czochralski furnace

Abstract

The present application relates to a kind of Czochralski furnace, comprising: furnace body;Crucible, in furnace body;First heat preservation device, periphery of crucible is surrounded, first heat preservation device has the gas heat preservation layer of containing gas and the gas inlet, exhaust port for gas in and out;First exhaust pipe, one end is located above crucible, the other end extends furnace body upwards, to discharge the gas generated in the process of pulling crystal;Heating device, with heating cavity, to accommodate the gas of first exhaust pipe outflow and heat;Recovery pipe, one end is communicated heating cavity, the other end is connected gas inlet, to make the gas of heating cavity flow into gas heat preservation layer.The technical scheme of the present application solves the problem of reducing the quality of pulling crystal and high power consumption caused by the expansion of small furnace cavity and the modification of large thermal field.

Description

Technical Field

[0001] This invention relates to the field of monocrystalline silicon manufacturing, and in particular to a Czochralski single crystal furnace. Background Technology

[0002] The Czochralski method (CZ) for growing monocrystalline silicon is the mainstream method for preparing monocrystalline silicon in the semiconductor and solar photovoltaic industries today. With continuous advancements in demand and technology, the diameter of monocrystalline silicon is increasing, for example, from 2 inches to the current ability to grow silicon rods with diameters of 18 inches and above. This necessitates the construction of larger single-crystal furnace hot zones; for example, the corresponding hot zone size has gradually increased from 18 inches to 36 inches. This results in the obsolescence of many smaller furnace types.

[0003] To make full use of obsolete small furnaces, they can be modified and larger crucibles can be installed to produce large-diameter single-crystal silicon. However, as the crucible size increases, the thermal space becomes limited, resulting in insufficient insulation of the insulation layer. If the heat loss caused by rapid heat dissipation is compensated solely by increasing the heater power, problems such as reduced crystal pulling quality and high power consumption will arise. Summary of the Invention

[0004] In view of this, the present invention provides a Czochralski single crystal furnace to solve the problems existing in the background art.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a Czochralski single crystal furnace, comprising:

[0007] Furnace body;

[0008] The crucible is located inside the furnace body;

[0009] A first heat preservation device is arranged around the circumference of the crucible. The first heat preservation device has a gas heat preservation layer for containing gas and an air inlet and an air outlet for gas to enter and exit.

[0010] The first exhaust pipe has one end located above the crucible and the other end extending upwards out of the furnace body to exhaust the gas generated during the crystal pulling process;

[0011] A heating device having a heating chamber for containing and heating the gas flowing out of the first exhaust pipe;

[0012] The recovery pipe has one end connected to the heating chamber and the other end connected to the air inlet, so that the gas in the heating chamber flows into the gas insulation layer.

[0013] In this embodiment of the invention, a first exhaust pipe is provided above the crucible, and a first heat-insulating device is provided around the circumference of the crucible. The first heat-insulating device has a hollow gas insulation layer. The gas discharged from the first exhaust pipe is further heated and then recycled back into the gas insulation layer, which improves the heat insulation effect of the crucible in the expansion of a small furnace cavity and the modification of a large hot field. Furthermore, since the gas discharged from the first exhaust pipe carries its own heat, the problem of excessive energy consumption caused by the expansion of a small furnace cavity and the modification of a large hot field is solved.

[0014] In one optional embodiment, the gas insulation layer includes multiple upper and lower separated insulation zones, each of which is connected to a recovery pipe.

[0015] Multiple upper and lower separated insulation zones can be set with different insulation efficiencies to create a suitable longitudinal temperature gradient. This ensures effective cooling of the crystals in the upper part of the free melt, which is conducive to stable crystal growth, while the lower part has sufficient temperature for melting, which is conducive to the full melting and mixing of raw materials. Furthermore, the insulation efficiency of the upper and lower separated insulation zones can be dynamically adjusted to obtain a suitable temperature gradient, increasing the flexibility of process adjustment and reducing energy consumption.

[0016] In one optional embodiment, the gas insulation layer includes a first insulation zone and a second insulation zone separated vertically, and the recovery pipe includes a first pipe and a second pipe respectively connecting the first insulation zone and the second insulation zone.

[0017] Thus, compared to having more than two insulation zones, the two insulation zones in this embodiment have a simpler structure, are easier to control, and can achieve a balance between effectiveness and cost.

[0018] In one optional embodiment, two heating devices are provided, with the air inlet of both heating devices connected to the first exhaust pipe and the air outlet connected to the first pipe and the second pipe respectively; the heating temperature of the two heating devices can be adjusted separately.

[0019] This makes it easier to adjust the temperature of the two insulation zones, allowing for more independent adjustments without interference between them.

[0020] In an optional embodiment, both the heating device and the first heat preservation device are equipped with temperature sensors. The heating device adjusts its operating power according to the detection results of the temperature sensors to form a longitudinal temperature gradient on the periphery of the crucible.

[0021] In one optional embodiment, the end of the first exhaust pipe located above the crucible has a trumpet-shaped expansion structure with an expansion angle of 15°–30°, which is used to expand the exhaust coverage area and reduce the impact of local negative pressure disturbance on the melt surface.

[0022] This reduces the disturbance of the molten surface caused by the airflow generated by the exhaust.

[0023] In an optional embodiment, the Czochralski single crystal furnace further includes a lifting mechanism for driving the first exhaust pipe to rise and fall, so that the first exhaust pipe follows the crucible to rise and fall.

[0024] This reduces the contact or disturbance of the molten surface by the first exhaust pipe.

[0025] In one optional embodiment, the Czochralski single crystal furnace further includes a second heat preservation device, the second heat preservation device including a heat preservation ring covering the top of the crucible; the inner side of the heat preservation ring abuts against the outer wall of the guide tube, and the outer side extends beyond the outer edge of the crucible; the first exhaust pipe passes through the heat preservation ring and is vertically linked with the heat preservation ring; the heat preservation ring is formed by nesting at least two materials.

[0026] In this way, the insulation ring covers the crucible from the top, effectively blocking heat loss from the free interface of the molten material inside the crucible, improving the insulation effect of the crucible, and reducing gas overflow to the outside of the crucible, which can deposit and corrode the graphite materials such as the heater, furnace wall, and electrode connection structure inside the crucible, thus extending their service life.

[0027] In one alternative embodiment, the bottom end of the insulation ring is spaced 2mm-10mm from the top end of the crucible.

[0028] This reduces interference with the crucible's rotation. The spacing needs to be set according to the actual production situation; too large a spacing is not conducive to heat preservation and argon escape, while too small a spacing may interfere with the crucible's rotation.

[0029] In one alternative embodiment, the insulation ring is formed by nesting at least two of the following materials:

[0030] Flexible thermal insulation materials;

[0031] Structural support and insulation materials;

[0032] Radiation-barrier insulation materials.

[0033] In this embodiment of the invention, a Czochralski single crystal furnace is provided with a first exhaust pipe above the crucible and a first heat preservation device surrounding the crucible. The first heat preservation device has a hollow gas insulation layer, and the gas discharged from the first exhaust pipe is further heated and then recycled into the gas insulation layer. This not only improves the heat preservation effect of the crucible in the expansion of a small furnace cavity and the modification of a large hot field, but also solves the problem of excessive energy consumption caused by the expansion of a small furnace cavity and the modification of a large hot field because the gas discharged from the first exhaust pipe carries its own heat.

[0034] Furthermore, the gas insulation layer that contains the heating gas provides more uniform heat distribution, reducing the problem of localized overheating or underheating in the crucible. It also more effectively controls convection losses, thereby improving overall energy efficiency.

[0035] Furthermore, in this embodiment of the invention, the first exhaust pipe is located above the crucible, which minimizes the flow path of the airflow and ensures that the airflow path does not come into contact with the graphite components in the hot zone. This improves the service life of the graphite components, effectively reduces the introduction of oxygen and carbon impurities, and enhances the quality of the crystal rod.

[0036] Furthermore, the multiple upper and lower separated heat preservation zones in this embodiment of the invention can each be set with different heat preservation efficiencies, which is beneficial for both stable crystal growth and thorough melting and mixing of raw materials. It also increases the flexibility of process adjustments and reduces energy consumption.

[0037] Furthermore, the insulation ring covers the crucible from the top, effectively blocking heat loss from the free interface of the melt inside the crucible and improving the insulation effect of the crucible. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0039] Figure 1 A schematic diagram of a Czochralski single crystal furnace provided in an embodiment of the present invention;

[0040] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle;

[0041] Figure 3 This is a schematic diagram of the first heat preservation device in the Czochralski single crystal furnace provided in an embodiment of the present invention;

[0042] Figure 4 for Figure 2 A magnified view of a portion of point B in the middle;

[0043] Figure 5 for Figure 4 A magnified view of a portion of point C.

[0044] Explanation of reference numerals in the attached figures:

[0045] 11. Furnace body; 12. Crucible; 13. Lifting mechanism; 14. Guide tube; 20. First exhaust pipe; 30. Heating device; 40. First insulation device; 41. First insulation zone; 42. Second insulation zone; 43. Exhaust port; 50. Recovery pipe; 61. Vacuum pump; 62. Filter device; 70. Gas storage tank; 80. Second insulation device; 81. Flexible insulation material; 82. Structural support insulation material; 83. Radiation barrier insulation material; 90. Crystal rod. Detailed Implementation

[0046] To make the technical solutions and beneficial effects of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below by listing specific embodiments. Obviously, the embodiments of the present invention are not exhaustive, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0047] The exemplary embodiments disclosed in this invention will now be described in more detail with reference to the accompanying drawings, providing detailed structures and steps to illustrate the technical solution of this invention. Note that the drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of those features.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and should not be construed as limiting the scope of the invention.

[0049] The following description provides numerous specific details to offer a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. To clearly define the inventive concept and avoid confusion with the content of this invention, technical features well-known in the art and conventionally understood by those skilled in the art are not described in detail. Specifically, this document does not fully list all features of actual embodiments, nor does it provide a detailed description of well-known functions and structures.

[0050] Before introducing the technical solution of this invention, let me briefly introduce the core steps and principles of the CZ direct pull method:

[0051] 1) Equipment preparation: The Furnace

[0052] The entire process takes place in a furnace chamber within a special vacuum or inert gas (usually argon) environment called a single crystal furnace. Key components include:

[0053] Quartz Crucible: Used to hold high-purity polycrystalline silicon.

[0054] Graphite Heater: Surrounded by a crucible, it provides high temperatures (the melting point of silicon is approximately 1414°C) to melt the silicon material.

[0055] Rotation and lifting mechanism: The crucible can be rotated and lifted, and the seed crystal rod can also be rotated and lifted in the opposite direction.

[0056] Control system: Precisely controls temperature, rotation speed, and lifting speed.

[0057] 2) Charging and Melting

[0058] Crushed high-purity polycrystalline silicon (and appropriate dopants, such as boron or phosphorus) is placed into a quartz crucible. After evacuation, an inert gas is introduced, and then the mixture is heated until the silicon is completely melted, forming a liquid silicon molten soup (Melt).

[0059] 3) Seed Dipping

[0060] A small, precisely oriented monocrystalline silicon seed crystal is fixed on the seed crystal rod and slowly lowered to near the surface of the molten silicon.

[0061] The surface of the melt is cooled to a temperature slightly above the melting point of silicon. The seed crystal is then gently immersed into the molten silicon. At this point, if the temperature is properly controlled, the molten silicon will not melt the seed crystal; instead, it will begin to crystallize using the atomic arrangement of the seed crystal as a "template."

[0062] 4) Shouldering

[0063] After successfully growing a dislocation-free neck, the pulling speed is reduced and the temperature is increased. The crystal diameter gradually increases, forming a conical "shoulder." By precisely controlling the temperature and pulling speed, the diameter is expanded to the target size (e.g., 200mm, 300mm, 450mm).

[0064] 5) Body Growing

[0065] This is the stage of growing the main body of the ingot. An automatic diameter control system (based on observation of crystal surface brightness or temperature feedback) dynamically adjusts the pulling speed and heating power to maintain a constant crystal diameter. During this process, the crucible rises slowly to maintain the relative stability of the molten silicon surface. The counter-rotation of the seed rod and the crucible helps to: ensure uniform distribution of melt temperature and dopant; and maintain the spherical symmetry of the grown crystal.

[0066] 6) Tail Growing

[0067] As most of the silicon melt has crystallized and the process nears completion, the pulling speed is gradually increased while the temperature is decreased. This causes the crystal diameter to gradually shrink, eventually forming a pointed tail that separates from the melt.

[0068] The above is a simplified process flow for the CZ direct pulling method.

[0069] As mentioned earlier, to make full use of obsolete small furnaces, they can be modified and larger crucibles can be installed to produce large-diameter single-crystal silicon. However, with a fixed furnace diameter, increasing the size of the thermal zone will lead to a reduction in the thickness of the thermal insulation felt, resulting in decreased thermal insulation performance. This leads to numerous problems, including higher crystal pulling power, shorter thermal zone lifespan, and decreased crystal pulling quality.

[0070] In traditional technologies, when faced with the problem of expanding a small furnace cavity into a large thermal field, it is necessary to redesign a new thermal field structure, find insulation materials with better insulation performance, and continuously optimize local structural components to avoid excessive heat loss.

[0071] The inventors of this invention discovered during the research and development that designing and optimizing the thermal field or replacing it with new materials within a limited furnace space is not only difficult and costly to modify, but also consumes a lot of power.

[0072] Furthermore, the inventors of this invention have discovered that when the thermal insulation performance of the thermal field decreases after the expansion of the small furnace cavity into a large thermal field, it will cause unreasonable temperature gradients, such as large radial temperature gradients, which in turn leads to deep solid-liquid interface depressions, severe melt thermal convection, and easy exceedance of oxygen and carbon content, among other technical problems.

[0073] Furthermore, the expansion of the furnace cavity and the resulting larger hot zone exacerbates the existing technical problem of graphite components being easily corroded by oxide gases during crystal pulling, thus reducing their service life. For example, after the hot zone is expanded, issues such as an unreasonable temperature gradient and severe melt thermal convection may increase the amount of oxide gases generated.

[0074] Specifically, the principle of oxide gas generation can be found in the following description.

[0075] I. Core Issue: Generation of By-products

[0076] During high-temperature crystal pulling (silicon melting point is 1414°C), graphite components in the thermal field (heater, crucible, insulation cylinder, electrodes, etc.) react with the surrounding environment, mainly producing two types of byproducts: SiO (silicon monoxide) gas: molten silicon (Si) reacts with the quartz crucible (silicon dioxide, SiO2) to form Si + SiO2 → SiO (silicon monoxide)↑. This is the most significant byproduct. CO (carbon monoxide) gas: graphite (C) reacts with SiO gas to form SiO + C → SiC (silicon carbide) + CO↑, or graphite reacts with trace amounts of oxygen to form C + O2 → CO↑. If these gaseous byproducts are not removed promptly and effectively, they will circulate within the thermal field, leading to deposition and corrosion reactions.

[0077] II. How airflow path and exhaust system affect graphite lifespan

[0078] The airflow path determines where these byproducts "go" and "stay." The exhaust system determines how quickly they are "drawn away."

[0079] Negative impact: Mechanism that accelerates the wear and tear of graphite (furnace walls, heaters, electrode connections, insulation cylinders, etc.).

[0080] a) The main mechanism of deposition and corrosion cycle (caused by airflow passing through graphite components):

[0081] Process: Gaseous SiO is carried by the gas flow to lower-temperature areas (such as the upper part of the insulation cover, furnace wall, and electrode connections), where a disproportionation reaction occurs: SiO → Si + SiO2. Result: The resulting solid Si and SiO2 deposit on the graphite surface. These deposits are insulating and alter the electromagnetic and thermal properties of the thermal field, forcing process adjustments (such as increased power) and indirectly affecting graphite components. More seriously, when the deposits accumulate to a certain extent and detach back into the high-temperature zone, they react with graphite again, forming a "SiO2-Si-C" cyclic corrosion that continuously consumes graphite material. Particularly concerning is the formation of a silicon carbide (SiC) hard shell on the heater surface; when this shell detaches, it causes localized thinning of the heater, creating hot spots and ultimately leading to burnout.

[0082] b) Stagnation and eddies:

[0083] If the airflow design is flawed, eddies or stagnant zones may form in certain corners or cavities, leading to excessively high concentrations of byproduct gases (especially SiO) in these areas. High concentrations of SiO significantly accelerate the reaction with graphite (SiO + 2C → SiC + CO↑), causing rapid corrosion of the graphite in localized areas. Electrodes and bolt connections are particularly vulnerable.

[0084] Therefore, through further research and development, the inventors proposed the following technical solution.

[0085] To address the technical problems in related technologies, embodiments of the present invention provide a Czochralski single crystal furnace. (Reference) Figures 1-3 The Czochralski single crystal furnace includes:

[0086] Furnace body 11;

[0087] Crucible 12 is located inside furnace body 11;

[0088] The first heat preservation device 40 is arranged around the crucible 12. The first heat preservation device 40 has a gas heat preservation layer for containing gas and an air inlet and an air outlet 43 for gas to enter and exit.

[0089] The first exhaust pipe 20 has one end located above the crucible 12 and the other end extending upwards out of the furnace body 11 to exhaust the gas generated during the crystal pulling process;

[0090] The heating device 30 has a heating chamber to contain and heat the gas flowing out of the first exhaust pipe 20;

[0091] The recovery pipe 50 is connected at one end to the heating chamber and at the other end to the air inlet, so that the gas in the heating chamber flows into the gas insulation layer.

[0092] Understandably, the Czochralski single crystal furnace in this embodiment of the invention is a single crystal furnace with a small furnace cavity expanded to a large thermal field. The small furnace cavity is a relative concept, referring to the large thermal field after expansion. Specifically, the single crystal furnace in this embodiment of the invention may have been originally designed to manufacture single crystal rods smaller than 18 inches, but after expansion, it can manufacture single crystal rods larger than 18 inches.

[0093] It is understood that the first heat preservation device 40 may be a newly added heat preservation device, and does not mean that the single crystal furnace of the present invention only has the first heat preservation device 40. As mentioned above, the heat preservation device of the single crystal furnace before capacity expansion in the embodiments of the present invention may sometimes still be retained. It is understood that the first heat preservation device 40 is arranged around the circumference of the crucible 12, and therefore mainly provides lateral heat preservation for the crucible 12.

[0094] Understandably, the gas heated by the heating device 30 enters the gas insulation layer through the recovery pipe 50 and the air inlet, and is discharged from the exhaust port 43, circulating continuously. This allows the gas in the gas insulation layer to continuously replenish new heat and also to quickly adjust the temperature according to the situation.

[0095] Unlike existing designs, the first exhaust pipe 20 of this invention is located above the crucible 12. That is, the oxide gas generated on the surface of the melt directly enters the first exhaust pipe 20 above the crucible 12, making the flow path of the gas flow close to the shortest. The gas flow path basically does not contact the graphite component of the hot field, which improves the service life of the graphite component, greatly reduces the generation of CO gas, effectively reduces the introduction of oxygen and carbon impurities, and improves the quality of the crystal rod 90.

[0096] In existing technology, the gas path involves a certain flow rate of argon gas entering from the top of the single crystal furnace 11, passing through the innermost part of the guide tube 14, and allowing the oxides volatilized from the melt surface to flow out along the gap between the guide tube 14 and the quartz crucible 12, before exiting through the exhaust port at the bottom of the thermal field. During this process, a large amount of oxides continuously corrodes and erodes the high-temperature graphite components, the bottom insulation felt, and especially the heat source of the graphite heater. On the one hand, reactions occur at high temperatures, producing large amounts of gases such as CO, polluting the thermal field environment and reducing the quality of the crystal rod 90; on the other hand, the oxides corrode the graphite components, resulting in a significant reduction in their lifespan.

[0097] Based on the problems in the prior art, the first exhaust pipe 20 of the present invention is located above the crucible 12, so that byproducts generated during crystal pulling, such as SiO gas, are guided to deposit in non-core, easy-to-clean areas (such as the water-cooled wall in the upper part of the furnace chamber), which facilitates regular maintenance and cleaning, thereby protecting the expensive graphite components.

[0098] The heating device 30 and the recovery pipe 50 can transport the heated gas into the gas insulation layer of the first insulation device 40 to improve the insulation capacity.

[0099] Understandably, the heated gas can flow freely within the gas insulation layer, making full contact with the surface of the object being insulated (such as the sidewall of the gas insulation layer). This flow characteristic makes the heat distribution on the sidewall of the gas insulation layer more uniform, reducing the problem of localized excessively high or low temperatures around the outer periphery of the crucible 12. For example, in this embodiment, the gas inlet and outlet 43 for gas to enter and exit the gas insulation layer are respectively located at both ends along its diameter.

[0100] Furthermore, compared to existing solid insulation materials, such as rock wool, which primarily rely on low thermal conductivity to reduce heat conduction but have limited control over convection losses, the gas insulation layer of this invention, through actively flowing hot air, can more effectively control convection losses, thereby improving overall energy efficiency.

[0101] Furthermore, compared to materials with fixed thermal insulation performance in the prior art, the gas in this embodiment of the invention can have its temperature adjusted by the heating device 30, which can more flexibly adapt to the thermal insulation requirements in different scenarios.

[0102] Furthermore, in this embodiment of the invention, the gas originates from the gas discharged from the crucible 12 and carries its own heat, thus reducing the energy consumption of the heating device 30. For example, the gas input into the first heat preservation device 40 is set to be heated to above 1400°C, while the gas discharged from the crucible 12 is generally also above 1400°C. Although it is cooled by the pipe, it still has a large residual heat. Therefore, the energy consumption of the heating device 30 can be greatly reduced.

[0103] In some embodiments of the present invention, the Czochralski single crystal furnace further includes a vacuum pump 61, which is connected to a first exhaust pipe 20 to adjust the exhaust rate.

[0104] In this way, the exhaust rate can be adjusted according to the specific conditions inside the crucible 12, further improving the service life of the graphite components and the quality of the crystal rod 90.

[0105] In some embodiments of the present invention, the gas insulation layer includes multiple upper and lower separated insulation zones, each of which is connected to a recovery pipe 50.

[0106] Understandably, crystal growth requires extremely strict temperature gradients, with different growth stages necessitating different temperature gradients. Multiple upper and lower separated insulation zones can be configured with varying insulation efficiencies to create a suitable longitudinal temperature gradient. A relatively low temperature gradient environment is created in the upper part of crucible 12 to ensure effective cooling of the crystal above the free melt, which is beneficial for stable crystal growth, reduces thermal stress caused by sudden temperature changes, and prevents defects such as dislocations and slip lines. A relatively high temperature gradient is set in the lower part of crucible 12 to ensure sufficient superheat of the melt, maintain good fluidity, and provide sufficient temperature for melting, allowing the raw materials to fully melt and mix.

[0107] Furthermore, multiple upper and lower separated insulation zones can increase the flexibility of process adjustments and reduce energy consumption. For example, different stages of crystal growth require different temperatures. In the later stages of crystal growth, the insulation efficiency of the lower insulation zone can be appropriately reduced to decrease heat input and thus reduce energy consumption. Operators can independently adjust the temperature and insulation performance of the upper and lower insulation zones based on actual crystal growth parameters such as crystal growth rate and crystal diameter. This better adapts to different production needs and crystal growth conditions, improving production stability and controllability.

[0108] In some embodiments of the present invention, the gas insulation layer includes a first insulation partition 41 and a second insulation partition 42 separated from each other, and the recovery pipe 50 includes a first pipe and a second pipe that are respectively connected to the first insulation partition 41 and the second insulation partition 42.

[0109] The design of the first insulation zone 41 and the second insulation zone 42, which are separated into upper and lower sections, is simpler in structure and easier to control than having more than two insulation zones, and can achieve a balance between performance and cost.

[0110] Furthermore, it can be used in conjunction with dedicated crystal growth simulation software (Crystal Growth Simulator, CGSIM) to adjust the temperature gradient of the thermal field formed in the upper and lower regions of the thermal field during the crystal pulling process, so that the originally fixed thermal field environment can be transformed and adjusted during the crystal pulling process.

[0111] In some embodiments of the present invention, the inner wall of the gas insulation layer is coated with a coating with a reflectivity lower than a preset value to reduce heat radiation loss and improve insulation efficiency. Specifically, the coating can be a pyrolytic carbon coating. On the one hand, the pyrolytic carbon coating is corrosion-resistant and can protect the insulation layer from corrosive substances such as vapor; on the other hand, the pyrolytic carbon coating has a very low reflectivity and high insulation effect.

[0112] This reduces heat loss, improves insulation efficiency, and thus reduces energy consumption.

[0113] Furthermore, the inner wall of the gas insulation layer can also be designed with a porous structure or flow-guiding ribs to guide the hot gas to form a uniform and stable laminar flow within the layer, avoiding local eddies or dead zones.

[0114] In some embodiments of the present invention, two heating devices 30 are provided, and the air inlet ends of the two heating devices 30 are connected to the first exhaust pipe 20, and the air outlet ends are connected to the first pipe and the second pipe respectively; the heating temperature of the two heating devices 30 can be adjusted separately.

[0115] In this way, by setting two heating devices 30, it is more convenient to adjust the temperature of the two insulation zones (including the first insulation zone 41 and the second insulation zone 42), making the adjustment more independent and without interference between them.

[0116] In some embodiments of the present invention, both the heating device 30 and the first heat preservation device 40 are provided with temperature sensors (not shown in the figure). The heating device 30 adjusts its working power according to the detection result of the temperature sensor to form a longitudinal temperature gradient on the periphery of the crucible 12.

[0117] Specifically, temperature sensors are provided on both sides of the heating device 30, and a temperature sensor is also provided on the inner side of the first heat preservation device 40.

[0118] Specifically, the heating device 30 can be a resistance pipe heating device. This allows for a rapid response to temperature regulation commands. It is understood that other similar heaters, such as induction heaters, could also be used.

[0119] Specifically, insulation boards, such as graphite boards or carbon-carbon composite boards, can be installed between adjacent insulation zones to reduce thermal crosstalk.

[0120] In some embodiments of the present invention, a flow regulating valve and a gas composition analyzer are provided on the first exhaust pipe 20; the gas composition analyzer is used to detect the proportion of gas components in the recovered gas in order to dynamically adjust the exhaust rate.

[0121] Therefore, if the detection shows a high content of SiO (silicon monoxide) or CO (carbon monoxide) gas, the exhaust rate can be increased to reduce the corrosion of graphite components by these gases.

[0122] In some embodiments of the present invention, the Czochralski single crystal furnace further includes a filter device 62 for filtering the gas in the first exhaust pipe 20; one end of the filter device 62 is connected to the first exhaust pipe 20 and the other end is connected to the heating device 30.

[0123] This reduces contamination of subsequent pipes, heating device 30, and first insulation device 40.

[0124] In some embodiments of the present invention, multiple first exhaust pipes 20 are provided and are evenly distributed around the circumference of the crucible 12; the distance between the bottom end face of the first exhaust pipe 20 and the surface of the melt inside the crucible 12 is 2mm-30mm, so as to reduce the contact between the crucible 12 and the surface of the melt during rotation or rise; the edge of the bottom end face is provided with a chamfer or rounded transition to reduce the influence of airflow disturbance on the stability of the melt surface.

[0125] Generally, the first exhaust pipe 20 can be configured to be linked with the crucible 12, at least vertically, so that it is not affected by the rising of the crucible 12. However, the surface of the melt may fluctuate during the rotation or rising of the crucible 12. Therefore, the end face of the first exhaust pipe 20 is set with a certain gap from the surface of the melt to reduce contact with the surface of the melt.

[0126] Specifically, the distance between the bottom surface of the first exhaust pipe 20 and the surface of the melt inside the crucible 12 can be 2mm, 3mm, 5mm, 8mm, 10mm, 15mm, 20mm, 22mm, 25mm, 28mm, 30mm, etc.

[0127] Understandably, from a fluid dynamics perspective, when fluid flows through a right angle, the airflow undergoes a sharp turn at the angle. Inside the right angle, a significant separation zone forms, where the fluid separates from the solid boundary, resulting in backflow. This separation leads to airflow turbulence and the formation of vortices. Furthermore, fluid flowing through a right angle experiences greater drag and energy loss. However, by using a chamfer or rounded corner, these effects can be reduced; therefore, the edges of the end face are provided with chamfers or rounded transitions.

[0128] In some embodiments of the present invention, the end of the first exhaust pipe 20 located above the crucible 12 has a trumpet-shaped expansion structure with an expansion angle of 15°–30°, which is used to expand the exhaust coverage area and reduce the impact of local negative pressure disturbance on the melt surface.

[0129] Understandably, this trumpet-shaped expansion structure, that is, the end expands outward, is similar to the chamfer or rounded corner mentioned above, but larger in size. This makes it more effective in reducing the disturbance of the molten surface caused by the airflow generated by the exhaust.

[0130] In some embodiments of the present invention, the Czochralski single crystal furnace further includes a lifting mechanism 13 for driving the first exhaust pipe 20 to rise and fall, so that the first exhaust pipe 20 follows the crucible 12 to rise and fall.

[0131] As mentioned above, this reduces the contact or disturbance of the molten surface by the first exhaust pipe 20.

[0132] In some embodiments of the present invention, the lifting mechanism 13 and the lifting device of the crucible 12 share the same control and drive system, and / or the lifting mechanism 13 is connected to the lifting shaft of the crucible 12 through a mechanical linkage rod to achieve synchronous lifting.

[0133] This simplifies control and reduces the asynchrony between the two movements.

[0134] In some embodiments of the present invention, reference is made to Figure 4 and Figure 5 The Czochralski single crystal furnace also includes a second heat preservation device 80, which includes a heat preservation ring covering the top of the crucible 12; the inner side of the heat preservation ring abuts against the outer wall of the guide tube 14, and the outer side extends beyond the outer edge of the crucible 12; a first exhaust pipe 20 passes through the heat preservation ring and is vertically linked with the heat preservation ring; in this embodiment, as Figure 5 As shown, the first exhaust pipe 20 is fixed to the top of the insulation ring, and the insulation ring has a through hole corresponding to the position of the first exhaust pipe 20 to form an airflow channel. The insulation ring is formed by nesting at least two materials.

[0135] The insulating ring covers the crucible 12 from the top, effectively blocking heat loss from the free interface of the melt inside the crucible 12 and improving the insulation effect of the crucible 12. Since the insulating ring is at the top of the crucible 12, it moves up and down with the crucible 12, meaning the insulating ring and the crucible 12 move in tandem in the vertical direction.

[0136] The first exhaust pipe 20 and the insulation ring are vertically linked, therefore, the first exhaust pipe 20 and the crucible 12 are also vertically linked. This reduces interference between the lower end of the first exhaust pipe 20 and the molten surface.

[0137] Specifically, the insulation ring does not rotate with the crucible 12 when it rotates (i.e., rotates horizontally) to reduce the complexity of the upper end of the first exhaust pipe 20 and the external interface.

[0138] Specifically, the insulation ring can be an annular ring, with the inner ring fitted around the outer periphery of the guide tube 14, the bottom end abutting the top of the crucible 12, and the outer side extending out of the crucible 12.

[0139] Furthermore, while maintaining heat, the insulation ring also reduces gas overflow to the outside of the crucible, preventing gas deposition and corrosion of the graphite materials inside the crucible, such as heaters, furnace walls, and electrode connection structures, thus extending their service life.

[0140] In some embodiments of the present invention, the bottom end of the heat-insulating ring is spaced 2mm-10mm from the top end of the crucible 12.

[0141] This reduces interference with the rotation of crucible 12. The spacing needs to be set according to the actual production situation. Too large a spacing is not conducive to heat preservation and argon escape, while too small a spacing may interfere with the rotation of crucible 12.

[0142] Specifically, the distance between the bottom end of the insulation ring and the top end of the crucible 12 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.

[0143] In some embodiments of the present invention, the insulation ring is formed by nesting at least two of the following materials:

[0144] Flexible thermal insulation material 81;

[0145] Structural support insulation material 82;

[0146] Radiation barrier insulation material 83.

[0147] For example, the insulation ring is formed by covering the flexible insulation material 81 with the structural support insulation material 82.

[0148] Understandably, the flexible insulation material 81 has extremely low thermal conductivity and a porous structure, which can form a high-resistance heat flow path. This can effectively reduce heat conduction, lower heat loss, and improve insulation performance. Specifically, the thermal conductivity of the flexible insulation material 81 can be between 0.02 W / (m·K) and 0.04 W / (m·K).

[0149] It should be noted that the structural support insulation material 82, in addition to serving as a structural support, also uses materials with a thermal conductivity significantly lower than that of metals, such as those with a thermal conductivity between 10 W / (m·K) and 50 W / (m·K). This effectively reduces heat conduction and improves the insulation effect.

[0150] For example, the insulation ring is formed by covering the structural support insulation material 82 with radiation barrier insulation material 83.

[0151] This reduces radiative heat transfer, decreases heat loss, and improves insulation performance.

[0152] For example, the insulation ring is formed by covering the flexible insulation material 81 with radiation-barrier insulation material 83.

[0153] In this way, both radiative heat transfer and heat conduction can be reduced, and the radiation barrier insulation material 83 generally has high structural strength, which can play a certain supporting role.

[0154] For example, the insulation ring is formed by covering the flexible insulation material 81 with the structural support insulation material 82, and then covering the structural support insulation material 82 with the radiation barrier insulation material 83.

[0155] This results in less heat loss and better insulation.

[0156] Specifically, the flexible insulation material 81 is insulation felt, the structural support insulation material 82 is carbon-carbon composite material, and the radiation barrier insulation material 83 is quartz.

[0157] Thermal insulation felts, such as ceramic fiber felts and aerogel felts, have low thermal conductivity, low cost, and long service life.

[0158] Under the influence of a temperature gradient, carbon-carbon composite materials exhibit high strength (tensile strength up to 200MPa-500MPa) and low coefficient of thermal expansion (1×10⁻⁶). -6 / ℃-2×10 -6 The ring shape ( / ℃) can be maintained to prevent cracking or deformation due to thermal stress, ensuring the durability of the middle layer's thermal insulation function. The carbon-carbon composite material is connected to the first exhaust pipe 20, which can be made of silicon carbide ceramic, characterized by high temperature resistance and high strength, and also plays a certain role in thermal insulation.

[0159] Quartz has excellent heat reflection capabilities, which maximizes the reflection and blocking of heat lost upward from the free interface of the melt within crucible 12 back into the melt, effectively reducing the longitudinal heat loss of traditional high-temperature melts through thermal radiation. Furthermore, quartz's high-temperature resistance reduces the reaction and adhesion of SiO (silicon monoxide) oxide volatilized from the silicon melt inside crucible 12, thus reducing the introduction of impurities into the melt.

[0160] It is understood that the flexible thermal insulation material 81, the structural support thermal insulation material 82, and the radiation barrier thermal insulation material 83 can also be other materials with the above properties, without limitation.

[0161] In some embodiments of the present invention, the Czochralski single crystal furnace further includes a gas storage tank 70.

[0162] Understandably, the flow rate and volume of hot gas flowing into the first insulation device can be controlled through the gas storage tank 70, so as to more accurately control the insulation efficiency of the first insulation device.

[0163] It should be noted that the various embodiments or implementation methods described herein can be presented in a progressive manner. Each embodiment focuses on describing the differences from other embodiments, and the same or similar parts between embodiments can be referred to mutually. It should be understood that in the various embodiments of the present invention, the embodiment numbers are merely for descriptive purposes and do not represent the superiority or inferiority of the embodiments.

[0164] Understandably, without conflict, the technical features in the technical solutions described in each embodiment can be arbitrarily combined to form new embodiments. For example, each structure in each embodiment can be implemented as an independent embodiment, and the structures can be arbitrarily combined; some or all of the structures in different embodiments can be arbitrarily combined. Each step in each embodiment can be implemented as an independent embodiment, and the steps can be arbitrarily combined; the order of the steps can be arbitrarily interchanged; some or all of the steps in different embodiments can be arbitrarily combined. Furthermore, regarding the table in the embodiments, each element, each row, or each column in the table can be implemented as an independent embodiment.

[0165] In this document, when the terms "embodiment," "implementation," or "example" are used, it means that the specific features described in connection with these implementations or examples are all included in at least one implementation, embodiment, or example of the present invention. It should be noted that the illustrative expressions of the above terms in this document do not necessarily refer to the same implementation, embodiment, or example. Furthermore, the specific features described, such as structures or steps, can be appropriately combined in any one or more implementations, embodiments, or examples.

[0166] In some embodiments, prefixes such as "first" and "second" are used merely to distinguish different descriptive objects and do not impose restrictions on the position, order, priority, or value of the descriptive objects. The description of the descriptive objects is given in the context of the embodiments, and the use of prefixes does not constitute unnecessary restrictions. For example, the numerical value of a descriptive object is not limited by ordinal numbers and can be one or more. Taking "first device" as an example, the numerical value of "device" can be one or more. Furthermore, objects modified by different prefixes can be the same or different. For example, if the descriptive object is "device," then "first device" and "second device" can be the same device or different devices, and their types can be the same or different. Describing "first" does not necessarily imply the existence of "second," and discussing "second" does not necessarily imply the existence of "first."

[0167] In some embodiments, unless otherwise stated, elements expressed in the singular form, such as "a," "the," "the," "the," "the," "the," etc., can mean "one and only one," or "one or more," "at least one," etc. For example, when using articles such as "a," "an," "the," etc. in translation, the noun following the article can be understood as either a singular or a plural expression. In some embodiments, "multiple" refers to two or more.

[0168] In some embodiments, the terms “at least one of”, “one or more”, “a plurality of”, “multiple”, etc., may be used interchangeably.

[0169] In some embodiments, the notation "at least one of A and B", "A and / or B", "A in one case, B in another", "A in one case, B in another", etc., may include the following technical solutions depending on the situation: in some embodiments, A (A is executed regardless of B); in some embodiments, B (B is executed regardless of A); in some embodiments, execution is selected from A and B (A and B are selectively executed); in some embodiments, both A and B are executed. The same applies when there are more branches such as A, B, C, etc.

[0170] In some embodiments, the notation "A or B" may include the following technical solutions, depending on the situation: in some embodiments, A (execution of A regardless of B); in some embodiments, B (execution of B regardless of A); in some embodiments, selective execution from A and B (A and B are selectively executed). The same applies when there are more branches such as A, B, and C.

[0171] In some embodiments, unless otherwise expressly defined, the terms "installation," "connection," "linking," "fixing," "setting," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can also refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment according to the specific circumstances.

[0172] In some embodiments, the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “height,” “up,” “down,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to simplify the description of the present invention and are not intended to indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. In other words, they should not be construed as limiting the present invention.

[0173] In some embodiments, unless otherwise expressly defined, "above" or "below" the second feature can mean that the first and second features are in direct contact, or indirect contact via an intermediate medium, or that they are not in contact, but simply indicate that the horizontal level of the first feature is higher than that of the second feature. Furthermore, "above" or "below" the second feature can mean that the first feature is directly above or diagonally above, directly below, or diagonally below the second feature.

[0174] In some embodiments, spatial relation terms such as “upper” and “lower” may be used for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, the description of an element or feature “below” other elements or features will change it to “upper” other elements or features. Therefore, the exemplary terms “upper” and “lower” can include both upper and lower orientations. The device may also be otherwise oriented (rotated 90 degrees or otherwise), and the spatial descriptive terms used herein will be interpreted accordingly.

[0175] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the technical solutions of this invention. Various modifications and changes can be made to the above embodiments without departing from the scope of this invention. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of this invention that may not be explicitly described. Therefore, the above embodiments only illustrate several implementations of this invention and do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

Claims

1. A Czochralski single crystal furnace, characterized in that, include: Furnace body (11); The crucible (12) is located inside the furnace body (11); The first heat preservation device (40) is arranged around the circumference of the crucible (12). The first heat preservation device (40) has a gas heat preservation layer for containing gas and an air inlet and an exhaust outlet for gas to enter and exit. The first exhaust pipe (20) has one end located above the crucible (12) and the other end extending upwards out of the furnace body (11) to exhaust the gas generated during the crystal pulling process; The heating device (30) has a heating chamber to contain and heat the gas flowing out of the first exhaust pipe (20); The recovery pipe (50) is connected to the heating chamber at one end and to the air inlet at the other end, so that the gas in the heating chamber flows into the gas insulation layer. The gas insulation layer includes multiple upper and lower separated insulation zones, and each insulation zone is connected to the recovery pipe (50).

2. The Czochralski single crystal furnace according to claim 1, characterized in that, The gas insulation layer includes a first insulation zone and a second insulation zone separated by upper and lower sections, and the recovery pipe (50) includes a first pipe and a second pipe that are respectively connected to the first insulation zone and the second insulation zone.

3. The Czochralski single crystal furnace according to claim 2, characterized in that, There are two heating devices (30). The air inlet of each heating device (30) is connected to the first exhaust pipe (20), and the air outlet is connected to the first pipe and the second pipe respectively. The heating temperature of the two heating devices (30) can be adjusted separately.

4. The Czochralski single crystal furnace according to claim 3, characterized in that, Both the heating device (30) and the first heat preservation device (40) are equipped with temperature sensors. The heating device (30) adjusts its working power according to the detection result of the temperature sensor to form a longitudinal temperature gradient on the periphery of the crucible (12).

5. The Czochralski single crystal furnace according to claim 1, characterized in that, The first exhaust pipe (20) has a horn-shaped expansion structure at one end above the crucible (12), with an expansion angle of 15°–30°, which is used to expand the exhaust coverage area and reduce the impact of local negative pressure disturbance on the melt surface.

6. The Czochralski single crystal furnace according to claim 1, characterized in that, The Czochralski single crystal furnace also includes a lifting mechanism (13) for driving the first exhaust pipe (20) to rise and fall, so that the first exhaust pipe (20) follows the crucible (12) to rise and fall.

7. The Czochralski single crystal furnace according to claim 1, characterized in that, The Czochralski single crystal furnace also includes a second heat preservation device (80), which includes a heat preservation ring covering the top of the crucible (12); the inner side of the heat preservation ring abuts against the outer wall of the guide tube (14), and the outer side extends beyond the outer edge of the crucible (12); the first exhaust pipe (20) passes through the heat preservation ring and is vertically linked with the heat preservation ring; the heat preservation ring is formed by nesting at least two materials.

8. The Czochralski single crystal furnace according to claim 7, characterized in that, The bottom of the insulation ring is 2mm-10mm away from the top of the crucible (12).

9. The Czochralski single crystal furnace according to claim 7, characterized in that, The insulation ring is formed by nesting at least two of the following materials: Flexible thermal insulation material (81); Structural support insulation material (82); Radiation barrier insulation material (83).

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