Composite heat preservation cover for crystalline silicon growth reduction furnace and preparation method of composite heat preservation cover

Abstract

The invention relates to the technical field of crystalline silicon growth equipment, and provides a composite heat preservation cover for a crystalline silicon growth reduction furnace and a preparation method, the composite heat preservation cover comprises a heat insulation layer and a function protection lining, and the heat insulation layer is arranged on the outer side of the function protection lining; the heat insulation layer is made of a high-purity fiber heat insulation material or a ceramic fiber heat insulation material, the metal impurity content of the heat insulation layer is smaller than 100 ppm, and the heat conductivity coefficient is smaller than or equal to 0.1 W / (m.K); the function protection lining is made of a high-purity and high-density carbon-ceramic composite material, and the metal impurity content of the high-purity and high-density carbon-ceramic composite material is smaller than or equal to 200 ppm; or the functional protection lining is made of a carbon-carbon composite material, and a silicon carbide coating and / or a silicon nitride coating are / is arranged on the surface of the functional protection lining. The high-purity and high-density carbon-ceramic composite material lining is compounded with the efficient thermal insulation material, so that high-speed gas scouring protection, corrosive atmosphere blocking and accurate axial heat flow regulation and control are synchronously realized. Compared with a traditional structure, the power consumption of the structure is reduced by more than 20%, and the service life reaches more than 6 months.

Description

Technical Field

[0001] This application belongs to the technical field of crystalline silicon production equipment, and more specifically, relates to a composite thermal insulation cover for a crystalline silicon growth reduction furnace. Background Art

[0002] In the Siemens process for polysilicon production, the reduction furnace is heated to about 1100 °C by the resistance of the silicon core, driving trichlorosilane (SiHCl3) to undergo chemical vapor deposition on the surface of the silicon rod to generate polysilicon. During this process, the thermal insulation structure needs to simultaneously meet the following requirements: 1) maintain a stable high-temperature reaction environment to reduce side reactions (such as the formation of SiCl4); 2) resist the penetration and erosion of corrosive HCl gas; 3) reduce the proportion of energy consumption caused by heat loss (usually accounting for 60%-70% of the total production energy consumption).

[0003] To improve the thermal efficiency, the prior art usually polishes or silver-plates the inner wall of the metal cover, but these methods have the following limitations:

[0004] (1) The thermal reflection effect drops sharply after the silicon layer is deposited on the surface;

[0005] (2) The coating is prone to corrosion failure in a high-temperature environment;

[0006] (3) The surface treatment layer is prone to peeling during cleaning and maintenance, resulting in high maintenance costs.

[0007] In recent years, the industry has tried to improve through the following solutions:

[0008] Solution A: Use a high-purity quartz thermal insulation layer, but the material undergoes crystallization embrittlement in a high-temperature HCl environment, and the service life is less than 3 months;

[0009] Solution B: Introduce a double-layer water-cooled jacket structure. Although it can reduce the surface temperature, it additionally increases the power consumption by 12%-15%, and is prone to causing a radial temperature gradient of the silicon rod (>25 °C), resulting in dendritic defects in the deposition layer. Summary of the Invention

[0010] In order to solve the problems existing in the above prior art, the purpose of the embodiments of this application is to provide a composite thermal insulation cover for a crystalline silicon growth reduction furnace. By combining a high-purity and high-density carbon-ceramic composite material lining with an efficient thermal insulation material, high-speed gas erosion protection, corrosive atmosphere barrier, and precise axial heat flow regulation are achieved simultaneously. Through experiments, this structure can reduce the unit power consumption of the reduction furnace to below 30 kWh / kg-Si (more than 20% lower than the traditional structure), and at the same time, the service life of the thermal insulation cover is up to more than 6 months, providing key technical support for cost reduction and efficiency improvement in the Siemens process for polysilicon production.

[0011] To achieve the above object, the technical solution adopted by this application is: to provide a composite thermal insulation cover for a polysilicon growth reduction furnace, including: a heat insulation layer and a functional protection lining, and the heat insulation layer is arranged outside the functional protection lining;

[0012] The heat insulation layer is made of high-purity fiber thermal insulation material or ceramic fiber thermal insulation material, the metal impurity content of the heat insulation layer < 100 ppm, and the thermal conductivity ≤ 0.1 W / (m·K);

[0013] The functional protection lining is made of high-purity and high-density carbon-ceramic composite material, and the metal impurity content of the high-purity and high-density carbon-ceramic composite material ≤ 200 ppm; or the functional protection lining is made of carbon-carbon composite material and is provided with a silicon carbide coating and / or a silicon nitride coating on the surface.

[0014] In one embodiment, the thickness of the heat insulation layer ≥ 2 mm.

[0015] In one embodiment, the heat insulation layer is made of high-purity carbon fiber felt, and its porosity is 60%-80%; or,

[0016] The heat insulation layer is made of ceramic fiber felt, and its porosity is 70%-90%; or,

[0017] The heat insulation layer includes high-purity carbon fiber felt and ceramic fiber felt; the porosity of the high-purity carbon fiber felt is 60%-80%, and the porosity of the ceramic fiber felt is 70%-90%; or,

[0018] The heat insulation layer includes multiple layers of high-purity carbon fiber felt and ceramic fiber felt, and the high-purity carbon fiber felt and the ceramic fiber felt are alternately stacked, the porosity of the high-purity carbon fiber felt is 60%-80%, and the porosity of the ceramic fiber felt is 70%-90%.

[0019] In one embodiment, the high-purity and high-density carbon-ceramic composite material is a carbon fiber reinforced carbon and silicon carbide dual matrix, its density ≥ 95%, the open porosity ≤ 5%, and the metal impurity content ≤ 200 ppm.

[0020] In one embodiment, the heat insulation layer and the functional protection lining are fixedly connected by a plurality of special screws.

[0021] In one embodiment, the special screws are carbon-carbon screws, carbon-ceramic screws or ceramic screws.

[0022] In one embodiment, the surface of the special screw is coated with a silicon carbide protective layer with a thickness of 10-200 μm.

[0023] In one embodiment, the heat insulation layer is fitted with the functional protection lining, and a plurality of sunk platforms are provided on the outer side wall of the functional protection lining, and the sunk platforms are fitted with the inner side wall of the heat insulation layer.

[0024] In one embodiment, the depth of the sunk platform ≥ 1 mm, and the distance between two adjacent sunk platforms ≥ 5 mm.

[0025] Another object of the present application is to provide a preparation method for a composite heat preservation cover for a polysilicon growth reduction furnace, which is used to prepare the above-mentioned composite protection cover, and is characterized in that the preparation method includes the following steps:

[0026] Prepare the functional protection lining:

[0027] A silicon carbide matrix is formed inside the carbon-carbon composite porous body by using a reactive melt infiltration process (RMI) or a chemical vapor infiltration process (CVI) or an impregnation pyrolysis (PIP) process to prepare the functional protection lining; or,

[0028] A carbon-carbon composite material (C / C) is prepared by using a chemical vapor infiltration process (CVI) or impregnation / carbonization, and a silicon carbide and / or silicon nitride coating is prepared by using a chemical vapor deposition process (CVD), a brushing or spraying process to prepare the functional protection lining;

[0029] Prepare the heat insulation layer:

[0030] A heat insulation layer with a predetermined porosity and thickness gradient is made by using ceramic fibers or carbon fibers;

[0031] Assembly:

[0032] Sunk platforms are machined or drilled on the outer surface of the functional protection lining, and the composite with the heat insulation layer is realized by using fasteners or embedded assembly.

[0033] The beneficial effects of the composite heat preservation cover and the preparation method for the polysilicon growth reduction furnace provided by the present application are as follows:

[0034] 1. Through the combination of a high-purity and high-density carbon-ceramic composite material lining and an efficient heat preservation material, high-speed gas erosion protection, corrosive atmosphere barrier and axial heat flow precise regulation are realized simultaneously. Through experiments, it is verified that this structure can reduce the unit power consumption of the reduction furnace to less than 30 kWh / kg-Si (more than 20% lower than the traditional structure), and at the same time, the service life of the heat preservation cover is more than 6 months, providing key technical support for the cost reduction and efficiency improvement of Siemens process polysilicon production.

[0035] 2. Heat efficiency improvement: The composite heat preservation cover can reduce the radiant heat loss by more than 40% through gradient thermal resistance design. When applied to the polysilicon growth of trichlorosilane in a modified Siemens process reduction furnace, the energy saving can reach more than 15%.

[0036] Hot field uniformity optimization: axial temperature gradient ≤ ±10 °C;

[0037] Process compatibility: compatible with the Czochralski method for single crystal silicon (1600 °C) and the Siemens method for polysilicon (1100 - 1200 °C), supporting large-scale production. Brief Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0039] Figure 1 It is a simplified cross-sectional structure schematic diagram of the composite thermal insulation cover for a silicon crystal growth reduction furnace provided by the embodiment of the present application;

[0040] Figure 2 It is a schematic diagram of the structure for fixing the heat insulation layer and the functional protection lining in the composite thermal insulation cover provided by the embodiment of the present application using special screws;

[0041] Figure 3 It is a schematic diagram of the structure of the heat insulation layer and the functional protection lining in the composite thermal insulation cover provided by the embodiment of the present application being embedded.

[0042] Among them, each reference numeral in the figure:

[0043] 1. Heat insulation layer; 2. Functional protection lining; 3. Special screw; 4. Counterbore. Detailed Description of the Embodiments

[0044] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the following further details the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0045] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0046] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0047] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0048] As Figure 1 shown, a composite thermal insulation cover for a polysilicon growth reduction furnace provided by an embodiment of the present application will now be described. The composite thermal insulation cover includes: a heat insulation layer 1 and a functional protection inner lining 2. The functional protection inner lining 2 is a support layer, and the heat insulation layer 1 is wrapped outside the functional protection inner lining 2.

[0049] Among them, the heat insulation layer 1 is made of high-purity fiber thermal insulation material or ceramic fiber thermal insulation material. The metal impurity content of the heat insulation layer 1 is <100 ppm, and the thermal conductivity is ≤0.1 W / (m•K); the heat conduction barrier can be achieved by adjusting the thickness and porosity of the heat insulation layer 1.

[0050] Among them, the functional protection inner lining 2 is made of high-purity and high-density carbon-ceramic composite material, and the metal impurity content of the high-purity and high-density carbon-ceramic composite material is ≤200 ppm; or the functional protection inner lining 2 is made of carbon-carbon composite material and is provided with a silicon carbide coating and / or a silicon nitride coating on the surface.

[0051] Through the synergistic effect of the heat insulation layer 1 and the functional protection inner lining 2, the composite thermal insulation cover constructs a gradient thermal resistance layer, so that the axial temperature gradient of the reduction furnace is controlled within ±10 °C, and the radiant heat loss is reduced by 40%.

[0052] In this embodiment, the overall thickness of the heat insulation layer 1 ≥ 2 mm. Specifically, in the first implementation, the heat insulation layer 1 is made of high-purity carbon fiber felt, and the high-purity carbon fiber felt can be a hard felt or a soft felt, with a porosity of 60% - 80%; in the second implementation, the heat insulation layer 1 is made of ceramic fiber felt, and the ceramic fiber felt can be a hard felt or a soft felt, with a porosity of 70% - 90%; in the third implementation, the heat insulation layer 1 includes a layer of high-purity carbon fiber felt and a layer of ceramic fiber felt; the porosity of the high-purity carbon fiber felt is 60% - 80%, and the porosity of the ceramic fiber felt is 70% - 90%; in the fourth implementation, the heat insulation layer 1 includes multiple layers of high-purity carbon fiber felt and ceramic fiber felt, and the high-purity carbon fiber felt and the ceramic fiber felt are alternately stacked, with the porosity of the high-purity carbon fiber felt being 60% - 80% and the porosity of the ceramic fiber felt being 70% - 90%. According to the characteristics of the temperature field of the Siemens process reduction furnace, the temperature uniformity in the reduction furnace can be controlled by changing the thickness gradient of the fiber felt in the axial direction; for example, along the axial direction, the thickness of the fiber felt can gradually increase or decrease from top to bottom, or the thickness of the fiber felt can gradually increase or decrease from the middle to both ends, and the specific design is based on the actual temperature field distribution.

[0053] Specifically, the high-purity and high-density carbon-ceramic composite material is carbon fiber reinforced carbon and silicon carbide dual matrix (C / C-SiC), with a density ≥ 95%, an open porosity ≤ 5%, and a metal impurity content ≤ 200 ppm.

[0054] As Figure 2 shown, in an implementation of this embodiment, the heat insulation layer 1 and the functional protection lining 2 are fixedly connected by a plurality of fasteners such as special screws 3. The heat insulation layer 1 is provided with mounting holes, and the functional protection lining 2 is provided with a number of corresponding threaded holes. The screw rod section of the special screw 3 passes through the mounting hole and is threadedly connected to the threaded hole. Among them, the special screw 3 is a carbon-carbon screw, a carbon-ceramic screw, or a ceramic screw. The surface of the special screw 3 is coated with a silicon carbide protective layer with a thickness of 10 - 200 μm to ensure its heat insulation performance.

[0055] As Figure 3 shown, in another implementation of this embodiment, the heat insulation layer 1 and the functional protection lining 2 are fitted. Specifically, a number of counterbores 4 are provided on the outer side wall of the functional protection lining 2, and the counterbores 4 are fitted with the inner side wall of the heat insulation layer 1; the counterbores 4 are surrounded by two upper and lower rings, the cross-section of the counterbores 4 is dovetail-shaped or trapezoidal, the depth of the counterbores 4 ≥ 1 mm, and the distance between two adjacent counterbores 4 ≥ 5 mm, that is, the thickness of the ring ≥ 5 mm. In actual process, the area and shape of the counterbores 4 can be adjusted according to the structure of the heat preservation cover.

[0056] The composite thermal insulation cover of this embodiment can be applied to a polysilicon Siemens reduction furnace, and is adapted to the temperature inside the furnace being 1000 - 1800 °C. The medium inside the furnace includes gases such as HCl, H2, or SiHCl3, etc.

[0057] This embodiment also provides a preparation method for a composite thermal insulation cover for a silicon crystal growth reduction furnace, which is used to prepare the above-mentioned composite protection cover. The preparation method includes the following steps:

[0058] Prepare the functional protection lining 2:

[0059] Adopt the reaction infiltration process (RMI process) or chemical vapor infiltration process (CVI process) or impregnation pyrolysis (PIP process) to form a silicon carbide matrix inside the carbon-carbon composite porous body to prepare the functional protection lining 2; or,

[0060] Adopt the chemical vapor infiltration process (CVI process) or impregnation / carbonization to prepare carbon-carbon composite (C / C), and adopt the chemical vapor deposition process (CVD process), brushing or spraying process to prepare a silicon carbide and / or silicon nitride coating to prepare the functional protection lining 2;

[0061] Prepare the heat insulation layer 1:

[0062] Make the heat insulation layer 1 with a ceramic fiber or carbon fiber having a predetermined porosity and thickness gradient;

[0063] Assembly:

[0064] Machine-process a counterbore 4 or drill holes on the outer surface of the functional protection lining 2, and use fasteners such as special screws 3 or embedded assembly to achieve the composite with the heat insulation layer 1.

[0065] In a specific embodiment, the functional protection lining 2 of this composite thermal insulation cover is prepared by the CVI process to form a C / C-SiC layer (density 97%, porosity 3%), with a thickness of 15 mm; the heat insulation layer 1 is a carbon fiber hard felt (porosity 70%, thickness 40 mm); connection method: mechanical locking with a carbon-carbon fastener (surface coated with a 30-μm silicon carbide coating); the actual effect of this composite thermal insulation cover: the axial temperature difference inside the furnace is ±8 °C, and the unit power consumption is reduced by 32%.

[0066] In another specific embodiment, the functional protection lining 2 of this composite thermal insulation cover is prepared by the RMI process to form a C / C-SiC layer (density 95%, porosity 5%), with a thickness of 20 mm; the heat insulation layer 1 is a ceramic fiber soft felt (porosity 85%, thickness 50 mm); connection method: embedded assembly of the counterbore 4 (depth of the counterbore 4 is 20 mm, spacing is 15 mm); the actual effect of this composite thermal insulation cover: the axial temperature difference inside the furnace is ±7 °C, and the unit power consumption is reduced by 45%.

[0067] As can be seen from the above, in this embodiment, through the collaborative innovation of materials-structure-process, the industry problems of low thermal efficiency, poor uniformity and insufficient material durability in the high-temperature thermal field management of polysilicon growth reduction furnaces are solved, providing core technical support for cost reduction and efficiency improvement in photovoltaic and semiconductor-grade polysilicon production.

[0068] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A composite heat-insulating cover for a reduction furnace for growing crystalline silicon, characterized in that, Comprising: A heat insulation layer (1) and a functional protection lining (2), the heat insulation layer (1) being provided on the outer side of the functional protection lining (2); The heat insulation layer (1) is made of high-purity fiber thermal insulation material or ceramic fiber thermal insulation material, the metal impurity content of the heat insulation layer (1) < 100 ppm, and the thermal conductivity ≤ 0.1 W / (m•K); The functional protection lining (2) is made of high-purity and high-density carbon-ceramic composite material, the metal impurity content of the high-purity and high-density carbon-ceramic composite material ≤ 200 ppm; or the functional protection lining (2) is made of carbon-carbon composite material and is provided with a silicon carbide coating and / or a silicon nitride coating on the surface.

2. The composite heat-insulating cover for a polysilicon growth reduction furnace according to claim 1, wherein: The thickness of the heat insulation layer (1) ≥ 2 mm.

3. The composite thermal insulation cover for a polysilicon growth reduction furnace according to claim 2, wherein: The heat insulation layer (1) is made of high-purity carbon fiber felt, and its porosity is 60% - 80%; or, The heat insulation layer (1) is made of ceramic fiber felt, and its porosity is 70% - 90%; or, The heat insulation layer (1) includes high-purity carbon fiber felt and ceramic fiber felt; the porosity of the high-purity carbon fiber felt is 60% - 80%, and the porosity of the ceramic fiber felt is 70% - 90%; or, The heat insulation layer (1) includes multiple layers of high-purity carbon fiber felt and ceramic fiber felt, and the high-purity carbon fiber felt and the ceramic fiber felt are alternately stacked, the porosity of the high-purity carbon fiber felt is 60% - 80%, and the porosity of the ceramic fiber felt is 70% - 90%.

4. The composite heat insulation cover for a reduction furnace for growing crystalline silicon as described in claim 1, wherein: The high-purity and high-density carbon-ceramic composite material is a carbon fiber reinforced carbon and silicon carbide dual matrix, its density ≥ 95%, the open porosity ≤ 5%, and the metal impurity content ≤ 200 ppm.

5. The composite thermal insulation cover for a polysilicon growth reduction furnace according to any one of claims 1-4, characterized in that: The heat insulation layer (1) and the functional protection lining (2) are fixedly connected by a plurality of special screws (3).

6. The composite heat-insulating cover for a polysilicon growth reduction furnace according to claim 5, wherein: The special screws (3) are carbon-carbon screws, carbon-ceramic screws or ceramic screws.

7. The composite thermal insulation cover for a polysilicon growth reduction furnace according to claim 6, characterized in that: The surface of the special screws (3) is coated with a silicon carbide protective layer with a thickness of 10 - 200 μm.

8. The composite heat-insulating cover for a reduction furnace for growing crystalline silicon according to any one of claims 1-4, characterized in that: The heat insulation layer (1) and the functional protection lining (2) are fitted, and a plurality of counterbores (4) are provided on the outer side wall of the functional protection lining (2), and the counterbores (4) are fitted with the inner side wall of the heat insulation layer (1).

9. The composite heat insulation cover for a polysilicon growth reduction furnace according to claim 8, characterized in that: The depth of the counterbore (4) ≥ 1 mm, and the distance between two adjacent counterbores (4) ≥ 5 mm.

10. A preparation method of a composite heat-insulating cover for a polysilicon growth reduction furnace, which is used to prepare the composite protective cover described in any one of claims 1-9, characterized in that, The preparation method includes the following steps: Preparing the functional protection lining (2): Using a reaction infiltration process, a chemical vapor infiltration process or an impregnation pyrolysis process to form a silicon carbide matrix inside a carbon-carbon composite porous body to prepare the functional protection lining (2); or, Using a chemical vapor infiltration process or an impregnation / carbonization to prepare a carbon-carbon composite material, and using a chemical vapor deposition process, a brushing or spraying process to prepare a silicon carbide and / or a silicon nitride coating to prepare the functional protection lining (2); Preparing the heat insulation layer (1): By making the ceramic fiber or carbon fiber into a heat insulation layer (1) with a predetermined porosity and thickness gradient; Assembly: Machining counterbores (4) or drilling holes on the outer surface of the functional protection lining (2), and using fasteners or embedded assembly to achieve the composite with the heat insulation layer (1).

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