CN116163006A - Preparation method of silicon carbide crystal - Google Patents

Abstract

The invention relates to the technical field of preparation of silicon carbide crystals, in particular to a preparation method of silicon carbide crystals. The embodiment of the invention provides a preparation method of a silicon carbide crystal, which comprises the following steps: adjusting the growth crucible to be embedded into the first nested crucible to obtain a nested combination; wherein the growth crucible is filled with growth raw materials; placing the nested combination in a crystal furnace; adjusting a seed rod to make the seed crystal level with the liquid level of the growth raw material; starting an induction coil to heat the nested combination with preset power to obtain a multi-variable temperature field matched with the range of 1600-2100 ℃ so as to grow silicon carbide crystals on the surface of the seed crystal; wherein the preset power is 5-11kw. The embodiment of the invention provides a preparation method of silicon carbide crystals, which can safely prepare high-quality silicon carbide crystals for a long time.

Description

Preparation method of silicon carbide crystal

Technical Field

The invention relates to the technical field of preparation of silicon carbide crystals, in particular to a preparation method of silicon carbide crystals.

Background

Silicon carbide (SiC) is one of extremely important third-generation semiconductor materials, and has characteristics of a specific large forbidden bandwidth, high critical breakdown field strength and the like, so that the SiC is an ideal material for manufacturing high-frequency, high-power, radiation-resistant and illumination integrated devices, and is widely applied to various fields of new energy automobiles, 5G communication, aerospace and the like.

Liquid phase processes are one of the main routes to the preparation of silicon carbide crystals. In the liquid phase method for preparing silicon carbide crystals, seed crystals are required to be arranged on the surface of a melt growth raw material, and then a dry pot containing the melt growth raw material is placed in a temperature field for heating to prepare the silicon carbide crystals. However, the high temperature growth feedstock solution may melt through the crucible during the long time silicon carbide preparation, resulting in equipment damage. Therefore, the preparation device is often adjusted to overcome the defects, but the growth of the silicon carbide is extremely sensitive to temperature, and corresponding process parameters are required to be adjusted correspondingly after the device is adjusted, so that the high-quality silicon carbide can be stably grown on the premise of protecting equipment.

Disclosure of Invention

The embodiment of the invention provides a preparation method of silicon carbide crystals, which can safely prepare high-quality silicon carbide crystals for a long time.

The embodiment of the invention provides a preparation method of a silicon carbide crystal, which comprises the following steps:

adjusting the growth crucible to be embedded into the first nested crucible to obtain a nested combination; the growth crucible is filled with growth raw materials, and the thickness of the first nested crucible is 5-30 mm;

placing the nested combination in a crystal furnace;

adjusting a seed rod to make the seed crystal level with the liquid level of the growth raw material;

starting an induction coil to heat the nested combination with preset power to obtain a multi-variable temperature field matched with the range of 1600-2100 ℃ so as to grow silicon carbide crystals on the surface of the seed crystal; wherein the preset power is 5-11kW.

In one possible design, before the conditioning growth crucible is embedded in the first nested crucible, further comprising:

arranging a first defect structure on the inner wall of the first nested crucible, wherein the first defect structure is recessed in a direction away from the growth crucible;

the regulated growth crucible is embedded in a first nested crucible, comprising:

and adjusting the growth crucible to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the first defect structure.

In one possible design, after said adjusting the seed rod to level the seed crystal with the liquid level of the growth feedstock, before said turning on the induction coil to heat the nested combination at a preset power, further comprising:

and rotating the seed crystal and/or rotating the growth crucible through the seed rod to enable the relative rotation speed between the seed crystal and the growth crucible to be a preset speed, wherein the preset speed is 10-200 rpm.

In one possible design, the conditioning growth crucible is embedded in a first nested crucible, resulting in a nested combination, comprising:

adjusting the growth crucible to be embedded into the first nested crucible;

embedding the first nested crucible into the second nested crucible to obtain a nested combination.

In one possible design, before the embedding the first nested crucible into the second nested crucible, the method further comprises:

a second defect structure is arranged on the inner wall of the second nested crucible, and the second defect structure is recessed in a direction away from the first nested crucible;

the embedding the first nested crucible into the second nested crucible comprises:

embedding the first nested crucible into the second nested crucible so that the plane of the liquid level of the growth raw material passes through the second defect structure.

In one possible design, the preset power is 5.8-11kW.

In one possible design, the predetermined rate is 50 to 200rpm.

In one possible design, the adjusting the growth crucible to embed in a first nested crucible such that the plane of the liquid surface of the growth feedstock passes through the first defect structure includes:

adjusting a growth crucible to be embedded into a first nested crucible so that a plane where the liquid level of the growth raw material is located passes through the bottom of the first defect structure;

or alternatively, the first and second heat exchangers may be,

and adjusting the growth crucible to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the middle part of the first defect structure.

In one possible design, the regulated growth crucible is embedded in a first nested crucible, comprising:

adjusting the growth crucible to be completely embedded into the first nested crucible;

or alternatively, the first and second heat exchangers may be,

the bottom of the growth crucible is regulated to be embedded into the first nested crucible.

In one possible design, the embedding the first nested crucible into the second nested crucible includes:

the first nested crucible is completely embedded into the second nested crucible;

or alternatively, the first and second heat exchangers may be,

and embedding the bottom of the first nested crucible into the second nested crucible.

Compared with the prior art, the invention has at least the following beneficial effects:

in the invention, the first nested crucible is arranged outside the growth crucible, and the inner diameter of the first nested crucible is equal to or slightly larger than the outer diameter of the growth crucible, so that the arrangement can keep better heat conduction between the growth crucible and the first nested crucible, and the growth crucible is not influenced to move up and down in the first nested crucible. By arranging the first nested crucible, equipment such as a growth furnace and the like can be effectively protected, and even when silicon carbide crystals are prepared for a long time, growth raw materials are melted through the growth crucible, and other preparation devices can be effectively protected due to the existence of the nested crucible.

However, after the first nested crucible is arranged, the heat received by the growth crucible is reduced due to the existence of the first nested crucible, and in order to ensure the stability of the temperature field of the growth crucible in the first nested crucible, the power of the induction coil needs to be increased. Specifically, in order to meet the requirement of producing silicon carbide safely for a long time, the thickness of the first nested crucible is 5-30 mm. In order to ensure the stability of the temperature field of the growth crucible, the power of the induction coil is raised to 5-11kW.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view of a silicon carbide crystal growth apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic view of another silicon carbide crystal growth apparatus according to an embodiment of the present invention;

fig. 3 is a schematic structural view of yet another silicon carbide crystal growth apparatus according to an embodiment of the present invention.

In the figure:

1-growing a crucible;

11-seed crystal through holes;

2-a first nested crucible;

21-a first opening;

22-a first defect structure;

3-a second nested crucible;

31-a second opening;

32-a second defect structure;

4-seed crystal rods;

5-seed crystal;

6-a growth raw material;

7-adjusting means.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.

In the description of embodiments of the present invention, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying any relative importance unless explicitly specified or limited otherwise; the term "plurality" means two or more, unless specified or indicated otherwise; the terms "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, integrally connected, or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the description of the present specification, it should be understood that the terms "upper", "lower", and the like used in the embodiments of the present invention are described in terms of the angles shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In the context of this document, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on the other element or be indirectly on the other element through intervening elements.

The embodiment of the invention provides a preparation method of silicon carbide crystals, which is applied to devices shown in fig. 1 to 3, and comprises the following steps:

adjusting the growth crucible to be embedded into the first nested crucible to obtain a nested combination; wherein the growth crucible is filled with growth raw materials, and the thickness of the first nested crucible is 5-30 mm;

placing the nested combination in a crystal furnace;

adjusting the seed rod to make the seed crystal level with the liquid level of the growth raw material;

starting an induction coil to heat the nested combination with preset power to obtain a multi-variable temperature field matched with the range of 1600-2100 ℃ so as to grow silicon carbide crystals on the surface of the seed crystal; wherein the preset power is 5-11kW.

In the invention, the first nested crucible is arranged outside the growth crucible, and the inner diameter of the first nested crucible is equal to or slightly larger than the outer diameter of the growth crucible, so that the arrangement can keep better heat conduction between the growth crucible and the first nested crucible, and the growth crucible is not influenced to move up and down in the first nested crucible. By arranging the first nested crucible, equipment such as a growth furnace and the like can be effectively protected, and even when silicon carbide crystals are prepared for a long time, growth raw materials are melted through the growth crucible, and other preparation devices can be effectively protected due to the existence of the nested crucible.

However, after the first nested crucible is arranged, the heat received by the growth crucible is reduced due to the existence of the first nested crucible, and in order to ensure the stability of the temperature field of the growth crucible in the first nested crucible, the power of the induction coil needs to be increased. Specifically, in order to meet the requirement of producing silicon carbide safely for a long time, the thickness of the first nested crucible is 5-30 mm. In order to ensure the stability of the temperature field of the growth crucible, the power of the induction coil is raised to 5-11kW.

In some embodiments of the invention, prior to adjusting the growth crucible to embed in the first nested crucible, further comprising:

arranging a first defect structure on the inner wall of the first nested crucible, wherein the first defect structure is recessed in a direction away from the growth crucible;

adjusting the growth crucible to embed into the first nested crucible, comprising:

the growth crucible is adjusted to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the first defect structure.

In this embodiment, the first nested crucible is provided with a first defect structure to increase the temperature difference between the surface of the growth material and the seed crystal, increasing the growth rate of the silicon carbide crystal.

In some embodiments of the invention, after adjusting the seed rod to level the seed crystal with the liquid level of the growth material, before turning on the induction coil to heat the nested combination at a preset power, further comprising:

the seed crystal is rotated by a seed rod and/or the growth crucible is rotated so that the relative rotation rate between the seed crystal and the growth crucible is a preset rate, and the preset rate is 10-200 rpm.

In this embodiment, since the silicon carbide crystal is grown under the seed crystal, the carbon consumption near the liquid surface of the growth material is faster and the concentration is rapidly lower as the growth rate of the silicon carbide crystal increases, resulting in a decrease in the carbon supply capacity of the growth material near the liquid surface, which may cause defects such as wrapping of the growth material. To solve this problem, the seed crystal and/or the growth crucible is rotated to cause strong convection of the growth material, and the solution having a high bottom carbon concentration is rapidly replenished to the vicinity of the liquid surface, so that the growth material solution in the vicinity of the liquid surface is always kept at a sufficient carbon content. To ensure the intensity of convection, the preset rate is made to be 10-200 rpm.

In some embodiments of the invention, adjusting the growth crucible to embed into the first nested crucible results in a nested combination comprising:

adjusting the growth crucible to be embedded into the first nested crucible;

embedding the first nested crucible into the second nested crucible to obtain a nested combination.

In this embodiment, two nested crucibles may further increase the duration of safe production. Of course, multiple crucibles may also be nested according to this method.

In some embodiments of the invention, prior to embedding the first nested crucible into the second nested crucible, further comprising:

a second defect structure is arranged on the inner wall of the second nested crucible, and the second defect structure is recessed in a direction away from the first nested crucible;

embedding the first nested crucible into the second nested crucible, comprising:

embedding the first nested crucible into the second nested crucible so that the plane of the liquid level of the growth raw material passes through the second defect structure.

In this embodiment, the two defect structures of the two nested crucibles further increase the temperature difference between the seed crystal and the surface of the growth material, further increasing the growth rate of the silicon carbide crystal.

In some embodiments of the invention, the preset power is 5.8-11kW.

In this embodiment, the two defect structure scheme requires higher power to heat, and therefore, power needs to be increased, and the preset power is 5.8-11kW.

In some embodiments of the invention, the preset rate is 50 to 200rpm.

In this example, the growth rate is increased and the convection intensity of the growth material is also required to be increased, so that the relative rotation rate between the seed crystal and the growth crucible is increased and the preset rate is adjusted to 50 to 200rpm.

In some embodiments of the invention, adjusting the growth crucible to embed in the first nested crucible such that the plane of the liquid surface of the growth material passes through the first defect structure comprises:

adjusting the growth crucible to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the bottom of the first defect structure;

or alternatively, the first and second heat exchangers may be,

the growth crucible is adjusted to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the middle part of the first defect structure.

In this embodiment, the liquid level is at a different position, the temperature difference between the seed crystal and the liquid level is different, and the temperature difference is the largest when the plane of the liquid level is at the bottom of the first defect structure, and the temperature difference is the smallest when the plane is at the middle.

In some embodiments of the invention, adjusting the growth crucible to embed in the first nested crucible comprises:

adjusting the growth crucible to be completely embedded into the first nested crucible;

or alternatively, the first and second heat exchangers may be,

the bottom of the growth crucible is regulated to be embedded into the first nested crucible.

In this embodiment, when the growth crucible is fully embedded in the first nested crucible, the growth crucible is at a greater temperature gradient; when the bottom of the growth crucible is embedded into the first nested crucible, the temperature gradient of the growth crucible is smaller.

In some embodiments of the invention, embedding a first nested crucible into a second nested crucible comprises:

completely embedding the first nested crucible into the second nested crucible;

or alternatively, the first and second heat exchangers may be,

embedding the bottom of the first nested crucible into the second nested crucible.

In this embodiment, when the first nested crucible is fully embedded in the second nested crucible, the first nested crucible is at a greater temperature gradient; when the bottom of the first nested crucible is embedded into the second nested crucible, the temperature gradient of the first nested crucible is smaller.

As shown in fig. 1 to 3, an embodiment of the present invention provides a silicon carbide crystal growth apparatus including a growth crucible 1 and a first nested crucible 2;

the first nested crucible 2 is provided with a first opening 21 through which the growth crucible 1 can enter the first nested crucible 2;

the growth crucible 1 is filled with a growth raw material 6, the growth crucible 1 is provided with a seed crystal through hole 11, a seed crystal rod 4 with a seed crystal 5 fixed at the bottom enters the growth crucible 1 through the seed crystal through hole 11, one end of the seed crystal rod 4 away from the seed crystal 5 is connected with a transmission device, and the transmission device is used for controlling the seed crystal rod 4 to move so as to enable the seed crystal 5 to be in contact with the liquid surface of the growth raw material 6.

In the invention, the first nested crucible 2 is arranged outside the growth crucible 1, and the inner diameter of the first nested crucible 2 is equal to or slightly larger than the outer diameter of the growth crucible 1, so that the arrangement can keep good heat conduction between the growth crucible 1 and the first nested crucible 2, and does not influence the up-and-down movement of the growth crucible 1 in the first nested crucible 2. By providing the first nested crucible 2, equipment such as a growth furnace and the like can be effectively protected, and even when a silicon carbide crystal is prepared for a long time, the growth raw material 6 is melted through the growth crucible 1, and other preparation devices can be effectively protected by the nested crucible.

In this embodiment, the growth crucible 1 includes a crucible main body and a crucible cover covering the crucible main body, and the seed crystal through hole 11 is provided in the crucible cover. The transmission device can control the lifting movement of the seed rod 4 and can also control the rotation of the seed rod 4.

In some examples, growth crucible 1 is a graphite high purity crucible having a density greater than 1.5g/cm ³ . The growth crucible 1 serves as a material container for growing a silicon carbide single crystal by a liquid phase method, and also serves as a carbon source for supplying carbon necessary for reaction for growth. The wall thickness of the growth crucible 1 is 3-30 mm, the bottom thickness is 5-40 mm, and the height is 50-300 mm. The diameter of the seed through hole 11 is 50-250 mm. The length of the connecting rod of the seed rod 4 is 150-750 mm, and the width of the connecting rod is 5-50 mm.

In some embodiments of the invention, the growth crucible 1 is connected to a regulating device 7, the regulating device 7 being used to regulate the position of the growth crucible 1 in the first nested crucible 2;

the inner wall of the first nested crucible 2 is provided with a first defect structure 22, the first defect structure 22 is recessed towards a direction away from the growth crucible 1, the position of the growth crucible 1 is regulated by the regulating device 7, so that the plane of the liquid level of the growth raw material 6 passes through the first defect structure 22 to increase the temperature gradient between the seed crystal 5 and the liquid level of the growth raw material 6, and further increase the growth speed of the silicon carbide crystal.

In this embodiment, a regulating device 7 is connected to the bottom of the growth crucible 1 through the first nested crucible 2 (if there is a second nested crucible 3, the regulating device 7 also penetrates the second nested crucible 3) for controlling the lifting of the growth crucible 1. The first nested crucible 2 is provided with a first defect structure 22, the inner wall of the crucible at the first defect structure 22 is far away from the growth crucible 1, heat loss is large in the process of transferring the first defect structure 22 to the growth crucible 1, and the temperature of the part of the growth crucible 1 at the first defect structure 22 is lower than that of other parts, so that a temperature gradient is formed. The liquid level of the growth raw material 6 is regulated to the first defect structure 22 by the regulating device 7, namely, the growth position of the silicon carbide crystal is regulated to the temperature gradient, an accurate and controllable temperature gradient is manufactured by the defect structure, and the growth speed of the silicon carbide single crystal can be obviously improved by the proper temperature gradient, so that the growth efficiency of the silicon carbide is improved, the energy is saved, and the cost is reduced.

The device provided by the invention can effectively regulate and control the temperature field, the precision of the device can be controlled within 2 ℃, and the repeatability of the temperature field is ensured to a great extent.

Since the liquid level gradually decreases as the silicon carbide crystal is formed and the growth raw material 6 is consumed, it is necessary to raise the growth crucible 1 at a rate of lowering the liquid level so that the seed crystal 5 or the bottom of the crystal is always level with the liquid level.

It will be appreciated that the temperature gradient formed is also different when the level of growth material 6 is at different levels of first defect structure 22, and that the temperature gradient may be further controlled by adjusting the level of growth material 6 to be at different levels of first defect structure 22.

It should be noted that, although the growth crucible 1 is located in the temperature field and the temperature of the growth crucible 1 can be adjusted by adjusting the position of the growth crucible 1 in the temperature field, the temperature gradient adjusted by the method is large, the temperature gradient is difficult to be accurately controlled and adjusted, and the unstable and uncontrollable crystal quality can be caused when the temperature gradient changes greatly. Therefore, the invention designs a defect structure to realize the effect of flexibly and accurately controlling the temperature gradient, so that the crystal can grow quickly and stably.

In some embodiments of the present invention, the surface of the growth material 6 is in a plane that passes through the bottom of the first defect structure 22.

In this embodiment, the temperature gradient is greatest when the level of the growth material 6 is in a plane that passes through the bottom of the first defect structure 22.

In some embodiments of the present invention, the plane of the surface of the growth material 6 passes through the middle of the first defect structure 22.

In this embodiment, the temperature gradient is minimal when the plane in which the liquid level of the growth material 6 lies passes through the middle of the first defect structure 22.

In some embodiments of the present invention, the longitudinal cross-section of the first defect structure 22 is rectangular, triangular or arcuate. For example, the first defect structure 22 may be rectangular in cross-section, recessed inward by 3-15 mm and 20-100 mm in length.

In the embodiment of the invention, the shapes of the first defects are different, the formed temperature gradients are different, and the shapes of the first defects can be designed according to requirements.

In some embodiments of the invention, the top of the growth crucible 1 extends beyond the first opening 21.

In this embodiment, the growth crucible 1 is located in a temperature field with decreasing temperature from bottom to top, the growth crucible 1 exceeding the first nested crucible 2 is directly heated by the heating device, the efficiency of the obtained heat is high relative to the heat obtained inside the first nested crucible 2, and compared with the scheme that the top of the growth crucible 1 does not exceed the first opening 21, the temperature gradient between the top and the bottom of the growth crucible 1 is reduced, and crystals with better quality can be obtained. The temperature gradient reduced by the method is within a reasonable range, so that the production of crystals is not affected by the overlarge change of the temperature gradient.

In some embodiments of the invention, the top of the growth crucible 1 does not exceed the first opening 21.

In this embodiment, the growth crucible 1 is entirely located in the first nested crucible 2, the growth crucible 1 is heated more uniformly, and the temperature gradient between the top and bottom of the growth crucible 1 increases, compared to the case where the top of the growth crucible 1 exceeds the first opening 21, so that the growth rate of the crystal can be improved.

It will be appreciated that the temperature gradient of the growth crucible 1 can be fine tuned by how much of the growth crucible 1 exceeds the first opening 21, and that accurate, controlled production of crystal quality and growth rate can be achieved as desired.

In some embodiments of the invention, a second nested crucible 3 is also included, the second nested crucible 3 being provided with a second opening 31, the first nested crucible 2 being accessible to the second nested crucible 3 through the second opening 31.

In this embodiment, the provision of the second nested crucible 3 can further protect the growth furnace apparatus from leakage of the high-temperature solution.

In some embodiments of the invention, the inner wall of the second nested crucible 3 is provided with a second defect structure 32, the second defect structure 32 being recessed away from the first nested crucible 2, the plane of the liquid surface of the growth material 6 passing through the second defect structure 32.

In this embodiment, the first defect structure 22 and the second defect structure 32 cooperate to form a larger temperature gradient, so that the growth rate of the silicon carbide crystal can be further increased.

In some embodiments of the invention, the top of the first nested crucible 2 exceeds the second opening 31;

or alternatively, the first and second heat exchangers may be,

the top of the first nested crucible 2 does not protrude beyond the second opening 31.

In this embodiment, the temperature gradient of the growth crucible can be adjusted by the first nested crucible 2 exceeding or not exceeding the second opening 31. By designing the first nested crucible 2 to exceed or not exceed the second opening 31, the growth crucible 1 to exceed or not exceed the first opening 21, and then matching with whether the first defect structure 22 and the second defect structure 32 are arranged, the size and the distribution of the temperature gradient of the growth crucible 1 can be flexibly and accurately regulated.

It will be appreciated that the outer part of the second nested crucible 3 may also be provided with a plurality of nested crucibles (for example, three, four, five or six nested crucibles) layer by layer, and that by providing a staggered distribution between the plurality of nested crucibles (whether the inner nested crucible exceeds the outer nested crucible) and designing the defect structure, the magnitude and distribution of the temperature gradient of the growth crucible 1 can be more precisely and finely adjusted.

In the production of a silicon carbide single crystal, the growth crucible 1 and/or the seed rod 4 may be rotated to cause convection of the growth material 6.

Example 1

Referring to the apparatus shown in fig. 1, the preparation method is as follows:

(1) The preparation stage: a. an experimental scheme is well set, and the liquid level height of the metal raw material after high-temperature melting is determined through a pre-experiment; b. placing a growth crucible 1 filled with raw materials into a first nested crucible 2, placing the first nested crucible 2 into a second nested crucible 3, and placing the first nested crucible into a crystal furnace; c. moving the growth crucible 1 by the adjusting device 7 until the bottom of the first defect structure 22 of the first nested crucible 2 is leveled with the liquid level; d. the seed rod 4 is placed at a proper position in the crucible through a seed rod 4 lifting transmission device of the long crystal furnace.

(2) Heating: the furnace is vacuumized, then special gases such as helium, nitrogen or argon are filled, then power is started to raise the temperature, raw materials in the crucible are melted, and then seed crystals 5 are inserted into the solution.

(3) And (3) a crystal growth stage: in the crystal growth stage, the rotation of the seed crystal 5 and the crucible is controlled to make the solution components uniform, and simultaneously the lifting or descending of the seed crystal 5 and the crucible is controlled to ensure the proper growth environment. Since the solid-liquid interface is located at the bottom of the first defect structure 22 of the nested crucible, the temperature at the solid-liquid interface is high, the temperature of the grown crystal is low after the crystal is pulled up, and a temperature gradient is formed, and in order to ensure the level between the lower edge of the pit and the growth liquid level, the rising speed of the crucible needs to be set according to the falling speed of the liquid level.

(4) And (3) a cooling stage: the seed crystal 5 is pulled out of the solution while the power is reduced for cooling.

(5) Sampling: separating the seed rod 4 from the crystal growing furnace, opening the furnace cover, taking out the upper layer heat insulation felt, taking out the crucible, and taking out the crystal. The invention can grow 1-6inch silicon carbide crystal.

When the method is adopted for growing the silicon carbide single crystal by the liquid phase method, at the same temperature, the growth speed of the single crystal is increased from 90 mu m/h to 120 mu m/h and is increased by about 30% due to the increase of the temperature gradient at the solid-liquid interface (the increase of 3 ℃/cm to 5.5 ℃/cm in an experimental system).

Other parts of the invention use the prior art.

Example 2

Please refer to the apparatus shown in fig. 2;

the method of preparation of example 2 is substantially the same as that of example 1, except that the apparatus used in example 2 is provided with a second nesting device having a second defective structure 32 as compared to the apparatus used in example 1.

This example requires sufficient carbon supply capacity of the co-solution, and does not suffer from the drawbacks of co-solution encapsulation, etc. due to lack of carbon content caused by too high growth rate. This example therefore requires a high carbon-dissolving capacity of the co-solution and a strong convection in the solution. By adopting the structure of the embodiment, the energy consumption requirement is high, because the carbon supply capacity needs to be improved, the carbon supply efficiency at high temperature can be improved, and the power is improved to ensure the supply of carbon for heating; in addition, the heat conduction at the defect is slower, the power needs to be increased to the same temperature in order to ensure that the growth temperature is not changed, the power needs to be increased by about 0.8kw compared with the prior (defect structure is not arranged) in order to reach a certain temperature, the temperature gradient at the liquid level is increased to about 9 ℃/cm, and the growth speed of the single crystal is increased by about 170 mu m/h and is increased by about 30% compared with that of the embodiment 1.

Example 3

Please refer to the apparatus shown in fig. 3;

the preparation method of example 3 is basically the same as that of example 1, except that the apparatus used in example 3 is not provided with a second nesting apparatus, and the first nesting apparatus is not provided with the first defective structure 22, as compared with the apparatus used in example 1.

This embodiment reduces the heat transfer layer, i.e. the second nested crucible 3, which reduces the furnace power and thus the energy consumption. However, the single crystal growth rate in this example was slow, and it was only about 90 μm/h.

Comparative example 1

In a conventional apparatus for growing a silicon carbide single crystal by a liquid phase method, a crucible for growth is placed in a crystal furnace and heated, and the specific method is as follows:

(1) Placing the prepared raw materials into a growth crucible 1, and placing the growth crucible 1 into a crystal furnace;

(2) Placing a seed crystal 5 in a crucible through a seed rod;

(3) Heating after pretreatment, and carrying out liquid-receiving growth;

(4) And cooling and pulling out the grown crystal.

Comparative example 1 used a growth apparatus for silicon carbide by the conventional liquid phase method, which could not realize long-time growth of crystals, and the crucible was dissolved or the crucible was penetrated by the carbon supplied from the crucible. And the device can not carry out the fine adjustment of the temperature field on the growth system, if the adjustment and control can only be carried out by adjusting the position of the crucible in the crystal furnace, but the operation can influence the whole temperature field and the crystal quality.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A method for producing a silicon carbide crystal, comprising:

adjusting the growth crucible to be embedded into the first nested crucible to obtain a nested combination; the growth crucible is filled with growth raw materials, and the thickness of the first nested crucible is 5-30 mm;

placing the nested combination in a crystal furnace;

adjusting a seed rod to make the seed crystal level with the liquid level of the growth raw material;

starting an induction coil to heat the nested combination with preset power to obtain a multi-variable temperature field matched with the range of 1600-2100 ℃ so as to grow silicon carbide crystals on the surface of the seed crystal; wherein the preset power is 5-11kW.

2. The method of preparing according to claim 1, further comprising, prior to embedding the regulated growth crucible in the first nested crucible:

arranging a first defect structure on the inner wall of the first nested crucible, wherein the first defect structure is recessed in a direction away from the growth crucible;

the regulated growth crucible is embedded in a first nested crucible, comprising:

and adjusting the growth crucible to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the first defect structure.

3. The method of claim 2, further comprising, after said adjusting the seed rod to level the seed crystal with the liquid level of the growth feedstock, before said turning on the induction coil to heat the nested combination at a preset power:

and rotating the seed crystal and/or rotating the growth crucible through the seed rod to enable the relative rotation speed between the seed crystal and the growth crucible to be a preset speed, wherein the preset speed is 10-200 rpm.

4. The method of preparing according to claim 2, wherein the conditioning growth crucible is embedded in a first nested crucible, resulting in a nested combination, comprising:

adjusting the growth crucible to be embedded into the first nested crucible;

embedding the first nested crucible into the second nested crucible to obtain a nested combination.

5. The method of preparing according to claim 4, further comprising, prior to said embedding the first nested crucible into the second nested crucible:

a second defect structure is arranged on the inner wall of the second nested crucible, and the second defect structure is recessed in a direction away from the first nested crucible;

the embedding the first nested crucible into the second nested crucible comprises:

embedding the first nested crucible into the second nested crucible so that the plane of the liquid level of the growth raw material passes through the second defect structure.

6. The method of claim 5, wherein the preset power is 5.8-11kW.

7. The method according to claim 5, wherein the predetermined rate is 50 to 200rpm.

8. The method of claim 2, wherein the adjusting the growth crucible to fit into the first nested crucible such that the plane of the liquid surface of the growth feedstock passes through the first defect structure comprises:

adjusting a growth crucible to be embedded into a first nested crucible so that a plane where the liquid level of the growth raw material is located passes through the bottom of the first defect structure;

or alternatively, the first and second heat exchangers may be,

and adjusting the growth crucible to be embedded into the first nested crucible so that the plane of the liquid level of the growth raw material passes through the middle part of the first defect structure.

9. The method of preparing according to claim 1, wherein the conditioning growth crucible is embedded in a first nested crucible, comprising:

adjusting the growth crucible to be completely embedded into the first nested crucible;

or alternatively, the first and second heat exchangers may be,

the bottom of the growth crucible is regulated to be embedded into the first nested crucible.

10. The method of preparing according to claim 4, wherein embedding the first nested crucible into the second nested crucible comprises:

the first nested crucible is completely embedded into the second nested crucible;

or alternatively, the first and second heat exchangers may be,

and embedding the bottom of the first nested crucible into the second nested crucible.

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