JPH04188554A - Irradiation lens system of electron microscope - Google Patents
Irradiation lens system of electron microscopeInfo
- Publication number
- JPH04188554A JPH04188554A JP2313880A JP31388090A JPH04188554A JP H04188554 A JPH04188554 A JP H04188554A JP 2313880 A JP2313880 A JP 2313880A JP 31388090 A JP31388090 A JP 31388090A JP H04188554 A JPH04188554 A JP H04188554A
- Authority
- JP
- Japan
- Prior art keywords
- electron beam
- irradiation
- optical axis
- objective lens
- lens
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 claims abstract description 32
- 238000010894 electron beam technology Methods 0.000 claims abstract description 29
- 230000008859 change Effects 0.000 claims abstract description 11
- 230000004907 flux Effects 0.000 claims abstract description 10
- 230000004075 alteration Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000005284 excitation Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000005856 abnormality Effects 0.000 description 1
- 201000009310 astigmatism Diseases 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、電子顕微鏡において最終像の像質を良くし分
解能を上げるための照射レンズ系に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an irradiation lens system for improving the image quality and resolution of a final image in an electron microscope.
対物レンズの諸収差による影響を少なくし、最終像の像
質を良くするため、試料に入射する電子線束は、照射レ
ンズ系および対物レンズの前磁場によって小さな照射角
で対物レンズの光軸に平行に入射することが要求される
。換言すれば最終像の結像に寄与する電子線束内の電子
が対物レンズの光軸に対しほぼ平行にそろって入射する
ことが要求される。そのためまず従来は第３図に示すよ
うに最終段の照射レンズによるクロスオーバー像８を対
物レンズの前磁場の焦点位置９に一致させることで対応
していた。In order to reduce the influence of various aberrations of the objective lens and improve the image quality of the final image, the electron beam incident on the sample is parallel to the optical axis of the objective lens at a small irradiation angle by the front magnetic field of the irradiation lens system and the objective lens. is required to be incident on the In other words, it is required that the electrons in the electron beam bundle contributing to the formation of the final image are incident on the objective lens in a line substantially parallel to the optical axis. Conventionally, this has been dealt with by first aligning the crossover image 8 produced by the final stage irradiation lens with the focal point 9 of the front magnetic field of the objective lens, as shown in FIG.
しかし照射面積を変えるため従来は第４図に示すように
、クロスオーバー像８の位置を変化させてしまうため電
子線束２で照射角１２をもってしまっていた。However, in order to change the irradiation area, as shown in FIG. 4, in the past, the position of the crossover image 8 was changed, so that the electron beam bundle 2 had an irradiation angle of 12.
そこで照射角を０としたまま照射面積を変化させるため
、特開昭５５−３３７１６号および特開昭６２−６１２
５２号に示されるように、最終段の照射レンズの焦点距
離とさらにその前段の照射レンズによるクロスオーバー
像の位置とを連動させ、常にクロスオーバー像８を対物
レンズの前磁場レンズ焦点位置に一致させその結果照射
領域を変えても、光軸に平行に電子線束を入射させる方
法があった。Therefore, in order to change the irradiation area while keeping the irradiation angle at 0,
As shown in No. 52, the focal length of the final stage irradiation lens is linked with the position of the crossover image by the previous stage irradiation lens, so that the crossover image 8 is always aligned with the front magnetic field lens focus position of the objective lens. There is a method in which the electron beam is incident parallel to the optical axis even if the irradiation area is changed as a result.
一般に対物レンズの前磁場レンズの焦点位置は、試料の
対物レンズに対する位置、対物レンズの励磁の強さ、電
子線の加速電圧等により変化するが従来技術では、それ
に対応して、実際に第３図に示すように電子線束が対物
レンズの光軸に対して平行に入射しているか確認して調
整する手段が無く、上記条件の変化に対応して光軸に対
し電子を平行に入射することができなかった。そのため
に対物レンズの諸収差の影響を受は高分解能像が得られ
ないという問題があった。In general, the focal position of the front magnetic field lens of the objective lens changes depending on the position of the sample with respect to the objective lens, the excitation strength of the objective lens, the accelerating voltage of the electron beam, etc., but in the conventional technology, the focal position of the front magnetic field lens of the objective lens is actually As shown in the figure, there is no means to check and adjust whether the electron beam flux is incident parallel to the optical axis of the objective lens, and it is necessary to make electrons incident parallel to the optical axis in response to changes in the above conditions. I couldn't do it. Therefore, there is a problem in that a high-resolution image cannot be obtained due to the influence of various aberrations of the objective lens.
本発明の目的は、従来技術による問題を解決し実際に試
料を観察している状態において、対物レンズの諸収差に
よる影響の少ない１分解能が高く像質の良い像を得るこ
とにある。An object of the present invention is to solve the problems caused by the prior art and to obtain a high-quality image with high resolution and less influence from various aberrations of an objective lens when a sample is actually observed.
上記目的を達成するために、電子線束の対物レンズに対
する傾斜角を変えずに、照射領域を任意の領域を中心に
回転あるいは往復運動させるために、偏向器とそれを駆
動する偏向電源および演算制御装置および操作点を備え
たものである。In order to achieve the above objective, a deflector, a deflection power source for driving it, and arithmetic control are used to rotate or reciprocate the irradiation area around an arbitrary area without changing the inclination angle of the electron beam with respect to the objective lens. equipment and operating points.
さらにそれらの偏向手段により偏向された電子線束によ
る最終像の変化を検出する手段と、その変化の結果から
照射レンズ系を調整する手段を備えたものである。The apparatus further includes means for detecting changes in the final image due to the electron beam deflected by the deflecting means, and means for adjusting the irradiation lens system based on the results of the changes.
演算制御装置と偏向電源により偏向器が動作させ、電子
線束を光軸に対する傾斜角を変えずに、照射領域のある
点を中心に回転または往復運動させる。その時の最終像
の変化の様子から電子線束内の電子が光軸に対しどのよ
うに入射しているかを判断し、その結果に基づき照射レ
ンズ系の焦点距離などの動作状態を、演算制御装置また
は操作卓より変化が最小になる様に調整する。その結果
、電子線束内の電子が光軸に平行に入射する様になり対
物レンズの諸収差による影響を少なくでき、分解能の高
い像質の良い最終像を得ることができる。The deflector is operated by the arithmetic and control unit and the deflection power source, and the electron beam is rotated or reciprocated around a certain point in the irradiation area without changing the inclination angle with respect to the optical axis. Based on the changes in the final image at that time, it is determined how the electrons in the electron beam flux are incident on the optical axis, and based on the results, the operating state such as the focal length of the irradiation lens system is determined by the arithmetic and control unit. Adjust so that the change is minimized from the control console. As a result, the electrons in the electron beam become incident parallel to the optical axis, thereby reducing the influence of various aberrations of the objective lens, making it possible to obtain a final image with high resolution and good image quality.
第１図は本発明による電子顕微鏡の実施例の光学的概略
図である。ここでは２段の照射レンズを用いた例で説明
する。FIG. 1 is an optical schematic diagram of an embodiment of an electron microscope according to the invention. Here, an example using two stages of irradiation lenses will be explained.
電子が発生すると見なせる仮想電子源１を出射した電子
束２は、第１照射レンズ３と第２照射レンズ６によって
収束されクロスオーバー像８を形成し、偏混器７ａ、７
ｂによって偏向されたのち、対物レンズの前磁場レンズ
１０によって収束され、試料１１に入射する。試料を透
過した電子は、数段のレンズを経て蛍光板１３上に最終
像を形成する。The electron flux 2 emitted from the virtual electron source 1, which can be regarded as generating electrons, is converged by the first irradiation lens 3 and the second irradiation lens 6 to form a crossover image 8, and the polarized mixers 7a, 7
After being deflected by b, it is focused by the front magnetic field lens 10 of the objective lens and enters the sample 11. The electrons that have passed through the sample form a final image on the fluorescent screen 13 after passing through several stages of lenses.
電子線束２は操作卓２０からの指定と演算制御装置１９
および偏向電源１８により駆動された偏向器７ａ、７ｂ
により、対物レンズの光軸１４に対する傾斜角を変化さ
せずに、試料の任意の領域を中心に照射領域を回転また
は往復運動するように偏向される。The electron beam 2 is specified by the operation console 20 and the arithmetic and control unit 19.
and deflectors 7a and 7b driven by the deflection power source 18.
As a result, the irradiation area is deflected so as to rotate or reciprocate around an arbitrary area of the sample without changing the inclination angle of the objective lens with respect to the optical axis 14.
以上の様な構成において、第１図の場合は、第２照射、
レンズによるクロスオーバー像８が対物レンズの前磁場
レンズ１０の焦点位置９と一致していないため、電子東
向の電子は、対物レンズの光軸（以下光軸と略）１４に
対し同一の傾斜角をもたず、電子東向で光軸に対する傾
斜角が、場所により異なる。換言すれば有限の照射角１
２を持つ。In the above configuration, in the case of FIG. 1, the second irradiation,
Since the crossover image 8 formed by the lens does not coincide with the focal position 9 of the front magnetic field lens 10 of the objective lens, the electrons heading east have the same inclination angle with respect to the optical axis (hereinafter referred to as optical axis) 14 of the objective lens. The inclination angle with respect to the optical axis differs depending on the location when the electrons are directed eastward. In other words, the finite beam angle 1
Has 2.
いま試料上のある点Ａに注目すると、ここでは電子は光
軸に平行に入射しているが照射領域周辺に行くに従い光
軸から傾斜して入射している。Now, if we focus on a certain point A on the sample, here the electrons are incident parallel to the optical axis, but as they move toward the periphery of the irradiation area, the electrons are incident at an angle from the optical axis.
ここで前期偏向手段により例えば点線で示すように偏向
しながら、点Ａを蛍光板１３上に投影された最終像にお
いて、観察すれば、偏向前の実線で示した場合比へ、点
Ａに入射する電子の方向が光軸に対して傾斜している。Here, if the point A is observed in the final image projected onto the fluorescent screen 13 while being deflected as shown by the dotted line by the first deflection means, the incident point A will be compared to the case shown by the solid line before deflection. The direction of the electrons is tilted with respect to the optical axis.
そのため観察している点Ａにおける最終像は偏向前と比
べ、例えば電圧軸が合っていない像となったり、非点収
差が現われたり、結晶性試料を観察している場合には結
晶に対する電子に入射方向が変化した像が現われたりす
る。その像の変化の方向と程度から電子線束がどのよう
に入射しているのか、換言すれば第２照射レンズ６にク
ロスオーバー像８と対物レンズの前磁場レンズの焦点位
置９がどのような関係にあるか、また、照射領域内で、
照射角をもった電子を入射したことによる像の異方性す
なわち、異常の有無を見積ることができる。Therefore, the final image at point A being observed may be different from the image before deflection, for example, the voltage axis may not be aligned, astigmatism may appear, or when observing a crystalline sample, the electrons relative to the crystal may An image whose incident direction has changed may appear. From the direction and degree of change in the image, we can determine how the electron beam is incident, in other words, what is the relationship between the crossover image 8 and the focal position 9 of the front magnetic field lens of the objective lens on the second irradiation lens 6. within the irradiated area,
It is possible to estimate the anisotropy of the image due to the incidence of electrons at an irradiation angle, that is, the presence or absence of an abnormality.
次に、第２図に示すように、前期偏向方法で、像を観察
しながら、第１または第２照射レンズの焦点距離を変化
させていく。変化させて行く過程でクロスオーバー像８
と焦点位置９が一致すると、偏向したことによっても光
軸に対する電子線の傾斜角が変化しなくなり、最終像は
変化しなくなる。Next, as shown in FIG. 2, the focal length of the first or second irradiation lens is changed while observing the image using the first deflection method. Crossover image 8 in the process of changing
When the focal position 9 coincides with that of the electron beam, the inclination angle of the electron beam with respect to the optical axis does not change even after deflection, and the final image does not change.
このことから電子線束が光軸対し、同じ傾斜角で入射し
ていることがわかる。This shows that the electron beams are incident at the same angle of inclination to the optical axis.
さらに例えばクロスオーバー像８と対物レンズの前磁場
レンズの焦点位置の上下関係が第１図と逆になった場合
、こんどは前記偏向方法による像の変化する方向が逆転
することからクロスオーバー像８と対物レンズの前磁場
レンズの焦点位置９との上下関係を判別できる。Furthermore, for example, if the vertical relationship between the crossover image 8 and the focal position of the front magnetic field lens of the objective lens is reversed to that shown in FIG. The vertical relationship between this and the focal position 9 of the front magnetic field lens of the objective lens can be determined.
以上の様にして、電子線束の光軸に対する傾斜角を検出
することにより、試料に入射する電子を光軸と平行にす
ることができ、対物レンズの諸収差による影響の少ない
像を得ることができる。As described above, by detecting the inclination angle of the electron beam with respect to the optical axis, the electrons incident on the sample can be made parallel to the optical axis, and an image that is less affected by various aberrations of the objective lens can be obtained. can.
尚、上記実施例において像の検出手段として蛍光板を用
いたがこれに限定されるものではなく、テレビカメラ等
を用いて、像の変化を電気信号として演算制御装置に入
力し、自動的に照射レンズ系を調整してもよい。In the above embodiments, a fluorescent screen was used as the image detection means, but the invention is not limited to this. Changes in the image are input as electrical signals to the arithmetic and control device using a television camera, etc., and the image is automatically irradiated. The lens system may also be adjusted.
本発明は以上説明したように構成されているので以下に
記載されているような効果を奏する。Since the present invention is configured as described above, it produces the effects described below.
電子の加速電圧、対物レンズの励磁、対物レンズに対す
る試料の位置などが変化することにより、対物レンズの
前磁場の焦点位置が変化しても５電子線束内の電子の光
軸に対する傾斜角をそろえるように調整することが可能
となり、その結果対物レンズの諸収差による影響を少な
くし、最終像の像質を良くし分解能を上げることができ
る。Even if the focal position of the front magnetic field of the objective lens changes due to changes in the electron accelerating voltage, excitation of the objective lens, the position of the sample relative to the objective lens, etc., the inclination angles of the electrons in the 5-electron beam flux with respect to the optical axis are aligned. As a result, the influence of various aberrations of the objective lens can be reduced, the quality of the final image can be improved, and the resolution can be increased.
またこの他の効果として、偏向器の制御手段１９を用い
て回転または往復運動または周期運動させた像を重畳し
てｌ［察することにより、光源径の小さな（または輝度
の高い）電子銃（例えば電界放出型電子銃）のクロスオ
ーバー像の大きさを実効的に大きくし、疑似的に光源径
の大きな（または輝度の低い）電子銃（例えば熱電子放
出型電子銃）と同様に使うことができるため、従来の光
源径の大きな電子銃のための電子顕微鏡技術をそのまま
利用できる。In addition, as another effect, by superimposing images rotated, reciprocated, or periodically moved using the control means 19 of the deflector, an electron gun with a small light source diameter (or high brightness), e.g. It is possible to effectively increase the size of the crossover image of a field emission electron gun (field emission electron gun) and use it in the same way as an electron gun with a pseudo-large light source diameter (or low brightness) (for example, a thermionic emission electron gun). Therefore, conventional electron microscope technology for electron guns with large light source diameters can be used as is.
第１図は本発明による照射レンズ系および電子顕微鏡の
光学的概略図、第２図は本発明によって、電子線束を対
物レンズの光軸に平行した場合の光学的概略図、第３図
および第４図は電子線束の試料への電子線束の照射面積
を調節した状況を示す光学的概略図である。
１・・・仮想電子源、２・・・電子線束、３・・・第１
照射レンズ、４・・・絞り、５・・・第１照射レンズに
よるクロスオーバー像、６・・・第２照射レンズ、７・
偏向器、８・・・第２照射レンズによるクロスオーバー
像、９・・・対物レンズの前磁場レンズの焦点位置、１
０・・対物レンズの前磁場レンズ、１１・・・試料、１
２・・・照射角、１３・・・蛍光板、１４・・光軸、１
５〜１７・・・励磁電源、１８・・偏向電源、１９・・
演算制御装置、２０・・・操作卓。
第１因
第２因
第３図
第４図FIG. 1 is an optical schematic diagram of the irradiation lens system and electron microscope according to the present invention, FIG. 2 is an optical schematic diagram when the electron beam is parallel to the optical axis of the objective lens, and FIG. FIG. 4 is an optical schematic diagram showing a situation in which the irradiation area of the electron beam onto the sample is adjusted. 1... Virtual electron source, 2... Electron beam flux, 3... First
Irradiation lens, 4... Aperture, 5... Crossover image by first irradiation lens, 6... Second irradiation lens, 7.
Deflector, 8... Crossover image by second irradiation lens, 9... Focal position of front magnetic field lens of objective lens, 1
0...Front magnetic field lens of objective lens, 11...Sample, 1
2... Irradiation angle, 13... Fluorescent screen, 14... Optical axis, 1
5-17... Excitation power supply, 18... Deflection power supply, 19...
Arithmetic control unit, 20...operation console. 1st cause 2nd cause 3rd figure 4th figure
Claims (1)
照射レンズと、前記対物レンズの前段に配置し前記電子
源から発せられた電子線束を偏向させるための偏向器な
どからなる電子顕微鏡において、試料の任意の領域を中
心に前記電子線束を前記対物レンズの光軸に対する傾斜
角を変えずに、照射領域を回転または往復運動させる自
動制御機構を備えたことを特徴とする電子顕微鏡。 ２、前記制御手段により前期電子線束の照射領域を変化
させながら、最終像の変化状態を検出する手段と、その
変化を最小とするように前記照射レンズ系を制御する手
段を設けたことを特徴とする請求項第１項記載の電子顕
微鏡。 ３、照射レンズと対物レンズの間に偏向器を設け、照射
レンズからの電子線束を対物レンズの光軸に対する角度
を変えずに、照射する領域のみを変化させ得る制御手段
をもつたことを特徴とする請求項第１項又は第２項記載
の電子顕微鏡の照射レンズ系。[Claims] 1. At least two or more irradiation lenses between an electron source and an objective lens, and a deflector disposed before the objective lens to deflect the electron beam emitted from the electron source. The electron microscope is characterized in that it is equipped with an automatic control mechanism that rotates or reciprocates the irradiation area of the electron beam flux around an arbitrary area of the sample without changing the inclination angle with respect to the optical axis of the objective lens. electron microscope. 2. Means for detecting a state of change in the final image while changing the irradiation area of the electron beam flux by the control means, and means for controlling the irradiation lens system so as to minimize the change. The electron microscope according to claim 1, wherein: 3. A deflector is provided between the irradiation lens and the objective lens, and it has a control means that can change only the area to be irradiated with the electron beam from the irradiation lens without changing the angle with respect to the optical axis of the objective lens. An irradiation lens system for an electron microscope according to claim 1 or claim 2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2313880A JPH04188554A (en) | 1990-11-21 | 1990-11-21 | Irradiation lens system of electron microscope |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2313880A JPH04188554A (en) | 1990-11-21 | 1990-11-21 | Irradiation lens system of electron microscope |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04188554A true JPH04188554A (en) | 1992-07-07 |
Family
ID=18046622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2313880A Pending JPH04188554A (en) | 1990-11-21 | 1990-11-21 | Irradiation lens system of electron microscope |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04188554A (en) |
-
1990
- 1990-11-21 JP JP2313880A patent/JPH04188554A/en active Pending
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