JP2007179867A - Electron source using fibrous carbon material - Google Patents
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本発明は繊維状炭素と導電性基材とで構成した電子源に係り、特に、電子顕微鏡，電子線描画装置に好適な電子源の材料，構造に関する。 The present invention relates to an electron source composed of fibrous carbon and a conductive substrate, and more particularly to an electron source material and structure suitable for an electron microscope and an electron beam drawing apparatus.
半導体の微細化技術の発展に伴い、汎用ＳＥＭ，測長ＳＥＭ，電子線描画装置等の電子線を用いた計測機器では、より高い分解能や精度が要求されている。これらの課題を解決する技術として、繊維状炭素を用いた電子源が冷陰極電子源，ショットキー電子源などに続く電子源として期待されている。これは、１本の繊維状炭素を導電性の基材に装着したものである。一般に、繊維状炭素はその先端径がナノレベルであり、仮想光源サイズが小さい。そのため、これを電子顕微鏡の電子源に適用した場合、高輝度な電子ビームが得られる。 With the development of semiconductor miniaturization technology, higher resolution and accuracy are required in measuring instruments using electron beams such as general-purpose SEM, length measuring SEM, and electron beam drawing apparatus. As a technique for solving these problems, an electron source using fibrous carbon is expected as an electron source following a cold cathode electron source and a Schottky electron source. This is one in which one fibrous carbon is mounted on a conductive substrate. In general, fibrous carbon has a nanometer tip diameter and a small virtual light source size. Therefore, when this is applied to the electron source of an electron microscope, a high-intensity electron beam can be obtained.
また、Ｘ線分光分析等に使用される微小Ｘ線源用の電子源として、炭素と共に、ボロン及び窒素からなる群から選択された少なくとも一種を含有する面電子源を使用することにより、電子放出効率が向上するということが、特開２００３−３６８０５号公報（特許文献１）に開示されている。 Electron emission by using a planar electron source containing at least one selected from the group consisting of boron and nitrogen together with carbon as an electron source for a micro X-ray source used for X-ray spectroscopic analysis and the like. It is disclosed in Japanese Patent Laid-Open No. 2003-36805 (Patent Document 1) that the efficiency is improved.
繊維状炭素を用いた電子源の実用化には、半導体微細化対応の観点から、エネルギー幅ならびに電子線の時間安定性をさらに高める必要がある。 For practical use of an electron source using fibrous carbon, it is necessary to further increase the energy width and the time stability of the electron beam from the viewpoint of miniaturization of semiconductors.
本発明で解決しようとする課題は、電子源の重要な性質の１つであるエネルギー幅、および電流安定性を向上させ、従来電子源以上の機能を付与することにある。すなわち、本発明の課題は、繊維状炭素を用いた電子源において、優れたエネルギー幅と電流安定性とを実現可能な電子源、およびそれを達成するための繊維状炭素物質を提供することにある。 The problem to be solved by the present invention is to improve the energy width and current stability, which are one of the important properties of an electron source, and to provide a function higher than that of a conventional electron source. That is, an object of the present invention is to provide an electron source capable of realizing an excellent energy width and current stability in an electron source using fibrous carbon, and a fibrous carbon material for achieving the electron source. is there.
また、高分解能の電子顕微鏡，高精度な電子線描画装置を実現することにある。 Another object is to realize a high-resolution electron microscope and a high-precision electron beam drawing apparatus.
上記第１の課題を解決する本発明の特徴は、繊維状炭素を導電性の基材に接合した電子源であって、該繊維状炭素にボロン，窒素，リン，硫黄の少なくとも１種類を０.１ 〜５原子％含有させ、そのラマン分光強度のＩＧ／ＩＤ比（ＩＧ；グラファイト構造における炭素の伸縮運動に対応するラマン散乱強度、ＩＤ；結晶格子乱れに対応するラマン散乱強度）を０.７５ 以上としたことにある。特に、繊維状炭素の先端部を閉構造にすることが好ましい。本発明者らは、ＩＧ／ＩＤが大きくなることに従って（グラファイト構造の割合が大きくなるに従って）エネルギー幅が小さくなることを見出した。つまり、結晶性がエネルギー幅に大きく影響し、炭素以外の元素、特にボロン，窒素，リン，硫黄を含有する繊維状炭素のグラファイト構造の割合を高めることにより、電子線のエネルギー幅が小さくなることを見出した。 A feature of the present invention that solves the first problem is an electron source in which fibrous carbon is bonded to a conductive substrate, and at least one of boron, nitrogen, phosphorus, and sulfur is added to the fibrous carbon. 0.1 to 5 atomic%, and the Raman spectral intensity IG / ID ratio (IG; Raman scattering intensity corresponding to the stretching motion of carbon in the graphite structure; ID; Raman scattering intensity corresponding to crystal lattice disorder) of 0. 75 or more. In particular, it is preferable to have a closed structure at the tip of the fibrous carbon. The inventors have found that the energy width decreases as IG / ID increases (as the ratio of the graphite structure increases). In other words, the crystallinity greatly affects the energy width, and the energy width of the electron beam is reduced by increasing the proportion of the graphite structure of fibrous carbon containing elements other than carbon, particularly boron, nitrogen, phosphorus, and sulfur. I found.
本発明によれば、繊維状炭素を用いた電子源において、電子線のエネルギー幅が小さく、電流安定性の高い電子源を提供できる。また、この電子源を用いることにより高分解能の電子顕微鏡、及び高精細な電子線描画装置を提供できる。 ADVANTAGE OF THE INVENTION According to this invention, in the electron source using fibrous carbon, the energy width of an electron beam is small and an electron source with high current stability can be provided. Further, by using this electron source, a high-resolution electron microscope and a high-definition electron beam drawing apparatus can be provided.
上記のとおり、本発明では、一定量のボロン，窒素，リン，硫黄をカーボンナノチューブのような繊維状炭素物質に含有させ、その結晶化度を高めてグラファイト構造を多くしたものを使用した電子源を提供する。 As described above, in the present invention, an electron source using a fibrous carbon material such as carbon nanotubes containing a certain amount of boron, nitrogen, phosphorus, and sulfur and increasing the crystallinity to increase the graphite structure. I will provide a.
特に、エネルギー幅の低減と電流安定性向上のためには、上記繊維状炭素は中実もしくは中空で、先端が概略軸対称（円錐形状のように、ナノチューブの中心軸に対して先端が対称）のものを使用することが好ましい。 In particular, in order to reduce energy width and improve current stability, the fibrous carbon is solid or hollow, and the tip is roughly axisymmetric (like the cone shape, the tip is symmetrical with respect to the central axis of the nanotube) Are preferably used.
また、エネルギー幅の低減のためには、上記のボロン，窒素，リン，硫黄等の不純物原子のいずれかが炭素と置換された構造とすることが好ましい。特に、上記のボロン，窒素，リン，硫黄のいずれかがピリジン構造を有するか、もしくはこれらの不純物原子の最近接位置に少なくとも同種の不純物原子が存在する構造となっているものを使用すると、もっともエネルギー幅が低減された。 In order to reduce the energy width, a structure in which any of the impurity atoms such as boron, nitrogen, phosphorus, and sulfur is substituted with carbon is preferable. In particular, when any of the above boron, nitrogen, phosphorus, or sulfur has a pyridine structure or has a structure in which at least the same kind of impurity atoms exists at the closest position of these impurity atoms, Energy width has been reduced.
また、エネルギー幅の低減のためには、１本の繊維状炭素より真空中に放出される電子のエネルギー幅は、電流密度０.０１〜０.１μＡの領域において、０.２５ｅＶ 以下とすることが好ましい。特に電流が０.０１〜０.１μＡの低い領域では、他の因子（空間電荷効果等）の影響を受けにくく、材料そのもののエネルギー幅が得られるため、優れた材料特性を活用することが可能である。 In order to reduce the energy width, the energy width of electrons emitted from one fibrous carbon into the vacuum should be 0.25 eV or less in the region where the current density is 0.01 to 0.1 μA. Is preferred. Especially in the region where the current is low from 0.01 to 0.1 μA, it is difficult to be affected by other factors (space charge effect, etc.) and the energy width of the material itself can be obtained, so it is possible to utilize excellent material properties. It is.
上記の構成によれば、電子のエネルギー分布の最大ピーク位置を基準点とした時に、電流０.１〜１.０μＡの領域で、高エネルギー側の半値幅位置を基準点から０.１５ｅＶ 以内、低エネルギー側の半値幅位置を基準点から０.３ｅＶ 以内とすることができ、好ましい。上記結果は電子が電界放出しており、エネルギー幅の大きい熱電子放出がないことにより得られる。 According to the above configuration, when the maximum peak position of the energy distribution of electrons is used as the reference point, the full width at half maximum on the high energy side is within 0.15 eV from the reference point in the current range of 0.1 to 1.0 μA. The half-value width position on the low energy side can be within 0.3 eV from the reference point, which is preferable. The above result is obtained by the fact that electrons are field-emitted and there is no thermal electron emission with a large energy width.
電流０.１μＡ〜１.０μＡの領域で、電子エネルギー分布の高エネルギー側の立ち上がり（半値幅）位置の電流に対する変化を０.２ｅＶ 以内にすることが好ましい。電子源の抵抗を小さくすることで、抵抗が大きいと発熱して発生する熱電子の放出を抑制できる。特に、繊維状炭素の先端構造を、概略半球状、もしくは先端部が局所的に平面構造を有するカップ状にすることが好ましい。 In the region of current 0.1 μA to 1.0 μA, it is preferable that the change with respect to the current at the rising (half-value width) position on the high energy side of the electron energy distribution is within 0.2 eV. By reducing the resistance of the electron source, it is possible to suppress the emission of thermoelectrons generated by heat generation when the resistance is large. In particular, it is preferable that the tip structure of the fibrous carbon is a substantially hemispherical shape or a cup shape in which the tip portion has a planar structure locally.
上記繊維状炭素として、１本もしくはバンドル状の繊維の直径を５０ｎｍ〜２００ｎｍとすることが好ましい。上記範囲にすることにより、電子密度が集中することによってエネルギー幅が増大するベルシェ効果を抑制できる。また、カーボンナノチューブの抵抗もさがり、発熱による熱電子放出を低減することができる。いずれの効果においても、エネルギー幅が低減される。 As the fibrous carbon, it is preferable that the diameter of one or a bundle of fibers is 50 nm to 200 nm. By setting it in the above range, it is possible to suppress the Bercher effect in which the energy width increases due to concentration of the electron density. In addition, the resistance of the carbon nanotube is reduced, and thermionic emission due to heat generation can be reduced. In any effect, the energy width is reduced.
繊維状炭素として２〜１０μｍ長のものを用い、導電性基材からの繊維状炭素の突出長さを０.５〜３.０μｍとすることが好ましい。特に、繊維状炭素を導電性基材に接合する際に、接合に用いる金属含有の堆積層の厚さを５０ｎｍ 以上とし、該炭素物質の０.５
μｍ以上の領域を被覆することが好ましい。また、導電性基材および繊維状炭素繊維の抵抗を合計で２０ｋΩ以下にすることが好ましい。電子放出中のＣＮＴの発熱による熱電子放出を低減することができ、エネルギー幅低減に効果がある。
The fibrous carbon having a length of 2 to 10 μm is preferably used, and the protruding length of the fibrous carbon from the conductive substrate is preferably set to 0.5 to 3.0 μm. In particular, when the fibrous carbon is bonded to the conductive substrate, the thickness of the metal-containing deposition layer used for bonding is set to 50 nm or more, and 0.5% of the carbon material is used.
It is preferable to cover a region of μm or more. Moreover, it is preferable that the resistance of the conductive base material and the fibrous carbon fiber is 20 kΩ or less in total. Thermionic emission due to heat generation of CNT during electron emission can be reduced, which is effective in reducing the energy width.
本発明で使用した繊維状炭素の作製方法を以下に記載する。
（１）ボロンをドーピングした繊維状炭素の作製法
Ｂ4Ｃ粉末を表面に塗布し、黒鉛板を＋極、ＴＩＧ溶接トーチのタングステン電極を−極に接続した。次に、アルゴンガスを流しながら電流２００Ａで１秒間放電させ、ボロンをドーピングした繊維状炭素を作製した。
（２）ボロン，リン，硫黄をドーピングした繊維状炭素の作製法
ボロン，リン，硫黄を含む黒鉛ターゲットをアルゴンガス中(５００Torr)で約１１００℃に加熱した。次にＮｄ：ＹＡＧレーザー（１０６４ｎｍ，１０Ｈｚ）をターゲットに照射し、ターゲットを溶発させることによって、ボロン，リン，硫黄をドーピングした繊維状炭素を作製した。
（３）窒素をドーピングした繊維状炭素の作製法
アルミニウムtri−sec−ブトキシ（８ｇ）をメタノール（５０ｍｌ）に溶解した後、溶液が透明になるまで希釈し、ＨＣｌ（０.０１ｍＭ）溶液を加えた。さらに、硝酸鉄
Ｆｅ(ＮＯ3)3・９Ｈ2Ｏ(３.２ｇ) を加えた後、アンモニア溶液を加え、ゲル化した。それを１００℃で乾燥させた後、６００℃で１０時間焼成し、支持触媒を作製した。その支持触媒を石英管が設置された管状の電気炉に入れ、アルゴンガス（２００sccm）を流しながら、８００℃まで昇温し、８００℃に達した時点で、水素（１００sccm）を１時間導入することにより、支持触媒の酸化物を還元した。その後、アルゴンガスをキャリアガスとして石英管にジメチルホルムアミドＨＯＣＮ(ＣＨ3)2を導入すると同時に、無水アンモニアガス（１００sccm）を導入することによって、窒素がドーピングされた繊維状炭素を作製した。
（４）窒素をドーピングした繊維状炭素の作製法（その２）
粉末状のメラミン（ｓ−triaminotriazine）とフェロセン(dicyclopentadieny−liron)の混合粉末（メラミン：フェロセン＝４：１）を石英管が設置された管状の電気炉に挿入し、アルゴンガス（０.８ｌ／min）を流した雰囲気で１０５０℃，１５分間加熱することにより、窒素がドーピングされた繊維状炭素を作製した。
（５）結晶度を高めた繊維状炭素の作製法
次に上記（１）〜（４）の手法で作製した繊維状炭素を、真空中において１０００〜
２１００℃の範囲で約３０分加熱した。
The method for producing the fibrous carbon used in the present invention is described below.
(1) Preparation method of boron-doped fibrous carbon B 4 C powder was applied to the surface, a graphite plate was connected to the + electrode, and a tungsten electrode of a TIG welding torch was connected to the − electrode. Next, discharge was performed at a current of 200 A for 1 second while flowing an argon gas, thereby producing fibrous carbon doped with boron.
(2) Fabrication method of fibrous carbon doped with boron, phosphorus and sulfur A graphite target containing boron, phosphorus and sulfur was heated to about 1100 ° C. in argon gas (500 Torr). Next, Nd: YAG laser (1064 nm, 10 Hz) was irradiated to the target, and the target was ablated to produce fibrous carbon doped with boron, phosphorus, and sulfur.
(3) Preparation method of fibrous carbon doped with nitrogen After dissolving aluminum tri-sec-butoxy (8 g) in methanol (50 ml), dilute until the solution becomes transparent and add HCl (0.01 mM) solution. It was. Further, iron nitrate Fe (NO 3 ) 3 .9H 2 O (3.2 g) was added, and then an ammonia solution was added to cause gelation. It was dried at 100 ° C. and then calcined at 600 ° C. for 10 hours to produce a supported catalyst. The supported catalyst is put into a tubular electric furnace in which a quartz tube is installed, and heated to 800 ° C. while flowing argon gas (200 sccm). When the temperature reaches 800 ° C., hydrogen (100 sccm) is introduced for 1 hour. As a result, the oxide of the supported catalyst was reduced. Thereafter, dimethylformamide HOCN (CH 3 ) 2 was introduced into the quartz tube using argon gas as a carrier gas, and at the same time, anhydrous ammonia gas (100 sccm) was introduced to produce fibrous carbon doped with nitrogen.
(4) Preparation method of fibrous carbon doped with nitrogen (part 2)
A mixed powder (melamine: ferrocene = 4: 1) of powdered melamine (s-triaminotriazine) and ferrocene (melamine: ferrocene = 4: 1) was inserted into a tubular electric furnace provided with a quartz tube, and argon gas (0.8 l / Heating was performed at 1050 ° C. for 15 minutes in an atmosphere with a flow of min) to produce fibrous carbon doped with nitrogen.
(5) Method for producing fibrous carbon with increased crystallinity Next, the fibrous carbon produced by the methods (1) to (4) above is 1000 to 1000 in a vacuum.
The mixture was heated at 2100 ° C. for about 30 minutes.
１０００度と２１００度以外の例もあるのであれば、文章だけでも追加ください。 If there are examples other than 1000 degrees and 2100 degrees, please add just the text.
１５００℃でも実施。ＩＧ／ＩＤは１０００と２１００の間の値を示した。 Even at 1500 ° C. IG / ID showed a value between 1000 and 2100.
図１は上記（４）の手法により窒素をドーピングした繊維状炭素の加熱前後におけるラマン分光スペクトルを示す。ＩＧ／ＩＤは各スペクトルのピークの部分の面積比から算出した。１０００℃、で熱処理した材料は、従来手法で作製した加熱前の比較材（図１●印で表示）のＩＧ／ＩＤ比がおよそ０.７であるのに対して、０.７５となった。 FIG. 1 shows a Raman spectrum before and after heating of fibrous carbon doped with nitrogen by the method (4). IG / ID was calculated from the area ratio of the peak portion of each spectrum. The material heat-treated at 1000 ° C. was 0.75, whereas the comparative material (indicated by the mark ● in FIG. 1) before heating produced by the conventional method had an IG / ID ratio of approximately 0.7. .
本発明の繊維状炭素を用いた電子源の概略構成を図２示す。電子源１は一本の繊維状炭素２を、それを導電性基材３上に接合する導電性被覆層４で構成されている。導電性基材３の材質としては、特に限定されるものではないが、融点，耐酸化性，機械的強度の点から、貴金属（具体的には、金，銀，白金族），結晶質カーボンあるいは高融点金属（具体的には、タングステン，タンタル，ニオブ，モリブデン等）が好ましい。繊維状炭素２の接合は、導電性元素を含む有機ガスを導入したチャンバー内で、接触部分の少なくとも一部に電子ビームを照射することにより導電性被覆層４を形成させて先端が閉構造の繊維状炭素２を導電性基材３に接合した。なお、接合プロセスで用いた有機ガスとしては、ピレンモノマー，タングステンカルボニル等が好適である。これらの有機ガスに電子ビームを照射することにより、繊維状炭素と導電性基材との接合部のみにカーボン層やタングステン層等の導電性材料を局所的に形成させることができる。
FIG. 2 shows a schematic configuration of an electron source using the fibrous carbon of the present invention. The
図３に窒素を含有するＣＮＴを１０００℃で加熱して作製した電子源のエネルギー幅の測定結果を示す。ＩＧ／ＩＤ比は０.７５ である。図３からわかるように、本発明の繊維状炭素を用いた電子源は、電流０.０１〜１.０μＡにおけるエネルギー幅は０.２５〜0.5ｅＶの値を示す。炭素のみからなるカーボンナノチューブを使用した場合の０.５〜０.７ｅＶに比べて優れた特性を有していることがわかった。今回の繊維状炭素で優れたエネルギー幅が得られた理由としては、ボロン，窒素，リン，硫黄を含有させることによって形成されたエネルギー準位が、炭素物質の結晶性の向上によって狭エネルギー幅化し、順位がシャープになった、あるいは結晶性の向上に伴って繊維状炭素の抵抗が減少し、エネルギー幅の増大に結びつく熱電子の放出が抑制されたことが考えられる。なお、図３において電流の増加に伴って０.１μＡ 以上の領域で顕著にエネルギー幅が増大しているのは、ベルシェ効果によるもので、繊維状炭素の径を増大することにより改善可能である。ベルシェによる増分は０.１ｅＶ 以下にするのが望ましいが、太さが１００ｎｍ以上であれば使用上問題のない改善が可能であった。 FIG. 3 shows the measurement result of the energy width of an electron source produced by heating CNTs containing nitrogen at 1000 ° C. The IG / ID ratio is 0.75. As can be seen from FIG. 3, in the electron source using the fibrous carbon of the present invention, the energy width at a current of 0.01 to 1.0 μA shows a value of 0.25 to 0.5 eV. It was found that the carbon nanotubes had excellent characteristics compared with 0.5 to 0.7 eV when carbon nanotubes made of only carbon were used. The reason why an excellent energy width is obtained with this fibrous carbon is that the energy level formed by containing boron, nitrogen, phosphorus, and sulfur is narrowed by improving the crystallinity of the carbon material. It is conceivable that the order became sharper or the resistance of the fibrous carbon decreased with the improvement of crystallinity, and the release of thermionic electrons that led to the increase in energy width was suppressed. In FIG. 3, the energy width significantly increases in the region of 0.1 μA or more with the increase in current is due to the Bercher effect, which can be improved by increasing the diameter of the fibrous carbon. . Although it is desirable that the increment by the Bercher is 0.1 eV or less, if the thickness is 100 nm or more, improvement without problems in use is possible.
図４に電流安定性を示す変動率（電流変動幅÷平均電流値）を示す。繊維状炭素は、先端部が閉じており、かつ軸対称で概略半球状のものを用いた。また、その結果、本発明においては変動率が２％以内と優れた電流安定性を示した。加熱処理を行わない場合には、約５％程度、もしくはそれ以上の変動率を示した。 FIG. 4 shows the fluctuation rate (current fluctuation width / average current value) indicating the current stability. Fibrous carbon having a closed end and an axially symmetric and approximately hemispherical shape was used. As a result, the present invention showed excellent current stability with a variation rate within 2%. When heat treatment was not performed, the fluctuation rate was about 5% or more.
また、作製した繊維状炭素の中では、ボロン，窒素，リン，硫黄を含有させることで、まっすぐな繊維状炭素物質の割合が高くなった。従って、高歩留まりで電子源を作製できることがわかった。 Moreover, in the produced fibrous carbon, the ratio of the straight fibrous carbon substance became high by containing boron, nitrogen, phosphorus, and sulfur. Therefore, it was found that an electron source can be manufactured with a high yield.
これらの元素を２〜５原子％含有させた繊維状炭素を分析したところ、窒素原子の最近接位置に窒素原子が存在するピリジン構造を有することがわかった。窒素原子の際近接位置に炭素が存在する単純置換構造と比較して、このように不純物原子の際近接位置に同種の不純物が存在する構造を有する繊維状炭素で電子源を構成し、エネルギー幅を測定した結果、図５に示す様に０.０１〜１.０μＡの領域において、０.２５ｅＶ 以下の極めて優れた値を示すことを見出した。これはフェルミ準位近傍にドーピングによる狭エネルギー幅の準位が形成されていることに起因すると考えられる。 Analysis of fibrous carbon containing 2 to 5 atom% of these elements revealed that it has a pyridine structure in which a nitrogen atom is present at the closest position of the nitrogen atom. Compared with a simple substitution structure in which carbon is present at a close position in the case of a nitrogen atom, an electron source is constituted by fibrous carbon having a structure in which the same kind of impurity is present at a close position in the case of an impurity atom as described above, As a result, it was found that an extremely excellent value of 0.25 eV or less was exhibited in the region of 0.01 to 1.0 μA as shown in FIG. This is thought to be due to the formation of a narrow energy level due to doping in the vicinity of the Fermi level.
次に、本発明で作製した別の電子源の実施例を説明する。電子源用の繊維状炭素の径は５０〜２００ｎｍφのものが好適であることがわかった。これより小さくすると、ベルシェ効果と呼ばれる電子のエネルギー幅が増大する現象が現れる。所定の電流を得るための電流密度が大きくなるためと思われる。逆に径を大きくすると、繊維状炭素が湾曲する傾向にある。本実施例の繊維状炭素としては、直径約６０ｎｍのナノチューブ，長さ約５
μｍのものを用いた。基材への接合の際、繊維状炭素としては３〜１０μｍ長のものが良いことを見出した。繊維状炭素が長くなるとハンドリングが難しくなり、逆に短すぎると基材との接触抵抗が増大するからである。導電性基材からの繊維状炭素の突出部の長さは、０.５ 〜３μｍが最適であった。これよりも長すぎると突出部の振動を起こした。また、電子源の抵抗が増大し、エネルギー幅を増大させる熱電子の放出が認められた。逆に突出部が短すぎると、電界強度が弱まるため電子放出がされにくくなった。
Next, another example of the electron source produced in the present invention will be described. It has been found that the diameter of the fibrous carbon for the electron source is preferably 50 to 200 nmφ. If it is smaller than this, a phenomenon called the Berch effect, in which the energy width of electrons increases, appears. It seems that the current density for obtaining a predetermined current increases. Conversely, when the diameter is increased, the fibrous carbon tends to bend. As the fibrous carbon of this example, a nanotube with a diameter of about 60 nm, a length of about 5
A μm one was used. When joining to a base material, it discovered that 3-10 micrometers long thing was good as fibrous carbon. This is because handling becomes difficult when the fibrous carbon becomes long, and conversely, when it is too short, the contact resistance with the substrate increases. The optimum length of the fibrous carbon protrusion from the conductive substrate was 0.5 to 3 μm. If it is longer than this, the protrusions vibrate. Moreover, the resistance of the electron source was increased, and thermionic emission was observed to increase the energy width. On the other hand, if the protruding portion is too short, the electric field intensity is weakened, so that it is difficult to emit electrons.
不純物元素としてＣＮＴに窒素２％を含有させた、ＩＧ／ＩＤ比が１.０ のナノチューブを用いて、基材からの突出長さを約１μｍ として作製した電子源からの電流値０.１
μＡの時の電子のエネルギー分布を図６に示す。電子のエネルギー分布の最大ピーク位置を基準点とした時に、電流０.１〜１.０μＡの領域で、電子エネルギーの基準点よりも高エネルギーで、半値幅位置（図６にＡで表示）までが０.１５ｅＶ 以内にあり、低エネルギー側（図６にＢで表示）では０.３ｅＶ 以内にあった。高エネルギー側の急峻な立ち上がりは、電界電子放出の特徴であり、このことから電界電子放出型の電子源を形成できたことを確認できた。
Current value 0.1 from an electron source produced by using a nanotube with an IG / ID ratio of 1.0 containing 2% nitrogen in CNT as an impurity element and having a protrusion length from a substrate of about 1 μm.
The energy distribution of electrons at μA is shown in FIG. When the maximum peak position of the electron energy distribution is used as a reference point, the energy is higher than the reference point of electron energy in the current range of 0.1 to 1.0 μA, and the half-width position (shown as A in FIG. 6). Was within 0.15 eV and on the low energy side (indicated by B in FIG. 6) was within 0.3 eV. The sharp rise on the high energy side is characteristic of field electron emission, and from this, it was confirmed that a field electron emission type electron source could be formed.
図７は作製した電子源を電流０.１〜５.６μＡの範囲で電流値を変化させた時のエネルギー分布変化を測定した結果を示す。エネルギー幅の変化は０が望ましく、変化しても
０.１ｅＶ 以下である必要があるが、図７からわかるように、電流の増加に伴い、高エネルギー側の立ち上がりが鈍くなり、かつエネルギー幅も顕著に増大した。これは主として、抵抗によってナノチューブが加熱され、それに伴って温度が上昇し、熱電子が放出されたことによると考えられる。
FIG. 7 shows the result of measuring the energy distribution change when the current value of the produced electron source was changed in the current range of 0.1 to 5.6 μA. The change in energy width is preferably 0, and even if it changes, it must be 0.1 eV or less. However, as can be seen from FIG. 7, as the current increases, the rise on the high energy side becomes dull and the energy width is also low. Increased significantly. This is considered to be mainly due to the fact that the nanotubes were heated by the resistance, the temperature rose accordingly, and thermionic electrons were emitted.
次に、図８は接合用の導電性被覆層の厚さを５０ｎｍ以上とし、該繊維状炭素の０.５μｍ以上を覆って形成した電子源のエネルギー分布の変化を示す。この場合の立ち上がり位置の変化は０.２ｅＶ 以内で、エネルギー幅の増大抑制できることを見出した。このような改善が見られたのは、接合部の抵抗を低減し、電子源としての抵抗を２０ｋΩ以下としたことによる。なお、図７の場合は、導電性被覆層の厚さを６０ｎｍとし、該繊維状炭素の０.７μｍ程度を覆った電子源である。 Next, FIG. 8 shows a change in the energy distribution of an electron source formed so that the thickness of the conductive coating layer for bonding is 50 nm or more and covers the fibrous carbon of 0.5 μm or more. In this case, the change in the rising position is within 0.2 eV, and it has been found that the increase in energy width can be suppressed. Such improvement was observed because the resistance of the junction was reduced and the resistance as the electron source was 20 kΩ or less. In the case of FIG. 7, it is an electron source in which the conductive coating layer has a thickness of 60 nm and covers about 0.7 μm of the fibrous carbon.
図９に本発明の電子銃を用いた走査型電子顕微鏡（ＳＥＭ）の全体構成図を示す。走査型電子顕微鏡は、電子銃から放出される電子ビームに沿って、アライメントコイル，コンデンサレンズ，非点補正コイル，偏向・走査コイル，対物レンズ，対物絞りが配置されている。試料は、試料ステージに設置され、電子ビームが照射されるようになっている。試料室内の側壁部に二次電子検出器が設けられている。また、試料室は排気系によって高真空に保持されるようになっている。このように構成されることから、電子銃から放出された電子ビームは陽極で加速され、電子レンズによって集束されて試料上の微小領域に照射される。この照射領域を二次元走査し、試料から放出される二次電子，反射電子等を二次電子検出器により検出し、その検出信号量の違いを基に拡大像を形成する。 FIG. 9 shows an overall configuration diagram of a scanning electron microscope (SEM) using the electron gun of the present invention. In a scanning electron microscope, an alignment coil, a condenser lens, an astigmatism correction coil, a deflection / scanning coil, an objective lens, and an objective aperture are arranged along an electron beam emitted from an electron gun. The sample is placed on a sample stage and irradiated with an electron beam. A secondary electron detector is provided on the side wall in the sample chamber. The sample chamber is maintained at a high vacuum by an exhaust system. With this configuration, the electron beam emitted from the electron gun is accelerated by the anode, focused by the electron lens, and irradiated onto a minute region on the sample. The irradiation area is scanned two-dimensionally, secondary electrons and reflected electrons emitted from the sample are detected by a secondary electron detector, and an enlarged image is formed based on the difference in the detected signal amount.
本発明の電子銃を走査型電子顕微鏡に適用することにより、従来機種と比べて格段に高分解能かつ高輝度な二次電子像や反射電子像を短時間で得られる走査型電子顕微鏡を実現することが可能となる。また、半導体プロセスにおける微細加工パターンの観察や寸法測長を行う測長ＳＥＭの電子光学系の基本構成も図１３と同様で、本発明の電子銃を適用することによって、同様の効果が得られる。 By applying the electron gun of the present invention to a scanning electron microscope, a scanning electron microscope capable of obtaining secondary electron images and reflected electron images with much higher resolution and higher brightness than conventional models in a short time is realized. It becomes possible. Further, the basic configuration of the electron optical system of the length measurement SEM for observing the microfabricated pattern and dimension measurement in the semiconductor process is the same as that in FIG. 13, and the same effect can be obtained by applying the electron gun of the present invention. .
なお、電界放出型電子銃を搭載する走査型電子顕微鏡の構成は図１３で示したものに限定されることはなく、電界放出型電子銃の特性が十分引出せる構成であれば従来周知の構成を採用できる。 Note that the configuration of the scanning electron microscope on which the field emission electron gun is mounted is not limited to that shown in FIG. 13, and any conventionally known configuration can be used as long as the characteristics of the field emission electron gun can be sufficiently extracted. Can be adopted.
図１０は本発明の電子銃を搭載した電子線描画装置の全体構成例である。電子光学系の基本構成は前記した走査型電子顕微鏡とほぼ同様である。電子銃から電界放射により得られた電子ビームをコンデンサレンズで絞り、対物レンズで試料上に絞込み、ナノメータオーダーのビームスポットを得る。この時、試料への電子ビーム照射のＯＮ／ＯＦＦを制御するブランキング電極の中心は、コンデンサレンズで作られるクロスオーバ点に一致した方が良い。 FIG. 10 shows an example of the overall configuration of an electron beam lithography apparatus equipped with the electron gun of the present invention. The basic configuration of the electron optical system is almost the same as that of the scanning electron microscope described above. An electron beam obtained by field emission from an electron gun is narrowed down with a condenser lens and narrowed down on a sample with an objective lens to obtain a beam spot of nanometer order. At this time, it is preferable that the center of the blanking electrode for controlling ON / OFF of the electron beam irradiation to the sample coincides with the crossover point formed by the condenser lens.
電子線描画は、電子ビームをブランキング電極でＯＮ／ＯＦＦしながら、偏光・走査コイルにより試料上で電子ビームを偏光，走査させながら照射することで実施される。 Electron beam drawing is performed by irradiating an electron beam while being polarized and scanned on a sample by a polarization / scanning coil while the electron beam is turned ON / OFF by a blanking electrode.
電子線描画装置は、電子線に感応するレジストを塗布した試料基板に電子ビームを照射し、各種回路パターンを形成するものであるが、各種回路パターンの高精細化に伴い、極細プローブ径が得られる電子銃が必要になってきている。本発明の電子銃を適用することにより、従来機種に比べ、格段に高輝度かつ極細プローブ径が得られるため、高効率かつ高精細な電子線描画が可能となる。 The electron beam lithography system irradiates a sample substrate coated with a resist sensitive to electron beams with an electron beam to form various circuit patterns. An electron gun is needed. By applying the electron gun of the present invention, it is possible to obtain an extremely high brightness and ultrafine probe diameter as compared with the conventional model, so that high-efficiency and high-definition electron beam drawing is possible.
本発明の電子源は、ならびにそれを実現する繊維状炭素繊維は、電子線を用いた分析装置，加工装置などに利用でき、特に、次世代，次々世代の半導体技術にも対応可能な計測システム，加工システムに適用できる。 The electron source of the present invention and the fibrous carbon fiber that realizes the electron source can be used for an analyzer, a processing apparatus, etc. using an electron beam, and in particular, a measurement system that can cope with the next generation and the next generation semiconductor technology. Can be applied to machining systems.
１…電子源、２…繊維状炭素、３…導電性基材、４…導電性被覆層、１３…電界放出型陰極、１４…電子銃、１５…アライメントコイル、１６…コンデンサレンズ、１７…非点補正コイル、１８…対物レンズ、１９…偏向，走査コイル、２０…試料、２１…二次電子検出器、２２…対物レンズ絞り、２３…試料ステージ、２４…排気系、２５…ブランカ。
DESCRIPTION OF
Claims (17)
該繊維状炭素はボロン，窒素，リン，硫黄の中の少なくとも１種類を０.１ 〜５原子％含有し、
前記繊維状炭素のラマン分光強度のＩＧ／ＩＤ比が０.７５以上であることを特徴とする電子源。 In an electron source having fibrous carbon and a conductive base material to which the fibrous carbon is bonded,
The fibrous carbon contains 0.1 to 5 atomic% of at least one of boron, nitrogen, phosphorus, and sulfur,
An electron source having an IG / ID ratio of Raman spectral intensity of the fibrous carbon of 0.75 or more.
An electron beam drawing apparatus using the electron source according to claim 1.
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| JP2005243389A (en) * | 2004-02-26 | 2005-09-08 | Daiken Kagaku Kogyo Kk | Electron source and its manufacturing method |
| JP2005325012A (en) * | 2004-04-15 | 2005-11-24 | Toray Ind Inc | Method for processing carbonaceous material, carbonaceous material with improved graphitic property, electron emitting material using it, and battery electrode material |
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- 2005-12-28 JP JP2005376860A patent/JP2007179867A/en active Pending
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2006
- 2006-12-27 CN CNB2006101714339A patent/CN100565772C/en not_active Expired - Fee Related
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| JP2000249712A (en) * | 1998-12-31 | 2000-09-14 | Yoshikazu Nakayama | Fusion probe for surface signal operation of electronic device and its manufacture |
| JP2004143652A (en) * | 2002-08-29 | 2004-05-20 | Showa Denko Kk | Finely graphitized carbon fiber, method for producing the same and use for the same |
| WO2004043858A1 (en) * | 2002-11-14 | 2004-05-27 | Cambridge University Technical Services Limited | Method for producing carbon nanotubes and/or nanofibres |
| JP2004165518A (en) * | 2002-11-14 | 2004-06-10 | Ricoh Co Ltd | Electron beam lithography system and manufacturing method of principal part thereof |
| JP2006506304A (en) * | 2002-11-14 | 2006-02-23 | ケンブリッジ・ユニヴァーシティ・テクニカル・サーヴィシズ・リミテッド | Method for producing carbon nanotubes and / or nanofibers |
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| JP2004360160A (en) * | 2003-05-09 | 2004-12-24 | Showa Denko Kk | Linear fine carbon fiber and resin composite material given by using the same |
| JP2005032500A (en) * | 2003-07-10 | 2005-02-03 | Hitachi High-Technologies Corp | Cold cathode, and electron source and electron beam apparatus using the cold cathode |
| JP2005100885A (en) * | 2003-09-26 | 2005-04-14 | Shimadzu Corp | Field emission electron source and microscope using this |
| JP2005243389A (en) * | 2004-02-26 | 2005-09-08 | Daiken Kagaku Kogyo Kk | Electron source and its manufacturing method |
| JP2005325012A (en) * | 2004-04-15 | 2005-11-24 | Toray Ind Inc | Method for processing carbonaceous material, carbonaceous material with improved graphitic property, electron emitting material using it, and battery electrode material |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009231286A (en) * | 2008-03-19 | 2009-10-08 | Qinghua Univ | Manufacturing method of field emission type electron source |
| JP2012121792A (en) * | 2010-11-16 | 2012-06-28 | Alps Electric Co Ltd | Method for producing boron-containing carbon material and boron-containing carbon material |
| RU2442993C1 (en) * | 2011-03-01 | 2012-02-20 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Национальный исследовательский университет "МИЭТ" (МИЭТ) | Probe for locally enhanced spectrums of surface-enhanced raman scattering |
| JP2015220036A (en) * | 2014-05-15 | 2015-12-07 | 国立大学法人 名古屋工業大学 | Air electrode, metal air battery, and carbon nanotube doped with nitrogen and method of manufacturing air electrode |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100565772C (en) | 2009-12-02 |
| CN1992142A (en) | 2007-07-04 |
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