CN118904129A - Chemical vapor deposition molecular scattering mixer - Google Patents

Abstract

The invention relates to the technical field of polysilicon production, and particularly discloses a chemical vapor deposition molecular scattering mixer; the inner cylinder is internally provided with a plurality of metal wire meshes, threading holes are formed in the positions, corresponding to the metal wire meshes, on the inner cylinder in the circumferential direction, the metal wire meshes are formed by weaving metal wires through the threading holes, each metal wire mesh is of a metal wire mesh transverse and longitudinal vertical net structure, an alpha degree of axial rotation is arranged between two adjacent metal wire meshes, and the outer wall of the inner cylinder is coated with the sealing layer; according to the invention, by utilizing the principle that collision between a metal wire and a macromolecular cluster damages van der Waals force among molecules to disperse the macromolecular cluster, various materials are mixed, so that the silicon crystal with consistent size is formed; meanwhile, a mode of punching holes on the inner cylinder and weaving metal wires into a metal wire mesh is adopted to replace a mode of welding components in a traditional mixer, so that the risk that materials are polluted by impurities in welding spots is reduced.

Description

A chemical vapor deposition molecular scrambling mixer

Technical Field

The invention relates to the technical field of polysilicon production, and in particular to a chemical vapor deposition molecule scattering mixer.

Background Art

Chemical Vapor Deposition (CVD) is a process technology in which reactants undergo chemical reactions at high temperature and in the gas phase. The solid phase crystals generated under certain process conditions are deposited on the surface of a heating substrate, reorganized and arranged to form a dense solid material. Currently, CVD is widely used in many areas such as protective film layers, microelectronics technology, solar energy utilization, optical fiber communications, superconducting technology, preparation of new materials, integrated circuits, etc. It is the most widely used method in industry for preparing semiconductor silicon materials.

In actual production, it is necessary to fully disperse and mix the precursor gas molecular clusters participating in the reaction, so a gas mixer is needed. The static mixer is currently widely used in the industry. It is a type of mixer composed of a reaction tube and a special structure internal component arranged statically inside. When two or more fluids are introduced, the internal components of the static mixer cut, rotate, mix, etc. on the fluids to make the fluids mix and stir by themselves. The mixed gas phase can be deposited on the surface of the substrate after sufficient reaction. However, the existing mixer has the following defects: 1. The dispersion and mixing effect of molecules with higher viscosity is poor, so that the difference between the molecular clusters of the mixed gas is large, the molar ratio is uneven, and the reaction rate is eventually low. In the process of generating crystals, the grain size and the gap or distance between the grains are very different. The content of amorphous single substances between the grains is very high, which will cause the crystals produced after deposition to be poorly formed. 2. The components used to disperse the gas material molecules in the existing mixer are connected by welding. When the gas reactants pass through, they will rub and collide with the welding points. Long-term work will erode the welding points, increasing the risk of reactant contamination.

Summary of the invention

The object of the present invention is to provide a chemical vapor deposition molecule dispersing mixer to solve the problems of poor gas material mixing effect and easy contamination of reactants in the prior art.

The present invention is implemented by the following technical scheme: a chemical vapor deposition molecular disintegration mixer, including an outer shell, an inner cylinder, a flange, an inlet connecting ring, an outlet connecting ring, a fixed column, a metal wire mesh and a sealing layer, wherein the inner cylinder is coaxially arranged in the outer shell, flanges are fixedly connected at both ends of the outer shell, the inlet connecting ring is sealedly connected to the inlet of the inner cylinder, the outlet of the inner cylinder is sealedly connected to the outlet, the inlet connecting ring and the outlet connecting ring are respectively sealedly connected to the flange, more than two fixed columns are fixedly arranged in the outer shell along the length direction of the inner cylinder, a plurality of metal wire meshes are arranged in the inner cylinder, a plurality of threading holes are opened in the circumferential direction at positions corresponding to the metal wire meshes on the inner cylinder, the metal wire mesh is woven by metal wires passing through the threading holes, the metal wire mesh is a horizontal and vertical mesh structure of metal wires, the axial rotation of two adjacent metal wire meshes is arranged at α degrees, the outer wall of the inner cylinder is coated with a sealing layer, and the coating layer is in contact with the fixed column.

Furthermore, when the molecular clusters are greater than 1000, the axial rotation angle α between two adjacent metal wire meshes is 15°, and the number of metal wire meshes is 7 or an integer multiple of 7; when the molecular clusters are less than 1000, the axial rotation angle α between two adjacent metal wire meshes is 30°, and the number of metal wire meshes is 4 or an integer multiple of 4.

Furthermore, when the mesh spacing coefficient is ≥1, the spacing between two adjacent metal wire meshes is 30cm, when 1＞mesh spacing coefficient ≥0.1, the spacing between two adjacent metal wire meshes is 20cm, when 0.1＞mesh spacing coefficient ≥0.01, the spacing between two adjacent metal wire meshes is 10cm, and when the mesh spacing coefficient is <0.01, the spacing between two adjacent metal wire meshes is 5cm.

Furthermore, the mesh coefficient = 1/( _μmix ×d), wherein μmix _is the viscosity of the mixed gas material, d is the diameter of the metal wire, and the diameter d of the metal wire is 1-5 mm.

Furthermore, the distance D between two adjacent parallel metal wires of the metal wire mesh is twice the diameter d of the metal wire.

Furthermore, the sealing layer is made of polytetrafluoroethylene or modified polytetrafluoroethylene.

Furthermore, the inner walls of the inner cylinder, flange, inlet connecting ring and outlet connecting ring, and the surface of the metal wire mesh are electrochemically polished, and the surface roughness Ra after the treatment is ≦0.2 μm.

Furthermore, the inlet connecting ring includes an inlet section, a transition section and an outlet section, the inner diameter of the inlet section is equal to the inner diameter of the inlet flange, the inner diameter of the outlet section is equal to the inner diameter of the inner tube, and the inclination angle between the transition section and the axis of the inner tube is 30°-60°.

Furthermore, the outlet connecting ring has a side connected to the inner tube with an inner diameter equal to that of the inner tube, the inner wall of the outlet connecting ring expands outward in an arc shape, and the outlet side of the outlet connecting ring is flush with the flange.

Advantages of the present invention:

1. By making the mixed gas pass through the metal wire mesh and collide with the metal wire, the metal wire and the macromolecular clusters are collided when the gas material passes through the metal wire mesh to destroy the van der Waals force between molecules and disperse the macromolecular clusters. The various materials are mixed evenly, so that trichlorosilane and hydrogen are fully contacted to achieve the molar ratio required for the reaction, which is more conducive to the formation of silicon crystals of uniform size. During the crystal growth process, the gaps between crystals and the crystal wall thickness of the fully mixed materials are consistent. It is easier to obtain crystal blocks of uniform size when crushed downstream, which is conducive to downstream reprocessing.

2. Determining the rotation angle and spacing between two adjacent metal wire meshes according to the molecular cluster size of the mixed gas material and the viscosity of the mixed gas material can increase the collision probability between the metal wire and the molecular clusters of the mixed material and improve the dispersion efficiency of the molecular clusters of the mixed material.

3. The method of punching holes in the inner cylinder and weaving metal wires into a metal mesh replaces the traditional method of welding the internal components of the mixer, reducing the risk of the material being contaminated by impurities in the welding points.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a cross-sectional view of the overall structure of the present invention.

FIG. 2 is a partial structural cross-sectional view of the inlet connecting ring.

FIG3 is a schematic diagram of the partial structure of the inner tube, the cladding layer and the fixing column.

FIG. 4 is a schematic diagram showing the arrangement between two adjacent layers of metal wire mesh.

FIG. 5 is a SEM microstructure diagram of a silicon single substance sample prepared in an embodiment of the present invention.

FIG. 6 is a SEM microstructure diagram of a silicon single substance sample prepared in a comparative example of the present invention.

In the figure: outer shell 1, inner tube 2, flange 3, inlet connecting ring 4, outlet connecting ring 5, fixing column 6, wire mesh 7, sealing layer 8, inlet section 401, transition section 402, outlet section 403.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the present invention, it should be noted that the terms "center", "up", "down", "front", "back", "top", "bottom", "left", "right", "vertical", "horizontal", "inside" and "outside" etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

As shown in Figures 1 and 2: A chemical vapor deposition molecular disintegration mixer, comprising an outer shell 1, an inner cylinder 2, a flange 3, an inlet connecting ring 4, an outlet connecting ring 5, a fixing column 6, a metal wire mesh 7 and a sealing layer 8. The inner cylinder 2 is coaxially arranged in the outer shell 1, and flanges 3 are fixedly connected at both ends of the outer shell 1. The inner cylinder 2, flange 3, inlet connecting ring 4, outlet connecting ring 5 and metal wire mesh 7 are all made of 316L stainless steel. The inner walls of the inner cylinder 2, flange 3, inlet connecting ring 4 and outlet connecting ring 5 and the surface of the metal wire mesh 7 are electrochemically polished, and the surface roughness Ra after treatment is ≦0.2μm to reduce the risk of contamination of gas materials. The inlet of the inner cylinder 2 is sealed with the inlet connecting ring 4, and the outlet of the inner cylinder 2 is sealed with the outlet connecting ring 5. The inlet connecting ring 4 and the outlet connecting ring 5 are sealed with the flange 3 respectively. Specifically, the flange 3 and the inner cylinder 2 are connected to the inlet connecting ring 4 and the outlet connecting ring 5. A seal made of polytetrafluoroethylene material can be used for mechanical sealing. The inlet connecting ring 4 includes an inlet section 401, a transition section 402 and an outlet section 403. The inner diameter of the inlet section 401 is equal to the inner diameter of the flange 3 at the inlet, and the inner diameter of the outlet section 403 is equal to the inner diameter of the inner tube 2. The inlet section 401 and the outlet section 403 are used to connect the flange 3 and the inner tube 2. In order to ensure the initial velocity of the fluid of the material gas and reduce the resistance loss, the inclination angle between the inner wall of the transition section 402 and the axis of the inner tube 2 is 30°-60°. The gradual reduction of the inner wall of the transition section 402 is conducive to reducing the turbulence of the fluid and reducing the resistance; the outlet connecting ring 5 is connected to the inner tube 2 on one side and has the same inner diameter as the inner tube 2. The inner wall of the outlet connecting ring 5 is arc-shaped and expands outwards. The outlet side of the outlet connecting ring 5 is flush with the flange 3. The arc-shaped expansion of the outlet 5 has a similar effect to that of the inlet connecting ring 4, both of which are to reduce the turbulence of the gas when passing through the mixer and reduce the overall fluid resistance of the mixer.

As shown in FIG3 , more than two fixing columns 6 are fixedly arranged in the outer shell 1 along the length direction of the inner cylinder. The fixing columns 6 are used to position the inner cylinder 2. A plurality of metal meshes 7 are arranged in the inner cylinder 2. A plurality of threading holes are opened along the circumferential direction at positions corresponding to the metal meshes 7 on the inner cylinder 2. The metal meshes 7 are woven by metal wires passing through the threading holes. The metal meshes 7 are a mesh structure of metal wires in a horizontal and vertical manner. The metal wires are spaced equally from each other. The distance D between two adjacent parallel metal wires of the metal mesh 7 is twice the diameter d of the metal wires. The metal wires arranged horizontally and vertically are arranged horizontally and vertically. The two adjacent metal meshes 7 are perpendicular to each other, and the axial rotation angle is α, that is, the transverse metal wires between the two adjacent metal meshes 7 are offset and deflected along the axis of the inner tube 2 by α degrees. The longitudinal metal wires of the two metal meshes 7 are perpendicular to the transverse metal wires, and are also deflected by the same α degrees. Each metal mesh 7 rotates counterclockwise or clockwise in turn until it returns to the angle position of the first metal mesh 7 after deflecting 90°, completing a whole cycle. When the gas passes through the metal mesh 7, the molecular clusters and the metal wires are generated. Collision and deflection, after all the metal meshes 7 in a whole cycle, a mixing cycle is completed. The axial rotation of the metal meshes 7 by α degrees can increase the collision probability between the metal wires and the molecular clusters of the mixed material, and the collision between the macromolecular clusters and the metal wires is used to disperse the macromolecular clusters, so as to achieve the effect of molecular dispersion and mixing; the outer wall of the inner cylinder 2 is coated with a sealing layer 8, and the sealing layer 8 is made of polytetrafluoroethylene or modified polytetrafluoroethylene. When using a low-temperature process (i.e., the operating temperature of the mixer is below 120°C), polytetrafluoroethylene can be selected. The material is preferably made of modified polytetrafluoroethylene in high temperature process (i.e. the mixer working temperature is 120°C-220°C). The sealing layer 8 is made by molding process. When making it, the metal mesh 7 is first woven on the inner cylinder 2, and then the polytetrafluoroethylene or modified polytetrafluoroethylene is coated on the outer side of the inner cylinder 2 by molding process. The coating layer 8 fills and seals the threading holes through which the metal wire passes, so that the inner cylinder 2 forms a whole sealed whole to prevent the mixed gas from escaping. The coating layer 8 is in contact with the fixing column 6, and the fixing column 6 fixes the inner cylinder 2 at the center of the outer shell 1 and keeps it concentric with the outer shell 1.

As shown in Figure 4: the mixer described in the present invention utilizes the principle that when the gas material passes through the metal wire mesh 7, the collision between the metal wire and the macromolecular clusters destroys the van der Waals force between the molecules to disperse the macromolecular clusters, thereby mixing multiple materials. The axial rotation angle between two adjacent metal wire meshes 7 is related to the size of the molecular clusters of the gas material to be mixed. According to empirical summary, when the molecular clusters are greater than 1000, the axial rotation angle α between two adjacent metal wire meshes 7 is 15°, and the number of metal wire meshes 7 required for the gas material to complete a mixing cycle is 7. In the actual production process, multiple mixing cycles can be set to ensure the mixing effect, and the number of metal wire meshes 7 is an integer multiple of 7; when the molecular clusters are less than 1000, the axial rotation angle α between two adjacent metal wire meshes 7 is 30°, and the number of metal wire meshes 7 required for the gas material to complete a mixing cycle is 4 or an integer multiple of 4. According to the above method, the axial rotation angle α between the metal wire meshes 7 and the number of metal wire meshes 7 can be determined according to the size of the molecular clusters of the gas material to be mixed.

The mesh spacing between two adjacent metal meshes 7 is related to the mesh spacing coefficient, and the mesh spacing coefficient is related to the viscosity μ of the _mixed gas material and the diameter d of the metal wire, that is, the mesh spacing coefficient = 1/( _μ ×d), the diameter of the metal wire is 1-5mm, when the mesh spacing coefficient ≥1, the surface spacing is selected to be 30cm, when 1＞mesh spacing coefficient ≥0.1, the mesh spacing is selected to be 20cm, when 0.1＞mesh spacing coefficient ≥0.01, the mesh spacing is selected to be 10cm, and when the mesh spacing coefficient <0.01, the mesh spacing is selected to be 5cm. In summary, when designing a chemical vapor deposition molecular decomposition mixer described in the present invention, the number of metal meshes 7, the axial rotation angle and the spacing between the meshes can be calculated and determined according to the molecular cluster size of the gas material to be _mixed , the viscosity μ of the mixed gas material and the diameter of the selected metal wire.

In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments are designed according to the above method as follows:

Embodiment: The mixer of the present invention is installed in the gas path system of the reduction furnace, the wire diameter is set to 1 mm, the gas flow rate in the mixer is set to 10 m/s, and the materials are trichlorosilane (SiHCl ₃ ) and hydrogen (H ₂ ), the molar ratio of the mixed gas according to the process design is 1:1, and the molecular cluster size of the mixed gas material is estimated to be 1545, so the axial rotation angle α between the mesh surfaces of two adjacent metal wire meshes 7 is set to 15°, and the number of metal wire meshes 7 is 14; the experiment measured that the viscosity μmix of the gas material under this mixing ratio _is 0.1885N·s/㎡, and the mesh spacing coefficient = 1/( _μmix ×d) = 5.31 is obtained according to the calculation. According to the mesh spacing coefficient, a woven metal wire mesh 7 with a spacing of 30cm should be selected, and a mixer made according to the above parameters is used to mix the gas material. The mixed gas material is reacted to prepare silicon element under the process conditions of trichlorosilane flow rate 200-1500kg/h, hydrogen flow rate 3-35kg/h, reaction temperature 550-950℃, reaction pressure 0.6Mpa, and electrode current 100-1800mA (the above process parameters increase with time).

FIG5 is a SEM micrograph of silicon single substance prepared by the mixed gas in this embodiment. From the image, it can be seen that the gaps between crystals are consistent, the thickness of the crystal walls is consistent, and it is easier to obtain crystal blocks of uniform size when crushed downstream, which is beneficial to downstream reprocessing.

Comparative example: The same material mixing ratio as in the embodiment was adopted, and the mixer described in the present invention was not installed in the gas path system of the reduction furnace. A 304 stainless steel circular pipe was used instead. The mixed gas materials were reacted using the same process parameters as in the embodiment, and sampling and detection were performed after preparing silicon element.

Figure 6 is a SEM micrograph of the silicon single substance prepared in the comparative example. From the image, it can be seen that the grain size and the gap or distance between the grains vary greatly. The content of amorphous single substances between the grains is very high, which will cause the crystals produced after deposition to be poorly formed, which is not conducive to subsequent reprocessing.

Claims (9)

1. A chemical vapor deposition molecular scrambling mixer, characterized in that it comprises an outer shell (1), an inner cylinder (2), a flange (3), an inlet connecting ring (4), an outlet connecting ring (5), a fixing column (6), a metal wire mesh (7) and a sealing layer (8), wherein the inner cylinder (2) is coaxially arranged in the outer shell (1), the flanges (3) are fixedly connected to both ends of the outer shell (1), the inlet of the inner cylinder (2) is sealedly connected to the inlet connecting ring (4), the outlet of the inner cylinder (2) is sealedly connected to the outlet connecting ring (5), the inlet connecting ring (4) and the outlet connecting ring (5) are respectively connected to the flanges. (3) Sealed connection, wherein more than two fixing columns (6) are fixedly provided in the outer shell (1) along the length direction of the inner cylinder, a plurality of metal wire meshes (7) are provided in the inner cylinder (2), a plurality of threading holes are opened in the circumferential direction at positions corresponding to the metal wire meshes (7) on the inner cylinder (2), the metal wire meshes (7) are woven by metal wires passing through the threading holes, the metal wire meshes (7) are a mesh structure of metal wires in a horizontal and vertical direction, two adjacent metal wire meshes (7) are arranged to be axially rotated at an angle of α, a sealing layer (8) is coated on the outer wall of the inner cylinder (2), and the coating layer (8) is in contact with the fixing columns (6). 2. A chemical vapor deposition molecular break-up mixer according to claim 1, characterized in that, when the molecular clusters are greater than 1000, the axial rotation angle α between two adjacent metal wire meshes (7) is 15°, and the number of metal wire meshes (7) is 7 or an integer multiple of 7; when the molecular clusters are less than 1000, the axial rotation angle α between two adjacent metal wire meshes (7) is 30°, and the number of metal wire meshes (7) is 4 or an integer multiple of 4. 3. A chemical vapor deposition molecular scrambling mixer according to claim 2, characterized in that, when the mesh spacing coefficient is ≥1, the spacing between two adjacent metal wire meshes (7) is selected to be 30 cm, when 1＞the mesh spacing coefficient is ≥0.1, the spacing between two adjacent metal wire meshes (7) is selected to be 20 cm, when 0.1＞the mesh spacing coefficient is ≥0.01, the spacing between two adjacent metal wire meshes (7) is selected to be 10 cm, and when the mesh spacing coefficient is <0.01, the spacing between two adjacent metal wire meshes (7) is selected to be 5 cm. 4. A chemical vapor deposition molecular disintegration mixer according to claim 3, characterized in that the mesh coefficient = 1/( _μmix ×d), wherein μmix _is the viscosity of the mixed gas material, d is the diameter of the metal wire, and the diameter d of the metal wire is 1-5 mm. 5. A chemical vapor deposition molecular scrambling mixer according to any one of claims 1 to 4, characterized in that the distance D between two adjacent parallel metal wires of the metal wire mesh (7) is twice the diameter d of the metal wire. 6. The chemical vapor deposition molecular scrambling mixer according to claim 1, characterized in that the sealing layer (8) is made of polytetrafluoroethylene or modified polytetrafluoroethylene. 7. A chemical vapor deposition molecular scrambling mixer according to claim 1, characterized in that the inner walls of the inner cylinder (2), flange (3), inlet connecting ring (4) and outlet connecting ring (5) and the surface of the metal wire mesh (7) are electrochemically polished, and the surface roughness Ra after the treatment is ≤ 0.2 μm. 8. A chemical vapor deposition molecular disintegration mixer according to claim 7, characterized in that the inlet connecting ring (4) includes an inlet section (401), a transition section (402) and an outlet section (403), the inner diameter of the inlet section (401) is equal to the inner diameter of the flange (3) at the inlet, the inner diameter of the outlet section (403) is equal to the inner diameter of the inner tube (2), and the inclination angle between the transition section (402) and the axis of the inner tube (2) is 30°-60°. 9. A chemical vapor deposition molecular disintegration mixer according to claim 8, characterized in that the outlet connecting ring (5) is connected to the inner tube (2) on one side with the same inner diameter as the inner tube (2), the inner wall of the outlet connecting ring (5) is arc-shaped and expands outward, and the outlet side of the outlet connecting ring (5) is flush with the flange (3).