Method for reducing crystal pulling power consumption of single crystal furnace

Abstract

The invention relates to the technical field of monocrystalline silicon manufacturing, in particular to a method for reducing crystal pulling power consumption of a single crystal furnace, which comprises the following steps: filling a cavity of the single crystal furnace with oxygen; an evacuating device at the bottom of the single crystal furnace is used for evacuating a cavity of the single crystal furnace, and a negative pressure state is formed in the cavity; after the single crystal furnace reaches vacuum, stopping the vacuumizing process, and performing leak detection on the cavity of the single crystal furnace by using an isolating valve; after leakage detection is completed, the single crystal furnace is filled with heat preservation gas; the heat preservation gas flows out through the gas guide hole 1 after passing through the heat preservation part in the circulation process. The cavity is formed in the furnace bottom and filled with the heat preservation gas, the filling gas replaces a traditional curing felt to serve as a heat preservation material, the heat preservation effect is better, pulverization is avoided, and the service life is longer. The bottom supporting point of the furnace bottom supporting device is made of a ceramic material, the strength of the ceramic supporting material is higher, and the problem that the crystal pulling quality is affected due to the fact that the strength of a traditional curing felt is reduced and the device cover distance is reduced in the high-temperature operation process of the single crystal furnace can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal silicon manufacturing, and in particular to a method for reducing the power consumption of a single crystal furnace for crystal pulling. Background Art

[0002] A single crystal furnace is a device that uses a heater to melt polycrystalline materials such as polysilicon in an inert gas environment and grows dislocation-free single crystals through the Czochralski method.

[0003] In traditional single crystal furnaces, the use of bottom insulation leads to high energy consumption. For example, the bottom insulation felt corrodes and wears away over time, resulting in a decrease in the thermal insulation performance of the bottom heat field. Furthermore, the high resistance between the cooling electrode and the heater also affects heating efficiency. Single crystal furnaces are energy-intensive equipment, so reducing energy consumption and improving operating efficiency are key design optimization goals.

[0004] With the development of new materials technology, the application of new materials in the single crystal production furnace industry will become more extensive, improving product performance while also reducing costs. Energy conservation and emission reduction are the current trends in social development. The single crystal production furnace industry is constantly developing high-efficiency energy-saving technologies to reduce energy consumption and improve energy efficiency.

[0005] The Czochralski single crystal furnace thermal system consists of a heater, insulation tube, graphite electrodes, graphite support bowl, graphite support rod, top insulation, and bottom insulation thermal field. In a single crystal furnace, the bottom insulation thermal field primarily serves to reduce heat loss and support the insulation tube.

[0006] At present, the furnace bottom insulation materials used in single crystal factories in the industry are mainly made of curing felt and graphite soft felt, which have a good thermal insulation effect. According to the different temperatures during the production process of carbon felt, it is divided into carbon felt (generally processed at a temperature of more than 900 degrees in China) and graphite felt (generally processed at a temperature of about 1700 degrees in China). During the operation of the single crystal furnace, the maximum temperature inside the furnace body can reach about 1950℃. During the high-temperature operation of the single crystal furnace, the curing felt will have the following defects: (1) The curing felt will be powdered during operation, and the thermal insulation performance will be reduced, resulting in an increase in the power of the single crystal furnace; (2) After the curing felt is powdered during operation, the physical strength of each contact point with the insulation tube changes, causing the entire thermal field to sink and the distance from the cover to become smaller, affecting the quality; (3) The curing felt needs to be replaced after a period of operation, which is costly; (4) The thermal conductivity of the curing felt currently used is large and the thermal insulation performance is poor.

[0007] Therefore, it is necessary to invent a method to reduce the power consumption of a single crystal furnace to solve the above problems. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for reducing the power consumption of single crystal furnace pulling, which solves the problem that traditional solidified felt is prone to felt powdering during high-temperature operation of single crystal furnace, resulting in reduced thermal insulation performance, increased energy consumption and reduced output of single crystal furnace.

[0009] To achieve this object, the present invention adopts the following technical solutions: A method for reducing the power consumption of a single crystal pulling furnace is provided, comprising the following steps: Step S1: Filling the single crystal furnace cavity with oxygen; Step S2: The vacuum device at the bottom of the single crystal furnace is activated to vacuum the cavity of the single crystal furnace, thereby forming a negative pressure state in the cavity; Step S3: After the single crystal furnace reaches vacuum, the evacuation process stops, and the cavity of the single crystal furnace is leak-checked using an isolation valve; Step S4: After the leak detection is completed, the interior of the single crystal furnace is filled with insulation gas; Step S5: The heat preservation gas flows through the heat preservation part and then flows out through the air guide holes; Step S6: storing and recovering the extracted insulation gas; Step S7: Continue to supply new insulation gas into the single crystal furnace.

[0010] As a preferred solution for a method of reducing the power consumption of a single crystal pulling furnace, after the leak detection in step S4 is completed, the isolation valve is restored to an open state.

[0011] As a preferred solution for reducing the power consumption of a single crystal pulling furnace, the insulation gas in step S4 is argon.

[0012] As a preferred solution for reducing the power consumption of a single crystal pulling furnace, the delivery and extraction rate of the insulation gas in steps S6-S7 is 70-90 slpm.

[0013] As a preferred solution for reducing the power consumption of a single crystal furnace pulling crystal, the insulation part in step S5 includes a furnace bottom support device located at the top of the single crystal furnace chassis, and a plurality of graphite soft felts are stacked on the top of the furnace bottom support device.

[0014] As a preferred solution for a method of reducing the power consumption of a single crystal furnace for crystal pulling, a plurality of supporting points are fixedly installed at the bottom end of the furnace bottom supporting device, and the furnace bottom supporting device is made of ceramic material.

[0015] As a preferred solution for reducing the power consumption of a single crystal furnace for pulling crystals, the gap between the bottom end of the furnace bottom support device and the top end of the single crystal furnace chassis is 20 to 40 mm.

[0016] As a preferred solution for reducing the power consumption of a single crystal furnace, the pipe used to recover the insulation gas in step S6 is wrapped around the outside of the delivery pipe in step S7, and waste heat is used to heat new insulation gas.

[0017] As a preferred solution for a method of reducing power consumption of a single crystal furnace for crystal pulling, in step S5, the heat-insulating gas passes through the cavity where the support point is located to form a heat-insulating layer.

[0018] The beneficial effects of the present invention are as follows: by providing a cavity at the furnace bottom and filling it with insulating gas, the filling gas replaces the traditional curing felt as the insulating material, achieving a better insulation effect, preventing pulverization, and extending the service life. The bottom support point of the furnace bottom support device is made of ceramic material. The ceramic support material has higher strength and can solve the problem of traditional curing felt losing strength and reducing the distance between the device and the cover during high-temperature operation of the single crystal furnace, thereby affecting the quality of crystal pulling. The heat transfer cross-sectional area between the furnace bottom ceramic support and the furnace bottom of the present invention is reduced, reducing heat conduction, thereby improving the thermal insulation of the thermal field. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0020] Figure 1 It is a schematic diagram of the overall structure of the single crystal furnace chassis described in the present invention.

[0021] Figure 2 It is a schematic diagram of the partial cross-sectional structure of the single crystal furnace chassis of the present invention.

[0022] Figure 3 It is a structural schematic diagram of the furnace bottom supporting device of the present invention.

[0023] In the picture: 1. Single crystal furnace chassis; 101. Gas guide hole; 2. Furnace bottom support device; 201. Support point; 202. Gas guide cylinder; 203. Electrode hole; 204. Central axis; 3. Graphite soft felt; 4. Copper electrode. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0025] Among them, the drawings are only used for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0026] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inside", "outside" and the like indicate an orientation or position relationship based on the orientation or position relationship shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0027] In the description of the present invention, unless otherwise expressly specified or limited, when the term "connection" or the like appears to indicate a connection relationship between components, such term should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be internal communication between two components or an interaction between two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0028] refer to Figures 1 to 3 The present invention provides a method for reducing the power consumption of a single crystal furnace for pulling crystals, comprising the following steps: Step S1: Filling the single crystal furnace cavity with oxygen; Step S2: The vacuum device at the bottom of the single crystal furnace is activated to vacuum the cavity of the single crystal furnace, thereby forming a negative pressure state in the cavity; Step S3: After the single crystal furnace reaches vacuum, the evacuation process stops, and the cavity of the single crystal furnace is leak-checked using an isolation valve; Step S4: After the leak detection is completed, the interior of the single crystal furnace is filled with insulation gas; Step S5: The heat-insulating gas flows through the heat-insulating portion and then flows out through the air guide hole 1; Step S6: storing and recovering the extracted insulation gas; Step S7: Continue to supply new insulation gas into the single crystal furnace.

[0029] The evacuation process is used to extract oxygen from the single crystal furnace cavity. After the oxygen extraction is completed, a leak detection process is performed to detect the sealing effect of the single crystal furnace cavity. After the leak detection process is completed, the isolation valve is reopened and argon is injected into the interior of the single crystal furnace cavity. After the argon filling is completed, it flows to the cavity at the bottom of the furnace bottom support device 2. By controlling the pumping rate, the top argon delivery rate is consistent with the bottom extraction rate. According to the different states of the single crystal furnace during crystal pulling, the pumping rate is adjusted accordingly. The lower thermal conductivity of argon is used to reduce the heat transfer of the furnace bottom support device 2, providing better insulation performance for the single crystal furnace, thereby reducing the overall power consumption of the single crystal furnace.

[0030] After the leak detection in step S4 is completed, the isolation valve returns to the open state.

[0031] The heat-insulating gas in step S4 is argon.

[0032] The delivery and extraction rate of the insulation gas in steps S6-S7 is 70-90 slpm.

[0033] The heat preservation part in step S5 includes a furnace bottom support device 2 located at the top of the single crystal furnace bottom plate 1 , and a plurality of graphite soft felts 3 are stacked on the top of the furnace bottom support device 2 .

[0034] The bottom end of the furnace bottom support device 2 is fixedly mounted with multiple support points 201. The furnace bottom support device 2 is made of ceramic. Ceramic materials generally have low thermal conductivity. As a furnace bottom support, it can reduce heat loss through the bottom structure to the cooling system or furnace frame below, helping to maintain the temperature gradient and stability at the bottom of the thermal field.

[0035] The gap between the bottom end of the furnace bottom supporting device 2 and the top end of the single crystal furnace bottom plate 1 is 20 to 40 mm.

[0036] The pipe used to recover the insulation gas in step S6 is wrapped around the outside of the delivery pipe in step S7, using the waste heat to heat new insulation gas. During the insulation gas recovery process, some heat may be drawn from within the single crystal furnace. Using the pipe used for recovered gas to assist in heating the insulation gas to be injected into the single crystal furnace reduces heat loss within the single crystal furnace and further reduces power consumption during single crystal pulling.

[0037] In step S5, the insulating gas forms an insulating layer through the cavity where the support point 201 is located. Compared to the insulating performance of conventional curing felt, the insulating layer formed by the insulating gas offers the following key advantages: it enables active dynamic control of the thermal field, completely eliminates aging contamination and the need for replacement of the curing felt material, significantly improves thermal field stability and crystal purity / consistency, and simplifies the furnace structure.

[0038] The primary way furnace bottom insulation materials dissipate heat is through heat conduction. Heat conduction relies on molecular motion to transfer heat, and the form of molecular motion is related to the molecular state within the object. Within solids, heat conduction is caused by the collision of adjacent molecules, which transfers vibrational energy. In gases, heat conduction relies on the transfer of kinetic energy through the irregular thermal motion of molecules. The basic formula for heat conduction is usually referred to as Fourier's law, which describes the process of heat conduction through an object. In one dimension, Fourier's law can be expressed as: [ Q = -k \cdot A \cdot \frac{dT}{dx} ] ( Q ) is the heat flux density through unit area (W / m²); ( k ) is the thermal conductivity of the material (W / (m·K)), which reflects the thermal conductivity of the material; (A) is the cross-sectional area of ​​heat transfer (m²); ( \frac{dT}{dx} ) is the temperature gradient (K / m), which represents the change in temperature per unit distance in the direction x.

[0039] The specific technical effects of implementation are: The gas in the single crystal furnace is argon. When it starts running, it needs to be evacuated. During the evacuation, the air in the cavity will be evacuated to form a negative pressure. When the pressure is increased, the argon will enter the cavity through the gap. When the evacuation process is completed, there is no strong convection in the single crystal furnace, the argon is stable in the cavity, and the thermal conductivity of argon is 0.055. Filling gas replaces the traditional curing felt as the insulation material. Since the thermal conductivity of argon is worse than that of curing felt, this embodiment uses ceramic supports to set a cavity at the bottom of the furnace and fill it with gas. The insulation effect of this embodiment is better, it will not be pulverized, and the service life is longer. The cross-sectional area of ​​heat transfer between the traditional curing felt and the furnace bottom is much larger than that of the furnace bottom ceramic support device. According to Fourier's law, the smaller the cross-sectional area of ​​heat transfer, the lower the thermal conductivity and the better the insulation effect. Therefore, the insulation effect of this embodiment is better.

[0040] The thickness of traditional curing felt (0.35-0.4) is generally 60-100 mm. The overall thickness is reduced to 20-30 mm by using a ceramic support device at the bottom, and the remaining part is replaced by viscose-based felt (thermal conductivity coefficient 0.15-0.2). According to Fourier's law, the lower the thermal conductivity coefficient, the lower the thermal conductivity performance, and the better the thermal insulation effect. Therefore, the thermal insulation effect of this embodiment is better. The present invention provides a cavity at the furnace bottom and fills it with insulating gas, replacing traditional curing felt as the insulating material. This provides better insulation, prevents pulverization, and extends service life. The bottom support point 201 of the furnace bottom support device 2 is made of ceramic. Ceramic support materials offer higher strength and address the issues of traditional curing felt weakening during high-temperature operation in single crystal furnaces, resulting in reduced cover distance and consequently, poor crystal pulling quality. The present invention reduces the heat transfer cross-sectional area between the furnace bottom ceramic support and the furnace bottom, reducing heat conduction and thereby improving thermal insulation.

[0041] It should be noted that the above-described specific embodiments are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that various modifications, equivalent substitutions, and variations may be made to the present invention. However, as long as these modifications do not depart from the spirit of the present invention, they are intended to be within the scope of protection of the present invention. Furthermore, certain terms used in the specification and claims of this application are not intended to be limiting and are provided solely for ease of description.

Claims

1. A method for reducing the power consumption of a single crystal furnace, characterized in that: The following steps are involved: Step S1: Filling the single crystal furnace cavity with oxygen; Step S2: The vacuum device at the bottom of the single crystal furnace is activated to vacuum the cavity of the single crystal furnace, thereby forming a negative pressure state in the cavity; Step S3: After the single crystal furnace reaches vacuum, the evacuation process stops, and the cavity of the single crystal furnace is leak-checked using an isolation valve; Step S4: After the leak detection is completed, the interior of the single crystal furnace is filled with insulation gas; Step S5: during the circulation process, the heat preservation gas passes through the heat preservation part and then flows out through the air guide hole (101); Step S6: storing and recovering the extracted insulation gas; Step S7: Continue to supply new insulation gas into the single crystal furnace.

2. The method for reducing power consumption of a single crystal pulling furnace according to claim 1, characterized in that: After the leak detection in step S4 is completed, the isolation valve returns to the open state.

3. The method for reducing power consumption of a single crystal pulling furnace according to claim 1, wherein: The heat-insulating gas in step S4 is argon.

4. The method for reducing power consumption of a single crystal pulling furnace according to claim 1, wherein: The delivery and extraction rate of the insulation gas in steps S6-S7 is 70-90 slpm.

5. The method for reducing power consumption of a single crystal pulling furnace according to claim 1, wherein: The heat preservation part in step S5 comprises a furnace bottom support device (2) located at the top of the single crystal furnace bottom plate (1), and a plurality of graphite soft felts (3) are stacked on the top of the furnace bottom support device (2).

6. The method for reducing power consumption of a single crystal pulling furnace according to claim 5, characterized in that: A plurality of support points (201) are fixedly mounted on the bottom end of the furnace bottom support device (2), and the furnace bottom support device (2) is made of ceramic material.

7. The method for reducing power consumption of a single crystal pulling furnace according to claim 6, characterized in that: The gap between the bottom end of the furnace bottom supporting device (2) and the top end of the single crystal furnace bottom plate (1) is 20 to 40 mm.

8. The method for reducing power consumption of a single crystal pulling furnace according to claim 1, characterized in that: The pipe used to recover the insulation gas in step S6 is wound around the outside of the delivery pipe in step S7, and the waste heat is used to heat the new insulation gas.

9. The method for reducing power consumption of a single crystal pulling furnace according to claim 5, characterized in that: In step S5, the heat-insulating gas passes through the cavity where the support point (201) is located to form a heat-insulating layer.

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