JP4584549B2 - Fluorine gas generator - Google Patents

Description

この実験結果に示すように、ＮａＦカートリッジ１２２を使用することにより、ミストによるガードフィルタの閉塞時間が５倍も伸びることが判明した。ＮａＦカートリッジ１２２の配管径が通常の配管より太いので、これに伴う流速の低減がライフタイム向上につながった可能性はある。しかし、捕獲用のガードフィルタ１２４、１２６の部分における配管径は同様の１／４インチであることから、単純な比較で考えても飛沫の捕獲にＮａＦカートリッジ１２２が有効であることが分かる。
【００３３】
以下に、このような知見に基づいて構成された本発明の実施の形態について図面を参照して説明する。なお、以下の説明において、略同一の機能及び構成を有する構成要素については、同一符号を付し、重複説明は必要な場合にのみ行う。
【００３４】
図１は本発明の実施の形態に係る、フッ素ガス生成装置を組込んだ半導体処理システムを示す概略図である。この半導体処理システムは、半導体ウエハやＬＣＤ基板等の被処理基板に、成膜、エッチング、或いは拡散等の処理を施す半導体処理装置１０を有する。
【００３５】
半導体処理装置１０は、被処理基板を収納すると共に半導体処理を施すための処理室１２を具備する。処理室１２内には、被処理基板を載置するための下部電極兼載置台（支持部材）１４が配設される。処理室１２内にはまた、載置台１４に対向して上部電極１６が配設される。両電極１４、１６間にＲＦ（高周波）電源１５からＲＦパワーが印加されることにより、処理ガスをプラズマに転化するためのＲＦ電界が処理室１２内に形成される。処理室１２の下部には、内部を排気すると共に真空に設定するための排気系１８が接続される。また、処理室１２の上部には、処理ガスを供給するためのガス供給系２０が接続される。
【００３６】
図２は図１図示のガス供給系２０と組み合わせて使用される半導体処理装置の変更例１０ｘを示す概略図である。半導体処理装置１０ｘは、被処理基板を収納すると共に半導体処理を施すための処理室１２を具備する。処理室１２内には、被処理基板を載置するための載置台（支持部材）１４が配設される。処理室１２の下部には、内部を排気すると共に真空に設定するための排気系１８が接続される。処理室１２の上部には、プラズマを生成するためのリモートプラズマ室１３が接続される。リモートプラズマ室１３の周囲には、コイルアンテナ１７が巻回される。コイルアンテナ１７にＲＦ（高周波）電源１５からＲＦパワーが印加されることにより、処理ガスをプラズマに転化するための誘導電界がリモートプラズマ室１３内に形成される。また、リモートプラズマ室１３の上部には、処理ガスを供給するためのガス供給系２０が接続される。
【００３７】
なお、本発明の実施の形態に係るフッ素ガス生成装置は、プラズマを利用しない半導体処理装置、例えば熱ＣＶＤ装置に対してクリーニングガス等を供給する場合にも適用することができる。
【００３８】
図１に戻り、ガス供給系２０には、処理室１２内に任意のガス、例えば半導体処理を行うための処理ガスや処理室１２内をクリーニングするための処理ガスを、選択的に切替え且つ所定の流量で供給するための流れ管理部２２が配設される。流れ管理部２２には、種々な活性ガスや不活性ガスを貯蔵する複数のガス源を有するガス貯蔵部２４が接続される。流れ管理部２２にはまた、フッ素ガス系の処理ガスを反応処理により生成するガス生成部２６が接続される。
【００３９】
流れ管理部２２及びガス生成部２６には、本発明の実施の形態に係るフッ素ガス生成装置３０が着脱可能に接続される。即ち、生成装置３０は、流れ管理部２２にフッ素ガスを直接供給するか、或いはガス生成部２６にフッ素ガス原料を供給するために使用される（切替え用のバルブは図示せず）。
【００４０】
生成装置３０は、フッ化水素を含む溶融塩からなる電解浴を収納する気密な電解槽３２を有する。溶融塩は、フッ化カリウム（ＫＦ）とフッ化水素（ＨＦ）との混合物（ＫＦ／２ＨＦ）或いはフレミー塩（Fremy's salt：ＫＦ／２ＨＦ＋添加物）からなる。電解槽３２は上方から溶融塩中に延びる仕切り板３５により、陽極室３４及び陰極室３６に分割される。陽極室３４及び陰極室３６内で、溶融塩中にはカーボン電極（陽極）４２及びニッケル電極（陰極）４４が夫々浸漬される。電解槽３２には、陽極４２及び陰極４４間に電流を供給するための電流源３８と、供給電流を積算する電流積算計４０とが付設される。
【００４１】
電解処理中、電解槽３２は付随するヒータ３３により８０〜９０℃に加熱保温される。電解浴中でフッ化水素を電解することにより、陽極室３４の気相部分にフッ素ガス（Ｆ₂ ）を主成分とするプロダクトガスが発生され、陰極室３６の気相部分に水素ガスを主成分とする副生ガスが発生される。プロダクトガス及び副生ガスの夫々には、原料の溶融塩中のフッ化水素ガスの蒸気圧分だけ、フッ化水素ガスが混入する（例えば５％）。陽極室３４及び陰極室３６には、夫々の気相部分の圧力を連続的に測定するため、第１及び第２圧力計４６、４８が配設される。
【００４２】
陽極室３４には、プロダクトガスを導出し、ガス供給系２０の流れ管理部２２及びガス生成部２６に送るための第１配管５２が接続される。第１配管５２には、上流側から順に、吸着カートリッジ５４、第１流量制御弁５６、ミニバッファタンク５８、コンプレッサ（吸引手段）６２、主バッファタンク６４等が配設される。陽極室３４で発生されたプロダクトガスは、コンプレッサ６２により第１配管５２が吸引されることにより、陽極室３４から強制的に引出され、主バッファタンク６４に貯留される。なお、図１において符号６６はラインフィルタを示す。
【００４３】
主バッファタンク６４には圧力計６５が配設され、タンク６４内の圧力が連続的に測定される。この測定結果は、電流源３８に付随する制御部材３９に伝達される。制御部材３９は、伝達された測定結果に基づいて電流源３８をオン／オフし、電解槽３２への電流の供給を制御する。即ち、タンク６４内の圧力が、ある圧力まで減少すると電流源３８がオンされてフッ素ガスの生成が開始され、また、ある圧力まで増加すると電流源３８がオフされてフッ素ガスの生成が停止される。これにより、電解槽３２内の陽極室３４及び陰極室３６間で溶融塩の液面レベルに差をつけずに電解を止めることができる。なお、タンク６４内の圧力は、例えば大気圧〜大気圧＋０．１８Ｍｐａに設定される。
【００４４】
一方、陰極室３６には、副生ガスを導出するための第２配管７２が接続される。第２配管７２は、例えば半導体製造工場の排気系（吸引手段）７９の配管に着脱可能に接続される。第２配管７２には、上流側から順に、吸着カートリッジ７４、第２流量制御弁７６、除害部７８等が配設される。陰極室３６で発生された副生ガスは、排気系７９により第２配管７２が吸引されることにより、陰極室３６から強制的に引出され、除害部７８を通過した後、排気系７９に送られる。
【００４５】
上述のように、電解処理中、種々の要因で、陽極室３４及び陰極室３６間の圧力バランスが崩れ、電解漕３２内で液面変動が起こりやすい。また、電解処理中以外でも、例えば、窒素ガスによる電解漕３２内のパージ、原料フッ化水素ガスの供給時終了後の窒素パージ工程等、主にガス切り替え工程の直後に、電解漕３２内で液面変動が起こりやすい。これ等は、フッ素ガス生成装置の安全性及び信頼性を損なう原因となる。
【００４６】
これに対して、図１図示のフッ素ガス生成装置においては、陽極室３４及び陰極室３６の夫々の気相部分の圧力が第１及び第２圧力計４６、４８により連続的に測定される。これ等の測定結果は、第１及び第２流量制御弁５６、７６の夫々に付随する第１及び第２制御部材５７、７７に伝達される。第１及び第２制御部材５７、７７は、伝達された測定結果に基づいて、陽極室３４及び陰極室３６の夫々の気相部分の圧力が互いに実質的に等しい第１及び第２設定値に維持されるように、第１及び第２流量制御弁５６、７６の開度を調整する。即ち、第１及び第２流量制御弁５６、７６は、夫々に付随する第１及び第２制御部材５７、７７の制御下で連続的に開度が調整される。
【００４７】
このように、陽極室３４及び陰極室３６の圧力が、夫々独立して常時測定され且つ制御されるため、陽極室３４及び陰極室３６における溶融塩の液面の状態が均一に維持される。換言すれば、この構成により、電解槽３２は、フッ素の発生状態、第１及び第２配管５２、７２内の状態、コンプレッサ６２や半導体製造工場の排気系７９の動作状態、その他の環境等の変動による悪影響から保護される。このため、高価な電極等に与える損害、例えば陽極効果を未然に回避することができ、安全にしかも突然の電解停止をすることなく処理を進行させることができる。
【００４８】
なお、上述の陽極室３４及び陰極室３６の夫々の気相部分の第１及び第２設定値は、望ましくは大気圧〜８２０Ｔｏｒｒ、より望ましくは大気圧〜７７０Ｔｏｒｒに設定される。また、陽極室３４及び陰極室３６の圧力を安定させるため、第１及び第２流量制御弁５６、７６は応答性よく開度が連続的に調整可能であることが必要である。かかる観点から、第１及び第２流量制御弁５６、７６としてピエゾバルブが望ましくは使用される。
【００４９】
更に、上述のように、プロダクトガス及び副生ガス中には、数パーセント（例えば５％）のフッ化水素が混入する。また、プロダクトガス及び副生ガス中には溶融塩のミスト（ＫＦを主成分とする）も電解槽から同伴する。このフッ化水素及び溶融塩のミストは、プロダクトガス及び副生ガスが夫々吸着カートリッジ５４、７４を通過する際に除去される。これにより、第１及び第２配管５２、７２の入口で溶融塩が固化してこれ等を閉塞させることがなくなり、頻繁にメンテナンスをする必要がなくなる。
【００５０】
フッ化水素及び溶融塩のミストを吸着により捕捉する吸着剤として、カートリッジ５４、７４内には、フッ化ナトリウム（ＮａＦ）の多数のペレットが内蔵される。ＮａＦのペレットは、取扱いや圧力損失を考慮し、気体流通路となる隙間がペレット間に形成されるように、適当な形状及び寸法に調製される。また、フッ化ナトリウムのフッ化水素を吸着する能力は温度により変化するため、カートリッジ５４、７４の周囲には、温度を調節するための温度調節ジャケット（ヒータ）５５、７５が夫々配設される。フッ化水素を最適に吸着する観点から、カートリッジ５４、７４は室温〜３００℃、望ましくは８０〜１２０℃に設定される。
【００５１】
なお、副生ガスは廃棄されるものであるため、必ずしも、副生ガスからフッ化水素を除去する必要はない。即ち、副生ガスが流れる第２配管７２に配設されるカートリッジ７４は、配管系統の閉塞を防止するため、溶融塩のミストを除去できるものであればよい。かかる観点から、副生ガス用のカートリッジ７４に充填される吸着剤としては、フッ化ナトリウムに代えて、フッ化カルシウム、フッ化カリウムなどの無機フッ素化合物を使用することができる。
【００５２】
なお、上記実施の形態において、電解槽３２内の状態を直接的或いは間接的に表す情報として、陽極室３４及び陰極室３６内の圧力を用いて、第１及び第２流量制御弁５６、７６の開度を調整している。しかし、本発明は、電解槽３２内の状態を直接的或いは間接的に表す他の情報、例えば、電解槽３２内の液面のレベルに基づいて、流量を制御する弁の開度を調整するような装置に対しても同様に適用することができる。
【００５３】
また、フッ素ガス生成装置３０は、半導体処理システムに着脱可能に組込まれているが、同システム内に固定的に据え付けられるものであってもよい。また、フッ素ガス生成装置３０内の幾つかの部材、例えば、コンプレッサ６２、主バッファタンク６４、除害部７８等は、半導体製造工場側に設置されたものを使用することもできる。また、フッ素ガスは、流れ管理部２２或いはガス生成部２６に択一的に供給されるが、このガスは、他の処理ガスとは別に直接処理室１２に供給するようにしてもよい。また、ガス生成部２６は、ハロゲン間フッ素化合物ガスではなく、他のフッ素系の処理ガスを生成するように構成することもできる。
【００５４】
その他、本発明の思想の範疇において、当業者であれば、各種の変更例及び修正例に想到し得るものであり、それら変更例及び修正例についても本発明の範囲に属するものと了解される。
【００５５】
【発明の効果】
以上説明したように、本発明によれば、長時間の運転においても高い安全性及び信頼性で作動することが可能なフッ素ガス生成装置を提供することができる。
【図面の簡単な説明】
【図１】図１は本発明の実施の形態に係る、フッ素ガス生成装置を組込んだ半導体処理システムを示す概略図。
【図２】図１図示のガス供給系と組み合わせて使用される半導体処理装置の変更例を示す概略図。
【図３】溶融塩のミストを除去するＮａＦカートリッジの機能を確認するための実験装置を示す概略図。
【符号の説明】
１０、１０ｘ…半導体処理装置、１２…処理室、１８…排気系、２０…ガス供給系、２２…流れ管理部、２４…ガス貯蔵部、２６…ガス生成部、３０…ガス生成装置、３２…電解槽、３４…陽極室、３６…陰極室、３８…電流源、４０…電流積算計、４２…陽極、４４…陰極、４６、４８…圧力計、５２、７２…配管、５４、７４…吸着カートリッジ、５５、７５…温度調節ジャケット（ヒータ）、５６、７６…流量制御弁、５７、７７…制御部材、５８…キャパシタ、６４…バッファタンク、６２…コンプレッサ、７８…除害部、７９…排気系。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluorine gas generator, and more particularly to a fluorine gas generator disposed in a gas supply system of a semiconductor processing system. Here, the semiconductor processing means that a semiconductor device, an insulating layer, a conductive layer, or the like is formed on a substrate to be processed such as a semiconductor wafer or an LCD substrate in a predetermined pattern, so that a semiconductor device or The various processes performed in order to manufacture the structure containing the wiring connected to a semiconductor device, an electrode, etc. are meant.
[0002]
[Prior art]
In the manufacture of semiconductor devices, various types of semiconductor processing such as film formation, etching, and diffusion are performed on a substrate to be processed, such as a semiconductor wafer or an LCD substrate. In a semiconductor processing system that performs such processing, fluorine (F) -based gas is used as a processing gas for various purposes, for example, when etching a silicon film or a silicon oxide film, or when cleaning a processing chamber. The Fluorine gas is attracting attention as a new etching gas and cleaning gas, but it is not common to generate fluorine at the manufacturing site of semiconductor devices because the problem has not been completely solved in terms of safety and reliability. Is not done.
[0003]
However, research and development in this field is underway. For example, Patent Document 1 discloses a semiconductor processing system in which fluorine is generated on site and supplied to a processing chamber as a cleaning gas. In the system disclosed in this document, fluorine is generated as a cleaning gas by electrolyzing hydrogen fluoride (HF) with a gas generator. The cleaning gas is supplied by a supply pipe that connects the gas generator and the processing chamber. A cooling tower is provided in the supply pipe, and hydrogen fluoride (HF) in the cleaning gas is removed by low-temperature condensation.
[0004]
On the other hand, for example, Patent Document 2 discloses an apparatus that generates fluorine gas in a gas manufacturing factory. In the fluorine gas generator disclosed in this document, an electrolytic bath made of a molten salt containing potassium fluoride and hydrogen fluoride is housed in an electrolytic cell, and hydrogen fluoride is electrolyzed in the electrolytic bath. Thereby, a product gas mainly containing fluorine gas is generated on the anode side, and a by-product gas mainly containing hydrogen gas is generated on the cathode side.
[0005]
In the apparatus of Patent Literature 2, a solenoid valve for liquid level control, a blank tower, an absorption tower, a filter tower, and the like are arranged in this order from the upstream side in a supply pipe for taking out product gas. In addition, a solenoid valve for liquid level control, a blank tower, an absorption tower, etc. (no filter tower) are also arranged in this order from the upstream side in the exhaust pipe for discharging the byproduct gas. The blank tower is used to remove electrolytic bath droplets contained in the product gas. The absorption tower contains sodium fluoride (NaF), thereby removing hydrogen fluoride (HF) contained in the product gas. Further, particles contained in the product gas are removed by the filter tower.
[0006]
[Patent Document 1]
US Patent Application Publication No. 2002/0074013 Specification
[Patent Document 2]
JP 2002-339090 A [0008]
[Problems to be solved by the invention]
According to the studies by the present inventors, it has been found that in the conventional apparatus, when the operation time becomes long, as described later, there are some problems in terms of safety and reliability. If such a problem is not solved, it becomes practically difficult to incorporate and use the fluorine gas generator in an automated production system, for example, a semiconductor device manufacturing system.
[0009]
The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a fluorine gas generation device capable of operating with high safety and reliability even during long-time operation. . In particular, an object of the present invention is to provide an apparatus for generating fluorine gas on-site and on-demand. Here, on-site means that the fluorine gas generation apparatus is combined with a predetermined main processing apparatus, for example, a main processing apparatus of a semiconductor processing system. On-demand means that gas can be supplied at the timing according to the request from the main processing apparatus and with necessary component adjustment.
[0010]
[Means for Solving the Problems]
A first aspect of the present invention is an apparatus for generating fluorine gas,
Electrolysis of hydrogen fluoride in an electrolytic bath made of a molten salt containing potassium fluoride and hydrogen fluoride generates a product gas containing fluorine gas as a main component in the first gas phase portion on the anode side, and a cathode An electrolytic cell for generating a by-product gas containing hydrogen gas as a main component in the second gas phase portion on the side;
First piping for deriving the product gas from the first gas phase portion;
A second pipe for deriving the by-product gas from the second gas phase portion;
A first valve for controlling a flow rate of gas passing through the first pipe disposed in the first pipe;
A first control member that adjusts the opening of the first valve based on information that directly or indirectly represents the state in the electrolytic cell;
A first cartridge that is disposed in the first pipe upstream of the first valve and contains a sodium fluoride pellet that adsorbs hydrogen fluoride mixed in the product gas and the molten salt mist;
It is characterized by comprising.
[0011]
According to a second aspect of the present invention, in the apparatus according to the first aspect, the apparatus further includes a second cartridge that is disposed in the second pipe and contains an adsorbent that adsorbs the mist of the molten salt. To do.
[0012]
According to a third aspect of the present invention, in the apparatus according to the second aspect, the adsorbent comprises sodium fluoride pellets.
[0013]
According to a fourth aspect of the present invention, in the apparatus according to the second or third aspect, a second valve for controlling a flow rate of gas passing through the second pipe disposed in the second pipe, and the inside of the electrolytic cell A second control member that adjusts the opening degree of the second valve based on information that directly or indirectly represents the state of the second valve, and the second cartridge is disposed upstream of the second valve. It is characterized by being.
[0014]
According to a fifth aspect of the present invention, in the apparatus according to the fourth aspect, the apparatus further includes first and second pressure gauges for measuring pressures of the first and second gas phase portions, and the first and second controls. The member is configured so that the pressure of the first and second valves is based on the measurement results of the first and second pressure gauges so that the pressures of the first and second gas phase portions are maintained at substantially equal set values. The opening is adjusted respectively.
[0015]
According to a sixth aspect of the present invention, in the apparatus according to any one of the first to fifth aspects, the apparatus further includes a temperature controller for adjusting the temperature of the first cartridge.
[0016]
Further, the embodiments of the present invention include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, when an invention is extracted by omitting some constituent elements from all the constituent elements shown in the embodiment, when the extracted invention is carried out, the omitted part is appropriately supplemented by a well-known common technique. It is what is said.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the course of the development of the present invention, the present inventors have studied the problems of safety and reliability in the conventional fluorine gas generator. As a result, the present inventors have obtained knowledge as described below.
[0018]
In a fluorine gas generator using an electrolytic cell, control of the electrolytic bath liquid level in the electrolytic cell is very important from the viewpoint of safety and reliability. In the apparatus of Patent Document 2, level probes are arranged on both the anode side and the cathode side of the electrolytic cell, and based on the detection result, electromagnetic waves arranged in the product gas supply pipe and the byproduct gas exhaust pipe are arranged. The valve is operated to control the electrolytic bath liquid level in the electrolytic cell. On the other hand, Patent Document 1 does not show any details on this point, but in order to control the electrolytic bath liquid level in the electrolytic cell, a control valve is provided between the gas generator and the cooling tower. Is essential. However, in these apparatus configurations, it is impossible to cope with an instant when an unexpected liquid level fluctuation occurs.
[0019]
On the other hand, the present inventors constantly monitor the pressure of each of the anode and the cathode and finely independently control the flow rate (for example, use of a flow rate controller also having a piezo valve), thereby allowing the inside of the electrolytic cell. It has been found that it is possible to control the pressure of each of the two electrodes very finely and with quick response (Japanese Patent Application No. 2002-202734). This type of flow control valve has a very small diameter of the gas flow path and may be clogged with foreign substances (for example, minute particles or dust) accompanying the gas. Therefore, a filter is provided on the upstream side of each pole. To protect the flow control valve.
[0020]
However, when this apparatus developed by the present inventors was further experimented, the electrolysis bath was well controlled at the initial stage of electrolysis, but in a portion where the differential pressure in the piping on both sides (for example, a filter) was generated for a short time. As a result, there was a new problem that a blockage occurred and continuous operation became impossible. As a cause of this, it has been found that molten salt mist accompanied by each gas generated in the electrolytic cell is deposited and clogged on the filter surface.
[0021]
In addition, the fine molten salt mist accompanied with gas penetrate | invades in each member which exists between piping or an electrolytic vessel, and a compressor. Since the mist has a melting point near 80 ° C., it exists as a solid in the pipe. As the amount of mist increases, problems such as pipe blockage or damage to the valve seat in the on / off valve occur.
[0022]
In the former case, it is necessary to immediately stop the operation of the electrolytic cell and remove salt clogged in the piping. Since the reactive gas fluorine is also present in the pipes, the removal work of the pipe internal parts involves the latest caution and danger. In the latter case, since leakage occurs in the valve, it is necessary to stop the operation of the electrolytic cell. In addition, since the on / off valve frequently repeats its operation, the life of the valve is shortened.
[0023]
When this point was examined by experiment, it was found from the measurement result of the electron microscope that the size distribution of the molten salt mist captured on the filter was 0.4 to 0.6 μm. It was also observed that the filter media was corroded by molten salt mist, especially when the filter media was made of stainless steel (eg SS316L). Furthermore, in the past, a filter was provided only on the anode side piping of the electrolytic cell where product gas (fluorine gas is the main component) is generated, but in the by-product gas (hydrogen gas is the main component) generated from the cathode. Was also found to contain molten salt mist (thus causing piping blockage).
[0024]
By the way, as also shown in Patent Document 2, sodium fluoride (NaF) is conventionally used to remove hydrogen fluoride (HF) contained in a product gas in a fluorine gas generator using an electrolytic cell. The In order to improve the fluorine gas generation apparatus, the present inventors conducted various experiments on the fluorine gas adsorption ability of NaF. At the same time, the inventors found the following functions of NaF.
[0025]
That is, in a certain experiment, a cartridge containing NaF pellets was installed in the product gas supply pipe of the fluorine gas generator, and the fluorine gas adsorption ability of NaF was examined. As a result, the NaF cartridge can remove the potassium fluoride (KF) component derived from the molten salt (the main component of the molten salt mist) to the sub PPB level in addition to hydrogen fluoride, which is the target component to be originally removed. It was found.
Further, it was found that other components accompanying the molten salt mist were almost removed downstream of the NaF cartridge. In this case, the metal analysis is performed by bubbling the product gas directly into a PFA container containing ultrapure water to capture metal impurities, and the resulting hydrogen fluoride water is used for high frequency induction plasma mass spectrometry (ICP- MS).
[0026]
Based on this result, it was further examined whether or not the NaF cartridge can be used to remove the mist of the molten salt.
[0027]
[Experiment]
When a 1/4 inch guard filter (0.04 μm) is used for each of the anode and cathode pipes of the fluorine gas generator, the lifetime until the filter is blocked by mist is 4 to 15 hours on the cathode side. The anode side was about 120 hours. For this reason, considering the merit of time, the experimental apparatus shown in FIG. 3 is arranged on the cathode side of the fluorine gas generator (the side where the by-product gas containing hydrogen gas as a main component is generated), and the molten salt mist An experiment was conducted to confirm the function of the NaF cartridge that removes.
[0028]
As shown in FIG. 3, a pressure gauge 116 and a piezo valve 118 were connected to the cathode of the fluorine gas generator through first and second pipes 112 and 114 that can be switched in parallel. The piezo valve 118 was configured to be controlled to open and close based on the pressure of the cathode of the fluorine gas generator. The first pipe 112 is provided with a cartridge 122 containing NaF pellets and a guard filter 124, and the second pipe 114 is provided with only a guard filter 126.
[0029]
The first and second pipes 112 and 114 were alternately used, and the time during which the guard filters 124 and 126 were blocked by mist was measured. The determination of the blockage was made when the state where the opening degree of the piezo valve 118 was 100% or more and the pressure of the pressure gauge 116 was −30 kPa or less continued for 1 minute or more. The piezo valve 118 was set to be held at a valve opening of about 60% in a normal state. The reason why the opening of the piezo valve 118 is large is that when the pressure on the cathode is increased due to the clogging on the upstream side, the opening is increased and more by-product gas is allowed to flow.
[0030]
The specific experimental procedure is as follows.
(1) First, in order to measure the closing time of the guard filter 126, the valves V1a and V1b are closed and the valves V2a and V2b are opened.
(2) Record the integrated electrolytic amount (Ah) before the start.
(3) 100A continuous electrolysis (fluorine generation amount is about 688 cc / min) is performed.
(4) Fluorine electrolysis is stopped at the time when the blockage judgment condition is satisfied, and the accumulated electrolysis amount of fluorine generation is recorded.
(5) Next, in order to measure the closing time of the guard filter 124, the temperature of the NaF cartridge 122 is raised to 200 ° C., the valves V1a and Vlb are opened, and the valves V2a and V2b are closed.
(6) Record the integrated electrolytic amount (Ah) before the start.
(7) 100A continuous electrolysis (fluorine generation amount is about 688 cc / min) is performed.
(8) Fluorine electrolysis is stopped at the time when the blockage judgment condition is satisfied, and the accumulated electrolysis amount of fluorine generation is recorded.
[0031]
Table 1 shows the results of the above experiment. In Table 1, “F124” and “F126” indicate the guard filter 124 (with the NaF cartridge 122) and the guard filter 126 (without the NaF cartridge 122), respectively. “IEs”, “IEe”, and “IEc” respectively indicate the accumulated electrolytic amount at the start, the accumulated electrolytic amount at the end, and the electrolytic amount (Ah) until the blockage.
[0032]

As shown in this experimental result, it has been found that the use of the NaF cartridge 122 extends the guard filter blocking time by mist by a factor of five. Since the pipe diameter of the NaF cartridge 122 is thicker than that of the normal pipe, there is a possibility that the reduction in the flow velocity accompanying this has led to the improvement of the lifetime. However, since the pipe diameters at the trapping guard filters 124 and 126 are the same ¼ inch, it can be seen that the NaF cartridge 122 is effective for trapping droplets even with a simple comparison.
[0033]
Hereinafter, an embodiment of the present invention configured based on such knowledge will be described with reference to the drawings. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.
[0034]
FIG. 1 is a schematic diagram showing a semiconductor processing system incorporating a fluorine gas generator according to an embodiment of the present invention. The semiconductor processing system includes a semiconductor processing apparatus 10 that performs processing such as film formation, etching, or diffusion on a substrate to be processed such as a semiconductor wafer or an LCD substrate.
[0035]
The semiconductor processing apparatus 10 includes a processing chamber 12 for storing a substrate to be processed and performing semiconductor processing. In the processing chamber 12, a lower electrode and mounting table (supporting member) 14 for mounting a substrate to be processed is disposed. An upper electrode 16 is also disposed in the processing chamber 12 so as to face the mounting table 14. By applying RF power from an RF (high frequency) power source 15 between both electrodes 14 and 16, an RF electric field for converting the processing gas into plasma is formed in the processing chamber 12. An exhaust system 18 for exhausting the inside and setting a vacuum is connected to the lower portion of the processing chamber 12. A gas supply system 20 for supplying a processing gas is connected to the upper portion of the processing chamber 12.
[0036]
FIG. 2 is a schematic view showing a modified example 10x of the semiconductor processing apparatus used in combination with the gas supply system 20 shown in FIG. The semiconductor processing apparatus 10x includes a processing chamber 12 for storing a substrate to be processed and performing semiconductor processing. A placement table (support member) 14 for placing a substrate to be processed is disposed in the processing chamber 12. An exhaust system 18 for exhausting the inside and setting a vacuum is connected to the lower portion of the processing chamber 12. A remote plasma chamber 13 for generating plasma is connected to the upper portion of the processing chamber 12. A coil antenna 17 is wound around the remote plasma chamber 13. By applying RF power from the RF (high frequency) power source 15 to the coil antenna 17, an induction electric field for converting the processing gas into plasma is formed in the remote plasma chamber 13. A gas supply system 20 for supplying a processing gas is connected to the upper part of the remote plasma chamber 13.
[0037]
The fluorine gas generation apparatus according to the embodiment of the present invention can also be applied to a case where a cleaning gas or the like is supplied to a semiconductor processing apparatus that does not use plasma, such as a thermal CVD apparatus.
[0038]
Returning to FIG. 1, the gas supply system 20 is selectively switched between a predetermined gas in the processing chamber 12, for example, a processing gas for performing semiconductor processing and a processing gas for cleaning the processing chamber 12. A flow management unit 22 for supplying at a flow rate of is provided. A gas storage unit 24 having a plurality of gas sources for storing various active gases and inert gases is connected to the flow management unit 22. The flow management unit 22 is also connected to a gas generation unit 26 that generates a fluorine gas-based processing gas by a reaction process.
[0039]
A fluorine gas generation device 30 according to an embodiment of the present invention is detachably connected to the flow management unit 22 and the gas generation unit 26. That is, the generation device 30 is used to supply the fluorine gas directly to the flow management unit 22 or to supply the fluorine gas raw material to the gas generation unit 26 (the switching valve is not shown).
[0040]
The production | generation apparatus 30 has the airtight electrolytic vessel 32 which accommodates the electrolytic bath which consists of molten salt containing hydrogen fluoride. The molten salt is composed of a mixture of potassium fluoride (KF) and hydrogen fluoride (HF) (KF / 2HF) or Fremy's salt (KF / 2HF + additive). The electrolytic cell 32 is divided into an anode chamber 34 and a cathode chamber 36 by a partition plate 35 extending from above into the molten salt. In the anode chamber 34 and the cathode chamber 36, a carbon electrode (anode) 42 and a nickel electrode (cathode) 44 are respectively immersed in the molten salt. The electrolytic cell 32 is provided with a current source 38 for supplying a current between the anode 42 and the cathode 44 and a current accumulator 40 for integrating the supply current.
[0041]
During the electrolytic treatment, the electrolytic cell 32 is heated and kept at 80 to 90 ° C. by the accompanying heater 33. By electrolyzing hydrogen fluoride in the electrolytic bath, a product gas containing fluorine gas (F ₂ ) as a main component is generated in the gas phase portion of the anode chamber 34, and hydrogen gas is mainly used in the gas phase portion of the cathode chamber 36. By-product gas as a component is generated. In each of the product gas and the by-product gas, hydrogen fluoride gas is mixed by the vapor pressure of the hydrogen fluoride gas in the molten salt of the raw material (for example, 5%). First and second pressure gauges 46 and 48 are disposed in the anode chamber 34 and the cathode chamber 36 in order to continuously measure the pressure in each gas phase portion.
[0042]
Connected to the anode chamber 34 is a first pipe 52 for extracting the product gas and sending it to the flow management unit 22 and the gas generation unit 26 of the gas supply system 20. In the first pipe 52, an adsorption cartridge 54, a first flow control valve 56, a mini buffer tank 58, a compressor (suction means) 62, a main buffer tank 64, and the like are disposed in order from the upstream side. The product gas generated in the anode chamber 34 is forcibly extracted from the anode chamber 34 by the first pipe 52 being sucked by the compressor 62 and stored in the main buffer tank 64. In FIG. 1, reference numeral 66 denotes a line filter.
[0043]
A pressure gauge 65 is disposed in the main buffer tank 64, and the pressure in the tank 64 is continuously measured. This measurement result is transmitted to the control member 39 associated with the current source 38. The control member 39 turns on / off the current source 38 based on the transmitted measurement result, and controls the supply of current to the electrolytic cell 32. That is, when the pressure in the tank 64 decreases to a certain pressure, the current source 38 is turned on and generation of fluorine gas is started. When the pressure in the tank 64 increases to a certain pressure, the current source 38 is turned off and generation of fluorine gas is stopped. The Thereby, electrolysis can be stopped without making a difference in the liquid level of the molten salt between the anode chamber 34 and the cathode chamber 36 in the electrolytic cell 32. The pressure in the tank 64 is set to, for example, atmospheric pressure to atmospheric pressure + 0.18 Mpa.
[0044]
On the other hand, the second piping 72 for deriving byproduct gas is connected to the cathode chamber 36. The second pipe 72 is detachably connected to, for example, a pipe of an exhaust system (suction unit) 79 of a semiconductor manufacturing factory. In the second pipe 72, an adsorption cartridge 74, a second flow rate control valve 76, an abatement part 78, and the like are disposed in order from the upstream side. The by-product gas generated in the cathode chamber 36 is forcibly extracted from the cathode chamber 36 by the second piping 72 being sucked by the exhaust system 79, passes through the abatement part 78, and then enters the exhaust system 79. Sent.
[0045]
As described above, during the electrolytic treatment, the pressure balance between the anode chamber 34 and the cathode chamber 36 is broken due to various factors, and the liquid level is likely to change in the electrolytic bath 32. Further, even during other than the electrolytic treatment, for example, in the electrolytic bath 32 immediately after the gas switching step, such as the purge in the electrolytic bath 32 with nitrogen gas, the nitrogen purge step after the supply of the raw material hydrogen fluoride gas, etc. Liquid level fluctuations are likely to occur. These cause damage to the safety and reliability of the fluorine gas generator.
[0046]
On the other hand, in the fluorine gas generator shown in FIG. 1, the pressures in the gas phase portions of the anode chamber 34 and the cathode chamber 36 are continuously measured by the first and second pressure gauges 46 and 48. These measurement results are transmitted to the first and second control members 57 and 77 associated with the first and second flow control valves 56 and 76, respectively. Based on the transmitted measurement results, the first and second control members 57 and 77 set the first and second set values so that the pressures in the gas phase portions of the anode chamber 34 and the cathode chamber 36 are substantially equal to each other. The opening degree of the first and second flow rate control valves 56 and 76 is adjusted so as to be maintained. That is, the opening degree of the first and second flow control valves 56 and 76 is continuously adjusted under the control of the first and second control members 57 and 77 attached thereto.
[0047]
As described above, the pressures in the anode chamber 34 and the cathode chamber 36 are always constantly measured and controlled independently, so that the state of the molten salt liquid level in the anode chamber 34 and the cathode chamber 36 is maintained uniformly. In other words, with this configuration, the electrolytic cell 32 has a fluorine generation state, a state in the first and second pipes 52 and 72, an operation state of the compressor 62 and the exhaust system 79 of the semiconductor manufacturing factory, and other environments. Protects against adverse effects of fluctuations. For this reason, damage to the expensive electrode or the like, for example, the anodic effect can be avoided in advance, and the process can be advanced safely and without suddenly stopping the electrolysis.
[0048]
Note that the first and second set values of the gas phase portions of the anode chamber 34 and the cathode chamber 36 are preferably set to atmospheric pressure to 820 Torr, and more preferably set to atmospheric pressure to 770 Torr. Further, in order to stabilize the pressure in the anode chamber 34 and the cathode chamber 36, the first and second flow rate control valves 56 and 76 need to be able to continuously adjust the opening degree with high responsiveness. From this point of view, piezo valves are preferably used as the first and second flow control valves 56 and 76.
[0049]
Furthermore, as described above, several percent (for example, 5%) of hydrogen fluoride is mixed in the product gas and the by-product gas. In addition, molten salt mist (mainly KF) is also entrained in the product gas and by-product gas from the electrolytic cell. The mist of hydrogen fluoride and molten salt is removed when the product gas and by-product gas pass through the adsorption cartridges 54 and 74, respectively. As a result, the molten salt does not solidify at the inlets of the first and second pipes 52 and 72 to block them, and the need for frequent maintenance is eliminated.
[0050]
A large number of pellets of sodium fluoride (NaF) are built in the cartridges 54 and 74 as adsorbents for capturing hydrogen fluoride and molten salt mist by adsorption. In consideration of handling and pressure loss, NaF pellets are prepared in an appropriate shape and size so that a gap serving as a gas flow path is formed between the pellets. Further, since the ability of sodium fluoride to adsorb hydrogen fluoride varies depending on the temperature, temperature adjustment jackets (heaters) 55 and 75 for adjusting the temperature are arranged around the cartridges 54 and 74, respectively. . From the viewpoint of optimally adsorbing hydrogen fluoride, the cartridges 54 and 74 are set to room temperature to 300 ° C., preferably 80 to 120 ° C.
[0051]
Since the byproduct gas is discarded, it is not always necessary to remove hydrogen fluoride from the byproduct gas. That is, the cartridge 74 disposed in the second pipe 72 through which the by-product gas flows may be any cartridge that can remove molten salt mist in order to prevent the piping system from being blocked. From this point of view, an inorganic fluorine compound such as calcium fluoride or potassium fluoride can be used as the adsorbent filled in the byproduct gas cartridge 74 instead of sodium fluoride.
[0052]
In the above-described embodiment, the first and second flow control valves 56 and 76 using the pressure in the anode chamber 34 and the cathode chamber 36 as information that directly or indirectly represents the state in the electrolytic cell 32. The degree of opening is adjusted. However, the present invention adjusts the opening of the valve that controls the flow rate based on other information that directly or indirectly represents the state in the electrolytic cell 32, for example, the level of the liquid level in the electrolytic cell 32. The same can be applied to such an apparatus.
[0053]
Moreover, although the fluorine gas production | generation apparatus 30 is incorporated in the semiconductor processing system so that attachment or detachment is possible, it may be fixedly installed in the system. In addition, some members in the fluorine gas generation device 30, for example, the compressor 62, the main buffer tank 64, the abatement part 78, etc., can be used installed on the semiconductor manufacturing factory side. Further, the fluorine gas is alternatively supplied to the flow management unit 22 or the gas generation unit 26, but this gas may be supplied directly to the processing chamber 12 separately from other processing gases. Further, the gas generating unit 26 can be configured to generate other fluorine-based processing gas instead of the interhalogen fluorine compound gas.
[0054]
In addition, in the category of the idea of the present invention, those skilled in the art can conceive of various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention. .
[0055]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a fluorine gas generation device that can operate with high safety and reliability even during long-time operation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a semiconductor processing system incorporating a fluorine gas generation device according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a modified example of a semiconductor processing apparatus used in combination with the gas supply system shown in FIG.
FIG. 3 is a schematic view showing an experimental apparatus for confirming the function of a NaF cartridge for removing mist of molten salt.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 10x ... Semiconductor processing apparatus, 12 ... Processing chamber, 18 ... Exhaust system, 20 ... Gas supply system, 22 ... Flow management part, 24 ... Gas storage part, 26 ... Gas generation part, 30 ... Gas generation apparatus, 32 ... Electrolytic cell, 34 ... anode chamber, 36 ... cathode chamber, 38 ... current source, 40 ... current accumulator, 42 ... anode, 44 ... cathode, 46, 48 ... pressure gauge, 52, 72 ... piping, 54, 74 ... adsorption Cartridge, 55, 75 ... Temperature control jacket (heater), 56, 76 ... Flow rate control valve, 57, 77 ... Control member, 58 ... Capacitor, 64 ... Buffer tank, 62 ... Compressor, 78 ... Abatement part, 79 ... Exhaust system.

Claims (5)

An apparatus for generating fluorine gas,
Electrolysis of hydrogen fluoride in an electrolytic bath made of a molten salt containing potassium fluoride and hydrogen fluoride generates a product gas containing fluorine gas as a main component in the first gas phase portion on the anode side, and a cathode An electrolytic cell for generating a by-product gas containing hydrogen gas as a main component in the second gas phase portion on the side;
First piping for deriving the product gas from the first gas phase portion;
A second pipe for deriving the by-product gas from the second gas phase portion;
A first valve for controlling a flow rate of gas passing through the first pipe disposed in the first pipe;
A first control member that adjusts the opening of the first valve based on information that directly or indirectly represents the state in the electrolytic cell;
A first cartridge that is disposed in the first pipe upstream of the first valve and contains a sodium fluoride pellet that adsorbs hydrogen fluoride mixed in the product gas and the molten salt mist;
A second cartridge containing an adsorbent that is disposed in the second pipe and adsorbs the mist of the molten salt;
A fluorine gas generation device comprising: The fluorine gas generation apparatus according to claim 1 , wherein the adsorbent comprises sodium fluoride pellets. A second valve that controls the flow rate of gas passing through the second pipe disposed in the second pipe, and the opening of the second valve based on information that directly or indirectly represents the state in the electrolytic cell. The fluorine gas generator according to claim 1 , further comprising a second control member that adjusts the degree, wherein the second cartridge is disposed upstream of the second valve. The apparatus further comprises first and second pressure gauges for measuring the pressures of the first and second gas phase portions, and the first and second control members are substantially equal in pressure to the first and second gas phase portions. so as to maintain equal set value, according to claim 3, characterized in that the opening of the first and second valves respectively adjusted based on the measurement result of the first and second pressure gauge Fluorine gas generator. The fluorine gas generation device according to claim 1 , further comprising a temperature controller that adjusts a temperature of the first cartridge.

Images