WO2024027340A1 - 一种在流化床内壁设置硅涂层的方法 - Google Patents

一种在流化床内壁设置硅涂层的方法 Download PDF

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WO2024027340A1
WO2024027340A1 PCT/CN2023/099424 CN2023099424W WO2024027340A1 WO 2024027340 A1 WO2024027340 A1 WO 2024027340A1 CN 2023099424 W CN2023099424 W CN 2023099424W WO 2024027340 A1 WO2024027340 A1 WO 2024027340A1
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fluidized bed
silicon
gas
wall
silicon coating
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PCT/CN2023/099424
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English (en)
French (fr)
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朱共山
兰天石
常露露
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江苏中能硅业科技发展有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/02—Cleaning by the force of jets or sprays
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/08—Cleaning containers, e.g. tanks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/08—Cleaning containers, e.g. tanks
    • B08B9/083—Removing scrap from containers, e.g. removing labels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/08—Cleaning containers, e.g. tanks
    • B08B9/093—Cleaning containers, e.g. tanks by the force of jets or sprays
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/029—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of monosilane
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/03—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/035—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
    • C04B35/565—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B28/00—Production of homogeneous polycrystalline material with defined structure
    • C30B28/12—Production of homogeneous polycrystalline material with defined structure directly from the gas state
    • C30B28/14—Production of homogeneous polycrystalline material with defined structure directly from the gas state by chemical reaction of reactive gases
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B15/00—Fluidised-bed furnaces; Other furnaces using or treating finely-divided materials in dispersion
    • F27B15/02—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B15/14—Arrangements of heating devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B2203/00—Details of cleaning machines or methods involving the use or presence of liquid or steam
    • B08B2203/002—Details of cleaning machines or methods involving the use or presence of liquid or steam the liquid being a degassed liquid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B2209/00—Details of machines or methods for cleaning hollow articles
    • B08B2209/02—Details of apparatuses or methods for cleaning pipes or tubes
    • B08B2209/027—Details of apparatuses or methods for cleaning pipes or tubes for cleaning the internal surfaces

Definitions

  • the present invention relates to equipment and methods for preparing polycrystalline silicon, in particular to equipment and methods for preparing granular silicon through fluidized bed equipment, and specifically to a method of providing a silicon coating on the inner wall of a fluidized bed.
  • Granular polysilicon is an extremely popular form of polysilicon product in recent years, also known as granular silicon. Compared with rod-shaped polycrystalline silicon, granular silicon is spherical in shape and smaller in size. It can be used directly in downstream processes, eliminating the need for crushing, saving process costs and avoiding the possibility of introducing contamination from the crushing device during the crushing process. . On the other hand, granular silicon products have better fluidity and can be used in automated production to improve production efficiency. The most critical thing is that the process for producing granular silicon consumes less energy, which is more environmentally friendly and increases the gross profit margin of granular silicon products.
  • Fluidized bed is a common equipment used to produce granular polysilicon.
  • Raw materials for production include silicon-containing gases such as monosilane (SiH 4 ), silicon tetrachloride (SiCl 4 ), trichlorosilane (SiHCl 3 ), dichlorosilane (SiH 2 Cl 2 ), etc. These silicon-containing raw materials are flowing
  • the polycrystalline silicon is heated and decomposed or reduced in the fluidized bed, and the polycrystalline silicon produced deposits and grows on the surface of the fine silicon particles (also called "seed crystals") in the fluidized bed, thereby producing granular polycrystalline silicon products.
  • the seed crystals added to the bed and the gradually grown granular silicon products are in a "fluidized” state floating up and down inside the bed under the action of the fluidizing gas flowing into the fluidized bed. This is why the fluidized bed gets its name.
  • the materials of the fluidized bed include silicon carbide, graphite, silicon dioxide, silicon nitride, quartz, boron nitride and other inorganic materials, and can also be tungsten carbide, molybdenum, nickel alloy and other metal materials.
  • the purity of solar-grade polysilicon products is generally required to be above 99.9999%.
  • the granular silicon since the granular silicon itself is in a fluidized state, it will constantly rub against the lining of the fluidized bed, leading to the introduction of contamination of the lining material and greatly reducing the purity of the granular silicon product. If the purity of the granular silicon products produced in a certain period of time is not enough, it will directly affect the product quality of the entire production cycle.
  • US5405658A discloses a preparation scheme for a silicon coating on the inner wall of a fluidized bed. This scheme first introduces polysilicon particles into the fluidized bed, and then heats the particles to 900 to 1300°C. At this temperature , polycrystalline silicon particles have good electrical conductivity. A changing magnetic field is then applied to these particles, and a silicon protective layer is formed inside the fluidized bed through the changing magnetic field. The silicon coating formed in this way is not easy to fall off.
  • this solution has high requirements for heating temperature and heating equipment, consumes a lot of energy, and is difficult to apply industrially.
  • the Chinese patent application document with publication number CN109453729A discloses a protective layer on the inner wall of the fluidized bed.
  • the protective layer contains 4-30% Mo, 5-25% Cr, 2-15% Co, ⁇ 3.5% Ti, ⁇ 2% Nickel-based superalloys of Fe, ⁇ 2% Al, ⁇ 1% Mn, ⁇ 1% Si, ⁇ 0.5% Cu, ⁇ 0.1% C, ⁇ 0.1% Zr, ⁇ 0.01% B and 23.4-89% nickel, and have Average thickness from 0.1mm to 1mm. Adopting this solution will still inevitably bring contamination of impurity elements to granular silicon products.
  • the raw material gas, working temperature, etc. are basically the same as those of normal particles.
  • the silicon production process remains the same, but no seed crystals are added to the inside of the fluidized bed.
  • the silicon-containing raw gas generates high-purity elemental silicon at high temperatures and adheres to the inner wall of the fluidized bed, achieving a high-purity silicon coating on the inner wall of the fluidized bed.
  • the fluidizing gas is usually introduced into the fluidized bed through a gas distributor provided at the bottom of the fluidized bed, the gas flow rate at the bottom of the fluidized bed is the fastest, resulting in The driving force is the largest, and the granular silicon is concentrated at the bottom due to gravity, causing the granular silicon at the bottom of the fluidized bed to move more violently, and the friction between the particles and between the particles and the inner wall is also more intense. Therefore, the bottom of the fluidized bed
  • the silicone coating on the inner wall is more susceptible to wear.
  • the process of silicon coating inside the fluidized bed is a pre-production process, which itself will not bring about output.
  • the result of such a silicon coating scheme is that the thickness of the silicon coating is thickest in the middle of the fluidized bed. Within a certain silicon coating time, the most worn position at the bottom of the fluidized bed cannot be protected by a sufficient thickness of silicon coating. If the silicon coating at the bottom of the fluidized bed wears away, there is a risk of contamination of the granular silicon product. In addition, due to the phenomenon of silicon deposition on the inner wall of the granular silicon production process, the silicon coating in the middle of the fluidized bed will become thicker and thicker, further deteriorating the uniformity of the silicon coating on the inner wall of the fluidized bed and creating the risk of falling off. And reduce the mechanical stability of the bed.
  • the present invention relates to a method for providing a silicon coating on the inner wall of a fluidized bed, which includes: the step of introducing a silicon coating reaction gas into the inside of the fluidized bed.
  • the silicon coating reaction gas includes silane and hydrogen, and silane and The molar ratio of hydrogen is 0.2% to 8%, and the flow rate of the silicon coating reaction gas is 0.3m/s to 1.5m/s; in the step of heating the fluidized bed, the heating temperature range of the inner wall of the fluidized bed is 300 to 900°C. ;
  • the silicon coating tail gas is the gas after the silicon coating reaction gas reacts inside the fluidized bed.
  • the silicon-coated reaction gas is introduced into the fluidized bed from the integrated air inlet of the fluidized bed, which is the inlet of the silicon-containing raw material gas under normal production conditions of the fluidized bed.
  • the step of introducing the silicon-coating reaction gas into the fluidized bed also includes: introducing the silicon-coating reaction gas through a gas distributor arranged at the bottom of the fluidized bed, and the silicon-coating reaction gas approaches the inner wall of the fluidized bed from the gas distributor. position leads into the fluidized bed.
  • the step of heating the fluidized bed further includes: providing a first alternating current to a first heating coil disposed at the lower part of the fluidized bed, and providing a second alternating current to a second heating coil disposed at the lower part of the fluidized bed. current; the second heating coil is located above the first heating coil; the effective value of the second alternating current is smaller than the effective value of the first alternating current.
  • the method of providing a silicon coating on the inner wall of the fluidized bed also includes the step of etching the silicon deposited on the inner wall of the fluidized bed before the step of passing the silicon coating reaction gas into the inside of the fluidized bed.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes the step of purifying the inner wall of the fluidized bed.
  • the purifying step includes using chlorine-containing liquid to clean the inner wall of the fluidized bed, and removing the liquid from the fluidized bed.
  • Product discharge port and/or integrated air inlet and/or fluidizing gas at the bottom Exhaust from the body air inlet.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes the step of purifying the inner wall of the fluidized bed.
  • the purifying step includes the step of purging the inner wall of the fluidized bed with high-flow purge gas;
  • the flow rate of the scavenging gas is greater than or equal to 5m/s.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes the step of heating the inner wall of the fluidized bed to a preheating temperature before passing the silicon coating reaction gas into the inside of the fluidized bed; the preheating temperature range is 600°C ⁇ 1200°C.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes the step of arranging a transition material on the inner wall of the fluidized bed after etching the deposited silicon on the inner wall of the fluidized bed; the linear thermal expansion coefficient of the transition material is between between the inner wall material of the bed and silicon.
  • the method of providing a silicon coating on the inner wall of the fluidized bed also includes the step of closing the seed crystal inlet of the fluidized bed before the step of introducing the silicon coating reaction gas into the inside of the fluidized bed.
  • the thickness of the thinnest part of the silicon coating is greater than or equal to 5 ⁇ m, and the thickness of the thickest part of the silicon coating is less than or equal to 500 ⁇ m.
  • the molar ratio of silane to hydrogen is 0.2% to 5%.
  • the flow rate of the silicon coating reaction gas is 0.3m/s ⁇ 0.8m/s.
  • the heating temperature range of the inner wall of the fluidized bed is 400°C to 800°C.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes: the step of preheating the silane gas, the preheating temperature of the silane gas is 50-200°C; the step of preheating the hydrogen gas, the preheating of the hydrogen gas.
  • the temperature is 300-600°C; in the step of mixing the preheated silane gas and hydrogen, the temperature of the mixed gas is 200-500°C.
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes the steps of calculating the amount of silane gas consumed; comparing the amount of silane gas consumed with a threshold, and when the amount of silane gas consumed is greater than or equal to the threshold, Stop flowing the silicon coating reaction gas into the fluidized bed; the steps for calculating the amount of silane gas consumed include: obtaining the molar amount of silane gas flowing into the fluidized bed at time t, and obtaining the first silane gas content value; obtaining the coating amount at time t
  • the molar amount of silane gas in the silicon tail gas is used to obtain the second silane gas content value; the difference between the first silane gas content value and the second silane gas content value at time t is calculated to obtain the silane gas consumption function f(t); according to ⁇
  • the specific values of the silane gas consumption function are obtained at each time interval of t; the integral of the silane gas consumption function f(t) over time under the ⁇ t interval is calculated to obtain the amount of
  • the method of arranging a silicon coating on the inner wall of the fluidized bed also includes: reading the temperature of the silicon-removal tail gas at the first moment to obtain the first tail gas temperature value; detecting the temperature of the silicon-removal tail gas at the second moment to obtain the second Exhaust gas temperature value; calculate the temperature difference between the first exhaust gas temperature value and the second exhaust gas temperature value. When the temperature difference is greater than the temperature threshold, stop flowing the silicon coating reaction gas into the fluidized bed.
  • Figure 1 shows an embodiment of a fluidized bed apparatus for granular polysilicon production
  • Figure 2 shows a schematic diagram of a gas distributor in a fluidized bed equipment for granular polysilicon production
  • Figure 3 shows another embodiment of a fluidized bed apparatus for granular polysilicon production.
  • connection includes various connection methods, including direct connection and indirect connection, which do not require physical contact between the various parts being connected, including snap connections, screw connections, and connections without fixed devices.
  • connection methods including connection, welding, riveting and one-piece molding.
  • fit clearance includes fit relationships such as clearance fit, transition fit, interference fit or variable clearance.
  • the fluidized bed 100 is the core device of the entire granular silicon production equipment.
  • the fluidized bed 100 includes a bed body 101.
  • the bed body 101 is made of hard and Materials that are easy to process include inorganic materials such as silicon carbide, graphite, silicon dioxide, silicon nitride, quartz, and boron nitride, as well as metal materials such as tungsten carbide, molybdenum, and nickel alloys.
  • the bed 101 forms a space for accommodating reaction raw materials and providing a space for accommodating reaction products. After the silicon-containing raw material gas enters this space, it is heated, undergoes thermal decomposition or reduction reaction, and generates granular polysilicon in this space.
  • the polysilicon product When the polysilicon product reaches a certain amount, the polysilicon product will be discharged from the fluidized bed through the product discharge pipe 104. Excreted from the body.
  • the bed 101 has a certain height and its cross-section is generally circular. The circular cross-section can make the heating of the silicon-containing raw material gas more uniform and make it easier to shape during the manufacturing process.
  • the bed 101 is provided with multiple gas inlets and outlets.
  • the comprehensive air inlet 102 is located at the bottom of the bed 101, and the other end of the bed 101 is connected to a gas supply device.
  • the gas supply device can supply raw material gases including granular silicon production.
  • gases including silicon coating gas for coating the inner wall of the fluidized bed with silicon and etching gas for depositing silicon on the inner wall of the fluidized bed.
  • the integrated air inlet 102 is connected to an integrated air inlet valve (not shown in the figure), and the integrated air inlet valve functions to close and/or switch the gas passage of the integrated air inlet 102 .
  • the raw material gas includes silicon-containing gases such as monosilane (SiH 4 ), silicon tetrachloride (SiCl 4 ), trichlorosilane (SiHCl 3 ), dichlorosilane (SiH 2 Cl 2 ), etc.
  • silicon-containing gases such as monosilane (SiH 4 ), silicon tetrachloride (SiCl 4 ), trichlorosilane (SiHCl 3 ), dichlorosilane (SiH 2 Cl 2 ), etc.
  • These gases can Generally called silane, in the embodiment of the present invention, monosilane (SiH 4 ) is mainly used as the raw material gas.
  • Monosilane can be prepared by various production processes including metal hydride method, silicon-magnesium alloy method, and trichlorosilane disproportionation method.
  • the bottom of the bed 101 is also provided with a fluidizing gas inlet 103.
  • the fluidizing gas is used to blow the silicon particles (seed crystals) inside the fluidized bed into a fluidized state. In this state, it contains The silicon raw material gas can fully and evenly contact the surface of the silicon particles (seed crystals), and generate elemental silicon on the surface of the silicon particles (seed crystals) to avoid adhesion between particles.
  • the fluidization gas can be selected from a variety of gases including nitrogen, argon, and helium. The principle of selecting this type of fluidization gas is that it does not react with the raw material gas in the fluidized bed or the material components of the bed.
  • the fluidizing gas can directly use raw material gas (including silane, chlorosilane, hydrogen chloride, etc.) or reducing gas (such as hydrogen). Although these gases participate in the reaction process, the reaction products of these gases will not be introduced. Other impurity elements.
  • the intake volume of the silicon-containing raw material gas and the fluidizing gas is maintained at a gas flow rate of 1.5 to 4.0 Umf.
  • the proportion of the silicon-containing raw material gas there is no limit to the proportion of the silicon-containing raw material gas.
  • the molar proportion of silane in the silicon-containing raw gas can be 10 mol% to 80 mol%, and the remainder is fluidizing gas (such as hydrogen, etc.).
  • a seed crystal inlet 105 is provided at the top of the bed 101 for providing seed crystals as cores of deposited silicon into the bed.
  • the particle size of granular silicon seed crystals is usually 50 to 1000 ⁇ m.
  • An exhaust gas outlet 107 is provided at the top of the bed 101. Since the raw material gas in the bed 101 flows upward after being heated, providing an exhaust gas outlet at the top of the bed 101 can more completely collect the production exhaust gas, silicon coating exhaust gas, and The etching exhaust gas is discharged, so that the exhaust gas can be processed and utilized.
  • the space formed by the bed 101 is roughly divided into a lower part 1011 and an upper part 1012 in the vertical direction.
  • the bottom of the fluidized bed is located at the lower part of the bed, and the top is located at the upper part of the bed.
  • the lower part of the fluidized bed is generally equipped with a heating device for heating the inner wall of the fluidized bed and the materials in the fluidized bed.
  • the air inlet 102 enters the interior of the bed The space moves upward to the upper part 1012 after the lower part 1011 is heated by the heating device.
  • the raw material gas, silicon coating gas, and etching gas undergo sufficient reactions in the fluidized bed and are discharged through the tail gas outlet 107.
  • a gas distributor 106 is provided at the lower part 1011 of the bed 101, and a connecting device or connecting portion is provided between the gas distributor 106 and the bed 101 for fixing the gas distributor to prevent gas
  • the distributor generates displacement within the bed.
  • the cross section of the bottom of the heating zone of the bed 101 is circular, and the shape of the gas distributor 106 is also circular.
  • the gas distributor 106 is connected to the fluidizing gas inlet 103 and forms a gas path.
  • the fluidizing gas inlet 103 is not provided on the fluidized bed, and the integrated gas inlet 102 is connected to the gas distributor 106. Create a path for gas.
  • a plurality of gas outlets are provided on the gas distributor 106.
  • the raw material gas, silicon coating gas or etching gas enters the gas distributor 106 through the integrated gas inlet 102 and/or the fluidizing gas inlet 103, and then passes through the gas distributor 106. Spray out from the vent.
  • the gas distributor is used to redistribute the raw material gas entering the bed, so that the raw material gas, silicon coating gas or etching gas can be distributed in the bed according to a specific flow direction and flow rate.
  • the use of a gas distributor can directly use the raw gas as a fluidizing gas.
  • the so-called fluidizing gas functions to pass through the solid particles inside the bed from bottom to top, so that the solid particles are moved under the thrust of the fluid. An upward force is generated.
  • the material of the gas distributor 106 includes quartz, silicon carbide, silicon nitride or elemental silicon. Using such non-metallic materials can avoid introducing metal element impurities into the granular silicon products and improve the quality of the granular silicon products. In order to reduce impurity elements introduced by the gas distributor, the surface of the gas distributor can also be coated with elemental silicon.
  • the gas distributor is provided with a plurality of openings, wherein the openings 1061 located inside the gas distributor are used for the passage of the raw material gas and/or the fluidizing gas.
  • This part The openings are far away from the inner wall of the fluidized bed, which can reduce the contact between the raw material gas and the inner wall of the fluidized bed, and reduce the deposition of elemental silicon on the inner wall of the fluidized bed.
  • the opening 1062 located at the edge of the gas distributor is used for the passage of silicon coating gas and/or etching gas.
  • the opening 1062 is closer to the inner wall of the fluidized bed. After the etching gas enters the bed through the opening, it can fully contact the inner wall of the fluidized bed. , improve the etching effect.
  • the opening in the center of the gas distributor is used to connect the product discharge pipe 104 .
  • the heating zone adopts induction heating.
  • a heating device 108 is provided at the bed position corresponding to the heating zone.
  • the heater 108 moves from outside to inside. They are the coil and the metal flux structure in turn.
  • an alternating current is provided to the coil to generate an alternating magnetic field.
  • the alternating magnetic field induces eddy currents in the metal magnetic flux structure, and the metal is heated under the action of the eddy current.
  • the magnetic flux structure then conducts heat to the interior of the bed.
  • no metal magnetic flux structure is provided, and an induced eddy current is directly generated in the shell of the bed to generate heat.
  • Induction heating has the characteristics of simple product structure, high thermal efficiency, and the ability to heat the silicon particles themselves.
  • various heating methods such as thermal resistance heating, microwave heating, and radiation heating can also be used to heat the fluidized bed and/or the materials in the fluidized bed.
  • the bottom of the bed 101 adopts an inclined design to form a slope. Through such an arrangement, the granular silicon product can be made to move downward along the inclined slope.
  • the rolling collection makes the process of discharging the granular silicon product from the product discharge pipe 104 smoother.
  • FIG. 3 is another embodiment of the fluidized bed of the present invention.
  • the fluidized bed 200 includes a bed body 201.
  • the bed body 201 has a lower part 2011 and an upper part 2012.
  • the bottom of the bed body 201 is provided with a comprehensive air inlet 202, a product discharge port 204 and a fluidizing gas inlet 203.
  • the top of the bed body is provided with a The seed crystal inlet 205 and the exhaust gas outlet 207.
  • An induction heating device 208 is provided at the lower part of the bed.
  • the induction heating device includes a first coil 2081 and a second coil 2082.
  • the second coil is disposed above the first coil. Using this segmented heating device, the heating power of the first coil and the second coil can be controlled respectively, thereby controlling the temperature gradient inside the fluidized bed.
  • the inner wall surface is flat and smooth and can be directly coated with silicone or pre-coated.
  • elemental silicon will be deposited on the inner wall of the fluidized bed to form a gradually thickening junction silicon layer.
  • the thickness, density, and voids of this junction silicon layer etc. are very uneven and cannot be directly coated with silicone on them. Therefore, the deposited silicon on the inner wall of the used fluidized bed needs to be etched first to obtain a relatively flat inner wall.
  • chlorine-containing gases such as silicon tetrachloride (SiCl 4 ), hydrogen chloride (HCl) and chlorine (Cl 2 ) can be used to react with the silicon deposited on the inner wall of the fluidized bed to etch.
  • Physical removal methods such as tapping and peeling after shutdown can also be used to remove the silicon blocks deposited on the inner wall of the fluidized bed.
  • the inner wall of the fluidized bed is purified to remove grease, fine silicon powder or other impurities adhering to the inner wall of the fluidized bed.
  • As a method of purifying the inner wall of the fluidized bed it includes using liquid hydrogen chloride, silicon tetrachloride, etc. to clean the inner wall of the fluidized bed, and collecting the cleaned liquid from the product discharge pipe or the pipe of the gas distributor. mixture. Through such liquid cleaning, impurities such as grease and fine silica powder on the inner wall of the fluidized bed can be removed.
  • high-temperature inert gas is used to purge the inner wall of the fluidized bed at a high flow rate, and impurities such as grease and fine silicon powder on the inner wall of the fluidized bed are purged away from the inner wall of the fluidized bed.
  • the components of the purge gas can be nitrogen, hydrogen, chlorine, hydrogen chloride, etc. or inert gases such as helium and argon.
  • the flow rate of purge gas used for purification is generally above 5m/s.
  • a gas distributor as shown in Figure 2 can be used to control the flow direction of the purge gas.
  • the purge gas flows out from the purge hole 1062 close to the inner wall of the fluidized bed and close to the fluidized bed. The inner wall moves upward to achieve a better purging effect.
  • silicon can be directly coated on the inner walls of these materials.
  • the thermal expansion coefficient is similar to that of silicon material, it can improve the adhesion of elemental silicon on the inner wall and prevent the silicon coating from falling off.
  • thermal expansion coefficient of the material is greatly different from that of silicon, temperature changes during the production process of silicon coating or granular silicon will cause cracks in the silicon coating on the inner wall, causing the silicon coating to fall off and affecting the fluidized bed.
  • Mechanical strength Therefore, for the inner wall of the fluidized bed of metal materials, it needs to be pre-coated in advance, and a transitional expansion pre-coating is provided on the inner wall.
  • the thermal expansion coefficient of the transition material used in the pre-coating is between that of the metal material of the inner wall and that of the elemental material.
  • the inner wall of the fluidized bed is made of Incoloy800H
  • a layer of transition material on the inner wall of the fluidized bed such as 80% Ni20% Cr, with a coating thickness of 50 ⁇ 100um
  • the silicon on the pre-coat Coating since the thermal expansion coefficient of the pre-coating is between that of nickel alloy and silicon, it can buffer the thermal expansion and avoid cracking and falling off of the silicon coating due to excessive thermal expansion difference.
  • the thickness of the silicon coating is one consideration, and the bonding strength of the silicon coating and the lining is also another important consideration.
  • the bonding strength between the silicon coating and the lining mainly depends on the bonding strength between the microscopic atoms between the silicon coating and the lining.
  • a pre-coat of elemental silicon can also be set on the inner wall of the fluidized bed: the fluidized bed is evacuated or the fluidized bed is filled without reacting with the material on the inner wall of the fluidized bed or with particles.
  • the silicon product introduces impurity gases, including nitrogen, hydrogen, chlorine, hydrogen chloride and other gases or inert gases such as helium and argon, and then heats the inner wall of the fluidized bed to 600°C to 800°C. When the inner wall of the fluidized bed is heated to this specific temperature, the silicon coating gas is then introduced into the fluidized bed.
  • the elemental silicon generated on the surface of the fluidized bed can form an alloy-like structure similar to a solid solution or a metal compound with the inner wall material of the fluidized bed.
  • the high-purity silicon pre-coating generated on the inner wall of the fluidized bed layer This kind of simple silicon pre-coating has high density and can fit closely with the inner wall. Setting an ordinary silicon coating on the simple silicon pre-coating can prevent the silicon coating from being damaged due to vibration, friction, etc.
  • a silicon coating on the inner wall of the fluidized bed mainly utilizes the cracking reaction of silane.
  • silane SiH 4
  • the typical reaction of the inner wall silicon coating process is:
  • the reaction of silane requires a certain temperature to proceed.
  • monosilane SiH 4
  • it has begun to decompose at a temperature of 300 to 400°C.
  • the Tammann Temperature of silicon is 0.52, it is low.
  • Silicon can only decompose into amorphous silicon at 600°C; in the normal production process of granular silicon, the reaction temperature of monosilane is controlled to be 600°C to 800°C. Therefore, the gas temperature needs to be heated to a certain level to start the reaction process of silane to generate crystalline silicon.
  • too high a temperature will cause a large amount of silane to decompose in the gas phase, generating a large amount of silicon powder, resulting in a non-dense coating.
  • reaction gas for inner wall silicon coating before the reaction gas for inner wall silicon coating enters the fluidized bed, it is preheated so that after entering the fluidized bed, it can start to react directly on the inner wall at the bottom of the fluidized bed to produce a product with a certain thickness.
  • silicone coating In this embodiment, silane and hydrogen are preheated separately. Taking monosilane (SiH 4 ) as an example, preheat it to 50 to 200°C, preheat the hydrogen to 300 to 600°C, and then mix the preheated silane and hydrogen. The temperature of the mixed gas is 100 ⁇ 500°C.
  • monosilane and hydrogen are preheated separately, and the preheating temperature of monosilane is set lower than its decomposition temperature, and then mixed with high-temperature hydrogen and quickly enters the fluidized bed, which can improve the silicon coating on the inner wall of the fluidized bed. layer reaction effect.
  • preheated and mixed silicon coating reaction gas is introduced from the gas inlet 102 at the bottom of the fluidized bed.
  • the silicon coating reaction gas includes mixed silane and hydrogen, and the molar ratio of silane and hydrogen is 0.2% to 8%.
  • the use of this low silicon content silicon coating reaction gas can avoid the formation of excessively thick silicon layers or silicon blocks in high gas concentration and high temperature areas in the fluidized bed, making the silicon coating on the inner wall of the fluidized bed more uniform and reducing the cost.
  • the decomposition ratio of silane gas in the gas phase in the fluidized bed allows more silane gas to react on the inner wall of the fluidized bed, improving the utilization rate of the silicon coating reaction gas.
  • the lower limit of the flow rate of the silicon coating reaction gas entering the fluidized bed is 0.3m/s, preferably 0.5m/s, and more preferably 0.8m/s.
  • the upper limit of the flow rate of the silicon coating reaction gas entering the fluidized bed is 1.8m/s, preferably 1.5m/s, and more preferably 1.3m/s. If the flow rate of the silicon-coating reaction gas is within the upper limit, the silicon-coating reaction gas can stay in the lower part of the fluidized bed for a relatively long time, thereby forming a relatively thick high-purity silicon coating in the lower part of the fluidized bed.
  • the granular silicon in the lower part of the fluidized bed moves chaotically driven by the fluidizing gas and rubs against the silicon coating on the inner wall of the fluidized bed. Therefore, a relatively thick high-purity layer is formed in the lower part of the fluidized bed.
  • the silicon coating can avoid the exposure of the lower wall of the fluidized bed caused by the friction of silicon particles in the early stage of granular silicon production.
  • the silicon-containing raw material gas will be deposited on the inner wall, offsetting the damage caused by the friction of the inner wall. Loss of silicone coating.
  • the flow rate of the silicon coating reaction gas is within the upper limit, which can ensure that the inner wall will not be exposed during the entire production cycle and avoid contamination of impurity elements to the granular silicon products.
  • the flow rate of the silicon-coating reaction gas is greater than the lower limit, which enables the silicon-coating reaction gas to have a certain initial velocity at this flow rate. After the silicon-coating reaction gas is further heated in the fluidized bed, it will move upward at a relatively higher speed. Movement, the movement of the silicon-coating reactant gas can prevent the silicon-coated reactant gas from being completely reacted in the lower part of the fluidized bed and failing to form a silicon coating of appropriate thickness in the upper part of the fluidized bed or other locations.
  • a high-purity silicon coating can be formed on the entire inner wall of the fluidized bed, and a relatively thick silicon coating can be formed at the lower part of the fluidized bed, which avoids the production process.
  • the inner wall is exposed due to particle friction.
  • the flow rate of the silicon coating reaction gas in the pipeline ranges from 0.3 to 1.8 m/s, preferably from 0.5 to 1.5 m/s, and more preferably from 0.8 to 1.3 m/s.
  • induction heating is used to heat the inner wall of the fluidized bed and the internal materials.
  • the heating method of the fluidized bed can also be a resistance heating method, a boiler heating method, or other heating methods.
  • the induction heating device includes two heating positions, where the first heating position is located at a lower position relative to the second heating position. In the process of preparing high-purity silicon pre-coating and fluidized bed inner wall silicon coating, the first heating position The temperature is higher than the second heating position.
  • the coating entering the fluidized bed can
  • the silicon reaction gas is heated to the reaction temperature as soon as possible and begins to react in the lower part of the fluidized bed, ensuring that a relatively thick silicon coating can be formed in the lower part of the fluidized bed.
  • the concentration of the silicon-coating reaction gas decreases, and it is further heated at the second heating position and moves to the upper part of the fluidized bed.
  • the temperature of the silicon-coating reaction gas rises again and further reacts in the upper part of the fluidized bed.
  • the remaining silicon coating tail gas is discharged from the top of the fluidized bed.
  • the thickness of the silicon coating in the lower part of the fluidized bed can be greater than that in the upper part of the fluidized bed, and because the temperature of the gas moving to the upper part of the fluidized bed is higher, although the concentration is reduced, the gas is flowing in the fluidized bed.
  • the upper part of the fluidized bed can still be fully reacted, so that the silane gas content in the tail gas finally discharged from the fluidized bed is relatively small, which improves the overall utilization of the silicon coating gas.
  • the thickest part of the silicon coating at the bottom of the fluidized bed is 100 to 500 ⁇ m, and the thinnest part of the silicon coating at the upper part of the fluidized bed is 5 to 50 ⁇ m.
  • the thickness of the silicon coating on the inner wall of the fluidized bed Gradient, on the one hand, the entire inner wall of the fluidized bed can be fully coated with silicon to avoid contamination of the inner wall material elements.
  • the thickest silicon coating thickness can be set at the most worn parts of the inner wall of the fluidized bed to avoid friction bands. The inner wall material of the fluidized bed is exposed.
  • the exhaust gas outlet pipe 104 is set at the top of the fluidized bed.
  • the tail gas can be discharged from the fluidized bed through the tail gas outlet.
  • the tail gas generated during the silicon coating process is mainly a mixture of silane gas and hydrogen.
  • the preheating temperature of the silicon coating gas and the power of the fluidized bed heating device are kept constant, and the temperature of the silicon coating exhaust gas generated during the silicon coating process is detected. Since the silicon-coated gas is introduced into the fluidized bed and the heating device is in normal working condition, the temperature of the exhaust gas will rise rapidly, then enter a relatively stable temperature stabilization stage, and then the temperature will gradually decrease. Entering the temperature drop stage. The temperature rise is mainly due to the introduction of preheated gas and the heat generated by the fluidized bed heating device, which is transferred to the exhaust gas outlet with the rising air flow.
  • the temperature of the exhaust gas When the increase or decrease in heat inside the fluidized bed reaches a balanced state, the temperature of the exhaust gas will enter. a relatively stable stage. Then, as the silicon deposited on the inner wall of the fluidized bed gradually becomes thicker, the heating efficiency of the fluidized bed heating device on the inner wall of the fluidized bed, especially the gas in the fluidized bed, will decrease. At the same preheating temperature of the silicon coating gas and the same When the power of the fluidized bed heating device is increased, the temperature of the silicon coating exhaust gas will gradually decrease. Detect the exhaust gas temperature during the temperature stabilization stage to obtain the first exhaust gas temperature detection value. Detect the exhaust gas temperature during the temperature reduction stage to obtain the second exhaust gas temperature detection value.
  • the second exhaust gas temperature detection value is lower than the first exhaust gas temperature detection value by 3°C and below, it is considered that the inner wall of the fluidized bed has been completely coated with silicon coating, and the thickness of the inner wall of the fluidized bed, especially the lower section of the fluidized bed (generally including the heating area), has reached the requirements.
  • the reaction process of the silicon-coating gas mainly depends on the effective reaction area of the inner wall of the fluidized bed, regardless of whether the inner wall is equipped with a silicon coating and regardless of the thickness of the silicon coating, the reaction rate and extent of the silicon-coating gas will depend on the entire silicon coating. The process remains basically stable, and it is difficult to judge the completion of the silicon coating process through the content of silane gas or other gases in the exhaust gas.
  • the state of the silicon coating on the inner wall of the fluidized bed can be obtained relatively accurately, and on the other hand, the thickness of the silicon coating on the inner wall of the heating zone provided at the lower part of the fluidized bed can be directly reflected.
  • the silicon coating operation can be switched to the normal granular silicon production process, including: introducing the silicon-containing raw material gas used in the normal production process into the fluidized bed, and controlling the power of the fluidized bed heating device to normal production. power, and at the same time inject seed crystals into the fluidized bed to start the normal granular silicon production process.
  • this switching method there is no need to When the machine is shut down, it can be immediately switched to the normal granular silicon production process, which improves production efficiency.
  • silane content in the silicon coating exhaust gas at point 104 is obtained, and the difference between the silane content in the silicon coating raw material gas and the discharged silicon coating exhaust gas is obtained, and the difference between the silicon coating raw material gas and the discharged silicon coating exhaust gas detected at time t is defined.
  • the difference in silane content in the silicon tail gas is f(t), which reflects the amount of silane gas used to generate the silicon coating on the inner wall of the fluidized bed at a specific moment.
  • the time interval between each exhaust gas detection is ⁇ t, using the formula: ⁇ f(t) ⁇ t
  • the amount of silane gas consumed to generate the silicon coating on the inner wall of the fluidized bed is obtained.
  • Different thresholds are set according to different inner wall areas of the fluidized bed. When the integrated amount of consumed silane gas exceeds the threshold, it is considered that the inner wall of the fluidized bed has been coated with a silicon coating of appropriate thickness, and it can be stopped at this time.
  • the silicon coating operation may be directly switched to passing the silicon-containing raw material gas used in the normal production process and adding seed crystals into the fluidized bed. Through this integration method, the thickness of the silicon layer on the inner wall of the fluidized bed can be judged more accurately.
  • the fluidized bed equipment listed in the examples and comparative examples of the present invention is Jiangsu Zhongneng GCL-GEN5035 model fluidized bed.
  • the heating method of this model of fluidized bed is electromagnetic coil induction heating, and the lining material is graphite.
  • the silane gas used is monosilane (SiH 4 ) produced by Jiangsu Zhongneng and prepared through a disproportionation reaction method. Its purity is 6N (greater than or equal to 99.9999%).
  • the hydrogen used is prepared through natural gas cracking method, and its purity is 6N (greater than or equal to 99.9999%).
  • the flow meter used to measure the air inlet of the fluidized bed is a CMF model flow meter produced by Emerson Company, with a range of 0 to 100kg/h.
  • the thermometer used to measure the exhaust gas temperature is a K-grading thermometer produced by Anhui Tiankang, with a range of 0 to 1000°C.
  • the fluidized beds targeted in the following examples or comparative examples are brand-new equipment or fluidized beds that use hydrogen chloride (HCl) to etch the deposited silicon on the inner wall of the fluidized bed and the etching is completed.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 5%
  • the gas flow rate is 0.3m/s
  • the tail gas stabilization stage temperature is 600°C
  • the minimum thickness of the silicon coating in the lower part of the fluidized bed (including the heating area) is 153 ⁇ m
  • the maximum thickness is 189 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 43 ⁇ m and a maximum thickness of 70 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of silane in silicon coating reaction gas The Er ratio is 3%, the gas flow rate is 0.5m/s, the exhaust gas stable stage temperature is 600°C, and it took a total of 35.2 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 180 ⁇ m, and the maximum thickness is 210 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 64 ⁇ m and a maximum thickness of 78 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 2%, the gas flow rate is 1.2m/s, the tail gas stabilization stage temperature is 700°C, and it takes 25.6 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 355 ⁇ m, and the maximum thickness is 400 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 41 ⁇ m and a maximum thickness of 63 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 0.2%
  • the gas flow rate is 1.5m/s
  • the temperature of the tail gas in the stable stage is 500°C
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 296 ⁇ m
  • the maximum thickness is 315 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 52 ⁇ m and a maximum thickness of 75 ⁇ m.
  • the silicon-coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 5%
  • the gas flow rate is 0.8m/s
  • the temperature of the tail gas in the stable stage is 600°C
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 234 ⁇ m
  • the maximum thickness is 350 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 70 ⁇ m and a maximum thickness of 110 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 5%
  • the gas flow rate is 0.8m/s
  • the tail gas stabilization stage temperature is 600°C, and it takes 16.9 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 252 ⁇ m
  • the maximum thickness is 337 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 61 ⁇ m and a maximum thickness of 99 ⁇ m.
  • the silicon coating reaction gas is passed into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 5%
  • the gas flow rate is 0.8m/s
  • the tail gas stabilization stage temperature is 400°C
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 199 ⁇ m
  • the maximum thickness is 373 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 95 ⁇ m and a maximum thickness of 152 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 8%, the gas flow rate is 0.5m/s, the tail gas stable stage temperature is 600°C, and it takes 14.8 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 272 ⁇ m, and the maximum thickness is 386 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 69 ⁇ m and a maximum thickness of 97 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 8%, the gas flow rate is 0.5m/s, the temperature of the tail gas in the stable stage is 600°C, and it takes 16.2 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 244 ⁇ m, and the maximum thickness is 328 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 89 ⁇ m and a maximum thickness of 116 ⁇ m.
  • the silicon coating reaction gas is introduced into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body is heated in stages.
  • the molar ratio of monosilane in the silicon coating reaction gas is 2%, the gas flow rate is 1.3m/s, the temperature of the tail gas in the stable stage is 600°C, and it takes 30.0 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 226 ⁇ m, and the maximum thickness is 301 ⁇ m.
  • the silicon coating on the upper part of the fluidized bed has a minimum thickness of 97 ⁇ m and a maximum thickness of 134 ⁇ m.
  • the silicon coating reaction gas is passed into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 15%, the gas flow rate is 0.8m/s, the tail gas stabilization stage temperature is 600°C, and it takes 7.8 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 523 ⁇ m, and the maximum thickness is 2453 ⁇ m.
  • the minimum thickness of the silicon coating on the upper part of the fluidized bed is 430 ⁇ m and the maximum thickness is 1790 ⁇ m.
  • the silicon coating reaction gas is passed into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 10%, the gas flow rate is 1.3m/s, the tail gas stable stage temperature is 800°C, and it takes 4.5 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 670 ⁇ m, and the maximum thickness is 2876 ⁇ m.
  • the minimum thickness of the silicon coating on the upper part of the fluidized bed is 589 ⁇ m, and the maximum thickness is 2535 ⁇ m.
  • the silicon coating reaction gas is passed from the bottom of the fluidized bed into the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 8%, the gas flow rate is 2m/s, the temperature of the tail gas in the stable stage is 600°C, and it takes 5.0 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 612 ⁇ m, and the maximum thickness is 2635 ⁇ m.
  • the minimum thickness of the silicon coating on the upper part of the fluidized bed is 601 ⁇ m and the maximum thickness is 2498 ⁇ m.
  • the silicon coating reaction gas is passed into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 5%
  • the gas flow rate is 2m/s
  • the temperature of the tail gas in the stable stage is 600°C
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 473 ⁇ m
  • the maximum thickness is 2036 ⁇ m.
  • the minimum thickness of the silicon coating on the upper part of the fluidized bed is 387 ⁇ m, and the maximum thickness is 1544 ⁇ m.
  • the silicon coating reaction gas is passed into the fluidized bed from the bottom of the fluidized bed, and the fluidized bed body does not use segmented heating.
  • the molar ratio of monosilane in the silicon coating reaction gas is 3%, the gas flow rate is 3m/s, the temperature of the tail gas in the stable stage is 600°C, and it takes 8.2 hours to complete the silicon coating.
  • the minimum thickness of the silicon coating at the lower part of the fluidized bed is 447 ⁇ m, and the maximum thickness is 1895 ⁇ m.
  • the minimum thickness of the silicon coating on the upper part of the fluidized bed is 369 ⁇ m, and the maximum thickness is 1601 ⁇ m.
  • Table 1 Parameter table of each embodiment and comparative example
  • Uniformity of silicon coating at specific parts of the inner wall of the fluidized bed For the upper or lower part of the fluidized bed, if the deviation rate between the minimum silicon coating thickness and the maximum silicon coating thickness is less than 50%, the thickness of the elemental silicon coated at this part is considered to be relatively Evenly. Uniform silicone coating results in avoiding excessive wear in specific areas.
  • the specific calculation method for the silicon coating uniformity (deviation rate between the minimum silicon coating thickness and the maximum silicon coating thickness) of a specific part is: (maximum thick coating -Minimum thickness)/Maximum thickness*100%. Referring to the table below, the silicon coating uniformity of Examples 1 to 10 is good, while the silicon coating uniformity of Comparative Examples 1 to 5 is poor.
  • Silicon coating thickness deviation rate For the entire fluidized bed, since the wear of the elemental silicon coating at the bottom of the fluidized bed is more serious, therefore, if the silicon coating thickness at the bottom of the fluidized bed is significantly greater than that at the top of the fluidized bed Thickness, such a thickness distribution of the silicon coating is more conducive to avoiding contamination of the granular silicon products inside the fluidized bed. Specifically, if the deviation rate of the thickness of the silicon coating at the upper and lower parts of the fluidized bed is greater than 50%, it is considered that the thickness distribution of the silicon coating at the upper and lower parts of the fluidized bed meets the silicon coating requirements.
  • the calculation method of the thickness deviation rate between the fluidized bed and the lower part is (the average value of the silicon coating at the lower part of the fluidized bed - the average value of the silicon coating at the upper part of the fluidized bed)/the average value of the silicon coating at the lower part of the fluidized bed * 100%.
  • the thickness deviation values of the silicon coating on the upper and lower parts of Examples 1 to 10 meet the requirements, while the thickness deviation values of the silicon coating on the upper and lower parts of Comparative Examples 1 to 5 do not meet the requirements.
  • the present invention is not limited to the specific device structures, arrangements and methods shown in the claims or description. As long as structures, steps or methods similar to those of the present invention are adopted and similar effects can be achieved, they should be considered to fall within the protection scope of the present invention. .

Abstract

本发明涉及一种在流化床内壁设置硅涂层的方法，包括：向流化床内部通入涂硅反应气的步骤，涂硅反应气包括硅烷与氢气，硅烷与氢气的摩尔比为0.2％～8％，涂硅反应气的流速为0.3m/s～1.5m/s；对流化床进行加热的步骤，流化床内壁的加热温度范围为300～900℃；将涂硅尾气排出流化床的步骤，涂硅尾气为涂硅反应气在流化床内部经过反应后的气体。本发明的能够在流化床内壁形成适当厚度的高纯度硅涂层，该硅涂层在流化床内颗粒硅产品的摩擦下较难产生流化床内壁的裸露。

Description

一种在流化床内壁设置硅涂层的方法 技术领域
本发明涉及多晶硅制备设备与方法，特别涉及通过流化床设备制备颗粒硅的设备与方法，具体涉及在流化床内壁设置硅涂层的方法。
背景技术
颗粒状多晶硅是近年来极受欢迎的一种多晶硅产品形态，又被称为颗粒硅。相比于棒状多晶硅，颗粒硅形态似球形，尺寸较小，可以在下游的工序中直接使用，省去了破碎的过程，节省了工序的成本并且避免了在破碎过程中引入破碎装置污染的可能。另一方面，颗粒硅产品的流动性较好，能够用于自动化的生产，提高生产效率。最关键的是，生产颗粒硅的工艺能耗较低，既对环境更加友好，也提高了颗粒硅产品的毛利率。
流化床是用来生产颗粒状多晶硅的常用设备。生产用原料包括甲硅烷(SiH4)、四氯化硅(SiCl4)、三氯硅烷(SiHCl3)、二氯硅烷(SiH2Cl2)等含硅的气体，这些含硅原料气在流化床内被加热分解或被还原，产生的多晶硅在流化床内的细微硅颗粒(又被称为“籽晶”)的表面上沉积并长大，从而生产颗粒状的多晶硅产品。在颗粒硅的生产过程中，加入的床体的籽晶以及逐渐长大的颗粒硅产品在通入流化床的流化气体的作用下在床体内部呈上下浮动的“流化”状态，流化床也是因此得名。
流化床床体的材料包括碳化硅、石墨、二氧化硅、氮化硅、石英、氮化硼等无机材料，还可以是碳化钨、钼、镍合金等金属材料。太阳能级的多晶硅产品的纯度一般要求在99.9999％以上。但是在颗粒硅的生产过程中，由于颗粒硅本身处于流化状态，会不断的与流化床内衬摩擦，导致引入内衬材料污染而极大降低颗粒硅产品的纯度。如果某个时间段生产的颗粒硅产品的纯度不够，将直接影响到整个生产周期的产品质量。
公开号为US5405658A的美国专利文件公开了一种流化床内壁硅涂层的制备方案，该方案首先向流化床内通入多晶硅颗粒，再将颗粒加热到900至1300℃，在该温度下，多晶硅颗粒的导电性良好。然后对这些颗粒施加一个变化的磁场，通过变化的磁场的作用在流化床内部形成硅保护层，通过这种方式形成的硅涂层不容易脱落。但是该方案对加热温度、加热设备的要求较高，能源消耗大且难以产业化应用。
公开号为CN109453729A的中国专利申请文件公开了一种流化床内壁保护层，保护层是包含4-30％Mo、5-25％Cr、2-15％Co、≤3.5％Ti、≤2％Fe、≤2％Al、≤1％Mn、≤1％Si、≤0.5％Cu、≤0.1％C、≤0.1％Zr、≤0.01％B和23.4-89％镍的镍基超合金，并具有0.1mm至1mm的平均厚度。采用这种方案仍然会不可避免的针对颗粒硅产品带来杂质元素的污染。
针对颗粒硅的内衬材料污染问题，存在这样的技术：在流化床内壁设置高纯度的硅涂层，避免颗粒硅与其他非高纯硅材料接触带来的污染。就涂硅的方法而言，其原料气体、工作温度等基本上与正常的颗粒 硅生产流程保持一致，但不会向流化床内部加入籽晶，含硅原料气在高温下生成高纯度单质硅并附着在流化床内壁，实现流化床内壁的高纯度硅涂层。在正常的生产过程中，由于加热设备的安装位置与高温气体向上运动，流化床中部的温度相对而言是最高的，并且进入流化床的气体的流速较快，在流化床底部只有较少的含硅气体被反应。因此，这种流化床内壁涂硅的方案将会使得流化床中部的涂硅厚度最厚，而底部以及上部的区域的硅涂层厚度则相对较薄。但就流化床内部的颗粒硅的流化状态而言，由于流化气体通常由设置在流化床底部的气体分布器通入流化床，在流化床底部的气体流速最快，产生的推动力最大，而颗粒硅由于重力作用又集中在底部，导致流化床底部的颗粒硅运动更加剧烈，颗粒之间以及颗粒与内壁之间的摩擦也更为剧烈，因此，流化床底部的内壁硅涂层更容易磨损。流化床内部涂硅的工序是生产前工序，本身不会带来产量，从生产效率而言，需要尽量减小生产前工序所占用的时间。因此，这样的涂硅方案的结果就是：流化床中部的涂硅厚度最厚，在一定的涂硅时间内，流化床底部磨损最激烈的位置反而无法获得充分厚度的硅涂层保护，如果流化床底部的硅涂层磨损，将会带来颗粒硅产品污染的风险。除此之外，由于颗粒硅生产过程中的内壁沉积硅现象，流化床中部的硅涂层将会越来越厚，进一步恶化了流化床内壁硅涂层的均匀性，产生脱落的风险并降低了床体的机械稳定性。
针对以上技术问题，提出本发明。
发明内容
在一个实施方案中，本发明涉及一种在流化床内壁设置硅涂层的方法，包括：向流化床内部通入涂硅反应气的步骤，涂硅反应气包括硅烷与氢气，硅烷与氢气的摩尔比为0.2％～8％，涂硅反应气的流速为0.3m/s～1.5m/s；对流化床进行加热的步骤，流化床内壁的加热温度范围为300～900℃；将涂硅尾气排出流化床的步骤，涂硅尾气为涂硅反应气在流化床内部经过反应后的气体。
进一步的，涂硅反应气从流化床的综合进气口通入流化床内，综合进气口为流化床在正常生产状态下的含硅原料气的进入口。
进一步的，向流化床内部通入涂硅反应气的步骤还包括：通过设置在流化床底部的气体分布器通入涂硅反应气，涂硅反应气从气体分布器靠近流化床内壁的位置通入流化床中。
进一步的，对流化床进行加热的步骤还包括：向设置在流化床下部的第一加热线圈提供第一交变电流，向设置在流化床下部的第二加热线圈提供第二交变电流；第二加热线圈位于第一加热线圈上方；第二交变电流的有效值小于第一交变电流的有效值。
进一步的，在流化床内壁设置硅涂层的方法还包括：在向流化床内部通入涂硅反应气步骤之前对流化床内壁沉积硅进行蚀刻的步骤。
进一步的，在流化床内壁设置硅涂层的方法还包括：对流化床内壁进行纯化的步骤，纯化的步骤包括利用含氯液体对流化床内壁进行清洗，并将液体从流化床底部的产品排出口和/或综合进气口和/或流化气 体进气口排出。
进一步的，在流化床内壁设置硅涂层的方法还包括：对流化床内壁进行纯化的步骤，纯化的步骤包括利用高流速的吹扫气体对流化床内壁进行吹扫的步骤；吹扫气体的流速大于等于5m/s。
进一步的，在流化床内壁设置硅涂层的方法还包括：在向流化床内部通入涂硅反应气的步骤之前将流化床内壁加热至预加热温度的步骤；预加热温度范围为600℃～1200℃。
进一步的，在流化床内壁设置硅涂层的方法还包括：在对流化床内壁的沉积硅进行蚀刻步骤之后在流化床内壁设置过渡材料的步骤；过渡材料的线性热膨胀系数介于流化床内壁材料与硅之间。
进一步的，在流化床内壁设置硅涂层的方法还包括：在向流化床内部通入涂硅反应气步骤之前封闭流化床的籽晶进入口的步骤。
进一步的，硅涂层的最薄处的厚度大于等于5μm，硅涂层的最厚处的厚度小于等于500μm。
进一步的，硅烷与氢气的摩尔比为0.2％～5％。
进一步的，涂硅反应气的流速为0.3m/s～0.8m/s。
进一步的，流化床内壁的加热温度范围为400℃～800℃。
进一步的，在流化床内壁设置硅涂层的方法还包括：对硅烷气进行预热的步骤，硅烷气的预热温度为50～200℃；对氢气进行预热的步骤，氢气的预热温度为300～600℃；将预热后的硅烷气与氢气进行混合的步骤，混合气体的温度为200～500℃。
进一步的，在流化床内壁设置硅涂层的方法还包括：计算消耗的硅烷气数量的步骤；将消耗的硅烷气数量与阈值进行比较，在消耗的硅烷气数量大于等于阈值的情况下，停止向流化床内通入涂硅反应气；计算消耗的硅烷气数量的步骤包括：获取t时刻通入流化床内部的硅烷气摩尔量，得到第一硅烷气含量数值；获取t时刻涂硅尾气中硅烷气摩尔量，得到第二硅烷气含量数值；计算t时刻第一硅烷气含量数值与第二硅烷气含量数值之间的差值，得到硅烷气消耗函数f(t)；按照△t的时间间隔分别获取硅烷气消耗函数的具体数值；计算硅烷气消耗函数f(t)在△t间隔下对时间的积分，得到消耗的硅烷气数量。
进一步的，在流化床内壁设置硅涂层的方法还包括：在第一时刻读取除硅尾气的温度，得到第一尾气温度值；在第二时刻检测除硅尾气的温度，得到第二尾气温度值；计算第一尾气温度值与第二尾气温度值的温度差值，当温度差值大于温度阈值时，停止向流化床内通入涂硅反应气。
附图说明
在附图的图示中通过举例而非限制的方式示出了实施方案，在附图中类似的附图标号指示类似的元件。应当指出的是，在本公开中提到“一”或“一个”的实施方案未必是同一的实施方案。
图1示出了用于颗粒状多晶硅生产流化床设备的一个实施例；
图2示出了用于颗粒状多晶硅生产流化床设备中气体分布器的示意图；
图3示出了用于颗粒状多晶硅生产流化床设备的另一个实施例。
具体实施方式
在这个部分中，我们将参考附图来解释本发明的若干实施方案。每当在实施方案中描述的部件的形状、相对位置和其它方面未明确限定时，本发明的范围并不仅局限于所示出的部件，所示出的部件仅用于例证的目的。另外，虽然阐述了许多细节，但应当理解，本发明的一些实施方案可在没有这些细节的情况下被实施。在其他情况下，未详细示出熟知的结构和技术，以免模糊对本描述的理解。
本文中所使用的术语仅是为了描述特定实施方案而并非旨在对本发明进行限制。空间相关术语，诸如“在……之下”、“在……下方”、“下”、“在……上方”、“上”等可在本文中用于描述的方便，以描述一个元件或特征与另外一个或多个元件或一个或多个特征的关系，如在附图中示出的。应当理解，空间相对术语旨在涵盖除了在附图中所示的取向之外的设备使用或操作过程中的不同取向。例如，如果附图中的设备被翻转，则被描述为在其他元件或特征“下方”或“之下”的元件然后可被取向成在其他元件或特征“上方”。因此，示例性术语“在……下方”可涵盖在……上方和在……下方这两个取向。设备可以另外的方式进行取向(例如，旋转90度或以其他取向)，并且在本文中使用的空间相对描述词被相应地解释。
如本文所用，单数形式“一个”、“该”等旨在同样包括复数形式，除非上下文另外指出。应当进一步理解，术语“包括”和/或“包含”限定特征、步骤、操作、元件、和/或部件的存在，但不排除一个或多个其他特征、步骤、操作、元件、部件和/或其集合的存在或添加。
本文所使用的术语“或”和“和/或”应被解释为包含性的或意指任意一个或任意组合。因此，“A、B或C”或“A、B和/或C”指“以下中的任意一种：A；B；C；A和B；A和C；B和C；A、B和C。”只有当元素、功能、步骤或行为的组合在某种程度上是固有地相互排斥时，才会出现该定义的例外情况。
本文中所称的“连接”包括直接连接与间接连接在内的各种连接方式，不要求被连接的各个部位之间存在物理上的接触，包括了卡扣连接、螺丝连接、无固定装置的连接、焊接、铆接、一体成型在内的各种具体连接方式。在部件配合的场合下，配合间隙包括了间隙配合、过渡配合、过盈配合或者可变间隙等配合关系。
本文针对流量、压力、温度、纯度等各类化学化工参数所称的“一致”或“恒定”并不要求被比较的两个参数在数值上完全一致，如果被比较的两个参数围绕近似的数值且在一定范围内上下波动，亦应当被看作是“一致”或者“恒定”。
流化床
流化床100是整个颗粒硅生产设备的核心装置。流化床100包括床体101，床体101采用质地较硬且 便于加工的材料，包括碳化硅、石墨、二氧化硅、氮化硅、石英、氮化硼等无机材料，还可以是碳化钨、钼、镍合金等金属材料。床体101形成一个空间，用于容纳反应原料并提供容纳反应产物的空间。含硅原料气进入该空间后被加热，进行热分解或者还原反应，并在该空间内生成颗粒状的多晶硅，当多晶硅产品达到一定数量后，多晶硅产品将通过产品排出管道104从流化床床体中排出。床体101具有一定的高度，其横截面大体呈圆形，圆形的截面能够使得针对含硅原料气的加热更加均匀，在制造过程中也更容易成型。
床体101设置有多个气体的出入口，其中，综合进气口102位于床体101的底部，其另一端与气体供应装置相连，气体供应装置可以供应包括颗粒硅生产用的原料气体、用于流化床内壁涂硅的涂硅气体、用于蚀刻流化床内壁沉积硅的蚀刻气体在内的各种类型的气体。综合进气口102连接有综合进气阀(图中未示出)，综合进气阀起到关闭和/或切换综合进气口102的气体通路的作用。其中，原料气包括甲硅烷(SiH4)、四氯化硅(SiCl4)、三氯硅烷(SiHCl3)、二氯硅烷(SiH2Cl2)等在内的含硅的气体，这些气体可以统称为硅烷，在本发明的实施例中，主要使用甲硅烷(SiH4)作为原料气。甲硅烷可以采用金属氢化物法、硅镁合金法、三氯氢硅歧化法在内的各种生产工艺进行制备。床体101的底部还设置有流化气体进入口103，流化气体用于对流化床内部的硅颗粒(籽晶)进行吹喷，使其呈流化状态，在这种状态下，含硅原料气体能够与硅颗粒(籽晶)的表面充分、均匀的接触，并在硅颗粒(籽晶)表面生成单质硅，避免颗粒之间产生粘连。流化气体可以选择氮气、氩气、氦气在内的多种气体，这一类流化气体的选用原则是不与流化床内的原料气或床体的材料成分反应。作为可选的实施方式，流化气体可以直接选用原料气(包括硅烷、氯硅烷、氯化氢等)或还原气体(如氢气)，虽然这些气体参与反应过程，但这些气体的反应产物并不会引入其他杂质元素。
含硅原料气体和流态化气体的进气量维持在气体流速为1.5～4.0Umf。含硅原料气体的比例没有任何限制，作为可选的方式，含硅原料气体中的硅烷的摩尔比例可以为10mol％～80mol％，剩下的为流态化气体(如氢气等)。
在床体101的顶部设置有籽晶加入口105，用于向床体内部提供作为沉积硅内核的籽晶。在流化床反应器中，颗粒硅籽晶的粒径通常在50～1000μm。
床体101的顶部设置有尾气出口107，由于床体101内的原料气经过加热后都向上流动，在床体101的顶部设置尾气出口能够较为完整地将床体内的生产尾气、涂硅尾气以及蚀刻尾气排出，从而能够对尾气进行处理与利用。
床体101所形成的空间在竖直方向上大体被分为下部1011与上部1012，流化床床体的底部位于床体下部，顶部位于床体上部。另外，流化床床体下部一般都安装有加热装置，用于对流化床内壁以及流化床内的物料进行加热。在多晶硅的生产、流化床内壁形成硅涂层、去除流化床内壁沉积硅等过程中，从气体的运动路径来看，原料气体、涂硅气体或蚀刻气体通过设置在床体底部的综合进气口102进入床体内部的 空间，在下部1011被加热装置加热后向上运动至上部1012，原料气、涂硅气体、蚀刻气体在流化床体内进行充分的反应后通过尾气出口107排出。
如图1、图2所示，在床体101的下部1011设置有气体分布器106，气体分布器106与床体101之间设置有连接装置或连接部，用于固定气体分布器，避免气体分布器在床体内产生位移。在本实施例中，床体101加热区的底部位置的横截面为圆形，气体分布器106的形状亦为圆形。气体分布器106与流化气体进入口103相连并形成气体的通路，作为可选的实施方式，流化床上不设置流化气体进入口103，综合进气口102与气体分布器106相连并形成气体的通路。在气体分布器106上设置有多个出气孔，原料气体、涂硅气体或蚀刻气体通过综合进气口102和/或流化气体进入口103进入气体分布器106，然后从气体分布器106的出气孔上喷出。采用气体分布器将进入床体内的原料气重新分布，能够使得原料气、涂硅气体或蚀刻气体在床体内能够按照特定的流向、流速进行分布。另一方面，采用气体分布器的设置能够直接将原料气作为流化气体，所谓流化气体的作用是自下而上穿过床体内部的固体颗粒，使得固体颗粒在流体的推力的作用下产生向上的作用力，在固体颗粒的向上作用力大于或等于固体颗粒本身的重力的情况下，床体内部的固体颗粒硅就会呈现悬浮或沸腾的状态，流化床中的“流化”两字即因此得名。气体分布器106的材料包括石英、碳化硅、氮化硅或单质硅，采用这样的非金属材料，能够避免给颗粒硅产品引入金属元素杂质，提高颗粒硅产品的质量。为了减少由气体分布器引入的杂质元素，气体分布器表面还可以涂布单质硅。
如图2所示，作为一种实施方式，气体分布器上设置有多个开孔，其中，位于气体分布器内部的开孔1061用于原料气体和/或流化气体的通路，这部分的开孔远离流化床体内壁，能够减小原料气与流化床内壁的接触，减少流化床内壁的单质硅沉积。位于气体分布器边缘的开孔1062用于涂硅气体和/或蚀刻气体的通路，开孔1062更加贴近流化床内壁，蚀刻气体通过开孔进入床体后能够充分地与流化床内壁接触，提高蚀刻的效果。气体分布器中央的开孔用于连接产品排出管道104。
作为一种实施方式，加热区采用感应加热的方式，在采用感应加热的场合，加热区所对应的床体位置设置有加热装置108，作为一种可选的实施方式，加热器108由外向内依次为线圈、金属磁通结构，在加热时，向线圈提供交变电流，以产生交替变化的磁场，交替变化的磁场在金属磁通结构中感应出涡电流，在涡电流的作用下加热金属磁通结构，进而向床体内部传导热量。作为可选的实施方式，不设置金属磁通结构，直接在床体的外壳中产生感应涡流电流进而产生热量。另外，由于硅本身具有一定的导电性，在流化床内处于流化状态的硅颗粒内部亦有可能通过感应形成电流，从而对硅颗粒本身进行加热。感应加热具有产品结构简单、热效率高、能够对硅颗粒本身进行加热的特点。
作为可选的实施方式，还可以采用热电阻加热、微波加热、辐射加热等各种加热方式对流化床和/或流化床内物料进行加热。
床体101的底部采用倾斜设计以形成斜坡，通过这样的设置，能够使得颗粒硅产品沿着倾斜斜坡向下 滚动汇集，从而使从产品排出管道104中排出颗粒硅产品的过程更加顺畅。
图3为本发明流化床的另一种实施方式。流化床200包括床体201，床体201具有下部2011以及上部2012，床体201的底部设置有综合进气口202、产品排出口204和流化气体进气口203，床体顶部设置有籽晶进入口205以及尾气排出口207。床体下部设置有感应加热装置208，感应加热装置包括第一线圈2081与第二线圈2082，第二线圈设置在第一线圈之上。采用这种分段的加热装置，能够分别对第一线圈、第二线圈的加热功率进行控制，从而得以控制流化床内部的温度梯度。
流化床内壁沉积硅蚀刻
对于全新的流化床，其内壁表面平整且光滑，可以直接进行涂硅或预涂层。对于已经投入使用的流化床而言，在流化床的生产过程中，单质硅会在流化床内壁沉积形成逐渐变厚的结硅层，这种结硅层的厚度、致密程度、空隙等非常不均匀，无法直接在其上进行涂硅的操作。因此，需要先对使用过的流化床内壁的沉积硅进行蚀刻，以获得相对平整的内壁。
就去除流化床内壁沉积硅的方法而言，可以采用含氯气体如四氯化硅(SiCl4)、氯化氢(HCl)和氯气(Cl2)等与流化床内壁沉积硅进行反应而蚀刻。也可以采用停机后敲击、剥离等物理去除的方法去除流化床内壁沉积的硅块。将流化床内壁的沉积硅清除干净后，即可参照全新的流化床内壁处理方式进行接下来的处理步骤。
流化床内壁纯化
在进行流化床表面涂硅操作及其对应的准备工作之前，对流化床内壁进行纯化，其目的是去除流化床内壁粘附的油脂、细微硅粉或其他杂质。
作为一种对流化床内壁进行纯化的方法，包括采用液态的氯化氢、四氯化硅等对流化床内壁进行清洗，并从产品排出管道、或气体分配器的管道中收集清洗后的液体混合物。通过这样的液体清洗，能够去除流化床内壁的油脂及细微硅粉等杂质。
作为可选的实施方式，利用高温的惰性气体在高流速下对流化床内壁进行吹扫，将流化床内壁的油脂以及细微硅粉等杂质吹扫脱离流化床内壁。吹扫气体的成分可以是氮气、氢气、氯气、氯化氢等也可以是氦气、氩气等惰性气体。用于纯化的吹扫气体的流速一般都在5m/s以上。作为可选的实施方式，可以利用如图2所示的气体分配器控制吹扫气体的流向，吹扫气体从紧贴流化床内壁的吹扫孔1062处流出，并紧贴着流化床内壁向上运动，以更好的实现吹扫效果。
具有过渡的热膨胀系数的预涂层
对于碳化硅、石墨、二氧化硅、氮化硅、石英、氮化硼等无机材料的流化床，由于这些无机材料的热膨胀系数与硅相似，可以直接在这些材料的内壁涂硅，在内壁的热膨胀系数与硅材料相似的情况下，能够提高单质硅在内壁上的粘附力，避免硅涂层的脱落。对于碳化钨、钼、镍合金等金属材料的流化床而言， 由于其材料的热膨胀系数与硅的热膨胀系数相差较大，在涂硅或者颗粒硅生产过程中的温度变化将会使内壁的硅涂层产生裂缝，导致硅涂层的脱落并影响流化床的机械强度。因此，针对金属材料的流化床内壁，需要事先对其进行预涂层处理，在其内壁设置过渡膨胀预涂层，该预涂层所用的过渡材料的热膨胀系数介于内壁的金属材质与单质硅之间，如当流化床内壁材质采用Incoloy800H的情况下，在流化床内壁涂一层过渡材料，如80％Ni20％Cr，涂层厚度50～100um，然后在预涂层上设置硅涂层，由于预涂层的热膨胀系数介于镍合金与硅之间，能够起到热膨胀缓冲的作用，避免由于热膨胀相差过大导致的硅涂层的开裂、脱落。
流化床内壁预加热
对于流化床内壁的硅涂层的机械强度而言，硅涂层的厚度是一方面的考虑，硅涂层与内衬的结合强度也是另一个重要的考虑因素。
硅涂层与内衬的结合强度主要取决于硅涂层与内衬之间的微观原子间的结合强度。在正式的内壁涂硅过程开始之前，还可以在流化床内壁设置单质硅预涂层：对流化床抽真空或者在流化床内充满不与流化床内壁材料反应或者不会对颗粒硅产品引入杂质的气体，包括氮气、氢气、氯气、氯化氢等气体或氦气、氩气等惰性气体，然后对流化床内壁进行加热至600℃～800℃。在流化床内壁加热到该特定温度的情况下，再向流化床内通入涂硅气体。涂硅气体与高温内壁解除后，在流化床表面生成的单质硅能够与流化床内壁材料形成类似固溶体或金属化合物的类合金的结构，在流化床内壁生成的高纯度的硅预涂层。这种单质硅预涂层的致密性较高，并且能够与内壁紧密贴合，在该单质硅预涂层上设置普通的硅涂层，能够避免硅涂层由于振动、摩擦等被破坏。
气体预热
在流化床内壁设置硅涂层主要利用了硅烷的裂解反应。以甲硅烷(SiH4)为例，内壁涂硅过程的典型反应为：
SiH4→Si+2H2
硅烷的反应需要在一定的温度下才能进行，对于甲硅烷(SiH4)而言，其在300～400℃的温度下已经开始分解，但是由于硅的塔曼温度(Tammann Temperature)为0.52，低于600℃硅只能分解成无定形硅；在正常的颗粒硅生产过程中，控制甲硅烷的反应温度为600℃～800℃。因此，需要使气体温度加热到一定的程度才能开始硅烷生成晶态硅的反应过程，同时温度过高会造成硅烷在气相中大量分解，生成大量硅粉，造成涂层不致密。
如果仅依赖流化床的加热装置对其进行加热，一方面会让较多的反应气体无法经过充分的反应即从尾气排出口排出，另一方面，由于进入流化床的气体温度较低，在流化床底部无法形成合适厚度的硅涂层，而底部的流化状态的硅颗粒粒径大、速度快、数量多，底部内壁的磨损程度最大。如果无法在流化床底部 形成合适厚度的硅涂层，将提高由于涂硅层磨损带来的颗粒硅产品被污染的风险。
在本实施例中，在用于内壁涂硅的反应气体进入流化床之前，对其进行预热，使其进入流化床后能够直接在流化床底部的内壁开始反应以生成具有一定厚度的硅涂层。在本实施方式中，对硅烷与氢气分别进行预热。以甲硅烷(SiH4)为例，将其预热至50～200℃，将氢气预热至300～600℃，然后将经过预热后的硅烷与氢气混合，混合后的气体的温度为100～500℃。因此将甲硅烷与氢气分别进行预热，并且将甲硅烷的预热的温度设置的低于其分解温度，然后再与高温的氢气混合，快速进入流化床，能够提高流化床内壁硅涂层反应效果。
对流化床内壁进行涂硅
如图1所示，在涂硅过程中，从流化床底部的气体入口102中通入经过预热且混合的涂硅反应气。涂硅反应气包括混合的硅烷与氢气，硅烷与氢气的摩尔比为0.2％～8％。采用这种低硅含量的涂硅反应气，能够避免在流化床内的高气体浓度及高温区域产生过厚的结硅层或硅块，使得流化床内壁涂硅更加均匀，也能够降低硅烷气在流化床内气相的分解比例，使硅烷气更多的在流化床内壁进行反应，提高涂硅反应气的利用率。
涂硅反应气进入流化床的流速为下限值为0.3m/s，优选为0.5m/s，更优选为0.8m/s。涂硅反应气进入流化床的流速上限为1.8m/s，优选为1.5m/s，更优选为1.3m/s。涂硅反应气的流速在上限值以内，能够使涂硅反应气在流化床下部停留相对较长的时间，从而在流化床的下部形成相对较厚的高纯硅涂层。在颗粒硅的生产过程中，流化床下部的颗粒硅在流化气体的推动下杂乱运动，与流化床内壁的硅涂层摩擦，因此，在流化床下部形成相对较厚的高纯硅涂层，能够避免在颗粒硅生产初期的硅颗粒摩擦带来的流化床下壁裸露，随着生产过程的推进，含硅原料气会在内壁上的沉积，抵销内壁摩擦带来的硅涂层的损耗。涂硅反应气的流速在上限值以内，能够确保在整个生产周期中不会有内壁的裸露，避免给颗粒硅产品带来杂质元素的污染。涂硅反应气的流速大于下限值，能够使得在该流速下，涂硅反应气具有一定的初速度，涂硅反应气在流化床内被进一步加热后，会以相对更高的速度向上运动，涂硅反应气的运动能够避免涂硅反应气在流化床下部被完全反应而无法在流化床的上部或其他位置形成合适厚度的硅涂层。通过设置涂硅反应气进入流化床的初速度，能够在流化床的整个内壁上都形成高纯度硅涂层，并且在流化床的下部形成相对较厚的硅涂层，避免生产过程中由于颗粒摩擦带来的内壁裸露。涂硅反应气在管道内的流速范围为0.3～1.8m/s，优选为0.5～1.5m/s，更优选为0.8～1.3m/s。
如图1所示，本实施例中采用感应加热的方式对流化床内壁及内部物料进行加热。作为可选的实施方式，流化床的加热方式还可以是电阻加热方式、锅炉加热方式或者其他加热方式。感应加热装置包括两段加热位置，其中第一加热位置位于相对于第二加热位置更低的位置，在制备高纯硅预涂层以及流化床内壁硅涂层的过程中，第一加热位置的温度高于第二加热位置。采用这样的设计，能够使得进入流化床内的涂 硅反应气第一时间加热至反应温度即开始在流化床下部被反应，确保在流化床下部能够形成厚度相对较厚的硅涂层。涂硅反应气在经过流化床下部之后浓度降低，在第二加热位置被进一步加热并向流化床上部运动，温度再次升高的涂硅反应气体在流化床上部进一步反应，在经过充分的反应之后，剩余的涂硅尾气从流化床顶部被排出。采用这种两段式加热方式，能够使流化床下部的硅涂层厚度大于流化床上部的厚度，并且由于运动至流化床上部的气体温度较高，虽然浓度降低，但气体在流化床上部仍然能够被充分的反应，使得最后排出流化床的尾气中的硅烷气含量相对较少，提高了涂硅气体整体的利用率。
在涂硅完成时，流化床下部的硅涂层最厚处为100～500μm，流化床上部的硅涂层的最薄处为5～50μm，通过设置流化床内壁的涂硅厚度的梯度，一方面能够充分地对整个流化床内壁进行涂硅，避免内壁材料元素的污染，另一方面能够在流化床内壁磨损最多的部位设置最厚的硅涂层厚度，避免由于摩擦带来的流化床内壁材料裸露。
涂硅尾气检测
如图1所示，尾气出口管104设置在流化床顶部，流化床正常生产过程中产生的尾气、流化床内壁沉积硅蚀刻过程产生的尾气、流化床内壁硅涂层制备过程产生的尾气等都可以通过该尾气排出口排出流化床。
涂硅过程产生的尾气主要是硅烷气与氢气的混合物。作为本发明的一种实施方式，使涂硅气体的预热温度以及流化床加热装置的功率保持不变，检测涂硅过程产生的涂硅尾气的温度。自向流化床内部通入涂硅气体及加热装置处于正常工作状态开始，尾气的温度呈一个快速上升的温度上升阶段，然后会进入一段温度相对平稳的温度稳定阶段，而后温度会逐渐下降，进入温度下降阶段。温度上升主要是因为预热气体的通入以及流化床加热装置产生的热量随着上升的气流传递至尾气出口，当流化床内部的热量增减达到平衡状态时，尾气的温度就会进入一个相对稳定的阶段。然后，随着流化床内壁沉积硅逐渐变厚，流化床加热装置对流化床内壁特别是流化床内气体的加热效率将会降低，在相同的涂硅气体预热温度以及相同的流化床加热装置功率的情况下，涂硅尾气的温度将会逐渐降低。在温度稳定阶段检测尾气温度，得到第一尾气温度检测值，在温度降低阶段检测尾气温度，得到第二尾气温度检测值，如果第二尾气温度检测值低于第一尾气温度检测值3℃及以下，则认为流化床内壁已经完整地涂覆硅涂层，并且流化床内壁特别是流化床下段(一般包括加热区域)的厚度已经达到要求。由于涂硅气体的反应过程主要取决于流化床内壁有效反应面积的大小，而无论内壁是否设置有硅涂层并且无论硅涂层的厚薄，涂硅气体的反应速率、程度在整个涂硅的过程中基本上保持稳定，较难通过尾气中的硅烷气或者其他气体的含量判断涂硅过程的完成度。通过检测涂硅尾气的温度，一方面能够相对精确地获知流化床内壁的硅涂层的状态，另一方面也能够直接反应设置在流化床下部的加热区内壁的硅涂层的厚度。通过该方式判定完成涂硅操作后，可以切换为正常的颗粒硅生产流程，包括：向流化床内通入正常生产过程所用的含硅原料气，控制流化床加热装置的功率为正常生产功率，同时向流化床内注入籽晶，以开始正常的颗粒硅生产流程。通过这样的切换方式，无需 停机即可第一时间切换为正常的颗粒硅生产过程，提高了生产效率。
作为另一种判断流化床内壁涂硅过程的方法，需要保持通入流化床内的硅烷的含量、气体的流速不变，通过气体分析仪检测在涂硅过程中流化床尾气排出口104处的涂硅尾气中硅烷的含量，得到通入的涂硅原料气与排出的涂硅尾气中的硅烷含量的差值，定义t时刻检测出的通入的涂硅原料气与排出的涂硅尾气中的硅烷含量的差值为f(t)，该差值反映了在特定时刻用于生成流化床内壁硅涂层的硅烷气体的数量。各尾气检测时刻间隔为△t，利用公式：
∫f(t)Δt
对以上差值进行按时间的积分，即得到了用于生成流化床内壁硅涂层所消耗的硅烷气数量。根据不同的流化床内壁面积设定不同的阈值，当积分所得的消耗硅烷气的数量超过该阈值时即认为流化床内壁已经完成的涂覆了合适厚度的硅涂层，此时可以停止涂硅的操作或者直接切换至通入正常生产过程所用的含硅原料气并向流化床内加入籽晶。通过这种积分的方法，能够更加精确的判断流化床内壁结硅层的厚度。
实施例与对比例
以下列举实施例及对比例以进一步描述本发明的公开内容。需要注意的是，以下实施例和对比例仅为就本发明公开的技术方案中的部分方案进行了的列举，以下实施例所列举的生产设备型号、尺寸、原料、工艺流程、参数等不应当直接看作是对本专利保护范围的限制。
本发明所列举的实施例与对比例针对的流化床设备为江苏中能GCL-GEN5035型号流化床，该型号流化床的加热方式为电磁线圈感应加热，内衬材料为石墨。所用的硅烷气为江苏中能生产的，通过歧化反应方法制备的甲硅烷(SiH4)，其纯度为6N(大于等于99.9999％)。所用氢气是通过天然气裂解方法制备的，其纯度为6N(大于等于99.9999％)。测量流化床进气口的流速计为艾默生公司生产的CMF型号流速计，量程为0～100kg/h。测量尾气温度的温度计为安徽天康生产的K分度型号温度计，量程为0～1000℃。以下实施例或对比例所针对的流化床为全新的设备或者利用氯化氢(HCl)对流化床内壁的沉积硅进行蚀刻且蚀刻完成后的流化床。
实施例1
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为5％，气体流速为0.3m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时29.0小时。涂硅完成后，流化床下部(包括加热区域)的硅涂层最小厚度为153μm，最大厚度为189μm。流化床上部的硅涂层最小厚度为43μm，最大厚度为70μm。
实施例2
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩 尔比为3％，气体流速为0.5m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时35.2小时。涂硅完成后，流化床下部的硅涂层最小厚度为180μm，最大厚度为210μm。流化床上部的硅涂层最小厚度为64μm，最大厚度为78μm。
实施例3
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为2％，气体流速为1.2m/s,尾气稳定阶段温度为700℃，涂硅完成共耗时25.6小时。涂硅完成后，流化床下部的硅涂层最小厚度为355μm，最大厚度为400μm。流化床上部的硅涂层最小厚度为41μm，最大厚度为63μm。
实施例4
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为0.2％，气体流速为1.5m/s,尾气稳定阶段温度为500℃，涂硅完成共耗时32.5小时。涂硅完成后，流化床下部的硅涂层最小厚度为296μm，最大厚度为315μm。流化床上部的硅涂层最小厚度为52μm，最大厚度为75μm。
实施例5
从流化床底部向流化床内通入涂硅反应气，流化床体未采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为5％，气体流速为0.8m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时17.6小时。涂硅完成后，流化床下部的硅涂层最小厚度为234μm，最大厚度为350μm。流化床上部的硅涂层最小厚度为70μm，最大厚度为110μm。
实施例6
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为5％，气体流速为0.8m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时16.9小时。涂硅完成后，流化床下部的硅涂层最小厚度为252μm，最大厚度为337μm。流化床上部的硅涂层最小厚度为61μm，最大厚度为99μm。
实施例7
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为5％，气体流速为0.8m/s,尾气稳定阶段温度为400℃，涂硅完成共耗时29.8小时。涂硅完成后，流化床下部的硅涂层最小厚度为199μm，最大厚度为373μm。流化床上部的硅涂层最小厚度为95μm，最大厚度为152μm。
实施例8
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为8％，气体流速为0.5m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时14.8小时。涂硅完成后，流化床下部的硅涂层最小厚度为272μm，最大厚度为386μm。流化床上部的硅涂层最小厚度为69μm，最大厚度为97μm。
实施例9
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为8％，气体流速为0.5m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时16.2小时。涂硅完成后，流化床下部的硅涂层最小厚度为244μm，最大厚度为328μm。流化床上部的硅涂层最小厚度为89μm，最大厚度为116μm。
实施例10
从流化床底部向流化床内通入涂硅反应气，流化床体采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为2％，气体流速为1.3m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时30.0小时。涂硅完成后，流化床下部的硅涂层最小厚度为226μm，最大厚度为301μm。流化床上部的硅涂层最小厚度为97μm，最大厚度为134μm。
对比例1
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为15％，气体流速为0.8m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时7.8小时。涂硅完成后，流化床下部的硅涂层最小厚度为523μm，最大厚度为2453μm。流化床上部的硅涂层最小厚度为430μm，最大厚度为1790μm。
对比例2
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为10％，气体流速为1.3m/s,尾气稳定阶段温度为800℃，涂硅完成共耗时4.5小时。涂硅完成后，流化床下部的硅涂层最小厚度为670μm，最大厚度为2876μm。流化床上部的硅涂层最小厚度为589μm，最大厚度为2535μm。
对比例3
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为8％，气体流速为2m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时5.0小时。涂硅完成后，流化床下部的硅涂层最小厚度为612μm，最大厚度为2635μm。流化床上部的硅涂层最小厚度为601μm，最大厚度为2498μm。
对比例4
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为5％，气体流速为2m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时8.9小时。涂硅完成后，流化床下部的硅涂层最小厚度为473μm，最大厚度为2036μm。流化床上部的硅涂层最小厚度为387μm，最大厚度为1544μm。
对比例5
从流化床底部向流化床内通入涂硅反应气，流化床体没有采用分段加热的方式。涂硅反应气中甲硅烷的摩尔比为3％，气体流速为3m/s,尾气稳定阶段温度为600℃，涂硅完成共耗时8.2小时。涂硅完成后，流化床下部的硅涂层最小厚度为447μm，最大厚度为1895μm。流化床上部的硅涂层最小厚度为369μm，最大厚度为1601μm。
表1：各实施例、对比例参数表
涂硅质量评价：
流化床内壁特定部位的涂硅均匀性：针对流化床上部或者下部而言，如果最小涂硅厚度与最大涂硅厚度的偏差率小于50％，则认为该部位涂的单质硅的厚度较为均匀。均匀的涂硅结果能够避免特定部位的过渡磨损。特定部位的涂硅均匀性(最小涂硅厚度与最大涂硅厚度偏差率)的具体计算方法为：(最大厚涂 -最小厚度)/最大厚度*100％。参考下表，实施例1～10的涂硅均匀性较好，对比例1～5的涂硅均匀性较差。
涂硅厚度偏差率：针对整个流化床床体而言，由于流化床底部单质硅涂层的磨损更加严重，因此，如果流化床底部的涂硅厚度明显大于流化床上部的涂硅厚度，这样的硅涂层的厚度分布更有利于避免流化床内部颗粒硅产品被污染。具体而言，如果流化床上部、下部硅涂层的厚度的偏差率大于50％，则认为流化床上部、下部的硅涂层厚度分布符合涂硅要求。流化床上、下部厚度偏差率的计算方法为(流化床下部硅涂层平均值-流化床上部硅涂层平均值)/流化床下部硅涂层平均值*100％。参考下表，实施例1～10的上部、下部涂硅厚度偏差值符合要求，对比例1～5的上部、下部涂硅厚度偏差值不符合要求。
表2：各实施例、对比例效果表
本发明并不限于权利要求或说明书所示的特定装置结构、布置和方法，只要采用了与本发明相类似的结构、步骤或者方法且能够实现类似的效果，都应当认为属于本发明的保护范围。

Claims (17)

  1. 一种在流化床内壁设置硅涂层的方法，包括：
    向流化床内部通入涂硅反应气的步骤，所述涂硅反应气包括硅烷与氢气，所述硅烷与氢气的摩尔比为0.2％～8％，所述涂硅反应气的流速为0.3m/s～1.5m/s；
    对流化床进行加热的步骤，对所述流化床内壁的加热温度范围为300℃～900℃；
    将涂硅尾气排出流化床的步骤，所述涂硅尾气为所述涂硅反应气在流化床内部经过反应后的气体。
  2. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述涂硅反应气从所述流化床的综合进气口通入流化床内，所述综合进气口为所述流化床在正常生产状态下的含硅原料气的进入口。
  3. 根据权利要求2的在流化床内壁设置硅涂层的方法，其特征在于：
    所述向流化床内部通入涂硅反应气的步骤还包括：
    通过设置在流化床底部的气体分布器通入所述涂硅反应气，所述涂硅反应气从所述气体分布器靠近所述流化床内壁的位置通入流化床中。
  4. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    对流化床进行加热的步骤还包括：
    向设置在流化床下部的第一加热线圈提供第一交变电流，向设置在流化床下部的第二加热线圈提供第二交变电流；
    所述第二加热线圈位于所述第一加热线圈上方；
    所述第二交变电流的有效值小于所述第一交变电流的有效值。
  5. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    在向流化床内部通入涂硅反应气步骤之前对流化床内壁沉积硅进行蚀刻的步骤。
  6. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    对所述流化床内壁进行纯化的步骤，所述纯化的步骤包括利用含氯液体对所述流化床内壁进行清洗，并将液体从所述流化床底部的产品排出口和/或综合进气口和/或流化气体进气口排出。
  7. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    对所述流化床内壁进行纯化的步骤，所述纯化的步骤包括利用高流速的吹扫气体对所述流化床内壁进行吹扫；
    所述吹扫气体的流速大于等于5m/s。
  8. 根据权利要求1～7任意一项所述的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    在向流化床内部通入涂硅反应气的步骤之前将所述流化床内壁加热至预加热温度的步骤；
    所述预加热温度范围为600℃～1200℃。
  9. 根据权利要求1～7任意一项所述的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    在对流化床内壁的沉积硅进行蚀刻步骤之后，在流化床内壁设置过渡材料的步骤；
    所述过渡材料的线性热膨胀系数介于所述流化床内壁材料与硅之间。
  10. 根据权利要求1～7任意一项所述的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    在向流化床内部通入涂硅反应气步骤之前封闭所述流化床的籽晶进入口的步骤。
  11. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述硅涂层的最薄处的厚度大于等于5μm，所述硅涂层的最厚处的厚度小于等于500μm。
  12. 根据权利要求11的在流化床内壁设置硅涂层的方法，其特征在于：
    所述硅烷与氢气的摩尔比为0.2％～5％。
  13. 根据权利要求11的在流化床内壁设置硅涂层的方法，其特征在于：
    所述涂硅反应气的流速为0.3m/s～0.8m/s。
  14. 根据权利要求11的在流化床内壁设置硅涂层的方法，其特征在于：
    所述流化床内壁的加热温度范围为400℃～800℃。
  15. 根据权利要求11～14任意一项所述的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    对硅烷气进行预热的步骤，所述硅烷气的预热温度为50～200℃；
    对氢气进行预热的步骤，所述氢气的预热温度为300～600℃；
    将预热后的硅烷气与氢气进行混合的步骤，所述混合气体的温度为200～500℃。
  16. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    计算消耗的硅烷气数量的步骤；
    将所述消耗的硅烷气数量与阈值进行比较，在所述消耗的硅烷气数量大于等于所述阈值的情况下，停止向流化床内通入所述涂硅反应气；
    所述计算消耗的硅烷气数量的步骤包括：
    获取t时刻通入所述流化床内部的硅烷气的摩尔量，得到第一硅烷气含量数值；
    获取t时刻所述涂硅尾气中硅烷气的摩尔量，得到第二硅烷气含量数值；
    计算t时刻第一硅烷气含量数值与第二硅烷气含量数值之间的差值，得到硅烷气消耗函数f(t)；
    按照△t的时间间隔分别获取硅烷气消耗函数的具体数值；
    计算硅烷气消耗函数f(t)在△t间隔下对时间的积分，得到所述消耗的硅烷气数量。
  17. 根据权利要求1的在流化床内壁设置硅涂层的方法，其特征在于：
    所述方法还包括：
    在第一时刻检测所述除硅尾气的温度，得到第一尾气温度值；
    在第二时刻检测所述除硅尾气的温度，得到第二尾气温度值；
    计算所述第一尾气温度值与所述第二尾气温度值的温度差值，当所述温度差值大于温度阈值时，停止向流化床内通入所述涂硅反应气。
PCT/CN2023/099424 2022-08-03 2023-06-09 一种在流化床内壁设置硅涂层的方法 WO2024027340A1 (zh)

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