JP3143325B2 - Analysis position determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic probe micro analyzer (Electron Probe x-ray Micro Analyzer).
Hereafter, the present invention relates to a method of determining an analysis position in an apparatus for performing X-ray analysis, such as EPMA).

[0002]

2. Description of the Related Art Conventionally, when performing elemental analysis or the like using EPMA, the analysis position of a sample is usually determined by observing a reflected electron image. That is, first, the electron beam is raster-scanned over the analysis range of the sample, and at that time, reflected electrons generated from the sample are detected to obtain a reflected electron image of the analysis range, and the reflected electron image is observed. The analysis position is determined.

After the analysis position is determined, the determined analysis position is irradiated with an electron beam, and at that time, X-rays emitted from the sample are detected and analyzed to perform elemental analysis. It is the current situation.

[0004]

However, when performing elemental analysis by EPMA, the location where the electron beam is irradiated is as follows:
As shown in FIG. 6A, it is desirable to irradiate a portion where the composition is uniform to a relatively deep place. This is because X-rays are also emitted from a deep portion of about 1 to 2 μm.

On the other hand, since the reflected electrons are generated from a place shallower than several hundreds of degrees, for example, as shown in FIG. 6B, the same substance as the substance shown in FIG. 6A exists only in a shallow place on the sample surface. 6A is similar to the reflected electron image of a uniform portion up to a relatively deep composition as shown in FIG. 6A.

Accordingly, the state of uniformity of the internal composition cannot be determined only by observing the reflected electron image. As a result, as shown in FIG. Although there is a desire to analyze a location, there is a problem that a location where the same composition exists only in a shallow portion of the sample surface is determined as an analysis location as shown in FIG. 6B.

[0007] However, when the location shown in FIG. 6B is analyzed, the composition in the depth direction is not uniform. Therefore, there is a difference in the analysis result between the case where the location shown in FIG. 6A is analyzed. It is clear that this will happen. Of course, in such a case, the element can be identified with a certain probability by performing statistical processing on the detection result, but such statistical processing is troublesome.
In addition, since a portion that is originally not desirable for analysis is also analyzed, the analysis time becomes longer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an analysis position determining method capable of determining a uniform portion having a relatively deep composition as an analysis position. is there.

[0009]

In order to achieve the above object, an analysis position determination method according to the present invention prepares a map of concentration for each specified element in a sample, and prepares a scatter diagram based on the map. In addition, the concentration value of the element at the position of the center of gravity of the cluster appearing in the scatter diagram is obtained, and the position on the map where the obtained concentration value is obtained is set as the analysis position.

[0010]

In the present invention, first, a map of the concentration is prepared for each of the specified elements in the sample. Then, a scatter diagram is created based on the map. The scatter diagram may be a scatter diagram showing the relationship between the concentrations of a plurality of arbitrarily selected elements or a scatter diagram based on principal component analysis.

Next, the position of the center of gravity of the cluster appearing in the scatter diagram is obtained. This position of the center of gravity is the position having the maximum value in the cluster.

Then, the concentration value of each element at the position of the center of gravity of the cluster is determined, and the position on the map where the concentration value is obtained is set as the analysis position.

Since the analysis position obtained as described above is very likely to be uniform to a relatively deep composition, the analysis result at this analysis position is good.
Thus, elemental analysis can be performed in a short time and efficiently.

[0014]

Embodiments will be described below with reference to the drawings.
FIG. 1 shows an EPM to which the analysis position determination method according to the present invention is applied.
1A is a diagram showing a configuration of an embodiment of the present invention, in which 1 is a scanning electron microscope (hereinafter, referred to as SEM), 2 is a deflection coil, 3
Is a sample, 4 is an X-ray detector, 5 is an X-ray analyzer, 6 is a scanning circuit, 10 is a control device, 11 is a CPU, 12 is an X-ray image memory, 13 is a scatter diagram memory, 14 is an input device, 15 Indicates a monitor.

In FIG. 1, a sample 3 is placed at a predetermined position of the SEM 1. The SEM 1 includes a deflection coil 2 for raster-scanning the electron beam over a predetermined range of the sample 3. A deflection current for raster-scanning this electron beam is supplied from a scanning circuit 6. In addition, SE
Various coils other than the deflecting coil 2 are arranged in the M1, but are not essential in the present invention, and are omitted here.

The X-ray detector 4 detects X-rays emitted from the sample. There are various types of X-ray detectors, but any type may be used.

The X-ray analyzer 5 analyzes and outputs the characteristic X-ray of what element the X-ray detected by the X-ray detector 4 is.

The control device 10 performs the analysis position determination processing according to the present invention based on the output from the X-ray analysis device 5, and includes a CPU 11, an X-ray image memory 12, and a scatter diagram memory 13. . The operation of the CPU 11, the X-ray image, and the scatter diagram will be described later in detail.

The input device 14 includes a keyboard, a light pen, and the like, and the monitor 15 is provided to display various data such as a display of a determined analysis position.

Next, the operation of the operator when performing the analysis position determination process and the operation of the CPU 11 at that time will be described. When the operator instructs the execution of the process of determining the analysis position from the input device 14, the CPU 11 instructs the scanning circuit 6 to generate a deflection current for raster scanning in response to the instruction.

Thus, raster scanning of the electron beam is performed over a predetermined range of the sample. At this time, X-rays emitted from the sample are detected by the X-ray detector 4 and analyzed by the X-ray analyzer 5. .

Then, the control device takes in the analysis result of the X-ray analyzer 5, creates a map for the designated element,
The created map is stored in the X-ray image memory 12. In addition,
The designated element has been previously input from the input device 14 by the operator. That is, the operator specifies which element to create a map before giving an instruction to execute the process, and the specified element is the specified element. Further, since the map is well known, a detailed description is omitted, but the density value of the element, that is, the count value of the characteristic X-ray of the element is written for each pixel.

Next, the CPU 11 creates a scatter diagram based on the specified element map. There are at least the following two types of scatter diagram.

One scatter diagram is a scatter diagram showing the relationship between the concentrations of the elements. For example, it is assumed that a map indicating the relationship between the concentrations of the element A and the element B is instructed. The CPU 11 reads the density values at the same coordinates of the map of the element A and the map of the element B, and determines the combination of the density values with the density value of the element A as one axis and the density value of the element B as the other axis. A scatter diagram is created by plotting the coordinates on the axes.

More specifically, as shown in FIG. 2A, in the map of the element A, the concentration value of the coordinates (X _P , Y _P ) is N _AP , and in the map of the element B as shown in FIG. Assuming that the concentration value of the coordinates (X _P , Y _P ) is N _BP , for example, as shown in FIG. 2C, the coordinates of the element A are represented on the horizontal axis and the concentration of the element B are represented on the vertical axis (N _AP). , N _BP ) for all pixels of the map.

It is known that the scatter diagram has the following properties. The points on the scatter diagram correspond one-to-one to the original map. Parts of the same composition form one cluster. The spread of a cluster indicates a variation in composition or a statistical variation in measurement. Clusters containing many points represent compositions that occupy a large area on the map. Clusters are connected in a region where one composition continuously changes to another composition. Exact compositions occupy the same coordinates on the scatter plot.

Although the creation of a scatter diagram showing the relationship between the concentrations of the two types of elements has been described above, it is often possible to similarly create a scatter diagram showing the relationship between the concentrations of the three types of elements. It is a known matter.

Further, when creating the scatter diagram, the type of element for which the scatter diagram is to be created may be set in advance by the operator from the input device 14, or the CPU 11 may set the point when the creation of the map is completed. Monitor 1
A menu for requesting designation of an element for creating a scatter diagram may be displayed at 5 and a scatter diagram may be created for the element set by the input device 14 at that time.

Another scatter diagram is a scatter diagram by principal component analysis. Although the principal component analysis method is widely known as one of the statistical processes, it is roughly described as follows.

[0030] Now, assuming that there are four clusters, as shown in FIG. 3A to scatter diagram created in the manner described above, the direction Z ₁ the cluster is distributed as shown in FIG.
(First principal component) and a direction Z ₂ (second principal component) orthogonal to the first principal component can be taken. Therefore, as shown in FIG. 3B, it is necessary to consider orthogonal coordinates having these two axes Z ₁ and Z _2. Can be. This is a scatter diagram based on principal component analysis. Note that the scatter diagram by the principal component analysis shown in FIG. 3B is obtained by giving parallel movement and rotation to the scatter diagram showing the relationship between the concentrations of the elements shown in FIG. 3A. It is clear that the coordinates correspond one-to-one with the coordinates of the scatter diagram showing the relationship between the concentrations of the elements.

As described above, the concentrations of the elements may be used as the two axes of the scatter diagram, or the principal component functions of the first principal component and the second principal component are calculated from the scatter diagram showing the mutual concentrations of the elements. The obtained first principal component and the second principal component may be set as two axes. Which scatter chart is to be created may be set in advance by the operator from the input device 14, or when the map creation is completed, the
A menu may be displayed on the monitor 15 for requesting the type of the scatter diagram to be created by the U11, and a scatter diagram of the type set by the input device 14 may be created at that time.

When the CPU 11 creates a scatter diagram, the CPU 11 stores the scatter diagram in the scatter diagram memory 13.

When the creation of the scatter diagram is completed, the CPU
11 performs clustering. This is a process in which an area in which points plotted in a scatter diagram are gathered into one unit. This clustering process is performed, for example, by a CPU.
11 may calculate the density of points on the scatter plot and automatically recognize the area having a certain density or more as one group, that is, as a cluster, or monitor the created scatter plot. 15, the operator may draw a closed area on the screen with a light pen, and the drawn closed area may be recognized as one cluster.

Assuming that a scatter diagram as shown in FIG. 4A is created by, for example, the above-described process by this clustering process, two clusters A and B are recognized as shown in FIG. 4B.

By the way, as is apparent from the characteristics of the scatter diagram, even if the positions on the map are different, if the composition is the same, that is, if the combination of the density is the same, the plot is plotted at the same position on the scatter diagram. Because it will be
A position on the map corresponding to a region where points are dense on the scatter diagram has a high possibility that the composition is uniform to a relatively deep position, and is desirable as an analysis position.

Then, for each cluster on the scatter diagram, the CPU 11 obtains the position of the maximum point where the most points are plotted. This is the center of gravity of the cluster. Although it is clear that the position of the local maximum point where the points are plotted more than the surroundings may be obtained, the position of the center of gravity is obtained here.

Then, the CPU 11 obtains the obtained density of the center of gravity, and stores the obtained density in a predetermined area of the internal memory. For example, the center of gravity of cluster A shown in FIG.
When was the position shown by, CPU 11 is seeking concentration N _BQ concentration N _AQ and element B of the element A in position of Q, is to store these concentration values.

The above is the description of the case where the scatter diagram showing the relationship between the concentrations of the elements is used. The same applies to the case where the scatter diagram based on the principal component analysis is used to obtain the concentration of each element at the center of gravity. Obviously you can do that.

That is, what is important here is not the position of the center of gravity on the scatter diagram, but the concentration value of each element at the center of gravity.

Next, it is necessary to find at which position on the map the density at the center of gravity was obtained. Therefore,
The CPU 11 reads out the density values of the pixels at the same coordinates from the map of all the elements used in the scatter diagram, compares the read density value with the density value of the center of gravity stored earlier, and reads out the values of all the elements read from the map. When the density value coincides with the density value of the center of gravity, the position of the coordinate is determined as an analysis point, and the coordinate value is stored.

By performing this processing for all the pixels of the map, all the analysis positions can be obtained.

The case of FIG. 2 is as follows.
Now, it is assumed that the position indicated by “•” in FIG. 2C is the center of gravity.
At this time, the CPU 11 first determines the concentration at the origin (0,0) of the map of the element A shown in FIG. 2A and the element B shown in FIG. 2B.
Read the density at the origin (0,0) of the map. _Assuming that the concentration of the element A at this coordinate is N _A00 and the concentration of the element B is N _B00 , the CPU 11 determines the concentration N _A00 of the element A on the map and the concentration N _A00 of the element A at the center of gravity.
_AP is compared, and similarly, the concentration N _B00 of the element B in the map.
And the concentration N _BP of the element B at the center of gravity. If N _A00 = N _AP and N _B00 = N _BP , the coordinates (0,0) on this map are determined as the analysis position.

When the processing for the coordinates (0,0) is completed, the CPU 11 performs the same processing for the next coordinates (1,0). It is obvious that all the analysis positions can be obtained by performing the above-described processing for all the coordinates of the map, that is, for all the pixels in this manner.

When the analysis position is obtained as described above, C
The PU 11 displays the coordinates on the map determined as the analysis position on the monitor 15. Although not shown in FIG. 1, the coordinates of the analysis position determined by providing a printer may be output to the printer. It is clear that a plurality of analysis positions can be obtained.

The above is the processing of the analysis position determination method according to the present invention. After the analysis position is obtained in this manner,
The actual position to be analyzed is arbitrary. It goes without saying that the analysis can be performed at all the obtained analysis positions, but it is also possible to select and analyze some analysis positions.

Although one embodiment of the present invention has been described above, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiment and various modifications are possible.

[0047]

According to the present invention, the location determined as the analysis position is very likely to have a uniform composition up to a relatively deep portion. Therefore, by performing the analysis at this analysis position, the elemental analysis can be shortened. It can be performed accurately in a short time, and the efficiency of analysis can be improved.

If the analysis is performed automatically based on the analysis position determined according to the present invention, the elemental analysis can be automated.

[Brief description of the drawings]

FIG. 1 shows an E to which an analysis position determination method according to the present invention is applied.
It is a figure showing composition of one example of PMA.

FIG. 2 is a diagram for explaining creation of a scatter diagram showing a relationship between concentrations of elements.

FIG. 3 is a diagram for explaining creation of a scatter diagram by principal component analysis.

FIG. 4 is a diagram for explaining clustering.

FIG. 5 is a diagram for explaining a process of obtaining the concentration of each element at the center of gravity of a scatter diagram.

FIG. 6 is a diagram for explaining a conventional problem.

[Explanation of symbols]

1. Scanning electron microscope, 2. Deflection coil, 3. Sample, 4.
X-ray detector, 5 ... X-ray analyzer, 6 ... scanning circuit, 10 ...
Control device, 11 CPU, 12 X-ray image memory, 13
Scatter chart memory, 14 ... input device, 15 ... monitor.

Claims (1)

(57) [Claims] 1. A map of the concentration of each specified element is prepared for a sample, a scatter diagram is prepared based on the map, and the concentration values of the elements at the positions of the centers of gravity of the clusters appearing in the scatter diagram are obtained. An analysis position determination method, wherein a position on a map where a value is obtained is set as an analysis position.