JP2006156134A - Reflection imaging electron microscope - Google Patents

Reflection imaging electron microscope Download PDF

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JP2006156134A
JP2006156134A JP2004345113A JP2004345113A JP2006156134A JP 2006156134 A JP2006156134 A JP 2006156134A JP 2004345113 A JP2004345113 A JP 2004345113A JP 2004345113 A JP2004345113 A JP 2004345113A JP 2006156134 A JP2006156134 A JP 2006156134A
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electron beam
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electron
reflected
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Hisaya Murakoshi
久弥 村越
Hideo Todokoro
秀男 戸所
Masaki Hasegawa
正樹 長谷川
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Hitachi Ltd
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<P>PROBLEM TO BE SOLVED: To increase the contrast of a mirror electron microscope. <P>SOLUTION: A separator 4 for separating an irradiated electron beam 101 and a reflected electron beam 102 of the mirror electron microscope is positioned between an objective lens 5 and an intermediate lens 8, and a restriction diaphragm 14 is positioned in a position 43 where the intermediate lens 8 projects an electron beam diffraction image of the reflected electron beam 102 formed in a focus position 41 of the objective lens 5. The restriction of the reflected electron beam using the restriction diaphragm 14 improves the contrast of a mirror electron microscope image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、試料の表面状態などを観察するミラー電子顕微鏡などの反射結像型電子顕微鏡に関する。   The present invention relates to a reflection imaging electron microscope such as a mirror electron microscope for observing a surface state of a sample.

電子線を用いて、試料を観察する装置としては、試料を透過した電子線を結像する透過型電子顕微鏡や試料上に集束した電子線を走査して、試料から発生した二次電子などの強度を画像化する走査型電子顕微鏡などがある。図７に示す従来の透過電子顕微鏡の構成では、対物レンズ５の後焦点面４１上に制限絞り１４を配置して、試料７との相互作用により散乱する電子線だけを通過させるいわゆる暗視野像条件で画像化することにより、散乱した電子線を強調する像形成をすることが可能となっていた。しかし、これらの電子顕微鏡は試料に電子線を照射することにより試料に損傷を与える恐れがあり、損傷しやすい試料の観察をおこなうことは困難であった。   As an apparatus for observing a sample using an electron beam, a transmission electron microscope that forms an image of an electron beam transmitted through the sample, a secondary electron generated from the sample by scanning the electron beam focused on the sample, etc. There are scanning electron microscopes that image intensity. In the configuration of the conventional transmission electron microscope shown in FIG. 7, a so-called dark field image in which only the electron beam scattered by the interaction with the sample 7 is passed by disposing the limiting aperture 14 on the back focal plane 41 of the objective lens 5. By imaging under conditions, it has become possible to form an image that emphasizes the scattered electron beam. However, these electron microscopes may damage the sample by irradiating the sample with an electron beam, and it is difficult to observe a sample that is easily damaged.

これらの従来方法に対して、試料を電子源電位とほぼ同電位に設定して、試料に電子線が入射する直前で試料の情報を反映した方向や強度を持って向きを反転して反射するミラー電子を画像化する技術が特開平２００３−２０２２１７に記載されている。図５に表面に凹凸のある試料に対して試料直上の等電位面Ａで反転するミラー電子の軌道を示す。試料直上の等電位面Ａでは試料の凹凸を反映した電位歪が生じており、この電位歪によってミラー電子が横方向に散乱される。この横方向に散乱された電子を含むミラー電子を画像化すれば、電位歪に関する情報を得ることができる。   In contrast to these conventional methods, the sample is set to substantially the same potential as the electron source potential, and the direction is reflected with the direction and intensity reflecting the sample information immediately before the electron beam is incident on the sample. Japanese Patent Application Laid-Open No. 2003-202217 describes a technique for imaging mirror electrons. FIG. 5 shows the trajectory of the mirror electrons that is inverted at the equipotential surface A immediately above the sample with respect to the sample having an uneven surface. On the equipotential surface A immediately above the sample, a potential distortion reflecting the unevenness of the sample is generated, and mirror electrons are scattered in the lateral direction due to the potential distortion. Information about potential distortion can be obtained by imaging the mirror electrons including the electrons scattered in the lateral direction.

特開平２００３−２０２２１７JP 2003-202217 A

従来のミラー電子顕微鏡では、照射電子線はあるエネルギーの広がりを持って試料に照射されるので、エネルギー幅の大きな照射電子線では、エネルギーの小さな照射電子は試料の直前まで達することなく試料より遠方の等電位面で反転してしまう。図６に示す試料から離れた等電位面Ｂで反転するミラー電子の軌道を示す。等電位面Ｂでは電位歪が小さく凹凸面上方のミラー電子も横方向に散乱されないようになる。このような条件では、横方向に散乱した電子線が大部分の散乱しないミラー電子線と区別できなくなり、ミラー電子画像のコントラストが小さくなってしまうという問題があった。図８に示すように照射電子線１０１と反射電子線１０２を分離させるセパレータ５１が、対物レンズ５より電子源側にあるため、対物レンズ５を含むセパレータ５１と試料７の間の区間では、照射電子線１０１と反射電子線１０２がほぼ同じ空間を運動することになる。   In conventional mirror electron microscopes, the irradiated electron beam irradiates the sample with a certain energy spread, so with an irradiated electron beam with a large energy width, the irradiated electron with a small energy does not reach just before the sample and is far from the sample. Inversion at the equipotential surface. FIG. 7 shows a trajectory of mirror electrons that is inverted at an equipotential surface B away from the sample shown in FIG. On the equipotential surface B, the potential distortion is small and the mirror electrons above the irregular surface are not scattered in the lateral direction. Under such conditions, there is a problem that the electron beam scattered in the lateral direction cannot be distinguished from most non-scattered mirror electron beams, and the contrast of the mirror electron image is reduced. As shown in FIG. 8, the separator 51 that separates the irradiated electron beam 101 and the reflected electron beam 102 is located on the electron source side with respect to the objective lens 5, so that irradiation is performed in the section between the separator 51 including the objective lens 5 and the sample 7. The electron beam 101 and the reflected electron beam 102 move in almost the same space.

ここで、反射電子線１０２の電子線回折像は対物レンズ５の焦点面４１上に形成されるので、制限絞り１４を対物レンズ５の焦点面４１上に配置して、特定の散乱方向の反射電子線１０２を選択して制限絞り１４を通過させることにより、散乱の少ない反射電子線を選択的に結像させる明視野像や散乱した反射電子線を選択的に結像させる暗視野像を得ることができる。しかし、この制限絞り１４は照射電子線１０１に対しても試料への照射角度を制限する制限絞りとして作用する位置に配置されるため、反射電子線の散乱方向に合わせて制限絞りを調整すると、照射電子線１０１が制限絞りに衝突してしまい、試料に照射できなくなるという問題があった。   Here, since the electron beam diffraction image of the reflected electron beam 102 is formed on the focal plane 41 of the objective lens 5, the limiting aperture 14 is disposed on the focal plane 41 of the objective lens 5 to reflect in a specific scattering direction. By selecting the electron beam 102 and passing through the limiting aperture 14, a bright field image for selectively forming a reflected electron beam with little scattering and a dark field image for selectively forming a scattered reflected electron beam are obtained. be able to. However, since the limiting aperture 14 is disposed at a position that also acts as a limiting aperture that limits the irradiation angle of the sample with respect to the irradiation electron beam 101, when the limiting aperture is adjusted in accordance with the scattering direction of the reflected electron beam, There was a problem that the irradiated electron beam 101 collided with the restriction aperture and the sample could not be irradiated.

本発明は、上述の点に着目してなされたものであり、ミラー電子顕微鏡で特定の散乱方向の反射電子線画像を、照射電子線１０１に影響を及ぼすことなく形成できる装置構成を実現することを目的とする。   The present invention has been made paying attention to the above points, and realizes an apparatus configuration capable of forming a reflected electron beam image in a specific scattering direction with a mirror electron microscope without affecting the irradiated electron beam 101. With the goal.

本発明の目的は、以下の方法で達成できる。
本発明では、反射電子線１０２の試料出射角度を制限する制限絞り１４を、電子線回折像が形成される対物レンズの焦点面４１近傍ではなく、セパレータ５１により照射電子線１０１と反射電子線１０２が分離後に形成される電子線回折像の後段レンズによる投影像面近傍に制限絞り１４を配置させることによって、暗視野像が形成できるようにした。本発明の原理を図９、図１０で詳細に説明する。
ここでは、セパレータ５１として、電界と磁界を交叉させて動作させるＥｘＢ偏向器４を用いることにする。ＥｘＢ偏向器は、電界と磁界を直交かつ重畳して動作させる偏向器である。図１１を用いてこの動作を説明する。加速電圧Ｖ０の電子線が図１１に示す長さ２ｌ、間隔ｄの平行平板電極型の静電偏向器で偏向される偏向角θEおよび長さ２ｌの均一磁界偏向器で偏向される偏向角θMは、それぞれ次式で与えられる。 The object of the present invention can be achieved by the following method.
In the present invention, the limiting aperture 14 for limiting the sample emission angle of the reflected electron beam 102 is not the vicinity of the focal plane 41 of the objective lens on which the electron beam diffraction image is formed, but the separator 51 and the irradiated electron beam 101 and the reflected electron beam 102. A dark field image can be formed by disposing a limiting aperture 14 in the vicinity of a projection image plane formed by a latter stage lens of an electron beam diffraction image formed after separation. The principle of the present invention will be described in detail with reference to FIGS.
Here, as the separator 51, the ExB deflector 4 that operates by crossing an electric field and a magnetic field is used. The ExB deflector is a deflector that operates by superimposing an electric field and a magnetic field in an orthogonal manner. This operation will be described with reference to FIG. The electron beam of the acceleration voltage V 0 is deflected by a uniform magnetic deflector having a deflection angle θ E and a length of 2 l deflected by a parallel plate electrode type electrostatic deflector having a length of 2 l and a distance d shown in FIG. The angle θ M is given by the following equation.

Figure 2006156134
Figure 2006156134

電界による偏向と磁界による偏向が打ち消しあう条件 Conditions in which deflection by electric field and deflection by magnetic field cancel each other

Figure 2006156134
Figure 2006156134

をウィーン条件と呼び、図１１でウィーン条件に設定されたＥ×Ｂ 偏向器に上方から入射した電子線は直進し、下方から入射した電子線はθE+θM＝２θEの偏向を受けるという特性を持つ。 Is referred to as the Wien condition, and the electron beam incident from above on the E × B deflector set to the Wien condition in FIG. 11 goes straight, and the electron beam incident from below undergoes deflection of θ E + θ M = 2θ E It has the characteristics.

照射電子線１０１の軌道を図９に示す。照射電子線１０１の光軸１０３と反射電子線１０２の光軸１０４は、θINの角度で交差している。ＥｘＢ偏向器４は照射電子線１０１に対しては偏向角θIN＝θE+θMの偏向器、反射電子線１０２に対してはウィーン条件θE＝θMが成り立ち、直進させるように動作する。すなわち、照射電子線１０１はＥｘＢ偏向器４により電子源を含む光軸１０３から試料に垂直な光軸１０４方向に角度θIN偏向された後、対物レンズ焦点面４１近傍に集束することにより、試料７を平行照射することができる。照射電子線１０１が試料７からミラー反射した反射電子線１０２の軌道を図１０に示すが、対物レンズ焦点面４１は透過電子顕微鏡の電子線回折像位置に相当し、試料７から同じ方向に散乱された電子線はこの焦点面４１上に集束するので、この対物レンズ焦点面（電子線回折像）位置に制限絞り１４を配置すれば反射電子線１０２の散乱方向を制限することができる。しかし、暗視野像を得るために制限絞り１４を結像系の光軸１０４から離すと、照射電子線１０１をすべて制限することになり、試料７に照射電子線１０１を照射することができなくなる。 The trajectory of the irradiation electron beam 101 is shown in FIG. The optical axis 103 of the irradiation electron beam 101 and the optical axis 104 of the reflected electron beam 102 intersect at an angle of θ IN . The ExB deflector 4 operates such that the deflection electron beam 101 has a deflection angle θ IN = θ E + θ M , and the reflected electron beam 102 has a Wien condition θ E = θ M, and moves straight. To do. That is, electron beam irradiation 101 after being angle theta IN deflected optical axis perpendicular 104 direction from the optical axis 103 to a sample containing an electron source by ExB deflector 4, by focusing near the objective lens focal plane 41, the sample 7 can be irradiated in parallel. FIG. 10 shows the trajectory of the reflected electron beam 102 where the irradiated electron beam 101 is mirror-reflected from the sample 7, and the objective lens focal plane 41 corresponds to the position of the electron diffraction image of the transmission electron microscope and is scattered from the sample 7 in the same direction. Since the emitted electron beam is focused on the focal plane 41, the scattering direction of the reflected electron beam 102 can be limited by disposing the limiting aperture 14 at the position of the objective lens focal plane (electron beam diffraction image). However, if the limiting aperture 14 is separated from the optical axis 104 of the imaging system in order to obtain a dark field image, all of the irradiation electron beam 101 is limited, and the sample 7 cannot be irradiated with the irradiation electron beam 101. .

この課題を解決するために、反射電子線１０２がセパレータを通過後に、中間レンズ８によって投影される電子線回折像の結像面４３に制限絞り１４を配置して、この結像面４３上を可動であるようにした。図中では、試料７から３つの方向に散乱された電子線の軌道を記述しているが、円孔状の制限絞り１４を図中光軸１０４より右側にずらして、試料から図中左上方向に散乱された反射電子線だけを通過させることにより、左上方向に散乱された電子線のみの投影像を観察することができる。また、制限絞りの形状を図１２に示すような円環状の形状とすれば、円環の内径Ｒ1及び外径Ｒ2で規定される散乱角度範囲のミラー電子による投影像を形成することができる。 In order to solve this problem, after the reflected electron beam 102 passes through the separator, the limiting aperture 14 is disposed on the imaging plane 43 of the electron beam diffraction image projected by the intermediate lens 8, and the imaging plane 43 is moved over the imaging plane 43. It was made movable. In the figure, the trajectories of the electron beams scattered in three directions from the sample 7 are described, but the circular aperture-shaped restricting aperture 14 is shifted to the right side from the optical axis 104 in the figure, and the upper left direction in the figure from the sample. By allowing only the reflected electron beam scattered by the beam to pass through, it is possible to observe a projection image of only the electron beam scattered in the upper left direction. Further, if the shape of the limiting diaphragm is an annular shape as shown in FIG. 12, a projected image by mirror electrons in the scattering angle range defined by the inner diameter R 1 and the outer diameter R 2 of the annular ring can be formed. it can.

ここで、上述の説明では暗視野像を得るために円孔形状の制限絞りを光軸から離した条件で用いていたが、照射電子線を試料に垂直に照射する条件でなく傾斜させて照射して、結像系の光軸方向に反射した反射電子線を取得することにより、反射電子線の軸外収差が小さい投影画像を得ることができる。この原理を図１３、図１４ により説明する。照射電子線１０１をＥｘＢ偏向器４により電子源を含む光軸１０３から試料に垂直な光軸１０３方向に角度θIN偏向した後、対物レンズ焦点面４１近傍に集束させることにより、試料７を試料に垂直な方向から平行照射させることができる。照射電子線１０１の軌道を図１３に示すが、ミラー電子顕微鏡条件では、照射電子線１０１と反射電子線１０２のエネルギーが等しいので、対物レンズによって試料５の反射電子線投影像が形成される像面位置４２近傍に配置されるＥ×Ｂ偏向器４の位置が、照射電子線１０１が試料５にクロスオーバを結ぶための照射電子線の物面位置に相当する。したがって、Ｅ×Ｂ偏向器４で照射電子線１０１を例えば角度θD偏向させると、円孔電極６に角度θAPの偏向角で入射し、光軸から傾斜した平行の照射電子線で試料上の同じ位置を照射することになる。したがって、照射電子線を円孔電極６に角度θAPの偏向角で入射させ試料の同じ場所を照射させるためには、Ｅ×Ｂ偏向器４のＸ偏向器、Ｙ偏向器に角度θDの偏向角に相当する偏向信号を偏向角θINに相当する偏向信号に重畳して供給すればよい。なお、このθAPとθINの関係はそれぞれのレンズ配置と動作条件が定まれば、一義的に決定されるものである。 Here, in the above description, in order to obtain a dark field image, the circular aperture-shaped limiting diaphragm was used under the condition that it was separated from the optical axis. Then, by obtaining a reflected electron beam reflected in the optical axis direction of the imaging system, a projection image with a small off-axis aberration of the reflected electron beam can be obtained. This principle will be described with reference to FIGS. After the irradiation electron beam 101 is deflected by the ExB deflector 4 from the optical axis 103 including the electron source in the direction of the optical axis 103 perpendicular to the sample by an angle θ IN , the sample 7 is focused on the objective lens focal plane 41. Parallel irradiation can be performed from a direction perpendicular to the direction. The trajectory of the irradiation electron beam 101 is shown in FIG. 13. Under the mirror electron microscope conditions, the energy of the irradiation electron beam 101 and that of the reflected electron beam 102 are equal, so that the reflected electron beam projection image of the sample 5 is formed by the objective lens. The position of the E × B deflector 4 arranged in the vicinity of the surface position 42 corresponds to the object surface position of the irradiation electron beam for the irradiation electron beam 101 to cross the sample 5. Therefore, when the irradiation electron beam 101 is deflected, for example, by the angle θ D by the E × B deflector 4, it enters the circular hole electrode 6 at a deflection angle of the angle θ AP and is applied to the sample by the parallel irradiation electron beam inclined from the optical axis. The same position is irradiated. Therefore, in order to irradiate the same position of the sample by irradiating the irradiation electron beam to the circular hole electrode 6 with the deflection angle of the angle θ AP , the X deflector and the Y deflector of the E × B deflector 4 have the angle θ D. a deflection signal corresponding to the deflection angle may be supplied by superimposing a deflection signal corresponding to a deflection angle theta iN. Note that the relationship between θ AP and θ IN is uniquely determined if the lens arrangement and the operating conditions are determined.

図１４に示す反射電子線１０２は、対物レンズ焦点面４１上で試料出射方向に対応する電子線回折図形を形成するが、この焦点面位置に制限絞り１４を配置すると、照射電子線１０１を制限してしまうので、反射電子線１０２がＥ×Ｂ偏向器４を通過後、中間レンズ８により電子線回折像が投影される位置４３に制限絞り１４を挿入する。反射電子線１０２がこのＥ×Ｂ偏向器４で偏向されると電子線回折像位置が変化してしまうが、このＥ×Ｂ偏向器４は反射電子線１０２に対して、Ｅ×Ｂ偏向器４の磁界と電界が逆方向に等しい大きさで作用するいわゆるウィーン条件が成り立つように動作させれば、反射電子線はＥ×Ｂ偏向器４で偏向されずに電子線回折像を投影することができる。   The reflected electron beam 102 shown in FIG. 14 forms an electron beam diffraction pattern corresponding to the sample exit direction on the focal plane 41 of the objective lens. When the limiting aperture 14 is arranged at this focal plane position, the irradiation electron beam 101 is limited. Therefore, after the reflected electron beam 102 passes through the E × B deflector 4, the limiting aperture 14 is inserted at a position 43 where the electron beam diffraction image is projected by the intermediate lens 8. When the reflected electron beam 102 is deflected by the E × B deflector 4, the position of the electron beam diffraction image changes, but the E × B deflector 4 is different from the reflected electron beam 102 in the E × B deflector. If the operation is performed so that the so-called Wien condition in which the magnetic field and the electric field of 4 act at the same magnitude in the opposite direction is satisfied, the reflected electron beam is projected without being deflected by the E × B deflector 4. Can do.

あるいは、試料７上の同一場所を照射角一定で照射方向を連続的に変化させて照射するいわゆるホローコーン照射する手段を設け、散乱された反射電子線のうち、光軸方向に散乱された反射電子線を選択する制限絞り１４を対物レンズ５の焦点面が中間レンズによって投影される投影面４３に配置することによって、特定の散乱角度の反射電子線のみを選択できる構成とすることもできる。この原理を図１５、図１６で説明する。照射電子線１０１の軌道を図１５に示す。Ｅ×Ｂ偏向器４の偏向電極で照射電子線１０１をＸ方向に角度θE偏向させるための電極供給電圧をＶXとし、ホローコーン照射のためにθD/2の角度を偏向させるための供給電圧をＶDとすると、図１７に示すようにＸ偏向器に、ＶX＋ＶDｃｏｓ（ｔ）、Ｙ偏向器にＶDｓｉｎ（ｔ）の偏向信号を供給する。さらに、磁界生成においても、常にＥ×Ｂ偏向器４が反射電子線に対してウィーン条件となるように、磁界を生成するための偏向コイルに、θD/2の角度を偏向させるための正弦波および余弦波信号を供給すると、照射電子線は歳差運動しながら試料の照射位置を変えずに照射することができる。図１６に示す反射電子線１０２は対物レンズ焦点面４１上に電子線回折図形を形成し、反射電子線１０２がＥ×Ｂ偏向器４を偏向されずに通過後、中間レンズ８によりこの電子線回折像が投影される位置４３に制限絞り１４を挿入することにより、ミラー電子顕微鏡の暗視野像を得ることができる。 Alternatively, a so-called hollow cone irradiating means for continuously irradiating the same place on the sample 7 with a constant irradiation angle and changing the irradiation direction is provided, and among the scattered reflected electron beams, the reflected electrons scattered in the optical axis direction are provided. By arranging the limiting aperture 14 for selecting a line on the projection plane 43 on which the focal plane of the objective lens 5 is projected by the intermediate lens, only a reflected electron beam having a specific scattering angle can be selected. This principle will be described with reference to FIGS. The trajectory of the irradiation electron beam 101 is shown in FIG. The electrode supply voltage for deflecting the irradiation electron beam 101 in the X direction by the angle θ E by the deflection electrode of the E × B deflector 4 is V X, and the supply for deflecting the angle θ D / 2 for the hollow cone irradiation. Assuming that the voltage is V D , as shown in FIG. 17, a deflection signal of V X + V D cos (t) is supplied to the X deflector and V D sin (t) is supplied to the Y deflector. Furthermore, also in the magnetic field generation, a sine for deflecting the angle θ D / 2 in the deflection coil for generating the magnetic field so that the E × B deflector 4 always has the Wien condition for the reflected electron beam. When the wave and cosine wave signals are supplied, the irradiated electron beam can be irradiated without changing the irradiation position of the sample while precessing. The reflected electron beam 102 shown in FIG. 16 forms an electron diffraction pattern on the focal plane 41 of the objective lens. After the reflected electron beam 102 passes through the E × B deflector 4 without being deflected, this electron beam is transmitted by the intermediate lens 8. A dark field image of the mirror electron microscope can be obtained by inserting the limiting aperture 14 at the position 43 where the diffraction image is projected.

本発明により、反射された電子線の散乱方向を選択的に制限できる投影画像を取得することで、軸外収差の少ないコントラストの高い像観察を行うことが可能となる。   According to the present invention, it is possible to perform high-contrast image observation with less off-axis aberrations by acquiring a projection image that can selectively limit the scattering direction of the reflected electron beam.

以下に、本発明の実施例について、図面を参照して詳細に説明する。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

図１は、実施例１の動作を説明するための構成を示したものである。セパレータとしてＥ×Ｂ偏向器４を反射電子線１０２の結像面４２近傍に配置させる。電子源を含む照射系の光軸１０３とウェハ７に垂直な結像系の光軸１０４とは、互いにθＩＮの角度で交叉している。コンデンサレンズ３と対物レンズ５の間にＥ×Ｂ偏向器４が配置されており、電子源１より放出された照射電子線１０１は、Ｅ×Ｂ偏向器４によりウェハ７に垂直な光軸に偏向される。Ｅ×Ｂ偏向器４により偏向された照射電子線１０１は、コンデンサレンズ３により対物レンズの焦点面近傍に集束され、試料上７をほぼ平行な照射電子線で照射することができる。 FIG. 1 shows a configuration for explaining the operation of the first embodiment. The E × B deflector 4 is disposed in the vicinity of the imaging surface 42 of the reflected electron beam 102 as a separator. The optical axis 103 and optical axis 104 of the imaging system perpendicular to the wafer 7 of the illumination system comprising an electron source, which intersect at an angle of theta IN together. An E × B deflector 4 is disposed between the condenser lens 3 and the objective lens 5, and the irradiation electron beam 101 emitted from the electron source 1 is placed on the optical axis perpendicular to the wafer 7 by the E × B deflector 4. Deflected. The irradiation electron beam 101 deflected by the E × B deflector 4 is focused by the condenser lens 3 in the vicinity of the focal plane of the objective lens, and the upper surface 7 of the sample can be irradiated with the substantially parallel irradiation electron beam.

試料７には、電子源１に印加される加速電圧Ｖ0とほぼ等しいかわずかに高い負の電位が、試料７を保持するステージを通じて、試料印加電源２７から供給されている。試料と対向する円孔電極６には、試料７に対して数ｋＶから数十ｋＶの範囲の正電圧が、円孔電極印加電源２６より供給されている。この円孔電極６と試料７との間の減速電界によって、面状の照射電子線１０１の大部分が試料７に衝突する直前で引き戻されてミラー電子となり、試料７の形状や電位、磁界などを反映した方向や強度を持って再び対物レンズ５に入射する。 A negative potential that is substantially equal to or slightly higher than the acceleration voltage V 0 applied to the electron source 1 is supplied to the sample 7 from a sample application power source 27 through a stage that holds the sample 7. A positive voltage in the range of several kV to several tens of kV with respect to the sample 7 is supplied from the circular hole electrode application power supply 26 to the circular hole electrode 6 facing the sample. Due to the deceleration electric field between the circular hole electrode 6 and the sample 7, most of the planar irradiation electron beam 101 is pulled back immediately before it collides with the sample 7 to become mirror electrons, and the shape, potential, magnetic field, etc. of the sample 7. It enters the objective lens 5 again with a direction and intensity reflecting the above.

このミラー電子による反射電子線１０２は、対物レンズ５により拡大されて、Ｅ×Ｂ偏向器４近傍にミラー投影像を結ぶ。このＥ×Ｂ偏向器４は反射電子線にはウィーン条件で作用させる。すなわち、反射電子線１０２に対してはＥ×Ｂ偏向器４は偏向作用を持たず、また、ミラー像がＥ×Ｂ偏向器４近傍に結像投影されるのでＥ×Ｂ偏向器４による偏向収差もほとんど発生しない。この対物レンズ５によるミラー像は、中間レンズ８および投影レンズ９により投影され、シンチレータ１０上に拡大されたミラー電子像が形成される。このミラー電子像はシンチレータ１０により光学像に変換され、光学レンズあるいは光ファイバー束１１によりＣＣＤカメラ１２上に投影され、ＣＣＤカメラ１２により電気信号に変換されたミラー電子像がモニタ１３により表示される。   The reflected electron beam 102 by the mirror electrons is magnified by the objective lens 5 and forms a mirror projection image in the vicinity of the E × B deflector 4. The E × B deflector 4 acts on the reflected electron beam under Wien conditions. That is, the E × B deflector 4 does not have a deflecting action with respect to the reflected electron beam 102, and the mirror image is formed and projected in the vicinity of the E × B deflector 4, so that the deflection by the E × B deflector 4 is performed. Little aberration occurs. The mirror image by the objective lens 5 is projected by the intermediate lens 8 and the projection lens 9, and an enlarged mirror electronic image is formed on the scintillator 10. The mirror electronic image is converted into an optical image by the scintillator 10, projected onto the CCD camera 12 by the optical lens or optical fiber bundle 11, and the mirror electronic image converted into an electric signal by the CCD camera 12 is displayed on the monitor 13.

Ｅ×Ｂ偏向器４を光軸垂直方向から見た断面は図１８に示す８極電磁極構造であり、各電磁極５１はパーマロイなどの磁性体で構成されている。各電磁極は電位を与えられることによって電極として動作し、各電磁極にＮ回巻かれているコイル５３に励磁電流を流すことによって磁極として動作する。図１８に示す電圧配分で各電磁極に電圧ＶXを印加すると、電子はx方向に偏向作用を受ける。また、図１９に示すような電流配分で電流ＩYを各コイルに流すと、図１９の紙面の裏側から表へ運動する電子はx方向の正方向、紙面の表から裏側へ運動する電子はｘ方向の負方向へ偏向作用を受ける。各電極の電圧および電流配分は実際の電磁極形状に電位あるいは磁位を与えた電磁界計算により均一な電磁界が発生するように最適化されており、例えば図中のα＝０．４１４に設定されている。 A cross section of the E × B deflector 4 viewed from the direction perpendicular to the optical axis has an octupole electromagnetic structure shown in FIG. 18, and each electromagnetic pole 51 is made of a magnetic material such as permalloy. Each electromagnetic pole operates as an electrode when a potential is applied, and operates as a magnetic pole by passing an exciting current through a coil 53 wound N times around each electromagnetic pole. When the voltage V X is applied to each electromagnetic pole with the voltage distribution shown in FIG. 18, the electrons are deflected in the x direction. Also, when current I Y is passed through each coil with current distribution as shown in FIG. 19, electrons moving from the back side to the front side of FIG. 19 are positive in the x direction, and electrons moving from the front side to the back side of the paper are It is deflected in the negative x direction. The voltage and current distribution of each electrode is optimized so that a uniform electromagnetic field is generated by an electromagnetic field calculation in which a potential or magnetic potential is applied to the actual electromagnetic pole shape. For example, α = 0.414 in the figure. Is set.

図２０はＥ×Ｂ偏向器４の光軸を含む断面図である。Ｅ×Ｂ偏向器をビームセパレータとして用いる場合、照射系と結像系の交叉角θＩＮは、二つの光学系が互いに干渉しない配置関係を考慮すると、３０度程度は取る必要がある。照射電子線１０１を３０°偏向しても電磁極に当たらないようにするためには、開口部の直径を電磁極長さより大きくしなければならないが、開口を広げると偏向させる電圧を増加させなければならないので、電磁極５１形状は電子軌道にほぼ沿った末広がりの円錐形状とした。また、電磁極の上下にはシールド電磁極５４を設け、電磁界の滲みだしを抑えるとともに、電界と磁界が同一の空間で作用するようにして、空間内で常にウィーン条件が成り立つ完全なＥ×Ｂ偏向器として動作するようにした。 FIG. 20 is a cross-sectional view including the optical axis of the E × B deflector 4. When the E × B deflector is used as a beam separator, the crossing angle θ IN between the irradiation system and the imaging system needs to be about 30 degrees in consideration of the arrangement relationship in which the two optical systems do not interfere with each other. In order to prevent the irradiated electron beam 101 from hitting the electromagnetic pole even if it is deflected by 30 °, the diameter of the opening must be made larger than the length of the electromagnetic pole, but if the opening is widened, the deflection voltage must be increased. Therefore, the shape of the electromagnetic pole 51 is a conical shape that spreads substantially along the electron trajectory. In addition, shield electromagnetic poles 54 are provided above and below the electromagnetic poles to suppress the bleeding of the electromagnetic field, and the electric field and the magnetic field act in the same space so that the Wien condition is always satisfied in the space. It was made to operate as a B deflector.

次にこのＥ×Ｂ偏向器４を用いた照射電子線１０１の調整手順について説明する。加速電圧Ｖ0が一定の条件では、ウィーン条件を満たすような電磁極印加電圧ＶXと電磁極供給電流ＩYの比は一定であるので、計算機シミュレーションなどの手法を用いてＶ0と強度比の関係はあらかじめ求められて、制御計算機３１に記憶されている。加速電圧Ｖ0を制御計算機３１にインプットすれば、制御計算機３１は電子源印加電源２１から電子源１へＶ0を印加するとともに、Ｅ×Ｂ偏向器用電圧電源２３から電磁極に印加する電圧ＶXとＥ×Ｂ偏向器用電流電源２４から電磁極に供給する電流ＩYの強度比を一定にする制御を行う。ＶXとＩYの強度比を一定のまま、ＶXとＩYを手動あるいは自動で増加させていくとともに、試料７をアース電位にして電流計を接続し、加速電圧Ｖ0の照射電子線を試料７に照射して吸収される電流を計測することによって、照射電子線が試料７に到達する条件、すなわち照射電子線のＥ×Ｂ偏向器４による偏向角θＩＮを求めることができる。 Next, a procedure for adjusting the irradiation electron beam 101 using the E × B deflector 4 will be described. The acceleration voltage V 0 is constant conditions, since the ratio of the electromagnetic poles applied voltage V X and the electromagnetic poles supply current I Y satisfying the Wien condition is constant, V 0 and the intensity ratio using techniques such as computer simulation Is obtained in advance and stored in the control computer 31. When the acceleration voltage V 0 is input to the control computer 31, the control computer 31 applies V 0 from the electron source application power source 21 to the electron source 1 and also applies the voltage V applied from the E × B deflector voltage power source 23 to the electromagnetic pole. Control is performed to make the intensity ratio of the current I Y supplied to the electromagnetic pole from the current source 24 for X and the E × B deflector constant. While keeping the intensity ratio of V X and I Y constant, V X and I Y are increased manually or automatically, the sample 7 is grounded, an ammeter is connected, and the irradiation electron beam with the acceleration voltage V 0 the by measuring the current absorbed by irradiating the sample 7, the conditions electron beam irradiation reaches the sample 7, i.e. it is possible to determine the deflection angle theta iN by E × B deflector 4 of electron beam irradiation.

次に、試料印加電源２７から試料を保持するステージを通じて試料７に印加する電圧を、電子線の加速電圧Ｖ0とほぼ等しいかわずかに高い負の電圧に、制御計算機３１が設定することにより、照射電子線は試料７の直上で向きを変えてミラー電子線になる条件となる。このミラー電子による反射電子線に対してＥ×Ｂ偏向器４が完全なウィーン条件になっていれば、反射電子線はＥ×Ｂ偏向器４内を直進して、ＣＣＤカメラ１２あるいは結像系光路上に置かれたファラデーカップなどの検出手段により検出されるが、もし反射電子線が検出されていなければ、制御計算機３１はＥ×Ｂ偏向器４に対して、ＶXとＩYの強度比を一定のままの微調整あるいはθＩＮを一定に保ったまま、電圧ＶXと電流ＩYの比率を変える制御を行う。比率を変える際の電圧の増分ΔＶと電流の増分ΔＩは Next, the control computer 31 sets the voltage applied to the sample 7 from the sample application power supply 27 through the stage holding the sample to a negative voltage that is substantially equal to or slightly higher than the acceleration voltage V 0 of the electron beam. The irradiation electron beam is in a condition to change its direction immediately above the sample 7 to become a mirror electron beam. If the E × B deflector 4 has perfect Wien conditions for the reflected electron beam by the mirror electrons, the reflected electron beam travels straight through the E × B deflector 4 and the CCD camera 12 or the imaging system. Although it is detected by a detecting means such as a Faraday cup placed on the optical path, if no reflected electron beam is detected, the control computer 31 gives the intensity of V X and I Y to the E × B deflector 4. Fine adjustment with the ratio kept constant or control to change the ratio between the voltage V X and the current I Y while keeping θ IN constant. The voltage increment ΔV and current increment ΔI when changing the ratio are

Figure 2006156134
Figure 2006156134

の関係が成り立つように制御する。εはおおむね１である。この調整により、照射電子線が試料に垂直に入射するとともに、反射電子線がＥ×Ｂ偏向器４を通過してＣＣＤカメラ１７に到達する条件を決定する。 Control so that ε is approximately 1. By this adjustment, the irradiation electron beam enters the sample perpendicularly, and the conditions under which the reflected electron beam passes through the E × B deflector 4 and reaches the CCD camera 17 are determined.

次にミラー電子による反射電子線１０２のコントラスト形成方法について説明する。反射電子線１０２は、対物レンズ５の像面４２に試料５の投影像を結ぶとともに、対物レンズ焦点面４１上に電子回折像を形成する。この電子回折像面では試料の同一方向に出射した反射電子線が集束するので、試料直上の電位歪がなく、横方向に偏向を受けない反射電子は光軸近傍に集束する。したがって、この対物レンズ焦点面位置（電子線回折像位置）４１に制限絞りを配置して絞り孔を光軸からずらせば、偏向を受けない電子をカットすることができるが、照射電子線１０１もほとんどカットされてしまうので、この位置に制限絞りを配置することは困難である。ここで、反射電子線１０２はＥ×Ｂ偏向器４により照射電子線１０１と分離されるので、照射電子線１０１と分離後に制限絞り１４を配置する。すなわち、反射電子線１０２の対物レンズ焦点面４１に形成される電子線回折像が中間レンズ８により投影される位置４３に制限絞り１４を配置すれば、反射電子線画像のコントラストを改善する暗視野像や明視野像を取得することができる。制限絞り１４の形状は図１２に示す形状であり、直径２ｒ２の円孔の同軸上に直径２ｒ１の円板を配置している。この円板はこの半径ｒ１から半径ｒ２の範囲の電子線をできるだけ通過させるように幅が細いブリッジで支持されている。制限絞り１４の円板の半径ｒ１は、通常散乱されないで反射したミラー電子を制限するような大きさ、すなわち試料を照射する照射角とほぼ等しい散乱角のミラー電子線を制限するように選べばよい。あるいは、制限絞り１４の形状を通常の円形形状として、特定方向の散乱電子線のみを通過させる構成でも良い。 Next, a method for forming the contrast of the reflected electron beam 102 using mirror electrons will be described. The reflected electron beam 102 forms a projection image of the sample 5 on the image plane 42 of the objective lens 5 and forms an electron diffraction image on the focal plane 41 of the objective lens. Since the reflected electron beam emitted in the same direction of the sample is focused on this electron diffraction image plane, the reflected electrons that do not have a potential distortion immediately above the sample and are not subjected to deflection in the lateral direction are focused near the optical axis. Therefore, if a limiting aperture is disposed at the focal plane position (electron beam diffraction image position) 41 of the objective lens and the aperture is shifted from the optical axis, electrons that are not subjected to deflection can be cut. Since it is almost cut, it is difficult to place the restriction aperture at this position. Here, since the reflected electron beam 102 is separated from the irradiation electron beam 101 by the E × B deflector 4, the limiting aperture 14 is disposed after the separation from the irradiation electron beam 101. That is, if the limiting aperture 14 is disposed at the position 43 where the electron beam diffraction image formed on the objective lens focal plane 41 of the reflected electron beam 102 is projected by the intermediate lens 8, a dark field that improves the contrast of the reflected electron beam image. Images and bright field images can be acquired. The shape of limiting aperture 14 is in the form shown in FIG. 12, are disposed a disk of a diameter 2r 1 coaxially circular hole of diameter 2r 2. This disk is supported by a narrow bridge so that an electron beam in the range of radius r 1 to radius r 2 can pass as much as possible. The radius r 1 of the disc of the limiting aperture 14 is selected so as to limit the mirror electron beam having a size that normally limits the mirror electrons reflected without being scattered, that is, the scattering electron beam having a scattering angle substantially equal to the irradiation angle for irradiating the sample. That's fine. Alternatively, a configuration in which only the scattered electron beam in a specific direction is allowed to pass through the limiting aperture 14 having a normal circular shape may be used.

結像モードとしては、通常観察モードと暗視野モードをユーザが選択することができる。通常観察モードではこの制限絞り１４は反射電子線の通路外にセットされているが、ユーザが暗視野モードを選択すると、制限絞り駆動部１５により制限絞り１４が反射電子線の通路上にセットされる。制限絞り駆動部１５は、微調整機構及びおよび祖調整機構より構成される。祖調整機構は制限絞りを電子線通路外と通路上との間で移動させる機構であり、ユーザが観察モードの切り替えを選択すると、制御計算機３１により祖調整機構へ駆動が指令される。微調整機構は、ユーザが像観察を行うときに絞りの位置を微調整する機構である。微調整機構はユーザが手動で調整できる機構でも良いが、たとえばロータリーエンコーダ付サーボモータで駆動する構成として、観察モードごとの制限絞りの位置アドレスを制御計算機３１に記憶させることにより、観察モードの切替えで絞りを自動的に記憶された位置アドレスに設定する構成としても良い。
以上のような装置構成でミラー電子線の散乱方向を選択的に制限できる投影画像を取得することにより、コントラストの高いミラー像観察を行うことができる。 As the imaging mode, the user can select a normal observation mode and a dark field mode. In the normal observation mode, the limiting aperture 14 is set outside the reflected electron beam path. However, when the user selects the dark field mode, the limiting aperture drive unit 15 sets the limiting aperture 14 on the reflected electron beam path. The The restriction aperture drive unit 15 is configured by a fine adjustment mechanism and an ancestor adjustment mechanism. The ancestor adjustment mechanism is a mechanism that moves the limiting aperture between the outside of the electron beam passage and on the passage. When the user selects switching of the observation mode, the control computer 31 instructs the ancestor adjustment mechanism to drive. The fine adjustment mechanism is a mechanism for finely adjusting the position of the stop when the user observes an image. The fine adjustment mechanism may be a mechanism that can be manually adjusted by a user. For example, as a configuration driven by a servo motor with a rotary encoder, the position address of the restriction aperture for each observation mode is stored in the control computer 31, thereby switching the observation mode. The aperture may be automatically set to the stored position address.
By acquiring a projection image that can selectively limit the scattering direction of the mirror electron beam with the apparatus configuration as described above, it is possible to perform mirror image observation with high contrast.

図２は実施例２の動作を説明するための構成を示したものである。本実施例では、照射電子線１０１を、試料７に対して照射位置を変えずに、照射角を傾斜させて照射し、結像系の光軸方向に反射した反射電子線を取得することにより、反射電子線の軸外収差が小さい投影像を得る。照射電子線１０１はＥｘＢ偏向器４により電子源を含む光軸１０３から試料に垂直な光軸１０３方向に偏向角度θINで偏向された後、対物レンズ焦点面４１近傍に集束して試料７を平行照射する。セパレータとしてＥ×Ｂ偏向器４は反射電子線１０２の結像面４２近傍に配置されており、照射電子線１０１はＥ×Ｂ偏向器４で角度θD偏向されると、円孔電極６に角度θAPの偏向角で入射し、円孔電極６で屈折して円孔電極６と試料の間の減速電界で減速された後、試料上の同じ位置に照射される。このθAPとθDの関係はそれぞれのレンズ配置と動作条件が定まれば一義的に定まるものであり、制御計算機３１に記憶されている。さらに、加速電圧Ｖ0が一定の条件では、ウィーン条件を満たすような電磁極印加電圧ＶXと電磁極供給電流ＩYの比は一定であるので、計算機シミュレーションなどの手法を用いてＶ0と強度比の関係はあらかじめ求められて、制御計算機３１に記憶されている。 FIG. 2 shows a configuration for explaining the operation of the second embodiment. In this embodiment, the irradiation electron beam 101 is irradiated to the sample 7 with the irradiation angle inclined without changing the irradiation position, and the reflected electron beam reflected in the optical axis direction of the imaging system is obtained. A projection image with small off-axis aberration of the reflected electron beam is obtained. The irradiated electron beam 101 is deflected by the ExB deflector 4 from the optical axis 103 including the electron source in the direction of the optical axis 103 perpendicular to the sample at a deflection angle θ IN , and then converges in the vicinity of the focal plane 41 of the objective lens to focus the sample 7. Parallel irradiation. The E × B deflector 4 as a separator is disposed in the vicinity of the imaging plane 42 of the reflected electron beam 102, and when the irradiation electron beam 101 is deflected by the angle θ D by the E × B deflector 4, The light is incident at a deflection angle of angle AP , refracted by the circular hole electrode 6 and decelerated by a deceleration electric field between the circular hole electrode 6 and the sample, and then irradiated to the same position on the sample. The relationship between θ AP and θ D is uniquely determined when the lens arrangement and operating conditions are determined, and are stored in the control computer 31. Further, under the condition where the acceleration voltage V 0 is constant, the ratio of the electromagnetic pole applied voltage V X and the electromagnetic pole supply current I Y that satisfies the Wien condition is constant, so that V 0 can be calculated using a method such as computer simulation. The relationship between the intensity ratios is obtained in advance and stored in the control computer 31.

加速電圧Ｖ0を制御計算機３１にインプットすれば、制御計算機３１は電子源印加電源２１から電子源１へＶ0を印加するとともに、Ｅ×Ｂ偏向器用電圧電源２３から電磁極に印加する電圧ＶXとＥ×Ｂ偏向器用電流電源２４から電磁極に供給する電流ＩYの強度比を一定にする制御を行う。Ｅ×Ｂ偏向器４のＸ偏向器、Ｙ偏向器に電磁極印加電圧ＶX、電磁極供給電流ＩYを供給することにより、θINの偏向角が得られ、試料を垂直に照射する条件となる。ここで、円孔電極６に角度θAPの偏向角で入射させて試料を傾斜照射する場合には、制御計算機３１はθAPの偏向角に対応するＥ×Ｂ偏向器４の偏向角θDおよび偏向角角度θDの偏向角に相当し、かつウィーン条件が保存されるような電磁極印加電圧ＶX１、電磁極供給電流ＩY１を計算して、各電極およびコイルに重畳して供給する。 When the acceleration voltage V 0 is input to the control computer 31, the control computer 31 applies V 0 from the electron source application power source 21 to the electron source 1 and also applies the voltage V applied from the E × B deflector voltage power source 23 to the electromagnetic pole. Control is performed to make the intensity ratio of the current I Y supplied to the electromagnetic pole from the current source 24 for X and the E × B deflector constant. The condition that the deflection angle of θ IN is obtained by supplying the electromagnetic pole applied voltage V X and the electromagnetic pole supply current I Y to the X deflector and Y deflector of the E × B deflector 4, and the sample is irradiated vertically. It becomes. Here, when the sample is tilted and incident on the circular hole electrode 6 at a deflection angle of θ AP , the control computer 31 causes the deflection angle θ D of the E × B deflector 4 corresponding to the deflection angle of θ AP. And an electromagnetic pole applied voltage V X1 and an electromagnetic pole supply current I Y1 that correspond to the deflection angle of the deflection angle angle θ D and preserve the Wien condition, and supply them by superimposing on each electrode and coil. .

反射電子線１０２は、対物レンズ焦点面４１上に試料出射方向に対応する電子線回折図形を形成するが、この焦点面位置に制限絞り１４を配置すると、照射電子線１０１を制限してしまうので、反射電子線１０２がＥ×Ｂ偏向器４を通過後、中間レンズ８により電子線回折像が投影される位置４３に制限絞り１４を挿入する。反射電子線１０２がこのＥ×Ｂ偏向器４で偏向されると電子線回折像位置が変化してしまうが、このＥ×Ｂ偏向器４は反射電子線１０２に対して、Ｅ×Ｂ偏向器４の磁界と電界が逆方向に等しい大きさで作用するいわゆるウィーン条件が成り立つように動作しているので、反射電子線はＥ×Ｂ偏向器４で偏向されずに制限絞り１４上に電子線回折像を投影することができる。
以上のような装置構成でミラー電子線の散乱方向を選択的に制限できる投影画像を取得することにより、軸外収差の少ないコントラストの高い像観察を行うことができる。 The reflected electron beam 102 forms an electron diffraction pattern corresponding to the sample exit direction on the focal plane 41 of the objective lens. However, if the limiting aperture 14 is disposed at this focal plane position, the irradiation electron beam 101 is limited. After the reflected electron beam 102 passes through the E × B deflector 4, the limiting aperture 14 is inserted at a position 43 where an electron beam diffraction image is projected by the intermediate lens 8. When the reflected electron beam 102 is deflected by the E × B deflector 4, the position of the electron beam diffraction image changes, but the E × B deflector 4 is different from the reflected electron beam 102 in the E × B deflector. Therefore, the reflected electron beam is not deflected by the E × B deflector 4 and is not deflected by the E × B deflector 4. A diffraction image can be projected.
By acquiring a projection image that can selectively limit the scattering direction of the mirror electron beam with the apparatus configuration described above, it is possible to perform image observation with low off-axis aberration and high contrast.

図３は、実施例３の動作を説明するための構成を示したものである。本実施例では、照射電子線１０１を試料７に対して照射位置を変えずに、試料７への照射角を一定にして照射するいわゆるホローコーン照射を行う。
Ｅ×Ｂ偏向器４の偏向電極で照射電子線１０１をＸ方向に角度θD/2偏向させるための電極供給電圧をＶXとし、ホローコーン照射のために円孔電極６に角度θAPの偏向角で入射するための供給電圧をＶDとすると、図１７に示すようにＸ偏向器に示すように、ＶX＋ＶDｃｏｓ（ｔ）、Ｙ偏向器にＶXｓｉｎ（ｔ）の偏向信号を供給する。さらに、磁界生成においても、常にＥ×Ｂ偏向器４が反射電子線に対してウィーン条件となるように、磁界を生成するための偏向コイルにθD/2の角度を偏向させるための正弦波および余弦波信号を供給すると、照射電子線を試料７上で照射位置を変えずに歳差運動させながら照射することができる。反射電子線１０２は、対物レンズ焦点面４１上に電子線回折図形を形成する。反射電子線１０２がＥ×Ｂ偏向器４を偏向されずに通過後、中間レンズ８によりこの電子線回折像が投影される位置４３に制限絞り１４を挿入することにより、ミラー電子顕微鏡の暗視野像を得ることができる。
以上のような装置構成でミラー電子線の散乱角度範囲を選択的に制限できる投影画像を取得することにより、軸外収差の少ないコントラストの高い像観察を行うことができる。 FIG. 3 shows a configuration for explaining the operation of the third embodiment. In the present embodiment, so-called hollow cone irradiation is performed in which the irradiation position of the irradiation electron beam 101 with respect to the sample 7 is not changed and the irradiation angle to the sample 7 is fixed.
The electrode supply voltage for deflecting the irradiation electron beam 101 in the X direction by the angle θ D / 2 at the deflection electrode of the E × B deflector 4 is set to V X, and the circular hole electrode 6 is deflected by the angle θ AP for hollow cone irradiation. Assuming that the supply voltage for incidence at an angle is V D , a deflection signal of V X + V D cos (t) and V X sin (t) is applied to the Y deflector as shown in the X deflector as shown in FIG. Supply. Furthermore, also in the magnetic field generation, a sine wave for deflecting the angle θ D / 2 in the deflection coil for generating the magnetic field so that the E × B deflector 4 always has a Wien condition with respect to the reflected electron beam. When the cosine wave signal is supplied, the irradiation electron beam can be irradiated while precessing on the sample 7 without changing the irradiation position. The reflected electron beam 102 forms an electron diffraction pattern on the objective lens focal plane 41. After the reflected electron beam 102 passes through the E × B deflector 4 without being deflected, a limiting aperture 14 is inserted at a position 43 where the electron beam diffraction image is projected by the intermediate lens 8, thereby dark field of the mirror electron microscope. An image can be obtained.
By acquiring a projection image that can selectively limit the scattering angle range of the mirror electron beam with the above-described apparatus configuration, it is possible to perform image observation with high off-axis aberration and high contrast.

図４に示す本実施例は、ミラー電子顕微鏡を高速ウェハ検査に適用した構成である。
電子源１より放出された照射電子線１０１は、コンデンサレンズ３により収束され試料上をほぼ平行に照射される。電子源１には、先端半径が１μｍ程度のZr/O/W型のショットキー電子源を用いた。この電子源を用いることにより、大電流ビーム（例えば、１.５μＡ）で、かつエネルギー幅が０.５ｅＶ以下の均一な面状電子線を安定に形成できる。 The present embodiment shown in FIG. 4 has a configuration in which a mirror electron microscope is applied to high-speed wafer inspection.
The irradiation electron beam 101 emitted from the electron source 1 is converged by the condenser lens 3 and irradiated on the sample substantially in parallel. As the electron source 1, a Zr / O / W type Schottky electron source having a tip radius of about 1 μm was used. By using this electron source, a uniform planar electron beam having a large current beam (for example, 1.5 μA) and an energy width of 0.5 eV or less can be stably formed.

セパレータとして、Ｅ×Ｂ偏向器４を反射電子線１０２の結像面近傍に配置させる。照射電子線１０１は、Ｅ×Ｂ偏向器４によりウェハ７に垂直な光軸に偏向される。Ｅ×Ｂ偏向器４は、上方からの電子線に対してのみ偏向作用を持つ。Ｅ×Ｂ偏向器４より偏向された電子線は、対物レンズ５により試料（ウェハ）表面に垂直な方向に面状の電子線が形成される。   As a separator, the E × B deflector 4 is disposed in the vicinity of the imaging surface of the reflected electron beam 102. The irradiation electron beam 101 is deflected to an optical axis perpendicular to the wafer 7 by the E × B deflector 4. The E × B deflector 4 has a deflecting action only on the electron beam from above. The electron beam deflected by the E × B deflector 4 is formed into a planar electron beam in a direction perpendicular to the sample (wafer) surface by the objective lens 5.

欠陥の検出にはミラー電子を使用する。ユーザがミラー電子顕微鏡モードに設定すると、試料印加電源２７によって試料（ウェハ）７には、電子線の加速電圧とほぼ等しいか、わずかに高い負の電位が印加されて、ウェハ７の表面には形成された半導体パターン形状や帯電の状態を反映した電界が形成される。この電界によって面状電子線の大部分がウェハ７に衝突する直前で引き戻され、ミラー電子としてウェハ７のパターン情報を反映した方向や強度を持って上がってくる。   Mirror electrons are used to detect defects. When the user sets the mirror electron microscope mode, a negative potential that is substantially equal to or slightly higher than the acceleration voltage of the electron beam is applied to the sample (wafer) 7 by the sample application power source 27, and the surface of the wafer 7 is applied to the surface. An electric field reflecting the shape of the formed semiconductor pattern and the charged state is formed. By this electric field, most of the planar electron beam is pulled back immediately before it collides with the wafer 7 and rises as mirror electrons with a direction and intensity reflecting the pattern information of the wafer 7.

ミラー電子は試料直上に形成される等電位面の歪により軌道を変えるが、結像レンズの焦点条件をずらして調整すれば、これらのミラー電子のほとんどを画像形成に用いることができる。すなわち、ミラー電子を用いれば、Ｓ／Ｎ比の高い画像が得られ、検査時間の短縮が期待できる。しかし、このように焦点をずらした画像形成では、一般の電子顕微鏡像とは大きく異なるので、試料の正確な形状及び位置に対応した情報を得ることは困難である。そこで、ミラー電子顕微鏡の暗視野モードを設けることにより、正焦点近傍で画像形成することが可能となり、試料の正確な形状及び位置に対応した情報を得ることができる。暗視野モードに設定すると、制限絞り駆動部１５により制限絞り１４が結像系光路上にセットされ、試料直上の等電位面で横方向に偏向を受けずに反転したミラー電子を制限絞り１４で吸収させることによって、欠陥部から散乱したミラー電子だけで画像化できるようになり、高コントラストの欠陥検出画像が得られるようになる。この画像は電気信号に変換され画像処理部61に送られる。   The mirror electrons change their trajectories due to distortion of the equipotential surface formed immediately above the sample. However, most of these mirror electrons can be used for image formation by adjusting the focus condition of the imaging lens. That is, if mirror electrons are used, an image with a high S / N ratio can be obtained, and shortening of the inspection time can be expected. However, in such image formation with the focus shifted, it is difficult to obtain information corresponding to the exact shape and position of the sample because it is very different from a general electron microscope image. Therefore, by providing the dark field mode of the mirror electron microscope, it is possible to form an image near the normal focal point, and information corresponding to the accurate shape and position of the sample can be obtained. When the dark field mode is set, the limiting diaphragm 14 is set on the imaging system optical path by the limiting diaphragm driving unit 15, and mirror electrons that are inverted without being laterally deflected on the equipotential surface immediately above the sample are converted by the limiting diaphragm 14. By absorbing it, it becomes possible to form an image only with the mirror electrons scattered from the defect portion, and a high-contrast defect detection image can be obtained. This image is converted into an electrical signal and sent to the image processing unit 61.

画像処理部６１は、画像信号記憶部６２及び６３、演算部６４、欠陥判定部６５より構成されている。画像記憶部６２と６３は同一パターンの隣接部の画像を記憶するようになっており、両者の画像を演算部６４で演算して両画像の異なる場所を検出する。この結果を欠陥判定部６５により欠陥として判定しその座標を制御計算機３１に記憶する。なお、取り込まれた画像信号はモニタ６６により画像表示される。   The image processing unit 61 includes image signal storage units 62 and 63, a calculation unit 64, and a defect determination unit 65. The image storage units 62 and 63 store images of adjacent portions of the same pattern, and both the images are calculated by the calculation unit 64 to detect different locations of both images. The result is determined as a defect by the defect determination unit 65 and the coordinates are stored in the control computer 31. The captured image signal is displayed on the monitor 66 as an image.

半導体ウェハ７表面上に形成された同一設計パターンを有する隣接チップＡ、Ｂ間でのパターンの比較検査をする場合には、先ず、チップＡ内の被検査領域についての電子線画像信号を取り込んで、記憶部６２内に記憶させる。次に、隣接するチップＢ内の上記と対応する被検査領域についての画像信号を取り込んで、記憶部６３内に記憶させながら、それと同時に、記憶部６２内の記憶画像信号と比較する。さらに、次のチップＣ内の対応する被検査領域についての画像信号を取得し、それを記憶部６２に上書き記憶させながら、それと同時に、記憶部６３内のチップＢ内の被検査領域についての記憶画像信号と比較する。このような動作を繰り返して、全ての被検査チップ内の互いに対応する被検査領域についての画像信号を順次記憶させながら、比較して行く。   In the case of performing a pattern inspection between adjacent chips A and B having the same design pattern formed on the surface of the semiconductor wafer 7, first, an electron beam image signal for a region to be inspected in the chip A is captured. And stored in the storage unit 62. Next, an image signal for the inspection region corresponding to the above in the adjacent chip B is captured and stored in the storage unit 63, and at the same time, compared with the stored image signal in the storage unit 62. Further, an image signal for the corresponding inspected area in the next chip C is acquired and stored in the storage unit 62 by overwriting, and at the same time, the storage for the inspected area in the chip B in the storage unit 63 is stored. Compare with image signal. Such an operation is repeated, and comparison is performed while sequentially storing image signals for corresponding inspection regions in all inspection chips.

上記の方法以外に、予め、標準となる良品（欠陥のない）試料についての所望の検査領域の電子線画像信号を記憶部６２内に記憶させておく方法を採ることも可能である。その場合には、予め制御計算機３１に上記良品試料についての検査領域および検査条件を入力しておき、これらの入力データに基づき上記良品試料についての検査を実行し、所望の検査領域についての取得画像信号を記憶部６２内に記憶する。次に、検査対象となるウェハ７をステージ上にロードして、先と同様の手順で検査を実行する。   In addition to the above method, it is also possible to adopt a method in which the electron beam image signal of a desired inspection region for a standard non-defective product (having no defect) is stored in the storage unit 62 in advance. In that case, the inspection area and the inspection conditions for the good product sample are input in advance to the control computer 31, the inspection for the good product sample is executed based on these input data, and the acquired image for the desired inspection region is obtained. The signal is stored in the storage unit 62. Next, the wafer 7 to be inspected is loaded on the stage, and the inspection is executed in the same procedure as before.

そして、上記と対応する検査領域についての取得画像信号を記憶部６３内に取り込むと同時に、この検査対象試料についての画像信号と先に記憶部６２内に記憶された上記良品試料についての画像信号とを比較する。これにより上記検査対象試料の上記所望の検査領域についてのパターン欠陥の有無を検出する。なお、上記標準（良品）試料としては、上記検査対象試料とは別の予めパターン欠陥が無いことが判っているウェハを用いても良いし、上記検査対象試料表面の予めパターン欠陥が無いことが判っている領域(チップ)を用いても良い。例えば、半導体試料(ウェハ)表面にパターンを形成する際、ウェハ全面にわたり下層パターンと上層パターン間での合わせずれ不良が発生することがある。このような場合には、比較対象が同一ウェハ内あるいは同一チップ内のパターン同士であると、上記のようなウェハ全面にわたり発生した不良(欠陥)は見落とされてしまう。   The acquired image signal for the inspection region corresponding to the above is taken into the storage unit 63, and at the same time, the image signal for the sample to be inspected and the image signal for the good sample previously stored in the storage unit 62, Compare Thereby, the presence / absence of a pattern defect in the desired inspection region of the inspection object sample is detected. The standard (non-defective) sample may be a wafer that is known to be free of pattern defects in advance, different from the sample to be inspected, or may have no pattern defects in advance on the surface of the sample to be inspected. A known area (chip) may be used. For example, when a pattern is formed on the surface of a semiconductor sample (wafer), misalignment failure between the lower layer pattern and the upper layer pattern may occur over the entire wafer surface. In such a case, if the comparison object is a pattern in the same wafer or the same chip, the defect (defect) generated over the entire wafer surface is overlooked.

しかし、本実施例によれば、予め良品(無欠陥)であることが判っている領域の画像信号を記憶しておき、この記憶画像信号と検査対象領域の画像信号とを比較するので、上記したようなウェハ全面にわたり発生した不良をも精度良く検出することができる。   However, according to this embodiment, the image signal of the area that is known to be non-defective (no defect) is stored in advance, and the stored image signal is compared with the image signal of the inspection target area. Such a defect that has occurred over the entire wafer surface can be detected with high accuracy.

記憶部６２、６３内に記憶された両画像信号は、それぞれ演算部６４内に取り込まれ、そこで、既に求めてある欠陥判定条件に基づき、各種統計量（具体的には、画像濃度の平均値、分散等の統計量）、周辺画素間での差分値等が算出され
る。これらの処理を施された両画像信号は、欠陥判定部６５内に転送されて、そこで比較されて両画像信号間での差信号が抽出される。これらの差信号と、既に求めて記憶してある欠陥判定条件とを比較して欠陥判定がなされ、欠陥と判定されたパターン領域の画像信号とそれ以外の領域の画像信号とが分別されるとともに、欠陥部のアドレスが制御計算機３１に記憶される。 Both image signals stored in the storage units 62 and 63 are taken into the calculation unit 64, where various statistics (specifically, average values of image density) are calculated based on the already determined defect determination conditions. , Statistics such as variance), difference values between neighboring pixels, and the like are calculated. Both image signals subjected to these processes are transferred into the defect determination unit 65, where they are compared and a difference signal between the two image signals is extracted. These difference signals are compared with the defect determination conditions that have already been obtained and stored, and defect determination is performed. The image signal of the pattern area determined to be a defect and the image signal of other areas are separated. The address of the defective portion is stored in the control computer 31.

以上のような装置構成にすることにより、ミラー電子線投影画像のコントラストが高い欠陥画像を取得できることが可能となり、欠陥検出感度の高いウェハ高速検査を実現することができる。
なお、上記実施例１から実施例４では反射電子線として試料に衝突しないで反射するミラー電子を画像化することについて説明してきたが、試料に衝突して散乱した後方散乱電子や試料に電子線を照射して試料から二次的に発生した二次電子を画像化する場合にもほぼ同様の構成で暗視野画像を取得することができる。 With the apparatus configuration as described above, it is possible to acquire a defect image with a high contrast of the mirror electron beam projection image, and it is possible to realize high-speed wafer inspection with high defect detection sensitivity.
In the first to fourth embodiments, imaging of mirror electrons reflected without colliding with the sample as a reflected electron beam has been described. However, backscattered electrons scattered by colliding with the sample and electron beams with the sample are scattered. A dark field image can be acquired with substantially the same configuration even when secondary electrons generated secondary from the sample are imaged.

本発明の第１の実施例になるミラー電子顕微鏡の構成を示す図。The figure which shows the structure of the mirror electron microscope which becomes the 1st Example of this invention. 本発明の第２の実施例の構成を説明する図。The figure explaining the structure of the 2nd Example of this invention. 本発明の第３の実施例の構成を説明する図。The figure explaining the structure of the 3rd Example of this invention. 本発明の第４の実施例の構成を説明する図。The figure explaining the structure of the 4th Example of this invention. ミラー電子の軌道を説明する図。The figure explaining the orbit of mirror electrons. ミラー電子の軌道を説明する図。The figure explaining the orbit of mirror electrons. 透過電子顕微鏡の構成を説明する図。The figure explaining the structure of a transmission electron microscope. ミラー電子顕微鏡の構成を説明する図。The figure explaining the structure of a mirror electron microscope. 本発明の原理の照射系を説明する図。The figure explaining the irradiation system of the principle of this invention. 本発明の原理の結像系を説明する図。1 is a diagram illustrating an imaging system according to the principle of the present invention. Ｅ×Ｂ偏向器の動作を説明する図。The figure explaining operation | movement of an E * B deflector. 制限絞りの構造を説明する図。The figure explaining the structure of a restriction aperture. 本発明の原理の照射系を説明する図。The figure explaining the irradiation system of the principle of this invention. 本発明の原理の結像系を説明する図。1 is a diagram illustrating an imaging system according to the principle of the present invention. 本発明の原理の照射系を説明する図。The figure explaining the irradiation system of the principle of this invention. 本発明の原理の結像系を説明する図。1 is a diagram illustrating an imaging system according to the principle of the present invention. ＥｘＢ偏向器に供給する電圧信号を説明する図。The figure explaining the voltage signal supplied to an ExB deflector. ８極型Ｅ×Ｂ偏向器の電圧配分を説明する図。The figure explaining the voltage distribution of an 8-pole type ExB deflector. ８極型Ｅ×Ｂ偏向器の電流配分を説明する図。The figure explaining the current distribution of an 8-pole type ExB deflector. ８極型Ｅ×Ｂ偏向器の断面図。Sectional drawing of an 8-pole type ExB deflector.

符号の説明Explanation of symbols

１：電子源、２：電子銃レンズ、３：コンデンサレンズ、４：Ｅ×Ｂ偏向器、５：対物レンズ、６：円孔電極、７：試料（ウェハ）、８：中間レンズ、９：投影レンズ、１０：シンチレータ、１１：光ファイバー束、１２：ＣＣＤカメラ、１３：モニタ、１４：制限絞り、１５：制限絞り駆動部、２１：電子源印加電源、２３：Ｅ×Ｂ偏向器用電圧電源、２４：Ｅ×Ｂ偏向器用電流電源、２５：対物レンズ電源、２６：円孔電極印加電源、２７：試料印加電源、２８：中間レンズ電源、２９：投影レンズ電源、３０：、３１：制御計算機、４１：対物レンズ焦点面、４２：対物レンズ結像面、４３：電子線回折像投影面、５１：電磁極、５２：ボビン、５３：コイル、５４：シールド、６１：画像処理部、６２：画像記憶部、６３：画像記憶部、６４：演算部、６５：欠陥判定部、６６：モニタ、１０１：照射電子線、１０２：反射電子線、１０３：照射系光軸、１０４：結像系光軸。   1: electron source, 2: electron gun lens, 3: condenser lens, 4: E × B deflector, 5: objective lens, 6: circular hole electrode, 7: sample (wafer), 8: intermediate lens, 9: projection Lens: 10: Scintillator, 11: Optical fiber bundle, 12: CCD camera, 13: Monitor, 14: Restriction diaphragm, 15: Restriction diaphragm drive unit, 21: Electron source application power supply, 23: Voltage power supply for E × B deflector, 24 : Current supply for E × B deflector, 25: Objective lens power supply, 26: Circular electrode application power supply, 27: Sample application power supply, 28: Intermediate lens power supply, 29: Projection lens power supply, 30 :, 31: Control computer, 41 : Objective lens focal plane, 42: objective lens imaging plane, 43: electron diffraction image projection plane, 51: electromagnetic pole, 52: bobbin, 53: coil, 54: shield, 61: image processing unit, 62: image storage Section, 63: image storage section 64: operation unit, 65: defect determining section, 66: monitor, 101: electron beam irradiation, 102: reflected electron beam, 103: illumination system optical axis, 104: imaging system optical axis.

Claims (9)

電子源に加速電圧を印加する電子源印加手段と、
試料を保持するステージに試料電圧を印加する試料電圧印加手段と、
前記電子源から出射した電子線を試料に二次元的な広がりを有する面状の照射電子線として照射する照射レンズ手段と、
前記照射電子線を前記試料に照射して前記試料から出射した反射電子線を投影拡大して試料像を検出器に投影結像させる手段と、
前記照射電子線と前記反射電子線をビームセパレータにより分離する手段を設けた反射結像型電子顕微鏡において、
前記照射電子線と前記反射電子線を分離するビームセパレータと前記検出器の間に前記反射電子線の試料出射時の角度を制限する手段を備えたことを特徴とする反射結像型電子顕微鏡。 An electron source applying means for applying an acceleration voltage to the electron source;
A sample voltage applying means for applying a sample voltage to a stage holding the sample;
Irradiation lens means for irradiating a sample with an electron beam emitted from the electron source as a planar irradiation electron beam having a two-dimensional spread;
Means for projecting and enlarging a sample image on a detector by projecting and enlarging a reflected electron beam emitted from the sample by irradiating the sample with the irradiation electron beam;
In a reflection imaging electron microscope provided with means for separating the irradiated electron beam and the reflected electron beam by a beam separator,
A reflection imaging electron microscope comprising a means for limiting an angle of the reflected electron beam when the sample is emitted between a beam separator for separating the irradiated electron beam and the reflected electron beam and the detector. 電子源と、
投影レンズと、
中間レンズと、
対物レンズと、
試料を保持する試料ステージと、
前記電子源から出射した電子線が試料に入射せずに向きを反転して反射する電圧を前記試料ステージないし前記試料に印加する手段と、
前記電子源より前記試料に対し放射された電子線と該電子線が試料に入射せずに向きを反転した反射電子線とをビームセパレータにより分離する手段と、
前記反射電子を検出する検出器とを備え、
前記投影レンズと中間レンズの間に前記反射電子線の電子線回折像を制限する絞りを備えることを特徴とする反射結像型電子顕微鏡。 An electron source,
A projection lens;
An intermediate lens,
An objective lens;
A sample stage for holding the sample;
Means for applying, to the sample stage or the sample, a voltage that reflects and reverses the direction of the electron beam emitted from the electron source without being incident on the sample;
Means for separating, by a beam separator, an electron beam radiated from the electron source to the sample and a reflected electron beam whose direction has been reversed without being incident on the sample;
A detector for detecting the reflected electrons,
A reflection imaging electron microscope comprising a stop for limiting an electron diffraction image of the reflected electron beam between the projection lens and the intermediate lens. 電子源と、
投影レンズと、
中間レンズと、
対物レンズと、
試料を保持する試料ステージと、
前記電子源から出射した電子線が試料に入射せずに向きを反転して反射する電圧を前記試料ステージないし前記試料に印加する手段と、
前記電子源より前記試料に対し放射された電子線と該電子線が試料に入射せずに向きを反転した反射電子線とをビームセパレータにより分離する手段と、
前記反射電子を検出する検出器とを有し、
前記投影レンズと中間レンズの間に前記反射電子線の電子線回折像を制限する絞りと、
前記絞りを可動に制御する制限絞り駆動部と、
前記制限絞り駆動部を制御する制御計算機を備え、
前記制限絞り駆動部は観察モードを切替える手段を備えることを特徴とする反射結像型電子顕微鏡。 An electron source,
A projection lens;
An intermediate lens,
An objective lens;
A sample stage for holding the sample;
Means for applying, to the sample stage or the sample, a voltage that reflects and reverses the direction of the electron beam emitted from the electron source without being incident on the sample;
Means for separating, by a beam separator, an electron beam radiated from the electron source to the sample and a reflected electron beam whose direction has been reversed without being incident on the sample;
A detector for detecting the reflected electrons,
A diaphragm for limiting an electron diffraction image of the reflected electron beam between the projection lens and the intermediate lens;
A limiting aperture driving unit for controlling the aperture to be movable;
A control computer for controlling the restriction aperture drive unit;
The reflection imaging electron microscope according to claim 1, wherein the limiting aperture driving unit includes means for switching an observation mode. 請求項１〜３のいずれかに記載の反射結像型電子顕微鏡において、
前記ビームセパレータは電界と磁界を交差させたＥ×Ｂ偏向器であることを特徴とする反射結像型電子顕微鏡。 The reflection imaging electron microscope according to any one of claims 1 to 3,
A reflection imaging electron microscope, wherein the beam separator is an E × B deflector in which an electric field and a magnetic field intersect. 請求項１〜３のいずれかに記載の反射結像型顕微鏡において、
前記検出器より検出された反射電子線像を画像処理する画像処理部を備えることを特徴とする反射結像型電子顕微鏡。 In the reflective imaging microscope according to any one of claims 1 to 3,
A reflection imaging electron microscope comprising: an image processing unit that performs image processing on a reflected electron beam image detected by the detector. 請求項に記載の反射結像型電子顕微鏡において、
前記画像処理部は、
前記検出器により検出された前記試料の第一の領域における第一の反射電子線像と前記試料の第二の領域における第二の反射電子線像を記憶する記憶部と、
前記第一の反射電子線像と第二の反射電子線像を比較する演算部と、
前記比較結果から前記試料の欠陥を判定する欠陥判定部を備えることを特徴とする反射結像型電子顕微鏡。 In the reflection imaging electron microscope according to claim,
The image processing unit
A storage unit for storing a first reflected electron beam image in a first region of the sample detected by the detector and a second reflected electron beam image in a second region of the sample;
A computing unit for comparing the first reflected electron beam image and the second reflected electron beam image;
A reflection imaging electron microscope comprising a defect determination unit that determines a defect of the sample from the comparison result. 請求項１〜７のいずれかに記載の反射結像型電子顕微鏡において
前記検出された反射電子線像を表示する表示部を備えることを特徴とする反射電子結像型電子顕微鏡。 8. A reflection electron imaging electron microscope according to claim 1, further comprising a display unit for displaying the detected reflection electron beam image. 請求項２に記載の反射結像型電子顕微鏡において
前記絞りを可動に制御する制限絞り駆動部を備え、
前記制限絞り駆動部を制御する制御計算機を備えることを特徴とする反射結像型電子顕微鏡。 The reflection imaging electron microscope according to claim 2, further comprising a limiting aperture driving unit that controls the aperture to be movable.
A reflection imaging electron microscope comprising a control computer for controlling the limiting aperture driving unit. 電子源を出射し加速された照射電子線を試料の直前で減速させて、試料に衝突しないで反転したミラー電子を含む反射電子線を、照射電子線と分離後に試料から出射したときの出射角に基づいて選別することを特徴とする反射結像型電子顕微鏡の観察方法。   The exit angle when the reflected electron beam, including the mirror electron that has been reversed without being collided with the sample, is emitted from the sample after being separated from the irradiated electron beam by decelerating the electron beam emitted from the electron source and accelerated immediately before the sample. A method for observing a reflection imaging electron microscope, characterized in that sorting is performed based on the above.
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