JPH0619967B2 - Sample position setting method for X-ray microanalyzer, etc. - Google Patents

Description

The present invention relates to a sample position setting method in an X-ray microanalyzer or the like.

(Prior Art) In the X-ray microanalyzer (XMA), the surface analysis method is adopted as one of the methods for measuring the element distribution on the sample surface. This surface analysis method uses XMA
Control, the sample irradiated with the electron beam is two-dimensionally moved, and the X-ray (or the electron beam) emitted by the electron beam irradiation from the sample surface is detected by a wavelength dispersive X-ray spectroscope or the like. It is detected by a device and displayed as a brightness modulation image on a CRT screen, for example.

In the analysis by the wavelength dispersive X-ray spectroscope, it is necessary to keep the positional relationship between the electron beam irradiation point (that is, the X-ray generation point) on the sample surface and the spectroscope constant. Direction) is set on the sample stage so that the flat surface of the sample is perpendicular to the surface, and the sample surface is moved within a plane perpendicular to the z-axis. Therefore, the sample stage includes an x-axis drive mechanism and a y-axis drive mechanism that move the sample in the x-axis direction perpendicular to the z-axis and the y-axis direction perpendicular to the z-axis and the x-axis. Further, a z-axis drive mechanism for moving the sample in the z-axis direction is provided, and the height of the z-axis drive mechanism is adjusted so that the optimum position is set when the sample is set on the sample stage.

This height adjustment can be performed, for example, by irradiating the sample with an electron beam while X
This is performed by monitoring the X-ray detection output by the line spectroscope and setting the height of the sample at a position where the maximum output value is obtained when the sample is moved up and down by the z-axis drive mechanism. After such height adjustment is completed, the above-mentioned x-axis drive mechanism and y-axis drive mechanism are controlled by a scanning signal to perform two-dimensional scanning on the sample surface by the electron beam.

However, when the moving direction of the sample stage is not exactly perpendicular to the z-axis or the sample is not correctly set on the sample stage, the z-direction of the sample surface position irradiated by the electron beam due to the movement of the sample stage. The coordinate in the axial direction fluctuates, and the generation point of the X-ray incident on the spectroscope cannot be kept constant. This height shift in the z direction adversely affects the X-ray detection efficiency, and correct surface analysis cannot be performed.

Therefore, conventionally, the heights (z coordinate values) of the four corners of the analysis area (rectangle) established inside the sample surface area before the measurement are measured by focusing the optical microscope, and z is measured during the surface analysis measurement. Position correction in the z-axis direction was performed by the shaft drive mechanism.

(Problems to be Solved by the Invention) When the analysis area is set inside the actual sample surface area, there is no particular problem even with the conventional position control correction. However, in the case of actually analyzing the sample, there are cases where it is desired to make the analysis region wider than the actual sample surface region and observe the entire image of the sample.

In the conventional sample position setting method, the positions of the four corners of the analysis region are always inside the sample surface region, and the z coordinates of the four corners of the analysis region can be determined. Therefore, when at least one of the four corners of the analysis area deviates from the sample surface area, such as when observing the entire surface of a sample whose shape is not rectangular (observation of the entire sample surface area), etc. It is not possible to obtain the z-coordinates of the above-mentioned positions deviating from the four corner positions, and it is not possible to sufficiently correct the position of the sample in the height direction (z-axis direction), so that accurate surface analysis of the sample can be performed. I couldn't. Further, since there is no objective numerical value indicating the flatness of the sample surface, there is a problem that the obtained surface analysis result lacks reliability.

The present invention has been made in view of such points,
Even if the analysis area is wider than the actual sample surface area, the position of the sample in the height direction (z-axis direction) can be accurately corrected, and the flatness of the sample surface can be used as an objective numerical value. It is to realize a sample position setting method in an X-ray microanalyzer or the like that can be obtained.

(Means for Solving Problems) The present invention which solves the problems described above is, when the sample is moved in the x-axis direction and the y-axis direction in order to obtain information on the two-dimensional element distribution of the analysis region, In a sample position setting method in an X-ray microanalyzer or the like that adjusts the height of the sample in the z-axis direction based on the (x, y, z) coordinate values of the four corners of the analysis region, the actual sample surface region is surrounded. The analysis area is formed by a rectangular area wider than the sample surface area, and x-coordinate values and y-coordinate values of the four corners of the analysis area are obtained (step), and on the sample surface area in the analysis area, x coordinate value and y
By defining four points specified by the coordinate values (a square is formed by connecting the four points with a straight line), the height of the sample surface is measured at the four points, and the z coordinate value of the four points is obtained. The (x, y, z) coordinate values of the four points are obtained (step), and assuming that the actual sample surface extends outside the sample surface area, the (x, y, z) of the four points on the sample surface area are assumed. , Y, z) coordinate values to determine (x, y, z) coordinate values at the four corners of the analysis area by calculating z coordinate values at the four corners of the analysis area (step). Based on the determined (x, y, z) coordinate values of the four corners of the analysis region, height adjustment in the z-axis direction is performed when the sample is moved in the x-axis direction and the y-axis direction (step). It is characterized by doing so.

(Operation) In the method of the present invention, the analysis region is formed by a rectangular region surrounding the actual sample surface region and wider than the sample surface region. Then, four points specified by the x-coordinate value and the y-coordinate value are defined in the analysis area on the sample surface area, the height of the sample surface is measured at the four points, and the z-coordinate value of the four points is determined. Ask. Next, based on the (x, y, z) coordinate values of the four points on the sample surface area, z coordinate values at the four corners of the analysis area are calculated, and the (x, y, z z) Determine the coordinate values. Based on the determined (x, y, z) coordinate values of the four corners of the analysis region, the height adjustment in the z-axis direction is performed when the sample is moved in the x-axis direction and the y-axis direction.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The analysis area in the present invention is a rectangular area that surrounds the actual sample surface area and is wider than the sample surface area. Here, as shown in FIG. 2, the four corners of the rectangular analysis region S2 are set to A,
B, C, and D, and the shape of the actual sample surface area S1 is not rectangular (the actual sample surface area S1 is included in the analysis area S2).

Step The analysis area is formed by a rectangular area that surrounds the actual sample surface area and is wider than the sample surface area, and x at the four corners of the analysis area is formed.
Obtain the axis coordinate value and the y coordinate value. The specific procedure within this step is as follows.

The length of each side of the analysis area is determined from the number of pixels in the x and y directions of the analysis sample surface and the pixel length.

As shown in FIG. 3, the electron beam irradiates the analysis region two-dimensionally. That is, two-dimensional scanning is performed with the main scanning in the x direction and the sub scanning in the y direction. Length of analysis area in x direction (side A
B) is Lx, and the length in the y direction (side BC) is Ly. x
y If the number of pixels and the pixel length in each direction are known, the length of each side can be obtained by the number of pixels × pixel length.

The coordinate values of the four corners of the analysis area are obtained by designating the coordinates of the center point of the analysis area.

This will be described with reference to FIG. If the coordinates (x ₀ , y ₀ ) of the center point 0 of the rectangle ABCD are specified, points A, B, C, D
The coordinates of can be easily obtained. For example, the coordinates of point C are as follows.

x coordinate value; x ₀ + (Lx / 2) y coordinate value; y ₀ + (Ly / 2) The other three points A, B, and D can be obtained in exactly the same manner.

Steps 4 points (quadrangle) on the actual sample surface area using the sample surface observing device and position specifying means such as a joystick or mouse
The (x, y, z) coordinate value of is calculated.

As shown in FIG. 2, four points (quadrilaterals) A ', B', C ', D'are determined on the actual sample S1. Quadrangle A ',
B ′, C ′ and D ′ do not necessarily have to be rectangular.
In determining the four points A ', B', C ', and D', it is desirable that the shape of the sample be well represented and as wide as possible. When the four points A ', B', C ', and D'are set, each point is then focused on the observation surface using a sample surface observation device such as an optical microscope and a joystick.

For each point, the coordinate value in each of the x and y directions can be obtained by moving each point to the observation surface position. Next, by focusing on the observation plane, the coordinate value of the point in the z direction can be obtained. As described above, the x-axis drive mechanism, the y-axis drive mechanism, and the z-axis drive mechanism described above are used to move in the x, y, and z directions using the joystick.

Step Based on the (x, y, z) coordinate values of the four points on the actual sample surface area, the z coordinate values of the four corners of the analysis area are obtained.

According to the previous step, four points A ', B', on the sample S1
The (x, y, z) coordinate values of C'and D'are obtained. A ',
When the (x, y, z) coordinate values of B ', C', D'are obtained,
The coordinate values of the four corners A, B, C, D of the analysis area S2 can be obtained. This will be described with reference to FIG. The points where the straight line connecting A ′ and D ′ intersects AB and DC are designated A ″ and D ″, and the points where the straight line connecting B ′ and C ′ also intersect AB and DC are designated B ″ and C ″. Since the (x, y, z) coordinate value of each point of A ', B', C ', D'is obtained, A ",
The (x, y, z) coordinate value of each point of B ″, C ″, D ″ is obtained as follows. The case of obtaining the (x, y, z) coordinate value of point A ″ will be described.

The x-coordinate of the point A ″ can be obtained from the x- and y-coordinates of D ′ and A ′ by the proportional relationship as follows. In addition, in the following equation, the subscript indicates that the coordinate of the point.

_{x A "= x D '+} (y A -y D') (X A '-X D' / (y A '+ y D' Moreover, A" y-coordinate of the point is equal to the y coordinate of the point A. Then The x coordinate of point A'and the y coordinate of point A are known.
This means that the x and y coordinate values of the A ″ point have been obtained. Next, z
A method of calculating coordinates will be described. This will be described with reference to FIG. The z coordinate value of the D ′ point is z ₁ and the z coordinate value of the A ′ point is z ₂
(Z ₁ and z ₂ are known). The y-direction distance between the D ′ point and the A ′ point is y ₁ , and the y-direction distance between the D ′ point and the A ″ point is y ₂ (y ₁ , y
₂ is known). The z coordinate value z ₃ of the A ″ point is given by the following equation.

z ₃ = z ₁ + y ₂ (z ₂ −z ₁ ) / y ₁ Similarly for the remaining B ″, C ″, D ″ (x,
The y, z) coordinate value can be obtained.

When the coordinate values of A ″, B ″, C ″, D ″ are obtained in this way, it is easy to similarly obtain the z coordinate values of the points A, B, C, D. When the z coordinate values of the points A, B, C, D are obtained, the coordinate values in the x and y directions are obtained in steps, so the (x, y, z) coordinate values of the four corners of the analysis area S2 are It has been decided.

(X, at the four corners of the analysis region S2 determined in the step
Based on the (y, z) coordinate values, the height adjustment in the z-axis direction is performed when the sample is moved in the x-axis direction and the y-axis direction. The analysis area S2 is a temporary empty area in a portion where the sample S1 protrudes, but is an area necessary for two-dimensionally scanning the sample S1. That is, the drive mechanism in each of the x-axis, y-axis, and z-axis directions performs position control based on the (x, y, z) coordinate values of the analysis area S2.

Here, the z-axis coordinate values of the four points A, B, C and D of the actual sample S1 are Az, Bz, Cz and Dz, respectively, and the z-coordinate value of the center point O is Oz. D = Oz- (Az + Bz + Cz + Dz) By defining × 1/4, it is possible to discriminate whether the analysis surface is convex, flat, or concave depending on whether the value of d is positive, O, or negative.
It is also possible to calculate the radius of curvature of the analysis surface by the value. Therefore, when the separation plane is determined, the plane state of the analysis surface can be objectively known by printing out the state of the analysis surface (convex, flat or concave) using a printer or the like. It can help improve the reliability of the analysis results.

FIG. 5 is a diagram showing a configuration example of a system for carrying out the method of the present invention. The thermoelectrons generated from the filament 1 heated in vacuum are accelerated by the Wehnelt 2 applied at high potential. Then, the electron beam 4 condensed by the focusing lens 3 is irradiated onto the surface of the sample 9 by the objective lens 5. The X-rays generated from the vicinity of the irradiation point are separated and condensed by the dispersive crystal 6, sent to the measuring device 8 via the X-ray detector 7, and the value read by the integrated control device 18 is stored in the storage device 19. It can be stored.

Here, the sample 9 is placed on the moving stage 10, and the driving mechanism 1 in the xy horizontal plane is mounted on this stage.
A drive mechanism 13 in the z-axis direction (vertical direction) is provided together with the first and the second drive units 12. Each x, y, and z axis drive mechanism is provided with an independent control device 14, 15 and 16, respectively, and is driven independently when a drive command is issued from the centralized control device 18. . Further control device 1
8 is connected to a joystick 17, and when the x, y and z axes are not driven, the joystick 17 is used to control the x, y
It is designed so that the y and z axes can be freely manipulated. A printer 20 is connected to the centralized control device 18 and prints out various information.

FIG. 6 is a diagram showing a state in which a sample is observed using an optical microscope. The same parts as those in FIG. 5 are designated by the same reference numerals. In the figure, 21 is an optical microscope with a shallow depth of focus as means for observing the entire surface of the sample 9, and the optical microscope includes an illumination lamp 22 and a half mirror 2.
3, a mirror 24, a concave mirror 25, a convex mirror 26, and an eyepiece lens barrel 27, which are arranged near the objective lens 5 without blocking the electron beam path. Optical microscope 21
The calculation of the coordinate value in the z-axis direction by is performed as follows. By adjusting the height as described above, the z-axis drive mechanism 13 is attached to the joystick 1 at one point on the sample, for example, A'point.
The optimum state is set by 7, and the z-axis coordinate (z
Store a) in the storage device 19. Then, in this state, the sample surface is observed by the optical microscope 21, and the optical microscope 21 is focused. Next, the x and y axis drive mechanism 11,
The point B'on the sample is moved to the electron beam irradiation position by 12 and the focusing means of the optical microscope 21 is fixed,
The z-axis drive mechanism is changed to focus the optical microscope image, and the z-axis coordinate (zb) at this time is stored. This utilizes the fact that the depth of focus of the optical microscope 21 is extremely short, but the same operation is repeated to obtain z coordinate values (zc, zd) for the C ′ point and D ′ line, and the storage device 19 is obtained.
Remember. Although the z-coordinate values of the points A ', B', C'and D'have been obtained as above, the other points can be obtained in exactly the same manner.

(Effect of the Invention) As described in detail above, according to the present invention, even if the analysis region is wider than the actual sample surface region, the position correction of the sample in the height direction (z-axis direction) is accurately performed. And the average of the z coordinate values at the four corners of the analysis area and the z of the center of the analysis area
It is possible to realize a sample position setting method in an X-ray microanalyzer or the like that can obtain the flatness of the sample surface as an objective numerical value by comparison with the coordinate values.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the method of the present invention,
2 to 4 are explanatory views of the method of the present invention, FIG. 5, and FIG.
The figure is a diagram showing a system configuration example for carrying out the method of the present invention. 1 ... Filament, 2 ... Fennert, 3 ... Focusing lens, 4 ... Electron beam, 5 ... Objective lens, 6 ... Spectroscopic crystal, 7 ... X-ray detector, 8 ... Measuring device, 9 ... Sample, 10 ...... Movement stage 11 to 13 ...... Driving mechanism, 14 to 16 ...... Control device 17 ...... Joystick 18 ...... Overall control device, 19 ...... Storage device 20 ...... Printer, 21 ...... Optical microscope 22 ...... Illumination lamp , 23 ... Half mirror 2 24 ... Mirror, 25 ... Concave mirror 26 ... Convex mirror, 27 ... Eyepiece lens barrel

Claims (1)

[Claims] 1. When the sample is moved in the x-axis direction and the y-axis direction in order to obtain information on the two-dimensional element distribution in the analysis region, the (x, y, z) coordinate values at the four corners of the analysis region are obtained. Based on this, in the sample position setting method in an X-ray microanalyzer or the like for adjusting the height of the sample in the z-axis direction, the analysis area is formed by a rectangular area that surrounds the actual sample surface area and is wider than the sample surface area. , X-coordinate values and y-coordinate values at four corners of the analysis area are calculated (step), and the x-coordinate value and the y-coordinate value are provided on the sample surface area in the analysis area.
By defining four points specified by the coordinate values (a square is formed by connecting the four points with a straight line), the height of the sample surface is measured at the four points, and the z coordinate value of the four points is obtained. The (x, y, z) coordinate values of the four points are obtained (step), and assuming that the actual sample surface extends outside the sample surface area, the (x, y, z) of the four points on the sample surface area are assumed. , Y, z) coordinate values to determine (x, y, z) coordinate values at the four corners of the analysis area by calculating z coordinate values at the four corners of the analysis area (step). Based on the determined (x, y, z) coordinate values of the four corners of the analysis region, height adjustment in the z-axis direction is performed when the sample is moved in the x-axis direction and the y-axis direction (step). A sample position setting method in an X-ray microanalyzer or the like characterized by the above.