JP7083629B2 - Quantitative analysis method and electron microscope - Google Patents

Description

The present invention relates to a quantitative analysis method and an electron microscope.

Electron beam tomography (TEM) is a method for three-dimensional structural observation and structural analysis of a sample in an electron microscope such as a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). electron tomography) is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-209050

However, electron tomography cannot perform qualitative and quantitative analysis. A three-dimensional atom probe (3 Dimensional Atom Probe, 3DAP) is known as a method for performing a three-dimensional quantitative analysis of a sample. In the three-dimensional atom probe, an electric field is applied to a sample processed into a needle shape, and an electric field-evaporated ion is detected by a two-dimensional detector, whereby three-dimensional quantitative analysis can be performed.

However, the three-dimensional atom probe has a problem that the sample is destroyed by the measurement. Further, the three-dimensional atom probe has a problem that the shape of the sample is limited to a needle shape.

With a three-dimensional atom probe, the shape of the sample is limited to a needle shape, so that it is difficult to analyze a thin film sample, for example. Further, the method of processing the sample into a needle shape is limited to processing using a focused ion beam (FIB). However, when the sample is processed with a focused ion beam, gallium ions are driven into the sample. Therefore, it is difficult to analyze a sample that is destroyed by the injection of gallium ions with a three-dimensional atom probe.

The present invention has been made in view of the above problems, and one of the objects according to some aspects of the present invention is to provide a quantitative analysis method capable of three-dimensional quantitative analysis. be. Further, one of the objects according to some aspects of the present invention is to provide an electron microscope capable of three-dimensional quantitative analysis.

One aspect of the quantitative analysis method according to the present invention is
It is a quantitative analysis method in an electron microscope.
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample, and
A process of generating a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
The process of calculating the quantitative value of the element for each voxel constituting the three-dimensional element map, and
including.
One aspect of the quantitative analysis method according to the present invention is
It is a quantitative analysis method in an electron microscope.
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample, and
A process of generating a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
A step of extracting information on three-dimensional particles based on the X-ray intensity from the three-dimensional element map and calculating a quantitative value for each of the extracted three-dimensional particles.
including.

In such a quantitative analysis method, a three-dimensional quantitative analysis can be performed by acquiring a two-dimensional element map for each inclination angle. Therefore, in such a quantitative analysis method, analysis can be performed without destroying the sample. Furthermore, analysis is possible without processing the sample into needles.

The electron microscope according to the present invention is
With an electron source
An irradiation system lens that irradiates the sample with the electron beam emitted from the electron source, and
A sample stage that holds the sample tiltably and
A detector that detects X-rays generated by irradiating the sample with an electron beam,
An analysis processing unit that performs quantitative analysis based on the X-ray detection result of the detector, and
Including
The analysis processing unit
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample.
A process to generate a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
The process of calculating the quantitative value of the element for each voxel constituting the three-dimensional element map, and
I do.

With such an electron microscope, three-dimensional quantitative analysis can be performed by acquiring a two-dimensional element map for each inclination angle.

The figure which shows the structure of the electron microscope which concerns on embodiment. The figure which shows typically the state that 2D EDS mapping is performed for each tilt angle of a sample. The figure which shows typically the state that 2D EDS mapping is performed for each tilt angle of a sample. The flowchart which shows an example of the quantitative analysis method which concerns on embodiment. The figure for demonstrating the difference between the information obtained by 3D quantitative analysis and the information obtained by 2D quantitative analysis. The figure which shows the 2D EDS element map of the coating film sample. The figure which shows the 3D EDS element map of the coating film sample. The figure which shows the 3D EDS element map of the coating film sample. The figure which shows the titanium particle extracted from the 3D EDS element map. The figure which shows the aluminum particle extracted from the 3D EDS element map. The figure which shows typically the state that 2D EDS mapping is performed for each tilt angle of a sample. The figure which shows an example of the arrangement of the EDS detector.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unreasonably limit the contents of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

1. 1. Electron Microscope First, an electron microscope according to this embodiment will be described. FIG. 1 is a diagram showing a configuration of an electron microscope 100 according to the present embodiment.

The electron microscope 100 is, for example, a scanning transmission electron microscope (STEM). The scanning transmission electron microscope is a device for scanning on a sample S with an electron probe, detecting electrons transmitted through the sample S, and obtaining a scanning transmission electron microscope image (STEM image). Further, the electron microscope 100 includes energy dispersive X-ray spectrometers (hereinafter, also referred to as “EDS detectors”) 40 and 50.

The electron microscope 100 includes an electron source 10, an irradiation system lens 12, a scanning coil 14, an objective lens 16, a sample stage 18, an intermediate lens 20, a projection lens 22, a STEM detector 30, and an EDS detector. It includes 40, 50, a signal processing unit 60, an analysis processing unit 70, and a stage control unit 80.

The electron source 10 emits an electron beam. The electron source 10 is, for example, a known electron gun.

The irradiation system lens 12 irradiates the sample S with the electron beam emitted from the electron source 10. Although not shown, the irradiation system lens 12 may be composed of a plurality of condenser lenses.

The scanning coil 14 two-dimensionally deflects the electron beam emitted from the electron source 10. The scanning coil 14 is a coil for scanning the sample S with an electron beam (electron probe).

The objective lens 16 converges the electron beam on the sample S to form an electron probe.

The sample stage 18 holds the sample S. The sample stage 18 has a sample holder 18a to which the sample S is fixed, and a sample positioning device 18b for moving and tilting the sample holder 18a.

The sample positioning device 18b includes a moving mechanism for moving the sample holder 18a in the horizontal direction (X direction and Y direction, see FIG. 2) and a vertical direction (Z direction), and a tilting mechanism for tilting the sample holder 18a. The sample S can be moved and tilted by moving and tilting the sample holder 18a with the sample positioning device 18b.

The sample holder 18a is provided with a mechanism for inclining the sample S. The tilting mechanism of the sample positioning device 18b tilts the sample S (for example, an axis parallel to the X axis), and the tilting mechanism of the sample holder 18a tilts the sample S (for example, an axis parallel to the Y axis). Are configured to be orthogonal to each other. This allows the sample S to be tilted with respect to the two axes.

The intermediate lens 20 and the projection lens 22 guide the electron beam transmitted through the sample S to the STEM detector 30.

The STEM detector 30 detects the electron beam that has passed through the sample S. The output signal of the STEM detector 30 is sent to a frame memory (not shown). The frame memory stores the output signal of the STEM detector 30 in the storage area of the address specified based on the scanning signal (the signal for scanning the electronic probe). As a result, the STEM image can be acquired.

The EDS detector 40 and the EDS detector 50 detect X-rays (characteristic X-rays) generated from the sample S by being irradiated with an electron beam. As the EDS detector 40 and the EDS detector 50, for example, a silicon drift detector (SDD) can be used. The detection signal (output pulse) of the EDS detector 40 and the detection signal (output pulse) of the EDS detector 50 are sent to the signal processing unit 60.

The signal processing unit 60 counts the detection signal of the EDS detector 40 and the detection signal of the EDS detector 50 for each X-ray energy to generate EDS spectrum information. The signal processing unit 60 is E.
The DS spectrum information is sent to the analysis processing unit 70.

The analysis processing unit 70 performs quantitative analysis based on the X-ray detection results of the EDS detectors 40 and 50. Specifically, the analysis processing unit 70 performs a process of generating a three-dimensional EDS element map based on the EDS spectrum information, a process of performing a three-dimensional quantitative analysis from the three-dimensional EDS element map, and the like. Here, three-dimensional quantitative analysis means performing quantitative analysis from information on the distribution of three-dimensional elements.

The stage control unit 80 controls the sample stage 18. The stage control unit 80 inclines the inclination angle θ (see FIG. 3) of the sample S in a predetermined step so that a two-dimensional EDS element map can be obtained for each inclination angle of the sample S. For example, the stage control unit 80 inclines the inclination angle θ of the sample S in 25 steps from + 60 ° to −60 ° in 5 ° steps. As a result, the analysis processing unit 70 can obtain 25 two-dimensional EDS element maps obtained at different inclination angles θ.

The functions of the analysis processing unit 70 and the stage control unit 80 can be realized, for example, by the CPU (central processing unit) executing a program stored in a storage device (not shown). Further, at least a part of the functions of the analysis processing unit 70 and the stage control unit 80 may be realized by a dedicated circuit.

2 and 3 are diagrams schematically showing how the electron microscope 100 performs two-dimensional EDS mapping for each inclination angle θ of the sample S.

As shown in FIGS. 2 and 3, the sample S held in the sample holder 18a is arranged between the upper pole 16a of the pole piece of the objective lens 16 and the lower pole 16b of the pole piece. The sample S can be tilted around the tilt axis TA by the tilt mechanism of the sample stage 18. In the electron microscope 100, for example, the sample S can be tilted in the range of ± 60 ° by the tilting mechanism of the sample stage 18. The tilt axis TA is an axis orthogonal to the optical axis of the objective lens 16 and is an axis parallel to the X axis in the illustrated example. The tilt axis TA is parallel to the central axis of the sample holder 18a.

The EDS detector 40 and the EDS detector 50 are arranged so as to sandwich the tilt axis TA of the sample S. The EDS detector 40 is located on the −X direction side of the sample S, and the EDS detector 50 is located on the + X direction side of the sample S. The EDS detector 40 is located on the −X direction side of the tilt axis TA, and the EDS detector 50 is located on the + X direction side of the tilt axis TA. High sensitivity can be achieved by detecting the X-rays generated in the sample S by the two EDS detectors 40 and 50.

When performing two-dimensional EDS mapping for each inclination angle θ of the sample S, first, as shown in FIG. 2, two-dimensional EDS mapping is performed at an inclination angle θ = 0 °, and an inclination angle θ = 0 °. Obtain a two-dimensional EDS element map. Next, as shown in FIG. 3, the sample S is tilted so that the tilt angle θ = a °, two-dimensional EDS mapping is performed at the tilt angle θ = a °, and the two-dimensional EDS with the tilt angle θ = a ° is performed. Get an element map. In this way, by performing two-dimensional EDS mapping while inclining the sample S, it is possible to acquire a two-dimensional EDS map for each inclination angle θ.

In the electron microscope 100, the stage control unit 80 controls the tilt angle θ of the sample S, so that the analysis processing unit 70 can acquire a two-dimensional EDS element map for each tilt angle θ. In this way, the electron microscope 100 can automatically acquire a two-dimensional EDS element map for each inclination angle θ.

2. 2. Quantitative analysis method Next, the quantitative analysis method according to the present embodiment will be described. FIG. 4 is a flowchart showing an example of the quantitative analysis method according to the present embodiment.

First, the analysis processing unit 70 acquires a two-dimensional EDS element map for each inclination angle θ obtained by performing element mapping for each inclination angle θ while inclining the sample S (S100). As described above, in the electron microscope 100, the stage control unit 80 controls the tilt angle θ of the sample S, so that the analysis processing unit 70 can acquire a two-dimensional EDS element map for each tilt angle θ.

Next, the analysis processing unit 70 generates a three-dimensional EDS element map by three-dimensionally reconstructing the two-dimensional EDS element map for each inclination angle θ (S102). The analysis processing unit 70 generates, for example, a three-dimensional EDS element map from a two-dimensional EDS element map for each inclination angle θ by a back projection method or the like. The three-dimensional EDS element map is a diagram showing the three-dimensional distribution of elements. Each voxel constituting the three-dimensional EDS element map contains information on the intensity of X-rays specific to the element. The analysis processing unit 70 stores the coordinates (x, y, z) of each voxel constituting the three-dimensional EDS element map and the information of the X-ray intensity of each element at each coordinate in a storage device (not shown). ..

Next, the analysis processing unit 70 calculates the quantitative value of each element constituting the sample S from the three-dimensional EDS element map (S104).

Hereinafter, a method for calculating a quantitative value from a three-dimensional EDS element map will be described. In this embodiment, the Cliff-Lorimer method used in the two-dimensional EDS element map quantification method is extended to the three-dimensional EDS element map quantification method to perform quantitative analysis. In the following, first, a quantification method using a two-dimensional EDS element map will be described.

When the sample S contains three kinds of elements, the two-dimensional EDS map is represented in the following format.

Element A Intensity value I _A (x, y)
Element _B Intensity value IB (x, y)
Element _C Intensity value IC (x, y)

In the quantitative analysis by the Cliff-Lolimer method, assuming that the composition ratio of element A is CA, the composition ratio of element _{B is C B ,} and the composition ratio of element C is C _C , the following formula is calculated for each pixel. The elemental composition ratio can be calculated.

Here, k is a k factor and is a constant determined by a reference element.

Next, a case where the above calculation formula is extended to three dimensions will be described. The three-dimensional EDS element map data obtained by EDS tomography is represented in the form of a stack of two-dimensional EDS element maps for each element, and the data set is represented as follows.

Element A Intensity value I _A (x, y, z)
Element _B Intensity value IB (x, y, z)
Element _C Intensity value IC (x, y, z)

Therefore, when the Cliff-Lorimer method is applied to the three-dimensional EDS element map, it becomes as follows.

By performing the above calculation, the composition ratio (quantitative value of each element) can be calculated for each voxel constituting the three-dimensional EDS element map. The analysis processing unit 70 stores, for example, the coordinates (x, y, z) of each voxel constituting the three-dimensional EDS element map and the information of the composition ratio at each coordinate in a storage device (not shown).

3. 3. Features The quantitative analysis method according to this embodiment has the following features, for example.

The quantitative analysis method according to the present embodiment includes a step of acquiring a two-dimensional element map for each inclination angle θ obtained by performing EDS element mapping for each inclination angle θ while inclining the sample S, and for each inclination angle θ. It includes a step of generating a three-dimensional EDS element map by three-dimensional reconstruction from the two-dimensional EDS element map of the above, and a step of calculating a quantitative value of an element from the three-dimensional EDS element map. Therefore, in the quantitative analysis method according to the present embodiment, three-dimensional quantitative analysis is possible by acquiring a two-dimensional element map for each inclination angle θ.

In the quantitative analysis method according to the present embodiment, since three-dimensional quantitative analysis is possible, the influence of the thickness of the sample S is extremely small, or the influence of the thickness of the sample S is not affected. The reason will be described below.

FIG. 5 is a diagram for explaining the difference between the information obtained by the three-dimensional quantitative analysis and the information obtained by the two-dimensional quantitative analysis.

The sample S has a structure in which the particles 4 are present in the film 2. At this time, if you want to know the composition of the particles 4, in the two-dimensional quantitative analysis, the X-rays emitted from the region 6 that is the path through which the electron beam EB passes through the sample S are detected and the quantitative analysis is performed. Information on the upper and lower films 2 of 4 is also included.

On the other hand, in the three-dimensional quantitative analysis, it is possible to extract only the information of the inside 8 of the particle 4. Therefore, in the three-dimensional quantitative analysis, the influence of the thickness of the sample S is extremely small, or the influence of the thickness of the sample S is not affected.

Further, in the quantitative analysis according to the present embodiment, since it is possible to perform a three-dimensional quantitative analysis by acquiring a two-dimensional element map for each inclination angle θ, the three-dimensional analysis is performed without destroying the sample S. Quantitative analysis can be performed. Further, since the sample S does not have to be processed into a needle shape, a three-dimensional quantitative analysis can be performed by the sample S prepared by a general method for preparing a TEM sample such as a microtome or ion milling. As described above, the quantitative analysis method according to the present embodiment has problems such as the problem of the three-dimensional atom probe, that the sample S is destroyed by the measurement, and that the sample must be processed into a needle shape. do not have.

In the quantitative analysis method according to the present embodiment, in the step of calculating the quantitative value, the quantitative value of the element is calculated by using the Cliff-Lolimer method. Therefore, in the quantitative analysis method according to the present embodiment, three-dimensional quantitative analysis is possible by generating a three-dimensional EDS element map from a two-dimensional element map for each inclination angle θ.

The electron microscope 100 according to the present embodiment includes an electron source 10, an irradiation system lens 12 that irradiates the sample S with an electron beam emitted from the electron source 10, a sample stage 18 that holds the sample S tiltably, and a sample. It includes EDS detectors 40 and 50 that detect X-rays generated by irradiating S with an electron beam, and an analysis processing unit 70 that performs quantitative analysis based on the detection signals of the EDS detectors 40 and 50. Further, the analysis processing unit 70 obtains a two-dimensional element map for each inclination angle θ obtained by performing element mapping for each inclination angle θ while inclining the sample S, and two-dimensional for each inclination angle θ. A process of generating a three-dimensional element map by three-dimensional reconstruction from the element map of No. 1 and a process of calculating a quantitative value of an element from the three-dimensional element map are performed. Therefore, in the electron microscope 100, three-dimensional quantitative analysis is possible by acquiring a two-dimensional element map for each inclination angle θ.

4. Examples Hereinafter, the present embodiment will be described with reference to examples, but the present invention is not limited thereto.

The sample to be analyzed in this example is a coating film sample processed into sections with a microtome. Titanium particles are dispersed in this coating film sample in the state of titanium dioxide. In this example, the accuracy of the quantitative analysis is confirmed by performing a three-dimensional quantitative analysis on the coating film sample having a known composition.

First, a two-dimensional EDS element map was obtained for the coating film sample using a transmission electron microscope (JEM-F200, manufactured by JEOL Ltd.) equipped with two EDS detectors having a light receiving area of 100 nm ² .

FIG. 6 is a diagram showing a two-dimensional EDS element map of the coating film sample. As shown in FIG. 6, titanium (Ti), iron (Fe), aluminum (Al), silicon (Si), oxygen (O), and carbon (C) were detected in the coating sample, and these elements were detected. A two-dimensional EDS element map was obtained for each.

In the field of view shown in FIG. 6, EDS mapping was performed for each tilt angle θ while tilting the sample to obtain a two-dimensional EDS map for each tilt angle θ of the sample, and a three-dimensional EDS element map was generated.

7 and 8 are diagrams showing a three-dimensional EDS element map of the coating film sample. FIG. 7 shows a three-dimensional EDS element map of titanium, a three-dimensional EDS element map of aluminum, a three-dimensional EDS element map of iron, a three-dimensional EDS element map of silicon, and a three-dimensional EDS element map of carbon. And a three-dimensional EDS element map in which these are superimposed is shown. Further, FIG. 8 shows a three-dimensional EDS element map in which three-dimensional EDS element maps of titanium, iron, aluminum, silicon, oxygen, and carbon are superimposed.

FIG. 9 is a diagram showing titanium particles extracted from the three-dimensional EDS element map shown in FIG. In this embodiment, as shown in FIG. 9, one titanium particle is extracted from the three-dimensional EDS element map, and the average value of the concentration values (X-ray intensity) of the region corresponding to the extracted titanium particles is used as an element. Calculated for each. Then, the composition ratio of the titanium particles was obtained from the average value of the concentration values calculated for each element. Table 1 below is a table showing the results of three-dimensional quantitative analysis of titanium particles.

As shown in Table 1, as a result of quantitative analysis of titanium particles, titanium was 31.86 at% (atomic percent) and oxygen was 65.51 at%. As described above, the ratio of titanium to oxygen was approximately Ti: O = 1: 2, and a quantitative result was obtained that the titanium particles were titanium dioxide. Therefore, it was found that the quantitative analysis method according to this example enables highly accurate quantitative analysis.

Table 2 below is a table comparing the results of the two-dimensional quantitative analysis (2D at%) and the results of the three-dimensional quantitative analysis (3D at%). In Table 2, 3D at% (particle) is the result of quantitative analysis of titanium particles, and 3D at% (matrix) is the result of quantitative analysis of the resin surrounding the titanium particles.

As shown in Table 2, as a result of two-dimensional quantitative analysis, titanium was 11.38 at% and oxygen was 14.23 at%. As described above, since the two-dimensional quantitative analysis includes information on the resin surrounding the titanium particles, the proportion of oxygen and carbon becomes large, and the composition of the titanium particles cannot be analyzed accurately. On the other hand, in the three-dimensional quantitative analysis, the composition of the titanium particles could be analyzed accurately.

FIG. 10 is a diagram showing aluminum particles extracted from the three-dimensional EDS element map shown in FIG. The three-dimensional EDS element map shown in FIG. 10 shows the cross section of the aluminum particles surrounded by the square in the DF-STEM image (dark field STEM image) shown in FIG. 10 cut by a line passing through the center of the square. ing.

Table 3 below is a table comparing the results of the three-dimensional quantitative analysis of the aluminum particles and the results of the two-dimensional quantitative analysis.

As shown in Table 3, as a result of three-dimensional quantitative analysis, 99.44 at% of aluminum was detected inside the aluminum particles. Further, on the surface of the aluminum particles, 41.89 at% of aluminum is detected and 52.12 at% of oxygen is detected. From this, it was found that the inside of the aluminum particles was aluminum, and the surface of the aluminum particles was aluminum oxide (Al ₂ O ₃ ). Such results cannot be obtained by two-dimensional quantitative analysis.

5. Modifications The present invention is not limited to the above-described embodiment, and various modifications can be carried out within the scope of the gist of the present invention.

5.1. First Modification Example In the above-described embodiment, two EDS detectors 40 and 50 were used to detect the X-rays generated in the sample S. Here, as shown in FIG. 3, when the sample S is tilted toward the EDS detector 40, the EDS detector 50 is the frame of the sample holder 18a or the shadow of the sample S when viewed from the X-ray source of the sample S. become. As a result, the X-rays generated in the sample S are shielded and the X-ray intensity is reduced. Further, the degree of decrease in the X-ray intensity due to the shadow of the EDS detector 50 varies depending on the inclination angle θ of the sample S. Therefore, the accuracy of three-dimensional quantitative analysis may decrease.

In this modification, the X-ray from the sample S is detected by using the detector on the side where the sample S is inclined out of the two EDS detectors 40 and 50. That is, the X-ray is detected by using the EDS detector in the direction in which the surface on which the electron beam of the sample S is incident faces. For example, as shown in FIG. 3, when the sample S is inclined toward the EDS detector 40, the detection signal of the EDS detector 40 is used to generate a two-dimensional EDS element map. Further, for example, as shown in FIG. 11, when the sample S is inclined toward the EDS detector 50, the detection signal of the EDS detector 50 is used to generate a two-dimensional EDS element map. As a result, the influence of the EDS detector being in the shadow of the sample holder 18a or the sample S can be reduced, and the accuracy of the three-dimensional quantitative analysis can be improved.

Further, for example, for the EDS detector 40, a standard sample may be used in advance to acquire correction data showing the relationship between the inclination angle θ of the sample S and the X-ray intensity detected by the EDS detector 40. good. Then, the detection signal of the EDS detector 40 may be corrected by using this correction data. Similarly, for the EDS detector 50, the detection signal may be corrected by using the correction data. As a result, the influence of the EDS detectors 40 and 50 being in the shadow of the sample holder 18a and the sample S can be reduced, and the accuracy of the three-dimensional quantitative analysis can be improved.

For example, in the EDS detector 40, when an X-ray intensity 0.9 times the reference tilt angle θ can be obtained at a tilt angle θ = a °, the detection signal of the EDS detector 40 is set to 1 at a tilt angle θ = a °. Multiply by /0.9 to generate a two-dimensional EDS element map.

5.2. Second Modification Example For example, in the above-described embodiment, the electron microscope 100 includes two EDS detectors 40 and 50 as shown in FIG. 2, but may have one EDS detector.

FIG. 12 is a diagram showing an example of the arrangement of the EDS detector 40. Note that FIG. 12 is a view of the sample holder 18a and the EDS detector 40 as viewed from the optical axis direction (Z direction) of the objective lens 16. FIG. 12 illustrates a case where only the EDS detector 40 is mounted on the electron microscope.

When only the EDS detector 40 mounted on the electron microscope is mounted, as shown in FIG. 12, the EDS detector 40 is arranged in the direction parallel to the tilt axis TA of the sample S. In the illustrated example, the EDS detector 40 is arranged in the + X direction of the sample S. As a result, the influence of the EDS detector 40 being in the shadow of the sample holder 18a and the sample S can be reduced, and the accuracy of the three-dimensional quantitative analysis can be improved.

Although not shown, the EDS detector 40 may be arranged in the + X direction of the sample S, and the EDS detector 50 may be arranged in the + Y direction (or −Y direction) of the sample S.

5.3. Third Modification Example In the above-described embodiment, the case where the analysis processing unit 70 calculates the quantitative value of the element for each voxel constituting the three-dimensional EDS element map has been described. The processing of the analysis processing unit 70 is not limited to this, and for example, the quantitative value of the element may be calculated for each particle extracted from the three-dimensional EDS element map.

Specifically, the analysis processing unit 70 first extracts particles from the three-dimensional EDS element map based on the X-ray intensity. For example, particles can be extracted from a three-dimensional EDS element map using known particle analysis techniques. Next, the analysis processing unit 70 calculates a quantitative value for each extracted particle. For example, the average value of the concentration value (X-ray intensity) in the region corresponding to the extracted particles is calculated for each element, and the quantitative value of each element is obtained from the average value of the concentration values calculated for each element. Then, the analysis processing unit 70 stores the information of the quantitative value (composition ratio) of each element calculated for each particle in the storage device. Thereby, for example, the amount of data for the three-dimensional quantitative analysis can be reduced as compared with the case where the composition ratio information is stored for each voxel.

5.4. Fourth Modification Example In the above-described embodiment, the case of calculating the quantitative value of an element by using the Cliff-Lolimer method has been described in the step of calculating the quantitative value, but the quantitative value of the element is quantified by using another calculation method. You may calculate the value. For example, the zeta factor (ζ factor) method may be used to calculate the quantitative values of the elements.

The zeta factor ζ is a proportional factor between the mass film thickness and the X-ray intensity, and the zeta factor ζ _A of the element A is expressed by the following equation.

However, ρt is the mass film thickness, CA is the composition (weight fraction) of the element _A , and _IA is the X-ray intensity. Since the above relational expression holds for all the elements contained in the sample, it is possible to calculate the quantitative value of the element (three-dimensional quantitative analysis) as in the case of using the Cliff-Lolimer method.

It should be noted that the above-described embodiments and modifications are merely examples, and the present invention is not limited thereto. For example, each embodiment and each modification can be combined as appropriate.

The present invention includes substantially the same configurations as those described in the embodiments (eg, configurations with the same function, method and result, or configurations with the same purpose and effect). The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the present invention includes a configuration having the same action and effect as the configuration described in the embodiment or a configuration capable of achieving the same object. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

2 ... film, 4 ... particles, 6 ... region, 8 ... inside, 10 ... electron source, 12 ... irradiation system lens, 14 ... scanning coil, 16 ... objective lens, 16a ... upper pole, 16b ... lower pole, 18 ... sample Stage, 18a ... sample holder, 18b ... sample positioning device, 20 ... intermediate lens, 22 ... projection lens, 30 ... STEM detector, 40 ... EDS detector, 50 ... EDS detector, 60 ... signal processing unit, 70 ... analysis Processing unit, 80 ... Stage control unit, 100 ... Electron microscope

Claims (6)

It is a quantitative analysis method in an electron microscope.
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample, and
A process of generating a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
The process of calculating the quantitative value of the element for each voxel constituting the three-dimensional element map, and
Quantitative analysis methods, including. In claim 1,
In the step of calculating the quantitative value of the element, a quantitative analysis method for calculating the quantitative value by using the Cliff-Lolimer method or the zeta factor method. In claim 1 or 2,
The electron microscope includes two detectors arranged across the tilt axis of the sample.
In the process of acquiring the two-dimensional element map,
A quantitative analysis method for detecting X-rays from a sample using the detector on the side where the sample is inclined. In claim 1 or 2,
The electron microscope includes a detector and
In the step of acquiring the two-dimensional element map, the X-ray intensity detected by the detector is corrected by using the data showing the relationship between the inclination angle of the sample and the X-ray intensity detected by the detector. , Quantitative analysis method. It is a quantitative analysis method in an electron microscope.
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample, and
A process of generating a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
A step of extracting information on three-dimensional particles based on the X-ray intensity from the three-dimensional element map and calculating a quantitative value for each of the extracted three-dimensional particles.
Quantitative analysis methods, including. With an electron source
An irradiation system lens that irradiates the sample with the electron beam emitted from the electron source, and
A sample stage that holds the sample tiltably and
A detector that detects X-rays generated by irradiating the sample with an electron beam,
An analysis processing unit that performs quantitative analysis based on the X-ray detection result of the detector, and
Including
The analysis processing unit
The process of acquiring a two-dimensional element map for each tilt angle obtained by performing element mapping for each tilt angle while tilting the sample.
A process to generate a three-dimensional element map by three-dimensional reconstruction from a two-dimensional element map for each inclination angle, and
The process of calculating the quantitative value of the element for each voxel constituting the three-dimensional element map, and
Do an electron microscope.

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