JP2011032127A - Exhaust dust collector of single crystal boosting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust dust collector of a single crystal boosting apparatus, which is installed in an exhaust system of the single crystal boosting apparatus, and can provide a sufficient dust removing effect. <P>SOLUTION: A plurality of straightening fixed vanes 28a-28d which swirl and guide dust-containing gas introduced from an introduction pipe 22 to the lower part of a cyclone body 21 in a swirling direction nearly coinciding with the swirling direction of the gas are provided in the cyclone body 21. The straightening fixed vanes are provided with a plurality of fins which are along predetermined planes orthogonal to the central axis of a cylinder part 24, and radially fixed and arranged between the outer periphery of an outflow pipe 23 inside the cyclone body 21 and the inner periphery of the cylinder part 24 or a frustoconical part 25. The plurality of fins have an inclination angle of 30-50° against a first plane orthogonal to the central axis of the cylinder part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust dust collector used for an exhaust system of a single crystal pulling apparatus during crystal production.

In the single crystal pulling apparatus using the Czochralski method, the chamber contains floating substances such as SiO _{2 that} evaporate from the silicon melt. If this suspended substance stays in the chamber, it adversely affects the quality of the produced single crystal. Therefore, conventionally, while supplying an inert gas such as Ar gas into the chamber, the inside of the chamber is depressurized by an exhaust system using a vacuum exhaust pump, and the gas in the chamber is discharged to keep the inside of the chamber clean. I have to.

However, if a large amount of dust, such as SiO ₂ contained in the exhausted gas, adheres to and accumulates on the rotor inside the vacuum exhaust pump (mechanical booster pump) by pulling the single crystal for a long time. In some cases, there is a problem that the pump stops or breaks. For this reason, it has been proposed to remove dust by providing an exhaust dust collection device using a cyclone device between the single crystal pulling device and the vacuum exhaust pump (see, for example, Patent Documents 1-3).

Japanese Patent No. 3367910 Japanese Patent No. 3478330 Japanese Patent No. 3632526

  However, in the exhaust dust collector using the conventional cyclone device, if the intake pressure of the cyclone device decreases during the process of pulling up the silicon single crystal, the cyclone device's original air swirl movement does not occur, and sufficient dust (exhaust gas) 5-10 μm particle size amorphous contained in the gas could not be collected. For this reason, in order to alleviate the problem of the stoppage or breakage of the above-mentioned pump, two vacuum exhaust pumps are connected in parallel at the subsequent stage of the exhaust dust collector, and these are always operated.

  Also, according to simulations by the inventors of the present invention, it is found that the cyclone device cannot obtain a dust separation effect because sufficient swirling motion of the air current does not occur when the pressure inside the cyclone body is low. It was. For example, when the atmospheric pressure in the cyclone main body is less than about 73 kPa (about 550 Torr) and the gas flow rate in the cyclone main body is set to several tens to 200 liters per minute with a predetermined apparatus configuration, a simulation that no airflow swirl motion occurs. I'm getting results. For this reason, in a single crystal pulling device, there is a concern that even if the cyclone device is used for the purpose of separating and removing dust from the exhaust system of the high vacuum device, a sufficient dust removing effect cannot be obtained.

  Furthermore, instead of a cyclone device, it is conceivable to use an electrostatic precipitator or a mesh filter to remove the dust, but the electrostatic precipitator has a risk of causing a dust explosion due to spontaneous ignition of charged dust. The mesh filter may be clogged and may not be able to maintain a desired degree of vacuum in the chamber of the single crystal pulling apparatus.

  Accordingly, an object of the present invention made by paying attention to these points is to provide an exhaust dust collecting apparatus of a single crystal pulling apparatus that can be connected to an exhaust system of the single crystal pulling apparatus and obtain a sufficient dust removing effect. There is to do.

The invention of the exhaust dust collector according to claim 1 for achieving the above object is as follows:
An exhaust gas collector provided in an exhaust system of the single crystal pulling apparatus provided with an exhaust pipe connected to the single crystal pulling apparatus and a vacuum pump for sucking dust-containing gas from the single crystal pulling apparatus through the exhaust pipe line A dust device,
A hollow cylinder having an introduction port for introducing dust-containing gas, and a hollow portion having an opening at the lower end with a diameter narrowing downward and being coupled to be located at the lower part of the cylindrical portion so as to be in the same axis as the cylindrical portion Connected to the truncated cone-shaped portion, the top plate portion that is located on the upper surface of the cylindrical portion and has a discharge port for discharging the gas separated from the dust-containing gas, and the opened lower end portion of the truncated cone-shaped portion A sealed cyclone main body having a dust collection unit,
An introduction pipe connected to the exhaust pipe for introducing dust-containing gas into the cyclone body from the introduction port provided in the cylinder part of the cyclone body in a substantially horizontal direction along the inner peripheral surface of the cylinder part; ,
One end portion extends from a discharge port provided in the top plate portion of the cyclone main body into the cyclone main body so as to be in the same axis as the cyclone main body, and an inner space portion that is two space portions in the cyclone main body And a cylindrical shape that discharges the gas separated from the dust-containing gas from the cyclone body by suction of the vacuum pump, with the other end connected to the vacuum pump. A discharge pipe,
A swirl direction that substantially coincides with the swirl direction of the dust-containing gas introduced into the cyclone body by the introduction pipe in a state where the cyclone body is in a predetermined reduced pressure atmosphere by suction through the discharge pipe by the vacuum pump. And rectifying means for guiding the dust-containing gas to the lower part of the cyclone body while swirling the dust-containing gas.

The invention according to claim 2 is the exhaust dust collector according to claim 1,
The predetermined reduced-pressure atmosphere is 73 kPa (about 550 Torr) or less.

The invention according to claim 3 is the exhaust dust collector according to claim 1 or 2, wherein the rectifying means is along the first plane orthogonal to the central axis of the cylindrical portion, and the outer space portion in the cyclone body. The rectifying fixed wing includes a plurality of fins fixedly arranged radially, and the plurality of fins have a predetermined inclination angle with respect to the first plane.

The invention according to claim 4 is the exhaust dust collector according to claim 3,
The rectifying means is constituted by a plurality of the rectifying fixed wings arranged at predetermined intervals in the axial direction of the cyclone body.

The invention according to claim 5 is the exhaust dust collector according to claim 3 or 4, wherein the predetermined inclination angle of the plurality of fins is not less than 30 degrees and not more than 50 degrees.

The invention according to claim 6 is the exhaust dust collector according to claim 3 or 4,
The predetermined inclination angle of the plurality of fins is approximately 40 degrees.

The invention according to claim 7 is the exhaust dust collector according to any one of claims 3 to 6,
The opening ratio of the rectifying fixed blade is 20% or more and 40% or less.

The invention according to claim 8 is the exhaust dust collector according to claim 7,
The opening ratio of the rectifying fixed blade is approximately 29.8%.

The invention according to claim 9 is the exhaust dust collector according to any one of claims 3 to 8,
The cyclone body is configured such that, in use, a pressure difference is generated in the cyclone body by the rectifying fixed blade.

  According to the present invention, since the rectifying means for guiding the gas to the lower part of the cyclone main body is provided in the swirling direction substantially coinciding with the swirling direction of the dust-containing gas introduced from the introduction pipe, Even when the pressure of the gas is lowered, a gas swirling motion can be generated by the suction force through the discharge pipe, and dust can be collected by the cyclone. Furthermore, the cost required for the manufacture and operation of the apparatus can be suppressed by using the fixedly arranged rectifying means.

It is a schematic block diagram which shows the state which connected the exhaust gas dust collector which concerns on 1st Embodiment of this invention to the exhaust system of the single crystal pulling-up apparatus. It is a perspective view when the schematic structure of the exhaust-gas dust collector which concerns on 1st Embodiment is seen from diagonally upward. It is a perspective view which shows a rectification fixed blade. It is a figure which shows the behavior of the powder in the exhaust-gas dust collector by simulation. It is a figure which shows schematic structure of the exhaust-gas dust collector which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a state in which an exhaust dust collecting apparatus according to a first embodiment of the present invention is connected to an exhaust system of a single crystal pulling apparatus.

  In FIG. 1, a single crystal pulling device 11 is a pulling device for a semiconductor single crystal such as silicon by the Czochralski method, and its chamber 11a is connected to an exhaust pipe 12 constituting a part of an exhaust system. Yes. The exhaust system includes the exhaust pipe 12, the throttle valve 13, a cyclone device 14 that is an exhaust dust collector, and a pump 15. An end of the exhaust pipe 12 different from the end to which the chamber 11a is connected is connected to an introduction pipe of a cyclone device 14 described later. The throttle valve 13 is provided in the pipe line of the exhaust pipe 12, and adjusts the pressure in the chamber 11a by adjusting the flow rate of the gas flowing through the exhaust pipe 12. Further, a later-described discharge pipe of the cyclone device 14 is connected to the pump 15. The pump 15 includes a mechanical booster pump (not shown) and a dry pump connected in series, and can reduce the pressure in the chamber 11a to a high vacuum of 0.13 Pa (1 mTorr) or less.

  Next, the cyclone device 14 will be described. FIG. 2 is a perspective view when the schematic configuration of the cyclone device 14 is viewed obliquely from above. The cyclone device 14 is mainly connected to the cyclone main body 21 and the exhaust pipe 12 to introduce a dust-containing gas into the cyclone main body 21, and connected to the pump 15 to suck the dust from the cyclone main body 21 by the pump 15. It is composed of a cylindrical discharge pipe 23 for discharging a gas from which dust is separated, and rectifying fixed wings 28 a to 28 d provided in the cyclone main body 21.

  The cyclone body 21 has a cylindrical portion 24 having an inlet for introducing dust-containing gas, and is coupled to the lower end portion of the cylindrical portion 24 so as to be in the same axis as the cylindrical portion 24 and has a diameter narrowing downward. A hollow frustoconical portion 25 having an opening at the top, a top plate portion 26 that is located on the upper surface of the cylindrical portion 24 and has a discharge port for discharging the gas separated from the dust-containing gas, and the frustoconical portion 25 A hollow structure composed of a dust collecting portion 27 coupled to the opened lower end of the inner space is hermetically sealed from the outside.

  The introduction pipe 22 is airtightly coupled to the cylindrical portion 24 so as to introduce gas horizontally from the introduction port of the cylindrical portion 24 of the cyclone main body 21 in the direction along the inner peripheral surface of the cylindrical portion 24. Further, the discharge pipe 23 extends from a discharge port provided at one end of the top plate portion 26 of the cyclone main body so as to be on the same axis as the cyclone main body 21, and a cylindrical middle cylinder portion 23 a inside the cyclone main body 21. Is forming. This middle cylinder part 23a partitions and forms the inner space part and the outer space part which are two space parts in a cyclone main body. Also here, the discharge port of the top plate portion 26 and the discharge pipe 23 are airtightly coupled. The other end of the discharge pipe 23 is connected to the pump 15. Further, in the cyclone main body 21, four rectifying fixed blades constituting a rectifying means are provided between the outer space, that is, between the outer peripheral surface of the middle cylindrical portion 23 a of the discharge pipe 23 and the inner peripheral surface of the cyclone main body 21. 28a-28d are provided.

  FIG. 3 is a perspective view showing the rectifying fixed wings 28a to 28d. Each of the rectifying fixed blades 28a to 28d includes an inner ring 31, an outer ring 32, and 50 elongated flat plate fins 33. The inner ring 31 is coupled to the outer periphery of the middle cylinder portion 23a of the discharge pipe 23 by bolting from three directions. One end of each fin 33 is coupled to the inner ring 31, and the fins 33 are arranged at equal intervals in a substantially radial direction centering on the central axis of the cylindrical portion 24 and the truncated cone portion 25. The other end is coupled to the outer ring 32 and thereby supports the outer ring 32. In addition, each fin 33 is inclined so that the gas passing through the rectifying fixed wing turns in the same turning direction as the turning direction of the gas introduced from the introduction pipe 22 along the inner periphery of the cylindrical portion. The inclination angle can be set to 30 ° or 45 ° with respect to a first plane orthogonal to the central axis of the cylindrical portion 24, that is, a horizontal plane including the inner ring and the outer ring in FIG.

  Next, the operation of the cyclone apparatus 14 when the single crystal pulling apparatus 11 performs crystal growth will be described with reference to FIGS.

During crystal growth, floating substance (amorphous powder) such as SiO _{2 that} evaporates from the silicon melt is generated in the chamber 11 a of the single crystal pulling apparatus 11. Since this suspended substance adversely affects the quality of the produced single crystal, an inert gas such as Ar gas is supplied to the chamber 11a from an introduction pipe (not shown), and this gas is discharged from the exhaust pipe 12 constituting the exhaust system. By discharging, it is discharged out of the chamber 11a together with the gas. Thereby, the cleanliness in the chamber 11a can be maintained.

Accordingly, the gas flowing through the exhaust system of the single crystal pulling apparatus 11 includes fine powder such as SiO ₂ . This powder flows together with the gas in the chamber 11 a through the exhaust pipe 12 and the throttle valve 13 from the introduction pipe 22 into the cyclone body 21 of the cyclone device 14 in the direction along the inner peripheral surface of the cylindrical portion 24. Further, the inflowing gas performs a turning motion by passing through each of the rectifying fixed wings 28a to 28d arranged in four stages.

  Here, the rectifying fixed wings 28a to 28d are pulled in the openings in the cyclone main body 21 of the discharge pipe 23 by the pump 15, so that the rectifying fixed wings 28a to 28d are formed in the spaces of the cyclone main body 21 separated by the rectifying fixed wings 28a to 28d. Then, a pressure difference is generated so that a high vacuum is sequentially applied from the upper part where the gas flows into the lower part. For this reason, the swirl speed of the gas passes through the rectifying fixed wings, and becomes gradually higher and reaches the lower part of the truncated cone part 25. The gas that has reached the lower portion of the truncated cone portion 25 is then discharged to the pump 15 via the discharge pipe 23. The pressure on the side of the cyclone body 21 to which the introduction pipe 22 is connected is about 2.7 kPa (about 20 Torr).

  Here, a part of the fine powder contained in the gas flowing into the cyclone main body 21 collides with the fins 33 of the rectifying fixed blades 28a to 28d and adheres to these fins. Due to the cyclone effect caused by the swirling flow that is generated, it is separated from the gas by centrifugal force, and is settled and collected in the dust collecting part 27 by gravity.

  As a result, the gas from which the fine powder has been separated and removed is sent to the pump 15, so that the powder adheres and accumulates on the rotor in the mechanical booster pump of the pump 15, and the pump stops. It is possible to prevent problems such as damage to the pump itself and accidents.

  FIG. 4 is a diagram showing the behavior of powder in a cyclone device that is an exhaust dust collector by simulation. FIG. 4A shows a conventional cyclone apparatus that does not have a rectifying fixed blade, and FIG. 4B uses a cyclone apparatus 14 according to the present invention. In this simulation, the atmospheric pressure in the cyclone device 14 is 27.2 kPa-28.0 kPa. The fins of the rectifying fixed wings 28a to 28d of the cyclone device 14 have an inclination of 45 degrees with respect to the first plane orthogonal to the central axis of the cylindrical portion 24, that is, the horizontal plane in FIG. According to this simulation, in the conventional cyclone apparatus shown in FIG. 4 (a) under the high vacuum, the swirl of the air current does not occur, and the gas does not descend to the vicinity of the dust collecting part 27, while the present invention shown in FIG. 4 (b). In the cyclone device 14, it was confirmed that the airflow swirled inside and swung down to the dust collecting unit 27 at high speed. Furthermore, in the cyclone device 14 of the present invention, it was confirmed that the fine powder was not transferred to the pump 15 but remained until the bent portion of the discharge pipe 23.

  Further, when the angle of the fin with respect to the horizontal plane is 30 degrees to 50 degrees (most preferably 40 degrees) and the opening ratio of the rectifying fixed blade is 20% to 40% (most preferably 29.8%), the rectification If two or more stages of fixed blades are provided, the gas can make a swivel motion even if the flow rate of the gas flowing through the cyclone body is 180 liters per minute and the inside of the cyclone body 21 is a high vacuum of 9.3 kPa to 25 kPa. Then, it was confirmed that powder having a diameter of 10 μm or more can be collected. Here, the “aperture ratio” is the ratio of the area of the gap between the fins of the rectifying fixed blade to the cross-sectional area of the cyclone body viewed in the direction of the central axis of the cylindrical portion.

  Further, according to experiments conducted by the inventors of the present application using an experimental machine, the flow rate of the gas flowing through the cyclone main body is 180 liters per minute, the atmospheric pressure inside the cyclone device 14 is 16 kPa to 20 kPa, When the angle was set to 45 degrees, the powder adhered only to the front surface of the fin 33 of the rectifying fixed blades 28a to 28d in the gas introduction direction, and a decrease in the amount of the powder adhered to the pump 15 was observed. It is understood that the powder does not adhere to the back surface of the fin because the gas swirl motion is generated in the cyclone device 14.

  As described above, according to the present embodiment, in the cyclone device that is an exhaust dust collecting device, the rectifying fixed blade that guides the airflow in a predetermined swirling direction is provided, so that the inside of the cyclone main body is evacuated to a vacuum, An air current swirling motion can be generated, and fine powder in the gas can be separated and removed from the gas. Furthermore, since fine powder adheres to the fins 33 of the rectifying fixed blades 28a to 28d, it acts as a filter, so that the powder removal efficiency can be further increased.

(Second Embodiment)
FIG. 5 is a side view showing a schematic configuration of a cyclone apparatus that is an exhaust dust collecting apparatus according to the second embodiment. In the exhaust dust collector according to the first embodiment, the present embodiment has two stages of rectifying fixed blades based on the result of the simulation described above. As shown in FIG. 5, the two rectifying fixed wings 28 a and 28 b are provided in the outer space portion of the cylindrical portion 24 of the cyclone main body 21. Further, the inclination angle of the fins 33 of the rectifying fixed blades 28a and 28b with respect to the first plane orthogonal to the central axis of the cylindrical portion 24, that is, the horizontal plane in FIG. The cyclone body 21 of this apparatus is configured to be split between the middle of the cylindrical portion and between the cylindrical portion and the truncated cone portion in consideration of maintainability. Since other configurations are the same as those of the cyclone device 14 according to the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  With the configuration as described above, the cyclone device 14 that is the exhaust dust collecting device of the present embodiment, like the cyclone device 14 of the first embodiment, swirls the air flow while exhausting the inside of the cyclone main body 21 to a vacuum. It was confirmed that movement can be generated. At this time, it was confirmed that fine powder having a size of 10 μm or more was collected and not sent to the pump 15. Therefore, according to the present embodiment, it is possible to separate and remove the fine powder by the cyclone effect similar to that of the first embodiment with a simpler and lighter device configuration in which the rectifying fixed blade is configured in two stages. It was.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, in the above-described embodiment, the rectifying fixed blade has a four-stage or two-stage configuration, but may have a different number of stages. Further, although the number of fins of each rectifying fixed wing 28a-28d is 50, the present invention is not limited to this, and a rectifying fixed wing using other number of fins may be used. Furthermore, although the shape of the fin 33 is a flat plate shape, the shape is not limited to this, and various shapes can be adopted to generate a swirling flow.

  In addition, the suitable range of the decompression atmosphere of the exhaust dust collector of this invention is about 9.3 kPa-73 kPa, and the suitable pressure difference between each rectification fixed blade is about 4.7 kPa-5.3 kPa.

  By using the exhaust dust collector of the present invention in the exhaust system of the single crystal pulling device, even when the pressure in the cyclone body is lowered, the gas swirl is generated by the suction force through the exhaust pipe, and the cyclone Can collect dust.

DESCRIPTION OF SYMBOLS 11 Single crystal pulling apparatus 11a Chamber 12 Exhaust pipe 13 Throttle valve 14 Cyclone apparatus 15 Pump 21 Cyclone main body 22 Introducing pipe 23 Discharge pipe 23a Middle cylinder part 24 Cylindrical part 25 Frustum part 26 Top plate part 27 Dust collection part 28a- 28d Commutation fixed wing 31 Inner ring 32 Outer ring 33 Fin

Claims (9)

An exhaust gas collector provided in an exhaust system of the single crystal pulling apparatus provided with an exhaust pipe connected to the single crystal pulling apparatus and a vacuum pump for sucking dust-containing gas from the single crystal pulling apparatus through the exhaust pipe line A dust device,
A hollow cylinder having an introduction port for introducing dust-containing gas, and a hollow portion having an opening at the lower end with a diameter narrowing downward and being coupled to be located at the lower part of the cylindrical portion so as to be in the same axis as the cylindrical portion Connected to the truncated cone-shaped portion, the top plate portion that is located on the upper surface of the cylindrical portion and has a discharge port for discharging the gas separated from the dust-containing gas, and the opened lower end portion of the truncated cone-shaped portion A sealed cyclone main body having a dust collection unit,
An introduction pipe connected to the exhaust pipe for introducing dust-containing gas into the cyclone body from the introduction port provided in the cylinder part of the cyclone body in a substantially horizontal direction along the inner peripheral surface of the cylinder part; ,
One end portion extends from a discharge port provided in the top plate portion of the cyclone main body into the cyclone main body so as to be in the same axis as the cyclone main body, and an inner space portion that is two space portions in the cyclone main body And a cylindrical shape that discharges the gas separated from the dust-containing gas from the cyclone body by suction of the vacuum pump, with the other end connected to the vacuum pump. A discharge pipe,
A swirl direction that substantially coincides with the swirl direction of the dust-containing gas introduced into the cyclone body by the introduction pipe in a state where the cyclone body is in a predetermined reduced pressure atmosphere by suction through the discharge pipe by the vacuum pump. And an rectifying means for guiding the dust-containing gas to the lower part of the cyclone main body while swirling the dust-containing gas.   The exhaust dust collector according to claim 1, wherein the predetermined reduced-pressure atmosphere is 73 kPa (550 Torr) or less.   The rectifying means is configured to include a rectifying fixed wing having a plurality of fins radially fixed to the outer space portion in the cyclone main body along a first plane orthogonal to the central axis of the cylindrical portion, The exhaust dust collector according to claim 1 or 2, wherein the plurality of fins have a predetermined inclination angle with respect to the first plane.   The exhaust dust collector according to claim 3, wherein the rectifying means is constituted by a plurality of the rectifying fixed blades arranged at predetermined intervals in the axial direction of the cyclone body.   The exhaust dust collector according to claim 3 or 4, wherein the predetermined inclination angle of the plurality of fins is not less than 30 degrees and not more than 50 degrees.   The exhaust dust collector according to claim 3 or 4, wherein the predetermined inclination angle of the plurality of fins is approximately 40 degrees.   The exhaust dust collector according to any one of claims 3 to 6, wherein the opening ratio of the rectifying fixed blade is 20% or more and 40% or less.   The exhaust dust collector according to claim 7, wherein an opening ratio of the rectifying fixed blade is approximately 29.8%.   The exhaust dust collector according to any one of claims 3 to 8, wherein the cyclone main body is configured such that a pressure difference is generated in the cyclone main body by the rectifying fixed wing during use. .

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