Exhaust device for pulling monocrystalline silicon and single crystal furnace

Abstract

The invention relates to the technical field of monocrystalline silicon crystal pulling exhaust, and provides an exhaust device for monocrystalline silicon crystal pulling and a single crystal furnace, the exhaust device comprises a gas guide cylinder body, and is characterized in that an inner cavity of the gas guide cylinder body forms a divergent structure along the gas flow direction, and the radius of the inner cavity is continuously increased from the gas inlet end to the gas outlet end; the divergence angle alpha of the gas guide cylinder is larger than or equal to 2 degrees and smaller than or equal to 12 degrees, and the divergence angle is an included angle between the axis of the gas guide cylinder and the tangent line of the inner wall; and a continuous flow channel without step mutation is formed on the surface of the inner wall of the gas guide cylinder body. According to the exhaust device and the single crystal furnace provided by the invention, the problems of oxide deposition, furnace pressure fluctuation and out-of-control oxygen content are synchronously solved without external intervention.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal silicon pulling production, and in particular to an exhaust device and a single crystal furnace used for single crystal silicon pulling. Background Art

[0002] In the Czochralski method of growing single crystal silicon, the inner cavity of the single crystal furnace needs to maintain a high-purity environment to ensure the quality of single crystal silicon. During this process, the oxide-containing gases (such as , CO, etc.) need to be quickly discharged through the exhaust device to avoid silicon melt contamination or crystal defects caused by gas retention.

[0003] Figure 1 The figure shows the schematic diagram of the structure of the traditional exhaust device. It adopts a vertical equal-diameter gas guide cylinder structure to connect the inner cavity of the single crystal furnace with the external exhaust pipeline. However, there is a significant problem of oxide deposition in practical applications. Specifically, the structural characteristics of the traditional equal-diameter gas guide cylinder provide a stable adhesion interface for the deposits: the precipitated oxide particles gather toward the lower part of the cylinder under the action of gravity, and the equal-diameter structure makes it easier for the particles to collide and deposit in the flow channel, forming a self-thickening annular scaling layer. When the oxygen-containing gas flows through the equal-diameter gas guide cylinder, the friction between the gas and the cylinder wall causes the boundary layer turbulence to intensify, especially in the middle and lower part of the cylinder (the area where the temperature gradient drops from 1000℃ to 600℃), the gas flow rate is significantly reduced, at this time, the gaseous oxides such as SiO2 reach a supersaturated state due to the drop in temperature, and a large number of solid SiO2 particles are precipitated and attached to the cylinder wall; as the deposition layer thickens, the effective flow cross-sectional area of ​​the gas guide cylinder gradually decreases, and the local pressure loss increases sharply (the measured pressure loss increase can reach 40%-70%). This phenomenon directly leads to: (1) uncontrolled pressure in the furnace: the increase in exhaust resistance causes the furnace chamber pressure to deviate from the set value (usually maintained in the range of 1-10 Pa). The increase in pressure will inhibit the volatilization efficiency of oxygen in the silicon melt, but increase the oxygen content of the melt; (2) oxygen content rebound: the decrease in exhaust efficiency leads to the inability to discharge volatile oxides in time, and some gases react in the furnace to generate oxygen impurities, which eventually causes the crystal oxygen content to exceed the standard (>15 ppm), resulting in uneven resistivity of the silicon ingot and even dislocation defects. Summary of the invention

[0004] To this end, the purpose of the present invention is to overcome the problems of exhaust blockage, furnace pressure fluctuation and oxygen content out of control caused by medium-diameter exhaust pipes in the prior art, and to provide an exhaust device and a single crystal furnace for single crystal silicon pulling, which can simultaneously solve the problems of oxide deposition, furnace pressure fluctuation and oxygen content out of control without external intervention.

[0005] In the first aspect, in order to solve the above-mentioned technical problems, the present invention provides an exhaust device for single crystal silicon pulling, comprising an air guide cylinder body, the inner cavity of the air guide cylinder body forming a gradually expanding structure along the air flow direction, the inner cavity radius of which continuously increases from the air inlet end to the air outlet end, and the expansion angle α of the air guide cylinder body satisfies 2°≤α≤12°, wherein the expansion angle is the angle between the axis of the air guide cylinder body and the tangent of the inner wall; the inner wall surface of the air guide cylinder body forms a continuous flow channel without step mutations.

[0006] In one embodiment of the present invention, the expansion angle α of the air guide cylinder satisfies 5°≤α≤8°.

[0007] In one embodiment of the present invention, the expansion curve of the gradually expanding structure satisfies a logarithmic spiral; The polar coordinate equation of the logarithmic spiral is expressed as ; r represents the polar diameter; θ represents the polar angle; a represents the initial radius scale factor, which is a constant and satisfies a∈[50, 150] mm; e represents the base of the natural logarithm; b represents the curvature control factor, which is a constant and satisfies b∈[0.02, 0.15].

[0008] In one embodiment of the present invention, the air guide cylinder body comprises at least two functional sections, which are, in order, along the air flow direction: A gradually expanding transition section, the length of which accounts for 60%-70% of the total length of the gas guide cylinder, and the expansion angle α satisfies α=5°±0.5°; The pressure stabilizing separation section has a length that accounts for 15%-30% of the total length of the gas guide cylinder body, and its expansion angle α satisfies α=12°±1°.

[0009] In one embodiment of the present invention, the inner wall surface of the gradually diverging transition section is provided with a three-level wettability gradient coating, and the three-level wettability gradient coating comprises: a hydrophobic coating region, which is configured as a composite coating of fluorinated carbon nanotubes and polytetrafluoroethylene; a transition coating zone configured as a plasma-sprayed Al2O3-TiO2 dual-phase ceramic layer; a hydrophilic coating region configured as a hydroxyapatite-based hydrophilic coating; Wherein, the hydrophobic coating area, the transition coating area and the hydrophilic coating area are arranged in sequence along the air flow direction.

[0010] In one embodiment of the present invention, the connection area of ​​the hydrophobic coating area, the transition coating area and the hydrophilic coating area forms a metallurgical bonding transition zone based on laser remelting.

[0011] In one embodiment of the present invention, it also includes a temperature control module, which is arranged on the outer wall of the air guide cylinder; wherein the temperature control module includes a plurality of groups of refrigeration components, and the plurality of groups of refrigeration components are evenly distributed along the circumferential direction, and the refrigeration power of each group of the refrigeration components decreases gradually along the airflow direction, and the refrigeration power gradient is positively correlated with the temperature gradient of the inner wall of the air guide cylinder.

[0012] In one embodiment of the present invention, the refrigeration component is configured as a semiconductor refrigeration sheet, the cold end of which is attached to the outer wall of the air guide cylinder, and the hot end is connected to the heat dissipation fins; The spacing between adjacent semiconductor cooling sheets is 1 / 12 to 1 / 8 of the circumference of the air inlet end of the air guide cylinder; and the cooling power gradient satisfies: ; P0 is the maximum power at the air inlet end of the air guide cylinder, L is the total length of the air guide cylinder, n is the attenuation index, and satisfies 1.2≤n≤1.8; x represents the coordinate along the air flow direction, and satisfies x∈[0,L]; P(x) represents the cooling power at position x.

[0013] In one embodiment of the present invention, an airflow monitoring module is further included, and the airflow monitoring module includes: An optical fiber sensor is embedded in the inner wall of the gas guide cylinder and is used to monitor the exhaust flow rate and particle concentration in real time; A controller is connected to the optical fiber sensor and the refrigeration component, and is used to adjust the refrigeration power of the refrigeration component according to the monitoring data of the optical fiber sensor.

[0014] In a second aspect, in order to solve the above-mentioned technical problem, the present invention provides a single crystal furnace, including the exhaust device for pulling single crystal silicon.

[0015] The above technical solution of the present invention has the following beneficial effects compared with the prior art: The exhaust device for single crystal silicon pulling of the present invention solves the problem of oxide deposition without external intervention.

[0016] Specifically, the radius of the inner cavity of the gas guide cylinder increases continuously along the direction of the airflow to form a smoothly expanding flow channel. According to the principles of fluid mechanics, when the gas flows in the gradually expanding flow channel, the flow velocity gradually decreases as the cross-sectional area of ​​the flow channel increases, and the flow velocity gradient changes gently. Compared with the abrupt expansion section of the equal-diameter structure, the shear stress between the gas and the wall is significantly reduced, thereby reducing the turbulence intensity and inhibiting the generation of boundary layer turbulence. The reduction in turbulence intensity directly reduces the collision frequency of oxide particles (such as SiO2) with the cylinder wall, thereby reducing the deposition of materials on the cylinder wall of the gas guide cylinder, solving the problem of exhaust blockage caused by deposition. At the same time, the gradually expanding structure allows the particles to disperse due to the expansion of the flow channel cross-sectional area when they move downward with the airflow, further reducing the particle concentration per unit area and avoiding local accumulation.

[0017] Among them, the expansion angle α of the gradual expansion structure satisfies 2°≤α≤12°, which is determined based on the multi-scale coupling optimization of fluid dynamics and thermodynamics, and is based on the optimal design of gas flow characteristics and deposition suppression requirements in the single crystal silicon pulling process. 2°≤α≤12° makes the airflow expansion rate match the boundary layer adhesion capacity, which can not only avoid flow separation, but also ensure that the gas residence time in the sensitive temperature zone is shortened.

[0018] In addition, the gradually expanding structure has a "self-cleaning" effect: in the lower part of the gas guide cylinder (the oxide precipitation sensitive area where the temperature drops to 600-800°C), the cross-sectional area of ​​the gradually expanding flow channel increases, causing the air flow velocity to further reduce to below the critical deposition velocity. At this time, the precipitated solid particles move downward due to gravity, but the gradually expanding structure does not provide a narrow attachment surface of the equal-diameter cylinder. The particles continue to move toward the exhaust channel under the carry of the low-speed airflow and are eventually discharged from the system.

[0019] In addition, there is no step mutation on the inner wall surface of the gas guide cylinder, which avoids the vortex zone (such as the flange connection) caused by the structural mutation of the traditional gas guide cylinder. The elimination of the vortex zone can prevent the oxide particles from being retained locally and forming initial deposition nuclei, thereby further solving the exhaust blockage problem caused by material deposition.

[0020] The single crystal furnace described in the present invention, based on the use of an exhaust device with an innovative structure, simultaneously solves the problems of furnace pressure fluctuation and uncontrolled oxygen content without external intervention. Specifically, the gradually expanding flow channel reduces the flow velocity and turbulence intensity, thereby reducing the gas flow resistance (pressure loss) compared to the equal-diameter structure. More importantly, the gradually expanding design avoids the nonlinear increase in pressure loss caused by thickening of the deposition in the traditional gas guide tube (i.e., the vicious cycle of blockage-pressure loss), thereby maintaining a stable exhaust flux; the stable exhaust flux ensures that the oxygen-containing gas volatilized by the silicon melt is continuously discharged, and the oxygen partial pressure in the furnace is always lower than the oxygen solubility threshold of the silicon melt. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0022] Figure 1 It is a structural schematic diagram of an air guide cylinder in the prior art; Figure 2 It is a schematic structural diagram of an exhaust device for single crystal silicon pulling in a preferred embodiment of the present invention; Figure 3 It is a schematic cross-sectional view of the air inlet end of the air guide cylinder in a preferred embodiment of the present invention; Figure 4 for Figure 2 A partial enlarged schematic diagram of area A in the middle.

[0023] Description of the Figures in the Specification: Air guide cylinder body, 21-gradually expanding transition section, 211-hydrophobic coating area, 212-transition coating area, 213-hydrophilic coating area; 22-pressure stabilizing separation section; 4-temperature control module, 41-refrigeration component; 6- airflow monitoring module, 61- optical fiber sensor, 62- controller. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0025] Reference Figure 2 and Figure 4 As shown, an embodiment of the present invention discloses an exhaust device for single crystal silicon pulling, comprising an air guide cylinder 2, wherein the inner cavity of the air guide cylinder 2 forms a gradually expanding structure along the air flow direction, and the inner cavity radius thereof continuously increases from the air inlet end to the air outlet end, and the expansion angle α of the air guide cylinder satisfies 2°≤α≤12°, wherein the expansion angle is the angle between the axis of the air guide cylinder and the tangent of the inner wall; the inner wall surface of the air guide cylinder forms a continuous flow channel without step mutations.

[0026] The exhaust device is used in a single crystal furnace for producing direct-pull single crystal silicon. The exhaust gas in the single crystal furnace is guided to the exhaust pipe at the rear end through the gas guide cylinder 2. The end of the gas guide cylinder 2 connected to the single crystal furnace is the air inlet end, and the end connected to the exhaust pipe is the air outlet end. The air flow direction is from the air inlet end to the air outlet end.

[0027] The expansion angle α is defined as the angle between the axis of the air guide cylinder and the tangent of the inner wall, which represents the expansion rate of the flow channel cross-sectional area along the flow direction. Its geometric relationship satisfies: ; D0 represents the initial inner diameter of the inlet end; D(z) represents the inner diameter at the axial position z; and L represents the axial length of the gradually expanding section.

[0028] Specifically, the inner radius of the gas guide cylinder 2 increases continuously along the direction of the airflow to form a smoothly expanding flow channel. According to the principles of fluid mechanics, when the gas flows in the gradually expanding flow channel, the flow velocity gradually decreases as the cross-sectional area of ​​the flow channel increases, and the flow velocity gradient changes gently. Compared with the abrupt expansion section of the equal-diameter structure, the shear stress between the gas and the wall is significantly reduced, thereby reducing the turbulence intensity and inhibiting the generation of boundary layer turbulence. The reduction in turbulence intensity directly reduces the collision frequency of oxide particles (such as SiO2) with the cylinder wall, thereby reducing the deposition of materials on the cylinder wall of the gas guide cylinder, solving the problem of exhaust blockage caused by deposition. At the same time, the gradually expanding structure allows the particles to disperse due to the expansion of the flow channel cross-sectional area when they move downward with the airflow, further reducing the particle concentration per unit area and avoiding local accumulation.

[0029] In addition, the gradually expanding structure has a "self-cleaning" effect: in the lower part of the gas guide cylinder 2 (the oxide precipitation sensitive area where the temperature drops to 600-800°C), the cross-sectional area of ​​the gradually expanding flow channel increases, causing the air flow velocity to further reduce to below the critical deposition velocity. At this time, the precipitated solid particles move downward due to gravity, but the gradually expanding structure does not provide a narrow attachment surface of the equal-diameter cylinder. The particles continue to move toward the exhaust channel under the carry-by-low-speed airflow and are eventually discharged from the system.

[0030] Reference Figure 2 and Figure 4 As shown, the expansion angle α of the gas guide cylinder satisfies 2°≤α≤12°, which is determined based on the multi-scale coupling optimization of fluid dynamics and thermodynamics, and is based on the optimal design of gas flow characteristics and deposition suppression requirements in the single crystal silicon pulling process. 2°≤α≤12° makes the airflow expansion rate match the boundary layer adhesion ability, which can avoid flow separation and ensure that the gas residence time in the sensitive temperature zone is shortened.

[0031] Specifically, when the expansion angle α is less than 2°, the gradually expanding flow channel is too long (the rate of change of cross-sectional area is too low at the same length), and the gas flow rate decreases too slowly. Although it can reduce the turbulence intensity, it will result in: the gas residence time in the sensitive temperature zone (600~800℃) is prolonged, and the oxides still have sufficient time to precipitate and deposit; the axial dimension of the gas guide cylinder 2 is too large, which conflicts with the compact spatial layout of the single crystal furnace and increases the manufacturing cost.

[0032] When the expansion angle α>12°, the flow channel cross-sectional area expands too fast, and the gas flow is prone to boundary layer separation (Flow Separation), forming a local vortex zone. Experiments show that when α=15°, the vortex zone length accounts for 30%, resulting in: the probability of particle collision in the vortex zone increases by 2~3 times, the deposition rate rebounds; the pressure loss increases by 15%~20% due to vortex disturbance, weakening the structural advantage.

[0033] Specifically, in the high-temperature zone at the top of the conductor cylinder (above 1000°C), a smaller expansion angle such as α=3° maintains a higher flow rate, allowing the gaseous oxides to pass quickly before reaching the precipitation temperature, thereby inhibiting premature phase change; in the low-temperature zone at the bottom of the gas-conducting cylinder (600~800°C), a larger expansion angle such as α=10° rapidly expands the flow channel cross-section, and the air flow velocity drops to 1~2 m / s (lower than the critical deposition velocity of SiO2 particles 1.5 m / s). At this time: the precipitated particles sink due to gravity, but the gradually expanding structure does not have the narrow attachment surface of the equal-diameter cylinder, and the particles continue to move toward the exhaust pipe under the drag force of the low-speed airflow; the expansion of the flow channel cross-sectional area dilutes the particle concentration, and the deposition per unit area is reduced by 70%~85%.

[0034] In particular, considering the balance between flow stability and turbulence suppression, the expansion angle α of the air guide cylinder satisfies 5°≤α≤8°.

[0035] Specifically, when α ≥ 9°, the flow channel expansion rate is too fast and it is easy to cause boundary layer separation (the simulation shows that when α = 10°, the critical Reynolds number of separation is reduced to ), resulting in the expansion of the local eddy zone (accounting for > 20%). When α≤8°, the flow channel expansion rate matches the gas viscous dissipation rate, completely suppressing flow separation (experimental verification shows that when α=8°, the critical Reynolds number for separation> ), the turbulence intensity is reduced to 15%~20% of the initial value. In the range of 5°~8°, the residence time of the gas in the oxide precipitation sensitive temperature zone (600~800℃) is shortened to 2.5~3.8 seconds (6~8 seconds for the traditional equal-diameter structure), so that the SiO2 particles are taken out of the system before reaching the critical deposition size, reducing the deposition probability.

[0036] Specifically, when 5°≤α≤6°, the cross-sectional area of ​​the upper part of the gas guide cylinder expands smoothly, maintaining the airflow velocity>5 m / s (higher than the critical velocity of SiO2 gasification 4.2 m / s), ensuring that the gaseous oxide does not undergo phase change and precipitation in the high-temperature zone. In the lower flow channel of 7°≤α≤8°, the cross-sectional area expansion rate accelerates, and the airflow velocity drops to 1.2~1.8 m / s (lower than the critical velocity of SiO2 particle deposition 1.5 m / s). At this time: the precipitated particles sink due to gravity, but the gradually expanding flow channel has no narrow attachment surface of equal diameter structure, and the particles continue to move toward the exhaust pipe under the drag force of the low-speed airflow; the expansion of the flow channel cross-sectional area dilutes the particle concentration and reduces the deposition per unit area.

[0037] In addition, the expansion angle of 5°~8° can be formed through a single CNC spinning process (the traditional multi-stage welding structure requires 3~5 processes), and the cost of the gas guide cylinder is controllable; at the same time, the stress concentration problem caused by the sudden change of the flow channel when α>10° ​​is avoided, thereby extending the service life of the gas guide cylinder.

[0038] Specifically, the expansion curve of the gradually expanding structure satisfies a logarithmic spiral; The polar coordinate equation of the logarithmic spiral is expressed as ; r represents the polar diameter; θ represents the polar angle; a represents the initial radius scale factor, which is a constant and satisfies a∈[50, 150] mm; e represents the base of the natural logarithm, also called the natural constant or Euler number, e≈2.71828; b represents the curvature control factor, which is a constant and satisfies b∈[0.02, 0.15].

[0039] Specifically, the curvature radius of the logarithmic spiral changes continuously and gradually, which is a nonlinear expansion. It avoids the local curvature mutation of the traditional linear gradual expansion structure, promotes the reduction of boundary layer separation risk, increases the turbulent kinetic energy decay rate, and reduces the frequency of particle collisions.

[0040] As a further improvement of the embodiment of the present invention, refer to Figure 3 As shown, the gas guide cylinder body 2 includes at least two functional sections, which are a gradually expanding transition section 21 and a pressure stabilizing separation section 22 along the air flow direction; wherein, the length of the gradually expanding transition section 21 accounts for 60%-70% of the total length of the gas guide cylinder body, and its expansion angle α satisfies α=5°±0.5°; the length of the pressure stabilizing separation section 22 accounts for 15%-30% of the total length of the gas guide cylinder body, and its expansion angle α satisfies α=12°±1°.

[0041] Specifically, in the embodiment of the present invention, the gas guide cylinder 2 is divided into a dual-function collaborative structure of a gradually expanding transition section 21 and a pressure-stabilizing separation section 22. The gradually expanding transition section 21 gradually expands at a small angle to maintain the laminar state of the airflow in the high-temperature zone, inhibit the premature phase change of SiO2 gas to solid SiO2, and reduce the amount of precipitation. The length of the gradually expanding transition section 21 accounts for 60%-70%, which matches the high-temperature zone of the single crystal furnace thermal field, ensuring that the residence time of the gaseous oxide in the high-temperature section is less than or equal to 2s (the traditional structure is greater than or equal to 4s), and avoiding deposition in the sensitive temperature zone. The pressure-stabilizing separation section 22 matches the steep expansion design of the low-temperature zone, the cross-sectional area of ​​the flow channel is accelerated, and the airflow velocity drops sharply, forming a "low-speed escape zone". The precipitated SiO2 particles sink under the action of gravity, but because the cross-sectional area of ​​the flow channel is rapidly expanded, the particles cannot adhere to avoid, and are continuously discharged from the system under the drag of the low-speed airflow.

[0042] Further, refer to Figure 2As shown, the inner wall surface of the gradually diverging transition section 21 is provided with a three-level wettability gradient coating, and the three-level wettability gradient coating includes a hydrophobic coating area 211, a transition coating area 212 and a hydrophilic coating area 213 arranged in sequence along the airflow direction, wherein the hydrophobic coating area 211 is configured as a composite coating of fluorinated carbon nanotubes and polytetrafluoroethylene; the transition coating area 212 is configured as a plasma-sprayed Al2O3-TiO2 two-phase ceramic layer; and the hydrophilic coating area 213 is configured as a hydroxyapatite-based hydrophilic coating.

[0043] The present invention provides a three-level wettability gradient coating (hydrophobic → transition → hydrophilic) on the inner wall of the gradually expanding transition section 21. The wettability gradient produces a directional capillary migration effect. Combined with the airflow direction and the temperature gradient change, the "dynamic repulsion-transition buffer-directional removal" synergistic mechanism of oxide particles is realized, which is specifically described as follows: The hydrophobic surface of the high-temperature hydrophobic coating area 211 inhibits the adhesion of molten silicon volatiles (such as SiO2 particles and metal vapor) through the bottom surface energy characteristics, so that SiO2 gaseous molecules cannot wet the wall surface due to the hydrophobic effect in the high-temperature section, reducing the adhesion of particles. More than 90% of the particles pass through in gaseous form, reducing the initial nucleation probability; among them, the chemical inertness of fluorinated carbon nanotubes F-CNTs inhibits the high-temperature cracking and carbon deposition of hydrocarbons, avoiding co-deposition with SiO2 to form a hard sintered layer.

[0044] The wettability transition of the transition coating zone 212 in the medium temperature section inhibits the retention of particles caused by the sudden change in wettability, and dissipates the kinetic energy of the remaining particles to avoid impact and breakage; the hydrophilic coating zone 213 in the low temperature section forms a liquid film scouring effect through water film migration and chemical bonding blocking, which directionally removes 95% of the escaped particles.

[0045] Among them, the surface energy of fluorinated carbon nanotubes (F-CNTs) is ≤15mN / m (close to the superhydrophobic threshold) and has high thermal conductivity, which can quickly dissipate local heat and reduce the risk of coating peeling caused by thermal stress; the nanotube array forms a micro-nano composite structure; the polytetrafluoroethylene (PTFE) substrate has a temperature resistance of 400 degrees Celsius and a friction coefficient of less than 0.05, which can resist high-temperature particle erosion and wear.

[0046] Al2O3 (thermal expansion coefficient 8.6×10 -6 / ℃) and TiO2 (thermal expansion coefficient 8.4×10 -6 / ℃) to match and relieve the hydrophobic area (PTFE thermal expansion coefficient ~100×10 -6 / ℃) and hydrophilic region (hydroxyapatite ~10×10 -6 / ℃) to prevent interface cracking.

[0047] Hydroxyapatite (HA) based coating: Chemical formula , surface energy>72 mN / m (contact angle <30°), part of the hydroxyl groups dehydrate at high temperature (600°C) to form a microporous structure (pore size 50~200 nm), HA forms a monomolecular adsorption water layer in the trace water vapor of the process gas (dew point -40°C), and the hydrophilic surface adsorbs trace water molecules in the argon gas (dew point below -40°C), and the submicron particles (such as 0.1-1μm SiO2) are aggregated into large particles through capillary action, accelerating gravity sedimentation. At the same time, the wettability of the hydrophilic coating area reduces the separation tendency of the airflow boundary layer, avoiding the generation of vortices due to the adverse pressure gradient in the pressure-stabilizing separation section.

[0048] Chemical bonding blocking is described as follows: HA Ca 2+ With SiO2 surface The groups undergo ion exchange to form a CaSiO3 transition layer, which reduces the binding energy between the particles and the wall and makes the sediments easily stripped by the airflow.

[0049] Furthermore, the connection area of ​​the hydrophobic coating area 211, the transition coating area 212 and the hydrophilic coating area 213 forms a metallurgical bonding transition zone based on laser remelting. The laser remelting transition zone forms a micron-level interpenetrating structure to ensure that the bonding strength between the coatings is ≥50MPa.

[0050] As a further improvement of the embodiment of the present invention, refer to Figure 2 and 3 As shown, the exhaust device also includes a temperature control module 4, and the temperature control module 4 is arranged on the outer wall of the air guide tube body 2; wherein, the temperature control module includes a plurality of groups of refrigeration components 41, and the plurality of groups of refrigeration components 41 are evenly distributed along the circumferential direction, and the refrigeration power of each group of the refrigeration components 41 decreases gradually along the air flow direction, and the refrigeration power gradient is positively correlated with the temperature gradient of the inner wall of the air guide tube.

[0051] In specific application scenarios, the refrigeration component 41 reduces the temperature of the outer wall of the air guide cylinder 2, forming a temperature gradient with hot inside and cold outside, reducing the thermal expansion effect of the gas near the wall, thereby further reducing the gas viscosity, suppressing turbulent pulsation, and enhancing the viscosity-dominant characteristics of the flow, reducing the Reynolds number, and delaying the transition from laminar flow to turbulent flow. Multiple groups of refrigeration components are evenly distributed along the circumference to eliminate the temperature asymmetry caused by unilateral cooling, avoid lateral secondary flow, and maintain an axisymmetric flow field. Through gradient refrigeration (high refrigeration power at the inlet end and low at the outlet end), the wall temperature gradient is controlled, so that the thermophoretic force of large particles is weak, mainly dominated by inertia, and is carried out by high-speed airflow; submicron particles have significant thermophoretic force, but forced refrigeration at the inlet end allows them to be adsorbed to the hydrophobic coating area in advance, reducing rear-end deposition.

[0052] In one embodiment of the present invention, the refrigeration component is configured as a semiconductor refrigeration sheet, the cold end of which is attached to the outer wall of the air guide cylinder, and the hot end is connected to the heat dissipation fins; The spacing between adjacent semiconductor cooling sheets is 1 / 12 to 1 / 8 of the circumference of the air inlet end of the air guide cylinder; and the cooling power gradient satisfies: ; P0 is the maximum power at the air inlet end of the air guide cylinder, L is the total length of the air guide cylinder, n is the attenuation index, and satisfies 1.2≤n≤1.8; x represents the coordinate along the air flow direction, and satisfies x∈[0,L]; P(x) represents the cooling power at position x.

[0053] In specific application scenarios, semiconductor refrigeration can accurately control the temperature, and the cooling power decreases along the airflow direction (n=1.5~2.5), so that the gas cooling rate is synchronized with the flow rate decrease, maintaining the Reynolds number less than 2 × 10 4 , reducing the thickness of the boundary layer and the probability of particle collision.

[0054] As a further improvement of an embodiment of the present invention, the exhaust device also includes an airflow monitoring module 6, which includes an optical fiber sensor 61 and a controller 62. The optical fiber sensor 61 is embedded in the inner wall of the air guide cylinder 2 for real-time monitoring of the exhaust flow rate and particle concentration; the controller 62 is connected to the optical fiber sensor 61 and the refrigeration component 41, and is used to adjust the refrigeration power of the refrigeration component 41 according to the monitoring data of the optical fiber sensor 61.

[0055] Specifically, the fiber optic sensor measures the airflow velocity in real time based on the Doppler frequency shift principle and dynamically identifies areas where the velocity decreases. Based on the change in backscattered Rayleigh scattering intensity, the concentration of SiO2 particles is monitored online to predict the risk of deposition in advance; when the particle concentration exceeds the threshold, the controller increases the cooling power in real time to cause the local temperature to drop sharply and inhibit the precipitation of oxides. Through the real-time feedback of the velocity distribution by the fiber optic sensor, the controller predicts the pressure loss change trend based on the PID algorithm and adjusts the cooling power gradient in advance. Embodiment 2

[0056] The present invention discloses a single crystal furnace, including the exhaust device for single crystal silicon pulling.

[0057] The single crystal furnace described in the present invention, based on the use of an exhaust device with an innovative structure, simultaneously solves the problems of furnace pressure fluctuation and uncontrolled oxygen content without external intervention. Specifically, the gradually expanding flow channel reduces the flow velocity and turbulence intensity, thereby reducing the gas flow resistance (pressure loss) compared to the equal-diameter structure. More importantly, the gradually expanding design avoids the nonlinear increase in pressure loss caused by thickening of the deposition in the traditional gas guide tube (i.e., the vicious cycle of blockage-pressure loss), thereby maintaining a stable exhaust flux; the stable exhaust flux ensures that the oxygen-containing gas volatilized by the silicon melt is continuously discharged, and the oxygen partial pressure in the furnace is always lower than the oxygen solubility threshold of the silicon melt.

[0058] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. An exhaust device for single crystal silicon pulling, comprising an air guide cylinder, characterized in that: The inner cavity of the air guide cylinder forms a gradually expanding structure along the air flow direction, and its inner cavity radius increases continuously from the air inlet end to the air outlet end, and the expansion angle α of the air guide cylinder satisfies 2°≤α≤12°, wherein the expansion angle is the angle between the axis of the air guide cylinder and the tangent of the inner wall; the inner wall surface of the air guide cylinder forms a continuous flow channel without step mutations.

2. The exhaust device for pulling single crystal silicon according to claim 1, characterized in that: The expansion angle α of the air guide cylinder satisfies 5°≤α≤8°.

3. The exhaust device for single crystal silicon pulling according to claim 1 or 2, characterized in that: The expansion curve of the gradually expanding structure satisfies a logarithmic spiral; The polar coordinate equation of the logarithmic spiral is expressed as ; r represents the polar diameter; θ represents the polar angle; a represents the initial radius scale factor, which is a constant and satisfies a∈[50, 150] mm; e represents the base of the natural logarithm; b represents the curvature control factor, which is a constant and satisfies b∈[0.02, 0.15].

4. The exhaust device for single crystal silicon pulling according to claim 1, characterized in that: The air guide cylinder body comprises at least two functional sections, which are, in order, A gradually expanding transition section, the length of which accounts for 60%-70% of the total length of the gas guide cylinder, and the expansion angle α satisfies α=5°±0.5°; The pressure stabilizing separation section has a length that accounts for 15%-30% of the total length of the gas guide cylinder body, and its expansion angle α satisfies α=12°±1°.

5. The exhaust device for pulling single crystal silicon according to claim 4, characterized in that: The inner wall surface of the gradually expanding transition section is provided with a three-level wettability gradient coating, and the three-level wettability gradient coating comprises: a hydrophobic coating region, which is configured as a composite coating of fluorinated carbon nanotubes and polytetrafluoroethylene; a transition coating zone configured as a plasma-sprayed Al2O3-TiO2 dual-phase ceramic layer; a hydrophilic coating region configured as a hydroxyapatite-based hydrophilic coating; Wherein, the hydrophobic coating area, the transition coating area and the hydrophilic coating area are arranged in sequence along the air flow direction.

6. The exhaust device for single crystal silicon pulling according to claim 5, characterized in that: The connection area of ​​the hydrophobic coating area, the transition coating area and the hydrophilic coating area forms a metallurgical bonding transition zone based on laser remelting.

7. The exhaust device for single crystal silicon pulling according to claim 1 or 4, characterized in that: It also includes a temperature control module, which is arranged on the outer wall of the air guide cylinder; wherein, the temperature control module includes multiple groups of refrigeration components, and the multiple groups of refrigeration components are evenly distributed along the circumferential direction, and the refrigeration power of each group of refrigeration components decreases gradually along the air flow direction, and the refrigeration power gradient is positively correlated with the temperature gradient of the inner wall of the air guide cylinder.

8. The exhaust device for pulling single crystal silicon according to claim 7, characterized in that: The refrigeration component is configured as a semiconductor refrigeration sheet, the cold end of which is attached to the outer wall of the air guide cylinder, and the hot end is connected to the heat dissipation fins; The spacing between adjacent semiconductor cooling sheets is 1 / 12 to 1 / 8 of the circumference of the air inlet end of the air guide cylinder; and the cooling power gradient satisfies: ； P0 is the maximum power at the air inlet end of the air guide cylinder, L is the total length of the air guide cylinder, n is the attenuation index, and satisfies 1.2≤n≤1.8; x represents the coordinate along the air flow direction, and satisfies x∈[0,L]; P(x) represents the cooling power at position x.

9. The exhaust device for pulling single crystal silicon according to claim 7, characterized in that: It also includes an airflow monitoring module, the airflow monitoring module includes: An optical fiber sensor is embedded in the inner wall of the gas guide cylinder and is used to monitor the exhaust flow rate and particle concentration in real time; A controller is connected to the optical fiber sensor and the refrigeration component, and is used to adjust the refrigeration power of the refrigeration component according to the monitoring data of the optical fiber sensor.

10. A single crystal furnace, characterized in that: An exhaust device for pulling single crystal silicon comprising the exhaust device described in any one of claims 1-9.

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