JP3862862B2 - Flame prevention device for semiconductor manufacturing exhaust gas abatement machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flame prevention device as a safety device installed for pretreatment of exhaust gas in a detoxifier of an electrothermal oxidation heating system for detoxifying various gases used for semiconductor manufacturing.
[0002]
[Prior art]
In semiconductor manufacturing by CVD, a deposit gas (for example, SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , TEOS, PH ₃ , B ₂ H ₆ , NH ₃ , N ₂ O, etc.) is used for forming various thin films. A cleaning gas (for example, NF ₃ , SF ₆ , C ₂ F ₆ , CF _4, etc.) is usually used to clean the inside of the CVD after the deposit process is completed.
[0003]
These gases inherently have various risk factors such as flammability, explosiveness, corrosiveness, and toxicity. Therefore, it must be detoxified (detoxified) using a detoxifier equipped with means such as oxidation heating before being released into the atmosphere.
[0004]
Within the CVD, a complicated decomposition reaction occurs with the gas used, and as a result, new decomposition products (for example, F ₂ , HF, HCl, SiO _X, etc.) are generated, which are undecomposed deposit gas and cleaning gas. And is discharged in conjunction.
[0005]
When such an unexpected mixed gas is thermally oxidized and decomposed in a zone (reaction cylinder) having a heat source in the presence of external air for oxidation, for example, in a SiH ₄ / N ₂ O / N ₂ mixed system, the SiH ₄ concentration Within the range of 1.9 to 87.1%, and in the SiH ₄ / NF ₃ / N ₂ mixed system, if there is a fire source in the region of SiH ₄ concentration 0.66 to 95.3%, it will become an explosive composition and actually cause an explosion phenomenon There is.
[0006]
In addition, as described in JP-A-7-323211, there are cases where a water injection facility is provided in the previous stage of a zone having a heat source, and the exhaust gas accompanied by dust as the decomposition product described above is washed. In this case, for example, when SiH ₂ Cl ₂ is present in the gas, SiH ₂ Cl ₂ + 4H ₂ O → Si (OH) ₄ + 2HCl + 2H ₂
In some cases, H ₂ gas is generated due to the hydrolysis reaction, which may cause an explosion phenomenon when mixed with external air.
[0007]
When these explosions occur, sudden pressure fluctuations occur in the closed piping, which affects the CVD apparatus. Furthermore, the generation of a local flame may propagate to a combustible gas (for example, SiH ₄ ) in the pipe leading to CVD, leading to an accident.
[0008]
As a general safety device in a detoxifier containing such a danger, a water-sealed safety device that diffuses gas into water and allows water to pass through, and N ₂ gas by detecting abnormal pressure and temperature phenomena with a sensor There is a backfire preventer that injects etc. toward the abatement device.
[0009]
However, the water-sealed safety device has a limited level of water-sealing level, making it difficult to cope with a wide range of explosion phenomena, and the backfire preventive device remains a cause of anxiety in the delay of the sensor detection time. ing.
[0010]
[Problems to be solved by the invention]
Therefore, there is a demand for a flame prevention device as a safety mechanism that can prevent the propagation of flame with a simple configuration in a semiconductor exhaust gas abatement device having a water injection facility in the previous stage of the heater zone.
[0011]
[Means for Solving the Problems]
A flame prevention device for a semiconductor production exhaust gas abatement device according to claim 1 of the present invention is a flame prevention device attached to the front stage of a heating reaction tube of an oxidation heating type semiconductor production exhaust gas abatement device, comprising a wire mesh (2 and), have a water injection nozzle (3) for injecting water toward the provided upwardly gold network (2) of the gold network (2), the water injection nozzle (3), from the gold network (2) Is also located upstream of the flow of the semiconductor manufacturing exhaust gas .
[0012]
The flame prevention device according to claim 2 is the flame prevention device according to claim 1, wherein the metal mesh (2a) is arranged at intervals at a plurality of locations, and the metal mesh (2a) arranged at each metal mesh arrangement portion. ) Is one sheet or a plurality of sheets, and a water jet nozzle (3) is provided above each wire netting portion.
[0013]
The flame prevention device of the present invention is a device in which a flame propagation prevention function is added to an auxiliary device in semiconductor manufacturing exhaust gas abatement treatment. The exhaust gas introduced from the CVD to the abatement device for the exhaust gas treatment contains dust typified by SiO ₂ , water-soluble components such as F ₂ , NH ₃ , SiH ₂ Cl ₂ , and hydrolysis components. If these substances enter the heating reaction tube that performs oxidation pyrolysis treatment, problems such as an increase in gas passage resistance, promotion of metal corrosion troubles, and generation of undesirable by-products such as NO _x are caused. Therefore, it is desirable to remove it in advance as much as possible, and for this purpose, treatment is carried out by spraying water with a water scrubber. It has been found that by installing a wire mesh in the water scrubber which is ancillary equipment, it has a function of preventing flames in addition to the above dust removal.
[0014]
The basic principle of a backfire prevention device using a wire mesh is that the energy of the flame is cooled by the wire mesh so that the flame is not emitted upstream of the exhaust gas introduction. Therefore, the net material needs to be a metal having heat resistance. In order to enhance the cooling effect, it is desirable that the net structure is dense and the flame does not come out of the net.
[0015]
However, it is necessary to eliminate clogging of dust typified by SiO ₂ and reduce the overall ventilation resistance, which contradicts the flame extinguishing function of the wire mesh. The trade-off was found, and the cooling effect was enhanced by adding water injection, and the actual condition of causing dust clogging to flow out was confirmed.
[0016]
That is, this flame prevention device is (a) pre-cleaning for semiconductor exhaust gas detoxification, (b) extinguishing action by wire mesh slits, (c) wire mesh cooling by dusty water and extinguishing of the flame itself, (d) It has a function to improve ventilation resistance by removing dust brought in by water jet.
[0017]
It is known that the flame propagation speed is inversely proportional to the opening of the wire mesh. The smaller the opening (in the case of Tyler, the larger the mesh number), the higher the flame speed at which the flame can be extinguished. In the case of the present invention, assuming a typical explosion H ₂ / air mixed system, the flame propagation speed is 2.8 m / Sec, and the opening of the wire mesh to be extinguished is usually about 3,500 in JIS. (Equivalent to Tyler mesh 6) is preferable.
[0018]
In the present invention, 2 to 5 wire meshes of Tyler meshes 3 to 8 are used. In that case, it does not matter whether a plurality of wire meshes are stacked or each wire mesh is installed with an interval. Note that when the number of sheets used exceeds five, the ventilation resistance increases, but the improvement of the flame-extinguishing effect is not recognized so much. Therefore, 5 sheets or less are suitable.
[0019]
The flame prevention device of the present invention may be prismatic or cylindrical. Match the wire mesh shape to the cross-sectional shape of the flame prevention device. For example, in the case of a prismatic shape, a 20 cm square or 20 × 15 cm can be exemplified, and in the case of a cylindrical shape, a diameter of 20 cm can be exemplified, but this is an example, and the present invention is not limited to specific dimensions. Similarly, although the height is exemplified by 30 to 80 cm, the present invention is not limited to specific dimensions.
[0020]
One nozzle is installed at least in the center of the ceiling of the box structure. In addition, wire mesh will be installed from 1 to 5 locations. In this case, one piece may be installed at one place, or a plurality of sheets may be stacked and installed. When installing a plurality of wire meshes at intervals, nozzles may be provided between the wire meshes.
[0021]
The nozzle to be used is preferably made of a Ni—Cr based iron alloy having corrosion resistance such as SUS304 and SUS316L.
[0022]
When the exhaust gas to be treated by the detoxifier has an air volume of up to 1000 liter / min, the total amount of water discharged from the nozzle is about 5 to 50 liter / min, and the water temperature may be room temperature.
[0023]
In the case of a semiconductor manufacturing exhaust gas abatement machine, the treatment of flammable and explosive gases as described above, the treatment of flammable and explosive gases (for example, H ₂ , ethanol, etc.) secondary generated by hydrolysis, In addition, flammable and explosive dust that cannot be fully elucidated as a result of reactions performed inside the CVD may be brought into the detoxifier, which is necessary for oxidative thermal decomposition in the detoxifier. Even if a flame is generated through external air and a heat source, the presence of the wire mesh and water jet prevents the flame from propagating and does not lead to an accident.
[0024]
The flame prevention device according to claim 3 is the flame prevention device according to claim 1, wherein the wire mesh is made of a Ni-Cr-based iron alloy and has a wire diameter of 0.7 mm or more and 1.7 mm or less, and a Tyler mesh of 3 or more and 8 or less. The metal mesh is one or two or more and five or less laminated or arranged one by one at 100 mm intervals, and water for spraying water in a mist toward the metal mesh above the metal mesh arrangement part. It has an injection nozzle.
[0025]
This is a study of a wire mesh structure suitable for treating the dust brought into the exhaust gas as well as providing a sufficient flame prevention effect. Further, the wire was made of a Ni—Cr-based iron alloy as a corrosion resistant material by a corrosive gas, and was determined in consideration of both the gas passage resistance and the flame extinguishing effect.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to preferred embodiments.
[Example 1]
FIG. 1 is a diagram showing an outline of a flame prevention apparatus of this example. A detoxifier equipped with this flame prevention apparatus was used to remove SiH ₄ gas in the explosion composition range.
[0029]
In this case, (1) is a cylindrical body that forms the box structure of the flame prevention device. In the example, the cylindrical body has a 20 cm square section and a 70 cm height. (2) is a wire mesh of Tyler mesh 6 made of SUS304 and having a wire diameter of 1.02 mm, and is installed in the vicinity of the bottom of the cylindrical body (1).
[0030]
In addition, one water injection nozzle (3) (Ikeuchi non-core full cone nozzle 3 / 8KSFL) is attached to the center of the cross section 10 cm below the head of the cylindrical body (1), and water is injected at 15 liters / min. did. In addition, the full cone nozzle was used in the examples because the full cone nozzle can spread water droplets over a wide range, and when aiming at extinguishing the flame, the heat transfer from the high temperature gas to the water droplets can be efficiently performed. This is because (the cooling efficiency is high).
[0031]
The detoxifier is equipped with a plurality of electric heaters set at a surface temperature of 700 ° C., supplying a mixed gas of 5% / min of 100% SiH _{4 and} 95 L / min of N ₂ via a flame prevention device, Furthermore, 175 liter / min of external air was mixed with the detoxifying gas at the place where it passed through the flame prevention device and exposed to the heat source of the heater.
[0032]
As a result, the SiH ₄ gas having a concentration of 5% was detoxified to a concentration of 0.1 ppm or less in the exhaust section of the detoxifier. Introducing at the concentration of SiH ₄ is 5% SiH ₄ / N ₂ system, 1.82% in the SiH ₄ / air / N ₂ system, which is the lower explosive limit composition value of SiH ₄ / air / N ₂ system 1. Although it exceeded 37%, in the present Example provided with the flame prevention apparatus, it was able to remove safely without causing an explosion. Moreover, there was no dust accumulation on the wire mesh surface.
[Example 2]
FIG. 2 is a diagram showing an outline of the flame prevention device of this embodiment. The cylindrical body (1) is the same as in the first embodiment. Five SUS316L wire meshes (2a) made of Tyler mesh 3 with a wire diameter of 1.63 mm are divided into three parts in two locations from the gas passage direction (upward in the drawing), two, and a total of five. installed. The interval between each installation location was set to 10 cm.
[0033]
Three water injection nozzles (3) identical to those used in Example 1 were installed in the center of the cross section 5 cm above each wire mesh installation location. Water was sprayed from the spray nozzle at a total water volume of 10 liters / min.
[0034]
A mixed gas (SiH ₂ Cl ₂ concentration of 4%) with 100% SiH ₂ Cl ₂ at 4 liters / min and N ₂ at 96 liters / min is applied to the abatement device set at a heater surface temperature of 750 ° C. from above the flame prevention device. The air was introduced, and outside air was mixed at 100 liters / min when passing through it and passed through the heat source of the heater.
[0035]
In this case, if hydrolysis progresses chemically, the H ₂ concentration in the passing gas body is 4% of the H ₂ / air explosion lower limit (LEL). Proceeded safely and stably, and the concentration of SiH ₂ Cl ₂ in the exhaust part of the abatement device was not actually measured. Further, no powder or sludge-like solid was present on the wire mesh.
[Comparative Example 1]
A comparative test was performed under the same conditions using the same abatement machine used in Example 1 except that the flame prevention device was removed.
[0036]
As a result, abnormal noise is generated at the location where the SiH ₄ / N ₂ mixed gas comes into contact with external air, pressure fluctuations in the system occur, the safe operation control mechanism of the abatement device operates, and the gas supply system The emergency stop signal worked, and the heater was turned off. That is, some kind of abnormal combustion has occurred.
[Example 3]
FIG. 3 is a diagram showing an outline of the configuration of this embodiment. In the figure, (5) is a flame cutoff nozzle narrowed so that the upstream diameter of the exhaust gas flow becomes smaller. In this embodiment, two are provided in the cylindrical body (4). In the embodiment, the shape of each flame cutoff nozzle (5) is such that the diameter of the throttle portion (5a) is 10 mmφ, and the diameter of the open portion (5b) (inner diameter of the cylindrical body (4)) is 100 mmφ. The interval between the flame cutoff nozzles (5) was 100 mm. Incidentally, (5c) is a rectifying part having a curved surface provided on the upstream side of the throttle part (5a) of the flame cutoff nozzle (5). The rectifying unit (5c) is provided to receive water droplets ejected from a water spray nozzle (6), which will be described later, and to reduce ventilation resistance when exhaust gas flows.
[0037]
(6) is the same water injection nozzle (full cone nozzle) used in Example 1, which is the middle of the two flame cutoff nozzles, that is, the uppermost (upstream side) of the lowermost (most downstream) flame cutoff nozzle. ), And water can be sprayed toward the flame cutoff nozzle at the lowest stage (the most downstream side). This water injection nozzle (6) was operated at a water pressure of 0.5 kgf / cm ² and a water discharge rate of 30 liters / min.
[0038]
If the exhaust gas introduction pipe that guides the exhaust gas to the reaction cylinder (7) has a diameter that can accommodate the flame cutoff nozzle (5) and the water injection nozzle (6), the exhaust gas introduction pipe is directly cylindrical. Can be used as body (4).
[0039]
As exhaust gases, 10 liters of 100% H _{2 and} 190 liters / min of N ₂ for dilution (H ₂ concentration in the mixed gas 5%) were introduced into the reaction cylinder (7) via the nozzle installation part. The reaction cylinder (7) was equipped with an electric heater, and the ambient temperature was set to 700 ° C.
[0040]
On the other hand, external air was directly supplied to the reaction cylinder (7) at a flow rate of 75 liters / min, mixed with H _{2 of} exhaust gas, and burned off. As a result, the H ₂ concentration in the gas on the treatment gas discharge hole side was 1000 ppm, and the calculated removal rate was 98%. There was no evidence that a flame came to the exhaust gas introduction side from the flame cutoff nozzle (5). The water tank water temperature after water injection was 55 ° C.
[0041]
In this embodiment, the number of flame cutoff nozzles is two, but it may be one or three or more. Further, in this embodiment, the water injection nozzle is provided only on the upstream side of the flame cutoff nozzle at the lowest stage (the most downstream side). However, when there are a plurality of flame cutoff nozzles, the water injection nozzle is also provided on the upstream side of the other flame cutoff nozzles. A water injection nozzle may be provided.
[Comparative Example 2]
A comparison was made using the same apparatus as in Example 3 except that the flame blocking nozzle (5) and the water injection nozzle (6) were not installed. The gas supply conditions (composition, air volume, concentration) were the same as in Example 3, the mixed exhaust gas was supplied to the reaction tube in the 700 ° C. atmosphere, and external air was directly introduced into the reaction tube as in Example 3.
[0042]
As a result, the combustion that occurred in the reaction cylinder partly broke through the discharge port provided in the reaction cylinder with an explosion phenomenon, and the other part caused a backfire propagation to the exhaust gas introduction pipe side. The reverse flame temperature exceeded 1000 ℃.
[0043]
【The invention's effect】
As described above, the present invention provides a flame prevention device as a safety mechanism capable of preventing the propagation of flame with a simple configuration in a semiconductor exhaust gas abatement device having a water injection facility in the previous stage of a heater zone. I was able to.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a configuration of a first embodiment.
FIG. 2 is a diagram showing an outline of a configuration of a second embodiment.
3 is a diagram showing an outline of the configuration of Embodiment 3. FIG.
[Explanation of symbols]
(1) Tubular body
(2) Wire mesh
(3) Water jet nozzle
(5) Flame blocking nozzle
(6) Water jet nozzle

Claims (3)

A flame prevention device attached to the front stage of a heating reaction tube of an oxidation heating type semiconductor manufacturing exhaust gas abatement machine,
And wire mesh, towards the gold net provided above the gold network have a water injection nozzle for injecting water, the water injection nozzle is disposed upstream of the flow of the semiconductor manufacturing exhaust gas than gold network A flame prevention apparatus for a semiconductor manufacturing exhaust gas abatement machine.   The metal mesh is arranged at a plurality of positions at intervals, and one or a plurality of metal meshes are arranged in each metal mesh arrangement part, and a water injection nozzle is provided above each metal mesh arrangement part. The flame prevention apparatus for a semiconductor manufacturing exhaust gas abatement apparatus according to claim 1. The wire mesh is made of a Ni-Cr-based iron alloy and has a wire diameter of 0.7 mm or more and 1.7 mm or less, and a Tyler mesh of 3 or more and 8 or less, and the wire mesh is laminated by 1 sheet or 2 or more and 5 sheets or less. Alternatively, it is disposed one by one at intervals of 100 mm, and has a water injection nozzle for spraying water in a mist toward the wire mesh above the wire mesh placement portion. Flame prevention device for harmful equipment.

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