JP2004025025A

JP2004025025A - Agent and method for purifying gas containing nitrogen fluoride

Info

Publication number: JP2004025025A
Application number: JP2002184410A
Authority: JP
Inventors: Kenji Otsuka; 大塚　健二; Yoji Nawa; 名和　洋二
Original assignee: Japan Pionics Ltd
Current assignee: Japan Pionics Ltd
Priority date: 2002-06-25
Filing date: 2002-06-25
Publication date: 2004-01-29
Anticipated expiration: 2022-06-25
Also published as: CN1299804C; KR20040002663A; CN1468646A; KR100963346B1; TW200401663A; TWI233374B; JP3816841B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purifying agent and purifying method, which can relatively stably and easily be stored and handled in air for purifying a gas containing nitrogen fluorides such as nitrogen trifluoride, which does not cause overheating for certain kinds of diluting gas during purifying or sudden heat generation or production of harmful gas in the subsequent treatment of purification, which does not induce increase in the pressure loss or clogging in a purification cylinder during purifying, which does not emit NOx but can efficiently purify a gas containing nitrogen fluorides. <P>SOLUTION: The purifying agent contains tin(II) oxide and at least one kind of compound selected from oxides, hydroxides and carbonates of alkaline earth metals and oxides, hydroxides and carbonates of lanthanoids as an effective component. The gas containing nitrogen fluorides is purified by bringing the gas into contact with the above purifying agent while heating. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は窒素弗化物を含有するガスの浄化剤及び浄化方法に関する。さらに詳細には、空気中で比較的に安定で保存、取扱いが容易であり、浄化中あるいは浄化後の後処理で危険を伴うことなく、またＮＯｘを排出することなく、半導体製造工程等から排出される窒素弗化物を含有するガスを、効率よく浄化することが可能な浄化剤及び浄化方法に関する。
【０００２】
【従来の技術】
半導体製造工業においては、シリコン、シリコン酸化物等のドライエッチングガスやＣＶＤ装置のチャンバークリーニングガスとして、三弗化窒素が使用されている。三弗化窒素は水に対する溶解度が小さく、酸やアルカリともほとんど反応しない等室温ではかなり安定であり、地球温暖化に対する影響が大きいことが認められているほか、許容濃度が１０ｐｐｍと報告されており、毒性が高く、大気にそのまま放出した場合は人体および環境に悪影響を与えるので、半導体製造工程で使用した後は浄化する必要がある。
【０００３】
また、三弗化窒素は常温、常圧では安定であるが、ドライエッチングやクリーニング工程中に熱、放電等により、四弗化二窒素、二弗化二窒素、六弗化二窒素等の窒素弗化物を生成する。これらのガスは三弗化窒素よりも毒性が強いため、三弗化窒素と同様に浄化しなければならない。
【０００４】
従来から、窒素弗化物の浄化剤としては、カルシウム及び／またはマグネシウムを有効成分とする浄化剤（特開平６−９９０３３号公報）、金属亜鉛、金属アルミニウムまたは両者の混合物を主成分とする浄化剤（特開平６−１３４２５６号公報）、ジルコニウムまたはジルコニウム系合金から成る浄化剤（特開平６−２３８１２８号公報）、酸化第一錫を有効成分とする浄化剤（特開平１１−５０１８号公報）等が開発されている。窒素弗化物は常温で安定であるため、いずれの浄化剤を使用する場合においても、加熱して浄化処理されている。
また、その他の浄化方法としては、窒素弗化物を含有するガスを、水素、メタン、プロパン等を用いた焼却炉の火炎中に導入して燃焼させる方法、加熱下で金属酸化物と接触させて浄化する方法等が行われている。
【０００５】
【発明が解決しようとする課題】
しかしながら、カルシウム及び／またはマグネシウムを有効成分とする浄化剤、あるいは、金属亜鉛、金属アルミニウムまたは両者の混合物を主成分とする浄化剤は、有効成分、主成分が、酸素あるいは水と反応しやすいため、保存、取扱いが難しいほか、浄化後の未反応浄化剤の後処理には急激な発熱、有害ガスの発生等の危険を伴うことがあった。また、ジルコニウムまたはジルコニウム系合金から成る浄化剤は、常温の空気中では安定であるが、浄化温度近辺の高温下では酸素と激しく反応する。更に三弗化窒素の濃度が高い等の理由により高温になると、通常三弗化窒素の希釈ガスとして使用される窒素とも激しく反応し、熱暴走を引き起こす虞があった。
【０００６】
また、酸化第一錫を有効成分とする浄化剤は、常温から高温の空気中で比較的に安定であるが、三弗化窒素を含むガスの浄化により生成するＳｎＦ_２の密度が、有効成分であるＳｎＯと比べて小さいため、浄化剤の除害反応が終了した部分が膨張して、浄化筒内で圧力損失の増加あるいは閉塞を起こし、浄化能力が残っているにもかかわらず新しい浄化剤と交換して浄化を継続する必要があった。
さらに、窒素弗化物を含有するガスを、焼却炉の火炎中に導入して燃焼させる方法、加熱下で金属酸化物と接触させて浄化する方法は、ＮＯｘを排出するという不都合があった。
【０００７】
従って、本発明が解決しようとする課題は、三弗化窒素等の窒素弗化物を含有するガスの浄化において、空気中で比較的に安定で保存、取扱いが容易であり、浄化中に希釈ガスの種類により熱暴走を引き起こしたり浄化後の後処理で急激な発熱や有害ガスの発生等の危険を起こすことがなく、また浄化中に浄化筒内で圧力損失の増加あるいは閉塞を起こすことがなく、さらにＮＯｘを排出することがなく、効率よく窒素弗化物を含有するガスを浄化できる浄化剤及びそれを用いた浄化方法を提供することである。
【０００８】
【課題を解決するための手段】
本発明者らは、これらの課題を解決すべく鋭意検討した結果、酸化第一錫、及び、アルカリ土類金属の酸化物、水酸化物、炭酸塩、ランタノイドの酸化物、水酸化物、炭酸塩から選ばれる１種以上の化合物を有効成分として含む浄化剤は、空気中で比較的に安定であり、保存、取扱い等が容易であることを見い出した。また、本発明者らは、有害成分として窒素弗化物を含有するガスを、加熱下で前記浄化剤と接触させることにより、浄化中に希釈ガスの種類により熱暴走を引き起こしたり浄化後の後処理で急激な発熱や有害ガスの発生等の危険を起こすことなく、また浄化中に浄化筒内で圧力損失の増加あるいは閉塞を起こすことなく、さらにＮＯｘを排出することなく、効率よく窒素弗化物を含有するガスを浄化できることを見い出し、本発明の窒素弗化物を含有するガスの浄化剤及び浄化方法に到達した。
【０００９】
すなわち本発明は、酸化第一錫、及び、アルカリ土類金属の酸化物、水酸化物、炭酸塩、ランタノイドの酸化物、水酸化物、炭酸塩から選ばれる１種以上の化合物を有効成分として含むことを特徴とする窒素弗化物を含有するガスの浄化剤である。
また、本発明は、有害成分として窒素弗化物を含有するガスを、加熱下で、酸化第一錫、及び、アルカリ土類金属の酸化物、水酸化物、炭酸塩、ランタノイドの酸化物、水酸化物、炭酸塩から選ばれる１種以上の化合物を有効成分として含む浄化剤と接触させて浄化することを特徴とする窒素弗化物を含有するガスの浄化方法でもある。
【００１０】
【発明の実施の形態】
本発明の窒素弗化物を含有するガスの浄化剤及び浄化方法は、窒素、アルゴン、ヘリウム等のガス中に含まれる三弗化窒素、四弗化二窒素、二弗化二窒素、六弗化二窒素等の窒素弗化物を浄化するための浄化剤及び浄化方法に適用される。本発明の窒素弗化物を含有するガスの浄化剤は、酸化第一錫、及び、アルカリ土類金属の酸化物、水酸化物、炭酸塩、ランタノイドの酸化物、水酸化物、炭酸塩から選ばれる１種以上の化合物を有効成分として含む浄化剤である。
また、本発明の窒素弗化物を含有するガスの浄化方法は、窒素弗化物を含有するガスを、加熱下で、前記浄化剤と接触させて浄化する浄化方法である。
【００１１】
以下、本発明の窒素弗化物を含有するガスの浄化剤について詳細に説明する。
本発明の浄化剤において、有効成分の一つとして用いられる酸化第一錫（ＳｎＯ）は、粉末等の状態で純度９８％以上のものが市販されているので、通常はこれらの市販品を用いることができる。
また、前記以外の有効成分であるアルカリ土類金属の酸化物、水酸化物、炭酸塩、ランタノイドの酸化物、水酸化物、炭酸塩としては、ベリリウム、マグネシウム、カルシウム、ストロンチウム、バリウム、ランタン、セリウム、プラセオジム、ネオジム、サマリウム、ユーロピウム等の酸化物、水酸化物、炭酸塩を例示することができるが、安価かつ入手しやすい点で、マグネシウム、カルシウム、ストロンチウム、またはランタンの酸化物、水酸化物、炭酸塩を用いることが好ましい。尚、これらのアルカリ土類金属化合物、ランタノイド化合物は単独で用いてもよく２種類以上を併用してもよい。
【００１２】
本発明の浄化剤は、浄化剤に含まれる錫の原子数と、アルカリ土類金属の原子数及びランタノイドの原子数を合せた原子数の比が、１：０．１〜２．０となるように、好ましくは０．３〜１．０となるように調製される。アルカリ土類金属の原子数及びランタノイドの原子数を合せた原子数が、錫の原子数の１０％未満である場合は、三弗化窒素を含むガスの浄化中に、主としてＳｎＯがＳｎＦ_２に変換される反応が起こる。ＳｎＦ_２は密度が４．５７ｇ／ｃｍ^３であり、主成分であるＳｎＯ（密度６．９５ｇ／ｃｍ^３）と比較して小さいため、浄化剤の除害反応が終了した部分が膨張して、浄化筒内で圧力損失の増加あるいは閉塞を起こす不都合を生じる。また、アルカリ土類金属の原子数及びランタノイドの原子数を合せた原子数が、錫の原子数の２．０倍を超える場合は、ＮＯｘを排出する不都合を生じる。
【００１３】
また、本発明の浄化剤は、造粒の際の成型性や成型強度を高めるために、有効成分のほかに成型助剤を加えることができる。このような成型助剤としては、弗化リチウム、弗化ナトリウム、弗化カリウム、弗化マグネシウム、弗化カルシウム、弗化ランタン等の金属弗化物を用いることができるが、この中でも成型強度を高める効果が優れている点で弗化カリウムを用いることが特に好ましい。これらは、単独あるいは２種類以上を混合して用いることもできる。これらの成型助剤を加える場合は、浄化剤を調製する際に有効成分に添加、混練される。成型助剤の添加量は、成型条件などによって異なり一概には特定できないが、少なすぎる場合は成型助剤としての効果が得られず、多すぎる場合は浄化能力が低下することから、通常は浄化剤全重量に対して０．１〜１０ｗｔ％であり、好ましくは０．５〜５ｗｔ％である。
【００１４】
また、本発明の浄化剤は、窒素弗化物の浄化に悪影響を及ぼさない不純物、不活性物質等を含んでいてもよい。さらに、使用前の浄化剤は水分を含んでいてもよいが含まない方が好ましく、通常は浄化剤中の水分が２ｗｔ％以下となるように調製される。尚、これらの成型助剤、不純物、不活性物質、水分等を含んだ場合においても、浄化剤中の有効成分の含有量は、通常は７０ｗｔ％以上、好ましくは９０ｗｔ％以上である。
【００１５】
本発明の浄化剤を成型する方法については特に制限はなく、例えば、浄化剤成分に水を加えてスラリーまたはケーキ状とした後、押出し成型し適当な長さに切断して乾燥させる方法、あるいは、浄化剤成分を打錠成型により造粒する方法等を用いることができる。
また、本発明の浄化剤は、酸化第一錫等と、前述のアルカリ土類金属化合物及びランタノイド化合物から選ばれる１種以上の化合物等を、混合し成型することにより調製しても、酸化第一錫等を成型するとともにアルカリ土類金属化合物及びランタノイド化合物から選ばれる１種以上の化合物等を成型した後、これらを混合することにより調製してもよい。
本発明の浄化剤においては、いずれの調製方法においても、通常は直径が１〜１０ｍｍ程度の球状、直径が０．５〜５ｍｍ程度で長さが２〜２０ｍｍ程度の円柱状、あるいはこれに類似する形状、またはこれに相当する大きさ及び形状となるように成型して調製される。
【００１６】
次に、本発明の窒素弗化物を含有するガスの浄化方法について詳細に説明する。
本発明の浄化方法は、窒素弗化物を含有するガスを、加熱下で前述のような浄化剤と接触させることにより浄化する方法である。但し、浄化剤の有効成分の一部として、アルカリ土類金属の水酸化物、炭酸塩、ランタノイドの水酸化物、炭酸塩を用いた場合は、前記のうちいくつかの化合物は加熱下では酸化物となり、アルカリ土類金属の酸化物、ランタノイドの酸化物として効果を発揮する。
【００１７】
三弗化窒素を含有するガスを、本発明の浄化方法により、酸化第一錫及び酸化カルシウムを有効成分として含む浄化剤と接触させることにより浄化する場合は、次の（式１）（式２）または（式３）の反応が起こると推測される。本発明の浄化方法においては、これらの反応式からも明らかなようにＣａＳｎＦ_６、ＳｎＯ_２、ＣａＦ_２が生成するが、これらの反応生成物を併せた体積と、反応する前の浄化剤の有効成分の体積の差は小さいので、浄化筒の充填部材（浄化剤及び反応生成物）が膨張して、浄化筒内で圧力損失の増加あるいは閉塞を起こす虞がない。例えば、（式３）の反応の場合、浄化剤の有効成分であるＳｎＯ、ＣａＯの密度は、各々６．９５ｇ／ｃｍ^３、３．３７ｇ／ｃｍ^３で、反応生成物であるＳｎＯ_２、ＣａＦ_２の密度は、各々７．０ｇ／ｃｍ^３、３．０８ｇ／ｃｍ^３であり、これらは等モル比なので、両者の平均密度の差は小さく体積の差も小さい。
【００１８】
【化１】

【００１９】
尚、前記の反応において、ＣａＯ等のアルカリ土類金属化合物の代わりにＬａ_２Ｏ_３等のランタノイド化合物を用いた場合は、前記の反応式に準じて窒素弗化物を含有するガスが浄化される。
【００２０】
本発明の浄化方法において、窒素弗化物を含有するガスと浄化剤を接触させる温度は、通常は２００〜８００℃、好ましくは２５０〜６００℃である。温度が２００℃よりも低い場合は、窒素弗化物の浄化能力が低下する。また、温度が８００℃よりも高い場合は、浄化筒にステンレス鋼を使用することができなくなり、より耐熱性の高い材質を必要とする不都合を生じる。
また、浄化を行なう際の浄化筒内の圧力は、通常は常圧であるが、例えば１ＫＰａのような減圧から０．２ＭＰａ（絶対圧力）のような加圧下で行なうこともできる。
【００２１】
本発明の浄化方法において、浄化剤を充填するための浄化筒は、通常は円筒状であり、大きさは通常は内径１０〜５００ｍｍ、長さは２０〜２０００ｍｍ程度である。浄化筒に充填される浄化剤の充填長は、通常は１０〜１０００ｍｍ程度、好ましくは５０〜５００ｍｍ程度である。浄化剤の充填長が１０ｍｍ以下の場合は、窒素弗化物を含有するガスの浄化が不充分となり、１０００ｍｍ以上の場合は圧力損失が大きくなる。また、浄化筒を加熱するための手段としては、通常は浄化筒の外側にヒーターが設置され、外部の制御装置により温度がコントロールされる。尚、本発明の浄化方法においては、浄化剤を固定床として用いるほか、移動床、流動床として用いることができる。
【００２２】
本発明の浄化方法を適用する場合の窒素弗化物を含有するガスの流速には特に制限はないが、一般的にガス中に含有される窒素弗化物の濃度が高いほど流速を小さくすることが望ましい。窒素弗化物の濃度は、通常は１％以下であるが、流量が小さい場合にはさらに高濃度の窒素弗化物を含有するガスの浄化処理も可能である。
浄化筒は窒素弗化物の濃度、流量等に応じて設計されるが、窒素弗化物の濃度が０．１％以下のような比較的低濃度では空筒線速度（ＬＶ）は０．５〜５０ｃｍ／ｓｅｃ、窒素弗化物の濃度が０．１〜１％程度ではＬＶは０．０５〜２０ｃｍ／ｓｅｃ、窒素弗化物の濃度が１％以上のような高濃度では１０ｃｍ／ｓｅｃ以下の範囲で設計することが好ましい。
【００２３】
【実施例】
次に、本発明の窒素弗化物を含有するガスの浄化剤及び浄化方法を、実施例により具体的に説明するが、本発明がこれらにより限定されるものではない。
【００２４】
実施例１
（浄化剤の調製）
市販の酸化第一錫（純度９９％）及び酸化カルシウム（純度９９％）を１００μｍ以下になるまで粉砕し、原子数の比（Ｓｎ：Ｃａ）が、１：０．５となるように混合した。混合物を内径２０ｍｍ、高さ５ｍｍの型に詰めた後、油圧ジャッキを用いて１５０〜１６０ｋｇ／ｃｍ^２の圧力で１０秒間加圧することにより成型して得られた剤を破砕して、さらに篩により３．３６ｍｍの目の開きを通過し２．００ｍｍの目の開きを通過しないものを浄化剤とした。
【００２５】
（浄化試験）
前記の浄化剤を、内径２３．９ｍｍ、長さ２００ｍｍのＳＵＳ３１６Ｌ製の浄化筒の内部に、充填長が１００ｍｍとなるように充填した。浄化筒の浄化剤の温度を４００℃に加熱した後、ＮＦ_３（流量１３．４６ｍｌ／ｍｉｎ）を含有する窒素（合計流量１３４６ｍｌ／ｍｉｎ）を浄化筒に導入してＮＦ_３を含むガスを浄化した。
この間、１０分毎に浄化筒の排出口から排出される浄化ガスの一部を採取し、ガスクロマトグラフ法（検出下限１０ｐｐｍ）によって分析を行ない、ＮＦ_３が検出されるまでの時間を測定して、浄化剤１Ｌ（リットル）当たりに対するＮＦ_３の浄化処理量（Ｌ）（浄化処理能力）を求めるとともに、ＮＯｘの排出の有無を検知管（（株）ガステック製）により調査した。その結果を表１に示す。
【００２６】
実施例２，３
実施例１の浄化剤の調製における酸化第一錫と酸化カルシウムの混合比を、原子数の比（Ｓｎ：Ｃａ）が、各々１：０．３、１：０．７５となるように混合したほかは、実施例１と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００２７】
実施例４，５
実施例１の浄化試験におけるＮＦ_３の濃度を各々０．２％、２．０％に変えたほかは実施例１と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００２８】
実施例６，７
実施例１の浄化剤の調製における酸化カルシウムを、各々水酸化カルシウム、炭酸カルシウムに替えたほかは実施例１と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００２９】
実施例８，９
実施例１の浄化剤の調製における酸化カルシウムを、各々酸化マグネシウム、酸化ストロンチウムに替えたほかは実施例１と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００３０】
実施例１０
（浄化剤の調製）
市販の酸化第一錫（純度９９％）及び酸化ランタン（純度９９％）を１００μｍ以下になるまで粉砕し、原子数の比（Ｓｎ：Ｌａ）が、１：０．５となるように混合した。混合物を内径２０ｍｍ、高さ５ｍｍの型に詰めた後、油圧ジャッキを用いて１５０〜１６０ｋｇ／ｃｍ^２の圧力で１０秒間加圧することにより成型して得られた剤を破砕して、さらに篩により３．３６ｍｍの目の開きを通過し２．００ｍｍの目の開きを通過しないものを浄化剤とした。
【００３１】
（浄化試験）
前記の浄化剤を、内径２３．９ｍｍ、長さ２００ｍｍのＳＵＳ３１６Ｌ製の浄化筒の内部に、充填長が１００ｍｍとなるように充填した。浄化筒の浄化剤の温度を４００℃に加熱した後、ＮＦ_３（流量１３．４６ｍｌ／ｍｉｎ）を含有する窒素（合計流量１３４６ｍｌ／ｍｉｎ）を浄化筒に導入してＮＦ_３を含むガスを浄化した。
この間、１０分毎に浄化筒の排出口から排出される浄化ガスの一部を採取し、ガスクロマトグラフ法（検出下限１０ｐｐｍ）によって分析を行ない、ＮＦ_３が検出されるまでの時間を測定して、浄化剤１Ｌ（リットル）当たりに対するＮＦ_３の浄化処理量（Ｌ）（浄化処理能力）を求めるとともに、ＮＯｘの排出の有無を検知管（（株）ガステック製）により調査した。その結果を表１に示す。
【００３２】
実施例１１，１２
実施例１０の浄化剤の調製における酸化第一錫と酸化ランタンの混合比を、原子数の比（Ｓｎ：Ｌａ）が、各々１：０．３、１：０．７５となるように混合したほかは、実施例１０と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１０と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００３３】
実施例１３，１４
実施例１０の浄化試験におけるＮＦ_３の濃度を各々０．２％、２．０％に変えたほかは実施例１０と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００３４】
実施例１５，１６
実施例１０の浄化剤の調製における酸化ランタンを、各々水酸化ランタン、炭酸ランタンに替えたほかは実施例１０と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１０と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００３５】
実施例１７
（浄化剤の調製）
市販の酸化第一錫（純度９９％）、酸化カルシウム（純度９９％）及び酸化ランタン（純度９９％）を１００μｍ以下になるまで粉砕し、原子数の比（Ｓｎ：Ｃａ：Ｌａ）が、１：０．３：０．２となるように混合した。混合物を内径２０ｍｍ、高さ５ｍｍの型に詰めた後、油圧ジャッキを用いて１５０〜１６０ｋｇ／ｃｍ^２の圧力で１０秒間加圧することにより成型して得られた剤を破砕して、さらに篩により３．３６ｍｍの目の開きを通過し２．００ｍｍの目の開きを通過しないものを浄化剤とした。
【００３６】
（浄化試験）
前記の浄化剤を、内径２３．９ｍｍ、長さ２００ｍｍのＳＵＳ３１６Ｌ製の浄化筒の内部に、充填長が１００ｍｍとなるように充填した。浄化筒の浄化剤の温度を４００℃に加熱した後、ＮＦ_３（流量１３．４６ｍｌ／ｍｉｎ）を含有する窒素（合計流量１３４６ｍｌ／ｍｉｎ）を浄化筒に導入してＮＦ_３を含むガスを浄化した。
この間、１０分毎に浄化筒の排出口から排出される浄化ガスの一部を採取し、ガスクロマトグラフ法（検出下限１０ｐｐｍ）によって分析を行ない、ＮＦ_３が検出されるまでの時間を測定して、浄化剤１Ｌ（リットル）当たりに対するＮＦ_３の浄化処理量（Ｌ）（浄化処理能力）を求めるとともに、ＮＯｘの排出の有無を検知管（（株）ガステック製）により調査した。その結果を表１に示す。
【００３７】
実施例１８
実施例１７の浄化剤の調製における酸化第一錫、酸化カルシウム、酸化ランタンの混合比を、原子数の比（Ｓｎ：Ｃａ：Ｌａ）が、１：０．２：０．３となるように混合したほかは、実施例１７と同様にして浄化剤を調製した。これらの浄化剤を用いて、実施例１７と同様にしてＮＦ_３の浄化試験を行なった。その結果を表１に示す。
【００３８】
比較例１
（浄化剤の調製）
市販の酸化第一錫（純度９９％）１０００ｇに、弗化カリウム（ＫＦ、関東化学（株）製、試薬特級）５０ｇを６５ｇの水に溶かした水溶液を加えてかき混ぜた。得られたケーキを押し出し成型機によって直径１．６ｍｍのノズル板より押し出し、得られた成型物を切断して長さ３〜５ｍｍ程度のペレットとし、窒素雰囲気下で１２０℃に加熱しながら約１２時間乾燥することによって浄化剤を調製した。
【００３９】
（浄化試験）
前記の浄化剤を用いたほかは実施例１と同様にしてＮＦ_３の浄化試験を行なった。しかし、ＮＦ_３が検出される前に浄化筒の圧力損失が大きくなったため浄化試験を中止した。ＮＯｘの排出の有無とともに、浄化試験を中止するまでの時間から、浄化剤１Ｌ（リットル）当たりに対するＮＦ_３の浄化処理量（Ｌ）（浄化処理能力）を求めた結果を表１に示す。
【００４０】
比較例２
市販の酸化カルシウム（純度９９％）を１００μｍ以下になるまで粉砕し、内径２０ｍｍ、高さ５ｍｍの型に詰めた後、油圧ジャッキを用いて１５０〜１６０ｋｇ／ｃｍ^２の圧力で１０秒間加圧した。成型して得られた剤を破砕して、さらに篩により３．３６ｍｍの目の開きを通過し２．００ｍｍの目の開きを通過しないものを浄化剤とした。
前記の浄化剤を用いたほかは実施例１と同様にしてＮＦ_３の浄化試験を行なった。しかし、浄化試験開始後すぐに数千ｐｐｍのＮＯの排出が確認されたため浄化試験を中止した。
【００４１】
比較例３
市販の酸化ランタン（純度９９％）を１００μｍ以下になるまで粉砕し、内径２０ｍｍ、高さ５ｍｍの型に詰めた後、油圧ジャッキを用いて１５０〜１６０ｋｇ／ｃｍ^２の圧力で１０秒間加圧した。成型して得られた剤を破砕して、さらに篩により３．３６ｍｍの目の開きを通過し２．００ｍｍの目の開きを通過しないものを浄化剤とした。
前記の浄化剤を用いたほかは実施例１と同様にしてＮＦ_３の浄化試験を行なった。しかし、浄化試験開始後すぐに数千ｐｐｍのＮＯの排出が確認されたため浄化試験を中止した。
【００４２】
【表１】

【００４３】
【発明の効果】
本発明の窒素弗化物を含有するガスの浄化剤により、その保存、取扱い等が容易にできるようになった。また、本発明の窒素弗化物を含有するガスの浄化方法により、浄化中に希釈ガスの種類により熱暴走を引き起こしたり浄化後の後処理で急激な発熱や有害ガスの発生等の危険を起こすことなく、また浄化中に浄化筒内で圧力損失の増加あるいは閉塞を起こすことなく、さらにＮＯｘを排出することなく、効率よく窒素弗化物を含有するガスを浄化できるようになった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a purifying agent and a purifying method for a gas containing nitrogen fluoride. More specifically, it is relatively stable in air, easy to store and handle, and can be discharged from semiconductor manufacturing processes without danger during purification or post-treatment after purification, and without emission of NOx. The present invention relates to a purifying agent and a purifying method capable of purifying a gas containing nitrogen fluoride efficiently.
[0002]
[Prior art]
In the semiconductor manufacturing industry, nitrogen trifluoride is used as a dry etching gas such as silicon or silicon oxide or a chamber cleaning gas for a CVD apparatus. Nitrogen trifluoride has a low solubility in water, is very stable at room temperature, such as it hardly reacts with acids or alkalis, and has been found to have a large effect on global warming. In addition, it has been reported that the allowable concentration is 10 ppm. It is highly toxic and, if released directly into the atmosphere, has a harmful effect on the human body and the environment. Therefore, it must be purified after use in the semiconductor manufacturing process.
[0003]
Nitrogen trifluoride is stable at normal temperature and normal pressure. However, during dry etching and cleaning processes, nitrogen, such as dinitrogen tetrafluoride, dinitrogen difluoride, dinitrogen hexafluoride, etc. Produces fluoride. These gases are more toxic than nitrogen trifluoride and must be purified in the same way as nitrogen trifluoride.
[0004]
Conventionally, as a purifying agent for nitrogen fluoride, a purifying agent containing calcium and / or magnesium as an active ingredient (JP-A-6-99033), a purifying agent mainly containing metallic zinc, metallic aluminum or a mixture of both. (JP-A-6-134256), a purifying agent composed of zirconium or a zirconium-based alloy (JP-A-6-238128), a purifying agent containing stannous oxide as an active ingredient (JP-A-11-5018), and the like. Is being developed. Nitrogen fluoride is stable at normal temperature, and therefore, when any of the purifying agents is used, the purifying treatment is performed by heating.
Further, as another purification method, a method of introducing a gas containing nitrogen fluoride into a flame of an incinerator using hydrogen, methane, propane, or the like and burning it, or contacting with a metal oxide under heating. Purification methods and the like have been implemented.
[0005]
[Problems to be solved by the invention]
However, a purifying agent containing calcium and / or magnesium as an active ingredient or a purifying agent containing metal zinc, metal aluminum or a mixture of both as a main component is likely to react with oxygen or water because the active component and the main component are easily reacted with oxygen or water. In addition, storage and handling are difficult, and post-treatment of the unreacted purifying agent after purification sometimes involves dangers such as rapid heat generation and generation of harmful gas. A purifying agent made of zirconium or a zirconium-based alloy is stable in air at normal temperature, but reacts violently with oxygen at a high temperature near the purifying temperature. Further, if the temperature becomes high due to a high concentration of nitrogen trifluoride or the like, it may react violently with nitrogen, which is usually used as a diluent gas of nitrogen trifluoride, and cause thermal runaway.
[0006]
Further, the purifying agent containing stannous oxide as an active ingredient is relatively stable in air at normal temperature to high temperature, but the density of SnF ₂ generated by purifying a gas containing nitrogen trifluoride increases the active ingredient. Is smaller than SnO, which is a part of the purifying agent that has completed the detoxification reaction, expands, causing an increase in pressure loss or blockage in the purifying cylinder, and a new purifying agent despite the remaining purifying ability. It was necessary to continue the purification in exchange for
Furthermore, the method of introducing a gas containing nitrogen fluoride into the flame of an incinerator and burning it, and the method of purifying the gas by contacting it with a metal oxide under heating have the disadvantage of emitting NOx.
[0007]
Accordingly, the problem to be solved by the present invention is to purify a gas containing nitrogen fluoride such as nitrogen trifluoride, which is relatively stable and easy to store and handle in air, and diluting gas during purification. It does not cause thermal runaway or danger of sudden heat generation or harmful gas generation in the post-treatment after purification depending on the type, and does not cause an increase in pressure loss or blockage in the purification column during purification. Another object of the present invention is to provide a purifying agent capable of efficiently purifying a gas containing nitrogen fluoride without emitting NOx, and a purifying method using the purifying agent.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve these problems, and as a result, stannous oxide, and oxides, hydroxides, carbonates, lanthanoid oxides, hydroxides, and carbonates of alkaline earth metals. It has been found that a purifying agent containing one or more compounds selected from salts as an active ingredient is relatively stable in the air and easy to store and handle. In addition, the present inventors contacted a gas containing nitrogen fluoride as a harmful component with the purifying agent under heating to cause thermal runaway depending on the type of diluent gas during purifying or post-treatment after purifying. Without causing dangers such as rapid heat generation and generation of harmful gases, without increasing pressure loss or clogging in the purification column during purification, and without discharging NOx, efficiently removing nitrogen fluoride. It has been found that the contained gas can be purified, and the present invention has reached the purifying agent and the purifying method for the gas containing nitrogen fluoride of the present invention.
[0009]
That is, the present invention provides, as an active ingredient, stannous oxide, and at least one compound selected from oxides, hydroxides, carbonates, lanthanoid oxides, hydroxides, and carbonates of alkaline earth metals. A purifying agent for a gas containing nitrogen fluoride.
In addition, the present invention provides a method of heating a gas containing nitrogen fluoride as a harmful component under heating, using stannous oxide, and oxides, hydroxides, carbonates, and lanthanoid oxides of alkaline earth metals, and water. The present invention also provides a method for purifying a gas containing nitrogen fluoride, which comprises purifying by contacting a purifying agent containing at least one compound selected from oxides and carbonates as an active ingredient.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The purifying agent and the purifying method for a gas containing nitrogen fluoride according to the present invention include a method for purifying a gas such as nitrogen, argon, and helium, which comprises nitrogen trifluoride, dinitrogen tetrafluoride, dinitrogen difluoride, and hexafluoride. The present invention is applied to a purifying agent and a purifying method for purifying nitrogen fluoride such as dinitrogen. The purifying agent for nitrogen fluoride-containing gas of the present invention is selected from stannous oxide, and oxides, hydroxides, carbonates, lanthanoid oxides, hydroxides, and carbonates of alkaline earth metals. It is a purifying agent containing at least one compound as an active ingredient.
Further, the method for purifying a gas containing nitrogen fluoride of the present invention is a purification method in which a gas containing nitrogen fluoride is brought into contact with the purifying agent under heating to purify the gas.
[0011]
Hereinafter, the purifying agent for a gas containing nitrogen fluoride of the present invention will be described in detail.
In the purifying agent of the present invention, stannous oxide (SnO) used as one of the active ingredients has a purity of 98% or more in the form of a powder or the like, and these commercially available products are usually used. be able to.
Further, as the active ingredients other than the above, alkaline earth metal oxides, hydroxides, carbonates, lanthanoid oxides, hydroxides, and carbonates include beryllium, magnesium, calcium, strontium, barium, lanthanum, Oxides such as cerium, praseodymium, neodymium, samarium, and europium, hydroxides, and carbonates can be exemplified.However, magnesium, calcium, strontium, or lanthanum oxide, hydroxide It is preferable to use a substance or a carbonate. These alkaline earth metal compounds and lanthanoid compounds may be used alone or in combination of two or more.
[0012]
In the purifying agent of the present invention, the ratio of the number of atoms of tin contained in the purifying agent to the total number of atoms of the alkaline earth metal and the number of lanthanoid atoms is 1: 0.1 to 2.0. Thus, it is preferably prepared to be 0.3 to 1.0. When the total number of atoms of the alkaline earth metal and the lanthanoid is less than 10% of the number of tin atoms, SnO is mainly converted to SnF ₂ during purification of the gas containing nitrogen trifluoride. A converted reaction takes place. Since SnF ₂ has a density of 4.57 g / cm ³ and is smaller than SnO (density 6.95 g / cm ³ ), which is the main component, the portion where the detoxification reaction of the purifying agent is completed expands, This causes a disadvantage that the pressure loss increases or the blockage occurs in the purification column. If the total number of atoms of the alkaline earth metal and the lanthanoid exceeds 2.0 times the number of tin atoms, there is a problem in that NOx is emitted.
[0013]
In addition, the purifying agent of the present invention may include a molding aid in addition to the active ingredient in order to enhance the moldability and molding strength during granulation. As such a molding aid, metal fluorides such as lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride and lanthanum fluoride can be used. Among them, the molding strength is enhanced. It is particularly preferable to use potassium fluoride because of its excellent effect. These can be used alone or in combination of two or more. When these molding aids are added, they are added to the active ingredient and kneaded when preparing the purifying agent. The amount of the molding aid added varies depending on the molding conditions and cannot be specified unconditionally. However, if the amount is too small, the effect of the molding aid cannot be obtained, and if the amount is too large, the purification ability is reduced. It is 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the total weight of the agent.
[0014]
Further, the purifying agent of the present invention may contain impurities, inert substances, and the like that do not adversely affect the purification of nitrogen fluoride. Further, the purifying agent before use may contain water, but preferably does not contain water. Usually, the purifying agent is prepared so that the water content in the purifying agent is 2 wt% or less. In addition, even when these molding aids, impurities, inert substances, moisture and the like are contained, the content of the active ingredient in the purifying agent is usually 70% by weight or more, preferably 90% by weight or more.
[0015]
There is no particular limitation on the method of molding the purifying agent of the present invention, for example, a method of adding water to the purifying agent component to form a slurry or a cake, extruding, cutting to an appropriate length, and drying, or For example, a method of granulating a purifying agent component by tablet molding can be used.
Further, the purifying agent of the present invention can be prepared by mixing and molding stannous oxide or the like and one or more compounds selected from the above-mentioned alkaline earth metal compounds and lanthanoid compounds. It may be prepared by molding one tin or the like and molding at least one compound selected from an alkaline earth metal compound and a lanthanoid compound, and then mixing them.
In any of the preparation methods, the purifying agent of the present invention usually has a spherical shape having a diameter of about 1 to 10 mm, a cylindrical shape having a diameter of about 0.5 to 5 mm and a length of about 2 to 20 mm, or a similar shape. It is prepared by molding so as to have a shape or a size and shape corresponding to the shape.
[0016]
Next, the method for purifying a gas containing nitrogen fluoride of the present invention will be described in detail.
The purification method of the present invention is a method of purifying a gas containing nitrogen fluoride by bringing the gas into contact with the above-mentioned purifying agent under heating. However, when hydroxides and carbonates of alkaline earth metals and hydroxides and carbonates of lanthanoids are used as a part of the effective components of the purifying agent, some of the above compounds are oxidized under heating. And exhibits an effect as an oxide of an alkaline earth metal or an oxide of a lanthanoid.
[0017]
When purifying a gas containing nitrogen trifluoride by contact with a purifying agent containing stannous oxide and calcium oxide as an active ingredient by the purifying method of the present invention, the following (formula 1) (formula 2) ) Or (Equation 3) is presumed to occur. In the purification method of the present invention, CaSnF ₆ , SnO ₂ , and CaF ₂ are produced as apparent from these reaction formulas. However, the combined volume of these reaction products and the effectiveness of the purification agent before the reaction are obtained. Since the difference in the volume of the components is small, there is no possibility that the filling member (purifying agent and reaction product) of the purifying cylinder expands to cause an increase in pressure loss or blockage in the purifying cylinder. For example, if the reaction of (Equation 3), the density of SnO, CaO, which is an active ingredient of the cleaning agent, respectively 6.95 g ^/ cm 3, at ^{_{3.37g / cm 3, SnO 2,}} CaF is the reaction product ₂ densities, respectively 7.0 g ^/ cm 3, a 3.08 g / cm ^3, because these are equimolar ratio, the difference in average density of both even small differences of small volume.
[0018]
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[0019]
In the above reaction, when a lanthanide compound such as La ₂ O ₃ is used instead of the alkaline earth metal compound such as CaO, the gas containing nitrogen fluoride is purified according to the above reaction formula. .
[0020]
In the purification method of the present invention, the temperature at which the gas containing nitrogen fluoride is brought into contact with the purifying agent is usually 200 to 800 ° C, preferably 250 to 600 ° C. When the temperature is lower than 200 ° C., the ability to purify nitrogen fluoride is reduced. On the other hand, if the temperature is higher than 800 ° C., stainless steel cannot be used for the purifying column, which causes a disadvantage that a material having higher heat resistance is required.
In addition, the pressure in the purification cylinder at the time of performing purification is usually normal pressure, but it can be performed under reduced pressure such as 1 KPa to increased pressure such as 0.2 MPa (absolute pressure).
[0021]
In the purifying method of the present invention, the purifying cylinder for filling the purifying agent is usually cylindrical, and usually has an inner diameter of about 10 to 500 mm and a length of about 20 to 2000 mm. The filling length of the purifying agent filled in the purifying column is usually about 10 to 1000 mm, preferably about 50 to 500 mm. When the filling length of the purifying agent is 10 mm or less, purification of the gas containing nitrogen fluoride becomes insufficient, and when the filling length is 1000 mm or more, the pressure loss increases. As means for heating the purifier, a heater is usually provided outside the purifier, and the temperature is controlled by an external control device. In the purifying method of the present invention, the purifying agent can be used not only as a fixed bed but also as a moving bed and a fluidized bed.
[0022]
The flow rate of the gas containing nitrogen fluoride when the purification method of the present invention is applied is not particularly limited, but generally, the flow rate can be reduced as the concentration of nitrogen fluoride contained in the gas is higher. desirable. The concentration of nitrogen fluoride is usually 1% or less, but if the flow rate is small, a gas containing a higher concentration of nitrogen fluoride can be purified.
The purifying cylinder is designed in accordance with the concentration and flow rate of nitrogen fluoride. At a relatively low concentration such as 0.1% or less of nitrogen fluoride, the cylinder linear velocity (LV) becomes 0.5 to 0.5%. When the concentration of nitrogen fluoride is 50 cm / sec and the concentration of nitrogen fluoride is about 0.1 to 1%, the LV is in the range of 0.05 to 20 cm / sec, and when the concentration of nitrogen fluoride is 1% or more, the LV is 10 cm / sec or less. It is preferable to design.
[0023]
【Example】
Next, the purifying agent and purifying method for a gas containing nitrogen fluoride of the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.
[0024]
Example 1
(Preparation of purifying agent)
Commercially available stannous oxide (purity 99%) and calcium oxide (purity 99%) were pulverized to 100 μm or less and mixed so that the ratio of the number of atoms (Sn: Ca) was 1: 0.5. . After packing the mixture in a mold having an inner diameter of 20 mm and a height of 5 mm, the agent obtained by molding by pressing with a hydraulic jack at a pressure of 150 to 160 kg / cm ² for 10 seconds is crushed, and further sieved. Those that passed through the 3.36 mm opening and did not pass through the 2.00 mm opening were used as purifying agents.
[0025]
(Purification test)
The purifying agent was filled in a SUS316L purifying cylinder having an inner diameter of 23.9 mm and a length of 200 mm so that the filling length became 100 mm. After the temperature of the purifying agent in the purifying column is heated to 400 ° C., nitrogen containing NF ₃ (flow rate 13.46 ml / min) (total flow rate 1346 ml / min) is introduced into the purifying column to purify gas containing NF _3. did.
During this time, a part of the purified gas discharged from the outlet of the purification column is sampled every 10 minutes, analyzed by gas chromatography (detection lower limit: 10 ppm), and the time until NF ₃ is detected is measured. In addition, the purification amount (L) (purification processing capacity) of NF ₃ per 1 L (liter) of the purifying agent was determined, and the presence or absence of NOx emission was investigated using a detector tube (manufactured by Gastech Co., Ltd.). Table 1 shows the results.
[0026]
Examples 2 and 3
The mixing ratio of stannous oxide and calcium oxide in the preparation of the purifying agent of Example 1 was mixed such that the ratio of the number of atoms (Sn: Ca) was 1: 0.3 and 1: 0.75, respectively. Otherwise, a purifying agent was prepared in the same manner as in Example 1. Using these purifying agents, a purification test of NF ₃ was performed in the same manner as in Example 1. Table 1 shows the results.
[0027]
Examples 4 and 5
A NF ₃ purification test was performed in the same manner as in Example 1 except that the concentration of NF ₃ in the purification test of Example 1 was changed to 0.2% and 2.0%, respectively. Table 1 shows the results.
[0028]
Examples 6 and 7
A purifying agent was prepared in the same manner as in Example 1 except that calcium oxide in the preparation of the purifying agent of Example 1 was changed to calcium hydroxide and calcium carbonate, respectively. Using these purifying agents, a purification test of NF ₃ was performed in the same manner as in Example 1. Table 1 shows the results.
[0029]
Examples 8 and 9
A purifying agent was prepared in the same manner as in Example 1, except that calcium oxide in the preparation of the purifying agent of Example 1 was changed to magnesium oxide and strontium oxide, respectively. Using these purifying agents, a purification test of NF ₃ was performed in the same manner as in Example 1. Table 1 shows the results.
[0030]
Example 10
(Preparation of purifying agent)
Commercially available stannous oxide (purity 99%) and lanthanum oxide (purity 99%) were pulverized to 100 μm or less and mixed so that the ratio of the number of atoms (Sn: La) became 1: 0.5. . After packing the mixture in a mold having an inner diameter of 20 mm and a height of 5 mm, the agent obtained by molding by pressing with a hydraulic jack at a pressure of 150 to 160 kg / cm ² for 10 seconds is crushed, and further sieved. Those that passed through the 3.36 mm opening and did not pass through the 2.00 mm opening were used as purifying agents.
[0031]
(Purification test)
The purifying agent was filled in a SUS316L purifying cylinder having an inner diameter of 23.9 mm and a length of 200 mm so that the filling length became 100 mm. After the temperature of the purifying agent in the purifying column is heated to 400 ° C., nitrogen containing NF ₃ (flow rate 13.46 ml / min) (total flow rate 1346 ml / min) is introduced into the purifying column to purify gas containing NF _3. did.
During this time, a part of the purified gas discharged from the outlet of the purification column is sampled every 10 minutes, analyzed by gas chromatography (detection lower limit: 10 ppm), and the time until NF ₃ is detected is measured. In addition, the purification amount (L) (purification processing capacity) of NF ₃ per 1 L (liter) of the purifying agent was determined, and the presence or absence of NOx emission was investigated using a detector tube (manufactured by Gastech Co., Ltd.). Table 1 shows the results.
[0032]
Examples 11 and 12
The mixing ratio of stannous oxide and lanthanum oxide in the preparation of the purifying agent of Example 10 was mixed such that the ratio of the number of atoms (Sn: La) was 1: 0.3 and 1: 0.75, respectively. Except for the above, a purifying agent was prepared in the same manner as in Example 10. Using these purifying agents, a purification test of NF ₃ was carried out in the same manner as in Example 10. Table 1 shows the results.
[0033]
Examples 13 and 14
A NF ₃ purification test was performed in the same manner as in Example 10 except that the concentration of NF ₃ in the purification test of Example 10 was changed to 0.2% and 2.0%, respectively. Table 1 shows the results.
[0034]
Examples 15 and 16
A purifying agent was prepared in the same manner as in Example 10, except that lanthanum hydroxide and lanthanum carbonate in the preparation of the purifying agent of Example 10 were respectively changed. Using these purifying agents, a purification test of NF ₃ was carried out in the same manner as in Example 10. Table 1 shows the results.
[0035]
Example 17
(Preparation of purifying agent)
Commercially available stannous oxide (purity 99%), calcium oxide (purity 99%) and lanthanum oxide (purity 99%) are pulverized to 100 μm or less, and the atomic ratio (Sn: Ca: La) is 1 : 0.3: 0.2. After packing the mixture in a mold having an inner diameter of 20 mm and a height of 5 mm, the agent obtained by molding by pressing with a hydraulic jack at a pressure of 150 to 160 kg / cm ² for 10 seconds is crushed, and further sieved. Those that passed through the 3.36 mm opening and did not pass through the 2.00 mm opening were used as purifying agents.
[0036]
(Purification test)
The purifying agent was filled in a SUS316L purifying cylinder having an inner diameter of 23.9 mm and a length of 200 mm so that the filling length became 100 mm. After the temperature of the purifying agent in the purifying column is heated to 400 ° C., nitrogen containing NF ₃ (flow rate 13.46 ml / min) (total flow rate 1346 ml / min) is introduced into the purifying column to purify gas containing NF _3. did.
During this time, a part of the purified gas discharged from the outlet of the purification column is sampled every 10 minutes, analyzed by gas chromatography (detection lower limit: 10 ppm), and the time until NF ₃ is detected is measured. In addition, the purification amount (L) (purification processing capacity) of NF ₃ per 1 L (liter) of the purifying agent was determined, and the presence or absence of NOx emission was investigated using a detector tube (manufactured by Gastech Co., Ltd.). Table 1 shows the results.
[0037]
Example 18
The mixing ratio of stannous oxide, calcium oxide, and lanthanum oxide in the preparation of the purifying agent of Example 17 was adjusted such that the ratio of the number of atoms (Sn: Ca: La) was 1: 0.2: 0.3. Except for mixing, a purifying agent was prepared in the same manner as in Example 17. Using these purifying agents, a purification test of NF ₃ was performed in the same manner as in Example 17. Table 1 shows the results.
[0038]
Comparative Example 1
(Preparation of purifying agent)
To 1000 g of commercially available stannous oxide (purity: 99%), an aqueous solution in which 50 g of potassium fluoride (KF, manufactured by Kanto Chemical Co., Ltd., special grade of reagent) was dissolved in 65 g of water was added and stirred. The obtained cake is extruded from a nozzle plate having a diameter of 1.6 mm by an extrusion molding machine, and the obtained molded product is cut into pellets having a length of about 3 to 5 mm. A purifying agent was prepared by drying for an hour.
[0039]
(Purification test)
A purification test for NF ₃ was performed in the same manner as in Example 1 except that the above-mentioned purifying agent was used. However, the purification test was stopped because the pressure loss of the purification column became large before NF ₃ was detected. Table 1 shows the results of determining the purification processing amount (L) (purification processing capacity) of NF ₃ per 1 L (liter) of the purifying agent based on whether or not NOx is discharged and the time until the purification test is stopped.
[0040]
Comparative Example 2
Commercially available calcium oxide (purity: 99%) was pulverized to 100 μm or less, packed in a mold having an inner diameter of 20 mm and a height of 5 mm, and then pressed with a hydraulic jack at a pressure of 150 to 160 kg / cm ² for 10 seconds. . The agent obtained by the molding was crushed, and a material passed through a sieve of 3.36 mm and not passing through a mesh of 2.00 mm was further used as a purifying agent.
A purification test for NF ₃ was performed in the same manner as in Example 1 except that the above-mentioned purifying agent was used. However, immediately after the start of the purification test, emission of several thousand ppm of NO was confirmed, so the purification test was stopped.
[0041]
Comparative Example 3
Commercially available lanthanum oxide (purity: 99%) was pulverized to 100 μm or less, packed in a mold having an inner diameter of 20 mm and a height of 5 mm, and then pressed with a hydraulic jack at a pressure of 150 to 160 kg / cm ² for 10 seconds. . The agent obtained by the molding was crushed, and a material passed through a sieve of 3.36 mm and not passing through a mesh of 2.00 mm was further used as a purifying agent.
A purification test for NF ₃ was performed in the same manner as in Example 1 except that the above-mentioned purifying agent was used. However, immediately after the start of the purification test, emission of several thousand ppm of NO was confirmed, so the purification test was stopped.
[0042]
[Table 1]

[0043]
【The invention's effect】
The gas purifying agent containing nitrogen fluoride of the present invention can easily be stored and handled. Further, according to the method for purifying a gas containing nitrogen fluoride of the present invention, a thermal runaway may be caused depending on a kind of a diluting gas during the purification, or a danger such as rapid generation of heat or generation of a harmful gas may be caused in a post-treatment after the purification. Thus, the gas containing nitrogen fluoride can be efficiently purified without increasing the pressure loss or clogging in the purification column during purification, and without discharging NOx.

Claims

It contains stannous oxide and at least one compound selected from the group consisting of oxides, hydroxides, and carbonates of alkaline earth metals, oxides, hydroxides and carbonates of lanthanoids as active ingredients. Purifier for gas containing nitrogen fluoride.

The purifying agent for a gas containing nitrogen fluoride according to claim 1, wherein the alkaline earth metal is magnesium, calcium, or strontium.

The purifying agent for a gas containing nitrogen fluoride according to claim 1, wherein the lanthanoid is lanthanum.

2. The purifying agent for a gas containing nitrogen fluoride according to claim 1, wherein the purifying agent contains 70% or more of the active ingredient as a weight ratio.

The nitrogen according to claim 1, wherein the ratio of the number of atoms of tin contained in the purifying agent to the number of atoms of the alkaline earth metal and the number of atoms of the lanthanoid is 1: 0.1 to 2.0. Purifier for gas containing fluoride.

The purifying agent for a gas containing nitrogen fluoride according to claim 1, wherein the purifying agent contains a metal fluoride as a molding aid together with the active ingredient.

7. The purifier for a gas containing nitrogen fluoride according to claim 6, wherein the metal fluoride is potassium fluoride.

2. The nitrogen fluoride-containing gas according to claim 1, wherein the nitrogen fluoride is at least one selected from nitrogen trifluoride, dinitrogen tetrafluoride, dinitrogen difluoride, and dinitrogen hexafluoride. Purifier.

Gas containing nitrogen fluoride as a harmful component, under heating, from stannous oxide and oxides, hydroxides, carbonates, lanthanoid oxides, hydroxides and carbonates of alkaline earth metals A method for purifying a gas containing nitrogen fluoride, wherein the gas is purified by contact with a purifying agent containing at least one selected compound as an active ingredient.

The method for purifying a gas containing nitrogen fluoride according to claim 9, wherein the contact temperature between the gas containing nitrogen fluoride and the purifying agent is 200 to 800C.