JP2009009949A - Scanning electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning electron microscope capable of effectively detecting a reflected electron generated from a sample at a low angle while realizing a short focus distance and forming a sample image. <P>SOLUTION: A secondary electron conversion electrode 7 for generating a secondary electron 9a caused by collision of the reflected electron 8a is arranged further toward an electron source side than an object lens 4 and toward a sample side than a secondary electron detector 5a. Thus, the reflected electron generated from the sample at a low angle can be effectively detected on the basis of the formation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electron beam apparatus, and more particularly to a scanning electron microscope suitable for detecting secondary electrons and reflected electrons generated from a sample with high efficiency and obtaining a high resolution image with high contrast.

  A scanning electron microscope accelerates electrons emitted from an electron source and converges them with an electrostatic lens or a magnetic lens to form a thin electron beam (primary electron beam). This primary electron beam is observed using a scanning deflector. The secondary signal generated secondaryly from the sample is detected by irradiating with the primary electron beam, and the detected signal intensity is used as the luminance modulation input of the cathode ray tube being scanned in synchronization with the primary electron beam scanning. Thus, the device obtains a two-dimensional scanned image.

  The secondary signal generated from the sample by irradiation of the primary electron beam has a wide energy distribution. For example, primary electrons incident on a sample are elastically scattered by atoms on a solid surface, and there are electrons that jump out of the sample surface. This is called a reflected electron and has an energy equivalent to or somewhat higher than that of the primary electron beam. In addition, there are electrons that are emitted to the outside when primary electrons incident on the sample interact with atoms in the sample, and electrons in the sample are excited to obtain kinetic energy. This is called a secondary electron and has an energy in the range of about 0 eV to about 50 eV.

  In Patent Document 1, using a deflector that deflects the secondary signal off-axis, the trajectories of the secondary electrons and the reflected electrons are separated, and each detector is arranged on the trajectory to reflect the secondary electrons and the reflected electrons. A technique for selectively detecting electrons is disclosed.

  Further, Patent Document 2 discloses a technique for providing a reflector having an opening through which an electron beam passes above a secondary electron detector and converting reflected electrons that collide therewith into secondary electrons to detect them. Has been.

  Patent Document 3 discloses a technique in which an annular detector divided above an objective lens is provided, and secondary electrons and reflected electrons are separated and detected using the convergence action of the objective lens.

  According to the techniques disclosed in these documents, secondary electrons and reflected electrons having different orbits can be separated or detected together due to the difference in energy.

  Each reflected electron or secondary electron has unique information because of the difference in its generation cause. According to the technique disclosed in the above document, a sample image based on unique information can be formed by selectively detecting reflected electrons or secondary electrons.

JP-A-7-192679 JP-A-9-171791 Japanese Patent Laid-Open No. 8-27369

  According to the technique disclosed in the above document, secondary electrons or reflected electrons can be detected separately or in combination, but there are the following problems.

  In Patent Document 1, the secondary electrons and the reflected electrons are selectively detected by arranging respective detectors or reflectors on the trajectories of the secondary electrons and the reflected electrons, but regarding the detection of the reflected electrons, Only the reflected electrons reflected along the optical axis of the primary electron beam are detected, and the reflected electrons generated at a shallow angle from the sample cannot be detected.

  This problem also applies to the backscattered electron detection technique using the reflector disclosed in Patent Document 2. Again, only the reflected electrons reflected almost along the optical axis are detected, and the reflected electrons generated at a shallow angle from the sample cannot be detected.

  According to the technique disclosed in Patent Document 3, secondary electrons are pulled up by an objective lens (electrostatic objective lens), and the trajectories of secondary electrons and reflected electrons are separated by the focusing action of the objective lens (magnetic objective lens). Although a detection technique is disclosed, since the detector has a detection surface in a direction perpendicular to the optical axis of the electron beam, the detection surface cannot be enlarged. Therefore, there is a problem that it is difficult to discriminate and detect reflected electrons generated from a shallow angle and reflected electrons or secondary electrons reflected at a high angle.

  Further, since the objective lenses disclosed in the above three documents all have a lens gap (gap between magnetic poles) formed in a direction perpendicular to the optical axis of the primary electron beam, the lens main surface and the sample There is also a problem that the distance between the two (focal length) becomes long.

  The present invention is to solve the above-described problems, and an object of the present invention is to provide a scanning electron microscope that detects reflected electrons generated at a shallow angle from a sample without increasing the focal length. .

  In order to achieve this object, the present invention forms an electron source, a scanning deflector that scans the sample with a primary electron beam generated from the electron source, and a converging magnetic field that converges the primary electron beam on the sample surface. A scanning electron microscope that includes an objective lens and a secondary signal detector that detects a secondary signal generated from a sample by irradiation of a primary electron beam, and obtains a two-dimensional scanned image of the sample. There is provided a scanning electron microscope characterized in that an electrode for generating secondary electrons is disposed between the objective lens and the secondary electron detector.

  According to the above configuration, it is possible to detect a secondary signal generated at a shallow angle from the sample among the secondary signals generated by irradiation with the primary electron beam.

  In the present invention, the reflected electrons generated at a shallower angle than the sample can be detected by forming a convergent magnetic field of the objective lens on the sample surface and using a secondary electron conversion electrode (reflecting plate) as the objective lens and the objective lens. This is because it is arranged between the secondary electron detectors.

  According to the scanning electron microscope having such a configuration, the reflected electrons reflected from the sample at a shallow angle draw a spiral trajectory by the convergence action of the objective lens. A conversion electrode that converts reflected electrons into secondary electrons is placed on this orbit, and reflected electrons reflected at a shallow angle from the sample are converted into secondary electrons, so that the reflected electrons generated at a shallow angle from the sample can be recovered. It can be detected by the secondary electron detector.

  On the other hand, since the secondary electron conversion electrode and the backscattered electron detector disclosed in Patent Literature 1 and Patent Literature 2 are both arranged above the secondary electron detector (on the electron source side), A large gap is generated between the secondary electron conversion electrode and the backscattered electron detector, and the backscattered electrons generated at a shallow angle from the sample cannot be captured.

  In all of the objective lenses disclosed in these publications, the gap between the magnetic poles (lens gap) is opened in a direction perpendicular to the optical axis of the electron beam, and the maximum focusing magnetic field on the primary electron beam is obtained. Since it is formed at almost the same height as the objective lens, a strong converging magnetic field cannot be formed on the sample surface, and a spiral motion cannot be given to reflected electrons generated at a shallow angle from the sample. In addition, the objective lens having this shape has a problem in that the aberration of the primary electron beam is increased because the distance (focal length) between the sample and the lens main surface is increased.

  Also in the technique disclosed in Patent Document 3, as in the technique disclosed in Patent Document 2, since the lens gap of the objective lens is opened in the direction perpendicular to the optical axis, the focal length of the primary electron beam is increased. There is a problem that becomes longer. In addition, since the electrostatic objective lens is interposed between the lens main surface and the sample, there is a problem that it is difficult to achieve a short focus of the objective lens.

  Specific means for solving the above problems will be described below with reference to the drawings.

  In general, reflected electrons generated at a shallow angle with respect to a sample (reflected electrons generated at a high angle with respect to the optical axis) result in a signal reflecting the unevenness information of the sample and internal information of the sample. According to the embodiment apparatus of the present invention, it is possible to efficiently detect the reflected electrons generated at a shallower angle than the sample as described above.

  FIG. 1 is a schematic diagram of an embodiment of the present invention. In a scanning electron microscope employing a type of objective lens (hereinafter referred to as in-lens) in which a sample is arranged between magnetic poles, two detections are made on the electron source side from the objective lens. The example which has arrange | positioned a means is shown.

  The reason for adopting the in-lens type objective lens in this embodiment is that it is an objective lens suitable for forming a strong converging magnetic field on the sample surface. Further, as the shape of the objective lens that forms a strong converging magnetic field on the sample surface, an objective lens having a lens gap opened downward as shown in FIG. The lower magnetic pole open type lens is an objective lens in which a gap (lens gap) between the upper magnetic pole and the lower magnetic pole is opened at least toward the sample surface. In such a lens-shaped objective lens, the maximum converging magnetic field for the primary electron beam is formed below the lower magnetic pole.

  Since the in-lens type objective lens and the lower magnetic pole open type objective lens can shorten the distance (focal length) between the sample and the main surface of the lens, the aberration of the primary electron beam can be reduced.

  In the apparatus shown in FIG. 1, gold particles (heavy metal) are sputter coated on the backscattered electron detection surface of the backscattered electron detector (YAG) in the order of several nm to several tens of nm.

  A primary electron beam 2 generated from the electron source 1 is scanned by deflection coils 3 a and 3 b arranged in two stages and converged on the sample 6 by the objective lens 4. By irradiation with the primary electron beam 2, secondary electrons 20 and reflected electrons 8 a and 8 b 1 are generated from the sample 6. Of the reflected electrons generated from the sample, the reflected electrons 8a are a low angle component generated at a shallow angle from the sample, and the reflected electrons 8b are a high angle component generated at a high angle from the sample. Thus, the reflected electrons generated at a high angle with respect to the sample are signals reflecting the composition information of the sample. In the embodiment apparatus of the present invention, two reflecting plates are provided so that not only the reflected electrons generated at a shallow angle from the sample but also the reflected electrons reflected almost in the direction of the optical axis can be detected. .

  The secondary electrons 20 are wound up and traveled toward the electron source side by the magnetic field generated by the objective lens 4, and are deflected to the secondary electron detector 5a side by the secondary electron deflector 12a and detected by the secondary electron detector 5a. Is done.

  On the other hand, the reflected electrons 8a (low angle component) collide with the secondary electron conversion electrode 7 arranged on the upper part of the objective lens 4 to generate secondary electrons 9a. The secondary electrons 9a are guided to the secondary electron deflector 12a by the pulling electrode 13 to which a positive voltage is applied by the voltage applying means 11b, deflected by the secondary electron deflector 12a, and then by the secondary electron detector 5a. Detected.

  In the apparatus of this embodiment, an E × B deflector (orthogonal electromagnetic field generator) is used as the secondary electron deflectors 12a and 12b for deflecting the secondary electrons to the secondary electron detectors 5a and 5b. Yes. The deflector includes a pair of electrodes (not shown) and magnetic field generating means (not shown) that forms a magnetic field orthogonal to the electric field formed between the pair of electrodes. This orthogonal electromagnetic field generator is disclosed in Patent Document 2, for example.

  The backscattered electrons 8b1 (high angle component) travels straight without receiving much of the deflection action of the secondary electron deflector 12a and is deflected by the secondary electron deflector 12b disposed above the deflection coils 3a and 3b to detect backscattered electrons. It collides with the gold particle sputter coating surface 17 on the surface of the vessel 18 (YAG).

  The sputter coating surface of heavy metals such as gold has high secondary electron generation efficiency, and enables detection by converting reflected electrons that cannot pass through the coating surface into secondary electrons.

  Among the high-angle components of the reflected electrons, the electrons 8 b 2 having particularly high energy pass through the gold particle sputter coating surface 17 and are detected by the reflected electron detector 18. Reflected electrons that cannot pass through the gold particle sputter coating surface 17 and are converted into secondary electrons 9b1 (electrons with low energy among the high angle components) are detected by the secondary electron detector 5b. With this configuration, it is possible to distinguish and detect a high-energy reflected electron and a low-energy reflected electron among high-angle reflected electrons.

  Further, when a positive voltage is applied to the secondary electron conversion electrode 7 by the voltage control means 11 a and the voltage (potential) of the pulling electrode 13 is controlled to a value lower than the voltage (potential) of the secondary electron conversion electrode 7, reflection occurs. The secondary electrons 9a generated by the collision of the electrons 8a do not reach the secondary electron deflector 12a due to the action of the electric field between the pulling electrode 13 and the secondary electron conversion electrode 7, and are not detected. Accordingly, it is possible to select whether or not to detect the secondary electrons 9a having low-angle reflected electron information from the sample while maintaining the state in which the secondary electrons 20 are detected.

  At this time, the secondary electrons 20 generated from the sample are subjected to the converging action of the converging magnetic field of the objective lens 4 and rise toward the electron source direction substantially along the optical axis. Therefore, the secondary electrons 20 are attracted to the secondary electron conversion electrode 7. Without being detected, the secondary electron detector 5a detects it.

  Further, when a negative charge is applied to the secondary electron conversion electrode 7 by the voltage control means 11 a, the secondary electrons 20 generated from the sample 6 are secondary electron deflector 12 a due to the negative potential of the secondary electron conversion electrode 7. Is not detected by the secondary electron detector 5a.

  At this time, if the potential of the pull-up electrode 13 is controlled to a value higher than the potential of the secondary electron conversion electrode 7, the secondary electrons 9a generated from the secondary electron conversion electrode 7 reach the secondary electron deflector 12a. Then, it is deflected by the action of the secondary electron deflector 12a and detected by the secondary electron detector 5a. Therefore, by controlling the potentials of the secondary electron conversion electrode 7 and the pulling electrode 13 respectively, the secondary electrons 20 from the sample and the secondary electrons 9a having low-angle reflected electron information can be detected individually, or It is possible to select combining and detecting.

  Among the reflected electrons, the low-angle component includes unevenness information on the sample surface, and the high-angle component includes composition information on the sample surface. Among the high-angle components of the reflected electrons, those having high energy contain composition information from the surface of the sample, and those having low energy contain composition information from the inside of the sample.

  By separating and selectively detecting each component of these reflected electrons, it is possible to obtain a sample image having a high unevenness contrast and a high composition contrast. As described above, the selective detection of each component of the secondary electrons and the reflected electrons is performed by the voltage control means 11 so that a relative voltage difference is generated between the secondary electron conversion electrode 7, the pulling electrode 13, and the secondary electron deflector 12. This is done by controlling the applied voltage. The detection signals of the secondary electrons 20 and the reflected electrons 8 are signal-selected, synthesized or colored by the signal processing means 14 and displayed on the display device 15.

  The secondary electron conversion electrode 7 is formed in a cylindrical shape having a passage for the primary electron beam 2 and further has an opening on the electron source side. The inner surface of the cylindrical body is a secondary electron conversion surface.

  The reason why it is formed in a cylindrical shape is to capture the low-angle reflected electrons 8a scattered in a spiral orbit more reliably.

  The secondary electron conversion electrode (reflector) and detector disclosed in Patent Document 2 and Patent Document 3 have a secondary electron conversion surface and a detection surface formed in a direction perpendicular to the optical axis of the electron beam. Therefore, the detection range for the low-angle reflected electrons 8a scattered in a spiral orbit is narrowed. In order to make these conversion surfaces and detection surfaces large, the diameter of the electron microscope column must be increased, but the space inside the electron microscope column that must maintain a high vacuum must be increased. Is practically difficult.

  By forming the secondary electron conversion electrode in a cylindrical shape as in the embodiment of the present invention, it is possible to enlarge the detection surface of low-angle backscattered electrons that draw a spiral trajectory due to the influence of the convergence magnetic field of the objective lens. Efficiency can be increased.

  Another reason is that the secondary electron 9a converted by the secondary electron conversion electrode 7 can be easily guided to the secondary electron detector 5a side by forming a large opening on the electron source side.

  In the embodiment of the present invention, the reflected electrons collide with the secondary electron conversion electrode to convert them into secondary electrons, and the secondary electrons are deflected and detected by the secondary electron deflector to the secondary electron detector. ing. The reason for detecting reflected electrons after converting them into secondary electrons is that the primary electron beam disperses energy when an electric field strong enough to deflect (suck) the reflected electrons to the secondary electron detector is applied to the primary electron beam. This is because in order not to cause energy dispersion, it is necessary to deflect (suck) electrons to the detector with a weak electric field.

  FIG. 2 is a diagram showing an arrangement example of secondary electron conversion electrodes for explaining the principle of the present invention in more detail.

  The reflected electrons generated from the sample 6 by the irradiation of the primary electron beam 2 have an angular distribution, and the trajectory differs depending on the generation angle. The reflected electrons generated from the sample take a spiral trajectory under the influence of the objective lens magnetic field, and leave the spiral trajectory when the influence of the objective lens magnetic field becomes small.

  Reflected electrons (low angle component) generated at a shallow angle from the sample leave the spiral orbit and then collide with the objective lens magnetic path (reflected electron low angle component 8a1), or trajectory far away from the optical axis (reflected electrons). The low angle component 8a2) is taken. By arranging the secondary electron conversion electrode 7 on this orbit, the low-angle reflected electrons 8a1 and 8a2 are converted into secondary electrons 9a1 and 9a2 generated by the collision with the secondary electron conversion electrode, and the secondary electron detector 5 Can be detected. The high-angle reflected electrons 8b generated at a high angle from the sample take a trajectory close to the optical axis even after being affected by the magnetic field of the objective lens, and hence detection means described later disposed further above the secondary electron detector 5. Detect by.

  FIG. 3 is a graph showing the number of electrons generated from a sample and its energy distribution when the sample is irradiated with a primary electron beam. The energy of reflected electrons is higher than that of secondary electrons, and there is little energy loss due to collision with the sample. Among the reflected electrons, the high angle component has less loss and the energy band is higher than the low angle component. By separating, selecting and detecting these components, the unevenness information on the sample surface (included in the detection signal of the low angle component of the reflected electrons) and the composition information of the sample surface (included in the detection signal of the high angle component of the reflected electrons) Can be obtained with high contrast.

  In addition, since the higher the energy, the closer to the sample surface is included in the high-angle components of the reflected electrons, so by separating and detecting the high energy component and the low component, Composition information can be obtained with high contrast.

  FIG. 4 shows an embodiment in which the secondary electron conversion electrode 7 (conductive member) is divided into a plurality of parts and a means for applying a voltage to each of them is arranged. In this embodiment, a mesh-like electrode 16 capable of transmitting electrons is disposed around the optical axis inside the secondary electron conversion electrode 7.

  Reflected electrons 8 (low angle component) generated from the sample 6 by irradiation with the primary electron beam 2 collide with the secondary electron conversion electrode 7 to generate secondary electrons 9. At this time, the distribution angle distribution of the reflected electrons 8a (low angle component) changes depending on the unevenness and inclination of the sample, and the collision position distribution on the secondary electron conversion electrode 7 also changes. Therefore, the secondary electron conversion electrode 7 is divided into a plurality of pieces (7a to 7d, 7a1 to 7a2) as in this embodiment, and the voltage of the secondary electron conversion electrode 7 is set to the voltage of the electrode 16 by the voltage application means 11. By relatively controlling, the secondary electrons 9 generated on the secondary electron conversion electrode 7 due to the collision of the reflected electrons 8 can be selectively introduced, and a sample image in which unevenness and inclination are emphasized can be obtained. Can do.

  For example, in the secondary electron conversion electrode 7a1 and the secondary electron conversion electrode 7a2, when it is desired to detect only the reflected electrons 7a1 that collide with the secondary electron conversion electrode 7a1, the voltage control means 11 applies the electron to the secondary electron conversion electrode 7a2. The voltage is controlled to be higher than the voltage of the electrode 16, and the voltage of the secondary electron conversion electrode 7 a 1 is controlled to be lower than the voltage of the electrode 16.

  The secondary electrons 9a2 generated on the secondary electron conversion electrode 7a2 are not detected because they are not pulled up in the direction of the detector due to the relative potential difference, but the secondary electrons 9a1 generated on the secondary electron conversion electrode 7a1 are not detected. Because of the potential difference (the voltage of the secondary electron conversion electrode 7a1 is lower than the voltage of the electrode 16), it is pulled up toward the detector and detected. Further, by arranging the electrode 16, it is possible to prevent a deflection electric field from being generated on the optical axis when a different voltage is applied to each element of the electrode.

  FIG. 5 shows an embodiment in which the secondary electron conversion electrode 10 is arranged on the electron source 1 side of the secondary electron deflector and detection is performed by converting high-angle reflected electrons into secondary electrons. The primary electron beam 2 generated from the electron source 1 is scanned by the deflection coils 3 a and 3 b arranged in two stages, and is converged on the sample 6 by the objective lens 4.

  By irradiation with the primary electron beam 2, secondary electrons 20 and reflected electrons 8 a and 8 b are generated from the sample 6. Of the reflected electrons generated from the sample, the reflected electrons 8a are a low angle component generated at a shallow angle from the sample, and the reflected electrons 8b are a high angle component generated at a high angle from the sample.

  The secondary electrons 20 are wound up to the electron source side by the magnetic field generated by the objective lens 4 and travel, and are deflected to the secondary electron detector 5 side by the secondary electron deflector 12 and detected by the secondary electron detector 5. Is done.

  On the other hand, the reflected electrons 8a (low angle component) collide with the secondary electron conversion electrode 7 arranged on the upper part of the objective lens 4 to generate secondary electrons 9a. The secondary electrons 9 a are guided to the secondary electron deflector 12 by the pulling electrode 13 to which a positive voltage is applied by the voltage applying unit 11 b, deflected, and detected by the secondary electron detector 5. The reflected electrons 8b (high angle component) collide with the secondary electron conversion electrode 10 disposed on the upper part of the secondary electron deflector 12, and similarly generate secondary electrons 9b. The secondary electrons 9 b are deflected by the secondary electron deflector 12 and detected by the secondary electron detector 5.

  Here, when a positive voltage is applied to the secondary electron conversion electrode 7 by the voltage control means 11a and the voltage (potential) of the pulling electrode 13 is controlled to a value lower than the voltage (potential) of the secondary electron conversion electrode 7, The secondary electrons 9a generated by the collision of the reflected electrons 8a do not reach the secondary electron deflector 12 due to the action of the electric field between the pulling electrode 13 and the secondary electron conversion electrode 7, and are thus not detected. The secondary electron 9a having low-angle reflected electron information from the sample can be selected as to whether or not it is detected.

  On the other hand, when a negative charge is applied to the secondary electron conversion electrode 7 by the voltage control means 11 a, the secondary electrons 20 generated from the sample 6 are secondary electron deflector 12 due to the negative potential of the secondary electron conversion electrode 7. Is not detected by the secondary electron detector 5. At this time, if the potential of the pulling electrode 13 is controlled to a value higher than the potential of the secondary electron conversion electrode 7, the secondary electrons 9 a generated from the secondary electron conversion electrode 7 reach the secondary electron deflector 12. Then, it is deflected by the action of the secondary electron deflector 12 and detected by the secondary electron detector 5. Therefore, by controlling the potentials of the secondary electron conversion electrode 7 and the pulling electrode 13 respectively, the secondary electrons 20 from the sample and the secondary electrons 9a having low-angle reflected electron information can be detected individually, or It is possible to select combining and detecting.

  Similarly, when a positive voltage is applied to the secondary electron conversion electrode 10 by the voltage control means 11d, the secondary electrons 9b generated by the collision of the reflected electrons 8b do not reach the secondary electron deflector 12 due to the action of the electric field and are not detected. Therefore, it can be detected separately from the secondary electrons 20 and the secondary electrons 9a. In addition, when the secondary electron conversion electrode 10 is structured so that it can be taken in and out of the vacuum, and high-angle reflected electron information is not required, the secondary electron conversion electrode 10 is kept away from the optical axis so that the reflected electrons do not collide. High-angle backscattered electronic information can be selected. In this case, it is not necessary to control the voltage of the secondary electron conversion electrode 10.

  In this way, the voltages applied to the secondary electron conversion electrode 7 and the pulling electrode 13, the secondary electron deflector 12, and the secondary electron conversion electrode 10 are controlled by the voltage control means 11 so that a relative voltage difference is generated. Is done. The secondary electrons detected by the secondary electron detector 5 are converted into electrical signals and then displayed on the display device 15 through the signal processing means 14.

  According to the embodiment apparatus of the present invention, it is possible to selectively detect high-angle reflected electrons, low-angle reflected electrons, or secondary electrons and form a sample image based on the electrons. Furthermore, it is possible to form a sample image by combining two or more of these electrons.

  As described above, according to the embodiment apparatus of the present invention, it is possible to select the reflected electrons according to the generation angle and energy without increasing the focal length, and to obtain information by dividing the information into composition information and shape information. It becomes possible.

It is the schematic of the Example of this invention, and is a figure which shows the scanning electron microscope provided with the in-lens type objective lens. It is a figure which shows the schematic of the arrangement | positioning Example of a secondary electron conversion electrode (electroconductive member). It is a figure which shows the electron which generate | occur | produces from a sample when a primary electron beam is irradiated, and its energy distribution. It is a figure which shows the schematic of the Example which divided | segmented the secondary electron conversion electrode into plurality. It is the schematic of the Example of this invention, and is a figure which shows the scanning electron microscope provided with the lower magnetic pole open type objective lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron source 2 Primary electron beam 3a, 3b Deflection coil 4 Objective lens 5a, 5b Secondary electron detector 6 Sample 7, 7a-7d, 7a1, 7a2 Secondary electron conversion electrode 8a, 8b, 8b1 Reflected electron 9a, 9b1, 20 Secondary electron 11b Voltage application means 12a, 12b E × B deflector (orthogonal electromagnetic field generator)
13 Lifting electrode 14 Signal processing means 15 Display device 16 Electrode 17 Sputter coding surface 18 Backscattered electron detector

Claims (20)

An electron source,
A scanning deflector for scanning a sample with a primary electron beam generated from an electron source;
An objective lens that forms on the sample a converging magnetic field for converging the primary electron beam;
A scanning electron microscope including a secondary signal detector that deflects and detects a secondary signal generated from a sample by irradiation of a primary electron beam, and obtains a two-dimensional scanning image of the sample,
The objective lens generates a magnetic field covering the irradiation position of the primary electron beam of the sample,
A scanning electron microscope characterized in that a secondary electron conversion electrode for generating secondary electrons by collision of reflected electrons is arranged on the electron source side with respect to the upper magnetic pole of the objective lens and on the sample side with respect to the deflector.   The scanning electron microscope according to claim 1, wherein the scanning electron microscope includes a second conversion electrode on the electron source side of the secondary signal detector.   3. The scanning electron microscope according to claim 1, wherein the objective lens is an in-lens type or an open bottom pole type objective lens.   4. The scanning electron microscope according to claim 1, wherein the secondary electron conversion electrode is a cylindrical body having an opening through which the primary electron beam passes. 5.   5. The scanning electron microscope according to claim 4, wherein the cylindrical body has a large opening on the electron source side.   5. The scanning type according to claim 4, wherein the cylindrical body is divided into at least two electrodes in an optical axis direction of the primary electron beam and / or a direction perpendicular to the optical axis. electronic microscope.   7. The scanning electron microscope according to claim 6, wherein voltage applying means is connected to each electrode forming the cylindrical body.   4. The scanning electron microscope according to claim 1, wherein a secondary electron extraction electrode is disposed on the electron source side from the secondary electron conversion electrode and on the sample side from the secondary signal detector. A scanning electron microscope.   4. The scanning electron microscope according to claim 1, further comprising means for applying a positive or negative voltage to the secondary electron conversion electrode.   The scanning electron microscope according to any one of claims 1 to 3, wherein an electrode is disposed closer to an electron source than the secondary electron conversion electrode and closer to a sample side than the secondary signal detector, and the electrode and the second A scanning type comprising voltage application means for applying a positive voltage to the secondary electron conversion electrode, wherein the voltage application means applies a voltage larger than the voltage applied to the electrode to the secondary electron conversion electrode. electronic microscope.   The scanning electron microscope according to any one of claims 1 to 3, wherein a porous electrode disposed between the secondary electron conversion electrode and an optical axis of the primary electron beam, the porous electrode and the secondary electron conversion A scanning electron microscope comprising voltage applying means for applying a voltage to an electrode.   The scanning electron microscope according to claim 11, wherein the secondary electron conversion electrode and the porous electrode are cylindrical bodies having openings through which the primary electron beam passes.   13. The scanning electron microscope according to claim 12, wherein the cylindrical body has a large opening on the electron source side. An electron source,
A scanning deflector for scanning a sample with a primary electron beam generated from an electron source;
An objective lens that forms on the sample a converging magnetic field for converging the primary electron beam;
A scanning electron microscope including a secondary signal detector that deflects and detects a secondary signal generated from a sample by irradiation of a primary electron beam, and obtains a two-dimensional scanning image of the sample,
The scanning electron microscope includes a deflector that deflects secondary electrons in the direction of the secondary signal detector,
The objective lens generates a magnetic field covering the irradiation position of the primary electron beam of the sample,
A scanning electron microscope characterized in that a secondary electron conversion electrode for generating secondary electrons by collision of reflected electrons is arranged on the electron source side with respect to the upper magnetic pole of the objective lens and on the sample side with respect to the deflector.   15. The scanning electron microscope according to claim 14, wherein the scanning electron microscope has a second conversion electrode on the electron source side with respect to the deflector.   16. The scanning electron microscope according to claim 14, wherein the objective lens is an in-lens type or a bottom pole open type objective lens.   4. The scanning electron microscope according to claim 1, wherein the secondary electron conversion electrode is a cylindrical body having an opening through which the primary electron beam passes. 5.   18. The scanning electron microscope according to claim 17, wherein the cylindrical body has a large opening on the electron source side.   18. The scanning type according to claim 17, wherein the cylindrical body is divided into at least two electrodes in an optical axis direction of the primary electron beam and / or a direction perpendicular to the optical axis. electronic microscope.   20. The scanning electron microscope according to claim 19, wherein voltage applying means is connected to each electrode forming the cylindrical body.

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