JP2014185940A - Method to evaluate metal concentration of metal surface by epma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analysis method for accurately measuring a concentration distribution in an EPMA analysis for a metal surface.SOLUTION: In a method to evaluate metal concentration by an EPMA, an analysis executes along procedures of: (1) setting a reference point on an analyzed surface of the metal surface, moving a sample table of the EPMA in an X-axis direction of an orthogonal coordinate system from the reference point to an X-axial end of the analyzed surface without scanning an electronic beam, and executing line analysis measurement X; (2) moving the sample table from the reference point in a Y-axis direction perpendicular to the X-axis direction by a distance equivalent to a diameter of the electronic beam; (3) executing the line analysis measurement X after the Y-axial movement; (4) executing the procedures (2) and (3) until a Y-axial end of the analyzed surface, and executing the line analysis measurement of the whole analyzed surface; and (5) statistically processing the measured line analysis measurement X and calculating metal element concentration of the analyzed surface.

Description

  The present invention relates to a method for evaluating a metal concentration on a metal surface using an electron beam microanalyzer (hereinafter referred to as EPMA).

As shown in FIG. 1, the principle of EPMA is to irradiate a sample 6 with an accelerated electron beam and use various signals emitted from the sample 6.
This EPMA has an elemental analysis as a basic function, and is an apparatus that analyzes using characteristic X-rays.
For detecting characteristic X-rays, a wavelength dispersion X-ray spectrometer (hereinafter referred to as WDS) is mainly used.
As shown in FIG. 2, the WDS 11 is a spectroscope that uses Bragg diffraction conditions, and the sample 6, the spectroscopic crystal 9, and the X-ray detector 10 are located on one circumference called a Roland circle. .
With such a mechanism, analysis of the constituent components at the point of interest is performed (Non-Patent Document 1).

  The analysis method using EPMA includes point analysis, line analysis, surface analysis, etc. Among them, the measurement method of line analysis is to irradiate a sample with an electron beam, and on an arbitrary line (basically, This is a method of measuring the concentration distribution of constituent elements by moving in the (linear) direction and detecting the emitted characteristic X-rays.

There are two methods for this line analysis.
As shown in FIG. 3, the first means is a method in which a normally used electron beam is fixed and the sample stage 7 is moved in a certain direction.
The second means is a method in which an electron beam is scanned and the sample stage 7 is fixed as shown in FIG.
By the way, as shown in FIG. 5, when the first means and the second means are simultaneously performed, that is, when the sample stage 7 is moved in a certain direction while scanning the electron beam, surface analysis is performed.

  Usually, when the region of the measurement location is larger than the beam diameter, if the line analysis is performed by the first means, only the width less than the beam diameter can be measured. On the other hand, when line analysis is performed by the second means, the region irradiated with the electron beam in the scanning direction of the electron beam can be measured, but the direction perpendicular to the scanning direction of the electron beam is perpendicular to the electron beam diameter. It is not possible to measure the area.

  Further, when measured by a surface analysis method, among characteristic X-rays generated from the sample 6 by electron beam irradiation, characteristic X-rays that do not reach the X-ray detector 10 because they do not reach the spectroscopic crystal 9 may appear. Yes (see FIG. 6). In this case, a measurement result representative of the measurement location cannot be obtained. For example, there is a problem that the concentration of all constituent elements is lowered.

Surface analysis technology selection book, "Electron probe / microanalyzer EPMA", Japan Surface Science Society, 1998.

  The present invention has been proposed in view of such circumstances, and an object thereof is to provide an analysis method for measuring an accurate concentration distribution in EPMA analysis of a metal surface.

  In view of such a situation, the first invention of the present invention is a method for evaluating the metal concentration of a metal surface by EPMA, and (1) a reference point is provided on the surface to be analyzed of the metal surface, and from the reference point The EPMA sample stage is moved in the X-axis direction of the Cartesian coordinate system to the end of the X-axis direction of the surface to be analyzed without scanning the electron beam, and line analysis measurement X is performed. (2) (3) The line analysis measurement X is performed after the movement in the Y-axis direction. (4) The ( 2), (3) is performed up to the end of the surface to be analyzed in the Y-axis direction, and the line analysis measurement of the entire surface to be analyzed is performed. (5) The measured line analysis measurement X is statistically processed, It analyzes according to the procedure of the above (1)-(5) which calculates metal element concentration, It is characterized by the above-mentioned.

  A second invention of the present invention is a method for evaluating a metal concentration on a metal surface by EPMA, wherein the metal in the first invention is a pure metal and an alloy composed of two or more elements.

  A third invention of the present invention is a method for evaluating a metal concentration on a metal surface by EPMA, wherein the statistical processing in the first and second inventions is an arithmetic average.

  In the present invention, the concentration distribution of all the constituent elements in the measurement region can be accurately measured by performing line analysis on the measurement region.

It is principle explanatory drawing of EPMA which shows typically a mode at the time of irradiating a sample with an electron beam. It is explanatory drawing which shows typically the wavelength dispersion type | mold detector which shows a mode that the electron beam is irradiated to a sample and the emitted characteristic X ray enters into a spectrometer and a detector further. It is a figure which shows typically the method of fixing an electron beam and moving a sample stand by a line analysis method. It is a figure which shows typically the method of scanning an electron beam with a line analysis method. It is a figure which shows typically the method of moving a sample stand, scanning an electron beam with a line analysis method. It is a figure which shows typically the problem of the method of moving a sample stand, scanning an electron beam with a line analysis method. It is a figure which shows typically the structural example of EPMA which concerns on embodiment of this invention. FIG. 8 is a diagram showing in detail the embodiment of the present invention in FIG. 7, schematically showing the state of the analysis method of the present invention which is repeatedly performed by the line analysis method performed by moving the sample stage while fixing the electron beam. . It is a graph which shows the density | concentration distribution of the structural element A in the sample measured by the analysis method of this invention. It is a graph which shows the density | concentration distribution of the structural element B in the sample measured by the analysis method of this invention. It is a graph which shows the density | concentration distribution of the structural element A in the sample measured by the analysis method of the prior art. It is a graph which shows the density | concentration distribution of the structural element B in the sample measured by the analysis method of the prior art.

Hereinafter, an example of specific implementation of EPMA analysis to which the present invention is applied will be described in detail.
<1. Configuration example of EPMA>
FIG. 7 is a diagram schematically showing a configuration example of EPMA.
The EPMA 20 includes a sample stage 7 on which a sample is attached, an electron beam irradiation unit 8 that irradiates the sample, and a detector 10 for characteristic X-rays generated from the sample 6.
Further, the EPMA 20 includes an optical microscope 5 for viewing the movement of the sample stage 7 and the height position of the sample stage.

  The sample stage 7 includes, for example, a horizontal movement mechanism that can move in two vertical dimensions and a horizontal movement mechanism that can move in the height direction. The two-dimensional direction and the height direction of the sample stage 7 are controlled through a “sample stage control unit” and a “system control unit” configured by a personal computer, for example.

The electron beam irradiation unit 8 generates an electron beam from the electron gun 1.
The electron beam generated from the electron gun 1 is finely focused on the sample surface by the focusing lens 2 and the objective lens 4, and scanned on the sample 6 by the scanning coil 3.
The position of the sample 6 is adjusted by the focal position of the built-in optical microscope 5.
The wavelength dispersive detector 11 generates characteristic X-rays from the sample 6 by the electron beam, and spectrally separates the wavelengths of the constituent elements at the measurement location from the wavelength of the characteristic X-rays using the spectroscopic crystal 9 according to Bragg's law. The intensity and concentration are detected by a detector 10 called a proportional counter.

<2. Analysis>
In the present invention, line analysis is performed on the entire region of the measurement range to obtain measurement data for the entire surface, and the obtained measurement data is statistically processed to evaluate the metal concentration.
The measurement procedure will be described with reference to the drawings.
First, the reference point P ₀ is set on the sample, and then the measurement region is set by giving the length and width from the reference point P ₀ . Furthermore, the beam diameter is set.

FIG. 8 is a diagram schematically showing a state in which a method of repeating the method of moving the sample stage while fixing the electron beam by the line analysis method in order to obtain measurement data of the entire surface is shown.
In the measurement, as shown in FIG. 8, the sample stage 7 is moved in the length direction by the length of the measurement range, and the measurement of the line analysis is performed through this movement.
Next, the sample stage 7 is returned to the position at the start of measurement (reference point P ₀ ), and then the sample stage 7 is moved in the width direction by the same length as the beam diameter, and line analysis is performed.
This series of operations is performed until the entire measurement range is covered (see FIG. 8).
After the measurement, the concentration of the metal element in the line analysis performed a plurality of times is statistically processed to obtain the concentration over the entire surface.

  Hereinafter, specific examples of the present invention will be described.

An alloy composed of metal elements A and B (A: 67%, B: 33%) is fixed to an EPMA sample stage and inserted into a sample chamber of EPMA (JXA-8100: manufactured by JEOL Ltd.), and a predetermined location. To place. Next, the XY stage is operated so that the center of the electron beam hits the reference point of the measurement area.
Note that the measurement region has a rectangular shape with a length of 3.5 mm and a width of 1.0 mm from the reference point. The beam diameter was set to 50 μm.

Next, the sample stage was moved 3.5 mm as a measurement region in the length direction, and measurement of line analysis was performed through this movement.
Next, the sample stage was returned to the position (reference point) at the start of measurement, and then the sample stage was moved in the width direction by 50 μm, which is the same as the beam diameter.

This series of operations was performed 20 times, and data for the entire surface was obtained for a measurement region having a length of 3.5 mm and a width of 1.0 mm.
After the measurement, the concentrations of the metal elements A and B in the line analysis performed 20 times were averaged to obtain a concentration profile representing the entire surface, and FIG. 9 as the metal element A and FIG. 10 as the metal element B were obtained.

(Comparative Example 1)
The same sample as in Example 1 was used, the same apparatus was used, and the measurement area (reference point, range size) was also the same as in Example 1. The beam diameter was 100 μm.
The sample stage was moved 3.5 mm as a measurement region in the length direction, and the beam was scanned 1.0 mm in the width direction throughout this movement to perform analysis measurement.
After the measurement, FIG. 11 as the metal element A and FIG. 12 as the metal element B were obtained.

(Evaluation)
In Example 1, the alloy composition is 67% for metal element A and 33% for metal element B. In Example 1, the metal element A concentration is 60 to 70% in FIG. 9, and the metal element B concentration is 30 to 30 in FIG. 40%.
On the other hand, in Comparative Example 1, the metal element A concentration is 30 to 60% in FIG. 11, and the metal element B concentration is 25 to 30% in FIG. 12, and the deviation from the alloy composition is remarkable. is there.

  In Comparative Example 1, the cause of the remarkable deviation from the alloy composition in the measurement result is X-rays that do not reach the spectroscopic crystal among the characteristic X-rays generated by scanning the electron beam. These X-rays are detected by X-rays. It is assumed that the measurement result representative of the measurement region was not obtained because it did not reach the vessel.

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Focusing lens 3 Scanning coil 4 Objective lens 5 Optical microscope 6 Sample 7 Sample stand 8 Electron beam irradiation part 9 Spectroscopic crystal 10 X-ray detector 11 Wavelength dispersion type detector 20 Electron beam microanalyzer (EPMA)
P ₀ reference point (sample start position when performing analysis)

Claims (3)

A method for evaluating a metal concentration on a metal surface by EPMA, wherein the metal concentration is analyzed according to the following procedures (1) to (5).
(1) A reference point is provided on the surface to be analyzed of the metal surface, and the EPMA sample stage is moved in the X-axis direction of the orthogonal coordinate system without scanning an electron beam from the reference point, and the X-axis direction of the surface to be analyzed. Move to the end and perform line analysis measurement X.
(2) The sample stage is moved a distance corresponding to the electron beam diameter from the reference point in the Y-axis direction perpendicular to the X-axis direction.
(3) After the movement in the Y-axis direction, the line analysis measurement X is performed.
(4) The above (2) and (3) are performed up to the end of the surface to be analyzed in the Y-axis direction, and the line analysis measurement of the entire surface to be analyzed is performed.
(5) The measured line analysis measurement X is statistically processed to calculate the metal element concentration on the surface to be analyzed.   2. The method for evaluating a metal concentration on a metal surface by EPMA according to claim 1, wherein the metal is a pure metal and an alloy composed of two or more elements.   The method for evaluating a metal concentration on a metal surface by EPMA according to claim 1, wherein the statistical processing is an arithmetic average.

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