Device, system and method for preparing silicon carbide crystals

Abstract

The invention relates to the technical field of silicon carbide crystal preparation, in particular to a device, system and method for preparing silicon carbide crystals. According to the invention, a mixed heating structure of'upper induction and lower resistance 'is adopted, that is, an upper seed crystal area is heated by a non-uniform turn pitch induction coil, and a lower raw material area is heated by a multi-area resistance heating assembly which can be independently controlled, so that the problem that low energy consumption and high conversion rate of raw materials are difficult to consider in an existing heating mode is solved. The system further comprises a central control unit and a sensing monitoring unit, and the central control unit executes closed-loop regulation and control based on gas phase component information and growth interface images obtained by the sensing monitoring unit in real time: when the gas phase silicon-carbon ratio deviates, the power of a corresponding heating area is automatically adjusted for compensation; and when an initial defect is monitored, applying a power pulse to generate a corrective gas phase flow for suppression or repair. According to the invention, through cooperative heating and intelligent closed-loop control, the yield of crystal preparation and the crystal quality are improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal preparation technology, and specifically to an apparatus, system and method for preparing silicon carbide crystals. Background Technology

[0002] Silicon carbide, as a core material for third-generation semiconductors, requires large-scale, low-cost, and high-quality fabrication, which is crucial for the industry's development. Currently, the physical vapor transport method is the mainstream fabrication technology, with its core heating method primarily employing either induction heating or resistance heating.

[0003] Induction heating, while low in energy consumption and high energy conversion efficiency, has a short effective heating area and insufficient heating of deep raw material areas, resulting in insufficient gas source supply and limiting growth efficiency and crystal thickness. Conversely, resistance heating, while capable of long-distance uniform heating and ensuring sufficient raw material sublimation, has high overall power consumption and low energy efficiency, leading to high production costs.

[0004] Based on the above, this application proposes an apparatus, system, and method for preparing silicon carbide crystals, which can effectively solve the above problems. Summary of the Invention

[0005] To address the problem that existing heating methods for preparing silicon carbide crystals cannot simultaneously achieve high raw material conversion rates and low equipment energy consumption, this application proposes an apparatus, system, and method for preparing silicon carbide crystals.

[0006] An apparatus, system, and method for preparing silicon carbide crystals include a crucible, a seed crystal holder, a non-uniform pitch induction coil, and a resistance heating assembly. The non-uniform pitch induction coil is disposed on the upper periphery of the crucible for heating the seed crystal region; the resistance heating assembly is disposed at the lower part of the crucible for heating the raw material region. This hybrid heating layout of "upper induction, lower resistance" utilizes induction heating for low-energy, high-efficiency heating of the seed crystal region, while simultaneously using the resistance heating assembly to provide sufficient and stable heating of the long-range raw material region at the lower part of the crucible. This synergistic working mode overcomes the limitations of a single heating method and helps to balance low energy consumption and high growth efficiency.

[0007] In one embodiment, the non-uniform turn-pitch induction coil includes a first induction section and a second induction section. The turn-pitch of the first induction section is smaller than that of the second induction section, and the projection range of the first induction section along the crucible axis at least partially covers the corresponding position of the seed crystal. Since the induction heating power density is positively correlated with the turn-number density, the first induction section with a smaller turn-pitch can couple energy more concentratedly to the seed crystal growth interface, achieving enhanced heating and precise temperature control of key growth areas.

[0008] In one embodiment, the resistance heating assembly is a segmented variable cross-section resistance heater, consisting of at least two heater segments stacked along the crucible axis and electrically insulated from each other. The wall thickness of each heater segment is non-uniform along its axis, with the region of minimum wall thickness projecting onto the material at least partially covering the material's position along the crucible axis. According to the law of resistance, a smaller cross-section results in greater resistance and higher heating power. By aligning the thinnest part of the heater wall with the material zone, efficient heating of the material can be achieved, ensuring complete sublimation. Simultaneously, the segmented design allows for independent power control of material zones at different depths, facilitating dynamic adjustments based on material consumption and improving material utilization.

[0009] In one embodiment, the device further includes a support isolator surrounding the lower end of the non-uniform pitch induction coil and the upper end of the segmented variable cross-section resistance heater, and in contact with at least one of the non-uniform pitch induction coil and the segmented variable cross-section resistance heater to provide mechanical support. This support isolator addresses the mechanical instability, thermal crosstalk, and electromagnetic interference that may occur when integrating different heating systems, providing reliable mechanical support while also serving as a thermal barrier and electromagnetic shield.

[0010] In one embodiment, the raw material zone is divided into a standard raw material chamber and an auxiliary raw material chamber by at least one partition. The resistance heating assembly is disposed on the lower bottom surface of the crucible and includes a standard heater and an auxiliary heater. The standard heater is disposed corresponding to the standard raw material chamber and is configured to heat the raw material in the standard raw material chamber. The auxiliary heater is disposed corresponding to the auxiliary raw material chamber and is configured to heat the raw material in the auxiliary raw material chamber. The standard raw material chamber is configured to be filled with standard silicon carbide raw material, and the auxiliary raw material chamber is configured to be filled with auxiliary raw material, which includes at least one of silicon-rich raw material and carbon-rich raw material.

[0011] This design solves the problem of in-situ control of the silicon-carbon ratio in the gas phase during traditional growth processes. By setting up independent heating units for different types of raw materials, the sublimation rate of various raw materials can be independently adjusted as needed during crystal growth, thereby achieving real-time dynamic control of key components during crystal growth, thus suppressing crystal growth defects and improving crystal quality.

[0012] In one embodiment, a system for preparing silicon carbide crystals includes the aforementioned apparatus for preparing silicon carbide crystals, and a central control unit electrically connected to the non-uniform pitch induction coil and the resistance heating assembly, configured to independently control the heating power of the non-uniform pitch induction coil and the heating power of different heating regions in the resistance heating assembly. The central control unit precisely and collaboratively allocates the power output of each heating region according to a preset process program, thereby establishing and stably maintaining the complex temperature field required for the entire growth system, such as the seed crystal interface temperature, the raw material zone temperature, and the temperature gradient between them.

[0013] In one embodiment, the system further includes a sensing and monitoring unit, which comprises a first monitoring module and a second monitoring module. The first monitoring module is configured to acquire real-time information on the gaseous chemical composition of the crystal growth environment, and the second monitoring module is configured to acquire real-time image information of the crystal growth interface. The sensing and monitoring unit is communicatively connected to the central control unit to feed back the real-time monitored information to the central control unit. This sensing and monitoring unit provides the central control unit with real-time image information of the crystal growth interface and information on the gaseous chemical composition of the crystal growth environment, so that the judgment of the growth process no longer relies on indirect parameters and empirical speculation, providing a real-time data foundation for realizing closed-loop feedback control.

[0014] In one embodiment, the central control unit is configured to dynamically adjust according to a program based on at least one preset mode when it is in operation: First mode: When the silicon-to-carbon ratio of the growth gas detected by the first monitoring module deviates from a preset range, the power of at least one heating area in the resistance heating component is automatically adjusted to change the sublimation rate of the corresponding raw material, thereby restoring the silicon-to-carbon ratio to the preset range. Second mode: When the second monitoring module detects a preset defect type at the growth interface, it applies a high-power pulse to the corresponding heating area in the resistance heating component that can provide the required gas phase component to eliminate the defect, thereby generating a gas phase pulse with the required component to the growth interface, thereby repairing or suppressing the defect.

[0015] Through preset intelligent algorithms, the central control unit can proactively respond to problems detected in real time: such as automatically adjusting the power of the resistance heating component to correct the gas phase composition, or generating a corrective gas phase flow by applying power pulses to repair crystal defects, thereby improving the success rate of crystal growth and the quality of the final product.

[0016] In one embodiment, a method for preparing silicon carbide crystals is performed by a central control unit of a system for preparing silicon carbide crystals as described above, and includes the following steps: (a) Control the non-uniform pitch induction coil to heat the upper part of the crucible to establish and maintain a preset temperature in the seed crystal region; (b) Controlling the resistance heating assembly to heat the lower part of the crucible to promote the sublimation of the raw materials and form a gas phase source; and (c) The power of the non-uniform pitch induction coil and the resistance heating component are adjusted in a coordinated manner to establish and maintain a preset temperature gradient for crystal growth between the seed crystal region and the raw material region.

[0017] By executing steps (a) and (b) in parallel, the precise crystallization temperature and sufficient gas source required for crystal growth are ensured to be met simultaneously and independently. The coordinated adjustment in step (c) integrates the separated temperature zones into a whole temperature field with a specific gradient that serves crystal growth, thereby ensuring that the crystal growth process can proceed efficiently and stably.

[0018] In one embodiment, the coordinated adjustment in step (c) further includes: Based on the real-time data received from the first monitoring module and the second monitoring module, perform at least one of the following dynamic control operations: When the real-time data indicates that the gas phase silicon-carbon ratio deviates from the preset range, the power of one or more heating zones in the resistance heating assembly is automatically adjusted to restore the silicon-carbon ratio to the preset range. When the real-time data indicates that a preset defect has appeared at the growth interface, a power pulse is automatically applied to one or more heating areas in the resistance heating component that can change the gas phase composition to repair the defect.

[0019] During long-term crystal growth, uneven consumption of raw materials can lead to deviations in the gas phase composition from optimal values. This method proactively maintains the optimal growth atmosphere through real-time monitoring and automatic compensation by the first monitoring module, preventing defects such as carbon pockets and silicon droplets caused by chemical imbalances from the outset, thus improving the yield. Furthermore, this method can also detect crystal surface defects in real time through the second monitoring module and apply power pulses to the corresponding heating areas to alter the local gas phase composition, thereby treating the defects and suppressing and repairing initial defects, improving crystal quality and effective output.

[0020] In summary, this application includes at least one of the following beneficial technical effects: 1. By adopting a hybrid heating structure that uses induction coils to heat the upper seed crystal area and resistance heating components to heat the lower raw material area, combined with the optimized design of non-uniform coils and variable cross-section heaters, low energy consumption and high efficiency are achieved, reducing the power cost per unit output while ensuring the quality and rate of crystal growth.

[0021] 2. By dividing the resistance heating component into multiple independently controllable heating zones, the relative temperature between the seed crystal zone and the raw material zone, as well as the axial temperature gradient in the key growth area, are adjusted and stabilized, creating a more controllable thermal environment for high-quality crystal growth.

[0022] 3. By setting up partitioned raw material chambers and combining them with partitioned resistance heating components, the sublimation rate of raw materials at different locations can be selectively adjusted, thereby actively and in real time changing the gaseous silicon-carbon ratio in the crucible during crystal growth, thus suppressing defects caused by composition deviation.

[0023] 4. By setting a central control unit, based on the real-time data provided by the first and second monitoring modules, when the gas phase silicon-carbon ratio is detected to deviate from the preset range, the corresponding heating power can be automatically adjusted to correct it; when a preset defect is detected at the growth interface, a power pulse can be automatically applied to repair it. Attached Figure Description

[0024] Figure 1 This is a cross-sectional schematic diagram of Example 1 of the apparatus, system and method for preparing silicon carbide crystals provided in this application.

[0025] Figure 2 for Figure 1 Enlarged diagram of point A in the middle.

[0026] Figure 3 This is a cross-sectional schematic diagram of Example 2 of the apparatus, system and method for preparing silicon carbide crystals provided in this application.

[0027] Figure 4 This is a cross-sectional schematic diagram of Example 3 of the apparatus, system and method for preparing silicon carbide crystals provided in this application.

[0028] Figure 5 This is a schematic diagram of the resistance heating component in Example 3 of the apparatus, system and method for preparing silicon carbide crystals provided in this application.

[0029] Figure 6 This is a schematic diagram of the overall process of an apparatus, system, and method for preparing silicon carbide crystals provided in this application.

[0030] Explanation of reference numerals in the attached figures: 1. Crucible; 11. Raw material area; 111. Standard raw material chamber; 112. Auxiliary raw material chamber; 12. Seed crystal growth area; 13. Insulation structure; 2. Seed crystal holder; 21. Silicon carbide seed crystal; 3. Non-uniform turn pitch induction coil; 31. First induction section; 32. Second induction section; 4. Resistance heating assembly; 41. Segmented variable cross-section resistance heater; 411. First heater section; 412. Second heater section; 413. Third heater section; 414. Spacer; 42. Standard heater; 43. Auxiliary heater; 5. Supporting isolation component; 6. Partition plate; 7. Central control unit; 8. Sensing and monitoring unit; 81. First monitoring module; 82. Second monitoring module; 9. Optical observation window. Detailed Implementation

[0031] This application provides an apparatus, system, and method for preparing silicon carbide crystals, which are described below in conjunction with the appendix. Figure 1-6 This application will be described in further detail.

[0032] Example 1 Reference Figure 1 , Figure 2 and Figure 6 An apparatus for preparing silicon carbide crystals includes a crucible 1, a seed crystal holder 2, a non-uniform pitch induction coil 3, and a resistance heating assembly 4, all coaxially arranged.

[0033] In this embodiment, crucible 1 is a container for holding raw materials and crystal growth, preferably a graphite crucible 1. The internal space of crucible 1 is functionally divided into two regions: the lower part is the raw material region 11, and the upper part is the seed crystal growth region 12. The raw material region 11 is used to fill polycrystalline silicon carbide raw materials as a source of gaseous substances. A seed crystal holder 2, also made of graphite, is threaded to the top of crucible 1. A silicon carbide seed crystal 21 is disposed on the lower surface of the seed crystal holder 2 facing the inside of crucible 1. The silicon carbide seed crystal 21 can be fixed to the seed crystal holder 2 by high-temperature bonding or physical snap-fit. In this embodiment, high-temperature bonding is preferred.

[0034] Specifically, in this embodiment, the seed crystal holder 2 is a solid structure, and the silicon carbide seed crystal 21 is a solid circular plate structure, with the growth surface of the silicon carbide seed crystal 21 facing the raw material area 11 directly below.

[0035] Specifically, a heat insulation structure 13 is provided around the crucible 1. In this embodiment, the heat insulation structure 13 is preferably a thick-walled cylinder made of multiple layers of graphite felt. This heat insulation structure 13 utilizes the low thermal conductivity of its material and the radiation shielding effect between the multiple layers to confine the heat of the crucible 1 to the interior of the thermal field to the maximum extent.

[0036] In this embodiment, the non-uniform pitch induction coil 3 and the resistance heating component 4 together constitute a hybrid heating component, which can perform targeted and efficient heating on the raw material area 11 and the seed crystal growth area 12 by being distributed in different regions along the axial direction of the crucible 1.

[0037] Specifically, a non-uniform pitch induction coil 3 is arranged around the upper periphery of the crucible 1, primarily for heating the seed crystal growth region 12. The non-uniform pitch induction coil 3 is preferably made of a hollow, square-round cross-section copper tube, and its overall dimensions are adapted to the specifications of the crystal being grown. For example, in a specific application for growing 6-8 inch silicon carbide crystals, the inner diameter of the non-uniform pitch induction coil 3 can be set between 100mm and 1000mm, its overall axial height between 100mm and 500mm, and the total number of turns between 10 and 20. In this embodiment, the inner diameter of the non-uniform pitch induction coil 3 is preferably 500mm, the overall axial height is preferably 300mm, and the total number of turns is preferably 15.

[0038] Specifically, the non-uniform pitch induction coil 3 is divided into a first induction section 31 and a second induction section 32 along its axial direction, with the first induction section 31 located below the second induction section 32. The projection of the first induction section 31 along the axial direction of the crucible 1 covers the plane where the silicon carbide seed crystal 21 is located, and the pitch of the first induction section 31 is smaller than that of the second induction section 32. Since the heating power of electromagnetic induction is proportional to the square of the magnetic field strength, and the magnetic field strength is positively correlated with the number of turns per unit length of the coil, the first induction section 31 with a smaller pitch can concentrate the high-frequency electromagnetic energy more effectively in the region where the silicon carbide seed crystal 21 is located in the crucible 1, thereby enhancing the heating of the seed crystal growth region 12. The second induction section 32 has a large turn spacing, and when the same high-frequency current passes through it, the magnetic field strength it generates is relatively weak. Consequently, the induction heating power generated in the corresponding area of ​​crucible 1 is also relatively low, providing appropriate heating for the upper area of ​​seed crystal support 2 and preventing these areas from becoming too cold, which would cause unnecessary sublimation of gaseous substances. At the same time, it works in conjunction with the strong heating area of ​​the first induction section 31 to jointly build a stable axial temperature gradient near the seed crystal growth interface.

[0039] Specifically, the resistance heating component 4 is entirely fitted around the lower half of the crucible 1 and mainly heats the raw material zone 11. In this embodiment, the resistance heating component 4 is preferably a barrel-shaped graphite resistance heater.

[0040] More specifically, the axial distance between the lowermost edge of the non-uniform pitch induction coil 3 and the uppermost edge of the resistance heating component 4 is between 30mm and 150mm, thereby forming an effective physical and electromagnetic isolation zone. In this embodiment, this axial distance is preferably 100mm.

[0041] In this embodiment, a system for preparing silicon carbide crystals includes the apparatus for preparing silicon carbide crystals described above, and also includes a central control unit 7, which is electrically connected to the non-uniform pitch induction coil 3 and the resistance heating component 4, and is configured to independently control the heating power of the non-uniform pitch induction coil 3 and the heating power of the resistance heating component 4.

[0042] In this embodiment, a method for preparing silicon carbide crystals, using the above-described apparatus and system, includes the following steps: 1. Load the standard silicon carbide raw material into the raw material area 11 at the bottom of the crucible 1. Fix the silicon carbide seed crystal 21 to the lower surface of the seed crystal holder 2 using a high-temperature adhesive. Tighten the seed crystal holder 2 to the crucible 1, place the crucible 1 in the heat preservation structure 13, and put it into the vacuum growth chamber.

[0043] 2. Fill the growth chamber with high-purity inert gas (such as argon) to a pressure of 10-100 kPa. The central control unit 7 independently controls the power of the resistance heating component 4 and the non-uniform pitch induction coil 3 to establish the growth temperature field. Power is supplied to the resistance heating component 4, which mainly heats the raw material zone 11 at the bottom of the crucible 1, so that its temperature reaches the 2200-2400℃ required for the sublimation of the raw material. A high-frequency current is passed through the non-uniform pitch induction coil 3. The first induction section 31, with a smaller turn pitch, heats the seed crystal growth region 12 to a temperature of 2100-2300℃. The second induction section 32, with a larger turn pitch, provides auxiliary heating to the upper part of the seed crystal support 2 to prevent unnecessary material sublimation.

[0044] The power of the two heating methods mentioned above can be independently adjusted to achieve temperature control between the raw material zone 11 and the seed crystal zone, thereby establishing an axial temperature gradient in the crucible 1, while controlling the axial temperature gradient at 5-15℃ / cm.

[0045] 3. Driven by the established temperature gradient, the gaseous material formed by the sublimation of the raw material at the bottom is transported upwards and crystallizes on the lower surface of the seed crystal at a lower temperature, and the crystal begins to grow along the axial direction. During the growth cycle, the central control unit 7 continuously monitors and adjusts the power of the two heating systems to compensate for system changes and maintain stable growth conditions.

[0046] 4. After the crystal grows to the predetermined length, the central control unit 7 synchronously and slowly reduces the power of the non-uniform pitch induction coil 3 and the resistance heating component 4.

[0047] 5. After the system has completely cooled to room temperature, remove crucible 1 component to obtain silicon carbide crystals.

[0048] The working principle of the apparatus, system, and method for preparing silicon carbide crystals provided in this embodiment is as follows: This embodiment utilizes a composite heating structure to achieve zoned control and independent adjustment of temperature in key crystal growth regions. The resistance heating component 4 at the bottom of the crucible 1 primarily heats the silicon carbide raw material as a whole, ensuring stable sublimation and providing sufficient vapor-phase growth material. The non-uniform pitch induction coil 3 at the top of the crucible 1 precisely controls the seed crystal growth region 12. The first induction section 31 with a smaller turn pitch concentrates energy at the seed crystal growth interface to set the crystallization temperature, while the second induction section 32 with a larger turn pitch provides supplementary heating to the upper part of the seed crystal support 2, optimizing the local temperature field and preventing impurity sublimation. The heating power of the resistance heating component 4 and the non-uniform pitch induction coil 3 can be independently controlled, meaning that the temperature adjustments of the raw material region 11 and the seed crystal region are isolated from each other; changing the temperature of one region has minimal impact on the temperature of the other.

[0049] Example 2 Reference Figure 3 and Figure 6 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the seed crystal holder 2 is a structure with a through hole in the middle, and the diameter of the through hole is smaller than the diameter of the silicon carbide seed crystal 21. The circumferential edge of the seed crystal holder 2 is coated with a high-temperature adhesive, and the silicon carbide seed crystal 21 is placed on the edge coated with the high-temperature adhesive, so that it covers the through hole of the seed crystal holder 2. Thus, the central area of ​​the silicon carbide seed crystal 21 is suspended above the through hole, and its complete lower surface is exposed to the growth space inside the crucible 1, forming the starting interface for crystal growth, while its upper surface faces the through hole, which can be observed by external monitoring equipment.

[0050] In this embodiment, the resistance heating assembly 4 is preferably a segmented variable cross-section resistance heater 41, which is integrally fitted onto the outside of the lower half of the crucible 1. The segmented variable cross-section resistance heater 41 consists of at least two heater segments stacked along the axial direction of the crucible 1 and electrically insulated from each other. In this embodiment, there are preferably three heater segments, namely, a first heater segment 411, a second heater segment 412, and a third heater segment 413 from top to bottom. A spacer 414 is provided between each heater segment. The spacer 414 is preferably a high-temperature resistant, electrically insulating ceramic gasket to achieve physical isolation and electrical insulation between the heater segments. Each heater segment has an independent electrode terminal.

[0051] More specifically, the wall thicknesses of the first heater section 411, the second heater section 412, and the third heater section 413 are all non-uniform. According to the law of resistance, when the current is constant, the smaller the cross-sectional area of ​​a conductor, the greater its resistance, and consequently, the higher the heating power. Based on this principle, the wall of each heater section is preferably designed as a variable cross-section structure along its axial height. The area with the thinnest wall thickness, i.e., the smallest cross-sectional area, projects onto the crucible 1 along its axial direction, precisely covering the raw material zone 11 corresponding to each heater section. This allows electrical energy to be efficiently converted into heat energy, directly acting on the raw material zone 11 that most needs sublimation, achieving efficient "targeted heating."

[0052] More specifically, a supporting isolator 5 is annularly arranged between the lower end of the non-uniform pitch induction coil 3 and the upper end of the resistance heating assembly 4. In this embodiment, the supporting isolator 5 is preferably made of boron nitride ceramic or carbon fiber composite material and provides mechanical support for the non-uniform pitch induction coil 3. At the same time, the supporting isolator 5 also serves as a thermal barrier and electrical insulator, blocking the thermal radiation generated by the segmented variable cross-section resistance heater 41 below from the non-uniform pitch induction coil 3, thereby protecting the non-uniform pitch induction coil 3 from overheating and preventing electrical crosstalk between the high-frequency non-uniform pitch induction coil 3 and the low-frequency segmented variable cross-section resistance heater 41.

[0053] In this embodiment, a system for preparing silicon carbide crystals includes the apparatus for preparing silicon carbide crystals described above, and also includes a central control unit 7, which is electrically connected to the non-uniform pitch induction coil 3 and the resistance heating assembly 4, and is configured to independently control the heating power of the non-uniform pitch induction coil 3 and the heating power of different heating areas in the resistance heating assembly 4.

[0054] In this embodiment, the system further includes a sensing and monitoring unit 8, which includes a first monitoring module 81 and a second monitoring module 82. The first monitoring module 81 is used for real-time monitoring of the gas phase composition inside the crucible 1. In this embodiment, it is preferably a mass spectrometer. The sampling probe of the mass spectrometer extends into the seed crystal growth region 12 inside the crucible 1, continuously extracting trace amounts of gas for analysis, and providing real-time relative concentrations of key gas phase molecules such as Si, C, Si2, and SiC2, thereby calculating the gas phase silicon-to-carbon ratio during crystal growth. The second monitoring module 82 is used for real-time monitoring of the seed crystal growth interface morphology. In this embodiment, it is preferably a high-resolution optical camera with a long working distance. This camera is located on the top of the crucible 1 and captures high-definition images of the seed crystal growth interface in real time through an optical observation window 9 and a through-hole on the seed crystal holder 2.

[0055] Specifically, the sensing and monitoring unit 8 is communicatively connected to the central control unit 7. The first monitoring module 81 and the second monitoring module 82 feed back the real-time monitored gas phase composition information and seed crystal growth interface image to the central control unit 7. The central control unit 7 compares and analyzes this information in real time with the preset process parameter model and defect feature database stored internally, and executes its internal control program based on the analysis results to achieve dynamic closed-loop feedback control of the power output of the non-uniform pitch induction coil 3 and the resistance heating component 4.

[0056] In this embodiment, when the central control unit 7 is running, it performs dynamic adjustments according to a program based on at least one of the following preset modes: First mode: When the gas phase silicon-carbon ratio detected by the first monitoring module 81 continuously deviates from the preset range due to the consumption of raw materials in the upper layer of the raw material zone 11, the central control unit 7 gradually and smoothly reduces the heating power of the first heater section 411 in the corresponding upper raw material zone 11 area, and simultaneously increases the heating power of the adjacent second heater section 412 below it, until the lower second heater section 412 becomes the new main heating area. At this time, the heating power of the first heater section 411 is zero. Similarly, when the gas phase silicon-carbon ratio deviates from the preset range again due to the consumption of raw materials in the middle layer of the raw material zone 11, the central control unit 7 will control the smooth switching of the heating power of the second heater section 412 and the third heater section 413.

[0057] Second mode: When the second monitoring module 82 identifies a specific pattern in the acquired growth interface image that matches the features of a preset defect image, it indicates that an initial defect has appeared in the crystal. At this time, the central control unit 7 applies a brief and high-power pulse to the heater section closest to the effective sublimation region of the current raw material.

[0058] Specifically, in the first mode, the preset range of the gas phase silicon-carbon ratio monitored by the first monitoring module 81 is preferably 1.5 to 2.5.

[0059] Specifically, in the second mode, the central control unit 7 applies a brief, high-power pulse to the heater segment closest to the effective sublimation region of the current raw material. This instantaneous surge in heater power causes the sublimation rate of the heated silicon carbide raw material to rise rapidly within a short time, forming a high-concentration gaseous species in a localized area—a gas cloud containing high concentrations of [unspecified substances]. This gas cloud then rushes at high speed towards the seed crystal growth interface, disrupting the stable growth environment of the crystal defect area and triggering in-situ etching of the defect area. This causes the defect to redissolve in the gas phase, effectively inhibiting its growth and achieving repair. After the pulse ends and the seed crystal growth surface returns to normal, a high-quality, defect-free crystal can continue to grow on the repaired area.

[0060] More specifically, in the second mode, the power pulse applied by the central control unit 7 is an instantaneous increase of 20%-50% on the basis of the reference power and lasts for 5-20 seconds. In this embodiment, it is preferably an instantaneous increase of 30% on the basis of the reference power and lasts for 10 seconds.

[0061] More specifically, the preset defect image features monitored by the second monitoring module 82 include polymorphs emerging on the crystal surface, protrusions, pits, hollow tubes of spiral dislocation cores, or accidentally fallen graphite particles on the crystal surface. These are all defects that will rapidly expand and affect the crystal quality once formed. Among them, the polymorphs emerging on the crystal surface mainly include polymorphs and polymorphs.

[0062] In this embodiment, a method for preparing silicon carbide crystals, using the above-described apparatus and system, includes the following steps: 1. The operator loads the standard silicon carbide raw material into the raw material area 11 of the crucible 1, and connects and fixes the pre-bonded silicon carbide seed crystal 21 to the crucible 1. The assembled crucible 1 is placed in the center of the thermal field and the growth chamber is sealed.

[0063] 2. Fill the growth chamber with high-purity inert gas (such as argon) to a pressure of 10-100 kPa, start the resistance heating component 4, raise the temperature inside crucible 1 to 2000-2500℃, and maintain this condition for 1-10 hours to perform in-situ high-temperature purification of all materials inside crucible 1.

[0064] 3. After purification, reduce the chamber pressure to 100-5000 Pa and maintain it for 1-5 hours to perform high-temperature gas etching on the seed crystal surface to obtain a smooth seed crystal growth surface.

[0065] 4. Readjust the pressure in the growth chamber to the target pressure for crystal growth, i.e., 100-1000 Pa. Simultaneously, the central control unit 7 regulates the power of the non-uniform pitch induction coil 3 and the segmented variable cross-section resistance heater 41, maintaining the temperature at the seed crystal interface between 2100-2200℃, while the highest temperature in the raw material zone 11 reaches 2200-2500℃, thus establishing an axial temperature gradient of 5-15℃ / cm between the seed crystal and the raw material zone 11. In the initial stage of growth, due to the relatively full raw material loading, higher power is mainly applied to the first heater section 411.

[0066] 5. The system enters the steady-state growth phase, which typically lasts 20-200 hours. During this period, the central control unit 7 continuously executes at least one of the following dynamic control programs: First mode: When the gas phase silicon-to-carbon ratio detected by the first monitoring module 81 continuously deviates from the preset range due to the consumption of raw materials in the upper layer of raw material zone 11, the system smoothly reduces the power of the first heater section 411 and simultaneously increases the power of the second heater section 412, so that the heating center of gravity follows the downward movement of the raw material surface. In the later stage of growth, the heating center of gravity can be further transferred to the third heater section 413.

[0067] Second mode: When the second monitoring module 82 identifies an initial defect on the seed crystal growth surface, the central control unit 7 applies a short and high-power pulse to the heater section that is currently playing a major heating role, generating a purely physical gas phase shock wave to the seed crystal growth surface to repair the defect.

[0068] 6. After crystal growth is complete, the chamber pressure is increased to 20-80 kPa to suppress material decomposition. Then, the temperature is reduced by a cooling program, and the high-quality silicon carbide crystal is removed after cooling.

[0069] The working principle of the apparatus, system, and method for preparing silicon carbide crystals provided in this embodiment is as follows: During the crystal preparation process, the first monitoring module 81 detects that the raw material is consumed from top to bottom and its sublimation surface is constantly moving downward. According to the progress of raw material consumption, the central control unit 7 dynamically shifts the heating center from the upper first heater section 411 to the lower second heater section 412 and third heater section 413, so that the heating point of the non-uniform pitch induction coil 3 actively tracks and matches the continuously descending raw material surface.

[0070] When the second monitoring module 82 detects initial defects such as polymorphs and micro-protrusions at the seed crystal growth interface, the central control unit 7 applies a brief high-power pulse to the heater section of the current effective heating area of ​​the raw material. This pulse causes a large amount of raw material to sublimate instantly, forming a high-concentration gas flow that impacts the seed crystal growth interface. This purely physical impact can etch and regenerate the tiny defects on the seed crystal growth interface in situ, thereby restoring normal crystal growth.

[0071] Example 3 Reference Figure 4 , Figure 5 and Figure 6This embodiment is basically the same as Embodiment 2, except that in this embodiment, the raw material zone 11 inside the crucible 1 is divided by one or more partitions 6 made of high-purity graphite material into a central standard raw material chamber 111 and multiple auxiliary raw material chambers 112 surrounding it. In this embodiment, the number of partitions 6 is preferably two, and the number of auxiliary raw material chambers 112 is also preferably two. The standard raw material chamber 111 is used to fill standard silicon carbide raw material, while the auxiliary raw material chambers 112 are specifically used to fill auxiliary raw materials. The auxiliary raw materials can be silicon-rich materials, such as a mixture of high-purity silicon powder and silicon carbide powder, or carbon-rich materials, such as high-purity graphite powder. In this embodiment, one auxiliary raw material chamber 112 is filled with silicon-rich raw material, and the other auxiliary raw material chamber 112 is filled with carbon-rich raw material.

[0072] In this embodiment, the resistance heating component 4 adopts a bottom heating structure different from that in embodiments 1 and 2. The resistance heating component 4 is disposed below the bottom surface of the crucible 1 and is in close contact with the lower insulation structure 13 used for bottom insulation. The resistance heating component 4 includes a standard heater 42 and an auxiliary heater 43, which are physically separate and completely independent in circuitry.

[0073] Specifically, in this embodiment, the standard heater 42 is preferably a serpentine resistance heating tube, the projection range of which on the bottom surface of the crucible 1 corresponds to the bottom position of the standard raw material chamber 111, and is specifically used to heat the standard silicon carbide raw material in the standard raw material chamber 111. In this embodiment, the auxiliary heater 43 is preferably the same serpentine resistance heating tube as the standard heater 42, the projection range of which on the bottom surface of the crucible 1 corresponds to the bottom position of the auxiliary raw material chamber 112, and is used to specifically and independently heat the auxiliary raw material.

[0074] More specifically, in this embodiment, the central control unit 7 dynamically adjusts the program based on at least one preset mode, depending on the composition of the resistance heating component 4 and the distribution of the raw material zone 11, which differs from those in Embodiment 1: First mode: When the first monitoring module 81 detects that the gaseous silicon-carbon ratio inside the crucible 1 deviates from the preset range, the central control unit 7 will perform the following operations: If the detected silicon content is too low or the carbon content is too high, it indicates that the seed crystal growth environment tends to be "carbon-rich", which is prone to defects such as carbon pockets. At this time, the central control unit 7 increases the power of the auxiliary heater 43 that heats the auxiliary raw material chamber 112 where the silicon-rich raw material is located, so as to increase the sublimation rate of the silicon component, thereby pulling the gas phase silicon-carbon ratio back to the preset range; If the detected silicon content is too high or the carbon content is too low, it indicates that the seed crystal growth environment tends to be "silicon-rich", which is prone to defects such as silicon droplets. At this time, the central control unit 7 increases the power of another auxiliary heater 43 that heats the auxiliary raw material chamber 112 where the carbon-rich raw material is located, in order to replenish the carbon component in the gas phase and bring the gas phase silicon-carbon ratio back to the preset range.

[0075] Second mode: When the second monitoring module 82 identifies a feature matching a preset defect type in the seed crystal growth interface image it captures, the central control unit 7 performs the following operations based on the chemical properties of the defect: If a carbon bag defect is identified, indicating that the carbon is oversaturated in a local area, the central control unit 7 applies a short and high-power pulse to the auxiliary heater 43 that heats the silicon-rich raw material, so that a modified gas phase flow rich in silicon components is generated inside the crucible 1. This gas flow reaches the seed crystal growth interface and dissolves or inhibits the continued growth of the carbon bag through chemical reaction or by changing the local atmosphere. Similarly, when silicon droplet defects caused by localized silicon enrichment are identified, a similar power pulse is applied to the auxiliary heater 43 that heats the carbon-rich raw material to generate a carbon-rich gas phase flow for repair.

[0076] In this embodiment, a method for preparing silicon carbide crystals, using the above-described apparatus and system, includes the following steps: 1. The operator loads the standard silicon carbide raw material into the central standard raw material chamber 111, loads the silicon-rich auxiliary raw material into one of the auxiliary raw material chambers 112, and loads the carbon-rich auxiliary raw material into the other auxiliary raw material chamber 112. Then, the seed crystal holder 2, to which the silicon carbide seed crystal 21 has been bonded, is connected and fixed to the crucible 1, and the entire assembled crucible 1 is placed in the center of the thermal field and the growth chamber is sealed.

[0077] 2. Fill the growth chamber with high-purity inert gas (such as argon) to a pressure of 10-100 kPa, start the non-uniform pitch induction coil 3, standard heater 42 and auxiliary heater 43, raise the temperature of the crucible 1 to 2000-2500℃, and maintain it under these conditions for 1-10 hours to perform in-situ high-temperature purification of the standard raw materials and auxiliary raw materials inside the crucible 1.

[0078] 3. After purification, the chamber pressure is reduced to 100-5000 Pa and maintained for 1-5 hours to perform high-temperature gas etching on the seed crystal surface to obtain a smooth growth surface. Subsequently, the pressure is reduced to the target crystal growth pressure of 100-1000 Pa. Simultaneously, the central control unit 7 coordinates the power of each resistance heating component 4 to maintain the seed crystal interface temperature at 2100-2200℃, and mainly controls the power of the standard heater 42 to achieve a temperature of 2200-2500℃ in the standard raw material zone 11, thereby establishing an axial temperature gradient of 5-15℃ / cm between the seed crystal and the main raw material zone 11. In this initial stage, the auxiliary heater 43 can be in a low-power standby state or turned off.

[0079] 4. The system enters a steady-state growth phase lasting 20-200 hours. During this period, the central control unit 7 continuously executes a preset program to maintain steady-state control inside the crucible 1: First mode: When the first monitoring unit detects that the gas phase silicon-carbon ratio deviates from the preset range, the central control unit 7 adjusts the power of the corresponding auxiliary heater 43: if the gas phase silicon-carbon ratio is detected to be "rich in carbon", the power of the auxiliary heater 43 for heating silicon-rich raw materials is increased; conversely, if the gas phase silicon-carbon ratio is detected to be "rich in silicon", the power of the auxiliary heater 43 for heating carbon-rich raw materials is increased.

[0080] Second mode: When the second monitoring module 82 detects carbon-rich defects such as carbon pockets on the seed crystal growth surface, the central control unit 7 applies a short high-power pulse to the auxiliary heater 43 that heats the silicon-rich raw material, generating a silicon-rich gas phase flow for chemical repair; conversely, when silicon-rich defects such as silicon droplets are identified, a pulse is applied to the auxiliary heater 43 that heats the carbon-rich raw material.

[0081] The working principle of the apparatus, system, and method for preparing silicon carbide crystals provided in this embodiment is as follows: During crystal preparation, the standard silicon carbide raw material heated by the standard heater 42 may experience a drift in the silicon-to-carbon ratio of the sublimated gaseous phase due to factors such as its own inhomogeneity, deviating from the preset range. When the first monitoring module 81 detects this deviation, the central control unit 7 adjusts the power of the auxiliary heater 43 that heats the silicon-rich or carbon-rich raw material to compensate for the silicon-to-carbon ratio of the gaseous phase, thus preventing the generation of defects such as carbon pockets and silicon droplets from the source.

[0082] When the second monitoring module 82 detects initial defects such as carbon pockets or silicon droplets at the seed crystal growth interface, the central control unit 7 applies a brief high-power pulse to the auxiliary heater 43 that heats the silicon-rich or carbon-rich raw materials, causing a high-concentration modified gas phase flow with targeted chemical composition to be generated instantly inside the crucible 1. This gas flow reaches the seed crystal growth interface and dissolves or inhibits the continued growth of carbon pockets or silicon droplets through chemical reactions or changes in the local atmosphere.

[0083] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An apparatus for preparing silicon carbide crystals, characterized in that, include: The crucible (1) includes a raw material zone (11) for holding the raw materials for preparing silicon carbide crystals; A seed crystal holder (2) is disposed on the top of the crucible (1), and the seed crystal holder (2) is configured to support a silicon carbide seed crystal (21); A non-uniform pitch induction coil (3) is disposed on the upper periphery of the crucible (1). The non-uniform pitch induction coil (3) includes a first induction section (31) and a second induction section (32) extending integrally therewith. The pitch of the first induction section (31) is smaller than the pitch of the second induction section (32). The projection range of the first induction section (31) on the axial direction of the crucible (1) at least partially covers the plane where the seed crystal is located. A resistance heating assembly (4) is disposed at the lower part of the crucible (1) and configured to heat the raw materials in the raw material zone (11).

2. The apparatus for preparing silicon carbide crystals according to claim 1, characterized in that, The resistance heating assembly (4) is a segmented variable cross-section resistance heater (41) disposed on the lower periphery of the crucible (1). The segmented variable cross-section resistance heater (41) consists of at least two heater segments stacked along the axial direction of the crucible (1) and electrically insulated from each other. The wall thickness of each heater segment is non-uniform along its axial direction, and the projection range of the region with the smallest wall thickness along the axial direction of the crucible (1) at least partially covers the region of the raw material.

3. The apparatus for preparing silicon carbide crystals according to claim 2, characterized in that, It also includes a support isolation member (5), which is arranged in a ring between the lower end of the non-uniform pitch induction coil (3) and the upper end of the segmented variable cross-section resistance heater (41), and is in contact with at least one of the non-uniform pitch induction coil (3) and the segmented variable cross-section resistance heater (41) to provide mechanical support.

4. The apparatus for preparing silicon carbide crystals according to claim 1, characterized in that, The raw material zone (11) is divided into a standard raw material chamber (111) and an auxiliary raw material chamber (112) by at least one partition (6). The resistance heating assembly (4) is disposed on the lower bottom surface of the crucible (1) and includes a standard heater (42) and an auxiliary heater (43). The standard heater (42) is disposed corresponding to the standard raw material chamber (111) and is configured to heat the raw material in the standard raw material chamber (111). The auxiliary heater (43) is disposed corresponding to the auxiliary raw material chamber (112) and is configured to heat the raw material in the auxiliary raw material chamber (112).

5. The apparatus for preparing silicon carbide crystals according to claim 4, characterized in that, The standard raw material chamber (111) is configured to be filled with standard silicon carbide raw material, and the auxiliary raw material chamber (112) is configured to be filled with auxiliary raw material, which includes at least one of silicon-rich raw material and carbon-rich raw material.

6. A system for preparing silicon carbide crystals, characterized in that, include: An apparatus for preparing silicon carbide crystals as described in claims 1-5; as well as A central control unit (7) is electrically connected to the non-uniform pitch induction coil (3) and the resistance heating assembly (4), and is configured to independently control the heating power of the non-uniform pitch induction coil (3) and the heating power of different heating areas in the resistance heating assembly (4).

7. The system for preparing silicon carbide crystals according to claim 6, characterized in that, It also includes a sensing and monitoring unit (8), which includes a first monitoring module (81) and a second monitoring module (82). The first monitoring module (81) is configured to acquire information on the gas phase chemical composition in the crystal growth environment in real time, and the second monitoring module (82) is configured to acquire image information of the crystal growth interface in real time. The sensing and monitoring unit (8) is communicatively connected to the central control unit (7) to feed back the real-time monitoring information to the central control unit (7).

8. The system for preparing silicon carbide crystals according to claim 7, characterized in that, The central control unit (7) is configured to dynamically adjust according to a program based on at least one of the following preset modes when it is in operation: First mode: When the silicon-to-carbon ratio of the growth gas detected by the first monitoring module (81) deviates from a preset range, the power of at least one heating area in the resistance heating component (4) is automatically adjusted to change the sublimation rate of the corresponding raw material, thereby restoring the silicon-to-carbon ratio to the preset range. Second mode: When the second monitoring module (82) detects a preset defect type at the growth interface, a high-power pulse is applied to the corresponding heating area in the resistance heating component (4) that can provide the required gas phase component to eliminate the defect, so as to generate a gas phase pulse with the required component to the growth interface, thereby repairing or suppressing the defect.

9. A method for preparing silicon carbide crystals, characterized in that, The method is performed by the central control unit (7) of the system as described in claims 6-8, and includes the following steps: (a) Control the non-uniform pitch induction coil (3) to heat the upper part of the crucible (1) to establish and maintain a preset temperature in the seed crystal region; (b) Controlling the resistance heating assembly (4) to heat the lower part of the crucible (1) to promote the sublimation of the raw materials and form a gas phase source; and (c) The power of the non-uniform pitch induction coil (3) and the resistance heating component (4) are adjusted in a coordinated manner to establish and maintain a preset temperature gradient for crystal growth between the seed crystal region and the raw material region (11).

10. The method according to claim 9, characterized in that, The coordinated adjustment in step (c) also includes: Based on the real-time data received from the first monitoring module (81) and the second monitoring module (82), perform at least one of the following dynamic control operations: When the real-time data indicates that the gas phase silicon-carbon ratio deviates from the preset range, the power of one or more heating zones in the resistance heating assembly (4) is automatically adjusted to restore the silicon-carbon ratio to the preset range; When the real-time data indicates that a preset defect has occurred at the growth interface, a power pulse is automatically applied to one or more heating areas in the resistance heating component (4) that can change the gas phase composition to repair the defect.

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