality of grooves, the plurality of grooves included in the groove group encircle a geometric center of the seed holder body;

a first interval is arranged between every two adjacent groove groups along the third direction;

a plurality of the first intervals are equal; alternatively, in the third direction, a plurality of the first intervals are gradually increased;

the third direction is the direction that the geometric center of the seed crystal support body points to the boundary of the seed crystal support body.

8. The seed holder of claim 7, wherein a ratio between a largest one of the first intervals and a smallest one of the first intervals is less than or equal to 3.

9. A seed holder as claimed in any one of claims 1 to 4, wherein a surface of the filling portion remote from a bottom surface of the recess is flush with the first surface;

the flatness of the surface of the seed crystal support, on which the seed crystal is arranged, is less than or equal to 150 mu m.

10. The seed holder of any one of claims 1-4, wherein the first material comprises a combination of any one or more of tantalum, tantalum carbide, and silicon carbide; and/or, the second material is graphite.

11. The seed holder of any one of claims 1-4 wherein the material forming the filling portion further comprises a modified epoxy.

12. The seed holder of claim 11, wherein a mass ratio of the first material to the modified epoxy resin in a material forming the filling portion is in a range of 3:1 to 5:1.

13. The preparation method of the seed crystal holder is characterized by comprising the following steps:

providing an initial seed crystal support body;

forming a plurality of grooves on a first initial surface of the initial seed holder body; the grooves are arranged at intervals; a first initial surface of the initial seed crystal holder body forms a first surface of the seed crystal holder body, and the first surface is used for setting seed crystals;

filling the grooves to form a plurality of filling parts correspondingly;

the material of the filling part comprises a first material, the material of the initial seed crystal support main body comprises a second material, and the heat conductivity coefficient of the first material is different from that of the second material.

14. The method of claim 13, wherein the recess is a cylindrical recess; forming a plurality of grooves in a first initial surface of the initial seed holder body includes: and grooving a set area of the first initial surface by utilizing a laser process to form a plurality of grooves.

15. The method of claim 13, wherein the recess is a prismatic mesa recess; forming a plurality of grooves in a first initial surface of the initial seed holder body includes: and grooving a set area of the first initial surface by utilizing an etching process to form a plurality of grooves.

16. A crystal growing apparatus comprising a seed holder according to any one of claims 1 to 12;

the seed crystal support is connected to the inner surface of the crucible cover.

17. A crystal growth method, characterized in that the crystal growth method is realized based on the crystal growth apparatus according to claim 16.

18. The crystal growth method according to claim 17, wherein in the crystal growth method, the crystal growth process includes:

In the first growth stage, nucleating growth is carried out to form crystal nuclei; the growth temperature in the first growth stage is 2150 ℃, and the heat preservation time is 8-12 h;

in the second growth stage, continuing the growth of the crystal to form a crystal growth body; the growth temperature of the second growth stage is 2280-2380 ℃, and the pressure of the growth environment is 400-800 Pa.