JP2004095193A - Observation method of fib-processed sample by electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an observation method of an FIB-processed sample by an electron microscope, which enables the identification of a processed part of the sample that is processed into a thin film for a short time by FIB (focused ion beam) and enables the reduction of the time duration from setting of the processed sample to observation of the processed position. <P>SOLUTION: When a sample 5 processed by an FIB apparatus is inserted into a body tube of the electron microscope, the microscope is automatically set into a scanning secondary electron image acquisition mode. Under this condition, two-dimensional scanning is performed on a designated area of the sample 5 with electron beam. Through this two-dimensional scanning, secondary electrons (se) generated from the surface of the sample 5 are detected by a detector 18. A detection signal is sent to a monitor 23, and subsequently a scanning electron microscope image is displayed on an image display area. According to the image displayed on the display area of the monitor, an area having a contrast as an evidence indicating the area is processed by FIB is identified. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for observing a processed sample by FIB by FIB, in which an observation region of a semiconductor device sample is processed into a thin film by a focused ion beam apparatus, and a transmission electron microscope image of the thinned sample is observed. .
[0002]
[Prior art]
In a scanning transmission electron microscope, an electron beam generated and accelerated from an electron gun is narrowly focused on a sample by a condenser lens and an objective lens, and a predetermined range on the sample is scanned by the electron beam. By irradiating the sample with an electron beam, electrons transmitted through the sample are detected, and this detection signal is supplied to a display in accordance with the scanning of the primary electron beam to display a scanning transmission electron microscope image of the sample. .
[0003]
In such a scanning transmission electron microscope, electrons transmitted through a sample are imaged, and a TV camera such as a CCD camera is arranged at an image forming position in place of a detector for a scanning transmission electron microscope image. The transmission electron microscope image can be obtained by displaying an image on a display based on the above.
[0004]
In such a scanning transmission electron microscope, a site to be observed is searched at a low magnification while moving a sample set in a column, and when a site to be observed is found, the site is compared at a relatively high magnification. Observe. In this case, the observation magnification is determined according to the selected observation visual field.
[0005]
[Problems to be solved by the invention]
By the way, with the increase in the number of layers and the increase in the density of semiconductor device elements, there is an increasing demand for observing an atomic-level image using an electron microscope (STEM) that can also observe a transmission electron microscope and a scanning transmission electron microscope image. On the other hand, a focused ion beam device (FIB) has been increasingly used as a sample preparation device for semiconductor device elements.
[0006]
In the scanning transmission electron microscope as described above, when searching for a target field of view of a sample, a low-magnification image is used while moving the sample. When a target visual field is found, the magnification is changed according to the visual field, and detailed observation and analysis are performed. In this case, what is required of the scanning transmission electron microscope to be used is that preparation of a sample, observation of a target image, and confirmation of the presence or absence of a defect can be performed in a short time. The magnification of the image for performing detailed observation is configured so that the magnification can be freely changed in fine steps so as to correspond to various kinds of observation.
[0007]
Generally, the range of a sample processed by the FIB is as narrow as 10 μm to 20 μm in a rectangular shape, and the range must be processed into a thin film having a thickness of about 3 μm. In such a partially thin film sample, electrons irradiated to the sample pass through only a narrow area processed into a thin film, and electrons do not pass through the sample area other than the processed area. An electron microscope image or a scanning transmission electron microscope image cannot be obtained, and no image appears on the observation screen of a cathode ray tube for transmission image observation or a liquid crystal display.
[0008]
For this reason, when searching for an observation position processed into a thin film in the sample using a transmission electron microscope image, the sample moving mechanism is driven to search for electrons transmitted from the processing range, but since the processing range is narrow, As long as a transmission image having a relatively high magnification, such as a transmission electron microscope image or a transmission scanning electron microscope image, is used, it often occurs that the processed position of the sample is lost. Therefore, it takes a considerable time to observe the target image.
[0009]
The present invention has been made in view of such a point, and an object of the present invention is to find a processed portion of a sample processed into a thin film by FIB in a short time, and to set a processing position from a set of processed samples to an electron microscope. An object of the present invention is to realize a method of observing a processed sample by FIB, which can reduce the time until observation of the sample by FIB.
[0010]
[Means for Solving the Problems]
The method of observing a processed sample by an electron microscope using the FIB according to the present invention is to irradiate a sample with an electron beam having a relatively large diameter by an irradiation lens system, and to transmit electrons transmitted through the sample to a screen of a TV camera by an imaging lens system. A transmission electron microscope image observation mode in which an image is formed and a video signal obtained from a TV camera is supplied to a display to display a transmission electron microscope image. The diameter of the electron beam probe to be irradiated is made relatively small, and the electron beam irradiating the sample is scanned two-dimensionally. Electrons generated upward by the electron beam irradiation are detected by the detector. The video signal detected and detected by the detector is supplied to a display in accordance with the scanning of the electron beam to display a scanned electronic image. An electron microscope capable of selectively switching between a scanning electron microscope image observation mode and a scanning electron microscope image observation when a sample processed by the FIB is set at a sample position of the electron microscope. The mode is switched to a mode, and a low magnification scanning electronic image is displayed on a display device.
[0011]
According to the present invention, when the sample processed by the FIB is set at the sample position of the electron microscope, the electron microscope is automatically switched to a scanning electron microscope image observation mode, and a low magnification scanning electron image is displayed on the display device. Will be displayed. The operator observes the scanned image, searches for a target visual field, moves the visual field to the center of the display, and then observes the image at a relatively high magnification using a transmission electron image.
[0012]
In the present invention, a transmission electron image or a scanning transmission electron image is used as the transmission electron image, and a secondary electron image or a reflection electron image is used as the scanning electron image. In addition, the method for observing a sample processed by FIB using an electron microscope according to the present invention finds the processing position of the sample processed by FIB using a scanning electron microscope image, and observes the sample at a high magnification at the processing position. This is performed by a transmission electron image obtained based on the transmitted electrons, the sample is moved, the coordinates of a desired observation position in the transmission electron image are detected and stored, and the processed portion of the sample is further processed by the FIB again. When making a thinner thin film sample and observing the transmission electron image again, move the sample based on the stored sample position, and observe the thin film sample at the desired observation position using the transmission electron image. It is characterized by doing.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a scanning transmission electron microscope used in the present invention. In this microscope, an electron beam is scanned on a sample, and a scanning electron microscope image based on secondary electrons from the sample surface is shown. Scans an electron beam on a sample and allows observation of multiple images: a scanning transmission electron microscope image based on the electrons transmitted through the sample and a transmission electron microscope image based on the electrons transmitted through the sample without scanning the electron beam. Is configured.
[0014]
In the figure, an electron beam EB generated from an electron gun 1 arranged above an electron microscope column is accelerated by an acceleration tube (not shown). The electron beam accelerated to, for example, 50 kV by the accelerator tube is focused by the condenser lens 2 and the condenser mini lens 3.
[0015]
The central portion of the electron beam focused by the condenser lenses 2 and 3 passes through the aperture of the condenser lens aperture (not shown), and the outside of the electron beam where the aberration is large is shielded by the aperture. The condenser lens aperture is provided with a plurality of apertures having different diameters, and is configured such that an aperture having any appropriate diameter is arranged on the optical axis according to various modes of the microscope. .
[0016]
The electron beam EB is applied to the sample 5 placed in the magnetic field of the objective lens 4 after the focus of the electron beam is finely adjusted by the condenser mini lens 3. Between the condenser lens 2 and the sample 5, a scanning coil 6 for scanning a predetermined two-dimensional range on the sample with an electron beam is arranged.
[0017]
Two intermediate lenses 7, 8 are arranged below the objective lens 4, and a projection lens 9 is arranged below the intermediate lens. An excitation current is supplied from the lens control unit 10 to the condenser lens 2, the condenser lens 3, the objective lens 4, the intermediate lenses 7, 8, and the projection lens 9. The forward magnetic field of the sample 5 by the objective lens 4 contributes to focusing of the electron beam, and the rear magnetic field of the sample 5 forms an imaging lens system by the intermediate lenses 7 and 8 and the projection lens 9 at the subsequent stage.
[0018]
A fluorescent plate 11 for displaying a transmission electron microscope image is provided below the projection lens 9. The fluorescent plate 11 is openable and closable from the optical axis position of the electron beam. And the fluorescent plate 11 are arranged on the optical axis.
[0019]
Below the fluorescent plate 11, a transmission electron detector 12 that can be inserted and removed on the optical axis (for observing a dark field image) and a transmission electron detector 13 that can be inserted and removed on the optical axis (for observing a bright field image) Are disposed. Further, a first TV camera 14 such as a CCD camera that can be inserted into and removed from the optical axis is disposed downstream of the bright-field image observation detector 13, and is disposed on an optical axis subsequent to the first TV camera 14. Is provided with a second TV camera 15 such as a CCD camera. Output signals (video signals) of the detectors 12, 13, 14, and 15 are supplied to a computer 17 via an amplifier 16.
[0020]
A secondary electron detector 18 is provided above the sample 5 at a position away from the optical axis. The secondary electron detector 18 is operated in the scanning electron microscope image observation mode. For example, a detector composed of a scintillator and a photomultiplier is used to accelerate secondary electrons from the sample. And lead it to the scintillator. Further, a backscattered electron detector 19 is provided above the sample 5. Output signals (video signals) of the secondary electron detector 18 and the backscattered electron detector 19 are supplied to the computer 17 via the amplifier 20.
[0021]
The computer 17 controls a scanning system control unit 21 that supplies a scanning signal to the scanning coil 6, a sample movement control unit 22 that controls a sample position, and a lens control unit 10 that controls an excitation current of each lens. Although not shown, a drive mechanism for the dark-field image observation detector 12, a drive mechanism for the bright-field image observation detector 13, and a drive mechanism for the first TV camera 14 are provided. The mechanism is controlled by a computer 17 and a specific detector or camera is located on the optical axis. The computer 17 controls the detection signal of either the secondary electron detector 18 or the backscattered electron detector 19 to be amplified by the amplifier 20 and supplied to the computer 17. Further, the computer 17 displays an image on the monitor 23 based on one of the output signals of the detection signals.
[0022]
A memory is connected to the computer 17, and the memory stores the lens strength, the selection of the detector, the selection of the aperture of the aperture (not shown), the observation mode of the electron microscope, the acceleration voltage of the electron gun, and the like. And stored in the form of a table according to the magnification.
[0023]
For example, when the acceleration voltage of the electron gun is changed, the electron beam is optimally focused on the sample 5 at the selected acceleration voltage, and the electron beam transmitted through the sample has, for example, a specified magnification. The lens intensities that are optimally projected on the screen of one TV camera 14 are stored in advance.
[0024]
Although not shown, a keyboard, a mouse, and a control panel are connected to the computer 17 so that commands and various condition settings to the computer 17 can be performed by the keyboard and the mouse. On the screen of the monitor 23, an image display area, a GUI (graphic user interface) for controlling the apparatus, and a pointer that moves on the screen with a mouse or a keyboard are displayed. Naturally, the computer 17 includes software for controlling various components of the electron microscope in accordance with designated modes and conditions. The operation of such a configuration will now be described.
[0025]
The scanning transmission electron microscope shown in FIG. 1 can observe a transmission electron microscope image, observe a scanning electron microscope image, and observe a transmission scanning electron microscope image. When observing the transmission electron microscope image, using a keyboard or a mouse, for example, a pointer is positioned in an area where a TEM is displayed in the GUI displayed on the monitor 23, and a mouse is clicked. Select TEM mode.
[0026]
When the TEM mode is selected, the computer 17 retreats the dark-field image detector 12 and the bright-field image detector 13 from the optical axis. Then, either one of the first TV camera 14 and the second TV camera 15 is arranged on the optical axis, and when the second TV camera 15 is used, the first TV camera 14 is retracted from the optical axis. Let it.
[0027]
The first TV camera 14 is mainly used when observing an image with a relatively low magnification for wide-field observation, and is arranged at a position close to the projection lens 9. The second TV camera 15 is a high-resolution TV camera, and is used when observing an image at a relatively high magnification. Which of the two types of TV cameras is used is determined by the magnification, and the magnification can be selected by the GUI of the monitor 23 of the computer 17.
[0028]
For example, when observing a transmission electron microscope image with a wide field of view and a low magnification, the first TV camera 14 is arranged on the optical axis. In this state, the computer 17 controls the excitation currents of the condenser lenses 2 and 3 and the objective lens 4 so that the probe having a relatively large diameter (1 nm) is irradiated on the sample 5. Further, the excitation current of the intermediate lenses 7 and 8 and the projection lens 9 is controlled so that an image formed by the electrons transmitted through the sample 5 is formed on the screen of the first TV camera 14.
[0029]
When the sample 5 is irradiated with the electron beam EB from the electron gun 1 by controlling each lens in this manner, a transmission electron microscope image of a specific wide field of view of the sample is projected on the screen of the first TV camera 14. . The image projected on the screen of the TV camera 14 is read out as a video signal and sent to the computer 17 via the amplifier 16. The video signal supplied to the computer 17 is supplied to the monitor 23, and a transmission electron microscope image of a wide area with a relatively low magnification is displayed on the image display area of the screen of the monitor 23.
[0030]
When observing a high-resolution transmission electron microscope image with a relatively high magnification, the first TV camera 14 is retracted from the optical axis. At that time, the lens intensities of the intermediate lenses 7, 8 and the projection lens 9 are adjusted, and control is performed so that an electronic image is formed on the screen of the second TV camera 15 arranged below the column. .
[0031]
The image projected on the screen of the TV camera 15 is read as a video signal and sent to the computer 17 via the amplifier 16. The video signal supplied to the computer 17 is supplied to the monitor 23, and a high-resolution high-resolution transmission electron microscope image is displayed on the image display area of the screen of the monitor 23. The image obtained by using the first TV camera 28 is used for searching for the visual field of the sample, and the image obtained by using the second TV camera 31 is used for searching the sample obtained by the visual field search. A high-resolution observation image of the region is obtained.
[0032]
Next, an operation for observing a scanning electron microscope image and a transmission scanning electron microscope image will be described. When observing the scanning electron microscope image or the scanning transmission electron microscope image, using a keyboard or a mouse, for example, in the GUI displayed on the monitor 23, position the pointer on an area where SEM or STEM is displayed, Click the mouse to select SEM or STEM mode.
[0033]
The operation when the mode for acquiring the secondary electron image is selected from the SEM mode will be described with reference to FIG. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. When the scan secondary electron image acquisition mode is selected by the GUI on the monitor, the computer 17 controls the excitation current of the condenser lens 2, the condenser mini lens 3, and the objective lens 4, that is, the excitation intensity (lens intensity) of the lens. Control is performed so that the sample 5 is irradiated with a probe having a relatively small diameter (about 0.2 nm).
[0034]
In FIG. 2, reference numerals 30 and 31 denote magnetic pole pieces of the objective lens 4, and a lens 33 indicated by a dotted line is a lens by a magnetic field in front of the objective lens. By controlling each lens in this way to irradiate the sample 5 with the electron beam EB from the electron gun 1 and supplying a two-dimensional scanning signal of the electron beam from the scanning system control unit 21 to the scanning coil 6, An electron beam is two-dimensionally scanned in a predetermined area.
[0035]
Secondary electrons se generated from the surface of the sample 5 based on the two-dimensional scanning of the electron beam on the sample are constrained in the vicinity of the optical axis by the forward magnetic field 33 of the objective lens 4 and extracted upward along the optical axis. . The secondary electrons se extracted upward are attracted toward the detector 18 by a high voltage of, for example, about 10 kV applied to the front surface of the secondary electron detector 18 and collide with the scintillator of the detector 18. The scintillator emits light by collision of secondary electrons, and the light is converted into photoelectrons by the photoelectric conversion surface. The photoelectrons are multiplied by a photomultiplier tube, and the multiplied signal is supplied to the computer 17 via the amplifier 20 as a video signal.
[0036]
The video signal supplied to the computer 17 is supplied to the monitor 23, and as a result, a scanning electron microscope image (secondary electron image) is displayed in the image display area. When a backscattered electron image is displayed, a signal detected by the backscattered electron detector 19 is supplied to the computer 17 via the amplifier 20.
[0037]
Next, when the STEM mode is selected, the computer 17 arranges one of the dark-field image detector 12 and the bright-field image detector 13 on the optical axis and retracts the other from the optical axis. In this state, the computer 17 controls the excitation currents of the condenser lens and the objective lens so that the sample 5 is irradiated with a probe having a relatively small diameter (about 0.2 nm). By controlling each lens in this way to irradiate the sample 5 with the electron beam from the electron gun 1 and supplying a two-dimensional scanning signal of the electron beam from the scanning system control unit 21 to the scanning coil 6, The region is scanned two-dimensionally with the electron beam.
[0038]
The electrons transmitted through the sample 5 based on the two-dimensional scanning of the electron beam on the sample are detected by either the dark-field image detector 12 or the bright-field image detector 13 arranged on the optical axis. The detected transmitted electron signal is supplied to the computer 17 via the amplifier 16 as a video signal. The video signal supplied to the computer 17 is supplied to the monitor 23. As a result, a bright-field or dark-field scanning transmission electron microscope image is displayed in the image display area.
[0039]
Next, a method of observing a sample processed by FIB using the above-mentioned scanning transmission electron microscope will be described. First, a portion to be observed of a sample is processed (cut) by a FIB device (not shown). Generally, the range of a sample to be processed by the FIB apparatus is as short as a rectangular shape having a side of 10 μm to 20 μm, and the range must be processed to a thin film having a thickness of about 3 μm.
[0040]
FIG. 3 shows a sample 5 processed by the FIB apparatus. A part of the sample 5 is processed by the FIB. The portion processed by the FIB is 35, and a thin film-shaped sample portion 36 is formed by this processing. However, in such a sample in which a part is formed into a thin film, the electrons irradiated on the sample are transmitted only through a narrow range processed into a thin film, and the sample region other than the processed range does not transmit electrons. A transmission electron microscope image or a scanning transmission electron microscope image cannot be obtained, and no image appears on an observation screen of a cathode ray tube for transmission image observation or a liquid crystal display.
[0041]
For this reason, when the observation position processed into a thin film shape in the sample is searched for by the transmission electron microscope image, the sample moving mechanism is driven to search for the transmitted electron from the processing range. Since the processed portion 35) is narrow, as long as a transmission image having a relatively high magnification such as a transmission electron microscope image or a transmission scanning electron microscope image is used, the processed position of the sample is often lost. Occurs. Therefore, it takes a considerable time to observe the target image.
[0042]
Next, an embodiment of the method according to the present invention will be described with reference to the flowchart of FIG. First, the sample 5 processed by the FIB device is placed on a sample holder (not shown), and this holder is inserted into the electron microscope column as the sample shown in FIG. Here, when the apparatus is selected to the search mode by the GUI on the monitor 23, the apparatus is automatically set to the scanning secondary electron image acquisition mode. Then, the magnification of the secondary electron image is set to, for example, about 40 times.
[0043]
As a means for setting the apparatus to the search mode, the search is performed by the GUI on the monitor 23, but it may be configured by a switch provided separately. When the apparatus is set to the secondary electron image acquisition mode in this way, the computer 17 controls the excitation current of the condenser lens 2, the condenser mini-lens 3, and the objective lens 4, and has a relatively small diameter (about 0.2 nm). Is controlled so that the sample 5 is irradiated on the sample 5.
[0044]
By controlling each lens in this way to irradiate the sample 5 with the electron beam EB from the electron gun 1 and supplying a two-dimensional scanning signal of the electron beam from the scanning system control unit 21 to the scanning coil 6, An electron beam is two-dimensionally scanned in a predetermined area. In this case, since the magnification is about 40 times, the scanning width of the primary electron beam in the X and Y directions is considerably widened.
[0045]
Secondary electrons se generated from the surface of the sample 5 based on the two-dimensional scanning of the electron beam on the sample are constrained in the vicinity of the optical axis by the forward magnetic field 33 of the objective lens 4 and extracted upward along the optical axis. . The secondary electrons se extracted upward are attracted toward the detector 18 by a high voltage of, for example, about 10 kV applied to the front surface of the secondary electron detector 18 and collide with the scintillator of the detector 18. The scintillator emits light by collision of secondary electrons, and the light is converted into photoelectrons by the photoelectric conversion surface. The photoelectrons are multiplied by a photomultiplier tube, and the multiplied signal is supplied to the computer 17 via the amplifier 20 as a video signal.
[0046]
The video signal supplied to the computer 17 is supplied to the monitor 23, and as a result, a scanning electron microscope image (secondary electron image) is displayed in the image display area.
On the display screen on this monitor, a secondary electron image of the sample at an extremely low magnification is displayed, and from this image, a region having a contrast showing a trace processed by the FIB can be confirmed.
[0047]
The sample 5 is moved while observing the displayed secondary electron image, and a region having a contrast (the thin film portion 36) showing a trace processed by the FIB is positioned at the center of the screen of the monitor 23. Note that the center of the monitor screen and the axis center (optical axis) of the electron microscope are adjusted in advance so as to match. After moving this image, the visual field position A (X1, Y1) is recorded in the sample movement control unit 22. The data on the visual field position is sent to the computer 17 via the sample movement control unit 22 and stored therein.
[0048]
Next, the image observation mode of the apparatus is switched from the secondary electron image acquisition mode to a mode for acquiring an image to be finally observed, for example, a transmission electron microscope image acquisition mode. The lens control unit 10 stores in advance the irradiation system lens and the imaging system lens strength when the transmission electron microscope image acquisition mode is selected. Each lens in the electron optical system of FIG. Then, under the control of the computer 17, the lens intensity is set for acquiring a transmission electron microscope image.
[0049]
Also, the fluorescent screen 11 is removed from the optical axis, and the first TV camera 14 is arranged on the optical axis. As a result, the thin film portion 36 of the sample 5 is irradiated with the electron beam, and an image based on the electrons transmitted through the thin film 36 is formed on the screen of the first TV camera 14 by the intermediate lenses 7, 8, and the projection lens 9. . The image projected on the screen is converted into a video signal by the first TV camera 14, and the video signal is supplied to the computer 17 via the amplifier 16. The signal supplied to the computer 17 is supplied to the monitor 23, and the monitor 23 displays a transmission electron microscope image of the thin film region 36 of the sample 5. The image magnification of the transmission electron microscope at this time is relatively small.
[0050]
The operator observes the image displayed on the monitor 23, searches for the target visual field, operates the computer 17, controls the sample movement control unit 22, moves the sample 5 appropriately, and sets the target visual field. Is moved to the center of the screen of the monitor 23. In this state, the magnification of the transmission electron microscope image is set to the optimal magnification for observation. The magnification is set by operating the computer 17 to control the lens control unit 10 and changing the intensity of each lens of the imaging lens system.
[0051]
At this time, the sample position (field position) B (X2, Y2) after the sample is moved is recorded in the sample movement control unit 22. The sample position recorded in the sample movement control unit 22 is supplied to the computer 17 and stored.
[0052]
Here, if the thin film portion 36 of the sample 5 observed by the monitor 23 is not processed to a sufficient thickness, the sample 5 is taken out of the electron microscope apparatus, the sample 5 is mounted again on the FIB device, and the thin film portion is again mounted. Processing is performed to create a thinner thin film 36. At this time, the position to be processed by the FIB is determined by the first processed coordinate position stored in the computer 17.
[0053]
Thus, when the second FIB processing is completed, the sample 5 is inserted again into the electron microscope apparatus, and the center of the observation position (observation visual field) stored in the computer 17 is positioned at the center of the screen of the monitor 23. The sample 5 is moved via the sample movement control unit 22 so that By observing the transmission electron microscope image of the thinned thin film portion 36 again in this manner, an image of a desired sample region can be obtained. If it is determined from the second observation of the thin film portion 36 that further processing of the thin film portion is to be performed, reprocessing by FIB is performed in the same manner as described above.
[0054]
In the above-described embodiment, the field of view of the transmission electron microscope image is searched by the first TV camera. However, when the final image is observed with a high magnification, the first TV camera 14 is used. Alternatively, the first TV camera 14 may be removed from the optical axis, and an image may be observed using the second TV camera 15.
[0055]
Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made. For example, although the final observation of the image is performed using a transmission electron microscope image, a desired observation may be performed using a scanning transmission electron microscope image. Further, although the secondary electron image is used to search for the processed region of the sample, the processed portion 35 of the sample 5 may be searched for by the reflected electron image.
[0056]
【The invention's effect】
As described above, the method for observing a sample processed by the FIB using an electron microscope according to the present invention is such that when the sample processed by the FIB is set at the sample position of the electron microscope, the electron microscope automatically scans the sample. The mode is switched to the microscope image observation mode, and a low-magnification scanning electron image is displayed on the display device. The operator observes the scanned image, searches for a target visual field, moves the visual field to the center of the display, and then can observe the image at a relatively high magnification by the transmission electron image. Therefore, since the observation field of view can be searched using a low-magnification scanning electron image, the sample portion processed into a thin film shape can be easily found, and the sample portion is moved to the center portion of the display, and then the detailed thin film portion is obtained. Observation of a microscope image can be performed in a short time.
[0057]
In addition, the method for observing a sample processed by FIB using an electron microscope according to the present invention finds the processing position of the sample processed by FIB using a scanning electron microscope image, and observes the sample at a high magnification at the processing position. This is performed by a transmission electron image obtained based on the transmitted electrons, the sample is moved, the coordinates of a desired observation position in the transmission electron image are detected and stored, and the processed portion of the sample is further processed by the FIB again. When making a thinner thin film sample and observing the transmission electron image again, move the sample based on the stored sample position, and observe the thin film sample at the desired observation position using the transmission electron image. It is characterized by doing. As a result, even when the same region of the sample is processed a plurality of times by FIB, the observation field of view of the thin film portion can be set easily and in a short time.
[Brief description of the drawings]
FIG. 1 shows an example of a scanning transmission electron microscope for performing a method according to the present invention.
FIG. 2 is a diagram showing a configuration for detecting secondary electrons in the scanning transmission electron microscope of FIG. 1;
FIG. 3 is a diagram showing a sample processed by FIB.
FIG. 4 is a flowchart for explaining an embodiment of the method according to the present invention.
[Explanation of symbols]
1 electron gun
2 Condenser lens
3 Condenser mini lens
4 Objective lens
5 samples
6 scanning coil
7, 8 Intermediate lens
9 Projection lens
10 Lens control unit
11 fluorescent screen
12, 13 detector
14,15 TV camera
16,20 amplifier
17 Computer
18 Secondary electron detector
19 backscattered electron detector
21 Scanning system controller
22 Sample movement control unit
23 monitors

Claims (7)

An irradiation lens system irradiates a sample with an electron beam having a relatively large diameter, and electrons transmitted through the sample are imaged on a screen of a TV camera by an imaging lens system, and a video signal obtained from the TV camera is displayed. And a transmission electron microscope image observation mode in which a transmission electron microscope image is displayed and a lens intensity of an irradiation lens system is changed so that a diameter of an electron beam probe irradiating a sample is relatively small. A two-dimensional scanning of the electron beam irradiated on the sample is performed, electrons generated upward from the sample by the irradiation of the electron beam are detected by a detector, and a video signal detected by the detector is converted into a signal of the electron beam. An electron microscope that can be selectively switched between a scanning electron microscope image observation mode in which a scanning electron image is supplied to a display in accordance with scanning and displayed. Therefore, when the sample processed by the FIB is set at the sample position of the electron microscope, the electron microscope is automatically switched to the scanning electron microscope image observation mode, and the secondary electron image of low magnification is displayed on the display device. The method of observing the processed sample by FIB with an electron microscope as shown in FIG. 2. The method of observing a processed sample by FIB according to claim 1, wherein a secondary electron detector is arranged above the sample so that a scanning secondary electron image can be observed. 2. The method according to claim 1, wherein a backscattered electron detector is arranged above the sample so that a scanning backscattered electron image can be observed. An irradiation lens system irradiates a sample with an electron beam having a relatively large diameter, and electrons transmitted through the sample are imaged on a screen of a TV camera by an imaging lens system, and a video signal obtained from the TV camera is displayed. And a transmission electron microscope image observation mode in which a transmission electron microscope image is displayed by controlling the lens intensity of an irradiation lens system to make a diameter of an electron beam probe irradiated on a sample relatively small. The two-dimensional scanning of the electron beam applied to the sample is performed, the electrons transmitted through the sample are detected, and the video signal detected by the detector is supplied to the display in accordance with the scanning of the electron beam, and the transmission scanning image is formed. A scanning transmission image observation mode for displaying, and a two-dimensional scanning of an electron beam irradiating the sample, and irradiating the sample upward by the electron beam irradiation. A scanning electron microscope image observation mode in which the generated electrons are detected by a detector, and the video signal detected by the detector is supplied to a display in accordance with the scanning of the electron beam to display a scanning electron image. An electron microscope that can be selectively switched, wherein the electron microscope is automatically switched to a scanning electron microscope image observation mode when a sample processed by the FIB is set at a sample position of the electron microscope, and has a low magnification. A method of observing a processed sample by FIB using a FIB in which a secondary electron image is displayed on a display device. 5. The method for observing a processed sample by FIB according to claim 4, wherein a secondary electron detector is arranged above the sample so that a scanning secondary electron image can be observed. 2. The method according to claim 1, wherein a backscattered electron detector is arranged above the sample so that a scanning backscattered electron image can be observed. The processing position of the sample processed by the FIB is found by a scanning electron microscope image, and the processing position of the sample is observed at a high magnification by a transmitted electron image obtained based on electrons transmitted through the sample, and the sample is moved. Then, the coordinates of the desired observation position in the transmission electron image are detected and stored, and the processed portion of the sample is further processed by the FIB to form a thinner thin film sample, and the transmission electron image is observed again. Is a method for observing a processed sample by FIB using a FIB in which a sample is moved based on a stored sample position and a thin film sample is observed at a desired observation position by a transmission electron image.

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