Device for promoting stable growth of silicon carbide crystal and working method thereof

Abstract

The present invention belongs to the field of silicon carbide single crystal growth, and specifically provides a device for promoting the stable growth of silicon carbide crystals and a working method thereof, wherein the device for promoting the stable growth of silicon carbide crystals performs stirring at a lower temperature by regulating the temperature of the stirring stage and the growth stage, thereby reducing corrosion to the crucible and the stirring paddle, and controlling the crucible to rotate forward and reverse in a periodic alternating manner. When the stirring assembly is fixed, the stirring paddle can be driven to rotate freely by the flow of the solution to complete the stirring of the solution; the solution can be quickly mixed under the impact of the opposite inertial forces generated by the forward and reverse rotation of the crucible, so that the solution is mixed evenly in a short time; the crucible periodically rotates forward and reversely to reduce the rotation speed when the desired stirring effect is achieved, thereby avoiding an increase in the carbon dissolution rate, thereby improving the stability of subsequent crystal production. After the stirring is completed, the crystal is grown at a higher temperature to increase the growth rate of the crystal.

Description

Technical Field

[0001] The present invention belongs to the field of silicon carbide single crystal growth, and specifically relates to silicon carbide crystal growth by a high-temperature solution method, and in particular to a device for promoting the stable growth of silicon carbide crystals and a working method thereof. Background Art

[0002] The essence of high-temperature solution growth of silicon carbide crystals is to dissolve the carbon solute in the auxiliary solution in the graphite crucible. Driven by the temperature gradient, the solute reaches supersaturation at the seed crystal growth interface, and then SiC crystals are precipitated to achieve epitaxial growth of the crystal. During the entire growth process, the stability of silicon carbide crystal growth is the key to ensuring its high quality and high performance.

[0003] In the related art, the preparation of silicon carbide crystals generally includes two stages, the first is the chemical material dissolution stage, and the second is the pulling growth stage. In the chemical material dissolution stage, additional small silicon carbide particles are formed in the solution. If the pulling growth stage is directly entered, these small particles will interfere with the normal growth of the crystal, resulting in an uneven crystal surface, the formation of polycrystalline clusters, an increase in internal defects in the crystal, and a reduction in the stability of the crystal during growth.

[0004] Therefore, how to reduce the formation of polycrystalline clusters while improving the stability of crystal growth is a technical problem that needs to be solved urgently.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the invention

[0006] The embodiments of the present disclosure at least provide a device for promoting the stable growth of silicon carbide crystals and a working method thereof.

[0007] In a first aspect, an embodiment of the present disclosure provides a device for promoting stable growth of silicon carbide crystals, comprising:

[0008] A crucible, which is used to hold the solution;

[0009] A heating assembly is arranged around the crucible;

[0010] A stirring component, used for stirring the solution in the crucible;

[0011] A driving mechanism, which is disposed below the crucible and is used to drive the crucible to rise, fall and rotate;

[0012] A seed crystal assembly, which is disposed above the crucible and is used for crystal growth;

[0013] The control module is configured to control the heating component to heat the solution to a first temperature during the stirring stage, and control the driving mechanism to drive the crucible to rise so as to completely immerse the stirring blades of the stirring component, and then control the driving mechanism to drive the crucible to rotate in a periodic forward and reverse rotation mode; and

[0014] During the growth phase, the heating component is controlled to heat the solution to a second temperature, and the seed crystal component is controlled to rotate and repeatedly pull to complete crystal growth.

[0015] In an optional embodiment, the control module controls the driving mechanism to drive the crucible to rotate in a periodic forward and reverse rotation mode, that is, the crucible rotates at a rotation speed calculated by the following formula:

[0016] ω= r×sin(K×t), where ω represents the rotation speed in rad / min, r represents the set crucible speed in rad / min, k represents the coefficient in ° / ms, and t represents the time in ms; where r ranges from 5 to 15 rad / min.

[0017] In an optional embodiment, the heating assembly includes an upper cover;

[0018] The seed crystal assembly includes a sealing cap;

[0019] The upper cover is provided with a circular heat dissipation hole arranged concentrically with the upper cover;

[0020] The control module is also configured to control the seed crystal assembly to rise during the stirring stage so that the sealing cover blocks the heat dissipation circular holes of the upper cover to reduce the temperature difference inside the solution; and to control the seed crystal assembly to descend during the growth stage so that the sealing cover opens the heat dissipation circular holes of the upper cover to increase the temperature difference of the solution in the vertical direction and promote rapid growth of crystals.

[0021] In an optional embodiment, the seed crystal assembly further includes:

[0022] Lifting rod, seed crystal body and driving part;

[0023] The seed crystal body is arranged below the lifting rod;

[0024] The driving part is used to drive the lifting rod to rise, fall and rotate;

[0025] The blocking cover is arranged in the middle of the lifting rod and is located below the heat dissipation circular hole of the upper cover;

[0026] The control module is electrically connected to the driving unit.

[0027] In an optional embodiment, the diameter of the blocking cap is R1;

[0028] The diameter of the seed crystal body is R2;

[0029] Among them, R1:R2=(1.05~1.1), so as to reduce the temperature difference in the horizontal direction of the solution.

[0030] In an optional embodiment, a plurality of guide grooves surrounding the heat dissipation circular holes are formed on the bottom surface of the upper cover;

[0031] The blocking cover and the guide groove are provided with a blocking block adapted to the guide groove at the corresponding position thereof;

[0032] The guide groove is inclined and is used to cooperate with the block in the stirring stage to seal the heat dissipation circular hole to reduce the temperature difference inside the solution; in the growth stage, the steam after the solution evaporates is guided to the heat dissipation circular hole to accelerate the discharge of hot air.

[0033] In an optional embodiment, the horizontal distance between the outer edge of the guide groove and the axis of the upper cover is L1;

[0034] The radius of the blocking cover is L2;

[0035] Wherein, L1 is greater than L2, so as to prevent the condensed solution from dripping onto the seed crystal body of the seed crystal assembly during the growth stage.

[0036] In an optional embodiment, the heating component further includes:

[0037] Induction coils, graphite heating tubes and graphite insulation felts;

[0038] The induction coil is sleeved on the graphite heating tube;

[0039] The graphite insulation felt is arranged between the induction coil and the graphite heating tube;

[0040] The upper cover is covered on the top of the graphite heating tube.

[0041] In an optional embodiment, the stirring assembly includes a plurality of stirrers;

[0042] A plurality of agitators are arranged in a circumferential array at the bottom of the upper cover;

[0043] The stirrer comprises a connecting rod and a stirring paddle;

[0044] The top of the connecting rod is connected to the bottom of the upper cover;

[0045] The stirring paddle comprises a bearing body and a plurality of stirring blades;

[0046] A plurality of stirring blades are arranged at intervals on the side wall of the outer sleeve of the bearing body;

[0047] The bottom of the connecting rod is connected to the inner sleeve of the bearing body.

[0048] In a second aspect, the embodiments of the present disclosure further provide a working method of using the above-mentioned device for promoting stable growth of silicon carbide crystals, the working method comprising:

[0049] Step S1, placing raw materials and a solvent into a crucible, and heating to a first temperature to completely melt the raw materials;

[0050] Step S2, controlling the driving mechanism to drive the crucible to rise, so that the stirring blades of the stirring assembly are immersed in the solution, and at the same time, the space where the crucible is located is sealed;

[0051] Step S3, controlling the driving mechanism to drive the crucible to rotate in a periodic forward and reverse rotation mode, and stirring for a preset time;

[0052] Step S4, controlling the driving mechanism to drive the crucible to descend, thereby releasing the seal of the space where the crucible is located;

[0053] Step S5, controlling the heating component to increase the temperature so that the solution is heated to a second temperature;

[0054] Step S6, controlling the seed crystal assembly to rotate and repeatedly pull to complete the growth of the crystal.

[0055] The beneficial effect of the present invention is that the device and working method for promoting the stable growth of silicon carbide crystals can stir at a lower temperature by regulating the temperature of the stirring stage and the growth stage, thereby reducing the corrosion of the crucible and the stirring paddle. At the same time, the crucible is controlled to rotate forward and reverse in a periodic alternating manner. When the stirring assembly is fixed, the stirring paddle can be driven to rotate freely by the flow of the solution to complete the stirring of the solution. At the same time, the periodic forward and reverse rotation of the crucible brings a certain degree of inertial force to the solution. Under the impact of the opposite inertial forces generated by the forward and reverse rotation of the crucible, the solution can be quickly mixed, so that the solution is mixed evenly in a short time; the periodic forward and reverse rotation of the crucible reduces the rotation speed when the desired stirring effect is achieved, thereby avoiding an increase in the carbon dissolution rate, thereby avoiding the formation of polycrystalline clusters inside the crystal during the growth stage, and thus improving the stability of subsequent crystal production. After the stirring is completed, the crystal is grown at a higher temperature to improve the stability of the crystal growth.

[0056] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0057] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, this article specifically cites preferred embodiments and provides detailed descriptions as follows in conjunction with the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1 A cross-sectional view of a device for promoting stable growth of silicon carbide crystals provided by an embodiment of the present disclosure during a stirring stage;

[0060] Figure 2 A cross-sectional view of a portion of the structure of the device for promoting stable growth of silicon carbide crystals provided by an embodiment of the present disclosure during a stirring stage;

[0061] Figure 3 A cross-sectional view of a device for promoting stable growth of silicon carbide crystals provided by an embodiment of the present disclosure during a growth phase;

[0062] Figure 4 A cross-sectional view of a portion of the structure of the device for promoting stable growth of silicon carbide crystals provided by an embodiment of the present disclosure during the growth stage;

[0063] Figure 5 A schematic diagram of a partial structure of a stirring assembly, a seed crystal assembly and a heating assembly provided in an embodiment of the present disclosure;

[0064] Figure 6 A structural schematic diagram of a part of the structure of a stirring assembly, a seed crystal assembly and a heating assembly provided in an embodiment of the present disclosure from another perspective;

[0065] Figure 7 A cross-sectional view of a portion of the structure of a stirring assembly, a seed crystal assembly, and a heating assembly provided in an embodiment of the present disclosure;

[0066] Figure 8 A flow chart of a working method of a device for promoting stable growth of silicon carbide crystals provided in an embodiment of the present disclosure;

[0067] Fig. 9 A block diagram of the control principle of the device for promoting the stable growth of silicon carbide crystals provided in an embodiment of the present disclosure.

[0068] In the figure: 100, crucible; 200, heating component; 210, upper cover; 211, heat dissipation circular hole; 212, guide groove; 220, induction coil; 230, graphite heating tube; 240, graphite insulation felt; 300, stirring component; 310, stirrer; 311, connecting rod; 312, stirring paddle; 3121, bearing body; 3122, stirring blade; 400, driving mechanism; 500, seed crystal component; 510, sealing cover; 511, blocking block; 520, lifting rod; 530, seed crystal body. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Herein, when it is mentioned that a first component is located on a second component, this may mean that the first component may be directly formed on the second component, or a third component may be interposed between the first component and the second component.

[0071] In response to the technical problems mentioned in the background technology, the inventors have discovered that if the raw materials are stirred in a single direction at a high speed, the following problems will occur. On the one hand, the high-speed rotation of the large-size crucible places extremely high requirements on the equipment, and malfunctions are prone to occur during the process; on the other hand, at high speed, the scouring of the side wall of the crucible by the solution will cause the carbon dissolution rate in the stirring stage to accelerate sharply. The rotation of the stirring blades and the crucible brings about forced convection. Under the action of forced convection, the carbon in the solution in the high-temperature zone is easily transferred to the low-temperature zone of the free liquid surface to form silicon carbide floating crystals, affecting the overall stability of the solution, resulting in the system in the solution being inconsistent before the seed crystal contacts the interface, and even in the initial stage of growth. There are obvious steps on the surface of the silicon carbide crystals that eventually grow, resulting in unstable crystal growth.

[0072] The defects existing in the above solutions are the results obtained by the inventor after practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the present invention in this article for the above problems should be the contributions made by the inventor to the present invention during the disclosure process.

[0073] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, in the drawings, the thickness of the components may be exaggerated or reduced in order to effectively describe the technical content.

[0074] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0075] See also Figure 1 and Figure 2 At least one embodiment provides a device for promoting stable growth of silicon carbide crystals, comprising the following structure:

[0076] The crucible 100 is used to hold the solution. The main material of the crucible 100 is graphite, which has the advantages of high temperature stability, good thermal conductivity, and low price.

[0077] The heating assembly 200 is disposed around the crucible 100 and is used to heat the solution in the crucible 100. The heating assembly 200 needs to heat the solution to different temperatures during the stirring stage and the growth stage. The solution is heated to a first temperature during the stirring stage and to a second temperature during the growth stage. The first temperature is lower than the second temperature, so that stirring can be performed at a lower temperature, thereby reducing corrosion to the crucible 100 and the stirring paddle 312.

[0078] The stirring assembly 300 is disposed in the heating assembly 200 and is used to stir the solution in the crucible 100. The stirring assembly 300 is a passive stirring structure, that is, the stirring assembly 300 does not require an additional driving source and stirs the solution by rotating the solution.

[0079] The driving mechanism 400 is disposed below the crucible 100 and is used to drive the crucible 100 to rise and fall and rotate. It should be noted that the detailed structure of the driving mechanism is not described in the accompanying drawings. As long as the structure can achieve the rotation and rise and fall of the crucible 100, it is within the protection scope of the embodiment. For example, the driving mechanism 400 can adopt a structure in which a cylinder drives a rotating motor to achieve the rise and fall and rotation.

[0080] The seed crystal assembly 500 is disposed above the crucible 100 and is used for crystal growth. The seed crystal is the basis for the growth of silicon carbide crystals, and its quality directly affects the quality and growth effect of the final crystal.

[0081] See also Fig. 9 , a control module, which is electrically connected to the heating component 200, the driving mechanism 400 and the seed crystal component 500.

[0082] The control module is configured to control the heating component 200 to heat the solution to a first temperature during the stirring stage, and control the driving mechanism 400 to drive the crucible 100 to rise (the rising direction is as shown in FIG. Figure 2As shown in F1 in the figure), until the solution in the crucible 100 completely immerses the stirring blade 3122 of the stirring assembly 300, and then controls the driving mechanism 400 to drive the crucible 100 to rotate in a periodic forward and reverse rotation mode to complete the stirring.

[0083] The crucible 100 is controlled to rotate forward and reverse in a periodic alternating manner. When the stirring assembly 300 is fixed, the stirring paddle 312 can be driven to rotate freely through the flow of the solution to complete the stirring of the solution. At the same time, the periodic forward and reverse rotation of the crucible 100 brings a certain degree of inertial force to the solution. Under the impact of the opposite inertial forces generated by the forward and reverse rotation of the crucible 100, the solution can be quickly mixed, so that the solution is mixed evenly in a short time; the crucible 100 is periodically rotated forward and reversed to reduce the rotation speed when the desired stirring effect is achieved, thereby avoiding an increase in the carbon dissolution rate, thereby improving the stability during subsequent crystal production.

[0084] Specifically, the control module controls the driving mechanism 400 to drive the crucible 100 to rotate in a periodic forward and reverse rotation mode, that is, the crucible 100 rotates at a rotation speed calculated by the following formula:

[0085] ω= r×sin(K×t), where ω represents the rotation speed in rad / min, r represents the set crucible 100 speed in rad / min, k represents the coefficient in ° / ms, and t represents the time in ms. When ω is a positive number, it rotates clockwise, and when ω is a negative number, it rotates counterclockwise. In other embodiments, when ω is a positive number, it rotates counterclockwise, and when ω is a negative number, it rotates clockwise. Wherein, the range of r is between 5 and 15 rad / min.

[0086] See also Figure 3 and Figure 4 The control module is further configured to control the heating component 200 to heat the solution to a second temperature during the growth phase, and control the seed crystal component 500 to rotate and repeatedly pull (the pulling direction is as shown in FIG. Figure 4 As shown in F2 in the figure, the crystal growth is completed.

[0087] It should be noted that, during the growth stage, the driving mechanism 400 needs to be controlled to drive the crucible 100 downward (the downward direction is as follows: Figure 4 As shown in F1 in the figure, the stirring component 300 is separated from the solution.

[0088] In order to adaptively adjust the temperature requirements in the stirring stage and the growth stage, in some embodiments, the heating assembly 200 includes an upper cover 210, and the seed crystal assembly 500 includes a blocking cover 510. The upper cover 210 is provided with a heat dissipation circular hole 211 arranged concentrically with the upper cover 210. The upper cover 210 and the blocking cover 510 are used to regulate the different temperature requirements in the stirring stage and the growth stage, further ensuring the stable growth of the crystal.

[0089] Specifically, the control module is further configured to control the seed crystal assembly 500 to rise (the rising direction is as follows) during the stirring stage. Figure 2 As shown in F2 in the figure, the blocking cover 510 blocks the heat dissipation circular hole 211 of the upper cover 210 to reduce the temperature difference inside the solution; in the growth stage, the seed crystal assembly 500 is controlled to descend (the descending direction is as shown in FIG. Figure 4 As shown in F2 in the figure, the blocking cover 510 opens the heat dissipation circular hole 211 of the upper cover 210, thereby increasing the temperature difference of the solution in the vertical direction and promoting the rapid growth of crystals.

[0090] During the stirring stage, in order to avoid the formation of a large temperature gradient at the bottom and top of the solution, rapid heating is adopted in a closed environment to ensure the consistency of the solution temperature and avoid the appearance of silicon carbide floating crystals.

[0091] In the growth stage, the temperature gradient of the growth surface is the driving force of crystal growth. The stability of the temperature gradient directly affects the stability of crystal growth. By lowering the blocking cover 510, the heat dissipation circular hole 211 of the upper cover 210 is opened, the closed environment is released, and the temperature of the solution growth surface is rapidly reduced, forming a larger temperature gradient, which promotes the rapid growth of the crystal. At the same time, the diameter of the heat dissipation circular hole 211 can be optimized to form the required temperature gradient on the growth surface, ensuring the stability of crystal growth.

[0092] See also Figure 1 and Figure 5 The seed crystal assembly 500 further includes: a lifting rod 520, a seed crystal body 530 and a driving unit. The driving unit drives the lifting rod 520 to lift and rotate, thereby driving the seed crystal body 530 to lift and rotate.

[0093] Specifically, the seed crystal body 530 is arranged below the lifting rod 520 , the driving unit is used to drive the lifting rod 520 to rise, fall and rotate, and the blocking cover 510 is arranged in the middle of the lifting rod 520 and is located below the heat dissipation circular hole 211 of the upper cover 210 .

[0094] It should be noted that when the lifting rod 520 is raised or lowered during the growth stage, the blocking cover 510 cannot block the heat dissipation circular hole 211 .

[0095] The control module is electrically connected to the driving unit. The driving unit is controlled by the control module to make the lifting rod 520 move up and down along a preset path.

[0096] See also Figure 7 , the diameter of the blocking cap 510 is R1; the diameter of the seed crystal body 530 is R2; wherein R1:R2=(1.05~1.1), so as to reduce the temperature difference in the horizontal direction of the solution. The diameter of the blocking cap 510 is larger than that of the seed crystal body 530, thereby reducing the heat dissipation speed of the solution facing the seed crystal body 530, thereby reducing the radial temperature difference during the crystal growth process, making the transfer of carbon solute on the growth surface more stable, thereby promoting the stable growth of the crystal.

[0097] See also Figure 6 and Figure 7 The bottom surface of the upper cover 210 is provided with a plurality of guide grooves 212 surrounding the heat dissipation circular holes 211. The interface of the guide grooves 212 can be annular or irregular polygonal.

[0098] The blocking cover 510 is provided with a blocking block 511 adapted to the guide groove 212 at a position corresponding to the guide groove 212. The blocking block 511 cooperates with the guide groove 212 to fix the upper cover 210, thereby preventing the stirring assembly 300 from moving when the crucible 100 rotates during the stirring stage.

[0099] Specifically, the guide groove 212 is arranged at an angle and is used to cooperate with the block 511 in the stirring stage to seal the heat dissipation circular hole 211 to reduce the temperature difference inside the solution; in the growth stage, the steam after the solution evaporates is guided to the heat dissipation circular hole 211 to accelerate the discharge of hot air.

[0100] Please continue reading Figure 7 The horizontal distance between the outer edge of the guide groove 212 and the axis of the upper cover 210 is L1; the radius of the blocking cover 510 is L2; ​​wherein L1 is greater than L2, thereby preventing the condensed solution from dripping onto the seed crystal body 530 of the seed crystal assembly 500 during the growth stage.

[0101] Since the temperature of the condensed liquid is relatively low, if it drips directly onto the seed crystal body 530 of the seed crystal assembly 500, it will cause uneven temperature on the growth surface of the seed crystal body 530, thereby affecting the stability of crystal growth. By setting the guide groove 212, the condensed water is guided outward to avoid the seed crystal body 530, thereby ensuring the consistency of the growth surface temperature.

[0102] See also Figure 1 The heating component 200 also includes: an induction coil 220 , a graphite heating tube 230 and a graphite insulation felt 240 .

[0103] The induction coil 220 is sleeved on the graphite heating tube 230 . The control module controls the magnitude of the induced current of the induction coil 220 to control the temperature in the graphite heating tube 230 , thereby heating the raw materials in the crucible 100 .

[0104] The graphite heat preservation felt 240 is disposed between the induction coil 220 and the graphite heating tube 230. The graphite heat preservation felt 240 is used to keep the graphite heating tube 230 warm.

[0105] The upper cover 210 covers the top of the graphite heating tube 230. By covering the upper cover 210 on the top of the graphite heating tube 230, the heat loss is reduced and the heating efficiency is improved.

[0106] See also Figure 5 and Figure 6 The stirring assembly 300 includes a plurality of stirrers 310. The plurality of stirrers 310 can simultaneously stir the solution in the crucible 100, thereby improving the stirring effect.

[0107] A plurality of stirrers 310 are arranged in a circumferential array at the bottom of the upper cover 210. The stirrer 310 is supported by the upper cover 210, and since the upper cover 210 is detachable, it is easy to disassemble, and after the stirring blades 3122 of the stirrer 310 are corroded, it is easy to replace the stirrer 310.

[0108] The stirrer 310 includes a connecting rod 311 and a stirring paddle 312; the top of the connecting rod 311 is connected to the bottom of the upper cover 210; the stirring paddle 312 includes a bearing body 3121 and a plurality of stirring blades 3122; the plurality of stirring blades 3122 are arranged at intervals on the side wall of the outer sleeve of the bearing body 3121; the bottom of the connecting rod 311 is connected to the inner sleeve of the bearing body 3121. The stirring paddle 312 is arranged in a bearing shape and can rotate freely. When the crucible 100 is forward or reversed, the inertial force generated by the solution drives the stirring blade 3122 to rotate, thereby completing the stirring of the solution.

[0109] See also Figure 8 At least one embodiment further provides a working method of using the above-mentioned device for promoting stable growth of silicon carbide crystals, the working method comprising:

[0110] S1: Put the raw materials and the solvent into the crucible 100 and heat them to a first temperature to completely melt the raw materials.

[0111] It should be noted that the heating temperature is the first temperature, so that stirring can be performed at a lower temperature, reducing corrosion to the crucible 100 and the stirring paddle 312.

[0112] S2: Control the driving mechanism 400 to drive the crucible 100 to rise, so that the stirring blades 3122 of the stirring assembly 300 are immersed in the solution, and at the same time, the space where the crucible 100 is located is sealed.

[0113] During the stirring stage, in order to avoid the formation of a large temperature gradient at the bottom and top of the solution, rapid heating is adopted in a closed environment to ensure the consistency of the solution temperature and avoid the appearance of silicon carbide floating crystals.

[0114] S3: Control the driving mechanism 400 to drive the crucible 100 to rotate in a periodic forward and reverse rotation mode and stir for a preset time.

[0115] That is, the crucible 100 rotates at a rotation speed calculated by the following formula:

[0116] ω= r×sin(K×t), where ω represents the rotation speed in rad / min, r represents the set crucible 100 speed in rad / min, k represents the coefficient in ° / ms, and t represents the time in ms. When ω is a positive number, it rotates clockwise, and when ω is a negative number, it rotates counterclockwise. In other embodiments, when ω is a positive number, it rotates counterclockwise, and when ω is a negative number, it rotates clockwise.

[0117] S4: Control the driving mechanism 400 to drive the crucible 100 to descend, thereby releasing the seal of the space where the crucible 100 is located.

[0118] In the growth stage, the temperature gradient of the growth surface is the driving force of crystal growth. The stability of the temperature gradient directly affects the stability of crystal growth. By lowering the blocking cover 510, the heat dissipation circular hole 211 of the upper cover 210 is opened, the closed environment is released, and the temperature of the solution growth surface is rapidly reduced, forming a larger temperature gradient, which promotes the rapid growth of the crystal. At the same time, the diameter of the heat dissipation circular hole 211 can be optimized to form the required temperature gradient on the growth surface, ensuring the stability of crystal growth.

[0119] S5: Control the heating component 200 to increase the temperature so that the solution is heated to a second temperature.

[0120] The second temperature is a temperature value required for crystal growth, which is greater than the first temperature.

[0121] S6: Control the seed crystal assembly 500 to rotate and repeatedly pull to complete the growth of the crystal.

[0122] In order to verify the stability of the grown crystal by the device that promotes the stable growth of silicon carbide crystal.

[0123] In Example 1, the device for promoting the stable growth of silicon carbide crystals is assembled in the above manner. The crystal growth is performed according to the following process:

[0124] Step 1: Close the furnace chamber, evacuate the chamber, and then fill the chamber with inert gas. Place the solvent raw material block treated by isostatic pressing technology in a crucible, heat it to 1550°C, and keep the temperature constant until the raw material is completely melted into a melt, wherein the solvent is a Si-Cr based solution.

[0125] Step 2: Move the crucible upward until the solution covers the stirring paddle. At this time, the crucible begins to rotate forward and reverse periodically, k=0.25° / ms, crucible speed r=20rad / min, and stirring time is 30min.

[0126] Step 3: After stirring, lower the crucible to the crystal growth position and then heat it to 1800°C.

[0127] Step 4: After the seed crystal body contacts the liquid surface, it is pulled up 1 mm and then crystal growth is carried out.

[0128] Finally, the 6-inch silicon carbide single crystal obtained has a smooth surface, no obvious macro steps, equal thickness at the center and edge, and belongs to planar growth. The crystal growth rate is 0.07mm / h.

[0129] In Example 2, the device for promoting the stable growth of silicon carbide crystals is assembled in the above manner. The crystal growth is performed according to the following process:

[0130] Step S1: Close the furnace chamber, perform vacuum treatment, and then fill the furnace chamber with inert gas. Place the solvent raw material block treated by isostatic pressing technology in a crucible, heat it to 1550°C, and keep the temperature constant until the raw material is completely melted into a melt, wherein the solvent is a Si-Cr based solution.

[0131] Step S2: Move the crucible upward until the solution covers the stirring paddle, and seal the space where the crucible is located.

[0132] Step S3: At this time, the crucible starts to rotate forward and reverse periodically, k=0.25° / ms, the crucible speed r=20rad / min, and the stirring time is 30min.

[0133] Step S4: the crucible is lowered, and the seal of the space where the crucible is located is released.

[0134] Step S5: After the stirring is completed, the crucible is lowered to the crystal growth position and then the temperature is raised to 1850°C.

[0135] Step S6: After the seed crystal body contacts the liquid surface, it is pulled up by 1 mm to start crystal growth.

[0136] Finally, the 6-inch silicon carbide single crystal has a smooth surface, no obvious macro steps, equal thickness at the center and edge, and belongs to planar growth. The crystal growth rate is 0.09mm / h.

[0137] The test results of Example 1 and Example 2 indicate that the increase in crystal growth temperature increases the crystal growth rate to a certain extent.

[0138] In Comparative Example 1, the experimental steps are substantially the same as those of Example 1, except that no stirring device is used for stirring.

[0139] The final 6-inch silicon carbide crystal had a rough surface, a large number of polycrystalline floating crystals, and a large amount of solvent inclusions at the beginning of growth, indicating that the solution was not mixed evenly at the initial stage of crystal growth, resulting in a large initial supersaturation of the growth surface and an unstable interface. This shows that the stirring stage can improve the stability of crystal growth.

[0140] In Comparative Example 2, the experimental steps are substantially the same as those of Example 1 except that the crucible is uniformly rotated at a speed of 20 rpm.

[0141] The surface of the 6-inch silicon carbide crystal obtained in the end still has obvious steps. This phenomenon shows that the crucible uniformly at 20rpm cannot achieve the effect of fully mixing the solution. Before the seed crystal contacts the interface or even in the initial stage of growth, the system in the solution is still inconsistent.

[0142] Through Example 1, Example 2, Comparative Example 1 and Comparative Example 2, it can be seen that the device for promoting the stable growth of silicon carbide crystals provided in this embodiment can promote the stable growth of crystals. The surface of the grown silicon carbide crystals is smooth, without obvious macroscopic steps, and the thickness of the center and the edge is equal, which belongs to planar growth.

[0143] In summary, the present invention provides a device for promoting the stable growth of silicon carbide crystals and a working method thereof, wherein the device for promoting the stable growth of silicon carbide crystals comprises: a crucible, which is used to hold a solution; a heating component, which is arranged around the crucible and is used to heat the solution in the crucible; a stirring component, which is arranged in the heating component and is used to stir the solution in the crucible; a driving mechanism, which is arranged below the crucible and is used to drive the crucible to rise and fall and rotate; A seed crystal assembly is arranged above the crucible and is used for crystal growth; a control module is electrically connected to the heating assembly, the driving mechanism and the seed crystal assembly; the control module is configured to control the heating assembly to heat the solution to a first temperature during the stirring stage, and control the driving mechanism to drive the crucible to rise until the solution in the crucible completely immerses the stirring blades of the stirring assembly, and then control the driving mechanism to drive the crucible to rotate in a periodic forward and reverse rotation mode to complete the stirring; the control module is also configured to control the heating assembly to heat the solution to a second temperature during the growth stage, and control the seed crystal assembly to rotate and repeatedly pull to complete the growth of the crystal. By regulating the temperature in the stirring stage and the growth stage, stirring is performed at a lower temperature to reduce corrosion to the crucible and the stirring paddle. At the same time, the crucible is controlled to rotate forward and reverse in a periodic alternating manner. When the stirring component is fixed, the stirring paddle can be driven to rotate freely through the flow of the solution to complete the stirring of the solution. At the same time, the periodic forward and reverse rotation of the crucible brings a certain degree of inertial force to the solution. Under the impact of the opposite inertial forces generated by the forward and reverse rotation of the crucible, the solution can be quickly mixed, so that the solution is mixed evenly in a short time; the periodic forward and reverse rotation of the crucible reduces the rotation speed when the desired stirring effect is achieved, thereby avoiding an increase in the carbon dissolution rate, thereby improving the stability of subsequent crystal production.

[0144] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A device for promoting stable growth of silicon carbide crystals, characterized in that: include: A crucible (100) for containing a solution; A heating component (200) disposed around the crucible (100); A stirring assembly (300), used for stirring the solution in the crucible (100); A driving mechanism (400) disposed below the crucible (100) and used to drive the crucible (100) to rise, fall and rotate; A seed crystal assembly (500), which is arranged above the crucible (100) and is used for crystal growth; The control module is configured to control the heating component (200) to heat the solution to a first temperature during a stirring stage, and control the driving mechanism (400) to drive the crucible (100) to rise so as to immerse the stirring blades (3122) of the stirring component (300), and then control the driving mechanism (400) to drive the crucible (100) to rotate in a periodic forward and reverse rotation mode; and in a growth stage, control the heating component (200) to heat the solution to a second temperature, and control the seed crystal component (500) to rotate and repeatedly pull to complete crystal growth.

2. The device for promoting stable growth of silicon carbide crystals according to claim 1, characterized in that: The control module controls the driving mechanism (400) to drive the crucible (100) to rotate in a periodic forward and reverse rotation mode, that is, the crucible (100) rotates at a rotation speed calculated by the following formula: ω = r × sin (K × t), where ω represents the rotation speed in rad / min, r represents the set crucible (100) rotation speed in rad / min, k represents the coefficient in ° / ms, and t represents the time in ms; Among them, the range of r is between 5~15rad / min.

3. The device for promoting stable growth of silicon carbide crystals according to claim 1, characterized in that: The heating component (200) comprises an upper cover (210); The seed crystal assembly (500) comprises a sealing cap (510); The upper cover (210) is provided with a heat dissipation circular hole (211) arranged concentrically with the upper cover (210); The control module is further configured to control the seed crystal assembly (500) to rise during the stirring stage so that the blocking cover (510) blocks the heat dissipation circular hole (211) of the upper cover (210) to reduce the temperature difference inside the solution; and to control the seed crystal assembly (500) to descend during the growth stage so that the blocking cover (510) opens the heat dissipation circular hole (211) of the upper cover (210) to increase the temperature difference of the solution in the vertical direction and promote rapid growth of crystals.

4. The device for promoting stable growth of silicon carbide crystals according to claim 3, characterized in that: The seed crystal assembly (500) further includes: A lifting rod (520), a seed crystal body (530) and a driving part; The seed crystal body (530) is arranged below the lifting rod (520); The driving unit is used to drive the lifting rod (520) to rise, fall and rotate; The blocking cover (510) is arranged in the middle of the lifting rod (520) and is located below the heat dissipation circular hole (211) of the upper cover (210); The control module is electrically connected to the driving unit.

5. The device for promoting stable growth of silicon carbide crystals according to claim 4, characterized in that: The diameter of the blocking cover (510) is R1; The diameter of the seed crystal body (530) is R2; Among them, R1:R2=1.05~1.1 to reduce the horizontal temperature difference of the solution.

6. The device for promoting stable growth of silicon carbide crystals according to claim 3, characterized in that: The bottom surface of the upper cover (210) is provided with a plurality of guide grooves (212) surrounding the heat dissipation circular holes (211); A blocking block (511) adapted to the guide groove (212) is provided at a position corresponding to the blocking cover (510) and the guide groove (212); The guide groove (212) is arranged obliquely and is used to cooperate with the block (511) in the stirring stage to seal the heat dissipation circular hole (211) and reduce the temperature difference inside the solution; in the growth stage, the steam after the solution evaporates is guided to the heat dissipation circular hole (211) to accelerate the discharge of hot gas.

7. The device for promoting stable growth of silicon carbide crystals according to claim 6, characterized in that: The horizontal distance between the outer edge of the guide groove (212) and the axis of the upper cover (210) is L1; The radius of the blocking cover (510) is L2; Wherein, L1 is greater than L2, thereby preventing the condensed solution from dripping onto the seed crystal body (530) of the seed crystal assembly (500) during the growth stage.

8. The device for promoting stable growth of silicon carbide crystals according to claim 3, characterized in that: The heating component (200) further comprises: An induction coil (220), a graphite heating tube (230), and a graphite thermal insulation felt (240); The induction coil (220) is sleeved on the graphite heating tube (230); The graphite thermal insulation felt (240) is arranged between the induction coil (220) and the graphite heating tube (230); The upper cover (210) covers the top of the graphite heating tube (230).

9. The device for promoting stable growth of silicon carbide crystals according to claim 3, characterized in that: The stirring assembly (300) includes a plurality of stirrers (310); A plurality of the stirrers (310) are arranged in a circumferential array at the bottom of the upper cover (210); The stirrer (310) comprises a connecting rod (311) and a stirring paddle (312); The top of the connecting rod (311) is connected to the bottom of the upper cover (210); The stirring paddle (312) comprises a bearing body (3121) and a plurality of stirring blades (3122); A plurality of stirring blades (3122) are arranged at intervals on the side wall of the outer sleeve of the bearing body (3121); The bottom of the connecting rod (311) is connected to the inner sleeve of the bearing body (3121).

10. A working method applied to the device for promoting stable growth of silicon carbide crystals as claimed in claim 1, characterized in that: The working method comprises: Step S1, placing a raw material and a solvent into a crucible (100), and heating to a first temperature to completely melt the raw material; Step S2, controlling the driving mechanism (400) to drive the crucible (100) to rise, so that the stirring blade (3122) of the stirring assembly (300) is immersed in the solution, and at the same time, the space where the crucible (100) is located is sealed; Step S3, controlling the driving mechanism (400) to drive the crucible (100) to rotate in a periodic forward and reverse rotation mode, and stirring for a preset time; Step S4, controlling the driving mechanism (400) to drive the crucible (100) to descend, thereby releasing the seal of the space where the crucible (100) is located; Step S5, controlling the heating component (200) to increase the temperature so that the solution is heated to a second temperature; and Step S6, controlling the seed crystal assembly (500) to rotate and repeatedly pull to complete the growth of the crystal.

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