JP3681908B2 - Mechanism for introducing a trace gas into an ultra-high vacuum chamber - Google Patents

Mechanism for introducing a trace gas into an ultra-high vacuum chamber Download PDF

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JP3681908B2
JP3681908B2 JP32300198A JP32300198A JP3681908B2 JP 3681908 B2 JP3681908 B2 JP 3681908B2 JP 32300198 A JP32300198 A JP 32300198A JP 32300198 A JP32300198 A JP 32300198A JP 3681908 B2 JP3681908 B2 JP 3681908B2
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JP2000146096A (en
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俊彦 進
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Kobe Steel Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は、極高真空チャンバへの微量ガス導入機構に関し、例えば宇宙環境の模擬実験装置などに用いて好適である。
【０００２】
【従来の技術】
近年、１０-7Ｐａ以下の極高真空にある部材に対する、微量ガスの与える影響が議論されている。例えば人工衛星のような部材は、たとえ極高真空の宇宙空間にある場合であっても、部材表面などから放出された１０-4〜１０-6Ｐａ程度の微量ガスの存在する環境にあることになる。かかる微量ガスを含んだ極高真空下において部材が受ける影響を実験室内で予め調べておくことは、今後の宇宙開発などにとってきわめて有効である。
【０００３】
チャンバ内に微量のガスを導入するための機構として、マスフローコントローラを用いるものと、バラトロン圧力計と制御弁により配管内の圧力をフィードバック制御し、リーク弁を介して、その圧力差により供給圧力を制御するものが知られている（「分子線エピタキシー」、４５頁〜４７頁、７６頁〜７９頁、権田俊一編著、培風館）。
【０００４】
【発明が解決しようとする課題】
しかるに、比較的小さな超高真空チャンバ内に、マスフローコントローラを用いてガス導入量を調節すると、一般的なマスフローコントローラの最小流量調節可能範囲が大きすぎるため、所望の導入ガス分圧に調整できない。また、供給圧力を調整することによりガス導入量を調節しても、バラトロン圧力計での圧力が大気圧以上であると、ガス導入量が多すぎるため、チャンバへの導入口をφ０．０１mm以下の微細な穴に加工する必要がある。このような加工は、技術的に困難であるため、所望の導入ガス分圧に調整できない。即ち、従来の機構によっては、１０-7Ｐａ以下の極高真空チャンバ内に所望の分圧（１０-4〜１０-6Ｐａ程度）で微量ガスを導入できないという問題点があった。
【０００５】
本発明は、上記問題に鑑みてなされたものであって、その目的とするところは、超高真空のチャンバ内に微量のガスを導入できる微量ガス導入機構を提供することである。
【０００６】
【課題を解決するための手段】
請求項１記載の発明は、ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、前記排気手段の上流側に接続された流量調整弁と、下流側が極高真空チャンバに接続されるとともに、上流側が前記流量調整弁より上流において前記排気手段と並列に前記ガス供給源に接続された開閉弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする。
【０００７】
ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できる。
また、排気手段により排気するガスの流量を制限できるため、排気ガスの無駄を減少できる。
【０００８】
請求項２記載の発明は、ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、下流側が極高真空チャンバに接続されるとともに、上流側が前記排気手段と並列に前記ガス供給源に接続された開閉弁と、前記ガス供給源の下流且つ前記開閉弁の前記排気手段への接続部より上流に、前記開閉弁の上流における圧力がフィードバックされることにより、前記開閉弁の上流側の圧力が一定となるように調整される圧力調整弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする。
ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できる。
また、開閉弁の上流側の圧力を一定に保つことができるため、極高真空チャンバ内への極微量の放出流量をより安定に保つことができる。
【０００９】
請求項３記載の発明は、ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、前記排気手段の上流側に接続された流量調整弁と、下流側が極高真空チャンバに接続されるとともに、上流側が前記流量調整弁より上流において前記排気手段と並列に前記ガス供給源に接続された開閉弁と、前記ガス供給源の下流且つ開閉弁の前記排気手段への接続部より上流に、前記開閉弁の上流における圧力がフィードバックされることにより前記開閉弁の上流側の圧力が一定となるように調整される圧力調整弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする。
ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できる。
また、排気手段により排気するガスの流量を制限できるため、排気ガスの無駄を減少できる。
また、開閉弁の上流側の圧力を一定に保つことができるため、極高真空チャンバ内への極微量の放出流量をより安定に保つことができる。
【００１０】
請求項４記載の発明は、請求項１乃至請求項３のいずれかに記載の発明の構成に加えて、前記ガス供給源から前記開閉弁までの間で前記ガスが凝縮しないように前記ガスを加熱する加熱手段をさらに有しており、前記排気手段により少なくとも前記開閉弁の上流における前記ガスの圧力が飽和蒸気圧以下とされることを特徴とする。
これにより、ガス供給源に液体状態で貯溜されていた物質であっても、ガスとしてわずかな分量だけ極高真空チャンバ内に導入することができる。
【００１２】
【発明の実施の形態】
以下、本発明の実施形態を図面に基づいて説明する。極高真空チャンバへの微量ガス導入機構１は、図１に示すように、極高真空チャンバ９とガス供給源であるガスボンベ２とが接続されて構成されており、極高真空チャンバ９内に極微量のガスを導入できるようになっている。ガスボンベ２には、減圧弁３が接続されており、減圧弁３の下流側へ流れるガス圧力を調整するようになっている。減圧弁３の下流側には、圧力調整装置４ａを備えた圧力調整弁４と圧力センサ５が接続されており、圧力センサ５は、圧力調整弁４の下流側から開閉弁を構成する超高速電磁弁８の上流側の圧力を検出し、圧力調整装置４ａは、検出圧力から圧力調整弁４をフィードバック制御するようになっている。圧力調整弁４の下流には、流量調整弁６と超高速電磁弁８が並列に接続されている。流量調整弁６の下流側には、排気手段を構成するガス系真空ポンプ７が接続されており、ガス系真空ポンプ７は、流量調整弁６の上流側が低圧になるようにガスを吸い込み大気へ放出するようになっている。流量調整弁６は、絞りを調整することによりガス系真空ポンプ７から大気へのガス放出量を制御するようになっている。また、超高速電磁弁８の下流側には、極高真空チャンバ９が接続されている。この極高真空チャンバ９には、図示されない真空ポンプがさらに接続されている。真空ポンプは、常に極高真空チャンバ９内のガスを排気しており、極高真空チャンバ９内は、真空状態に保たれるようになっている。超高速電磁弁８は、非常に短い時間だけ開状態にすることにより、１０-7Ｐａ程度の極高真空チャンバ９内へ導入される導入ガス量を極微量に制限するようになっている。
【００１３】
次に、上記の構成に基づいて、微量ガス導入機構１の動作を説明する。極高真空チャンバ９内には、図示されない真空ポンプによりガスが排気され、常に、真空状態に保たれる。ガスボンベ２から供給された導入ガスは、一旦減圧弁３により０．２ＭＰａ（約２気圧）程度まで減圧される。圧力調整弁４の下流側に放出されたガスの圧力を圧力センサ５により測定し、その測定圧力から圧力調整弁４をフィードバック制御して、圧力調整弁４の下流側から流量調整弁６及び超高速電磁弁８の上流側の圧力を一定圧力に調整する。次に、ガス系用真空ポンプ７により流量調整弁６の下流側を１００Ｐａ（約０．００１気圧）程度に保つ。これにより、流量調整弁６の下流側の圧力が流量調整弁６の上流側の圧力より小さくなるため、流量調整弁６を開けると、ガスボンベ２から放出されるガスは、超高速電磁弁８側へ流れずに、圧力の低い流量調整弁６下流側へ導かれる。そのため、超高速電磁弁８の上流側の圧力を大気圧以下（１００Ｐａ程度）まで減圧できる。
【００１４】
このように、超高速電磁弁８の上流側の圧力を大気圧以下に保つことができるため、超高速電磁弁８を開状態にしたとき、超高速電磁弁上流、下流の差圧を小さくすることができることにより、極高真空チャンバ９内へのガス導入量を極微量に調整できる。そして、超高速電磁弁８の開時間を２００μsec 〜８００μsec に制限し、動作インターバルを１Hz程度に設定すると、極高真空チャンバ９内に導入されるガスの平均の分圧を１０-4〜１０-6Ｐａの任意の圧力に調整できる。超高速電磁弁８の開時間は、１msec以下にすることが望ましい。これにより、ガス導入時間を極短時間に制限でき、微量のガスを正確に極高真空チャンバ９内に導入できる。
【００１５】
尚、極高真空チャンバ９内の微量ガス量は、超高速電磁弁８を介して導入されるガス量と、極高真空チャンバ９から図示しない真空ポンプによって、排気されるガス量とのバランスによって決定される。そのため、極高真空チャンバ９内のガス量は、極高真空チャンバ９に接続された真空ポンプの能力にも依存することになる。しかし、極高真空チャンバ９内の微量ガス量を迅速かつ安定に制御するためには、多量導入多量排出よりも少量導入少量排出の方が優れているため、この真空ポンプの能力をできるだけ小さくし、それに合わせて導入ガス量も少なくすることが好ましい。
【００１６】
次に、微量ガスとして水蒸気を極高真空チャンバ９内へ導入する場合を説明する。図２に示すように、微量ガス導入機構１０が上記の微量ガス導入機構１と異なる点は、加熱手段を構成するヒータ１３を設けた点と、減圧弁３を手動弁１２に置換した点と、ガスボンベ２をH2O タンク（ガス供給源）１１に置換した点である。
【００１７】
このガス導入機構１０は、ヒータ１３によりH2O タンク１１の下流側から超高速電磁弁８の上流側までの温度を４０度以上に保ち、H2O タンク１１から放出された水蒸気が再凝縮するのを防止する。次に、導入H2O 量の圧力を圧力センサ５により測定し、その測定圧力から圧力調整弁４をフィードバック制御して、圧力調整弁４の下流側から超高速電磁弁８の上流側までの圧力を一定圧力に調整する。次に、ガス系用真空ポンプ７の上流側から流量調整弁６の下流側は、ガス系用真空ポンプ７により、例えば１０００Ｐａ（約０．０１気圧）に保つ。これにより、圧力調整弁４の下流側から超高速電磁弁８の上流側までの圧力より流量調整弁６下流側の圧力が小さくなるため、流量調整弁６を開けると、H2O タンク１１から放出されるH2O は、流量調整弁６の下流側へ導かれるため、圧力調整弁４の下流側から超高速電磁弁８の上流側までの圧力を大気圧以下（１０００Ｐａ程度）まで減圧できる。このことから、圧力調整弁４の下流側から超高速電磁弁８の上流側までの温度が２９０Ｋ以下となっても、H2O が再凝縮しないように飽和蒸気圧以下に保つことができる。このように、圧力調整弁４の下流側から超高速電磁弁８の上流側までのH2O 圧を大気圧以下に保つことができるため、超高速電磁弁８を開状態にしたとき、極高真空チャンバ９内へのH2O 導入量を極微量に調整できる。そして、超高速電磁弁８の開時間を２００μsec 〜８００μsec に制限し、動作インターバルを１Hz程度に設定すると、真空度を１０-7Ｐａ以下に調整し、真空チャンバ９内に導入されるH2O の分圧を１０-4〜１０-6Ｐａに調整できる。
【００１８】
また、流量調整弁６の開度を絞ると、ガス系用真空ポンプ７により排出されるH2O の量を抑えることができる。このことからガス系真空ポンプ７に油回転ポンプを使用しても、H2O による油の劣化を抑えることができ、流量調整弁６をつけない場合よりメンテナンスサイクルの延長を図ることができる。尚、図２の実施形態では、油回転ポンプであるガス系用真空ポンプ７の油に水が混入して能力が低下するのを防止するため、ガスバラスト弁を開いて用いることが好ましい。
【００１９】
【実施例１】
極高真空チャンバ９には、２００ｍｍ×φ３００ｍｍのチャンバを使用し、導入ガスは、Ｎ2 ガスを使用して、超高速電磁弁８の上流側の圧力を１．３×１０3 Ｐａに設定する。超高速電磁弁８の動作時間は、開時間を８００μsec に設定し、動作インターバルを１Hzとする。ガス導入前の極高真空チャンバ９内の真空度は２×１０-7Ｐａ、ガス導入前のＮ2 ガス分圧は４×１０-8Ｐａである。このような実験条件下において、微量ガス導入機構１を使用すると、図３に示すように、ガス導入中のＮ2 ガス分圧が制御され、ガス導入中の真空度を平均６×１０-5Ｐａ、ガス導入中のＮ2 ガス分圧を平均６×１０-5Ｐａに調整できる。尚、図３に示すＮ2 分圧の変動幅は、圧力測定のためのサンプリング間隔を示しており、超高速電磁弁８の開閉周期を表すものではない。
【００２０】
【実施例２】
微量ガス導入機構１０を用いて以下の条件で実験を行った。超高速電磁弁８の上流側の圧力を６．５×１０2 Ｐａに設定する。超高速電磁弁８の動作時間は、開時間を８００μsec に設定し、動作インターバルを１Hzとした。H2O 導入前の真空度は６．２×１０-7Ｐａ、H2O 導入前のH2O 分圧は６．２×１０-7Ｐａである。これにより、H2O 導入中の真空度を７．３×１０-6Ｐａ、H2O 導入中のH2O 分圧を７．３×１０-6Ｐａに調整できる。
【００２１】
尚、本実施形態に係る微量ガス導入機構１、１０は、極高真空チャンバ９内に微量のガスを導入するものであるため、宇宙環境の模擬実験装置に限らず、分子線エピタキシャル装置のような半導体製造装置に使用してもよい。また、実施例１では、導入ガスをＮ2 ガスとし、実施例２では、導入ガスを水蒸気としたが、これに限るものではなく、Ｏ2 ガスや、ＣＨ4 ガス、ＣＯガス、ＣＯ2 ガス、アルコール等でもよい。
【００２２】
【発明の効果】
請求項１記載の発明は、ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できるという効果を奏する。
加えて、排気手段により排気するガスの流量を制限できるため、排気ガスの無駄を減少できるという効果を奏する。
【００２３】
請求項２記載の発明は、ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できるという効果を奏する。
加えて、開閉弁の上流側の圧力を一定に保つことができるため、極高真空チャンバ内への極微量の放出流量をより安定に保つことができるという効果を奏する。
【００２４】
請求項３記載の発明は、ガス供給源から供給された導入ガスを排気手段で排気することにより、排気手段と並列にガス供給源に接続された開閉弁の上流側の圧力を低く保つことができるため、開閉弁の上流側と下流側との差圧を小さくできる。これにより、極高真空チャンバ内への放出流量を極微量に調整できるという効果を奏する。
加えて、排気手段により排気するガスの流量を制限できるため、排気ガスの無駄を減少できるという効果を奏する。
加えて、開閉弁の上流側の圧力を一定に保つことができるため、極高真空チャンバ内への極微量の放出流量をより安定に保つことができるという効果を奏する。
【００２５】
請求項４記載の発明は、請求項１乃至請求項３のいずれかに記載の発明の効果に加えて、ガス供給源に液体状態で貯溜されていた物質であっても、ガスとしてわずかな分量だけ極高真空チャンバ内に導入できるという効果を奏する。
【図面の簡単な説明】
【図１】極高真空チャンバへの微量ガス導入機構を説明する図である。
【図２】極高真空チャンバへの微量ガス導入機構を説明する図である。
【図３】極高真空チャンバ内の導入ガスの分圧と時間の関係を説明するグラフである。
【符号の説明】
１、１０ 微量ガス導入機構
２ ガスボンベ
３ 減圧弁
４ 圧力調整弁
５ 圧力センサ
６ 流量調整弁
７ ガス系用真空ポンプ
８ 超高速電磁弁
９ 真空チャンバ
１１ H2O タンク
１２ 手動弁
１３ ヒータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mechanism for introducing a trace gas into an ultra-high vacuum chamber, and is suitable for use in, for example, a simulation experiment apparatus in a space environment.
[0002]
[Prior art]
In recent years, the influence of trace gas on members in an extremely high vacuum of 10 −7 Pa or less has been discussed. For example, a member such as an artificial satellite is in an environment where there is a trace gas of about 10 −4 to 10 −6 Pa emitted from the surface of the member even in an extremely high vacuum space. become. It is extremely effective for future space development and the like to investigate in advance in a laboratory the influence of a member under an extremely high vacuum containing such a trace gas.
[0003]
As a mechanism for introducing a very small amount of gas into the chamber, the pressure in the pipe is feedback controlled by using a mass flow controller and a Baratron pressure gauge and a control valve, and the supply pressure is controlled by the pressure difference via a leak valve. What is controlled is known ("Molecular Beam Epitaxy", pages 45-47, pages 76-79, edited by Shunichi Gonda, Baifukan).
[0004]
[Problems to be solved by the invention]
However, if the amount of gas introduced is adjusted using a mass flow controller in a relatively small ultra-high vacuum chamber, the minimum flow rate adjustable range of a general mass flow controller is too large, so that it cannot be adjusted to a desired introduced gas partial pressure. Also, even if the gas introduction amount is adjusted by adjusting the supply pressure, if the pressure at the Baratron pressure gauge is equal to or higher than atmospheric pressure, the gas introduction amount is too large, so the inlet to the chamber is φ0.01 mm or less It is necessary to process into fine holes. Since such processing is technically difficult, it cannot be adjusted to a desired partial pressure of introduced gas. That is, there is a problem in that a very small amount of gas cannot be introduced at a desired partial pressure (about 10 −4 to 10 −6 Pa) in an extremely high vacuum chamber of 10 −7 Pa or less depending on the conventional mechanism.
[0005]
The present invention has been made in view of the above problems, and an object thereof is to provide a trace gas introduction mechanism capable of introducing a trace amount of gas into an ultra-high vacuum chamber.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is connected to a gas supply source, and exhaust means for exhausting gas resulting from the gas supply source to the outside, a flow rate adjusting valve connected to the upstream side of the exhaust means, and a downstream An open / close valve connected to the gas supply source in parallel with the exhaust means upstream of the flow rate adjustment valve, and the exhaust means is upstream of the open / close valve. The pressure on the side is kept low, and when the on-off valve is opened , the differential pressure between the upstream side and the downstream side of the on-off valve is reduced.
[0007]
By exhausting the introduced gas supplied from the gas supply source by the exhaust means, the pressure on the upstream side of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low, so the upstream side of the on-off valve And the differential pressure between the downstream side can be reduced. As a result, the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
Moreover, since the flow rate of the gas exhausted by the exhaust means can be limited, waste of exhaust gas can be reduced.
[0008]
The invention according to claim 2 is connected to a gas supply source, the exhaust means for exhausting the gas resulting from the gas supply source to the outside, the downstream side is connected to the ultra-high vacuum chamber, and the upstream side is the exhaust And an on-off valve connected to the gas supply source in parallel with the means, and a pressure upstream of the on-off valve is fed back downstream of the gas supply source and upstream of the connection of the on-off valve to the exhaust means. The pressure adjusting valve is adjusted so that the pressure on the upstream side of the on-off valve becomes constant, and the exhaust means keeps the pressure on the upstream side of the on-off valve low and the on- off valve is opened. , characterized in that to reduce the differential pressure between the upstream side and the downstream side of the on-off valve.
By exhausting the introduced gas supplied from the gas supply source by the exhaust means, the pressure on the upstream side of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low, so the upstream side of the on-off valve And the differential pressure between the downstream side can be reduced. As a result, the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
Further, since the pressure on the upstream side of the on-off valve can be kept constant, a very small discharge flow rate into the ultra-high vacuum chamber can be kept more stable.
[0009]
The invention according to claim 3 is connected to a gas supply source, exhaust means for exhausting the gas resulting from the gas supply source to the outside, a flow rate adjusting valve connected to the upstream side of the exhaust means, and downstream An open / close valve connected to the gas supply source in parallel with the exhaust means upstream of the flow rate adjusting valve and connected to the gas supply source on the upstream side of the gas supply source and on the exhaust side of the open / close valve Upstream of the connection to the means, and a pressure adjusting valve that adjusts the pressure upstream of the on-off valve by feeding back the pressure upstream of the on-off valve, and the exhaust means The pressure on the upstream side of the on- off valve is kept low, and when the on-off valve is opened , the differential pressure between the upstream side and the downstream side of the on-off valve is reduced.
By exhausting the introduced gas supplied from the gas supply source by the exhaust means, the pressure on the upstream side of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low, so the upstream side of the on-off valve And the differential pressure between the downstream side can be reduced. As a result, the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
Moreover, since the flow rate of the gas exhausted by the exhaust means can be limited, waste of exhaust gas can be reduced.
Further, since the pressure on the upstream side of the on-off valve can be kept constant, a very small discharge flow rate into the ultra-high vacuum chamber can be kept more stable.
[0010]
Invention of claim 4, in addition to the configuration of the invention according to any one of claims 1 to 3, the gas so that the gas does not condense between from the gas supply source to the on-off valve The apparatus further comprises a heating means for heating, wherein the pressure of the gas at least upstream of the on-off valve is made equal to or lower than a saturated vapor pressure by the exhaust means.
Thereby, even a substance stored in a liquid state in the gas supply source can be introduced into the ultra-high vacuum chamber as a small amount of gas.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the mechanism 1 for introducing a very small amount of gas into an ultra-high vacuum chamber is configured by connecting an ultra-high vacuum chamber 9 and a gas cylinder 2 as a gas supply source. A very small amount of gas can be introduced. A pressure reducing valve 3 is connected to the gas cylinder 2, and the gas pressure flowing to the downstream side of the pressure reducing valve 3 is adjusted. A pressure regulating valve 4 having a pressure regulating device 4 a and a pressure sensor 5 are connected to the downstream side of the pressure reducing valve 3, and the pressure sensor 5 is an ultra-high speed constituting an on-off valve from the downstream side of the pressure regulating valve 4. The pressure on the upstream side of the electromagnetic valve 8 is detected, and the pressure adjustment device 4a feedback-controls the pressure adjustment valve 4 from the detected pressure. A flow rate adjusting valve 6 and an ultra high speed electromagnetic valve 8 are connected in parallel downstream of the pressure adjusting valve 4. A gas system vacuum pump 7 constituting exhaust means is connected to the downstream side of the flow rate adjustment valve 6. The gas system vacuum pump 7 sucks gas so that the upstream side of the flow rate adjustment valve 6 becomes a low pressure, and goes to the atmosphere. Released. The flow rate adjusting valve 6 controls the amount of gas released from the gas system vacuum pump 7 to the atmosphere by adjusting the throttle. An ultra-high vacuum chamber 9 is connected to the downstream side of the ultrahigh-speed electromagnetic valve 8. A vacuum pump (not shown) is further connected to the extreme high vacuum chamber 9. The vacuum pump always exhausts the gas in the ultra-high vacuum chamber 9, and the ultra-high vacuum chamber 9 is kept in a vacuum state. The ultrahigh-speed electromagnetic valve 8 is opened for a very short time to limit the amount of introduced gas introduced into the ultrahigh vacuum chamber 9 of about 10 −7 Pa to a very small amount.
[0013]
Next, the operation of the trace gas introduction mechanism 1 will be described based on the above configuration. In the ultra-high vacuum chamber 9, gas is exhausted by a vacuum pump (not shown) and is always kept in a vacuum state. The introduced gas supplied from the gas cylinder 2 is once depressurized by the pressure reducing valve 3 to about 0.2 MPa (about 2 atm). The pressure of the gas released to the downstream side of the pressure regulating valve 4 is measured by the pressure sensor 5, and the pressure regulating valve 4 is feedback-controlled from the measured pressure, and the flow regulating valve 6 and the The pressure on the upstream side of the high speed solenoid valve 8 is adjusted to a constant pressure. Next, the gas system vacuum pump 7 keeps the downstream side of the flow rate adjusting valve 6 at about 100 Pa (about 0.001 atm). As a result, the pressure on the downstream side of the flow rate adjustment valve 6 becomes smaller than the pressure on the upstream side of the flow rate adjustment valve 6, so that when the flow rate adjustment valve 6 is opened, the gas released from the gas cylinder 2 Without being flown to the flow control valve 6 at a low pressure. Therefore, the pressure on the upstream side of the ultrahigh-speed solenoid valve 8 can be reduced to an atmospheric pressure or lower (about 100 Pa).
[0014]
As described above, the pressure on the upstream side of the ultra-high speed solenoid valve 8 can be kept below the atmospheric pressure, so that when the ultra-high speed solenoid valve 8 is opened, the differential pressure upstream and downstream of the ultra-high speed solenoid valve is reduced. As a result, the amount of gas introduced into the ultra-high vacuum chamber 9 can be adjusted to a very small amount. When the opening time of the ultrafast solenoid valve 8 is limited to 200 μsec to 800 μsec and the operation interval is set to about 1 Hz, the average partial pressure of the gas introduced into the ultrahigh vacuum chamber 9 is 10 −4 to 10 −. The pressure can be adjusted to an arbitrary pressure of 6 Pa. The opening time of the ultrahigh speed solenoid valve 8 is desirably 1 msec or less. Thereby, the gas introduction time can be limited to an extremely short time, and a very small amount of gas can be accurately introduced into the ultra-high vacuum chamber 9.
[0015]
Note that the amount of trace gas in the ultra-high vacuum chamber 9 depends on the balance between the amount of gas introduced through the ultrahigh-speed electromagnetic valve 8 and the amount of gas exhausted from the ultra-high vacuum chamber 9 by a vacuum pump (not shown). It is determined. For this reason, the amount of gas in the ultra-high vacuum chamber 9 also depends on the capacity of the vacuum pump connected to the ultra-high vacuum chamber 9. However, in order to control a very small amount of gas in the ultra-high vacuum chamber 9 quickly and stably, a small amount introduction small amount discharge is superior to a large amount introduction large amount discharge. Accordingly, it is preferable to reduce the amount of introduced gas accordingly.
[0016]
Next, the case where water vapor is introduced into the ultra-high vacuum chamber 9 as a trace gas will be described. As shown in FIG. 2, the trace gas introduction mechanism 10 is different from the trace gas introduction mechanism 1 in that a heater 13 constituting a heating means is provided, and that the pressure reducing valve 3 is replaced with a manual valve 12. The gas cylinder 2 is replaced with an H 2 O tank (gas supply source) 11.
[0017]
This gas introduction mechanism 10 keeps the temperature from the downstream side of the H 2 O tank 11 to the upstream side of the ultrahigh-speed solenoid valve 8 by the heater 13 at 40 ° C. or higher, and the water vapor released from the H 2 O tank 11 is recondensed. To prevent it. Next, the pressure of the introduced H 2 O amount is measured by the pressure sensor 5, and the pressure regulating valve 4 is feedback-controlled from the measured pressure, and from the downstream side of the pressure regulating valve 4 to the upstream side of the ultra high speed solenoid valve 8. Adjust the pressure to a constant pressure. Next, the upstream side of the gas system vacuum pump 7 to the downstream side of the flow rate adjusting valve 6 is maintained at, for example, 1000 Pa (about 0.01 atm) by the gas system vacuum pump 7. As a result, the pressure on the downstream side of the flow rate adjustment valve 6 becomes smaller than the pressure from the downstream side of the pressure adjustment valve 4 to the upstream side of the ultra high speed solenoid valve 8, so that when the flow rate adjustment valve 6 is opened, the H 2 O tank 11 Since the released H 2 O is guided to the downstream side of the flow regulating valve 6, the pressure from the downstream side of the pressure regulating valve 4 to the upstream side of the ultra high speed solenoid valve 8 can be reduced to below atmospheric pressure (about 1000 Pa). . Therefore, even if the temperature from the downstream side of the pressure regulating valve 4 to the upstream side of the ultra high speed solenoid valve 8 is 290 K or less, it can be kept below the saturated vapor pressure so that H 2 O does not recondense. Thus, since the H 2 O pressure from the downstream side of the pressure regulating valve 4 to the upstream side of the ultra high speed solenoid valve 8 can be kept below atmospheric pressure, when the ultra high speed solenoid valve 8 is opened, The amount of H 2 O introduced into the high vacuum chamber 9 can be adjusted to a very small amount. When the opening time of the ultrafast solenoid valve 8 is limited to 200 μs to 800 μs and the operation interval is set to about 1 Hz, the degree of vacuum is adjusted to 10 −7 Pa or less, and H 2 O introduced into the vacuum chamber 9 is set. Can be adjusted to 10 −4 to 10 −6 Pa.
[0018]
Further, when the opening degree of the flow rate adjustment valve 6 is reduced, the amount of H 2 O discharged by the gas system vacuum pump 7 can be suppressed. Therefore, even if an oil rotary pump is used as the gas vacuum pump 7, the deterioration of the oil due to H 2 O can be suppressed, and the maintenance cycle can be extended as compared with the case where the flow rate adjusting valve 6 is not attached. In the embodiment of FIG. 2, it is preferable to open the gas ballast valve in order to prevent water from being mixed into the oil of the gas system vacuum pump 7 which is an oil rotary pump, thereby reducing the performance.
[0019]
[Example 1]
The ultra-high vacuum chamber 9 uses a chamber of 200 mm × φ300 mm, and N 2 gas is used as the introduction gas, and the pressure on the upstream side of the ultrahigh-speed solenoid valve 8 is set to 1.3 × 10 3 Pa. . The operating time of the ultra-high speed solenoid valve 8 is set to an opening time of 800 μsec and an operating interval of 1 Hz. The degree of vacuum in the ultra-high vacuum chamber 9 before gas introduction is 2 × 10 −7 Pa, and the N 2 gas partial pressure before gas introduction is 4 × 10 −8 Pa. Under such experimental conditions, when the trace gas introduction mechanism 1 is used, as shown in FIG. 3, the N 2 gas partial pressure during the gas introduction is controlled, and the average degree of vacuum during the gas introduction is 6 × 10 −5. Pa, N 2 gas partial pressure during gas introduction can be adjusted to an average of 6 × 10 −5 Pa. Note that the fluctuation range of the N 2 partial pressure shown in FIG. 3 indicates the sampling interval for pressure measurement, and does not represent the opening / closing cycle of the ultrafast electromagnetic valve 8.
[0020]
[Example 2]
The experiment was performed using the trace gas introduction mechanism 10 under the following conditions. The pressure on the upstream side of the ultrahigh speed solenoid valve 8 is set to 6.5 × 10 2 Pa. The operating time of the ultrafast solenoid valve 8 was set to an opening time of 800 μsec and an operating interval of 1 Hz. H 2 O introduced before the vacuum is 6.2 × 10 -7 Pa, H 2 O before introducing H 2 O partial pressure is 6.2 × 10 -7 Pa. Thus, the degree of vacuum in H 2 O introduced can be adjusted 7.3 × 10 -6 Pa, the partial pressure of H 2 O in H 2 O introduced into 7.3 × 10 -6 Pa.
[0021]
In addition, since the trace gas introduction mechanisms 1 and 10 according to the present embodiment introduce a trace amount of gas into the ultra-high vacuum chamber 9, they are not limited to a space environment simulation experiment apparatus, but are similar to a molecular beam epitaxial apparatus. It may be used for a semiconductor manufacturing apparatus. In addition, in Example 1, the introduced gas is N 2 gas, and in Example 2, the introduced gas is water vapor. However, the present invention is not limited to this, but O 2 gas, CH 4 gas, CO gas, CO 2 gas is used. Alcohol may be used.
[0022]
【The invention's effect】
According to the first aspect of the present invention, the pressure upstream of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low by exhausting the introduced gas supplied from the gas supply source by the exhaust means. Therefore, the differential pressure between the upstream side and the downstream side of the on-off valve can be reduced. As a result, the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
In addition, since the flow rate of the gas exhausted by the exhaust means can be limited, the waste of exhaust gas can be reduced.
[0023]
According to the second aspect of the present invention, the pressure on the upstream side of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low by exhausting the introduced gas supplied from the gas supply source by the exhaust means. Therefore, the differential pressure between the upstream side and the downstream side of the on-off valve can be reduced. As a result, the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
In addition, since the pressure on the upstream side of the on-off valve can be kept constant, an extremely small discharge flow rate into the ultra-high vacuum chamber can be maintained more stably.
[0024]
In the invention according to claim 3, the pressure on the upstream side of the on-off valve connected to the gas supply source in parallel with the exhaust means can be kept low by exhausting the introduced gas supplied from the gas supply source by the exhaust means. Therefore, the differential pressure between the upstream side and the downstream side of the on-off valve can be reduced. This produces an effect that the discharge flow rate into the ultra-high vacuum chamber can be adjusted to a very small amount.
In addition, since the flow rate of the gas exhausted by the exhaust means can be limited, the waste of exhaust gas can be reduced.
In addition, since the pressure on the upstream side of the on-off valve can be kept constant, an extremely small discharge flow rate into the ultra-high vacuum chamber can be maintained more stably.
[0025]
In addition to the effects of the invention described in any one of claims 1 to 3, the invention described in claim 4 is a small amount of gas even if the substance is stored in a liquid state in the gas supply source. Only the extremely high vacuum chamber can be introduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a mechanism for introducing a trace gas into an ultra-high vacuum chamber.
FIG. 2 is a diagram illustrating a mechanism for introducing a trace gas into an ultra-high vacuum chamber.
FIG. 3 is a graph for explaining the relationship between the partial pressure of the introduced gas in the ultra-high vacuum chamber and time.
[Explanation of symbols]
1, 10 Trace gas introduction mechanism 2 Gas cylinder 3 Pressure reducing valve 4 Pressure adjusting valve 5 Pressure sensor 6 Flow rate adjusting valve 7 Vacuum pump for gas system 8 Ultra-high speed solenoid valve 9 Vacuum chamber 11 H 2 O tank 12 Manual valve 13 Heater

Claims (4)

ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、前記排気手段の上流側に接続された流量調整弁と、下流側が極高真空チャンバに接続されるとともに、上流側が前記流量調整弁より上流において前記排気手段と並列に前記ガス供給源に接続された開閉弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする極高真空チャンバへの微量ガス導入機構。Connected to a gas supply source, an exhaust means for exhausting gas originating from the gas supply source to the outside, a flow rate adjusting valve connected to the upstream side of the exhaust means, and a downstream side connected to an ultra-high vacuum chamber. Rutotomoni, and a upstream said flow rate adjusting opening and closing valve connected to the gas supply source in parallel with the exhaust means in the upstream valve, the exhaust means, maintaining a low pressure on the upstream side of the on-off valve, the A mechanism for introducing a very small amount of gas into an ultra-high vacuum chamber , wherein the differential pressure between the upstream side and the downstream side of the on-off valve is reduced when the on-off valve is opened . ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、下流側が極高真空チャンバに接続されるとともに、上流側が前記排気手段と並列に前記ガス供給源に接続された開閉弁と、前記ガス供給源の下流且つ前記開閉弁の前記排気手段への接続部より上流に、前記開閉弁の上流における圧力がフィードバックされることにより、前記開閉弁の上流側の圧力が一定となるように調整される圧力調整弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする極高真空チャンバへの微量ガス導入機構。The gas supply source is connected to the gas supply source and exhausts the gas originating from the gas supply source to the outside, the downstream side is connected to the ultra-high vacuum chamber, and the upstream side is in parallel with the exhaust means. And an upstream side of the on-off valve by feeding back pressure upstream of the on-off valve downstream of the gas supply source and upstream of the connection of the on-off valve to the exhaust means. A pressure adjusting valve that adjusts the pressure of the valve to be constant, and the exhaust means keeps the pressure upstream of the on-off valve low, and when the on- off valve opens, A mechanism for introducing a very small amount of gas into an ultra-high vacuum chamber characterized by reducing the differential pressure with the downstream side. ガス供給源に接続されており、前記ガス供給源に起因するガスを外部に排気する排気手段と、前記排気手段の上流側に接続された流量調整弁と、下流側が極高真空チャンバに接続されるとともに、上流側が前記流量調整弁より上流において前記排気手段と並列に前記ガス供給源に接続された開閉弁と、前記ガス供給源の下流且つ開閉弁の前記排気手段への接続部より上流に、前記開閉弁の上流における圧力がフィードバックされることにより前記開閉弁の上流側の圧力が一定となるように調整される圧力調整弁とを備え、前記排気手段は、前記開閉弁の上流側の圧力を低く保ち、当該開閉弁が開いたとき、当該開閉弁の上流側と下流側との差圧を小さくすることを特徴とする極高真空チャンバへの微量ガス導入機構。Connected to a gas supply source, an exhaust means for exhausting gas originating from the gas supply source to the outside, a flow rate adjusting valve connected to the upstream side of the exhaust means, and a downstream side connected to an ultra-high vacuum chamber. The upstream side is upstream of the flow rate adjustment valve, and is connected to the gas supply source in parallel with the exhaust means, downstream of the gas supply source, and upstream of the connection portion of the open / close valve to the exhaust means. A pressure adjusting valve that adjusts the pressure upstream of the on-off valve to be constant by feeding back the pressure upstream of the on-off valve, and the exhaust means is located upstream of the on-off valve. A mechanism for introducing a trace gas into an ultra-high vacuum chamber, wherein the pressure is kept low and the differential pressure between the upstream side and the downstream side of the on- off valve is reduced when the on-off valve is opened . 前記ガス供給源から前記開閉弁までの間で前記ガスが凝縮しないように前記ガスを加熱する加熱手段をさらに有しており、前記排気手段により少なくとも前記開閉弁の上流における前記ガスの圧力が飽和蒸気圧以下とされることを特徴とする請求項１〜３のいずれか１項に記載の極高真空チャンバへの微量ガス導入機構。 The apparatus further includes heating means for heating the gas so that the gas does not condense between the gas supply source and the on-off valve, and the pressure of the gas at least upstream of the on-off valve is saturated by the exhaust means. The mechanism for introducing a trace gas into an ultra-high vacuum chamber according to any one of claims 1 to 3, wherein the mechanism is set to a vapor pressure or lower.
JP32300198A 1998-11-13 1998-11-13 Mechanism for introducing a trace gas into an ultra-high vacuum chamber Expired - Fee Related JP3681908B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
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CN106641716A (en) * 2016-11-14 2017-05-10 钟玲珑 Vacuum energy-saving gas supply system

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