JP4016532B2 - Reagent for decomposition of nitrogen fluoride and decomposition method - Google Patents

Description

【００４８】
（反応例）
図１に示したものと同じ原理の装置を使用して本発明法を実施した。すなわち、通電により発熱する発熱体（カンタル合金）を装着した管状炉（電気容量1.4kw、長さ400mm）の軸中心に沿って、内径１６ｍｍ、長さ５００ｍｍのインコネル６００からなる反応管を貫通させ、この反応管内の炉中心部にフッ化窒素分解用の反応剤３５ｃｃを充填した。
分解に供するフッ化窒素として三フッ化窒素（ＮＦ₃）を使用し、図１に示したように、この三フッ化窒素に酸素ガスを添加するか、またはしないで、窒素ガスをキャリヤとして前記の反応管に導入した。
その際、
被処理ガスの流量 ：０．２０l/min
被処理ガス中のフッ化窒素濃度：３vol％
被処理ガスの空塔速度 ：３４３hr^-1
被処理ガス線速度 ：１．０m/min
被処理ガス中の酸素濃度 ：０％または５vol％
の一定とした。ただし一部の試験では被処理ガス中にＨＦ、ＳｉＦ₄を混在させた。
【００４９】
また、いずれの例でも被処理ガスの導入に際しては発熱体への通電を開始し、反応剤の中心部の温度が所定の温度になったことを確かめた上で行った。反応の間は、反応剤の中心部（反応剤の嵩さのうち最も高温となる部位）に挿入した熱電対で計測される温度がその温度に維持されるように、管状炉の通電量を制御した。表２中の反応温度は、反応の間維持したこの温度のことを表している。
【００５０】
反応管から排出される排ガスの一部は、図１に示したようにガス分析器と苛性ソーダ溶液を入れたフッ素吸収瓶に導きサンプリングした。排ガスの分析は、フッ化窒素、その他のフッ素化合物、Ｏ₂、Ｎ₂、ＮＯ、Ｎ₂Ｏ、ＣＯ₂、ＣＯ、Ｆ^-について行った。
【００５１】
表１に示した比較反応剤１〜３と反応剤１〜１０を使用し、反応剤温度を種々変化させて前記の条件で三フッ化窒素の分解を行った。その結果を表２に示した。表２における副生成物濃度とＮＦ₃の分解率は反応開始６０分後の排ガス中の副生成物濃度とＮＦ₃の分解率であり、反応開始から６０分経過した時点の排ガスサンプリングから、排ガス中に残存している副生成物（Ｆ^-、ＮＯ、Ｎ₂Ｏ、ＣＦ₄、ＣＯ）とフッ化窒素を測定し、その副生成物の濃度と被処理ガス中のフッ化窒素に対する排ガス中のフッ化窒素の百分率をもって表したものである。
【００５２】
【表２】

【００５３】
表２に示したように、Ａｌ₂Ｏ₃（（II）群の化合物）だけを用いた比較例１の反応剤は、ＮＦ₃を１００％近く分解するには３００℃以上の反応温度が必要であり、しかもＮＯ_Xの生成を抑制することができないことがわかる。
【００５４】
活性炭とＡｌ₂Ｏ₃（（II）群の化合物）とを組み合わせた比較例２の反応剤は、ＮＦ₃を１００％近く分解するには２５０℃以上の反応温度でよいが、ＮＯ_X、Ｎ₂Ｏ、ＣＯの生成を抑制することができないことがわかる。しかしながら、反応温度を３００〜４００℃にすると、ＮＯ_X、Ｎ₂Ｏの生成が抑制されるが、４００℃付近でＣＦ₄が生成してくることがわかる。
【００５５】
活性炭、Ａｌ₂Ｏ₃（（II）群の化合物）及びＫ₂ＣＯ₃（（III）群の化合物）を組み合わせた比較例３の反応剤は、ＮＦ₃を１００％近く分解するのに２００℃以上の反応温度でよいが，比較例２の場合と同様、すべての温度でＣＯの生成を抑制することができず、しかも４５０℃付近でＣＦ₄が生成することがわかる。またＮＯ_XとＮ₂Ｏについては、反応温度が２５０℃以上であれば十分抑制できることがわかる。
【００５６】
このように（I）〜（III）群の化合物を組み合わせた反応剤は、２００℃以上の反応温度でＮＦ₃を１００％近く分解し、しかも反応温度を２５０℃〜４５０℃の範囲にすればＮＯ_X、Ｎ₂Ｏ、ＣＦ₄を同時に抑制することができるものの、ＣＯについてはその生成を同時に抑制することができない。
【００５７】
一方、本発明の１〜１０の分解剤は、（I）〜（III）群の化合物に（IV）群の化合物を加えたものであり、表２に示したように、ＮＦ₃の分解温度及びＮＯ_X、Ｎ₂Ｏ、ＣＦ₄を抑制できる温度範囲は比較例３を用いた場合と同様であったが、ＣＯは反応例１〜１０のいずれの温度でも生成しないことがわかった。さらに反応例２と３に示すように、被処理ガス中の酸素、ＳｉＦ₄、ＨＦの存在の有無に関係なくＮＦ₃は完全に分解しＮＯ_X、Ｎ₂Ｏ、ＣＦ₄、ＣＯも生成していない。また、Ｆ^-が検出されていないことから、ＳｉＦ₄、ＨＦも同時に除害されていることがわかった。
【００５８】
【発明の効果】
以上説明したように、本発明によるとフッ化窒素を比較的低温でかつ簡単な処方で効率的に分解することができ、分解したフッ素も無害物として固定できる。すなわち、本発明のフッ化窒素の分解法は簡易な分解装置で実施でき、処理操作が簡易で分解効率も高く、窒素酸化物・フッ化炭素・一酸化炭素の副生成物の生成を抑制する。しかも、分解生成物はＡｌＦ₃等の安定したフッ化物となるため、後処理が容易である。また反応剤の廉価性の点でも、これまでのものにはない効果を奏し、特に半導体製造工程で発生する使用済みフッ化窒素の分解に多大の貢献ができる。
【図面の簡単な説明】
【図１】 本発明法を実施する装置の一例を示した機器配置系統図である。
【図２】本発明法を実施する被処理ガス導入部の他の例を示した機器配置系統図である。
【図３】本発明法に従い反応剤を反応容器内から加熱する例を示す反応容器部の略断面図である。
【図４】本発明法に従い反応剤を反応容器内から加熱する他の例を示す反応容器部の略断面図である。
【図５】本発明法に従い反応剤を反応容器内外から加熱する例を示す反応容器部の略断面図である。
【図６】本発明の実施に際し、反応容器に入る前の被処理ガスと反応容器を出た排ガスを熱交換する例を示す図である。
【符号の説明】
1 反応容器
2 反応剤
3 通気性床
4 加熱炉
5 電気ヒーター
6 加熱炉の炉内雰囲気
7 被処理ガス導入口
8 フッ化窒素源
11 酸素ガス源
12，34 窒素ガス源
18，32 被処理ガス導入管路
20 ガス排出口
21 排ガス管路
35，38 通電により発熱する発熱体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reagent for decomposing nitrogen fluoride and a method for decomposing the same.
[0002]
[Prior art]
Nitrogen fluoride includes fluorinated azine (N_ThreeF), dinitrogen difluoride (N₂F₂), Nitrogen trifluoride (NF)_Three) And dinitrogen tetrafluoride (N₂F_Four), And a typical example is nitrogen trifluoride (NF)_Three). Nitrogen trifluoride is a physically and chemically stable gas at room temperature, but decomposes under conditions such as hot ultraviolet light and plasma discharge to release active species fluorine. For example, it is used for etching or cleaning in semiconductor processes. It is used as a gas.
[0003]
When nitrogen trifluoride gas is used for the above applications, dinitrogen tetrafluoride (N₂F_Four), Dinitrogen difluoride (N₂F₂) And undecomposed nitrogen trifluoride are released while contained in the exhaust gas. However, since these nitrogen fluorides are highly toxic and have a large global warming potential (GWP value), the nitrogen fluoride contained in the exhaust gas must be decomposed into harmless substances before being released into the atmosphere. .
[0004]
Conventionally, several techniques for decomposing nitrogen fluoride contained in such exhaust gas have been proposed. The method is roughly divided into (1) reactive agent (catalyst) decomposition method and (2) combustion decomposition method. The former method can in principle simplify the structure of the apparatus compared to the latter, and it is simple. Many have been proposed as easy technologies. In general, the content is a fluoride gas that easily decomposes the fluorine component of nitrogen fluoride, such as SiF._Four, BF_Three, WF₆Or a stable solid fluoride such as AlF_Three, FeF_ThreeOr fluorocarbon gas, such as CF_FourIt is to convert into a compound such as. However, the method of converting into gaseous fluoride that can be easily decomposed also requires secondary treatment of the fluoride gas, and the treatment process as a whole is not necessarily a simple method. Moreover, the method of converting into a stable solid fluoride is NO when using a metal oxide._XAs a by-product, NO_XTherefore, it is not always a simple and easy method. In addition, the method of converting to a stable gaseous fluorocarbon is not a preferable method because the fluorocarbon itself is a substance having a high global warming potential.
[0005]
[Problems to be solved by the invention]
The present invention is a method for decomposing nitrogen fluoride, particularly nitrogen trifluoride, which is used as a gas for etching or cleaning in a semiconductor process or the like, and does not produce a substance that adversely affects the environment. It is another object of the present invention to provide a reagent for decomposing nitrogen fluoride and a decomposing method that can be decomposed by simple and simple operations.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned conventional problems, the present inventors have found that the above-mentioned problem is a reaction agent using a compound of the following groups (I) to (IV), that is, (I) Elemental carbon as a group compound, aluminum compound, iron compound, manganese compound and / or alkaline earth metal compound as a compound of group (II), an alkali metal compound as a compound of group (III), as a compound of group (IV) It has been found that the problem can be solved by contacting nitrogen fluoride gas with a solid reactant containing a nickel compound, a tin compound and / or a copper compound. Furthermore, the present inventors have found that when the contact temperature with the reactant is in the range of 250 to 450 ° C., by-products of fluorocarbon, nitrogen oxides, and carbon monoxide can be suppressed, and the present invention is completed. It came. The present invention relates to a reagent for decomposing nitrogen fluoride and a method for decomposing the same as shown in the following (1) to (11).
[0007]
(1) Compounds of the following groups (I) to (IV)
(I) group: simple substance carbon
Group (II): Aluminum compound, iron compound, manganese compound and / or alkaline earth metal compound
(III) group: alkali metal compounds
(IV) group: nickel compound, tin compound and / or copper compound
A reactive agent for decomposing nitrogen fluoride, comprising:
(2) Nitrogen fluoride decomposition reaction according to (1) above, wherein the elemental carbon of group (I) contained in the reactant is activated carbon, carbon black, coke, char charcoal, coal, pitch, or charcoal. Agent.
(3) The aluminum compound of group (II) contained in the reactant is aluminum oxide or aluminum hydroxide, the iron compound is iron oxide or iron hydroxide, and the manganese compound is manganese oxide or manganese hydroxide. The reactive agent for decomposing nitrogen fluoride according to (1) or (2) above, wherein the alkaline earth metal compound is an oxide, hydroxide, or carbonate of an alkaline earth metal.
[0008]
(4) The above (1) to (III), wherein the alkali metal compound of group (III) contained in the reactant is an alkali metal oxide, hydroxide, carbonate, phosphate, aluminate, nitrate, or sulfate. (3) The reactive agent for decomposing nitrogen fluoride according to any one of (3).
(5) The nickel compound of group (IV) contained in the reactant is nickel oxide or nickel hydroxide, the tin compound is stannic oxide or metastannic acid, and the copper compound is copper oxide or water. The reactive agent for decomposing nitrogen fluoride according to any one of the above (1) to (4), which is copper oxide.
(6) The composition ratio of the compounds of groups (I) to (IV) contained in the reactant is that of groups (II) to (IV) when the atomic ratio of elemental carbon of group (I) is 1. In the atomic ratio of each metal contained in the compound, the compound of the (II) group is 0.05 to 1.0, the compound of the (III) group is 0.01 to 0.2, and the compound of the (IV) group is 0. The reactive agent for decomposing nitrogen fluoride according to any one of the above (1) to (5), which is 0.01 to 0.2.
[0009]
(7) The above (I) wherein the total weight of the group (I) elemental carbon contained in the reactant and the metal atoms contained in the compounds of the groups (II) to (IV) is 50% by weight or more of the reactant weight ( The reactive agent for decomposing nitrogen fluoride according to any one of 1) to (6).
(8) The reagent for decomposing nitrogen fluoride according to any one of (1) to (7), wherein the nitrogen fluoride is nitrogen trifluoride.
(9) A method for decomposing nitrogen fluoride, comprising bringing the gas containing nitrogen fluoride into contact with the decomposition reagent according to any one of (1) to (8) at 200 ° C. or higher.
(10) The decomposition reagent according to any one of (1) to (8) above is brought into contact with a gas containing nitrogen fluoride at a temperature of 450 ° C. or lower to suppress the by-product of fluorocarbon. The method for decomposing nitrogen fluoride according to (9) above.
(11) A gas containing nitrogen fluoride is brought into contact with the decomposition reagent according to any one of (1) to (8) above at a temperature of 250 ° C. or more, and nitrogen oxide, fluorocarbon, and carbon monoxide The method for decomposing nitrogen fluoride as described in (10) above, wherein the by-product is suppressed.
[0010]
That is, the present invention uses a reactive agent for decomposing nitrogen fluoride that decomposes nitrogen fluoride with high efficiency and simple operation, and efficiently fixes the decomposed fluorine to the reactive agent to render it harmless, and the reactive agent. This is a method for decomposing nitrogen fluoride that does not produce by-products that adversely affect the environment.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the reactive agent for decomposing nitrogen fluoride according to the present invention will be described.
The reactive agent for decomposing nitrogen fluoride of the present invention is characterized by containing the following compounds (I) to (IV).
(I) group: simple substance carbon
Group (II): Aluminum compound, iron compound, manganese compound and / or alkaline earth metal compound
(III) group: alkali metal compounds
(IV) group: nickel compound, tin compound and / or copper compound
[0012]
First, elemental carbon that is a compound of group (I) is solid carbon that exists in an elemental form, and contributes to the decomposition of nitrogen fluoride by coexisting with compounds of groups (II) to (IV). It is. For example, activated carbon, carbon black, coke, char charcoal, coal, pitch, or charcoal may be used, and carbon fiber, graphite, or inorganic carbonaceous matter may be contained as a main component. These simple carbons may be used alone or in combination of two or more at any ratio. The shape of the simple carbon is preferably powder or granular, preferably powdered activated carbon, carbon black or coke. The reason why activated carbon is preferable is that it has a strong adsorptive capacity or is cheaper and easier to obtain than other simple carbons.
[0013]
The content of each group of compounds in the reactant defines the relative proportion of the compounds of groups (II) to (IV) based on the content of elemental carbon. Therefore, the content of elemental carbon in the reactant is determined by the relationship with the compound content of the groups (II) to (IV). If the relative amount of elemental carbon is too small, nitrogen oxide by-products cannot be suppressed and a high decomposition rate cannot be obtained. Conversely, if the relative amount of elemental carbon is too large, By-products cannot be suppressed, and a high decomposition rate cannot be obtained.
[0014]
Next, the compound of (II) group is demonstrated.
(II) Group aluminum compounds, iron compounds, manganese compounds and alkaline earth metal compounds have the role of fixing and detoxifying fluorine in nitrogen fluoride in the form of metal fluorides stable to the metal in the compound. Fulfill.
Examples of the aluminum compound include aluminum oxide (Al₂O_Three) Or aluminum hydroxide [Al (OH)_Three], For example, iron compounds include iron oxide (FeO, Fe₂O_Three, Fe_ThreeO_Four) Or iron hydroxide [Fe (OH)₂, FeO (OH)], manganese compounds include, for example, manganese oxide (MnO, Mn₂O_Three, MnO₂) Or manganese hydroxide [Mn (OH)₂, MnO (OH)] can be added to the reactants. Preferred compounds among these aluminum compounds, iron compounds and manganese compounds are oxides, and alumina (Al₂O_Three), Iron oxide (Fe₂O_Three), Manganese dioxide (MnO₂These compounds are easily available as commercial products, stable and easy to handle.
[0015]
As the alkaline earth metal compound, for example, magnesium, calcium, strontium or barium oxide, hydroxide, bicarbonate or carbonate can be used. Magnesium or calcium oxides, hydroxides or carbonates are preferably used, and the compounds included in group (II) may be used alone or in combination of two or more in any proportion.
[0016]
The addition amount of the compound of group (II) is in the range of 0.05 to 1.0, preferably in the range of 0.1 to 1.0, in terms of atomic ratio when elemental carbon is 1.0. Preferably it is in the range of 0.2 to 0.8. When the atomic ratio is less than 0.05, the relative amount of elemental carbon is increased, so that it is not possible to suppress the by-production of fluorocarbons, and a high decomposition rate cannot be obtained. On the other hand, if the atomic ratio is larger than 1.0, the amount of the compounds in groups (I), (III) and (IV) decreases, and it becomes impossible to suppress the by-production of nitrogen oxides. .
[0017]
Next, the compound of group (III) will be described.
The (III) group alkali metal compound coexists with the elemental carbon of the (I) group, the compound of the (II) group and the (IV) group, so that the decomposition temperature of nitrogen fluoride is performed in a low temperature region, Suppresses by-products of oxides and fluorocarbons and contributes to decomposition at a high decomposition rate.
[0018]
Examples of alkali metal compounds are lithium, sodium, potassium, rubidium, cesium oxides, hydroxides, carbonates, phosphates, aluminates, nitrates, sulfates, and these compounds can be used alone or in combination of two or more. You may use combining in arbitrary ratios. Sodium or potassium hydroxide or carbonate is preferably used, and it has been found that these compounds remarkably perform the above action. In addition, these compounds may be blended by pulverizing them in a powdery state as they are, and in a bulky state to 100 μm or less, preferably 10 μm or less. Moreover, it can also add as aqueous solution of these compounds.
[0019]
The content of the compound of group (III) is in the range of 0.01 to 0.2, preferably in the range of 0.01 to 0.1, in terms of atomic ratio when the elemental carbon is 1.0. Preferably, it is within the range of 0.02 to 0.08, and even if this value is contained so as to be more than 0.2, the effect is saturated, and (I) group simple carbon, (II) It is not preferable because the content of the compounds of the group and the group (IV) is relatively lowered.
[0020]
Next, the compounds of group (IV) will be described.
The nickel compound, tin compound and copper compound of group (IV) coexist with the elemental carbon of group (I), the compound of group (II) and group (III), so that carbon monoxide, fluorocarbon gas and This contributes to the suppression of nitrogen oxide by-products or decomposition at a high decomposition rate.
[0021]
The nickel compound is, for example, nickel oxide (NiO, Ni, which is an oxide of nickel).₂O_Three, Ni_ThreeO_Four) Or nickel hydroxide [Ni (OH) which is a hydroxide₂The tin compound is tin oxide (SnO), which is an oxide of tin.₂) Or metastannic acid (SnO)₂・ NH₂As O), the copper compound is copper oxide (Cu) which is an oxide of copper.₂Copper hydroxide [Cu (OH)] which is O, CuO) or hydroxide₂] Can be added to the reactant. These nickel, tin and copper compounds are preferably oxides. Nickel is nickel oxide (NiO), and tin is stannic oxide (SnO).₂In the case of copper, copper oxide (CuO) is preferable. These oxides are easy to obtain as commercial products, and the compound form is stable and easy to handle, which is preferable.
[0022]
The content of the compound of group (IV) is in the range of 0.01 to 0.2, preferably in the range of 0.02 to 0.1, in terms of atomic ratio when the elemental carbon is 1.0. The range of 0.02 to 0.08 is preferable, and even if the atomic ratio is greater than 0.2, the effect is saturated, and (I) group of simple carbons, ( It is not preferable because the content of the compounds of group II) and group (III) is relatively lowered.
[0023]
The method for decomposing nitrogen fluoride according to the present invention comprises a group (I) substance (single carbon), a group (II) compound (aluminum compound, iron compound, manganese compound and / or alkaline earth metal compound), (III ) Group compound (alkali metal compound) and (IV) group compound (nickel compound, tin compound and / or copper compound) are used, which is characterized in that a solid decomposition reagent is used. The composition ratio of the decomposition reagent is the atomic ratio of metals contained in the compounds of groups (II) to (IV) when the atomic ratio of the substances of group (I) is 1.0. In the range of 0.05 to 1.0, in the range of (III) group of 0.01 to 0.2, in the range of (IV) group of 0.01 to 0.2 There should be. The composition ratio is expressed in atomic ratios when the compounds of groups (II) to (IV) are contained in various compounds such as oxides, hydroxides, carbonates, etc. This is because the content ratio of is important. When nitrogen fluoride gas is brought into contact with such a reactant at an appropriate temperature, nitrogen fluoride is decomposed, and the fluorine component produced by the decomposition reacts with a compound of group (II) in the reactant to form a metal fluoride. As fixed and detoxified. Furthermore, the substances of group (I) and the compounds of groups (III) and (IV) suppress the formation of, for example, fluorocarbon gas, nitrogen oxides and carbon monoxide, which are by-produced during the decomposition reaction. Decomposes nitrogen efficiently and safely.
[0024]
In addition, the total weight of metal atoms in the compounds contained in the group (I) elemental carbon and the compounds in the groups (II) to (IV) is preferably 50% by weight or more of the total reactants. Nitrogen fluoride can be decomposed even if the total weight is less than 50% by weight, but it is preferably 50% by weight or more in order to efficiently decompose nitrogen fluoride. As the remaining components, there are components other than the metal in the compound when the compounds of groups (II) to (IV) are added as metal salts, and most of the remaining components are preferably oxygen, Moisture and CO₂Or the component derived from other raw materials can also be included.
[0025]
As described above, the reactive agent for decomposing nitrogen fluoride of the present invention comprises (I) group simple carbon, (II) group aluminum compound, iron compound, manganese compound and / or alkaline earth metal compound, ( It is a solid containing the alkali metal compound of group III) and the nickel compound, tin compound and / or copper compound of group (IV) as essential components. The solid reactant is preferably granular in order to increase the chance of contact with nitrogen fluoride gas used for decomposition. Further, the particle diameter is preferably in the range of 0.1 to 10 mm, and preferably in the range of 1 to 5 mm.
[0026]
In order to obtain a granular reactant, the raw material powders of the groups (I) to (IV) described above are mixed, granulated with an appropriate amount of water, or optionally with an appropriate binder, and then granulated. A process of drying and evaporating moisture may be used. As the binder, an organic binder such as polyvinyl alcohol (PVA) or an inorganic binder such as silicon oxide can be used, but it is necessary that the amount does not affect the performance of the resulting decomposition reagent. is there.
[0027]
Each raw material powder should have a particle size of 100 μm or less and should be mixed uniformly using a kneader or the like. The kneader is preferably one that can be mixed and granulated simultaneously, but may be one that performs mixing and granulation separately. For example, if a Henschel mixer or a vertical mixer is used, mixing and granulation can be performed simultaneously. However, mixing of raw materials is performed with a Henschel mixer or V-type mixer, and then granulation is performed with a dish-type granulator or drum pelletizer. You may go.
[0028]
The drying temperature after granulation may be usually 100 to 200 ° C., but the decomposition reagent of the present invention preferably has a low water content, and the amount of water released when heated to 400 ° C. in an inert atmosphere is 5 It is preferable to dry until it becomes less than wt%.
[0029]
In addition, the granular reactant obtained by the above process can be subjected to a decomposition reaction after firing. The firing temperature is usually up to 400 ° C., but when a hydroxide is used as the compound of groups (II) to (IV), the firing is performed at a temperature sufficient for the hydroxide dehydration reaction to proceed. It is preferable to do. As described above, since the decomposition reactant of the present invention preferably has a low water content or does not generate water during the decomposition reaction, the amount of water released when heated to 400 ° C. in an inert atmosphere is 5%. It is preferable to process until it becomes less than weight%.
[0030]
This firing step is preferably performed under conditions that remove moisture and volatile components to obtain a fired product having an appropriate strength, but in an inert atmosphere to prevent oxidative consumption of carbon in the blended raw material. It is preferable to perform the heat treatment at, and if it is in an inert atmosphere, the treatment at a high temperature becomes possible, and a high-strength fired product is obtained. As the equipment used for sintering, a continuous type such as a rotary kiln can be used, but it can also be carried out in a fixed furnace.
[0031]
Next, the decomposition method using the reactant will be described.
According to the present invention, it is necessary to appropriately adjust the reaction conditions, for example, the reaction temperature, the nitrogen fluoride concentration and the oxygen concentration in the exhaust gas to be decomposed, the form of the reactants, the components of the reactants, etc. This is a very important condition. That is, in this reaction, there are reactions that generate carbon fluoride, nitrogen oxides, and carbon monoxide as side reactions, but the fluorine component in nitrogen fluoride is completely immobilized on the reactants, and the side reactions are suppressed. For this purpose, the contact temperature between nitrogen fluoride and the reactant may be actually 250 to 450 ° C, preferably 300 to 400 ° C. Nitrogen oxides are generated in a region where the reaction temperature is low, and fluorocarbons are generated in a region where the reaction temperature is high.
[0032]
Next, a method and a decomposition apparatus for decomposing nitrogen fluoride using the reactant will be described.
The method for decomposing and treating nitrogen fluoride according to the present invention can be carried out by passing a nitrogen fluoride-containing gas, which is a gas to be treated, through a reaction vessel filled with the reactant. In that case, while maintaining the temperature of a reaction agent and also reaction temperature at 200 degreeC or more, it can carry out in non-oxidizing atmosphere or weakly oxidizing atmosphere as reaction atmosphere. Even if the reaction atmosphere is a non-oxidizing atmosphere, the object can be sufficiently achieved, but in some cases, the reaction can be performed in a weakly oxidizing atmosphere, for example, an atmosphere containing less than 20 vol% oxygen in the gas to be treated. . The concentration of nitrogen fluoride in the gas to be treated is not particularly limited, and it can be decomposed even with 100% nitrogen fluoride gas, and may be diluted with an inert gas or an oxygen-containing gas. That is, the concentration of nitrogen fluoride in the gas to be treated for decomposition, the oxygen concentration in the gas to be treated, SV (superficial velocity), LV (linear velocity), mixed state with other gases, A preferable decomposition temperature is set according to the component ratio and form, and further, the amount of by-products such as nitrogen oxides, fluorocarbons, and carbon monoxide produced.
[0033]
This decomposition treatment includes a reaction vessel filled with the reactant, a gas inlet to be treated provided so as to communicate with the inside of the reaction vessel, a gas outlet provided so as to discharge the gas after reaction from inside the reaction vessel, It can be carried out by a decomposition apparatus comprising a furnace containing the reaction vessel, a heat source for raising the atmospheric temperature in the furnace to 200 ° C. or more, and a pipe connecting the gas inlet to be treated and the nitrogen fluoride-containing gas source.
[0034]
FIG. 1 shows an example of an apparatus for carrying out the present invention. In the figure, reference numeral 1 denotes a metal reaction vessel (tube) in which a reactant 2 made of the aforementioned reactant is filled. In the illustrated example, a tubular reaction vessel 1 is formed into a vertical type, and a reactant 2 is filled on an air-permeable bed 3 fixed in the vessel. As the metal tube of the reaction vessel 1, a tube made of stainless steel or nickel base alloy can be used.
[0035]
The reaction vessel 1 is installed in the heating furnace 4. The illustrated heating furnace 4 uses an electric heater 5 using a heating element that generates heat when energized as a heat source. The electric heater 5 raises the temperature of the atmosphere 6 in the furnace to a required temperature. Is transmitted to the reactant 2 through the metal reaction vessel wall. As long as the temperature of the furnace atmosphere 6 can be raised to a required temperature, the heat source is not limited to the electric heater. For example, high-temperature gas such as combustion exhaust gas can be used as a heat source.
[0036]
In this way, the reaction vessel 1 installed in the heating furnace 4 is provided with the gas inlet 7 to be processed, and this gas inlet 7 is connected to the vessel 8 containing nitrogen fluoride by piping. Further, a flow rate adjusting valve 10 is provided in the gas discharge pipe 9 from the container 8. In the embodiment of FIG. 1, in addition to the container 8, an oxygen gas cylinder 11 and a nitrogen gas cylinder 12 are separately provided, and oxygen gas and nitrogen gas are temporarily passed through gas discharge pipes 15 and 16 via flow rate adjusting valves 13 and 14, respectively. Guide to gas header 17. By introducing nitrogen fluoride to the header 17, nitrogen gas as a carrier is mixed with the nitrogen fluoride gas, and oxygen gas can be added as necessary. The gas to be treated mixed in the header 17 is sent to the gas to be treated inlet 7 of the reaction vessel 1 through the gas supply pipe 18.
[0037]
Note that the present invention is not limited to this example, and a mixed gas obtained by previously mixing nitrogen fluoride, nitrogen, and oxygen is prepared in one container, and the mixed gas is directly fed into the gas inlet 7 to be processed. Good. In any case, the oxygen gas introduction pipe is preferably connected to the container 8 itself or a pipe extending from the container 8 to the gas to be treated inlet 7 as necessary.
On the other hand, an exhaust gas conduit 20 is connected to the gas outlet 19 of the reaction vessel 1, and is discharged out of the system from 23. A sampling pipe 21 is attached to the exhaust gas pipe 20 as a branch pipe, and the gas sampling pipe 21 is connected to the halogen absorption bottle 22 and the gas analyzer 24 for sampling.
[0038]
In the apparatus of FIG. 1, the temperature of the reactant 2 in the reaction vessel 1 is controlled by the heat balance due to the reaction and the balance of the heat capacity in and out of the introduced gas and the exhaust gas, as the atmospheric temperature in the heating furnace 4 is transmitted through the vessel wall. Change. As shown in the figure, a temperature sensor (thermocouple) inserted approximately at the center of the reactant 2 detects the temperature of the reaction zone with a temperature measuring device 26, and the heat source is maintained so that this temperature is maintained at a predetermined temperature. The amount of heat supplied from 5 is controlled. Further, the temperature of the furnace atmosphere 6 in the heating furnace 4 is also detected by the temperature sensor 27, and the temperature control of the heating furnace itself is appropriately performed based on the detected value.
[0039]
In this way, nitrogen fluoride in the gas to be treated is almost completely decomposed (with a decomposition rate close to 100%). The decomposed fluorine reacts with the aluminum compound, iron compound, manganese compound and alkaline earth metal compound in the reactant to form a stable metal fluoride. Therefore, these nitrogen fluoride and fluorine components do not substantially remain in the exhaust gas.
[0040]
FIG. 2 shows an example in which used nitrogen fluoride used in the semiconductor manufacturing process is decomposed according to the present invention. Spent nitrogen fluoride 28 from the semiconductor manufacturing process is generally sent to a routine processing step 30 via a conduit 29. In applying the present invention, the nitrogen fluoride supply pipe 29 is connected to the gas inlet 7 of the reaction vessel 1. In the illustrated example, a branch pipe 32 is attached from the supply pipe 29 via a three-way valve 31, and the branch pipe 32 is connected to the gas inlet 7 to be processed. Further, a nitrogen gas supply pipe 33 is connected to the branch pipe 32 so that nitrogen gas can be supplied from the nitrogen gas source 34 into the branch pipe 32 at a variable flow rate. Thereby, when the three-way valve 31 is switched from the reaction vessel 1 side to the processing step 30 side, a necessary amount of nitrogen gas can be supplied from the nitrogen gas source 34 even if the gas to be processed does not flow to the branch pipe 32 side. .
[0041]
3 and 4 show an example of the present invention in which a heat source is installed inside the reaction vessel 1 so that heat is transferred from the inside of the vessel to the reactant 2. In both figures, 36 is a heat-resistant furnace material surrounding the reaction vessel 1, 7 is a gas introduction port to be treated into the vessel, and 19 is a gas discharge port from the vessel.
In the case of FIG. 3, a heating element 35 that generates heat when energized is disposed inside the packed bed of the reactant 2, and the heating element 35 is covered with a corrosion-resistant and heat-resistant cover. According to this example, since heat is transferred from the inside of the packed bed of the reactant 2, the temperature rising rate for raising the reactant to a desired temperature can be increased, and heat loss is reduced. In the case of FIG. 4, the inside of the reaction vessel 1 is divided into a packed bed of the reactant 2 and a heated layer so that the gas to be treated introduced into the vessel 1 flows into the reactant packed bed after passing through the heated layer. It is a thing. In the heating layer, a heating element 38 that generates heat when energized is attached to the container lid 37. The gas to be treated is given heat when passing through the heating layer and is also transferred to the reactant 2. In this example, since the electric heater is placed in the container, the heat utilization efficiency is increased.
[0042]
FIG. 5 shows that when the reaction vessel 1 is restricted in the height of the reaction vessel due to an increase in the size of the reaction vessel 1 or the like, the diameter of the reaction vessel may be increased. In the heating method of FIGS. 3 and 4, the heat transfer area is reduced, and accordingly, in the external heating method of FIG. 1, a large temperature gradient is generated in the central direction of the cross section in the reactant in the reaction vessel. Furthermore, in the internal preheating method of the gas to be processed in FIG. Therefore, the problem of the temperature gradient and the rate of temperature increase due to an increase in the size of the reaction vessel 1 is solved by adopting a heating method using the heating method of FIGS. 1, 3 and 4 together.
[0043]
FIG. 6 shows an example of the present invention in which a heat exchanger 39 for exchanging heat between the gas to be treated before being introduced into the reaction vessel 1 having a heating source and the exhaust gas emitted from the reaction vessel 2 is arranged. is there. By disposing the heat exchanger 39, the heat recovery is achieved by applying the sensible heat of the exhaust gas to the gas to be processed, so that the heat consumption of the heating source can be reduced.
[0044]
In the case of the apparatus described above, the decomposition reaction ends when the charged reactants are exhausted. This reaction end point can be known at the time when nitrogen fluoride starts to be detected in the exhaust gas. When the reaction is completed, the operation of the apparatus is stopped, and the reaction is started by charging a new reactant, so that nitrogen fluoride can be sequentially decomposed in the same apparatus.
In order to make this batch system continuous, a plurality of similar devices are installed together, while one device is operating, the reactants of the other device are replaced, and when one device stops, the other It is also possible to adopt a double tower switching system in which the gas flow path is switched to the apparatus. In addition, if one that allows continuous or intermittent supply of the reactant into the reaction vessel and continuous or intermittent discharge of the spent reactant from the reaction vessel is used, continuous operation can be performed for a long time in the same apparatus.
[0045]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
(Adjustment of comparative reactants 1 to 3)
Using the following compounds as raw materials, granular comparative reactants 1 to 3 were prepared.
Activated carbon powder C (coconut shell activated carbon made by Hokuetsu Carbon Industry)
Alumina powder Al₂O_Three   (Sumitomo Chemical Hydraulic Alumina BK112)
Potassium carbonate K₂CO_Three   (Pure Chemical Reagent grade 1)
Each of the above compounds is mixed with a Henschel mixer at the compounding ratio shown in Table 1, and after adding water and granulated, it is dried at 110 ° C. for 4 hours and then heat treated at 400 ° C. for 3 hours in a nitrogen atmosphere. The resulting fired product was sieved to obtain a granular product having a particle size of 0.85 to 2.8 mm.
[0046]
(Adjustment of reactants 1-10)
Using the compounds shown below as raw materials, granular decomposition reactants 1 to 10 were prepared.
Activated carbon powder C (coconut shell activated carbon made by Hokuetsu Carbon Industry)
Alumina powder Al₂O_Three   (Sumitomo Chemical Hydraulic Alumina BK112)
Calcium hydroxide Ca (OH)₂(Pure Chemical Reagent grade 1)
Manganese dioxide powder MnO₂    (Pure Chemical Reagent Chemical)
Ferric oxide powder Fe₂O_Three   (Pure Chemical Reagent Chemical)
Nickel Oxide Powder NiO (Pure Chemical Reagent Chemical)
Stannic oxide SnO₂    (Pure Chemical Reagent Chemical)
Cupric oxide powder CuO (Pure Chemical Reagent Chemical)
Potassium carbonate K₂CO_Three   (Pure Chemical Reagent grade 1)
The above-mentioned various compounds are mixed in various combinations and blending ratios shown in Table 1, mixed with a Henschel mixer, granulated by adding water, dried at 110 ° C. for 4 hours, and subjected to 3 hours at 400 ° C. in a nitrogen atmosphere. Heat treatment was performed for a period of time, followed by dehydration firing. The obtained fired product was sieved to obtain a granular product having a particle size of 0.85 to 2.8 mm.
[0047]
Table 1 shows combinations of various compounds for adjusting Comparative Reagents 1 to 3 and Reagents 1 to 10, the atomic ratio of each metal when carbon is 1.0, and metal atoms in the reactive agent containing carbon. The total weight% of was shown.
[Table 1]

[0048]
(Example of reaction)
The method of the present invention was carried out using an apparatus of the same principle as that shown in FIG. That is, a reaction tube made of Inconel 600 having an inner diameter of 16 mm and a length of 500 mm is passed through the axial center of a tubular furnace (electric capacity: 1.4 kw, length: 400 mm) equipped with a heating element (kanthal alloy) that generates heat when energized. The reactor center in this reaction tube was filled with 35 cc of a reagent for decomposing nitrogen fluoride.
Nitrogen trifluoride (NF) as nitrogen fluoride for decomposition_Three) And nitrogen gas was introduced into the reaction tube as a carrier with or without oxygen gas added to the nitrogen trifluoride as shown in FIG.
that time,
Processed gas flow rate: 0.20 l / min
Nitrogen fluoride concentration in gas to be treated: 3vol%
Superficial velocity of gas to be treated: 343 hr^-1
Processed gas linear velocity: 1.0 m / min
Oxygen concentration in gas to be treated: 0% or 5vol%
Was constant. However, in some tests, HF, SiF_FourMixed.
[0049]
In any of the examples, when the gas to be treated was introduced, energization of the heating element was started and it was confirmed that the temperature of the central part of the reactant had reached a predetermined temperature. During the reaction, the energization amount of the tubular furnace is adjusted so that the temperature measured by the thermocouple inserted in the central part of the reactant (the hottest part of the bulk of the reactant) is maintained at that temperature. Controlled. The reaction temperature in Table 2 represents this temperature maintained during the reaction.
[0050]
A part of the exhaust gas discharged from the reaction tube was guided to a fluorine absorption bottle containing a gas analyzer and a caustic soda solution as shown in FIG. Exhaust gas analysis includes nitrogen fluoride, other fluorine compounds, O₂, N₂, NO, N₂O, CO₂, CO, F^-Went about.
[0051]
Comparative Reagents 1 to 3 and Reagents 1 to 10 shown in Table 1 were used, and nitrogen trifluoride was decomposed under the above-mentioned conditions by changing the reactant temperature in various ways. The results are shown in Table 2. By-product concentration and NF in Table 2_ThreeDecomposition rate of the by-product in the exhaust gas 60 minutes after the start of the reaction and NF_ThreeThe decomposition rate of the by-product (F) remaining in the exhaust gas from the exhaust gas sampling after 60 minutes from the start of the reaction^-, NO, N₂O, CF_FourCO) and nitrogen fluoride are measured and expressed by the concentration of by-products and the percentage of nitrogen fluoride in the exhaust gas relative to nitrogen fluoride in the gas to be treated.
[0052]
[Table 2]

[0053]
As shown in Table 2, Al₂O_ThreeThe reactant of Comparative Example 1 using only (the compound of group (II)) is NF_ThreeTo decompose nearly 100% requires a reaction temperature of 300 ° C. or higher, and NO_XIt can be seen that the generation of can not be suppressed.
[0054]
Activated carbon and Al₂O_ThreeThe reactant of Comparative Example 2 in combination with (compound of group (II)) is NF_ThreeThe reaction temperature of 250 ° C or higher is sufficient to decompose nearly 100%, but NO_X, N₂It turns out that the production | generation of O and CO cannot be suppressed. However, when the reaction temperature is 300-400 ° C., NO_X, N₂O generation is suppressed, but CF is around 400 ° C._FourIt can be seen that is generated.
[0055]
Activated carbon, Al₂O_Three(Compounds of group (II)) and K₂CO_ThreeThe reactant of Comparative Example 3 combined with (compound of group (III)) is NF_ThreeAlthough the reaction temperature of 200 ° C. or higher is sufficient for decomposing nearly 100% of CO, the formation of CO cannot be suppressed at all temperatures as in the case of Comparative Example 2, and CF at about 450 ° C._FourIt can be seen that NO_XAnd N₂It can be seen that O can be sufficiently suppressed when the reaction temperature is 250 ° C. or higher.
[0056]
Thus, the reaction agent which combined the compound of (I)-(III) group is NF at the reaction temperature of 200 degreeC or more._ThreeIs decomposed by nearly 100% and the reaction temperature is in the range of 250 ° C to 450 ° C._X, N₂O, CF_FourAlthough CO can be suppressed at the same time, the generation of CO cannot be suppressed at the same time.
[0057]
On the other hand, the decomposition agents 1 to 10 of the present invention are obtained by adding a compound of group (IV) to a compound of groups (I) to (III), and as shown in Table 2, NF_ThreeDecomposition temperature and NO_X, N₂O, CF_FourAlthough the temperature range in which CO 2 can be suppressed was the same as in the case of using Comparative Example 3, it was found that CO was not generated at any temperature of Reaction Examples 1 to 10. Further, as shown in Reaction Examples 2 and 3, oxygen and SiF in the gas to be treated_FourNF regardless of the presence or absence of HF_ThreeCompletely decomposes and NO_X, N₂O, CF_Four, CO is not generated. F^-Is not detected, SiF_Four, HF was found to be abolished at the same time.
[0058]
【The invention's effect】
As described above, according to the present invention, nitrogen fluoride can be efficiently decomposed at a relatively low temperature and with a simple formulation, and the decomposed fluorine can be fixed as a harmless substance. That is, the method for decomposing nitrogen fluoride of the present invention can be carried out with a simple decomposing apparatus, the processing operation is simple and the decomposition efficiency is high, and the generation of by-products of nitrogen oxide, fluorocarbon, and carbon monoxide is suppressed. . Moreover, the decomposition product is AlF._ThreeTherefore, post-treatment is easy. In addition, the low cost of the reactants brings about an effect that has not been achieved so far, and can make a great contribution to the decomposition of used nitrogen fluoride generated in the semiconductor manufacturing process.
[Brief description of the drawings]
FIG. 1 is an equipment layout system diagram showing an example of an apparatus for carrying out the method of the present invention.
FIG. 2 is an equipment arrangement system diagram showing another example of a target gas introduction unit for carrying out the method of the present invention.
FIG. 3 is a schematic cross-sectional view of a reaction vessel portion showing an example in which a reactant is heated from the reaction vessel according to the method of the present invention.
FIG. 4 is a schematic cross-sectional view of a reaction vessel portion showing another example of heating a reactant from the reaction vessel according to the method of the present invention.
FIG. 5 is a schematic cross-sectional view of a reaction vessel portion showing an example of heating a reactant from inside and outside the reaction vessel according to the method of the present invention.
FIG. 6 is a diagram showing an example of heat exchange between the gas to be treated before entering the reaction vessel and the exhaust gas exiting the reaction vessel when the present invention is carried out.
[Explanation of symbols]
1 Reaction vessel
2 Reactant
3 Breathable floor
4 Heating furnace
5 Electric heater
6 Furnace atmosphere in the heating furnace
7 Processed gas inlet
8 Nitrogen fluoride source
11 Oxygen gas source
12, 34 Nitrogen gas source
18, 32 Gas to be treated pipeline
20 Gas outlet
21 Exhaust gas line
35, 38 Heating element that generates heat when energized

Claims (12)

Group (I) materials comprising elemental carbon, Group (II) compounds comprising aluminum oxide, Group (III) compounds comprising alkali metal carbonates, and Group (IV) comprising NiO and / or CuO A reactive agent for decomposing nitrogen fluoride, comprising a compound. The reactive agent for decomposing nitrogen fluoride according to claim 1, wherein the elemental carbon is activated carbon, carbon black, coke, char charcoal, coal, pitch and / or charcoal. The reactive agent for decomposing nitrogen fluoride according to claim 1 or 2, wherein the simple carbon is powdery or granular. The reactive agent for decomposing nitrogen fluoride according to claim 1, wherein the compound of group (II) further contains an alkaline earth metal hydroxide, MnO ₂ or Fe ₂ O ₃ in addition to aluminum oxide . The composition ratio of the compound of group (II) contained in the reactant is the atomic ratio of the metal contained in the compound of group (II) when the atomic ratio of elemental carbon of group (I) is 1. The reactive agent for decomposing nitrogen fluoride according to any one of claims 1 to 4, which is within a range of 0.05 to 1.0. The composition ratio of the compound of group (III) contained in the reactant is the atomic ratio of the metal contained in the compound of group (III) when the atomic ratio of elemental carbon of group (I) is 1. The reactive agent for decomposing nitrogen fluoride according to any one of claims 1 to 5, which is within a range of 0.01 to 0.2. The reactive agent for decomposing nitrogen fluoride according to claim 1, wherein the compound of group (IV) further contains stannic oxide in addition to NiO and / or CuO . The composition ratio of the compound of group (IV) contained in the reactant is the atomic ratio of the metal contained in the compound of group (IV) when the atomic ratio of elemental carbon of group (I) is 1. The reactive agent for decomposing nitrogen fluoride according to any one of claims 1 to 7, which is within a range of 0.01 to 0.2. The composition ratio of the compounds in groups (I) to (IV) contained in the reactant is contained in the compounds in groups (II) to (IV) when the atomic ratio of simple carbon in group (I) is 1. (II) group compound is 0.05 to 1.0, (III) group compound is 0.01 to 0.2, and (IV) group compound is 0.01 to The reactive agent for decomposing nitrogen fluoride according to any one of claims 1 to 8, which is 0.2. 10. The total weight of metal atoms contained in the group (I) elemental carbon and the compounds in groups (II) to (IV) contained in the reactant is 50% by weight or more of the weight of the reactant. The reaction agent for decomposing nitrogen fluoride according to any one of the above. The reactive agent for decomposing nitrogen fluoride according to any one of claims 1 to 10, wherein the nitrogen fluoride is nitrogen trifluoride. A method for decomposing nitrogen fluoride, comprising bringing a gas containing nitrogen fluoride into contact with the decomposition reagent according to any one of claims 1 to 11 at a temperature of 250 to 450 ° C.

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