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Method and device for visualizing distribution of local electric field

外国特許コード F110005408
整理番号 K02905WO
掲載日 2011年9月5日
出願国 アメリカ合衆国
出願番号 92199109
公報番号 20110068266
公報番号 8330102
出願日 平成21年3月13日(2009.3.13)
公報発行日 平成23年3月24日(2011.3.24)
公報発行日 平成24年12月11日(2012.12.11)
国際出願番号 JP2009054901
国際公開番号 WO2009113670
国際出願日 平成21年3月13日(2009.3.13)
国際公開日 平成21年9月17日(2009.9.17)
優先権データ
  • 特願2008-064682 (2008.3.13) JP
  • 特願2008-081187 (2008.3.26) JP
  • 2009JP054901 (2009.3.13) WO
発明の名称 (英語) Method and device for visualizing distribution of local electric field
発明の概要(英語) A method which visualizes the distribution of a local electric field formed near a sample 2 is disclosed.
A primary electron beam 1 which passes through the local electric field formed near the sample 2 is deflected by the local electric field, secondary electrons which are generated and emitted from a detection element provided downstream of an orbit of the deflected primary electron beam 1 are detected by a secondary electron detector 6, and an image formed based on the detected signal and a scanning electron beam image obtained by scanning the sample 2 are synthesized thus visualizing the distribution of the local electric field in multiple tones.
Due to such an operation, it is possible to provide a method for visualizing the distribution of a local electric field in which the distribution of a local electric field can be obtained in multiple tone and in real time by performing image scanning one time using a usual electron beam scanning optical system.
従来技術、競合技術の概要(英語) BACKGROUND ART
The visualization of a local electric field has been expected to give an important clue in the evaluation of performances or functions or a trouble analysis of a solid device, a CNT (carbon nanotube) transistor, a light emitting element, an electron emission element which constitutes a nano structural body or, to be more specific, a trouble diagnosis analysis of an LSI or the evaluation of performances or functions or a trouble analysis of a defect of a gate portion or the like.
As a method for visualizing a local electric field whose importance is increasing in the development and the analysis of such a nano structural body, there has been proposed a local electric field visualizing method which uses a scanning transmission electron microscope (STEM) (non-patent document 1).
FIG. 11 is a conceptual view of such a method.
An anode is arranged to face a conductive probe having a pointed tip end in an opposed manner, and when a voltage is applied to the anode, an extremely strong local electric field is induced on the tip end of the probe.
When the probe is electrically conductive, the whole probe has the same potential.
When the probe is placed in an electric field, that is, even when a potential gradient is present in a space, it is necessary to set the same potential to the whole probe.
Accordingly, an apparent charge is induced in the tip end of the probe so that the potential of the probe is adjusted such that the whole probe has the same potential.
That is, due to this apparent charge, a local electric field which is an extremely strong electric field is formed in the vicinity of the tip end of the probe to which the potential is applied.
When a primary electron beam of the scanning transmission electron microscope passes through this strong local electric field, an orbit of the primary electron beam is largely deflected.
That is, the deflection of the orbit of the primary electron beam is considered as the scattering where an electron orbit is deflected due to a Coulomb force between a point charge induced on the tip end of the probe and the primary electron beam, that is, is considered as Rutherford scattering.
Accordingly, in a transmission image of the scanning transmission electron microscope, electron beams are scattered and are deflected from an electron beam detector (STEM detector) mounted on a lower portion of a casing so that a detection signal is not generated in a region where the scattering occurs, thereby a black region appears surrounding the distal end of the probe.
In the Rutherford scattering, an electron draws a hyperbolic orbit.
An orbit from infinity approximates a point charge with a fixed distance b (impact parameter).
Thereafter, the orbit is bent and deflected due to a Coulomb interactive force between the electron and the point charge.
Here, the impact parameter b is expressed by a following formula.
(Equation image 1 not included in text)
In the formula, e indicates an elementary charge, z1e indicates an apparent point charge induced on a tip end of a probe, m indicates an electron mass, delta 0 indicates a dielectric constant in vacuum, v indicates velocity of a primary electron beam, and theta indicates a scattering angle.
As a result of such scattering, the orbit of the primary electron beam is deflected to the outside of the electron beam detector so that the black shadow is formed.
By extracting a completely black portion of an image, that is, a black portion of a level equal to brightness which imparts blackness of the probe or the electrode, a region subjected to the deflection to an extent that the scanning electron is completely displaced to the outside of the electron beam detector is specified.
It is needless to say that contrast and brightness can be arbitrarily adjusted in the scanning transmission electron microscope, and it is a premise that a darkest portion of a bright field image is not saturated.
From a black region on the tip end of the probe observed when the distal end of the probe and the anode are arranged with a gap of 10 mu m as shown in FIG. 12(a) and a potential of 258V is applied to the anode, brightness of a level equal to the brightness of the probe is extracted.
As a result, a white circular region shown in FIG. 12(b) is formed.
All primary electron beams incident within the circular region are displaced to the outside of the electron beam detector, and a radius 1.5 mu m of circular region at this point of time becomes the impact parameter b. The scattering angle theta is determined based on a radius of the electron beam detector and a distance between the electron beam detector and the tip end of the probe, and an electric field E on a boundary of the circular region is expressed by a following formula.
(Equation image 2 not included in text)
The electron field E is expressed by a following formula when the primary electron beam of low acceleration outside the application of relativity theory is used.
(Equation image 3 not included in text)
Here, V indicates an acceleration voltage of the primary electron beam.
A scattering angle can be obtained based on the use of such relationship formula due to the size of the black shadow which appears due to scattering of electrons so that the intensity of a local electric field at an edge of the shadow can be obtained.
Non-patent Document 1: J. Fujita et al. "In-situ Visualization of Local Field Enhancement in an Ultra Sharp Tungsten Emitter under a Low Voltage Scanning Transmission Electron Microscope" Jpn. J. Appl. Phys. 46 (2007) 498-501

特許請求の範囲(英語) [claim1]
1. A method for visualizing the distribution of a local electric field formed near a sample in an electron beam scanning optical system, wherein a primary electron beam which passes through the local electric field formed near the sample is deflected by the local electric field, secondary electrons which are generated and emitted from a detection element provided downstream of an orbit of the deflected primary electron beam are detected by a secondary electron detector, and an image formed based on the detected signal and a scanning electron beam image obtained by scanning the sample are synthesized thus visualizing the distribution of the local electric field in multiple tone.
[claim2]
2. The method for visualizing the distribution of a local electric field according to claim 1, wherein the sample has a projecting portion, and the local electric field is formed near the projecting portion.
[claim3]
3. The method for visualizing the distribution of a local electric field according to claim 1, wherein a potential is applied to the sample.
[claim4]
4. The method for visualizing the distribution of a local electric field according to any one of claim 1, wherein a detection element having the grid structure which is constituted of a plurality of linear portions arranged in a spaced-apart manner at a fixed interval is used as the detection element.
[claim5]
5. The method for visualizing the distribution of a local electric field according to claim 4, wherein a detection element in which two sets of grid structures each of which is constituted of a plurality of linear portions are arranged orthogonal to each other is used as the detection element.
[claim6]
6. The method for visualizing the distribution of a local electric field according to claim 4, wherein a detection element in which a grid is formed on a substrate, the grid is constituted of a metal element, and a constitutional element of the grid and a constitutional element of the substrate differ from each other in secondary electron generation efficiency with respect to a bombardment of a primary electron beam is used as the detection element.
[claim7]
7. The method for visualizing the distribution of a local electric field according to claim 6, wherein the detection element in which the grid is constituted of Al, Cu or Au is used.
[claim8]
8. The method for visualizing the distribution of a local electric field according to claim 4, wherein a bias voltage is applied to the grid.
[claim9]
9. The method for visualizing the distribution of a local electric field according to claim 8, wherein a contrast of an image which indicates the distribution of the local electric field is adjusted by adjusting intensity of the bias voltage applied to the grid.
[claim10]
10. The method for visualizing the distribution of a local electric field according to claim 4, wherein grid lines which constitute the detection element are individually connected to an A/D converter means, and a scattering angle of the primary electron beam based on the local electric field is detected based on a signal from the A/D converter means.
[claim11]
11. A method for evaluating a local electric field distribution characteristic, wherein a distribution characteristic of a local electric field of the sample is evaluated using the method for visualizing the distribution of a local electric field described in claim 1.
[claim12]
12. The method for evaluating a local electric field distribution characteristic according to claim 11, wherein the dependency of a mechanical distortion or an operation of the sample on the local electric field is evaluated.
[claim13]
13. A local electric field distribution visualizing device for visualizing the distribution of a local electric field formed near a sample in an electron beam scanning optical system in multiple tone, the local electric field distribution visualizing device comprising at least: (a) a scanning radiation part which irradiates a primary electron beam to the sample; (b) a detection part which detects the primary electron beam; (c) a detection element part which detects the primary electron beam deflected by a local electric field formed on the sample; (d) a secondary electron detection part which detects secondary electrons generated and emitted from the detection part which detects the primary electron beam; (e) an image conversion part which converts a signal from the secondary electron detection part; (f) an image conversion part which converts a signal from the primary electron beam detection part; and (g) an image synthesizing and displaying part which synthesizes and displays images from the image conversion parts (e), (f).
[claim14]
14. The local electric field distribution visualizing device according to claim 13, wherein the sample has a projecting portion, and the local electric field is formed near the projecting portion.
[claim15]
15. The local electric field distribution visualizing device according to claim 13, wherein a potential applying part which applies a potential to the sample is provided.
[claim16]
16. The local electric field distribution visualizing device according to claim 13, wherein the detection element part (c) includes a detection element having the grid structure which is constituted of a plurality of linear portions arranged in a spaced apart manner at a fixed interval.
[claim17]
17. The local electric field distribution visualizing device according to claim 16, wherein the detection element part (c) includes a detection element in which two sets of grid structures each of which is constituted of a plurality of linear portions are arranged orthogonal to each other.
[claim18]
18. The local electric field distribution visualizing device according to claim 16, wherein the device includes a grid bias voltage applying part which applies a bias voltage to the grid.
  • 発明者/出願人(英語)
  • FUJITA JUN-ICHI
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 250/307
参考情報 (研究プロジェクト等) PRESTO Search for nanomanufacturing technology and its development AREA
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