CN114839213A

CN114839213A - Surface analysis device

Info

Publication number: CN114839213A
Application number: CN202210032663.6A
Authority: CN
Inventors: 石川丈宽
Original assignee: Shimadzu Corp
Current assignee: Shimadzu Corp
Priority date: 2021-02-02
Filing date: 2022-01-12
Publication date: 2022-08-02
Also published as: JP2022118565A

Abstract

Provided is a surface analysis device which performs simple and highly versatile analysis using a ternary system state diagram based on data obtained by element mapping analysis. The device is provided with: a measurement unit that acquires signals reflecting the amounts of three or more elements to be analyzed at a plurality of positions on a sample; and a data processing unit that generates a ternary dispersion map for a predetermined three elements based on the measurement result of the measurement unit, wherein the data processing unit includes a first conversion unit that converts the signal intensities of the three elements into the sum of the concentrations of the three elements as a 100% concentration by weight or mass concentration, a second conversion unit that converts the concentration by weight or mass concentration of each element obtained by the first conversion unit into a 100% concentration by mole or atomic concentration by the sum of the concentrations of the three elements using the atomic weight of the element, and a dispersion map generation unit that generates the ternary dispersion map with the molar concentration or atomic concentration of the three elements as an axis.

Description

Surface analysis device

Technical Field

The present invention relates to a surface analyzer for investigating the distribution of components (elements, compounds) present in a one-dimensional or two-dimensional measurement region on a sample. The surface analyzing apparatus includes an Electron beam microanalyzer (Electron Probe Micro Analyzer: EPMA), a Scanning Electron Microscope (Scanning Electron Microscope: SEM), and the like.

Background

In the element mapping analysis using EPMA, the kind and amount of an element contained in each of a plurality of minute regions (measurement points) in a two-dimensional region on a sample can be examined. When analyzing the result obtained by such element mapping analysis, for example, the following method, i.e., phase analysis (or phase analysis), is often used: a scatter diagram of the signal intensity of characteristic X-rays relating to two or three elements specified by a user or a scatter diagram of the concentration of an element calculated from the signal intensity is created, and the kind and content ratio of a compound contained in a sample are confirmed from the distribution of plotted points on the scatter diagram.

For example, fig. 11 of patent document 1 shows an example of a ternary scatter diagram for three elements. The ternary scatter plot is a plot of the relative intensities or% concentrations of the elements, respectively, on three axes, normalized in such a way that their sum is 100%. In addition, when the axis of the ternary dispersion plot (the same applies to the binary dispersion plot) is concentration, the concentration is usually either weight concentration (wt%) or mass concentration (mass%).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-153858

Patent document 2: japanese patent laid-open publication No. 2006 and 125952

Non-patent document

Non-patent document 1: "quantification of EPMA garment Power" in the other dimension by analysis of the surface of the auxiliary island, S.S., Vol.S., seventh, No. 3, 1986

Disclosure of Invention

Problems to be solved by the invention

In the fields of mineralogy, alloy manufacturing, and the like, when the concentrations of a plurality of elements contained in a sample are measured by EPMA or the like, and the sample is classified by a chemical composition based on the measurement result, ternary system state diagrams disclosed in various documents such as technical papers are widely used. Ternary system state diagrams are also known in the metal art as Gibbs (Gibbs) triangles. Fig. 4 is a conceptual diagram of a ternary system state diagram used in mineralogy. In the ternary system state diagram, three elements or compounds (in fig. 4, [ a ], [ B ], and [ C ]) designated respectively correspond to the respective vertices of a regular triangle, and three sides are axes indicating the concentrations of the elements or compounds. Then, the mineral constituting the sample is identified based on the position in the triangle where the concentrations of the three elements contained in the sample to be measured are plotted (i, ii, iii … … in fig. 4). As a unit of a concentration axis in the ternary system state diagram, a molar concentration (mol%) is widely used.

In mineral analysis using the ternary state diagram as described above, conventionally, signal intensities of all elements (all elements that can be measured) present at a specific measurement point on a sample are generally measured by EPMA, and from the signal intensities, the weight concentration (or mass concentration) is calculated by conversion using a standard sensitivity method or a standard curve method. Then, the molar concentration is calculated from the weight concentration of all the elements and the atomic weight of each element, and the mineral at the measurement point existing on the sample is identified by plotting points corresponding to the molar concentration of all the elements on a ternary state diagram.

Since EPMA generally uses a wavelength dispersion type spectrometer, it is impossible to detect characteristic X-rays of a plurality of elements at the same time, and it takes time to obtain signal intensities of all elements. Therefore, in the element mapping analysis for a region that is large to some extent, only a few elements of interest are measured in many cases. Therefore, the molar concentration of all the elements contained in each measurement point cannot be obtained, and the measurement points cannot be plotted on a ternary state diagram. That is, it is difficult to determine, for example, what mineral the set of plot points on the ternary scatter diagram that can be grasped corresponds to by comparing the plot points on the ternary scatter diagram with the ternary state diagram.

In contrast, in the surface analyzer described in patent document 2, the concentration axis of the ternary system state diagram (three-component state diagram in patent document 2) can be switched between the mass concentration and the atomic concentration, and the comparison with the ternary dispersion diagram can be performed by selecting the mass concentration as the concentration axis. However, in the conventional surface analysis device, it is assumed that various ternary system state diagrams are recorded in the device and are converted into a database by using a scanner or the like in advance, and only a ternary scatter diagram generated by measurement can be compared with the ternary system state diagram converted into the database, which is a serious limitation. In addition, there are also problems as follows: the user cannot easily compare the ternary dispersion map created by the measurement with the ternary state map existing in the data at hand.

The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a surface analyzer capable of performing simple and versatile analysis using a ternary state diagram based on data obtained by element mapping analysis for a region that is large to some extent.

Means for solving the problems

One embodiment of a surface analyzer according to the present invention, which has been made to solve the above problems, includes:

a measurement unit that acquires signals reflecting the amounts of three or more elements to be analyzed at a plurality of positions on a sample; and

and a data processing unit that generates a ternary dispersion map for predetermined three elements based on a measurement result of the measurement unit, wherein the data processing unit includes a first conversion unit that converts signal intensities of the predetermined three elements into a sum of concentrations of the predetermined three elements of 100% by weight or mass concentration, a second conversion unit that converts the sum of the concentrations of the predetermined three elements into a molar concentration or an atomic concentration of each element obtained by the first conversion unit using an atomic weight of the element, and a dispersion map generation unit that generates the ternary dispersion map on the basis of the molar concentration or the atomic concentration of the predetermined three elements as an axis.

Typically, the surface analyzer according to the above aspect of the present invention is a surface analyzer including a wavelength dispersion spectrometer such as an EPMA or SEM. In such a surface analyzer, by repeating measurement while changing the position of irradiation with excitation radiation (electron beam, X-ray, or the like) on the sample, a signal reflecting the amount of the element present at each of a plurality of positions in a one-dimensional region or a two-dimensional region on the sample can be obtained.

ADVANTAGEOUS EFFECTS OF INVENTION

As described above, in general, the axes of the disclosed ternary system state diagram are expressed in terms of molar or atomic concentrations. According to the surface analysis apparatus of the above aspect of the present invention, the ternary dispersion map that can be created by the element mapping analysis is represented by using the molar concentration or the atomic concentration as an axis, and is not represented by using the weight concentration or the mass concentration as an axis, and therefore, the user can compare the ternary dispersion map with a general ternary state map to identify, for example, a mineral. Thus, the user can easily analyze the ternary system state diagram existing in the data at hand.

Drawings

Fig. 1 is a configuration diagram of a main part of an EPMA according to an embodiment of the present invention.

Fig. 2 is a flowchart showing the procedure from sample measurement to display of a ternary dispersion map in the EPMA according to the present embodiment.

Fig. 3 is a diagram showing an example of a ternary scatter diagram displayed in the EPMA according to the present embodiment.

Fig. 4 is a conceptual diagram illustrating an example of a general ternary system state diagram.

Fig. 5 is a diagram showing a display example of a surface observation image and a ternary dispersion map.

Detailed Description

An EPMA as an embodiment of a surface analyzer according to the present invention will be described with reference to the drawings. Fig. 1 is a configuration diagram of a main part of the EPMA according to the present embodiment.

As shown in fig. 1, the electron beam irradiation unit 1 includes an electron gun 100, a deflection yoke, and the like, which are not shown, and irradiates a sample 3 placed on a sample stage 2 with an electron beam having a very small diameter. After the sample 3 receives the electron beam, a characteristic X-ray having a wavelength specific to the element is emitted from the surface of the sample 3. The characteristic X-rays emitted from the sample 3 are wavelength-dispersed by the spectroscopic crystal 4, and the diffracted X-rays of a specific wavelength are detected by the X-ray detector 5. Although not shown, the EPMA includes a detection unit for detecting reflected electrons and secondary electrons, and the detection unit detects the reflected electrons and secondary electrons emitted from the sample 3 in response to the irradiation of the electron beam.

The electron beam irradiation position on the sample 3, the spectroscopic crystal 4, and the X-ray detector 5 are always positioned on a rowland circle, and the spectroscopic crystal 4 is tilted while being linearly moved by a drive mechanism not shown, and the X-ray detector 5 is rotated in conjunction with the movement. Thereby, wavelength scanning of X-rays as an analysis object is realized while maintaining a state in which bragg diffraction conditions are satisfied, that is, an incident angle of characteristic X-rays with respect to the spectroscopic crystal 4 is equal to an output angle of diffracted X-rays with respect to the spectroscopic crystal 4. The detection signal of the X-ray intensity obtained by the X-ray detector 5 is input to the data processing unit 6.

The sample stage 2 can be moved in two axial directions, i.e., X and Y axes, perpendicular to each other by the sample stage driving unit 7. By this movement, the irradiation position of the electron beam on the sample 3 is scanned two-dimensionally. In addition, the scanning of the irradiation position of the electron beam on the sample 3 can be performed by deflecting the emission direction of the electron beam in the electron beam irradiation unit 1 without moving the sample stage 2.

The data processing unit 6 includes, as functional blocks, an element intensity calculation unit 60, a data storage unit 61, a weight concentration conversion unit 62, a molarity conversion unit 63, a ternary dispersion map creation unit 64, a display processing unit 65, and the like.

The analysis controller 8 controls operations of the sample stage driver 7, the drive mechanism for moving the spectroscopic crystal 4 and the X-ray detector 5, and the like, to perform analysis of the sample 3. The central control unit 9 is responsible for control of the entire apparatus and input/output processing, and the central control unit 9 is connected to a display unit 11 and an operation unit 10 including a keyboard and a mouse (or other pointing devices).

Typically, all or a part of the central control unit 9, the analysis control unit 8, and the data processing unit 6 is constituted by a personal computer, and the respective functions can be realized by executing dedicated control/processing software installed in the computer by the computer.

Fig. 2 is a flowchart showing the procedure from sample measurement to display of a ternary dispersion map in the EPMA according to the present embodiment. Characteristic processing in the EPMA according to the present embodiment will be described with reference to fig. 2.

In the case of performing the element mapping analysis (surface analysis) in the EPMA of the present embodiment, the analysis control unit 8 fixes the position of the spectroscopic crystal 4 in accordance with the characteristic X-ray wavelength of the target element specified by the user in advance, and operates the sample stage driving unit 7, the electron beam irradiation unit 1, and the like so as to repeatedly detect the characteristic X-ray while changing the irradiation position of the electron beam in a predetermined order within a predetermined (usually specified by the user) two-dimensional region on the sample 3. Then, if the acquisition of the intensity distribution with respect to one target element is ended, the same measurement is performed on the other target elements. The element intensity calculating unit 60 acquires X-ray intensities of a plurality of target elements for each measurement point on the sample 3. The X-ray intensity data is stored in the data storage unit 61 (step S1).

In addition, when an energy-dispersive X-ray spectrometer is used instead of a wavelength-dispersive spectrometer, the element intensity calculation unit 60 may generate an X-ray spectrum for each measurement point in the two-dimensional region, detect a peak of a specific wavelength corresponding to the target element on the X-ray spectrum, and calculate the X-ray intensity of the target element by obtaining the peak intensity.

After the measurement of all the measurement points set in the two-dimensional region on the sample 3 is completed, when the user performs a predetermined operation from the operation unit 10, the weight concentration conversion unit 62 reads out the X-ray intensity data of three elements (hereinafter referred to as element A, B, C) for each measurement point from the data storage unit 61. Then, the weight concentration conversion unit 62 performs a process of converting the X-ray intensity into a weight concentration or a mass concentration. Here, the weight concentration or the mass concentration is a value normalized so that the sum of the weight concentrations or the mass concentrations of the three elements A, B, C becomes 100% (step S2).

The processing of step S2 can be performed using, for example, a standard sensitivity method or a standard curve method that has been generally performed conventionally as disclosed in non-patent document 1. By this processing, the weight concentration of the element A, B, C was obtained for each measurement point. In addition, the mass concentration may be used instead of the weight concentration. In a conventional general ternary dispersion diagram, one measurement point on the sample 3 is plotted as one point on the axis of the weight concentration (or the relative signal intensity before conversion to concentration) of these three elements.

Next, the molar concentration conversion unit 63 performs a process of converting the weight concentration of the element A, B, C into a molar concentration (or an atomic concentration) for each measurement point, using the atomic weight information of the element A, B, C provided in advance (step S3). Specifically, the molar concentration conversion unit 63 can perform the following calculation.

At present, the weight concentration (wt%) of element A, B, C at a certain measurement point on sample 3 is represented by W _A 、W _B 、W _C . According to the above regulation, W _A +W _B +W _C 100. When the atomic weight of the element A, B, C is represented by a, b, and c, the molar concentration (mol%) M of the element A, B, C _A 、M _B 、M _C Is M _A ＝K×(W _A /a)、M _B ＝K×(W _B /b)、M _C ＝K×(W _C And c) the reaction solution is mixed. Here, K is an unknown coefficient.

However, when the display of the three axes of the ternary dispersion diagram is converted from the weight concentration to the molar concentration, since the sum of the concentrations of the three elements is also constant at 100%, the ratio of the molar concentrations of the three elements does not depend on the molar concentrations of the elements other than the three elements contained in the sample. Thus, the molar concentration of the element A, B, C corresponding to one point plotted on the ternary dispersion plot is as follows.

M _A ＝{K×(W _A /a)}/[K×{(W _A /a)+(W _B /b)+(W _C /c)}]＝(W _A /a)/{(W _A /a)+(W _B /b)+(W _C /c)}

M _B ＝{K×(W _B /b)}/[K×{(W _A /a)+(W _B /b)+(W _C /c)}]＝(W _B /b)/{(W _A /a)+(W _B /b)+(W _C /c)}

M _C ＝{K×(W _C /c)}/[K×{(W _A /a)+(W _B /b)+(W _C /c)}]＝(W _C /c)/{(W _A /a)+(W _B /b)+(W _C /c)}

That is, the molar concentration of the element A, B, C can be determined from the weight concentration and the atomic weight, respectively, regardless of the unknown coefficient K.

In this manner, the molar concentration conversion unit 63 calculates the molar concentrations of the three elements A, B, C for each measurement point on the sample 3. Then, the ternary dispersion map creation unit 64 creates a ternary dispersion map indicating the relationship between the molar concentrations of the three elements A, B, C (step S4). The display processing unit 65 causes the central control unit 9 to display the created ternary scattergram on the screen of the display unit 11 (step S5).

Fig. 3 shows an example of the ternary scatter diagram thus produced and displayed. As shown in fig. 3, in the ternary scatter plot, the three concentration axes are all expressed in molarity. Fig. 5 is a diagram showing a ternary dispersion map in parallel with a surface observation image of the sample 3 prepared based on a detection signal of secondary electrons or reflected electrons. In fig. 5, one point on the right ternary dispersion map corresponds to one measurement point (measurement position) corresponding to the measurement target region on the sample 3 displayed on the left surface observation image.

The user can use the displayed ternary scatter plot and the ternary state plot present in the data at hand to identify minerals as follows.

In the ternary system state diagram shown in fig. 4, it is assumed that [ a ], [ B ], and [ C ] include the element A, B, C, and the other elements are common compounds. In this case, it can be considered that the three axes are substantially the same between the ternary dispersion diagram shown in fig. 3 and the ternary state diagram shown in fig. 4, and a certain point on the ternary dispersion diagram can be associated with the same position on the ternary state diagram. Therefore, a certain point on the ternary dispersion map can be associated with a certain mineral among the plurality of minerals shown on the ternary state diagram, and the mineral can be identified based on the position of the point. In the examples of fig. 3 and 4, the mineral iii corresponding to each point included in P forming the cluster in fig. 3 can be identified from fig. 4.

In the ternary scatter diagram on the display screen shown in fig. 5, when the user instructs the operation unit 10 to perform a predetermined operation so as to circle the points forming the cluster, the display processing unit 65 displays the positions corresponding to the instructed points on the sample 3 in a color distinguishable from other positions. In the example of fig. 5, instead of displaying the area corresponding to the point in color, the area is indicated by oblique lines. Thus, the positions of the measurement points having the three elements A, B, C in the three-dimensional scatter diagram, which form clusters, that is, the three elements A, B, C having close concentrations, on the sample 3 are visually clarified. Further, since the minerals corresponding to the measurement points forming clusters on the ternary scattergram are known by directly comparing the ternary scattergram with the ternary state diagram as described above, the minerals existing in a certain region on the sample 3 can be grasped.

Since the weight concentration and the mass concentration are substantially the same, the weight concentration can be replaced with the mass concentration in the above description. Similarly, since the molar concentration and the atomic concentration are substantially the same, the molar concentration can be replaced with the atomic concentration in the above description.

In displaying the ternary dispersion map, a button for switching the display of the concentration on the axis of the ternary dispersion map between the weight concentration (or the mass concentration) and the molarity (or the atomic concentration) may be displayed on the same screen, and the concentration on the axis of the displayed ternary dispersion map may be switched in accordance with an operation of the button.

Further, although the above embodiment is EPMA, the present invention can be applied to various analysis apparatuses such as SEM which can acquire signals reflecting the amounts of elements or components (compounds and the like) at a plurality of measurement points in a one-dimensional or two-dimensional region on a sample.

The above embodiments are merely examples of the present invention, and it is needless to say that the present invention is encompassed by the scope of the claims of the present application even if appropriate changes, modifications, additions and the like are made within the scope of the gist of the present invention.

[ various means ]

It should be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following modes.

(first aspect) one embodiment of a surface analyzing apparatus according to the present invention includes:

and a data processing unit that generates a ternary dispersion map for the predetermined three elements based on the measurement result of the measurement unit, wherein the data processing unit includes a first conversion unit that converts signal intensities of the predetermined three elements into a sum of concentrations of the predetermined three elements of 100% by weight or mass concentration, a second conversion unit that converts the weight or mass concentration of each element obtained by the first conversion unit into a sum of concentrations of the predetermined three elements of 100% by using an atomic weight of the element, and a dispersion map generation unit that generates the ternary dispersion map on the basis of the sum of the concentrations of the predetermined three elements of 100% by mole or atomic concentration.

(second term) in the surface analyzing apparatus according to the first term, the second conversion unit may perform the following calculation: the temporary value is obtained by dividing the weight concentration or mass concentration of each element obtained by the first conversion unit by the atomic weight of the element, and then normalizing the temporary value of each element so that the sum of the temporary values of the predetermined three elements becomes 100%.

According to the surface analysis apparatus described in the first and second aspects, the ternary dispersion map that can be created by elemental mapping analysis (surface analysis) is represented by using the molar concentration or the atomic concentration as an axis, and is not represented by using the weight concentration or the mass concentration as an axis, and therefore, a user can compare the ternary dispersion map with a general ternary state map to identify, for example, a mineral. Thus, the user can easily perform analysis such as mineral identification using the ternary state diagram existing in the data at hand.

(third) in the surface analyzer of the first or second aspect, the data processing unit may further include a display processing unit that displays a ternary dispersion map in which the concentration display of the axis is switched between a weight concentration or a mass concentration and a molar concentration or an atomic concentration.

According to the surface analysis device of the third aspect, the density display can be switched appropriately when the user wants to compare the ternary system state diagram with another one or when the user wants to confirm the distribution by the normal density display.

Description of the reference numerals

1: an electron beam irradiation unit; 100: an electron gun; 2: a sample stage; 3: a sample; 4: a spectroscopic crystal; 5: an X-ray detector; 6: a data processing unit; 60: an element intensity calculating section; 61: a data storage unit; 62: a weight concentration conversion unit; 63: a molar concentration conversion unit; 64: a ternary scatter diagram making part; 65: a display processing unit; 7: a sample stage driving section; 8: an analysis control unit; 9: a central control unit; 10: an operation section; 11: a display unit.

Claims

1. A surface analysis device is provided with:

2. A surface analysis apparatus according to claim 1,

the second conversion section performs the following calculation: the temporary value is obtained by dividing the weight concentration or mass concentration of each element obtained by the first conversion unit by the atomic weight of the element, and then normalizing the temporary value of each element so that the sum of the temporary values of the predetermined three elements becomes 100%.

3. A surface analysis apparatus according to claim 1 or 2,

the data processing unit further includes a display processing unit for displaying a ternary dispersion map in which the concentration display of the axis is switched between a weight concentration or a mass concentration and a molar concentration or an atomic concentration.