Scanning electron microscope and method for displaying absorption edge structure map

Abstract

To observe the two-dimensional spatial distribution of an absorption end structure of a sample over a wide range by using a scanning electron microscope.SOLUTION: A sample is irradiated at each position with an electron beam accelerated by a first acceleration voltage to acquire a spectrum A at each position, and the sample is irradiated at each position with an electron beam accelerated by a second acceleration voltage different from the first acceleration voltage to acquire a spectrum B at each position. The ratio A / B between the spectra at each position is calculated, and a waveform representing the spectrum ratio A / B is created. A value of the spectrum ratio A / B in an energy interest area is extracted from the waveform, and the extracted value is mapped to each point corresponding to each position on the sample to create a spectrum map. The spectrum map is displayed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a scanning electron microscope, and more particularly to a technique for visualizing the two-dimensional spatial distribution of the absorption edge structure of a sample. [Background technology]

[0002] 2. Description of the Related Art There is a known method for analyzing elements in a sample by irradiating the sample with electrons or X-rays, etc., and detecting electromagnetic waves generated from the sample.

[0003] One example is a technique in which a sample is irradiated with an electron beam, a charged particle beam, in an electron microscope, and the characteristic X-rays emitted from the sample are analyzed by spectroscopic analysis. This technique uses the characteristic X-rays to perform elemental analysis, since they have energies specific to the elements that make up the sample. The intensity spectrum of the characteristic X-rays represents the number of X-ray detections for each energy. The elements contained in the sample are identified from the energy of the peaks contained in the intensity spectrum. The content of the elements is also calculated from the area of ​​the peaks contained in the intensity spectrum. In wavelength-dispersive X-ray spectroscopy, the characteristic X-rays are dispersed by a diffraction grating, which generates an intensity spectrum. There is also a technique in which the spatially spreading characteristic X-rays emitted from the diffraction grating are detected together using a CCD camera.

[0004] Patent Document 1 describes an apparatus for identifying elements by calculating the ratio of intensity spectra acquired using two different accelerating voltages in a scanning electron microscope and comparing this ratio with information registered in a database.

[0005] Patent Document 2 describes an apparatus for detecting the distribution state of elements in the depth direction of a sample from X-ray maps acquired using two different accelerating voltages in a scanning electron microscope. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-151045 A [Patent Document 2] Patent No. 6328456 Summary of the Invention [Problem to be solved by the invention]

[0007] By the way, a method is known for analyzing the chemical bonding state of a sample by using TEM-EELS, which is a combination of a transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS). For example, the chemical bonding state can be analyzed by observing the near edge absorption fine structure (ELNES) that appears in the TEM-EELS spectrum. However, the method using TEM requires the sample to be thinned, so it is not possible to observe a wide area of ​​a bulk sample.

[0008] There is a method for observing the fine structure near the absorption edge based on X-ray absorption spectroscopy (XAFS) measured using synchrotron radiation, but this requires large-scale equipment and makes it difficult to observe a wide area of ​​the sample.

[0009] An object of the present invention is to observe the two-dimensional spatial distribution of the absorption edge structure of a sample over a wide area using a scanning electron microscope. [Means for solving the problem]

[0010] One form of the present invention is a scanning electron microscope comprising: an acquisition unit that acquires, for each acceleration voltage, an electron beam excited characteristic X-ray spectrum (hereinafter referred to as an emission spectrum) in the same soft X-ray region of the sample by separately irradiating the same region of the sample with an electron beam at two different acceleration voltages; a calculation unit that calculates a ratio of the emission spectra acquired by irradiating the electron beam at the two different acceleration voltages; and a display processing unit that extracts, from the calculated ratio, a ratio in an energy region of interest corresponding to the energy of the absorption edge of each element, and displays the extracted ratio on a display unit as a spectral map.

[0011] The above-mentioned scanning electron microscope may further include a memory unit that stores energy values ​​of X-ray absorption edges of elements, and when an energy value stored in the memory unit is included in an energy band of the calculated ratio, the display processing unit may define the energy value as the energy region of interest, extract a ratio at the energy value as a ratio in the energy region of interest, and display the extracted ratio as the spectral map on the display unit.

[0012] The calculation section may calculate the ratio of the emission spectra by changing the energy band depending on the element.

[0013] The display processing unit may further cause the display unit to display a graph generated by plotting the calculated ratio for each energy.

[0014] One form of the present invention is a method for displaying a map of an absorption edge structure, comprising: separately irradiating the same region of a sample with an electron beam at two different accelerating voltages, obtaining soft X-ray emission spectra in the same region of the sample for each accelerating voltage, calculating a ratio of the emission spectra obtained by irradiating the electron beam at the two different accelerating voltages, extracting from the calculated ratio a ratio in an energy region of interest corresponding to the energy of the absorption edge of each element, and displaying the extracted ratio as a spectral map. Effect of the Invention

[0015] According to the present invention, the two-dimensional spatial distribution of the absorption edge structure of a sample can be observed over a wide range using a scanning electron microscope. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing a scanning electron microscope according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing an analysis unit. [Diagram 3] 4 is a flowchart showing the flow of operations of the scanning electron microscope. [Figure 4]FIG. 1 is a diagram showing an emission spectrum of single element iron. [Diagram 5] FIG. 1 shows an emission spectrum for Fe2SiO4. [Figure 6] FIG. 1 is a diagram showing the spectral ratio for single element iron. [Figure 7] FIG. 1 shows the spectral ratios for Fe2SiO4. [Figure 8] FIG. [Figure 9] FIG. 13 is a diagram for explaining the creation of a spectral map representing a spectral ratio. [Figure 10] FIG. 13 is a diagram for explaining the creation of a spectral map representing a spectral ratio. [Figure 11] FIG. 13 is a diagram showing a specific example of a spectrum map. [Figure 12] 1 is a graph showing the value of the spectral ratio A / B for each component. [Figure 13] FIG. 1 is a diagram showing the spectral ratio for a single element Mn. [Figure 14] FIG. 2 shows the spectral ratios for MnO2. [Figure 15] FIG. 1 shows the spectral ratios for Mn2SiO4. [Figure 16] FIG. 1 shows the spectral ratios for MnCO3. [Figure 17] FIG. 1 shows the spectral ratios for (MnCa)3SiO9. [Figure 18] FIG. 1 shows the spectral ratios for (MnFe)2O3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A scanning electron microscope 10 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing a scanning electron microscope 10 according to an embodiment.

[0018] The scanning electron microscope 10 includes a wavelength dispersive X-ray spectrometer 12, an electron optical system 20, a sample stage 30, and an information processing device 60. The wavelength dispersive X-ray spectrometer 12 includes an X-ray focusing mirror (not shown), a diffraction grating 40 having irregularly spaced grooves, and a detection device 50.

[0019] The electron optical system 20 is a system for generating an electron probe. The electron optical system 20 includes an electron beam source 22 such as an electron gun, which generates an electron beam 24. In the electron beam source 22, electrons having a set energy are generated by changing an acceleration voltage that accelerates electrons. Although not shown, the electron optical system 20 further includes a slit, a focusing lens, a scanning coil, an objective lens, and the like. The electron optical system 20 performs focusing, scanning, and the like of the electron beam 24.

[0020] The sample stage 30 is a component for mounting the sample 100. When the electron beam 24 is irradiated onto the sample 100, characteristic X-rays 32 are generated in the sample 100. The characteristic X-rays 32 are X-rays generated in the process of electrons on outer orbitals (shallow orbitals) transitioning to inner orbitals when electrons on inner orbitals (deep orbitals) in atoms constituting the sample 100 are repelled by the electron beam 24. In particular, soft X-rays are useful signals for analyzing the composition, bonding state, crystal structure, and the like of a sample. The characteristic X-rays 32 emitted from the sample 100 are collected by an X-ray collecting mirror (not shown) and directed toward the diffraction grating 40. In this embodiment, soft X-rays are detected as the characteristic X-rays 32. The soft X-rays are, for example, X-rays having an energy of 1 keV or less, 500 eV or less, or 100 eV or less.

[0021] The diffraction grating 40 is an optical element (or a spectroscopic element) that disperses the characteristic X-rays 32 for each wavelength. That is, due to the diffraction phenomenon, the exit angle β with respect to the incident angle α has wavelength dependency, and each characteristic X-ray component is emitted at an angle according to its wavelength. In this way, the incident characteristic X-rays 32 are decomposed into components for each wavelength, that is, into components for each energy.

[0022] The detection device 50 includes a CCD detector 52 and a CCD controller 54. The CCD detector 52 has a two-dimensional light receiving element array that receives X-rays and converts them into electrical signals. By providing the CCD detector 52 that extends two-dimensionally, it is possible to simultaneously or collectively receive characteristic X-rays over a certain wavelength range (i.e., a certain energy range). For example, the CCD detector 52 has a first axis corresponding to the wavelength dispersion direction and a second axis perpendicular to the wavelength dispersion direction. For each wavelength, a plurality of detection signals are integrated in parallel to the second axis. The CCD controller 54 controls the operation of the CCD detector 52 and counts the electrical signals output from the CCD detector 52 for each light receiving element. For each wavelength, the count number is obtained for a set time (e.g., 1 second, 5 seconds, 10 seconds, etc.). This allows the emission spectrum of the characteristic X-rays 32 to be obtained.

[0023] The information processing device 60 has hardware and software. The hardware includes a CPU (Central Processing Unit) and a memory, etc. The software includes an OS (Operating System) and an application program, etc. The information processing device 60 may be configured by a PC (Personal Computer). The information processing device 60 may be configured by a single device or by multiple devices.

[0024] The information processing device 60 includes a control device 62 and an analysis device 64. The control device 62 controls the electron optical system 20 and the detection device 50. The analysis device 64 is a device that processes and analyzes a plurality of emission spectra (more precisely, a plurality of emission spectrum data) output in chronological order from the CCD controller 54.

[0025] In the measurement process, the sample 100 is continuously irradiated with the electron beam 24 while the characteristic X-rays 32 emitted from the sample 100 are continuously detected, and an emission spectrum is generated.

[0026] The scanning electron microscope 10 can measure the emission spectra of a plurality of different characteristic X-rays 32 of extremely low energy. For example, when the sample 100 is a transition metal compound, it is possible to simultaneously measure the emission spectrum of Lα rays and Lβ rays, which reflect the distribution of outer shell electrons, and the emission spectrum of Ll rays and Lnx rays, which reflect the distribution of inner shell electrons. In addition, the energy position can also be measured. This allows chemical bond information to be measured with high accuracy.

[0027] The analysis device 64 will now be described with reference to Fig. 2. Fig. 2 is a block diagram showing the analysis device 64.

[0028] The analysis device 64 includes an acquisition unit 70 , a calculation unit 72 , a display processing unit 74 , a display 76 , an operation device 82 , and a storage device 80 .

[0029] The acquisition unit 70 acquires the emission spectrum output from the CCD controller 54. The acquisition unit 70 creates a waveform (e.g., a line graph) representing each emission spectrum. The waveform is a waveform showing the intensity series that constitutes the emission spectrum. In the waveform representing the emission spectrum, the horizontal axis indicates energy, and the vertical axis indicates intensity.

[0030] The acquisition unit 70 irradiates the same region of the sample 100 with the electron beam 24 at two different acceleration voltages, thereby acquiring a soft X-ray emission spectrum in the same region of the sample 100.

[0031] Specifically, under the control of the control device 62, the electron beam source 22 generates the electron beam 24 by accelerating electrons at a first acceleration voltage. The electron beam 24 accelerated at the first acceleration voltage is irradiated onto the sample 100, and the characteristic X-rays 32 generated from the sample 100 are detected by the detection device 50. As a result, an emission spectrum obtained when the electrons are accelerated at the first acceleration voltage is obtained, and the acquisition unit 70 acquires this emission spectrum. Hereinafter, the emission spectrum obtained when the electrons are accelerated at the first acceleration voltage is referred to as "spectrum A."

[0032] Moreover, under the control of the control device 62, the electron beam source 22 generates the electron beam 24 by accelerating electrons at a second acceleration voltage different from the first acceleration voltage. The electron beam 24 accelerated at the second acceleration voltage is irradiated onto the sample 100, and the characteristic X-rays 32 generated from the sample 100 are detected by the detection device 50. As a result, an emission spectrum obtained when the electrons are accelerated at the second acceleration voltage is obtained, and the acquisition unit 70 acquires this emission spectrum. Hereinafter, the emission spectrum obtained when the electrons are accelerated at the second acceleration voltage is referred to as "spectrum B."

[0033] The control device 62 causes the electron beam 24 accelerated at a first acceleration voltage and the electron beam 24 accelerated at a second acceleration voltage to be irradiated from the electron beam source 22 separately to the same position on the sample 100. As a result, spectra A and B are obtained separately from the same position, and the acquisition unit 70 acquires spectra A and B at the same position.

[0034] Furthermore, the control device 62 changes the position on the sample 100 where the electron beam 24 is irradiated, and causes the electron beam 24 accelerated at the first acceleration voltage and the electron beam 24 accelerated at the second acceleration voltage to be irradiated from the electron beam source 22 to the sample 100 for each position separately. As a result, spectra A and B are obtained separately for each position, and the acquisition unit 70 acquires spectra A and B at each position.

[0035] The calculation unit 72 calculates the ratio of two emission spectra acquired at two different acceleration voltages, specifically, the ratio of the intensities of the two emission spectra. Hereinafter, the ratio of the two emission spectra will be referred to as the "spectral ratio." To explain the process of the calculation unit 72 in detail, the calculation unit 72 calculates the ratio of spectrum A and spectrum B obtained from the same position on the sample 100. The calculation unit 72 obtains the spectral ratio at each position by calculating the ratio of spectrum A and spectrum B at each position.

[0036] The calculation unit 72 generates a waveform representing a spectral ratio (ratio spectrum) by calculating the ratio between a waveform representing spectrum A and a waveform representing spectrum B. In the waveform representing the spectral ratio, the horizontal axis represents energy, and the vertical axis represents the spectral ratio.

[0037] The display processor 74 creates a spectral map on which the spectral ratios are mapped, and displays the spectral map on the display 76. To explain the processing of the display processor 74 in detail, the display processor 74 extracts the spectral ratios in the energy region of interest (ROI) from the waveform representing the spectral ratios at each position on the sample 100, and maps the extracted spectral ratios to points corresponding to the positions on the sample 100 to create a spectral map representing the spectral ratios at each position. In this way, a spectral map in the energy region of interest is created. The energy region of interest is an energy band corresponding to the absorption edge, or an energy band near the absorption edge. The position and width of the energy region of interest on the energy are, for example, determined in advance. The position and width of the energy region of interest may be changed according to the elements constituting the sample 100, or may be changed by the user. In addition, the display processor 74 changes the position of the energy region of interest to extract the spectral ratios, and creates a spectral map for each energy region of interest.

[0038] The storage device 80 is a storage device such as a hard disk drive or a memory. The energy value corresponding to the X-ray absorption edge of each element (i.e., the position of the absorption edge in the energy band) is measured or calculated in advance and stored in advance as a database in the storage device 80. For example, the energy values ​​corresponding to the X-ray absorption edges of metals, oxides, sulfides, compounds, semiconductors, etc. are stored in the storage device 80.

[0039] The operation device 82 is configured with a keyboard and a pointing device (for example, a mouse, a touch panel, a touch pad, etc.). Information is input to the information processing device 60 by the user operating the operation device 82.

[0040] The flow of operations of the scanning electron microscope 10 will be described below with reference to Fig. 3. Fig. 3 shows a flowchart showing the flow of operations.

[0041] First, the control device 62 irradiates each position on the sample 100 with the electron beam 24 accelerated at a first acceleration voltage from the electron beam source 22, and the acquisition unit 70 acquires a spectrum A at each position detected by the irradiation of the electron beam 24 (S01). For example, when the sample 100 is a transition metal, the first acceleration voltage is 1 to 3 kV, and an L-line spectrum A is acquired. When the sample 100 is a rare earth element, the first acceleration voltage is 1 to 3 kV, and an M-line spectrum A is acquired.

[0042] Next, the control device 62 irradiates each position on the sample 100 with the electron beam 24 accelerated at the second acceleration voltage from the electron beam source 22, and the acquisition unit 70 acquires a spectrum B at each position detected by the irradiation of the electron beam 24 (S02). The electron beam 24 accelerated at the second acceleration voltage is irradiated at the same position as the position irradiated with the electron beam 24 accelerated at the first acceleration voltage. For example, when the sample 100 is a transition metal, the second acceleration voltage is 5 to 15 kV, and an L-line spectrum B is acquired. When the sample 100 is a rare earth element, the second acceleration voltage is 5 to 15 kV, and an M-line spectrum B is acquired.

[0043] Next, the calculation unit 72 calculates the ratio between spectrum A and spectrum B at each position (S03). For example, the calculation unit 72 obtains the spectral ratio A / B at each position by dividing the intensity of spectrum A at each position by the intensity of spectrum B. As a result, a waveform representing the spectral ratio A / B at each position is created.

[0044] Next, the display processing unit 74 extracts the value of the spectral ratio A / B in the energy region of interest from the waveform representing the spectral ratio A / B at each position (S04), and creates a spectral map representing the spectral ratio A / B at each position by mapping the extracted value of the spectral ratio A / B to points corresponding to the positions on the sample 100 (S05). In this way, a spectral map in the energy region of interest is created.

[0045] The display processor 74 changes the position of the energy region of interest on the energy, extracts the value of the spectral ratio A / B in the energy region of interest from the waveform representing the spectral ratio A / B at each position, and creates a spectral map in the energy region of interest by mapping the extracted value of the spectral ratio A / B. The display processor 74 changes the position of the energy region of interest and creates a spectral map in each energy region of interest.

[0046] The display processing unit 74 causes the display 76 to display a spectral map in each energy region of interest (S06).

[0047] When the energy band of the waveform representing the spectral ratio A / B includes an energy value corresponding to an absorption edge stored in the storage device 80 constituting the database, the display processing unit 74 may define that energy as an energy region of interest, extract the value of the spectral ratio A / B corresponding to that energy from the waveform representing the spectral ratio A / B, and create a spectral map by mapping the extracted value of the spectral ratio A / B.

[0048] The embodiment will be described in more detail below with specific examples.

[0049] It is known that the higher the accelerating voltage, the more the waveform of the emission spectrum changes due to self-absorption of the sample 100. In other words, the effect of absorption is small at low accelerating voltages, and large at high accelerating voltages. By calculating the ratio between the emission spectrum obtained by irradiating the sample 100 with the electron beam 24 at a low accelerating voltage and the emission spectrum obtained by irradiating the sample 100 with the electron beam 24 at a high accelerating voltage, it is possible to observe the absorption edge specific to the compound.

[0050] For example, for elemental iron, the higher the accelerating voltage, the larger the Lα / Lβ value becomes, but for Fe2SiO4 (fayalite), the Lα / Lβ value becomes smaller.

[0051] The intensity of the emission spectrum for elemental iron is shown in Figure 4. In Figure 4, the horizontal axis represents energy, and the vertical axis represents intensity.

[0052] Figure 4 shows the emission spectra at accelerating voltages of 2, 3, 4, and 5 kV. The intensity of the Lα line does not change, or changes very little, when the accelerating voltage is changed, but the intensity of the Lβ line decreases as the accelerating voltage increases. Therefore, the ratio of the intensity of the Lα line to the intensity of the Lβ line, Lα / Lβ, increases as the accelerating voltage is increased.

[0053] The intensity of the emission spectrum for Fe2SiO4 is shown in Figure 5. In Figure 5, the horizontal axis represents energy, and the vertical axis represents intensity.

[0054] Figure 5 shows the emission spectra at accelerating voltages of 2, 3, 4, and 5 kV. The intensity of the Lα line does not change, or changes very little, when the accelerating voltage is changed, but the intensity of the Lβ line increases with increasing accelerating voltage. Therefore, the ratio Lα / Lβ decreases with increasing accelerating voltage. The main causes of this phenomenon are absorption effects and changes in the L3 and L2 absorption edges due to compounds.

[0055] FIG. 6 shows a waveform of the spectral ratio for the single element iron. In FIG. 6, the horizontal axis indicates energy, and the vertical axis indicates the spectral ratio. Here, as an example, the first acceleration voltage, which is a low acceleration voltage, is 2 kV, and the second acceleration voltage, which is a high acceleration voltage, is 5 kV. Spectrum A is acquired by the first acceleration voltage of 2 kV, and spectrum B is acquired by the second acceleration voltage of 5 kV. The spectral ratio A / B, which is the ratio between the intensity of spectrum A and the intensity of spectrum B, is calculated, and a waveform representing the spectral ratio A / B is created. The spectral ratio indicated by the vertical axis is the spectral ratio A / B. FIG. 6 shows the waveform of the spectral ratio A / B in the energy band (680 to 740 eV) including the energy of the Lα line.

[0056] A ratio spectrum reflecting the absorption edge L3, which is almost equivalent to the absorption spectrum obtained with synchrotron radiation, is obtained. The energy corresponding to the peak of the waveform of the spectral ratio A / B is the energy reflecting the absorption edge L3. For example, the value of that energy is 708.5 eV.

[0057] In Fig. 7, the waveform of the spectral ratio for Fe2SiO4 (fayalite) is shown, as well as for the iron element. The energy value corresponding to the peak of the waveform of the spectral ratio A / B is 707.8 eV. In other words, the energy reflecting the absorption edge L3 is 707.8 eV.

[0058] In the embodiment, a spectral map is created by mapping the spectral ratios based on the above relationship. The creation of the spectral map will be described below.

[0059] A sample 100 is shown in Fig. 8. Fig. 8 is a diagram of the sample 100 as viewed from the electron optical system 20 side. The X-axis and Y-axis are mutually perpendicular axes, and form a two-dimensional plane. Each position on the surface of the sample 100 is defined by the X-axis and the Y-axis.

[0060] The control device 62 irradiates the electron beam 24 accelerated at a first acceleration voltage from the electron beam source 22 to each position (positions P1, P2, P3, . . ., Pn(Xm, Xn), . . .) on the sample 100, and the acquisition unit 70 acquires the spectrum A at each position. That is, the control device 62 irradiates the electron beam 24 onto the surface of the sample 100 while changing the position to which the electron beam 24 is irradiated, and the acquisition unit 70 acquires the spectrum A at each position.

[0061] Similarly, the control device 62 irradiates the electron beam 24 accelerated at the second acceleration voltage from the electron beam source 22 to each position on the sample 100 (positions P1, P2, P3, . . ., Pn(Xm, Xn), . . .), and the acquisition unit 70 acquires the spectrum B at each position. That is, the control device 62 irradiates the electron beam 24 onto the surface of the sample 100 while changing the position to which the electron beam 24 is irradiated, and the acquisition unit 70 acquires the spectrum B at each position.

[0062] When spectra A and B are acquired at each position, the calculation section 72 calculates a spectral ratio A / B, which is the ratio between the intensity of spectrum A and the intensity of spectrum B at each position.

[0063] Hereinafter, the creation of a spectral map representing the spectral ratio A / B will be described with reference to Figures 9 and 10. Figures 9 and 10 show the spectral ratio and the spectral map.

[0064] 9 and 10 show the spectral ratio A / B at the position Pn(Xm, Yn).

[0065] The display processor 74 extracts the value of the spectral ratio A / B corresponding to the energy region of interest (ROI) from the waveform representing the spectral ratio A / B at the position Pn(Xm, Yn). In the example shown in FIG. 9, the energy region of interest is 705 to 706 eV, and the display processor 74 extracts the value of the spectral ratio A / B at 705 to 706 eV from the waveform representing the spectral ratio A / B. For example, the display processor 74 extracts the value of the spectral ratio A / B corresponding to the center position of 705 to 706 eV, or the average value of the spectral ratio A / B at 705 to 706 eV, as the value of the spectral ratio A / B corresponding to 705 to 706 eV. The display processor 74 extracts the value of the spectral ratio A / B in the energy region of interest in the same manner in the following processes. The display processor 74 maps the extracted value Sn(Xm, Yn) of the spectral ratio A / B to a point corresponding to the position Pn(Xm, Yn).

[0066] The display processing unit 74 extracts values ​​S1, S2, S3, . . ., Sn(Xm,Yn), . . of the spectral ratio A / B in the ROI of 705 to 706 eV from the waveforms representing the spectral ratio A / B at each of the positions P1, P2, P3, . . ., Pn(Xm,Yn), . ., and maps these values ​​to points corresponding to each position on the sample 100. In this way, a spectral map representing the spectral ratio A / B at each position in the range of 705 to 706 eV is created.

[0067] The spectral map 200 shown in FIG. 9 is a spectral map in which the ROI is 705 to 706 eV.

[0068] The display processor 74 creates a spectral map by changing the position of the energy region of interest (ROI). The ROI shown in FIG. 10 is 706 to 707 eV. The spectral map 210 shown in FIG. 10 is a spectral map in which the ROI is 706 to 707 eV. That is, the display processor 74 extracts the values ​​S1, S2, S3, . . . , Sn(Xm, Yn), . . . of the spectral ratio A / B at each position in the range of 706 to 707 eV, and maps these values ​​to points corresponding to each position on the sample 100. In this way, the spectral map 210 is created.

[0069] As described above, the display processing unit 74 changes the position of the energy region of interest and creates a spectrum map for each energy region of interest.

[0070] In the examples shown in FIGS. 9 and 10, the width of the energy region of interest is 1 eV, but the display processing unit 74 may change the width of the energy region of interest depending on the elements contained in the sample 100.

[0071] A specific example will be described below. A compound containing Fe·Si metal, Fe2SiO4, Fe3O4, and Fe2O3 is used as the sample 100. The first acceleration voltage is 2.5 kV, and the second acceleration voltage is 10 kV. That is, a spectrum A is acquired by a first acceleration voltage of 2.5 kV, and a spectrum B is acquired by a second acceleration voltage of 10 kV, and the spectrum ratio A / B is calculated. The energy range is 705 to 710 eV, and the width of the energy region of interest (ROI) is 1 eV. Under these conditions, a spectrum map is created. FIG. 11 shows the spectrum maps for Fe·Si metal and Fe2SiO4 created under these conditions.

[0072] Each of the spectral maps shown in Fig. 11 is a map created based on the ratio spectrum of Fe. That is, the calculation unit 72 calculates the spectral ratio A / B, which is the ratio between the spectrum A of Fe acquired at a first acceleration voltage of 2.5 kV and the spectrum B of Fe acquired at a second acceleration voltage of 10 kV, for each position on the sample 100. The display processing unit 74 extracts the value of the spectral ratio A / B from the waveform of the spectral ratio A / B for each energy region of interest (1 eV) within the range of 705 to 710 eV corresponding to the energy bands of the La line and Lβ line of Fe, and creates a spectral map by mapping it to a point corresponding to the position on the sample 100.

[0073] FIG. 11 shows spectral maps at various positions within regions 300A and 300B of sample 100.

[0074] Spectral map 302A is a spectral map that represents a spectral ratio A / B corresponding to an energy region of interest of 705 to 706 eV at each position within region 300A.

[0075] Spectral map 302B is a spectral map that represents a spectral ratio A / B corresponding to an energy region of interest of 705 to 706 eV at each position within region 300B.

[0076] Spectral map 304A is a spectral map showing a spectral ratio A / B corresponding to an energy region of interest of 706 to 707 eV at each position within region 300A.

[0077] Spectral map 304B is a spectral map that represents a spectral ratio A / B corresponding to the energy region of interest of 706 to 707 eV at each position within region 300B.

[0078] Spectral map 306A is a spectral map representing a spectral ratio A / B corresponding to an energy region of interest of 707-708 eV at each position within region 300A.

[0079] Spectral map 306B is a spectral map representing the spectral ratio A / B corresponding to the energy region of interest of 707-708 eV at each position within region 300B.

[0080] Spectral map 308A is a spectral map representing a spectral ratio A / B corresponding to an energy region of interest of 708-709 eV at each position within region 300A.

[0081] Spectral map 308B is a spectral map that represents the spectral ratio A / B corresponding to the energy region of interest of 708 to 709 eV at each position within region 300B.

[0082] Spectral map 310A is a spectral map that represents a spectral ratio A / B corresponding to an energy region of interest of 709 to 710 eV at each position within region 300A.

[0083] Spectral map 310B is a spectral map that represents a spectral ratio A / B corresponding to the energy region of interest of 709 to 710 eV at each position within region 300B.

[0084] Spectral map 312A is a spectral map representing a spectral ratio A / B corresponding to an energy region of interest of 710 to 711 eV at each position within region 300A.

[0085] Spectral map 312B is a spectral map representing a spectral ratio A / B corresponding to the energy region of interest of 710 to 711 eV at each position within region 300B.

[0086] The display processing unit 74 assigns a color to the spectrum map according to the magnitude of the value of the spectral ratio A / B. For example, within the range of red to blue, a color (e.g., red, yellow, green, blue, etc.) according to the magnitude of the value is assigned to the spectrum map. Red corresponds to a large value, and blue corresponds to a small value, and a color is assigned within the range of red to blue according to the magnitude of the value. The larger the value of the spectral ratio A / B, the closer to red the color is assigned.

[0087] The display processing unit 74 causes the display 76 to display the spectral maps 302A to 312A and 302B to 312B.

[0088] The energy band in which the peak of the spectral ratio A / B is measured is an energy band that includes an energy value corresponding to the absorption edge. By referring to the spectral map in which the spectral ratio A / B is mapped, the user can grasp the energy band in which a large value of the spectral ratio A / B is measured and the energy band in which the peak of the spectral ratio A / B is measured. According to the embodiment, it is possible to display the absorption edge obtained by synchrotron radiation as a spectral map.

[0089] When the energy band (e.g., 705 to 710 eV) in which the spectral ratio A / B is measured includes an energy value stored in the storage device 80 (i.e., an energy value registered in a database in which energy values ​​corresponding to the absorption edges of each element are registered), the display processing unit 74 may define the energy value as an energy region of interest (ROI) and extract the value of the spectral ratio A / B at the energy value as the value of the spectral ratio A / B in the energy ROI. The display processing unit 74 may create a spectral map by mapping the extracted values ​​of the spectral ratio A / B, and display the spectral map on the display 76.

[0090] The display processing unit 74 may refer to a database in which the energy values ​​corresponding to the absorption edges of the respective elements are registered, and identify the components of the respective regions on the spectrum maps 302A to 312A and 302B to 312B.

[0091] For example, a peak (0.533) of the spectral ratio A / B exists in the energy band of 708 to 709 eV. The energy band (708 to 709 eV) in which this peak is measured is an energy band including an energy value corresponding to the Fe·Si metal FeL absorption edge. The component having the peak of the spectral ratio A / B in the energy band of 708 to 709 eV is Fe·Si metal. In the database, 708 to 709 eV is registered in advance as an energy band including an energy value corresponding to the Fe·Si FeL absorption edge. The display processing unit 74 refers to the database and specifies the region in which the peak of the spectral ratio A / B exists in the energy band of 708 to 709 eV as a region made of Fe·Si.

[0092] Also, a peak (0.3095) of the spectral ratio A / B exists in the energy band of 707 to 708 eV. The energy band (707 to 708 eV) in which this peak is measured is an energy band including an energy value corresponding to the FeL absorption edge of Fe2SiO4. The component having the peak of the spectral ratio A / B in the energy band of 707 to 708 eV is Fe2SiO4. In the database, 707 to 708 eV is registered in advance as an energy band including an energy value corresponding to the FeL absorption edge of Fe2SiO4. The display processing unit 74 refers to the database and specifies the region in which the peak of the spectral ratio A / B exists in the energy band of 707 to 708 eV as a region made of Fe2SiO4.

[0093] Here, Fe·Si and Fe2SiO4 have been described as an example, but for Fe2O3 and Fe3O4, a region made of Fe2O3 and a region made of Fe3O4 are identified in the same manner. In this manner, in sample 100, a region made of Fe·Si metal component, a region made of Fe2SiO4 component, a region made of Fe2O3, and a region made of Fe3O4 are identified.

[0094] The display processor 74 may change the color for each component in the spectrum map and color the areas corresponding to each component. Specifically, the display processor 74 changes the color for each component in the spectrum map and colors the areas corresponding to the Fe·Si metal component, the Fe2SiO4 component, the Fe2O3 component, and the Fe3O4 component. For example, the display processor 74 displays the area corresponding to the Fe·Si metal component in red, the area corresponding to the Fe2SiO4 component in blue, the area corresponding to the Fe2O3 component in yellow, and the area corresponding to the Fe3O4 component in green. By displaying the color for each component in a different way in this way, the user can recognize each component by the difference in color. As another example, when each spectrum map is displayed in grayscale, the area corresponding to each component may be displayed with a shade according to each component.

[0095] Fig. 12 shows the spectral ratio A / B for each component constituting the sample 100. Fig. 12 is a graph showing the value of the spectral ratio A / B for each component. In Fig. 12, the horizontal axis represents energy, and the vertical axis represents the spectral ratio.

[0096] The display processing unit 74 extracts the value of the spectral ratio A / B for each energy at a certain position (for example, an arbitrary position in the region) in the sample 100 made of Fe·Si metal components from the spectral ratio A / B calculated by the calculation unit 72, and plots the extracted value of the spectral ratio A / B for each energy. For example, the display processing unit 74 extracts and plots the value of the spectral ratio A / B for each energy region of interest (ROI). In this example, the energy range is 705 to 711 eV, and the energy region of interest is 1 eV. The display processing unit 74 extracts the value of the spectral ratio A / B for each 1 eV within the range of 705 to 711 eV, and plots the extracted value of each spectrum A / B. A waveform 320 is a waveform obtained by the plot, and is a waveform showing the change in the spectral ratio A / B with respect to energy for Fe·Si metal.

[0097] For Fe2SiO4, Fe2O3, and Fe3O4, waveforms are created by plotting the spectral ratio A / B values ​​every 1 eV, just like for Fe·Si metal.

[0098] Waveform 322 is a waveform showing the change in the spectral ratio A / B versus energy for Fe2O3. Waveform 324 is a waveform showing the change in the spectral ratio A / B versus energy for Fe3O4. Waveform 326 is a waveform showing the change in the spectral ratio A / B versus energy for Fe2SiO4.

[0099] At a certain position in the region made of Fe2O3 (for example, an arbitrary position in the region), the value of the spectral ratio A / B is extracted in increments of 1 eV within the range of 705 to 711 eV, and the extracted value for 1 eV is plotted to create a waveform 322. The same is true for waveforms 324 and 326.

[0100] With reference to waveforms 320 to 326, the spectral ratio A / B of a metal (e.g., Fe·Si metal) is higher than the spectral ratio A / B of an oxide (e.g., Fe2O3, Fe3O4, Fe2SiO4). In other words, the spectral ratio A / B of a metal tends to be higher, while the spectral ratio A / B of an oxide tends to be lower.

[0101] Also, for Fe·Si metal, Fe2O3, and Fe3O4, the energy at which the peak of the spectral ratio A / B is measured (i.e., the energy corresponding to the absorption edge) is around 710 eV, but for Fe2SiO4, the energy at which the peak of the spectral ratio A / B is measured (i.e., the energy corresponding to the absorption edge) is around 708 eV. In this way, by graphing the spectral ratio A / B, it is possible to clearly display the difference in energy corresponding to the absorption edge.

[0102] Also, comparing the waveform 322 of Fe2O3 with the waveform 324 of Fe3O4, it can be seen that the slope to the peak top of the waveform 322 of Fe2O3 is higher than the slope of the waveform 324 of Fe3O4, which means that Fe2O3 is more affected by absorption compared to Fe3O4.

[0103] As described above, by creating a spectral map according to the embodiment, it becomes possible to observe a detailed absorption structure.

[0104] In the above-mentioned embodiment, a two-dimensional spectral map is created, but the spectral ratio A / B may be measured and displayed at one or more positions, or the spectral ratio A / B may be measured and displayed at each position on a line or curve. Point analysis or line analysis can shorten the analysis time.

[0105] In the above-described embodiment, the sample 100 containing Fe is used, but the sample 100 containing elements other than Fe, such as Ni, Mn, or Co, may be used and measured. For example, the valence change of Ni, Mn, and Co used as a positive electrode material of a battery due to charging and discharging may be observed. The oxidation state of steel and non-ferrous metals may be observed.

[0106] Hereinafter, the measurement results of the sample 100 containing manganese (Mn) will be described with reference to Fig. 13 to Fig. 18. Waveforms of the spectral ratio A / B relating to Mn are shown in Fig. 13 to Fig. 18. In Fig. 13 to Fig. 18, the horizontal axis indicates energy, and the vertical axis indicates the spectral ratio.

[0107] Here, as an example, the first acceleration voltage, which is a low acceleration voltage, is 2 kV, and the second acceleration voltage, which is a high acceleration voltage, is 5 kV. Spectrum A is acquired by the first acceleration voltage of 2 kV, and spectrum B is acquired by the second acceleration voltage of 5 kV. A spectral ratio A / B, which is the ratio between the intensity of spectrum A and the intensity of spectrum B, is calculated, and a waveform representing the spectral ratio A / B is created. The spectral ratio indicated by the vertical axis is the spectral ratio A / B. In addition, the spectral ratio A / B is created at 600 to 680 eV.

[0108] Figure 13 shows the waveform of the spectral ratio for a single element Mn. The energy corresponding to the peak of the waveform of the spectral ratio A / B is the energy reflecting the absorption edge. For example, the value of the energy is 641.62 eV or 652.445 eV.

[0109] The spectral ratio trace for MnO2 is shown in Figure 14. The energy value corresponding to the peak of the trace is 642.89 eV.

[0110] The spectral ratio trace for Mn2SiO4 is shown in Figure 15. The energy value corresponding to the peak of the trace is 640.984 eV or 651.8 eV.

[0111] The spectral ratio trace for MnCO3 is shown in Figure 16. The energy value corresponding to the peak of the trace is 640.34 eV.

[0112] The spectral ratio trace for (MnCa)3SiO9 is shown in Figure 17. The energy value corresponding to the peak of the trace is 641.62 eV.

[0113] The spectral ratio trace for (MnFe)2O3 is shown in Figure 18. The energy values ​​corresponding to the peaks of the trace are 642.89 eV or 660.89 eV.

[0114] An electron beam 24 accelerated by an acceleration voltage of 2 kV and an electron beam 24 accelerated by an acceleration voltage of 5 kV are separately irradiated to each position on the sample 100, and the spectral ratio A / B is calculated at each position on the sample 100. Next, as described with reference to Figures 9 and 10, the value of the spectral ratio A / B for each energy region of interest is extracted from the waveform of each spectral ratio, and the extracted value of the spectral ratio A / B is mapped to a point corresponding to the position on the sample 100, thereby creating a spectral map representing the spectral ratio A / B, similar to the spectral map shown in Figure 11.

[0115] The energy band including the energy value corresponding to the peak of the spectral ratio A / B differs depending on the components constituting the sample 100. For example, in the sample 100 including the Fe component, as shown in FIG. 6 and FIG. 7, the range of 680 to 740 eV is the energy band including the energy value corresponding to the peak of the spectral ratio A / B. On the other hand, in the sample 100 including the Mn component, as shown in FIG. 13 to FIG. 18, the range of 600 to 680 eV is the energy band including the energy value corresponding to the peak of the spectral ratio A / B. In this way, the energy band including the energy value corresponding to the peak of the spectral ratio A / B is different between Fe and Mn, so the calculation unit 72 calculates the spectral ratio A / B by changing the energy band according to the element. Specifically, the calculation unit 72 calculates the spectral ratio A / B for the sample 100 including the Fe component in the range of 680 to 740 eV, and calculates the spectral ratio A / B for the sample 100 including the Mn component in the range of 600 to 680 eV.

[0116] According to the above-described embodiment, the two-dimensional spatial distribution of the absorption edge structure of a sample can be observed over a wide range by using the scanning electron microscope 10 without using a TEM or an apparatus using synchrotron radiation.

[0117] For example, since a TEM is not used, it is possible to observe the absorption edge structure over a wide area of ​​a bulk sample. For example, it is possible to observe the two-dimensional spatial distribution of the absorption edge structure of a bulk sample with a maximum size of 10 cm square. In addition, since there is no need to thin the sample, this saves the operator the trouble of doing so. In addition, it is possible to observe the two-dimensional spatial distribution of the absorption edge structure of a sample over a wide area without using large-scale equipment such as equipment using synchrotron radiation.

[0118] Moreover, according to the embodiment, the following becomes possible. Valence electron information in the low energy band can be analyzed together with the X-ray spectrum that contributes to chemical bonds. The acceleration voltage of the electron beam can be changed between several hundreds of volts and a high acceleration voltage such as 20 kV to perform analysis in the same field of view, and the X-ray absorption effect can be accurately observed for each structure of the sample. In addition, it is possible to obtain a ratio spectrum corresponding to the absorption edge or a ratio spectrum in the vicinity thereof, and it is possible to obtain measurement results similar to those obtained using synchrotron radiation. Note that by outputting a large amount of data, a large amount of data (e.g., several thousand or more pieces of data) may be stored for each pixel (e.g., for each position irradiated with the electron beam 24) in the spectrum map. [Explanation of symbols]

[0119] 10 scanning electron microscope, 12 wavelength dispersive X-ray spectrometer, 20 electron optical system, 50 detection device, 60 information processing device, 62 control device, 64 analysis device, 70 acquisition unit, 72 calculation unit, 74 display processing unit, 76 display.

Claims

1. an acquisition unit that acquires a spectrum of soft X-rays in the same region of a sample for each acceleration voltage by separately irradiating the same region of the sample with an electron beam using two different acceleration voltages; A calculation unit that calculates a ratio of spectra acquired by irradiation with electron beams at the two different acceleration voltages; a display processing unit that extracts a ratio in an energy region of interest corresponding to an energy of an absorption edge of each element from the calculated ratio and displays the extracted ratio on a display unit as a spectrum map; A scanning electron microscope comprising:

2. 2. The scanning electron microscope according to claim 1, The device further includes a memory unit that stores an energy value of an X-ray absorption edge of the element, When an energy value stored in the storage unit is included in an energy band of the calculated ratio, the display processing unit defines the energy value as the energy region of interest, extracts a ratio in the energy value as a ratio in the energy region of interest, and displays the extracted ratio as the spectral map on the display unit.

1. A scanning electron microscope comprising:

3. 3. The scanning electron microscope according to claim 1, The calculation unit calculates a ratio of the spectra by changing an energy band depending on the element.

1. A scanning electron microscope comprising:

4. The scanning electron microscope according to any one of claims 1 to 3, The display processing unit further causes the display unit to display a graph generated by plotting the calculated ratio for each energy.

1. A scanning electron microscope comprising:

5. irradiating the same region of the sample with the electron beam at two different acceleration voltages, and acquiring a spectrum of the soft X-rays in the same region of the sample for each acceleration voltage; Calculating a ratio of the spectra obtained by irradiating the electron beam with the two different accelerating voltages; Extracting ratios in an energy region of interest corresponding to the energy of an absorption edge of each element from the calculated ratios; The extracted ratio is displayed as a spectral map. A method for displaying a map of an absorption edge structure.

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