CN116695254A

CN116695254A - Liquid phase growth device of silicon carbide single crystal

Info

Publication number: CN116695254A
Application number: CN202310677184.4A
Authority: CN
Inventors: 张泽盛; 张广宇; 黄岩
Original assignee: Beijing Crystal Field Semiconductor Co ltd
Current assignee: Beijing Crystal Field Semiconductor Co ltd
Priority date: 2023-06-08
Filing date: 2023-06-08
Publication date: 2023-09-05

Abstract

The invention relates to a liquid phase growth device of silicon carbide single crystal, comprising a growth crucible, a seed rod, an induction heating device and an insulating layer arranged between the growth crucible and the induction heating device; the growth crucible comprises a crucible main body filled with growth raw materials and a crucible cover with an opening, and one end of a seed rod, on which seed crystals are fixed, extends into the crucible main body through the opening; the heat preservation layer comprises an upper heat preservation area positioned above the growth crucible, a peripheral heat preservation area positioned around the growth crucible and a lower heat preservation area positioned below the growth crucible; the control of the temperature field of the liquid phase growth device is realized by changing the shape of the peripheral heat preservation area; the upper heat preservation area is provided with a through hole corresponding to the opening, and the through hole is used for allowing the seed rod to pass through. The device can carry out diversity regulation and control on the temperature field of crystal growth, and provides more possibility for the crystal growth.

Description

Liquid phase growth device of silicon carbide single crystal

Technical Field

The invention belongs to the technical field of silicon carbide single crystal production, and particularly relates to a liquid phase growth device of a silicon carbide single crystal.

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. The price of silicon carbide substrate wafers in the market at present is high, mainly because of low yield of silicon carbide single crystals, which results in a situation of undersupply in the market.

In the process of growing silicon carbide single crystals by a liquid phase method, control of a temperature field is important. A stable temperature field can effectively ensure the relatively stable environment for growing the crystal during the growth, can improve the repeatability of the experiment, and can provide more selectivity for the growth of the silicon carbide single crystal or pay attention to the growth quality or the growth speed and the like.

Therefore, it is very important to provide an adjustable stable temperature field device that is diversified, variable, and convenient, but it is difficult to achieve stable temperature field control by the liquid phase growth device for silicon carbide single crystals of the prior art.

Furthermore, for silicon carbide single crystal growth techniques, stable carbon source supply is a key factor for growth. Particularly when the liquid phase method is adopted for silicon carbide single crystal growth, if sufficient carbon supply cannot be ensured, problems such as solution-aiding encapsulation, crystal cracking and the like can occur during crystal growth. The technology for growing silicon carbide single crystal by liquid phase method is to carry out the transmission and supply of carbon element by the combined action of convection mass transfer and diffusion mass transfer, wherein the convection mass transfer comprises forced convection generated by rotation of seed crystal and natural convection combined action caused by concentration difference in a growth system, and the diffusion mass transfer is mainly the diffusion action of carbon source at the solid-liquid interface of crystal growth. However, the liquid phase method for growing silicon carbide single crystal is accompanied with crystal growth, because carbon elements on the surface of the growth crucible are consumed, the carbon supply position is further and further away from the growth position, the diffusion mass transfer effect is weakened, sufficient supply of carbon elements required during crystal growth is difficult to ensure, further, the defects of wrapping with a solution, crystal cracking and the like occur, the quality of the crystal is influenced, the quality of the crystal is poor, and secondly, when the method grows for a long time, the growth crucible (graphite crucible) serving as a carbon source is gradually consumed along with the growth, or the melting-through of the growth crucible can be caused, the solution flows into a furnace to damage the single crystal furnace, and the experiment is influenced to cause great economic loss.

Disclosure of Invention

In order to solve one or more technical problems existing in the prior art, the invention provides a liquid phase growth device of silicon carbide single crystals. The device of the invention realizes the control of the temperature field by changing the shape of the heat preservation layer, can carry out diversified regulation and control on the temperature field of crystal growth, and provides more possibility for the crystal growth.

The invention provides a liquid phase growth device of silicon carbide single crystals, which comprises a growth crucible, a seed rod fixed with seed crystals, an induction heating device for heating and a heat preservation layer, wherein the seed rod is fixed with seed crystals; the growth crucible comprises a crucible main body and a crucible cover, wherein the crucible main body is filled with growth raw materials, the crucible cover is provided with an opening, and one end of the seed rod, on which seed crystals are fixed, extends into the crucible main body through the opening; the heat preservation layer is arranged between the growth crucible and the induction heating device; the heat preservation layer comprises an upper heat preservation area positioned above the growth crucible, a peripheral heat preservation area positioned around the growth crucible and a lower heat preservation area positioned below the growth crucible; the control of the temperature field of the liquid phase growth device is realized by changing the shape of the peripheral heat preservation area; the upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for allowing a seed rod to pass through.

Preferably, the outer shape of the peripheral heat preservation area is cylindrical, right circular table-shaped, inverted circular table-shaped or calabash-shaped.

Preferably, when the outer shape of the peripheral insulating region is a perfect circular table shape, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, thereby increasing the growth rate of the silicon carbide single crystal.

Preferably, when the outer shape of the peripheral heat-insulating region is an inverted truncated cone shape, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is reduced, thereby reducing the growth rate of the silicon carbide single crystal.

Preferably, the materials adopted by the growth crucible are graphite; and/or one end of the seed rod, on which the seed crystal is not fixed, is connected with a transmission device, and the transmission device is used for controlling the lifting and the rotation of the seed rod.

Preferably, the thickness of the crucible wall of the crucible main body is 10-30mm, and the thickness of the bottom of the crucible main body is 15-40mm.

Preferably, the aperture of the through hole is 20-150mm.

Preferably, the growth feedstock comprises silicon and a metal feedstock, the metal feedstock being one or more of Al, ti, cr, fe, Y, yb, pr, la, cu, ce, sn, ge, co.

Preferably, the liquid phase growth apparatus further comprises a material block and a material block connector for providing growth raw materials; the material blocks capable of providing the growth raw materials are connected with the crucible wall of the growth crucible through the material block connecting pieces, and the density of the material blocks capable of providing the growth raw materials is smaller than that of the liquid growth raw materials.

Preferably, the mass connector is disposed against a crucible wall of the crucible body.

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

(1) The invention provides a liquid phase growth device of silicon carbide single crystal, which increases the plasticity of the device, further changes the temperature field condition of crystal growth by changing the shape structure of the peripheral heat preservation area of a heat preservation layer, and adopts a heat preservation structure in a layered mode to ensure the uniform heat dissipation of the temperature field.

(2) The liquid phase growth device of the silicon carbide single crystal in some preferred embodiments of the invention further comprises a material block and a material block connecting piece which can provide growth raw materials, wherein the material block and the material block connecting piece are preferably a graphite block for carbon supply and a graphite block connecting piece respectively, and the graphite block for carbon supply can move up and down along the crucible wall through the arrangement of the crucible wall clamping groove through the graphite block connecting piece; the graphite blocks for carbon supply in the device can stably suspend on the liquid level of the growth raw material for a long time through the graphite block connecting piece and the clamping groove, compared with the carbon supply arrangement in which the thickness of the crucible wall of the graphite crucible is thickened, carbon powder is directly added or graphite materials are stretched into the growth raw material solution, the carbon supply arrangement in the device is stable, the problem of influence on convection in a growth system is avoided, the problem of influence on the quality of grown crystals due to the influence on the convection is avoided due to the fact that the wall thickness is increased, the problem of influence on the quality of the grown crystals is avoided due to the fact that the wall thickness is increased is avoided, the device in the device not only plays a role of providing a carbon source sufficient and stable for a long time, but also can shorten the carbon supply distance and ensure that the carbon supply distance is unchanged, the carbon supply amount of diffusion mass transfer is ensured, the convection in the growth system is not influenced, and the grown crystals are more stable, and the device is a very stable carbon supply device.

Drawings

The drawings of the present invention are provided for illustrative purposes only, and the proportion, size, and number of the various parts in the drawings are not necessarily consistent with the actual product.

FIG. 1 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals provided in example 1 of the present invention;

FIG. 2 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals according to example 2 of the present invention;

FIG. 3 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals provided in example 3 of the present invention;

FIG. 4 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals provided in example 4 of the present invention;

FIG. 5 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals provided in example 5 of the present invention;

FIG. 6 is a schematic view showing the structure of a liquid phase growth apparatus for silicon carbide single crystals as provided in example 6 of the present invention;

FIG. 7 is a schematic view showing the positional relationship between the growth crucible, the carbon-supplying graphite block, and the graphite block connecting element included in FIG. 6;

FIG. 8 is a view showing the outline of a silicon carbide single crystal obtained in example 1 of the present invention;

FIG. 9 is a view showing the outline of a silicon carbide single crystal obtained in example 2 of the present invention;

FIG. 10 is a view showing the outline of a silicon carbide single crystal obtained in example 3 of the present invention;

FIG. 11 is a view showing the outline of a silicon carbide single crystal obtained in example 4 of the present invention;

FIG. 12 is a view showing the outline of a silicon carbide single crystal obtained in example 5 of the present invention;

FIG. 13 is a view showing the outline of a silicon carbide single crystal obtained in example 6 of the present invention;

FIG. 14 is a temperature gradient curve of a liquid phase growth apparatus for silicon carbide single crystals provided in examples 4 to 6 of the present invention; in fig. 14, (a) is a temperature gradient curve of the liquid phase growth apparatus for a silicon carbide single crystal provided in example 4, (b) is a temperature gradient curve of the liquid phase growth apparatus for a silicon carbide single crystal provided in example 5, and (c) is a temperature gradient curve of the liquid phase growth apparatus for a silicon carbide single crystal provided in example 6;

FIG. 15 is a schematic view showing the melting-through of a graphite crucible in the growth interface region after a silicon carbide single crystal is grown by a liquid phase method using the apparatus of comparative example 1 of the present invention;

FIG. 16 is a view showing the outline of a silicon carbide single crystal obtained in comparative example 1 of the present invention.

In the figure: 1: growing a crucible; 1-1: a crucible body; 1-2: a crucible cover; 2: seed rods; 3: seed crystal; 4: an induction coil; 5: a heat preservation layer; 5-1: an upper insulation area; 5-2: a peripheral insulation region; 5-3: a lower insulation region; 6: growing raw materials; 7: a clamping groove; 8: graphite blocks for carbon supply; 9: a graphite block connection; 10: and (3) a circular ring.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described in conjunction with 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. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The present invention provides a liquid phase growth apparatus of a silicon carbide single crystal, for example, as shown in fig. 1 to 3, comprising a growth crucible 1, a seed rod 2 to which a seed crystal 3 is fixed, an induction heating apparatus for heating (only an induction coil 4 is illustrated in the drawing), and a heat insulating layer 5; in the invention, the growth crucible 1 is a graphite crucible, and the induction heating device is used for heating the growth crucible 1, so that the growth raw material can be melted into a liquid state, and the growth temperature of the silicon carbide single crystal in a growth system can be maintained; the induction heating device has no special requirement, and is a conventional design in the field; the induction heating device comprises an induction coil 4 (also called a heating coil), the induction coil and the seed rod are coaxially arranged, and the induction heating device heats the growth crucible through electromagnetic induction; the growth crucible 1 comprises a crucible main body 1-1 and a crucible cover 1-2, wherein the crucible main body 1-1 and the crucible cover 1-2 are connected in a threaded connection mode, the wall thickness of the crucible main body is larger than that of the crucible cover, the outer side wall of the crucible main body is level with the outer side wall of the crucible cover, and the inner side wall of the crucible main body exceeds the inner side wall of the crucible cover; the crucible main body 1-1 is filled with a growth raw material 6, the crucible main body 1-1 is cylindrical, the crucible cover 1-2 is provided with an opening, and one end of the seed rod 2, to which a seed crystal is fixed, extends into the crucible main body 1-1 through the opening; the heat preservation layer 5 is arranged between the growth crucible 2 and the induction heating device, specifically, the heat preservation layer 5 is arranged between the growth crucible 2 and an induction coil 4 included in the induction heating device; in the present invention, the heat-insulating layer 5 is laid outside the growth crucible in a layer-by-layer manner, and is located between the growth crucible and the induction coil, and the growth crucible is placed at the central position inside the induction coil of the induction heating device; in the invention, the heat insulation layer 5 is formed by paving a graphite hard felt or a graphite soft felt in a layer-by-layer manner, preferably, the heat insulation layer is formed by paving a graphite soft felt in a layer-by-layer manner, the invention does not limit the graphite soft felt specifically, and products which can be purchased directly in the market can be adopted; in the invention, the induction coil of the induction heating device is positioned outside the growth crucible and is arranged coaxially with the seed rod.

In the invention, the whole liquid phase growth device is placed in the single crystal furnace, and the heat preservation layer is beneficial to playing a role in stabilizing a temperature field, so that the quality of crystals is improved; the heat preservation layer 5 comprises an upper heat preservation area 5-1 positioned above the growth crucible 1, a peripheral heat preservation area 5-2 positioned around the growth crucible 1 and a lower heat preservation area 5-3 positioned below the growth crucible 1; the upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for allowing a seed rod to pass through; specifically, the insulating layer 5 comprises an upper insulating region 5-1 positioned above the growth crucible 1 and between the induction coils 4, a peripheral insulating region 5-2 positioned between the periphery of the growth crucible 1 and the induction coils 4, and a lower insulating region 5-3 positioned between the lower side of the growth crucible 1 and the induction coils 4; the control of the temperature field of the liquid phase growth device is realized by changing the shape of the peripheral heat preservation area 5-2, in other words, the control of the temperature field of the liquid phase growth of the silicon carbide single crystal by adopting the liquid phase growth device is realized by changing the shape of the peripheral heat preservation area 5-2; the specific implementation mode can be that the control of the temperature field of the liquid phase growth device, namely the control of the temperature field of the silicon carbide single crystal grown by a liquid phase method is realized by enabling the appearance of the peripheral heat preservation area 5-2 to be cylindrical, right circular table-shaped, inverted circular table-shaped or calabash-shaped; in some embodiments, the peripheral insulating region 5-2 is cylindrical in shape, for example, as shown in FIG. 1; in some embodiments, the peripheral insulating region 5-2 has a shape of a right circular table, for example, as shown in fig. 2; in some embodiments, the peripheral insulating region 5-2 has an inverted truncated cone shape, for example, as shown in fig. 3; the outer diameter of the peripheral heat-insulating region 5-2 may be, for example, 130 to 480mm, preferably an integer value of 130 to 480mm, and specifically set according to the temperature field requirement, the upper heat-insulating region 5-1 is provided with a through hole corresponding to the opening of the crucible cover 1-2, the through hole is used for passing the seed rod 2, for example, the through hole is used for passing the end of the seed rod, to which the seed crystal is not fixed, and the aperture of the through hole may be, for example, an integer value of 20 to 150mm, preferably 20 to 150 mm.

The invention realizes the control of the temperature field of the liquid phase method for growing the silicon carbide single crystal by changing the shape of the peripheral heat preservation area, and discovers that the mode of changing the shape of the peripheral heat preservation area not only ensures the convenience in manufacturing the device and greatly ensures the repeatability of production, but also improves the yield of the silicon carbide single crystal, simultaneously increases the plasticity of the device, can realize the control of the stable change of the temperature field by changing the shape of the heat preservation layer, realizes the control of the temperature field of the liquid phase method for growing the silicon carbide single crystal by changing the shape of the peripheral heat preservation area, is a brand new control mode, can carry out diversified regulation and control on the temperature field of the silicon carbide single crystal growth, and provides more possibilities for the growth of the silicon carbide single crystal.

According to some preferred embodiments, the peripheral insulating region 5-2 has a cylindrical shape, a right circular table shape, an inverted circular table shape or a gourd shape in external shape.

According to some preferred embodiments, when the outer shape of the peripheral insulating region 5-2 is a right circular table shape, for example, as shown in fig. 2, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, and the growth speed of the silicon carbide single crystal is further increased, so that the crystal yield is improved, for example, when the device is not used, the range of the crystal growth speed is smaller when the temperature is constant, and the growth speed range can be enlarged to 15-280 μm/h after the device is selected, so that more possibility is provided for crystal growth.

According to some preferred embodiments, when the outer shape of the peripheral insulating region 5-2 is an inverted truncated cone shape, for example, as shown in fig. 3, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is reduced, thereby reducing the growth rate of the silicon carbide single crystal, resulting in sufficient carbon source supply and improved crystal quality.

In particular, the temperature field includes a temperature gradient, a temperature, a specific distribution of temperature, etc., and the temperature field may be stabilized by a large temperature gradient, the stabilization is mainly to maintain the state, and the temperature field may be said to be stabilized by a large temperature gradient or a small temperature gradient from the beginning to the end; in the invention, the temperature gradient change of the temperature field can be regulated and controlled and is not changed in the middle of growth, and for the invention, after the appearance of the peripheral heat preservation area is determined, the gradient change of the temperature field is determined before the growth of the silicon carbide single crystal, and then the whole growth process is in an equilibrium state.

The invention is not particularly limited to the parameters such as the size of the growth crucible and the like, and the design can be carried out by a person skilled in the art according to the requirements.

According to some preferred embodiments, the materials used for the growth crucible 1 are graphite, the graphite is high purity graphite, the purity of the graphite is not less than 99.95%, in the present invention, the graphite materials refer to graphite having a purity of not less than 99.95%, and in the absence of any particular description, the graphite has a density of 1.70-2.00 g/cm ³ Is a graphite of (2); and/or one in which the seed rod 2 is not fixed with a seed crystalThe end is connected with a transmission device, and the transmission device is used for controlling the lifting and the rotation of the seed rod, namely controlling the lifting and the rotation of the seed crystal; in the invention, the transmission device is not particularly limited, is a conventional design in the field, and can be used for controlling the lifting and the rotation of the seed rod; in the present invention, the apparatus for growing a silicon carbide single crystal by the liquid phase method may further include, for example, a rotating means for rotating the growth crucible; the present invention is not particularly limited to the arrangement of the rotating device, and may be arranged conventionally in the art.

According to some preferred embodiments, the crucible body 1-1 has a crucible wall thickness of 10 to 30mm and the crucible body 1-1 has a bottom thickness of 15 to 40mm.

According to some preferred embodiments, the aperture of the through-hole is 20 to 150mm, preferably the aperture of the through-hole is an integer value in the range of 20 to 150 mm.

According to some preferred embodiments, the outer diameter of the peripheral insulating region 5-2 is 130-480 mm, preferably an integer value in 130-480 mm, specifically set according to the temperature field requirements.

According to some preferred embodiments, the growth feedstock 6 comprises silicon and a metal feedstock, the metal feedstock being one or more of Al, ti, cr, fe, Y, yb, pr, la, cu, ce, sn, ge, co.

According to some embodiments, for example, as shown in fig. 1 to 3, the liquid phase growth apparatus of a silicon carbide single crystal includes a growth crucible 1, an insulating layer 5; the growth crucible is made of graphite material, and is used as a container for crystal growth and provides carbon elements for crystal growth; the growth crucible 1 comprises two parts, wherein one part is a crucible main body 1-1 for containing growth raw materials 6, the other part is a crucible cover 1-2 with an opening in the middle, and the diameter of the opening is larger than that of a seed rod 2, so that the seed rod 2 can pass through the opening. The heat preservation layer 5 is divided into three areas, namely a lower heat preservation area 5-3, an upper heat preservation area 5-1 and a peripheral heat preservation area 5-2 based on a growth crucible, and the three areas are combined together to realize the multi-temperature field regulation and control of a silicon carbide single crystal growth system; the size of the central region of the induction coil is not particularly limited in the present invention, and one skilled in the art can design the central region of the induction coil according to the need, for example, the central region of the induction coil may have a diameter of 350 to 500mm.

In the invention, when the liquid phase growth device of the silicon carbide single crystal is designed, the growth crucible and the induction coil are sized to determine the size of a graphite felt for heat preservation, so that the outer diameter of the heat preservation layer is slightly smaller than the size of the central area of the induction coil, for example, the diameter of the central area of the induction coil is 20-60 mm; determining the number of lower layers of graphite felt according to the height of the induction coil and the position of the growth crucible (the overall induction heating degree of the middle position of the growth crucible in the height direction of the induction coil is higher, the growth crucible is positioned in the lower area of the induction coil, the high-temperature line of the growth environment moves upwards, the crystal growth speed is slower, the growth crucible is positioned in the upper area of the induction coil, the high-temperature line of the growth environment moves downwards, and the crystal growth speed is faster); after the relative positions of a growth crucible and an induction coil are determined, for example, after the growth crucible is positioned at the middle position of the induction coil, specifically, for example, the growth crucible is determined to be positioned at the middle position of the induction coil in the radial direction and the height direction, so that the number of layers of graphite felts in a lower heat preservation area is determined, the placement of the graphite felts at the periphery of the growth crucible is further adjusted according to experimental requirements, in the invention, the graphite felts are placed in a layering mode, so that the peripheral heat preservation areas of the growth crucible have different appearances, the outer diameters of the graphite felts in the peripheral heat preservation areas are smaller than the diameter of the central area of the induction coil by 20-60 mm, the inner diameter is equal to the outer diameter of the growth crucible, the outer diameters of the graphite felts in the peripheral heat preservation areas can be the same or different, the heat preservation capacity of the areas with larger outer diameters is higher, the outer diameter of the areas with smaller outer diameters is better, and the outer diameters of the graphite felts in the position are determined according to experimental requirements, when the outer diameters of the graphite felts are the parts are the same from top to bottom, namely the outer diameters of the peripheral heat preservation areas are the outer diameters of the peripheral heat preservation areas, the crystal growth thermal insulation areas are gradually increased, and the heat preservation areas are gradually growing from top to bottom, and the outer diameters of the silicon crystal growth thermal insulation areas can grow gradually, and the thermal insulation silicon crystal growth has thermal insulation performance increases; when the outer diameter of the part of graphite felt is gradually decreased from top to bottom, namely the outer diameter of the peripheral heat preservation area is gradually decreased from top to bottom, namely the outer shape of the peripheral heat preservation area is in an inverted truncated cone shape, at the moment, the outer diameter of the peripheral heat preservation area is gradually decreased from top to bottom, so that the heat preservation capacity of the peripheral heat preservation area is gradually decreased from top to bottom, the temperature gradient between the seed crystal and the liquid level of the growth raw material can be reduced, the growth speed of the silicon carbide single crystal is further reduced, and sufficient carbon source supply is obtained and the crystal quality is improved; growing raw materials are filled in a growing crucible, and a seed rod connected with seed crystals is placed in a crucible main body; placing an upper graphite felt according to a set temperature field, wherein the outer diameter of the part of graphite felt (an upper heat preservation area) is 20-60 mm smaller than the diameter of the central area of the induction coil, and a through hole larger than the outer diameter of a seed rod is arranged in the center of the part of graphite felt, so that the seed rod can pass through the through hole; connecting the seed rod with a transmission device, wherein the device can drive the seed crystal to move up and down (lift) and rotate; when the device is used for growing silicon carbide monocrystal by a liquid phase method, after pretreatment such as vacuum, the power of an induction coil is started for heating; after the set time is reached, the growth raw material is melted, the seed crystal is lowered through the seed rod transmission device until the seed crystal contacts with the liquid level of the growth raw material, and single crystal growth is started; and after the growth is finished, cooling to room temperature, and taking out the obtained grown monocrystal, namely the silicon carbide monocrystal. By using the liquid phase growth device for silicon carbide single crystal shown in fig. 2 and 3 to carry out single crystal growth, the temperature field change of a growth system can be increased, such as increasing the temperature gradient to improve the crystal growth speed, improving the productivity (shown in fig. 2), or reducing the temperature gradient to reduce the crystal growth speed, thereby obtaining sufficient carbon source supply to improve the crystal quality (shown in fig. 3); when the device is not used, the range of the crystal growth speed is smaller when the temperature is constant, and the growth speed range can be enlarged to 15-280 mu m/h after the device is selected, so that more possibility is provided for the crystal growth.

In the present invention, the liquid phase growth apparatus for growing a silicon carbide single crystal by liquid phase method comprises, for example, the steps of:

(1) Selecting a growth raw material for growing silicon carbide single crystals;

(2) The growth raw materials are contained in a crucible main body of the growth crucible, and the growth crucible is heated by the induction heating device so as to melt the growth raw materials into a liquid state; specifically, after the growth raw material is contained in the crucible main body, the liquid phase growth device of the silicon carbide single crystal is assembled, the growth crucible is heated by the induction heating device to enable the growth raw material to be melted into a liquid state, for example, the crucible main body filled with the growth raw material, the seed crystal rod fixed with the seed crystal, the induction heating device, the heat preservation layer and the like are assembled into the liquid phase growth device of the silicon carbide single crystal, and the growth crucible is heated by the induction heating device to enable the growth raw material to be melted into the liquid state; in the present invention, the growth raw material is melted into a liquid state, for example, under a vacuum environment; heating: vacuumizing the single crystal furnace, then filling special gases such as helium, nitrogen or argon, and the like, and then starting power heating to enable the induction heating device to heat the graphite crucible so as to enable the growth raw materials to be completely melted into solution;

(3) The seed crystal fixed on the seed rod is lowered to be in contact with the liquid surface of the liquid growth raw material to grow the silicon carbide single crystal, so that the silicon carbide single crystal is obtained; in the invention, specifically, after the temperature reaches the process temperature, the seed crystal fixed on the seed rod is lowered to be in contact with the liquid level of the liquid growth raw material, and Si and C elements in the solution can be crystallized at the seed crystal due to the low temperature at the seed crystal, so that the growth of the silicon carbide single crystal is carried out, and the silicon carbide single crystal is obtained; in the crystal growth process, the seed crystal is pulled and rotated, in the crystal growth stage, the seed crystal starts to be pulled and rotated through program setting, and the crystal is grown in a continuous motion state, wherein the pulling speed can be 10-1500 mu m/h, and the rotating speed can be 5-300 rpm; in the invention, after the growth is finished, cooling to room temperature to obtain a silicon carbide ingot (silicon carbide single crystal), for example, reducing the power to cool, simultaneously pulling the crystal and liquid growth raw materials off and stopping rotating, opening a single crystal furnace body after the cooling is finished, taking out a graphite crucible, opening a crucible cover, taking out the grown crystal to obtain the silicon carbide single crystal; the invention does not limit the parameters in the crystal growth process, and the conventional silicon carbide crystal growth parameters in the field can be adopted.

According to some preferred embodiments, the liquid phase growth apparatus further comprises a mass and mass connector that can provide growth feedstock; in the invention, the material block capable of providing the growth raw material can be, for example, a carbon supply graphite block, a silicon carbide block or other material blocks capable of providing the growth raw material; the material blocks capable of providing the growth raw materials are connected with the crucible wall of the growth crucible through the material block connecting pieces, and the density of the material blocks capable of providing the growth raw materials is smaller than that of the liquid growth raw materials; in the present invention, when the material block that can provide the growth raw material is a graphite block for carbon, the material block connector may be, for example, a graphite block connector.

According to some preferred embodiments, the mass connector is disposed against a crucible wall of the crucible body.

According to some preferred embodiments, the material blocks capable of providing the growth raw materials are graphite blocks for carbon, the material block connectors are graphite block connectors, and the liquid phase growth device further comprises graphite blocks for carbon 8 and graphite block connectors 9; the graphite block 8 for carbon is connected to the crucible wall 1-1 of the growth crucible 1 through the graphite block connecting member 9, and the density of the graphite block for carbon is smaller than that of the liquid growth raw material, for example, as shown in fig. 4 to 7, specifically, the liquid phase growth apparatus further comprises the graphite block 8 for carbon (graphite material) and the graphite block connecting member 9; a clamping groove 7 is formed in the crucible wall of the crucible main body 1-1 downwards from the top, a circular ring 10 is arranged at one end (upper end) of the graphite block connecting piece 9, the circular ring 10 is clamped in the clamping groove 7, and a graphite block 8 for carbon supply is connected to the other end (lower end) of the graphite block connecting piece 9; in the present invention, by providing the ring and the clamping groove, the graphite block 8 for carbon supply is connected with the crucible wall 1-1 of the growth crucible 1 through the graphite block connecting piece 9, the density of the graphite block 8 for carbon supply is smaller than that of the liquid growth raw material 6, the graphite block 8 for carbon supply floats on the liquid surface of the liquid growth raw material 6, namely, in the process of growing silicon carbide single crystal by adopting the device to perform a liquid phase method, the graphite block 8 for carbon supply floats on the liquid surface of the growth raw material 6, so as to additionally improve the carbon source required by the growth of the silicon carbide single crystal, namely, in the process of growing the silicon carbide single crystal by adopting the liquid phase method, the crucible main body 1-1 is used as a main carbon source, and the liquid surface of the growth raw material 6 for carbon supply of the silicon carbide single crystal, which floats on the liquid surface of the graphite block 8 for carbon supply is used as a secondary carbon source, specifically: the invention relates to a method for preparing carbon-supplying graphite blocks, which is characterized in that the carbon-supplying graphite blocks are suspended (floated) on the liquid growth raw material liquid surface, and the parts of the carbon-supplying graphite blocks, which are contacted with the liquid growth raw material, are dissolved for supplying carbon, while the parts of the carbon-supplying graphite blocks, which are not contacted with the liquid growth raw material, are continuously suspended on the liquid growth raw material liquid surface and are continuously dissolved for continuously supplying carbon; in the invention, the clamping groove can enable the graphite block connecting piece to move up and down against the inner side of the crucible wall through the circular ring, so as to drive the graphite block for carbon to move up and down against the inner side of the crucible wall; in the present invention, the graphite block for carbon supply, the graphite block connecting material and the ring may be integrally formed, for example, and integrally connected.

The liquid phase growth device for the silicon carbide single crystal preferably comprises a graphite block for carbon supply and a graphite block connecting piece, the graphite block for carbon supply can move up and down along the crucible wall through the arrangement of the crucible wall clamping groove, and the graphite block for carbon supply has low density characteristic and density smaller than that of a growth raw material due to graphite material, so that the graphite block for carbon supply can be always suspended on the surface of a growth raw material solution in the long-time growth process, namely a growth interface, thereby providing sufficient carbon source for the growth of the silicon carbide single crystal, and the graphite block for carbon supply is only thinned at the position contacted with the liquid level of the growth raw material solution along with the extension of the growth process at the growth interface, and other arrangements have no change, so that the carbon supply distance is unchanged in the growth process of the silicon carbide single crystal, the growth quality of the silicon carbide single crystal is more stable, and the phenomenon that the crucible is fused is inhibited; the graphite blocks for carbon supply in the device can stably suspend on the liquid level of the growth raw material for a long time through the graphite block connecting piece and the clamping groove, compared with the carbon supply arrangement in which the thickness of the crucible wall of the graphite crucible is thickened or carbon powder is directly added or graphite material is stretched into the growth raw material solution, the carbon supply arrangement in the device is stable, the problem that convection in a growth system is not influenced is avoided, the problem that the quality of grown crystals is influenced due to the influence of convection is avoided, the device not only plays a role of providing sufficient carbon sources, but also can shorten the carbon supply distance and ensure that the carbon supply distance is unchanged, the convection in the growth system is not influenced, and the grown crystals are more stable, so that the device is a very stable carbon supply device; the liquid phase growth device preferably adopted by the invention firstly shortens the carbon supply distance and ensures that the carbon supply distance is unchanged in the liquid phase growth process of silicon carbide single crystals, secondly can provide sufficient and long-time stable carbon sources for the growth process of the silicon carbide single crystals, greatly reduces the generation of wrappage, effectively improves the quality of single crystal growth, simultaneously effectively inhibits the crucible wall from being fused through, particularly effectively inhibits the crucible wall at the surface of a growth raw material solution from being fused through, prevents the leakage of a co-solution (growth raw material) from affecting a temperature field and even damaging a single crystal furnace, further improves the repeatability and the stability of single crystal growth experiments, realizes long-time growth, reduces the thickness of the crucible wall and saves the cost.

According to some preferred embodiments, the graphite block connection 9 is arranged against the crucible wall of the crucible body 1-1; and/or the ring 10 can move up and down in the clamping groove 7.

According to some preferred embodiments, the graphite block connector 9 and the ring 10 are made of graphite.

The invention does not limit the parameters such as the thickness of the crucible wall of the crucible main body, the thickness of the bottom of the crucible main body, the depth of the clamping groove, the width of the clamping groove, the size of the graphite block for carbon supply and the like, and the invention can be designed by a person skilled in the art according to the needs; when the device for growing the silicon carbide single crystal by the liquid phase method is designed, the size of a crucible main body of a graphite crucible can be determined according to the size of the silicon carbide single crystal to be grown, the size of a crucible cover and the size of a middle opening are determined according to the size of the crucible main body, so that seed crystals can enter the crucible, the crucible main body and the crucible cover are made of graphite materials, a clamping groove is formed in the crucible wall at the top of the crucible main body downwards, a carbon supply graphite block can move up and down against the crucible wall of the crucible main body through the design of a graphite block connecting piece and a circular ring, for example, the wall thickness of the crucible main body can be made to be 10-30 mm, the distance from the starting position of the clamping groove to the inner side of the crucible wall at the top of the crucible wall of the crucible main body is 2-5 mm, the depth of the clamping groove is 10-50 mm, and the bottom thickness of the crucible main body is 15-40 mm.

According to some preferred embodiments, the crucible body 1-1 has a crucible wall thickness of 10-30 mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the crucible body 1-1 has a bottom thickness of 15-40 mm (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 mm); the starting position of the clamping groove 7 is arranged at the top of the crucible wall of the crucible main body 1-1, and the distance from the starting position to the inner side of the crucible wall is 2-5 mm (for example, 2, 2.5, 3, 3.5, 4, 4.5 or 5 mm); the depth of the clamping groove 7 is 10-50 mm (such as 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 mm), and preferably, the bottom of the clamping groove is higher than the liquid level of the contained liquid growth raw material in the height direction of the crucible main body; the width of the clamping groove is not particularly limited, for example, in the thickness direction of the crucible wall, the clamping groove does not penetrate through the thickness of the crucible wall, the distance from the starting position of the clamping groove to the inner side of the crucible wall is 2-5 mm, and the width of the clamping groove can be preferably 2-10 mm.

According to some preferred embodiments, the clamping groove 7 is arranged in the crucible wall of the crucible main body 1-1 in a surrounding manner; the clamping groove 7 is an annular clamping groove, the graphite block connecting piece 9 is an annular graphite block connecting piece, and the graphite block 8 for carbon supply is an annular graphite block for carbon supply; the thickness of the carbon-supplying graphite block 8 is 10 to 30mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the width of the carbon-supplying graphite block 8 is 10 to 30mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm).

According to some preferred embodiments, two symmetrical clamping grooves 7 are formed in the radial direction of the crucible wall of the crucible main body 1-1; the number of the graphite blocks 8 for carbon supply is two; the number of the graphite block connecting pieces 9 is two; the thickness of the graphite block 8 for carbon supply is 10 to 30mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm), the width of the graphite block 8 for carbon supply is 10 to 30mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm), and the sum of the lengths L of the two graphite blocks 8 for carbon supply is smaller than the difference between the inner diameter of the crucible main body 1-1 and the diameter of the seed crystal.

In the invention, the graphite crucible is firstly used for containing a growth raw material for growing silicon carbide single crystals by a liquid phase method, is secondly used as a main carbon source for crystal growth, is downwards provided with a clamping groove from the crucible wall at the top of the crucible, and can be used for enabling a circular ring of a graphite block connecting piece to be sleeved at the clamping groove to move up and down along the crucible wall, the graphite block for carbon supply is connected with the clamping groove of the circular ring and the graphite crucible through the graphite block connecting piece and is suspended in the crucible main body, and the clamping groove can be used for enabling the graphite block connecting piece to move up and down along the inner side of the crucible wall through the circular ring, so that the graphite block for carbon supply is driven to move up and down along the inner side of the crucible wall, and the density of the graphite block for carbon supply is smaller than that of the liquid growth raw material, so that the graphite block for carbon supply can always suspend on the liquid surface of the growth raw material, and a sufficient carbon source is provided for silicon carbide single crystal growth at a growth interface; seed crystals are adhered below the seed rods, the seed rods and the seed crystals can be adhered through epoxy resin or phenolic resin, enter the crucible main body through the crucible cover opening and are contacted with liquid growth raw materials, the upper parts of the seed rods are connected with a transmission device, and the upper ends of the seed rods are connected with the transmission device in a threaded connection mode to realize up-and-down movement and rotation operation of the seed crystals; the growth raw material is a mixture containing silicon and at least one metal raw material, provides silicon element required for growth of silicon carbide single crystal by a liquid phase method, and can dissolve a graphite crucible and a graphite block for carbon so as to provide carbon element for crystal growth.

In the present invention, when a liquid phase growth apparatus for growing a silicon carbide single crystal is used for a liquid phase method, which comprises the graphite block 8 for carbon supply, a graphite block connector 9 and a clamping groove 7, in the step (1), a growth raw material for growing the silicon carbide single crystal is selected, and it is necessary to ensure that the density of the growth raw material after being melted into a liquid state is greater than that of the graphite block for carbon supply; namely, the component types of the growth raw materials are selected, and the density of the selected growth raw materials is calculated, so that the density of the liquid growth raw materials obtained after melting is ensured to be larger than that of the graphite blocks for carbon; in the step (3), since the density of the graphite blocks 8 for carbon supply is smaller than that of the liquid growth raw material 6, and the graphite blocks are arranged by the aid of the graphite block connecting pieces 9, the circular rings 10 and the clamping grooves 7, the graphite blocks can float on the surface of the liquid growth raw material 6 and be dissolved by the liquid growth raw material 6 for carbon supply, and the undissolved graphite blocks 8 for carbon supply can be ensured to continuously float on the liquid surface of the liquid growth raw material 6 and be continuously dissolved for carbon supply; that is, in the step (3), during the crystal growth process, the graphite block 8 for carbon supply is suspended on the liquid surface of the liquid growth raw material 6 to continuously supply carbon for the growth of the silicon carbide single crystal, specifically: the carbon-supplying graphite block is suspended on the liquid growth material level, and the portion of the carbon-supplying graphite block, which is in contact with the liquid growth material, is dissolved for supplying carbon, while the portion of the carbon-supplying graphite block, which is not in contact with the liquid growth material, continues to float on the liquid growth material level and is continuously dissolved for continuous carbon supply.

The invention will be further illustrated by way of example, but the scope of the invention is not limited to these examples.

Example 1

The embodiment provides a liquid phase growth device of silicon carbide single crystal, and the schematic structural diagram of the device is shown in figure 1; the device comprises: the device comprises a growing crucible, a seed rod fixed with seed crystals, an induction heating device for heating and a heat preservation layer; the growth crucible is a graphite crucible and is used for containing growth raw materials for growing silicon carbide single crystals by a liquid phase method and providing a carbon source for growth, the growth crucible comprises a crucible main body and a crucible cover, the crucible main body is in threaded connection with the crucible cover, the crucible main body is filled with the growth raw materials, and an opening is formed in the middle of the crucible cover and is used for allowing seed crystals to enter; one end of the seed rod is fixed with a seed crystal, and the other end of the seed rod is connected with a transmission device, so that the lifting and the rotation of the seed crystal can be controlled; one end of the seed rod for fixing seed crystals (silicon carbide seed crystals) extends into the crucible main body through the opening of the crucible cover; an insulating layer is arranged between the growth crucible and an induction coil of the induction heating device; the heat preservation layer is formed by paving graphite soft felt outside the growth crucible in a layer-by-layer mode and is positioned between the growth crucible and the induction coil, the growth crucible is placed at the central position inside the induction coil of the induction heating device, and the induction coil and the seed rod are coaxially arranged; the heat preservation layer comprises an upper heat preservation area positioned between the upper part of the growth crucible and the induction coil, a peripheral heat preservation area positioned between the periphery of the growth crucible and the induction coil, and a lower heat preservation area positioned between the lower part of the growth crucible and the induction coil; the upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, the through hole is used for allowing a seed rod to pass through, the through hole is used for allowing the seed rod to pass through, the outer diameter of the upper heat preservation area is smaller than the diameter of the central area of the induction coil by 40mm, and the outer diameter of the lower heat preservation area is also smaller than the diameter of the central area of the induction coil by 40mm; the growth crucible is positioned at the middle position of the radial direction and the height direction of the induction coil, the peripheral heat preservation area of the growth crucible is cylindrical, the outer diameters of the peripheral heat preservation areas are equal from top to bottom, the outer diameter of the peripheral heat preservation area is smaller than the diameter of the central area of the induction coil by 40mm, the inner diameter is leveled with the outer diameter of the growth crucible, and the diameter of the central area of the induction coil is 420mm. The inner diameter of the adopted growth crucible (graphite crucible) is 150mm, the outer diameter is 185mm, and the height is 100mm; the silicon carbide seed crystal is 4H-SiC grown by a PVT method, and has the diameter of 100mm and the thickness of 0.5mm.

The liquid phase method for growing a silicon carbide single crystal using the liquid phase growth apparatus for a silicon carbide single crystal in this embodiment includes the steps of:

(1) the growth raw materials for growing the silicon carbide single crystal are selected, the growth raw materials adopted in the embodiment are formed by mixing Si, cr and Al, and the mass percentage of the three components in the growth raw materials is as follows: 50%, cr:40%, al:10%.

(2) The growth raw material is filled in the main body of graphite crucible, and the graphite crucible is vacuumized to 2X 10 by using molecular pump ^-4 Ar gas of 0.8atm is introduced as a shielding gas after Pa or less, and the graphite crucible is heated by an induction heating device to completely melt the growth raw material into a liquid state.

(3) After the temperature reaches 1800 ℃ of the process temperature, the seed crystal fixed on the seed rod is lowered to be in contact with the liquid surface of the liquid growth raw material, and Si and C elements in the solution can be crystallized at the seed crystal due to low temperature at the seed crystal, so that the silicon carbide single crystal is grown, and the silicon carbide single crystal is obtained; in the process of growing the crystal, pulling the seed crystal and enabling the seed crystal to rotate, slowly pulling the silicon carbide seed crystal at a speed of 0.02mm/h, rotating the silicon carbide seed crystal at a speed of 40rpm, and simultaneously rotating the graphite crucible in the opposite direction at a speed of 20 rpm; and after the whole crystal growth process lasts for 60 hours, the silicon carbide seed crystal is pulled upwards at the speed of 3mm/h, so that the grown silicon carbide single crystal is separated from the liquid level of the growth raw material, the rotation is stopped, and the temperature is slowly reduced to the room temperature, namely the whole liquid phase method growth process is completed, and the silicon carbide single crystal is obtained.

The device in this embodiment is used to grow silicon carbide single crystal by liquid phase method, the growth speed is moderate, but the carbon supply is poor in the later stage of crystal growth, so that more grooves appear on the surface of the crystal, the crystal quality is affected, and the appearance diagram of the silicon carbide single crystal obtained in this embodiment is shown in fig. 8.

Example 2

The embodiment provides a liquid phase growth device of silicon carbide single crystal, and the schematic structural diagram of the device is shown in fig. 2; the liquid phase growth device of the silicon carbide single crystal in this embodiment is substantially the same as that in embodiment 1, except that the outer shape of the peripheral heat-insulating region is different from that in embodiment 1, in this embodiment, the peripheral heat-insulating region is in a right circular table shape, the inner diameter of the peripheral heat-insulating region is leveled with the outer diameter of the growth crucible, the outer diameters of the peripheral heat-insulating regions are sequentially increased from top to bottom, so that the heat-insulating capability of the peripheral heat-insulating region can be sequentially increased from top to bottom, and the temperature gradient between the seed crystal and the liquid level of the growth raw material can be increased, and the growth speed of the silicon carbide single crystal can be increased, and the crystal productivity can be improved; in this embodiment, the top outer diameter of the peripheral insulating region is greater than the outer diameter of the growth crucible by 40mm, the bottom outer diameter of the peripheral insulating region is smaller than the diameter of the central region of the induction coil by 40mm, and the diameter of the central region of the induction coil is 420mm.

The apparatus in this embodiment is used to grow silicon carbide single crystal by liquid phase method, the growth speed is fast, the carbon supply is extremely insufficient during crystal growth, so that more large grooves appear on the surface of the crystal, the surface of the whole crystal is rugged, the crystal quality is seriously affected, and the appearance diagram of the silicon carbide single crystal obtained in this embodiment is shown in fig. 9.

Example 3

The embodiment provides a liquid phase growth device of silicon carbide single crystal, and the structure schematic diagram of the device is shown in fig. 3; the liquid phase growth device of the silicon carbide single crystal in this embodiment is substantially the same as that in embodiment 1, except that the outer shape of the peripheral heat-insulating region is different from that in embodiment 1, in this embodiment, the peripheral heat-insulating region is in an inverted truncated cone shape, the inner diameter of the peripheral heat-insulating region is equal to the outer diameter of the growth crucible, the outer diameters of the peripheral heat-insulating regions decrease in sequence from top to bottom, so that the heat-insulating capability of the peripheral heat-insulating region decreases in sequence from top to bottom, and the temperature gradient between the seed crystal and the liquid level of the growth raw material can be reduced, and the growth speed of the silicon carbide single crystal is further reduced, so that sufficient carbon source supply is obtained and the crystal quality is improved; in this embodiment, the top outer diameter of the peripheral insulating region is smaller than the diameter of the central region of the induction coil by 40mm, the bottom outer diameter of the peripheral insulating region is larger than the outer diameter of the growth crucible by 40mm, and the diameter of the central region of the induction coil is 420mm.

The apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method, and the growth rate was slow, but the growth surface was slightly deficient in carbon supply, which resulted in a bunching phenomenon in which growth steps were visible on the growth surface, and the profile of the silicon carbide single crystal obtained in this example was shown in fig. 10.

Example 4

The present embodiment provides a liquid phase growth apparatus for a silicon carbide single crystal, which is substantially the same as that in embodiment 1, except that a clamping groove is provided from the top to the bottom of a crucible wall of the crucible body, and specifically two symmetrical clamping grooves are provided in the radial direction of the crucible wall of the crucible body; the liquid phase growth device also comprises two graphite block connectors and two graphite blocks for carbon supply, wherein the number of the graphite blocks (graphite materials) for carbon supply is two; one end of the graphite block connecting piece (graphite material) is provided with a circular ring (graphite material), the circular ring is clamped in the clamping groove, the other end of the graphite block connecting piece is connected with a graphite block for carbon supply, the density of the graphite block for carbon supply is smaller than that of liquid growth raw materials, the graphite block for carbon supply floats on the liquid surface of the liquid growth raw materials and is used for additionally improving a carbon source required by growth of silicon carbide single crystals, the graphite block connecting piece is arranged along the crucible wall of the crucible main body, the circular ring can move up and down in the clamping groove, and the clamping groove can move up and down along the inner side of the crucible wall through the circular ring so as to drive the graphite block for carbon supply to move up and down along the inner side of the crucible wall; the starting position of the clamping groove is arranged at the top of the crucible wall of the crucible main body, the distance from the starting position to the inner side of the crucible wall is 4mm, the depth of the clamping groove is 35mm, the thickness of the graphite block for carbon supply is 20mm, the width of the graphite block for carbon supply is 20mm, the length of the graphite block for carbon supply is 15mm, the sum of the lengths of the two graphite blocks for carbon supply is 30mm, and the schematic structural diagram of the liquid phase growth device of the silicon carbide single crystal in the embodiment is shown in fig. 4.

(1) selecting a growth raw material for growing the silicon carbide single crystal, and ensuring that the density of the growth raw material after being melted into a liquid state is higher than that of a graphite block for carbon; the growth raw materials adopted in the embodiment are formed by mixing Si, cr and Al, and the mass percentage of the three components in the growth raw materials is as follows: 50%, cr:40%, al:10%.

(2) The evenly mixed growth raw materials are filled in a crucible main body of a graphite crucible, and the graphite crucible is vacuumized to 2 multiplied by 10 by a molecular pump ^-4 Ar gas of 0.8atm is introduced as a shielding gas after Pa or less, and the graphite crucible is heated by an induction heating device to completely melt the growth raw material into a liquid state.

(3) After the temperature reaches 1800 ℃ of the process temperature, the seed crystal fixed on the seed rod is lowered to be in contact with the liquid surface of the liquid growth raw material, and Si and C elements in the solution can be crystallized at the seed crystal due to low temperature at the seed crystal, so that the silicon carbide single crystal is grown, and the silicon carbide single crystal is obtained; in the process of growing the crystal, pulling the seed crystal and enabling the seed crystal to rotate, slowly pulling the silicon carbide seed crystal at a speed of 0.02mm/h, rotating the silicon carbide seed crystal at a speed of 40rpm, and simultaneously rotating the graphite crucible in the opposite direction at a speed of 20 rpm; in the crystal growth process, the graphite crucible is used as a main carbon source, and the liquid surface of the growth raw material for floating the graphite block for carbon supply in the liquid state is used as a secondary carbon source for continuous carbon supply of silicon carbide single crystal growth; and after the whole crystal growth process lasts for 60 hours, the silicon carbide seed crystal is pulled upwards at the speed of 3mm/h, so that the grown silicon carbide single crystal is separated from the liquid level of the growth raw material, the rotation is stopped, and the temperature is slowly reduced to the room temperature, namely the whole liquid phase method silicon carbide crystal growth process is completed, and the silicon carbide single crystal is obtained.

After the device in the embodiment is adopted to grow silicon carbide monocrystal for 60 hours by a liquid phase method, the phenomenon that a graphite crucible is penetrated by melting does not occur, and the phenomenon that the crucible wall at the liquid level of the growth raw material is penetrated by melting does not occur.

The apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method at a single crystal growth rate of 100 μm/h, and the apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method at a moderate growth rate, and the obtained silicon carbide single crystal had a smooth and flat surface and good quality, and the appearance of the silicon carbide single crystal obtained in this example was as shown in FIG. 11.

Example 5

The present embodiment provides a liquid phase growth apparatus for a silicon carbide single crystal, which is substantially the same as that in embodiment 2, except that a clamping groove is provided from the top to the bottom of a crucible wall of the crucible body, and specifically two symmetrical clamping grooves are provided in the radial direction of the crucible wall of the crucible body; the liquid phase growth device also comprises two graphite block connectors and two graphite blocks for carbon supply, wherein the number of the graphite blocks (graphite materials) for carbon supply is two; one end of the graphite block connecting piece (graphite material) is provided with a circular ring (graphite material), the circular ring is clamped in the clamping groove, the other end of the graphite block connecting piece is connected with a graphite block for carbon supply, the density of the graphite block for carbon supply is smaller than that of liquid growth raw materials, the graphite block for carbon supply floats on the liquid surface of the liquid growth raw materials and is used for additionally improving a carbon source required by growth of silicon carbide single crystals, the graphite block connecting piece is arranged along the crucible wall of the crucible main body, the circular ring can move up and down in the clamping groove, and the clamping groove can move up and down along the inner side of the crucible wall through the circular ring so as to drive the graphite block for carbon supply to move up and down along the inner side of the crucible wall; the starting position of the clamping groove is arranged at the top of the crucible wall of the crucible main body, the distance from the starting position to the inner side of the crucible wall is 4mm, the depth of the clamping groove is 35mm, the thickness of the graphite block for carbon supply is 20mm, the width of the graphite block for carbon supply is 20mm, the length of the graphite block for carbon supply is 15mm, the sum of the lengths of the two graphite blocks for carbon supply is 30mm, and the schematic structural diagram of the liquid phase growth device of the silicon carbide single crystal in the embodiment is shown in fig. 5.

The apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method, the growth rate of the single crystal being 140 μm/h; the device in this embodiment is used to grow silicon carbide single crystal by liquid phase method, so that the growth speed is fast, the crystal productivity can be improved, the overall quality of the crystal is moderate, but compared with the device in embodiment 4, the device can cause the smooth flatness of the crystal surface to be reduced, relatively more small grooves and step bunching phenomenon occur, the crystal quality can be affected to a certain extent, and the appearance diagram of the silicon carbide single crystal obtained in this embodiment is shown in fig. 12.

Example 6

The present embodiment provides a liquid phase growth apparatus for a silicon carbide single crystal, which is substantially the same as that in embodiment 3, except that a clamping groove is provided from the top to the bottom of a crucible wall of the crucible body, and specifically two symmetrical clamping grooves are provided in the radial direction of the crucible wall of the crucible body; the liquid phase growth device also comprises two graphite block connectors and two graphite blocks for carbon supply, wherein the number of the graphite blocks (graphite materials) for carbon supply is two; one end of the graphite block connecting piece (graphite material) is provided with a circular ring (graphite material), the circular ring is clamped in the clamping groove, the other end of the graphite block connecting piece is connected with a graphite block for carbon supply, the density of the graphite block for carbon supply is smaller than that of liquid growth raw materials, the graphite block for carbon supply floats on the liquid surface of the liquid growth raw materials and is used for additionally improving a carbon source required by growth of silicon carbide single crystals, the graphite block connecting piece is arranged along the crucible wall of the crucible main body, the circular ring can move up and down in the clamping groove, and the clamping groove can move up and down along the inner side of the crucible wall through the circular ring so as to drive the graphite block for carbon supply to move up and down along the inner side of the crucible wall; the starting position of the clamping groove is arranged at the top of the crucible wall of the crucible main body, the distance from the starting position to the inner side of the crucible wall is 4mm, the depth of the clamping groove is 35mm, the thickness of the graphite block for carbon supply is 20mm, the width of the graphite block for carbon supply is 20mm, the length of the graphite block for carbon supply is 15mm, the sum of the lengths of the two graphite blocks for carbon supply is 30mm, and the schematic structural diagram of the liquid phase growth device of the silicon carbide single crystal in the embodiment is shown in fig. 6.

The apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method, the growth rate of the single crystal being 60 μm/h; the apparatus in this example was used to grow a silicon carbide single crystal by a liquid phase method, the growth rate was slow, the surface of the obtained silicon carbide single crystal was very smooth and flat, the quality was very good, and no macroscopic defects were present.

The present invention also provides a liquid phase growth apparatus for silicon carbide single crystals in examples 4 to 6, wherein the apparatus is assembled and heated without placing a growth material, and a temperature gradient test is performed by: the temperature measuring point is positioned on the back of the seed crystal, the seed crystal is moved to a position 1cm away from the bottom of the crucible main body through a transmission device, the stable temperature at the position is obtained through temperature measuring equipment, the temperature at the position is controlled to be 1800 ℃, then the seed crystal is moved to obtain temperature values at the positions of 2cm < -3 > cm < -4 > cm < -5 > cm < -6 > cm respectively, and a temperature gradient curve under the temperature field of each embodiment is obtained through graphic calculation, and the result is shown in figure 14; from the results of FIG. 14, it can be seen that the temperature gradient in the temperature field of example 4 was about 20 ℃/cm, the temperature gradient in the temperature field of example 5 was about 28 ℃/cm, and the temperature gradient in the temperature field of example 6 was about 14 ℃/cm; when the temperature gradient increases, the crystal growth speed increases, and the crystal quality is relatively poor; and when the temperature gradient is lowered, the crystal growth rate is lowered, but the crystal quality is remarkably improved.

Comparative example 1

The liquid phase growth apparatus for silicon carbide single crystal used in this comparative example comprises:

the growth crucible (graphite crucible) is used for containing growth raw materials for growing silicon carbide single crystals by a liquid phase method and providing a carbon source for growth, the growth crucible comprises a crucible main body and a crucible cover, the crucible main body is in threaded connection with the crucible cover, the crucible main body is filled with the growth raw materials, and an opening is formed in the middle of the crucible cover and can be used for entering seed crystals.

The seed rod is characterized in that one end of the seed rod is fixedly provided with a seed crystal, and the other end of the seed rod is connected with a transmission device, so that the lifting and the rotation of the seed crystal can be controlled; one end of the seed rod for fixing seed crystals (silicon carbide seed crystals) extends into the crucible main body through the opening of the crucible cover.

And the induction heating device is used for heating the growth crucible, and an induction coil contained in the induction heating device is coaxially arranged with the seed rod.

The heat preservation, the heat preservation sets up growth crucible with between the induction coil, the heat preservation selects for use the graphite hard felt, confirms according to growth crucible and keeps warm with graphite hard felt size, carries out graphite hard felt processing according to this size for graphite hard felt parcel is in the outside of growth crucible is as the heat preservation, and the heat preservation in this comparative example is formed by graphite hard felt integrated into one piece processing, all places growth crucible and heat preservation in the stove, and makes growth crucible is located induction coil's central point put (in induction coil's radial direction and direction of height all be in central point), the external diameter of heat preservation is slightly less than induction coil's central point district's size, the external diameter of heat preservation is less than induction coil central point district diameter 40mm. The graphite crucible used in this comparative example has an inner diameter of 150mm, an outer diameter of 185mm and a height of 100mm; the silicon carbide seed crystal is 4H-SiC grown by a PVT method, and has the diameter of 100mm and the thickness of 0.5mm.

The liquid phase method for growing the silicon carbide single crystal by adopting the liquid phase growth device of the silicon carbide single crystal in the comparative example comprises the following steps:

(1) the growth raw materials for growing the silicon carbide single crystal are selected, the growth raw materials adopted in the comparative example are formed by mixing Si, cr and Al, and the mass percentage of the three components in the growth raw materials is as follows: 50%, cr:40%, al:10%.

(3) After the temperature reaches 1800 ℃ of the process temperature, the seed crystal fixed on the seed rod is lowered to be in contact with the liquid surface of the liquid growth raw material, and Si and C elements in the solution can be crystallized at the seed crystal due to low temperature at the seed crystal, so that the silicon carbide single crystal is grown, and the silicon carbide single crystal is obtained; in the process of growing the crystal, pulling the seed crystal and enabling the seed crystal to rotate, slowly pulling the silicon carbide seed crystal at a speed of 0.02mm/h, rotating the silicon carbide seed crystal at a speed of 40rpm, and simultaneously rotating the graphite crucible in the opposite direction at a speed of 20 rpm; and after the whole crystal growth process lasts for 60 hours, the silicon carbide seed crystal is pulled upwards at the speed of 3mm/h, so that the grown silicon carbide single crystal is separated from the liquid level of the growth raw material, the rotation is stopped, and the temperature is slowly reduced to the room temperature, namely the whole liquid phase method silicon carbide crystal growth process is completed, and the silicon carbide single crystal is obtained.

The comparative example selects a liquid phase growth device of silicon carbide single crystals which are mostly selected at present, after the size of a growth crucible is determined, the device is prepared by taking the heat preservation and the temperature field as references, once the device is prepared, the temperature field can not be modified, and the temperature field can be determined only through the adjustment of the temperature and the position of a heated body in an induction coil, so that the flexibility is poor, and the research and development capability of the liquid phase crystal growth is limited; and the device adopts a standard graphite crucible to carry out silicon carbide monocrystal growth, and as the growth is carried out, carbon in a region of the crucible which is easy to dissolve carbon is dissolved and transported due to the dual functions of convection and diffusion, so that crystals continuously grow. The easy-to-dissolve carbon area comprises a high-temperature area and a growth interface area which is beneficial to diffusion, and after the crucible in the growth interface area is dissolved, the distance between the growth surface of the single crystal and a carbon source becomes long, so that the defects of insufficient supply of carbon supply, solution wrapping and the like are caused. Furthermore, the crucible in the growth liquid level area is dissolved to cause leakage of the solution, and the solution has a certain probability of flowing into the single crystal furnace while affecting the temperature field to cause damage of equipment.

With the apparatus of this comparative example, silicon carbide single crystal growth was carried out for 60 hours, and a phenomenon in which the growth interface region of the growth crucible (graphite crucible) was significantly melted through was observed, as shown in FIG. 15.

The apparatus in this comparative example was used to grow a silicon carbide single crystal by a liquid phase method, the single crystal growth rate being 92 μm/h; the apparatus of this comparative example was used for growing a silicon carbide single crystal by the liquid phase method, the growth rate was moderate, but due to the shortage of diffusion mass transfer, many large grooves were remarkably formed on the surface due to the lack of carbon in the crystal, the quality was poor, and the profile of the silicon carbide single crystal obtained in this comparative example was as shown in fig. 16.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "above", "below", "top", "bottom", "inside", etc. are based on the directions or positional relationships shown in fig. 1 to 7, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements to be 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 invention.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the term "connected" should be construed broadly, and may be a fixed connection, a removable connection, or an integral connection, for example; may be directly connected, or indirectly connected through an intermediate medium, etc. The specific meaning of the term in the present invention can be understood as appropriate to one of ordinary skill in the art.

The invention is not described in detail in a manner known to those skilled in the art.

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

1. The liquid phase growth device of the silicon carbide single crystal is characterized by comprising a growth crucible, a seed rod fixed with seed crystals, an induction heating device for heating and a heat preservation layer;

the growth crucible comprises a crucible main body and a crucible cover, wherein the crucible main body is filled with growth raw materials, the crucible cover is provided with an opening, and one end of the seed rod, on which seed crystals are fixed, extends into the crucible main body through the opening;

the heat preservation layer is arranged between the growth crucible and the induction heating device;

the heat preservation layer comprises an upper heat preservation area positioned above the growth crucible, a peripheral heat preservation area positioned around the growth crucible and a lower heat preservation area positioned below the growth crucible; the control of the temperature field of the liquid phase growth device is realized by changing the shape of the peripheral heat preservation area;

The upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for allowing a seed rod to pass through.

2. The liquid phase growth apparatus according to claim 1, wherein:

the outer shape of the peripheral heat preservation area is cylindrical, right circular table-shaped, inverted circular table-shaped or calabash-shaped.

3. The liquid phase growth apparatus according to claim 2, wherein:

when the shape of the peripheral heat preservation area is a right circular table shape, the temperature gradient between the seed crystal and the liquid level of the growth raw material is increased, and then the growth speed of the silicon carbide single crystal is increased.

4. The liquid phase growth apparatus according to claim 2, wherein:

when the shape of the peripheral heat preservation area is in an inverted truncated cone shape, the temperature gradient between the seed crystal and the liquid level of the growth raw material is reduced, and then the growth speed of the silicon carbide single crystal is reduced.

5. The liquid phase growth apparatus according to claim 1, wherein:

the material adopted by the growth crucible is graphite; and/or

One end of the seed rod, which is not fixed with seed crystals, is connected with a transmission device, and the transmission device is used for controlling the lifting and the rotation of the seed rod.

6. The liquid phase growth apparatus according to claim 1, wherein:

the thickness of the crucible wall of the crucible main body is 10-30mm, and the thickness of the bottom of the crucible main body is 15-40mm.

7. The liquid phase growth apparatus according to claim 1, wherein:

the aperture of the through hole is 20-150mm.

8. The liquid phase growth apparatus according to claim 1, wherein:

the growth feedstock comprises silicon and a metal feedstock, the metal feedstock being one or more of Al, ti, cr, fe, Y, yb, pr, la, cu, ce, sn, ge, co.

9. The liquid phase growth apparatus according to any one of claims 1 to 8, wherein:

the liquid phase growth device also comprises a material block and a material block connecting piece, wherein the material block and the material block connecting piece can provide growth raw materials;

the material blocks capable of providing the growth raw materials are connected with the crucible wall of the growth crucible through the material block connecting pieces, and the density of the material blocks capable of providing the growth raw materials is smaller than that of the liquid growth raw materials.

10. The liquid phase growth apparatus according to claim 9, wherein:

the material block connecting piece is arranged against the crucible wall of the crucible main body.