JP3753628B2 - Electron beam equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam apparatus for observing a sample with an electron beam, and more particularly to an electron beam apparatus suitable for a scanning transmission electron microscope in which a sample is scanned with an electron beam to observe a transmission image.
[0002]
[Prior art]
One type of electron beam apparatus is an electron microscope. In this case, for high-precision observation, magnification correction of the sample image and correction of the camera length are necessary.
[0003]
By the way, for this magnification calibration and camera length correction, a standard sample is generally used as in the case of an objective micrometer in an optical microscope. For this reason, conventionally, an observation object is replaced with a standard sample as necessary. The calibration of the magnification and the correction of the camera length were performed using a standard sample.
[0004]
Here, recently, the need for length measurement in the nanometer region has increased, and as a result, the frequency of electron microscope magnification calibration and camera length correction has only increased in order to maintain and improve observation accuracy. In this case, the conventional method requires replacement of the sample with respect to the electron microscope each time, and the observation efficiency is lowered.
[0005]
Therefore, for example, according to Japanese Patent Application Laid-Open No. 7-288094, a standard sample is set in advance in the main body of the electron microscope, and can be observed by exchanging with the standard sample as necessary. Magnification calibration and camera length correction There has been proposed a method that can easily cope with this, and this is the state of the prior art.
[0006]
[Problems to be solved by the invention]
The above-mentioned prior art does not give consideration to the installation of an appropriate standard sample, and has problems in sharpening the sample image, calibrating the magnification, and correcting the camera length.
[0007]
In other words, it is assumed that astigmatism has been corrected in order to clarify the sample image with an electron microscope, correct magnification calibration, and camera length correction. In the prior art, it is necessary to correct this astigmatism. Since no consideration is given to the standard sample, problems arise in the sharpening of the sample image, the magnification calibration, and the camera length correction.
[0008]
An object of the present invention is to provide an electron beam apparatus capable of correcting astigmatism quickly in a short time and easily obtaining accurate magnification calibration and camera length correction with a clear sample image.
[0009]
[Means for Solving the Problems]
In the electron beam apparatus that scans a sample with an electron beam and performs image observation, a standard sample having both amorphous and crystalline regions is provided in the body of the electron beam apparatus. The process of correcting the astigmatism by observing the image of the amorphous region in the standard sample is executed, and then observing the image of the crystalline region to perform at least calibration of magnification and correction of the camera length. This is achieved by executing one process.
[0010]
At this time, the amorphous region is composed of an amorphous material substrate, and the crystalline region is composed of crystal grains having an island structure formed on the surface of the amorphous material substrate. Alternatively, the standard sample may be composed of an amorphous region and a crystalline region that are divided into two portions and arranged adjacent to each other.
[0011]
Further, at this time, the standard sample may be held in a sample holder different from the sample holder holding the sample to be observed, or may be held in the sample holder holding the sample to be observed. You may make it.
[0012]
Similarly, in the electron beam apparatus in which an image is observed by scanning the sample with an electron beam, a standard sample having both amorphous and crystalline regions is held in the body of the electron beam apparatus. And store the position of the sample holder holding the actual sample to be observed before executing the process of correcting the astigmatism by observing the image of the amorphous region in the standard sample. After the processing for correcting the astigmatism is executed, the image of the crystalline region is observed to execute at least one of the calibration of magnification and the correction of the camera length , and then the sample holding the actual sample position of the holder is achieved so as to execute the processing is automatically returned before term memory position.
[0013]
Similarly, in the electron beam apparatus in which an image is observed by scanning the sample with an electron beam, a standard sample having both amorphous and crystalline regions is held as an observation target. sample holder is held in the stores observation subject to the actual sample position before performing the process of correcting the observed astigmatism an image of the amorphous regions in the standard sample, the astigmatic after the process of correcting the aberration is performed, the performing at least one of the processing to observe the image with magnification of calibration and camera length of the correction of the crystalline regions, followed by the position of the actual sample has been pre-term memory location It is also achieved by executing the process automatically returned to step (b).
[0014]
Also in this case, the amorphous region is composed of an amorphous material base, and the crystalline region is composed of crystal grains having an island structure formed on the surface of the amorphous material base. Alternatively, the standard sample may be composed of an amorphous region and a crystalline region that are divided into two portions and arranged adjacent to each other.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an electron beam apparatus according to the present invention will be described in detail with reference to embodiments shown in the drawings.
[0016]
FIG. 1 shows an embodiment in which the present invention is applied to a scanning transmission electron microscope. FIG. 1 is a block diagram showing only the parts necessary for the basic functions of the scanning transmission electron microscope. 1 represents the main body of the scanning transmission electron microscope.
[0017]
In the microscope main body 1, an electron source 2, a converging lens 3, a scanning coil 4, a sample holder 5 for an actual sample, an objective lens 6, and a transmission electron detector 7 are sequentially arranged from the upper end (the upper end in the figure). Is provided.
[0018]
At this time, the sample P to be observed is placed on the sample holder 5. In this embodiment, in addition to the sample holder 5 for the actual sample, the sample holder 11 for the standard sample is further provided with the microscope main body. As shown in FIG. 3, the standard sample R is attached to the standard sample holder 11.
[0019]
The sample holder 5, the standard sample holder 11, and the scanning coil 4 are controlled by a control circuit 10, respectively. Here, the control circuit 10 uses a computer or the like on which a predetermined program is mounted. Provided, and configured to execute processing according to a predetermined sequence.
[0020]
Thereby, when observing the sample P, the positioning of the sample holder 4 is controlled so that the electrons 8 emitted from the electron source 2 are incident on the sample P as shown in FIG. As a result, the electrons 9 that have passed through the sample P are projected onto the transmission electron detector 7 by the objective lens 6 to detect the image signal, thereby obtaining an image (enlarged image) of the sample P.
[0021]
On the other hand, when observing the standard sample R for magnification calibration, camera length correction, and astigmatism correction, the electron beam 8 emitted from the electron source 2 is incident on the standard sample R as shown in FIG. Thus, the positioning of the standard sample holder 11 is controlled.
[0022]
Next, the standard sample R will be described.
[0023]
First, a crystalline sample is used as a standard sample used for magnification calibration and camera length correction.
[0024]
This is because crystal lattice fringes having various intervals and directions can be observed depending on the crystal orientation of the sample with respect to the incident electrons, and as a result, magnification calibration and camera length correction can be performed.
[0025]
More specifically, the interval between crystal lattice fringes represents the interval between atoms, and thus becomes a value determined as a physical property. Thus, the magnification can be calibrated by observing crystal lattice fringes using a material having a known atomic spacing as a sample and measuring the spacing, and the camera length can be corrected by observing an electron beam diffraction image.
[0026]
Next, an amorphous sample is used as a standard sample used for correcting astigmatism.
[0027]
Here, in the case of a crystalline sample, even when the image has astigmatism, depending on the amount of astigmatism, the connection of particles with directionality is observed in a state that closely resembles the image of the crystal lattice fringe. End up. Therefore, it is difficult to correct astigmatism of a transmission image using a crystalline sample.
[0028]
On the other hand, in the case of an amorphous sample, atoms are randomly arranged. Therefore, in this case, if atoms are observed aligned in a specific direction, it represents the astigmatism direction and amount of the objective lens, and astigmatism can be corrected.
[0029]
Therefore, in this embodiment, each correction can be performed as necessary by utilizing the difference in the appearance of the transmission image unique to the crystalline sample and the amorphous sample as described above.
[0030]
Here, as is clear from the above, it is important that the standard sample R includes both crystalline and amorphous materials.
[0031]
As a configuration for this purpose, as shown in FIG. 3, a standard sample in which crystal particles having an island structure are arranged on an amorphous film, or a crystalline part and an amorphous part as shown in FIG. A standard sample or the like can be considered. A method of preparing an amorphous sample and a crystalline sample separately is also conceivable.
[0032]
Among these, a standard sample having an island structure of crystal grains on an amorphous film is considered optimal.
[0033]
This is because astigmatism correction can be performed not only in the observation of the crystal lattice image but also in the low-magnification observation because of the directionality of the crystal grains.
[0034]
As described above, the standard sample R shown in FIG. 3 is an embodiment of the standard sample having this island structure. In the figure, a large number of particles are shown as island structure crystal particles, and the substrate is amorphous. Represents a membrane.
[0035]
In this embodiment, as an example, a sample prepared by depositing gold in the form of particles on the surface of an amorphous carbon film is used as the standard sample R.
[0036]
Here, since gold is a stable material that has a known atomic spacing and hardly changes with time, it can be said to be optimal for a standard sample.
[0037]
Next, the operation of this embodiment will be described in detail with reference to the flowchart of FIG.
[0038]
First, a desired sample P is placed on the sample stage 5 (S1), and then a desired observation condition is set in the electron beam apparatus corresponding to the sample P (S2).
[0039]
Here, the desired observation condition is, for example, axis adjustment in a normal electron beam apparatus such as movable aperture alignment, focus, voltage, center alignment, etc. in a scanning electron microscope or the like.
[0040]
Next, it is selected whether or not to correct astigmatism, and the control circuit 10 is instructed (S3).
[0041]
Here, when NO, that is, when there is an instruction not to correct astigmatism, the control circuit 10 operates the electron microscope under the observation conditions set in step S2. That is, in this case, normal observation processing is performed, and an image of the sample P can be observed (S4).
[0042]
On the other hand, if YES in step S3, that is, if execution of astigmatism correction is instructed, the process proceeds to step S5 and subsequent steps, and the control circuit 10 first determines the current position of the sample stage 5 on which the sample P is placed, for example, After storing the position represented by the rectangular coordinate system to be the position X, the sample stage 5 is removed from the electron beam path, and the sample stage 11 on which the standard sample R is placed is replaced with the electron beam path. The route is entered (S5). That is, at this time, the state shown in FIG. 1 is changed to the state shown in FIG.
[0043]
Therefore, an electron beam is incident on the amorphous region of the standard sample R placed on the sample stage 11, that is, the base region in FIG. 3, and the image of this region is observed so that astigmatism is minimized. Then, a correction process is performed (S6).
[0044]
The astigmatism correction process at this time is performed using an adjusting device provided in the scanning electron microscope.
[0045]
When the astigmatism correction is finished, this time, whether or not to execute the magnification calibration and the camera length correction is selected, and the control circuit 10 is instructed (S7).
[0046]
Here, when NO, that is, when it is instructed not to execute the magnification calibration and the camera length correction, the sample stage 11 is removed from the electron beam path, and this time, the sample stage 5 on which the sample P is placed is processed. Return to the position X stored in S5 (S8).
[0047]
Therefore, at this time, the state of FIG. 2 is returned to the state of FIG. 1 and the sample P placed on the sample stage 5 is placed in the path of the electron beam. In this case, The control circuit 10 controls the electron microscope so that the observation operation of the sample P can be performed under the observation conditions set in the processing S2, and as a result, the image of the sample P corrected for astigmatism can be observed. (S9).
[0048]
On the other hand, if YES in step S7, that is, if execution of magnification calibration and camera length correction is instructed, the process proceeds to step S10 and subsequent steps, and the observation of the standard sample R placed on the sample stage 11 is continued. In this case, an electron beam is incident on the crystalline region of the standard sample R, that is, the crystal grain portion of the island structure in FIG. 3, and the crystal lattice image and the electron diffraction image obtained from the crystalline region are observed.
[0049]
First, the crystal lattice image is observed, and the magnification is calibrated (S10).
[0050]
That is, as described above, the distance between crystal lattice stripes represents the distance between atoms and is a value determined as a physical property. In this case, the standard sample R deposits gold in the form of particles on the surface of the amorphous carbon film. Thus, the atomic spacing is known, and therefore the magnification can be calibrated by observing the crystal lattice fringes and measuring the spacing.
[0051]
As a result, the camera length can be corrected by observing the electron diffraction image.
[0052]
When the magnification calibration and the camera length correction are thus completed, the control circuit 10 is instructed to end the correction.
[0053]
As a result, the control circuit 10 removes the sample stage 11 from the electron beam path, and returns the sample stage 5 on which the sample P is placed to the position X stored in step S5 in the electron beam path ( S11).
[0054]
Therefore, also at this time, the state of FIG. 2 is returned to the state of FIG. 1, and the sample P placed on the sample stage 5 is again placed in the electron beam path.
[0055]
As a result, the electron microscope is controlled by the control circuit 10 so that the observation operation of the sample P can be performed under the observation conditions set in the process S2, and the image of the sample P can be observed ( S12) Here, the image of the sample P can be observed not only with astigmatism correction but also under the calibrated magnification and with the camera length corrected.
[0056]
According to this embodiment, as shown in FIG. 3, since the standard sample R in which crystal grains having an island structure are arranged on an amorphous film is used, a short time is required prior to magnification calibration and camera length correction. Astigmatism can be easily corrected.
[0057]
Therefore, according to this embodiment, as a result based on a clear image of the sample in which astigmatism is corrected, accurate magnification calibration and camera length correction can be obtained easily and in a short time.
[0058]
Here, in the case of this embodiment, the position (height) of the sample holder 11 for the standard sample is set so that the electron beam is focused when the current value of the objective lens 6 is a standard value. .
[0059]
Therefore, when the focus of the actual observation sample P and the standard sample holder 11 are different, the sample height of the actual observation sample is first adjusted to be focused, and the height of the observation sample P and the standard sample holder 11 is adjusted. It is desirable to keep the same level.
[0060]
This is because when the focus is adjusted by changing the amount of current of the objective lens 6, accurate correction becomes impossible.
[0061]
Next, another embodiment of the present invention will be described.
[0062]
In the case of a scanning electron microscope, an electron beam can be deflected to an arbitrary region on the sample surface, and that region can be scanned and observed.
[0063]
Therefore, in the embodiment of FIG. 5, a sample stage 14 provided with a sample mounting portion 17 is used instead of the sample holder 5, and the standard surface of the sample stage 14 is the same as the sample mounting surface of the sample mounting portion 17. By providing the sample R and deflecting the electron beam 8 by the scanning coil 4, when observing the sample P (not shown) placed on the sample mounting portion 17 and when observing the standard sample R, The incident position of the electron beam 8 is changed.
[0064]
Therefore, in the case of the embodiment of FIG. 5, the sample holder 11 in the embodiment of FIG. 1 is not necessary, so that the configuration can be simplified and the cost can be reduced.
[0065]
Incidentally, in the case of such a scanning transmission electron microscope, a sample holder 5A capable of oblique irradiation as shown in FIG. 6 is often used. According to the embodiment of FIG. 5, this sample holder 5A is used. Even when the sample is used, it can be simply implemented by simply providing the standard sample R on the sample stage 14.
[0066]
In the sample holder 5A of FIG. 6, the sample stage 14 is rotatably held by the shafts on the upper side and the lower side of the figure, and the sample holder 5A is used for restoring the sample tilt by being pushed by the operation rod 15 for tilting the sample. The observation surface can be tilted at an arbitrary angle against the restoring force of the spring 16.
[0067]
Next, FIG. 7 shows a case where a method of deflecting an electron beam 8 by a scanning coil 4 is applied to a scanning transmission electron microscope using both a sample holder 5 for observation and a sample holder 11 for a standard sample. Switching of the incident position of the electron beam 8 at the time of irradiation of the sample P placed on the holder 5 and at the time of irradiation of the standard sample R placed on the sample holder 11 is performed by deflection of the electron beam. 1 is an embodiment of the present invention.
[0068]
Here, FIG. 7 shows an embodiment in which the present invention is applied to an in-lens scanning transmission electron microscope. In FIG. 7, the pole piece ( A pole piece) 19 and a magnetic pole piece 20 on the lower side constitute part of an objective lens (corresponding to the objective lens 6 in the embodiment of FIG. 1). It comes from being in the objective lens system.
[0069]
According to the embodiment of FIG. 5 and FIG. 7, since it is not necessary to move the sample holder for switching between the sample P and the standard sample R to be observed, the configuration is simplified correspondingly, and the increase in cost is suppressed. Can do.
[0070]
Next, FIG. 8 shows another embodiment of the standard sample R, in which the entire sample is divided into a crystalline region and an amorphous region and then arranged adjacent to each other. Although not shown, a crystalline region and an amorphous region may be provided separately.
[0071]
Here, for the standard sample R in FIG. 8, a crystalline material and an amorphous material having a semicircular cross-sectional shape are prepared, and these are bonded to each other on a plane, and then a predetermined surface is perpendicular to the length direction. It can be easily obtained by slicing (thin slice) with a thickness of.
[0072]
【The invention's effect】
According to the present invention, it is possible to obtain magnification calibration and camera length correction using an image of a sample in which astigmatism is corrected without requiring replacement of the sample.
[0073]
Therefore, according to the present invention, accurate magnification calibration and camera length correction can be obtained easily and in a short time.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a certain operating state of a scanning transmission electron microscope to which an embodiment of the present invention is applied.
FIG. 2 is an explanatory diagram showing another operation state of a scanning transmission electron microscope to which an embodiment of the present invention is applied.
FIG. 3 is an explanatory diagram of a standard sample in one embodiment of the present invention.
FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention.
FIG. 5 is an operation explanatory diagram of a scanning transmission electron microscope to which another embodiment of the present invention is applied.
FIG. 6 is an explanatory diagram showing an example of a sample holder in another embodiment of the present invention.
FIG. 7 is an operation explanatory diagram of a scanning transmission electron microscope to which still another embodiment of the present invention is applied.
FIG. 8 is an explanatory diagram showing another example of a standard sample according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electron microscope main body 2 Electron source 3 Converging lens 4 Scan coil 5 Sample holder 6 of the sample for real observation Objective lens 7 Transmission electron detector 8 Incident electron beam 9 Transmission electron beam 10 Control circuit 11 Sample holder 14 for standard samples Sample stand 15 Sample tilting operation rod 16 Sample tilt restoring spring 17 Sample mounting portion 19 Magnetic pole piece 20 Magnetic pole piece P Sample R to be observed Standard specimen

Claims (9)

In an electron beam apparatus that scans a sample with an electron beam to perform image observation,
Provide a standard sample with both amorphous and crystalline regions in the body of the electron beam device,
Execute the process of correcting astigmatism by observing an image of an amorphous region in the standard sample,
Thereafter, an image of the crystalline region is observed, and at least one of calibration of magnification and correction of camera length is executed. In the invention of claim 1,
The amorphous region is composed of an amorphous material base,
2. The electron beam apparatus according to claim 1, wherein the crystalline region is composed of crystal particles having an island structure formed on a surface of the amorphous material base. In the invention of claim 1,
2. The electron beam apparatus according to claim 1, wherein the standard sample is composed of an amorphous region and a crystalline region which are divided into two parts and arranged adjacent to each other. In the invention of claim 1,
An electron beam apparatus, wherein the standard sample is held in a sample holder different from a sample holder holding a sample to be observed. In the invention of claim 1,
An electron beam apparatus, wherein the standard sample is held in a sample holder holding a sample to be observed. In an electron beam apparatus that scans a sample with an electron beam to perform image observation,
A sample holder holding a standard sample having both amorphous and crystalline regions is provided in the main body of the electron beam apparatus,
Store the position of the sample holder holding the actual sample to be observed before observing the image of the amorphous region in the standard sample and executing the process of correcting astigmatism,
After the processing for correcting the astigmatism is performed, the image of the crystalline region is observed to execute at least one of magnification calibration and camera length correction , and then a sample holder holding the actual sample electron beam apparatus the position of the is characterized by being configured to execute a process automatically returned before term memory position. In an electron beam apparatus that scans a sample with an electron beam to perform image observation,
A standard sample having both amorphous and crystalline regions is held in a sample holder that holds an actual sample to be observed,
Before observing the image of the amorphous region in the standard sample and correcting the astigmatism, store the position of the actual sample to be observed,
After said process of correcting astigmatism is performed, the crystalline by observing the image of the region to perform at least one of the process of the correction of the calibration and camera length magnification, then the position of the actual sample prior Symbol An electron beam apparatus configured to execute a process of automatically returning to a stored position. In the invention according to claim 6 or claim 7,
The amorphous region is composed of an amorphous material base,
2. The electron beam apparatus according to claim 1, wherein the crystalline region is composed of crystal particles having an island structure formed on a surface of the amorphous material base. In the invention according to claim 6 or claim 7,
2. The electron beam apparatus according to claim 1, wherein the standard sample is composed of an amorphous region and a crystalline region which are divided into two parts and arranged adjacent to each other.

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