WO2019008738A1 - Field emission-type electron source and charged particle beam device - Google Patents

Field emission-type electron source and charged particle beam device Download PDF

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Publication number
WO2019008738A1
WO2019008738A1 PCT/JP2017/024942 JP2017024942W WO2019008738A1 WO 2019008738 A1 WO2019008738 A1 WO 2019008738A1 JP 2017024942 W JP2017024942 W JP 2017024942W WO 2019008738 A1 WO2019008738 A1 WO 2019008738A1
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electrode
needle electrode
source
zirconia
needle
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PCT/JP2017/024942
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French (fr)
Japanese (ja)
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亜紀 武居
創一 片桐
宗一郎 松永
源 川野
土肥　隆
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株式会社日立ハイテクノロジーズ
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Priority to PCT/JP2017/024942 priority Critical patent/WO2019008738A1/en
Publication of WO2019008738A1 publication Critical patent/WO2019008738A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • H01J1/304—Field-emissive cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/46—Control electrodes, e.g. grid; Auxiliary electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H01J37/073—Electron guns using field emission, photo emission, or secondary emission electron sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems

Definitions

  • the present invention relates to a field emission type electron source and a charged particle beam apparatus using the same.
  • a scanning electron microscope Scanning Electron Microscope
  • TEM Transmission Electron Microscope
  • SEM Scanning Electron Microscope
  • TEM Transmission Electron Microscope
  • An image is obtained by detecting secondary electrons or reflected electrons obtained to obtain an image
  • TEM Transmission Electron Microscope
  • a field emission electron source is generally used for the electron gun of these electron microscopes.
  • Field emission type electron sources are roughly classified into cold cathode field emission type electron sources and hot cathode field emission type electron sources.
  • the cold cathode field emission electron source applies an electric field to the tip of a needle-like electrode having a tip of a single crystal tungsten wire sharpened to emit electrons.
  • zirconia is attached to the side surface of the needle-like electrode having the tip of the single-crystal tungsten wire pointed at the tip of the single-crystal tungsten wire, and an electric field is applied to the tip of the needle in a heated state to emit electrons.
  • This hot cathode field emission electron source is also called a Schottky electron source.
  • the Schottky electron source forms a low work function region by supplying zirconium and oxygen by thermal diffusion on a tungsten crystal face (100).
  • the heating temperature is about 1600 K to 1900 K, usually 1700 K to 1800 K.
  • a crystal face (100) is provided at the tip of a tungsten needle, and a strong electric field is applied to take out thermoelectrons passing the potential barrier and electrons transmitted by tunneling.
  • a needle-like electrode whose tip is a crystal orientation (100) of single crystal tungsten is fixed by spot welding to a heating tungsten filament.
  • the needle electrode is provided with zirconia which is a diffusion source.
  • the diffusion source is molded around the needle when viewed from the tip of the needle.
  • Patent Document 1 discloses a method of forming a diffusion source by forming a solution in which zirconium hydride fine particles are mixed in an organic solvent with a brush and adhering it to the side circumference of a tungsten needle and vacuum heating for sintering.
  • U.S. Pat. No. 5,959,095 discloses using scandium oxide as the diffusion source to reduce the work function of a single crystal tungsten tip (100) surface to operate at low temperatures.
  • scandium oxide powder is mixed with an organic solvent or the like to form a slurry and to be attached or vapor deposited.
  • Patent Document 3 discloses that a practically stable life can be obtained by controlling the thickness and length of zirconia as a diffusion source.
  • Non-Patent Document 1 is trying to elucidate the structure and composition of a Schottky electron source using a surface analysis method with respect to the selective lowering mechanism of the work function due to zirconia diffusion.
  • the zirconia of the diffusion source As the zirconia of the diffusion source is heated and diffused on the surface of the single crystal tungsten wire, the work function of the tungsten crystal face (100) at the tip of the needle-like electrode is lowered from 4.5 eV to about 2.8 eV.
  • the diffusion failure of zirconia occurs during emission, the state of the crystal plane at the tip of the tungsten needle changes, and the electron emission characteristics deteriorate irregularly.
  • zirconia needs to be stably diffused to the surface of the single crystal tungsten wire.
  • Equation 1 The relationship between the surface coverage of the diffusion substance and the diffusion distance when the substance diffuses on the surface is expressed by (Equation 1).
  • k diffusion coefficient
  • K evaporation coefficient
  • C surface coverage
  • x diffusion distance
  • FIG. 2 is manufactured by changing the sintering position of zirconia of the field emission type electron source, and shows the diffusion failure rate in comparison with the conventional case (point 20). It can be seen that, as the sintering position of zirconia is closer to the tip and the diffusion distance L to the tip of the needle electrode becomes shorter, the diffusion failure decreases and stable emission characteristics can be obtained.
  • the dotted lines in the figure estimate the relationship between the diffusion distance L and the diffusion failure from these experimental results, and the diffusion source is placed closer to the tip of the needle electrode so that the diffusion distance L becomes shorter. It shows that the emission characteristics are stable.
  • FIG. 3 shows a schematic view of an electron gun mounted with a Schottky electron source.
  • the electron source 101 has a tungsten needle electrode 1, a filament 3 and a suppressor electrode 4.
  • the tungsten needle electrode 1 is fixed to the filament 3.
  • a diffusion source 2 is formed around the tungsten needle electrode 1 to supply zirconia to the tip of the tungsten needle electrode 1 during emission.
  • the filament 3 and the tungsten needle electrode 1 are covered with the suppressor electrode 4 except that the tip of the tungsten needle electrode 1 protrudes from the suppressor electrode opening 5.
  • the filament 3 is heated by a heating power source 108, and zirconia is diffused and supplied from the diffusion source 2 to the tip (emitter) of the tungsten needle electrode 1.
  • a positive voltage is applied to the extraction electrode 103 from the extraction electrode power supply 105, and the thermal electrons are extracted from the tip (emitter) of the tungsten needle-like electrode 1.
  • the extracted electrons are accelerated by the accelerating electrode 104 to which a positive voltage is applied by the accelerating electrode power supply 107.
  • a negative voltage is applied by the bias power supply 106.
  • the tip of the tungsten needle electrode 1 is disposed between the extraction electrode 103 and the suppressor electrode 4, so a strong electric field is applied near the tip of the needle electrode 1. ing.
  • the diffusion source 2 is disposed near the tip of the needle electrode 1, the diffusion source 2 is affected by this electric field.
  • the diffusion source is arranged to be contained in the suppressor electrode which is not affected by the electric field. Since the tungsten needle electrode of a general field emission electron source is configured to protrude 250 ⁇ m from the suppressor electrode, the distance from the tip of the needle to the zirconia was at least 250 ⁇ m.
  • the present invention provides a field emission electron source that can suppress the influence of an electric field and obtain stable long-term emission characteristics even when a diffusion source is disposed closer to the tip of a needle electrode, and a charged particle beam device using the same. It is to do.
  • a field emission electron source in which a suppressor electrode is disposed so as to cover the filament and the needle electrode except for the portion of the needle electrode protruding from the opening of the suppressor electrode, around the needle electrode, on the surface thereof
  • a diffusion source is formed to supply the zirconia to be diffused, the diffusion source having a thickness of at least 10 ⁇ m at least in the part covered by the suppressor electrode and 100 nm in the part protruding from the opening 5 It is formed to have the above thickness.
  • such a field emission type electron source is configured as an electron source of a charged particle beam device.
  • the diffusion of zirconia on the surface of the needle electrode of the field emission electron source becomes stable, and stable long-term emission becomes possible.
  • FIG. 2 is a view showing the shape of a diffusion source of Example 1; It is a figure which estimates consumption length of the zirconia diffusion source of the tip side of needlelike electrode 1.
  • FIG. 6 is a view showing the shape of a diffusion source of Example 2;
  • FIG. 7 is a view showing the shape of a diffusion source in Example 3; It is a figure which shows the whole structure of a scanning electron microscope.
  • FIG. 1A shows the entire configuration of a field emission type electron source 101.
  • the bottom of the needle electrode 1 is spot-welded with the tip of the single crystal tungsten rod sharpened sharply.
  • the tip 8 of the needle electrode 1 is the (100) plane of tungsten single crystal.
  • the tungsten needle electrode 1 around which the diffusion source 2 is formed is covered by a suppressor electrode 4.
  • the suppressor electrode 4 is an inverted cup-type structure with a circular opening 5 at the center of the cup bottom.
  • the tip portion of the tungsten needle-like electrode 1 is fixed so as to protrude from the opening 5.
  • a diffusion source 2 is provided which extends to the side surface of the tip portion of the tungsten needle electrode 1 which protrudes from the opening 5 of the suppressor electrode 4.
  • the zirconia of the diffusion source is heated by the tungsten filament 3 to diffuse the surface of the needle-like electrode and lower the work function of the tip 8 of the needle-like electrode 1, but the diffusion also progresses simultaneously with evaporation. Therefore, when the zirconia is depleted, the field emission electron source can not emit electrons and has a lifetime. That is, the diffusion source needs a volume (amount) according to the life.
  • FIG. 4 shows the relation between the consumption length per unit time and the consumption volume with respect to the thickness of zirconia of the diffusion source. The graph in FIG. 4 is obtained by experimentally accelerating and evaluating the consumption of zirconia of the diffusion source by heating the needle electrode to 2000 K, which is 200 K to 300 K higher than the normal use temperature.
  • the normal use temperature is measured by measuring the ratio R of the amount of gas released at the time of heating at the normal use temperature (1700 K to 1800 K) and at the time of 2000 K heating, heating time h and consumption volume ⁇ V (total volume V).
  • the consumption length per unit time increases when the thickness is thinner than 10 ⁇ m, whereas it tends to converge to a constant value when the thickness exceeds 10 ⁇ m.
  • the consumption volume per unit time increases in proportion to the thickness.
  • the thickness of the diffusion source zirconia is set to 10 ⁇ m and adjust the lifetime by the length.
  • the lifetime can be easily controlled by setting the thickness of the entire zirconia to 10 ⁇ m, but if the diffused source located in the portion protruding from the opening of the suppressor electrode has an excessive level difference or unevenness, it may cause an electric discharge. Therefore, it is desirable that the diffusion source located outside the suppressor be gradually thinner from the opening to the tip of the suppressor electrode.
  • the shape of the diffusion source of Example 1 is shown in FIG.
  • the diffusion source 9 is formed using inkjet technology.
  • the diffusion source 9 is formed by dispersing zirconia particles in a liquid of 5 to 10 pl and applying it on the side surface of the needle electrode 1 with an ink jet coater.
  • the liquid in which the zirconia particles are dispersed may be either an organic solvent or an inorganic solvent.
  • the interval and the number of times of application of the zirconia dispersion are controlled so that they can be formed smoothly and thinly.
  • the application of zirconia by inkjet is easy in controlling the thickness and is excellent in that surface irregularities can be formed less.
  • the zirconia coating start position is a position 100 ⁇ m away from the tip 8 so as not to be affected by polishing for sharpening the tip of the needle electrode 1. It should be noted that in consideration of manufacturing errors and the like, the position may be 100 ⁇ 50 ⁇ m away from the tip. If zirconia is generally thinly applied as the diffusion source 9, the diffusion source will evaporate and be depleted in a short period of time, so long-term stable emission can not be obtained. For this reason, it is desirable that the thickness be at least 10 ⁇ m at a portion sufficiently away from the tip.
  • the length of the diffusion source 9 located outside the suppressor electrode 4 is 150 ⁇ m.
  • the diffusion source 9 having a length of 150 ⁇ m is thinly applied so as not to cause unevenness.
  • the thickness of the diffusion source 9 in the portion covered by the suppressor electrode 4 is gradually increased so as to be 10 ⁇ m or more.
  • the zirconia is sintered on the side of the needle electrode 1 by heating in vacuum after application.
  • the application of zirconia by inkjet is characterized in that surface irregularities can be reduced.
  • mechanical polishing and laser annealing are used. You may process which makes the surface smooth.
  • the diffusion source located in the portion projecting from the opening 5 of the suppressor electrode 4 needs a certain thickness.
  • the amount of zirconia lost by the action of diffusion, evaporation, and the like is larger than the amount of zirconia supplied from the diffusion source at the rear (filament side). If the diffusion distance L between the tip of the source and the tip of the needle electrode is increased, the effect is reduced. For this reason, it is necessary to have a thickness that can suppress the retraction of the tip of the diffusion source to some extent.
  • FIG. 6 shows the estimation of the length of zirconia consumed on the tip end of the needle electrode during continuous emission at 1700K.
  • the thickness of the diffusion source 9 located in the portion of the suppressor electrode 4 which protrudes from the opening 5 is preferably 100 nm or more, preferably 1 ⁇ m or more.
  • the inside diameter of the opening 5 of the suppressor electrode 4 is It is designed to be at least twice as large as the diameter of the tungsten needle electrode 1.
  • Such positional relationship with the opening 5 is a factor that restricts the thickness of the diffusion source 9.
  • the field emission type electron source thus configured is installed in the electron gun shown in FIG.
  • the electron source 101 is heated to a predetermined temperature by the heating power supply 108 and a predetermined voltage is applied to the extraction electrode 103 and the suppressor electrode 4 to apply an electric field to the tip of the needle electrode 1, continuation of normal electron emission confirmed. Also, there were no protrusions or cracks that would cause the electric field to concentrate on the zirconia surface.
  • the diffusion source 9 is formed by applying zirconia to the vicinity of the tip 8 of the tungsten needle electrode 1.
  • the angle and distance of the ink jet outlet are controlled so that zirconia can be applied thinly and uniformly to the pointed portion of the tip.
  • the angle and the distance of the tungsten needle electrode 1 itself may be adjusted. Apply so as to have a gentle roundness so that there is no step due to a sudden change in thickness.
  • the portion covered by the suppressor electrode should have a thickness of 10 ⁇ m or more so that the zirconia of the diffusion source is not depleted.
  • Zirconia was applied to the tips 8 of the plurality of tungsten needle electrodes 1 and the shape of the zirconia after heating and sintering was observed. As a result, there were no protrusions or cracks that would concentrate the electric field on the surface of the zirconia. Also, the variation of the amount of sintered zirconia was within 2%. As described above, in the case of the application by the ink jet, the film thickness control can be performed with high accuracy as compared with the prior art.
  • the tip of the tungsten needle electrode 1 protrudes from the opening 5 of the suppressor electrode 4, but in the protruding part, zirconia having a smooth surface on all surfaces except for the tip 8.
  • the electron gun was set up and evaluated, and it was found that a field emission type electron source having stable diffusion can be manufactured with good reproducibility.
  • FIG. 8 Yet another form of the diffusion source is shown in FIG. 8 to illustrate the method of formation.
  • Example 3 a portion other than the tip 8 of the tungsten needle electrode 1 is covered with a zirconia thin film.
  • a zirconia thin film 10a of about 10 to 100 nm is formed on the whole by using a vacuum evaporation method on the insulator, the conductive terminal, the heating filament 3 connected thereto, and the tungsten needle electrode 1. At this time, zirconia is prevented from being formed on the tungsten crystal face (100) of the tip 8.
  • the zirconia at the tip may be removed by etching.
  • the zirconia 10b serving as a diffusion source is made 10 ⁇ m or more thick by ink jet technology or dripping dispersion.
  • the needle electrode 1 is applied to the side surface. This prevents premature depletion of the zirconia of the diffusion source.
  • the zirconia 10 b is sintered on the side of the needle electrode 1 by heating in a vacuum.
  • the tip of the tungsten needle-like electrode 1 protrudes from the opening 5 of the suppressor electrode 4, but a zirconia thin film 10a having a smooth surface deposited is present in the protruding part. .
  • a field emission type electron source whose diffusion is stable can be manufactured.
  • the electron gun 100 includes the field emission type electron source 101, the extraction electrode 103 and the acceleration electrode 104 described as the first to third embodiments. The details are as shown in FIG.
  • the electron beam 131 emitted from the electron gun 100 passes through the first condenser lens 112 and the second condenser lens 113, and is irradiated by the objective lens 116 so as to form an image on the sample 117 held on the stage 118.
  • the objective lens 116 may be an electric field lens, a magnetic field lens, or an electric field magnetic field superposition lens.
  • an aligner 111 for controlling the beam axis of the electron beam 131 is disposed at the rear stage of the electron gun 100.
  • the present invention can also be applied to reflected electrons reflected in front of the sample, backscattered electrons generated from the inside of the sample, secondary electrons and tertiary electrons generated by the reflector and the like. . And in order to detect these electrons resulting from irradiation of an electron beam, detector 121 or detector 120 can change a kind and arrangement suitably.
  • a high quality image can be stably obtained by applying an electric field emission electron source whose emission characteristics according to the present embodiment are stable over a long period of time.
  • the present invention is not limited to an embodiment, and can be variously changed in the range which does not deviate from the gist.
  • the diffusion source is not limited to zirconia, and any of compounds and oxides of metal elements selected from Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, and lanthanoid series groups.
  • two or more elements may be freely combined.

Abstract

Provided are: a field emission-type electron source with which the influence of an electric field can be suppressed and stable long-term emission characteristics can be obtained even when a diffusion supply source is disposed close to the tip of a needle-like electrode; and a charged particle beam device using the same. According to the present invention, a suppressor electrode 4 is disposed to cover a filament 3 and the needle-like electrode 1 excluding a portion, of the needle-like electrode 1, protruding from an opening part 5 of the suppressor electrode 4, and a diffusion supply source 9 for supplying zirconia that is diffused onto the surface of the needle-like electrode 1 is formed around the needle-like electrode 1, wherein the diffusion supply source 9 has a thickness of 10 μm or more in at least the portion covered by the suppressor electrode 4, and has a thickness of 100 nm or more in the portion protruding from the opening part 5.

Description

電界放出型電子源および荷電粒子線装置Field emission type electron source and charged particle beam device
　本発明は、電界放出型電子源およびそれを用いた荷電粒子線装置に関する。 The present invention relates to a field emission type electron source and a charged particle beam apparatus using the same.
　走査型電子顕微鏡（ＳＥＭ：Scanning Electron Microscope）や透過型電子顕微鏡（ＴＥＭ：Transmission Electron Microscope）は、電子銃から放出される電子線を加速し、電子レンズにより細い電子ビームとし、これを一次電子ビームとして走査偏向器を用いて試料上を走査する。ＳＥＭであれば得られる二次電子あるいは反射電子を検出して像を得、ＴＥＭであれば、試料を透過した電子を検出して像を得る。 A scanning electron microscope (SEM: Scanning Electron Microscope) or a transmission electron microscope (TEM: Transmission Electron Microscope) accelerates an electron beam emitted from an electron gun and converts the electron beam into a thin electron beam, which is used as a primary electron beam. The scanning deflector is used to scan over the sample. In the case of SEM, an image is obtained by detecting secondary electrons or reflected electrons obtained to obtain an image, and in the case of TEM, an image is obtained by detecting electrons transmitted through a sample.
　これら電子顕微鏡の電子銃には電界型放出電子源が一般的に用いられている。電界放出型電子源には大きく分けて冷陰極電界放出型電子源と熱陰極電界放出型電子源とがある。冷陰極電界放出型電子源は、単結晶タングステン線材の先端を尖らせた針状電極の先端に電場を与えて電子を放出させる。熱陰極電界放出型電子源は、単結晶タングステン線材の先端を尖らせた針状電極の側面に、例えばジルコニアを付着させ、加熱した状態で針先端に電場を与えて電子を放出させる。この熱陰極電界放出型電子源はショットキー電子源とも呼ばれる。 A field emission electron source is generally used for the electron gun of these electron microscopes. Field emission type electron sources are roughly classified into cold cathode field emission type electron sources and hot cathode field emission type electron sources. The cold cathode field emission electron source applies an electric field to the tip of a needle-like electrode having a tip of a single crystal tungsten wire sharpened to emit electrons. For example, zirconia is attached to the side surface of the needle-like electrode having the tip of the single-crystal tungsten wire pointed at the tip of the single-crystal tungsten wire, and an electric field is applied to the tip of the needle in a heated state to emit electrons. This hot cathode field emission electron source is also called a Schottky electron source.
　ショットキー電子源は、タングステン結晶面（１００）上にジルコニウム、酸素を熱拡散により供給することにより、仕事関数の低い領域を形成する。加熱温度は１６００Ｋ～１９００Ｋ程度、通常は１７００Ｋ～１８００Ｋで使用する。タングステン針先端に結晶面（１００）を設け、強電場を印加することにより、ポテンシャル障壁を越える熱電子とトンネル効果によって透過する電子を取り出す。 The Schottky electron source forms a low work function region by supplying zirconium and oxygen by thermal diffusion on a tungsten crystal face (100). The heating temperature is about 1600 K to 1900 K, usually 1700 K to 1800 K. A crystal face (100) is provided at the tip of a tungsten needle, and a strong electric field is applied to take out thermoelectrons passing the potential barrier and electrons transmitted by tunneling.
　ショットキー電子源は、単結晶タングステンの結晶方位（１００）を先端にした針状電極が加熱用タングステンフィラメントにスポット溶接して固定されている。針状電極は拡散供給源であるジルコニアを備えている。この拡散供給源は、針の先端側から見ると針の周囲に成形されている。 In the Schottky electron source, a needle-like electrode whose tip is a crystal orientation (100) of single crystal tungsten is fixed by spot welding to a heating tungsten filament. The needle electrode is provided with zirconia which is a diffusion source. The diffusion source is molded around the needle when viewed from the tip of the needle.
　特許文献１には、拡散供給源の成形に、水素化ジルコニウム微粒子を有機溶剤に混ぜた液を刷毛でタングステン針の側周部に付着させ、真空加熱して焼結する方法が開示されている。特許文献２には、拡散供給源に酸化スカンジウムを用いて単結晶タングステン先端（１００）面の仕事関数を減少させ、低温度で動作させることを開示している。拡散供給源の成形には、酸化スカンジウム粉末を有機溶媒等に混合してスラリー状にして付着させる、あるいは蒸着させることが開示されている。特許文献３には、拡散供給源であるジルコニアの厚さと長さとを制御することにより、実用的に安定した寿命が得られることが開示されている。 Patent Document 1 discloses a method of forming a diffusion source by forming a solution in which zirconium hydride fine particles are mixed in an organic solvent with a brush and adhering it to the side circumference of a tungsten needle and vacuum heating for sintering. . U.S. Pat. No. 5,959,095 discloses using scandium oxide as the diffusion source to reduce the work function of a single crystal tungsten tip (100) surface to operate at low temperatures. For forming the diffusion source, it is disclosed that scandium oxide powder is mixed with an organic solvent or the like to form a slurry and to be attached or vapor deposited. Patent Document 3 discloses that a practically stable life can be obtained by controlling the thickness and length of zirconia as a diffusion source.
　また、非特許文献１には、ジルコニア拡散による仕事関数の選択的低下メカニズムに関し、表面分析手法をもちいたショットキー電子源の構造や組成の解明が試みられている。 In addition, Non-Patent Document 1 is trying to elucidate the structure and composition of a Schottky electron source using a surface analysis method with respect to the selective lowering mechanism of the work function due to zirconia diffusion.
特開平６－７６７３１号公報Japanese Patent Application Laid-Open No. 6-76731 特開平１０－３１９５５号公報Japanese Patent Application Laid-Open No. 10-31955 特開２０１３－８４５５０号公報JP, 2013-84550, A
　拡散供給源のジルコニアが加熱されて単結晶タングステン線材の表面を拡散することにより、針状電極先端のタングステン結晶面（１００）の仕事関数が4.5ｅＶから約2.8ｅＶに低下する。エミッション中にジルコニアの拡散不良が生じると、タングステン針先端の結晶面の状態が変化し、電子放出特性の劣化が不定期に発生する。また、その劣化の発生する頻度には個体差もある。安定した電子放出特性を得るためには、針状電極先端の仕事関数の低い領域を保つ必要があるが、このためにはジルコニアが単結晶タングステン線材表面に安定して拡散される必要がある。 As the zirconia of the diffusion source is heated and diffused on the surface of the single crystal tungsten wire, the work function of the tungsten crystal face (100) at the tip of the needle-like electrode is lowered from 4.5 eV to about 2.8 eV. When the diffusion failure of zirconia occurs during emission, the state of the crystal plane at the tip of the tungsten needle changes, and the electron emission characteristics deteriorate irregularly. In addition, there are individual differences in the frequency of occurrence of the deterioration. In order to obtain stable electron emission characteristics, it is necessary to maintain a low work function region of the tip of the needle electrode, but for this purpose, zirconia needs to be stably diffused to the surface of the single crystal tungsten wire.
　物質が表面拡散するときの拡散物質の表面被覆率と拡散距離との関係は（数１）にて表わされる。ここで、ｋ：拡散係数、Ｋ：蒸発係数、Ｃ：表面被覆率、ｘ：拡散距離である。 The relationship between the surface coverage of the diffusion substance and the diffusion distance when the substance diffuses on the surface is expressed by (Equation 1). Here, k: diffusion coefficient, K: evaporation coefficient, C: surface coverage, x: diffusion distance.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
　ｘ（拡散距離）＝０のとき、Ｃ（表面被覆率）＝１とすると、（数２）の関係が成立する。 Assuming that C (surface coverage) = 1 when x (diffusion distance) = 0, the relationship of (Equation 2) is established.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
　（数２）より拡散距離ｘが増加するほど、蒸発の影響を受け表面被覆率が減少することがわかる。これを実験により確認した。図２は、電界放出型電子源のジルコニアの焼結位置を変更して作製し、拡散不良率を従来（点２０）との比較で示したものである。ジルコニアの焼結位置をより先端に近く配置して針状電極先端までの拡散距離Ｌが短くなるほど拡散不良が減少し、安定したエミッション特性が得られることがわかる。図中の点線はこれらの実験結果から拡散距離Ｌと拡散不良との関係を推定したものであり、拡散距離Ｌが短くなるよう、拡散供給源を針状電極の先端により近い場所に配置するほどエミッション特性が安定することを示している。 From equation (2), it can be seen that as the diffusion distance x increases, the surface coverage decreases due to the influence of evaporation. This was confirmed by experiment. FIG. 2 is manufactured by changing the sintering position of zirconia of the field emission type electron source, and shows the diffusion failure rate in comparison with the conventional case (point 20). It can be seen that, as the sintering position of zirconia is closer to the tip and the diffusion distance L to the tip of the needle electrode becomes shorter, the diffusion failure decreases and stable emission characteristics can be obtained. The dotted lines in the figure estimate the relationship between the diffusion distance L and the diffusion failure from these experimental results, and the diffusion source is placed closer to the tip of the needle electrode so that the diffusion distance L becomes shorter. It shows that the emission characteristics are stable.
　図３にショットキー電子源を搭載した電子銃の模式図を示す。電子源１０１はタングステン針状電極１、フィラメント３、サプレッサ電極４を有する。タングステン針状電極１はフィラメント３に固定されている。タングステン針状電極１の周囲にはエミッション中にジルコニアをタングステン針状電極１の先端に供給する拡散供給源２が形成されている。タングステン針状電極１の先端がサプレッサ電極開口部５から突出しているのを除いては、フィラメント３およびタングステン針状電極１はサプレッサ電極４に覆われている。フィラメント３は加熱電源１０８により加熱され、拡散供給源２からジルコニアがタングステン針状電極１の先端（エミッタ）まで拡散供給される。引出電極１０３には引出電極電源１０５から正電圧が印加され、タングステン針状電極１の先端（エミッタ）から熱電子が引き出される。引き出された電子は、加速電極電源１０７により正電圧が印加された加速電極１０４により加速される。一方、サプレッサ電極４はタングステン針状電極１の先端（エミッタ）より放出される熱電子を遮蔽するため、バイアス電源１０６により負電圧が印加されている。 FIG. 3 shows a schematic view of an electron gun mounted with a Schottky electron source. The electron source 101 has a tungsten needle electrode 1, a filament 3 and a suppressor electrode 4. The tungsten needle electrode 1 is fixed to the filament 3. A diffusion source 2 is formed around the tungsten needle electrode 1 to supply zirconia to the tip of the tungsten needle electrode 1 during emission. The filament 3 and the tungsten needle electrode 1 are covered with the suppressor electrode 4 except that the tip of the tungsten needle electrode 1 protrudes from the suppressor electrode opening 5. The filament 3 is heated by a heating power source 108, and zirconia is diffused and supplied from the diffusion source 2 to the tip (emitter) of the tungsten needle electrode 1. A positive voltage is applied to the extraction electrode 103 from the extraction electrode power supply 105, and the thermal electrons are extracted from the tip (emitter) of the tungsten needle-like electrode 1. The extracted electrons are accelerated by the accelerating electrode 104 to which a positive voltage is applied by the accelerating electrode power supply 107. On the other hand, in order to shield the thermoelectrons emitted from the tip (emitter) of the tungsten needle electrode 1, a negative voltage is applied by the bias power supply 106.
　このようにショットキー電子源を搭載した電子銃では、タングステン針状電極１の先端は引出電極１０３とサプレッサ電極４の間に配置されるため、針状電極１の先端付近には強い電場がかかっている。拡散供給源２を針状電極１の先端付近に配置すると、拡散供給源２はこの電場の影響を受けることになる。 Thus, in the electron gun on which the Schottky electron source is mounted, the tip of the tungsten needle electrode 1 is disposed between the extraction electrode 103 and the suppressor electrode 4, so a strong electric field is applied near the tip of the needle electrode 1. ing. When the diffusion source 2 is disposed near the tip of the needle electrode 1, the diffusion source 2 is affected by this electric field.
　従来、拡散供給源の製法としては、粘度をもった有機溶剤に混ぜたジルコニア粒子液を刷毛やスポイトで滴下して付着させた後に焼結して作製することが一般的であった。このため、液中の粒子は均一に分散されず、真空中で焼結した後には表面凹凸やクラックが生じやすい。この凸部やクラック端に電界が集中すると、針の先端以外からの電子放出が生じやすくなり放電の要因になる。このため、拡散供給源を電場の影響を受けないサプレッサ電極内に収まるように配置している。一般的な電界放出型電子源のタングステン針状電極はサプレッサ電極から２５０μｍ突き出す形で構成されているため、針先端からジルコニアまでの距離は最短でも２５０μｍあった。 Heretofore, as a process for producing a diffusion source, it has been common to prepare a zirconia particle liquid mixed with an organic solvent having viscosity by dropping it with a brush or a dropper and then sintering it. For this reason, the particles in the solution are not uniformly dispersed, and surface unevenness and cracks are likely to occur after sintering in vacuum. When the electric field is concentrated on the convex portion or the crack end, electron emission from other than the tip of the needle is easily generated, which becomes a factor of discharge. For this reason, the diffusion source is arranged to be contained in the suppressor electrode which is not affected by the electric field. Since the tungsten needle electrode of a general field emission electron source is configured to protrude 250 μm from the suppressor electrode, the distance from the tip of the needle to the zirconia was at least 250 μm.
　本発明は、拡散供給源を針状電極の先端により近くに配置しても電場の影響を抑え、安定した長期エミッション特性が得られる電界放出型電子源およびそれを用いた荷電粒子線装置を提供することにある。 The present invention provides a field emission electron source that can suppress the influence of an electric field and obtain stable long-term emission characteristics even when a diffusion source is disposed closer to the tip of a needle electrode, and a charged particle beam device using the same. It is to do.
　サプレッサ電極の開口部より突き出した針状電極の部分を除いて、フィラメント及び針状電極を覆うようにサプレッサ電極が配置される電界放出型電子源において、針状電極の周りには、その表面に拡散されるジルコニアを供給する拡散供給源が形成されており、拡散供給源は、少なくともサプレッサ電極に覆われた部分においては１０μｍ以上の厚さを有し、開口部５より突き出した部分においては１００ｎｍ以上の厚さを有するように形成する。また、かかる電界放出型電子源を荷電粒子線装置の電子源として構成する。 In a field emission electron source in which a suppressor electrode is disposed so as to cover the filament and the needle electrode except for the portion of the needle electrode protruding from the opening of the suppressor electrode, around the needle electrode, on the surface thereof A diffusion source is formed to supply the zirconia to be diffused, the diffusion source having a thickness of at least 10 μm at least in the part covered by the suppressor electrode and 100 nm in the part protruding from the opening 5 It is formed to have the above thickness. Further, such a field emission type electron source is configured as an electron source of a charged particle beam device.
　電界放出型電子源の針状電極表面でのジルコニアの拡散が安定し、安定した長期エミッションが可能になる。 The diffusion of zirconia on the surface of the needle electrode of the field emission electron source becomes stable, and stable long-term emission becomes possible.
電界放出型電子源の全体構成を表す図である。It is a figure showing the whole structure of a field emission type electron source. 針状電極の先端を表す図である。It is a figure showing the tip of a needlelike electrode. 拡散距離と拡散不良との関係を表す実験結果である。It is an experimental result showing the relation between diffusion distance and diffusion failure. 電界放出型電子源を搭載する電子銃の模式図である。It is a schematic diagram of the electron gun carrying a field emission type electron source. ジルコニア拡散源の厚さと消費長さ及び消費容積との関係を示す実験結果である。It is an experimental result which shows the relationship between the thickness of a zirconia diffusion source, consumption length, and consumption volume. 実施例１の拡散供給源の形状を示す図である。FIG. 2 is a view showing the shape of a diffusion source of Example 1; 針状電極１の先端側のジルコニア拡散源の消費長さを推定する図である。It is a figure which estimates consumption length of the zirconia diffusion source of the tip side of needlelike electrode 1. FIG. 実施例２の拡散供給源の形状を示す図である。FIG. 6 is a view showing the shape of a diffusion source of Example 2; 実施例３の拡散供給源の形状を示す図である。FIG. 7 is a view showing the shape of a diffusion source in Example 3; 走査電子顕微鏡の全体構成を示す図である。It is a figure which shows the whole structure of a scanning electron microscope.
　以下、本発明の実施の形態を図面に基づいて詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail based on the drawings.
　図１Ａに電界放出型電子源１０１の全体構成を示す。絶縁碍子７に２本の固定された導電端子６があり、加熱用フィラメント３（タングステンフィラメント）の両端部付近がスポット溶接されている。湾曲させたフィラメント中央部には単結晶タングステン棒の先端を鋭く尖らせた針状電極１の底部がスポット溶接される。図１Ｂに示すように、針状電極１の先端８は、タングステン単結晶の（１００）面となっている。 FIG. 1A shows the entire configuration of a field emission type electron source 101. There are two fixed conductive terminals 6 in the insulator 7, and spot welding is performed in the vicinity of both ends of the heating filament 3 (tungsten filament). At the center of the curved filament, the bottom of the needle electrode 1 is spot-welded with the tip of the single crystal tungsten rod sharpened sharply. As shown in FIG. 1B, the tip 8 of the needle electrode 1 is the (100) plane of tungsten single crystal.
　拡散供給源２がその周囲に形成されたタングステン針状電極１はサプレッサ電極４により覆われている。サプレッサ電極４は、逆向きのカップ型構造でカップ底の中央部分に円形の開口部５がある。この開口部５からタングステン針状電極１の先端部分が突き出すように固定される。本実施例においては、タングステン針状電極１のサプレッサ電極４の開口部５から突き出した先端部分の側面にまで延伸する拡散供給源２を設ける。 The tungsten needle electrode 1 around which the diffusion source 2 is formed is covered by a suppressor electrode 4. The suppressor electrode 4 is an inverted cup-type structure with a circular opening 5 at the center of the cup bottom. The tip portion of the tungsten needle-like electrode 1 is fixed so as to protrude from the opening 5. In the present embodiment, a diffusion source 2 is provided which extends to the side surface of the tip portion of the tungsten needle electrode 1 which protrudes from the opening 5 of the suppressor electrode 4.
　拡散供給源のジルコニアはタングステンフィラメント３により加熱されることで針状電極表面を拡散し、針状電極１の先端８の仕事関数を下げるが、拡散と同時に蒸発も進行する。このため、ジルコニアが枯渇した時点で、この電界放出型電子源は電子を放出できなくなり寿命となる。すなわち、拡散供給源は、寿命に応じた容積（量）が必要である。図４に、拡散供給源のジルコニアの厚みに対する単位時間当たりの消費長さ、消費容積との関係を示す。図４のグラフは、通常使用温度よりも２００Ｋ～３００Ｋ高い２０００Ｋに針状電極を加熱して拡散供給源のジルコニアの消費状況を実験的に加速評価したものである。この評価では、加熱時間ｈと消耗容積ΔＶ（全容積Ｖ）、通常使用温度（１７００Ｋ～１８００Ｋ）での加熱時及び２０００Ｋ加熱時に放出するガス量の比Ｒをそれぞれ測定することで、通常使用温度での加熱時の寿命Ｔを、Ｔ＝Ｖ／ΔＶ×ｈ×Ｒにより推定することができる。 The zirconia of the diffusion source is heated by the tungsten filament 3 to diffuse the surface of the needle-like electrode and lower the work function of the tip 8 of the needle-like electrode 1, but the diffusion also progresses simultaneously with evaporation. Therefore, when the zirconia is depleted, the field emission electron source can not emit electrons and has a lifetime. That is, the diffusion source needs a volume (amount) according to the life. FIG. 4 shows the relation between the consumption length per unit time and the consumption volume with respect to the thickness of zirconia of the diffusion source. The graph in FIG. 4 is obtained by experimentally accelerating and evaluating the consumption of zirconia of the diffusion source by heating the needle electrode to 2000 K, which is 200 K to 300 K higher than the normal use temperature. In this evaluation, the normal use temperature is measured by measuring the ratio R of the amount of gas released at the time of heating at the normal use temperature (1700 K to 1800 K) and at the time of 2000 K heating, heating time h and consumption volume ΔV (total volume V). The life T at the time of heating at can be estimated by T = V / ΔV × h × R.
　グラフ４１に示されるように、単位時間あたりの消費長さは厚みが１０μｍより薄いと増加するのに対し、厚みが１０μｍを越えると一定値に収束する傾向にあることが分かる。一方、単位時間当たりの消費容積は、厚みに比例して増加する。 As shown in the graph 41, the consumption length per unit time increases when the thickness is thinner than 10 μm, whereas it tends to converge to a constant value when the thickness exceeds 10 μm. On the other hand, the consumption volume per unit time increases in proportion to the thickness.
　これにより、電子源の寿命を考える場合、拡散供給源のジルコニアの厚みを１０μｍとし、長さでその寿命を調節することが可能である。ジルコニア全体の厚みを１０μｍにすることで寿命が管理しやすいが、サプレッサ電極の開口部より突出した部分に位置する拡散供給源に極端な段差や凹凸があると放電の原因になりかねない。そこで、サプレッサ外に位置する拡散供給源は、サプレッサ電極の開口部から先端に向けて徐々に薄くなることが望ましい。 Thereby, when considering the lifetime of the electron source, it is possible to set the thickness of the diffusion source zirconia to 10 μm and adjust the lifetime by the length. The lifetime can be easily controlled by setting the thickness of the entire zirconia to 10 μm, but if the diffused source located in the portion protruding from the opening of the suppressor electrode has an excessive level difference or unevenness, it may cause an electric discharge. Therefore, it is desirable that the diffusion source located outside the suppressor be gradually thinner from the opening to the tip of the suppressor electrode.
　実施例１の拡散供給源の形状を図５に示す。拡散供給源９はインクジェット技術を用いて形成する。拡散供給源９は、ジルコニア粒子を５～１０ｐｌの液体中に分散させ、インクジェット式塗布機にて針状電極１の側面に塗布することで形成する。ジルコニア粒子を分散させる液体は、有機溶剤、無機溶剤のいずれであってもよい。先端により近い部分は、滑らかに薄く形成できるよう、ジルコニア分散液が吐出する間隔と塗布回数を制御する。インクジェットによるジルコニア塗布は厚さのコントロールが容易に行え、表面の凹凸を少なく形成できる点で優れている。 The shape of the diffusion source of Example 1 is shown in FIG. The diffusion source 9 is formed using inkjet technology. The diffusion source 9 is formed by dispersing zirconia particles in a liquid of 5 to 10 pl and applying it on the side surface of the needle electrode 1 with an ink jet coater. The liquid in which the zirconia particles are dispersed may be either an organic solvent or an inorganic solvent. In the portion closer to the front end, the interval and the number of times of application of the zirconia dispersion are controlled so that they can be formed smoothly and thinly. The application of zirconia by inkjet is easy in controlling the thickness and is excellent in that surface irregularities can be formed less.
　ジルコニア塗布開始位置は、針状電極１の先端を尖らせるための研磨の影響を受けないよう、先端８から１００μｍ離れた位置とする。なお、製造誤差等を考慮すると、先端から１００±５０μｍ離れた位置とすればよい。拡散供給源９としてジルコニアを全体的に薄く塗布すると、短期間で拡散供給源が蒸発し枯渇してしまうため、長期安定したエミッションが出来ない。このため、先端から充分に離れた部分においては、最低でも１０μｍの厚さにしたい。先端から１００μｍ離れた位置から塗布を開始した場合、サプレッサ電極４外に位置する拡散供給源９の長さは１５０μｍとなる。この１５０μｍの長さの拡散供給源９は、凹凸が生じないように薄く塗布する。一方、サプレッサ電極４で覆われる部分の拡散供給源９の厚さは、１０μｍ以上になるよう厚さを徐々に増加させる。 The zirconia coating start position is a position 100 μm away from the tip 8 so as not to be affected by polishing for sharpening the tip of the needle electrode 1. It should be noted that in consideration of manufacturing errors and the like, the position may be 100 ± 50 μm away from the tip. If zirconia is generally thinly applied as the diffusion source 9, the diffusion source will evaporate and be depleted in a short period of time, so long-term stable emission can not be obtained. For this reason, it is desirable that the thickness be at least 10 μm at a portion sufficiently away from the tip. When application is started from a position 100 μm away from the tip, the length of the diffusion source 9 located outside the suppressor electrode 4 is 150 μm. The diffusion source 9 having a length of 150 μm is thinly applied so as not to cause unevenness. On the other hand, the thickness of the diffusion source 9 in the portion covered by the suppressor electrode 4 is gradually increased so as to be 10 μm or more.
　塗布した後に真空中で加熱することでジルコニアが針状電極１側面に焼結される。インクジェットによるジルコニア塗布は表面の凹凸を少なくできるのが特徴であるが、焼結後のジルコニアの表面に放電が回避できないような凸部が確認された場合は、機械研磨およびレーザアニール法を用いてその表面を滑らかにする加工を施してもよい。 The zirconia is sintered on the side of the needle electrode 1 by heating in vacuum after application. The application of zirconia by inkjet is characterized in that surface irregularities can be reduced. However, when projections are found on the surface of the sintered zirconia that discharge can not be avoided, mechanical polishing and laser annealing are used. You may process which makes the surface smooth.
　サプレッサ電極４の開口部５より突出した部分に位置する拡散供給源にはある程度の厚みが必要である。針状電極１の先端側の拡散供給源の厚みによっては、後部（フィラメント側）の拡散供給源から供給されるジルコニア量よりも拡散、蒸発等の作用により失われるジルコニア量が勝ってしまい、拡散供給源の先端と針状電極先端との間の拡散距離Ｌが伸びてしまっては効果が低減する。このため、拡散供給源の先端の後退をある程度抑えられる程度の厚さを有する必要がある。図６は１７００Ｋで連続エミッション時における、針状電極先端側のジルコニア消費長さを推定したものである。図４の元となったジルコニア消費加速試験の実測値から換算したものである。針状電極１の先端は加熱源（フィラメント）から遠く、かつ後部からジルコニアが供給されるため、拡散供給源９の厚さが比較的薄くても消費長さが著しく低減することはないことが分かる。サプレッサ電極４の開口部５より突出した部分に位置する拡散供給源９の厚みは、１００ｎｍ以上、望ましくは１μｍ以上とすることが望ましい。 The diffusion source located in the portion projecting from the opening 5 of the suppressor electrode 4 needs a certain thickness. Depending on the thickness of the diffusion source on the tip side of the needle electrode 1, the amount of zirconia lost by the action of diffusion, evaporation, and the like is larger than the amount of zirconia supplied from the diffusion source at the rear (filament side). If the diffusion distance L between the tip of the source and the tip of the needle electrode is increased, the effect is reduced. For this reason, it is necessary to have a thickness that can suppress the retraction of the tip of the diffusion source to some extent. FIG. 6 shows the estimation of the length of zirconia consumed on the tip end of the needle electrode during continuous emission at 1700K. It is converted from the actual measurement value of the zirconia consumption accelerated test which became the origin of FIG. Since the tip of the needle electrode 1 is far from the heating source (filament) and zirconia is supplied from the rear, the consumption length can not be significantly reduced even if the thickness of the diffusion source 9 is relatively thin I understand. The thickness of the diffusion source 9 located in the portion of the suppressor electrode 4 which protrudes from the opening 5 is preferably 100 nm or more, preferably 1 μm or more.
　この一方で、サプレッサ電極４の開口部５と、拡散供給源９が設けられたタングステン針状電極１が極端に近づく場合は放電のリスクがあるため、サプレッサ電極４の開口部５の内径は、タングステン針状電極１の直径に対し、少なくとも２倍以上となるように設計されている。このような開口部５との位置関係は拡散供給源９の厚みを制約する要因となる。 On the other hand, there is a risk of discharge when the opening 5 of the suppressor electrode 4 and the tungsten needle electrode 1 provided with the diffusion source 9 approach extremely, so the inside diameter of the opening 5 of the suppressor electrode 4 is It is designed to be at least twice as large as the diameter of the tungsten needle electrode 1. Such positional relationship with the opening 5 is a factor that restricts the thickness of the diffusion source 9.
　このように構成した電界放出型電子源を図３に示す電子銃に設置する。加熱電源１０８により電子源１０１を所定の温度に加熱し、引出し電極１０３とサプレッサ電極４に所定の電圧を印加して針状電極１の先端に電場をかけたところ、正常な電子放出の継続を確認した。また、ジルコニア表面に電界が集中するような凸部やクラックが生じることはなかった。 The field emission type electron source thus configured is installed in the electron gun shown in FIG. When the electron source 101 is heated to a predetermined temperature by the heating power supply 108 and a predetermined voltage is applied to the extraction electrode 103 and the suppressor electrode 4 to apply an electric field to the tip of the needle electrode 1, continuation of normal electron emission confirmed. Also, there were no protrusions or cracks that would cause the electric field to concentrate on the zirconia surface.
　実施例１と異なる拡散供給源９の形状を図７に示し、形成方法について説明する。実施例２では、タングステン針状電極１の先端８の近傍までジルコニアを塗布して拡散供給源９を形成する。先端の尖らせた部分にも薄く均一にジルコニアが塗布できるよう、インクジェットの吐出部の角度と距離を制御する。このとき、タングステン針状電極１自体の角度と距離を調節してもよい。急激な厚さの変化による段差が生じないように、緩やかな丸みがつくように塗布する。サプレッサ電極に覆われる部分は、拡散供給源のジルコニアが枯渇しないよう、１０μｍ以上の厚さになるようにする。複数のタングステン針状電極１の先端８にジルコニア塗布を行い、加熱焼結後のジルコニア形状を観察したところ、ジルコニア表面に電界が集中するような凸部やクラックが生じることはなかった。また、焼結したジルコニア量のばらつきは２％以内に収まった。このようにインクジェットによる塗布は、従来と比較して高精度な膜厚制御が可能である。 The shape of the diffusion source 9 different from that of the first embodiment is shown in FIG. 7, and the forming method will be described. In the second embodiment, the diffusion source 9 is formed by applying zirconia to the vicinity of the tip 8 of the tungsten needle electrode 1. The angle and distance of the ink jet outlet are controlled so that zirconia can be applied thinly and uniformly to the pointed portion of the tip. At this time, the angle and the distance of the tungsten needle electrode 1 itself may be adjusted. Apply so as to have a gentle roundness so that there is no step due to a sudden change in thickness. The portion covered by the suppressor electrode should have a thickness of 10 μm or more so that the zirconia of the diffusion source is not depleted. Zirconia was applied to the tips 8 of the plurality of tungsten needle electrodes 1 and the shape of the zirconia after heating and sintering was observed. As a result, there were no protrusions or cracks that would concentrate the electric field on the surface of the zirconia. Also, the variation of the amount of sintered zirconia was within 2%. As described above, in the case of the application by the ink jet, the film thickness control can be performed with high accuracy as compared with the prior art.
　図７に示すように、サプレッサ電極４の開口部５からタングステン針状電極１の先端部分が突き出す構造になるが、突き出した部分には、先端８を除く全ての面に滑らかな表面を持つジルコニアが存在する。電子銃に設置し、評価したところ、拡散が安定した電界放出型電子源が再現性よく作製できることがわかった。 As shown in FIG. 7, the tip of the tungsten needle electrode 1 protrudes from the opening 5 of the suppressor electrode 4, but in the protruding part, zirconia having a smooth surface on all surfaces except for the tip 8. Exists. The electron gun was set up and evaluated, and it was found that a field emission type electron source having stable diffusion can be manufactured with good reproducibility.
　さらに別の拡散供給源の形状を図８に示し、形成方法について説明する。実施例３では、タングステン針状電極１の先端８以外をジルコニア薄膜で覆う。まず、絶縁碍子及び導電端子、これに接続された加熱用フィラメント３及びタングステン針状電極１に真空蒸着装法を用いて１０～１００ｎｍ程度のジルコニア薄膜１０ａを全体に形成する。このとき、先端８のタングステン結晶面（１００）にジルコニアが成膜されないようにする。あるいは、全体を成膜してから、エッチングで先端のジルコニアを除去してもよい。 Yet another form of the diffusion source is shown in FIG. 8 to illustrate the method of formation. In Example 3, a portion other than the tip 8 of the tungsten needle electrode 1 is covered with a zirconia thin film. First, a zirconia thin film 10a of about 10 to 100 nm is formed on the whole by using a vacuum evaporation method on the insulator, the conductive terminal, the heating filament 3 connected thereto, and the tungsten needle electrode 1. At this time, zirconia is prevented from being formed on the tungsten crystal face (100) of the tip 8. Alternatively, after depositing the entire film, the zirconia at the tip may be removed by etching.
　次に、針状電極先端から２５０μｍ以上離れた位置（サプレッサ電極４で覆われる位置）に、拡散供給源となるジルコニア１０ｂをインクジェット技術または分散液の滴下によって、１０μｍ以上の厚さになるようタングステン針状電極１側面に塗布する。これにより、早期に拡散供給源のジルコニアが枯渇することを防ぐ。ジルコニア分散液を塗布した後、真空中で加熱することで、ジルコニア１０ｂを針状電極１側面に焼結させる。 Next, at a position separated by 250 μm or more from the tip of the needle electrode (the position covered by the suppressor electrode 4), the zirconia 10b serving as a diffusion source is made 10 μm or more thick by ink jet technology or dripping dispersion. The needle electrode 1 is applied to the side surface. This prevents premature depletion of the zirconia of the diffusion source. After applying the zirconia dispersion, the zirconia 10 b is sintered on the side of the needle electrode 1 by heating in a vacuum.
　図８に示すように、サプレッサ電極４の開口部５からタングステン針状電極１の先端部分が突き出す構造になるが、突き出した部分には、蒸着された滑らかな表面を持つジルコニア薄膜１０ａが存在する。これにより、拡散が安定した電界放出型電子源が作製できる。 As shown in FIG. 8, the tip of the tungsten needle-like electrode 1 protrudes from the opening 5 of the suppressor electrode 4, but a zirconia thin film 10a having a smooth surface deposited is present in the protruding part. . As a result, a field emission type electron source whose diffusion is stable can be manufactured.
　荷電粒子線装置の例として、本実施例の電界型放出電子源を搭載した走査電子顕微鏡の全体構成を図９に示す。電子銃１００は、実施例１～３として説明した電界放出型電子源１０１、引出電極１０３及び加速電極１０４とを含む。この詳細は図３に示す通りである。電子銃１００から放出される電子ビーム１３１は、第１コンデンサレンズ１１２、第２コンデンサレンズ１１３を通り、対物レンズ１１６によりステージ１１８に保持される試料１１７上に結像するように照射される。対物レンズ１１６は電場レンズでもよく、磁場レンズでもよく、電場磁場重畳レンズであってもよい。また、電子銃１００の後段には電子ビーム１３１のビーム軸を制御するためのアライナー１１１が配置されている。 As an example of the charged particle beam apparatus, the entire configuration of a scanning electron microscope equipped with the electric field emission electron source of the present embodiment is shown in FIG. The electron gun 100 includes the field emission type electron source 101, the extraction electrode 103 and the acceleration electrode 104 described as the first to third embodiments. The details are as shown in FIG. The electron beam 131 emitted from the electron gun 100 passes through the first condenser lens 112 and the second condenser lens 113, and is irradiated by the objective lens 116 so as to form an image on the sample 117 held on the stage 118. The objective lens 116 may be an electric field lens, a magnetic field lens, or an electric field magnetic field superposition lens. Further, an aligner 111 for controlling the beam axis of the electron beam 131 is disposed at the rear stage of the electron gun 100.
　電子ビーム１３１と試料１１７の物質との相互作用により、試料１１７の表面から２次電子が放出される。比較的エネルギーの小さい２次電子は試料付近に置かれた検出器１２１により検出され、比較的エネルギーの大きい２次電子は検出器１２０により検出される。電子ビーム１３１が第１走査偏向器１１４及び第２走査偏向器１１５により２次元に走査されることにより、検出器１２１または検出器１２０からの検出信号に基づき、試料の２次元画像を得ることが出来る。また、上記で説明した２次電子以外にも、試料の手前にて反射する反射電子や試料の内部から生じる後方散乱電子、２次電子が反射板やその他に当たり生じる３次電子などにも適用できる。そして、電子ビームの照射に起因するこれらの電子を検出するために、検出器１２１または検出器１２０は、種類や配置を適宜変更することができる。 Due to the interaction between the electron beam 131 and the substance of the sample 117, secondary electrons are emitted from the surface of the sample 117. The relatively low energy secondary electrons are detected by the detector 121 placed near the sample, and the relatively high energy secondary electrons are detected by the detector 120. A two-dimensional image of the sample is obtained based on the detection signal from the detector 121 or 120 by scanning the electron beam 131 two-dimensionally by the first scanning deflector 114 and the second scanning deflector 115 It can. In addition to the secondary electrons described above, the present invention can also be applied to reflected electrons reflected in front of the sample, backscattered electrons generated from the inside of the sample, secondary electrons and tertiary electrons generated by the reflector and the like. . And in order to detect these electrons resulting from irradiation of an electron beam, detector 121 or detector 120 can change a kind and arrangement suitably.
　これら走査電子顕微鏡の構成要素は鏡体１１０において高真空状態に保たれている。本実施例によるエミッション特性が長期にわたって安定な電界型放出電子源を適用することにより、高画質な像を安定して得ることができる。 The components of these scanning electron microscopes are maintained at a high vacuum in the mirror 110. A high quality image can be stably obtained by applying an electric field emission electron source whose emission characteristics according to the present embodiment are stable over a long period of time.
　以上、本発明者によってなされた発明を実施の形態に基づき具体的に説明したが、本発明は実施の形態に限定されるものではなく、その要旨を逸脱しない範囲で種々変更可能である。例えば、拡散供給源は、ジルコニアに限られるものではなく、Ｃａ、Ｓｒ、Ｂａ、Ｓｃ、Ｙ、Ｌａ、Ｔｉ、Ｚｒ、Ｈｆ、及びランタノイド系列群から選ばれた金属元素の化合物、酸化物のいずれでもよく、自在に２種類以上の元素を組み合わせてもよい。 As mentioned above, although the invention made by the present inventor was concretely explained based on an embodiment, the present invention is not limited to an embodiment, and can be variously changed in the range which does not deviate from the gist. For example, the diffusion source is not limited to zirconia, and any of compounds and oxides of metal elements selected from Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, and lanthanoid series groups. Alternatively, two or more elements may be freely combined.
１・・・タングステン針状電極、２，９・・・拡散供給源、３・・・フィラメント、４・・・サプレッサ電極、５・・・サプレッサ電極開口部、６・・・導電端子、７・・・絶縁碍子、８・・・タングステン針状電極先端、１０ａ・・・ジルコニア薄膜、１０ｂ・・・拡散供給源となるジルコニア、１０１・・・電子源、１０３・・・引出電極、１０４・・・加速電極、１０５・・・引出電極電源、１０６・・・バイアス電源、１０７・・・加速電極電源、１０８・・・加熱電源、１００・・・電子銃、１１０・・・鏡体、１１１・・・アライナー、１１２，１１３・・・コンデンサレンズ、１１４，１１５・・・走査偏向器、１１６・・・対物レンズ、１１７・・・試料、１１８・・・ステージ、１２０，１２１・・・検出器、１３１・・・電子ビーム（１次電子）、１３２，１３３・・・２次電子。 DESCRIPTION OF SYMBOLS 1 ... tungsten needle- like electrode 2, 9 ... diffused source, 3 ... filament, 4 ... suppressor electrode, 5 ... suppressor electrode opening part, 6 ... electroconductive terminal, 7 ... · · · Insulator, 8 · · · tungsten needle electrode tip, 10a · · · zirconia thin film, 10b · · · · zirconia as a diffusion source, 101 · · · electron source, 103 · · · extraction electrode, 104 · · · Acceleration electrode 105 Extraction electrode power supply 106 Bias power supply 107 Acceleration electrode power supply 108 Heating power supply 100 Electron gun 110 Mirror body 111 · · Aligner, 112, 113 · · · Condenser lens, 114, 115 · · · Scanning deflector, 116 · · · Objective lens, 117 · · · · · · · · · · · · · · · · · · · · · · · · · Detectors , 131,. Electron beam (primary electrons), 132, 133 ... secondary electrons.

Claims (12)

  1. 　針状電極と、
    　前記針状電極の端部が溶接されたフィラメントと、
    　開口部を有するサプレッサ電極とを有し、
    　前記サプレッサ電極の前記開口部より突き出した前記針状電極の部分を除いて、前記フィラメント及び前記針状電極を覆うように前記サプレッサ電極が配置され、
    　前記針状電極の周りには、前記針状電極の表面に拡散されるジルコニアを供給する拡散供給源が形成され、
    　前記拡散供給源は、少なくとも前記サプレッサ電極に覆われた部分においては１０μｍ以上の厚さを有し、前記サプレッサ電極の前記開口部より突き出した部分においては１００ｎｍ以上の厚さを有する電界放出型電子源。     Needle electrode,
    A filament to which the end of the needle electrode is welded;
    And a suppressor electrode having an opening,
    The suppressor electrode is disposed to cover the filament and the needle electrode except for the portion of the needle electrode protruding from the opening of the suppressor electrode.
    A diffusion source is formed around the needle electrode to supply zirconia diffused to the surface of the needle electrode,
    The diffusion source has a thickness of 10 μm or more at least in a portion covered by the suppressor electrode, and a field emission type electron having a thickness of 100 nm or more in a portion protruding from the opening of the suppressor electrode. source.
  2. 　請求項１において、
    　前記針状電極はタングステン単結晶である電界放出型電子源。     In claim 1,
    The field emission electron source according to claim 1, wherein the needle electrode is a tungsten single crystal.
  3. 　請求項２において、
    　前記針状電極の先端から１００±５０μｍの位置に前記拡散供給源を配置する電界放出型電子源。     In claim 2,
    A field emission type electron source in which the diffusion source is disposed at a position of 100 ± 50 μm from the tip of the needle electrode.
  4. 　請求項２において、
    　前記拡散供給源は、前記サプレッサ電極の前記開口部から前記針状電極の先端に向けて徐々に薄くなる形状を有する電界放出型電子源。     In claim 2,
    The field emission electron source has a shape in which the diffusion source gradually becomes thinner from the opening of the suppressor electrode to the tip of the needle electrode.
  5. 　請求項４において、
    　前記拡散供給源は、インクジェットにより塗布されたジルコニア分散液を焼結し形成された電界放出型電子源。     In claim 4,
    The diffusion source is a field emission type electron source formed by sintering a zirconia dispersion applied by inkjet.
  6. 　請求項１において、
    　前記ジルコニアに代えて、Ｃａ、Ｓｒ、Ｂａ、Ｓｃ、Ｙ、Ｌａ、Ｔｉ、Ｚｒ、Ｈｆ、及びランタノイド系列群から選ばれた金属元素の化合物、酸化物を用いる電界放出型電子源。     In claim 1,
    A field emission electron source using a compound or oxide of a metal element selected from Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, and a lanthanoid series group in place of the zirconia.
  7. 　針状電極と、前記針状電極の端部が溶接されたフィラメントと、開口部を有するサプレッサ電極とを有し、試料へ電子ビームを放出する電界放出型電子源と、
    　コンデンサレンズと、
    　前記コンデンサレンズを通過した前記電子ビームを前記試料上に結像する対物レンズと、
    　前記電子ビームを前記試料へ照射したことに起因する電子を検出する検出器とを有し、
    　前記サプレッサ電極の前記開口部より突き出した前記針状電極の部分を除いて、前記フィラメント及び前記針状電極を覆うように前記サプレッサ電極が配置され、
    　前記針状電極の周りには、前記針状電極の表面に拡散されるジルコニアを供給する拡散供給源が形成されており、
    　前記拡散供給源は、少なくとも前記サプレッサ電極に覆われた部分においては１０μｍ以上の厚さを有し、前記サプレッサ電極の前記開口部より突き出した部分においては１００ｎｍ以上の厚さを有する荷電粒子線装置。     A field emission electron source having a needle electrode, a filament to which an end of the needle electrode is welded, and a suppressor electrode having an opening, and emitting an electron beam to a sample;
    With a condenser lens,
    An objective lens for imaging the electron beam that has passed through the condenser lens onto the sample;
    A detector for detecting electrons resulting from the irradiation of the electron beam to the sample;
    The suppressor electrode is disposed to cover the filament and the needle electrode except for the portion of the needle electrode protruding from the opening of the suppressor electrode.
    A diffusion source is formed around the needle electrode to supply zirconia diffused to the surface of the needle electrode,
    The charged particle beam device according to claim 1, wherein the diffusion source has a thickness of 10 μm or more at least in a portion covered by the suppressor electrode, and a thickness of 100 nm or more in a portion protruding from the opening of the suppressor electrode. .
  8. 　請求項７において、
    　前記針状電極はタングステン単結晶である荷電粒子線装置。     In claim 7,
    The charged particle beam device, wherein the needle electrode is a tungsten single crystal.
  9. 　請求項８において、
    　前記針状電極の先端から１００±５０μｍの位置に前記拡散供給源を配置する荷電粒子線装置。     In claim 8,
    The charged particle beam device which arranges the diffusion source at a position of 100 ± 50 μm from the tip of the needle electrode.
  10. 　請求項８において、
    　前記拡散供給源は、前記サプレッサ電極の前記開口部から前記針状電極の先端に向けて徐々に薄くなる形状を有する荷電粒子線装置。     In claim 8,
    The charged particle beam device according to claim 1, wherein the diffusion source gradually reduces in thickness from the opening of the suppressor electrode to the tip of the needle electrode.
  11. 　請求項１０において、
    　前記拡散供給源は、インクジェットにより塗布されたジルコニア分散液を焼結し形成された荷電粒子線装置。     In claim 10,
    The diffusion source is a charged particle beam device formed by sintering a zirconia dispersion applied by inkjet.
  12. 　請求項７において、
    　前記ジルコニアに代えて、Ｃａ、Ｓｒ、Ｂａ、Ｓｃ、Ｙ、Ｌａ、Ｔｉ、Ｚｒ、Ｈｆ、及びランタノイド系列群から選ばれた金属元素の化合物、酸化物を用いる荷電粒子線装置。     In claim 7,
    A charged particle beam device using a compound or oxide of a metal element selected from Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, and a lanthanoid series group in place of the zirconia.
PCT/JP2017/024942 2017-07-07 2017-07-07 Field emission-type electron source and charged particle beam device WO2019008738A1 (en)

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