JPH11151418A - Fire preventing device of harmful material removing machine for semiconductor production waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the propagation of fire with a simple structure by forming a fire preventing device mounted to the preceding stage of a heating reaction cylinder of a thermally oxidizing harmful material removing machine in semiconductor production waste gas so as to be provided with a wire mesh and a water jetting nozzle provided at the upper part of the wire mesh and for jetting water toward the wire mesh. SOLUTION: The fire preventing device has a cylindrical body 1 forming a box structure and one piece of the wire mesh 2 is installed near the bottom of the cylindrical body 1. One piece of a water jetting nozzle 3 is attached to the head part side of the cylindrical body 1 to eject water from the water jetting nozzle 3. In such a case, the fire propagation rate is inversely proportional to the sieve opening of the wire mesh and the smaller the sieve opening (larger the numbers of the mesh in Tyler) is, larger the fire rate to be extinguished is. Then preferably 1 to 85 pieces of the wire meshes 2, each of which is composed of a wire rod made of a Ni-Cr based alloy and having 0.7 to 1.7 mm diameter and has Tyler mesh of 3 to 8, are laminated or arranged one by one at 100 mm interval.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame prevention device as a safety device installed for pretreatment of exhaust gas introduction in an electrothermal oxidation heating type abatement machine for detoxifying various gases used in semiconductor manufacturing.

[0002]

2. Description of the Related Art In semiconductor manufacturing by CVD, each of
Depositing gas (eg, SiH
_Four, Si_TwoH₆, SiH_TwoCl_Two, TEOS, PH_Three, B
_TwoH₆, NH _Three, N_TwoO) etc. to finish the deposit process
Cleaning gas to clean the inside of the CVD
(For example, NF_Three, SF₆, C_TwoF₆, CF_FourEtc.) is usually
used.

[0003] These gases inherently have various danger factors such as flammability, explosiveness, corrosiveness, and toxicity. For this reason, it must be eliminated (detoxified) using an abatement machine equipped with a means such as oxidizing heating before being released to the atmosphere.

[0004] In the CVD, a complicated decomposition reaction is caused to the used gas, and as a result, new decomposition products (for example, F
_2, HF, and generates HCl, and the SiO _X, etc.), it is discharged entrained with deposit gas and cleaning gas undecomposed.

When such an unexpected mixed gas is heated and oxidized and decomposed in a zone (reaction tube) 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, Within the SiH ₄ concentration range of 1.9 to 87.1%,
In a SiH ₄ / NF ₃ / N ₂ mixed system, the SiH ₄ concentration
When there is a fire source in the area of 0.66 to 95.3%, it becomes explosive composition and may actually cause an explosion phenomenon.

Further, as described in Japanese Patent Application Laid-Open No. 7-323211, there is a case where a water injection facility is provided in a stage before a zone having a heat source to clean exhaust gas accompanied by dust as a decomposition product. is there. In this case, for example, SiH ₂ C
When l ₂ exists, SiH ₂ Cl ₂ + 4H ₂ O → Si (OH) ₄ + 2HCl + 2
May hydrolysis such as H ₂ is generated H ₂ gas going on, it may cause explosions in admixture with external air.

[0007] When these explosions occur, abrupt pressure fluctuations occur in the closed piping, which affects the CVD apparatus. Further, the generation of the local flame propagates to a combustible gas (for example, SiH ₄ or the like) in a pipe leading to the CVD,
An accident could result.

[0008] As a general safety device in the abatement machine including such a danger, a water seal type safety device that disperses gas into water and allows water to pass therethrough, or a sensor that detects abnormal phenomena of pressure and temperature with a sensor. There is a flashback preventer that injects N ₂ gas or the like toward the abatement apparatus.

However, the water ring type safety device is limited in the difference of the water ring level, and it is difficult to cope with a wide range of explosion phenomena, and the flashback prevention device is concerned about the delay of the detection time of the sensor. Factor remains.

[0010]

Therefore, in a semiconductor exhaust gas abatement system having a water injection facility at a stage prior to a heater zone, there is provided a flame prevention device as a safety mechanism capable of preventing the propagation of flame with a simple configuration. It has been demanded.

[0011]

According to a first aspect of the present invention, there is provided a flame preventing apparatus for an exhaust gas abatement apparatus for manufacturing semiconductor exhaust gas according to the present invention. A wire mesh (2), said wire mesh
It has a water injection nozzle (3) provided above (2) for injecting water toward the wire mesh (2).

According to a second aspect of the present invention, there is provided the flame arresting device according to the first aspect, wherein the wire nettings (2a) are arranged at a plurality of locations with an interval therebetween, and are arranged at each of the wire netting arranging portions. The number of the wire mesh (2a) is one or more, and a water injection nozzle (3) is provided above each wire mesh disposing portion.

The flame prevention device of the present invention is a semiconductor manufacturing exhaust gas.
Of flame spread prevention function to ancillary equipment in waste treatment
It was done. Abatement machine from CVD for exhaust gas treatment
The exhaust gas introduced into the_TwoDust,
And F_Two, NH_Three, SiH_TwoCl _TwoWater-soluble components such as water
Decomposition components are contained, and these substances are
Entering the heating reaction tube for processing increases the gas passage resistance.
Large, promotion of metal corrosion trouble, NO_XLike only want
Cause problems such as generation of various by-products.
It is desirable to remove it in advance, and
Treatment is performed by spraying water with a bath. With this ancillary equipment
By installing a wire mesh on a water scrubber, the dust
It has been found that it has a function of flame prevention other than removal.

[0014] The basic principle of the flashback prevention device using a wire mesh is that the energy of the flame is cooled by the wire mesh and the flame is not emitted upstream of the exhaust gas introduction. Therefore, the net material needs to be a metal having heat resistance.
Further, in order to enhance the cooling effect, it is desirable that the mesh structure is dense and the flame does not come out of the mesh.

However, it is necessary to eliminate clogging of dust typified by SiO ₂ and to reduce the overall ventilation resistance, which is inconsistent with the quenching function of the wire mesh.
We found out the trade-off, and added the water jet to enhance the cooling effect and confirmed the fact that the dust clogged out.

That is, the flame prevention device of the present invention comprises (a) pre-cleaning for removing semiconductor exhaust gas, (b) quenching action by wire mesh slits, (c) cooling of wire mesh by atomized water and extinction of the flame itself, (d) It has the function of improving the increase in airflow resistance by removing dust brought in by water injection.

It is known that the flame propagation speed is inversely proportional to the mesh size of the wire mesh. The smaller the mesh size (the larger the number of meshes in the case of Tyler), the larger the flame speed that can be extinguished. In the case of the present invention, assuming an H ₂ / air mixture system of a typical explosion phenomenon, the flame propagation speed is 2.8 m / Sec. (Equivalent to Tyler mesh 6) is preferable.

In the present invention, Tyler mesh 3 to 8
2 to 5 wire meshes are used. In this case, a plurality of wire meshes may be stacked or each wire mesh may be installed at intervals. When the number of used sheets exceeds 5, the ventilation resistance increases but the quenching effect is not significantly improved. Therefore, five or less sheets are preferable.

The flame prevention device of the present invention may be prismatic or cylindrical. The shape of the wire mesh is adjusted 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 c
m, a diameter of 20 cm, etc. can be exemplified in the case of a cylindrical shape, but this is an example, and the present invention is not limited to specific dimensions. Similarly, the height is illustrated as 30 to 80 cm, but the present invention is not limited to specific dimensions.

One nozzle is installed at least at the center of the ceiling of the box structure. In addition, wire mesh will be installed at one or more locations and up to five locations. In this case, one card may be installed in one place,
A plurality of sheets may be stacked and installed. When a plurality of wire meshes are installed at intervals, a nozzle may be installed between the wire meshes.

The nozzles used are SUS304, SUS3
It is desirable to use a Ni-Cr-based iron alloy having corrosion resistance such as 16L.

Exhaust gas processed by the abatement machine is 1000 liter / m
In the case of air volume up to in, the amount of water discharged from the nozzle is 5 in total
It is about 50 liter / min, and the water temperature may be room temperature.

In the case of an abatement system for semiconductor manufacturing exhaust gas, combustible and explosive gas (for example, H ₂ , ethanol, etc.) secondary generated by flammable and explosive gas abatement and hydrolysis as described above. In addition, as a result of the reaction performed inside the CVD, flammable or explosive generated dust whose process is not fully understood may be brought into the abatement machine, and these are oxidized and decomposed in the abatement machine. Therefore, even if the flame is generated through the external air and heat source required for the purpose, the presence of the wire mesh and the water jet prevents the flame from propagating and does not cause an accident.

According to a third aspect of the present invention, there is provided the flame prevention apparatus according to the first aspect, 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.
er mesh of 3 or more and 8 or less, and the wire mesh is one or two or more and five or less laminated or one at an interval of 100 mm.
It is characterized by having a water spray nozzle for distributing water in a mist state toward the wire mesh above the wire mesh arrangement section.

This is a study of the structure of a wire netting suitable for treating the dust brought in by the exhaust gas and ensuring a sufficient flame prevention effect. In addition, a wire made of a Ni-Cr-based iron alloy was used as a corrosion-resistant material by corrosive gas, and was determined in consideration of both the gas passage resistance and the quenching effect.

The flame preventing device according to the fourth aspect of the present invention has one or more flame shut-off nozzles which are installed in a preceding process of the thermal reaction tube and whose diameter decreases toward the upstream side of the gas flow. A water injection nozzle for injecting water toward the flame shutoff nozzle is provided at least on the upstream side of the flame shutoff nozzle installed at the most downstream side.

According to this, the flame is shut off by the flame shut-off nozzle and is cooled by the flame shut-off nozzle and the water injection nozzle, so that the flame does not flow out in the upstream direction of the exhaust gas introduction. In addition to water cooling, the water jet has an effect of preventing dust from clogging the flame shut-off nozzle.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments. Embodiment 1 FIG. 1 is a view showing an outline of a flame arresting device according to the present embodiment. An abatement machine equipped with this flame arresting device was used to remove SiH ₄ gas in an explosive composition range.

In this case, (1) is a cylindrical body forming a box structure of the flame arrestor, and in the embodiment, it is a prism having a cross section of 20 cm square and a height of 70 cm. (2) is a wire mesh of Tyler mesh 6 made of SUS304 and having a wire diameter of 1.02 mm, and was installed near the bottom of the tubular body (1).

Further, one water injection nozzle (3) (non-core full cone nozzle 3 / 8KSFL manufactured by Ikeuchi Co., Ltd.) is attached at the center of the cross section 10 cm below the head of the tubular body (1), and water is supplied at 15 liters / water. Injected at min. The reason for using the full-cone nozzle in the embodiment is that the full-cone nozzle is capable of spraying water droplets over a wide range, and in order to extinguish the flame, heat is efficiently transferred from the high-temperature gas to the water droplets. (High cooling efficiency).

The abatement machine has a plurality of electric heaters set at a surface temperature of 700 ° C.
% SiH ₄ is 5 l / min, N ₂ is 95 l / min
Was supplied, and 175 liters / min of external air was mixed with the abatement gas at a place where the gas passed through the flame arrestor and exposed to the heat source of the heater.

As a result, the SiH ₄ gas having a concentration of 5% was harmed to a concentration of 0.1 ppm or less in the exhaust part of the harm eliminator. SiH when introduced concentration of ₄ to 5 with SiH ₄ / N ₂ system
%, 1.82% in a SiH ₄ / air / N ₂ system,
_{Although the} lower limit of the explosion limit of the ₄ / air / N ₂ system was 1.37%, in this example equipped with a flame arrestor, it was possible to safely remove the harmless gas without causing an explosion. There was no accumulation of dust on the wire mesh surface. [Embodiment 2] FIG. 2 is a diagram showing an outline of a flame prevention device of this embodiment. The cylindrical body (1) is the same as in the first embodiment. Tyler made of SUS316L and having a wire diameter of 1.63 mm
Five wire nets (2a) made of the mesh 3 were divided into three places so as to be two, two, and one from the gas passage direction (upward in the drawing), and a total of five were installed. Each installation location is 1 space
0 cm.

The same water injection nozzle used in Example 1
(3) Three pieces were installed at the center of the cross section of 5 cm above each wire mesh installation location. Water was sprayed from the injection nozzle at a total flow rate of 10 liters / min.

[0034] 100% SiH ₂ Cl ₂ abatement machine set to the heater surface temperature 750 ° C. is 4 liters / min, N ₂ 9
6 liter / min mixed gas (SiH ₂ Cl ₂ concentration 4
%) Was introduced from above the flame arrestor, and at the point where it passed, 100 liter / min of external air was mixed and passed through the heat source of the heater.

In this case, if hydrolysis proceeds stoichiometrically, the H ₂ concentration in the passing gas is 4% of the lower limit of explosion (LEL) of H ₂ / air. The detoxification treatment proceeded safely and stably, and the SiH ₂ Cl ₂ concentration in the exhaust part of the detoxification equipment was not measured at all. Also, no powdery or sludge-like solids were present on the wire mesh. Comparative Example 1 Example 1 except that the flame prevention device was removed.
A comparative test was carried out under the same conditions using the same abatement apparatus used in the above.

As a result, an abnormal sound is generated at the place where the SiH ₄ / N ₂ mixed gas comes into contact with the external air, and the pressure in the system fluctuates. The emergency stop signal of the supply system was activated, and the energization of the heater was stopped. That is, some abnormal combustion has occurred. [Embodiment 3] FIG. 3 is a diagram showing an outline of the configuration of this embodiment. In the figure, reference numeral (5) denotes a flame shutoff nozzle narrowed so that the diameter on the upstream side of the flow of the exhaust gas becomes small. In this embodiment, two nozzles are provided on the cylindrical body (4). In the embodiment, the shape of each flame shut-off nozzle (5) is as follows.
The diameter of (5b) (the inner diameter of the cylindrical body (4)) is 100 mmφ. The interval between the flame shutoff nozzles (5) was 100 mm. Incidentally, (5c) is a rectifying section having a curved surface provided upstream of the throttle section (5a) of the flame shutoff nozzle (5). The rectifying section (5c) is provided to receive water droplets jetted from a water jet nozzle (6), which will be described later, and to reduce ventilation resistance when exhaust gas flows.

(6) is the same water injection nozzle (full cone nozzle) used in Example 1, which is located between the two flame shutoff nozzles, that is, the upper part of the lowermost (most downstream) flame shutoff nozzle. (Upstream side), and can inject water toward the lowermost (most downstream side) flame shutoff nozzle.
This water injection nozzle (6) has a water pressure of 0.5 kgf / cm ² ,
It was operated at liter / min.

When the exhaust gas introducing pipe for guiding the exhaust gas to the reaction tube (7) has a diameter capable of accommodating the flame shut-off nozzle (5) and the water injection nozzle (6), the exhaust gas introducing pipe is used. It can be used as it is as a tubular body (4).

As exhaust gas, 10 liters of 100% H _{2 and} 190 liters / min of N ₂ for dilution (5% H ₂ concentration in the mixed gas) were introduced into the reaction tube (7) via the nozzle installation section. The reaction tube (7) was provided with an electric heater, and the ambient temperature was set at 700 ° C.

On the other hand, external air was directly supplied to the reaction tube (7) at a flow rate of 75 liter / min, mixed with H _{2 of} the exhaust gas, and burned and harmed. As a result, the H ₂ concentration in the gas on the processing gas discharge hole side was 1000 ppm, and the calculated removal rate was 98%. There was no evidence that a flame came from the flame shutoff nozzle (5) to the exhaust gas introduction side. In addition, the water temperature of the water tank after the water injection was 55 ° C.

In this embodiment, the number of the flame shut-off nozzles is two, but may be one or three or more. Further, in this embodiment, the water injection nozzle is provided only on the upstream side of the lowermost (most downstream) flame shutoff nozzle. However, when there are a plurality of flame shutoff nozzles, the water injection nozzle is also provided on the upstream side of other flame shutoff 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 shutoff nozzle (5) and the water injection nozzle (6) were not provided. The mixed exhaust gas was supplied to the reaction tube in an atmosphere of 700 ° C. under the same gas supply conditions (composition, air volume, and concentration) as in Example 3, and external air was directly introduced into the reaction tube as in Example 3.

As a result, some of the combustion that occurred in the reaction tube broke through the explosion opening provided in the reaction tube with an explosion phenomenon, and the other portion caused backfire propagation to the exhaust gas introduction pipe side. The reverse flame exceeded 1000 ° C.

[0043]

As described above, according to the present invention, in a semiconductor exhaust gas abatement system having a water injection facility before a heater zone, a flame as a safety mechanism capable of preventing the propagation of flame with a simple structure. The prevention device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an outline of a configuration according to a first embodiment.

FIG. 2 is a diagram illustrating an outline of a configuration according to a second embodiment.

FIG. 3 is a diagram illustrating an outline of a configuration according to a third embodiment.

[Explanation of symbols]

 (1) Cylindrical body (2) Wire mesh (3) Water injection nozzle (5) Flame shut-off nozzle (6) Water injection nozzle

Claims (4)

[Claims] 1. A flame prevention device attached to a stage prior to a heating reaction tube of an oxidation heating type semiconductor manufacturing exhaust gas abatement system, comprising: a wire mesh; and water jetted toward the wire mesh provided above the wire mesh. A flame prevention device for a semiconductor manufacturing exhaust gas abatement machine, comprising: 2. A wire mesh is arranged at a plurality of locations with an interval, and one or a plurality of wire meshes are arranged in each wire mesh disposing portion, and a water injection nozzle is provided above each wire mesh disposing portion. The flame prevention device for a semiconductor manufacturing exhaust gas abatement apparatus according to claim 1, wherein: 3. A wire mesh made of a Ni—Cr-based iron alloy and having a Tyler mesh of 3 or more and 8 or less made of a wire having a wire diameter of 0.7 mm or more and 1.7 mm or less.
5. The method according to claim 1, wherein at least five or less sheets are stacked or arranged one by one at an interval of 100 mm, and a water jet nozzle for spraying water in a mist toward the wire mesh is provided above the wire mesh arrangement part. 2. A flame prevention device for a semiconductor manufacturing exhaust gas abatement apparatus according to claim 1. 4. The apparatus has one or a plurality of flame shut-off nozzles which are installed in a pre-process of the heating reaction tube and whose diameter decreases toward the upstream side of the gas flow, and are installed at least at the most downstream side. A flame prevention device for a semiconductor manufacturing exhaust gas abatement machine, characterized in that a water injection nozzle for injecting water toward the flame shutoff nozzle is provided upstream of the flame shutoff nozzle.