JP3707905B2

JP3707905B2 - Combustion apparatus for producing high-purity steam and high-purity steam production method

Info

Publication number: JP3707905B2
Application number: JP09172097A
Authority: JP
Inventors: 耕一白石; 浩人生野; 義展長峯; 昌憲藤本; 寛冨田; 良夫笠井; 圭希永井
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1997-03-26
Filing date: 1997-03-26
Publication date: 2005-10-19
Anticipated expiration: 2017-03-26
Also published as: JPH10270438A

Description

【０００１】
【発明の属する技術分野】
本発明は高純度水蒸気製造用燃焼装置及び高純度水蒸気製造方法に関し、特に、半導体製造プロセスの酸化工程に使用される高純度水蒸気ガスを製造する燃焼装置であって、ガス噴出ノズルの溶損を防止し、生成される水蒸気ガス中の不純物の低減を図ると共に耐久性に優れる高純度水蒸気製造用燃焼装置及び高純度水蒸気製造方法に関する。
【０００２】
【従来の技術】
半導体製造プロセスの酸化膜形成工程において、酸化膜形成方法の一つとして、ウエハを高温水蒸気ガスと接触させる方法がある。この酸化膜形成に使われる水蒸気ガスは、半導体ウエハを汚染するアルカリ金属等の不純物ができるかぎり低減された高純度なものが望まれ、一般に、高純度の水素ガスと酸素ガスとを接触させ水素ガスを燃焼させて製造されている。水素ガスの燃焼方式として、例えば特開昭５６−６２３２６号公報に開示されるように、加熱炉内に被酸化ウエハをセットし、加熱炉内に、直接、水素ガス及び酸素ガスを導入して燃焼させ水蒸気を発生させる方式がある。しかし、この方式は、加熱炉内温度が火炎によって左右され酸化処理条件を一定にすることが難しいという問題点があった。
【０００３】
上記問題を解決するため、例えば特開昭５７−１８３２８号公報に開示されるように、ウエハ酸化炉とは別に外部に燃焼装置を設けて水素ガスを燃焼させて水蒸気をガスを生成し、得られる水蒸気ガスを炉内に導入する方式が提案された。この外部燃焼方式で水蒸気ガスを製造する場合は、半導体製造工程の酸化処理条件が安定することから、現在、この方式が多く採用されている。この外部燃焼方式の水素ガス燃焼装置は、通常、例えば図８に概略構成図及び図９にそのＤ−Ｄ線断面における端面図を拡大して示したように、燃焼室７２、燃焼室７２で発生した高純度水蒸気を外部のウエハ熱処理炉等に供給する水蒸気供給管７３と水素及び酸素ガスを供給するガス供給管７４を有しており、主に石英ガラス材を用いて構成される。燃焼室７２の外周部には例えば水冷筒等の冷却装置７９が配設され、ガス供給管７４の外周部には、スタート時に供給する水素及び酸素ガスを加熱して自然着火させるための着火用の予熱用ヒータ８０が配設される。ガス供給管７４は、２重円管からなり中心部に水素ガス供給管７５が配置され、その外周に環状に酸素ガス供給管７６が配置され、水素ガス供給管７５及び酸素ガス供給管７６には、それぞれ水素ガス導入管７７及び酸素ガス導入管７８が接続される。また、ガス供給管７４の先端部に連続してガス噴出ノズルが配備され、ガス供給管７４の先端部の外周部には、通常、断熱材８１が配設される。水素及び酸素ガスは、予熱用ヒータ８０で加熱されガス噴出ノズルから燃焼室に噴出され、燃焼室内で接触し自然着火した後、水素ガスが酸化され燃焼して水蒸気を製造する。
【０００４】
上記のように構成される燃焼装置は、前記したように一般に石英ガラス材で形成されている。この場合、特に、燃焼時の高温によりガス噴出ノズル先端が溶損消耗したり、また、ガス噴出ノズル先端や燃焼室内壁が結晶化し剥離、脱落して破損するという問題が生じている。これらは、水蒸気を発生する燃焼装置の寿命が短いという耐久性の問題だけでなく、生成する水蒸気ガス中に上記溶損等により発生するパーティクルや石英ガラス材中の不純物が混入するため、水蒸気で酸化処理する半導体シリコンウエハを汚染するおそれがある。このため、最終的にはこれらの水蒸気を用いる半導体製造工程の半導体素子製造の歩留まりを低下させる原因ともなる。また、最近の半導体ウエハの大口径化に伴い、水蒸気製造量の増大が望まれているが、そのために供給ガス量を増加することは、ガス噴出ノズル先端及び燃焼室内をより高温とすることになり、ノズル先端の溶損等を一層増大させることから実施は難しい。
【０００５】
外部燃焼方式の上記問題を解決する方法として、例えば特開平６−２６７９３２号公報では、酸素ガス噴出ノズルを水素ガス噴出ノズル先端よりも燃焼室（容器）内方向に突出させると同時に、酸素ガスを広範囲に分散させて噴出させる複数の噴出孔を形成した分散型酸素ガス噴出ノズルを提案している。この方法は、前記特公昭６３−６０５２８号公報等に記載の従来の外部燃焼方式のガス供給管で一般的であった２重円管構造（中心管に水素ガス、外周管に酸素ガスを供給）のものと比較し、水素ガス噴出ノズルから遠い離れた位置で、且つ、広い範囲で酸素ガスを噴出させることで、酸素ガス噴出ノズル部に太い火炎を形成させるようにしたものである。これにより、従来のガス噴出ノズルに比し、水素ガス噴出ノズル先端が加熱されず、また燃焼室内温度が高温になることも防止できる。そのため、水素及び酸素ガスの供給量を増大させて従来より大量の高純度水蒸気ガスが製造でき、大口径化される半導体ウエハの酸化処理用に製造する水蒸気ガス量の増大を図るものである。
【０００６】
【発明が解決しようとする課題】
上記提案のガス噴出ノズルを改良した燃焼装置によれば、半導体製造工程の酸化処理プロセスの安定化や大口径ウエハの処理に要する大量の高純度水蒸気ガスの供給、燃焼装置の耐久性等の問題が解決される。しかしながら、発明者らによれば、燃焼室温度が低下するにも拘らず、水蒸気ガス中の不純物含有量レベルについては、十分満足できるレベルまで低減しないことが知見された。即ち、後記の比較例に示すように、上記提案の燃焼装置においても、前記した従来の２重管のガス供給管から構成されるガス噴出ノズルと比較して、製造される水蒸気ガス中の不純物含有量はほとんど同程度であることが確認された。
【０００７】
特開平６−２６７９３２号公報提案の燃焼装置において、水蒸気ガス中の不純物含有量が期待されるほど低減しない理由としては、水素ガス噴出ノズル付近は温度低下し、燃焼室（容器）の上部及び外周の温度も低下するが、燃焼室内で最も高温となる火炎が上記のように酸素ガス噴出ノズル近傍に形成される結果、酸素ガス噴出ノズル先端の温度上昇は避けられず、このため酸素ガス噴出ノズル先端では従来と同様に石英ガラス材が溶損し、パーティクルや石英ガラス部材中の不純物が水蒸気ガス中に混入するためと推定される。即ち、従来の水素ガス及び酸素ガスがほぼ同位置から噴出されて火炎が形成されるガス噴出ノズルでは、供給ガスのガス噴出ノズル全体の先端が溶損されるのに比し、上記提案のものでは水素ガス噴出ノズル先端の溶損等は防止できるが、酸素ガス噴出ノズル先端では同様の現象が生じるためであると推定される。また、上記提案の燃焼装置では、ガス供給管先端部でガス噴出ノズルの連続する部分外周部を、前記図８及び９で示した従来の燃焼装置と同様に断熱材を用いて被っているため、火炎からの熱が放出されにくく、ガス噴出ノズルの噴出部やガス供給管のガス噴出ノズルへの連続する部分付近の温度が高くなり易く、ガス噴出ノズル全体が高温となり、従来と同様にノズル先端の溶損等が生じるためと推定される。更に、上記断熱材としては、通常、アルミナ系やシリカ系の耐火物が用いられ、これら断熱材が予期しない高温に晒されることにもなり、断熱材中の不純物が隣接するノズル部材に拡散する可能性もあり、そのことも不純物を，増加させる原因になり得ると推定される。
【０００８】
発明者らは、先ず、上記した高純度水蒸気製造用燃焼装置において製造され、特に、半導体製造工程の酸化処理工程に導入する高純度水蒸気ガス中の不純物含有量の問題に鑑み、その水蒸気ガス中の不純物含有量の低減について検討した。例えば、ノズル構成部材を石英ガラスから高純度合成石英ガラスとする部材を高純度化する方法もあるが、ノズル付近の温度が上昇することによって外部から不純物が拡散するおそれもあり、また、高純度合成石英ガラスを用いても高温のガス噴出ノズル先端で石英ガラスがガス中に溶解して低温部で再析出してパーティクル生成することは従来の石英ガラス部材と同様である。このため、発明者らは、得られる水蒸気ガス中の不純物含有量を十分に低減させるため、燃焼装置のガス供給管及びガス噴出ノズルについてより根本的な解決を図るべく鋭意検討した。その結果、ガス供給管及びガス噴出ノズルの高温化を防止することにより不純物含有量の低減が顕著となることを見出し、本発明を完成した。
【０００９】
本発明にかかる高純度水蒸気製造用燃焼装置は、燃焼室と、水素ガス供給管及び酸素ガス供給管からなるガス供給管とを有する高純度水蒸気製造用燃焼装置において、前記ガス供給管のガス噴出ノズル先端部に溶損防御機構を具備し、前記溶損防御機構が、前記ガス供給管のガス噴出ノズル先端部の水素ガス供給管と酸素ガス供給管の間に介在して、冷却媒体を流通可能に形成した石英ガラス製の冷却部からなる放熱手段であることを特徴としている。
【００１０】
ここで、更に、酸素ガス供給管の外周部に、冷却媒体を流通可能に形成した石英ガラス製の冷却部を配備してなることが好ましく、また、水素ガス供給管と酸素ガス供給管の間に介在し、冷却媒体を流通可能に形成した石英ガラス製の冷却部は、水素ガス供給管の先端部径を細め、細くなった外環部に冷却媒体の供給管と排出管が配備して形成されていることが好ましい。更に、酸素ガス供給管はストレートに形成されていることが望ましい。
また、上記本発明にかかる高純度水蒸気製造用燃焼装置は、燃焼室と、水素ガス供給管及び酸素ガス供給管からなるガス供給管とを有する高純度水蒸気製造用燃焼装置において、前記ガス供給管のガス噴出ノズル先端部に溶損防御機構を具備し、前記溶損防御機構が、前記ガス供給管が３重管であって中心から水素ガス、不活性ガス及び酸素ガスの供給管となし、水素ガス供給管と酸素ガス供給管とが隣接することなく不活性ガス供給管を介して配置し、前記ガス噴出ノズル先端と所定の距離を有して火炎を形成させてなることを特徴としている。
また、上記本発明にかかる高純度水蒸気製造用燃焼装置は、燃焼室と、水素ガス供給管及び酸素ガス供給管からなるガス供給管とを有する高純度水蒸気製造用燃焼装置において、前記ガス供給管のガス噴出ノズル先端部に溶損防御機構を具備し、前記溶損防御機構が、前記ガス供給管が４重管であって中心から不活性ガス、水素ガス、不活性ガス及び酸素ガスの供給管となし、水素ガス供給管と酸素ガス供給管とが隣接することなく不活性ガス供給管を介して配置し、前記ガス噴出ノズル先端と所定の距離を有して火炎を形成させてなることを特徴としている。
【００１１】
また、本発明によれば、前記高純度水蒸気製造装置用燃焼装置を用い、前記ガス供給管を加熱して流通する水素ガス及び酸素ガスを予熱して、前記ガス噴出ノズルから燃焼室に噴出して着火させた後、前記ガス供給管の加熱を停止すると同時に、前記放熱手段により放熱して水素を燃焼させて水蒸気を生成することを特徴とする高純度水蒸気製造方法が提供される。
また、本発明によれば、前記高純度水蒸気製造装置用燃焼装置を用い、前記ガス供給管を加熱して流通する水素ガス及び酸素ガスを予熱して、前記ガス噴出ノズルから燃焼室に噴出して着火させた後、前記ガス供給管の加熱を停止すると同時に、水素ガス、酸素ガス、不活性ガスを所定量供給し、水素を燃焼させて水蒸気を生成することを特徴とする高純度水蒸気製造方法が提供される。
【００１２】
本発明の高純度水蒸気製造用装置は上記のように構成され、燃焼室に水素及び酸素を供給してそれら供給ガスを接触して燃焼させるに当たり、着火後、（１）ガス供給管のガス噴出ノズル先端部に冷却室等の放熱手段を配備することから、燃焼室に水素及び酸素ガスを噴出するガス噴出ノズル先端部を冷却でき、水素燃焼火炎で加熱されるガス噴出ノズル先端部の熱を冷却部で放熱することができ、ガス噴出ノズル全域、特にその先端部の高温化を防止でき、溶損が抑制される。また、（２）ガス供給管を３重管または４重管に形成し、水素ガスと酸素ガスの供給管を隣接せずに、その間に不活性ガス供給管を配置することから、水素ガス及び酸素ガスがそれぞれガス噴出ノズルから噴出された直後に接触することがなく、ガス噴出ノズル先端より離れた燃焼室内に水素燃焼火炎が形成されるため、ガス噴出ノズル先端の加熱を防止でき、その溶損が抑制される。
【００１３】
また、本発明の高純度水蒸気製造方法は、上記のように構成される高純度水蒸気製造用燃焼装置の運転において、操作開始時にガス供給管を加熱して、水素及び酸素ガスを予熱して着火させた後は、ガス供給管の加熱を停止し、ガス噴出ノズル先端部に具備される冷却部配設、火炎の隔離形成、断熱材不使用等の溶損防御機構の作用により、燃焼火炎でガス噴出ノズル先端部が加熱されても放熱されることから過度に高温化されることがない。このため、本発明において、これらガス噴出ノズルの過度な高温加熱が防止され、構成材料の石英ガラス材の溶損を抑制できることから、従来の燃焼装置からの水蒸気ガスに比し、本発明で製造される水蒸気ガス中の不純物含有量を著しく低減することができ、特に、半導体製造工程のウエハ酸化工程で要求される高純度水蒸気ガスとして好適である。
【００１４】
【発明の実施の形態】
以下、本発明の実施例について図面を参照しながら詳細に説明する。但し、本発明は下記実施例により制限されるものでない。
先ず、第１の実施例について説明する。図１は、本発明の高純度水蒸気発生装置に係る第１の実施例である燃焼装置の構造の概要を示した説明図であり、図２は、図１のＡ部分の拡大図である。図１及び図２において、燃焼装置１の主要部は、燃焼室２、燃焼室２で発生した高純度水蒸気をウエハ熱処理炉に供給する水蒸気供給管３、及び、燃焼室２に燃焼原料ガスを供給するガス供給管４で構成され、これらの主要部は従来と同様に石英ガラス材で形成される。ガス供給管４は、中心部に水素ガス供給管５が配置され、その外周に環状に酸素ガス供給管６が配置されて構成される。水素ガス供給管５及び酸素ガス供給管６には、それぞれ水素ガス導入管７及び酸素ガス導入管８がそれぞれ接続される。また、燃焼室２の外周部には例えば水冷筒等の冷却装置９が配設され、ガス供給管４の外周部には着火時に、供給する水素及び酸素ガスを加熱して自然着火させるための予熱用ヒータ１０が配設される。これらの構成は、前記した従来の燃焼装置とほぼ同様である。着火後は、各ガス供給量を燃焼装置、ノズルサイズ等の燃焼条件に応じて適宜選択制御し水素の酸化による燃焼で、高純度水蒸気を生成することができ、水蒸気供給管を経て所定の半導体シリコンウエハ熱処理工程に供給する。
【００１５】
本発明の燃焼装置１において、図２に拡大して示したように、石英ガラス製のガス供給管４の水素ガス供給管５及び酸素ガス供給管６の先端部の各ガス噴出ノズルには、それぞれ石英ガラス製の冷却部１１、１２が配備される。冷却部１１、１２には、それぞれ冷却媒体供給管１３、１４及び冷却媒体排出管１５、１６を配備し、各冷却部に水、Ｎ_２、Ａｒ等の冷却媒体を供給してノズル先端部を冷却媒体で冷却できるように構成する。水素ガス供給管５の先端の内周部に環状に配備する冷却部１１は、水素ガス供給管５の先端部径を細め、細くなった外環部に冷却媒体の供給管１３と排出管１４を配備して形成される。また、酸素ガス供給管６のノズル先端部の冷却部１２は、供給管６先端の外周部に環状管を配備して形成する。図２では、水素及び酸素ガスの各供給管の外周に、それぞれ冷却部を配備する形式を示したが、水素ガス供給管５と酸素ガス供給管６の間、即ち、水素ガス供給管５の外周壁と酸素ガス供給管６の内周壁が形成する冷却部１１のみを配備して冷却部を共有させ、各周壁を介して水素及び酸素ガスの両方を冷却することもできる。このように各ガス供給管のノズル先端部を冷却することにより、水素ガスと酸素ガスの燃焼の際に高温化し易いノズル先端部を直接的に放熱することができる。また、水素ガス供給管５の先端部径が細くなり、水素ガスの流速を速めることができ、一方、酸素ガス供給管はストレートに形成され、酸素ガスは直線状に噴出できることから、ガス供給管のノズル先端部が過度に加熱されることがない。このため、ノズル先端の失透や燃焼室内の過熱を防止することができ、水素ガス燃焼により高純度水蒸気を大量に発生させることができ、大口径化された半導体シリコンウエハ基板への酸化膜形成にも十分に対応することができる。なお、各冷却室の配備方式は、特に上記に限定されるものでなく各ガス供給管の先端部を所定に冷却できればよい。
【００１６】
次に、第２の実施例について説明する。図３は、本発明の高純度水蒸気発生装置に係る第２の実施例である燃焼装置の構造の概要を示した説明図であり、図４は図３におけるＢ−Ｂ線断面での端部の拡大図である。図３において、燃焼装置３１はガス供給管３４が３重円管に形成される以外は、図１の燃焼装置と同様である。図３において、図１と同一部材に関しては同一の符号を付し説明を省略する。図１と異なるガス供給管３４は、中心部に水素ガス供給管３５が配置され、その外周に二重に環状管を配備し、外側に酸素ガス供給管３６、内側に不活性ガスガス供給管３９を配置して構成される。水素ガス供給管３５、酸素ガス供給管３６及び不活性ガス供給管３９には、それぞれ水素ガス導入管３７、酸素ガス導入管３８及び不活性ガス導入管４０がそれぞれ接続される。図４にその断面端部を拡大して示したように、ガス供給管３４の３重円管は同心円状に形成される。このように三重円管として、水素ガスと酸素ガスの供給を、窒素ガス、ヘリウム、アルゴンガス等の不活性ガスを間に介して燃焼させることから、水素ガスと酸素ガスとがノズル先端直後で接触することなく離れた位置で接触して燃焼火炎が形成される。このためノズル先端部が高温になり失透して耐久性が短期化することを防止できる。不活性ガスとしては、窒素ガス、ヘリウム、アルゴンガス等が一般的である。このうち、アルゴンガスは高純度ガスが比較的安価に得られ、熱伝導率がよく好適である。
【００１７】
図５は、本発明の第２の他の実施例の燃焼装置の構造の概要を示した説明図であり、図６は図５におけるＣ−Ｃ線断面での端部の拡大図である。図５及び図６において、燃焼装置５１は、ガス供給管５４が同心円状の４重円管に形成される以外は、図３の燃焼装置と同様である。図５において図３と同一部材に関しては同一の符号を付し説明を省略する。４重円管のガス供給管５４は、中心に不活性ガス供給管５９を配置し、その外周に環状に最外管から順次、酸素ガス供給管５６、不活性ガス供給管６０及び水素ガス供給管５５が配置される。不活性ガス供給管５９、水素ガス供給管５５、不活性ガス供給管６０及び酸素ガス供給管５６には、それぞれ不活性ガス導入管６１、水素ガス導入管５７、酸素ガス導入管５８及び不活性ガス導入管６２がそれぞれ接続される。このようにガス供給管５４を４重円管とした場合、上記の３重円管ノズルと同様にノズル先端部より離れた位置に火炎を形成でき、ノズル先端部の失透による溶存を防止して耐久性を向上すると共に、中心部からの不活性ガスの流出量を適宜選択して流出することにより燃焼で形成される火炎の温度を制御することができ、燃焼室の過熱をより防止することができる。
【００１８】
上記の第２の実施例のいずれにおいて、ガス供給管３４または５４の外周部に配設された予熱ヒータ１０により供給する水素及び酸素ガスを加熱して自然着火させる場合、着火シーケンス時には、不活性ガス供給管３９、５９、６０への不活性ガスの供給を、流量減少または停止して着火させ、着火後、使用する燃焼装置の容量やノズルの大きさ等の燃焼条件に応じて、不活性ガス流量、水素ガス及び酸素ガスの流量を所定量に適宜選択して供給し、ノズルより流出させるのが好ましい。また、火炎状態をフレームセンサーにより検出し、常に安定な火炎状態を保持するように各供給ガス量を制御することが好ましい。また、フレームセンサー検出することにより、火炎が消えた場合には、水素ガス及び酸素ガスの供給を停止し、不活性ガスのみ供給して燃焼を停止する等の早急に対応することもできる。更に、本発明において、第２の実施例の多重円管のガス供給管の各ガス供給管の先端部に、前記の本発明の第１の実施例と同様に冷却部を所定に配備して各供給ガスを冷却してノズルより流出させ、燃焼室の過熱をより一層防止することもできる。この場合、冷却部は配備方式は制限されるものでなく、例えば、前記図１の方式と同様にガス供給管の最外管は先端外周に環状円管を配備して、内管は図１における水素ガス供給管５の先端部を細くする方式により冷却部を配備させることができる。
【００１９】
なお、前記ガス供給管のガス噴出ノズル先端部が石英ガラスよりなる場合には、該先端部の温度が９００℃以下となるように、冷却部を所定に配備して冷却することが好ましい。好ましくは７００℃以下、更に好ましくは５００℃以下に冷却するのが好ましい。
【００２０】
更に、上記本発明の高純度水蒸気製造用燃焼装置において、装置を主に形成する石英ガラス材として、その表面をフッ化水素酸処理、高温塩化水素ガス処理またはこれらを組合わせて処理することにより、表面から約１００μｍの深さの表面近傍におけるナトリウム、鉄、銅、アルミニウム等の金属不純物が１０ｎｇ／ｇ以下にして用いることが好ましく、または、燃焼装置に供給される水素ガスや発生する水蒸気による侵食のおそれを考慮して上記金属不純物が１０ｎｇ／ｇ以下の高バルク純度の合成石英ガラス材を用いることがより好ましい。これら高バルク純度の石英ガラス材を用いた高純度水蒸気製造用燃焼装置で製造される水蒸気の上記金属不純物の含有量は１０ｎｇ／ｍ^３以下となることから、より高純度な水蒸気が要求される場合に用いることができる。
【００２１】
【実施例】
以下、本発明を実施例に基づき更に詳細に説明する。但し、本発明は下記実施例により制限されるものでない。
実施例１
前記図１と同様に構成された燃焼装置を用い、水素ガス供給管５に水素ガスを６リットル／分で、酸素ガス供給管６に酸素ガスを５リットル／分で流通させてノズル先端から流出させ、予熱ヒータ１０によりガス供給管４を９５０℃に加熱して燃焼室２内で着火させて、そのまま１時間燃焼させた。この場合、それぞれ冷却部１１、１２へは、それぞれ冷却媒体供給管１３、１４から約１５℃の水を１リットル／分の流量で流通させて冷却媒体排出管１５、１６から排出し、水素ガス供給管５及び酸素ガス供給管６の先端部を約５０℃に冷却し、同時に水冷筒９に同様の水を流通させた。このようにして、燃焼室２では水素の酸化反応（燃焼）により水蒸気ガスを生成した。水蒸気供給管３から流出する水蒸気ガス中の不純物量を測定した。その結果を表１に示した。
【００２２】
実施例２
実施例１と同一の燃焼装置を用い、着火後、予熱用ヒーター１０の加熱を停止し、冷却効果をより高めた以外は、全く同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物量を測定した。その結果を表１に示した。
【００２３】
実施例３
実施例１と同一の燃焼装置を用い、冷却媒体をアルゴンとして、水素ガスの冷却部１１及び酸素ガスの冷却部１２へ、それぞれ冷却媒体供給管１３、１４を経て３リットル／分の流量で流通した以外は、予熱ヒータでの加熱を継続したことも含め全く同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物量を測定した。その結果を表１に示した。
【００２４】
【表１】

【００２５】
実施例４
予熱用ヒーター１０の加熱を停止し、冷却効果をより高めた以外は、実施例３と全く同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物量を測定した。その結果を表１に示した。
【００２６】
比較例１
実施例１と同一装置を用い、冷却部１１、１２に冷却媒体を流すことなく、前記した従来法と同様にガス供給管４の先端部に断熱材を配設した以外は、実施例１と同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物含有量を測定した。その結果を表１に示した。
【００２７】
比較例２
前記図８及び９に示した燃焼装置とほぼ同様であり、かつ酸素ガス噴出ノズルを水素ガス噴出ノズル先端よりも燃焼室内方向に突出させ、またガス分散円孔を複数形成した分散型酸素ガス噴出ノズルを用い、実施例１と同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物含有量を測定した。その結果を表１に示した。
【００２８】
上記実施例１〜４及び比較例１〜２により、ガス供給管の先端部に冷却部を配備して水素ガス及び酸素ガスを冷却することにより、生成され流出する水蒸気ガス中の不純物含有量が、従来の燃焼装置で得られる水蒸気ガスに比し、顕著に低減することが明らかである。また、この点からも本発明のガス供給管の先端部のガス噴出ノズル域に冷却手段を配備した燃焼装置において、ガス噴出ノズルの先端部の溶損が著しく抑制されることも分かる。
【００２９】
実施例５
前記図３と同様に構成された燃焼装置を用い、水素ガス供給管３５に水素ガスを２リットル／分で、酸素ガス供給管３６に酸素ガスを２リットル／分で、また不活性ガス供給管３９にアルゴンガスを５リットル／分で流通させてガス噴出ノズル先端から流出させ、予熱ヒータ１０によりガス供給管３４を９５０℃に加熱して燃焼室２内で着火させ、そのまま１時間燃焼させた。この場合、水冷筒９には１５℃の水を流通させた。このようにして、燃焼室２では水素の酸化反応（燃焼）により水蒸気ガスを生成した。水蒸気供給管３から流出する水蒸気ガス中の不純物量を測定した。その結果を表２に示した。また、燃焼室２内の図３に示した測定点ａ（ノズル近傍）及びｂ（火炎直上部の天板内面）で温度測定した。その結果を表２に示した。
【００３０】
【表２】

【００３１】
実施例６
前記図５と同様に構成された４重管のガス供給管を配備した燃焼装置を用い、水素ガス供給管５５に水素ガスを２リットル／分で、酸素ガス供給管５６に酸素ガスを２リットル／分で、また不活性ガス供給管２９及び３０にそれぞれアルゴンを０．５リットル／分で流通させてガス噴出ノズル先端から流出させ、実施例５と同様に予熱ヒータ１０によりガス供給管５４を加熱して燃焼室２内で着火させた。その後、予熱ヒータ１０の加熱をそのまま継続し、水素ガスを２リットル／分で、酸素ガスを２リットル／分で、またアルゴンガスをそれぞれ５リットル／分の流量に制御し１時間燃焼させた。実施例５と同様に流出する水蒸気ガス中の不純物量を測定した。その結果を表２に示した。また、燃焼室２内の図５に示した測定点ａ（ノズル近傍）及びｂ（火炎直上部の天板内面）で温度測定した。その結果を表２に示した。
【００３２】
実施例７
着火後予熱ヒータ１０の加熱を停止した以外は、実施例６と同様に水素ガスの燃焼を行い、同様に流出水蒸気ガスの不純物含有量を測定し、その結果を表２に示した。また、燃焼室２内の図５に示した測定点ａ及びｂでの温度測定も同様に行い、その結果を表２に示した。
【００３３】
比較例３
前記図８及び図９に示した従来の一般的な構造で、２重管のガス供給管を配備し燃焼装置７１を用い、水素ガス供給管５５及び酸素ガス供給管７６にそれぞれ水素ガス及び酸素ガスを流通させ、実施例５と同様に予熱ヒータ８０でガス供給管を加熱して燃焼室２内で着火させた。その後、予熱ヒータ８０の加熱をそのまま継続し、水素ガスを２リットル／分、酸素ガスを２リットル／分の流量に制御して１時間燃焼させた。実施例５と同様に流出する水蒸気ガス中の不純物量を測定した。その結果を表２に示した。また、燃焼室７２内の図７に示した測定点ａ（ノズル近傍）及びｂ（火炎直上部の天板内面）で温度測定した。その結果を表２に示した。
【００３４】
比較例４
前記図８及び９に示した燃焼装置とほぼ同様であり、かつ酸素ガス噴出ノズルを水素ガス噴出ノズル先端よりも燃焼室内方向に突出させ、またガス分散円孔を複数形成した分散型酸素ガス噴出ノズルを用い、比較例３と同様にして水素燃焼を行い、生成した水蒸気ガス中の不純物含有量を測定した。その結果を表１に示した。また、図８に示した燃焼室７２内のノズル近傍点（ａ点）及び火炎直上部の天板内面（ｂ点）で温度測定した。その結果を表２に示した。
【００３５】
上記実施例５〜７及び比較例３〜４により明らかなように、本発明のガス供給管の水素ガス供給管と酸素ガス供給管を隣接させることなく不活性ガス供給管を介して３重円管や４重円管に形成して所定に配置し、燃焼室内のガス噴出ノズル先端直後での水素ガスと酸素ガスとの接触を抑制して所定の間隔を有して燃焼火炎を形成させることにより、生成され流出する水蒸気ガス中の不純物含有量の低減が顕著であることが分かる。この点から本発明のガス供給管の先端部のガス噴出ノズル域に冷却手段を配備した燃焼装置において、ガス噴出ノズルの先端部の溶損が著しく抑制されることも分かる。また、燃焼室内の温度も低下することが分かる。
【００３６】
次に、石英ガラスの温度による消耗（エッチング）の程度を検証した。
この検証結果を図７に示す。図７は石英ガラスの温度と消耗（エッチング）量の関係を表した図であって、横軸に石英ガラスの温度を、縦軸に石英ガラスの３００℃における水素でのエッチング量を１とした時の各温度でのエッチング量の比率を示している。
従来のガス噴出ノズル先端部は１０００℃以上となり、この図から明らかなように、３００℃のエッチング量の２０倍以上の石英ガラスがエッチングされる。ガス噴出ノズル先端部の温度を９００℃以下にすることで、３００℃のエッチング量の１０倍以下に抑えることができ、また７００℃以下にすることで、３００℃のエッチング量の５倍以下に抑えることができ、更に、５００℃以下にすることで、３００℃のエッチング量と同様のエッチング量に抑えることができる。
したがって、本発明では、石英ガラスよりなるガス噴出ノズル先端部の温度を９００℃以下、好ましくは７００℃以下、更に好ましくは５００℃以下に冷却するのが良いことが判明した。
【００３７】
【発明の効果】
本発明の高純度水蒸気製造用燃焼装置は、主にガス噴出ノズル先端部の溶損の防御機構を配備したことにより、従来の燃焼装置で製造した水蒸気ガス中に含有されるアルカリ金属等の不純物の含有量が著しく低減された水蒸気ガスを製造できる。ガス噴出ノズル先端部の溶損が抑制されると共に、燃焼室内の温度も低下することから燃焼装置全体の耐久性も向上し、安定して高純度水蒸気ガスを製造できる。従って、特に、微量の不純物汚染も問題となる半導体製造工程の熱酸化処理工程等に好適に用いることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例の高純度水蒸気製造用燃焼装置の概略構成説明図
【図２】図１のＡ部の拡大説明図
【図３】本発明の第２の実施例の高純度水蒸気製造用燃焼装置の概略構成説明図
【図４】図３のＢ−Ｂ線断面の拡大端面図
【図５】本発明の第３の実施例の高純度水蒸気製造用燃焼装置の概略構成説明図
【図６】図５のＣ−Ｃ線断面の拡大端面図
【図７】石英ガラスの温度と消耗（エッチング）量の関係を表した図
【図８】従来の高純度水蒸気製造用燃焼装置の概略構成説明図
【図９】図８のＤ−Ｄ線断面の拡大端面図
【符号の説明】
１、３１、５１、７１水蒸気製造燃焼装置
２、７２燃焼室
３、７３水蒸気供給管
４、３４、５４、７４ガス供給管
５、３５、５５、７５水素ガス供給管
６、３６、５６、７６酸素ガス供給管
７、３７、５７、７７水素ガス導入管
８、３８、５８、７８酸素ガス導入管
３９、５９、６０不活性ガス供給管
４０、６２、６１不活性ガス導入管
９、７９水冷筒
１０、８０予熱用ヒータ
１１水素ガス供給管冷却部
１２酸素ガス供給管冷却部
１３、１４冷却媒体供給管
１５、１６冷却媒体排出管
８１断熱材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion apparatus for producing high-purity steam and a method for producing high-purity steam, and more particularly to a combustion apparatus for producing high-purity steam gas used in an oxidation process of a semiconductor manufacturing process, The present invention relates to a combustion apparatus for producing high-purity water vapor and a method for producing high-purity water vapor that prevent and reduce impurities in the produced steam gas and are excellent in durability.
[0002]
[Prior art]
In the oxide film forming step of the semiconductor manufacturing process, as one of oxide film forming methods, there is a method in which a wafer is brought into contact with high-temperature steam gas. The water vapor gas used for forming the oxide film is preferably a high-purity gas in which impurities such as alkali metals that contaminate the semiconductor wafer are reduced as much as possible. Generally, hydrogen gas is brought into contact with high-purity hydrogen gas and oxygen gas. Manufactured by burning gas. As a hydrogen gas combustion method, for example, as disclosed in JP-A-56-62326, a wafer to be oxidized is set in a heating furnace, and hydrogen gas and oxygen gas are directly introduced into the heating furnace. There is a method for generating water vapor by burning. However, this method has a problem that the temperature in the heating furnace is influenced by the flame and it is difficult to make the oxidation treatment conditions constant.
[0003]
In order to solve the above problem, as disclosed in, for example, Japanese Patent Laid-Open No. 57-18328, a combustion apparatus is provided outside the wafer oxidation furnace to burn hydrogen gas to generate water vapor gas. A method has been proposed in which steam gas is introduced into the furnace. In the case of producing water vapor gas by this external combustion method, this method is widely adopted at present because the oxidation treatment conditions in the semiconductor manufacturing process are stabilized. This external combustion type hydrogen gas combustion apparatus normally has, for example, a combustion chamber 72 and a combustion chamber 72 as shown in a schematic configuration diagram in FIG. 8 and an enlarged end view in a section taken along line DD in FIG. It has a water vapor supply pipe 73 that supplies the generated high-purity water vapor to an external wafer heat treatment furnace and the like, and a gas supply pipe 74 that supplies hydrogen and oxygen gas, and is mainly composed of a quartz glass material. A cooling device 79 such as a water-cooled cylinder is disposed on the outer peripheral portion of the combustion chamber 72, and the gas supply pipe 74 has an ignition portion for spontaneous ignition by heating hydrogen and oxygen gas supplied at the start. A preheating heater 80 is provided. The gas supply pipe 74 is composed of a double circular pipe, a hydrogen gas supply pipe 75 is arranged at the center, and an oxygen gas supply pipe 76 is arranged annularly on the outer periphery of the gas supply pipe 74, and the hydrogen gas supply pipe 75 and the oxygen gas supply pipe 76 are connected to each other. Are connected to a hydrogen gas introduction pipe 77 and an oxygen gas introduction pipe 78, respectively. In addition, a gas ejection nozzle is continuously provided at the distal end portion of the gas supply pipe 74, and a heat insulating material 81 is usually disposed on the outer peripheral portion of the distal end portion of the gas supply pipe 74. The hydrogen and oxygen gas are heated by the preheating heater 80 and ejected from the gas ejection nozzle to the combustion chamber. After contacting and spontaneously igniting in the combustion chamber, the hydrogen gas is oxidized and burned to produce water vapor.
[0004]
The combustion apparatus configured as described above is generally formed of a quartz glass material as described above. In this case, in particular, there is a problem that the tip of the gas jet nozzle is melted and consumed due to a high temperature during combustion, and the tip of the gas jet nozzle and the wall of the combustion chamber are crystallized, peeled off, dropped and broken. These are not only the problem of durability that the life of the combustion device that generates water vapor is short, but also the particles generated by the above-mentioned melting damage and impurities in the quartz glass material are mixed in the generated water vapor gas. There is a possibility of contaminating the semiconductor silicon wafer to be oxidized. For this reason, the yield of semiconductor element manufacturing in the semiconductor manufacturing process using these water vapors eventually decreases. In addition, with the recent increase in the diameter of semiconductor wafers, an increase in the amount of water vapor produced is desired. For this reason, increasing the amount of gas supplied is to increase the temperature of the gas ejection nozzle tip and the combustion chamber. Therefore, it is difficult to carry out because the melt damage of the nozzle tip is further increased.
[0005]
As a method for solving the above problem of the external combustion system, for example, in Japanese Patent Laid-Open No. 6-267932, the oxygen gas ejection nozzle is caused to protrude in the combustion chamber (container) inward from the tip of the hydrogen gas ejection nozzle, and at the same time, A distributed oxygen gas ejection nozzle having a plurality of ejection holes that are dispersed and ejected over a wide area is proposed. This method is a double tube structure (supplying hydrogen gas to the central tube and oxygen gas to the outer tube), which is common in the conventional external combustion type gas supply tube described in Japanese Patent Publication No. 63-60528. ), A thick flame is formed in the oxygen gas ejection nozzle portion by ejecting oxygen gas at a position far from the hydrogen gas ejection nozzle and in a wide range. Thereby, compared with the conventional gas ejection nozzle, the tip of the hydrogen gas ejection nozzle is not heated, and the temperature in the combustion chamber can be prevented from becoming high. Therefore, the supply amount of hydrogen gas and oxygen gas can be increased to produce a larger amount of high-purity water vapor gas than before, and the amount of water vapor gas produced for oxidation treatment of a semiconductor wafer having a large diameter is increased.
[0006]
[Problems to be solved by the invention]
According to the combustion apparatus with the improved gas injection nozzle proposed above, problems such as the stabilization of the oxidation process in the semiconductor manufacturing process, the supply of a large amount of high-purity water vapor gas required for processing large-diameter wafers, the durability of the combustion apparatus, etc. Is resolved. However, according to the inventors, it has been found that the impurity content level in the water vapor gas is not reduced to a sufficiently satisfactory level in spite of a decrease in the combustion chamber temperature. That is, as shown in a comparative example to be described later, even in the proposed combustion apparatus, impurities in the water vapor gas produced as compared with the gas jet nozzle constituted by the gas supply pipe of the conventional double pipe described above. It was confirmed that the content was almost the same.
[0007]
In the combustion apparatus proposed in Japanese Patent Laid-Open No. 6-267932, the reason why the impurity content in the water vapor gas is not reduced as much as expected is that the temperature in the vicinity of the hydrogen gas injection nozzle decreases, and the upper and outer circumferences of the combustion chamber (container) However, as a result of the formation of the highest temperature flame in the combustion chamber in the vicinity of the oxygen gas ejection nozzle as described above, the temperature rise at the tip of the oxygen gas ejection nozzle is unavoidable. It is presumed that the quartz glass material melts at the tip as in the conventional case, and particles and impurities in the quartz glass member are mixed into the water vapor gas. That is, in the conventional gas jet nozzle in which the hydrogen gas and the oxygen gas are jetted from substantially the same position to form a flame, the tip of the gas jet nozzle of the supply gas is melted as compared with the case where the tip of the entire gas jet nozzle is melted. In this case, it is estimated that the same phenomenon occurs at the tip of the oxygen gas ejection nozzle, although it is possible to prevent melting of the tip of the hydrogen gas ejection nozzle. Further, in the proposed combustion apparatus, since the peripheral portion of the gas jet nozzle continuous at the tip of the gas supply pipe is covered with a heat insulating material as in the conventional combustion apparatus shown in FIGS. The heat from the flame is difficult to be released, the temperature in the vicinity of the gas jet nozzle and the continuous part of the gas supply pipe to the gas jet nozzle tends to be high, and the gas jet nozzle as a whole becomes high temperature. This is presumed to be caused by melting of the tip. Furthermore, as the heat insulating material, an alumina-based or silica-based refractory is usually used, and these heat insulating materials may be exposed to an unexpectedly high temperature, and impurities in the heat insulating material diffuse to adjacent nozzle members. There is also a possibility, and it is presumed that this may also cause an increase in impurities.
[0008]
The inventors first manufactured in the above-described combustion apparatus for high-purity steam production, and in particular, in view of the problem of impurity content in the high-purity steam gas to be introduced into the oxidation process of the semiconductor manufacturing process, The reduction of the impurity content was investigated. For example, there is a method of purifying a member in which the nozzle constituent member is made of high-purity synthetic quartz glass from quartz glass, but there is a possibility that impurities may diffuse from the outside due to a rise in temperature near the nozzle, and high purity Even if synthetic quartz glass is used, the quartz glass is dissolved in the gas at the tip of the high temperature gas jet nozzle and re-precipitated in the low temperature portion to generate particles, as in the conventional quartz glass member. For this reason, the inventors diligently studied to achieve a more fundamental solution for the gas supply pipe and the gas ejection nozzle of the combustion apparatus in order to sufficiently reduce the impurity content in the obtained water vapor gas. As a result, the inventors have found that the reduction of the impurity content becomes significant by preventing the gas supply pipe and the gas ejection nozzle from becoming high temperature, and the present invention has been completed.
[0009]
  A combustion apparatus for producing high-purity steam according to the present invention is a combustion apparatus for producing high-purity steam comprising a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe. The nozzle tip is provided with a melt damage prevention mechanism, and the melt damage prevention mechanism is interposed between the hydrogen gas supply pipe and the oxygen gas supply pipe at the gas jet nozzle tip of the gas supply pipe to circulate the cooling medium. It is characterized by being a heat dissipating means comprising a quartz glass cooling section that can be formed.
[0010]
  Here, it is preferable that a quartz glass cooling part formed so that a cooling medium can be circulated is provided on the outer periphery of the oxygen gas supply pipe, and between the hydrogen gas supply pipe and the oxygen gas supply pipe. The cooling part made of quartz glass, which is formed in such a way that the cooling medium can be circulated, has a reduced diameter at the tip of the hydrogen gas supply pipe, and a cooling medium supply pipe and a discharge pipe are arranged in the narrowed outer ring part. Preferably it is formed. Furthermore, it is desirable that the oxygen gas supply pipe is formed straight.
  The combustion apparatus for producing high-purity steam according to the present invention is a combustion apparatus for producing high-purity steam comprising a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe. The gas ejection nozzle tip has a erosion protection mechanism, and the erosion protection mechanism has a triple supply pipe and a supply pipe for hydrogen gas, inert gas and oxygen gas from the center, The hydrogen gas supply pipe and the oxygen gas supply pipe are arranged via an inert gas supply pipe without being adjacent to each other, and a flame is formed with a predetermined distance from the tip of the gas ejection nozzle. .
  The combustion apparatus for producing high-purity steam according to the present invention is a combustion apparatus for producing high-purity steam comprising a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe. A gas blow nozzle is provided with a melt damage prevention mechanism, and the melt damage prevention mechanism has a quadruple gas supply pipe and supplies inert gas, hydrogen gas, inert gas, and oxygen gas from the center. A hydrogen gas supply pipe and an oxygen gas supply pipe are arranged through an inert gas supply pipe without being adjacent to each other, and a flame is formed with a predetermined distance from the tip of the gas ejection nozzle. It is characterized by.
[0011]
  Further, according to the present invention, the combustion apparatus for the high-purity steam production apparatus is used to preheat the hydrogen gas and oxygen gas flowing through heating the gas supply pipe, and then eject the gas from the gas ejection nozzle to the combustion chamber. Then, after the ignition, the heating of the gas supply pipe is stopped, and at the same time, the heat radiating means dissipates heat to burn hydrogen to generate water vapor.
  Further, according to the present invention, the combustion apparatus for the high-purity steam production apparatus is used to preheat the hydrogen gas and oxygen gas flowing through heating the gas supply pipe, and then eject the gas from the gas ejection nozzle to the combustion chamber. High purity steam production, characterized in that after the ignition of the gas supply pipe, heating of the gas supply pipe is stopped, and at the same time, hydrogen gas, oxygen gas, and inert gas are supplied in predetermined amounts, and hydrogen is burned to generate steam. A method is provided.
[0012]
  The apparatus for producing high-purity steam according to the present invention is configured as described above. When hydrogen and oxygen are supplied to a combustion chamber and the supplied gas is brought into contact with combustion, after ignition, (1) gas ejection from the gas supply pipe nozzleTipA gas jet nozzle that jets hydrogen and oxygen gas into the combustion chamber because it is equipped with heat dissipation means such as a cooling chamberTipThe heat of the gas jet nozzle tip heated by the hydrogen combustion flame can be dissipated by the cooling part, and the entire temperature of the gas jet nozzle, especially the tip of the gas jet nozzle, can be prevented from being heated, and the melting damage is suppressed. . (2) Since the gas supply pipe is formed in a triple pipe or a quadruple pipe and the hydrogen gas and oxygen gas supply pipes are not adjacent to each other and the inert gas supply pipe is disposed between them, Oxygen gas does not come into contact immediately after each gas is ejected from the gas ejection nozzle, and a hydrogen combustion flame is formed in the combustion chamber away from the gas ejection nozzle tip. Loss is suppressed.
[0013]
Further, the high purity steam production method of the present invention, in the operation of the combustion apparatus for producing high purity steam configured as described above, heats the gas supply pipe at the start of operation, preheats hydrogen and oxygen gas, and ignites. After that, the heating of the gas supply pipe is stopped, and the cooling flame provided at the tip of the gas ejection nozzle, the formation of flame isolation, and the action of a melting damage prevention mechanism such as the non-use of a heat insulating material cause a combustion flame. Even if the gas jet nozzle tip is heated, the heat is dissipated, so that the temperature is not excessively increased. For this reason, in the present invention, excessive high-temperature heating of these gas ejection nozzles is prevented, and the melting loss of the quartz glass material of the constituent material can be suppressed. The content of impurities in the generated steam gas can be remarkably reduced, and is particularly suitable as a high-purity steam gas required in the wafer oxidation process of the semiconductor manufacturing process.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited by the following examples.
First, the first embodiment will be described. FIG. 1 is an explanatory view showing an outline of the structure of a combustion apparatus according to a first embodiment of the high-purity steam generating apparatus of the present invention, and FIG. 2 is an enlarged view of a portion A in FIG. 1 and 2, the main part of the combustion apparatus 1 includes a combustion chamber 2, a steam supply pipe 3 that supplies high-purity steam generated in the combustion chamber 2 to a wafer heat treatment furnace, and combustion raw material gas in the combustion chamber 2. It comprises a gas supply pipe 4 to be supplied, and these main parts are formed of a quartz glass material as in the prior art. The gas supply pipe 4 is configured such that a hydrogen gas supply pipe 5 is arranged at the center and an oxygen gas supply pipe 6 is arranged annularly on the outer periphery thereof. A hydrogen gas introduction pipe 7 and an oxygen gas introduction pipe 8 are connected to the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, respectively. In addition, a cooling device 9 such as a water-cooled cylinder is disposed on the outer peripheral portion of the combustion chamber 2, and the outer periphery of the gas supply pipe 4 is heated to ignite spontaneously by heating the supplied hydrogen and oxygen gas. A preheating heater 10 is provided. These configurations are almost the same as those of the conventional combustion apparatus described above. After ignition, each gas supply amount is appropriately selected and controlled according to the combustion conditions such as the combustion device and nozzle size, and high purity water vapor can be generated by combustion by hydrogen oxidation. Supply to silicon wafer heat treatment process.
[0015]
In the combustion apparatus 1 of the present invention, as shown in an enlarged view in FIG. 2, the hydrogen gas supply pipe 5 of the quartz glass gas supply pipe 4 and the gas jet nozzles at the tip of the oxygen gas supply pipe 6 are respectively Quartz glass cooling units 11 and 12 are provided, respectively. The cooling units 11 and 12 are provided with cooling

medium supply pipes

13 and 14 and cooling

medium discharge pipes

15 and 16, respectively.₂A cooling medium such as Ar is supplied so that the nozzle tip can be cooled with the cooling medium. The cooling unit 11 arranged in an annular shape at the inner peripheral portion at the tip of the hydrogen gas supply pipe 5 has a reduced diameter at the tip of the hydrogen gas supply pipe 5, and a cooling medium supply pipe 13 and a discharge pipe 14 at the narrowed outer ring part. Deployed and formed. The cooling portion 12 at the tip of the nozzle of the oxygen gas supply pipe 6 is formed by arranging an annular pipe on the outer periphery of the tip of the supply pipe 6. In FIG. 2, the cooling unit is provided on the outer periphery of each of the hydrogen and oxygen gas supply pipes. However, between the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, that is, the hydrogen gas supply pipe 5. Only the cooling part 11 formed by the outer peripheral wall and the inner peripheral wall of the oxygen gas supply pipe 6 can be provided to share the cooling part, and both hydrogen and oxygen gas can be cooled through each peripheral wall. By cooling the nozzle tip of each gas supply pipe in this way, the nozzle tip that is likely to be heated at the time of combustion of hydrogen gas and oxygen gas can be directly radiated. Further, the diameter of the tip of the hydrogen gas supply pipe 5 is reduced, and the flow rate of the hydrogen gas can be increased. On the other hand, the oxygen gas supply pipe is formed straight, and the oxygen gas can be ejected in a straight line. The nozzle tip is not heated excessively. For this reason, devitrification of the nozzle tip and overheating in the combustion chamber can be prevented, high-purity water vapor can be generated in large quantities by hydrogen gas combustion, and oxide film formation on a large-diameter semiconductor silicon wafer substrate Can also respond sufficiently. In addition, the arrangement | positioning system of each cooling chamber is not specifically limited above, What is necessary is just to be able to cool the front-end | tip part of each gas supply pipe to predetermined.
[0016]
Next, a second embodiment will be described. FIG. 3 is an explanatory view showing an outline of the structure of the combustion apparatus according to the second embodiment of the high-purity water vapor generating apparatus of the present invention, and FIG. 4 is an end portion of the cross section taken along the line BB in FIG. FIG. In FIG. 3, the combustion apparatus 31 is the same as the combustion apparatus of FIG. 1 except that the gas supply pipe 34 is formed as a triple circular pipe. In FIG. 3, the same members as those in FIG. A gas supply pipe 34 different from that shown in FIG. 1 has a hydrogen gas supply pipe 35 disposed at the center, a double annular pipe disposed on the outer periphery thereof, an oxygen gas supply pipe 36 on the outer side, and an inert gas gas supply pipe 39 on the inner side. Arranged. A hydrogen gas introduction pipe 37, an oxygen gas introduction pipe 38, and an inert gas introduction pipe 40 are connected to the hydrogen gas supply pipe 35, the oxygen gas supply pipe 36, and the inert gas supply pipe 39, respectively. As shown in an enlarged view of the cross-sectional end in FIG. 4, the triple tube of the gas supply pipe 34 is formed concentrically. Thus, as a triple tube, the supply of hydrogen gas and oxygen gas is combusted through an inert gas such as nitrogen gas, helium, argon gas, etc., so that the hydrogen gas and oxygen gas are immediately after the nozzle tip. A combustion flame is formed by contact at a distant position without contact. For this reason, it can prevent that a nozzle front-end | tip part becomes high temperature, devitrifies, and shortens durability. Nitrogen gas, helium, argon gas, etc. are common as the inert gas. Of these, argon gas is preferable because it is a high-purity gas that is obtained at a relatively low cost and has good thermal conductivity.
[0017]
FIG. 5 is an explanatory view showing an outline of the structure of a combustion apparatus according to a second other embodiment of the present invention, and FIG. 6 is an enlarged view of an end portion taken along the line CC in FIG. 5 and 6, the combustion device 51 is the same as the combustion device of FIG. 3 except that the gas supply pipe 54 is formed as a concentric quadruple tube. In FIG. 5, the same members as those in FIG. The gas supply pipe 54 of a quadruple pipe has an inert gas supply pipe 59 arranged at the center, and an oxygen gas supply pipe 56, an inert gas supply pipe 60, and a hydrogen gas supply are sequentially formed from the outermost pipe in an annular shape on the outer periphery thereof. A tube 55 is arranged. The inert gas supply pipe 59, the hydrogen gas supply pipe 55, the inert gas supply pipe 60, and the oxygen gas supply pipe 56 are respectively an inert gas introduction pipe 61, a hydrogen gas introduction pipe 57, an oxygen gas introduction pipe 58, and an inert gas. The gas introduction pipes 62 are connected to each other. Thus, when the gas supply pipe 54 is a quadruple pipe, a flame can be formed at a position away from the nozzle tip as in the case of the triple pipe nozzle described above, and dissolution due to devitrification of the nozzle tip is prevented. In addition to improving durability, the temperature of the flame formed by combustion can be controlled by appropriately selecting the outflow amount of the inert gas from the central portion and flowing out, thereby further preventing overheating of the combustion chamber be able to.
[0018]
In any of the second embodiments described above, when hydrogen and oxygen gas supplied by the preheater heater 10 disposed on the outer periphery of the

gas supply pipe

34 or 54 are heated for spontaneous ignition, they are inactive during the ignition sequence. The supply of the inert gas to the

gas supply pipes

39, 59, 60 is ignited by reducing or stopping the flow rate, and after ignition, the inert gas is inactive according to the combustion conditions such as the capacity of the combustion device used and the size of the nozzle. It is preferable that the gas flow rate, the hydrogen gas flow rate, and the oxygen gas flow rate are appropriately selected and supplied to predetermined amounts and flowed out from the nozzle. In addition, it is preferable to detect the flame state with a flame sensor and control the amount of each supply gas so as to always maintain a stable flame state. Further, by detecting the flame sensor, when the flame is extinguished, the supply of hydrogen gas and oxygen gas can be stopped, and only the inert gas can be supplied to stop the combustion. Further, in the present invention, a cooling unit is provided in a predetermined manner at the tip of each gas supply pipe of the gas supply pipe of the multiple circular pipe of the second embodiment as in the first embodiment of the present invention. Each supply gas can be cooled and discharged from the nozzle to further prevent overheating of the combustion chamber. In this case, the arrangement of the cooling unit is not limited. For example, the outermost pipe of the gas supply pipe is provided with an annular circular pipe on the outer periphery of the tip, and the inner pipe is shown in FIG. The cooling unit can be provided by a method of narrowing the tip of the hydrogen gas supply pipe 5 in FIG.
[0019]
In addition, when the gas ejection nozzle tip of the gas supply pipe is made of quartz glass, it is preferable to cool by providing a cooling unit in a predetermined manner so that the temperature of the tip is 900 ° C. or less. It is preferable to cool to 700 ° C. or lower, more preferably to 500 ° C. or lower.
[0020]
Furthermore, in the combustion apparatus for producing high-purity steam according to the present invention, as a quartz glass material mainly forming the apparatus, the surface thereof is treated with hydrofluoric acid treatment, high-temperature hydrogen chloride gas treatment or a combination thereof. It is preferable to use metal impurities such as sodium, iron, copper, and aluminum in the vicinity of the surface at a depth of about 100 μm from the surface at 10 ng / g or less, or by hydrogen gas supplied to the combustion apparatus or generated steam In consideration of the risk of erosion, it is more preferable to use a synthetic quartz glass material having a high bulk purity with the metal impurities being 10 ng / g or less. The content of the metal impurities in the water vapor produced by the combustion apparatus for producing high-purity water vapor using these high bulk purity quartz glass materials is 10 ng / m.³Therefore, it can be used when higher-purity water vapor is required.
[0021]
【Example】
Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by the following examples.
Example 1
Using the combustion apparatus configured in the same manner as in FIG. 1, hydrogen gas is circulated through the hydrogen gas supply pipe 5 at 6 liters / minute, and oxygen gas is circulated through the oxygen gas supply pipe 6 at 5 liters / minute to flow out from the nozzle tip. Then, the gas supply pipe 4 was heated to 950 ° C. by the preheating heater 10 and ignited in the combustion chamber 2 and burned for 1 hour as it was. In this case, water of about 15 ° C. is circulated from the cooling

medium supply pipes

13 and 14 to the cooling units 11 and 12 at a flow rate of 1 liter / min, respectively, and is discharged from the cooling

medium discharge pipes

15 and 16. The tips of the supply pipe 5 and the oxygen gas supply pipe 6 were cooled to about 50 ° C., and at the same time, the same water was passed through the water-cooled cylinder 9. In this way, in the combustion chamber 2, water vapor gas was generated by the oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out from the steam supply pipe 3 was measured. The results are shown in Table 1.
[0022]
Example 2
Using the same combustion apparatus as in Example 1, after the ignition, the heating of the preheating heater 10 was stopped, and the cooling effect was further enhanced, hydrogen combustion was performed in exactly the same manner, and the amount of impurities in the generated steam gas Was measured. The results are shown in Table 1.
[0023]
Example 3
Using the same combustion apparatus as in Example 1, the cooling medium is argon, and the refrigerant flows through the cooling

medium supply pipes

13 and 14 to the hydrogen gas cooling section 11 and the oxygen gas cooling section 12, respectively, at a flow rate of 3 liters / minute. Except for the above, hydrogen combustion was performed in exactly the same manner including that the heating with the preheater was continued, and the amount of impurities in the generated water vapor gas was measured. The results are shown in Table 1.
[0024]
[Table 1]

[0025]
Example 4
Except that the heating of the preheating heater 10 was stopped and the cooling effect was further enhanced, hydrogen combustion was performed in exactly the same manner as in Example 3, and the amount of impurities in the generated steam gas was measured. The results are shown in Table 1.
[0026]
Comparative Example 1
Example 1 is the same as Example 1 except that the same apparatus as in Example 1 was used and a heat insulating material was disposed at the tip of the gas supply pipe 4 in the same manner as in the conventional method without flowing a cooling medium through the cooling units 11 and 12. Similarly, hydrogen combustion was performed, and the impurity content in the generated steam gas was measured. The results are shown in Table 1.
[0027]
Comparative Example 2
8 and 9 is the same as the combustion apparatus shown in FIGS. 8 and 9, and the oxygen gas injection nozzle protrudes in the direction of the combustion chamber from the tip of the hydrogen gas injection nozzle and has a plurality of gas dispersion holes. Hydrogen combustion was performed in the same manner as in Example 1 using a nozzle, and the impurity content in the generated water vapor gas was measured. The results are shown in Table 1.
[0028]
According to the above-described Examples 1 to 4 and Comparative Examples 1 and 2, the cooling unit is provided at the tip of the gas supply pipe to cool the hydrogen gas and the oxygen gas, thereby reducing the impurity content in the generated and flowing water vapor gas. It is clear that it is significantly reduced as compared with the water vapor gas obtained by the conventional combustion apparatus. Also from this point, it can be seen that in the combustion apparatus in which the cooling means is provided in the gas jet nozzle region at the tip of the gas supply pipe of the present invention, the melting of the tip of the gas jet nozzle is remarkably suppressed.
[0029]
Example 5
3 is used, the hydrogen gas supply pipe 35 is supplied with hydrogen gas at 2 liters / minute, the oxygen gas supply pipe 36 with oxygen gas at 2 liters / minute, and the inert gas supply pipe. Argon gas was circulated at a rate of 5 liters / minute through the gas jet nozzle tip 39, the gas supply pipe 34 was heated to 950 ° C. by the preheater 10 and ignited in the combustion chamber 2 and burned for 1 hour. . In this case, water at 15 ° C. was circulated through the water-cooled cylinder 9. In this way, in the combustion chamber 2, water vapor gas was generated by the oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out from the steam supply pipe 3 was measured. The results are shown in Table 2. Further, the temperature was measured at measurement points a (near the nozzle) and b (inner surface of the top plate immediately above the flame) shown in FIG. The results are shown in Table 2.
[0030]
[Table 2]

[0031]
Example 6
Using a combustion apparatus having a quadruple gas supply pipe constructed in the same manner as in FIG. 5, hydrogen gas is supplied to the hydrogen gas supply pipe 55 at 2 liters / minute, and oxygen gas is supplied to the oxygen gas supply pipe 56 at 2 liters. Per minute, and argon was allowed to flow through the inert gas supply pipes 29 and 30 at a rate of 0.5 liters / minute, respectively, and was discharged from the tip of the gas ejection nozzle. Heated and ignited in the combustion chamber 2. Thereafter, heating of the preheater 10 was continued as it was, and combustion was performed for 1 hour while controlling hydrogen gas at 2 liters / minute, oxygen gas at 2 liters / minute, and argon gas at flow rates of 5 liters / minute, respectively. The amount of impurities in the flowing steam gas was measured in the same manner as in Example 5. The results are shown in Table 2. Further, the temperature was measured at measurement points a (near the nozzle) and b (inner surface of the top plate immediately above the flame) shown in FIG. The results are shown in Table 2.
[0032]
Example 7
Except that the heating of the preheating heater 10 after ignition was stopped, hydrogen gas was burned in the same manner as in Example 6, and the impurity content of the outflow steam gas was measured in the same manner. The results are shown in Table 2. Further, the temperature measurement at the measurement points a and b shown in FIG. 5 in the combustion chamber 2 was similarly performed, and the results are shown in Table 2.
[0033]
Comparative Example 3
In the conventional general structure shown in FIGS. 8 and 9, a double gas supply pipe is provided and a combustion apparatus 71 is used. Hydrogen gas and oxygen gas are supplied to the hydrogen gas supply pipe 55 and the oxygen gas supply pipe 76, respectively. Gas was circulated, and the gas supply pipe was heated with the preheater 80 in the same manner as in Example 5 to ignite in the combustion chamber 2. Thereafter, the heating of the preheater 80 was continued as it was, and the hydrogen gas was controlled at a flow rate of 2 liters / minute, and the oxygen gas was controlled at a flow rate of 2 liters / minute to burn for 1 hour. The amount of impurities in the flowing steam gas was measured in the same manner as in Example 5. The results are shown in Table 2. Further, the temperature was measured at measurement points a (near the nozzle) and b (inner surface of the top plate immediately above the flame) shown in FIG. The results are shown in Table 2.
[0034]
Comparative Example 4
8 and 9 is the same as the combustion apparatus shown in FIGS. 8 and 9, and the oxygen gas injection nozzle protrudes in the direction of the combustion chamber from the tip of the hydrogen gas injection nozzle and has a plurality of gas dispersion holes. Using a nozzle, hydrogen combustion was performed in the same manner as in Comparative Example 3, and the impurity content in the generated water vapor gas was measured. The results are shown in Table 1. Further, the temperature was measured at the nozzle vicinity point (point a) in the combustion chamber 72 shown in FIG. 8 and the top plate inner surface (point b) immediately above the flame. The results are shown in Table 2.
[0035]
As is clear from Examples 5 to 7 and Comparative Examples 3 to 4, the gas supply pipe of the present invention has a triple circle through the inert gas supply pipe without adjoining the hydrogen gas supply pipe and the oxygen gas supply pipe. Forming into a tube or a quadruple tube and arranging them in a predetermined manner to suppress the contact between the hydrogen gas and the oxygen gas immediately after the gas jet nozzle tip in the combustion chamber and form a combustion flame with a predetermined interval Thus, it can be seen that the reduction of the impurity content in the generated and flowing water vapor gas is remarkable. From this point, it can also be seen that in the combustion apparatus in which the cooling means is provided in the gas jet nozzle region at the tip of the gas supply pipe of the present invention, the melting of the tip of the gas jet nozzle is remarkably suppressed. Moreover, it turns out that the temperature in a combustion chamber also falls.
[0036]
Next, the degree of consumption (etching) due to the temperature of the quartz glass was verified.
The verification result is shown in FIG. FIG. 7 is a diagram showing the relationship between the temperature of quartz glass and the amount of consumption (etching). The horizontal axis represents the temperature of quartz glass, and the vertical axis represents the etching amount of quartz glass at 300 ° C. with hydrogen. The ratio of the etching amount at each temperature is shown.
The tip of the conventional gas ejection nozzle is 1000 ° C. or higher, and as is clear from this figure, quartz glass that is 20 times or more of the etching amount at 300 ° C. is etched. By setting the temperature of the gas jet nozzle tip to 900 ° C. or less, it can be suppressed to 10 times or less of the etching amount at 300 ° C., and by making it 700 ° C. or less, it is reduced to 5 times or less of the etching amount at 300 ° C. Furthermore, when the temperature is set to 500 ° C. or lower, the etching amount can be suppressed to the same etching amount as 300 ° C.
Therefore, it has been found that in the present invention, the temperature of the gas jet nozzle tip made of quartz glass should be cooled to 900 ° C. or lower, preferably 700 ° C. or lower, more preferably 500 ° C. or lower.
[0037]
【The invention's effect】
The combustion apparatus for producing high-purity steam according to the present invention mainly includes impurities such as alkali metals contained in steam gas produced by a conventional combustion apparatus by providing a protection mechanism against melting damage at the tip of the gas ejection nozzle. It is possible to produce a water vapor gas in which the content of is significantly reduced. The melting of the gas jet nozzle tip is suppressed, and the temperature in the combustion chamber is also reduced, so that the durability of the entire combustion apparatus is improved and high-purity steam gas can be produced stably. Therefore, it can be suitably used for a thermal oxidation treatment process in a semiconductor manufacturing process in which a very small amount of impurity contamination is a problem.
[Brief description of the drawings]
FIG. 1 is a schematic configuration explanatory diagram of a combustion apparatus for producing high-purity steam according to a first embodiment of the present invention.
FIG. 2 is an enlarged explanatory view of a part A in FIG.
FIG. 3 is a schematic configuration explanatory diagram of a combustion apparatus for producing high-purity steam according to a second embodiment of the present invention.
4 is an enlarged end view of a cross section taken along line BB in FIG. 3;
FIG. 5 is an explanatory diagram of a schematic configuration of a combustion apparatus for producing high-purity steam according to a third embodiment of the present invention.
6 is an enlarged end view of a cross section taken along line CC in FIG. 5;
FIG. 7 is a graph showing the relationship between the temperature of quartz glass and the amount of consumption (etching).
FIG. 8 is a schematic configuration diagram of a conventional combustion apparatus for producing high-purity steam.
FIG. 9 is an enlarged end view of a cross section taken along the line DD of FIG.
[Explanation of symbols]
1, 31, 51, 71 Steam production combustion apparatus
2,72 Combustion chamber
3, 73 Water vapor supply pipe
4, 34, 54, 74 Gas supply pipe
5, 35, 55, 75 Hydrogen gas supply pipe
6, 36, 56, 76 Oxygen gas supply pipe
7, 37, 57, 77 Hydrogen gas introduction pipe
8, 38, 58, 78 Oxygen gas inlet pipe
39, 59, 60 Inert gas supply pipe
40, 62, 61 Inert gas introduction pipe
9, 79 Water-cooled tube
10, 80 Preheater heater
11 Hydrogen gas supply pipe cooling section
12 Oxygen gas supply pipe cooling section
13, 14 Cooling medium supply pipe
15, 16 Cooling medium discharge pipe
81 Insulation

Claims

In a combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe,
A gas blow nozzle tip of the gas supply pipe is equipped with a melting damage prevention mechanism,
The melting damage prevention mechanism is composed of a quartz glass cooling section formed between the hydrogen gas supply pipe and the oxygen gas supply pipe at the tip of the gas ejection nozzle of the gas supply pipe so as to allow a cooling medium to flow therethrough. A combustion apparatus for producing high-purity steam, wherein the combustion apparatus is a heat dissipating means.

The combustion apparatus for producing high-purity steam according to claim 1, further comprising a quartz glass cooling section formed on the outer periphery of the oxygen gas supply pipe so that a cooling medium can be circulated.

The quartz glass cooling part, which is interposed between the hydrogen gas supply pipe and the oxygen gas supply pipe so that the cooling medium can be circulated, narrows the tip of the hydrogen gas supply pipe and cools it to the thin outer ring part. The combustion apparatus for producing high-purity steam according to claim 1 or 2, wherein a medium supply pipe and a discharge pipe are provided.

The combustion apparatus for producing high-purity steam according to any one of claims 1 to 3, wherein the oxygen gas supply pipe is formed straight.

3. The combustion apparatus for producing high-purity steam according to claim 1 or 2 , wherein the gas supply pipe is heated to circulate hydrogen gas and oxygen gas, and are jetted from the gas jet nozzle into a combustion chamber. Then, after heating the gas supply pipe, the heating of the gas supply pipe is stopped, and at the same time, heat is radiated by the heat radiating means to burn hydrogen to generate water vapor.

In a combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe,
A gas blow nozzle tip of the gas supply pipe is equipped with a melting damage prevention mechanism,
The melting damage prevention mechanism is configured such that the gas supply pipe is a triple pipe and is provided with a supply pipe for hydrogen gas, inert gas and oxygen gas from the center, and the hydrogen gas supply pipe and the oxygen gas supply pipe are not adjacent to each other. A combustion apparatus for producing high-purity water vapor, which is disposed through an inert gas supply pipe and has a predetermined distance from the tip of the gas ejection nozzle to form a flame.

In a combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe,
A gas blow nozzle tip of the gas supply pipe is equipped with a melting damage prevention mechanism,
The erosion protection mechanism is configured such that the gas supply pipe is a quadruple pipe and a supply pipe for inert gas, hydrogen gas, inert gas and oxygen gas is provided from the center, and a hydrogen gas supply pipe and an oxygen gas supply pipe are provided. A combustion apparatus for producing high-purity water vapor, which is arranged through an inert gas supply pipe without being adjacent to each other and forms a flame having a predetermined distance from the tip of the gas ejection nozzle.

The combustion apparatus for producing high-purity steam according to claim 6 or 7 , wherein the gas supply pipe is heated to preheat hydrogen gas and oxygen gas, and is jetted from the gas jet nozzle to a combustion chamber. A method for producing high-purity steam, characterized in that after ignition, heating of the gas supply pipe is stopped, and at the same time, hydrogen gas, oxygen gas, and inert gas are supplied in predetermined amounts, and hydrogen is burned to generate steam. .