JP2022148891A - X-ray image display method and X-ray analysis device - Google Patents

Abstract

To display an X-ray image calculated using an appropriate background value in mapping analysis of an X-ray analysis device.SOLUTION: An X-ray image display method is a method for creating and displaying an X-ray image showing the two-dimensional distribution of elements in a sample by irradiating the sample with an electron beam and measuring X-rays emitted from the sample irradiated with the electron beam, and includes: performing a qualitative analysis of the sample; calculating a first background value for a peak wavelength of a specific element; using the first background value obtained in the qualitative analysis to calculate a second background value during mapping measurement; performing mapping measurement of the specific element of the sample; and displaying an X-ray image based on the second background value.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to an X-ray image display method and an X-ray analysis apparatus.

2. Description of the Related Art An X-ray analysis apparatus is known that analyzes the composition of a sample by irradiating the sample with an electron beam and measuring characteristic X-rays emitted from the sample irradiated with the electron beam. Patent Literature 1 discloses mapping analysis for measuring the distribution of elements according to positions within a measurement region of a sample in composition analysis using an X-ray analyzer.

Japanese Patent Application Laid-Open No. 2019-12019

Generally, in composition analysis by an X-ray analyzer using an electron beam, the detector detects not only characteristic X-rays unique to the element but also continuous X-rays. Continuous x-rays then form a background that boosts the detector counts. Appropriately subtract the background value to estimate the count value. For evaluating the background value at the peak wavelength of a particular element, the count values of wavelengths around the peak wavelength are usually used.

On the other hand, in mapping measurement, an appropriate X-ray image cannot be displayed unless an appropriate background value is subtracted from the count number at each measurement point.

The method of displaying an X-ray image of the present disclosure includes:
A method of creating and displaying an X-ray image showing a two-dimensional distribution of elements in a sample by irradiating the sample with an electron beam and measuring X-rays generated from the sample irradiated with the electron beam, comprising:
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
A mapping measurement of the specific element of the sample is made and an X-ray image based on the second background value is displayed.

The X-ray analysis device of the present disclosure is
An X-ray analysis apparatus for analyzing the composition of a sample by irradiating the sample with an electron beam and measuring the X-rays generated from the sample irradiated with the electron beam,
an electron beam irradiation unit for irradiating the sample with an electron beam;
an X-ray spectrometer that measures X-rays generated from the sample;
a display unit for controlling the electron beam irradiation unit and the X-ray spectroscope, receiving measurement data from the X-ray spectroscope, performing calculations, and displaying the calculated composition analysis data of the sample on the display unit; a control unit that displays in
with
The control unit
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
A mapping measurement of the specific element of the sample is performed, and an X-ray image based on the second background value is displayed on the display unit.

The line image display method and X-ray analysis apparatus of the present disclosure perform qualitative analysis and calculate background values before performing mapping analysis. This background value is converted and used as the background value for mapping analysis. By such a method, the background value at the time of mapping analysis can be obtained quickly and accurately before the background analysis, and the X-ray image showing the two-dimensional distribution of the specific element can be quickly and accurately displayed. can be done.

1 is a schematic diagram of the entire X-ray analysis apparatus 1 of the first embodiment; FIG. It is an example of the X-ray image obtained by the mapping analysis of the X-ray analysis apparatus 1 of 1st Embodiment. It shows the distribution of specific elements in the sample. It is an example of the X-ray image obtained by the mapping analysis of the X-ray analysis apparatus 1 of 1st Embodiment. The same data as in FIG. 2 are changed by using different numerical values as the maximum and minimum count values (background values). FIG. 4 is a diagram schematically showing an X-ray spectrum of a certain sample obtained by qualitative analysis; The horizontal axis indicates the wavelength, and the vertical axis indicates the count number of X-rays. 4B is an enlarged view showing the vicinity of the characteristic X-ray peak of element 3 in the X-ray spectrum of FIG. 4A. FIG. 4 is a flow chart showing a method for creating and displaying an X-ray image according to the first embodiment;

The X-ray analysis apparatus of the present disclosure performs composition analysis of a sample by irradiating the sample with an electron beam and measuring X-rays generated from the sample irradiated with the electron beam. The X-ray analyzer may be an electron probe microanalyzer (EPMA) or a scanning electron microscope (SEM). The X-ray analysis device has a spectroscope. When the X-ray analysis device is an electron probe microanalyzer, the spectrometer is usually equipped with a wavelength dispersive spectrometer (WDS). When the X-ray analysis apparatus is a scanning electron microscope, the spectroscope is usually an energy dispersive spectrometer (EDS).
<First embodiment>
(1) Configuration of X-ray Analysis Apparatus 1 The X-ray analysis apparatus 1 of this embodiment is an electron probe microanalyzer equipped with a wavelength dispersive spectroscope. The X-ray analysis apparatus 1 includes an electron beam irradiation section 10, a sample placement section 20, an X-ray spectroscope 30, and a control section 50, as shown in FIG. At least a part of the electron beam irradiation unit 10, the sample placement unit 20, and the X-ray spectroscope 30 is placed in a measurement chamber (not shown). During the measurement, the inside of the measuring chamber is evacuated.

The electron beam irradiation unit 10 irradiates the sample with an electron beam. The electron beam irradiation section 10 includes an electron gun 11 , a deflection coil 12 , a deflection coil control section 15 and an objective lens 13 .

The electron gun 11 is an excitation source that generates an electron beam E, and the beam current (specimen current) of the electron beam E can be adjusted by controlling a converging lens (not shown).

The deflection coil 12 forms a magnetic field by driving current supplied from the deflection coil control section 15 . The electron beam E can be deflected by the magnetic field.

The objective lens 13 is provided between the deflection coil 12 and the sample S, and narrows the diameter of the electron beam E that has passed through the deflection coil 12 .

The sample placement section 20 includes a sample stage 21 and a sample stage driving section 22 .

A sample S is placed on the sample stage 21 . The sample stage drive unit 22 drives the sample stage 21 to move the sample stage 21 within the horizontal plane.

In the X-ray analysis apparatus 1, the irradiation position of the electron beam E on the sample S is two-dimensionally determined by driving the sample stage 21 by the sample stage driving unit 22 and/or deflecting the electron beam by controlling the deflection coil 12. can be scanned to

The X-ray spectroscope 30 is a wavelength dispersive spectroscope (WDS). An energy dispersive spectrometer (EDS) may also be used. The X-ray spectroscope 30 measures X-rays generated from the sample. Although two spectroscopes 30 are drawn on the left and right in FIG. The configuration of each spectroscope 30 is the same except for the spectroscopic crystal 31 .

X-ray spectrometer 30 includes analyzing crystal 31 , detector 33 , and slit 34 . The irradiation position of the electron beam E on the sample S, the analyzing crystal 31, and the detector 33 are positioned on a Rowland circle (not shown). The analyzing crystal 31 changes its tilt angle while moving on the straight line 32 . The tilt angle of the detector 33 changes according to the movement of the analyzing crystal 31 so that the incident angle of the characteristic X-rays and the exit angle of the diffracted X-rays with respect to the analyzing crystal 31 satisfy Bragg's diffraction condition. Thereby, wavelength scanning of characteristic X-rays emitted from the sample S can be performed.

The control unit 50 is a computer. The control unit 50 has a CPU 51 , a memory 52 , an operation unit 53 and a display unit 54 . The control unit 50 controls the sample placement unit 20, the electron beam irradiation unit 10, and the X-ray spectrometer 30 to analyze the composition of the sample S. FIG. The control unit 50 also receives measurement data from each X-ray spectrometer 30 and processes the data. The CPU 51 performs calculations. The CPU 51 executes programs. The CPU 51 also stores programs and data in the memory 52 and reads the programs and data from the memory. Here, the memory 52 includes not only RAM (Random Access Memory) and ROM (Read Only Memory) but also external storage devices such as HDD (Hard Disk Drive). The CPU 51 displays the measurement program and measurement data on the display section 54 . The display unit 54 is a display. The operation unit 53 accepts user input. The CPU 51 executes programs according to commands input from the operation unit 53 . The operation unit 53 is a keyboard, a mouse, a touch panel integrated with the display unit 54, or the like.
(2) Qualitative Analysis Mode and Mapping Analysis Mode of X-ray Analysis Apparatus 1 The X-ray analysis apparatus 1 of this embodiment has a qualitative analysis mode and a mapping analysis mode.

In the qualitative analysis mode, a specific position of the sample S is irradiated with an electron beam, and the X-ray spectrometer 30 is scanned. This is a method of obtaining a spectrum (illustrated in FIG. 4A) with the count value as the vertical axis. The element can be measured by the wavelength of the detected peak, and the quantitative value can be measured by the count value of the peak.

In the mapping analysis mode, in each spectroscope 30, the position of the analyzing crystal 31 is fixed at the wavelength of the characteristic X-ray of a specific element, and the position of the electron beam E with which the sample S is irradiated is scanned. This is an analysis mode for obtaining an X-ray image showing the two-dimensional distribution of elements. An X-ray image is displayed on the display unit 54 . In the X-ray image, count values (intensity values) are displayed in grayscale or by color setting in multiple stages (16 gradations, 256 gradations, etc.). For example, the count values are displayed in the order of black, blue, light blue, green, yellowish green, yellow, orange, and red using rainbow colors from the lowest count value to the highest count value. If the count value at the boundary between black and blue is taken as the background value (minimum value), the black area can be displayed as an area where the count value is below the detection limit.
(3) Issues in setting the minimum value (background value) of X-ray images obtained by mapping analysis There is a method in which the software automatically multiplies the maximum value of the calculated count value by a coefficient.

FIG. 2 is an example of an X-ray image obtained in this way. In FIG. 2, since a color image is expressed in black and white, there are five gradations, and the width of each gradation is appropriately different as required. In the X-ray image of FIG. 2, the maximum number of counts is set to 5620 and the minimum number to 627.

FIG. 3 shows the same data as in FIG. 2, but with the minimum value changed to 100. It can be seen that there is a low-concentration region of the specific element, which was not seen in FIG. 2, around the island with the high-concentration specific element.

As shown in FIG. 2, the method of obtaining the minimum value by multiplying the maximum value of the count number by a certain coefficient cannot obtain the true background value and cannot display a preferable X-ray image. The present disclosure provides a method for determining an appropriate minimum, or background, value for use in displaying X-ray images in mapping analysis mode.
(4) Method for creating and displaying an X-ray image showing a two-dimensional distribution of elements in a sample The method for displaying an X-ray image by the X-ray analysis apparatus 1 of the present disclosure is as shown in the flow chart of FIG. Perform qualitative analysis, (b) determine the background value during mapping analysis using the analysis data of (a), (c) perform mapping analysis, and use the background value determined in (b) , to display the X-ray image. They will be explained in order below.

First, in (a), a sample is qualitatively analyzed. In the qualitative analysis, the position of the electron beam E irradiated to the sample is fixed, and X-rays emitted from the sample are scanned by the spectroscope 30 and detected. The qualitative analysis is set so as to include the characteristic X-ray wavelength of the element for which the mapping analysis is performed and the X-ray image is to be obtained.

The X-ray spectrum obtained by performing the qualitative analysis is schematically shown in FIG. 4A. In FIG. 4A, peaks corresponding to the characteristic X-ray wavelengths of element A, element B, and element C can be seen. Inevitably, continuous X-rays also appear in the X-ray spectrum as background.

FIG. 4B is an enlarged view of the vicinity of the characteristic X-ray peak of element 3 in FIG. 4A. A method of calculating the background value at the peak wavelength of the characteristic X-ray of element 3 will be described with reference to FIG. 4B. First, a curve L is obtained by extending a peripheral curve that is considered to be unaffected by the characteristic X-ray peak of element 3. FIG. This curve L is regarded as a continuous X-ray spectrum (background). The number of counts at the peak wavelength of the element 3 on this curve L is read and regarded as the background value at the peak wavelength of the characteristic X-ray of the element 3. In other words, the measured counts of the peak minus the background value is the true value of the characteristic x-ray of element 3.

Next, in (b), for a specific characteristic X-ray of a specific element, a background value to be used in mapping analysis is determined from the background value in the qualitative analysis calculated in (a).

_The background value BG1 used in the qualitative analysis is converted into the background value _BG2 used in the mapping analysis in consideration of the difference between the measurement conditions in the qualitative analysis and the measurement conditions in the mapping analysis. Here, the beam current value I1 and irradiation _time t1 of the electron beam E with which the sample is irradiated during qualitative analysis, and the beam current value _I2 and irradiation _{time t2} of the electron beam E with which the sample is irradiated during mapping analysis. , is used to perform the calculation of equation (1).

_BG2 =BG1* _{I2 /} I1 _* t2 _/ t1 ( ₁ )
The irradiation time t during qualitative analysis is determined according to the scanning speed of the detector. Also, the irradiation time during mapping analysis is determined depending on the scanning speed of the electron beam E or the sample stage 4 .

For example, (a) the measurement conditions in qualitative analysis are beam current value I ₁ =100 nA and irradiation time t ₁ =50 mS, and (c) the measurement conditions in map analysis are beam current value I ₂ =200 nA and irradiation time. Assuming that t ₂ =10 mS, substituting into equation (1),
_BG2 = BG1 * 200/100 * _10/50
= BG ₁ * 0.4
becomes.

Next, in (c), a mapping analysis is performed by scanning the position of the electron beam irradiated onto the sample. At this time, the wavelength to be detected is fixed to the wavelength of the characteristic X-ray of the element to be mapped. That is, the positions of the analyzing crystal 31 and the detector 33 are fixed. Here, the number of elements to be mapped is not limited to one, and up to five elements (X-ray wavelengths) can be mapped in this embodiment.

The control unit 50 performs mapping analysis and acquires count number data detected by the detector 33 . Data on the number of counts is displayed on the display unit 54 as a two-dimensional X-ray image of the element. The count number data may be displayed in real time each time the position is measured, or may be displayed at once by accumulating area two-dimensional data once measured. The number of counts is displayed in different colors in steps from the minimum value to the maximum value to be displayed. As the minimum value, the background value BG2 calculated in ( _b ) is used.

By setting the background value in the mapping analysis in this way, the X-ray image can be displayed appropriately, and it becomes possible to confirm the existence region of the low-concentration element.

Further, in the present embodiment, the count number displayed in the X-ray image (indicated by a bar on the right side of the X-ray image in FIGS. 2 and 3) indicates raw measurement data. Alternatively, the count number may be displayed as the measured count value minus the background value. In this case, the X-ray image itself is the same as in the present embodiment, but the count number of bars displayed on the right side is different, and the minimum value is zero.

An embodiment of the present disclosure has been described above, but the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the gist of the present disclosure. In particular, multiple embodiments described herein can be arbitrarily combined as desired.
(5) Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.
(Section 1) A method for displaying an X-ray image according to one aspect includes:
A method of creating and displaying an X-ray image showing a two-dimensional distribution of elements in a sample by irradiating the sample with an electron beam and measuring X-rays generated from the sample irradiated with the electron beam, comprising:
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
A mapping measurement of the specific element of the sample is made and an X-ray image based on the second background value is displayed.

In the X-ray image display method according to item 1, qualitative analysis is performed before mapping measurement, and the first background value BG ₁ obtained in the qualitative analysis is used to perform the second background value during mapping measurement. Since the background value BG2 is calculated, a _two -dimensional X-ray image obtained by mapping measurement can be accurately and quickly displayed.
(Section 2) In the X-ray image display method according to Section 1,
Calculation of the second background value BG ₂ during mapping analysis is based on the first background value BG ₁ during qualitative analysis, the beam current value I ₁ of the electron beam with which the sample is irradiated, and the irradiation time t ₁ of the electron beam. , the beam current value I ₂ of the electron beam irradiated to the sample during mapping analysis, and the irradiation time t ₂ of the electron beam, using the following equation (1).

_BG2 =BG1* _{I2 /} I1 _* t2 _/ t1 ( ₁ )
In the method of displaying an X-ray image according to item 2, the measurement conditions during qualitative analysis and the measurement conditions during mapping analysis are compared to determine the second background value, so an accurate second background Ground value can be determined.
(Section 3) In the X-ray image display method according to Section 1 or 2,
A wavelength dispersive spectrometer is used to measure the X-rays generated from the sample.

Since the X-ray analysis apparatus according to item 3 uses a wavelength dispersive spectroscope, it is possible to perform measurements with higher accuracy than with an energy dispersive spectroscope. Specifically, since the wavelength dispersive spectrometer has high accuracy, it is possible to separate multiple overlapping peaks and separate the peak from the background. Therefore, the method of the present disclosure is highly advantageous.

Further, the wavelength dispersive spectroscope scans the spectroscope during qualitative analysis, but does not need to scan the spectroscope during mapping analysis. Therefore, by using the background calculation of the present disclosure when mapping an element using a wavelength dispersive spectroscope, it is possible to quickly display an X-ray image with high accuracy.
(Section 4) An X-ray analysis device according to one aspect,
An X-ray analysis apparatus for analyzing the composition of a sample by irradiating the sample with an electron beam and measuring the X-rays generated from the sample irradiated with the electron beam,
an electron beam irradiation unit for irradiating the sample with an electron beam;
an X-ray spectrometer that measures X-rays generated from the sample;
a display unit for controlling the electron beam irradiation unit and the X-ray spectroscope, receiving measurement data from the X-ray spectroscope, performing calculations, and displaying the calculated composition analysis data of the sample on the display unit; a control unit that displays in
with
The control unit
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
A mapping measurement of the specific element of the sample is performed, and an X-ray image based on the second background value is displayed on the display unit.

The X-ray analysis device according to paragraph 4 performs qualitative analysis before mapping measurement, and uses the first background value BG ₁ obtained in the qualitative analysis to obtain the second background during mapping measurement Since the value BG2 is calculated, a _two -dimensional X-ray image obtained by mapping measurement can be displayed accurately and quickly.
(Section 5) In the X-ray analysis apparatus according to Section 4,
Calculation of the second background value BG ₂ during mapping analysis is based on the first background value BG ₁ during qualitative analysis, the beam current value I ₁ of the electron beam with which the sample is irradiated, and the irradiation time t ₁ of the electron beam. , the beam current value I ₂ of the electron beam irradiated to the sample during mapping analysis, and the irradiation time t ₂ of the electron beam, are calculated using the following formula (1),
_BG2 =BG1* _{I2 /} I1 _* t2 _/ t1 ( ₁ )
The X-ray analysis apparatus according to item 5 compares the measurement conditions during qualitative analysis and the measurement conditions during mapping analysis to determine the second background value, so the accurate second background value can be determined.
(Section 6) In the X-ray analysis apparatus according to Section 4 or 5,
The X-ray spectroscope is a wavelength dispersive spectroscope.

Since the X-ray analysis apparatus according to item 6 uses a wavelength dispersive spectroscope, it is possible to perform measurements with higher accuracy than with an energy dispersive spectroscope. Specifically, since the wavelength dispersive spectrometer has high accuracy, it is possible to separate multiple overlapping peaks and separate the peak from the background. Therefore, the method of the present disclosure is highly advantageous.

Further, the wavelength dispersive spectroscope scans the spectroscope during qualitative analysis, but does not need to scan the spectroscope during mapping analysis. Therefore, by using the background calculation of the present disclosure when mapping an element using a wavelength dispersive spectroscope, it is possible to quickly display an X-ray image with high accuracy.

1 X-ray analyzer 10 electron beam irradiation unit 11 electron gun 12 polarizing coil 13 objective lens 15 polarizing coil control unit 20 sample placement unit 21 sample stage 22 sample stage driving unit 30 X-ray spectrometer 31 analyzing crystal 32 straight line 33 detector 34 slit 50 control unit 51 CPU
52 memory 53 operation unit 54 display unit

Claims (6)

A method of creating and displaying an X-ray image showing a two-dimensional distribution of elements in a sample by irradiating the sample with an electron beam and measuring X-rays generated from the sample irradiated with the electron beam, comprising:
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
performing a mapping measurement of the specific element of the sample and displaying an X-ray image based on a second background value;
A method of displaying an X-ray image. Calculation of the second background value BG ₂ during mapping analysis is based on the first background value BG ₁ during qualitative analysis, the beam current value I ₁ of the electron beam with which the sample is irradiated, and the irradiation time t ₁ of the electron beam. , the beam current value I ₂ of the electron beam irradiated to the sample during mapping analysis, and the irradiation time t ₂ of the electron beam, are calculated using the following formula (1),
_BG2 =BG1* _{I2 /} I1 _* t2 _/ t1 ( ₁ )
The method for displaying an X-ray image according to claim 1. Using a wavelength dispersive spectrometer to measure X-rays generated from the sample,
The method for displaying an X-ray image according to claim 1 or 2. An X-ray analysis apparatus for analyzing the composition of a sample by irradiating the sample with an electron beam and measuring the X-rays generated from the sample irradiated with the electron beam,
an electron beam irradiation unit for irradiating the sample with an electron beam;
an X-ray spectrometer that measures X-rays generated from the sample;
a display unit for controlling the electron beam irradiation unit and the X-ray spectroscope, receiving measurement data from the X-ray spectroscope, performing calculations, and displaying the calculated composition analysis data of the sample on the display unit; a control unit that displays in
with
The control unit
performing a qualitative analysis of the sample and calculating a first background value for the peak wavelength of a particular element;
Using the first background value obtained in the qualitative analysis, calculate the second background value during the mapping measurement,
performing a mapping measurement of the specific element of the sample, and displaying an X-ray image based on the second background value on the display unit;
X-ray analyzer. Calculation of the second background value BG ₂ during mapping analysis is based on the first background value BG ₁ during qualitative analysis, the beam current value I ₁ of the electron beam with which the sample is irradiated, and the irradiation time t ₁ of the electron beam. , the beam current value I ₂ of the electron beam irradiated to the sample during mapping analysis, and the irradiation time t ₂ of the electron beam, are calculated using the following formula (1),
_BG2 =BG1* _{I2 /} I1 _* t2 _/ t1 ( ₁ )
The X-ray analysis apparatus according to claim 4. The X-ray spectrometer is a wavelength dispersive spectrometer,
The X-ray analysis apparatus according to claim 4 or 5.

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