JP2004160312A - Pfc gas decomposition system and method used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relate to a reaction furnace which decomposes organic halogen gas such as PFC,HFC to be used in a wafer etching device such as a semiconductor production device into a harmless substance with high temperature, and also relate to a reaction method used for the same. <P>SOLUTION: The PFC gas treatment system is provided with (1) a turbo pump to discharge exhaust gas containing PFC gas used inside a wafer etching chamber together with purging Ar to be supplied, a dry pump connected to the downstream side of the turbo pump, a first filter connected to downstream side of the dry pump and filtering particle substance in the exhaust gas, (2) a plasma reaction furnace installed on the downstream side of the first filter and decomposing the PFC gas by reaction with reaction gas supplied from gas system, and (3) exhaustion gas facilities to treat exhaust gas to be discharged on the downstream side of the plasma furnace. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reaction furnace and a reaction method for decomposing an organic halogen gas such as PFC (Perfluorocarbon) and / or HFC (Hydrofluorocompound) used in a wafer etching apparatus such as a semiconductor manufacturing apparatus into a harmless substance at a high temperature.
[0002]
[Prior art]
PFC gas used in a wafer etching apparatus which is a semiconductor manufacturing apparatus, that is, a chlorofluorocarbon gas composed of carbon, fluorine, and hydrogen, specifically, CF ₄ , C ₂ F ₆ , CaF ₈ , CHF ₃ , C ₆ F ₈ , and gas such as SF ₆ is a greenhouse gas, there are about 6000 times the greenhouse effect compared to the CO2 gas. In addition, the lifetime of PFC gas is very long, from several thousand years to tens of thousands of years, while the life of CO2 is about 100 years.
[0003]
As an international measure, the Kyoto Protocol in 1997 agreed to reduce these PFC gases to the 1995 level by 2010. Also, in April 1999, the World Semiconductor Association (World Semiconductor Council), that is, EECA (Europe), ElAJ (Japan), SIA (USA), and KSIA (Korea) by 1995, A further 10% reduction over the year level was agreed.
[0004]
In practice, however, global PFC gas usage in 2001 is increasing at an annual rate of 10%. Decomposing this PFC gas, converting it to a harmless substance and releasing it to the atmosphere is also urgently required in the semiconductor industry.
Conventionally, a method of processing and releasing PFC gas has been developed, and is mainly classified into the following three types.
[0005]
1 Combustion method 2 Catalytic method 3 Plasma method Among these, one of the combustion methods is to burn the gas discharged from the apparatus including PFC at high temperature, decompose it into CO ₂ and HF, and then dissolve HF in water and neutralize it. It is a method of neutralizing with a bed and draining. In this method, CO ₂ is emitted. The so-called NOX gases such as NO ₂ is generated during the combustion process of the NOX gases has not been found is still decisive way.
[0006]
The treatment of HF also uses a conventional water scrubber, but the liquid in the neutralization tank relies on a method of treating as industrial waste. Further, in this method, since the gas is heated to a high temperature, the amount of energy used becomes large. The result is an expensive and bulky device. In addition, such expensive and large-scale equipment is inevitably adopted as a method of treating the etching equipment, which is a semiconductor manufacturing equipment, in one place, instead of attaching it to a single base. Transport and large-scale piping are required.
[0007]
Next, the second catalytic method requires that the gas containing PFC be heated to about 600 to 800 ° C., which also requires a large amount of energy. Some catalysts need to be discharged after use and a new catalyst must be supplied, and a catalyst supply / discharge device is installed. After all, it becomes a large-scale device, and is not suitable for attaching to an etching device-table-table.
[0008]
FIG. 1 shows an apparatus manufactured by U.S. Litmas Co., Ltd., which is currently being evaluated in the market for the plasma method No. 3. As shown in FIG. 1, a reaction furnace 4 utilizing plasma is disposed downstream of a turbo pump 2 that evacuates the etching chamber 1, that is, between a dry pump 7 that evacuates the turbo pump 2, This is a method in which a gas containing PFC is reacted with H ₂ gas 5-1, O ₂ gas 5-1 or moisture 5-2, turned into plasma, decomposed, converted into CO ₂ gas, HF gas, etc., and discharged. In FIG. 1, 3-1 and 3-3 are gate valves.
[0009]
Further, the dry pump is supplied with N ₂ gas 7-1 for diluting a reactive gas such as HF. The scrubber 9 removes HF, particulate matter and the like contained in the exhaust gas. This plasma method supplies less energy and is more efficient than the previous two methods. The plasma reactor 4 generates plasma under reduced pressure (about 1 Torr).
[0010]
[Problems to be solved by the invention]
However, the above-described plasma method 3 has a problem by generating plasma downstream of the turbo pump 7.
(1) It has been reported that, when an apparatus using the PFC gas plasma method is used for a long time, deposition occurs in the plasma reactor 4 and it is necessary to periodically clean the apparatus. In order to clean the plasma reactor 4, the foreline of the turbo pump 2 needs to be returned to the atmospheric pressure. Returning the foreline to atmospheric pressure means returning all of the etching chamber 1, the turbo pump 2, and the dry pump 7 to atmospheric pressure, which results in a long downtime of the etching process.
[0011]
(2) Further, the acidic HF gas generated by the decomposition by the plasma flows to the dry pump 7 as it is, which may adversely affect the life of the dry pump 7.
[0012]
(3) Further, in this method, a water scrubber 9 for removing HF after the plasma treatment is required, and a device for neutralizing the water is required.
[0013]
(4) When viewed from the etching chamber, the reaction gas is introduced into the foreline, and the degree of vacuum in the etching chamber 1 changes. Further, there is a possibility that H ₂ as a reaction gas flowing into the plasma reactor 4 may flow back to the etching chamber 1 side, which may adversely affect the etching.
(5) It cannot be used in the etching chamber 1 where the turbo pump 7 is not used.
[0014]
Further, conventionally, an atmospheric pressure plasma reactor for generating plasma under atmospheric pressure (about 760 Torr) has already been proposed (JP-A-5-202481, JP-A-4-358076, etc.). It is known that by using a gas, that is, He gas or Ar gas, a discharge similar to a glow discharge in a vacuum can be obtained.
[0015]
The present invention has been made in order to solve the above-described problems, and generates plasma in a reaction furnace using Ar gas at atmospheric pressure, decomposes PFC gas, and recycles expensive Ar used. It is an object to provide a PFC gas decomposition system and a gas decomposition method.
[0016]
Further, the cleaning process does not cause a long downtime of the etching process, the HF gas generated by the decomposition by the plasma does not affect the life of the dry pump, there is no need to neutralize the water of the scrubber, and the wafer etching is not performed. A PFC gas decomposition apparatus which does not need to change the degree of vacuum in the chamber, does not cause H ₂ as a reaction gas of the plasma reaction to flow back to the etching chamber, and can be used in an etching chamber or an apparatus not using a turbo pump. The purpose is to provide.
[0017]
[Means for Solving the Problems]
To solve the above problems, the following invention is provided.
According to a first aspect of the present invention, there is provided a PFC gas decomposition system including the following members.
(1) A turbo pump for exhausting an exhaust gas containing a PFC gas (hereinafter, referred to as a gas to be processed) used inside a wafer etching chamber together with a purge Ar, a dry pump connected downstream thereof, and a turbo pump downstream thereof. A first filter for filtering particulate matter in the connected exhaust gas,
(2) a plasma reactor provided downstream of the first filter and decomposing the PFC gas by reacting with a reaction gas supplied from a gas system;
(3) An exhaust gas treatment facility for treating exhaust gas discharged downstream of the plasma reactor.
[0018]
According to a second aspect of the present invention, the exhaust gas equipment includes a first reaction tower for mainly removing gas components, a second filter for mainly removing particulate matter, and a second absorption tower for mainly removing gas components. A PFC gas decomposition system comprising: a gas tank provided for storing Ar gas discharged from the second absorption tower.
[0019]
A third aspect of the present invention is a PFC gas decomposition system, characterized in that the plasma reactor has the following structure for decomposing PFC gas contained in the gas to be treated introduced from the first filter. is there.
(1) a plasma reactor comprising an inner cylinder and an outer cylinder of an insulating refractory, wherein a space between the inner cylinder and the outer cylinder is cooled by a refrigerant;
(2) ignition means for starting discharge of the gas to be treated;
(2) magnetic field generating means for applying a magnetic field to the discharge gas started by the ignition means;
(3) Plasma adjusting means for shifting the discharge gas to a plasma state and maintaining the plasma.
[0020]
A fourth aspect of the present invention is the PFC gas decomposition system, wherein the ignition means is a discharge generator for applying a predetermined voltage between the electrode and the ground.
[0021]
According to a fifth aspect of the present invention, the magnetic field generating means includes a coil wound outside the reactor, a power supply for supplying a high-frequency current to the coil, and a voltage adjusting means. System.
[0022]
A sixth aspect of the present invention is the PFC gas decomposition system, wherein the gas system includes a bubbler for generating an Ar gas containing water vapor.
[0023]
According to a seventh aspect of the present invention, there is provided a PFC gas, wherein the first reaction tower is provided with soda lime for reacting and removing H ₂ O, HF and CO gases mainly generated when PFC gas is decomposed. It is a decomposition system.
[0024]
An eighth aspect of the present invention is the PFC gas decomposition system, wherein the second filter includes a membrane blender that mainly absorbs moisture in exhaust gas.
[0025]
A ninth aspect of the present invention is the PFC gas decomposition system, wherein the second absorption tower includes a zeolite for mainly removing particulate matter from exhaust gas.
[0026]
In a tenth aspect of the present invention, the gas system comprises an Ar gas supply source, a vacuum exhaust pump as a means for igniting plasma in the reactor, and an argon gas flow controller and a bubbler as means for supplying steam to the reactor. The PFC gas decomposition system according to claim 1, further comprising: a pipe configured to supply Ar gas from the tank via a third filter to a downstream of the Ar gas supply source.
[0027]
According to an eleventh aspect of the present invention, there is provided a turbo pump for exhausting a gas to be processed including a PFC gas used inside a wafer etching chamber, using Ar as a purge gas, and a dry pump connected to the downstream side using Ar as a purge gas. It comprises a pump, a filter for filtering particulate matter in exhaust gas, a plasma reactor for decomposing PFC gas, and the following steps using an exhaust gas treatment facility for treating exhaust gas from the reactor. This is a PFC gas decomposition method.
(1) The gas to be processed including the PFC gas used inside the wafer etching chamber is exhausted by a turbo pump using Ar as a purge gas and a dry pump connected downstream thereof using Ar as a purge gas, A step of filtering the particulate matter in the exhaust gas connected downstream thereof and supplying it to the plasma reactor,
(2) further supplying a reaction gas and decomposing the PFC gas in the plasma reaction chamber;
(3) a first step of reacting and removing the harmful gas discharged from the plasma reactor, a second step of mainly removing particles downstream of the first step, and an Ar gas discharged from the second step. The process of storing.
[0028]
A twelfth aspect of the present invention is the PFC gas decomposing method, comprising the following step of decomposing PFC gas contained in Ar gas introduced from the filter.
(1) a step of supplying a gas to be treated including a PFC gas to a plasma reactor which is composed of an inner cylinder and an outer cylinder of an insulating refractory and is cooled by a refrigerant between the inner cylinder and the outer cylinder;
(2) an ignition means for starting discharge of the processing gas;
(3) magnetic field generating means for applying a magnetic field to the discharge gas started by the ignition means;
(4) a step of shifting the discharge gas to a plasma state and maintaining the plasma;
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention is shown in FIGS. First, as shown in FIG. 2, a turbo pump 2 and a dry pump 7 for exhausting PFC gas from a wafer etching chamber 1 through a gate valve (not shown) together with Ar gas as a purge gas supplied from an Ar gas supply source. A reaction furnace 10 for decomposing PFC gas via a first filter is provided downstream of the reactor.
[0030]
Ar gas is supplied to the turbo pump 2 and the dry pump 7 from an Ar gas supply source 61 to dilute the PFC gas to protect the device. This PFC gas decomposition furnace 10 is an atmospheric pressure plasma reactor, which decomposes PFC gas by using Ar gas as a plasma excitation gas and Ar gas containing H ₂ O vapor supplied from a gas system 6 described later as a reaction gas. And finally convert to harmless substances and exhaust.
Instead of of H 2 _O vapor H _2, O ₂ gas may be supplied through a flow meter to.
[0031]
The other end of the reactor 30 is provided with the plasma adjusting means 12. When the inert gas is argon, the pressure in the reactor 30 is gradually increased from a reduced pressure of about 1 Torr to the atmospheric pressure. It has the function of maintaining the discharge / plasma state inside the reactor body 30 in a stable plasma that glows spherically through an initial stage, a transition stage, and a stable stage described later.
[0032]
The plasma reactor 10 is intended for processing by decomposing reacted gas to be treated, the CF _4, for example PFC gas at elevated temperatures. The CF ₄ gas reacts with the reaction gas in a sufficiently high temperature atmosphere and is decomposed into HF gas and CO ₂ gas.
[0033]
As shown in FIGS. 2 and 3, a substantially cylindrical reactor 30 for decomposing a gas to be treated by high temperature of plasma is provided at one end thereof with CF ₄ as a PFC gas as a gas to be treated. It is supplied via one filter 8. The filter 8 is connected to the dry pump 7, and further, an inert gas such as an argon gas as a plasma excitation gas is used as a reaction gas that reacts with a pipe 63-1 provided with a pump, a flow meter, and the like, and a gas to be processed. Ar gas containing water vapor is supplied via a valve 68.
[0034]
(High frequency coil)
As a means for generating a magnetic field, for example, a high-frequency coil 21 is helically disposed around the center in the longitudinal direction of the cylindrical reaction furnace body 30, and is connected to the high-frequency power supply 25 via a matching circuit 21-1. It is connected and supplies a magnetic force to the inside of the reactor to generate a magnetic field. A voltage adjusting means 27 is attached to the high frequency power supply 25.
[0035]
The high-frequency coil 11 is called an L-coupling because it is arranged in a spiral and generates a magnetic field, and is distinguished from a C-coupling in which a voltage is applied between both electrodes arranged as a pair. Desirable frequency is 1 MHz to 50 MHz, and voltage is preferably 1000 to 10000 Volt.
The means for generating the magnetic field is not limited to a high frequency, but may be a microwave. In the case of microwaves, a cavity resonator is used instead of a coil. As the microwave, for example, a microwave generator of 2.45 GHz may be provided.
[0036]
(Ignition means)
On the upper part of the reactor body 30, an ignition means 19 for generating discharge first is provided. The ignition means 19 uses, for example, a metal electrode provided outside the reactor body 30 and a ground around the metal electrode. The ignition means has, for example, an electrode disposed outside the reactor body 30 and a ground of the reactor body 30 as a pair, and has a C coupling in which a voltage is applied to the electrode. An AC voltage of 1,000 to 10,000 Volts is desirable. A Tesla transformer can be used instead of the C coupling device.
[0037]
(Exhaust gas treatment equipment)
The other end of the reactor 30 is connected to an exhaust gas treatment facility 24 (14, 16, 18, 20, 22) for absorbing and removing HF gas and CO ₂ gas contained in the treated gas. The exhaust gas treatment equipment 24 is provided with a first reaction tower and converts HF and CO ₂ coming out of the reaction path into harmless substances such as CaF ₂ (fluorite) and CaCO ₃ (marble).
[0038]
The structure of this atmospheric pressure plasma reactor in this embodiment will be described later in detail with reference to FIG. Downstream of the atmospheric pressure plasma reactor 10, a first reaction tower 14 having soda lime as shown in FIG. 2 is provided, and the gas converted in the atmospheric pressure plasma reactor 10 reacts with the soda lime. By doing so, they are converted into harmless substances.
[0039]
That is, CO ₂ , HF, and H ₂ O which are gases converted in the plasma reactor 10 are converted into soda lime (for example, NaOH-5%, Ca (OH) ₂ -80%, H ₂ O-15%, SiO 2 It is reacted with ₂ -0.2%), of the shift gas, CO ₂ in the CaCO _3, HF in CaF ₂ (fluorite) and _H 2 O (water), to convert each fully Harmless substances.
[0040]
Further, a second filter is provided on the downstream side of the first reaction tower 14, and mainly removes moisture in the exhaust gas by a membrane blender. Downstream, a second absorption tower is provided, which is equipped with zeolite and absorbs particulate matter in the exhaust gas (FIG. 2). The gas discharged from the second absorption tower is clean Ar and is stored in the tank 22 by the pump 20.
Further, a part of Ar stored in the tank 22 is further purified by the third filter, and is recycled through the regulator 64 and the check valve 65. When excess Ar gas is stored in the tank 22, it is released to the atmosphere via the relief valve 71.
[0041]
(Gas system)
In FIG. 2, a portion 6 surrounded by a dotted line is a gas system, which is a system for supplying Ar used in the present invention and for recycling once used Ar gas. The Ar gas is supplied from, for example, an argon source 61 such as a cylinder, and is supplied to the turbo pump 2 and the dry pump 7 through a pipe 63-1 via a regulator 62. Ar is supplied from this pipe to a bubbler 67 described later via a flow meter 66, becomes Ar containing water vapor, and is supplied to the reaction furnace 10 via a valve 68 as a reaction gas.
[0042]
(Reactor body)
Hereinafter, the details of the reactor shown in FIGS. Reactor body 30 is provided with coolant supply means 23 for cooling each part heated by the plasma. The reactor body 30 is composed of, for example, a transparent heat-resistant quartz tube 45 having a cylindrical outer periphery. Although FIG. 4 shows only the upper end of the reactor, only the upper end structure will be described because the lower end structure is substantially the same. A quartz tube 27 is connected to the upper end, and a gas to be processed is introduced. Refrigerant supply means 23 (FIG. 3) for supplying a refrigerant such as water is connected to both ends and the center of the reactor 30.
[0043]
The quartz tube 27 penetrates and is fixed to the cylindrical block 31 concentrically. A seal between the tube 27 and the block 31 is provided, for example, by placing a ring-shaped fluorine-based O-ring 33 at the end of the block 31 through which the quartz tube 27 passes, and the O-ring 33 is pressed by the fastener 35. A lid 37 for holding the fastener 35 is placed over the end of the columnar block 31 and screwed together with a screw 39 to be sealed by being tightened.
[0044]
A cavity 41 through which a coolant, for example, water flows, is formed inside the block 31, and a pair of water cooling tubes 43 is connected to the side surface of the block 31 in communication with the cavity 41. A cylindrical transparent quartz tube 45 that covers the insulating tube 25 is provided at the longitudinal center of the cylindrical insulating tube 25, and a gap 47 through which a coolant flows between the quartz tube 45 and the peripheral surface of the insulating tube 25. It is formed. Water cooling tubes 51 and 53 are connected to side surfaces of a cylindrical block 49 which communicates with the gap 47 and holds the quartz tube 45 from outside.
[0045]
The sealing between the quartz tube 45 and the peripheral surface of the insulating tube 25 is performed at two places. In the first place, a ring-shaped O-ring 55 is arranged at the end of the block 49, and the O-ring 55 is pressed by the fastener 57, and the lid 59 that holds the fastener 57 is attached to the cylindrical block 49. Is screwed with a screw 61 and tightened, whereby the block 49 and the peripheral surface of the insulating tube 25 are sealed.
[0046]
The second portion is a lower end portion of the reactor 30 and is schematically shown in FIG. 3 and has the same structure as the upper end portion, and details are omitted.
[0047]
The structure in which the water cooling tubes 43 and 51 are provided is provided symmetrically at both ends of the cylindrical insulating tube 25. The high-frequency coil 21 is formed of a copper pipe so that the refrigerant flows therein. A coolant is supplied to the water cooling tubes 43 and 51 and the high-frequency coil 21 from the coolant supply means 23, and the coolant is used.
[0048]
(Reactive gas)
The reaction gas is generated by the bubbler 67 shown in FIG. The bubbler contains water 6-7 in a container 6-5, and Ar gas is supplied from the tip of a pipe 6-1 immersed in water to generate Ar gas containing water vapor and react as a reaction gas 6-3. Supplied to the furnace. In order to control the amount of water vapor, the container 6-7 is heated by a heater 6-9 and the temperature is adjusted.
[0049]
(Plasma adjusting means)
The plasma adjusting means 12 includes a valve 69 and an exhaust pump 70 shown in FIG. The valve 69 is opened, the exhaust pump 70 is driven, and the reaction furnace 30 is first evacuated to about 1 Torr. When the glow discharge is started, the pressure in the reaction furnace 30 is increased to about 760 Torr in about 30 seconds while observing the discharge state. Adjust the displacement so that By such pressure adjustment, a discharge state described later as shown in FIG. 5, that is, a glow discharge, a transitional state, and a linearly shining portion increases in brightness, fluctuates from a linear shape, and changes to a tornado shape. In the latter half of the period, almost the center of the reactor body 30 shines brightly in a spherical shape, and a spherical thermal plasma 75 in the atmosphere is formed, whereby a stable phase process is obtained (FIGS. 5A to 5D).
[0050]
(Example)
[1] The pressure in the discharge tube as the reaction furnace body 30 is reduced to about 1 Torr using a small exhaust pump 70.
[0051]
[2] Ar gas was supplied to the reactor 30 having an inner diameter of 26 mm (outer diameter of 30 mm) through the filter 8 at a rate of 1 to 2 L / min.
[0052]
[3] The high-frequency coil 21 supplies high-frequency power to the inside of the reaction furnace 30, and a high voltage is supplied to the reaction furnace 30 by the C-coupling electrode as the ignition means 19.
[0053]
[4] Due to this high voltage, gas ionization occurs and glow discharge occurs. As a result, an initial process in which the entire inside of the reactor 30 shines blue-violet is obtained (FIG. 5A). In this glow discharge, high-frequency power is supplied through the stray capacitance in the reactor 30. Collisions between neutral molecules in the reactor 30 and electrons supplied from the inner wall of the reactor 30 further increase secondary electrons and maintain discharge.
[0054]
[5] In this state, the pressure in the reactor 30 is gradually increased. In about 30 seconds, the speed increases from 1 Torr to about 760 Torr. By adjusting the speed, the discharge state is changed in the furnace as follows.
[0055]
[6] First, from the state where the glow discharge is maintained by supplying high frequency power from the C coupling electrode as the ignition means 19, the mean free path of molecules is shortened by gradually increasing the pressure, and the electric field of the electric field is reduced. The discharge in the high area increases and the shining area in the furnace narrows. That is, a transition stage in which the center of the inside of the tubular reactor 30 is almost linearly illuminated in the vertical direction along the magnetic field and almost white (FIG. 5B).
[0056]
[7] When the discharge in the narrowed region becomes stronger, the effect of the magnetic field from the L coupling increases, the discharge energy is supplied from the magnetic field, and the temperature of the region further increases. As a result, the linearly shining portion increases in brightness, fluctuates from the linear shape, fluctuates in a tornado shape, and a late stroke of the transition period is obtained (FIG. 5C).
[0057]
[8] The temperature further rises, and not only secondary electrons due to collisions of electrons from the inner wall of the furnace with neutral molecules as in the case of glow discharge, but also thermionic emission due to the temperature rise of the molecules themselves is active. become. The discharge by the thermoelectrons is maintained, and the plasma is generated. That is, almost the center of the reactor body 30 shines brightly in a spherical shape, and a spherical thermal plasma 75 in the atmosphere is formed, so that a stable period process is obtained (FIG. 5D). The brightness of the spherical plasma 75 was confirmed to be considerably bright even with the naked eye, and it was supposed that the temperature of the plasma was considerably higher than that of normal plasma.
[0058]
[9] with the gas to be treated is to heat the plasma plateau stroke, the water vapor contained in the Ar gas is supplied as sufficient reactive gas to decompose 50 sccm, and the CF _4, CF _4, the gas to be treated Is decomposed by heat, emits electrons, and further maintains plasma. In this state, the operation of the device of the present invention is performed.
[0059]
[Evaluation of results]
It is visually confirmed that the brightness of the plasma obtained by the apparatus of this embodiment is considerably stronger than that of a normal glow discharge, and it is conceivable that the temperature is considerably high. In addition, it was indirectly confirmed that the decomposition efficiency of the apparatus of this embodiment was very high. In a comparison experiment with plasma under atmospheric pressure by C coupling (a method of discharging an object to be processed between parallel electrodes), the decomposition rate of PFC was 95.2%, the power consumption was 0.5 KW / cm ³ , On the other hand, in the example of the present invention, the decomposition rate was 99.99%, and the power consumption was 0.12 kw / cm ³ . Therefore, the power consumption has been dramatically improved.
[0060]
It can be inferred that such good results as a plasma reactor are caused by the following causes. That is, a high-temperature plasma discharge that cannot be obtained by the plasma discharge by the C coupling method under the atmospheric pressure (760 Torr) was obtained. That is, the initial stage in which the entire inside of the reactor body 30 shines, the transition stage in which the approximate center of the interior of the reactor body 30 shines linearly along the magnetic field, and the approximate center of the interior of the reactor body 30 at atmospheric pressure becomes spherical. It can be inferred that a special plasma state is obtained by maintaining the stable plasma 75 shining spherically through the bright shining stable period process.
[0061]
Also, as one of the reasons for the specialty, when Ar gas is used as the main plasma gas as the plasma excitation gas, Ar gas is less likely to release heat to the outside from the viewpoint of heat conduction than He gas which has been conventionally used, It can be inferred that the plasma temperature has been maintained high. In addition, since experiments on plasma under atmospheric pressure have not been carried out much, it can be inferred that a special plasma state could not be discovered until now.
[0062]
(Other embodiments)
In the above embodiments, the gas to be treated is a PFC gas, but in other embodiments, a CFC gas can also be treated. Further, any other gas to be treated which is desirably decomposed at a high temperature may be used.
[0063]
In the above embodiment, the ignition means causes glow discharge at the electrode of the C coupling. However, in other embodiments, other means, for example, a Tesla probe can be used.
In the above embodiments, the excitation gas is Ar gas. However, in other embodiments, it has been confirmed that Ar gas and a mixed gas of argon gas and oxygen gas can be used.
[0064]
【The invention's effect】
As described above, the present invention has the following effects.
(1) The downstream side of the PFC gas decomposition furnace is a portion at substantially atmospheric pressure, and it is not necessary to return the upstream side (foreline) of the -degree dry pump to atmospheric pressure during cleaning, and the wafer etching chamber is operated. The state can be left under reduced pressure, thus reducing the downtime of the etching process.
[0065]
(2) Further, since Ar gas is supplied to the turbo pump and the dry pump as a purge gas, and the PFC gas is diluted, the life of the turbo pump and the dry pump is not affected.
[0066]
(3) Further, by using soda lime in the first absorption tower instead of the conventional water scrubber, a device for neutralizing this water becomes unnecessary. In addition, CaF _2, which is a reactive product, can be recovered and used as a raw material for producing fluorine gas.
[0067]
(4) Since the PFC gas decomposition furnace is installed downstream of the dry pump, the degree of vacuum in the wafer etching chamber upstream of the drive pump does not change. Further, there is no possibility that steam supplied as a reaction gas to the PFC gas decomposing device provided on the downstream side of the turbo pump may flow back into the chamber upstream of the drive pump.
[0068]
(5) In particular, in the present invention, since expensive Ar gas is recycled and used, the operation cost of the apparatus can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is an overall block diagram showing an example of a conventional PFC gas decomposition apparatus.
FIG. 2 is a diagram showing an overall configuration of the present invention.
FIG. 3 is a diagram showing a configuration of a plasma reactor of the present invention.
FIG. 4 is a diagram showing a detailed structure of a plasma reactor of the present invention.
FIG. 5 is a diagram showing a change in plasma in the present invention.
FIG. 6 is a diagram showing a structure of a bubbler according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Etching chamber 2 of wafer etching apparatus 2 Turbo pump 6 Gas system 7 Dry pump 8 First filter 10 Plasma reactor 12 Plasma adjustment means 14 First reaction tower 16 Second filter 18 Second absorption tower 19 Ignition means 21 Coil 21-1 Matching circuit 22 Tank 23 Refrigerant supply means 24 Exhaust gas treatment equipment 25 Insulation tube 27 Quartz tube 30 Reactor body 31 Inner block 33 O-ring 35 Fastener 37 Cover 41 Space 43 Water cooling tube 45 Transparent quartz tube 47 Gap 49 Blocks 51, 53 Water cooling tube 55 O-ring 57 Fastener 59 Lid 60 Third filter 61 Ar supply source 67 Bubbler

Claims (12)

A PFC gas decomposition system comprising the following members.
(1) A turbo pump that exhausts an exhaust gas containing a PFC gas (hereinafter, referred to as a gas to be processed) used inside the wafer etching chamber together with a supplied Ar for purging, a dry pump connected downstream thereof, A first filter for filtering particulate matter in exhaust gas connected to the downstream side,
(2) a plasma reactor provided downstream of the first filter to decompose the PFC gas by reacting with a reaction gas supplied from a gas system; and (3) discharged to the downstream of the plasma reactor. Exhaust gas equipment for treating exhaust gas. The exhaust gas treatment equipment is a first reaction tower that mainly removes gas components,
A second filter for mainly removing moisture, a second absorption tower for mainly removing particulate matter, and a gas tank for storing purified Ar gas discharged from the second absorption tower are provided. The PFC gas decomposition system according to claim 1, wherein: 2. The PFC gas decomposition system according to claim 1, wherein the plasma reactor has the following structure for decomposing PFC gas contained in the gas to be processed introduced from the first filter.
(1) a plasma reactor comprising an inner cylinder of an insulating refractory and an outer cylinder, wherein a space between the inner cylinder and the outer cylinder is cooled by a refrigerant;
(2) ignition means for starting discharge of the gas to be treated;
(3) magnetic field generating means for applying a magnetic field to the discharge gas started by the ignition means;
(4) Plasma adjusting means for shifting the discharge gas to a plasma state and maintaining the plasma. 4. A PFC gas decomposition system according to claim 3, wherein said ignition means is a discharge generator for applying a predetermined voltage between an electrode and ground. The magnetic field generating means, a coil wound outside the reaction furnace,
The PFC gas decomposition system according to claim 3, further comprising a power supply for supplying a high-frequency current to the coil and a voltage adjusting means. The PFC gas decomposition system according to claim 1, wherein the reaction gas supplied from the gas system includes a bubbler that generates an Ar gas containing water vapor. 3. The PFC gas decomposition system according to claim 2, wherein the first reaction tower includes soda lime that reacts and renders H20, HF, and CO gases generated when PFC gas is mainly decomposed into harmless. The PFC gas decomposition system according to claim 2, wherein the second filter includes a membrane blender that mainly absorbs moisture in exhaust gas. The PFC gas decomposition system according to claim 2, wherein the absorption tower 2 includes a zeolite for mainly removing particulate matter from exhaust gas. The gas system includes an Ar gas supply source, an exhaust gas pump as a means for igniting plasma in the reactor, an argon gas flow controller and a bubbler as means for supplying steam to the reactor, and Ar gas from the tank. 2. The PFC gas decomposition system according to claim 1, further comprising: a pipe for supplying the Ar gas supply source downstream through the three filters. 3. A turbo pump using an argon gas as a purge gas for exhausting a gas to be processed including a PFC gas used inside the wafer etching chamber, a dry pump connected to the downstream side using an argon gas as a purge gas, A PFC gas decomposition method comprising: a filter for filtering particulate matter; a plasma reactor for decomposing PFC gas; and an exhaust gas treatment facility for treating exhaust gas from the reactor.
(1) Exhaust gas containing PFC gas used inside the wafer etching chamber is exhausted by a turbo pump using argon gas as a purge gas, and further dried by a dry pump using argon gas as a purge gas connected to the exhaust side. Exhausting, filtering the particulate matter in the exhaust gas connected downstream thereof and supplying it to the plasma reactor,
(2) further supplying a reaction gas and decomposing the PFC gas in the plasma reaction chamber;
(3) a first step of reacting and removing harmful gas components discharged from the plasma reactor, a second step connected downstream thereof for mainly removing particles, and discharging from the second step Storing the gas to be processed. 12. The PFC gas decomposition method according to claim 11, wherein the PFC gas decomposition method includes the following steps of decomposing PFC gas contained in Ar gas introduced from the filter.
(1) a step of supplying a gas to be processed including a PFC gas to a plasma reactor which is composed of an inner cylinder and an outer cylinder of an insulating refractory, and is cooled by a refrigerant between a warabi inner cylinder and an outer cylinder;
(2) an ignition means for starting discharge of the processing gas;
(3) magnetic field generating means for applying a magnetic field to the discharge gas started by the ignition means;
(4) a step of shifting the discharge gas to a plasma state and maintaining the plasma;

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