Optical device and charged particle beam system

Abstract

In order to make it possible to simultaneously detect signal electrons of different energies without deteriorating spatial resolution in a charged particle beam apparatus, the present disclosure proposes an optical device used in a charged particle beam apparatus, said optical device comprising: a first electrode having an axisymmetric shape with respect to the optical axis of a charged particle beam with which a sample to be observed is irradiated or the optical axis of a charged particle emitted from the sample by being irradiated with the charged particle beam; a second electrode disposed closer to the sample side than the first electrode and having an axisymmetric shape with respect to the optical axis of the charged particle beam or the optical axis of the charged particle; and a deflector configured to deflect the charged particle or the charged particle beam in a direction in which the charged particle or the charged particle beam passes between the first electrode and the second electrode and which intersects the optical axis of the charged particle beam or the optical axis of the charged particle (see FIG. 1).

Description

Optical Devices and Charged Particle Beam Systems

[0001] The present disclosure relates to optical devices and charged particle beam systems.

[0002] When observing a sample using a scanning electron microscope (SEM), which is a type of charged particle beam device, the contrast of the image may be optimized by detecting signal electrons with an appropriate energy depending on the material and shape of the object being observed. Here, signal electrons are a general term for secondary charged particle beams generated by the interaction of a primary electron beam with a sample, and generally include secondary electrons, backscattered electrons, Auger electrons, etc.

[0003] Regarding the detection of this secondary charged particle beam, for example, Patent Document 1 discloses the use of a deflector for separating signal electrons from a primary electron beam and a divider for dividing the separated secondary electrons into a high-energy beam and a low-energy beam. Patent Document 2 discloses the use of an electrostatic lens for efficiently transporting signal electrons emitted from a sample to the deflector and a spectrometer installed downstream to select the energy of the signal electrons. Patent Document 3 discloses the use of a deflector for adjusting the conditions for the signal electrons to be incident on a mesh-shaped energy filter to improve the resolution of energy selection.

[0004] JP 2006-261111 A U.S. Patent No. 10,541,103 JP 2013-004291 A

[0005] Sample observation using a charged particle beam device requires high-contrast imaging of samples of various materials, structures, and shapes. To achieve high-contrast imaging, it may be necessary to simultaneously detect secondary electrons emitted from the sample with energies of several eV and backscattered electrons emitted from the sample with energies ranging from several hundred eV to several tens of keV (signals of each energy may be detected and images of each may be observed). For example, when observing a pattern in which a microstructure on the surface of a sample and a boundary region formed of a different material are arranged in close proximity, detecting secondary electrons is effective for increasing the contrast of the microstructure, while detecting backscattered electrons is desirable for increasing the contrast between the different materials (boundary region).

[0006] As described above, in order to simultaneously optimize contrasts resulting from different mechanisms, it is necessary to simultaneously detect signal electrons with significantly different energies, such as secondary electrons and backscattered electrons. In this regard, Patent Documents 1, 2, and 3 disclose a method of separating signal electrons from a primary electron beam using a deflector, and a means and configuration for performing high-resolution energy discrimination on a group of signal electrons with different energies but not a large difference in energy.

[0007] However, when secondary electrons and backscattered electrons, which have significantly different energies, are separated from the primary electron beam by a deflector according to the method disclosed in Patent Document 1, the difference in deflection angle due to chromatic dispersion becomes very large. As a result, they cannot be simultaneously guided to the spectrometer, and appropriate energy selection cannot be performed. Patent Document 1 assumes that the trajectories of signal electrons with different energies are aligned, but this is not the case; in fact, the trajectories of signals with different energies do not match (they travel in different directions).

[0008] Also, methods using rotationally symmetric lenses, multipole lenses, Wien filters, etc. to correct chromatic dispersion are known. However, when such optical elements are arranged with respect to a signal electron beam separated from a primary electron beam, the optical elements become asymmetric with respect to the primary electron beam, which can lead to axis misalignment of the primary electron beam or the occurrence of unexpected aberrations, which can degrade the spatial resolution of the SEM. In view of these circumstances, the present disclosure proposes a technology for simultaneously detecting signal electrons of different energies without degrading the spatial resolution of a charged particle beam device.

[0009] In order to solve the above problems, the present disclosure proposes, as an example, an optical device for use in a charged particle beam apparatus, the optical device including: a first electrode having a shape axially symmetrical with respect to the optical axis of a charged particle beam irradiated onto a sample to be observed or the optical axis of charged particles emitted from the sample by irradiation with the charged particle beam; a second electrode arranged on the sample side of the first electrode and having a shape axially symmetrical with respect to the optical axis of the charged particle beam or the optical axis of the charged particles; and a deflector configured to pass the charged particles or charged particle beam between the first electrode and the second electrode and to deflect the charged particles or charged particle beam in a direction intersecting the optical axis of the charged particle beam or the optical axis of the charged particles.

[0010] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0011] By using the optical device according to the present disclosure, it becomes possible to simultaneously detect signal electrons (charged particles) with different energies while maintaining high spatial resolution in a charged particle beam device.

[0012] 1 is a diagram showing an example of the configuration of a charged particle beam system according to a first embodiment. FIG. 1 is a diagram showing an example of the configuration of an annular electrode, an explanatory diagram of a first example. FIG. 2 is a diagram showing an example of electrodes configured by arranging shapes obtained by cutting out portions of a ring so as to face each other. FIG. 3 is a diagram showing an example of electrodes configured by dividing a ring into four. FIG. 4 is a diagram showing an example of electrodes configured by dividing a ring into eight. FIG. 5 is a diagram showing an example of electrodes configured as rectangular flat plates. FIG. 6 is a diagram showing an example of the configuration of a charged particle beam system having signal electron trajectory adjustment electrodes 24 and 25 (grounded) arranged in a specified positional relationship with respect to signal electron trajectory adjustment electrodes 22 and 23, and configured so that a voltage is applied to the signal electron trajectory adjustment electrodes 22 and 23. FIG. 7 is a diagram showing an example in which ideal deflection conditions are not set and a signal electron trajectory 201 of a first energy is off-axis from a signal electron optical axis 200 when passing through the signal electron trajectory adjustment electrodes 20 and 21. FIG. 8 is a flowchart for explaining details (specific examples) of signal electron trajectory control in the charged particle beam system according to the first embodiment. FIG. 9 is a diagram showing an example of the configuration of a charged particle beam system according to a second embodiment. FIG. 10 is a diagram showing an example of the configuration of a charged particle beam system according to a third embodiment. FIG. 11 is a diagram showing an example of the configuration of a charged particle beam system according to a fourth embodiment. 1 is a diagram showing an example of a configuration of a truncated cone-shaped electrode. FIG. 1 is a diagram showing an example of an electrode configured by arranging shapes obtained by cutting out portions of a truncated cone so as to face each other. FIG. 2 is a diagram showing an example of an electrode configured by dividing a truncated cone into four (configured by four partial electrodes). FIG. 3 is a diagram showing an example of an electrode configured by arranging two rectangular electrodes in opposing positions spaced 180 degrees apart from each other. FIG. 4 is a diagram showing an example of a configuration of a charged particle beam system according to a fifth embodiment. FIG. 5 is a diagram showing an example of a configuration of an electrode in which an electrode pair configured by signal electron trajectory adjustment electrodes 51 and 52 made of a portion of a rectangular or truncated cone surface is arranged rotationally symmetrically with respect to a primary electron optical axis 100 between a truncated cone-shaped signal electron trajectory adjustment electrode 32 and a truncated cone-shaped signal electron trajectory adjustment electrode 33, and a deflection field is formed in a direction perpendicular to the plane of the drawing by applying voltages of opposite polarities. FIG. 6 is a diagram showing an example of a configuration of a charged particle beam system without using a charged particle control deflector 43. FIG. 7 is a diagram showing an example of a configuration of a charged particle beam system according to a sixth embodiment.

[0013] The present disclosure mainly proposes a technology for simultaneously detecting multiple charged particles (signal electrons: for example, secondary electrons and backscattered electrons) with significantly different energies without degrading the spatial resolution of the charged particle beam device, by arranging optical elements (electrodes) for adjusting the trajectory of the signal electrons symmetrically with respect to the optical axis of the primary electrons.

[0014] Hereinafter, each embodiment of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show specific embodiments and implementation examples in accordance with the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used in any way to interpret the present disclosure in a limiting manner.

[0015] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to practice the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0016] (1) First Embodiment <Configuration Example of Charged Particle Beam System> Fig. 1 is a diagram showing a configuration example of a charged particle beam system according to the first embodiment. By adopting this configuration, it becomes possible to simultaneously detect signal electrons with significantly different energies while maintaining high spatial resolution.

[0017] The charged particle beam system includes an electron source 1, an acceleration electrode 2, condenser lenses 1-3, condenser lenses 2-4, a signal electron separation deflector 5, an objective lens 7, a detector 9, signal electron trajectory adjusting electrodes 20, 21, 22, 23, a first power supply 26, a second power supply 27, and a computer 28. Note that the charged particle beam system also includes components other than those shown in Fig. 1 (for example, a display device and an input device), but Fig. 1 shows only the components related to the features of this embodiment, and omits the other components.

[0018] Primary electrons emitted from the electron source 1 are accelerated by an accelerating electrode 2 and then focused by at least one condenser lens onto the object plane position of an objective lens 7. Thereafter, the electrons are focused (irradiated) onto a sample 8 by the objective lens 7.

[0019] Signal electrons emitted from the sample 8 travel in the direction of the electron source 1 and are separated from the primary electron optical axis 100 by the signal electron separation deflector 5. Fig. 1 shows, as an example, a case where the trajectory 201 of the signal electrons of the first energy is deflected by 90 degrees with respect to the primary electron optical axis 100 (the voltage applied to the signal electron separation deflector 5 is controlled so as to deflect the electrons by 90 degrees; a power supply for applying voltage to the signal electron separation deflector 5 is not shown). Here, the signal electron separation deflector 5 can be an electrostatic deflector or a magnetic field deflector, or a Wien filter that combines an electrostatic deflector and a magnetic field deflector, or a magnetic sector, or multi-stage deflection using a plurality of deflectors.

[0020] The trajectory 220 of the signal electrons of the second energy (signal electrons with higher energy than the first energy: for example, backscattered electrons with several hundred eV to several tens of keV) is deflected at a different angle from the trajectory 201 of the signal electrons of the first energy due to chromatic dispersion generated by the signal electron separation deflector 5. The difference in the deflection angle between the signal electron trajectory 201 of the first energy and the signal electron trajectory 220 of the second energy depends on the energy difference, the energy of the primary electron beam accelerated by the accelerating electrode 2, the value of the negative voltage applied to the sample 8, and the like. However, the difference in the deflection angles of the secondary electrons and the backscattered electrons often becomes 10 degrees or more. If the trajectory deviation caused by the difference in deflection angle is large compared to the size of the detection surface of the detector 9, these signal electrons cannot be detected simultaneously. Note that the larger the energy difference, the larger the deflection angle difference.

[0021] When the passing state is adjusted in the signal electron separating deflector 5, the signal electron trajectory becomes like a signal electron trajectory 210 of the second energy. The signal electron trajectory 210 of the second energy is subjected to a converging action by a lens field generated by applying a voltage to the signal electron trajectory adjusting electrodes 20 and 21, and is controlled so that it intersects with the signal electron trajectory 201 of the first energy on the detection plane of the detector 9, or has an trajectory deviation that allows simultaneous detection by the detector 9. Such control makes it possible to simultaneously detect signal electrons with significantly different energies.

[0022] <Arrangement and Shape of Signal Electron Trajectory Adjusting Electrodes> The signal electron trajectory adjusting electrodes 20 and 21 are arranged symmetrically with respect to the primary electron optical axis 100. As an example, they may be annular as shown in FIG. 2A (the hollow regions of the signal electron trajectory adjusting electrodes 22 and 23 are larger than those of the signal electron trajectory adjusting electrodes 20 and 21). Alternatively, as shown in FIG. 2B, they may be arranged so that portions of the signal electron trajectory adjusting electrodes 20 and 21 are cut out and face each other. When the signal electron trajectory adjusting electrodes 20 and 21 are annular, they are arranged so that the primary electron optical axis 100 passes through the center of the signal electron trajectory adjusting electrodes 20 and 21 (so that the electrodes are symmetric with respect to the primary electron optical axis 100). Alternatively, they may be shaped as a quartered circle as shown in FIG. 2C or as an eighthed circle as shown in FIG. 2D. Furthermore, the annular electrodes may be divided into more parts as long as they are arranged symmetrically with respect to the primary electron optical axis 100. Furthermore, the shape of the signal electron trajectory adjusting electrodes 20 and 21 does not necessarily have to be annular, and they may be rectangular as shown in FIG. 2E. Although not shown, the rectangular electrode may be divided into four, eight or more parts and arranged symmetrically with respect to the primary electron optical axis 100 .

[0023] <Outline of Signal Electron Trajectory Control> Signal electron trajectory control using the signal electron trajectory adjusting electrodes 20 and 21 will be described. As shown in FIG. 1 , when voltages of the same polarity are applied to the signal electron trajectory adjusting electrodes 20 and 21, a lens field is formed due to a potential difference generated between the signal electron trajectory adjusting electrodes 20 and 21 and the grounded signal electron trajectory adjusting electrodes 22 and 23, or between the signal electron separating deflector 5 and the like. However, the signal electron trajectory adjusting electrodes 22 and 23 do not necessarily have to be provided as electrodes, and components arranged around the chamber, etc., may take on this role. When the signal electron trajectory adjusting electrodes 22 and 23 are provided, they are grounded (GND), which makes it possible to manage (prevent) the generation of an electric field between the signal electron trajectory adjusting electrodes 20 and 21 and the device chamber (not shown).

[0024] On the other hand, if it is desired to control with high precision the lens field generated when a voltage is applied to the signal electron trajectory adjusting electrodes 20 and 21 in order to reduce instrumental differences, it is possible to provide signal electron trajectory adjusting electrodes 24 and 25 (grounded) disposed in a specified positional relationship with the signal electron trajectory adjusting electrodes 22 and 23 as shown in Fig. 3, and apply a voltage to the signal electron trajectory adjusting electrodes 22 and 23. Alternatively, a new lens field may be generated by applying a voltage to the signal electron trajectory adjusting electrodes 20, 21, 24, and 25 in the configuration shown in Fig. 3.

[0025] If signal electron trajectory adjusting electrodes 24 and 25 are provided (i.e., the number of electrodes is increased), a lens field can also be generated by the signal electron trajectory adjusting electrodes 22 and 23 (the signal electron trajectory adjusting electrodes 24 and 25 are grounded). In this case, the signal electrons (secondary electrons) of the first energy are slightly deflected (bent) by the signal electron trajectory adjusting electrodes 20 and 21, and the signal electrons are further deflected (bent) by the signal electron trajectory adjusting electrodes 22 and 23, thereby adjusting the incident angle of the signal electron trajectory 210 of the second energy onto the detector 9 (the method of aligning the incident positions of the signal electrons of the first and second energies onto the detector 9 is the same as in the case of FIG. 1 ). Furthermore, when the difference in deflection angle from the signal electron separation deflector 5 between the signal electrons of the first energy and the signal electrons of the second energy is very large, it is desirable to apply as large a voltage as possible to the signal electron trajectory adjusting electrodes 20 and 21, but an excessive voltage cannot be applied when the electrodes are close to the signal electron separation deflector 5. Therefore, the trajectory is slightly corrected by the signal electron trajectory adjusting electrodes 20 and 21 located close to the signal electron separating deflector 5, and the signal electron trajectory 210 of the second energy is focused onto the detector 9 by applying a voltage to the signal electron trajectory adjusting electrodes 22 and 23. In this way, by providing the signal electron trajectory adjusting electrodes 24 and 25, it is possible to control the signal trajectory depending on the situation.

[0026] When the signal electrons are separated from the primary electron optical axis 100 by the signal electron separation deflector 5, ideal deflection conditions may not be set as shown in FIG. 4 , and the signal electron trajectory 201 of the first energy may deviate from the signal electron optical axis 200 when passing through the signal electron trajectory adjusting electrodes 20 and 21. In such cases, a deflection field may be formed by applying a voltage of opposite polarity to the signal electron trajectory adjusting electrodes 20 and 21 (superimposed on a voltage of the same polarity), thereby controlling the trajectory of the signal electrons. When the deflection field is formed simultaneously with the lens field, a voltage of L+D(V) is applied to the signal electron trajectory adjusting electrode 20, and a voltage of L−D(V) is applied to the signal electron trajectory adjusting electrode 21, where L(V) is the voltage of the same polarity that forms the lens field and D(V) is the voltage of the opposite polarity that forms the deflection field. With the above configuration, it is possible to simultaneously detect signal electrons with significantly different energies while suppressing the influence on the primary electron beam.

[0027] 5 is a flowchart for explaining details (specific examples) of signal electron trajectory control in the charged particle beam system of the first embodiment. Note that, below, the contents of signal electron trajectory control (automatic control) will be explained assuming that the computer 28 is the main operator of the processing of each step in FIG. 5 , but an operator (user) may sequentially change the voltages applied to the signal electron trajectory adjusting electrodes 20 and 21 and, while checking the signal amount from the detector 9, search for an applied voltage that allows the detector 9 to simultaneously detect signal electrons of the first energy (secondary electrons) and signal electrons of the second energy (backscattered electrons) (manual control while the user monitors).

[0028] (i) Step S501 The computer 28 acquires from the detector 9 the signal amount of the signal electrons (e.g., secondary electrons) of the first energy deflected (90 degrees) by the signal electron separation deflector 5. Note that the signal electrons of the second energy (e.g., backscattered electrons) are deflected at a different angle from the signal electrons of the first energy, and therefore do not enter the detector 9, and the signal amount thereof is not detected at this stage.

[0029] (ii) Step S502 Based on the signal amount of the signal electrons of the first energy acquired in step S501, the computer 28 determines whether or not the signal electrons of the first energy are off-axis from the signal electron optical axis 200. Whether or not the signal electrons of the first energy are off-axis can be determined, for example, by whether or not the signal amount of the signal electrons of the first energy is less than a preset threshold value (e.g., a range of signal values ​​that can determine that a signal is incident at the center of the detector 9).

[0030] If it is determined that the signal electrons of the first energy are traveling along the signal electron optical axis 200 (NO in step S502), the process proceeds to step S503. On the other hand, if it is determined that the signal electrons of the first energy are off-axis from the signal electron optical axis 200 (YES in step S502), the process proceeds to step S507.

[0031] (iii) Step S503 The computer 28 controls the first power supply 26 and the second power supply 27 to apply voltages of the same polarity (for example, a preset initial value) to the signal electron trajectory adjusting electrodes 20 and 21.

[0032] (iv) Step S504 The computer 28 acquires the signal amount of the signal electrons (for example, backscattered electrons) of the second energy from the detector 9.

[0033] (v) Step 505: Based on the signal amount of the signal electrons of the second energy acquired in step S504, the computer 28 determines whether the signal electrons of the second energy are incident on the center position of the detector 9 (the same position as the incident position of the signal electrons of the first energy on the detector 9) (this can be determined based on whether the signal amount is an appropriate value). Whether the value is appropriate can be determined, for example, based on whether the signal amount has reached its maximum value (in the loop for determining the appropriate value, if the previous signal amount is not updated, the previous signal amount is set to the maximum value), or whether it is equal to or greater than a preset threshold.

[0034] If the signal amount of the signal electrons of the second energy is an appropriate value (YES in step S505), the signal electron trajectory control process ends. On the other hand, if the signal amount of the signal electrons of the second energy has not reached the appropriate value (NO in step S505), the process proceeds to step S506.

[0035] (vi) Step S506: The computer 28 controls the first power supply 26 and the second power supply 27 to change the voltage values ​​of the voltages of the same polarity to be applied to the signal electron trajectory adjusting electrodes 20 and 21. The amount of change in the voltage values ​​can be, for example, a preset value. After changing the applied voltage values, the computer 28 executes the processes from step S504 onwards again.

[0036] (vii) Step S507 The computer 28 controls the first power supply 26 and the second power supply 27 to apply a plurality of pairs of same-polarity voltages (e.g., +Lk(V); k=1, 2, ...) and opposite-polarity voltages (e.g., ±Dk(V); k=1, 2, ...) to the signal electron trajectory adjusting electrodes 20 and 21, respectively, and searches for a plurality of pairs of applied voltages that correct the off-axis of the signal electrons of the first energy from the signal electron optical axis 200. For example, a plurality of pairs of same-polarity and opposite-polarity applied voltages (voltages applied to electrode 20, voltages applied to electrode 21) that correct the off-axis of the signal electrons of the first energy from the signal electron optical axis 200 are searched for, such as (L1+D1, L1-D1), (L5+D5, L5-D5), (L7+D7, L7-D7), (L11+D11, L11-D11), ...

[0037] (viii) Step S508 The computer 28 selects one set of applied voltages from the sets of applied voltages found in step S507, and acquires from the detector 9 the signal amount of the signal electrons of the second energy when the voltages of the selected set are applied to the signal electron trajectory adjusting electrodes 20 and 21.

[0038] (ix) Step S509 Based on the signal amount of the signal electrons of the second energy acquired in step S508, the computer 28 determines whether the signal electrons of the second energy are incident on the center position of the detector 9 (the same position as the incident position of the signal electrons of the first energy on the detector 9) (this can be determined based on whether the signal amount is an appropriate value). As in step S505, whether the signal amount is an appropriate value can be determined based on, for example, whether the signal amount has reached its maximum value (in the loop for determining the appropriate value, if the previous signal amount is not updated, the previous signal amount is set to the maximum value) or whether it is equal to or greater than a preset threshold.

[0039] If the signal amount of the signal electrons of the second energy is an appropriate value (YES in step S509), the signal electron trajectory control process ends. On the other hand, if the signal amount of the signal electrons of the second energy has not reached the appropriate value (NO in step S509), the process proceeds to step S510.

[0040] (x) Step S510 The computer 28 selects another set of applied voltages from the sets of applied voltages found in step S507, and acquires from the detector 9 the signal amount of the signal electrons of the second energy when the voltages of the selected set are applied to the signal electron trajectory adjusting electrodes 20 and 21. Thereafter, the computer 28 executes the processes from step S508 onwards again.

[0041] (2) Second Embodiment The second embodiment relates to a charged particle beam system that allows an appropriate spectrometer or detector to be selected from multiple spectrometers or detectors depending on the application. Known spectrometers include, for example, an energy filter that forms a potential barrier by applying a negative voltage to a mesh electrode, and an energy analyzer that uses an electrostatic hemispherical electrode. Each spectrometer has different energy resolution and operability. Known detectors include, for example, an ET detector frequently used in SEMs, and position-sensitive detectors such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor. The second embodiment proposes that such detectors or spectrometers can be selected depending on the observation target and observation method.

[0042] Fig. 6 is a diagram showing an example of the configuration of a charged particle beam system according to the second embodiment. As in Fig. 1, Fig. 6 shows only components related to the features of this embodiment, and omits other components.

[0043] As shown in FIG. 6 , the charged particle beam system according to the second embodiment includes multiple signal electron optical axes. The multiple signal electron optical axes include, for example, a signal electron optical axis 200 and a signal electron optical axis 300, which corresponds to the signal electron optical axis 200 rotated 180 degrees relative to the primary electron optical axis 100. A detector (e.g., an ET detector) 9 is installed downstream of the signal electron optical axis 200, and a spectrometer-equipped detector 10 is installed downstream of the signal electron optical axis 300. Instead of the spectrometer-equipped detector 10, a CCD or CMOS sensor may be used, as described above. The spectrometer-equipped detector 10 performs energy detection at high resolution, resulting in reduced signal yield. However, the spectrometer-equipped detector 10 is used when observing images with high energy resolution, even if the signal yield is reduced. Furthermore, with a CCD or CMOS sensor, the arrival position on the imaging plane of electrons emitted from the sample 8 varies depending on the angle. Taking advantage of this, a CCD or CMOS sensor can be used to capture only electrons at a specified angle to generate an image.

[0044] The signal electron optical axis can be selected by changing the deflection direction of the signal electrons by the signal electron separation deflector 5. For example, when a magnetic sector consisting of parallel plates is used, at least two signal electron optical axes can be selected as shown in Fig. 6. Alternatively, when a Wien filter is used, it is also possible to set the signal electron optical axis in any direction.

[0045] In the second embodiment, by using a configuration in which the detector 9 is disposed downstream of the signal electron optical axis 200 and the detector 10 (e.g., a detector with a spectrometer) is disposed downstream of the signal electron optical axis 300, it becomes possible to select the detector to be used simply by changing the voltage or current value applied to the signal electron separation deflector 5. For example, when the signal electron separation deflector 5 is configured with a Wien filter, the signal electron optical axis 200 or 300 can be switched by changing the directions of the generated magnetic and electric fields. Furthermore, when the signal electron separation deflector 5 is configured with a magnetic sector, the signal electron optical axis 200 or 300 can be switched by changing only the direction of the magnetic field.

[0046] Although not shown, by using a configuration including a spectroscope upstream of the detector 9 or 10 (corresponding to a detector with a spectroscope), different energy selection methods can be used depending on the application. The spectroscope, for example, can accurately separate secondary electrons and backscattered electrons. After separation, only either the secondary electrons or the backscattered electrons can be incident on the detector 10 (a desired image can be acquired and observed by switching the separation). That is, in this case, if the signal electron optical axis 200 is selected, the detector 9 can simultaneously detect signal electrons of two energies (e.g., secondary electrons and backscattered electrons). On the other hand, if the signal electron optical axis 300 is selected, the detector 10 can detect the desired electron from the two energy signal electrons.

[0047] As described above, the configuration of the second embodiment makes it possible to select an appropriate detector or spectrometer depending on the observation target and observation technique without requiring any major hardware changes (only the addition of the detector 10 is necessary). Note that the signal electron trajectory control process is the same as in the first embodiment, and therefore a detailed description thereof will be omitted.

[0048] (3) Third Embodiment The third embodiment relates to a charged particle beam system including components that control the positions and angles of signal electrons with significantly different energies that are separated from the primary electron optical axis 100 by a signal electron separation deflector 5.

[0049] In the first embodiment, a configuration has been described in which signal electrons with significantly different energies are simultaneously detected by the detector 9. However, the angles of incidence on the detector 9 are different between the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy. This is because the signal electrons of the second energy are incident on the detector at an angle along the signal electron trajectory 210 of the second energy. Such a difference in the angles of incidence between the signal electrons of the first energy and the signal electrons of the second energy may cause a difference in detection efficiency. Furthermore, when an energy filter using a mesh electrode is used, it may also cause a deterioration in energy resolution.

[0050] 7 is a diagram showing an example of the configuration of a charged particle beam system according to the third embodiment. In addition to the components of the system according to the first embodiment, the charged particle beam system according to the third embodiment includes a chromatic dispersion correction element 11 arranged on the signal electron optical axis 200. A detector 9 (not shown) is provided downstream of the chromatic dispersion correction element 11. The chromatic dispersion correction element 11 may be a rotationally symmetric lens or a multipole lens, or may be a Wien filter.

[0051] As an example, consider a case where a Wien filter is used as the chromatic dispersion compensation element 11. In this case, the Wien filter (chromatic dispersion compensation element 11) is placed at a predetermined position on the signal electron optical axis 200. Then, voltages applied to the signal electron trajectory adjusting electrodes 20 and 21 are controlled so that the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy intersect at the installation position of the Wien filter. Specifically, the computer 28 sets voltage and current values ​​to be applied to the chromatic dispersion compensation element 11 so that the signal electron trajectory 201 of the first energy is substantially not subjected to a deflection effect when passing through the chromatic dispersion compensation element 11. Next, the computer 28 causes the chromatic dispersion compensation element 11 to generate chromatic dispersion in the opposite direction, corresponding to the difference in the incident angles of the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy on the chromatic dispersion compensation element 11. This allows both the position and angle of the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy to be matched downstream of the chromatic dispersion compensation element 11 (as long as the ratio between the magnetic field and the electric field is maintained, the signal electron trajectory 201 of the first energy does not change, and only the signal electric trajectory 210 of the second energy can be deflected). Alternatively, the computer 28 can change the position of the chromatic dispersion compensation element 11 or the position at which the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy intersect, thereby matching only the angles of the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy downstream of the chromatic dispersion compensation element 11 and shifting their positions. In other words, downstream of the chromatic dispersion compensation element 11, the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy can travel in parallel while maintaining a constant distance between them. In this case, the signal electrons of the first energy and the signal electrons of the second energy can be separately detected by two detectors (not shown) installed downstream.

[0052] In the above description, the chromatic dispersion compensation element 11 is installed (fixed) at a predetermined position on the signal electron optical axis 200, and the voltages applied to the signal electron trajectory adjusting electrodes 20 and 21 are controlled so that the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy intersect at that position, but this is not limiting. For example, the chromatic dispersion compensation element 11 may be configured to be mechanically movable on the signal electron optical axis 200. In this case, first, the signal electron trajectory 201 of the first energy and the signal electron trajectory 210 of the second energy may be made to intersect at a desired position on the signal electron optical axis 200 (within the movable range of the chromatic dispersion compensation element 11), and then the chromatic dispersion compensation element 11 may be moved to the intersecting position of the signal electron trajectories.

[0053] As described above, according to the third embodiment, it is possible to easily control the conditions of incidence on a detector and a spectroscope (not shown) that are arranged downstream of the chromatic dispersion compensation element 11 .

[0054] (4) Fourth Embodiment The fourth embodiment relates to a charged particle beam system having a configuration for deflecting the signal electron trajectory 201 of the first energy at an angle other than 90 degrees with respect to the primary electron optical axis 100. Hereinafter, the shape and control of the signal electron trajectory adjusting electrode for deflecting the signal electron trajectory 201 of the first energy at an angle other than 90 degrees with respect to the primary electron optical axis 100 will be described.

[0055] FIG. 8 is a diagram showing an example of the configuration of a charged particle beam system according to the fourth embodiment. FIG. 8 shows an example in which the deflection angle is 45 degrees. In this case, by using truncated cone-shaped signal electron trajectory adjusting electrodes 32 and 33 with surfaces parallel or nearly parallel to the signal electron optical axis 200, control similar to that of the first to third embodiments described for the deflection angle of 90 degrees is possible. The hollow cylindrical (annular) electrode 30 and the annular electrode 31 are provided for ground management between the signal electron separation deflector 5 and the signal electron trajectory adjusting electrodes 32 and 33, but are not necessarily required. However, the provision of the power supplies 30 and 31 is expected to have the effect of reducing the effect of the voltage applied to the truncated cone-shaped signal electron trajectory adjusting electrode 32 on the primary electron optical axis 100.

[0056] The signal electron trajectory adjusting electrodes 32 and 33, each having a truncated cone shape, are arranged symmetrically with respect to the primary electron optical axis 100. The signal electron trajectory adjusting electrodes 32 and 33 may have a shape as shown in FIG. 9A , for example, or may have shapes obtained by cutting out a portion of a truncated cone as shown in FIG. 9B and arranged to face each other. Alternatively, the signal electron trajectory adjusting electrodes 32 and 33 may have a shape obtained by dividing a cone into four (composed of four partial electrodes) as shown in FIG. 9C , or may be divided into even more partial electrodes as long as they are arranged symmetrically with respect to the primary electron optical axis 100. In this specification, the term "frustum cone shape" also refers to a case where a portion of a truncated cone shape is formed by a plurality of partial electrodes (segmented electrodes) as shown in FIGS. 9B and 9C .

[0057] Furthermore, the overall shape of the oscillating electron orbit adjusting electrodes 32 and 33 does not necessarily have to be a truncated cone, but may be a rectangle as shown in FIG. 9D (or may be a shape other than a rectangle, such as a trapezoid or an ellipse, provided that the two rectangular electrodes are disposed in opposing positions spaced 180 degrees apart from each other). Although not shown, the rectangular partial electrodes may be divided into four, eight, or more and disposed symmetrically with respect to the primary electron optical axis 100.

[0058] When the configuration according to the fourth embodiment is used, the signal electron trajectory 201 of the first energy passes through the center between the truncated conical signal electron trajectory-adjusting electrode 30 and the truncated conical signal electron trajectory-adjusting electrode 31, or between the truncated conical signal electron trajectory-adjusting electrode 32 and the truncated conical signal electron trajectory-adjusting electrode 33. However, if voltages of the same polarity and magnitude are applied to the truncated conical signal electron trajectory-adjusting electrode 30 and the truncated conical signal electron trajectory-adjusting electrode 31, or to the truncated conical signal electron trajectory-adjusting electrode 32 and the truncated conical signal electron trajectory-adjusting electrode 33, the signal electron trajectory 201 of the first energy may be deflected. In order to compensate for the trajectory deviation due to such deflection, voltages of opposite polarities are superimposed and applied to the truncated conical signal electron trajectory-adjusting electrode 32 and the truncated conical signal electron trajectory-adjusting electrode 33, as described for the case in which the deflection angle of the signal electrons is 90 degrees in the first embodiment (see FIG. 4 ). As a result, a deflection field is formed between the signal electron trajectory adjusting electrode 32 and the truncated cone-shaped signal electron trajectory adjusting electrode 33, making it possible to control the trajectories of the signal electrons. Alternatively, compensation may be made by adjusting the deflection angle of the signal electrons by the signal electron separating deflector 5.

[0059] According to the fourth embodiment, even when the deflection angle of the signal electrons is other than 90 degrees, it is possible to simultaneously detect two signal electrons with significantly different energies by the detector 9 while suppressing the influence on the primary electron beam.

[0060] (5) Fifth Embodiment The fifth embodiment relates to a charged particle beam system having multiple electron sources or charged particle sources. In an SEM, which is one type of charged particle beam system, a probe electron beam that scans a sample to acquire an image may be used in combination with another electron beam that is irradiated onto the sample for purposes such as controlling sample charging. Another type using multiple charged particle sources is an FIB-SEM, which combines an electron beam for acquiring an SEM image with an ion source for processing. In a charged particle beam system having multiple electron sources, for example, one electron source may be an electron source that does not draw much current but achieves high-resolution observation, and another electron source may be an electron source that draws a large current but does not achieve high resolution. Alternatively, one electron source may be a high-energy electron source that tracks one electron source, and the other may be a low-energy electron source.

[0061] 10 is a diagram showing an example of the configuration of a charged particle beam system according to the fifth embodiment. Hereinafter, trajectory control of a charged particle beam in a charged particle beam system having a plurality of charged particle beams as shown in FIG.

[0062] The trajectory of the primary electrons emitted from the second charged particle source 41 (primary electron trajectory 401) travels along the primary electron optical axis 400 while being subjected to trajectory control by the acceleration electrode 42 or a converging effect by a condenser lens (not shown). On the other hand, the primary electrons emitted from the first charged particle source 1 travel along the primary electron optical axis 100 toward the sample.

[0063] 10 , for example, a deflector for charged particle control 43 is disposed at the intersection of a primary electron optical axis 400 and a primary electron optical axis 100. Unlike the above-mentioned deflector for signal electron separation 5, the deflector for charged particle control 43 is simply a deflector, and is provided to irradiate a desired position on a sample 8 with primary electrons from the charged particle source (electron source) 1 or primary electrons from the charged particle source (electron source) 41. Therefore, the primary electrons traveling along the optical axis 100 do not need to travel straight through the deflector for charged particle control 43.

[0064] In the first to third embodiments, a same-polarity voltage or an opposite-polarity voltage is applied to the signal electron trajectory adjusting electrodes 20 and 21 to form a lens field, but in the fifth embodiment, a lens field is not necessary, and therefore an opposite-polarity voltage that forms only a deflection field is applied to the signal electron trajectory adjusting electrodes 32 and 33 to correct axial deviation of the primary electron trajectory 401 (for example, axial deviation due to variations in hardware (deviation due to machine differences) or axial deviation due to an electron beam being obliquely emitted from the charged particle source 41).

[0065] In the fifth embodiment, the trajectories of a plurality of charged particle beams emitted from a plurality of charged particle sources are controlled to coincide after passing through the charged particle control deflector 43. At this time, for purposes such as downsizing of the device, it may be desirable to correct the angle of incidence of the primary electron trajectory 401 when it is incident on the charged particle control deflector 43 as close as possible to the charged particle control deflector 43. To achieve this, voltages of opposite polarities are applied to the truncated cone-shaped signal electron trajectory adjusting electrode 32 and the truncated cone-shaped signal electron trajectory adjusting electrode 33 to form a deflection field, which is used to control the trajectory of the electron beam. 9 is used, it is only possible to form a deflection field in the direction within the plane of the paper in FIG. 10. However, if it is desired to form a deflection field also in the direction perpendicular to the plane of the paper, as shown in FIG. 11, an electrode pair consisting of signal electron trajectory adjusting electrodes 51 and 52 formed of a rectangular or part of a truncated conical surface can be arranged between the truncated conical signal electron trajectory adjusting electrode 32 and the truncated conical signal electron trajectory adjusting electrode 33 so as to be rotationally symmetrical with respect to the primary electron optical axis 100, and a voltage of opposite polarity can be applied to form a deflection field in the direction perpendicular to the plane of the paper. Note that, as an example of an arrangement rotationally symmetrical with respect to the primary electron optical axis 100, FIG. 11 shows an example in which signal electron trajectory adjusting electrodes 53 and 54, which are an electrode pair having the same shape as the pair of signal electron trajectory adjusting electrodes 51 and 52, are arranged at a position rotated 180 degrees with respect to the primary electron optical axis 100. Alternatively, four pairs of electrodes may be provided at every 90-degree rotation, or even more pairs of electrodes may be arranged at regular rotation angles. Furthermore, in order to form a deflection field in a direction perpendicular to the plane of the drawing, a coil may be disposed in place of the electrode pair, and a deflection field may be formed by a magnetic field.

[0066] As an example of a configuration that does not use the charged particle control deflector 43, the sample 8 may be placed at the intersection of the primary electron optical axis 400 and the primary electron optical axis 100 as shown in Fig. 12. In this case, a deflection field can be formed by applying voltages of opposite polarities to the truncated cone-shaped signal electron trajectory adjusting electrode 32 and the truncated cone-shaped signal electron trajectory adjusting electrode 33, and this can be used to control the trajectory of the charged particle source. Furthermore, if the signal electron trajectory adjusting electrodes 30 to 33 are placed directly above the sample 8 and the objective lens is desired to be as close as possible to the sample 8, the truncated cone-shaped signal electron trajectory adjusting electrode 32 or the truncated cone-shaped signal electron trajectory adjusting electrode 33 may be made of a magnetic material and used to form part of the magnetic circuit of the objective lens (the signal electron trajectory adjusting electrodes 30 to 33 form the objective lens 7).

[0067] (6) Sixth Embodiment The sixth embodiment relates to a charged particle beam system, such as a secondary electron microscope or a mirror microscope, which forms a planar image on a detector 9 using an objective lens 7 and at least one condenser lens, of secondary electrons emitted from a sample 8 or a primary electron beam reflected by a negative voltage applied to the sample.

[0068] FIG. 13 is a diagram showing an example of the configuration of a charged particle beam system according to a sixth embodiment. This charged particle beam system is configured to acquire images by planar imaging. The eddy current beam system includes a detector 9 arranged in a straight line from the sample 8 and a charged particle source (electron source) 41 arranged at an angle from the signal electron optical axis 500. This configuration is adopted to obtain high resolution by planar imaging of secondary electrons emitted from the sample 8 or a reflected primary electron beam with low aberration. In this case, the computer 28 must use the charged particle control deflector 43 to control the voltage applied to the charged particle control deflector 43 so that the primary electron trajectory 401 is aligned with the signal electron optical axis 500 and perpendicularly incident on the sample 8. To achieve this, it is necessary to control the trajectory of the primary electron trajectory 401 when it enters the charged particle control deflector 43. However, for purposes such as miniaturization of the device, it may be desirable to perform the correction as close to the charged particle control deflector 43 as possible. Therefore, the computer 28 applies voltages of opposite polarities to the truncated cone-shaped signal electron trajectory adjusting electrode 32 and the truncated cone-shaped signal electron trajectory adjusting electrode 33 to form a deflection field therebetween, thereby controlling the trajectory of the charged particle source.

[0069] Furthermore, similarly to the fifth embodiment, a deflection field may be formed in the direction perpendicular to the plane of the page in Fig. 13 by using the signal electron trajectory adjusting electrodes 32 and 33 having the configuration shown in Fig. 11. In this way, the truncated cone-shaped signal electron trajectory adjusting electrodes 32 and 33 are rotationally symmetric with respect to the signal electron optical axis 500, and therefore it is possible to control the electron trajectory while preventing degradation of resolution by suppressing the occurrence of unexpected aberrations in the secondary electrons emitted from the sample 8 or the reflected primary electron beam.

[0070] (7) Summary (i) An embodiment of the present disclosure (common to all embodiments) proposes an optical device including: a first electrode (electrode 20 or electrode 32) having a shape axially symmetrical with respect to an optical axis 100 of a charged particle beam (primary electrons) that is irradiated onto a sample to be observed or an optical axis 200 of charged particles (secondary electrons) that are emitted from the sample 8 in response to irradiation with the charged particle beam (primary electrons); a second electrode (electrode 21 or electrode 33) that is arranged closer to the sample 8 than the first electrode and has a shape axially symmetrical with respect to the optical axis 100 of the charged particle beam (primary electrons) or the optical axis 200 of the charged particles (secondary electrons); and a deflector (signal electron separation deflector 5 or charged particle control deflector 43) configured to deflect the charged particles (secondary electrons) or the charged particle beam (primary electrons) in a direction that intersects the optical axis 100 of the charged particle beam or the optical axis 200 of the charged particles as the charged particles (secondary electrons) pass between the first electrode and the second electrode and to deflect the charged particles (secondary electrons) or the charged particle beam (primary electrons). Furthermore, the deflectors (the signal electron separation deflector 5 and the charged particle control deflector 43) are arranged symmetrically with respect to the optical axis 100 of the charged particle beam or the optical axis 200 of the charged particles, and are arranged between the first and second electrodes so as not to interfere with them. By using such an optical device in a charged particle beam instrument (e.g., a SEM), signal electrons with significantly different energies (e.g., secondary electrons and backscattered electrons) can be simultaneously detected according to the observation target while suppressing the influence on primary electrons (deterioration of spatial resolution) (first to fourth embodiments). Furthermore, by irradiating a sample with multiple charged particle beams, it is possible to obtain multiple types of images and perform processing and observation while suppressing the influence on primary electrons (deterioration of spatial resolution) (fifth embodiment). Furthermore, it is possible to suppress the occurrence of aberrations in secondary electrons and reflected primary electrons from the sample 8 (sixth embodiment). In other words, by using this optical device, it is possible to simultaneously optimize the contrast at multiple locations on the sample while maintaining high spatial resolution.

[0071] (ii) In the optical device according to the first embodiment, the electrodes 20 and 21 are each annular. As shown in FIG. 1 , the surfaces of the annular electrodes are arranged parallel to each other. When an appropriate voltage is applied to the signal electron separation deflector 5 under computer control, the signal electron separation deflector 5 deflects the charged particles (secondary electrons) of the first energy so that their trajectories 201 are parallel to the surfaces of the electrodes 20 and 21. The annular electrodes 20 and 21 may be configured with multiple segmented electrodes, as shown in FIGS. 2B to 2D . The multiple segmented electrodes are not connected to each other. However, when a voltage is applied to each segmented electrode, the multiple segmented electrodes as a whole operate in the same manner as an annular electrode. This configuration provides electrodes symmetrical with respect to the optical axis 100 of the primary electrons, thereby eliminating factors that degrade the spatial resolution of the charged particle beam device.

[0072] Furthermore, as shown in FIG. 1 , the optical device may include, in addition to electrodes 20 and 21, annular electrodes 22 and 23 that are axially symmetrical with respect to the optical axis 100 of the primary electrons. In this case, electrode 20 is disposed in the hollow portion of electrode 22. Similarly, electrode 21 is disposed in the hollow portion of electrode 23. Furthermore, the annular electrode surfaces of electrodes 22 and 23 are disposed parallel to each other. In this configuration, the signal electron separation deflector 5 deflects the secondary electrons so that their trajectories are parallel to the electrode surfaces of electrodes 22 and 23 in addition to electrodes 20 and 21. In this configuration example, electrodes 22 and 23 are grounded (GND). This stabilizes the electric field within the charged particle beam device.

[0073] Furthermore, the optical device may include annular electrodes 24 and 25 that are axially symmetrical with respect to the optical axis 100 of the primary electrons. In this case, electrodes 20 and 22 are disposed in the hollow portion of electrode 24. Electrodes 21 and 23 are disposed in the hollow portion of electrode 25. Furthermore, the annular electrode surfaces of electrodes 24 and 25 are disposed parallel to each other. In this configuration, the signal electron separation deflector 5 deflects the secondary electrons so that their trajectories are parallel to the electrode surfaces of electrodes 24 and 25. In this configuration example, the power supply is controlled so that a voltage is applied from electrode 20 to electrode 23, and electrodes 24 and 25 are grounded (GND). This stabilizes the electric field within the charged particle beam device.

[0074] When the optical device described above (configuration shown in FIGS. 1 to 4 ) is applied to a charged particle beam system, the computer 28 determines whether the trajectory 201 of the charged particles (secondary electrons) of the first energy deviates from the desired optical axis 200 of the secondary electrons based on the signal amount of the charged particles (secondary electrons) of the first energy detected by the detector 9 (step S501). If the computer 28 determines that the charged particles (secondary electrons) of the first energy deviate from the optical axis 200, the computer 28 applies a voltage of the same polarity and a voltage of the opposite polarity to the electrodes 20 and 21, respectively, so that the charged particles (secondary electrons) of the first energy are incident on the detector 9 at a position (central region of the detector 9) where the detected signal amount is equal to or greater than a predetermined value (preset threshold) by correcting the deviation from the optical axis 200, and the charged particles (backscattered electrons) of the second energy are deflected by the electrodes 20 and 21 and are incident on the detector 9 at a position (the signal electrons are incident on the central region of the detector 9) where the detected signal amount is equal to or greater than the predetermined value (the threshold).

[0075] (iii) The second embodiment relates to a charged particle beam system that applies the principle of the first embodiment. Charged particles (secondary electrons and backscattered electrons) emitted from a sample 8 are deflected in a plurality of different directions by a signal electron separation deflector 5, and are detected by separate detectors 9 and 10, respectively. More specifically, as shown in FIG. 6 , the charged particle beam system includes a detector 9 (e.g., an ET detector) that detects charged particles (secondary electrons and backscattered electrons) in a first direction, and a detector 10 (e.g., a detector with a spectrometer) that detects charged particles (secondary electrons and backscattered electrons) in a second direction different from the first direction (e.g., a direction 180 degrees different from the first direction). A computer 28 controls the voltage applied to the signal electron separation deflector 5 to change the direction of the electric or magnetic field, thereby switching the detection path between the detector 9 and the detector 10 to detect the charged particles (secondary electrons and backscattered electrons). Next, the computer 28 applies voltages of the same polarity to the electrodes 20 and 21, respectively, for the first energy charged particles (secondary electrons) and the second energy charged particles (backscattered electrons), which have different emission angles from the signal electron separation deflector 5, so that the secondary electrons travel straight between the electrodes 20 and 21 and are incident on the detector 9 or 10 at a position (the central region of each detector) where the detected signal amount is equal to or greater than a predetermined value, and the backscattered electrons are deflected by the electrodes 20 and 21 and are incident on the detector 9 or 10 at a position (the central region of the detector) where the detected signal amount is equal to or greater than a predetermined value. In this way, the detection mode of the charged particles can be switched as appropriate, making it possible to select the charged particles to be observed and the observation method according to the purpose without changing the hardware.

[0076] (iv) The third embodiment relates to a charged particle beam system that enables detection by matching the incident angles of each charged particle (secondary electrons and backscattered electrons) on the detector 9. Specifically, as shown in FIG. 7 , a chromatic dispersion compensation element 11 is positioned on a desired optical axis 200 of a first-energy charged particle (secondary electron). A computer 28 applies current and voltage to the chromatic dispersion compensation element 11 based on set values, thereby matching the angle of the secondary electron trajectory 201 and the angle of the backscattered electron trajectory 210 relative to the optical axis 200. When the incident positions of the two electrons on the chromatic dispersion compensation element 11 are matched, the two electrons after passing through the chromatic dispersion compensation element 11 are detected at the same position on the detector 9. On the other hand, when the incident positions of the two electrons on the chromatic dispersion compensation element 11 are separated by a predetermined distance, the secondary electrons are detected by the first detector and the backscattered electrons are detected by the second detector (they can be detected by separate detectors). This makes it possible to easily control the incident conditions on the detectors and spectrometers.

[0077] (v) As shown in FIG. 8 , the fourth embodiment uses electrodes 32 and 33 each having a truncated cone shape (see FIGS. 9A to 9C ; flat electrodes may also be used as shown in FIG. 9D ) instead of the annular electrodes 20 to 25 of the first embodiment. When electrodes 32 and 33 are arranged symmetrically with respect to optical axis 100, the electrode surfaces are parallel to each other. In this case, the signal electron separation deflector 5 deflects the secondary electrons so that the trajectories 201 of the first-energy charged particles (secondary electrons) are parallel to the electrode surfaces of electrodes 32 and 33. The trajectories 210 of the second-energy charged particles (backscattered electrons) are corrected by the deflection action of electrodes 32 and 33, and the electrons are controlled to enter the detector 9 at the positions at which the secondary electrons are incident. As in the first embodiment, the computer 28 applies a voltage of the same polarity to the electrodes 32 and 33, or, if the secondary electron trajectory 201 deviates from the desired optical axis 200 of the secondary electrons, applies a voltage of the same polarity and a voltage of the opposite polarity, thereby controlling the secondary electron trajectory 201 and the backscattered electron trajectory 210. In this way, even if the deflection angle of the signal electrons by the signal electron separation deflector 5 is other than 90 degrees, it becomes possible to simultaneously detect signal electrons of different energies (for example, secondary electrons and backscattered electrons) while suppressing the effect on the primary electrons (deterioration of spatial resolution).

[0078] (vi) The fifth embodiment relates to a charged particle beam system including two types of charged particle sources 1 and 41. For example, as shown in FIG. 10 , the charged particle source 1 is disposed directly above the sample 8. The other charged particle source 41 is disposed obliquely relative to the sample 8. The charged particle source 1 and the charged particle source 41 can be configured to emit different charged particles. For example, the charged particle source 1 can be an electron source capable of high-resolution observation or a high-energy electron source, while the charged particle source 41 can be an electron source with poor resolution or a low-energy electron source. As in the fourth embodiment, the electrodes 32 and 33 have axially symmetric shapes with respect to the optical axis 100 of the primary electrons and have truncated conical surfaces. The computer 28 applies voltages of opposite polarities to the electrodes 32 and 33 to deflect the charged particle beam from the charged particle source 41, thereby controlling its trajectory 401. Specifically, after the charged particle beam from the charged particle source 41 passes through the deflector 43, the application of voltages of opposite polarities to the electrodes 32 and 33 is controlled so that its trajectory 401 coincides with the primary electron trajectory 100. Note that either the charged particle source 1 or the charged particle source 41 may be used for sample charging, and the other may be used for sample image acquisition. Alternatively, either the charged particle source 1 or the charged particle source 41 may be used for sample processing, and the other may be used for sample image acquisition.

[0079] (vii) The sixth embodiment relates to a charged particle beam system that obliquely irradiates a sample 8 with a charged particle beam and detects signal electrons with a detector 9 disposed directly above the sample 8. As shown in FIG. 13 , a charged particle source 41 is disposed obliquely relative to the sample 8. The detector 9 is also disposed directly above the sample 8. In the sixth embodiment, the truncated cone-shaped electrodes 32 and 33 are also disposed axially symmetrically with respect to the signal electron optical axis 500. In this case, the computer 28 controls the voltages applied to the electrodes 32 and 33, the deflector 43, and the sample 8. When irradiating the sample 8 with a charged particle beam, the computer 28 applies voltages of opposite polarities to the electrodes 32 and 33 to deflect the charged particle beam for irradiating the sample and control its trajectory 401. In this system, the detector 9 is configured to detect secondary electrons emitted from the sample 8 or a primary electron beam reflected by a negative voltage applied to the sample 8. In this way, by using the rotationally symmetric electrodes 32 and 33 (signal electron trajectory adjusting electrodes), it becomes possible to suppress the occurrence of aberrations with respect to secondary electrons and reflected primary electrons.

[0080] (viii) The functions of this embodiment (control of the voltages applied to electrodes 20 and 21, electrodes 32 and 33, etc.) can also be realized by software program code. In this case, a storage medium on which the program code is recorded is provided to a system or device, and the computer (or CPU or MPU) of the system or device reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium on which it is stored constitute the present disclosure. Examples of storage media for providing such program code include flexible disks, CD-ROMs, DVD-ROMs, hard disks, optical disks, magneto-optical disks, CD-Rs, magnetic tape, non-volatile memory cards, and ROMs.

[0081] Furthermore, an operating system (OS) running on a computer may perform some or all of the actual processing based on instructions in the program code, and the functions of the above-described embodiments may be realized by this processing.Furthermore, after the program code is read from a storage medium and written to memory on the computer, a CPU of the computer may perform some or all of the actual processing based on instructions in the program code, and the functions of the above-described embodiments may be realized by this processing.

[0082] Furthermore, the program code of the software that realizes the functions of each embodiment may be distributed via a network and stored in a storage means such as a hard disk or memory of the system or device, or in a storage medium such as a CD-RW or CD-R, so that when used, the computer (or CPU or MPU) of the system or device reads and executes the program code stored in the storage means or storage medium.

[0083] The processes and techniques described herein are not inherently related to any specific device and can be implemented by a combination of components. Various types of general-purpose devices can also be added. A dedicated device may be constructed to perform the functions of the present embodiment. Various functions can also be formed by appropriately combining multiple components disclosed in the present embodiment. For example, some components may be omitted from all the components shown in each embodiment, or components from different embodiments may be appropriately combined.

[0084] Although each embodiment is specifically described in this specification, it is intended in all respects to be illustrative and not restrictive (to understand the technology of the present disclosure). Those skilled in the art will recognize that there are many combinations of hardware, software, and firmware suitable for implementing the technology of the present disclosure. For example, the described software can be implemented in a wide variety of programming or scripting languages, such as assembler, C / C++, Perl, Shell, PHP, Java (registered trademark), etc.

[0085] Furthermore, in the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. All components may be interconnected.

[0086] In addition, other implementations of the present disclosure will become apparent to those skilled in the art from consideration of the embodiments. The specification and examples are exemplary only, with the scope and spirit of the technology of the present disclosure being indicated by the following claims.

[0087] DESCRIPTION OF SYMBOLS 1, 41 Charged particle source (electron source) 2 Acceleration electrode 3 Condenser lens 1 4 Condenser lens 2 5 Signal electron separation deflector 7 Objective lens 8 Sample 9, 10 Detector 11 Chromatic dispersion correction element 20, 21, 22, 23, 24, 25, 51, 52, 53, 54 Signal electron trajectory adjustment electrode 26 First power supply 27 Second power supply 28 Computer 30 Cylindrical (cylindrical with a hollow portion: also called annular) signal electron trajectory adjustment electrode 31 Annular signal electron trajectory adjustment electrode 32, 33 Truncated cone-shaped signal electron trajectory adjustment electrode 42 Acceleration electrode 43 Charged particle control deflector 100, 401 Primary electron trajectory 200, 300, 500 Signal electron optical axis 201, 301 First energy signal electron trajectory 210, 220, 310: Signal electron orbit of second energy 400: Primary electron optical axis

Claims

1. An optical device used in a charged particle beam apparatus, comprising: a first electrode having a shape axially symmetrical with respect to the optical axis of a charged particle beam irradiated onto a sample to be observed or the optical axis of a charged particle emitted from the sample by irradiation with the charged particle beam; a second electrode arranged on the sample side of the first electrode and having a shape axially symmetrical with respect to the optical axis of the charged particle beam or the optical axis of the charged particles; and a deflector configured to deflect the charged particle or the charged particle beam in a direction intersecting the optical axis of the charged particle beam or the optical axis of the charged particles as the charged particle or the charged particle beam passes between the first electrode and the second electrode.

2. An optical device according to claim 1, wherein the deflector is disposed symmetrically with respect to the optical axis of the charged particle beam or the optical axis of the charged particles, and is disposed between the first electrode and the second electrode so as not to interfere with them.

3. An optical device according to claim 1, wherein the charged particles include charged particles of a first energy and charged particles of a second energy higher than the first energy, the first electrode and the second electrode each have a circular ring shape and the respective circular ring-shaped electrode surfaces are arranged parallel to each other, and the deflector deflects the charged particles of the first energy so that the trajectory of the charged particles of the first energy is parallel to the electrode surface of the first electrode and the electrode surface of the second electrode.

4. An optical device according to claim 3, wherein the first electrode and the second electrode are each composed of a plurality of divided electrodes, and the annular shape is formed by the plurality of divided electrodes.

5. An optical device as claimed in claim 3, further comprising third and fourth electrodes having an annular shape, which are axially symmetrical with respect to the optical axis of the charged particle beam and larger than the first and second electrodes, the first electrode being disposed in a hollow portion of the third electrode, the second electrode being disposed in a hollow portion of the fourth electrode, the third and fourth electrodes being disposed such that their respective annular electrode surfaces are parallel to each other, and the deflector further deflects the charged particles of the first energy so that the trajectory of the charged particles of the first energy is parallel to the electrode surface of the third electrode and the electrode surface of the fourth electrode.

6. An optical device according to claim 5, further comprising annular fifth and sixth electrodes which are axially symmetrical with respect to the optical axis of the charged particle beam and larger than the third and fourth electrodes, the first and third electrodes being disposed in a hollow portion of the fifth electrode, the second and fourth electrodes being disposed in a hollow portion of the sixth electrode, the fifth and sixth electrodes being disposed such that their respective annular electrode surfaces are parallel to each other, and the deflector further deflects the charged particles of the first energy such that the trajectory of the charged particles of the first energy is parallel to the electrode surface of the fifth electrode and the electrode surface of the sixth electrode.

7. An optical device according to claim 1, wherein the charged particles include charged particles of a first energy and charged particles of a second energy higher than the first energy, the first electrode and the second electrode each have a truncated cone shape and the electrode surfaces of the respective truncated cone shapes are arranged parallel to each other, and the deflector deflects the charged particles of the first energy so that the trajectory of the charged particles of the first energy is parallel to the electrode surface of the first electrode and the electrode surface of the second electrode.

8. An optical device according to claim 7, wherein the first electrode and the second electrode are each composed of a plurality of divided electrodes, and the plurality of divided electrodes form the truncated cone shape.

9. An optical device according to claim 7, further comprising a third electrode and a fourth electrode arranged axially symmetrically with respect to the optical axis of the charged particle beam or the optical axis of the charged particles of the first energy, the third electrode and the fourth electrode each having a circular ring shape, and the respective circular ring-shaped electrode surfaces being arranged parallel to each other.

10. A charged particle beam system that detects charged particles generated by irradiating a sample with a charged particle beam and acquires an image of the sample, comprising: the optical device of claim 1; a detector that detects the charged particles; and a computer system that controls the applied voltage according to an applied voltage control program for controlling the voltage applied to the first electrode and the second electrode, wherein the computer system executes a process of applying voltages of the same polarity to the first electrode and the second electrode for charged particles of a first energy having different exit angles from the deflector and charged particles of a second energy higher than the first energy, so that the charged particles of the first energy travel in a straight line between the first electrode and the second electrode and are incident on the detector at a position where a detection signal amount is equal to or greater than a predetermined value, and the charged particles of the second energy are deflected by the first electrode and are incident on the detector at a position where the detection signal amount is equal to or greater than a predetermined value.

11. A charged particle beam system according to claim 10, wherein in the optical device, the first electrode and the second electrode are each annular in shape, and the electrode surfaces of the respective annular electrodes are arranged parallel to each other, and the computer system executes a process of determining whether the trajectory of the charged particle of the first energy deviates from the optical axis of a desired charged particle based on the signal amount of the charged particle of the first energy detected by the detector, and a process of applying a voltage of the same polarity and a voltage of the opposite polarity to the first electrode and the second electrode, respectively, when the trajectory of the charged particle of the first energy deviates from the desired optical axis of the charged particle, so as to correct the deviation from the optical axis and cause the charged particle of the first energy to be incident on a position on the detector where the detection signal amount is equal to or greater than a predetermined value, and cause the charged particle of the second energy to be deflected by the first electrode and to be incident on a position on the detector where the detection signal amount is equal to or greater than the predetermined value.

12. A charged particle beam system as claimed in claim 10, further comprising a chromatic dispersion compensation device arranged on the optical axis of the charged particles of the first energy, wherein the computer system applies a current and a voltage to the chromatic dispersion compensation device based on set values, thereby matching the angle of the trajectory of the charged particles of the first energy with the angle of the trajectory of the charged particles of the second energy with respect to the optical axis of the charged particles of the first energy, and wherein the charged particles of the first energy and the charged particles of the second energy reach the detector with their trajectories matching with respect to the optical axis of the charged particles of the first energy.

13. A charged particle beam system for detecting charged particles generated by irradiating a sample with a charged particle beam and acquiring an image of the sample, comprising: an optical device according to claim 1; a first detector for detecting the charged particles in a first direction; a second detector for detecting the charged particles in a second direction different from the first direction; and a computer system for controlling the applied voltage to the first electrode and the second electrode in accordance with an applied voltage control program for controlling the applied voltage, wherein in the optical device, the first electrode and the second electrode are each annular in shape, and the respective annular electrode surfaces are arranged parallel to each other, and the computer system performs a process of switching between detecting the charged particles with the first detector or the second detector by changing the direction of the electric field or magnetic field in the deflector by controlling the voltage applied to the deflector to change the direction of the electric field or magnetic field in the deflector; a charged particle beam system that performs a process of applying voltages of the same polarity to the first electrode and the second electrode, respectively, for a charged particle of a first energy having a different emission angle from the deflector and a charged particle of a second energy higher than the first energy, so that the charged particle of the first energy travels straight between the first electrode and the second electrode and is incident on a position of the first detector or the second detector where a detection signal amount is equal to or greater than a predetermined value, and the charged particle of the second energy is deflected by the first electrode and the second electrode and is incident on a position of the first detector or the second detector where the detection signal amount is equal to or greater than a predetermined value.

14. A charged particle beam system that detects charged particles generated by irradiating a sample with a charged particle beam and acquires an image of the sample, comprising: the optical device described in claim 7; a detector that detects the charged particles; and a computer system that controls the applied voltage in accordance with an applied voltage control program for controlling the voltage applied to the first electrode and the second electrode, wherein the computer system executes a process of applying voltages of the same polarity to the first electrode and the second electrode for charged particles of a first energy having different exit angles from the deflector and charged particles of a second energy higher than the first energy, so that the charged particles of the first energy travel in a straight line between the first electrode and the second electrode and are incident on a position of the detector where a detection signal amount is equal to or greater than a predetermined value, and the charged particles of the second energy are deflected by the first electrode and the second electrode and are incident on a position of the detector where the detection signal amount is equal to or greater than a predetermined value.

15. A charged particle beam system for detecting charged particles generated by irradiating a sample with a charged particle beam and acquiring an image of the sample, comprising: the optical device according to claim 7; a first detector for detecting the charged particles in a first direction; a second detector for detecting the charged particles in a second direction different from the first direction; and a computer system for controlling the applied voltage in accordance with an applied voltage control program for controlling the voltage applied to the first electrode and the second electrode, wherein the computer system controls the voltage applied to the deflector to change the direction of the electric field or magnetic field in the deflector, thereby switching between detecting the charged particles with the first detector and the second detector; a charged particle beam system that performs a process of applying voltages of the same polarity to the first electrode and the second electrode, respectively, for a charged particle of a first energy having a different emission angle from the deflector and a charged particle of a second energy higher than the first energy, so that the charged particle of the first energy travels straight between the first electrode and the second electrode and is incident on a position of the first detector or the second detector where a detection signal amount is equal to or greater than a predetermined value, and the charged particle of the second energy is deflected by the first electrode and the second electrode and is incident on a position of the first detector or the second detector where the detection signal amount is equal to or greater than a predetermined value.

16. A charged particle beam system for detecting charged particles generated by irradiating a sample with a charged particle beam and acquiring an image of the sample, comprising: a first charged particle source arranged directly above the sample and emitting a first charged particle beam to be irradiated onto the sample; a second charged particle source arranged diagonally from the sample and emitting a second charged particle beam different from the first charged particle beam to be irradiated onto the sample; a first electrode having an axially symmetrical shape with respect to an optical axis of the first charged particle beam and having a truncated cone-shaped surface; a second electrode arranged closer to the sample than the first electrode and having an axially symmetrical shape with respect to the optical axis of the first charged particle beam and having a truncated cone-shaped surface; and a computer system for controlling voltages applied to the first electrode and the second electrode, wherein the computer system applies voltages of opposite polarities to the first electrode and the second electrode to deflect the second charged particle beam, thereby controlling the trajectory of the second charged particle beam.

17. A charged particle beam system according to claim 16, further comprising a deflector that deflects the first charged particle beam and the second charged particle beam in response to an applied voltage, and the computer system controls the application of the opposite polarity voltages to the first electrode and the second electrode so that the trajectory of the second charged particle beam coincides with the trajectory of the first charged particle beam after the second charged particle beam passes through the deflector.

18. A charged particle beam system according to claim 16, wherein: (i) one of the first charged particle source or the second charged particle source is used to charge the sample, and the other is used to acquire an image of the sample; or (ii) one of the first charged particle source or the second charged particle source is used to process the sample, and the other is used to acquire an image of the sample.

19. A charged particle beam system for detecting charged particles generated by irradiating a sample with a charged particle beam and acquiring an image of the sample, comprising: a charged particle source arranged in an oblique direction of the sample and emitting a charged particle beam to be irradiated to the sample; a detector arranged directly above the sample and detecting charged particles from the sample; a first electrode having an axisymmetric shape with respect to an optical axis of the charged particles from the sample and having a truncated cone-shaped surface; a second electrode arranged on the sample side of the first electrode and having an axisymmetric shape with respect to the optical axis of the charged particles from the sample and having a truncated cone-shaped surface; a deflector for deflecting the charged particle beam in response to an applied voltage; and a computer system for controlling the applied voltages to the first electrode, the second electrode, the deflector, and the sample, wherein the computer system controls the trajectory of the charged particle beam by applying voltages of opposite polarities to the first electrode and the second electrode to deflect the charged particle beam.

20. A charged particle beam system according to claim 19, wherein the detector detects secondary electrons emitted from the sample or a primary electron beam reflected by a negative voltage applied to the sample.

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