JP2004091810A

JP2004091810A - Ion implantation apparatus and ion implantation method

Info

Publication number: JP2004091810A
Application number: JP2002251403A
Authority: JP
Inventors: Etsuo Noda; 野田　悦夫; Shiro Asano; 浅野　史朗; Toru Sugawara; 菅原　亨; Takeshi Saito; 斎藤　武志; Toshiyuki Watanabe; 渡邊　敏行; Katsuhiko Seki; 関　克彦
Original assignee: Toshiba Corp; Toshiba Tungaloy Co Ltd
Current assignee: Toshiba Corp; Tungaloy Corp
Priority date: 2002-08-29
Filing date: 2002-08-29
Publication date: 2004-03-25

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion implantation apparatus and an ion implantation method of long service life and high reliability in which ions can be uniformly implanted even in a base body of a three-dimensional shape. <P>SOLUTION: The ion implantation apparatus comprises a vacuum vessel 1 to accommodate a base body 10, a feed means to feed gas of a substance to be implanted in the base body 10 into the vacuum vessel 1 via a gas inlet 5a of the vacuum vessel 1, and an evacuation pump to evacuate the vacuum vessel 1 via an exhaust port 6. Further, the apparatus comprises a base body holding base 11 which is accommodated in the vacuum vessel 1, is electrically insulated from the vacuum vessel 1, and holds the base body 10, a discharge plasma generating means comprising a filament 9 to generate discharge plasma around the base body 10 by the arc discharge of the gas in the vacuum vessel 1 fed by the feed means, a filament power source 16, and an arc power source 17, and a high frequency power source 40 to apply the high frequency voltage to the base body 10 and implant ions of the substance to be implanted in the base body 10 to be fed from the feed means to the base body 10 by the discharge plasma generated by the discharge plasma generation. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、例えばピストン、ベアリングなどの自動車部品、ドリルなどの切削工具のような基体にイオンを注入するためのイオン注入装置及びイオン注入方法（表面改質方法または膜生成方法）に関する。
【０００２】
【従来の技術】
自動車部品、切削工具等の製造に際し、該工具等の基体にイオンを注入することによって、基体の耐磨耗性、耐熱性、硬度などを向上させる試みが行われている。例えばステンレス鋼からなる基体に、チタン又は窒素を注入すると基体の耐磨耗性や疲労寿命が大幅に改善されることが知られている。
【０００３】
基体にイオンを注入する方法として、注入したい物質の正イオンを含む放電プラズマ中に基体を保持して、数十から数百ｋＶの負のパルス電圧を印加する方法が提案されている（参考文献：Ｊ．Ｒ．Ｃｏｎｒａｄ，ｅｔ．ａｌ．，”Ｐｌａｓｍａ　ｓｏｕｒｃｅ　ｉｏｎ−ｉｍｐｌａｎｔａｔｉｏｎ　ｔｅｃｈｎｉｑｕｅ　ｆｏｒ　ｓｕｒｆａｃｅ　ｍｏｄｉｆｉｃａｔｉｏｎ　ｏｆ　ｍａｔｅｒｉａｌｓ”，Ｊ．Ａｐｐｌ．Ｐｈｙｓ　６２（１１），１９８７，ｐｐ．４５９１−４５９６）。このイオン注入方式はＰＳＩＩ（Ｐｌａｓｍａ　Ｓｏｕｒｃｅ　Ｉｏｎ　Ｉｍｐｌａｎｔａｔｉｏｎ）またはＰＩＩＩ（Ｐｌａｓｍａ　Ｉｍｍｅｒｓｉｏｎ　Ｉｏｎ　Ｉｍｐｌａｎｔａｔｉｏｎ）という略称で呼ばれている。
【０００４】
係る方法を、イオン源から引き出した注入イオンを質量分離用の偏向磁石を通した後に加速して基体に注入するという従来法と比較すると、次に列挙する特徴がある。
【０００５】
（ａ）　基体が三次元形状をしている場合であっても、基体の周囲を取り囲んでいるプラズマから基体表面にほぼ垂直にイオン注入が行え、一方向からしかイオン注入の行えない従来法で必要だった基体の駆動機構が不要で注入時間も短くて済む。
【０００６】
（ｂ）　長距離のビーム輸送が不要なので装置構成を単純・安価にできる。
【０００７】
以下、従来のＰＳＩＩ装置について、図１１〜図１４を参照しながら説明する。このＰＳＩＩ装置は、例えば米国特許４７６４３９４号明細書などに記載されたものと同様のものである。
【０００８】
図１１及び図１２は従来のＰＳＩＩ装置を説明するための図であって、図１１は真空容器を縦断面して示す図であり、図１２は真空容器を横断面して示す図であり、図１３はＰＳＩＩ装置の斜視図である。
【０００９】
図１１〜図１３において、真空容器１は、軸方向上端面に配設された上板２と、軸方向下端面に配設された底板３と、上板２と底板３の間に配設された円筒状の側板４とに囲まれた有底円筒形状の容器である。底板３には図示しないガス源から真空容器１内に放電ガスを導入するガス導入口５ａ及び図示しない真空排気ポンプにより真空容器１内を真空に排気するための真空排気口６が設置されていいる。上板２と底板３の外壁には、複数の角棒状の永久磁石７ａ，７ｂが互いに平行に配設されている。
【００１０】
なお、永久磁石７ａ，７ｂは、上板２及び底板３の外壁に直角な方向に着磁され、隣接する磁石７同士の極性が互いに異なって配設される。更に側板４の外壁にも、複数の永久磁石８が垂直方向に互いに平行であって、また隣接する磁石８の極性が互いに異なるように配設されている。
【００１１】
このように永久磁石７ａ，７ｂ，８を配設することにより真空容器１の内壁全面を覆う磁力線２０ａ，２０ｂ，２０ｃが形成される。また、真空容器１の上板２及び底板３及び側板４には、上板２及び底板３及び側板４を陽極とすることに対し、陰極となるフィラメント９が配設される。
【００１２】
更に、真空容器１内にはイオンを注入すべき基体（ターゲット）１０を保持するための金属製の基体保持台（ターゲット保持台）１１がブッシング１２を介して真空容器１とは電位的に絶縁されて配設されている。
【００１３】
真空容器１には、フィラメント９に通電するためのフィラメント電源（図示しない）と、上板２及び底板３及び側板４を陽極、フィラメント９を陰極とするアーク放電を起こすためのアーク電源（図示しない）からなる放電電源ユニット１３が接続されている。基体１０には高圧ケーブル１４及びブッシング１２を経由してパルス高電圧電源１５からパルス状の高電圧が印加されるようになっている。
【００１４】
次に、このような構成からなる従来のＰＳＩＩ装置の動作について説明する。即ち、ガス導入口５ａから基体１０に注入したい物質のガス（窒素、酸素など）を供給しておき、放電電源ユニット１３のフィラメント電源によってフィラメント９に通電して加熱し、発生する熱電子を真空排気口６を用いて予め真空状態にしておいた真空容器１内に充満させておく。その後、ガス導入口５ａから基体１０に注入したい物質のガス（窒素、酸素など）を供給し、放電電源ユニット１３のアーク電源によりフィラメント９と真空容器１との間にアーク放電を発生させて放電プラズマ２１を生成する。
【００１５】
そして、イオンを注入する基体１０を載せた基体保持台１１にはパルス高電圧電源１５が接続されており、プラズマの生成とは独立に真空容器１に対して、図１４に示すようにパルス幅τがおよそ数マイクロ秒（数μｓ）〜数十マイクロ秒（数十μｓ）、その大きさが数十から数百ｋＶ程度の負のパルス電圧が印加される。
【００１６】
この結果、基体１０に負のパルス電圧が印加され、これにより基体１０を取り囲んだプラズマ中にシースが成長し、電子が基体から遠ざけられ、逆にイオンが基体方向に加速されて、イオンが基体に注入されることになる。
【００１７】
【発明が解決しようとする課題】
しかしながら、以上述べた従来の技術では、基体が絶縁物の場合や、イオン注入により作成する膜が絶縁物の場合には、実際に注入に寄与するパルス幅が極端に短くなってしまうため、数十マイクロ秒のパルスを印加しても注入されるのは、最初の数十〜数百ナノ秒となる。その結果、処理時間が極端に長くなり、生産性が悪くなる。
【００１８】
また、パルスの立ち上がり時はイオンが加速されるため、十分なエネルギーを持つことができない。この結果、絶縁物では、特に低エネルギーのイオンが多く照射されることになり、表面改質等の効果が十分得られないという欠点がある。
【００１９】
一方、基体及び膜が導体の場合には、イオンが加速される時間よりも十分長いパルスをかけることができるが、パルス幅が長くなると、基体近傍でアークが発生しやすくなる。アークは基体や生成した膜に損傷を与えるため、運転はアークが発生しないような電圧まで下げる必要がある。その結果、十分な加速電圧が得られなくなり、表面改質等の効果が十分得られないということになる。
【００２０】
本発明では、三次元形状の基体に対しても均一なイオン注入が可能であり、基体が絶縁物の場合や、イオン注入により作成する膜が絶縁物の場合にも、十分処理性能が得られ、且つアークの発生しにくい信頼性の高い安価なイオン注入装置、及び、イオン注入方法を提供することを目的とする。
【００２１】
【課題を解決するための手段】
前記目的を達成するため、請求項１に記載の発明は、イオンを注入すべき基体が収納される真空容器と、前記真空容器内に前記基体に注入したい物質のガス或いは蒸気を供給する供給手段と、前記真空容器内部を真空に排気する真空排気手段と、前記真空容器内に収納され、該真空容器と電気的に絶縁されると共に前記基体を保持する基体保持手段と、前記供給手段により供給された前記真空容器内にあるガス或いは蒸気をアーク放電により前記基体の周囲に放電プラズマを生成する放電プラズマ生成手段と、前記基体に高周波電圧が印加され、前記放電プラズマ生成手段によって生成された放電プラズマにより前記基体に前記供給手段から供給される前記基体に注入したい物質のイオンを注入させるための高周波電圧発生手段とを具備したイオン注入装置である。
【００２２】
前記目的を達成するため、請求項２に記載の発明は、請求項１に記載の高周波電圧発生手段並びに前記放電プラズマ生成手段の電源を、共通の高周波電源で共用したイオン注入装置である。
【００２３】
前記目的を達成するため、請求項３に記載の発明は、請求項１又は２に記載の高周波電圧発生手段を、周波数の異なる複数の高周波電圧をそれぞれ重畳するようにしたイオン注入装置である。
【００２４】
前記目的を達成するため、請求項４に記載の発明は、請求項１又は２に記載の高周波電圧発生手段を、前記基体に高周波電圧をパルス的に印加するようにしたイオン注入装置である。
【００２５】
前記目的を達成するため、請求項５に記載の発明は、請求項３に記載の高周波電圧発生手段として、前記基体に印加する周波数の異なる複数の高周波電圧を発生する２つ以上の周波数の高周波電圧のうち、少なくとも一方又は少なくとも周波数の高い方の高周波電圧をパルス的に印加するようにしたイオン注入装置である。
【００２６】
前記目的を達成するため、請求項６に記載の発明は、請求項３又は請求項５に記載の前記高周波電圧発生手段として、異なる周波数の高周波電圧を発生する複数の高周波電源と、該各高周波電源の出力側に夫々接続された複数のインピーダンス整合器と、該インピーダンス整合器の少なくとも一方の出力側に接続され、所定の周波数をブロックするフィルター回路とからなり、該フィルター回路の出力と前記インピーダンス整合器の出力を畳重させるか、又は前記各フィルター回路の出力を畳重させるようにしたイオン注入装置である。
【００２７】
前記目的を達成するため、請求項７に記載の発明は、請求項１、２、４のいずれか一つに記載の基体に印加する高周波電源の周波数が、基体の周囲に生成される放電プラズマのイオンプラズマ周波数よりも高く、且つ、電子プラズマ周波数よりも低く設定したイオン注入装置である。
【００２８】
前記目的を達成するため、請求項８に記載の発明は、請求項１、２、３、６のいずれか一つに記載の高周波電圧印加手段として、高周波電源と、該高周波電源の出力側に接続されるインピーダンス整合器と、該インピーダンス整合器の出力側に接続され、該インピーダンス整合器の出力を昇圧する高周波用昇圧トランスからなり、該高周波用昇圧トランスで昇圧された高電圧の高周波電圧を、前記基体に印加するようにしたイオン注入装置である。
【００２９】
前記目的を達成するため、請求項９に記載の発明は、請求項３又は請求項５に記載の高周波電圧印加手段として、異なる周波数の高周波電圧を発生する複数の高周波電源と、該各高周波電源の出力側に夫々接続された複数のインピーダンス整合器と、該各インピーダンス整合器の出力が重畳された電圧を昇圧して前記基体に印加する高周波用昇圧トランスとから構成したイオン注入装置である。
【００３０】
前記目的を達成するため、請求項１０に記載の発明は、請求項３、６、７のいずれか一つに記載の高周波電圧発生手段として、異なる周波数の高周波電圧を発生する複数の高周波電源と、該各高周波電源の出力側に夫々接続された複数のインピーダンス整合器と、該各インピーダンス整合器の出力側に接続され、該各インピーダンス整合器の出力電圧を夫々昇圧する複数の高周波用昇圧トランスと、前記高周波用昇圧トランスの少なくとも一方の出力部に設けた他の周波数をブロックするフィルター回路とからなり、前記フィルター回路の出力と前記高周波用昇圧トランスの出力を重畳させるか、又は前記各フィルター回路の出力を重畳させて前記基体に２つ以上の周波数の高周波電圧を印加するようにしたイオン注入装置である。
【００３１】
前記目的を達成するため、請求項１１に記載の発明は、真空容器内にイオンを注入すべき基体を該真空容器と電気的に絶縁して配設し、該真空容器内を真空状態とすると共に、該真空容器内に該基体に注入したい物質のガス或いは蒸気をガス又は蒸気が供給され、かつ該真空容器内であって該基体の周囲にプラズマを生成した状態で、前記基体に高周波電圧を印加することにより該基体に負電圧を発生させ、該基体にイオン注入を行うようにしたイオン注入方法である。
【００３２】
前記目的を達成するため、請求項１２に記載の発明は、真空容器内にイオンを注入すべき基体を該真空容器と電気的に絶縁して配設し、該真空容器内を真空状態とすると共に、該真空容器内に基体に注入したい物質のガス或いは蒸気が供給され、かつ該真空容器内であって該基体の周囲にプラズマを生成した状態で、前記基体に２つ以上の周波数の高周波電圧を印加することにより該基体に負電圧を発生させ、該基体にイオン注入を行うようにしたイオン注入方法である。
【００３３】
前記目的を達成するため、請求項１３に記載の発明は、請求項１１又は１２に記載の基体に印加する高周波電圧又は前記基体に２つ以上の周波数の高周波電圧のうちの少なくとも一方をパルス的に印加するようにしたイオン注入方法である。
【００３４】
前記目的を達成するため、請求項１４に記載の発明は、請求項１１又は１２に記載の基体に印加する高周波電源の周波数が、基体の周囲に生成されるプラズマのイオンプラズマ周波数よりも高く、且つ、電子プラズマ周波数よりも低い周波数でイオン注入を行うようにしたイオン注入方法である。
【００３５】
尚、本発明においては、基体に印加する高周波電源の周波数を工業周波数帯に設定してイオン注入を行うようにするのが好適である。
【００３６】
請求項１又は請求項１１に対応する発明によれば、基体に高周波電圧を印加することにより、基体や生成される膜が絶縁体であっても、高周波の半周期ごとに基体表面の電荷が中和されるため、基体や生成される膜が絶縁体であっても、注入イオンに対しては実効的に直流とみなせる負バイアスを印加できることになる。この負バイアスの大きさは、基体表面積と高周波電源の反対側の極に繋がれる真空容器の内側の表面積の比できまり、後者が前者の数倍以上あれば、高周波電圧のピーク値（Ｐ−Ｐ値の半分）にほぼ等しい電圧が負バイアスとして基体に印加され、この負バイアスによってイオンが基体に加速注入される。
【００３７】
また、請求項１又は請求項１１に対応する発明によれば、高周波で繰り返す高周波電圧を印加するため、電子の運動の向きは高速繰り返しで変化しており、パルス幅が長くてもアークが発生しにくく、そのため、高い電圧を印加することができ十分な注入効果が得られ、従来の技術よりも高性能で高速処理の表面改質方法または膜生成方法を得ることが可能となる。
【００３８】
請求項２又は請求項１３に対応する発明によれば、高周波電圧をパルス的（バースト的）に印加することにより、任意のパルス幅のバイアス電圧を基体に印加することもできる。
【００３９】
請求項３又は請求項１２に対応する発明によれば、基体に周波数の異なる複数の高周波電圧をそれぞれ重畳して印加することにより、高周波側の高周波でプラズマを生成し、低周波側の高周波でバイアス電圧を発生させることができ、その結果、前述した高密度プラズマの生成と高電圧印加が同時に達成され、より高性能で高速なイオン注入処理を行うことができる。
【００４０】
ここで、請求項３又は請求項１２に示すように構成する理由は、次のような特徴を考慮したからである。すなわち、基体と真空容器との間で発生する高周波放電によりプラズマを生成することもでき、こうすれば、基体に高周波電圧を印加するだけでプラズマ生成とバイアス電圧印加を同時に行うことができ、安価で信頼性の高いイオン注入技術が得られる。そして、より高性能で高速なイオン注入処理を行うためには、高密度プラズマの生成と高電圧印加が望ましい。この場合、高周波電圧の周波数を高くすると、プラズマ密度が高くなるが印加バイアス電圧が低くなる。一方、高周波電圧の周波数を低くすると、印加バイアス電圧が高くなるがプラズマ密度が低くなる。
【００４１】
請求項７又は請求項１４に対応する発明によれば、基体に高周波電圧を印加する際に、高周波電圧の発振周波数を基体の周囲に生成されるプラズマのイオンプラズマ周波数よりも高く選ぶことにより、基体に注入されるイオンがほぼ一定の電圧で加速されるようになるため、注入イオンに対して実効的に直流とみなせる負バイアスを印加できることになる。
【００４２】
【発明の実施の形態】
図１は本発明に係るイオン注入装置の第１の実施形態を説明するためのものであって、真空容器を横方向に断面して示す概略構成図である。真空容器１は、図１１〜図１３と同様に、軸方向上端面に配設された上板２と、軸方向下端面に配設された底板３と、上板２と底板３の間に配設された円筒状の側板４とに囲まれた有底円筒形状の容器である。
【００４３】
真空容器１の底板３には、図１１と同様に基体に注入したい物質のガス或いは蒸気を供給する供給手段（図示せず）から真空容器１内に放電ガスを導入するガス導入口５ａ及び図示しない真空排気手段例えば図示しない真空排気ポンプにより真空容器１内を真空に排気するための真空排気口６が設置されている。
【００４４】
真空容器１の上板２と底板３の外壁には、図１に示すように複数の角棒状の永久磁石８が互いに平行に配設されている。この場合、永久磁石８は上板２及び底板３の外壁に直角な方向に着磁され、隣接する磁石８同士の極性が互いに異なって配設される。更に側板４の外壁にも、複数の永久磁石８が垂直方向に互いに平行であって、また隣接する磁石８の極性が互いに異なるように配設されている。
【００４５】
このように永久磁石８を配設することにより、真空容器１の内壁全面には、該内壁全面を覆う磁力線２０ｃが形成される。
【００４６】
また、真空容器１の上板２及び底板３及び側板４には、上板２及び底板３及び側板４を接地陽極とすることに対し、陰極となるフィラメント９が配設されている。
【００４７】
更に、真空容器１内にはイオンを注入する基体１０を保持するための金属製の基体保持台１１がブッシング１２を介して真空容器１とは電気的（電位的）に絶縁されて配設されている。
【００４８】
真空容器１には、フィラメント９に通電するためのフィラメント電源１６と、真空容器１の上板２及び底板３及び側板４を陽極、フィラメント９を陰極とするアーク放電を起こすためのアーク電源１７からなる放電電源ユニット１３が接続されている。
【００４９】
基体１０には、真空容器１に貫通固定されたブッシング１２に、ケーブル１４及びインピーダンス整合器４２を介して高周波電源４０が接続されている。この場合の高周波電源４０は、数百ＫＨｚ〜数百ＭＨｚの電圧を発生するものである。なお、インピーダンス整合器４２は、高周波電源４０と基体１０のインピーダンスの整合をとるためのものである。
【００５０】
図２は、基体１０に印加する高周波電源４０の電圧とバイアス電圧の関係を簡単に示したものである。基体１０の表面積と、高周波電源４０の反対側の極に繋がれる真空容器１の内側の表面積の比が大きければ（数倍以上）、高周波電圧のピーク値（Ｐ─Ｐ値の半分）にほぼ等しい電圧が負バイアスとして基体１０に印加される。イオンはこの負バイアスによって加速注入される。
【００５１】
以上述べた実施形態によれば、基体１０に高周波電圧を印加することにより、基体１０や生成される膜が絶縁体であっても、高周波の半期毎に基体表面の電荷が中和されるため、基体や生成される膜が絶縁体であっても、注入イオンに対しては実効的に直流とみなせる負バイアスを印加できることになる。
【００５２】
この負バイアスの大きさは、基体表面積と高周波電源の反対側の極に繋がれる真空容器１の内側の表面積の比で決まり、後者が前者の数倍以上あれば、高周波電圧のピーク値にほぼ等しい電圧が負バイアスとして基体１０に印加され、この負バイアスによってイオンが基体に加速注入される。
【００５３】
また、本実施形態によれば、高周波で繰り返す高周波電圧を印加するため、電子の運動の向きは高速繰り返しで変化しており、パルス幅が長くてもアークが発生しにくく、そのため、高い電圧を印加することができ十分な注入効果が得られ、前述した従来の技術の課題を解決できるばかりでなく、従来の技術よりも高性能で高速処理の表面改質方法又は膜生成方法を得ることが可能となる。従来の技術では、処理速度を上げるために、基体に印加するパルスの幅を広げていくと、基体近傍でアークが発生しやすくなり、アークは基体や生成した膜に損傷を与えるため、運転はアークの発生しないような電圧まで下げる必要があり、その結果、十分な加速電圧をかけることができなくなり、十分な注入効果が得られなかった。
【００５４】
図３は、図１の変形例であって基体１０に高電圧の高周波を印加するために、図１のインピーダンス整合器４２とブッシング１２に電気的に接続されたケーブル１４の間に、高周波用昇圧トランス４５を接続して基体１０に電圧を印加するように構成したものである。これ以外の点は、図１と同一であるので、ここでは同一符号を付してその説明を省略する。
【００５５】
また、ここで用いる高周波電源４０の周波数は、前述したように、基体１０の周囲に生成されるプラズマのイオンプラズマ周波数よりも高く、且つ、電子プラズマ周波数よりも低いことが望ましい。このようにすることにより、基体１０に注入されるイオンがほぼ一定の電圧で加速されるようになるため、注入イオンに対して実効的に直流とみなせる負バイアスを印加できることになる。
【００５６】
さらに、この周波数が、例えば１３．５６ＭＨｚのような工業周波数帯に設定されていると、電磁シールド等の関係が楽になる。
【００５７】
また、プラズマ生成法については、図１では、フィラメント９によるアーク放電を用いたが、図４に示すように高周波のインダクティブカップリングによるプラズマ生成、具体的には真空容器１の軸方向端部に高周波コイル２４を巻回し、該高周波コイル２４に高周波電源を２５を接続し、高周波コイル２４により高周波電界を作り中性ガスを電離する方法である。この場合には、真空容器１の一端部にプラズマに電位を与えるための図示しない電極（電位固定電極）及び真空容器１の他端部に図示しないイオンを引き出す電極（イオン引出し電極）を備えている。
【００５８】
なお、図４では示していないが、場合によっては高周波コイル２４と、高周波電源２５の接続部にはそれぞれインピーダンス整合器を設けるようにしてもよい。
【００５９】
以上述べたプラズマ生成方法以外に、ＥＣＲ（電子サイクロトロン共鳴）によるプラズマ生成、また、アーク方式による金属プラズマ（蒸気）発生法など、多くの方式が利用できる。
【００６０】
次に第２の発明に係わる実施形態について、図５の概略構成図を参照して説明する。真空容器１の構成は図４と同じであるが、図４の高周波コイル２４に接続されている高周波電源２５を設けず、これに基体１０が接続されている高周波電源４０を共用させたものである。これ以外の点は、図１と同じであるので、その説明は省略する。
【００６１】
このように、プラズマ生成用の高周波電源２５として基体１０に印加するは高周波電源４０で共用しているため、装置構成が非常に簡単になる。
【００６２】
次に、図５の変形例である図６について、図６を参照して説明する。図６のインピーダンス整合器４２とブッシング１２の接続部に高周波用昇圧トランス４５を接続したものである。これ以外の構成は、図５と同一である。
【００６３】
以上述べた第２の実施形態についても、高周波の周波数は、基体１０の周囲に生成されるプラズマのイオンプラズマ周波数よりも高く、且つ、電子プラズマ周波数よりも低いことが望ましい。さらに、この周波数が、例えば１３．５６ＭＨｚのような工業周波数帯に設定されていると、電磁シールド等の関係が楽になる。
【００６４】
金属イオンを注入する場合には、さらに、これに、金属プラズマ（蒸気）を発生させる金属プラズマ（蒸気）源を付加することになる。
【００６５】
次に本発明に係る第３の発明に係わる実施形態について、図７、図８、図９を参照して説明する。図７は、高周波電圧印加手段として、異なる周波数の高周波電圧を発生する複数の高周波電源４０、４１と、該各高周波電源４０、４１の出力側に夫々接続されたインピーダンス整合器４２、４３と、該各インピーダンス整合器４２、４３に夫々接続され、所定の周波数をブロックする複数のフィルター回路４７、４８と、フィルター回路４７、４８の出力が重畳されて基体１０に印加するように構成したものである。
【００６６】
図８は、高周波電圧印加手段として、異なる周波数の高周波電圧を発生する複数の高周波電源４０、４１と、該各高周波電源４０、４１の出力側に夫々接続された複数のインピーダンス整合器４２、４３と、該各インピーダンス整合器４２、４３の出力が重畳された電圧を昇圧して基体１０に印加する高周波用昇圧トランス４５とから構成したものである。
【００６７】
図９は、高周波電圧印加手段として、異なる周波数の高周波電圧を発生する複数の高周波電源４０、４１と、該各高周波電源４０、４１の出力側に夫々接続された複数のインピーダンス整合器４２、４３と、該各インピーダンス整合器４２、４３の出力側に接続され、該各インピーダンス整合器４２、４３の出力電圧を夫々昇圧する複数の高周波用昇圧トランス４５、４６と、高周波用昇圧トランス４５、４６の少なくとも一方（ここでは両方）の出力部に設けた所定の周波数をブロックするフィルター回路４７、４８とからなり、フィルター回路４７、４８の出力と高周波用昇圧トランス４５、４６の出力を重畳させるか、又はフィルター回路４７、４８の出力を重畳させて基体１０に２つ以上の周波数の高周波電圧を印加するように構成したものである。
【００６８】
この場合も真空容器１の構成は図４と同じであるが、図４の高周波コイル２４に接続されている高周波電源２５を設けず、これに基体１０に接続されている高周波電圧発生手段、すなわち図７〜図９に示す高周波電源４０、４１、インピーダンス整合器４２、４３、高周波用昇圧トランス４５、４６、フィルター回路４７、４８等を組合わせたものを共用させたものである。これ以外の点は、図１と同じであるので、その説明を省略する。
【００６９】
このような構成の実施形態によれば、基体１０に周波数の異なる複数の高周波電圧を夫々重畳して印加することにより、高周波側の高周波でプラズマを生成し、低周波側の高周波でバイアス電圧を発生させることができ、その結果、前述した高密度プラズマの生成と高電圧印加が同時に達成され、より高性能なイオン注入処理を行うことができる。
【００７０】
また、基体１０へ高周波電圧を印加するための高周波電圧発生手段により、プラズマ生成用の電源を共用しているため、装置構成が非常に簡単であって、第１の実施形態と同様な作用効果が得られる。
【００７１】
なお、図７及び図９のフィルター４７、４８はどちらか１つでもよい。さらに、第３の実施形態についても、高周波電圧発生手段は、基体１０の周囲に生成されるプラズマのイオンプラズマ周波数よりも高く、且つ、電子プラズマ周波数よりも低いことが望ましい。また、周波数が、例えば１３．５６ＭＨｚのような工業周波数帯に設定されていると、電磁シールド等の関係が楽になる
本発明は、以上に述べた実施形態に限定されず例えば以下のようにしてもよい。基体１０へ金属イオンを注入する場合には、各実施形態に、金属プラズマ（蒸気）を発生させる金属プラズマ（蒸気）源を付加すればよい。また、プラズマ生成法についても、第１の実施形態で示したように、フィラメントによるアーク放電、高周波のインダクティブカップリングによるプラズマ生成、ＥＣＲによるプラズマ生成、また、アーク方式による金属プラズマ（蒸気）発生法などを併用してもよい。それにより、さらに高密度のプラズマを生成することができる。
【００７２】
さらに、第１、第２、第３の実施形態のどれに対しても、図１０に示すように高周波電圧をパルス的（バースト的）に印加することにより、任意のパルス幅のバイアス電圧を基体に印加することもできる。こうすることにより、基体１０への注入パワーを制御することができ、基体１０の温度上昇を抑えることができる。
【００７３】
なお、本願発明は、上記各実施形態に限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で種々に変形することが可能である。更に、上記実施形態には種々の段階の発明が含まれており、開示される複数の構成要件における適宜な組み合わせにより種々の発明が抽出される。例えば、実施形態に示される全構成要件から幾つかの構成要件が削除されても、発明が解決しようとする課題の欄で述べた課題の少なくとも１つが解決でき、発明の効果の欄で述べられている効果の少なくとも１つが得られる場合には、この構成要件が削除された構成が発明として抽出され得る。
【００７４】
【発明の効果】
以上述べた本発明によれば、三次元形状の基体に対しても均一なイオン注入が可能であり、基体が絶縁物の場合や、イオン注入により作成する膜が絶縁物の場合にも、十分処理性能が得られ、且つアークの発生しにくい信頼性の高い安価なイオン注入装置、及び、イオン注入方法を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るイオン注入装置の第１の実施形態を説明するための概略構成図。
【図２】図１の実施形態における基体に印加した高周波電圧とバイアス電圧の関係を説明するための図。
【図３】図１の実施形態における変形例を説明するための概略構成図。
【図４】第１の実施形態における変形例であって図３とは異なる変形例を説明するための概略構成図。
【図５】本発明に係るイオン注入装置の第２の実施形態を説明するための概略構成図。
【図６】図５の実施形態における変形例を説明するための概略構成図。
【図７】本発明に係るイオン注入装置の第３の実施形態を説明するための概略構成図。
【図８】図７の実施形態における変形例を説明するための概略構成図。
【図９】図７の実施形態における変形例であって図８とは異なる変形例を説明するための概略構成図。
【図１０】図７の実施形態において高周波電圧をパルス的に印加した時のパルス波形を説明するための図。
【図１１】従来のイオン注入装置の一例を説明するための概略縦断面図。
【図１２】従来のイオン注入装置の一例を説明するための概略縦断面図。
【図１３】従来のイオン注入装置の一例を説明するための概略斜視図。
【図１４】図１１〜図１３におけるイオン注入装置の基体に印加する電圧波形を説明するための図。
【符号の説明】
１…真空容器、５ａ…ガス導入口、６…真空排気口、７ａ、７ｂ、８…永久磁石、９…フィラメント、１０…基体、１１…基体保持台、１２…ブッシング、１３…放電電源ユニット、１４…高圧ケーブル、１６…フィラメント、１７…アーク電源、２０ａ、２０ｂ、２０ｃ…磁力線、２４…高周波コイル、２５…高周波電源ユニット、４０、４１…高周波電源、４２、４３…インピーダンス整合器、４５、４６…高周波用昇圧トランス、４７、４８…フィルター。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ion implantation apparatus and an ion implantation method (surface modification method or film generation method) for implanting ions into a substrate such as a car component such as a piston or a bearing, or a cutting tool such as a drill.
[0002]
[Prior art]
At the time of manufacturing automobile parts, cutting tools, and the like, attempts have been made to improve wear resistance, heat resistance, hardness, and the like of the base by implanting ions into the base of the tool or the like. For example, it is known that when titanium or nitrogen is injected into a substrate made of stainless steel, the wear resistance and fatigue life of the substrate are greatly improved.
[0003]
As a method for injecting ions into a substrate, a method has been proposed in which a substrate is held in a discharge plasma containing positive ions of a substance to be implanted and a negative pulse voltage of several tens to several hundreds of kV is applied (references). : JR Conrad, et.al., "Plasma source ion-implantation technology for surface modification of materials", J. Appl. Phys 62 (11), 1987, pp. 45-91. This ion implantation method is abbreviated as PSII (Plasma Source Ion Implantation) or PIII (Plasma Immersion Ion Implantation).
[0004]
This method has the following characteristics in comparison with the conventional method in which implanted ions extracted from an ion source are passed through a deflection magnet for mass separation and then accelerated and implanted into a substrate.
[0005]
(A) Even when the substrate has a three-dimensional shape, the ion implantation can be performed almost perpendicularly to the surface of the substrate from the plasma surrounding the periphery of the substrate, and the ion implantation can be performed only in one direction. The required driving mechanism for the base is unnecessary, and the injection time can be shortened.
[0006]
(B) Since the beam transport over a long distance is unnecessary, the configuration of the apparatus can be simple and inexpensive.
[0007]
Hereinafter, a conventional PSII device will be described with reference to FIGS. This PSII apparatus is similar to that described in, for example, US Pat. No. 4,764,394.
[0008]
11 and 12 are views for explaining a conventional PSII apparatus, FIG. 11 is a view showing a vacuum vessel in a longitudinal section, and FIG. 12 is a view showing a vacuum vessel in a transverse section. FIG. 13 is a perspective view of the PSII device.
[0009]
11 to 13, the vacuum vessel 1 is provided with an upper plate 2 disposed on an upper end surface in the axial direction, a bottom plate 3 disposed on a lower end surface in the axial direction, and disposed between the upper plate 2 and the bottom plate 3. A cylindrical container with a bottom surrounded by a cylindrical side plate 4 formed as described above. The bottom plate 3 is provided with a gas inlet 5a for introducing a discharge gas from a gas source (not shown) into the vacuum vessel 1 and a vacuum exhaust port 6 for evacuating the vacuum vessel 1 to a vacuum by a vacuum exhaust pump (not shown). . On the outer walls of the upper plate 2 and the bottom plate 3, a plurality of square bar-shaped permanent magnets 7a and 7b are arranged in parallel with each other.
[0010]
The permanent magnets 7a and 7b are magnetized in a direction perpendicular to the outer walls of the upper plate 2 and the bottom plate 3, and adjacent magnets 7 are arranged with different polarities. Further, a plurality of permanent magnets 8 are arranged on the outer wall of the side plate 4 so that the plurality of permanent magnets 8 are parallel to each other in the vertical direction and the polarities of the adjacent magnets 8 are different from each other.
[0011]
By disposing the permanent magnets 7a, 7b, 8 in this manner, the lines of magnetic force 20a, 20b, 20c covering the entire inner wall of the vacuum vessel 1 are formed. The upper plate 2, the bottom plate 3 and the side plate 4 of the vacuum vessel 1 are provided with a filament 9 which serves as a cathode while the upper plate 2, the bottom plate 3 and the side plate 4 are used as an anode.
[0012]
Further, a metal substrate holder (target holder) 11 for holding a substrate (target) 10 into which ions are to be implanted is electrically insulated from the vacuum container 1 via a bushing 12. It has been arranged.
[0013]
The vacuum vessel 1 has a filament power supply (not shown) for supplying electricity to the filament 9 and an arc power supply (not shown) for generating an arc discharge using the upper plate 2, the bottom plate 3 and the side plate 4 as anodes and the filament 9 as cathodes. ) Is connected. A pulsed high voltage is applied to the base 10 from a pulsed high voltage power supply 15 via a high voltage cable 14 and a bushing 12.
[0014]
Next, the operation of the conventional PSII device having such a configuration will be described. That is, a gas (nitrogen, oxygen, or the like) of a substance to be injected into the base 10 is supplied from the gas inlet 5a, and the filament 9 is energized and heated by the filament power supply of the discharge power supply unit 13, thereby generating thermionic electrons in a vacuum. The inside of the vacuum vessel 1 that has been previously evacuated is filled with the exhaust port 6. Thereafter, a gas (nitrogen, oxygen, etc.) of a substance to be injected into the base 10 is supplied from the gas inlet 5a, and an arc discharge is generated between the filament 9 and the vacuum vessel 1 by the arc power supply of the discharge power supply unit 13 to discharge. A plasma 21 is generated.
[0015]
A pulse high-voltage power supply 15 is connected to the substrate holding table 11 on which the substrate 10 into which ions are to be implanted, and the pulse width is supplied to the vacuum vessel 1 independently of the plasma generation as shown in FIG. A negative pulse voltage having a time of about several microseconds (several μs) to several tens of microseconds (several tens of μs) and a magnitude of about tens to hundreds of kV is applied.
[0016]
As a result, a negative pulse voltage is applied to the substrate 10, whereby a sheath grows in the plasma surrounding the substrate 10, electrons are moved away from the substrate, and ions are accelerated in the direction of the substrate. Will be injected.
[0017]
[Problems to be solved by the invention]
However, in the above-described conventional techniques, when the base is an insulator or when the film formed by ion implantation is an insulator, the pulse width actually contributing to the implantation becomes extremely short. Even if a pulse of 10 microseconds is applied, the injection is performed for the first several tens to several hundreds of nanoseconds. As a result, the processing time becomes extremely long, and the productivity deteriorates.
[0018]
In addition, ions are accelerated at the rise of the pulse, so that sufficient energy cannot be obtained. As a result, the insulator is irradiated with a large amount of low-energy ions in particular, and there is a disadvantage that the effect of surface modification or the like cannot be sufficiently obtained.
[0019]
On the other hand, when the substrate and the film are conductors, a pulse that is sufficiently longer than the time during which the ions are accelerated can be applied. However, when the pulse width is long, an arc is likely to be generated near the substrate. Since the arc damages the substrate and the formed film, it is necessary to reduce the operation to a voltage at which the arc does not occur. As a result, a sufficient acceleration voltage cannot be obtained, and a sufficient effect such as surface modification cannot be obtained.
[0020]
According to the present invention, uniform ion implantation is possible even for a three-dimensional substrate, and sufficient processing performance can be obtained even when the substrate is an insulator or when a film formed by ion implantation is an insulator. It is an object of the present invention to provide a highly reliable and inexpensive ion implantation apparatus and an ion implantation method which are less likely to cause an arc.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a vacuum vessel in which a substrate into which ions are to be implanted is stored, and supply means for supplying a gas or vapor of a substance to be injected into the substrate into the vacuum vessel. Vacuum evacuation means for evacuating the inside of the vacuum vessel to a vacuum, substrate holding means housed in the vacuum vessel, electrically insulated from the vacuum vessel and holding the substrate, and supplied by the supply means A discharge plasma generating means for generating a discharge plasma around the substrate by arc discharge of the gas or vapor in the vacuum vessel which has been discharged, and a discharge generated by the discharge plasma generation means when a high frequency voltage is applied to the substrate. High frequency voltage generating means for injecting ions of a substance to be implanted into the substrate supplied from the supply means to the substrate by plasma. It is on the injection device.
[0022]
In order to achieve the above object, a second aspect of the present invention is an ion implantation apparatus in which a power source of the high-frequency voltage generating means and the power source of the discharge plasma generating means of the first aspect is shared by a common high-frequency power source.
[0023]
In order to achieve the above object, a third aspect of the present invention is an ion implantation apparatus in which the high frequency voltage generating means according to the first or second aspect is configured to superimpose a plurality of high frequency voltages having different frequencies.
[0024]
In order to achieve the above object, a fourth aspect of the present invention is an ion implantation apparatus, wherein the high frequency voltage generating means according to the first or second aspect is configured to apply a high frequency voltage to the base in a pulsed manner.
[0025]
In order to achieve the above object, according to a fifth aspect of the present invention, as the high frequency voltage generating means according to the third aspect, a high frequency of two or more frequencies for generating a plurality of high frequency voltages having different frequencies applied to the substrate is provided. The ion implantation apparatus is configured to apply at least one of the voltages or at least a high frequency voltage having a higher frequency in a pulsed manner.
[0026]
In order to achieve the above object, according to a sixth aspect of the present invention, as the high frequency voltage generating means according to the third or fifth aspect, a plurality of high frequency power supplies for generating high frequency voltages of different frequencies, A plurality of impedance matching units respectively connected to the output side of the power supply; and a filter circuit connected to at least one output side of the impedance matching unit and blocking a predetermined frequency. The output of the filter circuit and the impedance An ion implantation apparatus configured to multiply the output of the matching unit or to multiply the output of each of the filter circuits.
[0027]
In order to achieve the above object, according to a seventh aspect of the present invention, the frequency of the high-frequency power supply applied to the substrate according to any one of the first to fourth aspects is a discharge plasma generated around the substrate. The ion implantation apparatus is set to be higher than the ion plasma frequency and lower than the electron plasma frequency.
[0028]
In order to achieve the above object, an invention according to claim 8 provides a high-frequency power supply unit according to any one of claims 1, 2, 3, and 6, wherein the high-frequency power supply includes: An impedance matching device to be connected, and a high-frequency boosting transformer connected to the output side of the impedance matching device and boosting the output of the impedance matching device, comprising a high-frequency high-frequency voltage boosted by the high-frequency boosting transformer. , An ion implantation apparatus adapted to apply a voltage to the substrate.
[0029]
In order to achieve the above object, according to a ninth aspect of the present invention, as the high frequency voltage applying means according to the third or fifth aspect, a plurality of high frequency power supplies generating high frequency voltages of different frequencies, and each of the high frequency power supplies And a high-frequency step-up transformer for boosting a voltage on which the output of each impedance matching device is superimposed and applying the boosted voltage to the base.
[0030]
In order to achieve the above object, an invention according to claim 10 is characterized in that, as the high-frequency voltage generating means according to any one of claims 3, 6, and 7, a plurality of high-frequency power supplies that generate high-frequency voltages of different frequencies are provided. A plurality of impedance matching units respectively connected to the output side of each of the high-frequency power supplies; and a plurality of high-frequency step-up transformers connected to the output side of each of the impedance matching units and boosting the output voltage of each of the impedance matching units. And a filter circuit for blocking another frequency provided at at least one output portion of the high-frequency step-up transformer, wherein the output of the filter circuit and the output of the high-frequency step-up transformer are superimposed, or each of the filters An ion implantation apparatus configured to apply a high frequency voltage of two or more frequencies to the base by superimposing an output of a circuit.
[0031]
In order to achieve the above object, according to the present invention, a substrate to be implanted with ions is disposed in a vacuum vessel while being electrically insulated from the vacuum vessel, and the inside of the vacuum vessel is evacuated. At the same time, a gas or a vapor of a substance to be injected into the substrate is supplied into the vacuum container, and a plasma is generated around the substrate in the vacuum container, and a high-frequency voltage is applied to the substrate. Is applied to generate a negative voltage on the substrate, and perform ion implantation on the substrate.
[0032]
In order to achieve the above object, according to a twelfth aspect of the present invention, a substrate into which ions are to be implanted is placed in a vacuum vessel so as to be electrically insulated from the vacuum vessel, and the inside of the vacuum vessel is evacuated. At the same time, a gas or a vapor of a substance to be injected into the substrate is supplied into the vacuum container, and a plasma is generated around the substrate in the vacuum container, and the substrate is supplied with a high frequency of two or more frequencies. This is an ion implantation method in which a negative voltage is generated in the substrate by applying a voltage, and ions are implanted into the substrate.
[0033]
In order to achieve the above object, an invention according to claim 13 is characterized in that at least one of a high-frequency voltage applied to the substrate according to claim 11 or 12 or a high-frequency voltage of two or more frequencies is applied to the substrate in a pulsed manner. This is an ion implantation method that is applied to the substrate.
[0034]
To achieve the object, the invention according to claim 14 is configured such that the frequency of the high-frequency power supply applied to the substrate according to claim 11 or 12 is higher than the ion plasma frequency of the plasma generated around the substrate, In addition, this is an ion implantation method in which ions are implanted at a frequency lower than the electron plasma frequency.
[0035]
In the present invention, it is preferable that the frequency of the high-frequency power supply applied to the base is set in the industrial frequency band to perform the ion implantation.
[0036]
According to the invention corresponding to claim 1 or claim 11, by applying a high-frequency voltage to the base, even if the base or the formed film is an insulator, the electric charge on the base surface is changed every half cycle of the high frequency. Because of the neutralization, even if the substrate or the film to be formed is an insulator, a negative bias that can be regarded as a direct current can be applied to the implanted ions effectively. The magnitude of this negative bias is determined by the ratio of the surface area of the substrate to the surface area inside the vacuum vessel connected to the opposite pole of the high-frequency power supply. If the latter is several times larger than the former, the peak value of the high-frequency voltage (P− A voltage substantially equal to (half the P value) is applied to the substrate as a negative bias, and ions are accelerated and implanted into the substrate by the negative bias.
[0037]
Further, according to the invention corresponding to claim 1 or claim 11, since the high frequency voltage which is repeated at a high frequency is applied, the direction of the movement of the electrons changes at a high speed and the arc is generated even if the pulse width is long. Therefore, a high voltage can be applied, a sufficient injection effect can be obtained, and it is possible to obtain a surface modification method or a film formation method that is higher in performance and faster than conventional techniques.
[0038]
According to the invention corresponding to claim 2 or claim 13, by applying a high-frequency voltage in a pulse-like (burst-like) manner, a bias voltage having an arbitrary pulse width can be applied to the substrate.
[0039]
According to the third or twelfth aspect of the present invention, a plurality of high-frequency voltages having different frequencies are superimposed and applied to the substrate to generate plasma at a high frequency on the high frequency side and generate a plasma at a high frequency on the low frequency side. A bias voltage can be generated, and as a result, the above-described high-density plasma generation and high-voltage application are simultaneously achieved, and higher-performance, higher-speed ion implantation can be performed.
[0040]
Here, the reason for configuring as in claim 3 or claim 12 is because the following features are considered. That is, plasma can be generated by high-frequency discharge generated between the base and the vacuum vessel. In this case, only by applying a high-frequency voltage to the base, plasma can be generated and bias voltage can be simultaneously applied. And a highly reliable ion implantation technique can be obtained. In order to perform high-performance and high-speed ion implantation, it is desirable to generate high-density plasma and apply a high voltage. In this case, when the frequency of the high-frequency voltage is increased, the plasma density increases, but the applied bias voltage decreases. On the other hand, when the frequency of the high-frequency voltage is reduced, the applied bias voltage increases, but the plasma density decreases.
[0041]
According to the invention corresponding to claim 7 or claim 14, when applying a high-frequency voltage to the base, by selecting an oscillation frequency of the high-frequency voltage higher than an ion plasma frequency of plasma generated around the base, Since ions to be implanted into the substrate are accelerated at a substantially constant voltage, it is possible to apply a negative bias to the implanted ions, which can be regarded as DC effectively.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a view for explaining a first embodiment of an ion implantation apparatus according to the present invention, and is a schematic configuration diagram showing a vacuum vessel in a cross section in a lateral direction. As in FIGS. 11 to 13, the vacuum vessel 1 has an upper plate 2 disposed on the upper end surface in the axial direction, a bottom plate 3 disposed on the lower end surface in the axial direction, and a space between the upper plate 2 and the bottom plate 3. It is a bottomed cylindrical container surrounded by the disposed cylindrical side plate 4.
[0043]
The bottom plate 3 of the vacuum vessel 1 has a gas inlet 5a for introducing a discharge gas into the vacuum vessel 1 from a supply means (not shown) for supplying a gas or vapor of a substance to be injected into the substrate, as shown in FIG. A vacuum exhaust port 6 for evacuating the inside of the vacuum vessel 1 to vacuum by a vacuum exhaust means, for example, a vacuum exhaust pump (not shown) is provided.
[0044]
On the outer walls of the upper plate 2 and the bottom plate 3 of the vacuum vessel 1, a plurality of square rod-shaped permanent magnets 8 are arranged in parallel with each other as shown in FIG. In this case, the permanent magnets 8 are magnetized in a direction perpendicular to the outer walls of the upper plate 2 and the bottom plate 3, and the adjacent magnets 8 are arranged with different polarities. Further, a plurality of permanent magnets 8 are arranged on the outer wall of the side plate 4 so that the plurality of permanent magnets 8 are parallel to each other in the vertical direction and the polarities of the adjacent magnets 8 are different from each other.
[0045]
By arranging the permanent magnets 8 in this manner, magnetic lines of force 20c covering the entire inner wall of the vacuum vessel 1 are formed.
[0046]
The top plate 2, bottom plate 3, and side plate 4 of the vacuum vessel 1 are provided with a filament 9, which serves as a cathode, while the top plate 2, bottom plate 3, and side plate 4 serve as ground anodes.
[0047]
Further, a metal base support 11 for holding a base 10 into which ions are to be implanted is provided in the vacuum chamber 1 so as to be electrically (potentially) insulated from the vacuum chamber 1 via a bushing 12. ing.
[0048]
The vacuum vessel 1 has a filament power supply 16 for energizing the filament 9 and an arc power supply 17 for generating an arc discharge using the top plate 2, bottom plate 3 and side plate 4 of the vacuum vessel 1 as an anode and the filament 9 as a cathode. Discharge power supply unit 13 is connected.
[0049]
A high-frequency power supply 40 is connected to the base 10 via a cable 14 and an impedance matching device 42 to a bushing 12 fixed through the vacuum vessel 1. In this case, the high frequency power supply 40 generates a voltage of several hundred KHz to several hundred MHz. The impedance matching unit 42 is for matching the impedance between the high-frequency power supply 40 and the base 10.
[0050]
FIG. 2 simply shows the relationship between the voltage of the high frequency power supply 40 applied to the base 10 and the bias voltage. If the ratio of the surface area of the base body 10 to the surface area inside the vacuum vessel 1 connected to the opposite pole of the high-frequency power supply 40 is large (several times or more), the peak value of the high-frequency voltage (half of the P─P value) is almost reached. An equal voltage is applied to the substrate 10 as a negative bias. The ions are accelerated by this negative bias.
[0051]
According to the embodiment described above, by applying a high-frequency voltage to the base 10, even if the base 10 and the film to be formed are insulators, the electric charge on the base surface is neutralized every half period of the high frequency. Even if the substrate or the film to be formed is an insulator, it is possible to apply a negative bias that can be regarded as a direct current to the implanted ions.
[0052]
The magnitude of the negative bias is determined by the ratio of the surface area of the substrate to the surface area of the inside of the vacuum vessel 1 connected to the opposite pole of the high-frequency power supply. An equal voltage is applied to the substrate 10 as a negative bias, which accelerates ions into the substrate.
[0053]
Further, according to the present embodiment, since the high-frequency voltage that is repeated at a high frequency is applied, the direction of the movement of the electrons is changed at a high speed and the arc is hardly generated even if the pulse width is long. A sufficient implantation effect can be obtained, and not only the problems of the conventional technology described above can be solved, but also a surface modification method or a film generation method with higher performance and higher speed processing than the conventional technology can be obtained. It becomes possible. In the conventional technology, if the width of the pulse applied to the substrate is increased in order to increase the processing speed, an arc is likely to be generated near the substrate, and the arc damages the substrate and the formed film. It was necessary to lower the voltage to such a level that no arc was generated. As a result, it was not possible to apply a sufficient accelerating voltage, and a sufficient injection effect was not obtained.
[0054]
FIG. 3 shows a modification of FIG. 1 in which a high-frequency high-frequency voltage is applied between the impedance matching unit 42 and the cable 14 electrically connected to the bushing 12 in order to apply a high-frequency high frequency to the base 10. The configuration is such that a step-up transformer 45 is connected to apply a voltage to the base 10. The other points are the same as those in FIG. 1, and thus the same reference numerals are given here and the description thereof will be omitted.
[0055]
Further, the frequency of the high-frequency power supply 40 used here is desirably higher than the ion plasma frequency of the plasma generated around the base 10 and lower than the electron plasma frequency, as described above. By doing so, the ions implanted into the base 10 are accelerated at a substantially constant voltage, so that it is possible to apply a negative bias to the implanted ions, which can be regarded as DC effectively.
[0056]
Further, if this frequency is set in an industrial frequency band such as 13.56 MHz, the relationship between the electromagnetic shield and the like becomes easier.
[0057]
In the plasma generation method, arc discharge by the filament 9 was used in FIG. 1, but as shown in FIG. 4, plasma was generated by high-frequency inductive coupling, specifically at the axial end of the vacuum vessel 1. In this method, a high-frequency coil 24 is wound, a high-frequency power supply 25 is connected to the high-frequency coil 24, and a high-frequency electric field is generated by the high-frequency coil 24 to ionize neutral gas. In this case, an electrode (potential fixed electrode) (not shown) for applying a potential to the plasma is provided at one end of the vacuum vessel 1 and an electrode (ion extraction electrode) for extracting ions (not shown) is provided at the other end of the vacuum vessel 1. I have.
[0058]
Although not shown in FIG. 4, an impedance matching device may be provided at the connection between the high-frequency coil 24 and the high-frequency power supply 25 in some cases.
[0059]
In addition to the plasma generation method described above, many other methods such as plasma generation by ECR (Electron Cyclotron Resonance) and metal plasma (steam) generation by an arc method can be used.
[0060]
Next, an embodiment according to the second invention will be described with reference to the schematic configuration diagram of FIG. The configuration of the vacuum vessel 1 is the same as that of FIG. 4 except that the high-frequency power supply 25 connected to the high-frequency coil 24 in FIG. 4 is not provided, and the high-frequency power supply 40 to which the base 10 is connected is shared. is there. The other points are the same as those in FIG. 1, and the description thereof is omitted.
[0061]
As described above, since the high-frequency power supply 40 is shared by the high-frequency power supply 40 and the high-frequency power supply 25 for plasma generation, the apparatus configuration is very simple.
[0062]
Next, FIG. 6 which is a modification of FIG. 5 will be described with reference to FIG. A high-frequency step-up transformer 45 is connected to the connection between the impedance matching device 42 and the bushing 12 in FIG. The other configuration is the same as that of FIG.
[0063]
Also in the above-described second embodiment, it is desirable that the high frequency is higher than the ion plasma frequency of the plasma generated around the base 10 and lower than the electron plasma frequency. Further, if this frequency is set in an industrial frequency band such as 13.56 MHz, the relationship between the electromagnetic shield and the like becomes easier.
[0064]
When metal ions are implanted, a metal plasma (steam) source for generating metal plasma (steam) is further added thereto.
[0065]
Next, a third embodiment according to the present invention will be described with reference to FIGS. 7, 8, and 9. FIG. FIG. 7 shows a plurality of high-frequency power supplies 40 and 41 for generating high-frequency voltages of different frequencies as impedance-applying means, and impedance matching devices 42 and 43 connected to the output sides of the high-frequency power supplies 40 and 41, respectively. A plurality of filter circuits 47 and 48 respectively connected to the impedance matching devices 42 and 43 for blocking a predetermined frequency, and outputs of the filter circuits 47 and 48 are superimposed and applied to the base 10. is there.
[0066]
FIG. 8 shows a plurality of high-frequency power supplies 40 and 41 for generating high-frequency voltages of different frequencies as a high-frequency voltage applying means, and a plurality of impedance matching devices 42 and 43 connected to the output sides of the high-frequency power supplies 40 and 41, respectively. And a high-frequency step-up transformer 45 for stepping up a voltage on which the outputs of the impedance matching devices 42 and 43 are superimposed and applying the stepped-up voltage to the base 10.
[0067]
FIG. 9 shows a plurality of high-frequency power supplies 40 and 41 for generating high-frequency voltages of different frequencies as a high-frequency voltage applying means, and a plurality of impedance matching devices 42 and 43 connected to the output sides of the high-frequency power supplies 40 and 41, respectively. And a plurality of high-frequency step-up transformers 45 and 46 connected to the output sides of the impedance matching units 42 and 43 to respectively boost the output voltages of the impedance matching units 42 and 43. And filter circuits 47 and 48 provided at at least one (in this case, both) output sections for blocking a predetermined frequency. The outputs of the filter circuits 47 and 48 and the outputs of the high-frequency step-up transformers 45 and 46 are superimposed. Or a configuration in which the outputs of the filter circuits 47 and 48 are superimposed and high-frequency voltages of two or more frequencies are applied to the base 10. Those were.
[0068]
In this case as well, the configuration of the vacuum vessel 1 is the same as that of FIG. 4 except that the high-frequency power supply 25 connected to the high-frequency coil 24 of FIG. A combination of the high-frequency power supplies 40 and 41, the impedance matching devices 42 and 43, the high-frequency step-up transformers 45 and 46, and the filter circuits 47 and 48 shown in FIGS. The other points are the same as those in FIG. 1, and the description thereof will be omitted.
[0069]
According to the embodiment having such a configuration, by superposing and applying a plurality of high-frequency voltages having different frequencies to the base 10, plasma is generated at a high frequency on the high frequency side, and a bias voltage is generated at the high frequency on the low frequency side. As a result, the above-described high-density plasma generation and high-voltage application are simultaneously achieved, and a higher-performance ion implantation process can be performed.
[0070]
Further, since the power supply for plasma generation is shared by the high-frequency voltage generating means for applying the high-frequency voltage to the base body 10, the apparatus configuration is very simple, and the same operation and effect as in the first embodiment are obtained. Is obtained.
[0071]
Note that either one of the filters 47 and 48 in FIGS. 7 and 9 may be used. Further, also in the third embodiment, it is desirable that the high-frequency voltage generating means is higher than the ion plasma frequency of the plasma generated around the base 10 and lower than the electron plasma frequency. Further, when the frequency is set to an industrial frequency band such as 13.56 MHz, the relationship between the electromagnetic shield and the like becomes easy.
The present invention is not limited to the embodiment described above, and may be, for example, as follows. When metal ions are implanted into the base 10, a metal plasma (vapor) source for generating metal plasma (vapor) may be added to each embodiment. As for the plasma generation method, as described in the first embodiment, arc discharge by filament, plasma generation by high-frequency inductive coupling, plasma generation by ECR, and metal plasma (steam) generation method by arc method You may use together. As a result, higher-density plasma can be generated.
[0072]
Further, in any of the first, second and third embodiments, a bias voltage having an arbitrary pulse width is applied to the substrate by applying a high-frequency voltage in a pulsed (burst-like) manner as shown in FIG. Can also be applied. By doing so, the power injected into the base 10 can be controlled, and a rise in the temperature of the base 10 can be suppressed.
[0073]
It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified in an implementation stage without departing from the scope of the invention. Furthermore, the above embodiments include inventions at various stages, and various inventions are extracted by appropriate combinations of a plurality of disclosed constituent features. For example, even if some components are deleted from all the components shown in the embodiment, at least one of the problems described in the column of the problem to be solved by the invention can be solved, and the problem described in the column of the effect of the invention can be solved. If at least one of the effects described above can be obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.
[0074]
【The invention's effect】
According to the present invention described above, it is possible to perform uniform ion implantation even on a three-dimensionally shaped base, and it is sufficient even when the base is an insulator or a film formed by ion implantation is an insulator. It is possible to provide a highly reliable and inexpensive ion implantation apparatus and an ion implantation method that can achieve processing performance and are less likely to generate an arc.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram for explaining a first embodiment of an ion implantation apparatus according to the present invention.
FIG. 2 is a diagram for explaining a relationship between a high-frequency voltage applied to a base and a bias voltage in the embodiment of FIG. 1;
FIG. 3 is a schematic configuration diagram for explaining a modification of the embodiment of FIG. 1;
FIG. 4 is a schematic configuration diagram for describing a modification example of the first embodiment that is different from FIG. 3;
FIG. 5 is a schematic configuration diagram illustrating a second embodiment of the ion implantation apparatus according to the present invention.
FIG. 6 is a schematic configuration diagram for explaining a modification of the embodiment in FIG. 5;
FIG. 7 is a schematic configuration diagram for explaining a third embodiment of the ion implantation apparatus according to the present invention.
FIG. 8 is a schematic configuration diagram for explaining a modification of the embodiment in FIG. 7;
FIG. 9 is a schematic configuration diagram for explaining a modification example of the embodiment of FIG. 7 which is different from that of FIG. 8;
FIG. 10 is a view for explaining a pulse waveform when a high-frequency voltage is applied in a pulsed manner in the embodiment of FIG. 7;
FIG. 11 is a schematic longitudinal sectional view for explaining an example of a conventional ion implantation apparatus.
FIG. 12 is a schematic longitudinal sectional view for explaining an example of a conventional ion implantation apparatus.
FIG. 13 is a schematic perspective view for explaining an example of a conventional ion implantation apparatus.
FIG. 14 is a view for explaining voltage waveforms applied to the base of the ion implantation apparatus in FIGS. 11 to 13;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 5a ... Gas introduction port, 6 ... Vacuum exhaust port, 7a, 7b, 8 ... Permanent magnet, 9 ... Filament, 10 ... Substrate, 11 ... Substrate holding stand, 12 ... Bushing, 13 ... Discharge power supply unit, 14 high-voltage cable, 16 filament, 17 arc power supply, 20a, 20b, 20c magnetic field lines, 24 high-frequency coil, 25 high-frequency power supply unit, 40, 41 high-frequency power supply, 42, 43 impedance matching unit, 45 46 ... High frequency step-up transformer, 47, 48 ... Filter.

Claims

A vacuum container in which a substrate to be implanted with ions is stored;
Supply means for supplying a gas or vapor of a substance to be injected into the substrate into the vacuum vessel,
Vacuum evacuation means for evacuating the inside of the vacuum vessel to a vacuum,
A substrate holding unit that is housed in the vacuum container and is electrically insulated from the vacuum container and holds the substrate.
Discharge plasma generation means for generating discharge plasma around the base by arc discharge of gas or vapor in the vacuum vessel supplied by the supply means,
A high-frequency voltage is applied to the base, a high-frequency voltage generator for injecting ions of a substance to be injected into the base supplied from the supply unit to the base by the discharge plasma generated by the discharge plasma generator,
An ion implantation apparatus comprising:

2. The ion implantation apparatus according to claim 1, wherein a power supply for said high-frequency voltage generation means and a power supply for said discharge plasma generation means are shared by a common high-frequency power supply.

The ion implantation apparatus according to claim 1, wherein the high-frequency voltage generator superimposes a plurality of high-frequency voltages having different frequencies.

The ion implantation apparatus according to claim 1, wherein the high-frequency voltage generating unit applies a high-frequency voltage to the base in a pulsed manner.

The high-frequency voltage generating means applies at least one or at least the higher frequency of the high-frequency voltages of two or more frequencies for generating a plurality of high-frequency voltages having different frequencies to be applied to the base in a pulsed manner. The ion implantation apparatus according to claim 3, wherein the ion implantation is performed.

The high-frequency voltage generating means includes a plurality of high-frequency power supplies that generate high-frequency voltages of different frequencies, a plurality of impedance matching devices respectively connected to the output side of each of the high-frequency power sources, and at least one output side of the impedance matching device. And a filter circuit for blocking a predetermined frequency, wherein the output of the filter circuit and the output of the impedance matching device are superposed, or the output of each of the filter circuits is superposed. The ion implanter according to claim 3 or claim 5, wherein

The frequency of a high frequency power supply applied to the base is set higher than an ion plasma frequency of a discharge plasma generated around the base and lower than an electron plasma frequency. The ion implantation apparatus according to any one of the above.

The high-frequency voltage applying means includes a high-frequency power supply, an impedance matching device connected to an output side of the high-frequency power source, and a high-frequency step-up transformer connected to the output side of the impedance matching device and boosting an output of the impedance matching device. 7. The ion according to claim 1, wherein a high-frequency voltage of a high voltage boosted by said high-frequency step-up transformer is applied to said base. Infusion device.

The high-frequency voltage applying means includes a plurality of high-frequency power supplies that generate high-frequency voltages of different frequencies, a plurality of impedance matching devices respectively connected to the output side of each of the high-frequency power supplies, and an output of each of the impedance matching devices. 6. The ion implantation apparatus according to claim 3, further comprising: a high-frequency step-up transformer for stepping up the applied voltage and applying the stepped-up voltage to the base.

The high-frequency voltage generating means includes a plurality of high-frequency power supplies for generating high-frequency voltages of different frequencies, a plurality of impedance matching devices respectively connected to the output sides of the respective high-frequency power supplies, and a plurality of impedance matching devices connected to the output sides of the respective impedance matching devices. A plurality of high-frequency step-up transformers each of which boosts an output voltage of each of the impedance matching devices; and a filter circuit provided at at least one output section of the high-frequency step-up transformer for blocking other frequencies, The output of a circuit and the output of the high-frequency step-up transformer are superimposed, or the output of each of the filter circuits is superimposed to apply a high-frequency voltage of two or more frequencies to the base. Item 10. The ion implantation apparatus according to any one of Items 3, 6, and 7.

A substrate into which ions are to be implanted is placed in a vacuum vessel while being electrically insulated from the vacuum vessel. The inside of the vacuum vessel is evacuated, and a gas or substance of a substance to be injected into the vacuum vessel is introduced into the vacuum vessel. The steam is supplied with gas or steam, and in a state where plasma is generated in the vacuum vessel and around the substrate,
An ion implantation method in which a negative voltage is generated in the substrate by applying a high-frequency voltage to the substrate to perform ion implantation into the substrate.

A substrate into which ions are to be implanted is placed in a vacuum container so as to be electrically insulated from the vacuum container. The inside of the vacuum container is evacuated, and a gas or vapor of a substance to be injected into the substrate is introduced into the vacuum container. Is supplied, and a plasma is generated around the substrate in the vacuum vessel,
An ion implantation method, wherein a high voltage of two or more frequencies is applied to the substrate to generate a negative voltage on the substrate and perform ion implantation on the substrate.

The ion implantation method according to claim 11, wherein at least one of a high-frequency voltage applied to the base and a high-frequency voltage having two or more frequencies is applied to the base in a pulsed manner.

The frequency of the high-frequency power source applied to the base is higher than the ion plasma frequency of the plasma generated around the base and the ion implantation is performed at a frequency lower than the electron plasma frequency. Item 13. The ion implantation method according to Item 11 or 12.