JP3899597B2 - Atmospheric pressure plasma generation method and apparatus, and surface treatment method - Google Patents

Description

【０１１０】
表１は、シリコン基板上に塗布したレジストを除去した時の除去速度である。処理条件は、１３．５６ＭＨｚ出力４００Ｗ、窒素ガス流量１０ｌ／ｍｉｎ、ワークと放電部の距離は、約６ｍｍに設定した。誘電体１端面からワークまでの距離は約１ｍｍ程度である。この時のレジスト除去速度は、レジスト深さ方向でガスの吹き出し直下において、１５０ｎｍ／ｍｉｎが得られた。
【０１１１】
比較のため、同一装置を用いて酸素ガスによりレジストをアッシングした結果を表１に示した。処理条件は、ガス種が異なる以外、窒素ガス処理と同一条件としている。酸素ガスによる除去速度は、１８０ｎｍ／ｍｉｎ程度であり、窒素ガスによるレジストン除去は、酸素のアッシング処理速度とほとんど差異が無いことがわかる。また、酸素ガスによるアッシングは放電部と被処理体の距離が離れるにつれて、アッシング速度が減少する割合がおおきく、窒素ガスを用いた場合には、比較的距離が離れても有機物の除去処理がされた。これは、放電中で生成される窒素の活性種の寿命が酸素の活性種より長いため、より拡散して処理反応が起きるためと推定される。
【０１１２】
また、周波数条件が異なる処理についての比較も行った。一般的に、図７のような間接放電方式の場合、有機物除去速度を向上させるには、放電部を被処理体に接近させるか印加出力を増加させるとよい。放電部を被処理体に接近させるのは、放電部で生成された活性種が被処理体に輸送される過程で、輸送距離が短いほど活性種の減衰が小さいため被処理体に多くの活性種が到達できるからであり、印加出力を増加させることにより、放電中に生成する活性種の絶対数が増加するからである。しかしながら、２０ｋＨｚの高電圧を用いた場合、印加される電圧が高いため、ある出力以上になると一対の電極間で放電が維持されるだけでなく、被処理体との間で放電が発生し、場合によっては被処理体が損傷してしまう。本実施例での２０ｋＨｚの低周波高圧電源を用いた比較実験では、被処理体と電極の距離は、印加出力が２００Ｗの時、約２５ｍｍ以上離さなければならない。これを処理条件とした時の２０ｋＨｚの低周波電源によるプラズマ処理では、窒素ガスのみならず酸素ガスを用いた場合においてもレジスト除去速度は極めて遅く、５ｎｍ／ｍｉｎ以下であった。
【０１１３】
以上の結果から、周波数の高い１３．５６ＭＨｚ高周波放電では、被処理基板を放電に晒すことなく、プラズマをより被処理体に接近させる事ができ、且つ印加可能な出力を増加させる事ができるため高密度のプラズマが形成できる。その結果、生成された高密度の活性種が被処理体に到達する事ができ、処理の高速化が図れた。
【０１１４】
ところで、本実施例において、空気を用いて同一条件にてレジストの除去を試みてみたが、レジストは全く除去されなかった。そこで窒素の酸素に対する混合率を
（窒素流量／（窒素流量十酸素流量））×１００％
と定義し、いくつかの混合率にて確認してみた結果、図９に示す様に、混合率９９％以上及び２０％以下においてレジスト除去効果を有し、その間の混合率のガス条件では、全くレジストが除去されない事がわかった。
【０１１５】
この理由については、以下の様に考えられる。まず、混合率２０％以下での反応は、従来の酸素アッシングと同様、酸化による有機物除去現象と推定される。これに対し、混合率９９％以上における反応は、プラズマ中で形成された窒素の活性種とレジストの反応で、レジストの酸化反応ではなく、窒化反応またはエネルギーの比較的高い粒子により有機物が分解されると考えられる。
【０１１６】
しかしながら、放電中、酸素がある一定以上混入すると、窒素の活性種と酸素の活性種が反応し、比較的安定な窒素酸化物が形成される。この安定な窒素酸化物は、有機物と反応することなく排気され、有機物反応は起きない。空気の窒素の酸素に対する混合率は約８０％程度であるため、窒素酸化物の影響により有機物の除去ができなかったと推定される。
【０１１７】
図１０は、本発明に関する第６の実施例であり、有機物除去方法を実施する装置の概略的な構成図てある。第５の実施例と共通部分については同一符号て示し、詳細な説明は省略する。
【０１１８】
すなわち本実施例においては、誘電体１を挟んで、接地された電極２ｂと電極２ａが設置されている。電極２ａには１３．５６ＭＨｚの電源１０がインピーダンス整合器６を介して接続されている。電極２ａ及び電極２ｂには、内部にヒータが設置されており、所定の温度まて電極を加熟し一定に保つことが出来る。
【０１１９】
次に、放電手順を説明する。まず、電極２ａ及び電極２ｂをヒーターにより加熱し、間接的に誘電体１の放電面を暖める。誘電体１の放電面を暖めるのは、表面からの二次電子又は熱電子の放出性を高めるためのものであり、この二次電子又は熱電子の放出が多いほど放電開始がし易くなる。したがって、誘電体１の放電面の表面温度が高いほど放電がし易い。誘電体１表面が暖まった後、誘電体１のセル内（ガス流路２３）に窒素ガスを導入し、１３．５６ＭＨｚの電圧を電極２ａに印加する。本実施例では、電極２ａ、２ｂの加熱温度を２００℃に設定したところ、１３．５６ＭＨｚの高周波電圧で窒素ガス単体で放電が開始することが出来た。すなわち、第５の実施例同様、窒素ガスを用いて高速のレジスト除去ができた。
【０１２０】
電極を加熱する手段は、電極２ａ又は電極２ｂの内部に設置したヒーターでなくとも、誘電体１の放電面を外部から赤外線等を用いて加熱する手段であってもかまわない。さらには、放電面の材料が二次電子放出の高いもの、もしくは熱電子放出の高いものであることが望ましい。例えば、ＳｒＯ、ＣａＯ、ＢａＯ等は仕事関数が小さく、比較的表面の温度が高くなくても熱電子が放出しやすいので電極表面材料に適している。これら材料は、誘電体表面に薄膜として構成されていても構わない。
【０１２１】
次に、本発明による窒素ガスを用いた被処理体の表面処理による濡れ性改善の実施例について説明する。
【０１２２】
本実施例に用いた表面処理装置は、第５及び第６の実施例と同一処理装置であり、詳細な説明は省略する。
【０１２３】
すなわち被処理体８としてガラス基板を用いて、本発明による表面処理方法によりガラス基板に活性な窒素ガス吹き付け処理を行い、純水の接触角により基板表面の濡れ性について評価を行った。評価用に用いたガラスは、ＯＡ−２。処理前のガラス表面の純水の接触角は、平均７０度であった。
【０１２４】
図１１は、ガラス基板の処理時間による接触角の変化を示す。比較のため、周波数の異なる条件について評価した結果についても示した。２０ｋＨｚの周波数を用いた処理の場合、第１の実施例において既に説明したとおり、高電圧を用いるため、条件に制約があり、表１に示した有機物除去条件と同一条件にて比較評価している。図１１からも解るように、本発明による１３．５６ＭＨｚを用いた窒素ガス放電処理は、２０ｋＨｚの放電処理に比ベ、濡れ性が明らかに短時間で飽和する。
【０１２５】
ところで、本実施例において、空気を用いた濡れ性の改善に処理について試みてみたが、ガラス基板表面の濡れ性の改善は極めて遅く、接触角が飽和するまでに５分以上かかった。そこで窒素の酸素に対する混合率を
（窒素流量／（窒素流量十酸素流量））×１００％
と定義し、処理時間３０秒における接触角について混合率を変化させ確認してみた結果、図１２に示す様に、混合率９９％以上及び２０％以下においては濡れ性の改善処理の速い条件があることが判明した。
【０１２６】
濡れ性の場合、幾つかの要因が考えられるが、現在のところ、濡れ性の処理速度改善効果の高い条件が、窒素ガスプラズマでも述べた有機物除去条件とほぼ一致していることから、基板表面に付着している有機物の汚れが除去された事による基板表面のクリーニング効果が大きいと推定される。但し、窒素ガスを用いた場合には、基板表面にＮＨ基等の親水基が生成してることが推定される。したがって、需れ性の改善のために用いるガスとしては、窒素ガスが望ましい。
【０１２７】
図１３は、第７実施例の斜視図と断面図である。この実施例は、局部的な表面処理を容易に行えるようにしたもので、例えば石英などの誘電体から形成したパイプ８２によってガス流路２３が形成してある。また、パイプ８２の直径方向両側には、第１電極２ａと第２電極２ｂとが配設してあり、これらの電極間でプラズマを生成するようになっている。そして、パイプ８２には、ガス導入管８４が接続してあって、同図（２）の矢印に示したように、ガス導入管８４を介して放電用ガス８６をガス流路２３に供給できるようにしてある。この第７実施例によるプラズマの生成は、第１実施例と同様に行うことができる。
【０１２８】
図１４は、第８実施例を示したものであって、被処理体のバッチ処理用のプラズマ生成装置である。本実施例においては、チャンバー９０内にガス流路２３を形成しているパイプ状の誘電体９２が配設してある。そして、誘電体９２の一端には、ガス導入管９４が接続してあって、ガス流路２３に放電用ガス８６を導入できるようにしてある。また、誘電体９２の他端には、フレキシブルパイプなどからなるプラズマ供給管９６が接続してある。このプラズマ供給管９６は、先端が処理ボックス９８に接続してある。処理ボックス９８の内部には、多数の被処理体８がラック１００などに配置した状態で収納してある。
【０１２９】
このように構成した第８実施例においては、誘電体９２の上下に配置した電極２ａ、２ｂ間に高周波電圧を印加し、第１実施例と同様にしてプラズマを発生させる。そして、プラズマの発生に伴い生成された活性種をプラズマ供給管９６を介して処理ボックス９８に導入して被処理体８に照射し、一度に多数の被処理体８のアッシングやエッチングなどを行う。
【０１３０】
図１５は、第９実施例の断面図と斜視図であって、エッチングなどに適した直接放電処理用のものである。このプラズマ生成装置１０２は、一方の誘電体１０４がコ字状に形成してあって、接地電極１０６の凸部を跨いで配置させるようになっている。そして、誘電体１０４と接地電極１０６とは、長手方向に相対移動できるようにしてある。
【０１３１】
誘電体１０４の上部には、高周波電極１０８が設けてあるとともに、ガス供給ヘッド１１０が取り付けてある。また、接地電極１０６の凸部上面には、被処理体８が配置される板状の誘電体１１２が設けてあり、この誘電体１１２と誘電体１０４とでガス流路２３が形成される。このように構成した第９実施例においては、被処理体８を直接放電に晒すことができるため、迅速なエッチングなどの表面処理を行うことができる。
【０１３２】
図１６は、さらに他の実施例を示したものである。図１６において、プラズマ生成装置１１４は、ガス流路２３が上下の誘電体１１６、１１８によって形成してある。また、プラズマ生成装置１１４は、高周波電極１２０と接地電極１２２とが誘電体１１６、１１８を挟んで対向するように設けてある。そして、誘電体１１６の上部には、高周波電極１２０を覆ってカバー１２４が取り付けてある。このカバー１２４の内面と高周波電極１２０との距離Ｌは、誘電体１２０、１２２間の距離（放電ギャップ）ｄより大きくしてある。また、このカバー１２４の内部には、空気より放電しにくい流体、例えば四フッ化炭素ガスが封入してある。
【０１３３】
このように構成したことにより、高周波電極１２０に高周波電圧を印加することによる沿面放電を防止することができる。すなわち、ヘリウムガスなどの希ガスを混入せずにプラズマを発生させる場合、希ガスを混入した場合よりも高電圧を必要とする。特に、四フッ化炭素ガスなどの空気より放電しずらいガスを使用する場合は、沿面放電が発生するおそれがあり、沿面放電が発生すると電圧が低下して放電の維持が困難となってプラズマを生成することができない。そこで、カバー１２４内に空気より放電しにく四フッ化炭素ガスなどを封入して沿面放電を防止する。
【０１３４】
なお、四フッ化炭素ガスに代えて絶縁油などを封入してもよい。また、図１６の破線に示したように、誘電体１１６にカバー１２４内とガス流路２３とを連通する連通孔１２６を形成し、カバー１２４内に流入させた四フッ化炭素ガスを連通孔１２６を介してガス流路２３に供給するようにしてもよい。このように、カバー１２４を介して四フッ化炭素ガスをガス流路２３に供給するようにすると、沿面放電の防止が図れるとともに、装置を小型化することができる。
【０１３５】
なお、沿面放電の防止を図るために、電極の近傍には何も配置せず、電極のみにすることが望ましい。そして、電極の近くに何かを配置する場合には、望ましくは２ｍｍ／ｖ以上の距離をおくとよい。また、誘電体は、ガス流路を形成する面ができるだけ凹凸の少ない平なものを使用することが望ましく、平均粗さが０．０２μｍ以下にすることが望ましい。これは、凹部が存在すると、その部分に電界が集中し、部分放電が生じて望ましくないことによる。
【０１３６】
さらに、図２に示したような場合、高周波電極６０は、セル（誘電体）４４からはみださないようにすることが望ましく、セル４４の端部より１ｃｍ以上内側に配置することが望ましい。これは、電極がセルの端からはみだすと、セル４４の側面をつたわった沿面放電を生じやすいことによる。
【０１３７】
【発明の効果】
以上に説明したように、本発明によれば、希ガスを使用せずに、又は希ガスに対する酸素ガスや四フッ化炭素ガスなどの割合を多くしたガスを用いて容易に大気圧プラズマを生成することができ、高価な希ガスの使用量の大幅な削減を図れて、表面処理に利用した場合に、表面処理のコスト低減と処理速度の向上を図ることができる。
【０１３８】
また、本発明によれば、大気圧下、ヘリウムを用いず安価な窒素ガスを使用して放電できるのでランニングコストが低減できる。さらには、ヘリウムを用いなくとも、窒素ガスや酸素ガスのような反応性ガスにより数ＭＨｚ以上の高周波電圧を用いて大気圧下放電が容易にでき、処理の高速化が可能である。また、大気圧下、窒素ガスを用いた高周波放電の実現により、酸素ガスを用いる事なく、酸素処理同様、有機物を除去や基板表面の濡れ性の改善ができるので、酸化を問題とする被処理体又は発火等の危険性がある雰囲気においてる被処理体の処理に適用でき、新たなプロセスが提言できる。
【図面の簡単な説明】
【図１】本発明の第１実施例に係る大気圧プラズマ生成装置の概略構成図である。
【図２】本発明の第２実施例の説明図であって、（１）は斜視図であり、（２）は平面図であり、（３）は（２）のＡ−Ａ線の沿った断面図である。
【図３】第２実施の形態に係るプラズマ生成装置による一定の酸素ガス流量に対するヘリウムガス流量と、グロー放電を開始時およびグロー放電ＯＦＦ時における高周波入力電力との関係を示し図である。
【図４】第２実施の形態に係るプラズマ生成装置による一定の四フッ化炭素ガス流量に対するヘリウムガス流量と、グロー放電を開始時およびグロー放電ＯＦＦ時における高周波入力電力との関係を示し図である。
【図５】第３実施例に係る大気圧プラズマ生成装置の断面図である。
【図６】第４実施例に係る大気圧プラズマ生成装置の断面図である。
【図７】第５実施例の概略構成図である。
【図８】低周波放電に高周波出力を重畳することによって得られる放電の発光強度を示す特性図である。
【図９】窒素ガスの酸素ガスに対する混合率による有機物除去速度を示す特性図である。
【図１０】第６実施例の概略的な装置構成図である。
【図１１】窒素ガスの周波数によるガラス基板表面の処理時間による接触角を示す特性図である。
【図１２】窒素ガスの酸素がすに対する混合率によるガラス基板表面の処理時間による接触角を示す特性図である。
【図１３】第７実施例の斜視図と断面図である。
【図１４】第８実施例の断面図である。
【図１５】第９実施例の断面図と斜視図である。
【図１６】さらに他の実施例の説明図である。
【符号の説明】
１ 誘電体
２ａ、２ｂ 電極
３、５ フィルター回路
４ 昇圧トランス
６ インピーダンス整合器
７ ステージ
８ 被処理体
９ 低周波電源（２０ｋＨｚ電源）
１０ 高周波電源（１３．５６ＭＨｚ電源）
１１ 窒素生成器
１２ 中間チャンバー
１３ ガス供給スリット
２０ ヒーター
２１ チャンバー
２２ プラズマ生成領域
２３、４６ ガス流路
２５ 高周波電源
２６ プラズマ検出手段（光センサ）
２８ 制御手段（コントローラ）
３４、３８ 第１ガス供給手段（酸素ガスボンベ、流量制御弁）
３６、４０ 第２ガス供給手段（ヘリウムガスボンベ、流量制御弁）
４２ プラズマ生成装置
４４ セル（誘電体）
５８ 低周波電極
６０ 高周波電極
６６ 接地電極
７０、７２ プラズマ生成装置
８２ パイプ
８６ 放電用ガス
９８ 処理ボックス
１０８、１２０ 高周波電極
１０６、１２２ 接地電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma generation method for generating plasma, and more particularly to an atmospheric pressure plasma generation method and apparatus for generating plasma for processing the surface of an object to be processed under atmospheric pressure, and a surface treatment method.
[0002]
[Prior art]
Conventionally, organic substances are removed by ashing in which oxygen plasma is formed in a vacuum and the organic substance applied to the semiconductor substrate or the like by the generated oxygen radicals, that is, a resist is oxidized and gasified to be removed, and corona is removed under atmospheric pressure. An ashing process for removing ozone generated by discharge or the like, or a process for decomposing and removing organic substances using UV (ultraviolet rays) is known.
[0003]
However, the organic substance removal method by ashing using vacuum plasma requires a vacuum vessel, an exhaust pump, etc., which increases the size and complexity of the apparatus and increases the processing cost. There is a problem that the quantity that can be processed is limited because it needs to be performed.
[0004]
Corona discharge treatment and silent discharge treatment, which are known as discharge treatment that does not use helium under atmospheric pressure, apply a high voltage boosted to a frequency of several tens of Hz to several tens of kHz and up to several tens of kV. Although ozone is generated by discharge and organic matter is removed by its oxidizing power, in this method, since the oxidizing power of ozone is smaller than that of the active species of oxygen, it is difficult to speed up the organic matter removing process.
[0005]
On the other hand, in order to solve such problems, as disclosed in, for example, Japanese Patent Application Laid-Open No. 07-1245192, it is formed at atmospheric pressure or a pressure in the vicinity thereof as a relatively inexpensive means for improving productivity. A method of processing with plasma has been proposed. In Japanese Patent Application Laid-Open No. 07-245192, in order to improve the adhesion between the IC of the object to be processed and the mold resin before encapsulating the mold resin, the organic matter adhering to the IC is removed to improve the wettability. A surface treatment is disclosed. As a plasma generating gas used when generating atmospheric pressure plasma in the above ashing treatment and surface treatment, it is known to use a gas that is easily discharged, for example, a helium gas having a low discharge starting voltage, In order to perform ashing, it is known to add oxygen together with a plasma generating gas.
[0006]
As a surface treatment method using atmospheric pressure plasma, a direct discharge treatment method in which an object to be treated is directly exposed to plasma, and an object to be treated is irradiated with active species generated by the plasma without directly exposing the object to be treated with plasma. There is an indirect discharge treatment method.
[0007]
In the direct discharge processing method, it is possible to increase the processing speed, but the target object is likely to be destroyed or the characteristic is shifted due to plasma damage. In particular, if the surface to be processed of the object to be processed is a metal, discharge tends to concentrate on the protrusions, and the surface to be processed cannot be uniformly processed. On the other hand, in the indirect discharge processing method, the above-described plasma damage does not occur because the object to be processed is not exposed to the discharge.
[0008]
[Problems to be solved by the invention]
By the way, since the active species generated in the discharge have a lifetime, and this lifetime is relatively short, in the case of the indirect discharge treatment method, if the workpiece is placed at a position away from the plasma generating portion, There is a problem that the number of active species that can be irradiated is reduced and the processing efficiency is greatly reduced.
[0009]
Also, in order to perform high-speed processing by the indirect discharge processing method, a large amount of helium gas must be used. This is because the helium gas is a gas that is relatively easily discharged and also serves as a transport gas for transporting more active species generated during the discharge to the workpiece. In this case, helium gas has a high cost per unit capacity, and there is a problem that a running cost becomes high when used in a large amount.
[0010]
Generally, it is known that the processing speed improves as the plasma density increases. The plasma density during discharge also depends on the frequency of the applied voltage, and it is said that the higher the frequency, the higher the plasma density. This is presumably because the higher the frequency, the more vibrant the electrons vibrate, increasing the probability of collision with the gas and increasing the ionization frequency. However, it is extremely difficult to start discharging other reactive gases using a frequency of several MHz or more without using helium gas at atmospheric pressure. This is because, for example, the discharge start voltage of a reactive gas such as nitrogen gas or oxygen gas has an extremely high spark voltage under atmospheric pressure as compared with helium gas, as shown by Paschen's discharge theory. In the case of nitrogen gas, when the distance between the electrodes is about 1 mm, about several kV to about several tens of KV is required to start discharge. Thus, since it is difficult to start high-frequency discharge without using helium, the composition of the plasma generation gas (discharge gas) is 90% or more of the discharge start voltage when generating atmospheric pressure plasma. The remaining 10% or less of the remaining helium gas is a reactive gas such as oxygen gas, and there is a problem that it is difficult to speed up the ashing or wettability improvement process using only the reactive gas. For this reason, expensive helium gas is used in large quantities, and it is difficult to reduce processing costs.
[0011]
Further, oxygen is always used for removing organic substances in the surface treatment method described above. For this reason, there exists a subject that the surface of a to-be-processed object will be oxidized simultaneously with the removal of the organic substance on a to-be-processed object. Therefore, it is difficult to remove organic substances using the above-described processing method in an object to be processed which is extremely problematic for surface oxidation.
[0012]
Moreover, since oxygen is used, generation of ozone is unavoidable even in treatment methods other than ozone treatment. As is well known, since ozone is harmful to the human body, safety measures such as detoxification are required especially for the generation of high-concentration ozone.
[0013]
In addition, atmospheric pressure plasma treatment is more convenient than vacuum plasma because it can be used open to the atmosphere, so it can be installed anywhere, but under conditions where a large amount of oxygen is used, it tends to be an ignition source in the treatment chamber. If an electrical system such as a relay or flammable material is installed, the oxygen concentration increases and there is a risk of ignition. Therefore, as with ozone, safety measures are required, and there are problems such as not only restrictions on the installation location of the apparatus but also an increase in apparatus cost.
[0014]
The present invention has been made in view of the above problems, and its object is to greatly reduce the amount of rare gas used such as helium gas and to easily generate plasma at atmospheric pressure. It is to be able to generate.
[0015]
Another object of the present invention is to be able to generate plasma under atmospheric pressure without using a rare gas.
[0016]
Furthermore, an object of the present invention is to improve the surface treatment speed such as the organic substance removal processing speed, the surface wettability processing speed, and the etching speed during the plasma processing.
[0017]
It is another object of the present invention to provide a surface treatment method capable of proposing a new process by reducing the running cost of a gas used for the treatment and further providing a new organic matter removing means that does not use oxygen.
[0018]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, in the atmospheric pressure plasma generation method according to the present invention, a discharge gas is introduced into a plasma generation region under an atmospheric pressure formed by a dielectric material or a pressure in the vicinity thereof, and the first electrode provided with the dielectric material interposed therebetween. In the atmospheric pressure plasma generation method of generating a plasma by applying a high frequency voltage to the second electrode and generating a plasma by supplying a mixed gas of a rare gas and a surface treatment gas to the plasma generation region, The supply of the rare gas is stopped.
[0019]
Further, an atmospheric pressure plasma generation method according to the present invention includes a grounding electrode provided with a discharge gas introduced into a plasma generation region under an atmospheric pressure formed by a dielectric or a pressure near the atmospheric pressure, and sandwiched with the dielectric. In an atmospheric pressure plasma generation method for generating plasma by applying a high frequency voltage to a first electrode and a second electrode, a rare gas is supplied to the plasma generation region to generate plasma, and then a surface treatment gas is The plasma generation region is supplied to generate plasma by the surface treatment gas, and the supply of the rare gas is stopped.
[0020]
The surface treatment gas is preferably either oxygen gas or carbon tetrafluoride gas. The trigger gas is preferably helium gas.
[0021]
Further, an atmospheric pressure plasma generation method according to the present invention includes a grounding electrode provided with a discharge gas introduced into a plasma generation region under an atmospheric pressure formed by a dielectric or a pressure near the atmospheric pressure, and sandwiched with the dielectric. In an atmospheric pressure plasma generation method for generating a plasma by applying a high frequency voltage to a first electrode and a second electrode, at least at the start of discharge in the plasma generation region, an electron or gaseous active species is added to the plasma generation region The plasma is generated by supplying together with the discharge gas. The electrons or active species may be thermoelectrons emitted from a heated filament, electrons emitted from an electron gun, or electrons or active species generated by generating a corona discharge.
[0022]
The discharge gas is preferably oxygen gas, carbon tetrafluoride gas, or a mixed gas of one of these and a rare gas.
[0023]
The atmospheric pressure plasma generation method according to the present invention is characterized in that the supply of the electrons or active species is stopped after the generation of the plasma. The electrons or active species may be continuously supplied even after the plasma is generated.
[0024]
The high-frequency voltage preferably has a frequency of 400 kHz to 100 MHz.
[0025]
An atmospheric pressure plasma generation apparatus that implements the above atmospheric pressure plasma generation method includes a dielectric that forms a plasma generation region and a surface treatment gas that is supplied to the plasma generation region at or near atmospheric pressure. A first gas supply means; a second gas supply means for supplying a rare gas to the plasma generation region at or near atmospheric pressure; a ground electrode, a first electrode, Two electrodes, a high-frequency power source for applying a high-frequency voltage between the ground electrode, the first electrode, and the second electrode, plasma detection means for detecting that plasma has been generated in the plasma generation region, and the plasma detection means And control means for controlling the second gas supply means based on the detection signal and stopping the supply of the rare gas to the plasma generation region.
[0026]
The control means may supply the surface treatment gas to the plasma generation region by controlling the first gas supply means after the generation of plasma by the rare gas.
The atmospheric pressure plasma generation apparatus according to the present invention includes a dielectric that forms a plasma generation region, a gas supply unit that supplies a discharge gas to the plasma generation region under atmospheric pressure or a pressure near the atmospheric pressure, A trigger supply means for supplying active species in the form of electrons or gases to the plasma generation region under atmospheric pressure or a pressure close thereto, a ground electrode, a first electrode and a second electrode provided with the dielectric interposed therebetween, A high-frequency power source that generates a plasma by applying a high-frequency voltage between the ground electrode, the first electrode, and the second electrode is provided.
[0027]
The atmospheric pressure plasma generation apparatus according to the present invention includes a dielectric that forms a plasma generation region, a gas supply unit that supplies a discharge gas to the plasma generation region under atmospheric pressure or a pressure near the atmospheric pressure, A trigger supply means for supplying active species in the form of electrons or gases to the plasma generation region under atmospheric pressure or a pressure close thereto, a ground electrode, a first electrode and a second electrode provided with the dielectric interposed therebetween, A high-frequency power source that generates a plasma by applying a high-frequency voltage between the ground electrode, the first electrode, and the second electrode; a plasma detection unit that detects that plasma is generated in the plasma generation region; and the plasma detection unit Control means for controlling the trigger supply means based on the detection signal to stop the supply of the electrons or active species.
[0028]
The high-frequency voltage output from the high-frequency power source preferably has a frequency of 400 kHz to 100 MHz.
[0029]
Further, the dielectric having the electrode connected to the high frequency power source is provided with a cover covering the electrode connected to the high frequency power source, and a fluid that is less likely to discharge than air is injected into the cover. It is preferable.
[0030]
The fluid that is more difficult to discharge than air is preferably carbon tetrafluoride gas. The dielectric is formed with a hole communicating the inside of the cover and the plasma generation region, and carbon tetrafluoride gas injected into the cover is supplied to the plasma generation region through the hole. It is preferable.
[0031]
The distance between the electrode connected to the high-frequency power source and the inner surface of the cover is preferably larger than the discharge gap of the plasma generation region.
The surface treatment method according to the present invention includes a cell formed of a pair of dielectrics under atmospheric pressure or a pressure near the atmospheric pressure, a ground electrode sandwiching the dielectrics, a first electrode, and a second electrode. A discharge gas is introduced into the cell, a high frequency voltage is applied between the ground electrode, the first electrode, and the second electrode to generate plasma, and the active species generated by the plasma are treated. In the surface treatment method for removing organic substances on the surface of the object to be treated by irradiation, the discharge gas is a gas containing nitrogen and oxygen, and the mixing ratio of nitrogen to oxygen = (nitrogen flow rate / (nitrogen flow rate). 10 oxygen flow rate)) × 100 is 99% or more.
[0032]
The surface treatment method according to the present invention includes a cell formed of a pair of dielectrics under atmospheric pressure or a pressure near the atmospheric pressure, a ground electrode sandwiching the dielectrics, a first electrode, and a second electrode. A discharge gas is introduced into the cell, a high frequency voltage is applied between the ground electrode, the first electrode, and the second electrode to generate plasma, and the active species generated by the plasma are treated. In the surface treatment method for hydrophilizing the surface of the object to be treated, the discharge gas is a gas containing nitrogen and oxygen, and the mixing ratio of nitrogen to oxygen = (nitrogen flow rate / (nitrogen flow rate +10 Oxygen flow rate)) × 100 is 99% or more.
[0033]
The surface treatment method according to the present invention is characterized in that, in the above, the discharge maintaining means for continuously generating the plasma applies a high frequency voltage of 1 MHz to 100 MHz.
[0034]
Further, in the surface treatment method according to the present invention, in the above, the discharge maintaining unit and the high voltage applying unit of 50 kHz or less are provided side by side on the electrode, and the high voltage applying unit is superimposed on the discharge maintaining unit and applied. After the discharge is started, the high voltage applying unit is used by superimposing the high voltage applying unit on the discharge maintaining unit alone or on the discharge maintaining unit.
Moreover, it is preferable to heat the discharge surface of the dielectric in advance before the start of discharge.
[0035]
The surface treatment method according to the present invention includes a cell formed of a pair of dielectrics under atmospheric pressure or a pressure near the atmospheric pressure, a ground electrode sandwiching the dielectrics, a first electrode, and a second electrode. A plasma is generated by introducing a discharge gas into the cell and applying a voltage between the ground electrode, the first electrode, and the second electrode, and the active species generated by the plasma is used as an object to be processed. In the surface treatment method for performing irradiation treatment, a voltage having a plurality of different frequencies is superimposed and applied between the first electrode and the second electrode at least for a predetermined period until plasma generation is started.
[0036]
The voltages having a plurality of different frequencies are preferably supplied from at least a first voltage source of 1 MHz to 100 MHz and a second voltage source of 50 kHz or less.
In the surface treatment method according to the present invention, a discharge gas is introduced into a plasma generation region formed of a dielectric under an atmospheric pressure or a pressure close thereto, and a ground electrode and a first electrode provided with the dielectric interposed therebetween. In the surface treatment method of generating a plasma by applying a high frequency voltage to the first electrode and the second electrode, and irradiating the object to be processed with active species generated by the plasma, the organic substance on the surface of the object to be processed is removed. A plasma is generated by supplying a mixed gas of a rare gas and an oxygen gas to the generation region, and thereafter, the supply of the rare gas is stopped to generate plasma by the oxygen gas.
[0037]
Further, the surface treatment method according to the present invention introduces a discharge gas into a plasma generation region under an atmospheric pressure formed by a dielectric material or a pressure near the atmospheric pressure, and a ground electrode provided between the first dielectric electrode and the ground electrode. In the surface treatment method of generating plasma by applying a high-frequency voltage to the electrode and the second electrode, and irradiating the object to be processed with active species generated by the plasma to remove organic substances on the surface of the object to be processed, A plasma is generated by supplying a rare gas to the plasma generation region, and then oxygen gas is supplied to the plasma generation region to generate plasma by oxygen gas, and the supply of the rare gas is stopped. .
[0038]
Further, the surface treatment method according to the present invention introduces a discharge gas into a plasma generation region under an atmospheric pressure formed by a dielectric material or a pressure near the atmospheric pressure, and a ground electrode provided between the first dielectric electrode and the ground electrode. In a surface treatment method in which a high frequency voltage is applied to an electrode and a second electrode to generate plasma, and an active species generated by the plasma is irradiated to the object to be processed to remove organic substances on the surface of the object to be processed. Alternatively, it is characterized in that plasma is generated by supplying gaseous active species to the plasma generation region together with a discharge gas composed of oxygen gas or a mixed gas of oxygen gas and rare gas.
[0039]
In the surface treatment method according to the present invention, a discharge gas is introduced into a plasma generation region formed of a dielectric under an atmospheric pressure or a pressure close thereto, and a ground electrode and a first electrode provided with the dielectric interposed therebetween. In the surface treatment method of generating a plasma by applying a high frequency voltage to the first electrode and the second electrode, irradiating the object to be processed with active species generated by the plasma and etching the surface of the object to be processed, the plasma generating region In addition, a mixed gas of rare gas and carbon tetrafluoride gas is supplied to generate plasma, and then supply of the rare gas is stopped to generate plasma by carbon tetrafluoride gas.
[0040]
Further, the surface treatment method according to the present invention introduces a discharge gas into a plasma generation region under an atmospheric pressure formed by a dielectric material or a pressure near the atmospheric pressure, and a ground electrode provided between the first dielectric electrode and the ground electrode. In the surface treatment method for generating plasma by applying a high frequency voltage to the electrode and the second electrode, and irradiating the object to be processed with active species generated by the plasma, the surface of the object to be processed is etched. After generating a plasma by supplying a rare gas to the region, supplying a carbon tetrafluoride gas to the plasma generation region to generate a plasma by the carbon tetrafluoride gas and stopping the supply of the rare gas It is characterized by.
[0041]
Further, the surface treatment method according to the present invention introduces a discharge gas into a plasma generation region under an atmospheric pressure formed by a dielectric material or a pressure near the atmospheric pressure, and a ground electrode provided between the first dielectric electrode and the ground electrode. In a surface treatment method in which a high frequency voltage is applied to an electrode and a second electrode to generate plasma, and the surface of the object to be processed is etched by irradiating the object to be processed with active species generated by the plasma. The active species in the form of carbon tetrafluoride gas or a discharge gas composed of a mixed gas of carbon tetrafluoride gas and a rare gas is supplied to the plasma generation region to generate plasma.
[0042]
The surface treatment method according to the present invention is characterized in that, in the above, supply of the electrons or active species to the plasma generation region is stopped after the plasma is generated.
[0043]
The surface treatment method according to the present invention is characterized in that, in the above, the high-frequency voltage has a frequency of 400 kHz to 100 MHz.
[0044]
[Action]
In the present invention configured as described above, an expensive rare gas is used only when starting up the plasma, and the supply of the rare gas is stopped after the plasma is started up. Can be significantly reduced, atmospheric pressure plasma can be obtained at low cost, and surface treatment using inexpensive atmospheric pressure plasma can be performed. As the surface treatment gas, oxygen gas can be used in the case of oxidizing and removing organic substances such as resist, and carbon tetrafluoride gas can be used in the case of etching a semiconductor substrate.
[0045]
In addition, since electrons or active species are supplied to the plasma generation region to make it easy to generate glow discharge, the amount of oxygen gas or carbon tetrafluoride gas mixed in the rare gas can be increased, or a rare gas can be used. Plasma can be generated by generating glow discharge using only oxygen gas or carbon tetrafluoride gas, the amount of rare gas used can be reduced, and the generation cost of atmospheric pressure plasma can be reduced. As the discharge gas, oxygen gas, carbon tetrafluoride gas, or a mixed gas of one of these and a rare gas can be used. In addition, after the plasma is generated, the supply of electrons or active species may be stopped or may be continuously supplied so that appropriate processing conditions can be obtained.
[0046]
In the above atmospheric pressure plasma generation method, when the frequency of the high-frequency voltage is not less than the cutoff frequency and not less than 400 kHz to 100 MHz, and preferably not more than about 400 kHz to 40 MHz, corona discharge (streamer due to electrons in the plasma generation region colliding with the electrode is caused. The transition to (discharge) can be prevented. When the frequency is lower than 400 kHz, the number of electrons colliding with the electrode increases, and corona discharge is likely to occur.
Further, when the frequency is higher than 100 MHz, the moving distance of electrons is shortened and sufficient energy due to the electric field cannot be obtained, and it becomes difficult to generate and maintain plasma.
[0047]
According to the atmospheric pressure plasma generation apparatus of the present invention, it is possible to easily generate atmospheric pressure plasma using a rare gas only when starting up the plasma and thereafter using no rare gas.
[0048]
In addition, in order to supply electrons or active species to the plasma generation region, it is possible to generate atmospheric pressure plasma by mixing a relatively large amount of oxygen gas or carbon tetrafluoride gas in the rare gas or without using the rare gas. it can.
[0049]
Moreover, when a fluid that is harder to discharge than air is injected by covering the electrode connected to the high frequency power source with a cover, creeping discharge can be reliably prevented even when a higher voltage is applied because no rare gas is used. Then, when carbon tetrafluoride gas is used as a fluid that is harder to discharge than air, the plasma is generated by supplying the carbon tetrafluoride gas injected into the cover to the plasma generation region through the holes provided in the dielectric. The cover can be used as a discharge gas supply path while avoiding creeping discharge, and the apparatus can be miniaturized and simplified. Furthermore, if the gap between the inner surface of the cover and the electrode is made larger than the discharge gap, the discharge between the cover and the electrode can be reliably prevented.
[0050]
And according to the surface treatment method in this invention, the following effects are acquired.
Nitrogen gas can be used to speed up the removal of organic substances and the surface wettability improvement process, so there is a high risk of treatment such as treatment of objects subject to surface oxidation or ignition in an oxygen atmosphere. It becomes possible to remove the organic matter of the object to be processed in the atmosphere.
[0051]
In addition, since a discharge of several MHz or more is used, high-density nitrogen plasma can be formed, and organic substances can be removed or wettability treatment can be accelerated. Further, it becomes possible to discharge with a reactive gas such as nitrogen gas alone at a high frequency voltage of several MHz or more and without using helium gas under atmospheric pressure. As a result, high-density nitrogen plasma can be generated, the processing speed can be increased, and an inexpensive nitrogen gas can be used, so that the running cost can be reduced.
[0052]
In addition, the functions of starting discharge and maintaining discharge are separated and can be controlled independently. It is known that the voltage at the start of discharge is higher than the voltage at the time of maintaining the discharge, and an appropriate and efficient voltage can be selected by separating the functions at the time of starting the discharge and maintaining the discharge. With only a single gas without using helium gas, even when nitrogen gas was discharged only at a high voltage in the range of several tens of Hz to several tens of kHz under atmospheric pressure, a high voltage was used only at the start of discharge. By switching to a high-frequency voltage during maintenance, high-frequency discharge of several MHz or more can be easily started, and the processing speed can be increased.
[0053]
In addition, by preheating the discharge surface, secondary electron emission from the electrode surface can be enhanced, and conventionally, only discharge of a high voltage in the range of several tens Hz to several tens kHz under atmospheric pressure starts. Even with the nitrogen gas that could not be generated, the discharge can be easily obtained by secondary electrons or thermal electrons at the time of triggering the discharge.
[0054]
Further, the voltage to be applied is divided into two roles of a discharge start function and a discharge maintenance function, and an appropriate voltage can be selected, so that the processing method can be optimized.
[0055]
In addition, for a gas having a high discharge start voltage, it is possible to apply a high voltage at the start of discharge and switch to a high frequency when maintaining the discharge.
[0056]
Furthermore, since a rare gas can be used only at the start-up of the plasma, and then a plasma can be generated using only oxygen gas, the amount of rare gas used can be greatly reduced, and the cost of ashing treatment using oxygen gas can be reduced. Reduction and improvement in processing speed can be achieved.
[0057]
Since the plasma is generated using the active species in the form of electrons or gas, plasma using oxygen gas can be generated without using any rare gas, and the cost can be further reduced. In addition, even when a rare gas is used, the amount of oxygen gas mixed in can be greatly increased, and the cost can be greatly reduced and the processing speed can be improved as compared with the prior art.
[0058]
Further, it is possible to generate plasma using only carbon tetrafluoride gas without using a rare gas, and it is possible to reduce the cost of etching treatment with carbon tetrafluoride gas and improve the processing speed.
[0059]
Then, after the plasma is started up, supply of electrons or active species to the plasma generation region can be stopped to set appropriate processing conditions. Furthermore, plasma can be easily generated, and high-density plasma can be obtained.
[0060]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an atmospheric pressure plasma generation method and apparatus and a surface treatment method according to the present invention will be described below with reference to the drawings.
[0061]
FIG. 1 is a schematic configuration diagram of an atmospheric pressure plasma generation apparatus according to a first embodiment of the present invention.
[0062]
In FIG. 1, the plasma generator has a plasma generator inside a chamber 21 that is open at the bottom. The plasma generation unit includes a pair of plate-like dielectrics 1 having a gap of about 1 mm to 3 mm and a pair of dielectrics 1 in order to form a flow path 23 for the supplied discharge gas. The electrode is composed of a pair of electrodes 2a and 2b which are second electrodes. The electrodes 2a and 2b are for generating glow discharge in the gas flow path 23 to generate plasma, and a plasma generation region 22 is formed between both electrodes. In the embodiment, the dielectric 1 is made of quartz glass in order to prevent cracking due to temperature rise due to discharge, but ceramic or the like may be used.
[0063]
A lower portion of the chamber 21 is a processing unit that performs a surface treatment of the object 8 to be processed, and a stage 7 for installing the object 8 to be processed is provided in the processing unit. The stage 7 is movable in the horizontal direction as indicated by an arrow 24 in FIG. 1, and the entire upper surface of the workpiece 8 can be processed by moving the stage 7. In the dielectric 1, the distance from the end surface close to the workpiece 8 to the workpiece 8 is maintained at about 1 to 2 mm. In addition, the gas flow path 23 is open at the lower end so that the active species generated by the plasma can be irradiated on the surface of the object 8 to be moved.
[0064]
One electrode 2b is grounded, and the other electrode 2a is connected to a high-frequency power source 25 via an impedance matching unit 6, and a high frequency of (400 kHz to 100 MHz) is set between the electrodes 2a and 2b. A voltage can be applied, and an optical sensor 26 as plasma detecting means is disposed at an appropriate location in the chamber 21 to detect and detect light due to glow discharge when plasma is generated. The signal is input to the controller 28 as control means.
[0065]
An intermediate chamber 12 is provided on the upper portion of the chamber 21. An oxygen gas cylinder 34 filled with oxygen gas as a discharge gas and a helium gas cylinder 36 filled with helium gas as a rare gas are connected to the intermediate chamber 12 through conduits 30 and 32. . The intermediate chamber 12 and the gas flow path 23 communicate with each other through a gas supply port 13 formed in the chamber 21 so that helium gas and oxygen gas flowing into the intermediate chamber 12 can be supplied to the gas flow path 23. It is. The pipe 30 is provided with a flow rate control valve 38 constituting a first gas supply means together with the oxygen gas cylinder 34. Further, the pipe 32 is provided with a flow rate control valve 40 that constitutes a second gas supply means together with the helium gas cylinder 36. These flow control valves 38 and 40 are configured such that the opening degree is controlled by the controller 28.
[0066]
Generation of atmospheric pressure plasma by the plasma generating apparatus configured as described above is performed as follows.
[0067]
The gas flow path 23 is maintained at atmospheric pressure without reducing pressure. Then, the controller 28 controls the flow rate control valves 38, 40 to flow a predetermined amount of oxygen gas and helium gas in the intermediate chamber 12, and supply the mixed gas to the plasma generation region 22 via the gas flow path 23. . The supply amount of the gas to the plasma generation region 22 is preferably 20% or less for oxygen gas and 80% or more for helium gas in flow rate ratio. Specifically, for example, when the width of the gas flow path 23 (the gap between the dielectrics 1 and 1) is 2.2 mm and the depth (the direction orthogonal to the paper surface of FIG. 1) is 38 mm, oxygen gas is 100 cc / min. If it flows, helium gas will flow 400cc / min or more. Thereafter, a high frequency voltage is applied between the electrodes 2a and 2b in a state where a gas is supplied.
[0068]
In the case of the present embodiment, the frequency of the applied voltage is 40.68 MHz, and glow discharge starts when the applied voltage has a peak-to-peak value of about 2.3 kV and plasma is generated. did it.
[0069]
When the glow discharge is started, the light accompanying the discharge is detected by the optical sensor 26, and a detection signal is input to the controller 28. When the controller 28 detects that glow discharge is started based on the output signal of the optical sensor 26 and plasma is generated, the flow rate of oxygen gas is present on the surface treatment of the object 8 to be processed, for example, on the surface of the object 8 to be processed. In addition to controlling the amount necessary for removing organic substances such as resist, the supply of helium gas is stopped. Thereby, it is possible to easily generate plasma using only oxygen gas that is difficult to generate using only oxygen gas. This is presumably because once the plasma is generated, a large amount of electrons are generated by the plasma, and these electrons collide with the oxygen gas and the oxygen gas is easily ionized.
[0070]
In the case of surface treatment of the object 8 to be processed by oxygen gas plasma, for example, ashing for oxidizing and removing organic substances present on the surface of the object 8 to be processed, active species generated by the oxygen gas plasma generated as described above are to be treated. Irradiate the surface of the treatment body 8.
[0071]
As described above, in this embodiment, helium gas is used as a trigger only when plasma is generated, and plasma using only oxygen gas can be generated during surface treatment of the object 8 to be processed. Can be significantly reduced, and the running cost of the ashing process can be significantly reduced. In addition, since the plasma is only oxygen gas, the active species can be greatly increased and the ashing speed can be greatly improved. For example, in the past, when ashing was performed by mixing 2% oxygen gas into helium gas and generating plasma, the ashing rate was several μm / min. It can be about 100 μm / min.
[0072]
In the above embodiment, the case where oxygen gas and helium gas are simultaneously flown to generate plasma has been described. However, only helium gas is supplied to the plasma generation region 22 when the plasma is started up, and helium gas is used. The supply of oxygen gas may be started after the plasma is generated, and the supply of helium gas may be stopped.
[0073]
In the above-described embodiment, the case where the optical sensor 26 is arranged inside the chamber 21 has been described. The sensor 26 may be disposed outside the chamber 21. When the optical sensor 26 is provided outside the chamber 21 as described above, the optical sensor 26 is not exposed to active species, and the optical sensor 26 is not damaged. In the embodiment described above, the case where the plasma detecting means is the optical sensor 26 has been described. However, the current of the circuit connected to the high frequency power supply 25 is detected, or the impedance matching state of the matching unit 6 is detected. The generation of plasma may be detected. In the embodiment, the case where helium gas is used has been described, but neon gas, argon gas, or the like may be used.
[0074]
Further, the wettability of solder, resin, etc. is improved by etching the object 8 with plasma of carbon tetrafluoride gas and removing contaminants (for example, organic substances) existing on the surface of the object 8 with air plasma. In this case, carbon tetrafluoride gas plasma and air plasma can be obtained in the same manner as the generation of plasma by the oxygen gas.
[0075]
FIG. 2 shows a second embodiment of the atmospheric pressure plasma generation apparatus, where (1) is a perspective view, (2) is a plan view, and (3) is along the line AA in (2). It is sectional drawing.
[0076]
In FIG. 2, the plasma generation apparatus 42 has a cell 44 formed of a dielectric such as quartz glass, and a rectangular gas flow path 46 provided in the center. In the embodiment, the gas flow path 46 is formed with a discharge gap (height) d of 2.2 mm and a width B of 38 mm. A first gas supply head 48 is fixed to the upper part on one end side of the cell 44.
[0077]
The inside of the first gas supply head 48 and the gas flow path 46 communicate with each other via a gas inlet 50 provided in the cell 44, and the trigger gas guided to the first gas supply head 48 via a pipe line 52. Can be supplied to one end of the gas flow path 46. And the trigger gas supplied to the gas flow path 46 flows toward the blowout port 56 on the opposite side, as shown by an arrow 54 in FIG.
[0078]
In the center of the upper surface of the cell 44, a low frequency electrode 58 constituting a trigger supply means is provided orthogonal to the gas flow path 46. The low-frequency electrode 58 is connected to a low-frequency power source through a low-pass filter (both not shown). Further, a high frequency electrode 60 as a first electrode is disposed on the upper surface of the cell 44. The high-frequency electrode 60 is for generating plasma, and is arranged in parallel to the low-frequency electrode 58 on the downstream side of the gas flow from the low-frequency electrode 58, and is connected to the high-frequency power source 25 via the impedance matching unit 6. Connected. In addition, the high frequency electrode 60 is arranged so that the end thereof is inward by D (about 10 mm in the case of the embodiment) from the edge of the cell 44 so as not to cause a discharge connecting the side surface of the cell 44. is there.
[0079]
A second gas supply head 62 is provided between the high-frequency electrode 60 and the low-frequency electrode 58. The second gas supply head 62 is for supplying a discharge gas comprising a mixed gas of helium gas and oxygen gas or helium gas and carbon tetrafluoride gas flowing in through the pipe line 63 to the gas flow path 46. It is in communication with the gas flow path 46 through the gas inlet 64. A ground electrode 66 serving as a second electrode is provided on the lower surface of the cell 44 so as to extend from at least the high frequency electrode 60 to the low frequency electrode 58. A portion corresponding to the high-frequency electrode 60 of the gas flow path 46 is the plasma generation region 22.
[0080]
Plasma generation by this plasma generation apparatus is performed as follows.
[0081]
A discharge gas composed of a mixed gas of helium gas and oxygen gas or helium gas and carbon tetrafluoride gas is supplied to the gas flow path 46 via the pipe line 63 and the second gas supply head 62, and the pipe line 52 is provided. The trigger gas having the same composition as the discharge gas is supplied to the gas flow path 46 via the first gas supply head 48. Then, a low frequency voltage (9.76 kHz, 10 kV ((peak peak value)) is applied between the low frequency electrode 58 and the ground electrode 66 and between the high frequency electrode 60 and the ground electrode 66. A high frequency voltage (in the example, a frequency of 40.68 MHz) is applied to.
[0082]
As a result, corona discharge occurs in the gas flow path 46 corresponding to the low-frequency electrode 58, a part of the trigger gas is ionized to generate electrons, and the trigger gas is activated. These electrons and active species are supplied to the plasma generation region 22 as a trigger for starting up plasma on the flow of the trigger gas and the discharge gas. The electrons receive energy from the high-frequency electric field in the plasma generation region 22 and collide with the active species or discharge gas molecules, ionize them to increase the electrons, generate glow discharge, and generate plasma. The high frequency voltage applied to the high frequency electrode 60 can be lowered, and plasma can be easily generated. The active species generated by the generation of the plasma can be irradiated to a target object (not shown) from the blowout port 56 and subjected to surface treatment such as ashing or etching.
[0083]
In the above embodiment, the case where a mixed gas of oxygen gas and helium gas or a mixed gas of carbon tetrafluoride gas and helium gas is used as a discharge gas and trigger is described. Alternatively, only carbon tetrafluoride gas may be used as the discharge gas or trigger gas. Further, air alone or helium gas mixed with air may be used as the discharge gas or trigger gas. Further, oxygen gas, carbon tetrafluoride gas, air, or a mixed gas of one of these and helium gas may be used as the discharge gas, and helium gas may be used as the trigger gas. In any of the above cases, in order to obtain appropriate processing conditions, when glow discharge occurs and the plasma rises, the supply of the trigger gas is stopped and the application of the low frequency voltage is stopped. Also good. In addition, when carbon tetrafluoride gas is used, the carbon tetrafluoride gas is passed through water in a bubbling device, and moisture (H ₂ O) may be used.
[0084]
3 and 4 show the results of an atmospheric pressure plasma generation experiment using the plasma generation apparatus 42 of the second embodiment. FIG. 3 shows oxygen gas (O ₂ ) Is fixed at 100 cc / min, and the high frequency input power at the start of glow discharge and at the time of glow discharge OFF (extinction) when the flow rate of helium gas (He) is changed is shown. FIG. 4 shows high-frequency input power at the start of glow discharge and when glow discharge is OFF when the flow rate of carbon tetrafluoride gas is fixed at 50 cc / min and the flow rate of helium gas is changed.
[0085]
In any case, the discharge gap d of the gas flow path 46 is 2.2 mm and the width B is 38 mm. The low-frequency voltage applied to the low-frequency electrode 58 has a frequency of 9.76 kHz, the voltage has a peak peak value of 10 kV, the high-frequency voltage applied to the high-frequency electrode 60 has a frequency of 40.68 MHz, and an output of 1 kW Is used.
[0086]
In FIG. 3, ○ is the input power value at the start of discharge when only the high frequency (RF) voltage is applied, and ● is the input power value when the discharge is turned off when only the high frequency voltage is applied. is there. Further, x in the figure indicates that no glow discharge occurred. Further, Δ is the power supplied to the high frequency electrode 60 at the start of glow discharge when a low frequency (LF) voltage is applied to the low frequency electrode 58 and a high frequency (RF) voltage is applied to the high frequency electrode 60. Is the power supplied to the high-frequency electrode 60 when the glow discharge is turned off.
[0087]
As shown in FIG. 3, when oxygen gas is supplied at 100 cc / min and only a high-frequency voltage is applied, glow discharge occurs when oxygen gas is 25% and helium gas is 75% (300 cc / min) at a flow rate ratio. No plasma was generated. However, when 400 cc / min of helium gas was flowed with respect to 100 cc / min of oxygen gas, glow discharge started at an applied voltage of about 2.3 kV. As the flow rate of helium gas relative to oxygen gas increases, the voltage at which glow discharge occurs decreases and the input power decreases. Further, the power for turning off the glow discharge also decreases as the flow rate of helium gas increases.
[0088]
On the other hand, when the low frequency voltage and the high frequency voltage are used together, as shown in FIG. 3, the flow rate of helium gas is 300 cc / min, that is, the oxygen gas is 25% and the helium gas is 75% in the flow rate ratio. However, glow discharge is generated and plasma can be generated. Therefore, the amount of helium gas used can be reduced, and the ashing processing cost can be reduced. In addition, since the amount of oxygen gas mixed in can be increased, the speed of the ashing process can be increased. Further, if the surface treatment is performed with the low frequency voltage applied to the low frequency electrode 58 even after the plasma is generated, the sustain voltage of the glow discharge can be lowered, and the active species generated by the low frequency voltage is caused by the plasma. Since it is superimposed on the active species, the processing speed can be further improved.
[0089]
In FIG. 4, ◯ is an input power value at the start of glow discharge when only a high frequency (RF) voltage is applied, and ● is an input power value when glow discharge is OFF when only a high frequency voltage is applied. And x shows that it did not discharge. Further, Δ is the power supplied to the high frequency electrode 60 at the start of glow discharge when a low frequency (LF) voltage is applied to the low frequency electrode 58 and a high frequency (RF) voltage is applied to the high frequency electrode 60. Is the power supplied to the high-frequency electrode 60 when the glow discharge is turned off.
[0090]
As shown in FIG. 4, when carbon tetrafluoride gas is flowed at 50 cc / min, discharge does not occur when the flow rate of helium gas is 400 cc / min. When the flow rate of helium gas is 500 cc / min, glow discharge can be generated only by applying a high frequency voltage, and the input power decreases as the flow rate of helium gas increases. When the low-frequency voltage and the high-frequency voltage are used in combination, even if the flow rate of helium gas is 500 cc / min, glow discharge can be performed with lower input power than when the high-frequency voltage alone is used. When carbon tetrafluoride gas is used as a processing gas (reaction gas), it is desirable to use ceramic as the dielectric material in order to avoid corrosion due to fluorine.
[0091]
In addition, in the said Example, although the case where the electron or active species produced | generated by applying a low frequency voltage as a trigger was used was demonstrated, it emitted | emitted from the thermoelectron radiated from the heated filament, an electron gun, etc. Electrons or active species generated thereby may be used as a trigger.
[0092]
FIG. 5 is a cross-sectional view of the atmospheric pressure plasma generation apparatus according to the third embodiment, showing a modification of the plasma generation apparatus 42 shown in FIG. That is, the plasma generating apparatus 70 is obtained by omitting the second gas supply head 62 shown in FIG. 2, and the other configuration is the same as that shown in FIG.
[0093]
The plasma generating apparatus 70 according to this embodiment introduces a discharge gas composed of helium gas and oxygen gas or a mixed gas of helium gas and carbon tetrafluoride gas into the gas flow path 46 via the gas supply head 48. . Then, the discharge gas is ionized or activated by the low frequency voltage applied to the low frequency electrode 58 to generate electrons and active species, and these are supplied as a trigger to the plasma generation region 22 corresponding to the high frequency electrode 60 to generate plasma. Is generated. With this configuration, the plasma generation apparatus can be simplified. Similarly, plasma can be generated when a gas in which air is mixed with helium gas is used.
[0094]
In addition, oxygen gas, carbon tetrafluoride gas or air is supplied from the gas supply head 48, and a low frequency voltage is applied to the low frequency electrode 58, and a high frequency voltage is applied to the high frequency electrode to generate oxygen gas and carbon tetrafluoride. Plasma by gas or air alone may be generated.
[0095]
FIG. 6 is a cross-sectional view of the atmospheric pressure plasma generation apparatus according to the fourth embodiment. In the plasma generator 72 of this embodiment, the cell 44 is formed in a T shape, and the gas flow path 46 communicating with the first gas supply head 48 is provided in the horizontal portion 74 of the cell 44. In the vertical portion 76 of the cell 44, a second flow path 78 connected to the gas flow path 46 is formed. A second gas supply head 62 is attached to the upper end portion of the vertical portion 76 so that the trigger gas flowing into the second gas supply head 62 can be guided to the gas flow path 46. Further, a low frequency electrode 58 is disposed on one side below the second gas supply head 62 in the vertical portion 76, and a ground electrode 80 is attached at a position corresponding to the low frequency electrode 58 on the opposite side. is there.
[0096]
The plasma generating method by the plasma generating apparatus 72 configured as described above is almost the same as the plasma generating apparatus 42 according to the second embodiment. That is, a trigger gas is introduced from the second gas supply head 62 and a low frequency voltage is applied to the low frequency electrode 58 to generate electrons and active species and supply them to the plasma generation region 22. The discharge gas is supplied to the first gas flow path 46 via the first gas supply head 48. Then, a high frequency voltage is applied to the high frequency electrode 60 to generate glow discharge to generate plasma. As indicated by the broken line, the low frequency electrode 58 may be provided on the horizontal portion 74 together with the low frequency electrode 58 to ionize or activate the discharge gas supplied from the first gas supply head 48.
[0097]
FIG. 7 is a schematic configuration diagram of an apparatus that is a fifth embodiment and that performs an organic substance removal method that is a surface treatment. The apparatus includes a gas supply unit that supplies a gas for generating plasma, a plasma generation unit that generates plasma and forms an active gas, and a processing unit that sprays the activated gas and processes an object to be processed. .
[0098]
The gas supply unit includes a nitrogen generator 11 that can generate nitrogen from compressed air that is extremely inexpensive. Instead of the nitrogen generator 11, it may be supplied from a commercially available nitrogen gas cylinder or the like. The nitrogen generator 11 can supply several tens of l / min of nitrogen gas having a purity of 99% or more.
[0099]
The plasma generator generates a discharge in a pair of dielectrics 1 having a gap of about 1 mm to 3 mm and a gas flow path formed by the pair of dielectrics 1 to form a flow path of the supplied gas. For this purpose, it is composed of a pair of electrodes 2a and 2b sandwiching the gas flow path. The dielectric 1 is made of quartz glass in order to prevent cracking due to temperature rise due to discharge.
[0100]
The processing unit includes a stage 7 on which the target object 8 is installed. The stage 7 is movable in the horizontal direction, and the entire target object can be processed by moving the stage 7. The distance from the end face of the dielectric 1 close to the object to be processed to the object 8 to be processed is maintained at about 1 to 2 mm.
[0101]
Nitrogen gas introduced from the gas supply unit is supplied to the intermediate chamber 12 installed on the upper part of the plasma generation unit. By providing the intermediate chamber 12, the gas is uniformly supplied to the object 8 to be processed from the gas supply port 13 opened in a slit shape via the gas flow path 23 formed of the pair of dielectrics 1. It is supplied with a gas flow velocity distribution.
[0102]
Two power supplies are connected to the electrode 2a so that voltages of two types of frequencies can be applied simultaneously. One is a 20 kHz power source 9, which is a step-up transformer 4 for boosting to a dozen kV, and a filter circuit 3 provided for preventing overload of the 20 kHz power source 9 by a 13.56 MHz high frequency power source output. Is connected to the electrode 2a. The other is a 13.56 MHz high frequency power supply 10 through an impedance matching unit 6 and a filter circuit 5 provided to prevent overload of the 13.56 MHz high frequency power supply 10 due to the output of the 20 kHz power supply 9. It is connected to the electrode 2a. These two power supplies 9 and 10 are controlled independently, and can apply a voltage independently or superimposed. The opposing electrode 2b is a ground electrode.
[0103]
Next, a discharge generation method will be described. In the high frequency power supply 10 of 13.56 MHz, since the frequency is high, only a voltage of about 2 to 3 kV can be applied. Therefore, discharge is not started in the atmosphere of nitrogen gas alone. Therefore, a high voltage of 20 kHz first boosted to a dozen kV is applied to the electrode 2a by the power source 9 to start corona discharge. The power supply output does not need a large output if the discharge can be started. Moreover, even if it is not discharged at this time, the voltage of more than ten kV should just be applied between electrodes.
[0104]
After the corona discharge is started, the power supply 10 applies a high frequency voltage of 13.56 MHz to the electrode 2a to which a voltage of 20 kHz is applied.
[0105]
FIG. 8 shows the change in the emission intensity of the discharge when the 20 kHz output is kept constant at 50 W and the superimposed 13.56 MHz high frequency output is gradually increased. The horizontal axis is the output of the 13.56 MHz power source 10, and the vertical axis is the emission intensity of the discharge. The light emission intensity of the discharge is obtained by taking the discharge portion from the gas outlet of the cell of the dielectric 1 with an optical fiber and spectrally decomposing it with a spectroscope and detecting it with a photomultiplier tube. The emission intensity is an arbitrary intensity, and the spectral wavelength is a nitrogen molecule spectrum of 336.9 nm.
[0106]
In the region a in the figure, the light emission intensity hardly changes even when the high frequency output of 13.56 MHz is gradually increased. Under this condition, the discharge stops when the high voltage of 20 kHz is cut off, and the discharge cannot be maintained with the high frequency voltage of 13.56 MHz alone. In the region b, a portion where the emission intensity is locally increased appears. In this discharge state, even if the high voltage of 20 kHz is cut off, the discharge can be sustained only with the high frequency voltage of 13.56 MHz. This is presumably because the electrons generated by the discharge can continue the ionization of the gas by the energy obtained from the high frequency voltage without using the high voltage of 20 kHz.
[0107]
The region c is a state in which high frequency discharge is formed on the entire surface of the electrode, and the discharge can be maintained with the high frequency voltage alone even when the high voltage of 20 kHz is cut off, similarly to the region b. Since the discharge having a strong emission intensity is formed almost on the entire surface of the electrode, this is the most suitable condition for uniformly processing the object 8 to be processed. The surface treatment of the object 8 can be performed without exposing the object to be processed by blowing the activated nitrogen gas to the object to be processed through the discharge thus obtained.
[0108]
Next, experimental results regarding organic substance removal in the surface treatment by the plasma generation apparatus of FIG. 7 will be described.
[0109]
[Table 1]

[0110]
Table 1 shows the removal speed when the resist applied on the silicon substrate is removed. The processing conditions were 13.56 MHz output 400 W, nitrogen gas flow rate 10 l / min, and the distance between the workpiece and the discharge part was set to about 6 mm. The distance from the end face of the dielectric 1 to the workpiece is about 1 mm. The resist removal speed at this time was 150 nm / min immediately under the blowing of gas in the resist depth direction.
[0111]
For comparison, the results of ashing the resist with oxygen gas using the same apparatus are shown in Table 1. The processing conditions are the same as the nitrogen gas processing except that the gas species are different. The removal rate by oxygen gas is about 180 nm / min, and it can be seen that the removal of resist by nitrogen gas is almost the same as the ashing rate of oxygen. In addition, ashing with oxygen gas increases the rate at which the ashing speed decreases as the distance between the discharge part and the object to be processed increases. When nitrogen gas is used, organic substances are removed even when the distance is relatively long. It was. This is presumed to be because the active species of nitrogen generated in the discharge has a longer lifetime than the active species of oxygen, so that the treatment reaction occurs more diffusely.
[0112]
In addition, comparisons were also made for processes with different frequency conditions. In general, in the case of the indirect discharge method as shown in FIG. 7, in order to improve the organic substance removal rate, it is preferable to bring the discharge part closer to the object to be processed or increase the applied output. The discharge part is brought close to the object to be processed in the process in which the active species generated in the discharge part are transported to the object to be processed. The shorter the transport distance, the smaller the attenuation of the active species. This is because the seeds can reach, and by increasing the applied output, the absolute number of active species generated during discharge increases. However, when a high voltage of 20 kHz is used, since the applied voltage is high, not only the discharge is maintained between the pair of electrodes when the output exceeds a certain output, but also a discharge occurs between the object to be processed, In some cases, the workpiece is damaged. In a comparative experiment using a 20 kHz low-frequency high-voltage power supply in this example, the distance between the object to be processed and the electrode must be about 25 mm or more when the applied output is 200 W. In the plasma treatment using a low frequency power source of 20 kHz when this is used as a treatment condition, the resist removal rate is extremely slow and 5 nm / min or less when not only nitrogen gas but also oxygen gas is used.
[0113]
From the above results, in the high frequency 13.56 MHz high frequency discharge, the plasma can be brought closer to the object to be processed without exposing the substrate to be processed, and the applicable output can be increased. High density plasma can be formed. As a result, the generated high-density active species can reach the object to be processed, and the processing speed can be increased.
[0114]
By the way, in this example, an attempt was made to remove the resist under the same conditions using air, but the resist was not removed at all. So the mixing ratio of nitrogen to oxygen
(Nitrogen flow rate / (nitrogen flow rate + oxygen flow rate)) × 100%
As a result of confirming at several mixing ratios, as shown in FIG. 9, it has a resist removal effect at a mixing ratio of 99% or more and 20% or less. It was found that the resist was not removed at all.
[0115]
The reason is considered as follows. First, the reaction at a mixing rate of 20% or less is presumed to be an organic matter removal phenomenon due to oxidation, as in conventional oxygen ashing. On the other hand, the reaction at a mixing ratio of 99% or more is a reaction between the active species of nitrogen formed in the plasma and the resist, not the oxidation reaction of the resist, but the nitriding reaction or organic matter is decomposed by particles having relatively high energy. It is thought.
[0116]
However, when oxygen exceeds a certain level during discharge, the active species of nitrogen and the active species of oxygen react to form a relatively stable nitrogen oxide. This stable nitrogen oxide is exhausted without reacting with organic matter, and no organic matter reaction occurs. Since the mixing ratio of nitrogen to oxygen in air is about 80%, it is estimated that organic substances could not be removed due to the influence of nitrogen oxides.
[0117]
FIG. 10 is a schematic configuration diagram of an apparatus for carrying out the organic substance removing method according to the sixth embodiment of the present invention. Portions common to the fifth embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0118]
That is, in the present embodiment, the grounded electrode 2b and the electrode 2a are provided with the dielectric 1 interposed therebetween. A power supply 10 of 13.56 MHz is connected to the electrode 2 a via the impedance matching unit 6. The electrode 2a and the electrode 2b are provided with heaters inside, and the electrode can be ripened to a predetermined temperature and kept constant.
[0119]
Next, the discharge procedure will be described. First, the electrodes 2a and 2b are heated by a heater to indirectly warm the discharge surface of the dielectric 1. The reason why the discharge surface of the dielectric 1 is warmed is to increase the emission of secondary electrons or thermionic electrons from the surface. The more the emission of secondary electrons or thermionic electrons, the easier the discharge starts. Therefore, the higher the surface temperature of the discharge surface of the dielectric 1, the easier the discharge. After the surface of the dielectric 1 is warmed, nitrogen gas is introduced into the cell (the gas flow path 23) of the dielectric 1 and a voltage of 13.56 MHz is applied to the electrode 2a. In this example, when the heating temperature of the electrodes 2a and 2b was set to 200 ° C., discharge could be started with nitrogen gas alone at a high frequency voltage of 13.56 MHz. That is, similar to the fifth embodiment, the resist could be removed at high speed using nitrogen gas.
[0120]
The means for heating the electrode may be a means for heating the discharge surface of the dielectric 1 from the outside using infrared rays or the like, instead of the heater installed inside the electrode 2a or 2b. Furthermore, it is desirable that the material of the discharge surface is a material having a high secondary electron emission or a material having a high thermal electron emission. For example, SrO, CaO, BaO, and the like are suitable for electrode surface materials because they have a small work function and easily emit thermoelectrons even when the surface temperature is not relatively high. These materials may be configured as a thin film on the dielectric surface.
[0121]
Next, examples of wettability improvement by surface treatment of an object to be treated using nitrogen gas according to the present invention will be described.
[0122]
The surface treatment apparatus used in the present embodiment is the same treatment apparatus as in the fifth and sixth embodiments, and detailed description thereof is omitted.
[0123]
That is, using a glass substrate as the object 8 to be processed, an active nitrogen gas spray treatment was performed on the glass substrate by the surface treatment method of the present invention, and the wettability of the substrate surface was evaluated by the contact angle of pure water. The glass used for evaluation is OA-2. The contact angle of pure water on the glass surface before the treatment was an average of 70 degrees.
[0124]
FIG. 11 shows the change of the contact angle with the processing time of the glass substrate. For comparison, the results of evaluation under different frequency conditions are also shown. In the case of processing using a frequency of 20 kHz, as already described in the first embodiment, since a high voltage is used, there are restrictions on the conditions, and comparative evaluation is performed under the same conditions as the organic matter removal conditions shown in Table 1. Yes. As can be seen from FIG. 11, in the nitrogen gas discharge treatment using 13.56 MHz according to the present invention, the wettability is clearly saturated in a short time as compared with the discharge treatment of 20 kHz.
[0125]
By the way, in this example, an attempt was made to improve the wettability using air. However, the improvement of the wettability of the glass substrate surface was extremely slow, and it took more than 5 minutes to saturate the contact angle. So the mixing ratio of nitrogen to oxygen
(Nitrogen flow rate / (nitrogen flow rate + oxygen flow rate)) × 100%
As a result of changing and confirming the mixing rate with respect to the contact angle at a processing time of 30 seconds, as shown in FIG. It turned out to be.
[0126]
In the case of wettability, several factors can be considered, but at present, the conditions for improving the wettability treatment speed are almost the same as the organic substance removal conditions described in the nitrogen gas plasma. It is presumed that the cleaning effect on the substrate surface due to the removal of organic contaminants attached to the substrate is great. However, when nitrogen gas is used, it is estimated that hydrophilic groups such as NH groups are generated on the substrate surface. Therefore, nitrogen gas is desirable as a gas used for improving demandability.
[0127]
FIG. 13 is a perspective view and a sectional view of the seventh embodiment. In this embodiment, local surface treatment can be easily performed, and the gas flow path 23 is formed by a pipe 82 formed of a dielectric such as quartz. Moreover, the 1st electrode 2a and the 2nd electrode 2b are arrange | positioned at the diameter direction both sides of the pipe 82, and generate | occur | produce plasma between these electrodes. A gas introduction pipe 84 is connected to the pipe 82, and the discharge gas 86 can be supplied to the gas flow path 23 through the gas introduction pipe 84 as shown by the arrow in FIG. It is like that. The plasma generation according to the seventh embodiment can be performed in the same manner as in the first embodiment.
[0128]
FIG. 14 shows an eighth embodiment, which is a plasma generation apparatus for batch processing of objects to be processed. In this embodiment, a pipe-like dielectric 92 that forms the gas flow path 23 is disposed in the chamber 90. A gas introduction pipe 94 is connected to one end of the dielectric 92 so that the discharge gas 86 can be introduced into the gas flow path 23. The other end of the dielectric 92 is connected to a plasma supply pipe 96 made of a flexible pipe or the like. The plasma supply tube 96 has a tip connected to the processing box 98. Inside the processing box 98, a large number of objects to be processed 8 are stored in a state where they are arranged in a rack 100 or the like.
[0129]
In the eighth embodiment configured as described above, a high frequency voltage is applied between the electrodes 2a and 2b arranged above and below the dielectric 92, and plasma is generated in the same manner as in the first embodiment. Then, active species generated with the generation of plasma are introduced into the processing box 98 through the plasma supply pipe 96 and irradiated to the object 8 to be processed, and a large number of objects 8 to be processed are subjected to ashing or etching at a time. .
[0130]
FIG. 15 is a sectional view and a perspective view of the ninth embodiment for direct discharge treatment suitable for etching and the like. In this plasma generating apparatus 102, one dielectric 104 is formed in a U-shape and is disposed across the convex portion of the ground electrode 106. The dielectric 104 and the ground electrode 106 can be moved relative to each other in the longitudinal direction.
[0131]
A high-frequency electrode 108 is provided on the dielectric 104 and a gas supply head 110 is attached. Further, a plate-like dielectric 112 on which the object 8 is disposed is provided on the upper surface of the convex portion of the ground electrode 106, and the gas flow path 23 is formed by the dielectric 112 and the dielectric 104. In the ninth embodiment configured as described above, the object to be processed 8 can be directly exposed to the discharge, so that surface treatment such as rapid etching can be performed.
[0132]
FIG. 16 shows still another embodiment. In FIG. 16, in the plasma generation apparatus 114, the gas flow path 23 is formed by upper and lower dielectric bodies 116 and 118. Further, the plasma generator 114 is provided so that the high-frequency electrode 120 and the ground electrode 122 face each other with the dielectrics 116 and 118 interposed therebetween. A cover 124 is attached to the top of the dielectric 116 so as to cover the high-frequency electrode 120. The distance L between the inner surface of the cover 124 and the high frequency electrode 120 is larger than the distance (discharge gap) d between the dielectrics 120 and 122. The cover 124 is filled with a fluid that is more difficult to discharge than air, for example, carbon tetrafluoride gas.
[0133]
With this configuration, creeping discharge caused by applying a high frequency voltage to the high frequency electrode 120 can be prevented. That is, when generating plasma without mixing a rare gas such as helium gas, a higher voltage is required than when a rare gas is mixed. In particular, when using a gas that is harder to discharge than air, such as carbon tetrafluoride gas, there is a risk of creeping discharge. Cannot be generated. Therefore, creeping discharge is prevented by sealing carbon tetrafluoride gas or the like in the cover 124 that is difficult to discharge from air.
[0134]
Insulating oil or the like may be enclosed instead of carbon tetrafluoride gas. Further, as shown by a broken line in FIG. 16, a communication hole 126 that connects the inside of the cover 124 and the gas flow path 23 is formed in the dielectric 116, and the carbon tetrafluoride gas that has flowed into the cover 124 is connected to the communication hole. The gas flow path 23 may be supplied via 126. Thus, if carbon tetrafluoride gas is supplied to the gas flow path 23 through the cover 124, creeping discharge can be prevented and the apparatus can be miniaturized.
[0135]
In order to prevent creeping discharge, it is desirable not to place anything in the vicinity of the electrode, but only the electrode. And when something is arranged near the electrode, it is desirable to set a distance of 2 mm / v or more. Moreover, it is desirable to use a dielectric having a flat surface with as few irregularities as possible, and an average roughness of 0.02 μm or less. This is because the presence of the concave portion is undesirable because the electric field concentrates on the portion and partial discharge occurs.
[0136]
Further, in the case shown in FIG. 2, it is desirable that the high-frequency electrode 60 does not protrude from the cell (dielectric material) 44, and it is desirable that the high-frequency electrode 60 be disposed at least 1 cm inside the end of the cell 44. . This is because, when the electrode protrudes from the end of the cell, creeping discharge is easily generated along the side surface of the cell 44.
[0137]
【The invention's effect】
As described above, according to the present invention, atmospheric pressure plasma can be easily generated without using a rare gas or using a gas in which the ratio of oxygen gas or carbon tetrafluoride gas to the rare gas is increased. The amount of expensive rare gas used can be greatly reduced, and when used for surface treatment, the cost of surface treatment can be reduced and the treatment speed can be improved.
[0138]
Further, according to the present invention, the running cost can be reduced because the discharge can be performed using an inexpensive nitrogen gas without using helium at atmospheric pressure. Furthermore, even if helium is not used, discharge under atmospheric pressure can be facilitated using a high frequency voltage of several MHz or more with a reactive gas such as nitrogen gas or oxygen gas, and the processing speed can be increased. In addition, by realizing high-frequency discharge using nitrogen gas under atmospheric pressure, it is possible to remove organic substances and improve the wettability of the substrate surface as well as oxygen treatment without using oxygen gas. It can be applied to the treatment of an object to be treated in an atmosphere with a risk of body or ignition, and a new process can be proposed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an atmospheric pressure plasma generation apparatus according to a first embodiment of the present invention.
FIG. 2 is an explanatory view of a second embodiment of the present invention, wherein (1) is a perspective view, (2) is a plan view, and (3) is along the line AA in (2). FIG.
FIG. 3 is a diagram showing a relationship between a helium gas flow rate with respect to a constant oxygen gas flow rate by the plasma generation apparatus according to the second embodiment and high-frequency input power when glow discharge is started and when glow discharge is OFF.
FIG. 4 is a diagram showing a relationship between a helium gas flow rate with respect to a constant carbon tetrafluoride gas flow rate and a high-frequency input power when glow discharge is started and when glow discharge is OFF by the plasma generation apparatus according to the second embodiment. is there.
FIG. 5 is a cross-sectional view of an atmospheric pressure plasma generation apparatus according to a third embodiment.
FIG. 6 is a sectional view of an atmospheric pressure plasma generation apparatus according to a fourth embodiment.
FIG. 7 is a schematic configuration diagram of a fifth embodiment.
FIG. 8 is a characteristic diagram showing light emission intensity of a discharge obtained by superimposing a high frequency output on a low frequency discharge.
FIG. 9 is a characteristic diagram showing the organic substance removal rate depending on the mixing ratio of nitrogen gas to oxygen gas.
FIG. 10 is a schematic device configuration diagram of a sixth embodiment.
FIG. 11 is a characteristic diagram showing the contact angle depending on the processing time of the glass substrate surface according to the frequency of nitrogen gas.
FIG. 12 is a characteristic diagram showing a contact angle depending on a processing time of a glass substrate surface according to a mixing ratio of nitrogen gas to oxygen soot.
FIG. 13 is a perspective view and a sectional view of a seventh embodiment.
FIG. 14 is a sectional view of an eighth embodiment.
FIG. 15 is a cross-sectional view and a perspective view of a ninth embodiment.
FIG. 16 is an explanatory diagram of still another embodiment.
[Explanation of symbols]
1 Dielectric
2a, 2b electrode
3, 5 Filter circuit
4 Step-up transformer
6 Impedance matching device
7 stage
8 Object
9 Low frequency power supply (20 kHz power supply)
10 High frequency power supply (13.56 MHz power supply)
11 Nitrogen generator
12 Intermediate chamber
13 Gas supply slit
20 Heater
21 Chamber
22 Plasma generation region
23, 46 Gas flow path
25 High frequency power supply
26 Plasma detection means (light sensor)
28 Control means (controller)
34, 38 First gas supply means (oxygen gas cylinder, flow control valve)
36, 40 Second gas supply means (helium gas cylinder, flow control valve)
42 Plasma generator
44 cells (dielectric)
58 Low frequency electrode
60 high frequency electrode
66 Ground electrode
70, 72 Plasma generator
82 pipe
86 Discharge gas
98 processing box
108, 120 High frequency electrode
106, 122 Ground electrode

Claims (8)

A discharge gas is introduced into a plasma generation region formed at or near atmospheric pressure formed by a dielectric, and a voltage is applied between a ground electrode and an electrode provided with the dielectric interposed therebetween to generate plasma. In the atmospheric pressure plasma generation method to be generated,
The electrode includes a first electrode for low frequency and a second electrode for high frequency,
Preparing a rare gas supply head and a surface treatment gas supply head for introducing the discharge gas;
The rare gas supply head is provided at the uppermost stream of the discharge gas flow path, the first electrode for low frequency is provided downstream of the rare gas supply head, and the surface is provided downstream of the first electrode for low frequency. A gas supply head for processing is provided, and the second electrode for high frequency is provided downstream of the gas supply head for surface treatment,
While supplying a rare gas from the rare gas supply head, obtaining a trigger gas for starting up plasma by energizing between the low frequency electrode and the ground electrode,
Supplying the surface treatment gas from the surface treatment gas supply head to the flow of the trigger gas, energizing between the high frequency electrode and the ground electrode to generate plasma,
Thereafter, the supply of the rare gas is stopped, and the atmospheric pressure plasma generation method is characterized. A dielectric that forms a plasma generation region; a first gas supply means that supplies a gas for surface treatment to the plasma generation region under a pressure at or near atmospheric pressure; and the pressure under a pressure at or near atmospheric pressure. Second gas supply means for supplying a rare gas to the plasma generation region, a ground electrode provided with the dielectric in between, a first electrode for high frequency, a ground electrode, a second electrode for low frequency, and the ground electrode A power source that applies a high-frequency voltage between the first electrode, the ground electrode, and the second electrode, a plasma detection unit that detects that plasma is generated in the plasma generation region, and a Control means for controlling the second gas supply means based on a detection signal and stopping the supply of the rare gas to the plasma generation region,
A gas supply means and an electrode are provided in the order of the second gas supply means, the second electrode, the first gas supply means, and the first electrode from the upstream of the surface treatment gas flow path. Atmospheric plasma generator. In claim 2,
The control means controls the first gas supply means to supply the surface treatment gas to the plasma generation region after the generation of the plasma by the rare gas. A dielectric that forms a plasma generation region; a first gas supply unit that supplies a surface treatment gas to the plasma generation region that is at or near atmospheric pressure; and a second gas supply unit that supplies a rare gas. A ground electrode, a first electrode for high frequency, a ground electrode, a second electrode for low frequency, the ground electrode, the first electrode, the ground electrode, and the second electrode, sandwiched between the dielectrics, And a power source for generating a plasma by applying a voltage between
From the upstream of the surface treatment gas flow path, the second gas supply means, the second electrode, the first gas supply means, and the first electrode are provided in the order of gas supply means and electrode,
Furthermore, the atmospheric pressure plasma generation apparatus further comprises trigger supply means for supplying electron or gaseous active species to the plasma generation region under atmospheric pressure or a pressure in the vicinity thereof. In any of claims 2 to 4,
The dielectric having the electrode connected to the power source is provided with a cover covering the electrode connected to the power source, and a fluid that is less likely to discharge than air is injected into the cover. An atmospheric pressure plasma generator. In claim 5,
An atmospheric pressure plasma generation apparatus, wherein a distance between an electrode connected to the power source and an inner surface of the cover is larger than a discharge gap of the plasma generation region. In the surface treatment method of generating plasma by the atmospheric pressure plasma generation method according to claim 1 and irradiating the object to be processed with active species generated by the plasma to remove organic substances on the surface of the object to be processed,
The surface treatment method, wherein the surface treatment gas or the discharge gas is oxygen gas. In the surface treatment method of generating plasma by the atmospheric pressure plasma generation method according to claim 1, irradiating the object to be processed with active species generated by the plasma and etching the surface of the object to be processed,
The surface treatment method, wherein the surface treatment gas or the discharge gas is a carbon tetrafluoride gas.

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