JP5478683B2 - Charged particle beam irradiation method and charged particle beam apparatus - Google Patents

Description

  The present invention relates to a charged particle beam irradiation method and a charged particle beam apparatus, and more particularly to a charged particle beam irradiation method and a charged particle beam apparatus capable of controlling the trajectory of a secondary signal emitted from a sample.

  A scanning electron microscope (hereinafter referred to as SEM), which is one type of charged particle beam apparatus, accelerates a primary electron beam (electron beam) emitted from an electron source and uses an electrostatic or magnetic lens on a sample. The focused spot beam is scanned two-dimensionally on the sample to detect secondary signals such as secondary electrons or reflected electrons generated secondary from the sample, and the detected signal intensity is synchronized with the scanning of the primary electron beam. This is a device that obtains a two-dimensional scanned image (SEM image) by using the luminance modulation input of the monitor to be scanned.

  In recent years, as the miniaturization of the semiconductor industry has progressed, SEM is used in the process of manufacturing semiconductor devices or inspection after completion of the process (for example, dimensional measurement using an electron beam or inspection of electrical operation) instead of an optical microscope. Became. In the observation of the multilayer thin film structure of the internal structure of a semiconductor device, the surface shape can be measured and the defect detection can be evaluated by efficiently detecting the backscattered electrons having tilt information in addition to the secondary electrons having information on the sample surface. . The latest SEM is equipped with an energy filter or the like that can separate signals of secondary electrons and reflected electrons, and can form an image contrast according to the purpose. In addition, ArF resists and Low-K materials used in recent semiconductor processes show shrinkage (shrink) and deformation due to electron beam irradiation when SEM observation is performed. This phenomenon can be mitigated by lowering the acceleration voltage. On the other hand, since the resolution of the SEM is lowered, high-resolution observation is difficult.

  Therefore, the retarding method in which a negative voltage is applied to the sample and the boosting method in which the chromatic aberration of the primary electron beam is reduced by arranging an acceleration electrode in the vicinity of the objective lens can be used even in a low acceleration voltage region. Resolution observation has become possible. On the other hand, in order to efficiently detect secondary signals such as secondary electrons and reflected electrons emitted from a sample, a detector using a quadrature electromagnetic field generator (EXB) for secondary signal separation is used. A typical example is described in Patent Document 1.

  Patent Document 2 describes a technique for forming a sample image with a desired contrast by configuring a detector with divided detection elements and performing signal processing according to an electron trajectory.

JP 2007-250560 A JP 2005-347281 A

  On the other hand, the trajectory of electrons emitted from the sample varies depending on the energy of the electron beam reaching the sample or the state of charging attached to the sample. Electrons emitted from the sample are detected by a detector or a secondary electron conversion electrode (an electrode that emits new secondary electrons by collision of electrons emitted from the sample, hereinafter the detector and the secondary electron conversion electrode are combined) If it collides with another structure or the like before reaching the device, the secondary electron information is lost, and the detection efficiency decreases. For example, Patent Documents 1 and 2 do not propose a method for detecting electrons traveling outward from a detector or the like around the optical axis of the electron beam.

  Hereinafter, a charged particle beam irradiation method and a charged particle beam apparatus for the purpose of enabling highly efficient detection of charged particles traveling in directions other than the detector will be described.

  In order to achieve the above object, a focusing element that focuses the trajectory of the charged particles emitted from the sample does not affect the charged particle beam toward the sample (or the influence can be suppressed). ) We propose a charged particle beam device arranged at a position and a charged particle beam irradiation method. The focusing action selectively affects the electrons emitted from the sample and suppresses the influence on the charged particle beam toward the sample, so the charged particles emitted from the sample and traveling in directions other than the detector are focused. It is possible to guide to a detector or the like.

  According to the above configuration, the charged particle detection efficiency can be controlled without affecting the charged particle beam directed to the sample.

The schematic block diagram of a scanning electron microscope. The figure explaining the track | orbit until the electron discharge | released from the sample reaches a detector. The figure explaining an example of the analysis result of a secondary signal orbit. The figure explaining an example of control of a secondary signal orbit. The figure which shows the relationship between a focusing electrode voltage and the electric current value detected by a Faraday cup. The figure explaining an example of control of a secondary signal orbit. The figure which shows the relationship between a focusing electrode voltage and an electric current value. The figure explaining an example of control of the secondary signal orbit at the time of sample charge. The figure explaining transition of the relationship between the focusing electrode voltage at the time of sample charging, and an electric current value. The flowchart of secondary signal track control. The figure explaining an example of a structure of a multistage focusing electrode. The figure explaining an example of a structure of the focusing electrode with a raising / lowering mechanism. The figure explaining the outline | summary of the optical system which does not make a crossover.

  Hereinafter, a charged particle beam apparatus capable of controlling the trajectory of a charged particle beam emitted from a sample will be described in detail with reference to the drawings. In the following description, a scanning electron microscope will be described as an example of a charged particle beam apparatus. However, the present invention is not limited to this, and a focused ion beam that scans a focused ion beam to form a scanned image is described. (Focused Ion Beam) Application to a device is also possible.

  In the SEM, for example, the trajectory of electrons emitted from the sample changes depending on the energy when the electron beam reaches the sample, the charging attached to the sample, etc., for example, secondary signals such as reflected electrons and secondary electrons are generated. Secondary signals are lost due to collision with other structures before reaching the detector, etc., or secondary signals coming out of the primary electron (electron beam) passage hole provided in the detector, etc. However, there is a problem that the detection efficiency is lowered. In addition, the secondary signal is deflected by the sample charging due to the irradiation of the primary electron beam, and the trajectory of the secondary signal changes with time, and the secondary signal cannot reach the detector etc. May not be able to respond.

  In the embodiment described below, the detection efficiency of the secondary signal emitted from the sample can be improved and the detection signal can be controlled to be constant.

  In the present embodiment, in order to achieve the above object, the focusing electrode is arranged between the objective lens and the secondary electron conversion electrode, and the crossover point of the primary electron beam is controlled to the center position of the focusing electrode, so that Only the trajectory of the next signal is controlled.

  In addition, a Faraday cup is placed outside the secondary electron conversion electrode, the secondary signal that did not collide with the secondary electron conversion electrode is converted to a current value, measured, and the current value is fed back and applied to the focusing electrode. The voltage to be determined is determined, and the trajectory of the secondary signal can be controlled in the secondary electron conversion electrode.

  FIG. 1 is a diagram showing a configuration of a scanning electron microscope. A voltage is applied between the cathode 1 and the first anode 2 by a high voltage control power source 30 controlled by a control arithmetic device 40 (control processor), and a predetermined emission current is drawn from the cathode 1. Since an acceleration voltage is applied between the cathode 1 and the second anode 3 by a high voltage control power source 30 controlled by the control arithmetic unit 40, the primary electron beam 4 emitted from the cathode 1 is accelerated and the latter lens system. Proceed to.

  The primary electron beam 4 (electron beam) is focused by the focusing lens 5 controlled by the focusing lens control power source 31, and after the unnecessary region of the primary electron beam 4 is removed by the diaphragm plate 8, the focusing lens control power source 32. The sample 10 is focused as a minute spot by the controlled focusing lens 6 and the objective lens 7 controlled by the objective lens control power source 36. The focusing lens 6 can control the object point of the objective lens 7 to an arbitrary position, and can control the incident angle of the objective lens 7.

  A negative voltage is applied to the sample 10 by the sample application power source 37 via the sample stage 11 so that an electric field for decelerating the primary electron beam can be formed (hereinafter referred to as a retarding method). Further, a boosting method in which an electrode that accelerates by applying a positive voltage for reducing chromatic aberration directly or in the vicinity of the objective lens 7 is also possible. The boosting method may be a method of selectively accelerating the electron beam in the electron beam path of the objective lens. For example, a cylindrical acceleration electrode is provided from the second anode 3 to the objective lens. A method of arranging and applying a positive voltage to the acceleration electrode may be used (hereinafter referred to as column boosting for convenience).

  The primary electron beam 4 is scanned two-dimensionally on the sample 10 by the scanning coil 9 controlled by the scanning coil control power source 33. Secondary signals 12 such as secondary electrons and reflected electrons generated from the sample 10 by the irradiation of the primary electron beam 4 have a finite spread on the upper portion of the objective lens 7 by the action of the pulling magnetic field or pulling electric field by the objective lens 7. It proceeds and collides with the secondary electron conversion electrode 13 to generate secondary electrons 14.

  The secondary electrons 14 are deflected toward the signal detector 17 by the deflection electric field formed by the deflection electrode 16. The signal detected by the signal detector 17 is amplified by the signal amplifier 18, transferred to the image memory 41, and displayed as a sample image on the image display device 42.

  The secondary signal 21 that deviates from the secondary electron conversion electrode 13 having a finite size is captured by the Faraday cup 20, and the secondary signal 12 that cannot be captured by the secondary electron conversion electrode by the ammeter 34 is used as the current. It is possible to measure. Further, the secondary signal 12 can be focused by the focusing electrode 19 controlled by the secondary signal control voltage 35 and the spread at the secondary electron conversion electrode 13 can be controlled. In addition, as a detector for capturing electrons traveling outside the secondary electron conversion electrode 13, a detector such as a micro channel plate (MCP) detector may be used instead of the Faraday cup. Is also possible.

  An embodiment for controlling the trajectory of the secondary signal 12 such as secondary electrons and reflected electrons emitted from the sample will be described below in detail with reference to FIG. FIG. 2 is a diagram conceptually showing the trajectory until the electrons emitted from the sample reach the detector.

  The primary electron beam 4 is focused to an arbitrary crossover point 23 by the focusing lens 6. The crossover point 23 can control the incident opening angle of the objective lens 7, and can set the minimum condition of the compound aberration due to spherical aberration, chromatic aberration, etc. in the objective lens 7, and as a result, high resolution can be realized. Conversely, by reducing the opening angle, it is possible to realize an optical condition with a deep focal depth.

  The primary electron beam 4 is focused on the sample 10 by the objective lens 7 into a minute spot, and the secondary signal 12 generated from the minute spot travels above the objective lens 7 by the pulling action and focusing action of the objective lens 7, and the crossover point. After focusing at 15, it collides with the secondary electron conversion electrode 13 with a finite extent.

  Secondary electrons 14 which are information from the sample converted by the secondary electron conversion electrode 13 are deflected to the signal detector 17 side by the deflection electrode 16 and are taken in as signals. The deflection electrode 16 may have a simple configuration of two opposing electrodes, but it is desirable to use a secondary signal separation orthogonal electromagnetic field generator (EXB) that does not generate deflection aberration with respect to the primary electron beam 4.

  The focusing electrode 19 functions as an electrostatic lens by the focusing electric field 22 and controls the trajectory of the secondary signal 12 rising from the sample 10. A Faraday cup 20 is disposed outside the secondary electron conversion electrode 13, supplements electrons that have not collided with the secondary electron conversion electrode 13, and is measured as a current value by an ammeter 34. By performing feedback control with the control arithmetic device 40 using this current value, the secondary signal 12 deviated from the trajectory from the secondary electron conversion electrode 13 is deflected toward the secondary electron conversion electrode 13, and secondary electron conversion is performed. It becomes possible to make it collide with the electrode 13. For example, a negative voltage is applied to the focusing electrode 19, and as the amount of electrons detected by the Faraday cup 20 is larger, control is performed such that the applied voltage is set higher. Can be guided to the secondary electron conversion electrode 13 without applying an excessive voltage. The Faraday cup 20 is disposed outside the secondary electron conversion electrode 13 with the optical axis of the primary electron beam 4 as the center.

  Actually, since the focusing electrode 19 is disposed in the path of the primary electron beam 4 (the same space as the vacuum atmosphere through which the primary electron beam 4 passes), the focusing action also acts on the primary electron beam 4, and the crossover point 23. May change, and the focus of the objective lens 7 may be deviated. However, by setting the crossover point 23 to the center position of the focusing electrode 19 as shown in FIG. 19 (so that it is the same height as the center of the focusing electrode 19), it is possible to focus only the trajectory of the secondary signal 12 without changing the crossover point 23 of the primary electron beam 4.

  Ideally, the center in the height direction of the focusing electric field 22 generated by the focusing electrode 19 should be the same height as the crossover 23. Strictly speaking, as long as the electric field has a certain extent, the influence of the focusing action of the focusing electrode 19 on the primary electron beam 4 may not be zero. However, the influence is relatively small compared to the influence on the secondary signal.

  The secondary signal 12 emitted from the sample 10 is emitted over a wide angular range on the sample and has a wide energy range from several eV to the energy corresponding to the acceleration voltage of the primary electron beam 4. The trajectory is not uniform. However, for secondary electrons having surface information in particular, the number of secondary signals that collide with the secondary electron conversion electrode 13 is a signal of the SEM image, so a secondary electron emission ratio of about 1 to 2 eV is large. Think about electron trajectories.

  On the other hand, for the reflected electrons having the angle information of the sample, an energy filter is disposed between the sample 10 and the secondary electron conversion electrode 13 to separate the secondary signal 12 into only the reflected electrons, and then the focusing electrode 19 is used. This can be achieved by controlling the spread of reflected electrons on the secondary electron conversion electrode 13.

  Further, in order for the secondary electron conversion electrode 13 to pass the primary electron beam 4, it is necessary to place a passage hole 24 larger than the diameter of the primary electron beam in the center of the secondary electron conversion electrode 13. For example, if the diameter of the primary electron beam 4 has a beam diameter of about 0.1 mm at the position of the secondary electron conversion electrode 13, it is natural that a hole larger than 0.1 is required. However, if the hole for allowing the primary electron beam 4 to pass through is too large, the secondary signal 12 coming up from the objective lens 7 also passes through the hole, leading to the loss of the secondary signal 12 and the S / N being reduced. .

  The through hole 24 should not be so large as to significantly lose the secondary signal 12. Accordingly, since the secondary signal 12 on the secondary electron conversion electrode 13 needs to spread so as not to reduce the S / N with respect to the passage hole 24, the passage hole has a width of 0.5 mm to 1.0 mm. A degree is desirable.

  FIG. 3 is an example in which the trajectory of the secondary signal is analyzed by simulation in the scanning electron microscope to which this embodiment is applied. The configuration of FIG. 3 is a configuration of a scanning electron microscope of the retarding method. However, the primary electron beam 4 accelerated from the cathode 1 to −3000 V has a landing voltage of 300 V, 1300 V, and 2000 V. A voltage of −1700 V is applied to the sample 10 at 2700 V, B, and −2000 V is applied to C. In addition to the configurations of A, B, and C, D, E, and F apply a positive voltage from the boosting power source 38 to the boosting electrode 25 disposed in the vicinity of the objective lens 7. The secondary signal 12 is calculated for secondary electrons of 2 eV representing the secondary electrons, and shows the trajectory of the secondary electrons emitted at an angle of 0 to 90 degrees on the sample. Under different acceleration voltages, the orbits of secondary electrons on the secondary electron conversion electrode 13 are different, the signal amount varies, and the S / N changes depending on the acceleration voltage. Further, in B, the secondary signal 12 greatly deviates from the secondary electron conversion electrode 13, or in C or F, the secondary signal 12 passes through the passage hole 24, so that the signal cannot be taken and the S / N is remarkably deteriorated. ing.

  FIG. 4 to FIG. 8 show an embodiment specifically showing a configuration for correcting the above contents. 4 and 6 indicate the trajectory of the secondary signal 12 when the focusing electrode 19 is not used.

  FIG. 4 shows an example in which the secondary signal 12 is focused using the focusing electrode 19 when the secondary signal 12 as shown by B in FIG. 3 deviates greatly from the secondary electron conversion electrode 13. The secondary signal 12 is focused by the focusing action of the focusing electric field 22 and collides with the secondary electron conversion electrode 13 when the voltage applied to the focusing electrode 19 exceeds a certain value. FIG. 5 shows the relationship between the voltage value applied to the focusing electrode 19 and the current value measured by the ammeter 34. Since the amount of electrons that the secondary signal 12 did not collide with the secondary electron conversion electrode 13 is a current value, the amount of current measured by the ammeter 34 is reduced by the focusing action of the focusing electrode 19. This means that the secondary signal 12 has collided with the secondary electron conversion electrode 13. Therefore, S / N can be improved when the voltage value of the focusing electrode 19 rises to the voltage 50 at which the current in FIG. Further, by controlling the voltage value of the focusing electrode 19 to the value of the voltage 50, it is possible to keep the spread of the secondary signal 12 hitting the secondary electron conversion electrode 13 constant. For example, the amount of secondary electrons 14 reaching the detector 17 by controlling the trajectory of the secondary signal 12 in the sample 10 even when the sample height changes due to the influence of the sample thickness, deflection, or the like. It is possible to prevent the S / N from deteriorating.

  As described above, there are aspects of maintaining a predetermined signal amount by controlling the trajectory of electrons emitted from the sample, and an aspect of increasing the signal amount detected as much as possible. As a specific method for that purpose, it is conceivable to perform control such that the amount of current detected by the ammeter 34 is as small as possible (ideally, zero), but in addition to this, the amount of current is zero. It is also conceivable to perform control so as to have a predetermined value other than. Even in such a control that the detection amount is set to a value other than zero, measurement stability based on the maintenance of the detection amount can be achieved.

In this example, an example in which the voltage value applied to the focusing electrode 19 is controlled based on the amount of electrons detected by the Faraday cup 20 has been described. For example, the voltage value is formed based on electrons detected by the detector 17. The voltage applied to the focusing electrode 19 may be controlled so that the brightness of the image to be set becomes a predetermined value. In this case, ABCC (Auto Brightness Control Control) technology may be used together to control the voltage applied to the focusing electrode 19 so that the brightness becomes a predetermined value. However, the detection efficiency can be improved more directly by controlling such that the electrons outside the secondary electron conversion electrode 13 are directly detected and then reduced.

  FIG. 6 shows an example of controlling the trajectory of the secondary signal 12 using the focusing electrode 19 when the secondary signal 12 as indicated by F in FIG. 3 is lost from the passage hole 24 of the secondary electron conversion electrode 13. ing. The secondary signal 12 connects the crossover point 26 between the focusing electrode 19 and the secondary electron conversion electrode 13 by the focusing electric field 22. The secondary signal 12 that has passed the crossover point 26 collides with the secondary electron conversion electrode 13 while spreading. FIG. 7 shows the relationship between the voltage value applied to the focusing electrode 19 and the current value read by the ammeter 34 in the above contents. When the voltage is increased, the secondary signal 12 becomes higher than a certain voltage value. It comes off from the secondary electron conversion electrode 13, enters the Faraday cup 20, and is measured as an electric current value by an ammeter 34. When the voltage value of the focusing electrode 19 rises to the voltage 51 where the current value exceeds 0, it means that the secondary signal 12 has spread to the same extent as the size on the secondary electron conversion electrode 13. Therefore, by keeping the voltage value of the focusing electrode 19 constant at the voltage 51, it is possible to prevent the loss of the secondary signal and keep the S / N of the SEM image constant.

  FIG. 8 is a schematic diagram of another embodiment. The trajectory of the secondary signal 12 having a low energy of about several eV, which is generated when the sample 10 is irradiated with the primary electron beam 4, is deflected by the electric field due to negative charging accumulated during the irradiation of the primary electron beam 4. As shown by the solid line, it is tilted in a direction having an angle perpendicular to the sample. The secondary signal 12 tilted from the vertical direction of the sample passes through the outside of the objective lens 7 from the secondary electrons emitted before the charge generation, so that the secondary signal 12 emitted from the secondary signal 12 before the charge generation is secondary. Incident on the outside of the electron conversion electrode 13. Since the secondary electron conversion electrode 13 has a finite size, the secondary signal 12 tilted from the vertical direction of the sample due to the influence of charging may not enter the secondary electron conversion electrode 13 and the detection efficiency may be reduced. is there. In addition, when positive charge is excited in the observation region, the emitted secondary signal 12 is over-converged and passes through the passage hole 24 formed in the center of the secondary electron conversion electrode 13, thereby reducing detection efficiency. . The present invention is also effective in making the detection efficiency of secondary electrons by such sample charging constant. FIG. 9 is a diagram schematically showing a method for controlling the focusing electrode 19 during sample charging. Since the charging phenomenon always proceeds during irradiation of the primary electron beam 4, the spread at the position of the secondary electron conversion electrode 13 always changes. Therefore, in order to suppress the secondary signal 12 to a constant spread according to the size of the secondary electron conversion electrode 13, the current value of the ammeter 34 is measured at a certain time interval, for example, every 0.1 ms. The control signal calculation unit 40 performs feedback control, and when the current value increases, the trajectory of the secondary signal 12 is set so that the voltage applied to the focusing electrode 19 is increased and the current value measured by the ammeter 34 is set to zero. This can be achieved by controlling in real time. Further, in this embodiment, the current value does not necessarily have to be 0, and some loss of the secondary signal deviating from the secondary electron conversion electrode 13 occurs, but for example, with respect to the current value I measured by the ammeter 34 It is also possible to keep the spread of the secondary signal 12 constant by feedback-controlling the voltage of the focusing electrode 19 so that a certain constant current value is satisfied, such as 1 pA ≦ I <3 pA. The above content is effective control not only during negative charging but also during positive charging.

  FIG. 10 shows an embodiment of a flowchart for controlling the secondary signal 12 to be constant. After moving the sample 10 to a predetermined observation position, the focus is adjusted by the objective lens 7 (S101). The applied voltage of the focusing electrode 19 is applied, for example, in 1V steps (S102), and the current value is measured by the Faraday cup 20 (S103). If the current value is not 0, the voltage applied to the focusing electrode 19 is further increased by 1 V (S104). When the current becomes zero, the operation is terminated.

  FIG. 11 shows the configuration of the focusing electrode 19. In the present invention, the focusing electrode 19 for controlling the trajectory of the secondary signal 12 is arranged at the crossover point 23 of the primary electron beam 4. The crossover point 23 of the primary electron beam 4 has an opening angle in the objective lens 7. Is an important factor that determines the performance of the scanning electron microscope, such as resolution and depth of focus, and the position changes depending on the optical condition (mode). As shown in FIG. 11, in the case of a multistage focusing electrode 19, the focusing electrode 19 can be selected according to the crossover point 23. Moreover, as shown in FIG. 12, it may have a raising / lowering mechanism, and the position of the focusing electrode 19 may be variable according to the position of the crossover 23.

  In addition, the position of the crossover point 23 and the focusing electrode 19 may be shifted depending on the change of the optical conditions, so that the voltage application to the focusing electrode 19 is prohibited depending on the optical mode and the lens conditions. If an error message is sent to notify the operator of the processing or if the crossover point and the position (height) of the focusing electrode are different, a voltage is applied to the focusing electrode, resulting in disturbance of the optical conditions. It is possible to eliminate such a situation.

  In the above description, an SEM equipped with a detection mechanism that converts electrons emitted from a sample into secondary electrons by a secondary electron conversion electrode and deflects the secondary electrons to a detector for detection will be described as an example. However, the present invention is not limited to this. For example, a detector such as an MCP detector is arranged on the trajectory of electrons emitted from the sample, and a detection mechanism for directly detecting electrons emitted from the sample is provided. It can also be applied to the SEM provided.

  Further, instead of the focusing electrode 19 for focusing the electrons emitted from the sample, it is possible to apply a focusing coil for generating a focusing magnetic field.

  Furthermore, another method for selectively focusing electrons emitted from the sample in a condition that does not affect the electron beam will be described with reference to FIG. FIG. 13 is a diagram illustrating an example of an optical system that does not create a crossover by the focusing lens 6 (in the case of this optical system, no focusing is performed). A shield electrode 43 is disposed between the focusing electrode 19 and the primary electron beam 4 (electron beam optical axis). The shield electrode 43 is a cylindrical body surrounding the electron beam optical axis, and suppresses the arrival of the focused electric field provided by the focusing electrode 19 to the primary electron beam 4. Since the focusing electric field formed by the focusing electrode 19 does not reach the electron beam optical axis, the trajectory of electrons passing outside the shield electrode 43 can be selectively controlled. According to such a configuration, even in an optical system that does not create a crossover or an optical system that creates a crossover, it is possible to apply a focusing electrode at a location other than the location where the crossover is created. The shield electrode 43 makes it possible to prevent the focused electric field formed by the focusing electrode 19 from reaching the primary electron beam 4, but it cannot bring about a focusing action on secondary electrons passing through the shield electrode 43. Furthermore, since the shield electrode 43 also serves as an obstacle for electrons traveling toward the detector, the focusing electrode 19 is preferably applied to an optical system that creates a crossover.

  When a focusing coil is used instead of the focusing electrode 43, a magnetic shield may be used instead of the shielding electrode 43.

  Furthermore, in the above description, it has been assumed that the retarding method is applied. However, in the case of the column boosting method described above, electrons emitted from the sample are directed toward the electron source by the cylindrical electrode to which a positive voltage is applied. Therefore, even if the retarding method is not adopted, electrons whose energy is close to 0 eV can be guided to the secondary electron conversion electrode (or detector). Of course, the present invention can also be applied to an optical system using a retarding method and a boosting method (or a column boosting method) in combination.

DESCRIPTION OF SYMBOLS 1 Cathode 2 1st anode 3 2nd anode 4 Primary electron beam 5, 6 Focusing lens 7 Objective lens 8 Diaphragm plate 9 Scan coil 10 Sample 11 Sample stand 12, 21 Secondary signal 13 Secondary electron conversion electrode 14 Secondary electron 15 , 23, 26 Crossover point 16 Deflection electrode 17 Signal detector 18 Signal amplifier 19 Focusing electrode 20 Faraday cup 22 Focusing electric field 24 Passing hole 25 Boosting electrode 30 High voltage control power supply 31, 32 Focusing lens control power supply 33 Scanning coil control power supply 34 Ammeter 35 Secondary signal control voltage 36 Objective lens control power supply 37 Sample application power supply 38 Boosting power supply 40 Control operation device 41 Image memory 42 Image display device

Claims (9)

In a charged particle beam irradiation method for irradiating a charged particle beam to a sample and detecting charged particles emitted from the irradiation position,
A focusing element that focuses charged particles emitted from the sample, a detector that detects charged particles emitted from the sample, or a secondary electron conversion member that converts the charged particles into secondary electrons, and the charged particle beam. Using a charged particle beam apparatus having an outer detector disposed outside the detector or the secondary electron conversion member as a center, the focusing is performed so that the amount of charged particles detected by the outer detector is reduced. A charged particle beam irradiation method comprising adjusting an element. In claim 1,
The charged particle beam irradiation method, wherein the focusing element is arranged at the same height as a crossover point of the charged particle beam. In claim 1,
The charged particle beam irradiated to the sample is surrounded between the position where the focusing element is disposed and the charged particle beam irradiated to the sample, and the focusing action of the focusing element on the charged particle beam is The charged particle beam irradiation method characterized by arrange | positioning the cylindrical body to suppress. A charged particle source;
A charged particle optical system that focuses the charged particle beam emitted from the charged particle source and scans it on the sample;
In a charged particle beam apparatus comprising a detector for detecting charged particles emitted from the sample or detecting electrons generated when the emitted charged particles collide with a secondary electron conversion member,
A focusing element for focusing charged particles emitted from the sample;
An outer detector disposed outside the detector or the secondary electron conversion member around the charged particle beam;
A charged particle beam apparatus comprising: a control device that controls the focusing element so that a charged particle amount detected by the outer detector is reduced. In claim 4,
The charged particle beam apparatus, wherein the focusing element is disposed at the same height as a crossover point of a charged particle beam emitted from the charged particle source. In claim 5,
A charged particle beam apparatus comprising a moving mechanism for moving the focusing element in accordance with the movement of the crossover point. In claim 5,
A plurality of the focusing elements are arranged along the optical axis of the charged particle beam, and the control device controls the focusing elements so that focusing is performed by a focusing element having the same height as the crossover point. Characterized charged particle beam device. In claim 4,
The charged particle beam irradiated to the sample is surrounded between the position where the focusing element is disposed and the charged particle beam irradiated to the sample, and the focusing action of the focusing element on the charged particle beam is A charged particle beam device characterized in that a cylindrical body to be suppressed is arranged. In claim 4,
The outer particle detector is a Faraday cup.

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