JP3400608B2 - Scanning electron microscope - Google Patents
Scanning electron microscopeInfo
- Publication number
- JP3400608B2 JP3400608B2 JP13484995A JP13484995A JP3400608B2 JP 3400608 B2 JP3400608 B2 JP 3400608B2 JP 13484995 A JP13484995 A JP 13484995A JP 13484995 A JP13484995 A JP 13484995A JP 3400608 B2 JP3400608 B2 JP 3400608B2
- Authority
- JP
- Japan
- Prior art keywords
- axis
- electron beam
- image
- objective lens
- electron microscope
- 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.)
- Expired - Fee Related
Links
- 238000010894 electron beam technology Methods 0.000 claims description 51
- 238000001514 detection method Methods 0.000 claims description 12
- 230000008859 change Effects 0.000 claims description 9
- 238000010586 diagram Methods 0.000 description 8
- 230000005284 excitation Effects 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 201000009310 astigmatism Diseases 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
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- Electron Sources, Ion Sources (AREA)
Description
【０００１】 [0001]
【産業上の利用分野】本発明は、走査電子顕微鏡に関
し、特に走査電子顕微鏡において対物レンズを通る電子
ビームの軸を対物レンズの中心軸に調整する装置の改良
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope, and more particularly to improvement of a device for adjusting the axis of an electron beam passing through an objective lens to the central axis of the objective lens in the scanning electron microscope.
【０００２】 [0002]
【従来の技術】走査電子顕微鏡等による試料像の観察あ
るいは試料の成分分析においては、その観察や分析の形
態に応じて試料上に照射される電子ビームのビーム電
流、すなわちビーム径を変える必要がある。例えば、高
倍率、高分解能像の形成にあたってはビームを細く絞る
必要があり、逆にＸ線分析などにあたってはビーム径を
太くしてビーム電流を大きくする必要がある。このビー
ム径の変更は、径の異なる複数の絞り孔を備えた可動式
多孔絞り装置では使用する絞りを選択することにより、
あるいは単一の絞りを備える絞り装置では装置に取り付
ける絞りを交換することによって行われるが、非点収差
等を避けるために、絞り孔を通りぬけた電子ビームを対
物レンズの中心軸に合わせる調整作業が必要である。2. Description of the Related Art In observing a sample image with a scanning electron microscope or analyzing the components of a sample, it is necessary to change the beam current of the electron beam irradiated onto the sample, that is, the beam diameter, depending on the form of the observation or analysis. is there. For example, in forming a high-magnification, high-resolution image, the beam needs to be narrowed down, and conversely, in X-ray analysis, it is necessary to increase the beam diameter to increase the beam current. This change in beam diameter can be achieved by selecting the diaphragm used in the movable porous diaphragm device equipped with multiple diaphragm holes with different diameters.
Alternatively, in the case of a diaphragm device with a single diaphragm, this is done by exchanging the diaphragm attached to the device, but in order to avoid astigmatism etc., adjustment work to align the electron beam that has passed through the diaphragm hole with the central axis of the objective lens. is necessary.
【０００３】この調整は、対物レンズの励磁電流を周期
的に変化（ワブラ）させて焦点位置を合焦位置の上下に
振り、その状態で検出像の中心位置が静止するように絞
りの位置を微調整することによって行われる。電子ビー
ムが対物レンズの中心を通っていれば、対物レンズの励
磁電流を微小変化させても、それによって検出像の中心
が移動することはない。一方、電子ビームが対物レンズ
の中心から外れた位置を通過していると、対物レンズの
励磁電流を周期的に変化させたとき検出像の中心位置も
画面上で上下方向や左右方向に周期的に移動する。この
現象を利用して、検出像を観察しながら手動にて絞りの
位置を微調整するわけである。In this adjustment, the exciting current of the objective lens is periodically changed (wobbler) to move the focus position above and below the in-focus position, and in that state, the position of the diaphragm is adjusted so that the center position of the detected image is stationary. It is done by fine-tuning. If the electron beam passes through the center of the objective lens, even if the exciting current of the objective lens is slightly changed, the center of the detected image will not be moved by it. On the other hand, if the electron beam is passing through a position deviated from the center of the objective lens, the center position of the detected image also changes periodically in the vertical and horizontal directions on the screen when the exciting current of the objective lens is changed cyclically. Move to. By utilizing this phenomenon, the position of the diaphragm is finely adjusted manually while observing the detected image.
【０００４】 [0004]
【発明が解決しようとする課題】電子ビームが対物レン
ズの中心から外れた状態で対物レンズの励磁電流を周期
的に変化させると、検出像は回転しながらその中心位置
が変化するという極めて複雑な動きをする。そのため、
上記従来の調整方法においては、対物レンズの励磁電流
の変化に基づく検出像の回転運動と電子ビームが対物レ
ンズの中心から外れていることに起因する像の中心位置
の移動を分離して観察しながら可動絞りの位置を手動調
整しなければならず、調整には熟練を要していた。When the exciting current of the objective lens is periodically changed with the electron beam deviated from the center of the objective lens, the detected image changes its center position while rotating, which is extremely complicated. Make a move. for that reason,
In the above conventional adjustment method, the rotational movement of the detected image based on the change of the exciting current of the objective lens and the movement of the central position of the image due to the electron beam deviating from the center of the objective lens are separately observed. However, it was necessary to manually adjust the position of the movable diaphragm, which required skill.
【０００５】本発明は、対物レンズの励磁電流を連続的
に変化させたときの検出像の振る舞いから絞りの位置調
整等によって行う電子ビームの軸調整を、特別な熟練を
要さずに簡単に行うことができるようにすることを目的
とする。According to the present invention, the axis of the electron beam can be easily adjusted by adjusting the position of the diaphragm or the like from the behavior of the detected image when the exciting current of the objective lens is continuously changed, without requiring special skill. The purpose is to be able to do.
【０００６】 [0006]
【課題を解決するための手段】本発明では、電子ビーム
の軸調整時に、対物レンズの励磁電流を周期的に変化さ
せるとともに、それに同期して偏向コイルによる試料走
査方向を補正し、検出像の回転を止めることによって前
記目的を達成する。すなわち、本発明は、試料上のビー
ム電流を可変するための絞り装置と、電子ビームを試料
上で２次元走査するための偏向手段と、電子ビームを試
料上に集束させて焦点を合わせるための対物レンズと、
試料から発生した信号を検出する検出手段と、前記検出
手段からの検出信号をもとに検出像を形成するための画
像形成手段と、前記対物レンズを通る電子ビームの軸を
調整するための軸調整手段と、前記偏向手段及び対物レ
ンズを制御する制御手段とを備える走査電子顕微鏡にお
いて、前記制御手段は、前記軸調整手段による電子ビー
ムの軸調整時に、前記対物レンズの励磁電流を周期的に
変化させるとともに該励磁電流の変化に同期して前記偏
向手段を制御して検出像の回転を止める制御を行うこと
を特徴とする。According to the present invention, when the axis of the electron beam is adjusted, the exciting current of the objective lens is periodically changed, and in synchronization with this, the sample scanning direction by the deflection coil is corrected to detect the detected image. The object is achieved by stopping the rotation. That is, according to the present invention, a diaphragm device for varying the beam current on the sample, a deflecting means for two-dimensionally scanning the electron beam on the sample, and a focusing device for focusing the electron beam on the sample for focusing. An objective lens,
Detecting means for detecting a signal generated from the sample, image forming means for forming a detection image based on the detection signal from the detecting means, and an axis for adjusting the axis of the electron beam passing through the objective lens. In a scanning electron microscope including an adjusting means and a control means for controlling the deflecting means and the objective lens, the control means periodically adjusts an exciting current of the objective lens when the axis of the electron beam is adjusted by the axis adjusting means. It is characterized in that the deflection means is controlled to change and the rotation of the detected image is stopped in synchronization with the change of the exciting current.
【０００７】軸調整手段は、絞り装置の絞り孔の位置を
機械的に調整するもの、あるいは電子ビームの近傍に配
置された電磁コイルとすることができる。対物レンズ
は、ヒステリシス補正用の空芯コイルを備え、自動焦点
合わせを行えるものであってもよい。また、画像処理手
段をさらに備え、軸調整手段による電子ビームの軸調整
時に、画像処理手段によって検出像の動く方向を認識
し、制御手段はこの認識した検出像の動きを止めるよう
に軸調整手段を制御するようになすことができる。The axis adjusting means may be one that mechanically adjusts the position of the diaphragm hole of the diaphragm device, or an electromagnetic coil arranged near the electron beam. The objective lens may be provided with an air-core coil for hysteresis correction and capable of automatic focusing. Further, the image processing means is further provided, and when the axis adjustment means adjusts the axis of the electron beam, the image processing means recognizes the moving direction of the detected image, and the control means stops the recognized movement of the detected image. Can be controlled.
【０００８】 [0008]
【作用】本発明によると、電子ビームの軸調整時に検出
像が回転しないため、検出像を止める調整を容易に行う
ことができる。また、検出像の動きは回転がなく並進運
動のみとなるため、画像処理によって検出像の運動方向
を認識することが容易になり、軸調整を自動的に行うこ
とが可能となる。According to the present invention, since the detected image does not rotate when the axis of the electron beam is adjusted, adjustment for stopping the detected image can be easily performed. Moreover, since the motion of the detected image is only translational motion without rotation, it becomes easy to recognize the motion direction of the detected image by image processing, and it becomes possible to automatically perform axis adjustment.
【０００９】 [0009]
【実施例】以下、本発明の実施例を図面に基づき詳述す
る。図１は、本発明の実施例の模式図である。図中、１
は電子ビーム、２は試料上のビーム電流を可変するため
の可動式多孔絞り装置、３は電子ビームを試料上で２次
元走査するための偏向コイルでＸ方向とＹ方向のコイル
を備えている。４は試料上に電子ビームの焦点を結ばせ
るための対物レンズで、その励磁電流を変化させること
により焦点位置を変えることができる。５は試料、６は
試料から発生する２次電子等の信号を検出する検出器、
７は検出信号を増幅する増幅回路、８は検出信号に基づ
いて画像を表示する表示装置、９はマイクロコンピュー
タ等を用いた制御回路で、偏向コイル３や対物レンズ４
の制御を行う。可動式多孔絞り装置４は径の異なる複数
個の絞り孔２ａを備え、電子ビーム１中に配置する絞り
孔を選択することによりビーム径すなわちビーム電流を
変えることができ、またネジ等により電子ビーム１に対
して垂直な面内で絞り孔２ａをＸ−Ｙ方向に移動してそ
の位置を微調整する機能を有する。Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an embodiment of the present invention. 1 in the figure
Is an electron beam, 2 is a movable porous diaphragm device for varying the beam current on the sample, and 3 is a deflection coil for two-dimensionally scanning the electron beam on the sample, which is provided with coils in X and Y directions. . Reference numeral 4 is an objective lens for focusing the electron beam on the sample, and the focus position can be changed by changing the exciting current. 5 is a sample, 6 is a detector for detecting signals such as secondary electrons generated from the sample,
Reference numeral 7 is an amplification circuit for amplifying the detection signal, 8 is a display device for displaying an image based on the detection signal, and 9 is a control circuit using a microcomputer or the like, which includes the deflection coil 3 and the objective lens 4
Control. The movable porous diaphragm device 4 is provided with a plurality of diaphragm holes 2a having different diameters, the beam diameter, that is, the beam current can be changed by selecting the diaphragm holes arranged in the electron beam 1, and the electron beam can be changed by a screw or the like. It has a function of moving the aperture hole 2a in the X-Y direction in a plane perpendicular to 1 and finely adjusting its position.
【００１０】電子ビーム１は、可動式多孔絞り装置２の
絞り孔２ａを通過した後、偏向コイル３の磁場により偏
向され、対物レンズ４によって試料５上に焦点を結び、
試料上を２次元走査する。試料５に電子ビームが照射さ
れると、試料から２次電子や反射電子等が発生する。こ
の２次電子や反射電子は、試料の凹凸により発生量が異
なるため、検出器６で検出した信号を増幅回路７で増幅
して表示装置８に入力することにより、表示装置８には
試料の表面形状に関する情報を担持した検出像が表示さ
れる。After passing through the aperture 2a of the movable porous aperture device 2, the electron beam 1 is deflected by the magnetic field of the deflection coil 3 and focused on the sample 5 by the objective lens 4.
Two-dimensional scanning is performed on the sample. When the sample 5 is irradiated with an electron beam, secondary electrons and reflected electrons are generated from the sample. Since the amount of generation of the secondary electrons and the reflected electrons differs depending on the unevenness of the sample, the signal detected by the detector 6 is amplified by the amplifier circuit 7 and input to the display device 8. A detected image carrying information about the surface shape is displayed.
【００１１】ここで、可動式多孔絞り装置２の絞り孔２
ａを通過した電子ビーム１が、対物レンズ４の中心軸を
通っていないと、非点収差が大きくなり良好な画像が得
られない。そのため通常、可動式多孔絞り装置２には電
子ビーム１を対物レンズ４の中心軸に合わせるための微
調整機構が備えられている。そして、前述のように、制
御回路９により対物レンズ４の励磁電流を周期的に変化
（ワブラ）させ、操作者は表示装置８上に表示された検
出像の上下左右の動きを止めるように可動式多孔絞り装
置２の微調整機構によって絞り孔２ａの位置を微調整す
る。Here, the diaphragm hole 2 of the movable porous diaphragm device 2
If the electron beam 1 that has passed through a does not pass through the central axis of the objective lens 4, astigmatism increases and a good image cannot be obtained. Therefore, the movable porous diaphragm device 2 is usually provided with a fine adjustment mechanism for adjusting the electron beam 1 to the central axis of the objective lens 4. Then, as described above, the control circuit 9 periodically changes (wobbles) the exciting current of the objective lens 4, and the operator can move the detection image displayed on the display device 8 so as to stop the movement in the vertical and horizontal directions. The position of the aperture 2a is finely adjusted by the fine adjustment mechanism of the multi-hole type aperture device 2.
【００１２】ところで、電子ビームは図２に示すように
対物レンズ４の磁場の作用により回転し、その回転量は
対物レンズ４の磁場の強さすなわち対物レンズの励磁電
流により変化するため、表示装置８に表示される画像も
電子ビームの回転に伴ない回転する。これにより、上記
の調整時の画像の動きは上下左右の動きと回転が重なっ
た複雑な動きとなり、上下左右の動きのみを止める調整
が困難となっていた。The electron beam rotates by the action of the magnetic field of the objective lens 4 as shown in FIG. 2, and the amount of rotation changes depending on the strength of the magnetic field of the objective lens 4, that is, the exciting current of the objective lens. The image displayed at 8 also rotates with the rotation of the electron beam. As a result, the movement of the image at the time of the above adjustment becomes a complicated movement in which the vertical and horizontal movements and the rotation overlap, and it is difficult to perform the adjustment to stop only the vertical and horizontal movements.
【００１３】本実施例では、対物レンズの励磁電流の変
化に同期して偏向コイル３による電子ビームの走査方向
を補正し、対物レンズ４による像の回転を画像表示装置
８上で打ち消すことで、画像の動きを並進運動のみとし
て上記の調整を容易にする。対物レンズ４の磁場内での
像回転角Φは、次式（１）のように対物レンズ内の磁束
密度Ｂ(ｚ)に比例する。式中、ｍ及びｅは電子の質量及
び電荷、Ｅは加速電圧、Ｂ(ｚ)は光軸上の磁束密度であ
り、Ｂ(ｚ)についての積分はレンズ磁界の有効範囲にわ
たって行う。In this embodiment, the scanning direction of the electron beam by the deflection coil 3 is corrected in synchronism with the change of the exciting current of the objective lens, and the rotation of the image by the objective lens 4 is canceled on the image display device 8. Only the translational movement of the image facilitates the above adjustment. The image rotation angle Φ in the magnetic field of the objective lens 4 is proportional to the magnetic flux density B (z) in the objective lens as in the following expression (1). In the equation, m and e are electron mass and charge, E is accelerating voltage, B (z) is the magnetic flux density on the optical axis, and integration for B (z) is performed over the effective range of the lens magnetic field.
【００１４】
Φ＝（ｅ／８ｍＥ）1/2∫Ｂ(ｚ)ｄｚ （１）
磁束密度Ｂ(ｚ)は励磁電流に比例し、前記像回転角Φは
対物レンズ４の励磁電流と一定の関係を有するので、こ
の関係を計算又は実験により予め求めて制御回路９内の
記憶手段あるいは外部の記憶手段に記憶させておく。制
御回路９は、対物レンズ４の励磁電流を周期的に変化さ
せるとともに、それに連動して変化させるべき偏向コイ
ル３による走査方向を前記関係から求め、それに基づい
て偏向コイルを駆動する。すなわち、Ｘ0(ｔ)及びＹ
0(ｔ)を標準的に用いる偏向電流信号（鋸波形）とする
とき、Ｘ方向の偏向コイル及びＹ方向の偏向コイルに次
式（２），（３）で表される偏向電流Ｘ(ｔ)，Ｙ(ｔ)を
供給し、各瞬間における電子ビームの走査方向を像の回
転を打ち消す方向に補正する。Φ = (e / 8mE) 1/2 ∫B (z) dz (1) The magnetic flux density B (z) is proportional to the exciting current, and the image rotation angle Φ is constant with the exciting current of the objective lens 4. Since there is a relationship, this relationship is obtained in advance by calculation or experiment and stored in the storage means in the control circuit 9 or an external storage means. The control circuit 9 periodically changes the exciting current of the objective lens 4, determines the scanning direction of the deflection coil 3 to be changed in conjunction with the excitation current, from the above relationship, and drives the deflection coil based on that. That is, X 0 (t) and Y
When 0 (t) is used as the standard deflection current signal (sawtooth waveform), the deflection current X (t shown in the following equations (2) and (3) is applied to the X-direction deflection coil and the Y-direction deflection coil. ), Y (t) are supplied, and the scanning direction of the electron beam at each moment is corrected to a direction that cancels the rotation of the image.
【００１５】
Ｘ(ｔ)＝Ｘ0(ｔ)ｃｏｓΦ(ｔ)＋Ｙ0(ｔ)ｓｉｎΦ(ｔ) （２）
Ｙ(ｔ)＝Ｙ0(ｔ)ｃｏｓΦ(ｔ)＋Ｘ0(ｔ)ｓｉｎΦ(ｔ) （３）
図３に、偏向コイル３に接続される走査方向補正回路の
具体例を示す。Ｘスキャン発生回路２１は標準偏向信号
Ｘ0(ｔ)を発生し、Ｙスキャン回路２２は標準偏向信号
Ｙ0(ｔ)を発生する。マイクロコンピュータ２３は、予
め記憶している演算式に基づいて各瞬間における対物レ
ンズ４の励磁電流からその瞬間の像回転角Φ(ｔ)を求
め、三角関数ｃｏｓΦ(ｔ)、ｓｉｎΦ(ｔ)を演算してＤ
／Ａコンバータ２４〜２７に与え、Ｘ0(ｔ)，Ｙ0(ｔ)に
前記三角関数を乗算する。Ｄ／Ａコンバータ２４と２７
の出力は加算器２８で加算されてＸ方向の偏向コイル３
ａに給電され、Ｄ／Ａコンバータ２５と２６の出力は加
算器２９で加算されてＹ方向の偏向コイル３ｂに給電さ
れる。こうして前記（２）及び（３）式に基づく走査方
向の補正が行われるため表示装置８に表示される画像の
回転が無くなり、画像の動きは電子ビームの軸ずれに基
づく上下左右の動きのみとなって、絞り孔位置の微調整
が容易となる。[0015] X (t) = X 0 ( t) cosΦ (t) + Y 0 (t) sinΦ (t) (2) Y (t) = Y 0 (t) cosΦ (t) + X 0 (t) sinΦ ( t) (3) FIG. 3 shows a specific example of the scanning direction correction circuit connected to the deflection coil 3. The X scan generation circuit 21 generates a standard deflection signal X 0 (t), and the Y scan circuit 22 generates a standard deflection signal Y 0 (t). The microcomputer 23 obtains the image rotation angle Φ (t) at that moment from the exciting current of the objective lens 4 at each moment on the basis of the arithmetic expression stored in advance, and calculates the trigonometric functions cosΦ (t) and sinΦ (t). Calculate and D
/ A converters 24 to 27 to multiply X 0 (t) and Y 0 (t) by the trigonometric function. D / A converters 24 and 27
Outputs are added by the adder 28 and are added to the deflection coil 3 in the X direction.
a is fed, the outputs of the D / A converters 25 and 26 are added by an adder 29, and fed to the Y-direction deflection coil 3b. In this way, since the scanning direction is corrected based on the equations (2) and (3), the rotation of the image displayed on the display device 8 is eliminated, and the image movement is only vertical and horizontal movement based on the axis deviation of the electron beam. As a result, fine adjustment of the aperture position becomes easy.
【００１６】偏向方向の補正は、演算式によらず、あら
かじめ対物レンズ４の励磁電流の変化Δｆiによる検出
像の回転Φiを測定し、図４に示すように励磁電流とそ
の回転を打ち消すための偏向電流の関係についてのテー
ブルを作成しておき、そのテーブルに基づいて偏向コイ
ル３に補正電流を与えるようにしてもよい。絞り孔の孔
径の変更は、図１に示した可動式多孔絞り装置によらず
に特定の孔径の１個の絞りのみを取り付けた固定式絞り
装置で絞りを孔径の異なるものに交換することによって
行ってもよく、この場合においても絞りを交換した後に
必要となる電子ビームの軸の微調整に本発明は有効であ
る。For the correction of the deflection direction, the rotation Φ i of the detected image due to the change Δf i of the exciting current of the objective lens 4 is measured in advance without depending on the arithmetic expression, and the exciting current and its rotation are canceled as shown in FIG. It is also possible to create a table for the relationship of the deflection current for the above, and to apply the correction current to the deflection coil 3 based on the table. The aperture diameter of the aperture is changed by changing the aperture to a different aperture with a fixed aperture having only one aperture with a specific aperture attached instead of the movable aperture aperture shown in FIG. The present invention is effective for fine adjustment of the electron beam axis, which is necessary even after the diaphragm is exchanged.
【００１７】また、電子ビームの軸調整は、絞りの位置
を機械的に調整する代わりに、図５に示すように、電子
ビームの近傍に配置された軸調整用電磁コイル１１を用
いて行うこともでき、この場合においても本発明は同様
に有効である。軸調整用電磁コイル１１は、偏向コイル
と同様に電子ビームを垂直平面方向に偏向させる機能を
有するコイルで、その偏向電流を制御することによっ
て、絞り孔２ａを通過した電子ビーム１を電磁的に対物
レンズ４の中心軸に合わせる機能を有する。Further, the axis adjustment of the electron beam is performed by using an axis adjusting electromagnetic coil 11 arranged near the electron beam, as shown in FIG. 5, instead of mechanically adjusting the position of the diaphragm. The present invention is similarly effective in this case as well. The axis adjusting electromagnetic coil 11 is a coil having a function of deflecting the electron beam in the vertical plane direction similarly to the deflection coil, and by controlling the deflection current, the electron beam 1 that has passed through the aperture 2a is electromagnetically changed. It has a function of aligning with the central axis of the objective lens 4.
【００１８】また、走査形電子顕微鏡では、得られた画
像を解析して自動焦点合わせを行うことができる。自動
焦点合わせは、焦点位置を光軸方向に振り、画像の微分
信号が極大となる焦点位置を探すことによって行われる
が、対物レンズは励磁電流の変化に対してヒステリシス
を有するため、精度良く焦点位置を探すことが困難であ
る。そのため、ヒステリシスの少ない空芯コイル１２
（図５参照）を用いて、その電流を周期的に変化させる
ことにより焦点位置の移動が行われる。このとき電子ビ
ームが空芯コイル１２の中心軸を通っていなければ、焦
点位置を移動させたとき、検出像が移動するため目的の
検出像のコントラストの微分信号がピークとなる焦点位
置を正確に検出することができず、自動焦点合わせを行
うことができない。従って、自動焦点合わせにおいては
空芯コイル１２の中心軸に電子ビーム１を軸調整する必
要がある。この場合にも本発明を適用し、空芯コイル１
２の電流制御に同期して偏向コイル３に流す偏向電流を
制御し、電子ビーム１の走査方向を補正して検出像の回
転を止めることで、電子ビームの軸調整を高精度に行う
ことができる。Further, in the scanning electron microscope, it is possible to analyze the obtained image and perform automatic focusing. Automatic focusing is performed by moving the focus position in the optical axis direction and searching for the focus position where the differential signal of the image is maximum, but the objective lens has hysteresis with respect to changes in the excitation current, so the focus can be adjusted accurately. It is difficult to find the position. Therefore, the air-core coil 12 with less hysteresis
(See FIG. 5), the focus position is moved by periodically changing the current. At this time, if the electron beam does not pass through the central axis of the air-core coil 12, when the focus position is moved, the detection image moves, so that the focus position where the differential signal of the contrast of the target detection image has a peak is accurately measured. It cannot be detected and cannot be autofocused. Therefore, in automatic focusing, it is necessary to axially adjust the electron beam 1 to the center axis of the air-core coil 12. Also in this case, the present invention is applied to the air-core coil 1
The axis of the electron beam can be adjusted with high accuracy by controlling the deflection current flowing in the deflection coil 3 in synchronization with the current control of 2 to correct the scanning direction of the electron beam 1 and stop the rotation of the detected image. it can.
【００１９】図６は、絞り孔の位置調整を自動化した実
施例の概念図である。可動式絞り装置２は、Ｘ，Ｙ方向
の可動部に各々、Ｘ軸用モータ１３ａ、Ｙ軸用モータ１
３ｂを備え、モータ１３ａ，１３ｂを制御回路９によっ
て駆動して絞り２ａのＸ，Ｙ方向位置を微調整できるよ
うになっている。制御回路９は、対物レンズ４の励磁電
流に同期して偏向コイル３の駆動電流を前述のように制
御することで、検出器６で検出した２次電子信号等によ
る検出像の回転を止める。すると、検出像の動きは絞り
孔２ａの位置ずれに起因する上下左右の動きのみになる
ため、画像処理回路１０で画像の動く方向を認識し、そ
の動きが無くなるようにＸ軸用モータ１３ａ及びＹ軸用
モータ１３ｂを駆動して絞り孔２ａのＸ，Ｙ方向位置を
調整する。FIG. 6 is a conceptual diagram of an embodiment in which the position adjustment of the diaphragm hole is automated. The movable diaphragm device 2 includes an X-axis motor 13a and a Y-axis motor 1 at the X- and Y-direction movable portions, respectively.
3b, the motors 13a and 13b are driven by the control circuit 9 so that the position of the diaphragm 2a in the X and Y directions can be finely adjusted. The control circuit 9 controls the drive current of the deflection coil 3 in synchronization with the exciting current of the objective lens 4 as described above, thereby stopping the rotation of the detected image due to the secondary electron signal detected by the detector 6. Then, since the movement of the detected image is only the movement in the vertical and horizontal directions due to the positional deviation of the aperture hole 2a, the image processing circuit 10 recognizes the moving direction of the image, and the X-axis motor 13a and the X-axis motor 13a are arranged to eliminate the movement. The Y-axis motor 13b is driven to adjust the position of the aperture 2a in the X and Y directions.
【００２０】画像処理回路１０による検出像の移動方向
の認識は、例えば画像記憶装置に検出像のコントラスト
分布を１フレーム分記憶し、次に対物レンズの励磁電流
を変化させたときの検出像のコントラスト分布を１フレ
ーム分記憶し、この２つの記憶像をもとにコントラスト
分布の移動方向を認識することで行うことができる。図
７のフローチャートは、画像処理により検出像の並進運
動の方向を検出し、その動きが無くなるように可動式絞
り装置２のＸ軸用モータ１３ａ及びＹ軸用モータ１３ｂ
を駆動する制御の流れの一例を示したものである。な
お、ここでは簡単のために、画像の左右方向の移動補正
をＸ軸用モータ１３ａで行い、画像の上下方向の移動補
正をＹ軸用モータ１３ｂで行うとして説明する。The movement direction of the detected image is recognized by the image processing circuit 10. For example, one frame of the contrast distribution of the detected image is stored in the image storage device, and then the detected image when the exciting current of the objective lens is changed is detected. This can be performed by storing the contrast distribution for one frame and recognizing the moving direction of the contrast distribution based on these two stored images. The flowchart of FIG. 7 detects the direction of the translational movement of the detected image by image processing, and eliminates the movement so that the X-axis motor 13a and the Y-axis motor 13b of the movable diaphragm device 2 are eliminated.
3 shows an example of the flow of control for driving the. Note that, for simplification, it is assumed that the horizontal movement correction of the image is performed by the X-axis motor 13a and the vertical movement movement of the image is performed by the Y-axis motor 13b.
【００２１】前述のように、制御回路９は、対物レンズ
４の励磁電流を周期的に変化させるとともに、この励磁
電流の変化に同期して偏向コイル３に流す偏向電流を制
御することで電子線の走査方向を補正して検出像の回転
を止める。この状態で、画像処理回路１０は、所定のタ
イミングで２フレーム分の画像検出を行い（ステップ３
１）、それを画像処理して画像の移動方向を判定する
（ステップ３２）。画像が右に動いたことが判定されれ
ば（ステップ３３）、Ｘ軸用モータ１３ａを＋方向に駆
動する（ステップ３４）。その後、ステップ３１に戻っ
て再び所定のタイミングで２フレーム分の画像を取り込
み、それを処理して画像の移動方向を判定する（ステッ
プ３２）。まだ画像が右方向に移動していれば、再度Ｘ
用モータ１３ａを＋方向に駆動し、Ｘ軸用モータの駆動
量が大きすぎたりして画像が左に動いたことが判定され
れば（ステップ３５）、Ｘ軸用モータ１３ａを−方向に
駆動する。同様に、ステップ３２の画像処理によって画
像が上に動いたことが判定されれば（ステップ３７）、
Ｙ軸用モータ１３ｂを＋方向に駆動し（ステップ３
８）、画像が下に動いたことが判定されれば（ステップ
３９）、Ｙ軸用モータ１３ｂを−方向に駆動する（ステ
ップ４０）。このように、本実施例によると絞りの位置
調整を自動的に行うことができる。As described above, the control circuit 9 cyclically changes the exciting current of the objective lens 4 and controls the deflection current flowing through the deflection coil 3 in synchronization with the change of the exciting current to control the electron beam. The scanning direction is corrected to stop the rotation of the detected image. In this state, the image processing circuit 10 performs image detection for two frames at a predetermined timing (step 3
1) The image is processed to determine the moving direction of the image (step 32). If it is determined that the image has moved to the right (step 33), the X-axis motor 13a is driven in the + direction (step 34). After that, the process returns to step 31, and the image for two frames is again captured at a predetermined timing, and the processed image is processed to determine the moving direction of the image (step 32). If the image is still moving to the right, X again
If the drive motor 13a is driven in the + direction, and it is determined that the image has moved to the left because the drive amount of the X-axis motor is too large (step 35), the X-axis motor 13a is driven in the-direction. To do. Similarly, if it is determined that the image has moved upward by the image processing in step 32 (step 37),
Drive the Y-axis motor 13b in the + direction (step 3
8) If it is determined that the image has moved downward (step 39), the Y-axis motor 13b is driven in the-direction (step 40). As described above, according to this embodiment, the position of the diaphragm can be automatically adjusted.
【００２２】また、Ｘ軸用モータ１３ａ及びＹ軸用モー
タ１３ｂの代わりに電磁コイルを用いて電子ビームの軸
調整を行う場合には、図７のステップ３４，３６，３
８，４０における制御をその電磁コイルに対して行うこ
とにより、電子ビームの軸調整を自動化することができ
る。Further, in the case of adjusting the electron beam axis by using an electromagnetic coil instead of the X-axis motor 13a and the Y-axis motor 13b, steps 34, 36 and 3 in FIG.
The axis adjustment of the electron beam can be automated by controlling the electromagnetic coils at 8 and 40.
【００２３】 [0023]
【発明の効果】本発明によると、走査電子顕微鏡におけ
る煩わしい操作の一つである電子ビームの軸調整が容易
となり、操作性が向上する。According to the present invention, the axis adjustment of the electron beam, which is one of the troublesome operations in the scanning electron microscope, becomes easy and the operability is improved.
【図面の簡単な説明】 [Brief description of drawings]
【図１】本発明の一実施例を示す図。 FIG. 1 is a diagram showing an embodiment of the present invention.
【図２】対物レンズによる電子ビームの回転を説明する
模式図。 FIG. 2 is a schematic diagram illustrating rotation of an electron beam by an objective lens.
【図３】偏向コイルの駆動電流補正回路の一実施例を示
す図。 FIG. 3 is a diagram showing an embodiment of a deflection coil drive current correction circuit.
【図４】対物レンズの励磁電流とその回転を打ち消すた
めの偏向電流の関係についてのテーブルの説明図。 FIG. 4 is an explanatory diagram of a table regarding a relationship between an excitation current of an objective lens and a deflection current for canceling its rotation.
【図５】軸調整用電磁コイル及び対物レンズのヒステリ
シス補正用空芯コイルの配置図。 FIG. 5 is a layout diagram of an axis adjusting electromagnetic coil and an air core coil for correcting hysteresis of an objective lens.
【図６】全自動軸調整の一実施例を示す図。 FIG. 6 is a diagram showing an example of fully automatic axis adjustment.
【図７】軸調整を自動化する制御のフローチャート。 FIG. 7 is a flowchart of control for automating axis adjustment.
１…電子ビーム、２…可動式多孔絞り装置、２ａ…絞り
孔、３…偏向コイル、４…対物レンズ、５…試料、６…
検出器、７…増幅回路、８…表示装置、９…制御回路、
１０…画像処理回路、１１…軸調整用電磁コイル、１２
…自動焦点合わせ用補正コイル、１３ａ…可動絞りのＸ
軸駆動用モータ、１３ｂ…可動絞りのＹ軸駆動用モー
タ、２１…Ｘスキャン発生回路、２２…Ｙスキャン発生
回路、２３…マイクロコンピュータ、２４〜２７…Ｄ／
Ａコンバータ、２８，２９…加算器DESCRIPTION OF SYMBOLS 1 ... Electron beam, 2 ... Movable porous diaphragm device, 2a ... Stopper hole, 3 ... Deflection coil, 4 ... Objective lens, 5 ... Sample, 6 ...
Detector, 7 ... Amplifying circuit, 8 ... Display device, 9 ... Control circuit,
10 ... Image processing circuit, 11 ... Electromagnetic coil for axis adjustment, 12
... correction coil for automatic focusing, 13a ... X of movable diaphragm
Axis drive motor, 13b ... Y-axis drive motor for movable diaphragm, 21 ... X scan generation circuit, 22 ... Y scan generation circuit, 23 ... Microcomputer, 24-27 ... D /
A converter, 28, 29 ... Adder
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭63−94544（ＪＰ，Ａ) 特開 平６−302294（ＪＰ，Ａ) 特開 平２−18845（ＪＰ，Ａ) 特開 平４−192244（ＪＰ，Ａ) 特開 昭58−75748（ＪＰ，Ａ) 特開 昭52−94768（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01J 37/04 H01J 37/22 H01J 37/09 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A 63-94544 (JP, A) JP-A 6-302294 (JP, A) JP-A 2-18845 (JP, A) JP-A 4- 192244 (JP, A) JP-A-58-75748 (JP, A) JP-A-52-94768 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) H01J 37/04 H01J 37 / 22 H01J 37/09
Claims (5)
り装置と、電子ビームを試料上で２次元走査するための
偏向手段と、電子ビームを試料上に集束させて焦点を合
わせるための対物レンズと、試料から発生した信号を検
出する検出手段と、前記検出手段からの検出信号をもと
に検出像を形成するための画像形成手段と、前記対物レ
ンズを通る電子ビームの軸を調整するための軸調整手段
と、前記偏向手段及び対物レンズを制御する制御手段と
を備える走査電子顕微鏡において、 前記制御手段は、前記軸調整手段による電子ビームの軸
調整時に、前記対物レンズの励磁電流を周期的に変化さ
せるとともに該励磁電流の変化に同期して前記偏向手段
を制御して検出像の回転を止める制御を行うことを特徴
とする走査電子顕微鏡。1. A diaphragm device for varying a beam current on a sample, a deflecting unit for two-dimensionally scanning an electron beam on a sample, and an objective for focusing the electron beam on the sample for focusing. A lens, a detection means for detecting a signal generated from a sample, an image forming means for forming a detection image based on a detection signal from the detection means, and an axis of an electron beam passing through the objective lens are adjusted. In the scanning electron microscope including an axis adjusting unit for controlling the deflection unit and the objective lens, the control unit controls the exciting current of the objective lens when adjusting the axis of the electron beam by the axis adjusting unit. A scanning electron microscope, wherein the scanning electron microscope is characterized by periodically changing and controlling the deflecting means in synchronism with a change in the exciting current to stop rotation of a detected image.
孔の位置を機械的に調整するものであることを特徴とす
る請求項１記載の走査電子顕微鏡。2. The scanning electron microscope according to claim 1, wherein the axis adjusting means mechanically adjusts a position of a diaphragm hole of the diaphragm device.
配置された電磁コイルであることを特徴とする請求項１
記載の走査電子顕微鏡。3. The axis adjusting means is an electromagnetic coil arranged in the vicinity of the electron beam.
The scanning electron microscope described.
の空芯コイルを備えることを特徴とする請求項３記載の
走査電子顕微鏡。4. The scanning electron microscope according to claim 3, wherein the objective lens includes an air-core coil for hysteresis correction.
による電子ビームの軸調整時に、前記画像処理手段によ
って検出像の動く方向を認識し、前記制御手段は前記認
識した検出像の動きを止めるように前記軸調整手段を制
御することを特徴とする請求項１〜４のいずれか１項記
載の走査電子顕微鏡。5. An image processing means is further provided, and when the axis adjustment means adjusts the axis of the electron beam, the image processing means recognizes the moving direction of the detected image, and the control means stops the recognized movement of the detected image. The scanning electron microscope according to claim 1, wherein the axis adjusting means is controlled as described above.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13484995A JP3400608B2 (en) | 1995-06-01 | 1995-06-01 | Scanning electron microscope |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13484995A JP3400608B2 (en) | 1995-06-01 | 1995-06-01 | Scanning electron microscope |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08329870A JPH08329870A (en) | 1996-12-13 |
| JP3400608B2 true JP3400608B2 (en) | 2003-04-28 |
Family
ID=15137914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13484995A Expired - Fee Related JP3400608B2 (en) | 1995-06-01 | 1995-06-01 | Scanning electron microscope |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3400608B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010198826A (en) * | 2009-02-24 | 2010-09-09 | Jeol Ltd | Alignment device of transmission type electron microscope |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3953309B2 (en) | 2001-12-04 | 2007-08-08 | 株式会社トプコン | Scanning electron microscope |
| JP5500868B2 (en) * | 2009-05-14 | 2014-05-21 | 株式会社日立ハイテクノロジーズ | Scanning electron microscope and image display method in scanning electron microscope |
| JP6957998B2 (en) * | 2017-06-07 | 2021-11-02 | 株式会社ニューフレアテクノロジー | Multi-charged particle beam drawing device and multi-charged particle beam adjustment method |
| JP7040927B2 (en) * | 2017-12-01 | 2022-03-23 | 株式会社日立ハイテク | Image pickup condition adjustment method in charged particle beam device and charged particle beam device |
| JP7047523B2 (en) * | 2018-03-26 | 2022-04-05 | 株式会社島津製作所 | Charged particle beam alignment device, charged particle beam irradiation device and charged particle beam alignment method |
| KR102093346B1 (en) * | 2018-11-20 | 2020-03-25 | 한국기초과학지원연구원 | Alignment apparatus for electron microscope and electron microscope comprising the same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5294768A (en) * | 1976-02-04 | 1977-08-09 | Jeol Ltd | Electronic microscope |
| JPS5875748A (en) * | 1981-10-30 | 1983-05-07 | Shimadzu Corp | Image revolution corrector for scanning type analyzer |
| JPH073774B2 (en) * | 1986-10-08 | 1995-01-18 | 株式会社日立製作所 | electronic microscope |
| JPH0656747B2 (en) * | 1988-07-07 | 1994-07-27 | 日本電子株式会社 | Aperture position control device for electron microscope |
| JP2733710B2 (en) * | 1990-11-27 | 1998-03-30 | 株式会社日立製作所 | electronic microscope |
| JPH06302294A (en) * | 1993-04-13 | 1994-10-28 | Jeol Ltd | Scanning type charged particle beam device |
-
1995
- 1995-06-01 JP JP13484995A patent/JP3400608B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010198826A (en) * | 2009-02-24 | 2010-09-09 | Jeol Ltd | Alignment device of transmission type electron microscope |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08329870A (en) | 1996-12-13 |
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