JP2010058009A - Method of decomposing nitrogen trifluoride and device using this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of decomposing a nitrogen trifluoride which can easily treat a product in order to make an exhaust gas harmless, as well as a device for decomposing the nitrogen trifluoride. <P>SOLUTION: The decomposition device 20 decomposes NF<SB>3</SB>through a connection with an exhaust gas system e.g. a CVD device for discharging an exhaust gas containing NF<SB>3</SB>. In addition, the device includes: a reaction chamber 22; a plasma generation chamber 25 which receives a reaction gas including a gas molecule containing a hydrogen atom, and connects with the side part of the reaction chamber 22 downstream; and a plasma source 27 which turns the gas molecule to a plasma state in the plasma generation chamber 25. In the plasma generation chamber 25, the gas molecule is turned into a plasma state, whereby the hydrogen atom contained in the gas molecule is dissociated into a hydrogen active species H<SP>*</SP>. Further, in the reaction chamber 22, NF<SB>3</SB>supplied from the CVD device reacts with the hydrogen active species H<SP>*</SP>flowing into the reaction chamber 22 from the plasma generation chamber 25, as shown by the chemical equation: (NF<SB>3</SB>+6H<SP>*</SP>→NH<SB>3</SB>+3HF), and then is decomposed into NH<SB>3</SB>and HF. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a treatment method and a treatment apparatus for decomposing nitrogen trifluoride into a substance having low toxicity and a small warming potential.

Nitrogen trifluoride (NF ₃ ) is a kind of PFC (PerFluoro Compound) gas, which is a substitute for chlorofluorocarbons. It is a process gas for dry etching and chemical vapor deposition (CVD) in the manufacturing process of semiconductors. ) Method as a cleaning gas for a film forming apparatus. And the gas exhausted from these apparatuses contains unreacted nitrogen trifluoride.

Like other PFC gases such as carbon tetrafluoride (CF ₄ ), nitrogen trifluoride is a greenhouse gas (global warming potential: 10800) and is toxic, so in exhaust gas containing nitrogen trifluoride It is necessary to separate, recover and reuse nitrogen trifluoride, or to make it harmless by decomposing it. As a method for decomposing PFC gas such as nitrogen trifluoride, a catalytic decomposition method (Patent Documents 1 to 3), a combustion method (Patent Documents 4 and 5), and a plasma decomposition method (Patent Documents 6 to 8) are disclosed. ing.

In the catalyst system, a reducing metal catalyst such as activated carbon, aluminum oxide (Al ₂ O ₃ ), nickel (Ni) or iron (Fe) is used as the catalyst. For example, the catalyst system described in Patent Document 3 is used. In, nitrogen trifluoride is hydrolyzed by the following reaction formula.
2NF ₃ + 3H ₂ O → NO + NO ₂ + 6HF

On the other hand, according to the combustion method and the plasma decomposition method, PFC gas, which is very stable at room temperature, can be activated with high thermal energy or electrical energy and decomposed into a substance having a small warming coefficient. For example, when the combustion treatment with propane (C ₃ H ₈ ) gas described in Patent Document 5 is applied to nitrogen trifluoride, nitrogen trifluoride is decomposed by the following reaction formula.
NF ₃ + C ₃ H ₈ + O ₂ → NO ₂ + HF + CO ₂

In the plasma decomposition methods described in Patent Documents 6 and 7, the PFC gas is decomposed by supplying a carrier gas or the like to the plasma torch to form a plasma jet and supplying it to the PFC gas. Moreover, in the plasma decomposition method described in Patent Document 8, the PFC gas is activated and decomposed by generating plasma in the PFC gas atmosphere. Such decomposition of nitrogen trifluoride by plasma is represented by the following reaction formula.
2NF ₃ → N ₂ + 3F ₂
Japanese Examined Patent Publication No. 6-69528 JP-A-7-171342 Japanese Patent No. 2001-149749 JP 2002-317916 A Japanese Patent Laid-Open No. 2002-364821 JP 2000-334294 A JP 2006-224066 A JP 2002-343785 A

However, among the conventional methods, in the catalytic system, hydrogen fluoride (HF) and nitrogen oxides (NOx) are produced in large quantities as a result of hydrolysis of the reaction formula. In particular, since hydrogen fluoride coexists with water (H ₂ O) in hydrolysis, it becomes highly corrosive hydrofluoric acid, and anticorrosion treatment is required for exhaust pipes and valves. Moreover, since nitrogen oxides are air pollutants, they need to be removed separately. In addition, the catalytic system is processed at a high temperature exceeding several hundred to 1000 ° C, but nitrogen trifluoride has the property of causing an explosive self-decomposition reaction or a reduction reaction at a high temperature or high pressure (near atmospheric pressure). It is difficult to manage in processing. Furthermore, when activated carbon is used as a catalyst, it is necessary to decompose the fluorinated carbon in order to produce fluorinated carbon such as CF ₄ which is a less stable but more stable greenhouse gas.

Further, when the combustion method is applied to nitrogen trifluoride, a large amount of nitrogen oxide is generated by oxygen (O ₂ ) as in the above reaction formula. Furthermore, depending on the conditions of temperature and processing amount, fluorocarbon may be generated, and further processing is required. Furthermore, the reaction may explosively proceed at a high temperature due to combustion, and it is difficult to manage the processing. Similarly, in the plasma decomposition method, nitrogen trifluoride is heated to a high temperature of 1000 ° C. or higher by bringing it into contact with a plasma jet formed using a high temperature plasma torch having a temperature near the center of about 10,000 ° C. Further, when the nitrogen trifluoride into a plasma, the fluorine radicals (F ^*) and fluoride ions (F ^-, F ⁺⁾ for corrosive active species such as to produce, corrosion resistance to the reaction chamber and the exhaust pipe or the like Required.

  The present invention has been made in view of the above problems, and decomposes nitrogen trifluoride into a substance having low toxicity and a low global warming potential, and does not produce a highly corrosive substance. It is an object of the present invention to provide a nitrogen trifluoride decomposition treatment method and decomposition treatment apparatus that are easy to handle.

  The inventors of the present invention have come up with the idea that nitrogen trifluoride itself is decomposed without being converted into plasma by activating another substance under plasma and bringing it into contact with nitrogen trifluoride under reduced pressure. And it discovered that it can take out as ammonia and hydrogen fluoride which are comparatively easy to handle by making the substance to activate into a hydrogen atom.

That is, nitrogen trifluoride decomposition treatment method according to the present invention, there in nitrogen trifluoride decomposition treatment to decompose the NF ₃ into NH ₃ and HF by NF ₃ reacts with hydrogen active species in the reaction chamber Then, the hydrogen active species are generated by converting gas molecules containing hydrogen atoms into plasma.

  In this way, hydrogen reactive species can be obtained by plasmaizing gas molecules containing hydrogen atoms, and nitrogen trifluoride that is extremely stable at room temperature can be decomposed. Since N and F constituting nitrogen are each bonded to a hydrogen atom (hydrogen active species), the produced substances are ammonia and hydrogen fluoride which are water-soluble and easy to process.

In addition, the nitrogen trifluoride decomposition treatment method according to the present invention supplies NF ₃ and the hydrogen active species generated in the plasma process to the reaction chamber sequentially or simultaneously from either one, and in the reaction chamber, the NF ₃ is a method of decomposing nitrogen trifluoride by decomposing the NF ₃ into NH ₃ and HF by reacting with the hydrogen active species, wherein the plasma forming step generates gas molecules containing hydrogen atoms into plasma. A step of supplying to a chamber; and a step of converting the gas molecules into plasma in the plasma generation chamber to dissociate at least a part of hydrogen atoms contained in the gas molecules to form the hydrogen active species. Features.

  In this way, the region where plasma is generated is outside the reaction chamber where nitrogen trifluoride is present, and nitrogen trifluoride reacts with the hydrogen active species in the reaction chamber, so that nitrogen trifluoride itself is plasma. Management is easy because it is not converted to Further, since hydrogen atoms are converted into plasma and then supplied to the reaction chamber, efficiency is high.

Furthermore, in the nitrogen trifluoride decomposition treatment method according to the present invention, the step of supplying the gas molecules containing hydrogen atoms to the plasma generation chamber includes the total number of hydrogen atoms contained in the supplied gas molecules. It is preferable to supply gas molecules so that the number of NF ₃ molecules supplied to the reaction chamber is 6 times or more. By supplying such an amount of gas molecules, almost all of the nitrogen trifluoride in the reaction chamber can be decomposed into ammonia and hydrogen fluoride without being discharged unreacted.

  Furthermore, in the nitrogen trifluoride decomposition treatment method according to the present invention, it is preferable that the gas molecule containing the hydrogen atom is turned into plasma by reduced pressure plasma. Since the low-pressure plasma is a low-temperature treatment, the hydrogen active species in contact with the nitrogen trifluoride does not become high temperature and management is easy.

Furthermore, in the nitrogen trifluoride decomposition treatment method according to the present invention, it is preferable that the environment in which NF ₃ reacts with the hydrogen active species is reduced to 0.1 to 10 Torr. By setting it as such a pressure reduction state, nitrogen trifluoride does not react excessively, but management becomes easy in a decomposition process.

Further, in the nitrogen trifluoride decomposition treatment method according to the present invention, gas molecules containing hydrogen _{atoms, H 2, CH 4, C} 2 H 6, C 3 H 8, C 2 H 4, C 2 H 2 , NH ₃ , or H ₂ O is preferable. These gas molecules are easy to handle as industrial gases.

The nitrogen trifluoride decomposition treatment apparatus according to the present invention is a decomposition treatment apparatus for decomposing NF ₃ into NH ₃ and HF, and a reaction chamber to which a gas containing the NF ₃ is supplied, and the reaction chamber A vacuum evacuation means for maintaining the pressure by reducing pressure and exhausting the gas containing NH ₃ and HF from the reaction chamber, a plasma generation chamber connected to the reaction chamber and supplying hydrogen active species, and the plasma A reactive gas supply means for supplying a reactive gas containing gas molecules having hydrogen atoms to the generation chamber; and the gas molecules are converted into plasma in the plasma generation chamber to dissociate at least a part of the hydrogen atoms contained in the gas molecules. And a plasma generating means for using the hydrogen active species.

  In this way, plasma is generated in a gas atmosphere containing gas molecules having hydrogen atoms in a plasma generation chamber in which nitrogen trifluoride does not exist, thereby facilitating management, and active hydrogen species generated in the plasma generation chamber react. Since nitrogen trifluoride is efficiently decomposed because it is supplied to the chamber, the substance to be produced becomes water-soluble ammonia and hydrogen fluoride which are easily treated.

Further, in the nitrogen trifluoride decomposition treatment apparatus according to the present invention, the reaction chamber is supplied with a gas containing NF ₃ from the upstream, and a vacuum exhaust means is connected downstream to constitute a pipe, and the plasma generation chamber is It is preferable that a reaction gas supply means is connected upstream and a side portion of the reaction chamber is connected downstream to constitute a branch pipe for the pipe. Alternatively, in the nitrogen trifluoride decomposition treatment apparatus according to the present invention, the reaction chamber and the plasma generation chamber constitute a double tube, and the reaction chamber is supplied with a gas containing NF ₃ from the upstream and is vacuumed downstream. One or more through-holes formed in the peripheral surface of the inner pipe, the exhaust means being connected to constitute the inner pipe of the double pipe, the plasma generation chamber constituting the outer pipe of the double pipe And is preferably connected to the reaction chamber.

  By configuring as described above, it is possible to easily connect to an exhaust system of an apparatus for exhausting exhaust gas containing nitrogen trifluoride, and to obtain a downsized decomposition treatment apparatus.

  Furthermore, in the nitrogen trifluoride decomposition processing apparatus according to the present invention, it is preferable that the plasma generating means generates inductively coupled plasma. If it is inductively coupled plasma, it is easy to generate high-density plasma under reduced pressure.

According to the method for decomposing nitrogen trifluoride according to the present invention, another greenhouse gas such as CF ₄ , a harmful substance such as NOx, and a highly reactive and corrosive substance such as F ₂ are not generated. The treatment and management of the product can easily decompose and detoxify nitrogen trifluoride. Moreover, according to the nitrogen trifluoride decomposition processing apparatus which concerns on this invention, the said processing method is realizable irrespective of a special installation.

Hereinafter, the best mode for carrying out the nitrogen trifluoride decomposition method and apparatus according to the present invention will be described.
FIG. 1 is a block diagram showing a configuration of a nitrogen trifluoride decomposition treatment apparatus (hereinafter referred to as a decomposition treatment apparatus) according to the present invention. In FIG. 1, the decomposition processing apparatus is shown with a CVD apparatus connected thereto.
The CVD apparatus 10 is a known apparatus applied to a manufacturing process of semiconductors and the like. In this embodiment, nitrogen trifluoride (NF ₃ ) is introduced from the introduction pipe 11 in order to clean the inside of the chamber (vacuum processing chamber) 12. Supplied. As an example of a method of cleaning the chamber 12 of the CVD apparatus 10, the pressure of the chamber 12 is 1.5 Torr, NF ₃ is introduced at a flow rate of 500 sccm, and RF power of 1200 W with an RF frequency of 13.56 MHz is supplied into the chamber 12 in parallel. Plasma is generated by a flat plate method. Although it depends on the plasma generation method, the decomposition efficiency of NF _{3 in} this plasma generally does not become 100%, and usually 10% or more of NF ₃ may remain in the chamber 12 in an unreacted state. Are known. After the cleaning is completed, the atmospheric gas containing unreacted NF ₃ (hereinafter referred to as NF ₃ -containing gas) is discharged from the discharge pipe 13 by the dry pump P which is a vacuum exhaust means.

In the present embodiment, a decomposition treatment apparatus 20 is connected between the chamber 12 of the CVD apparatus 10 and the dry pump P, that is, the discharge pipe 13. In addition to the NF ₃ -containing gas discharged from the CVD apparatus 10, the decomposition treatment apparatus 20 is supplied with a reaction gas containing gas molecules containing hydrogen atoms (hereinafter referred to as gas molecules as appropriate). The NF ₃ -containing gas is discharged to the water scrubber 30 after being subjected to the following NF ₃ decomposition treatment by the decomposition treatment device 20. The decomposed gas introduced into the water scrubber 30 dissolves water-soluble components in a sufficient amount of water and is processed as a waste liquid by a waste liquid treatment device, and other components are discharged out of the system as exhaust gas. .

Next, the mode of the decomposition processing apparatus according to the present invention and the NF ₃ decomposition processing method according to the present invention by the decomposition processing apparatus will be described with reference to FIGS.
FIG. 2 is a cross-sectional view of an essential part for schematically explaining the decomposition process of NF ₃ in the nitrogen trifluoride decomposition apparatus according to the first embodiment of the present invention. The decomposition treatment apparatus 20 includes a reaction chamber 22 that is a pipe connecting the CVD apparatus 10 and the dry pump P through an introduction port 21 and a discharge port 23. Further, the decomposition processing apparatus 20 includes a plasma generation chamber 25, a plasma source (plasma generation means) 27 for generating plasma in the plasma generation chamber 25, and a mass flow controller (reaction gas supply means) for supplying a reaction gas to the plasma generation chamber 25. 24 (see FIG. 1) and a hydrogen active species supply port 26 for connecting the plasma generation chamber 25 to the side of the reaction chamber 22. Therefore, the side view shape of the decomposition processing apparatus 20 according to the first embodiment is an inverted T shape as shown in FIG. The vacuum evacuation means of the decomposition processing apparatus 20 is also used by a dry pump P (see FIG. 1) that is a vacuum evacuation means of the CVD apparatus 10.

  The mass flow controller 24 controls the amount (flow rate) of the reaction gas and supplies it to the plasma generation chamber 25, and a known mass flow controller can be applied. The plasma generation chamber 25 is a region for converting gas molecules contained in the supplied reaction gas into plasma, and the reaction chamber 22 is connected to the upstream side by the mass flow controller 24 and the downstream side by the hydrogen active species supply port 26. . The plasma source 27 is a device that generates plasma for converting gas molecules in the reaction gas into plasma, and the type of plasma is not limited, but low-pressure plasma is preferable. Specifically, for example, a method such as inductively coupled plasma (ICP), microwave, capacitively coupled plasma (CCP), or the like can be applied. In the case of the ICP type plasma source 27 of the present embodiment, as shown in FIG. 2, by applying electric power to the coil wound around the plasma generation chamber 25 with an RF power source, the plasma generation chamber in a reduced pressure state is provided. 25 can generate high-density plasma.

With the decomposition processing apparatus 20 according to the first embodiment having such a configuration, the reaction gas supplied from the upstream to the plasma generation chamber 25 is circulated, and gas molecules of the reaction gas are converted into plasma. The hydrogen active species generated by the reaction described later can be continuously supplied from the hydrogen active species supply port 26 to the downstream reaction chamber 22. Furthermore, since the decomposition processing apparatus 20 generates plasma while the reaction gas is circulated by the mass flow controller 24, it is possible to prevent the NF ₃ -containing gas from flowing into the plasma generation chamber 25 from the reaction chamber 22 side.

In the present embodiment, the gas molecule is, for example, a hydrogen molecule (H ₂ , hydrogen gas). In the plasma generation chamber 25, the gas molecules (hydrogen molecules) contained in the reaction gas are dissociated as plasma active species H ^* as shown in the following formula (1). The hydrogen active species H ^* generated by the gasification of gas molecules has a high kinetic energy and a high reactivity. Here, the hydrogen active species H ^* is a hydrogen radical, a hydrogen ion, or atomic hydrogen.
H ₂ → 2H ^*・ ・ ・ Formula (1)

On the other hand, NF ₃ contained in the NF ₃ containing gas supplied to the decomposition treating apparatus 20 is decomposed as follows. The NF _{3 that} has flowed into the reaction chamber 22 from the discharge pipe 13 of the CVD apparatus 10 through the inlet 21 comes into contact with the hydrogen active species H ^* that has flowed in from the hydrogen active species supply port 26, whereby the reaction of the following formula (2) Produce.
NF ₃ + 6H ^* → NH ₃ + 3HF Formula (2)

In this way, by being introduced into the same system (reaction chamber 22) as the highly reactive hydrogen active species H ^* , NF _{3 that} is very stable at room temperature is decomposed and can be easily treated with ammonia (NH ₃ ) And hydrogen fluoride (HF). Moreover, since the reaction of Formula (2) generates high energy, this reaction is further promoted and proceeds spontaneously, so that the reaction efficiency is good. On the other hand, NH ₃ and HF generated by the formula (2) are both water-soluble, but since the interior of the decomposition treatment apparatus 20 (reaction chamber 22) is an anhydrous environment, it is discharged from the discharge port 23 in a gaseous state. Therefore, in the decomposition treatment apparatus 20, since HF does not dissolve in water and becomes hydrofluoric acid, it is not necessary to apply strong anticorrosion treatment to the reaction chamber 22 and the like.

In addition, as described above, the reaction chamber 22 is arranged downstream of the plasma generation chamber 25 so that NF ₃ is supplied so that the NF ₃ -containing gas does not flow into the plasma generation chamber 25, so that NF ₃ itself Will be activated by plasma. Furthermore, since the reaction chamber 22 is depressurized by the dry pump P, NF ₃ does not cause an explosive self-decomposition reaction, so that management is easy. The pressure in the reaction chamber 22 is preferably 0.1 to 10 Torr (≈13.3 to 1333 Pa). When the pressure is within this range, the decomposition treatment can be easily managed while maintaining the efficiency of the decomposition reaction high. Further, before the NF ₃ -containing gas is supplied to the reaction chamber 22, components other than NF ₃ may be removed by a known distribution method, or a rare gas such as argon (Ar) is mixed to NF _3. May be diluted.

The gas molecules supplied in the reaction gas are not particularly limited as long as they contain a hydrogen atom. In addition to hydrogen (H ₂ ), for example, CH ₄ , C ₂ H ₆ , C ₃ Examples thereof include hydrocarbon gases such as H ₈ , C ₂ H ₄ and C ₂ H ₂ , ammonia (NH ₃ ), and water (H ₂ O). These may be used alone or in combination of two or more. Further, it may be supplied diluted with a rare gas such as Ar. When applying the hydrocarbon gas such as methane (CH _4), it is preferable to mix the gaseous molecules containing oxygen atoms such as O ₂ in the reaction gas. This is because C is bonded to O, which is easier to bond, so that carbon (C) does not flow into the reaction chamber 22 and combine with F to generate fluorinated carbon such as CF ₄ . In this case, CO ₂ or the like is generated by the plasma generation in the plasma generation chamber 25 as shown in the following expression (3), and is directly discharged from the discharge port 23. Further, when H ₂ O, O ₂ or the like is supplied, water (H ₂ O) is present (generated) in the reaction chamber 22 depending on the supply amount, and therefore the corrosion prevention corresponding to hydrofluoric acid in the reaction chamber 22 and the like. It is preferable to perform the treatment.
CH ₄ + O ₂ → CO ₂ + 4H ^* Formula (3)

As shown in Formula (2), one NF ₃ molecule reacts with six hydrogen active species H ^* and decomposes. Thus, as more than six times the number of hydrogen atoms relative to the number of molecules of NF ₃ present in the reaction chamber 22 is present in the plasma generation chamber 25, NF ₃ in NF ₃ containing gas supplied from the CVD apparatus 10 It is preferable to adjust the flow rate of the reaction gas supplied to the plasma generation chamber 25 by the mass flow controller 24 (see FIG. 1) in accordance with the amount of gas. Thereby, almost all NF ₃ is decomposed in the reaction chamber 22.

As described with reference to FIG. 1, the exhaust gas containing NH _3, HF produced in reaction chamber 22 (NH _3, HF-containing gas) is discharged from the discharge port 23 by the dry pump P, introduced into water scrubber 30 Is done. As described above, since NH ₃ and HF are both water-soluble, they are dissolved in a sufficient amount of water by the water scrubber 30 and appropriately processed as a waste liquid by a known waste liquid processing apparatus. Moreover, the gas of the component which is not melt | dissolved by the water scrubber 30 is exhausted out of the system, after processing as needed.

FIG. 3 is a cross-sectional view of an essential part for schematically explaining the decomposition process of NF ₃ in the nitrogen trifluoride decomposition apparatus according to the second embodiment of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
As shown in FIG. 3, in the decomposition processing apparatus 20A, a reaction chamber 22 and a plasma generation chamber 25A constitute a double tube. The reaction chamber 22 is a double-pipe inner tube, and is a pipe that connects the CVD apparatus 10 and the dry pump P through the introduction port 21 and the discharge port 23 as in the first embodiment. The plasma generation chamber 25 </ b> A is a double tube outer tube and is connected to a mass flow controller 24 (see FIG. 1) for supplying a reaction gas as in the first embodiment. A plurality of hydrogen active species supply holes 26A penetrating through a partition wall (a peripheral surface forming the reaction chamber 22) between the reaction chamber 22 and the plasma generation chamber 25A is formed. In addition, the plasma source 27 is installed on the outer periphery of the double tube, and generates plasma in the plasma generation chamber 25A by a coil wound around the plasma generation chamber 25A, as in the first embodiment.

In the plasma generation chamber 25A, the gas molecules contained in the reaction gas are converted into plasma from the gas molecules on the outer peripheral side of the plasma generation chamber 25A by a coil wound around the plasma generation chamber 25A. Further, since the reaction gas is supplied to the plasma generation chamber 25A by the mass flow controller 24 (see FIG. 1), the hydrogen active species H ^* dissociated from the gas molecules by the plasma conversion as in the first embodiment is converted into the plasma generation chamber 25A. Flows into the reaction chamber 22 through the hydrogen active species supply hole 26 </ b> A formed in the inner peripheral surface (partition wall between the reaction chamber 22). Therefore, as in the first embodiment, it is possible to prevent the NF ₃ -containing gas from flowing into the plasma generation chamber 25A from the reaction chamber 22 side. On the other hand, NF ₃ contained in the NF ₃ containing gas, as in the first embodiment, the reaction of supplied into the reaction chamber 22 is hydrogen active species flowing from the hydrogen active species supply holes 26A and H ^* and the equation (2) To decompose into NH ₃ and HF. Since other details are the same as those of the first embodiment, description thereof will be omitted.

In the present embodiment, it is necessary that only the gas molecules of the reaction gas in the outer tube (plasma generation chamber 25A) are turned into plasma by the plasma source 27 and NF ₃ in the inner tube (reaction chamber 22) is not turned into plasma. Here, in a state in which gas molecule plasma (hydrogen plasma) is generated in the outer tube close to the plasma source 27 (coil), the induced current from the plasma source 27 flows only to the hydrogen plasma having a low impedance. NF ₃ is not turned into plasma. Therefore, in the present embodiment, control is performed so that hydrogen plasma is generated in the plasma generation chamber 25A before the supply of the NF ₃ -containing gas to the reaction chamber 22 is started.

  As mentioned above, although the form for implementing this invention has been described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below. It should be noted that the present invention is not limited by this embodiment, and can be implemented with appropriate modifications within the scope of the claims, all of which are included in the technical scope of the present invention. The

As a first example, an ICP source LG3000 (manufactured by Landmark Technology Co., Ltd.) having a structure in which the plasma generation chamber 25 is included in the plasma source 27 is connected to the side of the piping as the reaction chamber 22, and FIG. It was set as the decomposition processing apparatus 20 of the structure shown. A dry pump P is connected downstream of the pipe (reaction chamber 22) (exhaust side) as shown in FIG. 1, and the treated gas is sucked. Further, FT-IR (Fourier transform infrared spectroscopy) is connected to the exhaust side. A photometer was connected, and the component analysis of the treated gas was performed. Using this decomposition treatment apparatus 20, NF ₃ was supplied instead of the NF ₃ containing gas for decomposition treatment, and H ₂ was used as the reaction gas.

The reaction chamber 22 was supplied with the flow rate of NF ₃ controlled to 300 sccm, while the plasma source 27 was supplied to the plasma generation chamber 25 by changing the flow rate of H ₂ while applying RF power of 2500 W at a frequency of 2 MHz. . At this time, the pressure upstream of the reaction chamber 22 (inlet 21) was set to about 1.2 Torr. Then, to measure the NF ₃ concentration in the treated gas at FT-IR. NF ₃ was calculated NF ₃ decomposition rate from the concentration, as a graph to H ₂ flow rate, shown in Figure 4. The NF ₃ decomposition rate was calculated based on an NF ₃ concentration of 4512 ppm measured in a state where only NF ₃ was supplied at a flow rate of 300 sccm, H ₂ was not supplied, and RF power was not applied to the plasma source.

As shown in FIG. 4, H ₂ flow rate, from 100sccm up to three times the 900sccm of NF ₃ flow, NF ₃ decomposition rate with the flow rate of H ₂ increased rises. Furthermore, when the H ₂ flow rate was 1200 sccm, the NF ₃ concentration of the treated gas was 15 ppm or less, which was almost below the detection limit of FT-IR. Even when the H ₂ flow rate was 1500, 2000 sccm, a good NF ₃ decomposition rate close to 100% was obtained although it decreased slightly. Thus, H ₂ flow rate NF ₃ flow rate of 3 times or more, i.e., that the number of molecules H ₂ three times or more the number of molecules of NF _3, and 6 times or more in terms of the number of H atoms, NF ₃ Was able to disassemble almost everything.

As a second embodiment, an ICP source LG3000 (manufactured by Landmark Technology Co., Ltd.) having a structure in which the plasma generation chamber 25 (25A) is included in the plasma source 27 is inserted into the inner tube as the reaction chamber 22 to form a double tube. The decomposition processing apparatus 20A having the structure shown in FIG. Further, a through hole having a hole diameter of 1 mm was formed as the hydrogen active species supply hole 26A in the inner tube, and the opening area ratio between the reaction chamber 22 and the plasma generation chamber 25A was 40%. As in the first embodiment, a dry pump P is connected downstream of the inner pipe (reaction chamber 22) (exhaust side) as shown in FIG. FT-IR (Fourier transform infrared spectrophotometer) was connected to the gas, and the component analysis of the gas after a process was performed. Using this decomposition processing apparatus 20A, as in the first example, NF ₃ was supplied to the reaction chamber 22 at a flow rate of 300 sccm, and H ₂ was supplied as a reaction gas to the plasma generation chamber 25A at a flow rate of 1200 sccm. As a result, the NF ₃ concentration of the treated gas was 15 ppm or less, which was almost below the detection limit of FT-IR, and a good NF ₃ decomposition rate was obtained as in the first example. At this time, the pressure measured upstream (inlet 21) of the reaction chamber 22 was 1.33 Torr.

As a comparative example, in the decomposition processing apparatus 20 having the configuration shown in FIG. 2 used in the first embodiment, instead of the plasma source 27, an alumina tube provided with a tungsten catalyst heated to 1800 ° C. by a heater was installed. H ₂ in the plasma generation chamber 25 was heated to generate hydrogen active species by thermal decomposition and supplied to NF ₃ in the reaction chamber 22. As in the first example, the flow rate of NF ₃ was 300 sccm, the flow rate of H ₂ was 100 to 2000 sccm, and the pressure in the reaction chamber 22 was 1.2 Torr. As a result of analyzing the exhausted gas by FT-IR, the NF ₃ concentration was 4000 ppm or more regardless of the H ₂ flow rate, and NF ₃ was not decomposed. This indicates that the hydrogen active species generated by thermal decomposition has low energy and does not have high energy for causing the reaction of formula (2).

It is a block diagram which shows the structure of the nitrogen trifluoride decomposition processing apparatus which concerns on this invention. The decomposition process of the NF ₃ in nitrogen trifluoride decomposition treating apparatus according to a first embodiment of the present invention is a fragmentary cross-sectional view illustrating schematically. The decomposition process of the NF ₃ in nitrogen trifluoride decomposition treating apparatus according to a second embodiment of the present invention is a fragmentary cross-sectional view illustrating schematically. It is a graph showing the flow rate of H ₂ dependency of NF ₃ decomposition rate in Example.

Explanation of symbols

10 CVD apparatus 20, 20A decomposition processing apparatus (nitrogen trifluoride decomposition processing apparatus)
22 reaction chamber 24 mass flow controller (reaction gas supply means)
25, 25A Plasma generation chamber 27 Plasma source (plasma generation means)
P Dry pump (evacuation means)

Claims (10)

NF ₃ is a nitrogen trifluoride decomposition treatment to decompose the NF ₃ into NH ₃ and HF by reaction with hydrogen active species in the reaction chamber, by plasma gas molecules containing hydrogen atoms A method of decomposing and treating nitrogen trifluoride, wherein the hydrogen active species is generated. NF ₃ and hydrogen active species generated in the plasma process are supplied to the reaction chamber sequentially or simultaneously from either one, and the NF ₃ reacts with the hydrogen active species in the reaction chamber. ₃ is a nitrogen trifluoride decomposition treatment method for decomposing ₃ into NH ₃ and HF,
In the plasma forming step, a gas molecule containing hydrogen atoms is supplied to the plasma generation chamber, and the gas molecules are converted into plasma in the plasma generation chamber, so that at least a part of the hydrogen atoms contained in the gas molecules is converted. Dissociating it into the hydrogen active species, and performing a nitrogen trifluoride decomposition treatment method. The step of supplying the gas molecules containing hydrogen atoms to the plasma generation chamber is the sum of the number of hydrogen atoms contained in the supplied gas molecules, and the number of NF ₃ molecules supplied to the reaction chamber. The nitrogen trifluoride decomposition treatment method according to claim 2, wherein the gas molecules are supplied so as to be 6 times or more.   The nitrogen trifluoride decomposition treatment method according to any one of claims 1 to 3, wherein the gas molecules containing hydrogen atoms are converted into plasma by reduced-pressure plasma.   The nitrogen trifluoride decomposition treatment method according to claim 1, wherein the reaction chamber is depressurized to 0.1 to 10 Torr. Wherein the gas molecules containing hydrogen atoms is either _{H 2, CH 4, C 2} H 6, C 3 H 8, C 2 H 4, C 2 H 2, NH 3, H 2 O The nitrogen trifluoride decomposition treatment method according to any one of claims 1 to 5. A nitrogen trifluoride decomposition treatment apparatus for decomposing NF ₃ into NH ₃ and HF,
A reaction chamber to which a gas containing NF ₃ is supplied; a vacuum exhaust means for maintaining the pressure by reducing the pressure of the reaction chamber and discharging the gas containing NH ₃ and HF from the reaction chamber; A plasma generation chamber connected to the plasma generation chamber for supplying active hydrogen species, a reaction gas supply means for supplying a reaction gas containing gas molecules having hydrogen atoms to the plasma generation chamber, and the gas molecules are converted into plasma in the plasma generation chamber. And a plasma generating means for dissociating at least a part of the hydrogen atoms contained in the gas molecules into the hydrogen active species. The reaction chamber is supplied with a gas containing the NF ₃ from the upstream, and the vacuum evacuation means is connected downstream to constitute a pipe,
8. The trifluoride according to claim 7, wherein the plasma generation chamber is connected to the reaction gas supply means upstream and a side portion of the reaction chamber is connected downstream to constitute a branch pipe for the pipe. Nitrogen decomposition treatment equipment. The reaction chamber and the plasma generation chamber constitute a double tube,
The reaction chamber is supplied with the gas containing NF ₃ from the upstream, and the vacuum exhaust means is connected downstream to constitute an inner pipe of the double pipe,
The plasma generation chamber constitutes an outer tube of the double tube, and is connected to the reaction chamber by one or more through holes formed in a peripheral surface of the inner tube. The nitrogen trifluoride decomposition treatment apparatus according to 1.   The nitrogen trifluoride decomposition treatment apparatus according to any one of claims 7 to 9, wherein the plasma generation unit generates inductively coupled plasma in the plasma generation chamber.

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