A method for optimizing a thermal field for growing silicon carbide based on a liquid phase method

Abstract

This application discloses a thermal field optimization method for silicon carbide growth based on liquid phase method, which optimizes the thermal field based on a first heating parameter for silicon carbide growth at the first... f Heating the graphite crucible in its original state, so that it is in contact with the first... f The first performance parameter corresponding to the morphology satisfies the first preset condition; the first performance parameter includes the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes the first carbon concentration gradient being less than the preset carbon concentration gradient; based on the first carbon concentration gradient and the interface displacement calculation model, the target interface displacement of the graphite crucible after the target time is obtained; based on the first... f The shape and target interface displacement of the graphite crucible are obtained. f+1 Morphology; based on the second heating parameter, for the first f+1 Heating the graphite crucible in its original state, so that it is in contact with the first... f+1 If the first performance parameter corresponding to the morphology meets the first preset condition, this application can achieve thermal field optimization of silicon carbide and avoid the influence of graphite crucible deformation on silicon carbide crystal growth.

Description

Technical Field

[0001] This application belongs to the field of silicon carbide growth technology, specifically relating to a thermal field optimization method for silicon carbide growth based on liquid phase method. Background Technology

[0002] High-quality silicon carbide crystals can be grown using the liquid-phase method. In this method, the graphite crucible serves not only as a container but also as a heat source and carbon source for the molten silicon. The graphite crucible is heated using an electromagnetic induction heating coil and a graphite heater. During heating, the carbon in the graphite crucible dissolves into the molten silicon due to the high temperature and localized carbon unsaturation. The carbon is then transported below the seed crystal through convection and diffusion. The temperature below the seed crystal is typically relatively low, causing the carbon to become supersaturated, and silicon carbide crystals grow there.

[0003] During silicon carbide growth, the graphite crucible may deform. This deformation can affect the growth of silicon carbide crystals, for example, it may lead to the formation of polycrystalline silicon.

[0004] However, there is a lack of methods in the relevant technologies to avoid the impact of graphite crucible deformation on silicon carbide crystal growth. Summary of the Invention

[0005] The purpose of this application is to provide a thermal field optimization method for silicon carbide growth based on liquid phase method, which can solve the problem of the influence of graphite crucible deformation on silicon carbide crystal growth in related technologies.

[0006] This application provides a thermal field optimization method for silicon carbide growth based on liquid phase method, including:

[0007] Based on the first heating parameter, for the position of the first The graphite crucible in its original state is heated to make it compatible with the first... The first performance parameter corresponding to the morphology satisfies the first preset condition; the first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes: the first carbon concentration gradient is less than the preset carbon concentration gradient; , It is an integer greater than or equal to 2;

[0008] Based on the calculation model of the first carbon concentration gradient and interface displacement, the target interface displacement of the graphite crucible is obtained after the target time.

[0009] According to the first Based on the shape and the displacement of the target interface, the first [value] of the graphite crucible is obtained. form;

[0010] Obtain a second heating parameter, and based on the second heating parameter, adjust the heating parameters for the heating state at the first heating stage. The graphite crucible in its original state is heated to make it compatible with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0011] Optionally, the method further includes:

[0012] For each of the plurality of graphite crucibles, a first operation is performed; the first operation includes, based on the first heating parameter, adjusting the temperature of the first graphite crucible at the position of the first graphite crucible. The graphite crucible in its current state is heated until a second heating parameter is obtained. Based on the second heating parameter, the graphite crucible in the first state is then heated. The graphite crucible in its original state is heated to make it compatible with the first... The step of the first performance parameter corresponding to the shape satisfying the first preset condition; the inner diameter of the graphite crucible cover plate of the multiple graphite crucibles is different from each other.

[0013] After the first operation is completed, obtain the remaining amount of aluminum in the graphite crucible;

[0014] Based on the remaining amount of aluminum in the graphite crucible, a target graphite crucible cover inner diameter is determined from the graphite crucible cover inner diameters of the plurality of graphite crucibles, and the target graphite crucible cover inner diameter is determined as the optimal graphite crucible cover inner diameter for the graphite crucible used for silicon carbide crystal growth.

[0015] Optionally, obtaining the remaining amount of aluminum in the graphite crucible after performing the first operation includes:

[0016] Obtain the initial aluminum content in the graphite crucible before performing the first operation;

[0017] Based on the initial aluminum content and the aluminum transport control equation, the remaining amount of aluminum in the graphite crucible after the first operation is completed is obtained.

[0018] Optional, the transport control equations for aluminum include:

[0019]

[0020] in, This represents the density of Al. Indicates the concentration of Al. Indicates time, Indicates speed; This represents the diffusion coefficient of Al; l 'g' and 'g' represent the liquid phase and the gas phase, respectively.

[0021] Optionally, obtaining the interface displacement of the graphite crucible after the target time period based on the calculation model of the first carbon concentration gradient and interface displacement includes:

[0022] Obtain H preset times within the target duration; the duration between adjacent preset times is equal to the preset duration step size;

[0023] Obtain the second carbon concentration gradient of the silicon melt at the h-th preset time, and the comparison result between the second carbon concentration gradient and the preset concentration gradient; wherein, at the 1st preset time, the second carbon concentration gradient of the silicon melt is equal to the first carbon concentration gradient; h∈[1,H];

[0024] Substitute the second carbon concentration gradient and the preset time step into the interface displacement calculation model corresponding to the comparison result to obtain the interface displacement of the graphite crucible at the (h+1)th preset time.

[0025] The interface displacement of the graphite crucible at the Hth preset time is determined as the interface displacement of the graphite crucible after the target time.

[0026] Optionally, the method further includes:

[0027] If the comparison result indicates that the second carbon concentration gradient is greater than the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is:

[0028]

[0029] If the comparison result indicates that the second carbon concentration gradient is less than or equal to the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is:

[0030]

[0031] in, Indicates interface displacement. Represents a constant greater than 1. Indicates the molar mass of carbon. This indicates the molar mass of silicon carbide. The density of carbon, The density of carbon, This represents the mass diffusion coefficient of carbon in a silicon melt. Indicates the second carbon concentration. Represents a unit vector perpendicular to the crystal surface. t This represents the time step for transient solutions.

[0032] Optionally, the method further includes:

[0033] A steady-state numerical calculation model is constructed; the steady-state numerical calculation model includes the continuity equation, momentum equation, energy equation, and component transport control equation.

[0034] Based on the steady-state numerical calculation model, the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible is obtained.

[0035] Optionally, the first performance parameter further includes: the volume ratio of the carbon-saturated region in the silicon melt to the total volume of the silicon melt; the first preset condition further includes: the volume ratio being less than or equal to a preset volume ratio; the method further includes:

[0036] The silicon melt simulation model is meshed to obtain multiple silicon melt sub-regions;

[0037] The first carbon concentration and the second carbon concentration of each of the silicon melt sub-regions are obtained respectively;

[0038] The carbon supersaturation of the sub-region is obtained based on the first carbon concentration and the second carbon concentration.

[0039] Based on the comparison between the carbon supersaturation and the preset carbon saturation, a first judgment result is obtained as to whether the silicon melt sub-region is in a state of carbon supersaturation.

[0040] Based on the first judgment result corresponding to each of the silicon melt sub-regions, the volume of the carbon supersaturated region in the silicon melt is obtained.

[0041] Optionally, the first preset condition further includes at least one of the following: the first carbon concentration gradient is greater than a preset concentration gradient, the ratio of the volume of the carbon supersaturated region in the silicon melt to the volume of the silicon melt region is less than or equal to a preset ratio, and the carbon supersaturated region is located in a preset region near the silicon carbide growth interface.

[0042] Optionally, the method also includes:

[0043] Get multiple preset durations;

[0044] According to each preset duration, silicon carbide crystal pre-growth treatment is performed in the graphite crucible, and a second judgment result is obtained on whether polycrystalline formation occurs at a preset position of the graphite crucible;

[0045] Based on the second judgment result, the target duration is obtained from a plurality of preset durations.

[0046] In this embodiment, based on the first heating parameter, the heating element at the first position is... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the morphology satisfies the first preset condition; the first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible. The graphite crucible contains silicon melt; heating the graphite crucible allows carbon in the graphite crucible to integrate into the silicon melt, enabling the growth of silicon carbide crystals. Based on the first carbon concentration gradient and interface displacement calculation model, the target interface displacement of the graphite crucible is obtained after the target time; based on the first... The shape and target interface displacement can accurately determine the first [value / value] of the graphite crucible. Morphology. Obtain the second heating parameter, and based on the second heating parameter, adjust the heating state of the first heating stage. Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the shape satisfies a first preset condition. The first preset condition includes: the first carbon concentration gradient is less than a preset carbon concentration gradient; therefore, even if the graphite crucible deforms with increasing heating time, the deformation causes the graphite crucible to change from the first... Form changed to the first In this process, the heating parameters for the graphite crucible are changed from a first heating parameter to a second heating parameter, and the graphite crucible is heated based on the second heating parameter. This ensures that the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt within it is less than a preset carbon concentration gradient. This smaller-than-preset carbon concentration gradient at the interface between the graphite crucible and the silicon melt prevents polycrystalline growth on the inner wall of the graphite crucible, thus solving the problem in related technologies where deformation of the graphite crucible occurs with increasing growth time, leading to polycrystalline formation. Attached Figure Description

[0047] Figure 1 This application provides a step-by-step flowchart of a thermal field optimization method for silicon carbide growth based on liquid phase method. Figure 1 ;

[0048] Figure 2 This is a schematic diagram of an apparatus for growing silicon carbide based on a liquid phase method, provided in an embodiment of this application;

[0049] Figure 3 This application provides a step-by-step flowchart of a thermal field optimization method for silicon carbide growth based on liquid phase method. Figure 2 ;

[0050] Figure 4 This is a schematic diagram of a graphite crucible without a graphite crucible cover provided in an embodiment of this application;

[0051] Figure 5 This is a schematic diagram of a graphite crucible with a graphite crucible cover provided in an embodiment of this application;

[0052] Figure 6This is a framework diagram of a thermal field optimization device for silicon carbide growth based on liquid phase method provided in an embodiment of this application;

[0053] Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0054] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0055] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in this application, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects have an "or" relationship.

[0056] Reference Figure 1 The thermal field optimization method for silicon carbide growth based on the liquid phase method in this embodiment may include the following steps:

[0057] Step 101, based on the first heating parameter, for the first heating state... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0058] The first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes: the first carbon concentration gradient is less than the preset carbon concentration gradient. , It is an integer greater than or equal to 2.

[0059] For example, the preset carbon concentration gradient can be equal to 0.

[0060] For example, the first heating parameter may include at least one of the following: the amplitude and frequency of the current in the induction heating coil; and the power of the graphite heater. The induction heating coil and the graphite heater are used to heat the graphite crucible.

[0061] The method described in this embodiment is applicable to applications involving the growth of silicon carbide via solution processing. Solution processing, also known as top-seeded solution growth, produces silicon carbide crystals of higher quality and fewer defects compared to other methods, making it suitable for obtaining high-quality silicon carbide crystals. In the liquid-phase silicon carbide growth process, the graphite crucible serves not only as a container but also as a heat source and carbon source for the molten silicon.

[0062] Silicon carbide (SiC), as a third-generation semiconductor material, possesses excellent properties such as a large bandgap, high thermal conductivity, and high chemical stability, making it a promising semiconductor material for various applications. SiC growth methods can include three main approaches: physical vapor transport (PVT), high-temperature chemical vapor deposition (HCVD), and top-seeded solution method. Silicon carbide single crystals grown using the top-seeded solution method offer advantages such as high crystal quality, easy diameter expansion, and easy p-type doping.

[0063] Figure 2 This illustrates a growth system for silicon carbide single crystals grown via a top-seeded solution method, with reference to... Figure 2 A silicon melt 10 is placed in a graphite crucible 30, with a seed crystal rod 60 positioned above it. A graphite heater 40 is located outside the graphite crucible 30, and a side graphite heating element 50 is also located outside the crucible 30. A lower support 70 is located below the graphite crucible 30, and an insulation felt 90 is located outside the graphite heating element 50; a lower support 80 is located below the insulation felt 90. An induction heating coil 11 is located outside the insulation felt 90, and the entire system is housed within a stainless steel furnace shell 12. The graphite crucible 30 is heated by the induction heating coil 11 and the graphite heater 40. During the heating process, silicon carbide crystals 20 grow between the seed crystal rod 60 and the silicon melt 10.

[0064] The graphite crucible is heated by an induction heating coil and a graphite heater. Due to the high temperature and local unsaturation, carbon dissolves in the silicon melt. Then, the carbon is transported to the area below the seed crystal through convection and diffusion. The temperature near the seed crystal is relatively low, and the carbon below the seed crystal becomes supersaturated. Under these supersaturated conditions, silicon carbide single crystals grow. The supersaturation of carbon provides the driving force for the growth of silicon carbide.

[0065] The first heating parameters may include the heating parameters of the induction heating coil and / or the heating parameters of the graphite heater. Heating the graphite crucible in the p-th state based on the first heating parameters may include: heating the furnace body through the heating coil and the graphite heater based on the first heating parameters.

[0066] For example, an induction heating coil can be used to electromagnetically heat the graphite crucible to raise the temperature of the detection point at the bottom of the graphite crucible to 1800°C. Then, the graphite crucible can be precisely regulated by a graphite heater so that the first performance parameter corresponding to the p-th morphology meets the first preset condition.

[0067] Step 102: Based on the calculation model of the first carbon concentration gradient and interface displacement, obtain the target interface displacement of the graphite crucible after the target time.

[0068] In the liquid-phase growth of silicon carbide, carbon is gradually consumed. The graphite crucible, serving as the carbon source, deforms during the growth process, resulting in a corresponding change in its shape. This deformation affects the liquid flow in the silicon melt region, thereby influencing the carbon distribution and silicon carbide crystal growth. Furthermore, the deformation of the graphite crucible during silicon carbide growth can be characterized by interfacial displacement, the amount of which is time-dependent.

[0069] In this embodiment, the target duration can be determined based on the polycrystalline formation during silicon carbide growth. For example, the basic thermal field obtained from numerical simulation can be used to conduct silicon carbide crystal growth experiments, and the time interval between adjusting the graphite heater and the induction heating coil can be determined based on the polycrystalline formation observed during the growth experiment.

[0070] For example, the time cycle for growing silicon carbide crystals is one week, and pre-growth experiments can be carried out according to the following preset durations: 12 hours, 24 hours, 36 hours, and 48 hours.

[0071] In one embodiment, based on experimental results obtained under different preset durations, it was found that when the pre-growth experiment time was 12 hours and 24 hours, there was basically no polycrystalline formation at the bottom and corners of the graphite crucible.

[0072] However, 12 hours is too short. If 12 hours is taken as the target duration, the heater power parameters would need to be adjusted multiple times during each crystal growth experiment, which would consume a lot of manpower and resources. Therefore, the target duration for adjusting the heating parameters of the graphite crucible is set at 24 hours. Here, the target duration is equivalent to the time interval for adjusting the heating parameters.

[0073] Step 103, according to the first Based on the shape and target interface displacement, the first [value] of the graphite crucible is obtained. form.

[0074] Graphite crucible in the first An interface displacement is generated based on the morphology, and the magnitude of the interface displacement is equal to the interface displacement amount in this embodiment. After the interface displacement occurred based on the original shape, the shape of the graphite crucible changed. Specifically, it was caused by the... The form becomes the first form.

[0075] Among them, the graphite crucible is in the first Form and the first The structures in different forms can vary. For example, the differences in structure may include the difference in the flatness inside the graphite crucible.

[0076] The method in this embodiment can be implemented based on the simulation software Fluent. Using Fluent, according to the... The morphology and interface displacement of the graphite crucible were used to obtain the first... form.

[0077] For example, for the first The morphology and interface displacement are superimposed to obtain the first value of the graphite crucible. form

[0078] Step 104: Obtain the second heating parameter, and based on the second heating parameter, adjust the heating parameters for the heating process at the stage of... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0079] For example, the first heating parameter can be adjusted based on empirical data to obtain different heating parameters, and simulations can be performed to obtain the heating results of the first heating parameter using different heating parameters. When the graphite crucible is in its current state, the first performance parameters corresponding to different heating parameters are determined. Then, the heating parameters corresponding to the first performance parameters that satisfy the first preset conditions are determined as the second heating parameters in this step.

[0080] If localized areas of carbon in the silicon melt remain in a supersaturated state for an extended period, it can lead to polycrystalline formation, hindering the high-quality formation of silicon carbide crystals at the growth interface. To mitigate this, the temperature distribution between the graphite crucible and the silicon melt can be adjusted in real-time using a graphite heater and induction heating coil at consistent time intervals. This ensures that the interface between the graphite crucible and the silicon melt remains dissolved, minimizing the formation of polycrystalline material.

[0081] In this embodiment, based on the first heating parameter, the heating element at the first position is... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the morphology satisfies the first preset condition; the first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible. The graphite crucible contains silicon melt; heating the graphite crucible allows carbon in the graphite crucible to integrate into the silicon melt, enabling the growth of silicon carbide crystals. Based on the first carbon concentration gradient and interface displacement calculation model, the interface displacement of the graphite crucible after the target time is obtained; based on the first... The shape and interface displacement can accurately determine the first... Morphology. Obtain the second heating parameter, and based on the second heating parameter, adjust the heating state of the first heating stage. Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the shape satisfies a first preset condition. The first preset condition includes: the first carbon concentration gradient is less than a preset carbon concentration gradient; therefore, even if the graphite crucible deforms with increasing heating time, the deformation causes the graphite crucible to change from the first... Form changed to the first In this process, the heating parameters for the graphite crucible are changed from a first heating parameter to a second heating parameter, and the graphite crucible is heated based on the second heating parameter. This ensures that the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt within it is less than a preset carbon concentration gradient. This smaller-than-preset carbon concentration gradient at the interface between the graphite crucible and the silicon melt prevents polycrystalline growth on the inner wall of the graphite crucible, thus solving the problem in related technologies where deformation of the graphite crucible occurs with increasing growth time, leading to polycrystalline formation.

[0082] Figure 3 Another method for optimizing the thermal field of silicon carbide growth based on liquid phase method is shown, referring to... Figure 3 The method may include the following steps:

[0083] Step 201, based on the first heating parameter, for the first heating state... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0084] The first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes: the first carbon concentration gradient is less than the preset carbon concentration gradient; , It is an integer greater than or equal to 2.

[0085] For example, the first preset condition may also include at least one of the following: the first carbon concentration gradient is greater than the preset concentration gradient, the ratio of the volume of the carbon supersaturated region in the silicon melt to the volume of the silicon melt region is less than or equal to the preset ratio, and the carbon supersaturated region is located in a preset region near the silicon carbide growth interface.

[0086] For example, the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt within it can be obtained as follows:

[0087] Sub-step A1: Construct a steady-state numerical calculation model.

[0088] The steady-state numerical calculation model includes the continuity equation, momentum equation, energy equation, and component transport control equation.

[0089] For example, a steady-state numerical calculation model is established, and a steady-state solution is obtained from the model, yielding time-independent results. Specifically, the solution yields the thermal field, flow field, and concentration field distributions of the graphite crucible under the corresponding conditions.

[0090] For example, the temperature at the center of the bottom of the graphite crucible can be maintained at 1800℃ using an induction heating coil. Then, a graphite heater can be used to precisely control the temperature distribution, ensuring that the first carbon concentration gradient on the inner wall of the graphite crucible is less than 0, and that the inner wall of the graphite crucible is completely dissolved, preventing the formation of polycrystalline material. Furthermore, by adjusting the heating parameters of the induction heating coil and the graphite heater, the silicon melt region can meet the following conditions: the carbon supersaturated region is concentrated near the growth interface, and the supersaturated region in the silicon melt is small, while the unsaturated region is large. For instance, the volume ratio of the supersaturated region to the total volume of the silicon melt region can be obtained, ensuring that this volume ratio is less than or equal to a defined preset volume ratio (e.g., 0.05).

[0091] The continuity equation is:

[0092]

[0093] The momentum equation is:

[0094]

[0095] The energy equation is:

[0096]

[0097] The component transport control equation is:

[0098]

[0099] Furthermore, the steady-state numerical calculation model is simplified. This step involves solving the thermal field, flow field, and temperature field of the graphite crucible under a certain state. The solution process is time-independent; therefore, the component transport control equations... It can be ignored.

[0100] Furthermore, the processing only involves the transport and calculation of carbon, therefore During the solution process, in the initial state, there are no carbon atoms in the silicon melt. Therefore... The carbon in this process originates from the carbon at the surface of the graphite crucible dissolving into the silicon melt.

[0101] Furthermore, by converting the mass fraction into molar concentration, the final component transport control equation in this numerical calculation model is obtained as follows:

[0102]

[0103] in, Expresses speed, measured in m / s; Density is expressed in kg / m³. 3 ; This indicates pressure, expressed in Pa. This represents dynamic viscosity, expressed in Pa·s. Current, unit is A / m 2 ; This represents magnetic flux density, measured in tons (T). This represents the acceleration due to gravity, with units of m / s². 2 ; This represents the coefficient of thermal expansion, with units of K. -1 ; This indicates temperature, expressed in °C. This indicates the reference temperature, in °C. This indicates the specific heat capacity of Si silicon melt, expressed in J / (kg·K). This represents the thermal conductivity of Si molten silicon, expressed in W / (m·K). Indicates the heat source, with units of W / m². 3 t represents time, in seconds (s). This indicates the mass fraction of k distinct components. This represents the mass diffusion coefficient of k different components in the silicon melt, expressed in kg / (m·s). This represents the mass concentration source term of k different components in the silicon melt, and N represents the total number of different components; This represents the mass diffusion coefficient of carbon in silicon melt, expressed in kg / (m·s). This indicates the molar concentration of carbon, with units of mol / m³. 3 , x Represents spatial coordinates.

[0104] During the growth of silicon carbide crystals, the key factors affecting the growth quality and precipitation amount of silicon carbide crystals include the carbon concentration distribution in the silicon melt. Therefore, the component transport control equations are crucial in the solution process.

[0105] Before solving, appropriate boundary conditions need to be set to simulate the real situation. For example, a dissolution boundary condition is added at the interface between the graphite crucible and the silicon melt to simulate the dissolution of the graphite crucible; and a precipitation boundary condition is added at the interface between the silicon melt and the crystal, where both types of boundaries are equilibrium concentration boundaries of carbon.

[0106]

[0107] in, For carbon concentration, The molar mass of silicon is given in g / mol. The density of silicon (kg / m³) 3 e is the mathematical constant Euler number. T Let K be the temperature. At the free surface of the silicon melt (the interface between the silicon melt and the gas), set the normal gradient of concentration as follows:

[0108]

[0109] The normal gradient is set to simulate the real-world scenario where silicon carbide crystals do not precipitate on a free surface. In the actual process of growing silicon carbide using a graphite crucible, the internal region of the coil is typically water-cooled to keep the inner wall of the coil at room temperature. To save computational resources, the internal water cooling of the coil is simplified, and the temperature of the inner wall of the coil is given as room temperature during the solution; all other contact surfaces are set as temperature-continuous walls, with the left and right sides of contact surfaces of different structures being temperature-continuous.

[0110] Sub-step A2: Based on the steady-state numerical calculation model, obtain the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible.

[0111] Based on the steady-state numerical calculation model in sub-step A1, the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible is obtained. .

[0112] For example, the first performance parameter also includes: the volume ratio of the carbon-saturated region in the silicon melt to the total volume of the silicon melt; correspondingly, the first preset condition also includes: the volume ratio is less than or equal to a preset volume ratio; correspondingly, the method also includes the following sub-steps:

[0113] Sub-step B1 involves meshing the silicon melt simulation model to obtain multiple silicon melt sub-regions.

[0114] For example, a silicon melt simulation model can be a simulation model built in Fluent software, which is used to reflect the volumetric characteristics of silicon melt.

[0115] Sub-step B2: Obtain the first carbon concentration and the second carbon concentration for each silicon melt sub-region.

[0116] For example, the first and second carbon concentrations of each silicon melt sub-region are obtained according to the following method: The steady-state numerical calculation model (including the continuity equation, momentum equation, energy equation, and component transport control equation) in the aforementioned sub-step A1 is solved in steady state to obtain the carbon concentration distribution, which includes the first carbon concentration of each silicon melt sub-region. Based on the equilibrium concentration boundary equation for carbon in sub-step A1, the second carbon concentration is obtained. .

[0117] Sub-step B3: Based on the first carbon concentration and the second carbon concentration, the carbon supersaturation of the silicon melt sub-region is obtained.

[0118] For example, the carbon supersaturation of a silicon melt subregion is obtained using the following method:

[0119]

[0120] Where S represents the carbon supersaturation of the silicon melt subregion.

[0121] Sub-step B4: Based on the comparison between carbon supersaturation and preset carbon saturation, obtain the first judgment result on whether the silicon melt sub-region is in a state of carbon supersaturation.

[0122] For example, the carbon saturation is preset to 0; for instance, if the carbon supersaturation is greater than 0, then the silicon melt sub-region is determined to be in a carbon supersaturated state; otherwise, the silicon melt sub-region is determined not to be in a carbon supersaturated state.

[0123] Sub-step B5: Based on the first judgment result corresponding to each silicon melt sub-region, obtain the volume of the carbon supersaturated region in the silicon melt.

[0124] Obtain a silicon melt sub-region that is in the carbon supersaturated region, and based on the silicon melt sub-region that is in the carbon supersaturated region, obtain the volume of the carbon supersaturated region in the silicon melt.

[0125] For example, the silicon melt sub-region is a two-dimensional planar region, and the graphite crucible is cylindrical in shape, with the cross-section of the cylinder being the same. After obtaining the two-dimensional sub-region, the two-dimensional silicon melt sub-region can be integrated to obtain the volume corresponding to the sub-region.

[0126] When solving for component transport, it is necessary to solve for carbon dissolution and precipitation boundary layers. This solution process also requires meshing the silicon melt simulation model to obtain multiple silicon melt sub-regions.

[0127] For example, the first preset condition may also include the formation of polycrystalline material. Further, the first preset condition may include ensuring that the first carbon concentration gradient on the inner wall of the graphite crucible is less than 0, so that the inner wall of the graphite crucible is completely dissolved and no polycrystalline material is formed. In addition, it is necessary to ensure that the carbon supersaturated region in the silicon melt is concentrated near the growth interface, and that the supersaturated region in the silicon melt is small, with most areas being unsaturated. For example, the ratio of the volume of the supersaturated region to the volume of the silicon melt is less than 0.05.

[0128] Step 202: Obtain H preset moments within the target duration.

[0129] The duration between adjacent preset times is equal to the preset duration step.

[0130] For example, in adjusting the induction heating coil and graphite heater, if the time interval between two adjustments is too short, it will waste manpower and resources, resulting in high costs. Therefore, it is necessary to obtain a reasonable adjustment time interval. For instance, a reasonable adjustment time interval can be obtained based on the polycrystalline precipitation amount corresponding to different time intervals.

[0131] In one embodiment, the target duration in the foregoing embodiments can be obtained through the following sub-steps:

[0132] Sub-step D1: Obtain multiple preset durations.

[0133] For example, preset durations can include 12 hours, 24 hours, 36 hours, 48 ​​hours, and so on.

[0134] Sub-step D2 involves performing pre-growth treatment of silicon carbide crystals in a graphite crucible according to each preset duration, and obtaining a second judgment result on whether polycrystalline formation occurs at a preset position in the graphite crucible.

[0135] Sub-step D3: Based on the second judgment result, obtain the target duration from multiple preset durations.

[0136] The basic thermal field can be obtained based on the steady-state numerical calculation model in the aforementioned embodiments. Crystal growth experiments are then conducted based on the basic thermal field. The time interval between the heater and the coil is determined based on the polycrystalline formation obtained from the experiments.

[0137] Typically, the growth cycle of silicon carbide crystals is one week. In one embodiment, crystal growth experiments were conducted for 12 hours, 24 hours, 36 hours, and 48 hours, respectively.

[0138] In one embodiment, when the pre-growth experiment time was 12 hours and 24 hours, virtually no polycrystalline material was generated at the bottom and corners of the graphite crucible. Furthermore, the polycrystalline material generation for different preset durations is shown in Table 1.

[0139]

[0140] With preset durations of 12 hours and 24 hours, there was virtually no polycrystalline formation at the bottom and corners of the graphite crucible. However, 12 hours is too short. If 12 hours is used as the interval, the heater power parameters for each crystal growth experiment would need to be adjusted multiple times, consuming a lot of manpower and resources. Therefore, the target time was selected as 24 hours.

[0141] Step 203: Obtain the second carbon concentration gradient of the silicon melt at the h-th preset time, and the comparison result between the second carbon concentration gradient and the preset concentration gradient.

[0142] At the first preset time, the second carbon concentration gradient of the silicon melt is equal to the first carbon concentration gradient; where h∈[1,H], and H is an integer greater than or equal to 2.

[0143] For example, the preset concentration gradient can be 0.

[0144] Step 204: Substitute the second carbon concentration gradient and the preset time step into the interface displacement calculation model corresponding to the comparison result to obtain the interface displacement of the graphite crucible at the preset time h+1.

[0145] For example, the interface displacement calculation model corresponding to the comparison result in step 204 can be obtained through the following sub-steps:

[0146] In sub-step E1, if the comparison result shows that the second carbon concentration gradient is greater than the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is:

[0147]

[0148] in, This represents the interface displacement.

[0149] In sub-step E2, if the comparison result shows that the second carbon concentration gradient is less than or equal to the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is:

[0150]

[0151] in, Indicates interface displacement. Represents a constant greater than 1. Indicates the molar mass of carbon. This indicates the molar mass of silicon carbide. The density of carbon, The density of carbon, This represents the mass diffusion coefficient of carbon in a silicon melt. Indicates the second carbon concentration. A unit vector perpendicular to the crystal surface. t This represents the time step for transient solutions.

[0152] Step 205: Determine the interface displacement of the graphite crucible at the Hth preset time as the target interface displacement of the graphite crucible after the target time.

[0153] Step 206, according to the first Based on the shape and target interface displacement, the first [value] of the graphite crucible is obtained. form.

[0154] Step 207: Obtain the second heating parameter, and based on the second heating parameter, adjust the heating parameters for the heating process at the stage of... Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0155] For example, the method may also include the following steps:

[0156] Step 208: Perform the first operation for each of the multiple graphite crucibles.

[0157] The first operation includes, based on the first heating parameter, applying heat to the element in the first position... The graphite crucible in its current state is heated until a second heating parameter is obtained. Based on the second heating parameter, the graphite crucible in the first state is then heated. Heating the graphite crucible in its original state, so that it is in contact with the first... The steps of satisfying the first preset condition for the first performance parameter corresponding to the form.

[0158] Among them, the inner diameters of the graphite crucible lids of several graphite crucibles are different from each other.

[0159] Example: A schematic diagram of a graphite crucible without a graphite crucible cover is shown below. Figure 4 As shown, a schematic diagram of a graphite crucible with a graphite crucible lid is as follows. Figure 5 As shown. (Refer to...) Figure 4 The graphite crucible 30 does not have a crucible lid; see reference. Figure 5 The graphite crucible 30 has a crucible cover plate 13, and the distance between the crucible cover plate 13 and the seed crystal rod 60 is the inner diameter 14 of the crucible cover plate.

[0160] Step 209: Obtain the remaining amount of aluminum in the graphite crucible after the first operation is completed.

[0161] For example, step 209 may include the following sub-steps:

[0162] Sub-step F1 obtains the initial aluminum content in the graphite crucible before performing the first operation.

[0163] For example, the initial aluminum content in the graphite crucible can be set to 2000.

[0164] Sub-step F2, based on the initial aluminum content and the aluminum transport control equation, obtains the remaining amount of aluminum in the graphite crucible after the first operation is completed.

[0165] The transport control equations for aluminum include:

[0166]

[0167] in, This indicates the concentration of Al, expressed in mol / m³. 3 ; Indicates time, Indicates speed, This represents the diffusion coefficient of Al, expressed in m. 2 / s; This is the density of Al, in kg / m³. 3 . l and g These represent the liquid phase and the gas phase, respectively.

[0168] Step 210: Based on the remaining amount of aluminum in the graphite crucible, determine the inner diameter of the target graphite crucible cover from the inner diameters of the graphite crucible covers of multiple graphite crucibles, and determine the inner diameter of the target graphite crucible cover as the optimal inner diameter of the graphite crucible cover for silicon carbide crystal growth.

[0169] The inner diameter of the graphite crucible that saves the most graphite material can be selected; the smaller the inner diameter, the larger the volume of the cover plate. In one embodiment, the average growth rate of the entire crystal growth stage and the remaining amount of aluminum in the final silicon melt are obtained for each working condition, as shown in Table 2:

[0170]

[0171] In the high-temperature zone at the interface between the graphite crucible and the silicon melt, the carbon in the graphite crucible will dissolve, while in the low-temperature zone, polycrystalline silicon carbide may precipitate.

[0172] There are two main temperature distribution patterns in graphite crucibles: one where the temperature is higher on the sides and lower at the bottom, in which case the sides act as the carbon source while polycrystalline deposits occur at the bottom; and the other where the bottom is higher and the sides are lower, in which case the bottom acts as the carbon source while polycrystalline deposits occur on the sides, with polycrystalline deposits also forming at the corners. Through precise thermal field control, the interface between the graphite crucible and the molten silicon can be completely dissolved.

[0173] During the long-term growth process, the graphite crucible gradually dissolves, causing deformation of its inner wall and altering the temperature and flow fields within the silicon melt. This change leads to two main problems: First, excessive polycrystalline deposition at the bottom or corners of the graphite crucible results in inefficient utilization of most of the carbon. Furthermore, the polycrystalline material may be carried to the growth interface, affecting the normal growth of the crystals there. Second, prolonged carbon supersaturation in localized areas of the silicon melt can lead to the formation of polycrystalline material, which may also be carried to the growth interface, hindering crystal growth. The challenge for liquid-phase silicon carbide growth lies in how to achieve real-time control of the thermal field distribution to ensure the complete dissolution of the graphite crucible's inner wall while maintaining a balance between dissolved carbon and carbon consumed at the growth interface, and preventing excessive carbon supersaturation in the silicon melt.

[0174] Furthermore, in liquid-phase silicon carbide growth, aluminum is typically added to the silicon melt to produce higher-quality silicon carbide single crystals. However, aluminum is gradually consumed during the long-term growth process, reducing the amount of aluminum in the silicon melt. This reduction in aluminum affects the high-quality growth of silicon carbide single crystals. To avoid this problem, this embodiment determines the optimal inner diameter of the graphite crucible lid for silicon carbide crystal growth based on the remaining amount of aluminum. Silicon carbide growth based on this optimal inner diameter suppresses aluminum consumption.

[0175] Furthermore, the method of this embodiment may also include the following steps:

[0176] Step S1: Obtain the basic thermal field.

[0177] Specifically, a steady-state numerical calculation model is established, and a steady-state solution is performed on the model. This solution process is independent of time. Through the steady-state solution, the thermal field, flow field, and concentration field distributions within the graphite crucible furnace under a certain state can be obtained.

[0178] A graphite crucible is heated by an induction heating coil to maintain the temperature at the center of the bottom of the crucible at 1800℃. Then, a graphite heater is used to precisely control the temperature distribution, ultimately ensuring that the first carbon concentration gradient on the inner wall of the graphite crucible is less than 0, resulting in complete dissolution of the inner wall and preventing polycrystalline formation. The carbon supersaturated region in the silicon melt is concentrated near the growth interface, and the supersaturated region in the silicon melt is relatively small, with most areas being unsaturated. For example, the volume of the supersaturated region is... Total volume of silicon melt region The ratio is less than or equal to 0.05.

[0179] The steady-state numerical calculation model includes the governing equations, specifically the continuity equation, momentum equation, and energy equation. These three governing equations are as follows:

[0180]

[0181]

[0182]

[0183] Based on the governing equations of the three numerical calculation models mentioned above, the temperature field can be obtained. and flow field distribution μ Temperature field T and flow field distribution μ Substituting this into the component transport control equation, we can obtain the carbon concentration.

[0184] The initial component transport equation is:

[0185]

[0186] Furthermore, the initial component transport equations are simplified, and in the simplification process, neglecting... ,make , The carbon in this process originates from the dissolution of carbon from the graphite crucible wall into the silicon melt.

[0187] Converting mass fraction to molar concentration, the final component transport control equation in the steady-state numerical calculation model is obtained as follows:

[0188]

[0189] Before numerical solution, appropriate boundary conditions need to be set to simulate real-world conditions. A dissolution boundary condition is added at the interface between the graphite crucible and the silicon melt to simulate the dissolution of the graphite crucible; a precipitation boundary condition is added at the interface between the silicon melt and the crystal. Both types of boundaries are equilibrium concentration boundaries for carbon.

[0190] The supersaturation S is calculated as follows:

[0191]

[0192] Furthermore, when solving for component transport, it involves solving for carbon dissolution and precipitation boundary layers. During the solution process, it is necessary to mesh the silicon melt. In the meshing process, the boundary layer mesh is extremely important for the calculation of carbon concentration.

[0193] Based on the mesh independence verification, the boundary layer mesh can be obtained. In one embodiment, when growing silicon carbide by liquid phase method, the thickness of the first mesh layer on the side of the carbon-dissolved boundary layer silicon melt is 0.05 mm, and 10 boundary layer mesh layers are added, with a growth rate of 1.2 between each mesh layer.

[0194] The interface between the silicon melt and the crystal is a precipitation boundary. At this type of boundary, the carbon concentration is low near the solid (crystal) and high further away from the crystal. Through continuous refinement and analysis of the boundary layer mesh, it was determined that during the liquid-phase growth of silicon carbide, the thickness of the first mesh layer on the silicon melt side of the boundary layer at the precipitated crystal should be 0.05 mm. Twelve boundary layer mesh layers were added, with a growth rate of 1.2 between each mesh layer.

[0195] During mesh generation, the mesh is divided from sparse to dense. Furthermore, the carbon concentration gradient is related to the mesh size. If the carbon concentration does not change with the mesh density during the sparse-to-dense mesh generation process, the mesh densification process is stopped.

[0196] Step S2: Use the basic thermal field to conduct crystal growth experiments to obtain the time interval for subsequent thermal field optimization.

[0197] Crystal growth experiments can be conducted according to preset durations of 12 hours, 24 hours, 36 hours, and 48 hours. In one embodiment, the crystal growth results show that there is virtually no polycrystalline formation at the bottom and corners of the graphite crucible during the pre-crystal growth experiments of 12 hours and 24 hours. However, 12 hours is too short. If 12 hours is used as the interval, the heater power parameters need to be adjusted multiple times for each crystal growth experiment, which consumes a lot of manpower and resources. Therefore, a 24-hour interval is selected for adjustment.

[0198] Step S3: Perform preliminary optimization of transient numerical calculations.

[0199] Specifically, using transient numerical simulation technology, the heating parameters of the graphite heater are optimized and adjusted every 24 hours after crystal growth. The heating parameters are adjusted until the following conditions are met: the carbon concentration gradient on the inner wall of the graphite crucible is less than 0, ensuring that the inner wall of the graphite crucible is dissolved and no polycrystalline material is generated; in addition, the carbon supersaturated region in the silicon melt region is concentrated near the growth interface, and the supersaturated region in the silicon melt is small, with most of it being unsaturated regions, and the ratio of the volume of the supersaturated region VS to the volume of the silicon melt region Vtotal is less than 0.05.

[0200] For example, the parameters of the induction heating coil or the graphite heater can be adjusted. For ease of subsequent operation, when optimizing the adjustment, only the power of the graphite heater can be adjusted.

[0201] Among them, the transient numerical simulation technology is time-dependent. In the process of adjusting the heating parameters to adjust the temperature difference and flow field distribution, the governing equations of the numerical calculation model used include the continuity equation, momentum equation, energy equation, and component transport equation. These equations have been explained in the aforementioned step S1 and will not be repeated here.

[0202] When performing transient numerical simulations, the boundary conditions at the interface between the silicon melt and the crystal include the equilibrium concentration boundary of carbon and the amount of interface displacement.

[0203] The equilibrium concentration boundary of carbon at the interface between the silicon melt and the crystal is:

[0204]

[0205] in, It can be obtained through the method described in step S1 above.

[0206] Interfacial displacement at the interface between the silicon melt and the crystal for:

[0207]

[0208] At the interface between the graphite crucible and the silicon melt, if the first carbon concentration gradient generated by the dissolution of the graphite crucible satisfies:

[0209]

[0210] This represents the first carbon concentration gradient. If the value is greater than 0, a single crystal will be formed.

[0211] In this case, the equilibrium concentration boundary of carbon at the interface between the graphite crucible and the silicon melt is:

[0212]

[0213] The interfacial displacement at the interface between the graphite crucible and the silicon melt is:

[0214]

[0215] At the interface between the graphite crucible and the silicon melt, if the first carbon concentration gradient generated by the melting of the graphite crucible satisfies:

[0216]

[0217] This represents the first carbon concentration gradient. If the value is less than 0, polycrystalline structures will be formed.

[0218] In this case, the equilibrium concentration boundary for carbon is:

[0219]

[0220] The interface displacement is:

[0221]

[0222] in, It is a constant greater than 1. Generally, the rate of polycrystalline formation is relatively fast. In one embodiment, it was obtained experimentally... It is 2.0; This represents the time step for transient solutions.

[0223] M SiC The molar mass of silicon carbide is expressed in g / mol. This refers to the density of silicon carbide, expressed in kg / m³. 3 , It is a unit vector perpendicular to the crystal surface.

[0224] On the free surface of the silicon melt, using the same conditions as in the steady-state calculation, the normal gradient of the concentration is set as follows:

[0225]

[0226] Through the optimization in step S3, the optimal graphite heater power parameters can be obtained every 24 hours during crystal growth. These power parameters are equivalent to the second heating parameters in the aforementioned embodiment.

[0227] Step S4: Optimize the structure of the graphite crucible cover plate using the basic thermal field to suppress aluminum consumption.

[0228] During the growth of silicon carbide crystals, aluminum in the silicon melt is easily volatilized and consumed from the free liquid surface. In this embodiment, a graphite crucible cover structure can be used to suppress the volatilization of aluminum.

[0229] By combining step S4 and conducting multiple transient simulations, we can obtain the aluminum consumption under different inner diameters of graphite crucible lids during a complete crystal growth experiment (one week). Based on the aluminum consumption, we can determine the graphite crucible inner diameter that saves the most graphite material.

[0230] Furthermore, different cover plate structures affect the temperature distribution in the silicon melt region, thus influencing the crystal growth rate. Therefore, the average growth rate of the entire crystal growth stage under each operating condition can be obtained. The inner diameter of the graphite crucible cover plate is then selected based on the average growth rate.

[0231] When growing silicon carbide using graphite crucibles with different inner diameters of the graphite crucible lid, the numerical calculation model used to analyze its thermal field and process includes the continuity equation, momentum equation, energy equation, and carbon component transport equation. These equations are the same as those in the aforementioned embodiments and will not be repeated here.

[0232] During the long-term growth of silicon carbide, the evaporation and consumption of Al are calculated using transient methods.

[0233] Based on the flow field and thermal field obtained above, the governing equations for Al transport in solution and gas can be expressed as follows:

[0234]

[0235] in, This indicates the concentration of Al, expressed in mol / m³. 3 ,right Integrating this equation yields the remaining amount of aluminum in the graphite crucible; u represents the velocity. This represents the diffusion coefficient of Al, expressed in m. 2 / s, This is the density of Al, in kg / m³. 3 ; Subscript l and g These represent the liquid phase and the gas phase, respectively.

[0236] For example, at the interface between the silicon melt and the graphite crucible, no forward reaction consuming Al occurs; therefore, the Al flux at this interface can be considered zero. Based on this, the following boundary conditions can be set:

[0237]

[0238] At the free surface (i.e., the free liquid surface) of the silicon melt, Al evaporates into the gas phase in the form of Al vapor. Assuming that the reaction reaches equilibrium instantaneously, the partial pressure of Al on the gas side of this boundary is equal to the saturated vapor pressure of Al on the liquid side.

[0239] Assuming the Al concentration in the solution is low enough to obey Henry's Law, the free surface on both sides can eventually be obtained. and The relationship between them is:

[0240]

[0241] in, This indicates the concentration of Al in the silicon melt. This indicates the concentration of Al in the gas; c total This represents the total molar concentration of the solution and can be set as a constant.

[0242] γ represents the saturated vapor pressure of pure Al, in Pa, and γ represents the activity coefficient of Al.

[0243] in,

[0244] Where γ represents the activity coefficient of Al, its value can be obtained by the following formula:

[0245]

[0246] Al can be set as a mass continuity equation through another boundary condition of the free liquid surface, specifically:

[0247]

[0248] in, The diffusion coefficient (m) of Al in a gas is expressed as follows: 2 / s), The diffusion coefficient (m) of Al in silicon melt 2 / s).

[0249] At the interface between the gas and the various solid components, due to the lower surface temperature of the solid components, vaporized Al will condense on the surface of the solid components. Vaporized Al may deposit, and vaporized Al may also react with the surface of the graphite device. The specific reaction equations are as follows:

[0250]

[0251] Vaporized Al can also react with the surface of graphite devices, which is the main source of Al consumption in this system. Based on this, the boundary conditions at the interfaces between each solid device and the gas region are set as follows:

[0252]

[0253] in, P eq This represents the equilibrium vapor pressure of Al, where R is the gas constant in J / (mol·K), and T is the temperature in K. On the surface of the graphite solid component, Al undergoes a chemical reaction, and the equilibrium vapor pressure is: .

[0254] On the remaining solid components, Al vapor condenses on its surface, appearing as elemental Al, with an equilibrium vapor pressure of:

[0255]

[0256] At the interface between the silicon melt and the crystal (i.e., the growth interface), Al is incorporated into the grown silicon carbide crystal. This is one way to consume Al, but the amount consumed is so small that it can be ignored.

[0257] Furthermore, the boundary conditions at the interface between the silicon melt and the crystal are as follows:

[0258]

[0259] Step S5: Obtain optimization schemes for different growth periods.

[0260] Based on the aforementioned step S4, the optimal graphite crucible cover structure can be obtained.

[0261] Furthermore, by repeating steps S1 and S2, and using steady-state and transient numerical simulation methods, dynamic heating parameter adjustments are made to the graphite heater and / or induction heating coil during the long-term growth of silicon carbide crystals using a graphite crucible with the final optimized structure.

[0262] During the long-term growth of silicon carbide, deformation of the graphite crucible and volatilization of aluminum can affect crystal growth. The power of the graphite heater and induction heating coil can be dynamically adjusted in real time to regulate the temperature distribution in the graphite crucible and silicon melt region, as well as the carbon concentration distribution in the silicon melt region.

[0263] During the long-term growth of silicon carbide, excessive carbon content in the silicon melt can lead to polycrystalline formation; conversely, insufficient carbon content can hinder crystal growth and reduce the crystal growth command. Therefore, a relative balance between carbon dissolution in the graphite crucible and carbon consumption in the crystal is crucial. In this embodiment, the temperature distribution in the graphite crucible and silicon melt region, as well as the carbon concentration distribution in the silicon melt region, are dynamically and in real-time adjusted to prevent polycrystalline formation in the silicon melt region during growth, thereby improving the quality of the grown silicon carbide single crystal. Furthermore, the graphite crucible cover plate suppresses aluminum consumption.

[0264] Figure 6 This embodiment illustrates a thermal field optimization device for silicon carbide growth based on liquid phase method. The device 30 includes:

[0265] Heating simulation module 301 is used to simulate the heating process based on the first heating parameter, and to simulate the heating process at the first heating stage. Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the morphology satisfies the first preset condition; the first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes: the first carbon concentration gradient is less than the preset carbon concentration gradient; , It is an integer greater than or equal to 2.

[0266] The first acquisition module 302 is used to acquire the target interface displacement of the graphite crucible after the target time period based on the first carbon concentration gradient and the interface displacement calculation model.

[0267] The second acquisition module 303 is used to obtain information based on the first... Based on the shape and target interface displacement, the first [value] of the graphite crucible is obtained. form.

[0268] The third acquisition module 304 is used to acquire the second heating parameter, so as to determine the heating parameters based on the second heating parameter. Heating the graphite crucible in its original state, so that it is in contact with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

[0269] Reference Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Figure 7 As shown, the electronic device includes: a processor, a memory, a communication interface, and a communication bus. The processor, memory, and communication interface communicate with each other through the communication bus. The memory is used to store executable instructions, which cause the processor to execute the thermal field optimization method for growing silicon carbide based on the liquid phase method described in the previous embodiment.

[0270] A processor can be a CPU, a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable devices, transistor logic devices, hardware components, or any combination thereof. A processor can also be a combination that implements computational functions, such as a combination of one or more microprocessors, or a combination of a DSP and a microprocessor.

[0271] A communication bus can include a pathway for transmitting information between memory and a communication interface. The communication bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. Communication buses can be categorized into address buses, data buses, control buses, etc. For ease of representation, Figure 7 The symbol is represented by only one line, but this does not mean that there is only one bus or one type of bus.

[0272] The memory can be read-only memory (ROM) or other types of static storage devices that can store static information and instructions, random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM), magnetic tape, floppy disk, and optical data storage devices, etc.

[0273] This invention also provides a non-transitory computer-readable storage medium that, when the instructions in the storage medium are executed by a processor of an electronic device (server or terminal), enables the processor to execute the thermal field optimization method based on liquid-phase silicon carbide growth as shown in any embodiment of this application.

[0274] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0275] Although preferred embodiments of the present invention have been described, those skilled in the art, once they have learned the basic inventive concept, can make other changes and modifications to these embodiments.

[0276] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0277] The above provides a detailed description of the thermal field optimization method for silicon carbide growth based on liquid phase method provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for optimizing the thermal field of silicon carbide growth based on liquid phase method, characterized in that, include: Based on the first heating parameter, for the first... The graphite crucible in its original state is heated to make it compatible with the first... The first performance parameter corresponding to the form satisfies the first preset condition; The first performance parameter includes: the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible; the first preset condition includes: the first carbon concentration gradient is less than a preset carbon concentration gradient; , It is an integer greater than or equal to 2; Obtain H preset time points within the target duration; the duration between adjacent preset time points is equal to the preset duration step size; obtain the second carbon concentration gradient of the silicon melt at the h-th preset time point, and the comparison result between the second carbon concentration gradient and the preset concentration gradient; wherein, at the 1st preset time point, the second carbon concentration gradient of the silicon melt is equal to the first carbon concentration gradient; h∈[1,H]; substitute the second carbon concentration gradient and the preset duration step size into the interface displacement calculation model corresponding to the comparison result to obtain the interface displacement of the graphite crucible at the (h+1)-th preset time point; determine the interface displacement of the graphite crucible at the H-th preset time point as the target interface displacement of the graphite crucible after the target duration; According to the first Based on the shape and the displacement of the target interface, the first [value] of the graphite crucible is obtained. form; Obtain a second heating parameter, and based on the second heating parameter, adjust the heating parameters for the heating state at the first heating stage. The graphite crucible in its original state is heated to make it compatible with the first... The first performance parameter corresponding to the form satisfies the first preset condition.

2. The method according to claim 1, characterized in that, The method further includes: For each of the plurality of graphite crucibles, a first operation is performed; the first operation includes, based on the first heating parameter, adjusting the temperature of the first graphite crucible at the position of the first graphite crucible. The graphite crucible in its current state is heated until a second heating parameter is obtained. Based on the second heating parameter, the graphite crucible in the first state is then heated. The graphite crucible in its original state is heated to make it compatible with the first... The step of the first performance parameter corresponding to the shape satisfying the first preset condition; the inner diameter of the graphite crucible cover plate of the multiple graphite crucibles is different from each other. After the first operation is completed, obtain the remaining amount of aluminum in the graphite crucible; Based on the remaining amount of aluminum in the graphite crucible, a target graphite crucible cover inner diameter is determined from the graphite crucible cover inner diameters of the plurality of graphite crucibles, and the target graphite crucible cover inner diameter is determined as the optimal graphite crucible cover inner diameter for the graphite crucible used for silicon carbide crystal growth.

3. The method according to claim 2, characterized in that, The step of obtaining the remaining amount of aluminum in the graphite crucible after the first operation is completed includes: Obtain the initial aluminum content in the graphite crucible before performing the first operation; Based on the initial aluminum content and the aluminum transport control equation, the remaining amount of aluminum in the graphite crucible after the first operation is completed is obtained.

4. The method according to claim 3, characterized in that, The transport control equations for aluminum include: in, This represents the density of Al. Indicates the concentration of Al. Indicates time, Indicates speed; This represents the diffusion coefficient of Al; l 'g' and 'g' represent the liquid phase and the gas phase, respectively.

5. The method according to claim 1, characterized in that, The method further includes: If the comparison result indicates that the second carbon concentration gradient is greater than the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is: If the comparison result indicates that the second carbon concentration gradient is less than or equal to the preset concentration gradient, then the interface displacement calculation model corresponding to the comparison result is: in, Indicates interface displacement. Represents a constant greater than 1. Indicates the molar mass of carbon. This indicates the molar mass of silicon carbide. The density of carbon, The density of silicon carbide, This represents the mass diffusion coefficient of carbon in a silicon melt. Indicates the second carbon concentration. Represents a unit vector perpendicular to the crystal surface. t This represents the time step for transient solutions.

6. The method according to claim 1, characterized in that, The method further includes: A steady-state numerical calculation model is constructed; the steady-state numerical calculation model includes the continuity equation, momentum equation, energy equation, and component transport control equation. Based on the steady-state numerical calculation model, the first carbon concentration gradient at the interface between the graphite crucible and the silicon melt in the graphite crucible is obtained.

7. The method according to claim 1, characterized in that, The first performance parameter further includes: the volume ratio of the carbon-saturated region in the silicon melt to the total volume of the silicon melt; the first preset condition further includes: the volume ratio being less than or equal to a preset volume ratio; the method further includes: The silicon melt simulation model was meshed to obtain multiple silicon melt sub-regions; The first carbon concentration and the second carbon concentration of each of the silicon melt sub-regions are obtained respectively; The carbon supersaturation of the silicon melt sub-region is obtained based on the first carbon concentration and the second carbon concentration. Based on the comparison between the carbon supersaturation and the preset carbon saturation, a first judgment result is obtained as to whether the silicon melt sub-region is in a state of carbon supersaturation. Based on the first judgment result corresponding to each of the silicon melt sub-regions, the volume of the carbon supersaturated region in the silicon melt is obtained.

8. The method according to claim 1, characterized in that, The first preset condition further includes at least one of the following: the first carbon concentration gradient is greater than a preset concentration gradient, the ratio of the volume of the carbon supersaturated region in the silicon melt to the volume of the silicon melt region is less than or equal to a preset ratio, and the carbon supersaturated region is located in a preset region near the silicon carbide growth interface.

9. The method according to claim 1, characterized in that, The method further includes: Get multiple preset durations; According to each preset duration, silicon carbide crystal pre-growth treatment is performed in the graphite crucible, and a second judgment result is obtained on whether polycrystalline formation occurs at a preset position of the graphite crucible; Based on the second judgment result, the target duration is obtained from a plurality of preset durations.

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