JP2013008471A - Gas ion source - Google Patents

Gas ion source Download PDF

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JP2013008471A
JP2013008471A JP2011138730A JP2011138730A JP2013008471A JP 2013008471 A JP2013008471 A JP 2013008471A JP 2011138730 A JP2011138730 A JP 2011138730A JP 2011138730 A JP2011138730 A JP 2011138730A JP 2013008471 A JP2013008471 A JP 2013008471A
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ion source
tip
container
gas
electrode
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Toshiyuki Tsuji
敏之 辻
Chikara Ichihara
主税 一原
Akira Kobayashi
明 小林
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Kobe Steel Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide an ion source which can generate a stable high brightness ion beam continuously over a long term without bringing about decrease or destabilization of the electric field strength near the needle end of a field ionization electrode, by suppressing or preventing secondary electron emission from the surface of an ion source container incident to charge-up.SOLUTION: In the gas ion source generating an ion beam 8 by applying a voltage between a field ionization electrode 2 and an external electrode 3 so as to form an electric field near the tip of the field ionization electrode 2, and then field-ionizing a material gas jetted from a micro-opening O of an ion source container 1, partial surface of the ion source container 1, partial or entire surface of the external electrode 3, or the whole external electrode 3 located in a region near the tip of the field ionization electrode 2 are composed of the thin films Ta-Te of a secondary electron emission suppression material.

Description

本発明は例えば集束イオンビーム(FIB)装置などのイオンビームを用いた加工用装置や、走査イオン顕微鏡などの分析装置などに用いられる微小径イオンビーム発生用のイオン源に関するものであり、その中でもイオンの生成手段として電界電離を用いるイオン源に関する。   The present invention relates to an ion source for generating a small-diameter ion beam used in, for example, a processing apparatus using an ion beam such as a focused ion beam (FIB) apparatus or an analysis apparatus such as a scanning ion microscope. The present invention relates to an ion source using field ionization as a means for generating ions.

液体金属イオン源が開発されて以来、半導体工業等の分野では、近年、サブミクロン以下に細く集束したイオンビームの応用が急速に広まっている。また、液体金属イオン源では得られるイオン種に制限があり、特にアルゴンなどの不活性ガスや酸素などの集束イオンビームを得る場合には、液体金属イオン源よりガス相の電界電離型イオン源が適している。このガス相の電界電離型イオン源は、圧力が１０-１ Pa程度のガス中で、その先端部半径が５ｎｍ 〜１００ｎｍ程度に尖らされた金属の針状電極に５０ 〜 ６０Ｖ/ｎｍ程度の強電界を加えることで、針状電極の先端部近傍のガス分子を電界電離現象によりイオンと電子に分離し、イオンビームを得ることができる。このようなイオン源において発生するイオンビーム電流Ｉは、(１)式に示すようにガスの圧力Ｐに比例し、温度Ｔの２分の３乗に反比例する。
Ｉ ∝ Ｐ /Ｔ3/2 - - - - - - - - - - - - - - - (１) Since the development of the liquid metal ion source, in the fields of the semiconductor industry and the like, in recent years, the application of the ion beam finely focused to submicron or less has been rapidly spreading. In addition, there are limitations on the ion species that can be obtained with a liquid metal ion source. In particular, when obtaining a focused ion beam such as an inert gas such as argon or oxygen, a gas phase field ionization ion source is more suitable than a liquid metal ion source. Is suitable. This gas-phase field ion source is a metal needle-like electrode whose tip radius is pointed to about 5 to 100 nm in a gas having a pressure of about 10 −1 Pa, and a strong force of about 50 to 60 V / nm. By applying an electric field, gas molecules near the tip of the needle electrode can be separated into ions and electrons by the field ionization phenomenon, and an ion beam can be obtained. The ion beam current I generated in such an ion source is proportional to the gas pressure P as shown in the equation (1) and inversely proportional to the third power of the temperature T.
I ∝ P / T 3/2--------------- (1)

通常、イオン源ではイオン化後のイオンの消滅を最小限に抑えるため、このイオンを、１０−３〜 １０−６ Ｐａ程度の高真空容器内を飛行させる。したがって、容器内のガス圧力Ｐを大きくすることは不可能である。このため、従来技術では、ガス温度Ｔを数十Ｋ程度まで低くしてイオンビーム電流Ｉを大きくして、放出イオンの輝度を高めるような装置構成となっていた。 Usually, in an ion source, in order to minimize the disappearance of ions after ionization, the ions are caused to fly in a high vacuum chamber of about 10 −3 to 10 −6 Pa. Therefore, it is impossible to increase the gas pressure P in the container. For this reason, in the prior art, the device configuration is such that the gas temperature T is lowered to about several tens of K and the ion beam current I is increased to increase the brightness of emitted ions.

この放出イオン、すなわちイオンビームの輝度を高める従来のイオン源として、例えば、特許文献1（図２参照）に示されたように、針状のエミッタ（電界電離電極）１の軸線上に位置させた開口３を有する対向電極２とを具えて、イオン化室５に原料ガス４を導入することにより、エミッタ１の先端からイオン６を放出するようにし、エミッタ１の先端が対向電極２の内側面から外側に２ｍｍ程度(図示の寸法ｂ)突出するように配置した、イオンビーム露光装置の電界電離型イオン源が開示されている。このイオン源では、エミッタ１の先端が、前記のように突出しているため、エミッタ１周辺のガス圧力は、エミッタ１の先端部の基部で高くても先端部で低くなっており、イオン化室５内のガス圧力を高めても、高電界中で分極したガス分子の衝撃によるエミッタ１先端部の温度上昇が小さくなり、イオン化するガス分子の供給が阻害されず、放出イオンの輝度を高めることが可能であると述べられている。   As a conventional ion source for increasing the brightness of the emitted ions, that is, the ion beam, for example, as shown in Patent Document 1 (see FIG. 2), it is positioned on the axis of a needle-like emitter (field ionization electrode) 1. In addition, the source gas 4 is introduced into the ionization chamber 5 so that the ions 6 are emitted from the tip of the emitter 1, and the tip of the emitter 1 is the inner surface of the counter electrode 2. Discloses a field ionization ion source of an ion beam exposure apparatus arranged so as to protrude about 2 mm (dimension b in the drawing) from the outside. In this ion source, since the tip of the emitter 1 protrudes as described above, the gas pressure around the emitter 1 is high at the base of the tip of the emitter 1 but low at the tip, and the ionization chamber 5 Even if the gas pressure inside is increased, the temperature rise at the tip of the emitter 1 due to the impact of gas molecules polarized in a high electric field is reduced, the supply of ionized gas molecules is not hindered, and the brightness of emitted ions can be increased. It is stated that it is possible.

また特許文献２に示すように電界電離電極とイオン源容器に設けた微小開口の周りの開孔部電極とを同電位とし、外部電極を容器外に置き、電界電離電極を容器外に出すことで極低温の冷却が不要であり、簡易な装置構造で、高輝度かつビーム集束の効率がよいイオンビームが得られるイオン源を提供することが可能であることを示すものもある。   In addition, as shown in Patent Document 2, the field ionization electrode and the opening portion electrode around the minute opening provided in the ion source container are set to the same potential, the external electrode is placed outside the container, and the field ionization electrode is taken out of the container. In some cases, it is possible to provide an ion source that can obtain an ion beam with high brightness and high beam focusing efficiency with a simple apparatus structure that does not require cryogenic cooling.

また特許文献３においては、イオン源容器の電界電離電極先端付近の形状を工夫し、またその材料として、比誘電率(以降ε)が５以上、特に９以上の高誘電体材料、具体的にはアルミナ系セラミックスを用いることで、針状電極先端部の電界強度が向上し、針先に与える電圧に対して高効率に電解強度が得られることを示している。   In Patent Document 3, the shape of the ion source container near the tip of the field ionization electrode is devised, and the material is a high dielectric material having a relative dielectric constant (hereinafter ε) of 5 or more, particularly 9 or more. Shows that the use of alumina-based ceramics improves the electric field strength at the tip of the needle-like electrode, and the electrolytic strength can be obtained with high efficiency against the voltage applied to the needle tip.

また特許文献４においては、外部電極の位置をイオン源容器に接触させ、電界電離電極の先端部付近に近づけることで、針先付近の電界強度を上げることが可能であることを示している。   Patent Document 4 shows that the electric field strength in the vicinity of the needle tip can be increased by bringing the position of the external electrode into contact with the ion source container and approaching the vicinity of the tip of the field ionization electrode.

しかしながら、従来技術による改善、改良においてもなお未解決の課題が残されている。すなわち、これらの従来技術においても、イオンビームの高輝度化に焦点を当てて電界電離電極の針先付近の電界強度を確保するため、イオン源容器としてアルミナなどの高誘電体材料の使用を推奨しているが、このεが大きい高誘電体材料でイオン源容器を構成した場合、高速で噴射される原料ガスのイオン化によるイオンビームの生成に伴ってイオン源容器自体が正に帯電する（チャージアップ）問題がある。   However, there are still unsolved problems in the improvements and improvements of the prior art. That is, in these conventional technologies, it is recommended to use a high dielectric material such as alumina as the ion source container in order to secure the electric field strength in the vicinity of the needle tip of the field ionization electrode by focusing on increasing the brightness of the ion beam. However, when the ion source container is made of a high dielectric material having a large ε, the ion source container itself is positively charged as the ion beam is generated by ionization of the source gas injected at high speed (charge). Up) There is a problem.

これは、針状の電界電離電極の先端部にてイオン発生後、下流にむかってイオンが加速されたイオンがアパーチャ等の対象物に衝突し、対象物から２次電子が放出され、この２次電子は、正電圧を印加している針状の電極に向かって逆流する現象が起き、この逆流してきた電子の一部がイオン源容器に当たり、この衝撃によってイオン源容器の表面からさらに２次電子が放出するといった現象が繰り返されることになるからである。そして、アルミナなどの高誘電体材料は２次電子放出係数(以降γとする)が高いため、イオン源容器から放出される２次電子が、逆流して衝突した電子の何倍もの量に達する。
このようにして、イオン源容器は徐々に正に帯電して行き、この結果、電界電離電極の針先付近の電界強度が低下したり、不安定となり、また電極の針先の形状変化を引き起こすなど、高輝度の安定したイオンビームの生成に支障を来たすことになる。 This is because after ions are generated at the tip of the needle-shaped field ionization electrode, ions whose ions are accelerated toward the downstream collide with a target such as an aperture, and secondary electrons are emitted from the target. The secondary electrons reversely flow toward the needle-like electrode to which a positive voltage is applied, and a part of the backflowed electrons hits the ion source container. Due to this impact, secondary electrons are further secondary from the surface of the ion source container. This is because the phenomenon of electron emission is repeated. In addition, since a high dielectric material such as alumina has a high secondary electron emission coefficient (hereinafter referred to as γ), the secondary electrons emitted from the ion source container reach many times the number of electrons colliding in reverse flow. .
In this way, the ion source container gradually becomes positively charged, and as a result, the electric field strength near the needle tip of the field ionization electrode decreases or becomes unstable, and causes a change in the shape of the needle tip of the electrode. For example, this may hinder the generation of a stable and high-brightness ion beam.

特開昭６４−６３２４７号公報JP-A-64-63247 特開２００７−２２７１０２号公報JP 2007-227102 A 特開２００９−２７７４３４号公報JP 2009-277434 A 特開２００９−２７７４１６号公報JP 2009-277416 A

そこで、本発明ではこうした事情に鑑み、イオン源容器のチャージアップに伴う同容器表面からの２次電子の放出を抑制、防止し、電界電離電極の先端近傍の電界強度の低下や不安定化もたらすことなく長期に亘って継続して高輝度の安定したイオンビームを生成することが可能なガスイオン源を提供することをその課題としたものである。   Therefore, in view of such circumstances, the present invention suppresses and prevents the emission of secondary electrons from the surface of the ion source container due to charge-up, resulting in a decrease or instability of the electric field strength near the tip of the field ionization electrode. An object of the present invention is to provide a gas ion source that can continuously generate a high-brightness stable ion beam without a long period of time.

本発明は、上記課題を解決するための具体的手段として、以下のガスイオン源を提案する。
（１）高誘電体材料で構成され、供給された原料ガスをその微小開口を通じて外部に噴射するイオン源容器と、前記イオン源容器の内部にあってその先端が同容器の前記微小開口に配置された電界電離電極と、前記イオン源容器の外部に配設された外部電極とからなり、前記電界電離電極と前記外部電極との間に電圧を印加して電界電離電極の先端近傍に電界を形成し、前記イオン源容器の微小開口より噴射される原料ガスを電界電離することによりイオンビームを生成するガスイオン源において、前記電界電離電極の先端に近い領域に位置する、イオン源容器の一部の表面、前記外部電極の一部若しくは全部の表面、または同外部電極の全部を二次電子放出抑制材で構成したことを特徴とするガスイオン源（請求項１）。
（２）前記二次電子放出抑制材の二次電子放出係数が２以下である請求項１に記載のガスイオン源（請求項２）。
（３）前記二次電子放出抑制材の二次電子放出係数が０.５〜１.５である請求項２に記載のガスイオン源（請求項３）
（４）前記二次電子放出抑制材が薄膜である請求項１〜３のいずれかに記載のガスイオン源（請求項４）。
（５）前記イオン源容器がその微小開口を形成する内周側先端部を有するとともに、前記外部電極が、同容器の前記内周側先端部の外周部に一体的に配設されたものにおいて、前記二次電子放出抑制材の薄膜が、前記イオン源容器の内周側先端部の前面及び／または内周面及び／または前記外部電極の前面に被覆されてなる請求項４に記載のガスイオン源（請求項５）。 The present invention proposes the following gas ion source as a specific means for solving the above problems.
(1) An ion source container that is made of a high dielectric material and injects the supplied source gas to the outside through the minute opening, and the tip of the ion source container is disposed in the minute opening of the container. A field ionization electrode and an external electrode disposed outside the ion source container. A voltage is applied between the field ionization electrode and the external electrode to cause an electric field near the tip of the field ionization electrode. In a gas ion source that is formed and generates an ion beam by field ionizing a source gas injected from a minute opening of the ion source container, the ion source container is located in a region near the tip of the field ionization electrode. A gas ion source characterized in that the surface of a portion, the surface of a part or all of the external electrode, or the entire external electrode is made of a secondary electron emission suppressing material (Claim 1).
(2) The gas ion source according to claim 1, wherein the secondary electron emission suppressing material has a secondary electron emission coefficient of 2 or less.
(3) The gas ion source according to claim 2, wherein the secondary electron emission suppressing material has a secondary electron emission coefficient of 0.5 to 1.5.
(4) The gas ion source according to any one of claims 1 to 3, wherein the secondary electron emission suppressing material is a thin film.
(5) The ion source container has an inner peripheral tip that forms the minute opening, and the external electrode is integrally disposed on the outer peripheral part of the inner peripheral tip of the container. 5. The gas according to claim 4, wherein the thin film of the secondary electron emission suppressing material is coated on a front surface and / or an inner peripheral surface of the ion source container and / or a front surface of the external electrode. An ion source (Claim 5).

本発明のガスイオン源によれば、上記解決手段によりイオン源容器のチャージアップ及びこれに伴って発生する同容器表面からの２次電子の放出を有効に抑制、防止することができるから、アルミナなどの高誘電体材料をイオン源容器として用いた場合においても、電界電離電極の先端近傍の電界強度の低下や不安定化もたらすことなく長期に亘って継続して高輝度の安定したイオンビームを生成することが可能であるという優れた効果を奏する。   According to the gas ion source of the present invention, the above solution can effectively suppress and prevent the charge-up of the ion source container and the emission of secondary electrons generated from the surface of the ion source container. Even when a high-dielectric material such as is used as an ion source container, a stable, high-brightness ion beam can be produced over a long period of time without lowering or destabilizing the electric field strength near the tip of the field ionization electrode There is an excellent effect that it can be generated.

本発明イオン源の実施形態１における全体構成を示したもので左図はその縦断面、右図はその要部底面図である。The whole structure in Embodiment 1 of this invention ion source is shown, the left figure is the longitudinal cross-section, and the right figure is the principal part bottom view. 本発明ガスイオン源の実施形態２における同様な図である。It is the same figure in Embodiment 2 of this invention gas ion source. 本発明ガスイオン源の実施形態３における同様な図である。It is the same figure in Embodiment 3 of this invention gas ion source. 本発明ガスイオン源の実施形態４における同様な図である。It is the same figure in Embodiment 4 of this invention gas ion source. 本発明ガスイオン源の実施形態５における同様な図である。It is the same figure in Embodiment 5 of this invention gas ion source. 本発明ガスイオン源の実施形態６における同様な図である。It is the same figure in Embodiment 6 of the gas ion source of this invention.

本発明について、その実施形態を中心に図面を参照しながら以下に説明して行くことにする。   The present invention will be described below with reference to the drawings focusing on the embodiments.

図１は本発明ガスイオン源の典型的な実施形態１に関する構成を示したもので、本実施形態を参照して本発明の概要並びに特徴を含めてその構成を全体的に詳述する。   FIG. 1 shows a configuration relating to a typical embodiment 1 of the gas ion source of the present invention. The configuration including the outline and features of the present invention will be described in detail with reference to this embodiment.

本発明のガスイオン源の前提となる基本構成は、同図１のように、ベース７に固設され、その内部先端に５〜１００μｍの微小開口Ｏを有するノズル状のイオン源容器（本体）１と、原料ガス制御手段５を備えてこのイオン源容器１に接続された原料ガス供給管２と、同容器１の内部中心の軸線方向に沿って設けられ、その先端が前記微小開口Ｏに挿通して配置された針状の電界電離電極２と、外部電極である対向電極３と、これら電界電離電極２と対向電極３の間に電圧を印加する強電界印加用電源６とから成っている。また、これらは図示しないが真空槽に設置され、１×１０-６Ｐａ前後の高真空状態に保たれる。 As shown in FIG. 1, the basic configuration of the gas ion source of the present invention is a nozzle-like ion source container (main body) fixed to the base 7 and having a minute opening O of 5 to 100 μm at the inner tip. 1 and a source gas supply pipe 2 provided with a source gas control means 5 and connected to the ion source vessel 1, and provided along the axial direction of the inner center of the vessel 1. It consists of a needle-like field ionization electrode 2 that is inserted and disposed, a counter electrode 3 that is an external electrode, and a strong electric field application power source 6 that applies a voltage between the field ionization electrode 2 and the counter electrode 3. Yes. Although not shown, these are installed in a vacuum chamber and kept in a high vacuum state of around 1 × 10 −6 Pa.

こうした基本構成を有する電界電離型のガスイオン源により、ヘリウムやアルゴンなどの不活性ガスを原料ガスとして原料ガス供給管４からイオン源容器１に供給し、上記両電極２、３間に電圧を印加すると、電界電離電極２の先端近傍に数１０Ｖ/ｎｍの強電界が形成され、原料ガスは高真空中で電離して微小開口Ｏを起点とする高速のイオンビーム８が連続的に前方（図では下方）に引き出されて得られる。   With an ionization gas ion source having such a basic configuration, an inert gas such as helium or argon is supplied as a source gas from the source gas supply pipe 4 to the ion source container 1, and a voltage is applied between the electrodes 2 and 3. When applied, a strong electric field of several tens of V / nm is formed near the tip of the field ionization electrode 2, and the source gas is ionized in a high vacuum, and a high-speed ion beam 8 starting from the minute opening O is continuously forward ( It is obtained by pulling downward in the figure.

イオン源容器１はアルミナ、ジルコニア、高純度シリコン、ガラスなどの好ましくはεが５以上の高誘電体材料を使用する。ところで、前述したようにイオン源容器１として高誘電体材料を用いた場合、容器１がチャージアップして、同容器１の表面より、二次電子が電界電離電極２の先端に大量に放出、逆流する問題が生じる。   The ion source container 1 is made of a high dielectric material such as alumina, zirconia, high-purity silicon, or glass, preferably having an ε of 5 or more. By the way, when a high dielectric material is used as the ion source container 1 as described above, the container 1 is charged up, and a large amount of secondary electrons are emitted from the surface of the container 1 to the tip of the field ionization electrode 2. The problem of backflow occurs.

本発明は、この問題を解決するため、電界電離電極２の先端に近い領域に位置する、イオン源容器１や外部電極２の表面などを、二次電子放出抑制材で構成し、容器１の二次電子によるチャージアップ並びに容器１からの二次電子の放出を阻止することをその重要な特徴とするものである。   In order to solve this problem, the present invention is configured such that the surface of the ion source container 1 or the external electrode 2 located in the region near the tip of the field ionization electrode 2 is made of a secondary electron emission suppressing material. The important feature is to prevent charge-up by secondary electrons and emission of secondary electrons from the container 1.

この二次電子放出抑制材は文字通り、二次電子放出を抑制できるものであれば如何なる材料を選択しても良いが、その二次電子放出係数（γ）が２以下、特に０.５〜１.５の値を有する材料が好ましい。これに該当する具体的材料としては、ＴｉＮ、Ｃｒ２Ｏ３、Ｔｉ、Ａｌ、Ｓｉ、Ｎｉ、Ｃｕ、Ｂａ、ＤＬＣ（ダイヤモンドライクカーボン）などを挙げることができる。 Any material can be selected as the secondary electron emission suppressing material as long as it can suppress the secondary electron emission, but the secondary electron emission coefficient (γ) is 2 or less, particularly 0.5 to 1. A material having a value of .5 is preferred. Specific materials corresponding to this include TiN, Cr 2 O 3 , Ti, Al, Si, Ni, Cu, Ba, DLC (diamond-like carbon), and the like.

また、これら材料は薄膜の形態は、容器及びまたは外部電極の必要箇所、部分の表面に予めＰＶＤ、ＣＶＤなどのコーティング手段により成膜することにより実現できる。特にコーティング手段としてはスパッタリンッグを採用することが好適である。例えばアルミナ製の容器（ノズル）を対象としてこれにＴＩＮを成膜する際はＴｉをターゲットとし、アルゴンガス、窒素ガス雰囲気下で直流放電させ、反応性スパッタリンッグ法によりアルミナ表面に直接コーティングすることが望ましい。
そこで、図１に示す本実施形態においては、対向電極３がイオン源容器１の微小開口Ｏを形成する内周側先端部１-１の外周部が一体的に配設されたタイプで、この内周側先端部１-１の前面ａ（図では下面）及び内周面ｂが二次電子放出抑制材、例えばＴＩＮからなる薄膜Ｔａ及びＴｂで構成されている。この内周側先端部１-１は電界電離電極２の先端に最も近く位置（電極先端近傍）し、電極２に正の電圧が印加されており、且つアパーチャなどから逆流した二次電子が集中的にここに衝突するところからこの部分が最も帯電しやすい容器１の領域となり、とりわけ、前面ａを二次電子放出抑制材の薄膜Ｔａで構成することが重要且つ必須となる。 Further, these materials can be realized in the form of a thin film by previously forming a film on the surface of the container and / or the necessary portion or portion of the external electrode by a coating means such as PVD or CVD. In particular, it is preferable to employ sputtering as the coating means. For example, when a TIN film is formed on an alumina container (nozzle), Ti is used as a target, and direct current discharge is performed under an atmosphere of argon gas or nitrogen gas, and the alumina surface is directly coated by a reactive sputtering method. desirable.
Therefore, in the present embodiment shown in FIG. 1, the counter electrode 3 is a type in which the outer peripheral portion of the inner peripheral tip portion 1-1 that forms the minute opening O of the ion source container 1 is integrally disposed. The front surface a (the lower surface in the figure) and the inner peripheral surface b of the inner peripheral tip portion 1-1 are made of a secondary electron emission suppressing material, for example, thin films Ta and Tb made of TIN. This inner circumferential tip 1-1 is located closest to the tip of the field ionization electrode 2 (near the tip of the electrode), a positive voltage is applied to the electrode 2, and secondary electrons that have flowed back from the aperture are concentrated. In particular, this portion becomes the region of the container 1 that is most easily charged from the point where it collides here, and it is particularly important and essential that the front surface a is composed of the thin film Ta of the secondary electron emission suppressing material.

ここに適用される薄膜の厚みについて検討すると、二次電子が１０ｋＶ前後で入射する標準的な条件においては、上記薄膜Ｔａ及びＴｂの厚みは、２ｎｍ以上とすることが好ましい。２ｎｍ以上の厚みにすることで電極先端近傍の導電性が確保され、電界強度を向上させることができる。   Considering the thickness of the thin film applied here, the thickness of the thin films Ta and Tb is preferably 2 nm or more under standard conditions where secondary electrons are incident at around 10 kV. By setting the thickness to 2 nm or more, the electrical conductivity in the vicinity of the electrode tip can be secured, and the electric field strength can be improved.

次に、図２に示す実施形態２は、前記図１の実施形態１の領域に加えて、容器１の内周側先端部１-１の外周部に一体的に配設された対向電極３の前面ｃ（図では下面）も二次電子放出抑制材の薄膜Ｔｃで構成されている例である。ここに適用される薄膜Ｔａ、Ｔｂの厚みは前実施形態１と同様に２ｎｍ以上とすることが好ましい。対して、針先から離れたＴcにおいては２ｎｍ以下とし、電子放出係数を1に近づけてチャージアップの可能性を極力防ぐことが好ましいと考えられる。   Next, in the second embodiment shown in FIG. 2, in addition to the region of the first embodiment shown in FIG. 1, the counter electrode 3 disposed integrally with the outer peripheral portion of the inner peripheral side tip portion 1-1 of the container 1 is used. This is an example in which the front surface c (the lower surface in the figure) is also composed of a thin film Tc of a secondary electron emission suppressing material. The thicknesses of the thin films Ta and Tb applied here are preferably 2 nm or more as in the first embodiment. On the other hand, it is considered preferable to make the electron emission coefficient close to 1 and prevent the possibility of charge-up as much as possible at Tc far from the needle tip, with the electron emission coefficient approaching 1.

また、図３に示す実施形態３は前記実施形態の変形例で、容器１の内周側先端部１-１の前面ａと容器１一体的に配設された対向電極３の前面ｃに二次電子放出抑制材の薄膜Ｔａと薄膜Ｔｃが構成され、内周面ｂは薄膜を有さない例である。ここでも同じく、適用される薄膜Ｔａの厚みは２ｎｍ以上とし、対してＴcでは２ｎｍ以下とすることが好ましい。   In addition, Embodiment 3 shown in FIG. 3 is a modification of the above-described embodiment, and the front surface a of the inner peripheral side front end portion 1-1 of the container 1 and the front surface c of the counter electrode 3 disposed integrally with the container 1 are two. This is an example in which the thin film Ta and the thin film Tc of the secondary electron emission suppressing material are configured, and the inner peripheral surface b does not have a thin film. Here again, the thickness of the applied thin film Ta is preferably 2 nm or more, whereas it is preferably 2 nm or less in Tc.

次に、図４に示す実施形態４は、対向電極３が前記実施形態１〜３ のように容器１に一体的に配設されたものでなく、その少し前方（図では下方）に独立して設置されたタイプのものであって、容器１の内周側先端部１-１の前面ａと、その外周部の全面ｄが二次電子放出抑制材の薄膜Ｔａと薄膜Ｔｄで構成されている例である。ここに適用される薄膜Ｔａに関しては前記実施形態１〜３と異なり、２ｎｍ未満とすることが好ましい。これは膜厚を２ｎｍ以上に厚くすると導電性を有し、電極２の先端部の電界強度を低下させることになるためである。対して、Ｔdについては他の構成とおなじく２ｎｍ以下としてチャージアップを防ぐのが好ましい。   Next, Embodiment 4 shown in FIG. 4 does not have the counter electrode 3 integrally disposed in the container 1 as in Embodiments 1 to 3, but is slightly independent (downward in the figure). The front surface a of the inner peripheral side front end portion 1-1 of the container 1 and the entire surface d of the outer peripheral portion thereof are composed of the thin film Ta and the thin film Td of the secondary electron emission suppressing material. This is an example. Unlike the first to third embodiments, the thin film Ta applied here is preferably less than 2 nm. This is because if the film thickness is increased to 2 nm or more, it has conductivity and the electric field strength at the tip of the electrode 2 is reduced. On the other hand, Td is preferably 2 nm or less, which is the same as other configurations, to prevent charge-up.

次に、図５に示す実施形態５は、前記図４の実施形態４の領域に加えて、さらに独立した対向電極３の全表面ｅが二次電子放出抑制材の薄膜Ｔｅで構成されている例である。この実施形態は容器１の前方に位置する対向電極３の全表面ｅが薄膜を有するため、アパーチャから逆流してくる二次電子自体が容器１に到達するのを抑止する効果も併せ持っている。この実施形態に適用される薄膜については前記実施形態１〜３と同じ考え方に基づき、電極先端近傍の導電性を確保して電界強度を上げる意味で、２ｎｍ以上とすることが好ましい。一方、薄膜Ｔｅについては二次電子の跳ね返りや針先での電界強度低下を防ぐため、２ｎｍ未満とすることが望ましい。   Next, in the fifth embodiment shown in FIG. 5, in addition to the region of the fourth embodiment shown in FIG. 4, the entire surface e of the independent counter electrode 3 is composed of a thin film Te of a secondary electron emission suppressing material. It is an example. In this embodiment, since the entire surface e of the counter electrode 3 positioned in front of the container 1 has a thin film, it also has an effect of preventing the secondary electrons themselves flowing back from the aperture from reaching the container 1. About the thin film applied to this embodiment, it is preferable to set it as 2 nm or more in the meaning which ensures the electroconductivity near an electrode tip and raises an electric field strength based on the same view as the said Embodiment 1-3. On the other hand, the thickness of the thin film Te is preferably less than 2 nm in order to prevent secondary electrons from rebounding and lowering the electric field strength at the needle tip.

さらに、図６に示す実施形態６は、図３の前記実施形態３においては容器１に一体的に配設された対向電極３の前面ｃに薄膜Ｔｃが構成されていたが、これに替えてその表面だけでなく対向電極３そのものを薄膜Ｔｄで構成した例である。この場合のＴａは２ｎｍ以上とし、対してＴｄの厚みは二次電子の跳ね返りを考慮して２ｎｍ未満とすることが望ましい。   Further, in the sixth embodiment shown in FIG. 6, the thin film Tc is formed on the front surface c of the counter electrode 3 disposed integrally with the container 1 in the third embodiment shown in FIG. This is an example in which not only the surface but also the counter electrode 3 itself is composed of a thin film Td. In this case, Ta is preferably 2 nm or more, and the thickness of Td is preferably less than 2 nm in consideration of the bounce of secondary electrons.

１：イオン源容器（本体）１-１：内周側先端部 ２：電界電離電極
３：対向電極（外部電極） ４：原料ガス供給管 ５：原料ガス制御手段
６：強電界印加用電源 ７：ベース ８：イオンビーム
Ｏ：微小開口
Ｔａ、Ｔｂ、Ｔｃ、Ｔｄ：薄膜（二次電子放出抑制材）
1: Ion source container (main body) 1-1: inner peripheral tip 2: field ionization electrode 3: counter electrode (external electrode) 4: source gas supply pipe 5: source gas control means 6: power source for applying a strong electric field 7 : Base 8: Ion beam O: Minute aperture Ta, Tb, Tc, Td: Thin film (secondary electron emission suppressing material)

Claims (5)

高誘電体材料で構成され、供給された原料ガスをその微小開口を通じて外部に噴射するイオン源容器と、前記イオン源容器の内部にあってその先端が同容器の前記微小開口に配置された電界電離電極と、前記イオン源容器の外部に配設された外部電極とからなり、前記電界電離電極と前記外部電極との間に電圧を印加して電界電離電極の先端近傍に電界を形成し、前記イオン源容器の微小開口より噴射される原料ガスを電界電離することによりイオンビームを生成するガスイオン源において、前記電界電離電極の先端に近い領域に位置する、イオン源容器の一部の表面、前記外部電極の一部若しくは全部の表面、または同外部電極の全部を二次電子放出抑制材で構成したことを特徴とするガスイオン源。   An ion source container made of a high dielectric material and jetting the supplied source gas to the outside through the minute opening, and an electric field inside the ion source container, the tip of which is arranged in the minute opening of the container It consists of an ionization electrode and an external electrode disposed outside the ion source container, and forms an electric field near the tip of the field ionization electrode by applying a voltage between the field ionization electrode and the external electrode, In a gas ion source that generates an ion beam by field ionizing a source gas ejected from a minute opening of the ion source container, a part of the surface of the ion source container located in a region near the tip of the field ionization electrode A gas ion source characterized in that a part or all of the surface of the external electrode or all of the external electrode is made of a secondary electron emission suppressing material. 前記二次電子放出抑制材の二次電子放出係数が２以下である請求項１に記載のガスイオン源。   The gas ion source according to claim 1, wherein a secondary electron emission coefficient of the secondary electron emission suppressing material is 2 or less. 前記二次電子放出抑制材の二次電子放出係数が０.５〜１.５である請求項２に記載のガスイオン源。   The gas ion source according to claim 2, wherein a secondary electron emission coefficient of the secondary electron emission suppressing material is 0.5 to 1.5. 前記二次電子放出抑制材が薄膜である請求項１または２に記載のガスイオン源。   The gas ion source according to claim 1, wherein the secondary electron emission suppressing material is a thin film. 前記イオン源容器がその微小開口を形成する内周側先端部を有するとともに、 前記外部電極が、同容器の前記内周側先端部の外周部に一体的に配設されたものにおいて、前記二次電子放出抑制材の薄膜が、前記イオン源容器の内周側先端部の前面及び／または内周面及び／または前記外部電極の前面に被覆されてなる請求項３に記載のガスイオン源。
The ion source container has an inner peripheral tip that forms the minute opening, and the external electrode is integrally disposed on the outer periphery of the inner peripheral tip of the container. 4. The gas ion source according to claim 3, wherein a thin film of a secondary electron emission suppressing material is coated on a front surface and / or an inner peripheral surface of the ion source container and / or a front surface of the external electrode.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015132777A (en) * 2014-01-15 2015-07-23 富士通株式会社 Voice processing device, voice processing method, and voice processing program
KR20200131730A (en) 2019-05-14 2020-11-24 가부시끼가이샤 히다치 세이사꾸쇼 Gas field ionization source

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015132777A (en) * 2014-01-15 2015-07-23 富士通株式会社 Voice processing device, voice processing method, and voice processing program
KR20200131730A (en) 2019-05-14 2020-11-24 가부시끼가이샤 히다치 세이사꾸쇼 Gas field ionization source
US11367587B2 (en) 2019-05-14 2022-06-21 Hitachi, Ltd. Gas field ionization source
DE102020109610B4 (en) 2019-05-14 2022-08-04 Hitachi, Ltd. GAS FIELD IONIZATION SOURCE

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