Silicon carbide crystal production system and crystal growth method

Abstract

The invention relates to the technical field of silicon carbide preparation, in particular to a silicon carbide crystal production system and a crystal growth method.The silicon carbide crystal production system comprises a crucible module used for containing raw materials and conducting crystal growth; the carbon powder adding module is used for adding carbon powder; the lifting module is used for rotating and lifting the seed crystal fixer; the heating module is used for adjusting the temperature in the crystal growth process; the monitoring module is used for monitoring the voltage fluctuation in the crystal growth process and the rotating torque change of the seed crystal fixer; the detection module is used for acquiring stress parameters of the grown silicon carbide crystals; the control module is used for adjusting corresponding module parameters in the production system to corresponding values according to parameters measured in the monitoring module and the detection module, production parameters are optimized, and the growth speed and quality of silicon carbide crystals are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide preparation, and in particular to a silicon carbide crystal production system and a crystal growth method. Background Art

[0002] Silicon carbide is a wide bandgap semiconductor material with the characteristics of high temperature resistance, high voltage resistance, high frequency, high power, radiation resistance, and high efficiency. These characteristics make silicon carbide have important application value in the fields of radio frequency, new energy vehicles, photovoltaic power generation, rail transportation, smart grid, aerospace, etc.

[0003] The main methods for growing silicon carbide crystals include physical vapor transport, high-temperature chemical vapor deposition, liquid phase epitaxy, and high-temperature solution methods. Among them, liquid phase epitaxy can grow at a lower temperature, which helps to reduce dislocations caused by thermal stress, thereby obtaining silicon carbide crystals with lower dislocation density. In addition, the liquid phase epitaxy process can also achieve conversion between different dislocations, further reducing dislocation density and improving crystal quality.

[0004] Chinese Patent Publication No.: CN117051471B, discloses a device and method for growing silicon carbide crystals by liquid phase method, the device includes a heat preservation structure, a crucible and a seed crystal rod, the heat preservation structure includes a fixed heat preservation part, a lifting heat preservation part and a lifting drive part, the lifting heat preservation part can be lifted and lowered in the fixed heat preservation part and together with the inner wall of the fixed heat preservation part, form a heat preservation chamber, the lifting drive part is connected to the lifting heat preservation part, and is used to drive the lifting heat preservation part to lift and lower, so as to adjust the volume of the heat preservation chamber. The crucible is arranged in the heat preservation chamber, and is used to contain silicon-containing melt. The seed crystal rod is penetrated by the lifting drive part and a seed crystal for growing silicon carbide crystals is arranged at the bottom, and the seed crystal can contact or separate from the silicon-containing melt under the drive of the seed crystal rod. The device and the supporting method can simply and conveniently adjust the heating effect of the crucible by setting a heat preservation chamber with adjustable volume, so that the growth rate of the crystal can be adjusted according to actual needs. It can be seen that the above technical solution lacks necessary detection during the growth process of silicon carbide crystals, which makes it difficult to detect and control the fluctuations of key parameters in the preparation process in a timely manner, resulting in defects in silicon carbide crystals. Summary of the invention

[0005] To this end, the present invention provides a silicon carbide crystal production system and a crystal growth method to overcome the problem in the prior art that due to the lack of necessary detection during the growth process of silicon carbide crystals, fluctuations in key parameters during the preparation process lead to defects in the silicon carbide crystals.

[0006] To achieve the above objectives, on the one hand, the present invention provides a silicon carbide crystal production system, comprising:

[0007] A crucible module, comprising a lower crucible, an upper crucible connected to the lower crucible, and an annular barrier liner arranged inside the lower crucible, wherein the height of the annular barrier liner is less than the height of the lower crucible, wherein the outer wall of the annular liner and the inner wall of the lower crucible form a silicon carbide reaction chamber;

[0008] A carbon powder adding module, comprising a plurality of carbon powder adding units arranged at equal intervals in the circumferential direction on the outer wall of the lower crucible, wherein a single carbon powder adding unit comprises a storage chamber for storing carbon powder, a delivery pipe connected to the storage chamber, an output end of the delivery pipe is communicated with the silicon carbide reaction chamber, wherein each output end is provided with a solenoid valve;

[0009] A pulling module connected to the upper crucible, comprising a seed crystal holder for fixing a seed crystal, a first motor for driving the seed crystal holder to rotate, and a second motor for driving the seed crystal holder to rise and fall;

[0010] A heating module is arranged on the outer wall of the crucible module, comprising a first heating unit arranged below the lower crucible, a second heating unit arranged on the outer side wall of the lower crucible, and a third heating unit arranged on the outer side wall of the upper crucible;

[0011] A monitoring module, comprising a voltage monitoring unit for monitoring the voltage between the seed crystal and the molten silicon carbide in the lower crucible and a torque monitoring unit provided on the seed crystal holder for obtaining the rotation torque of the seed crystal holder;

[0012] A detection module, which is used to obtain stress parameters of the grown silicon carbide crystal;

[0013] A control module, which is respectively connected to the monitoring module, the detection module, the pulling module and the heating module, and is used to preliminarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard based on the voltage fluctuation evaluation value, and to secondarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency, or to determine the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation, and to determine whether the preparation of silicon carbide crystals meets the preset standard based on the average stress evaluation value.

[0014] Furthermore, the control module preliminarily determines whether the preparation of silicon carbide crystal under a single voltage fluctuation meets a preset standard according to the voltage fluctuation evaluation value, wherein:

[0015] If the voltage fluctuation evaluation value is less than the first preset evaluation threshold, the control module preliminarily determines that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, and continues to prepare the silicon carbide crystal according to the current preparation parameters;

[0016] If the voltage fluctuation evaluation value is greater than or equal to the first preset evaluation threshold and less than the second preset evaluation threshold, the control module preliminarily determines that the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard, and secondarily determines whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency;

[0017] If the voltage fluctuation evaluation value is greater than or equal to the second preset evaluation threshold, the control module preliminarily determines that the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, and determines the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation.

[0018] Furthermore, the voltage fluctuation evaluation value is determined by the duration and amplitude of a single fluctuation.

[0019] Furthermore, the control module determines whether the preparation of silicon carbide crystal under voltage fluctuation meets the preset standard based on the historical fluctuation frequency.

[0020] If the historical fluctuation frequency is less than a preset frequency characteristic threshold, the control module determines that the preparation of silicon carbide crystal under a single voltage fluctuation meets the preset standard;

[0021] If the historical fluctuation frequency is greater than or equal to the preset frequency characteristic threshold, the control module determines that the preparation of the silicon carbide crystal under the single voltage fluctuation does not meet the preset standard, and increases the heating power of the first heating unit according to the difference between the historical fluctuation frequency and the preset frequency characteristic threshold;

[0022] The historical fluctuation frequency is the number of times voltage fluctuations are monitored within a historical preset time period;

[0023] The control module records a single voltage fluctuation exceeding a first preset fluctuation amplitude as one voltage fluctuation.

[0024] Furthermore, the control module increases the heating power of the first heating unit according to the fluctuation frequency difference, wherein:

[0025] If the fluctuation frequency difference is less than the first preset fluctuation frequency difference, the control module uses the first preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value;

[0026] If the fluctuation frequency difference is greater than or equal to the first preset fluctuation frequency difference and less than the second preset fluctuation frequency difference, the control module uses the second preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value;

[0027] If the fluctuation frequency difference is greater than or equal to the second preset fluctuation frequency difference, the control module uses the third preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value;

[0028] The fluctuation frequency difference is the difference between the historical fluctuation frequency and the preset frequency characteristic threshold.

[0029] Further, the control module is provided with several heating power correction methods for the heating power of the first heating unit under the first preset condition, and each heating power correction method has a different correction range for the heating power of the first heating unit;

[0030] The first preset condition is that the control module completes the adjustment of the heating power of the heating unit and the average stress of the silicon carbide crystal after adjustment is greater than a preset stress threshold.

[0031] Furthermore, the control module determines the reason why the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard according to the change of the rotation torque under a single voltage fluctuation, wherein:

[0032] If the rotational torque remains unchanged, the control module determines that the reason why the preparation of the silicon carbide crystal under the single voltage fluctuation does not meet the preset standard is that the rotation speed of the seed crystal holder does not meet the standard, and reduces the rotation speed of the first motor according to the difference between the voltage fluctuation evaluation value and the second preset evaluation threshold;

[0033] If the rotational torque decreases, the control module determines that the reason why the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard is that the pulling speed of the seed crystal holder does not meet the standard, and reduces the speed of the second motor according to the magnitude of the reduction in the rotational torque.

[0034] Furthermore, the control module reduces the speed of the first motor according to the voltage fluctuation difference, wherein:

[0035] If the voltage fluctuation difference is less than the first preset voltage fluctuation difference, the control module uses the first preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value;

[0036] If the voltage fluctuation difference is greater than or equal to the first preset voltage fluctuation difference and less than the second preset voltage fluctuation difference, the control module uses the second preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value;

[0037] If the voltage fluctuation difference is greater than the second preset voltage fluctuation difference, the control module uses a third preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value;

[0038] The voltage fluctuation difference is a difference between the voltage fluctuation evaluation value and the second preset evaluation threshold.

[0039] Furthermore, the control module determines whether the preparation of the silicon carbide crystal meets a preset standard according to the average stress evaluation value, wherein:

[0040] If the average stress evaluation value is less than a preset average stress characteristic threshold, the control module determines that the preparation of the silicon carbide crystal meets the preset standard;

[0041] If the average stress evaluation value is greater than a preset average stress characteristic threshold, the control module determines that the preparation of the silicon carbide crystal does not meet the preset standard, and reduces the heating power of the second heating unit according to the difference between the average stress evaluation value and the preset average stress characteristic threshold;

[0042] The average stress evaluation value is obtained based on the detection module.

[0043] On the other hand, the present invention also provides a method for growing a silicon carbide crystal, comprising:

[0044] Step S1, after loading the silicon raw material into the lower crucible, start the heating module to heat the crucible module;

[0045] Step S2, in response to the silicon raw material being heated to a molten state, adding excess carbon powder into the silicon carbide reaction chamber based on the carbon powder adding module;

[0046] Step S3, standing to allow the silicon raw material and the carbon powder to react to obtain a silicon carbide melt;

[0047] Step S4, bringing the seed crystal holder into contact with the liquid surface of the silicon carbide melt, and starting the pulling module at a preset rotation speed and a preset pulling speed to prepare a silicon carbide crystal;

[0048] Step S5, the voltage monitoring unit monitors the voltage loaded during the preparation process of the silicon carbide crystal in real time, obtains the voltage fluctuation evaluation value according to the monitored voltage, and preliminarily determines whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value;

[0049] Step S6, when it is preliminarily determined that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, the preparation of the silicon carbide crystal is continued according to the current preparation parameters;

[0050] Step S7, when it is preliminarily determined that the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, a secondary determination is made based on the historical fluctuation frequency whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard, or the reason for not meeting the preset standard is determined based on the change of the rotational torque under a single voltage fluctuation;

[0051] Step S8, when the preparation of the silicon carbide crystal is completed and it is determined that the preparation of the silicon carbide crystal does not meet the preset standard according to the average stress evaluation value obtained by the detection module, reducing the heating power of the second heating unit;

[0052] Step S9: when it is determined according to the average stress evaluation value that the preparation of the silicon carbide crystal meets the preset standard, outputting the silicon carbide crystal that meets the preset standard.

[0053] Compared with the prior art, the beneficial effects of the present invention are: the present invention includes a crucible module for holding raw materials and performing crystal growth; a carbon powder adding module for adding carbon powder, and a pulling module for rotating and pulling a seed crystal holder; a heating module for regulating the temperature of the crystal growth process; a monitoring module for monitoring voltage fluctuations and changes in the rotational torque of the seed crystal holder during crystal growth; a detection module for obtaining stress parameters of the grown silicon carbide crystal; and a control module for adjusting the parameters of corresponding modules in the production system to corresponding values ​​according to the parameters measured in the monitoring module and the detection module, thereby optimizing the production parameters and improving the growth rate and quality of the silicon carbide crystal.

[0054] Furthermore, the control module preliminarily determines whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value obtained by the monitoring module, and performs a secondary determination on the preparation of silicon carbide crystals that do not meet the preset standard.

[0055] Furthermore, the control module determines whether the preparation of silicon carbide crystals under voltage fluctuations meets the preset standards based on the historical fluctuation frequency obtained by the monitoring module. When it does not meet the preset standards, it determines the problems in the production process and adjusts the parameters of the corresponding modules in the production system to improve the quality of the silicon carbide crystals.

[0056] Furthermore, the control module is provided with several power adjustment methods for increasing the heating power of the first heating unit according to the difference between the historical fluctuation frequency and the preset frequency characteristic threshold, and is provided with several power correction methods for adjusting the heating power of the first heating unit, so as to ensure that the average stress of the silicon carbide crystal after adjustment is greater than the preset stress threshold.

[0057] Furthermore, the control module determines the reason why the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standards based on the change of the rotational torque under a single voltage fluctuation; if the rotational torque remains unchanged, the speed of the first motor is reduced based on the difference between the voltage fluctuation evaluation value and the second preset evaluation threshold; if the rotational torque decreases, the speed of the second motor is reduced based on the magnitude of the reduction in the rotational torque.

[0058] Furthermore, the control module is provided with several power adjustment modes for reducing the rotation speed of the first motor according to the voltage fluctuation difference, so as to ensure the stability of the silicon carbide crystal growth process.

[0059] Furthermore, the module determines whether the preparation of the silicon carbide crystal meets the preset standard based on the average stress evaluation value. If it does not meet the preset standard, the control module reduces the heating power of the second heating unit based on the difference between the average stress evaluation value and the preset average stress characteristic threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a schematic diagram of the structure of a silicon carbide crystal production system according to an embodiment of the present invention;

[0061] Figure 2 This is a schematic structural diagram of a module of a silicon carbide crystal production system according to an embodiment of the present invention;

[0062] Figure 3 A flow chart of an embodiment of the present invention for preliminarily determining whether the preparation of silicon carbide crystals under a single voltage fluctuation meets a preset standard;

[0063] Figure 4 A flow chart of increasing the heating power of the first heating unit according to an embodiment of the present invention;

[0064] Figure 5 This is a flow chart of a method for growing silicon carbide crystals according to an embodiment of the present invention;

[0065] In the figure: 11, lower crucible; 12, upper crucible; 13, annular blocking lining; 21, storage chamber; 22, delivery pipe; 23, solenoid valve; 31, seed crystal holder; 32, first motor; 33, second motor; 41, first heating unit; 42, second heating unit 43, third heating unit; 51, voltage monitoring unit. DETAILED DESCRIPTION

[0066] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0067] Those skilled in the art will appreciate that the system of the present invention may determine a single parameter by selecting the value with the highest proportion as the preset standard parameter based on data distribution, using weighted summation to take the obtained value as the preset standard parameter, substituting each historical data into a specific formula and taking the value obtained by using the formula as the preset standard parameter, or other selection methods, as long as the system of the present invention can clearly define different specific situations in a single determination process through the obtained values.

[0068] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0069] See also Figure 1-Figure 5 As shown, they are respectively a schematic diagram of the structure of the silicon carbide crystal production system according to an embodiment of the present invention; a schematic diagram of the structure of the modules of the silicon carbide crystal production system and the crystal growth method according to an embodiment of the present invention; a flowchart of the embodiment of the present invention for preliminarily determining whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standards; a flowchart of the heating power increase adjustment of the first heating unit according to an embodiment of the present invention; and a flowchart of the silicon carbide crystal growth method according to an embodiment of the present invention.

[0070] The present invention provides a silicon carbide crystal production system and a crystal growth method, including:

[0071] A crucible module, comprising a lower crucible 11, an upper crucible 12 connected to the lower crucible 11, and an annular barrier liner 13 disposed inside the lower crucible 11, wherein the height of the annular barrier liner 13 is less than the height of the lower crucible 11, wherein the outer wall of the annular liner 13 and the inner wall of the lower crucible 11 form a silicon carbide reaction chamber;

[0072] A carbon powder adding module, comprising a plurality of carbon powder adding units arranged at equal intervals in the circumferential direction on the outer wall of the lower crucible 11, wherein a single carbon powder adding unit comprises a storage chamber 21 for storing carbon powder, a delivery pipe 22 connected to the storage chamber, an output end of the delivery pipe 22 is communicated with the silicon carbide reaction chamber, wherein each output end is provided with a solenoid valve 23;

[0073] A lifting module connected to the upper crucible 12, comprising a seed crystal holder 31 for fixing a seed crystal, a first motor 32 for driving the seed crystal holder 31 to rotate, and a second motor 33 for driving the seed crystal holder 31 to rise and fall;

[0074] A heating module is arranged on the outer wall of the crucible module, including a first heating unit 41 arranged below the lower crucible 11, a second heating unit 42 arranged on the outer wall of the lower crucible 11, and a third heating unit 43 arranged on the outer wall of the upper crucible 12;

[0075] A monitoring module, comprising a voltage monitoring unit for monitoring the voltage between the seed crystal and the molten silicon carbide in the lower crucible 11 and a torque monitoring unit provided on the seed crystal holder 31 for obtaining the rotation torque of the seed crystal holder 31;

[0076] A detection module, which is used to obtain stress parameters of the grown silicon carbide crystal;

[0077] A control module, which is respectively connected to the monitoring module, the detection module, the pulling module and the heating module, and is used to preliminarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard based on the voltage fluctuation evaluation value, and to secondarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency, or to determine the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation, and to determine whether the preparation of silicon carbide crystals meets the preset standard based on the average stress evaluation value.

[0078] Specifically, the raw materials and proportions of silicon carbide crystals are not specifically limited, and the corresponding raw materials and proportions can be determined according to actual production.

[0079] Specifically, the crucible module is, for example, a graphite crucible, which is not specifically limited, and is used to complete the growth of silicon carbide crystals.

[0080] Specifically, the voltage monitoring unit, such as a single-phase voltage monitor, is loaded with a voltage of 50V in a stable state, which is not specifically limited, and is used to monitor the voltage fluctuation between the seed crystal and the molten silicon carbide in the lower crucible.

[0081] Specifically, the torque monitoring unit, such as a mobile crane torque monitor, is used to monitor the rotational torque without limitation.

[0082] Specifically, the detection module, such as a stress detector, is used to measure the stress of the grown silicon carbide crystal without any specific limitation.

[0083] Specifically, the control module preliminarily determines whether the preparation of silicon carbide crystal under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value, wherein:

[0084] If the voltage fluctuation evaluation value is less than the first preset evaluation threshold value of 0.32, the control module preliminarily determines that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, and continues to prepare the silicon carbide crystal according to the current preparation parameters;

[0085] If the voltage fluctuation evaluation value is greater than or equal to the first preset evaluation threshold and less than the second preset evaluation threshold of 0.84, the control module preliminarily determines that the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard, and secondarily determines whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency;

[0086] If the voltage fluctuation evaluation value is greater than or equal to the second preset evaluation threshold, the control module preliminarily determines that the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, and determines the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation.

[0087] Specifically, the voltage fluctuation evaluation value is calculated by the following formula:

[0088]

[0089] In the formula, E represents the voltage fluctuation evaluation value, α represents the first evaluation coefficient, α is set to 0.68, U represents the voltage single fluctuation amplitude, Uy represents the fluctuation amplitude threshold, Uy is set to 15V, β represents the second evaluation coefficient, β is set to 0.30, T represents the voltage single fluctuation duration, Ty represents the voltage single fluctuation duration threshold, and Ty is set to 30ms.

[0090] Specifically, the control module determines whether the preparation under voltage fluctuation meets the preset standard based on the historical fluctuation frequency.

[0091] If the historical fluctuation frequency is less than the preset frequency characteristic threshold of 3 times / min, the control module determines that the preparation of silicon carbide crystal under a single voltage fluctuation meets the preset standard;

[0092] If the historical fluctuation frequency is greater than or equal to the preset frequency characteristic threshold, the control module determines that the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, and increases the heating power of the first heating unit according to the difference between the historical fluctuation frequency and the preset frequency characteristic threshold.

[0093] Specifically, the historical fluctuation frequency is the number of times voltage fluctuations are monitored within a historical preset time period of 5 minutes.

[0094] Specifically, the control module records a single voltage fluctuation exceeding the first preset fluctuation amplitude of 10V as one voltage fluctuation.

[0095] Specifically, the control module increases the heating power of the first heating unit according to the fluctuation frequency difference, wherein:

[0096] If the fluctuation frequency difference is less than the first preset fluctuation frequency difference of 2 times / min, the control module uses the first preset heating power adjustment coefficient of 1.01 to increase the heating power of the first heating unit to the corresponding value;

[0097] If the fluctuation frequency difference is greater than or equal to the first preset fluctuation frequency difference and less than the second preset fluctuation frequency difference of 5 times / min, the control module uses the second preset heating power adjustment coefficient of 1.03 to increase the heating power of the first heating unit to the corresponding value;

[0098] If the fluctuation frequency difference is greater than or equal to the second preset fluctuation frequency difference, the control module uses the third preset heating power adjustment coefficient 1.08 to increase the heating power of the first heating unit to a corresponding value;

[0099] The fluctuation frequency difference is the difference between the historical fluctuation frequency and the preset frequency characteristic threshold.

[0100] Specifically, the control module corrects the heating power of the first heating unit according to the correction difference under the first preset condition, wherein:

[0101] If the correction difference is less than the first preset correction difference of 1.25, the control module uses the first preset power correction coefficient of 1.07 to increase the operating power of the second motor to a corresponding value;

[0102] If the correction difference is greater than or equal to the first preset correction difference and less than the second preset correction difference of 2.18, the control module uses the second preset power correction coefficient of 1.05 to increase the operating power of the second motor to a corresponding value;

[0103] If the correction difference is greater than or equal to the second preset correction difference, the control module uses a third preset power correction coefficient of 1.02 to increase the operating power of the second motor to a corresponding value;

[0104] The correction difference is the difference between the average stress of the silicon carbide crystal after the heating power adjustment is completed and the preset stress threshold;

[0105] The first preset condition is that the control module completes the adjustment of the heating power of the heating unit and the average stress of the silicon carbide crystal after adjustment is greater than a preset stress threshold of 30 MPa.

[0106] Specifically, the control module determines the reason why the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard according to the change of the rotation torque under a single voltage fluctuation, wherein:

[0107] If the rotational torque remains unchanged, the control module determines that the reason why the preparation of the silicon carbide crystal under the single voltage fluctuation does not meet the preset standard is that the rotation speed of the seed crystal holder does not meet the standard, and reduces the rotation speed of the first motor according to the difference between the voltage fluctuation evaluation value and the second preset evaluation threshold;

[0108] If the rotational torque decreases, the control module determines that the reason why the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard is that the pulling speed of the seed crystal holder does not meet the standard, and reduces the speed of the second motor according to the magnitude of the reduction in the rotational torque.

[0109] Specifically, the reduction in the rotational speed of the second motor is positively correlated with the reduction in the rotational torque, wherein the positive correlation is, for example, a linear positive correlation or a nonlinear positive correlation, and the slope of the linear positive correlation is not specifically limited. It can be understood that the greater the reduction in the rotational speed of the second motor, the greater the reduction in the rotational torque.

[0110] Specifically, the control module reduces the speed of the first motor according to the voltage fluctuation difference, wherein:

[0111] If the voltage fluctuation difference is less than the first preset voltage fluctuation difference of 0.08, the control module uses the first preset power adjustment coefficient of 0.98 to reduce the speed of the first motor to a corresponding value;

[0112] If the voltage fluctuation difference is greater than or equal to the first preset voltage fluctuation difference and less than the second preset voltage fluctuation difference of 0.15, the control module uses the second preset power adjustment coefficient of 0.95 to reduce the speed of the first motor to a corresponding value;

[0113] If the voltage fluctuation difference is greater than the second preset voltage fluctuation difference, the control module uses a third preset power adjustment coefficient of 0.93 to reduce the speed of the first motor to a corresponding value;

[0114] The voltage fluctuation difference is a difference between the voltage fluctuation evaluation value and the second preset evaluation threshold.

[0115] Specifically, the control module determines whether the preparation of the silicon carbide crystal meets the preset standard according to the average stress evaluation value, wherein:

[0116] If the average stress evaluation value is less than the preset average stress characteristic threshold value of 28 MPa, the control module determines that the preparation of the silicon carbide crystal meets the preset standard;

[0117] If the average stress evaluation value is greater than a preset average stress characteristic threshold, the control module determines that the preparation of the silicon carbide crystal does not meet the preset standard, and reduces the heating power of the second heating unit according to the difference between the average stress evaluation value and the preset average stress characteristic threshold;

[0118] The average stress evaluation value is obtained based on the detection module, and the average stress evaluation value is the average value of stress values ​​of several equally spaced points on the silicon carbide crystal column that has completed growth.

[0119] Specifically, the silicon carbide crystal growth method of the present invention comprises:

[0120] Step S1, after loading the silicon raw material into the lower crucible, start the heating module to heat the crucible module;

[0121] Step S2, in response to the silicon raw material being heated to a molten state, adding excess carbon powder into the silicon carbide reaction chamber based on the carbon powder adding module;

[0122] Step S3, standing to allow the silicon raw material and the carbon powder to react to obtain a silicon carbide melt;

[0123] Step S4, bringing the seed crystal holder into contact with the liquid surface of the silicon carbide melt, and starting the pulling module at a preset rotation speed and a preset pulling speed to prepare a silicon carbide crystal;

[0124] Step S5, the voltage monitoring unit monitors the voltage loaded during the preparation process of the silicon carbide crystal in real time, obtains the voltage fluctuation evaluation value according to the monitored voltage, and preliminarily determines whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value;

[0125] Step S6, when it is preliminarily determined that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, the preparation of the silicon carbide crystal is continued according to the current preparation parameters;

[0126] Step S7, when it is preliminarily determined that the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, a secondary determination is made based on the historical fluctuation frequency whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard, or the reason for not meeting the preset standard is determined based on the change of the rotational torque under a single voltage fluctuation;

[0127] Step S8, when the preparation of the silicon carbide crystal is completed and it is determined that the preparation of the silicon carbide crystal does not meet the preset standard according to the average stress evaluation value obtained by the detection module, reducing the heating power of the second heating unit;

[0128] Step S9: when it is determined according to the average stress evaluation value that the preparation of the silicon carbide crystal meets the preset standard, outputting the silicon carbide crystal that meets the preset standard.

[0129] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A silicon carbide crystal production system, characterized in that: include: A crucible module, comprising a lower crucible, an upper crucible connected to the lower crucible, and an annular barrier liner arranged inside the lower crucible, wherein the height of the annular barrier liner is less than the height of the lower crucible, wherein the outer wall of the annular liner and the inner wall of the lower crucible form a silicon carbide reaction chamber; A carbon powder adding module, comprising a plurality of carbon powder adding units arranged at equal intervals in the circumferential direction on the outer wall of the lower crucible, wherein a single carbon powder adding unit comprises a storage chamber for storing carbon powder, a delivery pipe connected to the storage chamber, an output end of the delivery pipe is communicated with the silicon carbide reaction chamber, wherein each output end is provided with a solenoid valve; A pulling module connected to the upper crucible, comprising a seed crystal holder for fixing a seed crystal, a first motor for driving the seed crystal holder to rotate, and a second motor for driving the seed crystal holder to rise and fall; A heating module is arranged on the outer wall of the crucible module, comprising a first heating unit arranged below the lower crucible, a second heating unit arranged on the outer side wall of the lower crucible, and a third heating unit arranged on the outer side wall of the upper crucible; A monitoring module, comprising a voltage monitoring unit for monitoring the voltage between the seed crystal and the molten silicon carbide in the lower crucible and a torque monitoring unit provided on the seed crystal holder for obtaining the rotation torque of the seed crystal holder; A detection module, which is used to obtain stress parameters of the grown silicon carbide crystal; A control module, which is respectively connected to the monitoring module, the detection module, the pulling module and the heating module, and is used to preliminarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard based on the voltage fluctuation evaluation value, and to secondarily determine whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency, or to determine the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation, and to determine whether the preparation of silicon carbide crystals meets the preset standard based on the average stress evaluation value.

2. The silicon carbide crystal production system according to claim 1, characterized in that: The control module preliminarily determines whether the preparation of silicon carbide crystal under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value, wherein: If the voltage fluctuation evaluation value is less than the first preset evaluation threshold, the control module preliminarily determines that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, and continues to prepare the silicon carbide crystal according to the current preparation parameters; If the voltage fluctuation evaluation value is greater than or equal to the first preset evaluation threshold and less than the second preset evaluation threshold, the control module preliminarily determines that the preparation of silicon carbide crystals under a single voltage fluctuation does not meet the preset standard, and secondarily determines whether the preparation of silicon carbide crystals under a single voltage fluctuation meets the preset standard based on the historical fluctuation frequency; If the voltage fluctuation evaluation value is greater than or equal to the second preset evaluation threshold, the control module preliminarily determines that the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, and determines the reason for not meeting the preset standard based on the change of the rotational torque under a single voltage fluctuation.

3. The silicon carbide crystal production system according to claim 2, characterized in that: The voltage fluctuation evaluation value is determined by the duration and amplitude of a single fluctuation.

4. The silicon carbide crystal production system according to claim 3, characterized in that: The control module determines whether the preparation under voltage fluctuation meets the preset standard based on the historical fluctuation frequency. If the historical fluctuation frequency is less than a preset frequency characteristic threshold, the control module determines that the preparation of silicon carbide crystal under a single voltage fluctuation meets the preset standard; If the historical fluctuation frequency is greater than or equal to the preset frequency characteristic threshold, the control module determines that the preparation of the silicon carbide crystal under the single voltage fluctuation does not meet the preset standard, and increases the heating power of the first heating unit according to the difference between the historical fluctuation frequency and the preset frequency characteristic threshold; The historical fluctuation frequency is the number of times voltage fluctuations are monitored within a historical preset time period; The control module records a single voltage fluctuation exceeding a first preset fluctuation amplitude as one voltage fluctuation.

5. The silicon carbide crystal production system according to claim 4, characterized in that: The control module increases the heating power of the first heating unit according to the fluctuation frequency difference, wherein: If the fluctuation frequency difference is less than the first preset fluctuation frequency difference, the control module uses the first preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value; If the fluctuation frequency difference is greater than or equal to the first preset fluctuation frequency difference and less than the second preset fluctuation frequency difference, the control module uses the second preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value; If the fluctuation frequency difference is greater than or equal to the second preset fluctuation frequency difference, the control module uses the third preset heating power adjustment coefficient to increase the heating power of the first heating unit to a corresponding value; The fluctuation frequency difference is the difference between the historical fluctuation frequency and the preset frequency characteristic threshold.

6. The silicon carbide crystal production system according to claim 5, characterized in that: The control module is provided with a plurality of heating power correction modes for the heating power of the first heating unit under a first preset condition, and each heating power correction mode has a different correction range for the heating power of the first heating unit; The first preset condition is that the control module completes the adjustment of the heating power of the heating unit and the average stress of the silicon carbide crystal after adjustment is greater than a preset stress threshold.

7. The silicon carbide crystal production system according to claim 6, characterized in that: The control module determines the reason why the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard according to the change of the rotation torque under a single voltage fluctuation, wherein: If the rotational torque remains unchanged, the control module determines that the reason why the preparation of the silicon carbide crystal under the single voltage fluctuation does not meet the preset standard is that the rotation speed of the seed crystal holder does not meet the standard, and reduces the rotation speed of the first motor according to the difference between the voltage fluctuation evaluation value and the second preset evaluation threshold; If the rotational torque decreases, the control module determines that the reason why the preparation of silicon carbide crystal under a single voltage fluctuation does not meet the preset standard is that the pulling speed of the seed crystal holder does not meet the standard, and reduces the speed of the second motor according to the magnitude of the reduction in the rotational torque.

8. The silicon carbide crystal production system according to claim 7, characterized in that: The control module reduces the speed of the first motor according to the voltage fluctuation difference, wherein: If the voltage fluctuation difference is less than the first preset voltage fluctuation difference, the control module uses the first preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value; If the voltage fluctuation difference is greater than or equal to the first preset voltage fluctuation difference and less than the second preset voltage fluctuation difference, the control module uses the second preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value; If the voltage fluctuation difference is greater than the second preset voltage fluctuation difference, the control module uses a third preset power adjustment coefficient to reduce the speed of the first motor to a corresponding value; The voltage fluctuation difference is a difference between the voltage fluctuation evaluation value and the second preset evaluation threshold.

9. The silicon carbide crystal production system according to claim 8, characterized in that: The control module determines whether the preparation of the silicon carbide crystal meets the preset standard according to the average stress evaluation value, wherein: If the average stress evaluation value is less than a preset average stress characteristic threshold, the control module determines that the preparation of the silicon carbide crystal meets the preset standard; If the average stress evaluation value is greater than a preset average stress characteristic threshold, the control module determines that the preparation of the silicon carbide crystal does not meet the preset standard, and reduces the heating power of the second heating unit according to the difference between the average stress evaluation value and the preset average stress characteristic threshold; The average stress evaluation value is obtained based on the detection module.

10. A method for growing silicon carbide crystals applied to the system according to any one of claims 1 to 9, characterized in that: include: Step S1, after loading the silicon raw material into the lower crucible, start the heating module to heat the crucible module; Step S2, in response to the silicon raw material being heated to a molten state, adding excess carbon powder into the silicon carbide reaction chamber based on the carbon powder adding module; Step S3, standing to allow the silicon raw material and the carbon powder to react to obtain a silicon carbide melt; Step S4, bringing the seed crystal holder into contact with the liquid surface of the silicon carbide melt, and starting the pulling module at a preset rotation speed and a preset pulling speed to prepare a silicon carbide crystal; Step S5, the voltage monitoring unit monitors the voltage loaded during the preparation process of the silicon carbide crystal in real time, obtains the voltage fluctuation evaluation value according to the monitored voltage, and preliminarily determines whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard according to the voltage fluctuation evaluation value; Step S6, when it is preliminarily determined that the preparation of the silicon carbide crystal under the single voltage fluctuation meets the preset standard, the preparation of the silicon carbide crystal is continued according to the current preparation parameters; Step S7, when it is preliminarily determined that the preparation of the silicon carbide crystal under a single voltage fluctuation does not meet the preset standard, a secondary determination is made based on the historical fluctuation frequency whether the preparation of the silicon carbide crystal under a single voltage fluctuation meets the preset standard, or the reason for not meeting the preset standard is determined based on the change of the rotational torque under a single voltage fluctuation; Step S8, when the preparation of the silicon carbide crystal is completed and it is determined that the preparation of the silicon carbide crystal does not meet the preset standard according to the average stress evaluation value obtained by the detection module, reducing the heating power of the second heating unit; Step S9: when it is determined according to the average stress evaluation value that the preparation of the silicon carbide crystal meets the preset standard, outputting the silicon carbide crystal that meets the preset standard.

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