JP7823738B2 - Correction method, analysis device, and program - Google Patents

Description

The present invention relates to a correction method, an analytical device, and a program, and more particularly to an analytical device having a wavelength dispersive X-ray spectrometer, a correction method therefor, and a program therefor.

An electron probe microanalyzer (EPMA) is a well-known analytical device that uses a wavelength dispersive X-ray spectrometer (WDS). In an EPMA, characteristic X-rays generated by irradiating a sample with an electron beam are dispersed using multiple dispersive crystals with different spectral wavelength ranges. The wavelengths and intensities of the dispersed characteristic X-rays are then detected using a detector. Japanese Patent Application Laid-Open No. 2010-190810 (Patent Document 1) discloses an EPMA that performs qualitative or quantitative analysis of elements contained in a sample based on the wavelengths and X-ray intensities obtained in this manner.

JP 2010-190810 A

One typical example of such EPMA is one that stores standard sensitivity data, which includes sensitivity data obtained by measuring a standard sample whose contained elements and their concentrations are known, including the relationship between the wavelength and intensity of characteristic X-rays. In such an EPMA, the concentration of elements contained in a sample can be easily determined by comparing the sensitivity data obtained by measuring an actual sample with the standard sensitivity data.

However, in reality, it is known that the sensitivity to the characteristic X-rays emitted from a standard sample varies from device to device due to individual differences in the analyzing crystal, detector, etc. Therefore, as mentioned above, when measuring a sample based on standard sensitivity data, there is a possibility that errors may occur in the measurement results.

This disclosure has been made in consideration of these circumstances, and its purpose is to improve measurement accuracy by reducing the influence of individual differences in analytical devices that use wavelength dispersive X-ray spectrometers.

A first aspect of the present disclosure is a correction method for an analytical device using a wavelength-dispersive X-ray spectrometer. The analytical device stores standard sensitivity data including the relationship between the wavelength and intensity of characteristic X-rays generated from a standard sample. The correction method includes the steps of acquiring measured data resulting from measuring the wavelength and intensity of two or more different characteristic X-rays in the standard sample, calculating an intensity ratio between the intensity for a given wavelength in the measured data and the intensity for the corresponding wavelength in the standard sensitivity data, and correcting the standard sensitivity data based on the intensity ratio.

The correction method disclosed herein allows standard sensitivity data to be corrected based on actual measurement data obtained by measuring a standard sample using an analytical device. This makes it possible to obtain standard sensitivity data that reflects individual differences between analytical devices. This improves the accuracy of measurements using standard sensitivity data on analytical devices.

1 is a schematic diagram showing a configuration of an analyzer according to an embodiment of the present invention. FIG. 2 illustrates an example of a hardware configuration of a computer. FIG. 10 is a diagram showing an example of a default standard sensitivity screen. FIG. 10 is a diagram showing an example of an actual measurement data acquisition screen. FIG. 10 is a diagram illustrating an example of a correction coefficient setting screen. FIG. 10 is a diagram illustrating an example of a correction confirmation screen. FIG. 10 is a diagram showing an example of a standard sensitivity screen after correction. 10 is a flowchart illustrating a process related to correction of standard sensitivity data.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or equivalent parts in the drawings will be given the same reference numerals and their descriptions will not be repeated.

[1. Configuration of the analysis device]
1 is a schematic diagram showing the configuration of an analytical apparatus 100 according to an embodiment of the present invention. Analytical apparatus 100 according to the present embodiment is an X-ray analytical apparatus that measures and analyzes a sample using a WDS. Analytical apparatus 100 is, for example, an EPMA.

Referring to Figure 1, the analysis device 100 according to this embodiment comprises a computer 1, an irradiation unit 5, a display 16 and an input unit 17.

The computer 1 controls the analysis device 100 .
The irradiation unit 5 includes an electron gun 52, a deflection coil 53, an objective lens 54, a sample stage 57, a sample stage drive unit 50, a WDS 6, a deflection coil control unit 51, a secondary electron detection unit 55, and a backscattered electron detection unit 56. The electron gun 52, the deflection coil 53, the objective lens 54, the sample stage 57, the WDS 6, the secondary electron detection unit 55, and the backscattered electron detection unit 56 are provided in an irradiation chamber 59. During analysis of the sample S, the inside of the irradiation chamber 59 is evacuated to a near-vacuum state.

The electron gun 52 is an excitation source that generates the electron beam E. The electron beam E corresponds to one example of a "charged particle beam." The electron beam E is irradiated onto the irradiation position of the sample S on the sample stage 57. A converging lens (not shown) adjusts the beam of the electron beam E. The deflection coil 53 forms a magnetic field using a driving current supplied from the deflection coil control unit 51. The magnetic field formed by the deflection coil 53 deflects the electron beam E. The objective lens 54 is provided between the deflection coil 53 and the sample S placed on the sample stage 57. The objective lens 54 focuses the electron beam E that has passed through the deflection coil 53.

The sample stage 57 is a stage for placing the sample S. The sample stage 57 is driven by the sample stage drive unit 50 and is configured to be movable within a horizontal plane.

In the irradiation unit 5, the irradiation position of the electron beam E on the sample S can be scanned two-dimensionally by driving the sample stage 57 using the sample stage drive unit 50 and/or driving the deflection coil 53 using the deflection coil control unit 51. When the scanning range is relatively narrow, scanning is performed using the deflection coil 53. When the scanning range is relatively wide, scanning is performed by moving the sample stage 57.

WDS6 is a wavelength dispersive X-ray spectrometer for detecting the detection signal of characteristic X-rays emitted from the irradiation position of sample S.

Note that although only one WDS 6 is shown in Figure 1, in reality, multiple WDSs 6 are provided in the irradiation unit 5 to surround the sample S. Each WDS 6 has an analyzing crystal with a different spectral wavelength range. The configuration of each WDS 6 is the same except for the analyzing crystal.

The WDS 6 includes an analyzing crystal 61, a detector 62, and a slit 63. The irradiation position of the electron beam E on the sample S, the analyzing crystal 61, and the detector 62 are arranged on a Rowland circle (not shown).

The analyzing crystal 61 diffracts the characteristic X-rays emitted from the irradiation position of the sample S. The analyzing crystal 61 is one of a number of crystals with different spectral wavelength ranges, such as those made of lithium fluoride (LIF), pentaerythritol (PET), or rubidium phthalate (RAP). The analyzing crystal 61 is tilted while moving along a straight line 64 by a drive mechanism (not shown).

Detector 62 is an X-ray detector that detects the characteristic X-rays diffracted by the dispersing crystal 61. Detector 62 rotates as shown in the figure in response to the movement of dispersing crystal 61, using a drive mechanism (not shown), so that the angle of incidence of the characteristic X-rays on dispersing crystal 61 and the angle of emergence of the diffracted X-rays satisfy the Bragg diffraction condition. This allows wavelength scanning of the characteristic X-rays emitted from sample S. The characteristic X-rays are detected and amplified by detector 62 and sent as a pulsed signal from WDS 6 to computer 1. In computer 1, the intensity of the characteristic X-rays is measured as a pulse signal measured per unit time, typically expressed in units of cps. Note that the configuration of each WDS is not limited to the above, and various conventionally known configurations can be used.

The secondary electron detection unit 55 detects a detection signal of secondary electrons emitted from the irradiation position of the sample S. The detection signal of the secondary electron detection unit 55 is sent to the computer 1.

The backscattered electron detector 56 detects the detection signal of the backscattered electrons emitted from the irradiation position of the sample S. The detection signal of the backscattered electron detector 56 is sent to the computer 1.

The deflection coil control unit 51 controls the drive current supplied to the deflection coil 53 in accordance with instructions from the computer 1. The deflection coil control unit 51 controls the drive current in accordance with a predetermined drive current pattern (magnitude and change speed). This allows the irradiation position of the electron beam E on the sample S to be scanned at the desired scanning speed.

Computer 1 is connected to the irradiation unit 5 so that it can communicate with it. Computer 1 generates control signals to control the operation of each part of the irradiation unit 5 in accordance with the programs and tables stored in it. Computer 1 outputs the generated control signals to the irradiation unit 5.

In addition, the computer 1 generates an image of the irradiation position in response to scanning of the electron beam E at the irradiation position on the sample S. Specifically, the computer 1 generates an SEM image, which is a secondary electron image of the irradiation position on the sample S, based on the detection signal of the secondary electrons detected by the secondary electron detection unit 55. In addition, the computer 1 generates a backscattered electron image of the irradiation position on the sample S based on the detection signal of the backscattered electrons detected by the backscattered electron detection unit 56.

Computer 1 further generates a distribution image (X-ray image) of the elements to be analyzed at the irradiation position of sample S based on the detection signals of the characteristic X-rays detected by the four WDSs. Furthermore, computer 1 receives a wavelength scan of the X-rays at the irradiation position. Computer 1 generates an X-ray spectrum based on the received wavelength scan of the X-rays. Computer 1 performs qualitative and/or quantitative analysis based on the X-ray spectrum.

The display 16 is configured to be able to communicate with the computer 1. The display 16 displays images related to the control of the irradiation unit 5 in response to commands from the computer 1. The display 16 also displays reference images that the user refers to in order to control the irradiation position of the charged particle beam in response to commands from the computer 1. The reference images include at least one of an X-ray image, an SEM image, and a backscattered electron image. The display 16 may also be configured to display processing information related to the analysis of backscattered electrons, secondary electrons, and characteristic X-rays. In such a configuration, for example, the display 16 displays an X-ray spectrum and the results of qualitative and quantitative analysis based thereon.

The user can therefore provide various instructions to the computer 1 for controlling the irradiation unit 5 based on what is displayed on the display 16. The user can also use the computer 1 to analyze data detected by the irradiation unit 5 based on what is displayed on the display 16. That is, the user can use the display 16 to view, for example, numerical values indicating the observation conditions, observed images (e.g., X-ray images, SEM images, backscattered electron images), and graphs showing the analysis results of the obtained characteristic X-rays, secondary electrons, and backscattered electrons.

The input unit 17 is connected to the computer 1 and is configured to be able to communicate with the computer 1. The input unit 17 is used to input user commands to the computer 1. The input unit 17 is a pointing device, a keyboard, a touch panel, etc. The pointing device is, for example, a mouse.

As described above, the analytical device 100 is configured to irradiate the surface of the sample S with an electron beam and detect signals emitted from the surface of the sample S. The detected signals include characteristic X-rays, backscattered electrons, and secondary electrons having wavelengths specific to the elements contained on the surface of the sample S. The analytical device 100 can identify and quantify the elements present at the analysis position on the surface of the sample S by analyzing the wavelength and intensity of the detected characteristic X-rays.

The analytical device 100 also allows the shape and composition of the surface of the sample S to be observed using the detected secondary electrons and backscattered electrons. The user can search for the target portion to be analyzed on the surface of the sample S while observing the SEM image or backscattered electron image of the irradiation position. Specifically, while observing the electron image, the user determines that the irradiation position contains the target portion to be analyzed, and then determines the target portion. The user then performs qualitative and quantitative analysis of the target portion on the surface of the sample S.

2. Hardware Configuration
2 is a diagram showing an example of a hardware configuration of computer 1. Referring to FIG. 2, computer 1 includes a processor 10, a memory 11, an I/O (Input/Output) interface 13, a communication interface 15, a display 16, and an input unit 17.

The processor 10 is realized, for example, by at least one CPU (Central Processing Unit). The processor 10 controls the analysis device 100 in accordance with a program stored in the memory 11.

Memory 11 is realized by a storage device such as ROM (Read Only Memory), RAM (Random Access Memory), and HDD (Hard Disk Drive). ROM can store programs executed by processor 10. RAM can temporarily store data used during program execution by processor 10 and can function as temporary data memory used as a working area. HDD is a non-volatile storage device. In addition to or instead of the HDD, a semiconductor storage device such as flash memory may be used. Note that the above programs and/or data may be stored in an external storage device accessible by processor 10.

The communication interface 15 is an interface that allows the computer 1 to communicate wirelessly or wired with external devices. The I/O interface 13 is an interface for input to or output from the computer 1. As shown in Figure 2, the I/O interface 13 is connected to the display 16, input unit 17, and illumination unit 5.

The display 16 is realized by a display device. The input unit 17 is realized by an input device that accepts input from the user. The input unit 17 is, for example, a keyboard, a mouse, and/or a touch panel that is integrated with the display screen of the display 16.

Computer 1 does not have to be composed of a single computer, but may be composed of multiple computers. In other words, the processing performed by computer 1 may be distributed and performed by multiple computers. For example, computer 1 may be composed of a control computer that controls irradiation unit 5 and an analysis computer that analyzes the X-ray detection signals detected by irradiation unit 5. In this case, the control computer and analysis computer may each be equipped with an input unit and a display.

[3. Comparison with conventional analytical devices]
In an EPMA using a conventional WDS, a standard sample containing known elements and their concentrations is irradiated with an electron beam, thereby making it possible to obtain data including the wavelength and intensity of characteristic X-rays emitted from the standard sample (hereinafter also referred to as "standard sensitivity data"). Some EPMAs are sold with sensitivity data obtained by measuring a standard sample in a representative device stored as initial standard sensitivity data, and standard sensitivity curves approximated based on the initial standard sensitivity data.

This will be explained in more detail below.
The intensity of characteristic X-rays is proportional to the concentration of the element that generates them and to the current value of the irradiating electron beam. Therefore, when a standard sample containing known elements and their concentrations is irradiated with an electron beam having a known current value and the intensity of the characteristic X-rays is measured, the above-mentioned proportional relationship allows the characteristic X-ray intensity value measured when the concentration of the target element is 100% to be expressed as an intensity value per unit current of the irradiating electron beam, i.e., the standard sensitivity value. The standard sensitivity value is expressed, for example, as an intensity value per 1 A (ampere) of irradiation current, and the unit used is cps/A.

By multiplying the standard sensitivity value by the probe current value during measurement, it is possible to determine the intensity value that can be measured under those probe current conditions when the target element concentration is 100%, in other words, the 100% intensity value. By dividing the actually measured intensity value by this 100% intensity value, the concentration of the target element can be easily determined.

Typically, there are multiple characteristic X-rays within the spectral wavelength range of a single analyzing crystal. Characteristic X-rays are classified into the Kα series, Lα series, Mα series, etc. depending on the atomic nucleus that contributes to the generation of the X-rays. However, within the same series, the wavelengths of characteristic X-rays are arranged in order of atomic number, and it is known that the standard sensitivity value shows a curved change in relation to the wavelength value (see Figure 3: Default Standard Sensitivity Screen).

Using these characteristics, it is possible to curve-fit the change in standard sensitivity value versus wavelength value from a data set created by determining the wavelength and standard sensitivity value for each characteristic X-ray for each individual dispersing crystal and even for each X-ray series, i.e., standard sensitivity data. The curve obtained in this way is called a standard sensitivity curve. Because the standard sensitivity value can be calculated from the wavelength value using the approximation formula given to the standard sensitivity curve, standard sensitivity values can be given even for characteristic X-rays for which standard sensitivity values cannot be measured due to reasons such as difficulty in obtaining standard samples, and the intensity of the measured characteristic X-ray can be converted into a concentration value.

In EPMAs using conventional WDSs, the initial standard sensitivity data is data obtained by measuring the sensitivity of characteristic X-rays for each WDS in a representative instrument, for example, at a company that sells EPMAs. By measuring the intensities of as many characteristic X-rays as possible using many types of standard samples, the vendor sets the initial standard sensitivity data and standard sensitivity curve to accurately reflect the sensitivity of each WDS in that representative instrument.

In an EPMA that stores standard sensitivity data and standard sensitivity curves set in this way, it is possible to determine the elements contained in the sample and their concentrations by comparing the wavelength and intensity of the characteristic X-rays obtained by measuring the sample with each individual device with the standard sensitivity values obtained from the standard sensitivity curve.

However, in reality, the "sensitivity" of characteristic X-rays, i.e., the "intensity of X-rays obtained when a specified standard sample is measured under the same conditions," varies from device to device due to individual differences in the analyzing crystal, detector, and other mechanisms included in the WDS. Therefore, as mentioned above, measurement results obtained by comparing the wavelength and intensity of characteristic X-rays obtained by measuring a sample with an individual device with the initial standard sensitivity value may contain errors.

Therefore, it is desirable to correct the initial standard sensitivity data and standard sensitivity curve for each individual instrument to standard sensitivity data and standard sensitivity curve that reflect the sensitivity of that individual instrument. However, because the types of standard samples that users can prepare are limited, it is extremely difficult to remeasure the sensitivity of all characteristic X-rays measured by the manufacturer for each individual instrument. In addition, while instruments usually have the ability to update standard sensitivity data and standard sensitivity curves, if a user changes only part of the standard sensitivity data to the extent possible using their own standard samples, this may result in unnatural distortions in the standard sensitivity curve that is created, which may actually reduce the accuracy and validity of the standard sensitivity curve.

In this embodiment, an analytical device 100 is provided that uses initial standard sensitivity data as default standard sensitivity data, corrects the default standard sensitivity data based on sensitivity data obtained by actually measuring a relatively small number of standard samples, and uses the results to create a standard sensitivity curve. This allows users to use a standard sensitivity curve tailored to the characteristics of their individual device. This reduces the impact of individual device differences on measurement results, improving the accuracy of measurements for each device.

[4. Correction method for standard sensitivity data]
Next, a method for correcting the default standard sensitivity data will be described using display screens (FIGS. 3 to 7) displayed on the display 16 by the processor 10. The user corrects the standard sensitivity data by referring to the display screens.

In this specification, correction of the standard sensitivity data of a WDS with a PET dispersing crystal is described as an example of the standard sensitivity data of each WDS. Similar corrections can also be made to the standard sensitivity data of WDSs with other dispersing crystals.

(4-1. Default standard sensitivity screen)
3 is a diagram showing an example of a default standard sensitivity screen. The standard sensitivity screen is a screen for displaying standard sensitivity data. The standard sensitivity screen is displayed when the user inputs an instruction to display the standard sensitivity screen into the analytical device 100. In one implementation example, an operation screen (not shown) of the analytical device 100 displayed on the display 16 of the computer 1 includes a button for displaying the standard sensitivity screen. When the user selects this button, the standard sensitivity screen is displayed on the display 16. This selection is made, for example, by clicking using the input unit 17.

The standard sensitivity screen includes Table T1. In Table T1, each row contains a data set of standard sensitivity values for characteristic X-rays of the Kα series, Lα series, and Mα series, i.e., standard sensitivity data and its graph, a sensitivity graph. The Kα series sensitivity graph, Lα series sensitivity graph, and Mα series sensitivity graph will hereinafter also be referred to as the "Kα graph," "Lα graph," and "Mα graph," respectively.

In each sensitivity graph, the horizontal axis represents the spectral wavelength (Å), and the vertical axis represents the intensity of characteristic X-rays (cps/A). In each sensitivity graph, black circles such as those indicated by C1 represent default standard sensitivity data. In each sensitivity graph, the standard sensitivity data exhibits a curvilinear change. In the example of Figure 3, each sensitivity graph includes a standard sensitivity curve such as that indicated by the dashed line L1. The standard sensitivity curve is a curve obtained by polynomial approximation of the standard sensitivity data. In the example of Figure 3, the standard sensitivity curve is a cubic curve that best fits the standard sensitivity data. In this specification, the "best fitting curve" refers, for example, to the curve that has the smallest error from the original data. The error from the original data can be determined, for example, by the least squares method.

By referring to the standard sensitivity screen, users can check the standard sensitivity data currently used by the device. This standard sensitivity data can be corrected based on actual measurement data. Note that in this specification, "actual measurement data" refers to sensitivity data obtained by actually measuring a standard sample using the user's own device.

(4-2. Measurement data acquisition screen)
4 is a diagram showing an example of an actual measurement data acquisition screen. The actual measurement data acquisition screen is a screen for acquiring actual measurement data. The actual measurement data acquisition screen is displayed when a user inputs an instruction to correct the standard sensitivity curve into the analytical device 100. In one implementation example, an operation screen (not shown) of the analytical device 100 displayed on the display 16 of the computer 1 includes a button for executing correction of the standard sensitivity curve. When the user selects the button, the actual measurement data acquisition screen is displayed on the display 16.

The actual measurement data acquisition screen includes Table T2 and Button B1. The rows of Table T2 show the sensitivity data for the Kα series, Lα series, and Mα series, respectively. Table T2 includes a sensitivity graph in the left column and a sensitivity table, which is a table of sensitivity data, in the right column.

The sensitivity tables for the Kα series, Lα series, and Mα series are also called the Kα table, Lα table, and Mα table, respectively. Each sensitivity table includes the following items: "characteristic X-rays," "wavelength (Å)," "standard intensity (cps/A)," "measured intensity (cps/A)," and "intensity ratio."

The "Characteristic X-rays" item shows the name of each characteristic X-ray. The name of the characteristic X-ray is indicated by the element symbol and series. For example, the characteristic X-ray of the Kα series of silicon (element symbol Si) is indicated as "SiKα."

The item "wavelength (Å)" indicates the wavelength specific to the characteristic X-ray.
The item "standard intensity (cps/A)" indicates the intensity of the characteristic X-rays corresponding to the wavelength in the standard sensitivity data (hereinafter also referred to as "standard intensity").

The item "Measured Intensity (cps/A)" indicates the intensity of the characteristic X-ray corresponding to the wavelength in the measured data (hereinafter also referred to as "measured intensity").

The "Intensity Ratio" item indicates the ratio between the measured intensity and the standard intensity. In one implementation, the intensity ratio is the measured intensity divided by the standard intensity.

In one implementation example, the values of the items "Characteristic X-rays," "Wavelength (Å)," and "Standard Intensity (cps/A)" are pre-displayed based on the standard sensitivity data stored in memory 11. The value of the item "Measured Intensity (cps/A)" is configured to be input by the user. The value of the item "Intensity Ratio" is configured to be automatically displayed based on the value of the item "Standard Intensity (cps/A)" and the value of the item "Standard Intensity (cps/A)" on the same row when the value of the item "Standard Intensity (cps/A)" on the same row is input.

In each sensitivity graph, the horizontal axis represents the spectral wavelength (Å) and the vertical axis represents the characteristic X-ray intensity (cps/A). In each sensitivity graph, black circles such as those shown in C1 represent the default standard sensitivity data. In each sensitivity graph, white circles such as those shown in C2 represent measured data.

In one implementation example, the black circle indicating standard sensitivity data, such as that shown in C1, is displayed in advance based on the standard sensitivity data stored in memory 11. The white circle indicating actual measurement data, such as that shown in C2, is configured to be automatically displayed when the value of the "Actual Measurement Intensity (cps/A)" item in the sensitivity table is entered.

Button B1 is used to complete the acquisition of actual measurement data. When selected, button B1 is configured to display the correction coefficient setting screen shown in Figure 5.

The measurement data acquisition screen is used, for example, as follows: The user inputs the measured intensity into the cell for the "Measured Intensity (cps/A)" item. This input is performed by the user inputting the measured intensity based on the measured data of a standard sample stored in memory 11. Specifically, for example, the user references the measured data and inputs the measured intensity using input unit 17. Furthermore, for example, when the user selects a cell for the "Measured Intensity (cps/A)" item corresponding to a specific characteristic X-ray, the measured intensity from a previous measurement of the corresponding characteristic X-ray may be automatically input.

When the user enters the intensity corresponding to the "Measured Intensity (cps/A)" cell, the "Intensity Ratio" value in the same row is automatically calculated. Also, a white circle corresponding to the "Measured Intensity (cps/A)" as shown in C2 is displayed on the sensitivity graph.

As described above, actual measurement data can be acquired using the actual measurement data acquisition screen. Furthermore, by referring to the sensitivity graph, users can intuitively compare the input actual measurement intensity with the standard intensity.

When the user selects button B1 to complete the acquisition of actual measurement data, the correction coefficient setting screen shown in Figure 5 will be displayed.

(4-3. Correction coefficient setting screen)
5 is a diagram showing an example of a correction coefficient setting screen. The correction coefficient setting screen is a screen for setting a correction coefficient. The correction coefficient setting screen includes a table T3 and a button B2. Table T3 includes a graph (intensity ratio graph) in the left column and a table (intensity ratio table) in the right column for intensity ratio data.

The intensity ratio table includes the items "Characteristic X-rays," "Wavelength (Å)," and "Intensity Ratio." The items "Characteristic X-rays," "Wavelength (Å)," and "Intensity Ratio" are the same as the corresponding items in the sensitivity table in Figure 4 ("Characteristic X-rays," "Wavelength (Å)," and "Intensity Ratio"). The values corresponding to the items "Characteristic X-rays," "Wavelength (Å)," and "Intensity Ratio" in the intensity ratio table are entered as the values for the corresponding items ("Characteristic X-rays," "Wavelength (Å)," and "Intensity Ratio") in the row in the sensitivity table in Figure 4 where "Measured Intensity (cps/A)" is entered. In other words, for characteristic X-rays for which measured intensities have been obtained in the sensitivity table in Figure 4, the name, wavelength, and intensity ratio of that characteristic X-ray are automatically entered into the intensity ratio table in Figure 5.

In the intensity ratio graph, the horizontal axis represents wavelength, and the vertical axis represents intensity ratio or correction coefficient. In the intensity ratio graph, black circles such as those shown in C3 indicate the relationship between wavelength and intensity ratio in the intensity ratio table, and are automatically displayed based on the intensity ratio table.

The dashed line L2 on the intensity ratio graph is a polynomial approximation of the intensity ratio (black dots) versus wavelength, as shown in C3. This polynomial approximation is performed automatically by the processor 10 based on the relationship between wavelength and intensity ratio. More specifically, the coefficients of each polynomial term are determined, for example, using the least squares method, to minimize the error from the intensity ratio data. In the example of Figure 5, the dashed line L2 displays the results of fitting four data points by the processor 10 using a cubic equation. In this specification, this polynomial approximation value is referred to as the correction coefficient and is used to correct the standard sensitivity data. This configuration allows correction coefficients to be set even for wavelengths for which corresponding measured data has not been obtained. The line indicating the correction coefficient, shown as dashed line L2 on the intensity ratio graph, is also referred to as the "correction coefficient line" below.

Button B2 is used to complete the setting of the correction coefficient and confirm the results of the correction performed using the set correction coefficient. When selected, button B2 is configured to display the correction confirmation screen shown in Figure 6.

As described above, the correction coefficient is set on the correction coefficient setting screen. By referring to the intensity ratio graph, the user can intuitively understand the intensity ratio or correction coefficient value for wavelength. Furthermore, the user can confirm that the correction coefficient line is properly fitted to the intensity ratio.

When the user selects button B2 to complete setting the correction coefficient, the correction confirmation screen shown in Figure 6 will be displayed.

(4-4. Correction confirmation screen)
Fig. 6 is a diagram showing an example of a correction confirmation screen. The correction confirmation screen is a screen on which the user can confirm the correction of the standard sensitivity data using the correction coefficient set in Fig. 5. The correction confirmation screen includes a table T4 and a button B3.

In Table T4, each row contains sensitivity graphs for the Kα series, Lα series, and Mα series. In each sensitivity graph, the horizontal axis represents the spectral wavelength (Å) and the vertical axis represents the characteristic X-ray intensity (cps/A). In each sensitivity graph, black circles such as those indicated by C1 represent the default standard sensitivity data. In each sensitivity graph, white circles such as those indicated by C4 represent the standard sensitivity data after correction based on the correction coefficients set in Figure 5.

Button B3 is a button used to determine the correction of the standard sensitivity data. When selected, button B3 determines the correction of the standard sensitivity data and is configured to display the corrected standard sensitivity screen shown in Figure 7.

(4-5. Standard sensitivity screen after correction)
7 is a diagram showing an example of a standard sensitivity screen after correction. The standard sensitivity screen after correction includes Table T5. In Table T5, each row includes a sensitivity graph for each of the Kα series, Lα series, and Mα series.

In each sensitivity graph, the horizontal axis represents the spectral wavelength (Å) and the vertical axis represents the intensity of characteristic X-rays (cps/A). In each sensitivity graph, the corrected standard sensitivity data, as indicated by C4, exhibits a curved change. In the example of Figure 7, each sensitivity graph includes a corrected standard sensitivity curve, as indicated by the dashed line L3. The corrected standard sensitivity curve is a curve obtained by polynomial approximation of the corrected standard sensitivity data. In the example of Figure 7, the standard sensitivity curve is a cubic curve that best fits the standard sensitivity data.

The standard sensitivity curve is automatically calculated by the processor 10 based on the standard sensitivity data. This configuration also complements the intensity for wavelengths for which there are no data points in the standard sensitivity data. Therefore, even if a user measures a sample and detects characteristic X-rays at a wavelength for which there are no corresponding data points in the standard sensitivity data, the concentration of the corresponding element can be calculated using the standard sensitivity curve.

As shown in Figure 6, after the correction of the standard sensitivity data is completed, when the user inputs an instruction to display the standard sensitivity screen into the analytical device 100, the standard sensitivity screen of Figure 7 is displayed instead of the standard sensitivity screen of Figure 3. In this way, by referring to the standard sensitivity screen, the user can check the current standard sensitivity data.

[5. Correction Control]
Fig. 8 is a flowchart illustrating a process for correcting standard sensitivity data, which is executed by computer 1. Referring to Fig. 8, in step (hereinafter also referred to as ST) 02, processor 10 uses the actual measurement data acquisition screen (Fig. 4) to acquire actual measurement data of a standard sample that has been measured using an apparatus owned by the user.

In ST04, the processor 10 calculates the intensity ratio, which is the ratio between the intensity for a specified wavelength in the actual measurement data and the intensity for the corresponding wavelength in the standard sensitivity data. The calculated intensity ratio is displayed as a value corresponding to the "Intensity Ratio" item in the sensitivity table of Figure 4 and the intensity table of Figure 5.

In ST06, the processor 10 performs a polynomial approximation of the intensity ratio versus wavelength. The result of the polynomial approximation is displayed as a correction coefficient line (dashed line L2) on the intensity graph in Figure 5.

In ST08, the processor 10 sets the polynomial-approximated value as the correction coefficient.
In ST10, the processor 10 corrects the default standard sensitivity data based on the set correction coefficients. The corrected standard sensitivity data is displayed in the sensitivity graphs of FIGS.

In ST12, the processor 10 sets a standard sensitivity curve by polynomial approximating the corrected standard sensitivity data. The set standard sensitivity curve is displayed on the sensitivity graph in Figure 6. After completing ST12, the processor 10 ends the process.

The process shown in Figure 8 allows standard sensitivity data to be corrected based on actual measurement data obtained by measuring a standard sample using a user's own device. This makes it possible to obtain standard sensitivity data that reflects individual differences between devices. This improves the accuracy of measurements using standard sensitivity data on analytical devices.

[6. Supplementary Notes]
(6-1. Polynomial approximation of correction coefficients)
As shown in ST06 to ST08 in Figure 8, the analytical device 100 sets the correction coefficients by polynomial approximating the intensity ratio with respect to wavelength. In order to polynomially approximate the intensity ratio, it is necessary to obtain measured data in ST04, which is the result of actually measuring the wavelength and intensity of two or more different characteristic X-rays. "Two or more different characteristic X-rays" refers to characteristic X-rays having two or more different intrinsic wavelengths.

The inventors also found that in this polynomial approximation, a cubic curve best fits the measured data. In other words, when the correction coefficient is a cubic equation, the error (e.g., mean square error) with the measured data is small. Thus, to properly fit with a cubic curve, the measured data must contain at least four data points. Therefore, preferably, in ST04, processor 10 acquires measured data that is the result of actually measuring the wavelength and intensity for four or more different characteristic X-rays. In ST06, processor 10 also approximates the intensity ratio with respect to wavelength with a cubic equation.

However, the step of setting a correction coefficient based on the intensity ratio for wavelength shown in ST06 to ST08 is not necessarily limited to the polynomial approximation described above. For example, the correction coefficient may be set by linearly interpolating between the intensity ratio data points. In this case, the correction coefficient line will be a line graph that linearly connects each data point. However, using polynomial approximation is a better method for setting a correction coefficient.

For example, with a method that linearly interpolates intensity ratios, if the intensity ratio data contains even one extremely large or small outlier due to some factor, such as a failure to measure the actual intensity, the correction coefficient line near that outlier will also show extreme changes. Therefore, the standard sensitivity data corrected using that correction coefficient line will no longer be a smooth curve, which could result in measurement errors. On the other hand, when setting correction coefficients using a polynomial approximation of the intensity ratio, even if a single outlier occurs in the intensity ratio data, the influence of other points allows the correction coefficient line to be set smoothly, even if it is near the outlier. Therefore, the standard sensitivity data corrected using that correction coefficient line will also be a smooth curve, reducing the possibility of measurement errors.

Furthermore, compared to other methods that use line graphs, the polynomial approximation method allows for relatively appropriate correction of standard sensitivity data based on actual measurement data of standard samples. Furthermore, even if the 20 or so standard samples provided with an EPMA are used, for example, two to seven types of characteristic X-rays can be measured for each analyzing crystal, so there is the advantage that the standard sensitivity data can be corrected even within this range. Therefore, users do not need to obtain new standard samples to correct the standard sensitivity data, and correction can be performed easily.

(6-2. How to obtain actual measurement data)
Furthermore, the method of acquiring the measured data is not limited to the above example. For example, if the user inputs the values of the measured data for the intrinsic wavelength of the characteristic X-rays, the standard sensitivity data may be corrected automatically without any subsequent calculations being displayed on the display 16. In other words, the processes for correcting the standard sensitivity data described using the screens of Figures 5 to 8 may all be performed in the background. However, the display of the screens of Figures 5 to 8 has the advantage of allowing the user to visually confirm that the standard sensitivity data has been properly corrected.

Furthermore, when the user inputs an instruction to correct the standard sensitivity data into the analytical device 100, the analytical device 100 displays an instruction for the standard sample to be installed in the analytical device 100, and once the user installs the standard sample, the analytical device 100 can then automatically acquire the actual measurement data and correct the standard sensitivity data.

(6-3. Timing of correction)
The standard sensitivity data is corrected, for example, after a user purchases the instrument and before measuring a sample to be measured. This reduces the influence of individual differences between instruments and improves the accuracy of the measurement before measuring the sample.

It is also known that analytical instruments including WDSs experience changes in sensitivity over time due to repeated measurements. To reduce the effects of this change over time, the standard sensitivity data may be corrected periodically (e.g., once a year). In this case, the correction may be performed on the default standard sensitivity data, or on the most recently corrected standard sensitivity data.

(6-4. Correction of standard sensitivity data based on standard sensitivity curve)
Furthermore, the correction of the standard sensitivity data does not necessarily have to be a correction of the data points contained in the standard sensitivity data as described above, but may be, for example, a correction of the standard sensitivity curve.

Correction of the standard sensitivity curve is performed, for example, as follows: First, the ratio between the measured intensity of the characteristic X-ray and the value of the standard sensitivity curve for the corresponding wavelength is calculated as the intensity ratio. Next, a correction coefficient is calculated based on this intensity ratio. The product of the correction coefficient and the value of the standard sensitivity curve before correction is then recorded as the corrected standard sensitivity curve.

With this configuration, it is possible to correct the standard sensitivity curve even if the characteristic X-rays actually measured on the user's device are not included in the data points of the default standard sensitivity data. Furthermore, it is also possible to correct the standard sensitivity curve even for devices that, instead of the data points actually measured on a representative device, include only a standard sensitivity curve that is a polynomial approximation of those data points as the default standard sensitivity data.

[Aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Section 1) One aspect of the correction method is a correction method for an analytical device that uses a wavelength-dispersive X-ray spectrometer. The analytical device stores standard sensitivity data including the relationship between the wavelength and intensity of characteristic X-rays generated from a standard sample. The correction method includes the steps of acquiring measured data that is the result of measuring the wavelength and intensity of two or more different characteristic X-rays in the standard sample, calculating an intensity ratio that is the ratio between the intensity for a specified wavelength in the measured data and the intensity for the corresponding wavelength in the standard sensitivity data, and correcting the standard sensitivity data based on the intensity ratio.

The correction method described in paragraph 1 allows standard sensitivity data to be corrected based on actual measurement data obtained by measuring a standard sample using an analytical device. This makes it possible to obtain standard sensitivity data that reflects individual differences in the sensitivity of analytical devices. This improves the accuracy of measurements using standard sensitivity data on analytical devices.

(Clause 2) In the correction method described in paragraph 1, the correction step includes a step of setting a correction coefficient based on the intensity ratio, and a step of storing the product of the correction coefficient and the standard sensitivity data before correction as the standard sensitivity data after correction.

The correction method described in paragraph 2 allows a correction coefficient that reflects the intensity ratio, i.e., the ratio of sensitivity between devices, to be reflected in the standard sensitivity data. This makes it possible to obtain standard sensitivity data that reflects the sensitivity ratio between devices. This improves the accuracy of measurements using standard sensitivity data on analytical devices.

(Section 3) In the correction method described in Section 2, the setting step includes a step of polynomial approximating the intensity ratio to wavelength in the actual measurement data, and a step of setting the polynomial-approximated value as a correction coefficient.

The correction method described in paragraph 3 allows correction coefficients to be set even for wavelengths for which no corresponding measured data has been obtained. Furthermore, when correction coefficients are set for wavelengths for which no corresponding measured data has been obtained using polynomial approximation, the correction coefficient line can be set as a smooth curve even if the measured data contains outliers. Therefore, correcting standard sensitivity data using a correction coefficient line based on polynomial approximation reduces the possibility of measurement errors compared to, for example, correcting standard sensitivity data using a correction coefficient line that linearly interpolates the intensity ratio.

(4) In the correction method described in paragraph 3, the acquiring step includes a step of acquiring measured data that is the result of actually measuring the wavelength and intensity for four or more different characteristic X-rays, and the polynomial approximation step includes a step of approximating the intensity ratio to wavelength to a cubic equation.

The inventors discovered that in polynomial approximations of intensity ratios, a cubic curve best fits the measured data. Therefore, the correction method described in paragraph 4 can obtain a correction coefficient line that best fits the measured data. In other words, it is possible to set a correction coefficient that appropriately reflects the sensitivity of the analytical device. By using such a correction coefficient to correct the standard sensitivity data, the accuracy of measurements using the standard sensitivity data can be improved.

(Item 5) In the correction method described in any one of items 2 to 4, the correction step includes a step of setting a standard sensitivity curve by polynomial approximation of the corrected standard sensitivity data, and the standard sensitivity curve is used in an analytical device to calculate the concentration of elements contained in the sample based on the intensity of characteristic X-rays emitted from the sample to be measured.

According to the correction method described in Section 5, intensities for wavelengths for which there are no data points in the standard sensitivity data are also interpolated. Therefore, even if a user measures a sample and detects characteristic X-rays at a wavelength for which there are no corresponding data points in the standard sensitivity data, the concentration of the corresponding element can be calculated using the standard sensitivity curve.

(Clause 6) Another aspect of the analytical device is an analytical device that uses a wavelength dispersive X-ray spectrometer and is equipped with a memory that stores standard sensitivity data and actual measurement data, and a processor that executes the correction method described in any one of clauses 1 to 5.

(Section 7) A program relating to yet another aspect causes a computer to execute the correction method described in any one of Sections 1 to 6.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Computer, 5 Irradiation unit, 6 WDS, 10 Processor, 11 Memory, 13 I/O interface, 15 Communication interface, 16 Display, 17 Input unit, 50 Sample stage drive unit, 51 Deflection coil control unit, 52 Electron gun, 53 Deflection coil, 54 Objective lens, 55 Secondary electron detection unit, 56 Backscattered electron detection unit, 57 Sample stage, 61 Analyzing crystal, 62 Detector, 63 Slit, 100 Analysis device, B1, B2, B3 Buttons, E Electron beam.

Claims (8)

A method for correcting an analytical instrument using a wavelength dispersive X-ray spectrometer, comprising:
the analytical device stores standard sensitivity data including a relationship between wavelength and intensity of characteristic X-rays generated from a standard sample;
The correction method includes:
acquiring actual measurement data including two or more data points obtained by actually measuring wavelengths and intensities of two or more different characteristic X-rays in the standard sample;
calculating two or more intensity ratios that are ratios between the intensities of the two or more data points and the intensities in the standard sensitivity data corresponding to the wavelengths of the two or more data points ;
setting a correction coefficient line indicating the relationship between wavelength and intensity ratio based on the wavelengths of the two or more data points and the two or more intensity ratios;
A correction method comprising the step of correcting the standard sensitivity data using the correction coefficient line . The correcting step includes:
2. The correction method according to claim 1, further comprising the step of calculating and storing, for each wavelength, the product of the intensity ratio of the correction coefficient line and the intensity of the standard sensitivity data before correction as the intensity of the standard sensitivity data after correction . The setting step includes:
The correction method according to claim 1 or 2, further comprising the step of setting a correction coefficient line that interpolates the wavelength and intensity ratio between the two or more data points. The setting step includes:
fitting a polynomial to the ratio of intensity to wavelength at the two or more data points ;
3. The correction method according to claim 1 , further comprising the step of setting the polynomial-approximated value as the correction coefficient line . the acquiring step includes acquiring measured data including four or more data points obtained by actually measuring wavelengths and intensities for four or more different characteristic X-rays;
The correction method according to claim 4 , wherein the step of polynomial approximation includes a step of approximating the intensity ratio of the four or more data points to a cubic equation. the correcting step includes a step of setting a standard sensitivity curve by polynomial approximating the corrected standard sensitivity data,
3. The correction method according to claim 2 , wherein the standard sensitivity curve is used in the analytical device to calculate the concentration of an element contained in a sample to be measured based on the intensity of characteristic X-rays emitted from the sample. An analytical device using a wavelength dispersive X-ray spectrometer,
a memory for storing the standard sensitivity data and the actual measurement data;
An analysis device comprising: a processor that executes the correction method according to claim 1 or 2 . A program that causes a computer to execute the correction method according to claim 1 or 2 .