WO2014084172A1

WO2014084172A1 - Charged-particle beam device

Info

Publication number: WO2014084172A1
Application number: PCT/JP2013/081657
Authority: WO
Inventors: 正臣大野; 賢一平根; 幸太郎細谷
Original assignee: 株式会社日立ハイテクノロジーズ
Priority date: 2012-11-27
Filing date: 2013-11-25
Publication date: 2014-06-05
Also published as: JP2016035800A

Abstract

Provided is a charged-particle beam device whereby it is possible to carry out an optical axis adjustment with good precision and without being affected by a degree of proficiency of an operator. A charged-particle beam device comprises: a detector which detects secondary charged particles which are obtained by a projection of a primary charged-particle beam upon a specimen; a display unit which, when an optical axis adjustment of the primary charged-particle beam is to be carried out, displays an image for optical axis adjustment (15a) which is obtained on the basis of the secondary charged particles which are detected with the detector; and a control unit which displays, so as to be adjacent to or overlap with the image for optical axis adjustment, magnification information which represents a magnification when carrying out the image adjustment of adjusting such that at least one parameter relating to image quality of the image for optical axis adjustment reaches a predetermined value. The magnification information represents the magnification by, for example, the relative positions of a reference axis (40) and an indication line (41).

Description

Charged particle beam equipment

The present invention relates to a charged particle beam apparatus that performs image acquisition of a sample by irradiating the sample with a charged particle beam.

The charged particle beam device performs observation and analysis of the target sample by irradiating the target sample with the charged particle beam. For example, in a scanning electron microscope (SEM: Scanning Electron Microscope) or a transmission electron microscope (TEM: Transmission Electron Microscope), the target sample is irradiated with an electron beam as a charged particle beam and the amount of secondary electrons detected by the detector or A microscopic image of the target sample is generated based on the amount of transmitted electrons.

As such a charged particle beam device, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2008-84823) discloses a charged particle source, a converging lens for converging a primary charged particle beam emitted from the charged particle source, An objective lens for focusing the primary charged particle beam on the sample, an objective aperture disposed on the charged particle source side from the objective lens to limit the amount of irradiation of the primary charged particle beam to the sample, and the primary charged particle beam Discloses a technique relating to a charged particle beam apparatus including a detector that detects a secondary signal generated from a sample by irradiation of the above and an aligner for moving the center of the primary charged particle beam to the center of the objective aperture.

JP 2008-84823 A

By the way, in the charged particle beam apparatus, in order to obtain a highly accurate sample image, the alignment of the optical axis of the primary charged particle beam emitted from the charged particle gun and the central axis of a lens, a diaphragm, etc. (optical axis adjustment) ) Is necessary. This is because, for example, the primary charged particle beam is prevented from being blocked more than necessary by a diaphragm for limiting the amount of the primary charged particle beam irradiated to the sample. The optical axis adjustment is performed while the operator looks at the brightness of the optical axis adjustment image obtained by the primary charged particle beam passing through the stop.

However, skill is required to adjust the optical axis accurately depending on the brightness of the image for optical axis adjustment, and the quality of the sample image obtained varies depending on the level of skill of the operator performing the optical axis adjustment. There is also concern that this will occur.

The present invention has been made in view of the above, and it is an object of the present invention to provide a charged particle beam apparatus capable of accurately adjusting the optical axis without being affected by the skill level of an operator.

To achieve the above object, the present invention provides a charged particle gun, a converging lens that converges a primary charged particle beam emitted from the charged particle gun, a deflector that adjusts the optical axis of the primary charged particle beam, and a primary A limiting aperture that limits the amount of irradiation of the sample to be irradiated with the charged particle beam, a detector that detects secondary charged particles obtained by irradiating the sample with the primary charged particle beam, and two detectors detected by the detector Control for displaying magnification information representing magnification when performing image quality adjustment for adjusting at least one parameter relating to the image quality of an image obtained based on the next charged particle to a predetermined value so as to be adjacent to or superimposed on the image Part.

According to the present invention, the optical axis can be adjusted accurately without being affected by the skill level of the operator.

It is a figure which shows the whole structure of the scanning electron microscope which concerns on one embodiment of this invention. It is a figure which shows the mode of position adjustment (mechanical axis adjustment) of a cathode. It is a figure which shows the mode of the optical axis adjustment (electrical axis adjustment) by a deflector. It is a figure which shows an example of the image for optical axis adjustment displayed on a display apparatus when performing an optical axis adjustment, and is a figure which shows the state which optical axis adjustment is incomplete. It is a figure which shows an example of the image for optical axis adjustment displayed on a display apparatus when performing an optical axis adjustment, and is a figure which shows the state in which optical axis adjustment was performed appropriately. It is a flowchart which shows the procedure of an optical axis adjustment. It is a figure which shows one modification of this Embodiment. It is a figure which shows the other modification of this Embodiment. It is a figure which shows the further another modification of this Embodiment.

Hereinafter, a scanning electron microscope will be cited as an example of the charged particle beam apparatus according to the embodiment of the present invention, and a detailed description will be given with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of a scanning electron microscope according to the present embodiment.

1, a scanning electron microscope (SEM: Scanning Electron Microscope) includes an electron gun (charged particle gun) 17 having a cathode 1 as a charged particle source (electron source) and an anode 4 as an extraction electrode, and an electron gun 17. The first and second converging lenses 5 and 7 for converging the primary electron beam (primary charged particle beam) 3 emitted from the beam, the deflector 2 for adjusting the optical axis of the primary electron beam 3, and the irradiation of the primary electron beam 3 An objective lens aperture (limit aperture) 6 that limits the amount of irradiation to the target sample 15, upper and lower deflection coils 8 and 9 for scanning the sample 15 with the primary electron beam 3, and the sample 15 are irradiated. An objective lens 10 for narrowing the primary electron beam 3; a secondary electron detector (detector) 12 for detecting secondary electrons (secondary charged particles) obtained by irradiating the sample 15 with the primary electron beam 3; When the optical axis is adjusted, the secondary electron detector 1 In a display device (display unit) 30 for displaying the optical axis adjustment image obtained based on the detected secondary electrons, it is schematically a control unit 18 for controlling the entire operation of the scanning electron beam apparatus.

In the electron gun 17, the primary electron beam 3 emitted from the cathode 1 by an extraction voltage applied between the cathode 1 and an extraction electrode (not shown) is accelerated by a voltage Vacc applied between the cathode 1 and the anode 4. Then, the process proceeds to the electromagnetic lens system in the subsequent stage. The acceleration voltage Vacc is controlled by a high voltage control circuit 22 provided in the control device 18.

The primary electron beam 3 emitted from the electron gun 17 is adjusted by the deflector 2 and then converged by the first converging lens 5. The deflector 2 is controlled by the aligner control unit 21 of the control device 18. The first convergent lens 5 is controlled by the first convergent lens control unit 22 of the control device 18.

The primary electron beam 3 converged by the first converging lens 5 is limited in the amount of irradiation current to the sample by the objective lens aperture (limit aperture) 6 and then converged by the second convergence lens 7. The second convergent lens 7 is controlled by the second convergent lens control unit 23 of the control device 18.

The primary electron beam 3 converged by the second converging lens 7 is incident on the objective lens 10 through the upper and lower deflection coils 8 and 9 and is narrowed down and irradiated onto the sample 15. At this time, the primary electron beam 3 is scanned two-dimensionally on the sample 15 by the action of the upper and lower changing coils 8 and 9. The upper and lower deflection coils 8 and 9 are controlled by the deflection controller 24 of the control device 18. The objective lens 10 is controlled by the objective lens control unit 26 of the control device 18.

When the optical axis adjustment image is obtained, the relay switch 11 is turned on (closed) by the control unit 29, and the scanning signals of the upper and lower deflection coils 8 and 9 by the deflection control unit 24 are transmitted via the relay switch 11. Thus, the signal is synchronized with the signal of the deflector 2 that adjusts the optical axis.

The sample 15 is disposed on the sample fine movement device 14, and the position of the sample 15 is adjusted by horizontal movement so that the sample 15 becomes a desired position in the irradiation range (scanning range) of the primary electron beam 3. The sample fine movement device 14 is controlled by the sample fine movement control unit 27 of the control device 18.

Among the secondary electrons generated from the sample 15 by irradiation of the primary electron beam 3, those having low energy are wound up by the magnetic field of the objective lens 10 and detected by the detector 12. The detection signal from the detector 12 is amplified by the amplifier 16 and sent to the control unit 29 via the signal control unit 25 of the control device 18. Note that an orthogonal electromagnetic field (EXB) device 13 is disposed above the objective lens 10, and thereby the axial displacement of the primary electrons 3 due to the secondary electrons is suppressed.

The control units 20,..., 27 of the control device 18 are controlled by a higher-level control unit 29. In the control unit 29, an image of the sample is generated based on the secondary electrons detected by the detector 12 and the scanning information of the upper and lower stage changing coils 8 and 9 by the deflection control unit 24 and connected to the control device 18. It is displayed on the display device 30.

Further, the control unit 29 of the control device 18 performs various image processing on the observation image and an image acquisition device 31 for acquiring the observation image of the sample 15 displayed on the display device 30 as image information. An image processing device 32, a calculation device 33 for performing various calculations based on the results of image processing, a storage device 34 for storing observation images and calculation results, and an input device for inputting various set values and the like 35 is connected.

In such a charged particle beam apparatus (scanning electron microscope), when the cathode 1 consumed with use is replaced, other parts are replaced, or the conditions of the electron optical system are changed, the axis alignment of each member is performed. (Optical axis adjustment) needs to be performed.

FIG. 2 is a diagram showing a state of cathode position adjustment (mechanical axis adjustment), and FIG. 3 is a diagram showing a state of optical axis adjustment (electrical axis adjustment) by a deflector.

As shown in FIG. 2, in the electron gun 17, when the displacement between the replaced cathode 1 (position 1 a) and the central axis 4 a of the anode 4 is relatively large, the anode of the primary electron beam 3 emitted from the cathode 1. The amount (current amount) obstructed by 4 increases, and therefore the number of primary electron beams 3 that reach the sample 15 through the deflector 2 and the like decreases. Therefore, the primary electron beam 3 emitted from the cathode 1 and passing through the anode 4 is maximized by horizontally moving the cathode 1 and adjusting the position on the central axis 4a of the anode 4 (mechanical axis adjustment). The primary electron beam 3 irradiated to 15 is increased.

In addition, as shown in FIG. 2, when the deviation between the optical axis 3a of the primary electron beam 3 emitted from the cathode 1 and the central axis 6a of the cathode 4, the deflector 2, the objective lens aperture 6, etc. is relatively large. The amount (current amount) of the primary electron beam 3 emitted from the cathode 1 is blocked by the objective lens aperture 6 is increased, and therefore the primary electron beam 3 reaching the sample 15 is decreased. Therefore, the primary electron beam 3 is deflected by the deflector 2 and the optical axis is adjusted (electrical axis adjustment) along the central axis 6a, whereby the primary electron beam which is emitted from the cathode 1 and passes through the objective lens aperture 6. 3 is maximized, and the number of primary electron beams 3 irradiated on the sample 15 is increased.

4 and 5 are diagrams illustrating an example of an optical axis adjustment image displayed on the display device 30 when performing optical axis adjustment. FIG. 4 illustrates a state where the optical axis adjustment is incomplete, and FIG. Each of the figures shows a state in which the optical axis is properly adjusted.

4 and 5, an image 15a of the sample 15 obtained based on the secondary electrons detected by the detector 12 is displayed as the optical axis adjustment image. In addition, the display device 30 has an image quality adjustment (adjustment for adjusting at least one parameter (for example, contrast, brightness, or both) relating to the image quality of the optical axis adjustment image (image 15a) to a predetermined value. Magnification information indicating the magnification when performing auto contrast, auto brightness, or auto contrast / brightness) is displayed so as to be superimposed on the optical axis adjustment image 15a. The magnification information displayed on the display device 30 by the control of the control unit 29 includes a numerical value axis (axis line) 40 that serves as a reference for the size of the parameter, and an instruction line 41 that indicates a position on the numerical value axis 40. The magnification information is indicated by the relative position between the numerical value axis 40 and the instruction line 41. Note that the magnification and magnification information when performing image quality adjustment are, in other words, amplification factor and signal amplification factor information, respectively.

The magnification information represents the magnification at the time of performing image quality adjustment for adjusting the parameter relating to the image quality of the optical axis adjustment image (image 15a) to a predetermined value. That is, in the image quality adjustment, for example, the relationship among the numerical values when the contrast C of the obtained optical axis adjustment image, the predetermined contrast value C1 of the predetermined contrast, and the magnification B in the image quality adjustment is (contrast C) × The magnification B is determined so that (magnification B) = (prescribed value C1).

In the state where the optical axis adjustment is incomplete, as shown in FIG. 4, the parameters relating to the image quality of the optical axis adjustment image 15a, that is, the values of contrast and brightness are reduced, and as a result, the magnification B is increased. In other words, in the state where the optical axis adjustment is appropriately performed, the value of the parameter increases, and as a result, the magnification B decreases as shown in FIG. That is, by adjusting the optical axis so that the magnification B becomes smaller, the optical axis can be adjusted appropriately.

In the present embodiment, in the state of automatic image quality adjustment in which image quality adjustment is always performed, the deflector 2 is set using the input device 35 or the like while confirming the optical axis adjustment image 15a and magnification information of the display device 30. Adjust and adjust the optical axis. In accordance with the state of the optical axis adjustment by the deflector 2, the instruction line 41 moves in the magnification direction (vertical direction in FIGS. 4 and 5). In the magnification information, a marker 42 that follows the instruction line 41 and moves only downward (that is, in a direction in which the magnification is low) is provided. Therefore, the marker 42 is pushed down in accordance with the movement of the indication line 41, and as a result, the indication line 41 indicates a position where the minimum value is shown. Then, by adjusting the setting of the deflector 2 so that the indication line 41 matches the minimum value indicated by the marker 42, the magnification can be set smaller, and the optical axis can be adjusted easily and appropriately. Can do.

The procedure for adjusting the optical axis of the scanning electron microscope of the present embodiment configured as described above will be described with reference to FIG.

FIG. 6 is a flowchart showing the procedure of optical axis adjustment in the present embodiment.

In FIG. 6, first, image quality adjustment is started while acquiring the optical axis adjustment image 15a (step S10). Next, while performing mechanical axis adjustment for adjusting the horizontal position of the cathode 1 using a screw mechanism (not shown) or the like (step S20), the optical axis adjustment image 15a and magnification information are referred to (step S30). Then, it is determined whether or not the magnification information has become a minimum value (step S40). If the determination result is NO, steps S20 and S30 are repeated until the determination result is YES.

If the determination result in step S40 is YES, the optical axis adjustment image 15a and the magnification information are obtained while performing electrical axis adjustment for adjusting the setting of the deflector 2 using the input device 35 or the like (step S50). Reference is made (step S60). Then, it is determined whether or not the magnification information has become a minimum value (step S70). If the determination result is NO, steps S50 and S60 are repeated until the determination result is YES, and the determination result in step S70 is YES. In such a case, the optical axis adjustment is terminated.

The effect of the present embodiment configured as described above will be described.

In charged particle beam devices such as scanning electron microscopes and transmission electron microscopes, light from a primary electron beam (primary charged particle beam) emitted from an electron gun (charged particle gun) is used to obtain a highly accurate sample image. It is necessary to perform alignment (optical axis adjustment) between the axis and the central axis of the lens or the diaphragm. This is because, for example, the primary electron beam is prevented from being blocked more than necessary by a diaphragm for limiting the amount of the primary electron beam irradiated on the sample.

In the prior art, the optical axis adjustment is performed while the operator looks at the brightness of the optical axis adjustment image obtained by the primary charged particle beam passing through the stop. However, skill is required to adjust the optical axis accurately depending on the brightness of the image for optical axis adjustment, and the quality of the sample image obtained varies depending on the level of skill of the operator performing the optical axis adjustment. There is also concern that this will occur.

In contrast, in the present embodiment, the first and second converging lenses 5 and 7 (converging lenses) that converge the primary electron beam 3 (primary charged particle beam) emitted from the electron gun 1 (charged particle gun). A deflector 2 that adjusts the optical axis of the primary electron beam 3, an objective lens aperture 6 (limit aperture) that limits the amount of irradiation of the sample 15 to be irradiated with the primary electron beam 3, In a scanning electron microscope (charged particle beam apparatus) equipped with a detector 12 that detects secondary electrons (secondary charged particles) obtained by irradiating the sample, the detector 12 detects the optical axis when adjusting the optical axis. The optical axis adjustment image 15a obtained based on the secondary electrons is displayed on the display device 30 (display unit), and at least one parameter (such as contrast C) relating to the image quality of the optical axis adjustment image 15a is determined in advance. Value (specified value C1 ) Magnification information representing a magnification when performing image quality adjustment for adjusting (such as magnification B) so as to have configured to display to overlap the optical axis adjustment image 15a. As a result, the operator can easily grasp the adjustment state in the optical axis adjustment, so that the optical axis adjustment can be performed accurately without being affected by the skill level of the operator.

In addition, as in the prior art, when determining the optical axis adjustment state based only on the brightness of the optical axis adjustment image, it is not possible to grasp the occurrence of misalignment or other defects between other components. Although it is difficult and there is a concern that the irradiation angle of the primary electron beam to the sample becomes shallow and the contrast of the acquired sample image decreases, in this embodiment, the light is obtained while grasping the state of the sample image. Since the axis adjustment can be performed at the same time, it is possible to suppress adjustment in an unsuitable range in view of the purpose of acquiring a clear image of the sample, and the optical axis adjustment can be performed with high accuracy.

It should be noted that various changes can be made in the charged particle beam apparatus according to the present embodiment.

For example, as shown in FIG. 7, the numerical value axis 40 of the magnification information may not be displayed, and only the instruction line 41 may be used so as to be superimposed on the optical axis adjustment image 15a. Also in this case, since the magnification can be grasped intuitively as the instruction line 41 goes downward, the operator can easily grasp the adjustment state in the optical axis adjustment, and is affected by the skill level of the operator. Therefore, the optical axis can be adjusted accurately.

Further, as shown in FIG. 8, it may be configured to display the magnification information by the color tone of the image. For example, when the magnification is large, the color tone of the optical axis adjustment image 15a is set to be more red, and is configured to be blue as the magnification is reduced. Even in this case, the operator can easily grasp the adjustment state in the optical axis adjustment.

Furthermore, as shown in FIG. 9, the magnification information may be expressed by a numerical value 43 and displayed so as to be superimposed on a part of the optical axis adjustment image 15a. Even in this case, the operator can easily grasp the adjustment state in the optical axis adjustment.

The instruction line 41 and the numerical value 43 need only be within a range where the operator can simultaneously recognize the optical axis adjustment image 15a and the magnification information, and may be arranged adjacent to the optical axis adjustment image 15a.

In this embodiment, a scanning electron microscope (SEM) is shown and described as an example of a charged particle beam apparatus. However, a focused ion beam (TEM) apparatus, a focused ion beam scanning electron microscope (FIB-SEM), The present invention can also be applied to a scanning transmission electron microscope (STEM).

1 cathode 2 deflector 3 electron beam (charged particle beam)
4 Anode 5 First focusing lens 6 Objective lens aperture (limited aperture)
7 Second focusing lens 8 Upper deflection coil 9 Lower deflection coil 10 Objective lens 11 Relay switch 12 Secondary electron detector 13 Orthogonal electromagnetic field (EXB) device 14 Sample fine movement device 15 Sample 16 Amplifier 17 Charged particle gun 18 Control device 20 High Voltage control unit 21 Aligner control unit 22 First converging lens control unit 23 Second converging lens control unit 24 Deflection control unit 25 Signal control unit 26 Objective lens control unit 27 Sample fine movement device control unit 30 Display device 31 Image acquisition device 32 Image processing Device 33 Calculation device 34 Storage device 35 Input device 40 Numerical axis 41 Indicator line 42 Marker

Claims

With charged particle guns,
A converging lens that converges a primary charged particle beam emitted from the charged particle gun;
A deflector for adjusting the optical axis of the primary charged particle beam;
A limiting aperture that limits the amount of irradiation of the sample that is the target of irradiation with the primary charged particle beam;
A detector for detecting secondary charged particles obtained by irradiating the sample with the primary charged particle beam;
When performing the optical axis adjustment, a display unit for displaying an optical axis adjustment image obtained based on secondary charged particles detected by the detector;
Magnification information indicating the magnification when performing image quality adjustment for adjusting at least one parameter relating to the image quality of the optical axis adjustment image to a predetermined value is displayed so as to be adjacent to or superimposed on the optical axis adjustment image. A charged particle beam apparatus comprising:
With charged particle guns,
A converging lens that converges a primary charged particle beam emitted from the charged particle gun;
A deflector for adjusting the optical axis of the primary charged particle beam;
A limiting aperture that limits the amount of irradiation of the sample that is the target of irradiation with the primary charged particle beam;
A detector for detecting secondary charged particles obtained by irradiating the sample with the primary charged particle beam;
When an optical axis adjustment image obtained based on the secondary charged particles detected by the detector is displayed on the display unit, at least one parameter relating to the image quality of the optical axis adjustment image is a predetermined value. A charged particle beam apparatus comprising: a control unit that displays magnification information indicating magnification of image quality adjustment to be adjusted so as to be adjacent to or superimposed on the optical axis adjustment image.
An electron gun,
A converging lens that converges the primary electron beam emitted from the electron gun;
A deflector for adjusting the optical axis of the primary electron beam;
A limiting aperture that limits the amount of irradiation of the sample that is the target of irradiation with the primary electron beam;
A detector for detecting secondary electrons obtained by irradiating the sample with the primary electron beam;
When performing the optical axis adjustment, a display unit that displays a scanning electron microscope image obtained based on secondary electrons detected by the detector;
Control for displaying magnification information indicating magnification when performing image quality adjustment for adjusting at least one parameter relating to image quality of the scanning electron microscope image to a predetermined value so as to be adjacent to or superimposed on the scanning electron microscope image A charged particle beam device comprising a unit.
The charged particle beam apparatus according to any one of claims 1 to 3,
The charged particle beam apparatus characterized in that the parameter adjusted by the image quality adjustment is at least one of contrast and brightness.
The charged particle beam device according to claim 4,
The charged particle beam apparatus according to claim 1, wherein the magnification information represents the magnification by a relative position between a reference axis and an instruction line.
The charged particle beam device according to claim 4,
The charged particle beam device, wherein the magnification information represents the magnification by a numerical value.
The charged particle beam device according to claim 4,
The charged particle beam apparatus according to claim 1, wherein the magnification information represents the magnification by a color tone of an image to be subjected to the image quality adjustment.